The Study Of The Damage And Its Mechanisms On Lung Cells Induced By Ambient Particulate Matter In Beijing Urban Area

Objective: Air pollution is one of the most important risk factor which always affects public health. Particulate matter (PMs) is a landmark pollutant which is used as the quantitative evaluation of health hazards in air pollution study. Particulate matter, especially the inhalable particles with aerodynamic diameters less than 10μm (PM₁₀), is the main pollutants in many major cities of our coountry. In recent years, increasingly more studies on epidemiological and toxicological data show that PMs is closely associated with morbidity and mortality of human disease. It can cause asthma, decline of lung function, respiratory inflammation, even involving the cardiovascular system, nervous system, immune system, and cancer development. But the toxicology mechanisms are not clear. Therefore, the study of the toxicological mechanisms of PMs has important practical significance and will supply scientific base for strengthening particulate matter pollution control and the health protection of susceptible population.Methods: The coarse and fine particulate matters were collected in heating period in the urban area of Beijing. The total PM₁₀ and PM_2.5 were extracted by water ultrasonic method and were dissolved in different concentrations. Contents of metal elements and size distribution were determined by inductively coupled plasma chromatography-mass spectrometry and scanning electron microscope (SEM). Contents of organic components in PMs were measured by GC/MS analysis. RAW264.7 cells, A549 cells and RAW264.7-A549 cells models were applied which simulate the process of in vivo exposure. Cytotoxicity of PMs was measured by MTT assay. The damage degree of DNA single- and double-strand breaks were measure by Comet assay. The activity of NF-κB was measured by EMSA and ELISA binding assay. The levels of inflammatory cytokines NO expressions were determined using the nitrate reductase method. The NOS activity was detected by Colorimetry. The significance of results was determined by employing SPSS vl2.0 package. All data are expressed as mean±SD. One-way analysis of variance (ANOVA) , t test and linear correlation analysis were user in data treatment. Two tailed tests of significance were employed and significance was assumed at p≤0.05 or p≤0.01.Results: The results showed that (1) During the heating period in Beijing urban area, a number of metal elements, mainly including Ca, Fe, Zn, Mg, Al and Pb were detected. PM_2.5 have higher elements contents compared to PM₁₀. PM₁₀ and PM_2.5 also contain many organic contaminations, such as Benzene, alkane, fatty- hydrocarbon, benzaldehyde and their derivatives. The results showed that most of PMs' distributions were less 10μm by the particle size analysis. It suggested Automobile-exhaust have become the mainly polluting source in Beijing. (2) PM₁₀ and PM_2.5 had toxic effects to RAW264.7 and A549 that were treated for 24h. PMs in low doses induced cell proliferation, but inhibited cell proliferation in high doses, and the cell liabilities were decreased with the increased concentrations. (3) DNA single- and double-strand breaks were obviously increased in RAW264.7 cells, A549 cells and RAW264.7- A549 combined cells exposed to PM₁₀ and PM_2.5, with the significant dose-response relationship (r=0.970⁰.980, p<0.01), and double-strand damage is more serious than single-strand damage. (4) The activity of NF-κB were increased in cell nuclear, but decreased in cell plasma after exposed to PM₁₀ and PM_2.5 with the significant dose-response relationship (r=0.980～0.982, p<0.01), which suggest that activated NF-κB can move into the cell nuclear and produce effective function. (5) The levels of NO were increased in cells in PM₁₀ and PM_2.5, but the activity of NOS had not obvious relation with PM₁₀ and PM_2.5 concentration. (6) Suspension with activated factors induced by PMs in RAW264.7 cells can make A549 cells further to release more NO, increase the activity of NF-κB, produce DNA damage. It suggested A549 is the target of RAW264.7 cell. It may effects the cell through the expression of RAW264.7 cell.Conclusion: Both PM₁₀ and PM_2.5 contains a variety of metal elements and organic pollutants, and consist of particles which sizes are less than 1μm in Beijing urban area. PMs have toxic effect on RAW264.7 and A549 cell. PMs can induce oxidative and inflammatory damage after treated with PM₁₀ and PM_2.5 for 24h. A549 cell probably is the target of RAW264.7 cell, PM_2.5 may have more toxic than PM₁₀.