Immunohistological characterization of macrophage migration inhibitory factor expression in Plasmodium falciparum-infected placentas

Previously, we have shown that macrophage migration inhibitory factor (MIF) was highly elevated in the placental intervillous blood (IVB) of Plasmodium falciparum-infected women. Here, we compared the expression of MIF in placental tissues obtained from P. falciparum-infected and -uninfected women. Immunoperoxidase staining showed a consistent pattern of MIF expression in syncytiotrophoblasts, extravillous trophoblasts, IVB mononuclear cells, and amniotic epithelial cells, irrespective of their malaria infection status. Cytotrophoblast, villous stroma, and Hofbauer cells showed focal staining. Only amniotic epithelial and IVB mononuclear cells from P. falciparum-infected placentas exhibited significantly higher level of MIF expression than uninfected placentas. Stimulation of syncytilized human trophoblast BeWo cells with P. falciparum-infected erythrocytes that were selected to bind these cells resulted in significant increases in MIF secretion, whereas control erythrocytes, lipopolysaccharides, and synthetic beta-hematin had minimal effect. These findings suggest that placental malaria modulates MIF expression in different placental compartments.     

Laser capture microdissection and molecular analysis of Plasmodium yoelii liver-stage parasites

Comparing the steady-state expression levels of recombinant proteins in Toxoplasma gondii parasites indicates considerable variability, and this has sometimes caused difficulties in the engineering of transgenic parasites. Anecdotal observations suggested that alteration of the N-terminus, e.g. by engineering as a fusion protein, permits stable expression of various transgenes that were previously difficult to express in their native form. We have exploited the sensitivity and quantitative nature of fire-fly luciferase (LUC) to examine expression levels in further detail. Fusing the 26 N-terminal residues derived from chloramphenicol acetyl transferase (ΔCAT) to LUC permits efficient transient or stable luciferase expression in transgenic parasite tachyzoites, providing a useful reporter for studies in T. gondii. Site-directed mutagenesis was used to alter the second codon of ΔCAT-LUC to encode all 20 possible amino acids, and these constructs showed that changes in the second amino acid can have dramatic effects on luciferase activity, with Ala, Glu, and Asp codons yielding the highest expression levels. Similar results were observed for the expression of both GFP and the T. gondii HXGPRT gene, demonstrating the generality of this effect.     

Macrophage migration inhibitory factor homolog from Plasmodium yoelii modulates monocyte recruitment and activation in spleen during infection

Macrophage migration inhibitory factor (MIF) has been shown to be involved in the pathogenesis of severe malaria. Malaria parasites express an MIF homolog that may play a role in regulating host immune responses, and a recent study showed that overexpression of MIF reduced parasitemia in a mouse malaria model. Another recent study showed migration of monocytes to the spleen contributed to the control of blood stage infection. However, there are few papers describing the effect of MIF on monocyte recruitment/activation during the infection. We generated recombinant Plasmodium yoelii MIF (rPyMIF) and investigated its function on purified mouse CD11b⁺ cells in vitro and monocyte responses in vivo. The result shows that rPyMIF protein bound to mouse CD11b⁺ cells and inhibited their random migration in vitro. On the other hand, rPyMIF did not induce cytokine release from the cells directly or modulate lipopolysaccharide-induced cytokine release. Mice immunized with rPyMIF showed transient but significantly lower parasitemia than the control mice at day 3 after lethal Py17XL challenge. The total number of CD11b⁺ cells in the spleens was significantly higher in rPyMIF-immunized group. Further investigation revealed that there were significantly higher numbers of recruited and activated monocytes in the spleens of rPyMIF immunization group on day 3. These results indicate that PyMIF potentially modulates monocyte recruitment and activation during infection of P. yoelii erythrocytic stages.     

DNA immunization by Plasmodium falciparum liver-stage antigen 3 induces protection against Plasmodium yoelii sporozoite challenge

DNA-based immunization of mice by Plasmodium falciparum liver-stage antigen 3 (PfLSA3), a novel highly conserved P. falciparum preerythrocytic antigen, was evaluated. Animals developed a dominant Th1 immune response (high gamma interferon T-cell responses and predominance of immunoglobulin G2a) to each of three recombinant proteins spanning the molecule. We have exploited the immunological cross-reactivity of PfLSA3 with its putative homologue on sporozoites of the rodent parasite Plasmodium yoelii, and we show for the first time that responses induced by PfLSA3 in mice significantly protect against a heterologous challenge by P. yoelii sporozoites. These results support a significant effect of DNA-induced immune responses on preerythrocytic stages.     

巨噬细胞移动抑制因子在瘢痕疙瘩中的表达

背景：巨噬细胞移动抑制因子参与了多种疾病的发生、发展过程,它在肿瘤、自身免疫性疾病、炎症反应、血管新生、纤维化等方面发挥重要作用,这些生物学特征与瘢痕疙瘩较为相似。目的：检测巨噬细胞移动抑制因子(MIF)在瘢痕疙瘩、增生性瘢痕、正常皮肤组织中的表达情况,说明巨噬细胞移动抑制因子分布位置和数量的差异。方法：收集临床病理性瘢痕切除后标本共40例,其中瘢痕疙瘩组20例,增生性瘢痕组20例,另取正常皮肤标本10例作为对照。分别做苏木精-伊红染色和免疫组织化学染色观察巨噬细胞移动抑制因子在病理性瘢痕及正常皮肤中的表达情况。结果与结论：巨噬细胞移动抑制因子在正常皮肤、增生性瘢痕、瘢痕疙瘩中均有表达,但在瘢痕疙瘩中表达明显强于增生性瘢痕和正常皮肤(P < 0.01)。说明巨噬细胞移动抑制因子在瘢痕疙瘩中的异常浸润可能与瘢痕疙瘩的形成有关。中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程     

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.     

Role for macrophage migration inhibitory factor in acute respiratory distress syndrome

The critical role of macrophage migration inhibitory factor (MIF) in mediating inflammatory lung injury in acute respiratory distress syndrome (ARDS) has been raised recently. The present study has identified enhanced MIF protein expression in alveolar capillary endothelium and infiltrating macrophages in lung tissues from ARDS patients. The possibility that MIF up-regulates its synthesis in an autocrine fashion in ARDS was tested using cultured endothelial cells stimulated with MIF and a murine model of lipopolysaccharide (LPS)-induced acute lung injury. MIF induced significant MIF and tumour necrosis factor (TNF)-alpha synthesis in cultured endothelial cells and the effect was blocked by neutralizing anti-MIF antibody. A similar blocking effect was observed when MIF-stimulated endothelial cells were pretreated with neutralizing anti-TNF-alpha antibody or glucocorticoid, supporting the notion that MIF induced TNF-alpha production via an amplifying pro-inflammatory loop. Treatment with anti-MIF or glucocorticoid effectively attenuated pulmonary pathology and the synthesis of MIF or TNF-alpha in mice with LPS-induced acute lung injury. Mildly augmented expression of aquaporin 1 (AQP1) was also detected in alveolar capillary endothelium in ARDS. In vitro studies revealed that both MIF and TNF-alpha induced a small increase of AQP1 synthesis in cultured endothelial cells. These findings suggest that MIF plays a crucial pathological role leading to alveolar inflammation in ARDS. Anti-MIF and early glucocorticoid therapy may represent a novel therapeutic approach for reducing alveolar inflammation in ARDS.     

Lis1 is necessary for normal non-radial migration of inhibitory interneurons

Type I lissencephaly is a central nervous system (CNS) malformation characterized by mental retardation and epilepsy. These clinical features suggest a deficit in inhibitory neurons may, in part, underlie the pathogenesis of this disorder. Mutations in, or deletions of, LIS1 are the most commonly recognized genetic anomaly associated with type I lissencephaly. The pathogenesis of type I lissencephaly is believed to be a defect in radial neuronal migration, a process requiring LIS1. In contrast the inhibitory neurons migrate non-radially from the basal forebrain to the neocortex and hippocampus. Given that Lis1 is expressed in all neurons, we hypothesized that Lis1 also functions in non-radial migrating inhibitory neurons. To test this hypothesis we used a combination of in vivo and in vitro studies with Lis1 mutant mice and found non-radial cell migration is also affected. Our data indicate Lis1 is required for normal non-radial neural migration and that the Lis1 requirement is primarily cell autonomous, although a small cell non-autonomous effect could not be excluded. These data indicate inhibitory neuron migration is slowed but not absent, similar to that found for radial cell migration. We propose that the defect in non-radial cell migration is likely to contribute to the clinical phenotype observed in individuals with a LIS1 mutation.     

巨噬细胞移动抑制因子的信号转导研究进展

巨噬细胞移动抑制因子(MIF)是一种重要的多功能细胞因子,在机体中分布广泛,可能参与了机体多种病理生理反应,其信号转导机制复杂而广泛,主要有激活细胞外信号调节激酶1/2(ERK1/2)信号转导途径、NF-κB途径,Jab 1途径等;与众多自身免疫疾病密切相关。     

Stimulation of vascular smooth muscle cell migration by macrophage migration inhibitory factor

Macrophage migration inhibitory factor (MIF) is a well known proinflammatory factor that influences the migration and proliferation of various cell types, predominantly monocytes and macrophages. Recent evidence suggests an important role for MIF in the progression of atherosclerosis and restenosis. For this reason, we studied the effect of MIF on platelet-derived growth factor-BB (PDGF-BB)-induced migration and PDGF receptor protein expression in vascular smooth muscle cells (VSMCs). Furthermore, the possibility of MIF influencing the migration of VSMCs was investigated. Our results show that short-term incubation of MIF is able to enhance PDGF-BB-induced migration. Long-term incubation decreases PDGF-BB-induced migration, but preserves a short-term stimulatory effect. These effects are not regulated at the level of PDGF receptor protein expression. MIF also acts as a chemoattractant for VSMCs, with a maximum response at 15 ng/ml. In contrast, the proliferation of VSMCs was unaffected by MIF. We conclude that MIF has a biphasic effect on VSMC migration. It remains unclear whether this effect is direct or involves the secretion of unidentified promigratory factors. Exogenous MIF does not stimulate VSMC proliferation; however, a role for MIF in proliferation cannot be fully ruled out. In view of the known key contributions of macrophage-derived MIF and VSMCs, the observed effects may well play a role in the progression of atherosclerosis and restenosis.     

Promoter region polymorphism of macrophage migration inhibitory factor is strong risk factor for young onset of extensive alopecia areata

We have demonstrated that serum macrophage migration inhibitory factor (MIF) was significantly elevated in patients with extensive alopecia areata (AA). Recently, functional polymorphisms have been identified in the MIF promoter region. To address the functional and prognostic relevance of the -173G/C and -794[CATT]5-8 repeat polymorphisms in MIF genes in patients with extensive AA, 113 patients with extensive AA and 194 healthy controls were genotyped. We found that MIF-173*C was a risk factor for early onset (<20 years) of extensive AA (odds ratio for GC heterozygotes with -173G/C was 4.88 (95% CI, 2.04-11.8), P=0.00038; odds ratio for CC homozygotes with -173G/C was 10.42 (95% CI, 2.56-43.5), P=0.0011). We found no statistically significant differences in the genotype frequencies of the -794[CATT]5-8 repeat polymorphism and extensive AA. These results suggest that polymorphisms within the MIF-173*C allele confer an increased risk of susceptibility to the extensive forms of AA, especially with an early onset of disease. MIF is therefore suggested to be closely implicated in the pathogenesis of the more extensive forms of AA.     

Link between macrophage migration inhibitory factor and cellular redox regulation

Macrophage migration inhibitory factor (MIF) is an evolutionary conserved 12.5-kDa protein mediator with multiple functions in innate and acquired immunity. Upon leaderless secretion, MIF acts as a typical inflammatory cytokine, but there is no structural homology between MIF and any of the known cytokine protein families. Also, MIF is unique among cytokines in that it exhibits certain endocrine properties and has enzymatic activity. The catalytic thiol-protein oxidoreductase (TPOR) activity of MIF is mediated by a Cys-Ala-Leu-Cys active site between residues 57 and 60 that can undergo reversible intramolecular disulfide formation. Such a redox motif is typically found in TPORs of the thioredoxin (Trx) family of proteins. MIF seems to act as a disulfide reductase, and structure-function analyses of the redox site indicate that this activity is not only observed in vitro, but plays a role in cellular redox homeostasis, apoptosis inhibition, MIF-mediated monocyte/macrophage activation, and possibly the modulation of the activity of MIF-binding proteins. In this Forum review, the biochemical and biological evidence for a role of the TPOR activity for various MIF functions is summarized and discussed. In particular, the marked functional homologies with Trx proteins, the MIF redox/MHC II link, and recent attempts to discern the intra- versus extracellular roles of the MIF TPOR activity are dealt with.     

Purification of thymic macrophage migration inhibitory factor (MIF)

Aqueous extracts of the thymus of animals which had been challenged immunologically have been shown to contain MIF activity. This MIF could be purified by precipitation with 70% ethanol, concentrated by ultrafiltration between 30,000 and 50,000 daltons, isoelectrically focused at pH 6.8–7.1, and electrophoresed on preparative acrylamide gels. The resulting product is electrophoretically homogeneous at pH 4.3 in polyacrylamide-gel electrophoresis and SDS-gel electrophoresis. It has a molecular weight of 36,000 daltons. It is trypsin- and neuraminidase-labile and is thermostable. It degrades and reassembles in electrophoresis at pH 7.0. It is not chemotactic for macrophages but apparently activates them phagocytically. It has no proteolytic activity.Supported in part by a contract from the Office of Nival Research N00014-71-C-0203.     

Elucidation of the receptors in macrophage and Plasmodium yoelii interactions

Binding of hyperimmune serum opsonized merozoites of Plasmodium Yoelii nigerensis to trypsinized macrophages suggested it to be mediated by FcII receptor. Receptor blocking inhibition with monoclonal antibody 2.4G2 directed against Fc receptor for IgG1/IgG2b provided evidence that Fc delta 2b on macrophage played an important role in the merozoite-macrophage interactions. In addition, a neuraminidase sensitive receptor was noted to mediate the binding of P. yeelii merozoites in the absence of serum. Binding inhibition studies with two monosaccharides, D-mannose and alpha-methyl mannoside, indicated the role of Mannose/Fucose receptor on macrophage in this interaction.     

A role for macrophage migration inhibitory factor in protective immunity against Aspergillus fumigatus

Inflammation plays an important role in protective immunity against fungi, including the opportunistic pathogen, Aspergillus fumigatus. The balance between pro-inflammatory and anti-inflammatory cytokines is a key determinant of infection outcome. Since macrophage migration inhibitory factor (MIF) is an upstream regulator of many cytokines, we analyzed herein the role of endogenous MIF in the host control of hematogenously disseminated aspergillosis using MIF^−/− mice. As revealed by their mortality rate, MIF^−/− mice were more susceptible to disseminated infection than WT mice. Moreover, pharmacologic inhibition of MIF with (S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid methyl ester, (ISO-1) increased the susceptibility of WT mice to lethal infection. The higher tissue fungal burden early in sublethal infection indicated increased susceptibility of MIF^−/− mice to sublethal infection as well. Substantial down-regulation of innate and acquired antifungal responses, characterized by decreased production of IL-1β, IL-6, TNF-α, IFN-γ and IL-17 in the spleen was noted in sublethally infected MIF^−/− mice. In contrast, IL-4 was higher in MIF^−/− than in WT mice. Taken together, our findings show that MIF contributes to host resistance against progressive invasive A. fumigatus infection by controlling downstream pro-inflammatory versus anti-inflammatory cytokine production thus determining the outcome of infection.     

巨噬细胞移动抑制因子对固有免疫的调节作用

长期以来,巨噬细胞移动抑制因子(MIF)一直是一种功能不明的细胞因子.最近几年的研究发现,MIF是宿主抗微生物预警系统和应急反应(可以促进免疫细胞促炎症功能)的一个必要组成成份,是一种对固有免疫反应具有关键性调节作用的重要分子.研究表明,MIF参与了包括脓毒症、炎症和自身免疫性炎症疾病在内的一系列疾病的发病机制,这为未来使用靶向MIF疗法治疗相关的人类疾病提供了全新的思路.     

Beta cell function: the role of macrophage migration inhibitory factor

During evolution, beta cells adapted to a sole aim: the production and stimulus-dependent secretion of insulin. This acquired specificity was accompanied by a loss of protection mechanisms predisposing beta cell to a high vulnerability. Among beta cell-damaging molecules, a new one has been identified recently: macrophage migration inhibitory factor (MIF). MIF was at first designated as a T-cell product that inhibits random movement of macrophages. Over the years, the number of functions attributed to this protein increased significantly, positioning MIF at the top of inflammatory cascade in the combat against infection and in immunoinflammatory and autoimmune diseases. This exceptionally versatile molecule regulates insulin secretion in physiological conditions, while in pathological states it alters beta cell function and induces their apoptosis or necrosis and affects beta cell neoplasia.