Osteopontin Is a Blood Biomarker for Microglial Activation and Brain Injury in Experimental Hypoxic-Ischemic Encephalopathy.
Clinical management of neonatal hypoxic-ischemic encephalopathy (HIE) suffers from the lack of reliable surrogate marker tests. Proteomic analysis may identify such biomarkers in blood, but there has been no proof-of-principle evidence to support this approach. Here we performed in-gel trypsin digestion of plasma proteins from four groups of 10-d-old mice [untouched and 24 h after low-dose lipopolysaccharide (LPS) exposure, hypoxia-ischemia (HI), or LPS/HI injury; n = 3 in each group) followed by liquid chromatography-tandem mass spectrometry and bioinformatics analysis to search for HI- and LPS/HI-associated brain injury biomarkers. This analysis suggested the induction of plasma osteopontin (OPN) by HI and LPS/HI, but not by sham and injury-free LPS exposure. Immunoblot confirmed post-HI induction of OPN protein in brain and blood, whereas Opn mRNA was induced in brain but not in blood. This disparity suggests brain-derived plasma OPN after HI injury. Similarly, immunostaining showed the expression of OPN by Iba1+ microglia/macrophages in HI-injured brains. Further, intracerebroventricular injection of LPS activated microglia and up-regulated plasma OPN protein. Importantly, the induction of plasma OPN after HI was greater than that of matrix metalloproteinase 9 or glial fibrillary acid protein. Plasma OPN levels at 48 h post-HI also parallel the severity of brain damage at 7-d recovery. Together, these results suggest that OPN may be a prognostic blood biomarker in HIE through monitoring brain microglial activation.
['Li|Yikun|Y|0000-0002-2117-8057', 'Dammer|Eric B|EB|0000-0003-2947-7606', 'Zhang-Brotzge|Xiaohui|X|0000-0003-1390-7501', 'Chen|Scott|S|0000-0003-0948-530X', 'Duong|Duc M|DM|0000-0001-5880-1888', 'Seyfried|Nicholas T|NT|', 'Kuan|Chia-Yi|CY|', 'Sun|Yu-Yo|YY|']
D000818:Animals D015415:Biomarkers D001921:Brain D002135:Calcium-Binding Proteins D016893:Carotid Stenosis D004195:Disease Models, Animal D004660:Encephalitis D005260:Female D020925:Hypoxia-Ischemia, Brain D008070:Lipopolysaccharides D008264:Macrophages D008297:Male D008810:Mice, Inbred C57BL D008840:Microfilament Proteins D017628:Microglia D053495:Osteopontin D020543:Proteome D012720:Severity of Illness Index
HIE hypoxia-ischemia LC-MS/MS