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1Department of Pediatrics, Second Affiliated Hospital, 2Center of Pediatric Nephrology, 3Department of Nephrology, and 4Department of Neurology, Nanjing Children's Hospital, Nanjing Medical University, Nanjing, China; and 5Division of Nephrology, University of Utah and Salt Lake Veterans Affairs Medical Center, Salt Lake City, Utah
Submitted 5 March 2007 ; accepted in final form 27 August 2007
We previously showed that ANG II induces mesangial cell (MC) proliferation via the JNK-activator protein-1 pathway. The present study attempted to determine the upstream mediators of JNK activation, with emphasis on reactive oxygen species (ROS) and the epidermal growth factor (EGF) receptor (EGFR). In cultured human MCs (HMCs), as early as 3 min, ANG II time dependently increased intracellular ROS production, which was sensitive to 10 µM diphenyleneiodonium sulfate and 500 µM apocynin, two structurally distinct NADPH oxidase inhibitors. In contrast, inhibitors of other oxidant-producing enzymes, including the mitochondrial complex I inhibitor rotenone, the xanthine oxidase inhibitor allopurinol, the cyclooxygenase inhibitor indomethacin, the lipoxygenase inhibitor nordihydroguiaretic acid, the cytochrome P-450 oxygenase inhibitor ketoconazole, and the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester, were without effect. ANG II-induced ROS generation was inhibited by the angiotensin type 1 receptor antagonist losartan (10 µM) but not the angiotensin type 2 receptor antagonist PD-123319 (10 µM). ANG II induced translocation of p47phox and p67phox from the cytosol to the membrane. The antioxidants almost abolished the ANG II mitogenic response, as assessed by [3H]thymidine incorporation and cell number, associated with a remarkable blockade of the activation of EGFR (90% inhibition) and JNK (83% inhibition). The EGFR inhibitor AG-1478 was able to mimic the effect of antioxidants, in that it inhibited the mitogenic response and the JNK activation following ANG II treatment. Together, these data suggest that the ROS-EGFR-JNK pathway is involved in transducing the proliferative effect of ANG II in cultured HMCs.
glomerular disease; reactive oxygen species; cell growth
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