Human cytomegalovirus-mediated induction of MIF in fibroblasts

Human cytomegalovirus (HCMV) infection of fibroblasts induces the proinflammatory mediator macrophage migration inhibitory factor (MIF). Our in vitro experiments show that active HCMV infection alone is required to induce an early and sustained induction of MIF mRNA and protein production. Unlike in other infection models, in which MIF has been described to be released from preformed stores, our data conclusively show that HCMV infection triggers de novo synthesis and subsequent secretion of MIF. The kinetics of MIF protein production during HCMV infection points to an efficacious immune modulation, in which lymphocytes and monocytes are initially recruited by the early release of chemokines to sites of infection and locally activated by increasing concentrations of MIF.     

siRNA沉默MIF基因对糖皮质激素抑制脂质炎症介质释放的影响及其机制

 目的： 研究小干扰RNA（siRNA）阻断巨噬细胞移动抑制因子（macrophage migration-inhibitory factor,MIF）基因表达对糖皮质激素抑制脂质炎症介质释放的影响及其细胞内机制。方法：体外培养小鼠巨噬细胞系RAW2647,采用免疫荧光法观测siRNA转染效率,RT-PCR检测MIF mRNA的表达,Western blotting检测MIF蛋白的表达;RAW2647细胞转染MIF siRNA后观察地塞米松（Dex）抗炎作用的变化,用ELISA检测细胞上清中前列腺素E2(PGE2)和白三烯B4(LTB4)的含量,Western blotting检测胞浆膜联蛋白Annexin 1和下游胞浆磷酸酯酶A2α（cPLA2α）的蛋白表达变化。结果：与阴性对照相比,MIF siRNA能有效阻断细胞内源性MIF蛋白的表达,增强RAW2647细胞对Dex作用的敏感性;明显增强Dex抑制PGE2和LTB4产生的效应,增加胞浆蛋白Annexin 1的表达,抑制cPLA2α的磷酸化。结论：MIF siRNA能增强糖皮质激素抑制脂质炎症介质PGE2和LTB4的释放,且可能是通过影响Annexin 1-cPLA2α信号通路实现的。阻断内源性MIF蛋白的表达可显著增强RAW2647细胞对糖皮质激素抗炎作用的敏感性。     

RNA干扰对人肺泡上皮A549细胞巨噬细胞移动抑制因子基因表达抑制作用

目的探讨巨噬细胞移动抑制因子(MIF)小干扰RNA(siRNA)干扰对人肺泡上皮A549细胞株MIF基因表达的影响.方法将MIF siRNA用转染剂Interferin介导转染体外培养的A549细胞,通过RT-PCR方法观察不同浓度MIF siRNA转染后,对MIF mRNA表达的影响;采用细胞免疫荧光方法分析MIF蛋白表达的强弱;应用MTT方法测定MIF siRNA转染对细胞的毒性,及脂多糖(LPS)刺激对A549细胞生存率的影响.结果 (1)MIF siRNA转染人肺泡上皮A549细胞株后,可下调细胞中MIF mRNA的表达,只有当MIF siRNA转染浓度大于50 nmol/L时,才能明显下调MIF mRNA的表达;(2)MIF siRNA转染人肺泡上皮A549细胞株后,A549细胞MIF的荧光蛋白表达也明显降低,在此基础上再加入MIF刺激,MIF的蛋白表达又明显增加;(3)MIF siRNA转染对A549细胞几乎没有毒性,且对LPS刺激A549细胞导致细胞死亡及细胞的生存率下降有一定的保护作用.结论 MIF siRNA能在A549细胞特异沉默目的基因MIF和抑制MIF蛋白的表达,且对LPS刺激导致细胞死亡有一定的保护作用.     

Macrophage migration inhibitory factor reduces the growth of virulent Mycobacterium tuberculosis in human macrophages

Macrophage migration inhibitory factor (MIF) is a key mediator of the innate immune system and plays a crucial role in the host response to bacterial infections. Its role in immunity to intracellular pathogens has not been well studied. Here, we show that MIF released by infected human macrophages inhibits the growth of virulent Mycobacterium tuberculosis.     

Regulation of the immune response by macrophage migration inhibitory factor: biological and structural features

 The classical T cell cytokine macrophage migration inhibitory factor (MIF) has reemerged recently as a critical mediator of the host immune and stress response. MIF has been found to be a mediator of several diseases including gram-negative septic shock and delayed-type hypersensitivity reactions. Its immunological functions include the modulation of the host macrophage and T and B cell response. In contrast to other known cytokines, MIF production is induced rather than suppressed by glucocorticoids, and MIF has been found to override the immunosuppressive effects of glucocorticoids. Recently, elucidation of the three-dimensional structure of MIF revealed that MIF has a novel, unique cytokine structure. Here the biological role of MIF is reviewed in view of its distinct immunological and structural properties. Received: 12 May 1997 / Accepted: 20 June 1997     

Plasmodium yoelii macrophage migration inhibitory factor is necessary for efficient liver-stage development

Mammalian macrophage migration inhibitory factor (MIF) is a multifaceted cytokine involved in both extracellular and intracellular functions. Malaria parasites express a MIF homologue that might modulate host immune responses against blood-stage parasites, but the potential importance of MIF against other life cycle stages remains unstudied. In this study, we characterized the MIF homologue of Plasmodium yoelii throughout the life cycle, with emphasis on preerythrocytic stages. P. yoelii MIF (Py-MIF) was expressed in blood-stage parasites and detected at low levels in mosquito salivary gland sporozoites. MIF expression was strong throughout liver-stage development and localized to the cytoplasm of the parasite, with no evidence of release into the host hepatocyte. To examine the importance of Py-MIF for liver-stage development, we generated a Py-mif knockout parasite (P. yoelii Δmif). P. yoelii Δmif parasites grew normally as asexual erythrocytic-stage parasites and showed normal infection of mosquitoes. In contrast, the P. yoelii Δmif strain was attenuated during the liver stage. Mice infected with P. yoelii Δmif sporozoites either did not develop blood-stage parasitemia or exhibited a delay in the onset of blood-stage patency. Furthermore, P. yoelii Δmif parasites exhibited growth retardation in vivo. Combined, the data indicate that Plasmodium MIF is important for liver-stage development of P. yoelii, during which it is likely to play an intrinsic role in parasite development rather than modulating host immune responses to infection.     

The role of macrophage migration inhibitory factor in lethal Listeria monocytogenes infection in mice

Macrophage migration inhibitory factor (MIF) has been characterized as a proinflammatory cytokine. Previous studies have indicated that MIF may play a beneficial role or a detrimental role in microbial infections, depending on pathogens. In this study, we investigated the role of MIF in Listeria monocytogenes infection. The MIF titers increased 6h after lethal L. monocytogenes infection but not in the sublethal infection. The elimination of bacteria from the spleens and livers was not affected by anti-MIF antibody (Ab) injection in the sublethal infection, whereas anti-MIF Ab treatment rescued mice from the lethal infection, suggesting that MIF plays a deteriorating role in lethal L. monocytogenes infection. Anti-MIF Ab treatment significantly augmented interleukin (IL)-10 production in the spleens and livers 24h after infection, suggesting that MIF might down-regulate IL-10 production. Although the administration of anti-IL-10 monoclonal Ab showed no significant effect on the bacterial growth in the organs, the bacterial infection was deteriorated by the combined administration of Abs against MIF and IL-10. On the other hand, anti-MIF Ab treatment also increased in the serum cortisol titer 6h after infection compared with the control immunoglobulin G-injected group. Depletion of endogenous IL-10 decreased serum cortisol titers. These results suggested that IL-10 and cortisol might be involved in the deteriorating effect of MIF on lethal L. monocytogenes infection.     

Functional characterization of the Plasmodium falciparum and P. berghei homologues of macrophage migration inhibitory factor

Macrophage migration inhibitory factor (MIF) is a mammalian cytokine that participates in innate and adaptive immune responses. Homologues of mammalian MIF have been discovered in parasite species infecting mammalian hosts (nematodes and malaria parasites), which suggests that the parasites express MIF to modulate the host immune response upon infection. Here we report the first biochemical and genetic characterization of a Plasmodium MIF (PMIF). Like human MIF, histidine-tagged purified recombinant PMIF shows tautomerase and oxidoreductase activities (although the activities are reduced compared to those of histidine-tagged human MIF) and efficiently inhibits AP-1 activity in human embryonic kidney cells. Furthermore, we found that Plasmodium berghei MIF is expressed in both a mammalian host and a mosquito vector and that, in blood stages, it is secreted into the infected erythrocytes and released upon schizont rupture. Mutant P. berghei parasites lacking PMIF were able to complete the entire life cycle and exhibited no significant changes in growth characteristics or virulence features during blood stage infection. However, rodent hosts infected with knockout parasites had significantly higher numbers of circulating reticulocytes. Our results suggest that PMIF is produced by the parasite to influence host immune responses and the course of anemia upon infection.     

Macrophage migration inhibitory factor (MIF): its essential role in the immune system and cell growth.

Macrophage migration inhibitory factor (MIF) functions as a pleiotropic protein, participating in inflammatory and immune responses. MIF was originally discovered as a lymphokine involved in delayed hypersensitivity and various macrophage functions, including phagocytosis, spreading, and tumoricidal activity. Recently, MIF was reevaluated as a proinflammatory cytokine and pituitary-derived hormone potentiating endotoxemia. This protein is ubiquitously expressed in various organs, such as the brain and kidney. Among cytokines, MIF is unique in terms of its abundant expression and storage within the cytoplasm and, further, for its counteraction against glucocorticoids. MIF has unexpectedly been found to convert D-dopachrome, an enantiomer of naturally occurring L-dopachrome, to 5,6-dihydroxyindole. However, its physiologic significance remains to be elucidated. It was demonstrated that anti-MIF antibodies effectively suppress tumor growth and tumor-associated angiogenesis, suggesting that MIF is involved not only in inflammatory and immune responses but also in tumor cell growth. At present, MIF cannot be clearly categorized as either a cytokine, hormone, or enzyme. This review presents the latest findings on the role of MIF in the immune system and in cell growth, with regard to tumorigenesis and wound repair, and discusses its potential functions in various pathophysiologic states.     

MIF-driven activation of macrophages induces killing of intracellular Trypanosoma cruzi dependent on endogenous production of tumor necrosis factor,nitric oxide and reactive oxygen species

The proinflammatory cytokine macrophage migration inhibitory factor (MIF) is a key player in innate immunity. MIF has been considered critical for controlling acute infection by the protozoan Trypanosoma cruzi, but the underlying mechanisms are poorly understood. Our study aimed to analyze whether MIF could favor microbicidal activity of the macrophage, a site where T. cruzi grows and the initial effector cell against this parasite. Using murine macrophages infected in vitro, we examined the effect of MIF on their parasiticidal ability and attempted to identify inflammatory agents involved in MIF-induced protection. Our findings show that MIF is readily secreted from peritoneal macrophages upon T. cruzi infection. MIF activates both primary and J774 phagocytes boosting the endogenous production of tumor necrosis factor-alpha via mitogen-activated protein kinase p38 signaling, as well as the release of nitric oxide and reactive oxygen species, leading to enhanced pathogen elimination. MIF can also potentiate the effect of interferon-gamma on T. cruzi killing by J774 and mouse peritoneal macrophages, rendering these cells more competent in reducing intracellular parasite burden. The present results unveil a novel innate immune pathway that contributes to host defense and broaden our understanding of the regulation of inflammatory mediators implicated in early parasite containment that is decisive for resistance to T. cruzi infection.     

The Macrophage Migration Inhibitory Factor Homolog of Entamoeba histolytica Binds to and Immunomodulates Host Macrophages

The host inflammatory response contributes to the tissue damage that occurs during amebic colitis, with tumor necrosis factor alpha (TNF-α) being a key mediator of the gut inflammation observed. Mammalian macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine that plays an important role in the exacerbation of a wide range of inflammatory diseases, including colitis. We identified a MIF gene homolog in the Entamoeba histolytica genome, raising the question of whether E. histolytica MIF (EhMIF) has proinflammatory activity similar to that of mammalian MIF. In this report, we describe the first functional characterization of EhMIF. Antibodies were prepared against recombinantly expressed EhMIF and used to demonstrate that EhMIF is expressed as a 12-kDa protein localized to the cytoplasm of trophozoites. In a manner similar to that of mammalian MIF, EhMIF interacted with the MIF receptor CD74 and bound to macrophages. EhMIF induced interleukin-6 (IL-6) production. In addition, EhMIF enhanced TNF-α secretion by amplifying TNF-α production by lipopolysaccharide (LPS)-stimulated macrophages and by inhibiting the glucocorticoid-mediated suppression of TNF-α secretion. EhMIF was expressed during human infection, as evidenced by the presence of anti-EhMIF antibodies in the sera of children living in an area where E. histolytica infection is endemic. Anti-EhMIF antibodies did not cross-react with human MIF. The ability of EhMIF to modulate host macrophage function may promote an exaggerated proinflammatory immune response and contribute to the tissue damage seen in amebic colitis.     

Deficiency of the macrophage migration inhibitory factor gene has no significant effect on endotoxaemia

By targeted disruption of the MIF gene, we have established a mouse strain deficient in macrophage (Mphi) migration inhibitory factor (MIF). Despite previous reports indicating an essential role of MIF in endotoxaemia, an injection of lipopolysaccharide (LPS) into the MIF-deficient mice (maintained under specific pathogen-free conditions) caused shock. No significant difference was detected between the MIF-deficient mutant and normal mice in susceptibility to LPS for endotoxaemia or tumour necrosis factor-alpha (TNF-alpha) formation upon LPS injection. Peritoneal Mphi from the two strains produced TNF-alpha in response to LPS with similar dose responses. Dexamethasone suppressed the LPS-induced TNF-alpha response of Mphi, but no difference was detected between the Mphi from the two strains. These results suggest that endogenous MIF has no significant effect on the LPS-induced TNF-alpha production and no effect on suppression of the response by glucocorticoids. Thus, MIF is not crucial for LPS-induced immune responses leading to shock.     

Protein synthesis in vaccinia virus-infected cells

Summary Human Hep-2 cells were submitted to hypertonic shock (210 mM NaCl) to block host protein synthesis before infection with vaccinia virus. With the start of infection, the medium isotonicity (116 mM NaCl) was restored, and the effect of viral infection on the recovery of host polyribosomes and protein synthesis was studied. Although host translation blockage was released together with infection, vaccinia virus did not affect immediately host protein synthesis. During the first hour of recovery, infected cells could perfectly rebuild the polyribosome profile and recuperate the rate of protein synthesis. Also, during recovery, formation of the initiation complex for protein synthesis was not affected by viral infection. In this period, viral mRNA and proteins were detected by slot blot and SDS-polyacrylamide gel electrophoresis. The inhibitory effect of vaccinia virus on host translation was observed after the second hour of infection. These findings suggest that vaccinia virus-mediated shutoff occurs in a later period during infection, in parallel with viral mRNA accumulation in the polyribosomes and after the on-set of viral DNA replication.     

Recombinant adenovirus vector bearing antisense macrophage migration inhibitory factor cDNA prevents acute lipopolysaccharide-induced liver failure in mice

Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine involved in delayed hypersensitivity and cellular immunity. MIF also acts as a proinflammatory cytokine and counterregulates the anti-inflammatory effects of glucocorticoids. Exogenous gene transfer mediated by adenovirus is useful to study a particular molecular function as well as to develop gene therapy strategies. A recombinant adenovirus containing sense and antisense murine MIF (mMIF) cDNA inserts was constructed using a cosmid-terminal protein complex method. The sense mMIF adenovirus (AxCA-mMIFS) efficiently induced mMIF in COS-7 cells that endogenously lack mMIF in a dose-dependent manner. In contrast, the antisense mMIF adenovirus (AxCA-mMIFAS) inhibited the expression of mMIF in NIH3T3 cells in a dose-dependent manner. To assess the pathophysiologic role of MIF in acute liver failure, we induced acute onset of liver damage in mice (male Jcl:ICR) by a combined treatment of Bacille Calmette-Guerin (BCG) and lipopolysaccharide (LPS). mMIF level in the liver of mice infected with AxCA-mMIFAS showed a significant reduction in MIF production in response to BCG-LPS compared with mice treated without viral infection and with AxCA-mMIFS. In addition, the immunohistochemical staining demonstrated that F4/80 antigen on macrophage was enhanced in liver infected with AxCA-mMIFS but reduced in liver infected with AxCA-mMIFAS. The staining intensity is correlated with the mMIF antigen level in liver tissue. The survival rate of mice infected with AxCA-mMIFAS was significantly higher than that of mice treated with PBS and infected with AxCA-LacZ in BCG-LPS. These results suggest that inhibition of MIF production, using recombinant adenovirus bearing the antisense MIF gene, reduced the mortality rate in BCG-LPS-induced liver failure in mice. This finding might aid in the further development of gene therapy targeting MIF.     

Increased density of macrophage migration inhibitory factor (MIF) in tuberculosis granuloma

Granulomas, the pathologic hallmarks of tuberculosis, are composed of tightly numerous immune cells that respond to a variety of persistent stimuli during pathogen-host interaction. The granuloma is essential for host containment of mycobacterial infection, however, the mechanism of host and pathogen determinants to recruit immune cells at the site of inflammation and the formation of granulomas remains elusive until now. Macrophage migration inhibitory factor (MIF), a cytokine produced by many cell types, modulates cellular and humoral immune responses and promote lymphocytes migration to the site of infection. In this study, we evaluate the expression of MIF in tuberculous granulomas by three different models of diseases: mouse, human tissues and zebrafish. The overall results demonstrated that the expression of MIF positive signals markedly increased in the tissues which have been infected with mycobacterium, whereas a few presence of MIF in the PBS-treated animals (means the control group). In the mycobacterial-infected animals, the MIF positives distributed extensively within the granuloma especially in the multinucleated giant cells. Thus, three independent lines of evidence support the hypothesis that MIF may be an important player in aggregate immune cells to the granuloma microenvironments in these animal models of tuberculosis.