Caspase-12 Activation is Involved in Amyloid-beta Protein-Induced Synaptic Toxicity

Synapse loss is considered to be the best correlate of cognitive impairments in Alzheimer's disease (AD), and growing evidence supports the notion that certain events that trigger neuronal death in AD can be initiated by the local activation of caspases within the synaptic compartment. We have demonstrated previously that presynaptic terminals are particularly vulnerable to endoplasmic-reticulum (ER)-stress depending on amyloid-beta protein (A beta). This toxicity included a notable reduction of actin and synaptophysin protein and mitochondrial dysfunction. This synaptic damage was prevented by incubation with a wide range of caspase inhibitor, suggesting the activation of local synaptic apoptotic mechanisms. The ER-resident caspase-12 was initially identified as a mediator of A beta neurotoxicity. Thus, the current study was conducted to explore the presence and local activation of caspase-12 in cortical and hippocampal synaptosomes isolated from rat and from the triple transgenic mouse model of AD (3xTg-AD) in the presence of A beta and ryanodine. Under these conditions, we found mitochondrial failure accompanied by a reduction in actin levels which was dependent on caspase-12 activation suggesting its participation in A beta-induced synaptic toxicity.