A 'Frugal' EGFET Sensor for Waterborne H2S

Hydrogen sulphide (H2S) is a toxic gas soluble in water, H2Saq, as a weak acid. Since H2Saq usually originates from the decomposition of faecal matter, its presence also indicates sewage dumping and possible parallel waterborne pathogens associated with sewage. We here present a low footprint ('frugal') H2Saq sensor as an accessible resource for water quality monitoring. As a sensing mechanism, we find the chemical affinity of thiols to gold (Au) translates to H2Saq. When an Au electrode is used as a control gate (CG) or floating gate (FG) electrode in the electric double layer (EDL) pool of an extended gate field effect transistor (EGFET) sensor, EGFET transfer characteristics shift along the CG voltage axis in response to H2Saq. We rationalise this by the interface potential from the adsorption of polar H2S molecules to the electrode. The sign of the shift changes between Au CG and Au FG, and cancels when both electrodes are Au. The sensor is selective for H2Saq over the components of urine, nor does urine suppress the sensor's ability to detect H2Saq. Electrodes can be recovered for repeated use by washing in 1M HCl. Quantitatively, CG voltage shift is fitted by a Langmuir-Freundlich (LF) model, supporting dipole adsorption over an ionic (Nernstian) response mechanism. We find a limit-of-detection of 14.9 nM, 100 times below potability.

Endogenous hydrogen sulphide deficiency and exogenous hydrogen sulphide supplement regulate skin fibroblasts proliferation via necroptosis

An excessive proliferation of skin fibroblasts usually results in different skin fibrotic diseases. Hydrogen sulphide (H2 S) is regarded as an important endogenous gasotransmitter with various functions. The study aimed to investigate the roles and mechanisms of H2 S on primary mice skin fibroblasts proliferation. Cell proliferation and collagen synthesis were assessed with the expression of α-smooth muscle actin (α-SMA), proliferating cell nuclear antigen (PCNA), Collagen I and Collagen III. The degree of oxidative stress was evaluated by dihydroethidium (DHE) and MitoSOX staining. Mitochondrial membrane potential (ΔΨm) was detected by JC-1 staining. Necroptosis was evaluated with TDT-mediated dUTP nick end labelling (TUNEL) and expression of receptor-interacting protein kinase 1 (RIPK1), RIPK3 and mixed lineage kinase domain-like protein (MLKL). The present study found that α-SMA, PCNA, Collagen I and Collagen III expression were increased, oxidative stress was promoted, ΔΨm was impaired and positive rate of TUNEL staining, RIPK1 and RIPK3 expression as well as MLKL phosphorylation were all enhanced in skin fibroblasts from cystathionine γ-lyase (CSE) knockout (KO) mice or transforming growth factor-β1 (TGF-β1, 10 ng/mL)-stimulated mice skin fibroblasts, which was restored by exogenous sodium hydrosulphide (NaHS, 50 μmol/L). In conclusion, endogenous H2 S production impairment in CSE-deficient mice accelerated skin fibroblasts proliferation via promoted necroptosis, which was attenuated by exogenous H2 S. Exogenous H2 S supplement alleviated proliferation of skin fibroblasts with TGF-β1 stimulation via necroptosis inhibition. This study provides evidence for H2 S as a candidate agent to prevent and treat skin fibrotic diseases.

Effect of increased temperature and leachate recirculation on biogas production and settlement of municipal solid waste

This study evaluated the effects of increased temperature and leachate recirculation on volatile solids (VS), biogas, hydrogen sulphide (H₂S) leachate quality (pH and chemical oxygen demand) and the settlement of municipal solid waste (MSW). Three large-scale tests were conducted with no leachate recirculation at 21°C, weekly leachate recirculation at 20°C and weekly leachate recirculation at 50°C. Leachate recirculation and increased temperature accelerated biodegradation and pushed forward the onset time (from 27 to 8 days). The increase of biodegradation activity was reflected in the change of biogas production, VS and settlement. Compressibility index Cc, increased from 0.71 and 0.77 at 21°C to 0.83 when the temperature was 50°C. In addition, leachate recirculation and high temperature reduced H₂S concentration levels by inhibiting the growth of sulphate-reducing bacteria and leachate recirculation lowered H₂S production by dissolving the high H₂S presence. The results showed that MSW can have significantly changed mechanical and biochemical behaviour under different temperatures and saturations. The results help understand the processes in landfills for more effective short-term and long-term design and management.

Fatal sequelae of hydrogen sulphide poisoning

Hydrogen sulphide (H₂S) is a toxic, colourless gas abundantly present at waste plants and sewers due to the presence of anaerobic forming organisms. Hazardous exposure via accidental, intentional or occupational contact results in endothelium disruption, cellular instability, decreased respiratory functional capacity and cardiovascular compromise with a rapidly fatal clinical course. Clinical manifestations are variable depending on the level of exposure with moderate or heavy exposure associated with rapid fatality. Respiratory manifestations remain the primary reason for admission to critical care facilities. We describe a case of a 30-year-old sewer worker with a history of heavy accidental occupational exposure of inhaled H₂S admitted with acute respiratory distress syndrome and a rapid respiratory decline ultimately leading to death.

Wastewater Treatment Plants as a Source of Malodorous Substances Hazardous to Health, Including a Case Study from Poland

Using Poland as an example, it was shown that 41.6% of the requests for intervention in 2016-2021 by Environmental Protection Inspections were related to odour nuisance. Further analysis of the statistical data confirmed that approximately 5.4% of wastewater treatment plants in the group of municipal facilities were subject to complaints. Detailed identification of the subject of odour nuisance at wastewater treatment plants identified hydrogen sulphide (H₂S), ammonia (NH₃) and volatile organic compounds (VOCs) as the most common malodorous substances within these facilities. Moreover, the concentrations of hydrogen sulphide and ammonia exceed the reference values for some substances in the air (0.02 mg/m³ for H₂S and 0.4 mg/m³ for NH₃). A thorough assessment of the properties of these substances made it clear that even in small concentrations they have a negative impact on the human body and the environment, and their degree of nuisance is described as high. In the two WWTPs analysed in Poland (WWTP 1 and WWTP 2), hydrogen sulphide concentrations were in the range of 0-41.86 mg/m³ (Long-Term Exposure Limit for H₂S is 7.0 mg/m³), ammonia 0-1.43 mg/m³ and VOCs 0.60-134.79 ppm. The values recognised for H₂S cause lacrimation, coughing, olfactory impairment, psychomotor agitation, and swelling of the cornea with photophobia. Recognition of the methods used in practice at WWTPs to reduce and control malodorous emissions indicates the possibility of protecting the environment and human health, but these solutions are ignored in most facilities due to the lack of requirements specified in legislation.

Hydrogen Sulphide Alleviates Senescence of Human Periodontal Ligament Stem Cells by TRPV4 Channel Mediated Calcium Flux

OBJECTIVE

To explore whether hydrogen sulphide (H2S) could protect human periodontal ligament stem cells (PDLSCs) from senescence and the possible underlying mechanisms.

METHODS

Cell cycle assay and Ki-67 assay were used to measure proliferation of PDLSCs. Real-time polymerase chain reaction (PCR) was used to measure cellular senescence-related p16 and p21. Calcium influx was detected by measurement of Ca2+ imaging. In addition, we analysed the possible mechanisms underlying H2S acting on PDLSCs by microarray.

RESULTS

The cell proliferation rate of aging PDLSCs decreased significantly. The expression of cellular senescence-related p16 and p21 significantly increased in aging PDLSCs. H2S donor (GYY4137) treatment increased the proliferation rate of senescence PDLSCs. Furthermore, the donor of H2S treatment effectively prevented cell cycle arrest of PDLSCs during the aging process and inhibited the expression of cellular senescence-related markers. Mechanically, H2S donor treatment could activate the calcium influx in PDLSCs. Moreover, pretreatment with TRPV4 inhibitors significantly attenuated the calcium influx induced by H2S donor treatment in PDLSCs. It also alleviated the protective effect of H2S on the senescence of PDLSCs.

CONCLUSION

H2S alleviated the senescence of human PDLSCs by TRPV4 channel mediated calcium flux. These results provide a potential strategy to deal with cell aging and may facilitate cell therapy for oral diseases.

H2 O2 , NO, and H2 S networks during root development and signalling under physiological and challenging environments: Beneficial or toxic?

Hydrogen peroxide (H₂ O₂ ) is a reactive oxygen species (ROS) and a key modulator of the development and architecture of the root system under physiological and adverse environmental conditions. Nitric oxide (NO) and hydrogen sulphide (H₂ S) also exert myriad functions on plant development and signalling. Accumulating pieces of evidence show that depending upon the dose and mode of applications, NO and H₂ S can have synergistic or antagonistic actions in mediating H₂ O₂ signalling during root development. Thus, H₂ O₂ -NO-H₂ S crosstalk might essentially impart tolerance to elude oxidative stress in roots. Growth and proliferation of root apex involve crucial orchestration of NO and H₂ S-mediated ROS signalling which also comprise other components including mitogen-activated protein kinase, cyclins, cyclin-dependent kinases, respiratory burst oxidase homolog (RBOH), and Ca²⁺ flux. This assessment provides a comprehensive update on the cooperative roles of NO and H₂ S in modulating H₂ O₂ homoeostasis during root development, abiotic stress tolerance, and root-microbe interaction. Furthermore, it also analyses the scopes of some fascinating future investigations associated with strigolactone and karrikins concerning H₂ O₂ -NO-H₂ S crosstalk in plant roots.

Adsorption-Desorption Behavior of Hydrogen Sulfide Capture on a Modified Activated Carbon Surface

Metal-based adsorbents with varying active phase loadings were synthesized to capture hydrogen sulfide (H₂S) from a biogas mimic system. The adsorption-desorption cycles were implemented to ascertain the H₂S captured. All prepared adsorbents were evaluated by nitrogen adsorption, Brunauer-Emmett-Teller surface area analysis, scanning electron microscopy-energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. From the results, modified adsorbents, dual chemical mixture (DCM) and a core-shell (CS) had the highest H₂S adsorption performance with a range of 0.92-1.80 mg H₂S/g. After several cycles of heat/N₂ regeneration, the total H₂S adsorption capacity of the DCM adsorbent decreased by 62.1%, whereas the CS adsorbent decreased by only 25%. Meanwhile, the proposed behavioral model for H₂S adsorption-desorption was validated effectively using various analyses throughout the three cycles of adsorption-desorption samples. Moreover, as in this case, the ZnAc₂/ZnO/CAC_OS adsorbents show outstanding performances with 30 cycles of adsorption-desorption compared to only 12 cycles of ZnAc₂/ZnO/CAC_DCM. Thus, this research paper will provide fresh insights into adsorption-desorption behavior through the best adsorbents' development and the adsorbents' capability at the highest number of adsorption-desorption cycles.

Deaths due to hydrogen sulphide on a jack up rig at Bombay High: an avoidable accident

An enclosed space is an area with poor or no natural ventilation which is not designed for continuous occupancy, where access is limited and which may contain a dangerous atmosphere. Enclosed space atmospheres can be hazardous due to one or a combination of the conditions which includes oxygen deficiency; presence of toxic and/or flammable gases. When it is intended that personnel should enter or work in an enclosed space, care should be taken to create and maintain safe working conditions. The case report describes an incident on board an oil rig where the rig workers were exposed to noxious gases resulting in multiple fatalities. Work involved gas sampling/monitoring at various locations inside the "spud tanks" of the rig and certifying it free of noxious gases for marine surveyor's inspection. Contributory factors that have been frequently identified following enclosed space accident investigations are non-compliance with procedures, inappropriate equipment, poor supervision, complacency and over familiarity leading to short cuts being taken, detection and monitoring equipment not used or not working properly and improper action in an emergency. Preventive measures to avoid such accidents and create a safe working area are discussed.

Sulphide donors affect the expression of mucin and sulphide detoxification genes in the mucosal organs of Atlantic salmon (Salmo salar)

Hydrogen sulphide (H₂S) is a gas that affects mucosal functions in mammals. However, its detrimental effects are less understood in fish despite being known to cause mass mortality. Here we used explant models to demonstrate the transcriptional responses of Atlantic salmon (Salmo salar) mucosa to the sulphide donor sodium hydrosulphide (NaHS). The study focused on two groups of genes: those encoding for sulphide detoxification and those for mucins. Moreover, we performed pharmacological studies by exposing the organ explants to mucus-interfering compounds and consequently exposed them to a sulphide donor. Exposure to NaHS significantly affected the expression of sulphide:quinone oxidoreductase (sqor1, sqor2) and mucin-encoding genes (muc5ac, muc5b). The general profile indicated that NaHS upregulated the expression of sulphide detoxification genes while a significant downregulation was observed with mucins. These expression profiles were seen in both organ explant models. Pharmacological stimulation and inhibition of mucus production used acetylcholine (ACh) and niflumic acid (NFA), respectively. This led to a significant regulation of the two groups of marker genes in the gills and olfactory rosette explants. Treatment of the mucosal organ explants with the mucus-interfering compounds showed that low dose NFA triggered more substantial changes while a dose-dependent response could not be established with ACh. Pharmacological interference demonstrated that mucins played a crucial role in mucosal protection against H₂S toxicity. These results offer insights into how a sulphide donor interfered with mucosal responses of Atlantic salmon and are expected to contribute to our understanding of the least explored H₂S-fish interactions-particularly at the mucosa.

Exercise restores endogenous H2 S synthesis and mitochondrial function in the heart of old rats

BACKGROUND

Ageing is accompanied by a decrease in endogenous hydrogen sulphide (H₂ S) synthesis and the development of mitochondrial dysfunction. The aim of our work was to study the possible participation of exercise training-induced regulation of endogenous H₂ S production in the restoration of mitochondrial function in old rats.

MATERIALS AND METHODS

Male rats were divided into three groups: adult, old and exercise-trained old. Exercise training of old rats was performed for 4 weeks. The mRNA expression cystathionine-γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST) were determined using reverse transcription and real-time polymerase chain reaction analysis. Mitochondrial dysfunction was determined by mPTP opening, which was investigated by spectrophotometric registration of the swelling of mitochondria isolated from the rat heart. We also studied the effect of exercise on H₂ S content, oxidative stress and mtNOS activity.

RESULTS

Exercise training in old animals significantly increased the expression of H₂ S-synthesizing enzymes CSE and 3-MST and restored endogenous H₂ S production in cardiac tissue and cardiac mitochondria to levels of adult animals. In addition, the training significantly reduced oxidative stress in old rats, in particular the rate of formation of •O₂ ^- and H₂ O₂ , diene conjugates and malondialdehyde levels in the mitochondria of the heart. Simultaneously, in the hearts of these animals, resistance of mPTP to the inducer of its opening of calcium ions was increased.

CONCLUSIONS

Thus, exercise training restores endogenous H₂ S production, and significantly reduces oxidative stress in cardiac mitochondria of old rats that are associated with the inhibition of calcium-induced mPTP opening as an indicator of mitochondrial dysfunction.

Relaxation mechanisms of chloroform root extracts of Prangos heyniae and Prangos uechtritzii on mouse corpus cavernosum

Erectile dysfunction (ED) is the inability to achieve/maintain an erection. Because of the side effects, interactions, or ineffectiveness of currently used drugs, novel drug discovery studies are ongoing. The roots of Turkish endemic plants Prangos uechtritzii and Prangos heyniae are traditionally used as aphrodisiacs in Anatolia and contain coumarin-like relaxant compounds. This study aims to reveal the relaxant effect mechanisms of chloroform root extracts of P. heyniae (Ph-CE) and P. uechtritzii (Pu-CE). Isolated organ bath experiments were performed on Swiss albino mouse corpus cavernosum by DMT strip myograph. Relaxant responses to extract (10-7 -10-4  g/ml) were obtained in the presence/absence of NO and H2 S synthesis inhibitors nitro-l-arginine methyl ester (l-NAME, 100 μM) and aminooxyacetic acid (AOAA, 10 mM) respectively. Sodium nitroprusside (SNP, 10-9 to 10-4  M) and Na2 S (10-6 to 3 × 10-3  M)-induced relaxations and CaCl2 (10-6 to 10-4  M), KCl (10-2.1 to 10-0.9  M) and phenylephrine (3 × 10-8 to 3 × 10-5  M)-induced contractions were taken in the presence/absence of the extracts (10-4  g/ml). Relaxations induced by Ph-CE but not by Pu-CE were inhibited in the presence of l-NAME and AOAA. Ph-CE increased Na2 S- and SNP-induced relaxations. Ph-CE and Pu-CE decreased the contractions of KCl, phenylephrine, and CaCl2 . It was concluded that NO and H2 S synthesis/downstream mechanisms play roles in relaxations of Ph-CE but not in Pu-CE-induced relaxations. Inhibition of calcium influx appears to be involved in the relaxant effect of Ph-CE and Pu-CE. Since the extracts act directly by relaxing smooth muscle or through H2 S as well as NO, they may be a potential therapeutic agent in diseases such as ED where the bioavailability of NO is impaired.

Prophylactic Treatment with Hydrogen Sulphide Can Prevent Renal Ischemia-Reperfusion Injury in L-NAME Induced Hypertensive Rats with Cisplatin-Induced Acute Renal Failure

(Background and Objectives): Renal ischemia perfusion injury is one of the major issues in kidney transplant. The aim of the study was to investigate the hypothesis that prophylactic treatment-with a hydrogen sulphide donor to an acute renal failure case of hypertensive rats-can minimize the ischemia reperfusion injury of the kidney which is beneficial for kidney transplant. To check this hypothesis, the present study was designed to investigate the effect of chronic administration of a hydrogen sulphide (H2S) donor and sodium hydrosulfide (NaHS) on nuclear factor kappa B (NF-kB) and inter cellular adhesion molecule-1 (ICAM-1) concentration in non-renal failure (NRF) and acute renal failure (ARF) rats in the ischemia-reperfusion injury (IRI) model of the kidney in both normotensive WKY and hypertensive rats (L-nitro arginine methyl ester (L-NAME-induced); (Materials and Methods): A total number of 48 Sprague-Dawley rats were recruited into eight groups each consisting of six animals. Each of these eight groups was used to measure systemic and renal parameters, H2S, antioxidant parameters in plasma, plasma concentration of NF-kB and ICAM-1 and renal cortical blood pressure. ARF was induced by single intraperitoneal (i.p.) cisplatin injection (5 mg/kg). Hypertension was induced by oral administration of L-NAME in drinking water for four weeks at 40 mg/kg/day. NaHS was administered (i.p) at 56 µmol/kg for five weeks while dL-propargylglycine (PAG), a H2S generation inhibitor, was administered as a single intra-peritoneal injection (50 mg/kg). An acute surgical experiment was performed for the induction of renal ischemia for 30 min by renal artery clamping followed by reperfusion for three hours; (Results): Chronic administration of NaHS attenuated the severity of ARF in both normotensive and hypertensive animals (L-NAME) along with lowering the blood pressure in hypertensive groups. NaHS improved the oxidative stress parameters such as total superoxide dismutase (T-SOD), glutathione (GSH) and reduced the malondialdehyde (MDA) concentration along with reduction of NF-kB and ICAM-1 following renal IRI; Conclusions: These findings demonstrate that H2S not only reduced the severity of cisplatin induced ARF but also reduced the severity of renal IRI by upregulating antioxidants along with decreased concentrations of NF-kB and ICAM-1 in normotensive and L-NAME induced hypertensive rats.

Hydrogen sulfide protects against ischemic heart failure by inhibiting RIP1/RIP3/MLKL-mediated necroptosis

The aim of the present study was to explore whether hydrogen sulfide (H2S) protects against ischemic heart failure (HF) by inhibiting the necroptosis pathway. Mice were randomized into Sham, myocardial infarction (MI), MI + propargylglycine (PAG) and MI + sodium hydrosulfide (NaHS) group, respectively. The MI model was induced by ligating the left anterior descending coronary artery. PAG was intraperitoneally administered at a dose of 50 mg/kg/day for 4 weeks, and NaHS at a dose of 4 mg/kg/day for the same period. At 4 weeks after MI, the following were observed: A significant decrease in the cardiac function, as evidenced by a decline in ejection fraction (EF) and fractional shortening (FS); an increase in plasma myocardial injury markers, such as creatine kinase-MB (CK-MB) and cardiac troponin I (cTNI); an increase in myocardial collagen content in the heart tissues; and a decrease of H2S level in plasma and heart tissues. Furthermore, the expression levels of necroptosis-related markers such as receptor interacting protein kinase 1 (RIP1), RIP3 and mixed lineage kinase domain-like protein (MLKL) were upregulated after MI. NaHS treatment increased H2S levels in plasma and heart tissues, preserving the cardiac function by increasing EF and FS, decreasing plasma CK-MB and cTNI and reducing collagen content. Additionally, NaHS treatment significantly downregulated the RIP1/RIP3/MLKL pathway. While, PAG treatment aggravated cardiac function by activated the RIP1/RIP3/MLKL pathway. Overall, the present study concluded that H2S protected against ischemic HF by inhibiting RIP1/RIP3/MLKL-mediated necroptosis which could be a potential target treatment for ischemic HF.

Sewer gas poisoning causing transient and focal ST-segment elevation in the ECG: Case report

In India, a large number of sanitary care workers are involved in manual scavenging. This exposes them to sewer gas mainly consisting of hydrogen sulphide. Sewer gas toxicity primarily causes neurological injury, followed by cardiac and respiratory involvement. A few cases of diffuse ST-segment elevation in the electrocardiogram (ECG) following hydrogen sulphide poisoning are known in the literature. Here, we report a case of acute sewer gas poisoning in a 45-year-old man with transient and focal ST-segment elevation in the anteroseptal leads of the ECG mimicking acute anterior wall myocardial infarction.

Risk Characteristics of Hydrogen Sulphide Exposure in Wastewater Collection and Treatment Related Occupations

OBJECTIVES

Water and wastewater workers can be exposed to hydrogen sulphide (H2S), with an unpredictable exposure pattern, dominated by sharp peaks. These peaks can often be high above the ceiling value (CV) at 10 ppm.

METHODS

We have analyzed self-administrated H2S exposure data among 60 wastewater workers in the Municipality of Trondheim, Norway, from 2015 till 2021. The detection range of the personal alarm equipment used was 1.6 to 100 ppm H2S. The workers were divided in four similar exposed groups (SEGs): wastewater collection net, wastewater treatment plants, wastewater pumping stations and water distribution net.

RESULTS

We identified measurements from 7083 different workdays, approximately 10% of the workdays between 2015 and 2021. Within these, 1295 days had readings above 1.6 ppm H2S, and 424 (33%) of these days had readings that exceeded the CV of 10 ppm H2S. This percentage was similar across the SEGs. Only one workday had a time weighted average (TWA) exceeding the occupational exposure limit (OEL) of 5 ppm H2S, and only 14 days exceeded 0.5 ppm H2S, 1/10th of the OEL.

CONCLUSIONS

Wastewater workers in this study are regularly exposed to short peaks of H2S, but even high peaks do not influence the 8-h TWA values significantly. A preliminary measurement program over 3 days according to EN 689 to evaluate the need for further measurements would probably not find TWA values greater than 1/10 of OEL; the EN 689 standard is not made for evaluation to peak exposures. Exceedances of CV at 10 ppm H2S occur in 6% of workdays, and in 33% of days with exposure above 1.6 ppm. The toxicity and exposure profile of H2S makes continuous exposure monitoring necessary for alarm purposes. Reliance on the 8-h occupational exposure limit as has been the normal in Norway, will not be adequately protective for wastewater workers. H2S alarm equipment should continue to be used.

Hydrogen sulphide: an emerging regulator of plant defence signalling

Hydrogen sulphide (H₂ S), a gaseous signalling molecule in plants, has gained considerable attention in recent years because of its emerging roles in the regulation of plant growth and development and responses to abiotic stressors. Although the involvement of H₂ S in biotic stress is not well documented in the literature, a growing body of evidence indicates its potential role in plant defence, particularly against bacterial and fungal pathogens. Recent reports have suggested that H₂ S participates in plant defence signalling potentially by (1) regulating glutathione metabolism, (2) inducing expression of pathogenesis-related (PR) and other defence-related genes, (3) modulating enzyme activity through post-translational modifications, and (4) interacting with phytohormones such as jasmonic acid, ethylene and auxin. In this review, we discuss the biosynthesis, metabolism and interaction of H₂ S with phytohormones, and highlight evidence gathered so far to support the emerging roles of H₂ S in plant defence against invading pathogens.

Exogenous hydrogen sulphide alleviates copper stress impacts in Artemisia annua L.: Growth, antioxidant metabolism, glandular trichome development and artemisinin biosynthesis

A supply of plant micronutrients (some of which are metals) is necessary to regulate many plant processes; their excess, however, can have detrimental consequences and can hamper plant growth, physiology and metabolism. Artemisia annua is an important crop plant used in the treatment of malaria. In this investigation, the physio-biochemical mechanisms involved in exogenous hydrogen sulphide-mediated (H₂ S) alleviation of copper (Cu) stress in A. annua were assessed.. Two different levels of Cu (20, 40 mg·kg^-1 ), one H₂ S treatment (200 µm) and their combinations were introduced while one set of plants was retained as control. Results showed that the presence of excess Cu in the soil reduced growth and biomass, photosynthetic parameters, chlorophyll content and fluorescence, gas exchange parameters and induced antioxidant enzyme activity. Copper stress enhanced the production of thiobarbituric acid reactive substances (TBARS) and increased Cu content in both roots and shoots of affected plants. Exogenous application of H₂ S restored the physio-biochemical characteristics of Cu-treated A. annua plants by reducing lipid peroxidation and enhancing the activity of antioxidant enzymes in Cu-stressed plants as compared with the controls. Hydrogen sulphide also reduced the Cu content in different plant parts, increased photosynthetic efficiency, trichome density, average area of trichomes and artemisinin content. Therefore, our results provide a comprehensive assessment of the defensive role of H₂ S in Cu-stressed A. annua.

Harnessing the power of hydrogen sulphide (H2 S) for improving fruit quality traits

Hydrogen sulphide (H₂ S) is a gaseous molecule and originates endogenously in plants. It is considered a potential signalling agent in various physiological processes of plants. Numerous reports have examined the role of H₂ S in fruit ripening and in enhancing fruit quality traits. H₂ S coordinates the fruit antioxidant system, fruit ripening phytohormones, such as ethylene and abscisic acid, together with other ripening-related signalling molecules, including nitric oxide and hydrogen peroxide. Although many studies have increased understanding of various aspects of this complex network, there is a gap in understanding crosstalk of H₂ S with key players of fruit ripening, postharvest senescence and fruit metabolism. This review focused on deciphering fruit H₂ S metabolism, signalling and its interaction with other ripening-related signalling molecules during fruit ripening and postharvest storage. Moreover, we also discuss how H₂ S can be used as a tool for improving fruit quality and productivity and reducing postharvest loss of perishable fruits.

Hydrogen sulphide alleviates cadmium stress in Trigonella foenum-graecum by modulating antioxidant enzymes and polyamine content

Cadmium (Cd) toxicity reduces growth and yield of crops grown in metal-polluted sites. Research was conducted to estimate the potential of hydrogen sulphide (H₂ S) to mitigate toxicity caused by Cd in fenugreek seedlings (Trigonella foenum-graecum L.). Different concentrations of CdCl₂ (Cd1-1 mM, Cd2-1.5 mM, Cd3-2mM) and H₂ S (HS1-100 µM, HS2-150 µM, HS3-200 µM) were assessed. Seeds of fenugreek were primed with sodium hydrosulphide (NaHS), as H₂ S donor. Seedlings growing in Cd-spiked media treated with H₂ S were harvested after 2 weeks. Cd stress affected growth of fenugreek seedlings. Cd toxicity decreased leaf relative water content (LRWC), intercellular CO₂ concentration, net photosynthesis, stomatal conductance and transpiration. However, application of H₂ S significantly improved seedling morphological attributes by increasing the activity of antioxidant enzymes, i.e. APX, CAT and SOD, in Cd-contaminated soil. H₂ S treatment also regulated phenolic and flavonoid content. H₂ S-induced biosynthesis of spermidine (Spd) and putrescine (Put) could account for the enhancement of growth and physiological performance of fenugreek seedlings under Cd stress. H₂ S treatment also reduced H₂ O₂ production (38%) and electrolyte leakage (EL, 51%) in seedlings grown in different concentrations of Cd. It is recommended to evaluate the efficacy of H₂ S in alleviating Cd toxicity in other crop plants.

Hydrogen sulphide ameliorates hexavalent chromium toxicity in two cereal crops: Role of antioxidant enzymes and proline metabolism

Chromium pollution in soils is a major threat as it reduces crop yields. Hence, researchers seek methods/strategies which could curtail such losses. We report the role of H₂ S in alleviating hexavalent chromium [Cr(VI)] stress in two cereals crops, i.e. wheat and rice seedlings, by estimating various physiological attributes. Cr(VI) reduced shoot and root length in both cereals through increased accumulation of Cr(VI) in root tips and increased in oxidative stress markers, i.e. superoxide radicals (SOR), H₂ O₂ and lipid peroxidation (as MDA equivalent). Supplementation with H₂ S alleviated Cr(VI) toxicity in both cereal crops. Application of H₂ S increased tolerance to Cr(VI) stress by protecting photosynthesis and enhancing activity of antioxidant enzymes, particularly glutathione-S-transferase and content of proline. Rice was more resistant to Cr(VI) than wheat seedlings.

Hydrogen sulphide signalling in plant response to abiotic stress

Throughout their whole life cycle, higher plants are often exposed to diverse environmental stresses, such as drought, salinity, heavy metals and extreme temperatures. In response to such stress, plant cells initiate signalling transduction, resulting in downstream responses, such as specific gene transcription and protein expression. Accumulating evidence has revealed that hydrogen sulphide (H₂ S) serves as a signalling molecule in plant acclimation to stressful conditions. More important, H₂ S interacts with other signalling molecules and phytohormones, contributing to transcriptional regulation and post-translational modification. Overall, the H₂ S-mediated signalling pathway and its interaction with other signals remains elusive. Here, we describe the role of the H₂ S signalling network in regulating physiological and molecular processes under various abiotic stresses.

Hydrogen sulphide-mediated alleviation and its interplay with other signalling molecules during temperature stress

The sessile habit of plants does not provide choices to escape the environmental constraints, leading to negative impacts on their growth and development. This causes significant losses in the agriculture sector and raises serious issues on global food security. Extreme temperatures (high or low) influence several aspects of plant life and can cause reproduction malfunction. Therefore, a strategy for temperature amelioration is necessary for the management of agricultural productivity. Supplementation with various chemicals (e.g. phytohormones, gasotransmitters, osmolytes) is considered a good choice to manage plant stress. Gasotransmitters are well-recognized for stress mitigation in plants, among which hydrogen sulphide (H₂ S) has proved promising to alleviate stress. Temperature (heat/cold) stress can stimulate the endogenous production of H₂ S in plants, and many studies have reported the significance of H₂ S for temperature stress amelioration. Here, H₂ S led to positive changes in plant physiological, biochemical and molecular responses, which are usually compromised during stress. Further, H₂ S also coordinate with other signalling components that act either upstream or downstream during stress mitigation. This review focuses on the significance of H₂ S for mitigation of temperature stress, with a comprehensive discussion on cross-talk with other signalling components or supplements (e.g. NO, H₂ O₂ , salicylic acid, trehalose, proline). Finally, the review provides a rational assessment and holistic understanding of H₂ S-mediated mitigation of extreme temperature stress and addresses the prospects for development of an effective strategy to manage temperature stress.

Interactive effects of hydrogen sulphide and silicon enhance drought and heat tolerance by modulating hormones, antioxidant defence enzymes and redox status in barley (Hordeum vulgare L.)

Recent changes in climate have reduced crop productivity throughout much of the world. Drought and heat stress, particularly in arid and semi-arid regions, have seriously affected barley production. This study explored the separate and interactive effects of silicon (Si) and hydrogen sulphide (H₂ S) on plant growth and mitigation of the adverse effects of heat stress (DS) and drought stress (HS) in a barley pot experiment. The impacts of simultaneous DS + HS were more severe than individual stresses due to increased ROS production, malondialdehyde (MDA) content and higher electrolyte leakage (EL), thereby leading to reduced water, protein and photosynthetic pigment content. Exogenously applied Si and H₂ S alleviated the DS-, HS- and DS + HS-induced effects on barley by reducing ROS production, MDA and EL. A single application of H₂ S or Si + H₂ S increased plant biomass under all stress conditions, which can be ascribed to higher Si accumulation in barley shoots. A single application of Si or H₂ S significantly increased plant biomass. However, Si + H₂ S was the most effective treatment for metabolite accumulation and elevating activity of antioxidant enzymes to prevent toxicity from oxidative stress. This treatment also modulated osmolyte content, enhanced antioxidant activity and regulated the stress signalling-related endogenous hormones, abscisic acid (ABA) and indole acetic acid (IAA). Exogenous treatments regulated endogenous H₂ S and Si and resulted in higher tolerance to individual and combined drought and heat stress in barley.

Hydrogen sulphide (H2 S) in the hidden half: Role in root growth, stress signalling and rhizospheric interactions

Apart from nitric oxide (NO) and carbon monoxide (CO), hydrogen sulphide (H₂ S) has emerged as a potential gasotransmitter that has regulatory roles in root differentiation, proliferation and stress signalling. H₂ S metabolism in plants exhibits spatio-temporal differences that are intimately associated with sulphide signalling in the cytosol and other subcellular components, e.g. chloroplast and mitochondria. H₂ S biosynthesis in plant organs uses both enzymatic and non-enzymatic pathways. H₂ S generation in roots and aerial organs is modulated by developmental phase and changes in environmental stimuli. H₂ S has an influential role in root development and in the nodulation process. Studies have revealed that H₂ S is a part of the auxin and NO signalling pathways in roots, which induce lateral root formation. At the molecular level, exogenous application of H₂ S regulates expression of several transcription factors, viz. LBD (Lateral organ Boundaries Domain), MYB (myeloblastosis) and AP2/ERF (Apetala 2/ Ethylene Response Factor), which stimulate upregulation of PpLBD16 (Lateral organ boundaries domain 16), thereby significantly increasing the number of lateral roots. Concomitantly, H₂ S acts as a crucial signalling molecule in roots during various abiotic stresses, e.g. drought, salinity heavy metals (HMs), etc., and augments stress tolerance in plants. Interestingly, extensive crosstalk exists between H₂ S, NO, ABA, calcium and ethylene during stress, which escalate plant defence and regulate plant growth and productivity. Hence, the present review will elaborate the role of H₂ S in root development, stress alleviation, legume-Rhizobium symbiosis and rhizosphere signalling. The review also examines the mechanism of H₂ S-mediated abiotic stress mitigation and cross-talk with other signaling molecules.

Hydrogen sulphide infiltration downregulates oxidative metabolism and extends postharvest life of banana

Hydrogen sulphide (H₂ S) has emerged as a potential regulator of plant defence against different abiotic stresses. As a climacteric fruit, banana undergoes oxidative stresses shortly after harvest, resulting in faster ripening and senescence. This work examines the effects of vacuum infiltrated H₂ S on ripening inhibition of banana. Banana fruits were vacuum infiltrated with 1 mm H₂ S. Effects on oxidative stress markers, physiological changes, bioactive compounds and antioxidant potentials were examined during storage at 25 °C and 75-80% RH. Results indicate that treated fruits were less affected by oxidative stress, as evident by lower accumulation of ROS (superoxide and peroxide ions), elevated phenols content and antioxidant capacity. The ripening inhibitory effects of H₂ S delayed chlorophyll loss and reduced ethylene and CO₂ production. H₂ S infiltration also reduced MDA accumulation and electrolytic leakage, resulting in longer shelf life. Vacuum infiltration with H₂ S had a protective effect on postharvest banana through overcoming the deleterious effect of ROS and strengthening antioxidant potential. Thus, this method could be promising for enhanced preservation of banana during storage.

Ethylene and hydrogen sulphide are essential for mitigating hexavalent chromium stress in two pulse crops

Chromium toxicity to crops is a major scientific problem of the present time. Thus, scientific attempts have been made for reducing chromium toxicity to crop plants. In this study, we examined the potential of ethylene (ET, 25 µM) and hydrogen sulphide (H₂ S, 10 µM) to alleviate hexavalent chromium [Cr(VI), 50 µM] stress in two pulse crops, black bean and mung bean, by assessing physiological and biochemical attributes. Cr(VI) reduced shoot and root length in black bean and mung bean in comparison to the control. Plants had increased accumulation of oxidative stress markers, i.e. superoxide radicals (SOR), hydrogen peroxide (H₂ O₂ ) and lipid peroxidation (as malondialdehyde, MDA). The addition of AVG (an inhibitor of ET biosynthesis) and PAG (an inhibitor of H₂ S biosynthesis) to Cr(VI)-treated plants further increased Cr(VI) toxicity, suggesting their endogenous levels are important for tolerating Cr(VI) toxicity. However, supplementation with either ET or H₂ S alleviated Cr(VI) toxicity. Interestingly, ET did not rescue negative effects of PAG under Cr(VI) stress but NaHS rescued negative effect of AVG. Overall, results indicate that, although both ET and H₂ S alleviate Cr(VI) stress, endogenous H₂ S is better. Furthermore, H₂ S appears to be a downstream signal for ET in alleviating Cr(VI) stress in these two pulse crops.

Effect of postharvest hydrogen sulphide on lignification and biochemical markers of pointed gourd

Hydrogen sulphide (H₂ S) has emerged as a gasotransmitter molecule that modulates several physiological functions in plants, specially, different biotic and abiotic stresses. Pointed gourd (PG) fruits start losing their soft texture and appealing colour within 2-3 days of harvest, resulting in poor marketability and shelf life. Here, the effect of exogenous H₂ S (1 and 2 mm) application on lignification and other biochemical markers linked to ripening, shelf-life and edible quality of PG was assessed during cold (12 °C, 85-90% RH) and ambient (27 ± 2 °C, 55 ± 5% RH) storage. The synergistic effect of H₂ S was recorded during simulated storage at ambient conditions. Postharvest H₂ S treatment (1 mm) effectively delayed yellowing and chlorophyll loss (four-fold reduction) and maintained the phenolic content and higher antioxidant activity (36%). The H₂ S-treated PG fruits had significantly lower lignification and membrane permeability i.e. 15% and 13%, respectively, than control samples. H₂ S-treated fruit also maintained higher PAL and lower PPO activity. Therefore, postharvest application of H₂ S (2 mm) could be effective in maintaining postharvest quality of PG fruits and extending the marketing period.

Hydrogen sulphide and salicylic acid regulate antioxidant pathway and nutrient balance in mustard plants under cadmium stress

Cadmium (Cd), a pervasive noxious heavy metal, is a key threat to agricultural system. It is rapidly translocated and has detrimental effects on plant growth and development. Hydrogen sulphide (H₂ S) is emerging as a potential messenger molecule for modulating plant tolerance to Cd. Salicylic acid (SA), a phenolic signalling molecule, can alleviate Cd toxicity in plants. The present study investigated the mediatory role of H₂ S (100 µM) and SA (0.5 mM), individually and in combination, in modulating antioxidant defence machinery and nutrient balance to impart Cd (50 µM) resistance to mustard. Accumulation of Cd resulted in oxidative stress (TBARS and H₂ O₂ ), mineral nutrient imbalance (N, P, K, Ca), decreased leaf gas exchange and PSII efficiency, ultimately reducing plant growth. Both H₂ S and SA independently attenuated phytotoxic effects of Cd by triggering antioxidant systems, enhancing the nutrient pool, eventually leading to improved photosynthesis and biomass of mustard plants. The positive effects were more pronounced under combined application of H₂ S and SA, indicating a synergistic relationship between these two signalling molecules in mitigating the detrimental effects of Cd on nutrient homeostasis and overall health of mustard, primarily by boosting antioxidant pathway. Our findings provide new insights into H₂ S- and SA-induced protective mechanisms in mustard plants subjected to Cd stress and suggest their combined use as a feasible strategy to confer Cd tolerance.

Biogas Pollution and Mineral Deposits Formed on the Elements of Landfill Gas Engines

Municipal landfills generate a significant amount of high-energy biogas, which can be used as a renewable gaseous fuel. However, it is necessary to improve the quality of this biogas due to the presence of various chemical compounds. The most common pollutants in landfill biogas include volatile compounds of silicon, sulphur, phosphorus and chlorine. The aforementioned elements, as well as other metals, were found both in the deposits and in the engine oil. The paper presents detailed characteristics of the solid residues formed in selected parts of gas engines powered by landfill biogas. Its elemental composition and morphology were investigated in order to determine the structure and influence of these deposits. In order to better understand the observed features, selected analyses were also conducted for biogas, engine oil and the condensate generated during biogas dewatering. It was found that the content of individual elements in samples collected from the same part of the gas engine but sourced from various landfills vary. The occurrence of elements in deposits, e.g., Mg, Zn, P and Cr, depends on the location of sampling sites and the type of engine. It was also observed that the deposits formed in parts that come into contact with both biogas and engine oil contain Ca or Zn, which can be related to biogas pollutants as well as different oil additives. The presence of Al, Fe, Cu, Cr, Sn or Pb in selected motor oil samples can be explained by the penetration of metallic abrasives, which confirms the abrasive properties of the formed deposits. The analysis of the characteristic deposits may contribute to the selection of an appropriate landfill biogas purification technology, thus reducing the operating costs of energy cogeneration systems. Finally, we highlight challenges for biogas purification processes and anticipate the direction of future work.

Hydrogen sulphide in liver glucose/lipid metabolism and non-alcoholic fatty liver disease

BACKGROUND

For a long time, hydrogen sulphide (H₂ S) was considered only as a toxic gas, inhibiting mitochondrial respiration at the level of cytochrome c oxidase, and an environmental pollutant. Nowadays, H₂ S is recognized as the third mammalian gasotransmitter, playing an important role in inflammation, septic shock, ischaemia reperfusion events, cardiovascular disease and more recently in liver physiology and chronic liver diseases such as non-alcoholic fatty liver disease (NAFLD).

METHODS

This narrative review is based on literature search using PubMed.

RESULTS

From a bioenergetic perspective, H₂ S is a very unique molecule, serving as a mitochondrial poison at high concentrations or as an inorganic mitochondrial substrate at low concentrations. By using transgenic animal models to specifically modulate liver H₂ S biosynthesis or exogenous compounds that release H₂ S, several studies demonstrated that H₂ S is a key player in liver glucose and lipid metabolism. Liver H₂ S content and biosynthesis were also altered in NAFLD animal models with the in vivo administration of H₂ S-releasing molecules preventing the further escalation into non-alcoholic-steatohepatitis. Liver steady-state levels of H₂ S, and hence its cell signalling properties, are controlled by a tight balance between its biosynthesis, mainly through the transsulphuration pathway, and its mitochondrial oxidation via the sulphide oxidizing unit. However, studies investigating mitochondrial H₂ S oxidation in liver dysfunction still remain scarce.

CONCLUSIONS

Since H₂ S emerges as a key regulator of liver metabolism and metabolic flexibility, further understanding the physiological relevance of mitochondrial H₂ S oxidation in liver energy homeostasis and its potential implication in chronic liver diseases are of great interest.

Physiological, Pathological and Pharmacological Interactions of Hydrogen Sulphide and Nitric Oxide in the Myocardium of Rats with Left Ventricular Hypertrophy

Left ventricular hypertrophy (LVH) is characterized by increased myocardium thickness due to increased oxidative stress and downregulation of cystathione γ lyase (CSE) endothelial nitric oxide synthase (eNOS). Upregulation of CSE by hydrogen sulphide (H2S) and ENOS by L-arginine can arrest the progression of LVH individually. The present study explored the combined treatment of H2S and NO in the progression of LVH, and demonstrated that the response is due to H2S, NO or formation of either new molecule in physiological, pathological, and pharmacological in vivo settings of LVH. Exogenous administration H2S+NO in LVH significantly reduced (all p < 0.05) systolic blood pressure (SBP) and mean arterial pressure (MAP), LV index, heart index and oxidative stress when compared to the LVH group. There was downregulation of CSE mRNA and eNOS in the heart, and exogenous administration of H2S+NO groups upregulated eNOS MRNA while CSE MRNA remained downregulated in the hearts of the LVH group. Similar trends were observed with concentrations of H2S and NO in the plasma and tissue. It can be concluded that combined treatment of LVH with H2S and NO significantly ameliorate the progression of LVH by attenuating systemic hemodynamic and physical indices, and by decreasing oxidative stress. Molecular expression data in the myocardium of LVH depicts that combined treatment upregulated eNOS/NO while it downregulated CSE/H2S pathways in in vivo settings, and it is always eNOS/NO pathways which play a major role.

Hydrogen Sulphide (H2S) Exposure Hazard Assessment: An Algorithm for Generating Exposure Index Based on Direct Instrument Readings

OBJECTIVES

Increased use of small affordable alarm sensors with logging or network capabilities has improved the ability to monitor exposure. The large datasets generated from these monitors calls for development of a computer algorithm to assess these data.

METHODS

We examined 88 time series of hydrogen sulphide (H2S) from wastewater works previously used for developing the exposure index. The time series covered 331 h, where 16 h had readings different from zero.

RESULTS

The developed algorithm reproduced the manual assessed index almost perfectly (linear regression β = 1.02, R2 = 0.97, P < 0.001). Time-weighted average (TWA) values of the 88 time series showed a mean value of 0.04 ppm (range 0.0-0.9). The mean index value was 18 (range 0-337), with a good linear fit (β = 0.002, R2 = 0.93, and P < 0.001). The index gave us a better resolution and basis for risk assessment than the TWA, and managed to combine evaluation of TWA and exceedance of ceiling value in one number.

CONCLUSIONS

As long as peaks above ceiling value occur, we find alarm tools with an H2S sensor to be an essential personal protective equipment against H2S. The proposed method has been verified, and it removes some common human errors in graph evaluation. Use of the index is a possible way of quantifying risk level in exposure to H2S in one single number and provides better understanding of the risk of exposure, as it eases the analysis and evaluation of large numbers of time series.

Detoxification, Hydrogen Sulphide Metabolism and Wound Healing Are the Main Functions That Differentiate Caecum Protein Expression from Ileum of Week-Old Chicken

Simple Summary

Although the ileum and caecum represent adjacent parts of the gastrointestinal tract, both compartments differ by function as well as inner environment parameters such as oxygen availability or density of colonising microbiota. As the function of a particular tissue is generally reflected by protein expression, mass spectrometry proteomics was used to characterise expressed proteins of both segments of the gastrointestinal tract. Differentially expressed proteins were identified and grouped according to biological processes specific to both gut compartments.

Abstract

Sections of chicken gut differ in many aspects, e.g., the passage of digesta (continuous vs. discontinuous), the concentration of oxygen, and the density of colonising microbiota. Using an unbiased LC-MS/MS protocol, we compared protein expression in 18 ileal and 57 caecal tissue samples that originated from 7-day old ISA brown chickens. We found that proteins specific to the ileum were either structural (e.g., 3 actin isoforms, villin, or myosin 1A), or those required for nutrient digestion (e.g., sucrose isomaltase, maltase–glucoamylase, peptidase D) and absorption (e.g., fatty acid-binding protein 2 and 6 or bile acid–CoA:amino acid N-acyltransferase). On the other hand, proteins characteristic of the caecum were involved in sensing and limiting the consequences of oxidative stress (e.g., thioredoxin, peroxiredoxin 6), cell adhesion, and motility associated with wound healing (e.g., fibronectin 1, desmoyokin). These mechanisms are coupled with the activation of mechanisms suppressing the inflammatory response (galectin 1). Rather prominent were also expressions of proteins linked to hydrogen sulphide metabolism in caecum represented by cystathionin beta synthase, selenium-binding protein 1, mercaptopyruvate sulphurtransferase, and thiosulphate sulphurtransferase. Higher mRNA expression of nuclear factor, erythroid 2-like 2, the main oxidative stress transcriptional factor in caecum, further supported our observations.

Cysteine challenge test as a novel diagnostic tool to distinguish oral halitosis

BACKGROUND

The cysteine challenge test is often used to check the H₂ S production capacity of the mouth. Patients with oral halitosis group (n = 305) or non-oral halitosis group (n = 191) and healthy individuals (control group, n = 102) were compared with each other to identify any possible relationship between initial and cysteine-induced oral H₂ S concentrations.

SUBJECTS AND METHOD

The medical records of 598 participants were reviewed retrospectively. Oral H₂ S concentrations before (pre-CR) and after cysteine rinse (post-CR) with 5 mL of 20 mmol L-cysteine solution for 30 s were compared.

RESULTS

Pre-CR H₂ S concentrations were >0.8 ppm in 75.1% of oral group patients but less than <0.8 ppm in 87.3% of the non-oral group and 86.9% of controls. After cysteine rinse, oral H₂ S concentrations exceeded 12 ppm in 72% of the oral halitosis patients but were lower in 88% of non-oral group and 99% of controls. Whilst post-CR/pre-CR ratio was >12 in 74.5% of the oral group, it was <12 in 81.7% of the non-oral group and 83.4% of controls.

CONCLUSION

Cysteine challenge test can be used as a diagnostic tool to identify an individual's tendency to produce oral malodor, not only to quantify momentary halitosis level.

Hydrogen Sulphide Treatment Prevents Renal Ischemia-Reperfusion Injury by Inhibiting the Expression of ICAM-1 and NF-kB Concentration in Normotensive and Hypertensive Rats

Our main objective was to investigate the effect of chronic administration of hydrogen sulphide donor (sodium hydrosulphide) on the expression of intercellular adhesion molecule-1 (ICAM-1) and concentration of nuclear factor-kappa B (NF-kB) in a renal ischemia-reperfusion injury (IRI) model of WKY and L-nitro-arginine-methyl-ester (L-NAME)-induced hypertensive rats. Sodium hydrosulphide (NaHS) was administered intraperitoneally (i.p.) for 35 days while cystathionine gamma lyase (CSE) inhibitor dL-propargylglycine (PAG) was administered at a single dose of 50 mg/kg. Animals were anesthetised using sodium pentobarbitone (60 mg/kg) and then prepared to induce renal ischemia by clamping the left renal artery for 30 min followed by 3 h of reperfusion. Pre-treatment with NaHS improved the renal functional parameters in both WKY and L-NAME-induced hypertensive rats along with reduction of blood pressure in hypertensive groups. Oxidative stress markers like malondialdehyde (MDA), total superoxide dismutase (T-SOD) and glutathione (GSH) were also improved by NaHS treatment following renal IRI. Levels of ICAM-1 and NF-kB concentration were reduced by chronic treatment with NaHS and increased by PAG administration after renal IRI in plasma and kidney. Treatment with NaHS improved tubular morphology and glomerulus hypertrophy. Pre-treatment with NaHS reduced the degree of renal IRI by potentiating its antioxidant and anti-inflammatory mechanism, as evidenced by decreased NF-kB concentration and downregulation of ICAM-1 expression.

N-acetylcysteine (NAC) differentially affects arterial medial calcification and bone formation: The role of l-cysteine and hydrogen sulphide

Arterial medial calcification (AMC) is the deposition of calcium phosphate in the arteries. AMC is widely thought to share similarities with physiological bone formation; however, emerging evidence suggests several key differences between these processes. N-acetylcysteine (NAC) displays antioxidant properties and can generate hydrogen sulphide (H₂ S) and glutathione (GSH) from its deacetylation to l-cysteine. This study found that NAC exerts divergent effects in vitro, increasing osteoblast differentiation and bone formation by up to 5.5-fold but reducing vascular smooth muscle cell (VSMC) calcification and cell death by up to 80%. In vivo, NAC reduced AMC in a site-specific manner by 25% but had no effect on the bone. The actions of l-cysteine and H₂ S mimicked those of NAC; however, the effects of H₂ S were much less efficacious than NAC and l-cysteine. Pharmacological inhibition of H₂ S-generating enzymes did not alter the actions of NAC or l-cysteine; endogenous production of H₂ S was also unaffected. In contrast, NAC and l-cysteine increased GSH levels in calcifying VSMCs and osteoblasts by up to 3-fold. This suggests that the beneficial actions of NAC are likely to be mediated via the breakdown of l-cysteine and the subsequent GSH generation. Together, these data show that while the molecular mechanisms driving the actions of NAC appear similar, the downstream effects on cell function differ significantly between osteoblasts and calcifying VSMCs. The ability of NAC to exert these differential actions further supports the notion that there are differences between the development of pathological AMC and physiological bone formation. NAC could represent a therapeutic option for treating AMC without exerting negative effects on bone.

Conductive Polymer Composites for Hydrogen Sulphide Sensors Working at Sub-PPM Level and Room Temperature

Hybrid composites based on tin chloride and the conductive polymers, polyaniline (PAni) and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), were integrated into high-performance hydrogen sulphide (H2S) gas sensors working at room temperature. The morphology and chemical properties were studied by scanning and transmission electron microscopy (SEM, TEM), energy dispersive spectroscopy (EDS) and Fourier-transform infrared (FTIR). The composites demonstrated a slightly porous nanostructure and strong interactions between the polymers and the metal salt, which slightly dopes PAni. The hybrid sensors exhibited a very low detection limit (<85 ppb), fast response, repeatability, reproducibility and stability over one month. Moreover, this work presents how calibration based on the derivative of the signal can give hybrid sensors the ability to quantify the concentration of targeted gas, even during continuous variation of the analyte concentration. Finally, the effect of interfering species, such as water and ammonia, is discussed.

Hydrogen sulphide reduced the accumulation of lipid droplets in cardiac tissues of db/db mice via Hrd1 S-sulfhydration

Accumulation of lipid droplets (LDs) induces cardiac dysfunctions in type 2 diabetes patients. Recent studies have shown that hydrogen sulphide (H₂ S) ameliorates cardiac functions in db/db mice, but its regulation on the formation of LDs in cardiac tissues is unclear. Db/db mice were injected with NaHS (40 μmol·kg^-1 ) for twelve weeks. H9c2 cells were treated with high glucose (40 mmol/L), oleate (200 µmol/L), palmitate (200 µmol/L) and NaHS (100 µmol/L) for 48 hours. Plasmids for the overexpression of wild-type Hrd1 and Hrd1 mutated at Cys115 were constructed. The interaction between Hrd1 and DGAT1 and DGAT2, the ubiquitylation level of DGAT1 and 2, the S-sulfhydration of Hrd1 were measured. Exogenous H₂ S ameliorated the cardiac functions, decreased ER stress and reduced the number of LDs in db/db mice. Exogenous H₂ S could elevate the ubiquitination level of DGAT 1 and 2 and increased the expression of Hrd1 in cardiac tissues of db/db mice. The S-sulfhydration of Hrd1 by NaHS enhanced the interaction between Hrd1 and DGAT1 and 2 to inhibit the formation of LD. Our findings suggested that H₂ S modified Hrd1 S-sulfhydration at Cys115 to reduce the accumulation of LDs in cardiac tissues of db/db mice.

Application of Chemical Sensors and Olfactometry Method in Ecological Audits of Degraded Areas

Mineral excavation is a common process throughout the world. The open pits remaining after the closure of a mine require well-considered and meticulous reclamation activities aimed at restoring the environmental properties of a given area. The inspections carried out in Poland indicate numerous irregularities in implementing the reclamation process. The research in this study was conducted in six measurement series and includes both chemical and olfactometry determinations by devices: multisensor portable gas detector and field olfactometer. Statistical analysis of the results obtained show high concentrations in ambient air of both chemical compounds (NH₃, VOCs, H₂S, CH₃SH) and odour, excluding the possibility of occurrence in the pit of only waste types contained in the administrative decision on reclamation. In addition to the unpleasant odour, the listed compounds can have dangerous effects on the health and life of living organisms. This paper presents a suitable method of control and detection of irregularities in the conducted processes. The main advantage is the relatively low cost of purchasing sensors and field olfactometers compared to other devices, and the possibility to test the polluted air in situ, without the risk of chemical processes occurring during transport of gas samples to the laboratory.

Hydrogen sulphide attenuates neuronal apoptosis of substantia nigra by re-establishing autophagic flux via promoting leptin signalling in a 6-hydroxydopamine rat model of Parkinson's disease

Previous studies reveal that hydrogen sulphide (H₂ S) exerts neuroprotection against neurotoxin-induced Parkinson's disease (PD), but the underlying mechanism remains elusive. The present study was aimed to investigate whether H₂ S inhibits neuronal apoptosis of substantia nigra with the involvement of autophagy via promoting leptin signalling in 6-hydroxydopamine (6-OHDA)-induced PD rats. In this study, neuronal apoptosis was analysed by TUNEL staining, the activity of caspase-3 was measured by Caspase-3 fluorometric assay kit, the expressions of Bax, Bcl-2, Beclin-1, LC3II, P62 and leptin were determined by Western blot analysis, and the numbers of autophagosomes and autolysosomes were assessed by transmission electron microscopy. Results showed that NaHS, a donor of exogenous H₂ S, mitigates 6-OHDA-induced the increases in the numbers of TUNEL-positive cells, the activity of caspase-3 and the expression of Bax, and attenuates 6-OHDA-induced a decrease in the expression of Bcl-2 in substantia nigra of rats. In addition, 6-OHDA enhanced the expressions of Beclin-1, LC3-II and P62, increased the number of autophagosomes, and decreased the number of autolysosomes in the substantia nigra, which were also blocked by administration of NaHS. Furthermore, NaHS reversed 6-OHDA-induced the down-regulation of leptin expression in the substantia nigra, and treatment with leptin-OBR, a blocking antibody of leptin receptor, attenuated the inhibition of NaHS on neuronal apoptosis and the improvement of NaHS on the blocked autophagic flux in substantia nigra of 6-OHDA-treated rats. Taken together, these results demonstrated that H₂ S attenuates neuronal apoptosis of substantia nigra depending on restoring impaired autophagic flux through up-regulating leptin signalling in PD.

The Gasotransmitter Hydrogen Sulfide (H2S) Prevents Pathologic Calcification (PC) in Cartilage

Pathologic calcification (PC) is a painful and disabling condition whereby calcium-containing crystals deposit in tissues that do not physiologically calcify: cartilage, tendons, muscle, vessels and skin. In cartilage, compression and inflammation triggered by PC leads to cartilage degradation typical of osteoarthritis (OA). The PC process is poorly understood and treatments able to target the underlying mechanisms of the disease are lacking. Here we show a crucial role of the gasotransmitter hydrogen sulfide (H₂S) and, in particular, of the H₂S-producing enzyme cystathionine γ-lyase (CSE), in regulating PC in cartilage. Cse deficiency (Cse KO mice) exacerbated calcification in both surgically-induced (menisectomy) and spontaneous (aging) murine models of cartilage PC, and augmented PC was closely associated with cartilage degradation (OA). On the contrary, Cse overexpression (Cse tg mice) protected from these features. In vitro, Cse KO chondrocytes showed increased calcification, potentially via enhanced alkaline phosphatase (Alpl) expression and activity and increased IL-6 production. The opposite results were obtained in Cse tg chondrocytes. In cartilage samples from patients with OA, CSE expression inversely correlated with the degree of tissue calcification and disease severity. Increased cartilage degradation in murine and human tissues lacking or expressing low CSE levels may be accounted for by dysregulated catabolism. We found higher levels of matrix-degrading metalloproteases Mmp-3 and -13 in Cse KO chondrocytes, whereas the opposite results were obtained in Cse tg cells. Finally, by high-throughput screening, we identified a novel small molecule CSE positive allosteric modulator (PAM), and demonstrated that it was able to increase cellular H₂S production, and decrease murine and human chondrocyte calcification and IL-6 secretion. Together, these data implicate impaired CSE-dependent H₂S production by chondrocytes in the etiology of cartilage PC and worsening of secondary outcomes (OA). In this context, enhancing CSE expression and/or activity in chondrocytes could represent a potential strategy to inhibit PC.

Circulating levels of hydrogen sulphide negatively correlate to nitrite levels in gestational hypertensive and preeclamptic pregnant women

Endothelial dysfunction is a hallmark of preeclampsia and the role of nitric oxide (NO) has been extensively studied in this pregnancy complication. In recent years, hydrogen sulphide (H₂ S) has arisen as a new gasotransmitter with an impact on endothelial function. However, the involvement of H₂ S in the pathophysiology of preeclampsia is not fully understood, and only a few studies with limited sample size have investigated circulating levels of H₂ S in preeclamptic patients. Moreover, H₂ S levels have not been previously evaluated in gestational hypertension. Furthermore, the relationship between H₂ S and NO in these hypertensive disorders of pregnancy has yet to be determined. We measured H₂ S levels in plasma of 120 healthy pregnant women, 88 gestational hypertensive and 62 preeclamptic women. We also measured plasma nitrite in a subset of patients and carried out correlation analysis between plasma H₂ S and nitrite in these three groups. We found that plasma H₂ S was elevated in preeclampsia and further increased in gestational hypertension compared to healthy pregnancy. Plasma nitrite was reduced in gestational hypertension and preeclampsia, and these levels were negatively correlated with H₂ S in both gestational hypertension and preeclampsia, but not in healthy pregnancy. Our results indicate that increases in H₂ S may represent a mechanism triggered as an attempt to compensate reduced NO in gestational hypertension and preeclampsia. Future studies are warranted to investigate the mechanisms underlying H₂ S/NO interaction on mediating endothelial dysfunction in these hypertensive disorders of pregnancy.

A novel multi-phase treatment scheme for odorous rubber effluent

Despite the great profits of rubber latex production, its preliminary processing releases a large amount of wastewater into the water bodies from several processing steps. This rubber effluent is rich in total Kjeldahl nitrogen (TKN), total dissolved solids (TDS), biological oxygen demand (BOD) and chemical oxygen demand (COD). Therefore, the study addressed a liquid phase treatment of the effluent using an Upflow Anaerobic Sludge Blanket (UASB) reactor followed by coagu-flocculation and aeration. In addition, the gas phase (containing odorous hydrogen sulphide of 10-12% by volume) from the UASB reactor was sent to a caustic scrubber where the H₂S removal efficiency of 63 ± 5% was achieved. This integrated multi-phase treatment scheme proved to be an effective approach by reducing TKN, TDS, BOD and COD by 68-87%, 61-69%, 81-84% and 81-87% respectively in the final effluent.

H2 S catalysed by CBS regulates testosterone synthesis through affecting the sulfhydrylation of PDE

Testosterone deficiency resulted in increased mortality in men. Our previous work found that hydrogen sulphide (H₂S) significantly alleviated the spermatogenesis disorder. To investigate whether H₂S could regulate testosterone synthesis and the relative signalling pathways. Disorder model of testosterone synthesis was constructed in vitro and in vivo. The cell viability was detected using CCK‐8 method. The concentration of H₂S and testosterone were examined using ELISA kits. The relative mRNA and protein expression of CBS, PDE4A, PDE8A and proteins related to testosterone synthesis were detected by RT‐qPCR and western blotting. PAS staining was used to detect the inflammatory status of testis. The sulfhydryl level of PDE4A and PDE8A was determined by Biotin Switch Technique. CBS overexpression inhibited while knockdown promoted LPS + H₂O₂ induced injury in testosterone synthesis of MLTC‐1 cells, though regulating the level of H₂S. The LPS + H₂O₂ induced inhibition on cAMP and p‐PKA was recovered by CBS overexpression, while addition of the specific inhibitor of PKA had opposite effects. CBS overexpression alleviated the inflammation status in testis and promoted the expression of StAR, P450scc, P450c17 and 3β‐HSD. CBS could also exhibit its protective role through promoting sulfhydrylation of PDE4A and PDE8A. H₂S catalysed by CBS could recover testosterone synthesis in vitro and in vivo through inhibiting PDE expression via sulfhydryl modification and activating cAMP/PKA pathway.

The Scientific Basis for Occupational Exposure Limits for Hydrogen Sulphide-A Critical Commentary

OBJECTIVES

Occupational exposure limits for hydrogen sulphide (H₂S) vary considerably; three expert group reports, published from 2006 to 2010, each recommend different limits. Some jurisdictions are considering substantial reductions.

METHODS

This review assesses the scientific evidence used in these recommendations and presents a new systematic review of human studies from 2006-20, identifying 33 studies.

RESULTS

The three major reports all give most weight to two sets of studies: of physiological effects in human volunteers, and of effects in the nasal passages of rats and mice. The human studies were done in one laboratory over 20 years ago and give inconsistent results. The breathing style and nasal anatomy of rats and mice would make them more sensitive than humans to inhaled agents. Each expert group applied different uncertainly factors. From these reports and the further literature review, no clear evidence of detrimental health effects from chronic occupational exposures specific to H₂S was found. Detailed studies of individuals in communities with natural sources in New Zealand have shown no detrimental effects. Studies in Iceland and Italy show some associations; these and various other small studies need verification.

CONCLUSIONS

The scientific justification for lowering occupational exposure limits is very limited. There is no clear evidence, based on currently available studies, that lower limits will protect the health of workers further than will the current exposure limits used in most countries. Further review and assessment of relevant evidence is justified before exposure limits are set.

Diallyl trisulphide, a H2 S donor, compromises the stem cell phenotype and restores thyroid-specific gene expression in anaplastic thyroid carcinoma cells by targeting AKT-SOX2 axis

It is widely accepted that anaplastic thyroid carcinoma (ATC), a rare, extremely aggressive malignant, is enriched by cancer stem cells (CSCs), which are closely related to the pathogenesis of ATC. In the present study, we demonstrated that diallyl trisulphide (DATS), a well-known hydrogen sulphide (H₂ S) donor, suppressed sphere formation and restored the expression of iodide-metabolizing genes in human ATC cells, which were associated with H₂ S generation. Two other H₂ S donors, NaHS and GYY4137, could also suppress the self-renewal properties of ATC cells in vitro. Compared with normal thyroid tissues and papillary thyroid carcinomas (PTCs), the elevated expressions of SOX2 and MYC, two cancer stem cell markers, in ATCs were validated in the combined Gene Expression Omnibus (GEO) cohort. DATS decreased the expression of SOX2, which was mediated by H₂ S generation. Furthermore, knockdown of AKT or inhibition of AKT by DATS led to a decrease of SOX2 expression in ATC cells. AKT knockdown phenocopied restoration of thyroid-specific gene expression in ATC cells. Our data suggest that H₂ S donors treatment can compromise the stem cell phenotype and restore thyroid-specific gene expression of ATC cells by targeting AKT-SOX2 pathway, which may serve as a therapeutic strategy to intervene the CSC progression of ATC.

Hydrogen sulphide reduces hyperhomocysteinaemia-induced endothelial ER stress by sulfhydrating protein disulphide isomerase to attenuate atherosclerosis

Hyperhomocysteinaemia (HHcy)-impaired endothelial dysfunction including endoplasmic reticulum (ER) stress plays a crucial role in atherogenesis. Hydrogen sulphide (H₂ S), a metabolic production of Hcy and gasotransmitter, exhibits preventing cardiovascular damages induced by HHcy by reducing ER stress, but the underlying mechanism is unclear. Here, we made an atherosclerosis with HHcy mice model by ApoE knockout mice and feeding Pagien diet and drinking L-methionine water. H₂ S donors NaHS and GYY4137 treatment lowered plaque area and ER stress in this model. Protein disulphide isomerase (PDI), a modulation protein folding key enzyme, was up-regulated in plaque and reduced by H₂ S treatment. In cultured human aortic endothelial cells, Hcy dose and time dependently elevated PDI expression, but inhibited its activity, and which were rescued by H₂ S. H₂ S and its endogenous generation key enzyme-cystathionine γ lyase induced a new post-translational modification-sulfhydration of PDI. Sulfhydrated PDI enhanced its activity, and two cysteine-terminal CXXC domain of PDI was identified by site mutation. HHcy lowered PDI sulfhydration association ER stress, and H₂ S rescued it but this effect was blocked by cysteine site mutation. Conclusively, we demonstrated that H₂ S sulfhydrated PDI and enhanced its activity, reducing HHcy-induced endothelial ER stress to attenuate atherosclerosis development.

Inhibition of histone deacetylase promotes a neuroprotective mechanism in an experimental model of Parkinson's disease

Introduction

Therapies targeting histone deacetylase (HDAC) have gained wider attention in the treatment of various clinical conditions. However, the use of HDAC inhibitors in pre-clinical trials in the case of Parkinson's disease (PD) is very limited. In the present study, the HDAC inhibitor, entinostat, was tested in animals induced with Parkinson's disease experimentally.

Material and methods

Wistar male rats (150 ±10 g) were administered with rotenone (2 mg/kg/day, s.c.) for 21 days to induce PD, while entinostat (20 mg/kg) was given intraperitoneally. Then, the neurological functions, PD markers, and HDACs were analysed in the control and experimental animals.

Results

The results demonstrated that rats that received entinostat displayed progressive motor, behavioural, and neurological function with attenuated α-synuclein and improved tyrosine-hydroxylase compared to control cells. Moreover, the induction of PD in rats demonstrated reduced levels of H2S, dopamine, 3, and 4-dihydroxyphenylacetic acid (DOPAC), and increased monoamine oxidase activity in PD rats. However, the rats that received entinostat demonstrated progressive levels of dopa and DOPAC, with attenuated levels of HDAC-2, -4, and -6 mRNA in the PD rats compared to controls. On the other hand, elevated (p < 0.01) levels of PD marker genes such as GDF3 and NMDA2b were reduced, with a significant increase in neuroprotective genes such as VDAC3 and CBX5 in entinostat-supplemented rats.

Conclusions

The study results suggest that inhibition of HDAC systematically improves the neurological functions, and hence treatments, emphasizing that HDACI, as the speculated mechanism, will be a promising mode of treatment in PD.

Impairment of platelet NO signalling in coronary artery spasm: role of hydrogen sulphide

BACKGROUND AND PURPOSE

The pathophysiology of coronary artery spasm (CAS), with its associated ischaemic crises, is currently poorly understood and treatment is frequently ineffective. In view of increasing evidence that platelet-based defects may occur in CAS patients, we investigated platelet reactivity in CAS patients and whether symptomatic crises reflect activation of platelet-endothelial interactions.

EXPERIMENTAL APPROACH

CAS patients were evaluated during acute and/or chronic symptomatic phases and compared with healthy control subjects. Inhibition of ADP-induced platelet aggregation by the NO donor sodium nitroprusside (SNP) and plasma concentrations of syndecan 1 (glycocalyx shedding marker), tryptase (mast cell activation marker) and platelet microparticles were measured.

KEY RESULTS

Inhibition of platelet aggregation by SNP was diminished in chronic CAS, with further (non-significant) deterioration during symptomatic crises, whereas plasma concentrations of syndecan 1, tryptase and platelet microparticles increased. Treatment of patients with high-dose N-acetylcysteine (NAC) plus glyceryl trinitrate rapidly increased platelet responsiveness to SNP and decreased plasma syndecan 1 concentrations. The effect of NAC on platelet responsiveness to SNP was confirmed in vitro and mimicked by the H₂ S donor NaHS. Conversely, inhibition of enzymatic production of H₂ S attenuated NAC effect.

CONCLUSION AND IMPLICATIONS

CAS is associated with substantial impairment of platelet NO signalling. During acute symptomatic exacerbations, platelet resistance to NO is aggravated, together with mast cell activation and damage to both vasculature and platelets. NAC, via release of H₂ S, reverses platelet resistance to NO and terminates glycocalyx shedding during symptomatic crises: This suggests that H₂ S donors may correct the pathophysiological anomalies underlying CAS.