Henderson C J, Wolf C R, Kitteringham N, Powell H, Otto D, Park B K
Imperial Cancer Research Fund Molecular Pharmacology Unit, Biomedical Research Centre, Level 5, Ninewells Hospital and Medical School, Dundee, DD1 9SY, United Kingdom.
Proc Natl Acad Sci U S A. 2000 Nov 7;97(23):12741-5. doi: 10.1073/pnas.220176997.
Overdose of acetaminophen, a widely used analgesic drug, can result in severe hepatotoxicity and is often fatal. This toxic reaction is associated with metabolic activation by the P450 system to form a quinoneimine metabolite, N-acetyl-p-benzoquinoneimine (NAPQI), which covalently binds to proteins and other macromolecules to cause cellular damage. At low doses, NAPQI is efficiently detoxified, principally by conjugation with glutathione, a reaction catalyzed in part by the glutathione S-transferases (GST), such as GST Pi. To assess the role of GST in acetaminophen hepatotoxicity, we examined acetaminophen metabolism and liver damage in mice nulled for GstP (GstP1/P2((-/-))). Contrary to our expectations, instead of being more sensitive, GstP null mice were highly resistant to the hepatotoxic effects of this compound. No significant differences between wild-type (GstP1/P2((+/+))) mice and GstP1/P2((-/-)) nulls in either the rate or route of metabolism, particularly to glutathione conjugates, or in the levels of covalent binding of acetaminophen-reactive metabolites to cellular protein were observed. However, although a similar rapid depletion of hepatic reduced glutathione (GSH) was found in both GstP1/P2((+/+)) and GstP1/P2((-/-)) mice, GSH levels only recovered in the GstP1/P2((-/-)) mice. These data demonstrate that GstP does not contribute in vivo to the formation of glutathione conjugates of acetaminophen but plays a novel and unexpected role in the toxicity of this compound. This study identifies new ways in which GST can modulate cellular sensitivity to toxic effects and suggests that the level of GST Pi may be an important and contributing factor in the sensitivity of patients with acetaminophen-induced hepatotoxicity.
对乙酰氨基酚是一种广泛使用的镇痛药，过量服用会导致严重的肝毒性，且往往是致命的。这种毒性反应与细胞色素P450系统的代谢活化有关，会形成一种醌亚胺代谢物，即N - 乙酰 - 对苯醌亚胺（NAPQI），它会与蛋白质和其他大分子共价结合，从而导致细胞损伤。在低剂量时，NAPQI主要通过与谷胱甘肽结合而被有效解毒，这一反应部分由谷胱甘肽S - 转移酶（GST）催化，如GST Pi。为了评估GST在对乙酰氨基酚肝毒性中的作用，我们检测了GstP基因缺失（GstP1/P2(-/-)）小鼠的对乙酰氨基酚代谢和肝损伤情况。与我们的预期相反，GstP基因缺失小鼠非但没有更敏感，反而对该化合物的肝毒性具有高度抗性。在野生型（GstP1/P2(+/+)）小鼠和GstP1/P2(-/-)基因缺失小鼠之间，无论是代谢速率还是代谢途径，特别是与谷胱甘肽结合物的代谢，或者对乙酰氨基酚反应性代谢物与细胞蛋白的共价结合水平，均未观察到显著差异。然而，尽管在GstP1/P2(+/+)和GstP1/P2(-/-)小鼠中均发现肝脏还原型谷胱甘肽（GSH）有类似的快速消耗，但只有GstP1/P2(-/-)小鼠的GSH水平得以恢复。这些数据表明，GstP在体内对乙酰氨基酚谷胱甘肽结合物的形成并无贡献，但在该化合物的毒性方面发挥了一种新的、意想不到的作用。这项研究确定了GST调节细胞对毒性作用敏感性的新方式，并表明GST Pi的水平可能是对乙酰氨基酚诱导的肝毒性患者敏感性的一个重要影响因素。
