Hydrogen sulfide from a NaHS source attenuates dextran sulfate sodium (DSS)-induced inflammation via inhibiting nuclear factor-κB

Harnessing Gasotransmitters to Combat Age-Related Oxidative Stress in Smooth Muscle and Endothelial Cells

Age-related oxidative stress is a critical factor in vascular dysfunction, contributing to hypertension and atherosclerosis. Smooth muscle cells and endothelial cells are particularly susceptible to oxidative damage, which exacerbates vascular aging through cellular senescence, chronic inflammation, and arterial stiffness. Gasotransmitters-hydrogen sulfide (H2S), nitric oxide (NO), and carbon monoxide (CO)-are emerging as promising therapeutic agents for counteracting these processes. This review synthesizes findings from recent studies focusing on the mechanisms by which H2S, NO, and CO influence vascular smooth muscle and endothelial cell function. Therapeutic strategies involving exogenous gasotransmitter delivery systems and combination therapies were analyzed. H2S enhances mitochondrial bioenergetics, scavenges ROS, and activates antioxidant pathways. NO improves endothelial function, promotes vasodilation, and inhibits platelet aggregation. CO exhibits cytoprotective and anti-inflammatory effects by modulating heme oxygenase activity and ROS production. In preclinical studies, gasotransmitter-releasing molecules (e.g., NaHS, SNAP, CORMs) and targeted delivery systems show significant promise. Synergistic effects with lifestyle modifications and antioxidant therapies further enhance their therapeutic potential. In conclusion, gasotransmitters hold significant promise as therapeutic agents to combat age-related oxidative stress in vascular cells. Their multifaceted mechanisms and innovative delivery approaches make them potential candidates for treating vascular dysfunction and promoting healthy vascular aging. Further research is needed to translate these findings into clinical applications.

Nano-Selenium Alleviates Cd-Induced Chronic Colitis through Intestinal Flora

BACKGROUND

Cadmium (Cd) is an environmental contaminant that poses risks to human and animal health. Selenium (Se), a beneficial element, alleviates the detrimental consequences of colitis and Cd toxicity. Se is found in food products as both inorganic Se (sodium selenite) and organic Se (typically Se-enriched yeast). Nano-selenium (nano-Se; a novel form of Se produced through the bioreduction of Se species) has recently garnered considerable interest, although its effects against Cd-induced enterotoxicity are poorly understood. The aim of this study was to investigate the impact of nano-selenium on mitigating cadmium toxicity and safeguarding the integrity of the intestinal barrier.

METHODS

For a total of two cycles, we subjected 6-week-old C57 mice to chronic colitis by exposing them to Cd and nano-selenium for two weeks, followed by DSS water for one week.

RESULTS

The application of nano-selenium mitigated the intensity of colitis and alleviated inflammation in the colon. Nano-selenium enhanced the diversity of the intestinal flora, elevated the concentration of short-chain fatty acids (SCFAs) in feces, and improved the integrity of the intestinal barrier.

CONCLUSIONS

In summary, nano-Se may reduce intestinal inflammation by regulating the growth of intestinal microorganisms and protecting the intestinal barrier.

Protective Effects of H2S Donor Treatment in Experimental Colitis: A Focus on Antioxidants

Inflammatory bowel diseases (IBD) are chronic, inflammatory disorders of the gastrointestinal (GI) system, which have become a global disease over the past few decades. It has become increasingly clear that oxidative stress plays a role in the pathogenesis of IBD. Even though several effective therapies exist against IBD, these might have serious side effects. It has been proposed that hydrogen sulfide (H₂S), as a novel gasotransmitter, has several physiological and pathological effects on the body. Our present study aimed to investigate the effects of H₂S administration on antioxidant molecules in experimental rat colitis. As a model of IBD, 2,4,6-trinitrobenzenesulfonic acid (TNBS) was used intracolonically (i.c.) to induce colitis in male Wistar-Hannover rats. Animals were orally treated (2 times/day) with H₂S donor Lawesson's reagent (LR). Our results showed that H₂S administration significantly decreased the severity of inflammation in the colons. Furthermore, LR significantly suppressed the level of oxidative stress marker 3-nitrotyrosine (3-NT) and caused a significant elevation in the levels of antioxidant GSH, Prdx1, Prdx6, and the activity of SOD compared to TNBS. In conclusion, our results suggest that these antioxidants may offer potential therapeutic targets and H₂S treatment through the activation of antioxidant defense mechanisms and may provide a promising strategy against IBD.

Effects of Exogenous Hydrogen Sulfide in the Hypothalamic Paraventricular Nucleus on Gastric Function in Rats

Background: Hydrogen sulfide (H₂S) is a new type of gas neurotransmitter discovered in recent years. It plays an important role in various physiological activities. The hypothalamus paraventricular nucleus (PVN) is an important nucleus that regulates gastric function. This study aimed to clarify the role of H₂S in the paraventricular nucleus of the hypothalamus on the gastric function of rats.

Methods: An immunofluorescence histochemistry double-labelling technique was used to determine whether cystathionine-beta-synthase (CBS) and c-Fos neurons are involved in PVN stress. Through microinjection of different concentrations of NaHS, physiological saline (PS), D-2-Amino-5-phosphonovaleric acid (D-AP5), and pyrrolidine dithiocarbamate (PDTC), we observed gastric motility and gastric acid secretion.

Results: c-Fos and CBS co-expressed the most positive neurons after 1 h of restraint and immersion, followed by 3 h, and the least was at 0 h. After injection of different concentrations of NaHS into the PVN, gastric motility and gastric acid secretion in rats were significantly inhibited and promoted, respectively (p < 0.01); however, injection of normal saline, D-AP5, and PDTC did not cause any significant change (p > 0.05). The suppressive effect of NaHS on gastrointestinal motility and the promotional effect of NaHS on gastric acid secretion could be prevented by D-AP5, a specific N-methyl-D-aspartic acid (NMDA) receptor antagonist, and PDTC, an NF-κB inhibitor.

Conclusion: There are neurons co-expressing CBS and c-Fos in the PVN, and the injection of NaHS into the PVN can inhibit gastric motility and promote gastric acid secretion in rats. This effect may be mediated by NMDA receptors and the NF-κB signalling pathway.

Signaling Integration of Hydrogen Sulfide and Iron on Cellular Functions

Significance: Hydrogen sulfide (H₂S) is an endogenous signaling molecule, regulating numerous physiological functions from vasorelaxation to neuromodulation. Iron is a well-known bioactive metal ion, being the central component of hemoglobin for oxygen transportation and participating in biomolecule degradation, redox balance, and enzymatic actions. The interplay between H₂S and iron metabolisms and functions impacts significantly on the fate and wellness of different types of cells. Recent Advances: Iron level in vivo affects the production of H₂S via nonenzymatic reactions. On the contrary, H₂S quenches excessive iron inside the cells and regulates the redox status of iron. Critical Issues: Abnormal metabolisms of both iron and H₂S are associated with various conditions and diseases such as iron overload, anemia, oxidative stress, and cardiovascular and neurodegenerative diseases. The molecular mechanisms for the interactions between H₂S and iron are unsettled yet. Here we review signaling links of the production, metabolism, and their respective and integrative functions of H₂S and iron in normalcy and diseases. Future Directions: Physiological and pathophysiological importance of H₂S and iron as well as their therapeutic applications should be evaluated jointly, not separately. Future investigation should expand from iron-rich cells and tissues to the others, in which H₂S and iron interaction has not received due attention. Antioxid. Redox Signal. 36, 275-293.

Investigation of H2S Donor Treatment on Neutrophil Extracellular Traps in Experimental Colitis

Inflammatory bowel diseases (IBD) are chronic, immune-mediated disorders, which affect the gastrointestinal tract with intermittent ulceration. It is increasingly clear that neutrophil extracellular traps (NETs) seem to have a role in IBD; however, the associated pathogenesis is still not known. Furthermore, several conventional therapies are available against IBD, although these might have side effects. Our current study aimed to investigate the effects of hydrogen sulfide (H₂S) treatment on NETs formation and on the expression of inflammatory mediators in experimental rat colitis. To model IBD, 2,4,6-trinitrobenzenesulfonic acid (TNBS) was administered intracolonically (i.c.) to Wistar-Harlan male rats. Animals were treated (2 times/day) with H₂S donor Lawesson's reagent per os. Our results showed that H₂S treatment significantly decreased the extent of colonic lesions. Furthermore, the expression of members of NETs formation: peptidyl arginine deiminase 4 (PAD4), citrullinated histone H3 (citH3), myeloperoxidase (MPO) and inflammatory regulators, such as nuclear transcription factor-kappa B (NF-κB) and high-mobility group box 1 (HMGB1) were reduced in H₂S treated group compared to TNBS. Additionally, H₂S donor administration elevated the expression of ubiquitin C-terminal hydroxylase L1 (UCHL-1), a potential anti-inflammatory mediator. Taken together, our results showed that H₂S may exert anti-inflammatory effect through the inhibition of NETs formation, which suggests a new therapeutic approach against IBD.

Exogenous H2S Protects Colon Cells in Ulcerative Colitis by Inhibiting NLRP3 and Activating Autophagy

Hydrogen sulfide (H₂S) has been reported to participate in intestinal mucosal defense and repair. However, the precise regulatory mechanisms of H₂S in ulcerative colitis (UC) remain unclear. We explored the effects of sodium hydrosulfide (NaHS), a donor of H₂S, in dextran sulfate sodium (DSS)-induced colitis in rats. The pathologic features were determined by analyzing the hematoxylin and eosin-stained samples. Interleukin-1β (IL-1β), IL-6, tumor necrosis factor-α (TNF-α), and myeloperoxidase (MPO) levels were determined using ELISA. The presence of cystathionine-γ-lyase (CSE) and light chain 3B (LC3B) were determined using immunohistochemical and immunofluorescence (IF) approaches, respectively. Next, we investigated the effects of NaHS in lipopolysaccharide (LPS)-stimulated human colonic smooth muscle cells (H2940). The level of reactive oxygen species (ROS) was determined using IF. NOD-like receptor 3 (NLRP3) and CSE were detected using western blot and quantitative real-time polymerase chain reaction. Autophagy was determined using western blot, IF, and electron microscopy. NaHS treatment considerably diminished colitis-induced histological injury and proinflammatory cytokine expressions. MPO, CSE, and H₂S were downregulated, whereas LC3B was upregulated after NaHS administration in colitic rats. NaHS remarkably attenuated the levels of ROS, CSE, and NLRP3 in LPS-stimulated cells and enhanced autophagy, as was revealed by increased LC3-II-to-LC3-I ratio, elevated LC3, and decreased p62. Importantly, NaHS promoted autophagosome formation in LPS-treated cells. Exogenous H₂S ameliorates intestinal injury by downregulating inflammation and activation of autophagy, suggesting the potential of NaHS as a therapeutic agent for UC.

Cadmium exacerbates dextran sulfate sodium-induced chronic colitis and impairs intestinal barrier

The potential health risk of environmental pollutant, cadmium, has become a public concern due to its widespread existence and long biological half-life. High-dose cadmium can induce various adverse outcomes, however, the chronic biological influences of cadmium at an environmental dosage and its mechanism remain largely unclear. Here, we investigated the effect of long-term exposure of cadmium at the environmental-relevant concentration on intestinal function. A chronic colitis mouse model was established through multiple cycles of dextran sulfate sodium (DSS) challenge and recovery. 200 nM cadmium in drinking water intensified colonic inflammation induced by DSS (histological score, DSS vs. DSS + Cd: 7.4 ± 1.21 vs. 10.67 ± 0.67, P < 0.05), including fecal occult bleeding and fecal consistency loss. Multiple inflammatory cytokines were significantly up-regulated by cadmium both in colon and plasma (P < 0.05). In addition, intestinal integrity was compromised by cadmium. Goblet cells were markedly reduced (ctrl vs. Cd: 48.33 ± 3.07 vs. 37.5 ± 2.14, P < 0.05) and plasma D-lactate (ctrl vs. Cd: 1.88 ± 0.20 vs. 2.80 ± 0.15, P < 0.01) and diamine oxidase (ctrl vs. Cd: 5.00 ± 0.87 vs. 11.21 ± 2.17, P < 0.05) were increased in cadmium-treated mice, indicating an elevated intestinal permeability. In vitro results showed that long-term exposure of cadmium down-regulated the expression and membrane localization of adherent and tight junction proteins in a time-dependent manner. In conclusion, long-term exposure of environmental dose of cadmium aggravated DSS-induced chronic colitis and disrupted intestinal barrier and impaired the adherent and tight junction proteins. These findings provide a better understanding about the health risk of cadmium in the environment.

Hydrogen Sulfide Plays an Important Role by Influencing NLRP3 inflammasome

Inflammasome is a complex composed of several proteins and an important part of the natural immune system. Nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome is composed of NLRP3, apoptosis associated speck like protein (ASC) and pro-caspase-1. It plays an important role in many diseases. Hydrogen sulfide (H₂S) is an important signaling molecule that regulates many physiological and pathological processes. Recent studies indicated that H₂S played anti-inflammatory and pro-inflammatory roles in many diseases through influencing NLRP3 inflammasome, but its mechanism was not fully understood. This article reviewed the progress about the effects of H₂S on NLRP3 inflammasome and its mechanisms involved in recent years to provide theoretical basis for in-depth study.

Hydrogen sulfide protects against DSS-induced colitis by inhibiting NLRP3 inflammasome

Hydrogen sulfide (H₂S), as the third gasotransmitter, has been shown to be effective in the prevention of inflammation. In addition, the NLRP3 inflammasome is a key player in the pathogenesis of dextran sulfate sodium (DSS)-induced colitis. Therefore, the aim of our research was to determine whether H₂S exerts an anti-inflammatory effect on DSS-induced colitis by targeting NLRP3 inflammasome. Our data showed that DSS-induced colitis is attenuated by H₂S, lessening the shortening of the colon lengths and colonic pathological damages. The cytokines TNF-α, IL-1β, and IL-6 in colon samples were also significantly downregulated by H₂S. Besides, H₂S markedly suppressed the expression of NLRP3 and cleaved caspase-1 (p20) in colons from DSS-induced colitis mice. More importantly, CSE^-/- mice were more susceptive to DSS-induced colitis when compared to wild-type (WT) mice. Our experimental results also suggested that H₂S dose-dependently inhibits the activation of NLRP3 inflammasome in bone marrow-derived macrophages (BMDMs) by reducing the cleavage of caspase-1 and the secretion of IL-1β. Furthermore, the inhibitory effect of H₂S is due to a reduction in reactive oxygen species (ROS) generation and partly dependent on the disruption of nuclear erythroid 2-related factor-2 (Nrf2) activation. Collectively, our study confirms that H₂S exerts its protective effect on DSS-induced mouse colitis at least partly by inhibiting the activation of NLRP3 inflammasome pathway.

The H2S-Releasing Naproxen Derivative ATB-346 and the Slow-Release H2S Donor GYY4137 Reduce Intestinal Inflammation and Restore Transit in Postoperative Ileus

Objective: Intestinal inflammation triggers postoperative ileus (POI), commonly seen after abdominal surgery and characterized by impaired gastrointestinal transit; when prolonged, this leads to increased morbidity. Hydrogen sulfide (H2S) is recognized as an important mediator of many (patho)physiological processes, including inflammation, and is now investigated for anti-inflammatory application. Therefore, the aim of this study was to investigate the effect of the H2S-releasing naproxen derivative ATB-346, developed to reduce gastrointestinal injury by naproxen, and the slow-release H2S donor GYY4137 on intestinal inflammation and delayed gastrointestinal transit in murine POI. Methods: C57Bl6J mice were fasted for 6 h, anesthetized and after laparotomy, POI was induced by compressing the small intestine with two cotton applicators for 5 min (intestinal manipulation; IM). GYY4137 (50 mg/kg, intraperitoneally), ATB-346 (16 mg/kg, intragastrically) or naproxen (10 mg/kg, intragastrically) were administered 1 h before IM. At 24 h postoperatively, gastrointestinal transit was assessed via fluorescent imaging, and mucosa-free muscularis segments were prepared for later analysis. Inflammatory parameters and activity of inducible nitric oxide synthase (iNOS) and cyclo-oxygenase (COX)-2 were measured. Histological examination of whole tissue sections was done on hematoxylin-eosin stained slides. Results: Pre-treatment with GYY4137 (geometric center; GC: 7.6 ± 0.5) and ATB-346 (GC: 8.4 ± 0.3) prevented the delayed transit induced by IM (GC: 3.6 ± 0.5 vs. 9.0 ± 0.4 in non-operated controls) while naproxen only partially did (GC: 5.9 ± 0.5; n = 8 for all groups). GYY4137 and ATB-346 significantly reduced the IM-induced increase in muscular myeloperoxidase (MPO) activity and protein levels of interleukin (IL)-6, IL-1β and monocyte chemotactic protein 1; the reduction by naproxen was less pronounced and only reached significance for MPO activity and IL-6 levels. All treatments significantly reduced the increase in COX-2 activity caused by IM, whereas only GYY4137 significantly reduced the increase in iNOS activity. Naproxen treatment caused significant histological damage of intestinal villi. Conclusion: The study shows that naproxen partially prevents POI, probably through its inhibitory effect on COX-2 activity. Both ATB-346 and GYY4137 were more effective, the result with GYY4137 showing that H2S per se can prevent POI.

Determinants of hypoxia-inducible factor activity in the intestinal mucosa

The intestinal mucosa is exposed to fluctuations in oxygen levels due to constantly changing rates of oxygen demand and supply and its juxtaposition with the anoxic environment of the intestinal lumen. This frequently results in a state of hypoxia in the healthy mucosa even in the physiologic state. Furthermore, pathophysiologic hypoxia (which is more severe and extensive) is associated with chronic inflammatory diseases including inflammatory bowel disease (IBD). The hypoxia-inducible factor (HIF), a ubiquitously expressed regulator of cellular adaptation to hypoxia, is central to both the adaptive and the inflammatory responses of cells of the intestinal mucosa in IBD patients. In this review, we discuss the microenvironmental factors which influence the level of HIF activity in healthy and inflamed intestinal mucosae and the consequences that increased HIF activity has for tissue function and disease progression.