Phyllanthin and hypophyllanthin inhibit function of P-gp but not MRP2 in Caco-2 cells
Sukhaphirom, N.; Vardhanabhuti, N.; Chirdchupunseree, H.; Pramyothin, P.; Jianmongkol, S.
Journal of Pharmacy and Pharmacology 65(2): 292-299
The purposes of this study were to investigate the inhibitory effects of two lignans, phyllanthin and hypophyllanthin, on the function of P-glycoprotein (P-gp) and multidrug resistance protein 2 (MRP2), using the in-vitro model of Caco-2 cells. In addition, the effect of prolonged exposure to these two compounds on the expression of active P-gp was also determined. The activity of P-gp and MRP2 was determined in the uptake assays by monitoring the intracellular accumulation of their specific substrates (calcein acetoxymethyl ester and 5-carboxy-2?,7?-dichlorofluorescein diacetate, respectively) with fluorescence spectroscopy.Key findingsHypophyllanthin and phyllanthin inhibited P-gp function with comparable potencies, but neither compound affected MRP2 activity. When the lignans were washed out before addition of substrate, the inhibitory action of both compounds against P-gp function was lost. These results suggested the reversibility of the inhibition. Moreover, prolonged exposure of the Caco-2 cells to both lignans (up to 7 days) had no effect on P-gp function. Phyllanthin and hypophyllanthin directly inhibited P-gp activity and did not interfere with MRP2 activity. It was likely that both phyllanthin and hypophyllanthin could reversibly inhibit P-gp function.