Deacetylclivorine: A gender-selective metabolite of clivorine formed in female Sprague-Dawley rat liver microsomes
Deacetylclivorine: A gender-selective metabolite of clivorine formed in female Sprague-Dawley rat liver microsomes
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DOI：
10.1124/dmd.106.014100
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发表时间：
2007-04-01
影响因子：
3.9
通讯作者：
Zheng, Jiang
中科院分区：
文献类型：
--
作者：
Lin, Ge;Tang, Jun;Zheng, Jiang
Clivorine是一种天然存在的吡咯里西啶生物碱，通过其代谢活化产生毒性代谢物（吡咯酯）引起肝毒性。据报道，雌性Sprague-Dawley（SD）大鼠对君子兰碱中毒的敏感性低于雄性SD大鼠。然而，造成这种性别差异的生化机制在很大程度上是未知的。本文研究了君子兰碱在雌性大鼠肝微粒体中的代谢，以阐明其性别差异的机制。观察到直接代谢君子兰碱的两条途径。首先，在雌性大鼠中发现代谢活化产生毒性吡咯酸酯，随后形成结合吡咯、脱氢反曲菌素、7-谷胱甘肽脱氢反曲菌素和丁香酸，并鉴定了催化代谢活化的CYP 3A 1/2同工酶。与雄性大鼠（相似于21%）相比，雌性大鼠中的代谢活化显著较低（相似于4%），可能是由于雌性大鼠中表达的CYP 3A 1/2水平显著较低。其次，直接水解生成新型雌性大鼠特异性代谢物脱乙酰丁香碱被证明是雌性大鼠肝微粒体中的主要途径（类似于16%丁香碱代谢），并确定由微粒体水解酶A介导。此外，当代谢活化被酮康唑完全抑制时，孵育1小时形成的脱乙酰石蒜碱量从19.44 +/- 3.00 nmol/mg蛋白显著增加至54.87 +/- 9.30 nmol/mg蛋白，表明两种途径相互竞争。因此，雌性SD大鼠对君子兰碱中毒的敏感性较低，这可能是由于君子兰碱的直接水解程度明显较高，代谢活化程度较低所致。
Clivorine, a naturally occurring pyrrolizidine alkaloid, causes liver toxicity via its metabolic activation to generate toxic metabolite ( pyrrolic ester). Female Sprague-Dawley (SD) rats are reported to be less susceptible to clivorine intoxication than male SD rats. However, the biochemical mechanism causing such gender difference is largely unknown. The present study investigated hepatic microsomal metabolism of clivorine in female rats to delineate the mechanism of the gender difference. Two pathways, which directly metabolize clivorine, were observed. First, the metabolic activation to produce the toxic pyrrolic ester followed by formations of bound pyrroles, dehydroretronecine, 7-glutathionyldehydroretronecine, and clivoric acid were found in female rats, and CYP3A1/2 isozymes were identified to catalyze the metabolic activation. Compared with male rats ( similar to 21%), the metabolic activation in female rats was significantly lower ( similar to 4%) possibly because of significantly lower CYP3A1/2 levels expressed in female rats. Second, a direct hydrolysis to generate the novel female rat-specific metabolite deacetylclivorine was shown as the predominant pathway ( similar to 16% clivorine metabolism) in female rat liver microsomes and was determined to be mediated by microsomal hydrolase A. Furthermore, when the metabolic activation was completely inhibited by ketoconazole, the amount of deacetylclivorine formed in a 1-h incubation significantly increased from 19.44 +/- 3.00 to 54.87 +/- 9.30 nmol/mg protein, suggesting that the two pathways compete with each other. Therefore, the lower susceptibility of female SD rats to clivorine intoxication is suggested to be caused by the significantly higher extent of the direct hydrolysis and a lower degree of the metabolic activation.