This study shows that the NLRP3 inflammasome is up-regulated in myocardial fibroblasts post-MI, and may be a significant contributor to infarct size development during ischaemia-reperfusion.

G protein-coupled receptor (GPCR) kinases (GRKs) are critical regulators of cellular signaling and function. In cardiomyocytes, GRK2 and GRK5 are two GRKs important for myocardial regulation, and both have been shown to be up-regulated in the dysfunctional heart. We report that increased levels and activity of GRK5 in failing myocardium may have unique significance due to its nuclear localization, a property not shared by GRK2. We find that transgenic mice with elevated cardiac GRK5 levels have exaggerated hypertrophy and early heart failure compared with control mice after pressure overload. This pathology is not present in cardiac GRK2-overexpressing mice or in mice with overexpression of a mutant GRK5 that is excluded from the nucleus. Nuclear accumulation of GRK5 is enhanced in myocytes after aortic banding in vivo and in vitro in myocytes after increased Gαq activity, the trigger for pressure-overload hypertrophy. GRK5 enhances activation of MEF2 in concert with Gq signals, demonstrating that nuclear localized GRK5 regulates gene transcription via a pathway critically linked to myocardial hypertrophy. Mechanistically, we show that this is due to GRK5 acting, in a non-GPCR manner, as a class II histone deacetylase (HDAC) kinase because it can associate with and phosphorylate the myocyte enhancer factor-2 repressor, HDAC5. Moreover, significant HDAC activity can be found with GRK5 in the heart. Our data show that GRK5 is a nuclear HDAC kinase that plays a key role in maladaptive cardiac hypertrophy apparently independent of any action directly on GPCRs.

Our demonstration of enhanced systemic and myocardial NGAL expression in clinical and experimental HF further support a role for innate immune responses in the pathogenesis of HF.

Evidence from both experimental and clinical trials indicates that inflammatory mediators are of importance in the pathogenesis of chronic heart failure (HF) contributing to cardiac remodeling and peripheral vascular disturbances. Several studies have shown raised levels of inflammatory cytokines such as tumor necrosis factor (TNF)α, interleukin (IL)-1β and IL-6 in HF patients in plasma and circulating leukocytes, as well as in the failing myocardium itself. There is strong evidence that these mediators are involved in processes leading to cardiac remodeling such as hypertrophy, fibrosis and apoptosis. Some of these cytokines can also give useful prognostic information as reliable biomarkers in this disorder. In general, immunomodulating treatments have, with a few exceptions, been neutral or even harmful. However, the negative results of anti-TNF studies, for instance, do not necessarily argue against the ‘cytokine hypothesis’. These studies just underscore the challenges in developing treatment modalities that can modulate the cytokine network in HF patients and result in beneficial net effects. Future studies should identify the crucial actors and their mechanisms of action in the immunopathogenesis of chronic HF and, in particular, clarify the balance between adaptive and maladaptive effects of these molecules. Such studies are a prerequisite for the development of new treatment strategies that target inflammatory and immunopathogenic mechanisms in HF. In this review article, these issues are thoroughly discussed, and we also argue for the possibility of future therapeutic targets such as mediators in innate immunity, chemokines and mediators in matrix remodeling.

Abstract-Myocardial G protein-coupled receptor kinase (GRK)2 is a critical regulator of cardiac ␤-adrenergic receptor (␤AR) signaling and cardiac function. Its upregulation in heart failure may further depress cardiac function and contribute to mortality in this syndrome. Preventing GRK2 translocation to activated ␤AR with a GRK2-derived peptide that binds G ␤ ␥ (␤ARKct) has benefited some models of heart failure, but the precise mechanism is uncertain, because GRK2 is still present and ␤ARKct has other potential effects. We generated mice in which cardiac myocyte GRK2 expression was normal during embryonic development but was ablated after birth (␣MHC-CreϫGRK2 fl/fl) or only after administration of tamoxifen (␣MHC-MerCreMerϫGRK2 fl/fl) and examined the consequences of GRK2 ablation before and after surgical coronary artery ligation on cardiac adaptation after myocardial infarction. Absence of GRK2 before coronary artery ligation prevented maladaptive postinfarction remodeling and preserved ␤AR responsiveness. Strikingly, GRK2 ablation initiated 10 days after infarction increased survival, enhanced cardiac contractile performance, and halted ventricular remodeling. These results demonstrate a specific causal role for GRK2 in postinfarction cardiac remodeling and heart failure and support therapeutic approaches of targeting GRK2 or restoring ␤AR signaling by other means to improve outcomes in heart failure.

Abstract-With increasing knowledge of basic molecular mechanisms governing the development of heart failure (HF), the possibility of specifically targeting key pathological players is evolving. Technology allowing for efficient in vivo transduction of myocardial tissue with long-term expression of a transgene enables translation of basic mechanistic knowledge into potential gene therapy approaches. Gene therapy in HF is in its infancy clinically with the predominant amount of experience being from animal models. Nevertheless, this challenging and promising field is gaining momentum as recent preclinical studies in larger animals have been carried out and, importantly, there are 2 newly initiated phase I clinical trials for HF gene therapy. To put it simply, 2 parameters are needed for achieving success with HF gene therapy: (1) clearly identified detrimental/beneficial molecular targets; and (2) the means to manipulate these targets at a molecular level in a sufficient number of cardiac cells. However, several obstacles do exist on our way to efficient and safe gene transfer to human myocardium. Some of these obstacles are discussed in this review; however, it primarily focuses on the molecular target systems that have been subjected to intense investigation over the last decade in an attempt to make gene therapy for human HF a reality.

CCN2/connective tissue growth factor (CTGF), a CCN family matricellular protein repressed in healthy hearts after birth, is induced in heart failure of various etiologies. Multiple cellular and biological functions have been assigned to CCN2/CTGF depending on cellular context. However, the functions and mechanisms of action of CCN2/CTGF in the heart as well as its roles in cardiac physiology and pathophysiology remain unknown. Transgenic mice with cardiac-restricted overexpression of CTGF (Tg-CTGF) were generated and compared with nontransgenic littermate control (NLC) mice. Tg-CTGF mice displayed slightly lower cardiac mass and inconspicuous increase of myocardial collagen compared with NLC mice but no evidence of contractile dysfunction. Analysis of the myocardial transcriptome by DNA microarray revealed activation of several distinct gene programs in Tg-CTGF hearts involved in cardioprotection and growth inhibition. Indeed, Tg-CTGF mice subjected to ischemia-reperfusion injury by in situ transient occlusion of the left anterior descending coronary artery in vivo displayed reduced vulnerability with markedly diminished infarct size. These findings were recapitulated in isolated hearts perfused with recombinant human (h)CTGF before the ischemia-reperfusion procedure. Consistently, Tg-CTGF hearts, as well as isolated adult cardiac myocytes exposed to recombinant hCTGF, displayed enhanced phosphorylation and activity of the Akt/p70S6 kinase/GSK-3β salvage kinase pathway and induction of several genes with reported cardioprotective functions. Inhibition of Akt activities also prevented the cardioprotective phenotype of hearts from Tg-CTGF mice. This report provides novel evidence that CTGF confers cardioprotection by salvage phosphokinase signaling leading to inhibition of GSK-3β activities, activation of phospho-SMAD2, and reprogramming of gene expression.

Background-A salient characteristic of dysfunctional myocardium progressing to heart failure is an upregulation of the adenylyl cyclase inhibitory guanine nucleotide (G) protein ␣ subunit, G␣ i2 . It has not been determined conclusively whether increased Gi activity in the heart is beneficial or deleterious in vivo. Gi signaling has been implicated in the mechanism of cardioprotective agents; however, no in vivo evidence exists that any of the G␣ subunits are cardioprotective. We have created a novel molecular tool to specifically address the role of Gi proteins in normal and dysfunctional myocardium. Methods and Results-We have developed a class-specific Gi inhibitor peptide, GiCT, composed of the region of G␣ i2 that interacts specifically with G protein-coupled receptors. GiCT inhibits Gi signals specifically in vitro and in vivo, whereas Gs and Gq signals are not affected. In vivo expression of GiCT in transgenic mice effectively causes a "functional knockout" of cardiac G␣ i2 signaling. Inducible, cardiac-specific GiCT transgenic mice display a baseline phenotype consistent with nontransgenic mice. However, when subjected to ischemia/reperfusion injury, GiCT transgenic mice demonstrate a significant increase in infarct size compared with nontransgenic mice (from 36.9Ϯ2.5% to 50.9Ϯ4.3%). Mechanistically, this post-ischemia/reperfusion phenotype includes increased myocardial apoptosis and resultant decreased contractile performance. Conclusions-Overall, our results demonstrate the in vivo utility of GiCT to dissect specific mechanisms attributed to Gi signaling in stressed myocardium. Our results with GiCT indicate that upregulation of G␣ i2 is an adaptive protective response after ischemia to shield myocytes from apoptosis.