Perfluorooctane sulfonate induces apoptosis of cerebellar granule cells via a ROS-dependent protein kinase C signaling pathway

Abstract

Perfluorinated chemicals (PFCs) have been widely used in a variety of industry and consumer products. Perfluorooctane sulfonate (PFOS), a prominent member of perfluoroalkyls, is known as a neurotoxicant in developing brain and affects behavior and motor activity. However, mechanism of neurotoxicity still remains unknown. In this study, we attempted to analyze apoptotic effects of PFOS on developing neuron. Cerebellar granule cells derived from 7-day old SD rats and grown in culture for additional 7 days were used to mimic postnatal day (PND)-14 conditions. PFOS exposure increased ROS production, which was blocked by ROS inhibitor, N-acetylcysteine (NAC). PFOS selectively induced dose-dependent translocations of PKC-α, -βII and -ɛ among PKC isozymes tested. The translocation of these specific PKC isozymes was blocked by NAC. A panel of different approaches was utilized to detect apoptotic effects. PFOS induced caspase-3 activity and nucleosomal DNA fragmentation in a dose-dependent manner, which were blocked by pretreatment of NAC. These apoptotic effects were further confirmed by TUNEL staining. Increases of caspase-3 activity and nucleosomal DNA fragmentation were dampened by the inhibition of PKC isozymes using siRNA technique. Taken together, our results suggest that PFOS may induce apoptosis of cerebellar granule cells via a ROS-mediated PKC signaling pathway. PKC signal transduction pathway is pivotal in learning and memory and apoptosis of neuronal cells is a critical event in neurotoxicity. Thus, this study may contribute to understand a new mechanistic aspect of PFOS-induced neurotoxicities.