Mechanism of TFAM Mediated Cardiomyocyte Protection*

Although mitochondrial transcription factor A (TFAM) is a protective component of mitochondrial DNA and a regulator of calcium and reactive oxygen species (ROS) production, the mechanism remains unclear. In heart failure (HF), TFAM is significantly decreased and cardiomyocyte instability ensues. TFAM inhibits Nuclear Factor of Activated T cells (NFAT), which reduces ROS production; additionally, TFAM transcriptionally activates SERCA2a to decrease free calcium. Therefore, decreasing TFAM vastly increases protease expression and hypertrophic factors, leading to cardiomyocyte functional decline. To examine this hypothesis, treatments of 1.0 micrograms of a TFAM vector and 1.0 micrograms of a CRISPR-Cas9 TFAM plasmid were administered to HL-1 cardiomyocytes via lipofectamine transfection. Western blotting and confocal microscopy analysis show that CRISPR-Cas9 knockdown of TFAM significantly increased proteases Calpain1, MMP9 and regulators Serca2a, and NFAT4 protein expression. CRISPR knockdown of TFAM in HL-1 cardiomyocytes upregulates degratory factors, leading to cardiomyocyte instability. Hydrogen peroxide oxidative stress decreased TFAM expression and increased Calpain1, MMP9, and NFAT4 protein expression. TFAM overexpression normalizes pathological hypertrophic factor NFAT4 in the presence of oxidative stress.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author