The autoimmune inflammation of rheumatoid arthritis (RA) induces profound invasive and proliferative changes in the joint synovium. Our research has focused on the role of the cytokine MIF, which we initially cloned together with its two-component receptor and found to sustain inflammatory responses by counter-regulating glucocorticoid action and inhibiting activation-induced apoptosis. We identified functional polymorphisms in the MIF promoter that are associated with disease severity and we developed an anti-MIF monoclonal antibody that has entered phase I clinical testing. While investigating the mechanistic basis for phenotypic differences between MIF and MIF receptor deficient mice, we discovered a new MIF-like cytokine encoded by the Ddt locus. Our data indicate that DDT is expressed in RA and exerts immunoregulatory functions by interacting with the CD74, ligand- binding component of the MIF receptor. DDT shares structural features with MIF but there are differences that are important in considering the therapeutic inhibition of these cytokines or their signaling pathways. In this renewal application, we will determine the distinct immunologic actions of the novel cytokine DDT by pursuing three Specific Aims: 1. Define the Mechanism of DDT Signal Transduction. We hypothesize that DDT initiates signal transduction via the canonical MIF ligand-binding receptor CD74, and that it recruits additional co-receptors (CD44, CXCR2/4) to mediate shared or unique effector responses. We will ask if DDT, which lacks the pseudo-(E)LR motif by which MIF interacts with CXCR2/4, activates these or related co-receptors. We also will examine if DDT shares MIF's role in suppressing insulin signaling, as metabolic dysfunction and atherogenesis are important sequela of long-standing rheumatoid inflammation. 2. Define the Functional Importance of DDT in Inflammatory Arthritis. We hypothesize that DDT exerts a non-redundant role in the immunopathogenesis of inflammatory arthritis. We will define the phenotype of DDT-KO and MIF-DDT double-knockout (DKO) mice in experimental arthritis and compare them to MIF-KO and MIF receptor-KO (CD74-KO) mice. We will examine cross-regulation of MIF and DDT signaling in monocytes and fibroblasts from corresponding genetically-defined mouse strains. 3. Evaluate the Therapeutic Potential of Pharmacologic DDT Inhibition. We hypothesize that DDT neutralization ameliorates arthritis by innate and/or adaptive immune mechanisms. We will test a novel anti-DDT mAb and a soluble CD74-Fc fusion protein, which binds both MIF and DDT. We also will test the therapeutic activity of a small molecule, selective DDT inhibitor identified by computational screening. The discovery of DDT as a novel cytokine interacting with the MIF receptor CD74 was unforeseen but requires close examination for a better understanding of these cytokines in synovial inflammation and for the effective application of pharmacologic inhibitors.
Our knowledge of rheumatoid arthritis is incomplete and long-lasting remissions remain difficult to achieve. A genetic association between the immune cytokine MIF (macrophage migration inhibitory factor) and rheumatoid arthritis has been described, and a MIF-directed therapy has advanced into clinical testing. Investigation of the mechanism of action of DDT, a newly discovered MIF family cytokine, will accelerate the development of new and effective therapies for autoimmune arthritis.
|Meza-Romero, Roberto; Benedek, Gil; Jordan, Kelley et al. (2016) Modeling of both shared and distinct interactions between MIF and its homologue D-DT with their common receptor CD74. Cytokine 88:62-70|
|Yao, Jie; Leng, Lin; Sauler, Maor et al. (2016) Transcription factor ICBP90 regulates the MIF promoter and immune susceptibility locus. J Clin Invest 126:732-44|
|Meza-Romero, Roberto; Benedek, Gil; Leng, Lin et al. (2016) Predicted structure of MIF/CD74 and RTL1000/CD74 complexes. Metab Brain Dis 31:249-55|
|Assis, David N; Takahashi, Hiroki; Leng, Lin et al. (2016) A Macrophage Migration Inhibitory Factor Polymorphism Is Associated with Autoimmune Hepatitis Severity in US and Japanese Patients. Dig Dis Sci 61:3506-3512|
|Rowe, Meredith A; Harper, Lindsey R; McNulty, Margaret A et al. (2016) Deletion of Macrophage Migration Inhibitory Factor Reduces Severity of Osteoarthritis in Aged Mice. Arthritis Rheumatol :|
|GalvÃ£o, Izabela; Dias, Ana Carolina Fialho; Tavares, Livia Duarte et al. (2016) Macrophage migration inhibitory factor drives neutrophil accumulation by facilitating IL-1Î² production in a murine model of acute gout. J Leukoc Biol 99:1035-43|
|Djudjaj, Sonja; Lue, Hongqi; Rong, Song et al. (2016) Macrophage Migration Inhibitory Factor Mediates Proliferative GN via CD74. J Am Soc Nephrol 27:1650-64|
|Yoo, Seung-Ah; Leng, Lin; Kim, Bum-Joon et al. (2016) MIF allele-dependent regulation of the MIF coreceptor CD44 and role in rheumatoid arthritis. Proc Natl Acad Sci U S A 113:E7917-E7926|
|Gu, Ran; Santos, Leilani L; Ngo, Devi et al. (2015) Macrophage migration inhibitory factor is essential for osteoclastogenic mechanisms in vitro and in vivo mouse model of arthritis. Cytokine 72:135-45|
|Hwang, Seong-Hye; Jung, Seung-Hyun; Lee, Saseong et al. (2015) Leukocyte-specific protein 1 regulates T-cell migration in rheumatoid arthritis. Proc Natl Acad Sci U S A 112:E6535-43|
Showing the most recent 10 out of 79 publications