Toxic effects of bisphenol a in thyroid cells and evaluation of the protective role of selenium compounds

Bisphenol A (BPA) is a chemical compound that is used in the production of polycarbonates and epoxy resins. Humans are widely exposed to this compound by oral, inhalation and dermal routes in daily life. It is known to have estrogenic effects and is considered to be an endocrine disruptor. In recent studies, it has been stated that BPA could affect thyroid homeostasis, thyroid hormone production and interact with thyroid hormone receptors. Thyroid along with kidney, is the highest selenium containing tissue. Selenium is an essential trace element which is primarily by diet. Selenium is present in the structure of deiodinases, which have roles in thyroid hormone synthesis. In addition, as being a part of antioxidant selenoproteins, it protects the thyroid gland against oxidative stress. When organic and inorganic selenocompounds are taken at physiological doses, they can be protect the organism against the hazardous effects of several chemicals. In this thesis, we aimed to investigate the toxic effects of BPA on human papillary thyroid cancer cell line (B-CPAP) and the modifying effects of selenium supplementation against BPA toxicity. We evaluated the cytopathological changes, cytotoxicity, oxidant/antioxidant parameters and apoptosis caused by BPA on B-CPAP cells. Moreover, the protective roles of inorganic selenium (sodium selenite, SS) and organic selenium (selenomethionine, SM) were also assessed. Data have shown that BPA caused oxidative stress, elevated intracellular ROS and lipid peroxidation levels and decreases in total glutathione (GSH) levels in B-CPAP cell line. In addition, BPA also led to cytopathological alterations and apoptosis in these cells. Our findings suggest that selenocompounds could reduce the cytopathological changes, oxidant/antioxidant status alterations and apoptosis induced by BPA. We can conclude that one of the underlying mechanisms in the toxic effects of BPA in B-CPAP cells is oxidative stress. Inorganic and organic selenocompounds can be partially protective against BPA toxicity by their antioxidant functions in thyroid cells. Keywords: Bisphenol A, selenium, oxidative stress, apoptosis, B-CPAP cell line.