Günter Fingerle-Rowson

MIF is a noncognate ligand of CXC chemokine receptors in inflammatory and atherogenic cell recruitment

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.

Macrophage migration inhibitory factor (MIF) sustains macrophage proinflammatory function by inhibiting p53: Regulatory role in the innate immune response

The importance of the macrophage in innate immunity is underscored by its secretion of an array of powerful immunoregulatory and effector molecules. We report herein that macrophage migration inhibitory factor (MIF), a product of activated macrophages, sustains macrophage survival and function by suppressing activation-induced, p53-dependent apoptosis. Endotoxin administration to MIF−/− mice results in decreased macrophage viability, decreased proinflammatory function, and increased apoptosis when compared with wild-type controls. Moreover, inhibition of p53 in endotoxin-treated, MIF-deficient macrophages suppresses enhanced apoptosis and restores proinflammatory function. MIF inhibits p53 activity in macrophages via an autocrine regulatory pathway, resulting in a decrease in cellular p53 accumulation and subsequent function. Inhibition of p53 by MIF coincides with the induction of arachidonic acid metabolism and cyclooxygenase-2 (Cox-2) expression, which is required for MIF regulation of p53. MIFs effect on macrophage viability and survival provides a previously unrecognized mechanism to explain its critical proinflammatory action in conditions such as sepsis, and suggests new approaches for the modulation of innate immune responses.

Regulation of Macrophage Migration Inhibitory Factor Expression by Glucocorticoids in Vivo

Glucocorticoid hormones are important anti-inflammatory agents because of their anti-inflammatory and proapoptotic action within the immune system. Their clinical usefulness remains limited however by side effects that result in part from their growth inhibitory action on sensitive target tissues. The protein mediator, macrophage migration inhibitory factor (MIF), is an important regulator of the host immune response and exhibits both glucocorticoid-antagonistic and growth-regulatory properties. MIF has been shown to contribute significantly to the development of immunopathology in several models of inflammatory disease. Although there is emerging evidence for a functional interaction between MIF and glucocorticoids in vitro, little is known about their reciprocal influence in vivo. We investigated the expression of MIF in rat tissues after ablation of the hypothalamic-pituitary-adrenal axis and after high-dose glucocorticoid administration. MIF expression is constitutive and independent of the influence of adrenal hormones. Hypophysectomy and the attendent loss of pituitary hormones, by contrast, decreased MIF protein content in the adrenal gland. Administration of dexamethasone was found to increase MIF protein expression in those organs that are considered to be sensitive to the growth inhibitory effects of glucocorticoids (immune and endocrine tissues, skin, and muscle). This increase was most likely because of a posttranscriptional regulatory effect because tissue MIF mRNA levels were not influenced by dexamethasone treatment. Finally, MIF immunoneutralization enhanced lymphocyte egress from blood during stress-induced lymphocyte redistribution, consistent with a functional interaction between MIF and glucocorticoids on immune cell trafficking in vivo. These findings suggest a role for MIF in both the homeostatic and physiological action of glucocorticoids in vivo.

Deletion of macrophage migration inhibitory factor protects the heart from severe ischemia–reperfusion injury: A predominant role of anti-inflammation

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 (60 min/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.

Inhibiting the HSP90 chaperone destabilizes macrophage migration inhibitory factor and thereby inhibits breast tumor progression.

In several human cancer cell lines, HSP90 inhibitors destabilize macrophage inhibitory factor protein; systemic treatment with an HSP90 inhibitor slows tumor growth and extends overall survival in a mouse model of HER2-positive human breast cancer.

Macrophage migration inhibitory factor regulates neutrophil chemotactic responses in inflammatory arthritis in mice.

OBJECTIVE Macrophage migration inhibitory factor (MIF) facilitates multiple aspects of inflammatory arthritis, the pathogenesis of which has been significantly linked to the activity of neutrophils. The effects of MIF on neutrophil recruitment are unknown. This study was undertaken to investigate the contribution of MIF to the regulation of neutrophil chemotactic responses. METHODS K/BxN serum-transfer arthritis was induced in wild-type (WT), MIF(-/-) , and monocyte chemotactic protein 1 (MCP-1; CCL2)-deficient mice as well as in WT mice treated with monoclonal antibodies to cytokine-induced neutrophil chemoattractant (anti-KC). Leukocyte trafficking in vivo was examined using intravital microscopy, and neutrophil function in vitro was examined using migration chambers and assessment of MAP kinase activation. RESULTS K/BxN serum-transfer arthritis was markedly attenuated in MIF(-/-) mice, with reductions in the clinical and histologic severity of arthritis and the synovial expression of KC and interleukin-1. Arthritis was also reduced by anti-KC antibody treatment, but not in MCP-1-deficient mice. In vivo, neutrophil recruitment responses to KC were reduced in MIF(-/-) mice. Similarly, MIF(-/-) mouse neutrophils exhibited reduced chemotactic responses to KC in vitro, despite displaying unaltered chemokine receptor expression. Reduced chemotactic responses of MIF(-/-) mouse neutrophils were associated with reduced phosphorylation of p38 and ERK MAP kinases. CONCLUSION These findings suggest that MIF promotes neutrophil trafficking in inflammatory arthritis via facilitation of chemokine-induced migratory responses and MAP kinase activation. Therapeutic MIF inhibition could limit synovial neutrophil recruitment.

Macrophage migration inhibitory factor deficiency is associated with altered cell growth and reduced susceptibility to Ras-mediated transformation.

Macrophage migration inhibitory factor (MIF) has been shown to functionally inactivate the p53 tumor suppressor and to inhibit p53-responsive gene expression and apoptosis. To better understand the role of MIF in cell growth and tumor biology, we evaluated MIF-null embryonic fibroblasts with respect to their immortalization and transformation properties. Although minor deviations in the growth characteristics of MIF−/−fibroblasts were observed under normal culture conditions, MIF-deficient cells were growth-impaired following the introduction of immortalizing oncogenes. The growth retardation by the immortalized MIF−/− cultures correlated with their reduced susceptibility to Ras-mediated transformation. Our results identify E2F as part of the restraining mechanism that is activated in response to oncogenic signaling and show that the biological consequences of E2F induction in MIF−/− fibroblasts vary depending on the p53 status, inducing predominantly G1 arrest or apoptosis in p53-positive cells. This E2F activity is independent of Rb binding, but contingent on binding DNA. Resistance to oncogenic transformation by MIF−/− cells could be overcome by concomitant interference with p53- and E2F-responsive transcriptional control. Our results demonstrate that MIF plays a role in an E2F/p53 pathway that operates downstream of Rb regulation and implicate MIF as a mediator of normal and malignant cell growth.

Macrophage migration inhibitory factor and CD74 regulate macrophage chemotactic responses via MAPK and Rho GTPase.

Macrophage migration inhibitory factor (MIF) promotes leukocyte recruitment to sites of inflammation. However, whether this stems from a direct effect on leukocyte migration is unknown. Furthermore, the role of the MIF-binding protein CD74 in this response has not been investigated. Therefore, the aim of this study was to examine the contributions of MIF and CD74 to chemokine-induced macrophage recruitment. Intravital microscopy studies demonstrated that CCL2-induced leukocyte adhesion and transmigration were reduced in MIF−/− and CD74−/− mice. MIF−/− and CD74−/− macrophages also exhibited reduced chemotaxis in vitro, although CD74−/− macrophages showed increased chemokinesis. Reduced CCL2-induced migration was associated with attenuated MAPK phosphorylation, RhoA GTPase activity, and actin polymerization in MIF−/− and CD74−/− macrophages. Furthermore, in MIF−/− macrophages, MAPK phosphatase-1 was expressed at elevated levels, providing a potential mechanism for the reduction in MAPK phosphorylation in MIF-deficient cells. No increase in MAPK phosphatase-1 expression was observed in CD74−/− macrophages. In in vivo experiments assessing the link between MIF and CD74, combined administration of MIF and CCL2 increased leukocyte adhesion in both MIF−/− and CD74−/− mice, showing that CD74 was not required for this MIF-induced response. Additionally, although leukocyte recruitment induced by administration of MIF alone was reduced in CD74−/− mice, consistent with a role for CD74 in leukocyte recruitment induced by MIF, MIF-treated CD74−/− mice displayed residual leukocyte recruitment. These data demonstrate that MIF and CD74 play previously unappreciated roles in CCL2-induced macrophage adhesion and migration, and they indicate that MIF and CD74 mediate this effect via both common and independent mechanisms.

Neuroendocrine properties of macrophage migration inhibitory factor (MIF)

The cytokine macrophage migration inhibitory factor (MIF) is produced by neuroendocrine and immune tissues and possesses several features that allow it to be characterized as a neuroendocrine mediator. Its pro‐inflammatory action and its pathogenic role in inflammatory diseases, such as septic shock, arthritis and other diseases, have clearly been demonstrated and may be based in part on neuroendocrine mechanisms. Macrophage migration inhibitory factor possesses glucocorticoid‐antagonist properties within the immune system and participates in the regulation of several endocrine circuits. This review summarizes the current state of MIF research and focuses on MIF expression and function in nervous and endocrine tissues.

Impaired DNA damage checkpoint response in MIF-deficient mice

Recent studies demonstrated that proinflammatory migration inhibitory factor(MIF) blocks p53‐dependent apoptosis and interferes with the tumor suppressor activity of p53. To explore the mechanism underlying this MIF‐p53 relationship, we studied spontaneous tumorigenesis in genetically matched p53−/− and MIF−/−p53−/− mice. We show that the loss of MIF expression aggravates the tumor‐prone phenotype of p53−/− mice and predisposes them to a broader tumor spectrum, including B‐cell lymphomas and carcinomas. Impaired DNA damage response is at the root of tumor predisposition of MIF−/−p53−/− mice. We provide evidence that MIF plays a role in regulating the activity of Cul1‐containing SCF ubiquitin ligases. The loss of MIF expression uncouples Chk1/Chk2‐responsive DNA damage checkpoints from SCF‐dependent degradation of key cell‐cycle regulators such as Cdc25A, E2F1 and DP1, creating conditions for the genetic instability of cells. These MIF effects depend on its association with the Jab1/CSN5 subunit of the COP9/CSN signalosome. Given that CSN plays a central role in the assembly of SCF complexes in vivo, regulation of Jab1/CSN5 by MIF is required to sustain optimal composition and function of the SCF complex.