PI3K-AKT Pathway Protects Cardiomyocytes Against Hypoxia-Induced Apoptosis by MitoKATP-Mediated Mitochondrial Translocation of pAKT.

BACKGROUND/AIMS: The phosphatidylinositol-3-kinase -AKT (PI3K-AKT) is an important intracellular signal pathway in regulating cell proliferation, differentiation and apoptosis. In previous studies, we've demonstrated that PI3K-AKT pathway protects cardiomyocytes from ischemic and hypoxic apoptosis through mitochondrial function. However, the molecular mechanisms underlying hypoxia-induced cardiomyocyte apoptosis via PI3K-AKT pathway remain ill-defined. Here, we addressed this question.

METHODS

Cardiomyocytes were exposed to hypoxia, with/without different inhibitors and then protein levels were assessed by Western blotting.

RESULTS

We found that the PI3K-AKT pathway was activated in cardiomyocytes that were exposed to hypoxia. Moreover, the phospho-AKT (pAKT) translocated from cytosol to mitochondria via mitochondrial adenosine triphosphate-dependent potassium (mitoKATP), leading to an increase in cytochrome c oxidase (CcO) activity to suppress apoptosis. On the other hand, the mitoKATP specific blocker, 5-hydroxydecanote (5-HD), or suppression of CcO using siRNA, inhibited the pAKT mitochondrial translocation to maintain the CcO activity, resulting in mitochondrial dysfunction and cellular apoptosis induced by hypoxia.

CONCLUSION

These findings suggest that the anti-apoptotic effect of the PI3K-AKT pathway through pAKT translocation to mitochondrial via mitoKATP may be conducted through modification of CcO activity.