ritonavir and tariquidar

Triptolide (TP), a main bioactive component of Tripterygium wilfordii Hook F., is a promising agent for treatment of autoimmune diseases. However, a high incidence of dose-limiting hepatotoxicity was observed in the clinic. Sandwich-cultured rat hepatocyte model was used in this study to identify the involvement of P-glycoprotein (P-gp) in TP disposition and to evaluate TP-induced hepatotoxicity after modulation of P-gp by the known inhibitors, ritonavir and tariquidar, and known inducers, phenobarbital, quercetin, and H(2)O(2). Our data showed that biliary clearance of TP reduced 73.7% and 84.2% upon treatment of ritonavir (25 µM) and tariquidar (5 µM), respectively. In contrast, increases of 346%, 280%, and 273% in biliary clearance of TP were observed with treatment of phenobarbital (1.0 mM), quercetin (20 µM), and H(2)O(2) (0.5 mM), respectively. The TP-induced hepatotoxicity increased by twofold when CYP activity was blocked by 1-aminobenzotriazole, suggesting that CYP and P-gp may both contribute to the detoxification of TP in the SCRH model. In addition, hepatotoxicity and the expression of apoptosis proteins Bax and Bcl-2 were correlated qualitatively with the TP exposure duration and its intracellular concentration, which, in turn, can be modulated by P-gp inhibitors or inducers. Our results for the first time demonstrated that in addition to CYP-mediated metabolism, P-gp also plays an important role in the disposition of TP and TP-induced hepatotoxicity. Thus, the modulation of canalicular P-gp has a potential to cause drug-drug interaction between TP and the coadministered P-gp inhibitors or inducers in the clinic.

Topics: Adenosine Triphosphatases; Animals; ATP Binding Cassette Transporter, Subfamily B, Member 1; ATP Binding Cassette Transporter, Subfamily G, Member 2; ATP-Binding Cassette Transporters; bcl-2-Associated X Protein; Cytochrome P-450 CYP3A; Cytochrome P-450 Enzyme System; Diterpenes; Epoxy Compounds; Hepatocytes; Hydrogen Peroxide; Liver; Male; Phenanthrenes; Phenobarbital; Proto-Oncogene Proteins c-bcl-2; Quercetin; Quinolines; Rats; Rats, Sprague-Dawley; Ritonavir