In addition, we conducted studies to investigate potential blockade of toxicity associated with EtOH exposure by overexpression of Mcl-1L isoform. Neuronal progenitor cells were transfected with mammalian expression vectors encoding Mcl-1L or Mcl-1S isoforms and either exposed to 50 mM EtOH or left untreated. Cell viability were analyzed by MTT cell viability assay. As shown in Fig. 7, EtOH exposure caused a significant reduction in cellular viability (Fig. 7a, b), altered morphology (Fig. 7c), and induced cleaved caspase-3 activation (Fig. 7d) in neural progenitors. Interestingly, ectopic expression of Mcl-1L isoform showed a significant recovery of cellular morphology, viability, and cleaved caspase-3 activation suggesting that EtOH-mediated cellular toxicity was associated with the reduced levels of Mcl-1L isoforms in neural progenitors. On the other hand, ectopic expression of Mcl-IS did not affect cell viability or cleaved caspase-3 in ethanol-activated hNPCs cells. Overexpression of Mcl-1S did not show any significant impact on cellular viability and apoptosis in control-untreated cells. These results suggest that EtOH-mediated toxicity may not be associated with increased copies of Mcl-1S isoform, but may be related to the decreased copies
