Human neural stem cells are more sensitive than astrocytes to ethanol exposure

Abstract

Background: Exposure to ethanol (EtOH) can be deleterious to the developing central nervous system. The mechanisms by which EtOH exposure induces neural pathology in utero remain unclear. However, EtOH-induced increases in protein kinase C (PKC) have been associated with apoptosis in human primary cell cultures. Although the toxic effects of EtOH on differentiated neural cells have been studied in laboratory animal models, the susceptibility of the human neural stem cells (NSCs) that predominate in the central nervous system during embryonic development has not been addressed. Methods: For this study, fetal human brain cells, which satisfied the criteria for NSCs by being CD133-positive, nestin-positive, and differentiated glial fibrillary acidic protein-positive human astrocytes, were studied. The cytotoxic potential of EtOH in NSC and astrocyte cultures was studied by using morphological and biochemical methods. In addition, membrane and cytosolic fraction PKC activity for each cell type was assessed. Results: NSC showed a dose-dependent increase in EtOH-induced toxicity as estimated by terminal transferase-mediated dUTP nick end labeling (TUNEL) stain and viability assays. TUNEL staining indicating DNA degradation consistent with programmed (apoptotic) cell death was detectable in 90% of NSC 16 hr after 2 hr exposure to 10 mM EtOH. NSC also showed a concentration-dependent increase in membrane, but not cytosol, PKC activity over the same EtOH dose range. By contrast, astrocytes showed no cytotoxic effects at any concentrations of EtOH used (0-10 mM). PKC activity of both the membrane and cytosolic fragments from astrocytes also was unaffected by this range of doses. Conclusions: This study demonstrates the susceptibility of human NSCs, compared with astrocytes, to EtOH and indicates that alterations in PKC signal transduction in NSC may play a role in EtOH-induced neuropathological processes.