Prognostic Value of Lymphocyte G Protein-Coupled Receptor Kinase-2 Protein Levels in Patients With Heart Failure.

RATIONALE: Sympathetic nervous system hyperactivity is associated with poor prognosis in patients with heart failure (HF), yet routine assessment of sympathetic nervous system activation is not recommended for clinical practice. Myocardial G protein-coupled receptor kinase-2 (GRK2) is upregulated in HF patients, causing dysfunctional ß-adrenergic receptor signaling. Importantly, myocardial GRK2 levels correlate with levels found in peripheral lymphocytes of HF patients. OBJECTIVE: The independent prognostic value of blood GRK2 measurements in HF patients has never been investigated; thus, the purpose of this study was to evaluate whether lymphocyte GRK2 levels predict clinical outcome in HF patients. METHODS AND RESULTS: We prospectively studied 257 HF patients with mean left ventricular ejection fraction of 31.4±8.5%. At the time of enrollment, plasma norepinephrine, serum NT-proBNP, and lymphocyte GRK2 levels, as well as clinical and instrumental variables were measured. The prognostic value of GRK2 to predict cardiovascular (CV) death and all-cause mortality was assessed using the Cox proportional hazard model including demographic, clinical, instrumental, and laboratory data. Over a mean follow-up period of 37.5±20.2 months (range, 3-60 months), there were 102 CV deaths. Age, left ventricular ejection fraction, New York Heart Association class, chronic obstructive pulmonary disease, chronic kidney disease, N-terminal-pro brain natriuretic peptide, and lymphocyte GRK2 protein levels were independent predictors of CV mortality in HF patients. GRK2 levels showed an additional prognostic and clinical value over demographic and clinical variables. The independent prognostic value of lymphocyte GRK2 levels was also confirmed for all-cause mortality. CONCLUSIONS: Lymphocyte GRK2 protein levels can independently predict prognosis in patients with HF.

ß Adrenergic Receptor Kinase C-Terminal Peptide Gene-Therapy Improves ß2-Adrenergic Receptor-Dependent Neoangiogenesis after Hindlimb Ischemia.

After hindlimb ischemia (HI), increased catecholamine levels within the ischemic muscle can cause dysregulation of ß2-adrenergic receptor (ß2AR) signaling, leading to reduced revascularization. Indeed, in vivo ß2AR overexpression via gene therapy enhances angiogenesis in a rat model of HI. G protein-coupled receptor kinase 2 (GRK2) is a key regulator of ßAR signaling, and ß adrenergic receptor kinase C-terminal peptide (ßARKct), a peptide inhibitor of GRK2, has been shown to prevent ßAR down-regulation and to protect cardiac myocytes and stem cells from ischemic injury through restoration of ß2AR protective signaling (i.e., protein kinase B/endothelial nitric oxide synthase). Herein, we tested the potential therapeutic effects of adenoviral-mediated ßARKct gene transfer in an experimental model of HI and its effects on ßAR signaling and on endothelial cell (EC) function in vitro. Accordingly, in this study, we surgically induced HI in rats by femoral artery resection (FAR). Fifteen days of ischemia resulted in significant ßAR down-regulation that was paralleled by an approximately 2-fold increase in GRK2 levels in the ischemic muscle. Importantly, in vivo gene transfer of the ßARKct in the hindlimb of rats at the time of FAR resulted in a marked improvement of hindlimb perfusion, with increased capillary and ßAR density in the ischemic muscle, compared with control groups. The effect of ßARKct expression was also assessed in vitro in cultured ECs. Interestingly, ECs expressing the ßARKct fenoterol, a ß2AR-agonist, induced enhanced ß2AR proangiogenic signaling and increased EC function. Our results suggest that ßARKct gene therapy and subsequent GRK2 inhibition promotes angiogenesis in a model of HI by preventing ischemia-induced ß2AR down-regulation.

GRK2 as a therapeutic target for heart failure.

INTRODUCTION: G protein-coupled receptor (GPCR) kinase-2 (GRK2) is a regulator of GPCRs, in particular ß-adrenergic receptors (ARs), and as demonstrated by decades of investigation, it has a pivotal role in the development and progression of cardiovascular disease, like heart failure (HF). Indeed elevated levels and activity of this kinase are able to promote the dysfunction of both cardiac and adrenal α- and ß-ARs and to dysregulate other protective signaling pathway, such as sphingosine 1-phospate and insulin. Moreover, recent discoveries suggest that GRK2 can signal independently from GPCRs, in a 'non-canonical' manner, via interaction with non-GPCR molecule or via its mitochondrial localization. Areas covered: Based on this premise, GRK2 inhibition or its genetic deletion has been tested in several disparate animal models of cardiovascular disease, showing to protect the heart from adverse remodeling and dysfunction. Expert opinion: HF is one of the leading cause of death worldwide with enormous health care costs. For this reason, the identification of new therapeutic targets like GRK2 and strategies such as its inhibition represents a new hope in the fight against HF development and progression. Herein, we will update the readers about the 'state-of-art' of GRK2 inhibition as a potent therapeutic strategy in HF.

Aldosterone and Mineralocorticoid Receptor System in Cardiovascular Physiology and Pathophysiology.

The mineralocorticoid hormone aldosterone (Aldo) has been intensively studied for its ability to influence both the physiology and pathophysiology of the cardiovascular system. Indeed, although research on Aldo actions for decades has mainly focused on its effects in the kidney, several lines of evidence have now demonstrated that this hormone exerts disparate extrarenal adverse effects, especially in the circulatory system. Accordingly, in the last lusters, a number of studies in preclinical models (in vitro and in vivo) and in humans have established that Aldo, following the interaction with its receptor-the mineralocorticoid receptor (MR)-is able to activate specific intracellular genomic and nongenomic pathways, thus regulating the homeostasis of the cardiovascular system. Importantly, through this mechanism of action, this hormone becomes a crucial regulator of the function and growth of different types of cells, including fibroblasts, cardiomyocytes, and vascular cells. For this main reason, it is plausible that when Aldo is present at high levels in the blood, it profoundly modifies the physiology of these cells, therefore being at the foundation of several cardiovascular disorders, such as heart failure (HF). On these grounds, in this review, we will provide an updated account on the current knowledge concerning Aldo activity in the cardiovascular system and the most recent preclinical studies and clinical trials designed to test better approaches able to counter the hyperactivity of the Aldo/MR signaling pathway in the setting of cardiovascular diseases.

Long-Term Caloric Restriction Improves Cardiac Function, Remodeling, Adrenergic Responsiveness, and Sympathetic Innervation in a Model of Postischemic Heart Failure.

BACKGROUND: Caloric restriction (CR) has been described to have cardioprotective effects and improve functional outcomes in animal models and humans. Chronic ischemic heart failure (HF) is associated with reduced cardiac sympathetic innervation, dysfunctional ß-adrenergic receptor signaling, and decreased cardiac inotropic reserve. We tested the effects of a long-term CR diet, started late after myocardial infarction on cardiac function, sympathetic innervation, and ß-adrenergic receptor responsiveness in a rat model of postischemic HF. METHODS AND RESULTS: Adult male rats were randomly assigned to myocardial infarction or sham operation and 4 weeks later were further randomized to a 1-year CR or normal diet. One year of CR resulted in a significant reduction in body weight, heart weight, and heart weight/tibia length ratio when compared with normal diet in HF groups. At the end of the study period, echocardiography and histology revealed that HF animals under the CR diet had ameliorated left ventricular remodeling compared with HF rats fed with normal diet. Invasive hemodynamic showed a significant improvement of cardiac inotropic reserve in CR HF rats compared with HF-normal diet animals. Importantly, CR dietary regimen was associated with a significant increase of cardiac sympathetic innervation and with normalized cardiac ß-adrenergic receptor levels in HF rats when compared with HF rats on the standard diet. CONCLUSIONS: We demonstrate, for the first time, that chronic CR, when started after HF established, can ameliorate cardiac dysfunction and improve inotropic reserve. At the molecular level, we find that chronic CR diet significantly improves sympathetic cardiac innervation and ß-adrenergic receptor levels in failing myocardium.