Crystalline hydroxocobalamin and methemoglobin as a treatment of H2S intoxication

描述(申请人提供)：硫化氢(H_2S)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“直接危及生命的化学危险”。我们最近开发了一种范例，基于使用晶体形式的低剂量高铁血红蛋白(作为铁铁的来源)和高剂量的维生素B12(作为氧化钴的来源)，非常迅速地减少大鼠血液和组织中的硫化氢。这两种制剂都是安全的(大剂量的维生素B12已经被FDA批准用于氰化物中毒)，可以作为药盒储存，以粉末的形式储存，并且在接触硫化氢后很容易给人服用。该项目的目标是验证高铁血红蛋白或维生素B12溶液在接触硫化氢后可用作解毒剂的假设。在硫化氢中毒中给予维生素B12的剂量比氰化物中毒的剂量低10倍，这使得通过肌肉或鼻腔给药来传递这种药物成为可能。由于我们已经证明，在小型动物(啮齿动物)中，硫化氢会产生一种在大型哺乳动物中没有的特定保护性反应，因此我们打算在成年绵羊中进行研究。在这项建议中，我们将确定这些解毒剂在注入致死浓度的硫化氢后，降低成年绵羊血液和脑脊液中硫化氢及其氧化产物浓度的能力。脑脊液将被用作延髓神经元暴露的一个方便的标记，对硫化氢的毒性效应非常敏感。同时，我们将评估呼吸和心血管控制系统的变化。硫化氢中毒将通过静脉输液产生，由硫化氢供体NaHS的溶液制备，以防止与气态硫化氢暴露有关的对实验室人员的任何风险。一旦发生呼吸暂停，硫化氢输注将立即停止，此时，本申请中提出的终点将在对照组和高铁血红蛋白或维生素B12治疗的动物中进行评估，在停止硫化氢输注后1分钟或20分钟。最后，我们将在鼻腔或肌肉注射维生素B12后，测定血液中维生素B12的浓度以及血浆氧化外源性硫化氢的能力。这些拟议研究的结果将有助于确定正确的使用策略和这些解毒剂各自的好处。鼻腔或肌肉注射维生素B12代表了一种有趣的替代静脉输液的方法，非专业救援人员可以对大量患者实施这种方法。

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.