The desulfinylation enzyme sulfiredoxin-1 attenuates HSC activation and liver fibrosis by modulating the PTPN12-NLRP3...

Liver fibrosis is characterized by the progressive scarring of liver tissue. Oxidative stress is a critical causal factor of HSC activation and subsequent liver fibrogenesis, but the mechanism is not fully understood. Cysteine sulfinic acid (Cys-SO 2 H), 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 the ATP-dependent reduction of the Cys-SO 2 H 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 desulfinylating the phosphatase protein tyrosine phosphatase nonreceptor type 12 (PTPN12), which enhanced its phosphatase activity and protein stability, leading to decreased tyrosine phosphorylation and reduced activation of the profibrotic inflammasome protein NLRP3 (nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3). The antifibrotic 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.