Hydrogen Sulfide Alleviates Liver Injury Through the S-Sulfhydrated-Kelch-Like ECH-Associated Protein 1/Nuclear Erythroid 2–Related Factor 2/Low-Density Lipoprotein Receptor–Related Protein 1 Pathway

Background and Aims: Protein S-sulfhydration mediated by H₂S has been shown to play important roles in several diseases. However, its precise role in liver disease and the related mechanism remain unclear. Approach and Results: We showed that in streptozotocin (STZ)–treated and high-fat diet (HFD)–treated low-density lipoprotein receptor–negative (LDLr^−/−) mice, the H₂S donor GYY4137 ameliorated liver injury, decreased serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels, mitigated lipid deposition, and reduced hepatocyte death. Strikingly, S-sulfhydration of Kelch-like ECH-associated protein 1 (Keap1) was decreased in the livers of patients with fatty liver under diabetic conditions. In STZ+HFD-treated LDLr^−/− mice and in high glucose–treated and oxidized low-density lipoprotein (ox-LDL)–treated primary mouse hepatocytes, the GYY4137-mediated increase in Keap1 S-sulfhydration induced nuclear erythroid 2-related factor 2 (Nrf2) dissociation from Keap1, which enhanced the nuclear translocation of Nrf2 itself and the consequent expression of antioxidant proteins. Keap1 Cys151 mutation significantly reduced Keap1 S-sulfhydration and abolished the hepatoprotective effects of H₂S both in vivo and in vitro. Nrf2 deficiency inhibited the H₂S-induced beneficial impacts in Nrf2^−/− mice. Similarly, in CCl₄-stimulated mice, GYY4137 increased Keap1 S-sulfhydration, improved liver function, alleviated liver fibrosis, decreased hepatic oxidative stress, and activated the Nrf2 signaling pathway; and these effects were abrogated after Keap1 Cys151 mutation. Moreover, H₂S increased the binding of Nrf2 to the promoter region of LDLr-related protein 1 (Lrp1) and consequently up-regulated LRP1 expression, but these effects were disrupted by Keap1 Cys151 mutation. Conclusions: H₂S-mediated Keap1 S-sulfhydration alleviates liver damage through activation of Nrf2. Hence, administration of exogenous H₂S in the form of the H₂S donor GYY4137 may be of therapeutic benefit in the context of concurrent hyperlipidemia and hyperglycemia–induced or CCl₄-stimulated liver dysfunction.