. (2003) Reduction of calcium release from the endoplasmic reticulum could only provide partial neuroprotection against betaamyloid peptide toxicity.

Beta-amyloid (Ab) peptide has been suggested to play important roles in the pathogenesis of Alzheimer's disease (AD). Ab peptide neurotoxicity was shown to induce disturbance of cellular calcium homeostasis. However, whether modulation of calcium release from the endoplasmic reticulum (ER) can protect neurons from Ab toxicity is not clearly defined. In the present study, Ab peptide-triggered ER calcium release in primary cortical neurons in culture is modulated by Xestospongin C, 2-aminoethoxydiphenyl borate or FK506. Our results showed that reduction of ER calcium release can partially attenuate Ab peptide neurotoxicity evaluated by LDH release, caspase-3 activity and quantification of apoptotic cells. While stress signals associated with perturbations of ER functions such as up-regulation of GRP78 was significantly attenuated, other signaling machinery such as activation of caspase-7 transmitting death signals from ER to other organelles could not be altered. We further provide evidence that molecular signaling in mitochondria play also a significant role in determining neuronal apoptosis because Ab peptidetriggered activation of caspase-9 was not significantly reduced by attenuating ER calcium release. Our results suggest that neuroprotective strategies aiming at reducing Ab toxicity should include molecular targets linked to ER perturbations associated with ER calcium release as well as mitochondrial stress. Keywords: 2APB, beta-amyloid, calcium, caspase-3, caspase-9, GRP78. One of the pathological hallmarks of Alzheimer's disease (AD) is extracellular deposition of neuritic plaques composed primarily of densely aggregated beta-amyloid (Ab) peptide (Ray et al. 1998). Ab peptide is a heterogeneous 39-43-amino acid peptide generated by sequential cleavage of amyloid precursor protein by b-secretase and c-secretase (Ray et al. 1998). It is now generally considered that Ab peptide plays a pivotal role in the pathogenesis of Alzheimer's disease (for a review see Yankner 1996). Treatment of neurons in culture with Ab peptide can induce apoptosis (Loo et al. 1993;Chang et al. 2002) and necrosis (Behl et al. 1994). However, the specific intracellular signaling pathways leading to neuronal cell death triggered by Ab peptide have not yet been completely defined ATPase; PS-1, presenilin-1; XeC, Xestospongin C.

Beta-amyloid (Abeta) peptide-induced neurotoxicity has been implicated in the pathogenesis of Alzheimer's disease (AD). The exact mechanism by which Abeta peptides trigger neuronal death is not well defined and may be related to an abrupt increase in intracellular calcium, leading to the activation of many pro-apoptotic pathways. While modulation of intracellular calcium increase receives much attention for pharmaceutical intervention, Ca2+-mediated pro-apoptotic signalling pathways have not been systematically studied. We have reported our study on the roles of calcium/calmodulin-dependent protein kinase II (CaMKII) in Abeta peptide neurotoxicity. By treating the primary cortical neurons exposed to Abeta peptides (Abeta(25-35) and Abeta(1-42)) with two selective CaMKII inhibitors, autocamtide-related inhibitory peptide (AIP) and KN93, Abeta peptide neurotoxicity was significantly reduced. Release of LDH and DNA fragmentation/condensation (by DAPI staining) in neurons exposed to Abeta peptides were significantly decreased in the presence of AIP and KN93. While these inhibitors significantly attenuated Abeta peptide-triggered activation of caspase-2 and caspase-3, and AIP significantly decreased the degree of tau phosphorylation of the Abeta peptide-treated neurons at early time, they could elicit partial neuroprotection only. Pharmacological inhibitor targeting calmodulin, W7, did not provide neuroprotection. Morphine, which activates CaMKII via micro receptors, augments Abeta-induced LDH release, caspase-2 and caspase-3 activities and neuronal apoptosis. Taken together, although CaMKII plays a role in Abeta peptide neurotoxicity, pharmacological inhibition cannot afford complete neuroprotection.