Ethanol induces cytostasis of cortical basal progenitors

Abstract

BackgroundDeveloping brain is a major target for alcohol’s actions and neurological/functional abnormalities include microencephaly, reduced frontal cortex, mental retardation and attention-deficits. Previous studies have shown that ethanol altered the lateral ventricular neuroepithelial cell proliferation. However, the effect of ethanol on subventricular basal progenitors which generate majority of the cortical layers is not known.MethodsWe utilized spontaneously immortalized rat brain neuroblasts obtained from cultures of 18-day-old fetal rat cerebral cortices using in vitro ethanol exposures and an in utero binge model. In the in vitro acute model, cells were exposed to 86 mM ethanol for 8, 12 and 24 h. The second in vitro model comprised of chronic intermittent ethanol (CIE) exposure which consisted of 14 h of ethanol treatment followed by 10 h of withdrawal with three repetitions.ResultsE18 neuroblasts expressing Tbr2 representing immature basal progenitors displayed significant reduction of proliferation in response to ethanol in both the models. The decreased proliferation was accompanied by absence of apoptosis or autophagy as illustrated by FACS analysis and expression of apoptotic and autophagic markers. The BrdU incorporation assay indicated that ethanol enhanced the accumulation of cells at G1 with reduced cell number in S phase. In addition, the ethanol-inhibited basal neuroblasts proliferation was connected to decrease in cyclin D1 and Rb phosphorylation indicating cell cycle arrest. Further, in utero ethanol exposure in pregnant rats during E15-E18 significantly decreased Tbr2 and cyclin D1 positive cell number in cerebral cortex of embryos as assessed by cell sorting analysis by flow cytometry.ConclusionsAltogether, the current findings demonstrate that ethanol impacts the expansion of basal progenitors by inducing cytostasis that might explain the anomalies of cortico-cerebral development associated with fetal alcohol syndrome.Electronic supplementary materialThe online version of this article (doi:10.1186/s12929-016-0225-8) contains supplementary material, which is available to authorized users.

Episodic Prenatal Exposure To Ethanol Affects Postnatal Neurogenesis In The Macaque Dentate Gyrus And Visual Recognition Memory

“…Thus, ethanol exposure in vivo may target cells in the phases of the cell cycle other than the S phase. This is consistent with the efects of prenatal exposure to ethanol on cortical proliferative zones in vivo (Miller and Nowakowski, 1991;Miller and Kuhn, 1995) and neural stem cells in vitro (Higgins and Borenfreund, 1986;Santillano et al, 2005;Hicks et al, 2010;Riar et al, 2016) in which ethanol principally afects cells passing through the G1 phase. Note, however, that a recent analysis does show that the S phase of proliferating hippocampal cells of adult rats is more than halved following exposure to ethanol (McClain et al, 2011).…”

DNA Methylation program in normal and alcohol-induced thinning cortex

“…Second, the cortex-wide reduction of DNA methylation may be biased toward the lower cortical layers due to inherent cell number. Third, in light of several reports (Prock & Miranda, 2007; Riar et al, 2016) demonstrating a developmental delay of cortical progenitors devoid of apoptosis, it can be presumed that cellular density in the CP may be more compacted than in untreated CPs (see Fig. 6), thereby skewing the immunohisto-chemical abundance of DNA methylation markers.…”

“…Interestingly, one group has reported that alcohol-induced depletion of neural stem cells (and by default, their proliferation) is not due to neuroepithelial cell apoptosis, but rather is due to a premature transformation of the NEs into radial glial-like cells (Camarillo & Miranda, 2008). Another group has proposed that reduced progenitor proliferation may be the result of cytostasis, or cell cycle arrest in the absence of apoptosis (Riar et al, 2016). Whichever the case, the apparent result would denote a higher number of cells remaining in the VZ/SVZ, meaning that these cells do not survive past differentiation or represent a delay in development, given the similarities between the E17 alcohol-exposed cortex and E16 controls.…”

“…Cross-sectional neuroimaging studies have also recently revealed that children and adolescents suffering from FASD exhibit abnormalities in the thickness of different regions of the cerebral cortex, as compared to healthy controls (Robertson et al, 2016; Sowell et al, 2008; Yang, Roussotte, et al, 2012). While several observations have been made regarding the fundamental hindrance of alcohol on cortical development, e.g., apoptosis (Lebedeva et al, 2015), deficiency of neurotrophic factors, prevention of cell migration (Aronne, Guadagnoli, Fontanet, Evrard, & Brusco, 2011; Chikhladze, Ramishvili, Tsagareli, & Kikalishvili, 2011; Riar, Narasimhan, Rathinam, Henderson, & Mahimainathan, 2016), and abnormal somatic morphologies of cortical neurons (Chikhladze et al, 2011; Lawrence, Otero, & Kelly, 2012), the mechanism underlying the structural abnormality systemically occurring in relationship to alcohol exposure is not clear.…”

Ethanol (E) Impairs Fetal Brain GSH Homeostasis by Inhibiting Excitatory Amino-Acid Carrier 1 (EAAC1)-Mediated Cysteine Transport

“…Further, the E concentration used herein approximated those that were widely used to elicit a range of neurotoxic responses in various mouse and rat models [ 7 , 66 , 72 ]. E-treated plates were incubated for 24 h in an alcohol-pre-saturated incubator by placing a beaker filled with E for 24 h to prevent evaporation and maintain E concentrations in the culture media [ 69 , 73 ], while the control cells were maintained in the normal incubator.…”