Hydrogen sulfide and asthma

The Role of Hydrogen Sulfide in the Regulation of the Pulmonary Vasculature in Health and Disease

The gasotransmitter hydrogen sulfide (H2S; also termed sulfide) generally acts as a vasodilator in the systemic vasculature but causes a paradoxical constriction of pulmonary arteries (PAs). In light of evidence that a fall in the partial pressure in oxygen (pO2) increases cellular sulfide levels, it was proposed that a rise in sulfide in pulmonary artery smooth muscle cells (PASMCs) is responsible for hypoxic pulmonary vasoconstriction, the contraction of PAs which develops rapidly in lung regions undergoing alveolar hypoxia. In contrast, pulmonary hypertension (PH), a sustained elevation of pulmonary artery pressure (PAP) which can develop in the presence of a diverse array of pathological stimuli, including chronic hypoxia, is associated with a decrease in the expression of sulfide -producing enzymes in PASMCs and a corresponding fall in sulfide production by the lung. Evidence that PAP in animal models of PH can be lowered by administration of exogenous sulfide has led to an interest in using sulfide-donating agents for treating this condition in humans. Notably, intracellular H2S exists in equilibrium with other sulfur-containing species such as polysulfides and persulfides, and it is these reactive sulfur species which are thought to mediate most of its effects on cells through persulfidation of cysteine thiols on proteins, leading to changes in function in a manner similar to thiol oxidation by reactive oxygen species. This review sets out what is currently known about the mechanisms by which H2S and related sulfur species exert their actions on pulmonary vascular tone, both acutely and chronically, and discusses the potential of sulfide-releasing drugs as treatments for the different types of PH which arise in humans.

Physical Exercise: A Promising Treatment Against Organ Fibrosis

Fibrosis represents a terminal pathological manifestation encountered in numerous chronic diseases. The process involves the persistent infiltration of inflammatory cells, the transdifferentiation of fibroblasts into myofibroblasts, and the excessive deposition of extracellular matrix (ECM) within damaged tissues, all of which are characteristic features of organ fibrosis. Extensive documentation exists on fibrosis occurrence in vital organs such as the liver, heart, lungs, kidneys, and skeletal muscles, elucidating its underlying pathological mechanisms. Regular exercise is known to confer health benefits through its anti-inflammatory, antioxidant, and anti-aging effects. Notably, exercise exerts anti-fibrotic effects by modulating multiple pathways, including transforming growth factor-β1/small mother decapentaplegic protein (TGF-β1/Samd), Wnt/β-catenin, nuclear factor kappa-B (NF-kB), reactive oxygen species (ROS), microRNAs (miR-126, miR-29a, miR-101a), and exerkine (FGF21, irisin, FSTL1, and CHI3L1). Therefore, this paper aims to review the specific role and molecular mechanisms of exercise as a potential intervention to ameliorate organ fibrosis.

Hydrogen Sulfide: A Versatile Molecule and Therapeutic Target in Health and Diseases

In recent years, research has unveiled the significant role of hydrogen sulfide (H2S) in many physiological and pathological processes. The role of endogenous H2S, H2S donors, and inhibitors has been the subject of studies that have aimed to investigate this intriguing molecule. The mechanisms by which H2S contributes to different diseases, including inflammatory conditions, cardiovascular disease, viral infections, and neurological disorders, are complex. Despite noteworthy progress, several questions remain unanswered. H2S donors and inhibitors have shown significant therapeutic potential for various diseases. This review summarizes our current understanding of H2S-based therapeutics in inflammatory conditions, cardiovascular diseases, viral infections, and neurological disorders.

Highly Selective and Reversible Detection of Simulated Breath Hydrogen Sulfide Using Fe-Doped CuO Hollow Spheres: Enhanced Surface Redox Reaction by Multi-Valent Catalysts

The precise and reversible detection of hydrogen sulfide (H2S) at high humidity condition, a malodorous and harmful volatile sulfur compound, is essential for the self-assessment of oral diseases, halitosis, and asthma. However, the selective and reversible detection of trace concentrations of H2S (≈0.1 ppm) in high humidity conditions (exhaled breath) is challenging because of irreversible H2S adsorption/desorption at the surface of chemiresistors. The study reports the synthesis of Fe-doped CuO hollow spheres as H2S gas-sensing materials via spray pyrolysis. 4 at.% of Fe-doped CuO hollow spheres exhibit high selectivity (response ratio ≥ 34.4) over interference gas (ethanol, 1 ppm) and reversible sensing characteristics (100% recovery) to 0.1 ppm of H2S under high humidity (relative humidity 80%) at 175 °C. The effect of multi-valent transition metal ion doping into CuO on sensor reversibility is confirmed through the enhancement of recovery kinetics by doping 4 at.% of Ti- or Nb ions into CuO sensors. Mechanistic details of these excellent H2S sensing characteristics are also investigated by analyzing the redox reactions and the catalytic activity change of the Fe-doped CuO sensing materials. The selective and reversible detection of H2S using the Fe-doped CuO sensor suggested in this work opens a new possibility for halitosis self-monitoring.

Advances and Opportunities in H2S Measurement in Chemical Biology

Hydrogen sulfide (H2S) is an important biological mediator across all kingdoms of life and plays intertwined roles in various disciplines, ranging from geochemical cycles to industrial processes. A common need across these broad disciplines is the ability to detect and measure H2S in complex sample environments. This Perspective focuses on key advances and opportunities for H2S detection and quantification that are relevant to chemical biology. Specifically, we focus on methods for H2S detection and quantification most commonly used in biological samples, including activity-based H2S probes, the methylene blue assay, the monobromobimane assay, and H2S-sensitive electrode measurements. Our goal is to help simplify what at first may seem to be an overwhelming array of detection and measurement choices, to articulate the strengths and limitations of individual techniques, and to highlight key unmet needs and opportunities in the field.

Sensitive Detection of Various Forms of Hydrogen Sulfide via Highly Selective Naphthalimide-Based Fluorescent Probe

Hydrogen sulfide (H2S) is an important gasotransmitter, but only a few methods are available for real-time detection. Fluorescent probes are attractive tools for biological applications because of their high sensitivity, convenience, rapid implementation, noninvasive monitoring capability, and simplicity in fluorescent imaging of living cells and tissues. Herein, we report on a pro-fluorescent probe, NAP-Py-N3 based on naphthalimide derivative, which was found to show high selectivity toward H2S over various other analytes, including biothiols, making it feasible to detect H2S. After reaction with H2S, this probe showed rapid and significant turn-on green fluorescent enhancement at 553 nm (about 54-fold, k2 = 9.62 M-1s-1), high sensitivity (LOD: 15.5 nM), significant Stokes shift (118 nm), and it was found that the fluorescence quantum yield of fluorescence product can reach 0.36. Moreover, the probe has also been successfully applied to detect the gaseous H2S and to confirm the presence of H2S released from modern organic donors, which in recent years have been commonly used to investigate the role of H2S in biological systems. All the results indicate that this probe is excellent and highly valuable.

Severe Acute Bronchial Asthma with Sepsis: Determining the Status of Biomarkers in the Diagnosis of the Disease

Bronchial asthma is a widely prevalent illness that substantially impacts an individual's health standard worldwide and has a significant financial impact on society. Global guidelines for managing asthma do not recommend the routine use of antimicrobial agents because most episodes of the condition are linked to viral respiratory tract infections (RTI), and bacterial infection appears to have an insignificant impact. However, antibiotics are recommended when there is a high-grade fever, a consolidation on the chest radiograph, and purulent sputum that contains polymorphs rather than eosinophils. Managing acute bronchial asthma with sepsis, specifically the choice of whether or not to initiate antimicrobial treatment, remains difficult since there are currently no practical clinical or radiological markers that allow for a simple distinction between viral and bacterial infections. Researchers found that serum procalcitonin (PCT) values can efficiently and safely minimize antibiotic usage in individuals with severe acute asthma. Again, the clinical manifestations of acute asthma and bacterial RTI are similar, as are frequently used test values, like C-reactive protein (CRP) and white blood cell (WBC) count, making it harder for doctors to differentiate between viral and bacterial infections in asthma patients. The role and scope of each biomarker have not been precisely defined yet, although they have all been established to aid healthcare professionals in their diagnostics and treatment strategies.

Serum hydrogen sulphide levels in acute asthmatic children: a case control study

Background

It’s thought that respiratory epithelium-produced reduced hydrogen sulphide (H2S) plays a role in the pathophysiology of acute asthma. In this case–control research, blood H2S levels were examined between matched acutely asthmatic children and non-asthmatic controls. The grade of acute asthma, vital signs and absolute eosinophilic count in the asthmatic children were likewise associated with the blood H2S level.

Methods

Forty Egyptian asthmatic children had visited the emergency room and forty age- and sex-matched non-asthmatic controls had their blood H2S levels measured using enzyme-linked immunosorbent assay (ELISA).

Results

The serum H2S in the two groups did not differ statistically significantly. Serum H2S and respiratory rate showed a moderately significant inverse connection (r = -0.325, p = 0.041). However, serum H2S and other clinical or laboratory variables exhibited no meaningful relationships. Patients' absolute and percentage eosinophil counts were considerably higher than healthy controls. Serum H2S exhibited a sensitivity of 50% and a specificity of 32.5% for identifying children with acute asthma from non-asthmatic children.

Conclusion

Children with asthma and those without asthma had similar serum H2S levels. It has a lousy relationship with respiratory rate. It is indicated that it is an inadequate screening and diagnostic tool since it has low sensitivity (50%) and specificity (32.5%) in differentiating acute asthmatic children.

Low level exposure to hydrogen sulfide: a review of emissions, community exposure, health effects, and exposure guidelines

Hydrogen sulfide (H2S) is a toxic gas that is well-known for its acute health risks in occupational settings, but less is known about effects of chronic and low-level exposures. This critical review investigates toxicological and experimental studies, exposure sources, standards, and epidemiological studies pertaining to chronic exposure to H2S from both natural and anthropogenic sources. H2S releases, while poorly documented, appear to have increased in recent years from oil and gas and possibly other facilities. Chronic exposures below 10 ppm have long been associated with odor aversion, ocular, nasal, respiratory and neurological effects. However, exposure to much lower levels, below 0.03 ppm (30 ppb), has been associated with increased prevalence of neurological effects, and increments below 0.001 ppm (1 ppb) in H2S concentrations have been associated with ocular, nasal, and respiratory effects. Many of the studies in the epidemiological literature are limited by exposure measurement error, co-pollutant exposures and potential confounding, small sample size, and concerns of representativeness, and studies have yet to consider vulnerable populations. Long-term community-based studies are needed to confirm the low concentration findings and to refine exposure guidelines. Revised guidelines that incorporate both short- and long-term limits are needed to protect communities, especially sensitive populations living near H2S sources.

Multiplexed DNA-functionalized graphene sensor with artificial intelligence-based discrimination performance for analyzing chemical vapor compositions

This study presents a new technology that can detect and discriminate individual chemical vapors to determine the chemical vapor composition of mixed chemical composition in situ based on a multiplexed DNA-functionalized graphene (MDFG) nanoelectrode without the need to condense the original vapor or target dilution. To the best of our knowledge, our artificial intelligence (AI)-operated arrayed electrodes were capable of identifying the compositions of mixed chemical gases with a mixed ratio in the early stage. This innovative technology comprised an optimized combination of nanodeposited arrayed electrodes and artificial intelligence techniques with advanced sensing capabilities that could operate within biological limits, resulting in the verification of mixed vapor chemical components. Highly selective sensors that are tolerant to high humidity levels provide a target for "breath chemovapor fingerprinting" for the early diagnosis of diseases. The feature selection analysis achieved recognition rates of 99% and above under low-humidity conditions and 98% and above under humid conditions for mixed chemical compositions. The 1D convolutional neural network analysis performed better, discriminating the compositional state of chemical vapor under low- and high-humidity conditions almost perfectly. This study provides a basis for the use of a multiplexed DNA-functionalized graphene gas sensor array and artificial intelligence-based discrimination of chemical vapor compositions in breath analysis applications.

The effect of mitochondria-targeted slow hydrogen sulfide releasing donor AP39-treatment on airway inflammation

Mitochondrial dysfunction has been shown to contribute to the pathophysiology of airway diseases. Therefore, mitochondria are targeted in the development of new therapeutic approaches. Hydrogen sulfide (H₂S) has been shown to be involved in the pathophysiological processes of airway inflammation. We aimed to evaluate the effect of mitochondria-targeted slow H₂S releasing donor AP39 [(10-oxo-10-(4-(3-thioxo-3H-1,2-dithiol5yl)phenoxy)decyl)triphenylphosphoniumbromide)] on lipopolysaccharide (LPS)-induced airway inflammation in mice. LPS was applied to female Balb/c mice by intranasal (i.n.) route to induce airway inflammation and the subgroups of mice were treated with i.n. AP39 (250-1000 nmol/kg). 48 h after LPS administration airway reactivity was evaluated in vivo, then bronchoalveolar lavage (BAL) fluid and lungs were collected. LPS application led to bronchial hyperreactivity and neutrophil infiltration into the lung tissues along with increased TNF-α, IL-1β and IL-6 levels in BAL fluid. LPS also induced an increase in the rate of glycolysis, glycogenolysis and Krebs-cycle. AP39 treatment prevented the LPS-induced bronchial hyperreactivity and reversed the increase in TNF-α and IL-6 levels in BAL fluid. The increase in neutrophil numbers in BAL fluid was also prevented by AP39 treatment at the highest dose. Our results indicate that AP39 can prevent bronchial hyperreactivity and decrease airway inflammation. Targeting H₂S to the mitochondria may be a new therapeutic approach in airway inflammation.

Salen, salan and salalen zinc(II) complexes in the interaction with HS-: time-resolved fluorescence applications

In the current work we investigate the route of interaction of a newly synthesized family of zinc complexes with HS^- by a plethora of different spectroscopic techniques. A computational analysis on the time dependent density functional theory (TD-DFT) level explored the overall fluorescence properties of the title complexes and their different fluorescence responses to HS^-. Time-resolved fluorescence experiments were also performed and highlight the great potential of the current systems to be implemented as HS^- fluorescent sensors.

Targeting biomarkers in the gas phase through a chemoresistive electronic nose based on graphene functionalized with metal phthalocyanines

Electronic noses (e-noses) have received considerable interest in the past decade as they can match the emerging needs of modern society such as environmental monitoring, health screening, and food quality tracking. For practical applications of e-noses, it is necessary to collect large amounts of data from an array of sensing devices that can detect interactions with molecules reliably and analyze them via pattern recognition. The use of graphene (Gr)-based arrays of chemiresistors in e-noses is still virtually missing, though recent reports on Gr-based chemiresistors have disclosed high sensing performances upon functionalization of the pristine layer, opening up the possibility of being implemented into e-noses. In this work, with the aim of creating a robust and chemically stable interface that combines the chemical properties of metal phthalocyanines (M-Pc, M = Fe, Co, Ni, Zn) with the superior transport properties of Gr, an array of Gr-based chemiresistor sensors functionalized with drop-cast M-Pc thin layers has been developed. The sensing capability of the array was tested towards biomarkers for breathomics application, with a focus on ammonia (NH₃). Exposure to NH₃ has been carried out drawing the calibration curve and estimating the detection limit for all the sensors. The discrimination capability of the array has then been tested, carrying out exposure to several gases (hydrogen sulfide, acetone, ethanol, 2-propanol, water vapour and benzene) and analysing the data through principal component analysis (PCA). The PCA pattern recognition results show that the developed e-nose is able to discriminate all the tested gases through the synergic contribution of all sensors.

The Role of Hydrogen Sulfide in the Development and Progression of Lung Cancer

Lung cancer is one of the 10 most common cancers in the world, which seriously affects the normal life and health of patients. According to the investigation report, the 3-year survival rate of patients with lung cancer is less than 20%. Heredity, the environment, and long-term smoking or secondhand smoke greatly promote the development and progress of the disease. The mechanisms of action of the occurrence and development of lung cancer have not been fully clarified. As a new type of gas signal molecule, hydrogen sulfide (H₂S) has received great attention for its physiological and pathological roles in mammalian cells. It has been found that H₂S is widely involved in the regulation of the respiratory system and digestive system, and plays an important role in the occurrence and development of lung cancer. H₂S has the characteristics of dissolving in water and passing through the cell membrane, and is widely expressed in body tissues, which determines the possibility of its participation in the occurrence of lung cancer. Both endogenous and exogenous H₂S may be involved in the inhibition of lung cancer cells by regulating mitochondrial energy metabolism, mitochondrial DNA integrity, and phosphoinositide 3-kinase/protein kinase B co-pathway hypoxia-inducible factor-1α (HIF-1α). This article reviews and discusses the molecular mechanism of H₂S in the development of lung cancer, and provides novel insights for the prevention and targeted therapy of lung cancer.

Ultrasensitive Chemiresistive Gas Sensor Can Diagnose Asthma and Monitor Its Severity by Analyzing Its Biomarker H2S: An Experimental, Clinical, and Theoretical Study

Asthma is a chronic disease characterized by recurrent attacks of breathlessness and wheezing, which vary in severity and frequency from person to person. H₂S is considered as the biomarker of asthma. Here, an ultrasensitive chemiresistive H₂S gas sensor based on a γ-Bi₂MoO₆-CuO heterostructure with a detection limit of 5 ppb has been fabricated. It can distinguish asthmatic patients from healthy people roughly by analyzing the exhaled breaths of 28 asthmatic patients and 28 healthy people, suggesting that the sensor can be used to assist physicians in the diagnosis of asthma. Pathologically, it is discovered by this sensor that with the relief of asthma, the concentration of H₂S in one's exhaled breath gradually increases. This subtle concentration variation of H₂S can be accurately detected, indicating that this sensor can be used in the asthma severity monitoring too. Physical models have been built by first-principles calculation to reveal the causes of the sensor's ultrasensitivity. The stable adsorption of H₂S on the surface of CuO results in massive charge transferring and the appearance of the defect states, which play the major role in the ultrasensitivity of the sensor. Upon integrating this sensor with circuits, the cheap, smart, and portable H₂S sensing device can be obtained, which can make asthmatic patients' access to this device easy and make the severity monitoring of asthma convenient, especially for children and the aged.

A Cell Trappable Methyl Rhodol-Based Fluorescent Probe for Hydrogen Sulfide Detection

Hydrogen sulfide is a biologically important molecule and developing chemical tools that enable further investigations into the functions of H2 S is essential. Fluorescent turn-on H2 S probes have been developed for use in cellulo and in vivo, but the membrane permeability of these probes can lead to probe leakage and signal attenuation over time. Here we report a cell trappable fluorescent probe for H2 S, CT-MeRhoAz, which is based on a methylrhodolazide scaffold derivatized with an acetoxymethyl ester group. Prior to ester cleavage, the CT-MeRhoAz probe generates a 2500-fold turn-on response to H2 S, which is enhanced to a 3000-fold response for the carboxylic acid form of the probe. Additionally, the probe is highly selective for H2 S over other biologically relevant sulfur, oxygen, and nitrogen-based analytes. Live cell imaging experiments confirmed the biocompatibility of CT-MeRhoAz and also that it is cell trappable, unlike the parent MeRhoAz scaffold.

Exogenous H2S Protects against Septic Cardiomyopathy by Inhibiting Autophagy through the AMPK/mTOR Pathway

Background

Given the cardioprotective role of autophagy, this study aimed to investigate the protective effect of exogenous H₂S (NaHS) on infectious cardiomyopathy through the inhibition of the AMPK/mTOR pathway.

Methods

In this study, sepsis models were established by cecal ligation and puncture (CLP) induction in vivo and intraperitoneal injection of NaHS was performed. Autophagy- and apoptosis-related proteins were observed by western blot, isolated myocardial tissue morphology was observed by hematoxylin-eosin (H&E) staining, and myocardial apoptosis was evaluated by the tunnel method. The ultrastructure of autophagy was observed by using an electron transmission electron microscope.

Results

In an SD rat model of cecum ligation puncture-induced sepsis, the level of autophagy-related proteins was significantly increased, and hematoxylin and eosin staining showed irregular myocardial bands and swollen cardiomyocytes. Following NaHS treatment, the level of autophagy-related proteins decreased, and electron transmission microscopy revealed decreased autophagosomes. Echocardiography suggested an increase in ejection fraction and significant relief of myocardial inhibition.

Conclusions

Our results suggest that NaHS treatment can attenuate the cellular damage caused by excessive autophagy through the AMPK/mTOR pathway.

Physiological roles of hydrogen sulfide in mammalian cells, tissues and organs

H2S belongs to the class of molecules known as gasotransmitters, which also includes nitric oxide (NO) and carbon monoxide (CO). Three enzymes are recognized as endogenous sources of H2S in various cells and tissues: cystathionine g-lyase (CSE), cystathionine β-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (3-MST). The current article reviews the regulation of these enzymes as well as the pathways of their enzymatic and non-enzymatic degradation and elimination. The multiple interactions of H2S with other labile endogenous molecules (e.g. NO) and reactive oxygen species are also outlined. The various biological targets and signaling pathways are discussed, with special reference to H2S and oxidative posttranscriptional modification of proteins, the effect of H2S on channels and intracellular second messenger pathways, the regulation of gene transcription and translation and the regulation of cellular bioenergetics and metabolism. The pharmacological and molecular tools currently available to study H2S physiology are also reviewed, including their utility and limitations. In subsequent sections, the role of H2S in the regulation of various physiological and cellular functions is reviewed. The physiological role of H2S in various cell types and organ systems are overviewed. Finally, the role of H2S in the regulation of various organ functions is discussed as well as the characteristic bell-shaped biphasic effects of H2S. In addition, key pathophysiological aspects, debated areas, and future research and translational areas are identified A wide array of significant roles of H2S in the physiological regulation of all organ functions emerges from this review.

Progress on the reaction-based methods for detection of endogenous hydrogen sulfide

Hydrogen sulfide (H₂S) is a biologically signaling molecule that mediates a wide range of physiological functions, which is frequently misregulated in numerous pathological processes. As such, measurement of H₂S holds great attention due to its unique physiological and pathophysiological roles. Currently, a variety of methods based on the H₂S-involved reactions have been reported for detection of endogenous H₂S, bearing the advantages of good specificity and high sensitivity. This review describes in detail the types of reactions, their mechanisms, and their applications in biological research, thus hopefully providing some guidelines to the researchers in this field for further investigation.

Recent Trends in Exhaled Breath Diagnosis Using an Artificial Olfactory System

Artificial olfactory systems are needed in various fields that require real-time monitoring, such as healthcare. This review introduces cases of detection of specific volatile organic compounds (VOCs) in a patient's exhaled breath and discusses trends in disease diagnosis technology development using artificial olfactory technology that analyzes exhaled human breath. We briefly introduce algorithms that classify patterns of odors (VOC profiles) and describe artificial olfactory systems based on nanosensors. On the basis of recently published research results, we describe the development trend of artificial olfactory systems based on the pattern-recognition gas sensor array technology and the prospects of application of this technology to disease diagnostic devices. Medical technologies that enable early monitoring of health conditions and early diagnosis of diseases are crucial in modern healthcare. By regularly monitoring health status, diseases can be prevented or treated at an early stage, thus increasing the human survival rate and reducing the overall treatment costs. This review introduces several promising technical fields with the aim of developing technologies that can monitor health conditions and diagnose diseases early by analyzing exhaled human breath in real time.

Exploring the performance of a functionalized CNT-based sensor array for breathomics through clustering and classification algorithms: from gas sensing of selective biomarkers to discrimination of chronic obstructive pulmonary disease

An array of carbon nanotube (CNT)-based sensors was produced for sensing selective biomarkers and evaluating breathomics applications with the aid of clustering and classification algorithms. We assessed the sensor array performance in identifying target volatiles and we explored the combination of various classification algorithms to analyse the results obtained from a limited dataset of exhaled breath samples. The sensor array was exposed to ammonia (NH₃), nitrogen dioxide (NO₂), hydrogen sulphide (H₂S), and benzene (C₆H₆). Among them, ammonia (NH₃) and nitrogen dioxide (NO₂) are known biomarkers of chronic obstructive pulmonary disease (COPD). Calibration curves for individual sensors in the array were obtained following exposure to the four target molecules. A remarkable response to ammonia (NH₃) and nitrogen dioxide (NO₂), according to benchmarking with available data in the literature, was observed. Sensor array responses were analyzed through principal component analysis (PCA), thus assessing the array selectivity and its capability to discriminate the four different target volatile molecules. The sensor array was then exposed to exhaled breath samples from patients affected by COPD and healthy control volunteers. A combination of PCA, supported vector machine (SVM), and linear discrimination analysis (LDA) shows that the sensor array can be trained to accurately discriminate healthy from COPD subjects, in spite of the limited dataset.

Extensive application of clustering and classification algorithms shows the potential of a CNT-based sensor array in breathomics.

Gasping for Sulfide: A Critical Appraisal of Hydrogen Sulfide in Lung Disease and Accelerated Aging

Hydrogen sulfide (H₂S) is a gaseous signaling molecule involved in a plethora of physiological and pathological processes. It is primarily synthesized by cystathionine-β-synthase, cystathionine-γ-lyase, and 3-mercaptopyruvate sulfurtransferase as a metabolite of the transsulfuration pathway. H₂S has been shown to exert beneficial roles in lung disease acting as an anti-inflammatory and antiviral and to ameliorate cell metabolism and protect from oxidative stress. H₂S interacts with transcription factors, ion channels, and a multitude of proteins via post-translational modifications through S-persulfidation ("sulfhydration"). Perturbation of endogenous H₂S synthesis and/or levels have been implicated in the development of accelerated lung aging and diseases, including asthma, chronic obstructive pulmonary disease, and fibrosis. Furthermore, evidence indicates that persulfidation is decreased with aging. Here, we review the use of H₂S as a biomarker of lung pathologies and discuss the potential of using H₂S-generating molecules and synthesis inhibitors to treat respiratory diseases. Furthermore, we provide a critical appraisal of methods of detection used to quantify H₂S concentration in biological samples and discuss the challenges of characterizing physiological and pathological levels. Considerations and caveats of using H₂S delivery molecules, the choice of generating molecules, and concentrations are also reviewed. Antioxid. Redox Signal. 35, 551-579.

Relationship Between Endogenous Hydrogen Sulfide and Pulmonary Vascular Indexes on High-Resolution Computed Tomography in Patients with Chronic Obstructive Pulmonary Disease

Objective

To explore the relationship between endogenous hydrogen sulfide (H₂S) and high-resolution computed tomography (HRCT) indexes in pulmonary vascular remodeling.

Methods

A total of 94 stable chronic obstructive pulmonary disease (COPD) patients were recruited for the study．Plasma H₂S levels were measured using fluorescence probe. Fluorescence quantitative polymerase chain reaction was used to measure H₂S synthase cystathionine-γ-lyase (CSE) mRNA and cystathionine-β-synthesis enzyme (CBS) mRNA. The main pulmonary artery diameter (mPAD), axial diagonal mPAD, coronal mPAD, sagittal mPAD, right pulmonary artery diameter (RPAD), left pulmonary artery diameter (LPAD), and ascending aortic diameter (AAD) and the percentage of total cross-sectional area of vessels less than 5 mm² of total lung area (%CSA <5) on HRCT were measured. Pulmonary arterial systolic pressure (PASP) of echocardiography, blood gas analysis, and routine blood tests were performed. Correlation analysis and multivariate linear regression were performed using SPSS 22.0.

Results

H₂S was negatively correlated with mPAD, axial diagonal mPAD, and sagittal mPAD (r = -0.25~-0.32) and positively correlated with PaO₂ (r = 0.35). Relative expression of CSE mRNA was positively correlated with PASP, coronal mPAD, sagittal mPAD, white blood cell count (WBC), and neutrophil count (N) (r = 0.30~0.44). The relative expression of CBS mRNA was positively correlated with PASP, WBC, and N (r = 0.34~0.41). In separate models predicting pulmonary vascular indexes, a 1μmol/L increase in H₂S predicted lower pulmonary artery diameter (for axial diagonal mPAD, 0.76mm lower; for mPAD/AAD, 0.68mm lower). All P values were less than 0.05.

Conclusion

Endogenous H₂S may be involved in pulmonary vascular remodeling, providing a new method for the diagnosis and treatment of COPD. The generation of H₂S may be inhibited by hypoxia, inflammation, etc.

Review - Nutraceuticals Can Target Asthmatic Bronchoconstriction: NADPH Oxidase-Dependent Oxidative Stress, RhoA and Calcium Dynamics

Activation of various isoforms of NADPH oxidase contributes to the pathogenesis of asthma at multiple levels: promoting hypercontractility, hypertrophy, and proliferation of airway smooth muscle; enabling lung influx of eosinophils via VCAM-1; and mediating allergen-induced mast cell activation. Free bilirubin, which functions physiologically within cells as a feedback inhibitor of NADPH oxidase complexes, has been shown to have a favorable impact on each of these phases of asthma pathogenesis. The spirulina chromophore phycocyanobilin (PhyCB), a homolog of bilirubin's precursor biliverdin, can mimic the inhibitory impact of biliverdin/bilirubin on NADPH oxidase activity, and spirulina's versatile and profound anti-inflammatory activity in rodent studies suggests that PhyCB may have potential as a clinical inhibitor of NADPH oxidase. Hence, spirulina or PhyCB-enriched spirulina extracts merit clinical evaluation in asthma. Promoting biosynthesis of glutathione and increasing the expression and activity of various antioxidant enzymes - as by supplementing with N-acetylcysteine, Phase 2 inducers (eg, lipoic acid), selenium, and zinc - may also blunt the contribution of oxidative stress to asthma pathogenesis. Nitric oxide (NO) and hydrogen sulfide (H2S) work in various ways to oppose pathogenic mechanisms in asthma; supplemental citrulline and high-dose folate may aid NO synthesis, high-dose biotin may mimic and possibly potentiate NO's activating impact on soluble guanylate cyclase, and NAC and taurine may boost H2S synthesis. The amino acid glycine has a hyperpolarizing effect on airway smooth muscle that is bronchodilatory. Insuring optimal intracellular levels of magnesium may modestly blunt the stimulatory impact of intracellular free calcium on bronchoconstriction. Nutraceutical regimens or functional foods incorporating at least several of these agents may have utility as nutraceutical adjuvants to standard clinical management of asthma.

Hydrogen Sulfide Metabolism and Pulmonary Hypertension

Pulmonary hypertension (PH) is a severe and multifactorial disease characterized by a progressive elevation of pulmonary arterial resistance and pressure due to remodeling, inflammation, oxidative stress, and vasoreactive alterations of pulmonary arteries (PAs). Currently, the etiology of these pathological features is not clearly understood and, therefore, no curative treatment is available. Since the 1990s, hydrogen sulfide (H₂S) has been described as the third gasotransmitter with plethoric regulatory functions in cardiovascular tissues, especially in pulmonary circulation. Alteration in H₂S biogenesis has been associated with the hallmarks of PH. H₂S is also involved in pulmonary vascular cell homeostasis via the regulation of hypoxia response and mitochondrial bioenergetics, which are critical phenomena affected during the development of PH. In addition, H₂S modulates ATP-sensitive K⁺ channel (K_ATP) activity, and is associated with PA relaxation. In vitro or in vivo H₂S supplementation exerts antioxidative and anti-inflammatory properties, and reduces PA remodeling. Altogether, current findings suggest that H₂S promotes protective effects against PH, and could be a relevant target for a new therapeutic strategy, using attractive H₂S-releasing molecules. Thus, the present review discusses the involvement and dysregulation of H₂S metabolism in pulmonary circulation pathophysiology.

Hydrogen sulfide protects against IL-1β-induced inflammation and mitochondrial dysfunction-related apoptosis in chondrocytes and ameliorates osteoarthritis

The inflammatory environment and excessive chondrocyte apoptosis have been demonstrated to play crucial roles in the onset of osteoarthritis (OA). Hydrogen sulfide (H2 S), a gaseous signalling molecule, exerts an inhibitory effect on inflammation and apoptosis in several degenerative diseases. However, the protective effect of H2 S against OA has not been fully clarified, and its underlying mechanism should be examined further. In the current study, the role of endogenous H2 S in the pathogenesis of OA and its protective effects on interleukin (IL)-1β-induced chondrocytes were identified. Our data revealed decreased H2 S expression in both human degenerative OA cartilage tissue and IL-1β-induced chondrocytes. Pretreatment with the H2 S donor sodium hydrosulfide (NaHS) dramatically attenuated IL-1β-induced overproduction of inflammatory cytokines and improved the balance between anabolic and catabolic chondrocyte capacities, and these effects were dependent on PI3K/AKT pathway-mediated inhibition of nuclear factor kappa B (NF-κB). Moreover, mitochondrial dysfunction-related apoptosis was significantly reversed by NaHS in IL-1β-stimulated chondrocytes. Mechanistically, NaHS partially suppressed IL-1β-induced phosphorylation of the mitogen-activated protein kinase (MAPK) cascades. Furthermore, in the destabilization of the medial meniscus mouse model, OA progression was ameliorated by NaHS administration. Taken together, these results suggest that H2 S may antagonize IL-1β-induced inflammation and mitochondrial dysfunction-related apoptosis via selective suppression of the PI3K/Akt/NF-κB and MAPK signalling pathways, respectively, in chondrocytes and may be a potential therapeutic agent for the treatment of OA.

The Role of Hydrogen Sulfide in Respiratory Diseases

Respiratory diseases are leading causes of death and disability around the globe, with a diverse range of health problems. Treatment of respiratory diseases and infections has been verified to be thought-provoking because of the increasing incidence and mortality rate. Hydrogen sulfide (H₂S) is one of the recognized gaseous transmitters involved in an extensive range of cellular functions, and physiological and pathological processes in a variety of diseases, including respiratory diseases. Recently, the therapeutic potential of H₂S for respiratory diseases has been widely investigated. H₂S plays a vital therapeutic role in obstructive respiratory disease, pulmonary fibrosis, emphysema, pancreatic inflammatory/respiratory lung injury, pulmonary inflammation, bronchial asthma and bronchiectasis. Although the therapeutic role of H₂S has been extensively studied in various respiratory diseases, a concrete literature review will have an extraordinary impact on future therapeutics. This review provides a comprehensive overview of the effective role of H₂S in respiratory diseases. Besides, we also summarized H₂S production in the lung and its metabolism processes in respiratory diseases.

Hydrogen sulfide as a novel biomarker of asthma and chronic obstructive pulmonary disease

Hydrogen sulfide (H₂S) has recently been recognised as the third important gas-signalling molecule, besides nitric oxide and carbon monoxide. H₂S has been reported to be produced by many cell types in mammalian tissues and organs throughout the actions of H₂S-generating enzymes or redox reactions between the oxidation of glucose and element of sulfur. Although the pathological role of H₂S has not yet been fully elucidated, accumulative data suggest that H₂S may have biphasic effects. Briefly, it mainly has anti-inflammatory and antioxidant roles, although it can also have pro-inflammatory effects under certain conditions where rapid release of H₂S in tissues occur, such as sepsis. To date, there have been several clinical studies published on H₂S in respiratory disorders, including asthma and chronic obstructive pulmonary disease (COPD). According to previous studies, H₂S is detectable in serum, sputum, and exhaled breath, although a gold standard method for detection has not yet been established. In asthma and COPD, H₂S levels in serum and sputum can vary depending on the underlying conditions such as an acute exacerbation. Furthermore, sputum H₂S in particular correlates with sputum neutrophils and the degree of airflow limitation, indicating that H₂S has potential as a novel promising biomarker for neutrophilic airway inflammation for predicting current control state as well as future risks of asthma. In the future, concurrent measures of H₂S with conventional inflammatory biomarkers (fractional exhaled nitric oxide, eosinophils etc) may provide more useful information regarding the identification of inflammatory phenotypes of asthma and COPD for personalised treatment.

A Fluorescent Probe for Selective Facile Detection of H2S in Serum Based on an Albumin-Binding Fluorophore and Effective Masking Reagent

A fluorescent probe (4-(2-(4-(diethylamino)phenyl)-4-methyl-5-oxo-4,5-dihydrothieno[3,2-b]pyridin-7-yl)phenyl 2,4-dinitrobenzenesulfonate, KF-DNBS) for facile detection of H₂S in serum was developed based on the combination of an environment-sensitive fluorophore (2-(4-(diethylamino)phenyl)-7-(4-hydroxyphenyl)-4-methylthieno[3,2-b]pyridin-5(4H)-one, KF) with albumin and the 2,4-dinitrobenzene sulfonyl (DNBS) group as a recognition unit for H₂S. KF-DNBS showed remarkable fluorescence enhancement due to H₂S-triggered thiolysis followed by the formation of a fluorescent fluorophore (KF)-albumin complex. The H₂S detection limit of KF-DNBS was estimated to be 3.2 μM, and KF-DNBS achieves a high selectivity to H₂S over biothiols by employing 2-formyl benzene boronic acid (2-FBBA) as an effective masking reagent. Furthermore, under optimized sensing conditions, KF-DNBS could be applied to accurately determine spiked H₂S in human serum without the need for any further procedure for the removal of serum proteins.

H2S in acute lung injury: a therapeutic dead end(?)

This review addresses the plausibility of hydrogen sulfide (H₂S) therapy for acute lung injury (ALI) and circulatory shock, by contrasting the promising preclinical results to the present clinical reality. The review discusses how the narrow therapeutic window and width, and potentially toxic effects, the route, dosing, and timing of administration all have to be balanced out very carefully. The development of standardized methods to determine in vitro and in vivo H₂S concentrations, and the pharmacokinetics and pharmacodynamics of H₂S-releasing compounds is a necessity to facilitate the safety of H₂S-based therapies. We suggest the potential of exploiting already clinically approved compounds, which are known or unknown H₂S donors, as a surrogate strategy.

Effect of prenatal cigarette smoke exposure on sevoflurane-induced respiratory suppression in neonatal rats and the protective role of hydrogen sulfide

Prenatal cigarette smoke (CS) exposure causes numerous respiratory health problems in infants. This study aimed to investigate the effect of prenatal CS exposure on sevoflurane-induced respiratory suppression in neonatal rats and the protective role of H₂S. We found that at baseline, minute ventilation (V'_E), respiratory frequency (f_R), and tidal volume (V_T) were similar among tested groups, whereas sigh frequency (f_S) was lower in CS group than in the Control group. During 3 % sevoflurane anesthesia, V'_E was decreased, f_R was slowed, V_T was increased, and f_S was reduced in all groups; however, the decline in f_R and increase in V_T was greater in CS group than in the Control group. During the recovery, f_S remained lower in CS group. The above changes of respiratory response caused by prenatal CS exposure were alleviated by NaHS pretreatment (a donor of H₂S, 56 μmol/kg/d, intraperitoneal injection). These results indicated that prenatal CS exposure alters the breathing into a much slower and deeper manner in neonatal rats during sevoflurane anesthesia, and H₂S mitigates this respiratory change.

The Role of Host-Generated H2S in Microbial Pathogenesis: New Perspectives on Tuberculosis

For centuries, hydrogen sulfide (H₂S) was considered primarily as a poisonous gas and environmental hazard. However, with the discovery of prokaryotic and eukaryotic enzymes for H₂S production, breakdown, and utilization, H₂S has emerged as an important signaling molecule in a wide range of physiological and pathological processes. Hence, H₂S is considered a gasotransmitter along with nitric oxide (•NO) and carbon monoxide (CO). Surprisingly, despite having overlapping functions with •NO and CO, the role of host H₂S in microbial pathogenesis is understudied and represents a gap in our knowledge. Given the numerous reports that followed the discovery of •NO and CO and their respective roles in microbial pathogenesis, we anticipate a rapid increase in studies that further define the importance of H₂S in microbial pathogenesis, which may lead to new virulence paradigms. Therefore, this review provides an overview of sulfide chemistry, enzymatic production of H₂S, and the importance of H₂S in metabolism and immunity in response to microbial pathogens. We then describe our current understanding of the role of host-derived H₂S in tuberculosis (TB) disease, including its influences on host immunity and bioenergetics, and on Mycobacterium tuberculosis (Mtb) growth and survival. Finally, this review discusses the utility of H₂S-donor compounds, inhibitors of H₂S-producing enzymes, and their potential clinical significance.

A review: Red/near-infrared (NIR) fluorescent probes based on nucleophilic reactions of H2 S since 2015

The topics of human health and disease are always the focus of much attention. Hydrogen sulfide (H₂ S), as a double-edged sword, plays an important role in biological systems. Studies have revealed that endogenous H₂ S is important to maintain normal physiological functions. Conversely, abnormal levels of H₂ S may contribute to various diseases. Due to the importance of H₂ S in physiology and pathology, research into the effects of H₂ S has been active in recent years. Fluorescent probes with red/near-infrared (NIR) emissions (620-900 nm) are more suitable for imaging applications in vivo, because of their negligible photodamage, deep tissue penetration, and maximum lack of interference from background autofluorescence. H₂ S, an 'evil and positive' molecule, is not only toxic, but also produces significant effects; a 'greedy' molecule, is not only a strong nucleophile under physiological conditions, but also undergoes a continuous double nucleophilic reaction. Therefore, in this tutorial review, we will highlight recent advances made since 2015 in the development and application of red/NIR fluorescent probes based on nucleophilic reactions of H₂ S.

Development of a Sensing Array for Human Breath Analysis Based on SWCNT Layers Functionalized with Semiconductor Organic Molecules

A sensor array based on heterojunctions between semiconducting organic layers and single walled carbon nanotube (SWCNT) films is produced to explore applications in breathomics, the molecular analysis of exhaled breath. The array is exposed to gas/volatiles relevant to specific diseases (ammonia, ethanol, acetone, 2-propanol, sodium hypochlorite, benzene, hydrogen sulfide, and nitrogen dioxide). Then, to evaluate its capability to operate with real relevant biological samples the array is exposed to human breath exhaled from healthy subjects. Finally, to provide a proof of concept of its diagnostic potential, the array is exposed to exhaled breath samples collected from subjects with chronic obstructive pulmonary disease (COPD), an airway chronic inflammatory disease not yet investigated with CNT-based sensor arrays, and breathprints are compared with those obtained from of healthy subjects. Principal component analysis shows that the sensor array is able to detect various target gas/volatiles with a clear fingerprint on a 2D subspace, is suitable for breath profiling in exhaled human breath, and is able to distinguish subjects with COPD from healthy subjects based on their breathprints. This classification ability is further improved by selecting the most responsive sensors to nitrogen dioxide, a potential biomarker of COPD.

H2S-Releasing Composite: a Gasotransmitter Platform for Potential Biomedical Applications

Hydrogen sulfide (H₂S) is an endogenous gasotransmitter in the human body involved in various physiological functions including cytoprotection, maintaining homeostasis, and regulation of organ development. Therefore, H₂S-releasing polymers that can imitate endogenous H₂S release can offer great therapeutic potential. Despite decades of research, the use of H₂S donors in medical device applications is mostly unexplored largely due to the challenge of the steady H₂S release from a suitable polymeric platform that does not compromise the normal cellular functions of the host. In this work, an exogenous H₂S release system was developed by integrating sodium sulfide (Na₂S), a common H₂S donor, into a medical-grade thermoplastic silicone-polycarbonate-urethane polymer, Carbosil 20 80A (hereon as Carbosil), via a facile solvent evaporation technique. The spatial distribution and nature of Na₂S in Carbosil were characterized through X-ray diffraction (XRD) spectroscopy and field emission scanning electron microscopy (FESEM) with energy-dispersive spectroscopy (EDS), indicating an amorphous phase shift upon incorporating Na₂S in Carbosil. The composite, Na₂S-Carbosil, is responsive in physiological conditions, resulting in sustained H₂S release measured for 3 h. In vitro cellular responses of 3T3 mouse fibroblasts, human lung epithelial (HLE), and primary human umbilical vein endothelial cells (HUVEC) were investigated. Fibroblast cells showed cell proliferation in 24 h and complete cell migration in 42 h in vitro. The Na₂S-Carbosil composites were cytocompatible toward HUVEC and HLE cells. This study provided important in vitro proof of concept that warrants potential use of these H₂S-releasing platforms in engineering biomedical devices, tissue engineering, and drug delivery applications.

Biological Effects of Thermal Water-Associated Hydrogen Sulfide on Human Airways and Associated Immune Cells: Implications for Respiratory Diseases

Natural mineral (thermal) waters have been used for centuries as treatment for various diseases. However, the scientific background of such therapeutic action is mostly empiric and based on knowledge acquired over time. Among the various types of natural mineral waters, sulfurous thermal waters (STWs) are the most common type in the center of Portugal. STWs are characterized by high pH, poor mineralization, and the presence of several ions and salts, such as bicarbonate, sodium, fluoride, silica, and carbonate. Furthermore, these waters are indicated as a good option for the treatment of various illnesses, namely respiratory diseases (e.g., allergic rhinitis, asthma, and chronic obstructive pulmonary disease). From the sulfide species present in these waters, hydrogen sulfide (H₂S) stands out due to its abundance. In healthy conditions, H₂S-related enzymes (e.g., cystathionine β-synthase and cystathionine γ-lyase) are expressed in human lungs, where they have mucolytic, antioxidant, anti-inflammatory, and antibacterial roles, thus contributing to airway epithelium homeostasis. These roles occur mainly through S-sulfhydration, a post-translational modification through which H₂S is able to change the activity of several targets, such as ion channels, second messengers, proteins, among others. However, in respiratory diseases the metabolism of H₂S is altered, which seems to contribute somehow to the respiratory deterioration. Moreover, H₂S has been regarded as a good biomarker of airway dysfunction and severity, and can be measured in serum, sputum, and exhaled air. Hence, in this review we will recapitulate the effects of STWs on lung epithelial-immune crosstalk through the action of its main component, H₂S.

Large-Scale Synthesis of Hierarchically Porous ZnO Hollow Tubule for Fast Response to ppb-Level H2S Gas

Response and recovery time to toxic and inflammable hydrogen sulfide (H₂S) gas are important indexes for metal oxide sensors in real-time environmental monitoring. However, large-scale production of ZnO-based sensing materials for fast response to ppb-level H₂S has been rarely reported. In this work, hierarchically porous hexagonal ZnO hollow tubule was simply fabricated by zinc salt impregnation and subsequently calcination using absorbent cotton as the template. The influence of calcination temperature on the corresponding morphology and sensing properties is also explored. The hollow tubules calcined at 600 °C are constructed from abundant cross-linked nanoparticles (∼20 nm). Its Brunauer-Emmett-Teller surface area is 31 m²·g^-1 and the meso- and macroporous sizes are centered at 35 and 115 nm, respectively. The sensor with a lower detection limit of 10 ppb exhibits a fast response speed of 29 s toward the 50 ppb H₂S rather than those of the reported intrinsic and doped ZnO-based sensing materials. Furthermore, the sensor shows a wide linear range (10-1000 ppb), good reproducibility, and stability. Such excellent trace ppb-level H₂S performances are mainly related to the inherent characteristics of hierarchically porous hollow tubular structure and the surface-adsorbed oxygen control type mechanism.

Nanoscale fluorescent metal-organic framework composites as a logic platform for potential diagnosis of asthma

Asthma is a common chronic disorder, and the decreased hydrogen sulfide (H₂S) production in the lung has been considered as an early detection biomarker for asthma. However, the detection of H₂S in biological systems remains a challenge; because it requires the designed sensors to have the following features: nanoscale size, good biocompatibility, real-time detection, high selectivity/sensitivity, and good water stability. Here, we propose the potential of using nanoscale fluorescent metal-organic framework (MOF) composites Eu³⁺/Ag⁺@UiO-66-(COOH)₂ (hereafter denoted as EAUC) as a logic platform for tentative diagnosis of asthma by detecting the biomarker H₂S. This INHIBIT logic gate based on Eu³⁺@UiO-66-(COOH)₂ (EUC) can be produced by choosing Ag⁺ and H₂S as inputs and by monitoring the fluorescent signal (I₆₁₅) as an output. Our fluorescent studies indicate that the EAUC exhibits excellent selectivity, extreme sensitivity (limit of detection: 23.53 μM), and real-time in situ detection of H₂S. Further, MTT analysis in PC12 cells shows that the EAUC possesses low cytotoxicity and favourable biocompatibility that are suitable for the detection of biomarker H₂S in vivo, as demonstrated by the successful detection of spiked H₂S in the diluted serum samples. This work represents the possibility of using MOF-based logic platform for tentative diagnosis of asthma in clinical medicine.

Enhanced selectivity of target gas molecules through a minimal array of gas sensors based on nanoparticle-decorated SWCNTs

Layers of CNTs decorated with metal and metal–oxide nanoparticles can be used to develop highly selective gas sensor arrays.

Sputum-to-serum hydrogen sulphide ratio as a novel biomarker of predicting future risks of asthma exacerbation

BACKGROUND

Increased level of hydrogen sulphide (H₂ S) in sputum is reported to be a new biomarker of neutrophilic airway inflammation in chronic airway disorders. However, the relationship between H₂ S and disease activity remains unclear.

OBJECTIVE

We investigated whether H₂ S levels could vary during different conditions in asthma.

METHOD

H₂ S levels in sputum and serum were measured using a sulphide-sensitive electrode in 47 stable asthmatic subjects (S-BA), 21 uncontrolled asthmatic subjects (UC-BA), 26 asthmatic subjects with acute exacerbation (AE-BA) and 15 healthy subjects. Of these, H₂ S levels during stable, as well as exacerbation states, were obtained in 13 asthmatic subjects.

RESULTS

Sputum H₂ S levels were significantly higher in the AE-BA subjects compared to the UC-BA and healthy subjects (P < .05). However, serum H₂ S levels in the AE-BA subjects were lower than in the S-BA subjects (P < .001) and similar to those in healthy subjects. Thus, the sputum-to-serum ratio of H₂ S (H₂ S ratio) in the AE-BA subjects was significantly higher than in the S-BA, UC-BA and healthy subjects (P < .05). Among all subjects, sputum H₂ S levels showed a trend to decrease with FEV₁ %predicted and significantly positive correlations with sputum neutrophils (%), sputum IL-8 and serum IL-8. A multiple linear regression analysis showed that sputum H₂ S was independently associated with increased sputum neutrophils (%) and decreased FEV₁ %predicted (P < .05). The cut-off level of H₂ S ratio to indicate an exacerbation was ≥0.34 (area under the curve; 0.88, with a sensitivity of 81.8% and specificity of 72.7%, P < .001). Furthermore, half of the asthmatic subjects with H₂ S ratios higher than the cut-off level experienced asthma exacerbations over the following 3 months after enrolment.

CONCLUSIONS

The H₂ S ratio may provide useful information on predicting future risks of asthma exacerbation, as well as on obstructive neutrophilic airway inflammation as one of the non-Th2 biomarkers, in asthma.

Thiol-Activated Hydrogen Sulfide Donors Antiviral and Anti-Inflammatory Activity in Respiratory Syncytial Virus Infection

We have recently shown that endogenous hydrogen sulfide (H₂S), an important cellular gaseous mediator, exerts an antiviral and anti-inflammatory activity in vitro and in vivo, and that exogenous H₂S delivered via the synthetic H₂S-releasing compound GYY4137 also has similar properties. In this study, we sought to extend our findings to a novel class of H₂S donors, thiol-activated gem-dithiol-based (TAGDDs). In an in vitro model of human respiratory syncytial virus (RSV) infection, TAGDD-1 treatment significantly reduced viral replication, even when added up to six hours after infection. Using a mouse model of RSV infection, intranasal delivery of TAGDD-1 to infected mice significantly reduced viral replication and lung inflammation, markedly improving clinical disease parameters and pulmonary dysfunction, compared to vehicle treated controls. Overall our results indicate that this novel synthetic class of H₂S-releasing compounds exerts antiviral and anti-inflammatory activity in the context of RSV infection and represents a potential novel pharmacological approach to ameliorate viral-induced lung disease.

Effects of Hyperoxia on the Developing Airway and Pulmonary Vasculature

Although it is necessary and part of standard practice, supplemental oxygen (40-90% O₂) or hyperoxia is a significant contributing factor to development of bronchopulmonary dysplasia, persistent pulmonary hypertension, recurrent wheezing, and asthma in preterm infants. This chapter discusses hyperoxia and the role of redox signaling in the context of neonatal lung growth and disease. Here, we discuss how hyperoxia promotes dysfunction in the airway and the known redox-mediated mechanisms that are important for postnatal vascular and alveolar development. Whether in the airway or alveoli, redox pathways are important and greatly influence the neonatal lung.

Sulfated polysaccharide from Enteromorpha prolifera increases hydrogen sulfide production and attenuates non-alcoholic fatty liver disease in high-fat diet rats

EP upregulates hepatic CBS expression, thus increasing serum H₂S level, which reduces serum TG level and ameliorates NAFLD induced by a high-fat diet.

Age-Dependent Allergic Asthma Development and Cystathionine Gamma-Lyase Deficiency

AIMS

The pathogenic mechanisms for the higher prevalence of allergic asthma in children than in adults have not been settled. The aim of the present study is to examine whether the age-dependent development of allergic asthma is caused by age-dependent expression of cystathionine gamma-lyase (CSE), a key enzyme that catalyzes the production of hydrogen sulfide (H₂S).

RESULTS

Allergic asthma was induced with ovalbumin in wild-type (WT) and CSE knock-out (KO) mice at young and old ages. CSE expression and H₂S production were lower in immune cells of young WT mice than in those of old WT mice. Coincidentally, more severe asthmatic symptoms with a greater type-2 immunoreaction were found in young WT mice than old WT mice. H₂S supplementation reversed the asthmatic symptoms. Lower expression levels of CSE proteins were also found in human umbilical cord blood mononuclear cells in comparison with that of peripheral blood mononuclear cells from adult people. The age-dependent asthma propensity vanished in CSE-KO mice, but these mice developed more severe asthma than WT mice. More splenocytes were differentiated to type-2 cytokine-generating cells in young WT mice and in CSE-KO mice at all ages. This differentiation was inhibited by H₂S donors. GATA3 translocation to the nucleus and type-2 immunoreaction of splenocytes were inhibited after GATA3 was S-sulfhydrated by H₂S. Innovation and Conclusion: For the first time, this study demonstrated that lower abundance of CSE expression and H₂S production enhances type-2 immunoreaction and renders a higher incidence of allergic asthma at a young age. As such, H₂S level may be a biomarker for asthma development and a H₂S-based strategy can be perceived for asthma prevention and treatment. Antioxid. Redox Signal. 27, 931-944.

Hydrogen Sulfide Is an Antiviral and Antiinflammatory Endogenous Gasotransmitter in the Airways. Role in Respiratory Syncytial Virus Infection

Hydrogen sulfide (H₂S) is an endogenous gaseous transmitter whose role in the pathophysiology of several lung diseases has been increasingly appreciated. Our recent studies in vitro have shown, we believe for the first time, that H₂S has an important antiviral and antiinflammatory activity in respiratory syncytial virus (RSV) infection, the leading cause of bronchiolitis and viral pneumonia in children. Our objective was to evaluate the therapeutic potential of GYY4137, a novel slow-releasing H₂S donor, for the prevention and treatment of RSV-induced lung disease, as well as to investigate the role of endogenous H₂S in a mouse model of RSV infection. Ten- to 12-week-old BALB/c mice treated with GYY4137, or C57BL/6J mice genetically deficient in the cystathionine γ-lyase enzyme, the major H₂S-generating enzyme in the lung, were infected with RSV and assessed for viral replication, clinical disease, airway hyperresponsiveness, and inflammatory responses. Our results show that intranasal delivery of GYY4137 to RSV-infected mice significantly reduced viral replication and markedly improved clinical disease parameters and pulmonary dysfunction compared with the results in vehicle-treated control mice. The protective effect of the H₂S donor was associated with a significant reduction of viral-induced proinflammatory mediators and lung cellular infiltrates. Furthermore, cystathionine γ-lyase-deficient mice showed significantly enhanced RSV-induced lung disease and viral replication compared with wild-type animals. Overall, our results indicate that H₂S exerts a novel antiviral and antiinflammatory activity in the context of RSV infection and represent a potential novel pharmacological approach for ameliorating virus-induced lung disease.

Hydrogen sulfide protects against endoplasmic reticulum stress and mitochondrial injury in nucleus pulposus cells and ameliorates intervertebral disc degeneration

It has been suggested that excessive apoptosis in intervertebral disc cells induced by inflammatory cytokines, such as interleukin (IL)-1β, is related to the process of intervertebral disc degeneration (IVDD). Hydrogen sulfide (H₂S), a gaseous signaling molecule, has drawn attention for its anti-apoptosis role in various pathophysiological processes in degenerative diseases. To date, there has been no investigation of the correlation of H₂S production and IVDD or of the effects of H₂S on IL-1β-induced apoptosis in nucleus pulposus (NP) cells. Here, we found that the expression levels of cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE), two key enzymes in the generation of H₂S, were significantly decreased in human degenerate NP tissues as well as in IL-1β-treated NP cells. NaHS (H₂S donor) administration showed a protective effect by inhibiting the endoplasmic reticulum (ER) stress response and mitochondrial dysfunction induced by IL-1β stimulation in vitro, the effect was related to activation of the PI3K/Akt and ERK1/2 signaling pathways. Suppression of these pathways by specific inhibitors, LY294002 and PD98059, partially reduced the protective effect of NaHS. Moreover, in the percutaneous needle puncture disc degeneration rat tail model, disc degeneration was partially reversed by NaHS administration. Taken together, our results suggest that H₂S plays a protective role in IVDD and the underlying mechanism involves PI3K/Akt and ERK1/2 signaling pathways-mediated suppression of ER stress and mitochondrial dysfunction in IL-1β-induced NP cells.