Caffeic Acid Alkyl Amide Derivatives Ameliorate Oxidative Stress and Modulate ERK1/2 and AKT Signaling Pathways in a Rat Model of Diabetic Retinopathy

The purpose of this study was to examine the neuroprotective effects of caffeic acid hexyl ( CAF6 ) and dodecyl ( CAF12 ) amide derivatives on the early stage of retinopathy in streptozotocin‐induced diabetic rats. Animals were divided in five groups (n=8/group); one group consisted of non‐diabetic rats as control, while the other four were diabetic animals either non‐treated or treated with CAF6 , CAF12 or resveratrol intravitreally for four weeks. Retinal superoxide dismutase (SOD) activity and 8‐iso‐prostaglandin F_2α (iPF_2α) levels were evaluated by an ELISA assay. Phosphorylation of ERK1/2 and AKT was determined by immunoblotting in retinal homogenates. Retinal morphology was also examined using light microscopy. Treatment with CAF6 and CAF12 increased retinal SOD activity, while it decreased iPF_2α levels in diabetic rats. Phosphorylation of ERK1/2 was increased, while AKT phosphorylation was decreased in diabetic rats compared to normal control and these alterations were significantly reversed in diabetic rats treated with CAF6 and CAF12 . Furthermore, thickness of the whole retinal layer, outer nuclear layer, and ganglion cell count were decreased in diabetic rats compared to control and CAF6 and CAF12 treatments prevented these changes. CAF6 and CAF12 seem to be effective agents for treatment of diabetic retinopathy via attenuation of retinal oxidative stress and improvement of neuronal survival signaling.