NITRIC OXIDE AND THE METABOLISM OF TOXIC CHEMICALS AND DRUGS

工作总结：人们普遍认为，CCl4的肝脏毒性 CCl4代谢为三氯甲基自由基的结果 细胞色素P-450。这种自由基和相关的活性物种 通过启动脂质过氧化和共价引起细胞损伤 与蛋白质结合，最终导致细胞死亡。早期研究 据报道，亚致死剂量的CCl4处理的兔子是 比正常兔更容易受到细菌的致死作用 内毒素。从肠道吸收的内毒素参与了 其与腹膜和脾巨噬细胞相互作用的肝毒性 和库普弗细胞。当这些细胞受到刺激时，会产生反应性 介质，包括氧自由基，肿瘤坏死因子- α(肿瘤坏死因子-α)、白三烯和一氧化氮(NO)，从而导致 细胞损伤。因此，这是合理的，没有发挥重要的作用 在毒物所致肝坏死中的作用。体内一氧化氮的产生 而它在暴露于肝脏毒物的实验动物中的作用并没有 在这项工作之前就已经演示过了。NO在体内被检测为亚铁 血红蛋白亚硝基复合体、P450-NO、HbNO等和铁-硫 来源不明的二亚硝基络合物。NO络合作用抑制P450和 NO刺激鸟苷环化酶，但总体上不应导致 造成不可逆转的损害。相反，蛋白质硝基酪氨酸的形成 内容已成为检测的常用技术 不可逆的一氧化氮依赖的氧化组织损伤。形成 硝基酪氨酸通常被解释为体内过氧亚硝酸根的证据 队形。我们发现了一种依赖酪氨酸的自由基， 生成硝基酪氨酸的不依赖过氧亚硝酸盐的路线。

Summary of Work: It is widely accepted that the hepatotoxicity of CCl4 results from the metabolism of CCl4 to the trichloromethyl free radical by cytochrome P-450. This free radical and related reactive species cause cellular damage by initiating lipid peroxidation and covalently binding to protein, ultimately leading to cell death. Earlier studies reported that sublethally CCl4-treated rabbits were 120 times more susceptible than normal rabbits to the lethal effect of bacterial endotoxin. Endotoxin absorbed from the gut becomes involved in hepatotoxicity by its interaction with peritoneal and splenic macrophages and Kupffer cells. These cells, when stimulated, produce reactive mediators, including oxygen-derived free radicals, tumor necrosis factor- alpha (TNF-alpha), leukotrienes, and nitric oxide (NO), thereby causing cellular damage. Therefore it is plausible that NO plays an important role during hepatic necrosis caused by toxicants. In vivo NO production and its role in experimental animals exposed to hepatotoxicants had not been demonstrated before this work. NO is detected in vivo as ferrous hemoproteins nitrosyl complexes, P450-NO, HbNO, etc. and as iron-sulfur dinitrosyl complexes of unknown origin. NO complexation inhibits P450 and NO stimulates guanylate cyclase, but in general is not thoought to lead to irreversible damage. In contrast, protein nitrotyrosine formation content has become a frequently used technique for the detection of irreversible NO-dependent oxidative tissue damage. Formation of nitrotyrosine is usually interpreted as proof of in vivo peroxynitrite formation. We have discovered a tyrosyl radical-dependent, peroxynitrite-independent route to nitrotyrosine formation.