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INTERACTIONS OF THE NANO-SIZED CARBONACEOUS PARTICLES WITH LUNG EPITHELIAL CELLS AND ALVEOLAR MACROPHAGES
Citation:
SAXENA, R. K., M. D. HAYS, AND M. I. GILMOUR. INTERACTIONS OF THE NANO-SIZED CARBONACEOUS PARTICLES WITH LUNG EPITHELIAL CELLS AND ALVEOLAR MACROPHAGES. Presented at Society of Biological Chemists Annual Meeting, New Delhi, INDIA, December 08 - 11, 2006.
Description:
Human beings especially in urban areas are exposed to automobile exhaust from truck or car diesel engines. The bulk of the suspended particles in diesel exhaust (diesel exhaust particulate, DEP) is below 100 nm in size and comprises a carbonaceous core on which a variety of organic compounds are adsorbed. Nano-sized carbon particles like ultra-fine carbon black (UFCB) and single or multi walled carbon nano-tubes (SWCNT) are manufactured in huge quantities for a variety of industrial usages. Occupational exposure to such particles is therefore possible. Air borne carbonaceous particles of small size (less than 10μ) can easily reach and accumulate in lungs. Within the lungs, these particles come in immediate contact with epithelial cells that line the air ways and alveoli, and pulmonary macrophages. The health hazard of exposure to DEP is well documented and DEP have been shown to induce oxidative stress and inflammatory changes in lungs. The physical and biological mechanisms of interactions between DEP and other carbonaceous nano-sized particles with lung cells are, however, not well understood. In the present study we examined the kinetics and dose response of uptake of DEP and other ultrafine carbon particles by cultured lung epithelial cells and macrophages. A sensitive assay system to quantitatively estimate the amount of carbon particles taken up by the cells was developed. In this method, murine lung epithelial and alveolar macrophage cells exposed to DEP or UFCB were solubilized in hot 1% SDS solution followed by high speed centrifugation to isolate insoluble ingested particles. Amount of carbon in the pellets was estimated by using a thermo-optical carbon analyzer. Qualitative differences in the uptake of carbonaceous particles were seen between the lung epithelial cells and alveolar macrophages. Our results indicated that while both cell types efficiently ingested DEP, uptake of UFCB was about 4 fold higher in macrophages rather than the epithelial cells. Cytochalasin D, an inhibitor of actin polymerization, blocked the ingestion of DEP by macrophages but not by epithelial cells, indicating that different mechanisms may be involved in the uptake of particles by the two cell types. Taken together, these studies provide an insight into the mechanism for particle uptake by lung cells. This abstract does not reflect EPA¿s policy.