The molecular basis of atherosclerosis is not fully understood and mice studies have shown that Ephrins and EPH receptors play a role in the atherosclerotic process. We set out to assess the role... Show moreThe molecular basis of atherosclerosis is not fully understood and mice studies have shown that Ephrins and EPH receptors play a role in the atherosclerotic process. We set out to assess the role for monocytic EPHB2 and its Ephrin ligands in human atherosclerosis and show a role for EPHB2 in monocyte functions independently of its EphrinB ligands. Immunohistochemical staining of human aortic sections at different stages of atherosclerosis showed that EPHB2 and its ligand EphrinB are expressed in atherosclerotic plaques and that expression proportionally increases with plaque severity. Functionally, stimulation with EPHB2 did not affect endothelial barrier function, nor did stimulation with EphrinB1 or EphrinB2 affect monocyte-endothelial interactions. In contrast, reduced expression of EPHB2 in monocytes resulted in decreased monocyte adhesion to endothelial cells and a decrease in monocyte transmigration, mediated by an altered morphology and a decreased ability to phosphorylate FAK. Our results suggest that EPHB2 expression in monocytes results in monocyte accumulation by virtue of an increase of transendothelial migration, which can subsequently contribute to atherosclerotic plaque progression. Show less
The CXCR3‐CXCL11 chemokine‐signaling axis plays an essential role in infection and inflammation by orchestrating leukocyte trafficking in human and animal models, including zebrafish. Atypical... Show moreThe CXCR3‐CXCL11 chemokine‐signaling axis plays an essential role in infection and inflammation by orchestrating leukocyte trafficking in human and animal models, including zebrafish. Atypical chemokine receptors (ACKRs) play a fundamental regulatory function in signaling networks by shaping chemokine gradients through their ligand scavenging function, while being unable to signal in the classic G‐protein‐dependent manner. Two copies of the CXCR3 gene in zebrafish, cxcr3.2 and cxcr3.3, are expressed on macrophages and share a highly conserved ligand‐binding site. However, Cxcr3.3 has structural characteristics of ACKRs indicative of a ligand‐scavenging role. In contrast, we previously showed that Cxcr3.2 is an active CXCR3 receptor because it is required for macrophage motility and recruitment to sites of mycobacterial infection. In this study, we generated a cxcr3.3 CRISPR‐mutant to functionally dissect the antagonistic interplay among the cxcr3 paralogs in the immune response. We observed that cxcr3.3 mutants are more susceptible to mycobacterial infection, whereas cxcr3.2 mutants are more resistant. Furthermore, macrophages in the cxcr3.3 mutant are more motile, show higher activation status, and are recruited more efficiently to sites of infection or injury. Our results suggest that Cxcr3.3 is an ACKR that regulates the activity of Cxcr3.2 by scavenging common ligands and that silencing the scavenging function of Cxcr3.3 results in an exacerbated Cxcr3.2 signaling. In human, splice variants of CXCR3 have antagonistic functions and CXCR3 ligands also interact with ACKRs. Therefore, in zebrafish, an analogous regulatory mechanism appears to have evolved after the cxcr3 gene duplication event, through diversification of conventional and atypical receptor variants. Show less
The CXCR3‐CXCL11 chemokine‐signaling axis plays an essential role in infection and inflammation by orchestrating leukocyte trafficking in human and animal models, including zebrafish. Atypical... Show moreThe CXCR3‐CXCL11 chemokine‐signaling axis plays an essential role in infection and inflammation by orchestrating leukocyte trafficking in human and animal models, including zebrafish. Atypical chemokine receptors (ACKRs) play a fundamental regulatory function in signaling networks by shaping chemokine gradients through their ligand scavenging function, while being unable to signal in the classic G‐protein‐dependent manner. Two copies of the CXCR3 gene in zebrafish, cxcr3.2 and cxcr3.3, are expressed on macrophages and share a highly conserved ligand‐binding site. However, Cxcr3.3 has structural characteristics of ACKRs indicative of a ligand‐scavenging role. In contrast, we previously showed that Cxcr3.2 is an active CXCR3 receptor because it is required for macrophage motility and recruitment to sites of mycobacterial infection. In this study, we generated a cxcr3.3 CRISPR‐mutant to functionally dissect the antagonistic interplay among the cxcr3 paralogs in the immune response. We observed that cxcr3.3 mutants are more susceptible to mycobacterial infection, whereas cxcr3.2 mutants are more resistant. Furthermore, macrophages in the cxcr3.3 mutant are more motile, show higher activation status, and are recruited more efficiently to sites of infection or injury. Our results suggest that Cxcr3.3 is an ACKR that regulates the activity of Cxcr3.2 by scavenging common ligands and that silencing the scavenging function of Cxcr3.3 results in an exacerbated Cxcr3.2 signaling. In human, splice variants of CXCR3 have antagonistic functions and CXCR3 ligands also interact with ACKRs. Therefore, in zebrafish, an analogous regulatory mechanism appears to have evolved after the cxcr3 gene duplication event, through diversification of conventional and atypical receptor variants. Show less
The CXCR3‐CXCL11 chemokine‐signaling axis plays an essential role in infection and inflammation by orchestrating leukocyte trafficking in human and animal models, including zebrafish. Atypical... Show moreThe CXCR3‐CXCL11 chemokine‐signaling axis plays an essential role in infection and inflammation by orchestrating leukocyte trafficking in human and animal models, including zebrafish. Atypical chemokine receptors (ACKRs) play a fundamental regulatory function in signaling networks by shaping chemokine gradients through their ligand scavenging function, while being unable to signal in the classic G‐protein‐dependent manner. Two copies of the CXCR3 gene in zebrafish, cxcr3.2 and cxcr3.3, are expressed on macrophages and share a highly conserved ligand‐binding site. However, Cxcr3.3 has structural characteristics of ACKRs indicative of a ligand‐scavenging role. In contrast, we previously showed that Cxcr3.2 is an active CXCR3 receptor because it is required for macrophage motility and recruitment to sites of mycobacterial infection. In this study, we generated a cxcr3.3 CRISPR‐mutant to functionally dissect the antagonistic interplay among the cxcr3 paralogs in the immune response. We observed that cxcr3.3 mutants are more susceptible to mycobacterial infection, whereas cxcr3.2 mutants are more resistant. Furthermore, macrophages in the cxcr3.3 mutant are more motile, show higher activation status, and are recruited more efficiently to sites of infection or injury. Our results suggest that Cxcr3.3 is an ACKR that regulates the activity of Cxcr3.2 by scavenging common ligands and that silencing the scavenging function of Cxcr3.3 results in an exacerbated Cxcr3.2 signaling. In human, splice variants of CXCR3 have antagonistic functions and CXCR3 ligands also interact with ACKRs. Therefore, in zebrafish, an analogous regulatory mechanism appears to have evolved after the cxcr3 gene duplication event, through diversification of conventional and atypical receptor variants. Show less
Heuvel, D. van den; Jansen, M.A.E.; Bell, A.I.; Rickinson, A.B.; Jaddoe, V.W.V.; Dongen, J.J.M. van; ... ; Zelm, M.C. van 2017
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... Show moreInsight 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. J. Leukoc. Biol. 88: 1017-1029; 2010. Show less
Neoplastic diseases of macrophages (M-phi) and dendritic cells (DC), collectively called histiocytoses, are relatively rare. The etiology of most forms of histiocytosis is poorly understood, and... Show moreNeoplastic diseases of macrophages (M-phi) and dendritic cells (DC), collectively called histiocytoses, are relatively rare. The etiology of most forms of histiocytosis is poorly understood, and the development of animal models is crucial for further research in this field. Previously, an animal model for malignant histiocytosis (MH), involving transformed histiocytic cells, has been generated by infecting mice with malignant histiocytosis sarcoma virus (MHSV). However, increased insight into the heterogeneity of M-phi and DC, and the associated reappraisal of human proliferative diseases involving these cells inspired us to re-evaluate the mouse model. We analyzed spleen, bone marrow, and lymph nodes of susceptible mice at various time points after infection. From day 11 onwards, a heterogeneous population of cells, consisting of CD8 alpha(+) Langerin(+) DC, ER-MP58(+) CD11b(+) myeloid precursor cells, CD169(+) metallophilic M-phi, and CD71(hi) erythroblasts, was affected by viral transformation. In different mice, these subsets expanded at different rates in different organs, causing a variable disease profile in terminal stages. Cell lines, which were generated from MHSV-transformed tumors, showed a DC-like morphology and phenotype, and appeared to be arrested in different stages of maturation. Upon injection into healthy mice, different preferential homing patterns were observed for the various cell lines, and the cells acquired distinct phenotypes depending on the organ of homing. This indicates that these transformed cells adapt to their microenvironment by switching between precursor, DC/Langerhans cell, and M-phi phenotypes. Our results demonstrate that the MHSV model represents a heterogeneous neoplastic disease with characteristics of M-phi/DC sarcomas. J. Leukoc. Biol. 87: 949-958; 2010. Show less
