Macrophage migration inhibitory factor antagonizes pressure overload-induced cardiac hypertrophy

The distinct functions of MIF in inflammatory cardiomyopathy

The immune system plays a crucial role in cardiac homeostasis and disease, and the innate and adaptive immune systems can be beneficial or detrimental in cardiac injury. The pleiotropic proinflammatory cytokine macrophage migration inhibitory factor (MIF) is involved in the pathogenesis of many human disease conditions, including heart diseases and inflammatory cardiomyopathies. Inflammatory cardiomyopathies are frequently observed after microbial infection but can also be caused by systemic immune-mediated diseases, drugs, and toxic substances. Immune cells and MIF are implicated in many of these conditions and may affect progression of inflammatory cardiomyopathy (ICM) to myocardial remodeling and dilated cardiomyopathy (DCM). The potential for targeting MIF therapeutically in patients with inflammatory diseases is an active area of investigation. Here we review the current literature supporting the role(s) of MIF in ICM and cardiac dysfunction. We posit that future research to further elucidate the underlying functions of MIF in cardiac pathologies is warranted.

Overexpression of macrophage migration inhibitory factor protects against pressure overload-induced cardiac hypertrophy through regulating the miR-29b-3p/HBP1 axis

Cardiac hypertrophy is an adaptive response to stressors such as high cardiac workload, which might lead to abnormal cardiac function and heart failure. Previous studies have indicated that macrophage migration inhibitory factor (MIF) might play a protective role in cardiac hypertrophy. Here, we aimed to illustrate the mechanism of MIF in protecting against pressure overload-induced cardiac hypertrophy. Transverse aortic constriction (TAC) mouse model was established and we found that overexpression of MIF protected against pressure overload-induced cardiac hypotrophy in TAC treated mice, as evidenced by significantly decreased the heart weight. In addition, transthoracic echocardiography showed that overexpression of MIF restored ejection fraction in TAC-treated mice. While TAC treatment resulted in a much larger cardiomyocyte size in mice, MIF overexpression notably decreased the cardiomyocyte size. Next, we demonstrated that MIF overexpression promoted the expression of miR-29b-3p which further downregulated the expression of its downstream target HMG box protein 1 (HBP1). Overexpression of HBP1 reversed the effect of MIF in alleviating Ang-II induced oxidative stress in cardiomyocytes. In conclusion, our findings suggest that MIF could attenuate pressure overload-induced cardiac hypertrophy through regulating the miR-29b-3p/HBP1 axis.

Macrophages in cardiovascular diseases: molecular mechanisms and therapeutic targets

The immune response holds a pivotal role in cardiovascular disease development. As multifunctional cells of the innate immune system, macrophages play an essential role in initial inflammatory response that occurs following cardiovascular injury, thereby inducing subsequent damage while also facilitating recovery. Meanwhile, the diverse phenotypes and phenotypic alterations of macrophages strongly associate with distinct types and severity of cardiovascular diseases, including coronary heart disease, valvular disease, myocarditis, cardiomyopathy, heart failure, atherosclerosis and aneurysm, which underscores the importance of investigating macrophage regulatory mechanisms within the context of specific diseases. Besides, recent strides in single-cell sequencing technologies have revealed macrophage heterogeneity, cell-cell interactions, and downstream mechanisms of therapeutic targets at a higher resolution, which brings new perspectives into macrophage-mediated mechanisms and potential therapeutic targets in cardiovascular diseases. Remarkably, myocardial fibrosis, a prevalent characteristic in most cardiac diseases, remains a formidable clinical challenge, necessitating a profound investigation into the impact of macrophages on myocardial fibrosis within the context of cardiac diseases. In this review, we systematically summarize the diverse phenotypic and functional plasticity of macrophages in regulatory mechanisms of cardiovascular diseases and unprecedented insights introduced by single-cell sequencing technologies, with a focus on different causes and characteristics of diseases, especially the relationship between inflammation and fibrosis in cardiac diseases (myocardial infarction, pressure overload, myocarditis, dilated cardiomyopathy, diabetic cardiomyopathy and cardiac aging) and the relationship between inflammation and vascular injury in vascular diseases (atherosclerosis and aneurysm). Finally, we also highlight the preclinical/clinical macrophage targeting strategies and translational implications.

The role of CD74 in cardiovascular disease

Leukocyte differentiation antigen 74 (CD74), also known as invariant chain, is a molecular chaperone of major histocompatibility complex class II (MHC II) molecules involved in antigen presentation. CD74 has recently been shown to be a receptor for the macrophage migration inhibitory factor family proteins (MIF/MIF2). Many studies have revealed that CD74 plays an important role in cardiovascular disease. In this review, we summarize the structure and main functions of CD74 and then focus on the recent research progress on the role of CD74 in cardiovascular diseases. In addition, we also discuss potential treatment strategies that target CD74. Our systematic review of the role of CD74 in cardiovascular disease will fill some knowledge gaps in the field.

A Cross-Kingdom View on the Immunomodulatory Role of MIF/D-DT Proteins in Mammalian and Plant Pseudomonas Infections

Gram-negative Pseudomonas bacteria are largely harmless saprotrophs, but some species can be potent pathogens of both plants and mammals. Macrophage migration inhibitory factor (MIF) and its homolog D-dopachrome tautomerase (D-DT, also referred to as MIF-2) are multifunctional proteins that in addition to their intracellular functions also serve as extracellular signaling molecules (cytokines) in orchestrating mammalian immune responses. It recently emerged that plants also possess MIF-like proteins, termed MIF/D-DT-like (MDL) proteins. We here provide a comparative cross-kingdom view on the immunomodulatory role of MIF and MDL proteins during Pseudomonas infections in mammals and plants. Although in both kingdoms the lack of MIF/MDL proteins is associated with a reduction in bacterial load and disease symptoms, the underlying molecular principles seem to be different. We provide a perspective for future research activities to unravel additional commonalities and differences in the MIF/MDL-mediated adjustment of antibacterial immune activities.

Transcriptomic and Lipidomic Mapping of Macrophages in the Hub of Chronic Beta-Adrenergic-Stimulation Unravels Hypertrophy-, Proliferation-, and Lipid Metabolism-Related Genes as Novel Potential Markers of Early Hypertrophy or Heart Failure

Sympathetic nervous system overdrive with chronic release of catecholamines is the most important neurohormonal mechanism activated to maintain cardiac output in response to heart stress. Beta-adrenergic signaling behaves first as a compensatory pathway improving cardiac contractility and maladaptive remodeling but becomes dysfunctional leading to pathological hypertrophy and heart failure (HF). Cardiac remodeling is a complex inflammatory syndrome where macrophages play a determinant role. This study aimed at characterizing the temporal transcriptomic evolution of cardiac macrophages in mice subjected to beta-adrenergic-stimulation using RNA sequencing. Owing to a comprehensive bibliographic analysis and complementary lipidomic experiments, this study deciphers typical gene profiles in early compensated hypertrophy (ECH) versus late dilated remodeling related to HF. We uncover cardiac hypertrophy- and proliferation-related transcription programs typical of ECH or HF macrophages and identify lipid metabolism-associated and Na⁺ or K⁺ channel-related genes as markers of ECH and HF macrophages, respectively. In addition, our results substantiate the key time-dependent role of inflammatory, metabolic, and functional gene regulation in macrophages during beta-adrenergic dependent remodeling. This study provides important and novel knowledge to better understand the prevalent key role of resident macrophages in response to chronically activated beta-adrenergic signaling, an effective diagnostic and therapeutic target in failing hearts.

Protective role of Gremlin-1 in myocardial function

BACKGROUND

Gremlin-1 is a cystine knot protein and is expressed in organs developing fibrosis. Transient ischaemia leads to myocardial fibrosis, a major determinant of impaired myocardial function.

MATERIALS AND METHODS

Expression of Gremlin-1 was investigated in infarcted myocardium by real-time PCR, Western blot analysis, histological and immunohistochemistry staining. We further elaborated the colocalization of Gremlin-1 and TGF-β proteins by confocal microscopy and co-immunoprecipitation experiments. The interaction between Gremlin-1 and TGF-β was analysed by photon correlation spectroscopy. Gremlin-1 modulation of the TGF-β-dependent collagen I synthesis in fibroblasts was investigated using ELISA and immunohistochemistry experiments. The effect of prolonged administration of recombinant Gremlin-1 on myocardial function following ischaemia/reperfusion was accessed by echocardiography and immunohistochemistry.

RESULTS

Gremlin-1 is expressed in myocardial tissue and infiltrating cells after transient myocardial ischaemia (P < .05). Gremlin-1 colocalizes with the pro-fibrotic cytokine transforming growth factor-β (TGF-β) expressed in fibroblasts and inflammatory cell infiltrates (P < .05). Gremlin-1 reduces TGF-β-induced collagen production of myocardial fibroblasts by approximately 20% (P < .05). We found that Gremlin-1 binds with high affinity to TGF-β (K_D  = 54 nmol/L) as evidenced by photon correlation spectroscopy and co-immunoprecipitation. intravenous administration of _m Gremlin-1-Fc, but not of equivalent amount of Fc control, significantly reduced infarct size by approximately 20%. In the _m Gremlin-1-Fc group, infarct area was reduced by up to 30% in comparison with mice treated with Fc control (I/LV: 4.8 ± 1.2% vs 6.0 ± 1.2% P < .05; I/AaR: 15.2 ± 1.5% vs 21.1 ± 5%, P < .05).

CONCLUSIONS

The present data disclose Gremlin-1 as an antagonist of TGF-β and presume a role for Gremlin-1/TGF-β interaction in myocardial remodelling following myocardial ischaemia.

Autocrine Signaling in Cardiac Remodeling: A Rich Source of Therapeutic Targets

The myocardium consists of different cell types, of which endothelial cells, cardiomyocytes, and fibroblasts are the most abundant. Communication between these different cell types, also called paracrine signaling, is essential for normal cardiac function, but also important in cardiac remodeling and heart failure. Systematic studies on the expression of ligands and their corresponding receptors in different cell types showed that for 60% of the expressed ligands in a particular cell, the receptor is also expressed. The fact that many ligand-receptor pairs are present in most cells, including the major cell types in the heart, indicates that autocrine signaling is a widespread phenomenon. Autocrine signaling in cardiac remodeling and heart failure is involved in all pathophysiological mechanisms generally observed: hypertrophy, fibrosis, angiogenesis, cell survival, and inflammation. Herein, we review ligand-receptor pairs present in the major cardiac cell types based on RNA-sequencing expression databases, and we review current literature on extracellular signaling proteins with an autocrine function in the heart; these include C-type natriuretic peptide, fibroblast growth factors 2, F21, and 23, macrophage migration inhibitory factor, heparin binding-epidermal growth factor, angiopoietin-like protein 2, leptin, adiponectin, follistatin-like 1, apelin, neuregulin 1, vascular endothelial growth factor, transforming growth factor β, wingless-type integration site family, member 1-induced secreted protein-1, interleukin 11, connective tissue growth factor/cellular communication network factor, and calcitonin gene‒related peptide. The large number of autocrine signaling factors that have been studied in the literature supports the concept that autocrine signaling is an essential part of myocardial biology and disease.

CX3CR1 is a prerequisite for the development of cardiac hypertrophy and left ventricular dysfunction in mice upon transverse aortic constriction

The CX3CL1/CX3CR1 axis mediates recruitment and extravasation of CX3CR1-expressing subsets of leukocytes and plays a pivotal role in the inflammation-driven pathology of cardiovascular disease. The cardiac immune response differs depending on the underlying causes. This suggests that for the development of successful immunomodulatory therapy in heart failure due to chronic pressure overload induced left ventricular (LV) hypertrophy, the underlying immune patterns must be examined. Here, the authors demonstrate that Fraktalkine-receptor CX3CR1 is a prerequisite for the development of cardiac hypertrophy and left ventricular dysfunction in a mouse model of transverse aortic constriction (TAC). The comparison of C57BL/6 mice with CX3CR1 deficient mice displayed reduced LV hypertrophy and preserved cardiac function in response to pressure overload in mice lacking CX3CR1. Moreover, the normal immune response following TAC induced pressure overload which is dominated by Ly6C^low macrophages changed to an early pro-inflammatory immune response driven by neutrophils, Ly6C^high macrophages and altered cytokine expression pattern in CX3CR1 deficient mice. In this early inflammatory phase of LV hypertrophy Ly6C^high monocytes infiltrated the heart in response to a C-C chemokine ligand 2 burst. CX3CR1 expression impacts the immune response in the development of LV hypertrophy and its absence has clear cardioprotective effects. Hence, suppression of CX3CR1 may be an important immunomodulatory therapeutic target to ameliorate pressure-overload induced heart failure.

Basic Mechanisms of Diabetic Heart Disease

Diabetes mellitus predisposes affected individuals to a significant spectrum of cardiovascular complications, one of the most debilitating in terms of prognosis is heart failure. Indeed, the increasing global prevalence of diabetes mellitus and an aging population has given rise to an epidemic of diabetes mellitus-induced heart failure. Despite the significant research attention this phenomenon, termed diabetic cardiomyopathy, has received over several decades, understanding of the full spectrum of potential contributing mechanisms, and their relative contribution to this heart failure phenotype in the specific context of diabetes mellitus, has not yet been fully resolved. Key recent preclinical discoveries that comprise the current state-of-the-art understanding of the basic mechanisms of the complex phenotype, that is, the diabetic heart, form the basis of this review. Abnormalities in each of cardiac metabolism, physiological and pathophysiological signaling, and the mitochondrial compartment, in addition to oxidative stress, inflammation, myocardial cell death pathways, and neurohumoral mechanisms, are addressed. Further, the interactions between each of these contributing mechanisms and how they align to the functional, morphological, and structural impairments that characterize the diabetic heart are considered in light of the clinical context: from the disease burden, its current management in the clinic, and where the knowledge gaps remain. The need for continued interrogation of these mechanisms (both known and those yet to be identified) is essential to not only decipher the how and why of diabetes mellitus-induced heart failure but also to facilitate improved inroads into the clinical management of this pervasive clinical challenge.

Effects of postprandial hydroxytyrosol and derivates on oxidation of LDL, cardiometabolic state and gene expression: a nutrigenomic approach for cardiovascular prevention

BACKGROUND AND AIM

Cardiovascular diseases (CVDs) are the most frequent causes of death in the world. Inflammation and oxidative damage contribute significantly to the development of atherosclerosis and CVDs. European Food Safety Authority scientific opinion has acknowledged that hydroxytyrosol (3,4-dihydroxyphenylethanol) and derivatives, contained in extra virgin olive oil (EVOO), typically used in Mediterranean diet may play a crucial role in the reduction of the inflammatory pathway and in the prevention of CVDs. The aim of the study was to determine the effect in healthy volunteers of 25 g of phenols-rich EVOO (p-EVOO).

METHODS

The clinical study was a randomized, controlled trial to determine the acute effect in the postprandial time of 25 g of p-EVOO. We evaluated nutritional status using anthropometric parameters, body composition, serum metabolites, oxidative stress biomarkers and gene expression of eight genes related to oxidative stress and human inflammasome pathways, lasting 2 h after p-EVOO administration. Twenty-two participants resulted as eligible for the study.

RESULTS

A significant reduction of oxidized LDL, malondialdehyde, triglycerides and visceral adiposity index was highlighted (P < 0.05). Significant upregulation of catalase, superoxide dismutase 1 and upstream transcription factor 1 were observed (P < 0.05).

CONCLUSION

The current study shows that intake of 25 g of p-EVOO has been able to be modulated, in the postprandial time, the antioxidant profile and the expression of inflammation and oxidative stress-related genes, as superoxide dismutase 1, upstream transcription factor 1 and catalase. We also observed a significant reduction of oxidized LDL, malondialdehyde, triglycerides and visceral adiposity index. We have demonstrated that a daily intake of phenols and antioxidants can reduce the inflammatory pathway and oxidative stress and therefore the risk of atherosclerosis and CVDs. More studies on a larger population are necessary before definitive conclusions can be drawn.Trial registration ClinicalTrials.gov NCT01890070.

The Smad3-miR-29b/miR-29c axis mediates the protective effect of macrophage migration inhibitory factor against cardiac fibrosis

Although macrophage migration inhibitory factor (MIF) is known to have antioxidant property, the role of MIF in cardiac fibrosis has not been well understood. We found that MIF was markedly increased in angiotension II (Ang-II)-infused mouse myocardium. Myocardial function was impaired and cardiac fibrosis was aggravated in Mif-knockout (Mif-KO) mice. Functionally, overexpression of MIF and MIF protein could inhibit the expression of fibrosis-associated collagen (Col) 1a1, COL3A1 and α-SMA, and Smad3 activation in mouse cardiac fibroblasts (CFs). Consistently, MIF deficiency could exacerbate the expression of COL1A1, COL3A1 and α-SMA, and Smad3 activation in Ang-II-treated CFs. Interestingly, microRNA-29b-3p (miR-29b-3p) and microRNA-29c-3p (miR-29c-3p) were down-regulated in the myocardium of Ang-II-infused Mif-KO mice but upregulated in CFs with MIF overexpression or by treatment with MIF protein. MiR-29b-3p and miR-29c-3p could suppress the expression of COL1A1, COL3A1 and α-SMA in CFs through targeting the pro-fibrosis genes of transforming growth factor beta-2 (Tgfb2) and matrix metallopeptidase 2 (Mmp2). We further demonstrated that Mif inhibited reactive oxygen species (ROS) generation and Smad3 activation, and rescued the decrease of miR-29b-3p and miR-29c-3p in Ang-II-treated CFs. Smad3 inhibitors, SIS3 and Naringenin, and Smad3 siRNA could reverse the decrease of miR-29b-3p and miR-29c-3p in Ang-II-treated CFs. Taken together, our data demonstrated that the Smad3-miR-29b/miR-29c axis mediates the inhibitory effect of macrophage migration inhibitory factor on cardiac fibrosis.

miR-499-5p Attenuates Mitochondrial Fission and Cell Apoptosis via p21 in Doxorubicin Cardiotoxicity

Doxorubicin (DOX) is a broad-spectrum anti-tumor drug, but its cardiotoxicity limits its clinical application. A better understanding of the molecular mechanisms underlying DOX cardiotoxicity will benefit clinical practice and remedy heart failure. Our present study observed that DOX caused cardiomyocyte (H9c2) apoptosis via the induction of abnormal mitochondrial fission. Notably, the expression levels of p21 increased in DOX-treated cardiomyocytes, and the silencing of p21 using siRNA greatly attenuated mitochondrial fission and apoptosis in cardiomyocytes. We also found that miR-499-5p could directly target p21 and attenuated DOX-induced mitochondrial fission and apoptosis. The role of the miR-499-5p-p21 axis in the prevention of DOX cardiotoxicity was also validated in the mice model. DOX treatment induced an upregulation of p21, which induced subsequent abnormal mitochondrial fission and myocardial apoptosis in mouse heart. Adenovirus-harboring miR-499-5p-overexpressing mice exhibited significantly reduced p21 expression, mitochondrial fission and myocardial apoptosis in hearts following DOX administration. The miR-499-5p-overexpressing mice also exhibited improved cardiomyocyte hypertrophy and cardiac function after DOX treatment. However, miR-499-5p was not involved in the DOX-induced apoptosis of cancer cells. Taken together, these findings reveal an emerging role of p21 in the regulation of mitochondrial fission program. miR-499-5p attenuated mitochondrial fission and DOX cardiotoxicity via the targeting of p21. These results provide new evidence for the miR-499-5p-p21 axis in the attenuation of DOX cardiotoxicity. The development of new therapeutic strategies based on the miR-499-5p-p21 axis is a promising path to overcome DOX cardiotoxicity as a chemotherapy for cancer treatment.

Review on Chamber-Specific Differences in Right and Left Heart Reactive Oxygen Species Handling

Reactive oxygen species (ROS) exert signaling character (redox signaling), or damaging character (oxidative stress) on cardiac tissue depending on their concentration and/or reactivity. The steady state of ROS concentration is determined by the interplay between its production (mitochondrial, cytosolic, and sarcolemmal enzymes) and ROS defense enzymes (mitochondria, cytosol). Recent studies suggest that ROS regulation is different in the left and right ventricle of the heart, specifically by a different activity of superoxide dismutase (SOD). Mitochondrial ROS defense seems to be lower in right ventricular tissue compared to left ventricular tissue. In this review we summarize the current evidence for heart chamber specific differences in ROS regulation that may play a major role in an observed inability of the right ventricle to compensate for cardiac stress such as pulmonary hypertension. Based on the current knowledge regimes to increase ROS defense in right ventricular tissue should be in the focus for the development of future therapies concerning right heart failure.

Overexpression of small ubiquitin‑like modifier 2 ameliorates high glucose‑induced reductions in cardiomyocyte proliferation via the transforming growth factor‑β/Smad pathway

Hyperglycemia may induce diabetic cardiomyopathy (DC). In the current study, the mechanism underlying the alleviation of high glucose (HG)-induced impairments in the proliferation of H9c2 embryo cardiomyocyte proliferation by small ubiquitin-like modifier 2 (SUMO2) overexpression was investigated. H9c2 cell morphology was identified as classical long shuttle type by optical microscopy. The viability of HG-injured H9c2 cells was evaluated by a Cell Counting Kit-8 assay and the results indicated that viability was inhibited in a dose-dependent (5.6, 10, 20 and 30 mmol/l) and time-dependent (6, 12 and 24 h) manner. H9c2 cells treated with 20 mmol/l HG for 24 h were selected for subsequent experiments due to the extent of injury caused at a low density. Flow cytometry was conducted to confirm cell cycle arrest between G₁/S phases and apoptosis promotion in HG-injured H9c2 cells, and the subsequent alleviating effect of SUMO2 overexpression on these HG-induced effects. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot analysis were performed to detect mRNA and protein expression levels of cell cycle-and apoptosis-associated factors. The results indicated that the expression ofthe cell cycle-associated factors CyclinA2 and C-Myc was upregulated, and cyclin-dependent kinase inhibitor 1a was downregulated. The expression of the apoptosis-associated factor Bcl-2 was upregulated, while Bcl-2-associated X and caspase-3 expression was downregulated, by SUMO2 overexpression. Furthermore, the effect of SUMO2 overexpression on the transforming growth factor (TGF)-β/Smad pathway was also determined using RT-qPCR and western blot analysis. The results indicated the mRNA and protein levels of TGF-β1 and Smad3 in HG-injured H9c2 cells were significantly decreased following SUMO2 overexpression. Thus, the results demonstrated that overexpression of SUMO2 may alleviate H9c2 cardiomyocyte cell cycle arrest and apoptosis promotion induced by HG via regulation of cell cycle- and apoptosis-associated factors, as well as inhibition of the TGF-β/Smad pathway. These results may therefore provide a novel strategy for the protection of cardiomyocytes and may aid the diagnosis and prognosis of patients with DC.

Soluble CD74 Reroutes MIF/CXCR4/AKT-Mediated Survival of Cardiac Myofibroblasts to Necroptosis

Background Although macrophage migration inhibitory factor ( MIF ) has been demonstrated to mediate cardioprotection in ischemia/reperfusion injury and antagonize fibrotic effects through its receptor, CD 74, the function of the soluble CD 74 receptor ectodomain ( sCD 74) and its interaction with circulating MIF have not been explored in cardiac disease. Methods and Results Cardiac fibroblasts were isolated from hearts of neonatal mice and differentiated into myofibroblasts. Co-treatment with recombinant MIF and sCD 74 induced cell death ( P<0.001), which was mediated by receptor-interacting serine/threonine-protein kinase ( RIP) 1/ RIP 3-dependent necroptosis ( P=0.0376). This effect was specific for cardiac fibroblasts and did not affect cardiomyocytes. Gene expression analyses using microarray and RT - qPCR technology revealed a 4-fold upregulation of several interferon-induced genes upon co-treatment of myofibroblasts with sCD 74 and MIF (Ifi44: P=0.011; Irg1: P=0.022; Clec4e: P=0.011). Furthermore, Western blot analysis confirmed the role of sCD 74 as a modulator of MIF signaling by diminishing MIF -mediated protein kinase B ( AKT) activation ( P=0.0197) and triggering p38 activation ( P=0.0641). We obtained evidence that sCD 74 inhibits MIF -mediated survival pathway through the C-X-C chemokine receptor 4/ AKT axis, enabling the induction of CD 74-dependent necroptotic processes in cardiac myofibroblasts. Preliminary clinical data revealed a lowered sCD 74/ MIF ratio in heart failure patients (17.47±10.09 versus 1.413±0.6244). Conclusions These findings suggest that treatment of cardiac myofibroblasts with sCD 74 and MIF induces necroptosis, offering new insights into the mechanism of myofibroblast depletion during scar maturation. Preliminary clinical data provided first evidence about a clinical relevance of the sCD 74/ MIF axis in heart failure, suggesting that these proteins may be a promising target to modulate cardiac remodeling and disease progression in heart failure.

Trichomonas vaginalis Macrophage Migration Inhibitory Factor Mediates Parasite Survival during Nutrient Stress

Trichomonas vaginalis is responsible for the most prevalent non-viral sexually transmitted disease worldwide, and yet the mechanisms used by this parasite to establish and maintain infection are poorly understood. We previously identified a T. vaginalis homologue (TvMIF) of a human cytokine, human macrophage migration inhibitory factor (huMIF). TvMIF mimics huMIF’s role in increasing cell growth and inhibiting apoptosis in human host cells. To interrogate a role of TvMIF in parasite survival during infection, we asked whether overexpression of TvMIF (TvMIF-OE) confers an advantage to the parasite under nutrient stress conditions by comparing the survival of TvMIF-OE parasites to that of empty vector (EV) parasites. We found that under conditions of serum starvation, overexpression of TvMIF resulted in increased parasite survival. Serum-starved parasites secrete 2.5-fold more intrinsic TvMIF than unstarved parasites, stimulating autocrine and paracrine signaling. Similarly, we observed that addition of recombinant TvMIF increased the survival of the parasites in the absence of serum. Recombinant huMIF likewise increased the parasite survival in the absence of serum, indicating that the parasite may use this host survival factor to resist its own death. Moreover, TvMIF-OE parasites were found to undergo significantly less apoptosis and reactive oxygen species (ROS) generation under conditions of serum starvation, consistent with increased survival being the result of blocking ROS-induced apoptosis. These studies demonstrated that a parasitic MIF enhances survival under adverse conditions and defined TvMIF and huMIF as conserved survival factors that exhibit cross talk in host-pathogen interactions.

Macrophage migration inhibitory factor (MIF) is a conserved protein found in most eukaryotes which has been well characterized in mammals but poorly studied in other eukaryotes. The limited analyses of MIF proteins found in unicellular eukaryotes have focused exclusively on the effect of parasitic MIF on the mammalian host. This was the first study to assess the function of a parasite MIF in parasite biology. We demonstrate that the Trichomonas vaginalis MIF functions to suppress cell death induced by apoptosis, thereby enhancing parasite survival under adverse conditions. Our research reveals a conserved survival mechanism, shared by a parasite and its host, and indicates a role for a conserved protein in mediating cross talk in host-pathogen interactions.

Antioxidant Effects of a Hydroxytyrosol-Based Pharmaceutical Formulation on Body Composition, Metabolic State, and Gene Expression: A Randomized Double-Blinded, Placebo-Controlled Crossover Trial

Hydroxytyrosol (HT) plays a significant role in cardiovascular disease (CVD) protection, and its metabolites are able to protect from the endothelial dysfunction commonly present in atherosclerosis. This randomized double-blinded, placebo-controlled crossover trial determined the effect in healthy volunteers of two gastroresistant capsules containing 15 mg/day of HT, for a 3-week period (HTT). Evaluation of nutritional status, serum metabolites, oxidative stress biomarkers, and gene expression of 9 genes related to oxidative stress, inflammation, and CVDs was performed. Oxidation biomarkers like thiol group (p = 0.001), total antioxidant status (TAS) (p = 0.001), superoxide dismutase 1 (SOD1) (2^-ΔΔCt = 3.7), and plasma concentration of HT (2.83 μg·mL^-1) were significantly increased, while nitrite (p = 0.001), nitrate (p = 0.001), and malondialdehyde (MDA) (p = 0.02) were drastically reduced after HTT. A significant reduction of body fat mass percentage (p = 0.01), suprailiac skinfold (p = 0.01), and weight (p = 0.04; Δ% = -0.46%) was observed after HTT. This study shows that regular intake of 15 mg/day of HT changed body composition parameters and modulated the antioxidant profile and the expression of inflammation and oxidative stress-related genes. However, it is advisable to personalize HT doses in order to exert its health benefits in CVD prevention and protection of LDL-C particles from oxidative damage. This trial is registered with ClinicalTrials.gov NCT01890070.

MIF family cytokines in cardiovascular diseases and prospects for precision-based therapeutics

INTRODUCTION

Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine with chemokine-like functions that increasingly is being studied in different aspects of cardiovascular disease. MIF was first identified as a proinflammatory and pro-survival mediator within the immune system, and a second structurally related MIF family member, D-dopachrome tautomerase (a.k.a. MIF-2), was reported recently. Both MIF family members are released by myocardium and modulate the manifestations of cardiovascular disease, specifically in myocardial ischemia. Areas covered: A scientific overview is provided for the involvement of MIF family cytokines in the inflammatory pathogenesis of atherosclerosis, myocardial infarction, and ischemia-reperfusion injury. We summarize findings of experimental, human genetic and clinical studies, and suggest therapeutic opportunities for modulating the activity of MIF family proteins that potentially may be applied in a MIF allele specific manner. Expert opinion: Knowledge of MIF, MIF-2 and their receptor pathways are under active investigation in different types of cardiovascular diseases, and novel therapeutic opportunities are being identified. Clinical translation may be accelerated by accruing experience with MIF-directed therapies currently in human testing in cancer and autoimmunity.

Proinflammatory Signature of the Dysfunctional Endothelium in Pulmonary Hypertension. Role of the Macrophage Migration Inhibitory Factor/CD74 Complex

RATIONALE

Inflammation and endothelial dysfunction are considered two primary instigators of pulmonary arterial hypertension (PAH). CD74 is a receptor for the proinflammatory cytokine macrophage migration inhibitory factor (MIF). This ligand/receptor complex initiates survival pathways and cell proliferation, and it triggers the synthesis and secretion of major proinflammatory factors and cell adhesion molecules.

OBJECTIVES

We hypothesized that the MIF/CD74 signaling pathway is overexpressed in idiopathic PAH (iPAH) and contributes to a proinflammatory endothelial cell (EC) phenotype.

METHODS

Primary early passage cultures of human ECs isolated from lung tissues obtained from patients with iPAH and controls were examined for their ability to secrete proinflammatory mediators and bind inflammatory cells with or without modulation of the functional activities of the MIF/CD74 complex. In addition, we tested the efficacies of curative treatments with either the MIF antagonist ISO-1 or anti-CD74 neutralizing antibodies on the aberrant proinflammatory EC phenotype in vitro and in vivo and on the progression of monocrotaline-induced pulmonary hypertension.

MEASUREMENTS AND MAIN RESULTS

In human lung tissues, intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and E-selectin expressions are markedly up-regulated in the endothelium of distal iPAH pulmonary arteries. Circulating MIF levels are increased in the serum of patients with PAH compared with control subjects, and T-cell lymphocytes represent a source of this overabundance. In addition, CD74 is highly expressed in the endothelium of muscularized pulmonary arterioles and in cultured pulmonary ECs from iPAH, contributing to an exaggerated recruitment of peripheral blood mononuclear cells to pulmonary iPAH ECs. Finally, we found that curative treatments with the MIF antagonist ISO-1 or anti-CD74 neutralizing antibodies partially reversed development of pulmonary hypertension in rats and substantially reduced inflammatory cell infiltration.

CONCLUSIONS

We report here that CD74 and MIF are markedly increased and activated in patients with iPAH, contributing to the abnormal proinflammatory phenotype of pulmonary ECs in iPAH.

Macrophage migration inhibitory factor promotes expression of GLUT4 glucose transporter through MEF2 and Zac1 in cardiomyocytes

OBJECTIVE

Evidence shows that both macrophage migration inhibitory factor (MIF) and GLUT4 glucose transporter are involved in diabetic cardiomyopathy (DCM), but it remains largely unknown whether and how MIF regulates GLUT4 expression in cardiomyocytes. The present study aims to investigate the mechanism underlying the modulation of GLUT4 by MIF in cardiomyocytes.

MATERIAL AND METHODS

Activations of AKT and AMPK signaling, and expressions of MIF, GLUT4 and the candidate GLUT4 regulation associated transcription factors in the diabetic mouse myocardium were determined. The screened transcription factors mediating MIF-promoted GLUT4 expression were verified by RNA interference (RNAi) and electrophoretic mobility shift assay (EMSA), respectively.

RESULTS

MIF was increased, but GLUT4 was decreased in the diabetic mouse myocardium. MIF could enhance glucose uptake and up-regulate GLUT4 expression in NMVCs. Expressions of transcription factor MEF2A, -2C, -2D and Zac1 were significantly up-regulated in MIF-treated neonatal mouse ventricular cardiomyocytes (NMVCs), and markedly reduced in the diabetic myocardium. Knockdown of MEF2A, -2C, -2D and Zac1 could significantly inhibit glucose uptake and GLUT4 expression in cardiomyocytes. Moreover, EMSA results revealed that transcriptional activities of MEF2 and Zac1 were significantly increased in MIF-treated NMVCs. AMPK signaling was activated in MIF-stimulated NMVCs, and AMPK activator AICAR could enhance MEF2A, -2C, -2D, Zac1 and GLUT4 expression. Additionally, MIF effects were inhibited by an AMPK inhibitor compound C and siRNA targeting MIF receptor CD74, suggesting the involvement of CD74-dependent AMPK activation.

CONCLUSIONS

Transcription factor MEF2 and Zac1 mediate MIF-induced GLUT4 expression through CD74-dependent AMPK activation in cardiomyocytes.

Cardiomyocyte-specific Bmal1 deletion in mice triggers diastolic dysfunction, extracellular matrix response, and impaired resolution of inflammation

The mammalian circadian clock consists of multiple transcriptional regulators that coordinate biological processes in a time-of-day-dependent manner. Cardiomyocyte-specific deletion of the circadian clock component, Bmal1 (aryl hydrocarbon receptor nuclear translocator-like protein 1), leads to age-dependent dilated cardiomyopathy and decreased lifespan in mice. We investigated whether cardiomyocyte-specific Bmal1 knockout (CBK) mice display early alterations in cardiac diastolic function, extracellular matrix (ECM) remodeling, and inflammation modulators by investigating CBK mice and littermate controls at 8 and 28 wk of age (i.e., prior to overt systolic dysfunction). Left ventricles of CBK mice exhibited (P < 0.05): 1) progressive abnormal diastolic septal annular wall motion and reduced pulmonary venous flow only at 28 wk of age; 2) progressive worsening of fibrosis in the interstitial and endocardial regions from 8 to 28 wk of age; 3) increased (>1.5 fold) expression of collagen I and III, as well as the matrix metalloproteinases MMP-9, MMP-13, and MMP-14 at 28 wk of age; 4) increased transcript levels of neutrophil chemotaxis and leukocyte migration genes (Ccl2, Ccl8, Cxcl2, Cxcl1, Cxcr2, Il1β) with no change in Il-10 and Il-13 genes expression; and 5) decreased levels of 5-LOX, HO-1 and COX-2, enzymes indicating impaired resolution of inflammation. In conclusion, genetic disruption of the cardiomyocyte circadian clock results in diastolic dysfunction, adverse ECM remodeling, and proinflammatory gene expression profiles in the mouse heart, indicating signs of early cardiac aging in CBK mice.

Distinct metabolomic signatures are associated with longevity in humans

Alterations in metabolism influence lifespan in experimental models, but data in humans are lacking. Here we use liquid chromatography/mass spectrometry to quantify 217 plasma metabolites and examine their relation to longevity in a large cohort of men and women followed for up to 20 years. We find that, higher concentrations of the citric acid cycle intermediate, isocitrate, and the bile acid, taurocholate, are associated with lower odds of longevity, defined as attaining 80 years of age. Higher concentrations of isocitrate, but not taurocholate, are also associated with worse cardiovascular health at baseline, as well as risk of future cardiovascular disease and death. None of the metabolites identified are associated with cancer risk. Our findings suggest that some, but not all, metabolic pathways related to human longevity are linked to the risk of common causes of death.

Improved survival of mesenchymal stem cells by macrophage migration inhibitory factor

Macrophage migration inhibitory factor (MIF) is a critical inflammatory cytokine that was recently associated with progenitor cell survival and potently inhibits apoptosis. We examined the protective effect of MIF on hypoxia/serum deprivation (SD)-induced apoptosis of mesenchymal stem cells (MSCs), as well as the possible mechanisms. MSCs were obtained from rat bone marrow and cultured in vitro. Apoptosis was induced by culturing MSCs under hypoxia/SD conditions for up to 24 h and assessed by flow cytometry. Expression levels of c-Met, Akt, and FOXO3a were detected by Western blotting. CD74 expression was detected by qRT-PCR, Western blot, and immunofluorescence. Oxidative stress under hypoxia/SD was examined by detection of reactive oxygen species (ROS) and activity of superoxide dismutase (SOD) and malondialdehyde (MDA). Hypoxia/SD-induced apoptosis was significantly attenuated by recombinant rat MIF in a concentration-dependent manner. MIF induced CD74-asssociated c-Met activation, which was blocked by knocking down CD74 expression using siRNA. MIF also induced Akt and associated FOXO3a phosphorylation, and this effect was abolished by knocking down either CD74 or Akt. In addition, MIF decreased oxidative stress in MSCs, as shown by decreased ROS and MDA, and increased the activity of SOD. Knockdown of CD74, Akt, or FOXO3a largely attenuated the anti-apoptotic effect of MIF and its ability to protect against oxidative stress. MIF protected MSCs from hypoxia/SD-induced apoptosis by interacting with CD74 to stimulate c-Met, leading to downstream PI3K/Akt-FOXO3a signaling and decreased oxidative stress.

Ly6C(low) and not Ly6C(high) macrophages accumulate first in the heart in a model of murine pressure-overload

Cardiac tissue remodeling in the course of chronic left ventricular hypertrophy requires phagocytes which degrade cellular debris, initiate and maintain tissue inflammation and reorganization. The dynamics of phagocytes in left ventricular hypertrophy have not been systematically studied. Here, we characterized the temporal accumulation of leukocytes in the cardiac immune response by flow cytometry and fluorescence microscopy at day 3, 6 and 21 following transverse aortic constriction (TAC). Cardiac hypertrophy due to chronic pressure overload causes cardiac immune response and inflammation represented by an increase of immune cells at all three time points among which neutrophils reached their maximum at day 3 and macrophages at day 6. The cardiac macrophage population consisted of both Ly6C^low and Ly6C^high macrophages. Ly6C^low macrophages were more abundant peaking at day 6 in response to pressure overload. During the development of cardiac hypertrophy the expression pattern of adhesion molecules was investigated by qRT-PCR and flow cytometry. CD11b, CX3CR1 and ICAM-1 determined by qRT-PCR in whole cardiac tissue were up-regulated in response to pressure overload at day 3 and 6. CD11b and CX3CR1 were significantly increased by TAC on the surface of Ly6C^low but not on Ly6C^high macrophages. Furthermore, ICAM-1 was up-regulated on cardiac endothelial cells. In fluorescence microscopy Ly6C^low macrophages could be observed attached to the intra- and extra-vascular vessel-wall. Taken together, TAC induced the expression of adhesion molecules, which may explain the accumulation of Ly6C^low macrophages in the cardiac tissue, where these cells might contribute to cardiac inflammation and remodeling in response to pressure overload.

Macrophage migration inhibitory factor (MIF) knockout preserves cardiac homeostasis through alleviating Akt-mediated myocardial autophagy suppression in high-fat diet-induced obesity

Background

Macrophage migration inhibitory factor (MIF) plays a role in the development of obesity and diabetes. However, whether MIF plays a role in fat diet-induced obesity and associated cardiac anomalies still remains unknown. The aim of this study was to examine the impact of MIF knockout on high fat diet-induced obesity, obesity-associated cardiac anomalies and the underlying mechanisms involved with a focus on Akt-mediated autophagy.

Methods

Adult male wild-type (WT) and MIF knockout (MIF^−/−) mice were placed on 45% high fat diet for 5 months. Oxygen consumption, CO₂ production, respiratory exchange ratio (RER), locomotor activity, and heat generation were measured using energy calorimeter. Echocardiographic, cardiomyocyte mechanical and intracellular Ca²⁺ properties were assessed. Apoptosis was examined using TUNEL staining and western blot analysis. Akt signaling pathway and autophagy markers were evaluated. Cardiomyocytes isolated from WT and MIF^−/− mice were treated with recombinant mouse MIF (rmMIF).

Results

High fat diet feeding elicited increased body weight gain, insulin resistance, and caloric disturbance in WT and MIF^−/− mice. High fat diet induced unfavorable geometric, contractile and histological changes in the heart, the effects of which were alleviated by MIF knockout. In addition, fat diet-induced cardiac anomalies were associated with Akt activation and autophagy suppression, which were nullified by MIF deficiency. In cardiomyocytes from WT mice, autophagy was inhibited by exogenous rmMIF through Akt activation. In addition, MIF knockout rescued palmitic acid-induced suppression of cardiomyocyte autophagy, the effect of which was nullified by rmMIF.

Conclusions

These results indicate that MIF knockout preserved obesity-associated cardiac anomalies without affecting fat diet-induced obesity, probably through restoring myocardial autophagy in an Akt-dependent manner. Our findings provide new insights for the role of MIF in obesity and associated cardiac anomalies.

Role of MIF in myocardial ischaemia and infarction: insight from recent clinical and experimental findings

First discovered in 1966 as an inflammatory cytokine, MIF (macrophage migration inhibitory factor) has been extensively studied for its pivotal role in a variety of inflammatory diseases, including rheumatoid arthritis and atherosclerosis. Although initial studies over a decade ago reported increases in circulating MIF levels following acute MI (myocardial infarction), the dynamic changes in MIF and its pathophysiological significance following MI have been unknown until recently. In the present review, we summarize recent experimental and clinical studies examining the diverse functions of MIF across the spectrum of acute MI from brief ischaemia to post-infarct healing. Following an acute ischaemic insult, MIF is rapidly released from jeopardized cardiomyocytes, followed by a persistent MIF production and release from activated immune cells, resulting in a sustained increase in circulating levels of MIF. Recent studies have documented two distinct actions of MIF following acute MI. In the supra-acute phase of ischaemia, MIF mediates cardioprotection via several distinct mechanisms, including metabolic activation, apoptosis suppression and antioxidative stress. In prolonged myocardial ischaemia, however, MIF promotes inflammatory responses with largely detrimental effects on cardiac function and remodelling. The pro-inflammatory properties of MIF are complex and involve MIF derived from cardiac and immune cells contributing sequentially to the innate immune response evoked by MI. Emerging evidence on the role of MIF in myocardial ischaemia and infarction highlights a significant potential for the clinical use of MIF agonists or antagonists and as a unique cardiac biomarker.

Macrophage migration inhibitory factor in myocardial ischaemia/reperfusion injury

Acute myocardial infarction (AMI) remains one of the leading causes of death in the developed world. There is emerging evidence that the cytokine macrophage migration inhibitory factor (MIF) is a crucial player in AMI. Cardioprotection by MIF is likely to be a multifactorial phenomenon mediated by receptor-mediated signalling processes, intracellular protein-protein interactions, and enzymatic redox regulation. Co-ordinating several pathways in the ischaemic heart, MIF contributes to receptor-mediated regulation of cardioprotective AMP-activated protein kinase signalling, inhibition of pro-apoptotic cascades, and the reduction of oxidative stress in the post-ischaemic heart. Moreover, the cardioprotective properties of MIF are modulated by S-nitros(yl)ation. These effects in the pathophysiology of myocardial ischaemia/reperfusion injury qualify MIF as a promising therapeutic target in the future. We here summarize the findings of experimental and clinical studies and emphasize the therapeutic potential of MIF in AMI.

Macrophage migration inhibitory factor deletion exacerbates pressure overload-induced cardiac hypertrophy through mitigating autophagy

The proinflammatory cytokine macrophage migration inhibitory factor (MIF) has been shown to be cardioprotective under various pathological conditions. However, the underlying mechanisms still remain elusive. In this study, we revealed that MIF deficiency overtly exacerbated abdominal aorta constriction-induced cardiac hypertrophy and contractile anomalies. MIF deficiency interrupted myocardial autophagy in hypertrophied hearts. Rapamycin administration mitigated the exacerbated hypertrophic responses in MIF(-/-) mice. Using the phenylephrine-induced hypertrophy in vitro model in H9C2 myoblasts, we confirmed that MIF governed the activation of AMP-activated protein kinase-mammalian target of rapamycin-autophagy cascade. Confocal microscopic examination demonstrated that MIF depletion prevented phenylephrine-induced mitophagy in H9C2 myoblasts. Myocardial Parkin, an E3 ubiquitin ligase and a marker for mitophagy, was significantly upregulated after sustained pressure overload, the effect of which was prevented by MIF knockout. Furthermore, our data exhibited that levels of MIF, AMP-activated protein kinase activation, and autophagy were elevated concurrently in human failing hearts. These data indicate that endogenous MIF regulates the mammalian target of rapamycin signaling to activate autophagy to preserve cardiac geometry and protect against hypertrophic responses.

Macrophage migration inhibitory factor deficiency augments doxorubicin-induced cardiomyopathy

Background

Recent evidence has depicted a role of macrophage migration inhibitory factor (MIF) in cardiac homeostasis under pathological conditions. This study was designed to evaluate the role of MIF in doxorubicin‐induced cardiomyopathy and the underlying mechanism involved with a focus on autophagy.

Methods and Results

Wild‐type (WT) and MIF knockout (MIF^−/−) mice were given saline or doxorubicin (20 mg/kg cumulative, i.p.). A cohort of WT and MIF^−/− mice was given rapamycin (6 mg/kg, i.p.) with or without bafilomycin A1 (BafA1, 3 μmol/kg per day, i.p.) for 1 week prior to doxorubicin challenge. To consolidate a role for MIF in the maintenance of cardiac homeostasis following doxorubicin challenge, recombinant mouse MIF (rmMIF) was given to MIF^−/− mice challenged with or without doxorubicin. Echocardiographic, cardiomyocyte function, and intracellular Ca²⁺ handling were evaluated. Autophagy and apoptosis were examined. Mitochondrial morphology and function were examined using transmission electron microscopy, JC‐1 staining, MitoSOX Red fluorescence, and mitochondrial respiration complex assay. DHE staining was used to evaluate reactive oxygen species (ROS) generation. MIF knockout exacerbated doxorubicin‐induced mortality and cardiomyopathy (compromised fractional shortening, cardiomyocyte and mitochondrial function, apoptosis, and ROS generation). These detrimental effects of doxorubicin were accompanied by defective autophagolysosome formation, the effect of which was exacerbated by MIF knockout. Rapamycin pretreatment rescued doxorubicin‐induced cardiomyopathy in WT and MIF^−/− mice. Blocking autophagolysosome formation using BafA1 negated the cardioprotective effect of rapamycin and rmMIF.

Conclusions

Our data suggest that MIF serves as an indispensable cardioprotective factor against doxorubicin‐induced cardiomyopathy with an underlying mechanism through facilitating autophagolysosome formation.

Compartmentalized protective and detrimental effects of endogenous macrophage migration-inhibitory factor mediated by CXCR2 in a mouse model of myocardial ischemia/reperfusion

OBJECTIVE

Here, we aimed to clarify the role of CXC chemokine receptor (CXCR) 2 in macrophage migration-inhibitory factor (MIF)-mediated effects after myocardial ischemia and reperfusion. As a pleiotropic chemokine-like cytokine, MIF has been identified to activate multiple receptors, including CD74 and CXCR2. In models of myocardial infarction, MIF exerts both proinflammatory effects and protective effects in cardiomyocytes. Similarly, CXCR2 displays opposing effects in resident versus circulating cells.

APPROACH AND RESULTS

Using bone marrow transplantation, we generated chimeric mice with Cxcr2(-/-) bone marrow-derived inflammatory cells and wild-type (wt) resident cells (wt/Cxcr2(-/-)), Cxcr2(-/-) cardiomyocytes and wt bone marrow-derived cells (Cxcr2(-/-)/wt), and wt controls reconstituted with wt bone marrow (wt/wt). All groups were treated with anti-MIF or isotype control antibody before they underwent myocardial ischemia and reperfusion. Blocking MIF increased infarction size and impaired cardiac function in wt/wt and wt/CXCR2(-/-) mice but ameliorated functional parameters in Cxcr2(-/-)/wt mice, as analyzed by echocardiography and Langendorff perfusion. Neutrophil infiltration and angiogenesis were unaltered by MIF blockade or Cxcr2 deficiency. Monocyte infiltration was blunted in wt/Cxcr2(-/-) mice and reduced by MIF blockade in wt/wt and Cxcr2(-/-)/wt mice. Furthermore, MIF blockade attenuated collagen content in all groups in a CXCR2-independent manner.

CONCLUSIONS

The compartmentalized and opposing effects of MIF after myocardial ischemia and reperfusion are largely mediated by CXCR2. Although MIF confers protective effects by improving myocardial healing and function through CXCR2 in resident cells, thereby complementing paracrine effects through CD74/AMP-activated protein kinase, it exerts detrimental effects on CXCR2-bearing inflammatory cells by increasing monocyte infiltration and impairing heart function. These dichotomous findings should be considered when developing novel therapeutic strategies to treat myocardial infarction.

Congestive heart failure: experimental model

INTRODUCTION

Surgically induced, combined volume and pressure overload has been used in rabbits to create a simplified and reproducible model of acute left ventricular (LV) failure.

MATERIALS AND METHODS

New Zealand white male rabbits (n = 24, mean weight 3.1 ± 0.2 kg) were randomly assigned to either the Control group (n = 10) or to the Heart Failure group (HF, n = 14). Animals in the Control group underwent "sham" procedures. Animals in the HF group underwent procedures to induce LV volume overload by inducing severe aortic valve regurgitation with aortic cusp disruption and pressure overload using an occlusive silver clip positioned around the pre-renal abdominal aorta.

RESULTS

Following Procedure-1 (volume overload) echocardiography confirmed severe aortic regurgitation in all animals in the HF group, with increased mean pulse pressure difference from 18 ± 3 to 38 ± 3 mmHg (P < 0.0001). After Procedure-2 (pressure overload) all animals in the HF group showed clinical and echocardiographic signs of constriction of the abdominal aorta and echocardiography confirmed progressively declining LV function. At the end of the protocol there was a significant increase of the heart/body weight ratio in the HF group vs. Control group (4.6 ± 0.2 vs. 2.9 ± 0.1 g/kg, P < 0.05), and echocardiography showed in HF group significant increase of the LV end-diastolic diameter (2.15 ± 0.09 vs. 1.49 ± 0.03 cm, P < 0.001) and reduction of the LV shortening fraction (26.3 ± 3.8 vs. 41.3 ± 1.6%, P < 0.001).

CONCLUSION

This experimental model: (a) consistently produces LV hypertrophy/dilatation and subsequent congestive heart failure, (b) provides new data on the time course of LV dilatation, hypertrophy and failure, (c) allows study of the progress and evolution of LV systolic and diastolic dysfunction in the presence of induced LV failure, (d) is suitable to study intervention or pharmacological administration to reduce the negative effects of acute LV failure.