DNA repair in human bronchial epithelial cells

The purpose of this investigation was to compare the responseof human cell types (bronchial epithelial cells and fibroblastsand skin fibroblasts) to various DNA damaging agents. Repairof DNA single strand breaks (SSB) induced by 5 krads of X-raywas similar for all cell types; 90% of the DNA SSB were rejoinedwithin one hour. During excision repair of DNA damage from u.v.-radiation,the frequencies of DNA SSB as estimated by the alkaline elutiontechnique, were similar in all cell types. Repair replicationas measured by BND cellulose chromatography was also similarin epithelial and fibroblastic cells after u.v.-irradiation.Similar levels of SSB were also observed in epithelial and fibroblasticcells after exposure to chemical carcinogens: 7,12-dimethylbenz[a]anthracene;benzo[a]pyrene diol epoxidle (BPDE); or N-methyl-N-nitro-N-nitrosoguanidine.Significant repair replication of BPDE-induced DNA damage wasdetected in both bronchial epithelial and fibroblastic cells,although the level in fibroblasts was 40% of that in epithelialcells. The pulmonary carcinogen asbestos did not damage DNA.DNA-protein crosslinks induced by formaldehyde were rapidlyremoved in bronchial cells. Further, epithelial and fibroblasticcells, which were incubated with formaldehyde and the polymeraseinhibitor combination of cytosine arabinoside and hydroxyurea,accumulated DNA SSB at approximately equal frequencies. Theseresults should provide a useful background for further investigationsof the response of human bronchial cells to various DNA damagingagents.