Division of Pulmonary and Critical Care Medicine, Department of Medicine.
Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, Pennsylvania.
Toxicol Sci. 2019 Jul 1;170(1):82-94. doi: 10.1093/toxsci/kfz081.
Our study was aimed at (1) determining the efficacy of the dye methylene blue (MB), following a rapidly lethal cyanide (CN) intoxication in un-sedated rats; (2) clarifying some of the mechanisms responsible for the antidotal properties produced by this potent cyclic redox dye. Sixty-nine awake rats acutely intoxicated by CN (IP, KCN 7 mg/kg) received saline, MB (20 mg/kg) or hydroxocobalamin (HyCo, 150 mg/kg) when in deep coma. Survival in this model was very low, reaching 9% at 60 min without any treatment. Methylene blue significantly increased survival (59%, p < .001) at 60 min, versus 37% with HyCo (p < .01). In addition, 8 urethane-anesthetized rats were exposed to a sublethal CN intoxication (KCN, 0.75 mg/kg/min IV for 4 min); they received MB (20 mg/kg, IV) or saline, 5 min after the end of CN exposure. All MB-treated rats displayed a significant reduction in hyperlactacidemia, a restoration of pyruvate/lactate ratio-a marker of NAD/NADH ratio-and an increase in CO2 production, a marker of the activity of the TCA cycle. These changes were also associated with a 2-fold increase in the pool of CN in red cells. Based on series of in vitro experiments, looking at the effects of MB on NADH, as well as the redox effects of MB on hemoglobin and cytochrome c, we hypothesize that the antidotal properties of MB can in large part be accounted for by its ability to readily restore NAD/NADH ratio and to cyclically re-oxidize then reduce the iron in hemoglobin and the electron chain complexes. All of these effects can account for the rapid antidotal properties of this dye following CN poisoning.
（1）确定亚甲蓝（MB）在未镇静的大鼠中迅速致命氰化物（CN）中毒后的疗效；（2）阐明这种有效的环状氧化还原染料产生解毒特性的一些机制。69 只急性 CN（IP，KCN 7mg/kg）中毒的清醒大鼠在深度昏迷时接受生理盐水、MB（20mg/kg）或羟钴胺素（HyCo，150mg/kg）治疗。在没有任何治疗的情况下，该模型的存活率非常低，60 分钟时达到 9%。与 HyCo（p<.01）相比，MB 显著增加了 60 分钟时的存活率（59%，p<.001）。此外，8 只使用氨基甲酸乙酯麻醉的大鼠暴露于亚致死性 CN 中毒（KCN，0.75mg/kg/min IV 持续 4 分钟）；它们在 CN 暴露结束后 5 分钟接受 MB（20mg/kg，IV）或生理盐水治疗。所有接受 MB 治疗的大鼠均表现出明显的高乳酸血症降低，丙酮酸/乳酸比值恢复（NAD/NADH 比值的标志物），以及三羧酸循环活性的 CO2 产生增加。这些变化也与 RBC 中 CN 池增加了 2 倍有关。基于一系列体外实验，研究 MB 对 NADH 的影响，以及 MB 对血红蛋白和细胞色素 c 的氧化还原作用，我们假设 MB 的解毒特性在很大程度上可以归因于其能够快速恢复 NAD/NADH 比值，并循环重新氧化和还原血红蛋白和电子链复合物中的铁。所有这些效应都可以解释 MB 对 CN 中毒的快速解毒特性。
