Alzheimer’s disease (AD), characterized by cognitive decline and devastating neurodegeneration, is the most common age-related dementia. Since AD is a typical example of a complex disease that is affected by various genetic and environmental factors, various factors could be involved in preventing and/or treating AD. Extracellular accumulation of beta-amyloid peptide (Aβ) and intracellular accumulation of tau undeniably play essential roles in the etiology of AD. However, interestingly enough, medications targeting Aβ or tau all failed and the only clinically efficient medications for AD are drugs targeting the cholinergic pathway. Also, a very intriguing discovery in AD is that the Mediterranean diet (MeDi), containing an unusually large quantity of Lactobacilli, is very effective in preventing AD. Based on recently emerging findings, it is our opinion that the reduction of blood ammonia levels by Lactobacilli in MeDi is the therapeutic agent of MeDi for AD. The recent evidence of Lactobacilli lowering blood ammonia level not only provides a link between AD and MeDi but also provides a foundation of pharmabiotics for hyperammonemia as well as various neurological diseases. As the population ages, the incidence and prevalence of age-related diseases have been increasing year by year, posing a new global dilemma. Alzheimer’s disease (AD) is one of the most common age-related diseases and is a serious public health challenge, with over 5 million new cases each year, over 33 million patients worldwide and an economic burden exceeding half a trillion USD . It has N-methyl-d-aspartate antagonists and cholinesterase inhibitors to modulate those pathways [Characterized by dementia, AD starts from short-term memory loss, progresses into cognitive deficits and ultimately leads to death . Patientpathways . Howeverpathways ,5.The failure in developing efficient therapeutic agents for AD might originate from the fact that AD is a typical example of complex diseases. It has been well known that a combination of various genetic, environmental and lifestyle factors cause AD. Among the various determinant factors for AD, the significance of blood ammonia as an etiological agent has not been widely noted. Ammonia, which is produced as an end-product of protein catabolism, has been devoted much attention for its strong neurotoxicity. Although acute hyperammonemia manifests as encephalopathy, the clinical manifestations of chronic, slightly elevated blood ammonia levels have not been studied. However, considering the neurotoxic nature of ammonia, it would be reasonable to speculate that chronically elevated levels of ammonia are associated with AD. In fact, several initial studies declared the association between AD and blood ammonia level ,7, proviThe multiple different facets of AD and related pathophysiology obviously require us to consider a new paradigm to develop therapeutic agents for AD. Targeting gut microbiota could be an example of a new paradigmatic approach for the development of therapeutic agents for AD. Recent evidence show that gut microbiota play an intricate role in many different neuronal functions as well as various neurological diseases such as Autism spectrum disorder (ASD), Parkinson’s disease (PD), multiple sclerosis (MS), mood disorders, Gulf War Illness (GWI), multiple sclerosis, neuromyelitis optica spectrum disorders, Huntington disease and amyotrophic lateral sclerosis and so on ,12,13,14AD is a multifactorial neurodegenerative disease in which environmental risk factors  and genetic factors (including mutations of amyloid precursor protein (APP), presenilin genes (PSEN1 and 2) and allelic variation in apolipoprotein E (Apo E)) interact to enhance the incidence ,16. DespN-methyl-d-aspartate receptors (NMDARs) of the astrocytes’ partner neurons [2+ surges to induce dysfunctional mitochondria to pump out reactive oxygen species (ROS), which trigger tau hyperphosphorylation, oxidative damage, caspase 3 activation, excess production of ROS, nitric oxide (NO) and vascular endothelial growth factor (VEGF), thereby severing communications within the astrocytes’ neurons and beyond destroying neuronal synapses, dendritic spines [2+ surges increase the concentration of extracellular K+, inducing adenosine triphosphate (ATP) depletion, cell swelling and cell death [The most commonly used hypothesis is the amyloid hypothesis and recent studies have also focused on the role of Aβ oligomers in synaptic impairment ,18,19, w neurons ,24. The c spines ,25. Consll death  ) (GS) is predominantly used for ammonia removal [Ammonia is a normal end product of human tissues’ metabolism. Nevertheless, it is a highly neurotoxic compound at even sub-millimolar concentrations ,31. Thus removal . And, as removal .In the AD brain, the density of extracellular deposits of Aβ and senile plaques (SP) in the cortex induces the oxidative structural alterations of GS by interacting with it as well as enhances the neurotoxicity of Aβ . This caAmmonia significantly disrupts mitochondrial function and cerebral energy metabolism. High ammonia concentration suppresses the activities of alpha-ketoglutarate dehydrogenase and isocitrate dehydrogenase to increase the activity of ROS, superoxidase and Poly ADP-Ribose polymerase (PARP) in AD brain mitochondria . This caBesides mitochondrial dysfunction, energy metabolism is affected in AD brain. The reduction in glycolytic process was observed by comparing the enzymatic activity of glucose transporters, pyruvate dehydrogenase (PDH) , hexokinGamma-aminobutyric acid (GABA) is the chief inhibitory neurotransmitter in the CNS to play a critical role in AD, being extensively studied in AD and hyperammonemia. Some papers have proven that elevated ammonia level increase the GABA release to enhance the GABAergic system in AD which upregulates inhibitory neurotransmission to cause cognitive deficits in AD . FurtherThese observations support that ammonia is a potential neurotoxic factor which induces pathophysiological progression and typical symptoms of AD. Speculatively, the aim to predict the way of maintaining a normal ammonia level in brain might be the predominant therapeutic of AD.Lactobacillus plantarum decreased both blood and fecal ammonia levels in rodent models of hyperammonemia [Lactobacillus plantarum was constructed which overproduced alanine dehydrogenase and consumed in vitro higher amounts of ammonia than its wild-type counterpart. When given at doses of 109 CFU in vivo to mice suffering from acute liver failure with hyperammonemia, this modified strain had the same ability to decrease blood ammonia, to decrease mortality and to consume gut ammonia, such as that of wild-type Lactobacillus plantarum [Lactobacillus strains were able to decrease blood ammonia level and improve neuropsychological symptoms (High blood ammonia is an excessive accumulation of ammonia in the blood. It occurs due to increased production or decreased clearance of ammonia . In genemmonemia . A slighmmonemia . In thislantarum . Some clsymptoms . It appeLactobacillus found in yogurt on lowering blood ammonia levels has a significant impact on the pathology of AD. The first hint to the answer came from a recent study where the efficacy of Lactobacillus helveticus NS8 was tested in preventing cognitive decline and anxiety-like behavior in hyperammonemia rats [Lactobacillus helveticus NS8 (109 CFU mL−1) in drinking water as a daily supplementation. Although this study didn’t measure the difference in blood ammonia levels, it still presents interesting results that the administration of Lactobacillus helveticus NS8 significantly reduced the level of inflammatory markers, decreased 5-HT metabolism and restored cognitive function. Another recent study showed that the probiotic  administration for three months has favorable effects on Mini–Mental State Examination (MMSE) score, malonyl dialdehyde (MDA), high sensitive C-reactive protein (hs-CRP), markers of insulin metabolism and triglycerides levels of the AD patients [A key question is whether the effect of mia rats . Chronicpatients . In thisThe dietary pattern of populations bordering the Mediterranean Sea is called Medi and has been widely reported for its model of healthy eating and is often linked to the lower incidence rate of AD in the Mediterranean region . PopulatTypical components of Medi include proportionally high consumption of dairy products (mostly as yogurt and cheese), high intake of vegetables, legumes, fruits and cereals, high intake of unsaturated fatty acids, (mostly in the form of olive oil) and a low intake of meat and poultry . Medi efMedi has been the most investigated dietary pattern in many epidemiological studies. Several studies on Medi such as the Memory and Aging Project (MAP) , WashingRegarding causative factors in AD, various neurotoxins have been proposed but the effect of ammonia as a potent neurotoxin in relation to the pathology of AD has received less attention . A high Lactobacillus strains efficiently reduced blood ammonia levels cast a light on a historically long, nagging question on why the MeDi is beneficial for a healthy brain. We believe that Lactobacilli, especially abundant in the MeDi, help to maintain a low level of blood ammonia level. Because ammonia is the strongest natural neurotoxin, it would be unrealistic that maintaining blood ammonia at low levels does not contribute positively for health of brain.Various epidemiological studies have consistently shown that the MeDi slow cognitive decline in older adults reduces the risk of mild cognitive impairment, a transitional stage between the cognitive decline of normal aging and most interestingly, lowers the risk of AD. Despite the obvious fact that the MeDi is beneficial for healthy brain, the scientific reason is unclear even now. The MeDi consists of especially large quantity of yogurt, which means that Mediterraneans consume an extraordinary quantity of Lactobacilli. In this context, recent evidence showing that some The recent evidence of Lactobacilli lowering blood ammonia level not only provides a link between AD and MeDi but also suggest a possible role of gut microbiota in neurological diseases and neuronal functions. Because there could be a plenty of intestinal bacteria among the constituent of gut microbiota lowering blood ammonia levels, investigating various strains of intestinal bacteria will provide a foundation for pharmabiotics for hyperammonemia as well as various neurological diseases.


Editorial on the Research TopicImmunomodulatory Effects of Drugs for Treatment of Immune-Related DiseasesThe last 10 years have witnessed robust development of several drugs as a consequence of intense collaboration among academics, clinicians, scientists, and pharmaceutical companies. This has led to approval of these drugs for treatment of autoimmune diseases, cancer and AIDS, among many other diseases. This research topic focuses on the mechanism of action (MOA) of these drugs and reports new findings related to autophagy and adjuvanticity of drugs.Kim et al., the function of the chemical 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) was examined. This chemical has been previously used to facilitate the delivery of hydrophobic drugs and recently used as an adjuvant. The authors reported that HP-β-CD induced the maturation of dendritic cells (DCs), including upregulating the expression of co-stimulatory molecules and MHC class II molecules . This maturation promoted these cells to become professional antigen-presenting cells inducing the proliferation of T cells. The adjuvanticity of the chemical was further examined in a mouse footpad immunization model, and it was concluded that HP-β-CD functions as a potent adjuvant inducing DCs maturation, a process mediated through lipid draft formation.In an article by Miccadei et al., who reviewed the potential effects of ω3-polyunsaturated fatty acids (PUFA) as an adjuvant for chemotherapy and/or radiotherapy regiments to treat colorectal cancer. Interest has been recently generated in the effects of diets on cancer, obesity, diabetes, and many more metabolic disorders. Administration of PUFA-enriched diets may have several advantages in controlling inflammatory responses that may benefit patients with inflammatory disorders. Further, PUFA-enriched diets might also be considered for preventing colorectal cancer, provided that the MOA of this adjuvant is clearly understood.The theme of new adjuvants was further discussed in an article by Musters et al. advocated the use of off-label drugs to treat immune-mediated diseases that failed all other possible treatments. The authors described a case of multicentric Castleman’s disease (MCD) with disseminated polyclonal B cell proliferation throughout multiple lymph nodes. This patient was treated in the authors’ center with tocilizumab, a humanized monoclonal antibody against human IL-6 receptor, which was approved for treatment of rheumatoid arthritis (RA) and juvenile RA patients, but not for Castleman’s disease patients. The patient showed a remarkable response to the drug including lower C-reactive protein level, improved sedimentation rate, and normalization of hemoglobin level. The authors concluded that off-label prescription drugs can be used after carefully evaluating the efficacy and safety of these biologic drugs.Garrido et al.). NK cells are the predominant innate immune cells that are important to fight against HIV infection . The authors utilized several drugs including histone deacetylase (HDAC) inhibitors such as SAHA or vorinostat, romidepsin, and panobinostat, which are standard chemotherapeutic agents for several cancer patients. They also used protein kinase C (PKC) agonists including prostratin and ingenol. Intriguingly, exposure to romidepsin and panobinostat was detrimental for NK cell activity, whereas exposure to the PKC agonists may be beneficial. Hence, caution should be exercised before these drugs can be considered to eradicate HIV infection, particularly in relation to their effects on the antiviral/antitumor effectors NK cells.The effects of latency-reversing agents (LRAs) on natural killer (NK) cells during clearance of HIV infection was explored in this issue . It was observed that NK cells incubated in vitro with two drugs; one approved for treatment of multiple sclerosis (MS), namely, dimethyl fumarate (DMF), and the second known as monomethyl fumarate (MMF), upregulated the expression of chemokine receptor 10 (CCR10) on NK cell surfaces. This was corroborated with increased chemotaxis of these cells toward the concentration gradients of the ligands for CCR10 such as CCL27 and CCL28, as well as enhanced NK cell cytotoxicity against tumor cell lines. These results might have clinical implication for harnessing the antitumor effector cells in vitro in order to induce their migration toward the sites of tumor growth, particularly those secreting CCL27 and CCL28. Further, the potential therapeutic effects of DMF and MMF for various disorders including MS, neurodegenerative diseases, cancer, and gastrointestinal ulcers were reviewed in this issue (Al-Jaderi and Maghazachi). The authors described the effects of DMF and MMF on various immune cells including T cells, B cells, NK cells, DCs, macrophages, and neutrophils, as well as on keratinocytes, endothelial cells, microglia, astrocytes, and neurons (Al-Jaderi and Maghazachi).The potential effects of NK cells in cancer immunotherapy were also discussed  in exacerbating asthma. The authors suggested that autophagy-related 5 (ATG5) gene expression was positively correlated with the expression of COL5A1, and the subsequent deposition of collagen in the lungs of refractory asthmatic patients. These results indicate that dysregulation of autophagy may correlate with the fibrosis in the airway of asthmatic patients, suggesting that ATG5 might be a target for therapy in refractory asthmatic patients. On the other hand, Li et al. described beneficial effects for autophagy in autoimmune hepatitis, an autoimmune disorder characterized by abnormal Th1 activation and reduced apoptosis. It was observed that mice rich in n-3 PUFA resist liver damage after the administration of concanavalin-A, which induced hepatitis in these mice. The authors sought to examine the MOA of n-3 PUFA and observed that this fatty acid enhanced T cell autophagy and reduced T cell activation resulting in protection against severe liver injury. Collectively, these observations might form a basis for the potential therapeutic application of n-3 PUFA as well as other related fish products such as eicosapentaenoic acid or docosahexaenoic acid, toward liver damage and autoimmune hepatitis.The topic of autophagy was discussed in two separate publications. Brenner et al. studied the effects of chemokine receptor expression in 79 patients with acute myeloid leukemia (AML) an aggressive form of leukemia and reported that CCL28 is constitutively released by primary human AML cells. Therefore, this chemokine may play a role in the cross talk among leukemic cells and neighboring bone marrow cells. However, the effect can be either inhibitory for the growth of leukemia if stem cell factor or GM-CSF factor is present, whereas the final effect of CCL28 can be stimulatory when Flt3 ligand is exogenously released. Although it was suggested that blocking chemokine receptor in this model might be beneficial for AML patients, caution should be exercised as CCR10, the receptor for CCL28, has been found to be up-regulated on the surface of the anti-tumor NK cells, which may facilitate their recruitment toward the sites of tumor growth . Therefore, a balance between the stimulatory and inhibitory effects of chemokine/chemokine receptor expression must be carefully weighed before regiments of cancer therapy are developed based on this concept. In a subsequent study, the same authors examined cytokine-mediated cross talk among AML and mesenchymal stem cells (MSCs), and observed that MSCs release cytokines that increase the viability and proliferation of leukemic cells, despite the heterogeneity of AML . These findings may have implications in targeting the relevant cytokines or their receptors for therapeutic purposes of aggressive leukemia.Hematological disorders were described in two papers by the same authors. In the first, In summary, the topics described in this issue should form the basis for understanding the MOA of drugs that may facilitate the development of personalized medicine to treat solid tumors, blood lymphoproliferative disorders, autoimmune diseases, and inflammatory conditions.The author confirms being the sole contributor of this work and approved it for publication.The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Although adenosine has been approved for clinical use in the United States for the treatment of supraventricular tachycardia and coronary artery imaging, and the selective A2A agonist, regadenoson, for the latter, clinical use of adenosine receptor agonists for protecting the ischemic heart has not advanced beyond early trials. An examination of the literature indicates that existing experimental studies have several limitations in terms of clinical relevance, as well as lacking incorporation of recent new insights into adenosine receptor signaling. Such deficiencies include the lack of experimental studies in models that most closely mimic human cardiovascular disease. In addition, there have been very few studies in chronic models of myocardial ischemia, where limiting myocardial remodeling and heart failure, not reduction of infarct size, are the primary endpoints. Despite an increasing number of reports of the beneficial effects of adenosine receptor antagonists, not agonists, in chronic diseases, this idea has not been well-studied in experimental myocardial ischemia. There have also been few studies examining adenosine receptor subtype interactions as well as receptor heterodimerization. The purpose of this Perspective article is to discuss these deficiencies to highlight future directions of research in the field of adenosine receptor-mediated protection of ischemic myocardium.Since the seminal reports of adenosine receptor-mediated cardioprotection in the early 1990s, there have been a multitude of such reports in various species and preparations. Original observations of the beneficial effects of A Searching the database at “ClinicalTrials.gov” with the terms “ischemic heart disease” and “adenosine” yields 192 trials; changing the disease/condition to myocardial infarction (MI) yields only 40 trials. Nearly all of these trials have related to adenosine's effects on arrhythmias, coronary blood flow, and platelets. When searching this database with “adenosine receptor” 582 trials are shown, but combining with “myocardial infarction” only 9 trials are cited, and the majority of these trials used adenosine, not a receptor analog thereof. The only adenosine receptor agonists used in cardiac related clinical trials have been the AThis limited translation of hundreds of experimental studies, in every animal species tested to date, to the clinical arena raises the question of whether the past 30 years of adenosine receptor cardioprotection investigations have been for naught. This perspective will examine limitations of our existing knowledge of adenosine-mediated protection of the ischemic heart to help guide future studies to fully understand the cardioprotective effects of adenosine therapeutics and harness its potential in humans.1 and A3 adenosine receptor agonists CPA and Cl-IB-MECA to reduce ischemia-reperfusion injury  preconditioning in 18–20 month-old Wistar rats, whereas Kristo et al. (1 and A2A) agonist AMP579. A major difference in these rat studies is that the former was conducted in an isolated perfused heart preparation, whereas the latter was conducted in vivo, where the effects of the circulating agonist continued into reperfusion. Interestingly in both rat and mouse studies the effects of A1 and A2A agonists on heart rate and coronary flow in aged hearts were similar to those in young adult hearts. These findings are consistent with the reports of unaltered A2A agonist (regadenoson) increases in coronary flow in aged human hearts  in a porcine model of reversible myocardial ischemia-reperfusion injury. This effect was determined to be independent of effects on coronary blood flow, and the same infusion in normal myocardium had no effect on regional contractile function. In summary, the lack of experimental studies in clinically relevant models with appropriate treatment protocols, is likely to have contributed to the lack of clinical trials examining the efficacy of adenosine or receptor agonists for treating acute MI. The primary focus on reduction of acute injury is not only inconsistent with clinical trends of more patients living with chronic myocardial ischemia, but it also neglects some of the other recognized beneficial effects of adenosine receptors.However, the vast majority of experimental studies have initiated treatments during late ischemia or at the onset of reperfusion. Such early reperfusion treatments in the setting of acute myocardial infarction (MI) are not feasible given the time involved from the onset of patient symptoms to the diagnosis of MI and initiation of reperfusion therapy. In fact the results of the AMISTAD-II trial indicated that patients  receiving intravenous adenosine within 3 h of symptom onset showed significantly reduced 1 and 6 months mortality compared with placebo  and other sources indicate that over the past 40 years, deaths from acute MI have decreased significantly, whereas the incidence of heart failure and deaths from heart failure have increased , in a coronary microembolization-induced model of heart failure in canines, improved left ventricular function, decreased fibrosis, and reduced plasma n-terminal pro-brain natriuretic peptide concentrations  in patients with heart failure with reduced ejection fraction indicated that this agent was safe, although no beneficial effects on cardiac function were observed  with the A1 antagonist, rolofylline, failed to significantly impact cardiac or renal primary or secondary end points (Massie et al., 2B receptor antagonism in experimental models of post-MI remodeling have been reported. Toldo et al. (2B antagonist, GS-6201, immediately following a permanent occlusion in mice resulted in a thicker scar, less LV hypertrophy and improved post-MI cardiac function after 4 weeks. Similar findings were reported with the same A2B antagonist in a chronic occlusion-reperfusion model in rats (Zhang et al., To date there are only a very limited number of studies assessing potential beneficial effects of adenosine receptor blockade in chronic heart disease, both in experimental models and in clinical trials. Beneficial effects of Ao et al.  reportedIn addition to the above clinical-relevance issues, there are some unresolved basic science matters related to adenosine receptor-mediated cardioprotection. Adenosine receptors are differentially expressed on multiple cells types, thus altering the tissue and organ response to even selective agonists or antagonists (Chen et al., In conclusion, nearly 30 years of experimental findings support the hypothesis that adenosine receptors modulate acute myocardial ischemia-reperfusion injury. Despite this evidence, the use of adenosine, adenosine modulators, or adenosine analogs for treatment of cardiac injury has not been accepted clinically, nor have there been many clinical trials. Clearly the next phase of research on adenosine receptor cardioprotection needs to establish the role of adenosine receptor agonists and antagonists in more clinically relevant models of myocardial ischemia.The author confirms being the sole contributor of this work and approved it for publication.The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


The effect of hypoglycemia on the progression of atherosclerosis in patients with type 2 diabetes mellitus (T2DM) remains largely unknown. This is a post hoc analysis of a randomized trial to investigate the relationship between hypoglycemic episodes and changes in carotid intima-media thickness (IMT). Among 274 study subjects, 104 patients experienced hypoglycemic episodes. Increases in the mean IMT and left maximum IMT of the common carotid arteries (CCA) were significantly greater in patients with hypoglycemia compared to those without hypoglycemia. Classification of the patients into three groups according to the frequency of hypoglycemic episodes showed that high frequency of hypoglycemic events was associated with increases in mean IMT-CCA, and left max-IMT-CCA and right max-IMT-CCA. In addition, repetitive episodes of hypoglycemia were associated with a reduction in the beneficial effects of sitagliptin on carotid IMT. Our data suggest that frequency of hypoglycemic episodes was associated with changes in carotid atherosclerosis. While type 2 diabetes mellitus (T2DM) is a risk factor for cardiovascular disease (CVD), which is one of the major causes of morbidity and mortality in these patients23Hypoglycemia is a common adverse effect of management for diabetes, especially insulin therapy, and a barrier to optimal glycemic control. Hypoglycemia affects blood constituents681012Sitagliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, improves glycemic control without increasing the risk of hypoglycemia151819The aim of the present post hoc-analysis was to investigate the relationship between hypoglycemic events and changes in carotid IMT in insulin-treated patients with T2DM.In the original study, 104 of 274 patients experienced hypoglycemia  over the 104 week follow-up. There was no significant differences in the mean number of hypoglycemic events between the two groups . One episode of severe hypoglycemic event occurred in each group. Subgroup analysis according to the occurrence of hypoglycemia showed that patients with hypoglycemia were older, had lower estimated glomerular filtration rate (eGFR) level, lower C-peptide level and had more frequent use of sulfonylurea and α-glucosidase inhibitors, but were more lean, less likely to be smokers, had lower HbA1c, total-cholesterol, triglyceride, hs-CRP (high-sensitivity C-reactive protein) and interleulin-6, and few use of glinides .Of the 274 patients in the original study, 243 patients with available carotid IMT data at baseline and 104 weeks were included in this post hoc analysis. Among them, 98 patients experienced hypoglycemia . In the analysis of covariance models that included the occurrence of hypoglycemia, age, gender, baseline IMT and the original treatment group (model 1), the changes in mean IMT of the common carotid arteries (mean-IMT-CCA) and left maximum IMT of the common carotid artery (max-IMT-CCA), but not right max-IMT-CCA, were significantly higher in patients with hypoglycemia than those without . SimilarNext, we performed subgroup analysis according to type of treatment. As shown in Next, to investigate the relationship between the frequency of hypoglycemia and changes in carotid IMT, we divided patients with the occurrence of hypoglycemia into three groups; patients without hypoglycemia, patients with less than 1 times/month hypoglycemia, and patients with more than 1 times/month hypoglycemia. Trend associations across three groups and changes in IMT were evaluated by univariate and multivariate linear regression analyses . The freThe change in HbA1c  was comparable between the hypoglycemia group (−0.2 ± 0.9%) and no-hypoglycemia group (−0.4 ± 1.1%) (Supplementary Table 1). Similarly, there were no differences in changes in other risk factors for atherosclerosis such as hypertension and lipid parameters during the observation period (Supplementary Table 1).Hypoglycemia is a common adverse effect of insulin treatment for T2DM1819While most clinical data showing associations between hypoglycemia and adverse CV risk/mortality risk have derived from “serious hypoglycemic” episodes2425In this study, patients with hypoglycemia were older, suffered more severe renal dysfunction, had less endogenous insulin and more frequent use of sulfonylurea. Thus, it is possible that hypoglycemia is only a maker of patients with advanced stages of T2DM and/or those prone to CVD. However, the occurrence of hypoglycemia was still associated with the changes in carotid IMT even after adjustment for these confounders. Furthermore, the control of atherosclerosis risk factors was not consistently worse in patients with the occurrence of hypoglycemia because they were less obese, were less likely to be smokers, achieved better glycemic and lipid controls and had lower serum levels of inflammatory cytokines, reflecting patients who were at lower risk for CVD. Indeed, almost similar findings were observed in analysis of covariance models after adjustment for those confounding factors. These data support that hypoglycemia by itself seem to be a contributing factor for atherosclerosis.The mechanism of the deleterious effect of hypoglycemia on carotid vascular wall may be multidimensional and possibly involves changes in blood constituents681012What is the precise mechanism through which repeated episodes of hypoglycemia promote the progression of atherosclerosis? In the present study, we did not find any association between serum biomarkers of inflammation or endothelial injury and frequency of hypoglycemia or carotid IMT changes (data not shown). It is possible that this negative relationship may be due to several limiting features of such biomarkers. Indeed, the amount of such biomarkers is known to be affected by both transient and chronic non-atherosclerotic diseases and drug treatment within a relatively short time29It is reported that glucagon-like peptide-1 (GLP-1) attenuates hypoglycemia-induced oxidative stress, inflammation and endothelial dysfunction in patients with T1DMThe present study has certain limitations. First, this was a post hoc and exploratory analysis of a randomized unblinded trial and the sample size was relatively small. The analysis is limited by the study design and this make the significance of the findings less clear. Thus, the results should be interpreted with caution. Second, we evaluated self-reported hypoglycemic events through self-monitoring of blood glucose (SMBG) levels and hypoglycemic symptoms. Thus, there may be a risk of underestimation of the incidence of hypoglycemic episodes. In an effort to overcome possible recall bias, we confirmed the occurrence of hypoglycemia at each visit of each patient. Third, we did not evaluate hypoglycemia awareness status. Since some episodes of non-severe hypoglycemia could be asymptomatic, they were unreported by patients. Thus, we could not rule out possible underestimation of the deleterious effects of hypoglycemia on carotid atherosclerosis. Fourth, there were some discrepancies in the results of carotid IMT although the results showed a similar pattern. These differences may be due to the underpowered sample and side difference in IMT-CCAOur data suggest that frequent episodes of hypoglycemia were associated with changes in carotid atherosclerosis in insulin-treated patients with T2DM. Physicians need to take care in avoiding the occurrence of hypoglycemic episodes in the clinical setting in order to minimize the process of atherosclerogenesis.We performed a post hoc analysis from the Sitagliptin Preventive study of Intima-media thickness Evaluation (SPIKE). The study design, inclusion and exclusion criteria, study schedule and measurements were described in detail previously17All patients who agreed to participate were entered into the study. The protocol was approved by the Institutional Review Board of each participating institution  in compliance with the Declaration of Helsinki and current legal regulations in Japan. Written informed consent was obtained from all the participants after full explanation of the study. This study has been registered on the University Hospital Medical Information Network Clinical Trials Registry, which is a non-profit organization in Japan and meets the requirements of the International Committee of Medical Journal Editors (UMIN000007396).All adverse events including hypoglycemia were recorded at each visit during study, as described previouslyUltrasonographic scans of the carotid artery were performed by expert sonographers who were specifically trained to perform the prescribed study examination, as reported previously1717Data were reported as mean ± SD. Statistical analysis was performed using analysis of covariance models that included several variables in addition to occurrence of hypoglycemia, such as age, gender and baseline IMT .Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.


It is now clearly established that complex interactions between genes and environment are involved in multiple aspects of neuropsychiatric disorders, from determining an individual’s vulnerability to onset, to influencing its response to therapeutic intervention. In this perspective, it appears crucial to better understand how the organism reacts to environmental stimuli and provide a coordinated and adapted response. In the central nervous system, neuronal plasticity and neurotransmission are among the major processes integrating such complex interactions between genes and environmental stimuli. In particular, immediate early genes (IEGs) are critical components of these interactions as they provide the molecular framework for a rapid and dynamic response to neuronal activity while opening the possibility for a lasting and sustained adaptation through regulation of the expression of a wide range of genes. As a result, IEGs have been tightly associated with neuronal activity as well as a variety of higher order processes within the central nervous system such as learning, memory and sensitivity to reward. The immediate early gene and transcription factor early growth response 1 (EGR1) has thus been revealed as a major mediator and regulator of synaptic plasticity and neuronal activity in both physiological and pathological conditions. In this review article, we will focus on the role of EGR1 in the central nervous system. First, we will summarize the different factors influencing its activity. Then, we will analyze the amount of data, including genome-wide, that has emerged in the recent years describing the wide variety of genes, pathways and biological functions regulated directly or indirectly by EGR1. We will thus be able to gain better insights into the mechanisms underlying EGR1’s functions in physiological neuronal activity. Finally, we will discuss and illustrate the role of EGR1 in pathological states with a particular interest in cognitive functions and neuropsychiatric disorders. Despite a high level of heritability observed in the most common neuropsychiatric disorders, a clear genetic basis in their etiology has proven difficult to identify  are critical mediators of gene × environment interactions and thus have been the focus of an extensive research interest in order to elucidate how environmental stimuli trigger a fast response with enduring neuroadaptations on neuronal activity and plasticity  in the rat PC12 cells in the presence of the protein synthesis inhibitor cyclohexamide  zinc fingers DNA-binding domains, suggesting similarities in the DNA sequences recognized by each EGR protein and thus the possibility of overlap in their respective targets and functions  also up-regulate Egr1 mRNA levels in an NMDA receptor-dependent manner  and cyclic AMP-response element binding protein (CREB) transcription factors, which can bind their respective response elements located in the Egr1 promoter , activator protein-1 (AP-1), nuclear factor kappa B (NFκB), or EGR1 itself  and transcription factor(s) to directly regulate Egr1 transcriptional regulation can be resolved, however, when accounting for kinetics and interactions between transcription factor binding, cofactors recruitment and chromatin dynamics including histone methylation, acetylation and phosphorylation, as well as nucleosome positioning. Indeed, by focusing on Egr1 gene transcription in MLP29 mouse progenitor cells, Riffo-Campos et al. . Indeed, in peripheral tissues and several cancer cell lines, several studies report direct targeting of EGR1 by miR-543  following by microarray profiling in monocytic differentiation of human monoblastoma cells or following UV-induced apoptosis in prostate carcinoma cells . Indeed, EGR1 binds to Interestingly, recent genome-wide investigations of EGR1 transcriptional targets point towards a widespread regulation of genes associated with similar dynamics critical in regulating synaptic plasticity. Indeed, a multitude of genes related to vesicular transport and neurotransmitter release, clathrin-dependent endocytosis , or actin cytoskeleton, are commonly observed as direct EGR1 targets  of the hypothalamus  axis—but not in the hippocampus or cortical regions for which EGR1 signal was more related to the exploration of the environment  up-regulates EGR1 expression in the rat or mouse hippocampus, which mediates stress-related fear memories  gene promoter and activates its expression  MHR01 MH87583, MH099085 and MH109450 to MK.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Zea mays, all suggest that the genes in this lineage might have undergone pseudogenization. This study highlights that XTNX genes are a gene family originated anciently in land plants and underwent specific conservative pattern in evolution.The Toll-interleukin-1 receptor (TIR) and Nucleotide-binding site (NBS) domains are two major components of the TIR-NBS-leucine-rich repeat family plant disease resistance genes. Extensive functional and evolutionary studies have been performed on these genes; however, the characterization of a small group of genes that are composed of atypical TIR and NBS domains, namely XTNX genes, is limited. The present study investigated this specific gene family by conducting genome-wide analyses of 59 green plant genomes. A total of 143 XTNX genes were identified in 51 of the 52 land plant genomes, whereas no XTNX gene was detected in any green algae genomes, which indicated that XTNX genes originated upon emergence of land plants. Phylogenetic analysis revealed that the ancestral XTNX gene underwent two rounds of ancient duplications in land plants, which resulted in the formation of clades I/II and clades IIa/IIb successively. Although clades I and IIb have evolved conservatively in angiosperms, the motif composition difference and sequence divergence at the amino acid level suggest that functional divergence may have occurred since the separation of the two clades. In contrast, several features of the clade IIa genes, including the absence in the majority of dicots, the long branches in the tree, the frequent loss of ancestral motifs, and the loss of expression in all detected tissues of  Plants have evolved two layers of immunity system against environmental pathogens . The firProteins encoded by intact NBS-LRR genes usually possess a conserved NBS domain, which is accompanied by a highly variable C-terminal LRR domain and a subclass-specific N-terminal domain. We previously reported that NBS-LRR genes have diverged into three subclasses prior to the radiation of angiosperms . Based oArabidopsis are truncated versions of the RNL genes  of the XTNX genes, we comprehensively identified and conducted a phylogenetic reconstruction of homologs in 59 plant genomes of different lineages of green plants. Our findings demonstrated that the XTNX genes originated from a common ancestor of all land plants. In contrast to the extensive expansion of TNL genes or moderate expansion of T genes, only a single copy gene of each early diverged XTNX lineage was retained in most plant genomes. Expression analysis suggested that XTNX genes potentially play important roles in plant biological processes and functional differentiation may have occurred among different lineages.Supplementary Table S1). A total of 143 XTNX-encoding genes were identified from the genomes of the 59 plant species (Supplementary Table S2), but no gene was identified in seven algae genomes (Chlorophyta) or the lycophyte Selaginella moellendorffii. The absence of the XTNX genes in the algal species suggests that the XTNX genes in the green lineage might have originated from the common ancestor of land plants, while Selaginella may have lost the XTNX genes due to its sharply reduced genome. XTNX genes were detected at lower copy numbers from the rest 51 land plant genomes (except for S. moellendorffii), varying from only 1 copy to the maximum of 8 copies . Of all species surveyed, Kalanchoe marnieriana possessed the highest number of XTNX genes (8 copies), whereas only one XTNX gene was observed in Marchantia polymorpha, Sphagnum fallax, and Linum usitatissimum. In addition, two XTNX genes were identified in 23 species, three genes in fourteen species, four genes in seven species, five genes in two species (Ananas comosus and Panicum virgatum), and six genes in one species (Glycine max).Collectively 59 species, including green algae, mosses, lycophytes, one gymnosperm, as well as diverse families of angiosperms, were selected to represent major evolutionary nodes in the plant kingdom (Supplementary Table S3). The intron number in these genes varies from 1 to 8 (Supplementary Table S3). Amino acid sequence analysis revealed that although the TIR domain could be detected directly in nearly all XTNX genes using the online NCBI Conserved Domain Database, the NBS domain in XTNX proteins is too divergent to be identified for many sequences (Supplementary Table S4). Furthermore, the NBS domain in XTNX proteins is only half the length of a regular NBS domain of NBS-LRR genes, and is often annotated as AAA or P-loop superfamily domains by the online NCBI Conserved Domain database (Supplementary Table S4).Gene structure analysis revealed that most XTNX genes are intronless. Only 23 XTNX genes from 143 have annotated introns . The earlier one occurred in the common ancestor of seed plants and resulted in the formation of two XTNX clades (clades I and II), while the later one took place in the common ancestor of monocots and dicots, causing the further divergence of clade II (subclades IIa and IIb). The genes in subclade IIa were only detected in some monocot species and one basal dicot species (Aquilegia coerulea), suggesting that XTNX genes of subclade IIa were lost in dicot ancestors soon after the split of Aquilegia lineage. In addition, the branch length of subclade IIa was longer than the other clades, which indicates that this lineage evolved rapidly. Besides the two ancient duplication events, some lineage- and species-specific duplications could also be detected, which further shaped the XTNX diversity in lateral diverged species.To establish the evolutionary history of XTNX genes in land plants, a phylogenetic tree was constructed. The presence of one XTNX gene in two species, Supplementary Table S5). Among the 50 identified motifs, motifs 1 and 3 have the maximum lengths of 50 amino acids, whereas motifs 39 and 47 showed minimum motif lengths of 10 amino acids. The average motif length of 50 conserved motifs was 21.9. Figure 3 shows that motifs 2 and 4 occur in all species. Similarly, more than 20 motifs  appeared in most of the identified XTNX genes (>80%). There were also several clade-specific motifs; for example, motifs 31, 33, 38, 43, 48, and 49 are present in clade I but not in clade II XTNX genes, whereas motifs 27, 35, 40, 41, 44, 47, and 50 only occur in clade II genes. This result suggesting sequence divergence has occurred after the separation of clade I and II. Motifs 35 and 41 were lost in subclade IIa, and only appeared in subclade IIb. Motifs 44 and 50 were Poaceae species-specific in subclade IIb, whereas motif 40 was dicot species-specific in subclade IIb. When putting the motif profile of the XTNX genes under the background of its phylogeny , several motif gain and loss events could be easily detected. For example, the subclade IIb monocot XTNX genes gained lineage-specific motifs 44 and 50, whereas dicot XTNX genes within this subclade obtained motif 40. In contrast, frequent motif loss was detected in subclade IIa genes, suggesting a pseudogenization or neofunctionalization process.To further reveal the diversification of XTNX clades/subclades, we analyzed their conserved motifs using the MEME motif detection software. The motif compositions were listed and used to compare different clades (Table 1). This is in accordance with the motif difference pattern and further supported FD has occurred after the separation of the three XTNX clades.In addition to gain and loss of clade-specific motifs, amino acid substitution would also cause functional diversification (FD) of XTNX genes. To estimate FD among the three major clades of XTNX genes, the DIVERGE3.0 program  was adopAs supported by the phylogenetic analysis, two ancient gene duplication events occurred during XTNX gene evolution in land plants. To explore whether these two rounds of duplication are consequences of ancient polyploidization, we performed within-genome collinearity analysis. The collinearity of the XTNX genes from subclades IIa and IIb, or subclade I/II was not detected in any surveyed species, suggesting that these did not result from ancient polyploidization. This result is in accordance with the current knowledge on plant genome polyploidization that no whole genome duplication (WGD) or whole genome triplication (WGT) event has been documented in the two divergent nodes of land plants.Figure 2). To examine whether some of these duplicons are resulted from lineage-specific WGDs/WGTs, we performed collinearity analysis for all genes within each genome that fall into the same lineage. Our data revealed that 19 of the 28 lineage/species-specific duplicated genes are present on the syntenic blocks, and 10 of them are resulted from recently occurred WGDs/WGTs. For example, four soybean genes in subclade IIb are resulted from two rounds of WGDs that occurred 54 million years ago in the common ancestor of legumes and 10 million years ago in soybean, respectively . Apart from WGD/WGT event that resulted in gene duplication, examples of tandem duplication were detected, e.g., the three Citrus sinensis genes  and two C. clementina genes (Ciclev10018684 and Ciclev10018685) in subclades IIb. There were also some duplications that could not be determined as segmental or tandem duplications, which were designated as ectopic or other duplications (Supplementary Table S2).Besides the two ancient duplication events, there were also many lineage/species-specific duplications as suggested by more than one gene in a genome clustered in the same clade/subclade on the tree  and At4g23440 (clade IIb) are expressed in all tissues except for pollen. In most tissues, At4g23440 has relatively higher expression than At5g56220, although whether the differential expression between the two genes is significant could not be detected in the used data sets. The Z. mays genome contains three XTNX genes named GRMZM2G067555 (clade I), GRMZM2G039878 (clade IIa), and GRMZM2G132403 (clade IIb). While the clade I and clade IIb XTNX genes are also differentially expressed in most tissues as observed in Arabidopsis, the expression of the clade IIa gene GRMZM2G039878 was not detected in any tissue , which suggest that genes in this clade may either only express under certain stimulations or have underwent pseudogenization rather than neofunctionalization process.As one of the most conserved TIR or NBS domain containing genes, the exact function of the XTNX genes has not been well determined. To obtain some clues for the biological function of XTNX genes, we determined the expression of genes from different XTNX lineages in three angiosperm genomes, including Figure 5C shows that these recent duplicated gene pairs  that derived from the ∼10 million-year Glycine WGD also show different expression patterns. For example, the expression of Glyma.04G114100 in one sample (stem 2) is almost five times of Glyma.06G321200. This suggested that at least in some species, recent duplicated XTNX genes became to express differentially. However, more detailed experiments should be devoted to test expression difference between specific gene pairs.Because genome duplication events have resulted in gene duplication of the two retained XTNX subclades in soybean, we then explored whether these recent duplicated genes maintained similar expression pattern. Arabidopsis and rice genomes by two pioneer studies on plant disease resistance genes . For those XTNX genes that do have annotated introns, none of these were conserved among the XTNX genes of different plants. In contrast, all the three subclasses NBS-LRR genes have conserved introns  boundary . TheoretFigure 2). Considering that several independent WGD/WGT events occurred in different angiosperm lineages during the K-P boundary , indicating functional differentiation of the two lineages. This difference was also supported by our expression analysis of genes of the two different lineages in three different species. In both Arabidopsis and Z. mays, the clade IIb lineage genes showed higher expression than clade I genes in most of the tissues assessed. Comparing with the conservative evolution of clades I and IIb, clade IIa genes are more likely to have undergone pseudogenization, as indicated by the long branch on the tree, the frequent loss of ancestral motifs, and the undetectable expression levels in all tissues. However, we could not rule out the possibility that genes in this clade might have undergone neofunctionalization and are expressed specifically in certain organs or life stages which have not been detected by current experiments.Three groups of early diverged XTNX genes exhibit distinct evolutionary patterns as observed in our phylogenetic analysis. Two groups of these genes evolved conservatively in both dicots and monocots, with most species containing only one copy of the gene in each lineage. This evolutionary pattern differs from that of the TNL genes, which have experienced furious expansion since the origin of angiosperm . Even thArabidopsis XTNX gene enhances its resistance to the bacterial pathogen Pseudomonas syringae pv. tomato DC3000 and a necrotrophic fungal pathogen Fusarium oxysporum .A total of 59 genomes from different plant species were used, including seven species from Chlorophyta, three species from Bryophyta, one species from Lycophyta, one species from Gymnospermae and 47 species from Angiospermae. The genome sequence of A. thaliana were used as queries to perform BLASTp searches, with the threshold expectation value set to 0.001. All hit sequences were then analyzed with Conserved Domains Database (CDD2) and then manually checked to confirm the presence of both TIR and NBS domains. When two or more transcripts were annotated for a gene, the most intact one was selected. The exon position and intron phase of each gene were transformed from the GFF3 file of the reference genome. Genes with very short TIR or NBS domains less than half of those in A. thaliana XTNX genes were eliminated from the data sets.To identify the XTNX genes in each genome, the amino acid sequences of two known XTNX genes (At4G23440 and At5G56220) in Supplementary Data Sheet 1) was analyzed in MEGA 7.0 to select the optimal evolutionary model that adequately fit the sequence data. Finally, phylogenetic trees were generated with the maximum likelihood algorithm using PhyML software that integrated in the Seaview package  to investigate the syntenic relationship of XTNX genes within and among species  was retrieved from (Z. mays XTNX genes (FPKM) was obtained from (Glycine max XTNX genes, the raw transcriptome data of various tissues (The expression data of ved from . The expned from . To anal tissues  were dowY-MZ, Z-QS, and Y-YH conceived and designed the project. Y-MZ and Z-QS obtained and analyzed the data. J-YX, L-WL, X-QS, G-CZ, and MC participated in the data analysis. Y-MZ drafted the manuscript. J-YX, Z-QS, and Y-YH modified the manuscript. All authors have read and approved the manuscript for publication.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Circulating Tumor Cells (CTCs) are floating cell populations, which are resistant to anoikis after detachment from the primary sites and travel through the circulatory and lymphatic systems to disseminate throughout the body. CTCs are considered as seed cells for metastasis, and thus isolation of CTCs does not require any invasive procedure. Based on the nature and location of ovarian cancer and glioblastoma, the role of CTCs and hematogenous (carried by blood) spreading of tumor cells in these cancers were not understood well. Dysregulation of epidermal growth factor receptor (EGFR/ERBB) family members due to their overexpression and/or mutation have been known to contribute to the etiology and progression of ovarian cancer and glioblastoma. However, the role of ERBB receptors on CTC formation of ovarian cancer and glioblastoma is not well established. This report highlights the role of ERBB family receptors on resistance to anoikis and CTC formation in ovarian cancer and glioblastoma. Recent research on CTCs demonstrates that capturing ERBB receptor positive cells from circulating system is an efficient approach to isolate CTCs for genomic and proteomic characterization of tumor cells. Therefore, ERBB-targeted isolation of CTCs would help to design therapy to treat cancer, determine drug responses and drug-resistant mechanisms in cancer patients. Metastasis is the primary reason for cancer-related mortality. This hallmark of cancer, comprises of a sequence of processes whereby cancer cells invade the circulatory system and spread to distant organs. A growing body of evidence suggests that tumor cells spread to distant sites much earlier than was previously believed. Circulating tumor cells (CTCs), first observed by Thomas Ashworth in the blood of a metastatic cancer patient, were identical to the cells of the distant solid tumor from which they have been derived from.see Figure CTCs are tumor cells, which are detached from the primary tumor and enter into the bloodstream. CTCs do not bind to extracellular matrix (ECM) and survive in the bloodstream due to their resistance to anoikis. This provides opportunities to capture CTCs by noninvasive procedures, making this a powerful tool for detecting and tracking cancer and metastasis. Hematogenous metastasis of tumor cells comprises of several sequential steps, such as the detachment of cells from the primary tumor, intravasation into the vasculature, resistance to anoikis and extravasation into the secondary site Figure . StudiesERBB signaling is often dysregulated in a wide variety of solid tumors including breast, lung, ovarian and glioblastoma, where aberrant expression of ERBB receptors are found to be associated with poor clinical outcome and survival , 6. GeneOvarian cancer metastasizes primarily through peritoneal spreading , and Glioblastoma Multiforme (GBM) seldom metastasizes outside the central nervous system. Based on the nature and distribution of ovarian cancer and GBM, the precise contribution of CTCs to metastasis has been under-studied. Studies using parabiosis models on ovarian cancer, where two mice were surgically joined for a shared a circulatory system  and clinERBB receptor family plays a key role in normal development of ovarian follicles by regulating the growth of ovarian surface epithelium . ApproxiIn conjunction with the studies, which demonstrate the role of ERBB3 on metastasis of ovarian cancer, another study using immunohistochemical analysis identified that high levels of ERBB3 are associated with poor outcome in ovarian cancer patients . FurtherSeveral therapeutic agents are being used against the ERBB family members of ERBB2 and/or EGFR for treatment of human cancers in the clinic. In contrast, there has been relatively less emphasis on ERBB3 as a molecular target for therapy and no targeted therapies for ERBB3 have been approved for cancer treatment till to date Table .Since ERBB3 does not have a kinase activity, targeting ERBB3 using monoclonal antibodies is the only strategy to block ERBB3-mediated signaling. Importantly there are several monoclonal antibodies such as MM-121 and MM-111  and U3-1287/AMG-888  targeting ERBB3 are under preclinical and clinical development . In brieMost brain and spinal cord tumors develop from glial cells, which are the supporting cells of the brain and tumors that arise from the glial cells are referred to as gliomas . There aGBM is an aggressive form of glioma associated with a median patient survival of 12 to 14 months after any treatment modality, including surgery, radiation or chemotherapy. Given the low rate of extracranial metastases (0.4-0.5%), GBM patients have participated in organ donation programs. A study by Muller et al. demonstrated that the occurrence of CTCs in the peripheral blood is a more frequent event than overt extracranial metastases in GBM patients . ImportaIn vitro studies showed that GBM cell lines are sensitive either to ERBB2-inhibiting antibodies or dual tyrosine kinase inhibitor lapatinib, which targets EGFR and ERBB2, suggesting that ERBB2 and EGFR have critical roles in GBM cell growth and metastasis [Studies using clinical samples showed that EGFR amplification is associated with CTC formation in GBM, indicating that EGFR signaling is a critical factor for CTC formation and extracranial spreading of GBM , 9. EGFRtastasis . ImportaMost of the cancer deaths are due to metastasis rather than primary tumors. Ovarian cancer is the most frequent cause of deaths among gynecological cancers , 19, 20.CTCs could be employed as a source of readily accessible genetic information of patient's tumors. Therefore, the potential use of CTCs in future personalized medicine strategies for cancer therapy such as tailoring therapy based on molecular characterization of CTCs in cancer patients will have clinical implications. However, better methods of isolating CTCs in large quantities are required for characterization to further exploit the utilities of CTCs in the clinic.The prevailing model of metastasis suggests that metastatic subpopulation of cancer cells display characteristics of cancer stem cell-like (CSCs) traits and exhibits features of epithelial-to-mesenchymal transition (EMT). However, EMT and CSC paradigms have been highly challenged in the last several years, because the pathological evidence of EMT or CSCs in human cancer samples has not been well establishedyet. Furthermore, tumor cells also undergo the process of mesenchymal-to-epithelial transition (MET), which is the reverse of EMT and tumor cells may lose or alter expression of CSC markers during metastasis . Thus, tBOX 1The ERBB family comprises of four receptors such as EGFR, ERBB2, ERBB3, ERBB4 and 13 polypeptide ligands contains a conserved epidermal growth factor (EGF) domain. Each receptor contains an extracellular ligand-binding domain, a transmembrane domain, and an intracellular tyrosine kinase domain. ERBB receptors normally exist as inactive monomers, with a molecular structure preventing dimerization, except ERBB2. Homo-or heterodimer formation between ERBB family members occurs upon ligand binding, where ERBB2 do not contain a ligand binding domain. However, ERBB2 act as the key receptor of ERBB family receptors due to their dimerizing capacities either with EGFR, upon EGF binding, or with ERBB3, upon NRG1 binding. Ligand binding further leads to trans-phosphorylation and tyrosine kinase activation of receptors, except ERBB3 receptor, which do not have a catalytically active kinase domain.Independent of any ligand binding, overexpression of ERBB2 also leads to homo-dimerization of ERBB2. Dimerization ERBB receptors can instigate a number of potent signaling pathways, including the mitogen-activated protein kinase pathway and the PI3-kinase (PI3K)–AKT pathways . Other t


Pattern recognition receptors (PRRs) sensing commensal microorganisms in the intestine induce tightly controlled tonic signaling in the intestinal mucosa, which is required to maintain intestinal barrier integrity and immune homeostasis. At the same time, PRR signaling pathways rapidly trigger the innate immune defense against invasive pathogens in the intestine. Intestinal epithelial cells and mononuclear phagocytes in the intestine and the gut-associated lymphoid tissues are critically involved in sensing components of the microbiome and regulating immune responses in the intestine to sustain immune tolerance against harmless antigens and to prevent inflammation. These processes have been mostly investigated in the context of the bacterial components of the microbiome so far. The impact of viruses residing in the intestine and the virus sensors, which are activated by these enteric viruses, on intestinal homeostasis and inflammation is just beginning to be unraveled. In this review, we will summarize recent findings indicating an important role of the enteric virome for intestinal homeostasis as well as pathology when the immune system fails to control the enteric virome. We will provide an overview of the virus sensors and signaling pathways, operative in the intestine and the mononuclear phagocyte subsets, which can sense viruses and shape the intestinal immune response. We will discuss how these might interact with resident enteric viruses directly or in context with the bacterial microbiome to affect intestinal homeostasis. The microbiome comprises all microorganisms inhabiting the human body and is a substantial part of our physiology. The term microbiome was defined by Joshua Lederberg as “the ecological community of commensal, symbiotic, and pathogenic microorganisms that literally share our body space” . Over thCaudovirales and Microviridae taxa [Intensive characterization over the past decades has revealed that the intestinal microbiome confers beneficial functions to the host by aiding in digestion of food products, maintaining intestinal barrier function, protecting from pathogenic microbial infections and shaping the immune system (reviewed in ). Howevedae taxa .Recent studies have shed light on how resident enteric viruses may affect host physiology beyond causing disease ,10,11,12Circoviridae, Anelloviridae, Picobirnaviridae, Picornaviridae , Parvoviridae (mainly bocaviruses), and also Reoviridae (rotavirus) were frequently detected in virus-enriched preparations from a control group of 11 healthy children in a recent longitudinal study [Although eukaryotic viruses are rare within the enteric virome of healthy adults, they could also be detected in the aforementioned metagenomic studies and earlier studies ,16 and cal study , demonstal study  and specal study . Thus, eCaudovirales family [Resident enteric viruses maintaining low level immune stimulation in the intestinal mucosa have important protective and immunoregulatory effects on the intestine as shown recently in mice persistently infected with MNV . During s family , resembls family .Atg16L1, which is a susceptibility gene in Crohn’s disease, show Paneth cell abnormalities leading to defective antibacterial defense and a hyperinflammatory state in the intestine [Atg16L1-mutant mice developed increased intestinal pathology in the colon and blunting of villi in the ileum resembling Crohn’s disease [The beneficial and detrimental effects of resident enteric viruses are however very close together and immunodeficiency or host genetic factors affecting epithelial barrier function or immune regulation in the intestine can tip the balance towards pathologic effects of viruses residing in the intestine ,24,25,26ntestine . This ph disease . The obs disease . Thus, a disease , they ca disease ,27.Picornaviridae, Parvoviridae, Anelloviridae and Adenoviridae while bacteriophages were less affected [Enterobacteriaceae was linked to AIDS-associated enteropathy and rapid disease progression [Investigation of the enteric virome in human immunodeficiency virus (HIV)-infected patients or simian immunodeficiency virus (SIV)-infected macaques with acquired immune deficiency syndrome (AIDS) revealed an expansion of the enteric virome and outgrowth of several potentially pathogenic eukaryotic enteric viruses including affected ,25,26. Egression ,25,26. Agression . Interesgression . Taken tCaudovirales bacteriophages inversely correlated with decreased bacterial richness and diversity (dysbiosis) in inflammatory bowel disease (IBD) patients compared to controls living in the same households [Despite the incomplete picture of the taxonomic structure of the mammalian virome, it is clear that the majority of viruses residing in the intestine are not eukaryotic viruses but bacteriophages, including prophages stably integrated into the bacterial genome and lytic phages, which infect and lyse bacteria and can be released from them in response to stress signals . By shapuseholds . Barr etuseholds .Caudovirales bacteriophages correlates with dysbiosis in IBD patients [In addition to their effects on the bacterial microbiome and support of the epithelial barrier function, it is possible that bacterial cell wall components and bacterial and phage DNA, which are released as a consequence of the lysis of bacteria by phages, trigger pattern recognition receptors (PRRs) in epithelial cells or immune cells with contact to the lumen thereby influencing intestinal homeostasis and immunity . Alternapatients .Studies in immunocompromised animals and patients show that mainly the eukaryotic viruses residing in the intestine are under constant surveillance by the immune system. Therefore, eukaryotic viruses should for now be considered the primary modulators of intestinal homeostasis and immune responses within the enteric virome.It is not yet understood which cellular and molecular interactions are involved in the beneficial and/or detrimental effects of enteric viruses on intestinal homeostasis and stress resistance. To fully comprehend the role of the enteric virome in health and disease, it is crucial to obtain a comprehensive view of which host cell types and signaling cascades are employed in sensing and eliciting responses to enteric viruses. Another important question is which types of innate and adaptive immune responses against enteric viruses are generated and how these influence intestinal physiology.PRRs include membrane bound TLRs and C-type lectin receptors (CLRs) and cytosolic nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs), retinoic acid-inducible gene I (RIG-I)-Iike receptors (RLRs), and DNA sensors, such as absent in melanoma (AIM) 2-like receptors (ALRs) and cyclic GMP-AMP synthase (cGAS). These sensors, which recognize highly conserved microbial- or pathogen-associated molecular patterns (MAMPs or PAMPs) and trigger canonical innate immune response pathways, are important for the continuous immunosurveillance of tissues to detect the presence of microorganisms. Sensing of microbes by PRRs in the intestinal mucosa or other body surfaces is tightly controlled to avoid detrimental immune responses against harmless commensals and allows the generation of effective immune responses against invasive pathogens at the same time. Extending beyond this, innate and in some cases adaptive immune responses triggered by PRR activation shape the composition and function of the intestinal microorganisms to preserve a healthy microbiome. Thus, recognition of the components of the intestinal microbiome by PRRs is essential for maintaining homeostasis between the host and the microbiome and preventing intestinal pathology. This was shown in studies using knockout mice for diverse PRRs and central components of their signaling pathways, which demonstrate that constant low-level stimulation of these receptors by the microbiome is required to maintain intestinal barrier integrity and intestinal immune homeostasis ,43. As dInfluenzavirus A [Virus sensing by receptors of the innate immune system can be cell intrinsic when the ligands are produced in the infected cell  or cell extrinsic, when the virus itself or infected dead cells are internalized into phagosomes or endosomes . Cell-inavirus A ,53,54.Despite individual differences between the receptors and cell-type specific differences, virus sensing triggers several major signaling pathways that lead to the nuclear factor-kappa (NF-κ)B dependent induction of proinflammatory cytokines such as IL-1β, IL-6, TNF-α, IL-12 and to the interferon regulatory factor (IRF) 3 and/or IRF7-dependent transcription of type I IFN genes . TriggerType I IFNs are crucial in the control of virus infections. They comprise 16 members, 12 IFN-α subtypes, IFN-β, IFN-ε, IFN-κ and IFN-ω, which bind to and activate IFN-α/-β receptor (IFNAR) to induce the JAK (Janus kinase)/STAT  signaling pathway . BindingToll-like Receptors are transmembrane PRRs that comprise an ectodomain containing leucine-rich repeats (LRRs) for PAMP recognition, a transmembrane domain and a cytosolic Toll-IL-1 receptor (TIR) domain . The TLRDue to the constant presence of microorganisms containing TLR ligands in the gastrointestinal tract, it was of great interest whether TLRs are functionally expressed at the intestinal epithelial interface and which roles they play there. Among the 13 TLRs discovered, TLR1-TLR9 have been identified as being expressed in human IECs at low levels, however expression is adjusted during intestinal inflammation; e.g., TLR4 is upregulated in the intestinal epithelium during active ulcerative colitis and Crohn’s disease, whereas TLR3 is downregulated in active Crohn’s disease ,84. InteStudies in laboratory mice indicate that MyD88-dependent signaling downstream of the TLRs and tonic activation of NF-κB in IECs are critical for maintaining intestinal barrier defense against commensals and response to injury  while uRakoff-Nahoum and co-workers were the first to show that mice with global deficiency in MyD88 develop more severe colitis with colonic bleeding and increased mortality after chemical injury by oral application of DSS. This phenotype was not due to overgrowth of commensal bacteria or increased infiltration of leucocytes, but rather to impaired resistance to injury . DeletioIEC specific deletion of MyD88, TRAF6, NEMO (regulatory subunit of the IKK complex) and IKKα/β led to impaired epithelial barrier function and enhanced DSS-induced colitis ,96,97,98+ cells from the colon of DSS-treated mice after incubation with TLR3/7 agonists [The contribution of virus stimulation of TLRs for the described protective effects of TLR signaling in the intestinal mucosa is still unclear. The increased susceptibility to DSS-induced colitis in mice lacking TLR3 and 7, which primarily sense viruses, may indicate that sensing of resident enteric viruses by these receptors protects the epithelium from colitis . This waagonists . Lack ofagonists . Similaragonists , TLR7 [1agonists  and TLR9agonists  had protagonists ,105. TLRagonists . A recenagonists . It can Constitutive IFN plays a role in maintaining immune homeostasis in the intestine ,108, as Cell-intrinsic viral recognition is mediated by intracellular (mostly cytosolic) receptors from different families: DNA sensors ), RNA sensors of the RLR family (retinoic acid-inducible gene I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5)), as well as the NLRs.The major cytosolic DNA sensor, cGAS , generatDNA derived from commensal bacteria, endogenous DNA or DNA from enteric viruses could also trigger the cGAS/STING pathway. The cytosolic DNA sensors AIM2 and IFI16 have been reported to play a role in the detection of DNA viruses, especially herpesviruses ,118,119,The RLRs are a family of DExD/H box containing RNA helicases that are cytosolic sensors for RNA. There are three family members: RIG-I , MDA5 1 and laboThe production of type I IFNs and other cytokines by bone marrow derived DCs in response to MNV was dependent on MDA5. Replication of MNV CW3 strain, which causes acute infection, was controlled by MDA5 in the intestine and in lymphoid organs after peroral infection . In miceE. coli compared to wildtype (WT) mice due to decreased phagocytosis of bacteria [Several studies have shown that apart from sensing viral pathogens, RIG-I and MAVS, which mediates RIG-I and MDA5 signaling, play a role in maintaining gut homeostasis and preventing intestinal inflammation. Mice lacking RIG-I spontaneously developed a colitis-like phenotype with increased susceptibility to DSS-induced colitis  and are bacteria . The spobacteria . It has bacteria . RIG-I sbacteria ,147,148.bacteria . The probacteria . Systemibacteria ,149. Botbacteria ,149. Thibacteria  remains NOD-like Receptors comprise a large receptor family characterized by the presence of a conserved NOD motif . DependiNOD1 and NOD2 were the first NLRs reported to function as intracellular microbial sensors . NOD1 isIn addition to the NOD proteins, NLRP6 has been shown to be crucial for maintaining intestinal homeostasis and a healthy intestinal microbiome . NLRP6 iThe complex crosstalk between the described PRR signaling pathways that are involved in innate immune responses to the microbiome, maintenance of the epithelial barrier function and homeostasis is depicted in IECs themselves can directly respond to commensal bacteria and viruses and contribute to the production of type I and type III IFNs in the intestine in the steady state, and in response to viral infection as a first line of defense ,171. HowMNPs are present throughout the intestine and comprise different subsets, which form a complex network, whose functionality is crucial for intestinal homeostasis and protection against invading pathogens. MNPs not only sense environmental signals including microbes and initiate innate cytokine and chemokine responses, but they also interact with ILCs as well as T and B lymphocytes and thus shape the adaptive immune response in the intestine. Disturbance of the MNP network and their interplay with ILCs and the adaptive immune system can lead to intestinal inflammation or failure of the immune defense against enteric pathogens ,174.Dendritic cells are subdivided in two main groups, namely conventional and plasmacytoid DCs. Conventional DCs (cDCs) in general are especially capable of sampling and presenting endogenous and exogenous antigens to naïve T cells. Their ability to migrate from peripheral tissues to draining lymph nodes allows them to carry antigens to the T cell area of the lymph node, where antigen presentation takes place. Further, DCs shape the effector T cell differentiation by the secretion of cytokines. Plasmacytoid DCs (pDCs) have a unique capacity in rapidly producing large amounts of type I IFNs in response to viral infections , althougSalmonella induced cDC migration inside the epithelial layer and direct sampling of luminal antigens [Conventional DCs are found throughout the intestinal lamina propria, as well as in isolated lymphoid follicles and Peyer’s patches. As they are located deep in the lamina propria without direct access to the lumen, several mechanisms come into play for sampling insoluble luminal antigens. Goblet cells, tissue resident macrophages, as well as specialized epithelial cells in the small intestine (villus M-cells) function as passage ways, which deliver antigen from the lumen to DCs in the lamina propria ,179,180.antigens . After aantigens ,183.The importance of cDCs for resistance against intestinal inflammation was demonstrated in studies using CD11c-DTR mice, in which cDCs can be depleted by injection of diphteria toxin (DT) ,185. Fur+CD11b− (murine) or CD103+ SIRPα− (murine and human) cDC1 [+ T cells. They correspond to the CD8α+ cDC1 in the spleen, which were identified as the major crosspresenting DCs [+ T cells for induction of tolerance in the steady state and induction of protective immunity after vaccination [Intestinal cDCs are distinguished from macrophages by lack of CD64 and other monocyte/macrophage markers. To separate the two main cDC subsets in the intestine CD103, CD11b (in mice), XCR1 and SIRPα (in mice and humans) are commonly used as markers ,191,192.an) cDC1 , are maiting DCs  and alsocination ,196. cDCcination ,198. TLRcination ,200. Morcination . TLR12 hcination , TLR13 icination .+ cDC1 have been shown to play an important role for intestinal T cell homeostasis because mice with constitutive ablation of XCR1+ cDCs have greatly diminished levels of intraepithelial lymphocytes (IEL) and lamina propria T cells, which goes along with an increased susceptibility to DSS-induced colitis [+ CD103+ CD11b− cDC1 but not CD103+ CD11b+ cDC2 aggravated colitis in a low dose DSS model [+ cells, which lack XCR1+ CD103+ CD11b− cDC1, also had greatly reduced numbers of CD8αβ+ and CD4+ CD8αα+ T cells in the IEL fraction of the small intestine and lacked intestinal Th1 cells [+ CD103+ CD11b− cDC1 for their maintenance. This could be highly relevant for the antiviral defense in the intestine as activation of IELs was shown to protect IECs against viral infection by producing type I and type III IFNs, which induced the expression of ISGs in IECs [+ T cell help for CD8+ T cell responses to viral infection [+ CD11b− cDC1, which are absent in Batf3−/− mice, were required for the generation of rotavirus-specific CD8+ T cells in neonates [XCR1 colitis . SimilarSS model . Mice wih1 cells . Thus, I in IECs . cDC1 we in IECs . Interesnfection ,210. It neonates . Thus, I+ or SIRPα+ cDC2 in the intestine, the CD103+CD11b+ cells, which are the more frequent population in the small intestine [−CD11b+ cDC subpopulation, which is the more abundant population in the colon [+ CD11b+ and CD103− CD11b+ cDC are also important for inducing Th1 and Th2 responses in the intestine in the context of infection depending on the pathogen they encounter. The specific role of these intestinal cDC2 subpopulations in the response to enteric viruses has not been investigated. However, it was shown that migratory IRF4-dependent cDC2 are required for T follicular helper cell induction and antibody production for protection against influenza A virus infection in the lung [Within the CD11bntestine , were shntestine ,214,215.he colon , was shohe colon ,217. Botthe lung . cDC2 exthe lung . Concernthe lung .Plasmacytoid DCs are sparsely present in the intestine and appear to be mainly located in the small intestine where they home in a CCR9-dependent manner and contribute to intestinal immune tolerance, whereas they are almost absent in the colon in the steady state ,220. HowIn contrast to cDCs, pDCs are specialized in the expression of the endosomal TLRs with strong expression of TLR 7 and 9 ,227. MorArimura and co-workers propose a role of pDCs in colitis development, as pDC-ablated mice showed ameliorated symptoms upon colitis induction with DSS, decreased production of inflammatory cytokines and a lower leukocyte influx into the colonic lamina propria. The effect was independent of type I IFN, however, the exact mechanisms underlying this phenotype remain unclear . In resp2 reduced their type I IFN response suggesting that type I IFN production by pDCs is downregulated in the intestinal microenvironment [The type I IFN producing capacity of Peyer’s patch pDCs in response to TLR9 stimulation was found to be reduced compared to splenic pDCs and exposure of splenic pDCs to TGF-β, IL-10 or PGEironment ,242. Butironment . pDCs alironment . Howeverironment , demonstironment ,247. In ironment .Bacteriodes fragilis via TLR2 and induce Tregs, which produce IL-10 leading to protection against trinitrobenzenesulfonic acid (TNBS)-induced colitis [Moreover, pDCs were shown to have immunosuppressive functions and thereby contribute to oral tolerance and may alleviate colitis . For exa colitis . In a re colitis . A speci colitis . These s+ T cells [The differential equipment with PRRs between the DC subsets highlights their division of labor in sensing and responding to pathogens such as viruses. Whereas cDC2 cells are infected by e.g., HIV and allow viral gene expression and replication, cDC1 as well as pDCs remain resistant against infection with many enveloped viruses by a mechanism, which prevents release of viruses from the endosomal compartment . The inf T cells . During  T cells . Further T cells ,252. Thu+ cDCs by the expression of the Fc receptor CD64, as they can express all other known surface markers of the CD11b+ CD103−SIRPα+ cDC. This similarity is also found on a functional level, as intestinal Mϕ are also able to induce Th17 and ILC3 [+ cDC1, which induce Tregs [Unlike in other tissues, adult intestinal macrophages (Mϕ) are mostly of hematopoietic origin and derived from infiltrating inflammatory monocytes . When thand ILC3 . Additioand ILC3  or by prand ILC3 . The intce Tregs . In addice Tregs .Mϕ are equipped with a range of TLRs, both extra-  and intracellularly  ,271,272,Studies performed in the last years have shown that the viral component of the microbiome, the enteric virome, may have an important role in maintaining intestinal homeostasis, but can also become pathogenic in situations of a breakdown of local defense mechanisms and control by the immune system. We have summarized here the current knowledge on receptors, signaling pathways and cellular players involved in sensing viruses in the intestine and have discussed the few studies which provide evidence that some of these pathways also play an important role for mediating the responses to viruses residing in the intestine of the healthy organisms, thereby shaping intestinal physiology. It becomes clear from the existing data that virus sensing pathways form a complex network and cross-regulate each other to adjust responses. The differences between specific epithelial and immune cell populations in the expression and activation of these virus sensing pathways add another layer of complexity. Moreover, an important aspect is also the observation that constitutive activation of PRRs induces responses in the intestine, which in turn shape the composition of the microbiome including bacteria, viruses and fungi. Thus, the beneficial but also the detrimental effects of the enteric virome are dependent on the context of the local intestinal milieu and the complex interaction with other microorganisms residing in the intestine.Several issues remain to be resolved regarding the impact of the enteric virome on intestinal homeostasis and immune responses. First of all, it is necessary to clearly separate effects of the enteric virome and the bacterial microbiome to investigate if the enteric virome has a non-redundant role in regulating homeostasis in the intestine. Furthermore, the specific contribution of different enteric virus strains, which reside in the intestine remains to be investigated. It will be challenging to establish in vitro culture systems to propagate these viruses, which is a prerequisite to perform controlled infection experiments with individual virus strains in vitro and in vivo. The availability of such isolated virus strains would allow to investigate the cellular tropism of enteric viruses and the virus-host interactions that enable them to reside in the intestine as commensals for longer time periods. MNV infection is a great model to study infection and persistence of an enteric virus in the murine intestine and its effects on intestinal physiology as well as its modulation of the intestinal immune system. But, clearly, further models need to be studied to discover common effects of resident enteric viruses and specific effects of individual viruses residing in the intestine. As shown by the discovery of MNV, the use of immunodeficient mice may be useful to discover novel eukaryotic enteric viruses, which could serve as suitable models.To investigate effects of the enteric virome, we can try to copy reductionist approaches, which have been performed to study effects of the bacterial microbiome, such as using germ-free or antibiotic treated mice. An approach, which mimics the depletion of intestinal bacteria by antibiotic treatment would be oral and/or systemic application of antiviral drugs to investigate the role of enteric viruses. This approach has been tested and was found to increase colitis susceptibility in mice, however only a slight reduction in detectable viral sequences was observed, showing that enteric viruses have differential sensitivity to this treatment and broader acting antiviral agents need to be used. Additionally, microbiome changes were induced by a treatment making it difficult to separate effects of enteric bacteria and viruses . BacteriThe use of genetically modified mice especially cell type-specific and conditional knockout for specific virus sensors and signaling adaptors is a valuable approach to understand the complex host response to the enteric virome and the contribution of specific pathways to the beneficial and detrimental effects of enteric viruses. For the correct interpretation of these future studies it will be critical to perform experiments with co-housed or separately housed littermate controls to separate effects of the host genotype on the microbiome from the actual effects of the host genotype. Furthermore, it would be necessary at this point to always disclose the MNV status of the mouse colony when reporting experiments, in which effects of the enteric virome are investigated, especially when using mice lacking molecules important for innate or adaptive immune responses.The species-specificity of eukaryotic enteric viruses is suspected to be an obstacle for transferring insights from the mouse model to the human situation. It is challenging to stably infect mice with commensal enteric viruses found in humans. To investigate effects of the human enteric virome in vivo, a switch to another animal model might be warranted. For example, the germ-free or gnotobiotic pig-model can be colonized more easily with the human microbiota and whose intestinal physiology and immune system is very similar to that of humans. The enteric virome in pigs appears to be similar to that of humans  and gnotStudies performed so far clearly show that the effects of the enteric virome are dependent on the context of host genetic variation and composition of the whole microbiome as bacterial, viral and fungal components of the microbiome will influence each other and all components of the microbiome are under the tight control of local defense mechanisms as well as immune responses. Which immune responses have a major influence on the abundance and composition of the enteric virome? Regarding local defense mechanisms, type I and especially type III IFNs appear to be important for controlling the replication of enteric viruses. Viral interference with induction and signaling of these antiviral IFNs in intestinal host cells is important for allowing persistence and shedding of the enteric viruses and for the establishment of a symbiotic relationship with the host. It has not been investigated which virus sensing receptors and downstream signaling pathways are crucial for controlling the enteric virome. Studies using pathogenic enteric viruses  demonstrate that several pathways are activated upon viral infection of intestinal host cells; these pathways influence each other to adjust the response to the local requirements of the intestine. Evidence from human and animal studies indicate that in addition to innate immunity also adaptive immune responses exert control over the enteric virome to preserve the symbiosis with the host in the intestine. Future investigations will reveal which resident enteric viruses are capable of inducing these adaptive immune responses, which antigen-presenting cells present the viral antigens, and what is the outcome regarding T and B cell differentiation. A thorough understanding of enteric virome sensing and its subsequent effects on homeostasis and immune responses in the intestine is critical for harnessing the enteric viromes protective capacity or for designing drugs that mimic its beneficial effects on both intestinal barrier function and immune tolerance, for example, in the context of infection and inflammation.


MECP2 gene. RTT affects predominantly females, and has a prevalence of roughly 1 in every 10,000 female births. Prior to the discovery that mutations of MECP2 are the leading cause of RTT, there were suggestions that RTT could be a mitochondrial disease. In fact, several reports documented altered mitochondrial structure, and deficiencies in mitochondrial enzyme activity in different cells or tissues derived from RTT patients. With the identification of MECP2 as the causal gene, interest largely shifted toward defining the normal function of MeCP2 in the brain, and how its absence affects the neurodevelopment and neurophysiology. Recently, though, interest in studying mitochondrial function in RTT has been reignited, at least in part due to observations suggesting systemic oxidative stress does play a contributing role in RTT pathogenesis. Here we review data relating to mitochondrial alterations at the structural and functional levels in RTT patients and model systems, and present a hypothesis for how the absence of MeCP2 could lead to altered mitochondrial function and elevated levels of cellular oxidative stress. Finally, we discuss the prospects for treating RTT using interventions that target specific aspects of mitochondrial dysfunction and/or oxidative stress.First described over 50 years ago, Rett syndrome (RTT) is a neurodevelopmental disorder caused primarily by mutations of the X-linked  MECP2) are the underlying cause for the vast majority of people affected with typical Rett syndrome   and forkhead box g1 (FOXG1) also causal for other less common RTT cases  production and also contribute to ROS detoxification, mitochondrial dysfunction generally results in excessive ROS production and/or diminished ROS detoxification, which collectively heighten levels of oxidative stress. As mentioned previously, elevated oxidative stress has repeatedly been reported in RTT patients. In Sierra et al.  showed aMecp2308 mutated (pre-symptomatic and symptomatic) male and female mice  may be a potential mediator. ANT1 is a transmembrane protein responsible for the normal shuttling of ATP and ADP across the inner mitochondrial membrane (Forlani et al., MECP2 mutations are not generally associated with neurodegeneration (Tarquinio et al., It is important to note that many RTT patients live into their 5th or 6th decade, and There are data that support this possibility. For example, the administration of Trolox, a vitamin E derivative, to MeCP2-null hippocampal slices decreased levels of oxidative burden, and improved both short- and long-term synaptic potentiation deficits of the local circuitry (Großer et al., in vitro and perhaps in vivo in RTT patients suggests mitochondrial regulation represents a target that allows at least some functional rescue to be attained. Intriguingly, a role for Foxg1 in mitochondrial function has now been identified (Pancrazi et al., Considerable data show impaired mitochondrial function occurs in MeCP2-deficient cells, and mechanisms through which these functional alterations arise beginning to be identified. Studies to date indicate that the loss of MeCP2 function negatively affects the signaling efficiency of a host of intracellular signaling pathways, the communicative ability of neuronal populations, the excitability of neural networks, and the functional efficiency of mitochondria. Each of these alterations could conceivably represent targets for therapeutic development toward treating RTT. The fact that anti-oxidant strategies has improved local neural circuit activity NS: Conducted literature review for manuscript, wrote draft of manuscript, prepared Tables, collated citations. AA: Edited manuscript, refined model hypothesis, and provided field expertise to project. LM: Assisted in model development, edited manuscript, and provided field expertise to project. JE: Supervised project, wrote final draft of manuscript, and provided field expertise to project.This work was supported by an operating grant from the Canadian Institutes of Health Research to JE [MOP-81104], and by a Mary Gertrude I'Anson Graduate Scholarship received by NS from the University of Toronto.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.