DSpace Angular :: Browsing by Author "Inestrosa, Nibaldo C."

Browsing by Author "Inestrosa, Nibaldo C."

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A Multivariate Assessment of Age-Related Cognitive Impairment in Octodon degus
(2021) Rivera, Daniela S.; Lindsay, Carolina B.; Oliva, Carolina A.; Bozinovic, Francisco; Inestrosa, Nibaldo C.
Aging is a progressive functional decline characterized by a gradual deterioration in physiological function and behavior. The most important age-related change in cognitive function is decline in cognitive performance (i.e., the processing or transformation of information to make decisions that includes speed of processing, working memory, and learning). The purpose of this study is to outline the changes in age-related cognitive performance (i.e., short-term recognition memory and long-term learning and memory) in long-lived Octodon degus. The strong similarity between degus and humans in social, metabolic, biochemical, and cognitive aspects makes it a unique animal model for exploring the mechanisms underlying the behavioral and cognitive deficits related to natural aging. In this study, we examined young adult female degus (12- and 24-months-old) and aged female degus (38-, 56-, and 75-months-old) that were exposed to a battery of cognitive-behavioral tests. Multivariate analyses of data from the Social Interaction test or Novel Object/Local Recognition (to measure short-term recognition memory), and the Barnes maze test (to measure long-term learning and memory) revealed a consistent pattern. Young animals formed a separate group of aged degus for both short- and long-term memories. The association between the first component of the principal component analysis (PCA) from short-term memory with the first component of the PCA from long-term memory showed a significant negative correlation. This suggests age-dependent differences in both memories, with the aged degus having higher values of long-term memory ability but poor short-term recognition memory, whereas in the young degus an opposite pattern was found. Approximately 5% of the young and 80% of the aged degus showed an impaired short-term recognition memory; whereas for long-term memory about 32% of the young degus and 57% of the aged degus showed decreased performance on the Barnes maze test. Throughout this study, we outlined age-dependent cognitive performance decline during natural aging in degus. Moreover, we also demonstrated that the use of a multivariate approach let us explore and visualize complex behavioral variables, and identified specific behavioral patterns that allowed us to make powerful conclusions that will facilitate further the study on the biology of aging. In addition, this study could help predict the onset of the aging process based on behavioral performance.
Adiponectin and resistin modulate the progression of Alzheimer's disease in a metabolic syndrome model
(2023) Cisternas, Pedro; Gherardelli, Camila; Gutierrez, Joel; Salazar, Paulina; Mendez-Orellana, Carolina; Wong, G. William; Inestrosa, Nibaldo C.
Metabolic syndrome (MetS), a cluster of metabolic conditions that include obesity, hyperlipidemia, and insulin resistance, increases the risk of several aging-related brain diseases, including Alzheimer's disease (AD). However, the underlying mechanism explaining the link between MetS and brain function is poorly understood. Among the possible mediators are several adipose-derived secreted molecules called adipokines, including adiponectin (ApN) and resistin, which have been shown to regulate brain function by modulating several metabolic processes. To investigate the impact of adipokines on MetS, we employed a diet-induced model to induce the various complications associated with MetS. For this purpose, we administered a high-fat diet (HFD) to both WT and APP/PSN1 mice at a pre-symptomatic disease stage. Our data showed that MetS causes a fast decline in cognitive performance and stimulates A beta(42) production in the brain. Interestingly, ApN treatment restored glucose metabolism and improved cognitive functions by 50% while decreasing the A beta(42/40) ratio by approximately 65%. In contrast, resistin exacerbated Ab pathology, increased oxidative stress, and strongly reduced glucose metabolism. Together, our data demonstrate that ApN and resistin alterations could further contribute to AD pathology.
Age- and Sex-Associated Glucose Metabolism Decline in a Mouse Model of Alzheimer's Disease
(2022) Gherardelli, Camila; Cisternas, Pedro; Vera-Salazar, Roberto F.; Mendez-Orellana, Carolina; Inestrosa, Nibaldo C.
Background: Alzheimer's disease (AD) is characterized by a high etiological and clinical heterogeneity, which has obscured the diagnostic and treatment efficacy, as well as limited the development of potential drugs. Sex differences are among the risk factors that contribute to the variability of disease manifestation. Unlike men, women are at greater risk of developing AD and suffer from higher cognitive deterioration, together with important changes in pathological features. Alterations in glucose metabolism are emerging as a key player in the pathogenesis of AD, which appear even decades before the presence of clinical symptoms.
Age-Dependent Behavioral and Synaptic Dysfunction Impairment Are Improved with Long-Term Andrographolide Administration in Long-Lived Female Degus (Octodon degus)
(2023) Oliva, Carolina A.; Rivera, Daniela S.; Torres, Angie K.; Lindsay, Carolina B.; Tapia-Rojas, Cheril; Bozinovic, Francisco; Inestrosa, Nibaldo C.
In Octodon degus, the aging process is not equivalent between sexes and worsens for females. To determine the beginning of detrimental features in females and the ways in which to improve them, we compared adult females (36 months old) and aged females (72 months old) treated with Andrographolide (ANDRO), the primary ingredient in Andrographis paniculata. Our behavioral data demonstrated that age does not affect recognition memory and preference for novel experiences, but ANDRO increases these at both ages. Sociability was also not affected by age; however, social recognition and long-term memory were lower in the aged females than adults but were restored with ANDRO. The synaptic physiology data from brain slices showed that adults have more basal synaptic efficiency than aged degus; however, ANDRO reduced basal activity in adults, while it increased long-term potentiation (LTP). Instead, ANDRO increased the basal synaptic activity and LTP in aged females. Age-dependent changes were also observed in synaptic proteins, where aged females have higher synaptotagmin (SYT) and lower postsynaptic density protein-95 (PSD95) levels than adults. ANDRO increased the N-methyl D-aspartate receptor subtype 2B (NR2B) at both ages and the PSD95 and Homer1 only in the aged. Thus, females exposed to long-term ANDRO administration show improved complex behaviors related to age-detrimental effects, modulating mechanisms of synaptic transmission, and proteins.
Andrographolide promotes hippocampal neurogenesis and spatial memory in the APPswe/PS1ΔE9 mouse model of Alzheimer's disease
(2021) Arredondo, Sebastian B.; Reyes, Daniel T.; Herrera-Soto, Andrea; Mardones, Muriel D.; Inestrosa, Nibaldo C.; Varela-Nallar, Lorena
In Alzheimer ' s disease (AD) there is a reduction in hippocampal neurogenesis that has been associated to cognitive deficits. Previously we showed that Andrographolide (ANDRO), the main bioactive component of Andrographis paniculate, induces proliferation in the hippocampus of the APPswe/PSEN1 Delta E9 (APP/PS1) mouse model of AD as assessed by staining with the mitotic marker Ki67. Here, we further characterized the effect of ANDRO on hippocampal neurogenesis in APP/PS1 mice and evaluated the contribution of this process to the cognitive effect of ANDRO. Treatment of 8-month-old APP/PS1 mice with ANDRO for 4 weeks increased proliferation in the dentate gyrus as evaluated by BrdU incorporation. Although ANDRO had no effect on neuronal differentiation of newborn cells, it strongly increased neural progenitors, neuroblasts and newborn immature neurons, cell populations that were decreased in APP/PS1 mice compared to age-matched wild-type mice. ANDRO had no effect on migration or in total dendritic length, arborization and orientation of immature neurons, suggesting no effects on early morphological development of newborn neurons. Finally, ANDRO treatment improved the performance of APP/PS1 mice in the object location memory task. This effect was not completely prevented by co-treatment with the anti-mitotic drug TMZ, suggesting that other effects of ANDRO in addition to the increase in neurogenesis might underlie the observed cognitive improvement. Altogether, our data indicate that in APP/PS1 mice ANDRO stimulates neurogenesis in the hippocampus by inducing proliferation of neural precursor cells and improves spatial memory performance.
Andrographolide Reduces Neuroinflammation and Oxidative Stress in Aged Octodon degus
(SPRINGER, 2020) Lindsay, Carolina B.; Zolezzi, Juan M.; Rivera, Daniela S.; Cisternas, Pedro; Bozinovic, Francisco; Inestrosa, Nibaldo C.
Alzheimer's disease (AD) is a devastating neurodegenerative disorder in which superior brain functions, such as memory and cognition, are impaired. Currently, no effective treatment is available for AD. Although andrographolide (ANDRO), a compound extracted from the herb Andrographis paniculata, has shown interesting effects in models of several diseases, including AD, its effects on other molecular changes observed in AD, such as neuroinflammation and oxidative stress, have not yet been studied. To evaluate the impact of ANDRO-based intervention on the levels of amyloid-beta (A beta) and neuroinflammatory and oxidative stress markers in the brains of aged Octodon degus, a Chilean rodent, fifty-six-month-old O. degus were treated intraperitoneally with 2 or 4 mg/kg ANDRO. Vehicle-injected and 12-month-old O. degus were used as positive controls. Then, the protein levels of selected markers were assessed via immunohistochemistry and immunoblotting. ANDRO significantly reduced the total A beta burden as well as astrogliosis and interleukin-6 levels. Moreover, ANDRO significantly reduced the levels of 4-hydroxynonenal and N-tyrosine adducts, suggesting a relevant reduction in oxidative stress within aged O. degus brain. Considering that O. degus has been proposed as a potential "natural" model for sporadic AD due to the development of neuropathological markers that resemble this pathology, our results suggest that ANDRO should be further studied to establish its potential as a therapeutic drug for AD.
ATP Induces NO Production in Hippocampal Neurons by P2X₇ Receptor Activation Independent of Glutamate Signaling
(2013) Francisco Codocedo, Juan; Alejandro Godoy, Juan; Ines Poblete, Maria; Inestrosa, Nibaldo C.; Pablo Huidobro-Toro, Juan
To assess the putative role of adenosine triphosphate (ATP) upon nitric oxide (NO) production in the hippocampus, we used as a model both rat hippocampal slices and isolated hippocampal neurons in culture, lacking glial cells. In hippocampal slices, additions of exogenous ATP or 2'(3')-O-(4-Benzoylbenzoyl) ATP (Bz-ATP) elicited concentration-dependent NO production, which increased linearly within the first 15 min and plateaued thereafter; agonist EC50 values were 50 and 15 mu M, respectively. The NO increase evoked by ATP was antagonized in a concentration-dependent manner by Coomassie brilliant blue G (BBG) or by N-omega-propyl-L-arginine, suggesting the involvement of P2X(7)Rs and neuronal NOS, respectively. The ATP induced NO production was independent of N-methyl-D-aspartic acid (NMDA) receptor activity as effects were not alleviated by DL-2-Amino-5-phosphonopentanoic acid (APV), but antagonized by BBG. In sum, exogenous ATP elicited NO production in hippocampal neurons independently of NMDA receptor activity.
Canonical Wnt Signaling Modulates the Expression of Pre- and Postsynaptic Components in Different Temporal Patterns
(2020) Martinez, Milka; Torres, Viviana I.; Vio, Carlos P.; Inestrosa, Nibaldo C.
Wnt ligands play critical roles in neuronal development, synapse formation, synaptic activity, and plasticity. Synaptic plasticity requires molecular remodeling of synapses, implying the expression of key synaptic components. Some studies have linked Wnt signaling activity to changes in synaptic protein levels. However, the presynaptic and postsynaptic gene expression profiles of hippocampal neurons exposed to Wnt proteins have not been studied. Hence, we treated rat cultured hippocampal neurons with recombinant Wnt3a, lithium, and the Wnt inhibitor Dkk-1 for different treatment durations and measured the mRNA and protein levels of pre- and postsynaptic components. The ligand Wnt3a promoted the differential temporal expression of genes encoding presynaptic and postsynaptic proteins. Gene expression of the presynaptic proteins Rim1, piccolo (Pclo), Erc2, Ctbp1 and Rimbp2 increased in a specific temporal pattern. Simultaneously, the mRNA and protein levels of postsynaptic components showed a different temporal expression pattern, e.g., the mRNAs for postsynaptic scaffolding components such as postsynaptic density protein-95 (PSD-95/Dlg4), Homer1 and Shank1 were temporally regulated by both Wnt3a and lithium. On the other hand, the mRNA levels of the gene encoding the protein calcium/calmodulin-dependent protein kinase IV (Camk4), canonically upregulated by Wnt, were increased. Our results suggest that Wnt signaling orchestrates expressional changes in genes encoding presynaptic and postsynaptic components, probably as part of a synaptic plasticity mechanism in neurons.
Cardiovascular and autonomic dysfunction in long-COVID syndrome and the potential role of non-invasive therapeutic strategies on cardiovascular outcomes
(2023) Allendes, Francisca J.; Diaz, Hugo S.; Ortiz, Fernando C.; Marcus, Noah J.; Quintanilla, Rodrigo; Inestrosa, Nibaldo C.; Del Rio, Rodrigo
A significant percentage of COVID-19 survivors develop long-lasting cardiovascular sequelae linked to autonomic nervous system dysfunction, including fatigue, arrhythmias, and hypertension. This post-COVID-19 cardiovascular syndrome is one facet of "long-COVID," generally defined as long-term health problems persisting/appearing after the typical recovery period of COVID-19. Despite the fact that this syndrome is not fully understood, it is urgent to develop strategies for diagnosing/managing long-COVID due to the immense potential for future disease burden. New diagnostic/therapeutic tools should provide health personnel with the ability to manage the consequences of long-COVID and preserve/improve patient quality of life. It has been shown that cardiovascular rehabilitation programs (CRPs) stimulate the parasympathetic nervous system, improve cardiorespiratory fitness (CRF), and reduce cardiovascular risk factors, hospitalization rates, and cognitive impairment in patients suffering from cardiovascular diseases. Given their efficacy in improving patient outcomes, CRPs may have salutary potential for the treatment of cardiovascular sequelae of long-COVID. Indeed, there are several public and private initiatives testing the potential of CRPs in treating fatigue and dysautonomia in long-COVID subjects. The application of these established rehabilitation techniques to COVID-19 cardiovascular syndrome represents a promising approach to improving functional capacity and quality of life. In this brief review, we will focus on the long-lasting cardiovascular and autonomic sequelae occurring after COVID-19 infection, as well as exploring the potential of classic and novel CRPs for managing COVID-19 cardiovascular syndrome. Finally, we expect this review will encourage health care professionals and private/public health organizations to evaluate/implement non-invasive techniques for the management of COVID-19 cardiovascular sequalae.
Dietary Fructose Promotes Prostate Cancer Growth
(2021) Carreno, Daniela, V; Corro, Nestor B.; Cerda-Infante, Javier F.; Echeverria, Carolina E.; Asencio-Barria, Catalina A.; Torres-Estay, Veronica A.; Mayorga-Weber, Gonzalo A.; Rojas, Pablo A.; Veliz, Loreto P.; Cisternas, Pedro A.; Montecinos, Viviana P.; San Francisco, Ignacio F.; Varas-Godoy, Manuel A.; Sotomayor, Paula C.; Castro, Maite A.; Nualart, Francisco J.; Inestrosa, Nibaldo C.; Godoy, Alejandro S.
Clinical localization of primary tumors and sites of metastasis by PET is based on the enhanced cellular uptake of 2-deoxy-2-[F-18]-fluoro-D-glucose (FDG). In prostate cancer, however, PET-FDG imaging has shown limited clinical applicability, suggesting that prostate cancer cells may utilize hexoses other than glucose, such as fructose, as the preferred energy source. Our previous studies suggested that prostate cancer cells overexpress fructose transporters, but not glucose transporters, compared with benign cells. Here, we focused on validating the functional expression of fructose transporters and determining whether fructose can modulate the biology of prostate cancer cells in vitro and in vivo. Fructose transporters, Glut5 and Glut9, were significantly upregulated in clinical specimens of prostate cancer when compared with their benign counterparts. Fructose levels in the serum of patients with prostate cancer were significantly higher than healthy subjects. Functional expression of fructose transporters was confirmed in prostate cancer cell lines. A detailed kinetic characterization indicated that Glut5 represents the main functional contributor in mediating fructose transport in prostate cancer cells. Fructose stimulated proliferation and invasion of prostate cancer cells in vitro. In addition, dietary fructose increased the growth of prostate cancer cell line-derived xenograft tumors and promoted prostate cancer cell proliferation in patient- derived xenografts. Gene set enrichment analysis confirmed that fructose stimulation enriched for proliferation-related pathways in prostate cancer cells. These results demonstrate that fructose promotes prostate cancer cell growth and aggressiveness in vitro and in vivo and may represent an alternative energy source for prostate cancer cells.
Differential Role of Sex and Age in the Synaptic Transmission of Degus (Octodon degus)
(2022) Oliva, Carolina A.; Rivera, Daniela S.; Mariqueo, Trinidad A.; Bozinovic, Francisco; Inestrosa, Nibaldo C.
Octodon degus are a diurnal long-lived social animal widely used to perform longitudinal studies and complex cognitive tasks to test for physiological conditions with similitude in human behavior. They show a complex social organization feasible to be studied under different conditions and ages. Several aspects in degus physiology demonstrated that these animals are susceptible to environmental conditions, such as stress, fear, feeding quality, and isolation. However, the relevance of these factors in life of this animal depends on sex and age. Despite its significance, there are few studies with the intent to characterize neurological parameters that include these two parameters. To determine the basal neurophysiological status, we analyzed basic electrophysiological parameters generated during basal activity or synaptic plasticity in the brain slices of young and aged female and male degus. We studied the hippocampal circuit of animals kept in social ambient in captivity under controlled conditions. The study of basal synaptic activity in young animals (12-24 months old) was similar between sexes, but female degus showed more efficient synaptic transmission than male degus. We found the opposite in aged animals (60-84 months old), where male degus had a more efficient basal transmission and facilitation index than female degus. Furthermore, female and male degus develop significant but not different long-term synaptic plasticity (LTP). However, aged female degus need to recruit twice as many axons to evoke the same postsynaptic activity as male degus and four times more when compared to young female degus. These data suggest that, unlike male degus, the neural status of aged female degus change, showing less number or functional axons available at advanced ages. Our data represent the first approach to incorporate the effect of sex along with age progression in basal neural status.
Discovery of a Potent Dual Inhibitor of Acetylcholinesterase and Butyrylcholinesterase with Antioxidant Activity that Alleviates Alzheimer-like Pathology in Old APP/PS1 Mice
(2021) Viayna, Elisabet; Coquelle, Nicolas; Cieslikiewicz-Bouet, Monika; Cisternas, Pedro; Oliva, Carolina A.; Sanchez-Lopez, Elena; Ettcheto, Miren; Bartolini, Manuela; De Simone, Angela; Ricchini, Mattia; Rendina, Marisa; Pons, Megane; Firuzi, Omidreza; Perez, Belen; Saso, Luciano; Andrisano, Vincenza; Nachon, Florian; Brazzolotto, Xavier; Luisa Garcia, Maria; Camins, Antoni; Silman, Israel; Jean, Ludovic; Inestrosa, Nibaldo C.; Colletier, Jacques-Philippe; Renard, Pierre-Yves; Munoz-Torrero, Diego
The combination of the scaffolds of the cholinesterase inhibitor huprine Y and the antioxidant capsaicin results in compounds with nanomolar potencies toward human acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) that retain or improve the antioxidant properties of capsaicin. Crystal structures of their complexes with AChE and BChE revealed the molecular basis for their high potency. Brain penetration was confirmed by biodistribution studies in CS7BL6 mice, with one compound (Si) displaying better brain/plasma ratio than donepezil. Chronic treatment of 10 month-old APP/PS1 mice with 5i (2 mg/kg, i.p., 3 times per week, 4 weeks) rescued learning and memory impairments, as measured by three different behavioral tests, delayed the Alzheimer-like pathology progression, as suggested by a significantly reduced A beta 42/A beta 40 ratio in the hippocampus, improved basal synaptic efficacy, and significantly reduced hippocampal oxidative stress and neuroinflammation. Compound Si emerges as an interesting anti-Alzheimer lead with beneficial effects on cognitive symptoms and on some underlying disease mechanisms.
Disruption of Glucose Metabolism in Aged Octodon degus: A Sporadic Model of Alzheimer's Disease
(2021) Cisternas, Pedro; Gherardelli, Camila; Salazar, Paulina; Inestrosa, Nibaldo C.
Alzheimer's disease is a progressive neurodegenerative disorder and the most common cause of dementia. Although transgenic Alzheimer's disease (AD) animal models have greatly contributed to our understanding of the disease, therapies tested in these animals have resulted in a high rate of failure in preclinical trials for AD. A promising model is Octodon degus (degu), a Chilean rodent that spontaneously develops AD-like neuropathology. Previous studies have reported that, during aging, degus exhibit a progressive decline in cognitive function, reduced neuroinflammation, and concomitant increases in the number and size of amyloid beta (A beta) plaques in several brain regions. Importantly, in humans and several AD models, a correlation has been shown between brain dysfunction and neuronal glucose utilization impairment, a critical aspect considering the high-energy demand of the brain. However, whether degus develop alterations in glucose metabolism remains unknown. In the present work, we measured several markers of glucose metabolism, namely, glucose uptake, ATP production, and glycolysis and pentose phosphate pathway (PPP) flux, in hippocampal slices from degus of different ages. We found a significant decrease in hippocampal glucose metabolism in aged degus, caused mainly by a drop in glucose uptake, which in turn, reduced ATP synthesis. Moreover, we observed a negative correlation between age and PPP flux. Together, our data further support the use of degus as a model for studying the neuropathology involved in sporadic AD-like pathology and as a potentially valuable tool in the search for effective treatments against the disease.
Effects of long-lasting social isolation and re-socialization on cognitive performance and brain activity: a longitudinal study in Octodon degus
(2020) Rivera, Daniela S.; Lindsay, Carolina B.; Oliva, Carolina A.; Francisco Codocedo, Juan; Bozinovic, Francisco; Inestrosa, Nibaldo C.
Social isolation is considered a stressful situation that results in increased physiological reactivity to novel stimuli, altered behaviour, and impaired brain function. Here, we investigated the effects of long-term social isolation on working memory, spatial learning/memory, hippocampal synaptic transmission, and synaptic proteins in the brain of adult female and male Octodon degus. The strong similarity between degus and humans in social, metabolic, biochemical, and cognitive aspects, makes it a unique animal model that can be highly applicable for further social, emotional, cognitive, and aging studies. These animals were socially isolated from post-natal and post-weaning until adulthood. We also evaluated if re-socialization would be able to compensate for reactive stress responses in chronically stressed animals. We showed that long-term social isolation impaired the HPA axis negative feedback loop, which can be related to cognitive deficits observed in chronically stressed animals. Notably, re-socialization restored it. In addition, we measured physiological aspects of synaptic transmission, where chronically stressed males showed more efficient transmission but deficient plasticity, as the reverse was true on females. Finally, we analysed synaptic and canonical Wnt signalling proteins in the hypothalamus, hippocampus, and prefrontal cortex, finding both sex-and brain structure-dependent modulation, including transient and permanent changes dependent on stress treatment.
Emerging role of Metformin in Alzheimer's disease: A translational view
(2024) Rios, Juvenal A.; Borquez, Juan Carlos; Godoy, Juan A.; Zolezzi, Juan M.; Furrianca, Maria Cristina; Inestrosa, Nibaldo C.
Alzheimer's disease (AD) constitutes a major public-health issue of our time. Regrettably, despite our considerable understanding of the pathophysiological aspects of this disease, current interventions lead to poor outcomes. Furthermore, experimentally promising compounds have continuously failed when translated to clinical trials. Along with increased population ageing, Type 2 Diabetes Mellitus (T2DM) has become an extremely common condition, mainly due to unbalanced dietary habits. Substantial epidemiological evidence correlates T2DM with cognitive impairment as well. Considering that brain insulin resistance, mitochondrial dysfunction, oxidative stress, and amyloidogenesis are common phenomena, further approaching the common features among these pathological conditions. Metformin constitutes the first-choice drug to preclude insulin resistance in T2DM clinical management. Experimental evidence suggests that its functions might include neuroprotective effects, in addition to its hypoglycemic activity. This review aims to summarize and discuss current knowledge of experimental data on metformin on this path towards translational medicine. Finally, we discuss the controversial data of responses to metformin in vitro, and in vivo, animal models and human studies.
Evidence of Synaptic and Neurochemical Remodeling in the Retina of Aging Degus
(2020) Chang, Lily Y-L; Ardiles, Alvaro O.; Tapia-Rojas, Cheril; Araya, Joaquin; Inestrosa, Nibaldo C.; Palacios, Adrian G.; Acosta, Monica L.
Accumulation of amyloid-beta (A beta) peptides is regarded as the hallmark of neurodegenerative alterations in the brain of Alzheimer's disease (AD) patients. In the eye, accumulation of A beta peptides has also been suggested to be a trigger of retinal neurodegenerative mechanisms. Some pathological aspects associated with A beta levels in the brain are synaptic dysfunction, neurochemical remodeling and glial activation, but these changes have not been established in the retina of animals with A beta accumulation. We have employed the Octodon degus in which A beta peptides accumulated in the brain and retina as a function of age. This current study investigated microglial morphology, expression of PSD95, synaptophysin, Iba-1 and choline acetyltransferase (ChAT) in the retina of juvenile, young and adult degus using immunolabeling methods. Neurotransmitters glutamate and gamma-aminobutyric acid (GABA) were detected using immunogold labeling and glutamate receptor subunits were quantified using Western blotting. There was an age-related increase in presynaptic and a decrease in post-synaptic retinal proteins in the retinal plexiform layers. Immunolabeling showed changes in microglial morphology characteristic of intermediate stages of activation around the optic nerve head (ONH) and decreasing activation toward the peripheral retina. Neurotransmitter expression pattern changed at juvenile ages but was similar in adults. Collectively, the results suggest that microglial activation, synaptic remodeling and neurotransmitter changes may be consequent to, or parallel to A beta peptide and phosphorylated tau accumulation in the retina.
Frizzled-1 is involved in the neuroprotective effect of Wnt3a against aβ oligomers
(2008) Chacon, Marcelo A.; Varela-Nallar, Lorena; Inestrosa, Nibaldo C.
The activation of the canonical Writ signaling pathway protects hippocampal neurons against the toxicity of Alzheimer's amyloid-beta-peptide (A beta), however, the role played by the Writ receptors Frizzleds, has not been studied. We report here that Frizzled-1 mediates the activation of the canonical Wnt/beta-catenin pathway by Wnt3a in PC 12 cells. In addition, the protective effect of Wnt3a against the toxicity of A beta oligomers was modulated by Frizzled-1 expression levels in both PC 12 cells and hippocampal neurons. Over-expression of Frizzled-1 significantly increased cell survival induced by Wnt3a and diminished caspase-3 activation, while knocking-clown Frizzled-1 expression by antisense oligonucleotides decreased the Wnt3a protection. Over-expression of wild-type beta-catenin, but not a transcriptionally inactive mutated version, prevented the toxicity of A suggesting that the transcription of Writ target genes may be involved in these events. This was confirmed by co-transfecting both Frizzled-1 and the inactive form of beta-catenin, which does not elicited protection levels similar to those showed with endogenous beta-catenin. Our results indicate that Wnt3a protects from A beta-oligomers toxicity by activating the canonical Wnt signaling pathway through the Frizzled-1 receptor, suggesting a therapeutic potential for this signaling pathway in the treatment of Alzheimer's disease.
Genome-wide identification of new Wnt/β-catenin target genes in the human genome using CART method
(2010) Hodar, Christian; Assar, Rodrigo; Colombres, Marcela; Aravena, Andres; Pavez, Leonardo; Gonzalez, Mauricio; Martinez, Servet; Inestrosa, Nibaldo C.; Maass, Alejandro
Background: The importance of in silico predictions for understanding cellular processes is now widely accepted, and a variety of algorithms useful for studying different biological features have been designed. In particular, the prediction of cis regulatory modules in non-coding human genome regions represents a major challenge for understanding gene regulation in several diseases. Recently, studies of the Wnt signaling pathway revealed a connection with neurodegenerative diseases such as Alzheimer's. In this article, we construct a classification tool that uses the transcription factor binding site motifs composition of some gene promoters to identify new Wnt/beta-catenin pathway target genes potentially involved in brain diseases.
Glutamatergic Receptor Trafficking and Delivery: Role of the Exocyst Complex
(NLM (Medline), 2020) Lira, Matías; Mira, Rodrigo G.; Cerpa Nebott Waldo Francisco; Carvajal, Francisco J.; Inestrosa, Nibaldo C.; Zamorano, Pedro
Cells comprise several intracellular membrane compartments that allow them to function properly. One of these functions is cargo movement, typically proteins and membranes within cells. These cargoes ride microtubules through vesicles from Golgi and recycling endosomes to the plasma membrane in order to be delivered and exocytosed. In neurons, synaptic functions employ this cargo trafficking to maintain inter-neuronal communication optimally. One of the complexes that oversee vesicle trafficking and tethering is the exocyst. The exocyst is a protein complex containing eight subunits first identified in yeast and then characterized in multicellular organisms. This complex is related to several cellular processes, including cellular growth, division, migration, and morphogenesis, among others. It has been associated with glutamatergic receptor trafficking and tethering into the synapse, providing the molecular machinery to deliver receptor-containing vesicles into the plasma membrane in a constitutive manner. In this review, we discuss the evidence so far published regarding receptor trafficking and the exocyst complex in both basal and stimulated levels, comparing constitutive trafficking and long-term potentiation-related trafficking.
Heparin activates Wnt signaling for neuronal morphogenesis
(WILEY, 2008) Colombres, Marcela; Henriquez, Juan Pablo; Reig, German F.; Scheu, Jessica; Calderon, Rosario; Alvarez, Alejandra; Brandan, Enrique; Inestrosa, Nibaldo C.
Writ factors are secreted ligands that affect different aspects of the nervous system behavior like neurodevelopment, synaptogenesis and neurodegeneration. In different model systems, Wnt signaling has been demonstrated to be regulated by heparan sulfate proteoglycans (HSPGs). Whether HSPGs modulate Writ signaling in the context of neuronal behavior is currently unknown. Here we demonstrate that activation of Wnt signaling with the endogenous ligand Wnt-7a results in an increased of neurite outgrowth in the neuroblastoma N2a cell line. Interestingly, heparin induces glycogen synthase kinase-3 beta (GSK-3 beta) inhibition, beta-catenin stabilization and morphological differentiation in both N2a cells and in rat primary hippocampal neuronal cultures. We also show that heparin modulates Wnt-3a-induced stabilization of beta-catenin. Several extracellular matrix and membrane-attached HSPGs were found to be expressed in both in vitro neuronal models. Changes in the expression of specific HSPGs were observed upon differentiation of N2a cells. Taken together, our findings suggest that HSPGs may modulate canonical Writ signaling for neuronal morphogenesis.

Browsing by Author "Inestrosa, Nibaldo C."

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