Abstract
Exposure to particulate matter ≤2.5 µm in diameter (PM2.5) profoundly affects human health. However, the role of PM2.5 on lung injury and cytokine levels in mice is currently unknown. The aim was to examine the effect of PM2.5 pollution on lung injury in mice fed at an underground parking lot. A total of 20 female Kunming mice were randomly divided into control and polluted groups, with 10 rats in each group. The control group was kept in the laboratory, while the pollution group was fed in an underground parking lot. The concentrations of pollutants were measured using ambient air quality monitoring instruments. After 3 months of treatment, the lungs were collected and examined using electron microscopy, and the morphological structures were assessed using hematoxylin and eosin staining. The polarization of macrophages was evaluated by immunofluorescence. The concentration of interleukin (IL)-4, tumor necrosis factor (TNF)-α and transforming growth factor (TGF)-β1 in peripheral sera were assessed by ELISA. The mRNA and protein levels of IL-4, TNF-α, and TGF-β1 in lung tissues were assessed by reverse transcription-quantitative polymerase chain reaction and western blot analyses, respectively. In the polluted group, the levels of CO, NOx and PM2.5 were significantly higher compared with the control group. Compared with the controls, intracellular edema, an increased number of microvilli and lamellar bodies, smaller lamellar bodies in type II alveolar epithelial cells, and abundant particles induced by PM2.5 in macrophages were observed in the polluted group. The lung ultrastructure changed in the polluted group, revealing exhaust-induced lung injury: The tissues were damaged, and the number of inflammatory cells, neutrophils, polylymphocytes and eosinophils increased in the polluted group compared with the control group. The authors also observed that the number of M1 and M2 macrophages markedly increased after the exhaust treatment. The levels of IL-4, TNF-α and TGF-β1 in the sera and tissues were significantly increased in the polluted group. PM2.5 pollutants in underground garages can lead to lung injury and have a significant impact on the level of inflammatory cytokines in mice. Therefore, the authors suggest that PM2.5 can activate the inflammatory reaction and induce immune dysfunction, leading to ultrastructural damage.