USP4 deficiency exacerbates hepatic ischaemia/reperfusion injury via TAK1 signalling.

Ubiquitin-specific peptidase 4 (USP4) protein is a type of deubiquitination enzyme that is correlated with many important biological processes. However, the function of USP4 in hepatic ischaemia/reperfusion (I/R) injury remains unknown. The aim of this study was to explore the role of USP4 in hepatic I/R injury. USP4 gene knockout mice and primary hepatocytes were used to construct hepatic I/R models. The effect of USP4 on hepatic I/R injury was examined via pathological and molecular analyses. Our results indicated that USP4 was significantly upregulated in liver of mice subjected to hepatic I/R injury. USP4 knockout mice exhibited exacerbated hepatic I/R injury, as evidenced by enhanced liver inflammation via the NF-κB signalling pathway and increased hepatocyte apoptosis. Additionally, USP4 overexpression inhibited hepatocyte inflammation and apoptosis on hepatic I/R stimulation. Mechanistically, our study demonstrates that USP4 deficiency exerts its detrimental effects on hepatic I/R injury by inducing activation of the transforming growth factor β-activated kinase 1 (TAK1)/JNK signalling pathways. TAK1 was required for USP4 function in hepatic I/R injury as TAK1 inhibition abolished USP4 function in vitro In conclusion, our study demonstrates that USP4 deficiency plays a detrimental role in hepatic I/R injury by promoting activation of the TAK1/JNK signalling pathways. Modulation of this axis may be a novel strategy to alleviate the pathological process of hepatic I/R injury.