Overexpression of mitochondrial transcription factor A (TFAM) ameliorates delayed neuronal death due to transient forebrain ischemia in mice

Mitochondrial transcription factor A (TFAM) is an important regulator to maintain mitochondrial DNA copy number. However, no studies have denoted its roles in cerebral ischemia. Therefore, this study was aimed to assess whether the forced overexpression of TFAM ameliorates delayed neuronal death following transient forebrain ischemia. We have established human TFAM-transgenic (Tg) mice. Wild type (WT) and TFAM-Tg mice were subjected to 20-min bilateral common carotid artery occlusion (BCCAO). Immunostaining against cytochrome c was performed to estimate its release from mitochondria at 24 h after 20-min BCCAO. Histological analysis was performed to evaluate the effect of TFAM overexpression on delayed neuronal death at 72 h after 20-min BCCAO. The number of cytochrome c-positive neurons in the hippocampal CA1 sector was significantly smaller in TFAM-Tg mice than in WT mice (P = 0.005). The percentage of viable neurons in the hippocampal CA1 sector was significantly higher in TFAM-Tg mice than in WT mice (P < 0.001), and the number of TUNEL-positive neurons was significantly smaller in TFAM-Tg mice than in WT mice (P < 0.001). Our data strongly suggest that TFAM overexpression can reduce mitochondrial permeability transition and ameliorate delayed neuronal death in the hippocampus after transient forebrain ischemia.