Leukemia inhibitory factor is augmented in the heart in experimental heart failure

The Identification and Evaluation of Interleukin-7 as a Myokine Biomarker for Peripheral Artery Disease Prognosis

Background/Objectives: Myokines have been demonstrated to be associated with cardiovascular diseases; however, they have not been studied as biomarkers for peripheral artery disease (PAD). We identified interleukin-7 (IL-7) as a prognostic biomarker for PAD from a panel of myokines and developed predictive models for 2-year major adverse limb events (MALEs) using clinical features and plasma IL-7 levels. Methods: A prognostic study was conducted with a cohort of 476 patients (312 with PAD and 164 without PAD) that were recruited prospectively. Their plasma concentrations of five circulating myokines were measured at recruitment, and the patients were followed for two years. The outcome of interest was two-year MALEs (composite of major amputation, vascular intervention, or acute limb ischemia). Cox proportional hazards analysis was performed to identify IL-7 as the only myokine that was associated with 2-year MALEs. The data were randomly divided into training (70%) and test sets (30%). A random forest model was trained using clinical characteristics (demographics, comorbidities, and medications) and plasma IL-7 levels with 10-fold cross-validation. The primary model evaluation metric was the F1 score. The prognostic model was used to classify patients into low vs. high risk of developing adverse limb events based on the Youden Index. Freedom from MALEs over 2 years was compared between the risk-stratified groups using Cox proportional hazards analysis. Results: Two-year MALEs occurred in 28 (9%) of patients with PAD. IL-7 was the only myokine that was statistically significantly correlated with two-year MALE (HR 1.56 [95% CI 1.12-1.88], p = 0.007). For the prognosis of 2-year MALEs, our model achieved an F1 score of 0.829 using plasma IL-7 levels in combination with clinical features. Patients classified as high-risk by the predictive model were significantly more likely to develop MALEs over a 2-year period (HR 1.66 [95% CI 1.22-1.98], p = 0.006). Conclusions: From a panel of myokines, IL-7 was identified as a prognostic biomarker for PAD. Using a combination of clinical characteristics and plasma IL-7 levels, we propose an accurate predictive model for 2-year MALEs in patients with PAD. Our model may support PAD risk stratification, guiding clinical decisions on additional vascular evaluation, specialist referrals, and medical/surgical management, thereby improving outcomes.

Diagnostic and predictive abilities of myokines in patients with heart failure

Myokines are defined as a heterogenic group of numerous cytokines, peptides and metabolic derivates, which are expressed, synthesized, produced, and released by skeletal myocytes and myocardial cells and exert either auto- and paracrine, or endocrine effects. Previous studies revealed that myokines play a pivotal role in mutual communications between skeletal muscles, myocardium and remote organs, such as brain, vasculature, bone, liver, pancreas, white adipose tissue, gut, and skin. Despite several myokines exert complete divorced biological effects mainly in regulation of skeletal muscle hypertrophy, residential cells differentiation, neovascularization/angiogenesis, vascular integrity, endothelial function, inflammation and apoptosis/necrosis, attenuating ischemia/hypoxia and tissue protection, tumor growth and malignance, for other occasions, their predominant effects affect energy homeostasis, glucose and lipid metabolism, adiposity, muscle training adaptation and food behavior. Last decade had been identified 250 more myokines, which have been investigating for many years further as either biomarkers or targets for heart failure management. However, only few myokines have been allocated to a promising tool for monitoring adverse cardiac remodeling, ischemia/hypoxia-related target-organ dysfunction, microvascular inflammation, sarcopenia/myopathy and prediction for poor clinical outcomes among patients with HF. This we concentrate on some most plausible myokines, such as myostatin, myonectin, brain-derived neurotrophic factor, muslin, fibroblast growth factor 21, irisin, leukemia inhibitory factor, developmental endothelial locus-1, interleukin-6, nerve growth factor and insulin-like growth factor-1, which are suggested to be useful biomarkers for HF development and progression.

Sympatho-adrenergic mechanisms in heart failure: new insights into pathophysiology

The sympathetic nervous system is activated in the setting of heart failure (HF) to compensate for hemodynamic instability. However, acute sympathetic surge or sustained high neuronal firing rates activates β-adrenergic receptor (βAR) signaling contributing to myocardial remodeling, dysfunction and electrical instability. Thus, sympatho-βAR activation is regarded as a hallmark of HF and forms pathophysiological basis for β-blocking therapy. Building upon earlier research findings, studies conducted in the recent decades have significantly advanced our understanding on the sympatho-adrenergic mechanism in HF, which forms the focus of this article. This review notes recent research progress regarding the roles of cardiac β2AR or α1AR in the failing heart, significance of β1AR-autoantibodies, and βAR signaling through G-protein independent signaling pathways. Sympatho-βAR regulation of immune cells or fibroblasts is specifically discussed. On the neuronal aspects, knowledge is assembled on the remodeling of sympathetic nerves of the failing heart, regulation by presynaptic α2AR of NE release, and findings on device-based neuromodulation of the sympathetic nervous system. The review ends with highlighting areas where significant knowledge gaps exist but hold promise for new breakthroughs.

Cell death mechanisms of the anti-cancer drug etoposide on human cardiomyocytes isolated from pluripotent stem cells

Etoposide (ETP) and anthracyclines are applied for wide anti-cancer treatments. However, the ETP-induced cardiotoxicity remains to be a major safety issue and the underlying cardiotoxic mechanisms are not well understood. This study is aiming to unravel the cardiotoxicity profile of ETP in comparison to anthracyclines using physiologically relevant human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs). Using xCELLigence real-time cell analyser (RTCA), we found that single high dose of ETP induces irreversible increase in hPSC-CMs beating rate and decrease in beating amplitude. We also identified 58 deregulated genes consisting of 33 upregulated and 25 downregulated genes in hPSC-CMs after ETP treatment. Gene ontology (GO) and pathway analysis showed that most upregulated genes are enriched in GO categories like positive regulation of apoptotic process, regulation of cell death, and mitochondria organization, whereas most downregulated genes were enriched in GO categories like cytoskeletal organization, muscle contraction, and Ca²⁺ ion homeostasis. Moreover, we also found upregulation in 5 miRNAs (has-miR-486-3p, has-miR-34c-5p, has-miR-4423-3p, has-miR-182-5p, and has-miR-139-5p) which play role in muscle contraction, arginine and proline metabolism, and hypertrophic cardiomyopathy (HCM). Immunostaining and transmission electron microscopy also confirmed the cytoskeletal and mitochondrial damage in hPSC-CMs treated with ETP, as well as noticeable alterations in intracellular calcium handling and mitochondrial membrane potential were also observed. The apoptosis inhibitor, Pifithrin-α, found to protect hPSC-CMs from ETP-induced cardiotoxicity, whereas hPSC-CMs treated with ferroptosis inhibitor, Liproxstatin-1, showed significant recovery in hPSC-CMs functional properties like beating rate and amplitude after ETP treatment. We suggest that the damage to mitochondria is a major contributing factor involved in ETP-induced cardiotoxicity and the activation of the p53-mediated ferroptosis pathway by ETP is likely the critical pathway in ETP-induced cardiotoxicity. We also conclude that the genomic biomarkers identified in this study will significantly contribute to develop and predict potential cardiotoxic effects of novel anti-cancer drugs in vitro.

Differential STAT3 signaling in the heart: Impact of concurrent signals and oxidative stress

Multiple lines of evidence suggest that the transcription factor STAT3 is linked to a protective and reparative response in the heart. Thus, increasing duration or intensity of STAT3 activation ought to minimize damage and improve heart function under conditions of stress. Two recent studies using genetic mouse models, however, report findings that appear to refute this proposition. Unfortunately, studies often approach the question of the role of STAT3 in the heart from the perspective that all STAT3 signaling is equivalent, particularly when it comes to signaling by IL-6 type cytokines, which share the gp130 signaling protein. Moreover, STAT3 activation is typically equated with phosphorylation of a critical tyrosine residue. Yet, STAT3 transcriptional behavior is subject to modulation by serine phosphorylation, acetylation, and redox status of the cell. Unphosphorylated STAT3 is implicated in gene induction as well. Thus, how STAT3 is activated and also what other signaling events are occurring at the same time is likely to impact on the outcome ultimately linked to STAT3. Notably STAT3 may serve as a scaffold protein allowing it to interact with other singling pathways. In this context, canonical gp130 cytokine signaling may function to integrate STAT3 signaling with a protective PI3K/AKT signaling network via mutual involvement of JAK tyrosine kinases. Differences in the extent of integration may occur between those cytokines that signal through gp130 homodimers and those through heterodimers of gp130 with a receptor α chain. Signal integration may have importance not only for deciding the particular gene profile linked to STAT3, but for the newly described mitochondrial stabilization role of STAT3 as well. In addition, disruption of integrated gp130-related STAT3 signaling may occur under conditions of oxidative stress, which negatively impacts on JAK catalytic activity. For these reasons, understanding the importance of STAT3 signaling to heart function requires a greater appreciation of the plasticity of this transcription factor in the context in which it is investigated.

Heart failure causes cholinergic transdifferentiation of cardiac sympathetic nerves via gp130-signaling cytokines in rodents

Although several cytokines and neurotrophic factors induce sympathetic neurons to transdifferentiate into cholinergic neurons in vitro, the physiological and pathophysiological roles of this remain unknown. During congestive heart failure (CHF), sympathetic neural tone is upregulated, but there is a paradoxical reduction in norepinephrine synthesis and reuptake in the cardiac sympathetic nervous system (SNS). Here we examined whether cholinergic transdifferentiation can occur in the cardiac SNS in rodent models of CHF and investigated the underlying molecular mechanism(s) using genetically modified mice. We used Dahl salt-sensitive rats to model CHF and found that, upon CHF induction, the cardiac SNS clearly acquired cholinergic characteristics. Of the various cholinergic differentiation factors, leukemia inhibitory factor (LIF) and cardiotrophin-1 were strongly upregulated in the ventricles of rats with CHF. Further, LIF and cardiotrophin-1 secreted from cultured failing rat cardiomyocytes induced cholinergic transdifferentiation in cultured sympathetic neurons, and this process was reversed by siRNAs targeting Lif and cardiotrophin-1. Consistent with the data in rats, heart-specific overexpression of LIF in mice caused cholinergic transdifferentiation in the cardiac SNS. Further, SNS-specific targeting of the gene encoding the gp130 subunit of the receptor for LIF and cardiotrophin-1 in mice prevented CHF-induced cholinergic transdifferentiation. Cholinergic transdifferentiation was also observed in the cardiac SNS of autopsied patients with CHF. Thus, CHF causes target-dependent cholinergic transdifferentiation of the cardiac SNS via gp130-signaling cytokines secreted from the failing myocardium.

Chronic treatment with clenbuterol modulates endothelial progenitor cells and circulating factors in a murine model of cardiomyopathy

The purpose of this study was to determine the effects of chronic treatment with the beta 2 adrenergic receptor agonist clenbuterol on endothelial progenitor cells (EPC) in a well-characterized model of heart failure, the muscle LIM protein knockout (MLP(-/-)) mouse. MLP(-/-) mice were treated daily with clenbuterol (2 mg/kg) or saline subcutaneously for 6 weeks. Clenbuterol led to a 30% increase in CD31(+) cells in the bone marrow of MLP(-/-) heart failure mice (p < 0.004). Clenbuterol did not improve ejection fraction. Clenbuterol treatment in MLP(-/-) mice was associated with significant changes in the following circulating factors: tissue inhibitor of metalloproteinase-type 1, leukemia inhibitory factor 1, C-reactive protein, apolipoprotein A1, fibroblast growth factor 2, serum glutamic oxaloacetic transaminase, macrophage-derived chemokine, and monocyte chemoattractant protein-3. Clenbuterol treatment in the MLP(-/-) model of heart failure did not rescue heart function, yet did increase CD31(+) cells in the bone marrow. This is the first evidence that a beta 2 agonist increases EPC proliferation in the bone marrow in a preclinical model of heart failure.

Deletion of Shp2 tyrosine phosphatase in muscle leads to dilated cardiomyopathy, insulin resistance, and premature death

The intracellular signaling mechanisms underlying the pathogenesis of cardiac diseases are not fully understood. We report here that selective deletion of Shp2, an SH2-containing cytoplasmic tyrosine phosphatase, in striated muscle results in severe dilated cardiomyopathy in mice, leading to heart failure and premature mortality. Development of cardiomyopathy in this mouse model is coupled with insulin resistance, glucose intolerance, and impaired glucose uptake in striated muscle cells. Shp2 deficiency leads to upregulation of leukemia inhibitory factor-stimulated phosphatidylinositol 3-kinase/Akt, Erk5, and Stat3 pathways in cardiomyocytes. Insulin resistance and impaired glucose uptake in Shp2-deficient mice are at least in part due to impaired protein kinase C-zeta/lambda and AMP-kinase activities in striated muscle. Thus, we have generated a mouse line modeling human patients suffering from cardiomyopathy and insulin resistance. This study reinforces a concept that a compound disease with multiple cardiovascular and metabolic disturbances can be caused by a defect in a single molecule such as Shp2, which modulates multiple signaling pathways initiated by cytokines and hormones.

Survival pathways in hypertrophy and heart failure: the gp130-STAT3 axis

Circulating levels of interleukin (IL)-6 and related cytokines are elevated in patients with congestive heart failure and after myocardial infarction. Serum IL-6 concentrations are related to decreasing functional status of these patients and provide important prognostic information.Moreover, in the failing human heart, multiple components of the IL-6- glycoprotein (gp)130 receptor system are impaired, implicating an important role of this system in cardiac pathophysiology.Experimental studies have shown that the common receptor subunit of IL-6 cytokines is phosphorylated in response to pressure overload and myocardial infarction and that it subsequently activates at least three different downstream signaling pathways, the signal transducers and activators of transcription 1 and 3 (STAT1/3), the Src-homology tyrosine phosphatase 2 (SHP2)-Ras-ERK, and the PI3K-Akt system. Gp130 receptor mediated signaling promotes cardiomyocyte survival, induces hypertrophy, modulates cardiac extracellular matrix and cardiac function. In this regard, the gp130 receptor system and its main downstream mediator STAT3 play a key role in cardioprotection. This review summarizes the current knowledge of IL-6 cytokines, gp130 receptor and STAT3 signaling in the heart exposed to physiological (aging, pregnancy) and pathophysiological stress (ischemia, pressure overload, inflammation and cardiotoxic agents) with a special focus on the potential role of individual IL-6 cytokines.

Jak/STAT/SOCS signaling circuits and associated cytokine-mediated inflammation and hypertrophy in the heart

Cytokines are important mediators of cardiac disease. Accumulating evidence indicates that members of the interleukin-6 family of cytokines promote cardiac hypertrophy through the activation of the Janus kinase-signal transducer and activator of transcription (Jak/STAT) pathway. Aberrant Jak/STAT signaling may promote progression from hypertrophy to heart failure. Suppressor of cytokine signaling (SOCS) proteins are underexplored, negative regulators of Jak/STAT signaling. SOCS proteins may also interact with other inflammatory pathways known to affect cardiac function. A better understanding of the therapeutic potential of these proteins may lead to the controlled progression of heart failure and the limitation of myocardial depression. This review summarizes the cardiophysiological effect of the IL-6 cytokine family, outlines the mechanistic pathway of Jak/STAT signaling, explores the regulatory role of SOCS proteins in the heart, and discusses the potential of using SOCS proteins clinically.

Leukemia inhibitory factor induces endothelial differentiation in cardiac stem cells

The importance of interleukin 6 (IL-6)-related cytokines in cardiac homeostasis has been studied extensively; however, little is known about their biological significance in cardiac stem cells. Here we describe that leukemia inhibitory factor (LIF), a member of IL-6-related cytokines, activated STAT3 and ERK1/2 in cardiac Sca-1+ stem cells. LIF stimulation resulted in the induction of endothelial cell-specific genes, including VE-cadherin, Flk-1, and CD31, whereas neither smooth muscle nor cardiac muscle marker genes such as GATA4, GATA6, Nkx-2.5, and calponin were up-regulated. Immunocytochemical examination showed that about 25% of total cells were positively stained with anti-CD31 antibody 14 days after LIF stimulation. Immunofluorescent microscopic analyses identified the Sca-1+ cells that were also positively stained with anti-von Willebrand factor antibody, indicating the differentiating process of Sca-1+ cells into the endothelial cells. IL-6, which did not activate STAT3 and ERK1/2, failed to induce the differentiation of cardiac stem cells into the endothelial cells. In cardiac stem cells, the transduction with dominant negative STAT3 abrogated the LIF-induced endothelial differentiation. And the inhibition of ERK1/2 with the MEK1/2 inhibitor U0126 also prevented the differentiation of Sca-1+ cells into endothelial cells. Thus, both STAT3 and ERK1/2 are required for LIF-mediated endothelial differentiation in cardiac stem cells. Collectively, it is proposed that LIF regulates the commitment of cardiac stem cells into the endothelial cell lineage, contributing to neovascularization in the process of tissue remodeling and/or regeneration.

Proinflammatory cytokine genes are constitutively overexpressed in the heart in experimental systemic lupus erythematosus: a brief communication

The heart is one of a number of organs that may be affected in systemic lupus erythematosus (SLE), a prototypic autoimmune disease. Potential anatomical sites of involvement include the myocardium, pericardium, endocardium, valves, conduction system and blood vessels that subserve the heart. Typically, the severity of cardiovascular disease in lupus correlates with the degree of systemic inflammation, which is mirrored by the level of C-reactive protein (CRP) in the plasma. C-reactive protein, in turn is regulated by proinflammatory cytokines, such as interleukins (ILs) 1beta and 6. These cytokines have been found in functionally and/or structurally damaged areas of the heart and have been implicated in disease pathogenesis. It has been assumed that the source of these putatively pathogenetically relevant cytokines in the compromised heart is infiltrating mononuclear cells. This study tests the hypothesis that cardiomyocytes per se may contribute to proinflammatory cytokine production in the setting of systemic inflammation. Using as the experimental model MRL/MpJ-Tnfrs6(lpr) (MRL-lpr/lpr) mice, which spontaneously manifest an autoimmune syndrome that has clinical features of SLE, we show that ventricular homogenates and ventricular cardiomyocytes constitutively overexpress genes encoding the proinflammatory cytokines IL-1beta, IL-6, IL-10, and gamma interferon. The results suggest the possibility that proinflammatory cytokines emanating from the heart may actually contribute to the high levels of CRP that appear to aid in predicting subsequent cardiac events. Viewed in this setting, CRP becomes a footprint of an ongoing pathogenic process mediated, in part, by the heart muscle itself.