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“立即危及生命的化学危害”。我们最近开发了一种范例，基于使用低剂量高铁血红蛋白（作为三价铁的来源）和高剂量维生素B12（作为氧化钴的来源）的结晶形式，快速降低大鼠血液和组织中的H2S。这两种药剂都是安全的（高剂量的维生素B12已经被FDA批准用于氰化物中毒），可以作为试剂盒以粉末形式储存，并且可以在H2S暴露后容易地给予人类。本项目的目标是检验高铁血红蛋白或维生素B12溶液可用作H2S暴露后解毒剂的假设。在H2S中毒中以比氰化物中毒所用剂量低10倍的剂量施用维生素B12的可能性使得可以使用肌内或鼻内施用来递送该药剂。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未发现，因此我们打算在成年绵羊中进行研究。在这个建议中，我们将确定这些解毒剂的能力，以降低浓度的H2S，其氧化产物，在th血液和成年羊的脑脊液后，致命浓度的H2S输注。脑脊液将被用作一个方便的标记物的暴露的髓神经元，精致敏感的H2S的毒性作用。同时，我们将评估呼吸和心血管控制系统的变化。将通过静脉输注产生H2S中毒，由NaHS（H2S供体）溶液制备，以防止实验室人员暴露于气态H2S相关的任何风险。一旦发生呼吸暂停，将立即停止H2S输注，此时，将在对照组和H2S输注停止后1分钟或20分钟给予高铁血红蛋白或维生素B12的动物中评价本申请中提出的终点。最后，我们将确定维生素B12的血液浓度和血浆氧化外源性H2S的能力，鼻内或肌肉注射维生素B12后。这些拟议研究的结果将有助于确定适当的使用策略和这些解毒剂的各自益处。维生素B12的鼻内或肌内给药是静脉输注的一种有趣的替代方案，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.