Tang Herb Interacts With Efavirenz And Regulates CYP450 Enzymes

Tang herb is used as an adjuvant or alternative therapy for HIV-positive patients. However, the herb is very complex, whose effect on anti-HIV drug and mechanism are unknown. In order to decrease the potential drug-drug interaction, it is advised to take tang herb after EFV for one hour. However, this drug taking method affects the patient adhence. In this work, we study the pharmacokinetic effect and functional mechanism of tang herb on EFV through co-administrating tang herb and EFV; furthermore, we studied the effect of tang herb on CYP450 enzymes.Method First we evaluated the effect of tang herb on the pharmacokinetics of efavirenz in different delivery mode in rats. In this work, EFV was given to rats, alone, in combination with tang herb simultaneously or with a 60-min delay. The plasma EFV concentration was monitored by LC-MS/MS. In the second part, we studied CYP1A1、CYP1B1、CYP2B1、CYP2B2、CYP2E1 and CYP3A1 of CYP450 which related to EFV metabolism through real-time RT-PCR technology. Furthermore, microsome was enriched through differential centrifugation. Proteins were separated through SDS-PAGE. The three protein bands related to CYP450 enzymes were cut and identified by mass spectrometry (MS). Furthermore, in order to quantify the effect of tang herb on CYP450 enzymes, multiple reaction monitoring (MRM) mode based on MS was used. The CYP2C11 was selected based on the results from MS. The unique peptides of CYP2C11 were obtained through searching Expasy blast database. The fragment ions with m/z less than 800 were selected. Four MRM transitions from CYP2C11 (analyze) with m/z of 711.5�'232.1,711.5�'319.2,711.5�'466.2 and 711.5�'595.3, and four from ESAT-6 (internal standard (IS)) with m/z of 735.5�'215.3, 735.5�'389.3,735.5�'460.3 and 735.5-�'524.3 were selected. The peak area ratio of analyze to IS was used for quantification.Results We studied the tang herb and EFV interaction, and the functional mechanism of tang herb on EFV. The detail results were shown from the following three parts.1) In the rat model with sigle drug taking of tang herb or EFV, our results showed that the EFV mean area under the plasma concentration-time curve (AUCO-∞) values were 17.97、10.06 and 14.32 mg/l·h in EFV alone group, co-administered with the tang herb simultaneously and with a 60-min delays, respectively. Furthermore, according to statistic analysis, the AUC was significantly decreased in combination with tang herb simultaneously.2) Compared with the EFV alone group, tang herb did not affect the mRNA expression of six CYP450 enzymes related to EFV metabolism in the tang herb and EFV co-administration group. Through proteomic study of microsome from rat liver,16 CYP450 enzymes were identified. Of which, CYP2C11 protein was detected to be upregulated for 1.6-fold in EFV and tang herb combination group compared with EFV alone.Conclusion Tang herb decreased significantly the AUC of EFV when they were co-administrated simultaneously. It is necessary to take tang herb after EFV for 60-min. Tang herb is benefit of EFV dissolution in the environment of pH 2.0 or 6.0. Tang herb may regulate CYP450 enzymes such as CYP2C11 to affect drug metabolism, however, it is still necessary to study the mechanism of tang herb through other experiments.