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Cailing Liu, Yuming Chen, Irene E. Kochevar, Ula V. Jurkunas; Decreased DJ-1 Leads to Impaired Nrf2-Regulated Antioxidant Defense and Increased UV-A–Induced Apoptosis in Corneal Endothelial Cells. Invest. Ophthalmol. Vis. Sci. 2014;55(9):5551-5560. doi: https://doi.org/10.1167/iovs.14-14580.
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To investigate the role of DJ-1 in Nrf2-regulated antioxidant defense in corneal endothelial cells (CECs) at baseline and in response to ultraviolet A (UV-A)–induced oxidative stress.
DJ-1–deficient CECs were obtained by transfection of an immortalized normal human corneal endothelial cell line (HCECi) with DJ-1 small interfering RNA (siRNA) or by isolation of CECs from ex vivo corneas of DJ-1 knockout mice. Levels of reactive oxygen species (ROS), protein carbonyls, Nrf2 subcellular localization, Nrf2 target genes, and protein interaction between Keap1/Nrf2 and Cul3/Nrf2 were compared between normal and DJ-1–deficient CECs. Oxidative stress was induced by irradiating HCECi cells with UV-A, and cell death and levels of activated caspase3 and phospho-p53 were determined.
DJ-1 siRNA-treated cells exhibited increased levels of ROS production and protein carbonyls as well as a 2.2-fold decrease in nuclear Nrf2 protein when compared to controls. DJ-1 downregulation led to attenuated gene expression of Nrf2 and its target genes HO-1 and NQO1. Similar levels of Nrf2 inhibitor, Keap1, and Cul3/Nrf2 and Keap1/Nrf2 were observed in DJ-1 siRNA-treated cells as compared to controls. Ultraviolet A irradiation resulted in a 3.0-fold increase in cell death and elevated levels of activated caspase3 and phospho-p53 in DJ-1 siRNA-treated cells compared to controls.
Downregulation of DJ-1 impairs nuclear translocation of Nrf2, causing decreased antioxidant gene expression and increased oxidative damage. The decline in DJ-1 levels leads to heightened CEC susceptibility to UV-A light by activating p53-dependent apoptosis. Targeting the DJ-1–Nrf2 axis may provide a potential therapeutic approach for enhancing antioxidant defense in corneal endothelial disorders.
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