Cardiac overexpression of a mitochondrial SUR2A splice variant impairs cardiac function and worsens myocardial ischemia reperfusion injury in female mice.

The small splice variant of the sulfonylurea receptor protein isoform 2 A (SUR2A-55) targets mitochondria and enhances mitoK activity. In male mice the overexpression of this protein promotes cardioprotection, reducing myocardial injury after an ischemic insult. However, it is unclear what impact SUR2A-55 overexpression has on the female myocardium. To investigate the impact of SU2R2A-55 on the female heart, mice with cardiac specific transgenic overexpression of SUR2A-55 (TG) were examined by resting echocardiography and histopathology. In addition, hearts were subjected to ischemia reperfusion (IR) injury. Female TG mice had resting LV dysfunction and worse hemodynamic recovery with increased infarct size after IR injury. RNA-seq analysis found 227 differential expressed genes between WT and TG female mouse hearts that were enriched in pathways of cellular metabolism. This was in direct contrast to male mice that had only four differentially expressed genes. Female TG mice compared to female WT mice had reduced cardiomyocyte mitochondrial membrane potential without a change in electron transport chain protein expression. In addition, isolated mitochondria from female TG hearts displayed reduced sensitivity to ATP and diazoxide suggestive of increased mitoK activity. In conclusion, our data suggests that female TG mice are unable to tolerate a more active mitoK channel leading to LV dysfunction and worse response to IR injury. This is in direct contrast to our prior report showing cardioprotection in male mice overexpressing SUR2A-55 in heart. Future research directed at examining the expression and activity of mitoK subunits according to sex may elucidate different treatments for male and female patients.