Center for Molecular Studies of the Cell

Independencia, Chile

Center for Molecular Studies of the Cell

Independencia, Chile
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Gonzalez S.,University of Chile | Gonzalez S.,San Sebastián University | Gonzalez S.,Major University | Aguilera S.,INDISA Clinic | And 7 more authors.
Autoimmunity Reviews | Year: 2011

Differentiation of epithelial cells is required to define tissue architecture and appropriate function of these cells is associated with a specific pattern of gene expression. DNA methylation, post-translational modification of histones and chromatin remodeling are nuclear mechanisms implicated in epigenetic control of gene expression. All factors relevant to tissue differentiation, including cell adhesion and shape, extracellular stimuli and transcriptional control, modulate gene expression and, thus, some of them are likely to impact on nuclear mechanisms of epigenetic control. The epithelial cells of salivary glands from Sjögren's syndrome patients display alterations in cell adhesion and shape. In this review, we summarize how these alterations are thought to lead to chromatin remodeling and, in doing so, bring about changes in transcriptional patterns. Additionally, we discuss how mechanotransduction in cells with impaired structural organization is implicated in modifying gene expression in these patients. © 2010 Elsevier B.V.

Barrera M.-J.,University of Chile | Sanchez M.,University of Chile | Aguilera S.,INDISA Clinic | Alliende C.,University of Chile | And 13 more authors.
Journal of Autoimmunity | Year: 2012

Sjögren's syndrome (SS) is a chronic inflammatory autoimmune disease that mainly affects tear and salivary glands, whereby SS-patients frequently complain of eye and mouth dryness. Salivary acinar cells of SS-patients display alterations in their cell polarity; which may affect the correct localization and function of proteins involved in regulated exocytosis. Here we determined whether the expression and localization of SNARE proteins (membrane fusion receptors) involved in regulated secretion, such as VAMP8, syntaxin 3 (STX3), STX4 and SNAP-23 were altered in salivary glands (SG) from SS-patients. Additionally, we investigated SNARE proteins function, by evaluating their ability to form SNARE complexes under basal conditions. In SG from SS-patients and control subjects mRNA and proteins levels of SNARE complex components were determined by real-time PCR and Western blotting, respectively. SNARE protein distribution and mucin exocytosis were determined by indirect immunofluorescence. In SS-patients, the expression levels of mRNA and protein for VAMP8, STX4 and STX3 were altered. STX4, STX3, SNAP-23 and VAMP8 relocated from the apical to the basal region of acinar cells. Increased formation of SNARE complexes in a manner independent of external stimuli for secretion was detected. Mucins were detected in the extracellular matrix (ECM). Presence of mucins in the ECM, together with the observed alterations in SNARE protein localization is indicative of ectopic exocytosis. In the context of SS, such aberrantly localized mucins are likely to favor a pro-inflammatory response, which may represent an important initial step in the pathogenesis of this disease. © 2012 Elsevier Ltd.

Espinosa A.,University of Chile | Espinosa A.,Center for Molecular Studies of the Cell | Campos C.,University of Chile | Diaz-Vegas A.,University of Chile | And 11 more authors.
International Journal of Molecular Sciences | Year: 2013

Insulin resistance is defined as a reduced ability of insulin to stimulate glucose utilization. C57BL/6 mice fed with a high-fat diet (HFD) are a model of insulin resistance. In skeletal muscle, hydrogen peroxide (H2O2) produced by NADPH oxidase 2 (NOX2) is involved in signaling pathways triggered by insulin. We evaluated oxidative status in skeletal muscle fibers from insulin-resistant and control mice by determining H2O2 generation (HyPer probe), reduced-to-oxidized glutathione ratio and NOX2 expression. After eight weeks of HFD, insulin-dependent glucose uptake was impaired in skeletal muscle fibers when compared with control muscle fibers. Insulin-resistant mice showed increased insulin-stimulated H2O2 release and decreased reduced-to-oxidized glutathione ratio (GSH/GSSG). In addition, p47phox and gp91phox (NOX2 subunits) mRNA levels were also high (~3-fold in HFD mice compared to controls), while protein levels were 6.8- and 1.6-fold higher, respectively. Using apocynin (NOX2 inhibitor) during the HFD feeding period, the oxidative intracellular environment was diminished and skeletal muscle insulin-dependent glucose uptake restored. Our results indicate that insulin-resistant mice have increased H2O2 release upon insulin stimulation when compared with control animals, which appears to be mediated by an increase in NOX2 expression. © 2013 by the authors; licensee MDPI, Basel, Switzerland.

Amador C.A.,Center for Molecular Studies of the Cell | Amador C.A.,Millennium Institute on Immunology and Immunotherapy | Barrientos V.,Center for Molecular Studies of the Cell | Barrientos V.,Millennium Institute on Immunology and Immunotherapy | And 15 more authors.
Hypertension | Year: 2014

Adaptive immune response has been implicated in inflammation and fibrosis as a result of exposure to mineralocorticoids and a high-salt diet. We hypothesized that in mineralocorticoid-salt-induced hypertension, activation of the mineralocorticoid receptor alters the T-helper 17 lymphocyte (Th17)/regulatory T-lymphocyte/interleukin-17 (IL-17) pathway, contributing to cardiac and renal damage. We studied the inflammatory response and tissue damage in rats treated with deoxycorticosterone acetate and high-salt diet (DOCA-salt), with or without mineralocorticoid receptor inhibition by spironolactone. To determine whether Th17 differentiation in DOCA-salt rats is caused by hypertension per se, DOCA-salt rats received antihypertensive therapy. In addition, to evaluate the pathogenic role of IL-17 in hypertension and tissue damage, we studied the effect of IL-17 blockade with a specific antibody (anti-IL-17). We found activation of Th17 cells and downregulation of forkhead box P3 mRNA in peripheral tissues, heart, and kidneys of DOCA-salt-treated rats. Spironolactone treatment prevented Th17 cell activation and increased numbers of forkhead box P3-positive cells relative to DOCA-salt rats. Antihypertensive therapy did not ameliorate Th17 activation in rats. Treatment of DOCA-salt rats with anti-IL-17 significantly reduced arterial hypertension as well as expression of profibrotic and proinflammatory mediators and collagen deposits in the heart and kidney. We conclude that mineralocorticoid receptor activation alters the Th17/regulatory T-lymphocyte/IL-17 pathway in mineralocorticoid- dependent hypertension as part of an inflammatory mechanism contributing to fibrosis. © 2014 American Heart Association, Inc.

Castro I.,University of Chile | Aguilera S.,INDISA Clinic | Brockhausen I.,Queen's University | Alliende C.,University of Chile | And 13 more authors.
Rheumatology | Year: 2012

Objectives: To determine the expression and enzymatic activities of sulphotransferases involved in mucin hyposulphation in labial salivary glands (LSGs) from SS patients and to correlate sulphotransferase activity with clinical parameters such as secretion, inflammation and serology. Methods: LSG from 31 SS patients and 31 control subjects were studied. Relative mRNA and protein levels of Gal3-O-sulphotransferases (Gal3STs) and β1,3-galactosyltransferase-5 (β3GalT5) were determined by quantitative RT-PCR and western blotting, respectively. Enzymatic activities were quantified using radioactively labelled donor substrates and specific acceptor substrates. Products were purified by chromatography. Spearman's correlation analysis was used to compare data. Results: The levels of Gal3ST activity were significantly decreased in SS patients, without changes in mRNA and protein levels, while the enzymatic activities of glycosyltransferases involved in mucin glycosylation were similar in both groups. An inverse correlation was observed between Gal3ST activity and glandular function measured by scintigraphy, but not with unstimulated salivary flow. Gal3ST activity was inversely correlated with focus score, TNF-α levels and presence of the autoantibodies Ro/SS-A and La/SS-B. Conclusion: The decrease in sulphotransferase activity provides an explanation for mucin hyposulphation observed in the LSGs from SS patients. The decrease in Gal3STs activity was not a consequence of reduced gene expression, but probably due to alterations in the enzyme activity regulation. Interestingly, the levels of sulphotransferase activity detected correlated well with secretory function, inflammation and serology. Finally, we postulate that pro-inflammatory cytokines induced by autoantibodies, such as Ro/SS-A and La/SS-B in SS patients, may modulate Gal3ST activity, thereby altering mucin quality and leading to mouth dryness. © The Author 2011. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved.

Contreras-Ferrat A.,Center for Molecular Studies of the Cell | Contreras-Ferrat A.,Advanced Center for Chronic Disease iS | Contreras-Ferrat A.,University of Chile | Lavandero S.,Center for Molecular Studies of the Cell | And 3 more authors.
Cell Calcium | Year: 2014

Striated muscles (skeletal and cardiac) are major physiological targets of insulin and this hormone triggers complex signaling pathways regulating cell growth and energy metabolism. Insulin increases glucose uptake into muscle cells by stimulating glucose transporter (GLUT4) translocation from intracellular compartments to the cell surface. The canonical insulin-triggered signaling cascade controlling this process is constituted by well-mapped tyrosine, lipid and serine/threonine phosphorylation reactions. In parallel to these signals, recent findings reveal insulin-dependent Ca2+ mobilization in skeletal muscle cells and cardiomyocytes. Specifically, insulin activates the sarco-endoplasmic reticulum (SER) channels that release Ca2+ into the cytosol i.e., the Ryanodine Receptor (RyR) and the inositol 1,4,5-triphosphate receptor (IP3R). In skeletal muscle cells, a rapid, insulin-triggered Ca2+ release occurs through RyR, that is brought about upon S-glutathionylation of cysteine residues in the channel by reactive oxygen species (ROS) produced by the early activation of the NADPH oxidase (NOX2). In cardiomyocytes insulin induces a fast and transient increase in cytoplasmic [Ca2+]i trough L-type Ca2+ channels activation. In both cell types, a relatively slower Ca2+ release also occurs through IP3R activation, and is required for GLUT4 translocation and glucose uptake. The insulin-dependent Ca2+ released from IP3R of skeletal muscle also promotes mitochondrial Ca2+ uptake. We review here these actions of insulin on intracellular Ca2+ channel activation and their impact on GLUT4 traffic in muscle cells, as well as other implications of insulin-dependent Ca2+ release from the SER. © 2014 Elsevier Ltd.

Valenzuela M.,Center for Molecular Studies of the Cell | Valenzuela M.,Institute Ciencias Biomedicas | Valenzuela M.,Catholic University of Louvain | Bravo D.,Center for Molecular Studies of the Cell | And 7 more authors.
Journal of Infectious Diseases | Year: 2013

Helicobacter pylori is the etiologic agent of a series of gastric pathologies that may culminate in the development of gastric adenocarcinoma. An initial step in this process is the loss of glandular structures in the gastric mucosa, presumably as the consequence of increased apoptosis and reduced cellular regeneration, which may be attributed to the combination of several bacterial and host factors and to an unfavorable proinflammatory environment. In a previous study, we showed that survivin, a member of the inhibitor of apoptosis protein family, is expressed in the normal human gastric mucosa and that its levels decrease in the mucosa of infected patients and in gastric cells exposed in culture to the bacteria, coincident with increased cell death in the latter case. We investigated the bacterial factors responsible for loss of survivin in gastric cells exposed to H. pylori. The results of this study indicated that the loss of survivin due to H. pylori infection involves proteasome-mediated degradation of the protein. Studies with isogenic mutants deficient in either CagA, VacA, lipopolysaccharide, or gamma-glutamyl transpeptidase (GGT) implicated the latter in H. pylori-induced loss of survivin and cell viability. Moreover, experiments with the GGT inhibitor 6-diazo-5-oxo-l-norleucine and purified recombinant GGT protein indicated that secreted bacterial GGT activity was required and sufficient to induce these effects. © 2013 The Author 2013.

Sanmartin C.D.,Center for Molecular Studies of the Cell | Adasme T.,Center for Molecular Studies of the Cell | Hidalgo C.,Center for Molecular Studies of the Cell | Hidalgo C.,Biomedical Neuroscience Institute and Physiology and Biophysics Program | And 3 more authors.
Neurodegenerative Diseases | Year: 2012

Background: Soluble amyloid-β peptide oligomers (AβOs), which are centrally involved in the pathogenesis of Alzheimer's disease, trigger Ca 2+ influx through N-methyl-D-aspartate receptors and stimulate reactive oxygen species generation in primary hippocampal neurons. We have previously reported that AβOs promote Ca 2+ release mediated by ryanodine receptors (RyR), which in turn triggers mitochondrial fragmentation. We have also reported that the antioxidant N-acetylcysteine (NAC) prevents AβOs-induced Ca 2+ signal generation. Objectives: To determine if RyR-mediated Ca 2+ release activated by the specific agonist 4-chloro-m-cresol (4-CMC) induces fragmentation of the mitochondrial network, and to ascertain if NAC prevents the mitochondrial fragmentation induced by AβOs and/or 4-CMC. Methods: Mature primary rat hippocampal neurons were incubated for 24 h with sublethal concentrations of AβOs (500 nM) or for 1-3 h with 4-CMC (0.5-1 mM), ±10 mM NAC. Mitochondrial morphology was assessed by confocal microscopy of fixed neurons stained with anti-mHsp70. Intracellular Ca 2+ levels were determined by time series microscopy of neurons preloaded with Fluo-4 AM. Results: Preincubation of neurons for 30 min with NAC prevented the mitochondrial fragmentation induced by AβOs or 4-CMC. In addition, we confirmed that preincubation with NAC abolished the stimulation of RyR-mediated Ca 2+ release induced by AβOs or 4-CMC. Conclusion: The present results strongly suggest that the general antioxidant NAC prevents AβO-induced mitochondrial fragmentation by preventing RyR-mediated Ca 2+-induced Ca 2+ release. Copyright © 2012 S. Karger AG, Basel.

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