H2S Levels Research Articles

The hydrogen sulfide donor 4-carboxyphenyl-isothiocyanate decreases blood pressure and promotes cardioprotective effect through reduction of oxidative stress and nuclear factor kappa B/matrix metalloproteinase (MMP)-2 axis in hypertension

AimsOur aim was to evaluate whether the hydrogen sulfide (H2S) donor, 4-carboxyphenyl-isothiocyanate (4-CPI), exerts cardioprotective effect in the two kidney- one clip (2K-1C) rats through oxidative stress and MMP-2 activity attenuation and compare it with the classical H2S donor, Sodium Hydrosulfide (NaHS). Materials and methodsRenovascular hypertension (two kidneys-one clip; 2K-1C) was surgically induced in male Wistar rats. After two weeks, normotensive (2K) and hypertensive rats were intraperitoneally treated with vehicle (0.6 % dimethyl sulfoxide), NaHS (0.24 mg/Kg/day) or with 4-CPI (0.24 mg/Kg/day), for more 4 weeks. Systolic blood pressure (SBP) was evaluated weekly by tail-cuff plethysmography. Heart function was assessed by using the Millar catheter. Cardiac hypertrophy and fibrosis were evaluated by hematoxylin and eosin, and Picrosirius Red staining, respectively. The H2S was analyzed using WSP-1 fluorimetry and the cardiac oxidative stress was measured by lucigenin chemiluminescence and Amplex Red. MMP-2 activity was measured by in-gel gelatin or in situ zymography assays. Nox1, gp91phox, MMP-2 and the phospho-p65 subunit (Serine 279) nuclear factor kappa B (NF-κB) levels were evaluated by Western blotting. Key findings4-CPI reduced blood pressure in hypertensive rats, decreased cardiac remodeling and promoted cardioprotection through the enhancement of cardiac H2S levels. An attenuation of oxidative stress, with inactivation of the p65-NF-κB/MMP-2 axis was similarly observed after NaHS or 4-CPI treatment in 2K-1C hypertension. SignificanceH2S is a mediator that promotes cardioprotective effects and decreases blood pressure, and 4-CPI seems to be a good candidate to reverse the maladaptive remodeling and cardiac dysfunction in renovascular hypertension.

Hydrogen sulfide mitigates ox‑LDL‑induced NLRP3/caspase‑1/GSDMD dependent macrophage pyroptosis by S‑sulfhydrating caspase‑1.

Macrophage pyroptosis mediates vascular inflammation and atherosclerosis (AS). Hydrogen sulfide (H2S) exerts a protective role in preventing inflammation and AS. However, its molecular mechanisms of regulating the pyroptosis signaling pathway and inhibiting macrophage pyroptosis remain unexplored. The present study aimed to determine whether H2S mitigates macrophage pyroptosis by downregulating the pyroptosis signaling pathway and S‑sulfhydrating caspase‑1 under the stimulation of oxidized low‑density lipoprotein (ox‑LDL), a pro‑atherosclerotic factor. Macrophages derived from THP‑1 monocytes were pre‑treated using exogenous H2S donors sodium hydrosulfide (NaHS) and D,L‑propargylglycine (PAG), a pharmacological inhibitor of endogenous H2S‑producing enzymes, alone or in combination. Subsequently, cells were stimulated with ox‑LDL or the desulfhydration reagent dithiothreitol (DTT) in the presence or absence of NaHS and/or PAG. Following treatment, the levels of H2S in THP‑1 derived macrophages were measured by a methylene blue colorimetric assay. The pyroptotic phenotype of THP‑1 cells was observed and evaluated by light microscopy, Hoechst 33342/propidium iodide fluorescent staining and lactate dehydrogenase (LDH) release assay. Caspase‑1 activity in THP‑1 cells was assayed by caspase‑1 activity assay kit. Immunofluorescence staining was used to assess the accumulation of active caspase‑1. Western blotting and ELISA were performed to determine the expression of pyroptosis‑specific markers (NLRP3, pro‑caspase‑1, caspase‑1, GSDMD and GSDMD‑N) in cells and the secretion of pyroptosis‑related cytokines [interleukin (IL)‑1β and IL‑18] in the cell‑free media, respectively. The S‑sulfhydration of pro‑caspase‑1 in cells was assessed using a biotin switch assay. ox‑LDL significantly induced macrophage pyroptosis by activating the pyroptosis signaling pathway. Inhibition of endogenous H2S synthesis by PAG augmented the pro‑pyroptotic effects of ox‑LDL. Conversely, exogenous H2S (NaHS) ameliorated ox‑LDL‑and ox‑LDL + PAG‑induced macrophage pyroptosis by suppressing the activation of the pyroptosis signaling pathway. Mechanistically, ox‑LDL and the DTT increased caspase‑1 activity and downstream events (IL‑1β and IL‑18 secretion) of the caspase‑1‑dependent pyroptosis pathway by reducing S‑sulfhydration of pro‑caspase‑1. Conversely, NaHS increased S‑sulfhydration of pro‑caspase‑1, reducing caspase‑1 activity and caspase‑1‑dependent macrophage pyroptosis. The present study demonstrated the molecular mechanism by which H2S ameliorates macrophage pyroptosis by suppressing the pyroptosis signaling pathway and S‑sulfhydration of pro‑caspase‑1, thereby suppressing the generation of active caspase-1 and activity of caspase-1.

Hydrogen sulfide activates calcium signaling to confer tolerance against selenium stress in Brassica rapa

BackgroundSe (selenium) pollution is an emerging environmental concern. Excessive Se induces phytotoxicity. The endogenous H2S (hydrogen sulfide) was involved in plant adaptation to Se stress, but the signaling player of H2S remains unclear.MethodsThe study was conducted in a hydroponic system with different chemicals added to the treatment solution. Fluorescent tracking was performed to detect endogenous signaling molecules in plant tissues. Physiological changes were determined based on pharmaceutics and histochemical experiments. Gene expression was analyzed using qRT-PCR. The data were summarized using hierarchical cluster and Pearson correlation analysis.ResultsSe stress inhibited B. rapa growth (e.g. root elongation, shoot height, and seedling fresh weight and dry weight) in both dose- and time-dependent manners, with approximately 50% of root growth inhibition occurred at 20 µM Se. Se stress induced ROS (reactive oxygen species) accumulation and oxidative injury in B. rapa. Se exposure resulted in the upregulation of LCDs (L-cysteine desulfhydrase) and DCDs (D-cysteine desulfhydrase) encoding enzymes for H2S production in B. rapa at early stage of Se exposure, followed by downregulation of these genes at late stage. This was consistent with the change of endogenous H2S in B. rapa. Enhancing endogenous H2S level with NaHS (H2S donor) stimulates endogenous Ca2+ in B. rapa upon Se exposure, accompanied the attenuation of growth inhibition, ROS accumulation, oxidative injury, and cell death. The beneficial effects of H2S on detoxifying Se were blocked by decreasing endogenous Ca2+ level with Ca2+ channel blocker or Ca2+ chelator. Finally, hierarchical cluster combined with correlation analysis revealed that Ca2+ might acted as downstream of H2S to confer Se tolerance in B. rapa.ConclusionCa2+ was an important player of H2S in the regulation of plant physiological response upon Se stress. Such findings extend our knowledge of the mechanism for Se-induced phytotoxicity.Graphical

Dynamic changes of endogenous H2S generation during responding to developmental and environmental signals in Solanum lycopersicum L.

Increasing studies have confirmed the functions of hydrogen sulfide (H2S) as a gas signal molecule (gasotransmitter) in a variety of physiological activities in plants. However, the dynamic changes of endogenous H2S generation, especially the response speed and degree of H2S-generation-associated members, to both developmental and environmental cues in Solanum lycopersicum L. are still poorly understood. Here, we identified and charactered the H2S-generation-associated enzymes in tomato, including O-acetylserine (mercaptan) lyases (OAS-TL), L/D-Cysteine desulfhydrases (L/D-CDes) and nitrogen fixation S (NIFS)-like enzymes, possessing LCD-like activity. Analysis of cis-regulatory elements (CREs) showed that the promoter regions of these H2S-generation-associated genes contained lots of light-, hormone- and stresses-responsive CREs, and transcriptional factors (TFs) binding sites, suggesting that the regulatory mechanism of endogenous H2S generation might involve TFs mediated transcriptional regulation or/and interacting with phytohormones signals. Levels of endogenous H2S exhibited diversity in different organs and developmental stages in tomato, and the top and second highest level of H2S in flowers and ripened fruits hinted the significance of H2S signal in tomato reproduction and fruit development. Furthermore, the expression of SlOAS4, SlLCD, SlDCD2, SlNFS1, and SlNFS2 enhanced continuously during fruit ripening, and the SlOAS4 expression exhibited the most significant up-regulation. The SlDCD enzymatic activity responded more quickly to fruit development cues, while the SlLCD remained at a higher level almost throughout the whole fruit ripening. During environmental stimulus, it was found that the transcriptions of SlDCD2 and SlOAS2 responded faster and stronger to heat stress, while SlOAS4 and SlLCD were activated more quickly and significantly by drought stress. Both SlLCD and SlDCD enzymatic activities could be enhanced by drought and heat stress to varying degrees, and it seemed that the SlLCD was activated to a greater extent and remained at the higher activity for a longer period. With the extension of exogenous phytohormones (ABA, SA, GA, JA, ACC, NAA) treatment, the SlLCD activity and the endogenous H2S content increased in a specific time-dependent manner, and ABA, SA and NAA had more rapid effects on SlLCD activity. By widely explored the dynamic responses of endogenous H2S generation, our study would provide some references for understanding the regulatory mechanism upstream of H2S signaling in tomato growth developments and environmental adaptations.

Ammonia negatively impacted egg production and altered the diversity of microbial communities in cage-reared Muscovy ducks

The aim of this study was to examine the effects of NH3 variations across different positions within a cage-reared duck house on the egg production performance and fecal microbiome in Muscovy ducks. Totals of 3,168 female Muscovy ducks (180 ± 2 d) were randomly assigned to 1,056 cages. From d 293 to 300, the egg production rate and levels of NH3, H2S, CO2, temperature, humidity, light intensity, and dust particles were recorded. Two spatial distribution-based experimental classification methods were applied, one grouping ducks into Front, Middle, and End categories, and the other into First, Second, and Third layers. On d 300, serum and feces samples were collected for further analysis. The result showed that both the egg production rate and serum PROG level in the Front were higher than End (P < 0.05). However, no significant differences were found among the First, Second, and Third groups. Among the environmental factors, ammonia (NH3) is a major harmful gas in cage-reared duck houses, with observed concentrations showing a gradient from lower levels in the Front group to higher levels in the Middle group (P < 0.05), and even higher levels in the End group (P < 0.05). Gene sequencing of the 16S rRNA gene revealed a higher relative abundance of Firmicutes in both the Front and Middle groups compared to the End group (P < 0.05). Specifically, within the Firmicutes phylum, the relative abundance of Lactobacillus and Romboutsia was notably higher in the Front group compared to both the Middle and End groups (P < 0.05). What's more, the abundance of Lactobacillus had a negative correlation with NH3 concentration and positive correlation with egg production rate. In conclusion, NH3 concentrations showed variations across different areas of the cage-reared duck house, with higher levels detected at the rear. The elevated NH3 level was identified as the main factor negatively impacting egg production in Muscovy ducks and contributing to a decline in the abundance of Firmicutes, specifically Lactobacillus.

Fuzzy-decision tree modeling for H2S production management in an industrial-scale anaerobic digestion process

H2S is a byproduct in anaerobic digesters (ADs), causing significant challenges due to its negative impact on biogas quality and equipment corrosion. As a solution, previous researchers developed complex mechanistic models that are computationally expensive due to solving equations with many variables. These models were only tested within normal H2S ranges. This research introduces a novel hybrid fuzzy-decision tree (F-DT) model to predict H2S production from primary/secondary sludge ratio (P/S), dry solids (DS), and volatile solid (VS) reduction parameters in the Qom wastewater treatment plant in Iran. Notably, the H2S concentrations in this facility consistently surpass the acceptable thresholds reaching levels as high as 6500 ppm, in contrast to the designed accepted limit of 3000 ppm. The process involved collecting and pre-processing data, creating a decision tree classifier for rule generation, developing a fuzzy model suited for complex systems like AD, and optimizing it with a genetic algorithm. The analysis of the final model revealed that the P/S ratio significantly influences elevated H2S levels, indicating that maintaining a P/S ratio > 1.2 holds promise as an effective strategy. The model is both simple and interpretable, with decent accuracy in predicting H2S compared to previous models. This study not only introduces a useful method for optimizing industrial-scale ADs, but also aims to uncover the reasons behind high H2S levels.

Effect and mechanism of biochar-based hydrogel to alleviate drought stress in tobacco

Drought is an important abiotic stressor that adversely affects agricultural production, resulting in decreased crop yields and food insecurity. The objective of this study was to develop a novel hydrogel-based composite (S-B-AA) by incorporating biochar into hydrogel (S-AA) and evaluating its effects on tobacco plants under drought stress. The S-B-AA hydrogel exhibited enhanced water absorption and retention capabilities compared to the S-AA hydrogel. Under drought stress conditions, the S-B-AA hydrogel effectively increased the total water content, relative water content, and free water content of tobacco leaves, while reducing the bound water content and water saturation deficit. Additionally, it improved the stomatal status of tobacco leaves, significantly enhanced the photosynthetic capacity of tobacco seedlings, and promoted biomass accumulation. Moreover, the S-B-AA hydrogel alleviated the excessive accumulation of reactive oxygen species (ROS) induced by drought stress in tobacco seedlings, thereby alleviating ROS damage to cell membranes. It also reduced antioxidant enzyme activity and the levels of the signaling molecule H2S, while minimizing the impact of drought stress on tobacco osmotic regulation. Transcriptome analysis revealed that S-B-AA up-regulated 2826 DEGs and down-regulated 5225 DEGs compared to the control group. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis demonstrated that the differentially expressed genes were predominantly enriched in the mitogen-activated protein kinase (MAPK) signaling pathway, plant hormone signaling pathway, and photosynthesis pathway. This study provides a theoretical basis and practical guidance for the application of S-B-AA hydrogel in agriculture and environmental protection.

Effects of Plant Polysaccharides Combined with Boric Acid on Digestive Function, Immune Function, Harmful Gas and Heavy Metal Contents in Faeces of Fatteners.

The experiment aimed to investigate the effects of plant polysaccharides combined with boric acid on digestive function, immune function and harmful gas and heavy metal contents in the faeces of fatteners. For this study, 90 healthy crossbred fatteners were selected and randomly divided into five groups: the control group was fed with a basal diet (Con); experimental group I was fed with basal diet + 40 mg/kg boric acid (BA); experimental group II was fed with basal diet + 40 mg/kg boric acid + 400 mg/kg Astragalus polysaccharides (BA+APS); experimental group III was fed with basal diet + 40 mg/kg boric acid + 200 mg/kg Ganoderma lucidum polysaccharides (BA+GLP); and experimental group IV was fed with basal diet + 40 mg/kg boric acid + 500 mg/kg Echinacea polysaccharides (BA+EPS). Compared with Con, the average daily gain (ADG), the trypsin activities in the duodenum and jejunum, the IL-2 levels in the spleen, the T-AOC activities and GSH-Px contents in the lymph node of fattening were increased in the BA group (p < 0.05), but malondialdehyde content in the lymph and spleen, and the contents of NH3, H2S, Hg, Cu, Fe and Zn in the feces and urine were decreased (p < 0.05). Compared with the BA, the ADG, gain-to-feed ratio (G/F), the trypsin and maltase activities in the duodenum and jejunum were increased in the BA+APS (p < 0.05), and the T-SOD activities in the spleen and T-AOC activities in the lymph node were also increased (p < 0.05), but the H2S level was decreased in the feces and urine (p < 0.05). Compared with the BA, the ADG, G/F and the trypsin and maltase activities in the duodenum were increased in the BA+GLP and BA+EPS (p < 0.05), the activities of maltase and lipase in the duodenum of fatteners in the BA+GLP and the activities of trypsin, maltase and lipase in the BA+EPS were increased (p < 0.05). Gathering everything together, our findings reveal that the combined addition of boric acid and plant polysaccharides in the diet of fatteners synergistically improved their growth performance and immune status. That may be achieved by regulating the activity of intestinal digestive enzymes, improving the antioxidant function and then promoting the digestion and absorption of nutrients. Furthermore, the above results reduce the emission of harmful gases and heavy metals in feces and urine.

Diagnosis of Nonalcoholic Fatty Liver Disease via a H2S-Responsive Bioluminescent Probe Combined with Firefly Luciferase mRNA Delivery.

The early detection of nonalcoholic fatty liver disease (NAFLD) through bioluminescent probes is of great significance. However, there remains a challenge to apply them in nontransgenic natural animals due to the lack of exogenous luciferase. To address this issue, we herein report a new strategy for in situ monitoring of endogenous hydrogen sulfide (H2S) in the liver of NAFLD mice by leveraging a H2S-responsive bioluminescent probe (H-Luc) combined with firefly luciferase (fLuc) mRNA delivery. The probe H-Luc was created by installing a H2S recognition moiety, 2,4-dinitrophenol, onto the luciferase substrate (d-luciferin), which is allowed to release cage-free d-luciferin in the presence of H2S via a nucleophilic aromatic substitution reaction. In the meantime, the intracellular luciferase was introduced by lipid nanoparticle (LNP)-mediated fLuc mRNA delivery, rendering it suitable for bioluminescence (BL) imaging in vitro and in vivo. Based on this luciferase-luciferin system, the endogenous H2S could be sensitively and selectively detected in living cells, showing a low limit of detection (LOD) value of 0.72 μM. More importantly, after systematic administration of fLuc mRNA-loaded LNPs in vivo, H-Luc was able to successfully monitor the endogenous H2S levels in the NAFLD mouse model for the first time, displaying a 28-fold higher bioluminescence intensity than that in the liver of normal mice. We believe that this strategy may shed new light on the diagnosis of inflammatory liver disease, further elucidating the roles of H2S.

Exposure to sublethal levels of H2S does not influence the short-term growth or feed utilization in post-smolt Atlantic salmon (Salmo salar) during restrictive feeding

Hydrogen sulfide (H2S) related mass mortality events in land-based recirculating aquaculture systems (RAS) are associated with the sudden release of substantial amounts of H2S, resulting in acutely toxic exposure. However, the production and release of H2S can also occur at slower constant rates, leading to continuous exposure to sublethal H2S concentrations, the effects of which are unknown. Here, we examined growth rates, feed conversion ratios, and apparent nutrient digestibility in post-smolt Atlantic salmon, following a 10-day exposure to one of two sublethal concentrations of H2S, compared against a control group. The H2S concentrations of the low exposure (LE) and moderate exposure (ME) groups throughout the trial were 1.8 ± 0.8 μg/L and 4.1 ± 1.9 μg/L, respectively. Neither exposure regime affected growth, feed utilization, or the apparent nutrient digestibility. The results suggest that Atlantic salmon tolerate exposure to sublethal H2S concentrations for 10 days, without a discernible effect on the production performance. For aquaculture systems, specifically RAS, this means that while higher concentrations of H2S should be strictly avoided, the presence of low H2S concentrations for a limited period might not be detrimental to fish welfare or production. The RAS environment is complex, and the potential combined effects of H2S and factors pertinent to RAS may influence fish performance differently in a production setting.

Value of exhaled hydrogen sulfide in early diagnosis of esophagogastric junction adenocarcinoma.

Esophagogastric junction adenocarcinoma (EJA) has increased in recent years, and it exhibits a poor prognosis and a short survival period for patients. Hydrogen sulfide (H2S) plays an important role in the pathogenesis of cancer and has been studied as a diagnostic factor in some tumor diseases. However, few studies have explored the diagnostic value of H2S for EJA. In the present study, a total of 56 patients with early-stage EJA were enrolled while 57 healthy individuals were selected as the healthy control group. Clinical features were recorded, and exhaled H2S and blood samples were collected from both groups. Exhaled H2S and serum interleukin-8 (IL-8) expression levels were detected in both groups. The correlation between exhaled H2S and serum IL-8 levels was analyzed using Pearson's correlation method. Receiver operating characteristic (ROC) curve was used to evaluate the diagnostic value of exhaled H2S combined with IL-8 detection in EJA. The results showed that patients with EJA exhaled more H2S than healthy individuals. In addition, exhaled H2S was positively correlated with increased IL-8 expression. The ROC curve revealed that the exhaled H2S test had an acceptable diagnostic effect and could be used to diagnose EJA. The increase in H2S exhaled by patients with EJA indicated that H2S may be related to the occurrence and development of EJA; however, the in vivo mechanism needs to be further explored. Collectively, it was determined in the present study that exhaled H2S was significantly higher in patients with early-stage EJA than in healthy controls and combined diagnosis with patient serum IL-8 could improve diagnostic accuracy, which has potential diagnostic value for early diagnosis and screening of EJA.

PAG Masked Protective Physical Exercise-Induced High H2S Levels in 5/6 Nephrectomized Rats

Background: To investigate the mechanisms of exercise therapeutics in preclinical animal models of chronic kidney disease (CKD), PAG (D, L-propargylglycine), an inhibitor of hydrogen sulfide production, was used to examine the protective effects of physical activity on oxidative stress and inflammation levels during CKD. Methods: Male Wistar rats with CKD, induced by the 5/6 nephrectomy procedure and subjected to 8 weeks of exercise training, received injections of PAG, a cystathionine γ-lyase (CSE) inhibitor, at a dose of 19 mg/kg, i.p., twice a week during those 8 weeks. The systolic blood pressure (BP) and renal sympathetic nerve activity (RSNA) were assessed. Additionally, plasma creatinine, BUN, renal hydrogen sulfide (H2S) levels, oxidative stress, and inflammatory markers were evaluated. Results: In the PAG group, inhibition of H2S production significantly reversed the improvements in plasma creatinine, BUN, renal malondialdehyde (MDA) level, superoxide dismutase (SOD) activity, TNF-α, and IL-6 that were achieved by exercise. Additionally, high RSNA and high BP, which were also reversed in the PAG group, compared to the CKD group subjected to exercise training. Conclusions: The results suggest that the improvement in BP, oxidative stress, and inflammation status by exercise in CKD may be at least partially due to CSE/H2S signaling.

Persulfidation and phosphorylation of transcription factor SlWRKY6 differentially regulate tomato fruit ripening.

Cysteine desulfhydrase catalyses the generation of the signaling molecule hydrogen sulfide (H2S) in plants. In this study, we found that H2S can inhibit tomato (Solanum lycopersicum) fruit ripening and SlWRKY6 undergoes differential protein persulfidation in SlLCD1-overexpressing leaves. Then, further study indicated that SlWRKY6 could be persulfidated by H2S at Cys396. By construction of slwrky6 mutants and SlWRKY6-OE lines, we found that SlWRKY6 positively regulates leaf senescence and fruit ripening by activating the transcription of ripening-related genes STAYGREEN 1 (SlSGR1) and Senescence-Associated Gene 12 (SlSAG12). In addition, SlWRKY6 interacted with kinase SlMAPK4 and was phosphorylated at Ser33. Dual-luciferase transient expression assays and electrophoretic mobility shift assays indicated that SlWRKY6 persulfidation attenuated its transcriptional regulation of target genes SlSGR1 and SlSAG12, whereas SlWRKY6 phosphorylation by SlMAPK4 activated the transcription of target genes to promote fruit ripening. Moreover, we provided evidence that SlWRKY6 persulfidation attenuated its SlMAPK4-mediated phosphorylation to inhibit tomato fruit ripening. By transient expression of SlWRKY6, SlWRKY6C396A, SlWRKY6S33A, and SlWRKY6S33D in slwrky6 fruits, we found that SlWRKY6 persulfidation attenuated the expression of SlSGR1 and SlSAG12 thereby delaying tomato fruit ripening, while SlWRKY6 phosphorylation increased the expression of target genes. As tomato fruits ripened, endogenous H2S production decreased, while SlMAPK4 expression increased. Therefore, our findings reveal a model in which SlWRKY6 persulfidation due to higher endogenous H2S levels in un-ripened fruit inhibits its ability to activate SlSGR1 and SlSAG12 expression, while SlWRKY6 phosphorylation by SlMAPK4 activates its transcriptional activity, thereby promoting tomato fruit ripening.

A simple yet effective H2S‐activated fluorogenic probe for precise imaging of hepatitis and arthritis in situ

AbstractHepatitis and arthritis are prevalent inflammatory diseases, and the utilization of fluorogenic probes incorporating hydrogen sulfide (H2S) as a crucial mediator of inflammation presents significant opportunities for early detection. However, the poor in vivo biodistribution and limited targeted efficacy of molecule probes for inflammation imaging severely impede their ability to differentiate the extent of inflammation and provide real‐time monitoring of inflammatory levels. Therefore, we developed a highly efficient H2S‐activated near‐infrared (NIR) fluorogenic probe (hCy‐DNP) for real‐time tracking and capturing fluctuations in H2S levels within inflammatory lesions. hCy‐DNP demonstrates an exceptionally sensitive fluorescence response to H2S expression, enabling specific differentiation between various levels of lipopolysaccharide (LPS) ‐stimulated early hepatitis models in situ, while also facilitating visual monitoring for diagnosis and efficacy evaluation of arthritis. Therefore, hCy‐DNP offers an innovative tool for exploring early diagnosis and evaluating treatment effectiveness across diverse inflammatory diseases.

Hydrogen Sulfide Delivery to Enhance Bone Tissue Engineering Cell Survival.

Though crucial for natural bone healing, local calcium ion (Ca2+) and phosphate ion (Pi) concentrations can exceed the cytotoxic limit leading to mitochondrial overload, oxidative stress, and cell death. For bone tissue engineering applications, H2S can be employed as a cytoprotective molecule to enhance mesenchymal stem cell (MSC) tolerance to cytotoxic Ca2+/Pi concentrations. Varied concentrations of sodium hydrogen sulfide (NaSH), a fast-releasing H2S donor, were applied to assess the influence of H2S on MSC proliferation. The results suggested a toxicity limit of 4 mM for NaSH and that 1 mM of NaSH could improve cell proliferation and differentiation in the presence of cytotoxic levels of Ca2+ (32 mM) and/or Pi (16 mM). To controllably deliver H2S over time, a novel donor molecule (thioglutamic acid-GluSH) was synthesized and evaluated for its H2S release profile. Excitingly, GluSH successfully maintained cytoprotective level of H2S over 7 days. Furthermore, MSCs exposed to cytotoxic Ca2+/Pi concentrations in the presence of GluSH were able to thrive and differentiate into osteoblasts. These findings suggest that the incorporation of a sustained H2S donor such as GluSH into CaP-based bone graft substitutes can facilitate considerable cytoprotection, making it an attractive option for complex bone regenerative engineering applications.

Hydrogen Sulfide Regulates Erectile Function through Stimulation of Antioxidant Defense in the Corpus Cavernosum

Hydrogen sulfide (H2S) is a gaseous cell signaling molecule with vasodilatory properties. Diminished H2S production has been implicated in the pathology of several cardiovascular diseases. H2S may protect against oxidative stress through scavenging of reactive oxygen species (ROS) or through stimulation of the Nrf2-mediated cellular antioxidant defense systems. We have previously demonstrated that mice fed a western diet for 12 weeks develop elevated penile ROS levels and impaired erectile function, which coincides with diminished corpus cavernosal expression of cystathionine γ-lyase (CSE), a major H2S producing enzyme. The objective of this study was to investigate the role of H2S in the regulation of erectile function and penile redox balance. We hypothesized that H2S levels will be positively associated with cellular antioxidant defense and erectile function. Young male C57Bl/6J mice (n = 120) were fed a control diet (CD) or western diet (WD) ad libitum for 18 weeks. For the final six weeks of the dietary intervention, half of the mice were switched to an equivalent diet containing the H2S pro-drug SG1002 at approximately 20 mg/kg/day. Separately, male CSE knockout mice (n = 26) and wild type (WT) littermate controls (n = 26) were fed a standard diet and studied at 6 months. Following the interventions, erectile function was assessed by measuring intracavernosal pressure (ICP) and mean arterial pressure (MAP) during cavernous nerve stimulation (1, 2, 4 V). In separate mice, penile in vivo ROS production was measured via microdialysis. Relative expression of 18 genes related to cellular antioxidant defense were assessed from naïve corpus cavernosum tissue by qRT-PCR. Group differences were determined by two-way ANOVA, with an α-level of 0.05. Erectile function was impaired in CSE KO mice (2V ICP/MAP - WT: 0.70±0.039 vs. KO: 0.55±0.043; p&lt;0.05). Erectile function was similarly impaired in the untreated WD-fed mice (CD: 0.68±0.035 vs. WD: 0.49±0.012; p&lt;0.05), while SG1002 induced a 54% functional restoration in WD mice (WD+SG1002: 0.59±0.019; p&lt;0.05). Penile production of the ROS hydrogen peroxide and superoxide were elevated in CSE KO mice (WT: 0.73±0.04 vs. KO: 1.19±0.13; p&lt;0.01). Penile ROS were also elevated in the WD mice (CD: 0.71±0.07 vs. WD: 1.09±0.15; p&lt;0.01), which were normalized by SG1002 treatment (WD+SG1002: 0.83±0.07; p&lt;0.01 vs. WD). Five antioxidant genes (Gclc, Gpx1, Gpx4, Prdx3, and Hmox1) that were stimulated by SG1002 treatment were also downregulated in CSE KO cavernosal tissues. Conversely, Txnip, a negative regulator of the thioredoxin antioxidant system was suppressed by SG1002 treatment and increased in CSE KO tissues. These results indicate that H2S is a key regulator of the cellular antioxidant systems and ROS balance in the penis, which may also regulate erectile function. Grant number K01DK115540 from the National Institutes of Health. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Glutathione‐induced hydrogen sulfide enhances drought tolerance in sweet pepper (Capsicum annuum L.)

AbstractGlutathione (GSH) has been studied for its potential to enhance stress tolerance in plant systems, but the role of hydrogen sulfide (H2S) in GSH‐induced water stress tolerance in sweet pepper (Capsicum annuum L.) is still under investigation. This study explores how H2S and GSH modulate water stress tolerance in pepper plants, addressing a research gap. The joint effect of sodium hydrosulfide (NaHS), a donor of H2S, and GSH on water stress tolerance was determined through pre‐treatment with the H2S scavenger 0.1 mM hypotaurine (HT). Pepper seedlings were sprayed with 1.0 mM GSH or GSH + 0.2 mM NaHS once a week, with soil moisture content set at 80% and 40% for full irrigation and water stress conditions for a duration of 2 weeks. The results showed that water stress significantly reduced total plant dry weight, chlorophyll a and b content, Fv/Fm, leaf water potential, and relative water content by 50%, 56%, 33%, 27%, 52%, and 34%, while increasing hydrogen peroxide (H2O2), proline, and H2S levels by 152%, 134%, and77%, respectively. Treatment with GSH and NaHS reduced water stress‐induced H2O2 production and improved plant growth, photosynthetic traits, proline, and the activity of L‐cysteine desulfhydrase (L‐DES), leading to the generation of H2S content. GSH reduced NADPH oxidase (NOX), superoxide dismutase (SOD), and H2O2 but increased glutathione peroxidase (GPX) activities. The interaction of NaHS and GSH led to further reductions in NOX, SOD, and H2O2 values but increased GPX activity. The combined GSH and NaHS treatment increased nitric oxide (NO) production but decreased the activity of S‐nitrosoglutathione reductase (GSNOR), potentially accelerating S‐nitrosylation. Hypotaurine negated the positive impacts of GSH on water stress tolerance by reducing H2S concentration in pepper plants, but this was corrected by the concurrent application of NaHS and GSH + HT. Therefore, water stress tolerance requires H2S.

Hydrogen sulfide inhibits tomato fruit ripening by restraining fruit softening and ethylene production

Hydrogen sulfide (H2S) plays various roles in plant growth, development and stress response. However, the mechanism of action of H2S in fruit ripening remains unclear. This study investigated the roles and mechanisms of H2S in tomato (Solanum lycopersicum) fruit repining. The results showed that compared with the control (distilled water), H2S treatment significantly delayed the color and hardness transition of tomato fruit; while an H2S scavenger hypotaurine (HT) treatment promoted the color and hardness transition. H2S increased the endogenous chlorophyll content, activity of chlorophyll synthesis-related enzymes, and expression of chlorophyll synthesis-related genes and decreased the expression of chlorophyll degradation-related genes and lycopene content. In contrast, HT decreased the activity of chlorophyll synthesis-related enzymes and expression of related genes; and increased the expression of chlorophyll degradation-related genes. In addition, the activity of the softening-related enzymes, ACS and ACO, ethylene content, and the expression of softening- and ethylene biosynthesis-related genes were decreased by H2S but increased by HT. Exogenous H2S increases endogenous H2S levels. Therefore, H2S may delay tomato fruit ripening by down-regulating the expression of softening-related and ethylene synthesis-related genes and reducing the activity of softening-related and ethylene synthesis-related enzymes.

Construction of a NIR hydrogen sulfide fluorescent probe for revealing the role of astrocytes in hypothalamic inflammation

Hydrogen sulfide (H2S) is a crucial endogenous gas signaling molecule in the central nervous system, playing a significant role in anti-inflammation, anti-oxidation, and neuroprotection. Our studies have shown that the level of H2S is closely related to hypothalamic inflammation-induced obesity. Compared to neurons, astrocytes, exhibit a preferential activation in response to high-fat diet-induced hypothalamic inflammation. Whether the reduction of hydrogen sulfide in astrocytes is the cause of neuronal damage leading to hypothalamic inflammation is worth exploring. The key to discussing the role of astrocytes is to accurately and quickly detect the levels of H2S in the complex microenvironment of the brain. In this work, we designed and synthesized a H2S near-infrared fluorescence probe (NIR-HS) based on dicyanideisophorone. NIR-HS selectively responds to H2S at 668 nm, with an effective linear range (0–20 μM), high sensitivity (35 nM). This probe has been successfully applied to detect hydrogen sulfide levels in astrocytes and to perform H2S fluorescence imaging on the slices of the ventromedial nucleus of the hypothalamus. Additionally, the effect of the H2S donor drug allicin on the levels of H2S in the hypothalamus and its therapeutic effect on hypothalamic inflammation were confirmed using NIR-HS and a series of signal pathway studies. Ultimately, we revealed the mechanism of that H2S inhibits hypothalamic neuronal inflammation by suppressing the expression of the pro-inflammatory factor IL-1β in astrocytes.

Depletion and Downregulation of Hydrogen Sulfide Using an Activatable Probe for Promoting Photothermal Therapy toward Colorectal Cancers.

Since hydrogen sulfide (H2S) is an important endogenous gaseous mediator, therapeutic manipulation of H2S is promising for anticancer treatment. In this work, we develop a novel theranostic nanoplatform with H2S-specific and photocontrolled synergistic activation for imaging-guided H2S depletion and downregulation along with promoted photothermal therapy. Such a nanoplatform is fabricated by integration of a H2S-responsive molecule probe that can generate a cystathionine-β-synthase (CBS) inhibitor AOAA and a photothermal transducer into an NIR-light-responsive container. Our nanoplatform can turn on NIR fluorescence specifically in H2S-rich cancers, guiding further laser irradiation. Furthermore, prominent conversion of photoenergy into heat guarantees special container melting with controllable AOAA release for H2S-level downregulation. This smart regulation of the endogenous H2S level amplifies the PTT therapeutic effect, successfully suppressing colorectal tumor in living mice under NIR fluorescence imaging guidance. Thus, we believe that this nanoplatform may provide a powerful tool toward H2S-concerned cancer treatment with an optimized diagnostic and therapeutic effect.