The long-term goals of this research are to determine the mechanisms by which polychlorinated biphenyls (PCBs) disrupt thyroid hormone (TH) action during brain development, to define the neurological consequences of this disruption in rodent model systems, and to translate this information to study human populations. PCBs are widespread and persistent environmental contaminants, and incidental exposure to PCBs has been associated with reduced TH levels in pregnant women, lower birth weight and early growth rate, and neurological deficits. We propose that a combination of coplanar (dioxin-like) and non-coplanar PCBs are required to produce metabolites that bind to the TH receptor (TR), producing effects that are dependent on the TH response element (TRE), cellular context and TR isoform. The resulting effects on brain development are not predictable based on our current knowledge. To test this hypothesis and its implications, we will identify specific PCB metabolites in cell culture and in animals following treatments with defined mixtures. AhR-null and CYP1A1-null mice will be employed to confirm the role of AhR and CYP in the generation of PCB metabolites and effects on TH signaling. Specific metabolites will be tested for their ability to bind to rat and human TR11 and TR21 isoforms. Metabolites that exhibit binding will be characterized for their ability to interfere with TH signaling in selected cells in culture. In vitro studies will specifically address the ability of PCB metabolites to act as thyroid hormone agonists or antagonists. A combination of approaches including luciferase reporter assays, electrophoretic mobility shift (EMSA) and chromatin immunoprecipitation (ChIP) will be use in these in vitro studies. Human cells lines derived from liver, fibroblast, monocytes and neurons will be used to test whether these molecular events occur in humans. Endpoints of TH actions disrupted by PCBs in human fibroblasts or monocytes may be useful in studying these events in human populations.
Polychlorinated biphenyls (PCBs) are known to affect brain development in humans, but no child born in the United States is free of contamination with these chemicals. We are testing the novel hypothesis that a combination of PCB types must be present to induce the ability of the human body to modify the PCB structure;these modified structures appear to interfere directly with the ability of thyroid hormone to perform its normal role in development. These studies will provide important new information about the toxicity of PCBs, and perhaps other common contaminants in the human population.
|Zota, Ami R; Mitro, Susanna D; Robinson, Joshua F et al. (2018) Polybrominated diphenyl ethers (PBDEs) and hydroxylated PBDE metabolites (OH-PBDEs) in maternal and fetal tissues, and associations with fetal cytochrome P450 gene expression. Environ Int 112:269-278|
|Gore, A C; Chappell, V A; Fenton, S E et al. (2015) EDC-2: The Endocrine Society's Second Scientific Statement on Endocrine-Disrupting Chemicals. Endocr Rev 36:E1-E150|
|Wadzinski, Thomas L; Geromini, Katherine; McKinley Brewer, Judy et al. (2014) Endocrine disruption in human placenta: expression of the dioxin-inducible enzyme, CYP1A1, is correlated with that of thyroid hormone-regulated genes. J Clin Endocrinol Metab 99:E2735-43|
|Bansal, Ruby; Tighe, Daniel; Danai, Amin et al. (2014) Polybrominated diphenyl ether (DE-71) interferes with thyroid hormone action independent of effects on circulating levels of thyroid hormone in male rats. Endocrinology 155:4104-12|
|Zota, Ami R; Linderholm, Linda; Park, June-Soo et al. (2013) Temporal comparison of PBDEs, OH-PBDEs, PCBs, and OH-PCBs in the serum of second trimester pregnant women recruited from San Francisco General Hospital, California. Environ Sci Technol 47:11776-84|
|Vandenberg, Laura N; Colborn, Theo; Hayes, Tyrone B et al. (2013) Regulatory decisions on endocrine disrupting chemicals should be based on the principles of endocrinology. Reprod Toxicol 38:1-15|
|Paul, Katie B; Hedge, Joan M; Bansal, Ruby et al. (2012) Developmental triclosan exposure decreases maternal, fetal, and early neonatal thyroxine: a dynamic and kinetic evaluation of a putative mode-of-action. Toxicology 300:31-45|
|Zoeller, R Thomas; Brown, T R; Doan, L L et al. (2012) Endocrine-disrupting chemicals and public health protection: a statement of principles from The Endocrine Society. Endocrinology 153:4097-110|
|Vandenberg, Laura N; Colborn, Theo; Hayes, Tyrone B et al. (2012) Hormones and endocrine-disrupting chemicals: low-dose effects and nonmonotonic dose responses. Endocr Rev 33:378-455|
|Giera, Stefanie; Bansal, Ruby; Ortiz-Toro, Theresa M et al. (2011) Individual polychlorinated biphenyl (PCB) congeners produce tissue- and gene-specific effects on thyroid hormone signaling during development. Endocrinology 152:2909-19|
Showing the most recent 10 out of 25 publications