DSpace Angular :: Browsing by Author "Alvarez, Alejandra R."

Browsing by Author "Alvarez, Alejandra R."

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Amyloid β-Peptide Causes the Permanent Activation of CaMKIIα through Its Oxidation
(2022) Picon-Pages, Pol; Fanlo-Ucar, Hugo; Herrera-Fernandez, Victor; Auselle-Bosch, Sira; Galera-Lopez, Lorena; Gutierrez, Daniela A.; Ozaita, Andres; Alvarez, Alejandra R.; Oliva, Baldomero; Munoz, Francisco J.
Alzheimer's disease (AD) is characterised by the presence of extracellular amyloid plaques in the brain. They are composed of aggregated amyloid beta-peptide (A beta) misfolded into beta-sheets which are the cause of the AD memory impairment and dementia. Memory depends on the hippocampal formation and maintenance of synapses by long-term potentiation (LTP), whose main steps are the activation of NMDA receptors, the phosphorylation of CaMKII alpha and the nuclear translocation of the transcription factor CREB. It is known that A beta oligomers (oA beta) induce synaptic loss and impair the formation of new synapses. Here, we have studied the effects of oA beta on CaMKII alpha. We found that oA beta produce reactive oxygen species (ROS), that induce CaMKII alpha oxidation in human neuroblastoma cells as we assayed by western blot and immunofluorescence. Moreover, this oxidized isoform is significantly present in brain samples from AD patients. We found that the oxidized CaMKII alpha is active independently of the binding to calcium/calmodulin, and that CaMKII alpha phosphorylation is mutually exclusive with CaMKII alpha oxidation as revealed by immunoprecipitation and western blot. An in silico modelling of the enzyme was also performed to demonstrate that oxidation induces an activated state of CaMKII alpha. In brains from AD transgenic models of mice and in primary cultures of murine hippocampal neurons, we demonstrated that the oxidation of CaMKII alpha induces the phosphorylation of CREB and its translocation to the nucleus to promote the transcription of ARC and BDNF. Our data suggests that CaMKII alpha oxidation would be a pro-survival mechanism that is triggered when a noxious stimulus challenges neurons as do oA beta.
c-Abl Activation Linked to Autophagy-Lysosomal Dysfunction Contributes to Neurological Impairment in Niemann-Pick Type A Disease
(2022) Marin, Tamara; Dulcey, Andres E.; Campos, Fabian; de la Fuente, Catalina; Acuna, Mariana; Castro, Juan; Pinto, Claudio; Yanez, Maria Jose; Cortez, Cristian; McGrath, David W.; Saez, Pablo J.; Gorshkov, Kirill; Zheng, Wei; Southall, Noel; Carmo-Fonseca, Maria; Marugan, Juan; Alvarez, Alejandra R.; Zanlungo, Silvana
Niemann-Pick type A (NPA) disease is a fatal lysosomal neurodegenerative disorder caused by the deficiency in acid sphingomyelinase (ASM) activity. NPA patients present severe and progressive neurodegeneration starting at an early age. Currently, there is no effective treatment for this disease and NPA patients die between 2 and 3 years of age. NPA is characterized by an accumulation of sphingomyelin in lysosomes and dysfunction in the autophagy-lysosomal pathway. Recent studies show that c-Abl tyrosine kinase activity downregulates autophagy and the lysosomal pathway. Interestingly, this kinase is also activated in other lysosomal neurodegenerative disorders. Here, we describe that c-Abl activation contributes to the mechanisms of neuronal damage and death in NPA disease. Our data demonstrate that: 1) c-Abl is activated in-vitro as well as in-vivo NPA models; 2) imatinib, a clinical c-Abl inhibitor, reduces autophagy-lysosomal pathway alterations, restores autophagy flux, and lowers sphingomyelin accumulation in NPA patient fibroblasts and NPA neuronal models and 3) chronic treatment with nilotinib and neurotinib, two c-Abl inhibitors with differences in blood-brain barrier penetrance and target binding mode, show further benefits. While nilotinib treatment reduces neuronal death in the cerebellum and improves locomotor functions, neurotinib decreases glial activation, neuronal disorganization, and loss in hippocampus and cortex, as well as the cognitive decline of NPA mice. Our results support the participation of c-Abl signaling in NPA neurodegeneration and autophagy-lysosomal alterations, supporting the potential use of c-Abl inhibitors for the clinical treatment of NPA patients.
c-Abl Deficiency Provides Synaptic Resiliency Against Aβ-Oligomers
(2019) Gutierrez, Daniela A.; Vargas, Lina M.; Chandia-Cristi, America; de la Fuente, Catalina; Leal, Nancy; Alvarez, Alejandra R.
Spine pathology has been implicated in the early onset of Alzheimer & x2019;s disease (AD), where A & x3b2;-Oligomers (A & x3b2;Os) cause synaptic dysfunction and loss. Previously, we described that pharmacological inhibition of c-Abl prevents A & x3b2;Os-induced synaptic alterations. Hence, this kinase seems to be a key element in AD progression. Here, we studied the role of c-Abl on dendritic spine morphological changes induced by A & x3b2;Os using c-Abl null neurons (c-Abl-KO). First, we characterized the effect of c-Abl deficiency on dendritic spine density and found that its absence increases dendritic spine density. While A & x3b2;Os-treatment reduces the spine number in both wild-type (WT) and c-Abl-KO neurons, A & x3b2;Os-driven spine density loss was not affected by c-Abl. We then characterized A & x3b2;Os-induced morphological changes in dendritic spines of c-Abl-KO neurons. A & x3b2;Os induced a decrease in the number of mushroom spines in c-Abl-KO neurons while preserving the populations of immature stubby, thin, and filopodia spines. Furthermore, synaptic contacts evaluated by PSD95/Piccolo clustering and cell viability were preserved in A & x3b2;Os-exposed c-Abl-KO neurons. In conclusion, our results indicate that in the presence of A & x3b2;Os c-Abl participates in synaptic contact removal, increasing susceptibility to A & x3b2;Os damage. Its deficiency increases the immature spine population reducing A & x3b2;Os-induced synapse elimination. Therefore, c-Abl signaling could be a relevant actor in the early stages of AD.
c-Abl Kinase Is Required for Satellite Cell Function Through Pax7 Regulation
(2021) Montecino, Fabian; Gonzalez, Natalia; Blanco, Natasha; Ramirez, Manuel J.; Gonzalez-Martin, Adrian; Alvarez, Alejandra R.; Olguin, Hugo
Satellite cells (SCs) are tissue-specific stem cells responsible for adult skeletal muscle regeneration and maintenance. SCs function is critically dependent on two families of transcription factors: the paired box (Pax) involved in specification and maintenance and the Muscle Regulatory Factors (MRFs), which orchestrate myogenic commitment and differentiation. In turn, signaling events triggered by extrinsic and intrinsic stimuli control their function via post-translational modifications, including ubiquitination and phosphorylation. In this context, the Abelson non-receptor tyrosine kinase (c-Abl) mediates the activation of the p38 alpha/beta MAPK pathway, promoting myogenesis. c-Abl also regulates the activity of the transcription factor MyoD during DNA-damage stress response, pausing differentiation. However, it is not clear if c-Abl modulates other key transcription factors controlling SC function. This work aims to determine the role of c-Abl in SCs myogenic capacity via loss of function approaches in vitro and in vivo. Here we show that c-Abl inhibition or deletion results in a down-regulation of Pax7 mRNA and protein levels, accompanied by decreased Pax7 transcriptional activity, without a significant effect on MRF expression. Additionally, we provide data indicating that Pax7 is directly phosphorylated by c-Abl. Finally, SC-specific c-Abl ablation impairs muscle regeneration upon acute injury. Our results indicate that c-Abl regulates myogenic progression in activated SCs by controlling Pax7 function and expression.
Corticotropin-releasing factor binding protein enters the regulated secretory pathway in neuroendocrine cells and cortical neurons
(2011) Blanco, Elias H.; Pablo Zuniga, Juan; Estela Andres, Maria; Alvarez, Alejandra R.; Gysling, Katia
Corticotropin releasing factor binding protein (CRF-BP) is a 37 kDa glycoprotein that binds CRF with high affinity. CRF-BP controls CRF levels within plasma during human pregnancy. It has also been shown that CRF-BP is expressed in various brain nuclei. Main actions that have been proposed for brain CRF-BP are either decreasing available CRF or facilitating CRF ligand-induced activation of CRF-R2 receptors. For both actions, it is necessary the release of CRF-BP from CRF-BP expressing neurons. However, the secretion mode of CRF-BP is currently unknown. We used heterologous expression of CRF-BP-Flag in PC12 cells and in primary culture of rat cortical neurons to study CRF-BP secretion mode. We observed that CRF-BP-Flag immunoreactivity presents the typical cytoplasmatic punctuate pattern that has been described for neuropeptides and proteins that enter the regulated secretory pathway in PC12 cells. Quantitative analysis of double immunofluorescence confocal images showed that CRF-BP-Flag colocalizes with secretogranin II, marker of secretory granules, both in PC12 and in primary-cultured rat neurons. Furthermore, CRF-BP-Flag is released from PC12 cells upon high K(+)-depolarization. Thus, our results show that CRF-BP is efficiently sorted to the regulated secretory pathway in two cellular contexts, suggesting that the extracellular levels of CRF-BP in the central nervous system depends on neuronal activity. (C) 2011 Elsevier Ltd. All rights reserved.
Differential Detection of Amyloid Aggregates in Old Animals Using Gold Nanorods by Computerized Tomography: A Pharmacokinetic and Bioaccumulation Study
(2023) Jara-Guajardo, Pedro; Morales-Zavala, Francisco; Bolanos, Karen; Giralt, Ernest; Araya, Eyleen; Acosta, Gerardo A.; Albericio, Fernando; Alvarez, Alejandra R.; Kogan, Marcelo J.
Introduction: The development of new materials and tools for radiology is key to the implementation of this diagnostic technique in clinics. In this work, we evaluated the differential accumulation of peptide-functionalized GNRs in a transgenic animal model (APPswe/PSENd1E9) of Alzheimer's disease (AD) by computed tomography (CT) and measured the pharmacokinetic parameters and bioaccumulation of the nanosystem.Methods: The GNRs were functionalized with two peptides, Ang2 and D1, which conferred on them the properties of crossing the blood-brain barrier and binding to amyloid aggregates, respectively, thus making them a diagnostic tool with great potential for AD. The nanosystem was administered intravenously in APPswe/PSEN1dE9 model mice of 4-, 8- and 18-months of age, and the accumulation of gold nanoparticles was observed by computed tomography (CT). The gold accumulation and biodistribution were determined by atomic absorption.Results: Our findings indicated that 18-month-old animals treated with our nanosystem (GNR-D1/Ang2) displayed noticeable differences in CT signals compared to those treated with a control nanosystem (GNR-Ang2). However, no such distinctions were observed in younger animals. This suggests that our nanosystem holds the potential to effectively detect AD pathology.Discussion: These results support the future development of gold nanoparticle-based technology as a more effective and accessible alternative for the diagnosis of AD and represent a significant advance in the development of gold nanoparticle applications in disease diagnosis.
Imatinib therapy blocks cerebellar apoptosis and improves neurological symptoms in a mouse model of Niemann-Pick type C disease
(WILEY, 2008) Alvarez, Alejandra R.; Klein, Andres; Castro, Juan; Cancino, Gonzalo I.; Amigo, Julio; Mosqueira, Matias; Vargas, Lina M.; Yevenes, L. Fernanda; Bronfman, Francisca C.; Zanlungo, Silvana
Niemann-Pick type C (NPC) disease is a fatal autosomal recessive disorder characterized by the accumulation of free cholesterol and glycosphingo-lipids in the endosomal-lysosomal system. Patients with NPC disease have markedly progressive neuronal loss, mainly of cerebellar Purkinje neurons. There is strong evidence indicating that cholesterol accumulation and trafficking defects activate apoptosis in NPC brains. The purpose of this study was to analyze the relevance of apoptosis and particularly the proapoptotic c-Abl/p73 system in cerebellar neuron degeneration in NPC disease. We used the NPC1 mouse model to evaluate c-Abl/p73 expression and activation in the cerebellum and the effect of therapy with the c-Abl-specific inhibitor imatinib. The proapoptotic c-Abl/p73 system and the p73 target genes are expressed in the cerebellums of NPC mice. Furthermore, inhibition of c-Abl with imatinib preserved Purkinje neurons and reduced general cell apoptosis in the cerebellum, improved neurological symptoms, and increased the survival of NPC mice. Moreover, this prosurvival effect correlated with reduced mRNA levels of p73 proapoptotic target genes. Our results suggest that the c-Abl/p73 pathway is involved in NPC neurodegeneration and show that treatment with c-Abl inhibitors is useful in delaying progressive neurodegeneration, supporting the use of imatinib for clinical treatment of patients with NPC disease.
In vivo micro computed tomography detection and decrease in amyloid load by using multifunctionalized gold nanorods: a neurotheranostic platform for Alzheimer's disease
(Royal Soc Chemistry, 2021) Morales Zavala, Francisco; Jara Guajardo, Pedro; Chamorro Veloso, David Daniel; Riveros, Ana L.; Chandia Cristi, América Valeska; Salgado Cortés, Nicole Andrea; Pismante, Paola; Giralt, Ernest; Sanchez Navarro, Macarena; Araya, Eyleen; Vasquez, Rodrigo; Acosta, Gerardo; Albericio, Fernando; Alvarez, Alejandra R.; Kogan, Marcelo J.
The development and use of nanosystems is an emerging strategy for the diagnosis and treatment of a broad number of diseases, such as Alzheimer's disease (AD). Here, we developed a neurotheranostic nanosystem based on gold nanorods (GNRs) that works as a therapeutic peptide delivery system and can be detected in vivo for microcomputed tomography (micro-CT), being a diagnostic tool. GNRs functionalized with the peptides Ang2 (a shuttle to the Central Nervous System) and D1 (that binds to the A beta peptide, also inhibiting its aggregation) allowed detecting differences in vivo between wild type and AD mice (APPswe/PSEN1dE9) 15 minutes after a single dose by micro-CT. Moreover, after a recurrent treatment for one month with GNRs-D1/Ang2, we observed a diminution of amyloid load and inflammatory markers in the brain. Thus, this new designed nanosystem exhibits promising properties for neurotheranostics of AD.
Physiological Control of Nitric Oxide in Neuronal BACE1 Translation by Heme-Regulated eIF2α Kinase HRI Induces Synaptogenesis
(2015) ILL-Raga, Gerard; Tajes, Marta; Busquets-Garcia, Arnau; Ramos-Fernandez, Eva; Vargas, Lina M.; Bosch-Morato, Monica; Guivernau, Biuse; Valls-Comamala, Victoria; Eraso-Pichot, Abel; Guix, Francesc X.; Fandos, Cesar; Rosen, Mark D.; Rabinowitz, Michael H.; Maldonado, Rafael; Alvarez, Alejandra R.; Ozaita, Andres; Munoz, Francisco J.
Aims: Hippocampus is the brain center for memory formation, a process that requires synaptogenesis. However, hippocampus is dramatically compromised in Alzheimer's disease due to the accumulation of amyloid beta-peptide, whose production is initiated by beta-site APP Cleaving Enzyme 1 (BACE1). It is known that pathological stressors activate BACE1 translation through the phosphorylation of the eukaryotic initiation factor-2 alpha (eIF2 alpha) by GCN2, PERK, or PKR kinases, leading to amyloidogenesis. However, BACE1 physiological regulation is still unclear. Since nitric oxide (NO) participates directly in hippocampal glutamatergic signaling, we investigated the neuronal role of the heme-regulated eukaryotic initiation factor eIF2 alpha kinase (HRI), which can bind NO by a heme group, in BACE1 translation and its physiological consequences. Results: We found that BACE1 is expressed on glutamate activation with NO being the downstream effector by triggering eIF2 alpha phosphorylation, as it was obtained by Western blot and luciferase assay. It is due to the activation of HRI by NO as assayed by Western blot and immunofluorescence with an HRI inhibitor and HRI siRNA. BACE1 expression was early detected at synaptic spines, contributing to spine growth and consolidating the hippocampal memory as assayed with mice treated with HRI or neuronal NO synthase inhibitors. Innovation: We provide the first description that HRI and eIF2 alpha are working in physiological conditions in the brain under the control of nitric oxide and glutamate signaling, and also that BACE1 has a physiological role in hippocampal function. Conclusion: We conclude that BACE1 translation is controlled by NO through HRI in glutamatergic hippocampal synapses, where it plays physiological functions, allowing the spine growth and memory consolidation. Antioxid. Redox Signal. 22, 1295-1307.
STI571 prevents apoptosis, tau phosphorylation and behavioural impairments induced by Alzheimer's beta-amyloid deposits
(OXFORD UNIV PRESS, 2008) Cancino, Gonzalo I.; Toledo, Enrique M.; Leal, Nancy R.; Hernandez, Diego E.; Yevenes, L. Fernanda; Inestrosa, Nibaldo C.; Alvarez, Alejandra R.
There is evidence that amyloid beta-protein (A beta) deposits or A intermediates trigger pathogenic factors in Alzheimers disease patients. We have previously reported that c-Abl kinase activation involved in cell signalling regulates the neuronal death response to A fibrils (A beta(f)). In the present study we investigated the therapeutic potential of the selective c-Abl inhibitor STI57I on both the intrahippocampal injection of Af and APPsw/PSENI Delta E9 transgenic mice Alzheimers disease models. Injection of A beta(f) induced an increase in the numbers of p73 and c-Abl immunoreactive cells in the hippocampal area near to the lesion. Chronic intraperitoneal administration of STI571 reduced the rat behavioural deficit induced by A beta(f), as well as apoptosis and tau phosphorylation. Our in vitro studies suggest that inhibition of the c-Abl/p73 signalling pathway is the mechanism underlying of the effects of STI571 on A beta-induced apoptosis for the following reasons: (i) A beta(f) induces p73 phosphorylation, the TAp73 isoform levels increase so as to enhance its proapoptotic function, and all these effects where reduced by STI571; (ii) c-Abl kinase activity is required for neuronal apoptosis and (iii) STI571 prevents the A beta-induced increase in the expression of apoptotic genes. Furthermore, in the A-injected area there was a huge increase in phosphorylated p73 and a larger number of TAp73-positive cells, with these changes being prevented by STI571 coinjection. Moreover, the intraperitoneal administration of STI571 rescued the cognitive decline in APPsw/PSENI Delta E9 mice, p73 phosphorylation, tau phosphorylation and caspase-3 activation in neurons around A beta deposits. Besides, we observed a decrease in the number and size of A beta deposits in the APPsw/PSENI Delta E9-STI571-treated mice. These results are consistent with the role of the c-Abl/p73 signalling pathway in A beta neurodegeneration, and suggest that STI571-like compounds would be effective in therapeutic treatments of Alzheimer disease.
Synaptic Clustering of PSD-95 Is Regulated by c-Abl through Tyrosine Phosphorylation
(SOC NEUROSCIENCE, 2010) Perez de Arce, Karen; Varela Nallar, Lorena; Farias, Olivia; Cifuentes, Alejandra; Bull, Paulina; Couch, Brian A.; Koleske, Anthony J.; Inestrosa, Nibaldo C.; Alvarez, Alejandra R.
The c-Abl tyrosine kinase is present in mouse brain synapses, but its precise synaptic function is unknown. We found that c-Abl levels in the rat hippocampus increase postnatally, with expression peaking at the first postnatal week. In 14 d in vitro hippocampal neuron cultures, c-Abl localizes primarily to the postsynaptic compartment, in which it colocalizes with the postsynaptic scaffold protein postsynaptic density protein-95 (PSD-95) in apposition to presynaptic markers. c-Abl associates with PSD-95, and chemical or genetic inhibition of c-Abl kinase activity reduces PSD-95 tyrosine phosphorylation, leading to reduced PSD-95 clustering and reduced synapses in treated neurons. c-Abl can phosphorylate PSD-95 on tyrosine 533, and mutation of this residue reduces the ability of PSD-95 to cluster at postsynaptic sites. Our results indicate that c-Abl regulates synapse formation by mediating tyrosine phosphorylation and clustering of PSD-95.

Browsing by Author "Alvarez, Alejandra R."

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