Multidrug resistance(MDR)is a serious obstacle encountered in cancer treatment.This study was performed to explore the reversal MDR activity of ivermectin(IVM)from avermectin family and moxidectin(MOX)belonging to milbemycin family.The two compounds(5μmol•L-1)showed strong potency to increase adriamycin cytotoxicity toward adriamycin-resistant rat glioma cells C6/adr with fold reversal(FR)of 31.02 and 13.40,respectively.In addition,the mechanisms of them on p-glycoprotein(P-gp)-mediated MDR demonstrated that the two compounds significantly increased the intracellular accumulations of adriamycin and Rh123 via inhibiting P-gp efflux.Based on the analysis of P-gp,MDR1 and MRP1 gene expressions by using immunofluorescence flow cytometry and RT-PCR,the results revealed that the two compounds could down regulate the expression of P-gp,and that MDR1 and MRP1 gene expressions were down regulated.These findings suggested that ivermectin and moxidectin probably represented potent agents for reversing MDR in cancer therapy,and especially ivermectin was a better modulator.
