title: p53 induction and cell viability modulation by genotoxic individual chemicals and mixtures.
abstract: The binding of the p53 tumor suppression protein to DNA response elements after genotoxic stress can be quantified by cell-based reporter gene assays as a DNA damage endpoint. Currently, bioassay evaluation of environmental samples requires further knowledge on p53 induction by chemical mixtures and on cytotoxicity interference with p53 induction analysis for proper interpretation of results. We investigated the effects of genotoxic pharmaceuticals (actinomycin D, cyclophosphamide) and nitroaromatic compounds (4-nitroquinoline 1-oxide, 3-nitrobenzanthrone) on p53 induction and cell viability using a reporter gene and a colorimetric assay, respectively. Individual exposures were conducted in the absence or presence of metabolic activation system, while binary and tertiary mixtures were tested in its absence only. Cell viability reduction tended to present direct correlation with p53 induction, and induction peaks occurred mainly at chemical concentrations causing cell viability below 80%. Mixtures presented in general good agreement between predicted and measured p53 induction factors at lower concentrations, while higher chemical concentrations gave lower values than expected. Cytotoxicity evaluation supported the selection of concentration ranges for the p53 assay and the interpretation of its results. The often used 80% viability threshold as a basis to select the maximum test concentration for cell-based assays was not adequate for p53 induction assessment. Instead, concentrations causing up to 50% cell viability reduction should be evaluated in order to identify the lowest observed effect concentration and peak values following meaningful p53 induction.
authors.affiliation: Department of Ecosystem Analysis, Institute for Environmental Research, Aachen Biology and Biotechnology (ABBt), RWTH Aachen University, Aachen, Germany. carolina.dipaolo@bio5.rwth-aachen.de.
authors.forename: Carolina
authors.identifier: http://orcid.org/0000-0002-4281-1034
authors.initials: C
authors.lastname: Di Paolo
authors.affiliation: Department of Ecosystem Analysis, Institute for Environmental Research, Aachen Biology and Biotechnology (ABBt), RWTH Aachen University, Aachen, Germany.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Müller
authors.affiliation: Department of Ecosystem Analysis, Institute for Environmental Research, Aachen Biology and Biotechnology (ABBt), RWTH Aachen University, Aachen, Germany.
authors.forename: Beat
authors.initials: B
authors.lastname: Thalmann
authors.affiliation: Department of Ecosystem Analysis, Institute for Environmental Research, Aachen Biology and Biotechnology (ABBt), RWTH Aachen University, Aachen, Germany.|College of Resources and Environmental Science, Chongqing University, 1 Tiansheng Road, Beibei, Chongqing, 400715, China.|College of Environmental Science and Engineering and State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, 1239 Siping Road, Shanghai, China.|State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, China.
authors.forename: Henner
authors.initials: H
authors.lastname: Hollert
authors.affiliation: Department of Ecosystem Analysis, Institute for Environmental Research, Aachen Biology and Biotechnology (ABBt), RWTH Aachen University, Aachen, Germany.
authors.forename: Thomas-Benjamin
authors.initials: TB
authors.lastname: Seiler
mesh_terms: D015112:4-Nitroquinoline-1-oxide / Q000633:toxicity; D001551:Benz(a)Anthracenes / Q000633:toxicity; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D003520:Cyclophosphamide / Q000633:toxicity; D003609:Dactinomycin / Q000633:toxicity; D004785:Environmental Pollutants / Q000633:toxicity*; D006801:Humans; D009153:Mutagens / Q000633:toxicity*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics*
chemical_list: D001551:Benz(a)Anthracenes; D004785:Environmental Pollutants; D009153:Mutagens; D016159:Tumor Suppressor Protein p53; D003609:Dactinomycin; D015112:4-Nitroquinoline-1-oxide; D003520:Cyclophosphamide; C117220:3-nitrobenzanthrone
keywords: Cytotoxicity; DNA damage; Genotoxicity; Reporter gene cell line bioassay; p53 pathway; p53 tumor suppression protein