Glycyrrhetinic Acid Accelerates the Clearance of Triptolide through P‐gp In Vitro

Triptolide (TP) is an active ingredient isolated from Tripterygium wilfordii Hook. f. (TWHF), which is a traditional herbal medicine widely used for the treatment of rheumatoid arthritis and autoimmune disease in the clinic. However, its adverse reactions of hepatotoxicity and nephrotoxicity have been frequently reported which limited its clinical application. The aim of this study was to investigate the mechanism of glycyrrhetinic acid (GA) effecting on the elimination of TP in HK‐2 cells and the role of the efflux transporters of P‐gp and multidrug resistance‐associated proteins (MRPs) in this process. An ultra performance liquid chromatography–electrospray ionization–mass spectrometry (UPLC‐ESI‐MS) analytical method was established to determine the intracellular concentration of TP. In order to study the role of efflux transporters of P‐gp and MRPs in GA impacting on the accumulation of TP, the inhibitors of efflux transporters (P‐gp: verapamil; MRPs: MK571) were used in this study. The results showed that GA could enhance the elimination of TP and reduce the TP accumulation in HK‐2 cells. Verapamil and MK571 could increase the intracellular concentration of TP; in addition, GA co‐incubation with verapamil significantly increased the TP cellular concentration compared with the control group. In conclusion, GA could reduce the accumulation of TP in HK‐2 cells, which was related to P‐gp. This is probably one of the mechanisms that TP combined with GA to detoxify its toxicity. Copyright © 2017 John Wiley & Sons, Ltd.