Philipp von Hundelshausen - Academia.edu (original) (raw)
Papers by Philipp von Hundelshausen
Hämostaseologie, 2015
In atherosclerosis, activated platelets have been recently recognised not only to participate in ... more In atherosclerosis, activated platelets have been recently recognised not only to participate in thrombotic events but also to play an essential role in the development of atherosclerotic lesions. Upon their activation, platelets release several pro-inflammatory mediators including chemokines. Chemokines are key molecules in inflammation as they are able to recruit leukocytes, modulate their activation/differentiation and control their proliferation/apoptosis. In this review we will discuss recent findings regarding the specific roles of chemokines released by platelets on leukocytes and their effects on atherosclerosis.
Deutsche medizinische Wochenschrift (1946), 2013
The increasing gain of knowledge regarding the mechanistic details of the pathogenesis of chronic... more The increasing gain of knowledge regarding the mechanistic details of the pathogenesis of chronic inflammatory diseases e. g. of rheumatic origin, chronic viral infections and atherosclerosis have revealed in conjunction with detailed insights in acute inflammation interesting similarities and differences. Cytokines such as IL-1 and tumour necrosis factor-α are proximal components of inflammatory cascades of systemic mediators activating the endothelium which leads to an endothelial dysfunction and moreover alter the balance within lymphocytic subpopulations containing distinct arsenals of secretory mediators such as interferons, interleukins and chemokines. Proinflammatory lymphocyte subtypes are TH1 und TH17 cells whereas Treg and TH2 cells are anti-inflammatory opponents. Since several years, interleukin-1- and TNF-antagonists have expanded the spectrum of drugs against rheumatic diseases and are currently studied in the setting of cardiovascular prevention with positive results ...
Thrombosis and haemostasis, 2011
Beyond obvious functions in haemostasis and thrombosis, platelets are considered to be essential ... more Beyond obvious functions in haemostasis and thrombosis, platelets are considered to be essential in proinflammatory surroundings such as atherosclerosis, allergy, rheumatoid arthritis and even cancer. In atherosclerosis, platelets facilitate the recruitment of inflammatory cells towards the lesion sites and release a plethora of inflammatory mediators, thereby enriching and boosting the inflammatory milieu. Platelets do so by interacting with endothelial cells, circulating leukocytes (monocytes, neutrophils, dendritic cells, T-cells) and progenitor cells. This cross-talk enforces leukocyte activation, adhesion and transmigration. Furthermore, platelets are known to function in innate host defense through the release of antimicrobial peptides and the expression of pattern recognition receptors. In severe sepsis, platelets are able to trigger the formation of neutrophil extracellular traps (NETs), which bind and clear pathogens. The present antiplatelet therapies that target key pathw...
The American journal of physiology, 1999
The CD14(+)/CD16(+) subset of human blood monocytes, which expresses low levels of the lipopolysa... more The CD14(+)/CD16(+) subset of human blood monocytes, which expresses low levels of the lipopolysaccharide receptor CD14 and high levels of the Fc receptor CD16 and exhibits features of mature tissue macrophages, is expanded in certain inflammatory conditions and may be relevant in atherosclerosis. Scavenger receptors (ScR) are important for lipid accumulation into macrophage-derived foam cells in atherogenesis and for the clearance of pathogens. Hence, we compared the function and expression of ScR in CD33(low) CD16(+) and CD33(high) CD14(++) monocyte subsets. Double immunofluorescence analysis of isolated monocytes revealed that the CD33(low) subset showed lower specific, ScR-mediated binding of DiI-labeled modified low-density lipoproteins (LDL) than CD33(high) cells. Differences in modified LDL binding between subsets were accompanied by changes in mRNA expression. RT-PCR in sorted cells indicated lower ScR class A type I/II (ScR-AI/II) mRNA levels in CD14(+)/CD16(+) than in CD14...
Thrombosis and Haemostasis, 2013
Macrophage migration inhibitory factor (MIF) is an inflammatory cytokine with chemokine-like func... more Macrophage migration inhibitory factor (MIF) is an inflammatory cytokine with chemokine-like functions and a role in atherogenesis. MIF is secreted by various cells including endothelial cells and macrophages. Platelets are another prominent cell type with a role in atherogenesis and are a rich source of atherogenic chemokines. We asked whether platelets express and secrete MIF. In comparison, CXCL12 release was determined. We examined the subcellular localisation of MIF in platelets/megakaryocytes, studied its co-localisation with other platelet-derived mediators and asked whether platelets contain MIF mRNA. Moreover, we probed the functional role of platelet-derived MIF in inflammatory cell recruitment. Using Western blot and ELISA, we demonstrated and quantitated MIF protein in human and mouse platelets. Applying confocal-microscopy, MIF was found to localise in granular-like structures, but did not co-localise with known platelet cytokines. qPCR indicated that platelets contain low levels of MIF mRNA. ELISA measurements from human platelet supernatants showed that, whereas thrombin and collagen triggered the release of MIF and CXCL12, ADP and oxidised LDL promoted CXCL12 but not MIF secretion. Using Transwell assays, we demonstrated that platelet supernatants promoted monocyte chemotaxis and that this was blocked by neutralising MIF antibodies.This is the first report demonstrating MIF secretion from activated platelets, suggesting that platelets are a previously unrecognised source of MIF in inflammatory processes. There are distinct activating stimuli for MIF and CXCL12 secretion. A substantial portion of the chemotactic capacity of stimulated platelet supernatants is contributed by MIF, suggesting a role for platelet-derived MIF in atherogenic cell recruitment.
Thrombosis and Haemostasis, 2007
Undoubtedly, platelets are key elements in the regulation of thrombosis and haemostasis. Along wi... more Undoubtedly, platelets are key elements in the regulation of thrombosis and haemostasis. Along with their primary task to prevent blood loss from injured vessels, platelets have emerged as regulators of a variety of processes in the vasculature. Multiple challenges, from the contact and adhesion to subendothelial matrix after injury of the vessel wall, to interactions with blood cells in inflammatory conditions, result in platelet activation with concomitant shape change and release of numerous substances. Among these, chemokines have been found to modulate several processes in the vasculature, such as atherosclerosis and angiogenesis. In particular, the chemokines connective tissue activating protein III (CTAP-III) and its precursors, or truncation products (CXCL7), platelet factor 4, (PF4, CXCL4) and its variant PF4alt (CXCL4L1) or regulated upon activation and normal T cell expressed and secreted (RANTES, CCL5), have been investigated thoroughly. Defined common properties as their aptitude to bind glycosaminoglycans or their predisposition to associate and form homooligomers are pre-requisites for their role in the vasculature and function in vivo. The current review summarizes the development of these single chemokines, and their cooperative effects that may in part be dependent on their physical interactions.
Thrombosis and Haemostasis, 2010
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Stem Cells and Development, 2014
Mobilization of hematopoietic stem and progenitor cells (HPCs) is induced by treatment with granu... more Mobilization of hematopoietic stem and progenitor cells (HPCs) is induced by treatment with granulocyte-colony stimulating factor, chemotherapy, or irradiation. We observed that these treatments are accompanied by a release of chemotactic activity into the blood. This plasma activity is derived from the bone marrow, liver, and spleen and acts on HPCs via the chemokine receptor CXCR4. A human blood peptide library was used to characterize CXCR4-activating compounds. We identified CXCL12[22-88] and N-terminally truncated variants CXCL12[24-88], CXCL12[25-88], CXCL12[27-88], and CXCL12[29-88]. Only CXCL12[22-88] could effectively bind to CXCR4 and induce intracellular calcium flux and chemotactic migration of HPCs. CXCL12[25-88] and CXCL12[27-88] revealed neither agonistic nor antagonistic activities in vitro, whereas CXCL12[29-88] inhibited CXCL12[22-88]-induced chemotactic migration. Since binding to glycosaminoglycans (GAG) modulates the function of CXCL12, binding to heparin was analyzed. Surface plasmon resonance kinetic analysis showed that N-terminal truncation of Arg22-Pro23 increased the dissociation constant KD by one log10 stage ([22-88]: KD: 5.4 ± 2.6 μM; [24-88]: KD: 54 ± 22.4 μM). Further truncation of the N-terminus decreased the KD ([25-88] KD: 30 ± 4.8 μM; [27-88] KD: 23 ± 1.6 μM; [29-88] KD: 19 ± 5.4 μM), indicating increasing competition for heparin binding. Systemic in vivo application of CXCL12[22-88] as well as CXCL12[27-88] or CXCL12[29-88] induced a significant mobilization of HPCs in mice. Our findings indicate that plasma-derived CXCL12 variants may contribute to the regulation of HPC mobilization by modulating the binding of CXCL12[22-88] to GAGs rather than blocking the CXCR4 receptor and, therefore, may have a contributing role in HPC mobilization.
Circulation Research, 2007
Beyond an eminent role in hemostasis and thrombosis, platelets are characterized by expert functi... more Beyond an eminent role in hemostasis and thrombosis, platelets are characterized by expert functions in assisting and modulating inflammatory reactions and immune responses. This is achieved by the regulated expression of adhesive and immune receptors on the platelet surface and by the release of a multitude of secretory products including inflammatory mediators and cytokines, which can mediate the interaction with leukocytes and enhance their recruitment. In addition, platelets are characterized by an enormous surface area and open canalicular system, which in concert with specialized recognition receptors may contribute to the engulfment of serum components, antigens, and pathogens. Platelet-dependent increases in leukocyte adhesion may not only account for an exacerbation of atherosclerosis, for arterial repair processes, but also for lymphocyte trafficking during adaptive immunity and host defense. This review compiles a selection of platelet-derived tools for bridging inflammation and vascular disease and highlights the molecular key components governing platelet-mediated mechanisms operative in immune surveillance, vascular remodeling, and atherosclerosis. (Circ Res. 2007;100:27-40.)
Arteriosclerosis, Thrombosis, and Vascular Biology, 2007
Science translational medicine, Jan 9, 2015
In acute and chronic inflammation, neutrophils and platelets, both of which promote monocyte recr... more In acute and chronic inflammation, neutrophils and platelets, both of which promote monocyte recruitment, are often activated simultaneously. We investigated how secretory products of neutrophils and platelets synergize to enhance the recruitment of monocytes. We found that neutrophil-borne human neutrophil peptide 1 (HNP1, α-defensin) and platelet-derived CCL5 form heteromers. These heteromers stimulate monocyte adhesion through CCR5 ligation. We further determined structural features of HNP1-CCL5 heteromers and designed a stable peptide that could disturb proinflammatory HNP1-CCL5 interactions. This peptide attenuated monocyte and macrophage recruitment in a mouse model of myocardial infarction. These results establish the in vivo relevance of heteromers formed between proteins released from neutrophils and platelets and show the potential of targeting heteromer formation to resolve acute or chronic inflammation.
Circulation research, Jan 13, 2015
Besides their essential role in hemostasis, platelets also have functions in inflammation. In pla... more Besides their essential role in hemostasis, platelets also have functions in inflammation. In platelets, junctional adhesion molecule (JAM)-A was previously identified as an inhibitor of integrin αIIbβ3-mediated outside-in signaling and its genetic knockdown resulted in hyperreactivity. This gain-of-function was specifically exploited to investigate the role of platelet hyperreactivity in plaque development. JAM-A-deficient platelets showed increased aggregation and cellular and sarcoma tyrosine-protein kinase activation. On αIIbβ3 ligation, JAM-A was shown to be dephosphorylated, which could be prevented by protein tyrosine phosphatase nonreceptor type 1 inhibition. Mice with or without platelet-specific (tr)JAM-A-deficiency in an apolipoprotein e (apoe(-/-)) background were fed a high-fat diet. After ≤12 weeks of diet, trJAM-A(-/-)apoe-/- mice showed increased aortic plaque formation when compared with trJAM-A(+/+) apoe(-/-) controls, and these differences were most evident at ear...
Journal of leukocyte biology, 2000
The subset of human blood monocytes expressing low levels of CD14 and high levels of CD16 (CD14+C... more The subset of human blood monocytes expressing low levels of CD14 and high levels of CD16 (CD14+CD16+) exhibits features resembling mature tissue macrophages and can be expanded in inflammatory conditions. We analyzed expression of CC chemokine receptors (CCR) in CD14+CD16+ versus CD14++ monocytes, which may be crucial for specific trafficking. Multicolor flow cytometric analysis of whole peripheral blood revealed that, as opposed to CD14++ monocytes, the CD14+CD16+ subset lacked surface expression of monocyte chemotactic protein-1 (MCP-1) receptor CCR2, however, it showed significantly higher surface expression of the macrophage inflammatory protein 1alpha (MIP-1alpha)/RANTES receptor CCR5. This was paralleled by differences in mRNA expression in the subsets, as shown by reverse transcriptase-polymerase chain reaction using sorted cells. In comparison to CD14++ monocytes, CD14+CD16+ cells expressed lower CCR2 but higher CCR5 transcript levels, whereas CCR1 levels were equivalent. F...
Thrombosis and Haemostasis, 2014
The chemokine CCL5 recruits monocytes into inflamed tissues by triggering primarily CCR1-mediated... more The chemokine CCL5 recruits monocytes into inflamed tissues by triggering primarily CCR1-mediated arrest on endothelial cells, whereas subsequent spreading is dominated by CCR5. The CCL5-induced arrest can be enhanced by heteromer formation with CXCL4. To identify mechanisms for receptor-specific functions, we employed CCL5 mutants and transfectants expressing receptor chimeras carrying transposed extracellular regions. Mutation of the basic 50s cluster of CCL5, a coordinative site for CCL5 surface presentation, reduced CCR5-but not CCR1-mediated arrest and transmigration. Impaired arrest was restored by exchanging the CCR5-N-terminus for that of CCR1, which supported arrest even without the 50s cluster, whereas mutation of the basic 40s cluster essential for proteoglycan binding of CCL5 could not be rescued. The enhancement of CCL5-induced arrest by CXCL4 was mediated by CCR1 requiring its third extracellular loop. The domain exchanges did not affect formation and co-localisation of receptor dimers, indicating a sensing role of the third extracellular loop for hetero-oligomers in an arrest microenvironment. Our data identify confined targetable regions of CCR1 specialised to facilitate CCL5-induced arrest and enhanced responsiveness to the CXCL4-CCL5 heteromer.
Hämostaseologie, 2015
In atherosclerosis, activated platelets have been recently recognised not only to participate in ... more In atherosclerosis, activated platelets have been recently recognised not only to participate in thrombotic events but also to play an essential role in the development of atherosclerotic lesions. Upon their activation, platelets release several pro-inflammatory mediators including chemokines. Chemokines are key molecules in inflammation as they are able to recruit leukocytes, modulate their activation/differentiation and control their proliferation/apoptosis. In this review we will discuss recent findings regarding the specific roles of chemokines released by platelets on leukocytes and their effects on atherosclerosis.
Deutsche medizinische Wochenschrift (1946), 2013
The increasing gain of knowledge regarding the mechanistic details of the pathogenesis of chronic... more The increasing gain of knowledge regarding the mechanistic details of the pathogenesis of chronic inflammatory diseases e. g. of rheumatic origin, chronic viral infections and atherosclerosis have revealed in conjunction with detailed insights in acute inflammation interesting similarities and differences. Cytokines such as IL-1 and tumour necrosis factor-α are proximal components of inflammatory cascades of systemic mediators activating the endothelium which leads to an endothelial dysfunction and moreover alter the balance within lymphocytic subpopulations containing distinct arsenals of secretory mediators such as interferons, interleukins and chemokines. Proinflammatory lymphocyte subtypes are TH1 und TH17 cells whereas Treg and TH2 cells are anti-inflammatory opponents. Since several years, interleukin-1- and TNF-antagonists have expanded the spectrum of drugs against rheumatic diseases and are currently studied in the setting of cardiovascular prevention with positive results ...
Thrombosis and haemostasis, 2011
Beyond obvious functions in haemostasis and thrombosis, platelets are considered to be essential ... more Beyond obvious functions in haemostasis and thrombosis, platelets are considered to be essential in proinflammatory surroundings such as atherosclerosis, allergy, rheumatoid arthritis and even cancer. In atherosclerosis, platelets facilitate the recruitment of inflammatory cells towards the lesion sites and release a plethora of inflammatory mediators, thereby enriching and boosting the inflammatory milieu. Platelets do so by interacting with endothelial cells, circulating leukocytes (monocytes, neutrophils, dendritic cells, T-cells) and progenitor cells. This cross-talk enforces leukocyte activation, adhesion and transmigration. Furthermore, platelets are known to function in innate host defense through the release of antimicrobial peptides and the expression of pattern recognition receptors. In severe sepsis, platelets are able to trigger the formation of neutrophil extracellular traps (NETs), which bind and clear pathogens. The present antiplatelet therapies that target key pathw...
The American journal of physiology, 1999
The CD14(+)/CD16(+) subset of human blood monocytes, which expresses low levels of the lipopolysa... more The CD14(+)/CD16(+) subset of human blood monocytes, which expresses low levels of the lipopolysaccharide receptor CD14 and high levels of the Fc receptor CD16 and exhibits features of mature tissue macrophages, is expanded in certain inflammatory conditions and may be relevant in atherosclerosis. Scavenger receptors (ScR) are important for lipid accumulation into macrophage-derived foam cells in atherogenesis and for the clearance of pathogens. Hence, we compared the function and expression of ScR in CD33(low) CD16(+) and CD33(high) CD14(++) monocyte subsets. Double immunofluorescence analysis of isolated monocytes revealed that the CD33(low) subset showed lower specific, ScR-mediated binding of DiI-labeled modified low-density lipoproteins (LDL) than CD33(high) cells. Differences in modified LDL binding between subsets were accompanied by changes in mRNA expression. RT-PCR in sorted cells indicated lower ScR class A type I/II (ScR-AI/II) mRNA levels in CD14(+)/CD16(+) than in CD14...
Thrombosis and Haemostasis, 2013
Macrophage migration inhibitory factor (MIF) is an inflammatory cytokine with chemokine-like func... more Macrophage migration inhibitory factor (MIF) is an inflammatory cytokine with chemokine-like functions and a role in atherogenesis. MIF is secreted by various cells including endothelial cells and macrophages. Platelets are another prominent cell type with a role in atherogenesis and are a rich source of atherogenic chemokines. We asked whether platelets express and secrete MIF. In comparison, CXCL12 release was determined. We examined the subcellular localisation of MIF in platelets/megakaryocytes, studied its co-localisation with other platelet-derived mediators and asked whether platelets contain MIF mRNA. Moreover, we probed the functional role of platelet-derived MIF in inflammatory cell recruitment. Using Western blot and ELISA, we demonstrated and quantitated MIF protein in human and mouse platelets. Applying confocal-microscopy, MIF was found to localise in granular-like structures, but did not co-localise with known platelet cytokines. qPCR indicated that platelets contain low levels of MIF mRNA. ELISA measurements from human platelet supernatants showed that, whereas thrombin and collagen triggered the release of MIF and CXCL12, ADP and oxidised LDL promoted CXCL12 but not MIF secretion. Using Transwell assays, we demonstrated that platelet supernatants promoted monocyte chemotaxis and that this was blocked by neutralising MIF antibodies.This is the first report demonstrating MIF secretion from activated platelets, suggesting that platelets are a previously unrecognised source of MIF in inflammatory processes. There are distinct activating stimuli for MIF and CXCL12 secretion. A substantial portion of the chemotactic capacity of stimulated platelet supernatants is contributed by MIF, suggesting a role for platelet-derived MIF in atherogenic cell recruitment.
Thrombosis and Haemostasis, 2007
Undoubtedly, platelets are key elements in the regulation of thrombosis and haemostasis. Along wi... more Undoubtedly, platelets are key elements in the regulation of thrombosis and haemostasis. Along with their primary task to prevent blood loss from injured vessels, platelets have emerged as regulators of a variety of processes in the vasculature. Multiple challenges, from the contact and adhesion to subendothelial matrix after injury of the vessel wall, to interactions with blood cells in inflammatory conditions, result in platelet activation with concomitant shape change and release of numerous substances. Among these, chemokines have been found to modulate several processes in the vasculature, such as atherosclerosis and angiogenesis. In particular, the chemokines connective tissue activating protein III (CTAP-III) and its precursors, or truncation products (CXCL7), platelet factor 4, (PF4, CXCL4) and its variant PF4alt (CXCL4L1) or regulated upon activation and normal T cell expressed and secreted (RANTES, CCL5), have been investigated thoroughly. Defined common properties as their aptitude to bind glycosaminoglycans or their predisposition to associate and form homooligomers are pre-requisites for their role in the vasculature and function in vivo. The current review summarizes the development of these single chemokines, and their cooperative effects that may in part be dependent on their physical interactions.
Thrombosis and Haemostasis, 2010
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Stem Cells and Development, 2014
Mobilization of hematopoietic stem and progenitor cells (HPCs) is induced by treatment with granu... more Mobilization of hematopoietic stem and progenitor cells (HPCs) is induced by treatment with granulocyte-colony stimulating factor, chemotherapy, or irradiation. We observed that these treatments are accompanied by a release of chemotactic activity into the blood. This plasma activity is derived from the bone marrow, liver, and spleen and acts on HPCs via the chemokine receptor CXCR4. A human blood peptide library was used to characterize CXCR4-activating compounds. We identified CXCL12[22-88] and N-terminally truncated variants CXCL12[24-88], CXCL12[25-88], CXCL12[27-88], and CXCL12[29-88]. Only CXCL12[22-88] could effectively bind to CXCR4 and induce intracellular calcium flux and chemotactic migration of HPCs. CXCL12[25-88] and CXCL12[27-88] revealed neither agonistic nor antagonistic activities in vitro, whereas CXCL12[29-88] inhibited CXCL12[22-88]-induced chemotactic migration. Since binding to glycosaminoglycans (GAG) modulates the function of CXCL12, binding to heparin was analyzed. Surface plasmon resonance kinetic analysis showed that N-terminal truncation of Arg22-Pro23 increased the dissociation constant KD by one log10 stage ([22-88]: KD: 5.4 ± 2.6 μM; [24-88]: KD: 54 ± 22.4 μM). Further truncation of the N-terminus decreased the KD ([25-88] KD: 30 ± 4.8 μM; [27-88] KD: 23 ± 1.6 μM; [29-88] KD: 19 ± 5.4 μM), indicating increasing competition for heparin binding. Systemic in vivo application of CXCL12[22-88] as well as CXCL12[27-88] or CXCL12[29-88] induced a significant mobilization of HPCs in mice. Our findings indicate that plasma-derived CXCL12 variants may contribute to the regulation of HPC mobilization by modulating the binding of CXCL12[22-88] to GAGs rather than blocking the CXCR4 receptor and, therefore, may have a contributing role in HPC mobilization.
Circulation Research, 2007
Beyond an eminent role in hemostasis and thrombosis, platelets are characterized by expert functi... more Beyond an eminent role in hemostasis and thrombosis, platelets are characterized by expert functions in assisting and modulating inflammatory reactions and immune responses. This is achieved by the regulated expression of adhesive and immune receptors on the platelet surface and by the release of a multitude of secretory products including inflammatory mediators and cytokines, which can mediate the interaction with leukocytes and enhance their recruitment. In addition, platelets are characterized by an enormous surface area and open canalicular system, which in concert with specialized recognition receptors may contribute to the engulfment of serum components, antigens, and pathogens. Platelet-dependent increases in leukocyte adhesion may not only account for an exacerbation of atherosclerosis, for arterial repair processes, but also for lymphocyte trafficking during adaptive immunity and host defense. This review compiles a selection of platelet-derived tools for bridging inflammation and vascular disease and highlights the molecular key components governing platelet-mediated mechanisms operative in immune surveillance, vascular remodeling, and atherosclerosis. (Circ Res. 2007;100:27-40.)
Arteriosclerosis, Thrombosis, and Vascular Biology, 2007
Science translational medicine, Jan 9, 2015
In acute and chronic inflammation, neutrophils and platelets, both of which promote monocyte recr... more In acute and chronic inflammation, neutrophils and platelets, both of which promote monocyte recruitment, are often activated simultaneously. We investigated how secretory products of neutrophils and platelets synergize to enhance the recruitment of monocytes. We found that neutrophil-borne human neutrophil peptide 1 (HNP1, α-defensin) and platelet-derived CCL5 form heteromers. These heteromers stimulate monocyte adhesion through CCR5 ligation. We further determined structural features of HNP1-CCL5 heteromers and designed a stable peptide that could disturb proinflammatory HNP1-CCL5 interactions. This peptide attenuated monocyte and macrophage recruitment in a mouse model of myocardial infarction. These results establish the in vivo relevance of heteromers formed between proteins released from neutrophils and platelets and show the potential of targeting heteromer formation to resolve acute or chronic inflammation.
Circulation research, Jan 13, 2015
Besides their essential role in hemostasis, platelets also have functions in inflammation. In pla... more Besides their essential role in hemostasis, platelets also have functions in inflammation. In platelets, junctional adhesion molecule (JAM)-A was previously identified as an inhibitor of integrin αIIbβ3-mediated outside-in signaling and its genetic knockdown resulted in hyperreactivity. This gain-of-function was specifically exploited to investigate the role of platelet hyperreactivity in plaque development. JAM-A-deficient platelets showed increased aggregation and cellular and sarcoma tyrosine-protein kinase activation. On αIIbβ3 ligation, JAM-A was shown to be dephosphorylated, which could be prevented by protein tyrosine phosphatase nonreceptor type 1 inhibition. Mice with or without platelet-specific (tr)JAM-A-deficiency in an apolipoprotein e (apoe(-/-)) background were fed a high-fat diet. After ≤12 weeks of diet, trJAM-A(-/-)apoe-/- mice showed increased aortic plaque formation when compared with trJAM-A(+/+) apoe(-/-) controls, and these differences were most evident at ear...
Journal of leukocyte biology, 2000
The subset of human blood monocytes expressing low levels of CD14 and high levels of CD16 (CD14+C... more The subset of human blood monocytes expressing low levels of CD14 and high levels of CD16 (CD14+CD16+) exhibits features resembling mature tissue macrophages and can be expanded in inflammatory conditions. We analyzed expression of CC chemokine receptors (CCR) in CD14+CD16+ versus CD14++ monocytes, which may be crucial for specific trafficking. Multicolor flow cytometric analysis of whole peripheral blood revealed that, as opposed to CD14++ monocytes, the CD14+CD16+ subset lacked surface expression of monocyte chemotactic protein-1 (MCP-1) receptor CCR2, however, it showed significantly higher surface expression of the macrophage inflammatory protein 1alpha (MIP-1alpha)/RANTES receptor CCR5. This was paralleled by differences in mRNA expression in the subsets, as shown by reverse transcriptase-polymerase chain reaction using sorted cells. In comparison to CD14++ monocytes, CD14+CD16+ cells expressed lower CCR2 but higher CCR5 transcript levels, whereas CCR1 levels were equivalent. F...
Thrombosis and Haemostasis, 2014
The chemokine CCL5 recruits monocytes into inflamed tissues by triggering primarily CCR1-mediated... more The chemokine CCL5 recruits monocytes into inflamed tissues by triggering primarily CCR1-mediated arrest on endothelial cells, whereas subsequent spreading is dominated by CCR5. The CCL5-induced arrest can be enhanced by heteromer formation with CXCL4. To identify mechanisms for receptor-specific functions, we employed CCL5 mutants and transfectants expressing receptor chimeras carrying transposed extracellular regions. Mutation of the basic 50s cluster of CCL5, a coordinative site for CCL5 surface presentation, reduced CCR5-but not CCR1-mediated arrest and transmigration. Impaired arrest was restored by exchanging the CCR5-N-terminus for that of CCR1, which supported arrest even without the 50s cluster, whereas mutation of the basic 40s cluster essential for proteoglycan binding of CCL5 could not be rescued. The enhancement of CCL5-induced arrest by CXCL4 was mediated by CCR1 requiring its third extracellular loop. The domain exchanges did not affect formation and co-localisation of receptor dimers, indicating a sensing role of the third extracellular loop for hetero-oligomers in an arrest microenvironment. Our data identify confined targetable regions of CCR1 specialised to facilitate CCL5-induced arrest and enhanced responsiveness to the CXCL4-CCL5 heteromer.