Hydrogen Sulfide and Liver Health: Insights into Liver Diseases

Reconnecting the roots of hydrogen sulfide (H2S) with medicinal chemistry: Lessons accomplished and challenges so far

Previously known for its unpleasant odour and mortality in elevated concentrations, hydrogen sulfide (H2S) is currently considered a complex molecule having significant physiological advantages. After nitric oxide (NO) and carbon monoxide (CO), H2S is regarded as the third endogenous gasotransmitter, performing many biological functions in the human body. The essential functions include but are not limited to regulating inflammation, maintaining the redox potential, cellular signalling, and metabolic processes. Moreover, an imbalance in its expression or dysfunction of its precursors and associated enzymes in its biosynthesis leads to multiple pathological conditions, including cancer, diabetes, neurodegenerative disorders, COVID-19, etc. Nonetheless, its upregulation is also reported to dysregulate normal physiological conditions and precipitate different diseases and cancer, thus acting as a "Double-edged sword." Despite this, H2S is still being widely explored for its therapeutic potential in various disease states. The present review is put forth to focus on hydrogen sulfide's dichotomous properties, emphasising its critical functions and therapeutic applications. This compilation provides a state-of-the-art analysis of the broad application of H2S donors in developing therapeutic interventions, release mechanisms, and their use in numerous diseases and disorders. Furthermore, various analytical techniques for detecting and quantifying the H2S release in biological samples via the hybrid donors are also discussed. We herein expect that an in-depth comprehension of the multiple activities of H2S can aid in discovering novel therapeutic interventions critical for holistic disease management measures in the future.

Lipid metabolism in ferroptosis: mechanistic insights and therapeutic potential

Ferroptosis, an iron-dependent form of regulated cell death driven by lipid peroxidation, plays a pivotal role in various physiological and pathological processes. In this review, we summarize the core mechanisms of ferroptosis, emphasizing its intricate connections to lipid metabolism, including fatty acid synthesis, phospholipid remodeling, and oxidation dynamics. We further highlight advancements in detection technologies, such as fluorescence imaging, lipidomics, and in vivo PET imaging, which have deepened our understanding of ferroptotic regulation. Additionally, we discuss the role of ferroptosis in human diseases, where it acts as a double-edged sword, contributing to cancer cell death while also driving ischemia-reperfusion injury and neurodegeneration. Finally, we explore therapeutic strategies aimed at either inducing or inhibiting ferroptosis, including iron chelation, antioxidant modulation, and lipid-targeted interventions. By integrating mechanistic insights, disease relevance, and therapeutic potential, this review provides a comprehensive perspective on ferroptosis as a crucial interface between lipid metabolism and oxidative stress.

Development of a Rapid-Response Fluorescent Probe for H2S: Mechanism Elucidation and Biological Applications

Hydrogen sulfide (H2S) is an important signaling molecule involved in various physiological and pathological processes, making its accurate detection in biological systems highly desirable. In this study, two fluorescent probes (M1 and M2) based on 1,8-naphthalimide were developed for H2S detection via a nucleophilic aromatic substitution. M1 demonstrated high sensitivity and selectivity for H2S in aqueous media, with a detection limit of 0.64 µM and a strong linear fluorescence response in the range of 0-22 µM of NaHS. The reaction kinetics revealed a rapid response, with a reaction rate constant of 7.56 × 102 M-1 s-1, and M1 was most effective in the pH range of 6-10. Mechanism studies using 1H NMR titration confirmed the formation of 4-hydroxyphenyl-1,8-naphthalimide as the product of H2S-triggered nucleophilic substitution. M1 was applied in MDA-MB-231 cells for cell imaging, in which M1 provided significant fluorescence enhancement upon NaHS treatment, confirming its applicability for detecting H2S in biological environments. In comparison, M2, designed with extended conjugation for red-shifted emission, exhibited weaker sensitivity due to the reduced stability of its naphtholate product and lower solubility. These results demonstrate that M1 is a highly effective and selective fluorescent probe for detecting H2S, providing a valuable resource for investigating the biological roles of H2S in health and disease.

Cystathionine γ-lyase contributes to exacerbation of periodontal destruction in experimental periodontitis under hyperglycemia

BACKGROUND

Diabetes is one of the major inflammatory comorbidities of periodontitis via 2-way interactions. Cystathionine γ-lyase (CTH) is a pivotal endogenous enzyme synthesizing hydrogen sulfide (H2S), and CTH/H2S is crucially implicated in modulating inflammation in various diseases. This study aimed to explore the potential role of CTH in experimental periodontitis under a hyperglycemic condition.

METHODS

CTH-silenced and normal human periodontal ligament cells (hPDLCs) were cultured in a high glucose and Porphyromonas gingivalis lipopolysaccharide (P.g-LPS) condition. The effects of CTH on hPDLCs were assessed by Cell Counting Kit 8 (CCK8), real-time quantitative polymerase chain reaction (RT-qPCR), and enzyme-linked immunosorbent assay (ELISA). The model of experimental periodontitis under hyperglycemia was established on both Cth-/- and wild-type (WT) mice, and the extent of periodontal destruction was assessed by micro-CT, histology, RNA-Seq, Western blot, tartrate-resistant acid phosphatase (TRAP) staining and immunostaining.

RESULTS

CTH mRNA expression increased in hPDLCs in response to increasing concentration of P.g-LPS stimulation in a high glucose medium. With reference to WT mice, Cth-/- mice with experimental periodontitis under hyperglycemia exhibited reduced bone loss, decreased leukocyte infiltration and hindered osteoclast formation, along with reduced expression of proinflammatory cytokines interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) in periodontal tissue. RNA-seq-enriched altered NF-κB pathway signaling in healthy murine gingiva with experimental periodontitis mice under hyperglycemia. Accordingly, phosphorylation of p65 (P-p65) was alleviated in CTH-silenced hPDLCs, leading to decreased expression of IL6 and TNF. CTH knockdown inhibited activation of nuclear factor kappa-B (NF-κB) pathway and decreased production of proinflammatory cytokines under high glucose and P.g-LPS treatment.

CONCLUSION

The present findings suggest the potential of CTH as a therapeutic target for tackling periodontitis in diabetic patients.

Chronic Exposure to Arsenic and Fluoride Starting at Gestation Alters Liver Mitochondrial Protein Expression and Induces Early Onset of Liver Fibrosis in Male Mouse Offspring

The presence of arsenic (As) and fluoride (F-) in drinking water is of concern due to the enormous number of individuals exposed to this condition worldwide. Studies in cultured cells and animal models have shown that As- or F-induced hepatotoxicity is primarily associated with redox disturbance and altered mitochondrial homeostasis. To explore the hepatotoxic effects of chronic combined exposure to As and F- in drinking water, pregnant CD-1 mice were exposed to 2 mg/L As (sodium arsenite) and/or 25 mg/L F- (sodium fluoride). The male offspring continued the exposure treatment up to 30 (P30) or 90 (P90) postnatal days. GSH levels, cysteine synthesis enzyme activities, and cysteine transporter levels were investigated in liver homogenates, as well as the expression of biomarkers of ferroptosis and mitochondrial biogenesis-related proteins. Serum transaminase levels and Hematoxylin-Eosin and Masson trichrome-stained liver tissue slices were examined. Combined exposure at P30 significantly reduced GSH levels and the mitochondrial transcription factor A (TFAM) expression while increasing lipid peroxidation, free Fe 2+, p53 expression, and serum ALT activity. At P90, the upregulation of cysteine uptake and synthesis was associated with a recovery of GSH levels. Nevertheless, the downregulation of TFAM continued and was now associated with a downstream inhibition of the expression of MT-CO2 and reduced levels of mtDNA and fibrotic liver damage. Our experimental approach using human-relevant doses gives evidence of the increased risk for early liver damage associated with elevated levels of As and F- in the diet during intrauterine and postnatal period.

Increased hydrogen sulfide turnover serves a cytoprotective role during the development of replicative senescence

The mammalian gasotransmitter hydrogen sulfide (H2S) is produced by enzymes such as cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE), 3-mercaptopyruvate sulfurtransferase (3-MST). Prior studies suggest that H2S may have cytoprotective and anti-aging effects. This project explores the regulation and role of endogenous H2S in a murine model of replicative senescence. H2S and polysulfide levels in RAW 264.7 murine macrophages (control cells: passage 5-10; senescent cells: passage 30-40) were measured using fluorescent probes. The expression of H2S-related enzymes and the activity of senescence marker beta-galactosidase (SA-β-Gal) were also analyzed. CBS, CSE, and 3-MST were inhibited using selective pharmacological inhibitors. Senescence led to a moderate upregulation of CBS and in a significant increase in CSE and 3-MST. H2S degradation enzymes were also elevated in senescence. Inhibition of H2S-producing enzymes reduced H2S levels but increased polysulfides. Inhibition of H2S production during senescence suppressed cell proliferation, and elevated SA-β-Gal and p21 levels. Comparing young and old mice spleens revealed downregulation of CBS and ETHE1 and upregulation of rhodanese and SUOX in older mice. The results demonstrate that increased reactive sulfur turnover occurs in senescent macrophages and that reactive sulfur species support cell proliferation and regulate cellular senescence.

Near-infrared fluorescent probe based on the regulatory dye pKa for imaging of H2S in rice roots and living cells

Hydrogen sulfide (H2S) is a key factor in various biological processes such as plant grow and its response to environmental stress. Here, we develop a novel near-infrared (NIR) fluorescent probe for detecting hydrogen sulfide based on the regulatory NIR dye pKa values. After triggering the H2S substitution response, probe A with introducing the cyano moiety not only exhibits a significant near-infrared emission (Emax: 724 nm) response in physiological environments, but also shows a fast response, high selectivity, and sensitivity (LOD as 0.52 µM). In addition, probe A with low biological cytotoxicity is successfully used for imaging detection of cellular exogenous and endogenous hydrogen sulfide. More importantly, in situ imaging of probe A tracks the H2S fluctuations in the rice root system and its response to environmental stress. Hence, this work offers a new NIR fluorescence imaging monitoring tool for hydrogen sulfide in biological systems.

Hydrogen-Rich Water (HRW) Reduces Fatty Acid-Induced Lipid Accumulation and Oxidative Stress Damage through Activating AMP-Activated Protein Kinase in HepG2 Cells

Metabolic dysfunction-associated steatotic liver disease (MASLD) is characterized by excessive fat accumulation in the liver. Intracellular oxidative stress induced by lipid accumulation leads to various hepatocellular injuries including fibrosis. However, no effective method for mitigating MASLD without substantial side effects currently exists. Molecular hydrogen (H2) has garnered attention due to its efficiency in neutralizing harmful reactive oxygen species (ROS) and its ability to penetrate cell membranes. Some clinical evidence suggests that H2 may alleviate fatty liver disease, but the precise molecular mechanisms, particularly the regulation of lipid droplet (LD) metabolism, remain unclear. This study utilized an in vitro model of hepatocyte lipid accumulation induced by free fatty acids (FFAs) to replicate MASLD in HepG2 cells. The results demonstrated a significant increase in LD accumulation due to elevated FFA levels. However, the addition of hydrogen-rich water (HRW) effectively reduced LD accumulation. HRW decreased the diameter of LDs and reduced lipid peroxidation and FFA-induced oxidative stress by activating the AMPK/Nrf2/HO-1 pathway. Overall, our findings suggest that HRW has potential as an adjunctive supplement in managing fatty liver disease by reducing LD accumulation and enhancing antioxidant pathways, presenting a novel strategy for impeding MASLD progression.

Unraveling intestinal microbiota's dominance in polycystic ovary syndrome pathogenesis over vaginal microbiota

Background

Polycystic ovary syndrome (PCOS) is a prevalent endocrine disease in women, intricately linked to hormonal imbalances. The microbiota composition plays a pivotal role in influencing hormonal levels within the body. In this study, we utilized a murine model to investigate how intestinal and vaginal microbiota interact with hormones in the development of PCOS.

Methods

Twenty female mice were randomly assigned to the normal group (N) and the model group (P), where the latter received daily subcutaneous injections of 0.1 mL DHEA (6 mg/100 g). Throughout the experiment, we evaluated the PCOS mouse model by estrus cycle, serum total testosterone (T), prolactin (PRL) and luteinizing hormone (LH) levels, and ovarian pathological morphology. The microbial composition in both intestinal content and vaginal microbiota were studied by 16S rRNA gene high-throughput sequencing.

Results

Compared with the N group, the P group showed significant increases in body weight, T, and PRL, with significant decrease in LH. Ovaries exhibited polycystic changes, and the estrous cycle was disrupted. The intestinal microbiota result shows that Chao1, ACE, Shannon and Simpson indexes were decreased, Desulfobacterota and Acidobacteriota were increased, and Muribaculaceae, Limosilactobacillus and Lactobacillus were decreased in the P group. T was significantly positively correlated with Enterorhabdus, and LH was significantly positively correlated with Lactobacillus. The analysis of vaginal microbiota revealed no significant changes in Chao1, ACE, Shannon, and Simpson indices. However, there were increased in Firmicutes, Bacteroidota, Actinobacteriota, Streptococcus, and Muribaculaceae. Particularly, Rodentibacter displayed a robust negative correlation with other components of the vaginal microbiota.

Conclusion

Therefore, the response of the intestinal microbiota to PCOS is more significant than that of the vaginal microbiota. The intestinal microbiota is likely involved in the development of PCOS through its participation in hormonal regulation.