Nathalie Paul-Eugène

CD23 Regulates monocyte activation through a novel interaction with the adhesion molecules CD11b-CD18 and CD11c-CD18

CD23 is expressed on a variety of haemopoietic cells and displays pleiotropic activities in vitro. We report that in addition to CD21 and IgE, CD23 interacts specifically with the CD11b and CD11c, the alpha chains of the beta 2 integrin adhesion molecule complexes CD11b-CD18 and CD11c-CD18, on monocytes. Full-length recombinant CD23 incorporated into fluorescent liposomes was shown to bind to COS cells transfected with cDNA encoding either CD11b-CD18 or CD11c-CD18 but not with CD11a-CD18. The interaction was specifically inhibited by anti-CD11b or anti-CD11c, respectively, and by anti-CD23 MAbs. The functional significance of this ligand pairing was demonstrated by triggering CD11b and CD11c on monocytes with either recombinant CD23 or anti-CD11b and anti-CD11c MAbs to cause a marked increase in nitrite-oxidative products and pro-inflammatory cytokines (IL-1 beta, IL-6, and TNF alpha). These CD23-mediated activities were decreased by Fab fragments of MAbs to CD11b, CD11c, and CD23. These results demonstrate that CD11b and CD11c are receptors for CD23 and that this novel ligand pairing regulates important activities of monocytes.

Heterogeneous spontaneous and interleukin-4-induced nitric oxide production by human monocytes

The generation of nitric oxide by human monocytes has long been a subject of controversy because of the difficulty of rationalizing this production. In this work we evaluated the capacity of human monocytes to produce nitric oxide (NO) as measured by nitrite (NO2 ‐) release. Resting unstimulated monocytes (2 106 cells/ml) were found to produce significant amounts of NO2 ‐ after 8 to 12 days in culture. This production appeared to be highly heterogeneous. Indeed, approximatively, 75% of monocytes from the different donors produced up to 10 μM NO2 ‐ and were considered low producers; the last 25% produced higher amounts of NO2 ‐ (from 10 to 110 μM) and were considered high producers. In any case the spontaneous production of NO2 ‐ by monocytes was overcome in the presence of 1 mM Nω ‐monomethyl‐l‐arginine (LNMMA). This inhibitory effect was reversed in the presence of an excess of l‐arginine (5 mM), indicating that this process is effectively dependent on l‐arginine metabolism. Because interleukin‐4 (IL‐4) is considered an important NO‐regulatory cytokine, its regulatory effect on this spontaneous production of NO was also evaluated. In the presence of a defined dose of IL‐4 (1 to 100 ng/ml) the spontaneous production of the high‐producing population of monocytes was abrogated, whereas IL‐4 stimulated the production by the low‐producing population of monocytes, which was suppressed in the presence of LNMMA. The present data indicate that NO production by human monocytes is heterogeneous and that IL‐4 can be a potent inducer or inhibitor of this production, suggesting a variability in the activation state of these cells. J. Leukoc. Biol. 56: 15–20; 1994.

Ligation of CD23 activates soluble guanylate cyclase in human monocytes via an L-arginine-dependent mechanism.

Transduction through FcR2/CD23 was analyzed in normal human monocytes using immunoglobulin E (IgE)‐anti‐IgE immune complexes (IgE ICs) and monoclonal antibodies (mAbs) to CD23. Anti‐CD23 mAb and IgE IC triggered a time‐dependent increase in cGMP and cAMP in interleukin‐4–preincubated (CD23+) but not in unstimulated (CD23‐) monocytes. Maximal cGMP and cAMP accumulations were observed 10 and 20 min, respectively, after the onset of CD23 ligation. The increase in cGMP was inhibited with N ω‐monomethyl‐l‐arginine (L‐NMMA), which also partially affected cAMP accumulation. Addition of an anti‐CD23 mAb Fab fragment inhibited the IgE IC– and the anti‐CD23 mAb–induced cGMP and cAMP accumulation, confirming the engagement of CD23. In addition, IgE IC and anti‐CD23 mAb induced, at least in some donors, a production of nitrite that was inhibited in the presence of L‐NMMA. Taken together, these findings suggest a possible involvement of the nitric oxide synthase pathway in IgE IC–mediated activation of CD23+ monocytes. J. Leukoc. Biol. 57: 160–167; 1995.

Functional interaction between β2-adrenoceptor agonists and interleukin-4 in the regulation of CD23 expression and release and IgE production in human

Normal human peripheral blood mononuclear cells (PBMC) produced IgE when stimulated with IL-4. In the present report it was shown that beta 2-adrenoceptor agonists, salbutamol and fenoterol, potentiated the IL-4-induced IgE production without significantly affecting the expression of the low affinity receptor for IgE at the cell surface of monocytes and B lymphocytes. However, beta 2-adrenoceptor agonists were shown to enhance at day 7 the IL-4-induced release of the soluble form of CD23 (sCD23) by PBMC. This effect was specific since a beta-adrenoceptor antagonist, D,L-propranolol, inhibited the IL-4-induced IgE production by these cells. Alternatively, the beta 2-adrenoceptor agonists inhibited the production by these cells of interferon-gamma (IFN-gamma) but did not affect the production of IL-4 when stimulated with phytohemagglutinin A + a phorbol ester. These data suggest that beta 2-adrenoceptor agonists influence the IL-4-induced IgE production in humans by enhancing the release of sCD23 and inhibiting the production of endogenous IFN-gamma. In addition to the effect on the IL-4-induced IgE production it was shown that beta 2-adrenoceptor agonists potentiated the effect of IL-4 on a human promonocytic cell line, U 937, by enhancing CD23 expression and release and by inducing the differentiation of these cells into monocyte-like cells. Taken together, these data indicate that beta 2-adrenoceptor agonists potentiated the effect of IL-4 and that this functional interaction is different considering the cell-lineage and the stage of differentiation of these cells.

Modulation by interleukin-4 of cytokine release from mononuclear phagocytes in asthma

BACKGROUND Interleukin (IL)-4 is involved in IgE upregulation and downregulates cytokine release by mononuclear phagocytes. Mononuclear cells release greater amounts of IL-1, tumor necrosis factor-alpha, and IL-6 in patients with asthma than in control subjects, but the effect of IL-4 on cells from patients with asthma is unknown. The effects of IL-4 on the release of IL-1, tumor necrosis factor-alpha, and IL-6 by monocytes and alveolar macrophages were compared in 19 patients with asthma and 18 control subjects. METHODS The release of IL-1, tumor necrosis factor-alpha, and IL-6 from unstimulated and lipopolysaccharide stimulated monocytes and alveolar macrophages was measured by ELISA. The effect of 30 U of IL-4 on the release of these cytokines was studied. RESULTS Lipopolysaccharide-stimulated monocytes released significantly fewer cytokines in patients with asthma than in control subjects. IL-4 significantly inhibited cytokine release by monocytes of both groups. Unstimulated alveolar macrophages from patients with asthma released more cytokines than those of control subjects. Lipopolysaccharide induced a significantly greater increase in cytokine release in alveolar macrophages of control subjects in comparison with asthmatic subjects. IL-4 abolished the release of cytokines in alveolar macrophages from control subjects and had a minimal inhibitory effect on alveolar macrophages from patients with asthma. CONCLUSIONS Alveolar macrophages from patients with asthma are hyperreactive but less prone to lipopolysaccharide stimulation and IL-4-downregulation than those from normal subjects.

Beta 2-adrenoceptor agonists regulate the IL-4-induced phenotypical changes and IgE-dependent functions in normal human monocytes.

The β 2‐adrenoceptor agonists salbutamol and fenoterol were tested for their regulatory effects on human monocyte phenotype and functions, either alone or in combination with interleukin‐4 (IL‐4). These drugs enhanced in a dose‐dependent manner the IL‐4‐induced membrane and mRNA expression of the low‐affinity receptor for immunoglobulin E (IgE) (CD23), as well as the release of its soluble form, sCD23. Salbutamol and fenoterol alone elicited expression of the monomorphic β 2‐chain (CD18) of the leukocyte functional antigen (LEA1) family. This effect appeared to be restricted to CD11b (CR3) and CD11c (gp 150–95), because CD11a (LFA‐1α chain) was not modified, β 2‐Adrenoceptor stimulation was also found to potentiate the effect of IL‐4 on CD11b, CD11c, and CD18 expression. In contrast, these agents alone did not alter the level of major histocompatibility complex class II and CD14 antigens or modify their respective up‐ and down‐regulation by IL‐4. Ligation of CD23 on IL‐4‐preincubated (CD23*) monocytes with IgE/anti‐IgE immune complexes induced the release of free radicals nitric oxide and of the proinflammatory mediators IL‐6 and thromboxane B2 (TxB2). Addition of salbutamol, inactive alone, potentiated the generation of superoxide anion and of nitric oxide generation, as well as the production of IL‐6 and TxB2 triggered by CD23 ligation. These results indicate that β 2‐adrenoceptor stimulation potentiates in vitro the IL‐4‐induced phenotypical and functional changes on monocytes and suggest that such an interaction could occur in IgE‐dependent immune reactions. J. Leukoc. Biol. 55: 313–320; 1994.

Heterogenous nitrite production by IL-4-stimulated human monocytes and peripheral blood mononuclear cells

The capacity of human peripheral blood mononuclear cells and monocytes to generate nitrites, spontaneously or in response to Interleukin-4 was evaluated in vitro. Peripheral blood mononuclear cells and monocytes were found to release significant amounts of nitrites after 8 to 12 days in culture. This spontaneous production of nitrites was inhibited in the presence of 1 mM NG monomethyl-L-arginine, suggesting that this process was dependent upon the L-arginine metabolism. The present data also indicated that addition of Interleukin-4 generally resulted in an increased nitrite production, that was potentiated by IFN-gamma, inactive alone. The response of human monocytes to Interleukin-4 was more heterogenous than that observed with unfractionated peripheral blood mononuclear cells. These results suggest that cell/cell interactions could play an important role in the activation of the nitric oxide synthase pathway in human.

Pharmacological Modulation of the Antigen-Induced Expression of the Low-Affinity IgE Receptor (FcεRII/CD23) on Rat Alveolar Macrophages

Brown-Norway (BN) rats were sensitized by 3 aerosol exposures to ovalbumin (OA; 10 mg/ml) at days 1, 3 and 14. At day 21, the rats were challenged with the antigen or vehicle by aerosol. Alveolar macrophages (AM) were obtained by bronchoalveolar lavage and the expression of Fc epsilon RII/CD23 was assessed by flow cytometry after staining with the BB10 monoclonal antibody. A maximum of 74% of the AM from sensitized and challenged BN rats expressed FC epsilon RII/CD23 24 h after OA exposure, compared to 12% of the cells from rats exposed to vehicle. Sprague-Dawley rats were passively sensitized by intravenous injection of 0.1 or 0.05 ml/kg mouse ascitic fluid containing dinitrophenyl (DNP)-specific monoclonal IgE (2682-1) and after 24 h exposed to an aerosol of 5 mg/ml of DNP-bovine serum albumin for 30 min. In this case also, antigen exposure induced the expression of Fc epsilon RII/CD23 on 75% AM, compared to 17% AM from saline-challenged rats. Such an induction of Fc epsilon RII/CD23 on AM was, however, not observed when the animals were challenged with either histamine, serotonin or acetylcholine by aerosol. The antigen-induced expression of Fc epsilon RII/CD23 on AM was inhibited upon treatment of the rats with ketotifen or beclomethasone. In addition, oral or aerosol administration of respectively BN 50730 or BN 52021 (two structurally unrelated platelet-activating factor antagonists), inhibited the antigen-induced Fc epsilon RII/CD23 expression on AM, indicating the participation of this lipid mediator in this process.

Beta-2-Adrenoceptor Agonists Up-Regulate the in vitro FcEpsilon Receptor II/CD23 Expression on, and Release from, the Promonocytic Cell Line U937 and Human Blood Monocytes

The possible regulatory role of beta 2-adrenoceptor agonists in the modulation of CD23 on the human promonocytic cell line U937 and on human monocytes was investigated. Incubation for 48 h in the presence of interleukin-4 (IL-4; 30 U/ml) induced optimal expression and release of CD23 on both U937 cells and human monocytes. When a beta 2-adrenoceptor agonist, either salbutamol or fenoterol, was added to U937 cells or monocytes both the IL-4-induced CD23 expression and release were markedly up-regulated. This effect was dose-dependent, starting at 10 nM and reaching a maximum at 1 microM final concentration of either salbutamol or fenoterol. The potentiating effect of salbutamol and fenoterol on CD23 expression and release was not observed when a beta-adrenoceptor antagonist, either D,L-propranolol (1 microM) or butoxamine (1 microM), was added to the incubation medium. The alpha-adrenoceptor agonist norepinephrine (1 microM) was ineffective in enhancing the IL-4-induced expression and release of CD23 from U937 cells or human monocytes, demonstrating the specificity of the beta 2-adrenoceptor-mediated effect. In the absence of IL-4, a moderate but significant increase in the CD23 expression on U937 cells and human monocytes by these drugs was observed, as compared to the basal values. These results indicate that, besides their bronchodilator effect, beta 2-adrenoceptor agonists may regulate IgE-dependent processes.