Nrf2 Lowers the Risk of Lung Injury via Modulating the Airway Innate Immune Response Induced by Diesel Exhaust in Mice

In the present study, we investigated the role of Nrf2 in airway immune responses induced by diesel exhaust (DE) inhalation in mice. C57BL/6J Nrf2(+/+) and Nrf2(-/-) mice were exposed to DE or clean air for 8 h/day and 6 days/week for 4 weeks. After DE exposure, the number of neutrophils and macrophage inflammatory protein (MIP)-2 level in bronchoalveolar lavage fluid (BALF) and interleukin (IL)-17 level in the lung tissue increased in Nrf2(-/-) mice compared with Nrf2(+/+) mice; however, the lack of an increase in the level of tumor necrosis factor (TNF)-alpha in the lung tissue in Nrf2(+/+) mice and mild suppression of the level of TNF-alpha in Nrf2(-/-) mice were observed; the level of granulocyte macrophage colony-stimulating factor (GM-CSF) in the lung tissue decreased in Nrf2(-/-) mice than in Nrf2(+/+) mice; the number of DE particle-laden alveolar macrophages in BALF were larger in Nrf2(-/-) mice than in Nrf2(+/+) mice. The results of electron microscope observations showed alveolar type II cell injury and degeneration of the lamellar body after DE exposure in Nrf2(-/-) mice. Antioxidant enzyme NAD(P)H quinone dehydrogenase (NQO)1 mRNA expression level was higher in Nrf2(+/+) mice than in Nrf2(-/-) mice after DE exposure. Our results suggested that Nrf2 reduces the risk of pulmonary disease via modulating the airway innate immune response caused by DE in mice.