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Unlabelled: 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.

Rheumatoid arthritis (RA) is characterized by the interaction of multiple mediators, among the most important of which are cytokines. In recent years, extensive studies demonstrate a pivotal role for one cytokine, macrophage migration inhibitory factor (MIF), in fundamental events in innate and adaptive immunity. MIF has now been demonstrated to be involved in the pathogenesis of many diseases, but in the case of RA the evidence for a role of MIF is very strong. MIF is abundantly expressed in the sera of RA patients and in RA synovial tissue correlating with disease activity. MIF-deficient mice were used to induce arthritis by serum transfer from K/BxN mice. K/BxN serum transfer arthritis was markedly attenuated in MIF mice, with reduction in clinical index and histological severity as well as decrease in synovial cytokines. Macrophage transfers were done to investigate the specific role of macrophage-derived MIF. We show that adoptive transfer of wild-type macrophages into MIF mice restores the sensitivity of MIF mice to arthritis development, and this affect was associated with a restoration in serum IL-1β and IL-6 production. These results indicate that MIF plays a critical role in inflammation and joint destruction in K/BxN serum-induced arthritis and that the systemic expression of MIF by a subpopulation of macrophages is necessary and sufficient for the full development of arthritis. [ABSTRACT FROM AUTHOR]

The cytokine macrophage migration inhibitory factor (MIF) plays a critical role in inflammatory diseases and atherogenesis. We identify the chemokine receptors CXCR2 and CXCR4 as functional receptors for MIF. MIF triggered Gαi- and integrin-dependent arrest and chemotaxis of monocytes and T cells, rapid integrin activation and calcium influx through CXCR2 or CXCR4. MIF competed with cognate ligands for CXCR4 and CXCR2 binding, and directly bound to CXCR2. CXCR2 and CD74 formed a receptor complex, and monocyte arrest elicited by MIF in inflamed or atherosclerotic arteries involved both CXCR2 and CD74. In vivo, Mif deficiency impaired monocyte adhesion to the arterial wall in atherosclerosis-prone mice, and MIF-induced leukocyte recruitment required Il8rb (which encodes Cxcr2). Blockade of Mif but not of canonical ligands of Cxcr2 or Cxcr4 in mice with advanced atherosclerosis led to plaque regression and reduced monocyte and T-cell content in plaques. By activating both CXCR2 and CXCR4, MIF displays chemokine-like functions and acts as a major regulator of inflammatory cell recruitment and atherogenesis. Targeting MIF in individuals with manifest atherosclerosis can potentially be used to treat this condition. [ABSTRACT FROM AUTHOR]

Macrophage migration inhibitory factor (MIF) is a ubiquitously expressed pro-inflammatory mediator that has also been implicated in the process of oncogenic transformation and tumor progression. We used a genetic approach to show that deletion of the MIF gene in mice has several major consequences for the proliferative and transforming properties of cells. MIF-deficient cells exhibit increased resistance to oncogenic transformation. The transformation defects associated with MIF deficiency can be overcome through concomitant inactivation of the p53 and Rb/E2F tumor suppressor pathways. We have produced compelling evidence that the effects of MIF on cell survival and tumorigenesis are mediated through overlapping pathways, wherein MIF and p53 functionally antagonize each other in the cell. However, the involvement of MIF in p53 function is secondary to p53-independent mechanisms controlling protein stability, DNA damage checkpoints, and the integrity of the genome. Given the broad spectrum of cell types that normally express MIF and its elevated levels at sites of chronic inflammation, this pathway may be generic for many early stage tumors. [ABSTRACT FROM AUTHOR]

Abstract: Macrophage migration inhibitory factor (MIF) is a 12.5 kD polypeptide that serves as a critical regulator of cell functions such as gene expression, proliferation or apoptosis. However, the signal transduction pathways through which MIF takes part in cellular regulation are only incompletely understood. MIF leads to CD74-dependent “sustained” activation of ERK1/2 MAPK, but MIF''s role in “transient” ERK activation and the involved upstream pathways are unknown. Here we report that the transient ERK pathway was markedly activated by MIF. This effect involved the phosphorylation and activation of Raf-1, MEK, ERK, and Elk-1. Of note, rapid and transient ERK phosphorylation by MIF was measurable in MIF-deficient cells, suggesting that MIF acted in a non-autocrine fashion. Applying the inhibitor genistein, a tyrosine kinase (TPK) activity was identified as a critical upstream signalling event in MIF-induced transient ERK signalling. Experiments using the Src kinase inhibitor PP2 indicated that the involved TPK was a Src-type tyrosine kinase. A role for an upstream Src kinase was proven by applying Src-deficient cells which did not exhibit transient ERK activation upon treatment with MIF, but in which MIF-induced ERK signalling could be restored by re-expressing Src. Intriguingly, JAB1/CSN5, a signalosome component, cellular binding protein of MIF and regulator of cell proliferation and survival, had a marked, yet dual, effect on MIF-induced ERK signalling. JAB1 overexpression inhibited sustained, but not transient, ERK phosphorylation. By contrast, JAB1-knock-down by siRNA revealed that minimum JAB1 levels were necessary for transient activation of ERK by MIF. In conclusion, MIF rapidly and transiently activates the ERK pathway, an effect that has not been recognized previously. This signalling pathway involves the upstream activation of a Src-type kinase and is co-regulated by the cellular MIF binding protein JAB1/CSN5. Our study thus has unravelled a novel MIF-driven signalling pathway and an intricate regulatory system involving extra- and possibly intracellular MIF, and which likely critically participates in controlling cell proliferation and survival. [Copyright &y& Elsevier]

Excessive inflammation drives the progression from sepsis to septic shock. Macrophage migration inhibitory factor (MIF) is of interest because MIF promoter polymorphisms predict mortality in different infections, and anti-MIF antibody improves survival in experimental models when administered 8 hours after infectious insult. The recent description of a second MIF superfamily member, D-dopachrome tautomerase (D-DT/MIF-2), prompted closer investigation of MIF-dependent responses. We subjected Mif–/– and Mif-2–/– mice to polymicrobial sepsis and observed a survival benefit with Mif but not Mif-2 deficiency. Survival was associated with reduced numbers of small peritoneal macrophages (SPMs) that, in contrast to large peritoneal macrophages (LPMs), were recruited into the peritoneal cavity. LPMs produced higher quantities of MIF than SPMs, but SPMs expressed higher levels of inflammatory cytokines and the MIF receptors CD74 and CXCR2. Adoptive transfer of WT SPMs into Mif–/– hosts reduced the protective effect of Mif deficiency in polymicrobial sepsis. Notably, MIF-2 lacks the pseudo-(E) LR motif present in MIF that mediates CXCR2 engagement and SPM migration, supporting a specific role for MIF in the recruitment and accumulation of inflammatory SPMs. [ABSTRACT FROM AUTHOR]

Abstract: Inflammation plays an important role in mediating and exacerbating myocardial ischemia–reperfusion (I/R) injury. Macrophage migration inhibitory factor (MIF), a pleiotropic cytokine, facilitates inflammation and modulates metabolism. However, the role of MIF in mediating local inflammation subsequent to ischemic myocardial injury has not been established. We hypothesized that genetic deletion of MIF protects the heart against severe I/R injury by suppressing inflammation and/or modulating energy metabolism. We showed in the mouse I/R model that duration of both ischemia and reperfusion is a determinant for the degree of regional inflammation and tissue damage. Following a prolonged cardiac I/R (60min/24h) MIF KO mice had a significant reduction in both infarct size (26±3% vs. 45±4%, P <0.05) and cardiomyocyte apoptosis (1.4±0.2% vs. 5.4±0.4%, P <0.05) and preserved contractile function compared with WT. MIF KO mice with I/R had reduced expression of various inflammatory cytokines and mediators (P <0.05), suppressed infiltration of neutrophils (−40%) and macrophages (−33%, both P <0.05), and increased macrophage apoptosis (14.4±1.4% vs. 5.2±0.6%, P <0.05). Expression of toll-like receptor-4 (TLR-4), phosphorylation of c-Jun N-terminal kinase (JNK), and nuclear fraction of NF-κB p65 were also significantly lower in MIF KO hearts with I/R. Further, MIF KO mice exhibited a lower glucose uptake but higher fatty acid oxidation rate than that in WT (both P <0.05). In conclusion, MIF deficiency protected the heart from prolonged/severe I/R injury by suppressing inflammatory responses. We have identified a critical role of MIF in mediating severe I/R injury. Thus, MIF inhibitory therapy may be a novel strategy to protect the heart against severe I/R injury. [Copyright &y& Elsevier]