AMP‐activated protein kinase activation stimulates heme oxygenase‐1 gene expression to promote human endothelial cell survival

Abstract

AMP‐activated protein kinase (AMPK) is a ubiquitously distributed energy sensing enzyme that is activated by changes in cellular metabolism. Recent studies indicate that AMPK inhibits endothelial cell (EC) activation and apoptosis, but the underlying mechanisms remain unclear. Since heme oxygenase‐1 (HO‐1) is a highly inducible vasoprotective protein, the present study investigated whether HO‐1 contributes to the anti‐apoptotic action of AMPK. Treatment of cultured human umbilical vein ECs with the AMPK activator 5‐aminoimidazole‐4‐carboxamide‐1‐β‐D‐ribofuranoside (AICAR) stimulated a concentration‐ and time‐dependent increase in HO‐1 protein and mRNA that was prevented by the knockdown of AMPKα1/2. AICAR‐mediated HO‐1 expression was associated with a significant increase in Nrf2 protein, and overexpression of a dominant‐negative Nrf2 mutant or silencing of Nrf2 abrogated the induction of HO‐1. Finally, treatment of ECs with tumor necrosis factor‐α stimulated DNA fragmentation and caspase‐3 activation, that was blocked by AICAR. However, the anti‐apoptotic action of AICAR was abolished by the HO inhibitor tin protoporphryin‐IX or by the knockdown of HO‐1. In conclusion, this study demonstrates that AMPK stimulates HO‐1 gene expression in human ECs and that the induction of HO‐1 is required for the anti‐apoptotic effect of AMPK. Supported by NIH.