Abstract
In addition to their carcinogenic activity, polycyclic aromatic hydrocarbons (PAHs) are suspected to be developmental neurotoxicants. We evaluated the effects of PAHs with two in vitro models that assess distinct "decision nodes" in neurodifferentiation: neuronotypic PC12 cells, which characterize the transition from cell replication to neurodifferentiation, neurite outgrowth and neurotransmitter specification; and embryonic neural stem cells (NSCs), which evaluate the origination of neurons and glia from precursors. We compared an environmentally-derived PAH mixture from a Superfund contamination site (Elizabeth River Sediment Extract, ERSE) to those of a single PAH, benzo[a]pyrene (BaP). In PC12 cells, BaP impaired the transition from cell replication to neurodifferentiation, resulting in higher numbers of cells, but with reduced cell size and deficits in all indices of neuronal features (neurite formation, development of dopamine and acetylcholine phenotypes). ERSE was far less effective, causing only modest changes in cell numbers and size and no impairment of neurite formation or neurotransmitter specification; in fact, ERSE evoked a slight increase in emergence of the acetylcholine phenotype. In the NSC model, this relationship was entirely reversed, with far greater sensitivity to ERSE than to BaP. Furthermore, ERSE, but not BaP, enhanced NSC differentiation into neurons, whereas both ERSE and BaP suppressed the glial phenotype. Our studies provide a cause-and-effect relationship for the observed association of developmental PAH exposure to behavioral deficits. Further, PAH sensitivity occurs over developmental stages corresponding to rudimentary brain formation through terminal neurodifferentiation, suggesting that vulnerability likely extends throughout fetal brain development and into early childhood.