Effects of melatonin on the oxidant/antioxidant status and lung histopathology in rabbits exposed to cigarette smoke

Abstract

To evaluate the effects of cigarette smoking on the histopathology and the oxidant/antioxidant status of the lungs and to test the potential antioxidant benefits of melatonin on these induced changes. Rabbits were exposed to cigarette smoke in a glass chamber for 1 h daily for 1 month with or without intraperitoneal melatonin injection. A melatonin control group was given intraperitoneal melatonin only. A control group was exposed to clean air only. At the end of 1 month, animals were sacrificed and lung tissues were examined histopathologically. Blood levels of protein sulphydryls, carbonyls, prostaglandin F2alpha (PGF2alpha), malondialdehyde (MDA), glutathione peroxidase and superoxide dismutase (SOD) were measured. Intraparenchymal vascular congestion and thrombosis, intraparenchymal haemorrhage, respiratory epithelial proliferation, number of macrophages in the alveolar and bronchial lumen, alveolar destruction, emphysematous changes and bronchoalveolar haemorrhage scores were significantly increased in rabbits exposed to cigarette smoke compared with the control group. Protein sulphydryls and SOD levels were significantly decreased; carbonyls, PGF2alpha and MDA levels were significantly increased in the smoke exposed rabbits. Administration of melatonin to rabbits exposed to cigarette smoke caused a reduction in the bronchoalveolar haemorrhage score and blood carbonyls levels. Other parameters were unaffected by melatonin. Exposure to cigarette smoke causes severe histopathological changes and negatively affects the oxidant/antioxidant status in the lungs of rabbits. A low daily dose of melatonin has some protective effects on histopathological changes and oxidant/antioxidant status of the lungs in smoke exposed rabbits.