title: Involvement of endoplasmic reticulum Ca2+ release through ryanodine and inositol 1,4,5-triphosphate receptors in the neurotoxic effects induced by the amyloid-beta peptide.
abstract: Studies with in-vitro-cultured neurons treated with amyloid-beta (A beta) peptides demonstrated neuronal loss by apoptosis that is due, at least in part, to the perturbation of intracellular Ca(2+) homeostasis. In addition, it was shown that an endoplasmic reticulum (ER)-specific apoptotic pathway mediated by caspase-12, which is activated upon the perturbation of ER Ca(2+) homeostasis, may contribute to A beta toxicity. To elucidate the involvement of deregulation of ER Ca(2+) homeostasis in neuronal death induced by A beta peptides, we have performed a comparative study using the synthetic peptides A beta(25-35) or A beta(1-40) and thapsigargin, a selective inhibitor of Ca(2+) uptake into the ER. Incubation of cortical neurons with thapsigargin (2.5 microM) increased the intracellular Ca(2+) levels and activated caspase-3, leading to a significant increase in the number of apoptotic cells. Similarly, upon incubation of cortical cultures with the A beta peptides (A beta(25-35), 25 microM; A beta(1-40), 0.5 microM), we observed a significant increase in [Ca(2+)](i), in caspase-3-like activity, and in number of neurons exhibiting apoptotic morphology. The role of ER Ca(2+) release through ryanodine receptors (RyR) or inositol 1,4,5-trisphosphate receptors (IP(3)R) in A beta neurotoxicity has been also investigated. Dantrolene and xestospongin C, inhibitors of ER Ca(2+) release through RyR or IP(3)R, were able to prevent the increase in [Ca(2+)](i) and the activation of caspase-3 and to protect partially against apoptosis induced by treatment with A beta(25-35) or A beta(1-40). In conclusion, our results demonstrate that the release of Ca(2+) from the ER, mediated by both RyR and IP(3)R, is involved in A beta toxicity and can contribute, together with the activation of other intracellular neurotoxic mechanisms, to A beta-induced neuronal death. This study suggests that A beta accumulation may have a key role in the pathogenesis of AD as a result of deregulation of ER Ca(2+) homeostasis.
authors.affiliation: Center for Neuroscience and Cellular Biology of Coimbra, Institute of Biochemistry, Faculty of Medicine, University of Coimbra, Coimbra, Portugal.
authors.forename: Elisabete
authors.initials: E
authors.lastname: Ferreiro
authors.forename: Catarina R
authors.initials: CR
authors.lastname: Oliveira
authors.forename: Cláudia
authors.initials: C
authors.lastname: Pereira
mesh_terms: D016229:Amyloid beta-Peptides / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis / Q000502:physiology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D002540:Cerebral Cortex / Q000166:cytology / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D053496:Inositol 1,4,5-Trisphosphate Receptors; D009474:Neurons / Q000378:metabolism*; D009498:Neurotoxins / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism*
chemical_list: D016229:Amyloid beta-Peptides; D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D009498:Neurotoxins; D010446:Peptide Fragments; D018160:Receptors, Cytoplasmic and Nuclear; D019837:Ryanodine Receptor Calcium Release Channel; C078592:amyloid beta-protein (1-40); C074636:amyloid beta-protein (25-35); D002118:Calcium