Induction of DNA strand breaks by trihalomethanes in primary human lung epithelial cells

详细信息    查看全文

• 作者：Landi ; Stefano ; Naccarati ; Alessio ; Ross ; Matthew K. ; Hanley ; Nancy M. ; Dailey ; Lisa ; Devlin ; Robert B. ; et. al.
• 关键词：Trihalomethanes ; Comet ; DNA damage ; Human lung cells ; GSTT1-1
• 刊名：Mutation Research/Genetic Toxicology and Environmental Mutagenesis
• 出版年：2003
• 出版时间：July 8, 2003
• 年：2003
• 卷：538
• 期：1-2
• 页码：41-50
• 全文大小：249 K

文摘

Trihalomethanes (THMs) are disinfection by-products and suspected human carcinogens present in chlorinated drinking water. Previous studies have shown that many THMs induce sister chromatid exchanges and DNA strand breaks in human peripheral blood lymphocytes in vitro. Exposure to THMs occurs through oral, dermal, or inhalation routes, with the lung being a target of exposure by the latter route, although not a target for rodent carcinogenicity. Thus, to examine the genotoxicity of THMs in this tissue, we used the comet assay to examine the DNA damaging ability of five THMs in primary human lung epithelial cells. Cells were collected by scraping the large airways of four volunteers with a cytology brush and then passaging the cells no more than three times in order to have sufficient numbers for the experiments. Cells were exposed for 3h to 10, 100, or 1000μM CHCl₃, CHCl₂Br, CHClBr₂, or CHBr₃; CH₂Cl₂ was also used as a model dihalomethane for comparison to the THMs. The compounds ranked as follows for DNA damaging ability: CHCl₂Br>CHBr₃>CHCl₃CH₂Cl₂; CHClBr₂ was negative. Considerable inter-individual variation was observed. For example, CHCl₃ was genotoxic in only two subjects, and the interaction between dose and donor was highly significant (P<0.001). The same variation was observed for CHCl₂Br, which was positive only in the two subjects in which CHCl₃ was negative. This variation was not due to the GSTT1-1 genotype of the subjects. Although two subjects were GSTT1-1⁺, and two were GSTT1-1⁻, no cultured cells with a GSTT1-1⁺ genotype had detectable GSTT1-1 enzymatic activity nor did any frozen epithelial cells that had not been cultured. However, GSTT1-1 enzymatic activity was detected in fresh (neither frozen nor cultured) lung cells. These results show that freezing or culturing causes lung cells to lose GSTT1-1 activity and that factors other than GSTT1-1 activity play a role in the variable responses of these human cells to the genotoxicity of the halomethanes studied here.