Abstract
Purpose: Retinal ischemia in diabetic retinopathy (DR) is caused by the apoptosis of capillary pericytes and endothelial cells. In this study, we investigated the role of the Parkinson-associated protein DJ-1 (PARK7) in retinal capillary degeneration. Methods: DJ-1 levels were measured in diabetic and non-diabetic human retinas by immunostaining and Western blotting. Human retinal endothelial cells (HRECs) were cultured in high glucose or with a cytokine mixture (CM). The effect of inhibition of DJ-1 in HREC with isatin on Nε-carboxymethyl lysine (CML), inducible nitric oxide synthase (iNOS), nuclear factor erythroid 2-related factor (Nrf2), nuclear factor kappa (NF-κB), and cleaved caspase-3 was investigated. AAV2-PARK7, driven by the endothelial cell-specific Tie2 promoter, was intravitreally injected into the mouse's eyes, and the effect of the retinal transduced DJ-1 on capillaries was investigated following ischemia/reperfusion injury. Results: DJ-1 levels were observed to be reduced in human retinas with DR and in HREC cultured under high-glucose conditions. Isatin treatment increased the CML and iNOS levels in HREC. Treatment of HREC with CM promoted nuclear translocation of NF-κB and activation of caspase-3; co-treatment with isatin further exacerbated these effects. Isatin treatment significantly suppressed the CM-induced Nrf2 translocation in HREC. Intravitreal injection of AAV2-tie2-PARK7 resulted in high expression of DJ-1 in retinal capillaries and significantly reduced formation of acellular capillaries from ischemia/reperfusion injury. Conclusions: The results suggest that DJ-1 protects retinal capillary endothelial cells from damage caused by hyperglycemia and ischemia and that enhancing DJ-1 activity could be a strategy for mitigating early retinal damage in DR.