Methylene blue as an antidote against hydrogen sulfide intoxication

项目摘要/摘要 硫化氢(H2S)仍然是天然气和农业中的一种化学危险。这是很容易的 使用普通化学品进行生产，因此对平民人口构成潜在威胁。它也是 被用作自杀方式，其在美国的发生率最近有所上升。 硫化氢通过与多种金属蛋白(细胞色素C氧化酶)的高亲和力而发挥其毒性作用。 它与蛋白质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，心脏收缩能力下降， 与昏迷有关，在几分钟甚至几秒钟内发展，通过完全的电击导致死亡 心脏机械性分离。如果中毒程度较轻，则会迅速和自发地恢复 一旦暴露停止，昏迷就会发生。然而，在许多情况下，心源性休克将持续存在。 同时有发展成衰弱的运动或认知缺陷的风险。阻碍经济发展的主要挑战之一 我们努力为暴露后的硫化氢中毒提供有效的治疗方法是游离/可溶性的池 硫化氢几乎立即从体内消失，阻止试剂捕获游离的硫化氢(钴或铁 化合物)来发挥它们的保护作用。 我们发现亚甲基蓝(MB)似乎克服了这一挑战：亚甲基蓝显著降低了 硫化氢中毒性心源性休克的即刻死亡率及远期神经功能改善 结果。甲基溴似乎抵消了硫化氢中毒的后果，这些后果与持续的 蛋白质结合的硫化氢。 我们建议的目标有两个。首先，我们打算扩展我们之前关于疗效的发现。 在两种动物模型(大型哺乳动物-绵羊和未服用镇静剂的大鼠)中观察MB对H_2S中毒的保护作用 在动物法则下的基本先决条件，在条件(吸入硫化氢)下更忠于人类的醉酒。 甲基溴对短期和长期结果的影响将以两种不同的剂量进行确定 醉酒结束后最多30分钟。第二，我们将继续探索其作用机制。 MB使用分离的收缩心肌细胞(由张约瑟博士小组进行的研究 大学)，以及来自大鼠急性脑片的皮质神经元(由Brady博士小组进行的研究 约翰斯·霍普金斯大学利伯脑发育研究所的马赫)。 由于MB已被用于治疗人类高铁血红蛋白血症(1-2毫克/公斤静脉注射)已有数十年，我们的 最终目标是将亚甲基蓝，一种已经在世卫组织基本药物清单上的药物重新定位为 硫化氢中毒的关键救治。

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.