A defect in Nrf2 signaling constitutes a mechanism for cellular stress hypersensitivity in a genetic rat model of type 2 diabetes

• Published in: American journal of physiology: endocrinology and metabolism 2011-12, Vol.301 (6), p.E1119-E1129
• Main Authors: Bitar, Milad S, Al-Mulla, Fahd
• Format: Article
• Language: English
• Subjects: Adaptation, Physiological - drug effects; Adaptation, Physiological - genetics; Animals; Antioxidants; Cells, Cultured; Diabetes; Diabetes Mellitus, Type 2 - genetics; Diabetes Mellitus, Type 2 - metabolism; Diabetes Mellitus, Type 2 - pathology; Disease Models, Animal; Female; Gene expression; Glycogen Synthase Kinase 3 - genetics; Glycogen Synthase Kinase 3 - metabolism; Glycogen Synthase Kinase 3 beta; Hypersensitivity - genetics; Hypersensitivity - metabolism; Hypersensitivity - pathology; NF-E2-Related Factor 2 - antagonists & inhibitors; NF-E2-Related Factor 2 - genetics; NF-E2-Related Factor 2 - metabolism; NF-E2-Related Factor 2 - physiology; Oxidation-Reduction; Oxidative stress; Oxidative Stress - drug effects; Oxidative Stress - physiology; Proteins; Proto-Oncogene Proteins c-fyn - genetics; Proto-Oncogene Proteins c-fyn - metabolism; Rats; Rats, Transgenic; Rats, Wistar; Reactive Oxygen Species - adverse effects; RNA, Small Interfering - pharmacology; Rodents; Signal Transduction - drug effects; Signal Transduction - genetics; Signal Transduction - physiology
• ISSN: 0193-1849; 1522-1555
• DOI: 10.1152/ajpendo.00047.2011

Nrf2 regulates the expression and coordinated induction of a battery of antioxidant phase 2 genes that protect cells against the cumulative damaging effects of oxidative stress (OS), a major contributor in the development of chronic diabetic complications. Using cultured dermal fibroblasts from rats with type 2 diabetes (DFs), we investigated the intracellular redox status and the adaptive response to OS, in which Nrf2 plays a central role. Our data confirmed that the generation of superoxide by NADPH oxidase and the mitochondria was enhanced in DFs compared with corresponding controls. This was associated with a decrease in the antioxidant capacity and an increase in the sensitivity of these DFs to hydrogen peroxide-induced necrotic cell death. Nrf2 levels in total cell extracts were diminished, and this abnormality appears to stem from a diabetes-related decrease in Nrf2 protein stability. Endogenous (oligomycin) and exogenous (tert-butylhydroquinone) induction of OS enhanced the nuclear translocation of Nrf2 and increased the mRNA expression of Nrf2-sensitive genes in control but not DFs. The activity of the GSK-3β/Fyn axis was increased markedly in DFs when compared with the corresponding controls. Chemical inhibition of GSK-3β mitigated the diabetes-related suppression of the OS-induced nuclear accumulation of Nrf2 and the transcriptional activation of the genes downstream of Nrf2. Overall, these findings suggest that an augmentation in GSK-3β/Fyn signaling during diabetes contributes to a deficit in both the cellular redox state and the Nrf2-based adaptive response to OS. Moreover, they may also offer a new perspective in the understanding and treatment of nonhealing diabetic wounds.