Wadsworth Center, New York State Department of Health, Empire State Plaza, Box 509, Albany, NY 12201-0509, USA.
J Pharmacol Exp Ther. 2012 Nov;343(2):362-70. doi: 10.1124/jpet.112.198077. Epub 2012 Aug 14.
The aim of this study was to determine the role of small intestinal (SI) cytochrome P450 (P450) enzymes in the metabolic activation of diclofenac (DCF), a widely used nonsteroidal anti-inflammatory drug, and DCF-induced intestinal toxicity. DCF induces intestinal ulcers in humans and mice, but the underlying mechanisms, including the necessity for drug bioactivation in the target tissues and the sources and identities of reactive intermediates, are not fully understood. We found that the number of DCF-induced (at 50 mg/kg p.o.) intestinal ulcers was significantly smaller in an intestinal epithelium (IE)-specific P450 reductase (CPR) knockout (IE-Cpr-null) mouse model, which has little P450 activity in the IE, than in wild-type (WT) mice, determined at 14 h after DCF administration. The involvement of intestinal P450 enzymes was confirmed by large reductions (>80-90%) in the rates of in vitro formation, in SI microsomal reactions, of hydroxylated DCF metabolites and reactive intermediates, trapped as DCF-glutathione (GSH) conjugates, in the IE-Cpr-null, compared with WT mice. The SI levels of DCF-GSH conjugates (at 4 h after dosing) and DCF-protein adducts (at 14 h after dosing) were significantly lower in IE-Cpr-null than in WT mice. In additional experiments, we found that pretreatment of mice with grapefruit juice, which is known to inhibit SI P450 activity, ameliorated DCF-induced intestinal toxicity in WT mice. Our results not only strongly support the notion that SI P450 enzymes play an important role in DCF-induced intestinal toxicity, but also illustrate the possibility of preventing DCF-induced intestinal toxicity through dietary intervention.
本研究旨在确定小肠（SI）细胞色素 P450（P450）酶在代谢激活二氯芬酸（DCF）和 DCF 诱导的肠道毒性中的作用。DCF 会在人类和小鼠中引起肠道溃疡，但潜在机制，包括在靶组织中药物生物激活的必要性、反应性中间产物的来源和身份等，尚未完全阐明。我们发现，在肠道上皮细胞（IE）特异性细胞色素 P450 还原酶（CPR）敲除（IE-Cpr-null）小鼠模型中，与野生型（WT）小鼠相比，经口给予 50mg/kg DCF 后 14 小时，DCF 诱导的（50mg/kg 经口给予）肠道溃疡数量明显减少。这一结果证实了肠道 P450 酶的参与，因为在 IE-Cpr-null 小鼠中，SI 微粒体反应中 DCF 代谢物和反应性中间产物的羟基化产物形成速度（以 DCF-GSH 缀合物的形式捕获），与 WT 小鼠相比，降低了>80-90%。与 WT 小鼠相比，IE-Cpr-null 小鼠的 SI 水平的 DCF-GSH 缀合物（给予药物后 4 小时）和 DCF 蛋白加合物（给予药物后 14 小时）明显降低。在额外的实验中，我们发现，众所周知抑制 SI P450 活性的葡萄柚汁预处理可改善 WT 小鼠的 DCF 诱导的肠道毒性。我们的结果不仅强烈支持了 SI P450 酶在 DCF 诱导的肠道毒性中起重要作用的观点，而且还说明了通过饮食干预预防 DCF 诱导的肠道毒性的可能性。
