Browsing by Author "Inestrosa, Nibaldo C."
Now showing 1 - 10 of 10
Results Per Page
Sort Options
- ItemAndrographolide 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.
- ItemGlutamatergic 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, PedroCells 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.
- ItemHeparin 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.
- ItemHow Are Synapses Born? A Functional and Molecular View of the Role of the Wnt Signaling Pathway(2022) Bonansco, Christian; Cerpa Nebott, Waldo; Inestrosa, Nibaldo C.Synaptic transmission is a dynamic process that requires precise regulation. Early in life, we must be able to forge appropriate connections (add and remove) to control our behavior. Neurons must recognize appropriate targets, and external soluble factors that activate specific signaling cascades provide the regulation needed to achieve this goal. Wnt signaling has been implicated in several forms of synaptic plasticity, including functional and structural changes associated with brain development. The analysis of synapses from an electrophysiological perspective allows us to characterize the functional role of cellular signaling pathways involved in brain development. The application of quantal theory to principles of developmental plasticity offers the possibility of dissecting the function of structural changes associated with the birth of new synapses as well as the maturation of immature silent synapses. Here, we focus on electrophysiological and molecular evidence that the Wnt signaling pathway regulates glutamatergic synaptic transmission, specifically N-methyl-d-aspartate receptors (NMDARs), to control the birth of new synapses. We also focus on the role of Wnts in the conversion of silent synapses into functional synapses.
- ItemMethionine sulfoxide reductase A expression is regulated by the DAF-16/FOXO pathway in Caenorhabditis elegans(WILEY, 2009) Minniti, Alicia N.; Cataldo, Romina; Trigo, Carla; Vasquez, Luis; Mujica, Patricio; Leighton, Federico; Inestrosa, Nibaldo C.; Aldunate, RebecaP>The methionine sulfoxide reductase system has been implicated in aging and protection against oxidative stress. This conserved system reverses the oxidation of methionine residues within proteins. We analyzed one of the components of this system, the methionine sulfoxide reductase A gene, in Caenorhabditis elegans. We found that the msra-1 gene is expressed in most tissues, particularly in the intestine and the nervous system. Worms carrying a deletion of the msra-1 gene are more sensitive to oxidative stress, show chemotaxis and locomotory defects, and a 30% decrease in median survival. We established that msra-1 expression decreases during aging and is regulated by the DAF-16/FOXO3a transcription factor. The absence of this enzyme decreases median survival and affects oxidative stress resistance of long lived daf-2 worms. A similar effect of MSRA-1 absence in wild-type and daf-2 (where most antioxidant enzymes are activated) backgrounds, suggests that the lack of this member of the methionine repair system cannot be compensated by the general antioxidant response. Moreover, FOXO3a directly activates the human MsrA promoter in a cell culture system, implying that this could be a conserved mechanism of MsrA regulation. Our results suggest that repair of oxidative damage in proteins influences the rate at which tissues age. This repair mechanism, rather than the general decreased of radical oxygen species levels, could be one of the main determinants of organisms' lifespan.
- ItemPeroxisome proliferator-activated receptor gamma up-regulates the Bcl-2 anti-apoptotic protein in neurons and induces mitochondrial stabilization and protection against oxidative stress and apoptosis(AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC, 2007) Fuenzalida, Karen; Quintanilla, Rodrigo; Ramos, Patricio; Piderit, Daniela; Fuentealba, Rodrigo A.; Martinez, Gabriela; Inestrosa, Nibaldo C.; Bronfman, MiguelPeroxisome proliferator-activated receptor gamma(PPAR gamma) has been proposed as a therapeutic target for neurodegenerative diseases because of its anti-inflammatory action in glial cells. However, PPAR gamma agonists prevent beta-amyloid (A beta)-induced neurodegeneration in hippocampal neurons, and PPAR gamma is activated by the nerve growth factor (NGF) survival pathway, suggesting a neuroprotective anti-inflammatory independent action. Here we show that the PPAR gamma agonist rosiglitazone (RGZ) protects hippocampal and dorsal root ganglion neurons against A beta-induced mitochondrial damage and NGF deprivation-induced apoptosis, respectively, and promotes PC12 cell survival. In neurons and in PC12 cells RGZ protective effects are associated with increased expression of the Bcl-2 anti-apoptotic protein. NGF-differentiated PC12 neuronal cells constitutively overexpressing PPAR gamma are resistant to A beta-induced apoptosis and morphological changes and show functionally intact mitochondria and no increase in reactive oxygen species when challenged with up to 50 mu M H2O2. Conversely, cells expressing a dominant negative mutant of PPAR gamma show increased A beta-induced apoptosis and disruption of neuronal-like morphology and are highly sensitive to oxidative stress-induced impairment of mitochondrial function. Cells overexpressing PPAR gamma present a 4-to 5-fold increase in Bcl-2 protein content, whereas in dominant negative PPAR gamma-expressing cells, Bcl-2 is barely detected. Bcl-2 knockdown by small interfering RNA in cells overexpressing PPAR gamma results in increased sensitivity to A beta and oxidative stress, further suggesting that Bcl-2 up-regulation mediates PPAR gamma protective effects. PPAR gamma prosurvival action is independent of the signal-regulated MAPK or the Akt prosurvival pathways. Altogether, these data suggest that PPAR gamma supports survival in neurons in part through a mechanism involving increased expression of Bcl-2.
- ItemSTI571 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.
- ItemSynaptic 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.
- ItemWingless-type family member 5A (Wnt-5a) stimulates synaptic differentiation and function of glutamatergic synapses(NATL ACAD SCIENCES, 2010) Varela Nallar, Lorena; Alfaro, Ivan E.; Serrano, Felipe G.; Parodi, Jorge; Inestrosa, Nibaldo C.Growing evidence indicates that Wingless-type (Wnt) signaling plays an important role in the maturation of the central nervous system. We report here that Wingless-type family member 5A (Wnt-5a) is expressed early in development and stimulates dendrite spine morphogenesis, inducing de novo formation of spines and increasing the size of the preexisting ones in hippocampal neurons. Wnt-5a increased intracellular calcium concentration in dendritic processes and the amplitude of NMDA spontaneous miniature currents. Acute application of Wnt-5a increased the amplitude of field excitatory postsynaptic potentials (fEPSP) in hippocampal slices, an effect that was prevented by calcium-channel blockers. The physiological relevance of our findings is supported by studies showing that Wnt scavengers decreased spine density, miniature excitatory postsynaptic currents, and fEPSP amplitude. We conclude that Wnt-5a stimulates different aspects of synaptic differentiation and plasticity in the mammalian central nervous system.
- ItemWnt-induced activation of glucose metabolism mediates the in vivo neuroprotective roles of Wnt signaling in Alzheimer disease(WILEY, 2019) Cisternas, Pedro; Zolezzi, Juan M.; Martinez, Milka; Torres, Viviana I.; Wong, Guang William; Inestrosa, Nibaldo C.Dysregulated Wnt signaling is linked to major neurodegenerative diseases, including Alzheimer disease (AD). In mouse models of AD, activation of the canonical Wnt signaling pathway improves learning/memory, but the mechanism for this remains unclear. The decline in brain function in AD patients correlates with reduced glucose utilization by neurons. Here, we test whether improvements in glucose metabolism mediate the neuroprotective effects of Wnt in AD mouse model. APPswe/PS1dE9 transgenic mice were used to model AD, Andrographolide or Lithium was used to activate Wnt signaling, and cytochalasin B was used to block glucose uptake. Cognitive function was assessed by novel object recognition and memory flexibility tests. Glucose uptake and the glycolytic rate were determined using radiotracer glucose. The activities of key enzymes of glycolysis such as hexokinase and phosphofructokinase, Adenosine triphosphate (ATP)/Adenosine diphosphate (ADP) levels and the pentose phosphate pathway and activity of glucose-6 phosphate dehydrogenase were measured. Wnt activators significantly improved brain glucose utilization and cognitive performance in transgenic mice. Wnt signaling enhanced glucose metabolism by increasing the expression and/or activity of hexokinase, phosphofructokinase and AMP-activated protein kinase. Inhibiting glucose uptake partially abolished the beneficial effects of Wnt signaling on learning/memory. Wnt activation also enhanced glucose metabolism in cortical and hippocampal neurons, as well as brain slices derived from APPswe/PS1E9 transgenic mice. Combined, these data provide evidence that the neuroprotective effects of Wnt signaling in AD mouse models result, at least in part, from Wnt-mediated improvements in neuronal glucose metabolism.