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In vivo and in vitro neurochemical-based assessments of wastewater effluents from the Maumee River area of concern.
Citation:
Arini, A., J. Cavallin, J. Berninger, R. Marfil-Vega, M. Mills, Dan Villeneuve, AND N. Basu. In vivo and in vitro neurochemical-based assessments of wastewater effluents from the Maumee River area of concern. SOCIETY OF ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY JOURNAL. Society of Environmental Toxicology and Chemistry, Pensacola, FL, 211:9-19, (2016).
Impact/Purpose:
Both citizens and regulatory authorities such as the states, EPA’s regions, and the Office of Water have expressed concerns over potential adverse effects of contaminants of emerging concern (CECs) in surface waters. Because there are many chemicals present in the nation’s surface water for which little or no biological hazard information is available, assessing the potential risks associated with exposures to CECs detected in the environment can be problematic. Greater use of biological effects-based monitoring tools has been proposed as one means to help address this challenge, since they can provide a measure of the integrated bio-activity of all chemicals present in the sample. To date, however, most effects-based monitoring studies have focused on a fairly narrow spectrum of toxicological pathways. The current work employs a series of cell-free bioassays relevant to neuroendocrine signaling in the brain to screen surface water samples for potential neuroendocrine biological activity. The work demonstrates that a variety of neuroendocrine activities could be associated with contaminants in surface water collected from the Maumee River, a Great Lakes Area of Concern. Significantly, it also examined conservation of those responses across different taxa using homogenates prepared from representative Great Lakes species of different vertebrate classes. Coupled with AOP development relevant to the neuroendocrine pathways screened in the current study, the assays and approaches employed may offer additional, cost effective, analytical tools for assessing potential biological hazards associated with complex mixtures of chemicals found in surface waters.
Description:
Fathead minnows (Pimephales promelas) were caged for four days at multiple locations upstream and downstream of a wastewater treatment plant (WWTP) discharge into the Maumee River (USA, OH). Grab water samples collected at the same location were extracted using several different extraction methods optimized for detection of specific contaminant classes (e.g., alkylphenols, bisphenol A (BPA) and steroid hormones). Impacts of the extracts on neuroendocrine targets were analyzed using brain homogenates from four species relevant to Great Lakes ecosystems (rainbow trout (RT), river otter (RO), bald eagle (BE) and human (HU)). In vitro results for these species as well as fathead minnows were compared with in vivo results from the caged fish exposures. Specifically, the ability of the extracts, or contaminants present in the corresponding river water, to interact with enzymes (monoamine oxidase (MAO) and glutamine synthetase (GS)) and receptors (dopamine (D2) and N-methyl-D-aspartate receptor (NMDA)) involved in dopamine and glutamate-dependent neurotransmission were examined. In vivo exposure of FHM lead to significant decreases of NMDA receptor binding in females (24 to 42%), when compared to the control fish, whereas the MAO activity was increased in males (2.8- to 3.2-fold). Extracts optimized for analysis of alkylphenols significantly impacted receptor binding following in vitro exposure, causing D2 inhibition in all species (66% decrease in FHM; NMDA: 24-54% decrease in HU and RT). Exposure to BPA- and steroid hormone-targeted extracts yielded some significant changes but these were not consistent across tested water extracts or species. Steroid hormone-targeted extracts inhibited GS activity in all species except FHM, while they induced MAO activity in RT brain homogenates by 15%. BPA-targeted extracts caused a MAO inhibition in FHM, RT and BE brain homogenates, with the greatest impact being observed for BE, 16% decrease. Alkylphenol-targeted extracts had an opposite effect, inducing MAO activity in RT, RO, and BE brain homogenates. Our results suggest that four days of exposure to wastewater were sufficient to impact neurotransmitters and enzymes that are reproductively important in fish. The overall concordance of in vitro results across species support the use of these methods to address some of the uncertainties associated with extrapolating responses across species.
