Effects of Perfluorooctane Sulfonate on Cerebellar Cells via Inhibition of Type 2 Iodothyronine Deiodinase Activity

Perfluorooctane sulfonate (PFOS) has been used in a wide variety of industrial and commercial products. The adverse effects of PFOS on the developing brain are becoming of a great concern. However, the molecular mechanisms of PFOS on brain development have not yet been clarified. We investigated the effect of early-life exposure to PFOS on brain development and the mechanism involved. We investigated the change in thyroid hormone (TH)-induced dendrite arborization of Purkinje cells in the primary culture of newborn rat cerebellum. We further examined the mechanism of PFOS on TH signaling by reporter gene assay, quantitative RT-PCR, and type 2 iodothyronine deiodinase (D2) assay. As low as 10−7 M PFOS suppressed thyroxine (T4)-, but not triiodothyronine (T3)-induced dendrite arborization of Purkinje cells. Reporter gene assay showed that PFOS did not affect TRα1- and TRβ1-mediated transcription in CV-1 cells. RT-PCR showed that PFOS suppressed D2 mRNA expression in the absence of T4 in primary cerebellar cells. D2 activity was also suppressed by PFOS in C6 glioma-derived cells. These results indicate that early-life exposure of PFOS disrupts TH-mediated cerebellar development possibly through the disruption of D2 activity and/or mRNA expression, which may cause cerebellar dysfunction.