Since its activity was first reported in the mid-1960s, macrophage migration inhibitory factor (MIF) has gone from a cytokine activity modulating monocyte motility to a pleiotropic regulator of a vast array of cellular and biological processes. Studies in recent years suggest that MIF contributes to malignant disease progression on several different levels. Both circulating and intracellular MIF protein levels are elevated in cancer patients and MIF expression reportedly correlates with stage, metastatic spread and disease-free survival. Additionally, MIF expression positively correlates with angiogenic growth factor expression, microvessel density and tumor-associated neovascularization. Not coincidentally, MIF has recently been shown to contribute to tumoral hypoxic adaptation by promoting hypoxia-induced HIF-1alpha stabilization. Intriguingly, hypoxia is a strong regulator of MIF expression and secretion, suggesting that hypoxia-induced MIF acts as an amplifying factor for both hypoxia and normoxia-associated angiogenic growth factor expression in human malignancies. Combined, these findings suggest that MIF overexpression contributes to tumoral hypoxic adaptation and, by extension, therapeutic responsiveness and disease prognosis. This review summarizes recent literature on the contributions of MIF to tumor-associated angiogenic growth factor expression, neovascularization and hypoxic adaptation. We also will review recent efforts aimed at identifying and employing small-molecule antagonists of MIF as a novel approach to cancer therapeutics.

The rickettsial organism, Coxiella burnetii, is readily phagocytized by macrophages maintained in vitro. This phagocytosis does not lead to destruction of the organism but rather to intracellular multiplication within the macrophage. Specific antiserum added to the macrophage culture before or after infection, or reacted directly with C. burnetii organisms, fails to control subsequent intracellular replication. Macrophage cultures can be treated with lymphocyte products so that intracellular multiplication by C. burnetii is resisted. These lymphocyte products can be obtained from the culture supernatants of sensitized lymphocytes and antigens or from culture supernatants of Concanavalin A and normal lymphocytes. The activation activity of the lymphocyte supernatants paralleled their content of MIF.

The cytokine macrophage migration inhibitory factor (MIF) participates in fundamental events in innate and adaptive immunity. The profile of activities of MIF in vivo and in vitro is strongly suggestive of a role for MIF in the pathogenesis of many inflammatory diseases, including rheumatoid arthritis (RA), and hence antagonism of MIF is suggested as a potential therapeutic strategy in inflammatory disease. The best developed case for therapeutic antagonism of MIF is in RA. In RA, MIF is abundantly expressed in serum and synovial tissue. MIF induces synovial expression of key pro-inflammatory genes, regulates the function of endothelial cells and leucocytes, and is implicated in the control of synoviocyte proliferation and apoptosis via direct effects on the expression of the tumour suppressor protein p53. In animal models of RA, anti-MIF antibodies or genetic MIF deficiency are associated with significant inhibition of disease. A similar case has been made, for example using MIF-deficient mice, in models of atheroma, colitis, multiple sclerosis and other inflammatory diseases. The relationship with p53 also means MIF may be important in the link between inflammatory disease and cancer, such as is seen in RA or colitis. MIF also has a unique relationship with glucocorticoids, in that despite antagonizing their effects, the expression of MIF is in fact induced by glucocorticoids. Thus, MIF functions as a physiological counter-regulator of the anti-inflammatory effects of glucocorticoids. This may be entrained by selective activation of mitogen-activated protein kinases rather than nuclear factor kappa B. Therapeutic MIF antagonism may therefore provide a specific means of 'steroid sparing'. Exploitation of antibody, soluble receptor or small molecule technologies may soon lead to the ability to test in the clinic the importance of MIF in human inflammatory diseases.

OBJECTIVE

This prospective study aimed to assess regional and temporal patterns of extracellular matrix (ECM) changes post-myocardial infarction (MI).

BACKGROUND

A fundamental process in the development of ischemic left ventricular (LV) dysfunction is LV remodeling, characterized by structural and functional abnormalities throughout the myocardium including the noninfarcted (remote) myocardium and interstitium.

METHODS

Contrast-enhanced cardiac magnetic resonance (CMR) was performed on MI patients acutely (mean: 5 days post-MI, n = 25) and repeated subacutely (mean: 139 days post-MI, n = 21), and was also performed in a separate group of 15 patients with chronic MI (mean: 2,580 days post-MI, n = 15). Twenty volunteers without a history of MI acted as controls. CMR was used to evaluate LV morphology and function, with post-contrast T1 mapping to semiquantitatively assess changes in the ECM. Putative mediators of myocardial inflammation and fibrosis, including macrophage migration inhibitory factor (MIF), were also measured.

RESULTS

Age, sex, and diabetic and hypertensive status did not differ between MI groups and controls. Compared with controls, patients early post-acute MI demonstrated reduced LV ejection fraction (50.25 ± 7.29% vs. 66.7 ± 6.2% [controls], p < 0.0001). Myocardium remote to the infarction early post-acute MI, compared with controls, demonstrated reduced systolic thickening (60 ± 5.0% vs. 106 ± 7.6%, p ≤ 0.0002), and lower post-contrast myocardial T1 times suggestive of ECM expansion (437 ± 113 ms vs. 549 ± 119 ms, p = 0.01). In a subgroup analysis between early post-acute MI and controls of similar age and sex, the remote sector post-contrast myocardial T1 times remained significantly shorter post-acute MI compared with controls (420 ± 121 ms vs. 529 ± 113 ms, p = 0.03). Serum levels of MIF inversely correlated with global myocardial T1 time in patients early post-acute MI (r = -0.6, p = 0.01), suggesting a coupling of regional healing with acute LV remodeling.

CONCLUSIONS

Within a week of acute MI, the remote myocardium exhibits systolic dysfunction and expansion of the ECM, which is coupled with physiological infarct healing. Further prospective studies with larger sample sizes are needed to verify these important findings.

OBJECTIVE

The purpose of this study was to investigate the expression of metabolism-related proteins such as Glut-1 and carbonic anhydrase IX (CAIX) according to breast cancer molecular subtype.

METHODS

We generated a tissue microarray of 276 breast cancer patients and performed immunohistochemical staining for known metabolism-related proteins, which were evaluated according to the molecular subtype.

RESULTS

The expression of IGF-1, MIF, and HIF-1α was correlated with the HER-2 type (p < 0.05). Glut-1 overexpression and CAIX expression were associated with TNBC type, especially with basal-like type, high histologic grade, estrogen receptor negativity, and progesterone receptor negativity (p < 0.05). The expression of Glut-1 and CAIX was correlated with statistical significance (p < 0.001).

CONCLUSIONS

We identified different patterns of expression of metabolism-related proteins according to the molecular subtypes of breast cancer defined by surrogate immunohistochemistry. Increased expression of HIF-1α, IGF-1, and MIF was noted in HER-2 type breast cancer and increased expression of Glut-1 and CAIX was noted in TNBC type breast cancer, especially in the basal-like subtype, which exhibited a glycolytic and acid-resistant tumor phenotype.

Cytokines are the molecular messengers of the vertebrate immune system, coordinating the local and systemic immune responses to infective organisms. We report here functional and structural data on cytokine-like proteins from a eukaryotic pathogen. Two homologues of the human cytokine macrophage migration inhibitory factor (MIF) have been isolated from the parasitic nematode Brugia malayi. Both molecules (Bm-MIF-1 and Bm-MIF-2) show parallel functions to human MIF. They are chemotactic for human monocytes and activate them to produce IL-8, TNF-alpha, and endogenous MIF. The human and nematode MIF homologues share a tautomerase enzyme activity, which is in each case abolished by the mutation of the N-terminal proline residue. The crystal structure of Bm-MIF-2 at 1.8-A resolution has been determined, revealing a trimeric assembly with an inner pore created by beta-stranded sheets from each subunit. Both biological activity and crystal structure reveal remarkable conservation between a human cytokine and its parasite counterpart despite the considerable phylogenetic divide among these organisms. The strength of the similarity implies that MIF-mediated pathways play an important role in nematode immune evasion strategies.

Macrophage migration inhibitory factor (MIF) has a key role in regulation of innate and adaptive immunity and is implicated in sepsis, tumorigenesis, and autoimmune disease. MIF deficiency or immunoneutralization leads to protection against fatal endotoxic, exotoxic, and infective shock, and anti-inflammatory effects in other experimental models of inflammatory disease. We report a novel regulatory role of MIF in type 1 IL-1R and p55 TNFR expression and function. Compared with wild-type cells, MIF-deficient cells were hyporesponsive to IL-1- and TNF-induced MAPK activity, AP-1 activity, and cellular proliferation, while NF-kappaB function was preserved. Hyporesponsiveness of MIF-deficient cells was associated with down-regulation of cytokine receptor expression, which was restored by reconstitution of either an upstream kinase of MAPK, MAPK/ERK kinase, or MIF. These data suggest that endogenous MIF is required for cytokine activation of MAPK/AP-1 and cytokine receptor expression. This autocrine regulatory pathway defines an important amplifying role of endogenous MIF in cytokine-mediated immune and inflammatory diseases and provides further molecular evidence for the critical role of MIF in cellular activation.

Macrophage migration inhibitory factor (MIF) is a multifunctional cytokine that is overexpressed in lung cancer. The MIF receptor was recently discovered and found to be the invariant chain of the HLA class II molecule, CD74. We hypothesized that the expression of this receptor-ligand pair in lung cancer is associated with the angiogenic activity and level of CXC chemokine expression in human specimens of non-small cell lung cancer. We, therefore, performed immunolocalization of CD74 and compared it with the localization of MIF in non-small cell lung cancer to determine their respective locations, as well as the relationship between the co-expression of MIF-CD74 and angiogenic CXC chemokines with tumor angiogenesis. We found intense CD74 expression by immunohistochemistry in 57 of 70 tumors with minimal to no staining in the remaining 13 tumors. Comparing the localization of CD74 with its putative ligand, MIF, we found that CD74 and MIF were co-expressed in tumors in close proximity, and that co-expression of the MIF-CD74 pair was associated with both higher levels of tumor-associated angiogenic CXC chemokines (ie, the ELR score) and greater vascularity compared with tumors in which MIF-CD74 co-expression was not present. We also found that MIF induced angiogenic CXC chemokine expression in an autocrine manner in vitro, a function that was specifically inhibited by antibodies to CD74.

In order to investigate whether weight loss can lead to improvement of the mononuclear cell (MNC) proinflammatory state, 21 nondiabetic obese women with mean age 34+/-2 years (mean+/-s.e.m.) and BMI 32.5+/-1.2 kg/m2 were enrolled in a 12-week caloric restriction and light exercise-based weight loss program. Ten lean women served as controls. Reverse transcription-PCR of proinflammatory cytokines and adipocytokines as well as homeostasis model assessment of insulin resistance (HOMA-IR) were determined before and after weight reduction. Nuclear factor kappaB (NF-kappaB) binding to DNA and inhibitors of NF-kappaB (IkappaB-alpha and IkappaB-beta) obtained from peripheral MNCs were measured. Overall, subjects lost a mean of 4.0+/-0.4 kg (5.0+/-0.3% of their initial body weight) (P<0.01). In addition to significant reductions in BMI, fasting glucose and insulin concentrations, mean serum high-sensitivity C-reactive protein (hs-CRP), migration inhibitor factor (MIF), leptin and visfatin levels decreased by 49.0, 66.6, 17.2, and 50.2%, respectively (all P<0.05), while adiponectin concentrations rose by 33.9% (P<0.05). The DNA binding of the transcriptionally active NF-kappaB from (p65/p50) decreased by 38.1% (P<0.05). Elevated levels of mRNA of NF-kappaB related proinflammatory genes, tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), MIF, and matrix metalloproteinase-9 (MMP-9), decreased significantly after weight loss. Although mRNA expression of Rel-A, p105, IkappaB-alpha, IkappaB-beta decreased significantly, their protein levels did not change after weight loss. As a group, NF-kappaB binding activity correlated with HOMA-IR (r=0.332, P=0.049) and marginally with values of BMI (r=0.308, P=0.059). In conclusion, weight loss by 5% of initial weight in nondiabetic obese women led to significant improvement in activated intranuclear NF-kappaB binding as well as several transcriptions of proinflammatory genes regulated by NF-kappaB.

Macrophage migration inhibitory factor (MIF), a key mediator of the delayed-type hypersensitivity response, was originally thought to be produced by activated T cells. However, recent studies have found that MIF is produced in many cell types including monocytes/macrophages and anterior pituitary cells. The current study has examined MIF expression in normal and diseased kidney using in situ hybridization, immunohistochemistry, and Northern blotting. MIF mRNA and protein are constitutively expressed in normal kidney, being largely restricted to tubular epithelial cells and some glomerular visceral and parietal epithelial cells. During the development of rat anti-glomerular basement membrane glomerulonephritis, a model of macrophage-mediated renal injury, there was marked de novo expression of MIF by intrinsic kidney cells including endothelium and glomerular and tubular epithelial cells. Up-regulation of MIF expression correlated with macrophage accumulation within the glomerulus (P < 0.001) and tubulointerstitium (P < 0.001). Of significance, the accumulation of macrophages was exclusively localized to areas of strong MIF expression, contributing to focal glomerular and tubulointerstitial lesion formation. In addition, up-regulation of MIF expression by parietal epithelial cells was associated with macrophage accumulation within Bowman's space and crescent formation. Combined in situ hybridization and immunostaining also demonstrated MIF expression by macrophages, T cells, and fibroblast-like cells within renal lesions. In conclusion, these data provide the first demonstration that renal epithelial cells are a major source of MIF in both normal and diseased kidney. Furthermore, the up-regulation of MIF expression may play an important role in macrophage accumulation and progressive renal injury in rat crescentic glomerulonephritis.

Pancreatic adenocarcinoma upregulated factor (PAUF) is overproduced in certain types of cancer. However, little is known of the tumorigenic function of PAUF. In this study, we report the X-ray crystal structure of PAUF and reveal that PAUF is a mammalian lectin normally found in plant lectins. We also identify PAUF as an endogenous ligand of Toll-like receptor 2 (TLR2) and TLR4 by screening extracellular domain receptor pools. We further confirmed the specificity of the PAUF-TLR2 interaction. PAUF induces extracellular signal-regulated kinase (ERK) phosphorylation and activates the IKK-β-mediated TPL2/MEK/ERK signaling pathway through TLR2. In agreement with the result of TLR2-mediated ERK activation by PAUF, PAUF induces increased expression of the protumorigenic cytokines RANTES and MIF in THP-1 cells. However, PAUF does not fully activate Iκ-B-α signaling pathways in THP-1 cells, and fails to translocate the p65 subunit of the nuclear factor-κB (NF-κB) complex into the nucleus, resulting in no NF-κB activation. Surprisingly, we found that PAUF also associated with the CXC chemokine receptor (CXCR4)-TLR2 complex and inhibited CXCR4-dependent, TLR2-mediated NF-κB activation. Together, these findings suggest that the new cancer-associated ligand, PAUF, may activate TLR-mediated ERK signaling to produce the protumorigenic cytokines, but inhibits TLR-mediated NF-κB signaling, thereby facilitating tumor growth and escape from innate immune surveillance.

IL-6, a proinflammatory cytokine, has been implicated in the development of vascular diseases. We previously demonstrated that mechanical stress can initiate signaling pathways leading to smooth muscle cell (SMC) proliferation and apoptosis, but little is known concerning cyclic stress-induced inflammatory response. To explore the role of stretch in the upregulation of cytokine expression in SMCs we performed RNase protection assay for a panel of cytokines and found that mechanical stress resulted in a time-dependent induction of IL-6 mRNA but not other cytokines, e.g., IL-1alpha, IL-1beta, IL-6, IL-10, IL-12p35, IL-12p40, IL-18, IFN-gamma, and macrophage migration inhibitory factor (MIF). This induction also correlated with elevated IL-6 protein levels in the supernatant. Pretreatment of the cells with NF-kappaB inhibitors inhibited NF-kappaB activity and resulted in marked inhibition (50%) of IL-6 protein. Moreover, SMC lines stably expressing dominant-negative Ras (RasN17) or Rac (RacN17) exhibited a remarkable decrease in p38 MAPK activity and IL-6 mRNA induction by mechanical stress. Furthermore, a significant inhibition of 30 and 40% in IL-6 protein was observed in SMCs pretreated with inhibitors of p38 MAPK and ERK1/2, respectively, but not JNK. Interestingly, SMCs isolated from PKC-delta-deficient mice exhibited higher levels of IL-6 compared with wild-type cells. Finally, high levels of IL-6 expression were observed in atherosclerotic lesions of vein bypass grafts, which are related to altered biomechanical stress. Our findings demonstrate that biomechanical stress-induced IL-6 expression occurs via a mechanism that involves Ras/Rac/p38 MAPK/NF-kappaB/NF-IL6 signaling pathways, which is downregulated by PKC-delta, and suggest that modulation of this event contributes to the pathogenesis of atherosclerosis.

What is the nature of positional information during embryogenesis? By using Xenopus homeo box genes as anteroposterior (A-P) markers, we confirm the findings of others that mesoderm-inducing growth factors and retinoic acid (RA) can provide positional information along the axis of the body. Xenopus tissue culture-mesoderm-inducing factor (XTC-MIF) selectively activates an anteriorly expressed homeo box gene (XlHbox 1), while basic fibroblast growth factor (bFGF) activates selectively a posteriorly expressed homeo box gene (XlHbox 6). RA activates expression of the posterior gene XlHbox 6, but not of XlHbox 1. This activation, however, requires exposure to growth factors. The data suggest that growth factors and RA may cooperate with each other to provide positional information in vertebrates.

We have identified and characterized a Macrophage Migration Inhibitory Factor (MIF) family member in the Lophotrochozoan invertebrate, Biomphalaria glabrata, the snail intermediate host of the human blood fluke Schistosoma mansoni. In mammals, MIF is a widely expressed pleiotropic cytokine with potent pro-inflammatory properties that controls cell functions such as gene expression, proliferation or apoptosis. Here we show that the MIF protein from B. glabrata (BgMIF) is expressed in circulating immune defense cells (hemocytes) of the snail as well as in the B. glabrata embryonic (Bge) cell line that has hemocyte-like features. Recombinant BgMIF (rBgMIF) induced cell proliferation and inhibited NO-dependent p53-mediated apoptosis in Bge cells. Moreover, knock-down of BgMIF expression in Bge cells interfered with the in vitro encapsulation of S. mansoni sporocysts. Furthermore, the in vivo knock-down of BgMIF prevented the changes in circulating hemocyte populations that occur in response to an infection by S. mansoni miracidia and led to a significant increase in the parasite burden of the snails. These results provide the first functional evidence that a MIF ortholog is involved in an invertebrate immune response towards a parasitic infection and highlight the importance of cytokines in invertebrate-parasite interactions.

Macrophage migration inhibitory factor (MIF) was one of the first cytokines to be identified. In the early 1990s it was 'rediscovered' as a hormone that is secreted by the anterior pituitary gland and counter-regulates the anti-inflammatory effects of glucocorticoids. We now know that glucocorticoids stimulate the release of MIF from T cells and macrophages; this appears to be a physiological response to override the effects of glucocorticoids at the inflammatory site. However, this response can become pathological in acute respiratory distress syndrome (ARDS), in which high concentrations of MIF in the alveoli might contribute to ARDS pathogenesis. New insights into the structure and function of MIF, and the possibility of increasing the efficacy of glucocorticoids in the clinic by inhibiting MIF, are discussed in this review.

OBJECTIVE

Macrophage migration inhibitory factor (MIF) is a central cytokine in innate immunity. MIF expression can be regulated by glucose and insulin, but data on the association with type 2 diabetes are sparse. The aim of this study was to test whether MIF is associated with impaired glucose tolerance (IGT) and type 2 diabetes and whether these associations are independent of metabolic and immunological risk factors and to compare the associations of MIF and IGT/type 2 diabetes with those of C-reactive protein (CRP) and interleukin-6 (IL-6) with IGT/type 2 diabetes.

METHODS

The Cooperative Health Research in the Region of Augsburg/Kooperative Gesundheitsforschung im Raum Augsburg, Survey 4 (KORA S4) is a population-based survey performed in Southern Germany (1999-2001). Of 1,653 participants aged 55-74 years, 236 patients with type 2 diabetes, 242 subjects with IGT, and 244 normoglycemic control subjects matched for age and sex were included in this cross-sectional study. Serum concentrations of MIF were measured by enzyme-linked immunosorbent assay.

RESULTS

Serum MIF concentrations are highly increased in individuals with IGT and type 2 diabetes. The associations of MIF with IGT and type 2 diabetes were independent of classical risk factors and of CRP and IL-6 and were much stronger before and after multivariate adjustment than the associations of CRP and IL-6 with IGT and type 2 diabetes.

CONCLUSIONS

Our data suggest that elevations of systemic MIF concentrations precede the onset of type 2 diabetes. This finding may be relevant because MIF has been reported to contribute to the development of type 2 diabetes-related diseases such as atherosclerosis and cancer.

OBJECTIVE

To examine maximal strength, power and muscle cross-sectional area, maximal and submaximal cycling endurance characteristics, and serum hormone concentrations of testosterone (T), free testosterone (FT), and cortisol (C) in middle-aged and elderly men.

METHODS

Maximal knee extension force (isometric; MIF(KE)), power-load curves during concentric actions with loads ranging from 15% to 70% of 1 RM half-squat (1RM(HS)), muscle cross-sectional area of quadriceps femoris (CSA(QF)), workload, heart rate and lactate accumulation during incremental cycling, and serum hormone concentrations were measured in 26 middle-aged (M42 yr) and 21 elderly men (M65 yr).

RESULTS

The 1RM(HS) (14%), MIF(KE) (24%) and CSA(QF) (13%) were lower in M65 than in M42 (P < 0.05-0.01). Power during submaximal actions was lower (P < 0.05-0.001) in M65 than in M42, but the differences disappeared when expressed relative to CSA(QF). Serum FT was in M42 higher (P < 0.05) than in M65. Maximal workload, maximal heart rate and peak blood lactate during cycling in M65 were 31%, 11%, and 20% lower than in M42 (P < 0.01). During submaximal cycling blood lactate rose more rapidly with increasing workload in M65 than in M42 (P < 0.05-0.01), but the differences disappeared when expressed relative to CSA(QF). Significant correlations existed between individual values of serum FT:C ratio, C and T, and those of muscle strength and maximal workload.

CONCLUSIONS

Declines in maximal strength, muscle mass, and endurance performance seem to take place with increasing age, although muscle power and demand for aerobic energy per unit of muscle tissue during submaximal loads remain similar. The balance between anabolic and catabolic hormones in aging people over the years may be associated with age-related decreased strength and declines in maximal cycling workload.

Immunological reactivity in alcoholic hepatitis has bben attributed to alcoholic hyalin, the histological hallmark of this disease. A purified isolate of alcoholic hyalin with electron microscopic, biochemical, and serological characteristics documented previously was added to lymphocytes from healthy subjects and patients with alcoholic hepatitis or other hepatic disorders. Production of migration inhibition factor (MIF) in response to this material was used as an index to lymphocyte reactivity. MIF was significantly increased in lymphocytes obtained from patients with alcoholic hepatis, as compared to the healthy controls (P less than 0.001), and persons with other liver diseases (P less than 0.005). These observations indicate that immunological hyperreactivity to alcoholic hyalin occurs in patients with alcoholic hepatitis; such activity may be of key importance in the pathogenesis or sequelae (or both) of this disease.

OBJECTIVE

This study examined the effects of a single bout of high-intensity eccentric exercise (EE) on blood protein carbonyls, glutathione status, and muscle damage indicators to ascertain whether blood markers of oxidative stress are elevated at the time delayed onset of muscle soreness (DOMS) occurs.

METHODS

Eight healthy men (26.5 +/- 1.5 yr) performed 60 eccentric contractions at approximately 135-150% dominant arm maximum isometric force (MIF) using their nondominant arm elbow flexors. DOMS, range of motion (ROM), MIF, and blood were obtained before, immediately after, and 24, 48, 72, and 96 h after the EE. Blood samples were analyzed for plasma creatine kinase (CK) activity, and protein carbonyls (PC), and erythrocyte glutathione status.

RESULTS

A significant decrease in MIF occurred at all times after the EE. ROM decreased from 24 to 96 h, and DOMS increased 24 to 72 h in the nondominant arm as indicated by a repeated measure ANOVA. Plasma CK activity peaked at 72 h (1620 +/- 500 IU x L(-1)) compared with baseline (154 +/- 27 IU x L(-1). Erythrocyte-reduced glutathione (GSH) concentration was not significantly affected by the EE but tended to decrease 23% by 24 h and continued at this level for 96 h. Oxidized glutathione (GSSG) and total glutathione were unchanged over time. A significant increase in plasma PC occurred at 24 and 48 h after eccentric exercise.

CONCLUSIONS

The results suggest that 60 EE at 135-150% MIF can result in DOMS, with decreased muscle function and increases in plasma PC at 24 and 48 h without alterations in blood glutathione status.

This study aimed to analyze the role of endothelial progenitor cell (EPC)-derived angiogenic factors and chemokines in the multistep process driving angiogenesis with a focus on the recently discovered macrophage migration inhibitory factor (MIF)/chemokine receptor axis. Primary murine and murine embryonic EPCs (eEPCs) were analyzed for the expression of angiogenic/chemokines and components of the MIF/CXC chemokine receptor axis, focusing on the influence of hypoxic versus normoxic stimulation. Hypoxia induced an upregulation of CXCR2 and CXCR4 but not CD74 on EPCs and triggered the secretion of CXCL12, CXCL1, MIF, and vascular endothelial growth factor (VEGF). These factors stimulated the transmigration activity and adhesive capacity of EPCs, with MIF and VEGF exhibiting the strongest effects under hypoxia. MIF-, VEGF-, CXCL12-, and CXCL1-stimulated EPCs enhanced tube formation, with MIF and VEGF exhibiting again the strongest effect following hypoxia. Tube formation following in vivo implantation utilizing angiogenic factor-loaded Matrigel plugs was only promoted by VEGF. Coloading of plugs with eEPCs led to enhanced tube formation only by CXCL12, whereas MIF was the only factor which induced differentiation towards an endothelial and smooth muscle cell (SMC) phenotype, indicating an angiogenic and differentiation capacity in vivo. Surprisingly, CXCL12, a chemoattractant for smooth muscle progenitor cells, inhibited SMC differentiation. We have identified a role for EPC-derived proangiogenic MIF, VEGF and MIF receptors in EPC recruitment following hypoxia, EPC differentiation and subsequent tube and vessel formation, whereas CXCL12, a mediator of early EPC recruitment, does not contribute to the remodeling process. By discerning the contributions of key angiogenic chemokines and EPCs, these findings offer valuable mechanistic insight into mouse models of angiogenesis and help to define the intricate interplay between EPC-derived angiogenic cargo factors, EPCs, and the angiogenic target tissue.

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

Hypoxia and lymphangiogenesis are closely related processes that play a pivotal role in tumor invasion and metastasis. Intratumoral hypoxia is exacerbated as a result of oxygen consumption by rapidly proliferating tumor cells, insufficient blood supply and poor lymph drainage. Hypoxia induces functional responses in lymphatic endothelial cells (LECs), including cell proliferation and migration. Multiple factors (e.g., ET-1, AP-1, C/EBP-δ, EGR-1, NF-κB, and MIF) are involved in the events of hypoxia-induced lymphangiogenesis. Among them, HIF-1α is known to be the master regulator of cellular oxygen homeostasis, mediating transcriptional activation of lymphangiogenesis via regulation of signaling cascades like VEGF-A/-C/-D, TGF-β and Prox-1 in experimental and human tumors. Although the underlying molecular mechanisms remain incompletely elucidated, the investigation of lymphangiogenesis in hypoxic conditions may provide insight into potential therapeutic targets for lymphatic metastasis.

OBJECTIVE

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine with known actions in macrophage and T cell activation. MIF also has the unique capacity to reverse the inhibitory effects of glucocorticoids on these cells. We have recently demonstrated MIF expression in human rheumatoid arthritis (RA) synovium and cultured fibroblast-like synoviocytes (FLS), as well as the ability of FLS-derived MIF to induce monocyte release of tumor necrosis factor alpha. We investigated the effects of MIF on aspects of RA FLS activation, including the induction of phospholipase A2 (PLA2) and cyclooxygenase (COX).

METHODS

PLA2 activity was measured by 3H-arachidonic acid released from treated FLS supernatants. COX activity was measured by prostaglandin E2 enzyme-linked immunosorbent assay. Cytosolic PLA2 (cPLA2) and COX-2 messenger RNA (mRNA) were determined using semiquantitative reverse transcriptase-polymerase chain reaction.

RESULTS

Constitutive PLA2 activity was detected in RA FLS. Recombinant human MIF up-regulated PLA2 activity (P < 0.01) and cPLA2 mRNA expression, but had no effect on secretory PLA2. Recombinant human MIF up-regulated COX activity (P < 0.05) and COX-2 mRNA, but had no observable effect on COX-1. Interleukin-1beta (IL-1beta) significantly up-regulated PLA2 activity (P < 0.005) and cPLA2 mRNA expression while anti-MIF monoclonal antibody (mAb) significantly inhibited this IL-1beta-induced PLA2 activity (P < 0.02). Anti-MIF mAb significantly reduced IL-1beta-induced COX activity (P < 0.05) and COX-2 mRNA expression.

CONCLUSIONS

MIF exerts a proinflammatory effect on key aspects of RA FLS activation. That anti-MIF mAb inhibited IL-1beta up-regulation of FLS indicates an additional cofactor role for MIF in IL-1beta-induced FLS activation. These data suggest that MIF antagonism has important therapeutic potential in RA.

The present work aims at analyzing the structure of cortical connectivity during the attempt to move a paralyzed limb by a group of spinal cord injured (SCI) patients. Connectivity patterns were obtained by means of the Directed Transfer Function applied to the cortical signals estimated from high resolution EEG recordings. Electrical activity were estimated in normals (Healthy) and SCI patients on twelve regions of interest (ROIs) coincident with Brodmann areas. Degree distributions showed the presence of few cortical regions with a lot of outgoing connections in all the cortical networks estimated irrespectively of the frequency band investigated. For both of the groups (SCI and Healthy), bilateral cingulate motor area (CMA) acts as hub transmitting information flows. The efficiency index, allowed to assert the ordered properties of such estimated cortical networks in both populations. The comparison of such estimated networks with those obtained from random networks, elicited significant differences (P < 0.05, Bonferroni-corrected for multiple comparisons). A statistical comparison (ANOVA) between SCI patients and healthy subjects showed a significant difference (P < 0.05) between the local efficiency of their respective networks. For three frequency bands (theta 4-7 Hz, alpha 8-12 Hz, and beta 13-29 Hz) the higher value observed in the spinal cord injured population entails a larger level of internal organization and fault tolerance. This fact suggests a sort of compensative mechanism as local response to the alteration in their MIF areas, which is probably due to the indirect effects of the spinal injury.