Increased Na+ /Ca2+ exchanger expression/activity constitutes a point of inflection in the progression to heart failure of hypertensive rats

Spontaneously hypertensive rat (SHR) constitutes a genetic model widely used to study the natural evolution of hypertensive heart disease. Ca2+ -handling alterations are known to occur in SHR. However, the putative modifications of Ca2+ -handling proteins during the progression to heart failure (HF) are not well established. Moreover, the role of apoptosis in SHR is controversial. We investigated intracellular Ca2+ , Ca2+ -handling proteins and apoptosis in SHR vs. control Wistar rats (W) from 3 to 15 months (mo). Changes associated with the transition to HF (i.e. lung edema and decrease in midwall fractional shortening), occurred at 15 mo in 38% of SHR (SHRF). In SHRF, twitch and caffeine-induced Ca2+ transients, significantly decreased relative to 6/9 mo and 15 mo without HF signs. This decrease occurred in association with a decrease in the time constant of caffeine-Ca2+ transient decay and an increase in Na+ /Ca2+ exchanger (NCX) abundance (p, 0.05) with no changes in SERCA2a expression/activity. An increased Ca2+ -calmodulin-kinase II activity, associated with an enhancement of apoptosis (TUNEL and Bax/Bcl2) was observed in SHR relative to W from 3 to 15 mo. Conclusions: 1. Apoptosis is an early and persistent event that may contribute to hypertrophic remodeling but would not participate in the contractile impairment of SHRF. 2. The increase in NCX expression/activity, associated with an increase in Ca2+ efflux from the cell, constitutes a primary alteration of Ca2+ -handling proteins in the evolution to HF. 3. No changes in SERCA2a expression/activity are observed when HF signs become evident.Fil: Rodriguez, Jesica S.. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; ArgentinaFil: Velez Rueda, Jorge Omar. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; ArgentinaFil: Salas, Margarita. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; ArgentinaFil: Becerra, Romina Valeria. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "dr. Horacio Eugenio Cingolani"; ArgentinaFil: Di Carlo, Mariano Nahuel. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; ArgentinaFil: Said, Maria Matilde. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; ArgentinaFil: Vittone, Leticia Beatriz. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; ArgentinaFil: Rinaldi, Gustavo Juan. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; ArgentinaFil: Portiansky, Enrique Leo. Universidad Nacional de la Plata. Facultad de Ciencias Veterinarias; ArgentinaFil: Mundiña, Cecilia Beatriz. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; ArgentinaFil: Palomeque, Julieta. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; ArgentinaFil: Mattiazzi, Ramona Alicia. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; Argentin

β₂-Adrenergic stimulation is involved in the contractile dysfunction of the stunned heart

Endogenous catecholamines released during myocardial ischemia have been considered both to aggravate cell injury and exacerbate arrhythmias and to exert a protective action on the post-ischemic contractile function. The present work was addressed to look for evidence to explain this controversy. The effects of cardiac catecholamine depletion and of α- and β-adrenoceptor (AR) blockade on the post-ischemic contractile dysfunction, as well as its possible relationship with cardiac oxidative stress, were studied in isolated and perfused rat hearts submitted to 20 min of ischemia and 30 min of reperfusion (stunning). Catecholamine depletion improves the contractile recovery in the stunned heart. This mechanical effect was associated with decreased levels of lipid peroxidation. A similar enhancement of the contractile function during reperfusion was detected after the simultaneous blockade of α₁- and β-ARs with prazosin plus propranolol. To ascertain which specific AR pathway was involved in the effects of catecholamines on the stunned heart, selective AR blockers, prazosin (α₁-blocker), atenolol (β₁-blocker), ICI 118,551 (β₂-blocker) and selective inhibitors of Gi-PI3K pathway (pertussis toxin and wortmannin) were alternatively combined. The results indicate that catecholamines released during ischemia exert a dual action on the contractile behavior of the stunned heart: a deleterious effect, related to the activation of the β₂-AR-Gi-PI3K-pathway, which was counteracted by a beneficial effect, triggered by the stimulation of α₁-AR. Neither the depression nor the enhancement of the post-ischemic contractile recovery were related with the increase in ROS formation induced by endogenous catecholamines.Facultad de Ciencias MédicasCentro de Investigaciones Cardiovasculare

Mechanisms involved in the acidosis enhancement of the isoproterenol-induced phosphorylation of phospholamban in the intact heart

Previous experiments have shown that acidosis enhances isoproterenol-induced phospholamban (PHL) phosphorylation (Mundina-Weilenmann, C., Vittone, L., Cingolani, H. E., Orchard, C. H. (1996) Am. J. Physiol. 270, C107-C114). In the present experiments, performed in isolated Langendorff perfused rat hearts, phosphorylation site-specific antibodies to PHL combined with the quantitative measurement of 32P incorporation into PHL were used as experimental tools to gain further insight into the mechanism involved in this effect. At all isoproterenol concentrations tested (3-300 nM), phosphorylation of Thr17 of PHL was significantly higher at pHo 6.80 than at pHo 7.40, without significant changes in Ser16 phosphorylation. This increase in Thr17 phosphorylation was associated with an enhancement of the isoproterenol-induced relaxant effect. In the absence of isoproterenol, the increase in [Ca]o at pHo 6.80 (but not at pHo 7.40) evoked an increase in PHL phosphorylation that was exclusively due to an increase in Thr17 phosphorylation and that was also associated with a significant relaxant effect. This effect and the phosphorylation of Thr17 evoked by acidosis were both offset by the Ca2+/calmodulin-dependent protein kinase II inhibitor KN-62. In the presence of isoproterenol, either the increase in [Ca]o or the addition of a 1 microM concentration of the phosphatase inhibitor okadaic acid was able to mimic the increase in isoproterenol-induced Thr17 phosphorylation produced by acidosis. In contrast, these two interventions have opposite effects on phosphorylation of Ser16. Whereas the increase in [Ca]o significantly decreased phosphorylation of Ser16, the addition of okadaic acid significantly increased the phosphorylation of this residue. The results are consistent with the hypothesis that the increase in phospholamban phosphorylation produced by acidosis in the presence of isoproterenol is the consequence of two different mechanisms triggered by acidosis: an increase in [Ca2+]i and an inhibition of phosphatases.Centro de Investigaciones Cardiovasculare

CaMKII: cardiac physiological functions

Calcium-calmodulin-dependent protein kinase (CaMKII) is a Ser/Thr kinase whose activity is triggered by calcium (Ca2+), in response to various distinct signaling pathways in different organs, including the pancreas, liver, brain, and heart. CaMKII was discovered in the late sixties. Interestingly, the initial mentions of this kinase were nearly simultaneous in both the brain and the heart, despite it is more abundant in the brain, where it plays a crucial role in memory and learning processes. CaMKII is unique in that it is very widely distributed and can phosphorylate a broad range of proteins. These properties promptly suggested that CaMKII regulates many physiological responses to agonists that elevate intracellular Ca2+, leading to its designation as the "multifunctional Ca/CaM-dependent protein kinase" or "CaM-dependent multiprotein kinase". Encoded by four different genes (α, β, γ, and δ), CaMKIIδ is the predominant isoform in the heart, with two splice variants in the adult myocardium: δB, mainly localized in the nucleus, and δC, primarily found in the cytosol. Given its role in phosphorylating proteins related to Ca2+ handling and excitation-contraction coupling (ECC), CaMKII is believed to play an important role in physiological processes. However, unlike its well-established role in memory and learning, the physiological significance of CaMKII on cardiac function is less acknowledged. Indeed, its better-known associations lie in non-physiological actions within the heart, particularly in various cardiac pathologies such as heart failure (HF), myocardial infarction, and cardiomyopathies, leading to contractile dysfunction and malignant arrhythmias. This mini review aims to provide a concise summary of CaMKII's role on cardiac physiology.Sociedad Argentina de FisiologíaCentro de Investigaciones Cardiovasculare

Diseño de una propuesta de tutoría para alumnos recursantes de una asignatura de la carrera de Medicina de la Universidad Nacional de La Plata (UNLP)

Los temas del ingreso y el rendimiento de los alumnos durante los primeros años de la Facultad se tratan de forma recurrente en todas las unidades académicas de la UNLP, respetando y analizando las características particulares de cada una de ellas. En este marco consideramos que sería muy importante analizar también, la problemática de los alumnos que recursan y ver de qué manera podemos ayudarlos para que logren el objetivo de mejorar su aprendizaje durante la carrera y así finalizar la misma. Con el fin de detectar los alumnos recursantes de la Cátedra de Fisiología y Física Biológica de la cursada 2012 en la Facultad de Ciencias Médicas de la UNLP, se realizó una encuesta que nos permitió además evaluar las inquietudes particulares de cada uno de ellos.Facultad de Ciencias Médica

Pharmacological inhibition of translocon is sufficient to alleviate endoplasmic reticulum stress and improve Ca2+ handling and contractile recovery of stunned myocardium

Introduction: The function of endoplasmic reticulum (ER), a Ca2+ storage compartment and site of protein folding, is altered by disruption of intracellular homeostasis. Misfolded proteins accumulated in the ER lead to ER stress (ERS), unfolded protein response (UPR) activation and ER Ca2+ loss. Myocardial stunning is a temporary contractile dysfunction, which occurs after brief ischemic periods with minimal or no cell death, being oxidative stress and Ca2+ overload potential underlying mechanisms. Myocardial stunning induces ERS response with negatively impact on the post-ischemic mechanical performance through an unknown mechanism. Aims: In this study, we explored whether ER Ca2+ efflux through the translocon, a major Ca2+ leak channel, contributes to Ca2+ mishandling and the consequent contractile abnormalities of the stunned myocardium. Methods: Mechanical performance, cytosolic Ca2+, UPR markers and oxidative state were evaluated in perfused rat/mouse hearts subjected to a brief ischemia followed by reperfusion (I/R) in absence or presence of the translocon inhibitor, emetine (1 μM), comparing its effects with those of the chaperones TUDCA (30 μM) and 4-PBA (3 mM). Results: Emetine treatment precluded the I/R-induced increase in UPR signaling markers and improved the contractile recovery together with a remarkable attenuation in myocardial stiffness when compared to I/R hearts with no drug. This alleviation of I/R-induced mechanical abnormalities was more effective than that obtained with the chemical chaperones, TUDCA and 4-PBA. Moreover, emetine treatment produced a striking improvement in diastolic Ca2+ handling with a partial recovery of the I/R-induced oxidative stress. Conclusion: Blocking ER Ca2+ store depletion via translocon suppressed ER stress and improved mechanical performance and diastolic Ca2+ handling of stunned myocardium. Modulation of translocon permeability emerges as a therapeutic approach to face dysfunctional consequences of the I/R injury.Fil: Mariángelo, Juan Ignacio Elio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani". Universidad Nacional de La Plata. Facultad de Ciencias Médicas. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani"; ArgentinaFil: Valverde, Carlos Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani". Universidad Nacional de La Plata. Facultad de Ciencias Médicas. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani"; ArgentinaFil: Vittone, Leticia Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani". Universidad Nacional de La Plata. Facultad de Ciencias Médicas. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani"; ArgentinaFil: Said, Maria Matilde. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani". Universidad Nacional de La Plata. Facultad de Ciencias Médicas. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani"; ArgentinaFil: Mundiña, Cecilia Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani". Universidad Nacional de La Plata. Facultad de Ciencias Médicas. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani"; Argentin

Diseño de una propuesta de tutoría para alumnos recursantes de una asignatura de la carrera de Medicina de la Universidad Nacional de La Plata (UNLP)

Los temas del ingreso y el rendimiento de los alumnos durante los primeros años de la Facultad se tratan de forma recurrente en todas las unidades académicas de la UNLP, respetando y analizando las características particulares de cada una de ellas. En este marco consideramos que sería muy importante analizar también, la problemática de los alumnos que recursan y ver de qué manera podemos ayudarlos para que logren el objetivo de mejorar su aprendizaje durante la carrera y así finalizar la misma. Con el fin de detectar los alumnos recursantes de la Cátedra de Fisiología y Física Biológica de la cursada 2012 en la Facultad de Ciencias Médicas de la UNLP, se realizó una encuesta que nos permitió además evaluar las inquietudes particulares de cada uno de ellos.Facultad de Ciencias Médica

Role of phosphorylation of Thr17 residue of phospholamban in mechanical recovery during hypercapnic acidosis

Objectives: To assess the time course of phosphorylation of phospholamban residues, the underlying mechanisms determining these phosphorylations, and their functional impact on the mechanical recovery during acidosis. Methods: Langendorff perfused rat hearts were submitted to 30 min of hypercapnic acidosis. Contractility, relaxation, and phosphorylation of phospholamban residues, immunodetected by specific antibodies, were determined. Results: Acidosis produced a mechanical impairment followed by a spontaneous recovery, most of which occurred within the first 3 min of acidosis (early recovery). During this period, contractility and relaxation recovered by 67±9% and 77±11%, respectively, from its maximal depression, together with an increase in the Ca2+-calmodulin-dependent protein kinase II (CaMKII)-dependent phosphorylation of Thr17. The CaMKII inhibitor KN-93, at 1, 5 and 10 μM, decreased Thr17 phosphorylation to basal levels and produced a similar impairment of the early relaxation recovery (50%). However, only 5 and 10 μM KN-93 inhibited the early contractile recovery and completely blunted the late mechanical recovery. Inhibition of the reverse mode of the Na+/Ca2+ exchanger by KB-R7943 decreased Thr17 phosphorylation but accelerated the early contractile recovery. Conclusions: CaMKII-dependent Thr17 phosphorylation significantly increased at the beginning of acidosis, is responsible for 50% of the early relaxation recovery, and is linked to the activation of the reverse Na+/Ca2+ mode. The early contractile recovery and the late mechanical recovery are dependent on CaMKII but independent of the phosphorylation of the Thr17 residue of phospholamban. The reverse Na+/Ca2+ mode has an additional negative effect that opposes the early mechanical recovery.Facultad de Ciencias MédicasCentro de Investigaciones Cardiovasculare

Role of phosphorylation of Thr17 residue of phospholamban in mechanical recovery during hypercapnic acidosis

Objectives: To assess the time course of phosphorylation of phospholamban residues, the underlying mechanisms determining these phosphorylations, and their functional impact on the mechanical recovery during acidosis. Methods: Langendorff perfused rat hearts were submitted to 30 min of hypercapnic acidosis. Contractility, relaxation, and phosphorylation of phospholamban residues, immunodetected by specific antibodies, were determined. Results: Acidosis produced a mechanical impairment followed by a spontaneous recovery, most of which occurred within the first 3 min of acidosis (early recovery). During this period, contractility and relaxation recovered by 67±9% and 77±11%, respectively, from its maximal depression, together with an increase in the Ca2+-calmodulin-dependent protein kinase II (CaMKII)-dependent phosphorylation of Thr17. The CaMKII inhibitor KN-93, at 1, 5 and 10 μM, decreased Thr17 phosphorylation to basal levels and produced a similar impairment of the early relaxation recovery (50%). However, only 5 and 10 μM KN-93 inhibited the early contractile recovery and completely blunted the late mechanical recovery. Inhibition of the reverse mode of the Na+/Ca2+ exchanger by KB-R7943 decreased Thr17 phosphorylation but accelerated the early contractile recovery. Conclusions: CaMKII-dependent Thr17 phosphorylation significantly increased at the beginning of acidosis, is responsible for 50% of the early relaxation recovery, and is linked to the activation of the reverse Na+/Ca2+ mode. The early contractile recovery and the late mechanical recovery are dependent on CaMKII but independent of the phosphorylation of the Thr17 residue of phospholamban. The reverse Na+/Ca2+ mode has an additional negative effect that opposes the early mechanical recovery.Facultad de Ciencias MédicasCentro de Investigaciones Cardiovasculare

La utilidad del trabajo en equipo para generar soluciones que mejoren el aprendizaje de los alumnos

En la Cátedra de Fisiología y Física Biológica de la Facultad de Medicina de la UNLP se creó recientemente un programa de tutoría para los alumnos repitentes; en el mismo detectamos que muchos alumnos pertenecían al Profesorado de Ciencias Biológicas de la Facultad de Humanidades y Ciencias de la Educación (FaHCE), los cuales por muchos años han cursado la materia en la Cátedra citada. Dado que el enfoque de los contenidos de la materia, no siempre resulta significativo para el perfil profesional de éstos alumnos, a finales del año 2015 surgió por parte de docentes de ésta Cátedra y también de la Directora del Departamento de Ciencias Exactas y Naturales (FaHCE) la inquietud de crear un espacio /Cátedra propia considerando las necesidades específicas de los profesionales que se están formando. Objetivos: el objetivo del trabajo fue generar un espacio de pertenencia para los alumnos provenientes del Profesorado de Ciencias Biológicas de la FaHCE, que tenga en cuenta las necesidades específicas de estos alumnos.Facultad de Ciencias Médica