In vitro and in vivo regulation by macrophage migration inhibitory factor (MIF) of expression of MHC-II, costimulatory, adhesion, receptor, and cytokine molecules

The Role of MIF and IL-10 as Molecular Yin-Yang in the Modulation of the Host Immune Microenvironment During Infections: African Trypanosome Infections as a Paradigm

African trypanosomes are extracellular flagellated unicellular protozoan parasites transmitted by tsetse flies and causing Sleeping Sickness disease in humans and Nagana disease in cattle and other livestock. These diseases are usually characterized by the development of a fatal chronic inflammatory disease if left untreated. During African trypanosome infection and many other infectious diseases, the immune response is mediating a see-saw balance between effective/protective immunity and excessive infection-induced inflammation that can cause collateral tissue damage. African trypanosomes are known to trigger a strong type I pro-inflammatory response, which contributes to peak parasitaemia control, but this can culminate into the development of immunopathologies, such as anaemia and liver injury, if not tightly controlled. In this context, the macrophage migration inhibitory factor (MIF) and the interleukin-10 (IL-10) cytokines may operate as a molecular “Yin-Yang” in the modulation of the host immune microenvironment during African trypanosome infection, and possibly other infectious diseases. MIF is a pleiotropic pro-inflammatory cytokine and critical upstream mediator of immune and inflammatory responses, associated with exaggerated inflammation and immunopathology. For example, it plays a crucial role in the pro-inflammatory response against African trypanosomes and other pathogens, thereby promoting the development of immunopathologies. On the other hand, IL-10 is an anti-inflammatory cytokine, acting as a master regulator of inflammation during both African trypanosomiasis and other diseases. IL-10 is crucial to counteract the strong MIF-induced pro-inflammatory response, leading to pathology control. Hence, novel strategies capable of blocking MIF and/or promoting IL-10 receptor signaling pathways, could potentially be used as therapy to counteract immunopathology development during African trypanosome infection, as well as during other infectious conditions. Together, this review aims at summarizing the current knowledge on the opposite immunopathological molecular “Yin-Yang” switch roles of MIF and IL-10 in the modulation of the host immune microenvironment during infection, and more particularly during African trypanosomiasis as a paradigm.

Gene knockout or inhibition of macrophage migration inhibitory factor alleviates lipopolysaccharide-induced liver injury via inhibiting inflammatory response

BACKGROUND

Liver injury is one of the most common complications during sepsis. Macrophage migration inhibitory factor (MIF) is an important proinflammatory cytokine. This study explored the role of MIF in the lipopolysaccharide (LPS)-induced liver injury through genetically manipulated mouse strains.

METHODS

The model of LPS-induced liver injury was established in wild-type and Mif-knockout C57/BL6 mice. Serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and total bilirubin (TBil) were detected, and the expressions of MIF, tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) were measured. Liver histopathology was conducted to assess liver injury. Moreover, the inhibitions of MIF with (S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid methyl ester (ISO-1) and 4-iodo-6-phenylpyrimidine (4-IPP) were used to evaluate their therapeutic potential of liver injury.

RESULTS

Compared with wild-type mice, the liver function indices and inflammation factors presented no significant difference in the Mif^-/- mice. After 72 h of the LPS-induced liver injury, serum levels of ALT, AST, and TBil as well as TNF-α and IL-1β were significantly increased, but the knockout of Mif attenuated liver injury and inflammatory response. In liver tissue, mRNA levels of TNF-α, IL-1β and NF-κB p65 were remarkably elevated in LPS-induced liver injury, while the knockout of Mif reduced these levels. Moreover, in LPS-induced liver injury, the inhibitions of MIF with ISO-1 and 4-IPP alleviated liver injury and slightly attenuated inflammatory response. Importantly, compared to mice with LPS-induced liver injury, Mif knockout or MIF inhibitions significantly prolonged the survival of the mice.

CONCLUSIONS

In LPS-induced liver injury, the knockout of Mif or MIF inhibitions alleviated liver injury and slightly attenuated inflammatory response, thereby prolonged the survival of the mice. Targeting MIF may be an important strategy to protect the liver from injury during sepsis.

Macrophage migration inhibitory factor of Syrian golden hamster shares structural and functional similarity with human counterpart and promotes pancreatic cancer

Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine that increasingly is being studied in cancers and inflammatory diseases. Though murine models have been instrumental in understanding the functional role of MIF in different pathological conditions, the information obtained from these models is biased towards a specific species. In experimental science, results obtained from multiple clinically relevant animal models always provide convincing data that might recapitulate in humans. Syrian golden hamster (Mesocricetus auratus), is a clinically relevant animal model for multiple human diseases. Hence, the major objectives of this study were to characterize the structure and function of Mesocricetus auratus MIF (MaMIF) and finally evaluate its effect on pancreatic tumor growth in vivo. Initially, the recombinant MaMIF was cloned, expressed and purified in a bacterial expression system. The MaMIF primary sequence, biochemical properties, and crystal structure analysis showed greater similarity with human MIF. The crystal structure of MaMIF illustrates that it forms a homotrimer as known in human and mouse. However, MaMIF exhibits some minor structural variations when compared to human and mouse MIF. The in vitro functional studies show that MaMIF has tautomerase activity and enhances activation and migration of hamster peripheral blood mononuclear cells (PBMCs). Interestingly, injection of MaMIF into HapT1 pancreatic tumor-bearing hamsters significantly enhanced the tumor growth and tumor-associated angiogenesis. Together, the current study shows a structural and functional similarity between the hamster and human MIF. Moreover, it has demonstrated that a high level of circulating MIF originating from non-tumor cells might also promote pancreatic tumor growth in vivo.

Roles of macrophage migration inhibitory factor in Guillain-Barré syndrome and experimental autoimmune neuritis: beneficial or harmful?

INTRODUCTION

Macrophage migration inhibitory factor (MIF) plays an important role in the pathogenesis of Guillain-Barré syndrome (GBS) and its animal model experimental autoimmune neuritis (EAN), which may offer an opportunity for the development of the novel therapeutic strategies for GBS. Areas covered: 'macrophage migration inhibitory factor' and 'Guillain-Barré syndrome' were used as keywords to search for related publications on Pub-Med, National Center for Biotechnology Information (NCBI), USA. MIF is involved in the etiology of various inflammatory and autoimmune disorders. However, the roles of MIF in GBS and EAN have not been summarized in the publications we identified. Therefore, in this review, we described and analyzed the major roles of MIF in GBS/EAN. Primarily, this molecule aggravates the inflammatory responses in this disorder. However, multiple studies indicated a protective role of MIF in GBS. The potential of MIF as a therapeutic target in GBS has been recently demonstrated in experimental and clinical studies, although clinical trials have been unavailable to date. Expert opinion: MIF plays a critical role in the initiation and progression of GBS and EAN, and it may represent a potential therapeutic target for GBS.

Macrophage migration inhibitory factor is required for NLRP3 inflammasome activation

Macrophage migration inhibitory factor (MIF) exerts multiple effects on immune cells, as well as having functions outside the immune system. MIF can promote inflammation through the induction of other cytokines, including TNF, IL-6, and IL-1 family cytokines. Here, we show that inhibition of MIF regulates the release of IL-1α, IL-1β, and IL-18, not by affecting transcription or translation of these cytokines, but via activation of the NLRP3 inflammasome. MIF is required for the interaction between NLRP3 and the intermediate filament protein vimentin, which is critical for NLRP3 activation. Further, we demonstrate that MIF interacts with NLRP3, indicating a role for MIF in inflammasome activation independent of its role as a cytokine. These data advance our understanding of how MIF regulates inflammation and identify it as a factor critical for NLRP3 inflammasome activation.

MIF is a cytokine best known for its modulatory effect on expression of proinflammatory cytokines. Here the authors show that MIF facilitates the NLRP3–vimentin interaction, resulting in Nlrp3 inflammasome activation.

Hepatocyte-derived macrophage migration inhibitory factor mediates alcohol-induced liver injury in mice and patients

BACKGROUND & AIMS

Macrophage migration inhibitory factor (MIF) is a multi-potent cytokine that contributes to the inflammatory response to injury. MIF is expressed by multiple cell types; however, the cellular source and actions of MIF in alcoholic liver disease (ALD) are not well known. Here we tested the hypothesis that non-myeloid cells, specifically hepatocytes, are an important cellular source of MIF in ALD.

METHODS

MIF expression was measured in HuH7 and differentiated THP-1 cells in response to ethanol. Ethanol-induced liver injury was assessed in C57BL/6 (WT) and Mif^-/- bone marrow chimeras. MIF was measured in peripheral and suprahepatic serum, as well as visualized by immunohistochemistry in liver biopsies, from patients with alcoholic hepatitis (AH).

RESULTS

HuH7 hepatocytes, but not THP-1 macrophages, released MIF in response to ethanol challenge in culture. In chimeric mice expressing MIF in non-myeloid cells (Mif^-/-→WT), chronic ethanol feeding increased ALT/AST, hepatic steatosis, and expression of cytokine/chemokine mRNA. In contrast, chimeric mice not expressing MIF in non-myeloid cells (WT→Mif^-/-) were protected from ethanol-induced liver injury. Immunohistochemical staining of liver biopsies from patients with AH revealed a predominant localization of MIF to hepatocytes. Interestingly, the concentration of MIF in suprahepatic serum, but not peripheral serum, was positively correlated with clinical indicators of disease severity and with an increased risk of mortality in patients with AH.

CONCLUSIONS

Taken together, these data provide evidence that hepatocyte-derived MIF is critical in the pathogenesis of ALD in mice and likely contributes to liver injury in patients with AH. Lay summary: Alcoholic liver disease is a major cause of preventable mortality worldwide, and lacks specific pharmacological therapies. Recent studies have recognized that macrophage migration inhibitor factor (MIF) has a critical role in the inflammatory response to liver damage. However, the cells that produce this protein are still unknown. Our present findings reveal that hepatocytes, the main cell type in the liver, are primarily responsible for MIF production in response to alcohol, which promotes liver injury. Our study suggests that drugs inhibiting MIF production could be beneficial in treating patients with liver disease due to excessive alcohol consumption.

The role of autophagy in asparaginase-induced immune suppression of macrophages

Erwinia asparaginase, a bacteria-derived enzyme drug, has been used in the treatment of various cancers, especially acute lymphoblastic leukemia (ALL). One of the most significant side effects associated with asparaginase administration is immune suppression, which limits its application in clinic. Macrophages are phagocytic immune cells and have a central role in inflammation and host defense. We reported here that asparaginase disturbed the function of macrophages including phagocytosis, proliferation, ROS and nitric oxide secretion, interleukin 6 (IL-6) and tumor necrosis factor α (TNF-α) secretion, and major histocompatibility complex II (MHC-II) molecule expression, thus induced immune suppression in interferon-γ and lipopolysaccharide-stimulated macrophages. We also observed that asparaginase inhibited autophagy in macrophages via activating Akt/mTOR and suppressing Erk1/2 signaling pathway as evidenced by less formation of autophagosomes, downregulation of autophagy-related protein LC3-II, and decreased number of autophagy-like vacuoles. Further study discovered that treatment with autophagy inhibitor 3-MA in place of asparaginase on activated macrophages could also downregulate phagocytosis, cytokine secretion, and MHC-II expression. Moreover, incubation with autophagy inducer trehalose restored the capacity of phagocytosis, IL-6 and TNF-α secretion, and MHC-II expression in macrophages. These results prove the important role of autophagy in the function of macrophages, and activation of autophagy can overcome asparaginase-induced immune suppression in macrophages.

Macrophage migration inhibitory factor: a potential therapeutic target for rheumatoid arthritis

Macrophage migration inhibitory factor (MIF) is originally identified in the culture medium of activated T lymphocytes as a soluble factor that inhibits the random migration of macrophages. MIF is now recognized as a multipotent cytokine involved in the regulation of immune and inf lammatory responses. In rheumatoid arthritis (RA), MIF promotes inf lammatory responses by inducing proinflammatory cytokines and tissue-degrading molecules, promoting the proliferation and survival of synovial fibroblasts, stimulating neutrophil chemotaxis, and regulating angiogenesis and osteoclast differentiation. Expression of MIF in synovial tissue and synovial fluid levels of MIF are elevated in RA patients. Specifically, MIF levels correlate with RA disease activity and high levels are associated with bone erosion. In animal models of RA, the genetic and therapeutic inhibition of MIF has been shown to control inflammation and bone destruction. Based on the role of MIF in RA pathogenesis, small molecular inhibitors targeting it or its receptor pathways could provide a new therapeutic option for RA patients.

Altered Macrophage and Dendritic Cell Response in Mif-/- Mice Reveals a Role of Mif for Inflammatory-Th1 Response in Type 1 Diabetes

Macrophage migration inhibitory factor (Mif) is highly expressed in type 1 diabetes mellitus (T1DM). However, there is limited information about how Mif influences the activation of macrophages (Mφ) and dendritic cells (DC) in T1DM. To address this issue, we induced T1DM by administering multiple low doses of streptozotocin (STZ) to Mif-/- or wild-type (Wt) BALB/c mice. We found that Mif-/- mice treated with STZ (Mif-/-STZ) developed lower levels of hyperglycemia, inflammatory cytokines, and specific pancreatic islet antigen- (PIAg-) IgG and displayed reduced cellular infiltration into the pancreatic islets compared to Wt mice treated with STZ (WtSTZ). Moreover, Mφ and DC from Mif-/-STZ displayed lower expression of MHC-II, costimulatory molecules CD80, CD86, and CD40, Toll-like receptor- (TLR-) 2, and TLR-4 than WtSTZ. These changes were associated with a reduced capacity of Mφ and DC from Mif-/-STZ to induce proliferation in ovalbumin-specific T cells. All the deficiencies observed in Mif-/-STZ were recovered by exogenous administration of recombinant Mif. These findings suggest that Mif plays a role in the molecular mechanisms of Mφ and DC activation and drives T cell responses involved in the pathology of T1DM. Therefore, Mif is a potential therapeutic target to reduce the pathology of T1DM.

Evaluation of inflammation and oxidative stress in ankylosing spondylitis: a role for macrophage migration inhibitory factor

Ankylosing spondylitis (AS) is a chronic inflammatory disease mainly affecting the spine and sacroiliac joints. Mediators such as macrophage migration inhibitory factor (MIF) and interleukin-10 (IL-10) are thought to be involved in several inflammatory conditions, including AS. Proinflammatory cytokines regulate the production of oxidative stress markers, such as nitric oxide (NO) and malondialdehyde (MDA). Although oxidative stress and lipid peroxidation have been reported in AS, the association of AS with commonly known oxidative stress markers and cytokines remains uncertain. We have therefore studied whether serum MIF levels are elevated in patients with AS and whether the levels correlate with oxidative stress markers and disease activity parameters. Twenty-five AS patients and 18 healthy controls participated in this study; subjects with hypertension, diabetes, hyperlipidemia, and obesity were excluded. The levels of acute phase reactants, serum levels of glucose, lipids, MIF, IL-10, NO and MDA were studied. Spinal mobility was assessed by the Bath Ankylosing Spondylitis Metrology Index (BASMI). Patients were also assessed using with the Bath Ankylosing Spondylitis Functional Index and the Bath Ankylosing Spondylitis Disease Activity Index. Age and sex distribution were found to be comparable between AS patients and controls (p > 0.05). Acute phase reactants and MIF levels were significantly higher (p < 0.05) and IL-10 levels were significantly lower (<0.001) in the AS patients than in controls. There was a significant correlation between BASMI and MIF levels in AS patients (r = 0.714, p < 0.001). Based on these results, MIF may be involved in the pathogenesis of the chronic inflammation in AS and, consequently, targeting MIF may be beneficial in preventing complications or in initiating early treatment of the disease.

Reduced arthritis in MIF deficient mice is associated with reduced T cell activation: down-regulation of ERK MAP kinase phosphorylation

Macrophage migration inhibitory factor (MIF) is a pleiotropic pro-inflammatory cytokine with many cellular targets in rheumatoid arthritis (RA). MIF has been reported to activate cells via mitogen-activated protein kinase and serine/threonine kinase (AKT or protein kinase B)-dependent signal transduction pathways. Its contribution to T cell activation and signalling in RA is not known. Using MIF -/- mice and a T cell-mediated model of RA, antigen-induced arthritis, we investigated the role of MIF in T cell activation and signalling. Arthritis severity was significantly reduced in MIF -/- mice compared with wildtype mice. This reduction was associated with decreased T cell activation parameters including footpad delayed type hypersensitivity, antigen-induced splenocyte proliferation and cytokine production. Splenocyte proliferation required extracellular signal-regulated kinase (ERK)1/2 phosphorylation, and decreased T cell activation in MIF -/- mice was associated with decreased phosphorylation of ERK1/2 but not AKT. Collectively, these data suggest that MIF promotes antigen-specific immune responses via regulation of ERK phosphorylation in T cells.

Association of MIF-173 gene polymorphism with inflammatory bowel disease in Chinese Han population

AIM

To study whether macrophage migration inhibitory factor (MIF)-173 gene polymorphism correlates with inflammatory bowel disease (IBD) in Chinese Han population.

METHODS

MIF-173 single nucleotide polymorphism (SNP) was genotyped by tetra-primer amplification refractory mutation system (ARMS) and restriction fragment length polymorphisms (RFLP)-PCR in 142 healthy subjects and 98 patients with inflammatory bowel disease (IBD).

RESULTS

There were no discrepancies between the results obtained by tetra-primer ARMS and RFLP-PCR. The frequency of MIF-173 CC genotype was significantly higher in patients with ulcerative colitis (UC) 15.5% than in healthy individuals 5.6% (chi(2)=6.066, P=0.018, OR=3.067 and 95% CI=1.257-7.482). There was a trend towards a higher frequency of CC genotype among CD patients compared with healthy controls, however this did not attain the statistical significance (P=0.245).

CONCLUSION

MIF-173 CC genotype may be associated with susceptibility to UC.

An alteration in the levels of populations of CD4+ Treg is in part responsible for altered cytokine production by cells of aged mice which follows injection with a fetal liver extract

We have shown previously that a fetal sheep liver extract (FSLE) containing significant quantities of fetal ovine gamma globin chain (Hbgamma) and LPS injected into aged (>20 months) mice could reverse the altered polarization (increased IL-4 and IL-10 with decreased IL-2 and IFNgamma) in cytokine production seen from ConA stimulated lymphoid cells of those mice. The mechanism(s) behind this change in cytokine production were not previously investigated. We report below that aged mice show a >60% decline in numbers and suppressive function of both CD4(+)CD25(+)Foxp3(+) Treg and so-called Tr3 (CD4(+)TGFbeta(+)), and that their number/function is restored to levels seen in control (8-week-old) mice by FSLE. In addition, on a per cell basis, CD4(+)CD25(-)Treg from aged mice were >4-fold more effective in suppression of proliferation and IL-2 production from ConA-activated lymphoid cells of a pool of CD4(+)CD25(-)T cells from 8-week-old mice than similar cells from young animals, and this suppression by CD25(-)T cells was also ameliorated following FSLE treatment. Infusion of anti-TGFbeta and anti-IL-10 antibodies in vivo altered Treg development following FSLE treatment, and attenuated FSLE-induced alterations in cytokine production profiles.

Salmonella typhimurium disseminates within its host by manipulating the motility of infected cells

The mammalian host has a number of innate immune mechanisms designed to limit the spread of infection, yet many bacteria, including Salmonella, can cause systemic disease. Salmonella typhimurium-infected phagocytes traverse the gastrointestinal (GI) epithelium and enter the bloodstream within minutes after ingestion, thereby spreading throughout its host. Here, we provide a cellular and molecular basis for this phenomenon. We demonstrate that S. typhimurium manipulates the migratory properties of infected GI phagocytes with a type III secretion system. We show that one secreted effector, SrfH, interacts with the host protein TRIP6, a member of the zyxin family of adaptor proteins that regulate motility. SrfH promotes phagocyte motility in vitro and accelerates the systemic spread of infection away from the lumen of the intestine in the mouse. This is a previously uncharacterized mechanism by which an intracellular pathogen overcomes host defenses designed to immobilize infected cells.

Role of MIF and glutathione, in association with fetal ovine globin chain (Hbγ) and LPS, in induction of TNFα from cells of young and aged mice, and PBL from healthy human populations

Previous reports from our group have established that the fetal ovine gamma globin chain (Hbgamma) and LPS can synergize in the induction of pro-inflammatory cytokines, especially TNFalpha, from mouse and human leukocytes. A fetal sheep liver extract (FSLE) which was observed to have marked immunoregulatory properties in vivo and in vitro had independently been observed to contain significant amounts of each of these molecules. However, the biological activity of this extract (hereafter FSLE) was not explained solely by its content of Hbgamma and LPS, and independent analysis confirmed also the presence of migration inhibitory factor, MIF, and glutathione in FSLE. We have investigated whether MIF and the cellular anti-oxidant glutathione can further synergize with Hbgamma and LPS in TNFalpha induction from human cells in vitro, and mouse cells activated in vivo/in vitro. Our data show that indeed there is evidence for such a synergy. Treatment or mouse cells with FSLE produced an enhanced TNFalpha production which could be inhibited independently both by anti-Hbgamma and by anti-MIF, and optimally by a combination of these reagents.

Macrophage migration inhibitory factor and glucocorticoid sensitivity

Glucocorticoids (GCs) are widely used in the treatment of inflammatory diseases including rheumatoid arthritis (RA). Treatment with GC is associated with significant dose-dependent side-effects. The pro-inflammatory cytokine macrophage migration inhibitory factor (MIF) has emerged in recent years as a candidate factor which could regulate GC sensitivity. MIF is induced by GC, and is able to override anti-inflammatory actions of GCs. In this review, we summarize the pro-inflammatory actions of MIF with respect to RA, describe the interactions between MIF and GC and examine new evidence, which identifies MIF as a specific target for steroid sparing.

Reduction of the aortic inflammatory response in spontaneous atherosclerosis by blockade of macrophage migration inhibitory factor (MIF)

Atherosclerosis is an inflammatory response of the arterial wall to "injury", which is prominently driven by cytokines. The inflammatory mediator macrophage migration inhibitory factor (MIF) is a unique cytokine that was recently associated with atherogenesis. Here, we have investigated whether MIF has a role in spontaneous atherosclerosis by studying apolipoprotein E-deficient (ApoE(-/-)) mice treated with neutralizing anti-MIF monoclonal antibody and comparison with isotype IgG-treated controls. After 14 weeks, the aortas and heart valves were analyzed for inflammatory status, macrophage content and plaque areas. MIF expression in the aortic wall was elevated upon spontaneous atherogenesis, with foam cells representing a major source. Of note, MIF blockade led to a marked reduction in intimal Mac-1-positive macrophages. Similarly, treatment with anti-MIF antibody led to a reduction of a variety of inflammatory mediators typically associated with atherosclerosis including the circulating levels of fibrinogen, MIF and IL-6. Importantly, the local aortic expression of ICAM-1, MMP-2, TNF, IL-12, and CD40L was reduced by MIF blockade, as were the levels of the phospho-c-Jun and C/EBPbeta transcription factors. The observed strong reduction of inflammatory parameters by anti-MIF treatment was associated with a small, yet non-significant, reduction in aortic plaque area. Thus, although MIF's role is not directly linked to plaque volume expansion, in this mouse model of spontaneous atherogenesis, MIF plays an important role in intimal inflammation.

Macrophage migration inhibitory factor (MIF) seems crucially involved in Guillain-Barré syndrome and experimental allergic neuritis

Macrophage migration inhibitory factor (MIF) is a proinflammatory type 1 cytokine that plays a pathogenic role in several inflammatory and autoimmune diseases. The role of this cytokine in peripheral nerve inflammatory disease has not been evaluated. Therefore, to evaluate the role of macrophage migration inhibitory factor (MIF) in Guillain-Barré syndrome (GBS) and experimental allergic neuritis (EAN), we determined MIF circulating levels in a series of patients with GBS and healthy subjects with ELISA and evaluated the effect of two specific inhibitors of MIF, a neutralizing monoclonal antibody or a chemical inhibitor ISO1 on the course of murine EAN. The data show increased MIF plasma levels in GBS patients as compared to healthy controls (p<0.0001) and a progressive increase of MIF circulating concentration with patient's disability (p<0.0001). Both anti-MIF mAb and ISO1 favorably influenced the course of EAN. Treated mice had a lower cumulative severity score (p=0.001) and reduced disease duration than the control mice (p<0.03). MIF may promote immune reaction in GBS. Therapeutic effects of both anti-MIF mAb and ISO1 in EAN suggest that MIF could be a promising therapeutic target in inflammatory demyelinating peripheral nerve disorders.

Relationship between serum levels of macrophage migration inhibitory factor and the activity of antineutrophil cytoplasmic antibody-associated vasculitides

Macrophage migration inhibitory factor (MIF) is a central proinflammatory cytokine that regulates innate and adaptive immune responses. To evaluate its role in primary vasculitides, we determined MIF by enzyme-linked immunoassay in the sera of patients with Wegener's granulomatosis (WG; n=26), microscopic polyangiitis (MPA; n=10), polyarteritis nodosa (PAN; n=9) and giant cell arteritis (GCA; n=11). Healthy controls (n=26) and patients with sarcoidosis (n=14) were studied in parallel. Serum levels of MIF were significantly higher in patients with WG (median 41.1, range 3.2-120 ng/ml) than those in healthy controls (6.0, 0.015-36.5 ng/ml; P<0.001) and in patients with sarcoidosis (13.8, 0.015-67.1 ng/ml; P<0.05). MIF values were higher in MPA patients (29.5, 9.9-69.4 ng/ml; P<0.01) in comparison with those in healthy controls. In particular, increased levels of MIF were associated with active disease as assessed by the Birmingham Vasculitis Activity Score. Sequential studies showed decreased levels of MIF after initiation of immunosuppressive therapy, with clinical improvement in WG and MPA patients. In contrast, serum levels of MIF were not significantly elevated in patients with PAN and GCA. The results suggest that MIF contributes to the inflammatory process and correlates with disease activity in antineutrophil cytoplasmic antibody-associated vasculitides.

Helicobacter pylori-induced IL-8 production by gastric epithelial cells up-regulates CD74 expression

CD74, or the class II MHC-associated invariant chain, is best known for the regulation of Ag presentation. However, recent studies have suggested other important roles for this protein in inflammation and cancer studies. We have shown that CD74 is expressed on the surface of gastric cells, and Helicobacter pylori can use this receptor as a point of attachment to gastric epithelial cells, which lead to IL-8 production. This study investigates the ability of H. pylori to up-regulate one of its receptors in vivo and with a variety of gastric epithelial cell lines during infection with H. pylori. CD74 expression was increased dramatically on gastric biopsies from H. pylori-positive patients and gastric cell lines exposed to the bacteria. Gastric cells exposed to H. pylori-conditioned medium revealed that the host cell response was responsible for the up-regulation of CD74. IL-8 was found to up-regulate CD74 cell surface expression because blocking IL-8Rs or neutralizing IL-8 with Abs counteracted the increased expression of CD74 observed during infection with H. pylori. These studies demonstrate how H. pylori up-regulates one of its own receptors via an autocrine mechanism involving one of the products induced from host cells.

Helicobacter pylori binds to CD74 on gastric epithelial cells and stimulates interleukin-8 production

The pathogenesis associated with Helicobacter pylori infection requires consistent contact with the gastric epithelium. Although several cell surface receptors have been suggested to play a role in adhesion, the bacterium-host interactions that elicit host responses are not well defined. This study investigated the interaction of H. pylori with the class II major histocompatibility complex (MHC)-associated invariant chain (Ii; CD74), which was found to be highly expressed by gastric epithelial cells. Bacterial binding was increased when CD74 surface expression was increased by gamma interferon (IFN-gamma) treatment or by fibroblast cells transfected with CD74, while binding was decreased by CD74 blocking antibodies, enzyme cleavage of CD74, and CD74-coated bacteria. H. pylori was also shown to bind directly to affinity-purified CD74 in the absence of class II MHC. Cross-linking of CD74 and the engagement of CD74 were verified to stimulate IL-8 production by unrelated cell lines expressing CD74 in the absence of class II MHC. Increased CD74 expression by cells increased IL-8 production in response to H. pylori, and agents that block CD74 decreased these responses. The binding of H. pylori to CD74 presents a novel insight into an initial interaction of H. pylori with the gastric epithelium that leads to upregulation of inflammatory responses.

Reduced leukocyte-endothelial cell interactions in the inflamed microcirculation of macrophage migration inhibitory factor-deficient mice

OBJECTIVE

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine with established roles in a range of inflammatory conditions. However, it is not known whether MIF influences inflammation via the direct promotion of leukocyte-endothelial cell interactions. Therefore, the aim of these experiments was to investigate the ability of MIF to regulate leukocyte-endothelial cell interactions in the inflamed microvasculature.

METHODS

Intravital microscopy was used to examine postcapillary venules in the cremaster muscle and synovium of wild-type and MIF(-/-) mice. Leukocyte-endothelial cell interactions (rolling, adhesion, emigration) were compared under a range of inflammatory conditions.

RESULTS

In cremasteric postcapillary venules of MIF(-/-) mice, lipopolysaccharide (LPS)-induced leukocyte rolling, adhesion, and emigration were significantly reduced relative to that in wild-type mice. Similar responses were observed in response to tumor necrosis factor alpha and histamine. Examination of the synovial microvasculature following exposure to carrageenan revealed that leukocyte rolling and adhesion in synovial postcapillary venules and leukocyte entry into the joint space were also reduced significantly in MIF(-/-) mice. In each of these models, the level of P-selectin-dependent rolling was reduced in MIF(-/-) mice. Despite this, no difference in P-selectin expression was observed following LPS treatment. However, microvascular shear forces were elevated in MIF(-/-) mice, raising a possible mechanism to explain the reduced interactions in these animals.

CONCLUSION

MIF(-/-) mice consistently displayed a reduction in P-selectin-dependent rolling, suggesting that MIF exerts proinflammatory effects, in part, via the promotion of P-selectin-mediated rolling. Together, these data indicate that MIF promotes interactions between leukocytes and endothelial cells, thereby enhancing the entry of leukocytes into sites of inflammation.

Inhibition of macrophage migration inhibitory factor decreases proliferation and cytokine expression in bladder cancer cells

BACKGROUND

The importance of various inflammatory cytokines in maintaining tumor cell growth and viability is well established. Increased expression of the proinflammatory cytokine macrophage migration inhibitory factor (MIF) has previously been associated with various types of adenocarcinoma.

METHODS

MIF IHC was used to localize MIF in human bladder tissue. ELISA and Western blot analysis determined the synthesis and secretion of MIF by human bladder transitional cell carcinoma cells. The effects of MIF inhibitors (high molecular weight hyaluronate (HA), anti-MIF antibody or MIF anti-sense) on cell growth and cytokine expression were analyzed.

RESULTS

Human bladder cancer cells (HT-1376) secrete detectable amounts of MIF protein. Treatment with HA, anti-MIF antibody and MIF anti-sense reduced HT-1376 cell proliferation, MIF protein secretion, MIF gene expression and secreted inflammatory cytokines. Our evidence suggests MIF interacts with the invariant chain, CD74 and the major cell surface receptor for HA, CD44.

CONCLUSIONS

This study is the first to report MIF expression in the human bladder and these findings support a role for MIF in tumor cell proliferation. Since MIF participates in the inflammatory response and bladder cancer is associated with chronic inflammatory conditions, these new findings suggest that neutralizing bladder tumor MIF may serve as a novel therapeutic treatment for bladder carcinoma.

Blockade of macrophage migration inhibitory factor (MIF) in Schistosoma japonicum-infected mice results in an increased adult worm burden and reduced fecundity

Macrophage migration inhibitory factor (MIF), a cytokine produced by many cell types, modulates cellular and humoral immune responses. In schistosomiasis, ova in the portal circulation induce a delayed type hypersensitivity (DTH) that results in formation of hepatic granulomas (HG) which secrete MIF activity. Therefore, we hypothesized that endogenous MIF modulates immune responses in schistosomiasis. To test this hypothesis, Schistosoma japonicum-infected mice were injected with rabbit IgG or neutralizing rabbit IgG antibody to MIF 4.5-6.5 week post infection when HG form and female worms are laying eggs. Compared with controls, 6.5-7-week post-infection, antibody-treated mice had 1.7-3 times as many adult worms and half as many ova per worm pair in their livers. In contrast, antibody introduced before infection or 6-8 week post infection did not affect worm burden or fecundity. Thus, for the first time there is evidence that 4.5-6 week post-infection endogenous MIF somehow mediates reduction of adult worm burden and promotes fecundity. Splenocytes and HG cells from antibody-treated mice showed reduced intracellular expression of TNFalpha and/or IL-10. We hypothesize that endogenous MIF enhances adult worm attrition by up-regulating innate and adaptive immune responses by increasing expression of MHC-II, co-stimulatory, adhesion, receptor and cytokine molecules, and promotes fecundity by up-regulating TNFalpha expression.