Macrophage migration inhibitory factor is a critical mediator of the activation of immune cells by exotoxins of Gram-positive bacteria

Macrophage migration inhibitory factor expression correlates with inflammatory changes in human chronic hepatitis B infection

BACKGROUND

Macrophage migration inhibitory factor (MIF) has emerged to be a pivotal cytokine in immune-mediated diseases.

PATIENTS AND METHODS

To investigate the role of MIF in chronic hepatitis B infection, we studied two groups of hepatitis B surface antigen positive patients: group 1 (immune tolerant, n = 16) and group 2 (immune clearance, n = 16). Serum level of MIF was measured by enzyme-linked immunosorbent assay and intrahepatic expression of MIF, macrophage and T-cell localisation were detected by double immunohistochemistry.

RESULTS

An increased serum MIF correlated significantly with increased serum alanine aminotransferase activity (r = 0.73, P < 0.001) and the severity of necroinflammatory injury (r = 0.642, P < 0.001). In group 2, there was marked MIF mRNA expression in all KP-1+ macrophages and CD45RO+ activated T cells and, to a lesser extent, in hepatocytes within inflammatory areas. In contrast to its mRNA expression, the cytoplasmic MIF protein level in hepatocytes, infiltrating macrophages and T cells within the inflammatory area was reduced, which probably contributed to the increased serum MIF level.

CONCLUSIONS

Our data suggested that MIF played a role in sustaining cell-mediated hepatic injury during the immune-clearance phase of chronic hepatitis B infection.

Macrophage migration inhibitory factor levels correlate with fatal outcome in sepsis

Macrophage migration inhibitory factor (MIF) is a cytokine playing a critical role in the pathophysiology of experimental sepsis. The purpose of this study was to determine the levels of MIF and to compare those to interleukin-6 (IL-6) levels in predicting mortality among critically ill patients with sepsis. The levels of MIF and IL-6 were measured in 25 patients with septic shock, 17 patients with sepsis, and 11 healthy volunteers. The median plasma concentrations of MIF and IL-6 were significantly higher in patients with septic shock and in patients with sepsis than in healthy controls. MIF levels were significantly different between survivors and nonsurvivors, as were IL-6 levels. Discriminatory power in predicting mortality, as assessed by the areas under receiver operating characteristic curves (AUROC), was 0.793 for MIF and 0.680 for IL-6. Finally, high plasma levels of MIF (> 1100 pg/mL) had a sensitivity of 100% and a specificity of 64% to identify the patients who eventually would evolve to a fatal outcome. Thus, our data suggest that an elevated MIF level in recently diagnosed septic patients appears to be an early indicator of poor outcome and a potential entry criterion for future studies with therapeutic intervention aiming at MIF neutralization.

Macrophage migration inhibitory factor stimulated by Helicobacter pylori increases proliferation of gastric epithelial cells

AIM

Helicobacter pylori (H pylori) is associated with increased gastric inflammatory and epithelial expression of macrophage migration inhibitory factor (MIF) and gastric epithelial cell proliferation. This study aimed at determining whether H pylori directly stimulates release of MIF in monocytes, whether the cag pathogenicity island (PAI) is involved for this function, and whether MIF stimulated by H pylori increases gastric epithelial cell proliferation in vitro.

METHODS

A cytotoxic wild-type H pylori strain (TN2), its three isogenic mutants (TN2Deltacag, TN2DeltacagA and TN2DeltacagE) were co-cultured with cells of a human monocyte cell line, THP-1, for 24 h at different organism/cell ratios. MIF in the supernatants was measured by an ELISA. Cells of a human gastric cancer cell line, MKN45, were then co-cultured with the supernatants, with and without monoclonal anti-MIF antibody for 24 h. The cells were further incubated for 12 h after addition of 3H-thymidine, and the levels of incorporation of 3H-thymidine were measured with a liquid scintillation counter.

RESULTS

The wild-type strain and the isogenic mutants, TN2DeltacagA and TN2 DeltacagE, increased MIF release at organism/cell ratios of 200/1 and 400/1, but not at the ratios of 50/1 and 100/1. However, the mutant TN2delta cag did not increase the release of MIF at any of the four ratios. 3H-thymidine readings for MKN-45 cells were significantly increased with supernatants derived from the wild-type strain and the mutants TN2DeltacagA and TN2DeltacagE, but not from the mutant TN2Deltacag. Moreover, in the presence of monoclonal anti-MIF antibody, the stimulatory effects of the wild-type strain on cell proliferation disappeared.

CONCLUSION

H pylori stimulates MIF release in monocytes, likely through its cag PAI, but not related to cagA or cagE. H pylori-stimulated monocyte culture supernatant increases gastric cell proliferation, which is blocked by anti-MIF antibody, suggesting that MIF plays an important role in H pylori-induced gastric epithelial cell proliferation.

Heterologous expression of the filarial nematode alt gene products reveals their potential to inhibit immune function

Background

Parasites exploit sophisticated strategies to evade host immunity that require both adaptation of existing genes and evolution of new gene families. We have addressed this question by testing the immunological function of novel genes from helminth parasites, in which conventional transgenesis is not yet possible. We investigated two such novel genes from Brugia malayi termed abundant larval transcript (alt), expression of which reaches ~5% of total transcript at the time parasites enter the human host.

Results

To test the hypothesis that ALT proteins modulate host immunity, we adopted an alternative transfection strategy to express these products in the protozoan parasite Leishmania mexicana. We then followed the course of infection in vitro in macrophages and in vivo in mice. Expression of ALT proteins, but not a truncated mutant, conferred greater infectivity of macrophages in vitro, reaching 3-fold higher parasite densities. alt-transfected parasites also caused accelerated disease in vivo, and fewer mice were able to clear infection of organisms expressing ALT. alt-transfected parasites were more resistant to IFN-γ-induced killing by macrophages. Expression profiling of macrophages infected with transgenic L. mexicana revealed consistently higher levels of GATA-3 and SOCS-1 transcripts, both associated with the Th2-type response observed in in vivo filarial infection.

Conclusion

Leishmania transfection is a tractable and informative approach to determining immunological functions of single genes from heterologous organisms. In the case of the filarial ALT proteins, our data suggest that they may participate in the Th2 bias observed in the response to parasite infection by modulating cytokine-induced signalling within immune system cells.

Beyond sepsis pathophysiology with cytokines: what is their value as biomarkers for disease severity?

Sepsis is a major challenge in medicine. It is a common and frequently fatal infectious condition. The incidence continues to increase, with unacceptably high mortality rates, despite the use of specific antibiotics, aggressive operative intervention, nutritional support, and anti-inflammatory therapies. Typically, septic patients exhibit a high degree of heterogeneity due to variables such as age, weight, gender, the presence of secondary disease, the state of the immune system, and the severity of the infection. We are at urgent need for biomarkers and reliable measurements that can be applied to risk stratification of septic patients and that would easily identify those patients at the highest risk of a poor outcome. Such markers would be of fundamental importance to decision making for early intervention therapy or for the design of septic clinical trials. In the present work, we will review current biomarkers for sepsis severity and especially the use of cytokines as biomarkers with important pathophysiological role.

Overexpression of macrophage migration inhibitory factor induces angiogenesis and deteriorates prognosis after radical resection for hepatocellular carcinoma

BACKGROUND

Macrophage migration inhibitory factor (MIF) is a pivotal cytokine that regulates inflammatory and immune responses. Recently, many investigators reported that MIF is expressed highly in several tumors, including hepatocellular carcinoma (HCC). However, the role of MIF in tumor angiogenesis and patient prognosis has not been examined in patients with HCC.

METHODS

The authors evaluated MIF expression in 56 samples of HCC by Western blot analysis, and the results were correlated with clinicopathologic factors and patient prognosis. MIF localization was determined by immunohistochemical methods, and the results were compared with tumor microvessel density (MVD), as assessed by anti-CD34 antibody. Furthermore, to validate the role of MIF in angiogenesis, both MIF expression during culture of HCC cells (using the Hep3B, HepG2, and Huh7 cell lines) under hypoxic condition and the angiogenic potential of recombinant MIF in an in vitro angiogenic model were examined.

RESULTS

Tumors with high MIF expression had high alpha-fetoprotein levels (P = 0.049) and frequent intrahepatic recurrence (P = 0.043). Immunohistochemical MIF scores had a significant correlation with MVD (P = 0.007). Patients who had tumors with high MIF expression levels had a significantly worse (P = 0.025) disease-free survival, and this finding remained significant as an independent prognostic factor in the multivariate analysis. Hep3B cells had high expression of MIF at 6 hours and 12 hours after hypoxic stress and exogenous MIF stimulated endothelial tube formation in in vitro angiogenesis.

CONCLUSIONS

The current findings suggest that MIF expression may play a pivotal role in the dismal prognosis of patients with HCC that may be attributable to the modulation of angiogenesis.

The immunoneuroendocrine axis in critical illness: beneficial adaptation or neuroendocrine exhaustion?

PURPOSE OF REVIEW

Over the last years, endocrinology has been incorporated in critical care medicine, and acknowledgment of the complex neuro-endocrine adaption of critical illness has led to new insights and major breakthroughs in clarifying pathophysiological mechanisms and the targeting of therapeutic strategies. This review focuses on the important role of the hypothalamic-pituitary-adrenal (HPA) axis during critical illness and the occurrence of neuroendocrine failure.

RECENT FINDINGS

The distinction between acute (activated anterior pituitary function and inactivated peripheral anabolic pathways) and prolonged (reduced neuroendocrine stimulation) critical illness as different neuroendocrine paradigms has brought a new approach to the critically ill patient. The HPA adaptation in the prolonged phase is characterized by hypercortisolism induced by non-ACTH driven pathways as ACTH levels are low. In spite of the high-normal (total) cortisol levels, HPA insufficiency appears to be quite common. On the other hand, there is a marked depletion of corticosteroid-binding globulin (CBG) in the acute phase of critical illness, resulting in increased free and biologically active cortisol. There is a persistent marked depletion of dehydroeplandrosterone sulfate, possibly indicating adrenal exhaustion, while macrophage inhibitory factor is upregulated in sepsis, affecting and contraregulating the biological effects of glucocorticoids.

SUMMARY

The endocrine system is highly interrelated with the immune and neural systems, the neuroimmunoendocrine axis is subject to clear biphasic changes in the acute and chronic phases of critical illness, most likely reflecting a beneficial adaptation. These neuroendocrine dynamics should be considered when assessing the neuroendocrine system, in particular the HPA axis.

Macrophage migration inhibitory factor mediates late cardiac dysfunction after burn injury

We have recently demonstrated that macrophage migration inhibitory factor (MIF) is a myocardial depressant protein and that MIF mediates late, prolonged cardiac dysfunction after endotoxin challenge in mice. Because many factors, including endotoxin, have been implicated in the pathogenesis of cardiac dysfunction after burn injury, we tested the hypothesis that MIF might also be the mediator of prolonged cardiac dysfunction in this model. At 4 h after 40% total body surface area burn in anesthetized mice, serum MIF levels increased significantly compared with baseline (2.2-fold). This increase was accompanied by a significant decrease in cardiac tissue MIF levels (2.1-fold decrease compared with controls). This pattern was consistent with MIF release from preformed cytoplasmic stores in the heart and other organs. To determine whether MIF mediates cardiac dysfunction after burn injury, mice were pretreated with anti-MIF neutralizing monoclonal antibodies or isotype control antibodies. Beginning 4 h after burn injury (and continuing through 48 h), burned mice demonstrated a significantly depressed left ventricular shortening fraction of 38.6 +/- 1.8%, compared with the normal controls (56.0 +/- 2.6%). Mice treated with anti-MIF displayed an initial depression of cardiac function similar to nontreated animals but then showed rapid restoration of cardiac function with complete recovery by 24 h, which persisted for the duration of the protocol. This study is the first to demonstrate that MIF mediates late, prolonged cardiac dysfunction after burn injury and suggests that MIF blockade should be considered a therapeutic target for the treatment of burn injury.

Macrophage Migration Inhibitory Factor Gene Polymorphism is Associated with Psoriasis

Macrophage migration inhibitory factor (MIF), an important pro-inflammatory cytokine, is over-expressed in plaques of psoriasis and increased levels are found in the sera of patients with psoriasis. Promoter polymorphisms of the MIF gene are associated with increased production of MIF and have been found to confer increased risk of susceptibility to chronic inflammatory diseases. We investigated whether there is an association between promoter polymorphisms of the MIF gene and chronic plaque psoriasis. Two hundred and twenty-eight UK caucasian patients with chronic plaque psoriasis, and a control panel of 401 UK caucasian normal volunteers were studied. MIF promoter polymorphisms were genotyped by allelic discrimination, or by a fluorescently labeled primer method, and capillary gel electrophoresis. Carriage of either the MIF-173*C polymorphism or the MIF CATT(7) polymorphism was positively correlated with psoriasis (odds ratios (OR) 1.52 95% confidence intervals (CI) 1.05-2.19 (p=0.024) and OR 1.67 95% CI 1.1-2.5 (p=0.013), respectively. The OR for presence of the CATT(7)-MIF-173(*)C haplotype versus all other haplotypes combined was 1.69 95% CI 1.2-2.5 (p=0.008). The results provide evidence for polymorphisms in the MIF gene, and in particular the CATT(7)-MIF-173(*)C haplotype, being of importance in susceptibility to psoriasis.

Regulatory role of C5a on macrophage migration inhibitory factor release from neutrophils

There is evidence that C5a and macrophage migration inhibitory factor (MIF) both play important roles in experimental sepsis. Humans with sepsis also show elevated levels of both mediators in the blood. Regulation of MIF during sepsis is poorly understood. We now demonstrate that neutrophil depletion greatly reduced serum MIF levels in rats and mice during the onset of sepsis after cecal ligation and puncture. In vitro, C5a induced MIF release from rat and mouse neutrophils. In vivo blockade of C5aR or absence of C5aR led to significantly reduced MIF generation during the onset of sepsis. C5a-induced release in vitro of MIF from neutrophils appeared to be due to up-regulation of MIF in cytoplasmic granules of neutrophils via activation of the protein kinase B signaling pathway together with involvement of PI3K. Our data suggest that C5a plays a role in enhancing MIF release from neutrophils in vitro and during sepsis. These findings represent a previously unrecognized function of C5a and neutrophils in the appearance of MIF in sepsis.

Elevations in peritoneal fluid macrophage migration inhibitory factor are independent of the depth of invasion or stage of endometriosis

OBJECTIVE

To quantify levels of macrophage migration inhibitory factor (MIF) in the peritoneal fluid (PF) of women with endometriosis, and to correlate these levels with the extent of disease.

DESIGN

Controlled clinical study.

SETTING

Academic medical center.

PATIENT(S)

Peritoneal fluid samples were collected during laparoscopic surgery in 60 women with endometriosis and 16 controls undergoing tubal ligation; 52 of the women with endometriosis had received no hormonal treatment in the 6 months prior to surgery, while 8 were using gonadotropin-releasing hormone (GnRH) agonists.

MAIN OUTCOME MEASURE(S)

Peritoneal fluid migration inhibitory factor (PF MIF) levels.

RESULT(S)

Women with endometriosis had significantly higher PF MIF levels (10.8 +/- 0.9 ng/mL) than controls (3.0 +/- 0.7 ng/mL). However, no correlation existed between MIF levels and the stage of disease (r = 0.05) or the depth of endometriotic invasion (r = 0.08). Moreover, treatment with a GnRH agonist did not suppress PF MIF levels. Peritoneal fluid MIF levels did not vary significantly between the proliferative and secretory phases of the cycle, and did not distinguish women with endometriosis-associated infertility from women with endometriosis-associated pain.

CONCLUSION(S)

Peritoneal fluid migration inhibitory factor levels are markedly elevated in women with endometriosis but are independent of the extent of disease.

Macrophage migration inhibitory factor (MIF) in chinese amphioxus as a molecular marker of immune evolution during the transition of invertebrate/vertebrate

Macrophage migration inhibitory factor (MIF) is an important cytokine related to host defenses and autoimmune diseases. Here, we reported two full-length cDNA clones isolated from Chinese amphioxus (Branchiostoma belcheri tsingtaunese). Amino acid sequences analysis and structure prediction of these two molecules, called Bbt-MIF-I and Bbt-MIF-II, respectively, indicated that several conservative domains existed in the two amphioxus MIFs and their sequences were highly homologous to their counterparts of other species. Intriguingly, the Bbt-MIFs gene is present in multi-copy per haploid genome, which is very unusual compared with vertebrate's MIF gene given the known genome duplication theory. The genomic copy number, expression pattern of MIF gene and phylogenetic analysis of MIF proteins all suggested that a leap forward happened for MIF gene during the evolution from invertebrate to vertebrate. Considering the crucial role of MIF in innate immunity, MIF might serve as one of key molecular markers of evolution of immune system.

High concentrations of circulating macrophage migration inhibitory factor in patients with severe blunt trauma: Is serum macrophage migration inhibitory factor concentration a valuable prognostic factor?

OBJECTIVE

To determine serum concentrations of macrophage migration inhibitory factor and other cytokines in severe blunt trauma patients in critical settings and to evaluate their association with patient outcome.

DESIGN

Prospective, observational study.

SETTING

Emergency department and surgical intensive care unit of a university hospital.

PATIENTS

Fifty-four severe blunt trauma patients with systemic inflammatory response syndrome requiring intensive care, emergency surgical intervention, or both were enrolled in the study. Forty-four patients with minor injuries were the controls.

INTERVENTIONS

Serum macrophage migration inhibitory factor concentrations were measured in the emergency department <4 hrs postinjury (day 1) and the surgical intensive care unit 24 hrs later (day 2). Blood samples for determination of tumor necrosis factor-alpha, interleukin-6, interleukin-8, and interleukin-10 were measured both in patients with severe blunt trauma and in controls. The Acute Physiology and Chronic Health Evaluation II, Injury Severity Score, Revised Trauma Score, and Trauma Revised Injury Severity Score were used for clinical evaluation of trauma severity.

MEASUREMENTS AND MAIN RESULTS

Serum macrophage migration inhibitory factor concentrations were higher in severe blunt trauma patients than in controls; were significantly correlated with Acute Physiology and Chronic Health Evaluation II, Revised Trauma Score, and Trauma Revised Injury Severity Score scores in severe blunt trauma patients but not in controls; and were higher in nonsurvivors than in survivors.

CONCLUSIONS

Our data suggest that the serum macrophage migration inhibitory factor concentration is higher in severe blunt trauma and that it reflects the severity of trauma. The serum macrophage migration inhibitory factor concentration might be a valuable predictor for the outcome of severe blunt trauma.

Macrophage migration inhibitory factor in allergic rhinitis: its identification in eosinophils at the site of inflammation

The aim of this study was to assess the potential role of macrophage migration inhibitory factor (MIF) in the pathogenesis of allergic rhinitis (AR). Serum MIF concentrations were measured by a specific enzyme-linked immunosorbent assay. In order to elucidate the cellular source of MIF, we performed double immunostaining of biopsy specimens of the nasal mucous membrane with markers for MIF and for inflammatory cells. The mean MIF level in sera from patients with AR was significantly higher than that in sera from healthy controls. Moreover, the levels were significantly correlated with the severity of the clinical symptoms. The majority of the MIF-positive cells at the site of allergic inflammation were eosinophils. These data suggest that MIF plays a role in the initiation and maintenance of AR. Eosinophils formed the largest population of MIF-producing cells; this finding suggests that they may be a major source of MIF at inflammatory sites in atopic disease.

Analysis of Chicken TLR4, CD28, MIF, MD-2, and LITAF Genes in a Salmonella enteritidis Resource Population

Salmonella enteritidis is a foodborne pathogen that negatively affects both animal and human health. Genetic variations in response to pathogenic SE colonization or to SE vaccination were measured in a chicken resource population. Outbred broiler sires and 3 diverse, highly inbred dam lines produced 508 F1 progeny that were evaluated for either bacterial colonization after pathogenic SE inoculation or circulating antibody level after SE vaccination. Five candidate genes were selected for study, based on their biological function as possibly affecting response to SE: toll-like receptor 4 (TLR4), T-cell specific surface protein (CD28), macrophage migration inhibitory factor (MIF), MD-2, and lipopolysaccharide-induced tumor necrosis factor (TNF)-alpha factor (LITAF). Gene fragments were sequenced from the founder lines of the resource population. The LITAF and MIF genes were homozygous for all sires. Single nucleotide polymorphisms (SNP) were identified in 3 genes (TLR4, CD28, and MD-2) and were used to test for associations of sire SNP with SE response. Linear mixed models were used for statistical analyses. The CD28 broiler sire SNP was associated with both bacterial load in the cecum (P < 0.003) and vaccine antibody response (P < 0.05). The MD-2 SNP was associated (P < 0.04) with the bacterial load in the spleen. The use of these SNP in these genes in marker-assisted selection may result in enhancement of disease resistance.

Simultaneous activation of apoptosis and inflammation in pathogenesis of septic shock: a hypothesis

Sepsis, a widely prevalent disease with increasing morbidity and mortality, is thought to result from uncontrolled inflammatory responses to microbial infection and/or components. However, failure of several experimental anti-inflammatory therapies has necessitated re-evaluation of the paradigm underlying the pathogenesis of this complex disorder. Apoptotic cell death forms a second dominant feature of septic shock in patients and animal models. Anti-apoptotic strategies may protect animals from septic death. However, simultaneous occurrence of apoptosis and inflammation is necessary for septic death. At the cellular level, apoptosis plays a central role in the development of the lymphoid system and regulation of immune responses. Immune activation renders cells refractory to apoptosis while apoptosis of activated lymphocytes is an important immunoregulatory mechanism. Factors such as complement factor 5a, caspase-1 and mitogen-activated protein kinase, which participate in apoptosis as well as pro-inflammatory pathways, may be responsible for simultaneous activation of apoptosis and inflammation in sepsis. Further identification of other similar biochemical events capable of co-activating inflammation and apoptosis may provide new targets for therapy of this hitherto untreatable disease.

[Role of the innate immune response in sepsis]

The innate immune system succeeds against the majority of infections before the adaptive immune system is activated. New findings contribute to a better understanding of the pathophysiology of sepsis and lead to the development of new therapeutic strategies. The innate immune system, being responsible for the first response to infections, can trigger adaptive immune responses in case the initial response is ineffective. Both arms of the immune system interact with each other, mainly via cell-cell-interactions but also by soluble factors, such as cytokines and chemokines. Two sub-populations of helper T-cells direct both balanced activation and inhibition of the two arms of the immune systems using specific patterns of cytokine release. Results obtained in new animal models of sepsis, taking a progressive growth of bacteria into account, have implied that existing knowledge has to be reanalyzed. The idea of sepsis as a mere "over-reaction to inflammation" has to be abandoned. Various so-called pattern recognition receptors (e.g. toll-like receptors, TLRs, NOD proteins) are located intracellularly or in the plasma membrane of innate immune cells and recognize certain patterns expressed exclusively by extracellular pathogens. Upon receptor engagement, intracellular signaling pathways lead to cellular activation, followed by release of various cytokines and anti-microbial substances. During the course of sepsis a cytokine shift towards increasing immune suppression occurs. The innate immune system also contributes to the migration of leukocytes in inflammed tissue, involving chemokines and adhesion molecules. Leukocytes also secrete the tissue factor leading to formation of thrombin. The environment in sepsis can cause disseminated intravascular coagulation (DIC), but at the same time thrombin triggers the release of chemokines and adhesion molecules through endothelial cells, which represents a positive feedback mechanism for innate immune responses. New therapeutic strategies for sepsis try to establish a well-balanced immune response. Intervention is accomplished through inhibition of inflammatory cytokines, their receptors or through activation of immunostimulatory responses.

Elevation of free fatty acids induces inflammation and impairs vascular reactivity in healthy subjects

To test the possible acute proinflammatory effects of fatty acids, we induced an increase in plasma free fatty acid (FFA) concentrations after a lipid and heparin infusion for 4 h in 10 healthy subjects. We determined the nuclear factor-kappaB (NF-kappaB) binding activity in mononuclear cells (MNCs), the p65 subunit of NF-kappaB, reactive oxygen species (ROS) generation by MNC, and polymorphonuclear leukocytes (PMN). Brachial artery reactivity, using postischemic flow-mediated dilation, was also measured. NF-kappaB binding activity in the MNC nuclear extracts increased to 163 +/- 17% and 144 +/- 14% as compared with basal levels at 2 and 4 h (P < 0.005) and remained elevated (P < 0.05) at 6 h (2 h after cessation of lipid infusion). NF-kappaB p65 subunit protein expression in MNC homogenates also increased at 2, 4, and 6 h (P < 0.05). ROS generation by PMNs increased significantly at 2 and 4 h (P < 0.005), whereas that by MNCs increased at 4 h (P < 0.05). Plasma macrophage migration inhibitory factor increased at 2 (P < 0.05) and 4 h (P < 0.005), respectively, and declined to baseline at 6 h. The postischemic flow-mediated dilation of brachial artery decreased from 6.3 +/- 1.1% at baseline to 4.3 +/- 1.9% and 2.7 +/- 2.1% (P < 0.01) at 2, 4, and 6 h, respectively. We conclude that an increase in FFA concentration induces oxidative stress and has a proinflammatory effect; it also impairs postischemic flow-mediated vasodilation of the brachial artery.

Macrophage migration inhibitory factor: a regulator of innate immunity

Cytokines are essential effector molecules of innate immunity that initiate and coordinate the cellular and humoral responses aimed, for example, at the eradication of microbial pathogens.

Discovered in the late 1960s as a product of activated T cells, the cytokine macrophage migration inhibitory factor (MIF) has been discovered recently to carry out important functions as a mediator of the innate immune system.

Constitutively expressed by a broad spectrum of cells and tissues, including monocytes and macrophages, MIF is rapidly released after exposure to microbial products and pro-inflammatory mediators, and in response to stress. After it is released, MIF induces pro-inflammatory biological responses that act as a regulator of immune responses.

MIF activates the extracellular signal-regulated kinase 1 (ERK1)/ERK2–mitogen-activated protein kinase pathway, inhibits the activity of JUN activation domain-binding protein 1 (JAB1) — a co-activator of the activator protein 1 (AP1) — upregulates the expression of Toll-like receptor 4 to promote the recognition of endotoxin-expressing bacterial pathogens, sustains pro-inflammatory function by inhibiting p53-dependent apoptosis of macrophages and counter-regulates the immunosuppressive effects of glucocorticoids on immune cells.

As a pro-inflammatory mediator, MIF has been shown to be implicated in the pathogenesis of severe sepsis and septic shock, acute respiratory distress syndrome, and several other inflammatory and autoimmune diseases, including rheumatoid arthritis, glomerulonephritis and inflammatory bowel diseases.

Given its crucial role as a regulator of innate and acquired immunity, pharmacological or immunological modulation of MIF activity might offer new treatment opportunities for the management of acute and chronic inflammatory diseases.

For more than a quarter of a century, macrophage migration inhibitory factor (MIF) has been a mysterious cytokine. In recent years, MIF has assumed an important role as a pivotal regulator of innate immunity. MIF is an integral component of the host antimicrobial alarm system and stress response that promotes the pro-inflammatory functions of immune cells. A rapidly increasing amount of literature indicates that MIF is implicated in the pathogenesis of sepsis, and inflammatory and autoimmune diseases, suggesting that MIF-directed therapies might offer new treatment opportunities for human diseases in the future.

Macrophage migration inhibitory factor and host innate immune defenses against bacterial sepsis

Macrophages are essential effector cells of innate immunity that play a pivotal role in the recognition and elimination of invasive microorganisms. Mediators released by activated macrophages orchestrate innate and adaptive immune host responses. The cytokine macrophage migration inhibitory factor (MIF) is an integral mediator of the innate immune system. Monocytes and macrophages constitutively express large amounts of MIF, which is rapidly released after exposure to bacterial toxins and cytokines. MIF exerts potent proinflammatory activities and is an important cytokine of septic shock. Recent investigations of the mechanisms by which MIF regulates innate immune responses to endotoxin and gram-negative bacteria indicate that MIF acts by modulating the expression of Toll-like receptor 4, the signal-transducing molecule of the lipopolysaccharide receptor complex. Given its role in innate immune responses to bacterial infections, MIF is a novel target for therapeutic intervention in patients with septic shock.

Novel strategies for the treatment of sepsis

The history of therapeutic interventions in clinical trials for sepsis has been referred to as the "graveyard for pharmaceutical companies." That is now set to change, as research provides hope for new approaches that will be therapeutically effective in humans with sepsis.

Macrophage migration inhibitory factor exhibits a pronounced circadian rhythm relevant to its role as a glucocorticoid counter-regulator

In humans, maximal expression of T helper 1 cytokines coincide with the nocturnal nadir of plasma cortisol, whereas T helper 2 cytokine responses are dominant during day-time. The pro-inflammatory cytokine, macrophage migration inhibitory factor counter-regulates glucocorticoid-mediated immune suppression. To determine the relationship between cortisol and macrophage migration inhibitory factor, healthy volunteers had blood drawn hourly for 24 h for measurement of plasma cortisol and basal- and stimulated-macrophage migration inhibitory factor. Similar to cortisol, macrophage migration inhibitory factor peaked during the late morning whereas interferon-gamma, tumour necrosis factor-alpha, interleukin-1 and interleukin-12 demonstrated a nocturnal peak. After oral cortisone, plasma macrophage migration inhibitory factor rose 2-4-fold, whereas the other cytokines decreased. There was no correlation between cortisol during the insulin tolerance test and plasma macrophage migration inhibitory factor. The late morning peak of macrophage migration inhibitory factor, by antagonizing cortisol-mediated pro-inflammatory cytokine suppression may prolong the duration of early morning inflammation. These observations explain the beneficial role of macrophage migration inhibitory factor neutralization in models of inflammatory arthritis.

Macrophage migration inhibitory factor

Macrophage migration inhibitory factor (MIF) is a ubiquitous protein that is found in virtually all cells. Its precise function in the majority of cells is not known, but studies performed over the last decade indicate that it is a critical upstream regulator of the innate and acquired immune response. MIF is released under a variety of circumstances, regulates cytokine secretion and the expression of receptors that are involved in innate immunity, inhibits p53 function, and activates components of the mitogen-activated protein kinase and Jun-activation domain-binding protein-1 (Jab-1) pathways. Compelling in vitro and in vivo evidence has focused attention on this protein as a new therapeutic target for inflammatory and autoimmune diseases. Unique structural features, including an intrinsic catalytic activity, offer attractive opportunities for the discovery and design of therapeutic MIF inhibitors.

Macrophage migration inhibitory factor is a critical mediator of severe acute pancreatitis

BACKGROUND & AIMS

Macrophage migration inhibitory factor (MIF), originally described as an inhibitor of the random migration of macrophages, has been shown recently to be involved in the pathogenesis of several inflammatory diseases such as sepsis. The aim of this study was to clarify the role of MIF in acute pancreatitis (AP).

METHODS

Hemorrhagic necrotizing pancreatitis and edematous pancreatitis were induced by the injection of taurocholic acid (TCA pancreatitis) and cerulein (cerulein pancreatitis), respectively, on male Wistar rats. MIF levels in ascitic fluids, serum, and the organs were determined. The effects of anti-MIF antibody were examined on the prognosis of rats with TCA pancreatitis and of female CD-1 mice with choline-deficient, ethionine-supplemented, diet-induced model of severe AP. In addition, serum MIF levels in AP patients and in healthy controls were measured.

RESULTS

Serum and ascitic MIF levels in TCA pancreatitis were increased rapidly and decreased gradually thereafter. Ascitic MIF levels were also increased in cerulein pancreatitis, but to a lesser degree. MIF level was increased in the lung in TCA pancreatitis, but not in the pancreas and the liver. Prophylactic (1 hour before and immediately after induction) administration of anti-MIF antibody significantly improved the survival rate of rats with TCA pancreatitis. The survival rate of mice with severe AP was also improved significantly by the antibody treatment. Serum MIF levels were higher in severe AP patients than mild AP patients and healthy controls.

CONCLUSIONS

These results suggest a role of MIF in the pathogenesis of severe AP.

Macrophage migration inhibitory factor plays a critical role in mediating protection against the helminth parasite Taenia crassiceps

To determine the role of endogenous migration inhibitory factor (MIF) in regulation of immune response during murine cysticercosis caused by the helminth parasite Taenia crassiceps, we analyzed the course of T. crassiceps infection in MIF(-/-) BALB/c mice. MIF(-/-) mice were highly susceptible to T. crassiceps and developed significantly higher parasite loads compared to similarly infected MIF(+/+) mice. Throughout the course of infection, Taenia crassiceps soluble antigen-stimulated spleen cells from both MIF(+/+) and MIF(-/-) mice produced significant and comparable levels of interleukin-4 (IL-4), but those from MIF(-/-) mice produced significantly more IL-13, as well as gamma interferon (IFN-gamma), suggesting that the susceptibility of MIF(-/-) mice to T. crassiceps was not due to the lack of IFN-gamma production. Interestingly, low levels of both total and specific immunoglobulin G2a were observed in MIF(-/-) cysticercotic mice despite the high IFN-gamma levels; in addition, peritoneal macrophages obtained from T. crassiceps-infected MIF(-/-) mice at different time points failed to respond efficiently to stimulation in vitro with lipopolysaccharide plus IFN-gamma and produced significantly lower levels of IL-12, tumor necrosis factor alpha, and NO compared to those from MIF(+/+) mice. These findings demonstrate that MIF plays a critical role in mediating protection against T. crassiceps in vivo. Moreover, these findings also suggest that impaired macrophage function rather than the lack of Th1 development may be responsible for mediating susceptibility to T. crassiceps.

Macrophage migration inhibitory factor is associated with aneurysmal expansion

BACKGROUND

Macrophage migration inhibitory factor (MIF) is an inflammatory cytokine released mainly from macrophages and activated lymphocytes. Both atherosclerosis and abdominal aortic aneurysm (AAA) are inflammatory diseases tightly linked to the function of these cells. The correlation and contribution of MIF to these human diseases remain unknown, although a recent rabbit study showed expression of this cytokine in atherosclerotic lesions.

MATERIAL AND METHODS

MIF immunohistochemistry was performed on tissue sections from five normal aortas, seven atherosclerotic carotids, and six AAAs. A group of 112 men with small AAAs (defined as 3 to 5 cm) was recruited at the time of diagnosis, had serum samples taken, and was followed annually for 1 to 5 years (mean, 2.9 years) and referred for surgery if the AAA exceeded 5 cm in diameter. Of this study group, 98 had serum MIF measured with an enzyme-linked immunosorbent assay and 61 had detectable levels.

RESULTS

In human atherosclerotic and aneurysmal lesions, MIF protein colocalized in macrophages, endothelial cells, and smooth muscle cells, but normal arteries had negligible MIF expression. Furthermore, serum-MIF levels correlated significantly with annual expansion rate (r = 0.28; P =.005), persisting after adjustment for initial AAA size, smoking habits, diastolic blood pressure, ankle blood pressure index, and age. After exclusion of 38 cases with MIF levels below the detection limit, initial AAA size was also significantly correlated with the MIF levels (r = 0.42; P =.001), persisting after adjustment for similar confounders, and the correlation coefficient with expansion rate increased to 0.42 (P =.001).

CONCLUSION

Highly expressed MIF in macrophages, endothelial cells, and smooth muscle cells in lesions from atherosclerosis and AAA and significant association between serum MIF level and AAA initial size and AAA expansion rate in a group of patients with AAA suggest a potential involvement of this proinflammatory cytokine in the pathogenesis of these cardiovascular diseases.

The immunopathogenesis of sepsis

Sepsis is a condition that results from a harmful or damaging host response to infection. Many of the components of the innate immune response that are normally concerned with host defences against infection can, under some circumstances, cause cell and tissue damage and hence multiple organ failure, the clinical hallmark of sepsis. Because of the high mortality of sepsis in the face of standard treatment, many efforts have been made to improve understanding of the dysregulation of the host response in sepsis. As a result, much has been learnt of the basic principles governing bacterial-host interactions, and new opportunities for therapeutic intervention have been revealed.

Adhesion-dependent signaling by macrophage migration inhibitory factor (MIF)

Proper stimulation of cell cycle progression and DNA synthesis requires cooperating signals from integrin and growth factor receptors. We previously found that the proinflammatory peptide, macrophage migration inhibitory factor (MIF), functions as an autocrine mediator of growth factor-dependent ERK MAP kinase activation and cell cycle progression. We now report that MIF secretion is induced by cell adhesion to fibronectin in quiescent mouse fibroblasts. Adhesion-mediated release of MIF subsequently promotes integrin-dependent activation of MAP kinase, cyclin D1 expression, and DNA synthesis. Secretion of MIF requires protein kinase C activity, and recombinant MIF reconstitutes the activation of MAP kinases in the presence of protein kinase C inhibition. Finally, we show that cells deficient in MIF have significantly higher retinoblastoma tumor suppressor and lower E2F transcriptional activities. These results suggest that MIF is an important autocrine mediator of adhesion-dependent signaling events and may provide mechanistic insight into how MIF regulates proliferative and oncogenic processes.

Elevated levels of serum macrophage migration inhibitory factor in patients with pulmonary tuberculosis

Macrophage migration inhibitory factor (MIF) was originally described as a T-cell-derived cytokine that inhibits the random migration of macrophages and promotes the delayed-type hypersensitivity reaction. MIF plays an important role in the regulation of the Th1/Th2 balance in inflammatory response. This study investigated serum levels of circulating MIF in patients with pulmonary tuberculosis. The levels of MIF in sera were measured by enzyme-linked immunosorbent assay in 34 patients with pulmonary tuberculosis (16 males and 18 females) and 30 healthy controls (15 males and 15 females). The mean levels of circulating MIF values were significantly higher in those with pulmonary tuberculosis (19.84 +/- 11.27 ng/ml; P < 0.0001) than in the healthy controls (4.38 +/- 1.34 ng/ml). Circulating MIF values significantly correlated with circulating interferon-gamma values (r = 0.537, P < 0.0001). Thus, MIF may play an important role in immune responses to human infection with Mycobacterium tuberculosis.

Human V gamma 2V delta 2 T cells augment migration-inhibitory factor secretion and counteract the inhibitory effect of glucocorticoids on IL-1 beta and TNF-alpha production

In immune cells, proinflammatory cytokine gene expression is regulated by glucocorticoids, whereas migration-inhibitory factor (MIF), a pleiotropic cytokine, has the unique property of counteracting the inhibitory effect of glucocorticoids on TNF-alpha and IL-1beta secretion. A few lines of evidence suggest that gammadelta T cells play an important role in immunoregulation. However, it is unknown whether human gammadelta T cells participate in regulating MIF secretion, and how gammadelta T cells, glucocorticoids, and cytokines converge to give a unified physiological response. In this study, we demonstrate that human Vgamma2Vdelta2 T cells augment MIF secretion. Remarkably, these Vgamma2Vdelta2 T cells, functioning similarly to MIF in part, counteracted inhibition of dexamethasone on production of IL-1beta and TNF-alpha. SCID mice reconstituted with human PBMC that were mock depleted of Vdelta2 T cells and repeatedly infected with lethal dose of Escherichia coli had shorter survival time than those reconstituted with PBMC that were depleted of Vdelta2 T cells. Thus, human Vgamma2Vdelta2 T cells are likely to play broad-spectrum roles in immunoregulation and immunopathology by influencing MIF secretion and the immunomodulatory function of glucocorticoids.

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

The secretion of macrophage migration inhibitory factor (MIF) is enhanced by inflammatory and other stimuli. MIF regulates innate and adaptive immune responses, but the mechanisms of this regulation are poorly understood. Our hypothesis was that MIF generated by these stimuli regulates these responses by modulating key molecular expression. This hypothesis was tested by adding greater than constitutive concentrations of recombinant MIF to cultures of various cell types and flow cytometric assay. MIF modulated surface expression of MHC-II, B7-2, CD40, CD40 ligand, ICAM-1 and Fcgamma, CR1/CR2, and IL-10 receptors and intracellular expression of IL-10, TNFalpha, and p40 (IL-12). MIF increased expression of B7-1 by B cells and CD40 L by T cells in spleens from Schistosoma mansoni-infected mice. Footpad injection of MIF reduced expression of MHC-II and CD40 by B cells in draining lymph nodes. Footpad injection of Mab to MIF reduced expression of B7-2 and CR1/CR2 by B cells and B7-2 by macrophages in these nodes. These data support our hypothesis.

Macrophage migration inhibitory factor (MIF): mechanisms of action and role in disease

Macrophage migration inhibitory factor (MIF) is a unique cytokine and critical mediator of host defenses with a role in septic shock and chronic inflammatory and autoimmune diseases. Its mechanism of action is incompletely understood. Here, we attempt to correlate current knowledge on the molecular pathways of MIF activity with its functions in immunity and disease.

Response of serum macrophage migration inhibitory factor levels to stimulation or suppression of the hypothalamo-pituitary-adrenal axis in normal subjects and patients with Cushing's disease

Macrophage migration inhibitory factor (MIF) is a proinflammatory pituitary and immune cell cytokine and a critical mediator of septic shock. It has been reported that MIF is secreted in parallel with ACTH from the pituitary in response to stress or inflammatory stimuli. MIF release from immune cells is also induced rather than inhibited by glucocorticoids. It has therefore been suggested that MIF may be a novel counterregulatory hormone of glucocorticoid action that acts both as a paracrine and endocrine modulator of host responses. We have measured circulating MIF levels, using a human MIF ELISA, in normal subjects and patients under numerous pathophysiological conditions. Serum MIF was measured in normal subjects who underwent stimulation of the hypothalamo-pituitary-adrenal axis with an insulin tolerance test (n = 8), a CRH-stimulation test (n = 5), a short synacthen test (n = 5), and following a low-dose dexamethasone suppression test (n = 6). We also sampled from a peripheral vein and both inferior petrosal sinuses before and after CRH stimulation in four patients with a histologically proven diagnosis of Cushing's disease. Immunostaining of the pituitary tumors for MIF was also performed. In normal subjects serum MIF levels did not rise in parallel with cortisol during the insulin tolerance or CRH test or after administration of synthetic ACTH. In all subjects cortisol levels became undetectable after the low-dose dexamethasone suppression test, and no consistent change was observed in serum MIF levels during the test. In patients with Cushing's disease, there was no basal central-to-peripheral gradient in MIF, and no consistent changes occurred in serum MIF levels in either the left or right inferior petrosal sinus after CRH stimulation; however, immunostaining of the surgically removed pituitary tumors from the same patients showed strong staining for both ACTH and MIF. These results show that in humans acute modulation of the hypothalamo-pituitary-adrenal axis does not significantly alter circulating MIF levels. In addition, ACTH-secreting pituitary tumors that express MIF do not release MIF either spontaneously or in response to CRH stimulation, and there is no gradient for MIF in the venous drainage of the pituitary. Our study suggests that the pituitary gland is not the major contributor to circulating MIF; an autocrine or paracrine role for pituitary-derived MIF is more likely.

Expression of macrophage migration inhibitory factor in human breast cancer: association with nodal spread

Macrophage migration inhibitory factor (MIF) is known to exert pleiotropic functions including inhibition of macrophage migration, anchoring, and counteraction of the anti-inflammatory and immunosuppressive activity of glucocorticoids. Ninety-three primary breast cancer tissues and 64 sera of primary breast cancer patients were analyzed for the expression of MIF. The clinico-pathological significance of MIF expression was evaluated. It was found that MIF was frequently over-expressed in primary breast cancer tissues. RT-PCR and western blotting analysis confirmed that wild-type MIF is expressed, and immunohistochemical analysis showed that MIF expression was localized at tumor cells as well as stromal cells, including tumor-associated macrophages. Intratumoral MIF protein concentrations detected by enzyme-linked immunosorbent assay (ELISA) varied with a median value of 1821 ng/mg protein (range: 8 - 8126 ng/mg protein), and correlated inversely with nodal involvement (P = 0.039). No significant correlation was observed with other clinico-pathological factors including tumor size, menopausal status and hormone receptors. The circulating level of MIF protein ranged up to 105.7 ng/ml (median: 17.3 ng/ml), and it was also found to correlate inversely with the number of involved nodes (P = 0.02). A comparative study with other soluble inflammatory mediators showed that intratumoral levels of MIF were significantly associated with those of interleukin-1 beta, suggesting that interactions between tumor cells and tumor-associated macrophages play an important role in the up-regulation of MIF. The multifunctional inflammatory/immune mediator MIF was frequently expressed in primary breast cancer, and its expression level was inversely associated with nodal spread. Thus, MIF seems to play a role in tumor-stroma interactions of primary breast cancers, particularly those with a phenotype of node-negative or minimal nodal spread.

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. MIF's 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.

Inhibition of macrophage migration inhibitory factor (MIF) tautomerase and biological activities by acetaminophen metabolites

The cytokine macrophage migration inhibitory factor (MIF) has emerged to be an important regulator of the inflammatory response and is critically involved in the development of septic shock, arthritis, and glomerulonephritis. Although the biological activities of MIF are presumed to require a receptor-based mechanism of action, the protein is also a tautomerase and has a catalytically active N-terminal proline that is invariant in structurally homologous bacterial isomerases. This observation raises the possibility that MIF may exert its biological action via an enzymatic reaction. Physiologically relevant substrates for MIF have not been identified, nor have site-directed mutagenesis studies consistently supported the requirement for a functional catalytic site. Small molecule inhibitors of MIF's isomerase activity also have been developed, but none have been shown yet to inhibit MIF biological activity. We report herein that the iminoquinone metabolite of acetaminophen, N-acetyl-p-benzoquinone imine (NAPQI), inhibits both the isomerase and the biological activities of MIF. The reaction between NAPQI and MIF is covalent and produces a NAPQI-modified MIF species with diminished cell binding activity and decreased recognition by anti-MIF mAb. These data are consistent with a model by which the NAPQI reacts with the catalytic Pro-1 of MIF to disrupt the integrity of epitope(s) critical to MIF's biological activity and point to the importance of the catalytic domain, but not the catalytic activity per se, in MIF function. These results also point to a powerful approach for the design of small molecule inhibitors of MIF based on interaction with its catalytic site and constitute an example of a pharmacophore capable of irreversibly inhibiting the action of a proinflammatory cytokine.

In vivo blockade of macrophage migration inhibitory factor prevents skin graft destruction after indirect allorecognition

BACKGROUND

The effector mechanisms that ultimately destroy transplanted tissues are poorly understood. In particular, it is not clear how CD4+ T cells primed to donor-derived determinants expressed on recipient MHC molecules (the indirect pathway) can mediate graft destruction in the absence of cognate recognition of peptide: MHC on the graft cells themselves. Macrophage migration inhibitory factor (MIF) inhibits macrophage movement and is a proinflammatory and regulatory cytokine known to be essential for development of delayed-type hypersensitivity reactions.

METHODS

To test whether MIF participates in graft destruction following indirect recognition, we studied rejection of MHC-II-deficient skin grafts placed on allogeneic SCID recipients adoptively transferred with naïve CD4+ T cells, and the recipients were treated with neutralizing anti-MIF monoclonal antibody or isotype control IgG. In this model graft rejection can only occur indirectly as the graft cells lack MHC II for recognition by the recipient CD4+ T cells.

RESULTS

We found that in vivo blockade of MIF inhibited indirect CD4+ cell-mediated skin graft destruction, and markedly reduced detectable macrophages within the grafts. The neutralizing anti-MIF antibody significantly inhibited alloreactive DTH but did not prevent T cell priming or interferon-gamma release by primed T cells.

CONCLUSIONS

The results strongly implicate MIF as an active participant in skin graft destruction after indirect recognition and suggest that this effect is mediated through an inhibition of macrophage migration and/or function.

MIF regulates innate immune responses through modulation of Toll-like receptor 4

Macrophages are pivotal effector cells of the innate immune system, which is vital for recognizing and eliminating invasive microbial pathogens. When microbial products bind to pathogen-recognition receptors, macrophages become activated and release a broad array of cytokines that orchestrate the host innate and adaptive immune responses. Initially identified as a T-cell cytokine, macrophage migration inhibitory factor (MIF) is also a macrophage cytokine and an important mediator of inflammation and sepsis. Here we report that MIF is an essential regulator of macrophage responses to endotoxin (lipopolysaccharide) and Gram-negative bacteria. Compared with wild-type cells, MIF-deficient macrophages are hyporesponsive to lipopolysaccharide and Gram-negative bacteria, as shown by a profound reduction in the activity of NF-kappaB and the production of tumour-necrosis factor-alpha. This reduction is due to a downregulation of Toll-like receptor 4 (TLR4), the signal-transducing molecule of the lipopolysaccharide receptor complex, and is associated with decreased activity of transcription factor PU.1, which is required for optimal expression of the Tlr4 gene in myeloid cells. These findings identify an important role for MIF in innate immunity and provide a molecular basis for the resistance of MIF-deficient mice to endotoxic shock.

Development of chronic colitis is dependent on the cytokine MIF

The cytokine macrophage-migration inhibitory factor (MIF) is secreted by a number of cell types upon induction by lipopolysaccharide (LPS). Because colitis is dependent on interplay between the mucosal immune system and intestinal bacteria, we investigated the role of MIF in experimental colitis. MIF-deficient mice failed to develop disease, but reconstitution of MIF-deficient mice with wild-type innate immune cells restored colitis. In addition, established colitis could be treated with anti-MIF immunoglobulins. Thus, murine colitis is dependent on continuous MIF production by the innate immune system. Because we found increased plasma MIF concentrations in patients with Crohn's disease, these data suggested that MIF is a new target for intervention in Crohn's disease.

Macrophage migration inhibitory factor is an important mediator in the pathogenesis of gastric inflammation in rats

BACKGROUND & AIMS

Macrophage migration inhibitory factor (MIF) has been shown to play a pivotal role in inflammatory and immune-mediated diseases. This study investigates the role of MIF in gastric inflammation.

METHODS

Expression of MIF was examined in a rat gastric ulcer model induced by acetic acid, and the functional role of MIF in acute gastric ulcer was investigated by administration of a neutralizing anti-MIF antibody.

RESULTS

MIF messenger RNA and protein were markedly up-regulated in acute gastric ulcer, which correlated with the accumulation of macrophages (P < 0.001) and neutrophils (P < 0.05) at the site of inflammation. Macrophages, like neutrophils, were the major inflammatory cells infiltrating the ulcer base and they strongly expressed inducible nitric oxide synthase. However, macrophages, not neutrophils, were a rich source of MIF production in acute gastric ulcer. In vivo and in vitro blockade of MIF with the neutralizing anti-MIF antibody significantly inhibited the marked up-regulation of MIF, tumor necrosis factor alpha, inducible nitric oxide synthase, and intercellular adhesion molecule-1. This was associated with the marked inhibition of macrophage (70% reduced) and neutrophil (60% reduced) accumulation and activation, thus reducing ulcer sizes and attenuating ulceration.

CONCLUSIONS

This study has shown that MIF was markedly up-regulated during acute gastric ulcer. Inhibition of acute gastric ulcer by blockade of MIF indicates that MIF is a key inflammatory mediator and plays a pathogenic role in gastric inflammation.

Macrophage migration inhibitory factor and innate immune responses to bacterial infections

OBJECTIVES

To review the role of macrophage migration inhibitory factor (MIF) in host responses to infection and to explore the potential of MIF as a novel target for therapeutic intervention in patients with severe sepsis and septic shock.

DATA SOURCES

Published articles on the role of MIF in innate immune responses against microbial pathogens.

DATA SUMMARY

MIF has emerged recently as an important effector molecule of the innate immune system. MIF is expressed constitutively by monocytes/macrophages, T cells, B cells, endocrine cells, and epithelial cells. Microbial toxins and cytokines are powerful inducers of MIF release by immune cells. MIF expression is up-regulated during the course of inflammatory and infectious diseases and was found to play an important role in the pathogenesis of sepsis and septic shock.

CONCLUSION

Given the role of MIF in innate immune responses against microbial pathogens and in the regulation of inflammatory responses, modulation of MIF production or neutralization of its activity may offer new therapeutic options for the management of patients with sepsis.

Urine macrophage migration inhibitory factor concentrations as a diagnostic tool in human renal allograft rejection

BACKGROUND

Macrophage migration inhibitory factor (MIF) is a pro-inflammatory cytokine that is a potent activator of macrophages and T cells. Previous studies have shown that local MIF production is increased in acute renal allograft rejection, suggesting that it may play an important role in the rejection process.

AIMS

To determine if urine and serum MIF concentrations: (1) are increased in acute rejection, and (2) can be used as noninvasive tools to discriminate between acute rejection (AR) and cyclosporine nephrotoxicity (CyA toxicity).

METHODS

In a prospective study of nine renal allograft patients (five acute rejection and four stable), serial urine MIF concentrations were measured by ELISA in the first 14 days after transplantation. In a retrospective study, MIF concentrations in urine and serum were measured in 24 patients who were biopsied for acute renal transplant dysfunction (11 AR, 13 CyA toxicity). Urine and serum MIF were also measured in 23 stable renal transplant patients and 10 normals.

RESULTS

MIF was readily detected in the urine of normal healthy controls (106+/-61 pg/micromol creatinine). In the prospective study, the urinary MIF concentration was increased substantially on day 1 posttransplantation and subsequently fell in parallel with the serum creatinine. However, urine MIF increased before episodes of biopsy proven acute rejection. The retrospective study showed that urine MIF concentrations in patients with AR were increased 5-fold compared to normal controls (439+/-313 pg/micromol Cr; P<0.01). In contrast, urine MIF concentrations in CyA toxicity were not significantly different to normal controls (145+/-119 pg/micromol Cr; P=NS). A marked increase in MIF immunostaining was seen in biopsies of AR, but not in CyA toxicity. No significant differences were evident in serum MIF levels between normals and any transplant patient group.

CONCLUSIONS

These results suggest that measurement of urine MIF concentration may be useful in monitoring renal transplant patients for acute rejection and as a discriminator from cyclosporine nephrotoxicity.

Macrophage migration inhibitory factor and hypothalamo-pituitary-adrenal function during critical illness

In patients with septic shock (n = 32), multitrauma (n = 8), and hospitalized matched controls (n = 41), we serially measured serum macrophage inhibitory factor (MIF), cortisol, plasma ACTH, tumor necrosis factor-alpha, and interleukin-6 (IL-6) immunoreactivity during 14 days or until discharge/death. MIF levels were significantly elevated on day 1 in septic shock (14.3 +/- 4.5 microg/L), as opposed to trauma (3.1 +/- 1.7 microg/L) and control patients (2.5 +/- 2.1 microg/L). The time course of MIF, parallel to cortisol, but in contrast to ACTH, showed persistently elevated levels in septic patients. On admission, nonsurvivors of septic shock (n = 11) showed significantly higher MIF levels than survivors (18.4 +/- 4.8 and 10.2 +/- 4.2 microg/L, respectively). Patients with septic adult respiratory distress syndrome (ARDS; n = 8) showed higher MIF levels than those who did not develop ARDS (19.4 +/- 4.7 vs. 9.2 +/- 4.3 microg/L, respectively). Multiple logistic regression analysis demonstrated that both MIF and ARDS were independent predictors of adverse outcome. On admission, tumor necrosis factor-alpha, IL-6, procalcitonin, and lipopolysaccharide-binding protein levels were higher in patients with septic shock than in patients with multitrauma. In septic patients, regression analysis showed significant correlations between MIF and cortisol as well as between MIF and IL-6 levels and disease severity scores. No relation was found between MIF and markers of the acute phase response (procalcitonin, C- reactive protein, and lipopolysaccharide-binding protein). In multitrauma patients, MIF levels were not elevated at any time point and were not related to other variables. Our data suggest that during immune-mediated inflammation (such as septic shock) MIF is an important neuroendocrine mediator: a contraregulator of the immunosuppressive effects of glucocorticoids.

Coumarin and chromen-4-one analogues as tautomerase inhibitors of macrophage migration inhibitory factor: discovery and X-ray crystallography

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine released from T-cells and macrophages. Although a detailed understanding of the biological functions of MIF has not yet been clarified, it is known that MIF catalyzes the tautomerization of a nonphysiological molecule, D-dopachrome. Using a structure-based computer-assisted search of two databases of commercially available compounds, we have found 14 novel tautomerase inhibitors of MIF whose K(i) values are in the range of 0.038-7.4 microM. We also have determined the crystal structure of MIF complexed with the hit compound 1. It showed that the hit compound is located in the active site of MIF containing the N-terminal proline which plays an important role in the tautomerase reaction and forms several hydrogen bonds and undergoes hydrophobic interactions. A crystallographic study also revealed that there is a hydrophobic surface which consists of Pro-33, Tyr-36, Trp-108, and Phe-113 at the rim of the active site of MIF, and molecular modeling studies indicated that several more potent hit compounds have the aromatic rings which can interact with this hydrophobic surface. To our knowledge, our compounds are the most potent tautomerase inhibitors of MIF. One of these small, drug-like molecules has been cocrystallized with MIF and binds to the active site for tautomerase activity. Molecular modeling also suggests that the other hit compounds can bind in a similar fashion.