The Inhibition Of Schisandra Chinensis Extract On CES2 And CYP450s,and Its Effect On Relieving Diarrhea Caused By Irinotecan

Background :Irinotecan(CPT-11)is a water-soluble camptothecin semisynthetic derivative,It can be converted into 7-ethyl-10-hydroxycamptothecin(SN-38)by Carboxylesterases 2(CES2)in vivo,SN-38 can play an anti-tumor effect by blocking DNA replication.At the same time,SN-38 can also accumulate continuously in the intestine to damage intestinal mucosa,so as to cause delayed diarrhea.Therefore,inhibition of CES2 activity can be used as an effective way to reduce diarrhea caused by CPT-11.Chinese medicine Schisandra is a perennial leaves of plants,with a variety of effects,which convergence is one of its main function,It is often used to treat chronic diarrhea in clinical practice,and its efficacy is significant.Therefore,In this paper,we used Schisandra chinensis extract to study the inhibitory ability of Schisandra chinensis to CES2 in vitro,and thus to provide an effective method for relieving the intestinal toxicity of irinotecan.In addition,schisanhenol,one of the main active ingredients of Schisandra chinensis,,is mainly catalyzed by CYP450 s in internal metabolism,among them,CYP3A4 is the main metabolic enzyme.CYP3A4 belonging to the CYP450 s system is the major metabolic enzyme.Moreover,ketoconazole,which is the specific inhibitor of CYP3A4,completely inhibited the production of metabolites of schisandrin.Therefore,in order to clarify the effect of schisanhenol on the activity of CYP450 enzyme in human liver microsomes,in this study,the specific inhibitor of CYP450 s in human livermicrosomes was used as substrate and schisanhenol as inhibitors to carry out experiments of Phase I metabolism in vitro.Purpose:The aim of this study was to investigate the inhibitory effects of Schisandra chinensis extract on carboxylesterase 2 and cytochrome P450(CYP450s),To find a potential method of relieving diarrhea induced by irinotecan and to predict the effect of Schisandrin on the Phase I metabolism in vivo.Methods:1.Screening of CES2 Inhibitors of four kinds of lignans compounds in Schisandra chinensisand its effect on alleviating diarrhea induced by irinotecan:With four kinds of lignans compounds in Schisandra chinensisas inhibitors,and fluorescein diacetate(FD)as a probe substrate for CES2.The inhibitor and FD were added to the incubation system of human liver microsomes,and were co-incubated at 37?(control group without inhibitor,with dimethyl sulfoxide instead).Centrifuged to remove the protein after termination of the reaction,then the supernatant fraction was placed in a fluorescent microplate reader to determine the fluorescence intensity of the metabolites.By analyzing the inhibitory rate of metabolites,the Inhibitory effect of four main active components in Schisandra chinensis on CES2 were assessed.2.Inhibitory Effect of Schisanhenol on CYP450s:With Schisanhenol as an inhibitor,and the specific inhibitor of CYP450 enzyme as the substrate.Set a blank control group,the control group without inhibitor and with the methanol instead.The substrates,inhibitors,potassium phosphate buffer and human liver microsomes were added into the NADPH system,The reaction was terminated after incubation at 37? for the corresponding time.Then centrifuged to remove the protein,and the supernatant fraction was used to determine the peak area of metabolites with the instrument of high performance liquid chromatography-mass spectrometry LCMS-2010 EV.By analyzing the reduced rate of the peak area of metabolites,toassess the inhibitory effect of Schisanhenol on CYP450 s.Results: 1.Schisanhenol has a strong inhibitory effect on CES2 in vitro(IC50 < 10?mol·L-1),and the inhibitory effect of Gomisin J and Gomisin G on CES2 in vitro was weak(IC50>10 ?mol·L-1),and Gomisin O has little inhibitory effect on CES2 invitro(IC50>100 ?mol·L-1).2.According to the risk prediction of traditional Chinese medicine-drug interaction(HDI),we can see that Schisanhenol may cause the maximum exposure level of CES2-dependent substrates to reach up to39.7%,with a certain degree of risk of HDI.3.Schisanhenol has a moderate to weak inhibitory ability towards CYP3 A / 3A4 in vitro,and its inhibitory effect in the body is weak,but has almost no inhibitory effect on CYP2E1,CYP2D6 and CYP2C9.Conclusion:1.Schisanhenol,one of the main active ingredients of Schisandra chinensis,has a strong inhibitory effect on drugs that are metabolized by CES2,which may relieve diarrhea caused by irinotecan to some extent.2.When combined with Chinese medicine preparations of Schisandra chinensis,there is a need to guard against the occurrence of the risk of HDI,to prevent the adverse drug reactions induced by a significant increase of plasma concentration.3.In human body,Schisanhenol has a weak inhibitory effect on those drugs were metabolized and cleared by CYP3 A / 3A4,and do not make much sense as an inhibitor of Phase I metabolism.