Am. J. Respir. Crit. Care Med., Vol 153, No. 4, 04 1996, 1230-1233.
Ozone enhances the uptake of mineral particles by tracheobronchial epithelial cells in organ culture
A Churg, M Brauer and B Keeling
Department of Pathology, University of British Columbia, Vancouver, Canada.
We have previously shown that the basal uptake of mineral particles by
tracheobronchial epithelial cells in organ culture is mediated in part by
active oxygen species (AOS) and can be greatly augmented by exposure to
cigarette smoke, a concentrated source of AOS, and other radicals. We
hypothesized that ozone, another generator of AOS in tissues, might have
the same effect. To test this hypothesis, tracheal explants were exposed to
room air (control) or ozone in varying concentrations from 0.01 to 1.0 ppm
for 10 min, and subsequently to a suspension of either amosite asbestos or
titanium dioxide (rutile) for 1 h. Explants were then transferred to an
air/CO2 incubator for 1 wk to allow particle uptake to occur, and uptake
was determined by morphometry. We found that ozone exposure increased the
uptake of both asbestos and titanium dioxide in a dose-response fashion;
this effect appeared at lower exposure levels and was more marked with
titanium dioxide than with amosite. The ozone effect could be prevented by
addition of catalase but not superoxide dismutase to the particle
suspension, or by preincubation of the particles with deferoxamine. These
observations indicate that ozone can directly increase uptake of mineral
particles by tracheobronchial epithelial cells; this effect occurs with
brief exposures at very low ozone levels and appears to be mediated by
hydrogen peroxide and possibly by hydroxyl radical. These findings support
the general hypothesis that AOS are important mediators of epithelial
particle uptake in many different settings. Enhanced uptake may be one of
the mechanisms by which ozone impairs particle clearance from the lung and
may play a role in the increased morbidity seen in populations with
exposure to high levels of both ozone and atmospheric particulates.
