title: Calcium-sensing receptor antagonist (calcilytic) NPS 2143 specifically blocks the increased secretion of endogenous Aβ42 prompted by exogenous fibrillary or soluble Aβ25-35 in human cortical astrocytes and neurons-therapeutic relevance to Alzheimer's disease.
abstract: The "amyloid-β (Aβ) hypothesis" posits that accumulating Aβ peptides (Aβs) produced by neurons cause Alzheimer's disease (AD). However, the Aβs contribution by the more numerous astrocytes remains undetermined. Previously we showed that fibrillar (f)Aβ25-35, an Aβ42 proxy, evokes a surplus endogenous Aβ42 production/accumulation in cortical adult human astrocytes. Here, by using immunocytochemistry, immunoblotting, enzymatic assays, and highly sensitive sandwich ELISA kits, we investigated the effects of fAβ25-35 and soluble (s)Aβ25-35 on Aβ42 and Aβ40 accumulation/secretion by human cortical astrocytes and HCN-1A neurons and, since the calcium-sensing receptor (CaSR) binds Aβs, their modulation by NPS 2143, a CaSR allosteric antagonist (calcilytic). The fAβ25-35-exposed astrocytes and surviving neurons produced, accumulated, and secreted increased amounts of Aβ42, while Aβ40 also accrued but its secretion was unchanged. Accordingly, secreted Aβ42/Aβ40 ratio values rose for astrocytes and neurons. While slightly enhancing Aβ40 secretion by fAβ25-35-treated astrocytes, NPS 2143 specifically suppressed the fAβ25-35-elicited surges of endogenous Aβ42 secretion by astrocytes and neurons. Therefore, NPS 2143 addition always kept Aβ42/Aβ40 values to baseline or lower levels. Mechanistically, NPS 2143 decreased total CaSR protein complement, transiently raised proteasomal chymotrypsin activity, and blocked excess NO production without affecting the ongoing increases in BACE1/β-secretase and γ-secretase activity in fAβ25-35-treated astrocytes. Compared to fAβ25-35, sAβ25-35 also stimulated Aβ42 secretion by astrocytes and neurons and NPS 2143 specifically and wholly suppressed this effect. Therefore, since NPS 2143 thwarts any Aβ/CaSR-induced surplus secretion of endogenous Aβ42 and hence further vicious cycles of Aβ self-induction/secretion/spreading, calcilytics might effectively prevent/stop the progression to full-blown AD.
authors.affiliation: Department of Life and Reproduction Sciences, University of Verona Medical School, Verona, Italy. uarmato@hotmail.com
authors.forename: Ubaldo
authors.initials: U
authors.lastname: Armato
authors.forename: Anna
authors.initials: A
authors.lastname: Chiarini
authors.forename: Balu
authors.initials: B
authors.lastname: Chakravarthy
authors.forename: Franco
authors.initials: F
authors.lastname: Chioffi
authors.forename: Raffaella
authors.initials: R
authors.lastname: Pacchiana
authors.forename: Enzo
authors.initials: E
authors.lastname: Colarusso
authors.forename: James F
authors.initials: JF
authors.lastname: Whitfield
authors.forename: Ilaria
authors.initials: I
authors.lastname: Dal Prà
mesh_terms: D000328:Adult; D000544:Alzheimer Disease / Q000378:metabolism* / Q000473:pathology / Q000628:therapy; D016229:Amyloid beta-Peptides / Q000378:metabolism* / Q000502:physiology; D001253:Astrocytes / Q000187:drug effects* / Q000378:metabolism; D001708:Biopterins / Q000031:analogs & derivatives / Q000494:pharmacology; D002478:Cells, Cultured; D006801:Humans; D009281:Naphthalenes / Q000494:pharmacology* / Q000627:therapeutic use; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D044169:Receptors, Calcium-Sensing / Q000037:antagonists & inhibitors*
chemical_list: D016229:Amyloid beta-Peptides; C436740:N-(2-hydroxy-3-(2-cyano-3-chlorophenoxy)propyl)-1,1-dimethyl-2-(2-nephthyl)ethylamine; D009281:Naphthalenes; D044169:Receptors, Calcium-Sensing; D001708:Biopterins; C003402:sapropterin
keywords: AD; APP; Alzheimer's disease; Amyloid-β; Aβ; Aβ peptides; Aβ precursor protein; Aβ-degrading proteases; AβDPs; Aβs; BACE 1; CaSR; Calcium-sensing receptor; G-protein-coupled receptors; GCH-1; GPCRs; GTP cyclohydrolase-1; HCN; Human astrocyte; Human neuron; IFN-γ; IL-1β; LOAD; LRP1; N-methyl-d-aspartate; NFTs; NMDA; NOS; NPS 2143; NPS R-568; RAGE; TGN; TNF-α; amyloid-β; calcium-sensing receptor; fAβ; fibrillated Aβ; human cortical neurons; interferon-γ; interleukin-1β; late-onset AD; lipoprotein receptor-related protein 1; neurofibrillary tangles; nitric oxide synthase; p75 neurotrophin receptor; p75(NTR); receptor for advanced glycation endproducts; sAβ; soluble Aβ; trans-Golgi network; tumor necrosis factor-α; β-S; β-secretase; β-site APP-cleaving enzyme 1; γ-S; γ-secretase