OBJECTIVESParticulate air pollution is a serious problem all over the world, and the development of a method to evaluate the health effects of ambient particles is necessary. In this study, cells cultured in vitro were exposed to particles sampled at the side of a main road, and their protein expression levels were examined.

METHODSAmbient particles were collected at the side of a main road using a high-volume air sampler. Some of the collected particles (crude particles) were treated with an organic solvent to remove chemical components, and the resulting residues were used as residual particles. Cells from the mouse alveolar epithelial cell line LA-4 were inoculated into tissue-culture dishes at 1.4×10(4)/cm(2), exposed to each type of particle or artificial carbon particles (Printex 90) that were dispersed using an ultrasonic homogenizer by mixing in the medium twice at 24 and 48 hours, and incubated for up to 72 hours after the start of inoculation. After exposure, the number of cells and intracellular dehydrogenase activity were measured. Proteins extracted from the cells were subjected to two-dimensional gel electrophoresis with isoelectric focusing at pHs 4-7 using a 10% acrylamide gel, and their expression levels were analyzed after fluorescent staining.

RESULTSThe intracellular dehydrogenase activity of the cells significantly decreased as a result of exposure to the residual (0.70-fold) and crude (0.84-fold) particles compared with that of the control, but it showed no change as a result of exposure to Printex 90. The protein expression levels in the cells exposed to the particles increased or decreased similarly, but different expression levels were also observed. There were differences in the effects observed between the cells exposed to the artificial carbon particles and those exposed to particles collected from ambient air.

CONCLUSIONThis study indicates that protein expression levels in cells change in response to exposure to particles collected from ambient air. To evaluate the effects of particles on health, it is considered necessary to use particles collected from ambient air.