beta-Chemokines enhance parasite uptake and promote nitric oxide-dependent microbiostatic activity in murine inflammatory macrophages infected with Trypanosoma cruzi.
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In the present study, we describe the ability of Trypanosoma cruzi trypomastigotes to stimulate the synthesis of beta-chemokines by macrophages. In vivo infection with T. cruzi led to MIP-1alpha, RANTES, and JE/MCP1 mRNA expression by cells from peritoneal inflammatory exudate. In addition, in vitro infection with T. cruzi resulted in expression of beta-chemokine MIP-1alpha, MIP-1beta, RANTES, and JE mRNA by macrophages. The expression of the beta-chemokine MIP-1alpha, MIP-1beta, RANTES, and JE proteins by murine macrophages cultured with trypomastigote forms of T. cruzi was confirmed by immunocytochemistry. Interestingly, macrophage infection with T. cruzi also resulted in NO production, which we found to be mediated mainly by beta-chemokines. Hence, treatment with anti-beta-chemokine-specific neutralizing antibodies partially inhibited NO release by macrophages incubated with T. cruzi parasites. Further, the addition of the exogenous beta-chemokines MIP-1alpha, MIP-1beta, RANTES, and JE/MCP-1 induced an increased T. cruzi uptake, leading to enhanced NO production and control of parasite replication in a dose-dependent manner. L-NMMA, a specific inhibitor of the L-arginine-NO pathway, caused a decrease in NO production and parasite killing when added to cultures of macrophages stimulated with beta-chemokines. Among the beta-chemokines tested, JE was more potent in inhibiting parasite growth, although it was much less efficient than gamma interferon (IFN-gamma). Nevertheless, JE potentiates parasite killing by macrophages incubated with low doses of IFN-gamma. Together, these results suggest that in addition to their chemotactic activity, murine beta-chemokines may also contribute to enhancing parasite uptake and promoting control of parasite replication in macrophages and may play a role in resistance to T. cruzi infection. (+info)
Eotaxin and eotaxin receptor (CCR3) expression in Sephadex particle-induced rat lung inflammation.
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The beta chemokine eotaxin is a potent eosinophil activator and chemoattractant. We examined immunohistochemically eotaxin protein expression in a range of normal rat tissues and in rat lung during Sephadex particle-induced pulmonary inflammation. The time course of eotaxin expression in lung at various time points after Sephadex administration was related to the appearance of eosinophils in the bronchoalveolar lavage fluid and tissue distribution of eotaxin receptor (CCR3) positive cells. Results showed that eotaxin protein was constitutively expressed by both lung airway epithelial cells and gut epithelial cells in normal tissues in the absence of inflammation. During Sephadex induced pulmonary inflammation, eotaxin expression increased in alveolar macrophages prior to the major increase in eosinophil numbers which reached a peak at 72 h. The pattern of eotaxin pulmonary expression and the location of CCR3 receptor positive cells suggest a chemoattractant gradient resulting in migration firstly into the tissue and subsequently through the airway epithelium into the airways. Treatment of rats with the glucocorticoid dexamethasone or the immunosuppressant cyclosporin A reduced eosinophil entry into lung tissue and airways but had no apparent effect on eotaxin expression in vivo, indicating that both these drugs inhibit eosinophil recruitment either by an eotaxin-independent mechanism, or by targetting factors that synergise with eotaxin, or an event post eotaxin expression. (+info)
Macrophage-derived chemokine is localized to thymic medullary epithelial cells and is a chemoattractant for CD3(+), CD4(+), CD8(low) thymocytes.
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Macrophage-derived chemokine (MDC) is a recently identified CC chemokine that is a potent chemoattractant for dendritic cells, natural killer (NK) cells, and the Th2 subset of peripheral blood T cells. In normal tissues, MDC mRNA is expressed principally in the thymus. Immunohistochemical analysis performed on 5 human postnatal thymuses showed high MDC immunoreactivity, which was selectively localized to epithelial cells within the medulla. To examine the effects of MDC on immature T cells, we have identified cDNA clones for mouse and rat MDC. Expression of MDC in murine tissues is also highly restricted, with significant levels of mRNA found only in the thymus. Thymocytes express high-affinity binding sites for MDC (kd = 0.7 nmol/L), and, in vitro, MDC is a chemoattractant for these cells. MDC-responsive murine thymocytes express mRNA for CCR4, a recently identified receptor for MDC. Phenotypic analysis of MDC-responsive cells shows that they are enriched for a subset of double-positive cells that express high levels of CD3 and CD4 and that have reduced levels of CD8. This subset of MDC-responsive cells is consistent with the observed expression of MDC within the medulla, because more mature cells are found there. MDC may therefore play a role in the migration of T-cell subsets during development within the thymus. (+info)
CCR5 binds multiple CC-chemokines: MCP-3 acts as a natural antagonist.
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CCR5 was first characterized as a receptor for MIP-1alpha, MIP-1beta, and RANTES, and was rapidly shown to be the main coreceptor for M-tropic human immunodeficiency virus (HIV)-1 strains and simian immunodeficiency virus (SIV). Chemokines constitute a rapidly growing family of proteins and receptor-chemokine interactions are known to be promiscuous and redundant. We have therefore tested whether other CC-chemokines could bind to and activate CCR5. All CC-chemokines currently available were tested for their ability to compete with [(125)I]-MIP-1beta binding on a stable cell line expressing recombinant CCR5, and/or to induce a functional response in these cells. We found that in addition to MIP-1beta, MIP-1alpha, and RANTES, five other CC-chemokines could compete for [(125)I]-MIP-1beta binding: MCP-2, MCP-3, MCP-4, MCP-1, and eotaxin binding was characterized by IC(50) values of 0.22, 2.14, 5.89, 29.9, and 21.7 nmol/L, respectively. Among these ligands, MCP-3 had the remarkable property of binding CCR5 with high affinity without eliciting a functional response, MCP-3 could also inhibit the activation of CCR5 by MIP-1beta and may therefore be considered as a natural antagonist for CCR5. It was unable to induce significant endocytosis of the receptor. Chemokines that could compete with high affinity for MIP-1beta binding could also compete for monomeric gp120 binding, although with variable potencies; maximal gp120 binding inhibition was 80% for MCP-2, but only 30% for MIP-1beta. MCP-3 could compete efficiently for gp120 binding but was, however, found to be a weak inhibitor of HIV infection, probably as a consequence of its inability to downregulate the receptor. (+info)
Hodgkin/Reed-Sternberg cells induce fibroblasts to secrete eotaxin, a potent chemoattractant for T cells and eosinophils.
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Hodgkin's disease is histopathologically characterized by the relative scarcity of neoplastic Hodgkin and Reed-Sternberg cells and for yet unknown reasons by an abundant reactive background of T lymphocytes and often eosinophils. Eotaxin is a CC-chemokine attracting eosinophils and T helper 2 (Th2) cells in allergic inflammation. We now report that eotaxin is strongly expressed in fibroblasts of Hodgkin's disease tissues, whereas Hodgkin/Reed-Sternberg cells do not express this chemokine. In tissue culture, Hodgkin's disease tumor cells induce eotaxin expression in cocultured dermal fibroblasts in a concentration leading to a specific chemotactic response of a Th2 cell clone. Production of tumor necrosis factor-alpha (TNF-alpha) by Hodgkin/Reed-Sternberg cells appears to be responsible for this induction, because blocking of TNF-alpha by neutralizing antibodies prevented fibroblast eotaxin expression. Our data suggest that eotaxin is involved in the pathobiology of Hodgkin's disease by contributing to eosinophil and T-lymphocyte recruitment. (+info)
Eotaxin expression in Onchocerca volvulus-induced dermatitis after topical application of diethylcarbamazine.
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In persons with onchocerciasis, topical application of the anthelminthic diethylcarbamazine (DEC) induces clinical and histologic responses similar to acute papular onchodermatitis, including recruitment of eosinophils to the skin. To determine whether the eosinophil chemokine eotaxin is likely to be associated with eosinophil recruitment in onchodermatitis, DEC was applied to a 5-cm2 area on the skin of infected persons, and biopsies were taken from lesions 24 h later. Histologic analysis showed elevated dermal and epidermal eosinophils compared with tissue from an adjacent (untreated) site. Reverse transcription-polymerase chain reaction showed that eotaxin gene expression in DEC-treated skin was elevated 2- to 17-fold compared with control tissue. Eotaxin immunoreactivity was noted in mononuclear cells and eosinophils in the perivascular region of the dermis and in lymphatic and vascular endothelial cells. Together, these observations are consistent with a role for eotaxin in recruitment of eosinophils to the dermis in early stage onchocercal skin disease. (+info)
Cytomegalovirus-encoded beta chemokine promotes monocyte-associated viremia in the host.
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Chemokine homologs are encoded by many large DNA viruses, suggesting that they contribute to control of host leukocyte transmigration and trafficking during viral infection. Murine cytomegalovirus carries a CC (beta) chemokine homolog gene giving rise to two related proteins, murine cytomegalovirus chemokine 1 and 2 (MCK-1 and MCK-2). MCK-1 peptide was found to induce calcium signaling and adherence in murine peritoneal macrophages. Cells bearing human chemokine receptor CCR3 and the human macrophage THP1 cell line were responsive to MCK-1. This pattern suggested that MCK-1 might act as an agonist, promoting leukocyte trafficking during viral infection. Consistent with this prediction, MCK-1/MCK-2 mutant viruses exhibit dramatically reduced peak levels of monocyte-associated viremia in experimentally infected mice. Thus, MCK-1/MCK-2 appears to promote host leukocyte migration to initial sites of infection and may be responsible for attracting monocytes or macrophages that efficiently disseminate virus in the host. (+info)
Molecular cloning of a novel human CC chemokine (Eotaxin-3) that is a functional ligand of CC chemokine receptor 3.
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Previously, we mapped the novel CC chemokine myeloid progenitor inhibitory factor 2 (MPIF-2)/eotaxin-2 to chromosome 7q11.23 (Nomiyama, H., Osborne, L. R., Imai, T., Kusuda, J., Miura, R., Tsui, L.-C., and Yoshie, O. (1998) Genomics 49, 339-340). Since chemokine genes tend to be clustered, unknown chemokines may be present in the vicinity of those mapped to new chromosomal loci. Prompted by this hypothesis, we analyzed the genomic region containing the gene for MPIF-2/eotaxin-2 (SCYA24) and have identified a novel CC chemokine termed eotaxin-3. The genes for MPIF-2/eotaxin-2 (SCYA24) and eotaxin-3 (SCYA26) are localized within a region of approximately 40 kilobases. By Northern blot analysis, eotaxin-3 mRNA was constitutively expressed in the heart and ovary. We have generated recombinant eotaxin-3 in a baculovirus expression system. Eotaxin-3 induced transient calcium mobilization specifically in CC chemokine receptor 3 (CCR3)-expressing L1.2 cells with an EC(50) of 3 nM. Eotaxin-3 competed the binding of (125)I-eotaxin to CCR3-expressing L1.2 cells with an IC(50) of 13 nM. Eotaxin-3 was chemotactic for normal peripheral blood eosinophils and basophils at high concentrations. Collectively, eotaxin-3 is yet another functional ligand for CCR3. The potency of eotaxin-3 as a CCR3 ligand seems, however, to be approximately 10-fold less than that of eotaxin. Identification of eotaxin-3 will further promote our understanding of the control of eosinophil trafficking and other CCR3-mediated biological phenomena. The strategy used in this study may also be applicable to identification of other unknown chemokine genes. (+info)