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

Abstract

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.

• Authors: M Sedeek, G Callera, A Montezano, A Gutsol, F Heitz, C Szyndralewiez, P Page, C R J Kennedy, K D Burns, R M Touyz, R L Hébert
• Journal: American journal of physiology. Renal physiology (Am J Physiol Renal Physiol) Vol. 299 Issue 6 Pg. F1348-58 (Dec 2010) ISSN: 1522-1466 [Electronic] United States
• PMID: 20630933 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• 2-(2-chlorophenyl)-4-methyl-5-(pyridin-2-ylmethyl)-1H-pyrazolo(4,3-c)pyridine-3,6(2H,5H)-dione
• Cytochrome b Group
• Pyrazoles
• Pyridones
• RNA, Small Interfering
• Reactive Oxygen Species
• NADPH Oxidase 4
• NADPH Oxidases
• Nox4 protein, mouse
• Cyba protein, mouse
• neutrophil cytosolic factor 1
• p38 Mitogen-Activated Protein Kinases
• Glucose

Topics

• Animals
• Cells, Cultured
• Cytochrome b Group (biosynthesis)
• Diabetes Mellitus, Experimental (metabolism, pathology)
• Diabetic Nephropathies (metabolism, pathology)
• Fibrosis
• Glucose (pharmacology)
• Kidney (metabolism)
• Male
• Mice
• NADPH Oxidase 4
• NADPH Oxidases (biosynthesis, physiology)
• Oxidative Stress (drug effects)
• Pyrazoles (pharmacology)
• Pyridones (pharmacology)
• RNA, Small Interfering (pharmacology)
• Reactive Oxygen Species (metabolism)
• p38 Mitogen-Activated Protein Kinases (drug effects)