melatonin ameliorates the production of cox-2, inos, and the formation of 8-ohdg in the non-targeted lung tissue after pelvic irradiation

background: in this study, the bystander effect of radiation was evaluated on the regulation of cox-2, inos, and 8-ohdg in the lung tissues of sprague-dawley rats with and without pre-administration of melatonin. materials and methods: a 2×2 cm area of the pelvis of male sprague-dawley rats with and without pre-administration of melatonin (100 mg/kg) by oral and ip injection was irradiated with 3 gy dose of 1.25 mev γ-rays, and alterations in the level of cox-2, inos, and 8-ohdg in out-of-field lung of animals were detected by enzyme immunoassay. results: the bystander effect significantly increased the level of cox-2, inos, and 8-ohdg in non-targeted lung tissues (p < 0.05). melatonin ameliorated the bystander effect of radiation and reduced the level of all examined biomarkers significantly (p < 0.05). according to the results, the ameliorating effect of pre-intraperitoneal injection of melatonin was noticeably more compared to oral pre-administration. conclusion: our findings revealed that the bystander effect of radiation could induce oxidative dna damage and increase the level of imperative cox-2 and inos in non-targeted lung tissues. interestingly, melatonin could modulate the indirect destructive effect of radiation and reduce dna damage in non-targeted cells.