ABSTRACT
BACKGROUND: Soluble amyloid-ß peptide oligomers (AßOs), which are centrally involved in the pathogenesis of Alzheimer's disease, trigger Ca(2+) influx through N-methyl-D-aspartate receptors and stimulate reactive oxygen species generation in primary hippocampal neurons. We have previously reported that AßOs promote Ca(2+) release mediated by ryanodine receptors (RyR), which in turn triggers mitochondrial fragmentation. We have also reported that the antioxidant N-acetylcysteine (NAC) prevents AßOs-induced Ca(2+) signal generation. OBJECTIVES: To determine if RyR-mediated Ca(2+) release activated by the specific agonist 4-chloro-m-cresol (4-CMC) induces fragmentation of the mitochondrial network, and to ascertain if NAC prevents the mitochondrial fragmentation induced by AßOs and/or 4-CMC. METHODS: Mature primary rat hippocampal neurons were incubated for 24 h with sublethal concentrations of AßOs (500 nM) or for 1-3 h with 4-CMC (0.5-1 mM), ± 10 mM NAC. Mitochondrial morphology was assessed by confocal microscopy of fixed neurons stained with anti-mHsp70. Intracellular Ca(2+) levels were determined by time series microscopy of neurons preloaded with Fluo-4 AM. RESULTS: Preincubation of neurons for 30 min with NAC prevented the mitochondrial fragmentation induced by AßOs or 4-CMC. In addition, we confirmed that preincubation with NAC abolished the stimulation of RyR-mediated Ca(2+) release induced by AßOs or 4-CMC. CONCLUSION: The present results strongly suggest that the general antioxidant NAC prevents AßO-induced mitochondrial fragmentation by preventing RyR-mediated Ca(2+)-induced Ca(2+) release.
