The role of 5-hydroxymethylcytosine in mitochondria after ischemic stroke.

5-Hydroxymethylcytosine (5hmC) exists in DNA, RNA, and mitochondrial DNA (mtDNA) and plays an important role in many diseases. Specifically, 5hmC is involved in promoting gene expression, and this process is regulated by Tet enzymes. In this study, we identified that there is no difference in male mice and female mice at first; then we examined the levels of 5hmC in mtDNA and explored the relationship among 5hmC, mitochondrial gene expression and ATP production after acute brain ischemia. The abundance of mtDNA 5hmC was increased at 1 d and peaked at 2 d after ischemic injury, whereas that of mtDNA 5mC was unchanged. Furthermore, increased mitochondrial Tet2 expression was found to be responsible for the increase in mtDNA 5hmC. Tet2 inhibition decreased the mtDNA 5hmC abundance and increased the ATP levels in mitochondria, suggesting an association between the cellular ATP levels and mtDNA 5hmC abundance. We also demonstrated that mtDNA 5hmC increased the mRNA levels of mitochondrial genes after ischemia/reperfusion (I/R) injury.