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- Lizunkova, Polina
(författare)
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Impact of epidemiologically identified mixtures of endocrine disrupting chemicals on metabolic programming
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- We are ubiquitously exposed to a plethora of endocrine-disrupting chemicals (EDCs), i.e. substances that alter the function(s) of the endocrine system. While ample evidence show individual EDC's influence on developmental processes resulting in adverse health outcomes, less is known about the effects of human-relevant EDC mixtures exposure. Additionally, there is a lack of appropriate methodology to assess the hazard and risk of complex mixtures.This doctoral project aimed to examine the effects of two EDC mixtures and to compare individual components to its mixture, on the developing metabolic system. And to investigate additivity approach for predicting effects of complex mixtures. Studied EDC mixtures (G and G1) were previously identified using Swedish Environmental Longitudinal Mother and Child Asthma and Allergy (SELMA) study data, based on their association with lower birth weight. In this thesis, these mixtures, and mixture G1’s components, were tested for effects on adipogenesis and underlying epigenetic and transcriptional changes in human mesenchymal stem cells (hMSCs) and on metabolic rate in zebrafish larvae.In hMSCs, both mixtures induced adipogenesis at concentrations corresponding to SELMA cohort measured levels. Mixture G induced early transcriptional changes of over 1000 genes in a dose-dependent manner. These genes significantly overlapped with glucocorticoid-regulated genes and were involved in early osteogenesis. Mixture G1 induced significant DNA methylation changes at 713 positions and in six genomic regions in genes whose expression or methylation was previously associated with obesity or MSC differentiation. In zebrafish larvae, mixture G1 increased oxygen consumption rate. Compared to mixture G1, none of its individual components showed equally large effects on adipogenesis or metabolic rate. However, mixture G1 effect on both endpoints could be adequately predicted by the additivity model using experimental data from its constituents.In conclusion, this doctoral project showed that mixtures corresponding to human real-life exposures, in terms of proportions and concentrations, can induce molecular, cellular, and whole-organism changes relevant to developmental metabolic programming, which could underlie adverse outcomes later in life. The results emphasise that mixtures matter and should be accounted for in regulatory risk assessments, and provide support for additivity models as a pragmatic approach to mixture risk assessment.
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| 2. |
- Blanc, Mélanie, 1993-
(författare)
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How can an organism´s life experience affect their descendants? Insights from epigenetic and transgenerational effects of chemical exposure in zebrafish
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Environmental pollution causes approx. 10% of human diseases, and some develop in the progeny because of parental exposure. Effects passed on to subsequent generations may be a consequence of genetic mutations, or of inherited changes in epigenetic patterns. Epigenetics is the study of mitotically or meiotically heritable changes in gene function that cannot be explained by changes in the DNA sequence. Several chemicals have been suggested to induce epigenetic dysregulation leading to multigenerational and transgenerational effects, i.e. effects that can be observed in completely unexposed generations. However, mechanisms underlying the inheritance of epigenetic changes and their implication in phenotypic adversities are complex and not well-understood. The overall aim of this thesis was to study adverse effects and underlying molecular changes in several generations of zebrafish after parental exposure to selected industrial chemicals. To this end, molecular (lipidomic, transcriptomic, epigenomic) and behavioral analyses were performed. Zebrafish is an acknowledged model for vertebrates in toxicology and biomedicine; as such, the findings can be relevant to many organisms including human. The results from this thesis showed that different types of chemicals, polychlorinated biphenyls, polybromodiphenyl ethers, and permethrin, induced transgenerational effects in concentrations relevant to environmental or human exposures. Impact on anxiety and locomotor activity of zebrafish was observed over several generations. Gene expression and epigenetic (DNA methylation) alterations were partly inherited and suggest stable alteration of specific functions such as glutamatergic/GABAergic neurotransmission and synaptic plasticity. Finally, the findings shed light on experimental limitations and research perspectives, which we expect will contribute to the design of future studies on epigenetically inherited effects of any environmental stress.
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| 3. |
- Cediel-Ulloa, Andrea, 1989-
(författare)
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Novel Endpoints To Unravel Developmental Neurotoxicity : From DNA methylation responses to methylmercury to the in vitro identification of endocrine disruptors
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The developing brain is especially sensitive to environmental stressors due to its dependence on the precise spatiotemporal regulation of multiple signals, and the long time period required for its formation. Some chemicals can interfere with molecular and cellular processes driving brain development, including epigenetic processes such as DNA methylation. Hence, identification of DNA methylation changes induced by chemical exposure may serve as early molecular markers for developmental neurotoxicity (DNT). Chemicals known as endocrine disruptors (EDCs) can produce adverse effects due to their capability to alter the endocrine system. Since brain development is highly dependent on endocrine signals, the potential adverse effects of EDCs on brain development needs to be addressed. Detection of DNT in the regulatory context has been based on in vivo testing, however, the financial costs and time intensive characteristics of these methods have resulted in a limited assessment of the DNT hazard of chemicals. In addition, in order to regulate EDCs, it is paramount to demonstrate that their adverse effects are a product of disruption of endocrine signals. Yet, at the moment, there are no approved methods which address both an endocrine mode of action and adverse neurodevelopmental outcomes. This doctoral thesis had two main aims: Firstly, to identify epigenetic changes, at the level of DNA methylation, underlying DNT induced by exposure to methylmercury (MeHg); and secondly, to develop new approach methods (NAMs) for the detection of DNT induced by endocrine disruption. Epigenetic effects were studied both in epidemiological data and experimentally in vitro. Associations between prenatal MeHg exposure and DNA methylation of GRIN2B and NR3C1 were found in children. In vitro validation of DNA methylation changes found in epigenome-wide association studies of populations exposed to MeHg, uncovered the potential involvement of the Mediator Complex Subunit 31 (MED31) in MeHg DNT. To contribute to the endocrine disruption (ED)-induced DNT field, the applicability of an in vitro model composed of murine neural progenitor cells (the C17.2 cell-line) was evaluated. We found that C17.2 neural differentiation and morphology were sensitive to retinoic acid (RAR), retinoic X (RXR), peroxisome proliferator-activated β/δ (PPARβ/δ), and glucocorticoid (GR) agonism. Furthermore, two out of 25 tested EDCs decreased neurite outgrowth and branching in the C17.2 system. These effects were recovered by co-exposure of the chemicals with antagonists of RAR, RXR, or PPARβ/δ, indicating that their DNT effect is mediated by hormonal disruption. Altogether, this thesis contributed to the development of new methodologies and endpoints for the assessment of DNT induced by MeHg and EDCs.
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| 4. |
- Hases, Linnea
(författare)
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Estrogen signaling in colon inflammation and colorectal cancer
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Colorectal cancer (CRC) is the third most deadly form of cancer in the Western world. Although screening efforts have reduced the overall mortality, the incidence is increasing among young adults. The frequency of inflammatory bowel disease (IBD) and obesity are increasing in parallel, which suggest a common underlying environmental link between the conditions. This increase is thought to correlate to an increased intake of high fat diets, and obesity is a major risk factor for CRC. Chronic inflammation, which is a hallmark for CRC promotion, is a well-known underlying factor in both obesity and IBD. The gut microbiota is another hallmark, and an impaired relationship between the host and gut microbes can contribute to obesity, IBD and CRC. The risk-benefit balance of current CRC-preventative treatments is poor, and there is a need for safer and better preventatives in order to reduce the CRC mortality. Both obesity and IBD place men at a significant higher risk of CRC compared to women. This indicates a protective role for estrogen. The use of full Estrogen receptor (ER) β knockout mice has demonstrated ERβ protective effects against experimentally induced CRC. However, it is unknown through which cells these protective effects are mediated. There are only low mRNA levels of ERβ in the colon, unclear if adequate for a functional role, and ERβ may also be expressed in intestinal immune cells. Understanding the CRC-preventative effects of intestinal epithelial ERβ in both sexes is important and may provide the background for a novel CRC chemopreventive approach.The overall aim of the thesis is the functional characterization of intestinal epithelial ERβ during colon inflammation and colitis-induced CRC and identification of potential sex differences, which can ultimately provide novel opportunities for chemopreventive exploitation (Figure 1). In paper I we utilized intestinal epithelial ERβ knockout mice (ERβKOVil) of both sexes and induced colitis and colitis associated CRC (CA-CRC). We found that intestinal epithelial ERβ is protective against colitis and CA-CRC in both sexes, but in a sex-dependent manner. The underlying mechanism includes an intricate crosstalk with TNFα-induced NFκB signaling.In paper II we identify that both sex and intestinal epithelial ERβ impact the microbiota composition. This may contribute to the exacerbated colitis and colitis-induced tumor formation observed in ERβKOVil mice.In paper III we induced colon inflammation by feeding the mice a high-fat diet (HFD, 60%) for 13 weeks and explored treatment with estrogen receptor-selective ligands. We identified that estrogen signaling, via ERβ, modulated the HFD-induced changes in the colon microenvironment. This included sex-dependent effects on epithelial cell proliferation, macrophage infiltration, and regulation of core circadian clock gene expression.In paper IV we utilized paired-normal and CRC clinical samples and identified sex differences in the transcriptome of both normal colon and CRC. By applying data-driven feature selection and machine learning on sex-separated TCGA data, we proposed sex-specific diagnostic biomarkers and prognostic biomarkers using survival analysis. In summary, this thesis characterizes intestinal epithelial ERβ as a novel chemopreventative target for CA-CRC in both sexes, and identifies related biological pathways, including crosstalk with nuclear factor κB (NFκB) signaling and modulation of circadian clock genes. ERβ activity in intestinal epithelial cells is manifested by altered microbiota composition, cell proliferation and immune cell infiltration. The identification of several significant sex differences provides evidence for the need to take sex into account in colitis and CRC research to improve health interventions.
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| 5. |
- Tal, Tamara, et al.
(författare)
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New approach methods to assess developmental and adult neurotoxicity for regulatory use : a PARC work package 5 project
- 2024
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Ingår i: Frontiers in Toxicology. - : Frontiers Media S.A.. - 2673-3080. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- In the European regulatory context, rodent in vivo studies are the predominant source of neurotoxicity information. Although they form a cornerstone of neurotoxicological assessments, they are costly and the topic of ethical debate. While the public expects chemicals and products to be safe for the developing and mature nervous systems, considerable numbers of chemicals in commerce have not, or only to a limited extent, been assessed for their potential to cause neurotoxicity. As such, there is a societal push toward the replacement of animal models with in vitro or alternative methods. New approach methods (NAMs) can contribute to the regulatory knowledge base, increase chemical safety, and modernize chemical hazard and risk assessment. Provided they reach an acceptable level of regulatory relevance and reliability, NAMs may be considered as replacements for specific in vivo studies. The European Partnership for the Assessment of Risks from Chemicals (PARC) addresses challenges to the development and implementation of NAMs in chemical risk assessment. In collaboration with regulatory agencies, Project 5.2.1e (Neurotoxicity) aims to develop and evaluate NAMs for developmental neurotoxicity (DNT) and adult neurotoxicity (ANT) and to understand the applicability domain of specific NAMs for the detection of endocrine disruption and epigenetic perturbation. To speed up assay time and reduce costs, we identify early indicators of later-onset effects. Ultimately, we will assemble second-generation developmental neurotoxicity and first-generation adult neurotoxicity test batteries, both of which aim to provide regulatory hazard and risk assessors and industry stakeholders with robust, speedy, lower-cost, and informative next-generation hazard and risk assessment tools.
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