Inflammatory response and endothelial dysfunction in the hearts of mice co-exposed to SO2 , NO2 , and PM2.5.

SO2 , NO2 , and PM2.5 are typical air pollutants produced during the combustion of coal. Increasing evidence indicates that air pollution has contributed to the development and progression of heart-related diseases over the past decades. However, little experimental data and few studies of SO2 , NO2 , and PM2.5 co-exposure in animals exist; therefore, the relevant mechanisms underlying this phenomenon are unclear. An important characteristic of air pollution is that co-exposure persists at a low concentration throughout a lifetime. In the present study, we treated adult mice with SO2 , NO2 , and PM2.5 at various concentrations (0.5 mg/m3 SO2 , 0.2 mg/m3 NO2 6 h/d, with intranasal instillation of 1 mg/kg PM2.5 every other day during these exposures; or 3.5 mg/m3 SO2 , 2 mg/m3 NO2 6 h/d, and 10 mg/kg PM2.5 for 28 d). Blood pressure (BP), heart rate (HR), histopathological damage, and inflammatory and endothelial cytokines in the heart were assessed. The results indicate that co-exposure caused endothelial dysfunction by elevating endothelin-1 (ET-1) expression and repressing the endothelial nitric oxide synthase (eNOS) level as well as stimulating the inflammatory response by increasing the levels of cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). Additionally, these alterations were confirmed by histological staining. Furthermore, we observed decreased BP and increased HR after co-exposure. Our results indicate that co-exposure to SO2 , NO2 , and PM2.5 may be a major risk factor for cardiac disease and may induce injury to the hearts of mammals and contribute to heart disease.