Myocardial reperfusion injury: Reactive oxygen species vs. NHE-1 reactivation

Background/Aims: Flow restoration to ischemic myocardium reduces infarct size (IS), but it also promotes reperfusion injury. A burst of reactive oxygen species (ROS) and/or NHE-1 reactivation were proposed to explain this injury. Our study was aimed to shed light on this unresolved issue. Methods: Regional infarction (40 min-ischemia/2 hs-reperfusion) was induced in isolated and perfused rat hearts. Maximal doses of N-(2-mercaptopropionyl)-glycine (MPG 2mmol/L, ROS scavenger), cariporide (10μmol/L, NHE-1 inhibitor), or sildenafil (1μmol/L, phosphodiesterase5A inhibitor) were applied at reperfusion onset. Their effects on IS, myocardial concentration of thiobarbituric acid reactive substances (TBARS), ERK1/2, p90RSK, and NHE-1 phosphorylation were analyzed. Results: All treatments decreased IS ∼ 50% vs. control. No further protection was obtained by combining cariporide or MPG with sildenafil. Myocardial TBARS increased after infarction and were decreased by MPG or cariporide, but unaffected by sildenafil. In line with the fact that ROS induce MAPK-mediated NHE-1 activation, myocardial infarction increased ERK1/2, p90RSK, and NHE-1 phosphorylation. MPG and cariporide cancelled these effects. Sildenafil did not reduce the phosphorylated ERK1/2-p90RSK levels but blunted NHE-1 phosphorylation suggesting a direct dephosphorylating action. Conclusions: 1) Reperfusion injury would result from ROS-triggered MAPK-mediated NHE-1 phosphorylation (and reactivation) during reperfusion; 2) sildenafil protects the myocardium by favouring NHE-1 dephosphorylation and bypassing ROS generation.Facultad de Ciencias MédicasCentro de Investigaciones Cardiovasculare

Myocardial reperfusion injury: Reactive oxygen species vs. NHE-1 reactivation

Background/Aims: Flow restoration to ischemic myocardium reduces infarct size (IS), but it also promotes reperfusion injury. A burst of reactive oxygen species (ROS) and/or NHE-1 reactivation were proposed to explain this injury. Our study was aimed to shed light on this unresolved issue. Methods: Regional infarction (40 min-ischemia/2 hs-reperfusion) was induced in isolated and perfused rat hearts. Maximal doses of N-(2-mercaptopropionyl)-glycine (MPG 2mmol/L, ROS scavenger), cariporide (10μmol/L, NHE-1 inhibitor), or sildenafil (1μmol/L, phosphodiesterase5A inhibitor) were applied at reperfusion onset. Their effects on IS, myocardial concentration of thiobarbituric acid reactive substances (TBARS), ERK1/2, p90RSK, and NHE-1 phosphorylation were analyzed. Results: All treatments decreased IS ∼ 50% vs. control. No further protection was obtained by combining cariporide or MPG with sildenafil. Myocardial TBARS increased after infarction and were decreased by MPG or cariporide, but unaffected by sildenafil. In line with the fact that ROS induce MAPK-mediated NHE-1 activation, myocardial infarction increased ERK1/2, p90RSK, and NHE-1 phosphorylation. MPG and cariporide cancelled these effects. Sildenafil did not reduce the phosphorylated ERK1/2-p90RSK levels but blunted NHE-1 phosphorylation suggesting a direct dephosphorylating action. Conclusions: 1) Reperfusion injury would result from ROS-triggered MAPK-mediated NHE-1 phosphorylation (and reactivation) during reperfusion; 2) sildenafil protects the myocardium by favouring NHE-1 dephosphorylation and bypassing ROS generation.Facultad de Ciencias MédicasCentro de Investigaciones Cardiovasculare

Mitochondrial reactive oxygen species activate the slow force response to stretch in feline myocardium

When the length of the myocardium is increased, a biphasic response to stretch occurs involving an initial rapid increase in force followed by a delayed slow increase called the slow force response (SFR). Confirming previous findings involving angiotensin II in the SFR, it was blunted by AT1 receptor blockade (losartan). The SFR was accompanied by an increase in reactive oxygen species (ROS) of ∼30% and in intracellular Na+ concentration ([Na⁺]i) of ∼2.5 mmol l⁻¹ over basal detected by H2DCFDA and SBFI fluorescence, respectively. Abolition of ROS by 2-mercapto-propionyl-glycine (MPG) and EUK8 suppressed the increase in [Na⁺]i and the SFR, which were also blunted by Na⁺/H⁺ exchanger (NHE-1) inhibition (HOE642). NADPH oxidase inhibition (apocynin or DPI) or blockade of the ATP-sensitive mitochondrial potassium channels (5HD or glybenclamide) suppressed both the SFR and the increase in [Na⁺]i after stretch, suggesting that endogenous angiotensin II activated NADPH oxidase leading to ROS release by the ATP-sensitive mitochondrial potassium channels, which promoted NHE-1 activation. Supporting the notion of ROS-mediated NHE-1 activation, stretch increased the ERK1/2 and p90rsk kinases phosphorylation, effect that was cancelled by losartan. In agreement, the SFR was cancelled by inhibiting the ERK1/2 signalling pathway with PD98059. Angiotensin II at a dose that mimics the SFR (1 nmol l⁻¹) induced an increase in ·O₂− production of ∼30–40% detected by lucigenin in cardiac slices, an effect that was blunted by losartan, MPG, apocynin, 5HD and glybenclamide. Taken together the data suggest a pivotal role of mitochondrial ROS in the genesis of the SFR to stretch.Centro de Investigaciones Cardiovasculare

Phosphodiesterase 5A inhibition induces Na+/H+ exchanger blockade and protection against myocardial infarction

Acute phosphodiesterase 5A inhibition by sildenafil or EMD360527/5 promoted profound inhibition of the cardiac Na+/H+ exchanger (NHE-1), detected by the almost null intracellular pH recovery from an acute acid load (ammonium prepulse) in isolated papillary muscles from Wistar rats. Inhibition of phosphoglycerate kinase-1 (KT5823) restored normal NHE-1 activity, suggesting a causal link between phosphoglycerate kinase-1 increase and NHE-1 inhibition. We then tested whether the beneficial effects of NHE-1 inhibitors against the deleterious postmyocardial infarction (MI) remodeling can be detected after sildenafil-mediated NHE-1 inhibition. MI was induced by left anterior descending coronary artery ligation in Wistar rats, which were randomized to placebo or sildenafil (100 mg kg-1 day-1) for 6 weeks. Sildenafil significantly increased left ventricular phosphoglycerate kinase-1 activity in the post-MI group without affecting its expression. MI increased heart weight/body weight ratio, left ventricular myocyte cross-sectional area, interstitial fibrosis, and brain natriuretic peptide and NHE-1 expression. Sildenafil blunted these effects. Neither a significant change in infarct size nor a change in arterial or left ventricular systolic pressure was detected after sildenafil. MI decreased fractional shortening and the ratio of the maximum rate of rise of LVP divided by the pressure at the moment such maximum occurs, effects that were prevented by sildenafil. Intracellular pH recovery after an acid load was faster in papillary muscles from post-MI hearts (versus sham), whereas sildenafil significantly inhibited NHE-1 activity in both post-MI and sildenafil-treated sham groups. We conclude that increased phosphoglycerate kinase-1 activity after acute phosphodiesterase 5A inhibition blunts NHE-1 activity and protects the heart against post-MI remodeling and dysfunction.Facultad de Ciencias MédicasCentro de Investigaciones Cardiovasculare

Efecto del sildenafil en el remodelamiento ventricular izquierdo post- infarto agudo de miocardio en ratas

El concepto de remodelamiento ventricular fue introducido en 1985 por Pfeffer y col adjudicándolo a los cambios estructurales y funcionales del ventrículo izquierdo como resultado de la ligadura de una arteria coronaria en ratas. El remodelamiento post-infarto fue definido en 1990 como los cambios en la morfología ventricular que ocurren tanto en el período agudo como en la etapa crónica después de un infarto de miocardio, identificándose a partir de ese momento como un objetivo principal a corregir para mejorar la sobrevida en esos casos. El concepto se ha extendido actualmente y se lo aplica a los cambios que se observan en el corazón en respuesta a sobrecargas de presión y/o de volumen secundarios a diferentes mecanismos de sobrecarga. El remodelamiento secundario al infarto agudo está determinado por una serie de eventos adversos que ocurren progresivamente como la presencia de una zona infartada no contráctil y con posibilidades de expansión, la sobrecarga de volumen determinada por esa expansión y la sobrecarga de presión secundaria al aumento de volumen. Muchos de los eventos que ocurren en el remodelamiento miocárdico están regulados por estímulos extracelulares como el estiramiento mecánico, factores neurohormonales o citoquinas. Estos estímulos pueden causar la activación de diferentes vías de señalización intracelular que median cambios en el fenotipo de miocitos y fibroblastos. Takimoto y col. han descripto recientemente que la inhibición de la fosfodiesterasa–5A (PDE-5A) con sildenafil mejora el remodelamiento del ventrículo izquierdo en corazones sometidos a sobrecarga de presión lo cual deja abierta la posibilidad de analizar si esos hallazgos pueden ser extensivos al remodelamiento posterior al infarto agudo de miocardio. En el presente estudio se analizó el efecto de la administración crónica de sildenafil sobre la estructura y función del ventrículo izquierdo en ratas normotensas con infarto agudo de miocardio.Eje: Salud públicaFacultad de Ciencias Médica

Phosphodiesterase 5A inhibition induces Na+/H+ exchanger blockade and protection against myocardial infarction

Acute phosphodiesterase 5A inhibition by sildenafil or EMD360527/5 promoted profound inhibition of the cardiac Na+/H+ exchanger (NHE-1), detected by the almost null intracellular pH recovery from an acute acid load (ammonium prepulse) in isolated papillary muscles from Wistar rats. Inhibition of phosphoglycerate kinase-1 (KT5823) restored normal NHE-1 activity, suggesting a causal link between phosphoglycerate kinase-1 increase and NHE-1 inhibition. We then tested whether the beneficial effects of NHE-1 inhibitors against the deleterious postmyocardial infarction (MI) remodeling can be detected after sildenafil-mediated NHE-1 inhibition. MI was induced by left anterior descending coronary artery ligation in Wistar rats, which were randomized to placebo or sildenafil (100 mg kg-1 day-1) for 6 weeks. Sildenafil significantly increased left ventricular phosphoglycerate kinase-1 activity in the post-MI group without affecting its expression. MI increased heart weight/body weight ratio, left ventricular myocyte cross-sectional area, interstitial fibrosis, and brain natriuretic peptide and NHE-1 expression. Sildenafil blunted these effects. Neither a significant change in infarct size nor a change in arterial or left ventricular systolic pressure was detected after sildenafil. MI decreased fractional shortening and the ratio of the maximum rate of rise of LVP divided by the pressure at the moment such maximum occurs, effects that were prevented by sildenafil. Intracellular pH recovery after an acid load was faster in papillary muscles from post-MI hearts (versus sham), whereas sildenafil significantly inhibited NHE-1 activity in both post-MI and sildenafil-treated sham groups. We conclude that increased phosphoglycerate kinase-1 activity after acute phosphodiesterase 5A inhibition blunts NHE-1 activity and protects the heart against post-MI remodeling and dysfunction.Facultad de Ciencias MédicasCentro de Investigaciones Cardiovasculare

La disminución de la actividad del NHE-1 por sildenafil (SIL) se debe al aumento de la actividad de la fosfatasa PP1

El intercambiador Na+/H+ (NHE-1) es una proteína integral de membrana que participa en la regulación del pHi del miocardio, debido a que cataliza el intercambio electroneutro de un H+ intracelular por un Na+ extracelular. El NHE-1 tiene un rol importante en el daño por isquemia y reperfusión y en el remodelamiento del miocardio después del infarto, ya que se le atribuye el aumento del Ca+2 intracelular a través de la activación del modo reverso del intercambiador Na+/Ca+2. Recientemente, nosotros demostramos que sildenafil (SIL, inhibidor de la fosfodiesterasa 5A, PDE5A) protege al corazón del remodelamiento postinfarto en ratas con oclusión de la arteria coronaria, y esta protección está asociada con inhibición del NHE-1.Facultad de Ciencias Médica

La disminución de la actividad del NHE-1 por sildenafil (SIL) se debe al aumento de la actividad de la fosfatasa PP1

El intercambiador Na+/H+ (NHE-1) es una proteína integral de membrana que participa en la regulación del pHi del miocardio, debido a que cataliza el intercambio electroneutro de un H+ intracelular por un Na+ extracelular. El NHE-1 tiene un rol importante en el daño por isquemia y reperfusión y en el remodelamiento del miocardio después del infarto, ya que se le atribuye el aumento del Ca+2 intracelular a través de la activación del modo reverso del intercambiador Na+/Ca+2. Recientemente, nosotros demostramos que sildenafil (SIL, inhibidor de la fosfodiesterasa 5A, PDE5A) protege al corazón del remodelamiento postinfarto en ratas con oclusión de la arteria coronaria, y esta protección está asociada con inhibición del NHE-1.Facultad de Ciencias Médica

La disminución de la actividad del NHE-1 por sildenafil (SIL) se debe al aumento de la actividad de la fosfatasa PP1

El intercambiador Na+/H+ (NHE-1) es una proteína integral de membrana que participa en la regulación del pHi del miocardio, debido a que cataliza el intercambio electroneutro de un H+ intracelular por un Na+ extracelular. El NHE-1 tiene un rol importante en el daño por isquemia y reperfusión y en el remodelamiento del miocardio después del infarto, ya que se le atribuye el aumento del Ca+2 intracelular a través de la activación del modo reverso del intercambiador Na+/Ca+2. Recientemente, nosotros demostramos que sildenafil (SIL, inhibidor de la fosfodiesterasa 5A, PDE5A) protege al corazón del remodelamiento postinfarto en ratas con oclusión de la arteria coronaria, y esta protección está asociada con inhibición del NHE-1.Facultad de Ciencias Médica

Enero 2019: record histórico de lluvias

La Estación Experimental Agropecuaria Paraná del INTA, en Entre Ríos, cuenta con un observatorio agrometeorológico que releva datos desde 1934. En enero de 2019 se alcanzó un nuevo récord de lluvias mensuales: 364,6 mm. El registro histórico indica que desde 1978, año en que llovieron 357,7 mm, no teníamos un enero tan lluvioso en Paraná.Fil: Seehaus, Mariela Soledad. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná. Grupo de Recursos Naturales y Factores Abióticos; ArgentinaFil: Van Opstal, Natalia Verónica. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná. Grupo de Recursos Naturales y Factores Abióticos; ArgentinaFil: Gabioud, Emmanuel Adrián. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná. Grupo de Recursos Naturales y Factores Abióticos; ArgentinaFil: Wilson, Marcelo Germán. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná. Grupo de Recursos Naturales y Factores Abióticos; ArgentinaFil: Garciarena, Néstor. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná. Grupo de Recursos Naturales y Factores Abióticos; ArgentinaFil: Wingeyer, Ana Beatriz. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná. Grupo de Recursos Naturales y Factores Abióticos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Beghetto, Stella. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná. Grupo de Recursos Naturales y Factores Abióticos; ArgentinaFil: Sasal, Maria Carolina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná. Grupo de Recursos Naturales y Factores Abióticos; Argentin