Investigation of effect of cholecalciferol on retinal tissue in experimental diabetic rat model

Retinopathy is one of the most common complication of diabetes. It is among the leading causes of blindness in worldwide at working aged adults. In the pathophysiology of changes that increase the effect of diabetes on retinopathy; oxidative stress, apoptosis, and uncontrolled vascular proliferation. The aim of this study is investigate the effects of VEGF, TRPM2, PCNA immunoreactivity, apoptosis and oxidative stress levels in retinal tissue at streptozotocin induced diabetic rats, also effect of cholecalciferol on this parameters. In the study, a total of 41, 8-10 weeks old male Wistar albino rats were randomly selected and divided into 5 groups. Experimental animals in groups I, II and III consisted of 7 rats; group I (Control group received no administration during the 10-week experiment), II (Citrate Buffer; single dose 0.1 M sodium citrate buffer i.p) and III (Vitamin D; 200 IU/day orally), with 10 animals in groups IV and V; group IV (Diabetes; i.p in single dose 60 mg/kg STZ 0.1 M sodium citrate buffer (pH:4.5) and V (Diabetes+Vitamin D; in a single dose 60 mg/kg STZ 0.1 M sodium citrate buffer (pH:4.5) and vitamin D 200 IU/day orally). After 72 hours, blood was obtained from the tail vein of the rat and whose glucose level is over 250 mg/dl is considered diabetic. After 10 weeks, after the decapitation, all eyes were enucleated. The VEGF, TRPM2 and PCNA of the retinal tissues were examined by immunohistochemical method by taking sections from the tissues embedded in paraffin blocks. The TUNEL method was used to the tissue sections to identify apoptosis progressing cells. Histocorrection was performed based on the prevalence and severity of immunoreactivity in the stain. Total oxidant and antioxidant capacity was analyzed in serum by ELISA method. There was a statistically significant increase in TOS, VEGF, PCNA, TRPM2 and apoptosis levels in diabetes group compared to other groups; decrease in TAS level was observed (p<0.05). There was a statistically significant increase in TAS levels in the diabetes+ cholecalciferol group when compared with the diabetes group; TOS, VEGF, PCNA, TRPM2 levels and apoptotic cells decreased (p<0.05). As a result of this study, experimental diabetes increased apoptotic cells, VEGF, PCNA and TRPM2 levels in retinal tissue; it has been observed that cholecalciferol given as a treatment has reduced these parameters. It has been concluded that TRPM2 and PCNA may play an important role in the pathophysiological mechanism of diabetic retina effect as well as VEGF. In our study, it was concluded that cholecalciferol could reduce the effects of diabetes on the retina. Keywords: Rat, Diabetic retinopathy, Cholecalciferol, TRPM2, PCNA, VEGF