Abstract 1371: Overexpression Of Mitochondrial Transcription Factor A Protects Failing Myocardium From Oxidative Stress
Background: Reactive oxygen species (ROS) from mitochondria play a pivotal role in the pathogenesis and progression of heart failure. Mitochondrial transcription factor A (TFAM), a nucleus-encoded protein, in mitochondria promotes transcription of mitochondrial DNA (mtDNA), maintains mtDNA, and increases mtDNA copy number. We previously reported that overexpression of human TFAM ameliorated cardiac remodeling and improved survival by maintaining mitochondrial function. We investigated whether those beneficial effects result from the increase of antioxidative properties both in vivo and in vitro.
Methods and Results: [in vivo study] We created myocardial infarction (MI) in wild type (WT) mice and human TFAM transgenic (TG) mice as a model of heart failure. We evaluated free radical generation by in vivo ESR on 28th day after the operation. MI size did not different between WT and MI. Overexpression of TFAM ameliorated MI-induced cardiac hypertrophy (histology) and LV dysfunction (2D echo and cath). Furthermore, the rate of signal decay in in vivo ESR, indicative of oxidative stress, was accelerated in WT-MI (0.10 ± 0.01 vs 0.19 ± 0.02/min, n=4–5, P<0.01) whereas decelerated in TG-MI (0.12 ± 0.02/min; n=4, P<0.01). DNA microarrays analysis of myocardium (8 weeks old, male) indicated that TG overexpressed (double or more) antioxidant relevant genes mostly encoded in nuclear DNA, such as Mthfd2 and Adh1 without affecting mitochondrial respiratory enzyme activities. [in vitro study] We measured superoxide in Hela cells using Dihydroethidium in the presence of rotenone, a complex I inhibitor. Overexpression of TFAM in Hela cells significantly reduced superoxide production (72.8 %).
Conclusion: Overexpression of TFAM suppresses ROS. Such an antioxidative property of TFAM may contribute to its powerful anti-remodeling effect in failing heart.