Bisphenol A increases hydrogen peroxide generation by thyrocytes both in vivo and in vitro

Abstract

Bisphenol A (BPA) is the most common monomer in polycarbonate plastics and an endocrine disruptor. Though some effects of BPA on thyroid hormone (TH) synthesis and action have been described, the impact of this compound on thyroid H ₂O ₂ generation remains elusive. H ₂O ₂ is a reactive oxygen species (ROS), which could have deleterious effect on thyrocytes if in excess. Therefore, herein we aimed at evaluating the effect of BPA exposition both in vivo and in vitro on H ₂O ₂ generation in thyrocytes, besides other essential steps for TH synthesis. Female Wistar rats were treated with vehicle (control) or BPA 40 mg/kg BW for 15 days, by gavage. We then evaluated thyroid iodide uptake, mediated by sodium-iodide symporter (NIS), thyroperoxidase (TPO) and dual oxidase (DOUX) activities (H ₂O ₂ generation). Hydrogen peroxide generation was increased, while iodide uptake and TPO activity were reduced by BPA exposition. We have also incubated the rat thyroid cell line PCCL3 with 10 ⁻⁹ M BPA and evaluated Nis and Duox mRNA levels, besides H ₂O ₂ generation. Similar to that found in vivo, BPA treatment also led to increased H ₂O ₂ generation in PCCL3. Nis mRNA levels were reduced and Duox2 mRNA levels were increased in BPA-exposed cells. To evaluate the importance of oxidative stress on BPA-induced Nis reduction, PCCL3 was treated with BPA in association to N-acetylcysteine, an antioxidant, which reversed the effect of BPA on Nis. Our data suggest that BPA increases ROS production in thyrocytes, what could lead to oxidative damage thus possibly predisposing to thyroid disease.