Mitochondrial biogenesis in the brain is impaired in various neurological disorders including traumatic brain injury (TBI). The long-lasting effects of TBI may be, in part, attributed to epigenetic mechanisms such as DNA methylation. However, the role of DNA methylation on regulatory elements of nuclear and mitochondrial genome in mitochondrial biogenesis is not known. We examined the epigenetic regulation of mitochondrial transcription factor A (TFAM), and further probed its implications in mitochondrial dysfunction in the hippocampus of rats subjected to repeated mild TBI (rMTBI) using weight drop injury paradigm. rMTBI-induced hypermethylation at TFAM promoter resulted in deficits in its protein levels in mitochondria after immediate (48 h) and protracted (30 d) time points. Further, rMTBI also caused hypomethylation of mitochondrial DNA (mtDNA) promoters (HSP1 and HSP2), which further culminated into low binding of TFAM. rMTBI-induced changes weakened mitochondrial biogenesis in terms of reduced mtDNA-encoded rRNA, mRNA, and protein levels leading to shortages of ATP. To verify the potential role of mtDNA methylation in rMTBI-induced persistent mitochondrial dysfunction, rMTBI-induced rats were treated with methionine, a methyl donor. Methionine treatment restored the methylation levels on HSP1 and HSP2 resulting in efficient binding of TFAM and normalized the rRNA, mRNA, and protein levels. These findings suggest the crucial role of DNA methylation at nuclear and mitochondrial promoter regions in mitochondrial gene expression and ATP activity in the hippocampus after rMTBI.

大脑中的线粒体生物发生在包括创伤性脑损伤 (TBI) 在内的各种神经系统疾病中受损。TBI 的长期影响可能部分归因于 DNA 甲基化等表观遗传机制。然而，DNA甲基化对线粒体生物发生中核和线粒体基因组调控元件的作用尚不清楚。我们检查了线粒体转录因子 A ( TFAM ) 的表观遗传调控，并使用体重下降损伤范式进一步探讨了其对反复轻度 TBI (rMTBI) 大鼠海马线粒体功能障碍的影响。rMTBI 诱导的TFAM高甲基化启动子在立即（48 小时）和延长（30 天）时间点后导致其线粒体中蛋白质水平的缺陷。此外，rMTBI 还导致线粒体 DNA (mtDNA) 启动子 (HSP1 和 HSP2) 的低甲基化，这进一步导致 TFAM 的低结合。rMTBI 诱导的变化削弱了线粒体生物发生，降低了 mtDNA 编码的 rRNA、mRNA 和蛋白质水平，导致 ATP 短缺。为了验证 mtDNA 甲基化在 rMTBI 诱导的持续性线粒体功能障碍中的潜在作用，rMTBI 诱导的大鼠接受了甲基供体甲硫氨酸的治疗。蛋氨酸处理恢复了 HSP1 和 HSP2 上的甲基化水平，导致 TFAM 的有效结合并使 rRNA、mRNA 和蛋白质水平正常化。