Propolis and Caffeic Acid Phenethyl Ester Attenuate Oxidative and Nitrosative Stress in Rat Kidney Tissue After Cranial Irradiation

Radiation-induced bystander effect (RIBE) contributes to oxidative and nitrosative stress in non-irradiated tissues following ionizing radiation (IR). This study investigated the protective effects of propolis and caffeic acid phenethyl ester (CAPE) against RIBE-mediated renal injury after total cranial irradiation in rats. Forty-eight male Sprague–Dawley rats were assigned to six groups: IR, IR + propolis, IR + CAPE, propolis control, CAPE control, and sham. A single 5 Gy cranial gamma irradiation was administered. Propolis (80 mg/kg/day, orally) and CAPE (10 μmol/kg/day, intraperitoneally) were given for 10 days. Renal antioxidant (SOD, GSH-Px, GST), oxidative (XO, MDA), and nitrosative (NOS, NO) parameters were evaluated. Multivariate analyses, including principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA), were performed. IR significantly decreased SOD activity and increased XO, MDA, NOS, and NO levels. Both propolis and CAPE effectively reversed these alterations, with propolis showing a more pronounced effect on oxidative stress markers. GSH-Px and GST activities remained unchanged. The findings suggest that propolis and CAPE attenuated oxidative/nitrosative changes in kidney tissue, consistent with a possible bystander-associated systemic response.