Developmental exposure to perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) selectively decreases brain dopamine levels in northern leopard frogs

Abstract

Per- and polyfluoroalkyl substances (PFAS) are synthetic compounds that are a major public health concern due to widespread use, long environmental and biological half-lives, detection in most human plasma samples, and links to multiple adverse health outcomes. The literature suggests that some PFAS may be neurotoxic. However, there are major gaps in the literature with respect to how environmentally-relevant doses during development may influence the nervous system. To address this gap, we utilized a sentinel species, Northern leopard frogs (Lithobates pipiens) to determine the effects of developmental exposure to environmentally relevant perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) on major neurotransmitter systems. Frog larvae at Gosner stage 25 were exposed to 10, 100, or 1000 ppb PFOS or PFOA for 30 days before neurochemical analysis. High performance liquid chromatography (HPLC) with electrochemical detection or fluorescent detection assays was used to measure neurotransmitter levels, which were normalized to protein levels in each sample. Dopamine (DA) decreased significantly in the brains of frogs treated with PFOA (1000 ppb) and PFOS (100 and 1000 ppb). Significant increases in DA turnover also resulted from PFOA and PFOS treatment. Neither PFOS, nor PFOA produced detectable alterations in serotonin (nor its metabolite), norepinephrine, gamma-amino butyric acid (GABA), glutamate, or acetylcholine. PFAS body burdens showed that PFOS accumulated relative to dose, while PFOA did not. These data suggest that DArgic neurotransmission is selectively affected in developmentally exposed amphibians and that PFAS should be evaluated for a potential role in diseases that target the DA system.