Biomedical subjects

Triantafyllos Chavakis

Publications and source records attributed to Triantafyllos Chavakis.

At least 19 recordsLinked to original sources

PubMed2007

High-mobility group box 1 activates integrin-dependent homing of endothelial progenitor cells.

Endothelial progenitor cells (EPCs) are recruited to ischemic regions and improve neovascularization. Integrins contribute to EPC homing. High-mobility group box 1 (HMGB1) is a nuclear protein that is released extracellularly on cell necrosis and tissue damage, eliciting a proinflammatory response and stimulating tissue repair. In the present study, we investigated the effects of HMGB1 on EPC homing. EPCs express the HMGB1 receptors RAGE (receptor for advanced glycation end products) and TLR2 (Toll-like receptor 2). EPC migration was stimulated by HMGB1 in a RAGE-dependent manner. In addition, the HMGB1-induced migration of EPCs on fibronectin and fibrinogen was significantly inhibited by antibodies against beta1 and beta2 integrins, respectively. Short-term prestimulation of EPCs with HMGB1 also increased EPC adhesion to endothelial cell monolayers, and this effect was blocked by antibodies to beta2 integrins or RAGE. HMGB1 increased EPC adhesion to the immobilized integrin ligands intercellular adhesion molecule-1 and fibronectin in a RAGE-dependent manner. Strikingly, HMGB1 rapidly increased integrin affinity and induced integrin polarization. Using intravital microscopy in a tumor model of neovascularization, prestimulation of EPCs with HMGB1 enhanced the initial in vivo adhesion of EPCs to microvessels and the recruitment of EPCs in the tumor tissue. In addition, prestimulation of EPCs with HMGB1 increased the homing of EPCs to ischemic muscles. In conclusion, these data represent a link between HMGB1 and integrin functions of EPCs and demonstrate that HMGB1 stimulates EPC homing to ischemic tissues. These results may provide a platform for the development of novel therapeutic approaches to improve EPC homing.

Animals↗

PubMed2006

Junctional adhesion molecule-C regulates vascular endothelial permeability by modulating VE-cadherin-mediated cell-cell contacts.

We recently reported that junctional adhesion molecule (JAM)-C plays a role in leukocyte transendothelial migration. Here, the role of JAM-C in vascular permeability was investigated in vitro and in vivo. As opposed to macrovascular endothelial cells that constitutively expressed JAM-C in cell-cell contacts, in quiescent microvascular endothelial cells, JAM-C localized mainly intracellularly, and was recruited to junctions upon short-term stimulation with vascular endothelial growth factor (VEGF) or histamine. Strikingly, disruption of JAM-C function decreased basal permeability and prevented the VEGF- and histamine-induced increases in human dermal microvascular endothelial cell permeability in vitro and skin permeability in mice. Permeability increases are essential in angiogenesis, and JAM-C blockade reduced hyperpermeability and neovascularization in hypoxia-induced retinal angiogenesis in mice. The underlying mechanisms of the JAM-C-mediated increase in endothelial permeability were studied. JAM-C was essential for the regulation of endothelial actomyosin, as revealed by decreased F-actin, reduced myosin light chain phosphorylation, and actin stress fiber formation due to JAM-C knockdown. Moreover, the loss of JAM-C expression resulted in stabilization of VE-cadherin-mediated interendothelial adhesion in a manner dependent on the small GTPase Rap1. Together, through modulation of endothelial contractility and VE-cadherin-mediated adhesion, JAM-C helps to regulate vascular permeability and pathologic angiogenesis.

Animals↗

PubMed2006

The extracellular adherence protein from Staphylococcus aureus abrogates angiogenic responses of endothelial cells by blocking Ras activation.

The extracellular adherence protein (Eap), a broad-spectrum adhesin secreted by Staphylococcus aureus, was previously shown to curb acute inflammatory responses, presumably through its binding to endothelial cell (EC) ICAM-1. Examining the effect of Eap on endothelial function in more detail, we here show that, in addition, Eap functions as a potent angiostatic agent. Concomitant treatment of EC with purified Eap resulted in the complete blockage of the mitogenic and sprouting responses elicited by vascular endothelial growth factor (VEGF)165 or basic fibroblast growth factor (bFGF). Moreover, the induction of tissue factor and decay-accelerating factor were repressed by Eap, as determined by qRT-polymerase chain reaction (qRT-PCR), with a corresponding reduction in Egr-1 protein up-regulation seen. This angiostatic activity was accompanied by a corresponding inhibition in ERK1/2 phosphorylation, while activation of p38 was not affected. Inhibition occurred downstream of tyrosine kinase receptor activation, as comparable effects were seen on TPA-induced ERK1/2 phosphorylation. Similar to previously described angiostatic agents like angiopoietin-1 or the 16-kDa prolactin fragment, Eap blockage of the Ras/Raf/MEK/ERK cascade was localized by pull-down assay at the level of Ras activation. Eap's combined anti-inflammatory and antiangiogenic properties render this bacterial protein not only an important virulence factor during S. aureus infection but open new perspectives for therapeutic applications in pathological neovascularization.

Bacterial Proteins↗

PubMed2006

Suppression of experimental autoimmune encephalomyelitis by extracellular adherence protein of Staphylococcus aureus.

Multiple sclerosis (MS) is a devastating inflammatory disorder of the central nervous system (CNS). A major hallmark of MS is the infiltration of T cells reactive against myelin components. T cell infiltration is mediated by the interaction of integrins of the beta1 and beta2 family expressed by lymphocytes with their endothelial counter-receptors, vascular cell adhesion molecule 1 and intercellular adhesion molecule (ICAM)-1, respectively. We have reported previously that extracellular adherence protein (Eap) of Staphylococcus aureus exerts antiinflammatory activities by interacting with ICAM-1 and blocking beta2-integrin-dependent neutrophil recruitment. Here, we report that Eap inhibits experimental autoimmune encephalomyelitis (EAE) in mice. In vitro, Eap reduced adhesion of peripheral blood T cells to immobilized ICAM-1 as well as their adhesion and transmigration of TNF-activated human endothelium under static and shear flow conditions. These inhibitory effects were corroborated in two mouse models of inflammation. In a delayed-type hypersensitivity model, both T cell infiltration and the corresponding tissue edema were significantly reduced by Eap. In addition, Eap administration prevented the development of EAE and markedly decreased infiltration of inflammatory cells into the CNS. Strikingly, intervention with Eap after the onset of EAE suppressed the disease. Collectively, our findings indicate that Eap represents an attractive treatment for autoimmune neuroinflammatory disorders such as MS.

Amino Acid Sequence↗

PubMed2006

Extracellular matrix metalloproteinase inducer regulates matrix metalloproteinase activity in cardiovascular cells: implications in acute myocardial infarction.

BACKGROUND: Matrix metalloproteinases (MMPs) are thought to promote progression of atherosclerosis and cardiovascular complications such as plaque rupture. It has been suggested that, on tumor cells, the extracellular MMP inducer (EMMPRIN) is involved in MMP synthesis by as yet unknown mechanisms. On cardiovascular cells, regulation of EMMPRIN in vivo or any functional relevance for MMP induction in vitro has not yet been studied. Thus, we studied EMMPRIN expression on monocytes in acute myocardial infarction (MI) and its potential relevance for MMP activation. METHODS AND RESULTS: In 20 patients with acute MI, surface expression of EMMPRIN was significantly enhanced on monocytes compared with in 20 patients with chronic stable angina. EMMPRIN upregulation was associated with increased expression of the membrane type 1 MMP (MT1-MMP) on monocytes (flow cytometry) as well as MMP-9 activity (gelatin zymography) in the plasma. At 6 months after successful revascularization, EMMPRIN, MT1-MMP, and MMP-9 had normalized. The secretion of MMP-9 by monocytes was induced by monocyte adhesion to immobilized recombinant EMMPRIN or to EMMPRIN-transfected Chinese hamster ovary cells. Moreover, adherent EMMPRIN-transfected monocytic cells stimulated MMP-2 activity of human vascular smooth muscle cells. Gene silencing of EMMPRIN by small-interfering RNA hindered lipopolysaccharide-induced monocyte secretion of MMP-9, indicating a predominant role of EMMPRIN in MMP-9 induction. CONCLUSIONS: EMMPRIN and MT1-MMP are upregulated on monocytes in acute MI. During cellular interactions, EMMPRIN stimulates MMP-9 in monocytes and MMP-2 in smooth muscle cells, indicating that EMMPRIN may display a key regulatory role for MMP activity in cardiovascular pathologies.

Adult↗

PubMed2006

Lipoprotein(a) in atherosclerotic plaques recruits inflammatory cells through interaction with Mac-1 integrin.

Lipoprotein(a) [Lp(a)], consisting of LDL and the unique constituent apolipoprotein(a) [apo(a)], which contains multiple repeats resembling plasminogen kringle 4, is considered a risk factor for the development of atherosclerotic disorders. However, the underlying mechanisms for the atherogenicity of Lp(a) are not completely understood. Here, we define a novel function of Lp(a) in promoting inflammatory cell recruitment that may contribute to its atherogenicity. Through its apo(a) moiety Lp(a) specifically interacts with the beta2-integrin Mac-1, thereby promoting the adhesion of monocytes and their transendothelial migration in a Mac-1-dependent manner. Interestingly, the interaction between Mac-1 and Lp(a) was strengthened in the presence of proatherogenic homocysteine and was blocked by plasminogen/angiostatin kringle 4. Through its interaction with Mac-1, Lp(a) induced activation of the proinflammatory transcription factor NFkappaB, as well as the NFkappaB-related expression of prothrombotic tissue factor. In atherosclerotic coronary arteries Lp(a) was found to be localized in close proximity to Mac-1 on infiltrating mononuclear cells. Taken together, our data demonstrate that Lp(a), via its apo(a) moiety, is a ligand for the beta2-integrin Mac-1, thereby facilitating inflammatory cell recruitment to atherosclerotic plaques. These observations suggest a novel mechanism for the atherogenic properties of Lp(a).

Aged↗

PubMed2006

The role of junctional adhesion molecules in interactions between vascular cells.

Adhesive interactions between cells regulate tissue integrity as well as the process of inflammatory cell recruitment. Such intercellular interactions are regulated by adhesion receptors and can be homotypic, that is, between cells of the same type, for example, between adjacent endothelial cells in the vasculature, as well as heterotypic, that is, between different cells, such as the leukocyte endothelial interactions that take place during leukocyte extravasation. Emerging evidence points to the importance of the family of junctional adhesion molecules (JAMs), which are localized in interendothelial contacts and are implicated in the regulation of leukocyte extravasation. JAMs are members of the immunoglobulin superfamily and can undergo both homophilic and heterophilic interactions. This chapter deals with the role of JAMs in the regulation of adhesive interactions between vascular cells.

Animals↗

PubMed2005

The extracellular adherence protein (Eap) of Staphylococcus aureus inhibits wound healing by interfering with host defense and repair mechanisms.

Staphylococcus aureus is a major human pathogen interfering with host-cell functions. Impaired wound healing is often observed in S aureus-infected wounds, yet, the underlying mechanisms are poorly defined. Here, we identify the extracellular adherence protein (Eap) of S aureus to be responsible for impaired wound healing. In a mouse wound-healing model wound closure was inhibited in the presence of wild-type S aureus and this effect was reversible when the wounds were incubated with an isogenic Eap-deficient strain. Isolated Eap also delayed wound closure. In the presence of Eap, recruitment of inflammatory cells to the wound site as well as neovascularization of the wound were prevented. In vitro, Eap significantly reduced intercellular adhesion molecule 1 (ICAM-1)-dependent leukocyte-endothelial interactions and diminished the consequent activation of the proinflammatory transcription factor nuclear factor kappaB (NFkappaB) in leukocytes associated with a decrease in expression of tissue factor. Moreover, Eap blocked alphav-integrin-mediated endothelial-cell migration and capillary tube formation, and neovascularization in matrigels in vivo. Collectively, the potent anti-inflammatory and antiangiogenic properties of Eap provide an underlying mechanism that may explain the impaired wound healing in S aureus-infected wounds. Eap may also serve as a lead compound for new anti-inflammatory and antiangiogenic therapies in several pathologies.

Animals↗

PubMed2005

The role of junctional adhesion molecule-C (JAM-C) in oxidized LDL-mediated leukocyte recruitment.

The junctional adhesion molecule-C (JAM-C) was recently shown to be a counter receptor for the leukocyte beta2-integrin Mac-1 (CD11b/CD18), thereby mediating interactions between vascular cells, particularly in inflammatory cell recruitment. Here, we investigated the role of JAM-C in oxidized low-density lipoprotein (LDL)-mediated leukocyte recruitment. As compared with normal arteries, immunostaining of atherosclerotic vessels revealed a high expression of JAM-C in association with neointimal smooth muscle cells and the endothelium. Moreover, JAM-C was strongly up-regulated in the spontaneous early lesions in ApoE -/- mice. In vitro, cultured human arterial smooth muscle cells (HASMC) were found to express JAM-C, and oxLDL, as well as enzymatically modified LDL (eLDL) significantly up-regulated JAM-C on both HASMC and endothelial cells in a time- and dose-dependent manner. Although under quiescent conditions, JAM-C predominantly localized to interendothelial cell-cell contacts in close proximity to zonula occludens-1 (ZO-1), oxLDL treatment induced a disorganization of JAM-C localization that was no more restricted to the interendothelial junctions. JAM-C thereby mediated both leukocyte adhesion and leukocyte transendothelial migration upon oxLDL treatment of endothelial cells, whereas JAM-C on quiescent endothelial cells only mediates leukocyte transmigration. Thus, upon oxLDL stimulation endothelial JAM-C functions as both an adhesion, as well as a transmigration receptor for leukocytes. Taken together, JAM-C is up-regulated by oxLDL and may thereby contribute to increased inflammatory cell recruitment during atherosclerosis. JAM-C may therefore provide a novel molecular target for antagonizing interactions between vascular cells in atherosclerosis.

Aged↗

PubMed2005

Binding of Escherichia coli hemolysin and activation of the target cells is not receptor-dependent.

Production of a single cysteine substitution mutant, S177C, allowed Escherichia coli hemolysin (HlyA) to be radioactively labeled with tritiated N-ethylmaleimide without affecting biological activity. It thus became possible to study the binding characteristics of HlyA as well as of toxin mutants in which one or both acylation sites were deleted. All toxins bound to erythrocytes and granulocytes in a nonsaturable manner. Only wild-type toxin and the lytic monoacylated mutant stimulated production of superoxide anions in granulocytes. An oxidative burst coincided with elevation of intracellular Ca(2+), which was likely because of passive influx of Ca(2+) through the toxin pores. Competition experiments showed that binding to the cells was receptor-independent, and preloading of cells with a nonlytic HlyA mutant did not abrogate the respiratory burst provoked by a subsequent application of wild-type HlyA. In contrast to a previous report, expression or activation of the beta(2) integrin lymphocyte function-associated antigen-1 did not affect binding of HlyA. We conclude that HlyA binds nonspecifically to target cells and a receptor is involved neither in causing hemolysis nor in triggering cellular reactions.

Acylation↗

PubMed2005

Inhibition of pathologic retinal neovascularization by alpha-defensins.

Proliferative retinopathies, such as those complicating prematurity and diabetes, are major causes of blindness. A prominent feature of these retinopathies is excessive neovascularization, which is orchestrated by the hypoxia-induced vascular endothelial growth factor (VEGF) stimulating endothelial cells and the integrin-mediated adhesive interactions of endothelial cells with extracellular matrix components such as fibronectin (FN). Recently, we demonstrated that alpha-defensins interfere with alpha5beta1-FN interactions and dependent endothelial cell functions. Here, alpha-defensins were studied in hypoxia-induced proliferative retinopathy. In vitro, alpha-defensins specifically inhibited alpha5beta1-integrin-dependent migration of bovine retinal endothelial cells (BRECs) to FN, attenuated the VEGF-stimulated increase in endothelial permeability, and blocked BREC proliferation and capillary sprout formation in 3-dimensional fibrin-matrices. An up-regulation of beta1-integrin and FN was observed in the retinal vessels in the mouse model of hypoxia-induced retinal angiogenesis. Systemic and local administration of alpha-defensins reduced retinal neovascularization by 45% and 60%, respectively, and this effect was comparable to the inhibitory effect of alpha5beta1-blocking antibody. alpha-Defensins were detected in human diabetic retinas associated with normal retinal vessels but were absent from proliferative lesions. Together, these data show that alpha-defensins inhibit pathologic retinal neovascularization in vivo and may provide a clinically efficient strategy against proliferative retinopathies.

Animals↗

PubMed2005

Understanding RAGE, the receptor for advanced glycation end products.

Advanced glycation end products (AGEs), S100/calgranulins, HMGB1-proteins, amyloid-beta peptides, and the family of beta-sheet fibrils have been shown to contribute to a number of chronic diseases such as diabetes, amyloidoses, inflammatory conditions, and tumors by promoting cellular dysfunction via binding to cellular surface receptors. The receptor for AGEs (RAGE) is a multiligand receptor of the immunoglobulin superfamily of cell surface molecules acting as counter-receptor for these diverse molecules. Engagement of RAGE converts a brief pulse of cellular activation to sustained cellular dysfunction and tissue destruction. The involvement of RAGE in pathophysiologic processes has been demonstrated in murine models of chronic disease using either a receptor decoy such as soluble RAGE (sRAGE), RAGE neutralizing antibodies, or a dominant-negative form of the receptor. Studies with RAGE-/- mice confirmed that RAGE contributes, at least in part, to the development of late diabetic complications, such as neuropathy and nephropathy, macrovascular disease, and chronic inflammation. Furthermore, deletion of RAGE provided protection from the lethal effects of septic shock caused by cecal ligation and puncture (CLP). In contrast, deletion of RAGE had no effect on the host response in delayed-type hypersensitivity (DTH). Despite the lack of effect seen in adaptive immunity by the deletion of RAGE, administration of the receptor decoy, sRAGE, still afforded a protective effect in RAGE-/- mice. Thus, sRAGE is likely to sequester ligands, thereby preventing their interaction with other receptors in addition to RAGE. These data suggest that, just as RAGE is a multiligand receptor, its ligands are also likely to recognize several receptors in mediating their biologic effects.

Animals↗

PubMed2005

The homophilic binding of junctional adhesion molecule-C mediates tumor cell-endothelial cell interactions.

The junctional adhesion molecule C (JAM-C) was recently shown to undergo a heterophilic interaction with the leukocyte beta2 integrin Mac-1, thereby mediating interactions between vascular cells in inflammatory cell recruitment. Here, the homophilic interaction of JAM-C is presented and functionally characterized to mediate tumor cell-endothelial cell interactions. Recombinant soluble JAM-C in fluid phase bound to immobilized JAM-C as assessed in a purified system; moreover, JAM-C-transfected Chinese hamster ovary (CHO) cells adhered to immobilized JAM-C. The homophilic interaction of JAM-C was mediated by the isolated amino-terminal Ig domain (D1), but not the carboxyl-terminal Ig domain (D2), of the molecule. Dimerization of JAM-A is dependent on the sequence RVE in the amino-terminal Ig domain. This motif is conserved in JAM-C (Arg64-Ile65-Glu66), and a single amino acid mutation in this motif (E66R) abolished the homophilic interaction of JAM-C. The lung carcinoma cell line NCI-H522 was found to express JAM-C. NCI-H522 cells adhered to immobilized JAM-C, as well as to JAM-C-transfected CHO cells, but not to mock-transfected CHO cells or to CHO cells transfected with the JAM-C mutant (E66R). Adhesion of NCI-H522 cells to JAM-C protein or JAM-C-transfected CHO cells was abolished in the presence of soluble JAM-C or the isolated D1. Furthermore, the adhesion of NCI-H522 cells to endothelial cells was significantly blocked by soluble JAM-C or the isolated D1. Thus, JAM-C undergoes a homophilic interaction via the Arg64-Ile65-Glu66 motif on the membrane-distal Ig domain of the molecule. The homophilic interaction of JAM-C can mediate tumor cell-endothelial cell interactions and may thereby be involved in the process of tumor cell metastasis.

Amino Acid Motifs↗

PubMed2005

Staphylococcus aureus interactions with the endothelium: the role of bacterial "secretable expanded repertoire adhesive molecules" (SERAM) in disturbing host defense systems.

The intravascular manifestation of Staphylococcus aureus infection is often associated with a severe, and sometimes catastrophic disease. Many host factors contribute to endothelial tropism of S.aureus including subendothelial matrix proteins, endothelial cell receptors, and platelets that are engaged together with S. aureus cell wall adhesins such as the fibronectin binding proteins. Recently, the role of secreted staphylococcal factors that were initially identified by virtue of their binding function with host proteins and ligands, has been reappraised in this regard. Among these, bacterial proteins without significant homology among each other, coagulase (Coa), the extracellular fibrinogen binding protein (Efb), the extracellular matrix binding protein (Emp), or the extracellular adhesive protein (Eap), are the most prominent ones to be associated with endovascular disease. Newly discovered interactions with host components may account for profound effects on immunmodulation and wound healing which are summarized in this short review and which ascribe an important role of these molecules in acute and chronic endo- and extravascular staphylococcal disease. Further research in the complex functional role of these "secretable expanded repertoire adhesive molecules" (SERAM) may not only help to increase our understanding in the pathogenesis of S. aureus infection but can specify novel targets for preventive or therapeutic strategies.

Adhesins, Bacterial↗

PubMed2004

Role of beta2-integrins for homing and neovascularization capacity of endothelial progenitor cells.

The mechanisms of homing of endothelial progenitor cells (EPCs) to sites of ischemia are unclear. Here, we demonstrate that ex vivo-expanded EPCs as well as murine hematopoietic Sca-1+/Lin- progenitor cells express beta2-integrins, which mediate the adhesion of EPCs to endothelial cell monolayers and their chemokine-induced transendothelial migration in vitro. In a murine model of hind limb ischemia, Sca-1+/Lin- hematopoietic progenitor cells from beta2-integrin-deficient mice are less capable of homing to sites of ischemia and of improving neovascularization. Preactivation of the beta2-integrins expressed on EPCs by activating antibodies augments the EPC-induced neovascularization in vivo. These results provide evidence for a novel function of beta2-integrins in postnatal vasculogenesis.

Animals↗

PubMed2004

The junctional adhesion molecule-C promotes neutrophil transendothelial migration in vitro and in vivo.

The third member of the family of junctional adhesion molecules (JAMs), JAM-3, also called JAM-C, was recently shown to be a novel counter-receptor on platelets for the leukocyte beta(2)-integrin Mac-1 (alphaMbeta(2), CD11b/CD18). Here, new functional aspects of the role of endothelial cell JAM-C were investigated. Endothelial cells express JAM-C, which is predominantly localized within junctions at interendothelial contacts, since it codistributes with a tight junction component, zonula occludens-1. Whereas JAM-C does not participate in neutrophil adhesion to endothelial cells, it mediates neutrophil transmigration in a Mac-1-dependent manner. In particular, inhibition of JAM-C significantly reduced neutrophil transendothelial migration, and the combination of JAM-C and platelet/endothelial cell adhesion molecule-1 blockade almost completely abolished neutrophil transendothelial migration in vitro. In vivo, inhibition of JAM-C with soluble mouse JAM-C resulted in a 50% reduction of neutrophil emigration in the mouse model of acute thioglycollate-induced peritonitis. Thus, JAM-C participates in neutrophil transmigration and thereby provides a novel molecular target for antagonizing interactions between vascular cells that promote inflammatory vascular pathologies.

Animals↗

PubMed2004

Angiostatin is a novel anti-inflammatory factor by inhibiting leukocyte recruitment.

Angiogenesis and inflammation are closely related biologic processes in wound healing and the responses to vascular injury as well as in cardiovascular diseases; however, the molecular connections are poorly defined. In particular, it is yet unclear whether endogenous factors can regulate both angiogenesis and inflammation. Here, we show that the endogenous angiogenesis inhibitor, angiostatin (containing kringle domains 1-4 of plasminogen), serves an anti-inflammatory role, since the kringles 1-3 and its kringle 4 directly interact with leukocyte beta1- and beta2-integrins, respectively. In particular, a specific interaction between kringle 4 and alphaMbeta2-integrin (Mac-1) but not leukocyte function antigen 1 (LFA-1) was identified. Angiostatin thereby inhibited beta1- and beta2-integrin-mediated adhesion of leukocytes to extracellular matrix proteins and the endothelium as well as their transmigration through the endothelium in vitro. Moreover, angiostatin blocked the peritonitis-induced neutrophil emigration in vivo. In addition, through its interaction with Mac-1, angiostatin reduced activation of the proinflammatory transcription factor nuclear factor kappaB (NFkappaB), as well as the NFkappaB-related expression of tissue factor, a potent initiator of hemostasis following vascular injury. Finally, angiostatin forms were generated in vivo following skin injury/inflammation and were detectable during the following entire period of wound healing peaking at the terminal phase of the healing process. Taken together, over and above inhibition of neovascularization, angiostatin was identified as an antiadhesive/anti-inflammatory substance. These observations could provide the basis for new therapeutic applications of angiostatin to target chronic inflammatory processes in different pathologic situations.

Angiogenesis Inhibitors↗

PubMed2004

Regulation of neovascularization by human neutrophil peptides (alpha-defensins): a link between inflammation and angiogenesis.

Angiogenesis, the growth of new blood vessels, is a complex biological process that is orchestrated by several growth factors and components of the extracellular matrix, including fibronectin (FN) and its receptor the integrin alpha5beta1. Angiogenesis is a critical part of inflammation and wound repair, but the mechanism by which vascular proliferation and migration is regulated by inflammatory cells is not completely understood. We have previously shown that human neutrophil peptides (HNPs), also known as alpha-defensins, which are secreted in high concentrations when neutrophils are activated, bind specifically to FN in the extracellular matrix and inhibit plasminogen activation. Therefore, we asked whether HNPs act as a link between inflammation and angiogenesis. Alpha5beta1-mediated endothelial cell adhesion and migration to FN, both under control conditions and under stimulation by vascular endothelial growth factor (VEGF), were inhibited specifically and in a dose-dependent manner by HNPs, whereas endothelial cell adhesion and migration to other components of the extracellular matrix, such as vitronectin, collagen, or fibrinogen/fibrin were not. Consistent with this finding, HNPs bound to and promoted the binding of fibronectin to alpha5beta1 integrin in arginine-glycine-aspartic acid (RGD)-independent manner. HNPs also completely inhibited VEGF-induced proliferation and induced apoptosis of endothelial cells in a dose-dependent manner. Moreover, HNPs inhibited capillary tube formation in three-dimensional fibrin-matrices as well as neovascularization in vivo in the chicken chorioallantoic membrane assay. Taken together, these data indicate that HNPs can regulate angiogenesis by affecting endothelial cell adhesion and migration in an FN-dependent manner as well as endothelial cell proliferation. These findings provide new insight into the role of inflammatory cells in angiogenesis and might provide a platform for developing a novel class of anti-angiogenesis drugs.

Animals↗