Contribution of Neurons and Glial Cells to Complement-Mediated Synapse Removal during Development, Aging and in Alzheimer’s Disease

Synapse loss is an early manifestation of pathology in Alzheimer's disease (AD) and is currently the best correlate to cognitive decline. Microglial cells are involved in synapse pruning during development via the complement pathway. Moreover, recent evidence points towards a key role played by glial cells in synapse loss during AD. However, further contribution of glial cells and the role of neurons to synapse pathology in AD remain not well understood. This review is aimed at comprehensively reporting the source and/or cellular localization in the CNS-in microglia, astrocytes, or neurons-of the triggering components (C1q, C3) of the classical complement pathway involved in synapse pruning in development, adulthood, and AD.The authors thank Dr. Baleriola at Achucarro Basque Center for Neuroscience (Bilbao, Spain) and Dr. Sole-Domenech and Dr. Pipalia at Weill Cornell Medical College (Cornell University, New York, USA) for the helpful and critical revision of the manuscript. This study was supported by CIBERNED and by grants from Ministerio de Economia y Competitividad (SAF2016-75292-R), Gobierno Vasco (PIBA PI-2016-1-009-0016 and ELKARTEK 2016-00033), Ikerbasque, Basque Foundation for Science, and Universidad del Pais Vasco/Euskal Herriko Unibertsitatea UPV/EHU. Jone Zuazo held a fellowship from Gobierno Vasco and Celia Luchena from Fundacion Tatiana Perez de Guzman el Bueno

Linking Plasma Amyloid Beta and Neurofilament Light Chain to Intracortical Myelin Content in Cognitively Normal Older Adults

Evidence suggests that lightly myelinated cortical regions are vulnerable to aging and Alzheimer's disease (AD). However, it remains unknown whether plasma markers of amyloid and neurodegeneration are related to deficits in intracortical myelin content, and whether this relationship, in turn, is associated with altered patterns of resting-state functional connectivity (rs-FC). To shed light into these questions, plasma levels of amyloid-beta fragment 1-42 (A beta(1-42)) and neurofilament light chain (NfL) were measured using ultra-sensitive single-molecule array (Simoa) assays, and the intracortical myelin content was estimated with the ratio T1-weigthed/T2-weighted (T1w/T2w) in 133 cognitively normal older adults. We assessed: (i) whether plasma A beta(1-42) and/or NfL levels were associated with intracortical myelin content at different cortical depths and (ii) whether cortical regions showing myelin reductions also exhibited altered rs-FC patterns. Surface-based multiple regression analyses revealed that lower plasma A beta(1-42) and higher plasma NfL were associated with lower myelin content in temporo-parietal-occipital regions and the insular cortex, respectively. Whereas the association with A beta(1-42) decreased with depth, the NfL-myelin relationship was most evident in the innermost layer. Older individuals with higher plasma NfL levels also exhibited altered rs-FC between the insula and medial orbitofrontal cortex. Together, these findings establish a link between plasma markers of amyloid/neurodegeneration and intracortical myelin content in cognitively normal older adults, and support the role of plasma NfL in boosting aberrant FC patterns of the insular cortex, a central brain hub highly vulnerable to aging and neurodegeneration.This work was supported by the Spanish Ministry of Economy and Competitiveness (PID2020-119978RB-I00 to JLC and PID2020-118825GB-I00 to MA), CIBERNED (JLC, MA, CM, EC-Z, and FZ), Alzheimers Association (AARG-NFT-22-924702 to JLC), the Basque Government (IT1203-19; ELKARTEK KK-2020/00034 to EC-Z), the Research Program for a Long-Life Society of the Fundacion General CSIC (0551_PSL_6_E to JLC), the Junta de Andalucia (PY20_00858 to JLC), and the Andalucia-FEDER Program (UPO-1380913 to JLC)

New, Fully Implantable Device for Selective Clearance of CSF-Target Molecules: Proof of Concept in a Murine Model of Alzheimer’s Disease

[EN] We have previously proposed a radical change in the current strategy to clear pathogenic proteins from the central nervous system (CNS) based on the cerebrospinal fluid (CSF)-sink therapeutic strategy, whereby pathogenic proteins can be removed directly from the CNS via CSF. To this aim, we designed and manufactured an implantable device for selective and continuous apheresis of CSF enabling, in combination with anti-amyloid-beta (Aβ) monoclonal antibodies (mAb), the clearance of Aβ from the CSF. Here, we provide the first proof of concept in the APP/PS1 mouse model of Alzheimer’s disease (AD). Devices were implanted in twenty-four mice (seventeen APP/PS1 and seven Wt) with low rates of complications. We confirmed that the apheresis module is permeable to the Aβ peptide and impermeable to mAb. Moreover, our results showed that continuous clearance of soluble Aβ from the CSF for a few weeks decreases cortical Aβ plaques. Thus, we conclude that this intervention is feasible and may provide important advantages in terms of safety and efficacy.This work was supported by the Instituto de Salud Carlos III, under Grant DTS19-00071 to M.M.-G. and by the Fundación para el Fomento en Asturias de la Investigación Científica Aplicada y la Tecnología (FICYT), under Grant AYUD/2021/57540, to C.T.-Z

Amyloid β / PKC-dependent alterations in NMDA receptor composition are detected in early stages of Alzheimer´s disease

[EN] Amyloid beta (Abeta)-mediated synapse dysfunction is an early event in Alzheimer's disease (AD) pathogenesis and previous studies suggest that NMDA receptor (NMDAR) dysregulation may contribute to these pathological effects. Although Abeta peptides impair NMDAR expression and activity, the mechanisms mediating these alterations in the early stages of AD are unclear. Here, we observed that NMDAR subunit NR2B and PSD-95 levels were aberrantly upregulated and correlated with Abeta42 load in human postsynaptic fractions of the prefrontal cortex in early stages of AD patients, as well as in the hippocampus of 3xTg-AD mice. Importantly, NR2B and PSD95 dysregulation was revealed by an increased expression of both proteins in Abeta-injected mouse hippocampi. In cultured neurons, Abeta oligomers increased the NR2B-containing NMDAR density in neuronal membranes and the NMDA-induced intracellular Ca2+ increase, in addition to colocalization in dendrites of NR2B subunit and PSD95. Mechanistically, Abeta oligomers required integrin beta1 to promote synaptic location and function of NR2B-containing NMDARs and PSD95 by phosphorylation through classic PKCs. These results provide evidence that Abeta oligomers modify the contribution of NR2B to NMDAR composition and function in the early stages of AD through an integrin beta1 and PKC-dependent pathway. These data reveal a novel role of Abeta oligomers in synaptic dysfunction that may be relevant to early-stage AD pathogenesis.We thank S. Marcos, L. Escobar, A Martínez and Z. Martínez for technical assistance. This study was supported by the Basque Government (IT1203-19; PIBA_2020_1_0012; ELKARTEK KK-2020/00034; fellowship to T.Q-L, U.B. and J.Z-I), University of the Basque Country (UPV/EHU; fellowship to C.O-S) CIBERNED, MICINN (PID2019-108465RB-I00) and Fundación Tatiana Pérez de Guzmán el Bueno (fellowship to C.L)

Recombinant Integrin β1 Signal Peptide Blocks Gliosis Induced by Aβ Oligomers

Glial cells participate actively in the early cognitive decline in Alzheimer’s disease (AD) pathology. In fact, recent studies have found molecular and functional abnormalities in astrocytes and microglia in both animal models and brains of patients suffering from this pathology. In this regard, reactive gliosis intimately associated with amyloid plaques has become a pathological hallmark of AD. A recent study from our laboratory reports that astrocyte reactivity is caused by a direct interaction between amyloid beta (Aβ) oligomers and integrin β1. Here, we have generated four recombinant peptides including the extracellular domain of integrin β1, and evaluated their capacity both to bind in vitro to Aβ oligomers and to prevent in vivo Aβ oligomer-induced gliosis and endoplasmic reticulum stress. We have identified the minimal region of integrin β1 that binds to Aβ oligomers. This region is called signal peptide and corresponds to the first 20 amino acids of the integrin β1 N-terminal domain. This recombinant integrin β1 signal peptide prevented Aβ oligomer-induced ROS generation in primary astrocyte cultures. Furthermore, we carried out intrahippocampal injection in adult mice of recombinant integrin β1 signal peptide combined with or without Aβ oligomers and we evaluated by immunohistochemistry both astrogliosis and microgliosis as well as endoplasmic reticulum stress. The results show that recombinant integrin β1 signal peptide precluded both astrogliosis and microgliosis and endoplasmic reticulum stress mediated by Aβ oligomers in vivo. We have developed a molecular tool that blocks the activation of the molecular cascade that mediates gliosis via Aβ oligomer/integrin β1 signaling.E.A. was supported by MICINN (PID2019-108465RB-I00) and Basque Government (PIBA_2020_1_0012). C.M. was supported by MICINN (PID2019-109724RB-I00), Basque Government (IT1203-19) and CIBERNED (CB06/0005/0076). E.C.-Z. was supported by Basque Government (ELKARTEK KK-2020/00034; PIBA_2016_1_0009). J.L.Z. was supported by the Instituto de Salud Carlos III (PI18/00207), Basque Government (PIBA_2020_1_0048) and University of Basque Country Grant (US19/04)

Longitudinal evaluation of neuroinflammation and oxidative stress in a mouse model of Alzheimer disease using positron emission tomography

[EN] Background: Validation of new biomarkers of Alzheimer disease (AD) is crucial for the successful development and implementation of treatment strategies. Additional to traditional AT(N) biomarkers, neuroinflammation biomarkers, such as translocator protein (TSPO) and cystine/glutamine antiporter system (x(c)(-)), could be considered when assessing AD progression. Herein, we report the longitudinal investigation of [F-18]DPA-714 and [F-18]FSPG for their ability to detect TSPO and x(c)(-) biomarkers, respectively, in the 5xFAD mouse model for AD. Methods: Expression of TSPO and x(c)(-) system was assessed longitudinally (2-12 months of age) on 5xFAD mice and their respective controls by positron emission tomography (PET) imaging using radioligands [F-18]DPA-714 and [F-18]FSPG. In parallel, in the same mice, amyloid-beta plaque deposition was assessed with the amyloid PET radiotracer [F-18]florbetaben. In vivo findings were correlated to ex vivo immunofluorescence staining of TSPO and x(c)(-) in microglia/macrophages and astrocytes on brain slices. Physiological changes of the brain tissue were assessed by magnetic resonance imaging (MRI) in 12-month-old mice. Results: PET studies showed a significant increase in the uptake of [F-18]DPA-714 and [F-18]FSPG in the cortex, hippocampus, and thalamus in 5xFAD but not in WT mice over time. The results correlate with A beta plaque deposition. Ex vivo staining confirmed higher TSPO overexpression in both, microglia/macrophages and astrocytes, and overexpression of x(c)(-) in non-glial cells of 5xFAD mice. Additionally, the results show that A beta plaques were surrounded by microglia/macrophages overexpressing TSPO. MRI studies showed significant tissue shrinkage and microstructural alterations in 5xFAD mice compared to controls. Conclusions: TSPO and x(c)(-) overexpression can be assessed by [F-18]DPA-714 and [F-18]FSPG, respectively, and correlate with the level of A beta plaque deposition obtained with a PET amyloid tracer. These results position the two tracers as promising imaging tools for the evaluation of disease progression.J.L. and P.R. thank the Spanish Ministry of Science and Innovation MCIN/AEI/10.13039/501100011033 (PID2020-117656RB-100 and PID2020-118546RBI00, respectively) and the Interreg Atlantic Area Programme (EAPA_791/2018). Abraham Martin acknowledges funding from the Spanish Ministry of Education and Science (RYC-2017-22412, PID2019-107989RB-I00), the Basque Government (BIO18/IC/006), and Fundacio La Marato de TV3 (17/C/2017). Estibaliz Capetillo-Zarate acknowledges funding from the Basque Government (IT120319; ELKARTEK KK-2020/00034) and CIBERNED (CB06/0005/0076). The work was performed under the Maria de Maeztu Units of Excellence Programme -Grant MDM-2017-0720 funded by MCIN/AEI/10.13039/50110001103

Effects of Platelet-Rich Plasma on Cellular Populations of the Central Nervous System: The Influence of Donor Age

first_page settings Open AccessArticle Effects of Platelet-Rich Plasma on Cellular Populations of the Central Nervous System: The Influence of Donor Age by Diego Delgado 1, Ane Miren Bilbao 2, Maider Beitia 1, Ane Garate 1, Pello Sánchez 1, Imanol González-Burguera 3,4, Amaia Isasti 4,5, Maider López De Jesús 4,5,6, Jone Zuazo-Ibarra 7, Alejandro Montilla 7 [OrcID] , María Domercq 7 [OrcID] , Estibaliz Capetillo-Zarate 7,8, Gontzal García del Caño 3,4 [OrcID] , Joan Sallés 4,5,6, Carlos Matute 7 and Mikel Sánchez 1,2,* 1 Advanced Biological Therapy Unit, Hospital Vithas Vitoria, 01008 Vitoria-Gasteiz, Spain 2 Arthroscopic Surgery Unit, Hospital Vithas Vitoria, 01008 Vitoria-Gasteiz, Spain 3 Department of Neurosciences, Faculty of Pharmacy, University of the Basque Country (UPV/EHU), 01008 Vitoria-Gasteiz, Spain 4 Bioaraba, Neurofarmacología Celular y Molecular, 01008 Vitoria-Gasteiz, Spain 5 Department of Pharmacology, Faculty of Pharmacy, University of the Basque Country (UPV/EHU), 01008 Vitoria-Gasteiz, Spain 6 Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), 28029 Madrid, Spain 7 Achucarro Basque Center for Neuroscience, CIBERNED and Departamento de Neurociencias, Universidad del País Vasco (UPV/EHU), 48940 Leioa, Spain 8 IKERBASQUE, Basque Foundation for Science, 48009 Bilbao, Spain * Author to whom correspondence should be addressed. Academic Editor: Francesca Santilli Int. J. Mol. Sci. 2021, 22(4), 1725; https://doi.org/10.3390/ijms22041725 Received: 24 November 2020 / Revised: 12 January 2021 / Accepted: 3 February 2021 / Published: 9 February 2021 (This article belongs to the Section Molecular Endocrinology and Metabolism) Download PDF Browse Figures Citation Export Abstract Platelet-rich plasma (PRP) is a biologic therapy that promotes healing responses across multiple medical fields, including the central nervous system (CNS). The efficacy of this therapy depends on several factors such as the donor’s health status and age. This work aims to prove the effect of PRP on cellular models of the CNS, considering the differences between PRP from young and elderly donors. Two different PRP pools were prepared from donors 65–85 and 20–25 years old. The cellular and molecular composition of both PRPs were analyzed. Subsequently, the cellular response was evaluated in CNS in vitro models, studying proliferation, neurogenesis, synaptogenesis, and inflammation. While no differences in the cellular composition of PRPs were found, the molecular composition of the Young PRP showed lower levels of inflammatory molecules such as CCL-11, as well as the presence of other factors not found in Aged PRP (GDF-11). Although both PRPs had effects in terms of reducing neural progenitor cell apoptosis, stabilizing neuronal synapses, and decreasing inflammation in the microglia, the effect of the Young PRP was more pronounced. In conclusion, the molecular composition of the PRP, conditioned by the age of the donors, affects the magnitude of the biological response.This work was funded by the Provincial Council of Alava through the AlavaInnova Program, Basque Government through the GAITEK Program, Ministry of Economy, Industry and Competitiveness (CTQ2017-85686-R), Spanish Ministry of Education and Science (PID2019-109724RB-I00), Basque Government (IT1203-19, IT1230-19, and KK-2020/00034) and Centro de Investigación Biomédica en Red en Enfermedades Neurodegenerativas (CIBERNED)