Rajaraman Ganesh, Chen Jie, Chang Thomas K H
Faculty of Pharmaceutical Sciences, The University of British Columbia, 2146 East Mall, Vancouver, British Columbia, Canada V6T 1Z3.
Toxicol Appl Pharmacol. 2006 Dec 1;217(2):225-33. doi: 10.1016/j.taap.2006.09.005. Epub 2006 Sep 12.
The present cell culture study investigated the effect of Ginkgo biloba extract pretreatment on acetaminophen toxicity and assessed the role of ginkgolide A and cytochrome P450 3A (CYP3A) in hepatocytes isolated from adult male Long-Evans rats provided ad libitum with a standard diet. Acetaminophen (7.5-25 mM for 24 h) conferred hepatocyte toxicity, as determined by the lactate dehydrogenase (LDH) assay. G. biloba extract alone increased LDH leakage in hepatocytes at concentrations > or =75 mug/ml and > or =750 mug/ml after a 72 h and 24 h treatment period, respectively. G. biloba extract (25 or 50 mug/ml once every 24 h for 72 h) potentiated LDH leakage by acetaminophen (10 mM for 24 h; added at 48 h after initiation of extract pretreatment). The effect was confirmed by a decrease in [(14)C]-leucine incorporation. At the level present in a modulating concentration (50 mug/ml) of the extract, ginkgolide A (0.55 mug/ml), which increased CYP3A23 mRNA levels and CYP3A-mediated enzyme activity, accounted for part but not all of the potentiating effect of the extract on acetaminophen toxicity. This occurred as a result of CYP3A induction by ginkgolide A because triacetyloleandomycin (TAO), a specific inhibitor of CYP3A catalytic activity, completely blocked the effect of ginkgolide A. Ginkgolide B, ginkgolide C, ginkgolide J, quercetin, kaempferol, isorhamnetin, and isorhamnetin-3-O-rutinoside did not alter the extent of LDH leakage by acetaminophen. In summary, G. biloba pretreatment potentiated acetaminophen toxicity in cultured rat hepatocytes and ginkgolide A contributed to this novel effect of the extract by inducing CYP3A.
本细胞培养研究调查了银杏叶提取物预处理对乙酰氨基酚毒性的影响，并评估了银杏内酯A和细胞色素P450 3A（CYP3A）在从成年雄性Long-Evans大鼠分离的肝细胞中的作用，这些大鼠自由采食标准饮食。通过乳酸脱氢酶（LDH）测定法确定，乙酰氨基酚（7.5 - 25 mM，处理24小时）会导致肝细胞毒性。单独的银杏叶提取物在分别处理72小时和24小时后，浓度≥75μg/ml和≥750μg/ml时会增加肝细胞中LDH的泄漏。银杏叶提取物（25或50μg/ml，每24小时一次，共72小时）增强了乙酰氨基酚（10 mM，处理24小时；在提取物预处理开始后48小时添加）导致的LDH泄漏。[(14)C]-亮氨酸掺入量的减少证实了这一效应。在提取物的调节浓度（50μg/ml）下，增加CYP3A23 mRNA水平和CYP3A介导的酶活性的银杏内酯A（0.55μg/ml），部分但并非全部解释了提取物对乙酰氨基酚毒性的增强作用。这是由于银杏内酯A诱导CYP3A所致，因为CYP3A催化活性的特异性抑制剂三乙酰竹桃霉素（TAO）完全阻断了银杏内酯A的作用。银杏内酯B、银杏内酯C、银杏内酯J、槲皮素、山奈酚、异鼠李素和异鼠李素-3-O-芸香糖苷不会改变乙酰氨基酚引起的LDH泄漏程度。总之，银杏叶预处理增强了培养的大鼠肝细胞中乙酰氨基酚的毒性，并且银杏内酯A通过诱导CYP3A促成了提取物的这一新颖效应。
