title: Impact of the circadian clock on in vitro genotoxic risk assessment assays.
abstract: Our society expects safety assessment for drugs, chemicals, cosmetics, and foods, which to date cannot be achieved without the use of laboratory animals. At the same time, society aims at refining, reducing, and (ultimately) replacing animal testing. As a consequence, much effort is taken to establish alternatives, such as toxicogenomics-based risk assessment assays on cultured cells and tissues. Evidently, the properties of cells in vitro will considerably differ from the in vivo situation. This review will discuss the impact of the circadian clock, an internal time keeping system that drives 24-h rhythms in metabolism, physiology and behavior, on in vitro genotoxic risk assessment. Our recent observation that DNA damaging agents can synchronize the circadian clock of individual cells in culture (and as a consequence the cyclic expression of clock-controlled genes, comprising up to 10% of the transcriptome) implies that the circadian clock should not be neglected when developing cell or tissue-based alternatives for chronic rodent toxicity assays.
authors.affiliation: Department of Genetics, Center for Biomedical Genetics, Erasmus University Medical Center, 3000 CA Rotterdam, The Netherlands.
authors.forename: Eugin
authors.initials: E
authors.lastname: Destici
authors.forename: Małgorzata
authors.initials: M
authors.lastname: Oklejewicz
authors.forename: Romana
authors.initials: R
authors.lastname: Nijman
authors.forename: Filippo
authors.initials: F
authors.lastname: Tamanini
authors.forename: Gijsbertus T J
authors.initials: GT
authors.lastname: van der Horst
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002940:Circadian Rhythm / Q000187:drug effects* / Q000502:physiology; D004249:DNA Damage; D006801:Humans; D009152:Mutagenicity Tests; D009153:Mutagens / Q000145:classification / Q000633:toxicity*; D012107:Research Design; D018570:Risk Assessment; D013997:Time Factors
chemical_list: D009153:Mutagens