Discovery of cytochrome P450 enzymes-inhibiting components in traditional Chinese medicine / 中国中药杂志

With the widespread use of traditional Chinese medicine(TCM) and the integration of TCM and western medicine, drug-drug interaction(DDI) is considered as a major cause of therapeutic failures and side effects. Cytochrome P450 enzymes(CYPs) are responsible for large number of drug metabolism. CYP3 A4 and CYP2 D6, two important CYP isoforms, are responsible for about 80% drug metabolism of CYPs super family. The inhibition of CYPs is likely to be the most common factor leading to adverse DDI. Therefore, it is of great significance to predict potential CYP3 A4 and CYP2 D6 inhibitors to prevent the DDI. A fast and low-cost me-thod for calculating and predicting CYP inhibiting components was established in this paper, namely support vector machine(SVM) and molecular docking technology which are used to predict and screen drugs. Firstly, 12 qualitative models of two targets were established by using SVM, and the optimal model was selected to predict the compounds in traditional Chinese medicine database(TCMD). Then, molecular docking technology was used to establish docking model. By analyzing the key amino acids involved in drug-target interactions and combining with SVM model, potential inhibitors of CYP3 A4 and CYP2 D6 were found. From the computational results, astin D and epiberberine exhibited inhibition effect on CYP3 A4 and CYP2 D6, respectively. Astin D was only found in astins family from Aster tataricus, while epiberberine was considered to be the active constituent of Coptidis Rhizoma. Therefore, for the risk of DDI, extra attention should be paid to the source of these potential inhibitors, Asteris Radix et Rhizoma and Coptidis Rhizoma. This computational method provides technical support for discovering potential natural inhibitors of CYPs from Chinese herbs by using SVM and molecular docking model, and it is also helpful to recognize the CYPs-mediated DDI existing in TCM, providing research ideas for further pharmacovigilance of integrated therapy.

Prediction of potential drug interactions of apigenin based on molecular docking and in vitro inhibition experiments / 中国中药杂志

The purpose of this study was to investigate the effect of apigenin on UGT1 A1 enzyme activity and to predict the potential drug-drug interaction of apigenin in clinical use. First,on the basis of previous experiments,the binding targets and binding strength of apigenin to UGT1 A1 enzyme were predicted by computer molecular docking method. Then the inhibitory effect of apigenin on UGT1 A1 enzyme was evaluated by in vitro human liver microsomal incubation system. Molecular docking results showed that apigenin was docked into the active region of UGT1 A1 enzyme protein F,consistent with the active region of bilirubin docking,with moderate affinity. Apigenin flavone mother nucleus mainly interacted with amino acid residues ILE343 and VAL345 to form hydrophobic binding Pi-Alkyl. At the same time,the hydroxyl group on the mother nucleus and the amino acid residue LYS346 formed an additional hydrogen bond,which increased the binding of the molecule to the protein. These results suggested that the flavonoid mother nucleus structure had a special structure binding to the enzyme protein UGT1 A1,and the introduction of hydroxyl groups into the mother nucleus can increase the binding ability. In vitro inhibition experiments showed that apigenin had a moderate inhibitory effect on UGT1 A1 enzyme in a way of competitive inhibition,which was consistent with the results of molecular docking. The results of two experiments showed that apigenin was the substrate of UGT1 A1 enzyme,which could inhibit the activity of UGT1 A1 enzyme competitively,and there was a risk of drug interaction between apigenin and UGT1 A1 enzyme substrate in clinical use.

Inhibition of berberine on organ anion transporters and its bidirectional trans-membrane transport / 药物评价研究

Objective To study the inhibition of berberine on organ anion transporters (OATs) and its bidirectional trans-membrane transport.Method The transgene cell lines of the organ anion transporters including OAT1,OAT2,OAT3,OAT4,OAT7,and URAT1 were constructed and selected by animal cell transgenic method mediated by transporter Lipo 3000.Wild type (WT) cells were used as control group,and activity of OATs was verified by adding their radiolabeled substrates and inhibitors.The inhibition of 100 μmol/L berberine on the transporters was investigated in vitro.The IC50 of berberine on URAT1 was also determined.The bidirectional transport of berberine was studied through the Caco-2 model.Result The results showed that 100 μmol/L berberine inhibited the activity of OAT1,OAT2,OAT3,OAT4,OAT7 and URAT1 to (70.48±4.23)％,(69.13±1.28)％,(72.12±3.28)％,(79.77±6.49)％,(69.51 ±5.99)％ and (38.4 ± 2.67)％ respectively,the IC50 of berberine to URAT 1 was 13.19 μmol/L,the Papp (A-B) of 50 μmol/L and 100 μmol/L berberine were separately 0.28 × 10-6 and 0.40 × 10-6 cm/s,and the effiux rates were separately 3.18 and 3.15.Conclusion Berberine shows a stronger inhibition to URAT1 compared to OAT1,OAT2,OAT3,OAT4 and OAT7.Berberine may be the substrate of some effiux transporters.This study provides theoretical basis for explaining the low bioavailability ofberberine and forecasting the possible drug-drug interaction.

Inhibition of CYP3A4 and CYP2C9 by podophyllotoxin: Implication for clinical drug–drug interactions.

Podophyllotoxin (PPT) and its derivatives exert significant anti-cancer activities, and one derivative etoposide is often utilized to treat various cancers in the clinic. The aim of the present study is to investigate the inhibitory effects of PPT on major cytochrome P450 (CYP) isoforms in human livers. Inhibition of CYP3A4, CYP2C9, CYP2C8, CYP2D6, CYP2E1 and CYP2A6 by PPT was investigated in the human liver microsomal system. Time-dependent inhibition of CYP3A4 by PPT was also evaluated. The results showed that PPT strongly exhibited inhibitory effects on CYP3A4 and CYP2C9 in a concentration-dependent manner. Half inhibition concentration (IC50) was 1.1±0.3 and 4.6±0.3 μM for CYP3A4 and CYP2C9, respectively. Inhibition kinetic analysis showed that PPT exhibited competitive inhibition towards CYP3A4 and CYP2C9 with Ki of 1.6 and 2.0 μM, respectively. Additionally, PPT exerted time-dependent inhibition towards CYP3A4 and the kinetic parameters were 4.4±2.1 μM and 0.06±0.01 min–1 for KI and kinact, respectively. Our experimental data indicate that potential drug–drug interaction (DDI) might exist when PPT is co-administered with the substrates which mainly undergo CYP3A4- or CYP2C9-mediated metabolism.