Letter by Cingolani et al. regarding article, "Ventricular phosphodiesterase-5 expression is increased in patients with advanced heart failure and contributes to adverse ventricular remodeling after myocardial infarction in mice"

Pokreisz et al. recently published an interesting article in which they show increased cardiac left ventricular phosphodiesterase-5A (PDE5A) expression in patients with heart failure. They also generated a PDE5A transgenic mouse in which overexpression of this cGMP-selective phosphodiesterase worsened ventricular remodeling and function after myocardial infarction. Therefore, the obvious conclusion seems to be that inhibition of PDE5A might protect against postmyocardial infarction remodeling. Although the authors show cGMP to be related to these cardiac architectural changes, they raise new questions about the possible cGMP downstream signaling mechanisms involved.Facultad 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

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

In vivo key role of reactive oxygen species and NHE-1 activation in determining excessive cardiac hypertrophy

Growing in vitro evidence suggests NHE-1, a known target for reactive oxygen species (ROS), as a key mediator in cardiac hypertrophy (CH). Moreover, NHE-1 inhibition was shown effective in preventing CH and failure; so has been the case for AT1 receptor (AT1R) blockers. Previous experiments indicate that myocardial stretch promotes angiotensin II release and post-translational NHE-1 activation; however, in vivo data supporting this mechanism and its long-term consequences are scanty. In this work, we thought of providing in vivo evidence linking AT1R with ROS and NHE-1 activation in mediating CH. CH was induced in mice by TAC. A group of animals was treated with the AT1R blocker losartan. Cardiac contractility was assessed by echocardiography and pressure–volume loop hemodynamics. After 7 weeks, TAC increased left ventricular (LV) mass by ~45% vs. sham and deteriorated LV systolic function. CH was accompanied by activation of the redox-sensitive kinase p90RSK with the consequent increase in NHE-1 phosphorylation. Losartan prevented p90RSK and NHE-1 phosphorylation, ameliorated CH and restored cardiac function despite decreased LV wall thickness and similar LV systolic pressures and diastolic dimensions (increased LV wall stress). In conclusion, AT1R blockade prevented excessive oxidative stress, p90RSK and NHE-1 phosphorylation, and decreased CH independently of hemodynamic changes. In addition, cardiac performance improved despite a higher work load.Facultad de Ciencias MédicasCentro 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

In vivo key role of reactive oxygen species and NHE-1 activation in determining excessive cardiac hypertrophy

Growing in vitro evidence suggests NHE-1, a known target for reactive oxygen species (ROS), as a key mediator in cardiac hypertrophy (CH). Moreover, NHE-1 inhibition was shown effective in preventing CH and failure; so has been the case for AT1 receptor (AT1R) blockers. Previous experiments indicate that myocardial stretch promotes angiotensin II release and post-translational NHE-1 activation; however, in vivo data supporting this mechanism and its long-term consequences are scanty. In this work, we thought of providing in vivo evidence linking AT1R with ROS and NHE-1 activation in mediating CH. CH was induced in mice by TAC. A group of animals was treated with the AT1R blocker losartan. Cardiac contractility was assessed by echocardiography and pressure–volume loop hemodynamics. After 7 weeks, TAC increased left ventricular (LV) mass by ~45% vs. sham and deteriorated LV systolic function. CH was accompanied by activation of the redox-sensitive kinase p90RSK with the consequent increase in NHE-1 phosphorylation. Losartan prevented p90RSK and NHE-1 phosphorylation, ameliorated CH and restored cardiac function despite decreased LV wall thickness and similar LV systolic pressures and diastolic dimensions (increased LV wall stress). In conclusion, AT1R blockade prevented excessive oxidative stress, p90RSK and NHE-1 phosphorylation, and decreased CH independently of hemodynamic changes. In addition, cardiac performance improved despite a higher work load.Facultad de Ciencias MédicasCentro de Investigaciones Cardiovasculare

Cardioprotective Effect of Beta-3 Adrenergic Receptor Agonism Role of Neuronal Nitric Oxide Synthase

ObjectivesThe aim of this study was to determine whether activation of β3-adrenergic receptor (AR) and downstream signaling of nitric oxide synthase (NOS) isoforms protects the heart from failure and hypertrophy induced by pressure overload.Backgroundβ3-AR and its downstream signaling pathways are recognized as novel modulators of heart function. Unlike β1- and β2-ARs, β3-ARs are stimulated at high catecholamine concentrations and induce negative inotropic effects, serving as a “brake” to protect the heart from catecholamine overstimulation.MethodsC57BL/6J and neuronal NOS (nNOS) knockout mice were assigned to receive transverse aortic constriction (TAC), BRL37344 (β3 agonist, BRL 0.1 mg/kg/h), or both.ResultsThree weeks of BRL treatment in wild-type mice attenuated left ventricular dilation and systolic dysfunction, and partially reduced cardiac hypertrophy induced by TAC. This effect was associated with increased nitric oxide production and superoxide suppression. TAC decreased endothelial NOS (eNOS) dimerization, indicating eNOS uncoupling, which was not reversed by BRL treatment. However, nNOS protein expression was up-regulated 2-fold by BRL, and the suppressive effect of BRL on superoxide generation was abrogated by acute nNOS inhibition. Furthermore, BRL cardioprotective effects were actually detrimental in nNOS–/– mice.ConclusionsThese results are the first to show in vivo cardioprotective effects of β3-AR–specific agonism in pressure overload hypertrophy and heart failure, and support nNOS as the primary downstream NOS isoform in maintaining NO and reactive oxygen species balance in the failing heart