Methylene blue as an antidote against hydrogen sulfide intoxication

项目总结/摘要 硫化氢（H2S）仍然是天然气和农业行业中的化学危害。很容易 这是一种使用普通化学品制造的化学品，因此对平民构成潜在威胁。也是 作为自杀的一种方法，其发病率最近在美国有所增加。 H2S通过其与各种金属蛋白（细胞色素C氧化酶）的高亲和力发挥其毒性， 其与蛋白质的半胱氨酸残基的相互作用。后者最近被证明可以改变离子通道 在心肌细胞和神经元中。事实上，在严重的硫化氢中毒期间，心肌收缩力的降低， 与昏迷有关，在几分钟甚至几秒钟内发展，导致死亡，完全电- 心脏的机械性分离如果中毒程度较轻， 曝光一停止就发生彗差。然而，在许多情况下， 沿着发展为使人衰弱的运动或认知缺陷的风险。阻碍发展的主要挑战之一 我们努力提供一种有效的治疗方法，以防止暴露后的H2S中毒， H2S几乎立即从体内消失，防止试剂捕获游离H2S（钴或铁 化合物）发挥其保护作用。 我们发现，亚甲蓝（MB）似乎克服了这一挑战：MB大大降低了 H2S中毒引起的心源性休克的立即死亡率，并改善长期神经功能 结果。甲基溴似乎可以抵消与持久性汞池有关的硫化氢中毒的后果。 蛋白质结合H2S。 我们的建议有两个目的。首先，我们打算扩展我们以前的研究结果， 在两种动物模型（大型哺乳动物-绵羊和未镇静大鼠）中， 根据动物规则，在更接近人类中毒的条件下（吸入H2S），这是一个基本前提。 将在两种不同剂量下确定MB对短期和长期结局的影响 中毒结束后30分钟内。第二，我们将继续探索 使用分离的收缩心肌细胞的MB（由Temple的Joseph Cheung博士的小组进行的研究 大学）和大鼠急性脑切片的皮质神经元（由布雷迪博士的小组进行的研究 Maher，约翰霍普金斯大学利伯大脑发育研究所）。 由于MB已被用于治疗人类高铁血红蛋白血症（1-2 mg/kg iv）数十年，我们的研究表明， 最终目标是重新定位亚甲蓝，一种已经在世界卫生组织基本药物清单上的药物， H2S中毒的关键治疗。

PROJECT SUMMARY/ABSTRACT Hydrogen sulfide (H2S) remains a chemical hazard in the gas and farming industry. It is easy to manufacture from common chemicals and thus represents a potential threat for the civilian population. It is also employed as a method of suicide, for which incidence has recently increased in the US. H2S exerts its toxicity through its high affinity with various metallo-proteins (cytochrome C oxidase) and its interactions with the cysteine residues of proteins. The latter has been recently shown to alter ion channels in cardiomyocytes and neurons. Indeed, during severe H2S intoxication, a reduction in cardiac contractility, associated with a coma, develops within minutes or even seconds leading to death by complete electro- mechanical dissociation of the heart. If the level of intoxication is milder, a rapid and spontaneous recovery of the coma occurs as soon as the exposure stops. However, in many instances, a cardiogenic shock will persist along with a risk of developing debilitating motor or cognitive deficits. One of the major challenges impeding our effort to offer an effective treatment against H2S intoxication after exposure is that the pool of free/soluble H2S almost immediately disappears from the body, preventing agents trapping free H2S (cobalt or ferric compounds) to play their protective role. We found that methylene blue (MB) appears to overcome this challenge: MB drastically decreases the immediate mortality of H2S intoxication-induced cardiogenic shock and improves the long-term neurological outcome. MB appears to counteract the consequences of H2S intoxication related to the persistent pool of protein-bound H2S. The objective of our proposal is twofold. First, we intend to extend our previous findings on the efficacy of MB against H2S intoxication in two animal models (a large mammal -sheep- and unsedated rats), an essential prerequisite under the Animal Rule, in conditions (inhaled H2S) more faithful to human intoxication. The effects of MB on the short and long term outcomes will be established at two different doses administered up to 30 minutes after the end of intoxication. Second, we will continue to explore the mechanisms of action of MB using isolated contracting cardiomyocytes (studies performed by the group of Dr. Joseph Cheung, Temple University), and cortical neurons from acute brain slices in rats (studies performed by the group of Dr. Brady Maher, Lieber Institute for Brain Development, Johns Hopkins University). Since MB has been used for decades for treating methemoglobinemia (1-2 mg/kg iv) in humans, our ultimate goal is to reposition methylene blue, a drug already on the WHO's list of essential medications, as a key treatment of H2S intoxication.