Investigation of the protective effects of cafeic acid and cafeic acid phenethyl ester in ocular tissues in a diabetic rat model

Aim: We aimed to investigate the effect of caffeic acid phenethyl ester (CAPE) on retinal apoptosis and oxidant stress parameters in streptozotocin (STZ) induced diabetic rat model. Material and Methods: This study included 3 groups, control, STZ, and STZ+CAPE. Rats of STZ, and STZ+CAPE groups were injected with STZ (35mg/kg, i.p.) for induction of DM. In the STZ+CAPE group, 10 µmol/kg of CAPE were intraperitoneally injected for 4 weeks. Control and STZ groups were given only intraperitoneal serum physiologic. Rats were anaesthetized and sacrificed on the 4th week of the experiment. Total anti-oxidant status (TAS), total oxidant status (TOS), Paroxanase (PON) levels were measured on the dissected retinal tissues. Fellow eyes were used for histopathologic evaluation with caspase-3 and matrix metalloproteinase (MMP-2) ve MMP-9 evaluation. Results: Blood glucose levels were significantly decreased at 21st day of the experiment with CAPE treatment. However this hypoglisemic effect was not observed at 28th day. The oxidative stress parameters including TOS, and OSI were significantly higher in STZ group compared to STZ+CAPE and control groups. CAPE treatment prevented the elevation of TOS. However PON levels were comparable between STZ+CAPE and STZ groups. The MMP levels of both serum and retina were not different between groups. Retinal caspase-3 staining were also similar. Conclusion: This study demonstrated that the CAPE treatment may decrease the oxidative stress in the retinal tissue in STZ induced DM rat model. However the apoptosis was not observed in the retina. The retinal apoptosis can not be shown probably due to shorter period of diabetes. Key words: Caffeic acid phenethyl ester, streptozotocin, diabetes mellitus, diabetic retinopathy, caspase-3, oxidative stress, antioxidant capacity.