Calcium-sensing receptor antagonist (calcilytic) NPS 2143 specifically blocks the increased secretion of endogenous A¦Â₄₂ prompted by exogenous fibrillary or soluble A¦Â_25-35 in human cortical astrocytes and neurons¡ªTherapeutic rel

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• 作者：Ubaldo Armato ; Anna Chiarini ; Balu Chakravarthy ; Franco Chioffi ; Raffaella Pacchiana ; Enzo Colarusso ; James F. Whitfield ; Ilaria Dal Pr¨¤
• 关键词：A¦Â ; amyloid-¦Â ; A¦Âs ; A¦Â peptides ; AD ; Alzheimer's disease ; A¦ÂDPs ; A¦Â-degrading proteases ; APP ; A¦Â precursor protein ; BACE 1 ; ¦Â-site APP-cleaving enzyme 1 ; ¦Â-S ; ¦Â-secretase ; CaSR ; calcium-sensing receptor ; fA¦Â ; fibrillated A¦Â ; ¦Ã-S ; ¦Ã-secretase
• 刊名：Biochimica et Biophysica Acta (BBA)/Molecular Basis of Disease
• 出版年：2013
• 出版时间：October, 2013
• 年：2013
• 卷：1832
• 期：10
• 页码：1634-1652
• 全文大小：2112 K

文摘

The ¡°amyloid-¦Â (A¦Â) hypothesis¡± posits that accumulating A¦Â peptides (A¦Âs) produced by neurons cause Alzheimer's disease (AD). However, the A¦Âs contribution by the more numerous astrocytes remains undetermined. Previously we showed that fibrillar (f)A¦Â_25-35, an A¦Â₄₂ proxy, evokes a surplus endogenous A¦Â₄₂ 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 fA¦Â_25-35 and soluble (s)A¦Â_25-35 on A¦Â₄₂ and A¦Â₄₀ accumulation/secretion by human cortical astrocytes and HCN-1A neurons and, since the calcium-sensing receptor (CaSR) binds A¦Âs, their modulation by NPS 2143, a CaSR allosteric antagonist (calcilytic). The fA¦Â_25-35-exposed astrocytes and surviving neurons produced, accumulated, and secreted increased amounts of A¦Â₄₂, while A¦Â₄₀ also accrued but its secretion was unchanged. Accordingly, secreted A¦Â₄₂/A¦Â₄₀ ratio values rose for astrocytes and neurons. While slightly enhancing A¦Â₄₀ secretion by fA¦Â_25-35-treated astrocytes, NPS 2143 specifically suppressed the fA¦Â_25-35-elicited surges of endogenous A¦Â₄₂ secretion by astrocytes and neurons. Therefore, NPS 2143 addition always kept A¦Â₄₂/A¦Â₄₀ 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/¦Â-secretase and ¦Ã-secretase activity in fA¦Â_25-35-treated astrocytes. Compared to fA¦Â_25-35, sA¦Â_25-35 also stimulated A¦Â₄₂ secretion by astrocytes and neurons and NPS 2143 specifically and wholly suppressed this effect. Therefore, since NPS 2143 thwarts any A¦Â/CaSR-induced surplus secretion of endogenous A¦Â₄₂ and hence further vicious cycles of A¦Â self-induction/secretion/spreading, calcilytics might effectively prevent/stop the progression to full-blown AD.