| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2005: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 2004: ¥2,000,000 (Direct Cost: ¥2,000,000)
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| Research Abstract |
Exposure to ambient ultrafine particles induces airway inflammatory reactions and tissue remodeling. In this experiment, to determine whether ultrafine carbon black (ufCB) affects proliferation of airway epithelium and, if so, what the mechanism of action is, we studied human primary bronchial epithelial cell cultures. Incubation of cells in the serum-free medium with ufCB increased incorporations of [^3H]-thymidine and [^3H]-leucine into cells in a time- and dose-dependent manner. This effect was attenuated by a free radical scavenger and a NADH/NADPH oxidase inhibitor, and completely inhibited by pretreatment with the epidermal growth factor receptor (EGF-R) tyrosine kinase inhibitors AG1478 and BIBX1382, and the mitogen-activated protein kinase kinase (MEK) inhibitor PD98059. Transfection of a dominant negative mutant of H-Ras likewise abolished the effect ufCB. Stimulation with ufCB also induced processing of membrane anchored pro-heparin-binding (HB)-EGF, release of soluble HB-EGF into the medium, association of phosphorylated EGF-R and Shc with glutathione-S-transferase-Grb2 fusion protein, and phosphorylation of extracellular signal-regulated kinase (ERK). Pretreatment with each AG1478, [Glu^<52>]Diphtheria toxin, a specific inhibitor of HB-EGF, and neutralizing HB-EGF antibody inhibited ufCB-induced ERK activation. These results suggest that ufCB causes oxidative stress-mediated proliferation of airway epithelium, involving processing of HB-EGF and the concomitant activation of EGF-R and ERK cascade.
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