Abstract：Objective To study the methylation level and dynamic change of 5-hydroxymethylcytosine (5hmC) in mitochondrial DNA (mtDNA) in the cerebral cortex of neonatal rats with hypoxic-ischemic brain damage. Methods A total of 24 male Sprague-Dawley rats aged 7 days were randomly divided into control group, 24-hour model group and 48-hour model group (n=8 each). Common carotid artery ligation combined with hypoxic treatment was performed to establish an animal model of hypoxic-ischemic brain damage. The rats in the control group were not given ligation or hypoxic treatment. Oxidative bisulfte sequencing was used to measure the level of 5hmC in the cerebral cortex. Western blot was used to measure the expression of 5hmC-related enzymes TET1, TET2 and DNMT1. Results The 24- and 48-hour model groups had a signifcantly higher level of 5hmC than the control group (P < 0.05). Western blot showed a signifcant increase in the expression of DNMT1 in the 24- and 48-hour model groups (P < 0.05). Compared with the control group, the 24- and 48-hour model groups had signifcant differences in the 5hmC level at multiple mitochondrial genetic loci (P < 0.05). Conclusions The level of DNMT1, a key enzyme for 5hmC modifcation in mtDNA, in the cerebral cortex increases in neonatal rats with hypoxic-ischemic brain damage, suggesting that there is an abnormal methylation level of 5hmC after hypoxic-ischemic brain damage, which might be associated with the regulation of hypoxic-ischemic brain damage.
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