AJP - Lung Cellular and Molecular Physiology, Vol 268, Issue 5 832-L838, Copyright © 1995 by American Physiological Society
Rat mesothelial and tracheal epithelial cells show equal DNA sensitivity to hydrogen peroxide-induced oxidant injury
A. Churg, B. Keeling, B. Gilks, S. Porter and P. Olive
Department of Pathology, University of British Columbia, Vancouver, Canada.
To study the relative sensitivity of rat tracheal epithelial and
mesothelial cell DNA to oxidant damage, we used the comet assay, a gel
microelectrophoresis method that allows visual determination of DNA strand
breaks on a cell-by-cell basis, to evaluate damage after hydrogen peroxide
exposure. By both a qualitative and a quantitative assay, tracheal
epithelial mesothelial cells demonstrated a similar dose-response increase
in the number of cells showing strand breaks and the number of breaks per
cell after exposure to increasing concentrations of hydrogen peroxide; but
even at the highest concentration, some cells failed to show damage. By
contrast, 100% of cultured V79 lung fibroblasts showed evidence of damage.
Catalase and deferoxamine largely prevented the formation of strand breaks,
while superoxide dismutase was not protective. To evaluate DNA repair,
cells were exposed to 10 microM hydrogen peroxide for 10 min, washed, and
maintained in culture medium; by 2 h the proportion of mesothelial and
epithelial cells showing comets had returned to control levels for both
cell types. Both cell types also showed a similar pattern of increasing
damage after continuous exposure to 10 microM hydrogen peroxide for periods
up to 2 h. We conclude that, in this system, 1) mesothelial and
tracheobronchial epithelial cells show a similar pattern of DNA injury and
repair after hydrogen peroxide exposure; 2) hydrogen peroxide damages DNA
of both cell types via a mechanism probably related to the iron-catalyzed
formation of hydroxyl radical; and 3) both types of cells appear to be
heterogeneous in their sensitivity to oxidant damage, with some cells
showing extreme resistance to such damage.
