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Left ventricular remodeling, including the deposition of excess extracellular matrix, is key to the pathogenesis of heart failure. The stress-inducible transcriptional regulator p8 is increased in failing human hearts and is required both for agonist-stimulated cardiomyocyte hypertrophy and for cardiac fibroblasts matrix metalloprotease-9 (MMP9) induction. In the heart, upregulation of autophagy is an adaptive response to stress and plays a causative role in cardiomyopathies. We have recently shown that p8 ablation in cardiac cells upregulates autophagy and that, in vivo, loss of p8 results in a decrease of cardiac function. Here we investigated the effects of p8 genetic deletion in mediating adverse myocardial remodeling. Unstressed p8-/- mouse hearts manifested complex alterations in the expression of fibrosis markers. In addition, these mice displayed elevated autophagy and apoptosis compared with p8+/+ mice. Transverse aortic constriction (TAC) induced left ventricular p8 expression in p8+/+ mice. Pressure overload caused left ventricular remodeling in both genotypes, however, p8-/- mice showed less cardiac fibrosis induction. Consistent with this, although MMP9 induction was attenuated in the p8-/- mice, induction of MMP2 and MMP3 were strikingly upregulated while TIMP2 was downregulated. Left ventricular autophagy increased after TAC and was significantly higher in the p8-/- mice. Thus p8-deletion results in reduced collagen fibrosis after TAC, but in turn, is associated with a detrimental higher increase in autophagy. These findings suggest a role for p8 in regulating in vivo key signaling pathways involved in the pathogenesis of heart failure. [ABSTRACT FROM AUTHOR]

Left ventricular (LV) remodeling after myocardial infarction (MI) results from hypertrophy of myocytes and activation of fibroblasts induced, in part, by ligand stimulation of the ANG II type 1 receptor (AT1R). The purpose of the present study was to explore the specific role for activation of the AT1aR subtype in post-MI remodeling and whether gentler differences exist in the patterns of remodeling in wild-type and AT1aR knockout (KO) mice. AT1aR-KO mice and wild-type littermates underwent coronary ligation to induce MI or sham procedures; echocardiography and hemodynamic evaluation were performed 6 wk later, and LV tissue was harvested for infarct size determination, morphometric measurements, and gene expression analysis. Survival and infarct size were similar among all male and female wild-type and AT1aR-KO mice. Hemodynamic indexes were also similar except for lower systolic blood pressure in the AT1aR-KO mice compared with wild-type mice. Male and female wild-type and male AT1aR-KO mice developed similar increases in LV chamber size, LV mass corrected for body weight (LV/BW), and myocyte cross-sectional area (CSA). However, female AT1aR-KO mice demonstrated no increase in LV/BW and myocyte CSA post-MI compared with shams. Both male and female wild-type mice demonstrated higher atrial natriuretic peptide (ANP) levels after MI, with female wild types being significantly greater than males. However, male and female AT1aR-KO mice developed no increase in ANP gene expression with MI despite an increase in LV mass and myocyte size in males. These data support that gender-specific patterns of LV and myocyte hypertrophy exist after MI in mice with a disrupted AT1aR gene, and suggest that myocyte hypertrophy post-MI in females relies, in part, on activation of the AT1aR. Further work is necessary to explore the potential mechanisms underlying these gender-based differences. [ABSTRACT FROM AUTHOR]

Presents information on a study which examined the point to which left ventricular remodeling occurs after myocardial infarction in wild-type mice, while assessing the workability of quantifying hemodynamics and parameters of ventricular remodeling. Why mice are important in the study of cardiovascular disease; Illustration of a thoracotomy in which epicardial ischemia was induced.

Presents information on a study on ventricular remodeling following myocardial infarction in a mouse. Importance of transgenic strains of mice as experimental species; Methods used in the study; Results of the study.

Introduction: Myocardial cyclic GMP (cGMP) elevation and activation of cGMP-dependent protein kinase (PKG) have been shown to attenuate pathological cardiac hypertrophy and remodeling. Expression of cardiac phosphodiesterase 9A (PDE9) is increased in HF patients and in mouse models of cardiac hypertrophy. PDE9 catalyses the breakdown of cGMP and has been shown to promote cardiac hypertrophy. Recent evidence suggests that PDE9 inhibition may be beneficial in HF, increasing cGMP and exerting anti-hypertrophic effects via PKG stimulation. A novel PDE9 inhibitor, CRD-733, has demonstrated safety in both preclinical and human studies, but has not yet been studied in models of hypertrophy. Hypothesis: PDE9 inhibition with CRD-733 can reverse established pressure overload-induced LVH in a murine model of HF. Methods: Left ventricular hypertrophy (LVH) was induced by transaortic constriction (TAC) in male C57/BL6J mice (n=58), alongside sham controls (n=10). On day 7, after established LVH, TAC mice were randomized to vehicle (n=17); or to CRD-733 at doses of 200 (n=10), 600 (n=10), 1000 (n=10) or 2000 (n=11) mg/kg/day by oral gavage (days 7-21). Primary endpoints included organ weights, echocardiography and invasive hemodynamics. Results: TAC induced a 53% increase in LV weight normalized to tibia length in vehicle treated mice at day 21 (7.71±0.29mg/mm vs. sham 5.04±0.15mg/mm; P<0.001). This increase was attenuated in mice treated with 600, 1000, and 2000 mg/kg/day CRD-733 (maximum reduction of 2.0±0.11 mg/mm, to 5.71±0.26 mg/mm, 75% reduction from vehicle; P<0.001). These findings were associated with complete normalization of TAC-induced increases in lung mass (P<0.001) and trends towards lower LV end diastolic pressure in drug-treated TAC mice (13.0±1.4mmHg in CRD-733 600mg/kg/day vs. 21.0±3.1mmHg in vehicle; P=0.08). Echocardiographic analysis showed that TAC-induced cardiac hypertrophy and left atrial dilation were reversed from day 6 to day 20 with CRD-733 treatment, but not with vehicle (P<0.05). Conclusion: CRD-733 reversed TAC-induced cardiac hypertrophy in mice and led to a reduction in lung mass, left atrial size, and LV end diastolic pressure. These findings support the potential of CRD-733 as a novel therapeutic agent in HF. [ABSTRACT FROM AUTHOR]

Background: Despite the well-established association between T-cell-mediated inflammation and nonischemic heart failure, the specific mechanisms triggering T-cell activation during the progression of heart failure and the antigens involved are poorly understood. We hypothesized that myocardial oxidative stress induces the formation of isolevuglandin (IsoLG)-modified proteins that function as cardiac neoantigens to elicit CD4+ T-cell receptor (TCR) activation and promote heart failure.Methods: We used transverse aortic constriction in mice to trigger myocardial oxidative stress and T-cell infiltration. We profiled the TCR repertoire by mRNA sequencing of intramyocardial activated CD4+ T cells in Nur77GFP reporter mice, which transiently express GFP on TCR engagement. We assessed the role of antigen presentation and TCR specificity in the development of cardiac dysfunction using antigen presentation-deficient MhcII-/- mice and TCR transgenic OTII mice that lack specificity for endogenous antigens. We detected IsoLG protein adducts in failing human hearts. We also evaluated the role of reactive oxygen species and IsoLGs in eliciting T-cell immune responses in vivo by treating mice with the antioxidant TEMPOL and the IsoLG scavenger 2-hydroxybenzylamine during transverse aortic constriction, and ex vivo in mechanistic studies of CD4+ T-cell proliferation in response to IsoLG-modified cardiac proteins.Results: We discovered that TCR antigen recognition increases in the left ventricle as cardiac dysfunction progresses and identified a limited repertoire of activated CD4+ T-cell clonotypes in the left ventricle. Antigen presentation of endogenous antigens was required to develop cardiac dysfunction because MhcII-/- mice reconstituted with CD4+ T cells and OTII mice immunized with their cognate antigen were protected from transverse aortic constriction-induced cardiac dysfunction despite the presence of left ventricle-infiltrated CD4+ T cells. Scavenging IsoLGs with 2-hydroxybenzylamine reduced TCR activation and prevented cardiac dysfunction. Mechanistically, cardiac pressure overload resulted in reactive oxygen species-dependent dendritic cell accumulation of IsoLG protein adducts, which induced robust CD4+ T-cell proliferation.Conclusions: Our study demonstrates an important role of reactive oxygen species-induced formation of IsoLG-modified cardiac neoantigens that lead to TCR-dependent CD4+ T-cell activation within the heart. [ABSTRACT FROM AUTHOR]

Heart failure with preserved ejection fraction (HFpEF) is a widespread syndrome with limited therapeutic options and poorly understood immune pathophysiology. Using a 2-hit preclinical model of cardiometabolic HFpEF that induces obesity and hypertension, we found that cardiac T cell infiltration and lymphoid expansion occurred concomitantly with cardiac pathology and that diastolic dysfunction, cardiomyocyte hypertrophy, and cardiac phospholamban phosphorylation were T cell dependent. Heart-infiltrating T cells were not restricted to cardiac antigens and were uniquely characterized by impaired activation of the inositol-requiring enzyme 1a/X-box-binding protein 1 (IRE1a/XBP1) arm of the unfolded protein response. Notably, selective ablation of XBP1 in T cells enhanced their persistence in the heart and lymphoid organs of mice with preclinical HFpEF. Furthermore, T cell IRE1a/XBP1 activation was restored after withdrawal of the 2 comorbidities inducing HFpEF, resulting in partial improvement of cardiac pathology. Our results demonstrated that diastolic dysfunction and cardiomyocyte hypertrophy in preclinical HFpEF were T cell dependent and that reversible dysregulation of the T cell IRE1a/XBP1 axis was a T cell signature of HFpEF. [ABSTRACT FROM AUTHOR]

Myocardial hypertrophy is an independent risk factor for heart failure (HF), yet the mechanisms underlying pathological cardiomyocyte growth are incompletely understood. The c-Jun NH2-terminal kinase (JNK) signaling cascade modulates cardiac hypertrophic remodeling, but the upstream factors regulating myocardial JNK activity remain unclear. In this study, we sought to identify JNK-activating molecules as novel regulators of cardiac remodeling in HF. We investigated mixed lineage kinase-3 (MLK3), a master regulator of upstream JNK-activating kinases, whose role in the remodeling process had not previously been studied. We observed increased MLK3 protein expression in myocardium from patients with nonischemic and hypertrophic cardiomyopathy and in hearts of mice subjected to transverse aortic constriction (TAC). Mice with genetic deletion of MLK3 (MLK3-/-) exhibited baseline cardiac hypertrophy with preserved cardiac function. MLK3-/- mice subjected to chronic left ventricular (LV) pressure overload (TAC, 4 wk) developed worsened cardiac dysfunction and increased LV chamber size compared with MLK3+/+ littermates (n = 8). LV mass, pathological markers of hypertrophy (Nppa, Nppb), and cardiomyocyte size were elevated in MLK3-/- TAC hearts. Phosphorylation of JNK, but not other MAPK pathways, was selectively impaired in MLK3-/- TAC hearts. In adult rat cardiomyocytes, pharmacological MLK3 kinase inhibition using URMC-099 blocked JNK phosphorylation induced by neurohormonal agents and oxidants. Sustained URMC-099 exposure induced cardiomyocyte hypertrophy. These data demonstrate that MLK3 prevents adverse cardiac remodeling in the setting of pressure overload. Mechanistically, MLK3 activates JNK, which in turn opposes cardiomyocyte hypertrophy. These results support modulation of MLK3 as a potential therapeutic approach in HF. [ABSTRACT FROM AUTHOR]

Heart Failure ( HF) is associated with increased circulating levels of aldosterone and systemic inflammation. Mineralocorticoid receptor ( MR) antagonists block aldosterone action and decrease mortality in patients with congestive HF. However, the molecular mechanisms underlying the therapeutic benefits of MR antagonists remain unclear. MR is expressed in all cell types in the heart, including the endothelial cells ( EC), in which aldosterone induces the expression of intercellular adhesion molecule 1 ( ICAM-1). Recently, we reported that ICAM-1 regulates cardiac inflammation and cardiac function in mice subjected to transverse aortic constriction ( TAC). Whether MR specifically in endothelial cells ( EC) contributes to the several mechanisms of pathological cardiac remodeling and cardiac dysfunction remains unclear. Basal cardiac function and LV dimensions were comparable in mice with MR selectively deleted from ECs ( EC- MR−/−) and wild-type littermate controls ( EC- MR+/+). MR was specifically deleted in heart EC, and in EC-containing tissues, but not in leukocytes of TAC EC- MR−/− mice. While EC- MR−/− TAC mice showed preserved systolic function and some alterations in the expression of fetal genes, the proinflammatory cytokine TNF α and the endothelin receptors in the LV as compared to EC- MR+/+ TAC mice, no difference was observed between both TAC groups in overall cardiac hypertrophy, ICAM-1 LV expression and leukocyte infiltration, cardiac fibrosis or capillary rarefaction, all hallmarks of pathological cardiac remodeling. Our data indicate that EC- MR contributes to the transition of cardiac hypertrophy to systolic dysfunction independently of other maladaptive changes induced by LV pressure overload. [ABSTRACT FROM AUTHOR]

Hypertensive heart disease causes significant mortality in older patients, yet there is an incomplete understanding of molecular mechanisms that regulate age-dependent hypertensive left ventricular hypertrophy (LVH). Therefore, we tested the hypothesis that the cGMP-dependent protein kinase G I alpha (PKGIα) attenuates hypertensive LVH by evaluating the cardiac phenotype in mice with selective mutations of the PKGIα leucine zipper domain. These leucine zipper mutant (LZM) mice develop basal hypertension. Compared with wild-type controls, 8-month-old adult LZM mice developed increased left ventricular end-diastolic pressure but without frank LVH. In advanced age (15 months), the LZM mice developed overt pathological LVH. These findings reveal a role of PKGIα in normally attenuating hypertensive LVH. Therefore, mutation of the PKGIα LZ domain produces a clinically relevant model for hypertensive heart disease of aging. [ABSTRACT FROM PUBLISHER]

: Right ventricular (RV) failure is a major cause of mortality in acute or chronic lung disease and left heart failure. The objective of this study was to demonstrate a percutaneous approach to study biventricular hemodynamics in murine models of primary and secondary RV pressure overload (RVPO) and further explore biventricular expression of two key proteins that regulate cardiac remodeling: calcineurin and transforming growth factor beta 1 (TGFβ1). Methods: Adult, male mice underwent constriction of the pulmonary artery or thoracic aorta as models of primary and secondary RVPO, respectively. Conductance catheterization was performed followed by tissue analysis for changes in myocyte hypertrophy and fibrosis. Results: Both primary and secondary RVPO decreased biventricular stroke work however RV instantaneous peak pressure (dP/dtmax) and end-systolic elastance (Ees) were preserved in both groups compared to controls. In contrast, left ventricular (LV) dP/dtmax and LV-Ees were unchanged by primary, but reduced in the secondary RVPO group. The ratio of RV:LV ventriculo-arterial coupling was increased in primary and reduced in secondary RVPO. Primary and secondary RVPO increased RV mass, while LV mass decreased in primary and increased in the secondary RVPO groups. RV fibrosis and hypertrophy were increased in both groups, while LV fibrosis and hypertrophy were increased in secondary RVPO only. RV calcineurin expression was increased in both groups, while LV expression increased in secondary RVPO only. Biventricular TGFβ1 expression was increased in both groups. Conclusion: These data identify distinct effects of primary and secondary RVPO on biventricular structure, function, and expression of key remodeling pathways. [ABSTRACT FROM AUTHOR]

In clinical trials, aldosterone antagonists reduce cardiovascular ischemia and mortality by unknown mechanisms. Aldosterone is a steroid hormone that signals through renal mineralocorticoid receptors (MRs) to regulate blood pressure. MRs are expressed and regulate gene transcription in human vascular cells, suggesting that aldosterone might have direct vascular effects. Using gene expression profiling, we identify the pro-proliferative VEGF family member placental growth factor (PGF) as an aldosterone-regulated vascular MR target gene in mice and humans. Aldosterone-activated vascular MR stimulated Pgf gene transcription and increased PGF protein expression and secretion in the mouse vasculature. In mouse vessels with endothelial damage and human vessels from patients with atherosclerosis, aldosterone enhanced expression of PGF and its receptor, FMS-like tyrosine kinase 1 (Flt1). In atherosclerotic human vessels, MR antagonists inhibited PGF expression. In vivo, aldosterone infusion augmented vascular remodeling in mouse carotids following wire injury, an effect that was lost in Pgf-/- mice. In summary, we have identified PGF as what we believe to be a novel downstream target of vascular MR that mediates aldosterone augmentation of vascular injury. These findings suggest a non-renal mechanism for the vascular protective effects of aldosterone antagonists in humans and support targeting the vascular aldosterone/MR/PGF/Flt1 pathway as a therapeutic strategy for ischemic cardiovascular disease. [ABSTRACT FROM AUTHOR]

Menopause is associated with increased adiposity and greater risk of metabolic disease. In the ovariectomized (OVX) rodent model of menopause, increased adiposity is prevented by estrogen (E2) replacement, reflecting both anorexigenic and potentially metabolic actions of E2. To elucidate metabolic and molecular mechanisms by which E2 regulates fat storage and fat mobilization independently of reduced energy intake, C57 BL/6 mice were ovariectomized, randomized to estrogen (OVX-E2) or control pellet implants (OVX-C), and pairfed for 40 days. E2 treatment was associated with reduced adipose mass and adipocyte size and down-regulation of lipogenic genes in adipocytes under the control of sterol-regulatory element-binding protein 1c. Adipocytes of OVX-E2 mice contained »3-fold more perilipin protein than adipocytes of pairfed control (OVX) mice, and this difference was associated with enhanced ex vivo lipolytic response to catecholamines and with greater levels of serum-free fatty acids following fasting. As in adipose tissue, E2 decreased the expression of lipogenic genes in liver and skeletal muscle. In the latter, E2 appears to promote the partitioning of free fatty acids toward oxidation and away from triglyceride storage by up-regulating the expression of peroxisome proliferation activator receptor-δ and its downstream targets and also by directly and rapidly activating AMP-activated protein kinase. Thus, novel genomic and non-genomic actions of E2 promote leanness in OVX mice independently of reduced energy intake. [ABSTRACT FROM AUTHOR]

: ObjectivesThis study was designed to examine the effects of estrogen replacement on infarct size, ventricular remodeling, and mortality after myocardial infarction (MI) in mice.: BackgroundObservational and clinical studies suggest that the cardiovascular effects of hormone replacement therapy can differ depending on the patient population studied. No prospective studies have examined the effect of estrogen on outcomes following MI. We now examine the effects of estrogen replacement on infarct size, ventricular remodeling, and mortality after MI in mice.: MethodsMyocardial infarction was induced by left coronary artery ligation in ovariectomized female mice treated with 17-beta-estradiol (E2) or placebo. At either one day or six weeks after MI, hemodynamic function was assessed, animals were euthanized, and infarct size was determined.: Results17-Beta-estradiol–treated mice had smaller infarcts than placebo-treated animals both one day (18% decrease; p < 0.01), and six weeks (14% decrease; p < 0.05) following MI. E2 reduced cardiomyocyte apoptosis as assessed by the terminal deoxynucleotidyl transferase uridine nucleotide end-labeling method (50% reduction, p < 0.05) and caspase 3 activation (33% reduction, p < 0.05). Despite having smaller infarcts, however, left ventricular mass increased more in the E2-treated animals (16% greater; p < 0.01). Left ventricular weight was positively correlated with infarct size in the estrogen-treated animals (R2 = 0.79, p = 0.0001). 17-Beta-estradiol treatment also significantly increased mortality in the infarcted animals (relative risk of death = 2.4; 95% confidence interval 1.2 to 5.3).: ConclusionsEstrogen replacement therapy reduces infarct size and cardiomyocyte apoptosis in mice. However, estrogen increased post-MI ventricular remodeling and mortality. Further studies will be necessary to elucidate the mechanisms underlying the complex effects of estrogen observed in the present study. [Copyright &y& Elsevier]

Type 1 diabetic Akita mice develop severe cardiac parasympathetic dysfunction that we have previously demonstrated is due at least in part to an abnormality in the response of the end organ to parasympathetic stimulation. Specifically, we had shown that hypoinsulinemia in the diabetic heart results in attenuation of the G-protein coupled inward rectifying K channel (GIRK) which mediates the negative chronotropic response to parasympathetic stimulation due at least in part to decreased expression of the GIRK1 and GIRK4 subunits of the channel. We further demonstrated that the expression of GIRK1 and GIRK4 is under the control of the Sterol Regulatory element Binding Protein (SREBP-1), which is also decreased in response to hypoinsulinemia. Finally, given that hyperactivity of Glycogen Synthase Kinase (GSK)3β, had been demonstrated in the diabetic heart, we demonstrated that treatment of Akita mice with Li+, an inhibitor of GSK3β, increased parasympathetic responsiveness and SREBP-1 levels consistent with the conclusion that GSK3β might regulate IKACh via an effect on SREBP-1. However, inhibitor studies were complicated by lack of specificity for GSK3β. Here we generated an Akita mouse with cardiac specific inducible knockout of GSK3β. Using this mouse, we demonstrate that attenuation of GSK3β expression is associated with an increase in parasympathetic responsiveness measured as an increase in the heart rate response to atropine from 17.3 ± 3.5% (n = 8) prior to 41.2 ± 5.4% (n = 8, P = 0.017), an increase in the duration of carbamylcholine mediated bradycardia from 8.43 ± 1.60 min (n = 7) to 12.71 ± 2.26 min (n = 7, P = 0.028) and an increase in HRV as measured by an increase in the high frequency fraction from 40.78 ± 3.86% to 65.04 ± 5.64 (n = 10, P = 0.005). Furthermore, patch clamp measurements demonstrated a 3-fold increase in acetylcholine stimulated peak IKACh in atrial myocytes from GSK3β deficiency mice compared with control. Finally, western blot analysis of atrial extracts from knockout mice demonstrated increased levels of SREBP-1, GIRK1 and GIRK4 compared with control. Taken together with our prior observations, these data establish a role of increased GSK3β activity in the pathogenesis of parasympathetic dysfunction in type 1 diabetes via the regulation of IKACh and GIRK1/4 expression. [ABSTRACT FROM AUTHOR]

Women gain weight and their diabetes risk increases as they transition through menopause; these changes can be partly reversed by hormone therapy. However, the underlying molecular mechanisms mediating these effects are unknown. A novel knock-in mouse line with the selective blockade of the membrane-initiated estrogen receptor (ER) pathway was used, and we found that the lack of this pathway precipitated excessive weight gain and glucose intolerance independent of food intake and that this was accompanied by impaired adaptive thermogenesis and reduced physical activity. Notably, the central activation of protein phosphatase (PP) 2A improved metabolic disorders induced by the lack of membrane-initiated ER signaling. Furthermore, the antiobesity effect of estrogen replacement in a murine menopause model was abolished by central PP2A inactivation. These findings define a critical role for membrane-initiated ER signaling in metabolic homeostasis via the central action of PP2A. [ABSTRACT FROM AUTHOR]

Supplemental Digital Content is available in the text. Background: Heart failure is a growing cause of morbidity and mortality worldwide. Transforming growth factor beta (TGF-β1) promotes cardiac fibrosis, but also activates counterregulatory pathways that serve to regulate TGF-β1 activity in heart failure. Bone morphogenetic protein 9 (BMP9) is a member of the TGFβ family of cytokines and signals via the downstream effector protein Smad1. Endoglin is a TGFβ coreceptor that promotes TGF-β1 signaling via Smad3 and binds BMP9 with high affinity. We hypothesized that BMP9 limits cardiac fibrosis by activating Smad1 and attenuating Smad3, and, furthermore, that neutralizing endoglin activity promotes BMP9 activity. Methods: We examined BMP9 expression and signaling in human cardiac fibroblasts and human subjects with heart failure. We used the transverse aortic constriction–induced model of heart failure to evaluate the functional effect of BMP9 signaling on cardiac remodeling. Results: BMP9 expression is increased in the circulation and left ventricle (LV) of human subjects with heart failure and is expressed by cardiac fibroblasts. Next, we observed that BMP9 attenuates type I collagen synthesis in human cardiac fibroblasts using recombinant human BMP9 and a small interfering RNA approach. In BMP9–/– mice subjected to transverse aortic constriction, loss of BMP9 activity promotes cardiac fibrosis, impairs LV function, and increases LV levels of phosphorylated Smad3 (pSmad3), not pSmad1. In contrast, treatment of wild-type mice subjected to transverse aortic constriction with recombinant BMP9 limits progression of cardiac fibrosis, improves LV function, enhances myocardial capillary density, and increases LV levels of pSmad1, not pSmad3 in comparison with vehicle-treated controls. Because endoglin binds BMP9 with high affinity, we explored the effect of reduced endoglin activity on BMP9 activity. Neutralizing endoglin activity in human cardiac fibroblasts or in wild-type mice subjected to transverse aortic constriction–induced heart failure limits collagen production, increases BMP9 protein levels, and increases levels of pSmad1, not pSmad3. Conclusions: Our results identify a novel functional role for BMP9 as an endogenous inhibitor of cardiac fibrosis attributable to LV pressure overload and further show that treatment with either recombinant BMP9 or disruption of endoglin activity promotes BMP9 activity and limits cardiac fibrosis in heart failure, thereby providing potentially novel therapeutic approaches for patients with heart failure. [ABSTRACT FROM AUTHOR]

Introduction Activin receptor-like kinase 1 (ALK1) mediates signaling via the transforming growth factor beta-1 (TGFβ1), a pro-fibrogenic cytokine. No studies have defined a role for ALK1 in heart failure. Hypothesis We tested the hypothesis that reduced ALK1 expression promotes maladaptive cardiac remodeling in heart failure. Methods and results In patients with advanced heart failure referred for left ventricular (LV) assist device implantation, LV Alk1 mRNA and protein levels were lower than control LV obtained from patients without heart failure. To investigate the role of ALK1 in heart failure, Alk1 haploinsufficient ( Alk1 +/− ) and wild-type (WT) mice were studied 2 weeks after severe transverse aortic constriction (TAC). LV and lung weights were higher in Alk1 +/− mice after TAC. Cardiomyocyte area and LV mRNA levels of brain natriuretic peptide and β-myosin heavy chain were increased similarly in Alk1 +/− and WT mice after TAC. Alk-1 mice exhibited reduced Smad 1 phosphorylation and signaling compared to WT mice after TAC. Compared to WT, LV fibrosis and Type 1 collagen mRNA and protein levels were higher in Alk1 +/− mice. LV fractional shortening was lower in Alk1 +/− mice after TAC. Conclusions Reduced expression of ALK1 promotes cardiac fibrosis and impaired LV function in a murine model of heart failure. Further studies examining the role of ALK1 and ALK1 inhibitors on cardiac remodeling are required. [ABSTRACT FROM AUTHOR]

Activin like kinase-1 (AlK-1) mediates signaling via the transforming growth factor beta (TGFβ) family of ligands. AlK-1 activity promotes endothelial proliferation and migration. Reduced AlK-1 activity is associated with arteriovenous malformations. No studies have examined the effect of global AlK-1 deletion on indices of cardiac remodeling. We hypothesized that reduced levels of AlK-1 promote maladaptive cardiac remodeling. To test this hypothesis, we employed AlK-1 conditional knockout mice (cKO) harboring the ROSA26-CreER knock-in allele, whereby a single dose of intraperitoneal tamoxifen triggered ubiquitous Cre recombinase-mediated excision of floxed AlK-1 alleles. Tamoxifen treated wild-type (WT-TAM; n = 5) and vehicle treated AlK-1-cKO mice (cKO-CON; n = 5) served as controls for tamoxifen treated AlK-1-cKO mice (cKO-TAM; n = 15). AlK-1 cKO-TAM mice demonstrated reduced 14-day survival compared to cKO-CON controls (13 vs 100%, respectively, p < 0.01). Seven days after treatment, cKO-TAM mice exhibited reduced left ventricular (LV) fractional shortening, progressive LV dilation, and gastrointestinal bleeding. After 14 days total body mass was reduced, but LV and lung mass increased in cKO-TAM not cKO-CON mice. Peak LV systolic pressure, contractility, and arterial elastance were reduced, but LV end-diastolic pressure and stroke volume were increased in cKO-TAM, not cKO-CON mice. LV AlK-1 mRNA levels were reduced in cKO-TAM, not cKO-CON mice. LV levels of other TGFβ-family ligands and receptors (AlK5, TBRII, BMPRII, Endoglin, BMP7, BMP9, and TGFβ1) were unchanged between groups. Cardiomyocyte area and LV levels of BNP were increased in cKO-TAM mice, but LV levels of β-MHC and SERCA were unchanged. No increase in markers of cardiac fibrosis, Type I collagen, CTGF, or PAI-1, were observed between groups. No differences were observed for any variable studied between cKO-CON and WT-TAM mice. Global deletion of AlK-1 is associated with the development of high output heart failure without maladaptive remodeling. Future studies exploring the functional role of AlK-1 in cardiac remodeling independent of systemic AVMs are required. [ABSTRACT FROM AUTHOR]

Introduction Transient receptor potential (TRP) channels are broadly expressed cation channels that mediate diverse physiological stimuli and include canonical (TRPC), melastatin (TRPM), and vanilloid (TRPV) subtypes. Recent studies have implicated a role for TRPC6 channels as an important component of signaling via the cytokine, transforming growth factor beta 1 (TGFβ1) in right (RV) or left ventricular (LV) failure. Endoglin (Eng) is a transmembrane glycoprotein that promotes TRPC6 expression and TGFβ1 activity. No studies have defined biventricular expression of all TRP channel family members in heart failure. Hypothesis We hypothesized that heart failure is associated with distinct patterns of TRP channel expression in the LV and RV. Methods Paired viable LV and RV free wall tissue was obtained from human subjects with end-stage heart failure ( n =12) referred for cardiac transplantation or biventricular assist device implantation. Paired LV and RV samples from human subjects without heart failure served as controls ( n =3). To explore a functional role for Eng as a regulator of TRP expression in response to RV or LV pressure overload, wild-type ( Eng +/+ ) and Eng haploinsufficient ( Eng +/− ) mice were exposed to thoracic aortic (TAC) or pulmonary arterial (PAC) constriction for 8 weeks. Biventricular tissue was analyzed by real-time polymerase chain reaction. Results Compared to nonfailing human LV and RV samples, mRNA levels of TRPC1, 3, 4, 6, and TRPV-2 were increased and TRPM2, 3, and 8 were decreased in failing LV and RV samples. TRPC1 and 6 levels were higher in failing RV compared to failing LV samples. After TAC, murine LV levels of TPRC1 and 6 were increased in both Eng +/+ and Eng +/− mice compared to sham controls. LV levels of TRPC4, TRPM3 and 7, TRPV2 and 4 were increased in Eng +/+ , not in Eng +/− mice after TAC. After PAC, all TRP channel family members were increased in the RV, but not LV, of Eng +/+ compared to sham controls. In contrast to Eng +/+ , PAC did not increase RV or LV levels of TRP channels in Eng +/− mice. Conclusions This is the first study to demonstrate that TRP channels exhibit distinct profiles of expression in the LV and RV of patients with heart failure and in murine models of univentricular pressure overload. We further introduce that the TGFβ1 coreceptor Eng selectively regulates expression of multiple TRP channels in the setting of LV or RV pressure overload. [ABSTRACT FROM AUTHOR]

MicroRNA-offset RNAs (moRs) were first identified in simple chordates and subsequently in mouse and human cells by deep sequencing of short RNAs. MoRs are derived from sequences located immediately adjacent to microRNAs (miRs) in the primary miR (pri-miR). Currently moRs are considered to be simply a by-product of miR biosynthesis that lack biological activity. Here we show for the first time that a moR is biologically active. We demonstrate that endogenous or over-expressed moR-21 significantly alters gene expression and inhibits the proliferation of vascular smooth muscle cells (VSMC). In addition, we find that miR-21 and moR-21 may regulate different genes in a given pathway and can oppose each other in regulating certain genes. We report that there is a “seed region” of moR-21 as well as a “seed match region” in the target gene 3’UTR that are indispensable for moR-21-mediated gene down-regulation. We further demonstrate that moR-21-mediated gene repression is Argonaute 2 (Ago2) dependent. Taken together, these findings provide the first evidence that microRNA offset RNA alters gene expression and is biologically active. [ABSTRACT FROM AUTHOR]

R2804 --> 10.3 --> Introduction: Heart Failure with Preserved Ejection Fraction (HFpEF) is an uncurable widespread syndrome characterized by impaired cardiac relaxation (diastolic function), preserved cardiac contractility (systolic function), and the concordance of several comorbidities, such as obesity and hypertension. While T cell inflammation is known to contribute to HF with reduced cardiac contractility (HF with reduced EF), whether T cell inflammation occurs in HFpEF remains elusive. Recently, downregulation of the unfolded protein response (UPR) in cardiomyocytes was identified as a cardiometabolic HFpEF‐unique molecular signature. Interestingly, downregulation of the UPR has been reported to improve T cell anti‐tumor inflammatory responses. We hypothesized T cells contribute to diastolic dysfunction in HFpEF following T cell UPR downregulation in response to metabolic and nitrosative stress. Methods: We modeled cardiometabolic HFpEF in male C57/Bl6 (WT), Nur77‐GFP mice, reporter mice for T cell antigen engagement, and T cell receptor‐a (Tcra−/−) mice using high‐fat diet (HFD) and L‐NAME‐supplemented drinking water to mimic obesity and hypertension, respectively. Mice fed standard chow (STD) were used as controls. Invasive hemodynamic analyses were used to measure cardiac function. Immune populations in the heart, mediastinal lymph nodes (MdLN), and spleen were characterized using flow cytometry. CD4+ T cells from MdLN and spleen were isolated using magnetic‐assisted cell sorting, and UPR gene expression was assessed using qPCR. Results: We observed significant increases in cardiac CD4+ T cells in WT mice fed HFD/L‐NAME, concordant with diastolic dysfunction and preserved EF, compared to STD mice. We found increased effector CD4+CD62LloCD44hiIFNγ+ T cells in spleens and MdLN isolated from WT HFD/L‐NAME mice compared to STD controls. Nur77‐GFP mice revealed no antigen recognition by CD4+ T cells in the heart following HFD/L‐NAME. Tcra−/−mice fed HFD/L‐NAME did not develop diastolic dysfunction or cardiomyocyte hypertrophy. Strikingly, qPCR analysis of splenic T cells of WT HFD/L‐NAME mice revealed significantly decreased expression of spliced X box‐binding protein 1 (XBP1s), compared to controls, with no significant changes in unspliced XBP1 or activating transcription factor 4 (ATF4). ATF6 and C/EBP homologous protein (CHOP) gene expression was also reduced compared to T cells from control mice. Conclusion: Our data demonstrate that diastolic dysfunction and cardiomyocyte hypertrophy are T cell dependent in preclinical cardiometabolic HFpEF and reveal downregulation of two branches of the T cell UPR as a potential novel mechanism that contributes to T cell inflammation in HFpEF. [ABSTRACT FROM AUTHOR]

R3436 --> 10.4 --> Heart failure (HF) is a leading cause of death worldwide, associated with cardiac and systemic inflammation. However, no anti‐inflammatory therapies have shown success. Damage associated molecular patterns (DAMPs) released in the heart activate myeloid cells through the adaptor "Myeloid differentiation primary response 88" (MyD88). This signaling cascade promotes cardiac antigen presentation to activate helper T‐cells. Once activated, T‐cells then infiltrate the heart and bind to VCAM‐1 on cardiac fibroblasts, (CFB), transforming them to myofibroblasts which coordinate cardiac fibrosis. MyD88 is also expressed in T‐cells, yet whether it is pro or anti‐inflammatory is less explored, and evidence suggests is context dependent. To investigate the role of T‐cell MyD88 in HF, we reconstituted Tcra‐/‐ mice, normally protected from HF induced by transaortic constriction (TAC), with WT or Myd88‐/‐ Type 1 helper T‐cells (Th1) in the onset of TAC. Surprisingly, we found that mice receiving Myd88‐/‐ Th1 cells showed increased cardiac T‐cells and fibrosis compared to mice receiving WT cells. We hypothesized that T‐cell MyD88 regulates cardiac T‐cell recruitment and survival, and as a result subsequent cardiac fibrosis. We found that Myd88‐/‐ Th1 cells exhibited increased survival in vitro determined by real time imaging of propidium iodide incorporation, as well as in vivo by performing competitive survival studies in which Tcra‐/‐ mice received equal WT CD45.1 Th1 cells and Myd88‐/‐ CD45.2 Th1 cells. Myd88‐/‐ Th1 cells also induced higher CFB α‐smooth muscle actin staining when cultured together, as well as bound more frequently to CFB and immobilized VCAM‐1. Together these data demonstrate that MyD88 limits T‐cell mediated cardiac fibrosis by regulating T‐cell survival, as well as by dampening T‐cell/fibroblast interactions. We identify novel role for T‐cell MyD88 in cardiac inflammation that may be modulated in HF. [ABSTRACT FROM AUTHOR]

Decreased heart rate variability (HRV) is a major risk factor for sudden death and cardiovascular disease. We previously demonstrated that parasympathetic dysfunction in the heart of the Akita type 1 diabetic mouse was due to a decrease in the level of the sterol response element-binding protein (SREBP-1). Here we demonstrate that hyperactivity of glycogen synthase kinase-3β (GSK3β) in the atrium of the Akita mouse results in decreased SREBP-1, attenuation of parasympathetic modulation of heart rate, measured as a decrease in the high-frequency (HF) fraction of HRV in the presence of propranolol, and a decrease in expression of the G-protein coupled inward rectifying K+ (GIRK4) subunit of the acetylcholine (ACh)-activated inward-rectifying K+ channel (IKACh), the ion channel that mediates the heart rate response to parasympathetic stimulation. Treatment of atrial myocytes with the GSK3β inhibitor Kenpaullone increased levels of SREBP-1 and expression of GIRK4 and IKACh, whereas a dominant-active GSK3β mutant decreased SREBP-1 and GIRK4 expression. In Akita mice treated with GSK3β inhibitors Li+ and/or CHIR-99021, Li+ increased IKACh, and Li+ and CHIR-99021 both partially reversed the decrease in HF fraction while increasing GIRK4 and SREBP-1 expression. These data support the conclusion that increased GSK3β activity in the type 1 diabetic heart plays a critical role in parasympathetic dysfunction through an effect on SREBP-1, supporting GSK3β as a new therapeutic target for diabetic autonomic neuropathy. [ABSTRACT FROM AUTHOR]

Although a reduction in the high-frequency (HF) component of heart rate variability (HRV) is a major complication of diabetes and a risk factor for sudden death, its relationship to ventricular tachycardia (VT) is unknown. We developed a mouse model for the study of VT and its relationship to changes in HRV in the Akita type 1 diabetic mouse. Programmed ventricular stimulation of anesthetized mice demonstrated that Akita mice were more inducible for VT compared with wild-type mice: 78.6% versus 28.6% (P < 0.007). Optical mapping of perfused hearts demonstrated multifocal breakthroughs that occasionally gave rise to short-lived rotors consistent with focal initiation and maintenance of VT. Treatment of Akita mice with pravastatin, which had been previously shown clinically to decrease ventricular ectopy and to increase HRV, decreased the inducibility of VT: 36.8% compared with 75.0% with placebo treatment (P < 0.022). The HF fraction of HRV was reduced in Akita mice (48.6 ± 5.2% vs. 70.9 ± 4.8% in wild-type mice, P < 0.005) and was increased compared with placebo treatment in pravastatin-treated mice. Pretreatment of Akita mice with the muscarinic agonist carbamylcholine or the β-adrenergic receptor blocker propranolol decreased the inducibility of VT (P = 0.001). In conclusion, the increased inducibility of focally initiated VT and reduced HF fraction in Akita mice were partially reversed by both pravastatin treatment and pharmacologic reversal of parasympathetic dysfunction. In this new animal model for the study of the pathogenesis of VT in type 1 diabetes, pravastatin may play a role in the prevention of VT by attenuating parasympathetic dysfunction. [ABSTRACT FROM AUTHOR]

Background--Clinical trial and epidemiological data support that the cardiovascular effects of estrogen are complex, including a mixture of both potentially beneficial and harmful effects. In animal models, estrogen protects females from vascular injury and inhibits atherosclerosis. These effects are mediated by estrogen receptors (ERs), which, when bound to estrogen, can bind to DNA to directly regulate transcription. ERs can also activate several cellular kinases by inducing a rapid nonnuclear signaling cascade. However, the biological significance of this rapid signaling pathway has been unclear. Methods and Results--In the present study, we develop a novel transgenic mouse in which rapid signaling is blocked by overexpression of a peptide that prevents ERs from interacting with the scaffold protein striatin (the disrupting peptide mouse). Microarray analysis of ex vivo treated mouse aortas demonstrates that rapid ER signaling plays an important role in estrogen-mediated gene regulatory responses. Disruption of ER-striatin interactions also eliminates the ability of estrogen to stimulate cultured endothelial cell migration and to inhibit cultured vascular smooth muscle cell growth. The importance of these findings is underscored by in vivo experiments demonstrating loss of estrogen-mediated protection against vascular injury in the disrupting peptide mouse after carotid artery wire injury. Conclusions--Taken together, these results support the concept that rapid, nonnuclear ER signaling contributes to the transcriptional regulatory functions of ER and is essential for many of the vasoprotective effects of estrogen. These findings also identify the rapid ER signaling pathway as a potential target for the development of novel therapeutic agents. [ABSTRACT FROM AUTHOR]

Hypertension is a cardiovascular risk factor present in over two-thirds of people over age 60 in North America; elevated blood pressure correlates with increased risk of heart attack, stroke and progression to heart and kidney failure. Current therapies are insufficient to control blood pressure in almost half of these patients. The mineralocorticoid receptor (MR), acting in the kidney, is known to regulate blood pressure through aldosterone binding and stimulation of sodium retention. However, recent studies support the concept that the MR also has extrarenal actions and that defects in sodium handling alone do not fully explain the development of hypertension and associated cardiovascular mortality. We and others have identified functional MR in human vascular smooth muscle cells (SMCs), suggesting that vascular MR might directly regulate blood pressure. Here we show that mice with SMC-specific deficiency of the MR have decreased blood pressure as they age without defects in renal sodium handling or vascular structure. Aged mice lacking MR in SMCs (SMC-MR) have reduced vascular myogenic tone, agonist-dependent contraction and expression and activity of L-type calcium channels. Moreover, SMC-MR contributes to angiotensin II-induced vascular oxidative stress, vascular contraction and hypertension. This study identifies a new role for vascular MR in blood pressure control and in vascular aging and supports the emerging hypothesis that vascular tone contributes directly to systemic blood pressure. [ABSTRACT FROM AUTHOR]

Background--Heart failure is a major cause of morbidity and mortality worldwide. The ubiquitously expressed cytokine transforming growth factor-&bgr;l (TGF&bgr;1) promotes cardiac fibrosis, an important component of progressive heart failure. Membrane-associated endoglin is a coreceptor for TGF&bgr;1signaling and has been studied in vascular remodeling and preeclampsia. We hypothesized that reduced endoglin expression may limit cardiac fibrosis in heart failure. Methods and Results--We first report that endoglin expression is increased in the left ventricle of human subjects with heart failure and determined that endoglin is required for TGF&bgr;1 signaling in human cardiac fibroblasts using neutralizing antibodies and an siRNA approach. We further identified that reduced endoglin expression attenuates cardiac fibrosis, preserves left ventricular function, and improves survival in a mouse model of pressure-overloadinduced heart failure. Prior studies have shown that the extracellular domain of endoglin can be cleaved and released into the circulation as soluble endoglin, which disrupts TGF&bgr;1 signaling in endothelium. We now demonstrate that soluble endoglin limits TGF&bgr;1 signaling and type I collagen synthesis in cardiac fibroblasts and further show that soluble endoglin treatment attenuates cardiac fibrosis in an in vivo model of heart failure. Conclusion--Our results identify endoglin as a critical component of TGF&bgr;1 signaling in the cardiac fibroblast and show that targeting endoglin attenuates cardiac fibrosis, thereby providing a potentially novel therapeutic approach for individuals with heart failure. [ABSTRACT FROM AUTHOR]

Hypertension, a major cardiovascular risk factor and cause of mortality worldwide, is thought to arise from primary renal abnormalities. However, the etiology of most cases of hypertension remains unexplained. Vascular tone, an important determinant of blood pressure, is regulated by nitric oxide, which causes vascular relaxation by increasing intracellular cGMP and activating cGMP-dependent protein kinase I (PKGI). Here we show that mice with a selective mutation in the N-terminal protein interaction domain of PKGIα display inherited vascular smooth muscle cell abnormalities of contraction, abnormal relaxation of large and resistance blood vessels, and increased systemic blood pressure. Renal function studies and responses to changes in dietary sodium in the PKGIα mutant mice are normal. These data reveal that PKGIα is required for normal VSMC physiology and support the idea that high blood pressure can arise from a primary abnormality of vascular smooth muscle cell contractile regulation, suggesting a new approach to the diagnosis and therapy of hypertension and cardiovascular diseases. [ABSTRACT FROM AUTHOR]

Parasympathetic stimulation of the heart, which provides protection from arrhythmias and sudden death, involves activation of the G protein-coupled inward rectifying K+ channel GIRK1/4 and results in an acetylcholine-sensitive K+ current, I KACh. We describe a unique relationship between lipid homeostasis, the lipid-sensitive transcription factor SREBP-1, regulation of the cardiac parasympathetic response, and the development of ventricular arrhythmia. In embryonic chick atrial myocytes, lipid lowering by culture in lipoprotein-depleted serum increased SREBP-1 levels, GIRK1 expression, and I KACh activation. Regulation of the GIRK1 promoter by SREBP-1 and lipid lowering was dependent on interaction with 2 tandem sterol response elements and an upstream E-box motif. Expression of dominant negative SREBP-1 (DN-SREBP-1) reversed the effect of lipid lowering on I KACh and GIRK1. In SREBP-1 knockout mice, both the response of the heart to parasympathetic stimulation and the expression of GIRK1 were reduced compared with WT. I KACh, attenuated in atrial myocytes from SREBP-1 knockout mice, was stimulated by SREBP-1 expression. Following myocardial infarction, SREBP-1 knockout mice were twice as likely as WT mice to develop ventricular tachycardia in response to programmed ventricular stimulation. These results demonstrate a relationship between lipid metabolism and parasympathetic response that may play a role in arrhythmogenesis. [ABSTRACT FROM AUTHOR]

Parasympathetic stimulation of the heart, which provides protection from arrhythmias and sudden death, involves activation of the G protein-coupled inward rectifying K+ channel GIRK1/4 and results in an acetylcholine-sensitive K+ current, IKACh. We describe a unique relationship between lipid homeostasis, the lipid-sensitive transcription factor SREBP-1, regulation of the cardiac parasympathetic response, and the development of ventricular arrhythmia. In embryonic chick atrial myocytes, lipid lowering by culture in lipoprotein-depleted serum increased SREBP-1 levels, GIRK1 expression, and IKACh activation. Regulation of the GIRK1 promoter by SREBP-1 and lipid lowering was dependent on interaction with 2 tandem sterol response elements and an upstream E-box motif. Expression of dominant negative SREBP-1 (DN-SREBP-1) reversed the effect of lipid lowering on IKACh and GIRK1. In SREBP-1 knockout mice, both the response of the heart to parasympathetic stimulation and the expression of GIRK1 were reduced compared with WT. IKACh, attenuated in atrial myocytes from SREBP-1 knockout mice, was stimulated by SREBP-1 expression. Following myocardial infarction, SREBP-1 knockout mice were twice as likely as WT mice to develop ventricular tachycardia in response to programmed ventricular stimulation. These results demonstrate a relationship between lipid metabolism and parasympathetic response that may play a role in arrhythmogenesis. [ABSTRACT FROM AUTHOR]

Signaling through cAMP plays an important role in heart failure. Phosphorylation of cAMP response element binding protein (CREB) at serine-133 regulates gene expression in the heart. We examined the functional significance of CREB-S133 phosphorylation by comparing transgenic models in which a phosphorylation resistant CREB-S133A mutant containing either an intact or a mutated leucine zipper domain (CREB-S133A-LZ) was expressed in the heart. In vitro, CREB-S133A retained the ability to interact with wild-type CREB, whereas CREB-S133A-LZ did not. In vivo, CREB-S133A and CREB-S133A-LZ were expressed at comparable levels in the heart; however, CREB-S133A markedly suppressed the phosphorylation of endogenous CREB, whereas CREB-S133A-LZ had no effect. The one-year survival of mice from two CREB-S133A-LZ transgenic lines was equivalent to nontransgenic littermate control mice (NTG), whereas transgenic CREB- S133A mice died with heart failure at a median 30 wk of age (P < 0.0001). CREB-S133A mice had an altered gene expression characteristic of the failing heart, whereas CREB-S133A-LZ mice did not. Left ventricular contractile function was substantially reduced in CREB-S133A mice versus NTG mice and only modestly reduced in CREB-S133A-LZ mice (P < 0.02). When considered in light of other studies, these findings indicate that overexpression of the CREB leucine zipper is required for both inhibition of endogenous CREB phosphorylation and cardiomyopathy in this murine model of heart failure. [ABSTRACT FROM AUTHOR]

Nitric oxide (NO) inhibits vascular contraction by activating cGMP-dependent protein kinase I-a (PKGI-a), which causes dephosphorylation of myosin light chain (MLC) and vascular smooth muscle relaxation. Here we show that PKGI-a attenuates signaling by the thrombin receptor protease-activated receptor-1 (PAR-1) through direct activation of regulator of G-protein signaling-2 (RGS-2). NO donors and cGMP cause cGMP-mediated inhibition of PAR-1 and membrane localization of RGS-2. PKGI-a binds directly to and phosphorylates RGS-2, which significantly increases GTPase activity of Gq, terminating PAR-1 signaling. Disruption of the RGS-2-PKGI-a interaction reverses inhibition of PAR-1 signaling by nitrovasodilators and cGMP. Rgs2-/- mice develop marked hypertension, and their blood vessels show enhanced contraction and decreased cGMP-mediated relaxation. Thus, PKGI-a binds to, phosphorylates and activates RGS-2, attenuating receptor-mediated vascular contraction. Our study shows that RGS-2 is required for normal vascular function and blood pressure and is a new drug development target for hypertension. [ABSTRACT FROM AUTHOR]

R1600 --> Heart Failure with Preserved Ejection Fraction (HFpEF) is a prevalent and heterogenous cardiovascular syndrome characterized by impaired cardiac relaxation (diastolic function) with preserved contractility (systolic function), generally as a result of the presentation of several comorbidities. Despite its high and increasing prevalence, there are no therapies available to directly treat or cure HFpEF. Obesity and hypertension, the two dominant risk factors of HFpEF, have been independently associated with T cell inflammation, however, the inflammatory mechanisms driving HFpEF by these two comorbidities together, and T cell contributions, remain elusive. We hypothesized that T cell immune responses and cardiotropism promote diastolic dysfunction and HFpEF. C57/BL6 (wild‐type, WT) and T cell receptor alpha‐deficient (Tcra‐/‐) male mice were fed a high fat diet (HFD) with L‐NAME‐treated water (0.5 g/L) for 5 weeks to mimic obesity and hypertension, respectively, a recently established model of HFpEF. Age‐ and sex‐matched mice were fed standard chow (STD) as controls. Cardiac function was assessed using hemodynamic analyses, and plasma was collected to evaluate systemic levels of pro‐ and anti‐inflammatory cytokines. The heart, mediastinal lymph nodes, inguinal lymph nodes, and spleen were harvested to characterize cardiac and systemic immune cell populations by flow cytometry. Cardiac tissue was also collected for gene expression analysis by qPCR of markers of adverse cardiac remodeling and HFpEF. WT mice fed HFD/L‐NAME had increased cardiac CD11b+ cell abundance and increased CD4+ T cell infiltration compared to controls. Furthermore, in contrast to control mice, HFD/L‐NAME‐treated mice had an increased abundance of CD44hi/CD62Llo effector T cells in the mediastinal lymph nodes and spleen. This was associated with increased passive chamber stiffness (end‐diastolic pressure volume relationship, EDPVR) and decreased expression of the unfolded protein response (UPR) proteins spliced form of X‐box binding protein 1 and binding immunoglobulin protein (XBP1s and BIP), hallmarks of HFpEF. Additionally, HFD/L‐NAME induced a 2.5‐fold increase in plasma levels of IL‐17, without altering the levels of interferon‐gamma or IL‐2. Strikingly, Tcra‐/‐ mice did not develop diastolic dysfunction when fed HFD/L‐NAME, supporting a causal role of T cells in HFpEF pathology. We conclude that T cell activation and recruitment to the heart contribute to diastolic dysfunction in HFpEF. Further studies will interrogate the mechanisms by which combined risk factors prime T cells for cardiac infiltration and effector function in the heart to induce and drive HFpEF. [ABSTRACT FROM AUTHOR]

R1616 --> Percutaneous coronary interventions (PCI) are commonly used to improve blood flow in Peripheral Artery Disease. Complications of PCI are delayed re‐endothelialization and endothelial cell (EC) dysfunction leading to adverse clinical outcomes. Stimulator of Interferon Genes (STING), canonically activated downstream of the cGAS enzyme, is a signaling hub molecule modulating immune responses triggered by self‐derived and/or foreign DNA. We hypothesized that EC‐intrinsic STING regulates re‐endothelialization in response to vascular injury. We modeled PCI in WT, STING‐/‐, and in a newly generated inducible vascular EC‐ specific mouse (VECad5Cre‐ERT2STINGfl/fl mice: EC‐STING‐/‐) using the wire induced carotid injury model. We used Evans Blue Dye injection post injury to identify the areas denuded of EC and quantified the % of non‐blue (re‐endothelialized) area. We found that WT mice had complete re‐endothelialization five days post injury (95.16 ± 2.77 %). In contrast, injured carotid arteries in STING‐/‐ mice exhibited a decrease in re‐endothelialization at the same timepoint (43.57 ± 9.79%). Moreover, EC‐STING‐/‐ mice recapitulated the delayed re‐endothelialization (10.45 ± 1.56% in Tamoxifen treated mice to induce excision of STING in EC, compared to 40 ± 1.28% observed in vehicle treated VECad5Cre‐ERT2STINGfl/fl control mice 5 days post scratch) in the injured arteries, supporting a role of EC STING in re‐endothelialization post injury. To further investigate this EC‐specific effect of STING mechanistically in vitro, we performed scratch assays on WT and STING mouse heart EC (MHEC) monolayers, as well as on human EC monolayers lacking STING after CRISPR knock down and imaged wound healing in real time by IncuCyte. WT MHEC and HUVEC completely covered the scratch area within 24 hours, and 4 hours, respectively, whereas both EC lacking STING were delayed healing the scratch. Additionally, we found that the healing response was independent of cGAS, since cGAS KD HUVEC had similar post‐ scratch recovery time as control HUVEC. Ongoing experiments investigate the mechanisms involved in this novel STING dependent, cGAS‐independent pathway of EC response to injury, as well as the consequences of EC‐STING in adverse chronic vascular remodeling. [ABSTRACT FROM AUTHOR]

R3672 --> Gut dysbiosis has recently been associated with the severity of the complex syndrome of heart failure (HF) in patients. The mechanisms of action involving gut microbes and immune responses are starting to be characterized in experimental models of HF. More than 50% of HF patients present with HF with preserved ejection fraction (HFpEF), characterized by impaired relaxation (diastolic function) and preserved contractility (systolic function), which do not respond to any of the available treatments for HF. Obesity and hypertension are major risk factors for HFpEF, and have been independently associated with gut dysbiosis, and modulation of the microbiota in experimental models of these risk factors has revealed mechanistic insights. However, whether and how the microbiota contributes to HFpEF is unknown. Recently, a novel mouse model of HFpEF induced by a combination of high‐fat diet (HFD) and L‐NAME, to mimic obesity and hypertension, respectively. We hypothesize that specific microbiota and derived metabolites, are altered in HFpEF and contribute to systemic inflammation and diastolic dysfunction. C57/BL6 WT mice were fed HFD and L‐NAME (H/L) to induce HFpEF. We used invasive hemodynamics to determine diastolic and systolic function, and 16S rRNA sequencing in fecal samples to characterize gut bacteria and perform metabolic pathway analysis. The heart, the intestine and plasma were collected and evaluated for indicators of cardiac remodeling and gut permeability using flow cytometry and qPCR. As expected, H/L triggered diastolic dysfunction at 5 weeks. At this time, H/L intestinal epithelial cells (iECs) showed downregulation in gene expression of the junctional markers cadherin‐1, ZO‐1 and occludin, suggesting the induction of leaky gut. We also found increased concentration of proinflammatory molecules in serum (e.g. IL‐6, IL‐17 and CXCL1). Strikingly, H/L treatment resulted in gut dysbiosis in H/L mice compared to those that received standard diet (STD). The main phyla analysis showed a higher Firmicutes/Bacteroidetes ratio in H/L, which has been associated with obesity, compared to STD. At the family level, Ruminococcaceae, also linked to obesity in humans, showed elevated relative abundance in H/L group compared to STD, and Rikenellaceae and Christensenellaceae significantly decreased their numbers. Interestingly, gut bacteria from H/L‐treated mice revealed an enrichment of metabolic pathways related to synthesis and degradation of fatty acids. We studied the gene expression of the main short‐chain fatty acid (SCFA) receptors, associated with improvement in cardiovascular health. FFAR2 (GPR43) expression did not change in the heart neither the gut, but strikingly, FFAR3 (GPR41) expression was significantly upregulated in the heart in the H/L group compared to STD, but not in iECs. In conclusion, we demonstrated that a novel mouse model of HFpEF induced gut dysbiosis and alterations in gut permeability, and identified a dysregulation of fatty acid synthesis and degradation metabolic pathways. Mechanistic studies are needed to see the role of fatty acids and its receptors in cardiac inflammation during diastolic dysfunction. [ABSTRACT FROM AUTHOR]

Introduction: Diabetes increases ventricular tachycardia (VT) and sudden cardiac death risk in humans. We previously found the type I diabetic (DMI) heart displays: reduced responsiveness to parasympathetic stimulation; increased QRS/T Wave alternans (marker of proarrhythmic calcium dyshomeostasis); and hyperactive GSK3beta. Cardiac parasympathetic stimulation promotes production of intracellular cyclic GMP (cGMP). The effects of cGMP and its downstream effector PKG, on these indices of VT in type II diabetes (DMII) remain poorly understood. Hypothesis: PKGIa modulates inducibility of VT and QRS/TWA in the DMII heart and mediates the cGMP effect on VT through inhibition of myocardial GSK3beta. Methods: Using an established protocol of programmed ventricular stimulation we measured: VT incidence, duration, and QRS/T Wave alternans. We studied the following mice: wild type; Db/Db model of DMII; high fat high sucrose (HFHS) model of insulin resistance; and the PKGIa leucine zipper mutant (LZM) mouse, which has no DM but has PKGIa disrupting mutations. Mice were treated with or without the cGMP-augmenting phosphodiesterase inhibitor sildenafil 10 mg/kg, or the GSK3b inhibitor TWS119 20 mg/kg. Results: LVs of HFHS mice displayed 30 ± 8% reduction of cGMP compared with control (p<0.05, n=3 per group), while myocardial cGMP in LZM mice did not differ from control. In failing LVs from humans, there was also a 46% reduction in myocardial cGMP in DM compared with nondiabetic (p=.058, n=3 per group). Db/Db and HFHS mice had increased inducible VT (0.25 +/- 0.1 s in Db/Db, 2.2 +/- 1 s HFHS, vs 0 s in WT control, p <0.05), as well as TWA. Treatment with sildenafil reduced VT incidence, duration, and TWA in Db/Db and HFHS mice. LZM mice also had increased VT duration and TWA incidence (0 of 4 in WT vs 5 of 6 in LZM, p<0.05). Inhibition of GSK3β rescued inducibility of VT in Db/Db, HFHS, and in LZM mice. Conclusions: These findings support that in the DMII heart reduced cGMP promotes VT, whereas pharmacological augmentation of cGMP inhibits VT. Inducible VT and TWA in the PKG LZM mouse provides direct support that PKGIa opposes VT in the DMII heart. These support that cGMP activation of PKG inhibits GSK3beta, leading to reduced incidence of inducible VT. [ABSTRACT FROM AUTHOR]

Barth syndrome (BTHS) is an X-linked autosomal recessive disease caused by mutations in the tafazzin (TAZ) gene. These mutations lead to hypotonia, cyclic neutropenia, 3-methyglutaconic aciduria, and the most common cause of mortality in patients, cardiomyopathy. The TAZ gene encodes an enzyme that generates mature cardiolipin (CL) from monolysocardiolipin (MLCL)in the mitochondrial membrane, which is essential for normal mitochondrial morphology and function. Currently, there is no effective therapy for BTHS. In this study, we test an enzyme replacement therapy for BTHS in myocardial-specific TAZ conditional knockout mice which model the cardiomyopathy of BTHS. Serial echocardiograms showed that the BTHS mice developed increased septal wall thickness at 5 weeks of age. The BTHS mice were treated for 12 weeks with either vehicle or recombinant human TAZ fused to a cell penetrating peptide (hTAZ-CTP) to facilitate tissue uptake. During the treatment period, septal wall thickness in the vehicle-treated mouse continued to increase, whereas it remained stable in those treated with hTAZ-CTP. Pressure-volume (PV) loop analysis indicated that heart function was impaired in the vehicle-treated BTHS mouse while the protein-treated mice were shown to have PV loops similar to normal mice. The ratio of MLCL/CL, a direct measure of TAZ enzymatic activity, was measured in heart mitochondria isolated from BTHS and control floxed allele mice after treatment. The MLCL/CL ratio in the vehicle treated BTHS mouse was 20.4, consistent with a BTHS phenotype, whereas the MLCL/CL ratios in protein-treated and control mice were 0.01, indicating that injection of hTAZ-CTP successfully rescued the function of TAZ in BTHS mice. Histological observation of liver, spleen, kidney, and heart did not show any sign of toxicity for hTAZ-CTP injection. These results indicate that TAZ enzyme replacement therapy has great potential as a future treatment for BTHS. [ABSTRACT FROM AUTHOR]

Background: Heart failure is a growing cause of morbidity and mortality worldwide. Transforming growth factor beta (TGF-β1) promotes cardiac fibrosis, but also activates counterregulatory pathways that serve to regulate TGF-β1 activity in heart failure. Bone morphogenetic protein 9 (BMP9) is a member of the TGFβ family of cytokines and signals via the downstream effector protein Smad1. Endoglin is a TGFβ coreceptor that promotes TGF-β1 signaling via Smad3 and binds BMP9 with high affinity. We hypothesized that BMP9 limits cardiac fibrosis by activating Smad1 and attenuating Smad3, and, furthermore, that neutralizing endoglin activity promotes BMP9 activity.Methods: We examined BMP9 expression and signaling in human cardiac fibroblasts and human subjects with heart failure. We used the transverse aortic constriction-induced model of heart failure to evaluate the functional effect of BMP9 signaling on cardiac remodeling.Results: BMP9 expression is increased in the circulation and left ventricle (LV) of human subjects with heart failure and is expressed by cardiac fibroblasts. Next, we observed that BMP9 attenuates type I collagen synthesis in human cardiac fibroblasts using recombinant human BMP9 and a small interfering RNA approach. In BMP9-/- mice subjected to transverse aortic constriction, loss of BMP9 activity promotes cardiac fibrosis, impairs LV function, and increases LV levels of phosphorylated Smad3 (pSmad3), not pSmad1. In contrast, treatment of wild-type mice subjected to transverse aortic constriction with recombinant BMP9 limits progression of cardiac fibrosis, improves LV function, enhances myocardial capillary density, and increases LV levels of pSmad1, not pSmad3 in comparison with vehicle-treated controls. Because endoglin binds BMP9 with high affinity, we explored the effect of reduced endoglin activity on BMP9 activity. Neutralizing endoglin activity in human cardiac fibroblasts or in wild-type mice subjected to transverse aortic constriction-induced heart failure limits collagen production, increases BMP9 protein levels, and increases levels of pSmad1, not pSmad3.Conclusions: Our results identify a novel functional role for BMP9 as an endogenous inhibitor of cardiac fibrosis attributable to LV pressure overload and further show that treatment with either recombinant BMP9 or disruption of endoglin activity promotes BMP9 activity and limits cardiac fibrosis in heart failure, thereby providing potentially novel therapeutic approaches for patients with heart failure. [ABSTRACT FROM AUTHOR]

In cells capable of entering the cell cycle, including cancer cells, β-catenin has been termed a master switch, driving proliferation over differentiation. However, its role as a transcriptional activator in terminally differentiated cells is relatively unknown. Herein we utilize conditional, cardiac-specific deletion of the β-catenin gene and cardiac-specific expression of a dominant inhibitory mutant of Lef-1 (Lef-1Δ20), one of the members of the T-cell factor/lymphocyte enhancer factor (Tcf/Lef) family of transcription factors that functions as a coactivator with β-catenin, to demonstrate that β-catenin/Tcf/Lef-dependent gene expression regulates both physiologic and pathological growth (hypertrophy) of the heart. Indeed, the profound nature of the growth impairment of the heart in the Lef-1Δ20 mouse, which leads to very early development of heart failure and premature death, suggests β-catenin/Tcf/Lef targets are dominant regulators of cardiomyocyte growth. Thus, our studies, employing complementary models in vivo, implicate β-catenin/Tcf/Lef signaling as an essential growth-regulatory pathway in terminally differentiated cells. [ABSTRACT FROM AUTHOR]

Presents a correction to the article "Regulator of G-Protein Signaling-2 Mediates Vascular Smooth Muscle Relaxation and Blood Pressure" that was previously published in the 2003 issue of "Nature Medicine," Volume 9.