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Pharmacological and Activated Fibroblast Targeting of G??-GRK2 After Myocardial Ischemia Attenuates Heart Failure Progression.

ABSTRACT: BACKGROUND:Cardiac fibroblasts are a critical cell population responsible for myocardial extracellular matrix homeostasis. Upon injury or pathological stimulation, these cells transform to an activated myofibroblast state and play a fundamental role in myocardial fibrosis and remodeling. Chronic sympathetic overstimulation, a hallmark of heart failure (HF), induces pathological signaling through G protein ?? (G??) subunits and their interaction with G protein-coupled receptor kinase 2 (GRK2). OBJECTIVES:This study investigated the hypothesis that G??-GRK2 inhibition and/or ablation after myocardial injury would attenuate pathological myofibroblast activation and cardiac remodeling. METHODS:The therapeutic potential of small molecule G??-GRK2 inhibition, alone or in combination with activated fibroblast- or myocyte-specific GRK2 ablation-each initiated after myocardial ischemia-reperfusion (I/R) injury-was investigated to evaluate the possible salutary effects on post-I/R fibroblast activation, pathological remodeling, and cardiac dysfunction. RESULTS:Small molecule G??-GRK2 inhibition initiated 1 week post-injury was cardioprotective in the I/R model of chronic HF, including preservation of cardiac contractility and a reduction in cardiac fibrotic remodeling. Systemic small molecule G??-GRK2 inhibition initiated 1 week post-I/R in cardiomyocyte-restricted GRK2 ablated mice (also post-I/R) still demonstrated significant cardioprotection, which suggested a potential protective role beyond the cardiomyocyte. Inducible ablation of GRK2 in activated fibroblasts (i.e., myofibroblasts) post-I/R injury demonstrated significant functional cardioprotection with reduced myofibroblast transformation and fibrosis. Systemic small molecule G??-GRK2 inhibition initiated 1 week post-I/R provided little to no further protection in mice with ablation of GRK2 in activated fibroblasts alone. Finally, G??-GRK2 inhibition significantly attenuated activation characteristics of failing human cardiac fibroblasts isolated from end-stage HF patients. CONCLUSIONS:These findings suggested consideration of a paradigm shift in the understanding of the therapeutic role of G??-GRK2 inhibition in treating HF and the potential therapeutic role for G??-GRK2 inhibition in limiting pathological myofibroblast activation, interstitial fibrosis, and HF progression.

SUBMITTER: Travers JG

PROVIDER: S-EPMC5564231 | biostudies-literature | 2017 Aug

REPOSITORIES: biostudies-literature

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Pharmacological and Activated Fibroblast Targeting of Gβγ-GRK2 After Myocardial Ischemia Attenuates Heart Failure Progression.

Travers Joshua G JG Kamal Fadia A FA Valiente-Alandi Iñigo I Nieman Michelle L ML Sargent Michelle A MA Lorenz John N JN Molkentin Jeffery D JD Blaxall Burns C BC

Journal of the American College of Cardiology 20170801 8

<h4>Background</h4>Cardiac fibroblasts are a critical cell population responsible for myocardial extracellular matrix homeostasis. Upon injury or pathological stimulation, these cells transform to an activated myofibroblast state and play a fundamental role in myocardial fibrosis and remodeling. Chronic sympathetic overstimulation, a hallmark of heart failure (HF), induces pathological signaling through G protein βγ (Gβγ) subunits and their interaction with G protein-coupled receptor kinase 2 (G ...[more]

PMID: 28818206

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Project description:Aims A kinase interacting protein 1 (AKIP1) stimulates physiological growth in cultured cardiomyocytes and attenuates ischemia / reperfusion (I/R) injury in ex vivo perfused hearts. We aimed to determine whether AKIP1 modulates the cardiac response to acute and chronic cardiac stress in vivo. Methods and results Transgenic mice with cardiac-specific overexpression of AKIP1 (AKIP1-TG) were created. AKIP1-TG mice and their wild type (WT) littermates displayed similar cardiac structure and function. Likewise, cardiac remodeling in response to transverse aortic constriction or permanent coronary artery ligation was identical in AKIP1-TG and WT littermates, as evidenced by serial cardiac magnetic resonance imaging and pressure-volume loop analysis. Histological indices of remodeling, including cardiomyocyte cross-sectional diameter, capillary density and left ventricular fibrosis were also similar in AKIP1-TG mice and WT littermates. When subjected to 45 minutes of ischemia followed by 24 hours of reperfusion, AKIP1-TG mice displayed a significant 2-fold reduction in myocardial infarct size and reductions in cardiac apoptosis. In contrast to previous reports, AKIP1 did not co-immunoprecipitate with or regulate the activity of the signaling molecules NF-κB, protein kinase A or AKT. AKIP1 was, however, enriched in cardiac mitochondria and co-immunoprecipitated with a key component of the mitochondrial permeability transition (MPT) pore, ATP-synthase. Finally, mitochondria isolated from AKIP1-TG hearts displayed markedly reduced calcium induced swelling, indicative of reduced MPT pore formation. Conclusions In contrast to in vitro studies, AKIP1 overexpression does not influence cardiac remodeling in response to chronic cardiac stress. AKIP1 does, however, reduce myocardial I/R injury through stabilization of the MPT pore. These findings suggest that AKIP1 deserves further investigation as a putative treatment target for cardioprotection from I/R injury during acute myocardial infarction.

Dataset Information

Pharmacological and Activated Fibroblast Targeting of G??-GRK2 After Myocardial Ischemia Attenuates Heart Failure Progression.

Publications

Pharmacological and Activated Fibroblast Targeting of Gβγ-GRK2 After Myocardial Ischemia Attenuates Heart Failure Progression.

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