Calcium Sensing Receptor, Calcium Binding Proteins and Astrocytic Changes in Alzheimers Disease.

139 p.La enfermedad de Alzheimer (EA) es una enfermedad neurodegenerativa caracterizada por la pérdida de memoria y disfunciones cognitivas, entre las cuales se incluyen problemas del lenguaje, desorientación, pérdida de la capacidad de organización y planificación y otros síntomas neuropsiquiátricos, hasta la llegada a un estadio final, en el cual el paciente precisa de una asistencia total. Las principales característica patológicas son la atrofia cortical, la pérdida de neuronas y sinápsis, la acumulación de la proteína B-amiloide, la deposición de placas seniles y la formación de ovillos neurofibrilares (MNFs) constituidos por la proteína tau hiperfosforilada

Calcium Sensing Receptor, Calcium Binding Proteins and Astrocytic Changes in Alzheimers Disease.

139 p.La enfermedad de Alzheimer (EA) es una enfermedad neurodegenerativa caracterizada por la pérdida de memoria y disfunciones cognitivas, entre las cuales se incluyen problemas del lenguaje, desorientación, pérdida de la capacidad de organización y planificación y otros síntomas neuropsiquiátricos, hasta la llegada a un estadio final, en el cual el paciente precisa de una asistencia total. Las principales característica patológicas son la atrofia cortical, la pérdida de neuronas y sinápsis, la acumulación de la proteína B-amiloide, la deposición de placas seniles y la formación de ovillos neurofibrilares (MNFs) constituidos por la proteína tau hiperfosforilada

Calcium-sensing receptor antagonist (calcilytic) NPS 2143 prevents the increased secretion of endogenous Aβ42 prompted by exogenous Aβ25-35 in human cortical astrocytes and neurons

Previously we showed that adding fibrillar (f)Aβ25–35, a proxy retaining the main physical and biological features of Aβ42, stimulated untransformed astrocytes isolated from fragments of the adult human temporal lobe cerebral cortex to synthesize and accumulate large amounts of endogenous Aβ42 and its oligomers, while releasing excess amounts of nitric oxide (NO) and of vascular endothelial growth factor (VEGF-A) [1,2]. Here, 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, we studied whether calcium-CaSR signaling plays any role in such Aβ25-35-elicited effects and their modulation by NPS 2143, a CaSR allosteric antagonist (calcilytic). The fAβ25- 35-exposed astrocytes and 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 but NPS 2143 addition specifically suppressed the fAβ25-35-elicited surges of endogenous Aβ42 secretion by both cell types. Therefore, NPS 2143 addition always kept Aβ42/Aβ40 values to baseline or lower levels. 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 prevents any Aβ/CaSR-induced surplus secretion of endogenous Aβ42 and hence further vicious cycles of Aβ self-induction/secretion/ spreading, the CaSR antagonists like NPS 2143 might be novel therapeutic drugs for Alzheimer’s disease

Calcium Sensing Receptor, Calcium Binding Proteins and Astrocytic Changes in Alzheimers Disease.

139 p.La enfermedad de Alzheimer (EA) es una enfermedad neurodegenerativa caracterizada por la pérdida de memoria y disfunciones cognitivas, entre las cuales se incluyen problemas del lenguaje, desorientación, pérdida de la capacidad de organización y planificación y otros síntomas neuropsiquiátricos, hasta la llegada a un estadio final, en el cual el paciente precisa de una asistencia total. Las principales característica patológicas son la atrofia cortical, la pérdida de neuronas y sinápsis, la acumulación de la proteína B-amiloide, la deposición de placas seniles y la formación de ovillos neurofibrilares (MNFs) constituidos por la proteína tau hiperfosforilada

Loss of calretinin and parvalbumin positive interneurones in the hippocampal CA1 of aged Alzheimer’s disease mice

Neuronal degeneration associated with Alzheimer's disease (AD), is linked to impaired calcium homeostasis and to changes in calcium-binding proteins (CBPs). The AD-related modification of neuronal CBPs remains controversial. Here we analysed the presence and expression of calretinin (CR) and parvalbumin (PV) in the hippocampal CA1 neurones of 18 months old 3xTg-AD mice compared to non-Tg animals. We found a layer specific decrease in number of interneurones expressing CR and PV (by 33.7% and 52%, respectively). Expression of PV decreased (by 13.8%) in PV-positive neurones, whereas expression of CR did not change in CR positive cells. The loss of specific subpopulations of Ca2+-binding proteins expressing interneurones (CR and PV) together with the decrease of PV in the surviving cells may be linked to their vulnerability to AD pathology. Specific loss of inhibitory interneurones with age could contribute to overall increase in the network excitability associated with AD

Amyloid β-Exposed Human Astrocytes Overproduce Phospho-Tau and Overrelease It within Exosomes, Effects Suppressed by Calcilytic NPS 2143—Further Implications for Alzheimer's Therapy

The two main drivers of Alzheimer's disease (AD), amyloid-β (Aβ) and hyperphosphorylated Tau (p-Tau) oligomers, cooperatively accelerate AD progression, but a hot debate is still ongoing about which of the two appears first. Here we present preliminary evidence showing that Tau and p-Tau are expressed by untransformed cortical adult human astrocytes in culture and that exposure of such cells to an Aβ42 proxy, Aβ25−35, which binds the calcium-sensing receptor (CaSR) and activates its signaling, significantly increases intracellular p-Tau levels, an effect CaSR antagonist (calcilytic) NPS 2143 wholly hinders. The astrocytes also release both Tau and p-Tau by means of exosomes into the extracellular medium, an activity that could mediate p-Tau diffusion within the brain. Preliminary data also indicate that exosomal levels of p-Tau increase after Aβ25−35 exposure, but remain unchanged in cells pre-treated for 30-min with NPS 2143 before adding Aβ25−35. Thus, our previous and present findings raise the unifying prospect that Aβ•CaSR signaling plays a crucial role in AD development and progression by simultaneously activating (i) the amyloidogenic processing of amyloid precursor holoprotein, whose upshot is a surplus production and secretion of Aβ42 oligomers, and (ii) the GSK-3β-mediated increased production of p-Tau oligomers which are next released extracellularly inside exosomes. Therefore, as calcilytics suppress both effects on Aβ42 and p-Tau metabolic handling, these highly selective antagonists of pathological Aβ•CaSR signaling would effectively halt AD's progressive spread preserving patients' cognition and life quality

Increased calcium-sensing receptor immunoreactivity in the hippocampus of a triple transgenic mouse model of Alzheimer's disease

The Calcium-Sensing Receptor (CaSR) is a G-protein coupled, 7-transmembrane domain receptor ubiquitously expressed throughout the body, brain including. The role of CaSR in the CNS is not well understood; its expression is increasing during development, which has been implicated in memory formation and consolidation, and CaSR localization in nerve terminals has been related to synaptic plasticity and neurotransmission. There is an emerging evidence of CaSR involvement in neurodegenerative disorders and Alzheimer's disease (AD) in particular, where the over-production of beta-amyloid peptides was reported to activate CaSR. In the present study, we performed CaSR immunohistochemical and densitometry analysis in the triple transgenic mouse model of AD (3xTg-AD). We found an increase in the expression of CaSR in hippocampal CA1 area and in dentate gyrus in the 3xTg-AD mice when compared to non-transgenic control animals. This increase was significant at 9 months of age and further increased at 12 and 18 months of age. This increase paralleled the accumulation of beta-amyloid plaques with age. Increased expression of CaSR favors beta-amyloidogenic pathway following direct interactions between beta-amyloid and CaSR and hence may contribute to the pathological evolution of the AD. In the framework of this paradigm CaSR may represent a novel therapeutic target.We thank Dr Fatima Zallo Diaz, for her help and assistance with the figures. Authors research was supported by Alzheimer's Research Trust (UK) Programme Grant [grant number ART/PG2004A/1 (to AV and JR)]; by the Grant Agency of the Czech Republic [grant number GACR 309/09/1696 (to JR); GACR 305/08/1381 and GACR 305/08/1384 (to AV)] as well as by the Spanish Government Plan Nacional de I+D+I 2008-2011, and ISCIII Subdireccion General de Evaluacion y Fomento de la investigacion co-financed by FEDER [grant number PI10/02738 (to JR and AV)]. The Government of the Basque Country [grant number AE-2010-1-28; AEGV10/16, GV2011111020 (to JR)]; as well as by the Spanish Ministerio de Economia y Competitividad, RETOS Colaboracion [grant number RTC-2015-3542-1 co-financed by FEDER (to JR)] and by the Ministry of Italian University and Research (MIUR) to EG, AC, UA, and ID

Preventing the spread of Alzheimer's disease neuropathology: a role for calcilytics?

The "amyloid cascade hypothesis" posits that an extracellular build-up of amyloid-\u3b2 oligomers (A\u3b2-os) and polymers (fibrils) subsequently inducing toxic hyperphosphorylated (p)-Tau oligomers (p-Tau-os) and neurofibrillary tangles starts the sporadic late-onset Alzheimer's disease (LOAD) in the aged lateral entorhinal cortex. Conversely, mutated genes cause a diffuse cerebral A\u3b2s/A\u3b2-os overproduction promoting early-onset familiar AD (EOFAD). Surplus exogenous A\u3b2-os exert toxic actions at several levels. They reach the nuclei of human astrocyte-neurons teams (ANTs) to enhance the transcription of A\u3b2 precursor protein (APP) and \u3b2-secretase/BACE1 genes. The overexpressed APP and BACE1 proteins act in concert with \u3b3-secretase to overproduce endogenous A\u3b2s/A\u3b2-os, of which a few enter the nuclei to upkeep A\u3b2s overproduction, while the rest gather in the cytoplasm, damage mitochondria, and are oversecreted. Simultaneously, extracellular A\u3b2-os bind the ANTs' calcium-sensing receptors (CaSRs) activating signalings that hinder the proteolysis and hence favor the surplus hoarding/secretion of A\u3b2s/A\u3b2-os. Overreleased A\u3b2-os spread, reach growing numbers of adjacent ANTs to recruit them to overproduce/oversecrete further A\u3b2-os amounts via the just mentioned mechanisms. Alongside, A\u3b2\u2022CaSR signalings elicit a noxious overproduction/overrelease of nitric oxide (NO) and vascular endothelial growth factor (VEGF)-A from ANTs' astrocytes. While astrocytes survive the toxic onslaught, neurons die. Thus, AD progression is driven by ceaselessly self-sustaining neurotoxic cycles, which engender first A\u3b2-os and later p-Tau-os that cooperatively destroy increasingly wider cognition-related cortical areas. Notably, a highly selective allosteric CaSR antagonist (calcilytic), like NPS 2143, does preserve human cortical postnatal HCN-1A neurons viability notwithstanding the presence of exogenous A\u3b2-os by suppressing the otherwise elicited oversecretion and spread of newly synthesized A\u3b2-os. Therefore, if given at minimal cognitive impairment or earlier stages, calcilytics could halt AD progression and preserve the patients' cortical neurons, cognitive abilities, and eventually life

Calcium-Sensing Receptors of Human Astrocyte-Neuron Teams: Amyloid-\u3b2-Driven Mediators and Therapeutic Targets of Alzheimer's Disease.

It is generally assumed that the neuropathology of sporadic (late-onset or nonfamilial) Alzheimer\u2019s disease (AD) is driven by the overproduction and spreading of first Amyloid-\u3b2x-42 (A\u3b242) and later hyperphosphorylated (hp)-Tau oligomeric \u201cinfectious seeds\u201d. Hitherto, only neurons were held to make and spread both oligomer types; astrocytes would just remove debris. However, we have recently shown that exogenous fibrillar or soluble A\u3b2 peptides specifically bind and activate the Ca(2+)-sensing receptors (CaSRs) of untransformed human cortical adult astrocytes and postnatal neurons cultured in vitro driving them to produce, accrue, and secrete surplus endogenous A\u3b242. While the A\u3b2-exposed neurons start dying, astrocytes survive and keep oversecreting A\u3b242, nitric oxide (NO), and vascular endothelial growth factor (VEGF)-A. Thus astrocytes help neurons\u2019 demise. Moreover, we have found that a highly selective allosteric CaSR agonist (\u201ccalcimimetic\u201c), NPS R-568, mimics the just mentioned neurotoxic actions triggered by A\u3b2\u25cfCaSR signaling. Contrariwise, and most important, NPS 2143, a highly selective allosteric CaSR antagonist (\u201ccalcilytic\u201c), fully suppresses all the A\u3b2\u25cfCaSR signaling-driven noxious actions. Altogether our findings suggest that the progression of AD neuropathology is promoted by unceasingly repeating cycles of accruing exogenous A\u3b242 oligomers interacting with the CaSRs of swelling numbers of astrocyte-neuron teams thereby recruiting them to overrelease additional A\u3b242 oligomers, VEGF-A, and NO. Calcilytics would beneficially break such A\u3b2\u25cfCaSR-driven vicious cycles and hence halt or at least slow the otherwise unstoppable spreading of AD neuropathology