Modulation of Radiation-Induced NADPH Oxidases in Rat’s Heart Tissues by Melatonin

Background: Experimental studies have shown that infiltration of inflammatory cells as well as upregulation of some cytokines play a central role in the development of late effects of ionizing radiation in heart tissues. Evidences have shown that an increased level of TGF-β has a direct correlation with late effects of exposure to ionizing radiation such as chronic oxidative stress and fibrosis. Recent studies have shown that TGF-β, through upregulation of pro-oxidant enzymes such as NOX2 and NOX4, promotes continuous ROS production and accumulation of fibrosis. Objective: In present study, we aimed to evaluate the expression of NOX2 and NOX4 signaling pathways as well as possible modulatory effects of melatonin on the expression of these genes.Material and Methods: In this experimental study, four groups of 20 rats (5 in each) were used as follows; G1: control; G2: melatonin; G3: radiation; G4: radiation + melatonin. 100 mg/kg of melatonin was administrated before irradiation of heart tissues with 15 Gy gamma rays. 10 weeks after irradiation, heart tissues were collected for real-time PCR. Results: Results showed a significant increase in the expression of TGF-β, Smad2, NF-kB, NOX2 and NOX4. The upregulation of NOX2 was more obvious by 20-fold compared to other genes. Except for TGF-β, melatonin could attenuate the expression of other genes. Conclusion: This study indicated that exposure of rat’s heart tissues to radiation leads to upregulation of TGF-β-NOX4 and TGF-β-NOX2 pathways. Melatonin, through modulation of these genes, may be able to alleviate radiationinduced chronic oxidative stress and subsequent consequences.