The effect of light/dark cycle changes on vascular permeability, inflammation and visual cycle in streptoyotocin-induced diabezic retinophaty in rats

Abstract

Introduction: Diabetic retinopathy (DR) is not cured efficiently and changes of lifestyle measures may alleviate its course. The aim of our study was to investigate the effects of shortened daily photoperiod on inflammation and visual cycle in rat retina and retinal pigment epithelium (RPE) in DR. Methodology: Male Wistar rats were divided into the following groups: 1. control; 2. diabetic group (DM) treated with a single intraperitoneal injection of streptozotocin (100 mg/kg); 3. group exposed to light/dark cycle 6/18h for 3 months (6/18); 4. diabetic group exposed to light/dark cycle 6/18h (DM+6/18). Retinal blood vessel permeability was estimated immunohistochemically based on lectin staining, while the expression of genes involved in the visual cycle (SOX9, LRAT, RPE65, OTX2), and inflammation (IL-1, TNF-α) was determined by qRT-PCR in the retina and RPE. Results: Shortened photoperiod reduced neovascularisation and the expression of IL-1 and TNF-α in both retina and RPE. The expression of IL-1 and TNF-α genes in the retina was significantly higher in DM vs. control group (P=0.001). In contrast, retinal IL-1 and TNF-α expressions were significantly lower in DM+6/18 vs. DM group (P=0.001). The expression of IL-1 and TNF-α in RPE was significantly higher in DM vs. control group, however the expression of these genes was significantly lower in DM+6/18 vs. DM group (PIL-1=0.008 and PTNF-α=0.002). The expression of visual cycle genes was significantly up-regulated in RPE in DM+6/18 vs. DM group (P=0.001). Conclusion: Shortened daily photoperiod reduces blood vessel permeability in DR via its anti-inflammatory effect associated with accelerated visual cycle in the retina.