Transcription factor Nrf2-mediated antioxidant defense system in the development of diabetic retinopathy

• Published in: Investigative ophthalmology & visual science Vol. 54; no. 6; pp. 3941 - 3948
• Main Authors: Zhong, Qing, Mishra, Manish, Kowluru, Renu A
• Format: Journal Article
• Language: English
• Published: United States The Association for Research in Vision and Ophthalmology 06.06.2013
• Subjects: Adult; Aged; Animals; Antioxidants - metabolism; Cell Nucleus - metabolism; Chromatin Immunoprecipitation; Diabetes Mellitus, Experimental - metabolism; Diabetic Retinopathy - metabolism; Endothelial Cells; Endothelium, Vascular - drug effects; Endothelium, Vascular - metabolism; Fluorescent Antibody Technique, Indirect; Gene Expression; Glutamate-Cysteine Ligase - metabolism; Glutathione - metabolism; Humans; Hydroquinones - pharmacology; Intracellular Signaling Peptides and Proteins - metabolism; Kelch-Like ECH-Associated Protein 1; Male; Middle Aged; NF-E2-Related Factor 2 - physiology; Oxidative Stress - drug effects; Rats; Rats, Wistar; Reactive Oxygen Species - metabolism; Real-Time Polymerase Chain Reaction; Retinal Vessels - cytology; RNA, Small Interfering - metabolism; Signal Transduction - physiology; diabetic retinopathy; Nrf2; antioxidant defense
• ISSN: 1552-5783; 0146-0404; 1552-5783
• DOI: 10.1167/iovs.13-11598

Increase in reactive oxygen species (ROS) is one of the major retinal metabolic abnormalities associated with the development of diabetic retinopathy. NF-E2-related factor 2 (Nrf2), a redox sensitive factor, provides cellular defenses against the cytotoxic ROS. In stress conditions, Nrf2 dissociates from its cytosolic inhibitor, Kelch like-ECH-associated protein 1 (Keap1), and moves to the nucleus to regulate the transcription of antioxidant genes including the catalytic subunit of glutamylcysteine ligase (GCLC), a rate-limiting reduced glutathione (GSH) biosynthesis enzyme. Our aim is to understand the role of Nrf2-Keap1-GCLC in the development of diabetic retinopathy. Effect of diabetes on Nrf2-Keap1-GCLC pathway, and subcellular localization of Nrf2 and its binding with Keap1 was investigated in the retina of streptozotocin-induced diabetic rats. The binding of Nrf2 at GCLC was quantified by chromatin immunoprecipitation technique. The results were confirmed in isolated retinal endothelial cells, and also in the retina from human donors with diabetic retinopathy. Diabetes increased retinal Nrf2 and its binding with Keap1, but decreased DNA-binding activity of Nrf2 and also its binding at the promoter region of GCLC. Similar impairments in Nrf2-Keap1-GCLC were observed in the endothelial cells exposed to high glucose and in the retina from donors with diabetic retinopathy. In retinal endothelial cells, glucose-induced impairments in Nrf2-GCLC were prevented by Nrf2 inducer tBHQ and also by Keap1-siRNA. Due to increased binding of Nrf2 with Keap1, its translocation to the nucleus is compromised contributing to the decreased GSH levels. Thus, regulation of Nrf2-Keap1 by pharmacological or molecular means could serve as a potential adjunct therapy to combat oxidative stress and inhibit the development of diabetic retinopathy.