A functional macrophage migration inhibitory factor promoter polymorphism is associated with reduced diffusing capacity

Cigarette smoke exposure is the leading modifiable risk factor for chronic obstructive pulmonary disease (COPD); however, the clinical and pathologic consequences of chronic cigarette smoke exposure are variable among smokers. Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine implicated in the pathogenesis of COPD. Within the promoter of the MIF gene is a functional polymorphism that regulates MIF expression (-794 CATT_5-8 microsatellite repeat) ( rs5844572 ). The role of this polymorphim in mediating disease susceptibility to COPD-related traits remains unknown. We performed a cross-sectional analysis of DNA samples from 641 subjects to analyze MIF-794 CATT_5-8 ( rs5844572 ) polymorphism by standard methods. We generated multivariable logistic regression models to determine the risk of low expressing MIF alleles for airflow obstruction [defined by forced expiratory volume in 1 s (FEV₁)/forced vital capacity ratio <0.70] and an abnormal diffusion capacity [defined by a diffusion capacity for carbon monoxide (DL_CO) percent predicted <80%]. We then used generalized linear models to determine the association of MIF genotypes with FEV₁ percent predicted and DL_CO percent predicted. The MIF-794 CATT₅ allele was associated with an abnormal diffusion capacity in two cohorts [odds ratio (OR): 9.31, 95% confidence interval (CI): 1.97-4.06; and OR: 2.21, 95% CI: 1.03-4.75]. Similarly, the MIF-794 CATT₅ allele was associated with a reduced DL_CO percentage predicted in these two cohorts: 63.5 vs. 70.0 ( P = 0.0023) and 60.1 vs. 65.4 ( P = 0.059). This study suggests an association between a common genetic polymorphism of an endogenous innate immune gene, MIF, with reduced DL_CO, an important measurement of COPD severity.

MIF-CD74 signaling impedes microglial M1 polarization and facilitates brain tumorigenesis

Microglial cells in the brain tumor microenvironment are associated with enhanced glioma malignancy. They persist in an immunosuppressive M2 state at the peritumoral site and promote the growth of gliomas. Here, we investigated the underlying factors contributing to the abolished immune surveillance. We show that brain tumors escape pro-inflammatory M1 conversion of microglia via CD74 activation through the secretion of the cytokine macrophage migration inhibitory factor (MIF), which results in a M2 shift of microglial cells. Interruption of this glioma-microglial interaction through an antibody-neutralizing approach or small interfering RNA (siRNA)-mediated inhibition prolongs survival time in glioma-implanted mice by reinstating the microglial pro-inflammatory M1 function. We show that MIF-CD74 signaling inhibits interferon (IFN)-γ secretion in microglia through phosphorylation of microglial ERK1/2 (extracellular signal-regulated protein kinases 1 and 2). The inhibition of MIF signaling or its receptor CD74 promotes IFN-γ release and amplifies tumor death either through pharmacological inhibition or through siRNA-mediated knockdown. The reinstated IFN-γ secretion leads both to direct inhibition of glioma growth as well as inducing a M2 to M1 shift in glioma-associated microglia. Our data reveal that interference with the MIF signaling pathway represents a viable therapeutic option for the restoration of IFN-γ-driven immune surveillance.

Macrophage migration inhibitory factor promotes eosinophil accumulation and tissue remodeling in eosinophilic esophagitis

Macrophage migration inhibitory factor (MIF) is involved in eosinophil biology and in type 2 inflammation, contributing to allergic and helminthic diseases. We hypothesized that MIF participates in the pathogenesis of eosinophilic esophagitis (EoE), an allergic condition characterized by esophageal eosinophilic inflammation. MIF is highly expressed in esophageal mucosa of patients with EoE, compared with gastro-esophageal reflux disease and control patients, where it co-localizes predominantly with eosinophils. In vitro, recombinant MIF promotes human eosinophil chemotaxis, while MIF antagonist and CXCR4 antagonist, AMD3100, revert this effect. In a model of EoE induced by ovalbumin, Mif-deficient mice have reduced inflammation and collagen deposition compared with wild-type (WT) mice. Importantly, treatment of WT mice with anti-MIF or with AMD3100 during the challenge phase prevents accumulation of eosinophils and tissue remodeling. Conversely, recombinant MIF promoted tissue eosinophil inflammation in allergic mice. Together, these results implicate MIF in the pathogenesis of esophageal inflammation and suggest that targeting MIF might represent a novel therapy for EoE.

Macrophage migration inhibitory factor: association of -794 CATT5-8 and -173 G>C polymorphisms with TNF-α in systemic lupus erythematosus

Macrophage migration inhibitory factor (MIF) is an upstream immunoregulatory cytokine associated with the pathogenesis of autoimmune inflammatory diseases. There is evidence that MIF functions in a positive feedback loop with TNF-α that could perpetuate the inflammatory process in systemic lupus erythematosus (SLE). In this case-control study we investigated whether commonly occurring functional MIF polymorphisms are associated with SLE as well as with MIF and TNF-α serum levels in a Mexican-Mestizo population. Genotyping of the -794 CATT5-8 (rs5844572) and -173 G>C (rs755622) MIF polymorphisms was performed by PCR and PCR-RFLP, respectively in 186 SLE patients and 200 healthy subjects. MIF and TNF-α serum levels were determined by ELISA. A significant increase of MIF and TNF-α levels was found in SLE patients. According to a genetic model, we found a significant association of genotypes carrying the -794 CATT7 and -173(∗)C risk alleles with susceptibility to SLE and with a significant increase of TNF-α. In conclusion, MIF gene polymorphisms are associated with SLE susceptibility and with an increase of TNF-α serum levels in a Mexican-Mestizo population.

Platelets are a previously unrecognised source of MIF

Macrophage migration inhibitory factor (MIF) is an inflammatory cytokine with chemokine-like functions and a role in atherogenesis. MIF is secreted by various cells including endothelial cells and macrophages. Platelets are another prominent cell type with a role in atherogenesis and are a rich source of atherogenic chemokines. We asked whether platelets express and secrete MIF. In comparison, CXCL12 release was determined. We examined the subcellular localisation of MIF in platelets/megakaryocytes, studied its co-localisation with other platelet-derived mediators and asked whether platelets contain MIF mRNA. Moreover, we probed the functional role of platelet-derived MIF in inflammatory cell recruitment. Using Western blot and ELISA, we demonstrated and quantitated MIF protein in human and mouse platelets. Applying confocal-microscopy, MIF was found to localise in granular-like structures, but did not co-localise with known platelet cytokines. qPCR indicated that platelets contain low levels of MIF mRNA. ELISA measurements from human platelet supernatants showed that, whereas thrombin and collagen triggered the release of MIF and CXCL12, ADP and oxidised LDL promoted CXCL12 but not MIF secretion. Using Transwell assays, we demonstrated that platelet supernatants promoted monocyte chemotaxis and that this was blocked by neutralising MIF antibodies.This is the first report demonstrating MIF secretion from activated platelets, suggesting that platelets are a previously unrecognised source of MIF in inflammatory processes. There are distinct activating stimuli for MIF and CXCL12 secretion. A substantial portion of the chemotactic capacity of stimulated platelet supernatants is contributed by MIF, suggesting a role for platelet-derived MIF in atherogenic cell recruitment.

CD84 is a survival receptor for CLL cells

Chronic lymphocytic leukemia (CLL) is characterized by the accumulation of CD5+ B lymphocytes in peripheral blood, lymphoid organs and bone marrow. The main feature of the disease is accumulation of the malignant cells due to decreased apoptosis. CD84 belongs to the signaling lymphocyte activating molecule family of immunoreceptors, and has an unknown function in CLL cells. Here, we show that the expression of CD84 is significantly elevated from the early stages of the disease, and is regulated by macrophage migration inhibitory factor and its receptor, CD74. Activation of cell surface CD84 initiates a signaling cascade that enhances CLL cell survival. Both downmodulation of CD84 expression and its immune-mediated blockade induce cell death in vitro and in vivo. In addition, analysis of samples derived from an on-going clinical trial, in which human subjects were treated with humanized anti-CD74 (milatuzumab), shows a decrease in CD84 messenger RNA and protein levels in milatuzumab-treated cells. This downregulation was correlated with reduction of Bcl-2 and Mcl-1 expression. Thus, our data show that overexpression of CD84 in CLL is an important survival mechanism that appears to be an early event in the pathogenesis of the disease. These findings suggest novel therapeutic strategies based on the blockade of this CD84-dependent survival pathway.

Macrophage migration inhibitory factor (MIF): genetic evidence for participation in early onset and early stage rheumatoid arthritis

Macrophage migration inhibitory factor (MIF) is an upstream pro-inflammatory cytokine that is associated with the pathogenesis of autoimmune inflammatory diseases including rheumatoid arthritis (RA). Two polymorphisms in the upstream region exist in the MIF gene and are associated with RA susceptibility or severity in different populations. In this case-control study, we investigated whether MIF polymorphisms are associated with RA susceptibility or activity in a western Mexican population .The relationship of MIF levels with clinical features of disease also was assessed. Genotyping of the -794 CATT5-8 (rs5844572) and the -173 G>C (rs755622) polymorphisms was performed by PCR and PCR-RFLP respectively on 226 RA patients and 210 healthy subjects. Serum MIF levels were determined by ELISA. We found a significant association between the -794 CATT5-8 6,7 MIF genotype with RA. Moreover, we detected an association between the -794 CATT7 allele with early onset RA. The -794 CATT7 and -173(*)C alleles, which are in linkage disequilibrium, were associated with high disease activity on RA patients. A positive correlation between circulating MIF levels and C-reactive protein, erythrocyte sedimentation rate, rheumatoid factor, anti-citrullinated protein/peptides antibodies and TNFα was detected. MIF levels appear to be associated with disease progression rather than disease activity, which is distinct from the established relationship between disease activity and TNFα levels. In conclusion, the MIF gene and protein are associated with RA in a western Mexican population, with a main contribution onto early onset and early stages of disease.

Distribution maps of D-dopachrome tautomerase in the mouse brain

D-Dopachrome tautomerase is an enzyme related by amino acid sequence and catalytic activity to macrophage migration inhibitory factor. Both of these small molecules are pro-inflammatory cytokines mediating broad innate immune responses. Although it is well established that the gene product of D-dopachrome tautomerase is widely expressed in liver and kidney cells, no study has mapped the distribution pattern of this tautomeric enzyme in the mammalian nervous system. Here, we address this void by characterizing the cellular localization of D-dopachrome tautomerase in the adult mouse brain. Two well-characterized polyclonal antibodies were used for Western blotting and immunohistochemical localization of the endogenous tautomeric enzyme. Our results show that D-dopachrome tautomerase is present throughout the brain parenchyma with a large fraction of heterogeneous interneurons harboring a stable and robust expression of the enzyme. These data point to a potential involvement of D-dopachrome tautomerase activity in the mature mouse brain, and suggest some functional and evolutionary relationship between innate immunity and tautomerization of D-dopachrome in mammalian species.

Elevated levels of macrophage migration inhibitory factor in women with metabolic syndrome

Metabolic syndrome is a complex clinical disorder characterized by obesity, a disturbance of glucose metabolism, dyslipidemia, and hypertension, leading to increased cardiovascular risk. Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine produced both by innate immune cells and by adipocytes, and it plays an important role in inflammatory and cardiovascular diseases. The goal of this study was to evaluate the expression of circulating MIF in patients with metabolic syndrome. A study was conducted involving 172 persons who attended the Jeju National University Hospital Health Promotion Center. Among the 172 subjects, 88 patients with metabolic syndrome and 84 healthy control subjects were included. Serum MIF levels were considerably higher in patients with metabolic syndrome than in healthy subjects (mean±SEM, 1413.0-pg/ml±102.6 vs. 1077.0-pg/ml±-91.3, p=0.016). Among the metabolic syndrome patients, MIF levels were significantly increased in women (1403.0-pg/ml±114.2 vs. 921.3 pg/ml±117.3, p=0.005), but not in men. Even after further linear regression adjustment for age and body mass index, the expression of MIF for women with metabolic syndrome was still clearly elevated when compared to healthy subjects (p=0.011). Circulating MIF concentrations showed a gender disparity between healthy and metabolic syndrome subjects. An elevation of systemic MIF in women with metabolic syndrome may contribute to pathogenesis of metabolic syndrome or to the development of metabolic syndrome-related diseases, such as atherosclerosis and type 2 diabetes mellitus.

Macrophage migration inhibitory factor (MIF) gene polymorphisms are associated with increased prostate cancer incidence

Recurrent or persistent inflammation has emerged as an important factor in cancer development. Overexpression of macrophage migration inhibitory factor (MIF), an upstream regulator of innate immunity with pleiotropic effects on cell proliferation, has been implicated in prostate cancer (CaP). Two polymorphisms in the promoter of the MIF gene (-173G to C transition and seven copies of the -794 CATT repeat) are associated with increased MIF expression in vivo and poor prognosis in autoimmune diseases. We conducted a retrospective analysis of 131 CaP patients and 128 controls from a group of Veterans' Administration patients undergoing routine prostate-specific antigen screening. Patients with CaP were enrolled regardless of treatment. Inclusion criteria for the control group were absence of documented diagnosis of cancer and/or chronic inflammation within patient computerized records. Logistic regression demonstrated a significant association between CaP and the -173G/C, the -173C/C and the -794 7-CATT MIF polymorphisms (P<0.001). Patients with the -794 7-CATT allele had an increased risk of CaP recurrence at 5 years. Individuals with -173G/C, -173C/C and -794 7-CATT MIF genotypes have an increased incidence of CaP and these genotypes may serve as an independent marker for cancer recurrence.

Macrophage migration inhibitory factor (MIF) promotes cell survival by activation of the Akt pathway and role for CSN5/JAB1 in the control of autocrine MIF activity

The phosphoinositide-3-kinase (PI3K)/Akt signaling pathway plays an important role in cell survival and the development of cancer. Macrophage migration inhibitory factor (MIF) is a critical inflammatory cytokine that was recently associated with tumorigenesis and that potently inhibits apoptosis. This may involve inhibition of p53-dependent genes, but the initiating molecular mechanism of how MIF controls survival/apoptosis is unknown. Here, we show that MIF prevents apoptosis and promotes tumor cell survival by directly activating the Akt pathway. MIF enhanced Akt activity in primary and immortalized fibroblasts (MEF and NIH/3T3), HeLa cervix carcinoma cells and various breast cancer cell lines. Activation was abolished by kinase inhibitors Ly294002 and PP2 and in Src/Yes/Fyn(SYF)(-/-) and CD74(-/-)(MEFs), while being enhanced in CD74-overexpressing MEFs, demonstrating that the MIF-induced Akt pathway encompasses signaling through the MIF receptor CD74 and the upstream kinases Src and PI3K. Akt was activated by exogenous rMIF and autocrine MIF action, as revealed by experiments in MIF(-/-)MEFs and antibody blockade. siRNA knockdown of CSN5/JAB1, a tumor marker and MIF-binding protein, showed that JAB1 controls autocrine MIF-mediated Akt signaling by inhibition of MIF secretion. Akt activation by MIF led to phosphorylation of the proapoptotic proteins BAD and Foxo3a. Apoptosis inhibition by MIF was functionally associated with Akt activation as it was abolished by overexpression of the Akt pathway inhibitor PTEN and occurred independently of p53. This was shown by studying DNA damage-induced apoptosis in fibroblasts, the Fas death pathway in HeLa cells that do not express functional p53, and etoposide-induced apoptosis in breast carcinoma cells expressing mutant p53. Importantly, dependence of breast cancer cell survival on MIF correlated with Akt activation and the PTEN status of these cells. Thus, MIF can directly promote cell survival through activation of the PI3K/Akt pathway and this effect is critical for tumor cell survival.

Association between serum levels of soluble receptor for advanced glycation end products and circulating advanced glycation end products in type 2 diabetes

AIMS/HYPOTHESIS

Activation of the receptor for advanced glycation end products (RAGE, also known as AGE-specific receptor [AGER]) has been implicated in the development of diabetic vascular complications. Blockade of RAGE using a soluble form of the receptor (sRAGE) suppressed vascular hyperpermeability and atherosclerosis in animal models. Since little is known about the regulation of endogenous sRAGE levels, we determined whether serum sRAGE is influenced by circulating AGEs and the severity of nephropathy in type 2 diabetic patients.

MATERIALS AND METHODS

We recruited 150 healthy control and 318 diabetic subjects. Diabetic subjects were subdivided into those with proteinuria, microalbuminuria or normoalbuminuria. Serum sRAGE was assayed by ELISA and serum AGEs by competitive ELISA using a polyclonal rabbit antiserum raised against AGE-RNase.

RESULTS

Diabetic subjects had higher sRAGE (1,029.5 pg/ml [766.1-1,423.0] interquartile range vs 1,002.6 [726.5-1,345.3], p<0.05) and AGEs (4.07+/-1.13, SD, unit/ml vs 3.39+/-1.05, p<0.01) than controls. Proteinuric subjects had the highest sRAGE levels and there was a significant trend between the severity of nephropathy and sRAGE (p=0.01). In diabetic subjects, serum log(sRAGE) correlated with AGEs (r=0.27, p<0.001), log(plasma creatinine) (r=0.31, p<0.001), log(urine AER) (r=0.24, p<0.01) and log(triglycerides) (r=0.15, p<0.01). On stepwise linear regression analysis, AGEs and creatinine levels were the main independent determinants of sRAGE concentration.

CONCLUSIONS/INTERPRETATION

Serum sRAGE levels and circulating AGEs are associated with the severity of nephropathy in type 2 diabetic patients. Prospective studies are required to determine whether endogenous sRAGE potentially influences the development of diabetic vascular complications.

Ras transformation requires metabolic control by 6-phosphofructo-2-kinase

Neoplastic cells transport large amounts of glucose in order to produce anabolic precursors and energy within the inhospitable environment of a tumor. The ras signaling pathway is activated in several cancers and has been found to stimulate glycolytic flux to lactate. Glycolysis is regulated by ras via the activity of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatases (PFK2/FBPase), which modulate the intracellular concentration of the allosteric glycolytic activator, fructose-2,6-bisphosphate (F2,6BP). We report herein that sequential immortalization and ras-transformation of mouse fibroblasts or human bronchial epithelial cells paradoxically decreases the intracellular concentration of F2,6BP. This marked reduction in the intracellular concentration of F2,6BP sensitizes transformed cells to the antimetabolic effects of PFK2/FBPase inhibition. Moreover, despite co-expression of all four mRNA species (PFKFB1-4), heterozygotic genomic deletion of the inducible PFKFB3 gene in ras-transformed mouse lung fibroblasts suppresses F2,6BP production, glycolytic flux to lactate, and growth as soft agar colonies or tumors in athymic mice. These data indicate that the PFKFB3 protein product may serve as an essential downstream metabolic mediator of oncogenic ras, and we propose that pharmacologic inhibition of this enzyme should selectively suppress the high rate of glycolysis and growth by cancer cells.

Role for macrophage migration inhibitory factor in asthma

Macrophage migration inhibitory factor (MIF) is an immunologic regulator that is expressed in inflammatory and autoimmune disorders. We investigated MIF's role in asthma using genetic approaches in a mouse model and in a cohort of asthma patients. Mice genetically deficient in MIF that were primed and aerosol-challenged with ovalbumin showed less pulmonary inflammation and lower airway hyperresponsiveness than genetically matched, wild-type controls. MIF deficiency also resulted in lower titers of specific IgE, IgG(1), and IgG(2a), and decreased pulmonary, T(H)2 cytokine levels. IL-5 concentrations were lower and corresponded to decreased eosinophil numbers in bronchoalveolar lavage fluid. T cell studies also showed a lower level of antigen-specific responses in MIF-KO versus wild-type mice. In an analysis of 151 white patients with mild, moderate, or severe asthma (Global Initiative for Asthma criteria), a significant association was found between mild asthma and the low-expression, 5-CATT MIF allele. Pharmacologic inhibition of MIF may be beneficial and could be guided by the MIF genotype of affected individuals.

The p53-dependent effects of macrophage migration inhibitory factor revealed by gene targeting

Macrophage migration inhibitory factor (MIF) is a mediator of host immunity and functions as a high, upstream activator of cells within the innate and the adaptive immunological systems. Recent studies have suggested a potentially broader role for MIF in growth regulation because of its ability to antagonize p53-mediated gene activation and apoptosis. To better understand MIF's activity in growth control, we generated and characterized a strain of MIF-knockout (MIF-KO) mice in the inbred, C57BL/6 background. Embryonic fibroblasts from MIF-KO mice exhibit p53-dependent growth alterations, increased p53 transcriptional activity, and resistance to ras-mediated transformation. Concurrent deletion of the p53 gene in vivo reversed the observed phenotype of cells deficient in MIF. In vivo studies showed that fibrosarcomas induced by the carcinogen benzo[alpha]pyrene are smaller in size and have a lower mitotic index in MIF-KO mice relative to their WT counterparts. The data provide direct genetic evidence for a functional link between MIF and the p53 tumor suppressor and indicate an important and previously unappreciated role for MIF in carcinogenesis.

Macrophage migration inhibitory factor expression is increased in pituitary adenoma cell nuclei

Macrophage migration inhibitory factor (MIF) is an essential regulator of the macrophage responses to endotoxin. MIF also has the ability to override the anti-inflammatory actions of glucocorticoids during an immune response, and is thus an important pro-inflammatory factor. The presence of MIF in cells of the anterior pituitary has been described, and high levels of MIF in other rapidly proliferating tIssues have also been demonstrated. It has been hypothesised that MIF release from these cells is influenced by the hypothalamo-pituitary-adrenal axis, and that ACTH and MIF are released simultaneously to exert counter-regulatory effects on cortisol. However, another intracellular role for MIF has also been suggested as it has been shown that MIF exerts an effect on the inhibitory cell cycle control protein p27 through an interaction with Jab1, a protein implicated in p27 degradation. We studied MIF expression in different normal and adenomatous human pituitary samples using immunohistochemistry and RT-PCR. There was evidence of co-immunoprecipitation of MIF with Jab1, suggesting an interaction of the two proteins. Our results showed that there is increased expression of MIF protein in the nuclei of all pituitary adenomas compared with normal tIssue (P=0.0067), but there was no statistically significant difference in nuclear MIF expression between the different adenoma types. Nuclear MIF expression correlated positively with p27 and its phosphorylated form in normal tIssue (P=0.0028 and P<0.0001); however, this relationship was not seen in the adenoma samples. Cytoplasmic expression of MIF was found to be variable both in normal and adenomatous samples, with no consistent pattern. MIF mRNA was demonstrated to be present in all tumour and normal samples studied. Somatotroph tumours showed higher MIF mRNA expression compared with normal pituitary or other types of adenomas. In conclusion, MIF is expressed in cell nuclei in pituitary adenomas to a greater extent than in normal pituitary tIssue. We speculate that it may play a role in the control of the cell cycle, but whether its higher level in adenomas is a cause or a consequence of the tumorigenic process remains to be clarified.

Macrophage migratory inhibitory factor (MIF) expression in acute graft-versus-host disease (GVHD) in allogeneic hemopoietic stem cell transplant recipients

Graft-versus-host disease (GVHD) is a major complication after hemopoietic stem cell transplantation (HSCT), but its pathogenesis remains uncertain. Macrophage migratory inhibitory factor (MIF) is an important mediator in the allo-immune reaction during renal transplantation, yet its role in hemopoietic stem cell transplantation (HSCT) remains unexplored. This study investigated the potential role of MIF in acute graft-versus-host disease (aGVHD) following allogeneic HSCT. Forty-six randomly selected patients undergoing autologous or allogeneic HSCT were studied. Immunohistochemistry and in situ hybridization were performed to examine tissue MIF mRNA and protein expression on skin and colonic biopsy specimens. The associated T cell and macrophage activation was also studied by immunohistochemical studies. A semi-quantitative method was used to assess MIF staining, as well as T cell and macrophage staining. Serial blood samples were analyzed by ELISA for serum MIF levels. Immunohistochemistry and in situ hybridization performed in 15 skin and 19 colonic biopsies from 17 patients who developed moderate to severe aGVHD showed a significant increase in MIF mRNA and protein expression compared with normal controls (seven skin and five colonic biopsies). MIF was localized within the epidermis and the vascular area of skin, but diffusely expressed in the entire thickness of colon. Macrophage and T lymphocyte infiltration was confined to areas of strong MIF expression. Serial analysis by ELISA showed that only patients who developed aGVHD (n = 19) exhibited an increase (two- to three-fold) in serum MIF during HSCT, but not in the allogeneic HSCT recipients without aGVHD (n = 7) or those who received autologous HSCT (n = 8). In 14 out of 19 patients, serum MIF peaked before the onset of aGVHD. Local and systemic up-regulation of MIF expression is associated with the occurrence of acute GVHD. Its pathogenetic role remains to be further determined.

A role for peripheral blood fibrocytes in Lyme disease?

It is proposed that peripheral blood fibrocytes will be a new and important player in the pathogenesis of Lyme disease. Peripheral blood fibrocytes are a circulating leukocyte subpopulation that: (a) express collagen; (b) are an abundant source of cytokines, chemoattractants and growth factors; and (c) are able to recruit and activate naive T-cells and memory T-cells. We predict that peripheral blood fibrocytes will represent a new and important antigen-presenting cell which will play an important role in directing the immune response from the pathogenic Th1 to the protective Th2 response cell in Borrelia infections.

A functional promoter polymorphism in the macrophage migration inhibitory factor (MIF) gene associated with disease severity in rheumatoid arthritis

The macrophage migration inhibitory factor (MIF) is a potent pro-inflammatory cytokine and regulates the anti-inflammator effects of glucocorticoids. An important role for MIF within the cytokine cascade is to act in concert with endogenous glucocorticoids to control the set-point and magnitude of the inflammatory response. Elevated expression of MIF in the circulation and in the synovial joint has been documented in rheumatoid arthritis. MIF also has been linked to the development of joint damage and disease pathology in experimental animal models. We describe herein a novel CATT-tetranucleotide repeat polymorphism at position -794 of the human Mif gene and show that it functionally affects the activity of the MIF promoter in gene reporter assays. We describe four genotypes which comprise 5, 6, 7, or 8-CATT repeat units and show that the 5-CATT allele has the lowest level of basal and stimulated MIF promoter activity in vitro. The presence of the low expressing, 5-CATT repeat allele correlated with low disease severity in a cohort of rheumatoid arthritis patients.

Macrophage migration inhibitory factor in rheumatoid arthritis: clinical correlations

OBJECTIVE

Cytokines play an important role in the pathology of rheumatoid arthritis (RA). Macrophage migration inhibitory factor (MIF) is a cytokine with a broad spectrum of actions, including induction of monocyte tumour necrosis factor alpha (TNF-alpha). Evidence of the expression and proinflammatory activity of MIF has recently been demonstrated in RA synovium and in animal models of RA. We wished to assess the relationship between MIF expression in synovium and clinical disease.

METHODS

Computer-assisted analysis of the cytokine content of arthroscopically obtained biopsies of RA synovium, using paired samples from eight patients with active and inactive/treated disease, was compared with documented clinical parameters.

RESULTS

Synovial MIF immunostaining correlated strongly with disease activity as measured by CRP concentration. Reductions in clinical disease parameters, including CRP, tender and swollen joint counts, were accompanied by significant reductions in synovial MIF. Synovial TNF-alpha, transforming growth factor beta (TGF-beta) and interleukin (IL) 10 also showed a significant reduction in association with reduced disease activity, while IL-1 beta and IL-1 receptor agonist did not.

CONCLUSION

The correlation of synovial MIF with disease activity corroborates existing evidence of the role of this cytokine in RA. The demonstration that only MIF and TNF-alpha show significant variation in synovial cytokine content with clinical remission suggests that MIF is an important member of the cytokine hierarchy in RA.

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.

Immunological detection of a novel advanced glycation end-product

BACKGROUND

The advanced stage of the Maillard reaction that leads to the formation of advanced glycation end-products (AGEs) plays an important role in the pathogenesis of angiopathy in diabetic patients and in the aging process. Recently, it has been proposed that the intermediates contributing to AGE formation include dicarbonyl intermediates such as glyoxal, methylglyoxal, and 3-deoxyglucosone (3-DG). In the present study, we developed a novel, non-carboxymethyllysine (CML) anti-AGE antibody that recognizes serum proteins and peptides modified by 3-DG in vivo.

MATERIALS AND METHODS

AGE-modified serum albumins were prepared by incubation of rabbit serum albumin with 3-DG or D-glucose. After immunization of rabbits, anti-AGE antisera were subjected to affinity chromatography on a Sepharose 4B column coupled with CML-BSA, or AGE-BSA created by incubation with 3-DG (AGE-6) or D-glucose (AGE-1). The AGE-Ab-6 and AGE-Ab-1 thus obtained was used to investigate AGEs in serum from diabetic patients on hemodialysis.

RESULTS

Characterization of the novel AGE-Ab-6 obtained by immunoaffinity chromatography was performed with a competitive ELISA and immunoblot analysis. This antibody specifically cross-reacted with proteins modified by 3-DG. AGE-6 was detected in diabetic serum as three peaks with apparent molecular weights of 200, 1.15, and 0.85 kD, while AGE-1 was detected as four peaks with apparent molecular weights of 200, 65, 1.15, and 0.85 kD.

CONCLUSION

This study provides new data on the pathways of AGE formation from 3-DG and methods for the immunochemical detection of AGEs. We also provide immunochemical evidence for the existence of six distinct AGEs in vivo among the AGE-modified proteins and peptides in the serum of diabetic patients on hemodialysis.

Fibrocytes induce an angiogenic phenotype in cultured endothelial cells and promote angiogenesis in vivo

Angiogenesis is an ordered process requiring the inter-play of numerous cellular and humoral factors. Studies over the past 20 years have identified several growth factors, cytokines, and enzymes that promote blood vessel formation. Most have revealed how individual factors promote an angiogenic phenotype in endothelial cells in vitro or contribute to blood vessel formation in vivo. However, the fundamental question that remains unanswered is how the cellular microenvironment contributes to angiogenesis. Fibrocytes are a recently characterized mesenchymal cell type isolated from peripheral blood that rapidly enter subcutaneously implanted wound chambers and sites of tissue injury. Here we describe the induction of an angiogenic phenotype in microvascular endothelial cells in vitro and promotion of angiogenesis in vivo by cultured fibrocytes. Fibrocytes constitutively secrete extracellular matrix-degrading enzymes, primarily matrix metalloproteinase 9, which promotes endothelial cell invasion. In addition, fibrocytes secrete several proangiogenic factors including VEGF, bFGF, IL-8, PDGF, and hematopoietic growth factors that promote endothelial cell migration, proliferation, and/or tube formation. By contrast, they do not produce representative antiangiogenic factors. Finally, both autologous fibrocytes and fibrocyte-conditioned media were found to induce blood vessel formation in vivo using the Matrigel angiogenesis model.

Characterization of a novel hemoglobin-glutathione adduct that is elevated in diabetic patients

BACKGROUND

Typically, a diagnosis of diabetes mellitus is based on elevated circulating blood glucose levels. In an attempt to discover additional markers for the disease and predictors of prognosis, we undertook the characterization of HbA1d3 in diabetic and normal patients.

MATERIAL AND METHODS

PolyCAT A cation exchange chromatography and liquid chromatography-mass spectroscopy was utilized to separate the alpha- and beta-globin chains of HbA1d3 and characterize their presence in normal and diabetic patients.

RESULTS

We report the characterization of HbA1d3 as a glutathionylated, minor hemoglobin subfraction that occurs in higher levels in diabetic patients (2.26 +/- 0.29%) than in normal individuals (1.21 +/- 0.14%, p < 0.001). The alpha-chain spectrum displayed a molecular ion of m/z 15126 Da, which is consistent with the predicted native mass of the HbA0 alpha-globin chain. By contrast, the mass spectrum of the beta-chain showed a mass excess of 307 Da (m/z = 16173 Da) versus that of the native HbA0 beta-globin chain (m/z = 15866 Da). The native molecular weight of the modified beta-globin chain HbA0 was regenerated by treatment of HbA1d3 with dithiothreitol, consistent with a glutathionylated adduct.

CONCLUSIONS

We propose that HbA1d3 (HbSSG) forms normally in vivo, and may provide a useful marker of oxidative stress in diabetes mellitus and potentially other pathologic situations.

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.

Mechanisms for modulating TNF alpha in immune and inflammatory disease

The development of tumor necrosis factor-alpha (TNF alpha) inhibitors has been one of the most active areas of drug development over the last ten years for the treatment of inflammatory diseases. Following the definition of TNF alpha as a key mediator of inflammatory disease and the success demonstrated by various anti-TNF alpha strategies in the treatment of rheumatoid arthritis and inflammatory bowel disease, many investigators have sought to refine mechanisms by which to modulate TNF alpha in vivo. Many advances are presently being made in the understanding of how TNF alpha production is regulated, and with this knowledge comes the identification of new targets and pathways for therapeutic intervention. Here, we review the development of the currently available therapeutics and the progressive steps that are being made to improve clinical efficacy of anti-TNF alpha strategies.

Identification and characterization of a homologue of the pro-inflammatory cytokine Macrophage Migration Inhibitory Factor in the tick, Amblyomma americanum

Studying tick feeding and digestion, we discovered in a cDNA library from partially fed Amblyomma americanum ticks the first known arthropod homologue of a human cytokine, the pro-inflammatory Macrophage Migration Inhibitory Factor (MIF). The tick origin of the MIF cDNA clone was confirmed by sequencing a genomic fragment that contained the full-length tick MIF gene with two introns. Antiserum to a tick MIF-specific peptide as well as antiserum to complete tick MIF revealed the expression of tick MIF in the salivary gland and midgut tissues of A. americanum ticks. In an in vitro functional assay, recombinant tick MIF inhibited the migration of human macrophages to the same extent that recombinant human MIF did.

Neuroendocrine properties of macrophage migration inhibitory factor (MIF)

The cytokine macrophage migration inhibitory factor (MIF) is produced by neuroendocrine and immune tissues and possesses several features that allow it to be characterized as a neuroendocrine mediator. Its pro-inflammatory action and its pathogenic role in inflammatory diseases, such as septic shock, arthritis and other diseases, have clearly been demonstrated and may be based in part on neuroendocrine mechanisms. Macrophage migration inhibitory factor possesses glucocorticoid-antagonist properties within the immune system and participates in the regulation of several endocrine circuits. This review summarizes the current state of MIF research and focuses on MIF expression and function in nervous and endocrine tissues.

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.

Peripheral blood fibrocytes: differentiation pathway and migration to wound sites

Fibrocytes are a distinct population of blood-borne cells that display a unique cell surface phenotype (collagen I+/CD11b+/CD13+/CD34+/CD45RO+/MHC class II+/CD86+) and exhibit potent immunostimulatory activities. Circulating fibrocytes rapidly enter sites of tissue injury, suggesting an important role for these cells in wound repair. However, the regulatory processes that govern the differentiation of blood-borne fibrocytes and the mechanisms that underlie the migration of these cells to wound sites are currently not known. We report herein that ex vivo cultured fibrocytes can differentiate from a CD14+-enriched mononuclear cell population and that this process requires contact with T cells. Furthermore, we demonstrate that TGF-beta1 (1-10 ng/ml), an important fibrogenic and growth-regulating cytokine involved in wound healing, increases the differentiation and functional activity of cultured fibrocytes. Because fibrocytes home to sites of tissue injury, we examined the role of chemokine/chemokine receptor interactions in fibrocyte trafficking. We show that secondary lymphoid chemokine, a ligand of the CCR7 chemokine receptor, acts as a potent stimulus for fibrocyte chemotaxis in vitro and for the homing of injected fibrocytes to sites of cutaneous tissue injury in vivo. Finally, we demonstrate that differentiated, cultured fibrocytes express alpha smooth muscle actin and contract collagen gels in vitro, two characteristic features of wound-healing myofibroblasts. These data provide important insight into the control of fibrocyte differentiation and trafficking during tissue repair and significantly expand their potential role during wound healing.

Role of macrophage migration inhibitory factor (MIF) in murine antigen-induced arthritis: interaction with glucocorticoids

(MIF) is a broad-spectrum proinflammatory cytokine implicated in human rheumatoid arthritis. The synthesis of MIF by synovial cells is stimulated by glucocorticoids, and previous studies suggest that MIF antagonizes the anti-inflammatory effects of glucocorticoids. This has not been established in a model of arthritis. We wished to test the hypothesis that MIF can act to reverse the anti-inflammatory effects of glucocorticoids in murine antigen-induced arthritis (AIA). Cutaneous DTH reactions and AIA were induced by intradermal injection and intra-articular injection, respectively, of methylated bovine serum albumin in presensitized mice. Animals were treated with anti-MIF MoAbs, recombinant MIF, and/or dexamethasone (DEX). Skin thickness of DTH reactions was measured with callipers and arthritis severity was measured by blinded quantitative histological assessment of synovial cellularity. Cutaneous DTH to the disease-initiating antigen was significantly inhibited by anti-MIF MoAb treatment (P < 0.001). AIA was also significantly inhibited by anti-MIF MoAb (P < 0.02). DEX treatment induced a dose-dependent inhibition of AIA, which was significant at 0.2 mg/kg (P < 0.05). MIF treatment reversed the effect of therapeutic DEX on AIA (P < 0.001). DEX also significantly inhibited DTH reactions (P < 0.05) but rMIF had no effect on this effect of DEX. DTH and AIA are MIF-dependent models of inflammation and arthritis. The reversal of glucocorticoid suppression of AIA by MIF supports the concept that MIF is a counter-regulator of glucocorticoid control of synovial inflammation. Although DTH was observed to be MIF-dependent and glucocorticoid-sensitive, rMIF had no reversing effect on the suppression of DTH by glucocorticoids. This suggests that inflammatory processes in specific tissues may respond differently to MIF in the presence of glucocorticoids.

Regulation of the CTL response by macrophage migration inhibitory factor

Macrophage migration inhibitory factor (MIF) has been shown to be a pivotal cytokine that mediates host inflammatory and immune responses. Recently, immunoneutralization of MIF has been found to inhibit tumor growth in mice; however, the contributing mechanisms underlying this effect have not been well defined. We investigated whether MIF plays a regulatory role in the expression of CTL activity. In a mouse model of the CTL response using the OVA-transfected tumor cell line EL4 (EG.7), we found that cultures of splenocytes obtained from EG.7-primed mice secrete high levels of MIF following Ag stimulation in vitro. Notably, parallel splenocyte cultures treated with neutralizing anti-MIF mAb showed a significant increase in the CTL response directed against EG.7 cells compared with control mAb-treated cultures. This effect was accompanied by elevated expression of IFN-gamma. Histological examination of the EG. 7 tumors from anti-MIF-treated animals showed a prominent increase in both CD4(+) and CD8(+) T cells as well as apoptotic tumor cells, consistent with the observed augmentation of CTL activity in vivo by anti-MIF. This increased CTL activity was associated with enhanced expression of the common gamma(c)-chain of the IL-2R that mediates CD8(+) T cell survival. Finally, CD8(+) T lymphocytes obtained from the spleens of anti-MIF-treated EG.7 tumor-bearing mice, when transferred into recipient tumor-bearing mice, showed increased accumulation in the tumor tissue. These data provide the first evidence of an important role for MIF in the regulation and trafficking of anti-tumor T lymphocytes in vivo.

Purification and characterization of macrophage migration inhibitory factor as a secretory protein from rat epididymis: evidences for alternative release and transfer to spermatozoa

BACKGROUND

The cytokine macrophage migration inhibitory factor (MIF), originally described as a T cell product, has recently been identified to mediate cellular interactions in several endocrine organs. Western blots analysis of rat epididymal homogenates using an anti-MIF antibody indicated the presence of substantial amounts of an immunoreactive protein with the apparent Mr of 12 kDa. Our study aimed to characterize the molecular nature of this immunoreactive factor.

MATERIALS AND METHODS

The purified 12 kDa protein and a cloned cDNA fragment were characterized by sequence analysis. Furthermore, expression pattern and localization of the 12 kDa protein were investigated using in situ hybridization, immunohistochemistry, immunoelectron microscopy, and western blots experiments on epididymal sections, isolated epididymal vesicles, and outer dense fibers from spermatozoa.

RESULTS

The N-terminal amino acid sequence analysis over 10 amino acids revealed a 100% homology of the 12 kDa protein to the N-terminus of the cytokine MIF. These data were confirmed by sequence analysis of a reverse transcription polymerase chain reaction (RT-PCR) amplified cDNA fragment from rat epididymis, which also showed complete homology to the MIF cDNA sequence. MIF protein and mRNA were localized in the epithelial cells of the epididymis in a regional distribution manner, with the expression maximal in the caput. Immune cells were not labeled. MIF is the first classical cytokine identified to be expressed by the epididymal epithelial cells. Immunoelectron microscopy detected MIF immunoreactivity in the cytoplasm, with no reaction visible in the Golgi complex and the cisternae of the endoplasmic reticulum. At the apical cell surface, MIF accumulated in stereocilia and vesicles that were pinched off from the plasma membrane. MIF detection in vesicles isolated from epididymal secretion together with the lack of a N-terminal signal sequence for translocation in the endoplasmic reticulum strongly suggested a nonclassical secretion mode. Furthermore, MIF was identified as a new component of the outer dense fibers (ODF), a cytoskeletal element of the mid- and principal piece of the sperm tail.

CONCLUSION

The cytokine MIF was identified in substantial amounts in the epithelial cells of rat epididymis and in the outer dense fibers of rat epididymal spermatozoa. Our results indicate a nonclassical secretion mode for MIF and suggest a cell-to-cell transfer of MIF via vesicles to the sperm cells.

De novo expression of macrophage migration inhibitory factor in atherogenesis in rabbits

Macrophage migration inhibitory factor (MIF) has been shown to play an important role in macrophage-mediated diseases. We investigate the potential role of MIF in atherogenesis using a hypercholesterolemic rabbit model. New Zealand White rabbits fed with a 2% cholesterol diet developed hypercholesterolemia and early fatty streaks at 1 month. The lesions became advanced at 3 months and were associated with de novo MIF expression by vascular endothelial cells (VECs) and smooth muscle cells (SMCs), as demonstrated by immunohistochemistry, reverse transcriptase-polymerase chain reaction, and in situ hybridization. By contrast, there was no increase in MIF levels in rabbits fed a normal diet. In early atherogenesis, marked upregulation of MIF mRNA and protein by VECs and some intimal cells were closely associated with CD68(+) monocyte adhesion onto and subsequent migration into subendothelial space. Of significance, the accumulation of macrophages was exclusively localized to areas of strong MIF expression, which may be associated with the macrophage-rich fatty streak lesion formation. Upregulation of MIF by SMCs is transient during atherogenesis. Importantly, strong MIF expression by activated macrophages may be responsible for the development of foam cell-rich lesions. Finally, the ability of MIF to induce intercellular adhesion molecule-1 expression by VECs implicates its pathogenic role in atherogenesis. In conclusion, the present study provides the first demonstration that MIF is markedly upregulated during atherogenesis. Upregulation of MIF by VECs and SMCs may play a role in macrophage adhesion, transendothelial migration, accumulation, and, importantly, transformation into foam cells. Furthermore, strong MIF expression by macrophages may both initiate and amplify the atherogenesis process.

Peripheral blood fibrocytes: mesenchymal precursor cells and the pathogenesis of fibrosis

Peripheral blood fibrocytes are a novel population of cells that rapidly enter sites of tissue injury and contribute to connective scar formation. Fibrocytes display a distinct cell surface phenotype (CD34+/CD45+/collagen I+), and are an abundant source of cytokines and growth factors that function to attract and activate inflammatory and connective tissue cells. Fibrocytes also are specialized to activate naïve T cells against foreign antigen, and may play a critical role in the initiation of cognate immunity during the earliest phases of tissue injury. Recently, immunohistochemical studies of fibrotic tissues have shown that fibrocytes co-localize to areas of connective tissue matrix deposition. Peripheral blood fibrocytes thus may participate in the generation of excessive fibroses associated with various autoimmune disorders involving a persistent T-cell activation, as occurs in scleroderma.

Neurotoxicity of advanced glycation end-products for cultured cortical neurons

The Maillard reaction that leads to the formation of advanced glycation end-products (AGEs) plays an important role in the pathogenesis of angiopathy in diabetic patients and in aging. AGEs are believed also to contribute to the pathology of Alzheimer disease (AD) and other neurodegenerative processes. Incubation of cortical neurons with 5 immunochemically distinct AGEs, designated AGEs-1 to -5, produced a dose-dependent increase in neuronal cell-death, as assessed by MTT assay, Trypan blue and Hoechst 33258 staining. The structural epitope designated AGE-2 was found to have the greatest cytopathic effect and the neurotoxicity of AGE-2 was neutralized by the addition of an anti-AGE-2-specific antibody, but not by other types of anti-AGE antibodies. Distinct classes of AGE structures also have been established to circulate in the blood of individuals with diabetes mellitus and end-stage renal disease treated by hemodialysis (DM-HD). We fractionated serum from normal control and DM-HD patients by gel filtration and identified 2 fractions that contained AGE epitopes-1 to -5 and as well as the defined AGE structure carboxymethyllysine (CML). The addition of these 2 fractions led to the death of cultured neuronal cells and this cytotoxic effect was completely prevented by the addition of the anti-AGE-2-specific antibody. We propose that the structural epitope AGE-2 is an important toxic moiety for neuronal cells.

The proinflammatory mediator macrophage migration inhibitory factor induces glucose catabolism in muscle

Severe infection or tissue invasion can provoke a catabolic response, leading to severe metabolic derangement, cachexia, and even death. Macrophage migration inhibitory factor (MIF) is an important regulator of the host response to infection. Released by various immune cells and by the anterior pituitary gland, MIF plays a critical role in the systemic inflammatory response by counterregulating the inhibitory effect of glucocorticoids on immune-cell activation and proinflammatory cytokine production. We describe herein an unexpected role for MIF in the regulation of glycolysis. The addition of MIF to differentiated L6 rat myotubes increased synthesis of fructose 2,6-bisphosphate (F2,6BP), a positive allosteric regulator of glycolysis. Increased expression of the enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2) enhanced F2,6BP production and, consequently, cellular lactate production. The catabolic effect of TNF-alpha on myotubes was mediated by MIF, which served as an autocrine stimulus for F2, 6BP production. TNF-alpha administered to mice decreased serum glucose levels and increased muscle F2,6BP levels; pretreatment with a neutralizing anti-MIF mAb completely inhibited these effects. Anti-MIF also prevented hypoglycemia and increased muscle F2,6BP levels in TNF-alpha-knockout mice that were administered LPS, supporting the intrinsic contribution of MIF to these inflammation-induced metabolic changes. Taken together with the recent finding that MIF is a positive, autocrine stimulator of insulin release, these data suggest an important role for MIF in the control of host glucose disposal and carbohydrate metabolism.