Antioxidant Amelioration of Dilated Cardiomyopathy Caused by Conditional Deletion of NEMO/IKKγ in Cardiomyocytes

NF-κB-Specific Suppression in Cardiomyocytes Unveils Aging-Associated Responses in Cardiac Tissue

Background/Objectives: Aging is associated with structural and functional changes in the heart, including hypertrophy, fibrosis, and impaired contractility. Cellular mechanisms such as senescence, telomere shortening, and DNA damage contribute to these processes. Nuclear factor kappa B (NF-κB) has been implicated in mediating cellular responses in aging tissues, and increased NF-κB expression has been observed in the hearts of aging rodents. Therefore, NF-κB is suspected to play an important regulatory role in the cellular and molecular processes occurring in the heart during aging. This study investigates the in vivo role of NF-κB in aging-related cardiac alterations, focusing on senescence and associated cellular events. Methods: Young and old wild-type (WT) and transgenic male mice with cardiomyocyte-specific NF-κB suppression (3M) were used to assess cardiac function, morphology, senescence markers, lipofuscin deposition, DNA damage, and apoptosis. Results: Kaplan-Meier analysis revealed reduced survival in 3M mice compared to WT. Echocardiography showed evidence of eccentric hypertrophy, and both diastolic and systolic dysfunction in 3M mice. Both aged WT and 3M mice exhibited cardiac hypertrophy, with more pronounced hypertrophic changes in cardiomyocytes from 3M mice. Additionally, cardiac fibrosis, senescence-associated β-galactosidase activity, p21 protein expression, and DNA damage (marked by phosphorylated H2A.X) were elevated in aged WT and both young and aged 3M mice. Conclusions: The suppression of NF-κB in cardiomyocytes leads to pronounced cardiac remodeling, dysfunction, and cellular damage associated with the aging process. These findings suggest that NF-κB plays a critical regulatory role in cardiac aging, influencing both cellular senescence and molecular damage pathways. This has important implications for the development of therapeutic strategies aimed at mitigating age-related cardiovascular diseases.

The role of autophagy in cardiovascular disease: Cross-interference of signaling pathways and underlying therapeutic targets

Autophagy is a conserved lysosomal pathway for the degradation of cytoplasmic proteins and organelles, which realizes the metabolic needs of cells and the renewal of organelles. Autophagy-related genes (ATGs) are the main molecular mechanisms controlling autophagy, and their functions can coordinate the whole autophagic process. Autophagy can also play a role in cardiovascular disease through several key signaling pathways, including PI3K/Akt/mTOR, IGF/EGF, AMPK/mTOR, MAPKs, p53, Nrf2/p62, Wnt/β-catenin and NF-κB pathways. In this paper, we reviewed the signaling pathway of cross-interference between autophagy and cardiovascular diseases, and analyzed the development status of novel cardiovascular disease treatment by targeting the core molecular mechanism of autophagy as well as the critical signaling pathway. Induction or inhibition of autophagy through molecular mechanisms and signaling pathways can provide therapeutic benefits for patients. Meanwhile, we hope to provide a unique insight into cardiovascular treatment strategies by understanding the molecular mechanism and signaling pathway of crosstalk between autophagy and cardiovascular diseases.

Cardiac-Specific Expression of Cre Recombinase Leads to Age-Related Cardiac Dysfunction Associated with Tumor-like Growth of Atrial Cardiomyocyte and Ventricular Fibrosis and Ferroptosis

Transgenic expression of Cre recombinase driven by a specific promoter is normally used to conditionally knockout a gene in a tissue- or cell-type-specific manner. In αMHC-Cre transgenic mouse model, expression of Cre recombinase is controlled by the myocardial-specific α-myosin heavy chain (αMHC) promoter, which is commonly used to edit myocardial-specific genes. Toxic effects of Cre expression have been reported, including intro-chromosome rearrangements, micronuclei formation and other forms of DNA damage, and cardiomyopathy was observed in cardiac-specific Cre transgenic mice. However, mechanisms associated with Cardiotoxicity of Cre remain poorly understood. In our study, our data unveiled that αMHC-Cre mice developed arrhythmias and died after six months progressively, and none of them survived more than one year. Histopathological examination showed that αMHC-Cre mice had aberrant proliferation of tumor-like tissue in the atrial chamber extended from and vacuolation of ventricular myocytes. Furthermore, the αMHC-Cre mice developed severe cardiac interstitial and perivascular fibrosis, accompanied by significant increase of expression levels of MMP-2 and MMP-9 in the cardiac atrium and ventricular. Moreover, cardiac-specific expression of Cre led to disintegration of the intercalated disc, along with altered proteins expression of the disc and calcium-handling abnormality. Comprehensively, we identified that the ferroptosis signaling pathway is involved in heart failure caused by cardiac-specific expression of Cre, on which oxidative stress results in cytoplasmic vacuole accumulation of lipid peroxidation on the myocardial cell membrane. Taken together, these results revealed that cardiac-specific expression of Cre recombinase can lead to atrial mesenchymal tumor-like growth in the mice, which causes cardiac dysfunction, including cardiac fibrosis, reduction of the intercalated disc and cardiomyocytes ferroptosis at the age older than six months in mice. Our study suggests that αMHC-Cre mouse models are effective in young mice, but not in old mice. Researchers need to be particularly careful when using αMHC-Cre mouse model to interpret those phenotypic impacts of gene responses. As the Cre-associated cardiac pathology matched mostly to that of the patients, the model could also be employed for investigating age-related cardiac dysfunction.

Protein biomarkers of cardiac remodeling and inflammation associated with HFpEF and incident events

There is increasing evidence that HFpEF is a heterogeneous clinical entity and distinct molecular pathways may contribute to pathophysiology. Leveraging unbiased proteomics to identify novel biomarkers, this study seeks to understand the underlying molecular mechanisms of HFpEF. The discovery cohort consisted of HFpEF cases and non-HF controls from the CATHGEN study (N = 176); the validation cohort consisted of participants from the TECOS trial of patients with diabetes (N = 109). Proteins associated with HFpEF were included in a LASSO model to create a discriminative multi-protein model and assessed in the validation cohort. Survival models and meta-analysis were used to test the association of proteins with incident clinical outcomes, including HF hospitalization, mortality and HFpEF hospitalization in CATHGEN, TECOS and the Jackson Heart Study. In the derivation set, 190 proteins were associated with HFpEF in univariate analysis, of which 65 remained significant in the multivariate model. Twenty (30.8%) of these proteins validated in TECOS, including LCN2, U-PAR, IL-1ra, KIM1, CSTB and Gal-9 (OR 1.93-2.77, p < 0.01). LASSO regression yielded a 13-protein model which, when added to a clinical model inclusive of NT-proBNP, improved the AUC from 0.82 to 0.92 (p = 1.5 × 10-4). Five proteins were associated with incident HF hospitalization, four with HFpEF hospitalization and eleven with mortality (p < 0.05). We identified and validated multiple circulating biomarkers associated with HFpEF as well as HF outcomes. These biomarkers added incremental discriminative capabilities beyond clinical factors and NT-proBNP.

Clonal haematopoiesis of indeterminate potential-related mutations and outcome in dilated and ischaemic cardiomyopathy

AIMS

Clonal haematopoiesis of indeterminate potential (CHIP)-associated mutation is a risk factor for the development of ischaemic cardiomyopathy (ICM), but its association with non-ischaemic dilated cardiomyopathy (DCM) remains unclear. We aimed to determine the prevalence of CHIP in patients with DCM and define its risk for disease progression.

METHODS AND RESULTS

Next-generation sequencing targeting 54 common CHIP-associated genes was performed in 48 ICM and 52 DCM patients. The patients were monitored for a median of 3.1 years, and a COX proportional hazards model was used to examine the association between CHIP and adverse clinical outcome with regard to all-cause death or all-cause hospitalization. Overall, the prevalence of CHIP mutations was 19% and 13% in DCM and ICM, respectively. Seventeen per cent of ICM patients over 75 years were CHIP carriers. In DCM cohort, mutation event had already been observed in the patients who were under the age of 45 (13%). Among 54 genes analysed, DNMT3A had the highest mutation frequency, followed by TET2 and CUX1. Kaplan-Meier curve over a median of 3.1 year tracking period showed a trend towards poor clinical outcome in the DCM patients who carried DNMT3A or TET2 mutation; however, such association was not statistically significant.

CONCLUSIONS

The prevalence of CHIP is detected at a young age in DCM, and accumulation of mutational frequency in DCM patients is independent of age. However, a larger patient cohort is required to validate the association between CHIP and clinical progression in the DCM patients.

Cardiomyocyte-specific regression of nitrosative stress-mediated S-Nitrosylation of IKKγ alleviates pathological cardiac hypertrophy

IKKγ prototypically promotes NFκBp65 activity by regulating the assembly of the IKK holocomplex. In hypertrophied cardiomyocytes, the p65-p300 complex-induced regenerative efforts are neutralized by the p53-p300 complex-mediated apoptotic load resulting in compromised cardiac function. The present study reports that nitrosative stress leads to S-Nitrosylation of IKKγ in hypertrophied cardiomyocytes in a pre-clinical model. Using a cardiomyocyte-targeted nanoconjugate, IKKγ S-Nitrosylation-resistant mutant plasmids were delivered to the pathologically hypertrophied heart that resulted in improved cardiac function by amelioration of cardiomyocyte apoptosis and simultaneous induction of their cell cycle re-entry machinery. Mechanistically, in IKKγ S-Nitrosyl mutant-transfected hypertrophied cells, increased IKKγ-p300 binding downregulated the binding of p53 and p65 with p300. This shifted the binding preference of p65 from p300 to HDAC1 resulting in upregulated expression of cyclin D1 and CDK2 via the p27/pRb pathway. This approach has therapeutic advantage over mainstream anti-hypertrophic remedies which concomitantly reduce the regenerative prowess of resident cardiomyocytes during hypertrophy upon downregulation of myocyte apoptosis. Therefore, cardiomyocyte-targeted delivery of IKKγ S-Nitrosyl mutants during hypertrophy can be exploited as a novel strategy to re-muscularize the diseased heart.

NF-κB, A Potential Therapeutic Target in Cardiovascular Diseases

Cardiovascular diseases (CVDs) are the leading cause of death globally. Atherosclerosis is the basis of major CVDs - myocardial ischemia, heart failure, and stroke. Among numerous functional molecules, the transcription factor nuclear factor κB (NF-κB) has been linked to downstream target genes involved in atherosclerosis. The activation of the NF-κB family and its downstream target genes in response to environmental and cellular stress, hypoxia, and ischemia initiate different pathological events such as innate and adaptive immunity, and cell survival, differentiation, and proliferation. Thus, NF-κB is a potential therapeutic target in the treatment of atherosclerosis and related CVDs. Several biologics and small molecules as well as peptide/proteins have been shown to regulate NF-κB dependent signaling pathways. In this review, we will focus on the function of NF-κB in CVDs and the role of NF-κB inhibitors in the treatment of CVDs.

Transcription Factors Involved in the Development and Prognosis of Cardiac Remodeling

To compensate increasing workload, heart must work harder with structural changes, indicated by increasing size and changing shape, causing cardiac remodeling. However, pathological and unlimited compensated cardiac remodeling will ultimately lead to decompensation and heart failure. In the past decade, numerous studies have explored many signaling pathways involved in cardiac remodeling, but the complete mechanism of cardiac remodeling is still unrecognized, which hinders effective treatment and drug development. As gene transcriptional regulators, transcription factors control multiple cellular activities and play a critical role in cardiac remodeling. This review summarizes the regulation of fetal gene reprogramming, energy metabolism, apoptosis, autophagy in cardiomyocytes and myofibroblast activation of cardiac fibroblasts by transcription factors, with an emphasis on their potential roles in the development and prognosis of cardiac remodeling.

Fibroblast-specific IKKβ deficiency ameliorates angiotensin II-induced adverse cardiac remodeling in mice

Cardiac inflammation and fibrosis contribute significantly to hypertension-related adverse cardiac remodeling. IκB kinase β (IKK-β), a central coordinator of inflammation through activation of NF-κB, has been demonstrated as a key molecular link between inflammation and cardiovascular disease. However, the cell-specific contribution of IKK-β signaling toward adverse cardiac remodeling remains elusive. Cardiac fibroblasts are one of the most populous nonmyocyte cell types in the heart that play a key role in mediating cardiac fibrosis and remodeling. To investigate the function of fibroblast IKK-β, we generated inducible fibroblast-specific IKK-β–deficient mice. Here, we report an important role of IKK-β in the regulation of fibroblast functions and cardiac remodeling. Fibroblast-specific IKK-β–deficient male mice were protected from angiotensin II–induced cardiac hypertrophy, fibrosis, and macrophage infiltration. Ablation of fibroblast IKK-β inhibited angiotensin II–stimulated fibroblast proinflammatory and profibrogenic responses, leading to ameliorated cardiac remodeling and improved cardiac function in IKK-β–deficient mice. Findings from this study establish fibroblast IKK-β as a key factor regulating cardiac fibrosis and function in hypertension-related cardiac remodeling.

Identification of novel pheno-groups in heart failure with preserved ejection fraction using machine learning

Objective

Heart failure with preserved ejection fraction (HFpEF) is a heterogeneous syndrome. We aimed to derive HFpEF phenotype-based groups ('phenogroups') based on clinical and echocardiogram data using machine learning, and to compare clinical characteristics, proteomics and outcomes across the phenogroups.

Methods

We applied model-based clustering to 32 echocardiogram and 11 clinical and laboratory variables collected in stable condition from 320 HFpEF outpatients in the Karolinska-Rennes cohort study (56% female, median 78 years (IQR: 71–83)). Baseline proteomics and the composite end point of all-cause mortality or heart failure (HF) hospitalisation were used in secondary analyses.

Results

We identified six phenogroups, for which significant differences in the prevalence of concomitant atrial fibrillation (AF), anaemia and kidney disease were observed (p<0.05). Fifteen out of 86 plasma proteins differed between phenogroups (false discovery rate, FDR<0.05), including biomarkers of HF, AF and kidney function. The composite end point was significantly different between phenogroups (log-rank p<0.001), at short-term (100 days), mid-term (18 months) and longer-term follow-up (1000 days). Phenogroup 2 was older, with poorer diastolic and right ventricular function and higher burden of risk factors as AF (85%), hypertension (83%) and chronic obstructive pulmonary disease (30%). In this group a third experienced the primary outcome to 100 days, and two-thirds to 18 months (HR (95% CI) versus phenogroups 1, 3, 4, 5, 6: 1.5 (0.8–2.9); 5.7 (2.6–12.8); 2.9 (1.5–5.6); 2.7 (1.6–4.6); 2.1 (1.2–3.9)).

Conclusions

Using machine learning we identified distinct HFpEF phenogroups with differential characteristics and outcomes, as well as differential levels of inflammatory and cardiovascular proteins.

Cardiac-Specific Cre Induces Age-Dependent Dilated Cardiomyopathy (DCM) in Mice

The genetic modification of the mouse genome using the cre-lox system has been an invaluable tool in deciphering gene and protein function in a temporal and/or spatial manner. However, it has its pitfalls, as researchers have shown that the unregulated expression of cre recombinase can cause DNA damage, the consequences of which can be very detrimental to mouse health. Previously published literature on the most utilized cardiac-specific cre, αMHC-cre, mouse model exhibited a nonlethal hypertrophic cardiomyopathy (HCM) with aging. However, using the same αMHC-cre mice, we observed a cardiac pathology, resulting in complete lethality by 11 months of age. Echocardiography and histology revealed that the αMHC-cre mice were displaying symptoms of dilated cardiomyopathy (DCM) by seven months of age, which ultimately led to their demise in the absence of any HCM at any age. Molecular analysis showed that this phenotype was associated with the DNA damage response through the downregulation of activated p38 and increased expression of JNK, p53, and Bax, known inducers of myocyte death resulting in fibrosis. Our data urges strong caution when interpreting the phenotypic impact of gene responses using αMHC-cre mice, since a lethal DCM was induced by the cre driver in an age-dependent manner in this commonly utilized model system.

Placental Expression of NEMO Protein in Normal Pregnancy and Preeclampsia

Background

Preeclamptic pregnancies often present an intensified inflammatory state associated with the nuclear activity of NFκB. NEMO is an essential regulator of nuclear factor kappa B (NFκB) in cytoplasmic and nuclear cellular compartments. The aim of the present study is to examine the level and localization of the NEMO protein in preeclamptic and nonpreeclamptic placentas.

Methods

The study includes 97 preeclamptic cases and 88 controls. NEMO distribution was analyzed immunohistochemically. Its localization in the nuclear and cytoplasmic fractions, as well as in total homogenates of placental samples, was studied by western blot and ELISA.

Results

The western blot and ELISA results indicate a significant difference in NEMO concentration in the total and nuclear fractions between preeclamptic and control samples (p < 0.01 and p < 0.001, respectively). In the cytoplasmic complement, similar levels of NEMO were found in preeclamptic and control placentas. In addition, immunohistochemical staining revealed that the NEMO protein is mainly localized in the syncytiotrophoblast layer, with controls demonstrating a stronger reaction with NEMO antibodies. This study also shows that the placental level of NEMO depends on the sex of the fetus.

Conclusions

The depletion of the NEMO protein in the cellular compartments of placental samples may activate one of the molecular pathways influencing the development of preeclampsia, especially in pregnancies with a female fetus. A reduction of the NEMO protein in the nuclear fraction of preeclamptic placentas may intensify the inflammatory state characteristic for preeclampsia and increase the level of apoptosis and necrosis within preeclamptic placentas.

Bakuchiol protects against pathological cardiac hypertrophy by blocking NF-κB signaling pathway

Bakuchiol (Bak), a monoterpene phenol isolated from the seeds of Psoralea corylifolia, has been widely used to treat a large variety of diseases in both Indian and Chinese folkloric medicine. However, the effects of Bak on cardiac hypertrophy remain unclear. Therefore, the present study was designed to determine whether Bak could alleviate cardiac hypertrophy. Mice were subjected to aortic banding (AB) to induce cardiac hypertrophy model. Bak of 1 ml/100 g body weight was given by oral gavage once a day from 1 to 8 weeks after surgery. Our data demonstrated for the first time that Bak could attenuate pressure overload-induced cardiac hypertrophy and could attenuate fibrosis and the inflammatory response induced by AB. The results further revealed that the effect of Bak on cardiac hypertrophy was mediated by blocking the activation of the NF-κB signaling pathway. In vitro studies performed in neonatal rat cardiomyocytes further proved that the protective effect of Bak on cardiac hypertrophy is largely dependent on the NF-κB pathway. Based on our results, Bak shows profound potential for its application in the treatment of pathological cardiac hypertrophy, and we believe that Bak may be a promising therapeutic candidate to treat cardiac hypertrophy and heart failure.

NF-κB inhibition rescues cardiac function by remodeling calcium genes in a Duchenne muscular dystrophy model

Duchenne muscular dystrophy (DMD) is a neuromuscular disorder causing progressive muscle degeneration. Although cardiomyopathy is a leading mortality cause in DMD patients, the mechanisms underlying heart failure are not well understood. Previously, we showed that NF-κB exacerbates DMD skeletal muscle pathology by promoting inflammation and impairing new muscle growth. Here, we show that NF-κB is activated in murine dystrophic (mdx) hearts, and that cardiomyocyte ablation of NF-κB rescues cardiac function. This physiological improvement is associated with a signature of upregulated calcium genes, coinciding with global enrichment of permissive H3K27 acetylation chromatin marks and depletion of the transcriptional repressors CCCTC-binding factor, SIN3 transcription regulator family member A, and histone deacetylase 1. In this respect, in DMD hearts, NF-κB acts differently from its established role as a transcriptional activator, instead promoting global changes in the chromatin landscape to regulate calcium genes and cardiac function.

The NF-κB Family of Transcription Factors and Its Role in Thyroid Physiology

The nuclear factor (NF)-κB signaling pathway controls a variety of important biological functions, including immune and inflammatory responses, differentiation, cell growth, tumorigenesis, and apoptosis. Two distinct pathways of NF-κB activation are known. The classical, canonical pathway is found virtually in all mammalian cells and NF-κB activation is mediated by the IKK complex, consisting of the IKK1/IKKα and IKK2/IKKβ catalytic kinase subunits and the NF-κB essential modulator (NEMO)/IKKγ protein. The NF-κB-driven transcriptional responses to many different stimuli have been widely characterized in the pathophysiology of the mammalian immune system, mainly because this transcription factor regulates the expression of cytokines, growth factors, and effector enzymes in response to ligation of cellular receptors involved in immunity and inflammation. However, an impressive literature produced in the last two decades shows that NF-κB signaling plays an important role also outside of the immune system, performing different roles and functions depending on the type of tissue and organ. In thyroid, NF-κB signaling is crucial for thyrocytes survival and expression of critical thyroid markers, including Nis, Ttf1, Pax8, Tpo, and thyroglobulin, making this transcription factor essential for maintenance of normal thyroid function.

Thymosin Beta-4 Is Elevated in Women With Heart Failure With Preserved Ejection Fraction

BACKGROUND

Thymosin beta-4 (TB4) is an X-linked gene product with cardioprotective properties. Little is known about plasma concentration of TB4 in heart failure (HF), and its relationship with other cardiovascular biomarkers. We sought to evaluate circulating TB4 in HF patients with preserved (HFpEF) or reduced (HFrEF) ejection fraction compared to non-HF controls.

METHODS AND RESULTS

TB4 was measured using a liquid chromatography and mass spectrometry assay in age- and sex-matched HFpEF (n=219), HFrEF (n=219) patients, and controls (n=219) from a prospective nationwide study. Additionally, a 92-marker multiplex proximity extension assay was measured to identify biomarker covariates. Compared with controls, plasma TB4 was elevated in HFpEF (985 [421-1723] ng/mL versus 1401 [720-2379] ng/mL, P<0.001), but not in HFrEF (1106 [556-1955] ng/mL, P=0.642). Stratifying by sex, only women (1623 [1040-2625] ng/mL versus 942 [386-1891] ng/mL, P<0.001), but not men (1238.5 [586-1967] ng/mL versus 1004 [451-1538] ng/mL, P=1.0), had significantly elevated TB4 in the setting of HFpEF. Adjusted for New York Heart Association class, N-terminal pro B-type natriuretic peptide, age, and myocardial infarction, hazard ratio to all-cause mortality is significantly higher in women with elevated TB4 (1.668, P=0.036), but not in men (0.791, P=0.456) with HF. TB4 is strongly correlated with a cluster of 7 markers from the proximity extension assay panel, which are either X-linked, regulated by sex hormones, or involved with NF-κB signaling.

CONCLUSIONS

We show that plasma TB4 is elevated in women with HFpEF and has prognostic information. Because TB4 can preserve EF in animal studies of cardiac injury, the relation of endogenous, circulating TB4 to X chromosome biology and differential outcomes in female heart disease warrants further study.

Novel Protective Role of Myeloid Differentiation 1 in Pathological Cardiac Remodelling

Myeloid differentiation 1 (MD-1), a secreted protein interacting with radioprotective 105 (RP105), plays an important role in Toll-like receptor 4 (TLR4) signalling pathway. Previous studies showed that MD-1 may be restricted in the immune system. In this study, we demonstrated for the first time that MD-1 was highly expressed in both human and animal hearts. We also discovered that cardiac-specific overexpression of MD-1 significantly attenuated pressure overload-induced cardiac hypertrophy, fibrosis, and dysfunction, whereas loss of MD-1 had the opposite effects. Similar results were observed for in vitro angiotensin II-induced neonatal rat cardiomyocyte hypertrophy. The antihypertrophic effects of MD-1 under hypertrophic stimuli were associated with the blockage of MEK-ERK 1/2 and NF-κB signalling. Blocking MEK-ERK 1/2 signalling with a pharmacological inhibitor (U0126) greatly attenuated the detrimental effects observed in MD-1 knockout cardiomyocytes exposed to angiotensin II stimuli. Similar results were observed by blocking NF-κB signalling with a pharmacological inhibitor (BAY11–7082). Our data indicate that MD-1 inhibits cardiac hypertrophy and suppresses cardiac dysfunction during the remodelling process, which is dependent on its modulation of the MEK-ERK 1/2 and NF-κB signalling pathways. Thus, MD-1 might be a novel target for the treatment of pathological cardiac hypertrophy.

Sub-cellular localization specific SUMOylation in the heart

Although the majority of SUMO substrates are localized in the nucleus, SUMOylation is not limited to nuclear proteins and can be also detected in extra-nuclear proteins. In this review, we will highlight and discuss how SUMOylation in different cellular compartments regulate biological processes. First, we will discuss the key role of SUMOylation of proteins in the extra-nuclear compartment in cardiomyocytes, which is overwhelmingly cardio-protective. On the other hand, SUMOylation of nuclear proteins is generally detrimental to the cardiac function mainly because of the trans-repressive nature of SUMOylation on many transcription factors. We will also discuss the potential role of SUMOylation in epigenetic regulation. In this review, we will propose a new concept that shuttling of SUMO proteases between the nuclear and extra-nuclear compartments without changing their enzymatic activity regulates the extent of SUMOylation in these compartments and determines the response and fate of cardiomyocytes after cardiac insults. Approaches focused specifically to inhibit this shuttling in cardiomyocytes will be necessary to understand the whole picture of SUMOylation and its pathophysiological consequences in the heart, especially after cardiac insults. This article is part of a Special Issue entitled: Genetic and epigenetic control of heart failure - edited by Jun Ren & Megan Yingmei Zhang.

Signaling Pathways in Cardiac Myocyte Apoptosis

Cardiovascular diseases, the number 1 cause of death worldwide, are frequently associated with apoptotic death of cardiac myocytes. Since cardiomyocyte apoptosis is a highly regulated process, pharmacological intervention of apoptosis pathways may represent a promising therapeutic strategy for a number of cardiovascular diseases and disorders including myocardial infarction, ischemia/reperfusion injury, chemotherapy cardiotoxicity, and end-stage heart failure. Despite rapid growth of our knowledge in apoptosis signaling pathways, a clinically applicable treatment targeting this cellular process is currently unavailable. To help identify potential innovative directions for future research, it is necessary to have a full understanding of the apoptotic pathways currently known to be functional in cardiac myocytes. Here, we summarize recent progress in the regulation of cardiomyocyte apoptosis by multiple signaling molecules and pathways, with a focus on the involvement of these pathways in the pathogenesis of heart disease. In addition, we provide an update regarding bench to bedside translation of this knowledge and discuss unanswered questions that need further investigation.

Smad Nuclear Interacting Protein 1 Acts as a Protective Regulator of Pressure Overload-Induced Pathological Cardiac Hypertrophy

Background

Smad nuclear interacting protein 1 (SNIP1) plays a critical role in cell proliferation, transformation of embryonic fibroblasts, and immune regulation. However, the role of SNIP1 in cardiac hypertrophy remains unclear.

Methods and Results

Here we examined the role of SNIP1 in pressure overload–induced cardiac hypertrophy and its mechanisms. Our results demonstrated that SNIP1 expression was downregulated in human dilated cardiomyopathic hearts, aortic banding‐induced mice hearts, and angiotensin II–treated cardiomyocytes. Accordingly, SNIP1 deficiency significantly exacerbated aortic banding–induced cardiac hypertrophy, fibrosis, and contractile dysfunction, whereas cardiac‐specific overexpression of SNIP1 markedly recovered pressure overload–induced cardiac hypertrophy and fibrosis. Besides that, SNIP1 protected neonatal rat cardiomyocytes against angiotensin II–induced hypertrophy in vitro. Moreover, we identified that SNIP1 suppressed nuclear factor‐κB signaling during pathological cardiac hypertrophy, and inhibition of nuclear factor‐κB signaling by a cardiac‐specific conditional inhibitor of κB^S32A/S36A transgene blocked these adverse effects of SNIP1 deficiency on hearts.

Conclusions

Together, our findings demonstrated that SNIP1 had protective effects in pressure overload–induced pathological cardiac hypertrophy via inhibition of nuclear factor‐κB signaling. Thus, SNIP1 may be a novel approach for the treatment of heart failure.

NF-κB Essential Modulator (NEMO) Is Critical for Thyroid Function

The I-κB kinase (IKK) subunit NEMO/IKKγ (NEMO) is an adapter molecule that is critical for canonical activation of NF-κB, a pleiotropic transcription factor controlling immunity, differentiation, cell growth, tumorigenesis, and apoptosis. To explore the functional role of canonical NF-κB signaling in thyroid gland differentiation and function, we have generated a murine strain bearing a genetic deletion of the NEMO locus in thyroid. Here we show that thyrocyte-specific NEMO knock-out mice gradually develop hypothyroidism after birth, which leads to reduced body weight and shortened life span. Histological and molecular analysis indicate that absence of NEMO in thyrocytes results in a dramatic loss of the thyroid gland cellularity, associated with down-regulation of thyroid differentiation markers and ongoing apoptosis. Thus, NEMO-dependent signaling is essential for normal thyroid physiology.

The alpha1-adrenergic receptors in cardiac hypertrophy: signaling mechanisms and functional implications

Cardiac hypertrophy is a complex remodeling process of the heart induced by physiological or pathological stimuli resulting in increased cardiomyocyte size and myocardial mass. Whereas cardiac hypertrophy can be an adaptive mechanism to stressful conditions of the heart, prolonged hypertrophy can lead to heart failure which represents the primary cause of human morbidity and mortality. Among G protein-coupled receptors, the α1-adrenergic receptors (α1-ARs) play an important role in the development of cardiac hypertrophy as demonstrated by numerous studies in the past decades, both in primary cardiomyocyte cultures and genetically modified mice. The results of these studies have provided evidence of a large variety of α1-AR-induced signaling events contributing to the defining molecular and cellular features of cardiac hypertrophy. Recently, novel signaling mechanisms have been identified and new hypotheses have emerged concerning the functional role of the α1-adrenergic receptors in the heart. This review will summarize the main signaling pathways activated by the α1-AR in the heart and their functional implications in cardiac hypertrophy.

Identifying panaxynol, a natural activator of nuclear factor erythroid-2 related factor 2 (Nrf2) from American ginseng as a suppressor of inflamed macrophage-induced cardiomyocyte hypertrophy

ETHNOPHARMACOLOGICAL RELEVANCE

American ginseng is capable of ameliorating cardiac dysfunction and activating Nrf2, a master regulator of antioxidant defense, in the heart. This study was designed to isolate compounds from American ginseng and to determine those responsible for the Nrf2-mediated resolution of inflamed macrophage-induced cardiomyocyte hypertrophy.

MATERIALS AND METHODS

A standardized crude extract of American ginseng was supplied by the National Research Council of Canada, Institute for National Measurement Standards. A bioassay-based fractionization of American ginseng was performed to identify the putative substances which could activate Nrf2-mediated suppression of pro-inflammatory cytokine expression in macrophages and macrophage-mediated pro-hypertrophic growth in cardiomyocytes.

RESULTS

A hexane fraction of an anti-inflammatory crude extract of American ginseng was found to be most effective in suppressing the inflammatory responses in macrophages. Preparative, reverse-phase HPLC and a comparative analysis by analytical scale LC-UV/MS revealed the hexane fraction contains predominantly C17 polyacetylenes and linolenic acid. Panaxynol, one of the major polyacetylenes, was found to be a potent Nrf2 activator. Panaxynol posttranscriptionally activated Nrf2 by inhibiting Kelch-like ECH-associated protein (Keap) 1-mediated degradation without affecting the binding of Keap1 and Nrf2. Moreover, panaxynol suppressed a selected set of cytokine expression via the activation of Nrf2 while minimally regulating nuclear factor-kappa B (NF-κB)-mediated cytokine expression in macrophages. It also dramatically inhibited the inflamed macrophage-mediated cardiomyocyte death and hypertrophy by activating Nrf2 in macrophages.

CONCLUSIONS

These results demonstrate that American ginseng-derived panaxynol is a specific Nrf2 activator and panaxynol-activated Nrf2 signaling is at least partly responsible for American ginseng-induced health benefit in the heart.

Testosterone protects cardiac myocytes from superoxide injury via NF-κB signalling pathways

AIMS

Cellular and molecular mechanisms underlying the effects of androgenic hormone testosterone on the heart remain unclear. This study examined the impact of testosterone on viability of cardiac myocytes and the role of NF-κB signalling pathways.

MATERIALS AND METHODS

Rat H9c2 myocytes were cultured in steroid-free media and incubated with hydrogen peroxide (H2O2, 200 μM, 6h). NF-κB expression was knocked down by RelA (p65) siRNA interference. Testosterone (5-100 nM, 24-48 h) was provided into the media and androgen receptor (AR) blocked by flutamide (100 nM). Cell apoptotic/necrotic death was determined by morphological examination and flow-cytometric analysis. Gene expression was examined by Western blotting analysis.

KEY FINDINGS

Testosterone supplements reduced the superoxide-induced apoptotic/necrotic death, stimulated NF-κB (RelA) expression, activated Akt activity, and inhibited Caspase-3 expression in the cardiac myocytes. The hormonal effects were abolished by either AR blocker flutamide or NF-κB-knockdown. Testosterone also induced ERK1/2 activation, which was not affected by flutamide or NF-κB knockdown, and blocking the ERK activity did not affect the protective effect of the hormone on the cells.

SIGNIFICANCE

This study demonstrates that exogenous testosterone supplementation protects cardiac myocytes from superoxide injury via AR mediation and dependent on normally functional canonical NF-κB (RelA/p50) signalling pathways. The NF-κB signalling may be an important key molecular basis for myocardial benefits of hormone (testosterone) therapy.

Degradation systems in heart failure

Heart failure is a complex clinical syndrome that results from any structural or functional impairment of ventricular filling or the ejection of blood, and is a leading cause of morbidity and mortality in industrialized countries. The mechanisms underlying the development of heart failure are multiple, complex and not well understood. Cardiac mass and its homeostasis are maintained by the balance between protein synthesis and degradation, and an imbalance is likely to result in cellular dysfunction and disease. The protein degradation systems are the principle mechanisms for maintaining cellular homeostasis via protein quality control. Three major protein degradation systems have been identified, namely the calpain system, autophagy, and the ubiquitin proteasome system. Proinflammatory mediators involve the development and progression of heart failure. DNA and RNA degradation systems play a critical role in regulating inflammation and maintaining cellular homeostasis mediated by damaged DNA clearance and posttranscriptional regulation, respectively. This review discusses some recent advances in understanding the role of these degradation systems in heart failure.

Deubiquitinating enzyme CYLD mediates pressure overload-induced cardiac maladaptive remodeling and dysfunction via downregulating Nrf2

Ubiquitin proteasome system (UPS) consists of ubiquitin, ubiquitin-activating enzymes (E1s), ubiquitin-conjugating enzymes (E2s), ubiquitin ligases (E3s), proteasomes, and deubiquitinating enzymes (DUBs). Ubiquitin, E1s, several E2s, E3s, and proteasomes play an important role in the regulation of cardiac homeostasis and dysfunction; however, less is known about the role of DUBs in the heart. Here, we uncovered a crucial role of cyclindromatosis (CYLD), a DUB, in mediating cardiac maladaptive remodeling and dysfunction. CYLD expression was dramatically upregulated in the cardiomyocytes of hypertrophic and failing human and murine hearts. Knockout of CYLD improved survival rate and alleviated cardiac hypertrophy, fibrosis, apoptosis, oxidative stress, and dysfunction in mice that were subjected to sustained pressure overload induced by transverse aortic constriction. Deep sequencing and gene array analyses revealed that the most dramatically changed genes are those involving in the free radical scavenging pathway and cardiovascular disease, including fos, jun, myc, and nuclear factor erythroid-2 related factor 2 (Nrf2) in the heart. Moreover, knockdown of CYLD enhanced mitogen-activated protein kinase (MAPK) ERK- and p38-mediated expression of c-jun, c-fos, and c-myc, which govern Nrf2 expression in cardiomyocytes. The CYLD deficiency-induced suppression of reactive oxygen species (ROS) formation, death and hypertrophy in cardiomyocytes was blocked by additional knockdown of Nrf2. Taken together, our findings demonstrate for the first time that CYLD mediates cardiac maladaptive remodeling and dysfunction, most likely via enhancing myocardial oxidative stress in response to pressure overload. At the molecular level, CYLD interrupts the ERK- and p38-/AP-1 and c-Myc pathways to suppress Nrf2-operated antioxidative capacity, thereby enhancing oxidative stress in the heart.

Cardiomyocyte p65 nuclear factor-κB is necessary for compensatory adaptation to pressure overload

BACKGROUND

Nuclear factor κB (NF-κB) is often implicated in contributing to the detrimental effects of cardiac injury. This ostensibly negative view of NF-κB competes with its important role in the normal host inflammatory and immune response. We have previously demonstrated that pharmacological inhibition of NF-κB at the time of acute pressure overload accelerates the progression of left ventricular hypertrophy to heart failure in mice. NF-κB regulates angiogenesis and other factors responsible for compensatory reaction to intracellular hypoxia. We hypothesized that impaired angiogenesis may be the trigger, not the result, of pathological left ventricular hypertrophy through NF-κB-related pathways.

METHODS AND RESULTS

Transgenic mice were generated with cardiomyocyte-specific deletion of the p65 subunit of NF-κB. Mice underwent transverse aortic constriction and serially followed up with echocardiography for 6 weeks. Cardiomyocyte p65 NF-κB deletion promoted maladaptive left ventricular hypertrophy and accelerated progression toward heart failure as measured by ejection fraction, left ventricular mass, and lung congestion. Transgenic mice had higher levels of fibrosis and periostin expression. Whole-field digital microscopy revealed increased capillary domain areas in knockout mice while concurrently demonstrating decreased microvessel density. This observation was associated with decreased expression of hypoxia-inducible factor 1α.

CONCLUSIONS

Rather than developing compensatory left ventricular hypertrophy, pressure overload in cardiomyocyte NF-κB-deficient mice resulted in functional deterioration that was associated with increased fibrosis, decreased hypoxia-inducible factor expression, and decreased microvessel density. These observations mechanistically implicate NF-κB, and its regulation of hypoxic stress, as an important factor determining the path between adaptive hypertrophy and maladaptive heart failure.

Cardiac-specific suppression of NF-κB signaling prevents diabetic cardiomyopathy via inhibition of the renin-angiotensin system

Activation of NF-κB signaling in the heart may be protective or deleterious depending on the pathological context. In diabetes, the role of NF-κB in cardiac dysfunction has been investigated using pharmacological approaches that have a limitation of being nonspecific. Furthermore, the specific cellular pathways by which NF-κB modulates heart function in diabetes have not been identified. To address these questions, we used a transgenic mouse line expressing mutated IκB-α in the heart (3M mice), which prevented activation of canonical NF-κB signaling. Diabetes was developed by streptozotocin injections in wild-type (WT) and 3M mice. Diabetic WT mice developed systolic and diastolic cardiac dysfunction by the 12th week, as measured by echocardiography. In contrast, cardiac function was preserved in 3M mice up to 24 wk of diabetes. Diabetes induced an elevation in cardiac oxidative stress in diabetic WT mice but not 3M mice compared with nondiabetic control mice. In diabetic WT mice, an increase in the phospholamban/sarco(endo)plasmic reticulum Ca(2+)-ATPase 2 ratio and decrease in ryanodine receptor expression were observed, whereas diabetic 3M mice showed an opposite effect on these parameters of Ca(2+) handling. Significantly, renin-angiotensin system activity was suppressed in diabetic 3M mice compared with an increase in WT animals. In conclusion, these results demonstrate that inhibition of NF-κB signaling in the heart prevents diabetes-induced cardiac dysfunction through preserved Ca(2+) handling and inhibition of the cardiac renin-angiotensin system.

Interferon regulatory factor 7 functions as a novel negative regulator of pathological cardiac hypertrophy

Cardiac hypertrophy is a complex pathological process that involves multiple factors including inflammation and apoptosis. Interferon regulatory factor 7 (IRF7) is a multifunctional regulator that participates in immune regulation, cell differentiation, apoptosis, and oncogenesis. However, the role of IRF7 in cardiac hypertrophy remains unclear. We performed aortic banding in cardiac-specific IRF7 transgenic mice, IRF7 knockout mice, and the wild-type littermates of these mice. Our results demonstrated that IRF7 was downregulated in aortic banding-induced animal hearts and cardiomyocytes that had been treated with angiotensin II or phenylephrine for 48 hours. Accordingly, heart-specific overexpression of IRF7 significantly attenuated pressure overload-induced cardiac hypertrophy, fibrosis, and dysfunction, whereas loss of IRF7 led to opposite effects. Moreover, IRF7 protected against angiotensin II-induced cardiomyocyte hypertrophy in vitro. Mechanistically, we identified that IRF7-dependent cardioprotection was mediated through IRF7 binding to inhibitor of κB kinase-β, and subsequent nuclear factor-κB inactivation. In fact, blocking nuclear factor-κB signaling with cardiac-specific inhibitors of κBα(S32A/S36A) super-repressor transgene counteracted the adverse effect of IRF7 deficiency. Conversely, activation of nuclear factor-κB signaling via a cardiac-specific conditional inhibitor of κB kinase-β(S177E/S181E) (constitutively active) transgene negated the antihypertrophic effect of IRF7 overexpression. Our data demonstrate that IRF7 acts as a novel negative regulator of pathological cardiac hypertrophy by inhibiting nuclear factor-κB signaling and may constitute a potential therapeutic target for pathological cardiac hypertrophy.

Dihydro-CDDO-trifluoroethyl amide suppresses inflammatory responses in macrophages via activation of Nrf2

Nuclear factor erythroid 2-related factor (Nrf2) is the major regulator of cellular defenses against various pathological stresses in a variety of organ systems, thus Nrf2 has evolved to be an attractive drug target for the treatment and/or prevention of human disease. Several synthetic oleanolic triterpenoids including dihydro-CDDO-trifluoroethyl amide (dh404) appear to be potent activators of Nrf2 and exhibit chemopreventive promises in multiple disease models. While the pharmacological efficacy of Nrf2 activators may be dependent on the nature of Nrf2 activation in specific cell types of target organs, the precise role of Nrf2 in mediating biological effects of Nrf2 activating compounds in various cell types remains to be further explored. Herein we report a unique and Nrf2-dependent anti-inflammatory profile of dh404 in inflamed macrophages. In lipopolysaccharide (LPS)-inflamed RAW264.7 macrophages, dh404 dramatically suppressed the expression of pro-inflammatory cytokines including inducible nitric oxide synthase (iNOS), monocyte chemotactic protein-1 (MCP-1), and macrophage inflammatory protein-1 beta (MIP-1β), while minimally regulating the expression of interleulin-6 (IL-6), IL-1β, and tumor necrosis factor alpha (TNFα). Dh404 potently activated Nrf2 signaling; however, it did not affect LPS-induced NF-κB activity. Dh404 did not interrupt the interaction of Nrf2 with its endogenous inhibitor Kelch-like ECH associating protein 1 (Keap1) in macrophages. Moreover, knockout of Nrf2 blocked the dh404-induced anti-inflammatory responses in LPS-inflamed macrophages. These results demonstrated that dh404 suppresses pro-inflammatory responses in macrophages via an activation of Nrf2 independently of Keap1 and NF-κB, suggesting a unique therapeutic potential of dh404 for specific targeting a Nrf2-mediated resolution of inflammation.

NF-κB mediated miR-21 regulation in cardiomyocytes apoptosis under oxidative stress

Oxidative stress, defined as an excess production of reactive oxygen species (ROS), is shown to play an important role in the pathophysiology of cardiac remodeling including cell death and contractile dysfunction. Therefore, the balance between ROS production and removal of excess ROS is essential in maintaining the redox state and homeostasis balance in the cell. The increased ROS further activates nuclear factor-κB (NF-κB), a redox-sensitive transcription factor and promotes cell death. Recently, microRNAs (miRNAs) have been identified as critical regulators of various pathophysiological processes of cardiac remodeling; however, NF-κB-mediated miRNA's role in cardiomyocytes under oxidative stress remains undetermined. The miR-21 has been implicated in diverse cardiac remodeling; but, NF-κB-mediated miR-21 modulation in oxidative stress is currently unknown. Neonatal cardiomyocytes were transfected with IκBα mutant, miR-21 mimetic, and inhibitors separately, and were challenged with H2O2. The target gene, programmed cell death 4 (PDCD4), ROS activity, and NF-κB translocation were analyzed. Our results indicated that NF-κB positively regulated miR-21 expression under oxidative stress, and PDCD4 was a direct target for miR-21. NF-κB further regulated the expression of PDCD4 in H2O2-induced oxidative stress. Moreover, H2O2-induced ROS activity and cardiomyocytes apoptosis were partly protected by overexpression of miR-21 and displayed an important role in ROS-mediated cardiomyocytes injury. We evaluated a critical role of NF-κB-mediated miR-21 modulation in H2O2-induced oxidative stress in cardiomyocytes by targeting PDCD4. Our data may provide a new insight of miR-21's role in cardiac diseases primarily mediated by ROS.

Cardiomyocyte-specific p65 NF-κB deletion protects the injured heart by preservation of calcium handling

NF-κB is a well-known transcription factor that is intimately involved with inflammation and immunity. We have previously shown that NF-κB promotes inflammatory events and mediates adverse cardiac remodeling following ischemia reperfusion (I/R). Conversely, others have pointed to the beneficial influence of NF-κB in I/R injury related to its anti-apoptotic effects. Understanding the seemingly disparate influence of manipulating NF-κB is hindered, in part, by current approaches that only indirectly interfere with the function of its most transcriptionally active unit, p65 NF-κB. Mice were generated with cardiomyocyte-specific deletion of p65 NF-κB. Phenotypically, these mice and their hearts appeared normal. Basal and stimulated p65 expression were significantly reduced in whole hearts and completely ablated in isolated cardiomyocytes. When compared with wild-type mice, transgenic animals were protected from both global I/R by Langendorff as well as regional I/R by coronary ligation and release. The protected, transgenic hearts had less cytokine activity and decreased apoptosis. Furthermore, p65 ablation was associated with enhanced calcium reuptake by the sarcoplasmic reticulum. This influence on calcium handling was related to increased expression of phosphorylated phospholamban in conditional p65 null mice. In conclusion, cardiomyocyte-specific deletion of the most active, canonical NF-κB subunit affords cardioprotection to both global and regional I/R injury. The beneficial effects of NF-κB inhibition are related, in part, to modulation of intracellular calcium homeostasis.

Role of telomere dysfunction in cardiac failure in Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD), the most common inherited muscular dystrophy of childhood, leads to death due to cardiorespiratory failure. Paradoxically, mdx mice with the same genetic deficiency of dystrophin exhibit minimal cardiac dysfunction, impeding the development of therapies. We postulated that the difference between mdx and DMD might result from differences in telomere lengths in mice and humans. We show here that, like DMD patients, mice that lack dystrophin and have shortened telomeres (mdx/mTR(KO)) develop severe functional cardiac deficits including ventricular dilation, contractile and conductance dysfunction, and accelerated mortality. These cardiac defects are accompanied by telomere erosion, mitochondrial fragmentation and increased oxidative stress. Treatment with antioxidants significantly retards the onset of cardiac dysfunction and death of mdx/mTR(KO) mice. In corroboration, all four of the DMD patients analysed had 45% shorter telomeres in their cardiomyocytes relative to age- and sex-matched controls. We propose that the demands of contraction in the absence of dystrophin coupled with increased oxidative stress conspire to accelerate telomere erosion culminating in cardiac failure and death. These findings provide strong support for a link between telomere length and dystrophin deficiency in the etiology of dilated cardiomyopathy in DMD and suggest preventive interventions.

Low-salt diet and cyclosporine nephrotoxicity: changes in kidney cell metabolism

Cyclosporine (CsA) is a highly effective immunosuppressant used in patients after transplantation; however, its use is limited by nephrotoxicity. Salt depletion is known to enhance CsA-induced nephrotoxicity in the rat, but the underlying molecular mechanisms are not completely understood. The goal of our study was to identify the molecular effects of salt depletion alone and in combination with CsA on the kidney using a proteo-metabolomic strategy. Rats (n = 6) were assigned to four study groups: (1) normal controls, (2) low-salt fed controls, (3) 10 mg/kg/d CsA for 28 days on a normal diet, (4) 10 mg/kg/d CsA for 28 days on low-salt diet. Low-salt diet redirected kidney energy metabolism toward mitochondria as indicated by a higher energy charge than in normal-fed controls. Low-salt diet alone reduced phospho-AKT and phospho-STAT3 levels and changed the expression of ion transporters PDZK1 and CLIC1. CsA induced macro- and microvesicular tubular epithelial vacuolization and reduced energy charge, changes that were more significant in low-salt fed animals, probably because of their more pronounced dependence on mitochondria. Here, CsA increased phospho-JAK2 and phospho-STAT3 levels and reduced the phospho-IKKγ and p65 proteins, thus activating NF-κB signaling. Decreased expression of lactate transport regulator CD147 and phospho-AKT was also observed after CsA exposure in low-salt rats, indicating a decrease in glycolysis. In summary, our study suggests a key role for PDZK1, CD147, JAK/STAT, and AKT signaling in CsA-induced nephrotoxicity and proposes mechanistic explanations on why rats fed a low-salt diet have higher sensitivity to CsA.

Association of DJ-1/PTEN/AKT- and ASK1/p38-mediated cell signalling with ischaemic cardiomyopathy

AIMS

Dilated cardiomyopathies from chronic ischaemia (ISCM) or idiopathic (IDCM) pathological mechanisms are accompanied by similar clinical symptoms but may differ in protein expression, cell metabolism, and signalling processes at the cellular level. Using a combination of proteomic and metabolomic profiling, we sought to decipher the relationships between the metabolism and cellular signalling pathways in human heart tissues collected from patients with ISCM, IDCM, and those without heart disease and dilation.

METHODS AND RESULTS

The comparative analysis suggested a decrease in glycolysis, Krebs cycle, and malate-aspartate shuttle activities in both types of cardiomyopathies and an increase in ketone body oxidation only in ISCM. Chronic ischaemic injury was associated with increased DJ-1 and decreased phosphatase and tensin homolog (PTEN) protein expression. The reduced PTEN expression was accompanied by increased phosphorylation of cell-protective AKT. Phosphorylation at T845 of apoptosis signal-regulating kinase 1 and p38 mitogen-activated protein kinase proteins, with no change in the phosphorylation of extracellular signal-regulated kinases, was also observed. The downregulation of peptidyl-prolyl cis/trans isomerase and NF-κB essential modulator potentially inhibits NF-κB-initiated processes.

CONCLUSION

The present study characterized differences in the molecular mechanisms, metabolism, and pathological cell signalling associated with ISCM and IDCM, which may provide novel targets for intervention at the cellular level.

Thymosin beta 4 protects cardiomyocytes from oxidative stress by targeting anti-oxidative enzymes and anti-apoptotic genes

Background

Thymosin beta-4 (Tβ4) is a ubiquitous protein with many properties relating to cell proliferation and differentiation that promotes wound healing and modulates inflammatory mediators. The mechanism by which Tβ4 modulates cardiac protection under oxidative stress is not known. The purpose of this study is to dissect the cardioprotective mechanism of Tβ4 on H₂O₂ induced cardiac damage.

Methods

Rat neonatal cardiomyocytes with or without Tβ4 pretreatment were exposed to H₂O₂ and expression of antioxidant, apoptotic, and anti-inflammatory genes was evaluated by quantitative real-time PCR and western blotting. ROS levels were estimated by DCF-DA using fluorescent microscopy and fluorimetry. Selected antioxidant, anti-inflammatory and antiapoptotic genes were silenced by siRNA transfections in neonatal cardiomyocytes and effect of Tβ4 on H₂O₂-induced cardiac damage was evaluated.

Results

Pre-treatment of Tβ4 resulted in reduction of the intracellular ROS levels induced by H₂O₂ in cardiomyocytes. Tβ4 pretreatment also resulted in an increase in the expression of antiapoptotic proteins and reduction of Bax/BCl₂ ratio in the cardiomyocytes. Pretreatment with Tβ4 resulted in stimulating the expression of antioxidant enzymes copper/zinc SOD and catalase in cardiomyocytes at both transcription and translation levels. Tβ4 treatment resulted in the increased expression of anti-apoptotic and anti-inflammatory genes. Silencing of Cu/Zn SOD and catalase gene resulted in apoptotic cell death in the cardiomyocytes which was prevented by treatment with Tβ4.

Conclusion

This is the first report that demonstrates the effect of Tβ4 on cardiomyocytes and its capability to selectively upregulate anti-oxidative enzymes, anti-inflammatory genes, and antiapoptotic enzymes in the neonatal cardiomyocytes thus preventing cell death thereby protecting the myocardium. Tβ4 treatment resulted in decreased oxidative stress and inflammation in the myocardium under oxidative stress.

Cardiomyocyte-specific IκB kinase (IKK)/NF-κB activation induces reversible inflammatory cardiomyopathy and heart failure

Inflammation is a major factor in heart disease. IκB kinase (IKK) and its downstream target NF-κB are regulators of inflammation and are activated in cardiac disorders, but their precise contributions and targets are unclear. We analyzed IKK/NF-κB function in the heart by a gain-of-function approach, generating an inducible transgenic mouse model with cardiomyocyte-specific expression of constitutively active IKK2. In adult animals, IKK2 activation led to inflammatory dilated cardiomyopathy and heart failure. Transgenic hearts showed infiltration with CD11b(+) cells, fibrosis, fetal reprogramming, and atrophy of myocytes with strong constitutively active IKK2 expression. Upon transgene inactivation, the disease was reversible even at an advanced stage. IKK-induced cardiomyopathy was dependent on NF-κB activation, as in vivo expression of IκBα superrepressor, an inhibitor of NF-κB, prevented the development of disease. Gene expression and proteomic analyses revealed enhanced expression of inflammatory cytokines, and an IFN type I signature with activation of the IFN-stimulated gene 15 (ISG15) pathway. In that respect, IKK-induced cardiomyopathy resembled Coxsackievirus-induced myocarditis, during which the NF-κB and ISG15 pathways were also activated. Vice versa, in cardiomyocytes lacking the regulatory subunit of IKK (IKKγ/NEMO), the induction of ISG15 was attenuated. We conclude that IKK/NF-κB activation in cardiomyocytes is sufficient to cause cardiomyopathy and heart failure by inducing an excessive inflammatory response and myocyte atrophy.

Inhibitory kappa-B kinase-β inhibition prevents adaptive left ventricular hypertrophy

BACKGROUND

Most cardiovascular studies have implicated the central transcription factor nuclear factor kappa-B (NF-κB) as contributing to the detrimental effects of cardiac injury. This ostensibly negative view of NF-κB competes with its important role in the normal host inflammatory and immune response. Pressure overload, left ventricular hypertrophy (LVH), and heart failure represent a spectrum of disease that has both adaptive and maladaptive components. In contrast to its known effects related to myocardial ischemia-reperfusion, we hypothesized that NF-κB is necessary for the compensatory phase of cardiac remodeling.

METHODS

C57BL6 mice underwent minimally invasive transverse aortic constriction with or without inhibition of the proximal NF-κB kinase, inhibitory kappa-B kinase-β. Isolated cardiomyocytes were cultured. Transthoracic echocardiography was performed on all mice.

RESULTS

Inhibitory kappa-B kinase-β inhibition successfully decreased cardiomyocyte expression of phosphorylated p65 NF-κB and decreased expression of hypertrophic markers with stimulation in vitro. Three weeks after transverse aortic constriction, the mice treated with inhibitory kappa-B kinase-β inhibition more aggressively developed LVH, as measured by heart weight/body weight ratio, left ventricular mass, and wall thickness. These mice also demonstrated a functional decline, as measured by decreased fractional shortening and ejection fraction. These findings were associated with decreased protein expression of p65 NF-κB.

CONCLUSIONS

Although short-term pressure-overload results in compensatory LVH with normal cardiac function, NF-κB inhibition resulted in increased LVH that was associated with functional deterioration. These observations suggest that NF-κB is an important part of the adaptive phase of LVH, and its inhibition detrimentally affects cardiac remodeling.

Interaction between NFκB and NFAT coordinates cardiac hypertrophy and pathological remodeling

RATIONALE

Both nuclear factors of activated T cells (NFAT) and nuclear factor-κB (NFκB) are Rel homology domain (RHD)-containing transcription factors whose independent activities are critically involved in regulating cardiac hypertrophy and failure.

OBJECTIVE

To determine the potential functional interaction between NFAT and NFκB signaling pathways in cardiomyocytes and its role in cardiac hypertrophy and remodeling.

METHODS AND RESULTS

We identified a novel transcriptional regulatory mechanism whereby NFκB and NFAT directly interact and synergistically promote transcriptional activation in cardiomyocytes. We show that the p65 subunit of NFκB coimmunoprecipitates with NFAT in cardiomyocytes, and this interaction maps to the RHD within p65. Overexpression of the p65-RHD disrupts the association between endogenous p65 and NFATc1, leading to reduced transcriptional activity. Overexpression of IκB kinase β (IKKβ) or p65-RHD causes nuclear translocation of NFATc1, and expression of a constitutively nuclear NFATc1-SA mutant similarly facilitated p65 nuclear translocation. Combined overexpression of p65 and NFATc1 promotes synergistic activation of NFAT transcriptional activity in cardiomyocytes, whereas inhibition of NFκB with IκBαM or dominant negative IKKβ reduces NFAT activity. Importantly, agonist-induced NFAT activation is reduced in p65 null mouse embryonic fibroblasts (MEFs) compared with wild-type MEFs. In vivo, cardiac-specific deletion of p65 using a Cre-loxP system causes a ≈50% reduction in NFAT activity in luciferase reporter mice. Moreover, ablation of p65 in the mouse heart decreases the hypertrophic response after pressure overload stimulation, reduces the degree of pathological remodeling, and preserves contractile function.

CONCLUSIONS

Our results suggest a direct interaction between NFAT and NFκB that effectively integrates 2 disparate signaling pathways in promoting cardiac hypertrophy and ventricular remodeling.

mIGF-1/JNK1/SirT1 signaling confers protection against oxidative stress in the heart

Oxidative stress contributes to the pathogenesis of aging-associated heart failure. Among various signaling pathways mediating oxidative stress, the NAD(+) -dependent protein deacetylase SirT1 has been implicated in the protection of heart muscle. Expression of a locally acting insulin-like growth factor-1 (IGF-1) propeptide (mIGF-1) helps the heart to recover from infarct and enhances SirT1 expression in cardiomyocytes (CM) in vitro, exerting protection from hypertrophic and oxidative stresses. To study the role of mIGF-1/SirT1 signaling in vivo, we generated cardiac-specific mIGF-1 transgenic mice in which SirT1 was depleted from adult CM in a tamoxifen-inducible and conditional fashion. Analysis of these mice confirmed that mIGF-1-induced SirT1 activity is necessary to protect the heart from paraquat (PQ)-induced oxidative stress and lethality. In cultured CM, mIGF-1 increases SirT1 expression through a c-Jun NH(2)-terminal protein kinase 1 (JNK1)-dependent signaling mechanism. Thus, mIGF-1 protects the heart from oxidative stress via SirT1/JNK1 activity, suggesting new avenues for cardiac therapy during aging and heart failure.

The NF-κB subunit c-Rel stimulates cardiac hypertrophy and fibrosis

Cardiac remodeling and hypertrophy are the pathological consequences of cardiovascular disease and are correlated with its associated mortality. Activity of the transcription factor NF-κB is increased in the diseased heart; however, our present understanding of how the individual subunits contribute to cardiovascular disease is limited. We assign a new role for the c-Rel subunit as a stimulator of cardiac hypertrophy and fibrosis. We discovered that c-Rel-deficient mice have smaller hearts at birth, as well as during adulthood, and are protected from developing cardiac hypertrophy and fibrosis after chronic angiotensin infusion. Results of both gene expression and cross-linked chromatin immunoprecipitation assay analyses identified transcriptional activators of hypertrophy, myocyte enhancer family, Gata4, and Tbx proteins as Rel gene targets. We suggest that the p50 subunit could limit the prohypertrophic actions of c-Rel in the normal heart, because p50 overexpression in H9c2 cells repressed c-Rel levels and the absence of cardiac p50 was associated with increases in both c-Rel levels and cardiac hypertrophy. We report for the first time that c-Rel is highly expressed and confined to the nuclei of diseased adult human hearts but is restricted to the cytoplasm of normal cardiac tissues. We conclude that c-Rel-dependent signaling is critical for both cardiac remodeling and hypertrophy. Targeting its activities could offer a novel therapeutic strategy to limit the effects of cardiac disease.

Multiple facets of NF-κB in the heart: to be or not to NF-κB

The progression from cardiac injury to symptomatic heart failure has been intensely studied over the last decade, and is largely attributable to a loss of functional cardiac myocytes through necrosis, intrinsic and extrinsic apoptosis pathways and autophagy. Therefore, the molecular regulation of these cellular programs has been rigorously investigated in the hopes of identifying a potential cell target that could promote cell survival and/or inhibit cell death to avert, or at least prolong, the degeneration toward symptomatic heart failure. The nuclear factor (NF)-κB super family of transcription factors has been implicated in the regulation of immune cell maturation, cell survival, and inflammation in many cell types, including cardiac myocytes. Recent studies have shown that NF-κB is cardioprotective during acute hypoxia and reperfusion injury. However, prolonged activation of NF-κB appears to be detrimental and promotes heart failure by eliciting signals that trigger chronic inflammation through enhanced elaboration of cytokines including tumor necrosis factor α, interleukin-1, and interleukin-6, leading to endoplasmic reticulum stress responses and cell death. The underlying mechanisms that account for the multifaceted and differential outcomes of NF-κB on cardiac cell fate are presently unknown. Herein, we posit a novel paradigm in which the timing, duration of activation, and cellular context may explain mechanistically the differential outcomes of NF-κB signaling in the heart that may be essential for future development of novel therapeutic interventions designed to target NF-κB responses and heart failure following myocardial injury.

Innate immunity and remodelling

A wide variety of cardiac disease states can induce remodelling and lead to the functional consequence of heart failure. These complex disease states involve a plethora of parallel signal transduction events, which may be associated with tissue injury or tissue repair. Innate immunity is activated in hearts injured in different ways, evident as cytokine release from the heart, activation of toll-like receptors involved in recognizing danger, and activation of the transcription factor nuclear factor kappa B. Nuclear factor kappa B regulates gene programmes involved in inflammation as well as the resolution of inflammation. The impact of this is an enigma; while cytokines, toll-like receptors, and nuclear factor kappa B appear to elicit myocardial protection in studies of preconditioning, the literature strongly indicates a detrimental role for activation of innate immunity in studies of acute ischaemia–reperfusion injury. The impact of activation of cardiac innate immunity on the long-term outcome in in vivo models of hypertrophy and remodelling is less clear, with conflicting results as to whether it is beneficial or detrimental. More research using genetically engineered mice as tools, different models of evoking remodelling, and long-term follow-up is required for us to conclude whether activation of the innate immune system is good, bad, or unimportant in chronic injury models.

TNFα in myocardial ischemia/reperfusion, remodeling and heart failure

TNFα is crucially involved in the pathogenesis and progression of myocardial ischemia/reperfusion injury and heart failure. The formation and release of TNFα and its downstream signal transduction cascade following activation of its two receptor subtypes are characterized. Myocardial TNFα and TNF receptor activation have an ambivalent role in myocardial ischemia/reperfusion injury and protection from it. Excessive TNFα expression and subsequent cardiomyocyte TNF receptor type 1 stimulation induce contractile dysfunction, hypertrophy, fibrosis and cell death, while a lower TNFα concentration and subsequent cardiomyocyte TNF receptor type 2 stimulation are protective. Apart from its concentration and receptor subtype, the myocardial action of TNFα depends on the duration of its exposure and its localization. While detrimental during sustained ischemia, TNFα contributes to ischemic preconditioning protection, no matter whether it is the first, second or third window of protection, and both TNF receptors are involved in the protective signal transduction cascade. Finally, the available clinical attempts to antagonize TNFα in cardiovascular disease, notably heart failure, are critically discussed.

Toll-like receptors as potential therapeutic targets in cardiac dysfunction

INTRODUCTION

The innate immune system can detect the highly conserved, relatively invariant structural motifs of pathogens. The most important innate immune receptors, Toll-like receptors (TLRs), represent a first line of defense against infectious pathogens, and play a pivotal role in initiating and shaping innate and adaptive immune responses. TLRs are not only expressed in immune cells, but also in cardiovascular cells. In addition to their role in response to microbial infections, evidence suggests that TLRs can also recognize endogenous ligands and may play a role in mediating cardiomyocyte cell death and survival after non-infectious injury.

AREAS COVERED

TLRs could be a link between cardiovascular diseases and the immune system. Experimentally, there is good evidence that TLR activation contributes to development and progression of both acute cardiac injury and chronic heart failure. The role of TLRs in myocardial ischemia-reperfusion, remodeling, septic cardiomyoparthy, autoimmune- and viral myocarditis, anthracycline-induced cardiomyopathy and cardiac hypertrophy, in basic as well as clinical science are discussed.

EXPERT OPINION

Evidence, mainly from animal experiments, indicates that TLRs contribute to all of the myocardial disease states reviewed in this paper. However, the relevance of TLRs as therapeutic targets remains to be defined as clinical data is sparse.

Cardiomyocyte NF-κB p65 promotes adverse remodelling, apoptosis, and endoplasmic reticulum stress in heart failure

AIMS

the role of nuclear factor (NF)-κB in heart failure (HF) is not well defined. We sought to determine whether myocyte-localized NF-κB p65 activation in HF exacerbates post-infarction remodelling and promotes maladaptive endoplasmic reticulum (ER) stress.

METHODS AND RESULTS

non-transgenic (NTg) and transgenic (Tg) mice with myocyte-restricted overexpression of a phosphorylation-resistant inhibitor of κBα (IκBα(S32A,S36A)) underwent coronary ligation (to induce HF) or sham operation. Over 4 weeks, the remote myocardium of ligated hearts exhibited robust NF-κB activation that was almost exclusively p65 beyond 24 h. Compared with sham at 4 weeks, NTg HF hearts were dilated and dysfunctional, and exhibited hypertrophy, fibrosis, up-regulation of inflammatory cytokines, increased apoptosis, down-regulation of ER protein chaperones, and up-regulation of the ER stress-activated pro-apoptotic factor CHOP. Compared with NTg HF, Tg-IκBα(S32A,S36A) HF mice exhibited: (i) improved survival, chamber remodelling, systolic function, and pulmonary congestion, (ii) markedly diminished NF-κB p65 activation, cytokine expression, and fibrosis, and (iii) a three-fold reduction in apoptosis. Moreover, Tg-IκBα(S32A,S36A) HF hearts exhibited maintained expression of ER chaperones and CHOP when compared with sham. In cardiomyocytes, NF-κB activation was required for ER stress-mediated apoptosis, whereas abrogation of myocyte NF-κB shifted the ER stress response to one of adaptation and survival.

CONCLUSION

persistent myocyte NF-κB p65 activation in HF exacerbates cardiac remodelling by imparting pro-inflammatory, pro-fibrotic, and pro-apoptotic effects. p65 modulation of cell death in HF may occur in part from NF-κB-mediated transformation of the ER stress response from one of adaptation to one of apoptosis.

IKK{gamma} protein is a target of BAG3 regulatory activity in human tumor growth

BAG3, a member of the BAG family of heat shock protein (HSP) 70 cochaperones, is expressed in response to stressful stimuli in a number of normal cell types and constitutively in a variety of tumors, including pancreas carcinomas, lymphocytic and myeloblastic leukemias, and thyroid carcinomas. Down-regulation of BAG3 results in cell death, but the underlying molecular mechanisms are still elusive. Here, we investigated the molecular mechanism of BAG3-dependent survival in human osteosarcoma (SAOS-2) and melanoma (M14) cells. We show that bag3 overexpression in tumors promotes survival through the NF-kappaB pathway. Indeed, we demonstrate that BAG3 alters the interaction between HSP70 and IKKgamma, increasing availability of IKKgamma and protecting it from proteasome-dependent degradation; this, in turn, results in increased NF-kappaB activity and survival. These results identify bag3 as a potential target for anticancer therapies in those tumors in which this gene is constitutively expressed. As a proof of principle, we show that treatment of a mouse xenograft tumor model with bag3siRNA-adenovirus that down-regulates bag3 results in reduced tumor growth and increased animal survival.