title: Cadmium alters the formation of benzo[a]pyrene DNA adducts in the RPTEC/TERT1 human renal proximal tubule epithelial cell line.
abstract: Previously, we demonstrated the sensitivity of RPTEC/TERT1 cells, an immortalized human renal proximal tubule epithelial cell line, to two common environmental carcinogens, cadmium (Cd) and benzo[a]pyrene (B[a]P). Here, we measured BPDE-DNA adducts using a competitive ELISA method after cells were exposed to 0.01, 0.1, and 1 μM B[a]P to determine if these cells, which appear metabolically competent, produce BPDE metabolites that react with DNA. BPDE-DNA adducts were most significantly elevated at 1 μM B[a]P after 18 and 24 hours with 36.34 +/- 9.14 (n = 3) and 59.75 +/- 17.03 (n = 3) adducts/108nucleotides respectively. For mixture studies, cells were exposed to a non-cytotoxic concentration of Cd, 1 μM, for 24 hours and subsequently exposed to concentrations of B[a]P for 24 hours. Under these conditions, adducts detected at 1 μM B[a]P after 24 hours were significantly reduced, 17.28 +/- 1.30 (n = 3) adducts/108nucleotides, in comparison to the same concentration at previous time points without Cd pre-treatment. We explored the NRF2 antioxidant pathway and total glutathione levels in cells as possible mechanisms reducing adduct formation under co-exposure. Results showed a significant increase in the expression of NRF2-responsive genes,GCLC, HMOX1, NQO1, after 1 μM Cd × 1 μM B[a]P co-exposure. Additionally, total glutathione levels were significantly increased in cells exposed to 1 μM Cd alone and 1 μM Cd × 1 μM B[a]P. Together, these results suggest that Cd may antagonize the formation of BPDE-DNA adducts in the RPTEC/TERT1 cell line under these conditions. We hypothesize that this occurs through priming of the antioxidant response pathway resulting in an increased capacity to detoxify BPDE prior to BPDE-DNA adduct formation.
authors.affiliation: Graduate Program in Biomedical Sciences, Tulane University School of Medicine, New Orleans, LA 70112 ; Department of Global Environmental Health Sciences, Tulane University School of Public Health and Tropical Medicine, New Orleans, LA 70112.
authors.forename: Bridget R
authors.initials: BR
authors.lastname: Simon
authors.affiliation: Department of Global Environmental Health Sciences, Tulane University School of Public Health and Tropical Medicine, New Orleans, LA 70112.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Wilson
authors.affiliation: Graduate Program in Biomedical Sciences, Tulane University School of Medicine, New Orleans, LA 70112 ; Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, New Orleans, LA 70112.
authors.forename: Diane A
authors.initials: DA
authors.lastname: Blake
authors.affiliation: Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, New Orleans, LA 70112.
authors.forename: Haini
authors.initials: H
authors.lastname: Yu
authors.affiliation: Graduate Program in Biomedical Sciences, Tulane University School of Medicine, New Orleans, LA 70112 ; Department of Global Environmental Health Sciences, Tulane University School of Public Health and Tropical Medicine, New Orleans, LA 70112.
authors.forename: Jeffrey K
authors.initials: JK
authors.lastname: Wickliffe
keywords: BPDE-DNA adducts; Mixtures toxicology; RPTEC/TERT1; renal cancer