Toxicogenomics Responses in the in Vitro Liver : a View on Human Interindividual Variation
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Toxicogenomics responses in the in vitro liver : a view on human interindividual variation Citation for published version (APA): Jetten, M. J. A. (2014). Toxicogenomics responses in the in vitro liver : a view on human interindividual variation. Maastricht University. https://doi.org/10.26481/dis.20141205mj Document status and date: Published: 01/01/2014 DOI: 10.26481/dis.20141205mj Document Version: Publisher's PDF, also known as Version of record Please check the document version of this publication: • A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. 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If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license above, please follow below link for the End User Agreement: www.umlib.nl/taverne-license Take down policy If you believe that this document breaches copyright please contact us at: [email protected] providing details and we will investigate your claim. Download date: 11 Oct. 2021 Toxicogenomics responses in the in vitro liver A view on human interindividual variation ISBN: 978 94 6295 011 5 © Marlon J.A. Jetten Coverdesign: Paul van Cruchten Lay-out: Paul van Cruchten Production: Proefschriftmaken.nl || Uitgeverij BOXPress The studies presented in this thesis were performed at the School for Oncology and Developmental Biology (GROW), accredited by the Royal Netherlands Academy of Arts and Sciences (KNAW). The research was fund- ed by the carcinoGENOMICS project [LSHB-CT-2006-037712] an FP6 project from the European Union and the ASAT (Assuring Safety without Animal Testing) program an initiative from the Dutch ministry of Health, Welfare and Sports. Toxicogenomics responses in the in vitro liver A view on human interindividual variation PROEFSCHRIFT ter verkrijging van de graad van doctor aan de Universiteit Maastricht, op gezag van de Rector Magnificus, Prof. dr. L. L .G. Soete volgens het besluit van het College van Decanen, in het openbaar te verdedigen op vrijdag 5 december 2014 om 10.00 uur door Marlon Jacoba Anne Jetten geboren te Roermond op 24 juni 1983 Promotor Prof. Dr. J.C.S. Kleinjans Beoordelingscommissie Prof. Dr. F.C.S. Ramaekers (voorzitter) Prof. Dr. C.H.C. Dejong Prof. Dr. G.M.M. Groothuis (Rijks Universiteit Groningen) Prof. Dr. H. van Loveren Prof. Dr. B. van de Water (Universiteit Leiden) Contents Chapter 1 9 General introduction Chapter 2 33 Interindividual variation in response to xenobiotic exposure established in precision-cut human liver slices Chapter 3 57 Interindividual variation in gene expression responses and metabolite formation in acetaminophen-exposed primary human hepatocytes Chapter 4 83 Baseline and genotoxic compound induced gene expression profiles in HepG2 and HepaRG compared to primary human hepatocytes. Chapter 5 109 Does the epigenome predispose for susceptibility to DNA damage? Chapter 6 143 'Omics analysis of low dose acetaminophen intake demonstrates novel response pathways in humans Chapter 7 167 Summary and general discussion Samenvatting en algemene discussie Addendum I 190 Valorization Dankwoord 197 Curriculum Vitae 198 List of publications 199 8 9 Chapter 1 General introduction Chapter 1 10 Adverse effects to xenobiotic exposure Xenobiotics are defined as any chemical substance of which the occurrence of, or the unusually high concentration in an organism is abnormal. Thus, xenobiotics would typically not be produced by, or be present in an organism. Nevertheless, contact to xenobiotics is an inevitable part of daily life for any organism [1]. For instance, the inhalation of products of combustion whiles breathing or the consumption of food contaminants while feeding are unavoidable scenarios of xenobiotic exposure. Some of the xenobiotics humans are exposed to through air inhalation or food consumption are well known chemical carcinogens; in other words these xenobiotics are chemicals that are known to cause cancer [2]. Chemical carcinogenesis, e.g. the development of cancer after exposure to a chemical, is a multi-step process. In the first step, the initiation phase, a mutation is introduced in the genetic code. In chemical carcinogenesis this is usually caused through covalent binding of a reactive metabolite to the DNA-strand, leading to a DNA-strand break which, if falsely repaired, causes a mutation in the DNA [3, 4]. When these mutations appear in genes involved in for instance cell differentiation/growth or tumor suppression/promotion, the development of cancerous cells can be induced [5]. The harm done during the initiation phase can still be reversed by the DNA-repair mechanisms. However, when these mechanisms fail mutations become final and a second stage, the promotion stage is entered. This phase promotes cell growth of the mutated cell over a longer period in time leading to the development of non-malignant tumors. Then, during the progression phase, the already mutated cells can acquire even more mutations resulting in unlimited cell growth that will eventually become invasive leading to malignant and metastatic forms of cancer [6]. Another important source of xenobiotics in humans is caused by the exposure to pharmaceuticals/drugs. Organ-related toxicity responses are amongst the unwanted side-effects from xenobiotics coming from the exposure to pharmaceutical chemicals [7]. Adverse reactions to drugs are major issues concerning drug treatment and development, resulting in a high number of deaths and medical costs [8]. Furthermore, idiosyncratic responses impose a financial burden on the pharmacological industry [7, 9]. Chapter 1 11 Interindividual variation in the human population Interindividual variation in adverse responses to xenobiotic exposure within the human population is a well-known phenomenon [10, 11]. For instance, though smoking causes lung cancer, not all individuals that smoke will eventually succumb to this disease. Also, individuals exhibit different side-effects when exposed to similar doses of a pharmaceutical. Environmental factors, but also genetic factors have been proposed as causative elements for the interindividual variation within the human population [10, 11]. Many studies have focused on finding a single or maybe a few factors explaining the variation within a population in response to xenobiotics, for instance the expression level of a single or a few genes [12]. However, a single factor in general does not seem to be able to provide sufficient explanation for the interindividual differences in a population, implying that the variation is rather caused by multiple factors [12]. Nevertheless, up till now the (genetic) factors causing interindividual variation are still largely unknown. Animal models and human risk assessment In an attempt to elucidate the factors influencing sensitivity of individuals towards xenobiotic exposure and in order to establish a system for risk assessment of human xenobiotic exposure, researchers have resorted to the use of in vivo animal models; especially rodent models (mice, rats, etc.). In addition, for the preservation of the current levels of human health and environmental protection many regulatory bodies emphasize the need for toxicity testing [13]. As a result, the use of animal models has become deeply manifested into the rules and regulations around toxicity testing, as such becoming an obligatory hurdle to take to ensure human safety [14]. However, the use of animal models brings along a heavy financial burden, and also goes hand-in- hand with ethical and moral dilemmas [15]. In addition, over the recent years the reliability and applicably of animal model-derived data towards the human situation has been questioned [15]. Currently, risk-assessment methods based on data-extrapolation from the animal to the human situation make use of a golden standard, the 100-fold safety factor [16]. This factor is applied to the outcome of animal model-derived data in order to establish a dose for a compound/xenobiotic that should be safe for human use. The factor is composed of two parts; a 10-fold margin of safety allowing for the extrapolation from the animal to human situation, and another 10- Chapter 1 12 fold margin of safety is included to account for human interindividual variation in susceptibility [16, 17]. Especially the latter 10-fold factor for interindividual variation is a topic of discussion at this moment in time [18]. An overestimation of interindividual