Am. J. Respir. Cell Mol. Biol., Vol 10, No. 6, 06 1994, 683-688.
Iron enhances uptake of mineral particles and increases lipid peroxidation in tracheal epithelial cells
B Keeling, KY Li and A Churg
Department of Pathology, University of British Columbia, Vancouver, Canada.
The factors that determine whether an exogenous mineral particle will be
taken up by tracheobronchial epithelial cells are unclear. We have
previously proposed that active oxygen species play a role in this process,
most likely through iron-catalyzed formation of hydroxyl radical and
subsequent lipid peroxidation of cell membranes. To further examine this
hypothesis, we prepared rat tracheal explant cultures and exposed them for
1 h to suspensions of amosite asbestos or titanium dioxide (rutile) that
had been preincubated with varying concentrations of a mixture of ferrous
and ferric chloride. Explants were then maintained in organ culture in
air/CO2 for 1 wk to allow particle or fiber uptake to occur. Particles or
fibers in the tracheal epithelium were determined by light microscopic
morphometry. Similarly treated explants were assayed for malondialdehyde as
a measure of lipid peroxidation in the epithelial cells. Asbestos fibers
without added iron caused lipid peroxidation, but this was not true of
titanium dioxide particles. For both types of dust, increasing adsorbed
iron concentrations were associated with increasing particle uptake and
increasing lipid peroxidation. These observations suggest that cationic
iron may play a major role in particle uptake by tracheobronchial
epithelia, and that particle uptake is also related to iron-mediated lipid
peroxidation.
