Abstract
Background: Geniposide (GE) is the main bioactive component of Gardenia jasminoides Ellis, which has many pharmacological effects, such as anti-inflammatory, anti-oxidation, and anti-angiogenesis. GE has low absolute bioavailability after oral administration, and speculated that GE might have an effect on P-glycoprotein (P-gp) described in our previous study. However, intestinal absorption characteristics involved in the Caco-2 cells of GE are still unknown. Therefore, we aimed to investigate absorption mechanisms of GE and the effects on P-gp. Methods: By establishing the Caco-2 cells model and HPLC method, bidirectional transport of GE in the different conditions and the presence of P-gp inhibitors－verapamil were conducted to observe its absorption mechanisms. Transport assays of digoxin, a P-gp substrate, were also performed in the presence of GE or verapamil. The effects of GE on the function and expression of P-gp were analyzed by flow cytometry and Western blot using rhodamine-123 (rho-123) and the antibody, respectively. Results: Both absorption and secretion of GE were positively correlated with concentration and time at Caco-2 cell monolayer. The Papp of bidirectional transport was decreased in low temperature and the Papp(BL-AP) of GE decreased significantly in the presence of verapamil. Meanwhile, the ER value was higher than 1.5. In addition, in the bidirectional transport of digoxin, the values of Papp(BL-AP) and ER decreased significantly in the presence of GE, just like verapamil. GE increased the intracellular accumulation of rho-123 and also have a significant decrease on P-gp expression. Conclusion: Transepithelial transport mechanism of GE in Caco-2 cell monolayer is mainly passive diffusion and P-gp mediated active transportation. GE was a potential inhibitor of P-gp, can inhibit transport of digoxin and the function and expression of P-gp.
Overcoming Multidrug Resistance: Flavonoid and Terpenoid Nitrogen-Containing Derivatives as ABC Transporter Modulators
