Objective:The purpose of this study was to detect the signaling pathways involved in angiotensinⅡ(AngⅡ)-induced mesangial cell(MC) proliferation. Methods:The incorporation of 3H-thymidine(3H-TdR) and cell count were used as the measure of mesangial cell proliferation. Reactive oxygen species(ROS) production was determined by DCFDA fluorescence. Nicotinamide adenine dinucleotide phosphate(NADPH) oxidase activity was examined by lucigenin chemiluminescence. c-Jun animoterminal kinase(JNK) activation was assayed by Western blot. Results:AngⅡ time-dependently and dose-dependently increased intracellular ROS production in cultured human MCs as early as 3 min and peak at 60 min. Incubation with different dose of AngⅡ(1 nmol/L,10 nmol/L, and 100 nmol/L AngⅡ) for 60 min, ROS production increased for 1.82-, 2.92-, and 4.08-fold, respectively. AngⅡ-induced ROS generation was inhibited by the AT1R antagonist losartan but not the AT2R antagonist PD123319, as well as NADPH oxidase inhibitors diphenyleneiodonium sulfate(DPI) and apocynin. In contrast, inhibitors of other oxidant-producing enzymes, including rotenone, allopurinol, indomethacin, nordihydroguiaretic acid, ketoconazole and G-nitro-L-arginine methyl ester(L-NAME) have no effect on AngⅡ-induced ROS production and MC proliferation. AngⅡ treatment induced translocation of cytosolic of p47phox and p67phox to the membrane and p47phox and p67phox gene expression. Conclusion:NADPH oxidase-derived ROS involved in AngⅡ-induced JNK/AP-1 activation and mesangial cell proliferation.