Topical Potassium Channel Blockage Improves Pharyngeal Collapsibility: A Translational, Placebo-Controlled Trial.

BACKGROUND: Potassium (K+) channel inhibition has been identified in animal models as a potential target to increase pharyngeal dilator muscle activity and to treat OSA. However, these findings have not yet been translated to humans. RESEARCH QUESTION: Does a novel, potent, tandem of P domains in a weak inward rectifying K+ channel (TWIK)-related acid-sensitive K+ (TASK) 1/3 channel antagonist, BAY2586116, improve pharyngeal collapsibility in pigs and humans, and secondarily, what is the optimal dose and method of topical application? STUDY DESIGN AND METHODS: In the preclinical study, pharyngeal muscle activity and upper-airway collapsibility via transient negative pressure application was quantified in 13 anesthetized pigs during administration of placebo, 0.3 µg, 3 µg, and 30 µg nasal drops of BAY2586116. In the clinical study, 12 people with OSA instrumented with polysomnography equipment, an epiglottic pressure catheter, pneumotachograph, and nasal mask to monitor sleep and breathing performed up to four detailed upper airway sleep physiology studies. Participants received BAY2586116 (160 µg) or placebo nasal spray before sleep via a double-masked, randomized, crossover design. Most participants also returned for three additional overnight visits: (1) nasal drops (160 µg), (2) half-dose nasal spray (80 µg), and (3) direct endoscopic application (160 µg). The upper-airway critical closing pressure (Pcrit) during sleep was quantified at each visit. RESULTS: Consistent and sustained improvements in pharyngeal collapsibility to negative pressure were found with 3 and 30 µg of BAY2586116 vs placebo in pigs. Similarly, BAY2586116 improved pharyngeal collapsibility by an average of approximately 2 cm H2O vs placebo, regardless of topical application method and dose (P < .008, mixed model) in participants with OSA. INTERPRETATION: Acute topical application of BAY2586116 improves upper-airway collapsibility in anesthetized pigs and sleeping humans with OSA. These novel physiologic findings highlight the therapeutic potential to target potassium channel mechanisms to treat OSA. TRIAL REGISTRY: ClinicalTrials.gov; No.: NCT04236440; URL: www. CLINICALTRIALS: gov.

Mice lacking calsarcin-1 are sensitized to calcineurin signaling and show accelerated cardiomyopathy in response to pathological biomechanical stress.

Signaling by the calcium-dependent phosphatase calcineurin profoundly influences the growth and gene expression of cardiac and skeletal muscle. Calcineurin binds to calsarcins, a family of muscle-specific proteins of the sarcomeric Z-disc, a focal point in the pathogenesis of human cardiomyopathies. We show that calsarcin-1 negatively modulates the functions of calcineurin, such that calcineurin signaling was enhanced in striated muscles of mice that do not express calsarcin-1. As a consequence of inappropriate calcineurin activation, mice with a null mutation in calsarcin-1 showed an excess of slow skeletal muscle fibers. The absence of calsarcin-1 also activated a hypertrophic gene program, despite the absence of hypertrophy, and enhanced the cardiac growth response to pressure overload. In contrast, cardiac adaptation to other hypertrophic stimuli, such as chronic catecholamine stimulation or exercise, was not affected. These findings show important roles for calsarcins as modulators of calcineurin signaling and the transmission of a specific subset of stress signals leading to cardiac remodeling in vivo.

Calsarcin-1 protects against angiotensin-II induced cardiac hypertrophy.

BACKGROUND: We have previously shown that deficiency for the z-disc protein calsarcin-1 (CS1) sensitizes the heart to calcineurin signaling and to stimuli of pathological hypertrophy. In the present study we asked whether overexpression of CS1 might exhibit antihypertrophic effects, and therefore we tested this hypothesis both in vitro and in vivo. METHODS AND RESULTS: Adenoviral gene transfer of CS1 into neonatal cardiomyocytes inhibited hypertrophy as a result of Gq-agonist stimulation, including angiotensin-II (Ang-II), endothelin-1, and phenylephrine. Consistently, Adenoviral gene transfer of CS1 also led to the reduction of increased levels of atrial natriuretic factor (mRNA) and the calcineurin-sensitive gene MCIP1.4, suggesting that CS1 inhibits calcineurin-dependent signaling. Furthermore, we generated CS1-overexpressing transgenic mice (CS1Tg). Unchallenged CS1Tg mice did not exhibit a pathological phenotype as assessed by echocardiography and analysis of cardiac gene expression. Likewise, when subjected to long-term infusion of Ang-II, both CS1Tg and wild-type mice developed a similar degree of arterial hypertension. Yet, in contrast to wild-type mice, Ang-II-treated CS1Tg animals did not display cardiac hypertrophy. Despite the absence of hypertrophy, both fractional shortening and dP/dt(max) were preserved in CS1Tg Ang-II-treated mice as assessed by echocardiography and cardiac catheterization, respectively. Moreover, induction of the hypertrophic gene program (atrial natriuretic factor, brain natriuretic peptide) was markedly blunted, and expression of the calcineurin-dependent gene MCIP1.4 was significantly reduced in CS1Tg mice, again consistent with an inhibitory role of CS1 on calcineurin. CONCLUSIONS: The sarcomeric protein CS1 prevents Ang-II-induced cardiomyocyte hypertrophy at least in part via inhibition of calcineurin signaling. Thus, overexpression of CS1 might represent a novel approach to attenuate pathological cardiac hypertrophy.

Fas receptor signaling inhibits glycogen synthase kinase 3 beta and induces cardiac hypertrophy following pressure overload.

Congestive heart failure is a leading cause of mortality in developed countries. Myocardial hypertrophy resulting from hypertension often precedes heart failure. Understanding the signaling underlying cardiac hypertrophy and failure is of major interest. Here, we identified Fas receptor activation, a classical death signal causing apoptosis via activation of the caspase cascade in many cell types, as a novel pathway mediating cardiomyocyte hypertrophy in vitro and in vivo. Fas activation by Fas ligand induced a hypertrophic response in cultured cardiomyocytes, which was dependent on the inactivation of glycogen synthase kinase 3 beta (GSK3 beta) by phosphorylation. In vivo, lpr (lymphoproliferative disease) mice lacking a functional Fas receptor demonstrated rapid-onset left ventricular dilatation and failure, absence of compensatory hypertrophy, and significantly increased mortality in response to pressure overload induction that was accompanied by a failure to inhibit GSK3 beta activity. In contrast, Fas ligand was dispensable for the development of pressure overload hypertrophy in vivo. In vitro, neonatal cardiomyocytes from lpr mice showed a completely abrogated or significantly blunted hypertrophic response after stimulation with Fas ligand or angiotensin II, respectively. These findings indicate that Fas receptor signaling inhibits GSK3 beta activity in cardiomyocytes and is required for compensation of pressure overload in vivo.

Concentric left ventricular remodeling in endothelial nitric oxide synthase knockout mice by chronic pressure overload.

OBJECTIVE: Heart failure as a consequence of sustained hemodynamic overload is among the most prevalent diseases in developed countries. The aim of the present study was to investigate the specific role of endothelial nitric oxide synthase (eNOS) in pressure overload-induced left ventricular (LV) hypertrophy. METHODS AND RESULTS: Chronic pressure-overload LV hypertrophy was induced by abdominal aortic banding (AC) in wild-type (WT) and eNOS(-/-) mice. Six weeks after abdominal AC, the consequences of the sustained pressure overload on LV morphology and function were noninvasively and invasively assessed using echocardiography and a 1.4 F conductance catheter. Sham-operated eNOS(-/-) mice had significantly increased systolic blood pressure, slightly enhanced systolic function (preload recruitable stroke work) and normal diastolic function but no evidence of left ventricular hypertrophy when compared to sham-operated WT animals. AC resulted in a greater increase in anterior wall thickness in eNOS(-/-) mice (0.8+/-0.03 mm) compared to WT mice (0.7+/-0.03 mm; P<0.05). The LV end-diastolic diameter was unchanged by AC in eNOS(-/-) mice (sham: 3.8+/-0.1 mm, AC: 3.7+/-0.2 mm) but significantly increased in WT mice (sham: 3.9+/-0.1 mm, AC: 4.5+/-0.2 mm; P<0.05). Interstitial fibrosis and myocyte hypertrophy were greater in eNOS(-/-) than in WT mice after AC. AC in eNOS(-/-) mice caused a greater diastolic than systolic dysfunction compared to WT mice. CONCLUSION: Chronic pressure overload in eNOS(-/-) mice results in concentric LV hypertrophy without LV dilation and impaired systolic and diastolic function. These findings suggest that eNOS limits LV remodeling and dysfunction and modulates extracellular matrix proteins under chronic pressure overload.

Effects of combined inhibition of the Na+-H+ exchanger and angiotensin-converting enzyme in rats with congestive heart failure after myocardial infarction.

1 We investigated the single vs the combined long-term inhibition of Na(+)-H(+) exchanger-1 (NHE-1) and ACE in rats with congestive heart failure induced by myocardial infarction (MI). 2 Rats with MI were randomized to receive either placebo, cariporide (3000 p.p.m. via chow), ramipril (1 mg kg(-1) day(-1) via drinking water) or their combination for 18 weeks starting on day 3 after surgery. 3 Cardiac morphology and function was assessed by echocardiography and by means of a 2.0 F conductance catheter to determine left ventricular (LV) pressure volume relationships. 4 MI for 18 weeks resulted in an increase in LV end-diastolic diameter (LVDed) in the placebo-treated group when compared to sham (placebo: 1.1+/-0.04 cm; sham: 0.86+/-0.01; P<0.05). Combined inhibition of NHE-1 and ACE, but not the monotherapies, significantly reduced LVDed (1.02+/-0.02 cm). 5 Preload recruitable stroke work (PRSW), dp/dt(max) (parameter of systolic function) and end-diastolic pressure volume relationship (EDPVR, diastolic function) were significantly impaired in placebo-treated MI group (PRSW: 39+/-7 mmHg; dp/dt(max): 5185+/-363 mmHg s(-1); EDPVR: 0.042+/-0.001 mmHg microl(-1); all P<0.05). Cariporide treatment significantly improved PRSW (64+/-7 mmHg), dp/dt(max) (8077+/-525 mmHg s(-1)) and EDPVR (0.026+/-0.014 mmHg microl(-1)), and reduced cardiac hypertrophy in rats with MI. Combined inhibition of NHE-1 and ACE had even a more pronounced effect on PRSW (72+/-5 mmHg) and EDPVR (0.026+/-0.014 mmHg microl(-1)), as well as cardiac hypertrophy that, however, did not reach statistical significance compared to cariporide treatment alone. 6 The NHE-1 inhibitor cariporide significantly improved LV remodeling and function in rats with congestive heart failure induced by MI. The effect of cariporide was comparable or tended to be stronger (e.g. systolic function) compared to ramipril. Combined treatment with cariporide and ramipril tended to be more effective on LV remodeling in rats with heart failure than the single treatments. Thus, inhibition of the NHE-1 may be a promising novel therapeutic approach for the treatment of congestive heart failure.