Crystalline hydroxocobalamin and methemoglobin as a treatment of H2S intoxication

描述（由申请人提供）：硫化氢（H2S）是一种致命气体，被国土安全部视为潜在的化学威胁，被疾病控制中心视为“对生命有直接危险的化学危害”。我们最近开发了一种范例，通过使用低剂量高铁血红蛋白（作为铁的来源）和高剂量维生素B12（作为氧化钴的来源）的结晶形式，可以非常迅速地减少大鼠血液和组织中的H2S。这两种药物都是安全的（高剂量的维生素B12已经被FDA批准用于氰化物中毒），可以作为试剂盒储存，以粉末形式储存，并且可以很容易地在H2S暴露后给人服用。本项目的目的是验证高铁血红蛋白或维生素B12溶液可以作为H2S暴露后的解毒剂的假设。在H2S中毒中，以比氰化物中毒低10倍的剂量给药维生素B12的可能性使得通过肌肉注射或鼻内给药这种药物成为可能。由于我们已经证明H2S在小动物（啮齿动物）中产生特定的保护反应，而在大型哺乳动物中没有发现，我们打算在成年绵羊中进行我们的研究。在这项提议中，我们将确定这些解毒剂在输注致死浓度的H2S后降低成年羊血液和脑脊液中H2S及其氧化产物浓度的能力。脑脊液将被用作髓质神经元暴露的方便标记，髓质神经元对H2S的毒性作用非常敏感。同时，我们将评估呼吸和心血管控制系统的变化。H2S中毒将通过静脉输注产生，由H2S供体NaHS溶液配制，以防止与气态H2S暴露有关的实验室人员的任何风险。一旦出现呼吸暂停，应立即停止H2S输注，此时将在对照组和在停止H2S输注1分钟或20分钟后使用高铁血红蛋白或维生素B12治疗的动物中评估本申请中提出的终点。最后，我们将测定维生素B12的血药浓度和血浆氧化外源性H2S的能力，在鼻内或肌肉内给予维生素B12。这些拟议研究的结果将有助于确定这些解毒剂的适当使用策略和各自的益处。鼻内或肌肉内给药维生素B12是静脉输注的一种有趣的替代方法，可以由非专业救援人员对大量患者实施。

DESCRIPTION (provided by applicant): Hydrogen sulfide (H2S) is a lethal gas regarded as a potential chemical threat by the Department of Homeland Security and a "chemical hazard immediately dangerous to life" by the Centers for Disease Control. We have recently developed a paradigm to decrease H2S very rapidly in the blood and tissues of rats based on the use of the crystalline form of low dose of methemoglobin (as a source of ferric Iron) and high dose of Vitamin B12 (as a source of oxidized Cobalt). Both agents are safe (high dose of Vitamin B12 is already FDA approved for cyanide poisoning), can be stored as a kit, in a powder form, and can easily be administered to humans following H2S exposure. The goal of this project is to test the hypothesis that solutions of methemoglobin or Vitamin B12 can be used as antidotes following H2S exposure. The possibility of administering Vitamin B12 in H2S intoxication at a dose 10 times lower than the dose used for cyanide intoxication makes it possible to deliver this agent using intramuscular or intranasal administration. Since we have demonstrated that H2S produces in small animals (rodents) a specific protective response, not found in larger mammals, we intend to conduct our studies in adult sheep. In this proposal, we will determine the ability of these antidotes to lower the concentration of H2S, and its oxidative products, in th blood and the cerebrospinal fluid of adult sheep following infusion of lethal concentrations of H2S. The cerebrospinal fluid will be used as a convenient marker of the exposure of the medullary neurons, exquisitely sensitive to the toxic effects of H2S. At the same time, we will assess the alterations of the respiratory and cardiovascular control systems. H2S intoxication will be generated by intravenous infusion, prepared from a solution of NaHS, a H2S donor, to prevent any risk to the laboratory personnel related to gaseous H2S exposure. H2S infusion will be stopped as soon as an apnea occurs and at this time the end-points proposed in this application will be evaluated in controls and in animals treated with either methemoglobin or Vitamin B12 given one or 20 minutes following the cessation of H2S infusion. Finally, we will determine the blood concentration of Vitamin B12 and the ability of the plasma to oxidize exogenous H2S, following intranasal or intramuscular administration of Vitamin B12. The results of these proposed studies will help determine the proper strategy of use and the respective benefits of these antidotes. Intranasal or intramuscular administration of Vitamin B12 represents an interesting alternative to intravenous infusion that could be implemented by non-professional rescuers to a large number of patients.