Activated AXL Ameliorates Alcohol-associated Steatotic Liver Ischemia-Reperfusion Injury by Inhibiting ER stress and Mitochondria-associated Apoptosis.

Abstract

Hepatic ischemia-reperfusion (I/R) injury can cause poor prognosis of liver transplantation and hepatectomy, especially in patients with alcohol-associated liver disease (ALD). Apoptosis is closely related to different stages of liver injury, and the death of hepatocytes caused by endoplasmic reticulum (ER) and mitochondria homeostasis perturbation may be key to liver injury. The receptor tyrosine kinases AXL encoded by the gene axl, is a member of the TAM (TYRO3, AXL, and MERTK) family, which participates in various biological processes by binding to the ligand of growth arrest-specific protein 6 (Gas6). However, whether AXL is involved in apoptosis pathways, and the detailed mechanism in hepatic I/R injury remains unknown. In the present study, we found that total AXL is up-regulated while phosphorylated AXL (p-AXL, the active form of AXL) was down-regulated after I/R in human liver tissues from liver transplantation. Consistently, total AXL was found up-regulated while p-AXL was down-regulated during hepatic I/R injury in mice. Pretreatment with Gas6 increased p-AXL expression, reduced ER stress-associated cell apoptosis, alleviated liver damage, and restored ER and mitochondria ultrastructure during hepatic I/R in mice. Furthermore, the ALD model was established by chronic-plus-binge ethanol feeding to explore the role of AXL in I/R liver injury with ethanol-associated steatosis. We found that ALD mice had a lower p-AXL level and were more susceptible to hepatic I/R injury. Importantly, activated AXL ameliorated liver injury by inhibiting IRE1 and PERK pathway to reduce ER stress-associated apoptosis. In conclusion, activated AXL protects alcohol-associated steatotic liver against I/R injury by inhibiting ER stress and mitochondria-associated apoptosis, suggesting that targeting AXL serves as a potential strategy for liver I/R injury, particularly for marginal liver donors with alcohol-associated steatosis.