This project will test the hypothesis that polychlorinated biphenyls(PCBs) have estrogenic or antiestrogenic properties that are dependent on both the structure and metabolism of the specific PCB. Alteration in estrogen metabolism could provide an additional mechanism for PCB potentiated changes in neurochemical function. Previous studies have shown that PCBs exhibit estrogenic effects in non-human systems. Our goal is to evaluate the estrogenicity of PCBs and their metabolites in human derived systems.
This project is focused on the estrogenic effects of lower chlorinated and hydroxylated PCBs. Through the use of the MCF-7 Focus Assay it is possible to assess the estrogenic effects of specific compounds on human breast cells. MCF-7 breast cells form a uniform cell mosaic, however, foci or nodules form in those cell cultures affected by estrogenic compounds. This estrogen dependent growth of cell foci or nodules is inhibited by antiestrogens, and therefore this assay can be used to quantatively determine whether a compound is estrogenic or antiestrogenic.
Using the human breast cancer cell line, MCF-7, this project is evaluating the in vitro
estrogenicity and antiestrogenicity of PCB congeners and their hydroxylated metabolites. To
evaluate this, the assay uses the induction of estrogen dependent end points. These endpoints are
increased tissue plasminogen activity and focal point development (proliferation and clustering
of cells). This allows the development of structure-function relationships and establishes whether
the metabolism of the PCBs in an essential prerequisite for their estrogenic action.
This project is also characterizing the metabolism in human systems of those PCB congeners that yield estrogenic metabolites. We are using human P450s in microsomes from induced or control MCF-7 cells, human hepatocytes and human P450s expressed in mammalian systems. This demonstrates whether estrogenic PCB metabolites can be produced by human p450s and will provide a basis for further determination of whether PCBs play a role in neurotoxicity due to estrogenic properties. This project is also characterizing the PCB metabolism potential in microsomes prepared from the liver, brain, kidney, and uterus of PCB exposed rats generated by the neurotoxicity projects. The specific congeners used will be those determined to be estrogenic or antiestrogenic.
