Resistance of rat pulmonary alveolar epithelial cells to neutrophil- and oxidant-induced injury.
We have previously reported that rat pulmonary alveolar epithelial cells are resistant to neutrophil-generated oxidants in contrast to the situation described for endothelial cells. In the present study, we investigated the roles of intracellular catalase and glutathione-dependent reactions in providing protection against cytotoxic concentrations of H2O2 and stimulated neutrophils. Catalase was found to be instrumental in protecting epithelial cells because when inhibited by either azide or 3-amino-1,2,4-triazole, there was an increase in the cytotoxic effect of exogenous H2O2 and stimulated neutrophils. Associated with this potentiation of injury was a reduction in epithelial cell clearance of H2O2. Partial inhibition of glutathione-dependent reactions by depleting intracellular glutathione with buthionine sulfoximine or by inhibiting the enzyme glutathione reductase with 1,3-bis(2-chloroethyl)-1-nitrosourea also augmented the cytotoxic effect of both H2O2 and stimulated neutrophils. This increase in neutrophil-induced cytotoxicity was caused by the addition of an oxidant-dependent mechanism of killing on top of the previously described oxidant-independent pathway. Importantly, the increased susceptibility to injury caused by inhibition of glutathione-dependent reactions was not associated with a reduction in epithelial cell consumption of exogenous H2O2, contrary to the case with catalase. This suggests that there are glutathione-dependent reactions that protect epithelial cells in ways separate from reducing the total burden of exogenous H2O2 on the cells.
Simon
R H
RH
Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor.
DeHart
P D
PD
Nadeau
D M
DM
D000640:Amitrole / Q000494:pharmacology; D000818:Animals; D001386:Azides / Q000494:pharmacology; D019328:Buthionine Sulfoximine; D002330:Carmustine / Q000494:pharmacology; D002374:Catalase / Q000378:metabolism; D002478:Cells, Cultured; D004848:Epithelium / Q000187:drug effects / Q000502:physiology; D005978:Glutathione / Q000502:physiology; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D008717:Methionine Sulfoximine / Q000031:analogs & derivatives / Q000494:pharmacology; D009504:Neutrophils / Q000502:physiology*; D010084:Oxidation-Reduction; D011650:Pulmonary Alveoli / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D011916:Rats, Inbred F344
D001386:Azides; D008717:Methionine Sulfoximine; D019328:Buthionine Sulfoximine; D006861:Hydrogen Peroxide; D002374:Catalase; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D005978:Glutathione; D002330:Carmustine; D000640:Amitrole