Time-dependent changes in hypoxia- and gliosis-related factors in experimental diabetic retinopathy

Limin Gu,Jingfa Zhang,Chaoyang Zhang,Hua Xu,Qian Yang,Limei Zhang

doi:10.1038/s41433-018-0268-z

Abstract

Diabetes causes various biochemical changes in the retina; long-term changes in the factors associated with hypoxia and gliosis have rarely been reported. The present study was conducted to explore the changes in these factors in a time-dependent manner in experimental diabetic retinopathy (DR). Diabetes was induced in Sprague–Dawley rats by intraperitoneal injection of streptozotocin. The expression of the following factors was examined using immunofluorescence and western blot analysis at 0.5, 1, 2, 4 and 6 months after diabetes onset: hypoxia-inducible factor-1alpha (HIF-1alpha), vascular endothelial growth factor (VEGF), erythropoietin (EPO), erythropoietin receptor (EPOR), glial fibrillary acidic protein (GFAP), vimentin, glutamate-aspartate transporter (GLAST) and glutamine synthase (GS). The expression of factors such as HIF-1alpha, VEGF, EPO, EPOR, GFAP and vimentin, was up-regulated with the progression of diabetes in the diabetic rat retinas compared to the expression in normal control retinas, whereas the expression of GS and GLAST was down-regulated. Changes in EPO and EPOR appeared 2 weeks after diabetes onset. HIF-1alpha, VEGF and GFAP started to increase at 1 month and vimentin at 4 months after diabetes onset. GS and GLAST started to decrease at 1 month after diabetes onset. The expression of these factors, which are involved in the processes of hypoxia and gliosis, varied at different stages of DR. The time-course change may be helpful in the evaluation of the progression of DR, and it may indicate the optimal intervention time points for DR.

Highlights

Diabetic retinopathy (DR) remains a major complication of diabetes and a leading cause of blindness among adults worldwide
Immunofluorescence showed mild HIF-1alpha staining in the normal control group, whereas there was enhanced staining in the 4-month diabetic retinas; the staining was mainly confined to the area of retinal vasculature (Fig. 2b)
● Diabetes causes various biochemical changes in the retina; long-term changes in the factors associated with hypoxia and gliosis have rarely been reported

Summary

Introduction

Diabetic retinopathy (DR) remains a major complication of diabetes and a leading cause of blindness among adults worldwide. Hyperglycaemia induces abnormal functioning of the mitochondria, up-regulates the production of excess reactive oxygen species, injures vascular endothelial cells and increases inflammatory factors. These changes promote leukostasis and micro-thrombosis formation, which induce local capillary occlusion resulting in retinal hypoxia; this leads to increased expression of hypoxia-inducible factor1alpha (HIF-1alpha), vascular endothelial growth factor (VEGF), erythropoietin (EPO) and EPO receptor (EPOR) [4]. VEGF is the main factor causing breakdown of the blood–retinal barrier (BRB) and retinal neovascularisation, which lead to diabetic macular oedema (DME) and proliferative DR [5, 6]. Anti-VEGF therapy has become popular in the treatment of different ophthalmic diseases, such as proliferative DR [7], DME [8], neovascular age-related macular degeneration [9], retinopathy of prematurity [10]

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