Desulfinylation of the deubiquitinase USP7 by SRXN1 attenuates oxidative acute liver injury

Protein S -sulfinylation is a reversible oxidative cysteine modification, but its contribution to acute liver injury such as those induced by acetaminophen (APAP) overdose has not been reported. Sulfiredoxin-1 (SRXN1) is the only oxidoreductase known to reduce the sulfinylated proteins, yet the substrates and mechanisms through which it protects against acute liver injury are unclear. Here, we show that hepatic protein S -sulfinylation was markedly upregulated in APAP-overdose patients and mice. Hepatocyte-specific knockout or pharmacological inhibition of Srxn1 sensitized mice to APAP-induced acute liver injury. In contrast, overexpression of SRXN1, but not its oxidoreductase-dead C99S mutant, protected mice from APAP-induced liver injury. Mechanistically, we identified the deubiquitinase ubiquitin-specific protease 7 (USP7) as an SRXN1 substrate required for hepatoprotection. USP7 inhibition worsened APAP-induced liver injury, whereas its overexpression alleviated injury by stabilizing its deubiquitinase substrate heme oxygenase-1 (HO-1). Loss of SRXN1 enhanced S -sulfinylation of USP7 at Cys315, promoting its ubiquitination and degradation. SRXN1 expression correlated with USP7 levels in human liver samples. Delayed lipid nanoparticle (LNP) delivery of SRXN1 messenger RNA (mRNA) mitigated established APAP-induced liver injury beyond the therapeutic window of N -acetylcysteine. These findings define an SRXN1-USP7-HO-1 axis as a promising therapeutic target for oxidative liver injury and highlight LNP-mediated SRXN1 mRNA delivery as a potential treatment approach.