Modulation of mediator release from human basophils and pulmonary mast cells and macrophages by auranofin

Auranofin, a new orally absorbable gold compound, inhibits IgE-(anti-IgE) and non-IgE-mediated (f-met-peptide and the Ca2+ ionophore A23187) histamine release from human basophils. Auranofin inhibits the release of histamine induced by phorbol myristate (TPA) and bryostatin 1 both in the presence and absence of extracellular Ca2+. Increasing the Ca2+ concentrations in the extracellular medium does not reduce the inhibitory effect of auranofin on anti-IgE- or A23187-induced secretion. Auranofin inhibits the de novo synthesis of sulfidopeptide leukotriene C4 (LTC4) induced by anti-IgE from basophils and mast cells purified from human lung. However, in both systems auranofin has a significantly greater inhibitory effect on LTC4 release than on histamine secretion. Finally, auranofin induces a concentration-dependent inhibition of A23187-induced leukotrine B4 (LTB4) release from purified human lung macrophages. These data suggest that auranofin modulates the release of preformed (histamine) and de novo synthesized (LTC4 and LTB4) chemical mediators from human inflammatory cells isolated from peripheral blood and human lung tissues.     

Differential inhibition of histamine release from mast cells by protein kinase C inhibitors: staurosporine and K-252a.

Pretreatment of rat peritoneal mast cells with either staurosporine or an analog K-252a [(8R*,9S*,11S*)-(-)-9-hydroxyl-9-methoxycarbonyl-8-methyl-2,3, 9,10-tetrahydro-8,11-epoxy-1H,8H,11H-2,7b,11-atrizadibenzo- [a,g]cycloocta[cde]trinden-1-one] led to a concentration-related inhibition of histamine release when the cells were stimulated with anti-IgE (IC50: staurosporine = 110 nM; K-252a = 100 nM). In contrast, the two protein kinase C (PKC) inhibitors (1-1000 nM) partially (less than 15%) inhibited histamine release induced by compound 48/80 (0.5 to 1 micrograms/mL). Furthermore, prostaglandin E2 (PGE2) synthesis mediated by anti-IgE from rat peritoneal mast cells was also inhibited by staurosporine and K-252a (IC50 = 100 nM). Exposure of anti-arsenate IgE (anti-Ars-IgE) sensitized mouse bone marrow derived mast cells to arsenate-bovine serum albumin (Ars-BSA) led to the release of both histamine (510 +/- 12.6 ng/10(6) cells) and immunoreactive leukotriene C4 (LTC4) (27.0 +/- 2.6 ng/10(6) cells). Both histamine and LTC4 release was inhibited by staurosporine and K-252a with an IC50 of 50 nM for both compounds. We also characterized a 45K molecular weight protein which is phosphorylated by PKC after Ars-BSA or phorbol, 12-myristate, 13-acetate (PMA) stimulation. This protein is phosphorylated in a broken cell preparation in which PKC is activated by phosphatidylserine/Diolein and Ca2+. Peptide mapping by V8 protease of the phosphorylated 45K protein revealed that the 45K protein phosphorylation patterns induced by IgE or PMA or in the broken cell preparation are identical. Pretreatment of 32P-labeled mouse bone marrow derived mast cells with either staurosporine or K-252a led to a concentration-related inhibition of 45K protein phosphorylation induced by PMA or Ars-BSA. This inhibition of protein phosphorylation correlated well with the inhibition of histamine and leukotriene release in bone marrow derived mast cells.     

The effects of phosphodiesterase type 4 inhibitors on tumour necrosis factor-alpha and leukotriene B4 in a novel human whole blood assay

1. The aim of this study was to assess the inhibitory activities of phosphodiesterase type 4 (PDE4) inhibitors on tumour necrosis factor-alpha (TNF-alpha) and leukotriene B4 (LTB4) production in a novel human whole blood assay. 2. Lipopolysaccharide (LPS) stimulation of human whole blood caused a time dependent increase in TNF-alpha and prostaglandin E2 (PGE2) plasma levels. Inhibition of LPS-induced TNF-alpha by the selective PDE4 inhibitor RP73401 was proportionally enhanced with endogenous PGE2 (maximal after 24 h). In contrast, blocking endogenous PGE2 production with indomethacin in blood stimulated with LPS for 24 h decreased the potency of RP73401 to that observed with a 4 h LPS incubation. 3. Non-selective and selective PDE4 inhibitors showed greater inhibition of LPS-induced TNF-alpha after 24 h compared to 4 h. Stereoselectivity was only achieved in the 24 h method. 4. LPS-stimulation of whole blood for either 30 min or 24 h followed by N-formyl-Met-Leu-Phe (fMLP) activation resulted in low plasma LTB4 levels. Combination of both treatments resulted in a greater than 7 fold increase in plasma LTB4 levels. Inhibition of the double LPS and fMLP-activated LTB4 production was observed with non-selective and PDE4-selective inhibitors. Their LTB4 inhibitory potencies were similar to that observed in the 24 h LPS-induced TNF-alpha assay. Thus, stimulation of human whole blood with two LPS stimulations followed by fMLP gives rise to both TNF-alpha and LTB4 and their inhibition by various compounds can be assessed in the same blood sample. 5. Calcium ionophore (A23187) stimulation of whole blood resulted in plasma LTB4 levels similar to the double LPS and fMLP method. Inhibition of A23187-induced LTB4 biosynthesis was also achieved by PDE4-selective inhibitors as well as the direct 5-lipoxygenase (5-LO) inhibitor L-739,010. 6. These results confirm the anti-inflammatory properties of PDE4 inhibitors. Thus, this novel human whole blood can be used to assess the biochemical efficacy of PDE4 inhibitors in human subjects.     

Stem cell factor: a hemopoietic cytokine with important targets in asthma

We review evidence that Stem Cell Factor (SCF) plays an important role in the pathophysiology of asthma. SCF is produced by a wide variety of cells present in asthmatic lung, including mast cells and eosinophils. Its receptor, c-kit, is broadly expressed on mature mast cells and eosinophils. SCF promotes recruitment of mast cell progenitors into tissues, as well as their local maturation and activation. It also promotes eosinophil survival, maturation and functional activation. SCF enhances IgE-dependent release of mediators from mast cells, including histamine, leukotrienes, cytokines (TNF-alpha, IL-5, GM-CSF) and chemokines (RANTES/CCL5, MCP-1/CCL2, TARC/CCL17 e MDC/CCL22); it is required for IL-4 production in mast cells. SCF, acting in concert with IgE, also upregulates the expression and function of CC chemokine receptors in mast cells. Structural and resident airway cells express increased levels of SCF in the bronchus of asthmatic patients. In a murine model of asthma, allergen exposure increased production of SCF by epithelial cells and alveolar macrophages, which was transient and paralleled by histamine release. SCF induced long-lived airway hyperreactivity, which was prevented by local neutralization of SCF, as well as by inhibitors of the production or activity of cysteinyl-leukotrienes. Together, these observations suggest that SCF has an important role in asthma.     

Inhibition of histamine release from human granulocytes by ions of the rare earth elements lanthanum and cerium.

The influence of the ATPase inhibitors, lanthanum or cerium, on histamine release in basophils and mast cells was studied. Both compounds inhibited IgE- or A23187-induced histamine release. To exclude a general inhibition of calcium-dependent reactions in the cell, we tested the influence of these compounds on phagocytosis and superoxide production of neutrophil granulocytes. Phagocytosis of Candida albicans was inhibited partially, superoxide generation, measured by the INT test after stimulation with zymosan or aggregated gamma globulin, was not affected. Because of the inhibitory effect of lanthanum or cerium compounds on membrane ATPase and immunological function of epidermal Langerhans cells we propose that these compounds may be used in the treatment of atopic eczema, where both histamine-releasing mast cells and IgE-bearing Langerhans cell play a pathogenetically important role.     

Effects of phosphodiesterase inhibitors on interleukin-4 and interleukin-13 generation from human basophils

The aim of the present study was to determine whether inhibition of cyclic nucleotide phosphodiesterase (PDE) modulates the stimulated generation of the cytokines, interleukin-4 (IL-4) and IL-13, from human basophils. This was addressed by evaluating the effects of both nonselective and selective inhibitors of PDEs on the generation of cytokines from basophils. The nonselective PDE inhibitors, isobutyl-methylxanthine (IBMX) and theophylline, attenuated the IgE-mediated generation of IL-4 and IL-13 and, also, the release of histamine from basophils. The effects of the isoform-selective inhibitors, 8-methoxymethyl-IBMX (PDE 1 inhibitor), siguazodan (PDE3 inhibitor), rolipram (PDE4 inhibitor), denbufylline (PDE4 inhibitor), Org 30029 (mixed PDE3 and 4 inhibitor) and zaprinast (PDE5 inhibitor), were studied. Of these selective compounds, only rolipram, denbufylline and Org 30029 inhibited the IgE-dependent generation of IL-4, IL-13 and histamine from basophils to a statistically significant (P<0.05) degree. The effects of isoform-selective inhibitors on basophils activated by IL-3 were evaluated. The IL-3-induced generation of IL-4, IL-13 and histamine was inhibited to a statistically significant (P<0.05) extent, only by compounds that act as inhibitors of PDE4. These data suggest that inhibition of PDE4 can regulate the generation of cytokines from human basophils.     

Inhibition of IgE-mediated release of histamine and peptide leukotriene from human basophils and mast cells by forskolin

Forskolin, a diterpene compound isolated from the roots of Coleus forskohlii, activates adenylate cyclase in membranes from a variety of mammalian tissues. We found that forskolin (10(-7) to 3 X 10(-5) M) caused a concentration-related inhibition of IgE-mediated release of histamine and peptide leukotriene C4 (LTC4) from human basophils and lung mast cells. There was a significant linear correlation between the per cent inhibition of histamine and LTC4 release from both cell types. However, in both systems forskolin exerted a significantly greater inhibitory effect on LTC4 release than on histamine release. The concentration-response inhibition curve was paralleled by a forskolin-induced rise in cAMP levels in human leukocyte and mast cell preparations. The relationship between the effect of forskolin and the cAMP concentration was supported by the finding that forskolin inhibited the "first stage" of antigen-induced histamine release, but not the release caused by the Ca2+ ionophore, A23187. Propranolol, a competitive beta-receptor antagonist, did not block the inhibition of mediator release or the cAMP accumulation caused by forskolin. These data suggest that forskolin modulates the release of mediators of immediate hypersensitivity reactions via the activation of adenylate cyclase in human basophils and mast cells.     

Role of PDE4 in superoxide anion generation through p44/42MAPK regulation: a cAMP and a PKA-independent mechanism

We investigated the generation of reactive oxygen species (ROS) from bronchoalveolar lavage (BAL) cells of either control or LPS-exposed rats and the effects of PDE4 inhibitors on ROS production. The PDE4 inhibitors, rolipram and Ariflo (cilomilast, SB 207499) dose-dependently (0.1-10 microm) inhibited fMLP-induced superoxide anion (O(2)(*-)) production (IC(50)s: 0.03 and 0.55 microm, respectively) in BAL cells of Wistar rats collected 3 h after an LPS-aerosol (200 micrograms ml(-1), 1 h). These BAL contained 85-95% neutrophils (BAL cells enriched in neutrophils). In contrast, BAL cells collected at the end of the challenge contained only macrophages and in these conditions, rolipram and Ariflo (0.1-10 microm) could only inhibit 25 and 45% of fMLP-induced O(2)(*-) release, respectively. We also observed that the inhibition of p44/42(MAPK) by PD98059 (1-10 microm) increased O(2)(*-) release by BAL cells enriched in neutrophils, but not by macrophages, and prevented the inhibition of O(2)(*-) production induced by PDE4 inhibitors. Western blot analysis showed that PDE4 inhibitors strongly activated p44/42(MAPK) in BAL cells enriched in neutrophils but not in macrophages. And in these cells, PDE4 and p44/42(MAPK) were co-immunoprecipitated by a polyclonal anti-PDE4 antibody. The following cell permeable-cAMP analogues, dbcAMP (10 microm-1 mm), 8-CPT-cAMP (1 mm) and 8-pMeOPT-2'-O-Me-cAMP (0.5 mm), could not reduce fMLP-induced O(2)(*-) production and both PKA inhibitors, PKA inhibitor 14-22 amide myristoylated (50 nm-1 microm) and H-89 (100 nm-1 microm), did not affect the decrease of O(2)(*-) release induced by PDE4 inhibitors in BAL cells enriched in neutrophils. These data suggest that PDE4 inhibitors decreased fMLP-induced O(2)(*-) release in BAL cells enriched in neutrophils but not in macrophages, through p44/42(MAPK) activation by a cAMP- and a PKA-independent mechanism.     

Phosphodiesterase inhibitors in airways disease

Phosphodiesterases hydrolyse intracellular cyclic nucleotides, cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) into inactive 5' monophosphates, and exist as 11 families. They are found in a variety of inflammatory and structural cells. Inhibitors of PDEs allow the elevation of cAMP and cGMP which lead to a variety of cellular effects including airway smooth muscle relaxation and inhibition of cellular inflammation or of immune responses. PDE4 inhibitors specifically prevent the hydrolysis of cAMP, and PDE4 isozymes are present in inflammatory cells. Selective PDE4 inhibitors have broad spectrum anti-inflammatory effects such as inhibition of cell trafficking, cytokine and chemokine release from inflammatory cells, such as neutrophils, eosinophils, macrophages and T cells. The second generation PDE4 inhibitors, cilomilast and roflumilast, have reached clinical trial stage and have some demonstrable beneficial effects in asthma and chronic obstructive pulmonary disease (COPD). The effectiveness of these PDE4 inhibitors may be limited by their clinical potency using doses that have minimal effects on nausea and vomiting. Topical administration of PDE4 inhibitors may provide a wider effective to side-effect profile. Development of inhibitors of other PDE classes, combined with PDE4 inhibition, may be another way forward. PDE5 is an inactivator of cGMP and may have beneficial effects on hypoxic pulmonary hypertension and vascular remodelling. PDE3 and PDE7 are other cAMP specific inactivators of cAMP. PDE7 is involved in T cell activation and a dual PDE4-PDE7 inhibitor may be more effective in asthma and COPD. A dual PDE3-PDE4 compound may provide more bronchodilator and bronchoprotective effect in addition to the beneficial PDE4 effects.     

Effect of interleukin 3 on the differentiation and histamine content of cultured bone marrow mast cells.

Mouse bone marrow hematopoietic stem cells were isolated from mouse femur bone and cultured in RPMI 1640 supplemented medium with 20 units/ml of the purified T-cell lymphokine, interleukin 3 (IL-3), IL-3 was uniquely able to induce the proliferation and differentiation of mature mast cells in vitro. The sparse granulation of the bone marrow-derived mast cells (BMMC) can be seen by day 5, progressing to definable mast cells by day 7, the mast cells appear morphologically mature and comprise a 96% pure population after 14 days of the culture. The monocytes macrophages, eosinophils and neutrophils disappeared by day 9. After 4 weeks of tissue culture, mast cells are fully mature and completely granulated at 98% cell purity. The BMMC are mononuclear, oval or round in shape and appear smaller than rat peritoneal mast cells. BMMC are stable over 3-5 months in conditioned medium. The homogeneous mast cell population possesses membrane receptors and mediators, such as histamine in their metachromatic granules. The histamine content of BMMC in culture between 2 to 4 weeks rose from 1.43 to 1.82 pg/cell. Moreover, the percentage of histamine release caused by 0.1 microM and 1.0 microM ionophore A23187 was 15% and 35%, respectively. By contrast, the histamine releasing activity of 0.01% and 0.001% compound 48/80 were 12 +/- 2% and 59 +/- 7% respectively. The granular density, histamine content and histamine release activity of BMMC are different from that of peritoneal mast cells.     

Inhibition of histamine release from dispersed human lung and tonsillar mast cells by nicardipine and nifedipine

Calcium entry blocking drugs attenuate antigen-induced bronchoconstriction in asthma which is mast cell mediated. We have investigated the effects of two calcium uptake blockers, nicardipine and nifedipine on histamine secretion from human mast cells dispersed from lung and tonsillar tissue. Mast cells were activated for secretion with anti-human IgE or calcium ionophore, A23187. Nicardipine and nifedipine caused a concentration-related inhibition of IgE-dependent histamine release from both lung (IC30 10 microM and 4.4 microM) and tonsillar (IC30 21 microM and 47 microM) mast cells. Nicardipine and nifedipine also inhibited mast cell histamine release induced by A23187 with IC30 values of 14 microM and 67 microM for lung and 15 microM and 30 microM for tonsillar mast cells. In the absence of drugs, increasing the extracellular calcium concentrations from 0.2 to 5 mM caused a concentration related increase in IgE-dependent histamine release from tonsillar mast cells. Both nicardipine and nifedipine (50 microM) displaced the concentration-effect curve to the right. Nicardipine (0.01-100 microM) caused a concentration related inhibition of rat kidney histamine methyltransferase activity used in the radioenzymatic assay of histamine (ki of 7.5-12 microM) whereas nifedipine was only a weak inhibitor. Nicardipine also interfered with the spectrofluorimetric assay after exposure to ultraviolet light. These observations demonstrate that nicardipine and nifedipine inhibit IgE-dependent and ionophore stimulated mediator secretion from human mast cells. The lack of stimulus-related specificity and the high drug concentrations required suggest that classical calcium channel blockade is not responsible for inhibition of mast cell mediator release. Furthermore, we suggest that inhibition of mast cell mediator release is unlikely to be the mechanism by which these drugs alleviate asthma.     

Substance P-induced histamine release from rat peritoneal mast cells and its inhibition by antiallergic agents and calmodulin inhibitors.

Substance P-induced histamine release and Ca2+ release from the intracellular Ca store of rat peritoneal mast cells were inhibited by both antiallergic drugs and microtubule inhibiting agents. It was found that in the case of antiallergic compounds, histamine release inhibition may be intimately related to the inhibition of Ca2+ release from the intracellular store in which the microtubules play an important role. When mast cells were pretreated with either theophylline or dibutyryl cAMP, the inhibition of histamine release was closely related to the inhibition of Ca2+ release from the intracellular Ca store. Calmodulin inhibitors were also effective in inhibiting histamine release from mast cells induced by substance P. The inhibitory potencies of calmodulin inhibitors on histamine release from mast cells were closely correlated with those exerted on calmodulin activity.     

Nedocromil sodium inhibits the A23187- and opsonized zymosan-induced leukotriene formation by human eosinophils but not by human neutrophils

1. Inflammatory cells such as eosinophils and neutrophils are thought to contribute actively to the pathogenesis of asthma by the release of bronchoconstrictor mediators including leukotrienes. Previous studies have revealed the almost exclusive synthesis of leukotriene C4 (LTC4) by human eosinophils and of leukotriene B4 (LTB4), 20-OH-LTB4 and the non-enzymatically formed LTB4-isomers by neutrophils when stimulated in vitro with the calcium ionophore A23187 or opsonized zymosan (OZ). In this study we have investigated whether nedocromil sodium, a new anti-asthma drug, was capable of inhibiting A23187- and OZ-induced leukotriene formation by these cells. 2. Nedocromil sodium inhibited A23187- and OZ-induced LTC4 formation by eosinophils in a concentration-dependent manner (mean IC30 for A23187: 5.6 X 10(-5) M; mean IC30 for OZ: 6.3 X 10(-5) M), whereas it did not inhibit A23187- and OZ-induced LTB4 formation by neutrophils. 3. Extension of the preincubation time of the cells with the drug did not alter the observed inhibitory capacity. The optimal preincubation time was 5 min. 4. The in vitro inhibition of LTC4 formation by eosinophils by nedocromil sodium may be a valuable property of this drug in the treatment of asthma.     

Inhibitory effect of p38 mitogen-activated protein kinase inhibitors on cytokine release from human macrophages

BACKGROUND AND PURPOSE: Macrophages release cytokines that may contribute to pulmonary inflammation in conditions such as chronic obstructive pulmonary disease. Thus, inhibition of macrophage cytokine production may have therapeutic benefit. p38 MAPK may regulate cytokine production, therefore, the effect of two p38 MAPK inhibitors, SB239063 and SD-282, on the release of TNF-alpha, GM-CSF and IL-8 from human macrophages was investigated. EXPERIMENTAL APPROACH: Cytokine release was measured by ELISA. Immunoblots and mRNA expression studies were performed to confirm p38 MAPK isoform expression and activity. Macrophages were isolated from lung tissue of current smokers, ex-smokers and emphysema patients and exposed to lipopolysaccharide. These cells then released cytokines in a concentration-dependent manner. KEY RESULTS: SB239063 only inhibited TNF-alpha release (EC50 0.3 +/- 0.1 microM). Disease status had no effect on the efficacy of SB239063. SD-282 inhibited both TNF-alpha and GM-CSF release from macrophages (EC50 6.1 +/- 1.4 nM and 1.8 +/- 0.6 microM respectively) but had no effect on IL-8 release. In contrast, both inhibitors suppressed cytokine production in monocytes. CONCLUSIONS AND IMPLICATIONS: The differential effects of p38 MAPK inhibitors between macrophages and monocytes could not be explained by differences in p38 MAPK isoform expression or activity. However, the stability of TNF-alpha mRNA was significantly increased in macrophages compared to monocytes. These data suggest a differential involvement for p38 MAPK in macrophage cytokine production compared with monocytes. These effects are not due to lack of p38 activation or p38alpha expression in macrophages but may reflect differential effects on the stability of cytokine mRNA.     

The effect of cyclic AMP and cyclic GMP phosphodiesterase inhibitors on the superoxide burst of guinea-pig peritoneal macrophages.

1. The cyclic nucleotide phosphodiesterase (PDE) activity of guinea-pig peritoneal macrophages was partially characterized and the effects of selective and non-selective inhibitors of adenosine 3':5'-cyclic monophosphate (cyclic AMP PDE) and guanosine 3':5'-cyclic monophosphate (cyclic GMP PDE) phosphodiesterases on superoxide generation were investigated using peritoneal macrophages from horse-serum pretreated guinea-pigs. 2. The non-selective PDE inhibitor, 3-isobutyl-1-methylxanthine (IBMX) and the PDE I/V selective inhibitor, zaprinast, inhibited spontaneous superoxide generation with IC50s of 30.7 +/- 11.3 microM and 145 +/- 17 microM respectively (n = 6 and 5). The concentration-response curves for the PDE IV selective inhibitors rolipram and Ro20-1724 were biphasic; mean maximum inhibitions were 56.9 +/- 5.9% and 66.8 +/- 10.5% respectively at 300 microM, but in 2 out of 6 (rolipram) and 2 out of 5 (Ro20-1724) experiments inhibition was < 50%. The PDE III inhibitor SK&F 94120 was without effect. Spontaneous superoxide generation was reduced 57 +/- 10% by 1 microM prostaglandin E2 (PGE2) and 62.6 +/- 3.76% by 1 microM salbutamol. 3. The increase in superoxide generation elicited by FMLP (10(-9)-10(-5)M) was unaffected by any of the PDE inhibitors studied. Inhibition of FMLP-stimulated superoxide generation by PGE2 was enhanced in the presence of 10 microM IBMX. 4. Macrophages were found to contain a predominantly membrane bound cyclic AMP PDE (90% of total activity) which was unaffected by cyclic GMP or calcium/calmodulin. The cyclic AMP PDE activity in the cytosolic fraction was enhanced in the presence of calcium/calmodulin.(ABSTRACT TRUNCATED AT 250 WORDS)     

Inhibitory effects of glucocorticoids on rat eosinophil superoxide generation and chemotaxis

Eosinophil infiltration into inflammatory tissues and the subsequent release of inflammatory mediators are the hallmarks of several inflammatory allergic diseases. Although there have been a considerable number of publications on anti-inflammatory effects of glucocorticoids, little is known about whether glucocorticoids affect the activation of eosinophils directly. We studied the effects of three glucocorticoids, mometasone furoate, dexamethasone and beclomethasone dipropionate, on superoxide generation and the chemotaxis of rat eosinophils. Highly purified rat eosinophils were treated for 6 h with mometasone furoate, dexamethasone or beclomethasone dipropionate. Eosinophils were stimulated with phorbol myristate acetate (PMA) for superoxide generation, while for induction of chemotaxis, platelet-activating factor (PAF) or leukotriene B(4) (LTB(4)) was used. None of the glucocorticoids used in the present study caused significant suppressive effects on superoxide generation induced by PMA. On the other hand, both PAF- and LTB(4)-induced migration of rat eosinophils were inhibited in a concentration-dependent manner by glucocorticoids. Mometasone furoate showed a significant effect at concentrations higher than 10(-11) M. Dexamethasone and beclomethasone dipropionate also caused a significant inhibition at concentrations higher than 10(-8) and 10(-7) M, respectively. These results indicated that the anti-inflammatory effects of glucocorticoids were mediated by direct inhibition of eosinophil migration. Furthermore, mometasone furoate was suggested to be more useful than the other drugs in the treatment of allergic diseases responsible for eosinophil chemotaxis.     

Differential regulation of human eosinophil, macrophage, and neutrophil functions by the allergic mediator release inhibitor CI-959.

The cell activation inhibitor CI-959 [5-methoxy-3-(1-methyl-ethoxy)-N-1H- tetrazol-5-ylbenzo[b]thiophene-2-carboxamide, monosodium salt] was evaluated for its effect on the activation of human eosinophils, macrophages, and neutrophils by the phagocytic stimulus serum-opsonized zymosan (SOZ). CI-959 inhibited the respiratory burst of eosinophils and neutrophils, measured as the generation of superoxide anion, with IC50s of 9.6 and 14.5 microM, respectively. In contrast, 100 microM CI-959 inhibited superoxide anion generation by human macrophages by only 22.7%. The compound exhibited a different inhibition profile for lysosomal enzyme release from these cells. At 100 microM, CI-959 inhibited the release of eosinophil peroxidase and macrophage N-acetyl-beta-D-glucosaminidase by only 19.5 and 25.6%, respectively. In contrast, CI-959 inhibited the release of the neutrophil primary granule enzyme myeloperoxidase with an IC50 of 7.5 microM, while inhibiting release of lysozyme from secondary granules by only 11.4% at 100 microM. These results demonstrate that oxygen radical generation and lysosomal enzyme release by human leukocyte populations are differentially regulated by CI-959.     

Histamine inhibits chemotaxis, phagocytosis, superoxide anion production, and the production of TNFalpha and IL-12 by macrophages via H2-receptors

Histamine is released from stimulated basophils and mast cells, and plays an important role in the pathogenesis of allergic inflammatory processes. In vitro treatment of macrophages with histamine resulted in inhibition of chemotaxis. Moreover, histamine at l0(-5) M markedly inhibited the production of superoxide anions by both opsonized zymosan-A and phorbol 12-myristate 13-acetate (PMA) stimulated macrophages and histamine at a concentration range of 10(-7) to 10(-5) M significantly inhibited phagocytosis of Escherichia coli by macrophages. In addition, H2-selective receptor agonist dimaprit resulted in inhibition of macrophage chemotaxis and markedly inhibited the production of superoxide anion by PMA-stimulated macrophages and phagocytosis of E. coli by macrophages. On the other hand, histamine and dimaprit both resulted in a concentration-dependent inhibition of lipopolysaccharide-induced production of TNFalpha and IL-12 by macrophages. These results suggest that histamine and dimaprit may inhibit chemotaxis, phagocytosis, superoxide anion production, and the production of TNFalpha and IL-12 by macrophages via H2-histamine receptors. reserved.     

Histamine release from rat mast cells induced by metabolic activation of polyunsaturated fatty acids into free radicals.

Polyunsaturated fatty acids (PUFA: arachidonic and linoleic acid) release histamine from isolated purified rat serosal mast cells only in the presence of oxidizing systems such as phenobarbital-induced rat liver microsomes, prostaglandin-H-synthetase (PHS) or soybean lipoxygenase. The release of mast cell histamine by activated PUFA has a long time-course and the electron microscopical features are consistent with an exocytotic secretion in the case of arachidonic acid and cell lysis in the case of linoleic acid. The phenomenon is associated with a significant increase in malonyldialdehyde (MDA) and conjugated diene generation, suggesting a relationship between histamine release and membrane lipid peroxidation. The secretion of histamine was inhibited by anti-free radical interventions such as D-mannitol, reduced glutathione and alpha-tocopherol. Some cyclooxygenase and lipoxygenase inhibitors, cimetidine and carnitine derivatives, are differentially active in the inhibition of mast cell histamine release by activated arachidonic acid. These results suggest that free radical derivatives of PUFA, generated by metabolic activation, trigger mast cell histamine release.