Exacerbating Pressure Overload-Induced Cardiac Hypertrophy: Novel Role of Adaptor Molecule Src Homology 2-B3

Indoleamine 2,3-Dioxygenase 1 Deletion-Mediated Kynurenine Insufficiency Inhibits Pathological Cardiac Hypertrophy

BACKGROUND

Aberrant amino acid metabolism is implicated in cardiac hypertrophy, while the involvement of tryptophan metabolism in pathological cardiac hypertrophy remains elusive. Herein, we aimed to investigate the effect and potential mechanism of IDO1 (indoleamine 2,3-dioxygenase) and its metabolite kynurenine (Kyn) on pathological cardiac hypertrophy.

METHODS

Transverse aortic constriction was performed to induce cardiac hypertrophy in IDO1-knockout (KO) mice and AAV9-cTNT-shIDO1 mice. Liquid chromatography-mass spectrometry was used to detect the metabolites of tryptophan-Kyn pathway. Chromatin immunoprecipitation assay and dual luciferase assay were used to validate the binding of protein and DNA.

RESULTS

IDO1 expression was upregulated in both human and murine hypertrophic myocardium, alongside with increased IDO1 activity and Kyn content in transverse aortic constriction-induced mice's hearts using liquid chromatography-mass spectrometry analysis. Myocardial remodeling and heart function were significantly improved in transverse aortic constriction-induced IDO1-KO mice, but were greatly exacerbated with subcutaneous Kyn administration. IDO1 inhibition or Kyn addition confirmed the alleviation or aggravation of hypertrophy in cardiomyocyte treated with isoprenaline, respectively. Mechanistically, IDO1 and metabolite Kyn contributed to pathological hypertrophy via the AhR (aryl hydrocarbon receptor)-GATA4 (GATA binding protein 4) axis.

CONCLUSIONS

This study demonstrated that IDO1 deficiency and consequent Kyn insufficiency can protect against pathological cardiac hypertrophy by decreasing GATA4 expression in an AhR-dependent manner.

Modulation of JAK-STAT Signaling by LNK: A Forgotten Oncogenic Pathway in Hormone Receptor-Positive Breast Cancer

Breast cancer remains the most frequently diagnosed cancer in women worldwide. Tumors that express hormone receptors account for 75% of all cases. Understanding alternative signaling cascades is important for finding new therapeutic targets for hormone receptor-positive breast cancer patients. JAK-STAT signaling is commonly activated in hormone receptor-positive breast tumors, inducing inflammation, proliferation, migration, and treatment resistance in cancer cells. In hormone receptor-positive breast cancer, the JAK-STAT cascade is stimulated by hormones and cytokines, such as prolactin and IL-6. In normal cells, JAK-STAT is inhibited by the action of the adaptor protein, LNK. However, the role of LNK in breast tumors is not fully understood. This review compiles published reports on the expression and activation of the JAK-STAT pathway by IL-6 and prolactin and potential inhibition of the cascade by LNK in hormone receptor-positive breast cancer. Additionally, it includes analyses of available datasets to determine the level of expression of LNK and various members of the JAK-STAT family for the purpose of establishing associations between expression and clinical outcomes. Together, experimental evidence and in silico studies provide a better understanding of the potential implications of the JAK-STAT-LNK loop in hormone receptor-positive breast cancer progression.

MIR22HG Aggravates Oxygen-Glucose Deprivation and Reoxygenation-Induced Cardiomyocyte Injury through the miR-9-3p/SH2B3 Axis

Reperfusion therapy, the standard treatment for acute myocardial infarction (MI), can trigger necrotic death of cardiomyocytes and provoke ischemia/reperfusion (I/R) injury. However, molecular mechanisms that regulate cardiomyocyte death remain largely unknown. The abnormal expression of lncRNA MIR22HG has been found in types of diseases. The current study was aimed at exploring the function and mechanism of MIR22HG in I/R injury. In this study, mouse myocardial cells (HL-1) treated with oxygen-glucose deprivation and reoxygenation (OGD/R) were used as the in vitro models, and myocardial ischemia reperfusion injury (MIRI) animal models in vivo were established in male C57BL/6 mice. Experiments including CCK-8, flow cytometry, TUNEL, HE staining, RT-qPCR, western blotting, and luciferase reporter assays were performed to explore the function and potential mechanism of MIR22HG in MIRI in vitro and in vivo. Bioinformatics analysis was performed to predict the binding site between miR-9-3p and MIR22HG (or SH2B3). Our results indicated that the MIR22HG level was upregulated in cardiomyocytes after OGD/R treatment. The knockdown of MIR22HG promoted cell viability and inhibited apoptosis and extracellular matrix (ECM) production in OGD/R-treated HL-1 cells. In mechanism, MIR22HG binds to miR-9-3p, and miR-9-3p targets the SH2B3 3 ${}^{\prime }$ untranslated region (UTR). Moreover, SH2B3 expression was positively regulated by MIR22HG but negatively modulated by miR-9-3p. Rescue assays suggested that the suppressive effect of MIR22HG knockdown on cell viability, apoptosis, and ECM accumulation was reversed by the overexpression of SH2B3. The in vivo experiments demonstrated that MIR22HG knockdown alleviated cardiomyocyte apoptosis and reduced myocardial infarct size in MIRI mice. In summary, MIR22HG knockdown alleviates myocardial injury through the miR-9-3p/SH2B3 axis.

Role of the microRNA-29 family in myocardial fibrosis

Myocardial fibrosis (MF) is an inevitable pathological process in the terminal stage of many cardiovascular diseases, often leading to serious cardiac dysfunction and even death. Currently, microRNA-29 (miR-29) is thought to be a novel diagnostic and therapeutic target of MF. Understanding the underlying mechanisms of miR-29 that regulate MF will provide a new direction for MF therapy. In the present review, we concentrate on the underlying signaling pathway of miR-29 affecting MF and the crosstalk regulatory relationship among these pathways to illustrate the complex regulatory network of miR-29 in MF. Additionally, based on our mechanistic understanding, we summarize opportunities and challenges of miR-29-based MF diagnosis and therapy.

Hematopoietic stem-cell senescence and myocardial repair - Coronary artery disease genotype/phenotype analysis of post-MI myocardial regeneration response induced by CABG/CD133+ bone marrow hematopoietic stem cell treatment in RCT PERFECT Phase 3

Background

Bone marrow stem cell clonal dysfunction by somatic mutation is suspected to affect post-infarction myocardial regeneration after coronary bypass surgery (CABG).

Methods

Transcriptome and variant expression analysis was studied in the phase 3 PERFECT trial post myocardial infarction CABG and CD133⁺ bone marrow derived hematopoetic stem cells showing difference in left ventricular ejection fraction (∆LVEF) myocardial regeneration Responders (n=14; ∆LVEF +16% day 180/0) and Non-responders (n=9; ∆LVEF -1.1% day 180/0). Subsequently, the findings have been validated in an independent patient cohort (n=14) as well as in two preclinical mouse models investigating SH2B3/LNK antisense or knockout deficient conditions.

Findings

1. Clinical: R differed from NR in a total of 161 genes in differential expression (n=23, q<0•05) and 872 genes in coexpression analysis (n=23, q<0•05). Machine Learning clustering analysis revealed distinct RvsNR preoperative gene-expression signatures in peripheral blood acorrelated to SH2B3 (p<0.05). Mutation analysis revealed increased specific variants in RvsNR. (R: 48 genes; NR: 224 genes). 2. Preclinical:SH2B3/LNK-silenced hematopoietic stem cell (HSC) clones displayed significant overgrowth of myeloid and immune cells in bone marrow, peripheral blood, and tissue at day 160 after competitive bone-marrow transplantation into mice. SH2B3/LNK^−/− mice demonstrated enhanced cardiac repair through augmenting the kinetics of bone marrow-derived endothelial progenitor cells, increased capillary density in ischemic myocardium, and reduced left ventricular fibrosis with preserved cardiac function. 3. Validation: Evaluation analysis in 14 additional patients revealed 85% RvsNR (12/14 patients) prediction accuracy for the identified biomarker signature.

Interpretation

Myocardial repair is affected by HSC gene response and somatic mutation. Machine Learning can be utilized to identify and predict pathological HSC response.

Funding

German Ministry of Research and Education (BMBF): Reference and Translation Center for Cardiac Stem Cell Therapy - FKZ0312138A and FKZ031L0106C, German Ministry of Research and Education (BMBF): Collaborative research center - DFG:SFB738 and Center of Excellence - DFG:EC-REBIRTH), European Social Fonds: ESF/IV-WM-B34-0011/08, ESF/IV-WM-B34-0030/10, and Miltenyi Biotec GmbH, Bergisch-Gladbach, Germany. Japanese Ministry of Health : Health and Labour Sciences Research Grant (H14-trans-001, H17-trans-002)

Trial registration

ClinicalTrials.gov NCT00950274

Genome Editing for the Understanding and Treatment of Inherited Cardiomyopathies

Cardiomyopathies are diseases of heart muscle, a significant percentage of which are genetic in origin. Cardiomyopathies can be classified as dilated, hypertrophic, restrictive, arrhythmogenic right ventricular or left ventricular non-compaction, although mixed morphologies are possible. A subset of neuromuscular disorders, notably Duchenne and Becker muscular dystrophies, are also characterized by cardiomyopathy aside from skeletal myopathy. The global burden of cardiomyopathies is certainly high, necessitating further research and novel therapies. Genome editing tools, which include zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs) and clustered regularly interspaced short palindromic repeats (CRISPR) systems have emerged as increasingly important technologies in studying this group of cardiovascular disorders. In this review, we discuss the applications of genome editing in the understanding and treatment of cardiomyopathy. We also describe recent advances in genome editing that may help improve these applications, and some future prospects for genome editing in cardiomyopathy treatment.

Treatment of Dyslipidemia Using CRISPR/Cas9 Genome Editing

PURPOSE OF REVIEW

Clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated 9 (Cas9) has recently emerged as a top genome editing technology and has afforded investigators the ability to more easily study a number of diseases. This review discusses CRISPR/Cas9's advantages and limitations and highlights a few recent reports on genome editing applications for alleviating dyslipidemia through disruption of proprotein convertase subtilisin/kexin type 9 (PCSK9).

RECENT FINDINGS

Targeting of mouse Pcsk9 using CRISPR/Cas9 technology has yielded promising results for lowering total cholesterol levels, and several recent findings are highlighted in this review. Reported on-target mutagenesis efficiency is as high as 90% with a subsequent 40% reduction of blood cholesterol levels in mice, highlighting the potential for use as a therapeutic in human patients. The ability to characterize and treat diseases is becoming easier with the recent advances in genome editing technologies. In this review, we discuss how genome editing strategies can be of use for potential therapeutic applications.

Genome Editing for the Study of Cardiovascular Diseases

PURPOSE OF REVIEW

The opportunities afforded through the recent advent of genome-editing technologies have allowed investigators to more easily study a number of diseases. The advantages and limitations of the most prominent genome-editing technologies are described in this review, along with potential applications specifically focused on cardiovascular diseases.

RECENT FINDINGS

The recent genome-editing tools using programmable nucleases, such as zinc-finger nucleases, transcription activator-like effector nucleases, and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated 9 (Cas9), have rapidly been adapted to manipulate genes in a variety of cellular and animal models. A number of recent cardiovascular disease-related publications report cases in which specific mutations are introduced into disease models for functional characterization and for testing of therapeutic strategies. Recent advances in genome-editing technologies offer new approaches to understand and treat diseases. Here, we discuss genome editing strategies to easily characterize naturally occurring mutations and offer strategies with potential clinical relevance.

From engineering to editing the rat genome

Since its domestication over 100 years ago, the laboratory rat has been the preferred experimental animal in many areas of biomedical research (Lindsey and Baker The laboratory rat. Academic, New York, pp 1-52, 2006). Its physiology, size, genetics, reproductive cycle, cognitive and behavioural characteristics have made it a particularly useful animal model for studying many human disorders and diseases. Indeed, through selective breeding programmes numerous strains have been derived that are now the mainstay of research on hypertension, obesity and neurobiology (Okamoto and Aoki Jpn Circ J 27:282-293, 1963; Zucker and Zucker J Hered 52(6):275-278, 1961). Despite this wealth of genetic and phenotypic diversity, the ability to manipulate and interrogate the genetic basis of existing phenotypes in rat strains and the methodology to generate new rat models has lagged significantly behind the advances made with its close cousin, the laboratory mouse. However, recent technical developments in stem cell biology and genetic engineering have again brought the rat to the forefront of biomedical studies and enabled researchers to exploit the increasingly accessible wealth of genome sequence information. In this review, we will describe how a breakthrough in understanding the molecular basis of self-renewal of the pluripotent founder cells of the mammalian embryo, embryonic stem (ES) cells, enabled the derivation of rat ES cells and their application in transgenesis. We will also describe the remarkable progress that has been made in the development of gene editing enzymes that enable the generation of transgenic rats directly through targeted genetic modifications in the genomes of zygotes. The simplicity, efficiency and cost-effectiveness of the CRISPR/Cas gene editing system, in particular, mean that the ability to engineer the rat genome is no longer a limiting factor. The selection of suitable targets and gene modifications will now become a priority: a challenge where ES culture and gene editing technologies can play complementary roles in generating accurate bespoke rat models for studying biological processes and modelling human disease.

Translocase of Inner Membrane 50 Functions as a Novel Protective Regulator of Pathological Cardiac Hypertrophy

BACKGROUND

Translocase of inner membrane 50 (TIM50) is a member of the translocase of inner membrane (TIM) complex in the mitochondria. Previous research has demonstrated the role of TIM50 in the regulation of oxidative stress and cardiac morphology. However, the role of TIM50 in pathological cardiac hypertrophy remains unknown.

METHODS AND RESULTS

In the present study we found that the expression of TIM50 was downregulated in hypertrophic hearts. Using genetic loss-of-function animal models, we demonstrated that TIM50 deficiency increased heart and cardiomyocyte size with more severe cardiac fibrosis compared with wild-type littermates. Moreover, we generated cardiomyocyte-specific TIM50 transgenic mice in which the hypertrophic and fibrotic phenotypes were all alleviated. Next, we tested reactive oxygen species generation and the activities of the antioxidant enzymes superoxide dismutase and catalase, and also respiratory chain complexes I, II, and IV, finding that all the activities were regulated by TIM50. Meanwhile, expression of the ASK1-JNK/P38 axis was increased in TIM50-deficient mice, and TIM50 overexpression decreased the activity of the ASK1-JNK/P38 axis. Finally, we treated mice with the antioxidant N-acetyl cysteine to reduce oxidative stress. After N-acetyl cysteine treatment, the deteriorative hypertrophic and fibrotic phenotypes caused by TIM50 deficiency were all remarkably reversed.

CONCLUSIONS

These data indicated that TIM50 could attenuate pathological cardiac hypertrophy primarily by reducing oxidative stress. TIM50 could be a promising target for the prevention and therapy of cardiac hypertrophy and heart failure.

Critical Role of ADAMTS2 (A Disintegrin and Metalloproteinase With Thrombospondin Motifs 2) in Cardiac Hypertrophy Induced by Pressure Overload

ADAMTS2 (A Disintegrin and Metalloproteinase With Thrombospondin Motifs 2) is recognized as a metalloproteinase that promotes the cleavage of amino propeptides of types I, II, III, and V procollagens. However, the role of ADAMTS2 in the heart has not yet been defined. Herein, we observed the upregulated expression of ADAMTS2 in failing human hearts and hypertrophic murine hearts. Mice lacking ADAMTS2 display exacerbated cardiac hypertrophy on pressure overload-induced hypertrophic response, whereas mice with cardiac-specific overexpression of ADAMTS2 display alleviation of this detrimental phenotype. Consistent with these results, in vitro loss or gain of function experiments in neonatal rat cardiomyocytes confirmed that ADAMTS2 negatively regulates cardiomyocyte hypertrophy in response to Ang II. Mechanistically, blockage of the PI3K (phosphoinositide 3-kinase)/AKT (protein kinase B)-dependent signaling pathway with specific inhibitors both in vivo and in vitro could rescue the aggravated hypertrophic response to the loss of ADAMTS2. Collectively, we propose that ADAMTS2 regulates the hypertrophic response through inhibiting the activation of the PI3K/AKT-dependent signaling pathway. Because ADAMTS2 is an extracellular protein, it could be effectively manipulated using pharmacological means to modulate cardiac hypertrophy.

Noninvasive Positive Pressure Ventilation in Chronic Heart Failure

Instruction and Objectives. Noninvasive positive pressure ventilation (NPPV) alleviates sleep-disordered breathing (SDB) and it may improve cardiac function in SDB patients. Because large randomized controlled trials directly evaluating the impact of NPPV on cardiac function are lacking, we conducted a meta-analysis of published data on effectiveness of NPPV in improving cardiac function in patients with chronic heart failure regardless of SDB presence. Methods. Controlled trials were identified in PubMed, OVID, and EMBASE databases. Both fixed and randomized models were used in meta-analysis with primary outcomes of left ventricular ejection fraction (LVEF). Results. Nineteen studies were included with a total of 843 patients. Compared to standard medical treatment (SMT) plus sham-NPPV or SMT only, NPPV plus SMT was associated with improvement in LVEF (weighted mean difference 5.34, 95% CI, [3.85,6.82]; P < 0.00001) and plasma brain natriuretic peptide (BNP) level (weighted mean difference -117.37, 95% CI, [-227.22, -7.52]; P = 0.04) and no influence on overall mortality (RR 1.00, 95% CI, [0.96,1.04]; P = 0.95). Conclusions. In the present meta-analysis, use of NPPV plus SMT improved LVEF and reduced plasma BNP level but did not improve overall mortality in patients with chronic heart failure.

Genome editing in cardiovascular diseases

Genome-editing tools, which include zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated 9 (Cas9) systems, have emerged as an invaluable technology to achieve somatic and germline genomic manipulation in cells and model organisms for multiple applications, including the creation of knockout alleles, introducing desired mutations into genomic DNA, and inserting novel transgenes. Genome editing is being rapidly adopted into all fields of biomedical research, including the cardiovascular field, where it has facilitated a greater understanding of lipid metabolism, electrophysiology, cardiomyopathies, and other cardiovascular disorders, has helped to create a wider variety of cellular and animal models, and has opened the door to a new class of therapies. In this Review, we discuss the applications of genome-editing technology throughout cardiovascular disease research and the prospect of in vivo genome-editing therapies in the future. We also describe some of the existing limitations of genome-editing tools that will need to be addressed if cardiovascular genome editing is to achieve its full scientific and therapeutic potential.

Suppressor of IKKɛ is an essential negative regulator of pathological cardiac hypertrophy

Although pathological cardiac hypertrophy represents a leading cause of morbidity and mortality worldwide, our understanding of the molecular mechanisms underlying this disease is still poor. Here, we demonstrate that suppressor of IKKɛ (SIKE), a negative regulator of the interferon pathway, attenuates pathological cardiac hypertrophy in rodents and non-human primates in a TANK-binding kinase 1 (TBK1)/AKT-dependent manner. Sike-deficient mice develop cardiac hypertrophy and heart failure, whereas Sike-overexpressing transgenic (Sike-TG) mice are protected from hypertrophic stimuli. Mechanistically, SIKE directly interacts with TBK1 to inhibit the TBK1-AKT signalling pathway, thereby achieving its anti-hypertrophic action. The suppression of cardiac remodelling by SIKE is further validated in rats and monkeys. Collectively, these findings identify SIKE as a negative regulator of cardiac remodelling in multiple animal species due to its inhibitory regulation of the TBK1/AKT axis, suggesting that SIKE may represent a therapeutic target for the treatment of cardiac hypertrophy and heart failure.

Identifying pathways that cause pathological cardiac hypertrophy holds great therapeutic potential. Here the authors discover one such pathway and show that SIKE, an inhibitor of interferon signalling, prevents pathological but not physiological cardiac hypertrophy by interacting with TBK1 and modulating the TBK1/AKT signalling in rodents and monkeys.

C-C Motif Chemokine Receptor 9 Exacerbates Pressure Overload-Induced Cardiac Hypertrophy and Dysfunction

Background

Maladaptive cardiac hypertrophy is a major risk factor for heart failure, which is the leading cause of death worldwide. C‐C motif chemokine receptor 9 (CCR9), a subfamily of the G protein–coupled receptor supergene family, has been highlighted as an immunologic regulator in the development and homing of immune cells and in immune‐related diseases. Recently, CCR9 was found to be involved in the pathogenesis of other diseases such as cardiovascular diseases; however, the effects that CCR9 exerts in cardiac hypertrophy remain elusive.

Methods and Results

We observed significantly increased CCR9 protein levels in failing human hearts and in a mouse or cardiomyocyte hypertrophy model. In loss‐ and gain‐of‐function experiments, we found that pressure overload–induced hypertrophy was greatly attenuated by CCR9 deficiency in cardiac‐specific CCR9 knockout mice, whereas CCR9 overexpression in cardiac‐specific transgenic mice strikingly enhanced cardiac hypertrophy. The prohypertrophic effects of CCR9 were also tested in vitro, and a similar phenomenon was observed. Consequently, we identified a causal role for CCR9 in pathological cardiac hypertrophy. Mechanistically, we revealed a lack of difference in the expression levels of mitogen‐activated protein kinases between groups, whereas the phosphorylation of AKT/protein kinase B and downstream effectors significantly decreased in CCR9 knockout mice and increased in CCR9 transgenic mice after aortic binding surgery.

Conclusions

The prohypertrophic effects of CCR9 were not attributable to the mitogen‐activated protein kinase signaling pathway but rather to the AKT–mammalian target of rapamycin–glycogen synthase kinase 3β signaling cascade.

Cardiac-Specific EPI64C Blunts Pressure Overload-Induced Cardiac Hypertrophy

The calcium-responsive molecule, calcineurin, has been well characterized to play a causal role in pathological cardiac hypertrophy over the past decade. However, the intrinsic negative regulation of calcineurin signaling during the progression of cardiomyocyte hypertrophy remains enigmatic. Herein, we explored the role of EPI64C, a dual inhibitor of both Ras and calcineurin signaling during T-cell activation, in pressure overload-induced cardiac hypertrophy. We generated a cardiac-specific Epi64c conditional knockout mouse strain and showed that loss of Epi64c remarkably exacerbates pressure overload-induced cardiac hypertrophy. In contrast, EPI64C gain-of-function in cardiomyocyte-specific Epi64c transgenic mice exerts potent protective effects against cardiac hypertrophy. Mechanistically, the cardioprotective effects of EPI64C are largely attributed to the disrupted calcineurin signaling but are independent of its Ras suppressive capability. Molecular studies have indicated that the 406 to 446 C-terminal amino acids in EPI64C directly bind to the 287 to 337 amino acids in the catalytic domain of calcineurin, which is responsible for the EPI64C-mediated suppressive effects. We further extrapolated our studies to cynomolgus monkeys and showed that gene therapy based on lentivirus-mediated EPI64C overexpression in the monkey hearts blunted pressure overload-induced cardiac hypertrophy. Our study thus identified EPI64C as a novel negative regulator in cardiac hypertrophy by targeting calcineurin signaling and demonstrated the potential of gene therapy and drug development for treating cardiac hypertrophy.

Intercellular Adhesion Molecule 1 Regulates Left Ventricular Leukocyte Infiltration, Cardiac Remodeling, and Function in Pressure Overload-Induced Heart Failure

Background

Left ventricular dysfunction and heart failure are strongly associated in humans with increased circulating levels of proinflammatory cytokines, T cells, and soluble intercellular cell adhesion molecule 1 (ICAM1). In mice, infiltration of T cells into the left ventricle contributes to pathological cardiac remodeling, but the mechanisms regulating their recruitment to the heart are unclear. We hypothesized that ICAM1 regulates cardiac inflammation and pathological cardiac remodeling by mediating left ventricular T‐cell recruitment and thus contributing to cardiac dysfunction and heart failure.

Methods and Results

In a mouse model of pressure overload–induced heart failure, intramyocardial endothelial ICAM1 increased within 48 hours in response to thoracic aortic constriction and remained upregulated as heart failure progressed. ICAM1‐deficient mice had decreased T‐cell and proinflammatory monocyte infiltration in the left ventricle in response to thoracic aortic constriction, despite having numbers of circulating T cells and activated T cells in the heart‐draining lymph nodes that were similar to those of wild‐type mice. ICAM1‐deficient mice did not develop cardiac fibrosis or systolic and diastolic dysfunction in response to thoracic aortic constriction. Exploration of the mechanisms regulating ICAM1 expression revealed that endothelial ICAM1 upregulation and T‐cell infiltration were not mediated by endothelial mineralocorticoid receptor signaling, as demonstrated in thoracic aortic constriction studies in mice with endothelial mineralocorticoid receptor deficiency, but rather were induced by the cardiac cytokines interleukin 1β and 6.

Conclusions

ICAM1 regulates pathological cardiac remodeling by mediating proinflammatory leukocyte infiltration in the left ventricle and cardiac fibrosis and dysfunction and thus represents a novel target for treatment of heart failure.

Regulator of G-Protein Signaling 10 Negatively Regulates Cardiac Remodeling by Blocking Mitogen-Activated Protein Kinase–Extracellular Signal-Regulated Protein Kinase 1/2 Signaling

Regulator of G-protein signaling 10 (RGS10) is an important member of the RGS family and produces biological effects in multiple organs. We used a genetic approach to study the role of RGS10 in the regulation of pathological cardiac hypertrophy and found that RGS10 can negatively influence pressure overload–induced cardiac remodeling. RGS10 expression was markedly decreased in failing human hearts and hypertrophic murine hearts. The extent of aortic banding–induced cardiac hypertrophy, dysfunction, and fibrosis in RGS10-knockout mice was exacerbated, whereas the heart of transgenic mice with cardiac-specific RGS10 overexpression exhibited an alleviated response to pressure overload. Consistently, RGS10 also inhibited an angiotensin II–induced hypertrophic response in isolated cardiomyocytes. Mechanistically, cardiac remodeling improvement elicited by RGS10 was associated with the abrogation of mitogen-activated protein kinase kinase 1/2–extracellular signal-regulated protein kinase 1/2 signaling. Furthermore, the inhibition of mitogen-activated protein kinase kinase–extracellular signal-regulated protein kinase 1/2 transduction abolished RGS10 deletion-induced hypertrophic aggravation. These findings place RGS10 and its downstream signaling mitogen-activated protein kinase kinase–extracellular signal-regulated protein kinase 1/2 as crucial regulators of pathological cardiac hypertrophy after pressure overload and identify this pathway as a potential therapeutic target to attenuate the pressure overload–driven cardiac remodeling.

Growth Arrest-Specific 6 Exacerbates Pressure Overload-Induced Cardiac Hypertrophy

Growth arrest-specific 6 (GAS6) is a member of the vitamin K-dependent protein family that is involved in the regulation of the cardiovascular system, including vascular remodeling, homeostasis, and atherosclerosis. However, there is still no study that systemically elucidates the role of GAS6 in cardiac hypertrophy. Here, we found that GAS6 was upregulated in human dilated cardiomyopathic hearts, hypertrophic murine hearts, and angiotensin II-treated cardiomyocytes. Next, we examined the influence of GAS6 expression in response to a cardiac stress by inducing chronic pressure overload with aortic banding in wild-type and GAS6-knockout mice or cardiac-specific GAS6 overexpressing mice. Under basal conditions, the GAS6-knockout mice had normal left ventricular structure and function but after aortic banding, the mice demonstrated less hypertrophy, fibrosis, and contractile dysfunction when compared with wild-type mice. Conversely, cardiac-specific overexpression of GAS6 exacerbated aortic banding-induced cardiac hypertrophy, fibrosis, and dysfunction. Furthermore, we demonstrated that GAS6 activated the mitogen-activated protein kinase kinase 1/2-extracellular signal-regulated kinase 1/2 pathway during pressure overload-induced cardiac hypertrophy, and the pharmacological mitogen-activated protein kinase kinase 1/2 inhibitor U0126 almost completely reversed GAS6 overexpression-induced cardiac hypertrophy and fibrosis, resulting in improved cardiac function. Collectively, our data support the notion that GAS6 impairs ventricular adaptation to chronic pressure overload by activating mitogen-activated protein kinase kinase 1/2-extracellular signal-regulated kinase 1/2 signaling. Our findings suggest that strategies to reduce GAS6 activity in cardiac tissue may be a novel approach to attenuate the development of congestive heart failure.