大鼠肝脏和肠道羧酸酯酶CES2对伊立替康的部位特异性代谢作用

摘要

目的 探讨羧酸酯酶同工酶CES2在大鼠肝脏和肠道的表达特征,并研究其对伊立替康(CPT-11)的水解代谢作用.方法 采用CPT-11与大鼠肝脏和各肠段S9组分共同孵育,高效液相色谱法测定代谢产物SN-38的生成量.采用荧光定量PCR技术(RT-PCR)对各组织中的CES2进行定量分析.结果 大鼠肝脏和肠道表现出对CPT-11的部位特异性水解作用,肝脏的水解活性强于肠道,各肠段水解CPT-11的作用强度依次为:十二指肠>空肠>回肠>结肠.RT-PCR结果 同样显示CES2的两个主要同工酶AB010635和AY034877在肝脏中的含量明显高于肠道,并随着肠段的下行而递减.结论 CPT-11在大鼠肝脏和肠道S9中可被有效水解,但代谢产物SN-38的生成量在各组织中不一致这一现象与CES2在不同组织中的部位特异性分布有关.该研究结果 为通过抑制CES2预防CPT-11毒副作用的策略开发提供了基础.%Objective To investigate the expression of carboxylesterases isoenzymes(CES2)in rat liver and intestines, and study its hydrolytic activity to irinotecan (CPT-11 ). Methods CPT-11 was incubated with S9 fractions of rat liver and intestinal tissues and the site-specific hydrolytic activity of CES2 was determined by the formation rate of metabolite SN-38. Furthermore,the mRNA expression of CES2 was detected by real-time fluorescent quantitative reverse transcription-polymerase chain reaction ( RT-PCR). Results The results obtained from the formation of SN-38 showed a site-specific degradation in rat liver and intestine homogenates. Hydrolysis of CPT-11 in homogenates from intestine homogenates was low compared to that from liver homogenates. Segmental difference in intestine was observed in the degradation of CPT-11 as: duodenum＞jejunum＞ileum＞ colon. The mRNA expression levels for the CES2 isozymes AB010635 and AY034877 also indicated that rat liver possessed much higher CES2 activity than intestines, with a gradual decrease of CES2 activity existed along the intestine. Conclusion CPT-11 undergoes conversion to its metabolite in rat liver and intestine S9 fractions, and there is tissue variability in the extent of SN-38 formation, which is associated with the site-specific distribution of CES2 in these tissues. The results provide a basis for the strategies preventing side effects of CPT-11 via CESs inhibition.