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

Role of MIF and D-DT in immune-inflammatory, autoimmune, and chronic respiratory diseases: from pathogenic factors to therapeutic targets

Macrophage migration inhibitory factor (MIF) is a protein that acts as a cytokine-, enzyme-, endocrine- and chaperon-like molecule. It binds to the cell-surface receptor CD74 in association with CD44, which activates the downstream signal transduction pathway. In addition, MIF acts also as a noncognate ligand for C-X-C chemokine receptor type 2 (CXCR2), type 4 (CXCR4), and type 7 (CXCR7). Recently, D-dopachrome tautomerase (D-DT), a second member of the MIF superfamily, was identified. From a pharmacological and clinical point of view, the nonredundant biological properties of MIF and D-DT anticipate potential synergisms from their simultaneous inhibition. Here, we focus on the role of MIF and D-DT in human immune-inflammatory, autoimmune, and chronic respiratory diseases, providing an update on the progress made in the identification of specific small-molecule inhibitors of these proteins.

CATT polymorphism in MIF gene promoter is closely related to human pulmonary tuberculosis in a southwestern China population

Macrophage migration inhibitory factor (MIF) is deemed as an immunoregulatory and proinflammatory cytokine related to the progression of tuberculosis. A CATT short tandem repeat (STR) polymorphism at position −794 in the MIF gene promoter region is associated with the susceptibility to tuberculosis (TB). To investigate whether macrophage MIF gene mif CATT variants are associated with susceptibility to retreatment cases of TB and drug-resistant TB prevalence, genotyping of MIF −794 CATT polymorphism and quantifying of serum MIF were performed to associate MIF−794 CATT polymorphism with new patients and retreatment cases. Significant increases in MIF −794 CATT genotypes 7/8 and allele CATT 8 were observed in TB patients. Significant differences in the genotypic frequencies of MIF −794 CATT (5/X + 6/X vs 7/7 + 7/8) were demonstrated upon comparing the total cases and the new cases of TB with the controls. Significant differences in the allelic frequencies of MIF −794 CATT (5 + 6 vs 7 + 8) were observed in the total cases and new cases of TB. No differences in the genotypic frequencies of the MIF −794 CATT (5/X + 6/X vs 7/7 + 7/8) were observed between the retreatment cases and the controls or between the new cases and retreatment cases. In conclusion, the MIF −794 CATT genotypes 7/8 and allele CATT 8 were highly associated with TB; no differences in the genotypic frequencies of the MIF −794 CATT (5/X + 6/X vs 7/7 + 7/8) were observed between the new cases and retreatment cases.

A comprehensive review on adult onset Still's disease

Adult-onset Still's disease (AOSD) is a systemic inflammatory disorder of unknown etiology usually affecting young adults; spiking fever, arthritis and evanescent rash are commonly observed during the disease. Other frequently observed clinical features include sore throat, hepatomegaly, splenomegaly, lymphadenopathy and serositis. Furthermore, AOSD patients may experience different life-threating complications. Macrophage activation syndrome (MAS) has been reported up to 15% of AOSD patients and it is considered to be the most severe complication of the disease being characterised by high mortality rate. During AOSD, laboratory tests reflect the systemic inflammatory process showing high levels of erythrocyte sedimentation rate and C-reactive protein. In addition, the ferritin levels are typically higher than those observed in other autoimmune, inflammatory, infectious, or neoplastic diseases. Analysing AOSD disease course, 3 different clinical patterns of AOSD have been identified: i. monocyclic pattern, characterised by a systemic single episode; ii. polycyclic pattern, characterised by multiple, ≤ 1 year lasting, flares, alternating with remissions; iii. chronic pattern, related to a persistently active disease with associated polyarthritis. At present, AOSD therapeutic strategy is aimed at targeting pro-inflammatory signs and symptoms, preventing organ damage and life-threating complications and minimising adverse effects of treatment. However, the treatment of AOSD remains largely empirical, lacking controlled clinical trials. High dosages of corticosteroids are usually the first line therapy when the systemic symptoms predominate. Despite this treatment, a large percentage of patients experiences several flares with an evolution toward the chronic disease course and up to 16% of patients die during the follow up, due to AOSD-related complications. On these bases, in the last years, biological agents have been successfully used in refractory cases. Finally, multiple recent lines of evidence have suggested new insights in AOSD pathogenesis unmasking further therapeutic targets. In fact, small molecules, used in experimental MAS models, might represent new therapeutic options.

Small-molecule inhibitors of macrophage migration inhibitory factor (MIF) as an emerging class of therapeutics for immune disorders

Macrophage migration inhibitory factor (MIF) is an important cytokine for which an increasing number of functions is being described in the pathogenesis of inflammation and cancer. Nevertheless, the availability of potent and druglike MIF inhibitors that are well-characterized in relevant disease models remains limited. Development of highly potent and selective small-molecule MIF inhibitors and validation of their use in relevant disease models will advance drug discovery. In this review, we provide an overview of recent advances in the identification of MIF as a pharmacological target in the pathogenesis of inflammatory diseases and cancer. We also give an overview of the current developments in the discovery and design of small-molecule MIF inhibitors and define future aims in this field.

Overexpression of macrophage migration inhibitory factor and functionally-related genes, D-DT, CD74, CD44, CXCR2 and CXCR4, in glioblastoma

The macrophage migration inhibition factor (MIF) is a cytokine with multiple biological functions, including the cancer-associated processes, cell cycle deregulation, angiogenesis and metastatization. The present study investigated the expression of MIF and its functionally associated genes (D-DT, CD74, CD44, CXCR2 and CXCR4) in glioblastoma multiforme (GBM). The data were obtained from The Cancer Genome Atlas databank, through the cBioportal web-based utility (cbioportal.org/). A significant increase was observed in the majority of these genes in GBM samples compared with lower grade gliomas, however no significant correlation among the selected genes and the overall survival of the patients was identified. In contrast, the expression of MIF exhibited a trend toward an increase in overall survival and a significant increase of MIF expression was observed in samples of patients who underwent neoadjuvant treatment. In conclusion these data indicate that MIF and its receptors are involved in GBM progression and maintenance. Deciphering the precise biological significance in GBM would favor the adoption of tailored approaches to modulate the function of MIF and its associated genes for the treatment of the disease.

Optimization of Pyrazoles as Phenol Surrogates to Yield Potent Inhibitors of Macrophage Migration Inhibitory Factor

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine that is implicated in the regulation of inflammation, cell proliferation, and neurological disorders. MIF is also an enzyme that functions as a keto-enol tautomerase. Most potent MIF tautomerase inhibitors incorporate a phenol, which hydrogen bonds to Asn97 in the active site. Starting from a 113-μm docking hit, we report results of structure-based and computer-aided design that have provided substituted pyrazoles as phenol alternatives with potencies of 60-70 nm. Crystal structures of complexes of MIF with the pyrazoles highlight the contributions of hydrogen bonding with Lys32 and Asn97, and aryl-aryl interactions with Tyr36, Tyr95, and Phe113 to the binding.

Advances and Insights for Small Molecule Inhibition of Macrophage Migration Inhibitory Factor

Macrophage migration inhibitory factor (MIF) is an upstream regulator of the immune response whose dysregulation is tied to a broad spectrum of inflammatory and proliferative disorders. As its complex signaling pathways and pleiotropic nature have been elucidated, it has become an attractive target for drug discovery. Remarkably, MIF is both a cytokine and an enzyme that functions as a keto-enol tautomerase. Strategies including in silico modeling, virtual screening, high-throughput screening, and screening of anti-inflammatory natural products have led to a large and diverse catalogue of MIF inhibitors as well as some understanding of the structure-activity relationships for compounds binding MIF's tautomerase active site. With possible clinical trials of some MIF inhibitors on the horizon, it is an opportune time to review the literature to seek trends, address inconsistencies, and identify promising new avenues of research.

Macrophage Migration Inhibitory Factor (MIF) Prevents Maternal Death, but Contributes to Poor Fetal Outcome During Congenital Toxoplasmosis

Migration inhibitory factor (MIF) is a pro-inflammatory cytokine that plays important roles in physiology, pathology, immunology and parasitology, including the control of infection by protozoa parasites such as Toxoplasma gondii. As the MIF function in congenital toxoplasmosis is not fully elucidated yet, the present study brings new insights for T. gondii infection in the absence of MIF based on pregnant C57BL/6MIF-/- mouse models. Pregnant C57BL/6MIF-/- and C57BL/6WT mice were infected with 05 cysts of T. gondii (ME49 strain) on the first day of pregnancy (dop) and were euthanized at 8 dop. Non-pregnant and non-infected females were used as control. Our results demonstrated that MIF-/- mice have more accentuated change in body weight and succumbed to infection first than their WT counterparts. Otherwise, pregnancy outcome was less destructive in MIF-/- mice compared to WT ones, and the former had an increase in the mast cell recruitment and IDO expression and consequently presented less inflammatory cytokine production. Also, MIF receptor (CD74) was upregulated in MIF-/- mice, indicating that a compensatory mechanism may be required in this model of study. The global absence of MIF was associated with attenuation of pathology in congenital toxoplasmosis, but resulted in female death probably because of uncontrolled infection. Altogether, ours results demonstrated that part of the immune response that protects a pregnant female from T. gondii infection, favors fetal damage.

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.

Design, Synthesis, and Biological Activity of New N-(Phenylmethyl)-benzoxazol-2-thiones as Macrophage Migration Inhibitory Factor (MIF) Antagonists: Efficacies in Experimental Pulmonary Hypertension

Macrophage migration inhibitory factor (MIF) is a key pleiotropic mediator and a promising therapeutic target in cancer as well as in several inflammatory and cardiovascular diseases including pulmonary arterial hypertension (PAH). Here, a novel series of N-(phenylmethyl)-benzoxazol-2-thiones 5-32 designed to target the MIF tautomerase active site was synthesized and evaluated for its effects on cell survival. Investigation of structure-activity relationship (SAR) particularly at the 5-position of the benzoxazole core led to the identification of 31 that potently inhibits cell survival in DU-145 prostate cancer cells and pulmonary endothelial cells derived from patients with idiopathic PAH (iPAH-ECs), two cell lines for which survival is MIF-dependent. Molecular docking studies helped to interpret initial SAR related to MIF tautomerase inhibition and propose preferred binding mode for 31 within the MIF tautomerase active site. Interestingly, daily treatment with 31 started 2 weeks after a subcutaneous monocrotaline injection regressed established pulmonary hypertension in rats.

A global view of structure-function relationships in the tautomerase superfamily

The tautomerase superfamily (TSF) consists of more than 11,000 nonredundant sequences present throughout the biosphere. Characterized members have attracted much attention because of the unusual and key catalytic role of an N-terminal proline. These few characterized members catalyze a diverse range of chemical reactions, but the full scale of their chemical capabilities and biological functions remains unknown. To gain new insight into TSF structure-function relationships, we performed a global analysis of similarities across the entire superfamily and computed a sequence similarity network to guide classification into distinct subgroups. Our results indicate that TSF members are found in all domains of life, with most being present in bacteria. The eukaryotic members of the cis-3-chloroacrylic acid dehalogenase subgroup are limited to fungal species, whereas the macrophage migration inhibitory factor subgroup has wide eukaryotic representation (including mammals). Unexpectedly, we found that 346 TSF sequences lack Pro-1, of which 85% are present in the malonate semialdehyde decarboxylase subgroup. The computed network also enabled the identification of similarity paths, namely sequences that link functionally diverse subgroups and exhibit transitional structural features that may help explain reaction divergence. A structure-guided comparison of these linker proteins identified conserved transitions between them, and kinetic analysis paralleled these observations. Phylogenetic reconstruction of the linker set was consistent with these findings. Our results also suggest that contemporary TSF members may have evolved from a short 4-oxalocrotonate tautomerase-like ancestor followed by gene duplication and fusion. Our new linker-guided strategy can be used to enrich the discovery of sequence/structure/function transitions in other enzyme superfamilies.

Role of macrophage migration inhibitory factor in head and neck cancer and novel therapeutic targets: A systematic review

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine involved in systemic, autoimmune, and inflammatory diseases, such as obesity, rheumatoid arthritis, and systemic lupus erythematosus. For the 2 past decades, MIF has been reported to participate in carcinogenesis, disease prognosis, tumor cell proliferation, invasion, and tumor-induced angiogenesis in many cancers. The purpose of this article is to review published experimental and clinical data for MIF and its involvement in upper aerodigestive tract cancers. Based on the current literature, we propose a biomolecular model describing the mechanisms underlying the involvement of MIF in the initiation, progression, apoptosis, and proliferation of head and neck tumor cells. In reference to this model, potential therapeutic approaches based on the use of MIF antagonists and neutralizing antibodies are described. It is concluded that MIF is a promising target for future therapeutic strategies, both with and without chemoradiation strategies.