银杏叶提取物对黄曲霉毒素B_1诱发大鼠肝癌过程中生物标志物的影响

Effects of Ginkgo biloba extract on biomarker expressions during aflatoxin B_1-induced hepatocarcinogenesis in Wistar rats

目的:探讨银杏叶提取物(extract 761 fromGinkgo biloba,EGb761)对黄曲霉毒素B1(aflatoxin B1,AFB1)在大鼠体内代谢的影响。方法:经AFB1和EGb761不同处理,获得AFB1组、AFB1+EGb761组和空白对照组3组大鼠,分别于实验第14、28及42周给予抽血及肝活检,并于第64周全部处死。观察大鼠肝癌发生率,用分光光度法检测肝组织Ⅰ相酶CYP450和Ⅱ相酶GST活性,用高效液相色谱法检测血清AFB1-赖氨酸加合物水平,以及应用免疫组织化学法检测8-羟基脱氧鸟嘌呤核苷(8-hydroxydeoxyguanosine,8-OHdG)蛋白表达情况。结果:肝癌诱发率在AFB1+EGb761组明显低于AFB1组(P<0.001),而对照组无肿瘤发生;EGb761对Ⅰ相代谢酶CYP450及Ⅱ相代谢酶GST活性无明显影响。血清AFB1-赖氨酸加合物的最高水平(4 356.01 pg/mg albumin)发生于实验第14周的AFB1组。在实验第14、42周时EGB761显著抑制了血清AFB1-赖氨酸加合物的形成,抑制率分别为13.07%(P=0.033)、73.63%(P=0.002)。在各检测点的8-OHdG蛋白表达强度显示,AFB1+EGb 761组均显著低于AFB1组(P<0.05)。结论:EGb761阻断AFB1致肝癌发生的主要机制可能不完全是通过影响肝脏Ⅰ、Ⅱ相代谢酶活性的途径实现的。EGb761能够抑制AFB1-赖氨酸加合物的形成,降低8-OHdG蛋白的表达,减轻DNA的氧化损伤,这可能是其最终抑制或延缓AFB1诱发肝癌发生、发展的机制之一。

Objective：To study the effect of Ginkgo biloba extract（EGb761） on metabolism of aflatoxin B1（AFB1）in Wistar rats.Methods：Seventy one Wistar rats were divided into three groups at random： group A（AFB1 group）,group B（AFB1＋EGb761 group）,and group C（control group）.The rats in groups A and B were given AFB1（intraperitoneal injection,100-200 μg/ kg body weight,1-3 times/week）.The rats in group B were fed the food containing EGb761 while the rats in groups A and C were given normal food.Blood samples were collected and liver biopsy was performed on the 14th,28th and 42nd week.All the rats were sacrificed at the 64th week.The incidence of hepatoma was observed.The hepatic phase Ⅰ drug-metabolizing enzyme CYP450 and phase Ⅱ enzyme GST were detected by spectrometry.The serum AFB1-lysine adduct was determined by high performance liquid chromatography（HPLC）.The expression of 8-hydroxydeoxyguanosine（8-OHdG）was measured by immunohistochemistry.Results：The incidence of hepatocellular carcinoma（HCC） in group B was significantly lower than that in group A（26.92% vs 76.00%,P0.001）.No hepatocellular carcinoma developed in group C.EGb761 had no effects on the activities of CYP450 and GST in rat liver tissues.The level of AFB1-lysine adduct reached the peak（4 356.01 pg/mg albumin） at the 14th week in group A.EGb761 significantly inhibited the formation of AFB1-lysine adducts in serum by 13.07% at the 14th week（P=0.033）,and 73.63% at the 42nd week（P=0.002）.The expression of 8-OHdG protein in rat liver tissues in group B was significantly lower than that in group A at the 28th,42nd,and 64th week（P0.05）.Conclusion：The main mechanism underlying the effect of EGb761 in blocking hepatogenesis induced by AFB1 may not be fully related with its influence on the activity of liver phase Ⅰ and phase Ⅱ metabolizing enzymes.EGb761 inhibites the production of AFB1-lysine addcuts,decreases the expression of 8-OHdG protein,and finally alleviates the DNA oxidative injury,which may be one of the mechanisms for the effects of EGb761 in inhibiting or delaying hepatogenesis induced by AFB1.