Mieke Gouwy

Universitair Ziekenhuis Leuven, Louvain, Flanders, Belgium

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Publications (31)156.18 Total impact

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    ABSTRACT: Serum amyloid A (SAA) is an acute phase protein which is up-regulated in inflammatory diseases and chemoattracts monocytes, lymphocytes and granulocytes via its G protein-coupled receptor FPRL1/FPR2. Here, we demonstrated that the SAA1α isoform also chemoattracts monocyte-derived immature dendritic cells (DCs) in the Boyden and μ-slide chemotaxis assay and that its chemotactic activity for monocytes and DCs was indirectly mediated via rapid chemokine induction. Indeed, SAA1 induced significant amounts (≥5 ng/ml) of MIP-1α/CCL3 and IL-8/CXCL8 in monocytes and DCs in a dose-dependent manner within 3 h. However, SAA1 also directly activated monocytes and DCs for signaling and chemotaxis without chemokine interference. SAA1-induced monocyte migration was nevertheless significantly prevented (60 to 80% inhibition) in the constant presence of desensitizing exogenous MIP-1α/CCL3, neutralizing anti-MIP-1α/CCL3 antibody or a combination of CCR1 and CCR5 antagonists, indicating that this endogenously produced CC chemokine was indirectly contributing to SAA1-mediated chemotaxis. Further, anti-IL-8/CXCL8 antibody neutralized SAA1-induced monocyte migration, suggesting that endogenous IL-8/CXCL8 acted in concert with MIP-1α/CCL3. This explained why SAA1 failed to synergize with exogenously added MIP-1α/CCL3 or SDF-1α/CXCL12 in monocyte and DC chemotaxis. In addition to direct leukocyte activation, SAA1 induces a chemotactic cascade mediated by expression of cooperating chemokines to prolong leukocyte recruitment to the inflammatory site.This article is protected by copyright. All rights reserved
    European Journal of Immunology 10/2014; · 4.97 Impact Factor
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    ABSTRACT: CXC chemokines influence a variety of biological processes, such as angiogenesis, both in a physiological and pathological context. Platelet factor-4 (PF-4)/CXCL4 and its variant PF-4var/CXCL4L1 are known to favor angiostasis by inhibiting endothelial cell proliferation and chemotaxis. CXCL4L1 in particular is a potent inhibitor of angiogenesis with anti-tumoral characteristics, both through regulation of neovascularization and through attraction of activated lymphocytes. However, its underlying signaling pathways remain to be elucidated. Here, we have identified various intracellular pathways activated by CXCL4L1 in comparison with other CXCR3 ligands, including CXCL4 and interferon-γ-induced protein 10/CXCL10. Signaling experiments show involvement of the mitogen-activated protein kinase (MAPK) family in CXCR3A-transfected cells, activated lymphocytes and human microvascular endothelial cells (HMVEC). In CXCR3A transfectants, CXCL4 and CXCL4L1 activated p38 MAPK, as well as Src kinase within 30 and 5 min, respectively. Extracellular signal-regulated kinase (ERK) phosphorylation occured in activated lymphocytes, yet was inhibited in microvascular and lymphatic endothelial cells. CXCL4L1 and CXCL4 counterbalanced the angiogenic chemokine stromal cell-derived factor-1/CXCL12 in both endothelial cell types. Notably, inhibition of ERK signaling by CXCL4L1 and CXCL4 in lymphatic endothelial cells implies that these chemokines might also regulate lymphangiogenesis. Furthermore, CXCL4, CXCL4L1 and CXCL10 slightly enhanced forskolin-stimulated cAMP production in HMVEC. Finally, CXCL4, but not CXCL4L1, induced activation of p70S6 kinase within 5 min in HMVEC. Our findings confirm that the angiostatic chemokines CXCL4L1 and CXCL4 activate both CXCR3A and CXCR3B and bring new insights into the complexity of their signaling cascades.
    Angiogenesis 01/2014; · 4.41 Impact Factor
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    ABSTRACT: Dendritic cells (DCs) are potent antigen presenting cells, described as the initiators of adaptive immune responses. Immature monocyte-derived DCs (MDDC) showed decreased CD14 expression, increased cell surface markers DC-SIGN and CD1a and enhanced levels of receptors for the chemokines CCL3 (CCR1/CCR5) and CXCL8 (CXCR1/CXCR2) compared with human CD14(+) monocytes. After further MDDC maturation by LPS, the markers CD80 and CD83 and the chemokine receptors CXCR4 and CCR7 were upregulated, whereas CCR1, CCR2 and CCR5 expression was reduced. CCL3 dose-dependently synergized with CXCL8 or CXCL12 in chemotaxis of immature MDDC. CXCL12 augmented the CCL3-induced ERK1/2 and Akt phosphorylation in immature MDDC, although the synergy between CCL3 and CXCL12 in chemotaxis of immature MDDC was dependent on the Akt signaling pathway but not on ERK1/2 phosphorylation. CCL2 also synergized with CXCL12 in immature MDDC migration. Moreover, two CXC chemokines not sharing receptors (CXCL12 and CXCL8) cooperated in immature MDDC chemotaxis, whereas two CC chemokines (CCL3 and CCL7) sharing CCR1 did not. Further, the non-chemokine G protein-coupled receptor ligands chemerin and fMLP synergized with respectively CCL7 and CCL3 in immature MDDC signaling and migration. Finally, CXCL12 and CCL3 did not cooperate, but CXCL12 synergized with CCL21 in mature MDDC chemotaxis. Thus, chemokine synergy in immature and mature MDDC migration is dose-dependently regulated by chemokines via alterations in their chemokine receptor expression pattern according to their role in immune responses.
    Immunobiology 10/2013; · 2.81 Impact Factor
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    ABSTRACT: Bovine serum is a rich source of cytokines and growth factors supporting in vitro cell culture. Here, a novel bovine monocyte chemotactic factor (boMCF-1) was isolated from commercial bovine serum by a four step purification procedure including adsorption to silicic acid, heparin affinity and cation-exchange chromatography and reversed phase HPLC. Homogeneous boMCF-1 was characterized as a 7717Da protein by mass spectrometry and identified by Edman degradation as the predicted product of bovine macrophage inflammatory protein-1α gene (boMIP-1α/CCL3) isoform 2 (lacking three NH(2)-terminal amino acids), belonging to the MIP subfamily of CC chemokines. Monocyte chemotactic activity of boCCL3 isoform 2 was completely desensitized by human CCL3 and CCL5, partially by CCL7 and not by CCL2. Its activity was better inhibited by CCR1 than by CCR5 blockade. BoCCL3 isoform 2, present in bovine serum at about 10ng/ml, functioned as a most potent chemoattractant for immature (but not mature) dendritic cells with a minimal effective concentration of 0.03ng/ml and a maximal chemotactic index of 30 at 0.3ng/ml. Its chemotactic activity on immature dendritic cells was significantly desensitized by human CCL3, CCL5 and CCL7. Blockade of CCR5 rather than CCR1 partially prevented chemotactic activity, whereas blockade of both further enhanced this inhibition. BoCCL3 isoform 2 was not chemokinetic but, like human CCL3, synergized with CXCL12 in monocytic cell chemotaxis. Since it cannot be deduced which is the exact human homolog of boCCL3 isoform 2, further research is required to study the biology of other boCCL3 family members.
    Biochemical pharmacology 12/2012; · 4.25 Impact Factor
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    ABSTRACT: The arrest and directed migration of leukocytes during homeostasis, tumour development and inflammation is orchestrated by a multitude of chemokines, which govern leukocyte migratory activities. Immune cells are particularly adept at adjusting rapidly to changes within the environment by migration in response to chemokines. The confrontation of leukocytes with different combination of chemokines that are concomitantly produced under physiological or pathological conditions in vivo is complex. There are different ways to enhance or reduce leukocyte migration mediated by chemokines such as posttranslational modifications. Here, we described a positive regulatory mechanism in leukocyte trafficking, by the synergism between chemokines to rapidly augment the local leukocyte influx, thereby enhancing the outcome of an inflammatory response in vivo. The cellular mechanisms involved in chemokine synergy are still debated, but probably include chemokine and/or receptor heterodimerization and subsequent cooperation in signal transduction.
    Immunology letters 07/2012; 145(1-2):10-4. · 2.91 Impact Factor
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    ABSTRACT: One of the most important functions of chemokines and their receptors is the regulation of directional migration of leukocytes within tissues. In specific tissue compartments, cells are exposed to multiple chemokines presented in complex dimensional and temporal patterns. Therefore, a leukocyte requires the mechanisms to integrate the various directional signals it receives from different chemoattractants. In this study, we report that CCL3, CCL5, and CCL8, three potent mononuclear cell chemoattractants, are able to synergize with the homeostatic chemokine CXCL12 in the migration of CD14(+) monocytes, CD3(+) T-lymphocytes, or PHA-activated lymphoblasts. In addition, CCL5 augmented the CXCR4 ligand-driven ERK phosphorylation in mononuclear cells. Furthermore, the synergistic effect between CCL5 and CXCL12 in monocyte chemotaxis is inhibited in the presence of specific CCR1 antibody and AMD3100, but not by maraviroc. In HIV-1 infection assays, a combination of CXCL12 and CCL5 cooperated to inhibit the replication of the dual-tropic (R5/X4) HIV-1 HE strain. Finally, although the dual-tropic HIV-1 strain was barely suppressed by AMD3100 or maraviroc alone, HIV-1 infection was completely blocked by the combination of these two receptor antagonists. Our data demonstrate the cooperation between CCL5 and CXCL12, which has implications in migration of monocytes/lymphocytes during inflammation and in HIV-1 infection.
    European Journal of Immunology 01/2011; 41(4):963-73. · 4.97 Impact Factor
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    ABSTRACT: The CXC and CC chemokine gene clusters provide an abundant number of chemotactic factors selectively binding to shared G protein-coupled receptors (GPCR). Hence, chemokines function in a complex network to mediate migration of the various leukocyte subsets, expressing specific GPCRs during the immune response. Further fine-tuning of the chemokine system is reached through specific posttranslational modifications of the mature proteins. Indeed, enzymatic processing of chemokines during an early phase of inflammation leads to activation of precursor molecules or cleavage into even more active or receptor specific chemokine isoforms. At a further stage, proteolytic processing leads to loss of GPCR signaling, thereby providing natural chemokine receptor antagonists. Finally, further NH(2)-terminal cleavage results in complete inactivation to dampen the inflammatory response. During inflammatory responses, the two chemokines which exist in a membrane-bound form may be released by proteases from the cellular surface. In addition to proteolytic processing, citrullination and glycosylation of chemokines is also important for their biological activity. In particular, citrullination of arginine residues seems to reduce the inflammatory activity of chemokines in vivo. This goes along with other positive and negative regulatory mechanisms for leukocyte migration, such as chemokine synergy and scavenging by decoy receptors.
    Experimental Cell Research 12/2010; 317(5):642-54. · 3.56 Impact Factor
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    ABSTRACT: Insight into molecular and cellular mechanisms of innate immunity is critical to understand viral pathogenesis and immunopathology and might be exploited for therapy. Whereas the molecular mechanisms of the IFN defense are well established, cellular mechanisms of antiviral immunity are only emerging, and their pharmacological triggering remains unknown. COAM is a polysaccharide derivative with antiviral activity but without comprehension about its mechanism of action. The COAM mixture was fractionated, and prophylactic treatment of mice with COAM polymers of high MW resulted in a conversion from 100% lethal mengovirus infection to an overall survival rate of 93% without obvious clinical sequelae. Differential and quantitative analysis of peritoneal leukocytes demonstrated that COAM induced a profound influx of neutrophils. Selective cell depletion experiments pointed toward neutrophils and macrophages as key effector cells in the rescue of mice from lethal mengovirus. COAM was able to induce mRNA and protein expression of the mouse neutrophil chemokine GCP-2. Binding of GCP-2 to COAM was demonstrated in solution and confirmed by SPR technology. Although COAM was not chemotactic for neutrophils, COAM-anchored muGCP-2 retained chemotactic activity for human and mouse neutrophils. In conclusion, this study established that COAM rescued mice from acute and lethal mengovirus infection by recruiting antiviral leukocytes to the site of infection, as proposed through the induction, binding, and concentration of endogenous chemokines. These findings reinforce the role of neutrophils and macrophages as critical cells that can be manipulated toward antiviral defense.
    Journal of leukocyte biology 11/2010; 88(5):1017-29. · 4.99 Impact Factor
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    ABSTRACT: We investigated possible cellular receptors for the human CXC chemokine platelet factor-4 variant/CXCL4L1, a potent inhibitor of angiogenesis. We found that CXCL4L1 has lower affinity for heparin and chondroitin sulfate-E than platelet factor-4 (CXCL4) and showed that CXCL10 and CXCL4L1 could displace each other on microvascular endothelial cells. Labeled CXCL4L1 also bound to CXCR3A- and CXCR3B-transfectants and was displaced by CXCL4L1, CXCL4, and CXCL10. The CXCL4L1 anti-angiogenic activity was blocked by anti-CXCR3 antibodies (Abs) in the Matrigel and cornea micropocket assays. CXCL4L1 application in CXCR3(-/-) or in wild-type mice treated with neutralizing anti-CXCR3 Abs, resulted in reduced inhibitory activity of CXCL4L1 on tumor growth and vascularization of Lewis lung carcinoma. Furthermore, CXCL4L1 and CXCL4 chemoattracted activated T cells, human natural killer cells, and human immature dendritic cells (DCs). Migration of DCs toward CXCL4 and CXCL4L1 was desensitized by preincubation with CXCL10 and CXCL11, inhibited by pertussis toxin, and neutralized by anti-CXCR3 Abs. Chemotaxis of T cells, natural killer cells, and DCs is likely to contribute to the antitumoral action. However, the in vivo data indicate that the angiostatic property of CXCL4L1 is equally important in retarding tumor growth. Thus, both CXCR3A and CXCR3B are implicated in the chemotactic and vascular effects of CXCL4L1.
    Blood 10/2010; 117(2):480-8. · 9.78 Impact Factor
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    ABSTRACT: Posttranslational modifications, e.g. proteolysis, glycosylation, and citrullination regulate chemokine function, affecting leukocyte migration during inflammatory responses. Here, modification of CXCL5/epithelial cell-derived neutrophil-activating protein-78 (ENA-78) by proteases or peptidylarginine deiminases (PAD) was evaluated. Slow CXCL5(1-78) processing by the myeloid cell marker aminopeptidase N/CD13 into CXCL5(2-78) hardly affected its in vitro activity, but slowed down the activation of CXCL5 by the neutrophil protease cathepsin G. PAD, an enzyme with a potentially important function in autoimmune diseases, site-specifically deiminated Arg(9) in CXCL5 to citrulline, generating [Cit(9)]CXCL5(1-78). Compared with CXCL5(1-78), [Cit(9)]CXCL5(1-78) less efficiently induced intracellular calcium signaling, phosphorylation of extracellular signal-regulated kinase, internalization of CXCR2, and in vitro neutrophil chemotaxis. In contrast, conversion of CXCL5 into the previously reported natural isoform CXCL5(8-78) provided at least 3-fold enhanced biological activity in these tests. Citrullination, but not NH(2)-terminal truncation, reduced the capacity of CXCL5 to up-regulate the expression of the integrin α-chain CD11b on neutrophils. Truncation nor citrullination significantly affected the ability of CXCL5 to up-regulate CD11a expression or shedding of CD62L. In line with the in vitro results, CXCL5(8-78) and CXCL5(9-78) induced a more pronounced neutrophil influx in vivo compared with CXCL5(1-78). Administration of 300 pmol of either CXCL5(1-78) or [Cit(9)]CXCL5(1-78) failed to attract neutrophils to the peritoneal cavity. Citrullination of the more potent CXCL5(9-78) lowers its chemotactic potency in vivo and confirms the tempering effect of citrullination in vitro. The highly divergent effects of modifications of CXCL5 on neutrophil influx underline the potential importance of tissue-specific interactions between chemokines and PAD or proteases.
    Journal of Biological Chemistry 09/2010; 285(39):29750-9. · 4.65 Impact Factor
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    ABSTRACT: During inflammatory reactions, endogenously produced cytokines and chemokines act in a network and interact with hormones and neurotransmitters to regulate host immune responses. These signaling circuitries are even more interfaced during infections, when microbial agonists activate TLR, RLR, and NLR receptors. On the basis of the discovery of synergy between chemokines for neutrophil attraction, we extend here this phenomenon between the chemokine MCP-1/CCL2 and the GPCR ligand fMLP or the TLR4 agonist LPS on monocytes. In fact, the bacterial tripeptide fMLP, but not the cytokines IL-1beta or IFN-gamma, significantly and dose-dependently synergized with CCL2 in monocyte chemotaxis. Furthermore, LPS rapidly induced the expression of IL-8/CXCL8 but not of the CCL2 receptor CCR2 in monocytic cells. In turn, the induced CXCL8 synergized with CCL2 for mononuclear cell chemotaxis, and the chemotactic effect was mediated by CXCR1/CXCR2, because CXCL8 receptor antagonists or antibodies were capable of blocking the synergy, while keeping the responsiveness to CCL2 intact. These data recapitulate in vitro the complexity of innate immune regulation, provide a novel mechanism of enhancing monocyte chemotaxis during bacterial infections with gram-negative bacteria and demonstrate the importance of local contexts in inflammatory and infectious insults.
    Journal of leukocyte biology 06/2009; 86(3):671-80. · 4.99 Impact Factor
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    ABSTRACT: Chemokines mediate the inflammatory response by attracting various leukocyte types. MCP-2/CC chemokine ligand 8 (CCL8) was induced at only suboptimal levels in fibroblasts and endothelial cells by IL-1beta or IFN-gamma, unless these cytokines were combined. IFN-gamma also synergized with the TLR ligands peptidoglycan (TLR2), dsRNA (TLR3) or LPS (TLR4). Under these conditions, intact MCP-2/CCL8(1-76) produced by fibroblasts was found to be processed into MCP-2/CCL8(6-75), which lacked chemotactic activity for monocytic cells. Furthermore, the capacity of MCP-2/CCL8(6-75) to increase intracellular calcium levels through CCR1, CCR2, CCR3 and CCR5 was severely reduced. However, the truncated isoform still blocked these receptors for other ligands. MCP-2/CCL8(6-75) induced internalization of CCR2, inhibited MCP-1/CCL2 and MCP-2/CCL8 ERK signaling and antagonized the chemotactic activity of several CCR2 ligands (MCP-1/CCL2, MCP-2/CCL8, MCP-3/CCL7). In contrast to MCP-3/CCL7, parvoviral delivery of MCP-2/CCL8 into B78/H1 melanoma failed to inhibit tumor growth, partially due to proteolytic cleavage into inactive MCP-2/CCL8 missing five NH(2)-terminal residues. However, in an alternative tumor model, using HeLa cells, MCP-2/CCL8 retarded tumor development. These data indicate that optimal induction and delivery of MCP-2/CCL8 is counteracted by converting this chemokine into a receptor antagonist, thereby losing its anti-tumoral potential.
    European Journal of Immunology 03/2009; 39(3):843-57. · 4.97 Impact Factor
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    ABSTRACT: Posttranslational proteolytic processing of chemokines is a natural mechanism to regulate inflammation. In this study, we describe modification of the CXC chemokine stromal cell-derived factor 1alpha/CXCL12 by peptidylarginine deiminase (PAD) that converts arginine residues into citrulline (Cit), thereby reducing the number of positive charges. The three NH(2)-terminal arginines of CXCL12, Arg(8), Arg(12), and Arg(20), were citrullinated upon incubation with PAD. The physiologic relevance of citrullination was demonstrated by showing coexpression of CXCL12 and PAD in Crohn's disease. Three CXCL12 isoforms were synthesized for biologic characterization: CXCL12-1Cit, CXCL12-3Cit, and CXCL12-5Cit, in which Arg(8), Arg(8)/Arg(12)/Arg(20), or all five arginines were citrullinated, respectively. Replacement of only Arg(8) caused already impaired (30-fold reduction) CXCR4 binding and signaling (calcium mobilization, phosphorylation of ERK and protein kinase B) properties. Interaction with CXCR4 was completely abolished for CXCL12-3Cit and CXCL12-5Cit. However, the CXCR7-binding capacities of CXCL12-1Cit and CXCL12-3Cit were, respectively, intact and reduced, whereas CXCL12-5Cit failed to bind CXCR7. In chemotaxis assays with lymphocytes and monocytes, CXCL12-3Cit and CXCL12-5Cit were completely devoid of activity, whereas CXCL12-1Cit, albeit at higher concentrations than CXCL12, induced migration. The antiviral potency of CXCL12-1Cit was reduced compared with CXCL12 and CXCL12-3Cit and CXCL12-5Cit (maximal dose 200 nM) could not inhibit infection of lymphocytic MT-4 cells with the HIV-1 strains NL4.3 and HE. In conclusion, modification of CXCL12 by one Cit severely impaired the CXCR4-mediated biologic effects of this chemokine and maximally citrullinated CXCL12 was inactive. Therefore, PAD is a potent physiologic down-regulator of CXCL12 function.
    The Journal of Immunology 02/2009; 182(1):666-74. · 5.52 Impact Factor
  • Cytokine 01/2009; 48(1):117-117. · 2.52 Impact Factor
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    ABSTRACT: Biological functions of proteins are influenced by posttranslational modifications such as on/off switching by phosphorylation and modulation by glycosylation. Proteolytic processing regulates cytokine and chemokine activities. In this study, we report that natural posttranslational citrullination or deimination alters the biological activities of the neutrophil chemoattractant and angiogenic cytokine CXCL8/interleukin-8 (IL-8). Citrullination of arginine in position 5 was discovered on 14% of natural leukocyte-derived CXCL8(1-77), generating CXCL8(1-77)Cit(5). Peptidylarginine deiminase (PAD) is known to citrullinate structural proteins, and it may initiate autoimmune diseases. PAD efficiently and site-specifically citrullinated CXCL5, CXCL8, CCL17, CCL26, but not IL-1beta. In comparison with CXCL8(1-77), CXCL8(1-77)Cit(5) had reduced affinity for glycosaminoglycans and induced less CXCR2-dependent calcium signaling and extracellular signal-regulated kinase 1/2 phosphorylation. In contrast to CXCL8(1-77), CXCL8(1-77)Cit(5) was resistant to thrombin- or plasmin-dependent potentiation into CXCL8(6-77). Upon intraperitoneal injection, CXCL8(6-77) was a more potent inducer of neutrophil extravasation compared with CXCL8(1-77). Despite its retained chemotactic activity in vitro, CXCL8(1-77)Cit(5) was unable to attract neutrophils to the peritoneum. Finally, in the rabbit cornea angiogenesis assay, the equally potent CXCL8(1-77) and CXCL8(1-77)Cit(5) were less efficient angiogenic molecules than CXCL8(6-77). This study shows that PAD citrullinates the chemokine CXCL8, and thus may dampen neutrophil extravasation during acute or chronic inflammation.
    Journal of Experimental Medicine 10/2008; 205(9):2085-97. · 13.21 Impact Factor
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    ABSTRACT: Interactions between chemokines and enzymes are vital in immunoregulation. Structural protein citrullination by peptidylarginine deiminase (PAD) has been associated with autoimmunity. In this report, we identified a novel naturally occurring posttranslational modification of chemokines, that is, the deimination of arginine at position 5 into citrulline of CXC chemokine ligand 10 (CXCL10) by rabbit PAD and human PAD2. Citrullination reduced (>/= 10-fold) the chemoattracting and signaling capacity of CXCL10 for CXC chemokine receptor 3 (CXCR3) transfectants; however, it did not affect CXCR3 binding. On T lymphocytes, though, citrullinated CXCL10 remained active but was again weaker than authentic CXCL10. PAD was also able to convert CXCL11, causing an impairment of CXCR3 signaling and T-cell activation, though less pronounced than for CXCL10. Similarly, receptor binding properties of CXCL11 were not altered by citrullination. However, deimination decreased heparin binding properties of both CXCL10 and CXCL11. Overall, chemokines are the first immune modulators reported of being functionally modified by citrullination. These data provide new structure-function dimensions for chemokines in leukocyte mobilization, disclosing an anti-inflammatory role for PAD. Additionally because citrullination has severe consequences for chemokine biology, this invites to reassess the involvement and impact of PAD and citrullinated peptides in inflammation, autoimmunity, and hematologic disorders.
    Blood 10/2008; 112(7):2648-56. · 9.78 Impact Factor
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    ABSTRACT: CC and CXC chemokines coinduced in fibroblasts and leukocytes by cytokines and microbial agents determine the number of phagocytes infiltrating into inflamed tissues. Interleukin-8/CXCL8 and stromal cell-derived factor-1/CXCL12 significantly and dose-dependently increased the migration of monocytes, expressing the corresponding CXC chemokine receptors CXCR2 and CXCR4, toward suboptimal concentrations of the monocyte chemotactic proteins CCL2 or CCL7. These findings were confirmed using different chemotaxis assays and monocytic THP-1 cells. In contrast, the combination of two CC chemokines (CCL2 plus CCL7) or two CXC chemokines (CXCL8 plus CXCL12) did not provide synergy in monocyte chemotaxis. These data show that chemokines competing for related receptors and using similar signaling pathways do not synergize. Receptor heterodimerization is probably not essential for chemokine synergy as shown in CXCR4/CCR2 cotransfectants. It is noteworthy that CCL2 mediated extracellular signal-regulated kinase 1/2 phosphorylation and calcium mobilization was significantly enhanced by CXCL8 in monocytes, indicating cooperative downstream signaling pathways during enhanced chemotaxis. Moreover, in contrast to intact CXCL12, truncated CXCL12(3-68), which has impaired receptor signaling capacity but can still desensitize CXCR4, was unable to synergize with CCL2 in monocytic cell migration. Furthermore, AMD3100 and RS102895, specific CXCR4 and CCR2 inhibitors, respectively, reduced the synergistic effect between CCL2 and CXCL12 significantly. These data indicate that for synergistic interaction between chemokines binding and signaling of the two chemokines via their proper receptors is necessary.
    Molecular pharmacology 06/2008; 74(2):485-95. · 4.53 Impact Factor
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    ABSTRACT: Chemokines affect inflammation and cancer through leukocyte attraction and angiogenesis. Here, we demonstrate that CXCL4L1/platelet factor-4 variant (PF-4var), a highly angiostatic chemokine, is poorly chemotactic for phagocytes and is inducible in monocytes by inflammatory mediators but remained undetectable in macrophages and neutrophils. In addition, CXCL4L1/PF-4var production by mesenchymal tumor cells was evidenced in vitro and in vivo by specific ELISA and immunohistochemistry. CXCL4L1/PF-4var, but not CXCL4/PF-4, was coinduced with the angiogenic chemokine CXCL6/granulocyte chemotactic protein-2 (GCP-2) by cytokines, e.g., IL-1beta and IL-17, in sarcoma cells, but not in diploid fibroblasts. Furthermore, the induction of CXCL6/GCP-2 in endothelial cells by IL-1beta was enhanced synergistically by TNF-alpha but inhibited by IFN-gamma, which synergized with IL-1beta to produce the angiostatic CXCL10/IFN-gamma-induced protein-10. These findings indicate that the equilibrium between angiostatic and angiogenic factors during inflammation and tumor progression is rather complex and differs depending on the chemokine, cell type, and stimulus. Selective intervention in the chemokine network may drastically disturb this delicate balance of angiogenesis and tissue repair. Application of angiostatic CXCL4L1/PF-4var without attraction of protumoral phagocytes may be beneficial in cancer therapy.
    Journal of Leukocyte Biology 01/2008; 82(6):1519-30. · 4.57 Impact Factor
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    ABSTRACT: CXCR3 ligands were secreted by tissue fibroblasts and peripheral blood-derived mononuclear leukocytes in response to interferon-gamma (IFN-gamma) and Toll-like receptor (TLR) ligands. Subsequent purification and identification revealed the presence of truncated CXCL11 variants missing up to 6 amino acids. In combination with CD26/dipeptidyl peptidase IV, the metalloprotease aminopeptidase N (APN), identical to the myeloid cell marker CD13, rapidly processed CXCL11, but not CXCL8, to generate truncated CXCL11 forms. Truncated CXCL11 had reduced binding, signaling, and chemotactic properties for lymphocytes and CXCR3- or CXCR7-transfected cells. CD13/APN-truncated CXCL11 failed to induce an intracellular calcium increase but was still able to bind and desensitize CXCR3 for intact CXCL11 signaling. CXCL11 efficiently bound to CXCR7, but CXCL11 was not able to induce calcium signaling or ERK1/2 or Akt phosphorylation through CXCR7. CD26-truncated CXCL11 failed to attract lymphocytes but still inhibited microvascular endothelial cell (HMVEC) migration. However, further processing of CXCL11 by CD13 resulted in significant reduction of inhibition of HMVEC migration. Taken together, during inflammation or cancer, CXCL11 processing by CD13 may lead to a reduced number of tumor-infiltrating lymphocytes and in a more angiogenic environment.
    Blood 08/2007; 110(1):37-44. · 9.78 Impact Factor

Publication Stats

769 Citations
156.18 Total Impact Points

Institutions

  • 2003–2013
    • Universitair Ziekenhuis Leuven
      • Department of General internal medicine
      Louvain, Flanders, Belgium
  • 2002–2012
    • KU Leuven
      • Department of Microbiology and Immunology
      Leuven, VLG, Belgium