Loss of PI3Kα Mediates Protection From Myocardial Ischemia–Reperfusion Injury Linked to Preserved Mitochondrial Function

BACKGROUND: Identifying new therapeutic targets for preventing the myocardial ischemia–reperfusion injury would have profound implications in cardiovascular medicine. Myocardial ischemia–reperfusion injury remains a major clinical burden in patients with coronary artery disease. METHODS AND RESULTS: We studied several key mechanistic pathways known to mediate cardioprotection in myocardial ischemia–reperfusion in 2 independent genetic models with reduced cardiac phosphoinositide 3‐kinase‐α (PI3Kα) activity. P3Kα‐deficient genetic models (PI3KαDN and PI3Kα‐Mer‐Cre‐Mer) showed profound resistance to myocardial ischemia–reperfusion injury. In an ex vivo reperfusion protocol, PI3Kα‐deficient hearts had an 80% recovery of function compared with ≈10% recovery in the wild‐type. Using an in vivo reperfusion protocol, PI3Kα‐deficient hearts showed a 40% reduction in infarct size compared with wild‐type hearts. Lack of PI3Kα increased late Na(+) current, generating an influx of Na(+), facilitating the lowering of mitochondrial Ca(2+), thereby maintaining mitochondrial membrane potential and oxidative phosphorylation. Consistent with these functional differences, mitochondrial structure in PI3Kα‐deficient hearts was preserved following ischemia–reperfusion injury. Computer modeling predicted that PIP3, the product of PI3Kα action, can interact with the murine and human Na(V)1.5 channels binding to the hydrophobic pocket below the selectivity filter and occluding the channel. CONCLUSIONS: Loss of PI3Kα protects from global ischemic–reperfusion injury linked to improved mitochondrial structure and function associated with increased late Na(+) current. Our results strongly support enhancement of mitochondrial function as a therapeutic strategy to minimize ischemia–reperfusion injury.