Critical modifications of the ISO-1 scaffold improve its potent inhibition of macrophage migration inhibitory factor (MIF) tautomerase activity

Based on the scaffold of (S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid methyl ester (ISO-1), an inhibitor of the proinflammatory cytokine MIF, two critical modifications and chiral resolution have significantly improved the potency of the inhibition. Compound (R)-17 is 20-fold more potent than ISO-1 and inhibits MIF tautomerase activity with an IC(50) of 550 nM.     

Novel anti-inflammatory activity of epoxyazadiradione against macrophage migration inhibitory factor: inhibition of tautomerase and proinflammatory activities of macrophage migration inhibitory factor

Macrophage migration inhibitory factor (MIF) is responsible for proinflammatory reactions in various infectious and non-infectious diseases. We have investigated the mechanism of anti-inflammatory activity of epoxyazadiradione, a limonoid purified from neem (Azadirachta indica) fruits, against MIF. Epoxyazadiradione inhibited the tautomerase activity of MIF of both human (huMIF) and malaria parasites (Plasmodium falciparum (PfMIF) and Plasmodium yoelii (PyMIF)) non-competitively in a reversible fashion (K(i), 2.11-5.23 μm). Epoxyazadiradione also significantly inhibited MIF (huMIF, PyMIF, and PfMIF)-mediated proinflammatory activities in RAW 264.7 cells. It prevented MIF-induced macrophage chemotactic migration, NF-κB translocation to the nucleus, up-regulation of inducible nitric-oxide synthase, and nitric oxide production in RAW 264.7 cells. Epoxyazadiradione not only exhibited anti-inflammatory activity in vitro but also in vivo. We tested the anti-inflammatory activity of epoxyazadiradione in vivo after co-administering LPS and MIF in mice to mimic the disease state of sepsis or bacterial infection. Epoxyazadiradione prevented the release of proinflammatory cytokines such as IL-1α, IL-1β, IL-6, and TNF-α when LPS and PyMIF were co-administered to BALB/c mice. The molecular basis of interaction of epoxyazadiradione with MIFs was explored with the help of computational chemistry tools and a biological knowledgebase. Docking simulation indicated that the binding was highly specific and allosteric in nature. The well known MIF inhibitor (S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid methyl ester (ISO-1) inhibited huMIF but not MIF of parasitic origin. In contrast, epoxyazadiradione inhibited both huMIF and plasmodial MIF, thus bearing an immense therapeutic potential against proinflammatory reactions induced by MIF of both malaria parasites and human.     

The tautomerase active site of macrophage migration inhibitory factor is a potential target for discovery of novel anti-inflammatory agents

Macrophage migration inhibitory factor (MIF) is an immunoregulatory protein that is a potential therapeutic target for a number of inflammatory diseases. Evidence exists that an unexpected catalytic active site of MIF may have a biological function. To gain further insight into the role of the catalytic active site, a series of mutational, structural, and biological activity studies were performed. The insertion of an alanine between Pro-1 and Met-2 (PAM) abolishes a non-physiological catalytic activity, and this mutant is defective in the in vitro glucocorticoid counter-regulatory activity of MIF. The crystal structure of MIF complexed to (S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid methyl ester (ISO-1), an inhibitor of MIF d-dopachrome tautomerase activity, reveals that ISO-1 binds to the same position of the active site as p-hydroxyphenylpyruvic acid, a substrate of MIF. ISO-1 inhibits several MIF biological activities, further establishing a role for the catalytic active site of MIF.     

Ketone bodies affect the enzymatic activity of macrophage migration inhibitory factor

Macrophage migration inhibitory factor (MIF), a long known proinflammatory cytokine exhibits perplexing enzymatic activities: tautomeric conversion of D-dopachrome and phenylpyruvate. Whether these catalytic activities bear functional relevance regarding MIF's multifaceted roles is under current scrutiny. Nevertheless, intense search has already started for pharmacological agents that target MIF's tautomerase activity. We have probed several antiinflammatory compounds against keto--enol (enolase) and enol--keto (ketonase) conversion of phenylpyruvate by MIF with spectrophotometry. We have identified acidic CH groups as markers of inhibitor potency toward MIF phenylpyruvate tautomerase. Among simple model molecules with strong acidic CH groups we found acetylacetone the best inhibitor particularly against the ketonase activity. Ketones of physiological importance - ketone bodies - also feature acidic CH groups and have been reported to exert certain anti-inflammatory effects. In this paper we report that ketone bodies inhibit preferentially the ketonase activity of MIF in vitro. Future studies should address whether such an interaction might operate in vivo and delineate its possible relevance concerning cytokine and non-cytokine roles of MIF.     

Macrophage migration inhibitory factor (MIF) is rendered enzymatically inactive by myeloperoxidase-derived oxidants but retains its immunomodulatory function

Macrophage migration inhibitory factor (MIF) is an important player in the regulation of the inflammatory response. Elevated plasma MIF is found in sepsis, arthritis, cystic fibrosis and atherosclerosis. Immunomodulatory activities of MIF include the ability to promote survival and recruitment of inflammatory cells and to amplify pro-inflammatory cytokine production. MIF has an unusual nucleophilic N-terminal proline with catalytic tautomerase activity. It remains unclear whether tautomerase activity is required for MIF function, but small molecules that inhibit tautomerase activity also inhibit the pro-inflammatory activities of MIF. A prominent feature of the acute inflammatory response is neutrophil activation and production of reactive oxygen species, including myeloperoxidase (MPO)-derived hypochlorous acid and hypothiocyanous acid. We hypothesized that MPO-derived oxidants would oxidize the N-terminal proline of MIF and alter its biological activity. MIF was exposed to hypochlorous acid and hypothiocyanous acid and the oxidative modifications on MIF were examined by LC-MS/MS. Imine formation and carbamylation was observed on the N-terminal proline in response to MPO-dependent generation of hypochlorous and hypothiocyanous acid, respectively. These modifications led to a complete loss of tautomerase activity. However, modified MIF still increased CXCL-8/IL-8 production by peripheral blood mononuclear cells (PBMCs) and blocked neutrophil apoptosis, indicating that tautomerase activity is not essential for these biological functions. Pre-treatment of MIF with hypochlorous acid protected the protein from covalent modification by the MIF inhibitor 4-iodo-6-phenylpyrimidine (4-IPP). Therefore, oxidant generation at inflammatory sites may protect MIF from inactivation by more disruptive electrophiles, including drugs designed to target the tautomerase activity of MIF.     

A small-molecule macrophage migration inhibitory factor antagonist protects against glomerulonephritis in lupus-prone NZB/NZW F1 and MRL/lpr mice

Autoimmunity leads to the activation of innate effector pathways, proinflammatory cytokine production, and end-organ injury. Macrophage migration inhibitory factor (MIF) is an upstream activator of the innate response that mediates the recruitment and retention of monocytes via CD74 and associated chemokine receptors, and it has a role in the maintenance of B lymphocytes. High-expression MIF alleles also are associated with end-organ damage in different autoimmune diseases. We assessed the therapeutic efficacy of (S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid methyl ester (ISO-1), an orally bioavailable MIF antagonist, in two distinct models of systemic lupus erythematosus: the NZB/NZW F1 and the MRL/lpr mouse strains. ISO-1, like anti-MIF, inhibited the interaction between MIF and its receptor, CD74, and in each model of disease, it reduced functional and histological indices of glomerulonephritis, CD74(+) and CXCR4(+) leukocyte recruitment, and proinflammatory cytokine and chemokine expression. Neither autoantibody production nor T and B cell activation were significantly affected, pointing to the specificity of MIF antagonism in reducing excessive proinflammatory responses. These data highlight the feasibility of targeting the MIF-MIF receptor interaction by small-molecule antagonism and support the therapeutic value of downregulating MIF-dependent pathways of tissue damage in systemic lupus erythematosus.     

Alternative chemical modifications reverse the binding orientation of a pharmacophore scaffold in the active site of macrophage migration inhibitory factor

Pharmacophores are chemical scaffolds upon which changes in chemical moieties (R-groups) at specific sites are made to identify a combination of R-groups that increases the therapeutic potency of a small molecule inhibitor while minimizing adverse effects. We developed a pharmacophore based on a carbonyloxime (OXIM) scaffold for macrophage migration inhibitory factor (MIF), a protein involved in the pathology of sepsis, to validate that inhibition of a catalytic site could produce therapeutic benefits. We studied the crystal structures of MIF.OXIM-based inhibitors and found two opposite orientations for binding to the active site that were dependent on the chemical structures of an R-group. One orientation was completely unexpected based on previous studies with hydroxyphenylpyruvate and (S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid methyl ester (ISO-1). We further confirmed that the unexpected binding mode targets MIF in cellular studies by showing that one compound, OXIM-11, abolished the counter-regulatory activity of MIF on anti-inflammatory glucocorticoid action. OXIM-11 treatment of mice, initiated 24 h after the onset of cecal ligation and puncture-induced sepsis, significantly improved survival when compared with vehicle-treated controls, confirming that inhibition of the MIF catalytic site could produce therapeutic effects. The crystal structures of the MIF inhibitor complexes provide insight for further structure-based drug design efforts.     

Neutralization of macrophage migration inhibitory factor (MIF) by fully human antibodies correlates with their specificity for the β-sheet structure of MIF

The macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine that recently emerged as an attractive therapeutic target for a variety of diseases. A diverse panel of fully human anti-MIF antibodies was generated by selection from a phage display library and extensively analyzed in vitro. Epitope mapping studies identified antibodies specific for linear as well as structural epitopes. Experimental animal studies revealed that only those antibodies binding epitopes within amino acids 50-68 or 86-102 of the MIF molecule exerted protective effects in models of sepsis or contact hypersensitivity. Within the MIF protein, these two binding regions form a β-sheet structure that includes the MIF oxidoreductase motif. We therefore conclude that this β-sheet structure is a crucial region for MIF activity and a promising target for anti-MIF antibody therapy.     

Identification and Characterization of Novel Classes of Macrophage Migration Inhibitory Factor (MIF) Inhibitors with Distinct Mechanisms of Action

Macrophage migration inhibitory factor (MIF), a proinflammatory cytokine, is considered an attractive therapeutic target in multiple inflammatory and autoimmune disorders. In addition to its known biologic activities, MIF can also function as a tautomerase. Several small molecules have been reported to be effective inhibitors of MIF tautomerase activity in vitro. Herein we employed a robust activity-based assay to identify different classes of novel inhibitors of the catalytic and biological activities of MIF. Several novel chemical classes of inhibitors of the catalytic activity of MIF with IC₅₀ values in the range of 0.2–15.5 μm were identified and validated. The interaction site and mechanism of action of these inhibitors were defined using structure-activity studies and a battery of biochemical and biophysical methods. MIF inhibitors emerging from these studies could be divided into three categories based on their mechanism of action: 1) molecules that covalently modify the catalytic site at the N-terminal proline residue, Pro¹; 2) a novel class of catalytic site inhibitors; and finally 3) molecules that disrupt the trimeric structure of MIF. Importantly, all inhibitors demonstrated total inhibition of MIF-mediated glucocorticoid overriding and AKT phosphorylation, whereas ebselen, a trimer-disrupting inhibitor, additionally acted as a potent hyperagonist in MIF-mediated chemotactic migration. The identification of biologically active compounds with known toxicity, pharmacokinetic properties, and biological activities in vivo should accelerate the development of clinically relevant MIF inhibitors. Furthermore, the diversity of chemical structures and mechanisms of action of our inhibitors makes them ideal mechanistic probes for elucidating the structure-function relationships of MIF and to further determine the role of the oligomerization state and catalytic activity of MIF in regulating the function(s) of MIF in health and disease.     

A Novel Allosteric Inhibitor of Macrophage Migration Inhibitory Factor (MIF)

Macrophage migration inhibitory factor (MIF) is a catalytic cytokine and an upstream mediator of the inflammatory pathway. MIF has broad regulatory properties, dysregulation of which has been implicated in the pathology of multiple immunological diseases. Inhibition of MIF activity with small molecules has proven beneficial in a number of disease models. Known small molecule MIF inhibitors typically bind in the tautomerase site of the MIF trimer, often covalently modifying the catalytic proline. Allosteric MIF inhibitors, particularly those that associate with the protein by noncovalent interactions, could reveal novel ways to block MIF activity for therapeutic benefit and serve as chemical probes to elucidate the structural basis for the diverse regulatory properties of MIF. In this study, we report the identification and functional characterization of a novel allosteric MIF inhibitor. Identified from a high throughput screening effort, this sulfonated azo compound termed p425 strongly inhibited the ability of MIF to tautomerize 4-hydroxyphenyl pyruvate. Furthermore, p425 blocked the interaction of MIF with its receptor, CD74, and interfered with the pro-inflammatory activities of the cytokine. Structural studies revealed a unique mode of binding for p425, with a single molecule of the inhibitor occupying the interface of two MIF trimers. The inhibitor binds MIF mainly on the protein surface through hydrophobic interactions that are stabilized by hydrogen bonding with four highly specific residues from three different monomers. The mode of p425 binding reveals a unique way to block the activity of the cytokine for potential therapeutic benefit in MIF-associated diseases.     

Structural and functional characterization of a secreted hookworm Macrophage Migration Inhibitory Factor (MIF) that interacts with the human MIF receptor CD74

Hookworms, parasitic nematodes that infect nearly one billion people worldwide, are a major cause of anemia and malnutrition. We hypothesize that hookworms actively manipulate the host immune response through the production of specific molecules designed to facilitate infection by larval stages and adult worm survival within the intestine. A full-length cDNA encoding a secreted orthologue of the human cytokine, Macrophage Migration Inhibitory Factor (MIF) has been cloned from the hookworm Ancylostoma ceylanicum. Elucidation of the three-dimensional crystal structure of recombinant AceMIF (rAceMIF) revealed an overall structural homology with significant differences in the tautomerase sites of the human and hookworm proteins. The relative bioactivities of human and hookworm MIF proteins were compared using in vitro assays of tautomerase activity, macrophage migration, and binding to MIF receptor CD74. The activity of rAceMIF was not inhibited by the ligand ISO-1, which was previously determined to be an inhibitor of the catalytic site of human MIF. These data define unique immunological, structural, and functional characteristics of AceMIF, thereby establishing the potential for selectively inhibiting the hookworm cytokine as a means of reducing parasite survival and disease pathogenesis.     

Structural Study of the Complex Formed by Ceruloplasmin and Macrophage Migration Inhibitory Factor

Macrophage migration inhibitory factor (MIF) is a key proinflammatory cytokine. Inhibitors of tautomerase activity of MIF are perspective antiinflammatory compounds. Ceruloplasmin, the copper-containing ferroxidase of blood plasma, is a noncompetitive inhibitor of tautomerase activity of MIF in the reaction with p-hydroxyphenylpyruvate. Small-angle X-ray scattering established a model of the complex formed by MIF and ceruloplasmin. Crystallographic analysis of MIF with a modified active site supports the model. The stoichiometry of 3 CP/MIF trimer complex was established using gel filtration. Conformity of novel data concerning the interaction regions in the studied proteins with previous biochemical data is discussed.     

Pro-1 of macrophage migration inhibitory factor functions as a catalytic base in the phenylpyruvate tautomerase activity.

Macrophage migration inhibitory factor (MIF) is an important immunoregulatory molecule with a unique ability to suppress the anti-inflammatory effects of glucocorticoids. Although considered a cytokine, MIF possesses a three-dimensional structure and active site similar to those of 4-oxalocrotonate tautomerase and 5-carboxymethyl-2-hydroxymuconate isomerase. Moreover, a number of catalytic activities have been defined for MIF. To gain insight into the role of catalysis in the biological function of MIF, we have begun to characterize the catalytic activities in more detail. Here we report the crystal structure of MIF complexed with p-hydroxyphenylpyruvate, a substrate for the phenylpyruvate tautomerase activity of MIF. The three binding sites for p-hydroxyphenylpyruvate in the MIF trimer lie at the interface between two subunits. The substrate interacts with Pro-1, Lys-32, and Ile-64 from one subunit and Tyr-95 and Asn-97 from an adjacent subunit. Pro-1 is positioned to function as a catalytic base. There is no functional group that polarizes the alpha-carbonyl of the substrate to weaken the adjacent C-H bond. Mutation of Pro-1 to glycine substantially reduces the catalytic activity. The insertion of an alanine between Pro-1 and Met-2 essentially abolishes activity. Structural studies of these mutants define a source of the reduced activity and provide insight into the mechanism of the catalytic reaction.     

Enzymatically inactive macrophage migration inhibitory factor inhibits monocyte chemotaxis and random migration.

Macrophage migration inhibitory factor (MIF) is a cytokine that was first described as an inhibitor of the random migration of monocytes and macrophages and has since been proposed to have a number of immune and catalytic functions. One of the functions assigned to MIF is that of a tautomerase that interconverts the enol and keto forms of phenylpyruvate and (p-hydroxyphenyl)pyruvate and converts D-dopachrome, a stereoisomer of naturally occurring L-dopachrome, to 5,6-dihydroxyindole-2-carboxylic acid. The physiological significance of the MIF enzymatic activity is unclear. The three-dimensional structure of MIF is strikingly similar to that of two microbial enzymes (4-oxalocrotonate tautomerase and 5-carboxymethyl-2-hydroxymuconate isomerase) that otherwise share little sequence identity with MIF. MIF and these two enzymes have an invariant N-terminal proline that serves as a catalytic base. Here we report a new biological function for MIF, as an inhibitor of monocyte chemoattractant protein 1- (MCP-1-) induced chemotaxis of human peripheral blood monocytes. We find that MIF inhibition of chemotaxis does not occur at the level of the CC chemokine receptor for MCP-1, CCR2, since MIF does not alter the binding of (125)I-MCP-1 to monocytes. The role of MIF enzymatic activity in inhibition of monocyte chemotaxis and random migration was studied with two MIF mutants in which the N-terminal proline was replaced with either a serine or a phenylalanine. Both mutants remain capable of inhibiting monocyte chemotaxis and random migration despite significantly reduced or no phenylpyruvate tautomerase activity. These data suggest that this enzymatic activity of MIF does not play a role in its migration inhibiting properties.     

Synthesis and bio-evaluation of human macrophage migration inhibitory factor inhibitor to develop anti-inflammatory agent

Macrophage migration inhibitory factor (MIF), a pro-inflammatory cytokine, is involved in the development of an array of inflammatory disorders including rheumatoid arthritis, inflammatory bowel disease, psoriasis, multiple sclerosis and sepsis. The synthesis of MIF-inhibitor is a rationale approach to develop novel anti-inflammatory agent to treat multitude of inflammatory diseases. In this work, we have synthesized and evaluated MIF-inhibitory activity of a series of small molecules containing isoxazoline skeleton. Mode of binding of this inhibitor to human MIF (huMIF) was determined by docking studies. The synthesized molecules inhibit tautomerase activity of huMIF. The anti-inflammatory activity of the most active inhibitor, 4-((3-(4-hydroxy-3-methoxyphenyl)-4, 5-dihydroisoxazol-5-yl) methoxy) benzaldehyde (4b) was evaluated against huMIF-induced inflammation in a cellular model (RAW 264.7 cell). Compound 4b significantly inhibits huMIF-mediated NF-κB translocation to the nucleus, up-regulation of inducible nitric oxide synthase and nitric oxide production in RAW 264.7 cell which are the markers for inflammation. The compound 4b is not cytotoxic as evident from cell viability assay. Hence, the compound 4b has potential to be a novel anti-inflammatory agent.     

The MIF Antagonist ISO-1 Attenuates Corticosteroid-Insensitive Inflammation and Airways Hyperresponsiveness in an Ozone-Induced Model of COPD

Introduction

Macrophage migration inhibitory factor (MIF) is an inflammatory cytokine associated with acute and chronic inflammatory disorders and corticosteroid insensitivity. Its expression in the airways of patients with chronic obstructive pulmonary disease (COPD), a relatively steroid insensitive inflammatory disease is unclear, however.

Methods

Sputum, bronchoalveolar lavage (BAL) macrophages and serum were obtained from non-smokers, smokers and COPD patients. To mimic oxidative stress-induced COPD, mice were exposed to ozone for six-weeks and treated with ISO-1, a MIF inhibitor, and/or dexamethasone before each exposure. BAL fluid and lung tissue were collected after the final exposure. Airway hyperresponsiveness (AHR) and lung function were measured using whole body plethysmography. HIF-1α binding to the Mif promoter was determined by Chromatin Immunoprecipitation assays.

Results

MIF levels in sputum and BAL macrophages from COPD patients were higher than those from non-smokers, with healthy smokers having intermediate levels. MIF expression correlated with that of HIF-1α in all patients groups and in ozone-exposed mice. BAL cell counts, cytokine mRNA and protein expression in lungs and BAL, including MIF, were elevated in ozone-exposed mice and had increased AHR. Dexamethasone had no effect on these parameters in the mouse but ISO-1 attenuated cell recruitment, cytokine release and AHR.

Conclusion

MIF and HIF-1α levels are elevated in COPD BAL macrophages and inhibition of MIF function blocks corticosteroid-insensitive lung inflammation and AHR. Inhibition of MIF may provide a novel anti-inflammatory approach in COPD.     

Dissection of the enzymatic and immunologic functions of macrophage migration inhibitory factor. Full immunologic activity of N-terminally truncated mutants.

Macrophage migration inhibitory factor (MIF) is a cytokine with broad regulatory functions in innate immunity. MIF belongs to the few cytokines displaying catalytic activities, i.e. MIF has a Pro2-dependent tautomerase and a Cys-Ala-Leu-Cys (CALC) cysteine-based thiol-protein oxidoreductase activity. Previous studies have addressed the roles of the catalytic site residues and the C-terminus. The two activities have not been directly compared. Here we report on the N-terminal mutational analysis and minimization of MIF and on a dissection of the two catalytic activities by comparing mutants P2AMIF, Delta4MIF, Delta5MIF, Delta6MIF, Delta7MIF, Delta8MIF, and Delta10MIF with the cysteine mutants of MIF. As N-terminal deletion was predicted to interfere with protein structure due to disruption of the central beta sheet, it was surprising that deletion of up to six N-terminal residues resulted in normally expressed proteins with wild-type conformation. Strikingly, such mutants exhibited full MIF-specific immunologic activity. While mutation of Pro2 eliminated tautomerase activity, the CALC cysteine residues had no influence on this activity. However, mutant C81SMIF, which otherwise has full biologic activity, only had 32% tautomerase activity. Deletion of four N-terminal residues did not interfere with insulin reduction by MIF. By contrast, reduction of 2-hydroxyethyldisulfide (HED) was markedly affected by N-terminal manipulation, with P2AMIF and Delta2MIF exhibiting 40% activity, and Delta4MIF completely failing to reduce HED. This study constitutes the first comparison of the two catalytic activities of MIF and should assist in understanding the molecular links between the catalytic and immunologic activities of this cytokine and in providing guidelines for N-terminal protein minimization.     

The Dexamethasone-induced Inhibition of Proliferation, Migration, and Invasion in Glioma Cell Lines Is Antagonized by Macrophage Migration Inhibitory Factor (MIF) and Can Be Enhanced by Specific MIF Inhibitors

Glioblastomas (GBMs) are the most frequent and malignant brain tumors in adults. Glucocorticoids (GCs) are routinely used in the treatment of GBMs for their capacity to reduce the tumor-associated edema. Few in vitro studies have suggested that GCs inhibit the migration and invasion of GBM cells through the induction of MAPK phosphatase 1 (MKP-1). Macrophage migration inhibitory factor (MIF), an endogenous GC antagonist is up-regulated in GBMs. Recently, MIF has been involved in tumor growth and migration/invasion and specific MIF inhibitors have been developed on their capacity to block its enzymatic tautomerase activity site. In this study, we characterized several glioma cell lines for their MIF production. U373 MG cells were selected for their very low endogenous levels of MIF. We showed that dexamethasone inhibits the migration and invasion of U373 MG cells, through a glucocorticoid receptor (GR)- dependent inhibition of the ERK1/2 MAPK pathway. Oppositely, we found that exogenous MIF increases U373 MG migration and invasion through the stimulation of the ERK1/2 MAP kinase pathway and that this activation is CD74 independent. Finally, we used the Hs 683 glioma cells that are resistant to GCs and produce high levels of endogenous MIF, and showed that the specific MIF inhibitor ISO-1 could restore dexamethasone sensitivity in these cells. Collectively, our results indicate an intricate pathway between MIF expression and GC resistance. They suggest that MIF inhibitors could increase the response of GBMs to corticotherapy.     

Tetralone derivatives are MIF tautomerase inhibitors and attenuate macrophage activation and amplify the hypothermic response in endotoxemic mice

Macrophage migration inhibitory factor (MIF) is a pro-inflammatory cytokine playing crucial role in immunity. MIF exerts a unique tautomerase enzymatic activity that has relevance concerning its multiple functions and its small molecule inhibitors have been proven to block its pro-inflammatory effects. Here we demonstrate that some of the E-2-arylmethylene-1-tetralones and their heteroanalogues efficiently bind to MIF’s active site and inhibit MIF tautomeric (enolase, ketolase activity) functions. A small set of the synthesised derivatives, namely compounds (4), (23), (24), (26) and (32), reduced inflammatory macrophage activation. Two of the selected compounds (24) and (26), however, markedly inhibited ROS and nitrite production, NF-κB activation, TNF-α, IL-6 and CCL-2 cytokine expression. Pre-treatment of mice with compound (24) exaggerated the hypothermic response to high dose of bacterial endotoxin. Our experiments suggest that tetralones and their derivatives inhibit MIF’s tautomeric functions and regulate macrophage activation and thermal changes in severe forms of systemic inflammation.