Regulation of glutamate transport and neuroinflammation in a term newborn rat model of hypoxic-ischaemic brain injury.

In the newborn brain, moderate-severe hypoxia-ischaemia induces glutamate excitotoxicity and inflammation, possibly via dysregulation of candidate astrocytic glutamate transporter ( Glt1 ) and pro-inflammatory cytokines (e.g. Tnfα , Il1β , Il6 ). Epigenetic mechanisms may mediate dysregulation. Hypotheses: (1) hypoxia-ischaemia dysregulates mRNA expression of these candidate genes; (2) expression changes in Glt1 are mediated by DNA methylation changes; and (3) methylation values in brain and blood are correlated. Seven-day-old rat pups ( n  = 42) were assigned to nine groups based on treatment (for each timepoint: naïve ( n  = 3), sham ( n  = 3), hypoxia-ischaemia ( n  = 8) and timepoint for tissue collection (6, 12 and 24 h post-hypoxia). Moderate hypoxic-ischemic brain injury was induced via ligation of the left common carotid artery followed by 100 min hypoxia (8% O 2 , 36°C). mRNA was quantified in cortex and hippocampus for the candidate genes, myelin ( Mbp ), astrocytic ( Gfap ) and neuronal ( Map2 ) markers (qPCR). DNA methylation was measured for Glt1 in cortex and blood (bisulphite pyrosequencing). Hypoxia-ischaemia induced pro-inflammatory cytokine upregulation in both brain regions at 6 h. This was accompanied by gene expression changes potentially indicating onset of astrogliosis and myelin injury. There were no significant changes in expression or promoter DNA methylation of Glt1 . This pilot study supports accumulating evidence that hypoxia-ischaemia causes neuroinflammation in the newborn brain and prioritises further expression and DNA methylation analyses focusing on this pathway. Epigenetic blood biomarkers may facilitate identification of high-risk newborns at birth, maximising chances of neuroprotective interventions.