Ischemic preconditioning attenuates ERS-dependent apoptosis of hepatocyte through regulating autophagy in hepatic ischemia reperfusion injury

Abstract Hepatic ischemia reperfusion injury (HIRI) usually occurs in subtotal hepatectomy and severely damages liver function during perioperative period. Endoplasmic reticulum stress (ERS) dependent apoptosis was suggested to crucially participate in the progression of HIRI. The present study focused on the regulatory effect of autophagy activation induced by ischemic preconditioning (IPC) on ERS-dependent apoptosis of hepatocyte in HIRI. HIRI mice model and oxygen glucose deprivation/reperfusion (OGD/R) AML-12 hepatocyte cell lines were both constructed to evaluate the protective effect of IPC in vivo and in vitro, separately. The protein levels of p-eIF2α, CHOP, cleaved caspase-12 were used to evaluate the ERS-dependent apoptosis, while LC3-II and p62 were regarded as the autophagy activation markers. The beneficial molecular chaperones GRP78, HSP60, HSP70 were also tested to evaluate autophagy. The results showed that HIRI significantly increased the ERS-dependent apoptosis markers and the number of apoptotic cells, and damaged liver function. The ERS inhibitor Salubrinal (Sal) intraperitoneally greatly alleviated liver injury in HIRI mice and OGD/R hepatocytes. Further, both remote IPC (RIPC) and direct IPC (DIPC) significantly alleviated liver injury and inflammatory cell infiltration. IPC also up-regulated LC3-II and down-regulated p62 expression, and increased the mRNA levels of GRP78, HSP60, HSP70 in HIRI mice and OGD/R hepatocytes, indicating the autophagy activation by IPC. Autophagy inhibitor 3-methyladenine (3-MA) significantly attenuated the protective effects of IPC on ERS-dependent apoptosis and liver function, while autophagy activator rapamycin (RAP) mimicked the protective effects of IPC on ERS-dependent apoptosis in vitro, suggesting the regulatory roles of autophagy on ERS-dependent apoptosis. These results all demonstrated that IPC could induce moderate autophagy and up-regulate some molecular chaperones to strengthen the endogenous defense mechanisms, which was beneficial to alleviate ERS-dependent apoptosis and protect hepatocytes from HIRI.