Interferon Regulatory Factor 1 Activates Autophagy to Aggravate Hepatic Ischemia-Reperfusion Injury by Increasing High Mobility Group Box 1 Release

Abstract

Background/Aims: Interferon regulatory factor 1(IRF-1) and high mobility group box 1(HMGB1) have been independently identified as being key players in hepatic ischemia-reperfusion injury (IRI). We attempted to determine whether IRF-1 activates autophagy to aggravate hepatic IRI by increasing HMGB1 release. Methods: The hepatic IRI model was generated in C57BL/6 mice, euthanized at 2, 6, 12 or 24 h after reperfusion. To examine the effects of HMGB1 release inhibition, Glycyrrhiza acid (GA) was administered to the mice and at six hours after injectiont. AML12 cells were immersed in mineral oil for 90 min and then cultured in complete Dulbecco’s Modified Eagle’s Medium (DMEM)/F12 to simulate IRI. AML12 cells were treated with IRF-1 siRNA, Ad-IRF-1 or GA. The serum levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT), as well as histological changes were examined. Next, autophagic vacuoles were detected by transmission electron microscopy (TEM) or LC3 dots. The expression of IRF-1 and HMGB1 mRNA were measured by real-time polymerase chain reaction. The expression of IRF-1, microtubule-associated protein 1 light chain 3 (LC3), Bcl-2, Beclin 1, HMGB1 were detected by western blotting or immunohistochemistry. Results: The levels of hepatic IRF-1, mRNA and protein were significantly increased in livers after exposure to IRI, together with, IRI-induced increase of HMGB1 mRNA and release of HMGB1 in liver tissue. Knockout of IRF-1 decreased expression and release of HMGB1 in liver, and inhibiting the release of HMGB1 could alleviate hepatic IRI. In addition, knockout of IRF-1 downregulated LC3II and Beclin1, while number of autophagosomes or LC3 dots were increased. Up-regulating IRF-1 expression could increase the levels of LC3Ⅱ expression in AML12 cells after exposure to IRI. The levels of HMGB1 in Ad-IRF-1 transfected AML12 cell supernatants increased, together with number of LC3 dots increasing. However, GA could inhibit both Ad-IRF-1 induced HMGB1 release and the increase in the number of LC3 dots. Conclusions: IRF-1 activates autophagy to aggravate hepatic IRI by increasing HMGB1 release.