Novel Insights into the Distribution and Effects of Perfluorooctanesulfonic acid (PFOS) in the Nervous System of a Frog Tadpole Model by Mass Spectrometry Imaging

Determining how environmental contaminants localize within tissues is essential for understanding the consequences of sublethal exposures. Therefore, we optimized a mass spectrometry imaging (MSI) workflow to study the distribution and biological effects of contaminants in an environmentally relevant frog tadpole model. We applied the method to the entire tadpole head postexperimental exposure to the legacy contaminant, perfluorooctanesulfonic acid (PFOS; 0.1-100 μg/L, 48 h). At 10 μg/L, PFOS unexpectedly localized mainly to the olfactory epithelium. At 100 μg/L, PFOS was distributed throughout all tissues except for the brain, where only the pineal gland showed significant accumulation. The pineal gland, a neuroendocrine organ regulating the circadian rhythm, is not protected by the blood-brain barrier. Together, these findings indicate that PFOS did not readily cross the blood-brain barrier. In both the olfactory epithelium and pineal gland, effects of PFOS were reflected in changes in the abundances of endogenous lipids. The results open questions for the most adverse outcomes of PFOS exposure, including effects on the olfactory-mediated behavior and circadian rhythm. The present study exemplifies how MSI advances our analytical toolbox. The ability to localize contaminants within biological compartments is critical for the characterization of their toxic effects and risks to wildlife and humans.