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PubMed2001

Mechanism of the inhibitory effect of protease inhibitor on tumor necrosis factor alpha production of monocytes.

If the inflammatory response becomes excessive or uncontrolled by some stimuli, inappropriate inflammatory responses occur. Monocytes are extremely important cells for regulating the cytokine network and tumor necrosis factor alpha (TNFalpha) and interleukin- (IL) 10, which are mainly synthesized by monocytes, are representative cytokines that play a central role in the cytokine network. Protease inhibitors such as gabexate mesilate (GM) and ulinastatin (UTI) have been shown to have various beneficial effects by inhibiting the activation of leukocytes, but the mechanism for this has yet to be fully elucidated. In this study we investigated the mechanism of the inhibitory effect of protease inhibitors on the proinflammatory cytokine production of lipopolysaccharide- (LPS) stimulated monocytes. LPS-stimulated monocytes were treated with GM or UTI. The value of TNFalpha and IL-10 in the culture medium of monocytes was measured and each mRNA expression was assayed. The inhibitory effect of protease inhibitors on the activity of intracellular signal transduction pathways such as protein kinase C (PKC) and nuclear factor kappa B (NFkappaB) were also evaluated. GM decreased the TNFalpha production of LPS-stimulated monocytes as shown by the inhibition of mRNA expression and increased the IL-10 production of LPS-stimulated monocytes. GM also suppressed the NFkappaB activity of LPS-stimulated monocytes. UTI decreased the TNFalpha production of LPS-stimulated monocytes, but did not inhibit the TNFalpha mRNA expression. The present study shows that the inhibitory effect of GM on the TNFalpha production of activated human monocytes is mediated by the suppression of NFkappaB activation, while the mechanism of UTI inhibiting TNFalpha production of human monocytes may be due to the inhibition of either the translation or secretion of TNFalpha.

Cells, Cultured↗
PubMed2003

Transmission of pseudorabies virus from immune-masked blood monocytes to endothelial cells.

Pseudorabies virus (PRV) may cause abortion, even in the presence of vaccination-induced immunity. Blood monocytes are essential to transport the virus in these immune animals, including transport to the pregnant uterus. Infected monocytes express viral proteins on their cell surface. Specific antibodies recognize these proteins and should activate antibody-dependent cell lysis. Previous work showed that addition of PRV-specific polyclonal antibodies to PRV-infected monocytes induced internalization of viral cell surface proteins, protecting the cells from efficient antibody-dependent lysis in vitro (immune-masked monocytes). As a first step to reach the pregnant uterus, PRV has to cross the endothelial cell barrier of the maternal blood vessels. The current aim was to investigate in vitro whether immune-masked PRV-infected monocytes can transmit PRV in the presence of virus-neutralizing antibodies via adhesion and fusion of these monocytes with endothelial cells. Porcine blood monocytes, infected with a lacZ-carrying PRV strain, were incubated with PRV-specific antibodies to induce internalization. Then, cells were co-cultivated with endothelial cells for different periods of time. Only PRV-infected monocytes with internalized viral cell surface proteins adhered efficiently to endothelial cells. LacZ transmission to endothelial cells, as a measure for monocyte-endothelial cell fusion, could be detected after co-cultivation from 30 min onwards. Virus transmission was confirmed by the appearance of plaques. Adhesion of immune-masked PRV-infected monocytes to endothelial cells was mediated by cellular adhesion complex CD11b-CD18 and subsequent fusion was mediated by the virus. In conclusion, immune-masked PRV-infected monocytes can adhere and subsequently transmit virus to endothelial cells in the presence of PRV-neutralizing antibodies.

Animals↗
PubMed2003

Circulating CD14+ CD16+ monocytes are expanded in sarcoidosis patients.

Sarcoidosis is a systemic disease of unknown etiology characterized by noncaseating granulomas, consisting mainly of epithelioid cells and multinucleated giant cells derived from monocyte-macrophage lineage cells. Monocytes fall into subpopulations comprising CD14++ CD16-, and CD14+ CD16+ cells, and expansion of the later monocytes has been reported under some pathological conditions. In this study, we examined the immunophenotype of blood monocytes in patients with sarcoidosis using two-color immunofluorescence flow cytometry. In healthy controls CD14+ CD16+ monocytes account for 5.8 +/- 2.8% of monocytes. The percentage of CD14+ CD16+ monocytes was significantly higher (p <0.02) in the sarcoidosis patients (11.8 +/- 4.9%) compared with those in healthy control subjects. The serum ACE levels were significantly correlated with the percentage of CD14+ CD16+ monocytes (p <0.05). In contrast, the percentage was not correlated with purinergic receptor expression of monocytes as estimated by LDH release from BzATP-stimulated monocytes. These findings suggest that CD14+ CD16+ monocytes represent a sensitive marker for the disease activity of sarcoidosis.

Adult↗
PubMed1989

Killing of alveolar macrophages and of monocytes that have responded to granulocyte-macrophage colony-stimulating factor by human lymphokine-activated killer cells.

The susceptibilities of human blood monocytes and alveolar macrophages (AM) to cytotoxicity mediated by lymphokine (IL-2)-activated killer (LAK) cells were examined. Monocytes and AM of healthy donors were obtained by counter-flow centrifugal elutriation (CCE) and bronchoalveolar lavage, respectively. The LAK activity induced by incubation of blood mononuclear cells (MNC) for 4 days with recombinant interleukin 2 (IL-2) was measured by a 4-h 51Cr release assay. The LAK cells were not cytotoxic to freshly isolated monocytes, but were cytotoxic to autologous fresh AM and monocytes that had been incubated for more than 4 days in medium alone. Blood monocytes that had been incubated for 4 days in medium with granulocyte-macrophage colony-stimulating factor (GM-CSF), macrophage colony-stimulating factor (M-CSF) or interleukin 3(IL-3) were much more susceptible than untreated monocytes to the cytotoxicity of LAK cells. When blood monocytes were separated by CCE into subpopulations of three sizes (small, medium and large), the medium- and large-sized monocytes showed greater responses to GM-CSF in terms of DNA synthesis and colony formation than the small-sized cells. After treatment with GM-CSF for 4 days, these medium and large monocytes were more susceptible than the small monocytes to the cytotoxic action of LAK cells. These results suggest that LAK cells may be important in situ in down-regulating the functions of mature macrophages and blood monocytes that have responded to GM-CSF.

Biological Factors↗
PubMed1993

Increased adhesion of human monocytes to IL-4-stimulated human venous endothelial cells via CD11/CD18, and very late antigen-4 (VLA-4)/vascular cell adhesion molecule-1 (VCAM-1)-dependent mechanisms.

Expression of adhesion molecules on endothelial cells (EC) can be up-regulated or induced by cytokines. The aim of the present study was to investigate the effect of IL-4 on both the expression of adhesion molecules on EC and monocyte adhesion to EC. Flow cytometric analysis showed that VCAM-1 expression on EC was up-regulated after stimulation with IL-4 for 24 h, whereas the expression of E-selectin (formerly called endothelial leucocyte adhesion molecule-1 (ELAM-1)) was not enhanced, and that of intercellular adhesion molecule-1 (ICAM-1) only slightly. The adhesion of monocytes to EC increased to maximum values upon stimulation of EC with IL-4 for 24 h. Coating of monocytes with MoAb against the integrin beta 2-subunit (CD18) significantly inhibited their adhesion to IL-4-stimulated EC; maximal inhibition was found when monocytes were coated with anti-CD18 MoAb in combination with MoAb against CD49d (the alpha-chain of VLA-4), whereas no inhibition was found when monocytes were coated only with MoAb against CD49d. Monocyte adhesion was not significantly inhibited when IL-4-stimulated EC were coated with MoAbs against ICAM-1 or VCAM-1 alone or in combination. Adhesion of monocytes was inhibited to a greater extent when in addition to coating of monocytes with MoAb against CD18 the EC were coated with MoAb against VCAM-1. From these results we conclude that monocytes bind to IL-4-stimulated EC via interaction of CD11/CD18 molecules on the monocytes with an as yet unknown endothelial ligand, and interaction of VLA-4 on monocytes with VCAM-1 on EC.

Antigens, CD↗
PubMed2005

An increased MRP8/14 expression and adhesion, but a decreased migration towards proinflammatory chemokines of type 1 diabetes monocytes.

In the early development of type 1 diabetes macrophages and dendritic cells accumulate around the islets of Langerhans at sites of fibronectin expression. It is thought that these macrophages and dendritic cells are derived from blood monocytes. Previously, we showed an increased serum level of MRP8/14 in type 1 diabetes patients that induced healthy monocytes to adhere more strongly to fibronectin (FN). Here we show that MRP8/14 is expressed and produced at a higher level by type 1 diabetes monocytes, particularly after adhesion to FN, creating a positive feedback mechanism for a high fibronectin-adhesive capacity. Also adhesion to endothelial cells was increased in type 1 diabetes monocytes. Despite this increased adhesion the transendothelial migration of monocytes of type 1 diabetes patients was decreased towards the proinflammatory chemokines CCL2 and CCL3. Because non-obese diabetic (NOD) mouse monocytes show a similar defective proinflammatory migration, we argue that an impaired monocyte migration towards proinflammatory chemokines might be a hallmark of autoimmune diabetes. This hampered monocyte response to proinflammatory chemokines questions whether the early macrophage and dendritic cell accumulation in the diabetic pancreas originates from an inflammatory-driven influx of monocytes. We also show that the migration of type 1 diabetes monocytes towards the lymphoid tissue-related CCL19 was increased and correlated with an increased CCR7 surface expression on the monocytes. Because NOD mice show a high expression of these lymphoid tissue-related chemokines in the early pancreas it is more likely that the early macrophage and dendritic cell accumulation in the diabetic pancreas is related to an aberrant high expression of lymphoid tissue-related chemokines in the pancreas.

Adult↗
PubMed2005

Monocyte enrichment of mononuclear apheresis preparations with a multistep back-flush procedure on a cord blood filter.

INTRODUCTION: Monocytes or mononuclear cells have been investigated for the treatment of chronic wounds and spinal cord injuries, as well as serve as a source for dendritic or endothelial cell culture. Because these cells may have clinical benefit yet no rapid and inexpensive closed system for monocyte purification is commercially available, a method was investigated to enrich monocytes from mononuclear apheresis units using a cord blood filter. METHODS: A 4-step method for monocyte enrichment was developed which involved 1) filtering a mononuclear apheresis unit through a cord blood filter, 2) chasing with medium to remove non-adherent residual cells and plasma, 3) back-flushing under low shear conditions to remove loosely adherent lymphocytes, and 4) back-flushing under high shear conditions to collect a fraction enriched in monocytes. Apheresis units and enriched monocyte preparations were characterized by cell count and differential, filter-isolated preparations were cryopreserved, and thawed preparations were assayed for viability, and phagocytosis. Enriched monocyte preparations were also assayed for inflammatory cytokines secretion and secretion of prostaglandin E2 during short-term culture. RESULTS: Monocytes were viable, capable of phagocytosis, and enriched using the multistep filter elution technique to represent 42 +/- 13-percent of white cells in the final preparation. Fifty-three-percent of monocytes were recovered in the final preparation, while total cell counts of red cells, platelets, neutrophils and lymphocytes were reduced to 3.0, 3.0, 4.5 and 16-percent, respectively, from levels present in mononuclear apheresis units. Filter enriched monocyte preparations secreted IL-8, IL-6, MCP-1, and MIP-1alpha, during short term culture. CONCLUSION: The use of a multi-step back flush procedure with a cord blood filter resulted in rapid enrichment of viable and functional monocytes from mononuclear apheresis units with significant reduction of contaminating platelets and red cells.

Blood Component Removal↗
PubMed2005

Effects of platelet binding on whole blood flow cytometry assays of monocyte and neutrophil procoagulant activity.

BACKGROUND: Monocytes and neutrophils form heterotypic aggregates with platelets initially via engagement of platelet surface P-selectin with leukocyte surface P-selectin glycoprotein ligand-1 (PSGL-1). The resultant intracellular signaling causes the leukocyte surface expression of tissue factor and activation of leukocyte surface Mac-1 (integrin alphaMbeta2, CD11b/CD18). The activation-dependent conformational change in monocyte surface Mac-1 results in the binding of coagulation factor Xa (FXa) and/or fibrinogen to Mac-1. The aim of this study was to develop whole blood flow cytometry assays of these procoagulant activities and to investigate the effects of platelet binding to monocytes and neutrophils. METHODS: Citrate or D-Phe-Pro-Arg-chloromethylketone (PPACK) anticoagulated whole blood was incubated with monoclonal antibodies against CD14 (PECy5), CD42a (PE), FITC-conjugated test antibody and an agonist, and then fixed with FACS lyse. Appropriate isotype negative controls were prepared in parallel. A BD FACSCalibur was used to analyze monocytes and neutrophils, which were identified based on CD14 fluorescence, forward and 90 degrees light scatter. These populations were further gated into CD42a-positive (platelet-bound) and CD42a-negative (platelet-free). Geometric mean fluorescence and per cent positive data were collected for each subpopulation to measure the binding of test antibodies directed at CD42a, tissue factor, coagulation FXa, bound fibrinogen, activated Mac-1, and CD11b. Compensation controls were prepared on six normal donors prior to the study and these settings were used throughout the 10 donor study. Negative controls verified the lack of cross talk, particularly in the quantified FITC and PE parameters. RESULTS: The physiologic agonists collagen and ADP increased monocyte-platelet and neutrophil-platelet aggregates and increased leukocyte surface Mac-1/CD11b and surface-bound tissue factor, FXa and fibrinogen. Whereas the increases in Mac-1/CD11b were mainly independent of leukocyte-platelet binding, the increases in surface-bound tissue factor, FXa and fibrinogen were mainly dependent on leukocyte-platelet binding. CONCLUSIONS: (i) We have developed novel whole blood flow cytometry assays to measure bound tissue factor, coagulation FXa, fibrinogen, activated Mac-1 and CD11b on the surface of monocytes and neutrophils, allowing independent analysis of monocytes and neutrophils with and without surface-adherent platelets. (ii) The monocyte and neutrophil surface binding of tissue factor, FXa and fibrinogen is mainly dependent on platelet adherence to monocytes and neutrophils, whereas the monocyte and neutrophil surface expression of CD11b and activated Mac-1 is mainly independent of platelet adherence to monocytes and neutrophils.

Adenosine Diphosphate↗
PubMed2005

Monocyte-induced endothelial calcium signaling mediates early xenogeneic endothelial activation.

Hallmarks of delayed xenograft rejection include monocyte infiltration, endothelial cell activation and disruption of the endothelial barrier. The monocyte is an important initiator of this type of rejection because monocytes accumulate within hours after xenografting and prior monocyte depletion suppresses the development of this type of rejection. However, the mechanisms that mediate monocyte-induced xenograft injury are unclear at present. Here we report that human monocytes activate xenogeneic endothelial cells through calcium signals. Monocyte contact with porcine but not human endothelium leads to an endothelial calcium transient mediated via a G-protein-coupled receptor (GPCR) that results in up-regulation of porcine VCAM-1 and E-selectin. Although human monocyte adhesion was greater to porcine than to human endothelium, especially when studied under laminar flow, blockade of the xeno-specific endothelial calcium signals did not reduce adhesion of human monocytes to porcine endothelium. Human monocyte contact to porcine endothelium also resulted in reorganization of the F-actin cytoskeleton with a concomitant increase in endothelial monolayer permeability. In contrast to the effect on adhesion, these changes appear to be regulated through endothelial calcium signals. Taken together, these data suggest that human monocytes are capable of activating xenogeneic endothelial cells through calcium transients, as well as other distinct pathways.

Animals↗
PubMed2000

Fluoroquinolone transport by human monocytes: characterization and comparison to other cells of myeloid lineage.

Human monocytes transport and accumulate ciprofloxacin and other fluoroquinolones. Although little is known about the mechanisms of transport, we expected monocytes to be similar to other cells of myeloid lineage. In the present study, monocyte fluoroquinolone transport was characterized and compared to the corresponding transport pathways of human polymorphonuclear leukocytes (PMNs) and HL-60 cells. Ciprofloxacin transport by monocytes was saturable, temperature dependent, sodium independent, and relatively insensitive to pH. Quiescent monocytes transported ciprofloxacin with a K(m) of 171 microg/ml and a V(max) of 32.7 ng/min/10(6) cells. Adenine competitively inhibited ciprofloxacin transport by quiescent monocytes (K(i) = 3.8 mM), but nucleosides had no significant inhibitory effect. In all of these respects, transport by monocytes was similar to that observed for quiescent PMNs and immature HL-60 cells. Unlike PMNs, however, monocytes and immature HL-60 cells did not exhibit dramatically enhanced ciprofloxacin transport when activated by phorbol myristate acetate (PMA). Consistent with this finding, HL-60 cells committed to granulocytic differentiation exhibited a significant component of PMA-inducible ciprofloxacin transport activity, while HL-60 cells committed to monocytic differentiation did not. In PMNs, the PMA-inducible component of transport appeared to be mobilized from a granule compartment, since its activity could be modulated by agents that enhance or inhibit stimulated degranulation. Thus, quiescent monocytes, PMNs, and HL-60 cells take up ciprofloxacin via similar energy-dependent transport mechanisms. Unlike granulocytes, monocytes do not express a second, higher-affinity pathway for ciprofloxacin accumulation when they are activated by PMA.

Adenine↗
PubMed1988

Cytokine regulation of the intracellular growth of Mycobacterium paratuberculosis in bovine monocytes.

In this study we examined the influence of various crude and recombinant cytokines on the ingestion and intracellular survival of Mycobacterium paratuberculosis within bovine monocytes and monocyte-derived macrophages. Cytokine pretreatment had little effect on the ingestion of M. paratuberculosis by bovine monocytes and macrophages. Monocytes that were continuously incubated with virus-induced crude bovine interferon (100 U) or recombinant bovine alpha interferon (100 U) significantly restricted the subsequent intracellular growth of M. paratuberculosis, as determined by microscopic counts of acid-fast bacilli and by recovery of CFU from lysed monocyte monolayers. In contrast to their effects on freshly adherent monocytes, these cytokines had little effect on the growth of M. paratuberculosis within monocyte-derived macrophages. In two separate experiments, we also observed inhibition of bacillary growth in monocytes treated with unpurified recombinant human granulocyte-macrophage colony-stimulating factor. Conversely, intracellular growth of M. paratuberculosis was enhanced in monocytes that were pretreated with culture supernatants from M. paratuberculosis-stimulated peripheral blood mononuclear cells obtained from an immunized calf. The growth-enhancing activity of these supernatants was labile at pH 2.0, suggesting a role for gamma interferon; however, subsequent experiments indicated that recombinant gamma interferon alone neither enhanced nor restricted intracellular bacillary growth. To determine the possible contributions of monocyte oxidative activity to cytokine-induced bacteriostasis, we compared the release of superoxide anion from cytokine-treated and control monocytes. No obvious relationship was observed between the release of superoxide anion and the subsequent intracellular fate of the bacilli.

Animals↗
PubMed2000

Coxiella burnetii survives in monocytes from patients with Q fever endocarditis: involvement of tumor necrosis factor.

Endocarditis is the most frequent form of chronic Q fever, an infectious disease caused by Coxiella burnetii. As this obligate intracellular bacterium inhabits monocytes and macrophages, we wondered if pathogenesis of Q fever endocarditis is related to defective intracellular killing of C. burnetii by monocytes. Monocytes from healthy controls eliminated virulent C. burnetii within 3 days. In contrast, monocytes from patients with ongoing Q fever endocarditis were unable to eliminate bacteria even after 6 days. In patients who were cured of endocarditis, the monocyte infection was close to that of control monocytes. This killing deficiency was not the consequence of generalized functional impairment, since patient monocytes eliminated avirulent C. burnetii as did control cells. The addition of supernatants of C. burnetii-stimulated monocytes from patients with ongoing endocarditis to control monocytes enabled them to support C. burnetii survival, suggesting that some soluble factor is responsible for bacterial survival. This factor was related to tumor necrosis factor (TNF): expression of TNF mRNA and TNF release were increased in response to C. burnetii in patients with ongoing endocarditis compared to cured patients and healthy controls. In addition, neutralizing anti-TNF antibodies decreased C. burnetii internalization, an early step of bacterial killing, in monocytes from patients with ongoing endocarditis but did not affect delayed steps of intracellular killing. We suggest that Q fever-associated activation of monocytes allows the survival of C. burnetii by modulating early phases of microbial killing.

Adult↗
PubMed2005

GRO family chemokines are specialized for monocyte arrest from flow.

Chemokines participate in various processes of monocyte recruitment including monocyte arrest and migration. Our group and others have demonstrated that growth-related oncogene (GRO)-alpha (CXCL1) can support monocyte arrest in models of inflammation. Here we employed a parallel plate-flow chamber and Transwell reconstitution assay to test whether GRO family chemokines were sufficient for Mono Mac 6 (a human monocytic cell line) and isolated human monocyte recruitment. Our study shows that 1) GRO-alpha, -beta (CXCL2), and -gamma (CXCL3) all act as arrest chemokines for monocyte adhesion on vascular cell adhesion molecule (VCAM)-1 under flow in the presence of P-selectin; 2) CXCR2 is the functional receptor for GRO-family chemokines in monocyte arrest; however, CXCR2 is not an arrest chemokine receptor in general, since epithelial neutrophil-activating peptide ENA-78 failed to arrest monocytes; 3) GRO-alpha, -beta, and -gamma all fail to increase intracellular free Ca2+ or mediate monocyte chemotaxis; and 4) signaling through G alpha(i) protein, phosphoinositide 3-kinase, and actin polymerization but not Ca2+ mobilization or the mitogen-activated kinases p38 and MAPK/extracellular signal-related kinase are necessary for GRO-alpha-mediated Mono Mac 6 cell arrest under flow. We conclude that the GRO-family chemokines are specialized monocyte-arrest chemokines. Their role in monocyte recruitment in inflammation can be inhibited by blocking CXCR2 function or downstream signaling events.

Actins↗
PubMed1989

Tumor-promoting phorbol esters inhibit monocyte adherence to endothelial cells.

Monocyte adherence to endothelial cells (EC) is an important event in the development of a monocytic inflammatory response, yet the effects of inflammatory mediators on monocyte adherence to EC are not well described. We compared the effects of phorbol esters known to activate protein kinase C, including phorbol myristate acetate (PMA) and phorbol 12,13-dibutyrate (PDA), on monocyte adherence to bovine aortic EC. Human monocytes (purity 90 +/- 1% SE) were isolated by centrifugal elutriation to obtain monocytes not previously exposed to a surface. Kinetic studies revealed that 51Cr-labeled monocyte adherence to EC reached a plateau after a 45-min incubation. Concentrations of PMA between 10 and 1,000 ng/ml significantly decreased monocyte adherence to EC (26 +/- 10 and 35 +/- 8% decrease compared with control, respectively). Concentrations of PDA of 100 and 1,000 ng/ml had a similar inhibitory effect. In contrast, the chemotactic stimulus, zymosan-activated serum, significantly increased monocyte adherence (40 +/- 14% increase compared with control). Thus inflammatory stimuli have different effects on the adhesive interaction of monocytes to EC. This may provide a mechanism to selectively modulate monocyte egress from the circulation into extravascular inflammatory sites.

Animals↗
PubMedDate not supplied

Monocyte-related determinants of inflammation in patients on peritoneal dialysis.

AIMS: We studied markers of monocyte activation, i.e., the cell surface expression of CD11b and CD62L, and the serum concentrations of monocyte chemotactic protein 1 (MCP-1; a monocyte-specific chemoattractant) and soluble vascular cell adhesion molecule 1 (sVCAM-1; an adhesion molecule involved in monocyte recruitment) in 20 patients on peritoneal dialysis (PD), in 25 patients with chronic renal insufficiency, and in 27 healthy subjects. RESULTS: Monocytes obtained from the peripheral blood of PD patients had a significantly higher expression of CD62L (p = 0.02) as compared with monocytes from healthy subjects and a lower CD11b/CD18 expression as compared with monocytes collected from healthy subjects (p < 0.001) and from patients with renal insufficiency (p < 0.001). Monocytes from PD patients had, however, the capacity to increase the expression of CD11b following stimulation with a potent chemotactic factor. The serum concentrations of MCP-1 and sVCAM-1 were higher in PD patients (575 +/- 51 and 1,517 +/- 89 ng/ml) than in healthy subjects (225 +/- 17 and 668 +/- 64 ng/ml, respectively; p < 0.001 for both comparisons). There was a correlation between the levels of sVCAM-1 and MCP-1 (r = 0.48, p < 0.05) in patients on PD, but neither correlated with the monocyte expression of CD11b/CD18 or CD62L. The concentration of C-reactive protein was higher in patients on PD as compared with healthy subjects and correlated significantly with the concentration of sVCAM-1 (r = 0.63, p < 0.01). CONCLUSIONS: Monocytes in the peripheral circulation of patients on PD have a CD62L(high)/CD11b(low) phenotype, indicating that they have not undergone complete differentiation. Patients also have an increase in the systemic chemotactic activity for monocytes in combination with increased levels of sVCAM-1 and C-reactive protein. These inflammatory aberrations may play a pathophysiological role in the response to inflammatory and infectious diseases in patients on PD.

Adult↗
PubMed2002

Monocyte activation in peripheral blood and dialyser eluates: phenotypic profile and cytokine release.

BACKGROUND/AIMS: Monocyte activation and subsequent cytokine generation is presumed to be involved in haemodialysis (HD)-related morbidity. The present study was designed to investigate HD-induced changes in monocytes, with respect to their phenotypic profile and cytokine release, both in peripheral blood (PB) and dialyser eluates (DE). In addition, the effect of the type of dialyser on monocyte activation was assessed. METHODS: Dialyser elution was performed in 8 patients after 3 h of HD, using cuprammonium (CU) and polysulfon (PS) dialysers in a randomised cross-over design. PB samples and DE were analysed for both the expression of a variety of monocyte cell surface markers (CD62L, CD11b, CD25, HLA-DR, CD64 and CD14) by flow cytometry and IL-1beta levels. Monocytes were identified by dual labelling with antibodies against CD14. RESULTS: In PB, the expression of CD11b increased during HD with both devices, but was more pronounced with CU (CU versus PS: p < 0.05). CD62L decreased during HD, but only significantly for PS (p < 0.02). HLA-DR was downregulated during HD with CU (p = 0.056). The expression of CD64 was higher during HD with CU (p = 0.02). Finally, CD14 increased during HD with both dialysers (p < 0.03). DE yielded a mean cell count of 51 x 10(6) cells. The proportion of monocytes in DE was 3% for CU and 4% for PS. In eluted monocytes, a significant upregulation of CD11b, CD25, and HLA-DR was observed. CD62L was downregulated when compared to PB at t(180) (p < 0.001). In DE, no correlation was found between the type of dialyser and the phenotypic changes. In 10 of 16 DE supernatants, 6 CU and 4 PS, IL-1beta release could be demonstrated, CU yielding significantly more of this cytokine than PS (p = 0.03). CONCLUSIONS: According to both their phenotypic profile and cytokine release, monocytes sticking to the dialyser membrane after HD are considerably more activated than circulating monocytes. Activation of eluted monocytes appeared independent of the type of dialyser, suggesting an effect of mechanical stress rather than bioincompatibility. In contrast, phenotypic activation of peripheral blood monocytes and cytokine release in the DE supernatant were mainly dialyser-dependent.

Adult↗
PubMed1996

Human monocyte-endothelial cell interaction induces synthesis of granulocyte-macrophage colony-stimulating factor.

BACKGROUND: Adhesion of monocytes to the endothelium is an initial step in the early stages of atherosclerosis and inflammation. Granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulates a range of functional activities of monocytes, including regulation of monocyte adhesion and induction of cytokine production. We investigated in this study whether CM-CSF synthesis was induced by the direct cell-to-cell interaction between human monocytes and human umbilical vein endothelial cells (ECs). METHODS AND RESULTS: The expressions of GM-CSF mRNA and protein were analyzed by Northern blotting and ELISA, respectively. Coculture of monocytes and ECs induced the high levels of GM-CSF mRNA expression, whereas culture of ECs or monocytes alone or coculture of neutrophils with ECs induced no GM-CSF mRNA expression. A large amount of GM-CSF was secreted into the supernatant upon coculture of monocytes with ECs. The supernatant from the coculture markedly stimulated 02- release in neutrophils, and this effect was significantly inhibited by anti-GM-CSF antibody (Ab). Immunohistochemistry and in situ hybridization revealed that GM-CSF protein and mRNA were clearly detectable in both ECs and monocytes adhered to ECs but not in nonadherent monocytes. The GM-CSF production by the coculture was markedly inhibited by genistein and partially inhibited by Abs against interleukin-1 and tumor necrosis factor-alpha. CONCLUSIONS: The present results indicate that GM-CSF is produced by direct interaction between monocytes and ECs and suggest that GM-CSF produced locally by monocyte-EC adhesive interaction plays an important role in the pathogenesis of atherosclerosis and inflammation by modulating monocyte/macrophage functions in vivo.

Adult↗
PubMed1995

Neutrophils activated by granulocyte colony-stimulating factor suppress tumor necrosis factor-alpha release from monocytes stimulated by endotoxin.

We investigated the in vitro effects of granulocyte colony-stimulating factor (G-CSF) on tumor necrosis factor-alpha (TNF-alpha) release from monocytes. Peripheral blood monocytes and neutrophils were obtained from healthy donors (n = 8). Neutrophils alone, neutrophils plus monocytes, and monocytes alone were incubated with and without G-CSF (10 ng/ml) and were studied for TNF-alpha release; monocytes subsequently were stimulated by endotoxin (lipopolysaccharide [LPS] at 10 and 1,000 ng/ml). Neutrophils alone did not produce TNF-alpha after LPS stimulation irrespective of G-CSF treatment. TNF-alpha release from monocytes was suppressed significantly by pretreatment with G-CSF in the presence of neutrophils (P < 0.01). Suppression of TNF-alpha release after LPS was not observed when monocytes were preincubated with G-CSF in the absence of neutrophils. TNF-alpha release from monocytes stimulated by LPS was not inhibited when monocytes were incubated with the supernatant from G-CSF-activated neutrophils. Pretreatment with G-CSF inhibited intracellular TNF-alpha production, as measured by flow cytometry, of monocytes stimulated by LPS (P < 0.05). These data suggest that neutrophils activated by G-CSF directly suppress TNF-alpha release from monocytes stimulated by LPS.

Adult↗