Excessive autophagy contributes to neuron death in cerebral ischemia

Abstract

AimsTo determine the extent to which autophagy contributes to neuronal death in cerebral hypoxia and ischemia.MethodsWe performed immunocytochemistry, western blot, cell viability assay, and electron microscopy to analyze autophagy activities in vitro and in vivo.ResultsIn both primary cortical neurons and SH‐SY5Y cells exposed to oxygen and glucose deprivation (OGD) for 6 h (hours) and reperfusion (RP) for 24, 48 and 72 h respectively, an increase of autophagy was observed as determined by the increased ratio of LC3‐II to LC3‐I and Beclin‐1 (BECN1) expression. Using Fluoro‐Jade C and monodansylcadaverine (MDC) double‐staining, and electron microscopy we found the increment in autophagy after OGD/RP was accompanied by increased autophagic cell death, and this increased cell death was inhibited by the specific autophagy inhibitor, 3‐Methyladenine (3‐MA). The presence of large autolysosomes and numerous autophagosomes in cortical neurons were confirmed by electron microscopy. Autophagy activities were increased dramatically in the ischemic brains 3 to 7 days post‐injury from a rat model of neonatal cerebral hypoxia/ischemia as shown by increased punctate LC3 staining and Beclin‐1 expression.ConclusionExcessive activation of autophagy contributes to neuronal death in cerebral ischemia. This study was supported by CIHR, MHRC, MICH and Canadian Stroke Network.