Harman A W, Kyle M E, Serroni A, Farber J L
Department of Pathology, Thomas Jefferson University, Philadelphia, PA 19107.
Biochem Pharmacol. 1991 Apr 15;41(8):1111-7. doi: 10.1016/0006-2952(91)90648-o.
The killing of isolated hepatocytes by N-acetyl-p-benzoquinone imine (NAPQI), the major metabolite of the oxidation of the hepatotoxin acetaminophen, has been studied previously as a model of liver cell injury by the parent compound. Such studies assume that the toxicity of acetaminophen is mediated by NAPQI and that treatment with exogenous NAPQI reproduces the action of the endogenously produced product. The present study tested these assumptions by comparing under identical conditions the toxicity of acetaminophen and NAPQI. The killing of hepatocytes by acetaminophen was mediated by oxidative injury. Thus, it depended on a cellular source of ferric iron; was potentiated by 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), an inhibitor of glutathione reductase; and was sensitive to antioxidants. By contrast, the cytotoxicity of NAPQI was not prevented by chelation of ferric iron; was unaffected by BCNU; and was insensitive to antioxidants. Thus, the killing of cultured hepatocytes by NAPQI occurs by a mechanism different from that of acetaminophen. The killing by NAPQI was preceded by a collapse of the mitochondrial membrane potential and a depletion of ATP. Monensin potentiated the cell killing, and extracellular acidosis prevented it. These manipulations are characteristic of the toxicity of mitochondrial poisons, and are without effect on the depletion of ATP and the loss of mitochondrial energization. Thus, mitochondrial de-energization by a mechanism unrelated to oxidative stress is a likely basis of the cell killing by NAPQI. It is concluded that treatment of cultured hepatocytes with NAPQI does not model the cytotoxicity of acetaminophen in these cells.
对乙酰氨基酚是一种肝毒素，其氧化代谢产生的主要代谢产物N - 乙酰 - 对苯醌亚胺（NAPQI）对分离的肝细胞的杀伤作用，先前已作为母体化合物导致肝细胞损伤的模型进行了研究。此类研究假定对乙酰氨基酚的毒性是由NAPQI介导的，并且用外源性NAPQI进行处理可重现内源性产生产物的作用。本研究通过在相同条件下比较对乙酰氨基酚和NAPQI的毒性来检验这些假设。对乙酰氨基酚对肝细胞的杀伤作用是由氧化损伤介导的。因此，它依赖于三价铁的细胞来源；被谷胱甘肽还原酶抑制剂1,3 - 双（2 - 氯乙基）-1 - 亚硝基脲（BCNU）增强；并且对抗氧化剂敏感。相比之下，三价铁螯合并不能阻止NAPQI的细胞毒性；它不受BCNU影响；并且对抗氧化剂不敏感。因此，NAPQI对培养肝细胞的杀伤作用是通过一种不同于对乙酰氨基酚的机制发生的。NAPQI导致的细胞杀伤之前有线粒体膜电位的崩溃和ATP的消耗。莫能菌素增强细胞杀伤作用，而细胞外酸中毒则可阻止这种作用。这些操作是线粒体毒物毒性的特征，并且对ATP的消耗和线粒体能量化的丧失没有影响。因此，通过与氧化应激无关的机制使线粒体去能化可能是NAPQI导致细胞杀伤的一个基础。得出的结论是，用NAPQI处理培养的肝细胞并不能模拟对乙酰氨基酚在这些细胞中的细胞毒性。
