Paracrine regulation of vascular endothelial growth factor--a expression during macrophage-melanoma cell interaction: role of monocyte chemotactic protein-1 and macrophage colony-stimulating factor.

Tumor-associated macrophages are major infiltrates of human solid malignancies and play an important role in tumor angiogenesis by production of angiogenic factors. In the present study, we examined whether macrophage- melanoma cell interaction regulates vascular endothelial cell growth factor-A (VEGF-A) expression in macrophages. We analyzed the expression of mediators of monocyte recruitment and differentiation, such as monocyte chemotactic protein-1 (MCP-1) and macrophage colony-stimulating factor (M-CSF) in malignant melanoma specimens and tumor cells with different metastatic potential. Our data demonstrate that MCP-1 and M-CSF are differentially expressed in human malignant melanomas from different thickness and depth of invasion and cell lines. Next, we examined the effect of MCP-1 and M-CSF on modulation of VEGFA expression in monocytes/macrophages. Treatment of human monocytes with M-CSF and MCP-1 enhanced VEGF-A expression by increased hypoxia-inducible factor-1alpha (HIF-1alpha) expression and enhanced activation of the hypoxia response element (HRE). Further activation of monocytes and monocyte-derived macrophages (MDM) by lipopolysaccharide (LPS) caused an increase in VEGF-A expression. We demonstrate that coculture of melanoma cells with monocytes enhanced VEGF-A secretion, and conditioned medium from MDMs enhanced melanoma cell expression of VEGF-A. Furthermore, conditioned medium from melanoma cells enhanced VEGF-A expression in human monocytes, which was abrogated by anti-M-CSF neutralizing antibody. In summary, we demonstrate that MCP-1 and M-CSF, critical for monocyte recruitment, activation, and differentiation, differentially regulate VEGF-A expression and may play an important role in monocyte/macrophage- mediated tumor angiogenesis.     

Production of monocyte chemoattractant protein-1 by malignant fibrous histiocytoma: relation to the origin of histiocyte-like cells.

Human malignant fibrous histiocytoma (MFH) comprise both fibroblast-like cells and histiocyte-like cells. We previously showed that the latter are not neoplastic cells, but are infiltrating macrophages. Since migration of blood monocytes into the tumor might be a response to a locally elaborated monocyte chemoattractant, we designed experiments to determine if the fibroblast-like tumor cells produced a chemoattractant for human monocytes. Malignant fibrous histiocytoma from three patients was put into culture. Cells of all three lines had a spindle shape, and showed no reactivity with antibodies against macrophages (MAC387), HLA-DR (LN3), or leukocyte common antigen. Immunohistochemically, they stained with antibody against human monocyte chemoattractant protein-1 (MCP-1). Culture supernatants of the three cell lines had chemotactic activity for monocytes. This activity was due to MCP-1, since it was absorbed by an anti-MCP-1 column. The production of MCP-1 by MFH tumor lines was confirmed by immunoprecipitation of metabolically labeled MCP-1. These results suggest that the histiocyte-like cells are the infiltrated macrophages that originate from blood monocytes attracted by tumor-derived MCP-1.     

Host-derived MCP-1 and MIP-1α regulate protective anti-tumor immunity to localized and metastatic B16 melanoma

Leukocytic infiltration into malignant melanoma lesions is tightly regulated by chemokines. To assess the role of the CC chemokines monocyte chemotactic protein-1 (MCP-1/chemokine ligand 2) and macrophage inflammatory protein-1α (MIP-1α/chemokine ligand 3) in this process, s.c. primary and metastatic B16 F10 melanoma tumor growth levels were examined in mice lacking MCP-1 or MIP-1α. Primary s.c. B16 F10 melanoma growth was augmented by loss of MCP-1 or MIP-1α. Similarly, lung metastasis was enhanced by the deficiency of MCP-1 or MIP-1α. Enhanced tumor outgrowth was associated with decreased percentages of infiltrating CD4(+) T cells, CD8(+) T cells, and natural killer cells. In the absence of MCP-1 or MIP-1α, melanoma outgrowth was correlated with reduced local expression of interferon-γ, IL-6, tumor necrosis factor-α, and transforming growth factor-β. Among these cytokines, reduced expression levels of interferon-γ and tumor necrosis factor-α on leukocytes from the spleen were associated with the development of lung metastasis in chemokine-deficient mice. The local s.c. administration of these four cytokines significantly augmented another chemokine's expression and suppressed primary melanoma growth in mice deficient for MCP-1 or MIP-1α. The s.c. injection of MCP-1 or MIP-1α significantly inhibited the primary tumor growth in wild-type mice. These results indicate that host-derived MCP-1 and MIP-1α regulate protective anti-tumor immunity to B16 F10 melanoma by promoting lymphocyte infiltration into the tumor and subsequent cytokine production.     

Expression of monocyte chemoattractant protein 1 in human inflamed gingival tissues.

Gingival inflammation is initiated by bacterial colonization on the tooth surface. It is characterized by infiltration of mononuclear cells, a common feature of many forms of chronic inflammation. Monocyte chemoattractant protein 1 (MCP-1) is the predominant monocyte chemoattractant secreted by a variety of different cells in vitro. For this report, we examined MCP-1 expression in bacterially induced gingival inflammation by immunohistochemistry and in situ hybridization. The cell types expressing MCP-1 are identified as vascular endothelial cells and monocytes/macrophages. Correlation analysis shows that the number of cells expressing MCP-1 is related to the degree of inflammation. Our finding that MCP-1 is expressed in inflamed gingival tissue suggests that MCP-1 plays an important role in the recruitment of monocytes and amplification of inflammatory signals in bacterially induced inflammation.     

Variables affecting production of monocyte chemotactic factor 1 from human leukocytes stimulated with Cryptococcus neoformans.

The chemokine monocyte chemoattractant protein 1 (MCP-1) is produced predominantly by mononuclear phagocytes and stimulates recruitment into infected tissues of blood monocytes and T cells. These cell types are thought to be critical to host defenses against infections due to Cryptococcus neoformans, a major cause of disease in persons with AIDS and other disorders of cell-mediated immunity. Accordingly, in the present study, we examined the conditions under which human monocytes and bronchoalveolar macrophages (BAM) are stimulated by C. neoformans to produce MCP-1. C. neoformans was a potent inducer of MCP-1 release from monocytes, with levels of chemokine secreted similar to that seen following stimulation with lipopolysaccharide (LPS). BAM, in contrast, were stimulated by LPS, but not by C. neoformans, to secrete MCP-1. A peak in MCP-1 mRNA was seen 8 h following cryptococcal stimulation of monocytes. Nine strains of C. neoformans stimulated monocytes to release MCP-1, and there was only modest variation between strains. However, when an individual strain was used, the capacity of C. neoformans to stimulate monocyte MCP-1 release did vary, depending upon the conditions used to grow the fungal stimuli. Finally, C. neoformans stimulated comparable quantities of MCP-1 release in monocytes from donors with and without human immunodeficiency virus infection. These data establish C. neoformans as a potent stimulator of MCP-1 in monocytes, but not in BAM. The failure of C. neoformans to stimulate MCP-1 in BAM, if occurring in vivo, could result in a diminished cell-mediated inflammatory response following inhalation of airborne fungi.     

Cytokine-activated human endothelial cells synthesize and secrete a monocyte chemoattractant, MCP-1/JE.

We have demonstrated inducible expression of the mRNA encoding the monocyte chemoattractant MCP-1, the human homolog of the JE gene, in endothelial cells within 3 hours of treatment with IL-1 beta and tumor necrosis factor. IFN-gamma also induced expression of this mRNA after 24 hours, but to a lesser extent. MCP-1/JE protein steadily accumulated in the medium of endothelial cells during a 48-hour exposure to IL-1 beta. Medium conditioned by IL-1 beta-treated endothelial cells contained monocyte chemoattractant activity that was immunoadsorbed by anti-MCP-1 antibodies. These results suggest that endothelial cells secrete a monocyte chemoattractant, MCP-1/JE, in response to inflammatory mediators, and thus may contribute to the accumulation of monocytes at sites of inflammation.     

Thrombin Regulates Chemokine Induction during Human Retinal Pigment Epithelial Cell/Monocyte Interaction

Thrombin, an important clotting factor, extravasates at sites of blood-retina barrier breakdown that is often associated with many retinal diseases. Here we investigated the effects of thrombin on human retinal pigment epithelial (HRPE) cells, monocytes, and HRPE cell/monocyte co-cultures. Thrombin induced secretion and mRNA expression of HRPE interleukin (IL)-8 and monocyte chemoattractant protein-1 (MCP-1). Thrombin also enhanced IL-8 and MCP-1 by HRPE cell/monocyte co-cultures, by apparently enhancing cell-cell contact mechanisms. The thrombin effects on IL-6 secretion were similar to those on chemokine secretion. Thrombin-induced chemokines by co-cultures were inhibited by anti-tumor necrosis factor-alpha (TNF-alpha) antibody, but not by anti-IL-1beta antibody. TNF-alpha was detected in cell lysates of monocytes detached from HRPE cells after co-culture stimulation with thrombin. HRPE cells mainly produced these chemokines. However, thrombin generally potentiated exogenous IL-1beta- and TNF-alpha-induced chemokine production by HRPE cells, monocytes, and co-cultures. Interferon-gamma potentiated chemokine secretion by co-cultures with or without thrombin. Our results indicate that thrombin may cause leukocyte recruitment by inducing HRPE cell and monocyte chemokine and by enhancing HRPE cell/monocyte interactions, in part because of monocyte TNF-alpha induction, suggesting important mechanisms for ocular inflammation during blood-retina barrier breakdown and intra-ocular hemorrhage.     

Actinobacillus actinomycetemcomitans serotype b-specific polysaccharide antigen stimulates production of chemotactic factors and inflammatory cytokines by human monocytes.

Serotype b-specific polysaccharide antigen (SPA) was extracted from whole cells of Actinobacillus actinomycetemcomitans Y4 by autoclaving and purified by chromatography on DEAE-Sephadex A-25 and Sephacryl S-300. SPA induced the release of monocyte and leukocyte chemotactic factors by human monocytes. Polymyxin B had almost no effect on the release of monocyte chemotactic factor, but a monoclonal antibody against SPA markedly inhibited it. Human monocytes stimulated with SPA exhibited the increased mRNA expression of monocyte chemoattractant protein 1 (MCP-1) and a neutrophil chemotactic factor, interleukin-8 (IL-8). On the other hand, SPA induced the release of IL-1, IL-6, and tumor necrosis factor (TNF) and enhanced the expression of IL-1alpha, IL-1beta, IL-6, and TNF alpha (TNF-alpha) mRNAs. Human monocytes expressed MCP-1 and IL-8 mRNAs when stimulated by human recombinant IL-1alpha, I1-1beta, IL-6, and TNF-alpha, suggesting that these inflammatory cytokines induced by SPA might participate in the production of chemotactic factors in human monocytes.     

Heterogeneous susceptibility of human melanoma clones to monocyte cytotoxicity: role of ICAM-1 defined by antibody blocking and gene transfer.

Five clones derived from the same human malignant melanoma lesion were studied for their susceptibility to killing by human monocytes activated by exposure to interferon (IFN)-gamma and lipopolysaccharide. Melanoma clones were heterogeneous in their susceptibility to human monocyte cytotoxicity, with one clone (2/21) exhibiting extremely low levels of lysis. The different levels of susceptibility to monocyte cytotoxicity were not accounted for by susceptibility or resistance to monokines [tumor necrosis factor (TNF), interleukin (IL)-1 and IL-6] because: (a) these effector molecules had little (TNF) or no (IL-1 and IL-6) cytolytic activity under these conditions; and (b) anti-TNF antibodies had marginal effects on cytotoxicity. Monocytes bound less to resistant than to susceptible melanoma cells. Monocyte-resistant 2/21 melanoma cells expressed substantially lower levels of ICAM-1 and VLA-4 than susceptible cells. Anti-CD18 and, to a lesser extent, anti-ICAM-1 mAb inhibited binding and cytotoxicity of human monocytes on malignant melanoma whereas anti-VLA-4 had no inhibitory action. Transfection of the ICAM-1 gene under the control of a constitutive promotor resulted in high levels of expression of ICAM-1 in 2/21 melanoma cells and, concomitantly, in augmented susceptibility to activated monocyte cytotoxicity. The augmented killing of ICAM-1 transfected 2/21 cells was inhibited by anti-ICAM-1 mAb. These results demonstrate that the CD18-ICAM-1 adhesion pathway can play an important role in the expression of human monocyte cytotoxicity on melanoma target cells and that heterogeneity in expression of ICAM-1 can underlie differences in susceptibility to tumoricidal activity.     

Infection of human endothelial cells with Staphylococcus aureus induces the production of monocyte chemotactic protein-1 (MCP-1) and monocyte chemotaxis.

Bacterial infection coincides with migration of leucocytes from the circulation into the bacterium-infected tissue. Recently, we have shown that endothelial cells, upon binding and ingestion of Staphylococcus aureus, exhibit proinflammatory properties including procoagulant activity and increased intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) expression on the cell surface, resulting in hyperadhesiveness, mainly for monocytes. The enhanced extravasation of monocytes to bacterium-infected sites is facilitated by the local production of chemotactic factors. From another study we concluded that the locally produced chemokine MCP-1 is important in the recruitment of monocytes to the peritoneal cavity in a model of bacterial peritonitis. In the present study we investigated whether cultured human endothelial cells after infection with bacteria produce and release MCP-1, which in turn stimulates monocyte chemotaxis. We observed that endothelial cells released significant amounts of MCP-1 within 48 h after ingestion of S. aureus. This was dependent on the number and the virulence of the bacteria used to infect the endothelial cells. The kinetics as well as the amount of MCP-1 released by S. aureus-infected endothelial cells differed markedly from that released by endothelial cells upon stimulation with IL-1beta. Supernatant from S. aureus-infected or IL-1beta-stimulated cells promoted monocyte chemotaxis which was almost entirely abrogated in the presence of neutralizing anti-MCP-1 antibody, indicating that most of the chemotactic activity was due to the release of MCP-1 into the supernatant. Our findings support the notion that endothelial cells can actively initiate and sustain an inflammatory response after an encounter with pathogenic microorganisms, without the intervention of macrophage-derived proinflammatory cytokines.     

LPS down-regulates the expression of chemokine receptor CCR2 in mice and abolishes macrophage infiltration in acute inflammation

Interactions between chemokines and their specific receptors are important for leukocyte trafficking. The CC-chemokine monocyte chemoattractant protein-1 (MCP-1) and its specific receptor CCR2 are essential in monocytic infiltration and have been associated with several inflammatory diseases. It has been reported that several endotoxin and proinflammatory cytokines inhibit CCR2 expression in vitro in human monocytes. We report here that lipopolysaccharides (LPS) down-regulated CCR2 expression both in vitro and in vivo. Injection of LPS into mice dramatically reduced the expression of CCR2 on the surface of peripheral blood cells and completely blocked macrophage infiltration into the peritoneal cavity in response to thioglycollate elicitation. In addition, treatment of mice with LPS reduced their efficiency to clear Listeria monocytogenes infection. These results suggest that down-regulation of CCR2 and blockage of monocyte infiltration may contribute to the inhibition of macrophage function in vivo by a low dose of LPS.     

Lysophosphatidylcholine- and MCP-1-induced chemotaxis of monocytes requires potassium channel activity

One of the earliest cellular responses in atherogenesis is the focal recruitment of circulating monocytes, while the most important atherogenic chemoattractants are monocyte chemoattractant protein-1 (MCP-1) and lysophosphatidylcholine (LPC). Invading monocytes transform into activated macrophages and foam cells, which stimulate inflammatory processes and promote atherosclerosis. In this study, we have searched for common mechanisms involved in MCP-1- and LPC-stimulated monocyte migration. We have found that migration of THP-1 monocytes stimulated with MCP-1 was reduced upon inhibition of G_i/o proteins with pertussis toxin and upon inhibition of platelet activating factor receptors with BN52021, whereas LPC-stimulated monocyte chemotaxis remained unaffected by both inhibitors. Furthermore, Cl^? channels were only required for MCP-1-induced chemotaxis. However, activity of voltage-gated K⁺ channels and of Ca²⁺-activated K⁺ channels was found to be involved in migration of monocytes stimulated with either MCP-1 or LPC. Inhibition of voltage-gated K⁺ channels with 4-aminopyridine or margatoxin partially inhibited MCP-1- and LPC-stimulated migration of monocytes. Blockade of Ca²⁺-activated K⁺ channels with TRAM-34 also partially reduced migration of MCP-1- and LPC-stimulated monocytes. Simultaneous inhibition of voltage-gated and Ca²⁺-activated K⁺ channels abolished MCP-1- and LPC-induced chemotaxis of monocytes. Thus, K⁺ channel inhibition may represent a novel powerful strategy to reduce monocyte infiltration and subsequent inflammation in atherosclerosis.     

Primary central nervous system lymphoma secretes monocyte chemoattractant protein 1

The majority of primary central nervous system lymphomas (PCNSL) are diffuse large B-cell lymphomas. Histologically, reactive T lymphocytes and monohistiocytic cells are found within PCNSL tissue. To clarify the mechanisms of the cellular infiltration, the presence of monocyte chemoattractant protein (MCP-1) was investigated in biopsy samples of 19 cases of PCNSL by means of immunohistochemical staining, double staining with a confocal laser microscope, and Western blot analysis. MCP-1 expression was observed in all PCNSL immunohistochemically. Western blot analysis showed that the concentration of MCP-1 in PCNSL was as high as that in a metastatic brain tumor. In normal brain tissue, MCP-1 was not detected. Confocal laser microscope revealed MCP-1 signals were present in the cells with CD20, a B-cell marker. We concluded that lymphoma cells produced MCP-1, which is an additional cytokine involved in the pathogenesis of PCNSL.     

Inhibition of T cell recruitment and cutaneous delayed-type hypersensitivity-induced inflammation with antibodies to monocyte chemoattractant protein-1.

Leukocytes express chemokine receptors that, upon ligand recognition, are believed to activate and induce the directed migration of these cells from the vasculature to sites of tissue injury. Previous investigations of human and animal inflammatory tissue have revealed that expression of chemokines can be increased in association with leukocyte infiltration. Monocyte chemotactic protein-1 (MCP-1) mediates monocyte chemotaxis in vitro and migration of monocytes to inflammatory sites in vivo. More recently T cell chemotaxis to MCP-1 has been observed in vitro, but the contribution of this protein to T cell migration in vivo and to lymphocyte-mediated inflammation has not been determined. In this report, we show that using a rat model of cutaneous delayed hypersensitivity, MCP-1 expression correlates spatially and kinetically with T cell and monocyte recruitment and that antibodies directed to MCP-1 when administered therapeutically to animals undergoing delayed hypersensitivity can almost completely abolish T cell migration and inflammatory sequelae. Moreover the concentration of antibody needed to inhibit T cell trafficking to inflammatory sites is almost on order of magnitude lower than that needed to impede monocyte recruitment. Therefore, MCP-1 is functionally relevant in the genesis of delayed hypersensitivity and may be a useful therapeutic target for diseases mediated in part by T lymphocytes.     

Cyclic mechanical stretch augments both interleukin-8 and monocyte chemotactic protein-3 production in the cultured human uterine cervical fibroblast cells

Intensive local leukocyte infiltration in the uterine cervix is a characteristic feature in the process of cervical ripening. The infiltrated leukocytes include neutrophils, macrophages and monocytes, which are believed to play important roles in cervical ripening by secreting elastase, matrix metalloproteinase and interleukin-1 (IL-1). Interleukin-8 (IL-8) and monocyte chemotactic protein-3 (MCP-3) belong to the CXC and CC chemokine families, and mediate the chemotaxis of neutrophils and monocytes/macrophages respectively. The aim of the present study was to investigate the possible involvement of IL-8 and MCP-3 in leukocyte chemotaxis in cervical ripening. Immunohistochemistry and RT-PCR detected both IL-8 and MCP-3 expression in human pregnant uterine cervices. Labour-like cyclic mechanical stretch for 48 h significantly elevated both IL-8 (555%) and MCP-3 (360%) secretion from cultured human uterine cervical fibroblast (CxF) cells (P<0.05 for both). Cyclic mechanical stretch for 24, 36 and 48 h significantly increased both IL-8 and MCP-3 mRNA expression in CxF cells (P<0.05 for all). The stretch-induced augmentation of both IL-8 and MCP-3 expression was significantly suppressed by an activator protein-1 (AP-1) inhibitor, curcumin. These data suggest that cyclic mechanical stretch of the uterine cervix by the presenting part of the fetus during labour may augment both IL-8 and MCP-3 production in the uterine cervix via AP-1 activation.     

Cysteinyl leukotrienes induce monocyte chemoattractant protein 1 in human monocytes/macrophages

BACKGROUND: Monocytes/macrophages have a cysteinyl leukotriene 1 (CysLT1) receptor, but its function is poorly understood. Objective To elucidate the biological function of the CysLT1 receptor of human monocytes/macrophages. METHODS: We examined the production of TNF-alpha, IL-1beta, IL-2, IL-4, IL-6, IL-8, IL-10, monocyte chemoattractant protein 1 (MCP-1), macrophage colony-stimulating factor (M-CSF), and eotaxin induced by CysLTs (leukotriene (LT)C4, -D4, and -E4) in THP-1 cells, a human monocytic leukaemia cell line, and peripheral blood CD14+ monocytes/macrophages. Moreover, we examined the effect of CysLTs on the expression of beta-chemokine receptor 2B (CCR2B) as the receptor of MCP-1 by Western blot analysis. RESULTS: ELISA revealed that CysLTs induced MCP-1 in THP-1 cells and peripheral blood CD14+ monocytes/macrophages, but not other cytokines. PCR demonstrated that CysLTs increased MCP-1 mRNA expression in THP-1 cells, and Western blotting showed that CysLTs increased the expression of CCR2B in THP-1 cells. Moreover, we demonstrated that pranlukast, a CysLT1 receptor antagonist, blocked MCP-1 production by CysLTs in THP-1 cells almost completely, and partially inhibited MCP-1 release by CysLTs in peripheral blood CD14+ monocytes/macrophages and CCR2B expression by CysLTs in THP-1 cells. CONCLUSION: CysLTs induce MCP-1 and increase CCR2B expression in human monocytes/macrophages.     

Selective induction of the monocyte-attracting chemokines MCP-1 and IP-10 in vesicular stomatitis virus-infected human monocytes.

It is characteristic of viral infections that monocytes/macrophages and lymphocytes infiltrate infected tissue, and neutrophils are absent. CC and non-ELR CXC chemokines predominantly attract mononuclear leukocytes, whereas the ELR motif-expressing CXC chemokines primarily act on neutrophils. To investigate the general role of chemokines in viral diseases, we determined their release and expression patterns after infection of human monocytes with vesicular stomatitis virus (VSV). Human monocytes were productively infected by VSV. Surprisingly, VSV did not induce the release of the proinflammatory cytokines tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and IL-6. In contrast, we found a strong induction of the CC chemokine monocyte chemotactic protein-1 (MCP-1) and the non-ELR CXC chemokine interferon-gamma (IFN-gamma) inducible protein-10 (IP-10) by VSV on the gene and protein level. The expression and release of the neutrophil chemoattractants IL-8 and growth-related oncogene-alpha (GRO-alpha) remained unaffected after VSV infection. Our results indicate that the typical monocyte and lymphocyte-dominated leukocyte infiltration of virus-infected tissue is based on a selective induction of mononuclear leukocyte-attracting chemokines.     

Induction of monocyte chemoattractant protein-1 (MCP-1) production by Pseudomonas nitrite reductase in human pulmonary type II epithelial-like cells

Monocyte chemoattractant protein-1 (MCP-1), a chemoattractant for monocytes, is presumed to play a pivotal role in the recruitment and accumulation of monocytes in various diseases including pulmonary infections. We examined here whether or not Pseudomonas nitrite reductase (PNR), a recently identified IL-8 inducer in various respiratory cells, could stimulate human pulmonary type II epithelial-like cells (A549) to induce MCP-1 production. A time- and dose-dependent induction of MCP-1 protein synthesis associated with an increase of MCP-1 mRNA expression by A549 cells was observed in response to PNR. New protein translation was not required for PNR-mediated MCP-1 mRNA expression in the same cells. When anti-human MCP-1 monoclonal antibody was used for neutralizing of monocyte chemotactic factor (MCF) activities in the culture supernatants of these cells stimulated with PNR, significant reductions of MCF activities (the mean reduction rate; 49-59%, P<0. 05) were observed. These data suggest that PNR may contribute to monocyte migration, through inducing pulmonary epithelial cell-derived MCP-1 production in the airway of patients with pneumonia due to P. aeruginosa.     

Expression of Adhesion Molecules on Granulocytes and Monocytes from Patients with Asthma Stimulated in Vitro with Interleukin-8 and Monocyte Chemotactic Protein-1

Upregulation of adhesion molecule expression on endothelial cells (EC) and circulating leukocytes, by locally produced inflammatory mediators, may result in the enhanced infiltration of leukocytes into tissue, e.g. the airways of asthma patients. The present study investigates whether the expression of adhesion molecules on granulocytes and monocytes from asthma patients is affected by chemotactic factors, i.e. interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1). Flow cytometric analysis showed that the intrinsic expression of the various adhesion molecules on peripheral blood phagocytes from asthma patients was not different from that of healthy individuals. However, stimulation of monocytes with MCP-1 resulted only in upregulation of the expression of CD14 on monocytes from symptomatic asthma patients but not on monocytes from asymptomatic asthma patients and healthy individuals. Stimulation of granulocytes with IL-8 did not change the expression of the various ₁-and ₂-integrin molecules, such as VLA-4, LFA-1, CR3 and p150,95. Since earlier studies have shown that CD14 on monocytes mediates monocyte adhesion to activated vascular EC the present findings suggest that during the active phase of asthma upregulation of CD14 on monocytes by MCP-1 may lead to an increased adhesion of monocytes to vascular endothelium and their subsequent transendothelial migration into the tissue of the airways.