The developing brain undergoes several developmental cycles during which it exhibits a higher sensitivity to exogenous disturbances. On such period is the so named “Brain growth spurt” (BGS) which in humans occurs beginning with the third trimester of pregnancy and throughout the first few years of life. The corresponding period in rats and mice is the first postnatal weeks. Exposure to relatively modest concentrations of the brominated flame retardant PBDE-99 in the second week of life in mice leads to a pretty much permanent impairment in the ability of the animals to adjust effectively to environmental changes at adulthood. This “late response on early exposure” reflects the long-term implications of disrupting the developing brain during a sensitive time period. The cellular mechanisms underlying the behavioral impacts are far from clear. To address the primary damage occurring around the time of exposure, the strategy employed in this dissertation is to use proteomics to evaluate the effects of PBDE-99 on protein expression soon (24 hours) after exposure of the neonatal mouse on postnatal day (PND) 10. The thesis includes the effects on the proteome in 3 distinct brain parts: cerebral cortex, striatum and the hippocampus. Additionally, an in vitro model was created and utilized to assess the PBDE-99 effects on cultured cerebral cortex cells from embryonic rat brains.Gel-based proteomics (2D-DIGE) coupled to MALDI- or ESI-MS has been utilized throughout for the proteomics experiments, but other techniques targeted at analyzing both proteins and mRNA have also been employed to better characterize the effects. Even if the protein complements expressed by the different brain parts and separated with 2D-DIGE are somewhat similar, the results are evidently specific for the different brain regions.
In hippocampus, PBDE causes effects on proteins linked to metabolism and energy production, while the impacts in striatum point towards effects on neuroplasticity. PBDE-99 changes the expression of cytoskeletal proteins in the cerebral cortex 24 hours after exposure. Curiously, in vitro exposure of cerebral cortex cells to a PBDE-99 concentration in the same order of magnitude as in the in vivo neonatal brain also induces cytoskeletal effects, in the absence of cytotoxicity. This could suggest effects on regulatory aspects of cytoskeletal dynamics for example those involved in neurite sprouting. This thesis also handles the issues associated with presenting proteomics data. Many of the available techniques and methods for presenting transcriptomics data aren’t ideal for isoform rich protein data. Modifications of existing methods and the development of a new approach (DEPPS) is also shown. Above all, the dissertation presents the application and effectiveness of proteomics as hypothesis generating techniques in neurotoxicology.
Proteomic Characterization of Induced Developmental Neurotoxicity Downloads
Source: Sodertorn University
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