| 1. |
- Bal-Price, Anna, et al.
(författare)
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Putative adverse outcome pathways relevant to neurotoxicity
- 2015
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Ingår i: Critical reviews in toxicology. - : Informa UK Limited. - 1040-8444 .- 1547-6898. ; 45:1, s. 83-91
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Forskningsöversikt (refereegranskat)abstract
- The Adverse Outcome Pathway (AOP) framework provides a template that facilitates understanding of complex biological systems and the pathways of toxicity that result in adverse outcomes (AOs). The AOP starts with an molecular initiating event (MIE) in which a chemical interacts with a biological target(s), followed by a sequential series of KEs, which are cellular, anatomical, and/or functional changes in biological processes, that ultimately result in an AO manifest in individual organisms and populations. It has been developed as a tool for a knowledge-based safety assessment that relies on understanding mechanisms of toxicity, rather than simply observing its adverse outcome. A large number of cellular and molecular processes are known to be crucial to proper development and function of the central (CNS) and peripheral nervous systems (PNS). However, there are relatively few examples of well-documented pathways that include causally linked MIEs and KEs that result in adverse outcomes in the CNS or PNS. As a first step in applying the AOP framework to adverse health outcomes associated with exposure to exogenous neurotoxic substances, the EU Reference Laboratory for Alternatives to Animal Testing (EURL ECVAM) organized a workshop (March 2013, Ispra, Italy) to identify potential AOPs relevant to neurotoxic and developmental neurotoxic outcomes. Although the AOPs outlined during the workshop are not fully described, they could serve as a basis for further, more detailed AOP development and evaluation that could be useful to support human health risk assessment in a variety of ways.
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| 2. |
- 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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| 3. |
- Sethi, Sunjay, et al.
(författare)
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Comparative Analyses of the 12 Most Abundant PCB Congeners Detected in Human Maternal Serum for Activity at the Thyroid Hormone Receptor and Ryanodine Receptor
- 2019
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 53:7, s. 3948-3958
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Tidskriftsartikel (refereegranskat)abstract
- Polychlorinated biphenyls (PCBs) pose significant risk to the developing human brain; however, mechanisms of PCB developmental neurotoxicity (DNT) remain controversial. Two widely posited mechanisms are tested here using PCBs identified in pregnant women in the MARBLES cohort who are at increased risk for having a child with a neurodevelopmental disorder (NDD). As determined by gas chromatography-triple quadruple mass spectrometry, the mean PCB level in maternal serum was 2.22 ng/mL. The 12 most abundant PCBs were tested singly and as a mixture mimicking the congener profile in maternal serum for activity at the thyroid hormone receptor (THR) and ryanodine receptor (RyR). Neither the mixture nor the individual congeners (2 fM to 2 μM) exhibited agonistic or antagonistic activity in a THR reporter cell line. However, as determined by equilibrium binding of [3H]ryanodine to RyR1-enriched microsomes, the mixture and the individual congeners (50 nM to 50 μM) increased RyR activity by 2.4-19.2-fold. 4-Hydroxy (OH) and 4-sulfate metabolites of PCBs 11 and 52 had no TH activity; but 4-OH PCB 52 had higher potency than the parent congener toward RyR. These data support evidence implicating RyRs as targets in environmentally triggered NDDs and suggest that PCB effects on the THR are not a predominant mechanism driving PCB DNT. These findings provide scientific rationale regarding a point of departure for quantitative risk assessment of PCB DNT, and identify in vitro assays for screening other environmental pollutants for DNT potential.
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