Ethanol is a neuroteratogen and neurodegeneration is the most devastating consequence of developmental exposure to
ethanol. The mechanisms underlying
ethanol-induced neurodegeneration are complex.
Ethanol exposure produces
reactive oxygen species (ROS) which cause oxidative stress in the brain. We hypothesized that
ethanol would activate autophagy to alleviate oxidative stress and neurotoxicity. Our results indicated that
ethanol increased the level of the autophagic marker Map1lc3-II (LC3-II) and upregulated LC3 puncta in SH-SY5Y
neuroblastoma cells. It also enhanced the levels of LC3-II and BECN1 in the developing brain; meanwhile,
ethanol reduced SQSTM1 (p62) levels.
Bafilomycin A(1), an inhibitor of autophagosome and lysosome fusion, increased p62 levels in the presence of
ethanol.
Bafilomycin A(1) and
rapamycin potentiated
ethanol-increased LC3 lipidation, whereas
wortmannin and a BECN1-specific
shRNA inhibited
ethanol-promoted LC3 lipidation.
Ethanol increased mitophagy, which was also modulated by BECN1
shRNA and
rapamycin. The evidence suggested that
ethanol promoted autophagic flux. Activation of autophagy by
rapamycin reduced
ethanol-induced ROS generation and ameliorated
ethanol-induced neuronal death in vitro and in the developing brain, whereas inhibition of autophagy by
wortmannin and BECN1-specific
shRNA potentiated
ethanol-induced ROS production and exacerbated
ethanol neurotoxicity. Furthermore,
ethanol inhibited the MTOR pathway and downregulation of MTOR offered neuroprotection. Taken together, the results suggest that autophagy activation is a neuroprotective response to alleviate
ethanol toxicity.
Ethanol modulation of autophagic activity may be mediated by the MTOR pathway.