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Am J Physiol Renal Physiol. 2010 Dec;299(6):F1348-58. doi: 10.1152/ajprenal.00028.2010. Epub 2010 Jul 14.

Critical role of Nox4-based NADPH oxidase in glucose-induced oxidative stress in the kidney: implications in type 2 diabetic nephropathy.

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Kidney Research Centre, Ottawa Hospital Research Institute and Deptartment of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada.


Molecular mechanisms underlying renal complications of diabetes remain unclear. We tested whether renal NADPH oxidase (Nox) 4 contributes to increased reactive oxygen species (ROS) generation and hyperactivation of redox-sensitive signaling pathways in diabetic nephropathy. Diabetic mice (db/db) (20 wk) and cultured mouse proximal tubule (MPT) cells exposed to high glucose (25 mmol/l, D-glucose) were studied. Expression (gene and protein) of Nox4, p22(phox), and p47(phox), but not Nox1 or Nox2, was increased in kidney cortex, but not medulla, from db/db vs. control mice (db/m) (P < 0.05). ROS generation, p38 mitogen-activated protein (MAP) kinase phosphorylation, and content of fibronectin and transforming growth factor (TGF)-β1/2 were increased in db/db vs. db/m (P < 0.01). High glucose increased expression of Nox4, but not other Noxes vs. normal glucose (P < 0.05). This was associated with increased NADPH oxidase activation and enhanced ROS production. Nox4 downregulation by small-interfering RNA and inhibition of Nox4 activity by GK-136901 (Nox1/4 inhibitor) attenuated d-glucose-induced NADPH oxidase-derived ROS generation. High d-glucose, but not l-glucose, stimulated phosphorylation of p38MAP kinase and increased expression of TGF-β1/2 and fibronectin, effects that were inhibited by SB-203580 (p38MAP kinase inhibitor). GK-136901 inhibited d-glucose-induced actions. Our data indicate that, in diabetic conditions: 1) renal Nox4 is upregulated in a cortex-specific manner, 2) MPT cells possess functionally active Nox4-based NADPH, 3) Nox4 is a major source of renal ROS, and 4) activation of profibrotic processes is mediated via Nox4-sensitive, p38MAP kinase-dependent pathways. These findings implicate Nox4-based NADPH oxidase in molecular mechanisms underlying fibrosis in type 2 diabetic nephropathy.

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