The Radioprotective Effects of Caffeic Acid Phenethyl Ester and Thymoquinone on Oxidative and Nitrosative Stress in Liver Tissue of Rats Exposed to Total Head Irradiation.

Objective The aim of this study is to investigate the effects of addition of caffeic acid phenethyl ester (CAPE) and thymoquinone (TQ) on oxidative and nitrosative stress in the liver tissue of irradiated rats. Methods Forty Sprague-Dawley rats were divided into five groups to test the radioprotective effectiveness of TQ and CAPE administered by intraperitoneal injection. Appropriate control groups were also studied. Results Liver antioxidant capacity, as measured by levels of total superoxide scavenger activity (TSSA), non-enzymatic superoxide scavenger activity (NSSA) and glutathione-S-transferase (GST) activity except superoxide dismutase (SOD) activity, were statistically lower in the irradiation (IR) group compared to all other groups. Total superoxide scavenger activity and NSSA were statistically higher in the IR plus TQ and IR plus CAPE groups compared to all other groups. In contrast, glutathione peroxidase (GSH-Px) activity was significantly found to increase in the IR plus CAPE group compared to control groups. The xanthine oxidase (XO), nitric oxide synthase (NOS) activities, nitric oxide (NO●) and malondialdehyde (MDA) levels in the IR group were statistically higher than in the other groups. Moreover, XO activity in the IR plus TQ group was statistically lower than all other groups including the IR plus CAPE group. In addition, NO● level was found to increase in all groups when compared to the normal control group. Conclusions Thymoquinone and CAPE decrease oxidative and nitrosative stress markers and have antioxidant effects, which also increase antioxidant capacity in the liver tissue of irradiated rats.