Atherosclerosis with its clinical manifestations myocardial

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1 Basic Science for Clinicians Macrophage Migration Inhibitory Factor in Cardiovascular Disease Alma Zernecke, MD; Jürgen Bernhagen, PhD; Christian Weber, MD Abstract The highly conserved and archetypical yet atypical cytokine macrophage migration inhibitory factor (MIF) fulfills pleiotropic immune functions in many acute and chronic inflammatory diseases. Recent evidence has emerged from both expression and functional studies to implicate MIF in various aspects of cardiovascular disease. The present review is aimed at providing a synopsis of the involvement of MIF in the inflammatory pathogenesis of atherosclerosis and its consequences, namely unstable plaque formation, remodeling after arterial injury, aneurysm formation, myocardial infarction, or ischemia-reperfusion injury. In addition, other forms of myocardial dysfunction and inflammation and the role of MIF in angiogenesis are reviewed. The functional data are reconciled with recent progress in the identification of heptahelical (CXC chemokine) receptors for MIF, its prototypic role as their noncanonical ligand, and its signal transduction profile operative in atherogenic and inflammatory recruitment of mononuclear cells and in the oxidative damage and apoptosis of cardiomyocytes. Its unique features and functions clearly distinguish MIF from other cytokines implicated in atherogenesis and make it a prime target for achieving therapeutic regression of atherosclerosis. The potential of targeting or exploiting MIF for therapeutic strategies or as a diagnostic marker in the management of cardiovascular diseases or disorders is scrutinized. (Circulation. 2008;117: ) Key Words: atherosclerosis cytokines inflammation myocardium remodeling Atherosclerosis with its clinical manifestations myocardial infarction, stroke, and peripheral artery disease is close to becoming the leading cause of death worldwide. An impressive body of evidence supports the concept that atherosclerosis is a chronic inflammatory disease of the arterial wall characterized by an influx of immunocompetent mononuclear cells 1 3 that determine the delicately adjusted 2-edged immune balance and proinflammatory or antiinflammatory response. The atherogenic recruitment of leukocytes is controlled by functionally specialized chemokines. 2,4 Secreted into the soluble phase, chemokines were first discovered to mediate directed chemotaxis of leukocytic cell types. Subsequently, chemokines have been recognized as being transported and presented on the endothelial surface, where they are instrumental in triggering the integrin-mediated arrest of rolling leukocytes. 5,6 In the context of atherosclerosis, this arrest function has been best established for the platelet-derived chemokine CCL5, the CXC chemokines, and the CXCR2 ligands CXCL1 and CXCL8. 4 MIF is an evolutionarily ancient and highly conserved cytokine. 7,8 From a historical perspective, MIF was originally described as a soluble factor expressed by T cells in delayedtype hypersensitivity responses exerting inhibitory effects on macrophage migration 9 and may thereby represent the first known member of the cytokine family. Recently, MIF has been acknowledged to play pleiotropic roles in acute and chronic inflammatory diseases such as septic shock, rheumatoid arthritis, and colitis. 4,10 12 Moreover, MIF has emerged as a key player in cardiovascular disease As a molecule that is detectable in the circulation and at sites of inflammation, MIF might be an indicator of disease severity. In addition, MIF is unique among proinflammatory cytokines in that it is inducible by glucocorticoids (the Table), a mechanism that might be implicated in an acceleration of atherosclerosis associated with many diseases requiring glucocorticoid therapy. Here, we discuss the novel receptor signaling routes of MIF and its functional role as a culprit and risk marker in vascular and myocardial processes and as a potential regulator of angiogenesis. We propose that MIF belongs to the group of chemokine-like function chemokines or microchemokines. This includes chemotactic polypeptides such as the -defensins, which cannot be classified into known chemokine subfamilies but share structural or functional features and can signal through chemokine receptors. 16,17 MIF in Primary Atherosclerosis Hypercholesterolemia as the best documented risk factor contributing to atherogenesis instigates early endothelial ac- From the Institute for Molecular Cardiovascular Research (A.Z., C.W.) and Department of Biochemistry and Molecular Cell Biology (J.B.), Molekulare Herz-Kreislaufforschung, RWTH Aachen University, Aachen, Germany. Correspondence to Dr Christian Weber, Institut für Molekulare Herz-Kreislaufforschung, Universitätsklinikum der RWTH Aachen, Pauwelsstraβe 30, Aachen, Germany ( cweber@ukaachen.de); or Dr Jürgen Bernhagen, Institut für Biochemie, Universitätsklinikum der RWTH Aachen, Pauwelsstraβe 30, Aachen, Germany ( jbernhagen@ukaachen.de) American Heart Association, Inc. Circulation is available at DOI: /CIRCULATIONAHA

2 Zernecke et al MIF in Cardiovascular Disease 1595 Table. Unique Features and Cardiovascular Effects of MIF Reference General, eg, reviewed in references 8, 10 12, 84 Evolutionary conserved but no homologies to other cytokines Trimer formation, tautomerase, and redox activity Glucocorticoid-inducible and glucocorticoid-overriding activity Atherosclerosis, arterial remodeling, and plaque stability Upregulation by oxldl, CD40L, ATII in monocytes, ECs, and 14, 15, 22 SMCs Upregulation in SMCs (early) and ECs and macrophages 15 (later phase) after arterial injury Induction of CCL2 release, TNF, ICAM-1 in ECs 21, 41, 42 Short-term enhancement of PDGF-stimulated SMC migration 58 but long-term impairment of PDGF-BB induced vascular SMC migration Induces MMPs, cathepsins in SMCs, and MMP-1 and 24, 27 MMP-9 in vulnerable plaques Blockade reduces the aortic expression of MMP-2, CD40L, 26 and TNF- in Apoe / mice Blockade reduces macrophage recruitment and plaque area 26 in the aorta Deficiency reduces diet-induced aortic intimal thickening 27 and lipid deposition in Ldlr / mice Blockade reduces macrophage content and foam cell 15 formation and increases SMC content after arterial injury Blockade inhibits neointimal formation, reduces the 57 proliferation of medial and neointimal cells, but increases apoptosis after experimental angioplasty Blockade results in regression of established aortic root 13 plaques in Apoe / mice and reduces both macrophage and T-cell content in plaques Aneurysm formation Coexpression of MIF with MMP-1, MMP-9, and MMP-12 in 63 the AAA Correlation of serum levels with initial AAA size and annual 62 aneurysm expansion Angiogenesis Expressed by embryonic endothelial progenitor cells 74 Expressed in tumor-associated neovasculature 67, 68 Induces the migration and tube formation in matrigel assays 67 Blockade suppressed tumor growth and tumor-associated 68, 69 angiogenesis Ischemia-reperfusion, myocardial infarction, and dysfunction in sepsis Upregulated in cardiomyocytes, macrophages, and serum 64 after acute myocardial infarction Upregulated in cardiomyocytes by hypoxia and oxidative 65, 66 stress Upregulated by LPS in ECs 77 Released from the lungs during sepsis 81 Induces kinase activation and phosphorylation in the heart 81 (indicating myocardial depression) Blockade enhances cardiomyocytes survival and myocardial 77, 78 function Blockade restores cardiac depression after burn injury 80 oxldl indicates oxidized LDL; ATII, angiotensin II; ECs, endothelial cells; TNF-, tumor necrosis factor- ; ICAM-1, intracellular adhesion molecule-1; PDGF, platelet-derived growth factor; AAA, abdominal aortic aneurysm; and LPS, lipopolysaccharide. tivation or dysfunction accompanied by the expression of adhesion molecules and chemokines and thereby leads to early subintimal infiltration with mononuclear cells, the first morphological sign of inflammation in the arteries. 2,18,19 Associated with the progression and severity of atherosclerotic disease, the expression of MIF has been shown to correlate with increased intima-media thickening and lipid deposition in the aorta of mice, in advanced human carotid artery plaques, and in rabbits fed an atherogenic diet. 14,20 22 Moreover, elevations in systemic MIF concentrations have been shown to precede the onset of type 2 diabetes, which might be relevant in light of the fact that atherosclerotic vascular disease is more prevalent in diabetic patients than nondiabetic subjects. 23 Different proatherogenic factors such as oxidized low-density lipoprotein (LDL), CD40 ligand, or angiotensin II have been shown to induce the expression of MIF in endothelial cells, smooth muscle cells (SMCs), mononuclear cells, and macrophages during the development of atherosclerotic lesions in humans, rabbits, and mice. 14,15,22 As a cytokine, MIF is unique in that it is inducible by glucocorticoids and overrides or reverses glucocorticoid effects. 24 This is particularly notable in light of recent findings that the inhibition of enzymatic generation of cortisol from inactive cortisone, lowering intracellular glucocorticoid levels, resulted in a dramatic reduction in atherosclerosis. 25 This was associated with an increase in proinflammatory chemokines, suggesting an induction of local cytokines, ie, putatively MIF, by glucocorticoids to explain the proatherogenic effects and to provide a mechanistic link between glucocorticoids and atheroma formation. 11 Evidence for the in vivo relevance of MIF in disease progression was obtained by antibody inhibition studies and animal models using the genetic deletion of MIF. In apolipoprotein E deficient (Apoe / ) mice fed a normal chow, the neutralization of MIF impaired the atherogenic recruitment of macrophages and the aortic expression of inflammatory mediators, eg, matrix metalloproteinase (MMP)-2, CD40 ligand, and tumor necrosis factor, and was associated with a slight reduction in the development in atherosclerotic plaque area in the aorta. 26 Similarly, the genetic deletion of Mif in LDL receptor deficient (Ldlr / ) mice retarded diet-induced atherogenesis, manifest as a decrease in intimal thickening and lipid deposition in the aorta. 27 More recently, MIF deficiency in bone marrow cells after reconstitution in chimeric Apoe / mice was found to markedly impair the recruitment of monocytes to lesion-prone areas, and the treatment with a blocking MIF antibody notably resulted in a regression of established atherosclerotic lesions with reduced macrophage and T-cell content in the aortic root. 13 In these studies, strong evidence has been put forward that a major proportion of proatherogenic MIF effects are due to a direct enhancement of macrophage and T-cell recruitment (Figure 1). Chemokine-Like Functions of MIF in Inflammatory Cell Recruitment The superfamily of chemokines governs leukocyte trafficking and deployment during immune and inflammatory reactions by signaling through corresponding G i protein coupled re-

3 1596 Circulation March 25, 2008 lumen LDL arterial wall ATII CD40L ROS oxldl rapid integrin activation and arest MIF macrophage oxldl foam cell formation monocyte / CD3 + T cell recruitment via CXCR2 / CXCR4 CCL2 MIF scavenger receptor foam cell Upregulation VCAM-1 / ICAM-1 TNF progression to unstable plaques injury PDGF-BB platelets neointimal hyperplasia modulation of SMC migration and proliferation MMP1/2/9/12, cathepsin induction elastin and collagen degradation Figure 1. Cellular mechanisms of MIF in the context of atherogenesis. The expression of MIF can be induced in cells of the vascular wall and intimal macrophages by various proatherogenic stimuli, eg, oxidized LDL (oxldl) or angiotensin II (ATII). Subsequently, MIF can upregulate endothelial cell adhesion molecules (eg, vascular [VCAM-1] and intracellular [ICAM-1] adhesion molecules) and chemokines (eg, CCL2) and trigger direct activation of the respective integrin receptors (eg, LFA-1 and VLA-4) by binding and signaling through its heptahelical (chemokine) receptors CXCR2 and CXCR4. This entails the recruitment of mononuclear cells (monocytes and T cells) and the conversion of macrophages into foam cells, inhibiting apoptosis and regulating (eg, impairing) the migration or proliferation of SMCs. By inducing MMPs and cathepsins, MIF promotes elastin and collagen degradation, ultimately leading to the progression into unstable plaques. ROS indicates reactive oxygen species; PDGF-BB, platelet-derived growth factor-bb. ceptors of the CXCR and CCR family. 28,29 Molecular mimicry of chemokines is exploited by viruses to infect cells, eg, by HIV-1, which invades host cells after interaction of its capsid protein gp120 with host CXCR4. Similarly, mechanisms of facilitated viral dissemination and evasion from host defense comprise interactions with chemokine receptors. For example, herpesviruses expressing macrophage inflammatory proteins operate as CCR agonists/antagonists, and toxoplasma gondii-derived cyclophilin-18 binds and signals through CCR Surprisingly, it is increasingly being appreciated that a number of host proteins also rely on direct interactions with chemokine receptors to regulate inflammatory and immune processes, acting as noncanonical ligands for CXCRs and CCRs. Antimicrobial -defensins display chemotactic activity for T-cell and dendritic cell subsets by binding to CCR6, whereas the cognate ligand CCL20 shares antimicrobial properties because of a similar surface topology of positively charged residues. 17,33 Autoantigenic aminoacyltrna synthetases and their fragments, released from damaged cells, induce chemotactic cell migration through binding to CCR5 (HisRS) and CCR3 (AsnRS), and fragments of TyrRS mediate proangiogenic activity by direct binding to CXCR1 through a CXCL8-like N-terminal ELR motif. 37,38 The recent discovery that the host cytokine MIF fulfills chemokine-like functions in inflammatory cell recruitment indicates that alarmins such as the defensins 39 and host autoantigens released from dying cells or after pathogen challenge exploit the chemokine receptor system to further encompass the recruitment of mononuclear cells and neutrophils. The receptor mechanism(s) underlying its cytokine activities have been elusive for decades. Insight into the mechanisms involved in monocyte recruitment by MIF was first gathered in vitro. Adhesion assays revealed that short-term incubation of aortic endothelial cells with MIF triggered the arrest of monocytes under flow conditions. Moreover, monocyte arrest of endothelial cells induced by oxidized LDL was mediated by endogenously produced endothelial MIF. 15 This observation supported a model whereby MIF directly affects endothelium-monocyte interactions by a novel mechanism that resembles the function of immobilized chemokines. The molecular machinery that underlies these effects has only recently been better understood as a consequence of the identification of the chemokine receptors CXCR2 and CXCR4 as functional receptors for MIF. 13 MIF can trigger a calcium influx through CXCR2 or CXCR4, induces a rapid activation of integrins, and can subsequently mediate the G i- and integrindependent arrest and the chemotaxis of monocytes and T cells (Figures 2 and 3). Thus, the earlier inhibition of macrophage migration giving rise to the original designation of MIF 9 may possibly correspond to an inhibition of random migration while favoring directed migration. Although roles for both MIF and CXCR2 in the initiation and progression of atherosclerosis have been established in various models, 15,27,40 we only recently have been able to show that blocking Mif (as a dual Cxcr2/Cxcr4 agonist), but not the neutralization of the canonical ligands of Cxcr2, ie, KC, led to a regression of preexisting atherosclerotic plaques in Apoe / mice and that both macrophage content and T-cell content are reduced, consistent with a more stable plaque phenotype. 13 Importantly, the function of MIF as a T-cell agonist and the notion that blockade of MIF impaired CXCR4-supported T-cell recruitment also may be important for driving lesion development. 13 Thus, MIF is involved in leukocyte recruitment in a more universal sense than hitherto appreciated, and a picture evolves as to whether MIF has an

4 Zernecke et al MIF in Cardiovascular Disease 1597 extracellular MIF myocardial infarction sepsis hypoxia ROS LPS Endocytosis Intracellular MIF Nucleus redox JAB-1 CXCR integrin activity Gα i Ca 2+ MAPK/ERK RTK-like complex CD74 CD44 Src-kinase PI3K/Akt efficacy similar to specialist cognate ligand chemokines but, in contrast to these ligands CXCL8 and CXCL12, which act in a more cell-restricted manner, promotes the recruitment of both monocytes and T cells by interacting with CXCR2 and CXCR4, respectively. Moreover, through CXCR2, the chemotactic activity of MIF extends to neutrophils. 13 Besides these chemokine-like functions of MIF, a part of the effect on macrophage recruitment may be due to an enhancement of CCL2 release and induction of other inflammatory mediators such as adhesion molecules and tumor necrosis factor 42 aggravating and sustaining the mononuclear cell influx. In fact, MIF might act sequentially by first directly promoting monocyte arrest through the CXCR axis and then promoting monocyte transmigration through the intermediate production of CCL2 (Figure 1). By analogy to complement-based defense mechanisms, MIF thus has been proposed to represent an archaic master regulator or preformed source code for leukocyte arrest and chemotaxis. 13 This term also may be appreciated and justified from the plethora and multitude of unique features and cardiovascular effects of MIF (the Table), which make it stand out from many other cytokines and may indeed indicate a proximal role in the hierarchy of cytokines. Hence, we propose that the emergence of host proteins with structural relationships to bona fide chemokines and with direct evidence for binding and signaling through chemokine receptors warrants an amendment of the current chemokine classification scheme 43 by the addition of CC chemokine-like and CXC chemokine-like ligands (J.B. and C.W., unpublished data, 2007). p53 gene expression/ cell cycle/ inhibition of apoptotis Figure 2. Signaling via a functional MIF receptor complex. MIF can be induced by glucocorticoids overriding their function by regulating cytokine production and, after its endocytosis, can interact with intracellular proteins, namely JAB-1, thereby downregulating MAPK signals and modulating cellular redox homeostasis. On the other hand, extracellular MIF has been found to bind to the cell surface protein CD74 (invariant chain Ii). CD74 lacks a signal-transducing intracellular domain but interacts with the proteoglycan CD44 and mediates signaling via CD44 to induce activation of Src-family kinase and MAPK/extracellular signal-regulated kinase (ERK), to activate the PI3K/Akt pathway, or to initiate p53-dependent inhibition of apoptosis. MIF also can bind and signal through G protein coupled chemokine receptors (CXCR2 and CXCR4) alone. Complex formation of CXCR2 with CD74, enabling accessory binding, appears to facilitate GPCR activation and formation of a GPCR-RTK like signaling complex to trigger calcium influx and rapid integrin activation. PKC ERK cardiomyocyte apoptosis eepc MIF pro-angiogenic effects CXCR2/4 MAPK/PI3K Figure 3. Effects of MIF in myocardial pathology. In the context of ischemia-reperfusion, hypoxia, reactive oxygen species (ROS), and endotoxins (eg, lipopolysaccharide [LPS]) in sepsis can induce the secretion of MIF from cardiomyocytes through a protein kinase C (PKC) dependent mechanism and can result in extracellular signal-regulated kinase (ERK) activation, which may contribute to cardiomyocyte apoptosis. Expressed by surviving cardiomyocytes or by endothelial progenitor cells (eg, eepcs) used for therapeutic injection, MIF may promote angiogenesis via its receptors CXCR2 and CXCR4, requiring MAPK and PI3K activation. The Functional MIF Receptor Complex for Atherogenesis Notably, the atherogenic or inflammatory monocyte recruitment induced by MIF not only relied on CXCR2 binding but also involved the MIF-binding protein CD74, which colocalized with CXCR2 in the cell membrane of macrophages and after ectopic expression in B cells. The interaction of CXCR2 and CD74 strongly indicates that MIF signals via a functional CXCR/CD74 complex, which may explain downstream events such as calcium influx, mitogen-activated protein kinase (MAPK) activation, or G i-dependent integrin activation (Figure 2). Although CD74 lacks a signal-transducing intracellular domain, MIF-induced signaling via CD74 has been found to involve the proteoglycan CD44 and Src kinases. 44 It is conceivable that CD74, CD44, and Src could form a functional receptor tyrosine kinase (RTK) like complex. Although MIF can bind to CXCR2 alone, as evident in cells devoid of CD74, accessory binding to CD74 45 may facilitate G protein-coupled receptor (GPCR) activation and formation of a signaling complex with Src kinases, resembling the use of CD44 as an auxiliary receptor by CCL5. 46 Interestingly, phosphatidylinositol 3-kinase (PI3K) inhibitors potently interfered with MIF-induced chemotaxis of monocytes. This could indicate that engagement of the RTK/ GPCR-like MIF receptor signaling complex may lead to the upstream recruitment of PI3K and Akt, consistent with data showing a promotion of cell survival via activation of the PI3K/Akt pathway by MIF in fibroblasts or tumor cells. 47 The notion that CD74 contributes to MIF-independent CXCR2 functions in atherogenic recruitment 13 is underscored by its preferential expression on mononuclear cells relevant to atherosclerosis 45 and by a moderate recruitment activity of MIF in neutrophils lacking CD74 but also may reflect a more general involvement of CD74 in chemokine receptor signaling. In addition, MIF taken up by endocytosis has been found to interact directly with intracellular proteins such as jun-c activation domain-binding protein-1 (JAB-1), which colocalizes with MIF in atheroma. Intracellular MIF can negatively regulate MAPK signaling or can modulate cell functions by regulating cellular redox homeostasis through JAB-1 as a possible feedback loop. 11,14,48 As the only known cytokine,

5 1598 Circulation March 25, 2008 MIF has been described to downregulate basic and phosphorylated p53 expression (Figure 2), resulting in inhibition of apoptosis and prolonged survival of macrophages in particular after cellular stress. 49,50 This may contribute to increased foam cell formation 15 and may partially explain the atheroprotective effect of blocking MIF because p53 deficiency promotes primary atherosclerosis. 51 MIF During Arterial Remodeling After Injury The mechanical injury of stenotic atherosclerotic lesions by percutaneous intervention such as balloon angioplasty or stenting as a therapeutic measure in the treatment of atherosclerotic and narrowed arteries induces the development of neointimal hyperplasia in virtually all patients. 52,53 In contrast to primary atherosclerosis, the acute injury of the vessel wall comprises the acute endothelial denudation and platelet adhesion, as well as a massive apoptosis of SMCs in the medial vessel wall. The accumulation of phenotypically unique SMCs within the intimal layer in response to injury functions to restore the integrity of the arterial vessel wall but subsequently leads to the progressive narrowing of the vessel. 52,54,55 A study of balloon injury in cholesterol-fed rabbits showed that the early intimal monocyte infiltration precedes the accumulation of SMCs and suggested that monocyte recruitment subsequently triggers a more sustained and chronic inflammatory response, possibly by releasing cytokines and growth factors, leading to the ongoing monocyte influx and SMC accumulation during neointimal growth. 56 The role of MIF in neointimal lesion formation was first studied after arterial air desiccation in Ldlr / mice in which antibody blockade of MIF inhibited neointimal formation and was associated with reduced inflammation and cellular proliferation but increased apoptosis. 57 Furthermore, the contribution of MIF to neointimal hyperplasia was analyzed after wire injury of carotid arteries in Apoe / mice. 15 MIF expression was upregulated in SMCs early after endothelial denudation but was found predominantly in endothelial cells and macrophage-derived foam cells at later stages. The neutralization of MIF after injury led to a marked reduction in neointimal macrophage content and inhibited their conversion into foam cells. Conversely, the content of SMCs and collagen in the neointima was increased. 15 Although only a slight reduction in neointimal area was observed, these changes reflect a remarkable shift in the cellular composition of the neointima toward a more stable plaque phenotype. MIF in Disease Progression and Plaque Stability The impact of MIF in the regulation of SMC migration was investigated more closely in vitro and demonstrated a biphasic effect of MIF. Although short-term incubation with MIF enhanced the platelet-derived growth factor-bb induced vascular SMC migration, long-term incubation with MIF decreased platelet-derived growth factor-bb induced migration. 58 Because platelet-derived growth factor-bb, together with MIF, is present in vascular lesions, an impaired SMC migration might contribute to plaque destabilization. 58 In addition, the proliferation of vascular cells also is influenced by MIF 27,58 and might contribute to the increase in plaque cellularity and continuous growth. In this regard, it is interesting to note that CXCR4, which has been implicated in neointimal hyperplasia and the neointimal recruitment of SMC progenitor cells, 59 also can function as a receptor of MIF. Thus, the MIF-induced proliferation of SMCs might involve CXCR4 and play an important role in the progression of neointimal formation and restenosis. These data underscore the importance of MIF in arterial macrophage accumulation and regulation of the lesional SMC content, support the concept that MIF is strongly involved not only in primary atherogenesis and plaque progression but also after vascular injury, and imply a pathway for unstable lesion formation involving MIF. The genetic deletion of Mif also is associated with a decrease in protease expression. 27 Although MIF is known to induce the expression of MMPs and cathepsins in vascular SMCs, MIF also has been demonstrated to induce MMP-1 and MMP-9 in vulnerable plaques, 27,60 indicating a role of MIF in collagen degradation and weakening of the fibrous cap and plaque destabilization. Of note, polymorphisms in the MIF gene functionally affecting the transcriptional activity of MIF have been correlated with low disease severity in a cohort of rheumatoid arthritis patients 11,61 and might be relevant and useful for the determination of disease progression and severity of atherosclerosis. Aneurysm Formation In association with advanced atherosclerosis, abdominal aortic aneurysms can occur as localized dilatations of the arterial wall resulting from an extensive breakdown of structural proteins caused by activated MMPs. These aortic aneurysms can continuously expand and may eventually rupture, frequently causing the death of the patient. Similar to advanced plaques, the upregulated expression of MIF can be detected in stable abdominal aortic aneurysm and is intensified further in ruptured aneurysm. Notably, MIF serum levels are correlated with initial aortic aneurysm size and annual aneurysm expansion rates. 62 Although MIF is expressed in endothelial cells, SMCs, macrophages, and T cells, specific MMPs (MMP-1, MMP-9, MMP-12) are upregulated and coexpressed with MIF, 63 implying an active role of MIF in the weakening of vessel wall structures. A direct causal link needs to be investigated by antibody inhibition and neutralization studies. MIF in Ischemia-Reperfusion and Myocardial Infarction An upregulation of myocardial MIF expression also has been observed in surviving cardiomyocytes and macrophages in a rat model of acute myocardial ischemic injury. 64 In the pathogenesis of ischemia/reperfusion injury, reactive oxygen species play an important role and can be generated from cardiac myocytes and activate the transcription of several genes (Figure 3). Both hypoxia and oxidative stress have been demonstrated to induce the secretion of MIF from cardiomyocytes through an atypical protein kinase C dependent export mechanism and to result in extracellular signal-regulated kinase activation. 65,66 Increased serum concentrations of MIF also can be detected in patients with acute myocardial

6 Zernecke et al MIF in Cardiovascular Disease 1599 infarction. MIF may thus play a role in the pathogenesis of myocardial ischemia and contribute to macrophage accumulation in the infarcted region and to their proinflammatory role in myocyte damage during infarction. MIF and Angiogenesis Tissue repair after myocardial infarction relies heavily on neoangiogenesis of the infarcted area. Recent evidence supports a role for MIF as an angiogenic factor because it mediates migration and tube formation in matrigel assays and induces angiogenesis in matrigel plugs and the corneal bioassay (Figure 3). These effects required MAPK and PI3K activation. 67 In addition, MIF can be detected in tumorassociated neovasculature. 67,68 Conversely, antibody blockade of MIF has been found to suppress tumor growth in models of B-cell lymphoma and colon adenocarcinoma and to inhibit tumor-associated angiogenesis. 68,69 Interestingly, MIF expression in non small-cell lung cancer occurs in close association with angiogenic CXC chemokines and vessel density, and high levels correlate with the risk of recurrence after resection. 70 Because both chemokine receptors CXCR2 and CXCR4 have been involved in proangiogenic effects in various models of postnatal angiogenesis, including postischemic adaption, their function as signaling receptors for MIF may provide the molecular mechanism of action for the contribution of MIF to angiogenesis. These data may provide a rationale for using MIF in therapeutic neovascularization for collateral development in ischemic cardiovascular disease. Indeed, embryonic endothelial progenitor cells induce blood vessel growth and cardioprotection under conditions of severe acute and chronic ischemia in a mouse ischemia-reperfusion model and a rat hind-limb ischemia model and have been attributed to the expression of a broad range of proangiogenic and remodeling factors, most prominently MIF. 74 MIF Contributes to Myocardial Dysfunction and Sepsis The dramatic improvement in survival from lethal endotoxemia by inhibition of MIF with a neutralizing antibody has initially and convincingly implicated MIF as an important factor in potentiating severe sepsis. 75 Myocardial dysfunction as a major consequence of septic shock strongly contributes to the high mortality rates of sepsis. Although the endotoxin lipopolysaccharide was shown to induce MIF expression in human endothelial and vascular SMCs, 76 lipopolysaccharide challenge also induced the expression of MIF in the heart. In addition, MIF has been implicated to be induced by endotoxins during sepsis and to function as an initiating factor in myocardial inflammatory responses, cardiac myocyte apoptosis, and cardiac dysfunction (Figure 3). Surprisingly, the early neutralization of MIF has been shown to lead to a significant increase in survival factors (eg, Bcl-2, Bax, and phospho-akt) and an improvement in cardiomyocyte survival and myocardial function, confirming an important role for MIF as a depressant factor in sepsis-induced myocardial dysfunction. 77,78 In line with these findings, the antiinflammatory mediator glucan phosphate, known to attenuate cardiac dysfunction and to improve survival rates in septic mice, has recently been shown to act by inhibiting the cardiac expression of MIF and reducing cardiomyocyte apoptosis. 79 Similarly, MIF has been shown to mediate the late and prolonged cardiac depression after burn injury associated with major tissue damage that was restored by anti-mif treatment. 80 Notably, an increase in MIF within the alveolar space during late experimental sepsis or MIF instilled exogenously into the lungs induced kinase activation and phosphorylation in the heart, eg, of MAPK, as indicative of myocardial depression, suggesting that MIF released from the lungs during sepsis may in part be responsible for the cardiac dysfunction accompanying sepsis. 81 A crucial role of MIF also has been revealed in the pathogenesis of experimental autoimmune myocarditis, as shown by antibody neutralization, which inhibited the onset and reduced the severity of disease in a therapeutic setting. 82 Toward Therapeutic Targeting As a key regulator governing inflammatory recruitment and subsequent events, MIF is a very accessible target for therapeutic intervention in immune-mediated and inflammatory diseases such as atherosclerosis. 11 Given that mice genetically deficient in MIF display a rather normal and benign phenotype (compared, for instance, with deletion of other CXCR2 ligands) when unchallenged and that MIF is present at more abundant and less sharply fluctuating levels (again compared with CXCR2 ligands such as KC), MIF may represent a suitable target to avoid major adverse effects. The development of protein-based biological therapeutics such as anti-cytokine antibodies and soluble cytokine receptors may also prove to be a highly feasible approach for therapeutic targeting in the case of MIF. 11 The favorable efficacy of an antibody to extracellular MIF has been supported not only in an animal model of sepsis but also in chronic inflammatory diseases. 12,75,83 Importantly, an MIF antibody has been reported to be among the first strategies successful in inducing the regression of already apparent and established atherosclerotic lesions, 13 reducing both macrophage and T-cell content resulting from the function of MIF as a dual CXCR agonist, and converting the composition of complex plaques into a more stable phenotype. 15 Alternatively, soluble forms of CD74 recently identified as a cell-surface binding site for MIF on immune cells may be explored for this purpose by analogy to tumor necrosis factor-. Notably, MIF features 2 evolutionarily conserved motifs that have otherwise been identified only in bacterial enzymes and catalyze isomerization/tautomerization and oxidoreductase activities in vitro Whether this catalytic center, which includes an N-terminal proline residue at position 2, is required for cytokine function of MIF in vivo remains a matter of controversy 11,87 ; however, the homotrimeric tertiary structure of MIF has been implicated in both the assembly of the tautomerase region and interactions with CD Moreover, small-molecule inhibitors interacting with the active tautomerase pocket of MIF, namely the N-terminus incorporating the proline residue, can inhibit its cytokine function. 88 As reviewed, 89 these inhibitors comprise derivatives of hydroxycinnamate, Schiff-based tryptophan analogs, or imino-

7 1600 Circulation March 25, 2008 quinone metabolites of acetaminophen and could either directly affect critical residues or invoke a conformational change in MIF that prevents receptor or substrate interactions. It is tempting to speculate that targeting the N-terminal catalytic pocket of MIF with small-molecule inhibitors also would interfere with motifs relevant for CXCR2 binding and signaling. With regard to the recruitment function of MIF, it is noteworthy that MIF displays an atypical ELR motif characteristic of CXCR2 ligands with adequately spaced D and R residues in adjacent loops. Likewise, this could apply to an MIF-like redox-active peptide (MIF[50 65]), which can adopt MIF-like structural features and mimic MIF signal transduction events. 90 Alternatively, peptide motifs from this region may serve as an alternative template for the development of small-molecule inhibitors. This approach could combine the usual advantages of small-molecule inhibitors (eg, oral availability, low antigenicity, and affordable production costs) with a cytokine-specific activity profile. The emergence of numerous chemokine receptor antagonists exhibiting effects on mononuclear cell recruitment extends the current evidence supporting this therapeutic strategy despite the apparent redundancy in the chemokine receptor system. 91 Given that MIF is becoming increasingly recognized as a target for treating inflammatory and cardiovascular disease 11 and in light of intense efforts aimed at validating therapeutic benefits of chemokine receptor antagonists, an intriguing option of selectively targeting different MIF agonist activities in human disease may become available through specific or combined chemokine receptor antagonists. Conclusions It has become evident that MIF is a master regulator of vascular disease and myocardial damage (the Table) that is currently under intense investigation as a therapeutic target. In particular, the abundance of unique features and the effects of MIF, most notably the first cytokine, the blockade of which results in both regression and stabilization of atherosclerotic plaques, clearly make MIF stand out among other cytokines implicated in the pathogenesis of atherosclerosis and may explain why its potential as a therapeutic target should be prioritized. Careful analysis of the structurefunction relationship of MIF and its receptors will provide valuable information for customized drug development that may be feasible, eg, for cyclic anti-mif treatment schemes. Given the remarkable benefits of blocking MIF in achieving plaque regression and stability and recent clinical disappointments encountered in exploring other strategies toward this end, eg, acyl-coenzyme A cholesterol acyltransferase or cholesteryl ester transfer protein inhibition, 92,93 this concept would be highly attractive as a long-anticipated antiinflammatory treatment of established and unstable atherosclerosis beyond the use of statins. In light of the challenging obstacles, however, meticulous clinical testing is mandatory to validate and translate promising experimental data from animal experiments. Note Added in Proof While this article was in press, an intriguing report was published that demonstrated that MIF released in the ischemic heart stimulates AMP-activated protein kinase and thereby protects the heart against ischemia-reperfusion injury. 94 Sources of Funding This work was supported by Deutsche Forschungsgemeinschaft (FOR809, ZE827/1-1, BE1977/4-1, WE1913/ , SFB542- A7) and the Interdisciplinary Center for Clinical Research Biomat. None. Disclosures References 1. Hansson GK. Inflammation, atherosclerosis, and coronary artery disease. N Engl J Med. 2005;352: Libby P. Inflammation in atherosclerosis. Nature. 2002;420: Tedgui A, Mallat Z. Cytokines in atherosclerosis: pathogenic and regulatory pathways. Physiol Rev. 2006;86: Weber C, Schober A, Zernecke A. Chemokines: key regulators of mononuclear cell recruitment in atherosclerotic vascular disease. Arterioscler Thromb Vasc Biol. 2004;24: Weber C. Novel mechanistic concepts for the control of leukocyte transmigration: specialization of integrins, chemokines, and junctional molecules. J Mol Med. 2003;81: Laudanna C, Alon R. Right on the spot: chemokine triggering of integrinmediated arrest of rolling leukocytes. Thromb Haemost. 2006;95: Sun HW, Bernhagen J, Bucala R, Lolis E. Crystal structure at 2.6-A resolution of human macrophage migration inhibitory factor. Proc Natl Acad Sci U S A. 1996;93: Bernhagen J, Calandra T, Bucala R. Regulation of the immune response by macrophage migration inhibitory factor: biological and structural features. J Mol Med. 1998;76: David JR. Delayed hypersensitivity in vitro: its mediation by cell-free substances formed by lymphoid cell-antigen interaction. Proc Natl Acad Sci U S A. 1966;56: Donnelly SC, Bucala R. Macrophage migration inhibitory factor: a regulator of glucocorticoid activity with a critical role in inflammatory disease. Mol Med Today. 1997;3: Morand EF, Leech M, Bernhagen J. MIF: a new cytokine link between rheumatoid arthritis and atherosclerosis. Nat Rev Drug Discov. 2006;5: Calandra T, Roger T. Macrophage migration inhibitory factor: a regulator of innate immunity. Nat Rev Immunol. 2003;3: Bernhagen J, Krohn R, Lue H, Gregory JL, Zernecke A, Koenen RR, Dewor M, Georgiev I, Schober A, Leng L, Kooistra T, Fingerle-Rowson G, Ghezzi P, Kleemann R, McColl SR, Bucala R, Hickey MJ, Weber C. MIF is a noncognate ligand of CXC chemokine receptors in inflammatory and atherogenic cell recruitment. Nat Med. 2007;13: Burger-Kentischer A, Goebel H, Seiler R, Fraedrich G, Schaefer HE, Dimmeler S, Kleemann R, Bernhagen J, Ihling C. Expression of macrophage migration inhibitory factor in different stages of human atherosclerosis. Circulation. 2002;105: Schober A, Bernhagen J, Thiele M, Zeiffer U, Knarren S, Roller M, Bucala R, Weber C. Stabilization of atherosclerotic plaques by blockade of macrophage migration inhibitory factor after vascular injury in apolipoprotein E deficient mice. Circulation. 2004;109: Degryse B, de Virgilio M. The nuclear protein HMGB1, a new kind of chemokine? FEBS Lett. 2003;553: Yang D, Chertov O, Bykovskaia SN, Chen Q, Buffo MJ, Shogan J, Anderson M, Schroder JM, Wang JM, Howard OM, Oppenheim JJ. Beta-defensins: linking innate and adaptive immunity through dendritic and T cell CCR6. Science. 1999;286: Zernecke A, Weber C. Inflammatory mediators in atherosclerotic vascular disease. Basic Res Cardiol. 2005;100: Weber C, Fraemohs L, Dejana E. The role of junctional adhesion molecules in vascular inflammation. Nat Rev Immunol. 2007;7: Korshunov VA, Nikonenko TA, Tkachuk VA, Brooks A, Berk BC. Interleukin-18 and macrophage migration inhibitory factor are associated with increased carotid intima-media thickening. Arterioscler Thromb Vasc Biol. 2006;26: Lin SG, Yu XY, Chen YX, Huang XR, Metz C, Bucala R, Lau CP, Lan HY. De novo expression of macrophage migration inhibitory factor in atherogenesis in rabbits. Circ Res. 2000;87:

8 Zernecke et al MIF in Cardiovascular Disease Schmeisser A, Marquetant R, Illmer T, Graffy C, Garlichs CD, Bockler D, Menschikowski D, Braun-Dullaeus R, Daniel WG, Strasser RH. The expression of macrophage migration inhibitory factor 1alpha (MIF 1alpha) in human atherosclerotic plaques is induced by different proatherogenic stimuli and associated with plaque instability. Atherosclerosis. 2005;178: Herder C, Kolb H, Koenig W, Haastert B, Muller-Scholze S, Rathmann W, Holle R, Thorand B, Wichmann HE. Association of systemic concentrations of macrophage migration inhibitory factor with impaired glucose tolerance and type 2 diabetes: results from the Cooperative Health Research in the Region of Augsburg, Survey 4 (KORA S4). Diabetes Care. 2006;29: Calandra T, Bernhagen J, Metz CN, Spiegel LA, Bacher M, Donnelly T, Cerami A, Bucala R. MIF as a glucocorticoid-induced modulator of cytokine production. Nature. 1995;377: Hermanowski-Vosatka A, Balkovec JM, Cheng K, Chen HY, Hernandez M, Koo GC, Le Grand CB, Li Z, Metzger JM, Mundt SS, Noonan H, Nunes CN, Olson SH, Pikounis B, Ren N, Robertson N, Schaeffer JM, Shah K, Springer MS, Strack AM, Strowski M, Wu K, Wu T, Xiao J, Zhang BB, Wright SD, Thieringer R. 11beta-HSD1 inhibition ameliorates metabolic syndrome and prevents progression of atherosclerosis in mice. J Exp Med. 2005;202: Burger-Kentischer A, Gobel H, Kleemann R, Zernecke A, Bucala R, Leng L, Finkelmeier D, Geiger G, Schaefer HE, Schober A, Weber C, Brunner H, Rutten H, Ihling C, Bernhagen J. Reduction of the aortic inflammatory response in spontaneous atherosclerosis by blockade of macrophage migration inhibitory factor (MIF). Atherosclerosis. 2006; 184: Pan JH, Sukhova GK, Yang JT, Wang B, Xie T, Fu H, Zhang Y, Satoskar AR, David JR, Metz CN, Bucala R, Fang K, Simon DI, Chapman HA, Libby P, Shi GP. Macrophage migration inhibitory factor deficiency impairs atherosclerosis in low-density lipoprotein receptor-deficient mice. Circulation. 2004;109: Rot A, von Andrian UH. Chemokines in innate and adaptive host defense: basic chemokinese grammar for immune cells. Annu Rev Immunol. 2004; 22: Charo IF, Ransohoff RM. The many roles of chemokines and chemokine receptors in inflammation. N Engl J Med. 2006;354: Alcami A. Viral mimicry of cytokines, chemokines and their receptors. Nat Rev Immunol. 2003;3: Aliberti J, Valenzuela JG, Carruthers VB, Hieny S, Andersen J, Charest H, Reis e Sousa C, Fairlamb A, Ribeiro JM, Sher A. Molecular mimicry of a CCR5 binding-domain in the microbial activation of dendritic cells. Nat Immunol. 2003;4: Murphy PM. Viral exploitation and subversion of the immune system through chemokine mimicry. Nat Immunol. 2001;2: Hoover DM, Boulegue C, Yang D, Oppenheim JJ, Tucker K, Lu W, Lubkowski J. The structure of human macrophage inflammatory protein- 3alpha /CCL20: linking antimicrobial and CC chemokine receptor-6- binding activities with human beta-defensins. J Biol Chem. 2002;277: Biragyn A, Surenhu M, Yang D, Ruffini PA, Haines BA, Klyushnenkova E, Oppenheim JJ, Kwak LW. Mediators of innate immunity that target immature, but not mature, dendritic cells induce antitumor immunity when genetically fused with nonimmunogenic tumor antigens. J Immunol. 2001;167: Howard OM, Dong HF, Su SB, Caspi RR, Chen X, Plotz P, Oppenheim JJ. Autoantigens signal through chemokine receptors: uveitis antigens induce CXCR3- and CXCR5-expressing lymphocytes and immature dendritic cells to migrate. Blood. 2005;105: Howard OM, Dong HF, Yang D, Raben N, Nagaraju K, Rosen A, Casciola-Rosen L, Hartlein M, Kron M, Yang D, Yiadom K, Dwivedi S, Plotz PH, Oppenheim JJ. Histidyl-tRNA synthetase and asparaginyltrna synthetase, autoantigens in myositis, activate chemokine receptors on T lymphocytes and immature dendritic cells. J Exp Med. 2002;196: Wakasugi K, Schimmel P. Two distinct cytokines released from a human aminoacyl-trna synthetase. Science. 1999;284: Yang XL, Skene RJ, McRee DE, Schimmel P. Crystal structure of a human aminoacyl-trna synthetase cytokine. Proc Natl Acad Sci U S A. 2002;99: Oppenheim JJ, Yang D. Alarmins: chemotactic activators of immune responses. Curr Opin Immunol. 2005;17: Boisvert WA, Rose DM, Johnson KA, Fuentes ME, Lira SA, Curtiss LK, Terkeltaub RA. Up-regulated expression of the CXCR2 ligand KC/GRO-alpha in atherosclerotic lesions plays a central role in macrophage accumulation and lesion progression. Am J Pathol. 2006;168: Gregory JL, Morand EF, McKeown SJ, Ralph JA, Hall P, Yang YH, McColl SR, Hickey MJ. Macrophage migration inhibitory factor induces macrophage recruitment via CC chemokine ligand 2. J Immunol. 2006; 177: Lan HY, Bacher M, Yang N, Mu W, Nikolic-Paterson DJ, Metz C, Meinhardt A, Bucala R, Atkins RC. The pathogenic role of macrophage migration inhibitory factor in immunologically induced kidney disease in the rat. J Exp Med. 1997;185: Murphy PM, Baggiolini M, Charo IF, Hebert CA, Horuk R, Matsushima K, Miller LH, Oppenheim JJ, Power CA. International union of pharmacology, XXII: nomenclature for chemokine receptors. Pharmacol Rev. 2000;52: Shi X, Leng L, Wang T, Wang W, Du X, Li J, McDonald C, Chen Z, Murphy JW, Lolis E, Noble P, Knudson W, Bucala R. CD44 is the signaling component of the macrophage migration inhibitory factor-cd74 receptor complex. Immunity. 2006;25: Leng L, Metz CN, Fang Y, Xu J, Donnelly S, Baugh J, Delohery T, Chen Y, Mitchell RA, Bucala R. MIF signal transduction initiated by binding to CD74. J Exp Med. 2003;197: Roscic-Mrkic B, Fischer M, Leemann C, Manrique A, Gordon CJ, Moore JP, Proudfoot AE, Trkola A. RANTES (CCL5) uses the proteoglycan CD44 as an auxiliary receptor to mediate cellular activation signals and HIV-1 enhancement. Blood. 2003;102: Lue H, Thiele M, Franz J, Dahl E, Speckgens S, Leng L, Fingerle- Rowson G, Bucala R, Luscher B, Bernhagen J. 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. Oncogene. 2007;26: Kleemann R, Hausser A, Geiger G, Mischke R, Burger-Kentischer A, Flieger O, Johannes FJ, Roger T, Calandra T, Kapurniotu A, Grell M, Finkelmeier D, Brunner H, Bernhagen J. Intracellular action of the cytokine MIF to modulate AP-1 activity and the cell cycle through Jab1. Nature. 2000;408: Hudson AR, Antley CM, Kohler S, Smoller BR. Increased p53 staining in normal skin of posttransplant, immunocompromised patients and implications for carcinogenesis. Am J Dermatopathol. 1999;21: Mitchell RA, Liao H, Chesney J, Fingerle-Rowson G, Baugh J, David J, Bucala R. Macrophage migration inhibitory factor (MIF) sustains macrophage proinflammatory function by inhibiting p53: regulatory role in the innate immune response. Proc Natl Acad Sci U S A. 2002;99: Mercer J, Figg N, Stoneman V, Braganza D, Bennett MR. Endogenous p53 protects vascular smooth muscle cells from apoptosis and reduces atherosclerosis in ApoE knockout mice. Circ Res. 2005;96: Bittl JA. Advances in coronary angioplasty. N Engl J Med. 1996;335: Schober A, Zernecke A. Chemokines in vascular remodeling. Thromb Haemost. 2007;97: Schwartz RS, Topol EJ, Serruys PW, Sangiorgi G, Holmes DR Jr. Artery size, neointima, and remodeling: time for some standards. J Am Coll Cardiol. 1998;32: Ward MR, Pasterkamp G, Yeung AC, Borst C. Arterial remodeling: mechanisms and clinical implications. Circulation. 2000;102: Schober A, Weber C. Mechanisms of monocyte recruitment in vascular repair after injury. Antioxid Redox Signal. 2005;7: Chen Z, Sakuma M, Zago AC, Zhang X, Shi C, Leng L, Mizue Y, Bucala R, Simon D. Evidence for a role of macrophage migration inhibitory factor in vascular disease. Arterioscler Thromb Vasc Biol. 2004;24: Schrans-Stassen BH, Lue H, Sonnemans DG, Bernhagen J, Post MJ. Stimulation of vascular smooth muscle cell migration by macrophage migration inhibitory factor. Antioxid Redox Signal. 2005;7: Zernecke A, Schober A, Bot I, von Hundelshausen P, Liehn EA, Mopps B, Mericskay M, Gierschik P, Biessen EA, Weber C. SDF-1alpha/CXCR4 axis is instrumental in neointimal hyperplasia and recruitment of smooth muscle progenitor cells. Circ Res. 2005;96: Galis ZS, Khatri JJ. Matrix metalloproteinases in vascular remodeling and atherogenesis: the good, the bad, and the ugly. Circ Res. 2002;90: Baugh JA, Chitnis S, Donnelly SC, Monteiro J, Lin X, Plant BJ, Wolfe F, Gregersen PK, Bucala R. A functional promoter polymorphism in the

9 1602 Circulation March 25, 2008 macrophage migration inhibitory factor (MIF) gene associated with disease severity in rheumatoid arthritis. Genes Immun. 2002;3: Pan JH, Lindholt JS, Sukhova GK, Baugh JA, Henneberg EW, Bucala R, Donnelly SC, Libby P, Metz C, Shi GP. Macrophage migration inhibitory factor is associated with aneurysmal expansion. J Vasc Surg. 2003;37: Verschuren L, Lindeman JH, van Bockel JH, Abdul-Hussien H, Kooistra T, Kleemann R. Up-regulation and coexpression of MIF and matrix metalloproteinases in human abdominal aortic aneurysms. Antioxid Redox Signal. 2005;7: Yu CM, Lai KW, Chen YX, Huang XR, Lan HY. Expression of macrophage migration inhibitory factor in acute ischemic myocardial injury. J Histochem Cytochem. 2003;51: Takahashi M, Nishihira J, Shimpo M, Mizue Y, Ueno S, Mano H, Kobayashi E, Ikeda U, Shimada K. Macrophage migration inhibitory factor as a redox-sensitive cytokine in cardiac myocytes. Cardiovasc Res. 2001;52: Fukuzawa J, Nishihira J, Hasebe N, Haneda T, Osaki J, Saito T, Nomura T, Fujino T, Wakamiya N, Kikuchi K. Contribution of macrophage migration inhibitory factor to extracellular signal-regulated kinase activation by oxidative stress in cardiomyocytes. J Biol Chem. 2002;277: Amin MA, Volpert OV, Woods JM, Kumar P, Harlow LA, Koch AE. Migration inhibitory factor mediates angiogenesis via mitogen-activated protein kinase and phosphatidylinositol kinase. Circ Res. 2003;93: Chesney J, Metz C, Bacher M, Peng T, Meinhardt A, Bucala R. An essential role for macrophage migration inhibitory factor (MIF) in angiogenesis and the growth of a murine lymphoma. Mol Med. 1999;5: Ogawa H, Nishihira J, Sato Y, Kondo M, Takahashi N, Oshima T, Todo S. An antibody for macrophage migration inhibitory factor suppresses tumour growth and inhibits tumour-associated angiogenesis. Cytokine. 2000;12: White ES, Flaherty KR, Carskadon S, Brant A, Iannettoni MD, Yee J, Orringer MB, Arenberg DA. Macrophage migration inhibitory factor and CXC chemokine expression in non-small cell lung cancer: role in angiogenesis and prognosis. Clin Cancer Res. 2003;9: Tachibana K, Hirota S, Iizasa H, Yoshida H, Kawabata K, Kataoka Y, Kitamura Y, Matsushima K, Yoshida N, Nishikawa S, Kishimoto T, Nagasawa T. The chemokine receptor CXCR4 is essential for vascularization of the gastrointestinal tract. Nature. 1998;393: Keane MP, Belperio JA, Xue YY, Burdick MD, Strieter RM. Depletion of CXCR2 inhibits tumor growth and angiogenesis in a murine model of lung cancer. J Immunol. 2004;172: Mehrad B, Keane MP, Strieter RM. Chemokines as mediators of angiogenesis. Thromb Haemost. 2007;97: Kupatt C, Horstkotte J, Vlastos GA, Pfosser A, Lebherz C, Semisch M, Thalgott M, Buttner K, Browarzyk C, Mages J, Hoffmann R, Deten A, Lamparter M, Muller F, Beck H, Buning H, Boekstegers P, Hatzopoulos AK. Embryonic endothelial progenitor cells expressing a broad range of proangiogenic and remodeling factors enhance vascularization and tissue recovery in acute and chronic ischemia. FASEB J. 2005;19: Bernhagen J, Calandra T, Mitchell RA, Martin SB, Tracey KJ, Voelter W, Manogue KR, Cerami A, Bucala R. MIF is a pituitary-derived cytokine that potentiates lethal endotoxaemia. Nature. 1993;365: Nishihira J, Koyama Y, Mizue Y. Identification of macrophage migration inhibitory factor (MIF) in human vascular endothelial cells and its induction by lipopolysaccharide. Cytokine. 1998;10: Garner LB, Willis MS, Carlson DL, DiMaio JM, White MD, White DJ, Adams GA 4th, Horton JW, Giroir BP. Macrophage migration inhibitory factor is a cardiac-derived myocardial depressant factor. Am J Physiol Heart Circ Physiol. 2003;285:H2500 H Chagnon F, Metz CN, Bucala R, Lesur O. Endotoxin-induced myocardial dysfunction: effects of macrophage migration inhibitory factor neutralization. Circ Res. 2005;96: Ha T, Hua F, Grant D, Xia Y, Ma J, Gao X, Kelley J, Williams DL, Kalbfleisch J, Browder IW, Kao RL, Li C. Glucan phosphate attenuates cardiac dysfunction and inhibits cardiac MIF expression and apoptosis in septic mice. Am J Physiol Heart Circ Physiol. 2006;291:H1910 H Willis MS, Carlson DL, Dimaio JM, White MD, White DJ, Adams GAt, Horton JW, Giroir BP. Macrophage migration inhibitory factor mediates late cardiac dysfunction after burn injury. Am J Physiol Heart Circ Physiol. 2005;288:H795 H Lin X, Sakuragi T, Metz CN, Ojamaa K, Skopicki HA, Wang P, Al-Abed Y, Miller EJ. Macrophage migration inhibitory factor within the alveolar spaces induces changes in the heart during late experimental sepsis. Shock. 2005;24: Matsui Y, Okamoto H, Jia N, Akino M, Uede T, Kitabatake A, Nishihira J. Blockade of macrophage migration inhibitory factor ameliorates experimental autoimmune myocarditis. J Mol Cell Cardiol. 2004;37: Calandra T, Echtenacher B, Roy DL, Pugin J, Metz CN, Hultner L, Heumann D, Mannel D, Bucala R, Glauser MP. Protection from septic shock by neutralization of macrophage migration inhibitory factor. Nat Med. 2000;6: Thiele M, Bernhagen J. Link between macrophage migration inhibitory factor and cellular redox regulation. Antioxid Redox Signal. 2005;7: Rosengren E, Bucala R, Aman P, Jacobsson L, Odh G, Metz CN, Rorsman H. The immunoregulatory mediator macrophage migration inhibitory factor (MIF) catalyzes a tautomerization reaction. Mol Med. 1996;2: Kleemann R, Kapurniotu A, Frank RW, Gessner A, Mischke R, Flieger O, Juttner S, Brunner H, Bernhagen J. Disulfide analysis reveals a role for macrophage migration inhibitory factor (MIF) as thiol-protein oxidoreductase. J Mol Biol. 1998;280: Stamps SL, Fitzgerald MC, Whitman CP. Characterization of the role of the amino-terminal proline in the enzymatic activity catalyzed by macrophage migration inhibitory factor. Biochemistry. 1998;37: Senter PD, Al-Abed Y, Metz CN, Benigni F, Mitchell RA, Chesney J, Han J, Gartner CG, Nelson SD, Todaro GJ, Bucala R. Inhibition of macrophage migration inhibitory factor (MIF) tautomerase and biological activities by acetaminophen metabolites. Proc Natl Acad Sci U S A. 2002;99: Morand EF, Leech M, Iskander M. Therapeutic opportunities for antagonism of macrophage migration inhibitory factor. Expert Opin Ther Patents. 2003;8: Nguyen MT, Beck J, Lue H, Funfzig H, Kleemann R, Koolwijk P, Kapurniotu A, Bernhagen J. A 16-residue peptide fragment of macrophage migration inhibitory factor, MIF-(50 65), exhibits redox activity and has MIF-like biological functions. J Biol Chem. 2003;278: Weber C, Koenen RR. Fine-tuning leukocyte responses: towards a chemokine interactome. Trends Immunol. 2006;27: Nissen SE, Tardif JC, Nicholls SJ, Revkin JH, Shear CL, Duggan WT, Ruzyllo W, Bachinsky WB, Lasala GP, Tuzcu EM. Effect of torcetrapib on the progression of coronary atherosclerosis. N Engl J Med. 2007;356: Nissen SE, Tuzcu EM, Brewer HB, Sipahi I, Nicholls SJ, Ganz P, Schoenhagen P, Waters DD, Pepine CJ, Crowe TD, Davidson MH, Deanfield JE, Wisniewski LM, Hanyok JJ, Kassalow LM. Effect of ACAT inhibition on the progression of coronary atherosclerosis. N Engl J Med. 2006;354: Miller EJ, Li J, Leng L, McDonald C, Atsumi T, Bucala R, Young LH. Macrophage migration inhibitory factor stimulates AMP-activated protein kinase in the ischaemic heart. Nature. 2008;451:

10 Macrophage Migration Inhibitory Factor in Cardiovascular Disease Alma Zernecke, Jürgen Bernhagen and Christian Weber Circulation. 2008;117: doi: /CIRCULATIONAHA Circulation is published by the American Heart Association, 7272 Greenville Avenue, Dallas, TX Copyright 2008 American Heart Association, Inc. All rights reserved. Print ISSN: Online ISSN: The online version of this article, along with updated information and services, is located on the World Wide Web at: Permissions: Requests for permissions to reproduce figures, tables, or portions of articles originally published in Circulation can be obtained via RightsLink, a service of the Copyright Clearance Center, not the Editorial Office. Once the online version of the published article for which permission is being requested is located, click Request Permissions in the middle column of the Web page under Services. Further information about this process is available in the Permissions and Rights Question and Answer document. Reprints: Information about reprints can be found online at: Subscriptions: Information about subscribing to Circulation is online at: