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

Abstract

Background and aims: Protein S-sulfhydration mediated by 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.

Approach and results: We showed that in streptozotocin (STZ)-treated and high-fat diet (HFD)-treated low-density lipoprotein receptor-negative (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-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 H₂ S both in vivo and in vitro. Nrf2 deficiency inhibited the H₂ S-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, H₂ S 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: H₂ S-mediated Keap1 S-sulfhydration alleviates liver damage through 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.