The radioprotective effects of melatonin and nano selenium on DNA double-strand breaks in peripheral lymphocytes caused by I-131

One of the treatment modalities for thyroid cancer and hyperthyroidism is radioiodine-131 (I-131) therapy. The use of this therapeutic modality is not completely safe and can lead to oxidative stress, eventually DNA damages. However, these radiation-induced damages can be reduced by antioxidants. This study aimed to investigate the potential radioprotective effects of melatonin and selenium nanoparticles (SeNPs) on DNA double-stranded breaks (DSBs) caused by I-131. After obtaining informed consent, 6 ml blood was taken from each volunteer. The samples were divided into two general groups of control (without I-131) and with I-131. Each group was also divided into three subgroups, including without antioxidant, melatonin, and SeNPs. The samples of control group were incubated for 2 h after adding the antioxidants. The samples of I-131 group were first incubated for 1 h with the antioxidants and then the samples re-incubated for another 1 h after adding the I-131. Then, the samples were prepared for γH2AX assay. The findings showed that after 1 h of incubation with 20 μCi I-131/2 mL, the Dnsb levels increased by 102.9% in comparison with the control group. In the I-131 group, there were significant reductions of the DSB levels after incubation with melatonin (P < 0.001) and SeNPs (P < 0.001) in comparison with the without antioxidant subgroup. Furthermore, the DSB levels at the melatonin + I-131 and the SeNPs + I-131 subgroups decreased to 38% and 30%, respectively, compared to the I-131 subgroup. According to the obtained findings, it can be concluded that the use of melatonin and SeNPs (as radioprotector agents) can reduce the DSB levels induced by I-131 in peripheral lymphocytes. (author)