Biomedical subjects

L Koenderman

Publications and source records attributed to L Koenderman.

At least 109 records · Page 6Linked to original sources

PubMed1992

Release of platelet-activating factor is important for the respiratory burst induced in human eosinophils by opsonized particles.

The respiratory burst induced in human eosinophils by serum-treated zymosan (STZ) was found to be almost completely prevented by preincubation of the cells with WEB 2086, an antagonist of platelet-activating factor (PAF). When eosinophils were primed by the addition of 1 mumol/L PAF, subsequent addition of WEB 2086 had only a minor effect on the STZ-induced respiratory burst. These results suggest a role for PAF synthesis and PAF release in the activation of the respiratory burst by STZ. Indeed, supernatant of STZ-stimulated eosinophils was able to prime fresh eosinophils (as did PAF itself), and this effect was again inhibited by WEB 2086. This indicates that eosinophils synthesize and release PAF during STZ stimulation. Measurements of total PAF and PAF release showed that most of the PAF synthesized by eosinophils was released in the extracellular medium. This study shows that synthesis and release of PAF is important for respiratory burst activity induced in human eosinophils by STZ.

Azepines↗

PubMed1992

In vivo priming of platelet-activating factor-induced eosinophil chemotaxis in allergic asthmatic individuals.

The cytokines granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin (IL)-3, and IL-5 are important modulators of eosinophilia and eosinophil function. Eosinophil chemotaxis is known to be particularly sensitive for cytokine priming. In the present study, we compared chemotactic responses of eosinophils derived from peripheral blood of allergic asthmatics to responses of eosinophils from peripheral blood of healthy individuals. Eosinophils from allergic asthmatics exhibited a markedly increased sensitivity in their chemotactic response toward platelet-activating factor (PAF) compared with eosinophils from normal donors. In contrast, C5a-induced eosinophil chemotaxis between both groups was similar. This in vivo-primed phenotype could be mimicked in vitro, by preincubating eosinophils from peripheral blood of healthy individuals with picomolar concentrations of either GM-CSF, IL-3, or IL-5. The chemotactic response of eosinophils derived from the circulation of allergic asthmatic patients toward GM-CSF was significantly lower compared with the response of eosinophils of healthy individuals. Our data strongly suggest that release of cytokines may be an important in vivo priming mechanism for eosinophils in the circulation of allergic asthmatic patients. Such an in vivo priming can subsequently result in selective upregulation and downregulation of chemotactic responses toward various chemoattractants release in the lung tissue.

Asthma↗

PubMed1992

Cloning of T lymphocytes from bronchoalveolar lavage fluid.

We have prepared T-cell clones from bronchoalveolar lavage fluid (BALF) from four healthy, nonsmoking persons and from four patients with allergic asthma. T cells were cloned by direct limiting dilution and with the use of a fluorescent activated cell sorter with an automated cell deposition unit. T-cell clones from the blood (PB) were prepared as well. The cloning efficiencies of T cells from BALF ranged from 3 to 40% and were lower than those obtained from PB T cells (18 to 72%). The cloning conditions generated CD4+ as well as CD8+ clones. The very late antigen-4, VLA-4, was more frequently expressed on CD4+ T-cell clones from BALF than from the blood (P < 0.05). CD8+ clones from BALF were more frequently VLA-1+ than those from blood (P < < 0.01). Mitogen- and monoclonal antibody-driven proliferation of CD4+ clones showed that BALF clones were well responsive to proliferation stimuli similar to those from the blood. Analysis of interleukin-4 production by 10 BALF and 10 PB clones showed large variations between individual CD4+ clones (BALF: range, < 100 to 700 pg/ml; PB: range, < 100 to 1,100 pg/ml), indicating the generation of different types of clones, which was also clear from analysis of interferon-gamma production. The analysis of properties of BALF T-cell clones and their regulation will improve insight into immunologic reactions in the lungs.

Adult↗

PubMed1991

Modulation and induction of eosinophil chemotaxis by granulocyte-macrophage colony-stimulating factor and interleukin-3.

Eosinophilia and eosinophil function are regulated by cytokines such as granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3), and IL-5. We have investigated the modulatory role of GM-CSF and IL-3 on the platelet-activating factor (PAF)-, neutrophil-activating factor (NAF/IL-8)-, leukotriene B4 (LTB4)-, N-formyl-methionyl-leucyl-phenylalanine (FMLP)-, and human complement factor C5a-induced chemotaxis of eosinophils from normal individuals. These eosinophils show a chemotactic response toward PAF, LTB4, and C5a, but not to NAF/IL-8 and FMLP. Preincubation of the eosinophils with picomolar concentrations of GM-CSF caused a significant increase in the response toward LTB4 and induced a significant chemotactic response toward NAF/IL-8 and FMLP. Preincubation of the eosinophils with picomolar concentrations of IL-3 also induced a chemotactic response toward NAF/IL-8 and FMLP, and enhanced the PAF-induced chemotaxis response toward C5a was not influenced by both cytokines. Nanomolar concentrations of GM-CSF or IL-3 caused a significant inhibition of the C5a-induced chemotaxis. The LTB4-induced chemotaxis was also significantly inhibited in case of GM-CSF. At these concentrations both GM-CSF and IL-3 acted as chemotaxins for eosinophils were washed after pretreatment with GM-CSF and IL-3 the potentiation of the chemotactic response remained, whereas the inhibitory mode of action disappeared. Our data indicate that at picomolar concentrations the cytokines GM-CSF and IL-3 can modulate eosinophil chemotaxis and at nanomolar concentrations these cytokines can act as chemotaxins for eosinophils.

Chemotaxis, Leukocyte↗

PubMed1991

Differential activation of human basophils by anti-IgE and formyl-methionyl-leucyl-phenylalanine. Indications for protein kinase C-dependent and -independent activation pathways.

Upon activation, basophilic granulocytes release inflammatory mediators such as histamine. We studied histamine release of human basophils (64.1 +/- 9.6% pure) after cross-linking of membrane-bound IgE via anti-IgE, or after binding of the chemoattractant formyl-methionyl-leucyl-phenylalanine (fMLP). A variability in the extent of histamine release upon stimulation by either anti-IgE or fMLP was found between donors. Kinetic studies revealed that the histamine release induced by anti-IgE (t1/2 greater than 240 s) was more than 20-fold slower than the almost instantaneous release upon stimulation with fMLP (t1/2 less than 10 s). Differences in the cell activation pathways triggered by these stimuli were further analyzed with staurosporine, an inhibitor of protein kinase C (PKC) and with wortmannin, an inhibitor of a PKC-independent pathway. Inhibition of PKC resulted in a partial inhibition of the anti-IgE-induced release, whereas the fMLP-induced release was slightly potentiated. The anti-IgE-induced release was completely inhibited in the presence of wortmannin. This inhibitor too, had no effect on the fMLP-induced release. We conclude that major differences exist in the signal-response coupling between the anti-IgE and fMLP-induced histamine release in human basophils. The so-called releasability of human basophils may be due to the availability of different cell activation pathways.

Alkaloids↗

PubMed1991

Characteristics of CR3-mediated aggregation in human eosinophils: effect of priming by platelet-activating factor.

We have used double-color fluorescence-activated cell sorter analysis to characterize the homotypic aggregation response of human eosinophils (EOs). With this method, we demonstrate for the first time that EOs are able to form stable aggregates. The aggregation response induced by the phorbol ester, phorbol myristate acetate (PMA), was low and was not primed by platelet-activating factor (PAF). In contrast, the aggregation response induced by opsonized particles was markedly enhanced after priming with PAF. Additional experiments with several blocking monoclonal antibodies indicate that the CR3 receptor present on human EOs mediates the homotypic aggregation induced by PMA and by small opsonized particles through a putative "cell-adhesion" site on CR3, which binds to its counter structure on the opposing cell. The signal that initiates this binding event is generated after PMA addition or activation of the iC3b-binding site and is not sensitive for priming by PAF. The priming by PAF of the aggregation response induced by opsonized particles is restricted to an action on the iC3b-binding site, possibly by enhancing the affinity for its ligand.

Antigens, CD↗

PubMed1990

Priming of the respiratory burst in human eosinophils is accompanied by changes in signal transduction.

Addition of platelet-activating factor (PAF) to human eosinophils leads to the modulation of eosinophil responses. The respiratory burst, induced by opsonized particles, consists of an initiation and a propagation phase and is greatly enhanced ("primed") after pretreatment with PAF. This priming event induces the following changes in signal transduction between the opsonin receptors (in particular the CR3 receptor) and activation of the respiratory burst: 1) an enhanced activation of protein kinase C (PK-C): the initiation of the respiratory burst in untreated eosinophils is not sensitive to PK-C inhibition (via staurosporine) and is not accompanied by accumulation of diglycerides and changes in [Ca2+]i. After pretreatment with PAF, the initiation of the response is partly sensitive to inhibition of PK-C (via staurosporine) and is accompanied by accumulation of diglycerides and a fast and sustained increase in [Ca2+]i; and 2) an enhancement of a PK-C-independent initiation of the respiratory burst. The propagation phase in both primed and unprimed cells is sensitive for inhibition by staurosporine. Our results indicate that in eosinophils the phospholipase(s) responsible for the accumulation of the diglycerides and changes in [Ca2+]i during the initiation phase of the serum-treated zymosan response seem(s) to become associated with the signal transduction route only after priming with PAF. This results in the occurrence of two signal transduction routes that can act independently of each other.

Alkaloids↗

PubMed1990

Adherence of human neutrophils changes Ca2+ signaling during activation with opsonized particles.

Changes in the cytosolic free Ca2+ concentration ([Ca2+]i) upon activation of human neutrophils by opsonized particles (serum-treated zymosan; STZ) were evaluated by three different methods: (i) measurement of total fluorescence changes in indo-1 loaded neutrophils activated in suspension; (ii) measurement of fluorescence changes in individual indo-1 loaded neutrophils in a flow cytometer and (iii) measurement of fluorescence changes in individual fura-2 loaded neutrophils adherent to serum-coated coverslips. Our study shows that the opsonized particle-induced change in [Ca2+]i in neutrophils is altered during adherence of the cells to a serum-coated surface. These observations might be of importance for neutrophil function in vivo, since adherence is a prerequisite for diapedesis and chemotaxis.

Calcium↗

PubMed1990

NADPH:O2 oxidoreductase of human eosinophils in the cell-free system.

The NADPH oxidase of human eosinophils, measured in the cell-free system, shows the same characteristics as the enzyme from human neutrophils. All proteins required for activity of the enzyme are expressed in eosinophils at a higher level than in neutrophils. Eosinophils isolated from patients with chronic granulomatous disease show the same molecular defects as the neutrophils from these patients.

Alkaline Phosphatase↗

PubMed1990

Continuous cell activation is necessary for stable interaction of complement receptor type 3 with its counter-structure in the aggregation response of human neutrophils.

Human neutrophils aggregate after stimulation with various stimuli; this response is completely absent in neutrophils from patients with leukocyte adhesion deficiency (LAD). To investigate the cellular requirements of this process a method was used in which neutrophils are separately loaded with hydroethidine (HE) and sulfofluorescein (SFDA), to give them either red fluorescence or green fluorescence. After mixing HE- and SFDA-labeled cells in a ratio of 1:1, the number of double-colored aggregates formed after activation was determined by analysis on a fluorescence-activated cell sorter. In this way, essential information is obtained when cells of different origin are used. The formation of aggregates between neutrophils of an LAD patient and control neutrophils was thus quantified. Because neutrophil aggregation is dependent mostly on the presence of complement receptor type 3 (CR3), which is not present on LAD neutrophils, this result revealed the presence of a counter-structure for CR3 on LAD neutrophils (and hence on normal human neutrophils). In addition to the presence of these proteins on the cell surface, aggregation required continuous cell triggering as indicated by the transient aggregation induced by short-term activation of protein kinase C. This phenomenon was substantiated by the fact that energy depletion caused profound disaggregation. The present study reveals that neutrophil aggregation is a well-controlled process, which needs constant activation of CR3 for a stable interaction with a constitutively expressed counter-structure.

Adenosine Triphosphate↗

PubMed1990

Epidermal growth factor and bombesin differ strikingly in the induction of early responses in Swiss 3T3 cells.

Swiss 3T3 cells express receptors for both the polypeptide epidermal growth factor (EGF) and the tetradecapeptide bombesin and respond mitogenically to these substances. These cells thus provide a system to analyze potential signal transduction pathways involved in mitogenic stimulation. Here we have determined and compared the early ionic responses elicited by EGF and bombesin and their relation to diacylglycerol (DG) and inositolphosphate (InsPn) production. Whereas EGF fails to cause any significant change in intracellular Ca2+, bombesin effectively induces prompt and transient Ca2+ mobilization from intracellular stores. Further support of the idea that these receptors utilize distinct signalling pathways comes from the measurements of cytoplasmic pH (pHi). As in most target cells, EGF induces a delayed (1 min) but sustained intracellular alkalinization that reaches a new steady state after approximately 10 min. Bombesin, in contrast, elicits a biphasic response; within seconds, a rapid but transient rise in pHi is observed, followed by a further slower sustained alkalinization. Inhibition of the Na+/H+ exchanger prevents both EGF as well as bombesin-induced alkalinization. However, under these conditions, bombesin evokes a rapid and sustained acidification related to the Ca2+ response. Apparently, bombesin initiates a Ca2(+)-dependent acidifying process immediately after binding of the hormone to its receptor. Furthermore, we could demonstrate that the bombesin-induced alkalinization depends on protein kinase C activation whereas the EGF response does not. Determination of the total DG and InsPn accumulation revealed that EGF is ineffective in stimulating phospholipase C-mediated production of these second messengers. In contrast, bombesin causes a rapid DG and InsPn production coinciding with the Ca2+ response and the first phase of the rise in pHi followed by a slower DG accumulation coinciding with the second alkalinization phase. Our results show that in Swiss 3T3 cells the bombesin receptor activates the hydrolysis of inositol lipids as a mechanism of signal transduction, which consequently causes changes in Ca2+i and pHi. Clearly, the EGF receptor utilizes different pathways to evoke mitogenesis and stimulates Na+/H+ exchange independently of DG production and protein kinase C activation.

Animals↗

PubMed1990

Differential mechanisms in the stimulus-secretion coupling in human basophils: evidence for a protein-kinase-C-dependent and a protein-kinase-C-independent route.

Upon activation, basophilic granulocytes release inflammatory mediators, such as histamine. We studied histamine release (HR) of purified (64 +/- 10%) human basophils after cross-linking of membrane-bound IgE via anti-IgE or after binding of the chemoattractant formyl-methionyl-leucyl-phenylalanine (FMLP). A variability in the extent of histamine release upon stimulation by either anti-IgE or FMLP was found between donors. Non-responders for FMLP showed high histamine release for anti-IgE, and vice versa. Inhibition of protein kinase C (PKC) by staurosporine (STSP) resulted in partial inhibition of the anti-IgE-induced HR, whereas inhibition of a PKC-independent pathway by wortmannin (WTM) totally blocked the anti-IgE induced histamine release. The HR induced by FMLP was not affected by either of these inhibitors. We conclude that major differences exist in the signal-response coupling between the anti-IgE and FMLP-induced HR in human basophils. The so-called releasability of human basophils may be due to the availability of different cell activation pathways.

Alkaloids↗

PubMed1989

Platelet-activating factor (PAF) acts as an intercellular messenger in the changes of cytosolic free Ca2+ in human neutrophils induced by opsonized particles.

Addition of opsonized particles to human neutrophils in suspension leads to a biphasic elevation in the cytosolic free Ca2+ concentration ([Ca2+]i). The rise in [Ca2+]i during the second phase (greater than 3 min) is pronounced (about 400 nM), in contrast to the rise during the first phase, which is relatively small (less than 100 nM). The second and large rise in [Ca2+]i is brought about by messenger(s) released from the cell after addition of opsonized particles. This second rise in [Ca2+]i is not observed in the presence of the platelet-activating factor (PAF) antagonist WEB 2086, indicating that PAF can act as an intercellular messenger affecting Ca2+ homeostasis in human neutrophils.

Azepines↗

PubMed1989

The 40-kDa Fc gamma receptor (FcRII) on human neutrophils is essential for the IgG-induced respiratory burst and IgG-induced phagocytosis.

Neutrophils express two types of receptor for the Fc region of IgG, FcRII and FcRIII. Per neutrophil, 10,000 to 20,000 molecules of FcRII (40 kDa) and 100,000 to 200,000 molecules of FcRIII (50 to 80 kDa) are expressed. Via these receptors, neutrophils bind IgG complexes that contain more than one IgG molecule. This binding activates functional processes, such as the respiratory burst and phagocytosis. We studied the contribution of FcRII and FcRIII in the activation of these processes, using well-defined complexes (both large and small) in combination with mAb against FcRII and FcRIII. Small (dimeric) IgG complexes appeared to bind via FcRIII. However, binding to FcRIII alone, when FcRII is blocked by an anti-FcRII mAb, did not induce a respiratory burst. Induction of the respiratory burst by a large immune complex, such as Staphylococcus aureus Wood opsonized with IgG antibodies, was mediated by binding to FcRII, because it was blocked by an anti-FcRII mAb but not by an anti-FcRIII mAb. This indicates that these IgG-opsonized bacteria can cross-link FcRII and activate the cells without the need to adhere to the FcRIII. The respiratory burst induced by IgG-latex was not inhibited by an anti-FcRII mAb, because the avidity for FcRII of IgG-latex, a particle of the same size as a Staphylococcus but with a two to three times higher IgG content, is increased by its simultaneous binding to FcRIII. This enhanced avidity results in removal of anti-FcRII mAb from the FcRII by IgG-latex. This increased avidity of large complexes for FcRII, created by concurrent binding to FcRIII, is not necessary for activation of human neutrophils, because neutrophils from patients with paroxysmal nocturnal hemoglobinuria, with about 10% of the normal FcRIII expression, showed a normal metabolic response upon addition of IgG-latex. Phagocytosis of IgG-opsonized 14C-labeled S. aureus Wood was inhibited equally well by anti-FcRII mAb and by anti-FcRII in combination with anti-FcRIII mAb. Thus, FcRII is not only essential for the IgG-induced activation of the NADPH oxidase system, but also for the IgG-induced phagocytosis.

Antigens, Differentiation↗

PubMed1989

1,2-Diacylglycerol accumulation in human neutrophils does not correlate with respiratory burst activation.

Measurements of the level of 1,2-diacylglycerol (1,2-DG) during activation of the respiratory burst of human neutrophils by formyl-methionyl-leucyl-phenylalanine (fMLP) in the presence of platelet-activating factor (PAF) or by opsonized particles show that a correlation between accumulation of 1,2-DG and O2 consumption does not exist. Inhibition of protein kinase C activity with staurosporine before addition of opsonized particles demonstrates that the first phase of the respiratory burst is not inhibited, whereas the second phase, which is accompanied by a rise in the content of 1,2-DG, is strongly inhibited. This study indicates that accumulation of 1,2-DG cannot be the sole signal for the initiation of the respiratory burst in human neutrophils.

Alkaloids↗

PubMed1989

Dual mechanisms in priming of the chemoattractant-induced respiratory burst in human granulocytes. A Ca2+-dependent and a Ca2+-independent route.

After interaction with so-called priming agents, the respiratory burst in human granulocytes does not become activated, but is enhanced upon subsequent stimulation with the chemoattractant FMLP. Investigating the mechanism of the priming reaction, we found that a transient rise in the cytosolic free calcium concentration [( Ca2+]i) suffices to irreversibly prime human granulocytes. Thus, platelet-activating factor (PAF) induced a transient increase in [Ca2+]i and primed the cells to an enhanced respiratory burst upon subsequent interaction with FMLP. Artificially, the transient rise in [Ca2+]i was mimicked by addition and subsequent removal of the Ca2+ ionophore ionomycin; this treatment too, primed the respiratory burst of the granulocytes. The priming induced by ionomycin was completely abolished when [Ca2+]i changes were buffered during exposure of the cells to the ionophore. The priming induced by PAF was only partially inhibited under [Ca2+]i-buffering conditions during priming, indicating that multiple pathways exist in the priming of granulocytes by PAF.

Buffers↗

PubMed1989

Leukotriene C4 formation by purified human eosinophils can be induced by arachidonic acid in the absence of calcium-ionophore A23187.

Addition of arachidonic acid (50 microM) to purified human eosinophils leads to the formation of considerable amounts of LTC4 [11.3 +/- 1.3) x 10(6) molecules/cell, mean +/- SEM, n = 10), 15-HETE [412 +/- 142) x 10(6) molecules/cell, mean +/- SEM, n = 3) and 15-series leukotrienes [35 +/- 15) x 10(6) molecules/cell, mean +/- SEM, n = 3). The ratio of the amounts of LTC4 and 15-lipoxygenase products was found to be strongly dependent on the arachidonic acid concentration, being relatively large at low arachidonic acid concentrations and very small at high arachidonic acid concentrations. Platelet activating factor (1 microM) was able to enhance significantly the production of LTC4 but not that of 15-lipoxygenase products. As arachidonic acid was found to be capable of inducing a fast, transient rise in the cytosolic free Ca2+ concentration, this explains, at least partly, its ability to induce the Ca2+-dependent formation of LTC4.

Arachidonic Acids↗

PubMed1989

Increased sensitivity of the chemoattractant-induced chemiluminescence in eosinophils isolated from atopic individuals.

Eosinophilia in peripheral blood is a common phenomenon associated with atopic condition. The present study illustrates the enhanced sensitivity of these eosinophils for formyl-methionyl-leucylphenylalanine (FMLP) and platelet-activating-factor (PAF) (measured as luminol-enhanced chemiluminescence) compared with eosinophils isolated from the peripheral blood of normal individuals. The PAF-induced chemiluminescence, which is peroxidase dependent and of extracellular origin, is inhibited by the PAF antagonist BN52021. The enhanced sensitivity of eosinophils isolated from atopic patients for FMLP and PAF might reflect a 'primed' state of these cells, relevant for the pathogenesis of atopic disease.

Asthma↗