The de-sulfinylation enzyme sulfiredoxin-1 attenuates hepatic stellate cell activation and liver fibrosis by modulating the PTPN12-NLRP3 axis.

Abstract

Liver fibrosis is characterized by the progressive scarring of liver tissue. Oxidative stress is a critical causal factor of hepatic stellate cell (HSC) activation and the subsequent liver fibrogenesis, but the mechanism is not fully understood. Cysteine sulfinic acid (Cys-SO2H), a modification of reactive cysteine residues, is a unique form of oxidative response that alters the structure and function of proteins. Sulfiredoxin 1 (SRXN1) is responsible for ATP-dependent reduction of the Cys-SO2H to sulfenic acid (Cys-SOH). We found that the expression of SRXN1 was increased in activated HSCs and in human and mouse fibrotic livers. HSC-specific ablation of Srxn1 or pharmacological inhibition of Srxn1 exacerbated HSC activation and sensitized mice to liver fibrosis. Mechanistically, SRXN1 inhibited HSC activation by de-sulfinylating the phosphatase protein tyrosine phosphatase non-receptor type 12 (PTPN12), which enhanced its phosphatase activity and protein stability, leading to decreased tyrosine phosphorylation and reduced activation of the pro-fibrotic inflammasome protein NLRP3. The anti-fibrotic effect of SRXN1 was abolished when NLRP3 was inhibited. In contrast, overexpression of PTPN12 attenuated NLRP3 activation, and this effect was further amplified by the C164A S-sulfinylation resistant mutant of PTPN12. Our findings have uncovered an important role of SRXN1 and protein S-sulfinylation in HSC activation and liver fibrosis. The SRXN1-PTPN12-NLRP3 axis represents potential therapeutic targets for liver fibrosis.