Autoimmune diseases: MIF as a therapeutic target

Dominance of the strongest: inflammatory cytokines versus glucocorticoids

Pro-inflammatory cytokines are involved in the pathogenesis of many inflammatory diseases, and the excessive expression of many of them is normally counteracted by glucocorticoids (GCs), which are steroids that bind to the glucocorticoid receptor (GR). Hence, GCs are potent inhibitors of inflammation, and they are widely used to treat inflammatory diseases, such as asthma, rheumatoid arthritis and inflammatory bowel disease. However, despite the success of GC therapy, many patients show some degree of GC unresponsiveness, called GC resistance (GCR). This is a serious problem because it limits the full therapeutic exploitation of the anti-inflammatory power of GCs. Patients with reduced GC responses often have higher cytokine levels, and there is a complex interplay between GCs and cytokines: GCs downregulate pro-inflammatory cytokines while cytokines limit GC action. Treatment of inflammatory diseases with GCs is successful when GCs dominate. But when cytokines overrule the anti-inflammatory actions of GCs, patients become GC insensitive. New insights into the molecular mechanisms of GR-mediated actions and GCR are needed for the design of more effective GC-based therapies.

Significance of the vascular endothelial growth factor and the macrophage migration inhibitory factor in the progression of hepatocellular carcinoma

The aim of the present study was to investigate the expression of vascular endothelial growth factor (VEGF) and macrophage migration inhibitory factor (MIF) in HCC progression and their correlation with clinicopathological factors as well as the relationship between their expression levels. The expression of serum VEGF and MIF was evaluated in 150 patients with HCC and in 30 normal volunteers by enzyme-linked immunosorbent assay (ELISA). VEGF and MIF expression levels were evaluated by immunohistochemistry on tissue microarrays containing 150 HCCs with paired adjacent non-cancer liver tissues. VEGF and MIF mRNA levels were determined by quantitative PCR in another 48 HCCs. The correlation of VEGF and MIF with clinicopathological factors was analyzed in HCC. Serum VEGF and MIF concentrations were higher in HCC patients than the levels in the controls. The expression levels of VEGF and MIF in the HCC tissues were both higher than those in the adjacent non-tumor liver tissues. Overexpression of VEGF and MIF was significantly associated with tumor size (P=0.027 and 0.022, respectively), intrahepatic metastasis (P=0.032 and 0.027, respectively), vascular invasion (P=0.044 and 0.039, respectively) and TNM stage (P=0.028 and 0.013, respectively). Furthermore, VEGF and MIF mRNA levels were higher in HCC compared to levels in the paired non-cancer liver tissues. VEGF and MIF mRNA levels were correlated with tumor stage and metastasis. The expression of VEGF was positively related with MIF expression in HCC. The expression of MIF and VEGF in HCC was markedly positively correlated, which suggests that MIF and VEGF play an important role in the progression of HCC. Both factors may concomitantly accelerate the progression of HCC.

Macrophage migration inhibitory factor (MIF) and thyroid hormone alterations in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV)

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine known to be released from lymphocytes, macrophages and endothelial cells and also in animal models shown to be inducible with glucocorticoids (GC). In contrast, thyroxine seems to antagonize MIF activity. To investigate whether MIF is increased in active antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) and possible correlations with GC dosing and thyroid hormone levels, 27 consecutive patients with active AAV were studied and followed prospectively. Disease activity was assessed using Birmingham Vasculitis Activity Score 2003 (BVAS) at baseline and at follow-up at 3 and 6 months, along with MIF, thyroid hormones free triiodothyronine (fT3) and free thyroxine (fT4), C-reactive protein (CRP) and creatinine. MIF was elevated significantly at baseline compared with follow-up at 3 and 6 months (8,618 pg/mL versus 5,696 and 6,212 respectively; P < 0.002) but did not correlate to CRP, GC dose, creatinine or organ involvement. fT3 was depressed significantly at baseline compared with follow-up (1.99 pg/mL versus 2.31 and 2.67 respectively; P = 0.01) and correlated inversely to the BVAS score at baseline. We found a significant correlation between the MIF/fT4 ratio at baseline versus MIF/fT4 ratio at 6 months (ρ = 0.52, P < 0.005) and a trend between the baseline MIF/fT3 ratio versus MIF/fT3 ratio at 6 months (ρ = 0.39, P = 0.05). These results suggest a possible role for MIF and thyroid status in AAV. Further studies could reveal whether the association between AAV and thyroid hormone levels in the context of elevated MIF may present a link as well as a target of treatment.

Association between MIF gene variation and Meniere's disease

Several pieces of evidence support the involvement of immune system in Menière's disease (MD). Macrophage migration inhibitory factor (MIF) plays a key role in immune-mediated reactions. Several studies have shown an association between MIF gene polymorphisms and susceptibility to various inflammatory and autoimmune disorders. The aim of this study was to explore the association between MIF-173 G/C polymorphism and MD in an Iranian population. In this case-control association study, MD cases (N = 72) were recruited and were comprised of definitive MD (N = 58) and probable MD (N = 14) subjects. Normal healthy subjects (N = 100) were also included. Genotyping for MIF-173 G/C polymorphism was carried out using PCR-RFLP technique. There was a significant increase in genotype GG in patients with MD compared with the control group. (GG vs. GC + CC, P = 0.02, OR = 2.08, 95% CI: 1.02-4.3). This was more significant when definitive MD was stratified and compared with the controls (GG vs. GC + CC, P = 0.009, OR = 2.6, 95% CI = 1.19-6.18). This study's result indicates the potential role of MIF in MD of which further evaluation is required. Also, the more significant association between MIF gene polymorphism and definitive MD designates the involvement of specific pathogenic mechanisms which may be considered as a marker for diagnosis.

Ribosomal protein S19 is a novel therapeutic agent in inflammatory kidney disease

RPS19 (ribosomal protein S19), a component of the 40S small ribosomal subunit, has recently been identified to bind the pro-inflammatory cytokine macrophage MIF (migration inhibitory factor). In vitro experiments identify RPS19 as the first endogenous MIF inhibitor by blocking the binding of MIF to its receptor CD74 and MIF functions on monocyte adherence to endothelial cells. In the present study, we sought to establish whether recombinant RPS19 can exert anti-inflammatory effects in a mouse model of anti-GBM (glomerular basement membrane) GN (glomerulonephritis) in which MIF is known to play an important role. Accelerated anti-GBM GN was induced in C57BL/6J mice by immunization with sheep IgG followed 5 days later by administration of sheep anti-mouse GBM serum. Groups of eight mice were treated once daily by intraperitoneal injection with 6 mg of RPS19/kg of body weight or an irrelevant control protein (human secretoglobin 2A1), or received no treatment, from day 0 until being killed on day 10. Mice that received control or no treatment developed severe crescentic anti-GBM disease on day 10 with increased serum creatinine, declined creatinine clearance and increased proteinuria. These changes were associated with up-regulation of MIF and its receptor CD74 activation of ERK (extracellular-signal-regulated kinase) and NF-κB (nuclear factor κB) signalling, prominent macrophage and T-cell infiltration, as well as up-regulation of Th1 [T-bet and IFNγ (interferon γ)] and Th17 [STAT3 (signal transducer and activator of transcription 3) and IL (interleukin)-17A] as well as IL-1β and TNFα (tumour necrosis factor α). In contrast, RPS19 treatment largely prevented the development of glomerular crescents and glomerular necrosis, and prevented renal dysfunction and proteinuria (all P<0.001). Of note, RPS19 blocked up-regulation of MIF and CD74 and inactivated ERK and NF-κB signalling, thereby inhibiting macrophage and T-cell infiltration, Th1 and Th17 responses and up-regulation of pro-inflammatory cytokines (all P<0.01). These results demonstrate that RPS19 is a potent anti-inflammatory agent, which appears to work primarily by inhibiting MIF signalling.

Control of tumor-associated macrophage alternative activation by macrophage migration inhibitory factor

Tumor stromal alternatively activated macrophages are important determinants of antitumor T lymphocyte responses, intratumoral neovascularization, and metastatic dissemination. Our recent efforts to investigate the mechanism of macrophage migration inhibitory factor (MIF) in antagonizing antimelanoma immune responses reveal that macrophage-derived MIF participates in macrophage alternative activation in melanoma-bearing mice. Both peripheral and tumor-associated macrophages (TAMs) isolated from melanoma bearing MIF-deficient mice display elevated proinflammatory cytokine expression and reduced anti-inflammatory, immunosuppressive, and proangiogenic gene products compared with macrophages from tumor-bearing MIF wild-type mice. Moreover, TAMs and myeloid-derived suppressor cells from MIF-deficient mice exhibit reduced T lymphocyte immunosuppressive activities compared with those from their wild-type littermates. Corresponding with reduced tumor immunosuppression and neo-angiogenic potential by TAMs, MIF deficiency confers protection against transplantable s.c. melanoma outgrowth and melanoma lung metastatic colonization. Finally, we report for the first time, to our knowledge, that our previously discovered MIF small molecule antagonist, 4-iodo-6-phenylpyrimidine, recapitulates MIF deficiency in vitro and in vivo, and attenuates tumor-polarized macrophage alternative activation, immunosuppression, neoangiogenesis, and melanoma tumor outgrowth. These studies describe an important functional contribution by MIF to TAM alternative activation and provide justification for immunotherapeutic targeting of MIF in melanoma patients.

Delayed development of chronic lymphocytic leukemia in the absence of macrophage migration inhibitory factor

Survival of chronic lymphocytic leukemia (CLL) cells depends on stimuli provided by a suitable microenvironment. The factors and mechanisms providing this growth support for CLL cells are not fully understood. We found that plasma levels of macrophage migration inhibitory factor (MIF), a proinflammatory and immunoregulatory chemokine, were elevated in CLL patients. Therefore, we characterized the functional role of MIF in a CLL mouse model. For this purpose, we crossed Eμ-TCL1 mice with MIF knockout (MIF-/-) mice. The resulting TCL1+/wtMIF/ mice showed a delayed onset of leukemia, reduced splenomegaly and hepatomegaly, and a longer survival than TCL1+/wtMIFwt/wt controls. Immunohistochemical examination of the lymphoid organs showed that the numbers of macrophages were significantly reduced in the spleen and bone marrow of TCL1+/wtMIF/ mice compared with TCL1+/wtMIFwt/wt controls. Mechanistic studies in vitro revealed that the absence of MIF rendered CLL cells more susceptible to apoptosis. Accordingly, incubation with an anti-MIF antibody reduced the survival of CLL cells on a macrophage feeder layer. In addition, the migratory activity of TCL1+/wtMIF/ macrophages was decreased compared with TCL1+/wtMIFwt/wt macrophages. Taken together, our results provide evidence that MIF supports the development of CLL by enhancing the interaction of CLL cells with macrophages.

KEY POINTS

Targeted deletion of the gene for macrophage migration inhibitory factor (MIF) delays development of chronic lymphocytic leukemia and prolongs survival in mice. MIF recruits leukemia-associated macrophages to spleen or liver.

Macrophage migration inhibitory factor gene polymorphisms and plasma levels in children with obstructive sleep apnea

INTRODUCTION

Obstructive sleep apnea (OSA) is associated with increased risk for cardiovascular and metabolic dysfunction in both adults and children. In adults with OSA, serum levels of macrophage migration inhibitory factor (MIF) are elevated. Therefore, we assessed plasma MIF levels and MIF allelic variant frequencies in children with and without OSA (NOSA).

METHODS

A total of 614 consecutive children ages 5-8 years were recruited. Children were divided into those with OSA and NOSA based on the apnea-hypopnea index (AHI). In addition to lipid profile, hsCRP, and fasting insulin and glucose levels, plasma MIF levels were assayed using ELISA, and 28 single nucleotide polymorphisms (SNPs) covering the region were genotyped. Linkage disequilibrium and haplotype blocks were analyzed using Haploview version 4.2 software.

RESULTS

Morning plasma MIF levels were increased in children with OSA. Of the 28 SNPs tested, the frequency of rs10433310 minor allele was significantly decreased in OSA. This SNP was also associated with reduced fasting insulin and hsCRP levels in OSA. The minor allele frequency of all other 27 SNPs was similar in OSA and NOSA groups.

CONCLUSIONS

Childhood OSA is associated with higher plasma MIF, hsCRP, and fasting insulin levels that promote cardiometabolic risk, and the MIF gene SNP rs10433310 may account for some of the variance in such risk.

New insights into the role and mechanism of macrophage migration inhibitory factor in steroid-resistant patients with systemic lupus erythematosus

INTRODUCTION

Glucocorticoid (GC) therapy remains important in improving the prognosis of patients with systemic lupus erythematosus (SLE). However, some patients do not achieve an effective response with GC treatment, creating an obstacle to the remission of SLE. Identification of the underlying mechanisms responsible for steroid resistance can be significant. Macrophage migration inhibitory factor (MIF) arouses our interest because of its reciprocal relationship with GCs. In the present study, we investigated for the first time whether MIF correlated with steroid resistance in SLE and explored potential mechanisms of action.

METHODS

Sixty-two patients with SLE (40 steroid sensitive and 22 steroid resistant) and 21 normal controls were recruited. Serum levels of MIF were measured by ELISA. Cytosolic MIF and IκB expression in peripheral blood mononuclear cells (PBMCs) were determined by western blotting. The electrophoretic mobility shift assay was assessed by NF-κB in nuclear aliquots. Gene silencing was applied to reduce expression of MIF in PBMCs in steroid-resistant patients. PBMCs obtained from steroid-sensitive patients were treated with recombinant human MIF of different concentrations.

RESULTS

MIF levels in serum and PBMCs were higher in steroid-resistant patients compared with steroid-sensitive patients and controls. In contrast to the steroid-sensitive group, NF-κB levels were significantly higher and IκB levels lower in steroid-resistant patients. After MIF gene silencing, IκB levels in cells from steroid-resistant patients were increased. In steroid-sensitive patients, a decrease in IκB levels and an increase in NF-κB expression from baseline were detected in PBMCs treated with a higher concentration of recombinant human MIF. Treatment with recombinant human MIF did not regulate expression of IκB and NF-κB in PBMCs from patients treated with an anti-MIF monoclonal antibody.

CONCLUSIONS

Our results indicated that MIF may play a role in the formation of steroid resistance in SLE by affecting the NF-κB/IκB signaling cascade. As a regulator of glucocorticoid sensitivity, MIF may be a potential target for steroid sparing.

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.

A functional microsatellite of the macrophage migration inhibitory factor gene associated with meningococcal disease

Macrophage migration inhibitory factor (MIF) is an abundantly expressed proinflammatory cytokine playing a critical role in innate immunity and sepsis and other inflammatory diseases. We examined whether functional MIF gene polymorphisms (-794 CATT(5-8) microsatellite and -173 G/C SNP) were associated with the occurrence and outcome of meningococcal disease in children. The CATT(5) allele was associated with the probability of death predicted by the Pediatric Index of Mortality 2 (P=0.001), which increased in correlation with the CATT(5) copy number (P=0.04). The CATT(5) allele, but not the -173 G/C alleles, was also associated with the actual mortality from meningoccal sepsis [OR 2.72 (1.2-6.4), P=0.02]. A family-based association test (i.e., transmission disequilibrium test) performed in 240 trios with 1 afflicted offspring indicated that CATT(5) was a protective allele (P=0.02) for the occurrence of meningococcal disease. At baseline and after stimulation with Neisseria meningitidis in THP-1 monocytic cells or in a whole-blood assay, CATT(5) was found to be a low-expression MIF allele (P=0.005 and P=0.04 for transcriptional activity; P=0.09 and P=0.09 for MIF production). Taken together, these data suggest that polymorphisms of the MIF gene affecting MIF expression are associated with the occurrence, severity, and outcome of meningococcal disease in children.

The D-dopachrome tautomerase (DDT) gene product is a cytokine and functional homolog of macrophage migration inhibitory factor (MIF)

Macrophage migration inhibitory factor (MIF) is a pivotal regulator of the immune response. Neutralization or genetic deletion of MIF does not completely abrogate activation responses, however, and deletion of the MIF receptor, CD74, produces a more pronounced phenotype than MIF deficiency. We hypothesized that these observations may be explained by a second MIF-like ligand, and we considered a probable candidate to be the protein encoded by the homologous, D-dopachrome tautomerase (D-DT) gene. We show that recombinant D-DT protein binds CD74 with high affinity, leading to activation of ERK1/2 MAP kinase and downstream proinflammatory pathways. Circulating D-DT levels correlate with disease severity in sepsis or malignancy, and the specific immunoneutralization of D-DT protects mice from lethal endotoxemia by reducing the expression of downstream effector cytokines. These data indicate that D-DT is a MIF-like cytokine with an overlapping spectrum of activities that are important for our understanding of MIF-dependent physiology and pathology.

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.

Benzisothiazolones as modulators of macrophage migration inhibitory factor

Substituted N-phenylbenzisothiazolones have been investigated as inhibitors of the tautomerase activity of the proinflammatory cytokine MIF (macrophage migration inhibitory factor). Numerous compounds were found to possess antagonist activity in the low micromolar range with the most potent being the 6-hydroxy analog 1w. Compound 1w and the p-cyano analog 1c were also shown to exhibit significant inhibition of the binding of MIF to its transmembrane receptor CD74. Consistently, both compounds were also found to retard the MIF-dependent phosphorylation of ERK1/2 in human synovial fibroblasts.