Identification of an alveolar macrophage-derived activity in bronchial asthma that enhances leukotriene C4 generation by human eosinophils stimulated by ionophore A23187 as a granulocyte-macrophage colony-stimulating factor

Refractory asthma: mechanisms, targets, and therapy

Asthma is a common medical condition affecting 300 million people worldwide. Airway inflammation, smooth muscle bronchoconstriction leading to airflow obstruction, and mucous hypersecretion are clinical hallmarks of asthma. The NHLBI Expert Panel Report 3 recommends inhaled corticosteroids (ICS) for patients with moderate to severe persistent asthma. Inhaled corticosteroids (ICS) target gene transcription through their interactions with the glucocorticoid (GC) receptor (GR) at the glucocorticoid response element (GRE). The GC/GR complex enhances anti-inflammatory but inhibits pro-inflammatory mediator production. Classically, asthma has been described as a Th2-associated eosinophil-predominant disease, but recently alternative models have been described including a Th17-mediated neutrophil-predominant phenotype resulting in patients with more severe disease who may be less responsive to steroids. Additional mechanisms of steroid resistance include increased activity of GR phosphorylating kinases which modify the interactions of GR with transcription factors to inhibit the ability of GR to bind with GRE, leading to an increase in pro-inflammatory gene transcription. Oxidative stress also affects the balance between pro-inflammatory and anti-inflammatory gene transcription through the modification of transcription factors and cofactors (such as PI3K) leading to the inhibition of histone deacetylase 2. Continued investigations into the mechanisms behind glucocorticoid resistance will lead to novel treatments that improve control of severe refractory asthma.

Protein tyrosine kinase but not protein kinase C inhibition blocks receptor induced alveolar macrophage activation

The selective enzyme inhibitors genistein and Ro 31-8220 were used to assess the importance of protein tyrosine kinase (PTK) and protein kinase C (PKC), respectively, in N-formyl-methionyl-leucyl-phenylalanine (FMLP) induced generation of superoxide anion and thromboxane B₂ (TXB₂) in guinea-pig alveolar macrophages (AM). Genistein (3–100 μM) dose dependently inhibited FMLP (3 nM) induced superoxide generation in non-primed AM and TXB₂ release in non-primed or in lipopolysaccharide (LPS) (10 ng/ml) primed AM to a level > 80% but had litle effect up to 100 μM on phorbol myristate acetate (PMA) (10 nM) induced superoxide release. Ro 31-8220 inhibited PMA induced superoxide generation (IC₅₀ 0.21 ± 0.10 μM) but had no effect on or potentiated (at 3 and 10 μM) FMLP responses in non-primed AM. In contrast, when present during LPS priming as well as during FMLP challenge Ro 31-8220 (10 μM) inhibited primed TXB₂ release by > 80%. The results indicate that PTK activation is required for the generation of these inflammatory mediators by FMLP in AM. PKC activation appears to be required for LPS priming but not for transducing the FMLP signal; rather, PKC activation may modulate the signal by a negative feedback mechanism.

Prostaglandin cyclooxygenase products but not thromboxane A(2) are involved in the pathogenesis of ewthromelalgia in thrombocythaemia

Fluid of artificial blisters from erythromelalgic skin areas in primary thrombocythaemia contained a high amount of prostaglandin-E-like activity. Dazoxiben did not alleviate the erythromelalgia in patients with primary thrombocythaemia despite complete inhibition of platelet malondialdehyde and thromboxane B(2) synthesis and no inhibition of prostaglandin-E-like material. During a 10-day dazoxiben treatment period, persistent erythromelalgia was associated with a significant shortened mean platelet life span of 3.2 days. During subsequent treatment with low dose acetylsalicylic acid daily complete relief of erythromelalgia was associated with inhibition of platelet prostaglandin endoperoxide production and correction of platelet mean life span to normal, 7.9 days. These observations indicate that prostaglandin E(2), or another prostaglandin endoperoxide metabolite, is involved in the pathogenesisof erythromelalgia. The presented study does not give one single clue as to the origin (platelet, vessel wall or other) of the prostanoid, but very likely originates from platelets because a very low dose of acetylsalicylic acid (250 to 500 mg every other day), which irreversibly inhibits platelet cyclooxygenase, is highly effective in the prevention of erythromelalgia in thrombocythaemia.

Dendritic cells in allergic airway inflammation

Dendritic cells (DCs) are primary antigen-presenting cells involved in interactions with T cells leading to the proliferation of TH1 or TH2 cell types. In asthma, predominance of TH2 cells appears to be responsible for disease pathogenesis. Differentiation of TH2 cells is driven by a variety of factors such as the expression of high levels of costimulatory molecules, the cytokine profile, and the subset of DCs. Many inflammatory cells involved in the pathogenesis of asthma either directly or indirectly modulate DC function. Traditional treatments for asthma decrease the number of airway DCs in animals as well as in patients with asthma. Immunomodulators including interleukin (IL)-10, transforming growth factor (TGF)-beta, cytosine-phosphate-guanosine-containing oligodeoxynucleotides (CpG-ODN), 1alpha,25-dihydroxyvitamin D3, and fetal liver tyrosine kinase 3 ligand (Flt3L) are involved in the modulation of the function of DCs. Based on the critical review of the interaction between DCs and other inflammatory cells, we propose that activation of T cells by DCs and sensitization to inhaled allergen and resulting airway inflammation are dependent on plasmacytoid and myeloid subset of lung DCs to induce an immune response or tolerance and are tightly regulated by T-regulatory cells. Effects of various therapeutic agents to modulate the function of lung myeloid DCs have been discussed.

Gq signaling is required for allergen-induced pulmonary eosinophilia

The complexity and magnitude of interactions leading to the selective infiltration of eosinophils in response to inhaled allergens are formidable obstacles to a larger understanding of the pulmonary pathology associated with allergic asthma. This study uses knockout mice to demonstrate a novel function for the heterotrimeric G protein, G(q), in the regulation of pulmonary eosinophil recruitment. In the absence of G(q) signaling, eosinophils failed to accumulate in the lungs following allergen challenge. These studies demonstrate that the inhibition of eosinophil accumulation in the airways is attributed to the failure of hemopoietically derived cells to elaborate GM-CSF in the airways. The data suggest that activation of a G(q)-coupled receptor(s) on resident leukocytes in the lung elicits expression of GM-CSF, which, in turn, is required for allergen-induced pulmonary eosinophilia, identifying a novel pathway of eosinophil-associated effector functions leading to pulmonary pathology in diseases such as asthma.

Spontaneous expression of mRNA for IL-10, GM-CSF, TGF-beta, TGF-alpha, and IL-6 in peripheral blood mononuclear cells from atopic dermatitis

BACKGROUND

Monocytes and T helper cells play major roles in the immunologic dysfunction of atopic dermatitis (AD). There have been many studies on the cytokine pattern to evaluate abnormalities of immune cells in AD, but the results were conflicting and most of these previous reports were performed with various mitogen-stimulation.

OBJECTIVE

The purpose was to investigate de novo cytokine pattern in AD peripheral blood mononuclear cells (PBMC). We focused on the expression of cytokines that have effects on monocytes and T cells.

METHODS

We measured mRNA expression of IL-10, GM-CSF, TGF-beta, TNF-alpha, and IL-6 in freshly isolated PBMC with semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR). The intensity of cytokine cDNA were normalized to that of beta-actin product as a standard marker.

RESULTS

Interleukin-10 mRNA expression was significantly enhanced in AD compared with control subjects (P < .05). Spontaneous mRNA expression of TGF-beta and TNF-alpha was significantly lower in AD patients (P < .01). The level of GM-CSF mRNA expression was heterogenous and spontaneous mRNA expression was slightly increased in AD although the difference didn't reach the statistical significance. Interleukin-6 mRNA was not detected in most of AD and controls.

CONCLUSION

Our data could represent in vivo cytokine expression state associated with monocytes and other immune cells. Increased expression of IL-10 and GM-CSF may be associated with monocyte dysfunction in AD although increase in the expression of GM-CSF mRNA was not statistically significant. Inhibitory effect of increased IL-10 was suggested on decreased expression of TNF-alpha mRNA. The role of TGF-beta in AD remains to be seen.

New immunopharmacologic approaches to asthma: role of cytokine antagonism

This article involves an elucidation of the potential inflammatory mechanisms associated with the treatment of allergic disease and asthma, and the possibility of cytokine antagonism as a potential therapeutic mechanism for the treatment of those diseases. There is a review of the role of cytokines in the allergic process and a description of a number of studies done with the capacity of certain cytokine antagonists to develop potential amelioration of immune dysregulation in asthma and atopic states.

Regulation of major histocompatibility complex class II antigens on human alveolar macrophages by granulocyte-macrophage colony-stimulating factor in the presence of glucocorticoids

Alveolar macrophages (AM) present antigen poorly to CD4+ T cells and respond weakly to interferon-gamma (IFN-gamma) for up-regulation of major histocompatibility complex (MHC) class II and costimulatory molecule expression. In atopic asthma, however, AM exhibit enhanced antigen-presenting cell (APC) activity. Since granulocyte-macrophage colony-stimulating factor (GM-CSF) is increased in the airways of asthmatic patients, we have investigated its role in modulating the APC function of AM. The effects of glucocorticoids were also studied since earlier studies showed optimal induction of MHC antigens on monocytes by GM-CSF in their presence. GM-CSF in the presence, but not the absence, of dexamethasone enhanced the expression of HLA-DR, -DP and -DQ antigens by AM. However AM and monocytes differed in the optimal concentration of steroid required to mediate this effect (10-10 m and 10-7 m, respectively). Induction of MHC antigens was glucocorticoid specific and independent of IFN-gamma. These studies suggest the existence of an IFN-gamma-independent pathway of macrophage activation, which may be important in regulating APC function within the lung.

Decreased Leukotriene C4 Synthesis Accompanies Adherence-Dependent Nuclear Import of 5-Lipoxygenase in Human Blood Eosinophils

The enzyme 5-lipoxygenase (5-LO) catalyzes the synthesis of leukotrienes (LTs) from arachidonic acid (AA). Adherence or recruitment of polymorphonuclear neutrophils (PMN) induces nuclear import of 5-LO from the cytosol, which is associated with enhanced LTB4 synthesis upon subsequent cell stimulation. In this study, we asked whether adherence of human eosinophils (EOS) causes a similar redistribution of 5-LO and an increase in LTC4 synthesis. Purified blood EOS examined either in suspension or after adherence to fibronectin for 5 min contained only cytosolic 5-LO. Cell stimulation resulted in activation of 5-LO, as evidenced by its translocation to membranes and LTC4 synthesis. As with PMN, adherence of EOS to fibronectin for 120 min caused nuclear import of 5-LO. Unexpectedly, however, adherence also caused a time-dependent decrease in LTC4 synthesis: EOS adhered for 120 min produced 90% less LTC4 than did cells adhered for 5 min. Adherence did not diminish the release of [3H]AA from prelabeled EOS or reduce the synthesis of the prostanoids thromboxane and PGE2. Also, inhibition of LTC4 production caused by adherence could not be overcome by the addition of exogenous AA. Adherence increased, rather than decreased, LTC4 synthase activity. However, the stimulation of adherent EOS failed to induce translocation of 5-LO from the nucleoplasm to the nuclear envelope. This resistance to activation of the nuclear pool of 5-LO with diminished LT production represents a novel mode of regulation of the enzyme, distinct from the paradigm of up-regulated LT synthesis associated with intranuclear localization of 5-LO observed in PMN and other cell types.

Cultured human airway smooth muscle cells stimulated by interleukin-1beta enhance eosinophil survival

Airway smooth muscle may be an important cellular source of proinflammatory mediators and cytokines and may participate directly in airway inflammation. In this study we have examined whether airway smooth muscle cells could contribute to mechanisms of eosinophil accumulation by prolonging their survival. To investigate this possibility, conditioned medium from human airway smooth muscle cells stimulated with interleukin (IL)-1beta was examined on the in vitro survival of highly purified human peripheral blood eosinophils. After 7 d, when cultured in control medium, less than 1 +/- 0.2% of the initial eosinophil population remained viable. In contrast, culture in medium conditioned for 96 h by human airway smooth muscle cells stimulated with IL-1beta (1 pg-100 ng/ml) resulted in a concentration-dependent increase in eosinophil survival. (The concentration that produced 50% of this effect was 0.03 ng/ml IL-1beta.) Maximum eosinophil survival occurred at 1 to 3 ng/ml IL-1beta. This effect was also time-dependent and was readily detected in airway smooth muscle cell-conditioned medium after just 3 h of stimulation with IL-1beta (1 ng/ml). It continued to increase before reaching a plateau around 24 h, with no decrease in activity for up to 120 h of stimulation. Conditioned medium from unstimulated airway smooth muscle cells did not enhance eosinophil survival. The survival-enhancing activity was completely inhibited (the concentration that inhibited 50% [IC50] was 6.9 microg/ml) by a polyclonal goat antihuman antibody to granulocyte-macrophage colony stimulating factor (GM-CSF) (0.3-100 microg/ml), but antibodies (10-100 microg/ml) to IL-3 and IL-5, and a normal goat immunoglobulin G control had no effect on the eosinophil survival-enhancing activity. GM-CSF levels in culture medium from smooth muscle cells were markedly increased by IL-1beta and were maximum at 30 ng/ml (0.037 ng/ml/10(6) cells versus 3.561 ng/ml/10(6) cells, unstimulated versus 30 ng/ml IL-1beta). The IL-1 receptor antagonist inhibited both the production of GM-CSF (IC50 19. 1 ng/ml) and the eosinophil survival-enhancing (IC50 53.7 ng/ml) activity stimulated by IL-1beta. Release of GM-CSF elicited by IL-1beta was inhibited by dexamethasone but not by indomethacin. These data indicate that cultured human airway smooth muscle cells stimulated with IL-1beta support eosinophil survival through production of GM-CSF and thus may contribute to the local control of inflammatory cell accumulation in the airways.

Expression of interleukin-5 and granulocyte-macrophage colony-stimulating factor in aspirin-sensitive and non-aspirin-sensitive asthmatic airways

Increased numbers of eosinophils and mast cells in the bronchial mucosa are characteristic features in subjects with aspirin-sensitive asthma. Interleukin-5 (IL-5) and granulocyte-macrophage colony-stimulating factor (GM-CSF) are involved in the activation, maturation, and perpetuation of survival of eosinophils. Immunohistochemical techniques were therefore used to study the expression of IL-5 and GM-CSF on frozen bronchial biopsies from 13 aspirin-sensitive asthmatic (ASA) and 8 non-ASA (NASA) subjects. Aspirin sensitivity was diagnosed by lysine-aspirin inhalation provocation. ASA airways demonstrated a significant 2-fold increase in the total number of submucosal inflammatory cells expressing IL-5 (p = 0.03) and approximate 4- and 2-fold increases in the numbers of mast cells expressing IL-5 and GM-CSF (p = 0.02 and p = 0.04, respectively). There was also a 4-fold increase in the number of eosinophils expressing IL-5 (p = 0.004). These results suggest a central role for the mast cell and eosinophil in regulation of the inflammatory cell infiltrate of ASA airways by secretion of the hemopoietic cytokines IL-5 and GM-CSF.

GM-CSF increases the ability of cultured macrophages to support autologous CD4+ T-cell proliferation in response to Dermatophagoides pteronyssinus and PPD antigen

Previous studies have demonstrated an infiltration of monocytes and increased levels of granulocyte-macrophage colony-stimulating factor (GM-CSF) in the asthmatic lung. To study the possible effects of this cytokine upon the differentiation and function of these newly recruited monocytes, we have developed a model in which monocytes isolated from human peripheral blood were differentiated into macrophages in serum in the presence or absence of GM-CSF. After 7 days, the macrophages increased in size and granularity, had increased phagocytic activity, and expressed various adhesion molecules, CD14 and major histocompatibility complex (MHC) class II. The effects of GM-CSF on antigen presentation by cultured macrophages on the antigen-specific proliferative response of CD4+ T cells to Dermatophagoides pteronyssinus or purified protein derivative of tuberculin and the mitogen phytohaemagglutinin was determined. CD4+ T-cell proliferation was reduced when either antigen was presented by macrophages cultured in serum alone, compared with the values obtained with freshly isolated monocytes. However, CD4+ cell proliferation was comparable to that observed with monocytes when antigen was presented by macrophages which had been pre-cultured with 50 U/ml GM-CSF. CD4+ T-cell proliferation to phytohaemagglutinin was similar when all three populations were used as accessory cells. High numbers of macrophages partially suppressed CD4+ T-cell proliferation in response to antigen presented by monocytes, but there was no significant difference between macrophages cultured in the presence or absence of GM-CSF. This data suggests that GM-CSF directs monocyte differentiation into macrophages with an antigen-presenting, rather than a suppressive, phenotype. Elevated levels of GM-CSF in the asthmatic lung may therefore maintain recently recruited monocytes in an inflammatory and T-cell activating state.

Effect of interleukin-4 on allergen-induced arachidonic acid metabolism of rat peritoneal macrophages during immediate hypersensitivity reactions

The aim of this study was to investigate the [3H]arachidonic acid metabolism of rat peritoneal macrophages, induced by allergen (ovalbumin) and the impact of interleukin-4 on this process. We established that ovalbumin induces an increase of [3H]arachidonic acid mobilisation from membrane lipids and of [3H]arachidonic acid catabolism, principally by the 5-lipoxygenase pathway, when the macrophages are sensitized and when serum is present. The allergen effect is not modified by the presence of interleukin-4 in the culture medium of macrophages 15 h before the allergen challenge. We also showed that, whereas the basal [3H]arachidonic acid metabolism of macrophages from control and actively sensitized rats is not different, interleukin-4 increases the [3H]arachidonic acid mobilisation and catabolism by cyclooxygenase and 5-lipoxygenase pathways in macrophages from control rats although it does not in macrophages from actively sensitized rats. In macrophages from control rats, the interleukin-4 effect is diminished by the addition of IgEs to their culture medium. In summary, interleukin-4 has an enhancer effect on the macrophage arachidonic acid catabolism that depends on the sensitization condition of the cell but that has no consequences on the further increased arachidonic acid metabolism induced by the allergen.

TH2-type cytokines in asthma

TH2-type cytokines, particularly interleukin-5, together with granulocyte-macrophage colony-stimulating factor and interleukin-3, orchestrate the eosinophil response in asthma. Eosinophils are believed to be prime proinflammatory effector cells causing bronchial damage, which in turn, leads to chronic asthma symptoms. Although many cells may secrete cytokines (e.g., mast cells, epithelial cells, macrophages), all of which influence eosinophil differentiation, survival, and function, the TH2-type T cell is seen as having a central role since it is capable of direct antigen recognition. The putative "driving" antigen for asthmatic inflammation may be allergen, although other antigens (e.g., viral, epithelial) are also possible candidates. Although T cells also influence the synthesis of IgE, IgE-mediated mechanisms are seen as playing a secondary role only in atopic subjects, where they may be responsible for acute, short-lived symptoms superimposed on the chronic, on-going cell-mediated inflammatory disease.

Cyclic AMP-elevating agents prolong or inhibit eosinophil survival depending on prior exposure to GM-CSF

1. Purified human eosinophils survived for up to 7 days when cultured in vitro in the presence of 1 ng ml-1 granulocyte-macrophage colony stimulating factor (GM-CSF) with a viability of 73%. In the absence of GM-CSF, eosinophil viability decreased after one day in culture, and only 4% of cells were viable by day 4. 2. Culture of eosinophils with cholera toxin produced a concentration-dependent decrease in GM-CSF-induced survival at 7 days (IC50 = 7 ng ml-1) which was associated with a 6 fold increase in the intracellular cyclic AMP concentration. This inhibition of cell survival could be prevented by the addition of the protein kinase A inhibitor, H89 (10(-6)M). 3. When eosinophils were cultured with dibutyryl cyclic AMP, there was a concentration-dependent inhibition of GM-CSF-induced survival at 7 days with an IC50 of 200 microM. The related cyclic nucleotide analogue, dibutyryl cyclic GMP did not inhibit GM-CSF-induced eosinophil survival over the same concentration range. 4. Culture of eosinophils with forskolin, or with the phosphodiesterase inhibitors, rolipram and SK&F94120, had no effect on GM-CSF-induced eosinophil survival at any concentration examined. 5. After 7 days' culture in the absence of GM-CSF, fractionation of eosinophil DNA on agarose gels demonstrated a 'ladder' pattern characteristic of apoptosis. GM-CSF prevented DNA fragmentation and this protection could be overcome by both cholera toxin and dibutyryl cyclic AMP. 6. GM-CSF did not affect intracellular cyclic AMP concentrations in unstimulated eosinophils or in cells stimulated by cholera toxin. Thus, GM-CSF does not apparently increase eosinophil survival by affecting cyclic AMP levels. 7. In the absence of GM-CSF both cholera toxin and dibutyryl cyclic AMP decreased the rate of eosinophil death, when compared to cells cultured with medium alone. The t1/2 values for cell death were 1.63 +/- 0.3, 2.46 +/- 0.3 and 4.62 +/- 1.0 days for cells cultured in the presence of medium, cholera toxin and dibutyryl cyclic AMP respectively. 8. In conclusion, cyclic AMP exerts opposing effects on eosinophil survival depending on prior exposure of the cells to GM-CSF.

Blood eosinophils, eosinophil-derived proteins, and leukotriene C4 generation in relation to bronchial hyperreactivity in children with atopic dermatitis

To assess the relation among eosinophil-related variables in the peripheral blood, bronchial hyperreactivity, and the presence of atopic dermatitis in children aged 5-14 years, we studied 11 patients with atopic dermatitis alone, six with asthma and atopic dermatitis, 12 with asthma alone, and 12 healthy controls. Eosinophil counts, levels of eosinophil cationic protein, and the capacity of eosinophils to generate leukotriene (LT) C4, as well as bronchial hyperreactivity and a severity score for atopic dermatitis, were determined. Eosinophil variables were significantly higher in both patient groups with atopic dermatitis than in normal controls. In particular, ionophore A 23187 LTC4 generation was higher in patients with atopic dermatitis alone (median 82, range 25-273 ng/10(6) cells) and patients with combined asthma and atopic dermatitis (median 68, range 32-583 ng/10(6) cells) than in normal controls (median 9, range 1-67 ng/10(6) cells). However, there was no difference between the group of atopic dermatitis patients with asthma and without asthma. We conclude that eosinophil variables in the peripheral blood are mainly influenced by the presence of atopic dermatitis, and not the presence and the severity of asthma in patients with both asthma and atopic dermatitis.

The airway inflammatory response in allergic asthma and its relationship to clinical disease

Endobronchial biopsy and lavage studies have revealed the presence of mast cell, eosinophil, T-lymphocyte and epithelial cell activation in asthma, along with the structural changes of tissue eosinophil infiltration, loss of superficial columnar ciliated epithelial cells and enhanced collagen deposition in the laminar reticularis. As these cellular and structural changes underlie the clinical features of asthma, i.e., symptom expression, variable airflow obstruction and bronchial hyperresponsiveness, and understanding of their induction and regulation is essential to the understanding of the asthmatic process. The acute airway response to allergen has been studied by the technique of local endobronchial allergen challenge with direct airway sampling in asthma. These studies identify allergen-mast cell interaction as the initial airway event, with mediator release inducing bronchoconstriction and enhancing vascular permeability. As preformed cytokines are present in mast cells, cytokine release from this cell population is likely to initiate the process of endothelial cell activation, with upregulation of cell adhesion molecules, and tissue cell recruitment. Subsequent cytokine elaboration from airway macrophages and T-lymphocytes will perpetuate this response while in chronic clinical disease T-lymphocytes, mast cells, matrix tissue, epithelial cells and eosinophils themselves are all likely to contribute to the cytokine pool within the airways and thus to the regulation of inflammatory cell migration and activation.

Granulocyte macrophage colony-stimulating factor contributes to enhanced monocyte survival in chronic atopic dermatitis

Evidence suggesting that prolonged effector cell survival may contribute to perpetuation of inflammation prompted us to ask whether monocyte macrophages, the predominate inflammatory cell in the lesion of chronic atopic dermatitis (AD), exhibit enhanced survival in AD. Cultures of peripheral blood monocytes from patients with chronic AD, psoriasis, and from normal (NL) donors were examined for morphologic features and DNA fragmentation characteristic of cells undergoing the process of apoptosis (programmed cell death). Cultures of AD monocytes exhibited a significantly lower incidence of apoptosis than did cultures of NL monocytes (45 vs 68%, P < 0.01), or psoriatic monocytes (45 vs 80%, P < 0.01). Furthermore, AD monocytes were unresponsive to both IL-1, an inhibitor of apoptosis, and IL-4, an enhancer of apoptosis, in comparison to cultured NL monocytes. Of note, GM-CSF in a concentration-dependent fashion, decreased the incidence of apoptosis in NL monocyte cultures and rendered them unresponsive to these cytokines. These findings suggested that GM-CSF may enhance monocyte survival in AD. In support of this hypothesis, AD monocyte cultures produced fivefold more GM-CSF than did cultures of NL monocytes or psoriatic monocytes (P < 0.05). Additionally, there was a significantly greater number of GM-CSF mRNA expressing cells detected by in situ hybridization in biopsies of lesions of chronic AD than in acute AD or NL skin (P < 0.05). Finally, NL monocytes incubated with supernatants obtained from monocytes of AD patients exhibited significant inhibition of apoptosis, an effect that could be ablated by a neutralizing antibody to GM-CSF. Taken together, these data strongly suggest that increased production of GM-CSF by cells from patients with AD inhibits monocyte apoptosis and may contribute to the chronicity of this inflammatory disease.

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.

Correlation of GM-CSF mRNA in bronchoalveolar fluid with indices of clinical activity in sarcoidosis

BACKGROUND

Granulocyte-macrophage colony stimulating factor (GM-CSF) has several proinflammatory effects, some of which potentially favour granuloma formation. Its mRNA expression by the inflammatory cells recovered from lungs of patients with pulmonary sarcoidosis has been previously reported. In this study an association between GM-CSF expression and manifestations of the disease was explored.

METHODS

GM-CSF mRNA was detected by reverse transcription polymerase chain reaction in the cells of bronchoalveolar lavage (BAL) fluid of 20 patients with pulmonary sarcoidosis.

RESULTS

GM-CSF mRNA expression was positive in 15 of 20 patients with sarcoidosis. Fourteen of the 15 patients with positive mRNA expression had worsening or unchanged disease during the year preceding this study, on the basis of radiographic or physical findings, or both, whereas all five "negative" patients were judged to be improving. Similarly, serum levels of angiotensin converting enzyme, the proportion of lymphocytes in BAL fluid, and the CD4+/CD8+ ratio of lymphocytes in BAL fluid were significantly higher in the positive patients.

CONCLUSIONS

There was an association between the presence of GM-CSF mRNA in the cells in BAL fluid and other indices of disease activity in sarcoidosis.

Effect of leukotriene D4 and platelet-activating factor on human alveolar macrophage eicosanoid and PAF synthesis

Leukotrienes (LT) and platelet-activating factor (PAF) can increase nonspecific airway reactivity in normal subjects, and they have been proposed as putative mediators of asthma. Alveolar macrophages (AM), which have receptors for and synthesize leukotrienes and PAF, also may play a role in the pathogenesis of asthma. The present study was designed to determine the effects LTD4 and PAF have on bronchoalveolar lavage (BAL) fluid and cells, including AM eicosanoid and PAF synthesis, and to relate them to changes in nonspecific airway reactivity. Airway reactivity to methacholine was measured in healthy, male volunteers at least 2 days before and 6 h, 1, 3, and 7 days after inhaling either LTD4 or PAF. At least 3 wk later subjects inhaled in random order either methacholine or the mediator to which they were previously exposed, and BAL was performed the next day. This sequence was repeated with the other chemical 3 wk or more later. LTD4 inhalation increased airway reactivity and stimulated AM thromboxane synthesis while it reduced stimulated AM LTB4 synthesis. LTD4 did not affect the number of percentage of BAL cells or the BAL fluid protein and histamine concentrations. PAF inhalation increased airway reactivity and the proportion of neutrophils and eosinophils recovered by BAL, but it did not alter AM eicosanoid and PAF synthesis or the BAL fluid protein and histamine concentrations. A relationship was identified between the PAF-induced increase in airway reactivity and the percentage of BAL neutrophils, but no correlation was found between LTD4- or PAF-induced changes in airway reactivity and stimulated AM eicosanoid or PAF synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Detection of GM-CSF in asthmatic bronchial epithelium and decrease by inhaled corticosteroids

The presence of granulocyte-macrophage colony-stimulating factor (GM-CSF) in airway epithelial cells in vivo was assessed in 15 asthmatic and 9 normal subjects. GM-CSF was analyzed using immunohistochemistry with a polyclonal and a monoclonal antibody. Hue saturation intensity color image analysis was used to quantify staining. Asthmatic airway epithelial cells stained significantly more with anti-GM-CSF than those from normal subjects (p = 0.0013 and p = 0.0003 for the polyclonal and monoclonal antibodies, respectively). Additionally, 8 asthmatic individuals inhaled 1,000 micrograms beclomethasone diproprionate per day for 8 wk and 6 asthmatic patients inhaled matching placebo. There was a significant reduction of GM-CSF in the epithelium in the patients who were given corticosteroids (p = 0.014), whereas the group of subjects who were given placebo showed no significant change in GM-CSF staining. There was a correlation between the percentage suppression of GM-CSF staining by inhaled corticosteroids and the percentage increase in FEV1 (r = 0.61, p < 0.05) and percentage decrease in carbachol responsiveness (r = 0.80, p < 0.01). These findings suggest that GM-CSF may play a role in the inflammatory processes of bronchial asthma and that the epithelial cell may be a target cell for drug action.

Lack of increased numbers of low-density eosinophils in the circulation of asthmatic individuals

The density distribution pattern of eosinophils over discontinuous isotonic Percoll gradients from the blood of normal, asymptomatic allergic and non-allergic asthmatic individuals was investigated. There was a completely identical distribution pattern between the investigated groups. Analysis of the expression of surface markers for complement receptors CR1 and CR3 and immunoglobulin G receptor on eosinophils derived from the density bands 1.080, 1.085 and 1.090 g/ml supported this finding since they did not reveal differences in expression between the bands within one group but also not between the three groups. Eosinophils of the various density bands were further purified and stimulated in vitro to produce leukotriene C4 (LTC4) by the calcium ionophore A23187 or serum treated zymosan. Equal amounts of LTC4 were synthesized by the eosinophils of the various density bands within one group. However, it appeared that the eosinophils of all density bands of allergic and non-allergic asthmatics synthesized significantly more LTC4 than the eosinophils from normal individuals (five- to tenfold). Probably this indicates in vivo priming of the eosinophils in asthmatic individuals which is not reflected by a change in density. Control experiments, dealing with possible artifacts due to the isolation procedure or the patient selection, to find differences in distribution patterns over discontinuous Percoll density gradients of the eosinophils of asthmatic compared to normal individuals failed to show such a difference. Therefore, the density distribution pattern of eosinophils over these gradients does not reflect cell activation, whereas LTC4 formation clearly does. This could mean that LTC4 formation is a more sensitive parameter for cell activation than density distribution or cell surface marker expression.

Elevated release of tumor necrosis factor-alpha and interferon-gamma by bronchoalveolar leukocytes from patients with bronchial asthma

Bronchoalveolar lavage (BAL) leukocyte-secreted cytokines are considered to be important mediators of the inflammatory and allergic reactions in the lung. This study examines quantitative changes in the level of tumor necrosis factor-alpha (TNF alpha) and interferon-gamma (IFN gamma) production in BAL cell cultures derived from patients (n = 11) with bronchial asthma. The secretion of TNF alpha and IFN gamma was determined in intact (unstimulated) and phytohemagglutinin/phorbol myristate acetate (PHA + PMA)-stimulated BAL leukocyte cultures and compared with that in control cultures. In all patients studied, the background and PHA + PMA-induced secretion of TNF alpha and IFN gamma was significantly (p < 0.001) higher than that in parallel control cultures. In contrast to BAL cell preparations, the capacity of TNF alpha and IFN gamma secretion by patients' peripheral blood mononuclear cells (PBMC) did not differ from that of control subjects. High spontaneous release of TNF alpha and IFN gamma by patients' BAL leukocytes, but not PBMC, suggest that in the pathophysiology of bronchial asthma, these cytokines may act as local pathogenic agents in the lung.

T cells and eosinophils in the pathogenesis of asthma

Persistent asthma is characterized by chronic inflammation of the bronchial mucosa, where T cells and eosinophils are prominent. This article summarizes the evidence that asthmatic bronchial inflammation is initiated and propagated by cytokines secreted by activated T cells and other cells, and describes how the release of specific cytokines could result in local preferential accumulation and activation of eosinophils.

Increases in activated T lymphocytes, eosinophils, and cytokine mRNA expression for interleukin-5 and granulocyte/macrophage colony-stimulating factor in bronchial biopsies after allergen inhalation challenge in atopic asthmatics

Immunohistology and in situ hybridization were used to evaluate the presence, activation status, and cytokine mRNA profile of cells in the bronchial mucosa during human allergen-induced asthma. Fifteen atopic asthmatic subjects underwent inhalation challenge with allergen and with allergen diluent, performed in random order separated by an interval of at least 3 wk. Bronchial biopsies were obtained 24 h after challenge. Immunostaining revealed increases in the numbers of secreting eosinophils (EG2+; P < 0.05) and in interleukin-2 receptor (IL-2R)-positive cells (CD25+; P < 0.01) after allergen compared with diluent challenge. No differences were observed in the numbers of total leukocytes (CD45+), T lymphocytes (CD3+, CD4+, and CD8+), elastase-positive neutrophils, macrophages (CD68+), or mast cell subtypes (MCT+ or MCTC+). In situ hybridization revealed significant increases in the numbers of cells expressing mRNA for IL-5 (P < 0.02) and granulocyte/macrophage colony-stimulating factor (P < 0.01) after allergen compared with diluent challenge. A significant inverse relationship was observed between the number of cells expressing mRNA for IL-4 and for interferon-gamma (r = -0.75, P < 0.02). The results support the view that cytokines possibly from activated T lymphocytes may contribute to local eosinophil accumulation during allergen-induced asthma.

Asthma

There is an active inflammatory process in the airways of patients with asthma, even when the patients are asymptomatic. Some of the types of cells involved in this process possess the necessary biologic activities to produce many of the pathophysiologic features of asthma, but the underlying mechanisms have not yet been elucidated. Reducing the severity of the inflammatory process appears to be a reasonable goal of therapy, with potential long-range implications for the morbidity of asthma. Whether this theoretical benefit will be realized awaits further observation.

Inflammation and airway reactivity in asthma

The increased airway reactivity characteristic of asthma may be due to contraction of airway smooth muscle, mucus hypersecretion, edema and thickening of airway walls, and the presence of serum proteins and inflammatory cells and their products in the airways. Increased airway reactivity in asthma correlates with airway epithelial damage and is clearly related to airway inflammation, a process that most likely involves a complex interaction among mast cells, lymphocytes, eosinophils, and macrophages. Thus, although symptomatic treatment of airway narrowing is best accomplished with bronchial smooth muscle relaxants, treatment of the basic pathophysiologic defect should attempt to reduce airway inflammation. Bronchodilators (inhaled beta-agonists and, occasionally, theophylline), which do not decrease airway reactivity, are often used to treat the symptoms of patients with mild or episodic asthma; inhaled corticosteroids, which do decrease airway inflammation and reactivity, are used to treat patients with more severe symptoms. Methotrexate and cromolyn sodium may also be used, although their role in treating the underlying pathophysiology remains controversial. Identification of new agents that are as effective as corticosteroids but that do not produce their side effects would represent a major therapeutic advance for patients with asthma.

Immunohistochemical characterization of the cellular infiltration in asthmatic bronchi

Bronchial biopsies obtained from 16 asthmatic patients and six normal subjects were analyzed by immunohistochemistry. In the asthmatic patients, the total numbers of macrophages infiltrating the airway mucosa were increased. Many of the macrophages had the phenotypic characteristics of blood monocytes. HLA Class II antigen was expressed on infiltrating cells and airway epithelial cells. In biopsies from the asthmatics there was a significant increase in activated eosinophils, but not in neutrophils. There was also a significant increase in the numbers of T-lymphocytes in the asthmatics, but very few B-lymphocytes were detected. These results suggest that lung macrophages may have a central role to play in the mechanisms of the chronic immune-mediated inflammatory response seen in the airway mucosa of asthmatic patients.

Enhanced leukotriene synthesis in leukocytes of atopic and asthmatic subjects

1. We have investigated the capacities of peripheral leukocytes from atopic asthmatic (AA) (n = 7), atopic non-asthmatic (AN) (n = 7), and normal (N) (n = 7) subjects to generate the bronchoconstrictor and proinflammatory mediators leukotrienes (LTs) B4 and C4. 2. Mixed leukocyte preparations containing 61-84% neutrophils, 2.4-15% eosinophils, and 13-29% mononuclear cells were incubated in vitro at 37 degrees C in the presence of calcium ionophore A23187. Synthesis of LTB4 and LTC4 was quantitated by radioimmunoassay. 3. Both in dose-response experiments (0-10 microM A23187 for 5 min), and in time-course investigations (2 microM A23187 for 0-30 min), the mixed leukocytes of the AA and AN subjects generated on average 4- to 5-fold more LTB4 and 3- to 5-fold more LTC4 than the normal leukocytes (P less than 0.01 in all cases; ANOVA). 4. This enhanced LT synthesis by the AN and AA leukocytes was not due to differences in the counts of leukocyte sub-types, or to altered rates of LT catabolism between the subject groups. 5. LTB4 synthesis correlated significantly with LTC4 synthesis in the leukocytes of the AN and AA subjects (r = 0.81, n = 14, P less than 0.01), but not in those of the normal subjects (r = 0.19, n = 7, P greater than 0.05). 6. Our results demonstrate an up-regulation of the leukotriene synthetic pathway in the circulating leukocytes of atopic non-asthmatic and atopic asthmatic subjects, which may have important implications in the pathophysiology of asthma and allergy.

Predominant TH2-like bronchoalveolar T-lymphocyte population in atopic asthma

BACKGROUND

In atopic asthma, activated T helper lymphocytes are present in bronchial-biopsy specimens and bronchoalveolar-lavage (BAL) fluid, and their production of cytokines may be important in the pathogenesis of this disorder. Different patterns of cytokine release are characteristic of certain subgroups of T helper cells, termed TH1 and TH2, the former mediating delayed-type hypersensitivity and the latter mediating IgE synthesis and eosinophilia. The pattern of cytokine production in atopic asthma is unknown.

METHODS

We assessed cells obtained by BAL in subjects with mild atopic asthma and in normal control subjects for the expression of messenger RNA (mRNA) for interleukin-2, 3, 4, and 5, granulocyte-macrophage colony-stimulating factor (GM-CSF), and interferon gamma by in situ hybridization with 32P-labeled complementary RNA. Localization of mRNA to BAL T cells was assessed by simultaneous in situ hybridization and immunofluorescence and by in situ hybridization after immunomagnetic enrichment or depletion of T cells.

RESULTS

As compared with the control subjects, the subjects with asthma had more BAL cells per 1000 cell that were positive for mRNA for interleukin-2 (P less than 0.05), 3 (P less than 0.01), 4 (P less than 0.001), and 5 (P less than 0.001) and GM-CSF (P less than 0.001). There was no significant difference between the two groups in the number of cells expressing mRNA for interferon gamma. In the subjects with asthma, mRNA for interleukin-4 and 5 was expressed predominantly by T lymphocytes.

CONCLUSIONS

Atopic asthma is associated with activation in the bronchi of the interleukin-3, 4, and 5 and GM-CSF gene cluster, a pattern compatible with predominant activation of the TH2-like T-cell population.

The pathobiology of bronchial asthma

Early studies of patients dying from status asthmaticus revealed marked inflammation of the bronchial tree. Subsequent histological studies of the airways and examination of bronchoalveolar lavage fluid of subjects with mild asthma have confirmed the presence of airway inflammation in life. There is epithelial edema and desquamation, subepithelial deposition of collagen and fibronectin, and an inflammatory cell infiltrate in the mucosa. There are increased numbers of activated eosinophils, CD25-positive T lymphocytes, and immature macrophages with the phenotypic characteristics of blood monocytes. An increased expression of HLA class II is present on epithelium, macrophages, and other infiltrating cells. The severity of clinical asthma correlates with several measurements of the severity of the inflammatory response, suggesting a crucial role for airway inflammation in the pathophysiology of the disease. There is considerable interest and research into the mechanisms underlying the pathogenesis and maintenance of the inflammatory response in asthma. The development and maintenance of the inflammatory response in asthma is likely to be a consequence of a complicated interaction between various cells and the mediators they generate. The characterization of an ever-increasing number of cytokines is of particular interest. Interleukin-3, interleukin-5, and granulocyte-macrophage colony-stimulating factor are hematopoietic growth factors that increase the survival of eosinophils in culture and enhance certain eosinophil functions, such as mediator generation and toxicity. Alveolar macrophages derived from asthmatic subjects produce twofold to threefold more GM-CSF than do those from normal control subjects. Using in situ hybridization, the presence of IL-5 mRNA has been demonstrated in bronchial biopsies from asthmatic subjects. Thus IL-3, IL-5, and GM-CSF influence eosinophil function and survival, and may be generated by T lymphocytes and/or alveolar macrophages within the airways in asthma. In addition to these three cytokines, IL-4 and interferon-gamma may be crucial to the regulation of IgE biosynthesis. TNF-alpha and IL-1 are potentially important in the up-regulation of endothelial adhesion molecules. An important step in the recruitment of leukocytes to an inflammatory focus is margination to the vascular endothelium. Our understanding of the molecular events involved in migration of leukocytes to an inflammatory focus has been advanced by the discovery and characterization of a variety of cell adhesion molecules. The potential role of ELAM-1 and ICAM-1 in allergic inflammation is suggested by their up-regulation on vascular endothelium in association with late cutaneous responses to allergen and by their role in certain primate models of asthma.(ABSTRACT TRUNCATED AT 400 WORDS)

Asthma: cells and cytokines

The pathology of bronchial asthma demonstrates a multicellular process. In an attempt to elucidate the cellular biology of airways inflammation, it becomes important to understand not only the biology of each individual cell type but also the interaction between different cells. This review focuses on a documentation of some of the biological effects of the constituent cells in the airway mucosa and a discussion of their potential interactions through the release and action of different cytokines. It seems likely that future research will address the in vivo release of different cytokine molecules in the asthmatic process using techniques of molecular biology. There likely will be increasing information available about the regulation and the actions of these molecules on target cells and tissues. Elucidation of some of the complex interactions between different cells and the role of different cytokine molecules may provide a novel approach to the therapy of bronchial asthma.

Increased numbers of hypodense alveolar macrophages in patients with bronchial asthma

Alveolar macrophages (AM) are among the cells involved in the bronchial inflammation of asthma. It has been shown that AM are a heterogeneous cell population in normal subjects. The heterogeneity of AM from 36 asthmatic patients and 23 normal subjects was studied using Percoll density fractionation. AM recovered from asthmatic patients are mainly in the lower density fractions (1.03 and 1.04 g/ml), whereas AM from normal subjects are in the higher density fractions (1.05 and 1.07 g/ml). Electron microscopic studies showed that low density AM of both asthmatic and normal subjects appear to have morphologic characteristics of activated cells by comparison with high density AM that present characteristics of quiescent cells in both asthmatic and normal subjects. The functional activity of AM fractions of asthmatic and control subjects was assessed using the release of the oxygen free radicals induced by opsonized zymosan and TxB2 generation by A23187. There was no difference between the five fractions of asthmatic or control subjects with regard to oxygen species release. The TxB2 generation was increased in the low density AM from asthmatics when compared with the same fractions of normal subjects. The hypodense cells produced less TxB2 than did cells of higher density in both asthmatic and normal subjects. The density of AM was correlated with the recent instability of the asthma but not with the severity of it. This study shows that AM from asthmatic subjects, when compared with those from control subjects, are heterogeneous, hypodense cells and that they predominate. Hypodense AM did not appear to be hyperresponsive in vitro and may have been already committed into the airways.

Proinflammatory cytokines in acute asthma

Cytokine-mediated interactions between monocytes/macrophages, lymphocytes, and eosinophils may be important in regulation of airway inflammation in asthma. Peripheral blood cytokine concentrations were measured in twenty adults with severe, acute asthma, ten with mild asthma (intermittent inhaled beta-agonists), twelve with chronic asthma (high-dose inhaled steroids), and in sixteen healthy subjects. Interleukin-1 beta, tumour necrosis factor, and interferon gamma were not detected in most subjects. Granulocyte macrophage colony-stimulating factor concentrations were higher in patients with severe asthma than in healthy subjects (median 179 vs 80 pg/ml; 95% confidence interval for difference 16-168; p = 0.009). Plasma concentrations of soluble interleukin-2 receptor (sIL-2R) were similar in all asthma groups (geometric mean in severe acute group 570 U/ml, mild group 559 U/ml, and chronic group 560 U/ml) and higher than those in healthy controls (361 U/ml, p less than 0.01). Sequential sIL-2R measurements were done in fifteen of the patients with severe acute asthma. There was no difference between baseline concentrations and those after 2 days of steroid treatment but by day 7 they had fallen significantly (ratio day 7/day 3 = 0.74, [95% CI 0.67-0.82]; p less than 0.001); however, there was no correlation with improvement in peak expiratory flow. This study provides further evidence for T-lymphocyte activation in asthma but shows that plasma sIL-2R is not a useful marker of disease activity.

Endobronchial allergen challenge in asthma. Demonstration of cellular source of granulocyte macrophage colony-stimulating factor by in situ hybridization

Airway inflammation is thought to play an important role in the pathogenesis of asthma. We have used in situ hybridization and an immunoassay to determine whether granulocyte macrophage colony-stimulating factor (GM-CSF) (a cytokine capable of eosinophil activation) is present in the airway of asthmatics (n = 6) who have 37.0 +/- 15.1% airway eosinophilia after endobronchial allergen challenge. Levels of immunoreactive GM-CSF (less than 4 pg/ml pre-allergen versus 180.5 +/- 46.9 pg/ml post-allergen) increased significantly 24 h after endobronchial allergen stimulation. The cellular source of bronchoalveolar lavage (BAL) GM-CSF, as determined by in situ hybridization and immunoperoxidase staining, was derived predominantly from UCHL-1 positive BAL lymphocytes, as well as from a smaller population of alveolar macrophages. Before local endobronchial allergen challenge, less than 1% of lymphocytes and alveolar macrophages recovered by BAL expressed GM-CSF mRNA, whereas after allergen stimulation 92.6 +/- 3.4% of lymphocytes and 17.5 +/- 22.7% of alveolar macrophages expressed GM-CSF mRNA. This study provides evidence that in an experimental model of allergen-induced asthma, activation of the immune and inflammatory response (BAL lymphocyte and alveolar macrophage production of GM-CSF) is temporally associated with an inflammatory cell influx of eosinophils into the airway.