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Aldose Reductase Inhibitor Fidarestat Alleviates Diabetes–Induced Retinal Oxidative–Nitrosative Stress and Poly(ADP–Ribose) Polymerase Activation

¹ Division of Nutrition and Chronic Disease, Pennington Biomedical Research Center of the Louisiana State University System, Baton Rouge, LA
² Internal Medicine, University of Michigan, Ann Arbor, MI
³ Research Dept., Inotek Pharmaceuticals Corp., Beverly, MA
⁴ National Institute of Alcohol Abuse and Alcoholism, NIH, Bethesda, MD

Commercial Relationships: I.G. Obrosova, Sanwa Kagaku Kenkyusho Co., Ltd F; C. Szabo, None; M.J. Stevens, None; P. Pacher, None.

Support: ADA Research Grant, NIH Grant DK59809–01, JDRFI Center Grant 4–200–421

Abstract

Purpose: Aldose reductase inhibitors (ARIs), antioxidants, and, recently, PARP inhibitors were found to prevent manifestations of diabetic retinopathy in animal models. We studied the relation among three mechanisms, by evaluating the potent and specific ARI fidarestat (F) on retinal oxidative–nitrosative stress and PARP activity in STZ–diabetic rats and high glucose–exposed endothelial cells.

Methods: We used control rats and STZ–diabetic rats treated with or without F (16 mg kg^–1d^–1) starting from induction of diabetes. The duration of experiment was 6 wks. Sorbitol pathway intermediates were assessed by enzymatic spectrofluorometric methods, lipid peroxidation products by standard colorimetric method with N–methyl–2–phenylindole, and nitrotyrosine and PARP activity by immunohistochemistry. In in vitro studies, bovine retinal endothelial cells were cultured in 5 mM glucose, 30 mM glucose and 30 mM glucose plus 1 µM F. Oxidative–nitrosative stress was evaluated using CM–H₂DCFDA and flow cytometry, and PARP activity by CELISA.

Results: Retinal nitrotyrosine and poly(ADP–ribose) immunoreactivities were increased in diabetic rats vs controls. F treatment resulted in 1) normalization of sorbitol pathway activity (manifested by both sorbitol and fructose concentrations), without affecting retinal glucose concentrations; and 2) suppression of lipid peroxidation, nitrosative stress and PARP activity, in the retina of diabetic rats. In vitro, F decreased CM–H₂DCFDA fluorescence (a marker of intracellular oxidative–nitrosative stress) and poly(ADP–ribose) accumulation in high glucose–exposed endothelial cells. F did not affect poly(ADP–ribose) formation in cell–free system containing PARP and NAD.

Conclusions: Aldose reductase inhibition counteracts oxidative–nitrosative stress and PARP activation, two phenomena implicated in the pathogenesis of diabetic retinopathy.

Keywords: diabetic retinopathy • oxidation/oxidative or free radical damage • pharmacology

© 2005, The Association for Research in Vision and Ophthalmology, Inc., all rights reserved. For permission to reproduce any part of this abstract, contact the ARVO Office at arvo{at}arvo.org.