苯并[a]芘暴露大鼠的皮层代谢组学研究

Changes of cerebral cortical metabolomics in rats following benzo[a]pyrene exposure

目的基于气相色谱/质谱联用技术(GC/MS)的代谢组学方法,分析苯并[a]芘(B[a]P)暴露后大鼠皮层内源性小分子代谢物的变化,研究其神经毒性机制。方法将五日龄SD大鼠随机分为对照组和B[a]P暴露组(2 mg/kg),连续灌胃染毒7周以构建B[a]P暴露模型。染毒结束后,Morris水迷宫(MWM)测定大鼠的空间学习能力;电镜观察皮层神经元超微结构;GC/MS检测皮层代谢谱,结合偏最小二乘法判别分析(PLS-DA)和两独立样本t检验分析筛选两组间的差异代谢物,Cytoscape软件分析与差异代谢物相关的代谢通路。结果与对照组相比,B[a]P暴露大鼠出现较长的逃避潜伏期(P<0.05)、较短的目标象限停留时间(P<0.05);与对照组相比,B[a]P暴露大鼠出现突触间隙增宽、突触后膜增厚以及胞浆肿胀;两组大鼠的皮层中存在18个差异代谢物(VIP>1,P<0.05),分析差异代谢物得到9条与B[a]P神经毒性机制相关的通路,这些通路涉及氨基酸代谢、三羧酸循环以及维生素B3(烟酸和烟酰胺)代谢。结论 B[a]P可干扰机体的正常代谢,其神经毒性机制可能与氨基酸类代谢紊乱、三羧酸循环紊乱以及维生素代谢紊乱等有关。

Objective To analyze the changes in endogenous small molecule metabolites after benzo[a]pyrene（B[a]P） exposure in rat cerebral cortex and explore the mechanism of B[a]P neurotoxicity.Methods Five-day-old SD rats were subjected to gavage administration of 2 mg/kg B[a]P for 7 consecutive weeks.After the exposure,the rats were assessed for spatial learning ability using Morris water maze test,ultrastructural changes of the cortical neurons under electron microscope,and metabolite profiles of the cortex using GC/MS.The differential metabolites between the exposed and control rats were identified with partial least squares discriminant analysis（PLS-DA） and the metabolic pathways related with the differential metabolites were analyzed using Cytoscape software.Results Compared with the control group,the rats exposed to B[a]P showed significantly increased escape latency（P〈0.05） and decreased time spent in the target area（P〈0.05）.The exposed rats exhibited widened synaptic cleft,thickened endplate membrane and swollen cytoplasm compared with the control rats.Eighteen differential metabolites（VIP1,P〈0.05） in the cortex were identified between the two groups,and 9 pathways associated with B[a]P neurotoxicity were identified involving amino acid metabolism,tricarboxylic acid cycle and Vitamin B3（niacin and nicotinamide） metabolism.Conclusion B[a]P can cause disturbance in normal metabolisms and its neurotoxicity is possibly related with disorders in amino acid metabolism,tricarboxylic acid cycle and vitamin metabolism.