A fluorinated analog of ISO-1 blocks the recognition and biological function of MIF and is orally efficacious in a murine model of colitis

Highly Selective MIF Ketonase Inhibitor KRP-6 Diminishes M1 Macrophage Polarization and Metabolic Reprogramming

Macrophage polarization is highly involved in autoimmunity. M1 polarized macrophages drive inflammation and undergo metabolic reprogramming, involving downregulation of mitochondrial energy production and acceleration of glycolysis. Macrophage migration inhibitory factor (MIF), an enigmatic tautomerase (ketonase and enolase), was discovered to regulate M1 polarization. Here, we reveal that KRP-6, a potent and highly selective MIF ketonase inhibitor, reduces MIF-induced human blood eosinophil and neutrophil migration similarly to ISO-1, the most investigated tautomerase inhibitor. We equally discovered that KRP-6 prevents M1 macrophage polarization and reduces ROS production in IFN-γ-treated cells. During metabolic reprogramming, KRP-6 improved mitochondrial bioenergetics by ameliorating basal respiration, ATP production, coupling efficiency and maximal respiration in LPS+IFN-γ-treated cells. KRP-6 also reduced glycolytic flux in M1 macrophages. Moreover, the selective MIF ketonase inhibitor attenuated LPS+IFN-γ-induced downregulation of PARP-1 and PARP-2 mRNA expression. We conclude that KRP-6 represents a promising novel therapeutic compound for autoimmune diseases, which strongly involves M1 macrophage polarization.

Protective effect of ISO-1 with inhibition of RIPK3 up-regulation and neutrophilic accumulation on acetaminophen-induced liver injury in mice

Overdose use of acetaminophen (APAP) often occurs a severe liver injury, and its liver injury is lethal in some cases. Macrophage migration inhibitory factor (MIF) is expressed in a variety of cells and has multifunctional roles. However, the role of MIF in APAP-induced liver injury has not been fully investigated. In this study, we investigated whether treatment with (S,R)-3-(4-hydroxyphenil)-4,5-dihydro-5-isoxazole acetic acid methyl ester (ISO-1), a MIF inhibitor, protected mice from acute APAP-induced liver injury. Acute liver injury was induced by injection of APAP (300 mg/kg body weight). Mice were treated with a single injection of ISO-1(15 mg/kg body weight) 1 h (h) before APAP administration. Histological, biochemical and molecular analyses were performed in liver of mice 12 h after APAP administration. ISO-1 remarkably improved the histological findings of APAP-induced liver injury in mice. The increases in serum levels of alanine aminotransferase (ALT), and macrophage inflammatory protein-2 (MIP-2) by APAP were inhibited by ISO-1. In addition, ISO-1 reduced the increased number of the myeloperoxidase-staining cells and that of TUNEL-positive staining cells in the liver of mice with APAP-induced liver injury. Up-regulation of hepatic receptor interacting protein kinase (RIPK)3 and heat shock protein70 by APAP was suppressed in the liver of mice given ISO-1. These results provide the additional evidence that inhibition of MIF activity may be clinically effective for treatment of acute APAP-induced liver injury.

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.

Obacunone causes sustained expression of MKP-1 thus inactivating p38 MAPK to suppress pro-inflammatory mediators through intracellular MIF

Obacunone (OBA) is a highly oxygenated triterpenoid with various pharmacological activities. In this study, we explored its anti-inflammatory effect and underlying mechanisms in LPS-activated macrophages. Our data showed that OBA potently decreased pro-inflammatory mediators (eg, NO, IL-6, IL-1β, and MCP-1) at the transcriptional and translational levels without cytotoxicity. A mechanism study showed that OBA significantly suppressed p38-mediated AP-1 signaling by stabilizing the mRNA of mitogen-activated protein kinase phosphatase 1 (MKP-1), thus prolonging the expression time of the MKP-1 protein. Next, we used computational target-fishing technology to predict the possible target of OBA. Only one potential target, macrophage migration inhibitory factor (MIF), was presented. Experimentally, the interaction between OBA and MIF was also confirmed. By using an anti-mouse MIF antibody, extracellular MIF (exMIF) was neutralized. Our results showed that autocrine MIF had slight influence on the pro-inflammatory mediator production. Correspondingly, the anti-inflammatory activity of OBA was also not affected. Accordingly, we knocked down the MIF gene in RAW 264.7 cells and obtained stable MIF deficient cells MIF(-), in which the effects of OBA on p38 phosphorylation, AP-1 activation, and pro-inflammatory mediator production in response to LPS nearly disappeared. In contrast to MIF(+) cells, the MKP-1 protein expression time of the MIF(-) cells was markedly prolonged. We conclude that OBA exerts its anti-inflammatory effect by targeting intracellular MIF (inMIF) inhibition to regulate the MKP-1/p38/AP-1 pathway. Our findings also provide a chain of evidence that the inhibition of inMIF, rather than exMIF, may become a novel target for inflammation.

Macrophage migration inhibitory factor: a key cytokine and therapeutic target in colon cancer

Macrophage migration inhibitory factor (MIF) was one of the first cytokines to be discovered, over 40 years ago. Since that time a burgeoning interest has developed in the role that MIF plays in both the regulation of normal physiology and the response to pathology. MIF is a pleotropic cytokine that functions to promote inflammation, drive cellular proliferation, inhibit apoptosis and regulate the migration and activation state of immune cells. These functions are particularly relevant for the development of cancer and it is notable that various solid tumours over express MIF. This includes tumours of the gastrointestinal tract and MIF appears to play a particularly prominent role in the development and progression of colonic adenocarcinoma. Here we review the role that MIF plays in colonic carcinogenesis through the promotion of colonic inflammation, as well as the progression of primary and metastatic colon cancer. The recent development of various antagonists and antibodies that inhibit MIF activity indicates that we may soon be able to classify MIF as a therapeutic target in colon cancer patients.

Multiple binding modes of isothiocyanates that inhibit macrophage migration inhibitory factor

Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine that has roles in the innate immune response, and also contributes to inflammatory disease. While the biological properties of MIF are closely linked to protein-protein interactions, MIF also has tautomerase activity. Inhibition of this activity interferes with the interaction of MIF with protein partners e.g. the CD74 receptor, and tautomerase inhibitors show promise in disease models including multiple sclerosis and colitis. Isothiocyanates inhibit MIF tautomerase activity via covalent modification of the N-terminal proline. We systematically explored variants of benzyl and phenethyl isothiocyanates, to define determinants of inhibition. In particular, substitution with hydroxyl, chloro, fluoro and trifluoro moieties at the para and meta positions were evaluated. In assays on treated cells and recombinant protein, the IC50 varied from 250 nM to >100 μM. X-ray crystal structures of selected complexes revealed that two binding modes are accessed by some compounds, perhaps owing to strain in short linkers between the isothiocyanate and aromatic ring. The variety of binding modes confirms the existence of two subsites for inhibitors and establishes a platform for the development of potent inhibitors of MIF that only need to target one of these subsites.

Potent inhibition of macrophage migration inhibitory factor (MIF) by myeloperoxidase-dependent oxidation of epicatechins

We report the ability of oxidized epicatechins to modify the N-terminal proline of the pro-inflammatory cytokine MIF at equimolar concentrations.

Virtual Screening of Some Active Human Macrophage Migration Inhibitory Factor Antagonists

Macrophage migration inhibitory factor (MIF) is an autocrine- and paracrine-acting cytokine that is involved in several inflammatory, autoimmune, infectious, and oncogenic diseases. Clinical data have shown that inhibition of MIF, especially its tautomerase activity, with small compounds has been beneficial in some disease models. A virtual screening (VS) experiment is conducted for searching some active compounds to inhibit the tautomerase activity of MIF from the ZINC database. By using an x-ray-determined structure OXIM-11 as the query and an in-house developed two-dimensional scaffold comparing method designated as Sfilter, we have screened out some 1500 compounds for ranking by our previously published docking method ADDock. After further ranking by ADDock on 119 compounds screened, we have decided to choose 17 of them for measuring their inhibitory activity IC50 against the MIF tautomerase experimentally. The IC50's are measured using both human monocytic THP-1 cell lysate and purified recombinant human MIF protein. We have found that the IC50's measured for three searched compounds (namely, ZINC02693801, ZINC00141102, and ZINC12368346) are better than that determined for ISO-1, a known MIF tautomerase inhibitor and standard used throughout our VS experiment. Moreover, the scaffolds of most of our active compounds searched are also quite different from those searched and published by others previously.

Human single-chain variable fragment antibody inhibits macrophage migration inhibitory factor tautomerase activity

Macrophage migration inhibitory factor (MIF) is a pro-inflammatory cytokine, secreted from a variety of immune cells, that regulates innate and adaptive immune responses. Elevation of MIF levels in plasma correlates with the severity of inflammatory diseases in humans. Inhibition of MIF or its tautomerase activity ameliorates disease severity by reducing inflammatory responses. In this study, the human single-chain variable fragment (HuScFv) antibody specific to MIF was selected from the human antibody phage display library by using purified recombinant full-length human MIF (rMIF) as the target antigen. Monoclonal HuScFv was produced from phage-transformed bacteria and tested for their binding activities to rMIF by indirect enzyme-linked immunosorbent assay as well as to native MIF by western blot analysis and immunofluorescence assay. The HuScFv with highest binding signal to rMIF also inhibited the tautomerase activities of both rMIF and native MIF in human monoblastic leukemia (U937) cells in a dose-dependent manner. Mimotope searching and molecular docking concordantly demonstrated that the HuScFv interacted with Lys32 and Ile64 in the MIF tautomerase active site. To the best of our knowledge, this is the first study to focus on MIF-specific fully-human antibody fragment with a tautomerase-inhibitory effect that has potential to be developed as anti-inflammatory biomolecules for human use.

Testing agents for prevention or reversal of type 1 diabetes in rodents

We report the results of an independent laboratory's tests of novel agents to prevent or reverse type 1 diabetes (T1D) in the non-obese diabetic (NOD) mouse, BioBreeding diabetes prone (BBDP) rat, and multiple autoimmune disease prone (MAD) rat models. Methods were developed to better mimic human clinical trials, including: prescreening, randomization, blinding, and improved glycemic care of the animals. Agents were suggested by the research community in an open call for proposals, and selected for testing by an NIDDK appointed independent review panel. Agents selected for testing to prevent diabetes at later stages of progression in a rodent model were a STAT4 antagonist (DT22669), alpha1 anti-trypsin (Aralast NP), celastrol (a natural product with anti-inflammatory properties), and a Macrophage Inflammatory Factor inhibitor (ISO-092). Agents tested for reversal of established T1D in rodent models were: alpha1 anti-trypsin (Aralast NP), tolerogenic peptides (Tregitopes), and a long-acting formulation of GLP-1 (PGC-GLP-1). None of these agents were seen to prevent or reverse type 1 diabetes, while the positive control interventions were effective: anti-CD3 treatment provided disease reversal in the NOD mouse, dexamethasone prevented T1D induction in the MAD rat, and cyclosporin prevented T1D in the BBDP rat. For some tested agents, details of previous formulation, delivery, or dosing, as well as laboratory procedure, availability of reagents and experimental design, could have impacted our ability to confirm prior reports of efficacy in preclinical animal models. In addition, the testing protocols utilized here provided detection of effects in a range commonly used in placebo controlled clinical trials (for example, 50% effect size), and thus may have been underpowered to observe more limited effects. That said, we believe the results compiled here, showing good control and repeatability, confirm the feasibility of screening diverse test agents in an independent laboratory.

Elaborate ligand-based modeling reveal new migration inhibitory factor inhibitors

Recent research suggested the involvement of migration inhibitor factor (MIF) in cancer and inflammatory diseases, which prompted several attempts to develop new MIF inhibitors. Accordingly, we investigated the pharmacophoric space of 79 MIF inhibitors using seven diverse subsets of inhibitors to identify plausible binding hypotheses (pharmacophores). Subsequently, we implemented genetic algorithm and multiple linear regression analysis to select optimal combination of pharmacophores and physicochemical descriptors capable of explaining bioactivity variation within the training compounds (QSAR model, r63=0.62, F=42.8, rLOO(2)=0.721,rPRESS(2) against 16 external test inhibitors=0.58). Two orthogonal pharmacophores appeared in the optimal QSAR model suggestive of at least two binding modes available to ligands inside MIF binding pocket. Subsequent validation using receiver operating characteristic (ROC) curves analysis established the validity of these two pharmacophores. We employed these pharmacophoric models and associated QSAR equation to screen the National Cancer Institute (NCI) list of compounds. Eight compounds gave >50% inhibition at 100μM. Two molecules illustrated >75% inhibition at 10μM.

D-dopachrome tautomerase (D-DT or MIF-2): doubling the MIF cytokine family

D-dopachrome tautomerase (D-DT) is a newly described cytokine and a member of the macrophage migration inhibitory factor (MIF) protein superfamily. MIF is a broadly expressed pro-inflammatory cytokine that regulates both the innate and the adaptive immune response. MIF activates the MAP kinase cascade, modulates cell migration, and counter-acts the immunosuppressive effects of glucocorticoids. For many cell types, MIF also acts as an important survival or anti-apoptotic factor. Circulating MIF levels are elevated in the serum in different infectious and autoimmune diseases, and neutralization of the MIF protein via antibodies or small molecule antagonists improves the outcome in numerous animal models of human disease. Recently, a detailed investigation of the biological role of the closely homologous protein D-DT, which is encoded by a gene adjacent to MIF, revealed an overlapping functional spectrum with MIF. The D-DT protein also is present in most tissues and circulates in serum at similar concentrations as MIF. D-DT binds the MIF cell surface receptor complex, CD74/CD44, with high affinity and induces similar cell signaling and effector functions. Furthermore, an analysis of the signaling properties of the two proteins showed that they work cooperatively, and that neutralization of D-DT in vivo significantly decreases inflammation. In this review, we highlight the similarities and differences between MIF and D-DT, which we propose to designate "MIF-2", and discuss the implication of D-DT/MIF-2 expression for MIF-based therapies.

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.

Macrophage migration inhibitory factor (MIF) is essential for inflammatory and neuropathic pain and enhances pain in response to stress

Stress and glucocorticoids exacerbate pain via undefined mechanisms. Macrophage migration inhibitory factor (MIF) is a constitutively expressed protein that is secreted to maintain immune function when glucocorticoids are elevated by trauma or stress. Here we show that MIF is essential for the development of neuropathic and inflammatory pain, and for stress-induced enhancement of neuropathic pain. Mif null mutant mice fail to develop pain-like behaviors in response to inflammatory stimuli or nerve injury. Pharmacological inhibition of MIF attenuates pain-like behaviors caused by nerve injury and prevents sensitization of these behaviors by stress. Conversely, injection of recombinant MIF into naïve mice produces dose-dependent mechanical sensitivity that is exacerbated by stress. MIF elicits pro-inflammatory signaling in microglia and activates sensory neurons, mechanisms that underlie pain. These data implicate MIF as a key regulator of pain and provide a mechanism whereby stressors exacerbate pain. MIF inhibitors warrant clinical investigation for the treatment of chronic pain.

Vitamin E is a MIF Inhibitor

Macrophage migration inhibitory factor (MIF) is known to contribute to the pathogenesis of inflammatory hyperalgesia and neuropathic pain. Prior studies have shown that Vitamin E treatment is associated with attenuated hyperalgesia and reduced neuropathic pain in rodents. Given these observations, we investigated the possibility that Vitamin E is a MIF inhibitor. Dopachrome tautomerase assays revealed that Vitamin E inhibits the enzymatic activity of purified human recombinant MIF (rhMIF) in a dose-dependent manner (45%, 74%, 92% and 100% inhibition at 3, 10, 30 and 100μM, respectively). Cell-free ELISA based assays showed that Vitamin E binds onto rhMIF thereby blocking its recognition (48% inhibition at 100μM). Circular dichroism studies indicated the Vitamin E has a strong affinity to bind to rhMIF (binding constant 19.52±1.4μM). In silico studies demonstrated that Vitamin E docks well in the active site of MIF with the long aliphatic chain of Vitamin E exhibiting strong van der Waals interactions with MIF. Most importantly, human cell-based assays revealed that Vitamin E significantly inhibits rhMIF-induced production of pro-inflammatory cytokines in a dose-dependent manner (77%, 80%, and 96% inhibition of IL-6 production, respectively, at 10, 30 and 100μM). Taken together, these results demonstrate that Vitamin E inhibits not only the enzymatic activity of MIF but more importantly the biological function of MIF. Our findings suggest that Vitamin E may be attenuating hyperalgesia and reducing neuropathic pain at least in part by inhibiting MIF activity.

Drug repositioning and pharmacophore identification in the discovery of hookworm MIF inhibitors

The screening of bioactive compound libraries can be an effective approach for repositioning FDA-approved drugs or discovering new pharmacophores. Hookworms are blood-feeding, intestinal nematode parasites that infect up to 600 million people worldwide. Vaccination with recombinant Ancylostoma ceylanicum macrophage migration inhibitory factor (rAceMIF) provided partial protection from disease, thus establishing a "proof-of-concept" for targeting AceMIF to prevent or treat infection. A high-throughput screen (HTS) against rAceMIF identified six AceMIF-specific inhibitors. A nonsteroidal anti-inflammatory drug (NSAID), sodium meclofenamate, could be tested in an animal model to assess the therapeutic efficacy in treating hookworm disease. Furosemide, an FDA-approved diuretic, exhibited submicromolar inhibition of rAceMIF tautomerase activity. Structure-activity relationships of a pharmacophore based on furosemide included one analog that binds similarly to the active site, yet does not inhibit the Na-K-Cl symporter (NKCC1) responsible for diuretic activity.

The cytokine macrophage migration inhibitory factor (MIF) acts as a neurotrophin in the developing inner ear of the zebrafish, Danio rerio

Macrophage migration inhibitory factor (MIF) plays versatile roles in the immune system. MIF is also widely expressed during embryonic development, particularly in the nervous system, although its roles in neural development are only beginning to be understood. Evidence from frogs, mice and zebrafish suggests that MIF has a major role as a neurotrophin in the early development of sensory systems, including the auditory system. Here we show that the zebrafish mif pathway is required for both sensory hair cell (HC) and sensory neuronal cell survival in the ear, for HC differentiation, semicircular canal formation, statoacoustic ganglion (SAG) development, and lateral line HC differentiation. This is consistent with our findings that MIF is expressed in the developing mammalian and avian auditory systems and promotes mouse and chick SAG neurite outgrowth and neuronal survival, demonstrating key instructional roles for MIF in vertebrate otic development.

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.

Phenotypic and genotypic assessment of concomitant drug-induced toxic effects in liver, kidney and blood

Several studies have characterized drug-induced toxicity in liver and kidney. However, the majority of these studies have been performed with 'individual' organs in isolation. Separately, little is known about the role of whole blood as a surrogate tissue in drug-induced toxicity. Accordingly, we investigated the 'concurrent' response of liver, kidney and whole blood during a toxic assault. Rats were acutely treated with therapeutics (acetaminophen, rosiglitazone, fluconazole, isoniazid, cyclophosphamide, amphotericin B, gentamicin and cisplatin) reported for their liver and/or kidney toxicity. Changes in clinical chemistry parameters (e.g. AST, urea) and/or observed microscopic tissue damage confirmed induced hepatotoxicity and/or nephrotoxicity by all drugs. Drug-induced toxicity was not confined to an 'individual' organ. Not all drugs elicited significant alterations in phenotypic parameters of toxicity (e.g. ALT, creatinine). Accordingly, the transcriptional profile of the organs was studied using a toxicity panel of 30 genes derived from literature. Each of the test drugs generated specific gene expression patterns which were unique for all three organs. Hierarchical cluster analyses of purported hepatotoxicants and nephrotoxicants each led to characteristic 'fingerprints' (e.g. decrease in Cyp3a1 indicative of hepatotoxicity; increase in Spp1 and decrease in Gstp1 indicative of nephrotoxicity). In whole blood cells, a set of genes was derived which closely correlated with individual drug-induced concomitant changes in liver or kidney. Collectively, these data demonstrate drug-induced multi-organ toxicity. Furthermore, our findings underscore the importance of transcriptional profiling during inadequate phenotypic anchorage and suggest that whole blood may be judiciously used as a surrogate for drug-induced extra-hematological organ toxicity.

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 IC(50) values in the range of 0.2-15.5 microm 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, Pro(1); 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.

Autoimmune diseases: MIF as a therapeutic target

IMPORTANCE OF THE FIELD

Autoimmune inflammatory diseases occur commonly in developed countries. The treatment of these diseases is usually non-curative and is aimed at suppressing inflammatory end-organ damage. Macrophage migration inhibitory factor (MIF) is a multipotent cytokine that has been implicated in the pathogenesis of numerous autoimmune inflammatory disorders. The selective targeting of MIF with either anti-MIF antibody or specific MIF antagonists may offer new therapeutic avenues for these diseases.

AREAS COVERED IN THIS REVIEW

Our aim is to discuss MIF-directed therapies as a novel therapeutic approach. The review covers literature from the past 10 years.

WHAT THE READER WILL GAIN

MIF inhibition has been shown to be efficacious in many experimental and pre-clinical studies of autoimmune inflammatory diseases. The close regulatory relationship between MIF and glucocorticoids makes therapeutic antagonism of MIF a potential steroid-sparing therapy in patients with refractory autoimmune diseases.

TAKE HOME MESSAGE

We expect that MIF antagonism by either small-molecule- or antibody-based approaches will find wide application in the treatment of autoimmune inflammatory diseases. Such therapy also may be informed by the MIF genotype of affected patients.

Kinetic-based high-throughput screening assay to discover novel classes of macrophage migration inhibitory factor inhibitors

Macrophage migration inhibitory factor (MIF) is a major mediator of innate immunity and inflammation and presents a potential therapeutic target for various inflammatory, infectious, and autoimmune diseases, including cancer. Although a number of inhibitors have been identified and designed based on the modification of known nonphysiological substrates, the lack of a suitable high-throughput assay has hindered the screening of chemical libraries and the discovery of more diverse inhibitors. Herein the authors report the development and optimization of a robust high-throughput kinetic-based activity assay for the identification of new MIF inhibitors. Using this assay, they screened 80,000 small molecules and identified and validated 13 novel inhibitors of MIF catalytic activity. These small molecules demonstrated inhibition constant (K(i,app)) values ranging from 0.5 to 13 microM.

A preferential p110alpha/gamma PI3K inhibitor attenuates experimental inflammation by suppressing the production of proinflammatory mediators in a NF-kappaB-dependent manner

A promising therapeutic approach to diminish pathological inflammation is to inhibit the increased production and/or biological activity of proinflammatory cytokines (e.g., TNF-alpha, IL-6). The production of proinflammatory cytokines is controlled at the gene level by the activity of transcription factors, such as NF-kappaB. Phosphatidylinositol 3-kinase (PI3K), a lipid kinase, is known to induce the activation of NF-kappaB. Given this, we hypothesized that inhibitors of PI3K activation would demonstrate anti-inflammatory potential. Accordingly, we studied the effects of a preferential p110alpha/gamma PI3K inhibitor (compound 8C; PIK-75) in inflammation-based assays. Mechanism-based assays utilizing human cells revealed that PIK-75-mediated inhibition of PI3K activation is associated with dramatic suppression of downstream signaling events, including AKT phosphorylation, IKK activation, and NF-kappaB transcription. Cell-based assays revealed that PIK-75 potently and dose dependently inhibits in vitro and in vivo production of TNF-alpha and IL-6, diminishes the induced expression of human endothelial cell adhesion molecules (E-selectin, ICAM-1, and VCAM-1), and blocks human monocyte-endothelial cell adhesion. Most importantly, PIK-75, when administered orally in a therapeutic regimen, significantly suppresses the macroscopic and histological abnormalities associated with dextran sulfate sodium-induced murine colitis. The efficacy of PIK-75 in attenuating experimental inflammation is mediated, at least in part, due to the downregulation of pertinent inflammatory mediators in the colon. Collectively, these results provide first evidence that PIK-75 possesses anti-inflammatory potential. Given that PIK-75 is known to exhibit anti-cancer activity, the findings from this study thus reinforce the cross-therapeutic functionality of potential drugs.

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.