Background and Aims:Critical role of endoplasmic reticulum (ER) stress has been found in ischemia and reperfusion(IR) injury models. However, the role of CCAAT-Enhancer-Binding Protein Homologous Protein (CHOP) signaling in liver IR injury still remains unclear. The aim of this study is to determine the role and its underlying mechanism of CHOP signaling in liver IR injury.

Methods: Wild-type (WT) and CHOP KO mice were subjected to a murine liver partial warm ischemia model. Liver injury and hepatocellular apoptosis was compared between groups. Autophagy and its regulatory signaling pathways were analyzed both in the liver tissues and the primary hepatocytes. CHOP and autophagy signaling pathways were also studied in human liver tissues post ischemia.

Results: CHOP KO significantly decreased liver IR injury, as evidenced by lower sALT levels and better preserved liver architectures. Liver IR induced marked hepatocellular cell apoptosis, as indicated by HE/TUNEL staining and western blot analysis of cleaved-Caspase-3, BCL-2 and BCL-XL. CHOP KO mice demonstrated much less hepatocellular apoptosis but enhanced autophagy. Primary hepatocytes were isolated and subjected to an in vitro hypoxia/reoxygenation (H/R) model. CHOP KO in hepatocytes resulted in reduced cell death, as measured by LDH and CCK8 assay. Autophagy was enhanced in CHOP KO hepatocytes as evaluated by LC3B staining and the electron microscope examination. Beclin-1 activation was significantly increased in CHOP KO hepatocytes post H/R. Functionally, Beclin-1 siRNA or autophagy specific inhibitor (3-MA) effectively blocked autophagy in hepatocytes and abrogated the protective role of CHOP KO both in liver IR and hepatocyte H/R models. Finally, human liver tissues were collected in patients undergoing liver partial resection with hepatic portal blockade. CHOP and Beclin-1 activation was analyzed by Western blot. Indeed, CHOP activation was increased by liver ischemia. On the contrary, Beclin-1 activation was decreased post ischemia.

Conclusion: Our results indicated that CHOP activation promoted liver IR injury by inhibiting Beclin-1-mediated autophagy in hepatocytes. Strategies targeting CHOP or autophagy signaling may provide therapeutic effects against liver IR injury in patients.

CITATION INFORMATION: Zhou H., Rao Z., Xia Y., Liu R., Zhou S., Wang X., Zhai Y., Lu L. CCAAT-Enhancer-Binding Protein Homologous Protein Promotes Liver Ischemia and Reperfusion Injury by Inhibiting Beclin-1-Mediated Autophagy in Hepatocytes Am J Transplant. 2017;17 (suppl 3).

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