Function of gaseous hydrogen sulfide in liver fibrosis

Cystathionine gamma-lyase deficiency exaggerates diethylnitrosamine-induced liver damage in mice

Cystathionine gamma-lyase (CSE) is a key enzyme in reverse transsulfuration pathway and contributes to the majority of H2S generation in liver tissues via cysteine metabolism. Dysfunction of the CSE/H2S system is linked to both chronic and acute liver damage. This study investigated the regulatory role of CSE deficiency on diethylnitrosamine (DEN)-induced liver damage in mice. A single injection of DEN was administered into 4-week-old male CSE knockout (CSE-KO) mice and wild-type (WT) littermates, and the mice were sacrificed at 28 weeks of age. Compared to age-matched WT mice, CSE-KO mice spontaneously developed steatosis with increased oxidative stress and higher expressions of inflammation and fibrosis-related genes at 28-weeks of age. Following DEN injection, CSE-KO mice experienced more severe liver damage in comparison with the WT group as reflected by elevated levels of lipid accumulation, increased activities of alanine aminotransferase and aspartate aminotransferase, higher oxidative stress and fibrosis development, and increased expressions of inflammation and fibrosis-related genes. No visible tumors were observed in both types of mice with DEN treatment. In addition, the expression levels of the three H2S-generating proteins (CSE, cystathionine beta-synthase, and 3-mercaptopyruvate sulfurtransferase) and the H2S production rate in liver tissues were unaffected by DEN. Taken together, our study demonstrates that CSE provides a significant hepatoprotective effect and deficiency of CSE exaggerates DEN-induced liver damage in mice. Based on these findings, it can be suggested that targeting the CSE/H2S signaling pathway could be a potential therapeutic target for the treatment of liver diseases.

Protective role of hydrogen sulfide against diabetic cardiomyopathy by inhibiting pyroptosis and myocardial fibrosis

Diabetic cardiomyopathy (DCM) contributes significantly to the heightened mortality rate observed among diabetic patients, with myocardial fibrosis (MF) being a pivotal element in the disease's progression. Hydrogen sulfide (H2S) has been shown to mitigate MF, but the specific underlying mechanisms have yet to be thoroughly understood. A connection has been established between the evolution of DCM and the incidence of cardiomyocyte pyroptosis. Our research offers insights into H2S protective impact and its probable mode of action against DCM, analyzed through the lens of MF. In this study, a diabetic rat model was developed using intraperitoneal injections of streptozotocin (STZ), and hyperglycemia-stimulated cardiomyocytes were employed to replicate the cellular environment of DCM. There was a marked decline in the expression of cystathionine γ-lyase (CSE), a catalyst for H2S synthesis, in both the STZ-induced diabetic rats and hyperglycemia-stimulated cardiomyocytes. Experimental results in vivo indicated that H2S ameliorates MF and enhances cardiac functionality in diabetic rats by mitigating cardiomyocyte pyroptosis. In vitro assessments highlighted the induction of cardiomyocyte pyroptosis and the subsequent decline in cell viability under hyperglycemic conditions. However, the administration of sodium hydrosulfide (NaHS) curtailed cardiomyocyte pyroptosis and augmented cell viability. In contrast, propargylglycine (PAG), a CSE inhibitor, reversed the effects rendered by NaHS administration. Additional exploration indicated that the mitigating effect of H2S on cardiomyocyte pyroptosis is modulated through the ROS/NLRP3 pathway. In essence, our findings corroborate the potential of H2S in alleviating MF in diabetic subjects. This therapeutic effect is likely attributable to the regulation of cardiomyocyte pyroptosis via the ROS/NLRP3 pathway. This discovery furnishes a prospective therapeutic target for the amelioration and management of MF associated with diabetes.

Long non-coding RNAs: key regulators of liver and kidney fibrogenesis

Fibrosis is a pathological condition that is characterized by an abnormal buildup of extracellular matrix (ECM) components, such as collagen, in tissues. This condition affects various organs of the body, including the liver and kidney. Early diagnosis and treatment of fibrosis are crucial, as it is a progressive and irreversible process in both organs. While there are certain similarities in the fibrosis process between the liver and kidney, there are also significant differences that must be identified to determine molecular diagnostic markers and potential therapeutic targets. Long non-coding RNAs (lncRNAs), a class of RNA molecules that do not code for proteins, are increasingly recognized as playing significant roles in gene expression regulation. Emerging evidence suggests that specific lncRNAs are involved in fibrosis development and progression by modulating signaling pathways, such as the TGF-β/Smad pathway and the β-catenin pathway. Thus, identifying the precise lncRNAs involved in fibrosis could lead to novel therapeutic approaches for fibrotic diseases. In this review, we summarize lncRNAs related to fibrosis in the liver and kidney, and propose their potential as therapeutic targets based on their functions. [BMB Reports 2023; 56(7): 374-384].