Protective Role of AMP-Activated Protein Kinase-Evoked Autophagy on an In Vitro Model of Ischemia/Reperfusion-Induced Renal Tubular Cell Injury

Ischemia/reperfusion (I/R) injury is a common cause of injury to target organs such as brain, heart, and kidneys. Renal injury from I/R, which may occur in renal transplantation, surgery, trauma, or sepsis, is known to be an important cause of acute kidney injury. The detailed molecular mechanism of renal I/R injury is still not fully clear. Here, we investigate the role of AMP-activated protein kinase( AMPK)-evoked autophagyin the renal proximal tubular cell death in an in vitro I/R injury model. To mimic in vivo renal I/R injury, LLC-PK1 cells, a renal tubular cell line derived from pig kidney, were treated with antimycinA and 2- deoxyglucoseto mimic ischemia injury followed by reperfusion with growth medium. This I/R injury model markedly induced apoptosis and autophagyin LLC-PK1 cells in a time-dependent manner. Autophagyinhibitor 3-methyladenine (3MA) significantly enhanced I/R injury-induced apoptosis. I/R could also up-regulate the phosphorylation of AMPKand down-regulate the phosphorylation of mammalian target of rapamycin (mTOR). Cells transfected with small hairpin RNA(shRNA) for AMPKsignificantly increased the phosphorylation of mTOR as well as decreased the induction of autophagyfollowed by enhancing cell apoptosis during I/R. Moreover, the mTOR inhibitor RAD001 significantly enhanced autophagyand attenuated cell apoptosis during I/R. Taken together, these findings suggest that autophagyinduction protects renal tubular cell injury via an AMPK-regulated mTOR pathway in an in vitro I/R injury model. AMPK-evoked autophagymay be as a potential target for therapeutic intervention in I/R renal injury.