Insight into the biology of Macrophage Migration Inhibitory Factor (MIF) revealed by the cloning of its cell surface receptor

Distinctive Macrophage Migration Inhibitory Factor Receptor Patterns and Soluble Biomarkers in Rheumatoid Arthritis: Unveiling Key Associations with Disease Activity

We previously reported the peripheral blood cell patterns of expression for the migration inhibitory factor (MIF) canonical (CD74/CD44) and noncanonical receptors (CXCR2, CXCR4, and CXCR7) in rheumatoid arthritis (RA) patients and correlated this with clinical biomarkers and disease activity. This study aimed to evaluate the expression of these receptors alongside the serum levels of CXCL12 and CXCL8 (ligands for CXCR2, CXCR4, and CXCR7), which potentially regulate the action of these receptors and the influence the downstream effects of MIF. Additionally, we evaluated soluble levels of MIF, as well as its soluble cognate receptor (sCD74), in the serum of RA patients and control subjects (CS). Our findings revealed distinctive membrane expression patterns of MIF receptors in active (moderate and high disease activity) and non-active (low activity and remission) RA patients. Furthermore, RA patients exhibited elevated serum sCD74 levels, which correlated with disease activity, and elevated CXCL12 levels, which correlated with rheumatoid factor titers. Regarding serum CXCL8 and MIF levels, we observed higher CXCL8 levels in RA patients compared to CS, while MIF levels did not significantly differ between groups or by disease activity. The circulating sCD74/MIF ratio was elevated in RA patients, particularly in cases of moderate disease activity. Our study also indicated that treatment protocols did not significantly impact circulating MIF levels or the expression of its receptors. This study extends previous findings by supporting a role for sCD74 in downregulating MIF action and in the potential value of the sCD74/MIF ratio as a disease biomarker in RA.

Integrin CD11c regulates B cell homeostasis

CD11c is widely known as a cell surface marker for dendritic cells, but we recently showed that it regulates neutrophil and T cell functions. Because we found that CD11c knockout (KO) mice had lower blood B cell counts, we characterized B cell profile in developmental stages. We found that CD11c KO recirculating and mature B cells was significantly fewer compared with wild type, associated with exaggerated proliferation and apoptosis. Because they did not express CD11c, we sought for the possibility of CD11c-mediated non-intrinsic regulation of B cell proliferation and apoptosis. Here we hypothesized that dendritic cells, major cells expressing CD11c would regulate B cells indirectly. The proteomics of dendritic cells cultured in vitro indicated the downregulation of macrophage migration inhibitory factor (MIF). Less MIF was also confirmed by ELISA. Furthermore, plasma MIF level was significantly lower in naïve CD11c KO mice. Because MIF regulates B cell survival, we demonstrated a novel regulatory mechanism of naïve B cells via CD11c.

Deletion of MIF gene from live attenuated LdCen-/- parasites enhances protective CD4+ T cell immunity

Vaccination with live attenuated Leishmania parasites such as centrin deleted Leishmania donovani (LdCen^-/-) against visceral leishmaniasis has been reported extensively. The protection induced by LdCen^-/- parasites was mediated by both CD4⁺ and CD8⁺ T cells. While the host immune mediators of protection are known, parasite determinants that affect the CD4⁺ and CD8⁺ T cell populations remain unknown. Parasite encoded inflammatory cytokine MIF has been shown to modulate the T cell differentiation characteristics by altering the inflammation induced apoptosis during contraction phase in experimental infections with Leishmania or Plasmodium. Neutralization of parasite encoded MIF either by antibodies or gene deletion conferred protection in Plasmodium and Leishmania studies. We investigated if the immunogenicity and protection induced by LdCen^-/- parasites is affected by deleting MIF genes from this vaccine strain. Our results showed that LdCen^-/-MIF^-/- immunized group presented higher percentage of CD4⁺ and CD8⁺ central memory T cells, increased CD8⁺ T cell proliferation after challenge compared to LdCen^-/- immunization. LdCen^-/-MIF^-/- immunized group presented elevated production of IFN-γ⁺ and TNF-α⁺ CD4⁺ T cells concomitant with a reduced parasite load in spleen and liver compared to LdCen^-/-group following challenge with L. infantum. Our results demonstrate the role of parasite induced factors involved in protection and long-term immunity of vaccines against VL.

Transcriptomic and Bioinformatic Analyses Identifying a Central Mif-Cop9-Nf-kB Signaling Network in Innate Immunity Response of Ciona robusta

The Ascidian C. robusta is a powerful model for studying innate immunity. LPS induction activates inflammatory-like reactions in the pharynx and the expression of several innate immune genes in granulocyte hemocytes such as cytokines, for instance, macrophage migration inhibitory factors (CrMifs). This leads to intracellular signaling involving the Nf-kB signaling cascade that triggers downstream pro-inflammatory gene expression. In mammals, the COP9 (Constitutive photomorphogenesis 9) signalosome (CSN) complex also results in the activation of the NF-kB pathway. It is a highly conserved complex in vertebrates, mainly engaged in proteasome degradation which is essential for maintaining processes such as cell cycle, DNA repair, and differentiation. In the present study, we used bioinformatics and in-silico analyses combined with an in-vivo LPS exposure strategy, next-generation sequencing (NGS), and qRT-PCR to elucidate molecules and the temporal dynamics of Mif cytokines, Csn signaling components, and the Nf-κB signaling pathway in C. robusta. A qRT-PCR analysis of immune genes selected from transcriptome data revealed a biphasic activation of the inflammatory response. A phylogenetic and STRING analysis indicated an evolutionarily conserved functional link between the Mif-Csn-Nf-kB axis in ascidian C. robusta during LPS-mediated inflammation response, finely regulated by non-coding molecules such as microRNAs (miRNAs).

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.

OxMIF: a druggable isoform of macrophage migration inhibitory factor in cancer and inflammatory diseases

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine with a pleiotropic spectrum of biological functions implicated in the pathogenesis of cancer and inflammatory diseases. MIF is constitutively present in several cell types and non-lymphoid tissues and is secreted after acute stress or inflammation. MIF triggers the release of proinflammatory cytokines, overrides the anti-inflammatory effects of glucocorticoids, and exerts chemokine function, resulting in increased migration and recruitment of leukocytes into inflamed tissue. Despite this, MIF is a challenging target for therapeutic intervention because of its ubiquitous nature and presence in the circulation and tissue of healthy individuals. Oxidized MIF (oxMIF) is an immunologically distinct disease-related structural isoform found in the plasma and tissues of patients with inflammatory diseases and in solid tumor tissues. MIF converts to oxMIF in an oxidizing, inflammatory environment. This review discusses the biology and activity of MIF and the potential for autoimmune disease and cancer modification by targeting oxMIF. Anti-oxMIF antibodies reduce cancer cell invasion/migration, angiogenesis, proinflammatory cytokine production, and ERK and AKT activation. Anti-oxMIF antibodies also elicit apoptosis and alter immune cell function and/or migration. When co-administered with a glucocorticoid, anti-oxMIF antibodies produced a synergistic response in inflammatory models. Anti-oxMIF antibodies therefore counterregulate biological activities attributed to MIF. oxMIF expression has been observed in inflammatory diseases (eg, sepsis, psoriasis, asthma, inflammatory bowel disease, and systemic lupus erythematosus) and oxMIF has been detected in ovarian, colorectal, lung, and pancreatic cancers. In contrast to MIF, oxMIF is specifically detected in plasma and/or tissues of diseased patients, but not in healthy individuals. Therefore, as a druggable isoform of MIF, oxMIF represents a potential new therapeutic target in inflammatory diseases and cancer. Fully human, monoclonal anti-oxMIF antibodies have been shown to selectively bind oxMIF in preclinical and phase I studies; however, additional clinical assessments are necessary to validate their use as either a monotherapy or in combination with standard-of-care regimens (ie, immunomodulatory agents/checkpoint inhibitors, anti-angiogenic drugs, chemotherapeutics, and glucocorticoids).

A secreted MIF homologue from Trichinella spiralis binds to and interacts with host monocytes

Trichinella spiralis is a very successful parasite capable of surviving in many mammal hosts and residing in muscle tissues for long periods, indicating that it must have some effective strategies to escape from or guard against the host immune attack. The functions of MIF have been studied in other parasites and demonstrated to function as a virulence factor aiding in their survival by modulating the host immune response. However, the functions of Trichinella spiralis MIF (TsMIF) have not been addressed. Here, we successfully obtained the purified recombinant TsMIF and anti-TsMIF serum. Our results showed that TsMIF was expressed in all the Trichinella spiralis developmental stages, especially highly expressed in the muscle larvae (ML) and mainly located in stichocytes, midgut, cuticle, muscle cells of ML and around intrauterine embryos of female adults. We also observed TsMIF could be secreted from ML and bind to host monocytes. Next, our data demonstrated that TsMIF not only stimulated the phosphorylation of ERK1/2 and cell proliferation by binding to the host cell surface receptor CD74, but also interacted with a host intracellular protein, Jab1, which is a coactivator of AP-1 transcription. We concluded the secreted TsMIF plays an important role in the interaction between Trichinella spiralis and its host and could be a potential drug or vaccine target molecule against Trichinella spiralis infection.

Transcriptional and in silico analyses of MIF cytokine and TLR signalling interplay in the LPS inflammatory response of Ciona robusta

The close phylogenetic relationship between Ciona robusta and vertebrates makes it a powerful model for studying innate immunity and the evolution of immune genes. To elucidate the nature and dynamics of the immune response, the molecular mechanisms by which bacterial infection is detected and translated into inflammation and how potential pattern recognition receptors (PRRs) are involved in pathogen recognition in tunicate C. robusta (formerly known as Ciona intestinalis), we applied an approach combining bacterial infections, next-generation sequencing, qRT-PCR, bioinformatics and in silico analyses (criteria of a p-value < 0.05 and FDR < 0.05). A STRING analysis indicated a functional link between components of the Tlr/MyD88-dependent signalling pathway (Tlr2, MyD88, and Irak4) and components of the Nf-κB signalling pathway (Nf-κB, IκBα, and Ikkα) (p-value < 0.05, FDR < 0.05). A qRT-PCR analysis of immune genes selected from transcriptome data revealed Mif as more frequently expressed in the inflammatory response than inflammation mediator or effector molecules (e.g., Il-17s, Tnf-α, Tgf-β, Mmp9, Tlrs, MyD88, Irak4, Nf-κB, and galectins), suggesting close interplay between Mif cytokines and Nf-κB signalling pathway components in the biphasic activation of the inflammatory response. An in silico analyses of the 3′-UTR of Tlr2, MyD88, IκBα, Ikk, and Nf-κB transcripts showed the presence of GAIT elements, which are known to play key roles in the regulation of immune gene-specific translation in humans. These findings provide a new level of understanding of the mechanisms involved in the regulation of the C. robusta inflammatory response induced by LPS and suggest that in C. robusta, as in humans, a complex transcriptional and post-transcriptional control mechanism is involved in the regulation of several inflammatory genes.

Structural and functional insights into macrophage migration inhibitory factor from Oncomelania hupensis, the intermediate host of Schistosoma japonicum

Oncomelania hupensis is the unique intermediate host of Schistosoma japonicum. As an irreplaceable prerequisite in the transmission and prevalence of schistosomiasis japonica, an in-depth study of this obligate host-parasite interaction can provide glimpse into the molecular events in the competition between schistosome infectivity and snail immune resistance. In previous studies, we identified a macrophage migration inhibitory factor (MIF) from O. hupensis (OhMIF), and showed that it was involved in the snail host immune response to the parasite S. japonicum. Here, we determined the crystal structure of OhMIF and revealed that there were distinct structural differences between the mammalian and O. hupensis MIFs. Noticeably, there was a projecting and structured C-terminus in OhMIF, which not only regulated the MIF's thermostability but was also critical in the activation of its tautomerase activity. Comparative studies between OhMIF and human MIF (hMIF) by analyzing the tautomerase activity, oxidoreductase activity, thermostability, interaction with the receptor CD74 and activation of the ERK signaling pathway demonstrated the functional differences between hMIF and OhMIF. Our data shed a species-specific light on structural, functional, and immunological characteristics of OhMIF and enrich the knowledge on the MIF family.

MIF -173G/C (rs755622) polymorphism modulates coronary artery disease risk: evidence from a systematic meta-analysis

BACKGROUND

Coronary artery disease (CAD) remains one of the major causes of death in humans. Genetic testing may allow early detection and prevention of this disease. This study aimed to investigate the association between the macrophage migration inhibitory factor (MIF) -173G/C (rs755622) polymorphism and susceptibility to CAD based on a meta-analysis.

METHODS

We searched several databases to identify observational case-control studies investigating the association between the MIF -173G > C (rs755622) polymorphism and CAD risk published before July 30, 2019. Data were analyzed using the STATA software.

RESULTS

Six studies, comprising a total of 1172 CAD cases and 1564 controls evaluated for MIF polymorphisms, were included. The occurrence of CAD was found to be associated with the C allele of the MIF rs755622 SNP in the total population (C/G, OR = 1.489, 95% CI = 1.223-1.813). Further, MIF -173G/C polymorphism was significantly associated with CAD under the allelic model in the Asian (C/G, OR = 1.775, 95% CI = 1.365-2.309) and Caucasian (C/G, OR = 1.288, 95% CI 1.003-1.654) subgroups. The data showed that the risk of CAD was higher in the population carrying the C allele.

CONCLUSIONS

We found evidence of associations between MIF -173C/G and CAD susceptibility in the Asian and Caucasian populations.

Twenty-five-year research progress in hookworm excretory/secretory products

Hookworm infection is a major public health problem that threatens about 500 million people throughout tropical areas of the world. Adult hookworms survive for many years in the host intestine, where they suck blood, causing iron deficiency anemia and malnutrition. Numerous molecules, named excretory/secretory (ES) products, are secreted by hookworm adults and/or larvae to aid in parasite survival and pathobiology. Although the molecular cloning and characterization of hookworm ES products began 25 years ago, the biological role and molecular nature of many of them are still unclear. Hookworm ES products, with distinct structures and functions, have been linked to many essential events in the disease pathogenesis. These events include host invasion and tissue migration, parasite nourishment and reproduction, and immune modulation. Several of these products represent promising vaccine targets for controlling hookworm disease and therapeutic targets for many inflammatory diseases. This review aims to summarize our present knowledge about hookworm ES products, including their role in parasite biology, host-parasite interactions, and as vaccine and pharmaceutical targets and to identify research gaps and future research directions in this field.

D-dopachrome tautomerase from Japanese sea bass ( Lateolabrax japonicus) is a chemokine-like cytokine and functional homolog of macrophage migration inhibitory factor

D-dopachrome tautomerase (DDT), a member of the macrophage migration inhibitory factor (MIF) protein superfamily, is a newly described cytokine with chemokine-like characteristics. However, research on fish DDT remains limited. In this study, we identified a DDT homolog (LjDDT) from the Japanese sea bass, Lateolabrax japonicus. Sequence analysis showed that LjDDT had typical sequence features of known DDT and MIF homologs and was most closely related to DDT of rock bream ( Oplegnathus fasciatus). LjDDT transcripts were detected in all tested tissues of healthy Japanese sea bass, with the highest expression found in the liver. Upon infection with Vibrio harveyi, LjDDT transcripts were significantly down-regulated in the three tested tissues, including the liver, spleen, and head kidney. Recombinant LjDDT (rLjDDT) and the corresponding antibody (anti-rLjDDT) were subsequently prepared. The administration of 100 μg/g anti-rLjDDT had a statistically significant protective effect on the survival of V. harveyi-infected fish. Moreover, rLjDDT was able to induce the migration of monocytes/macrophages (MO/MФ) and lymphocytes both in vitro and in vivo, but without significant influence on the migration of neutrophils. rLjDDT exhibited chemotactic activity for lipopolysaccharide (LPS) -stimulated M1-type MO/ MΦ in vitro, but not for cAMP-stimulated M2-type MO/MΦ. Furthermore, the knockdown of LjCD74, but not LjCXCR4, significantly down-regulated the rLjDDT-enhanced migration of MO/MΦ and relieved the rLjMIF-inhibited migration of MO/MΦ. These results indicate that LjCD74 may be the major chemotactic receptor of LjDDT and LjMIF in Japanese sea bass MO/MΦ. Combined rLjDDT+ rLjMIF treatment had no significant effect on the migration of MsiRNA, LjCD74si-, or LjCXCR4sitreated MO/MΦ compared to the control group, suggesting that the roles of LjDDT and LjMIF may be antagonistic. In conclusion, our study demonstrates for the first time that DDT may play a role in the immune responses of fish against bacterial infection through chemotactic recruitment of MO/MΦ via mediation of CD74 as an antagonist of MIF.

TWEAK increases CD74 expression and sensitizes to DDT proinflammatory actions in tubular cells

CD74 is a multifunctional protein and a receptor for Macrophage Migration Inhibitory Factor (MIF) and MIF-2 / D-dopachrome tautomerase (DDT) cytokines, upregulated in diabetic kidney disease. However, the drivers of CD74 expression and DDT function in kidney cells are poorly characterized. TWEAK is a proinflammatory cytokine that promotes kidney injury. We have now identified CD74 gene expression as upregulated in the kidneys in response to systemic TWEAK administration in mice, and have characterized the in vivo CD74 expression and the functional consequences in cultured cells. TWEAK administration to mice resulted in a progressive time-dependent (up to 24h) upregulation of kidney CD74 mRNA (RT-PCR) and protein (Western blot). Furthermore, the CD74 ligands MIF and DDT were also upregulated at the protein level 24h after TWEAK administration. Immunohistochemistry localized the increased CD74, MIF and DDT expression to tubular cells. In cultured tubular cells, TWEAK increased CD74 mRNA and protein expression dose-dependently, with a temporal pattern similar to in vivo. TWEAK-induced CD74 localized to the cell membrane, where it can function as a cytokine receptor. For the first time, we explored the actions of DDT in tubular cells and found that DDT amplified the increase in MCP-1 and RANTES expression in response to TWEAK. By contrast, DDT did not significantly modify TWEAK-induced Klotho downregulation. In conclusion, TWEAK upregulates CD74 and its ligands MIF and DDT in renal tubular cells. This may have functional consequences for kidney injury since DDT amplified the inflammatory response to TWEAK.

Characterization of a secreted macrophage migration inhibitory factor homologue of the parasitic nematode Haemonchus Contortus acting at the parasite-host cell interface

Modulation and suppression of the immune response of the host by nematode parasites have been reported extensively and the migration inhibitory factor (MIF) is identified as one of the major immunomodulator. In the present study, we cloned and produced recombinant MIF protein from the small ruminant’s nematode parasite Haemonchus contortus (rHCMIF-1), and investigated its immunomodulatory effects on goat monocyte. Enzymatic assays indicated that rHCMIF-1 possessed tautomerase activity. Immunohistochemical test demonstrated that the native HCMIF-1 protein was predominantly localized at the body surface and internal surface of the worm’s gut. We demonstrated that rHCMIF-1 could be distinguished by antisera from goats experimentally infected with H. contortus and could bind by goat monocytes. The immunomodulatory effects of HCMIF-1 on cytokine secretion, MHC molecule expression, NO production and phagocytosis were observed by co-incubation of rHCMIF-1 with goat monocytes. The results showed that the interaction of rHCMIF-1 decreased the production of TNF-α, IL-1β and IL-12p40, where as, it significantly increased the secretion of IL-10 and TGF β in goat monocytes. After rHCMIF-1 exposure, the expression of MHC-II on goat monocytes was inhibited. Moreover, rHCMIF-1 could down-regulate the LPS induced NO production of goat monocytes. Phagocytotic assay by FITC-dextran internalization showed that rHCMIF-1 could inhibit the phagocytosis of goat monocytes. Our findings provided potential targetas immunoregulator, and will be helpful to elucidate the molecular basis of host–parasite interactions and search for new potential protein as vaccine and drug target candidate.

Identification of CPE and GAIT elements in 3'UTR of macrophage migration inhibitory factor (MIF) involved in inflammatory response induced by LPS in Ciona robusta

Innate immune responses face infectious microorganisms by inducing inflammatory responses. Multiple genes within distinct functional categories are coordinately and temporally regulated by transcriptional 'on' and 'off' switches that account for the specificity of gene expression in response to external stimuli. Mechanisms that control transcriptional and post-transcriptional regulation are important in coordinating the initiation and resolution of inflammation. Macrophage migration inhibitory factor (MIF) is an important cytokine that, in Ciona robusta, is related to inflammatory response. It is well known that in C. robusta, formerly known as Ciona intestinalis, the pharynx is involved in the inflammatory reaction induced by lipopolysaccharide (LPS) injection in the body wall. Using this biological system, we describe the identification of two C. robusta MIFs (CrMIF1 and CrMIF2). The phylogenetic tree and modeling support a close relationship with vertebrate MIF family members. CrMIF1 and CrMIF2 possess two evolutionally conserved catalytic sites: a tautomerase and an oxidoreductase site with a conserved CXXC motif. Real-time PCR analysis shows a prompt expression induced by LPS inoculation in CrMIF1 and a late upregulation of CrMIF2 and in silico analyses of 3'UTR show a cis-acting GAIT element and a CPE element in 3'-UTR, which are not present in the 3'-UTR of CrMIF1, suggesting that different transcriptional and post-transcriptional control mechanisms are involved in the regulation of gene expression of MIF during inflammatory response in C. robusta.

The Modulatory Effect of Lead Drug Candidates on Inflammatory Gene Expression in Sepsis: A Mini-Review

Sepsis is a debilitating clinical syndrome of systemic inflammation in response to microorganisms especially Gram-positive and Gram-negative bacteria. A minority of sepsis cases could be due to non-pathogenic insult such as trauma. Much of the tissue and organ injury observed among septic patients is a consequence of the inflammatory response. The search for effective treatments of sepsis has led to several studies by different research groups across the globe. Although many targets and molecules have been identified, there is still no effective treatment for sepsis. The aim of this report is to review the literature on drugs and drug candidates against sepsis and how they modulate the expression of inflammatory genes. Many compounds have been identified to regulate inflammatory gene expression by interacting with targets such as topoisomerase 1 and nuclear factor kappa B, which regulate the production of pro- and anti-inflammatory cytokines. Even though these compounds appear promising as potential drugs against sepsis, no effective therapies have been discovered to date and thus the fight against sepsis continues.

Macrophage migration inhibitory factor promoter polymorphisms (-794 CATT5-8): Relationship with soluble MIF levels in coronary atherosclerotic disease subjects

Background

We analyzed the relationship of −794 CATT5–8 MIF polymorphisms with soluble MIF in Coronary Atherosclerotic Disease (CAD) patients.

Methods

A total of 256 patients selected, on which 186 normal-coronary and 70 Coronary artery disease subjects, were recruited in the study (Retrospectively registered). Genotyping of −794 CATT5–8 polymorphisms were performed by PCR and DNA sequencing. Serum MIF levels were measured using an ELISA kit. Patients were classified by coronary angiogram, and CAD based on Gensini’s integral degree (angiographic scoring system).

Results

The allele frequency and genotype frequency of −794 CATT5–8 did not show any differences in normal-coronary subjects and CAD subjects. In CAD patients, serum MIF levels was lower in CATT (5) subjects than in CATT (7) subjects, while the genotype of −794 CATT5–8 did not show differences in serum MIF levels. In addition, we found a decrease in serum MIF levels in carriers of the (5/5) genotypes the −794 CATT5–8 MIF polymorphisms, although it was not significant. There was no relationship of CAD class and the allele frequency of −794 CATT5–8.

Conclusions

This study found no association between CAD class and −794 CATT5–8 MIF polymorphisms with soluble MIF levels in CAD Subjects.

Trial registration

NCT01750502 (November 2012, Retrospectively registered).

Reprint of: The non-mammalian MIF superfamily

Macrophage migration inhibitory factor (MIF) was first described as a cytokine 50 years ago, and emerged in mammals as a pleiotropic protein with pro-inflammatory, chemotactic, and growth-promoting activities. In addition, MIF has gained substantial attention as a pivotal upstream mediator of innate and adaptive immune responses and with pathologic roles in several diseases. Of less importance in mammals is an intrinsic but non-physiologic enzymatic activity that points to MIF's evolution from an ancient defense molecule. Therefore, it is not surprising that mif-like genes also have been found across a range of different organisms including bacteria, plants, protozoa, helminths, molluscs, arthropods, fish, amphibians and birds. While Genebank analysis identifying mif-like genes across species is extensive, contained herein is an overview of the non-mammalian MIF-like proteins that have been most well studied experimentally. For many of these organisms, MIF contributes to an innate defense system or plays a role in development. For parasitic organisms however, MIF appears to function as a virulence factor aiding in the establishment or persistence of infection by modulating the host immune response. Consequently, a combined targeting of both parasitic and host MIF could lead to more effective treatment strategies for parasitic diseases of socioeconomic importance.

The non-mammalian MIF superfamily

Macrophage migration inhibitory factor (MIF) was first described as a cytokine 50 years ago, and emerged in mammals as a pleiotropic protein with pro-inflammatory, chemotactic, and growth-promoting activities. In addition, MIF has gained substantial attention as a pivotal upstream mediator of innate and adaptive immune responses and with pathologic roles in several diseases. Of less importance in mammals is an intrinsic but non-physiologic enzymatic activity that points to MIF's evolution from an ancient defense molecule. Therefore, it is not surprising that mif-like genes also have been found across a range of different organisms including bacteria, plants, ‎protozoa, helminths, molluscs, arthropods, fish, amphibians and birds. While Genebank analysis identifying mif-like genes across species is extensive, contained herein is an overview of the non-mammalian MIF-like proteins that have been most well studied experimentally. For many of these organisms, MIF contributes to an innate defense system or plays a role in development. For parasitic organisms however, MIF appears to function as a virulence factor aiding in the establishment or persistence of infection by modulating the host immune response. Consequently, a combined targeting of both parasitic and host MIF could lead to more effective treatment strategies for parasitic diseases of socioeconomic importance.

MIF, a controversial cytokine: a review of structural features, challenges, and opportunities for drug development

INTRODUCTION

Macrophage migration inhibitory factor (MIF) has emerged as a promising drug target in diseases including sepsis, rheumatoid arthritis, and cancer. MIF has multiple properties that favor development of specific, targeted therapies: it is expressed broadly among human cells, has noted roles in diverse inflammatory and oncological processes, and has intrinsic enzymatic activity amenable to high-throughput screening. Despite these advantages, anti-MIF therapy remains well behind other cytokine-targeted therapeutics, with no small molecules in the pipeline for clinical development and anti-MIF antibodies only recently beginning clinical trials. Areas covered: In this review we summarize current literature regarding MIF structure and function-including challenges and controversies that have arisen in studies of anti-MIF therapeutics-and propose a strategy for development of clinically relevant anti-MIF drugs. Expert opinion: We believe that the field of anti-MIF therapeutics would benefit from capitalizing on the protein's multiple assets while acknowledging their flaws. The tautomerase enzymatic site of MIF may not be active biologically, but can nonetheless offer a high-throughput method to highlight molecules of interest that can affect its other, frequently intertwined bioactivities. Future work should also focus on developing more robust assays for MIF bioactivity that can be used for second-pass screening and specificity studies.

Involvement of macrophage migration inhibitory factor in cancer and novel therapeutic targets

Macrophage migration inhibitory factor (MIF) was originally identified in 1966 by Bloom and Bennett as a pro-inflammatory cytokine involved in the inhibition of macrophage motility. Since then, studies have investigated the functional contribution of this pro-inflammatory cytokine in several immune diseases, including rheumatoid arthritis and lupus erythematous. Recently, MIF has been reported to be involved in a variety of neoplastic diseases. The present review discusses previous cancer research studies that have investigated the involvement of MIF in carcinogenesis, disease prognosis, tumor cell proliferation and invasion, and tumor-induced angiogenesis. Finally, potential therapeutic approaches based on the use of MIF antagonists and neutralizing antibodies are examined. The review concludes that MIF could be a good prognostic biomarker in several types of cancer, but also that the inhibition of MIF could represent a novel therapy against cancer.

Expression of MIF and CD74 in leukemic cell lines: correlation to DR expression destiny

Invariant chain (Ii) or CD74 is a non-polymorphic glycoprotein, which apart from its role as a chaperone dedicated to MHCII molecules, is known to be a high-affinity receptor for macrophage migration inhibitory factor (MIF). The present study aimed to define the roles of CD74 and MIF in the immune surveillance escape process. Towards this direction, the cell lines HL-60, Raji, K562 and primary pre-B leukemic cells were examined for expression and secretion of MIF. Flow cytometry analysis detected high levels of MIF and intracellular/membrane CD74 expression in all leukemic cells tested, while MIF secretion was shown to be inversely proportional to intracellular HLA-DR (DR) expression. In the MHCII-negative cells, IFN-γ increased MIF expression and induced its secretion in HL-60 and K562 cells, respectively. In K562 cells, CD74 (Iip33Iip35) was shown to co-precipitate with HLA-DOβ (DOβ), inhibiting thus MIF or DR binding. Induced expression of DOα in K562 (DOα-DOβ+) cells in different transfection combinations decreased MIF expression and secretion, while increasing surface DR expression. Thus, MIF could indeed be part of the antigen presentation process.

Cationic antimicrobial peptide, magainin down-regulates secretion of pro-inflammatory cytokines by early placental cytotrophoblasts

BACKGROUND

Human placental villous cytotrophoblasts exhibit relative externalization of negatively charged moieties to the outer leaflet of the plasma membrane during the time of syncytialization rendering their reactivity to positively charged cationic antimicrobial peptides (CAMPs) during the window of implantation and early placentation. Vaginal administration of a synthetic CAMP, Ala(8,13,18)-magainin II amide (AMA) inhibited blastocyst implantation and early placentation in monkeys. Furthermore, the administration of AMA resulted in significant inhibition of cell differentiation, enhancement in apoptosis and loss of viability in first trimester placental villous cytotrophoblasts in primary culture. The present study examines the effect of in vitro application of different doses (0, 1, 10, 100, 1000 ng/ml) of AMA on the secreted cytokine profiles of cytotrophoblasts obtained from placental villi samples (n = 13) collected during 8-9 weeks of gestation and grown on three-dimensional collagen matrix in vitro.

METHODS

A panel of forty-eight (48) cytokines in conditioned medium was analysed using multiplex immunoassays technique. Further, the steady state transcript levels of four cytokines (CCL4, CCL5, IL1B, IL6), the concentrations of which were affected by AMA in the isolated cytotrophoblasts, as well as, two cytokines (IL1A and TNF) which were not affected by AMA were estimated. Input list of cytokines secreted by cytotrophoblasts and showing differential secretion in response to AMA were used in enrichment analysis for the generation of biological networks.

RESULTS

Placental cytotrophoblasts secreted 27 cytokines, 13 of which are affected by AMA in vitro with significantly decreased secretion of CCLs-2, 3, 4, 5, CXCLs-1 and 8, FGF2 and MCSF and that of IL1B, IL6 and MIF, and increased secretion of IL16 and IL-2RA. Of the above cytokines showing differential secretion, only IL-2RA, IL16 and MIF showed significant correspondence in the steady state expression of their respective transcript levels. Post-hoc Enrichment analysis revealed Toll-like receptor (TLR) mediated pathways were the top-scored target pathways that were affected by AMA.

CONCLUSIONS

Administration of a CAMP causes shift in the balance of immune-inflammatory responses involving downstream pathways of TLRs in cytotrophoblast function. Further verification of functions of placental trophoblasts on administration of CAMP with pregnancy outcome is necessary.

Interaction of MIF Family Proteins in Myocardial Ischemia/Reperfusion Damage and Their Influence on Clinical Outcome of Cardiac Surgery Patients

AIMS

Cardiac surgery involves myocardial ischemia/reperfusion (I/R) with potentially deleterious consequences. Macrophage migration inhibitory factor (MIF) is a stress-regulating chemokine-like cytokine that protects against I/R damage, but functional links with its homolog, d-dopachrome tautomerase (MIF-2), and the circulating soluble receptor CD74 (sCD74) are unknown. In this study, we investigate the role of MIF, MIF-2, sCD74, and MIF genotypes in patients scheduled for elective single or complex surgical procedures such as coronary artery bypass grafting or valve replacement.

RESULTS

MIF and MIF-2 levels significantly increased intraoperatively, whereas measured sCD74 decreased correspondingly. Circulating sCD74/MIF complexes were detectable in 50% of patients and enhanced MIF antioxidant activity. Intraoperative MIF levels were independently associated with a reduced risk for the development of atrial fibrillation (AF) (odds ratio 0.99 [0.98-1.00]; p=0.007). Circulating levels of MIF-2, but not MIF, were associated with an increased frequency of organ dysfunction and predicted the occurrence of AF (area under the curve [AUC]=0.663; p=0.041) and pneumonia (AUC=0.708; p=0.040). Patients with a high-expression MIF genotype exhibited a reduced incidence of organ dysfunction compared with patients with low-expression MIF genotypes (3 vs. 25; p=0.042).

INNOVATION

The current study comprehensively highlights the kinetics and clinical relevance of MIF family proteins and the MIF genotype in cardiac surgery patients.

CONCLUSION

Our findings suggest that increased MIF levels during cardiac surgery feature organ-protective properties during myocardial I/R, while the soluble MIF receptor, sCD74, may enhance MIF antioxidant activity. In contrast, high MIF-2 levels are predictive of the development of organ dysfunction. Importantly, we provide first evidence for a gene-phenotype relationship between variant MIF alleles and clinical outcome in cardiac surgery patients.

Functional roles of HIV-1 Vpu and CD74: Details and implications of the Vpu-CD74 interaction

HIV-1 Vpu has a variety of functions, including CD4 degradation and the downregulation of MHCII. Downregulation of the MHCII occurs through Vpu binding to the cytoplasmic domain of CD74, the chaperone for antigen presentation. The CD74 cytoplasmic domain also plays a vital role in cell signaling through the activation of an NF-κB signal cascade for the maturation, proliferation and survival of B cells as well as by binding the macrophage inhibitory factor. In view of these functions, it follows that the Vpu-CD74 interaction has multiple downstream consequences for the immune system as it not only impairs foreign antigen presentation but may also have an effect on signal transduction cascades. It is thought that Vpu specifically targets intracellular CD74 while other HIV-1 proteins cannot. Therefore, this protein-protein interaction would be a potential drug target in order to reduce viral persistence. We review the functional importance and specific binding site of Vpu and CD74.

Macrophage migration inhibitory factor polymorphism is associated with susceptibility to inflammatory coronary heart disease

Background. Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine. This study explored the association of 173G/C polymorphism of the MIF gene with coronary heart disease (CHD). Methods. Sequencing was carried out after polymerase chain reaction with DNA specimens from 186 volunteers without CHD and 70 patients with CHD. Plasma MIF levels on admission were measured by ELISA. Patients were classified into either stable angina pectoris (SAP) or unstable angina pectoris (UAP). Genotype distribution between cases and controls and the association of patients' genotypes with MIF level and plaque stability were statistically evaluated (ethical approval number: 2012-01). Results. The frequency of the C genotype was higher in CHD patients than in the control (P = 0.014). The frequency of the 173^*CC genotype was higher in CHD patients than in the control (P = 0.005). The plasma MIF level was higher in MIF173^*C carriers than in MIF173^*G carriers (P = 0.033). CHD patients had higher plasma MIF levels than the control (P = 0.000). Patients with UAP had higher plasma MIF levels than patients with SAP (P = 0.014). Conclusions. These data suggest that MIF −173G/C polymorphism may be related to the development of CHD in a Chinese population. Plasma MIF level is a predictor of plaque stability. This trial is registered with NCT01750502 .

Identification and biochemical characterization of macrophage migration inhibitory factor-2 (MIF-2) homologue of human lymphatic filarial parasite, Wuchereria bancrofti

Homologues of human macrophage migration inhibitory factor (hMIF) have been reported from vertebrates, invertebrates and prokaryotes, as well as plants. Filarial parasites produce two homologues of hMIF viz., MIF-1 and MIF-2, which play important role in the host immune modulation. Earlier, we have characterized MIF-1 (Wba-mif-1) from Wuchereria bancrofti, the major causal organism of human lymphatic filariasis. Here, we are reporting the molecular and biochemical characterization of MIF-2 from this parasite (Wba-mif-2). The complete Wba-mif-2 gene and its cDNA were amplified, cloned and sequenced. The size of Wba-mif-2 gene and cDNA were found to be 4.275 kb and 363 bp, respectively. The gene annotation revealed the presence of a large intron of 3.912 kb interspersed with two exons of 183 bp and 180 bp. The alignment of derived amino acid sequences of Wba-MIF-2 with Wba-MIF-1 showed 44% homology. The conserved CXXC oxido-reductase catalytic site present in Wba-mif-1 was found absent in Wba-mif-2 coding sequence. The amplified Wba-mif-2 cDNA was cloned into an expression vector pRSET-B and transformed into salt inducible Escherichia coli strain GJ1158. The expressed recombinant Wba-MIF-2 protein showed tautomerase activity against L-dopachrome methyl ester and the specific activity was determined to be 18.57±0.77 μmol/mg/min. Three known inhibitors of hMIF tautomerase activity significantly inhibited the tautomerase activity of recombinant Wba-MIF-2. Although the conserved CXXC oxido-reductase motif is absent in Wba-mif-2, the recombinant protein showed significant oxido-reductase activity in the insulin reduction assay, possibly because of the presence of vicinal cysteine residues.

Macrophage migration inhibitory factor is involved in ectopic endometrial tissue growth and peritoneal-endometrial tissue interaction in vivo: a plausible link to endometriosis development

Pelvic inflammation is a hallmark of endometriosis pathogenesis and a major cause of the disease's symptoms. Abnormal immune and inflammatory changes may not only contribute to endometriosis-major symptoms, but also contribute to ectopic endometrial tissue growth and endometriosis development. A major pro-inflammatory factors found elevated in peritoneal fluid of women with endometriosis and to be overexpressed in peritoneal fluid macrophages and active, highly vascularized and early stage endometriotic lesions, macrophage migration inhibitory factor (MIF) appeared to induce angiogenic and inflammatory and estrogen producing phenotypes in endometriotic cells in vitro and to be a possible therapeutic target in vivo. Using a mouse model where MIF-knock out (KO) mice received intra-peritoneal injection of endometrial tissue from MIF-KO or syngeneic wild type (WT) mice and vice versa, our current study revealed that MIF genetic depletion resulted in a marked reduction ectopic endometrial tissue growth, a disrupted tissue structure and a significant down regulation of the expression of major inflammatory (cyclooxygenease-2), cell adhesion (αv and β3 integrins), survival (B-cell lymphoma-2) and angiogenic (vascular endothelial cell growth) factorsrelevant to endometriosis pathogenesis, whereas MIF add-back to MIF-KO mice significantly restored endometriosis-like lesions number and size. Interestingly, cross-experiments revealed that MIF presence in both endometrial and peritoneal host tissues is required for ectopic endometrial tissue growth and pointed to its involvement in endometrial-peritoneal interactions. This study provides compelling evidence for the role of MIF in endometriosis development and its possible interest for a targeted treatment of endometriosis.

Macrophage migration inhibitory factor down-regulates the RANKL-RANK signaling pathway by activating Lyn tyrosine kinase in mouse models

OBJECTIVE

Macrophage migration inhibitory factor (MIF) is an important modulator of innate and adaptive immunity as well as local inflammatory responses. We previously reported that MIF down-regulated osteoclastogenesis through a mechanism that requires CD74. The aim of the current study was to examine whether MIF modulates osteoclastogenesis through Lyn phosphorylation, and whether down-regulation of RANKL-mediated signaling requires the association of CD74, CD44, and Lyn.

METHODS

CD74-knockout (CD74-KO), CD44-KO, and Lyn-KO mouse models were used to investigate whether Lyn requires these receptors and coreceptors. The effects of MIF on osteoclastogenesis were assessed using Western blot analysis, small interfering RNA (siRNA)-targeted down-regulation of Lyn, Lyn-KO mice, and real-time imaging of Lyn molecules to surface proteins.

RESULTS

MIF treatment induced Lyn expression, and MIF down-regulated RANKL-induced activator protein 1 (AP-1) and the Syk/phospholipase Cγ cascade during osteoclastogenesis through activated Lyn tyrosine kinase. The results of immunoprecipitation studies revealed that MIF receptors associated with Lyn in response to MIF treatment. Studies using Lyn-specific siRNA and Lyn-KO mice confirmed our findings.

CONCLUSION

Our findings indicate that the tyrosine kinase Lyn is activated when MIF binds to its receptor CD74 and its coreceptor CD44 and, in turn, down-regulates the RANKL-mediated signaling cascade by suppressing NF-ATc1 protein expression through down-regulation of AP-1 and calcium signaling components.

Coalescence of B cell receptor and invariant chain MHC II in a raft-like membrane domain

The BCR binds antigen for processing and subsequent presentation on MHC II molecules. Polyvalent antigen induces BCR clustering and targeting to endocytic processing compartments, which are also accessed by Ii-MHC II. Here, we report that clustered BCR is able to team up with Ii-MHC II already at the plasma membrane of mouse B-lymphocytes. Colocalization of BCR and Ii-MHC II on the cell surface required clustering of both types of molecules. The clustering of only one type did not trigger the recruitment of the other. Ii-bound MIF (a ligand of Ii) also colocalized with clustered BCR upon oligomerization of MIF on the surface of the B cell. Abundant surface molecules, such as B220 or TfnR, did not cocluster with the BCR. Some membrane raft-associated molecules, such as peptide-loaded MHC II, coclustered with the BCR, whereas others, such as GM1, did not. The formation of a BCR- and Ii-MHC II-containing membrane domain by antibody-mediated clustering was independent of F-actin and led to the coendocytosis of its constituents. With a rapid Brij 98 extraction method, it was possible to capture this membrane domain biochemically as a DRM. Ii and clustered BCR were present on the same DRM, as shown by immunoisolation. The coalescence of BCR and Ii-MHC II increased tyrosine phosphorylation, indicative of enhanced BCR signaling. Our work suggests a novel role for MIF and Ii-MHC II in BCR-mediated antigen processing.

Association between the -794 (CATT)5-8 MIF gene polymorphism and susceptibility to acute coronary syndrome in a western Mexican population

The macrophage migration inhibitory factor (MIF) is related to the progression of atherosclerosis, which, in turn, is a key factor in the development of acute coronary syndrome (ACS). MIF has a CATT short tandem repeat (STR) at position -794 that might be involved in its expression rate. The aim of this study was to investigate the association between the -794 (CATT)5-8  MIF gene polymorphism and susceptibility to ACS in a western Mexican population. This research included 200 ACS patients classified according to the criteria of the American College of Cardiology (ACC) and 200 healthy subjects (HS). The -794 (CATT)5-8  MIF gene polymorphism was analyzed using a conventional polymerase chain reaction (PCR) technique. The 6 allele was the most frequent in both groups (ACS: 54% and HS: 57%). The most common genotypes in ACS patients and HS were 6/7 and 6/6, respectively, and a significant association was found between the 6/7 genotype and susceptibility to ACS (68% versus 47% in ACS and HS, resp., P = 0.03). We conclude that the 6/7 genotype of the MIF -794 (CATT)5-8 polymorphism is associated with susceptibility to ACS in a western Mexican population.

Involvement of CD74 in head and neck squamous cell carcinomas

PURPOSE

While macrophage migration inhibitory factor (MIF) has been extensively studied in the context of inflammation and inflammatory disorders, less work has been devoted to its involvement in cancer, notably in neoplastic progression. In a previous study, we have found evidence that MIF plays a role in head and neck squamous cell carcinomas (HNSCC). The current investigations were undertaken in order to estimate the importance of the MIF receptor, CD74 in the progression of HNSCC.

METHODS AND RESULTS

In a cohort of 46 cases of oral cavity carcinomas, immunohistochemical staining revealed an increase in CD74 expression during progression from benign lesions to carcinoma. As shown by cell culture experiments using squamous carcinoma cell line (SCCVII) transduced with anti-CD74 shRNA, the amount of cell-produced VEGF was lower in SCCVII CD74KD cell line compared with control SCCVII CD74sc cell line, suggesting that CD74 could be implicated in angiogenesis in vivo. Furthermore, knockdown of CD74 decreased proliferation of SCCVII cells in vitro. The migration of SCCVII cells, as well as the cell secretion of matrix metallopeptidase 9, was also negatively affected by CD74 knockdown. These observations in vitro were confirmed in an orthotopic mouse model of SCC where tumors produced by SCCVII CD74KD cell inoculation were found to grow more slowly than tumors generated by SCCVII CD74sc cells.

CONCLUSION

The clinical observations and experimental data reported here suggest that CD74, as well as MIF, plays a pivotal role in HNSCC progression.

MIF: mood improving/inhibiting factor?

Although major depressive disorder imposes a serious public health burden and affects nearly one in six individuals in developed countries over their lifetimes, there is still no consensus on its pathophysiology. Inflammation and cytokines have emerged as a promising new avenue in depression research, and, in particular, macrophage migration inhibitory factor (MIF) has been shown to be significant in depression physiology. In this review we summarize current research on MIF and depression. We highlight the arguments for MIF as a pro- and antidepressant species and discuss the potential implications for therapeutics.

Dexamethasone-conjugated polyethylenimine/MIF siRNA complex regulation of particulate matter-induced airway inflammation

Inhalation of airborne particulate matter (PM), such as silicon dioxide (SiO2) and titanium dioxide (TiO2), induces acute lung inflammation. siRNA therapy has been proposed as a method to repair acute lung inflammation. To determine whether DEXA-PEI/MIF siRNA contributes to SiO2-induced acute lung inflammation repair, we administered Dexa-PEI/MIF siRNA in SiO2-treated Beas-2b cells and instilled DEXA-PEI-MIF siRNA intratracheally in mice with SiO2-induced acute lung inflammation. Using genetic (MIF mRNA RT-PCR), histological (H&E and PAS) and immunohistochemical (MIF and Muc5ac) analyses, we estimated the acute lung inflammation in Beas-2b cells and BALB/c mice. Cells and mice treated with SiO2 particles demonstrated pulmonary inflammation. DEXA-PEI/MIF siRNA restricted the extent of the pulmonary inflammation reaction to SiO2 in cells and mice. In case of SiO2-treated Beas-2b cells, only DEXA-PEI treatment failed to effectively regulate MIF mRNA release. At the same time, only DEXA-PEI treatment adjusted the amount of MIF mRNA to some extent in SiO2-treated BALB/c mice. siRNA treatment did not markedly control MIF mRNA release in mice. We also observed that the amount of MIF mRNA was decreased in cells and mice treated with DEXA-PEI/MIF siRNA. The increase of MIF mRNA markedly increased Muc5ac; in contrast, the decrease of MIF mRNA using DEXA-PEI/MIF siRNA effectively lowered Muc5ac in SiO2-treated cells and mice. These results suggest that DEXA-PEI plays a role in delivering siRNA to the nucleus as a carrier and limits the extent of acute lung inflammation. MIF siRNA also contributed to the reparative lung response in SiO2-induced pulmonary inflammation.

Macrophage migration inhibitory factor of Sciaenops ocellatus regulates immune cell trafficking and is involved in pathogen-induced immune response

Macrophage migration inhibitory factor (MIF) is a multi-functional cytokine involved in immunoregulation and inflammation. In this study, we examined the expression and biological function of a MIF, SoMIF, from red drum Sciaenops ocellatus. SoMIF is composed of 115 residues and shares 85-99% overall sequence identities with the MIF of a number of teleost. SoMIF expression was detected in a wide range of tissues and upregulated by bacterial and viral infection in a time-dependent manner. In head kidney (HK) leukocytes, pathogen infection induced SoMIF expression, and the expressed SoMIF was secreted into the extracellular milieu. Recombinant SoMIF (rSoMIF) purified from Escherichia coli inhibited the migration of both HK monocytes and lymphocytes, and this inhibitory effect was abolished by the presence of anti-rSoMIF antibodies. When rSoMIF was administered into red drum, it stimulated the production of reactive oxygen species in HK monocytes both in the presence and absence of pathogen infection. In vivo infection study showed that compared to untreated fish, fish pre-treated with rSoMIF before bacterial infection exhibited significantly lower bacterial loads in blood, kidney, spleen, and liver. Taken together, these results indicate that SoMIF is a secreted protein that regulates immune cell trafficking and is involved in pathogen-induced immune response.

Spirohexenolide A targets human macrophage migration inhibitory factor (hMIF)

Spirohexenolides A and B comprise a unique family of spirotetronate natural products. We report on the identification of their binding to and modulation of human macrophage migration inhibitor factor (hMIF). Using an immunoaffinity-fluorescent labeling method, the properties of this interaction are detailed and evidence is provided that hMIF plays a key role in the cytostatic activity of the spirohexenolides.

Macrophage migration inhibitory factor in head and neck squamous cell carcinoma: clinical and experimental studies

PURPOSE

The present in vivo/in vitro study was undertaken in order to evaluate the importance of macrophage migration inhibitory factor (MIF) in the progression of head and neck squamous cell carcinoma (HNSCC).

METHODS

Tumor tissue expression (MIF immunostaining) and plasma levels (ELISA) of MIF were determined in HNSCC patients and correlated with tumor recurrence and metastasis, and overall survival. Furthermore, the impact of MIF expression on cell proliferation and anticancer drug sensitivity was examined in murine squamous carcinoma cell line SCCVII after MIF knockdown (MIF-KD).

RESULTS

As revealed by quantitative analysis of MIF immunostaining, tumor progression was accompanied by an increase in mean optical density (MOD) and labeling index (LI). Likewise, an elevation of MIF serum levels was noted in HNSCC patients (n = 66) versus healthy individuals (n = 16). Interestingly, comparison of laryngeal carcinoma patients on the basis of MIF tissue expression (high expression, LI ≥ 47, versus low expression, LI < 47) disclosed a significant difference between disease-free survival curves for local and nodal recurrence, and overall survival curve. In vitro, MIF knockdown in murine SCCVII cells resulted in reduced cell proliferation and a decrease in cell motility. In mice inoculated with SCCVII cells, MIF-KD tumors grew more slowly and also appeared more sensitive to chemotherapy.

CONCLUSIONS

Both clinical observations and experimental data suggest that MIF plays a pivotal role in the progression of HNSCC.

Deletion of CD74, a putative MIF receptor, in mice enhances osteoclastogenesis and decreases bone mass

CD74 is a type II transmembrane protein that can act as a receptor for macrophage migration inhibitory factor (MIF) and plays a role in MIF-regulated responses. We reported that MIF inhibited osteoclast formation and MIF knockout (KO) mice had decreased bone mass. We therefore examined if CD74 was involved in the ability of MIF to alter osteoclastogenesis in cultured bone marrow (BM) from wild-type (WT) and CD74-deficient (KO) male mice. We also measured the bone phenotype of CD74 KO male mice. Bone mass in the femur of 8-week-old mice was measured by micro-computed tomography and histomorphometry. Bone marrow cells from CD74 KO mice formed 15% more osteoclast-like cells (OCLs) with macrophage colony-stimulating factor (M-CSF) and receptor activator of NF-κB ligand (RANKL) (both at 30 ng/mL) compared to WT. Addition of MIF to WT cultures inhibited OCL formation by 16% but had no effect on CD74KO cultures. The number of colony forming unit granulocyte-macrophage (CFU-GM) in the bone marrow of CD74 KO mice was 26% greater than in WT controls. Trabecular bone volume (TBV) in the femurs of CD74 KO male mice was decreased by 26% compared to WT. In addition, cortical area and thickness were decreased by 14% and 11%, respectively. Histomorphometric analysis demonstrated that tartrate-resistant acid phosphatase (TRAP)(+) osteoclast number and area were significantly increased in CD74 KO by 35% and 43%, respectively compared to WT. Finally, we examined the effect of MIF on RANKL-induced-signaling pathways in bone marrow macrophage (BMM) cultures. MIF treatment decreased RANKL-induced nuclear factor of activated T cells, cytoplasmic 1 (NFATc1) and c-Fos protein in BMM cultures by 70% and 41%, respectively. Our data demonstrate that CD74 is required for MIF to affect in vitro osteoclastogenesis. Further, the bone phenotype of CD74 KO mice is similar to that of MIF KO mice. MIF treatment of WT cultures suppressed RANKL-induced activator protein 1 (AP-1) expression, which resulted in decreased osteoclast differentiation in vitro. We propose that CD74 plays a critical role in the MIF inhibition of osteoclastogenesis.

Brain miffed by macrophage migration inhibitory factor

Macrophage migration inhibitory factor (MIF) is a cytokine which also exhibits enzymatic properties like oxidoreductase and tautomerase. MIF plays a pivotal role in innate and acquired immunity as well as in the neuroendocrine axis. Since it is involved in the pathogenesis of acute and chronic inflammation, neoangiogenesis, and cancer, MIF and its signaling components are considered suitable targets for therapeutic intervention in several fields of medicine. In neurodegenerative and neurooncological diseases, MIF is a highly relevant, but still a hardly investigated mediator. MIF operates via intracellular protein-protein interaction as well as in CD74/CXCR2/CXCR4 receptor-mediated pathways to regulate essential cellular systems such as redox balance, HIF-1, and p53-mediated senescence and apoptosis as well as multiple signaling pathways. Acting as an endogenous glucocorticoid antagonist, MIF thus represents a relevant resistance gene in brain tumor therapies. Alongside this dual action, a functional homolog-annotated D-dopachrome tautomerase/MIF-2 has been uncovered utilizing the same cell surface receptor signaling cascade as MIF. Here we review MIF actions with respect to redox regulation in apoptosis and in tumor growth as well as its extracellular function with a focus on its potential role in brain diseases. We consider the possibility of MIF targeting in neurodegenerative processes and brain tumors by novel MIF-neutralizing approaches.

HIV-1 glycoprotein 41 ectodomain induces activation of the CD74 protein-mediated extracellular signal-regulated kinase/mitogen-activated protein kinase pathway to enhance viral infection

Besides mediating the viral entry process, the human immunodeficiency virus (HIV-1) envelope protein gp41 can bind to many host cell components and regulate cell functions. Using a yeast two-hybrid system, we screened a human bone marrow cDNA library and identified a novel gp41-binding protein, CD74 (the MHC class II-associated invariant chain). Here, we report possible biological effects mediated by interaction between gp41 and CD74. We found that HIV-1 gp41 could bind directly to host CD74 in HIV-1-infected cells, and the peptide 6358 derived from gp41 loop region (aa 597-611) could effectively block the gp41-CD74 interaction. As a result of this binding, recombinant soluble gp41 and gp41 peptide 6358 activated the CD74-mediated ERK/MAPK pathway and significantly enhanced HIV-1 infection in vitro. Conversely, the enhancing effect could be suppressed by the recombinant CD74 extracellular domain. These results reveal a novel mechanism underlying gp41 mediation of HIV-1 infection and replication.

Characterization of a secreted macrophage migration inhibitory factor homologue of the parasitic nematode Strongyloides acting at the parasite-host cell interface

Strongyloidiasis is a tropical parasitosis characterized by an alternation between free-living and parasitic stages, and by long-term infection via autoinfection. Since invasion and evasion processes of helminth parasites are substantially attained by the involvement of excretory-secretory products, we identified and characterized the 13.5 kDa macrophage migration inhibitory factor (MIF)-like protein in Strongyloides ratti. Sra-MIF is mainly secreted from the infective stage larvae (iL3), while the transcript was found at lower levels in parasitic and free-living females. Sequence analysis of the full-length cDNA showed the highest homology to the human pathogen Strongyloides stercoralis, and both are related to the MIF type-2. Unlike other mif genes, the Sra-mif includes no intron. The protein was recombinantly expressed in Escherichia coli and purified. Sra-MIF exhibited no in vitro tautomerase activity. The exposure of Sra-MIF to the host immune system is confirmed by high IgG reactivities found in the hosts' sera following infection or immunization. Flow cytometric analysis indicated the binding of Sra-MIF to the monocytes/macrophage lineage but not to peripheral lymphocytes. After exposure to Sra-MIF, monocytes released IL-10 but not TNF-alpha suggesting the involvement of the secreted parasite MIF in host immune responses.

MIF as a disease target: ISO-1 as a proof-of-concept therapeutic

Macrophage migration inhibitory factor (MIF) is a pleiotropic proinflammatory cytokine that has been implicated as playing a causative role in many disease states, including sepsis, pneumonia, diabetes, rheumatoid arthritis, inflammatory bowel disease, psoriasis and cancer. To inhibit the enzymatic and biologic activities of MIF, we and others have developed small-molecule MIF inhibitors. Most MIF inhibitors bind within the hydrophobic pocket that contains highly conserved amino acids known to be essential for MIF's proinflammatory activity. The best characterized of these small-molecule MIF inhibitors, (S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid methyl ester (ISO-1) has been validated in scores of laboratories worldwide. Like neutralizing anti-MIF antibodies, ISO-1 significantly improves survival and reduces disease progression and/or severity in multiple murine models where MIF is implicated. This MIF inhibitor, its derivatives and other MIF-targeted compounds show great promise for future testing in disease states where increased MIF activity has been discovered.

Ectopic expression of CD74 in Ikkβ-deleted mouse hepatocytes

CD74, a Type II membrane glycoprotein and MHC class II chaperone involved in antigen processing, is normally expressed by cells associated with the immune system. CD74 also forms heterodimers with CD44 to generate receptors to macrophage migration inhibitory factor (MIF), a proinflammatory cytokine. Following targeted Alb-Cre-mediated deletion of Ikkβ in Ikkβ(Δhep) mice (Ikkβ(F/F):Alb-Cre, a strain highly susceptible to chemically induced hepatotoxicity and hepatocarcinogenesis), CD74 is expressed abundantly by adult hepatocytes throughout liver acini, albeit more intensely in midzonal-to-centrilobular regions. By comparison, CD74 expression is not observed in Ikkβ(F/F) hepatocytes, nor is it augmented in the livers of Ikkβ(+/+):Alb-Cre mice; CD74 is barely detectable in cultured embryonic fibroblasts from Ikkβ(-/-) mice. Microarray profiling shows that constitutive CD74 expression in Ikkβ(Δhep) hepatocytes is accompanied by significantly augmented expression of CD44 and key genes associated with antigen processing and host defense, including MHC class II I-Aα, I-Aβ, and I-Eβ chains, CIITA and CD86. Taken together, these observations suggest that Ikkβ(Δhep) hepatocytes might express functional capacities for class II-restricted antigen presentation and heightened responsiveness to MIF-signaling, and also suggest further roles for intrahepatocellular IKKβ in the suppression or inactivation of molecules normally associated with the formation and differentiation of cells of the immune system.

Stoichiometry of HLA class II-invariant chain oligomers

BACKGROUND

The HLA gene complex encodes three class II isotypes, DR, DQ, and DP. HLA class II molecules are peptide receptors that present antigens for recognition by T lymphocytes. In antigen presenting cells, the assembly of matched α and β subunits to heterodimers is chaperoned by invariant chain (Ii). Ii forms a homotrimer with three binding sites for class II heterodimers. The current model of class II and Ii structure states that three αβ heterodimers bind to an Ii trimer.

METHODOLOGY/PRINCIPAL FINDINGS

[corrected] We have now analyzed the composition and size of the complexes of class II and Ii using epitope tagged class II subunits and density gradient experiments. We show here that class II-Ii oligomers consist of one class II heterodimer associated with one Ii trimer, such that the DR, DQ and DP isotypes are contained within separate complexes with Ii.

CONCLUSION/SIGNIFICANCE

We propose a structural model of the class II-Ii oligomer and speculate that the pentameric class II-Ii complex is bent towards the cell membrane, inhibiting the binding of additional class II heterodimers to Ii.

Structural and functional characterization of a macrophage migration inhibitory factor homologue from the marine cyanobacterium Prochlorococcus marinus

Macrophage migration inhibitory factor (MIF) is a multifunctional mammalian cytokine, which exhibits tautomerase and oxidoreductase activity. MIF homologues with pairwise sequence identities to human MIF ranging from 31% to 41% have been detected in various cyanobacteria. The gene encoding the MIF homologue from the marine cyanobacterium Prochlorococcus marinus strain MIT9313 has been cloned and the corresponding protein (PmMIF) overproduced, purified, and subjected to functional and structural characterization. Kinetic and (1)H NMR spectroscopic studies show that PmMIF tautomerizes phenylenolpyruvate and (p-hydroxyphenyl)enolpyruvate at low levels. The N-terminal proline of PmMIF is critical for these reactions because the P1A mutant has strongly reduced tautomerase activities. PmMIF shows high structural homology with mammalian MIFs as revealed by a crystal structure of PmMIF at 1.63 A resolution. MIF contains a Cys-X-X-Cys motif that mediates oxidoreductase activity, which is lacking from PmMIF. Engineering of the motif into PmMIF did not result in oxidoreductase activity but increased the tautomerase activity 8-fold. The shared tautomerase activities and the conservation of the beta-alpha-beta structural fold and key functional groups suggest that eukaryotic MIFs and cyanobacterial PmMIF are related by divergent evolution from a common ancestor. While several MIF homologues have been identified in eukaryotic parasites, where they are thought to play a role in modulating the host immune response, PmMIF is the first nonparasitic, bacterial MIF-like protein characterized in detail. This work sets the stage for future studies which could address the question whether a MIF-like protein from a free-living bacterium possesses immunostimulatory features similar to those of mammalian MIFs and MIF-like proteins found in parasitic nematodes and protozoa.

Growth factors and chemotactic factors from parasitic helminths: molecular evidence for roles in host-parasite interactions versus parasite development

For decades molecular helminthologists have been interested in identifying proteins expressed by the parasite that have roles in modulating the host immune response. In some cases, the aim was targeting parasite-derived orthologues of mammalian cytokines and growth factors known to have functions in immune modulation. In others, novel proteins without homology to mammalian cytokines were isolated by investigating effects of purified worm extracts on various immunological processes. Often, the role parasite-derived growth factors play in worm development was ignored. Here, we review growth factors and chemotactic factors expressed by parasitic helminths and discuss their recognised and potential roles in immunomodulation and/or parasite development.

The crystal structures of macrophage migration inhibitory factor from Plasmodium falciparum and Plasmodium berghei

Malaria, caused by Plasmodium falciparum and related parasites, is responsible for millions of deaths each year, mainly from complications arising from the blood stages of its life cycle. Macrophage migration inhibitory factor (MIF), a protein expressed by the parasite during these stages, has been characterized in mammals as a cytokine involved in a broad spectrum of immune responses. It also possesses two catalytic activities, a tautomerase and an oxidoreductase, though the physiological significance of neither reaction is known. Here, we have determined the crystal structure of MIF from two malaria parasites, Plasmodium falciparum and Plasmodium berghei at 2.2 Å and 1.8 Å, respectively. The structures have an α/β fold and each reveals a trimer, in agreement with the results of analytical ultracentrifugation. We observed open and closed active sites, these being distinguished by movements of proline-1, the catalytic base in the tautomerase reaction. These states correlate with the covalent modification of cysteine 2 to form a mercaptoethanol adduct, an observation confirmed by mass spectrometry. The Plasmodium MIFs have a different pattern of conserved cysteine residues to the mammalian MIFs and the side chain of Cys58, which is implicated in the oxidoreductase activity, is buried. This observation and the evident redox reactivity of Cys2 suggest quite different oxidoreductase characteristics. Finally, we show in pull-down assays that Plasmodium MIF binds to the cell surface receptor CD74, a known mammalian MIF receptor implying that parasite MIF has the ability to interfere with, or modulate, host MIF activity through a competitive binding mechanism.

Hypothesis: Targeted Ikkβ deletion upregulates MIF signaling responsiveness and MHC class II expression in mouse hepatocytes

Macrophage migration inhibitory factor (MIF) is causally related to the pathogenesis of chronic liver disease but its hepatocellular mechanisms of action are largely unknown. Scattered reports in the literature hint at functional connections between the expression of MIF and major histocompatibility complex (MHC) Class II molecules. Not surprisingly, these relationships have not yet been explored in hepatocytes because MIF and MHC Class II cell surface receptors are commonly expressed by other cell types including various antigen presenting cells of the immune system. On the other hand, mounting evidence suggests that heteromeric MIF receptors share a common molecule with intracellular MHC Class II complexes, viz., CD74, which also serves as the MHC Class II chaperone; and, while it is unclear what cancer-related role(s) MHC Class II receptors might play, increasing evidence suggests that MIF and CD74 are also implicated in the biology of hepatocellular carcinoma. These reports are provocative for two reasons: firstly, Ikkβ^Δhep mice carrying hepatocyte-targeted deletions of Ikkβ, an IκB kinase complex subunit required for the activation of the transcription factor NF-κB (nuclear factor-κB), have been shown to display heightened susceptibilities to hepatotoxins and chemical hepatocarcinogens; secondly, microarray profiling observations indicate that Ikkβ^Δhep hepatocytes constitutively and “ectopically” overexpress genes, particularly CD74, CD44 (a MIF-receptor subunit) and MHC Class II I-A/E β and I-A α chains, and gene families that regulate host immune process and immune defense responses. These findings together suggest that Ikkβ^Δhep mice might express functional MIF and MHC Class II receptors, leading to increased hepatocellular sensitivity to MIF signaling as well as to the unusual property of antigen presentation; both functions might contribute to the heightened liver disease phenotypes of Ikkβ^Δhep mice. The findings raise questions about the potential existence of cohorts of human patients with genetic abnormalities of Ikkβ that might confer heightened susceptibility to liver disease including hepatocellular carcinoma.

Spinal macrophage migration inhibitory factor contributes to the pathogenesis of inflammatory hyperalgesia in rats

Pro-inflammatory cytokine production after nociceptive stimuli is pivotal for hyperalgesia. As macrophage migration inhibitory factor (MIF), a pleiotropic cytokine produced mainly by nonneuronal tissue, has been involved in the regulation of neuronal functions, herein we examined the role for MIF in formalin-induced inflammatory pain model. MIF critically contributed to nociceptive behaviors following formalin injection. Specifically, spinal administration of a MIF inhibitor (ISO-1) prevented and reversed flinching responses in rats. Further examination showed that levels of both MIF and the MIF receptor CD74 were substantially increased within the ipsilateral spinal cord dorsal horn after formalin administration. Mechanistic studies revealed that MIF upregulated the expression of the spinal NMDA receptor subunit NR2B via the MAPK signaling pathway. Moreover, microglial cells were found to be the major source of spinal MIF after formalin administration by fluorescence colocalization. These data highlight spinal MIF plays a critical role in the pathogenesis of formalin-induced inflammatory pain and suggest MIF may be a potential target for therapy of such pathological condition.