Hydrogen sulfide alleviates liver injury via S‐sulfhydrated‐Keap1/Nrf2/LRP1 pathway

Protein S-sulfhydration mediated by hydrogen sulfide (H2 S) has been shown to play important roles in several diseases. However, its precise role in liver disease and the related mechanism remain unclear. We showed that in streptozotocin (STZ)- and high-fat diet (HFD)-treated LDLr(-/-) mice, the H2 S 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- 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 H2 S both in vivo and in vitro. Nrf2 deficiency inhibited the H2 S-induced beneficial impacts in Nrf2(-/-) mice. Similarly, in carbon tetrachloride (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, H2 S increased the binding of Nrf2 to the promoter region of LDL-related protein 1 (Lrp1) and consequently upregulated LRP1 expression, but these effects were disrupted by Keap1 Cys151 mutation. In conclusion, H2 S-mediated Keap1 S-sulfhydration alleviates liver damage via activation of Nrf2. Hence, administration of exogenous H2 S in the form of the H2 S donor GYY4137 may be of therapeutic benefit in the context of concurrent hyperlipidemia and hyperglycemia-induced or CCl4 -stimulated liver dysfunction.