Cuprizone decreases intermediate and late-stage progenitor cells in hippocampal neurogenesis of rats in a framework of 28-day oral dose toxicity study

Abstract

Developmental exposure to cuprizone (CPZ), a demyelinating agent, impairs intermediate-stage neurogenesis in the hippocampal dentate gyrus of rat offspring. To investigate the possibility of alterations in adult neurogenesis following postpubertal exposure to CPZ in a framework of general toxicity studies, CPZ was orally administered to 5-week-old male rats at 0, 120, or 600mg/kg body weight/day for 28days. In the subgranular zone (SGZ), 600mg/kg CPZ increased the number of cleaved caspase-3(+) apoptotic cells. At ≥120mg/kg, the number of SGZ cells immunoreactive for TBR2, doublecortin, or PCNA was decreased, while that for SOX2 was increased. In the granule cell layer, CPZ at ≥120mg/kg decreased the number of postmitotic granule cells immunoreactive for NEUN, CHRNA7, ARC or FOS. In the dentate hilus, CPZ at ≥120mg/kg decreased phosphorylated TRKB(+) interneurons, although the number of reelin(+) interneurons was unchanged. At 600mg/kg, mRNA levels of Bdnf and Chrna7 were decreased, while those of Casp4, Casp12 and Trib3 were increased in the dentate gyrus. These data suggest that CPZ in a scheme of 28-day toxicity study causes endoplasmic reticulum stress-mediated apoptosis of granule cell lineages, resulting in aberrations of intermediate neurogenesis and late-stage neurogenesis and following suppression of immediate early gene-mediated neuronal plasticity. Suppression of BDNF signals to interneurons caused by decreased cholinergic signaling may play a role in these effects of CPZ. The effects of postpubertal CPZ on neurogenesis were similar to those observed with developmental exposure, except for the lack of reelin response, which may contribute to a greater decrease in SGZ cells.

Keywords: 28-day oral toxicity study; Adult neurogenesis; Cholinergic signaling; Cuprizone (CPZ); Hippocampal dentate gyrus; Myelin toxicant.