Melanie Merk

Macrophage migration inhibitory factor (MIF): a promising biomarker.

Macrophage migration inhibitory factor (MIF) is an immunoregulatory cytokine, the effect of which on arresting random immune cell movement was recognized several decades ago. Despite its historic name, MIF also has a direct chemokine-like function and promotes cell recruitment. Multiple clinical studies have indicated the utility of MIF as a biomarker for different diseases that have an inflammatory component; these include systemic infections and sepsis, autoimmune diseases, cancer, and metabolic disorders such as type 2 diabetes and obesity. The identification of functional promoter polymorphisms in the MIF gene (MIF) and their association with the susceptibility or severity of different diseases has not only served to validate MIFs role in disease development but also opened the possibility of using MIF genotype information to better predict risk and outcome. In this article, we review the clinical data of MIF and discuss its potential as a biomarker for different disease applications.

Cardiac macrophage migration inhibitory factor inhibits JNK pathway activation and injury during ischemia/reperfusion

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine that also modulates physiologic cell signaling pathways. MIF is expressed in cardiomyocytes and limits cardiac injury by enhancing AMPK activity during ischemia. Reperfusion injury is mediated in part by activation of the stress kinase JNK, but whether MIF modulates JNK in this setting is unknown. We examined the role of MIF in regulating JNK activation and cardiac injury during experimental ischemia/reperfusion in mouse hearts. Isolated perfused Mif-/- hearts had greater contractile dysfunction, necrosis, and JNK activation than WT hearts, with increased upstream MAPK kinase 4 phosphorylation, following ischemia/reperfusion. These effects were reversed if recombinant MIF was present during reperfusion, indicating that MIF deficiency during reperfusion exacerbated injury. Activated JNK acts in a proapoptotic manner by regulating BCL2-associated agonist of cell death (BAD) phosphorylation, and this effect was accentuated in Mif-/- hearts after ischemia/reperfusion. Similar detrimental effects of MIF deficiency were observed in vivo following coronary occlusion and reperfusion in Mif-/- mice. Importantly, excess JNK activation also was observed after hypoxia-reoxygenation in human fibroblasts homozygous for the MIF allele with the lowest level of promoter activity. These data indicate that endogenous MIF inhibits JNK pathway activation during reperfusion and protects the heart from injury. These findings have clinical implications for patients with the low-expression MIF allele.

Impaired macrophage migration inhibitory factor-AMP-activated protein kinase activation and ischemic recovery in the senescent heart.

Background— Elderly patients are more sensitive than younger patients to myocardial ischemia, which results in higher mortality. We investigated how aging affects the cardioprotective AMP-activated protein kinase (AMPK) signaling pathway. Methods and Results— Ischemic AMPK activation was impaired in aged compared with young murine hearts. The expression and secretion of the AMPK upstream regulator, macrophage migration inhibitory factor (MIF), were lower in aged compared with young adult hearts. Additionally, the levels of hypoxia-inducible factor 1&agr;, a known transcriptional activator of MIF, were reduced in aged compared with young hearts. Ischemia-induced AMPK activation in MIF knockout mice was blunted, leading to greater contractile dysfunction in MIF-deficient than in wild-type hearts. Furthermore, intramyocardial injection of adenovirus encoding MIF in aged mice increased MIF expression and ischemic AMPK activation and reduced infarct size. Conclusions— An impaired MIF-AMPK activation response in senescence thus may be attributed to an aging-associated defect in hypoxia-inducible factor 1&agr;, the transcription factor for MIF. In the clinical setting, impaired cardiac hypoxia-inducible factor 1&agr; activation and consequent reduced MIF expression may play an important role in the increased susceptibility to myocardial ischemia observed in older cardiac patients.

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.

A Leishmania Ortholog of Macrophage Migration Inhibitory Factor Modulates Host Macrophage Responses

Parasitic organisms have evolved specialized strategies to evade immune defense mechanisms. We describe herein an ortholog of the cytokine, macrophage migration inhibitory factor (MIF), which is produced by the obligate intracellular parasite, Leishmania major. The Leishmania MIF protein, Lm1740MIF, shows significant structural homology with human MIF as revealed by a high-resolution x-ray crystal structure (1.03 Å). Differences between the two proteins in the N-terminal tautomerization site are evident, and we provide evidence for the selective, species-specific inhibition of MIF by small-molecule antagonists that target this site. Lm1740MIF shows significant binding interaction with the MIF receptor, CD74 (Kd = 2.9 × 10−8 M). Like its mammalian counterpart, Lm1740MIF induces ERK1/2 MAP kinase activation in a CD74-dependent manner and inhibits the activation-induced apoptosis of macrophages. The ability of Lm1740MIF to inhibit apoptosis may facilitate the persistence of Leishmania within the macrophage and contribute to its evasion from immune destruction.

The Golgi-Associated Protein p115 Mediates the Secretion of Macrophage Migration Inhibitory Factor

Macrophage migration inhibitory factor (MIF) is a leaderless protein that is secreted from cells by a specialized, nonclassical export pathway. The release of MIF nevertheless is regulated and its production in response to different inflammatory, mitogenic, and hormonal stimuli plays an important role in diverse physiologic and pathologic processes. We report herein the identification of the Golgi complex-associated protein p115 as an intracellular binding partner for MIF. MIF interacts with p115 in the cytoplasm and the stimulated secretion of MIF results in the accumulation of both proteins in supernatants, which is consistent with MIF release from cells in conjunction with p115. The depletion of p115 from monocytes/macrophages decreases the release of MIF but not other cytokines following inflammatory stimulation or intracellular bacterial infection. Notably, the small molecule MIF inhibitor 4-iodo-6-phenylpyrimidine inhibits MIF secretion by targeting the interaction between MIF and p115. These data reveal p115 to be a critical intermediary component in the regulated secretion of MIF from monocytes/macrophages.

The role of macrophage migration inhibitory factor in autoimmune liver disease

The role of the cytokine, macrophage migration inhibitory factor (MIF), and its receptor, CD74, was assessed in autoimmune hepatitis (AIH) and primary biliary cirrhosis (PBC). Two MIF promoter polymorphisms, a functional −794 CATT5‐8 microsatellite repeat (rs5844572) and a −173 G/C single‐nucleotide polymorphism (rs755622), were analyzed in DNA samples from over 500 patients with AIH, PBC, and controls. We found a higher frequency of the proinflammatory and high‐expression −794 CATT7 allele in AIH, compared to PBC, whereas lower frequency was found in PBC, compared to both AIH and healthy controls. MIF and soluble MIF receptor (CD74) were measured by enzyme‐linked immunosorbent assay in 165 serum samples of AIH, PBC, and controls. Circulating serum and hepatic MIF expression was elevated in patients with AIH and PBC versus healthy controls. We also identified a truncated circulating form of the MIF receptor, CD74, that is released from hepatic stellate cells and that binds MIF, neutralizing its signal transduction activity. Significantly higher levels of CD74 were found in patients with PBC versus AIH and controls. Conclusions: These data suggest a distinct genetic and immunopathogenic basis for AIH and PBC at the MIF locus. Circulating MIF and MIF receptor profiles distinguish PBC from the more inflammatory phenotype of AIH and may play a role in pathogenesis and as biomarkers of these diseases. (Hepatology 2014;59:580–591)

Glucocorticoid-induced MIF expression by human CEM T cells.

Macrophage migration inhibitory factor (MIF) is an upstream activator of the immune response that counter-regulates the immunosuppressive effects of glucocorticoids. While MIF is released by cells in response to diverse microbial and invasive stimuli, evidence that glucocorticoids in low concentrations also induce MIF secretion suggests an additional regulatory relationship between these mediators. We investigated the expression of MIF from the human CEM T cell line, which exists in two well-characterized, glucocorticoid-sensitive (CEM-C7) and glucocorticoid-resistant (CEM-C1) variant clones. Dexamethasone in low concentrations induced MIF secretion from CEM-C7 but not CEM-C1 T cells by a bell-shaped dose response that was similar to that reported previously for the release of MIF by monocytes/macrophages. Glucocorticoid stimulation of CEM-C7 T cells was accompanied by an MIF transcriptional response, which by promoter analysis was found to involve the GRE and ATF/CRE transcription factor binding sites. These data support a glucocorticoid-mediated MIF secretion response by T cells that may contribute to the regulation of the adaptive immune response.

The role of macrophage migration inhibitory factor in autoimmune liver disease: Assis et al.

The role of the cytokine, macrophage migration inhibitory factor (MIF), and its receptor, CD74, was assessed in autoimmune hepatitis (AIH) and primary biliary cirrhosis (PBC). Two MIF promoter polymorphisms, a functional −794 CATT5‐8 microsatellite repeat (rs5844572) and a −173 G/C single‐nucleotide polymorphism (rs755622), were analyzed in DNA samples from over 500 patients with AIH, PBC, and controls. We found a higher frequency of the proinflammatory and high‐expression −794 CATT7 allele in AIH, compared to PBC, whereas lower frequency was found in PBC, compared to both AIH and healthy controls. MIF and soluble MIF receptor (CD74) were measured by enzyme‐linked immunosorbent assay in 165 serum samples of AIH, PBC, and controls. Circulating serum and hepatic MIF expression was elevated in patients with AIH and PBC versus healthy controls. We also identified a truncated circulating form of the MIF receptor, CD74, that is released from hepatic stellate cells and that binds MIF, neutralizing its signal transduction activity. Significantly higher levels of CD74 were found in patients with PBC versus AIH and controls. Conclusions: These data suggest a distinct genetic and immunopathogenic basis for AIH and PBC at the MIF locus. Circulating MIF and MIF receptor profiles distinguish PBC from the more inflammatory phenotype of AIH and may play a role in pathogenesis and as biomarkers of these diseases. (Hepatology 2014;59:580–591)

THE ROLE OF MACROPHAGE MIGRATION INHIBITORY FACTOR (MIF) IN AUTOIMMUNE LIVER DISEASE

The role of the cytokine, macrophage migration inhibitory factor (MIF), and its receptor, CD74, was assessed in autoimmune hepatitis (AIH) and primary biliary cirrhosis (PBC). Two MIF promoter polymorphisms, a functional −794 CATT5‐8 microsatellite repeat (rs5844572) and a −173 G/C single‐nucleotide polymorphism (rs755622), were analyzed in DNA samples from over 500 patients with AIH, PBC, and controls. We found a higher frequency of the proinflammatory and high‐expression −794 CATT7 allele in AIH, compared to PBC, whereas lower frequency was found in PBC, compared to both AIH and healthy controls. MIF and soluble MIF receptor (CD74) were measured by enzyme‐linked immunosorbent assay in 165 serum samples of AIH, PBC, and controls. Circulating serum and hepatic MIF expression was elevated in patients with AIH and PBC versus healthy controls. We also identified a truncated circulating form of the MIF receptor, CD74, that is released from hepatic stellate cells and that binds MIF, neutralizing its signal transduction activity. Significantly higher levels of CD74 were found in patients with PBC versus AIH and controls. Conclusions: These data suggest a distinct genetic and immunopathogenic basis for AIH and PBC at the MIF locus. Circulating MIF and MIF receptor profiles distinguish PBC from the more inflammatory phenotype of AIH and may play a role in pathogenesis and as biomarkers of these diseases. (Hepatology 2014;59:580–591)