β Amyloid protein (Aβ) and acetylcholinesterase (AChE) have been shown to be closely implicated in the pathogenesis of Alzheimer's disease. In the current study, we investigated the effects of bis(7)-tacrine, a novel dimeric AChE inhibitor, on Aβ-induced neurotoxicity in primary cortical neurons. Bis(7)-tacrine, but not other AChE inhibitors, elicited a marked reduction of both fibrillar and soluble oligomeric forms of Aβ-induced apoptosis as evidenced by chromatin condensation and DNA specific fragmentation. Both nicotinic and muscarinic receptor antagonists failed to block the effects of bis(7)-tacrine. Instead, nimodipine, a blocker of L-type voltage-dependent Ca2+channels (VDCCs), attenuated Aβ neurotoxicity, whereas N-, P/Q- or R-type VDCCs blockers and ionotropic glutamate receptor antagonists did not. Fluorescence Ca2+imaging assay revealed that, similar to nimodipine, bis(7)-tacrine reversed Aβ-triggered intracellular Ca2+increase, which was mainly contributed by the extracellular Ca2+instead of endoplasmic reticulum and mitochondria Ca2+. Concurrently, using whole cell patch-clamping technique, it was found that bis(7)-tacrine significantly reduced the augmentation of high voltage-activated inward calcium currents induced by Aβ. These results suggest that bis(7)-tacrine attenuates Aβ-induced neuronal apoptosis by regulating L-type VDCCs, offers a novel modality as to how the agent exerts neuroprotective effects.
- β amyloid
- Ca 2+
- L-type voltage-dependent Ca channels 2+
- Cellular and Molecular Neuroscience