Evaluation of the radioprotective effects of thymoquinone on dynamic thiol-disulphide homeostasis during total-body irradiation in rats

Abstract

Ionizing radiation-induced free radicals cause functional and structural harmful effects. Thiol, an important antioxidant, plays a major role in the eradication of reactive oxygen molecules. Thiol/disulphide homeostasis is a marker of oxidative stress. The objective of this study was to assess the potential radioprotective effects of thymoquinone (TQ) on the dynamic thiol/disulphide homeostasis of rats receiving total-body irradiation (IR). Twentytwo rats were divided into three groups to test the radioprotective effectiveness of TQ. The sham control group did not receive TQ or IR. The IR group received only total-body IR. The TQ + IR group received IR plus TQ. Following IR, blood samples were taken. The thiol/disulphide homeostasis parameters were analysed by a newly established method. In the IR group, native thiol and the native thiol/total thiol ratio were significantly decreased (P = 0.003 and P = 0.003, respectively), whereas the disulphide/native thiol and disulphide/total thiol ratios were significantly increased when compared with those of the sham control group (P = 0.003 and P = 0.003, respectively). In the TQ + IR group, the mean disulphide, native thiol and total thiol levels and the disulphide/ native thiol, disulphide/total thiol and native thiol/total thiol ratios were not found to be significantly different when compared with those of the sham control group (P > 0.05 for all). Thiol/disulphide homeostasis was found to be disturbed after IR exposure. The results showed that TQ had antioxidant effects and reduced the IRinduced oxidative stress, which was demonstrated through the dynamic thiol/disulphide homeostasis. Thus, the use of TQ before radiation treatment helped protect the rats from oxidant side effects.