Oral exposure to high-dose ethanol for 28 days in rats reduces neural stem cells and immediate nascent neural progenitor cells as well as FOS-expressing newborn granule cells in adult hippocampal neurogenesis

Abstract

Drinking alcohol during pregnancy may cause fetal alcohol spectrum disorder. In rats, developmental exposure to ethanol (EtOH) at high doses has shown to induce aberrant neurogenesis in neural progenitor cells (NPCs) during weaning and suppress synaptic plasticity of newborn granule cells after maturation; neuroinflammation was even sustained until the adult stage in the hippocampal dentate gyrus (DG). To investigate whether hippocampal neurogenesis is affected by EtOH exposure in a general toxicity study, EtOH was administered orally to 5-week-old Sprague-Dawley rats at 0%, 10%, and 16% (w/v) in drinking water for 28 days. Exposure to 16% EtOH decreased type-1 neural stem cells (NSCs) and type-2a NPCs in the DG subgranular zone. A reduction in reelin-positive (reelin+) interneurons and an increased number of parvalbumin+ interneurons in the DG hilus, as well as downregulation of Mcm6 and Calb2 in the DG, suggested that self-renewal and proliferation of type-1 NSCs were suppressed. Exposure to 16% EtOH also induced M1-type microglia/peripheral macrophages, and upregulated Il1a and Tnf, suggesting that neuroinflammation might be responsible for the suppressed neurogenesis. In contrast, Drd2 and Tgfb3 upregulation might be ameliorating responses against suppressed neurogenesis. EtOH exposure (16%) also decreased the number of FOS+ granule cells, suggesting that synaptic plasticity was suppressed; concurrent upregulation of glutamate receptor/transporter genes may have occurred as a compensatory response against suppressed synaptic plasticity. Thus, high-dose EtOH exposure in young adult rats disrupted hippocampal neurogenesis differently to exposure during development. However, induction of neuroinflammation and suppressed synaptic plasticity occurred at both EtOH exposure stages.