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

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.

Distinct roles of MIF in the pathogenesis of ischemic heart disease

The role of macrophage migration inhibitory factor (MIF) as a multifunctional cytokine in immunomodulation and inflammatory response is increasingly appreciated. Ischemic heart disease (IHD), the leading cause of global mortality, remains a focal point of research owing to its intricate pathophysiology. MIF has been identified as a critical player in IHD, where it exerts distinct roles. On one hand, MIF plays a protective role by enhancing energy metabolism through activation of AMPK, resisting oxidative stress, inhibiting activation of the JNK pathway, and maintaining intracellular calcium ion homeostasis. Additionally, MIF exerts protective effects through mesenchymal stem cells and exosomes. On the other hand, MIF can assume a pro-inflammatory role, which contributes to the exacerbation of IHD's development and progression. Furthermore, MIF levels significantly increase in IHD patients, and its genetic polymorphisms are positively correlated with prevalence and severity. These findings position MIF as a potential biomarker and therapeutic target in the management of IHD. This review summarizes the structure, source, signaling pathways and biological functions of MIF and focuses on its roles and clinical characteristics in IHD. The genetic variants of MIF associated with IHD is also discussed, providing more understandings of its complex interplay in the disease's pathology.

Comprehensive macro and micro views on immune cells in ischemic heart disease

Ischemic heart disease (IHD) is a prevalent cardiovascular condition that remains the primary cause of death due to its adverse ventricular remodelling and pathological changes in end-stage heart failure. As a complex pathologic condition, it involves intricate regulatory processes at the cellular and molecular levels. The immune system and cardiovascular system are closely interconnected, with immune cells playing a crucial role in maintaining cardiac health and influencing disease progression. Consequently, alterations in the cardiac microenvironment are influenced and controlled by various immune cells, such as macrophages, neutrophils, dendritic cells, eosinophils, and T-lymphocytes, along with the cytokines they produce. Furthermore, studies have revealed that Gata6+ pericardial cavity macrophages play a key role in regulating immune cell migration and subsequent myocardial tissue repair post IHD onset. This review outlines the role of immune cells in orchestrating inflammatory responses and facilitating myocardial repair following IHD, considering both macro and micro views. It also discusses innovative immune cell-based therapeutic strategies, offering new insights for further research on the pathophysiology of ischemic heart disease and immune cell-targeted therapy for IHD.

Analysis of the differences in immune-related genes and immune cell subtypes in acute myocardial infarction

Acute myocardial infarction (AMI) continues to be a leading cause of death globally, with distinct immune cell dynamics in ST-segment elevation myocardial infarction (STEMI) and non-ST-segment elevation myocardial infarction (NSTEMI) playing a critical role in disease progression and patient outcomes. Sample data for STEMI and NSTEMI were downloaded from the Sequence Read Archive (SRA) database (https://www.ncbi.nlm.nih.gov/sra). Differences and correlations of immune infiltrating cells were assessed by CIBERSORT. Differentially expressed genes (DEGs) were identified between STEMI and NSTEMI, followed by functional analysis. Immune-related DEGs were further identified. Some immune-related DEGs were selected to perform expression verification using real-time PCR. There was a significant difference in immune cells between STEMI and NSTEMI, including activated dendritic cells, memory CD4 T cells, mast cells, and CD8 T cells. A total of 229 DEGs were identified, with functions related to inflammatory regulation and drug metabolism. A total of 21 immune-related DEGs, which may play important roles in STEMI and NSTEMI, were identified. Among the 21 immune-related DEGs, genes like CCL18, NRP2, CXCR2, CXCL9, KIR2DL4, BPIFB1, and IL33 were significantly correlated with immune cells and had a tendency for differential expression between STEMI and NSTEMI patients. Our study reveals differences in the distribution of immune cell subsets between STEMI and NSTEMI, highlighting key immune-related genes and their association with immune cells, which may provide new insights into the treatment of AMI.

Myeloid Cells in Myocardial Ischemic Injury: The Role of the Macrophage Migration Inhibitory Factor

Ischemic heart disease, manifesting as myocardial infarction (MI), remains the leading cause of death in the western world. Both ischemia and reperfusion (I/R) cause myocardial injury and result in cardiac inflammatory responses. This sterile inflammation in the myocardium consists of multiple phases, involving cell death, tissue remodeling, healing, and scar formation, modulated by various cytokines, including the macrophage migration inhibitory factor (MIF). Meanwhile, different immune cells participate in these phases, with myeloid cells acting as first responders. They migrate to the injured myocardium and regulate the initial phase of inflammation. The MIF modulates the acute inflammatory response by affecting the metabolic profile and activity of myeloid cells. This review summarizes the role of the MIF in regulating myeloid cell subsets in MI and I/R injury and discusses emerging evidence of metabolism-directed cellular inflammatory responses. Based on the multifaceted role of the MIF affecting myeloid cells in MI or I/R, the MIF can be a therapeutic target to achieve metabolic balance under pathology and alleviate inflammation in the heart.

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

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

Multiomics analyses reveal dynamic bioenergetic pathways and functional remodeling of the heart during intermittent fasting

Intermittent fasting (IF) has been shown to reduce cardiovascular risk factors in both animals and humans, and can protect the heart against ischemic injury in models of myocardial infarction. However, the underlying molecular mechanisms behind these effects remain unclear. To shed light on the molecular and cellular adaptations of the heart to IF, we conducted comprehensive system-wide analyses of the proteome, phosphoproteome, and transcriptome, followed by functional analysis. Using advanced mass spectrometry, we profiled the proteome and phosphoproteome of heart tissues obtained from mice that were maintained on daily 12- or 16 hr fasting, every-other-day fasting, or ad libitum control feeding regimens for 6 months. We also performed RNA sequencing to evaluate whether the observed molecular responses to IF occur at the transcriptional or post-transcriptional levels. Our analyses revealed that IF significantly affected pathways that regulate cyclic GMP signaling, lipid and amino acid metabolism, cell adhesion, cell death, and inflammation. Furthermore, we found that the impact of IF on different metabolic processes varied depending on the length of the fasting regimen. Short IF regimens showed a higher correlation of pathway alteration, while longer IF regimens had an inverse correlation of metabolic processes such as fatty acid oxidation and immune processes. Additionally, functional echocardiographic analyses demonstrated that IF enhances stress-induced cardiac performance. Our systematic multi-omics study provides a molecular framework for understanding how IF impacts the heart's function and its vulnerability to injury and disease.

Trypanosoma cruzi dysregulates expression profile of piRNAs in primary human cardiac fibroblasts during early infection phase

Trypanosoma cruzi, the etiological agent of Chagas Disease, causes severe morbidity, mortality, and economic burden worldwide. Though originally endemic to Central and South America, globalization has led to increased parasite presence in most industrialized countries. About 40% of infected individuals will develop cardiovascular, neurological, and/or gastrointestinal pathologies. Accumulating evidence suggests that the parasite induces alterations in host gene expression profiles in order to facilitate infection and pathogenesis. The role of regulatory gene expression machinery during T. cruzi infection, particularly small noncoding RNAs, has yet to be elucidated. In this study, we aim to evaluate dysregulation of a class of sncRNAs called piRNAs during early phase of T. cruzi infection in primary human cardiac fibroblasts by RNA-Seq. We subsequently performed in silico analysis to predict piRNA-mRNA interactions. We validated the expression of these selected piRNAs and their targets during early parasite infection phase by stem loop qPCR and qPCR, respectively. We found about 26,496,863 clean reads (92.72%) which mapped to the human reference genome. During parasite challenge, 441 unique piRNAs were differentially expressed. Of these differentially expressed piRNAs, 29 were known and 412 were novel. In silico analysis showed several of these piRNAs were computationally predicted to target and potentially regulate expression of genes including SMAD2, EGR1, ICAM1, CX3CL1, and CXCR2, which have been implicated in parasite infection, pathogenesis, and various cardiomyopathies. Further evaluation of the function of these individual piRNAs in gene regulation and expression will enhance our understanding of early molecular mechanisms contributing to infection and pathogenesis. Our findings here suggest that piRNAs play important roles in infectious disease pathogenesis and can serve as potential biomarkers and therapeutic targets.

Peli1 deletion in macrophages attenuates myocardial ischemia/reperfusion injury by suppressing M1 polarization

The polarization of macrophages to the M1 or M2 phenotype has a pivotal role in inflammatory response following myocardial ischemia/reperfusion injury. Peli1, an E3 ubiquitin ligase, is closely associated with inflammation and autoimmunity as an important regulatory protein in the Toll-like receptor signaling pathway. We aimed to explore the function of Peli1 in macrophage polarization under myocardial ischemia/reperfusion injury and elucidate the possible mechanisms. We show here that Peli1 is upregulated in peripheral blood mononuclear cells from patients with myocardial ischemia/reperfusion, which is correlated with myocardial injury and cardiac dysfunction. We also found that the proportion of M1 macrophages was reduced and myocardial infarct size was decreased, paralleling improvement of cardiac function in mice with Peli1 deletion in hematopoietic cells or macrophages. Macrophage Peli1 deletion lessened M1 polarization and reduced the migratory ability in vitro. Mechanistically, Peli1 contributed to M1 polarization by promoting K63-linked ubiquitination and nuclear translocation of IRF5. Moreover, Peli1 deficiency in macrophages reduced the apoptosis of cardiomyocytes in vivo and in vitro. Together, our study demonstrates that Peli1 deficiency in macrophages suppresses macrophage M1 polarization and alleviates myocardial ischemia/reperfusion injury by inhibiting the nuclear translocation of IRF5, which may serve as a potential intervention target for myocardial ischemia/reperfusion injury.

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.

D-dopachrome tautomerase in cardiovascular and inflammatory diseases-A new kid on the block or just another MIF?

Macrophage migration inhibitory factor (MIF) as well as its more recently described structural homolog D-dopachrome tautomerase (D-DT), now also termed MIF-2, are atypical cytokines and chemokines with key roles in host immunity. They also have an important pathogenic role in acute and chronic inflammatory conditions, cardiovascular diseases, lung diseases, adipose tissue inflammation, and cancer. Although our mechanistic understanding of MIF-2 is relatively limited compared to the extensive body of evidence available for MIF, emerging data suggests that MIF-2 is not only a functional phenocopy of MIF, but may have differential or even oppositional activities, depending on the disease and context. In this review, we summarize and discuss the similarities and differences between MIF and MIF-2, with a focus on their structures, receptors, signaling pathways, and their roles in diseases. While mainly covering the roles of the MIF homologs in cardiovascular, inflammatory, autoimmune, and metabolic diseases, we also discuss their involvement in cancer, sepsis, and chronic obstructive lung disease (COPD). A particular emphasis is laid upon potential mechanistic explanations for synergistic or cooperative activities of the MIF homologs in cancer, myocardial diseases, and COPD as opposed to emerging disparate or antagonistic activities in adipose tissue inflammation, metabolic diseases, and atherosclerosis. Lastly, we discuss potential future opportunities of jointly targeting MIF and MIF-2 in certain diseases, whereas precision targeting of only one homolog might be preferable in other conditions. Together, this article provides an update of the mechanisms and future therapeutic avenues of human MIF proteins with a focus on their emerging, surprisingly disparate activities, suggesting that MIF-2 displays a variety of activities that are distinct from those of MIF.

Identification of novel tumor microenvironment-associated genes in gastric cancer based on single-cell RNA-sequencing datasets

Tumor microenvironment and heterogeneity play vital roles in the development and progression of gastric cancer (GC). In the past decade, a considerable amount of single-cell RNA-sequencing (scRNA-seq) studies have been published in the fields of oncology and immunology, which improve our knowledge of the GC immune microenvironment. However, much uncertainty still exists about the relationship between the macroscopic and microscopic data in transcriptomics. In the current study, we made full use of scRNA-seq data from the Gene Expression Omnibus database (GSE134520) to identify 25 cell subsets, including 11 microenvironment-related cell types. The MIF signaling pathway network was obtained upon analysis of receptor–ligand pairs and cell–cell interactions. By comparing the gene expression in a wide variety of cells between intestinal metaplasia and early gastric cancer, we identified 64 differentially expressed genes annotated as immune response and cellular communication. Subsequently, we screened these genes for prognostic clinical value based on the patients’ follow-up data from The Cancer Genome Atlas. TMPRSS15, VIM, APOA1, and RNASE1 were then selected for the construction of LASSO risk scores, and a nomogram model incorporating another five clinical risk factors was successfully created. The effectiveness of least absolute shrinkage and selection operator risk scores was validated using gene set enrichment analysis and levels of immune cell infiltration. These findings will drive the development of prognostic evaluations affected by the immune tumor microenvironment in GC.

CCR6 Deficiency Increases Infarct Size after Murine Acute Myocardial Infarction

Ischemia-reperfusion injury after the reopening of an occluded coronary artery is a major cause of cardiac damage and inflammation after acute myocardial infarction. The chemokine axis CCL20-CCR6 is a key player in various inflammatory processes, including atherosclerosis; however, its role in ischemia-reperfusion injury has remained elusive. Therefore, to gain more insight into the role of the CCR6 in acute myocardial infarction, we have studied cardiac injury after transient ligation of the left anterior descending coronary artery followed by reperfusion in Ccr6-/- mice and their respective C57Bl/6 wild-type controls. Surprisingly, Ccr6-/- mice demonstrated significantly reduced cardiac function and increased infarct sizes after ischemia/reperfusion. This coincided with a significant increase in cardiac inflammation, characterized by an accumulation of neutrophils and inflammatory macrophage accumulation. Chimeras with a bone marrow deficiency of CCR6 mirrored this adverse Ccr6-/- phenotype, while cardiac injury was unchanged in chimeras with stromal CCR6 deficiency. This study demonstrates that CCR6-dependent (bone marrow) cells exert a protective role in myocardial infarction and subsequent ischemia-reperfusion injury, supporting the notion that augmenting CCR6-dependent immune mechanisms represents an interesting therapeutic target.

Association of Circulating, Inflammatory-Response Exosomal mRNAs With Acute Myocardial Infarction

Background: Although many cardiovascular disease studies have focused on the microRNAs of circulating exosomes, the profile and the potential clinical diagnostic value of plasma exosomal long RNAs (exoLRs) are unknown for acute myocardial infarction (AMI).

Methods: In this study, the exoLR profile of 10 AMI patients, eight stable coronary artery disease (CAD) patients, and 10 healthy individuals was assessed by RNA sequencing. Bioinformatic approaches were used to investigate the characteristics and potential clinical value of exoLRs.

Results: Exosomal mRNAs comprised the majority of total exoLRs. Immune cell types analyzed by CIBERSORT showed that neutrophils and monocytes were significantly enriched in AMI patients, consistent with clinical baseline values. Biological process enrichment analysis and co-expression network analysis demonstrated neutrophil activation processes to be enriched in AMI patients. Furthermore, two exosomal mRNAs, ALPL and CXCR2, were identified as AMI biomarkers that may be useful for evaluation of the acute inflammatory response mediated by neutrophils.

Conclusions: ExoLRs were assessed in AMI patients and found to be associated with the acute inflammatory response mediated by neutrophils. Exosomal mRNAs, ALPL and CXCR2, were identified as potentially useful biomarkers for the study of AMI.

Vascular and Cardiac Oxidative Stress and Inflammation as Targets for Cardioprotection

Cardiac and vascular diseases are often associated with increased oxidative stress and inflammation, and both may contribute to the disease progression. However, successful applications of antioxidants in the clinical setting are very rare and specific anti-inflammatory therapeutics only emerged recently. Reasons for this rely on the great diversity of oxidative stress and inflammatory cells that can either act as cardioprotective or cause tissue damage in the heart. Recent large-scale clinical trials found that highly specific anti-inflammatory therapies using monoclonal antibodies against cytokines resulted in lower cardiovascular mortality in patients with pre-existing atherosclerotic disease. In addition, unspecific antiinflammatory medication and established cardiovascular drugs with pleiotropic immunomodulatory properties such as angiotensin converting enzyme (ACE) inhibitors or statins have proven beneficial cardiovascular effects. Normalization of oxidative stress seems to be a common feature of these therapies, which can be explained by a close interaction/crosstalk of the cellular redox state and inflammatory processes. In this review, we give an overview of cardiac reactive oxygen species (ROS) sources and processes of cardiac inflammation as well as the connection of ROS and inflammation in ischemic cardiomyopathy in order to shed light on possible cardioprotective interventions.

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

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

Lack of Macrophage Migration Inhibitory Factor Reduces Susceptibility to Ventricular Arrhythmias During the Acute Phase of Myocardial Infarction

Background

Macrophages are involved in inflammatory responses and play a crucial role in aggravating ventricular arrhythmias (VAs) after myocardial infarction (MI). Macrophage migration inhibitory factor (MIF) participates in inflammatory responses during acute MI. In the present study, we hypothesized that knockout (KO) of MIF may prevent VAs during the acute phase of MI by inhibiting macrophage-derived pro-inflammatory mediators.

Methods and Results

We demonstrated that MIF-KO mice in a mouse model of MI exhibited a significant decrease in susceptibility to VAs both in vivo (84.6% vs 40.7%, P < 0.05) and ex vivo (86.7% vs 40.0%, P < 0.05) at day 3 after MI compared with that in wild-type (WT) mice. Both WT and MIF-KO mice presented similar left ventricular contractility, peri-infarct myocardial fibrosis and sympathetic reinnervation, and circulating and local norepinephrine levels during the acute phase of MI. Meanwhile, MIF-KO mice had inhibited macrophage aggregation, alleviated connexin 43 (Cx43) redistribution, and reduced level of pro-inflammatory mediators, including tumor necrosis factor-α and interleukin-1β (P < 0.05) at day 3 after MI. The differences in susceptibility to VAs, expression of pro-inflammatory mediators, and Cx43 redistribution after MI between WT and MIF-KO mice disappeared by macrophage depletion with clodronate liposomes in both groups. Furthermore, the pro-inflammatory activity of cultured peritoneal macrophages was inhibited by MIF deficiency and recovered with replenishment of exogenous MIF in vitro.

Conclusion

In conclusion, we found that lack of MIF reduced the susceptibility to VAs in mouse heart during the acute phase of MI by inhibiting pro-inflammatory activity of macrophages and improving gap-junction and electrical remodeling.

Association between microRNA binding site polymorphisms in immunoinflammatory genes and recurrence risk of ischemic stroke

MicroRNA binding site polymorphisms in immunoinflammatory genes have been implicated as candidate biomarkers for prediction of complex human diseases. However, the roles of microRNA binding site polymorphisms in stroke onset and prognosis remain unclear. Thus, for the first time, five potential functional polymorphisms in immunoinflammatory genes (CXCR2 rs1126579, TLR4 rs11536889, ADIPOR2 rs12342, MMP-2 rs7201 and MMP-9 rs1056628) were genotyped in 657 patients with ischemic stroke. These five polymorphisms were not related with age onset of ischemic stroke. However, we found that ADIPOR2 rs12342 was significantly associated with a decreased recurrence risk, especially for the patients with small-vessel disease. Moreover, by using multivariate Cox regression, the variant genotype GG/GA of rs12342 was observed as an independent protective factor for stroke recurrence, even after Bonferroni correction. In addition, after the addition of rs12342 in the model with clinical factors, the new model showed the improved discriminatory ability to predict stroke recurrence. In short, our results suggested that ADIPOR2 rs12342 may be a novel genetic biomarker and therapeutic target for ischemic stroke recurrence. Further studies are required to replicate our findings and clarify the potential biological mechanism.

The protective role of macrophage migration inhibitory factor in acute kidney injury after cardiac surgery

Acute kidney injury (AKI) represents the most frequent complication after cardiac surgery. Macrophage migration inhibitory factor (MIF) is a stress-regulating cytokine that was shown to protect the heart from myocardial ischemia-reperfusion injury, but its role in the pathogenesis of AKI remains unknown. In an observational study, serum and urinary MIF was quantified in 60 patients scheduled for elective conventional cardiac surgery with the use of cardiopulmonary bypass. Cardiac surgery triggered an increase in MIF serum concentrations, and patients with high circulating MIF (>median) 12 hours after surgery had a significantly reduced risk of developing AKI (relative risk reduction, 72.7%; 95% confidence interval, 12 to 91.5%; P = 0.03). Experimental AKI was induced in wild-type and Mif^-/- mice by 30 min of ischemia followed by 6 or 24 hours of reperfusion, or by rhabdomyolysis. Mif-deficient mice exhibited increased tubular cell injury, increased regulated cell death (necroptosis and ferroptosis), and enhanced oxidative stress. Therapeutic administration of recombinant MIF after ischemia-reperfusion in mice ameliorated AKI. In vitro treatment of tubular epithelial cells with recombinant MIF reduced cell death and oxidative stress as measured by glutathione and thiobarbituric acid reactive substances in the setting of hypoxia. Our data provide evidence of a renoprotective role of MIF in experimental ischemia-reperfusion injury by protecting renal tubular epithelial cells, consistent with our observation that high MIF in cardiac surgery patients is associated with a reduced incidence of AKI.

Immune cells as targets for cardioprotection: new players and novel therapeutic opportunities

New therapies are required to reduce myocardial infarct (MI) size and prevent the onset of heart failure in patients presenting with acute myocardial infarction (AMI), one of the leading causes of death and disability globally. In this regard, the immune cell response to AMI, which comprises an initial pro-inflammatory reaction followed by an anti-inflammatory phase, contributes to final MI size and post-AMI remodelling [changes in left ventricular (LV) size and function]. The transition between these two phases is critical in this regard, with a persistent and severe pro-inflammatory reaction leading to adverse LV remodelling and increased propensity for developing heart failure. In this review article, we provide an overview of the immune cells involved in orchestrating the complex and dynamic inflammatory response to AMI-these include neutrophils, monocytes/macrophages, and emerging players such as dendritic cells, lymphocytes, pericardial lymphoid cells, endothelial cells, and cardiac fibroblasts. We discuss potential reasons for past failures of anti-inflammatory cardioprotective therapies, and highlight new treatment targets for modulating the immune cell response to AMI, as a potential therapeutic strategy to improve clinical outcomes in AMI patients. This article is part of a Cardiovascular Research Spotlight Issue entitled 'Cardioprotection Beyond the Cardiomyocyte', and emerged as part of the discussions of the European Union (EU)-CARDIOPROTECTION Cooperation in Science and Technology (COST) Action, CA16225.

Chemokines as Therapeutic Targets in Cardiovascular Disease

With the incidence and impact of atherosclerotic cardiovascular disease and its clinical manifestations still rising, therapeutic options that target the causal mechanisms of this disorder are highly desired. Since the CANTOS trial (Canakinumab Antiinflammatory Thrombosis Outcome Study) has demonstrated that lowering inflammation can be beneficial, focusing on mechanisms underlying inflammation, for example, leukocyte recruitment, is feasible. Being key orchestrators of leukocyte trafficking, chemokines have not lost their attractiveness as therapeutic targets, despite the difficult road to drug approval thus far. Still, innovative therapeutic approaches are being developed, paving the road towards the first chemokine-based therapeutic against inflammation. In this overview, recent developments for chemokines and for the chemokine-like factor MIF (macrophage migration inhibitory factor) will be discussed.

Correlation between Plasma Macrophage Migration Inhibitory Factor Levels and Long-Term Prognosis in Patients with Acute Myocardial Infarction Complicated with Diabetes

Macrophage migration inhibitory factor (MIF), a widely expressed pleiotropic cytokine, is reportedly involved in several cardiovascular diseases, in addition to inflammatory diseases. Plasma MIF levels are elevated in the early phase of acute cardiac infarction. This study is aimed at investigating the correlation between plasma MIF levels and cardiac function and prognosis in patients with acute ST-segment elevation myocardial infarction (STEMI) with or without diabetes mellitus. Overall, 204 patients with STEMI who underwent emergency percutaneous coronary intervention were enrolled: 57 and 147 patients in the diabetes and nondiabetes STEMI groups, respectively. Sixty-five healthy people were selected as controls. Plasma MIF levels were measured at the time of diagnosis. Basic clinical data and echocardiographic findings within 72 h of admission were collected. Patients were followed up, and echocardiograms were reviewed at the 12-month follow-up. Plasma MIF levels were significantly higher in the diabetes and nondiabetes STEMI groups than in the control group and in patients with Killip grade ≥ II STEMI than in those with Killip grade I. Plasma MIF levels were negatively correlated with the left ventricular ejection fraction (LVEF) of myocardial infarction in patients with or without diabetes in the acute phase of infarction, whereas the left ventricular diastolic dysfunction (LVDD) was positively correlated. MIF levels in the nondiabetes STEMI group were positively correlated with N-terminal pro-b-type natriuretic peptide levels and were associated with LVEF and LVDD at the 12-month follow-up. The risk of adverse cardiovascular and cerebrovascular events was significantly higher in the MIF high-level group (≥52.7 ng/mL) than in the nondiabetes STEMI group 36 months after presentation. Thus, MIF levels in STEMI patients with or without diabetes can reflect acute cardiac function. In STEMI patients without diabetes, MIF levels can also indicate cardiac function and long-term prognosis at the 12-month follow-up.

The pretreatment of chronic restraint stress exerts little impact on the progression of heart failure in mice

Stress is a potent risk factor for depression. Chronic stress can exacerbate and induce symptoms of depression. Clinical studies suggested that depressive patients are more likely to develop coronary artery diseases. However, the causal relationship between depression and heart failure progression remains unclear. In this study, we aimed to explore the relevance between stress and heart failure (HF) in a mouse model subjected to chronic restraint stress and left anterior descending coronary artery (LAD) ligation. Mice were restrained for 3 h daily for 21 days and the processes were repeated once 3 months later. After the repeated chronic restraint stress, mice showed dramatically increased immobility time in the forced swim test, indicating a state of despair. Restrained and control mice were further subjected to LAD ligation surgery. Echocardiography was conducted 1 week, 2 weeks, and 1 month afterward. LAD-operated mice showed a significant decrease in the values of left ventricular ejection fraction (LVEF), and there was no difference in the LVEF values between the restrained and control mice. Relevant gene expression, neurotransmitter system, glial activation, and morphology of the heart-brain axis were comprehensively evaluated. We found no overall differences between the restrained and control mice with HF. Our results revealed that the repeated chronic restraint stress may have little effects on the progression of heart failure.

Admission macrophage migration inhibitory factor predicts long-term prognosis in patients with ST-elevation myocardial infarction

Aims

We previously showed in patients with ST-segment elevated myocardial infarction (STEMI) that admission levels of macrophage migration inhibitory factor (MIF) predict infarct size. We studied whether admission MIF alone or in combination with other biomarkers is useful for risk assessment of acute and chronic clinical outcomes in STEMI patients.

Methods and results

A total of 658 STEMI patients treated with primary percutaneous coronary intervention (PCI) were consecutively recruited. MIF level was determined at admission and echocardiography performed on day-3 and then 12 months post-MI. Patients were followed for a median period of 64 months. Major endpoints included ST-segment resolution, all-cause mortality, and major adverse cardiovascular events (MACE). High MIF level was associated with larger enzymatic infarct size, incomplete resolution of ST-segment elevation post-PCI, impaired left ventricular ejection fraction (LVEF), and poorer improvement of LVEF (all P < 0.001). After adjustment for classical risk factors standard biomarkers and day-3 LVEF, admission MIF remained independently prognostic for all-cause mortality [hazard ratio (HR) 2.27, 95% confidence interval (CI) 1.43-3.22], and MACE (HR 1.39, 95% CI 1.12-1.71, both P < 0.05). MIF was a significant additive predictor of all-cause mortality with a net reclassification improvement of 0.34 (P = 0.02). Furthermore, patients in high tertile of both admission MIF and day-3 Nt-proBNP had the highest mortality risk relative to other tertile groups (HR 11.28, 95% CI 4.82-26.94; P < 0.001).

Conclusion

STEMI patients with high admission MIF level experienced a poorer recovery of cardiac function and worse long-term adverse outcomes. Combination of Nt-proBNP with MIF further improves prognostic capability.

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.

Translational overview of cytokine inhibition in acute myocardial infarction and chronic heart failure

Many cytokines are currently under investigation as potential target to improve cardiac function and outcome in the setting of acute myocardial infarction (MI) or chronic heart failure (HF). Here we aim to provide a translational overview of cytokine inhibiting therapies tested in experimental models and clinical studies. In various experimental studies, inhibition of interleukin-1 (IL-1), -6 (IL-6), -8 (IL-8), monocyte chemoattractant protein-1 (MCP-1), CC- and CXC chemokines, and tumor necrosis factor-α (TNF-α) had beneficial effects on cardiac function and outcome. On the other hand, neutral or even detrimental results have been reported for some (IL-1, IL-6, IL-8, and MCP-1). Ambivalence of cytokine function, differences in study designs, treatment regimens and chosen endpoints hamper the translation of experimental research into clinical practice. Human studies are currently limited to IL-1β inhibition, IL-1 receptor antagonists (IL-1RA), IL-6 receptor antagonists (IL-6RA) or TNF inhibition. Despite favorable effects on cardiovascular events observed in retrospective cohort studies of rheumatoid arthritis patients treated with TNF inhibition or IL-1RA, most prospective studies reported disappointing and inconsistent results. Smaller studies (n < 100) generally reported favorable results of anticytokine therapy on cardiac function, but only one of the larger studies (n > 100) evaluating IL-1β inhibition presented positive results on outcome. In conclusion, of the 10 anticytokine therapies tested in animals models beneficial effects have been reported in at least one setting. In larger clinical studies, findings were unsatisfactory in all but one. Many anticytokine therapies with promising animal experimental data continue to require further evaluation in humans.

Red blood cells: The primary reservoir of macrophage migration inhibitory factor in whole blood

Red blood cells are widely accepted to be inert carriers of oxygen and haemoglobin, but there is growing evidence that they play a much more critical role in immune function. Macrophage migration inhibitory factor (MIF) is a key cytokine in disease with additional oxido-reductase activity, which aids in managing oxidative stress. Although two studies have reported the presence of MIF in red blood cells, no study has quantified the levels of this protein. In this study, freshly isolated plasma, platelets, leukocytes, and red blood cells from healthy individuals were collected and the concentration of MIF was determined using an enzyme linked immunosorbent assay. This analysis demonstrated that MIF in red blood cells was present at 25 µg per millilitre of whole blood, which is greater than99% of the total MIF and 1000-fold higher concentration than plasma. This result was supported by electrophoresis and Western blot analysis, which identified MIF in its monomer structural form following sample processing. Furthermore, by assessing the level of tautomerase activity in red blood cell fractions in the presence of a MIF inhibitor, it was determined that the red blood cell-derived MIF was also functionally active. Together, these findings have implications on the effect of haemolysis during sample preparation and provide some clue into the inflammatory processes that occur following haemolysis in vivo. These results support the hypothesis that red blood cells are a major reservoir of this inflammatory protein and may play a role in inflammation.

Role of MIF/CD74 signaling pathway in the development of pleural mesothelioma

Macrophage migration inhibitory factor (MIF) is a pro-inflammatory cytokine implicated in acute and chronic inflammatory diseases. MIF is overexpressed in various tumors. It displays a number of functions that provide a direct link between the process of inflammation and tumor growth. Our group recently identified the MIF-receptor CD74 as an independent prognostic factor for overall survival in patients with malignant pleural mesothelioma.

In the present study, we compared the levels of expression of MIF and CD74 in different human mesothelioma cell lines and investigated their physiopathological functions in vitro and in vivo.

Human mesothelioma cells expressed more CD74 and secreted less MIF than non tumoral MeT5A cells, suggesting a higher sensitivity to MIF. In mesothelioma cells, high MIF levels were associated with a high multiplication rate of cells. In vitro, reduction of MIF or CD74 levels in both mesothelioma cell lines showed that the MIF/CD74 signaling pathway promoted tumor cell proliferation and protected MPM cells from apoptosis. Finally, mesothelioma cell lines expressing high CD74 levels had a low tumorigenic potential after xenogeneic implantation in athymic nude mice.

All these data highlight the complexity of the MIF/CD74 signaling pathway in the development of mesothelioma.

MIF Inhibitor ISO-1 Protects Photoreceptors and Reduces Gliosis in Experimental Retinal Detachment

Photoreceptor death and retinal gliosis underlie the majority of vision threatening retinal diseases including retinal detachment (RD). Although the underlying pathobiology of vision limiting processes in RD is not fully understood, inflammation is known to play a critical role. We conducted an iTRAQ proteomic screen of up- and down-regulated proteins in a murine model of RD to identify potential targetable candidates. Macrophage migration inhibitory factor (MIF) was identified and evaluated for neurotoxic and pro-gliotic effects during RD. Systemic administration of the MIF inhibitor ISO-1 significantly blocked photoreceptor apoptosis, outer nuclear layer (ONL) thinning, and retinal gliosis. ISO-1 and MIF knockout (MIFKO) had greater accumulation of Müller glia pERK expression in the detached retina, suggesting that Müller survival pathways might underlie the neuroprotective response. Our data show the feasibility of the MIF-inhibitor ISO-1 to block pathological damage responses in retinal detachment and provide a rationale to explore MIF inhibition as a potential therapeutic option for RD.

Macrophage Migration Inhibitory Factor Limits Renal Inflammation and Fibrosis by Counteracting Tubular Cell Cycle Arrest

Renal fibrosis is a common underlying process of progressive kidney diseases. We investigated the role of macrophage migration inhibitory factor (MIF), a pleiotropic proinflammatory cytokine, in this process. In mice subjected to unilateral ureteral obstruction, genetic deletion or pharmacologic inhibition of MIF aggravated fibrosis and inflammation, whereas treatment with recombinant MIF was beneficial, even in established fibrosis. In two other models of progressive kidney disease, global Mif deletion or MIF inhibition also worsened fibrosis and inflammation and associated with worse kidney function. Renal MIF expression was reduced in tubular cells in fibrotic compared with healthy murine and human kidneys. Bone marrow chimeras showed that Mif expression in bone marrow-derived cells did not affect fibrosis and inflammation after UUO. However, Mif gene deletion restricted to renal tubular epithelial cells aggravated these effects. In LPS-stimulated tubular cell cultures, Mif deletion led to enhanced G2/M cell-cycle arrest and increased expression of the CDK inhibitor 1B (p27Kip1) and of proinflammatory and profibrotic mediators. Furthermore, MIF inhibition reduced tubular cell proliferation in vitro In all three in vivo models, global Mif deletion or MIF inhibition caused similar effects and attenuated the expression of cyclin B1 in tubular cells. Mif deletion also resulted in reduced tubular cell apoptosis after UUO. Recombinant MIF exerted opposing effects on tubular cells in vitro and in vivo Our data identify renal tubular MIF as an endogenous renoprotective factor in progressive kidney diseases, raising the possibility of pharmacologic intervention with MIF pathway agonists, which are in advanced preclinical development.

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.

Exogenous Administration of Recombinant MIF at Physiological Concentrations Failed to Attenuate Infarct Size in a Langendorff Perfused Isolated Mouse Heart Model

Purpose

Evidence suggests a two-pronged role of endogenous macrophage migration inhibitory factor (MIF) release in ischemia/reperfusion injury. We aimed to assess whether its exogenous administration confers cardioprotection.

Methods

Male C57/BL6 mice were randomly allocated to receive recombinant mouse MIF (rMIF) at physiological (ng/mL) concentrations in a dose–response fashion before or after a protocol of 35 min of ischemia and 2 h of reperfusion in an isolated Langendorff-perfused model with infarct size as endpoint. Isolated primary cardiomyocytes were also used for cell survival studies using rMIF at a supra-physiological concentration of 1 μg/mL. Pro-survival kinase activation was also studied using Western blot analyses.

Results

Exogenous MIF did not elicit a cardioprotective effect either when administered before the ischemic insult or when applied at reperfusion. rMIF did not confer protection when it was applied immediately before or after a hypoxia/reoxygenation insult in primary isolated cardiomyocytes. Consistently, hearts treated with MIF did not show a significant increase in phosphorylated Akt and ERK1/2.

Conclusion

The exogenous administration of rMIF in a physiological concentration range both before ischemia and at reperfusion did not show cardioprotective effects. Although these results do not address the role of endogenous MIF after an ischemic insult followed by reperfusion, they may limit the potential translational value of rMIF.

Cardiomyocyte Hypertrophy in Arrhythmogenic Cardiomyopathy

Arrhythmogenic cardiomyopathy (AC) is a hereditary disease leading to sudden cardiac death or heart failure. AC pathology is characterized by cardiomyocyte loss and replacement fibrosis. Our goal was to determine whether cardiomyocytes respond to AC progression by pathological hypertrophy. To this end, we examined tissue samples from AC patients with end-stage heart failure and tissue samples that were collected at different disease stages from desmoglein 2-mutant mice, a well characterized AC model. We find that cardiomyocyte diameters are significantly increased in right ventricles of AC patients. Increased mRNA expression of the cardiac stress marker natriuretic peptide B is also observed in the right ventricle of AC patients. Elevated myosin heavy chain 7 mRNA expression is detected in left ventricles. In desmoglein 2-mutant mice, cardiomyocyte diameters are normal during the concealed disease phase but increase significantly after acute disease onset on cardiomyocyte death and fibrotic myocardial remodeling. Hypertrophy progresses further during the chronic disease stage. In parallel, mRNA expression of myosin heavy chain 7 and natriuretic peptide B is up-regulated in both ventricles with right ventricular preference. Calcineurin/nuclear factor of activated T cells (Nfat) signaling, which is linked to pathological hypertrophy, is observed during AC progression, as evidenced by Nfatc2 and Nfatc3 mRNA in cardiomyocytes and increased mRNA of the Nfat target regulator of calcineurin 1. Taken together, we demonstrate that pathological hypertrophy occurs in AC and is secondary to cardiomyocyte loss and cardiac remodeling.

Characterization of adipose tissue macrophages and adipose-derived stem cells in critical wounds

Background

Subcutaneous adipose tissue is a rich source of adipose tissue macrophages and adipose-derived stem cells which both play a key role in wound repair. While macrophages can be divided into the classically-activated M1 and the alternatively-activated M2 phenotype, ASCs are characterized by the expression of specific stem cell markers.

Methods

In the present study, we have investigated the expression of common macrophage polarization and stem cell markers in acutely inflamed adipose tissue. Subcutaneous adipose tissue adjacent to acutely inflamed wounds of 20 patients and 20 healthy subjects were harvested and underwent qPCR and flow cytometry analysis.

Results

Expression levels of the M1-specific markers CD80, iNOS, and IL-1b were significantly elevated in inflammatory adipose tissue when compared to healthy adipose tissue, whereas the M2-specific markers CD163 and TGF-β were decreased. By flow cytometry, a significant shift of adipose tissue macrophage populations towards the M1 phenotype was confirmed. Furthermore, a decrease in the mesenchymal stem cell markers CD29, CD34, and CD105 was observed whereas CD73 and CD90 remained unchanged.

Discussion

This is the first report describing the predominance of M1 adipose tissue macrophages and the reduction of stem cell marker expression in acutely inflamed, non-healing wounds.

The time-of-day of myocardial infarction onset affects healing through oscillations in cardiac neutrophil recruitment

Myocardial infarction (MI) is the leading cause of death in Western countries. Epidemiological studies show acute MI to be more prevalent in the morning and to be associated with a poorer outcome in terms of mortality and recovery. The mechanisms behind this association are not fully understood. Here, we report that circadian oscillations of neutrophil recruitment to the heart determine infarct size, healing, and cardiac function after MI. Preferential cardiac neutrophil recruitment during the active phase (Zeitgeber time, ZT13) was paralleled by enhanced myeloid progenitor production, increased circulating numbers of CXCR2^hi neutrophils as well as upregulated cardiac adhesion molecule and chemokine expression. MI at ZT13 resulted in significantly higher cardiac neutrophil infiltration compared to ZT5, which was inhibited by CXCR2 antagonism or neutrophil‐specific CXCR2 knockout. Limiting exaggerated neutrophilic inflammation at this time point significantly reduced the infarct size and improved cardiac function.

Serum macrophage migration inhibitory factor levels are associated with infarct volumes and long-term outcomes in patients with acute ischemic stroke

PURPOSE

Previous studies have shown that macrophage migration inhibition factor (MIF) plays a significant role in stroke. The aim of this study was to investigate the association of the serum MIF level with both infarct volume and long-term outcome in patients with acute ischemic stroke (AIS).

METHODS

This study included 146 patients who were identified within 24 h of first experiencing AIS symptoms. Serum MIF levels were tested at the time of admission and three months later. Logistic regression was used to evaluate the risk and long-term outcome of stroke according to serum MIF level.

RESULTS

Serum MIF levels were only higher in acute-stage AIS patients compared with those of the normal controls (p < 0.0001). Chronic-stage serum MIF levels were significantly lower than acute-stage serum MIF levels (p < 0.001) and were similar to serum MIF levels in the controls (p = 0.392). The serum MIF level was positively associated with infarct volume (r = 0.5515, p < 0.0001) and NIHSS score (r = 0.5190, p < 0.0001). After adjusting for other significant outcome predictors, the serum MIF level was an independent predictor of long-term outcome, with an adjusted OR of 1.113 (p = 0.005, 95% CI: 1.051-1.238).

CONCLUSIONS

This study demonstrated that serum MIF levels were significantly increased after AIS. Serum MIF levels at admission were positively correlated with infarct volume and long-term outcome in patients with AIS. The serum MIF level could serve as a useful prognostic marker in patients with AIS.

Pathophysiology of cancer therapy-provoked atrial fibrillation

Atrial fibrillation (AF) occurs with increased frequency in cancer patients, especially in patients who undergo surgery or chemotherapy. AF disturbs the prognosis of cancer patients and challenges therapeutic outcomes of cancer treatment. Elucidating the mechanisms of cancer-induced AF would help identify specific strategies for preventing AF occurrence. In addition to concurrent risk factors of cancer and AF, cancer surgery, side effects of anticancer agents, and cancer-associated immune responses play critical roles in the genesis of AF. In this review, we provide succinct potential mechanisms of AF genesis in cancer patients.

Macrophage Migration Inhibitory Factor Mediates Proliferative GN via CD74

Pathologic proliferation of mesangial and parietal epithelial cells (PECs) is a hallmark of various glomerulonephritides. Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine that mediates inflammation by engagement of a receptor complex involving the components CD74, CD44, CXCR2, and CXCR4. The proliferative effects of MIF may involve CD74 together with the coreceptor and PEC activation marker CD44. Herein, we analyzed the effects of local glomerular MIF/CD74/CD44 signaling in proliferative glomerulonephritides. MIF, CD74, and CD44 were upregulated in the glomeruli of patients and mice with proliferative glomerulonephritides. During disease, CD74 and CD44 were expressed de novo in PECs and colocalized in both PECs and mesangial cells. Stress stimuli induced MIF secretion from glomerular cells in vitro and in vivo, in particular from podocytes, and MIF stimulation induced proliferation of PECs and mesangial cells via CD74. In murine crescentic GN, Mif-deficient mice were almost completely protected from glomerular injury, the development of cellular crescents, and the activation and proliferation of PECs and mesangial cells, whereas wild-type mice were not. Bone marrow reconstitution studies showed that deficiency of both nonmyeloid and bone marrow-derived Mif reduced glomerular cell proliferation and injury. In contrast to wild-type mice, Cd74-deficient mice also were protected from glomerular injury and ensuing activation and proliferation of PECs and mesangial cells. Our data suggest a novel molecular mechanism and glomerular cell crosstalk by which local upregulation of MIF and its receptor complex CD74/CD44 mediate glomerular injury and pathologic proliferation in GN.

The CXCR1/2 Pathway: Involvement in Diabetes Pathophysiology and Potential Target for T1D Interventions

Although numerous chemokine/chemokine receptor pathways have been described to be implicated in the pathogenesis of type 1 diabetes (T1D), the CXCR1/2 axis has recently been proved to be crucial for leucocyte recruitment involved in insulitis and β cell damage. Multiple strategies blocking the CXCR1/2 pathway are available such as neutralizing antibodies, small molecules and peptide-derived inhibitors. They were firstly and widely used in cancer thanks to their anti-tumorigenic activity and only recently they were tested as a new interventional approach for T1D. As well, CXCR1/2 inhibition has been demonstrated to prevent inflammation- and autoimmunity-mediated damage of the pancreatic islets through inhibiting the migration of CXCR1/2-expressing cells. Among them, neutrophils, macrophages, and, although to a smaller extent, lymphoid cells are the main CXCR1/2-expressing cells. These results supported the active role of the innate immunity in the autoimmune process and opened new interventional approaches for the management of T1D.

An Analysis of MIF Structural Features that Control Functional Activation of CD74

For more than 15 years, the tautomerase active site of macrophage migration inhibitory factor (MIF) and its catalytic residue Pro1 have been being targeted for the development of therapeutics that block activation of its cell surface receptor, CD74. Neither the biological role of the MIF catalytic site nor the mechanistic details of CD74 activation are well understood. The inherently unstable structure of CD74 remains the biggest obstacle in structural studies with MIF for understanding the basis of CD74 activation. Using a novel approach, we elucidate the mechanistic details that control activation of CD74 by MIF surface residues and identify structural parameters of inhibitors that reduce CD74 biological activation. We also find that N-terminal mutants located deep in the catalytic site affect surface residues immediately outside the catalytic site, which are responsible for reduction of CD74 activation.

Diversity and Inter-Connections in the CXCR4 Chemokine Receptor/Ligand Family: Molecular Perspectives

CXCR4 and its ligand CXCL12 mediate the homing of progenitor cells in the bone marrow and their recruitment to sites of injury, as well as affect processes such as cell arrest, survival, and angiogenesis. CXCL12 was long thought to be the sole CXCR4 ligand, but more recently the atypical chemokine macrophage migration inhibitory factor (MIF) was identified as an alternative, non-cognate ligand for CXCR4 and shown to mediate chemotaxis and arrest of CXCR4-expressing T-cells. This has complicated the understanding of CXCR4-mediated signaling and associated biological processes. Compared to CXCL12/CXCR4-induced signaling, only few details are known on MIF/CXCR4-mediated signaling and it remains unclear to which extent MIF and CXCL12 reciprocally influence CXCR4 binding and signaling. Furthermore, the atypical chemokine receptor 3 (ACKR3) (previously CXCR7) has added to the complexity of CXCR4 signaling due to its ability to bind CXCL12 and MIF, and to evoke CXCL12- and MIF-triggered signaling independently of CXCR4. Also, extracellular ubiquitin (eUb) and the viral protein gp120 (HIV) have been reported as CXCR4 ligands, whereas viral chemokine vMIP-II (Herpesvirus) and human β3-defensin (HBD-3) have been identified as CXCR4 antagonists. This review will provide insight into the diversity and inter-connections in the CXCR4 receptor/ligand family. We will discuss signaling pathways initiated by binding of CXCL12 vs. MIF to CXCR4, elaborate on how ACKR3 affects CXCR4 signaling, and summarize biological functions of CXCR4 signaling mediated by CXCL12 or MIF. Also, we will discuss eUb and gp120 as alternative ligands for CXCR4, and describe vMIP-II and HBD-3 as antagonists for CXCR4. Detailed insight into biological effects of CXCR4 signaling und underlying mechanisms, including diversity of CXCR4 ligands and inter-connections with other (chemokine) receptors, is clinically important, as the CXCR4 antagonist AMD3100 has been approved as stem cell mobilizer in specific disease settings.

AMPK: energy sensor and survival mechanism in the ischemic heart

AMP-activated protein kinase (AMPK) is a critical regulator of cellular metabolism and plays an important role in diabetes, cancer, and vascular disease. In the heart, AMPK activation is an essential component of the adaptive response to cardiomyocyte stress that occurs during myocardial ischemia. During ischemia-reperfusion, AMPK activation modulates glucose and fatty acid metabolism, mitochondrial function, endoplasmic reticulum (ER) stress, autophagy, and apoptosis. Pharmacological activation of AMPK prevents myocardial necrosis and contractile dysfunction during ischemia-reperfusion and potentially represents a cardioprotective strategy for the treatment of myocardial infarction. This review discusses novel mechanisms of AMPK activation in the ischemic heart, the role of endogenous AMPK activation during ischemia, and the potential therapeutic applications for AMPK-directed therapy.

MIF and CXCL12 in Cardiovascular Diseases: Functional Differences and Similarities

Coronary artery disease (CAD) as part of the cardiovascular diseases is a pathology caused by atherosclerosis, a chronic inflammatory disease of the vessel wall characterized by a massive invasion of lipids and inflammatory cells into the inner vessel layer (intima) leading to the formation of atherosclerotic lesions; their constant growth may cause complications such as flow-limiting stenosis and plaque rupture, the latter triggering vessel occlusion through thrombus formation. Pathophysiology of CAD is complex and over the last years many players have entered the picture. One of the latter being chemokines (small 8-12 kDa cytokines) and their receptors, known to orchestrate cell chemotaxis and arrest. Here, we will focus on the chemokine CXCL12, also known as stromal cell-derived factor 1 (SDF-1) and the chemokine-like function chemokine, macrophage migration-inhibitory factor (MIF). Both are ubiquitously expressed and highly conserved proteins and play an important role in cell homeostasis, recruitment, and arrest through binding to their corresponding chemokine receptors CXCR4 (CXCL12 and MIF), ACKR3 (CXCL12), and CXCR2 (MIF). In addition, MIF also binds to the receptor CD44 and the co-receptor CD74. CXCL12 has mostly been studied for its crucial role in the homing of (hematopoietic) progenitor cells in the bone marrow and their mobilization into the periphery. In contrast to CXCL12, MIF is secreted in response to diverse inflammatory stimuli, and has been associated with a clear pro-inflammatory and pro-atherogenic role in multiple studies of patients and animal models. Ongoing research on CXCL12 points at a protective function of this chemokine in atherosclerotic lesion development. This review will focus on the role of CXCL12 and MIF and their differences and similarities in CAD of high risk patients.

Blockade of CCR3 retains the neutrophils, preserving their survival during healing after myocardial infarction

BACKGROUND: Chemokines are critical mediators in controlling and monitoring the healing and ventricular remodeling after myocardial infarction (MI). They proved to be valuable targets for therapeutic measures to reduce the scar formation and to preserve heart function in patients suffering MI. In the present study, the role of CCR3 in myocardial ischemia/reperfusion was established. METHODS AND RESULTS: One week after infarct induction in a mouse coronary ligation model, the functional and morphological parameters of the heart were analyzed. Isolated-heart Langendorff perfusion showed no significantly differences in heart function, infarction size and post infarction angiogenesis after CCR3 blockade. Apoptotic, proliferation signals as well as collagen synthesis were not affected in CCR3 antagonist treated mice. Notably, CCR3 inhibition was accompanied by massive neutrophil infiltration, while leaving the presence of other immune cell subsets in heart unaffected. CONCLUSION: Since neutrophils represents one of the most widely explored therapeutic targets in the treatment of cardiac disease, this study may open a new perspective for a better understanding of the physiology and homeostasis of neutrophils and points out new directions for intervention in acute MI.

Role of macrophage migration inhibitory factor in age-related lung disease

The prevalence of many common respiratory disorders, including pneumonia, chronic obstructive lung disease, pulmonary fibrosis, and lung cancer, increases with age. Little is known of the host factors that may predispose individuals to such diseases. Macrophage migration inhibitory factor (MIF) is a potent upstream regulator of the immune system. MIF is encoded by variant alleles that occur commonly in the population. In addition to its role as a proinflammatory cytokine, a growing body of literature demonstrates that MIF influences diverse molecular processes important for the maintenance of cellular homeostasis and may influence the incidence or clinical manifestations of a variety of chronic lung diseases. This review highlights the biological properties of MIF and its implication in age-related lung disease.

Minimal invasive surgical procedure of inducing myocardial infarction in mice

Myocardial infarction still remains the main cause of death in western countries, despite considerable progress in the stent development area in the last decades. For clarification of the underlying mechanisms and the development of new therapeutic strategies, the availability of valid animal models are mandatory. Since we need new insights into pathomechanisms of cardiovascular diseases under in vivo conditions to combat myocardial infarction, the validity of the animal model is a crucial aspect. However, protection of animals are highly relevant in this context. Therefore, we establish a minimally invasive and simple model of myocardial infarction in mice, which assures a high reproducibility and survival rate of animals. Thus, this models fulfils the requirements of the 3R principle (Replacement, Refinement and Reduction) for animal experiments and assure the scientific information needed for further developing of therapeutical strategies for cardiovascular diseases.

Ischemia and reperfusion related myocardial inflammation: A network of cells and mediators targeting the cardiomyocyte

Occlusion of a coronary artery if maintained for longer period of time results in damage of the cardiac tissue. However, restoration of blood flow to previously ischemic tissue can itself induce further cardiac damage, a phenomenon known as myocardial reperfusion injury. Cardiac homoeostasis is supported by a network of direct and indirect interactions between cardiomyocytes and resident cell types such as fibroblasts, adipocytes, and endothelial cells or invading blood cells. This review will discuss the role of the cellular interplay in ischemia-reperfusion injury from a cardiomyocyte-centered view, although we are aware that other cellular interactions are equally important. We will try to work out currently unresolved questions and potential future directions in the field.

CXCR6 deficiency attenuates pressure overload-induced monocytes migration and cardiac fibrosis through downregulating TNF-α-dependent MMP9 pathway

An immerging role of TNF-α in collagen synthesis and cardiac fibrosis implies the significance of TNF-α production in the development of myocardial remodeling. Our previous study showed a reduction of TNF-α and attenuated cardiac remodeling in CXCR6 knockout (KO) mice after ischemia/reperfusion injury. However, the potential mechanism of TNF-α-mediated cardiac fibrosis with pressure overload has not been well elucidated. In the present study, we aim to investigate the role of CXCR6 in TNF-α release and myocardial remodeling in response to pressure overload. Pressure overload was performed by constriction of transverse aorta (TAC) surgery on CXCR6 KO mice and C57 wild-type (WT) counterparts. At 6 weeks after TAC, cardiac remodeling was assessed by echocardiography, cardiac TNF-α release and its type I receptor (TNFRI), were detected by ELISA and western blot, collagen genes Col1a1 (type I) and Col3a1 (type III) were examined by real-time PCR. Compared with CXCR6 WT mice, CXCR6 KO mice exhibited less cardiac dysfunction, reduced expression of TNFRI, Col1a1 and Col3a. In vitro, we confirmed that CXCR6 deficiency led to reduced homing and infiltration of CD11b(+) monocytes, which contributed to attenuated TNF-α release in myocardium. Furthermore, TNFRI antagonist pretreatment blocked AT1 receptor signaling and NOX4 expression, reduced collagen synthesis, and blunted the activity of MMP9 in CXCR6 WT mice after TAC, but these were not observed in CXCR6 KO mice. In the present work, we propose a mechanism that CXCR6 is essential for pressure overload-mediated myocardial recruitment of monocytes, which contributes to cardiac fibrosis through TNF-α-dependent MMP9 activation and collagen synthesis.

The CXCL12/CXCR4 chemokine ligand/receptor axis in cardiovascular disease

The chemokine receptor CXCR4 and its ligand CXCL12 play an important homeostatic function by mediating the homing of progenitor cells in the bone marrow and regulating their mobilization into peripheral tissues upon injury or stress. Although the CXCL12/CXCR4 interaction has long been regarded as a monogamous relation, the identification of the pro-inflammatory chemokine macrophage migration inhibitory factor (MIF) as an important second ligand for CXCR4, and of CXCR7 as an alternative receptor for CXCL12, has undermined this interpretation and has considerably complicated the understanding of CXCL12/CXCR4 signaling and associated biological functions. This review aims to provide insight into the current concept of the CXCL12/CXCR4 axis in myocardial infarction (MI) and its underlying pathologies such as atherosclerosis and injury-induced vascular restenosis. It will discuss main findings from in vitro studies, animal experiments and large-scale genome-wide association studies. The importance of the CXCL12/CXCR4 axis in progenitor cell homing and mobilization will be addressed, as will be the function of CXCR4 in different cell types involved in atherosclerosis. Finally, a potential translation of current knowledge on CXCR4 into future therapeutical application will be discussed.