Translocation of Glomerular p47phox and p67phox by Protein Kinase C-β Activation Is Required for Oxidative Stress in Diabetic Nephropathy

  1. Munehiro Kitada,
  2. Daisuke Koya,
  3. Toshiro Sugimoto,
  4. Motohide Isono,
  5. Shin-ichi Araki,
  6. Atsunori Kashiwagi and
  7. Masakazu Haneda
  1. From the Department of Medicine, Shiga University of Medical Science, Otsu, Shiga, Japan
  1. Address correspondence and reprint requests to Masakazu Haneda, Department of Medicine, Shiga University of Medical Science, Otsu, Shiga, 520-2192, Japan. E-mail: haneda{at}belle.shiga-med.ac.jp

Abstract

Oxidative stress is implicated to play an important role in the development of diabetic vascular complications, including diabetic nephropathy. It is unclear whether oxidative stress is primarily enhanced in the diabetic glomeruli or whether it is merely a consequence of diabetes-induced glomerular injury. To address this issue, we examined diabetic glomeruli to determine whether oxidative stress is enhanced, as well as examined the role of protein kinase C (PKC)-β activation in modulating NADPH oxidase activity. Urinary 8-hydroxydeoxyguanosine excretion and its intense immune-reactive staining in the glomeruli were markedly higher in diabetic than in control rats, and these alterations were ameliorated by a treatment with a selective PKC-β inhibitor, ruboxistaurin (RBX; LY333531) mesylate, without affecting glycemia. NADPH oxidase activity, which was significantly enhanced in diabetic glomeruli and the source of reactive oxygen species (ROS) generation, was also improved by RBX treatment by preventing the membranous translocation of p47phox and p67phox from cytoplasmic fraction without affecting their protein levels. Adenoviral-mediated PKC-β2 overexpression enhanced ROS generation by modulating the membranous translocation of p47phox and p67phox in cultured mesangial cells. We now demonstrate that oxidative stress is primarily enhanced in the diabetic glomeruli due to a PKC-β-dependent activation of NADPH oxidase resulting in ROS generation.

Footnotes

    • Accepted July 14, 2003.
    • Received March 13, 2003.
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