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PubMed1996

Differential expression of function-related antigens on newborn and adult monocyte subpopulations.

Umbilical cord blood and adult peripheral blood monocytes were separated into two subpopulations, based on the intensity of CD14 expression, and the coexpression of various antigens associated with monocyte function was examined. The majority of cord and adult monocytes expressed CD14 at a high density (CD14bright) while approximately 15% of monocytes expressed this antigen at a lower level (CD14dim). Three times as many CD14dim monocytes expressed CD16 (Fc gamma RIII) as did CD14bright monocytes in both cord and adult preparations, while its level of expression (mean fluorescence intensity) was significantly reduced on cord CD14dim monocytes relative to adult CD14dim monocytes. The percentage of cord blood CD14dim monocytes expressing human leucocyte antigen-DR (major histocompatibility complex class II antigen) was significantly reduced relative to adult CD14dim cells; however, the level of expression of this antigen was greater on both cord and adult CD14dim monocytes compared with CD14bright cells. Cord CD14bright cells expressed CD36 (OKM5) to a greater extent than did their adult counterparts. The level of expression of CD62L was reduced on cord CD14dim cells compared with adult CD14dim cells. CD11b (CR3) was expressed both on a higher percentage of cells and also with a greater intensity on both cord and adult CD14bright monocytes compared with their CD14dim counterpart. These results show that significant differences exist between cord and adult monocyte subpopulations with regard to expression of various antigens associated with specific effector function.

Adult↗

PubMed1999

Binding of monocytes from normolipidemic hyperglycemic patients with type 1 diabetes to endothelial cells is increased in vitro.

Increased endothelial binding and emigration of monocytes play a dominant role in the pathogenesis of atherosclerosis in diabetes mellitus. Previous studies revealed that hyperlipidemia correlates with monocyte binding in vitro. The aim of this study was to characterize the monocyte-endothelial interaction of leucocytes of hyperglycemic patients with type 1 diabetes but lacking hyperlipidemia. We isolated monocytes from healthy controls and normolipidemic type 1 diabetes patients with elevated levels of HbA1c and quantified monocyte binding by an immunoilluminometric cell adhesion assay. Purity of isolated monocytes was at least 98%. Endothelial binding of monocytes from patients with type 1 diabetes was found to be significantly increased compared to controls (19.2 +/- 3.9% vs. 14.9 +/- 3.5%). This difference of monocyte binding remained unchanged if the endothelial cells were stimulated with 27.7 mmol/l glucose for seven days prior to adhesion studies (31.5 +/- 4.9% in diabetes patients vs. 25.8 +/- 4.1% in controls) whereby monocyte binding markedly increased under these hyperglycemic conditions. Furthermore, an increased CD11b expression could be demonstrated on monocytes of normolipidemic hyperglycemic type 1 diabetes patients. Thus, we suggest that hyperglycemia per se may contribute to increased monocyte binding to endothelial cells by promoting leucocyte integrin expression. Recently performed studies of our group strengthen the hypothesis that this monocyte activation is mediated by stimulation of the beta-isoform of proteinkinase C.

Adult↗

PubMed1999

Protein kinase calpha regulates human monocyte O-2 production and low density lipoprotein lipid oxidation.

Our previous studies have shown that human native low density lipoprotein (LDL) can be oxidized by activated human monocytes. In this process, both activation of protein kinase C (PKC) and induction of superoxide anion (O-2) production are required. PKC is a family of isoenzymes, and the functional roles of individual PKC isoenzymes are believed to differ based on subcellular location and distinct responses to regulatory signals. We have shown that the PKC isoenzyme that is required for both monocyte O-2 production and oxidation of LDL is a member of the conventional PKC group of PKC isoenzymes (Li, Q., and Cathcart, M. K. (1994) J. Biol. Chem. 269, 17508-17515). The conventional PKC group includes PKCalpha, PKCbetaI, PKCbetaII, and PKCgamma. With the exception of PKCgamma, each of these isoenzymes was detected in human monocytes. In these studies, we investigated the requirement for select PKC isoenzymes in the process of monocyte-mediated LDL lipid oxidation. Our data indicate that PKC activity was rapidly induced upon monocyte activation with the majority of the activity residing in the membrane/particulate fraction. This enhanced PKC activity was sustained for up to 24 h after activation. PKCalpha, PKCbetaI, and PKCbetaII protein levels were induced upon monocyte activation, and PKCalpha and PKCbetaII substantially shifted their location from the cytosol to the particulate/membrane fraction. To distinguish between these isoenzymes for regulating monocyte O-2 production and LDL oxidation, PKCalpha or PKCbeta isoenzyme-specific antisense oligonucleotides were used to selectively suppress isoenzyme expression. We found that suppression of PKCalpha expression inhibited both monocyte-mediated O-2 production and LDL lipid oxidation by activated human monocytes. In contrast, inhibition of PKCbeta expression (including both PKCbetaI and PKCbetaII) did not affect O-2 production or LDL lipid oxidation. Further studies demonstrated that the respiratory burst oxidase responsible for O-2 production remained functionally intact in monocytes with depressed levels of PKCalpha because O-2 production could be restored by treating the monocytes with arachidonic acid. Taken together, our data reveal that PKCalpha, and not PKCbetaI or PKCbetaII, is the predominant isoenzyme required for O-2 production and maximal oxidation of LDL by activated human monocytes.

Base Sequence↗

PubMed1987

Induction of interferon alpha from human lymphocytes by autologous, dengue virus-infected monocytes.

Human monocytes actively replicate dengue virus. To dissect the primary immune responses to dengue virus-infected monocytes (DV-monocytes), we analyzed the interaction between autologous DV-monocytes and the peripheral blood lymphocytes (PBL) of dengue nonimmune donors. Interferon (IFN) activity was detected when PBL were cultured with DV-monocytes. Cell contact between PBL and DV-monocytes was required for IFN production; however, MHC compatibility between PBL and monocytes was not necessary. DV-monocytes fixed with paraformaldehyde or glutaraldehyde, which produced no infectious virus, also induced high levels of IFN from PBL. The ability of DV-monocytes to induce IFN correlated with the appearance of dengue antigens. The PBL that produce IFN were characterized by FACS sorting using monoclonal and polyclonal antibodies. HLA-DR+ and T3- cells produced high titers of IFN, while HLA-DR- and T3+ cells produced very low or undetectable levels of IFN. Moderate titers of IFN were produced by cells contained in B cell fractions (surface immunoglobulin-positive, B1+, and Leu-12+), and cells contained in natural killer cell fractions (Leu-11+ and OKM1+). Therefore, IFN-producing cells are heterogeneous, and the predominant producer cells are characterized as HLA-DR+ and non-T lymphocytes. The IFN produced was characterized by RIA using mAbs to IFN-alpha and IFN-gamma. The IFN-alpha was the predominant IFN produced; in addition, a low level of IFN-gamma was also detected in some experiments. The culture fluids obtained from PBL exposed to autologous DV-monocytes, which contained high IFN activity, completely inhibited dengue virus infection of monocytes. These results suggest that IFN-alpha produced by PBL exposed to DV-monocytes may play an important role in controlling primary dengue virus infection.

Antibodies, Monoclonal↗

PubMed2005

Down-regulation of activating Fcgamma receptors on monocytes of patients with rheumatoid arthritis upon methotrexate treatment.

OBJECTIVE: To determine the effect of methotrexate (MTX) on expression levels of activating receptors for IgG (FcgammaRs) on monocytes of rheumatoid arthritis (RA) patients in relation to changes in disease activity. METHODS: The effect of MTX on FcgammaRs on monocytes of RA patients was evaluated ex vivo as well as in vitro. Recently diagnosed, disease-modifying antirheumatic drug (DMARD)-naive RA patients were treated with low-dose MTX. At baseline and 16 weeks after the start of MTX treatment, changes in FcgammaR expression levels on peripheral blood monocytes were evaluated by fluorescence-activated cell sorting analysis and were correlated to changes in disease parameters. To study the direct effects of MTX on monocytes, these cells were isolated from peripheral blood monocytes of healthy controls and cultured with MTX. Other monocyte surface molecules (CD40, CD80, CD86, MHC class II) were also determined to test the specificity of the effect on FcgammaR expression levels. RESULTS: Eleven out of 15 patients improved clinically (mean disease activity score before 6.2 +/- 0.8 vs 4.3 +/- 1.7 after). Sixteen weeks after the start of MTX therapy, the expression levels of FcgammaRI and IIa on monocytes were significantly decreased, whereas the decreases in FcgammaRIIIa expression levels on monocytes were less marked. The percentage decrease in FcgammaRI expression correlated with the percentage decrease in CRP and well-being. In vitro MTX selectively decreased FcgammaRI and FcgammaRIIa expression levels of isolated monocytes, in contrast to other surface molecules. CONCLUSION: The disease-modifying effect of MTX in the treatment of RA is accompanied by down-regulation of activating FcgammaRI and IIa on monocytes, which could be a direct effect of MTX on monocytes. This down-regulation represents a new mode of action of MTX which should be considered in RA patients, especially during conditions that could give rise to monocyte activation by IgG-containing immune complexes, e.g. during antibody-based therapy of RA.

Administration, Oral↗

PubMed2001

Role of interleukin-10 in monocyte hyporesponsiveness associated with septic shock.

OBJECTIVES: The purpose of this study was to examine the pattern of tumor necrosis factor (TNF)-alpha and interleukin (IL)-10 release in endotoxin-stimulated septic monocytes and to determine the role of IL-10 and transforming growth factor (TGF)-beta in monocyte hyporesponsiveness during septic shock. DESIGN: Monocytes isolated from ten healthy controls and ten patients with septic shock were incubated with endotoxin and cytokine release was assessed. Next, normal monocytes were incubated with either normal or septic serum and stimulated with endotoxin. Finally, normal monocytes were incubated with septic serum either with anti-IL-10 antibodies or anti-TGF-beta antibodies and then stimulated with endotoxin. MEASUREMENTS: TNF-alpha, IL-10, and TGF-beta levels were measured in the serum and in culture supernatants by enzyme-linked immunosorbent assay. SETTING: Research laboratory. MAIN RESULTS: IL-10 and TNF-alpha levels were significantly increased in septic serum, whereas TGF-beta levels were not different from controls. Normal monocytes increased TNF-alpha and IL-10 release in response to endotoxin. In contrast, septic monocyte TNF-alpha release was attenuated in response to endotoxin (1.8 +/- 0.5 vs. 1.0 +/- 0.4 ng/mL, stimulated vs. baseline), whereas IL-10 release increased significantly from baseline (173 +/- 91 vs. 8 +/- 4 pg/mL, stimulated vs. baseline). Incubation of normal monocytes with septic serum attenuated TNF-alpha release in response to endotoxin (32% +/- 8% of normal serum; p < .01), whereas IL-10 release was increased (285% +/- 84% of normal serum; p < .05). When normal monocytes were incubated with septic serum combined with anti-IL-10 antibodies, TNF-alpha release increased significantly to 75% +/- 17% of normal serum (p < .05 vs. septic serum alone). Incubation of normal monocytes with anti-TGF-beta antibodies did not significantly affect either TNF-alpha or IL-10 release in response to endotoxin. CONCLUSION: Monocytes from patients with septic shock exhibit persistent IL-10 release at a time when TNF-alpha release is downregulated. The continued release of IL-10 may contribute to impairment of monocyte proinflammatory cytokine release and the development of immune dysfunction in septic shock.

Down-Regulation↗

PubMed1994

Interleukin 4 and human immunodeficiency virus stimulate LFA-1-ICAM-1-mediated aggregation of monocytes and subsequent giant cell formation.

The effects of recombinant interleukin 4 (IL-4) on cell cluster and multinucleated giant cell (MGC) formation from human immunodeficiency virus (HIV)-infected and uninfected monocytes were examined. Human blood monocytes were isolated by centrifugal elutriation and monoclonal antibody-complement-dependent lysis of residual T cells, and infected with low passage HIV strains. Monocytes were exposed to recombinant IL-4 (1 to 20 ng/ml), continuously after inoculation with HIV. Monocyte expression of ICAM-1 but not LFA-1 was significantly enhanced by IL-4 although substrate adherence was a more potent stimulus. Monocyte cluster and MGC formation was quantified after fixation and staining with Giemsa. Clusters of HIV-infected and uninfected monocytes were consistently and significantly increased at 4 to 7 days after IL-4 stimulation. The combination of HIV and IL-4 was more stimulatory than either treatment alone. In two out of five uninfected and three out of seven HIV-infected monocyte cultures, MGC formation was also markedly increased at 10 to 14 days after stimulation. Incubation with anti-LFA-1 (anti-CD11a, anti-CD18) and anti-ICAM-1 (anti-CD54) monoclonal antibodies reduced IL-4-stimulated aggregation in HIV-infected and uninfected monocytes and subsequently reduced MGC formation. Anti-ICAM-1 was not as effective as anti-CD11a or anti-CD18 in inhibiting aggregation of HIV-infected monocytes and in these cultures anti-ICAM-2 was also inhibitory. Extracellular HIV antigen concentrations were not consistently reduced by anti-CD11a or anti-ICAM-1. Hence IL-4 markedly enhanced monocyte aggregation in both HIV-infected and uninfected monocytes, probably through enhanced LFA-1-ICAM-1 interactions in all cultures and LFA-1-ICAM-2 interactions in infected monocytes, leading subsequently to MGC formation in some cultures.

Antibodies, Monoclonal↗

PubMed2006

CD2 identifies a monocyte subpopulation with immunoglobulin E-dependent, high-level expression of Fc epsilon RI.

BACKGROUND: Fc epsilon RI expression by monocytes can affect monocyte function via multiple mechanisms, thereby potentially influencing the generation of allergic inflammation. Previous studies on the in vivo regulation of monocyte Fc epsilon RI expression by ambient IgE have yielded conflicting results. OBJECTIVE: We hypothesized that monocyte Fc epsilon RI expression is limited to a specific monocyte subset, and that within that subset Fc epsilon RI surface expression is correlated to serum IgE. METHODS: Study 1: Blood was obtained from non-allergic subjects (n=14) and subjects with allergic asthma (n=18), hypereosinophilic syndrome (n=2), hyper-IgE syndrome (n=6), and helminth infection (n=4). Study 2: Blood was obtained from allergic subjects in a clinical trial of omalizumab before and during study drug treatment. Monocyte surface Fc epsilon RI expression was measured using flow cytometry. RESULTS: Fc epsilon RI expression was significantly greater in the CD2(high) vs. CD2(low) monocyte subsets (31% vs. 1.9% median Fc epsilon RI+, respectively). In asthmatic and non-atopic healthy control subjects, CD2(low) monocytes expressed little or undetectable Fc epsilon RI. In study 1, Fc epsilon RI expression was highly correlated to serum IgE in the CD2(high), but not in the CD2(low) monocyte subpopulation (R values of 0.67 and 0.41, respectively). In study 2, omalizumab, but not placebo, caused a significant and sustained decline in Fc epsilon RI expression within the CD2(high) monocyte subset. CONCLUSIONS: CD2 defines a monocyte subset with high Fc epsilon RI expression, whose magnitude is highly correlated to serum IgE. As such, this new description of CD2(high) monocytes as Fc epsilon RI-bearing cells suggests that they may be potential targets of anti-IgE immunomodulatory therapies.

Adult↗

PubMed1981

Male-female differences in the cytotoxic activity of human monocytes in vitro.

The cytotoxic activity of human monocytes towards anti-D-sensitized Rh(D)-positive red cells in vitro was studied in relation to the age and sex of healthy monocyte donors. It was found that cytotoxic activity of monocytes from young females (age range 18-40 years) was significantly less than that of monocytes from age-matched males, irrespective of the use of oral contraceptives. No such difference was found between monocytes from older males and females (age range 43-63 years). The cytotoxic activity of monocytes from the two latter groups of donors was similar to that of young males. In the presence of cytochalasin B, which enhances the cytotoxic activity of monocytes, no male-female difference was detected, indicating that the maximal cytotoxic capacity of monocytes from young females is similar to that of monocytes from young males. We have previously presented evidence that the cytotoxic activity of monocytes is mediated by lysosomal enzymes released by these cells. These present data suggest that the reduction in cytotoxic activity of monocytes from young females might be a result of a reduced lysosomal enzyme release which is possibly related to the in vivo action of female sex hormones. However, we were not able to detect an inhibitory effect of oestrogens and progestagens on cytotoxic activity of monocytes from males in vitro.

Adolescent↗

PubMed1982

Chemotaxis of purified human monocytes in vitro: lack of accessory cell requirement.

This study was undertaken to determine whether cell cooperation, either among monocytes or between monocytes and lymphocytes, is a prerequisite for monocyte chemotactic responsiveness. We compared Ficoll-Hypaque-separated mononuclear cells and a preparation of 99% pure monocytes obtained by chemotaxis in a newly designed separation chamber. Monocytes of both preparations migrated to chemoattractants without a lag phase, and no further increase in migrated cells was observed after 70 min. The cell dose-response was linear for both preparations over a wide range of cell concentrations in the cell input well of the chemotaxis chamber, suggesting that no monocyte-monocyte interaction was required. Since only 20 to 60% of the monocytes purified by chemotaxis migrated a second time, the possibility of a requirement for an accessory cell was tested. The addition to purified monocytes of several different mononuclear cell preparations comprising lymphocytes or nonmigrating monocytes had no effect on monocyte migration. These experiments show that normal human blood monocytes in vitro do not require stimuli from other cells to respond to chemoattractants. Their behavior is profoundly different from that of mouse peritoneal macrophages, which exhibit a time lag in vitro before migration toward an attractant and become more responsive with either increasing cell concentration or addition of purified lymphocytes.

Cell Communication↗

PubMed1998

Expression of CCR5 increases during monocyte differentiation and directly mediates macrophage susceptibility to infection by human immunodeficiency virus type 1.

The stage of differentiation and the lineage of CD4+ cells profoundly affect their susceptibility to infection by human immunodeficiency virus type 1 (HIV-1). While CD4(+) T lymphocytes in patients are readily susceptible to HIV-1 infection, peripheral blood monocytes are relatively resistant during acute or early infection, even though monocytes also express CD4 and viral strains with macrophage (M)-tropic phenotypes predominate. CCR5, the main coreceptor for M-tropic viruses, clearly contributes to the ability of CD4+ T cells to be infected. To determine whether low levels of CCR5 expression account for the block in infection of monocytes, we examined primary monocyte lineage cells during differentiation. Culturing of blood monocytes for 5 days led to an increase in the mean number of CCR5-positive cells from <20% of monocytes to >80% of monocyte-derived macrophages (MDM). Levels of CCR5 expression per monocyte were generally lower than those on MDM, perhaps below a minimum threshold level necessary for efficient infection. Productive infection may be restricted to the small subset of monocytes that express relatively high levels of CCR5. Steady-state CCR5 mRNA levels also increased four- to fivefold during MDM differentiation. Infection of MDM by M-tropic HIV-1JRFL resulted in >10-fold-higher levels of p24, and MDM harbored >30-fold more HIV-1 DNA copies than monocytes. In the presence of the CCR5-specific monoclonal antibody (MAb) 2D7, virus production and cellular levels of HIV-1 DNA were decreased by >80% in MDM, indicating a block in viral entry. There was a direct association between levels of CCR5 and differentiation of monocytes to macrophages. Levels of CCR5 were related to monocyte resistance and macrophage susceptibility to infection because infection by the M-tropic strain HIV-1JRFL could be blocked by MAb 2D7. These results provide direct evidence that CCR5 functions as a coreceptor for HIV-1 infection of primary macrophages.

Cell Differentiation↗

PubMed1995

MCP-1-stimulated monocytes preferentially utilize beta 2-integrins to migrate on laminin and fibronectin.

Recruitment of monocytes to inflammatory sites involves a series of sequential attachments and detachments to extracellular matrix proteins in response to a chemoattractant gradient. In this study we compared the migration of human peripheral blood monocytes on different extracellular matrix proteins in response to monocyte chemoattractant protein-1 (MCP-1) and N-formylmethionyl-leucyl-phenylalanine. Monocytes migrated more effectively on laminin compared with other extracellular matrix proteins. In contrast, this preference was not observed with neutrophils, suggesting that the monocytes and neutrophils may have differences in their migration on extracellular matrix proteins. To study this further, function-blocking monoclonal antibodies were used to examine mechanistically whether beta 1- and beta 2-integrins were involved in monocyte migration on fibronectin or laminin in response to MCP-1. Monocyte migration on both laminin and fibronectin was blocked 100% (P < 0.05) by intact monoclonal antibody, F(ab') fragments, and F(ab')2 fragments to beta 2-integrins. We also determined that antibodies to beta 2-integrins block monocyte migration that has already been initiated. In contrast, antibody to the beta 1-integrins inhibited monocyte migration by approximately 40% (P < 0.05). Thus monocytes that express both beta 1- and beta 2-integrins require utilization of beta 2-integrins in migration on extracellular matrix proteins. The results also suggest that beta 1-integrins facilitate monocyte migration but that monocyte migration is not absolutely dependent on the interaction of beta 1-integrins with extracellular matrix proteins. In contrast, neutrophil migration is beta 2-integrin dependent and is not facilitated by beta 1-integrins.

CD18 Antigens↗

PubMed2004

CCR2-positive monocytes recruited to inflamed lungs downregulate local CCL2 chemokine levels.

The CC chemokine ligand-2 (CCL2) and its receptor CCR2 are essential for monocyte trafficking under inflammatory conditions. However, the mechanisms that determine the intensity and duration of alveolar monocyte accumulation in response to CCL2 gradients in inflamed lungs have not been resolved. To determine the potential role of CCR2-expressing monocytes in regulating alveolar CCL2 levels, we compared leukocyte recruitment kinetics and alveolar CCL2 levels in wild-type and CCR2-deficient mice in response to intratracheal LPS challenge. In wild-type mice, LPS elicited a dose- and time-dependent alveolar monocyte accumulation accompanied by low CCL2 levels in bronchoalveolar lavage fluid (BALF). In contrast, LPS-treated CCR2-deficient mice lacked alveolar monocyte accumulation, which was accompanied by relatively high CCL2 levels in BALF. Similarly, wild-type mice that were treated systemically with the blocking anti-CCR2 antibody MC21 completely lacked LPS-induced alveolar monocyte trafficking that was associated with high CCL2 levels in BALF. Intratracheal application of anti-CCR2 antibody MC21 to locally block CCR2 on both resident and recruited cells did not affect LPS-induced alveolar monocyte trafficking but led to significantly increased BALF CCL2 levels. Reciprocally bone marrow-transplanted, LPS-treated wild-type and CCR2-deficient mice showed a strict inverse relationship between alveolar monocyte recruitment and BALF CCL2 levels. In addition, freshly isolated human and mouse monocytes were capable of integrating CCL2 in vitro. LPS-induced alveolar monocyte accumulation is accompanied by monocytic CCR2-dependent consumption of CCL2 levels in the lung. This feedback loop may limit the intensity of monocyte recruitment to inflamed lungs and play a role in the maintenance of homeostasis.

Animals↗

PubMed1994

Monocytes recruited to sites of inflammation express a distinctive proinflammatory (P) phenotype.

Only a minor proportion of monocytes responds to chemoattractants. To test the possibility that chemoattractant-responsive monocytes have distinctive functional characteristics, we enriched or depleted monocyte preparations for cells having a proinflammatory (P) phenotype and tested their responses to biologically relevant chemoattractants. We prepared monocyte subpopulations by one of three independent techniques to minimize the chances of artifacts: 1) depletion of P monocytes by adherence to fibronectin; 2) enrichment for P monocytes by negative selection for HLA-DR antigen; and 3) flow cytometric sorting. We measured responsiveness of monocyte subpopulations to N-formyl-Met-Leu-Phe, C5a, zymosan-activated serum, and monocyte chemoattractant protein-1 by three parameters: 1) polarization, 2) actin polymerization, and 3) directed migration. With each chemoattractant and each parameter, there was a striking direct relationship between the responsiveness of the monocyte preparations and their content of P monocytes. Our data indicate that the capacity of monocytes to be recruited rapidly from the vasculature into sites of inflammation is a property of a subpopulation of monocytes with a distinctive, neutrophil-like proinflammatory phenotype.

Actins↗

PubMed2006

Role of exercise intensities in oxidized low-density lipoprotein-mediated redox status of monocyte in men.

Exercise significantly influences the progression of atherosclerosis. Oxidized LDL (ox-LDL), as a stimulator of oxidative stress, facilitates monocyte-related atherogenesis. This study investigates how exercise intensity impacts ox-LDL-mediated redox status of monocytes. Twenty-five sedentary healthy men exercised mildly, moderately, and heavily (i.e., 40, 60, and 80% maximal oxygen consumption, respectively) on a bicycle ergometer. Reactive oxygen species (ROS) production, cytosolic and mitochondrial superoxide dismutase (c-SOD and m-SOD, respectively) activities, and total and reduced-form gamma-glutamylcysteinyl glycine (t-GSH and r-GSH, respectively) contents in monocytes mediated by ox-LDL were measured. This experiment obtained the following findings: 1) ox-LDL increased monocyte ROS production and was accompanied by decreased c-SOD and m-SOD activities, as well as t-GSH and r-GSH contents, whereas treating monocytes with diphenyleneiodonium (DPI) (a NADPH oxidase inhibitor) or rotenone/2-thenoyltrifluoroacetone (TTFA) (mitochondrial complex I/II inhibitors) hindered ox-LDL-induced monocyte ROS production; 2) production of ROS and reduction of m-SOD activity and r-GSH content in monocyte by ox-LDL were enhanced by heavy exercise and depressed by mild and moderate exercise; and 3) heavy exercise augmented the inhibition of ox-LDL-induced monocyte ROS production by DPI and rotenone/TTFA, whereas these DPI- and rotenone/TTFA-mediated monocyte ROS productions were unchanged in response to mild and moderate exercise. We conclude that heavy exercise increases ox-LDL-induced monocyte ROS production, possibly by decreasing m-SOD activity and r-GSH content in monocytes. However, mild and moderate exercise likely protects individuals against suppression of anti-oxidative capacity of monocyte by ox-LDL.

Adult↗

PubMed2002

Expression of Fc gamma receptor III (CD16) on monocytes during hemodialysis in patients with chronic renal failure.

BACKGROUND/AIMS: Circulating CD14+CD16+ monocytes, a potent phagocytosing and antigen-presenting monocyte population, have been reported to be expanded in patients on hemodialysis (HD). In this study, changes in the population of CD14+CD16+ monocytes were analyzed during a single session of HD therapy, and the influence of dialyzer membrane materials on these monocytes was investigated. METHODS: Nine patients were hemodialyzed using regenerated cellulose (RC) membranes and thereafter polysulfone (PS) membranes. Peripheral blood cells were taken from these subjects, and these cells were stained with anti-CD14 and anti-CD16 antibodies. The percentages of CD14- and CD16-expressing monocytes were analyzed by two-color flow cytometric analysis. Moreover, the serum soluble CD14 (sCD14) levels were measured with an ELISA kit. RESULTS: It was found that CD14+CD16+ monocytes before HD were significantly increased in patients on HD as compared to healthy controls. In the RC group, CD14+CD16+ monocytes were decreased at both 30 and 240 min after the initiation of HD. The reduction rate of CD14+CD16+ monocytes in the RC group was higher than that in the PS group. There was no significant difference in sCD14 levels between the two groups. CONCLUSION: Monocytes are activated in patients on HD. Furthermore, the population of CD14+CD16+ monocytes was stimulated to a greater extent during HD in the RC group than in the PS group. The significant reduction in CD14+CD16+ monocytes by RC membranes indicated that the level of CD14+CD16+ monocytes is a sensitive marker for the biocompatibility of HD membranes.

Adult↗

PubMed1996

In hypercholesterolemia, lower peripheral monocyte count is unique among the major predictors of atherosclerosis.

Many studies have shown that enhanced monocyte adherence is an important factor in the initiation of atherosclerosis. Because the relationships between circulating monocyte count and atherosclerosis or its major predictors have received little attention, we conducted this study with the aim of clarifying these relationships. The study included 409 men and women who underwent a carotid artery duplex study and white blood cell analysis (Sysmex Cell Counter) during a 2-day health check at our hospital in 1994. We found no correlation between preexisting carotid atherosclerosis and monocyte count. After adjustment for age and sex, hypercholesterolemia, among the major predictors of atherosclerosis, showed a unique correlation with both lower monocyte count and percentage (P < .001, P < .0001, respectively), whereas smoking was correlated with a higher monocyte count (P < .001). There was a slight but nonsignificant increase in monocyte count in hypertension, diabetes, and hypertriglyceridemia. Our results imply that: (1) hypercholesterolemia has a strong, peripheral monocyte-reducing effect, probably due to direct enhancement of monocyte adhesion to the endothelium, which subsequently initiates the atherosclerotic process, and (2) the mechanisms of other predictor(s)-induced atherosclerosis may be quite different from that of hypercholesterolemia. Another possible explanation for the inverse correlation between monocyte count and serum cholesterol level is that decreased monocyte levels might lead to hypercholesterolemia because of decreased uptake of cholesterol from the plasma by less monocyte-derived macrophages. The reasons why preexisting carotid atherosclerosis did not correlate with monocyte count are also discussed.

Arteriosclerosis↗

PubMed1997

Cytokine modulation of LDL oxidation by activated human monocytes.

There is considerable evidence to suggest that cytokines modulate the pathological cellular events that occur in human atherosclerosis. We sought to determine the effects of T-helper-lymphocyte (TH)-1- and TH2-type cytokines on the ability of human monocytes to oxidize LDL, one of the pathological processes believed to occur in atherosclerosis. The ability of opsonized zymosan (ZOP)-activated human monocytes to oxidize LDL in a 24-hour period was significantly enhanced by pretreatment of the monocytes with the TH2 cytokines, interleukin (IL)-4, or IL-13 compared with untreated monocytes. In contrast, interferon (IFN)-gamma, a TH1 cytokine, inhibited LDL oxidation by activated monocytes. Treatment with IFN-gamma also prevented the IL-4- and IL-13-mediated enhancement of LDL oxidation by ZOP-activated monocytes. Untreated or cytokine-treated unactivated monocytes did not oxidize LDL. The enhancement of LDL oxidation mediated by IL-4 or IL-13 treatment was not due to a mitogenic effect of the cytokines on the monocytes, nor to modulation of superoxide anion (O2-) production. The cytokine regulation of 15-lipoxygenase (LO) in the monocytes was also examined. IL-4 and IL-13 induction of 15-LO mRNA and 15-LO activity in the monocytes was confirmed, as was the previously reported inhibition of induction by IFN-gamma. In summary, IL-4 and IL-13 enhance the ability of activated human monocytes to oxidize LDL, whereas IFN-gamma inhibits the cell-mediated oxidation. The up- and downregulation of activated monocyte-mediated LDL oxidation by these cytokines correlates with the expression of 15-LO activity. Considerable evidence suggests that the progression of atherosclerosis includes events that are immunologically mediated, lending potential physiological relevance to these in vitro observations.

Cells, Cultured↗