Study On The Inhibition Of UGT1A4 By Common Natural Steroid Derivatives

Objective: Evaluate the potential inhibition of steroids and their saponins toward UDP-glucuronosyltransferases 1A4(UGT1A4)and further assay the selectivity among 12 recombinant UGT isoforms;The inhibition kinetic were analysis and related kinetic parameters were measuredto predict the possibility of the in vivo interaction of common steroids and clinical drugs;To evaluate the quantitative structure-activity relationship(QASR)between the structure of steroids or their saponins and their inhibition activity in order to provide guidance for the prediction of in vivo HDIs and the rational use of steroidal saponins in clinical.Methods:(1)In vitro experiments: using in vitro incubation system,to evaluate the potential inhibition of different steroids and their saponins toward the UGT1A4-catalyzed TFP glucuronidation reaction and the selectivity of inhibitory effect toward UGT-catalyzed 4-MU glucuronidation in other 11 recombinant UGT isoforms;(2)Systematically analysis the inhibition kinetics of UGT1A4 inhibited by steroidal saponins and aglycone compounds,calculating the inhibition kinetic parameters(Ki),combined with the drugs pharmacokinetic parameters in vivo,the possible drug-drug interaction is inferred by the correlation equation;Imitating in vivometabolic environment,to evaluate the DDI between steroids derivatives and clinical drugs metabolized by UGT1A4 in human primary hepatocy;(3)To assay the inhibitory effect(IC50)of 43 steroids and their saponins towards UGT1A4,the IC50 and compound structure by comparative molecular field analysis(COMFA)and comparative molecular similarity analysis method(COMSIA)to build a model,further evaluate the quantitative structure-activity relationship(3D-QSAR),for steroidal saponins compounds and its structural analogs in the clinical rational application providing reasons.Results: In the experiment,43 compounds including different steroids and saponins,37 compounds exhibit potent inhibition toward UGT1A4,among them,hecogenin(1),gitogenin(4),tigogenin(5),solasodine(6),trillin(15)and gracillin(24),exhibited specific inhibition toward UGT1A4 rather than other UGT isoforms,while,saponins with glucoside moieties,such as prosapogenin A(19),spongipregnoloside A(20),pseudoprotodioscin(35),YS-IX(36),pallidifloside A(37)and pallidifloside H(38)showed slight activity toward various UGTs but without obvious specificities toward UGT1A4.Diosgenin(2),ruscogenin(3),gitogenin(4),tigogenin(5),solasodine(6),trillin(15)exhibit a competitively inhibition toward the glucuronidation of TFP with the inhibition parameters(Ki)of 0.6,0.18,1.1,0.7,0.8,and 12.3 μM,respectively.In human liver microsomes,steroidal derivatives such as diosgenin(2),ruscogenin(3),tigogenin(5)and solasodine(6)can inhibitethe glucuronidation of some clinical drugs such as trifluoperazine,olanzapine,midazolam and tamoxifen which can be catalyzed by UGT1A4 and their IC50 values were less than 10μM.Furthermore,a drug-drug interaction were detected in human primary hepatocytes between some clinical drugs and inhibitors such asdiosgenin(2),ruscogenin(3),tigogenin(5)and solasodine(6)in the incubation system.By using the inhibitory effect(IC50)of 43 compounds toward UGT1A4,Co MFA model and Co MSIA model was successfully constructed and the prediction of in vivo HDIs were performed based on the structure of different.All of which provides valuable advice for steroidal derivatives reasonable application in clinical.Conclusion:This work indicated tha gitogenin(4),tigogenin(5),solasodine(6)can be used as selective inhibitors for the in vitro metabolism study.Additionally,the inhibition type of some compounds toward UGT1A4 were verified to be a competitively inhibition.More importantly,diosgenin(2),ruscogenin(3),tigogenin(5)and solasodine(6)could significant inhibit the glucuronide of tamoxifen in human primary hepatocytes,which indicated a herb drug-drug interaction would be occurredin the co-administration of herbs,foods containing abundant steroids and saponins,with some clinical drugs which metabolized by UGT1A4.In order to further characterize the relation between the structures of steroids or saponins and their inhibition activity toward UGT1A4,a quantitative structure-activity relationship(QSAR)were also performed,Co MFA model and Co MSIA model was successfully constructed for the prediction of in vivo HDIs.All of our findings would give the vital guidance for the rational use of some herbs,foods which contains abundant steroids and their saponins.