Catharina Belge

Endothelial beta3-adrenoreceptors mediate nitric oxide-dependent vasorelaxation of coronary microvessels in response to the third-generation beta-blocker nebivolol.

Background—The therapeutic effects of nonspecific β-blockers are limited by vasoconstriction, thus justifying the interest in molecules with ancillary vasodilating properties. Nebivolol is a selective β1-adrenoreceptor antagonist that releases nitric oxide (NO) through incompletely characterized mechanisms. We identified endothelial β3-adrenoreceptors in human coronary microarteries that mediate endothelium- and NO-dependent relaxation and hypothesized that nebivolol activates these β3-adrenoreceptors. Methods and Results—Nebivolol dose-dependently relaxed rodent coronary resistance microarteries studied by videomicroscopy (10 &mgr;mol/L, −86±6% of prostaglandin F2α contraction); this was sensitive to NO synthase (NOS) inhibition, unaffected by the β1-2-blocker nadolol, and prevented by the β1-2-3-blocker bupranolol (P<0.05; n=3 to 8). Importantly, nebivolol failed to relax microarteries from β3-adrenoreceptor–deficient mice. Nebivolol (10 &mgr;mol/L) also relaxed human coronary microvessels (−71±5% of KCl contraction); this was dependent on a functional endothelium and NO synthase but insensitive to β1-2-blockade (all P<0.05). In a mouse aortic ring assay of neoangiogenesis, nebivolol induced neocapillary tube formation in rings from wild-type but not β3-adrenoreceptor– or endothelial NOS–deficient mice. In cultured endothelial cells, 10 &mgr;mol/L nebivolol increased NO release by 200% as measured by electron paramagnetic spin trapping, which was also reversed by NOS inhibition. In parallel, endothelial NOS was dephosphorylated on threonine495, and fura-2 calcium fluorescence increased by 91.8±23.7%; this effect was unaffected by β1-2-blockade but abrogated by β1-2-3-blockade (all P<0.05). Conclusions—Nebivolol dilates human and rodent coronary resistance microarteries through an agonist effect on endothelial β3-adrenoreceptors to release NO and promote neoangiogenesis. These properties may prove particularly beneficial for the treatment of ischemic and cardiac failure diseases through preservation of coronary reserve.

Cardiomyocyte-restricted overexpression of endothelial nitric oxide synthase (NOS3) attenuates beta-adrenergic stimulation and reinforces vagal inhibition of cardiac contraction.

Background—In the heart, nitric oxide synthases (NOS) modulate cardiac contraction in an isoform-specific manner, which is critically dependent on their cellular and subcellular localization. Defective NO production by NOS3 (endothelial NOS [eNOS]) in the failing heart may precipitate cardiac failure, which could be reversed by overexpression of NOS3 in the myocardium. Methods and Results—We studied the influence of NOS3 in relation to its subcellular localization on the function of cardiomyocytes isolated from transgenic mice overexpressing NOS3 under the &agr;-myosin heavy chain promoter (NOS3-TG). Immunoblot analysis demonstrated moderate (5-fold) NOS3 overexpression in cardiomyocytes from NOS3-TG heterozygotes. Caveolar localization of transgenic eNOS was demonstrated by immunofluorescence, coimmunoprecipitation with caveolin-3, sucrose gradient fractionation, and immunogold staining revealed by electron microscopy. Compared with wild-type littermate, contractility of NOS3-TG cardiomyocytes analyzed by videomicroscopy revealed a lower incidence of spontaneous arrhythmic contractions (n=32, P<0.001); an attenuation of the &bgr;-adrenergic positive inotropic response (isoproterenol, 10−7 mol/L: 62.1±7.8% versus 90.8±8.0% of maximum Ca2+ response; n=10 to 17; P<0.05); a potentiation of the muscarinic negative chronotropic response (carbamylcholine, 3.10−8 mol/L: −63.9±14% versus −27.7±5.6% of basal rate; n=8 to 10; P<0.05), confirmed by telemetry in vivo; and an attenuation of the accentuated antagonism of &bgr;-adrenergically stimulated contraction (−14.6±1.5% versus −3.5±1.5; n=7 to 11; P<0.05). Cardiomyocyte NOS inhibition reversed all 4 effects (P<0.05). Conclusions—Moderate overexpression of NOS3, targeted to caveolae in murine cardiomyocytes, potentiates the postsynaptic muscarinic response and attenuates the effect of high concentrations of catecholamines. Cardiomyocyte NOS3 may represent a promising therapeutic target to restore the sympathovagal balance and protect the heart against arrhythmia.

Enhanced Expression of β3-Adrenoceptors in Cardiac Myocytes Attenuates Neurohormone-Induced Hypertrophic Remodeling Through Nitric Oxide Synthase

Background— &bgr;1-2-adrenergic receptors (AR) are key regulators of cardiac contractility and remodeling in response to catecholamines. &bgr;3-AR expression is enhanced in diseased human myocardium, but its impact on remodeling is unknown. Methods and Results— Mice with cardiac myocyte-specific expression of human &bgr;3-AR (&bgr;3-TG) and wild-type (WT) littermates were used to compare myocardial remodeling in response to isoproterenol (Iso) or Angiotensin II (Ang II). &bgr;3-TG and WT had similar morphometric and hemodynamic parameters at baseline. &bgr;3-AR colocalized with caveolin-3, endothelial nitric oxide synthase (NOS) and neuronal NOS in adult transgenic myocytes, which constitutively produced more cyclic GMP, detected with a new transgenic FRET sensor. Iso and Ang II produced hypertrophy and fibrosis in WT mice, but not in &bgr;3-TG mice, which also had less re-expression of fetal genes and transforming growth factor &bgr;1. Protection from Iso-induced hypertrophy was reversed by nonspecific NOS inhibition at low dose Iso, and by preferential neuronal NOS inhibition at high-dose Iso. Adenoviral overexpression of &bgr;3-AR in isolated cardiac myocytes also increased NO production and attenuated hypertrophy to Iso and phenylephrine. Hypertrophy was restored on NOS or protein kinase G inhibition. Mechanistically, &bgr;3-AR overexpression inhibited phenylephrine-induced nuclear factor of activated T-cell activation. Conclusions— Cardiac-specific overexpression of &bgr;3-AR does not affect cardiac morphology at baseline but inhibits the hypertrophic response to neurohormonal stimulation in vivo and in vitro, through a NOS-mediated mechanism. Activation of the cardiac &bgr;3-AR pathway may provide future therapeutic avenues for the modulation of hypertrophic remodeling.

Nitric oxide and the heart: update on new paradigms.

Abstract: The role of nitric oxide (NO) as a regulator of cardiac contraction was suggested in the early nineties, but a consensual view of its main functions in cardiac physiology has only recently emerged with the help of experiments using genetic deletion or overexpression of the three nitric oxide synthase (NOS) isoforms in cardiomyocytes. Contrary to the effects of exogenous, pharmacologic NO donors, signaling by endogenous NO is restricted to intracellular effectors co‐localized with NOS in specific subcellular compartments. This both ensures coordinate signaling by the three NOS isoforms on different aspects of the cardiomyocyte function and helps to reconcile previous apparently contradictory observations based on the use of non‐isoform‐specific NOS inhibitors. This review will emphasize the role of NOS on excitation‐contraction coupling in the normal and diseased heart. Endothelial NOS and neuronal NOS contribute to maintain an adequate balance between adrenergic and vagal input to the myocardium and participate in the early and late phases of the Frank‐Starling adaptation of the heart. At the early phases of cardiac diseases, inducible NOS reinforces these effects, which may become maladaptive as disease progresses.

Sepsis is associated with an upregulation of functional beta3 adrenoceptors in the myocardium.

To analyze the implication of the β3‐adrenoceptor (β3‐AR) pathway in human septic myocardium and a murine model of sepsis, a condition associated with myocardial depression.

Noninvasive ventilation improves sleep in amyotrophic lateral sclerosis: a prospective polysomnographic study.

STUDY OBJECTIVE To evaluate the effects of noninvasive ventilation (NIV) on sleep in patients with amyotrophic lateral sclerosis (ALS) after meticulous titration with polysomnography (PSG). METHODS In this prospective observational study, 24 ALS patients were admitted to the sleep laboratory during 4 nights for in-hospital NIV titration with PSG and nocturnal capnography. Questionnaires were used to assess subjective sleep quality and quality of life (QoL). Patients were readmitted after one month. RESULTS In the total group, slow wave sleep and REM sleep increased and the arousal-awakening index improved. The group without bulbar involvement (non-bulbar) showed the same improvements, together with an increase in sleep efficiency. Nocturnal oxygen and carbon dioxide levels improved in the total and non-bulbar group. Except for oxygen saturation during REM sleep, no improvement in respiratory function or sleep structure was found in bulbar patients. However, these patients showed less room for improvement. Patient-reported outcomes showed improvement in sleep quality and QoL for the total and non-bulbar group, while bulbar patients only reported improvements in very few subscores. CONCLUSIONS This study shows an improvement of sleep architecture, carbon dioxide, and nocturnal oxygen saturation at the end of NIV titration and after one month of NIV in ALS patients. More studies are needed to identify the appropriate time to start NIV in bulbar patients. Our results suggest that accurate titration of NIV by PSG improves sleep quality. COMMENTARY A commentary on this article appears in this issue on page 511.

Non-invasive ventilation in amyotrophic lateral sclerosis

Abstract Non-invasive ventilation (NIV) is widely used to improve alveolar hypoventilation in amyotrophic lateral sclerosis. Several studies indicate a better survival when NIV is used, certainly in patients with none to moderate bulbar dysfunction. Data on quality of life (QoL) are rather disputable. Overall QoL is shown to be equivalent in patients with or without NIV, although health-related QoL is shown to be increased in patients with none to moderate bulbar dysfunction. NIV improves sleep quality, although patient-ventilator asynchronies are demonstrated. FVC < 50%, seated or supine, has been widely applied as threshold to initiate NIV. Today, measurements of respiratory muscle strength, nocturnal gas exchange and symptomatic complaints are used as indicators to start NIV. Being compliant with NIV therapy increases QoL and survival. Cough augmentation has an important role in appropriate NIV. Patients have today more technical options and patients with benefit from these advances are growing in number. Tracheal ventilation needs to be discussed when NIV seems impossible or becomes insufficient.

Noninvasive ventilation in amyotrophic lateral sclerosis: effects on sleep quality and quality of life

Objectives: Little is known about the effects of noninvasive ventilation (NIV) on sleep quality in amyotrophic lateral sclerosis (ALS). We aim to evaluate the long-term effects of NIV on sleep quality and quality of life in patients with ALS. Methods: In this prospective observational study, 13 ALS patients were followed for one year after initiating NIV. We evaluated sleep quality, quality of life and functional status with several questionnaires: Epworth sleepiness Scale (ESS), Pittsburg sleep quality index (PSQI), Short Form 36 Health Questionnaire (SF-36), McGill Quality of Life questionnaire (McGillQoL) and revised Amyotrophic Lateral Sclerosis Functional Rating Scale scores (ALSFRS-R). Results: Median and interquartile range (IQR) at the start of NIV was 59 (53–65) years. The ALSFRS-R at start was 30 (24–37) (median, IQR), with three patients having severe bulbar impairment (ALSFRS-R-bulbar ≤ 9). The PaCO2 at start of NIV treatment was 48 (43–52) mmHg (median, IQR). During the one-year follow-up period, a significant decrease in the ALSFRS-R was observed. The impact of NIV in a short term (1 month) revealed a statistically significant decrease in ESS, decrease in total PSQI and of four PSQI subscales and improvement of almost all subscales of the McGill questionnaire. Long-term analyses (9 months to 1 year) revealed that amelioration in ESS and total PSQI was sustained. Conclusion: We conclude that accurately titrated NIV in ALS patients can stabilize sleep quality and quality of life for at least one year, despite significant disease progression.

Upper Airway Obstruction during Noninvasive Ventilation Induced by the Use of an Oronasal Mask

In patients with neuromuscular disorders, no randomized studies have been performed whether nasal or oronasal masks should be preferred. Oronasal masks are often used in acute respiratory failure, while nasal masks are preferred in patients with chronic respiratory failure. However, the use of nasal masks can result in mouth leaks with implications on sleep quality. To reduce these leaks, oronasal masks have been applied during home noninvasive ventilation (NIV). Until now, upper airway obstruction during NIV has been thought to be induced by nasal obstruction, pharyngeal collapse, and/or glottis closure. We report a case indicating another cause of upper airway obstruction: use of an oronasal mask can induce obstructive events in the upper airways, possibly resulting in sleep fragmentation and decreased efficiency of NIV.

Patient-ventilator asynchrony, leaks and sleep in patients with amyotrophic lateral sclerosis

Abstract Sleeping with non-invasive ventilation (NIV) in amyotrophic lateral sclerosis appears to be accompanied by a high patient-ventilator asynchrony (PVA) index. This prospective observational cohort study quantifies PVA and leaks, and searches for effects of these events on sleep after polysomnographic NIV titration. Full-video polysomnography, with incorporation of transcutaneous carbon dioxide and ventilator software, was used to analyse sleep epoch-by-epoch and respiratory events and PVA breath-by-breath in 35 patients (17 non-bulbar). After diagnostic polysomnography, NIV was titrated during three consecutive nights. Sleep, PVA and leaks were evaluated at discharge and after one month. Results showed that non-bulbar patients improved in sleep architecture and oxygen and carbon dioxide levels while bulbar patients only improved oxygen saturation. PVA remained present at discharge (non-bulbar 54 (21–101) and bulbar 31 (9–39)/h sleep) and one month (non-bulbar 31 (9–39) and bulbar 32 (17–55)/h sleep), with ineffective effort as most prominent asynchrony. Leaks also persisted after titration (non-bulbar 16.6 (3.1–44.6) and bulbar 5.1 (0.0–19.5)% of total sleep time (TST)) and one month (non-bulbar 7.7 (1.4–29.3) and bulbar 12.7 (0.0–35.2)% TST). PVA and leaks have none to minor effect on sleep architecture. In conclusion, although PVA and leaks remain present after meticulous NIV titration, these events seem not to interfere with sleep.