Macrophage down-regulation by interleukin-1 receptor antagonist.
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Down-Regulation↗
Biomedical subjects
P Conti
Publications and source records attributed to P Conti.
Blocking the interleukin-1 receptor inhibits leukotriene B4 and prostaglandin E2 generation in human monocyte cultures.
Interleukin-1 is a potent stimulator of arachidonic acid (AA) metabolism and this activity could be attributed to the activation of the prostaglandin-forming enzyme cyclooxygenase or of the arachidonic-releasing enzyme phospholipase A2 or both. Prostaglandin E2 (PGE2), a cyclooxygenase product, and LTB4 (5-(S),12-(R)-dihydroxy-6,14-cis-8,10-trans-eicosatetraenoic acid), a lipoxygenase product, are potent mediators of inflammation. Recently a new cytokine produced by macrophages and named interleukin-1 receptor antagonist (IL-1ra) (MW 22,000 Da) which specifically binds and blocks IL-1 receptors, has proven to be a potent inflammatory inhibitor. In our studies we found that monocyte suspensions, pretreated with hrIL-1ra at increasing concentrations (0.25-250 ng/ml) for 10 min and then treated with LPS in an overnight incubation inhibits, in a dose-dependent manner, the generation of LTB4 as measured by the highly sensitive radioimmunoassay method. In monocytes pretreated with hrIL-1ra (250 ng/ml) for 10 min and treated with arachidonic acid (10(-5)-10(-9) M) and LPS overnight, the release of LTB4 was partially inhibited when compared to hrIL-1ra-untreated cells. Moreover, hrIL-1ra (250 ng/ml) caused a partial inhibition of monocyte LTB4 production when the cells were activated with AA (10(-7) M) and then treated with IL-1 beta (5 ng/ml) overnight or 24 hr incubation. In addition, human monocytes pretreated for 10 min with increasing doses of hrIL-1ra (0.25-250 ng/ml) and then treated with hrIL-1 alpha (5 ng/ml) or beta (5 ng/ml) for 18 hr, also resulted in the inhibition of PGE2 generation as measured by RIA when compared with hrIL-1ra-untreated cells. When the cells were treated with hrIL-1ra (250 ng/ml) and activated for 18 and 48 hr with increasing doses of hrIL-1 beta a strong inhibitory effect was found on PGE2 production. HrIL-1ra used at 15 ng/ml gave a partial inhibition of LTB4 generation, after LPS (1-100 ng/ml) treatment, while NDGA totally blocked the production of LTB4. Moreover, PGE2 released by macrophages activated with LPS (100 ng/ml) or hrIL-1 beta (5 ng/ml) at 18 hr incubation time was strongly inhibited when hrIL-1ra (250 ng/ml) was used. These data suggest that the inhibition of LTB4 and PGE2 by this new macrophage-derived monokine IL-1ra occurs through the block of the IL-1 receptor, rather than phospholipase A2, and thus IL-1ra may offer a potential therapeutic approach to inflammatory states.
Arachidonic Acid↗
Role of lipoxins A4 and B4 in the generation of arachidonic acid metabolites by rat mast cells and their effect on [3H]serotonin release.
Basophils located in tissues are called mast cells and are found in connective tissue. Many different compounds are secreted from basophil granules upon appropriate stimulation. Products such as heparin, histamine, serotonin (5-hydroxytryptamine, 5-HT), and membrane-derived materials which give rise to arachidonic acid metabolites, such as prostaglandins and leukotrienes, are some of the more important compounds released by mast cells. These compounds, when released after stimulation with a variety of molecules, such as IgE, specific antigen anaphylotoxin, as well as the compound 48/80 (C48/80) or calcium ionophore A23187, cause contraction of endothelial cells and mediate atopic or anaphylactic hypersensitivity. In this report, we study the generation of some arachidonic acid products, namely leukotrienes C4, D4, E4, and B4 and the prostaglandins D2 and E2 by rat peritoneal mast cells (RPMC), using calcium ionophore A23187 as a degranulating agonist. We have also studied the new lipoxygenase products, lipoxins A4 and B4, on RPMC secretion using C48/80 as a secretagogue. A rat basophilic leukemia cell line (RBL) was also used to compare results with RPMC. In this paper we have demonstrated that RPMC stimulated with A23187 release LTC4, LTD4, LTE4 and LTB4 and also PGD2 but not PGE2. These results were also confirmed when RBLs were used. In addition, we have shown that mast cells pretreated with LTC4, LTD4, LTE4 or 15-HETE do not modify the release of [3H]5HT exerted by C48/80 (0.5 microgram/ml) or A23187 (5 micrograms/ml). When LXA4 or B4 was used, mast cells were inhibited slightly (not statistically significant) from degranulating after the secretagogue treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Granulocyte-macrophage colony stimulating factor potentiates human polymorphonuclear leukocyte aggregation responses to formyl-methionyl-leucyl-phenylalanine.
Polymorphonuclear leukocytes (PMN) are known to be activated by several lymphokines and can be induced to release lysosomal enzymes, prostaglandins (PG), thromboxanes (TX) and lipoxygenase products that may be involved in PMN aggregation responses during inflammatory reactions. Granulocyte-macrophage colony stimulating factor (GM-CSF), a glycoprotein cytokine released by immunocompetent cells, has been found to prime neutrophil responses, such as increased cell aggregation after exposure to various biological stimulants. In this study, we examined the effects of the cytokine GM-CSF on human neutrophilic aggregation stimulated by N-formyl-methionyl-leucyl-phenylalanine (FMLP) and its influence on the production of various arachidonic acid metabolites. Neutrophil aggregation of purified PMNs was measured by the percent change in light transmission in a standard aggregometer, and the arachidonic acid products leukotriene B4 (LTB4) and thromboxane A2 (TXA2) were quantified by radioimmunoassay. We found that GM-CSF and other cytokines, used alone, did not cause any significant increase in aggregation of the PMN. However, prior exposure of PMN to GM-CSF markedly increased the aggregation induced by FMLP as opposed to that detected with PMN stimulated with only FMLP. This priming effect was not observed with PMN preincubated with interleukin-1 (IL-1), tumor necrosis factor (TNF) or interleukin-6 (IL-6). In addition, GM-CSF and IL-6 both failed to stimulate the production of LTB4 and TXA2, products which are known to induce PMN aggregation. These findings provide new evidence suggesting that GM-CSF facilitates the action of FMLP on the adhesion dependent cellular functions of the inflammatory response, serving as an important co-factor in neutrophil aggregation.
Calcimycin↗
Human recombinant interleukin-1 receptor antagonist (hrIL-1ra) enhances the stimulatory effect of interleukin-2 on natural killer cell activity against MOLT-4 target cells.
Interleukin-1 (IL-1) is considered an enhancer of host defence against malignancies. Patients with different diseases, including cancer patients with large tumour burdens, have demonstrated a reduced production of IL-1 from circulating leukocytes, in vitro. There are many naturally occurring substances which inhibit IL-1 activity aspecifically. Recently an interleukin-1 receptor antagonist (IL-1ra) has been discovered, which is secreted by human macrophages and is structurally similar to IL-1 beta (26% homology). The pretreatment of human peripheral blood mononuclear cells (PBMC) with hrIL-1ra (0.25-250 ng/ml) inhibits IL-1 alpha or IL-1 beta and enhances, in a dose-dependent manner, the stimulatory effect of IL-2 on their natural killer (NK) activity against a lymphoid cell line MOLT-4. The enhancing effect of IL-1ra on IL-2 activity was similar to that provoked by IL-1 beta. However, when IL-1ra was used alone without IL-2, no stimulatory effect was found compared with the control. In our data we show that a member of the IL-1 family, IL-1ra, has a significant effect on IL-2-stimulated NK activity against the MOLT-4 cell line. These studies provide new evidence of the biological potential of IL-1ra since this new protein enhances IL-2 activity on NK cells.
Cytotoxicity, Immunologic↗
Inhibition of interleukin-1 (alpha and beta), interleukin-2 secretion and surface expression of interleukin-2 receptor (IL-2R) by a novel cytokine interleukin-1 receptor antagonist (IL-1ra).
IL-1 is a mediator of the acute inflammatory response and plays a key role in influencing growth and differentiation of immunocompetent lymphocytes. It can enhance transcription and secretion of the T-cell growth factor interleukin-2 (IL-2) and can stimulate the expression of membrane receptors for IL-2. However, the regulation and control of IL-1 activities are poorly understood. Recently an IL-1 inhibitor, interleukin-1 receptor antagonist (IL-1ra), has been described and cloned. This protein is a monokine originally found in the urine of febrile patients and in supernatants of human monocytes adhering to an IgG-coated surface, with an approximate molecular weight of 17 kDa, which is similar to IL-1 beta but having no IL-1-like activity and antagonizing IL-1 by binding to its cell surface receptor. These studies have examined some biological properties of hrIL-1ra, such as its effects on the secretion of IL-1 alpha or IL-1 beta and IL-2, the surface expression of IL-2R and DNA synthesis by peripheral blood mononuclear cells (PBMC). PBMC from normal volunteers were separated and used at a concentration of 2.5 x 10(6) cells/ml. The cells were pretreated for 2 h with hrIL-1ra (0.025-250 ng/ml), treated with LPS (10 ng/ml), and IL-1 alpha and IL-1 beta secretion were determined by an ELISA method. In addition the influence of hrIL-1ra (25 ng/ml) on IL-2 generation was determined. In another set of experiments, flow cytometric analysis with an anti-CD25 monoclonal antibody was determined on PHA-stimulated PBMC pretreated with hrIL-1ra (2 h) and cultured for 48 h. The inhibition by hrIL-1ra of IL-2R expression was dose-dependent and when hrIL-1ra was used at 250 ng/ml the IL-2R was completely abolished. Lymphocyte DNA synthesis calculated from the net uptake of [3H]-thymidine (3H-TdR) was also inhibited by hrIL-1ra (0.025-25 ng/ml). In this report we found that hrIL-1ra inhibits, in a dose-dependent manner, the secretion of IL-1 alpha, IL-1 beta, IL-2, the surface expression of IL-2R and 3H-TdR incorporation in PBMC in vitro. These data suggest a new biological activity of hrIL-1ra and further extend the immunomodulatory potential and significance of this new cytokine. The action of IL-1ra on modulating the synthesis of IL-1 may be of paramount importance in the regulation of these effects.
Concanavalin A↗
[A rare case of intramedullary epidermoid cyst diagnosed by MRI].
Intramedullary epidermoid cysts are rare entities. A case recently seen on MRI led us to review the literature on the subject. A 9 year old boy developed in a four month-time a spastic paraparesis with a T7-T8 sensitive level. The MRI showed a widening of the spinal cord at the T6 level with an area of decreased signal on T1 weighted images, and a homogeneous round shaped area of increased signal on T2 weighted images. The authors discuss the contribution of MRI to the diagnosis of this lesion. The number of cases of intramedullar epidermoid cysts, like dermoid cysts, diagnosed with this neuroradiological method, is still very limited and the literature only mentions isolated cases.
Child↗
Inhibition of leukotriene B4(LTB4) by recombinant interleukin-1 receptor antagonist (IL-1RA) on human monocytes.
Macrophages are a primary source of interleukin-1 (IL-1), a glycoprotein which plays an important and essential role in the immune response and inflammation. Cytokines stimulate many different cells to produce increasing amounts of arachidonic acid metabolites such as prostaglandins and leukotrienes. Recently, interleukin-1 receptor antagonist (IL-1ra), a natural inhibitor of IL-1 released by macrophages, has been reported to inhibit PGE2. In accordance with these data our results show that the pretreatment, for 60 min, of purified human peripheral monocytes with IL-1ra at different concentrations (0.25-250 ng/ml) inhibits, in a dose-dependent manner, the generation of LTB4 released after 10 min treatment with calcium ionophore A23187 (5 microM). The inhibition of LTB4 synthesis by hrIL-1ra suggests the possibility that this new glycoprotein plays a modulatory role in immunity and inflammation.
Calcimycin↗
Inhibition of interleukin-1 beta mRNA expression and interleukin-1 alpha and beta secretion by a specific human recombinant interleukin-1 receptor antagonist in human peripheral blood mononuclear cells.
The transcription and translation of interleukin-1 (IL-1) may have a pleiotropic effect on the immune system and inflammatory diseases. Recently it has been reported that human monocytes not only produce IL-1 but also induce, with adherent IgG, the secretion of an IL-1 receptor antagonist (IL-1Ra), which can play an essential in vivo and in vitro role in the regulation of IL-1 activity. Recombinant human (rh) IL-1Ra is structurally similar to IL-1 beta but with no IL-1-like activity, and specifically binds to the IL-1 receptor. To more fully evaluate and clarify the inhibitory effect of rhIL-1 receptor antagonist on IL-1 we have studied the influence of rhIL-1Ra on IL-1 transcription and translation. In this report we show that IL-1 beta mRNA from peripheral blood mononuclear cells (PBMC) is strongly inhibited (66%) when rhIL-1Ra (250 ng/ml) was added to cultured cells activated with lipopolysaccharide (LPS) (100 ng/ml) for 4 hr, determined with the slot blot analysis. The addition of exogenous rhIL-1 beta to the cell culture diminished the inhibitory effect (44%). Moreover, we report that the block of IL-1 mRNA transcription consequently leads to the inhibition of IL-1 alpha and IL-1 beta secretion in human PBMC, as measured by ELISA method. In fact, herein we show that LPS activates human PBMC to secrete IL-1 beta and IL-1 alpha, an effect inhibited, in a dose-dependent fashion by rhIL-1Ra (0.025-250 ng/ml) in an overnight incubation. Since IL-1 is a strong inducer of IL-1 synthesis in vivo and in vitro, in our study we used rh IL-1 alpha to stimulate the secretion of IL-1 beta in human PBMC. This activation, carried out overnight, also provoked the release of IL-1 beta in a dose-dependent manner, which was strongly inhibited by rhIL-1Ra used at different concentrations (0.025-250 ng/ml). The inhibitory effect exerted by IL-1Ra on human PBMC IL-1 mRNA transcription and the down-regulation of secretion of IL-1 beta stimulated by IL-1 alpha, may contribute to therapeutic effects in inflammatory diseases such as rheumatoid arthritis and other autoimmune diseases.(ABSTRACT TRUNCATED AT 400 WORDS)
Cells, Cultured↗
Human recombinant interleukin-1 receptor antagonist inhibits lymphocyte blastogenesis induced by concanavalin A. Restorative effect of hrIL-1.
Interleukin-1 (IL-1), mainly produced by monocyte-macrophages, is a polypeptide cytokine with pleiotropic biological effects. IL-1 plays an important role in mediating immune response and inflammation. Recently a natural inhibitor to IL-1 has been discovered, interleukin-1 receptor antagonist (IL-1ra), produced by human monocytes cultured on adherent IgG which binds to the IL-1 receptors. In our study we found that the pretreatment of cells with serial dilutions of IL-1ra (250 ng/ml-2.5 pg/ml) inhibits, in a dose-dependent manner, lymphocyte DNA synthesis stimulated with Con A (10 micrograms/ml). IL-1ra did not have any effect on resting peripheral blood mononuclear cells (PBMC). Time course experiments show that IL-1ra at 250 ng/ml has its maximum inhibitory effect on lymphocyte blastogenesis when cells are pretreated 2 h before Con A. No effect was found when hrIL-1ra was added after Con A. Moreover, hrIL-1ra also inhibits the enhancing effects of exogenous hrIL-1 (400, 200, 100 and 50 ng/ml) on lymphocytes stimulated with Con A; while when hrIL-1ra was used on cells treated with only Con A, the inhibition was more pronounced. When PBMC were removed from monocytes, by adherence, the Con A-treated lymphocytes were not influenced by 2 h pretreatment of hrIL-1ra; while a strong inhibition was found when exogenous hrIL-1 was added at different concentrations. In addition, hrIL-1ra also inhibits the enhancing effect of hrIL-2 on lymphocyte DNA synthesis. In another set of experiments PBMC were pretreated with hrIL-1ra (250 ng/ml) for 2 h and then added LPs (10 ng/ml) and IL-1 alpha generation was determined using ELISA. In these experiments IL-1ra completely abolished the generation of IL-1 alpha. These data suggest that hrIL-1ra exhibits a dose-response inhibition of lymphocyte blastogenesis induced by Con A, probably through the down-regulation of IL-1 synthesis necessary as an early signal for T-cell activation and IL-2 production.
Cells, Cultured↗
Inhibition of leukotriene B4 in neutrophils by lipoxins A4 and B4.
Lipoxins are derived from the oxygenation products of arachidonic acid in human leukocytes. They have exhibited selective biological effects different from those of other eicosanoids. We have examined the effect of lipoxin A4 and B4 (LXA4, LXB4) on the production of leukotriene B4 (LTB4) in human neutrophils. Cultured human polymorphonuclear leukocytes were preincubated with LXA and B and their ability to inhibit LTB4 generation was assessed after incubation with calcium ionophore A23187. We found that the pretreatment of neutrophils with lipoxins inhibit the release of LTB4 by A23187 stimulated PMNs. Our data suggests that LXA4 and B4 can contribute to immunosuppression in an inflammatory state via the inhibition of LTB4 synthesis.
Calcimycin↗
Reduced mitogen stimulation of DNA synthesis in human lymphocytes by a human recombinant interleukin-1 receptor antagonist.
The monokine interleukin-1 is produced by monocytes/macrophages after antigen/LPS stimulation and is an important early signal for the activation of resting T cells to become antigen specific T cells. However, little is known about the regulation and inhibition of IL-1. Recently, a new monokine has been described, generated by human macrophages, called interleukin-1 receptor antagonist (IL-1ra). This new monokine adheres to IL-1 in solution and blocks IL-1 receptor binding. IL-1ra is a glycoprotein structurally similar to IL-1 beta but having no interleukin-1-like activity. Using as a model mitogen (PHA 20 micrograms/ml)-stimulated lymphocyte DNA synthesis, we found that hrIL-1ra (30 min lymphocyte pretreatment) inhibits [3H]thymidine incorporation in a dose-dependent manner. This effect is most probably due to the inhibition of endogenous IL-1, which is a very important signal for T cell activation. The inhibition was maximum at the highest hrIL-1ra concentration used (250 ng/ml). However, when hrIL-1ra was added 2 h after PHA (20 micrograms/ml), a little, if any, inhibition of lymphocyte proliferation was found. The addition of hrIL-1ra simultaneously to the cell cultures with [3H]thymidine [( 3H]TdR) 6 h before the end of culture incubation did not significantly modify the results compared to the cells treated with PHA alone, indicating no interference of hrIL-1ra on [3H]TdR lymphocyte incorporation. We also found that the antibody anti-IL-1 beta inhibits mitogen stimulated lymphocyte DNA synthesis in dose-dependent concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)
DNA↗
Nocturnal bruxism and self reports of stress-related symptoms.
Of 511 undergraduates responding to a questionnaire, 96 identified themselves as bruxers and reported more symptoms of stress than the nonbruxers. Stress may contribute etiologically to bruxism.
Adult↗
Activation of human natural killer cells by lipopolysaccharide and generation of interleukin-1 alpha, beta, tumour necrosis factor and interleukin-6. Effect of IL-1 receptor antagonist.
The presence in the body of an antigen species or a bacterial lipopolysaccharide (LPS) has a pleiotropic effect on the immune system activating macrophages, lymphocytes and natural killer (NK) cells. Recently it has been reported that human macrophages not only secrete interleukin-1 (IL-1) but also its inhibitor, called IL-1 receptor antagonist (IL-1ra), structurally similar to IL-1 beta, but with no IL-1-like activity and which binds to the IL-1 receptor. In this study we show that LPS stimulates NK cell activity and IL-1ra potentiates the stimulatory effect of human recombinant interleukin-2 (hrIL-2) on NK cell activity. In addition, we found that hrIL-1ra inhibits DNA synthesis in lymphocyte culture stimulated with phytohaemagglutinin (PHA) (20 micrograms/ml), presumably via IL-1 inhibition. We also found that LPS is a potent stimulator of monokines: IL-6, tumour necrosis factor-alpha (TNF-alpha), and IL-1 beta, as determined by radioimmunoassay method, and interferon-gamma (IFN-gamma), IL-2, TNF-alpha and IL-1 alpha, as determined by ELISA method, in peripheral blood mononuclear cells (PBMC). We used PBMC as effector cells since LPS requires the presence of accessory cells to activate lymphocytes and bind to the HLA-DR molecule on accessory cells. The effect of LPS on PBMC cytotoxicity has been compared with an endotoxin-free extract of Escherichia coli, OM-8990, which did not provoke cytokine production nor did it cause enhancement of NK cell activity. We found that human recombinant IL-1ra potentiates the stimulatory effect of IL-2 on NK cell activity, similar to hrIL-1 beta. The potentiation of IL-2 in stimulating NK cell activity by IL-1ra is not yet understood. Since IL-1ra is a part of the IL-1 family, it may work in a similar fashion to IL-1, which also potentiates IL-2 to enhance NK cell activity but has been shown not to be directly important in tumour cell killing. In addition, hrIL-1ra can amplify the effect of IL-2 on NK activity, possibly by inhibiting the cyclo-oxygenase products, which are immunosuppressive and are generated in antigen-stimulated PBMC cultures. The generation of IFN-gamma by PBMC after treatment with LPS strongly suggests that the enhancement of NK cell activity may be indirectly due to IFN production.
Cytotoxicity, Immunologic↗
Interleukin-1 (IL-1) and interleukin-1 receptor antagonist (IL-1ra).
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Animals↗
Lipoxins increase granuloma formation induced by potassium permanganate in vivo.
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Animals↗
Lipoxins A4 and B4 inhibit leukotriene B4 generation from human neutrophil leukocyte suspensions.
Lipoxins A4 and B4 (5,6,15L-trihydroxy-7,9,11,13-eicosatetraenoic and 5D,14,15-trihydroxy-6,8,10,12-eicosatetraenoic acids, respectively) were examined in several biological systems and have proven to have many different activities from those of other eicosanoids. Cultured human polymorphonuclear leukocytes were preincubated with LXA and B and their ability to inhibit leukotriene B4 generation was assessed after incubation with the calcium ionophore A23187. The preincubation time of neutrophils with lipoxin A4 and B4 was 15 min. After that time the cells were incubated for 6 min with A23187 (5 microM) for the release of LTB4. We found that the pretreatment of neutrophils with lipoxins inhibited the release of LTB4 by A23187-stimulated PMNs. Nordihydroguaiaretic acid (NDGA) (10 microM), used as a control, strongly inhibited the generation of LTB4. Since LTB4 has been shown to be a modulator of cellular immunity, our data suggest that lipoxin A4 and B4 can contribute to the immunosuppression via inhibition of LTB4 generation. Moreover, the inhibition of LTB4 by lipoxins in neutrophils could have an important regulatory role in inflammation.
Calcimycin↗
Leukocyte inhibitory factor activates human neutrophils and macrophages to release leukotriene B4 and thromboxanes.
Recent evidence has proved that cytokines can stimulate the production of 5-lipoxygenase products. Leukotriene B4 (LTB4) is a major mediator of leukocyte activation in acute inflammatory reactions, which produce chemotaxis, lysosomal enzyme release, and cell aggregation. Leukocyte inhibitory factor (LIF) also causes biological responses related to inflammation, i.e., LIF directly induces specific granule secretion by polymorphonuclears (PMNs) and potentiates many formyl-methionyl-leucyl-phenylalanine (FMLPs) mediated responses. Since arachidonic acid products are important mediators of inflammation, we have studied the effects of LIF on the arachidonic acid cascade products LTB4 and thromboxane A2 (TxA2). Resuspended at a final concentration of greater than 95% polymorphonuclear PMNs were isolated and tested with some cytokines on the release of LTB4 and TxA2. Peripheral blood mononuclear cells were isolated and seeded in Petri dishes and incubated for 60 min. Adherent macrophages were used for the cytokine stimulation study. Both types of leukocytes were treated with LIF, interleukin 6 (IL 6), and granulocyte-monocyte colony stimulating factor (GM-CSF) at different concentrations, and test agents A23187 and FMLP. Radioimmunoassay for LTB4 and TxB2 was determined by the resulting supernatants. Treatment of PMNs and macrophages with LIF at different concentrations proved to generate significant increases in LTB4 and TxA2 production. This was compared with IL 6 and GM-CSF, which had no effects. In these experiments, TxA2 generations could not be attributed to platelet contamination of PMN suspensions. The quantity of platelet contamination was not sufficient to influence how much TxB2 was produced. The similarities of LIF to other arachidonate stimulating cytokines suggest a similar mode of action in producing hematologic changes typical of tissue injury.(ABSTRACT TRUNCATED AT 250 WORDS)
Calcimycin↗