Hyperglycaemia Exacerbates Choroidal Neovascularisation in Mice via the Oxidative Stress-Induced Activation of STAT3 Signalling in RPE Cells

Choroidal neovascularisation (CNV) that occurs as a result of age-related macular degeneration (AMD) causes severe vision loss among elderly patients. The relationship between diabetes and CNV remains controversial. However, oxidative stress plays a critical role in the pathogenesis of both AMD and diabetes. In the present study, we investigated the influence of diabetes on experimentally induced CNV and on the underlying molecular mechanisms of CNV. CNV was induced via photocoagulation in the ocular fundi of mice with streptozotocin-induced diabetes. The effect of diabetes on the severity of CNV was measured. An immunofluorescence technique was used to determine the levels of oxidative DNA damage by anti-8- hydroxy-2-deoxyguanosine (8-OHdG) antibody, the protein expression of phosphorylated signal transducer and activator of transcription 3 (p-STAT3) and vascular endothelial growth factor (VEGF), in mice with CNV. The production of reactive oxygen species (ROS) in retinal pigment epithelial (RPE) cells that had been cultured under high glucose was quantitated using the 2',7'-dichlorofluorescein diacetate (DCFH-DA) method. p-STAT3 expression was examined using Western blot analysis. RT-PCR and ELISA processes were used to detect VEGF expression. Hyperglycaemia exacerbated the development of CNV in mice. Oxidative stress levels and the expression of p-STAT3 and VEGF were highly elevated both in mice and in cultured RPE cells. Treatment with the antioxidant compound N-acetyl-cysteine (NAC) rescued the severity of CNV in diabetic mice. NAC also inhibited the overexpression of p-STAT3 and VEGF in CNV and in RPE cells. The JAK-2/STAT3 pathway inhibitor AG490 blocked VEGF expression but had no effect on the production of ROS in vitro. These results suggest that hyperglycaemia promotes the development of CNV by inducing oxidative stress, which in turn activates STAT3 signalling in RPE cells. Antioxidant supplementation helped attenuate the development of CNV. Thus, our results reveal a potential strategy for the treatment and prevention of diseases involving CNV.