Hypoxic preconditioning protects cardiomyocytes against hypoxia/reoxygenation injury through AMPK/eNOS/PGC-1α signaling pathway.

OBJECTIVE: AMP-activated protein kinase (AMPK) is an important regulator of multiple cellular pathways in the setting of energetic stress. Whether AMPK plays a critical role in hypoxic preconditioning (HPC), protecting cardiomyocytes against hypoxia reoxygenation (H/R) injury remains uncertain.

METHODS: H9c2 cells were preconditioned by exposing to 10 min of hypoxia and 30 min of reoxygenation. Then, the preconditioned and non-preconditioned cardiomyocytes were exposed to 90 min of hypoxia followed by 120 min of reoxygenation.

RESULTS: HPC protected H9c2 cells against H/R injury, the AMPK inhibitor or eNOS inhibitor abolished the effect of HPC. Compared with H/R group, HPC significantly increased the expression of p-AMPK (Thr172). HPC also markedly increased p-eNOS (Ser1177) expression, which was abolished by AMPK inhibition. HPC significantly increased PGC-1α expression, which were nullified by AMPK inhibition or eNOS inhibition. HPC attenuated the oxidative stress by increasing the SOD activity and decreasing the MDA and ROS level, which were abolished by AMPK inhibition or eNOS inhibition. Interestingly, the AMPK activator metformin mimicked the effects of HPC in part.

CONCLUSIONS: These results indicated that HPC protects H9c2 cells against H/R injury by reducing oxidative stress partly via AMPK/eNOS/PGC-1α signaling pathway.