ritonavir and triptolide

Triptolide is the most active ingredient of Tripterygium wilfordii Hook F, which is used to treat rheumatoid arthritis. (5R)-5-Hydroxytriptolide is a hydroxylation derivative of triptolide with a reduced toxicity. To investigate the metabolic enzymes of the two compounds and the drug-drug interactions with enzyme inducers or inhibitors, a series of in vitro and in vivo experiments were conducted. In vitro studies using recombinant human cytochrome P450 enzyme demonstrated that cytochrome P450 3A4 (CYP3A4) was predominant in the metabolism of triptolide and (5R)-5-hydroxytriptolide, accounting for 94.2% and 64.2% of the metabolism, respectively. Pharmacokinetics studies were conducted in male SD rats following administration of triptolide or (5R)-5-hydroxytriptolide (0.4 mg/kg, po). The plasma exposure to triptolide and (5R)-5-hydroxytriptolide in the rats was significantly increased when co-administered with the CYP3a inhibitor ritonavir (30 mg/kg, po) with the values of AUC

Topics: Administration, Oral; Animals; Cytochrome P-450 CYP3A; Cytochrome P-450 CYP3A Inducers; Cytochrome P-450 CYP3A Inhibitors; Dexamethasone; Diterpenes; Drug Interactions; Epoxy Compounds; Humans; Male; Phenanthrenes; Rats, Sprague-Dawley; Ritonavir

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