RAGE-Induced Cytosolic ROS Promote Mitochondrial Superoxide ... : Journal of the American Society of Nephrology (original) (raw)

BASIC RESEARCH

RAGE-Induced Cytosolic ROS Promote Mitochondrial Superoxide Generation in Diabetes

Coughlan, Melinda T.; Thorburn, David R.; Penfold, Sally A.; Laskowski, Adrienne; Harcourt, Brooke E.; Sourris, Karly C.; Tan, Adeline L.Y.; Fukami, Kei; Thallas-Bonke, Vicki; Nawroth, Peter P.; Brownlee, Michael; Bierhaus, Angelika; Cooper, Mark E.; Forbes, Josephine M.

*Juvenile Diabetes Research Foundation Einstein Centre for Diabetes Complications, Division of Diabetes Complications, Baker IDI Heart and Diabetes Institute, Melbourne, and †Murdoch Children's Research Institute, Royal Children's Hospital and Department of Paediatrics, University of Melbourne, Parkville, Victoria, Australia; ‡Department of Medicine I, University of Heidelberg, Heidelberg, Germany; and §Diabetes Research Center, Albert Einstein College of Medicine, Bronx, New York

Correspondence: Dr. Melinda T. Coughlan, JDRF Einstein Centre for Diabetes Complications, Baker IDI Heart and Diabetes Institute, P.O. Box 6492, St. Kilda Road Central, Melbourne, 8008, Australia. Phone: +61-3-8532-1278; Fax: +61-3-8532-1100; E-mail: [email protected]

Accepted October 22, 2008

Received May 19, 2008

Abstract

Damaged mitochondria generate an excess of superoxide, which may mediate tissue injury in diabetes. We hypothesized that in diabetic nephropathy, advanced glycation end-products (AGEs) lead to increases in cytosolic reactive oxygen species (ROS), which facilitate the production of mitochondrial superoxide. In normoglycemic conditions, exposure of primary renal cells to AGEs, transient overexpression of the receptor for AGEs (RAGE) with an adenoviral vector, and infusion of AGEs to healthy rodents each induced renal cytosolic oxidative stress, which led to mitochondrial permeability transition and deficiency of mitochondrial complex I. Because of a lack of glucose-derived NADH, which is the substrate for complex I, these changes did not lead to excess production of mitochondrial superoxide; however, when we performed these experiments in hyperglycemic conditions in vitro or in diabetic rats, we observed significant generation of mitochondrial superoxide at the level of complex I, fueled by a sustained supply of NADH. Pharmacologic inhibition of AGE-RAGE–induced mitochondrial permeability transition in vitro abrogated production of mitochondrial superoxide; we observed a similar effect in vivo after inhibiting cytosolic ROS production with apocynin or lowering AGEs with alagebrium. Furthermore, RAGE deficiency prevented diabetes-induced increases in renal mitochondrial superoxide and renal cortical apoptosis in mice. Taken together, these studies suggest that AGE-RAGE–induced cytosolic ROS production facilitates mitochondrial superoxide production in hyperglycemic environments, providing further evidence of a role for the advanced glycation pathway in the development and progression of diabetic nephropathy.