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?-adrenergic receptor-mediated cardiac contractility is inhibited via vasopressin type 1A-receptor-dependent signaling.

ABSTRACT: Enhanced arginine vasopressin levels are associated with increased mortality during end-stage human heart failure, and cardiac arginine vasopressin type 1A receptor (V1AR) expression becomes increased. Additionally, mice with cardiac-restricted V1AR overexpression develop cardiomyopathy and decreased ?-adrenergic receptor (?AR) responsiveness. This led us to hypothesize that V1AR signaling regulates ?AR responsiveness and in doing so contributes to development of heart failure.Transaortic constriction resulted in decreased cardiac function and ?AR density and increased cardiac V1AR expression, effects reversed by a V1AR-selective antagonist. Molecularly, V1AR stimulation led to decreased ?AR ligand affinity, as well as ?AR-induced Ca(2+) mobilization and cAMP generation in isolated adult cardiomyocytes, effects recapitulated via ex vivo Langendorff analysis. V1AR-mediated regulation of ?AR responsiveness was demonstrated to occur in a previously unrecognized Gq protein-independent/G protein receptor kinase-dependent manner.This newly discovered relationship between cardiac V1AR and ?AR may be informative for the treatment of patients with acute decompensated heart failure and elevated arginine vasopressin.

SUBMITTER: Tilley DG

PROVIDER: S-EPMC4229385 | biostudies-literature | 2014 Nov

REPOSITORIES: biostudies-literature

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β-adrenergic receptor-mediated cardiac contractility is inhibited via vasopressin type 1A-receptor-dependent signaling.

Tilley Douglas G DG Zhu Weizhong W Myers Valerie D VD Barr Larry A LA Gao Erhe E Li Xue X Song Jianliang J Carter Rhonda L RL Makarewich Catherine A CA Yu Daohai D Troupes Constantine D CD Grisanti Laurel A LA Coleman Ryan C RC Koch Walter J WJ Houser Steven R SR Cheung Joseph Y JY Feldman Arthur M AM

Circulation 20140909 20

<h4>Background</h4>Enhanced arginine vasopressin levels are associated with increased mortality during end-stage human heart failure, and cardiac arginine vasopressin type 1A receptor (V1AR) expression becomes increased. Additionally, mice with cardiac-restricted V1AR overexpression develop cardiomyopathy and decreased β-adrenergic receptor (βAR) responsiveness. This led us to hypothesize that V1AR signaling regulates βAR responsiveness and in doing so contributes to development of heart failure ...[more]

PMID: 25205804

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Project description:AimsTo determine the mechanisms by which the ?1A-adrenergic receptor (AR) regulates cardiac contractility.BackgroundWe reported previously that transgenic mice with cardiac-restricted ?1A-AR overexpression (?1A-TG) exhibit enhanced contractility but not hypertrophy, despite evidence implicating this G?q/11-coupled receptor in hypertrophy.MethodsContractility, calcium (Ca(2+)) kinetics and sensitivity, and contractile proteins were examined in cardiomyocytes, isolated hearts and skinned fibers from ?1A-TG mice (170-fold overexpression) and their non-TG littermates (NTL) before and after ?1A-AR agonist stimulation and blockade, angiotensin II (AngII), and Rho kinase (ROCK) inhibition.ResultsHypercontractility without hypertrophy with ?1A-AR overexpression is shown to result from increased intracellular Ca(2+) release in response to agonist, augmenting the systolic amplitude of the intracellular Ca(2+) concentration [Ca(2+)]i transient without changing resting [Ca(2+)]i. In the absence of agonist, however, ?1A-AR overexpression reduced contractility despite unchanged [Ca(2+)]i. This hypocontractility is not due to heterologous desensitization: the contractile response to AngII, acting via its G?q/11-coupled receptor, was unaltered. Rather, the hypocontractility is a pleiotropic signaling effect of the ?1A-AR in the absence of agonist, inhibiting RhoA/ROCK activity, resulting in hypophosphorylation of both myosin phosphatase targeting subunit 1 (MYPT1) and cardiac myosin light chain 2 (cMLC2), reducing the Ca(2+) sensitivity of the contractile machinery: all these effects were rapidly reversed by selective ?1A-AR blockade. Critically, ROCK inhibition in normal hearts of NTLs without ?1A-AR overexpression caused hypophosphorylation of both MYPT1 and cMLC2, and rapidly reduced basal contractility.ConclusionsWe report for the first time pleiotropic ?1A-AR signaling and the physiological role of RhoA/ROCK signaling in maintaining contractility in the normal heart.

Project description:AimsEpidermal growth factor receptor (EGFR) is essential to the development of multiple tissues and organs and is a target of cancer therapeutics. Due to the embryonic lethality of global EGFR deletion and conflicting reports of cardiac-overexpressed EGFR mutants, its specific impact on the adult heart, normally or in response to chronic stress, has not been established. Using complimentary genetic strategies to modulate cardiomyocyte-specific EGFR expression, we aim to define its role in the regulation of cardiac function and remodelling.Methods and resultsA floxed EGFR mouse model with α-myosin heavy chain-Cre-mediated cardiomyocyte-specific EGFR downregulation (CM-EGFR-KD mice) developed contractile dysfunction by 9 weeks of age, marked by impaired diastolic relaxation, as monitored via echocardiographic, haemodynamic, and isolated cardiomyocyte contractility analyses. This contractile defect was maintained over time without overt cardiac remodelling until 10 months of age, after which the mice ultimately developed severe heart failure and reduced lifespan. Acute downregulation of EGFR in adult floxed EGFR mice with adeno-associated virus 9 (AAV9)-encoded Cre with a cardiac troponin T promoter (AAV9-cTnT-Cre) recapitulated the CM-EGFR-KD phenotype, while AAV9-cTnT-EGFR treatment of adult CM-EGFR-KD mice rescued the phenotype. Notably, chronic administration of the β-adrenergic receptor agonist isoproterenol effectively and reversibly compensated for the contractile dysfunction in the absence of cardiomyocyte hypertrophy in CM-EGFR-KD mice. Mechanistically, EGFR downregulation reduced the expression of protein phosphatase 2A regulatory subunit Ppp2r3a/PR72, which was associated with decreased phosphorylation of phospholamban and Ca2+ clearance, and whose re-expression via AAV9-cTnT-PR72 rescued the CM-EGFR-KD phenotype.ConclusionsAltogether, our study highlights a previously unrecognized role for EGFR in maintaining contractile homeostasis under physiologic conditions in the adult heart via regulation of PR72 expression.

Project description:BACKGROUND:?2-adrenergic receptors (?2ARs) are the target of catecholamines and play fundamental roles in cardiovascular, pulmonary, and skeletal muscle physiology. An important action of ?2AR stimulation on skeletal muscle is anabolic growth, which has led to the use of agonists such as clenbuterol by athletes to enhance muscle performance. While previous work has demonstrated that ?2ARs can engage distinct signaling and functional cascades mediated by either G proteins or the multifunctional adaptor protein, ?-arrestin, the precise role of ?-arrestin in skeletal muscle physiology is not known. Here, we tested the hypothesis that agonist activation of the ?2AR by clenbuterol would engage ?-arrestin as a key transducer of anabolic skeletal muscle growth. METHODS:The contractile force of isolated extensor digitorum longus muscle (EDL) and calcium signaling in isolated flexor digitorum brevis (FDB) fibers were examined from the wild-type (WT) and ?-arrestin 1 knockout mice (?arr1KO) followed by chronic administration of clenbuterol (1?mg/kg/d). Hypertrophic responses including fiber composition and fiber size were examined by immunohistochemical imaging. We performed a targeted phosphoproteomic analysis on clenbuterol stimulated primary cultured myoblasts from WT and ?arr1KO mice. Statistical significance was determined by using a two-way analysis with Sidak's or Tukey's multiple comparison test and the Student's t test. RESULTS:Chronic administration of clenbuterol to WT mice enhanced the contractile force of EDL muscle and calcium signaling in isolated FDB fibers. In contrast, when administered to ?arr1KO mice, the effect of clenbuterol on contractile force and calcium influx was blunted. While clenbuterol-induced hypertrophic responses were observed in WT mice, this response was abrogated in mice lacking ?-arrestin 1. In primary cultured myoblasts, clenbuterol-stimulated phosphorylation of multiple pro-hypertrophy proteins required the presence of ?-arrestin 1. CONCLUSIONS:We have identified a previously unappreciated role for ?-arrestin 1 in mediating ?2AR-stimulated skeletal muscle growth and strength. We propose these findings could have important implications in the design of future pharmacologic agents aimed at reversing pathological conditions associated with skeletal muscle wasting.

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?-adrenergic receptor-mediated cardiac contractility is inhibited via vasopressin type 1A-receptor-dependent signaling.

Publications

β-adrenergic receptor-mediated cardiac contractility is inhibited via vasopressin type 1A-receptor-dependent signaling.

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