The cardiovascular inhibition functions of hydrogen sulfide within the nucleus tractus solitarii are mediated by the activation of KATP channels and glutamate receptors mechanisms

Hydrogen sulfide (H2S), the colorless gas with the smell of rotten eggs, has been regarded as a novel gaseous signaling molecule. Although H2S has been proved been involved into the cardiovascular functions, the cardiovascular functions of H2S within the nucleus tractus solitarii (NTS) are not clear. Unilateral microinjection of NaHS (2 to 200 pmol), a H2S donor, into the NTS caused transient and dose-dependent hypotension and bradycardia (P<0.01). Microinjection of CBS allosteric activator S-ademetionine (SAM) into the NTS also produced significant decreases in BP (from 101 +/- 8 to 82 +/- 7 mmHg, P < 0.01) and HR (from 469 +/- 16 to 449 +/- 14 bpm, P<0.01), which was very similar to those of NaHS. Pretreatment with hydroxylamine, a CBS inhibitor, failed to affect the cardiovascular functions of intra-NTS NaHS. However, pretreatment with glibenclamide (10 nmol), a KATP channel blocker, eliminated the on BP (from -23 +/- 4 to -5 +/- 1 mmHg, P<0.01) and HR (from -24 +/- 2 to -5 +/- 1 bpm, P<0.01) by 78% and 79%, respectively, of intra-NTS NaHS (20 pmol). Likewise, pretreatment with kynurenic acid (Kyn, 5 nmol) also attenuated the effects of NaHS on BP (from -29 +/- 3 to -12 +/- 3 mmHg, P<0.01) and HR (from -19 +/- 2 to -9 +/- 2 bpm, P<0.01) by 59% and 53%, respectively, of intra-NTS NaHS (20 pmol). These data support the hypothesis that endogenous H2S produces cardiovascular inhibition functions in the NTS, mainly mediated by KATP channels regulation or/and glutamate receptors.

[Changes in ageing pace and major immune parameters among individuals with long exposure to hydrogen sulfide]

The authors revealed increase in ageing pace, higher level of pro-inflammatory cytokine Interleukin-8 and apoptosis marker (p53 protein) in individuals with chronic exposure to gas containing hydrogen sulfide. The immune parameters studied could serve as markers of premature ageing in individuals engaged into gas extraction.

[Characteristics of cytokine state and processes of apoptosis under the influence of the combine action of production factors of the gas producing enterprise]

People exposed to chronic influence of hydrogen sulphide gas demonstrate accelerated aging, increase of proinflammatory cytokine interleukin-8 level and the marker of apoptosis protein p53. Researched immunologic indices can serve as markers of premature aging in persons involved in gas producing enterprise.

[Case followed by delayed loss of consciousness after exposure to hydrogen sulfide that was treated with intermittent administration of sodium nitrite]

A 49-year-old man lost consciousness after being accidentally exposed to what was probably hydrogen sulfide gas while performing maintenance on a machine producing feather meal. He was immediately taken to the hospital. Upon admission, his consciousness level was 14 (E4V4M6) on the Glasgow Coma Scale (GCS), but it subsequently decreased, and the patient was intubated when his respirations became depressed as well. About 5 hours after the initial incident, he was transferred to our department. His consciousness level was GCS 9 (E2V2M5), his blood pressure was 95/78 mmHg, and his heart rate was 90 beats per min. There was no metabolic acidosis. Mechanical ventilation was begun and 10% sodium nitrite was intermittently administered intravenously, with the goal of lowering arterial blood methemoglobin saturation to 20%. Two days following admission, the patient regained full consciousness and sodium nitrite administration was stopped. The following day mechanical ventilation was also discontinued. This patient exhibited severe recurring neurologic symptoms without metabolic acidosis; thus, the manifestations of toxicity in this case might have been due to the direct neurologic toxicity of hydrogen sulfide, hypoxia, or delayed post-ischemic cerebral hypoperfusion syndrome. The patient made a full recovery without any sequelae; therefore we would like to hypothesize that repetitive intravenous administration of sodium nitrite is effective in cases of hydrogen sulfide exposure.

[Effect of synthesized GYY4137, a slowly releasing hydrogen sulfide donor, on cell viability and distribution of hydrogen sulfide in mice]

OBJECTIVE

To improve a method of a new hydrogen sulfide slow-releasing donor, to observe its cellular toxicity in HepG2 cells and tissue distribution and metabolic pathway after administration of the donor by intraperitoneal injection in ICR mice and to afford experimental evidences for rationally using this donor in hydrogen sulfide research.

METHODS

We synthesized the new chemical compound which slowly released hydrogen sulfide. After administration of the donor, the cell toxicity was evaluated for cell viability using trypan blue staining in HepG2 cells and lactate dehydrogenase (LDH) activity in culture medium. After administration of this donor by intrasperitoneal injection, we measured the tissue hydrogen sulfide content in the liver, heart, kidney and brain using sensitive-sulfur electrode assay.

RESULTS

We successfully prepared the donor which could release hydrogen sulfide. The releasing ability of the donor solution stored at 4 °C or 20 °C did not change as compared with the freshly-prepared one. Treated at various concentrations of the donor (0.062 5, 0.125, 0.25, 0.5, 1 and 2 mmol/L) for 24 hours in HepG2 cells, the cell viability and LDH leak from the cells were not different as compared with the controls. The donor (2 mmol/L) was administrated everyday and the culture medium was changed every 3 days. After 9 days, the cell viability and LDH leak did not change. Administration of the donor (200 μmol/kg) quickly increased the tissue hydrogen sulfide concentrations in the liver and heart and maintained about 20 min; the hydrogen sulfide level in the kidney elevated and maintained a longer time, then recovered after 2 hours, which implicated that the donor might exclude the kidney; the hydrogen sulfide concentration in the brain did not change in the present study, which suggested that the donor could not pass the blood-brain barrier. Long time (4 weeks) treatment with this compound might induce hepatic or cutaneous injury.

CONCLUSION

The new chemical compound is a relative stable, slow-releasing donor of hydrogen sulfide with low cellular toxicity, which may be used to study the regulatory role of hydrogen sulfide in the cellular physiological and pathophysiological mechanism of the animal model with acute diseases.

DNA damage and toxicogenomic analyses of hydrogen sulfide in human intestinal epithelial FHs 74 Int cells

Hydrogen sulfide (H(2)S), a metabolic end product of sulfate-reducing bacteria, represents a genotoxic insult to the colonic epithelium, which may also be linked with chronic disorders such as ulcerative colitis and colorectal cancer. This study defined the early (30 min) and late (4 hr) response of nontransformed human intestinal epithelial cells (FHs 74 Int) to H(2)S. The genotoxicity of H(2)S was measured using the single-cell gel electrophoresis (comet) assay. Changes in gene expression were analyzed after exposure to a genotoxic, but not cytotoxic, concentration of H(2)S (500 muM H(2)S) using pathway-specific quantitative RT-PCR gene arrays. H(2)S was genotoxic in a concentration range from 250 to 2,000 microM, which is similar to concentrations found in the large intestine. Significant changes in gene expression were predominantly observed at 4 hr, with the greatest responses by PTGS2 (COX-2; 7.92-fold upregulated) and WNT2 (7.08-fold downregulated). COX-2 was the only gene upregulated at both 30 min and 4 hr. Overall, the study demonstrates that H(2)S modulates the expression of genes involved in cell-cycle progression and triggers both inflammatory and DNA repair responses. This study confirms the genotoxic properties of H(2)S in nontransformed human intestinal epithelial cells and identifies functional pathways by which this bacterial metabolite may perturb cellular homeostasis and contribute to the onset of chronic intestinal disorders.

Implications of aerated stabilization basin dredging on potential effluent toxicity to fish

Benthal solids accumulated in aerated stabilization basins (ASBs) must be dredged to regain treatment capacity. While dredging restores treatment performance, it has been associated occasionally with the failure to meet regulatory effluent toxicity limits at the time of dredging. A first study of its kind was undertaken to investigate the implications of ASB dredging on potential effluent toxicity to fish. The study showed that benthal solid slurry removed from the quiescent zone of an ASB with a hydraulic dredge was toxic to rainbow trout with a 96-hour median lethal concentration (LC50) of 2.2%. The high ammonia concentration in the sample was the main cause of fish mortality. Hydrogen sulfide and resin and fatty acids also were present in the dredged material at concentrations that could cause fish mortality. These findings have led to best management practices that can be used to mitigate or eliminate fish toxicity issues during dredging operations.

Increased thiol biosynthesis of transgenic poplar expressing a wheat O-acetylserine(thiol) lyase enhances resistance to hydrogen sulfide and sulfur dioxide toxicity

O-acetylserine(thiol) lyase (OASTL), a key enzyme of the plant sulfur assimilatory pathway, catalyses the formation of cysteine from sulfide and O-acetylserine. Transgenic hybrid poplar (Populus sieboldi x P. grandidentata 'Y63') plants expressing cys1, encoding a wheat cytosolic OASTL, were developed in order to examine the role of this enzyme in thiol production following hydrogen sulfide or sulfur dioxide exposure and in the extent of damage induced in the plants by these pollutants. The transgenic cys1 plants accumulated up to several-fold higher cysteine and glutathione levels and were significantly more resistant in terms of foliar damage to the pollutants than WT plants. The transgenic poplar also showed higher tolerance to sulfite and hydrogen peroxide and, interestingly, accumulated several-fold higher sulfite reductase transcripts than WT plants in response to sulfur dioxide. These data clearly demonstrate the important role of OASTL and the sulfur reduction pathway in sulfur and oxidative stress amelioration, and support the notion that transgenic trees resistant to such pollutants can be generated for phytoremediation strategies.

Associations between immune function in yearling beef cattle and airborne emissions of sulfur dioxide, hydrogen sulfide, and VOCs from oil and natural gas facilities

Researchers assessed the associations between airborne emissions from oil and gas field facilities and the structure and function of the immune system of yearling beef cattle in 27 herds during spring 2002. They evaluated the immune systems of these animals by enumerating B lymphocytes and T-lymphocyte subtypes (CD4, CD8, gammadelta, and WC1) in peripheral circulation and by measuring systemic antibody production in response to vaccination. Researchers prospectively measured exposure to sulfur dioxide, hydrogen sulfide, and volatile organic compounds (VOCs) by using air-quality data from passive monitors installed in pastures and wintering areas. They estimated the mean exposure of each animal over the 6-month period before the start of sample collection. The researchers used mixed models, which adjusted for clustering by herd and accounted for known risk factors, to examine potential associations between exposure to airborne sulfur dioxide, VOCs (measured as concentrations of benzene and toluene) and hydrogen sulfide, as well as proximity to emission sources (well-site density), and the immune system outcomes. Increasing exposure to VOCs measured as toluene was associated with significant CD4 T lymphocytopenia. The number of CD4 T lymphocytes was 30% lower in cattle exposed to VOCs measured as toluene in the highest quartile (> 0.823 microg/m3) than in cattle exposed in the lowest quartile (< 0.406 microg/m3).

Associations between in utero exposure to airborne emissions from oil and gas production and processing facilities and immune system outcomes in neonatal beef calves

To determine if oil- and gas-facility emissions prospectively measured as airborne sulfur dioxide and volatile organic compounds (VOCs) were associated with immunomodulation in neonatal beef calves, veterinarians collected samples from 325 calves from 60 western Canadian herds in the spring of 2002. Researchers assessed immune system effects by enumerating B-lymphocytes and specific T-lymphocyte subtypes (CD4, CD8, gammadelta, and WC1) in peripheral circulation using flow cytometry. They estimated in utero exposure for each calf from the earliest possible breeding date of the dam to the calving date, using air-quality data from passive monitors installed in pastures and wintering areas. Numbers of circulating CD4 and CD8 T-lymphocytes were 42% and 43% lower, respectively, in calves exposed to the highest quartile (> or = 0.378 microg/m3) of VOCs measured as airborne concentrations of benzene compared with calves exposed to concentrations in the lowest quartile (< 0.276 microg/m3). Similarly, the number of CD4 T-lymphocytes was 40% lower in calves exposed to VOCs measured as concentrations of toluene in the highest quartile (> or = 0.713 microg/m3), compared with calves exposed to concentrations in the lowest quartile (< 0.348 microg/m3). There was no statistically significant association between in utero exposure and numbers of B-lymphocytes and gammadelta and WC1 T-lymphocyte subtypes in calf blood samples.

Molecular Mechanisms of Hydrogen Sulfide Toxicity

RATIONALE

The toxicity of H2S has been attributed to its ability to inhibit cytochrome c oxidase in a similar manner to HCN. However, the successful use of methemoglobin for the treatment of HCN poisoning was not successful for H2S poisonings even though the ferric heme group of methemoglobin scavenges H2S. Thus, we speculated that other mechanisms contribute to H2S induced cytotoxicity. Experimental procedure. Hepatocyte isolation and viability and enzyme activities were measured as described by Moldeus et al. (1978), and Steen et al. (2001).

RESULTS

Incubation of isolated hepatocytes with NaHS solutions (a H2S source) resulted in glutathione (GSH) depletion. Moreover, GSH depletion was also observed in TRIS-HCl buffer (pH 6.0) treated with NaHS. Several ferric chelators (desferoxamime and DETAPAC) and antioxidant enzymes (superoxide dismutase [SOD] and catalase) prevented cell-free and hepatocyte GSH depletion. GSH-depleted hepatocytes were very susceptible to NaHS cytotoxicity, indicating that GSH detoxified NaHS or H2S in cells. Cytotoxicity was also partly prevented by desferoxamine and DETAPC, but it was increased by ferric EDTA or EDTA. Cell-free oxygen consumption experiments in TRIS-HCl buffer showed that NaHS autoxidation formed hydrogen peroxide and was prevented by DETAPC but increased by EDTA. We hypothesize that H2S can reduce intracellular bound ferric iron to form unbound ferrous iron, which activates iron. Additionally, H2S can increase the hepatocyte formation of reactive oxygen species (ROS) (known to occur with electron transport chain). H2S cytotoxicity therefore also involves a reactive sulfur species, which depletes GSH and activates oxygen to form ROS.

Western Canada study of animal health effects associated with exposure to emissions from oil and natural gas field facilities. Study design and data collection I. Herd performance records and management

Beef cow-calf herds are the most common livestock operation in Western Canada. Beef cows also have the greatest opportunity for direct contact with their environment through continuous sampling of the air, water, vegetation, and soil. These factors combine to make cow-calf herds a potentially useful sentinel of environmental change. Researchers individually tracked more than 33,000 cows in 205 beef cow-calf herds from spring 2001 to the end of the calving season in 2002 to examine the potential effects of emissions from the oil and gas industry on productivity. This article describes the study design and methodology of the Western Canada Study, with emphasis on herd-selection criteria and study implementation, the collection of herd-production data, and the challenges of tracking individual animals in a large prospective observational study-as the Western Canada Study is the largest on-farm study of its kind in North American cow-calf herds to date. The primary objective of this project was to examine the potential association between reproductive success and cumulative chronic exposure to sulfur dioxide, hydrogen sulfide, and volatile organic compounds in beef herds. Herd-selection criteria included potential exposure to oil and gas facilities, herd size, quality of available records, an established relationship with a local veterinary clinic, and participant interest. With the cooperation of local herd owners and veterinarians, on-farm collection of detailed individual animal data was successful in this group of cow-calf operations. Of the 212 herds initially selected to participate, complete calving season data for 2002 were available for 203 herds (96%). Individual animal records were available for more than 98% of eligible cows for each measurement period throughout the study. Herd-production records were rated as satisfactory or better in 94% of the herds. These process outcomes confirm the practicality of using cow-calf herds as sentinel populations for environmental exposures and support the validity of subsequent research on these animal populations.

The association between exposure to the oil and gas industry and beef calf mortality in Western Canada

Researchers assessed the association between exposure to emissions from oil and gas field facilities and newborn calf survival and health status by determining the risks of calf mortality and treatment reported for 27,511 beef calves born to cows in 203 herds, which were followed from the beginning of the 2001 breeding season through the 2002 calving season. They prospectively measured exposures to sulfur dioxide, hydrogen sulfide, and volatile organic compounds (VOCs) by using data from passive air monitors. They also used the density of oil and gas well sites surrounding each pasture as an additional measure of exposure. The researchers found that well-site density as well as exposures to hydrogen sulfide and VOCs measured as benzene or toluene were not associated with the odds of calf mortality in the first 3 months of life. After adjusting for cow-and herd-level risk factors, they found that exposure to sulfur dioxide near the time of calving was associated with an increased risk of calf mortality during this period. Exposure to sulfur dioxide in the 3-month period before calving was most suggestive of a causal exposure-response relationship (the odds ratio for every 1 ppb increase in sulfur dioxide=1.32; 95% confidence interval=1.13-1.54; p=0004). Exposure to sulfur dioxide, hydrogen sulfide, and VOCs measured as benzene or toluene during gestation was not associated with the odds of calf treatment in the first 3 months of life. However, exposure to sulfur dioxide, hydrogen sulfide, and VOCs measured as benzene or toluene, and sulfur dioxide in the first month after calving, was associated with a small increase in the odds of calf treatment after the first month of life when risk was compared across quartiles for exposure; only the association between hydrogen sulfide exposure and the odds of treatment was consistent with a causal exposure.

Western Canada study of animal health effects associated with exposure to emissions from oil and natural gas field facilities. Study design and data collection III. Methods of assessing animal exposure to contaminants from the oil and gas industry

Researchers measured exposure to oil and gas industry emissions in 205 cow-calf herds located in Western Canada. They measured airborne concentrations of sulfur dioxide, hydrogen sulfide, and volatile organic compounds with passive monitors placed in each pasture, wintering, or calving area that contained study animals from the start of the breeding season in the spring of 2001 until June 30, 2002. Researchers continued air monitoring in a subset of herds to the end of the study in fall 2002. Each sampling device was exposed for 1 month and then shipped to the laboratory for analysis. New samplers were installed and the shelters relocated, as necessary, to follow the movements of herd-management groups between pastures. Researchers linked the results of the air-monitoring analysis to individual animals for the relevant month. For the 205 herds examined at pregnancy testing in 2001, monthly mean exposures on the basis of all available data were as follows: sulfur dioxide, geometric mean (GM)=0.5 ppb, geometric standard deviation (GSD)=2.2; hydrogen sulfide, GM=0.14 ppb, GSD=2.3; benzene, GM=0.247 microg/m3, GSD=2.5; and toluene, GM=0.236 microg/m3, GSD=2.7. Benzene and toluene were surrogates for volatile organic compound exposure. In addition to passive measurements of air quality, researchers obtained data from provincial regulatory agencies on the density of oil and gas field facilities and on flaring and venting from the surrounding facilities. They developed the data into additional measures of exposure that were linked to each animal at each location for each month of the study.

[Toxic waste and health effects in Abidjan City, Ivory Coast]

Accidental chemical pollution can have serious effects on human health. In 2006, the tanker vessel Probo Koala discharged hundreds of tons of toxic waste at many sites in Abidjan City, Ivory Coast. In the following days and weeks, thousands of people presented signs of poisoning. Analysis of the waste demonstrated the presence of toxic chemicals such as mercaptans and hydrogen sulfide. The final toll was 8 dead, dozens hospitalized, and about 100,000 seeking medical advice. This event provides evidence that, like international immigration, exportation of industrial waste can result in serious public health hazards.

Hydrogen sulfide inhibits activity of three isoforms of recombinant nitric oxide synthase

To clarify the presence of cross-talk between H(2)S and NO, we investigated effect of NaHS, an H(2)S donor, on activity of recombinant NO synthase (NOS) isoforms. Activity of all nNOS, iNOS and eNOS was inhibited by NaHS (IC(50): 0.13-0.21 mM). In contrast, Na(2)SO(3), L-cysteine and threo-1,4-dimercapto-2,3-butanediol, a reductant, exerted poor inhibition of NOS activity. Increasing concentrations of tetrahydrobiopterin (BH(4)) reversed the NaHS inhibition of nNOS and eNOS, but not iNOS. Our data thus demonstrate inhibition of three NOS isoforms by NaHS/H(2)S, and suggest involvement of interaction of NaHS/H(2)S with BH(4) in inhibition of nNOS and eNOS, but not iNOS.

Release of hydrogen sulfide by asteroid impacts in Black Sea and risks for inland human population

The hydrogen sulfide rich waters of the Black Sea pose a potential danger for the surrounding land regions. The impact of an asteroid may cause a catastrophic poisonous gas release in the atmosphere. Some effects of this last phenomenon on the Eastern Black Sea coastal regions are evaluated in this article. Two simple models are proposed to describe the generation of the H(2)S cloud. The initial diameter of the cloud depends on asteroid size. The initial thickness of the cloud depends, in addition, on sea depth at impact location. The wind speed plays an important role in H(2)S cloud dynamics. At 10 m/s wind-speed the cloud margins may be seen at about 150 km from impact location in about 3.2 h. The maximum distance traveled by the hydrogen sulfide cloud increases by increasing the asteroid size and wind speed. The influence of the impact position on the distance traveled by hydrogen sulfide clouds is rather weak, as far as the seawater depth does not change significantly. Two values are considered when referring to the effect of hydrogen sulfide concentrations on humans: the lower concentration limit of 19.88 ppm (which corresponds to fatigue, loss of appetite, headache, irritability, poor memory, dizziness) and the upper concentration limit of 497 ppm (which corresponds to death after single exposures). The land surface area covered by the H(2)S cloud generated by a 1000 m size asteroid during the run-in ranges between about 6080 and 11,520 km(2). This may affect between 145,000 and 276,000 people. When a 250 m size asteroid is considered, the covered land surface area ranges between about 840 and 1,890 km(2) and between 20,000 and 45,000 people may be affected. In case of a 70 m size asteroid, the cloud covers up to 105 km(2) of land during the run-in. This may affect about 2500 people. These are moderate estimates. They do not include the urban population and may be 10 times underestimated for some particular wind directions. General recommendations to diminish the social effects of the impacts are presented.

[Clinical significance of sulfate-reducing bacteria for ulcerative colitis]

Ulcerative colitis(UC) is colon localized disease. Broad epithelial cell damage, crypt abscesses and accumulation of neutrophils are recognized for UC. Although the cause of UC is indistinct at this time, there is a growing consensus that abnormal intestinal microflora would be related with UC. There have been several evidences that excessive production of hydrogen sulfide by bacteria in colon would be associated with UC. Sulfate reducing bacteria are able to utilize sulfate as an electron receptor for dissimilation of organic substrate and hydrogen gas, resulting in generating toxic hydrogen sulfide. This review is dealt with the association between sulfate reducing bacteria and UC in aetiology and bacterial pathogenesis.