Pressure overload-induced cardiac remodeling and dysfunction in the absence of interleukin 6 in mice

Piezo1-Mediated Neurogenic Inflammatory Cascade Exacerbates Ventricular Remodeling After Myocardial Infarction

BACKGROUND

Heart failure is associated with a high rate of mortality and morbidity, and ventricular remodeling invariably precedes heart failure. Ventricular remodeling is fundamentally driven by mechanotransduction that is regulated by both the nervous system and the immune system. However, it remains unknown which key molecular factors govern the neuro/immune/cardio axis that underlies mechanotransduction during ventricular remodeling. Here, we investigated whether the mechanosensitive Piezo cation channel-mediated neurogenic inflammatory cascade underlies ventricular remodeling-related mechanotransduction.

METHODS

By ligating the left coronary artery of rats to establish an in vivo model of chronic myocardial infarction (MI), lentivirus-mediated thoracic dorsal root ganglion (TDRG)-specific Piezo1 knockdown rats and adeno-associated virus-PHP.S-mediated TDRG neuron-specific Piezo1 knockout mice were used to investigate whether Piezo1 in the TDRG plays a functional role during ventricular remodeling. Subsequently, neutralizing antibody-mediated TDRG IL-6 (interleukin-6) inhibition rats and adeno-associated virus-PHP.S-mediated TDRG neuron-specific IL-6 knockdown mice were used to determine the mechanism underlying neurogenic inflammation. Primary TDRG neurons were used to evaluate Piezo1 function in vitro.

RESULTS

Expression of Piezo1 and IL-6 was increased, and these factors were functionally activated in TDRG neurons at 4 weeks after MI. Both knockdown of TDRG-specific Piezo1 and deletion of TDRG neuron-specific Piezo1 lessened the severity of ventricular remodeling at 4 weeks after MI and decreased the level of IL-6 in the TDRG or heart. Furthermore, inhibition of TDRG IL-6 or knockdown of TDRG neuron-specific IL-6 also ameliorated ventricular remodeling and suppressed the IL-6 cascade in the heart, whereas the Piezo1 level in the TDRG was not affected. In addition, enhanced Piezo1 function, as reflected by abundant calcium influx induced by Yoda1 (a selective agonist of Piezo1), led to increased release of IL-6 from TDRG neurons in mice 4 weeks after MI.

CONCLUSIONS

Our findings point to a critical role for Piezo1 in ventricular remodeling at 4 weeks after MI and reveal a neurogenic inflammatory cascade as a previously unknown facet of the neuronal immune signaling axis underlying mechanotransduction.

Identification of Circulating Plasma Proteins as a Mediator of Hypertension-Driven Cardiac Remodeling: A Mediation Mendelian Randomization Study

BACKGROUND

This study focused on circulating plasma protein profiles to identify mediators of hypertension-driven myocardial remodeling and heart failure.

METHODS

A Mendelian randomization design was used to investigate the causal impact of systolic blood pressure (SBP), diastolic blood pressure (DBP), and pulse pressure on 82 cardiac magnetic resonance traits and heart failure risk. Mediation analyses were also conducted to identify potential plasma proteins mediating these effects.

RESULTS

Genetically proxied higher SBP, DBP, and pulse pressure were causally associated with increased left ventricular myocardial mass and alterations in global myocardial wall thickness at end diastole. Elevated SBP and DBP were linked to increased regional myocardial radial strain of the left ventricle (basal anterior, mid, and apical walls), while higher SBP was associated with reduced circumferential strain in specific left ventricular segments (apical, mid-anteroseptal, mid-inferoseptal, and mid-inferolateral walls). Specific plasma proteins mediated the impact of blood pressure on cardiac remodeling, with FGF5 (fibroblast growth factor 5) contributing 2.96% (P=0.024) and 4.15% (P=0.046) to the total effect of SBP and DBP on myocardial wall thickness at end diastole in the apical anterior segment and leptin explaining 15.21% (P=0.042) and 23.24% (P=0.022) of the total effect of SBP and DBP on radial strain in the mid-anteroseptal segment. Additionally, FGF5 was the only mediator, explaining 4.19% (P=0.013) and 4.54% (P=0.032) of the total effect of SBP and DBP on heart failure susceptibility.

CONCLUSIONS

This mediation Mendelian randomization study provides evidence supporting specific circulating plasma proteins as mediators of hypertension-driven cardiac remodeling and heart failure.

The Anti-Inflammatory Mediator 17(R)-Resolvin D1 Attenuates Pressure Overload-Induced Cardiac Hypertrophy and Fibrosis

Background

Increased inflammation contributes to pressure overload-induced myocardial remodeling. 17(R)-Resolvin D1 (17(R)-RvD1), a potent lipid mediator derived from docosahexaenoic acid, possesses anti-inflammatory and pro-resolving properties. However, the association between 17(R)-RvD1 and pressure overload-induced cardiac hypertrophy remains unclear.

Methods

Transverse aortic constriction (TAC) surgery was performed to establish a cardiac hypertrophy model. C57BL/6J mice were randomly assigned to the Sham, TAC and TAC+17(R)-RvD1 groups. 17(R)-RvD1 was injected (2 μg/kg, i.p.) before TAC surgery and once every other day after surgery for 4 weeks. The same volume of saline was injected into the mice in both Sham group and TAC group. Then, cardiac function was evaluated and heart tissues were collected for biological analysis.

Results

17(R)-RvD1 treatment attenuated TAC-induced increase in left ventricular diameter and decrease in left ventricular contractility, mitigated increased cardiomyocyte cross-sectional area, and downregulated the expression of hypertrophic genes. Besides, 17(R)-RvD1 attenuated myocardial fibrosis, as indicated by the decreased LV collagen volume and expression of fibrotic genes. In addition, 17(R)-RvD1 ameliorated the inflammatory response in cardiac tissue, as illustrated by the decreased infiltration of CD68+ macrophages and reduced production of pro-inflammatory cytokines, including TNF-α, IL-1β, and IL-6. 17(R)-RvD1 treatment significantly suppressed the activation of NLRP3 inflammasome after TAC surgery, which might be responsible for the attenuation of inflammation in cardiac tissue.

Conclusion

17(R)-RvD1 attenuated pressure overload-induced cardiac hypertrophy and fibrosis, and the possible mechanism may be associated with the inhibition of NLRP3 inflammasome. 17(R)-RvD1 may serve as a potential drug for the treatment of cardiac hypertrophy.

Deficiency of Tregs in hypertension-associated left ventricular hypertrophy

Left ventricular hypertrophy (LVH) is the most common target organ damage in hypertension. Abnormal numbers or functions of CD4+ CD25+ Foxp3+ regulatory T lymphocytes (Tregs) can cause immune disorders, which participates in LVH. This study aimed to explore the role of Tregs in LVH by investigating circulating Tregs and associated cytokine levels in hypertensive patients with or without LVH. Blood samples were collected from 83 hypertensive patients without LVH (essential hypertension group, EH), 91 hypertensive patients with LVH (left ventricular hypertrophy group, LVH), and 69 normotensive controls without LVH (control group, CG). Tregs and cytokines were measured by flow cytometry and enzyme-linked immunosorbent assays. We found that circulating Tregs were significantly lower in hypertensive patients than in CG subjects. It was lower in LVH than in EH patients. No correlation between blood pressure regulation and Tregs was found in EH or LVH patients. Furthermore, Tregs in older females were lower than those in older males among LVH patients. Additionally, serum interleukin-10 (IL-10) and transforming growth factor beta 1 (TGFβ1) decreased in hypertensive patients, and interleukin-6 (IL-6) increased in LVH patients. Tregs were negatively correlated with creatine kinase, low-density lipoprotein cholesterol, apoprotein B, high-sensitivity C-reactive protein, and left ventricular mass index (LVMI) values. In general, our study demonstrates significantly decreased circulating Tregs in hypertensive LVH patients. Decreased circulating Tregs in LVH is independent of blood pressure regulation. IL-6, IL-10, and TGF-β1 are related with LVH in hypertension.

Targeting Myocardial Fibrosis—A Magic Pill in Cardiovascular Medicine?

Fibrosis, characterized by an excessive accumulation of extracellular matrix, has long been seen as an adaptive process that contributes to tissue healing and regeneration. More recently, however, cardiac fibrosis has been shown to be a central element in many cardiovascular diseases (CVDs), contributing to the alteration of cardiac electrical and mechanical functions in a wide range of clinical settings. This paper aims to provide a comprehensive review of cardiac fibrosis, with a focus on the main pathophysiological pathways involved in its onset and progression, its role in various cardiovascular conditions, and on the potential of currently available and emerging therapeutic strategies to counteract the development and/or progression of fibrosis in CVDs. We also emphasize a number of questions that remain to be answered, and we identify hotspots for future research.

Genetic deletion of IL-6 increases CK-MB, a classic cardiac damage marker, and decreases UPRmt genes after exhaustive exercise

The intensity, duration, type of contraction, and muscle damage influence interleukin-6 (IL-6) response to acute exercise. However, in response to an exhaustive exercise session, the upregulation of IL-6 in the serum and heart is associated with an inflammatory condition and can inhibit autophagy. This study aimed to investigate the role of IL-6 in autophagy pathway responses and mitochondrial function in the heart of mice submitted to acute exhaustive physical exercise. The mice were allocated into three groups, five animals per group, for the wild type (WT) and the IL-6 knockout (IL-6 KO): Basal (sedentary; Basal), 1 h (after 1 h of the acute exercise; 1 h), and 3 h (after 3 h of the acute exercise; 3 h). After the specific time for each group, the blood was collected, each mouse heart was removed, and the left ventricle (LV) was isolated. In summary, under basal conditions, without the influence of the acute exercise, the IL-6 KO group showed lower number of nuclei in the cardiac tissue, but higher collagen deposition; lower messenger RNA (mRNA) levels of Prkaa1 and Mtco1, but higher mRNA levels of Ulk1; and higher protein levels of the ratio p-AMPK/AMPK in the heart when compared to WT at the same time point. After the acute exercise (1 and 3 h), the IL-6 KO group had lower mRNA levels of Tfam, Mtnd1, Mtco1, and Nampt in the heart when compared to WT after exercise; higher serum levels of creatine kinase (CK), CK-MB, and lactate dehydrogenase for the IL-6 group when compared to the WT group after the exercise. Specifically, the heat-shock protein 60 protein levels in the heart increased 3 h after exhaustive exercise in the WT group, but not in the IL-6 KO group. The study emphasizes that IL-6 may offer cardioprotective effects, including mitochondrial adaptations in response to acute exhaustive exercise.

ADAM17, A Key Player of Cardiac Inflammation and Fibrosis in Heart Failure Development During Chronic Catecholamine Stress

Heart failure development is characterized by persistent inflammation and progressive fibrosis owing to chronic catecholamine stress. In a chronic stress state, elevated catecholamines result in the overstimulation of beta-adrenergic receptors (βARs), specifically β2-AR coupling with Gαi protein. Gαi signaling increases the activation of receptor-stimulated p38 mitogen-activated-protein-kinases (p38 MAPKs) and extracellular signal-regulated kinases (ERKs). Phosphorylation by these kinases is a common way to positively regulate the catalytic activity of A Disintegrin and Metalloprotease 17 (ADAM17), a metalloprotease that has grown much attention in recent years and has emerged as a chief regulatory hub in inflammation, fibrosis, and immunity due to its vital proteolytic activity. ADAM17 cleaves and activates proinflammatory cytokines and fibrotic factors that enhance cardiac dysfunction via inflammation and fibrosis. However, there is limited information on the cardiovascular aspect of ADAM17, especially in heart failure. Hence, this concise review provides a comprehensive insight into the structure of ADAM17, how it is activated and regulated during chronic catecholamine stress in heart failure development. This review highlights the inflammatory and fibrotic roles of ADAM17’s substrates; Tumor Necrosis Factor α (TNFα), soluble interleukin-6 receptor (sIL-6R), and amphiregulin (AREG). Finally, how ADAM17-induced chronic inflammation and progressive fibrosis aggravate cardiac dysfunction is discussed.

Anthelmintic niclosamide attenuates pressure-overload induced heart failure in mice

The heart is a high energy demand organ and enhancing mitochondrial function is proposed as the next-generation therapeutics for heart failure. Our previous study found that anthelmintic drug niclosamide enhanced mitochondrial respiration and increased adenosine triphosphate (ATP) production in cardiomyocytes, therefore, this study aimed to determine the effect of niclosamide on heart failure in mice and the potential molecular mechanisms. The heart failure model was induced by transverse aortic constriction (TAC) in mice. Oral administration of niclosamide improved TAC-induced cardiac hypertrophy, cardiac fibrosis, and cardiac dysfunction in mice. Oral administration of niclosamide reduced TAC-induced increase of serum IL-6 in heart failure mice. In vitro, niclosamide within 0.1 μM increased mitochondrial respiration and ATP production in mice heart tissues. At the concentrations more than 0.1 μM, niclosamide reduced the increased interleukin- 6 (IL-6) mRNA expression in lipopolysaccharide (LPS)-stimulated RAW264.7 and THP-1 derived macrophages. In cultured primary cardiomyocytes and cardiac fibroblasts, niclosamide (more than 0.1 μM) suppressed IL-6- and phenylephrine-induced cardiomyocyte hypertrophy, and inhibited collagen secretion from cardiac fibroblasts. In conclusion, niclosamide attenuates heart failure in mice and the underlying mechanisms include enhancing mitochondrial respiration of cardiomyocytes, inhibiting collagen secretion from cardiac fibroblasts, and reducing the elevated serum inflammatory mediator IL-6. The present study suggests that niclosamide might be therapeutic for heart failure.

Connecting different heart diseases through intercellular communication

Well-orchestrated intercellular communication networks are pivotal to maintaining cardiac homeostasis and to ensuring adaptative responses and repair after injury. Intracardiac communication is sustained by cell-cell crosstalk, directly via gap junctions (GJ) and tunneling nanotubes (TNT), indirectly through the exchange of soluble factors and extracellular vesicles (EV), and by cell-extracellular matrix (ECM) interactions. GJ-mediated communication between cardiomyocytes and with other cardiac cell types enables electrical impulse propagation, required to sustain synchronized heart beating. In addition, TNT-mediated organelle transfer has been associated with cardioprotection, whilst communication via EV plays diverse pathophysiological roles, being implicated in angiogenesis, inflammation and fibrosis. Connecting various cell populations, the ECM plays important functions not only in maintaining the heart structure, but also acting as a signal transducer for intercellular crosstalk. Although with distinct etiologies and clinical manifestations, intercellular communication derailment has been implicated in several cardiac disorders, including myocardial infarction and hypertrophy, highlighting the importance of a comprehensive and integrated view of complex cell communication networks. In this review, I intend to provide a critical perspective about the main mechanisms contributing to regulate cellular crosstalk in the heart, which may be considered in the development of future therapeutic strategies, using cell-based therapies as a paradigmatic example. This Review has an associated Future Leader to Watch interview with the author.

Alleviation of Inflammation and Oxidative Stress in Pressure Overload-Induced Cardiac Remodeling and Heart Failure via IL-6/STAT3 Inhibition by Raloxifene

BACKGROUND

Inflammation and oxidative stress are involved in the initiation and progress of heart failure (HF). However, the role of the IL6/STAT3 pathway in the pressure overload-induced HF remains controversial.

METHODS AND RESULTS

Transverse aortic constriction (TAC) was used to induce pressure overload-HF in C57BL/6J mice. 18 mice were randomized into three groups (Sham, TAC, and TAC+raloxifene, n = 6, respectively). Echocardiographic and histological results showed that cardiac hypertrophy, fibrosis, and left ventricular dysfunction were manifested in mice after TAC treatment of eight weeks, with aggravation of macrophage infiltration and interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) expression in the myocardium. TAC (four and eight weeks) elevated the phosphorylation of signal transducer and activator of transcription 3 (p-STAT3) and prohibitin2 (PHB2) protein expression. Importantly, IL-6/gp130/STAT3 inhibition by raloxifene alleviated TAC-induced myocardial inflammation, cardiac remodeling, and dysfunction. In vitro, we demonstrated cellular hypertrophy with STAT3 activation and oxidative stress exacerbation could be elicited by IL-6 (25 ng/mL, 48 h) in H9c2 myoblasts. Sustained IL-6 stimulation increased intracellular reactive oxygen species, repressed mitochondrial membrane potential (MMP), decreased intracellular content of ATP, and led to decreased SOD activity, an increase in iNOS protein expression, and increased protein expression of Pink1, Parkin, and Bnip3 involving in mitophagy, all of which were reversed by raloxifene.

CONCLUSION

Inflammation and IL-6/STAT3 signaling were activated in TAC-induced HF in mice, while sustained IL-6 incubation elicited oxidative stress and mitophagy-related protein increase in H9c2 myoblasts, all of which were inhibited by raloxifene. These indicated IL-6/STAT3 signaling might be involved in the pathogenesis of myocardial hypertrophy and HF.

Divergent and Overlapping Roles for Selected Phytochemicals in the Regulation of Pathological Cardiac Hypertrophy

Plant-based foods, like fruits, vegetables, whole grains, legumes, nuts, seeds and other foodstuffs, have been deemed as heart healthy. The chemicals within these plant-based foods, i.e., phytochemicals, are credited with protecting the heart. However, the mechanistic actions of phytochemicals, which prevent clinical endpoints, such as pathological cardiac hypertrophy, are still being elucidated. We sought to characterize the overlapping and divergent mechanisms by which 18 selected phytochemicals prevent phenylephrine- and phorbol 12-myristate 13-acetate-mediated cardiomyocyte enlargement. Of the tested 18 compounds, six attenuated PE- and PMA-mediated enlargement of neonatal rat ventricular myocytes. Cell viability assays showed that apigenin, baicalein, berberine hydrochloride, emodin, luteolin and quercetin dihydrate did not reduce cell size through cytotoxicity. Four of the six phytochemicals, apigenin, baicalein, berberine hydrochloride and emodin, robustly inhibited stress-induced hypertrophy and were analyzed further against intracellular signaling and genome-wide changes in mRNA expression. The four phytochemicals differentially regulated mitogen-activated protein kinases and protein kinase D. RNA-sequencing further showed divergence in gene regulation, while pathway analysis demonstrated overlap in the regulation of inflammatory pathways. Combined, this study provided a comprehensive analysis of cardioprotective phytochemicals. These data highlight two defining observations: (1) that these compounds predominantly target divergent gene pathways within cardiac myocytes and (2) that regulation of overlapping signaling and gene pathways may be of particular importance for the anti-hypertrophic actions of these phytochemicals. Despite these new findings, future works investigating rodent models of heart failure are still needed to understand the roles for these compounds in the heart.

Key Player in Cardiac Hypertrophy, Emphasizing the Role of Toll-Like Receptor 4

Toll-like receptor 4 (TLR4), a key pattern recognition receptor, initiates the innate immune response and leads to chronic and acute inflammation. In the past decades, accumulating evidence has implicated TLR4-mediated inflammatory response in regulation of myocardium hypertrophic remodeling, indicating that regulation of the TLR4 signaling pathway may be an effective strategy for managing cardiac hypertrophy's pathophysiology. Given TLR4's significance, it is imperative to review the molecular mechanisms and roles underlying TLR4 signaling in cardiac hypertrophy. Here, we comprehensively review the current knowledge of TLR4-mediated inflammatory response and its interaction ligands and co-receptors, as well as activation of various intracellular signaling. We also describe the associated roles in promoting immune cell infiltration and inflammatory mediator secretion, that ultimately cause cardiac hypertrophy. Finally, we provide examples of some of the most promising drugs and new technologies that have the potential to attenuate TLR4-mediated inflammatory response and prevent or reverse the ominous cardiac hypertrophy outcomes.

Inflammatory Cytokines and Chemokines as Therapeutic Targets in Heart Failure

Heart failure exhibits remarkable pathophysiologic heterogeneity. A large body of evidence suggests that regardless of the underlying etiology, heart failure is associated with induction of cytokines and chemokines that may contribute to the pathogenesis of adverse remodeling, and systolic and diastolic dysfunction. The pro-inflammatory cytokines tumor necrosis factor (TNF)-α, interleukin (IL)-1, and IL-6 have been extensively implicated in the pathogenesis of heart failure. Inflammatory cytokines modulate phenotype and function of all myocardial cells, suppressing contractile function in cardiomyocytes, inducing inflammatory activation in macrophages, stimulating microvascular inflammation and dysfunction, and promoting a matrix-degrading phenotype in fibroblasts. Moreover, cytokine-induced growth factor synthesis may exert chronic fibrogenic actions contributing to the pathogenesis of heart failure with preserved ejection fraction (HFpEF). In addition to their role in adverse cardiac remodeling, some inflammatory cytokines may also exert protective actions on cardiomyocytes under conditions of stress. Chemokines, such as CCL2, are also upregulated in failing hearts and may stimulate recruitment of pro-inflammatory leukocytes, promoting myocardial injury, fibrotic remodeling, and dysfunction. Although experimental evidence suggests that cytokine and chemokine targeting may hold therapeutic promise in heart failure, clinical translation remains challenging. This review manuscript summarizes our knowledge on the role of TNF-α, IL-1, IL-6, and CCL2 in the pathogenesis of heart failure, and discusses the promises and challenges of targeted anti-cytokine therapy. Dissection of protective and maladaptive cellular actions of cytokines in the failing heart, and identification of patient subsets with overactive or dysregulated myocardial inflammatory responses are required for design of successful therapeutic approaches.

Inhibition of the ROS-EGFR Pathway Mediates the Protective Action of Nox1/4 Inhibitor GKT137831 against Hypertensive Cardiac Hypertrophy via Suppressing Cardiac Inflammation and Activation of Akt and ERK1/2

Oxidative stress, inflammation, and hypertension constitute a self-perpetuating vicious circle to exacerbate hypertension and subsequent hypertensive cardiac hypertrophy. NADPH oxidase (Nox) 1/4 inhibitor GKT137831 alleviates hypertensive cardiac hypertrophy in models of secondary hypertension; however, it remains unclear about its effect on hypertensive cardiac hypertrophy in models of essential hypertension. This study is aimed at determining the beneficial role of GKT137831 in hypertensive cardiac hypertrophy in spontaneously hypertensive rats (SHRs) and its mechanisms of action. Treating with GKT137831 prevented cardiac hypertrophy in SHRs. Likewise, decreasing production of reactive oxygen species (ROS) with GKT137831 reduced epidermal growth factor receptor (EGFR) activity in the left ventricle of SHRs. Additionally, EGFR inhibition also reduced ROS production in the left ventricle and blunted hypertensive cardiac hypertrophy in SHRs. Moreover, inhibition of the ROS-EGFR pathway with Nox1/4 inhibitor GKT137831 or selective EGFR inhibitor AG1478 reduced protein and mRNA levels of proinflammatory cytokines tumor necrosis factor α (TNF-α), interleukin 6 (IL-6), and interleukin 1β (IL-1β), as well as the activities of Akt and extracellular signal-regulated kinase (ERK) 1/2 in the left ventricle of SHRs. In summary, GKT137831 prevents hypertensive cardiac hypertrophy in SHRs, Nox-deprived ROS regulated EGFR activation through positive feedback in the hypertrophic myocardium, and inhibition of the ROS-EGFR pathway mediates the protective role of GKT137831 in hypertensive cardiac hypertrophy via repressing cardiac inflammation and activation of Akt and ERK1/2. This research will provide additional details for GKT137831 to prevent hypertensive cardiac hypertrophy.

Inhibition of Interleukin-6/glycoprotein 130 signalling by Bazedoxifene ameliorates cardiac remodelling in pressure overload mice

The role of IL-6 signalling in hypertensive heart disease and its sequelae is controversial. Our group demonstrated that Bazedoxifene suppressed IL-6/gp130 signalling in cancer cells but its effect on myocardial pathology induced by pressure overload is still unknown. We explored whether Bazedoxifene could confer benefits in wild-type C57BL/6J mice suffering from transverse aortic constriction (TAC) and the potential mechanisms in H9c2 myoblasts. Mice were randomized into three groups (Sham, TAC, TAC+Bazedoxifene, n = 10). Morphological and histological observations suggested TAC aggravated myocardial remodelling while long-term intake of Bazedoxifene (5 mg/kg, intragastric) attenuated pressure overload-induced pathology. Echocardiographic results indicated Bazedoxifene rescued cardiac function in part. We found Bazedoxifene decreased the mRNA expression of IL-6, MMP2, Col1A1, Col3A1 and periostin in murine hearts after 8-week surgery. By Western blot detection, we found Bazedoxifene exhibited an inhibition of STAT3 activation in mice three hours and 8 weeks after TAC. Acute TAC stress (3 hours) led to down-regulated ratio of LC3-Ⅱ/LC3-Ⅰ, while in mice after long-term (8 weeks) TAC this ratio becomes higher than that in Sham mice. Bazedoxifene inverted the autophagic alteration induced by TAC at both two time-points. In H9c2 myoblasts, Bazedoxifene suppressed the IL-6-induced STAT3 activation. Moreover, IL-6 reduced the ratio of LC3-Ⅱ/LC3-Ⅰ, promoted P62 expression but Bazedoxifene reversed both changes in H9c2 cells. Our data suggested Bazedoxifene inhibited IL-6/gp130 signalling and protected against cardiac remodelling together with function deterioration in TAC mice.

Resveratrol suppresses interleukin-6 expression through activation of sirtuin 1 in hypertrophied H9c2 cardiomyoblasts

Inflammatory cytokine, interleukin-6 (IL-6), plays an important role in the pathogenesis of cardiac hypertrophy. Recent studies have documented that resveratrol exhibits cardioprotective effects. The present study attempts to explore whether resveratrol suppreses IL-6 in hypertrophied H9c2 cardiomyoblasts through histone deacetylase, sirtuin 1 (SIRT1). To induce hypertrophy, the cells were incubated with angiotensin II (Ang II). Treatment groups were treated with different doses (1, 10, 25, 50, 75, and 100 μM) of resveratrol (R). Cell viability was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Cell size was determined using crystal violet staining. Gene expression was assessed by real-time polymerase chain reaction technique. Enzyme-linked immunosorbent assay was used to measure IL-6 concentration. The results showed that cell area and ANP messenger RNA (mRNA) levels decreased significantly in R25+Ang, R50+Ang, and R100+Ang groups, as compared with Ang group. Therefore, 10, 20, 30, 40, and 50 μM of resveratrol were used to to evaluate its anti-inflammatory effects. The results revealed that Ang II upregulated IL-6 at both mRNA and protein levels (p < .001 vs. normal) and resveratrol (50 μM) decreased IL-6 mRNA (p < .01) and protein (p < .05) significantly in comparison to Ang group. However, in groups in which the cells were pretreated with SIRT1 inhibitor, EX-527, the response of resveratrol was partially reversed. Transcription levels of IL-6 receptor components (gp130 and gp80) did not change significantly among the experimental groups. The current data suggests that resveratrol protects H9c2 cells against Ang II-induced hypertrophy by suppression of IL-6 through SIRT1 activation.

Cardiac hypertrophy or failure? - A systematic evaluation of the transverse aortic constriction model in C57BL/6NTac and C57BL/6J substrains

Background

The mouse model of transverse aortic constriction (TAC) has been widely used as a cardiac stress in the investigation of the molecular mechanisms of cardiac hypertrophy. Recently, the International Knockout Mouse Consortium has selected the C57BL/6NTac (BL/6N) mouse strain to generate null alleles for all mouse genes; however, a range of genetic and cardiac phenotypic differences have been reported between this substrain and the commonly used C57BL/6J (BL/6J) substrain. It has been reported by Garcia-Menendez and colleagues that 12-week C57BL/6NTac mice are susceptible to heart failure but little is known about the cardiac remodeling in this substrain as cardiac function progresses from compensation to decompensation.

Methods

BL/6J and BL/6N mice were subjected to pressure overload via TAC. The impact of both age and duration of cardiac pressure overload induced by TAC on cardiac remodelling were systematically assessed.

Results

Our data showed that BL/6N mice developed eccentric hypertrophy with age- and time-dependent deterioration in cardiac function, accompanied by considerable interstitial fibrosis. In contrast, BL/6J mice were more resilient to TAC-induced cardiac stress and developed variable cardiac phenotypes independent of age and the duration of pressure overload. This was likely due to the greater variability in pre-TAC aortic arch dimension as measured by echocardiography. In addition to increased expression of brain natriuretic peptide and collagen gene type 1 and 3, BL/6N mice also had greater angiotensin II type 2 receptor (AT2R) gene expression than BL/6J counterparts at baseline and after 2-weeks TAC, which may contribute to the exacerbated interstitial fibrosis.

Conclusions

BL/6N and BL/6J mice have very different responses to TAC stimulation and these differences should be taken into consideration when using the substrains to investigate the mechanisms of hypertrophy and heart failure.

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The first study to show that adult BL/6NTac mice have an age-dependent cardiac response to pressure overload.

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The first study to show BL/6NTac mice have a time-dependent cardiac response to pressure overload.

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C57BL/6J mice have variable cardiac remodelling that positively correlates with the original size of the aorta.

The role of interleukin-6 in intracellular signal transduction after chronic β-adrenergic stimulation in mouse myocardium

INTRODUCTION

Inflammatory mediators play an important role in development and progression of cardiovascular disease. Both adrenergic stimulation and high levels of interleukin-6 (IL-6) indicate an unfavorable outcome in patients with myocardial infarction or heart failure. Understanding the interaction between β-adrenergic stimulation and IL-6 in the myocardium may contribute to developing more effective treatments. The aim of this study was to verify the role of IL-6 in the effects of β-adrenergic stimulation in activating selected intracellular signaling pathways in mouse myocardium.

MATERIAL AND METHODS

Experiments were performed on 12-week-old male mice: 16 C57BL/6JIL6^{‑/‑TMKopf} (IL-6 KO) and 17 C57BL/6J (WT). Animals received intraperitoneal injections of isoproterenol (ISO, 50 mg/kg) or placebo (0.9% NaCl) once a day for 16 days. The phosphorylation of STAT3 (signal transducer and activator of transcription 3), ERK1/2 (extracellular-regulated kinases 1/2), Akt1/2/3, p-38, c-Raf and expression of SOCS3 (suppressor of cytokine signaling 3), PIAS1/3 (protein inhibitors of activated STAT) was assessed by western blotting in the myocardium 24 h after the last injection. Evaluation of gene expression downstream of these pathways was performed by real-time PCR.

RESULTS

Chronic ISO treatment leads to increased fibrosis of the myocardium in mice lacking IL-6, which is accompanied by increased activity of ERK1/2, p38 and reduced expression of SOCS3. Administration of ISO in IL-6 KO animals intensified gene expression of proteins activated by MAPK/ERK (myc; CEBPB; BMP4; Fasn; Tank), while it reduced expression of genes repressed by ERK 1/2 (Wisp1, Wnt1).

CONCLUSIONS

IL-6 plays an important role in regulating the activation of MAPK pathways in the mouse myocardium in response to chronic β-adrenergic stimulation.

Inflammation and NLRP3 Inflammasome Activation Initiated in Response to Pressure Overload by Ca2+/Calmodulin-Dependent Protein Kinase II δ Signaling in Cardiomyocytes Are Essential for Adverse Cardiac Remodeling

BACKGROUND

Inflammation is associated with cardiac remodeling and heart failure, but how it is initiated in response to nonischemic interventions in the absence of cell death is not known. We tested the hypothesis that activation of Ca²⁺/calmodulin-dependent protein kinase II δ (CaMKIIδ) in cardiomyocytes (CMs) in response to pressure overload elicits inflammatory responses leading to adverse remodeling.

METHODS

Mice in which CaMKIIδ was selectively deleted from CMs (cardiac-specific knockout [CKO]) and floxed control mice were subjected to transverse aortic constriction (TAC). The effects of CM-specific CaMKIIδ deletion on inflammatory gene expression, inflammasome activation, macrophage accumulation, and fibrosis were assessed by quantitative polymerase chain reaction, histochemistry, and ventricular remodeling by echocardiography.

RESULTS

TAC induced increases in cardiac mRNA levels for proinflammatory chemokines and cytokines in ≤3 days, and these responses were significantly blunted when CM CaMKIIδ was deleted. Apoptotic and necrotic cell death were absent at this time. CMs isolated from TAC hearts mirrored these robust increases in gene expression, which were markedly attenuated in CKO. Priming and activation of the NOD-like receptor pyrin domain-containing protein 3 inflammasome, assessed by measuring interleukin-1β and NOD-like receptor pyrin domain-containing protein 3 mRNA levels, caspase-1 activity, and interleukin-18 cleavage, were increased at day 3 after TAC in control hearts and in CMs isolated from these hearts. These responses were dependent on CaMKIIδ and associated with activation of Nuclear Factor-kappa B and reactive oxygen species. Accumulation of macrophages observed at days 7 to 14 after TAC was diminished in CKO and, by blocking Monocyte Chemotactic Protein-1 signaling, deletion of CM Monocyte Chemotactic Protein-1 or inhibition of inflammasome activation. Fibrosis was also attenuated by these interventions and in the CKO heart. Ventricular dilation and contractile dysfunction observed at day 42 after TAC were diminished in the CKO. Inhibition of CaMKII, Nuclear Factor-kappa B, inflammasome, or Monocyte Chemotactic Protein-1 signaling in the first 1 or 2 weeks after TAC decreased remodeling, but inhibition of CaMKII after 2 weeks did not.

CONCLUSIONS

Activation of CaMKIIδ in response to pressure overload triggers inflammatory gene expression and activation of the NOD-like receptor pyrin domain-containing protein 3 inflammasome in CMs. These responses provide signals for macrophage recruitment, fibrosis, and myocardial dysfunction in the heart. Our work suggests the importance of targeting early inflammatory responses induced by CM CaMKIIδ signaling to prevent progression to heart failure.

Arterial Hypertension and Interleukins: Potential Therapeutic Target or Future Diagnostic Marker?

Hypertension as a multifactorial pathology is one of the most important cardiovascular risk factors, affecting up to 30-40% of the general population. Complex immune responses are involved in the inflammatory mechanism of hypertension, with evidence pointing to increased inflammatory mediators even in prehypertensive patients. Increased vascular permeability, thrombogenesis, and fibrosis, effects that are associated with sustained hypertension, could be attributed to chronic inflammation. Chronic inflammation triggers endothelial dysfunction via increased production of ROS through proinflammatory cytokines. Increased serum level of proinflammatory cytokines such as IL-1β, IL-6, IL-8, IL-17, IL-23, TGFβ, and TNFα in hypertensive patients has been associated with either increased blood pressure values and/or end-organ damage. Moreover, some cytokines (i.e., IL-6) seem to determine a hypertensive response to angiotensin II, regardless of blood pressure values. Understanding hypertension as an inflammatory-based pathology gives way to new therapeutic targets. As such, conventional cardiovascular drugs (statins, calcium channels blockers, and ACEIs/ARBs) have shown additional anti-inflammatory effects that could be linked to their blood pressure lowering properties. Moreover, anti-inflammatory drugs (mycophenolate mofetil) have been shown to decrease blood pressure in hypertensive patients or prevent its development in normotensive individuals. Further research is needed to evaluate whether drugs targeting hypertensive-linked proinflammatory cytokines, such as monoclonal antibodies, could become a new therapeutic option in treating arterial hypertension.

Recent Developments on the Crosstalk Between STAT3 and Inflammation in Heart Function and Disease

The transcription factor STAT3 has a protective function in the heart. Until recently, the role of STAT3 in hypertension-induced cardiac hypertrophy was unsettled. Earlier studies revealed that global reduction of STAT3 activity reduced cardiac hypertrophy with hypertension, but caused a disruption of myofilaments and increased contractile dysfunction. However, newer studies with cardiomyocyte-specific deletion of STAT3 indicate that STAT3 does not cause cardiac hypertrophy with increased blood pressure. Rather, cardiac STAT3 is important for maintaining metabolic homeostasis, and loss of STAT3 in cardiomyocytes makes the heart more susceptible to chronic pathological insult, for example by disrupting glucose metabolism and protective signaling networks via the upregulation of certain microRNAs. This scenario has implications for understanding peripartum cardiomyopathy as well. In viral myocarditis, STAT3 opposes the initiation of the dilated phenotype by maintaining membrane integrity via the expression of dystrophin. STAT3 signaling was also found to attenuate myocarditis by polarizing macrophages to a less inflammatory phenotype. On the other hand, STAT3 contributes to immune-mediated myocarditis due to IL-6-induced complement component C3 production in the liver, as well as the differentiation of Th17 cells, which play a role in initiation and development of myocarditis. Besides canonical signaling pathways, unphosphorylated STAT3 (U-STAT3) and redox-activated STAT3 have been shown to couple to transcription in the heart. In addition, tissue signaling cytokines such as IL-22 and IL-17 have been proposed to have actions on the heart that involve STAT3, but are not fully defined. Understanding the novel and often protective aspects of STAT3 in the myocardium could lead to new therapeutic approaches to treat heart disease.

Cardiac fibrosis: new insights into the pathogenesis

Cardiac fibrosis is defined as the imbalance of extracellular matrix (ECM) production and degradation, thus contributing to cardiac dysfunction in many cardiac pathophysiologic conditions. This review discusses specific markers and origin of cardiac fibroblasts (CFs), and the underlying mechanism involved in the development of cardiac fibrosis. Currently, there are no CFs-specific molecular markers. Most studies use co-labelling with panels of antibodies that can recognize CFs. Origin of fibroblasts is heterogeneous. After fibrotic stimuli, the levels of myocardial pro-fibrotic growth factors and cytokines are increased. These pro-fibrotic growth factors and cytokines bind to its receptors and then trigger the activation of signaling pathway and transcriptional factors via Smad-dependent or Smad independent-manners. These fibrosis-related transcriptional factors regulate gene expression that are involved in the fibrosis to amplify the fibrotic response. Understanding the mechanisms responsible for initiation, progression, and amplification of cardiac fibrosis are of great clinical significance to find drugs that can prevent the progression of cardiac fibrosis.

Cardiac fibrosis: Cell biological mechanisms, molecular pathways and therapeutic opportunities

Cardiac fibrosis is a common pathophysiologic companion of most myocardial diseases, and is associated with systolic and diastolic dysfunction, arrhythmogenesis, and adverse outcome. Because the adult mammalian heart has negligible regenerative capacity, death of a large number of cardiomyocytes results in reparative fibrosis, a process that is critical for preservation of the structural integrity of the infarcted ventricle. On the other hand, pathophysiologic stimuli, such as pressure overload, volume overload, metabolic dysfunction, and aging may cause interstitial and perivascular fibrosis in the absence of infarction. Activated myofibroblasts are the main effector cells in cardiac fibrosis; their expansion following myocardial injury is primarily driven through activation of resident interstitial cell populations. Several other cell types, including cardiomyocytes, endothelial cells, pericytes, macrophages, lymphocytes and mast cells may contribute to the fibrotic process, by producing proteases that participate in matrix metabolism, by secreting fibrogenic mediators and matricellular proteins, or by exerting contact-dependent actions on fibroblast phenotype. The mechanisms of induction of fibrogenic signals are dependent on the type of primary myocardial injury. Activation of neurohumoral pathways stimulates fibroblasts both directly, and through effects on immune cell populations. Cytokines and growth factors, such as Tumor Necrosis Factor-α, Interleukin (IL)-1, IL-10, chemokines, members of the Transforming Growth Factor-β family, IL-11, and Platelet-Derived Growth Factors are secreted in the cardiac interstitium and play distinct roles in activating specific aspects of the fibrotic response. Secreted fibrogenic mediators and matricellular proteins bind to cell surface receptors in fibroblasts, such as cytokine receptors, integrins, syndecans and CD44, and transduce intracellular signaling cascades that regulate genes involved in synthesis, processing and metabolism of the extracellular matrix. Endogenous pathways involved in negative regulation of fibrosis are critical for cardiac repair and may protect the myocardium from excessive fibrogenic responses. Due to the reparative nature of many forms of cardiac fibrosis, targeting fibrotic remodeling following myocardial injury poses major challenges. Development of effective therapies will require careful dissection of the cell biological mechanisms, study of the functional consequences of fibrotic changes on the myocardium, and identification of heart failure patient subsets with overactive fibrotic responses.

T helper cells with specificity for an antigen in cardiomyocytes promote pressure overload-induced progression from hypertrophy to heart failure

We investigated whether CD4⁺-T cells with specificity for an antigen in cardiomyocytes promote the progression from hypertrophy to heart failure in mice with increased pressure load due to transverse aortic constriction (TAC). OT-II mice expressing a transgenic T cell receptor (TCR) with specificity for ovalbumin (OVA) on CD4⁺-T cells and cMy-mOVA mice expressing OVA on cardiomyocytes were crossed. The resulting cMy-mOVA-OT-II mice did not display signs of spontaneous autoimmunity despite the fact that their OVA-specific CD4⁺-T cells were not anergic. After TAC, progression to heart failure was significantly accelerated in cMy-mOVA-OT-II compared to cMy-mOVA mice. No OVA-specific antibodies were induced in response to TAC in cMy-mOVA-OT-II mice, yet more CD3⁺ T cells infiltrated their myocardium when compared with TAC-operated cMy-mOVA mice. Systemically, the proportion of activated CD4⁺-T cells with a Th₁ and Th₁₇ cytokine profile was increased in cMy-mOVA-OT-II mice after TAC. Thus, T helper cells with specificity for an antigen in cardiomyocytes can directly promote the progression of heart failure in response to pressure overload independently of autoantibodies.

T cell costimulation blockade blunts pressure overload-induced heart failure

Heart failure (HF) is a leading cause of mortality. Inflammation is implicated in HF, yet clinical trials targeting pro-inflammatory cytokines in HF were unsuccessful, possibly due to redundant functions of individual cytokines. Searching for better cardiac inflammation targets, here we link T cells with HF development in a mouse model of pathological cardiac hypertrophy and in human HF patients. T cell costimulation blockade, through FDA-approved rheumatoid arthritis drug abatacept, leads to highly significant delay in progression and decreased severity of cardiac dysfunction in the mouse HF model. The therapeutic effect occurs via inhibition of activation and cardiac infiltration of T cells and macrophages, leading to reduced cardiomyocyte death. Abatacept treatment also induces production of anti-inflammatory cytokine interleukin-10 (IL-10). IL-10-deficient mice are refractive to treatment, while protection could be rescued by transfer of IL-10-sufficient B cells. These results suggest that T cell costimulation blockade might be therapeutically exploited to treat HF.

Abatacept is an FDA-approved drug used for treatment of rheumatoid arthritis. Here the authors show that abatacept reduces cardiomyocyte death in a mouse model of heart failure by inhibiting activation and heart infiltration of T cells and macrophages, an effect mediated by IL-10, suggesting a potential therapy for heart failure.

Chronic Heart Failure and Inflammation

As a greater proportion of patients survive their initial cardiac insult, medical systems worldwide are being faced with an ever-growing need to understand the mechanisms behind the pathogenesis of chronic heart failure (HF). There is a wealth of information about the role of inflammatory cells and pathways during acute injury and the reparative processes that are subsequently activated. We discuss the different causes that lead to chronic HF development and how the sum of initial inflammatory and reparative responses only sets the trajectory for disease progression. Unfortunately, comparatively little is known about the contribution of the immune system once the trajectory has been set, and chronic HF has been established—which clinically represents the majority of patients. It is known that chronic HF is associated with circulating inflammatory cytokines that can predict clinical outcomes, yet the causative role inflammation plays in disease progression is not well defined, and the majority of clinical trials that target aspects of inflammation in patients with chronic HF have largely been negative. This review will present what is currently known about inflammation in chronic HF in both humans and animal models as a means to highlight the gap in our knowledge base that requires further examination.

Deletion of Interleukin-6 Attenuates Pressure Overload-Induced Left Ventricular Hypertrophy and Dysfunction

RATIONALE

The role of interleukin (IL)-6 in the pathogenesis of cardiac myocyte hypertrophy remains controversial.

OBJECTIVE

To conclusively determine whether IL-6 signaling is essential for the development of pressure overload-induced left ventricular (LV) hypertrophy and to elucidate the underlying molecular pathways.

METHODS AND RESULTS

Wild-type and IL-6 knockout (IL-6(-/-)) mice underwent sham surgery or transverse aortic constriction (TAC) to induce pressure overload. Serial echocardiograms and terminal hemodynamic studies revealed attenuated LV hypertrophy and superior preservation of LV function in IL-6(-/-) mice after TAC. The extents of LV remodeling, fibrosis, and apoptosis were reduced in IL-6(-/-) hearts after TAC. Transcriptional and protein assays of myocardial tissue identified Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) and signal transducer and activator of transcription 3 (STAT3) activation as important underlying mechanisms during cardiac hypertrophy induced by TAC. The involvement of these pathways in myocyte hypertrophy was verified in isolated cardiac myocytes from wild-type and IL-6(-/-) mice exposed to prohypertrophy agents. Furthermore, overexpression of CaMKII in H9c2 cells increased STAT3 phosphorylation, and exposure of H9c2 cells to IL-6 resulted in STAT3 activation that was attenuated by CaMKII inhibition. Together, these results identify the importance of CaMKII-dependent activation of STAT3 during cardiac myocyte hypertrophy via IL-6 signaling.

CONCLUSIONS

Genetic deletion of IL-6 attenuates TAC-induced LV hypertrophy and dysfunction, indicating a critical role played by IL-6 in the pathogenesis of LV hypertrophy in response to pressure overload. CaMKII plays an important role in IL-6-induced STAT3 activation and consequent cardiac myocyte hypertrophy. These findings may have significant therapeutic implications for LV hypertrophy and failure in patients with hypertension.

Deletion of interleukin-6 prevents cardiac inflammation, fibrosis and dysfunction without affecting blood pressure in angiotensin II-high salt-induced hypertension

OBJECTIVE

Inflammation has been proposed as a key component in the development of hypertension and cardiac remodeling associated with different cardiovascular diseases. However, the role of the proinflammatory cytokine interleukin-6 in the chronic stage of hypertension is not well defined. Here, we tested the hypothesis that deletion of interleukin-6 protects against the development of hypertension, cardiac inflammation, fibrosis, remodeling and dysfunction induced by high salt diet and angiotensin II (Ang II).

METHODS

Male C57BL/6J and interleukin-6-knock out (KO) mice were implanted with telemetry devices for blood pressure (BP) measurements, fed a 4% NaCl diet, and infused with either vehicle or Ang II (90 ng/min per mouse subcutaneously) for 8 weeks. We studied BP and cardiac function by echocardiography at baseline, 4 and 8 weeks.

RESULTS

Myocyte cross-sectional area (MCSA), macrophage infiltration, and myocardial fibrosis were also assessed. BP increased similarly in both strains when treated with Ang II and high salt (Ang II-high salt); however, C57BL/6J mice developed a more severe decrease in left ventricle ejection fraction, fibrosis, and macrophage infiltration compared with interleukin-6-KO mice. No differences between strains were observed in MCSA, capillary density and MCSA to capillary density ratio.

CONCLUSION

In conclusion, absence of interleukin -6 did not alter the development of Ang II-high salt-induced hypertension and cardiac hypertrophy, but it prevented the development of cardiac dysfunction, myocardial inflammation, and fibrosis. This indicates that interleukin-6 plays an important role in hypertensive heart damage but not in the development of hypertension.

Cardiomyocyte loss is not required for the progression of left ventricular hypertrophy induced by pressure overload in female mice

Left ventricular (LV) hypertrophy in response to hypertension and increased afterload frequently progresses to heart failure. It is under debate whether the loss of cardiomyocytes contributes to this transition. To address this question, female C57BL/6 wild-type mice were subjected to transverse aortic constriction (TAC) and developed compensated LV hypertrophy after 1 week, which progressed to heart failure characterized by reduced ejection fraction and pulmonary congestion 4 weeks post-TAC. Quantitative, design-based stereology methods were used to estimate number and mean volume of LV cardiomyocytes. DNA strand breaks were visualized using the TUNEL method 6 weeks post-TAC to quantify the number of apoptotic cell nuclei. The volume of the LV myocardium as well as the cardiomyocyte mean volume increased progressively after TAC. In contrast, the number of LV cardiomyocytes remained constant 1 and 4 weeks post-TAC in comparison to sham-operated mice. Moreover, there was no significant difference in the number of cardiomyocyte nuclei stained for DNA strand breaks at 6 weeks post-TAC. It was concluded that the loss of cardiomyocytes is not required for the transition from compensated hypertrophy to heart failure induced by TAC in the female murine heart.

IL-6/STAT3 signaling in mice with dysfunctional type-2 ryanodine receptor

Mice with genetically modified cardiac ryanodine receptor (Ryr2^ADA/ADA mice) are impaired in regulation by calmodulin, develop severe cardiac hypertrophy and die about 2 weeks after birth. We hypothesized that the interleukin 6 (IL-6)/signal transducer and activator of transcription-3 (STAT3) signaling pathway has a role in the development of the Ryr2^ADA/ADA cardiac hypertrophy phenotype, and determined cardiac function and protein levels of IL-6, phosphorylation levels of STAT3, and downstream targets c-Fos and c-Myc in wild-type and RyR2^ADA/ADA mice, mice with a disrupted IL-6 gene, and mice treated with STAT3 inhibitor NSC74859. IL-6 protein levels were increased at postnatal day 1 but not day 10, whereas pSTAT3-Tyr705/STAT3 ratio and c-Fos and c-Myc protein levels increased in hearts of 10-day but not 1-day old Ryr2^ADA/ADA mice compared with wild type. Both STAT3 and pSTAT3-Tyr705 accumulated in the nuclear fraction of 10-day old Ryr2^ADA/ADA mice compared with wild type. Ryr2^{ADA /ADA} /IL-6^−/− mice lived 1.5 times longer, had decreased heart to body weight ratio, and reduced c-Fos and c-Myc protein levels. The STAT3 inhibitor NSC74859 prolonged life span by 1.3-fold, decreased heart to body weight ratio, increased cardiac performance, and decreased pSTAT-Tyr705/STAT3 ratio and IL-6, c-Fos and c-Myc protein levels of Ryr2^{ADA /ADA} mice. The results suggest that upregulation of IL-6 and STAT3 signaling contributes to cardiac hypertrophy and early death of mice with a dysfunctional ryanodine receptor. They further suggest that STAT3 inhibitors may be clinically useful agents in patients with altered Ca²⁺ handling in the heart.

Interleukin-6 mediates exercise preconditioning against myocardial ischemia reperfusion injury

Interleukin-6 (IL-6) is a pleiotropic cytokine that protects against cardiac ischemia-reperfusion (I/R) injury following pharmacological and ischemic preconditioning (IPC), but the affiliated role in exercise preconditioning is unknown. Our study purpose was to characterize exercise-induced IL-6 cardiac signaling ( aim 1) and evaluate myocardial preconditioning ( aim 2). In aim 1, C57 and IL-6−/− mice underwent 3 days of treadmill exercise for 60 min/day at 18 m/min. Serum, gastrocnemius, and heart were collected preexercise, immediately postxercise, and 30 and 60 min following the final exercise session and analyzed for indexes of IL-6 signaling. For aim 2, a separate cohort of exercise-preconditioned (C57 EX and IL-6−/− EX) and sedentary (C57 SED and IL-6−/− SED) mice received surgical I/R injury (30 min I, 120 min R) or a time-matched sham operation. Ischemic and perfused tissues were examined for necrosis, apoptosis, and autophagy. In aim 1, serum IL-6 and IL-6 receptor (IL-6R), gastrocnemius, and myocardial IL-6R were increased following exercise in C57 mice only. Phosphorylated (p) signal transducer and activator of transcription 3 was increased in gastrocnemius and heart in C57 and IL-6−/− mice postexercise, whereas myocardial iNOS and cyclooxygenase-2 were unchanged in the exercised myocardium. Exercise protected C57 EX mice against I/R-induced arrhythmias and necrosis, whereas arrhythmia score and infarct outcomes were higher in C57 SED, IL-6−/− SED, and IL-6−/− EX mice compared with SH. C57 EX mice expressed increased p-p44/42 MAPK (Thr202/Tyr204) and p-p38 MAPK (Thr180/Tyr182) compared with IL-6−/− EX mice, suggesting pathway involvement in exercise preconditioning. Findings indicate exercise exerts cardioprotection via IL-6 and strongly implicates protective signaling originating from the exercised skeletal muscle.

The calcium release-activated calcium channel Orai1 represents a crucial component in hypertrophic compensation and the development of dilated cardiomyopathy

As exceptionally calcium selective store-operated channels, Orai channels play a prominent role in cellular calcium signaling. While most studied in the immune system, we are beginning to recognize that Orai1 provides unique calcium signaling pathways in numerous tissue contexts. To assess the involvement of Orai1 in cardiac hypertrophy we used transverse aortic constriction to model pressure overload cardiac hypertrophy and heart failure in Orai1 deficient mice. We demonstrate that Orai1 deficient mice have significantly decreased survival in this pressure overload model. Transthoracic echocardiography reveals that Orai1 deficient mice develop rapid dilated cardiomyopathy, with greater loss of function, and histological and molecular data indicate that this pathology is associated with significant apoptosis, but not major differences in cellular hypertrophy, fibrosis, and some major hypertrophic makers. Orai1 represents a crucial calcium entry mechanism in the compensation of the heart to pressure overload over-load, and the development of dilated cardiomyopathy.

The physiology of cardiovascular disease and innovative liposomal platforms for therapy

Heart disease remains the major cause of death in males and females, emphasizing the need for novel strategies to improve patient treatment and survival. A therapeutic approach, still in its infancy, is the development of site-specific drug-delivery systems. Nanoparticle-based delivery systems, such as liposomes, have evolved into robust platforms for site-specific delivery of therapeutics. In this review, the clinical impact of cardiovascular disease and the pathophysiology of different subsets of the disease are described. Potential pathological targets for therapy are introduced, and promising advances in nanotherapeutic cardiovascular applications involving liposomal platforms are presented.