Interaction of composite fume suppression and order elimination agents with crumb rubber modified asphalt: Inhibition behavior of volatile organic compounds (VOCs) and inorganic fume

The production and construction of crumb rubber modified asphalt (RMA) at high temperatures can produce a large amount of toxic fume, which is detrimental to human health and environment. In this study, a series of composite fume suppression and odor elimination agents (CSEAs) with both physical adsorption and chemical capture functions were adopted to reduce the emissions of volatile organic compounds (VOCs) and hydrogen sulfide (H2S). The material composition, microstructure, and specific surface area of CSEA were analyzed by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and N2 adsorption-desorption isotherm (BET). The inhibitory effects of adding CSEA on toxic fume emissions from RMA at high temperatures were investigated through a combination of fume emission tests, H2S gas detection, gel permeation chromatography (GPC), and gas chromatography-mass spectrometry technology (GC-MS). The adsorption behavior of CSEA on H2S was analyzed through adsorption dynamics. Results showed that the physical and chemical properties of CSEA are stable while chemical adsorption dominates the CSEA's effect on H2S. ZnO and Ca(OH)2 exhibit good crystallization effects on the surface of the carrier by forming mesoporous structures mostly above 3.4 nm in size. The incorporation of CSEA significantly reduced the total emissions of RMA fume and the main components of VOCs in which the average inhibition rate of H2S can reach 44 % at an initial 30 mins.

Hydrogel-based radio frequency H2S sensor for in situ periodontitis monitoring and antibacterial treatment

Periodontitis, a chronic disease, can result in irreversible tooth loss and diminished quality of life, highlighting the significance of timely periodontitis monitoring and treatment. Meanwhile, hydrogen sulfide (H2S) in saliva, produced by pathogenic bacteria of periodontitis, is an important marker for periodontitis monitoring. However, the easy volatility and chemical instability of the molecule pose challenges to oral H2S sensing. Here, we report a wearable hydrogel-based radio frequency (RF) sensor capable of in situ H2S detection and antibacterial treatment. The RF sensor comprises an agarose hydrogel containing conjugated silver nanoparticles-chlorhexidine (AG-AgNPs-CHL hydrogel) integrated with split-ring resonators. Adhered to a tooth, the hydrogel-based RF sensor enables wireless transmission of sensing signals to a mobile terminal and a concurrent release of the broad-spectrum antibacterial agent chlorhexidine without complex circuits. With the selective binding of the AgNPs to the sulfidion, the RF sensor demonstrates good sensitivity, a wide detection range (2-30 μM), and a low limit of detection (1.2 μM). Compared with standard H2S measurement, the wireless H2S sensor can distinguish periodontitis patients from healthy individuals in saliva sample tests. The hydrogel-based wearable sensor will benefit patients with periodontitis by detecting disease-related biomarkers for practical oral health management.

Impact of hydrogen sulfide on anammox and nitrate/nitrite-dependent anaerobic methane oxidation coupled technologies

The coupling between anammox and nitrate/nitrite-dependent anaerobic methane oxidation (n-DAMO) has been considered a sustainable technology for nitrogen removal from sidestream wastewater and can be implemented in both membrane biofilm reactor (MBfR) and granular bioreactor. However, the potential influence of the accompanying hydrogen sulfide (H2S) in the anaerobic digestion (AD)-related methane-containing mixture on anammox/n-DAMO remains unknown. To fill this gap, this work first constructed a model incorporating the C/N/S-related bioprocesses and evaluated/calibrated/validated the model using experimental data. The model was then used to explore the impact of H2S on the MBfR and granular bioreactor designed to perform anammox/n-DAMO at practical levels (i.e., 0∼5% (v/v) and 0∼40 g/S m3, respectively). The simulation results indicated that H2S in inflow gas did not significantly affect the total nitrogen (TN) removal of the MBfR under all operational conditions studied in this work, thus lifting the concern about applying AD-produced biogas to power up anammox/n-DAMO in the MBfR. However, the presence of H2S in the influent would either compromise the treatment performance of the granular bioreactor at a relatively high influent NH4+-N/NO2--N ratio (e.g., >1.0) or lead to increased energy demand associated with TN removal at a relatively low influent NH4+-N/NO2--N ratio (e.g., <0.7). Such a negative effect of the influent H2S could not be attenuated by regulating the hydraulic residence time and should therefore be avoided when applying the granular bioreactor to perform anammox/n-DAMO in practice.

Hydrogen sulfide inhibits the rupture of fetal membranes throngh anti-aging pathways

INTRODUCTION

To investigate the relationship between hydrogen sulfide(H2S) and the senescence level of the fetal membranes, and to elucidate how H2S affects the integrity of the fetal membranes.

METHODS

The H2S and the senescence levels of fetal membranes, and the expressions of H2S synthase CBS and CSE were detected in the preterm (PT) group and the preterm premature ruptured membranes (pPROM) group. The effects of H2S donors and knockdown of CBS on the senescence level of amniotic epithelial cells, and the expression level of matrix metalloproteinases (MMPs) and epithelial-mesenchymal translation (EMT) were observed.

RESULTS

The level of H2S in the fetal membranes in the pPROM group is significantly lower than that in the PT group matched for gestational age. The level of H2S is negatively correlated with the senescence level of fetal membranes. Treatment with H2S donors reduced cell senescence and MMPs expression, but did not affect EMT. CBS siRNA transfection accelerated the senescence of amniotic epithelial cells, and promoted the expression of MMPs and EMT occurrence, but l-cysteine could reverse these effects.

DISCUSSION

Our study suggests that H2S, through its anti-aging effect, can influence the expression of MMPs and EMT, thereby contributing to the maintenance of fetal membrane integrity.

Physiological role of hydrogen sulfide in the kidney and its therapeutic implications for kidney diseases

For over three centuries, hydrogen sulfide (H2S) has been known as a toxic and deadly gas at high concentrations, with a distinctive smell of rotten eggs. However, studies over the past two decades have shown that H2S has risen above its historically notorious label and has now received significant scientific attention as an endogenously produced gaseous signaling molecule that participates in cellular homeostasis and influences a myriad of physiological and pathological processes at low concentrations. Its endogenous production is enzymatically regulated, and when dysregulated, contributes to pathogenesis of renal diseases. In addition, exogenous H2S administration has been reported to exhibit important therapeutic characteristics that target multiple molecular pathways in common renal pathologies in which reduced levels of renal and plasma H2S were observed. This review highlights functional anatomy of the kidney and renal production of H2S. The review also discusses current understanding of H2S in renal physiology and seeks to lay the foundation as a new targeted therapeutic agent for renal pathologies such as hypertensive nephropathy, diabetic kidney disease and water balance disorders.

Application and value of hydrogen sulfide modulated autophagy in sepsis

Sepsis is is anabnormalhost immune responsecausedbyinfection. Antibiotics, anti-viral drugs, and vasoactive drugs have always been used in the traditional treatment of sepsis, but there are no specific and effective drugs in clinical practice. Autophagy is a highly conservative process in biological evolution, and plays an important role in maintaining intracellular homeostasis and cellular self-renewal. Autophagy can remove and degrade misfolding proteins and damaged organelles in cells, providing materials for cell repair and self-renewal. Hydrogen sulfide (H2S) is a colorless gas that smells likerotteneggs. It is the third endogenous gas signal molecule discovered after nitric oxide and carbon monoxide and has become a research hotspot in recent years. H2S has a variety of biological functions and plays an important role in various physiological and pathological processes. Thereisgrowingevidencethat H2S can regulate autophagy. The intervention of autophagy is a promising therapeutic strategy to improve sepsis organ damage. This article reviews the organ protection of autophagy in sepsis and the role of H2S in regulating autophagy in sepsis, revealing that H2S intervention with autophagy may be a a worthy target in sepsis treatment.

Surfactant enhances anaerobic fermentative hydrogen sulfide production: Changes in sulfur-containing organics structure and microbial community

The presence of surfactants in waste activated sludge (WAS) system is generally regarded as beneficial to sludge treatment such as enhancing sludge dewatering and improving value-added fermentation products generation. However, in this study, it was firstly found that sodium dodecylbenzene sulfonate (SDBS, a typical surfactant) obviously increased toxic hydrogen sulfide (H₂S) gas production from WAS anaerobic fermentation at environmentally relevant concentrations. Experimental results showed that H₂S production from WAS significantly increased from 53.24 × 10^-3 to 111.25 × 10^-3 mg/g volatile suspended solids (VSS) when SDBS level increased from 0 to 30 mg/g total suspended solid (TSS). It was found that SDBS presence destroyed WAS structure and enhanced sulfur containing organics release. SDBS reduced the proportion of α-helix structure, damaged disulfide bridges and protein conformation, and effectively destroyed protein structure. SDBS promoted sulfur containing organics degradation and provided more readily hydrolyzed micro-molecule organics for sulfide production. Microbial analysis showed that SDBS addition enhanced the abundance of functional genes encoding protease, ATP-binding cassette transporters, and amino acids lyase, enhanced the activities and abundance of hydrolytic microbes, thus increased sulfide production from the hydrolysis of sulfur containing organics. Compared with the control, 30 mg/g TSS SDBS increased organic sulfurs hydrolysis and amino acids degradation by 47.1 % and 63.5 %, respectively. Key genes analysis further showed that SDBS addition promoted sulfate transport system and dissimilatory sulfate reduction. SDBS presence also lowered fermentation pH, promoted the chemical equilibrium transformation of sulfide, thus increased H₂S gas release.

Revealing an unrecognized role of free ammonia in sulfur transformation during sludge anaerobic treatment

Free ammonia (FA), the unionized form of ammonium, is presented in anaerobic fermentation of waste activated sludge (WAS) at high levels. However, its potential role in sulfur transformation, especially H₂S production, during WAS anaerobic fermentation process was unrecognized previously. This work aims to unveil how FA affects anaerobic sulfur transformation in WAS anaerobic fermentation. It was found that FA significantly inhibited H₂S production. With an increase of FA from 0.04 to 159 mg/L, H₂S production reduced by 69.9%. FA firstly attacked tyrosine-like proteins and aromatic-like proteins in sludge EPSs, with CO groups being responded first, which decreased the percentage of α-helix/(β-sheet + random coil) and destroyed hydrogen bonding networks. Cell membrane potential and physiological status analysis showed that FA destroyed membrane integrity and increased the ratio of apoptotic and necrotic cells. These destroyed sludge EPSs structure and caused cell lysis, thus strongly inhibited the activities of hydrolytic microorganisms and sulfate reducing bacteria. Microbial analysis showed that FA reduced the abundance of functional microbes (e.g., Desulfobulbus and Desulfovibrio) and genes (e.g., MPST, CysP, and CysN) involved in organic sulfur hydrolysis and inorganic sulfate reduction. These findings unveil an actually existed but previously overlooked contributor to H₂S inhibition in WAS anaerobic fermentation.

Effect of exogenous CaO addition on H2S production from waste activated sludge and its influence mechanism

Hydrogen sulfide (H₂S) production from waste activated sludge (WAS) is the main reason for odor emission during anaerobic fermentation system. CaO has been reported to effectively improve the resources recovery of WAS, but its potential effect on H₂S production in anaerobic fermentation process remains unrecognized. In present study, it was found that the addition of 60 mg/g VSS CaO greatly inhibited H₂S production and the maximum yield of H₂S was 60.1 ± 1.8% lower than the control. Mechanism investigation demonstrated that CaO destroyed sludge structure and increased the release of intracellular organic matter with hydrogen bonding networks destroying, but had a mild effect on the transformation of sulfur containing organic matters and inorganic sulfate reduction. Additionally, the enhancement in H⁺ and S^2- consumption by alkaline condition and metal ions release was another reason for the inhibition of H₂S production in CaO addition reactors. Furthermore, microbial analysis showed that CaO addition importantly reduced the hydrolysis microorganism, particularly denitrification hydrolytic bacterias (e.g., unclassified_f_Chitinophagaceae and Dechloromonas), sulfate reducing bacterias (SRBs) (e.g., unclassified_c_Deltaproteobacteria and Desulfosarcina) and genes (e.g., PepD, cysN/D, CysH/C and Sir) involved in organic sulfur hydrolysis and sulfate reduction. Results from this study provides theoretical insights into the practical applications of CaO.

A turn-on fluorescent nanosensor for H2S detection and imaging in inflammatory cells and mice

Hydrogen sulfide (H₂S) is an endogenously generated gaseous signaling molecule and is known to be involved in the occurrence and development of inflammation. To better understand its physiological and pathological process of inflammation, reliable tools for H₂S detection in living inflammatory models are desired. Although a number of fluorescent sensors have been reported for H₂S detection and imaging, water-soluble and biocompatibility nanosensors are more useful for imaging in vivo. Herein, we developed a novel biological imaging nanosensor, XNP1, for inflammation-targeted imaging of H₂S. XNP1 was obtained by self-assembly of amphiphilic XNP1, which was constructed by the condensation reaction of the hydrophobic, H₂S response and deep red-emitting fluorophore with hydrophilic biopolymer glycol chitosan (GC). Without H₂S, XNP1 showed very low background fluorescence, while a significant enhancement in the fluorescence intensity of XNP1 was observed in the presence of H₂S, resulting in a high sensitivity toward H₂S in aqueous solution with a practical detection limit as low as 32.3 nM, which could be meet the detection of H₂S in vivo. XNP1 also has a good linear response concentration range (0-1 μM) toward H₂S with high selectivity over other competing species. These characteristics facilitate direct H₂S detection of the complex living inflammatory cells and drug-induced inflammatory mice, demonstrating its practical application in biosystems.

Intranasal administration of polysulfide prevents neurodegeneration in spinal cord and rescues mice from delayed paraplegia after spinal cord ischemia

BACKGROUND

Delayed paraplegia is a devastating complication of thoracoabdominal aortic surgery. Hydrogen sulfide (H₂S) was reported to be protective in a mouse model of spinal cord ischemia and the beneficial effect of H₂S has been attributed to polysulfides. The objective of this study was to investigate the effects of polysulfides on delayed paraplegia after spinal cord ischemia.

METHODS AND RESULTS

Spinal cord ischemia was induced in male and female C57BL/6J mice by clamping the aortic arch and the left subclavian artery. Glutathione trisulfide (GSSSG), glutathione (GSH), glutathione disulfide (GSSG), or vehicle alone was administered intranasally at 0, 8, 23, and 32 h after surgery. All mice treated with vehicle alone developed paraplegia within 48 h after surgery. GSSSG, but not GSH or GSSG, prevented paraplegia in 8 of 11 male mice (73%) and 6 of 8 female mice (75%). Intranasal administration of ³⁴S-labeled GSSSG rapidly increased ³⁴S-labeled sulfane sulfur species in the lumbar spinal cord. In mice treated with intranasal GSSSG, there were increased sulfane sulfur levels, and decreased neurodegeneration, microglia activation, and caspase-3 activation in the lumbar spinal cord. In vitro studies using murine primary cortical neurons showed that GSSSG increased intracellular levels of sulfane sulfur. GSSSG, but not GSH or GSSG, dose-dependently improved cell viability after oxygen and glucose deprivation/reoxygenation (OGD/R). Pantethine trisulfide (PTN-SSS) also increased intracellular sulfane sulfur and improved cell viability after OGD/R. Intranasal administration of PTN-SSS, but not pantethine, prevented paraplegia in 6 of 9 male mice (66%).

CONCLUSIONS

Intranasal administration of polysulfides rescued mice from delayed paraplegia after transient spinal cord ischemia. The neuroprotective effects of GSSSG were associated with increased levels of polysulfides and sulfane sulfur in the lumbar spinal cord. Targeted delivery of sulfane sulfur by polysulfides may prove to be a novel approach to the treatment of neurodegenerative diseases.

Hydrogen sulfide and nitric oxide regulate the adaptation to iron deficiency through affecting Fe homeostasis and thiol redox modification in Glycine max seedlings

Iron (Fe) is a vital microelement required for the growth and development of plants. Hydrogen sulfide (H₂S) and nitric oxide (NO), as messenger molecules, participated in the regulation of plant physiological processes. Here, we studied the interaction effects of H₂S and NO on the adaptation to Fe deficiency in Glycine max L. Physiological, biochemical and molecular approaches were conducted to analyze the role of H₂S and NO in regulating the adaptation to Fe deficiency in soybean. We found that H₂S and NO had obvious rescuing function on the Fe deficiency-induced the plant growth inhibition, which was significantly correlated with the increase in Fe content in the leaves, stems, and roots of soybean. Meanwhile, H⁺-flux, ferric chelate reductase (FCR) activity, and root apoplast Fe content were significantly affected by H₂S and NO. Under Fe deficiency conditions NO and H₂S regulated the expression of genes related to Fe homeostasis. Moreover, photosynthesis (Pn) and photosystem II (PSII) efficiency were enhanced by H₂S and NO, and thiol redox modification was important for regulating the adaptation of Fe deficiency. The aforementioned affirmative influences caused by H₂S and NO were also totally reversed by cPTIO (a NO scavenger). Our results suggested that H₂S might act upstream of NO in response to Fe deficiency by affecting the Fe homeostasis enzyme activities and gene expression, and by promoting Fe accumulation in plant tissues as well as by enhancing thiol redox modification and photosynthesis in soybean plants.

Potential application of a hydrotalcite-like compound for reduction of toxicity to aquatic organisms via rapid and efficient removal of hydrogen sulfide

Hydrogen sulfide (H₂S) is known to have wide ranging toxicities not only as a gas but also as dissolved forms in aquatic environments. The diversity of aquatic organisms can be severely affected by hydrogen sulfide at very low concentrations, indicating the urgent necessity to develop an efficient method for removal of hydrogen sulfide in water. In this study, the removal capacity for hydrogen sulfide of our originally developed hydrotalcite-like compound composed of magnesium and iron (MF-HT) was investigated and its potential application for reduction of toxicity to aquatic organisms was evaluated. The MF-HT experimentally showed a high adsorption capacity of 146.5 mg/g with a fast adsorption equilibrium time of 45 min, both of which are top-class compared with those of other adsorbents previously reported. In fact, removal of hydrogen sulfide (1.2-152.5 mg/L) at an average rate of >97.6% was achieved in groundwater samples (n = 16) by the MF-HT within 60 min. The toxicities of groundwater, indicated by inhibition rate for microalgae (primary producers) and immobilization rate for crustaceans (secondary consumers), were reduced by 96.1% and 82.5% in 2-fold and 4-fold diluted groundwater, respectively, after treatment with the MF-HT for 60 min. These results indicate that MF-HT has an excellent safety record for aquatic organisms. After clarifying the adsorption mechanism, excellent reusability of MF-HT was also confirmed after regeneration using 1 M Na₂CO₃ solution. Considering the efficacy, speed, safety and cost of MF-HT, it could be a novel promising material for solving the problem of hydrogen sulfide pollution in the hydrosphere.

Rhamnolipid increases H2S generation from waste activated sludge anaerobic fermentation: An overlooked concern

Rhamnolipid (RL), one representative biosurfactant, is widely regarded as an economically feasible and environmentally beneficial additive to improve fermentation efficiency and resource recovery from waste activated sludge (WAS). However, its potentially detrimental impact on WAS fermentation such as H₂S generation was overlooked previously. This study therefore aims to fill the gap through exploring whether and how the presence of RL affects H₂S generation from WAS anaerobic fermentation. Experimental results showed that when RL increased from 0 to 40 mg/g total suspended solids (TSS), the cumulative H₂S yield enhanced from 323.6 ×  10^-4 to 620.3 ×  10^-4 mg/g volatile suspended solids (VSS). Mechanism analysis showed that RL reduced WAS surface tension, which benefited transformations of organic sulfurs (e.g., aliphatic-S and sulfoxide) and inorganic sulfate from solid to liquid phase. The presence of RL not only reduced the ratio of α-helix/(β-sheet + random coil) and damaged the hydrogen bonding networks of organic sulfurs but also promoted substrate surface charges and cell membrane permeability. These facilitated the contact between hydrolase and organic sulfurs, thereby increasing sulfide production from organic sulfurs hydrolysis. Further investigations showed that RL promoted the expression of key genes (e.g., aprA/B and dsrA/B) involved in the dissimilatory sulfate reduction, which accelerated the reaction of adenosine 5'-phosphosulfate (APS)→ sulfite→ sulfide. Meanwhile, RL inhibited the corresponding key genes such as CysH, and Sir, responsible for assimilatory sulfate reduction (APS→3'-phosphoadenosine-5'phosphosulfate→organosulfur), which reduced substrate competition in favor of H₂S production from dissimilatory sulfate reduction. Besides, RL decreased the fermentation pH, which benefited the transformation of HS^- to H₂S.

Alpha-lipoic acid treatment improves adverse cardiac remodelling in the diabetic heart - The role of cardiac hydrogen sulfide-synthesizing enzymes

INTRODUCTION

Alpha-lipoic acid (ALA) is a licensed drug for the treatment of diabetic neuropathy. We recently reported that it also improves diabetic cardiomyopathy (DCM) in type 2 diabetes mellitus (T2DM). In this study, we present evidence supporting our hypothesis that the cardioprotective effect of ALA is via upregulation of cardiac hydrogen sulfide (H₂S)-synthesizing enzymes.

METHODS

Following 12 h of overnight fasting, T2DM was induced in 23 out of 30 male Sprague-Dawley rats by intraperitoneal administration of nicotinamide (110 mg/kg) followed by streptozotocin (55 mg/kg) while the rest served as healthy control (HC). T2DM rats then received either oral administration of ALA (60 mg/kg/day; n = 7) or 40 mg/kg/day DL-propargylglycine (PAG, an endogenous H₂S inhibitor; n = 7) intraperitoneally for 6 weeks after which all rats were sacrificed and samples collected for analysis. Untreated T2DM rats served as diabetic control (DCM; n = 9).

RESULTS

T2DM resulted in weight loss, islet destruction, reduced pancreatic β-cell function and hyperglycemia. Histologically, DCM rats showed significant myocardial damage evidenced by myocardial degeneration, cardiomyocyte vacuolation and apoptosis, cardiac fibrosis and inflammation, which positively correlated with elevated levels of cardiac damage markers compared to HC rats (p < 0.001). These pathological alterations worsened significantly in PAG-treated rats (p < 0.05). However, ALA treatment restored normoinsulemia, normoglycemia, prevented DCM, and improved lipid and antioxidant status. Mechanistically, ALA significantly upregulated the expression of cardiac H₂S-synthesizing enzymes and increased plasma H₂S concentration compared to DCM rats (p < 0.001).

CONCLUSION

ALA preserves myocardial integrity in T2DM likely by maintaining the expression of cardiac H₂S-synthezing enzymes and increasing plasma H₂S level.

Activation of renal CSE/H2S pathway by alpha-lipoic acid protects against histological and functional changes in the diabetic kidney

INTRODUCTION

We previously reported that alpha-lipoic acid (ALA) supplementation protects against progression of diabetic kidney disease (DKD). In this study, we aim to investigate whether the mechanism of renal protection by ALA involves renal cystathionine γ-lyase/hydrogen sulfide (CSE/H₂S) system in type 2 diabetes mellitus (T2DM).

METHODS

Thirty-seven male Sprague-Dawley rats underwent 12 h of overnight fasting. To induce T2DM, 30 of these rats received intraperitoneal administration of nicotinamide (110 mg/kg) and streptozotocin (55 mg/kg). T2DM rats then received either oral administration of ALA (60 mg/kg/day) or intraperitoneal administration of 40 mg/kg/day DL-propargylglycine (PAG, a CSE inhibitor) or both for 6 weeks after which rats were sacrificed and samples collected for analysis. Untreated diabetic and non-diabetic rats served as diabetic and healthy controls respectively.

RESULTS

T2DM was characterized by reduced pancreatic β-cell function and hyperglycemia. Histologically, untreated diabetic rats showed significantly damaged pancreatic islets, glomerular and tubular injury, with elevated levels of renal function markers compared to healthy control rats (p < 0.001). These pathological changes worsened significantly following PAG administration (p < 0.05). While some renal protection was observed in ALA+PAG rats, ALA administration in untreated diabetic rats provided superior protection comparable to healthy control rats, with improved antioxidant status, lipid profile and reduced inflammation. Mechanistically, ALA significantly activated renal CSE/H₂S system in diabetic rats, which was markedly suppressed in PAG-treated rats (p < 0.001).

CONCLUSION

Our data suggest that ALA protects against DKD development and progression by activating renal CSE/H₂S pathway. Hence, CSE/H₂S pathway may represent a therapeutic target in the treatment or prevention of DKD in diabetic patients.

Cysteine supplementation enhanced inhibitor tolerance of Zymomonas mobilis for economic lignocellulosic bioethanol production

Inhibitors in lignocellulosic hydrolysates are toxic to Zymomonas mobilis and reduce its bioethanol production. This study revealed cysteine supplementation enhanced furfural tolerance in Z. mobilis with a 2-fold biomass increase. Transcriptomic study illustrated that cysteine biosynthesis pathway was down-regulated while cysteine catabolism was up-regulated with cysteine supplementation. Mutants for genes involved in cysteine metabolism were constructed, and metabolites in cysteine metabolic pathway including methionine, glutathione, NaHS, glutamate, and pyruvate were supplemented into media. Cysteine supplementation boosted glutathione synthesis or H₂S release effectively in Z. mobilis leading to the reduced accumulation of reactive oxygen species (ROS) induced by furfural, while pyruvate and glutamate produced in the H₂S generation pathway promoted cell growth by serving as the carbon or nitrogen source. Finally, cysteine supplementation was confirmed to enhance Z. mobilis tolerance against ethanol, acetate, and corncob hydrolysate with an enhanced ethanol productivity from 0.38 to 0.55 g^-1∙L^-1∙h^-1.

Renal consequences of the novel coronavirus disease 2019 (COVID-19) and hydrogen sulfide as a potential therapy

The novel coronavirus disease 2019 (COVID-19), caused by SARS-CoV-2, is a global pandemic which is primarily considered a respiratory illness. However, emerging reports show that the virus exhibits both pulmonary and extra-pulmonary manifestations in humans, with the kidney as a major extra-pulmonary target due to its abundant expression of angiotensin-converting enzyme 2 and transmembrane protease serine 2, which facilitate entry of the virus into cells. Acute kidney injury has become prevalent in COVID-19 patients without prior any history of kidney dysfunction. In addition, the virus also worsens kidney conditions and increases mortality of COVID-19 patients with pre-existing chronic kidney disease, renal cancer, diabetic nephropathy, end-stage kidney disease as well as dialysis and kidney transplant patients. In the search for antiviral agents for the treatment of COVID-19, hydrogen sulfide (H₂S), the third established member of gasotransmitter family, is emerging as a potential candidate, possessing important therapeutic properties including antiviral, anti-inflammatory, anti-thrombotic and antioxidant properties. A recent clinical study revealed higher serum H₂S levels in survivors of COVID-19 pneumonia with reduced interleukin-6 levels compared to fatal cases. In this review, we summarize the global impact of COVID-19 on kidney conditions and discuss the emerging role of H₂S as a potential COVID-19 therapy.

H2S donor molecules against cold ischemia-reperfusion injury in preclinical models of solid organ transplantation

Cold ischemia-reperfusion injury (IRI) is an inevitable and unresolved problem that poses a great challenge in solid organ transplantation (SOT). It represents a major factor that increases acute tubular necrosis, decreases graft survival, and delays graft function. This complicates graft quality, post-transplant patient care and organ transplantation outcomes, and therefore undermines the success of SOT. Herein, we review recent advances in research regarding novel pharmacological strategies involving the use of different donor molecules of hydrogen sulfide (H₂S), the third established member of the gasotransmitter family, against cold IRI in different experimental models of SOT (kidney, heart, lung, liver, pancreas and intestine). Additionally, we discuss the molecular mechanisms underlying the effects of these H₂S donor molecules in SOT, and suggestions for clinical translation. Our reviewed findings showed that storage of donor organs in H₂S-supplemented preservation solution or administration of H₂S to organ donor prior to organ procurement and to recipient at the start and during reperfusion is a novel, simple and cost-effective pharmacological approach to minimize cold IRI, limit post-transplant complications and improve transplantation outcomes. In conclusion, experimental evidence demonstrate that H₂S donors can significantly mitigate cold IRI during SOT through inhibition of a complex cascade of interconnected cellular and molecular events involving microcirculatory disturbance and microvascular dysfunction, mitochondrial injury, inflammatory responses, cell damage and cell death, and other damaging molecular pathways while promoting protective pathways. Translating these promising findings from bench to bedside will lay the foundation for the use of H₂S donor molecules in clinical SOT in the future.

Alginate hydrogel containing hydrogen sulfide as the functional wound dressing material: In vitro and in vivo study

Functional and bioactive wound dressing materials are revolutionary for wound care and healing applications. In this concept, we fabricated alginate hydrogel (Alg) containing H₂S as the wound dressing materials and assessed the morphology, swelling, degradation, and release behavior, as well as the biocompatibility, cytocompatibility, and wound healing activity. The results depicted that the prepared hydrogels have a porous structure with the pore size in the range of 50 to 100 μm. Swelling and degradation studies showed that the hydrogel absorbed water about 179 ± 5% of initial dry weight during 96 h and loos about 80% of the initial dry weight after 7 days. The in vitro assessments illustrated that the optimum concentration of H₂S was 0.5% and the higher concentration induced hemolysis and cell toxicity. The in vivo study revealed that the treatment by Alg/H₂S 0.5% induced the highest wound closure percent with a value of 98 ± 1.22%. Moreover, the treatment by Alg/H₂S 0.5% elicited the formation of sebaceous glands, hair follicles, and complete epithelization without any fibroplasia or inflammation, revealed by the histopathological observations. Accordingly, these results illustrated that the prepared Alg/H₂S 0.5% could be applied as the functional and bioactive wound dressing materials.

Exogenous hydrogen sulfide donor NaHS alleviates nickel-induced epithelial-mesenchymal transition and the migration of A549 cells by regulating TGF-β1/Smad2/Smad3 signaling

Nickel compounds are known to be common environmental and occupational carcinogens which also promote the migration of lung cancer cells. However, the molecular mechanism yet remains to be clarified. Hydrogen sulfide (H₂S) is involved in cancer biological processes. However, the exact effect and functionality of H₂S on nickel, towards the promotion of the migration ability of lung cancer cells, remains to be unknown. In this study, we have found that the nickel chloride (NiCl₂) treatment significantly downregulates the protein levels of endogenous H₂S enzyme cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE) and 3-Mercaptopyruvate sulfurtransferase (3-MST). A correlation between NiCl₂-induced epithelial-mesenchymal transition (EMT) and the migration ability of lung cancer A549 cells has been observed. Exogenous H₂S donor, sodium hydrogen sulfide (NaHS) (100 μmol/L), can reverse NiCl₂-induced EMT as well as the migration ability of A549 cells. NiCl₂ treatment is able to upregulate the protein level of transforming growth factor-β1 (TGF-β1), p-Smad2, p-Smad3, p-JNK, p-ERK and p-P38 in a time-dependent fashion, indicating that both TGF-β1/Smad2/Smad3 and mitogen-activated protein kinase (MAPK) signaling cascades (a non-Smad pathway) may play essential roles in NiCl₂-dependent EMT as well as cell migration of human lung cancer cells. Furthermore, exogenous NaHS alleviates the NiCl₂-induced EMT and the migration ability of A549 cells only by regulating TGF-β1/Smad2/Smad3, rather than the MAPK, signaling pathway. These results indicate that the exogenous administration of NaHS might be a potential therapeutic strategy against nickel-induced lung cancer progression.

Hydrogen sulfide upregulates miR-16-5p targeting PiK3R1 and RAF1 to inhibit neutrophil extracellular trap formation in chickens

Hydrogen sulfide (H₂S) is a toxic air pollutant that causes immune damage. Recent studies have found that neutrophil extracellular trap (NET) formation is one way in which neutrophils exert immune functions. In addition, the formation of NETs is also related to thrombosis and autoimmune diseases. Recent studies have shown that miRNAs are involved in the regulation of a variety of pathophysiological processes. Here, we investigated the role of H₂S in regulating the formation of NETs by affecting miR-16-5p. Our study established an in vitro H₂S exposure model for neutrophils using phorbol-myristate-acetate (PMA) to induce NET formation. We observed the morphological changes of cells with scanning electron microscopy and fluorescence microscopy. Then, the content of extracellular DNA and the expression of MPO and NE in each group were detected. The results showed that H₂S inhibited the formation of NETs. The expression of miR-16-5p and its target genes PiK3R1 and RAF1 was then measured by qRT-PCR. H₂S upregulated miR-16-5p and inhibited expression of the target genes PiK3R1 and RAF1, and it subsequently inhibited the Pi3K/AKT and ERK pathways and decreased respiratory burst levels. Furthermore, H₂S attenuated inositol 1,4,5-trisphosphate receptor (IP3R)-mediated endoplasmic reticulum calcium outflow as well as autophagy caused by PMA. This study enriches H₂S immunotoxicity research and provides a possible solution for the treatment of NET-related diseases.

Hydrogen sulfide regulates circadian-clock genes in C2C12 myotubes and the muscle of high-fat-diet-fed mice

Hydrogen sulfide (H₂S) is an endogenous novel gasotransmitter which is implicated in the pathophysiology of the metabolic syndrome. Core clock genes (CCG) and its controlled genes disruption is implicated in the progression of metabolic syndrome. We examined whether H₂S has any effect on CCG in the skeletal muscle of mice fed a high-fat diet (HFD) and in myotubes. In the muscle of HFD-mice, the expression of H₂S biosynthesis enzyme genes (CSE, CBS, and 3-Mpst) along with antioxidant genes (GCLC, GCLM, GSS, and GSR) involved in GSH biosynthesis and recycling were reduced significantly, but the oxidative stress (OS) increased. Expression of the CCG (Bmal1, Clock, RORα, Cry2, Per2) and clock-controlled genes (PPARγ, PGC-1α, RXRα) was downregulated, whereas the levels of PPARα mRNA were upregulated. Similar to that in the muscle of HFD-mice, in vitro myotubes exposed to high glucose or palmitate to mimic metabolic syndrome, showed an increased OS and decreased in CSE mRNA, H₂S production and CCG mRNA levels were also downregulated. TNF and MCP-1 treatment on the myotubes was similar to that observed in HFD-muscle, with that the Rev-erbα mRNA was upregulated. Inhibition (siRNA/pharmacological inhibitors) of both CSE and GCLC (the rate-limiting enzyme in GSH biosynthesis) decreased H₂S, and increased OS; Bmal1 and Clock mRNA levels were downregulated, while Rev-erbα increased significantly in these conditions. CSE KD myotubes were post-treated with an H₂S donor partially restored the mRNA levels of core clock genes. These findings report that the deficiencies of H₂S/GSH impair expression of CCG and treatment with H₂S donor or GSH precursor exert a positive effect over CCG. Thus, suggest that H₂S as a new endogenous factor for regulating circadian clock, and its donors could provide a novel chrono-pharmacological therapy to manage metabolic disorders.

Impact of a high ammonia-ammonium-pH system on methane-producing archaea and sulfate-reducing bacteria in mesophilic anaerobic digestion

A novel strategy for acclimation to ammonia stress was implemented by stimulating a high ammonia-ammonium-pH environment in a high-solid anaerobic digestion (AD) system in this study. Three semi-continuously stirred anaerobic reactors performed well over the whole study period under mesophilic conditions, especially in experimental group (R-2) when accommodated from acclimation period which the maximum total ammonia nitrogen (TAN) and free ammonia nitrogen (FAN) increased to 4921 and 2996mg/L, respectively. Moreover, when it accommodated the high ammonia-ammonium-pH system, the daily biogas production and methane content were similar to those in R-1 (the blank control to R-2), but the hydrogen sulfide (H₂S) content lower than the blank control. Moreover, mechanistic studies showed that high ammonia stress enhanced the activity of coenzyme F₄₂₀. The results of real-time fluorescent quantitative polymerase chain reaction (PCR) showed that ammonia stress decreased the abundance of sulfate-reducing bacteria and increased the abundance of methane-producing archaea.

The smell of renal protection against chronic kidney disease: Hydrogen sulfide offers a potential stinky remedy

Chronic kidney disease (CKD) is a common global health challenge characterized by irreversible pathological processes that reduce kidney function and culminates in development of end-stage renal disease. It is associated with increased morbidity and mortality in addition to increased caregiver burden and higher financial cost. A central player in CKD pathogenesis and progression is renal hypoxia. Renal hypoxia stimulates induction of oxidative and endoplasmic reticulum stress, inflammation and tubulointerstitial fibrosis, which in turn, promote cellular susceptibility and further aggravate hypoxia, thus forming a pathological vicious cycle in CKD progression. Although the importance of CKD is widely appreciated, including improvements in the quality of existing therapies such as dialysis and transplantation, new therapeutic options are limited, as there is still increased morbidity, mortality and poor quality of life among CKD patients. Growing evidence indicates that hydrogen sulfide (H₂S), a small gaseous signaling molecule with an obnoxious smell, accumulates in the renal medulla under hypoxic conditions, and functions as an oxygen sensor that restores oxygen balance and increases medullary flow. Moreover, plasma H₂S level has been recently reported to be markedly reduced in CKD patients and animal models. Also, H₂S has been established to possess potent antioxidant, anti-inflammatory, and anti-fibrotic properties in several experimental models of kidney diseases, suggesting that its supplementation could protect against CKD and retard its progression. The purpose of this review is to discuss current clinical and experimental developments regarding CKD, its pathophysiology, and potential cellular and molecular mechanisms of protection by H₂S in experimental models of CKD.

H2S as a possible therapeutic alternative for the treatment of hypertensive kidney injury

Hypertension is the most common cause of cardiovascular morbidities and mortalities, and a major risk factor for renal dysfunction. It is considered one of the causes of chronic kidney disease, which progresses into end-stage renal disease and eventually loss of renal function. Yet, the mechanism underlying the pathogenesis of hypertension and its associated kidney injury is still poorly understood. Moreover, despite existing antihypertensive therapies, achievement of blood pressure control and preservation of renal function still remain a worldwide public health challenge in a subset of hypertensive patients. Therefore, novel modes of intervention are in demand. Hydrogen sulfide (H₂S), a gaseous signaling molecule, has been established to possess antihypertensive and renoprotective properties, which may represent an important therapeutic alternative for the treatment of hypertension and kidney injury. This review discusses recent findings about H₂S in hypertension and kidney injury from both experimental and clinical studies. It also addresses future direction regarding therapeutic use of H₂S.

Diabetic nephropathy: A potential savior with 'rotten-egg' smell

Diabetic nephropathy (DN) is currently the leading cause of end-stage renal disease. Despite optimal management, DN is still a major contributor to morbidity and mortality of diabetic patients worldwide. The major pathological alterations in DN include excessive accumulation and deposition of extracellular matrix, leading to expansion of mesangial matrix, thickening of glomerular basement membrane and tubulointerstitial fibrosis. At the molecular level, accumulating evidence suggests that hyperglycemia or high glucose mediates renal injury in DN via multiple molecular mechanisms such as induction of oxidative stress, upregulation of renal transforming growth factor beta-1 expression, production of proinflammatory cytokines, activation of fibroblasts and renin angiotensin system, and depletion of adenosine triphosphate. Also worrying is the fact that existing therapies only retard the disease progression but do not prevent it. Therefore, there is urgent need to identify novel therapies to target additional disease mechanisms. Hydrogen sulfide (H₂S), the third member of the gasotransmitter family, has recently been identified and demonstrated to possess important therapeutic characteristics that prevent the development and progression of DN in experimental animals by targeting several important molecular pathways, and therefore may represent an alternative or additional therapeutic approach for DN. This review discusses recent experimental findings on the molecular mechanisms underlying the therapeutic effects of H₂S against the development and progression of DN and its clinical application in the future.

Targeting the transsulfuration-H2S pathway by FXR and GPBAR1 ligands in the treatment of portal hypertension

Cirrhosis is a end-stage disease of the liver in which fibrogenesis, angiogenesis and distortion of intrahepatic microcirculation lead to increased intrahepatic resistance to portal blood flow, a condition known as portal hypertension. Portal hypertension is maintained by a variety of molecular mechanisms including sinusoidal endothelial cells (LSECs) hyporeactivity, activation of hepatic stellate cells (HSCs), reduction in hepatic endothelial nitric oxide synthase (eNOS) activity along with increased eNOS-derived NO generation in the splanchnic and systemic circulations. A reduction of the expression/function of the two major hydrogen sulfide (H2S)-producing enzymes, cystathionine γ-lyase (CSE) and cystathionine β-synthase (CBS), has also been demonstrated. A deficit in the transsulfuration pathway leading to the accumulation of homocysteine might contribute to defective generation of H2S and endothelial hyporeactivity. Bile acids are ligands for nuclear receptors, such as farnesoid X receptor (FXR), and G-protein-coupled receptors (GPCRs), such as the G-protein bile acid receptor 1 (GPBAR1). FXR and GPBAR1 ligands regulate the expression/activity of CSE by both genomic and non-genomic effects and have been proved effective in protecting against endothelial dysfunction observed in rodent models of cirrhosis. GPBAR1, a receptor for secondary bile acids, is selectively expressed by LSECs and its activation increases the expression of CSE and attenuates the production of endotelin-1, a potent vasoconstrictor agent. In vivo GPBAR1 ligand attenuates the imbalance between vasodilatory and vaso-constricting agents, making GPBAR1 a promising target in the treatment of portal hypertension.

Hydrogen sulfide: A novel nephroprotectant against cisplatin-induced renal toxicity

Cisplatin is a potent chemotherapeutic agent for the treatment of various solid-organ cancers. However, a plethora of evidence indicates that nephrotoxicity is a major side effect of cisplatin therapy. While the antineoplastic action of cisplatin is due to formation of cisplatin-DNA cross-links, which damage rapidly dividing cancer cells upon binding to DNA, its nephrotoxic effect results from metabolic conversion of cisplatin into a nephrotoxin and production of reactive oxygen species, causing oxidative stress leading to renal tissue injury and potentially, kidney failure. Despite therapeutic targets in several pre-clinical and clinical studies, there is still incomplete protection against cisplatin-induced nephrotoxicity. Hydrogen sulfide (H2S), the third discovered gasotransmitter next to nitric oxide and carbon monoxide, has recently been identified in several in vitro and in vivo studies to possess specific antioxidant, anti-inflammatory and anti-apoptotic properties that modulate several pathogenic pathways involved in cisplatin-induced nephrotoxicity. The current article reviews the molecular mechanisms underlying cisplatin-induced nephrotoxicity and displays recent findings in the H2S field that could disrupt such mechanisms to ameliorate cisplatin-induced renal injury.

Hydrogen sulfide (H2S) attenuates uranium-induced acute nephrotoxicity through oxidative stress and inflammatory response via Nrf2-NF-κB pathways

As an endogenous gaseous mediator, H2S exerts anti-oxidative, anti-inflammatory and cytoprotective effects in kidneys. This study was designed to investigate the protective effect of H2S against uranium-induced nephrotoxicity in adult SD male rats after in vivo effect of uranium on endogenous H2S formation was explored in kidneys. The levels of endogenous H2S and H2S-producing enzymes (CBS and CSE) were measured in renal homogenates from rats intoxicated by an intraperitoneally (i.p.) injection of uranyl acetate at a single dose of 2.5, 5 or 10 mg/kg. In rats injected i.p. with uranyl acetate (5 mg/kg) or NaHS (an H2S donor, 28 or 56 μmol/kg) alone or in combination, we determined biochemical parameters and histopathological alteration to assess kidney function, examined oxidative stress markers, and investigated Nrf2 and NF-κB pathways in kidney homogenates. The results suggest that uranium intoxication in rats decreased endogenous H2S generation as well as CBS and CSE protein expression. NaHS administration in uranium-intoxicated rats ameliorated the renal biochemical indices and histopathological effects, lowered MDA accumulation, and restored GSH level and anti-oxidative enzymes activities like SOD, CAT, GPx and GST. NaHS treatment in uranium-intoxicated rats activated uranium-inhibited protein expression and nuclear translocation of transcription factor Nrf2, which increased protein expression of downstream target-Nrf2 genes HO-1, NQO-1, GCLC, and TXNRD-1. NaHS administration in uranium-intoxicated rats inhibited uranium-induced nuclear translocation and phosphorylation of transcription factor κB/p65, which decreased protein expression of target-p65 inflammatory genes TNF-α, iNOS, and COX-2. Taken together, these data implicate that H2S can afford protection to rat kidneys against uranium-induced adverse effects through induction of antioxidant defense by activating Nrf2 pathway and reduction of inflammatory response by suppressing NF-κB pathway.

Diallyl trisulfide protects against high glucose-induced cardiac apoptosis by stimulating the production of cystathionine gamma-lyase-derived hydrogen sulfide

BACKGROUND

Cystathionine-γ-lyase (CSE)-derived hydrogen sulfide (H2S) is a potent cardioprotective agent. We investigated the effects of diallyl trisulfide (DATS) on CSE expression and H2S generation in myocardium and examined whether DATS-mediated H2S generation effectively protects rat heart from diabetes-induced cardiac damage.

METHODS

The correlations between the effects of hyperglycemia and diabetes on CSE expression and the effects of DATS and H2S on hyperglycemia and diabetes were examined in vitro in the cardiomyocyte cell line H9c2 and in vivo in hearts from rats with streptozotocin-induced diabetes mellitus (DM).

RESULTS

Expression of CSE, a catalyst of H2S production, was suppressed in H9c2 cells treated with high glucose (33 mM) and in DM rat hearts. CSE suppression also correlated with a decrease in the activation of the pro-survival protein kinase Akt. Treatment of H9c2 cells with DATS resulted in increased CSE expression and a reduction in apoptosis via a mechanism involving IGF1R/pAkt signaling and by modulating the expression of reactive oxygen species-related enzymes. The role CSE plays in the cardioprotective effects of DATS was further confirmed by CSE inhibition assays including inhibitors and siRNA.

CONCLUSION

DATS produces H2S as efficiently as NaSH and DATS-derived H2S provides effective cardioprotection. Further, our data indicate that H2S plays a major role in the protective effect of DATS against apoptosis of cardiomyocytes.

The immunomodulation of inducible hydrogen sulfide in Pacific oyster Crassostrea gigas

Hydrogen sulfide (H2S) is an important gasotransmitter, which plays indispensable roles in cardiovascular, nervous and immune systems of vertebrates. However, the information about the immunomodulation of H2S in invertebrates is still very limited. In the present study, the temporal expression profile of cystathionine γ lyase in oyster Crassostrea gigas (CgCSE) was investigated after the oysters were stimulated by lipopolysaccharide. The expression levels of CgCSE mRNA transcripts in hemocytes increased significantly at 12h (1.31-fold of the PBS group, P<0.05) after LPS stimulation. The immunomodulation of inducible H2S in oyster was examined by monitoring the alterations of both cellular and humoral immune parameters in response to the stimulations of LPS, LPS+Na2S and LPS+propargylglycine (PAG). The total hemocyte counts (THC) and hemolymph PO activity increased significantly after LPS stimulation, and the increase could be further enhanced by adding PAG, while inhibited by appending Na2S. The phagocytosis activity of hemocytes was also increased firstly after LPS treatment, and the increase was enhanced by adding Na2S but inhibited after appending PAG. The anti-bacterial activity in hemolymph increased at 3h post LPS treatment, and then decreased after adding PAG. The total SOD activity of hemolymph was also elevated at 6h post LPS treatment, and the elevated activity was depressed by adding Na2S. These results collectively indicated that H2S might play crucial roles in the immune response of oyster via modulating the turnover and phagocytosis of hemocytes, and regulating the anti-bacterial activity and proPO activation in the hemolymph.