Effects of polystyrene particle density on type II pneumocytes

Studies into the effects of ultrafine particles on the lung have shown adverse outcomes and are do in part to the particle size. Inhalation of small particles is associated with exacerbation of respiratory diseases in epidemiological studies. Ultrafine particles have been hypothesized to play an important role, but it is unclear as to whether a dose response type of relationship exists. The aim of the present study was to investigate the role of ultrafine particle number on lung cells and to describe the effects due to phagocytosis of particles by the cells. A549 cells are a transformed cell line similar to type II lung pneumocytes. A549 cells seeded at a density of 5 x 10(4) cells were treated with 1000, 5000, and 10,000 polystyrene particles and incubated at 37 degrees C for periods of 24, 48, and 72 hours. Cell number, protein, and MDA levels were determined on the treated cells and compared with untreated controls. The lung cells were also observed microscopically to assess cell damage. Lung cells exposed for 24 hours with 1,000 and 5,000 particles showed the greatest increase in cell number. Cellular protein levels were similar for all groups (p > 0.05) for the duration of the study. MDA levels for treated groups at 24 and 72 hours were not statistically different from the control groups. Cells treated at 48 hours with 5,000 and 10,000 particles showed slight increases in the MDA levels above low particle number and control treated groups. Morphological evaluation of the cells revealed increased inclusions with increasing dose. The results from this study indicate the ability of A549 cells to respond to a challenge with ultrafine particles. The concentrations tested caused an initial stimulation cell proliferation at 24 hours followed by increased damage at 48 hours. Future studies will focus on the inflammatory products formed by ingestion of the ultrafine particles.