P171 EXPOSURE TO THE ENDOCRINE DISRUPTORS TRIPHENYL PHOSPHATE AND DIPHENYL PHOSPHATE ALTERS THE DNA BASE EXCISION REPAIR PATHWAY IN NORMAL THYROID CELLS

BACKGROUND-AIM Thyroid diseases and carcinogenesis are complex, multifactorial conditions involving thyroid hormone metabolism and oxidative DNA damage. Environmental pollution appears to be the most significant risk factor for the increased incidence of thyroid disease. At present, insufficient data are available on the role of aryl phosphate esters (APEs) metabolite in human thyroid pathophysiology, especially on the ability to interfere with the signals linked to oxidative DNA damage repair. The TPhP metabolite DPhP (diphenylphosphate) was detected in the urine and blood of individuals with thyroid disorders. This study evaluates the molecular effects of exposure to environmental pollutants DPhP and TPhP on a human thyroid follicular epithelium model. METHODS We evaluated the effects of aryl phosphate esters pollutans (DPhP and TPhP) on Nthy-ori3-1 cells using the following methods: cell viability by MTS, extracellular production of H2O2 by Ros-Glo, ability to internalize pollutant metabolites by HPLC, cytology shape analysis, gene and protein expression of components of the DNA base excision repair system (BER) and EGFR pathway by real-time PCR and Western blot. RESULTS Exposure to the metabolite DPhP and the endocrine disruptor TPhP increased mitochondrial activity, hydrogen peroxide production, and cellular stress in proliferating Nthy-ori 3-1 cells. Significant alterations in gene and protein expression of BER components, EGFR, ERbB2 and TPO were observed. The expression of genes involved in BER was modulated by both TPhP and DPhP, exhibiting hormetic, biphasic effects. In particular, DPhP [2μM] induced MUTYH and APE-1/Ref-1 increasing expression, while DPHP [10μM] induced a significant reduction of OGG1 expression. THPH [10μM] increased the expression of ErbB2 and BER proteins, while DPhP [10μM] increased the expression of HER2/ErbB2 and MUTYH in Nthy-ori3-1 cells. The results of this study demonstrate that the DPhP as metabolite of TPhP can induce cellular stress, H2O2 production and alteration of the BER pathway due to bioaccumulation. CONCLUSIONS This study is the first to demonstrate that aryl phosphate ester exposure can induce cellular stress and alter the expression of thyroid peroxidase, ErbB2, OGG1, and MUTYH via potential bioaccumulation in the thyroid follicular epithelium. Further studies are needed to better understand the role of pollutant disruptors in dysregulating thyroid function in humans.