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

In this study, we evaluated the bystander effect of radiation on the regulation of cyclooxygenase- 2 (cox-2), inducible nitric oxide synthase (inos), and 8-hydroxydeoxyguanosine (8-ohdg) in lung tissues of sprague-dawley rats with and without pre-administration of melatonin. a 2×2 cm2 area of the pelvis of male sprague-dawley rats with and without pre-administration of melatonin (100 mg/kg) by oral and intraperitoneal injection was irradiated with a 3 gy dose of 1.25 mev γ-rays. alterations in the levels of cox-2, inos, and 8-ohdg in the out-of-field lung areas of the animals were detected by enzyme immunoassay. the bystander effect significantly increased cox-2, inos, and 8-ohdg levels in non-targeted lung tissues (p<0.05). melatonin ameliorated the bystander effect of radiation and significantly reduced the level of all examined biomarkers (p<0.05). the results indicated that the ameliorating effect of a pre-intraperitoneal (ip) injection of melatonin was noticeably greater compared to oral pre-administration. our findings revealed that the bystander effect of radiation could induce oxidative dna damage and increase the levels 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.