A(1) and A(3) adenosine receptors inhibit LPS-induced hypoxia-inducible factor-1 accumulation in murine astrocytes.
Adenosine (Ado) exerts neuroprotective and anti-inflammatory functions by acting through four receptor subtypes A1, A2A, A2B and A3. Astrocytes are one of its targets in the central nervous system. Hypoxia-inducible factor-1 (HIF-1), a master regulator of oxygen homeostasis, is induced after hypoxia, ischemia and inflammation and plays an important role in brain injury. HIF-1 is expressed by astrocytes, however the regulatory role played by Ado on HIF-1α modulation induced by inflammatory and hypoxic conditions has not been investigated. Primary murine astrocytes were activated with lipopolysaccharide (LPS) with or without Ado, Ado receptor agonists, antagonists and receptor silencing, before exposure to normoxia or hypoxia. HIF-1α accumulation and downstream genes regulation were determined. Ado inhibited LPS-increased HIF-1α accumulation under both normoxic and hypoxic conditions, through activation of A1 and A3 receptors. In cells incubated with the blockers of p44/42 MAPK and Akt, LPS-induced HIF-1α accumulation was significantly decreased in normoxia and hypoxia, suggesting the involvement of p44/42 MAPK and Akt in this effect and Ado inhibited kinases phosphorylation. A series of angiogenesis and metabolism related genes were modulated by hypoxia in an HIF-1 dependent way, but not further increased by LPS, with the exception of GLUT-1 and hexochinase II that were elevated by LPS only in normoxia and inhibited by Ado receptors. Instead, genes involved in inflammation, like inducible nitric-oxide synthase (iNOS) and A2B receptors, were increased by LPS in normoxia, strongly stimulated by LPS in concert with hypoxia and inhibited by Ado, through A1 and A3 receptor subtypes. In conclusion A1 and A3 receptors reduce the LPS-mediated HIF-1α accumulation in murine astrocytes, resulting in a downregulation of genes involved in inflammation and hypoxic injury, like iNOS and A2B receptors, in both normoxic and hypoxic conditions.
['Gessi|Stefania|S|', 'Merighi|Stefania|S|', 'Stefanelli|Angela|A|', 'Fazzi|Debora|D|', 'Varani|Katia|K|', 'Borea|Pier Andrea|PA|']
D000241:Adenosine D000818:Animals D001253:Astrocytes D015687:Cell Hypoxia D002478:Cells, Cultured D005786:Gene Expression Regulation D051795:Hypoxia-Inducible Factor 1, alpha Subunit D008070:Lipopolysaccharides D051379:Mice D008807:Mice, Inbred BALB C D052247:Nitric Oxide Synthase Type II D058906:Purinergic P1 Receptor Agonists D058915:Purinergic P1 Receptor Antagonists D043682:Receptor, Adenosine A1 D043684:Receptor, Adenosine A3
Adenosine receptors adenosine hypoxia-inducible factor-1 Astrocytes Ado central nervous system HIF-1 Hypoxia Inflammation lipopolysaccharide LPS p44/42 MAPK hexochinase II inducible nitric-oxide synthase iNOS 1,4-diamino-2,3-dicyano-1,4-bis(2-aminophenylthio)butadiene 1-[2-chloro-6-[[(3-iodophenyl)methyl]amino]-9H-purin-9-yl]-1-deoxy-N-methyl-β-d-ribofuranuronamide 1-butyl-8-(hexahydro-2,5-methanopentalen-3a(1H)-yl)-3,7-dihydro-3-(3-hydroxypropyl)-1H-purine-2,6-dione 2-[[6-amino-3,5-dicyano-4-[4-(cyclopropylmethoxy)phenyl]-2-pyridinyl]thio]-acetamide 2-p-(2-carboxyethyl)phenethylamino-5′-N-ethylcarboxamidoadenosine hydrochloride hydrate 3-propyl-6-ethyl-5[(ethylthio)carbonyl]-2-phenyl-4-propyl-3-pyridinecarboxylate 4¢,6¢-diamino-2-phenyl-indole ADA ActD BAY 60-6583 CGS 21680 CHA CNS Cl-IB-MECA DAPI GAPDH GFAP GLUT HK2 MRS 1523 N(6)-cyclohexyladenosine PI3K PSB 36 SH5 U0126 VEGF actinomycin D adenosine deaminase antiglial fibrillary acidic protein d-3-deoxy-2-O-methyl-myo-inositol 1-[(R)-2-methoxy-3-(octadecyloxy)propyl hydrogen phosphate] glucose transporter glyceraldehyde 3-phosphate dehydrogenase mitogen-activated protein kinase phosphoinositide 3-kinases siRNA small interfering RNA vascular endothelial growth factor