Macrophage inflammatory protein-1 alpha. A novel chemotactic cytokine for macrophages in rheumatoid arthritis

Angiogenesis and chemokines in rheumatoid arthritis and other systemic inflammatory rheumatic diseases

Angiogenesis, the formation of new vessels, is important in the pathogenesis of rheumatoid arthritis (RA) and other inflammatory diseases. Chemotactic cytokines termed chemokines mediate the ingress of leukocytes, including neutrophils and monocytes into the inflamed synovium. In this review, authors discuss the role of the most important angiogenic factors and angiogenesis inhibitors, as well as relevant chemokines and chemokine receptors involved in chronic inflammatory rheumatic diseases. RA was chosen as a prototype to discuss these issues, as the majority of studies on the role of angiogenesis and chemokines in inflammatory diseases were carried out in arthritis. However, other systemic inflammatory (autoimmune) diseases including systemic lupus erythematosus (SLE), systemic sclerosis (SSc), Sjögren's syndrome (SS), mixed connective tissue disease (MCTD), polymyositis/dermatomyositis (PM/DM) and systemic vasculites are also discussed in this context. As a number of chemokines may also play a role in neovascularization, this issue is also described here. Apart from discussing the pathogenic role of angiogenesis and chemokines, authors also review the regulation of angiogenesis and chemokine production by other inflammatory mediators, as well as the important relevance of neovascularization and chemokines for antirheumatic intervention.

Hypercholesterolaemia and circulating levels of CXC chemokines in apoE*3 Leiden mice

Hyperlipidaemia may accelerate the development of atherosclerosis by enhancing the expression of chemokines by cells within the arterial wall. Chemokines of the CC subfamily are clearly implicated in atherogenesis; however, recent reports suggest that CXC chemokines may play a hitherto unrecognised role in monocyte recruitment into atheromatous lesions expressing these molecules. Here, we examine whether circulating levels of CXC chemokines may reflect the pathogenic changes occurring during early atherogenesis. ApoE*3 Leiden mice developed marked hypercholesterolaemia, and early Type I 'fatty streak' lesions, following consumption of an atherogenic diet high in saturated fat and cholesterol, and containing sodium cholate, for up to 4 weeks. By contrast, their non-transgenic littermates (C57BL/6J) exhibited a much less pronounced hypercholesterolaemia and did not develop fatty streak lesions, when fed the same diet. Under these conditions, serum concentrations of CXC chemokines, KC and Macrophage Inflammatory Protein-2 (MIP-2) were significantly (P<or=0.0005) elevated in apoE*3 Leiden mice consuming HFC/C diet, compared with apoE*3 Leiden mice consuming a chow diet. Further, serum concentrations of KC were significantly (P<0.02) higher at 4 weeks in apoE*3 Leiden mice fed HFC/C diet compared with their non-transgenic littermates consuming the same diet. Expression of KC mRNA was detected in both aortic and hepatic tissues of apoE*3 Leiden mice, and the non-transgenic controls. Thus, hypercholesterolaemia is associated with elevated serum concentrations of CXC chemokines, KC and MIP-2 that probably reflect chronic inflammation during atherogenesis.

A subset of natural killer cells is greatly expanded within inflamed joints

OBJECTIVE

To determine whether natural killer (NK) cells are present within inflamed joints and whether they might play a role in amplifying the inflammatory process.

METHODS

Paired samples of peripheral blood and synovial fluid were obtained from 22 patients with inflammatory arthritis. The frequency and phenotype of the peripheral and synovial NK cells were analyzed using a panel of monoclonal antibodies. Further experiments were performed to investigate the functional capacity of the synovial NK cells.

RESULTS

The study showed that the CD3-, CD56(bright) subset of NK cells was greatly expanded within inflamed joints. Our experiments suggested that this subset of cells was preferentially recruited from the periphery and that NK cells may be further activated by cytokines present within the joint. Furthermore, synovial NK cells responded to a combination of interleukin-12 (IL-12) and IL-15, cytokines that are secreted by cells of the monocyte/macrophage lineage, by rapidly secreting interferon-gamma, a cytokine that can, in turn, activate macrophages.

CONCLUSION

A subset of NK cells was expanded within inflamed joints. The functional properties of these NK cells rendered them good candidates for a role in interacting with the macrophage/monocyte population within the joint, thus amplifying the production of proinflammatory cytokines.

Expression of the duffy antigen/receptor for chemokines (DARC) by the inflamed synovial endothelium

The expression of chemokine binding sites on the endothelial cells of venules in inflamed synovia was examined and whether the Duffy antigen/receptor for chemokines (DARC) was involved. In situ binding assays were performed to determine the expression of chemokine binding sites from rheumatoid (n = 10) and non-rheumatoid (n = 10) synovia. The expression of DARC protein and mRNA was examined by immunohistochemistry and northern blotting. The involvement of DARC in chemokine binding was studied by incubating sections with blocking antibodies to DARC (Fy3 and 6), to find out if these reduced 125I-IL-8 binding. Binding of radiolabelled chemokines IL-8, RANTES, MCP-1, but not MIP-1alpha, was found on venular endothelial cells in inflamed synovia from both rheumatoid and non-rheumatoid patients. Excess homologous unlabelled chemokine displaced binding and excess unlabelled RANTES could displace radiolabelled IL-8 binding. DARC protein expression was demonstrated on venular endothelial cells in all samples and DARC mRNA could be detected in extracts from synovia. There was downregulation of DARC protein and mRNA in rheumatoid samples. Binding of IL-8 to both rheumatoid and non-rheumatoid synovia was significantly reduced in the presence of anti-DARC Fy3 and Fy6 monoclonal antibodies. These findings show the expression of a multispecific chemokine binding site on the inflamed synovial endothelium, with evidence for involvement of DARC. This suggests a potential role for DARC in the inflammatory processes involved in synovitis.

Stromal cell-derived factor 1 (CXCL12) induces monocyte migration into human synovium transplanted onto SCID Mice

OBJECTIVE

The mechanisms by which monocyte/macrophage cells migrate to the joint involve a series of integrated adhesion and signaling events in which chemokines and their receptors are strongly implicated. This study was undertaken to investigate the hypothesis that stromal cell-derived factor 1 (SDF-1), a CXC chemokine (CXCL12), plays a critical role in monocyte/macrophage localization to synovium.

METHODS

SDF-1 and CXC receptor 4 (CXCR4) expression in rheumatoid arthritis (RA) and osteoarthritis synovium and graft SDF-1, tumor necrosis factor alpha (TNF alpha), and human and murine vascular markers were examined by immunohistochemistry and double-immunofluorescence. The functional capacity of SDF-1 to modulate monocyte migration into joints was investigated by examining the localization of pro-myelomonocytic U937 cells into synovial tissue transplanted into SCID mice. SDF-1, TNF alpha, or saline was injected into graft sites and response determined by the number of fluorescently labeled U937 cells (injected intravenously) detected in grafts by ultraviolet microscopy.

RESULTS

SDF-1 and CXCR4 were highly expressed in CD68+ cells in the RA synovium. SDF-1 induced U937 cell migration in vitro and in vivo in a dose-dependent manner and, in vivo, SDF-1 was more effective than TNF alpha. In contrast to TNF alpha, SDF-1 did not induce intracellular adhesion molecule 1 in transplant microvasculature. Furthermore, intragraft injection of SDF-1 did not up-regulate TNF alpha, or vice versa.

CONCLUSION

This study demonstrates, for the first time, that SDF-1 is functional in vivo when injected into synovial grafts. In addition, SDF-1 is more potent than TNF alpha, and its mechanisms of action appear to be autonomous. Therefore, SDF-1 may be an important TNF-independent molecule involved in the migration to and retention of inflammatory effector cells in the joint.

Selective lymphocyte chemokine receptor expression in the rheumatoid joint

OBJECTIVE

In patients with rheumatoid arthritis (RA), chemokines and their receptors are important for lymphocyte trafficking into the inflamed joint. This study was undertaken to characterize the expression of chemokine receptors CCR1, CCR2, CCR3, CCR4, CCR5, CCR6, CXCR3, and CX3CR1 in normal (NL) peripheral blood (PB), RA PB, and RA synovial fluid (SF).

METHODS

Using flow cytometry, immunohistochemistry, and 2-color immunofluorescence, we defined the expression of chemokine receptors on CD3+ T lymphocytes in RA synovial tissue (ST), RA SF, RA PB, and NL PB.

RESULTS

The percentage of CD3+ lymphocytes expressing CCR2, CCR4, CCR5, and CX3CR1 was significantly elevated in RA PB compared with that in NL PB, while the percentage of CD3+ lymphocytes expressing CCR5 was significantly enhanced in RA SF compared with that in NL and RA PB. In contrast, similar percentages of CD3+ lymphocytes in NL PB, RA PB, and RA SF expressed CCR6 and CXCR3. Immunohistochemistry of RA ST showed lymphocyte expression of CCR4, and 2-color immunofluorescence staining revealed RA ST CD3+ lymphocytes intensely immunoreactive for CXCR3, suggesting that these 2 receptors may be particularly important for CD3+ lymphocyte trafficking to the inflamed joint. In comparisons of chemokine receptor expression on naive (CD45RA+) and memory (CD45RO+) CD3+ lymphocytes, there were greater percentages of memory CD3+/CD4+ lymphocytes expressing CCR4, CCR5, and CXCR3 than naive CD3+/CD4+ lymphocytes in RA PB and RA SF, and greater percentages of memory CD3+/CD8+ lymphocytes expressing CCR4, CCR5, and CXCR3 than naive CD3+/CD8+ lymphocytes in RA SF, suggesting receptor up-regulation upon lymphocyte activation. In contrast, percentages of CD3+/CD8+ memory lymphocytes expressing CX3CR1 were significantly less than percentages of naive CD3+/CD8+ lymphocytes in RA PB, suggesting that this receptor may be down-regulated upon lymphocyte activation. A major difference between the RA PB and NL PB groups was significantly more CCR4+ memory leukocytes and memory CCR5+/ CD3+/CD8+ lymphocytes in RA PB than NL PB, further suggesting that these receptors may be particularly important for lymphocyte homing to the RA joint.

CONCLUSION

These results identify CCR4, CCR5, CXCR3, and CX3CR1 as critical chemokine receptors in RA.

Surface expression of CC- and CXC-chemokine receptors on leucocyte subsets in inflammatory joint diseases

Chemokine receptors play a crucial role in the recruitment of leucocyte subsets into inflamed tissue. Using FACS analysis we have studied the surface expression of different CC- and CXC-chemokine receptors on synovial fluid (SF) and peripheral blood leucocytes from 20 patients with various forms of arthritis. In the SF the majority T cells stained positive for CCR5 (93%) and CCR2 (57%), compared to the peripheral blood (36% and 25%). In addition, most of the T cells expressed CXCR4 in both compartments, with a somewhat higher percentage in the SF (90%) versus peripheral blood (83%). To date little information is available on chemokine receptor expression on monocytes in arthritis. We report a marked increase of CCR5(+) monocytes in the SF (87%) compared to the peripheral blood (22%). In contrast, the frequency of CXCR1(+), CXCR2(+), CXCR4(+) and CCR1(+) monocytes was considerably lower in the SF than in the peripheral blood. Moreover, we report the expression CXCR4 on neutrophils in the SF. Approximately 60% of neutrophils stained positive for CXCR4 in the SF, while in the peripheral blood the number of CXCR4(+) neutrophils was low (24%). Surface expression of CXCR1 and CXCR2 was significantly reduced on SF neutrophils (53% and 68%) compared to the peripheral blood. Chemokine receptors are differentially expressed on leucocyte subsets in arthritis. The identification of their pattern of expression might help to identify suitable targets for therapeutic intervention.

Enhancing effect of IL-1, IL-17, and TNF-alpha on macrophage inflammatory protein-3alpha production in rheumatoid arthritis: regulation by soluble receptors and Th2 cytokines

Macrophage inflammatory protein (MIP)-3alpha is a chemokine involved in the migration of T cells and immature dendritic cells. To study the contribution of proinflammatory cytokines and chemokines to the recruitment of these cells in rheumatoid arthritis (RA) synovium, we looked at the effects of the monocyte-derived cytokines IL-1beta and TNF-alpha and the T cell-derived cytokine IL-17 on MIP-3alpha production by RA synoviocytes. Addition of IL-1beta, IL-17, and TNF-alpha induced MIP-3alpha production in a dose-dependent manner. At optimal concentrations, IL-1beta (100 pg/ml) was much more potent than IL-17 (100 ng/ml) and TNF-alpha (100 ng/ml). When combined at lower concentrations, a synergistic effect was observed. Conversely, the anti-inflammatory cytokines IL-4 and IL-13 inhibited MIP-3alpha production by activated synoviocytes, but IL-10 had no effect. Synovium explants produced higher levels of MIP-3alpha in RA than osteoarthritis synovium. MIP-3alpha-producing cells were located in the lining layer and perivascular infiltrates in close association with CD1a immature dendritic cells. Addition of exogenous IL-17 or IL-1beta to synovium explants increased MIP-3alpha production. Conversely, specific soluble receptors for IL-1beta, IL-17, and TNF-alpha inhibited MIP-3alpha production to various degrees, but 95% inhibition was obtained only when the three receptors were combined. Similar optimal inhibition was also obtained with IL-4, but IL-13 and IL-10 were less active. These findings indicate that interactions between monocyte and Th1 cell-derived cytokines contribute to the recruitment of T cells and dendritic cells by enhancing the production of MIP-3alpha by synoviocytes. The inhibitory effect observed with cytokine-specific inhibitors and Th2 cytokines may have therapeutic applications.

Vascular endothelial growth factor expression by activated synovial leukocytes in rheumatoid arthritis: critical involvement of the interaction with synovial fibroblasts

OBJECTIVE

To examine the expression and regulation of the angiogenic factor, vascular endothelial growth factor (VEGF), by fibroblast-like synoviocytes (FLS), monocytes, and polymorphonuclear neutrophils (PMNs) isolated from the synovial fluid (SF) of rheumatoid arthritis (RA) patients.

METHODS

Monocytes or PMNs obtained from RA SF were cocultured with unstimulated, semiconfluent RA FLS. Culture supernatants were assayed for the proliferation and in vitro tube formation of endothelial cells, and for the production of VEGF, by enzyme-linked immunosorbent assay. The expression of VEGF messenger RNA and protein was also determined by reverse transcription-polymerase chain reaction and immunohistochemistry, respectively.

RESULTS

We found that the interaction of inflammatory, activated leukocytes with FLS resulted in synergistic increases in VEGF expression and secretion, which contributed to the proliferation of endothelial cells and to in vitro endothelial tube formation. The induction of VEGF was mediated via specific adhesion molecules, as indicated by the finding that anti-integrin antibodies significantly inhibited VEGF. Furthermore, the levels of VEGF secretion correlated with the expression of cell surface integrin (CD11b and CD18) on both monocytes and PMNs in the SF.

CONCLUSION

VEGF expression within inflamed joints thus appears to be regulated not only by inflammatory cytokines, but also by the physical interaction of activated leukocytes and FLS. Once expressed, VEGF likely plays a crucial role in the neovascularization of the pannus and the progressive joint destruction associated with the synovial inflammation of RA.

Interleukin-18 induces rheumatoid arthritis synovial fibroblast CXC chemokine production through NFkappaB activation

Interleukin-18 (IL-18) is a novel proinflammatory cytokine that was recently found in synovial fluids and in synovial tissues from patients with rheumatoid arthritis (RA). To determine the participation of IL-18 in the inflammation observed in RA, we investigated the effect of IL-18 on RA synovial fibroblast chemokine production. Using FACS analysis, we showed that IL-18 induced a doubling in the production of intracellular IL-8 by RA synovial fibroblasts, and this result was confirmed by Western blot. At the extracellular level, IL-18 up-regulated the secretion of IL-8 in a dose- and time-dependent manner. IL-18 also up-regulated the other CXC chemokines, epithelial-neutrophil activating protein (ENA-78) and growth-regulated oncogene (groalpha), in a dose dependent manner, but failed to induce the production of the CC chemokine, macrophage inflammatory protein (MIP)-1alpha. By immunofluorescence and Western blot, we demonstrated that IL-18 activates the translocation of the transcription factor nuclear factor kappa B (NFkappaB) into the nucleus of RA synovial fibroblasts. IL-18 induces IL-8 secretion through NFkappaB because RA synovial fibroblasts pretreated with antisense to NFkappaB p65 oligonucleotide produce a mean of 44% less IL-8 compared with cells pretreated with the control sense oligonucleotide. These results indicate a novel role for IL-18 in inducing RA synovial fibroblast expression of CXC chemokines through NFkappaB and place this cytokine in a strategic role in the local inflammation observed in RA.

Expression of chemokines and matrix metalloproteinases in early rheumatoid arthritis

OBJECTIVE

To compare macrophage infiltration and expression of chemokines and matrix metalloproteinases (MMPs) in synovial tissue between patients with early and long-standing rheumatoid arthritis (RA).

METHODS

Knee synovial biopsies were taken from 22 patients with early (<1 yr) and 22 patients with long-standing (>5 yr) RA and immunostained with antibodies specific for CD68; macrophage inflammatory protein (MIP)-1alpha and monocyte chemoattractant protein (MCP)-1; MMP-1 and -3 and the tissue inhibitors of metalloproteinases (TIMP)-l and -2. Immunostaining was quantified using a colour video image analysis system.

RESULTS

CD68+ macrophage infiltration and the expression of MIP-1alpha, MCP-1, MMP-1, MMP-3, TIMP-1, and TIMP-2 were observed in synovial tissue of patients with early RA. In long-standing RA, there was a further increase in CD68+ macrophage infiltration and MIP-1alpha expression in the synovial lining layer. CD68 expression correlated with MIP-1alpha (R=0.39, P=0.01), but not with MCP-1 expression.

CONCLUSION

Macrophage accumulation, and the expression of chemokines and MMPs in synovial tissue occur in early RA. Targeting chemokines which play a role in the migration of macrophages into the joints may be of therapeutic benefit in RA patients.

High concentrations of beta-chemokines in BAL fluid of patients with diffuse panbronchiolitis

BACKGROUND

T cells are important cellular components of bronchial inflammation in diffuse panbronchiolitis (DPB). beta-Chemokines such as RANTES (regulated on activation, normal T-cell expressed and secreted) and macrophage inflammatory peptide (MIP)-1alpha are closely related to the migration of inflammatory cells into the lung. In this study, we investigate the contribution of beta-chemokines to the accumulation of T cells in the lungs of patients with DPB.

PATIENTS AND METHODS

We determined the levels of beta-chemokines in BAL fluid (BALF) and the correlation between these levels and T-cell subsets in BALF of 23 patients with DPB and 16 healthy subjects by sandwich enzyme-linked immunosorbent assay and flow cytometry.

RESULTS

Percentages of CD3+ human leukocyte antigen (HLA)-DR+, CD8+, and CD8+HLA-DR+ cells in BALF of patients were significantly higher than in the control BALF. The absolute number of CD8+HLA-DR+ cells was also higher in BALF of patients than in the control BALF (p < 0.0001). Phenotypic analysis of CD4+ cells in BALF showed a similar percentage of CD4+CD45RA+ cells and CD4+CD29+ cells in patients and normal subjects. The concentrations of RANTES and MIP-1alpha in BALF of patients with DPB were significantly higher than in BALF of normal subjects (p < 0.05). In addition, there was a significant correlation between the absolute number or percentage of CD8+HLA-DR+ cells and MIP-1alpha concentration in BALF.

CONCLUSIONS

Our results suggest that the interaction between activated CD8+ T cells and MIP-1alpha may contribute to the pathogenesis of DPB.

Wound healing in MIP-1alpha(-/-) and MCP-1(-/-) mice

A salient feature of normal wound healing is the development and resolution of an acute inflammatory response. Although much is known about the function of inflammatory cells within wounds, little is known about the chemotactic and activation signals that influence this response. As the CC chemokines macrophage inflammatory protein-1alpha (MIP-1alpha) and monocyte chemotactic protein-1 (MCP-1) are abundant in acute wounds, wound repair was examined in MIP-1alpha(-/-) and MCP-1(-/-) mice. Surprisingly, wound re-epithelialization, angiogenesis, and collagen synthesis in MIP-1alpha(-/-) mice was nearly identical to wild-type controls. In contrast, MCP-1(-/-) mice displayed significantly delayed wound re-epithelialization, with the greatest delay at day 3 after injury (28 +/- 5% versus 79 +/- 14% re-epithelialization, P < 0.005). Wound angiogenesis was also delayed in MCP-1(-/-) mice, with a 48% reduction in capillary density at day 5 after injury. Collagen synthesis was impeded as well, with the wounds of MCP-1(-/-) mice containing significantly less hydroxyproline than those of control mice (25 +/- 3 versus 50 +/- 8 microg/wound at day 5, P < 0.0001). No change in the number of wound macrophages was observed in MCP-1(-/-) mice, suggesting that monocyte recruitment into wounds is independent of this chemokine. The data suggest that MCP-1 plays a critical role in healing wounds, most likely by influencing the effector state of macrophages and other cell types.

Fractalkine, a novel chemokine in rheumatoid arthritis and in rat adjuvant-induced arthritis

OBJECTIVE

To examine the expression of the novel CX3C chemokine fractalkine (Fkn) and its receptor (CX3CR1) in rheumatoid arthritis (RA) and rat adjuvant-induced arthritis (AIA), a model of RA.

METHODS

Immunohistochemistry, flow cytometry, enzyme-linked immunosorbent assay (ELISA), reverse transcriptase-polymerase chain reaction (RT-PCR), and chemotaxis assays were used.

RESULTS

In rat AIA, synovial tissue (ST) macrophages, fibroblasts, endothelial cells, and dendritic cells were Fkn immunopositive, whereas lymphocytes did not significantly express Fkn. Significant staining for CX3CR1 was found in ST macrophages, fibroblasts, and dendritic cells, whereas only a small percentage of endothelial cells stained for CX3CR1 in rat AIA. We immunolocalized Fkn to RA ST macrophages, fibroblasts, endothelial cells, and dendritic cells. We also found intense ST macrophage and dendritic cell staining for CX3CR1 in RA ST. Flow cytometry analysis of RA synovial fluid (SF) and peripheral blood revealed a greater percentage of monocytes expressing Fkn and CX3CR1 compared with T cells. By ELISA, we found significantly elevated soluble Fkn (sFkn) levels in RA SF compared with SF from patients with osteoarthritis or other forms of arthritis. By RT-PCR, we found enhanced expression of Fkn and CX3CR1 mRNA on day 18 in rat AIA, a time of pronounced inflammation in the rat joint. Soluble Fkn-depleted RA SF showed significantly decreased chemotactic activity for monocytes compared with sham-depleted RA SF.

CONCLUSION

These results indicate that Fkn and its receptor are both expressed in RA and in rat AIA, and that sFkn is up-regulated in RA SF. Furthermore, our data suggest a new role for Fkn in monocyte chemotaxis in the inflamed RA joint.

Soluble E-selectin induces monocyte chemotaxis through Src family tyrosine kinases

Cellular adhesion molecules such as E-selectin function to recruit leukocytes into the inflammatory lesions of diseases such as rheumatoid arthritis (RA) and atherosclerosis. Monocytes are the key components of the cellular infiltrates present in these disorders. We hypothesized that soluble E-selectin (sE-selectin) might mediate the chemotaxis of monocytes. In this report, we show that sE-selectin induced normal human peripheral blood monocyte migration in the nanomolar range in a concentration-dependent manner. Neutralization studies using RA human joint synovial fluids and anti-E-selectin antibody showed a mean 31% reduction in RA synovial fluid-mediated monocyte chemotaxis (p < 0.05), indicating that sE-selectin is a major monocyte recruiter in RA. Next, we investigated the role of tyrosine phosphorylation pathways in sE-selectin-induced monocyte chemotaxis. Human peripheral blood monocytes stimulated with sE-selectin showed a time-dependent increase in the tyrosine phosphorylation of a broad range of cellular proteins, predominantly in the molecular size range of Src family kinases (50-60 kDa) and mitogen-activated protein kinases (MAPKs). Western blot analysis of Src family kinases showed a time-dependent increase in Src, Hck, and Lyn phosphorylation. The pretreatment of monocytes with the Src inhibitor AG1879: 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolol[3,4-d]pyrimidine (PP2) prior to stimulation with sE-selectin markedly inhibited Hck and Lyn phosphorylation, whereas the phosphorylation of Src was partially inhibited. In addition, the sE-selectin stimulation of monocytes resulted in the increased phosphorylation of extracellular signal-related kinase (ERK1/2) and p38 MAPK. The pretreatment of monocytes with PP2 showed 89 and 83% inhibition of ERK1/2 and p38 MAPK phosphorylation, respectively. sE-selectin also showed a time-dependent activation of Ras kinase. Furthermore, the pretreatment of monocytes with PP2 completely inhibited sE-selectin-mediated monocyte chemotaxis. Taken together, our data demonstrate a novel function for sE-selectin as a monocyte chemotactic agent and suggest that sE-selectin might be mediating its biological functions through the Src-MAPK pathway.

Differential expression of chemokine receptors on peripheral blood, synovial fluid, and synovial tissue monocytes/macrophages in rheumatoid arthritis

OBJECTIVE

Since it is likely that monocytes utilize chemokines to migrate to the rheumatoid arthritis (RA) joint, we investigated the expression of C-C chemokine receptors (CCR) 1-6 and C-X-C receptor 3 (CXCR3) in the peripheral blood (PB), synovial fluid (SF), and synovial tissue of patients with RA as well as in the PB of normal subjects.

METHODS

We compared chemokine receptor expression on CD14+ monocytes from normal PB, RA PB, and RA SF using 2-color flow cytometry. Correlations with patient clinical data were determined. Chemokine and receptor expression were investigated in RA synovial tissue by immunohistochemistry and 2-color immunofluorescence to identify CD68+ macrophages.

RESULTS

Most normal PB monocytes expressed CCR1 (87%) and CCR2 (84%), but not CCRs 3, 4, 5, or 6 or CXCR3. RA PB monocytes expressed CCR1 (56%) and CCR2 (76%), with significantly more expressing CCR3 (18%), CCR4 (38%), and CCR5 (17%) compared with normal PB monocytes. Significantly fewer SF monocytes from RA patients expressed CCR1 (17%), CCR2 (24%), and CCR4 (6%) while significantly more expressed CCR3 (35%) and CCR5 (47%) compared with RA and normal PB monocytes; CCR6 and CXCR3 were rarely detected. Clinically, the erythrocyte sedimentation rate was inversely correlated with the expression of CCR1 and CCR4 by RA PB, and CCR5 expression by RA SF was correlated with the SF white blood cell count. CCR1-, CCR2-, and CCR5-immunoreactive cells were found in RA synovial tissue and colocalized with CD68+ macrophages. RA synovial tissue RANTES (regulated upon activation, normally T cell expressed and secreted chemokine)- and monocyte chemoattractant protein 1-immunoreactive cells colocalized with CCR1 and CCR2, respectively, on serial sections. Macrophage inflammatory protein 1alpha (MIP-1alpha) was principally restricted to vascular endothelium, and MIP-1beta+ macrophages were found throughout the sections.

CONCLUSION

Monocytes mainly express CCR1 and CCR2 in normal and RA PB, CCR3 and CCR5 in RA PB and RA SF, and CCR4 in RA PB. The differential expression of chemokine receptors suggests that certain receptors aid in monocyte recruitment from the circulation while others are important in monocyte retention in the joint.

Ligation of CD11b and CD11c beta(2) integrins by antibodies or soluble CD23 induces macrophage inflammatory protein 1alpha (MIP-1alpha) and MIP-1beta production in primary human monocytes through a pathway dependent on nuclear factor-kappaB

Chemokines and adhesion molecules such as integrins play a major part in the trafficking, extravasation, and recruitment of leukocytes to inflammatory sites. This study investigated the effects of beta(2) integrin engagement on chemokine production by freshly isolated human monocytes. We found that ligation of CD11b or CD11c but not CD11a alpha chains of beta(2) integrins by antibodies or soluble CD23 (sCD23) fusion proteins rapidly induced transcription and secretion of interleukin 8, macrophage inflammatory protein (MIP) 1alpha, and MIP-1beta. Because the promoters of these chemokine genes contain kappaB binding sites, we assessed the possible role of nuclear factor-kappaB (NF-kappaB) in controlling induction of the genes through beta(2) integrin engagement. Electrophoretic mobility shift assays showed that sCD23 or antibodies to CD11b or to CD11c up-regulated DNA-binding activity of NF-kappaB. Activation of NF-kappaB was accompanied by degradation of its cytosolic inhibitor IkappaB-alpha. Blockade of depletion of IkappaB-alpha by proteasome inhibitors (proteasome inhibitor I or acetyl-leucinyl-leucinyl-norleucinal) led to concomitant inhibition of NF-kappaB DNA-binding activity and expression of MIP-1alpha and MIP-1beta messenger RNA induced by beta(2) integrin ligation. These results suggest that triggering of CD11b or CD11c beta(2) integrin on primary human monocytes provides activation signals leading to nuclear translocation of NF-kappaB and subsequent secretion of MIP-1alpha and MIP-1beta that may have an important role in recruitment of other inflammatory cells during initiation of an inflammatory response.

Pathogenesis of rheumatoid arthritis. The role of T cells and other beasts

The evidence coming from the different experimental approaches reviewed in this article strongly supports the hypothesis that RA is T-cell driven at all stages of the disease. Although the effector phases responsible for the events that lead to joint destruction involve several different cell types, cytokines, and other mediators, T cells still direct operations behind the scenes. Direct experimental proof of this proposition in patients is still lacking, but the development of nondepleting modulating CD4 monoclonal antibodies may provide new tools to test this hypothesis. In this respect, it is encouraging that using one such reagent, we have recently shown that not only did the activity of the disease improve but, more importantly, the inflammatory indices and production of non-T-cell cytokines were reduced. This is not to dissimilar from the results of experiments described in animals, where by blocking synovial T cells, the production of IL-1 beta and TNF alpha could be decreased by more than 90%. From this perspective, it may be predicted that by modulating T cells in the joint, it is possible to achieve our ultimate goal of permanently switching off the disease.

Lymph draining from foot joints in rheumatoid arthritis provides insight into local cytokine and chemokine production and transport to lymph nodes

OBJECTIVE

Rheumatoid arthritis (RA) is characterized by inflammatory reactions in joints and adjacent tissues unaccompanied by clinically evident changes in lymphatics and lymph nodes draining the inflamed areas. The explanation for this phenomenon, which contrasts with infectious processes in joints and soft tissues that evoke major changes in the lymphatic system, is unclear. To determine which inflammatory factors produced in the joints of RA patients are transported in lymph to lymph nodes, we measured levels of immunoglobulins, cytokines, and chemokines in prenodal lymph from the foot joints of RA patients and quantified their rate of transport to regional lymph nodes.

METHODS

Lymph was collected from the cannulated lymphatics draining the foot joints, tendons, fascia, and skin of 20 RA patients. Lymph flow rate and concentrations of proteins and immunoglobulins were measured. Cytokine and chemokine levels were quantified by enzyme-linked immunosorbent assays. Results were compared with those obtained in 20 control subjects.

RESULTS

In the cannulated vessel, the mean +/- SEM lymph flow rate in RA patients was almost 2-fold that in control subjects (22.6 +/- 3.2 ml/24 hours versus 13.2 +/- 1.1 ml/24 hours; P < 0.01). Lymph concentrations of total protein, IgG, and IgM were 1.80 +/- 0.14 gm/dl, 384 +/- 45 mg/dl, and 32.0 +/- 1.5 mg/dl, respectively, in RA patients and 1.66 +/- 0.14 gm/dl, 238 +/- 32 mg/dl, and 15.0 +/- 1.3 mg/dl, respectively, in control subjects. The corresponding lymph:serum (L:S) ratios were 0.21 +/- 0.02, 0.22 +/- 0.02, and 0.15 +/- 0.02, respectively, in RA patients and 0.22 +/- 0.02, 0.19 +/- 0.02, and 0.11 +/- 0.02, respectively, in control subjects. The L:S ratios of <1 and the absence of significant differences between groups suggested a lack of local production of immunoglobulins. In RA patients, lymph concentrations (in pg/ml) were as follows: interleukin-1beta (IL-1beta) 14.8 +/- 3.9, IL-6 511 +/- 143, tumor necrosis factor alpha (TNFalpha) 9.9 +/- 1.1, IL-1 receptor antagonist (IL-1Ra) 4,274 +/- 737, IL-10 13.3 +/- 4.4, IL-8 846 +/- 174, IL-15 6.2 +/- 0.9, granulocyte-macrophage colony-stimulating factor (GM-CSF) 2.30 +/- 0.15, vascular endothelial growth factor (VEGF) 80.4 +/- 8.6, and macrophage inflammatory protein 1alpha (MIP-1alpha) 171 +/- 34. In control subjects, these values were as follows: IL-1beta 1.50 +/- 0.25, IL-6 79.0 +/- 14.6, TNFalpha 4.4 +/- 1.1, IL-1Ra 208 +/- 52, IL-10 0.0, IL-8 216 +/- 83, IL-15 5.00 +/- 0.45, GM-CSF 0.40 +/- 0.05, VEGF 42.0 +/- 2.4, and MIP-1alpha 3.4 +/- 1.7 (P < 0.05 versus RA patients for all except IL-15). The L:S ratio was >1 in all RA patient samples for IL-1beta, IL-6, IL-1Ra, IL-8, GM-CSF, IL-10, IL-15, TNFalpha, and MIP-1alpha, indicating local production of cytokines. Great variability in lymph cytokine concentrations, presumably reflecting differences in the intensity of local inflammation, was not reflected in serum cytokine concentrations. Intravenously infused methylprednisolone decreased lymph cytokine levels to normal within 12 hours. In contrast, their concentrations in serum showed little or no change.

CONCLUSION

High lymph concentrations of cyto kines and chemokines, exceeding those in serum, were found in RA patients. The L:S concentration ratios of > 1 indicate the local production of these cytokines and chemokines in the inflamed tissues. High flow rates of lymph containing high cytokine concentrations through the regional lymph nodes are likely to affect node lymphocytes and dendritic cells. Analysis of cytokines in lymph should provide insight into events in inflamed tissues in RA and in regional lymph nodes.

Effects of intraarticular glucocorticoids on macrophage infiltration and mediators of joint damage in osteoarthritis synovial membranes: findings in a double-blind, placebo-controlled study

OBJECTIVE

To investigate the effects of intraarticular glucocorticoid treatment on macrophage infiltration, the expression of the chemokines monocyte chemoattractant protein 1 (MCP-1) and macrophage inflammatory protein 1alpha (MIP-1alpha), and the expression of matrix metalloproteinases 1 and 3 (MMPs 1 and 3) and their inhibitors, the tissue inhibitors of metalloproteinases 1 and 2 (TIMPs 1 and 2), in osteoarthritis (OA) synovial membranes.

METHODS

Forty patients underwent arthroscopic biopsy before and 1 month after intraarticular injection of glucocorticoids. Twenty-one patients received 120 mg of methylprednisolone acetate (Depo-Medrol; Upjohn, Kalamazoo, MI), and 20 patients received placebo (1 patient received placebo in 1 knee and methylprednisolone acetate in the other). Immunoperoxidase staining for the expression of CD68, MCP-1, MIP-1alpha, MMP-1, MMP-3, TIMP-1, and TIMP-2 was performed, and the immunostaining was quantified by color video image analysis.

RESULTS

CD68, MCP-1, MIP-1alpha, MMP-1, MMP-3, TIMP-1, and TIMP-2 immunostaining was observed in all synovial membranes. Intraarticular glucocorticoid treatment was associated with a small (30%) but statistically significant (P = 0.048) reduction in CD68+ macrophage staining in the synovial lining layer, but there was no change in the CD68 expression in the synovial sublining layer. No significant differences were observed for MCP-1, MIP-1alpha, MMP-1, MMP-3, TIMP-1, and TIMP-2 immunostaining in the synovial lining or sublining layers.

CONCLUSION

Intraarticular glucocorticoids may reduce CD68+ macrophage infiltration into the synovial lining layer, but not the expression of MCP-1, MIP-1alpha, MMP-1, MMP-3, TIMP-1, and TIMP-2 in the synovial membrane, in patients with OA.

CXCR3 and CCR5 ligands in rheumatoid arthritis synovium

The pathogenesis of rheumatoid arthritis (RA) may be mediated by Th1-type T cells. Since chemokine receptors CXCR3 and CCR5 are preferentially expressed on Th1 cells, we tested the expression and regulation of several chemokines, including those that signal through CXCR3 (interferon-gamma-inducible protein of 10 kDa, IP-10, CXCL10; and monokine induced by interferon-gamma, Mig, CXCL9) and CCR5 (macrophage inflammatory protein (Mip)-1 alpha, CCL3; and Mip-1 beta, CCL4) in RA synovial fluids, synovial tissues, and blood. Synovial fluid (SF) protein levels of IP-10 (32.1 +/- 10.5 ng/ml), Mig (15.0 +/- 6.4 ng/ml), Mip-1 beta (0.7 +/- 0.3 ng/ml), and Mip-1 alpha (0.8 +/- 0.1 ng/ml) were 100-, 50-, 25-, and 2-fold elevated in RASF compared to control SF (P < 0.001, P < 0.001, P < 0. 001, and P < 0.02, respectively). Tissue levels of IP-10, Mig, and Mip-1 beta were significantly higher in RA than in OA (P < 0.01). Serum levels of IP-10 (3.1 +/- 1.2 ng/ml) were higher in patients with seropositive RA compared to controls (1.2 +/- 0.2 ng/ml) (P < 0.02). There was a gradient of IP-10, Mig, Mip-1 alpha, and Mip-1 beta from the blood into the synovial fluid in RA. Infiltrating T cells around high endothelial venules in RA synovium and 90 +/- 3% of SF CD3(+)CD4(+) T cells expressed CXCR3, and 85 +/- 2% of SF CD3(+)CD4(+) T cells expressed CCR5. Chemokines, including IP-10, Mig, Mip-1 alpha, and Mip-1 beta, may participate in the selective recruitment of CCR5(+)CXCR3(+) T cells to the inflamed synovium.

Regulation of angiogenesis by the C-X-C chemokines interleukin-8 and epithelial neutrophil activating peptide 78 in the rheumatoid joint

OBJECTIVE

Angiogenesis, the growth of new blood vessels, is vital to the ingress of inflammatory leukocytes in rheumatoid arthritis (RA) synovial tissue and to the growth and proliferation of RA pannus. The factors that mediate the growth of new blood vessels have not been completely defined. This study examined the ability of Glu-Leu-Arg (ELR)-containing chemokines to induce angiogenesis in the RA joint.

METHODS

To reflect angiogenic activity in vivo, we selected a model using whole human synovial tissue rather than isolated cells. Tissues were examined by immunohistochemistry and enzyme-linked immunosorbent assay, and tissue homogenates were immunoneutralized and assayed for their ability to induce endothelial cell chemotaxis and rat corneal neovascularization.

RESULTS

Cells expressing interleukin-8 (IL-8) and epithelial neutrophil activating peptide 78 (ENA-78) were located in proximity to factor VIII-related antigen-immunopositive endothelial cells. RA homogenates produced more IL-8 and ENA-78 compared with normal synovial tissue homogenates. Moreover, homogenates from RA synovial tissue produced significantly more chemotactic activity for endothelial cells in vitro and angiogenic activity in the rat cornea in vivo than did normal synovial tissue homogenates. The effects of IL-8 and ENA-78 accounted for a significant proportion of the chemotactic activity of endothelial cells and angiogenic activity found in RA synovial tissue homogenates.

CONCLUSION

These results indicate that the ELR-containing chemokines IL-8 and ENA-78 are important contributors to the angiogenic activity found in the inflamed RA joint. It is possible that efforts aimed at down-regulating these chemokines offer a novel targeted therapy for the treatment of RA.

Significance of chemokines and activated platelets in patients with diabetes

Levels of platelet-derived microparticles (PMPs), platelet activation markers (P-selectin expressed on, or annexin V binding to, platelets (plt:P-selectin or plt:annexin V, respectively)), chemokines (IL-8, monocyte chemotactic peptide-1 (MCP-1), and regulated on activation normally T-cell expressed and secreted (RANTES)), and soluble P- and E-selectins were compared in peripheral blood from diabetic and control patients in order to develop a better understanding of their potential contribution to diabetic vascular complications. Significant increases were found for PMPs, plt:P-selectin, MCP-1, RANTES and soluble P- and E-selectins in diabetic individuals, whereas IL-8 levels were similar. Furthermore, after ticlopidine treatment, most of these factors receded to baseline levels observed in non-diabetic patients. Our findings indicate that ticlopidine might be able to prevent or reduce vascular complications in diabetic patients.

Regulation of TNF-alpha expression in normal macrophages: the role of C/EBPbeta

C/EBPbeta is present in monocytes and macrophages, binds to the proximal region of the TNF-alpha promoter, and contributes to its regulation. This study was performed to characterize the ability of C/EBPbeta to regulate the TNF-alpha gene in myelomonocytic cells and primary macrophages. In transient transfection assays, overexpression of wild type C/EBPbeta resulted in a 3-4-fold activation of a 120 base pair TNF-alpha promoter-reporter construct, while overexpression of a dominant negative (DN) C/EBPbeta inhibited LPS-induced activation. In vitro monocyte-differentiated macrophages, infected with an adenoviral vector expressing the DN C/EBPbeta (AdDNC/EBPbeta) or the control Adbetagal, expressed their transgenes weakly, however expression was greatly enhanced in the presence of PMA. Infection with AdDNC/EBPbeta resulted in 60% suppression of LPS induced TNFalpha secretion compared to Adbetagal infection (P<0.001) in PMA-treated macrophages. Northern blot analysis demonstrated approximately a 40% reduction of the TNF-alpha mRNA in the presence of the DN C/EBPbeta, suggesting that the effect of the DN C/EBPbeta was at the transcriptional level. In contrast, AdDNC/EBPbeta infection did not result in inhibition of LPS-induced TNF-alpha secretion in the absence of PMA. Further, DN versions of both C/EBPbeta and c-Jun, but not NF-kappaB p65, suppressed PMA-induced TNF-alpha secretion in macrophages. These observations demonstrate that, C/EBPbeta and c-Jun contribute to the regulation of the TNF-alpha gene in normal macrophages following treatment with PMA.

Human chondrocytes express functional chemokine receptors and release matrix-degrading enzymes in response to C-X-C and C-C chemokines

OBJECTIVE

Human chondrocytes produce different C-X-C and C-C chemokines under basal conditions and upon activation with proinflammatory cytokines. We investigated whether human chondrocytes also have chemokine receptors and examined the effects of chemokines on chondrocyte activity.

METHODS

The expression of chemokine receptors was determined by immunochemical analysis of frozen sections from normal and osteoarthritic cartilage and by flow cytometry of isolated cells. The messenger RNA expression for chemokine receptors was studied by reverse transcriptase-polymerase chain reaction. Isolated chondrocytes were stimulated with different chemokines, and the responses were evaluated by assaying the release of matrix metalloprotease 3 (MMP-3) and of the lysosomal enzyme N-acetyl-beta-D-glucosaminidase in the supernatants.

RESULTS

A wide variety of chemokine receptors (CCR-1, CCR-2, CCR-3, CCR-5, CXCR-1, and CXCR-2) was detected on human chondrocytes. Interaction of these receptors with the corresponding ligands induced the release of MMP-3. This response was abrogated by pretreatment of the cells with Bordetella pertussis toxin, demonstrating involvement of G proteins of the Gi type. The response decreased in the presence of cycloheximide, indicating dependence on protein synthesis. Chemokines also induced the exocytosis of N-acetyl-beta-D-glucosaminidase, which was prevented by receptor blockage with anti-CCR-3 and by treatment with B pertussis toxin. Chondrocytes obtained from osteoarthritic tissue showed an increased expression of CCR-3 and possibly of CXCR-1, and an augmented release of matrix-degrading enzymes compared with chondrocytes from normal donors.

CONCLUSION

Our findings suggest the existence in human chondrocytes of a novel catabolic pathway, primed by chemokines and their receptors, that leads to the breakdown of cartilage matrix components.

Human T-cell lymphotropic virus type-I tax gene induces interleukin-8 secretion by autocrine mechanism and has No effect on interleukin-16 in transfected Jurkat cells

Human T-cell lymphotropic virus I (HTLV-I) Tax has been shown to transactivate several cellular genes. In this study, we show that interleukin-8 (IL-8) is expressed and secreted in tax-transfected Jurkat cells that were further augmented by mitogen stimulation. Expression of high-affinity IL-8-R (Type A) mRNA in these cells suggests an autocrine role for this chemokine in HTLV-I-infected T-cells. However, interleukin-16 (IL-16) mRNA expression or protein secretion was not significantly modulated either constitutively or even upon mitogen stimulation in these tax-transfected cells.

Stimulation of Fc gamma R receptors induces monocyte chemoattractant protein-1 in the human monocytic cell line THP-1 by a mechanism involving I kappa B-alpha degradation and formation of p50/p65 NF-kappa B/Rel complexes

THP-1 monocytic/macrophage cells were stimulated via their FcgammaR receptors with insoluble aggregates of human IgG and the production of the C-C chemokine monocyte chemoattractant protein (MCP)-1 assayed. A dose- and time-dependent production of MCP-1 comparable to that produced by the most potent agonists could be detected in the culture medium by a sensitive ELISA assay. This was accompanied by a parallel activation of the transcription factor NF-kappaB as judged from both the appearance of kappaB-binding activity containing p50/p65 NF-kappaB/Rel complexes in the nuclear extract and the disappearance of the NF-kappaB inhibitor IkappaB-alpha in the cell lysate. In contrast, IkappaB-beta and IkappaB-epsilon expression was not modified, thus pointing to the occurrence of a selective degradation of IkappaB-alpha under those conditions. Attempts to modulate MCP-1 production with compounds that display inhibitory effects on the activation of NF-kappaB such as the proteasome inhibitor N-acetyl-leucinyl-leucinyl-norleucinal, the antioxidant pyrrolidine dithiocarbamate and the salicylate derivative 2-hydroxy-4-trifluoromethylbenzoic acid showed a parallel effect on both MCP-1 production and NF-kappaB activation, thus pointing to the involvement of kappaB-binding sites on the transcriptional regulation of MCP-1 production. Our findings suggest the existence in monocytic cells of a signaling mechanism initiated by cross-linking of low-affinity FcgammaR, most likely of the FcgammaRII family since THP-1 cells do not express FcgammaRIII receptors, that involves activation of NF-kappaB associated to the proteolytic degradation of IkappaB-alpha and leads to the transcriptional up-regulation of MCP-1.

Cutaneous injection of human subjects with macrophage inflammatory protein-1 alpha induces significant recruitment of neutrophils and monocytes

Macrophage inflammatory protein (MIP-1 alpha), a member of the CC chemokine subfamily, has been shown to attract T cells and monocytes in vitro and to be expressed at sites of inflammation. Although the in vitro activities of MIP-1 alpha have been well documented, the in vivo biological activities of MIP-1 alpha in humans have not been studied. To address this, we challenged human subjects by intradermal injection with up to 1000 pmol of MIP-1 alpha and performed biopsies 2, 10, and 24 h later. Although no acute cutaneous or systemic reactions were noted, endothelial cell activation, as indicated by the expression of E-selectin, was observed. In agreement with its in vitro activity, monocyte, lymphocyte, and, to a lesser degree, eosinophil infiltration was observed, peaking at 10-24 h. Surprisingly, in contrast to its reported lack of in vitro neutrophil-stimulating activity, a rapid infiltration of neutrophils was observed in vivo. This neutrophil infiltration occurred as early as 2 h, preceding the appearance of other cells, and peaked at 10 h. Interestingly, we found that neutrophils in whole blood, but not after isolation, expressed CCR1 on their cell surface. This CCR1 was thought to be functional as assessed by neutrophil CD11b up-regulation following whole-blood MIP-1 alpha stimulation. These studies substantiate the biological effects of MIP-1 alpha on monocytes and lymphocytes and uncover the previously unrecognized activity of MIP-1 alpha to induce neutrophil infiltration and endothelial cell activation, underscoring the need to evaluate chemokines in vivo in humans.

Elevated levels of beta-chemokines in bronchoalveolar lavage fluid (BALF) of individuals infected with human T lymphotropic virus type-1 (HTLV-1)

Pulmonary complications are known to develop in HTLV-1 carriers, including T lymphocytic alveolitis, and increased IL-2 receptor alpha (CD25)-bearing T cells have been found in BALF. Several chemokines may contribute to accumulation of T lymphocytes in the lungs of HTLV-1 carriers. Here, we compared the distribution of T lymphocyte subsets and beta-chemokines, such as macrophage inflammatory peptide-1alpha (MIP-1alpha), regulated on activation normal T expressed and secreted (RANTES), and macrophage chemoattractant protein-1 (MCP-1), in BALF and peripheral blood between HTLV-1 carriers and non-infected healthy normal subjects. Flow cytometric analysis with MoAbs to cell surface antigens was used to identify T lymphocyte subsets in BALF samples from HTLV-1 carriers (n = 13) and non-infected healthy controls (n = 10). The levels of different beta-chemokines were estimated by ELISA. High percentages of CD3+ cells, CD3 expressing HLA-DR antigen and CD3+CD25+ cells were detected in BALF of HTLV-1 carriers compared with non-infected controls. The concentration of MIP-1alpha in BALF of patients was significantly higher than in non-infected healthy controls and correlated well with the percentage of CD3+CD25+ cells. The level of RANTES in BALF was also significantly high in HTLV-1 carriers, but did not correlate with the percentage of CD3+CD25+ cells. On the other hand, the level of MCP-1 in BALF of HTLV-1 carriers was not different from that of controls. Our results suggest a possible interaction between activated T cells bearing CD25 and beta-chemokines, especially MIP-1alpha, which may contribute to the pulmonary involvement in HTLV-1 carriers.

Key role of chemokines and chemokine receptors in inflammation, immunity, neoplasia, and infectious disease

Leukocyte homing is a complex, multistep process involving the coordinated expression of adhesion molecules and certain chemotactic cytokines, termed chemokines. Although chemokines initially burst into the literature as potent inflammatory mediators, it is now clear that they are involved in a variety of processes including lymphocyte maturation, angiogenesis, and tumor growth. Furthermore, a variety of important pathogens manipulate various chemokine/receptor pathways to infect the host and evade the immune system.

Human T-cell lymphotrophic virus type-I tax gene induces secretion of human macrophage inflammatory protein-1alpha

Human T-cell lymphotropic virus I (HTLV-I) encodes for a 40-kDa protein, Tax, which is important for the immortalization of T cells. Tax has been shown to transactivate several cellular genes. In this study, we show that MIP-1alpha is selectively expressed and secreted in the tax transfected Jurkat cell line upon mitogen stimulation. Expression of MIP-1alpha-R mRNA in these cells suggests an autocrine role for this chemokine in HTLV-I infected T-cells. Induced MIP-1alpha expression and secretion in PMA/PHA stimulated tax transfected cells correlate with the noninduction of MNP-1 transcription factor, which is intimately involved in downmodulating the MIP-1alpha gene.

Flow cytometric analysis of intracellular chemokines in chondrocytes in vivo: constitutive expression and enhancement in osteoarthritis and rheumatoid arthritis

Chemokines play a key role in modulating leukocyte functions at sites of inflammation. To assess chondrocyte contribution to the chemotactic environment of inflamed joints the intracellular content of CC and CXC chemokines was investigated. IL-8, GROalpha, MCP-1, RANTES, MIP-1alpha and MIP-1beta expression was evaluated by flow cytometric analysis and RT-PCR in chondrocytes isolated from cartilage specimens obtained from patients with osteoarthritis and rheumatoid arthritis and multiorgan donors as normal controls. All the chemokines except RANTES were found in normal chondrocytes, with different degrees of staining intensity. In osteoarthritis and rheumatoid arthritis patients, an enhancement of IL-8, GROalpha, MIP-1alpha and MIP-1beta was observed.

Augmented production of chemokines (monocyte chemotactic protein-1 (MCP-1), macrophage inflammatory protein-1alpha (MIP-1alpha) and MIP-1beta) in patients with systemic sclerosis: MCP-1 and MIP-1alpha may be involved in the development of pulmonary fibrosis

To determine the role of chemokines in the pathogenesis of systemic sclerosis (SSc), we examined serum levels, spontaneous production by peripheral blood mononuclear cells (PBMC), and histological distribution in the affected skin, of MCP-1, MIP-1alpha and MIP-1beta in SSc patients. Serum levels of these chemokines were examined by ELISA in 58 patients with SSc and 20 normal controls. The levels of these chemokines in culture supernatants from PBMC were also measured by ELISA. Serum levels and spontaneous production levels by PBMC of MCP-1, MIP-1alpha, and MIP-1beta were significantly elevated in patients with SSc compared with normal controls. Elevated serum levels of MCP-1 and MIP-1alpha significantly correlated with the presence of pulmonary fibrosis. MCP-1 expression in the skin of SSc was immunohistochemically examined using anti-MCP-1 MoAb. MCP-1 was strongly expressed in the epidermis, inflammatory mononuclear cells, and vascular endothelial cells in the sclerotic skin of SSc patients, but not expressed in any control skin. Furthermore, the MCP-1 expression in inflammatory mononuclear cells and endothelial cells significantly correlated with earlier onset of SSc. Thus, MCP-1, MIP-1alpha and MIP-1beta may be involved in the disease process, possibly by augmenting leucocyte migration into the affected tissues in SSc. Furthermore, MCP-1 and MIP-1alpha may play an important role in the development of pulmonary fibrosis in SSc.

Chemokine expression by subchondral bone marrow stromal cells isolated from osteoarthritis (OA) and rheumatoid arthritis (RA) patients

We analysed the spontaneous and cytokine-stimulated production and expression in vitro of IL-8, GROalpha, MCP-1, RANTES, MIP-1alpha, MIP-1beta, by subchondral bone marrow stromal cells (BMSC) isolated from RA, OA, post-traumatic (PT) patients and normal donors (ND). BMSC were cultured in vitro in the presence or absence of IL-1beta and tumour necrosis factor-alpha (TNF-alpha), and assessed for chemokine production, expression and immunolocalization. BMSC from different sources constitutively released MCP-1, GROalpha and IL-8, but not MIP-1alpha or MIP-1beta, while BMSC from ND constitutively released only IL-8 and MCP-1. IL-8, GROalpha and RANTES production in basal conditions was significantly higher in RA patients than in ND. RANTES production was also higher in OA and RA than in PT patients. The combination of TNF-alpha and IL-1beta synergistically increased the production of all chemokines tested except for RANTES. Reverse transcriptase-polymerase chain reaction (RT-PCR) demonstrated that all chemokines not detectable in the supernatants were expressed at the mRNA level. Chemokine immunostaining was localized around the nuclei. This work demonstrates that BMSC from subchondral bone produce chemokines and indicates that these cells could actively participate in the mechanisms directly or indirectly causing cartilage destruction and bone remodelling.

Macrophage inflammatory protein 1 alpha expression by synovial fluid neutrophils in rheumatoid arthritis

OBJECTIVE

To determine the contribution made by synovial fluid (SF) neutrophils to the augmented expression of macrophage inflammatory protein 1 alpha (MIP-1alpha) in rheumatoid arthritis (RA).

METHODS

Neutrophils were isolated from samples of SF from RA patients and peripheral blood (PB) samples from RA patients and healthy controls. Cell associated MIP-1alpha was visualised immunohistochemically, and cell associated MIP-1alpha as well as MIP-1alpha secreted into the SF was assayed by ELISA. Steady state expression of MIP-1alpha mRNA was assessed by reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

Freshly isolated SF neutrophils contained significantly higher concentrations of both MIP-1alpha protein and its transcript than PB neutrophils from either RA patients or healthy controls; incubation in the absence or presence of tumour necrosis factor alpha for 24 hours resulted in a significant increase in MIP-1alpha secretion by RA SF neutrophils compared with neutrophils obtained from either normal PB or RA PB; and expression of MIP-1alpha by SF neutrophils was well correlated with both RA disease activity and SF mononuclear cell (MNC) counts.

CONCLUSION

Expression and secretion of MIP-1alpha by SF neutrophils may be indicative of local and systemic inflammation in RA. Moreover, this C-C chemokine may contribute to the recruitment of MNCs from the bloodstream into synovial joints and tissues.

Predominance of mononuclear cells expressing the chemokine receptor CCR5 in synovial effusions of patients with different forms of arthritis

OBJECTIVE

To study the role of the chemokine receptors CCR5 and CCR2 in patients with arthritis.

METHODS

CCR5 expression on peripheral blood leukocytes was compared with the expression on leukocytes isolated from the synovial fluid of 20 patients with different rheumatic joint diseases. Three additional samples were studied for CCR2 expression. The expression of chemokine receptors on blood and synovial fluid leukocytes was determined by 3-color flow cytometry analysis. To test CCR5 receptor down-modulation from the cell surface, leukocytes were incubated in vitro with a RANTES (regulated on activation, normal T cell expressed and secreted) derivative, aminooxypentane (AOP)-RANTES. Patients were genotyped for the delta32 CCR5 deletion by polymerase chain reaction.

RESULTS

A high percentage of CCR5-expressing CD4+ and CD8+ T cells (74% and 81%, respectively), monocytes (51%), and natural killer cells (35%) was found in the synovial fluid of all patients, whereas in the peripheral blood, only a small percentage of these cells expressed CCR5 (13%, 32%, 7.8%, and 4%, respectively). Infiltration of CCR5-positive leukocytes was not reduced in CCR5-heterozygous patients. A similar, but less pronounced, distribution was observed for CCR2-positive T cells. In vitro, CCR5 was completely down-modulated on synovial fluid leukocytes by AOP-RANTES.

CONCLUSION

The predominance of CCR5-positive mononuclear cells in the synovial effusions of patients with arthritis suggests an important role for CCR5 in the process of joint inflammation, and identifies CCR5 as a possible new target for therapeutic intervention.

On the edge: the physiological and pathophysiological role of chemokines during inflammatory and immunological responses

Most, if not all, chemokines bind to seven transmembrane spanning G protein-coupled receptors and activate cellular migration. Stimulated chemokine expression is essential for directing leukocyte emigration from the circulation into sites of inflammation and tissue damage. In contrast, constitutive chemokine expression plays a role in the development of lymphoid cells, organs, and tissues. The present review examines rheumatoid arthritis and transplantation rejection as two examples of pathological conditions where chemokine directed leukocyte infiltration aids in the pathogenesis of the disease. We further discuss insights into leukocyte trafficking gained by chemokine and chemokine receptor transgenic and null mutant mice.

The CC chemokine MIP-1alpha induces a selective monocyte infiltration following intradermal injection into nonhuman primates

The in vitro chemotactic activity of chemokines have been well documented. However, study of their in vivo effects where components of rolling, adherence and diapedesis are pre-requisites to leukocyte infiltration have not been examined in higher species. In this study, we examined the biological activity of the CC chemokine, MIP-1alpha, in rhesus monkeys. Following an intradermal injection, a significant cellular infiltrate and an increase in the number of inflamed vessels were observed. This response peaked at 24 h and was sustained for up to 48 hours after injection. Phenotypically, the specific infiltrate consisted exclusively of CD68+ monocytes with no increase in other cell types over the saline injected controls. These studies represent the first examination of the in vivo effects of MIP-1alpha in higher species and indicate that MIP-1alpha is a selective monocyte recruiting agent in vivo.

Mucosal macrophage inflammatory protein-1alpha activity in Helicobacter pylori infection

Mucosal chemokines are considered to be important in the pathogenesis of Helicobacter pylori-associated gastritis. The aims of this study are to examine the levels of macrophage inflammatory protein-1alpha (MIP-1alpha) in organ cultures, the expression of MIP-1alpha mRNA and the cellular source of MIP-1alpha, using the antral mucosal specimens obtained from H. pylori-positive and -negative patients. Enzyme-linked immunosorbent assay was used to measure the levels of MIP-1alpha in organ cultures of mucosal tissues and cell cultures of fractionated mucosal cells. The expression of MIP-1alpha mRNA and protein was analysed in fresh biopsy tissues with reverse transcriptase-polymerase chain reaction (RT-PCR) and double immunofluorescence microscopy, respectively. The mucosal specimens obtained from H. pylori-positive patients exhibited significantly higher values of MIP-1alpha activity in organ cultures with increased numbers of CD68+ macrophages, myeloperoxidase+ neutrophils and mononuclear cells in the lamina propria compared with those from H. pylori-negative patients. The RT-PCR analysis detected MIP-1alpha mRNA in more than 50% of the specimens with H. pylori infection, but not in those without infection. In cell cultures, the macrophage fraction contained substantially higher amounts of MIP-1alpha on a per cell basis than the lymphocyte fraction and MIP-1alpha activity was not detected in cultures of gastric epithelial cells. This observation was also confirmed by a double immunofluorescence microscopic study in which most (>90%) MIP-1alpha-positive infiltrating cells were CD68+ macrophages. This study indicates that synthesis and secretion of MIP-1alpha are increased in H. pylori-infected antral mucosa and that mucosal macrophages are the main cell type responsible for this phenomenon.

Role of pro-inflammatory cytokines in rheumatoid arthritis

Rheumatoid arthritis (RA) is well known to be a chronic autoimmune/inflammatory disease which leads to progressive joint damage and destruction. Less well known is the fact that in severe cases of RA, with extra-articular manifestations and multiple joint involvement, there is also a significant reduction in life expectancy [28]. Hence the need for new therapeutic agents. With the cloning of cDNAs encoding cytokines in the early to mid 1980s, it became possible to use new assays to evaluate cytokine expression in the local site of autoimmunity, the rheumatoid synovium. There were two goals. First would understanding cytokine expression help us understand the pathogenesis of RA? Secondly, would it be possible to learn enough about the cytokine network to establish possible therapeutic targets? While a complete understanding of either of these questions remains elusive, here we review the state of knowledge in early 1998, which shows that much progress has been made and that these goals have been partly reached. The clinical benefits of this knowledge are documented elsewhere in this compilation, as is the role of chemokines, anti-inflammatory cytokines and the cytokines involved in neovascularisation.

Exogenous and endogenous catecholamines inhibit the production of macrophage inflammatory protein (MIP) 1 alpha via a beta adrenoceptor mediated mechanism

Noradrenaline (NA) and adrenaline (Ad) are modulators of cytokine production. Here we investigated the role of these neurotransmitters in the regulation of macrophage inflammatory protein (MIP)-1alpha expression. Pretreatment of RAW 264.7 macrophages with NA or Ad decreased, in a concentration-dependent manner (1 nM-100 microM), MIP-1alpha release induced by bacterial lipopolysaccharide (LPS 10 ng ml(-1) LPS). The effect of NA was reversed by the selective beta-adrenoceptor antagonist propranolol (10 microM), but not by the alpha-adrenoceptor antagonist phentolamine (10 microM). In the concentration range of 10 nM-10 microM, isoproterenol, a beta-adrenoceptor agonist, but not phenylephrine (a selective alpha1-adrenoceptor agonist) or UK-14304 (a selective alpha2-adrenoceptor agonist) mimicked the inhibitory effects of catecholamines on MIP-1alpha production. Increases in intracellular cyclic adenosine monophosphate, elicited either by the selective type IV phosphodiesterase inhibitor rolipram (0.1 - 10 microM), or by prostaglandin E2, (10 nM-10 microM) decreased MIP-1alpha release, suggesting that increased cyclic AMP may contribute to the suppression of MIP-1alpha release by beta-adrenoceptor stimulation. Northern blot analysis demonstrated that NA (100 nM-10 microM), Ad, isoproterenol, as well as rolipram (100 nM-10 microM) decreased LPS-induced MIP-1alpha mRNA accumulation. NA and Ad (1-100 microM) also decreased MIP-1alpha production in thioglycollate-elicited murine peritoneal macrophages. Pretreatment of mice with either isoproterenol (10 mg kg(-1), i.p.) or rolipram (25 mg kg(-1), i.p.) decreased LPS-induced plasma levels of MIP-1alpha, while propranolol (10 mg kg(-1), i.p.) augmented the production of this chemokine, confirming the role of a beta-adrenoceptor mediated endogenous catecholamine action in the regulation of MIP-1alpha production in vivo. Thus, based on our data we conclude that catecholamines are important endogenous regulators of MIP-1alpha expression in inflammation.

RANTES expression and contribution to monocyte chemotaxis in arthritis

Rheumatoid arthritis (RA) is characterized by recruitment of leukocytes from the vasculature into inflamed synovial tissue (ST) and synovial fluid (SF), which depends, in part, upon the continued maintenance of chemotactic stimuli. RANTES is a potent chemoattractant for leukocytes including monocytes and CD45RO+ memory T lymphocytes. The aim of this study was to determine the production, the source, and the function of antigenic RANTES in arthritis. We detected antigenic RANTES in SFs from RA and OA patients (100 +/- 22.7 and 72 +/- 30.7 pg/ml, respectively). CM from RA ST fibroblasts stimulated with interleukin-1beta or tumor necrosis factor-alpha contained significantly more antigenic RANTES than unstimulated CM (452 +/- 181.6 and 581 +/- 200.2 pg/ml, respectively, versus 12 +/- 4.4 pg/ml, P < 0.05). PHA-stimulated RA SF mononuclear cells secreted 5- to 15-fold more antigenic RANTES than did nonstimulated mononuclear cells, while LPS induced secretion up to 4-fold. We immunolocalized antigenic RANTES to sublining macrophages (28 +/- 3.7 and 8 +/- 2.0% immunopositive cells), perivascular macrophages (56 +/- 6.9 and 19 +/- 3.4%), and synovial lining cells (37 +/- 5.8 and 60 +/- 10.4%) in RA and OA tissue, respectively. Anti-RANTES neutralized 20.2 +/- 1.3% of the RA SF chemotactic activity for normal peripheral blood monocytes (P < 0.05). These results demonstrate antigenic RANTES in RA and OA ST and SF and identify RANTES as a chemoattractant for monocytes in the RA joint.

High levels of macrophage inflammatory protein-1alpha correlate with prolactin in female patients with active rheumatoid arthritis

The relationship between the endocrine immune modulator prolactin and the macrophage activation parameter MIP-1alpha (macrophage inflammatory protein-1alpha) was investigated in 61 females with rheumatoid arthritis (RA). The chemokine MIP-1alpha was found to be twice as high in active than in inactive RA. Parallel to the inflammatory activity (acute phase response and joint count) and high levels of MIP-1alpha there were markable changes of serum prolactin. MIP-1alpha seems to have an influence on the pituitary hormone secretion. A significant correlation between prolactin and MIP-1alpha (r = 0.67; p < or = 0.00001) point out the bidirectional influence of the immune and endocrine system in RA.

A novel endogenous corticotropin release inhibiting factor

ACTH is the major regulator of the body's adaptive response to stress and the physiological stimulus for glucocorticoid secretion. A hypothalamic corticotropin release inhibiting factor (CRIF) that inhibits ACTH synthesis and secretion has long been postulated but was not characterized until recently. We have recently identified a 22 amino acid peptide, prepro-thyrotropin releasing hormone (TRH) 178-199 that inhibits basal and stimulated ACTH synthesis and secretion in vitro and stress-induced ACTH secretion in vivo. Prepro-TRH 178-199 is abundant in several brain regions, including the external zone of the median eminence, where its concentration changes in response to stress. We propose that this peptide is a physiological regulator of ACTH production: an endogenous CRIF. Because prepro-TRH 178-199 is encoded within the same precursor as TRH, its expression is likely to be negatively regulated by thyroid hormones leading to changes in endogenous glucocorticoid levels. Streptococcal cell wall (SCW)-induced inflammation, a model of rheumatoid arthritis (RA), was alleviated after long-term thyroxine treatment. Inversely, a hypothyroid milieu led to decreased basal hypothalamic-pituitary-adrenal activity, but increased expression of IL-1 beta and MIP-1 alpha, specific markers for RA in humans. These results suggest that this putative CRIF may be an important component in the development of RA and that regulation of prepro TRH may be highly relevant to the development of other autoimmune diseases that are also exacerbated by low endogenous glucocorticoid levels.

Production of proinflammatory cytokines and inflammatory mediators in human intestinal epithelial cells after invasion by Trichinella spiralis

Epithelial cells are the first point of host contact for invasive intestinal pathogens and may initiate mucosal inflammatory responses via production of proinflammatory cytokines and mediators. The aim of the present study was to investigate in vitro the initial invasion of a parasitic nematode (Trichinella spiralis), to measure the early production of specific epithelial cytokines and inflammatory mediators after invasion, and to compare these responses with those to invasive bacteria. Monolayers of human colonic epithelial cell lines (HT29, T84, and Caco-2) were infected by T. spiralis or Listeria monocytogenes. Bile-activated infective larvae of T. spiralis invaded and migrated into the epithelial cell monolayers, leaving trails of dead cells. Transmission electron microscopy studies of damaged cells along the trail showed a progressive increase in size, disruption of cell membranes, loss or dilution of cytoplasmic proteins, and swelling of mitochondria and nuclei. However, no nuclear fragmentation was observed. With reverse transcription-PCR and an enzyme-linked oligonucleotide chemiluminescent assay, mRNA transcripts of interleukin-1beta (IL-1beta), IL-8, and epithelial neutrophil-activating peptide 78 were shown to increase in epithelial cells invaded by T. spiralis or L. monocytogenes, but only L. monocytogenes elicited increased inducible nitric oxide synthase (iNOS) mRNA. No increase in tumor necrosis factor alpha or transforming growth factor beta mRNA was seen after T. spiralis invasion. Increased levels of IL-8 were also released from the basolateral surfaces of infected monolayers as detected by sandwich enzyme-linked immunosorbent assay. Induction and secretion of proinflammatory cytokines in epithelial cells after nematode or bacterial invasion may initiate the acute inflammatory response of the small intestine. The upregulation of iNOS in bacterial infections may contribute to mucosal defense and may also be associated with subsequent cell death, whereas different mechanisms appear to operate after nematode invasion.