Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana 47907-1333, USA.
Toxicol Sci. 2010 Jun;115(2):569-76. doi: 10.1093/toxsci/kfq084. Epub 2010 Mar 24.
Cyanide inhibits aerobic metabolism by binding to the binuclear heme center of cytochrome c oxidase (CcOX). Amyl nitrite and sodium nitrite (NaNO(2)) antagonize cyanide toxicity in part by oxidizing hemoglobin to methemoglobin (mHb), which then scavenges cyanide. mHb generation is thought to be a primary mechanism by which the NO(2)(-) ion antagonizes cyanide. On the other hand, NO(2)(-) can undergo biotransformation to generate nitric oxide (NO), which may then directly antagonize cyanide inhibition of CcOX. In this study, nitrite-mediated antagonism of cyanide inhibition of oxidative phosphorylation was examined in rat dopaminergic N27 cells. NaNO(2) produced a time- and concentration-dependent increase in whole-cell and mitochondrial levels of NO. The NO scavenger 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxy 3-oxide (PTIO) reversed this increase in cellular and mitochondrial NO. NO generated from NaNO(2) decreased cellular oxygen consumption and inhibited CcOX activity. PTIO reversed the NO-mediated inhibition, thus providing strong evidence that NO mediates the action of NaNO(2). Under similar conditions, KCN (20muM) inhibited cellular state-3 oxygen consumption and CcOX activity. Pretreatment with NaNO(2) reversed KCN-mediated inhibition of both oxygen consumption and CcOX activity. The NaNO(2) antagonism of cyanide was blocked by pretreatment with the NO scavenger PTIO. It was concluded that NaNO(2) antagonizes cyanide inhibition of CcOX by generating of NO, which then interacts directly with the binding of KCN x CcOX to reverse the toxicity. In vivo antagonism of cyanide by NO(2)(-) appears to be due to both generation of mHb and direct displacement of cyanide from CcOX by NO.
氰化物通过与细胞色素 c 氧化酶（CcOX）的双核血红素中心结合来抑制有氧代谢。亚硝酸戊酯和亚硝酸钠（NaNO₂）通过将血红蛋白氧化为高铁血红蛋白（mHb）来部分拮抗氰化物的毒性，mHb 然后清除氰化物。mHb 的产生被认为是 NO₂⁻离子拮抗氰化物的主要机制。另一方面，NO₂⁻可以进行生物转化生成一氧化氮（NO），然后可能直接拮抗 CcOX 对氰化物的抑制作用。在这项研究中，研究了亚硝酸盐介导的对大鼠多巴胺能 N27 细胞中氰化物抑制氧化磷酸化的拮抗作用。NaNO₂产生了时间和浓度依赖性的全细胞和线粒体中 NO 水平的增加。NO 清除剂 2-苯-4,4,5,5-四甲基咪唑啉-1-氧基 3-氧化物（PTIO）逆转了细胞和线粒体中 NO 的增加。NaNO₂产生的 NO 降低了细胞耗氧量并抑制了 CcOX 活性。PTIO 逆转了 NO 介导的抑制作用，从而提供了强有力的证据表明 NO 介导了 NaNO₂的作用。在相似的条件下，20μM 的 KCN 抑制了细胞状态 3 的耗氧量和 CcOX 活性。用 NaNO₂预处理可逆转 KCN 对耗氧量和 CcOX 活性的抑制作用。NaNO₂对氰化物的拮抗作用被 NO 清除剂 PTIO 阻断。因此得出结论，NaNO₂通过生成 NO 来拮抗 CcOX 对氰化物的抑制作用，然后与 KCN x CcOX 的结合直接相互作用以逆转毒性。NO₂⁻在体内对氰化物的拮抗作用似乎是由于 mHb 的产生和 NO 直接从 CcOX 中取代氰化物所致。
