Methylene blue protects against paraquat-induced acute lung injury in rats.

Methylene blue (MB) attenuates acute lung injury (ALI) induced by liver or pancreas ischemia-reperfusion. But the protective effects of MB on paraquat (PQ)-induced ALI have not been elucidated. In this study, we aimed to study the effects of MB on ALI caused by PQ in rats. Male Sprague-Dawley rats were challenged acutely by PQ (25mg/kg, i.p.) with or without MB posttreatment (2mg/kg, i.p.) 2h after PQ administration. Lung specimens and the bronchoalveolar lavage fluid were isolated for pathological examinations and biochemical analyses 24h after PQ exposure. We found that the administration of MB significantly increased the activity of superoxide dismutase and decreased lung wet dry radio, the content of malondialdehyde and lactate dehydrogenase, the total cell number and the level of myeloperoxidase in bronchoalveolar lavage fluid. Pathological examination also revealed that MB alleviated PQ-induced histological damage. These results provide evidence that MB may be a new therapy in the treatment of PQ-induced ALI.