Decreased levels of hydrogen sulfide in the hypothalamic paraventricular nucleus contribute to sympathetic hyperactivity induced by cerebral infarction

Paroxysmal sympathetic hyperactivity (PSH) is a common clinical feature secondary to ischemic stroke (IS), but its mechanism is poorly understood. We aimed to investigate the role of H2S in the pathogenesis of PSH. IS patients were divided into malignant (MCI) and non-malignant cerebral infarction (NMCI) group. IS in rats was induced by the right middle cerebral artery occlusion (MCAO). H2S donor (NaHS) or inhibitor (aminooxy-acetic acid, AOAA) were microinjected into the hypothalamic paraventricular nucleus (PVN). Compared with the NMCI group, patients in the MCI group showed PSH, including tachycardia, hypertension, and more plasma norepinephrine (NE) that was positively correlated with levels of creatine kinase, glutamate transaminase, and creatinine respectively. The 1-year survival rate of patients with high plasma NE levels was lower. The hypothalamus of rats with MCAO showed increased activity, especially in the PVN region. The levels of H2S in PVN of the rats with MCAO were reduced, while the blood pressure and renal sympathetic discharge were increased, which could be ameliorated by NaHS and exacerbated by AOAA. NaHS completely reduced the disulfide bond of NMDAR1 in PC12 cells. The inhibition of NMDAR by MK-801 microinjected in PVN of rats with MCAO also could lower blood pressure and renal sympathetic discharge. In conclusion, PSH may be associated with disease progression and survival in patients with IS. Decreased levels of H2S in PVN were involved in regulating sympathetic efferent activity after cerebral infarction. Our results might provide a new strategy and target for the prevention and treatment of PSH.

Oxygen-binding properties of blood in insulin resistance with different asprosin content

The oxygen-binding properties of blood were studied in male patients with insulin resistance (IR) with different levels of asprosin. The content of asprosin, parameters of blood oxygen transport function, as well as gas transmitters, nitrogen monoxide and hydrogen sulfide, were determined in the venous blood plasma. In the studied IR patients with increased blood asprosin content, impaired blood oxygenation was noted; IR patients with normal body weight had increased hemoglobin affinity for oxygen, while in IR patients with overweight and the 1st degree obesity, this parameter decreased. The detected increase in the concentration of nitrogen monoxide and the decrease in hydrogen sulfide may be important for the oxygen-binding properties of the blood and the development of metabolic imbalance.

Reductions in Hydrogen Sulfide and Changes in Mitochondrial Quality Control Proteins Are Evident in the Early Phases of the Corneally Kindled Mouse Model of Epilepsy

Epilepsy is a heterogenous neurological disorder characterized by recurrent unprovoked seizures, mitochondrial stress, and neurodegeneration. Hydrogen sulfide (H₂S) is a gasotransmitter that promotes mitochondrial function and biogenesis, elicits neuromodulation and neuroprotection, and may acutely suppress seizures. A major gap in knowledge remains in understanding the role of mitochondrial dysfunction and progressive changes in H₂S levels following acute seizures or during epileptogenesis. We thus sought to quantify changes in H₂S and its methylated metabolite (MeSH) via LC-MS/MS following acute maximal electroshock and 6 Hz 44 mA seizures in mice, as well as in the early phases of the corneally kindled mouse model of chronic seizures. Plasma H₂S was acutely reduced after a maximal electroshock seizure. H₂S or MeSH levels and expressions of related genes in whole brain homogenates from corneally kindled mice were not altered. However, plasma H₂S levels were significantly lower during kindling, but not after established kindling. Moreover, we demonstrated a time-dependent increase in expression of mitochondrial membrane integrity-related proteins, OPA1, MFN2, Drp1, and Mff during kindling, which did not correlate with changes in gene expression. Taken together, short-term reductions in plasma H₂S could be a novel biomarker for seizures. Future studies should further define the role of H₂S and mitochondrial stress in epilepsy.

Maternal Garlic Oil Supplementation Prevents High-Fat Diet-Induced Hypertension in Adult Rat Offspring: Implications of H2S-Generating Pathway in the Gut and Kidneys

SCOPE

Perinatal high-fat (HF) diet induces hypertension in adult offspring. Garlic, a naturally dietary source of Hydrogen sulfide (H2 S) donor, has been shown benefits in hypertension. The article examines whether maternal garlic oil supplementation can prevent hypertension induced by HF diet and elucidate its protective effects.

METHODS AND RESULTS

Pregnant rats are given either a normal diet or HF diet. Rat dams are given garlic oil or vehicle daily by oral gavage at 100 mg kg-1 day-1 during pregnancy and lactation. Male offspring are sacrificed at 16 weeks of age. Garlic oil supplementation during pregnancy and lactation protected against hypertension induced by HF diet in adult male offspring. The beneficial effects of garlic oil are associated with increased renal mRNA expression and activity of H2 S-generating enzymes, increased NO bioavailability, increased plasma short chain fatty acid levels, and alterations of gut microbiota composition. Garlic oil supplementation increases abundance of genus Lactobacillus, but decreases genera Turicibacter and Staphylococcus.

CONCLUSION

The data reveals associations between H2 S-generating pathway in the gut and kidneys, NO system, gut microbiota, and microbiota-derived metabolites in hypertension induced by HF intake and provide insight to garlic oil as a hypertension reprogramming strategy for further translational research.

Cardiovascular "Patterns" of H2S and SSNO--Mix Evaluated from 35 Rat Hemodynamic Parameters

This work is based on the hypothesis that it is possible to characterize the cardiovascular system just from the detailed shape of the arterial pulse waveform (APW). Since H₂S, NO donor S-nitrosoglutathione (GSNO) and their H₂S/GSNO products (SSNO⁻-mix) have numerous biological actions, we aimed to compare their effects on APW and to find characteristic “patterns” of their actions. The right jugular vein of anesthetized rats was cannulated for i.v. administration of the compounds. The left carotid artery was cannulated to detect APW. From APW, 35 hemodynamic parameters (HPs) were evaluated. H₂S transiently influenced all 35 HPs and from their cross-relationships to systolic blood pressure “patterns” and direct/indirect signaling pathways of the H₂S effect were proposed. The observed “patterns” were mostly different from the published ones for GSNO. Effect of SSNO⁻-mix (≤32 nmol kg⁻¹) on blood pressure in the presence or absence of a nitric oxide synthase inhibitor (L-NAME) was minor in comparison to GSNO, suggesting that the formation of SSNO⁻-mix in blood diminished the hemodynamic effect of NO. The observed time-dependent changes of 35 HPs, their cross-relationships and non-hysteresis/hysteresis profiles may serve as “patterns” for the conditions of a transient decrease/increase of blood pressure caused by H₂S.

Changes in nitric oxide, carbon monoxide, hydrogen sulfide and male reproductive hormones in response to chronic restraint stress in rats

Gasotrasmitters are endogenously synthesized gaseous molecules that are engaged in cellular physiological and pathological processes. Stress influences various physiological aspects of an organism and amends a normal system's functions, including those of the reproductive system. This study aims to investigate the effect of long-term exposure to restraint stress on the male reproductive system as well as the possible impact of stress on the levels of nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H₂S), and the expression of their producing-enzymes. In this study, rats were subjected to the restraint condition for 2 h per day and 7 days per week for 8 consecutive weeks. The results revealed decreases in the serum levels of kisspeptin-1(Kiss-1), gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH), follicle stimulating hormone (FSH), testosterone and dehydroepiandrosterone sulfate (DHEA-s); however, corticosterone, gonadotropin-inhibitory hormone (GnIH), estradiol (E2) and prolactin levels increased following restraint stress. The mRNA expression levels of NO synthases (NOSs); neuronal NOS (nNOS), inducible NOS (iNOS) and H₂S synthases; cystathionine-γ-lyase- (CSE), 3-mercaptopyruvate-sulfurtransferase- (3MST) and CO-producing enzyme; heme oxygenase-2 (HO-2) were upregulated in the hypothalamus of restraint rats. Testicular mRNA expression levels of endothelial NOS (eNOS), nNOS, HO-1 and HO-2 were upregulated whereas cystathionine β-synthase (CBS), CSE and 3MST expression levels were downregulated following restraint stress. Concentrations of NO increased in the testes but decreased in the semen of restraint rats. On the contrary, CO levels were reduced in the testes while they were elevated in the semen, whereas H₂S concentrations decreased in both testes and semen of restraint rats. Concentrations of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX), as well as total antioxidant capacity (TAC) rose in the testes, while they declined in the semen of the restraint group. Restraint stress decreases the levels of reactive oxygen species (ROS) and malondialdehyde (MDA) in the testes while increasing them in the semen. Collectively, restraint stress negatively impacts male reproductive functions and modulates gasotransmitters producing-enzymes expression in the hypothalamus and testes.

Copper ion modified graphitic C3N4 nanosheets enhanced luminol-H2O2 chemiluminescence system: Toward highly selective and sensitive bioassay of H2S in human plasma

A high-efficient chemiluminescence (CL) platform for highly selective and sensitive H₂S detection was constructed on the basis of the quenching effect of S^2- on the copper ion modified graphitic carbon nitride nanosheets (Cu²⁺-g-C₃N₄ NSs) enhanced luminol-H₂O₂ system. Cu²⁺-g-C₃N₄ NSs with horseradish peroxidase-like catalytic activity were prepared and provide a great improvement for luminol-H₂O₂ system. The presence of S^2- induced the formation of CuS precipitate on g-C₃N₄ NSs surface. The precipitate can block the catalytic Cu²⁺ sites on the g-C₃N₄ NSs surface, resulting in a great CL decrease of CL system. Based on such a mechanism, a simple, highly selective and sensitive CL biosensor for H₂S detection was designed. Under the optimized conditions, luminol-H₂O₂-Cu²⁺-g-C₃N₄ NSs system gave a decrease of CL intensity with the Na₂S concentration increasing. The CL biosensor is in a linear range of 10.0 pM-50.0 nM and the detection limit for detecting Na₂S is as low as 2.0 pM. Moreover, the method here has enjoyed a successful application for determining H₂S in human plasma samples and the recovery is between 95.7% and 110.0%.

Effect of changes in serum levels of endogenous hydrogen sulfide on fracture healing: Study protocol clinical trial (SPIRIT compliant)

BACKGROUND

Fracture is a common disease; many factors affect fracture healing. Recent studies have confirmed that hydrogen sulfide (H2S) plays an essential role in bone formation, but most of these studies are drawing conclusions based on animal experiment; whether H2S could promote fracture healing in patients is still unclear. We aim to investigate the change of serum H2S in fracture patients, and analyze its effort on fracture healing.

METHODS

This is a single-center, prospective cohort study. Patients with spinal or limb fracture will be recruited. Patient's serum and urine will be collected at baseline for examination (serum H2S, β-CTX, OC, PINP, 25-OH-VitD3, S-CTX, urinary calcium, and urinary creatinine). All patients will be followed-up for 24 months in outpatients settings, the image of X-ray or CT will be reviewed and fracture healing will be judged by 2 experienced orthopedic physicians. The difference in serum parameters especially H2S will be compared between patients with fracture healed within 9 months and those with fracture unhealed at 9 months.

DISCUSSION

Results of the trial could provide insight into influence of H2S on fracture healing.

ETHICS AND DISSEMINATION

The study was approved by the ethics committee of School of Medicine UESTC & Sichuan Provincial People's Hospital Ethics Committee. All the participants will be asked to provide written informed consent before data collection. The findings of the study will be published in peer-reviewed journals and will be presented at national or international conferences.

Cardiovascular phenotype of mice lacking 3-mercaptopyruvate sulfurtransferase

RATIONALE

Hydrogen sulfide (H₂S) is a physiological mediator that regulates cardiovascular homeostasis. Three major enzymes contribute to the generation of endogenously produced H₂S, namely cystathionine γ-lyase (CSE), cystathionine β-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (3-MST). Although the biological roles of CSE and CBS have been extensively investigated in the cardiovascular system, very little is known about that of 3-MST. In the present study we determined the importance of 3-MST in the heart and blood vessels, using a genetic model with a global 3-MST deletion.

RESULTS

3-MST is the most abundant transcript in the mouse heart, compared to CSE and CBS. 3-MST was mainly localized in smooth muscle cells and cardiomyocytes, where it was present in both the mitochondria and the cytosol. Levels of serum and cardiac H₂S species were not altered in adult young (2-3 months old) 3-MST^-/- mice compared to WT animals. No significant changes in the expression of CSE and CBS were observed. Additionally, 3-MST^-/- mice had normal left ventricular structure and function, blood pressure and vascular reactivity. Interestingly, genetic ablation of 3-MST protected mice against myocardial ischemia reperfusion injury, and abolished the protection offered by ischemic pre- and post-conditioning. 3-MST^-/- mice showed lower expression levels of thiosulfate sulfurtransferase, lower levels of cellular antioxidants and elevated basal levels of cardiac reactive oxygen species. In parallel, 3-MST^-/- mice showed no significant alterations in endothelial NO synthase or downstream targets. Finally, in a separate cohort of older 3-MST^-/- mice (18 months old), a hypertensive phenotype associated with cardiac hypertrophy and NO insufficiency was observed.

CONCLUSIONS

Overall, genetic ablation of 3-MST impacts on the mouse cardiovascular system in an age-dependent manner. Loss of 3-MST exerts a cardioprotective role in young adult mice, while with aging it predisposes them to hypertension and cardiac hypertrophy.

H2S-activatable near-infrared afterglow luminescent probes for sensitive molecular imaging in vivo

Afterglow luminescent probes with high signal-to-background ratio show promise for in vivo imaging; however, such probes that can be selectively delivered into target sites and switch on afterglow luminescence remain limited. We optimize an organic electrochromic material and integrate it into near-infrared (NIR) photosensitizer (silicon 2,3-naphthalocyanine bis(trihexylsilyloxide) and (poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]) containing nanoparticles, developing an H2S-activatable NIR afterglow probe (F12+-ANP). F12+-ANP displays a fast reaction rate (1563 ± 141 M-1 s-1) and large afterglow turn-on ratio (~122-fold) toward H2S, enabling high-sensitivity and -specificity measurement of H2S concentration in bloods from healthy persons, hepatic or colorectal cancer patients. We further construct a hepatic-tumor-targeting and H2S-activatable afterglow probe (F12+-ANP-Gal) for noninvasive, real-time imaging of tiny subcutaneous HepG2 tumors (<3 mm in diameter) and orthotopic liver tumors in mice. Strikingly, F12+-ANP-Gal accurately delineates tumor margins in excised hepatic cancer specimens, which may facilitate intraoperative guidance of hepatic cancer surgery.

Expression of H2S in Gestational Diabetes Mellitus and Correlation Analysis with Inflammatory Markers IL-6 and TNF-α

BACKGROUND

Gestational diabetes mellitus (GDM) is a severe threat to the health of both mother and child. The pathogenesis of GDM remains unclear, although much research has found that the levels of hydrogen sulfide (H₂S) play an important role in complications of pregnancy.

METHODS

We collected venous blood samples from parturient women and umbilical vein blood (UVB) and peripheral venous blood (PVB) samples one hour after childbirth in the control, GDM-, and GDM+ groups in order to determine the concentration of glucose and H₂S in plasma; to measure levels of TNF-α, IL-1β, IL-6, TGF-β1, and ADP in parturient women and the UVB of newborns; and to find the correlation of H₂S with regression.

RESULTS

We found that, with the elevation of glucose, the level of H₂S was decreased in GDM pregnant women and newborns and the concentrations of IL-6 and TNF-α were upregulated. With regression, IL-6 and TNF-α concentrations were positively correlated with the level of blood glucose and negatively correlated with H₂S concentration.

CONCLUSION

This study shows that downregulation of H₂S participates in the pathogenesis of GDM and is of great significance in understanding the difference of H₂S between normal and GDM pregnant women and newborns. This study suggests that IL-6 and TNF-α are correlated with gestational diabetes mellitus. The current study expands the knowledge base regarding H₂S and provides new avenues for exploring further the pathogenesis of GDM.

Comprehensive analysis of how experimental parameters affect H2S measurements by the monobromobimane method

A rapidly increasing number of studies report on widespread biological functions for endogenous hydrogen sulfide. However, the use of multiple, chemically distinct analytical methods to measure free hydrogen sulfide levels in biological samples accumulate data that are not in agreement with each other. In this work a widely appreciated technique, the monobromobimane method, was thoroughly investigated with the overall aims i) to demonstrate how results obtained by different versions of the method should be interpreted and ii) to provide an easy protocol for the community in order to obtain reliable and comparable results. We demonstrate that none of the previously published versions of the method measure free sulfide concentrations in blood serum or plasma samples due to significant interferences with the biomolecule-bound sulfide pool. On the other hand, we stress the biological relevance of these measurements in cases in which they are carefully conducted. To aid future studies, we extensively investigated the entire procedure from sample withdrawal through handling and storing of injection-ready samples until the detection protocol in order to pinpoint all parameters that can affect the final readouts. Based on our rigorous analytical investigations a set of recommendations were compiled that are necessary to ensure reliable, reproducible and comparable results in the field and a detailed standardized protocol is provided.

Lymphocyte hydrogen sulfide production predicts intravenous immunoglobulin resistance in children with Kawasaki disease: A preliminary, single-center, case-control study

The aim of the study was to identify whether lymphocyte hydrogen sulfide production is a potential biomarker to predict intravenous immunoglobulin (IVIG) resistance in children with Kawasaki disease (KD).This preliminary, single-center, case-control study conducted between June 2016 and March 2018 in Shaanxi Provincial People's Hospital, 85 children (50 with KD and 35 healthy controls) were included. Laboratory biomarkers were collected from the medical records. All patients with KD received 1 g/kg/d IVIG for 2 days and 30-50 mg/kg/d oral aspirin. The aspirin dose was reduced from 3 to 5 mg/kg/d after body temperature normalized. Plasma hydrogen sulfide levels were detected using sulfide electrode. Lymphocyte hydrogen sulfide levels were detected using the human hydrogen sulfide ELISA kits at the acute stage.Of 50 patients with KD, 31 and 19 were diagnosed with complete KD (cKD) and incomplete KD (iKD), respectively. Eleven patients with KD were resistant to IVIG treatment. The laboratory biomarker findings and levels of plasma and lymphocyte hydrogen sulfide were significantly different between the patients with KD and control group (P < .001). Moreover, lymphocyte hydrogen sulfide production was significantly greater in IVIG-resistant patients than in the IVIG-responsive patients, both in cKD and iKD (P = .018 and P < .001 respectively). Receiver operating characteristic curve indicated that when the lymphocyte hydrogen sulfide production was >15.285 nmol/min/10 lymphocytes, the sensitivity and specificity for predicting IVIG resistance were 90.9% and 76.9%, respectively.Lymphocyte hydrogen sulfide production could serve as a predictor of the therapeutic efficacy of IVIG in children with KD.

[Prooxidant-antioxidant balance depending on endothelial nitric oxide synthase G894T polymorphism]

The aim of the study was to assess the prooxidant-antioxidant balance depending on endothelial nitric oxide synthase G894T polymorphism. The frequency distribution of alleles and genotypes of G894T polymorphism, nitrite concentration, hydrogen sulphide, lipid peroxidation products (diene conjugates, malonic dialdehyde), antioxidants (reduced glutathione, catalase, ceruloplasmin, retinol) were determined in venous blood of healthy males. The incidence of the GG genotype was 49.1%, GT - 44.2%, TT - 6.7%. The level of malonic dialdehyde in erythrocytes with the GG genotype is 16.8% lower than in the genotype GT. The concentration of hydrogen sulphide in the blood with the GG genotype was 27.5 [18,2; 32,5] mM, GT - 28.6 [22.9; 33.8] mM, TT - 36.3 [33.8; 42.5] mM. The content of total nitrites in plasma with the GG genotype was 10.4 [9,0; 12,5] mM, GT - 10.4 [8.9; 11.8] mM, TT - 9.4 [8.8; 9.8] mM. The genotype GG causes a lower level of malonic dialdehyde in comparison with the heterozygous genotype. The G894T polymorphism allele T is associated with a low content of total nitrites in the plasma and a high concentration of hydrogen sulfide. The data obtained suggest that if the oxygen supply of the organism is impaired, the endothelial nitric oxide synthase G894T polymorphism may be important for the oxidative stress development.

Definitions and pathophysiology of vasoplegic shock

Vasoplegia is the syndrome of pathological low systemic vascular resistance, the dominant clinical feature of which is reduced blood pressure in the presence of a normal or raised cardiac output. The vasoplegic syndrome is encountered in many clinical scenarios, including septic shock, post-cardiac bypass and after surgery, burns and trauma, but despite this, uniform clinical definitions are lacking, which renders translational research in this area challenging. We discuss the role of vasoplegia in these contexts and the criteria that are used to describe it are discussed. Intrinsic processes which may drive vasoplegia, such as nitric oxide, prostanoids, endothelin-1, hydrogen sulphide and reactive oxygen species production, are reviewed and potential for therapeutic intervention explored. Extrinsic drivers, including those mediated by glucocorticoid, catecholamine and vasopressin responsiveness of the blood vessels, are also discussed. The optimum balance between maintaining adequate systemic vascular resistance against the potentially deleterious effects of treatment with catecholamines is as yet unclear, but development of novel vasoactive agents may facilitate greater understanding of the role of the differing pathways in the development of vasoplegia. In turn, this may provide insights into the best way to care for patients with this common, multifactorial condition.

Low Plasma Hydrogen Sulfide Is Associated with Impaired Renal Function and Cardiac Dysfunction

BACKGROUND

Chronic kidney disease (CKD) has been proposed to associate with decreased hydrogen sulfide (H2S) level. Nevertheless, the role of H2S in the pathogenesis of CKD has not been fully investigated. Our study aimed to investigate the plasma level of endogenous H2S in patients with different stages of CKD, and to identify the role of H2S in the progression of CKD and its relationship with cardiovascular diseases.

METHODS

A total of 157 non-dialysis CKD patients were recruited in our study, with 37 age- and sex-matched healthy individuals as control. Plasma concentration of H2S was measured with spectrophotometry. Sulfhemoglobin, the integration of H2S and hemoglobin, was characterized and measured by dual wavelength spectrophotometry. Serum levels of homocysteine (Hcy), cardiac troponin T (cTnT), and N-terminal pro B type natriuretic peptide were measured using automated analyzers. Conventional transthoracic echocardiography was performed and left ventricular ejection fraction (LVEF) was analyzed as a sensitive parameter of cardiac dysfunction.

RESULTS

The plasma H2S level (μmol/L) in CKD patients was significantly lower than those in healthy controls (7.32 ± 4.02 vs. 14.11 ± 5.24 μmol/L, p < 0.01). Plasma H2S level was positively associated with estimated glomerular filtration rate (eGFR; ρ = 0.577, p < 0.01) and negatively associated with plasma indoxyl sulfate concentration (ρ = -0.554, p < 0.01). The mRNA levels of cystathionine β-synthase and cystathionine γ-lyase, 2 catalytic enzymes of H2S formation, were significantly lower in blood mononuclear cells of CKD patients with respect to controls; however, the mRNA level of 3-mercaptopyruvate sulfurtransferase, as another H2S-producing enzyme, was significantly higher in CKD patients. The serum concentration of Hcy, acting as the substrate of H2S synthetase, was higher in the CKD group (p < 0.01). Specifically, the content of serum Hcy in CKD stages 3-5 patients was significantly higher than that in CKD stages 1-2, indicating an increasing trend of serum Hcy with the decline of renal function. Examination of ultrasonic cardiogram revealed a negative -correlation between plasma H2S level and LVEF (ρ = -0.204, p < 0.05) in CKD patients. The H2S level also correlated negatively with cTnT concentration (ρ = -0.249, p < 0.01).

CONCLUSIONS

Plasma H2S level decreased with the decline of eGFR, which may contribute to the cardiac dysfunction in CKD -patients.

Nitric oxide and hydrogen sulfide - markers of acute period of polytrauma

OBJECTIVE

Introduction: Polytrauma or multiple organ damage is connected with shock and organ failure, which in severely injured patients and if untreated quick can lead to death.). The aim: To investigate levels of NO, NOx and H2S in patients with acute trauma period at the time of hospitalization and for 24 hours after trauma.

PATIENTS AND METHODS

Materials and method: Etiology of trauma: traffic accident - 78 %, drop from the altitude - 5 %, everyday trauma - 17 %. Blood tests were performed during patient admission and 24 hours after admission.

RESULTS

Results: Results of the study in patients with severe polytrauma showed increase of serum NO and its metabolites, but decrease of H2S. Suggest increase of NОx is connected with severity of trauma and can be as indicator of prognosis for severity of injury in polytrauma. So detection of NO and its metabolites and H2S can be use as early markers of detection for severity of polytrauma.

CONCLUSION

Conclusions: Intensive care management in acute polytrauma period leads to increase of NO level and its metabolites on the background of H2S decrease. Detection of NO, NOx, H2S and valuation of its balance in acute period of polytrauma can serve as severity indicators and prognosis of these disease. In comparation to general clinical parameters, gasotrasmitters react on changes in homeostasis faster and more sensitive what allows to use them more widely as biomarkers of organ disfunction development in acute polytrauma period.

The changes of some bioregulators and gas transmitters in patients with hypertonic disease under the influence of physical loading

OBJECTIVE

Introduction: Nowadays arterial hypertension is supposed to be a pathogenetic factor of numerous cardiovascular diseases (CVD) and 18% cases of the preterm death. Due to the data of the American Heart Association in 77% of patients, who had stroke, the arterial pressure overexceeded 140/90 mm Hg. In Ukraine, according to the epidemiologic study more than 1/3 of the population have increased arterial pressure. One of the extremely important aspects of struggle with CVD is diagnosis and prevention of hypertonic disease. The prevalence of arterial hypertension worldwide increases averagely for 3-4% per year that corresponds with the level of a true epidemy. The aim: Was to evaluate nitrosooxidative status, content of hydrogen sulphide and cortisol in blood serum of patients with a II stage arterial hypertension under the conditions of physical loading.

PATIENTS AND METHODS

Materials and methods: 30 patients with II stage arterial hypertension were examined. Examined patients were exposed to two-stage physical loading using veloergometer with the intensity relevant to 50 and 75 % of the proper maximal oxygen uptake (MOU) of the body.

RESULTS

Results: In blood serum of patients before and after physical loading the content of TBA-active products, hydrogen sulphide, L-arginine, nitric anion, sum of nitrite-nitrate, cortisol, activity of SOD, catalase and arginase were determined. Significant increase of L-arginine and hydrogen sulphide on the background of the decrease of nitrite-anion and sum of nitrite-nitrate was noted. It may be suggested that in individuals with hypertonic disease under the influence of physical loading synthesis of NO decreases and vasodilatation and vasoprotection occur by means of increase of the hydrogen sulphide level.

CONCLUSION

Conclusions: The indices of L-arginine, nitrite-anion and Н2S in blood serum after physical loading reflect the changes in the system of vasodilatation in patients with arterial hypertension. The parameters of gaseous messengers NO and Н2S are the fastest to react to veloergometry on the background of insignificant changes of the level of cortisol, activity of arginase, SOD and catalase in patients with II stage hypertonic disease. Increase of the level of L-arginine and hydrogen sulphide as well as decrease of nitrite-anion level may be considered to be markers of evaluation of immediate changes in patients with arterial hypertension after physical loading.

Novel H2S-NO hybrid molecule (ZYZ-803) promoted synergistic effects against heart failure

Therapeutic strategies that increase hydrogen sulfide (H₂S) or nitric oxide (NO) are cytoprotective in various models of cardiovascular injury. However, the nature of interaction between H₂S and NO in heart failure and the underlying mechanisms for the protective effects remain undefined. The present study tested the cardioprotective effect of ZYZ-803, a novel synthetic H₂S-NO hybrid molecule that decomposed to release H₂S and NO. ZYZ-803 dose dependently improved left ventricular remodeling and preserved left ventricular function in the setting of isoprenaline-induced heart failure. The cardioprotective effect of ZYZ-803 is significantly more potent than that of H₂S and/or NO donor alone. ZYZ-803 stimulated the expression of cystathionine γ-lyase (CSE) for H₂S generation and the activity of endothelial NO synthase (eNOS) for NO production. Blocking CSE and/or eNOS suppressed ZYZ-803-induced H₂S and NO production and cardioprotection. ZYZ-803 increased vascular endothelial growth factor (VEGF) concentration and cyclic guanosine 5′-monophosphate (cGMP) level. Moreover, ZYZ-803 upregulated the endogenous antioxidants, glutathione peroxidase (GPx) and heme oxygenase 1 (HO-1). These findings indicate that H₂S and NO cooperatively attenuates left ventricular remodeling and dysfunction during the development of heart failure through VEGF/cGMP pathway and ZYZ-803 provide expanding insight into strategies for treatment of heart failure.

Changes in hydrogen sulfide in rats with hepatic cirrhosis in different stages

This study aimed to observe changes in the hydrogen sulfide (H₂S) system in the blood and liver tissue of rats with hepatic cirrhosis at different stages by studying the effect of H₂S on the course of hyperdynamic circulation in rats with hepatic cirrhosis. H₂S concentration in the blood from the portal vein and inferior vena cava of hepatic cirrhosis rat model induced with carbon tetrachloride was detected on the 15th, 30th, and 52nd day. The expression of cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE) protein, and CBS and CSE mRNA in the liver was detected by immunohistochemistry and reverse transcriptase polymerase chain reaction (RT-PCR), respectively. The results indicated that H₂S concentration in the blood from the portal vein and inferior vena cava of rats with hepatic cirrhosis was significantly lower than that in the control group. H₂S was gradually decreased with the development of the disease and significantly lower in the blood from portal vein than in the blood of inferior vena cava at the mid-stage and the late stage groups. The expression levels of CBS and CSE protein, and CBS and CSE mRNA in the livers with hepatic cirrhosis at different stages were all higher than those in the control group, and the expression gradually increased with the development of the disease. The expression of CBS was lower than CSE in the same stages. The results indicated that the CSE mRNA was expressed predominantly in the cirrhosis groups as compared with CBS mRNA. Among experimental rats, the H₂S system has an important effect on the occurrence and development of hyperdynamic circulation in rats with hepatic cirrhosis. This finding adds to the literature by demonstrating that H₂S protects vascular remodelling in the liver, and that CSE is indispensable in this process.

SULPHUR-CONTAINING AMINO ACIDS METABOLISM IN EXPERIMENTAL HYPER- AND HYPOTHYROIDISM IN RATS

Hyper- and hypothyroidism are some of the most common endocrinopathies that cause many metabolic disorders including amino acids metabolism. However, a specific molecular mechanism of thyroid hormones influence on sulphur-containing amino acids metabolism has not been established. The aim of our research was to investigate experimentally the influence of thyroid gland functional state on the main enzymatic systems of sulphur-containing amino acids metabolism in liver and kidneys, the content of homocysteine, cysteine and H2S in blood. The rats were administered with L-thyroxine and mercazolil to simulate the states of hyper- and hypothyroidism, which were confirmed by the content of fT3, fT4 and TSH in the blood. In liver and kidneys of the animals with hypothyroidism we observed the decrease in the activity of enzymes of remethylation cycle of S-adenosylmethioninsyntase, S-adenosylhomocysteinhyhdrolase, betaine-homocysteine methyltransferase. Suppression of transsulfuration transformation of homocysteine to cysteine in hypothyroidism was mainly due to the inhibition of cystathionine synthase activity of cystathionine-β-synthase, wherein cystathionase activity of cystathionine-γ-lyase was not changed. In animals with hypothyroidism we also noticed the inhibition of cysteine desulfunation reactions: the activity of enzymes of cystathionine-β-synthase, cystathionine-γ-lyase and cysteine aminotransferase significantly decreased in liver and kidneys. Experimental hyperthyroidism was accompanied by increase in activity of remethylation cycle enzymes, increase in cystationine synthase activity of cystathionine-β-synthase in liver and activity of these enzymes in kidneys. The simulation of hyperthyroidism led to the decrease of homocysteine concentration, and of hypothyroidism - to the increase of homocysteine and cysteine concentrations and reduced H2S content in blood of the animals. Thus, the significant risk factors for the development of atherosclerosis, endothelial dysfunction and hypercoagulation in hypothyroid conditions may be the disorders in the processes of remethylation, transsulfuration, and desulfuration of sulphur-containing amino acids in organs.

Significance of interleukin and matrix metalloproteinase in patients with cognitive dysfunction after single valve replacement

OBJECTIVE

To investigate the changes in serum neurological function parameters, interleukin (IL) and matrix metalloproteinase (MMP) in patients with cognitive dysfunction after single valve replacement.

PATIENTS AND METHODS

51 cases of senile patients with cognitive dysfunction after general anesthesia were selected as the observation group, and 51 senile patients without cognitive dysfunction after general anesthesia were selected as the control group. Serum neurological function parameters and IL and MMP levels were examined and compared between the two groups. The detected levels were also compared among patients with mild, moderate and severe cognitive dysfunction in the observation group. The relationship between these serum biomarkers and postoperative cognitive dysfunction was analyzed.

RESULTS

The serum neurological function parameters and IL and MMP levels were significantly higher in the observation group than those in the control group. Levels in the severe cognitive impairment group were higher than those in the mild and moderate groups, while those in the moderate group were higher than those in the mild group. Logistic analysis showed that the above indices were closely related to postoperative cognitive dysfunction in elderly patients with general anesthesia. The differences between the groups were statistically significant (p < 0.05).

CONCLUSIONS

Elderly patients with postoperative cognitive dysfunction after valve replacement surgery were presented with abnormalities in serum neurological function parameters and IL and MMP levels. There were significant differences in these indices between patients with varying degrees of cognitive dysfunction.

Treatment with hydrogen sulfide attenuates sublesional skeletal deterioration following motor complete spinal cord injury in rats

Treatment with hydrogen sulfide mitigates spinal cord injury-induced sublesional bone loss, possibly through abating oxidative stress, suppressing MMP activity, and activating Wnt/β-catenin signaling.

INTRODUCTION

Spinal cord injury (SCI)-induced sublesional bone loss represents the most severe osteoporosis and is resistant to available treatments to data. The present study was undertaken to explore the therapeutic potential of hydrogen sulfide (H₂S) against osteoporosis in a rodent model of motor complete SCI.

METHODS

SCI was generated by surgical transaction of the cord at the T3-T4 levels in rats. Treatment with NaHS was initiated through intraperitoneal injection of 0.1 ml/kg/day of 0.28 mol/l NaHS from 12 h following the surgery and over 14 subsequent days.

RESULTS

H₂S levels in plasma of SCI rats were lower, which was restored by treatment with exogenous H₂S. Treatment of SCI rats with exogenous H₂S had no significant effect on body mass but increased bone mineral density in femurs and tibiae, increased BV/TV, Tb.Th, and Tb.N and reduced Tb.Sp in proximal tibiae, and increased mineral apposition rate (MAR), bone formation rate (BFR), and osteoblast surface and reduced eroded surface and osteoclast surface in proximal tibiae. More importantly, H₂S treatment led to a significant enhancement in ultimate load, stiffness, and energy to max force of femoral diaphysis. Treatment of SCI rats with exogenous H₂S reduced malondialdehyde (MDA) levels in serum and femurs, decreased hydroxyproline levels, suppressed activities of matrix metallopeptidase 9 (MMP9), and upregulated Wnt3a, Wnt6, Wnt10, and ctnnb1 expression in femurs.

CONCLUSION

Treatment with H₂S mitigates SCI-induced sublesional bone loss, possibly through abating oxidative stress, suppressing MMP activity, and activating Wnt/β-catenin signaling.

Hydrogen Sulfide Improves Myocardial Remodeling via Downregulated Angiotensin Ⅱ/AT1R Pathway in Renovascular Hypertensive Rats

BACKGROUND

Hydrogen sulfide (H₂S) is an important endogenous gaseous transmitter in many physiological functions. Plasma H₂S decreased, and angiotensin II (Ang II) type 1 receptor (AT1R) increased in the myocardial tissues in 2-kidney 1-clip (2K1C) rats than in normotensive rats. Accumulating evidences suggest that H₂S inhibited Ang II/AT1R pathway to regulate cardiovascular function. Therefore, we hypothesized that H₂S may exert beneficial effects on myocardial remodeling in 2K1C rat models of renovascular hypertension.

METHODS AND RESULTS

Sodium hydrosulfide (NaHS, 56 µmol/kg/day) was administered intraperitoneally to the rats from the 7th day after 2K1C operation. Systolic blood pressure was significantly increased from the first week after the operation and was lowered after NaHS treatment for 4 weeks. H₂S could also inhibit the ratio of left ventricle and septum weight to body weight, improve cross-sectional area, and ameliorate ventricular dysfunction. Additionally, the protein expression of AT1R and Ang II serum content were downregulated, whereas superoxide dismutase (SOD) protein was upregulated in 2K1C rats by NaHS treatment for 4 weeks. Furthermore, the reactive oxygen species level and AT1R protein were increased, whereas SOD protein was decreased in cardiomyocytes treated with Ang II compared with the control group. NaHS could reverse these changes. Losartan and N-acetylcysteine could also reverse Ang II-induced changes.

CONCLUSIONS

The protective effect of H₂S is attributable to the suppression of oxidative stress. This process involves the inhibition of the Ang II/AT1R pathway and upregulation of antioxidant enzymes in 2K1C rats.

Clinical Implication of Plasma Hydrogen Sulfide Levels in Japanese Patients with Type 2 Diabetes

Objective The goal of the present study was to investigate the plasma hydrogen sulfide (H₂S) levels in patients with type 2 diabetes, as the plasma H₂S levels in Japanese patients with type 2 diabetes remain unclear. Methods The plasma H₂S levels were measured in 154 outpatients with type 2 diabetes and 66 outpatients without diabetes. All blood samples were collected in the outpatient department from 09:00 to 10:00. The patients had fasted from 21:00 the previous evening and had not consumed alcohol or caffeine or smoked until sample collection. The plasma H₂S levels were measured using the methylene blue assay. The plasma H₂S levels were determined in triplicate, and the average concentrations were calculated against a calibration curve of sodium sulfide. Results The patients with type 2 diabetes showed a progressive reduction in the plasma H₂S levels (45.115.5 M versus 54.026.4 M, p<0.05), which paralleled poor glycemic control. There was a significant correlation between a reduction in the plasma H₂S levels and the HbA1c levels (=-0.505, p<0.01), Furthermore, a reduction in the plasma H₂S levels was found to be related to a history of cardiovascular diseases in patients with type 2 diabetes (39.913.8 M versus 47.515.9 M, p<0.01). Conclusion Collectively, the plasma H₂S levels were reduced in patients with type 2 diabetes, which may have implications in the pathophysiology of cardiovascular disease in diabetic patients. The trial was registered with the University Hospital Medical Information Network (UMIN no. #000020549).

Hydrogen Sulfide Induces Keap1 S-sulfhydration and Suppresses Diabetes-Accelerated Atherosclerosis via Nrf2 Activation

Hydrogen sulfide (H2S) has been shown to have powerful antioxidative and anti-inflammatory properties that can regulate multiple cardiovascular functions. However, its precise role in diabetes-accelerated atherosclerosis remains unclear. We report here that H2S reduced aortic atherosclerotic plaque formation with reduction in superoxide (O2 (-)) generation and the adhesion molecules in streptozotocin (STZ)-induced LDLr(-/-) mice but not in LDLr(-/-)Nrf2(-/-) mice. In vitro, H2S inhibited foam cell formation, decreased O2 (-) generation, and increased nuclear factor erythroid 2-related factor 2 (Nrf2) nuclear translocation and consequently heme oxygenase 1 (HO-1) expression upregulation in high glucose (HG) plus oxidized LDL (ox-LDL)-treated primary peritoneal macrophages from wild-type but not Nrf2(-/-) mice. H2S also decreased O2 (-) and adhesion molecule levels and increased Nrf2 nuclear translocation and HO-1 expression, which were suppressed by Nrf2 knockdown in HG/ox-LDL-treated endothelial cells. H2S increased S-sulfhydration of Keap1, induced Nrf2 dissociation from Keap1, enhanced Nrf2 nuclear translocation, and inhibited O2 (-) generation, which were abrogated after Keap1 mutated at Cys151, but not Cys273, in endothelial cells. Collectively, H2S attenuates diabetes-accelerated atherosclerosis, which may be related to inhibition of oxidative stress via Keap1 sulfhydrylation at Cys151 to activate Nrf2 signaling. This may provide a novel therapeutic target to prevent atherosclerosis in the context of diabetes.

[PARTICIPATION OF GASEOUS TRANSMITTERS IN BLOOD OXYGEN TRANSPORT FUNCTION MODIFICATION UNDER THE INFLUENCE OF MAGNETIC FIELD]

Gaseous transmitters contribution in blood oxygen transport function modification under the influence of the magnetic field was studied. It is found, that irradiation of the tail artery of rats for 10 days during 10 minutes increases p50 value, indicating a decrease in the hemoglobin affinity for oxygen and is accompanied by increased concentrations of nitrate/nitrite, and hydrogen sulfide. Administration of L-arginine and nitroglycerin during magnetic field action is accompanied by a decrease of hemoglobin affinity for oxygen, which is absent when NO-synthase enzyme inhibitor (L-NAME) is added. These data suggest an important role in the formation of blood oxygen transport function such gaseous transmitters as nitrogen monoxide and hydrogen sulfide.

The novel compound Sul-121 inhibits airway inflammation and hyperresponsiveness in experimental models of chronic obstructive pulmonary disease

COPD is characterized by persistent airflow limitation, neutrophilia and oxidative stress from endogenous and exogenous insults. Current COPD therapy involving anticholinergics, β2-adrenoceptor agonists and/or corticosteroids, do not specifically target oxidative stress, nor do they reduce chronic pulmonary inflammation and disease progression in all patients. Here, we explore the effects of Sul-121, a novel compound with anti-oxidative capacity, on hyperresponsiveness (AHR) and inflammation in experimental models of COPD. Using a guinea pig model of lipopolysaccharide (LPS)-induced neutrophilia, we demonstrated that Sul-121 inhalation dose-dependently prevented LPS-induced airway neutrophilia (up to ~60%) and AHR (up to ~90%). Non-cartilaginous airways neutrophilia was inversely correlated with blood H2S, and LPS-induced attenuation of blood H2S (~60%) was prevented by Sul-121. Concomitantly, Sul-121 prevented LPS-induced production of the oxidative stress marker, malondialdehyde by ~80%. In immortalized human airway smooth muscle (ASM) cells, Sul-121 dose-dependently prevented cigarette smoke extract-induced IL-8 release parallel with inhibition of nuclear translocation of the NF-κB subunit, p65 (each ~90%). Sul-121 also diminished cellular reactive oxygen species production in ASM cells, and inhibited nuclear translocation of the anti-oxidative response regulator, Nrf2. Our data show that Sul-121 effectively inhibits airway inflammation and AHR in experimental COPD models, prospectively through inhibition of oxidative stress.

Antihypertensive and cardioprotective effects of Cerebralcare granule® on spontaneously hypertensive rats from the perspective of the gaseous triumvirate NO-CO-H2S system

Cerebralcare granule(®) (CG) has been reported to have hypotensive effect. However, several pathways involved in the mechanism of hypotension are still unclear. This study was designed to verify the antihypertensive effect of CG and to characterize its mechanism of action, especially from the perspective of gasotrasmmiter NO/cGMP, CO/HO and H2S/CSE systems. By using the widely used in vitro model of rat isolated thoracic aortic rings, the vasorelaxant effect of CG were studied. Furthermore, we assessed the chronic hypotensive effect of CG on spontaneously hypertensive rats (SHRs) and further to explore the potential mechanisms of its antihypertensive activity. Data in the present study demonstrated that oral treatment with CG could induce a potent antihypertensive effect. CG could reduce the intima-media thickness (IMT) of thoracic aorta significantly and increase the serum NO and H2S levels. In addition, the present results indicated that CG played a critical protective role against pressure overload-induced cardiac hypertrophy. CG not only inhibited the development of cardiac hypertrophy but also improved ventricular function. In vitro, the results showed that CG induced relaxation in rat aortic rings through an endothelium-dependent pathway mediated by NO/cGMP, CO/HO and H2S/CSE systems. Taken together, the present study demonstrated that CG could induce a potent antihypertensive effect that was partly due to the improvement of endothelial function. Also CG played a critical protective role against pressure overload-induced cardiac hypertrophy. In addition, CG could induce relaxation in rat aortic rings.

Hydrogen sulfide reduces serum triglyceride by activating liver autophagy via the AMPK-mTOR pathway

Autophagy plays an important role in liver triglyceride (TG) metabolism. Inhibition of autophagy could reduce the clearance of TG in the liver. Hydrogen sulfide (H2S) is a potent stimulator of autophagic flux. Recent studies showed H2S is protective against hypertriglyceridemia (HTG) and noalcoholic fatty liver disease (NAFLD), while the mechanism remains to be explored. Here, we tested the hypothesis that H2S reduces serum TG level and ameliorates NAFLD by stimulating liver autophagic flux by the AMPK-mTOR pathway. The level of serum H2S in patients with HTG was lower than that of control subjects. Sodium hydrosulfide (NaHS, H2S donor) markedly reduced serum TG levels of male C57BL/6 mice fed a high-fat diet (HFD), which was abolished by coadministration of chloroquine (CQ), an inhibitor of autophagic flux. In HFD mice, administration of NaSH increased the LC3BII-to-LC3BI ratio and decreased the p62 protein level. Meanwhile, NaSH increased the phosphorylation of AMPK and thus reduced the phosphorylation of mTOR in a Western blot study. In cultured LO2 cells, high-fat treatment reduced the ratio of LC3BII to LC3BI and the phosphorylation of AMPK, which were reversed by the coadministration of NaSH. Knockdown of AMPK by siRNA in LO2 cells blocked the autophagic enhancing effects of NaSH. The same qualitative effect was observed in AMPKα2(-/-) mice. These results for the first time demonstrated that H2S could reduce serum TG level and ameliorate NAFLD by activating liver autophagy via the AMPK-mTOR pathway.

[Nanocerium restores the erythrocytes stability to acid hemolysis by inhibition of oxygen and nitrogen reactive species in old rats]

In experiments in vivo the effect of nanocerium (cerium oxide nanoparticles) on the stability of red blood cells to acid hemolysis, levels of both ROS and RNS generation and H2S pools in plasma and erythrocytes of old rats were investigated. In red blood cells of old rats the proton penetration into the matrix of erythrocytes showed a significant raising and the fate of labile "aging" erythrocytes in old animals compared with adult were up- regulated. These phenomena paralleled with significant up-regulation of ROS and RNS generation. Introduction for 14 days per os to old rats 0.1 mg/kg of nanocerium fully restored resistance of erythrocytes to acid hemolysis by ROS and RNS in both plasma and erythrocytes reduction. Nanocerium decreased the erythrocytes and, conversely, significantly increased the plasma's pools of H2S.

The role of miR-34a in the hepatoprotective effect of hydrogen sulfide on ischemia/reperfusion injury in young and old rats

Hydrogen sulfide (H2S) can protect the liver against ischemia-reperfusion (I/R) injury. However, it is unknown whether H2S plays a role in the protection of hepatic I/R injury in both young and old patients. This study compared the protective effects of H2S in a rat model (young and old animals) of I/R injury and the mechanism underlying its effects. Young and old rats were assessed following an injection of NaHS. NaHS alone reduced hepatic I/R injury in the young rats by activating the nuclear erythroid-related factor 2 (Nrf2) signaling pathway, but it had little effect on the old rats. NaHS pretreatment decreased miR-34a expression in the hepatocytes of the young rats with hepatic I/R. Overexpression of miR-34a decreased Nrf-2 and its downstream target expression, impairing the hepatoprotective effect of H2S on the young rats. More importantly, downregulation of miR-34a expression increased Nrf-2 and the expression of its downstream targets, enhancing the effect of H2S on hepatic I/R injury in the old rats. This study reveals the different effects of H2S on hepatic I/R injury in young and old rats and sheds light on the involvement of H2S in miR-34a modulation of the Nrf-2 pathway.

[Serum hydrogen sulfide levels in children with benign infantile convulsions associated with mild gastroenteritis]

OBJECTIVE

To study the changes and significance of serum hydrogen sulfide (H2S) levels in children with benign infantile convulsions associated with mild gastroenteritis (BICE).

METHODS

Forty-two hospitalized children diagnosed with BICE were recruited to the observation group, and 46 children admitted due to acute gastroenteritis alone were recruited to the control group. Serum H2S levels were measured by a spectrophotometer.

RESULTS

The serum H2S level in the observation group was significantly lower than in the control group (28±12 μmol/L vs 45±10 μmol/L; P<0.01). The patients with a number of convulsions greater than or equal to two had significantly lower serum H2S levels than those with a number less than two (P<0.05). The number of convulsions was negatively correlated with serum H2S level in BICE patients (r=-0.485, P=0.001). When a convulsion exceeded 5 minues in duration, the duration was negatively correlated with serum H2S level (r=-0.736, P=0.004).

CONCLUSIONS

The reduction in endogenous H2S level might be one of the causes of convulsions in BICE patients. The degree of reduction in H2S level is associated with the number of convulsions and the duration of convulsion (when it exceeds 5 minues). Further investigation is needed to determine the clinical significance of these results.

Hydrogen sulfide and nitric oxide metabolites in the blood of free-ranging brown bears and their potential roles in hibernation

During winter hibernation, brown bears (Ursus arctos) lie in dens for half a year without eating while their basal metabolism is largely suppressed. To understand the underlying mechanisms of metabolic depression in hibernation, we measured type and content of blood metabolites of two ubiquitous inhibitors of mitochondrial respiration, hydrogen sulfide (H2S) and nitric oxide (NO), in winter-hibernating and summer-active free-ranging Scandinavian brown bears. We found that levels of sulfide metabolites were overall similar in summer-active and hibernating bears but their composition in the plasma differed significantly, with a decrease in bound sulfane sulfur in hibernation. High levels of unbound free sulfide correlated with high levels of cysteine (Cys) and with low levels of bound sulfane sulfur, indicating that during hibernation H2S, in addition to being formed enzymatically from the substrate Cys, may also be regenerated from its oxidation products, including thiosulfate and polysulfides. In the absence of any dietary intake, this shift in the mode of H2S synthesis would help preserve free Cys for synthesis of glutathione (GSH), a major antioxidant found at high levels in the red blood cells of hibernating bears. In contrast, circulating nitrite and erythrocytic S-nitrosation of glyceraldehyde-3-phosphate dehydrogenase, taken as markers of NO metabolism, did not change appreciably. Our findings reveal that remodeling of H2S metabolism and enhanced intracellular GSH levels are hallmarks of the aerobic metabolic suppression of hibernating bears.

Role of hydrogen sulfide in portal hypertension and esophagogastric junction vascular disease

AIM: To investigate the association between endogenous hydrogen sulfide (H₂S) and portal hypertension as well as its effect on vascular smooth muscle cells.

METHODS: Portal hypertension patients were categorized by Child-Pugh score based on bilirubin and albumin levels, prothrombin time, ascites and hepatic encephalopathy. Plasma H₂S concentrations and portal vein diameters (PVDs) were compared between portal hypertension patients and control participants, as well as between portal hypertension patients with varying degrees of severity. In addition, we established a rabbit hepatic schistosomiasis portal hypertension (SPH) model and analyzed liver morphology, fibrosis grade, plasma and liver tissue H₂S concentrations, as well as cystathionine γ-lyase (CSE) activity and phosphorylated extracellular signal-regulated kinase (pERK)1/2, B cell lymphoma (Bcl)-2 and Bcl-XL expression in portal vein smooth muscle cells, in addition to their H₂S-induced apoptosis rates.

RESULTS: In portal hypertension patients, endogenous H₂S levels were significantly lower than those in healthy controls. The more severe the disease was, the lower were the H₂S plasma levels, which were inversely correlated with PVD and Child-Pugh score. Liver tissue H₂S concentrations and CSE expression were significantly lower in the SPH rabbit livers compared with the control animals, starting at 3 wk, whereas pERK 1/2 expressions gradually increased 12-20 wk after SPH model establishment. In portal vein smooth muscle cells, increasing H₂S levels led to increased apoptosis, while Bcl-2 and Bcl-XL expression decreased.

CONCLUSION: H₂S prevents vascular restructuring caused by excessive proliferation of smooth muscle cells via apoptosis induction, which helps to maintain normal vascular structures.

[Expressions of CSE and CBS in the corpus cavernosum of spontaneous hypertensive rats]

OBJECTIVE

To investigate the expressions of cystathionine gamma-lyase (CSE) and cystathionine beta-synthase (CBS) in the corpus cavernosum of spontaneous hypertensive rats (SHR) and their relationship with erectile dysfunction.

METHODS

This study included 10 male SHRs and 10 healthy male Wistar-Kyoto (WKY) rats as controls, all aged 12 weeks. We applied a series of electric stimuli to the major pelvic ganglions of the rats, observed changes in the ratio of intracavernosal to mean arterial blood pressure (ICP/MAP), measured the levels of serum testosterone (T) and endogenous H2S, and determined the expressions of CSE and CBS in the corpus cavernosum by Western blot and immunohistochemistry.

RESULTS

No obvious difference was found in the serum T level between the two groups. Compared with the WKY rats, the SHRs showed significant reduction in the ICP/MAP ratio, the contents of plasma H2S ([21.92 +/- 2.75] micromol/L vs [10.49 +/- 1.35] micromol/L, P < 0.05) and endogenous corpus cavernosal H2S ([87.67 +/- 2.12] nmol/mg prot vs [52.60 +/- 3.44] nmol/mg prot, P < 0.05), the level of endogenous H2S synthesis ([4.35 +/- 0.32] nmol/mg per min vs [1.14 +/- 0.07] nmol/mg per min, P < 0.05) and the expressions of CBS and CSE (P < 0.05). Immunohistochemistry showed that CSE and CBS were distributed mainly in the smooth muscle cells and vascular endothelial cells of the corpus cavernosum. The ICP/MAP ratio was highly positively correlated with the expressions of CSE (r = 0.977, P < 0.05) and CBS (r = 0.955, P < 0.05) in the corpus cavernosal tissue.

CONCLUSION

Hypertension inhibits endogenous H2S synthesis by suppressing the expressions of CSE and CBS in the corpus cavernosum, which might be related with hypertension-induced reduction of erectile function.

Immune regulation of hydrogen sulfide in children with acute lymphoblastic leukemia

BACKGROUND

Acute lymphoblastic leukemia (ALL) and chemotherapy can cause immune imbalance, and gaseous molecule hydrogen sulfide (H2S) can participate in the process of immune response. This study aimed to investigate the immune regulation of H2S in pediatric ALL.

METHODS

Children (n = 78) with ALL admitted during 2010-2013 were included in this study. Two blood samples were collected in period of before chemotherapy, bone marrow remission and two days after chemotherapy, respectively. Serum contents of H2S and cytokines, including interleukin-1β (IL-1β), interleukin-2 (IL-2), interferon-γ (IFN-γ), tumor necrosis factor (TNF-α), interleukin-4 (IL-4), interleukin-6 (IL-6), interleukin-10 (IL-10) and macrophage inflammatory protein-1α (MIP-1α), were detected using ELISA method. Stepwise regression was used to analyze the correlation between H2S and cytokines. Furthermore, human Jurkat cells were cultured in vitro, and nucleoprotein of Jurkat cells and peripheral blood mononuclear cells (PBMCs) were collected, contents of cystathionine γ-lyase (CSE) and certain cytokines were measured by Western blotting.

RESULTS

Serum concentrations of H2S, IL-1β, IL-6, IL-10 and MIP-1a in children with ALL were increased significantly (P < 0.01), while concentrations of IL-2, TNF-α, IFN-γ and IL-4 decreased obviously (P < 0.01). In patients after chemotherapy, concentrations of H2S and IL-10 were decreased significantly (P < 0.05), but IL-4 and IFN-γ concentrations increased markedly (P < 0.05). At remission stage, H2S, IL-1β, IL-4, IL-6, IL-10 and MIP-1α concentrations were further decreased markedly (P < 0.05), but concentrations of IL-2, TNF-α and IFN-γ increased again (P < 0.05). Protein contents of CSE, IL-10, IL-4 and IL-2 of PBMCs also increased markedly in children with ALL. Moreover, changes of CSE protein contents of PBMCs were consistent with serum H2S contents, and there were significant correlation between H2S and certain cytokines based on stepwise regression analysis. Furthermore, compared with those of PBMCs group, in vitro study indicated that Jurkat cells of H2S group expressed IFN-γ, IL-10, IL-4 and IL-2 protein increased obviously (P < 0.05), while IL-4, IL-2 and CSE expression of PPG group decreased markedly (P < 0.05).

CONCLUSION

Gaseous molecule H2S might participate in the process of immune regulation in pediatric ALL through modulating transcription and expression of cytokines.

[Change in plasma H2S level and therapeutic effect of H2S supplementation in tubulointerstitial fibrosis among rats with unilateral ureteral obstruction]

OBJECTIVE

To observe the level in plasma hydrogen sulfide (H2S) and the expression of cystathionine beta-synthase (CBS) and cystathionine gamma-lyase (CSE) (two key synthetases for endogenous H2S generation in the kidney) in obstructed kidney tissue among rats with tubulointerstitial fibrosis (TIF) induced by unilateral ureteral obstruction (UUO), and to explore the role of H2S in TIF.

METHODS

Ninety-six male Sprague-Dawley rats were randomly divided into sham-operated, model, low-dose NaHS and high-dose NaHS groups (n=24 each). TIF was induced by UUO in the model, low-dose NaHS and high-dose NaHS groups. The low-dose and high-dose NaHS groups were intraperitoneally injected with NaHS (1.4 and 7.0 μmol/kg respectively) twice daily immediately after operation, and the sham-operated and model groups were intraperitoneally injected with an identical volume of normal saline. In each group, 8 rats were randomly selected and sacrificed at 7, 14 or 21 days after operation. Plasma H2S concentration was measured by deproteinization. The obstructed kidney tissue was subjected to hematoxylin and eosin staining and Masson staining, and the renal tubulointerstitial injury was evaluated under a microscope. mRNA and protein expression of CBS and CSE in the obstructed kidney tissue was measured by RT-PCR and immunohistochemistry respectively.

RESULTS

The degree of UUO-induced renal tubulointerstitial injury was negatively correlated with plasma H2S concentration in (r=-0.891, P<0.01). With H2S supplementation, renal tubulointerstitial injury was reduced (P<0.01), the expression of mRNA and protein of CBS and CSE in the kidney tissue and plasma H2S level were upregulated (P<0.01), and the degree of TIF was reduced (P<0.01). There were no significant differences in plasma H2S level and mRNA and protein expression of CBS and CSE between the low-dose and high-dose NaHS groups (P>0.05).

CONCLUSIONS

H2S is involved in the development of UUO-induced TIF, and the CBS/H2S and CSE/H2S systems play key roles in this process. H2S supplementation can delay the progression of TIF.

Hydrogen sulfide preconditioning protects rat liver against ischemia/reperfusion injury by activating Akt-GSK-3β signaling and inhibiting mitochondrial permeability transition

Hydrogen sulfide (H2S) is the third most common endogenously produced gaseous signaling molecule, but its impact on hepatic ischemia/reperfusion (I/R) injury, especially on mitochondrial function, remains unclear. In this study, rats were randomized into Sham, I/R, ischemia preconditioning (IPC) or sodium hydrosulfide (NaHS, an H2S donor) preconditioning groups. To establish a model of segmental (70%) warm hepatic ischemia, the hepatic artery, left portal vein and median liver lobes were occluded for 60 min and then unclamped to allow reperfusion. Preconditioning with 12.5, 25 or 50 μmol/kg NaHS prior to the I/R insult significantly increased serum H2S levels, and, similar to IPC, NaHS preconditioning decreased alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels in the plasma and prevented hepatocytes from undergoing I/R-induced necrosis. Moreover, a sub-toxic dose of NaHS (25 μmol/kg) did not disrupt the systemic hemodynamics but dramatically inhibited mitochondrial permeability transition pore (MPTP) opening and thus prevented mitochondrial-related cell death and apoptosis. Mechanistic studies revealed that NaHS preconditioning markedly increased the expression of phosphorylated protein kinase B (p-Akt), phosphorylated glycogen synthase kinase-3 beta (p-GSK-3β) and B-cell lymphoma-2 (Bcl-2) and decreased the release of mitochondrial cytochrome c and cleaved caspase-3/9 levels. Therefore, NaHS administration prior to hepatic I/R ameliorates mitochondrial and hepatocellular damage through the inhibition of MPTP opening and the activation of Akt-GSK-3β signaling. Furthermore, this study provides experimental evidence for the clinical use of H2S to reduce liver damage after perioperative I/R injury.

Microbial regulation of host hydrogen sulfide bioavailability and metabolism

Hydrogen sulfide (H2S), generated through various endogenous enzymatic and nonenzymatic pathways, is emerging as a regulator of physiological and pathological events throughout the body. Bacteria in the gastrointestinal tract also produce significant amounts of H2S that regulates microflora growth and virulence responses. However, the impact of the microbiota on host global H2S bioavailability and metabolism remains unknown. To address this question, we examined H2S bioavailability in its various forms (free, acid labile, or bound sulfane sulfur), cystathionine γ-lyase (CSE) activity, and cysteine levels in tissues from germ-free versus conventionally housed mice. Free H2S levels were significantly reduced in plasma and gastrointestinal tissues of germ-free mice. Bound sulfane sulfur levels were decreased by 50-80% in germ-free mouse plasma and adipose and lung tissues. Tissue CSE activity was significantly reduced in many organs from germ-free mice, whereas tissue cysteine levels were significantly elevated compared to conventional mice. These data reveal that the microbiota profoundly regulates systemic bioavailability and metabolism of H2S.

[Modified methylene blue method for measurement of hydrogen sulfide level in plasma]

In past decade, hydrogen sulfide (H₂S) as a novel gasotransmitter, covered many fields in biological and medical research. However, there is no effective, convenient and high-throughput method for determination of circulatory H₂S until now. Here, we aim to develop an easy method for measurement of circulatory H₂S by modified methylene blue method. In the present study, we added Zn²⁺ to plasma sample to deposit H₂S, HS⁻ and S²⁻, as well as plasma protein, then used NaOH to re-dissolve plasma protein. ZnS deposition was re-dissolved by the addition of N, N-dimethyl-p-phenylenediamine, and the remnant protein was deposited by trichloroacetic acid. After centrifugation, ferriammonium sulfate was added to the supernatant fluid to generate methylene blue, which was analyzed by spectrophotometer at 665 nm. Using the present method, we found that most ions including sulfate and thiosulfate did not affect detection of H₂S concentration, but albumin (physiological concentration) reduced the detection value, which suggested the binding of serum albumin and a certain amount of H₂S. The relative recovery ratio of present method is 81.9%, which implies that the method is relative accurate for the determination of H₂S concentration in plasma or serum. H₂S levels of frozen plasma samples from 65 healthy volunteers detected by the present method were (13.93 ± 4.98) µmol/L. There was no obvious difference between the detection values of fresh and frozen samples from the same SD rats. These results suggest the modified methylene blue assay is stable, sensitive, convenient and high-throughput. The method can be used to analyze the circulatory H₂S in clinical and basic research.

Effect of plasma treatment on multi-walled carbon nanotubes for the detection of H2S and SO2

H(2)S and SO(2) are important characteristic gases of partial discharge (PD) generated by latent insulated defects in gas insulated switchgear (GIS). The detection of H(2)S and SO(2) is of great significance in the diagnosis and assessment of the operating status of GIS. In this paper, we perform experiments on the gas sensitivity of unmodified multi-walled carbon nanotubes (MWNTs) and those modified by atmospheric pressure dielectric barrier discharge (DBD) air plasma at different times (30, 60 and 120 s) for H(2)S and SO(2), respectively. The results show that the sensitivity and response time of modified MWNTs to H(2)S are both improved, whereas the opposite effects are observed for SO(2). The modified MWNTs have almost zero sensitivity to SO(2). Thus, the MWNTs modified by atmospheric pressure DBD air plasma present good selectivity to H(2)S, and have great potential in H(2)S detection.

[Effect of nitric oxide on the preterm neonatal rabbit ductus arteriosus cystathionine-γ-lyase/hydrogen sulfide pathway]

OBJECTIVE

To investigate the impact of sodium nitroprusside (a nitric oxide donor) in the ductus arteriosus in preterm rabbits on hydrogen sulfide (H(2)S)-cystathionine-γ-lyase (CSE) system.

METHODS

For 16 Japanese white rabbits pregnant for 21 days were randomly divided into four groups, each of the following groups had 4 rabbits: control group, intraperitoneal injection of sodium nitroprusside 1 mg/kg, 2.5 mg/kg, and 5.0 mg/kg groups. The rabbits in control group had a peritoneal puncture with a simple hollow needle, and those in the other groups were given corresponding dose of intraperitoneal injection of sodium nitroprusside at gestational age 23 and 25 days, respectively. At gestational age 26 days the fetuses of the pregnant rabbits were removed surgically, and 28 fetal rabbits were obtained from the control group, 27 from the sodium nitroprusside small dose group, 29 from the medium dose group, and 26 from the large dose group. The fetal heart blood sample of 1 ml was taken from each fetus, and immediately after sampling the arterial ductal tissues were dissected. Fetal rabbit plasma proteins hydrogen sulfide content was determined by using de-protein method, and real time quantitative RT-PCR was used for determination of arterial tissue CSE gene and western-blotting was used for measuring protein expression of CSE.

RESULTS

In control group hydrogen sulfide content of fetal rabbits plasma (55.68 ± 6.57) µmol/L and arterial tissue CSE mRNA expression was 1.07 ± 4.12; the parameters in intraperitoneal injection of sodium nitroprusside group 1 mg/kg were (60.02 ± 6.09) µmol/L and 3.46 ± 0.18; in intraperitoneal injection of sodium nitroprusside group 2.5 mg/kg, were (64.71 ± 7.12) µmol/L and 10.95 ± 0.22; and in intraperitoneal injection of sodium nitroprusside group 1 mg/kg were (70.63 ± 8.07) µmol/L and 19.56 ± 0.17. Comparison between small dose group and control group, medium dose group and small dose group, high dose group and medium dose group showed that the above data were significantly different P < 0.05, with the injection of sodium nitroprusside CSE protein expression increased gradually with increasing doses.

CONCLUSION

Sodium nitroprusside showed an enhancing effect on preterm CSE-H(2)S system in rabbit ductus arteriosus in a certain range of concentration in a dose-dependent manner.

Erythrocytic or serum hydrogen sulfide association with hypertension development in untreated essential hypertension

BACKGROUND

Endogenous hydrogen sulfide (H(2)S) plays an important role in hypertension. The aim of this study was to investigate the role of erythrocyte and serum H(2)S in patients with untreated essential hypertension.

METHODS

We recruited 62 patients (age 22 - 74 years) with untreated prehypertension or hypertension, and 64 normotensive subjects (age 18 - 64 years). We assessed the 3-mercaptopyruvate sulphurtransferase (MPST) protein expression in erythrocytes and measured the H(2)S production from erythrocytes and serum H(2)S levels, then analyzed the association of erythrocytic or serum H(2)S content and blood pressure or cardiovascular risk factors (e.g., age, body mass index (BMI) and dyslipidemia). A stepwise regression analysis was used to evaluate the possible relationship of erythrocytic H(2)S in hypertension.

RESULTS

In hypertensive patients, erythrocyte H(2)S production ((111.04 ± 29.20) nmol/min per 10(8) erythrocytes) was higher than that in controls ((78.85 ± 19.38) nmol/min per 10(8) erythrocytes), and serum H(2)S was also higher. The erythrocytic H(2)S production was associated with increased systolic blood pressure (sBP), diastolic blood pressure (dBP), age, BMI, level of C-reactive protein (CRP), as well as triglycerides (TG) and high density lipoprotein cholesterol (HDL-C). Serum H(2)S was not associated with age or CRP. Stepwise regression analysis showed that erythrocytic H(2)S production was correlated with sBP, TG, HDL-C, low density lipoprotein cholesterol (LDL-C) and blood urea nitrogen (BUN) and serum H(2)S was correlated with dBP and TG. Results of receiver-operating characteristic curve analysis suggested that erythrocytic H(2)S production was a more sensitive predictor of hypertension development than serum H(2)S.

CONCLUSION

Erythrocytic or serum H(2)S production is sensitive predictor of hypertension.

Changes in plasma hydrogen sulfide and nitric oxide levels and their clinical significance in children with Kawasaki disease

BACKGROUND

Cardiac involvement is the most common complication of Kawasaki disease (KD); however, the underlying mechanisms are not understood. The present study was designed to investigate changes in plasma hydrogen sulfide (H(2)S) and nitric oxide (NO) levels in the acute and recovery stages of KD children and to examine their clinical significance.

METHODS

Thirty-five KD patients and 32 healthy children were enrolled in the study. KD patients were divided into two subgroups: a non-cardiac involvement group and a cardiac involvement group. Plasma H(2)S levels were measured using the sulfur-sensitive electrode method and plasma NO levels and NO synthase activity were determined using the nitrate reductase method both before and after intravenous immune globulin (IVIG) therapy.

RESULTS

Plasma H(2)S levels significantly decreased in KD patients during the acute phase of the disease and NO levels were significantly increased, compared with the control group (P < 0.01). After treatment with IVIG, both plasma H(2)S and NO levels significantly increased (P < 0.01). The plasma levels of H(2)S were significantly lower in the cardiac involvement group compared with the non-cardiac involvement group (P < 0.05).

CONCLUSION

H(2)S and NO may play a role in the pathophysiological process of inflammation during the acute phase of KD. Endogenous H(2)S may exert protective effects with respect to cardiac complications in KD.

Hydrogen sulfide attenuates carbon tetrachloride-induced hepatotoxicity, liver cirrhosis and portal hypertension in rats

BACKGROUND

Hydrogen sulfide (H(2)S) displays vasodilative, anti-oxidative, anti-inflammatory and cytoprotective activities. Impaired production of H(2)S contributes to the increased intrahepatic resistance in cirrhotic livers. The study aimed to investigate the roles of H(2)S in carbon tetrachloride (CCl(4))-induced hepatotoxicity, cirrhosis and portal hypertension.

METHODS AND FINDINGS

Sodium hydrosulfide (NaHS), a donor of H(2)S, and DL-propargylglycine (PAG), an irreversible inhibitor of cystathionine γ-lyase (CSE), were applied to the rats to investigate the effects of H(2)S on CCl(4)-induced acute hepatotoxicity, cirrhosis and portal hypertension by measuring serum levels of H(2)S, hepatic H(2)S producing activity and CSE expression, liver function, activity of cytochrome P450 (CYP) 2E1, oxidative and inflammatory parameters, liver fibrosis and portal pressure. CCl(4) significantly reduced serum levels of H(2)S, hepatic H(2)S production and CSE expression. NaHS attenuated CCl(4)-induced acute hepatotoxicity by supplementing exogenous H(2)S, which displayed anti-oxidative activities and inhibited the CYP2E1 activity. NaHS protected liver function, attenuated liver fibrosis, inhibited inflammation, and reduced the portal pressure, evidenced by the alterations of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), hyaluronic acid (HA), albumin, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6 and soluble intercellular adhesion molecule (ICAM)-1, liver histology, hepatic hydroxyproline content and α-smooth muscle actin (SMA) expression. PAG showed opposing effects to NaHS on most of the above parameters.

CONCLUSIONS

Exogenous H(2)S attenuates CCl(4)-induced hepatotoxicity, liver cirrhosis and portal hypertension by its multiple functions including anti-oxidation, anti-inflammation, cytoprotection and anti-fibrosis, indicating that targeting H(2)S may present a promising approach, particularly for its prophylactic effects, against liver cirrhosis and portal hypertension.

H2S donor, S-propargyl-cysteine, increases CSE in SGC-7901 and cancer-induced mice: evidence for a novel anti-cancer effect of endogenous H2S?

Background

S-propargyl-cysteine (SPRC), an H₂S donor, is a structural analogue of S-allycysteine (SAC). It was investigated for its potential anti-cancer effect on SGC-7901 gastric cancer cells and the possible mechanisms that may be involved.

Methods and Findings

SPRC treatment significantly decreased cell viability, suppressed the proliferation and migration of SPRC-7901 gastric cancer cells, was pro-apoptotic as well as caused cell cycle arrest at the G₁/S phase. In an in vivo study, intra-peritoneal injection of 50 mg/kg and 100 mg/kg of SPRC significantly reduced tumor weights and tumor volumes of gastric cancer implants in nude mice, with a tumor growth inhibition rate of 40–75%. SPRC also induced a pro-apoptotic effect in cancer tissues and elevated the expressions of p53 and Bax in tumors and cells. SPRC treatment also increased protein expression of cystathione-γ-lyase (CSE) in cells and tumors, and elevated H₂S levels in cell culture media, plasma and tumoral CSE activity of gastric cancer-induced nude mice by 2, 2.3 and 1.4 fold, respectively. Most of the anti-cancer functions of SPRC on cells and tumors were significantly suppressed by PAG, an inhibitor of CSE activity.

Conclusions

Taken together, the results of our study provide insights into a novel anti-cancer effect of H₂S as well as of SPRC on gastric cancer through inducing the activity of a new target, CSE.

Measurement of plasma hydrogen sulfide in vivo and in vitro

The gasotransmitter hydrogen sulfide is known to regulate multiple cellular functions during normal and pathophysiological states. However, a paucity of concise information exists regarding quantitative amounts of hydrogen sulfide involved in physiological and pathological responses. This is primarily due to disagreement among various methods employed to measure free hydrogen sulfide. In this article, we describe a very sensitive method of measuring the presence of H₂S in plasma down to nanomolar levels, using monobromobimane (MBB). The current standard assay using methylene blue provides erroneous results that do not actually measure H₂S. The method presented herein involves derivatization of sulfide with excess MBB in 100 mM Tris-HCl buffer (pH 9.5, 0.1 mM DTPA) for 30 min in 1% oxygen at room temperature. The fluorescent product sulfide-dibimane (SDB) is analyzed by RP-HPLC using an eclipse XDB-C18 (4.6 × 250 mm) column with gradient elution by 0.1% (v/v) trifluoroacetic acid in acetonitrile. The limit of detection for sulfide-dibimane is 2 nM and the SDB product is very stable over time, allowing batch storage and analysis. In summary, our MBB method is suitable for sensitive quantitative measurement of free hydrogen sulfide in multiple biological samples such as plasma, tissue and cell culture lysates, or media.