Identification of a functional dddD-Rh for dimethyl sulfide production in the Antarctic Rhodococcus sp. NJ-530

Dimethylsulfoniopropionate (DMSP) is widespread in the oceans, and its biological metabolite, dimethyl sulfide (DMS), plays an important role in the atmosphere. The Antarctic region has become a hotspot in DMS studies due to the high spatial and temporal variability in DMS(P) concentration, but the level of bacterial DMS production remains unclear. In this study, a bacterium isolated from Antarctic floating ice, Rhodococcus sp. NJ-530, was found to metabolize DMSP into DMS, and the rate of DMS production was measured as 3.96 pmol·mg protein⁻¹·h⁻¹. Rhodococcus sp. NJ-530 had a DddD-Rh enzyme containing two CaiB domains, which belonged to the CoA-transferase III superfamily. However, the DddD-Rh had a molecular weight of 73.21 kDa, which was very different from previously characterized DddD enzymes in sequence and evolution. In vitro assays showed that DddD-Rh was functional in the presence of acetyl-CoA. This was the first functional DddD from Gram-positive Actinobacteria. Moreover, a quantitative real-time polymerase chain reaction revealed that high temperature facilitated the expression of dddD-Rh, and changes of salinity had little effect on it. This study adds new evidence to the bacterial DMS production in the Southern Ocean and provides a basis for investigating the metabolic mechanism of DMSP in extreme environments.     

Effects of Hyperkinetic,a β Subunit of Shaker Voltage-Dependent K+ Channels,on the Oxidation State of Presynaptic Nerve Terminals

The Drosophila Hyperkinetic (Hk) gene encodes a β subunit of Shaker (Sh) K⁺ channels and shows high sequence homology to aldoketoreductase. Hk mutations are known to modify the voltage dependence and kinetics of Sh currents, which are also influenced by the oxidative state of the N-terminus region of the Sh channel, as demonstrated in heterologous expression experiments in frog oocytes. However, an in vivo role of Hk in cellular reduction/oxidation (redox) has not been demonstrated. By using a fluorescent indicator of reactive oxygen species (ROS), dihydrorhodamine-123 (DHR), we show that the presynaptic nerve terminal of larval motor axons is metabolically active, with more rapid accumulation of ROS in comparison with muscle cells. In Hk terminals, DHR fluorescence was greatly enhanced, indicating increased ROS levels. This observation implicates a role of the Hk β subunit in redox regulation in presynaptic terminals. This phenomenon was paralleled by the expected effects of the mutations affecting glutathione S-transferase S1 as well as applying H₂O₂ to wild-type synaptic terminals. Thus, our results also establish DHR as a useful tool for detecting ROS levels in the Drosophila neuromuscular junction.     

Therapeutic potential of new hydrogen sulfide-releasing hybrids

A new class of hydrogen sulfide (H₂S)-donating hybrids combined with pharmacologically active compounds is presented in this article. The pharmacological profiles of some hybrid lead compounds in the areas of inflammation, H₂S-donating diclofenac (ACS 15); cardiovascular, H₂S-donating aspirin (ACS 14); urology, H₂S-donating sildenafil (ACS 6); and neurodegenerative, H₂S-donating latanoprost (ACS 67) for glaucoma treatment and H₂S-donating levodopa (ACS 84) for Parkinson’s disease, are described. The new H₂S-releasing hybrids demonstrate remarkable improvement in activity and tolerability as compared with the related parent compounds, suggesting an active pharmacological role for H₂S. Finally the mechanism(s) of action of glutathione-dependent and independent, and of gas (H₂S) release (spontaneous or enzymatic) and its implications for clinical pharmacology perspectives will be also discussed.     

Hydroxocobalamin in cyanide poisoning

Introduction. On theoretical grounds, hydroxocobalamin is an attractive antidote for cyanide poisoning as cobalt compounds have the ability to bind and detoxify cyanide. This paper reviews the pharmacokinetic and pharmacodynamic aspects of hydroxocobalamin, its efficacy in human cyanide poisoning and its adverse effects. Methods. PubMed was searched for the period 1952 to April 2012. A total of 71 papers were identified in this way; and none was excluded. Pharmacokinetics and pharmacodynamics. Pharmacokinetic studies in dogs and humans suggest a two-compartment model, with first order elimination kinetics. Pharmacodynamic studies in animals suggest that hydroxocobalamin would be a satisfactory antidote for human cyanide poisoning. Efficacy in human poisoning. There is limited evidence that hydroxocobalamin alone is effective in severe poisoning by cyanide salts. The evidence for the efficacy of hydroxocobalamin in smoke inhalation is complicated by lack of evidence for the importance of cyanide exposure in fires and the effects of other chemicals as well as confounding effects of other therapeutic measures, including hyperbaric oxygen. Evidence that hydroxocobalamin is effective in poisoning due to hydrogen cyanide alone is lacking; extrapolation of efficacy from poisoning by ingested cyanide salts may not be valid. The rate of absorption may be greater with inhaled hydrogen cyanide and the recommended slow intravenous administration of hydroxocobalamin may severely limit its clinical effectiveness in these circumstances. Adverse effects. Both animal and human data suggest that hydroxocobalamin is lacking in clinically significant adverse effects. However, in one human volunteer study, delayed but prolonged rashes were observed in one-sixth of subjects, appearing 7 to 25 days after administration of 5 g or more of hydroxocobalamin. Rare adverse effects have included dyspnoea, facial oedema, and urticaria. Conclusions. Limited data on human poisonings with cyanide salts suggest that hydroxocobalamin is an effective antidote; data from smoke inhalation are less clear-cut. Although clinically important reactions to hydroxocobalamin have not been seen, some, non-life threatening, adverse reactions can occur.     

Hazards after the storm: Floodwater drainage pump stations and exposure to hydrogen sulfide

A hurricane can present unique hazards that exist long after the strong winds and heavy rains have subsided. These hazards may not only be physical, but chemical as well. Hydrogen sulfide (H₂S) represents an important and potentially overlooked hazard that can be naturally produced in floodwaters following a hurricane. In August of 2012, in the wake of Hurricane Isaac, Plaquemines Parish, Louisiana was submerged under a blanket of floodwater. To remove floodwaters that had breached the levee system designed to keep water out, temporary drainage pump stations were installed at strategic locations. The transfer of floodwaters at these drainage stations resulted in the generation of elevated concentrations of airborne H₂S at the pumping stations. The generation of H₂S at these pumping stations represented a potential inhalation hazard for workers; thus, awareness for possible H₂S exposure at these installments is crucial.     

Theoretical study of hydrogen peroxide interacting with DNA base and DNA base pair in terms of ab initio method and ABEEMσπ/MM fluctuating charge potential model

The optimized geometries, interaction energies, dipole moments, and vibrational frequencies of guanine-hydrogen peroxide (GHP), cytosine-hydrogen peroxide (CHP), adenine-hydrogen peroxide (AHP), thymine-hydrogen peroxide (THP), guanine–cytosine-hydrogen peroxide (GC-(HP)_n(n = 1–2)), and adenine–thymine-hydrogen peroxide (AT-(HP)_n(n = 1–2)) complexes are investigated by ab initio methods and ABEEMσπ/MM fluctuating charge potential model. All geometries of guanine–cytosine-hydrogen peroxide (G–C-HP) and adenine–thymine-hydrogen peroxide (A–T-HP) complexes were obtained using B3LYP/6-311++G(d,p) method, and the energies were determined at the MP2/6-311++G(2d,2p) level with BSSE corrections. The ABEEMσπ/MM model gives reasonable geometries and interaction energies compared with the present ab initio methods. For G–C-HP and A–T-HP clusters, the linear coefficient of the interaction energies all reaches 0.998, and the average absolute deviation (AAD) are 0.95 and 1.42 kcal/mol, respectively, when compared with MP2/6-311++G(2d,2p)‖B3LYP/6-311++G(d,p) method. Moreover, the variations of hydrogen bond length of guanine–cytosine and adenine–thymine base pair affected by hydrogen peroxide molecules computed by ABEEMσπ/MM model are all obtained reasonable accordance with B3LYP results. The current study will avail to understanding the physiological relevance in DNA damage.     

Malodorous volatile organic sulfur compounds: Sources,sinks and significance in inland waters

Volatile Organic Sulfur Compounds (VOSCs) are instrumental in global S-cycling and greenhouse gas production. VOSCs occur across a diversity of inland waters, and with widespread eutrophication and climate change, are increasingly linked with malodours in organic-rich waterbodies and drinking-water supplies. Compared with marine systems, the role of VOSCs in biogeochemical processes is far less well characterized for inland waters, and often involves different physicochemical and biological processes. This review provides an updated synthesis of VOSCs in inland waters, focusing on compounds known to cause malodours. We examine the major limnological and biochemical processes involved in the formation and degradation of alkylthiols, dialkylsulfides, dialkylpolysulfides, and other organosulfur compounds under different oxygen, salinity and mixing regimes, and key phototropic and heterotrophic microbial producers and degraders (bacteria, cyanobacteria, and algae) in these environs. The data show VOSC levels which vary significantly, sometimes far exceeding human odor thresholds, generated by a diversity of biota, biochemical pathways, enzymes and precursors. We also draw attention to major issues in sampling and analytical artifacts which bias and preclude comparisons among studies, and highlight significant knowledge gaps that need addressing with careful, appropriate methods to provide a more robust understanding of the potential effects of continued global development.     

Role of Aggregatibacter actinomycetemcomitans in glutathione catabolism

Introduction:  Our previous studies demonstrated that three enzymes, γ-glutamyltransferase (GGT), cysteinylglycinase (CGase) and cystalysin, are required for the catabolism of glutathione to produce hydrogen sulfide (H₂S) in Treponema denticola . In this study, we examined glutathione catabolism in Aggregatibacter actinomycetemcomitans .
Methods:  The GGT and CGase of A. actinomycetemcomitans were determined by biological methods and GGT was characterized using a molecular biological approach.
Results:  A. actinomycetemcomitans showed GGT and CGase activity, but could not produce H₂S from glutathione. The addition of recombinant T. denticola cystalysin, an l -cysteine desulfhydrase, to whole cells of A. actinomycetemcomitans resulted in the production of H₂S from glutathione. Subsequently, we cloned A. actinomycetemcomitans GGT gene ( ggt ) and overexpressed the 63 kDa GGT protein. The recombinant A. actinomycetemcomitans GGT was purified and identified. The K _cat/ K _m of the recombinant GGT from N -γ- l -glutamyl-4-nitroaniline as substrate was 31/μ m /min. The activity of GGT was optimum at pH 6.9–7.1 and enhanced by thiol-containing compounds.
Conclusion:  The results demonstrated that A. actinomycetemcomitans had GGT and CGase activities and that the GGT was characterized. The possible role of A. actinomycetemcomitans in glutathione metabolism and H₂S production from oral bacteria was discussed.     

硫化氢保护被ATP损伤的PC12细胞

目的:观察硫化氢的供体硫氢化钠(Na HS)对三磷酸腺苷(ATP)诱导的PC12细胞活力、胞内Ca2+浓度([Ca2+]i)及膜通透性的变化,探讨硫化氢神经保护作用的嘌呤信号机制。方法:将对数生长期高分化的PC12细胞,随机分为4组,分别为(1)正常对照组:常规培养,不进行ATP处理;(2)ATP组:接种细胞24 h后ATP处理;(3)Na HS+ATP组:Na HS预先孵育30 min后再用ATP处理,并且Na HS始终存在于反应体系中;(4)KN-62(P2X7受体阻断剂)+ATP组:KN-62预先孵育30 min,其余同Na HS+ATP组。MTT检测各组细胞活力,Fura-2/AM荧光染料检测各组[Ca2+]i,检测荧光染料YO-PRO-1的相对荧光单位以反映膜的通透性。结果:(1)0.3mmol/L ATP对细胞活力无影响,但1、3、5、10 mmol/L ATP则呈浓度依赖式明显降低细胞活力,200μmol/L Na HS干预可明显逆转ATP引起的细胞活力下降(P0.05),而800μmol/L Na HS预处理则加剧ATP对PC12细胞的损伤(P0.05)。(2)ATP处理PC12细胞会引起[Ca2+]i迅速升高并且呈浓度依赖性,Na HS预处理能对抗ATP引起的[Ca2+]i升高(P0.05)。(3)随着ATP浓度的增加及作用时间的延长,PC12细胞内YO-PRO-1的荧光强度显著增加,Na HS预处理可明显减少细胞对YO-PRO-1的摄取(P0.05)。结论:硫化氢可保护ATP损伤的PC12细胞,可能与其抑制[Ca2+]i升高和YO-PRO-1荧光增强有关。