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

Repair of the Infarcted Heart: Cellular Effectors, Molecular Mechanisms and Therapeutic Opportunities

The adult mammalian heart has limited endogenous regenerative capacity and heals through the activation of inflammatory and fibrogenic cascades that ultimately result in the formation of a scar. After infarction, massive cardiomyocyte death releases a broad range of damage-associated molecular patterns that initiate both myocardial and systemic inflammatory responses. TLRs (toll-like receptors) and NLRs (NOD-like receptors) recognize damage-associated molecular patterns (DAMPs) and transduce downstream proinflammatory signals, leading to upregulation of cytokines (such as interleukin-1, TNF-α [tumor necrosis factor-α], and interleukin-6) and chemokines (such as CCL2 [CC chemokine ligand 2]) and recruitment of neutrophils, monocytes, and lymphocytes. Expansion and diversification of cardiac macrophages in the infarcted heart play a major role in the clearance of the infarct from dead cells and the subsequent stimulation of reparative pathways. Efferocytosis triggers the induction and release of anti-inflammatory mediators that restrain the inflammatory reaction and set the stage for the activation of reparative fibroblasts and vascular cells. Growth factor-mediated pathways, neurohumoral cascades, and matricellular proteins deposited in the provisional matrix stimulate fibroblast activation and proliferation and myofibroblast conversion. Deposition of a well-organized collagen-based extracellular matrix network protects the heart from catastrophic rupture and attenuates ventricular dilation. Scar maturation requires stimulation of endogenous signals that inhibit fibroblast activity and prevent excessive fibrosis. Moreover, in the mature scar, infarct neovessels acquire a mural cell coat that contributes to the stabilization of the microvascular network. Excessive, prolonged, or dysregulated inflammatory or fibrogenic cascades accentuate adverse remodeling and dysfunction. Moreover, inflammatory leukocytes and fibroblasts can contribute to arrhythmogenesis. Inflammatory and fibrogenic pathways may be promising therapeutic targets to attenuate heart failure progression and inhibit arrhythmia generation in patients surviving myocardial infarction.

Growth/differentiation factor 15 (GDF15) expression in the heart after myocardial infarction and cardioprotective effect of pre-ischemic rGDF15 administration

Growth/differentiation factor-15 (GDF15) is considered an unfavourable prognostic biomarker for cardiovascular disease in clinical data, while experimental studies suggest it has cardioprotective potential. This study focuses on the direct cardiac effects of GDF15 during ischemia-reperfusion injury in Wistar male rats, employing concentrations relevant to patients at high cardiovascular risk. Initially, we examined circulating levels and heart tissue expression of GDF15 in rats subjected to ischemia-reperfusion and sham operations in vivo. We then evaluated the cardiac effects of GDF15 both in vivo and ex vivo, administering recombinant GDF15 either before 30 min of ischemia (preconditioning) or at the onset of reperfusion (postconditioning). We compared infarct size and cardiac contractile recovery between control and rGDF15-treated rats. Contrary to our expectations, ischemia-reperfusion did not increase GDF15 plasma levels compared to sham-operated rats. However, cardiac protein and mRNA expression increased in the infarcted zone of the ischemic heart after 24 h of reperfusion. Notably, preconditioning with rGDF15 had a cardioprotective effect, reducing infarct size both in vivo (65 ± 5% in control vs. 42 ± 6% in rGDF15 groups) and ex vivo (60 ± 4% in control vs. 45 ± 4% in rGDF15 groups), while enhancing cardiac contractile recovery ex vivo. However, postconditioning with rGDF15 did not alter infarct size or the recovery of contractile parameters in vivo or ex vivo. These novel findings reveal that the short-term exogenous administration of rGDF15 before ischemia, at physiologically relevant levels, protects the heart against ischemia-reperfusion injury in both in vivo and ex vivo settings. The ex vivo results indicate that rGDF15 operates independently of the inflammatory, endocrine and nervous systems, suggesting direct and potent cardioprotective properties against ischemia-reperfusion injury.

Impact of Hemoglobin Level in Ex Vivo Heart Perfusion on Donation After Circulatory Death Hearts: A Juvenile Porcine Experimental Model

BACKGROUND

Ex vivo heart perfusion (EVHP) of donation after circulatory death (DCD) hearts has become an effective strategy in adults; however, the small circulating volume in pediatrics poses the challenge of a low-hemoglobin (Hb) perfusate. We aimed to determine the impact of perfusate Hb levels during EVHP on DCD hearts using a juvenile porcine model.

METHODS

Sixteen DCD piglet hearts (11-14 kg) were reperfused for 4 h in unloaded mode followed by working mode. Metabolism, cardiac function, and cell damage were compared between the low-Hb (Hb, 5.0-5.9 g/dL; n = 8) and control (Hb, 7.5-8.4 g/dL; n = 8) groups. Between-group differences were evaluated using 2-sample t-tests or Fisher's Exact tests.

RESULTS

During unloaded mode, the low-Hb group showed lower myocardial oxygen consumption (P < 0.001), a higher arterial lactate level (P = 0.001), and worse systolic ventricular function (P < 0.001). During working mode, the low-Hb group had a lower cardiac output (mean, 71% versus 106% of normal cardiac output, P = 0.010) and a higher arterial lactate level (P = 0.031). Adjusted cardiac troponin-I (P = 0.112) did not differ between the groups. Morphological myocyte injury in the left ventricle was more severe in the low-Hb group (P = 0.028).

CONCLUSIONS

Low-Hb perfusate with inadequate oxygen delivery induced anaerobic metabolism, resulting in suboptimal DCD heart recovery and declined cardiac function. Arranging an optimal perfusate is crucial to organ protection, and further endeavors to refine the priming volume of EVHP or the transfusion strategy are required.

Production of a p65fl/fl/LysMCre mouse model with dysfunctional NF-κB signaling in bone marrow-derived macrophages

Here, we describe the production and characterization of a novel p65fl/fl/LysMCre mouse model, which lacks canonical nuclear factor-kappaB member RelA/p65 (indicated as p65 hereafter) in bone marrow-derived macrophages. Cultured bone marrow-derived macrophages that lack p65 protein reveal NF-κB signaling deficiencies, a reduction in phagocytic ability, and reduced ability to produce nitrites. Despite abnormal bone marrow-derived macrophage function, p65fl/fl/LysMCre mice do not exhibit differences in naïve systemic immune profiles or colony forming units and time to death following Salmonella infection as compared to controls. Additionally, p65fl/fl/LysMCre mice, especially females, display splenomegaly, but no other obvious physical or behavioral differences as compared to control animals. As bone marrow-derived macrophages from this transgenic model are almost completely devoid of canonical nuclear factor-kappaB pathway member p65, this model has the potential for being very useful in investigating bone marrow-derived macrophage NF-kappaB signaling in diverse biological and biomedical studies.

Inflammation in Myocardial Ischemia/Reperfusion Injury: Underlying Mechanisms and Therapeutic Potential

Acute myocardial infarction (MI) occurs when blood flow to the myocardium is restricted, leading to cardiac damage and massive loss of viable cardiomyocytes. Timely restoration of coronary flow is considered the gold standard treatment for MI patients and limits infarct size; however, this intervention, known as reperfusion, initiates a complex pathological process that somewhat paradoxically also contributes to cardiac injury. Despite being a sterile environment, ischemia/reperfusion (I/R) injury triggers inflammation, which contributes to infarct expansion and subsequent cardiac remodeling and wound healing. The immune response is comprised of subsets of both myeloid and lymphoid-derived cells that act in concert to modulate the pathogenesis and resolution of I/R injury. Multiple mechanisms, including altered metabolic status, regulate immune cell activation and function in the setting of acute MI, yet our understanding remains incomplete. While numerous studies demonstrated cardiac benefit following strategies that target inflammation in preclinical models, therapeutic attempts to mitigate I/R injury in patients were less successful. Therefore, further investigation leveraging emerging technologies is needed to better characterize this intricate inflammatory response and elucidate its influence on cardiac injury and the progression to heart failure.

RELA governs a network of islet-specific metabolic genes necessary for beta cell function

AIMS/HYPOTHESIS

NF-κB activation unites metabolic and inflammatory responses in many diseases yet less is known about the role that NF-κB plays in normal metabolism. In this study we investigated how RELA impacts the beta cell transcriptional landscape and provides network control over glucoregulation.

METHODS

We generated novel mouse lines harbouring beta cell-specific deletion of either the Rela gene, encoding the canonical NF-κB transcription factor p65 (βp65KO mice), or the Ikbkg gene, encoding the NF-κB essential modulator NEMO (βNEMOKO mice), as well as βA20Tg mice that carry beta cell-specific and forced transgenic expression of the NF-κB-negative regulator gene Tnfaip3, which encodes the A20 protein. Mouse studies were complemented by bioinformatics analysis of human islet chromatin accessibility (assay for transposase-accessible chromatin with sequencing [ATAC-seq]), promoter capture Hi-C (pcHi-C) and p65 binding (chromatin immunoprecipitation-sequencing [ChIP-seq]) data to investigate genome-wide control of the human beta cell metabolic programme.

RESULTS

Rela deficiency resulted in complete loss of stimulus-dependent inflammatory gene upregulation, consistent with its known role in governing inflammation. However, Rela deletion also rendered mice glucose intolerant because of functional loss of insulin secretion. Glucose intolerance was intrinsic to beta cells as βp65KO islets failed to secrete insulin ex vivo in response to a glucose challenge and were unable to restore metabolic control when transplanted into secondary chemical-induced hyperglycaemic recipients. Maintenance of glucose tolerance required Rela but was independent of classical NF-κB inflammatory cascades, as blocking NF-κB signalling in vivo by beta cell knockout of Ikbkg (NEMO), or beta cell overexpression of Tnfaip3 (A20), did not cause severe glucose intolerance. Thus, basal p65 activity has an essential and islet-intrinsic role in maintaining normal glucose homeostasis. Genome-wide bioinformatic mapping revealed the presence of p65 binding sites in the promoter regions of specific metabolic genes and in the majority of islet enhancer hubs (~70% of ~1300 hubs), which are responsible for shaping beta cell type-specific gene expression programmes. Indeed, the islet-specific metabolic genes Slc2a2, Capn9 and Pfkm identified within the large network of islet enhancer hub genes showed dysregulated expression in βp65KO islets.

CONCLUSIONS/INTERPRETATION

These data demonstrate an unappreciated role for RELA as a regulator of islet-specific transcriptional programmes necessary for the maintenance of healthy glucose metabolism. These findings have clinical implications for the use of anti-inflammatories, which influence NF-κB activation and are associated with diabetes.

Advanced glycation end products modulate electrophysiological remodeling of right ventricular outflow tract cardiomyocytes: A novel target for diabetes-related ventricular arrhythmogenesis

Diabetes mellitus is associated with cardiovascular disease and cardiac arrhythmia. Accumulation of advanced glycation end products closely correlates with cardiovascular complications through mitochondrial dysfunction or oxidative stress and evoke proliferative, inflammatory, and fibrotic reactions, which might impair cardiac electrophysiological characteristics and increase the incidence of cardiac arrhythmia. This study examined the mechanisms how advanced glycation end products may contribute to arrhythmogenesis of right ventricular outflow tract-a unique arrhythmogenic substrate. A whole-cell patch clamp, conventional electrophysiological study, fluorescence imaging, Western blot, and confocal microscope were used to study the electrical activity, and Ca2+ homeostasis or signaling in isolated right ventricular outflow tract myocytes with and without advanced glycation end products (100 μg/ml). The advanced glycation end products treated right ventricular outflow tract myocytes had a similar action potential duration as the controls, but exhibited a lower L-type Ca2+ current, higher late sodium current and transient outward current. Moreover, the advanced glycation end products treated right ventricular outflow tract myocytes had more intracellular Na+ , reverse mode Na+ -Ca2+ exchanger currents, intracellular and mitochondrial reactive oxygen species, and less intracellular Ca2+ transient and sarcoplasmic reticulum Ca2+ content with upregulated calcium homeostasis proteins and advanced glycation end products related signaling pathway proteins. In conclusions, advanced glycation end products modulate right ventricular outflow tract electrophysiological characteristics with larger late sodium current, intracellular Na+ , reverse mode Na+ -Ca2+ exchanger currents, and disturbed Ca2+ homeostasis through increased oxidative stress mediated by the activation of the advanced glycation end products signaling pathway.

Potential cardioprotective effects of Amentoflavone in doxorubicin-induced cardiotoxicity in mice

Doxorubicin (DOX) is an available chemotherapeutic drug for treating various tumors. However, its effectiveness is limited by cardiotoxicity. Amentoflavone (AMF), a natural biflavonoid separated from Cycas thouarsii ethyl acetate fraction, displays promising anticancer, anti-inflammatory, and antioxidant effects. Thus, our research aims to explore whether AMF could boost cardioprotective effects against DOX cardiotoxicity and reveal the potential underlying mechanisms of cardioprotection. Mice were classified into four groups; Normal control, Untreated DOX group, and DOX groups treated with AMF (40 and 80 mg/kg, respectively) intraperitoneal injection daily for four days before doxorubicin administration and for additional three days following DOX administration to assess cardiotoxicity. Echocardiography showed that AMF 80 treated group was protected from DOX cardiotoxicity. Additionally, it alleviated histopathological structural alterations and effectively restored heart weight and body weight ratio. These effects were confirmed biochemically by a substantially reduced serum creatine kinase-MB (CK-MB) and aspartate aminotransferase (AST) levels. AMF effectively restored nuclear respiratory factor-1(NRF-1), mitochondrial transcription factor A (TFAM), and normalized heat shock protein - 27(HSP-27) expression levels compared to the DOX group. Moreover, AMF mitigated oxidative stress conditions and significantly suppressed NADPH oxidase (NOX) expression levels. It also showed significant anti-inflammatory effects via suppressing interleukin-6 (IL-6) expression and decreasing nuclear factor Kabba B (NF-κb) immune-staining. In addition, AMF markedly reduced FAS ligand (FASL) expression and p53 immune staining in cardiac tissue. This study is the first for the in vivo potential beneficial effects of AMF against acute DOX cardiotoxicity, possibly via exerting antioxidant, anti-inflammatory, and anti-apoptotic effects and restoring mitochondrial function.

E-cigarette aerosol exacerbates cardiovascular oxidative stress in mice with an inactive aldehyde dehydrogenase 2 enzyme

Background

E-cigarette aerosol containing aldehydes, including acetaldehyde, are metabolized by the enzyme aldehyde dehydrogenase 2 (ALDH2). However, little is known how aldehyde exposure from e-cigarettes, when coupled with an inactivating ALDH2 genetic variant, ALDH2*2 (present in 8% of the world population), affects cardiovascular oxidative stress.

Objectives

The study was to determine how e-cigarette aerosol exposure, coupled with genetics, impacts cardiovascular oxidative stress in wild type ALDH2 and ALDH2*2 knock-in mice.

Methods

Using selective ion flow mass spectrometry, we determined e-cigarette aerosol contains acetaldehyde levels 10-fold higher than formaldehyde or acrolein. Based on this finding, we tested how isolated ALDH2*2 primary cardiomyocytes respond to acetaldehyde and how intact ALDH2*2 knock-in rodents instrumented with telemeters respond physiologically and at the molecular level to 10 days of e-cigarette aerosol exposure relative to wild type ALDH2 rodents.

Results

For ALDH2*2 isolated cardiomyocytes, acetaldehyde (1 μM) caused a 4-fold greater peak calcium influx, 2-fold increase in ROS production and 2-fold increase in 4-HNE-induced protein adducts relative to wild-type ALDH2 cardiomyocytes. The heart rate in ALDH2*2 mice increased ∼200 beats/min, while, heart rate in ALDH2 mice increased ∼150 beats/min after 10 days of e-cigarette exposure, relative to air-exposed mice. E-cigarette aerosol exposure triggered ∼1.3 to 2-fold higher level of protein carbonylation, lipid peroxidation, and phosphorylation of NF-κB for both strains of mice, with this response exacerbated for ALDH2*2 mice.

Conclusions

Our findings indicate people carrying an ALDH2*2 genetic variant may be more susceptible to increases in cardiovascular oxidative stress from e-cigarette aerosol exposure.

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~540 million people have a genetic variant in aldehyde dehydrogenase 2 (ALDH2*2) that limits aldehyde metabolism.

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Little is known how e-cigarette exposure, when coupled with the ALDH2*2 variant, impacts cardiovascular oxidative stress.

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ALDH2*2 cardiomyocytes and rodents vs. wild type have higher oxidative stress levels after aldehyde or e-cigarette exposure.

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People with an ALDH2*2 variant may be more susceptible to cardiovascular oxidative stress from e-cigarette exposure.

Nanoparticle-Delivered microRNA-153-3p Alleviates Myocardial Infarction-Induced Myocardial Injury in a Rat Model

Although microRNA-153-3p (miR-153-3p) has been demonstrated to confer protective roles in ischemia/reperfusion injury, its potential role in myocardial infarction (MI) remains undefined. Small-molecule modifiers and nanoparticles loaded with microRNAs (miRNAs) have emerged as potential therapeutic reagents for MI treatment. In this study, we prepared liposome nanoparticles, hyaluronic acid (HA)-cationic liposomes (CLPs) complex, for the delivery of miR-153-3p and delineated the mechanistic actions of miR-153-3p modified by nHA-CLPs in MI-induced injury. Our data suggested that nHA-CLPs-loaded miR-153-3p protected cardiomyocytes against MI-induced cardiomyocyte apoptosis and myocardial injury. miR-153-3p was bioinformatically predicted and experimentally verified to bind to Krüppel-like factor 5 (KLF5) 3'UTR and negatively regulate its expression. Hypoxia was adopted to stimulate MI-induced injury to cardiomyocytes in vitro, in which miR-153-3p presented anti-apoptotic potential. However, restoration of KLF5 reversed this anti-apoptotic effect of miR-153-3p. Furthermore, KLF5 was demonstrated to be an activator of the NF-κB pathway. KLF5 enhanced cardiomyocyte apoptosis and inflammation under hypoxic conditions through NF-κB pathway activation, while nHA-CLPs-loaded miR-153-3p suppressed inflammation by blocking the NF-κB pathway. Collectively, our findings suggested the cardioprotective role of miR-153-3p against MI and the successful delivery of miR-153-3p by nHA-CLPs. The identification of KLF5-mediated activation of NF-κB pathway as an apoptotic and inflammatory mechanism aids in better understanding of the biology of MI and development of novel therapeutic strategies for MI.

Acellular human amniotic fluid protects the ischemic/reperfused rat myocardium

Amniotic products are potent immunomodulators utilized clinically to repair tissue injury. Little information exists regarding the potential of cell-free human amniotic fluid (hAF) to treat cardiovascular disease. Herein, we sought to determine the influence and efficacy of acellular hAF on myocardial ischemia/reperfusion injury. Processed hAF was obtained from volunteer donors at the time of elective caesarean section and manufactured using proprietary methods. Left anterior descending coronary artery ligation was performed on rats for 60 minutes. Thirty minutes after release and reperfusion, either saline or hAF was injected intramyocardially. Serial echocardiography revealed that compared to saline injected rats, hAF animals maintained their ejection fraction and did not adversely remodel through the 4-week period. This preserved ventricular function correlated with decreased infarct size, less fibrosis, and reduced expression of cytokines and infiltrating inflammatory cells. Comparative arrays of different donor hAF lots confirmed the presence of a wide array of immunomodulatory and host-defense proteins. The observed functional cardioprotection was furthermore evident when given intravenously and across multiple hAF donors. In conclusion, our data demonstrate, for the first time, the cardioprotective effect of acellular hAF on myocardial injury. These observations spanned across diverse donors and likely result from the mixture of a plethora of naturally produced cytokines, chemokines, and immune-modulating proteins rather than a single, defined mechanistic culprit. The ubiquitous availability of hAF as a cell-free solution further suggests its potential for widespread adoption as a therapy for myocardial ischemia/reperfusion injury.

Ventricular TLR4 Levels Abrogate TLR2-Mediated Adverse Cardiac Remodeling upon Pressure Overload in Mice

Involvement of the Toll-like receptor 4 (TLR4) in maladaptive cardiac remodeling and heart failure (HF) upon pressure overload has been studied extensively, but less is known about the role of TLR2. Interplay and redundancy of TLR4 with TLR2 have been reported in other organs but were not investigated during cardiac dysfunction. We explored whether TLR2 deficiency leads to less adverse cardiac remodeling upon chronic pressure overload and whether TLR2 and TLR4 additively contribute to this. We subjected 35 male C57BL/6J mice (wildtype (WT) or TLR2 knockout (KO)) to sham or transverse aortic constriction (TAC) surgery. After 12 weeks, echocardiography and electrocardiography were performed, and hearts were extracted for molecular and histological analysis. TLR2 deficiency (n = 14) was confirmed in all KO mice by PCR and resulted in less hypertrophy (heart weight to tibia length ratio (HW/TL), smaller cross-sectional cardiomyocyte area and decreased brain natriuretic peptide (BNP) mRNA expression, p < 0.05), increased contractility (QRS and QTc, p < 0.05), and less inflammation (e.g., interleukins 6 and 1β, p < 0.05) after TAC compared to WT animals (n = 11). Even though TLR2 KO TAC animals presented with lower levels of ventricular TLR4 mRNA than WT TAC animals (13.2 ± 0.8 vs. 16.6 ± 0.7 mg/mm, p < 0.01), TLR4 mRNA expression was increased in animals with the largest ventricular mass, highest hypertrophy, and lowest ejection fraction, leading to two distinct groups of TLR2 KO TAC animals with variations in cardiac remodeling. This variation, however, was not seen in WT TAC animals even though heart weight/tibia length correlated with expression of TLR4 in these animals (r = 0.078, p = 0.005). Our data suggest that TLR2 deficiency ameliorates adverse cardiac remodeling and that ventricular TLR2 and TLR4 additively contribute to adverse cardiac remodeling during chronic pressure overload. Therefore, both TLRs may be therapeutic targets to prevent or interfere in the underlying molecular processes.

Loss of exosomal LncRNA HCG15 prevents acute myocardial ischemic injury through the NF-κB/p65 and p38 pathways

Exosomes are nanosized bilayer membrane vesicles that may mediate intercellular communication by transporting bioactive molecules, including noncoding RNAs, mRNAs, and proteins. Research has shown that exosomes play an important role in acute myocardial infarction (AMI), but the function and regulation of exosomal long noncoding RNAs (lncRNAs) in AMI are unclear. Thus, RNA sequencing (RNA-Seq) was conducted to investigate the exosomal lncRNA transcriptome from MI patients and identified 65 differentially expressed lncRNAs between the MI and control groups. HCG15, one of the differentially expressed lncRNAs, was verified to have the highest correlation with cTnT by qRT-PCR, and it also contributed to the diagnosis of AMI by receiver operating characteristic (ROC) analysis. Upregulation of HCG15 expression facilitated cardiomyocyte apoptosis and inflammatory cytokine production and inhibited cell proliferation. We also confirmed that HCG15 was mainly wrapped in exosomes from AC16 cardiomyocytes under hypoxia, which contributed to cardiomyocyte apoptosis, the release of inflammatory factors, and inhibition of cell proliferation via the activation of the NF-κB/p65 and p38 pathways, whereas suppressing the expression of HCG15exerted opposite effects, In addition, Overexpression of HCG15 aggravated cardiac IR injury in C57BL/6J mice. This study not only helps elucidate exosomal lncRNA function in AMI pathogenesis but also contributes to the development of novel therapeutic strategies.

Interleukin 1 receptor antagonism abrogates acute pressure-overload induced murine heart failure

BACKGROUND

Recent clinical trials have suggested that blockade of interleukin-1 can favorably impact patients with myocardial infarction and heart failure. However, the mechanism of how antagonism of this specific cytokine in mediating cardiac disease remains unclear. Hence, we sought to determine the influence of IL-1 blockade on acute hypertensive remodeling.

METHODS

Transverse aortic constriction (TAC) was performed in C57BL mice with or without intraperitoneal administration of interleukin 1 receptor antagonism (IL-1ra). Function, structure, and molecular diagnostics were subsequently performed and analyzed.

RESULTS

Six weeks after TAC, a progressive decline of ejection fraction and increases in LV mass and dimensions was effectively mitigated with IL-1ra. TAC resulted in an expected profile of hypertrophic markers including myosin heavy chain, atrial natriuretic peptide, and skeletal muscle actin which were all significantly lower in IL-1ra treated mice. While trichrome staining 2-weeks post TAC demonstrated similar levels of fibrosis, IL-1ra reduced expression of collagen-1, TIMP1, and periostin. Investigating the angiogenic response to pressure overload, similar levels of VEGF were observed, but IL-1ra was associated with more SDF-1. Immune cell infiltration (macrophages and lymphocytes) was also decreased in IL-1ra treated mice. Similarly, cytokine concentrations of IL-1, IL-18, and IL-6 were all reduced in IL-1ra-treated animals.

CONCLUSIONS

IL-1ra prevents the progression towards heart failure associated with acute pressure overload. This functional response was associated with reductions in mediators of fibrosis, cellular infiltration, and cytokine production. These results provide mechanistic insight into recent clinical trials and could springboard future investigations in patients with pressure-overload based cardiomyopathies.

Post-ischemic Myocardial Inflammatory Response: A Complex and Dynamic Process Susceptible to Immunomodulatory Therapies

Following acute occlusion of a coronary artery causing myocardial ischemia and implementing first-line treatment involving rapid reperfusion, a dynamic and balanced inflammatory response is initiated to repair and remove damaged cells. Paradoxically, restoration of myocardial blood flow exacerbates cell damage as a result of myocardial ischemia-reperfusion (MI-R) injury, which eventually provokes accelerated apoptosis. In the end, the infarct size still corresponds to the subsequent risk of developing heart failure. Therefore, true understanding of the mechanisms regarding MI-R injury, and its contribution to cell damage and cell death, are of the utmost importance in the search for successful therapeutic interventions to finally prevent the onset of heart failure. This review focuses on the role of innate immunity, chemokines, cytokines, and inflammatory cells in all three overlapping phases following experimental, mainly murine, MI-R injury known as the inflammatory, reparative, and maturation phase. It provides a complete state-of-the-art overview including most current research of all post-ischemic processes and phases and additionally summarizes the use of immunomodulatory therapies translated into clinical practice.

Severe T-System Remodeling in Pediatric Viral Myocarditis

Chronic heart failure (HF) in adults causes remodeling of the cardiomyocyte transverse tubular system (t-system), which contributes to disease progression by impairing excitation-contraction (EC) coupling. However, it is unknown if t-system remodeling occurs in pediatric heart failure. This study investigated the t-system in pediatric viral myocarditis. The t-system and integrity of EC coupling junctions (co-localization of L-type Ca²⁺ channels with ryanodine receptors and junctophilin-2) were analyzed by 3D confocal microscopy in left-ventricular (LV) samples from 5 children with myocarditis (age 14 ± 3 months), undergoing ventricular assist device (VAD) implantation, and 5 children with atrioventricular septum defect (AVSD, age 17 ± 3 months), undergoing corrective surgery. LV ejection fraction (EF) was 58.4 ± 2.3% in AVSD and 12.2 ± 2.4% in acute myocarditis. Cardiomyocytes from myocarditis samples showed increased t-tubule distance (1.27 ± 0.05 μm, n = 34 cells) and dilation of t-tubules (volume-length ratio: 0.64 ± 0.02 μm²) when compared with AVSD (0.90 ± 0.02 μm, p < 0.001; 0.52 ± 0.02 μm², n = 61, p < 0.01). Intriguingly, 4 out of 5 myocarditis samples exhibited sheet-like t-tubules (t-sheets), a characteristic feature of adult chronic heart failure. The fraction of extracellular matrix was slightly higher in myocarditis (26.6 ± 1.4%) than in AVSD samples (24.4 ± 0.8%, p < 0.05). In one case of myocarditis, a second biopsy was taken and analyzed at VAD explantation after extensive cardiac recovery (EF from 7 to 56%) and clinical remission. When compared with pre-VAD, t-tubule distance and density were unchanged, as well as volume-length ratio (0.67 ± 0.04 μm² vs. 0.72 ± 0.05 μm², p = 0.5), reflecting extant t-sheets. However, junctophilin-2 cluster density was considerably higher (0.12 ± 0.02 μm⁻³ vs. 0.05 ± 0.01 μm⁻³, n = 9/10, p < 0.001), approaching values of AVSD (0.13 ± 0.05 μm⁻³, n = 56), and the measure of intact EC coupling junctions showed a distinct increase (20.2 ± 5.0% vs. 6.8 ± 2.2%, p < 0.001). Severe t-system loss and remodeling to t-sheets can occur in acute HF in young children, resembling the structural changes of chronically failing adult hearts. T-system remodeling might contribute to cardiac dysfunction in viral myocarditis. Although t-system recovery remains elusive, recovery of EC coupling junctions may be possible and deserves further investigation.

Cardioprotective role of phyllanthin against myocardial ischemia-reperfusion injury by alleviating oxidative stress and inflammation with increased adenosine triphosphate levels in the mice model

BACKGROUND

Ischemic heart disease is an imperative cause of high morbidity and mortality globally. The cardiac ischemia/reperfusion damage occur in both reperfusion and ischemia.

OBJECTIVE

In this exploration, we have planned to examine the cardio-protective action of phyllanthin against the myocardial ischemic-reperfusion injury in mice.

MATERIALS AND METHODS

The myocardial ischemic reperfusion injury (MI-RI) stimulated via coronary artery occlusion, followed by the 10 mg/kg of phyllanthin treatment. The serum cardiac markers and pro-inflammatory markers level was investigated by using the assay kits. The expressions of oxidative stress and inflammatory markers level were investigated by immunohistochemical analysis. Lipid peroxidation, antioxidant enzymes, and ATPase levels level was examined by standard methods. The expression of oxidative stress markers were inspected by the reverse transcription polymerase chain reaction technique. The heart histology was investigated microscopically.

RESULTS

The phyllanthin treatment increased the body weight, and heart weight also diminished the infarct size in the MI/RI mice. Cardiac markers status was diminished and the blood pressure markers were augmented by the phyllanthin. Histological analysis revealed the protective role of phyllanthin. Suppressed lipid peroxidation and enhanced antioxidant enzymes were noted in the phyllanthin treated mice MI-RI mice. Phyllanthin appreciably suppressed the pro-inflammatory regulators that is, NF-αB p65, IL-6, IL-1β, and TNF-α and enhanced the antioxidant marker expressions. ATPase levels were improved by the phyllanthin in the MI-RI mice.

CONCLUSION

These novel findings were confirmed the therapeutic role of phyllanthin against the MI-RI in mice. Hence, it can be a promising agent to treat the MI-RI induced cardiac dysfunction.

Damage-Associated Molecular Patterns in Myocardial Infarction and Heart Transplantation: The Road to Translational Success

In the setting of myocardial infarction (MI), ischemia reperfusion injury (IRI) occurs due to occlusion (ischemia) and subsequent re-establishment of blood flow (reperfusion) of a coronary artery. A similar phenomenon is observed in heart transplantation (HTx) when, after cold storage, the donor heart is connected to the recipient's circulation. Although reperfusion is essential for the survival of cardiomyocytes, it paradoxically leads to additional myocardial damage in experimental MI and HTx models. Damage (or danger)-associated molecular patterns (DAMPs) are endogenous molecules released after cellular damage or stress such as myocardial IRI. DAMPs activate pattern recognition receptors (PRRs), and set in motion a complex signaling cascade resulting in the release of cytokines and a profound inflammatory reaction. This inflammatory response is thought to function as a double-edged sword. Although it enables removal of cell debris and promotes wound healing, DAMP mediated signalling can also exacerbate the inflammatory state in a disproportional matter, thereby leading to additional tissue damage. Upon MI, this leads to expansion of the infarcted area and deterioration of cardiac function in preclinical models. Eventually this culminates in adverse myocardial remodeling; a process that leads to increased myocardial fibrosis, gradual further loss of cardiomyocytes, left ventricular dilation and heart failure. Upon HTx, DAMPs aggravate ischemic damage, which results in more pronounced reperfusion injury that impacts cardiac function and increases the occurrence of primary graft dysfunction and graft rejection via cytokine release, cardiac edema, enhanced myocardial/endothelial damage and allograft fibrosis. Therapies targeting DAMPs or PRRs have predominantly been investigated in experimental models and are potentially cardioprotective. To date, however, none of these interventions have reached the clinical arena. In this review we summarize the current evidence of involvement of DAMPs and PRRs in the inflammatory response after MI and HTx. Furthermore, we will discuss various current therapeutic approaches targeting this complex interplay and provide possible reasons why clinical translation still fails.

MiR-324/SOCS3 Axis Protects Against Hypoxia/Reoxygenation-Induced Cardiomyocyte Injury and Regulates Myocardial Ischemia via TNF/NF-κB Signaling Pathway

We aimed at exploring the function of microRNA-324/cytokine signaling 3 (miR-324/SOCS3) axis in hypoxia/reoxygenation (H/R) -induced cardiomyocyte injury and its underlying mechanism. The differential expression genes were analyzed based on the GSE83500 and GSE48060 datasets from the Gene Expression Omnibus (GEO) database. Then, to conduct the function enrichment analysis, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases were used. The upstream regulatory microRNAs (miRNAs) of the identified genes were predicted by miRanda, miRWalk, and TargetScan websites. MiR-324 expression was measured with quantitative real-time polymerase chain reaction (qRT-PCR). The target binding of miR-324 and SOCS3 was established by dual-luciferase reporter assay. Cardiomyocyte proliferation was analyzed by cell counting kit-8 (CCK-8) assay, whereas the apoptosis was investigated via flow cytometry. The expression of TNF pathway-related proteins was detected by western blot analysis. SOCS3 was upregulated in patients with myocardial infarction (MI), and function enrichment analyses proved that SOCS3 was enriched in TNF signaling pathway. Moreover, we found that miR-324 was the upstream regulatory miRNA of SOCS3 and negatively regulated SOCS3 expression. MiR-324 was downregulated in cardiomyocytes with H/R-induced injury, inhibiting cell proliferation. In the H/R model, SOCS3 suppresses cardiomyocyte proliferation, which was recovered by miR-324, and induces cell apoptosis, which was repressed by miR-324 via regulating the expression of cleaved caspase-3 and p P38-MAPK. MiR-324 upregulation decreased the protein levels of TNF-α, p-P65, and p-IκBα in cardiomyocytes that suffered from H/R, which was reversed with SOCS3 overexpression. MiR-324/SOCS3 axis could improve the H/R-induced injury of cardiomyocytes via regulating TNF/NF-κB signaling pathway, and this might provide a new therapy strategy for myocardial ischemia.

Cathepsin B aggravated doxorubicin‑induced myocardial injury via NF‑κB signalling

Myocyte apoptosis and oxidative stress key critical roles in the process of doxorubicin (DOX)-induced cardiotoxicity. However, how apoptosis and oxidative stress arise in DOX-induced heart injury remains largely unknown. Cathepsin B (CTSB) is a typical lysosomal cysteine protease that is associated with apoptosis, inflammatory responses, oxidative stress and autophagy. The present study aimed to investigate the role of CTSB in DOX-induced heart injury and its potential mechanism. H9C2 cells were infected with adenovirus or transfected with small interfering RNA to overexpress or knock down CTSB, respectively, and then stimulated with DOX. DOX induced increased CTSB expression levels in H9C2 cells. DOX-induced cardiomyocyte apoptosis and oxidative stress were attenuated by CTSB knockdown but aggravated by CTSB overexpression in vitro. Mechanistically, the present study showed that CTSB activated the NF-κB pathway in response to DOX. In summary, CTSB aggravated DOX-induced H9C2 cell apoptosis and oxidative stress via NF-κB signalling. CTSB constitutes a potential therapeutic target for the treatment of DOX-induced cardiotoxicity.

NFκB promotes oxidative stress-induced necrosis and ischemia/reperfusion injury by inhibiting Nrf2-ARE pathway

In this study, we identified an unexpected pro-cell death role for NFκB in mediating oxidative stress-induced necrosis, and provide new mechanistic evidence that NFκB, in cooperation with HDAC3, negatively regulates Nrf2-ARE anti-oxidative signaling through transcriptional silencing. We showed that genetic inactivation of NFκB-p65 inhibited, whereas activation of NFκB promoted, oxidative stress-induced cell death and HMGB1 release, a biomarker of necrosis. Moreover, NFκB-luciferase activity was elevated in cardiomyocytes after simulated ischemia/reperfusion (sI/R) or doxorubicin (DOX) treatment, and inhibition of NFκB with Ad-p65-shRNA or Ad-IκBαM diminished sI/R- and DOX-induced cell death and HMGB1 release. Importantly, NFκB negatively regulated Nrf2-ARE activity and the expression of antioxidant proteins. Mechanistically, co-immunoprecipitation revealed that p65 was required for Nrf2-HDAC3 interaction and transcriptional silencing of Nrf2-ARE activity. Further, the ability of HDAC3 to repress Nrf2-ARE activity was lost in p65 deficient cells. Pharmacologic inhibition of HADCs or NFκB with trichostatin A (TSA) or BMS-345541, respectively, increased Nrf2-ARE activity and promoted cell survival after sI/R. In vivo, NFκB transcriptional activity in the mouse heart was significantly elevated after ischemia/reperfusion (I/R) injury, which was abolished by cardiomyocyte-specific deletion of p65 using p65fl/flNkx2.5-Cre mice. Moreover, genetic ablation of p65 in the mouse heart attenuated myocardial infarct size after acute I/R injury and improved cardiac remodeling and functional recovery after chronic myocardial infarction. Thus, our results identified NFκB as a key regulator of oxidative stress-induced necrosis by suppressing the Nrf2-ARE antioxidant pathway through an HDAC3-dependent mechanism. This study also revealed a new pathogenic role of NFκB in cardiac ischemic injury and pathological remodeling.

Ischemic postconditioning reduced myocardial ischemia-reperfusion injury: The roles of melatonin and uncoupling protein 3

Objective:

Protective effects of ischemic postconditioning (PostC) decrease/disappear with age and chronic heart diseases. Similarly, low serum melatonin levels have been reported in the same risk groups. The aims of this study were to investigate the effects of melatonin on the protection of PostC in ischemia–reperfusion (I/R)-induced infarct size and roles of uncoupling protein (UCP) 3, irisin, and nuclear factor kappa B (NFkB) levels.

Methods:

Rats were pinealectomized (Px) or sham operated (non-Px) 2 months before the I/R studies. The left main coronary artery was occluded for 30 min followed by 120 min reperfusion. PostC was induced with three cycles of R/I (10 s each) after ischemia.

Results:

The infarct size was found to be significantly higher in Px rats (54.68±1.5%) than in the control group (35.1±2.5%). PostC and melatonin administrations to non-Px rats significantly reduced the infarct size. On the other hand, PostC did not create a significant effect in Px rats, but protection was provided when PostC was co-administrated with melatonin. While significant decreases were detected in the UCP3 levels, irisin and NFkB levels increased with I/R and Px. Treatment with PostC and melatonin in non-Px groups and their co-administration in Px groups were found to return all the genes close to normal levels.

Conclusion:

The physiological and pharmacological concentrations of melatonin may play a role in the protection of PostC. In cases when physiological melatonin is reduced, such as aging and heart diseases, this protection may decrease, and this effect may be restored by melatonin replacement. PostC and melatonin may regulate energy metabolism and inflammatory mediators and protect mitochondria by affecting the UCP3, irisin, and NFkB levels.

Lactate Suppresses Macrophage Pro-Inflammatory Response to LPS Stimulation by Inhibition of YAP and NF-κB Activation via GPR81-Mediated Signaling

Recent evidence from cancer research indicates that lactate exerts a suppressive effect on innate immune responses in cancer. This study investigated the mechanisms by which lactate suppresses macrophage pro-inflammatory responses. Macrophages [Raw 264.7 and bone marrow derived macrophages (BMDMs)] were treated with LPS in the presence or absence of lactate. Pro-inflammatory cytokines, NF-κB and YAP activation and nuclear translocation were examined. Our results show that lactate significantly attenuates LPS stimulated macrophage TNF-α and IL-6 production. Lactate also suppresses LPS stimulated macrophage NF-κB and YAP activation and nuclear translocation in macrophages. Interestingly, YAP activation and nuclear translocation are required for LPS stimulated macrophage NF-κB activation and TNFα production. Importantly, lactate suppressed YAP activation and nuclear translocation is mediated by GPR81 dependent AMKP and LATS activation which phosphorylates YAP, resulting in YAP inactivation. Finally, we demonstrated that LPS stimulation induces an interaction between YAP and NF-κB subunit p65, while lactate decreases the interaction of YAP and NF-κB, thus suppressing LPS induced pro-inflammatory cytokine production. Our study demonstrates that lactate exerts a previously unknown role in the suppression of macrophage pro-inflammatory cytokine production via GPR81 mediated YAP inactivation, resulting in disruption of YAP and NF-κB interaction and nuclear translocation in macrophages.

Immunity and Stress Responses Are Induced During Ex Situ Heart Perfusion

BACKGROUND

Ex situ heart perfusion (ESHP) preserves the donated heart in a perfused, beating condition preventing cold storage-related ischemia and provides a platform to evaluate myocardial viability during preservation. However, myocardial function declines gradually during ESHP. Extracorporeal circulation systems are associated with the induction of systemic inflammatory and stress responses. Our aim was to evaluate the incidence of inflammation and induction of endoplasmic reticulum stress responses during an extended period of ESHP.

METHODS

Cardiac function, myocardial tissue injury, markers of inflammation, oxidative stress, and endoplasmic reticulum stress were assessed in healthy pig hearts, perfused for 12 hours either in nonworking mode (non-WM=7) or working mode (WM, n=6).

RESULTS

Cardiac function declined during ESHP but was significantly better preserved in the hearts perfused in WM (median 11-hour cardiac index/1-hour cardiac index: WM=27% versus non-WM=9.5%, P=0.022). Myocardial markers of endoplasmic reticulum stress were expressed higher in ESHP hearts compared with in vivo samples. The proinflammatory cytokines and oxidized low-density lipoprotein significantly increased in the perfusate throughout the perfusion in both perfusion groups. The left ventricular expression of the cytokines and malondialdehyde was induced in non-WM, whereas it was not different between WM and in vivo.

CONCLUSIONS

Myocardial function declines during ESHP regardless of perfusion mode. However, ESHP in WM may lead to superior preservation of myocardial function and viability. Both inflammation and endoplasmic reticulum stress responses are significantly induced during ESHP and may contribute to the myocardial functional decline, representing a potential therapeutic target to improve the clinical donor heart preservation.

A miR-1275 mimic protects myocardiocyte apoptosis by regulating the Wnt/NF-κB pathway in a rat model of myocardial ischemia-reperfusion-induced myocardial injury

This study evaluated the cardioprotective effects of a miR-1275 mimic in a rat model of myocardial ischemia-reperfusion (I/R)-induced myocardial injury (MI). Three groups of rats were established: a sham-operated group, a MI group and a MI+miR-1275 group pretreated for 1 week i.p. with a miR-1275 mimic at a concentration of 30 pmol/mL. MI was induced by I/R. The levels of myocardial enzymes in serum were estimated in all rats, together with haemodynamic functions. The effects of the miR-1275 mimic were determined based on the serum concentrations of inflammatory mediators in the treated vs. sham and MI rats. In addition, western blot assay and immunohistochemical analyses were performed to examine the effect of the miR-1275 mimic on the Wnt/NF-kB signalling pathway in MI rats. Treatment with the miR-1275 mimic attenuated the altered levels of myocardial enzymes and haemodynamic functions seen in MI rats. The myocardial infarct was smaller in rats treated with the miR-1275 mimic than in MI rats. The miR-1275 mimic also reduced myocardiocyte apoptosis and ameliorated the altered Wnt/KF-kB pathway. These results demonstrate the efficacy of the miR-1275 mimic in preventing myocardial I/R-induced MI in rats, by regulating the Wnt/NF-κB pathway.

Improvement of insulin signalling rescues inflammatory cardiac dysfunction

Inflammation resulting from virus infection is the cause of myocarditis; however, the precise mechanism by which inflammation induces cardiac dysfunction is still unclear. In this study, we investigated the contribution of insulin signalling to inflammatory cardiac dysfunction induced by the activation of signalling by NF-κB, a major transcriptional factor regulating inflammation. We generated mice constitutively overexpressing kinase-active IKK-β, an essential kinase for NF-κB activation, in cardiomyocytes (KA mice). KA mice demonstrated poor survival and significant cardiac dysfunction with remarkable dilation. Histologically, KA hearts revealed increased cardiac apoptosis and fibrosis and the enhanced recruitment of immune cells. By molecular analysis, we observed the increased phosphorylation of IRS-1, indicating the suppression of insulin signalling in KA hearts. To evaluate the contribution of insulin signalling to cardiac dysfunction in KA hearts, we generated mice with cardiac-specific suppression of phosphatase and tensin homologue 10 (PTEN), a negative regulator of insulin signalling, in the KA mouse background (KA-PTEN). The suppression of PTEN successfully improved insulin signalling in KA-PTEN hearts, and interestingly, KA-PTEN mice showed significantly improved cardiac function and survival. These results indicated that impaired insulin signalling underlies the mechanism involved in inflammation-induced cardiac dysfunction, which suggests that it may be a target for the treatment of myocarditis.

MicroRNA-155 inhibition attenuates endoplasmic reticulum stress-induced cardiomyocyte apoptosis following myocardial infarction via reducing macrophage inflammation

Endoplasmic reticulum stress (ERS)-induced cardiomyocyte apoptosis plays an important role in the pathological process following myocardial infarction (MI). Macrophages that express microRNA-155 (miR-155) mediate cardiac inflammation, fibrosis, and hypertrophy. Therefore, we investigated if miR-155 regulates ERS-induced cardiomyocyte apoptosis after MI using a mouse model, lipopolysaccharide (LPS)-induced rat bone marrow derived macrophages (BMDMs)and hypoxia-induced neonatal rat cardiomyocytes (NRCMs). In vivo, miR-155 levelswere significantly higher in the MI group compared to the sham group. MI increasedmacrophage infiltration, nuclear factor-κB (NF-κB) activation, ERS induced-apoptosis, and SOCS1 expression, all of which were attenuated by the miR-155 antagomir, with the exception of SOCS1 expression. Additionally, post-MI cardiac dysfunction was significantly improved by miR-155 inhibition. In vitro, LPS upregulated miR-155 expression in BMDMs, and the miR-155 antagomir decreased LPS-induced macrophage inflammation and NF-κB pathway activation, but increased expression of SOCS1. Hypoxia increased NF-κB pathway activation, ERS marker expression, and apoptosis in NRCMs. Interestingly, conditioned medium from LPS-induced macrophages in combination with the miR-155 antagomir decreased, while the miR-155 agomir increased, the hypoxia-induced effects in NRCM's. The miR-155 agomir effects were reversed by inhibiting the NF-κB pathway in cardiomyocytes. Moreover, SOCS1 knockdown in LPS-induced macrophages promoted NF-κB pathway activation and ERS-induced cardiomyocyte apoptosis in the hypoxia-induced NRCMs, but the SOCS1-siRNA-induced effects were markedly decreased by miR-155 antagomir treatment. These data suggest that miR-155 inhibition attenuates ERS-induced cardiomyocyte apoptosis after MI via reducing macrophage inflammation through the SOCS1/NF-κB pathway.

Innate Immune Signaling and Its Role in Metabolic and Cardiovascular Diseases

The innate immune system is an evolutionarily conserved system that senses and defends against infection and irritation. Innate immune signaling is a complex cascade that quickly recognizes infectious threats through multiple germline-encoded cell surface or cytoplasmic receptors and transmits signals for the deployment of proper countermeasures through adaptors, kinases, and transcription factors, resulting in the production of cytokines. As the first response of the innate immune system to pathogenic signals, inflammatory responses must be rapid and specific to establish a physical barrier against the spread of infection and must subsequently be terminated once the pathogens have been cleared. Long-lasting and low-grade chronic inflammation is a distinguishing feature of type 2 diabetes and cardiovascular diseases, which are currently major public health problems. Cardiometabolic stress-induced inflammatory responses activate innate immune signaling, which directly contributes to the development of cardiometabolic diseases. Additionally, although the innate immune elements are highly conserved in higher-order jawed vertebrates, lower-grade jawless vertebrates lack several transcription factors and inflammatory cytokine genes downstream of the Toll-like receptors (TLRs) and retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs) pathways, suggesting that innate immune signaling components may additionally function in an immune-independent way. Notably, recent studies from our group and others have revealed that innate immune signaling can function as a vital regulator of cardiometabolic homeostasis independent of its immune function. Therefore, further investigation of innate immune signaling in cardiometabolic systems may facilitate the discovery of new strategies to manage the initiation and progression of cardiometabolic disorders, leading to better treatments for these diseases. In this review, we summarize the current progress in innate immune signaling studies and the regulatory function of innate immunity in cardiometabolic diseases. Notably, we highlight the immune-independent effects of innate immune signaling components on the development of cardiometabolic disorders.

β-Integrin mediates LPS-induced coelomocyte apoptosis in sea cucumber Apostichopus japonicus via the integrin/FAK/caspase-3 signaling pathway

Lipopolysaccharides (LPS) can induce the apoptosis of coelomocytes in Apostichopus japonicus (A. japonicus), and β-integrin serves as an apoptotic inhibitor during this process. However, the underlying mechanism in invertebrates is largely unknown. Integrin/focal adhesion kinase (FAK) signaling pathway modulates the apoptosis in vertebrates. In this study, a novel FAK was identified from A. japonicus (designated as AjFAK) by β-integrin (designated as AjITGB) -mediated GST-pull down assay. This interaction was further validated in the LPS-exposed coelomocytes through co-immunoprecipitation and immunofluorescence analyses. To investigate the functional role of AjFAK in AjITGB-mediated coelomocyte apoptosis, we cloned the full-length cDNA of AjFAK and characterized its relationship with AjITGB through real-time PCR. The mRNA expression levels of AjFAK exhibited consistent expression patterns with those of AjITGB in our previous work with 0.48- and 0.22-fold decreases at 12 and 96 h in LPS-exposed coelomocytes and in Vibrio splendidus challenged sea cucumber, respectively. Moreover, the expression level of AjFAK decreased to 0.35-fold in AjITGB knockdown treatment by specific small interference RNA (siRNA). We further performed an assay for the apoptotic rate of coelomocytes in AjITGB, AjFAK, and AjITGB/AjFAK silencing conditions and found that their apoptotic percentages increased to 26%, 25%, and 30%, respectively, compared with those of the control. Finally, the expression levels of four caspases from A. japonicus were also investigated to determine the apoptotic effector. After AjITGB or AjFAK was silenced, the mRNA levels of caspase-3 were 6.6-fold and 2.5-fold higher than those of the control, respectively. In addition, the enzymatic activity of caspase-3 was enhanced to 1.82- and 1.79-fold that of the control in the two groups. However, no significant changes were detected in caspase-2/6/8. All our results supported that β-integrin mediated the LPS-induced coelomocyte apoptosis in sea cucumber via the integrin/FAK/caspase-3 signaling pathway.

Interleukin-37: The Effect of Anti-Inflammatory Response in Human Coronary Artery Endothelial Cells

Interleukin-37 (IL-37) is unique in the IL-1 family since it broadly suppresses innate immunity and elevates in humans with inflammatory and autoimmune diseases. IL-37 shows definite groups and transcripts for human IL37 gene, but it is still not completely understood the effect and mechanisms of inflammatory response in endothelial cells. It is well accepted that endothelial dysfunction caused by inflammation is a key initiating event in atherosclerotic plaque formation, which leads to the occurrence and development of the cardiovascular adverse events in clinical since the inflammatory responses of endothelial cells could induce and enhance the deposition of extensive lipid and the formation of atherosclerotic plaque in the intima. Thus, it is essential to investigate the role and potential mechanisms in endothelial inflammatory response to prevent the formation and development of many cardiovascular diseases including atherosclerosis. So far, the recent studies have revealed that IL-37 is able to inhibit inflammatory response by suppressing the TLR2-NF-κB-ICAM-1 pathway intracellularly in human coronary artery endothelial cells (HCAECs). Further, the role of IL-37 may be related to the IL-18 pathway extracellularly and involved in the adhesion and transmigration of neutrophils in HCAECs.

Nanoparticle-mediated delivery of Tanshinone IIA reduces adverse cardiac remodeling following myocardial infarctions in a mice model: role of NF-κB pathway

Our previous works have shown that tanshinone IIA inhibited maladaptive extracellular matrix remodeling in cardiac fibroblasts implicating its potential role in treating of pathologic cardiac remodeling. However, the intrinsically poor solubility and bioavailability of tanshinone IIA hindered its clinical application. Here we develop monomethoxy-poly (ethylene glycol)-poly (lactic acid)-D-α-Tocopheryl polyethylene glycol 1000 succinate (mPEG-PLA-TPGS) nanoparticle incorporating tanshinone IIA (tanshinone IIA-NPs) and study its efficacy in post-infarction left ventricular (LV) remodeling. Male C57BL/6 mice underwent left coronary artery ligation followed by subsequent intravenously injected tanshinone IIA-NPs therapy for 5 consecutive days. Treatment with tanshinone IIA-NP improved cardiac function, limited infarct expansion, and prevented left ventricle dilation at 4 weeks post-MI. Furthermore, cardiomyocytes inflammation, apoptosis and myocardial fibrosis were significantly attenuated in tanshinone IIA-NP treated mice. These effects also correlated with inhibition of IκB protein phosphorylation and NF-κB activation, leading to suppression of proinflammatory cytokine expression. Together, these results demonstrate tanshinone IIA-NP attenuated adverse cardiac remodeling and dysfunction mediated through prevention of IκB phosphorylation and NF-κB activation. Tanshinone IIA-NP is a novel approach to treat myocardial IR injury in patients with MI.

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.

White Wine Consumption Influences Inflammatory Phase of Repair After Myocardial Infarction in Rats

Effects of white wine (WW) consumption on the expression of inflammatory markers/mediators (MMP-2, MMP-9, NF-ĸB p65 and TGF-β1) in myocardial tissue after experimentally induced permanent myocardial ischemia was investigated. Male Sprague-Dawley rats were given either a combination of WW and water or only water, for 28 days. After coronary ligation, animals were left to survive for 24 hours. Three representative areas: infarct/ischemic, peri-infarct/border zone, and control/non-ischemic zones were analyzed for expression of immunoreactivity by measuring the threshold area % of signal density. For MMP-9, significantly smaller expression was found in all 3 zones of wine drinking animals (P < 0.001). There was no difference in MMP-2 immunoreactivity between the 2 groups, except in peri-infarct zones, where the signal was significantly decreased (P < 0.001). The same pattern of expression was found for the NF-κB p65 signal, although no differences between experimental groups were observed for TGF-β1. White wine consumption decreases the expression of the 3 investigated inflammatory markers/mediators in the peri-infarct zone, suggesting its significant modulatory effect. For MMP-9 and MMP-2, expression was similar to the effect of postischemic reperfusion. No effect on TGF-β1 was observed, highlighting its role in being the master-switch, changing from the inflammatory to the proliferative stage of infarct healing.

High doses of digoxin increase the myocardial nuclear factor-kB and CaV1.2 channels in healthy mice. A possible mechanism of digitalis toxicity

BACKGROUND

Toxic effects of digoxin may occur with normal therapeutic serum level. However, the underlying mechanisms are not fully understood. Nuclear factor kappa-B (NF-kB) is an important transcription factor in most organ systems and is often implicated in the harmful effects of cardiac injury. NF-kB promotes inflammatory responses, mediates adverse cardiac remodeling and has a function correlation with calcium. The voltage-gated L-type calcium channel CaV1.2 mediates the influx of Ca+2 into the cell in response to membrane depolarization. Our aim was to characterize the role of NF-kB during digoxin toxicity and to assess its correlation with Cav 1.2 in healthy mice in vivo.

METHODS

To address these questions, digoxin was administered in doses of 0.1, 1 or 5 mg/kg orally daily for seven days to the animals. Serum digoxin, serum calcium, atrial and ventricular calcium levels were measured. We, also, looked for NF-kB and CaV1.2 channel expression in cardiac muscle of mice.

RESULTS

Digoxin at a dose of 0.1 mg/kg did not enhance serum, atrial, and ventricular Ca+2 levels, but were increased when digoxin dose of 1 and 5 mg/kg were administered. Histologically, myocardial necrosis and cellular infiltration on day 7 were significantly more severe in the 5 mg/kg/day digoxin group. Immunohistochemical studies showed more expression of both NF-kB and CaV1.2 in 1 and 5 mg/kg/day digoxin groups.

CONCLUSIONS

These data suggest that NF-kB may be responsible for digoxin toxicity, at least partially via modulation of CaV1.2 and intracellular calcium homeostasis in the myocardium.

Over-expression of growth differentiation factor 15 (GDF15) preventing cold ischemia reperfusion (I/R) injury in heart transplantation through Foxo3a signaling

Ischemia reperfusion (I/R) injury which inevitably occurs during heart transplantation is the major factor leading to organ failure and graft rejection. In order to develop new therapies to prevent I/R injury, we used both a murine heart transplantation model with 24 hour cold I/R and an in vitro cell culture system to determine whether growth differentiation factor 15 (GDF15) is a protective factor in preventing I/R injury in heart transplantation and to further investigate underlying mechanisms of I/R injury. We found that cold I/R caused severe damage to the endocardium, epicardium and myocardium of heart grafts from wild type C57BL/6 mice, whereas grafts from GDF15 transgenic (TG) mice showed less damage as demonstrated by decreased cell apoptosis/death, decreased neutrophils infiltration and the preservation of the normal structure of the heart. Over-expression of GDF15 reduced expression of phosphorylated RelA p65, pre-inflammatory and pro-apoptotic genes while it enhanced Foxo3a phosphorylation in vitro and in vivo. Over-expression of GDF15 inhibited cell apoptosis/death and reduced neutrophil infiltration. In conclusion, this study, for the first time, demonstrates that GDF15 is a promising target for preventing cold I/R injury in heart transplantation. This study also shows that the resultant protective effects are mediated by the Foxo3 and NFκB signaling pathways.

Interleukin-37: A crucial cytokine with multiple roles in disease and potentially clinical therapy

Interleukin (IL)-37, a new IL-1 family member, has received increasing attention in recent years. In the past decade, it has been determined that IL-37 is expressed in various normal cells and tissues and is regulated by inflammatory stimuli and pro-cytokines via different signal transduction pathways. Recently, it has been found that IL-37 is expressed in a variety of cancers, chronic inflammatory and autoimmune disorders, and exerts anti-inflammatory effects. Moreover, a growing body of literature demonstrates that IL-37 plays a vital role in inhibiting both innate and adaptive immune responses as well as inflammatory reactions. In addition, IL-37 may prove to be a new and potentially useful target for effective cytokine therapy. Further evidence is needed to clarify in more detail the effects of IL-37 in experimental and clinical studies. Based on an extensive summary of published data, the aim of this review is to outline the current knowledge of IL-37, including the location, structure, expression, regulation and function, as well as the potential clinical applications of this cytokine.

Sequence variation in PPP1R13L results in a novel form of cardio-cutaneous syndrome

Dilated cardiomyopathy (DCM) is a life-threatening disorder whose genetic basis is heterogeneous and mostly unknown. Five Arab Christian infants, aged 4-30 months from four families, were diagnosed with DCM associated with mild skin, teeth, and hair abnormalities. All passed away before age 3. A homozygous sequence variation creating a premature stop codon at PPP1R13L encoding the iASPP protein was identified in three infants and in the mother of the other two. Patients' fibroblasts and PPP1R13L-knocked down human fibroblasts presented higher expression levels of pro-inflammatory cytokine genes in response to lipopolysaccharide, as well as Ppp1r13l-knocked down murine cardiomyocytes and hearts of Ppp1r13l-deficient mice. The hypersensitivity to lipopolysaccharide was NF-κB-dependent, and its inducible binding activity to promoters of pro-inflammatory cytokine genes was elevated in patients' fibroblasts. RNA sequencing of Ppp1r13l-knocked down murine cardiomyocytes and of hearts derived from different stages of DCM development in Ppp1r13l-deficient mice revealed the crucial role of iASPP in dampening cardiac inflammatory response. Our results determined PPP1R13L as the gene underlying a novel autosomal-recessive cardio-cutaneous syndrome in humans and strongly suggest that the fatal DCM during infancy is a consequence of failure to regulate transcriptional pathways necessary for tuning cardiac threshold response to common inflammatory stressors.

The Biological Basis for Cardiac Repair After Myocardial Infarction: From Inflammation to Fibrosis

In adult mammals, massive sudden loss of cardiomyocytes after infarction overwhelms the limited regenerative capacity of the myocardium, resulting in the formation of a collagen-based scar. Necrotic cells release danger signals, activating innate immune pathways and triggering an intense inflammatory response. Stimulation of toll-like receptor signaling and complement activation induces expression of proinflammatory cytokines (such as interleukin-1 and tumor necrosis factor-α) and chemokines (such as monocyte chemoattractant protein-1/ chemokine (C-C motif) ligand 2 [CCL2]). Inflammatory signals promote adhesive interactions between leukocytes and endothelial cells, leading to extravasation of neutrophils and monocytes. As infiltrating leukocytes clear the infarct from dead cells, mediators repressing inflammation are released, and anti-inflammatory mononuclear cell subsets predominate. Suppression of the inflammatory response is associated with activation of reparative cells. Fibroblasts proliferate, undergo myofibroblast transdifferentiation, and deposit large amounts of extracellular matrix proteins maintaining the structural integrity of the infarcted ventricle. The renin-angiotensin-aldosterone system and members of the transforming growth factor-β family play an important role in activation of infarct myofibroblasts. Maturation of the scar follows, as a network of cross-linked collagenous matrix is formed and granulation tissue cells become apoptotic. This review discusses the cellular effectors and molecular signals regulating the inflammatory and reparative response after myocardial infarction. Dysregulation of immune pathways, impaired suppression of postinfarction inflammation, perturbed spatial containment of the inflammatory response, and overactive fibrosis may cause adverse remodeling in patients with infarction contributing to the pathogenesis of heart failure. Therapeutic modulation of the inflammatory and reparative response may hold promise for the prevention of postinfarction heart failure.

PTPIP51 regulates mouse cardiac ischemia/reperfusion through mediating the mitochondria-SR junction

Protein tyrosine phosphatase interacting protein 51 (PTPIP51) participates in multiple cellular processes, and dysfunction of PTPIP51 is implicated in diseases such as cancer and neurodegenerative disorders. However, there is no functional evidence showing the physiological or pathological roles of PTPIP51 in the heart. We have therefore investigated the role and mechanisms of PTPIP51 in regulating cardiac function. We found that PTPIP51 was markedly upregulated in ischemia/reperfusion heart. Upregulation of PTPIP51 by adenovirus-mediated overexpression markedly increased the contact of mitochondria-sarcoplasmic reticulum (SR), elevated mitochondrial Ca²⁺ uptake from SR release through mitochondrial Ca²⁺uniporter. Inhibition or knockdown of mitochondrial Ca²⁺uniporter reversed PTPIP51-mediated increase of mitochondrial Ca²⁺ and protected cardiomyocytes against PTPIP51-mediated apoptosis. More importantly, cardiac specific knockdown of PTPIP51 largely reduced myocardium infarction size and heart injury after ischemia/reperfusion. Our study defines a novel and essential function of PTPIP51 in the cardiac ischemia/reperfusion process by mediating mitochondria-SR contact. Downregulation of PTPIP51 improves heart function after ischemia/reperfusion injury, suggesting PTPIP51 as a therapeutic target for ischemic heart diseases.

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.

Simulated ischemia/reperfusion-induced p65-Beclin 1-dependent autophagic cell death in human umbilical vein endothelial cells

Myocardial ischemia/reperfusion (I/R) injury detrimentally alters the prognosis of patients undergoing revascularization after acute myocardial infarction. Our previous study demonstrated that NF-κB-induced autophagy plays a detrimental role in cardiac I/R injury using a rabbit myocardial I/R model. In this study, we sought to explore the specific mechanism of this autophagy-mediated cell damage in an in vitro simulated ischemia/reperfusion (sI/R) model using human umbilical vein endothelial cells. Our current study demonstrates that simulated I/R induces autophagy in a p65-Beclin 1-dependent manner, which can be suppressed with the inhibition of NF-κB. Furthermore, rapamycin which promotes autophagy, exacerbates sI/R-induced cell death. While 3-methyladenine rescues cell damage. Our data thus suggest that I/R promotes NF-κB p65 activity mediated Beclin 1-mediated autophagic flux, thereby exacerbating myocardial injury.

Resolvin D1 Reduces Infarct Size Through a Phosphoinositide 3-Kinase/Protein Kinase B Mechanism

This study was designed to determine if Resolvin D1 (RvD1), a pro-resolution metabolite of the omega-3 polyunsaturated fatty acid docosahexaenoic acid, could decrease myocardial infarct size with delivered at the onset of ischemia. Male Sprague Dawley rats underwent 40 minutes of myocardial ischemia followed by reperfusion. These animals received 1 intraventricular injection of RvD1 (0.01, 0.1, or 0.3 μg RvD1) or vehicle (saline) before coronary occlusion. Infarct size and neutrophil accumulation were evaluated 24 hours after the onset of reperfusion. Caspase-3, caspase-8, protein kinase B (Akt) activities were evaluated 30 minutes after the reperfusion. Rats receiving 0.1 or 0.3 μg RvD1 showed a significant decrease of infarct size and caspase-3 and caspase-8 activities compared with the vehicle controls. Neutrophil accumulations were reduced in rats administered RvD1 compared with vehicle, independently of dose level. Akt activation was increased only in animals receiving 0.1 or 0.3 μg, whereas no change was observed in the 0.01 μg group. When they were treated with LY-294002, a phosphoinositide 3-kinase (PI3K)/Akt inhibitor, cardioprotection by RvD1 was abrogated. RvD1 treatment at the onset of ischemia decreases infarct size by a mechanism involving the PI3K/Akt pathway.

N-myc downstream-regulated gene 4, up-regulated by tumor necrosis factor-α and nuclear factor kappa B, aggravates cardiac ischemia/reperfusion injury by inhibiting reperfusion injury salvage kinase pathway

N-myc downstream-regulated gene 4 (NDRG4) is expressed weakly in heart and has been reported to modulate cardiac development and QT interval duration, but the role of NDRG4 in myocardial ischemia/reperfusion (I/R) injury remains unknown. In the present study, we analyzed the expression as well as potential function of cardiac NDRG4 and investigated how NDRG4 expression is regulated by inflammation. We found that NDRG4 was weakly expressed in cardiomyocytes and that its expression increased significantly both in I/R injured heart and in hypoxia-reoxygenation (H/R) injured neonatal rat ventricular myocytes (NRVMs). The increased NDRG4 expression aggravated myocardial I/R injury by inhibiting the activation of the reperfusion injury salvage kinase (RISK) pathway. Forced over-expression of NDRG4 inhibited RISK activation and exacerbated injury not only in I/R injured heart, but also in H/R treated NRVMs, whereas short hairpin RNA (shRNA)-mediated knock-down of NDRG4 enhanced RISK activation and attenuated injury. Upon injury, myocardial NDRG4 expression was induced by tumor necrosis factor-α (TNF-α) through nuclear factor kappa B (NF-κB), and we found that pre-treatment with inhibitors of either TNF-α or NF-κB blocked NDRG4 expression as well as I/R injury in vivo and H/R injury in vitro. Our study indicates that up-regulation of NDRG4 aggravates myocardial I/R injury by inhibiting activation of the RISK pathway, thereby identifying NDRG4 as a potential therapeutic target in I/R injury.

Pathophysiology of Myocardial Infarction

Myocardial infarction is defined as sudden ischemic death of myocardial tissue. In the clinical context, myocardial infarction is usually due to thrombotic occlusion of a coronary vessel caused by rupture of a vulnerable plaque. Ischemia induces profound metabolic and ionic perturbations in the affected myocardium and causes rapid depression of systolic function. Prolonged myocardial ischemia activates a "wavefront" of cardiomyocyte death that extends from the subendocardium to the subepicardium. Mitochondrial alterations are prominently involved in apoptosis and necrosis of cardiomyocytes in the infarcted heart. The adult mammalian heart has negligible regenerative capacity, thus the infarcted myocardium heals through formation of a scar. Infarct healing is dependent on an inflammatory cascade, triggered by alarmins released by dying cells. Clearance of dead cells and matrix debris by infiltrating phagocytes activates anti-inflammatory pathways leading to suppression of cytokine and chemokine signaling. Activation of the renin-angiotensin-aldosterone system and release of transforming growth factor-β induce conversion of fibroblasts into myofibroblasts, promoting deposition of extracellular matrix proteins. Infarct healing is intertwined with geometric remodeling of the chamber, characterized by dilation, hypertrophy of viable segments, and progressive dysfunction. This review manuscript describes the molecular signals and cellular effectors implicated in injury, repair, and remodeling of the infarcted heart, the mechanistic basis of the most common complications associated with myocardial infarction, and the pathophysiologic effects of established treatment strategies. Moreover, we discuss the implications of pathophysiological insights in design and implementation of new promising therapeutic approaches for patients with myocardial infarction.

Effects of interleukin-37 on cardiac function after myocardial infarction in mice

BACKGROUND

Interleukin-37 (IL-37) is a new discovered member of the interleukin family and plays anti-inflammatory effect in some inflammatory disease. A recent study found that IL-37 elevated significantly in peripheral blood of patients with acute myocardial infarction. We aimed to explore the effect IL-37 on cardiac function after mice myocardial infarction (MI) and its mechanism.

METHODS

Acute MI mouse model was established and divided into three groups: sham group, MI group and IL-37 treatment group. MPO expression was detected by immunohistochemistry; NF-κB signaling pathway was tested by Western blot; and cardiac function was measured by echocardiography.

RESULTS

Compared with MI mice, IL-37 treatment showed an obvious decrease of MPO expression, suppression of p-p65 expression, and improved cardiac function by decreasing left ventricular shortening fraction (LVFS).

CONCLUSION

IL-37 may improve MI mice cardiac function via inhibition of inflammatory NF-κB signaling pathway.

MCP-1-induced protein attenuates post-infarct cardiac remodeling and dysfunction through mitigating NF-κB activation and suppressing inflammation-associated microRNA expression

MCP-1-induced protein (MCPIP, also known as ZC3H12A) has recently been uncovered to act as a negative regulator of inflammation. Expression of MCPIP was elevated in the ventricular myocardium of patients with ischemic heart failure. However, the role of MCPIP in the development of post-infarct cardiac inflammation and remodeling is unknown. The objective of the present study was to investigate whether MCPIP exerts an inhibitory effect on the cardiac inflammatory response and adverse remodeling after myocardial infarction (MI). Mice with cardiomyocyte-specific expression of MCPIP and their wild-type littermates (FVB/N) were subjected to permanent ligation of left coronary artery. The levels of MCPIP were significantly increased in the ischemic myocardium and sustained for 4 weeks after MI. Acute infarct size was comparable between groups. However, constitutive overexpression of MCPIP in the murine heart resulted in improved survival rate, decreased cardiac hypertrophy, less of fibrosis and scar formation, and better cardiac performance at 28 days after MI, along with a markedly reduced monocytic cell infiltration, less cytokine expression, decreased caspase-3/7 activities and apoptotic cell death compared to the wild-type hearts. Cardiomyocyte-specific expression of MCPIP also attenuated activation of cardiac NF-κB signaling and expression of inflammation-associated microRNAs (miR-126, -146a, -155, and -199a) when compared with the post-infarct wild-type hearts. In vitro, MCPIP expression suppressed hypoxia-induced NF-κB-luciferase activity in cardiomyocytes. In conclusion, MCPIP expression in the ischemic myocardium protects against adverse cardiac remodeling and dysfunction following MI by modulation of local myocardial inflammation, possibly through mitigating NF-κB signaling and suppressing inflammation-associated microRNA expression.

Astragaloside IV attenuates injury caused by myocardial ischemia/reperfusion in rats via regulation of toll-like receptor 4/nuclear factor-κB signaling pathway

Myocardial ischemia/reperfusion (MI/R) injury, in which inflammatory response and cell apoptosis play a vital role, is frequently encountered in clinical practice. Astragaloside IV (AsIV), a small molecular saponin of Astragalus membranaceus, has been shown to confer protective effects against many cardiovascular diseases. The present study was aimed to investigate the antiinflammatory and antiapoptotic effects and the possible mechanism of AsIV on MI/R injury in rats. Rats were randomly divided into sham operation group, MI/R group and groups with combinations of MI/R and different doses of AsIV. The results showed that the expressions of myocardial toll-like receptor 4 (TLR4) and nuclear factor-κB (NF-κB) were significantly increased, and apoptosis of cardiomyocytes was induced in MI/R group compared with that in sham operation group. Administration of AsIV attenuated MI/R injury, downregulated the expressions of TLR4 and NF-κB and inhibited cell apoptosis as evidenced by decreased terminal deoxynucleotidyl transferase dUTP nick end labeling positive cells, B-cell lymphoma-2 associated X protein and caspase-3 expressions and increased B-cell lymphoma-2 expression compared with that in MI/R group. In addition, AsIV treatment reduced levels of inflammatory cytokines induced by MI/R injury. In conclusion, our results demonstrated that AsIV downregulates TLR4/NF-κB signaling pathway and inhibits cell apoptosis, subsequently attenuating MI/R injury in rats.

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.