title: Exposure of Human Lung Cells to Tobacco Smoke Condensate Inhibits the Nucleotide Excision Repair Pathway.
abstract: Exposure to tobacco smoke is the number one risk factor for lung cancer. Although the DNA damaging properties of tobacco smoke have been well documented, relatively few studies have examined its effect on DNA repair pathways. This is especially true for the nucleotide excision repair (NER) pathway which recognizes and removes many structurally diverse DNA lesions, including those introduced by chemical carcinogens present in tobacco smoke. The aim of the present study was to investigate the effect of tobacco smoke on NER in human lung cells. We studied the effect of cigarette smoke condensate (CSC), a surrogate for tobacco smoke, on the NER pathway in two different human lung cell lines; IMR-90 lung fibroblasts and BEAS-2B bronchial epithelial cells. To measure NER, we employed a slot-blot assay to quantify the introduction and removal of UV light-induced 6-4 photoproducts and cyclobutane pyrimidine dimers. We find a dose-dependent inhibition of 6-4 photoproduct repair in both cell lines treated with CSC. Additionally, the impact of CSC on the abundance of various NER proteins and their respective RNAs was investigated. The abundance of XPC protein, which is required for functional NER, is significantly reduced by treatment with CSC while the abundance of XPA protein, also required for NER, is unaffected. Both XPC and XPA RNA levels are modestly reduced by CSC treatment. Finally, treatment of cells with MG-132 abrogates the reduction in the abundance of XPC protein produced by treatment with CSC, suggesting that CSC enhances proteasome-dependent turnover of the protein that is mediated by ubiquitination. Together, these findings indicate that tobacco smoke can inhibit the same DNA repair pathway that is also essential for the removal of some of the carcinogenic DNA damage introduced by smoke itself, increasing the DNA damage burden of cells exposed to tobacco smoke.
authors.affiliation: Department of Toxicology and Cancer Biology, The Markey Cancer Center, University of Kentucky, Lexington, Kentucky, United States of America.
authors.forename: Nathaniel
authors.initials: N
authors.lastname: Holcomb
authors.affiliation: Department of Toxicology and Cancer Biology, The Markey Cancer Center, University of Kentucky, Lexington, Kentucky, United States of America.
authors.forename: Mamta
authors.initials: M
authors.lastname: Goswami
authors.affiliation: Toxicology Laboratory, Department of Food Science and Biotechnology of Animal Resources, College of Animal Bioscience and Technology, Konkuk University, Seoul, Republic of Korea.
authors.forename: Sung Gu
authors.initials: SG
authors.lastname: Han
authors.affiliation: Department of Toxicology and Cancer Biology, The Markey Cancer Center, University of Kentucky, Lexington, Kentucky, United States of America.
authors.forename: Samuel
authors.initials: S
authors.lastname: Clark
authors.affiliation: Department of Toxicology and Cancer Biology, The Markey Cancer Center, University of Kentucky, Lexington, Kentucky, United States of America.
authors.forename: David K
authors.initials: DK
authors.lastname: Orren
authors.affiliation: Department of Toxicology and Cancer Biology, The Markey Cancer Center, University of Kentucky, Lexington, Kentucky, United States of America.
authors.forename: C Gary
authors.initials: CG
authors.lastname: Gairola
authors.affiliation: Department of Toxicology and Cancer Biology, The Markey Cancer Center, University of Kentucky, Lexington, Kentucky, United States of America.
authors.forename: Isabel
authors.initials: I
authors.lastname: Mellon
mesh_terms: D002460:Cell Line; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism* / Q000473:pathology; D005347:Fibroblasts / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D008168:Lung / Q000378:metabolism* / Q000473:pathology; D014028:Tobacco Smoke Pollution / Q000009:adverse effects*; D051760:Xeroderma Pigmentosum Group A Protein / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D014028:Tobacco Smoke Pollution; C497314:XPA protein, human; D051760:Xeroderma Pigmentosum Group A Protein; C086984:XPC protein, human