Molecular Mechanisms of Marine Organohalogen Bioaccumulation and Neurotoxicity

摘要

ABSTRACT There is urgent public health need to better understand the relative risks and benefits associated with consumption of seafood. The overall mission of this project is to understand the toxicity of marine organohalogen pollutants. We take a powerful approach to understanding and mitigating this risk by asking two questions, central to future efforts to predict and minimize risk. Aim 1 of this project asks how these compounds bioaccumulate, focusing on xenobiotic transporters, which are a key pathway for limiting accumulation of foreign chemicals. We will determine the interactions of the four major human xenobiotic transporters (XTs) with environmentally relevant natural and man-made marine organohalogens. The results will extend and expand the scope of our previous work indicating that several of these compounds can act as potent inhibitors of transporter function. In parallel, we will take advantage of recent progress with heterologous transporter-expression and CRISPR/CAS9 gene editing in sea urchins, to dissect the functional role of XTs in governing bioaccumulation in marine cells. This will be supported by a structure guided approach to determine how evolutionary changes in transporter structure modify interactions with TICs, following up on recent progress towards purification and crystallization of marine XTs in complex with pollutants. Aim 2 of this project will determine the structure activity relationships governing neurotoxicity of marine pollutants. These studies are motivated by preliminary data indicating that naturally produced organohalogens are highly potent inhibitors of ryanodine sensitive Ca2+ channels (RyRs) and Ca2+ ATPase transporters (SERCAs), which are arguably the most direct targets of environmentally relevant organohalogens in the brain. We will use primary cultures of hippocampal neurons cultured from male and female wild type mice to determine how activity at these molecular targets alter neuronal network Ca2+ dynamics and morphology using real-time fluorescence cell imaging and morphometric approaches. In addition, we will determine how hippocampal neurons that express mutation RyR1-R163C known to confer heat stress intolerance, alter sensitivity to organohalogens, and ask whether these effects are gender-specific. These studies will address the critical need to better understand the molecular mechanisms by which naturally occurring and man-made seafood pollutants accumulate in target cells and perturb the Ca2+ dynamics essential for normal neuronal network development.