The contribution of alveolar macrophages to hyperreactive airway disease

Cell surface antigen expression by peripheral blood monocytes in allergic asthma: results of 2.5 years therapy with inhaled beclomethasone dipropionate

At present, inhaled glucocorticoids are widely accepted as the therapy of choice in chronic asthma. Treatment with inhaled glucocorticoids significantly suppresses local airway inflammation in asthmatics, but may also have systemic effects, e.g. a reduction of the number of circulating hypodense eosinophils or a down-modulation of HLA-DR antigen (Ag) expression by T lymphocytes in peripheral blood. However, the effect of long-term therapy with inhaled glucocorticoids on peripheral blood monocytes (PBM), which are the precursors of the most numerous cell type in the lung, the alveolar macrophage, have not yet been evaluated. We therefore investigated the expression of various cell surface Ag on PBM from non-smoking patients with allergic asthma who were treated for 2.5 years with a β₂-receptor agonist plus either an inhaled glucocorticoid (beclomethasone dipropionate, BDP) (n = 4) or an anticholinergic or placebo (n = 8). We compared the results with healthy volunteers (n = 7). Long-term treatment of allergic asthmatics with inhaled BDP, but not anticholinergic or placebo therapy, was associated with a significantly lower CDllb Ag expression (p < 0.04) and higher expression of CD13, CD14 and CD18 Ag (p < 0.05, p < 0.02 and p < 0.04, respectively) when compared with the healthy control subjects (n = 7). Most interestingly, PBM of asthmatics treated with inhaled BDP expressed an almost two-fold higher level of CD14 Ag on their cell surface than PBM of patients treated with anticholinergic or placebo (p < 0.03). No significant differences in the expression of CD16, CD23, CD25, CD32 and CD64 Ag or HLA-DR were observed between PBM from the different patient groups or healthy controls. Taken together, this study shows that long-term local therapy with inhaled BDP coincides with an altered expression of at least one cell surface Ag on PBM from allergic asthmatics.

Inflammatory responses after endothelin B (ETB) receptor activation in human monocytes: new evidence for beneficial anti-inflammatory potency of ETB-receptor antagonism

Endothelin (ET) stimulates potent ETA/ETB receptors important in the pathogenesis of pulmonary arterial hypertension (PAH) and fibrosis. Though therapy with ET-receptor antagonists is well established uncertainty exists whether selective ETA or dual ETA/ETB-receptor antagonism is superior in PAH. The objective of this study was to further elucidate the pro-inflammatory effects of ET-1 on ETB receptors in cultured human monocytes (10(5)/20 h) compared with non-specific stimulation with LPS in vitro and to define the antagonizing effects of bosentan, a dual ETA/ETB-receptor antagonist, on inflammatory mediator production. We further hypothesized that ETB-receptor antagonism reduces the requirement of PGE2 to control inflammatory mediator production. Activation of the monocyte ETB subtype by ET (1 ng/ml) concentration-dependently stimulated TNF-alpha (744%) >PGE2 (570%) > IL-1 beta (112%) and had no effect on 5-lipoxygenase metabolism. Compared with ET a different profile of IL-1 beta >TNF-alpha >PGE2 was induced by LPS. ETB-receptor antagonism attenuated ET- and LPS-responses in monocytes, in particular of TNF-alpha and PGE2 to a similar extend (40%) that were only demonstrable following LPS at therapeutic plasma concentrations of bosentan and had no effect on IL-1 beta. Inhibition of ETB receptors in LPS-stimulated monocytes by bosentan was responded with suppression of PGE2 and increased production of leukotrienes indicating strong effects in the cyclooxygenase pathway that is known to control cellular ET transcription. These data suggest an important signaling pathway between ET-induced cytokine production following ETB-receptor activation with no further control of ET transcription by PGE2 required following ETB receptor antagonism. Therefore, in states of inflammation increased ETB-receptor expression and activation mediated by elevated ET concentrations may be an underestimated mechanism, which warrants the application of combined ETA/ETB-receptor antagonists.

Serotonin modulates the cytokine network in the lung: involvement of prostaglandin E2

Serotonin, well known for its role in depression, has been shown to modulate immune responses. Interestingly, the plasma level of serotonin is increased in symptomatic asthmatic patients and the use of anti-depressants, known to reduce serotonin levels, provokes a decrease in asthma symptoms and an increase in pulmonary function. Thus, we tested the hypothesis that serotonin affects alveolar macrophage (AM) cytokine production, altering the cytokine network in the lung and contributing to asthma pathogenesis. AMs were treated with different concentrations of serotonin (10(-11)-10(-9) M) or 5-HT(1) and 5-HT(2) receptor agonists for 2 h prior stimulation. T helper 1 (Th1) and Th2 cytokines, prostaglandin-E(2) (PGE(2)) and nitric oxide (NO) were measured in cell-free supernatants. Serotonin significantly inhibited the production of tumour necrosis factor (TNF) and interleukin (IL)-12, whereas IL-10, NO and PGE(2) production were increased. These immunomodulatory effects of serotonin were mimicked by 5-HT(2) receptor agonist but were not abrogated by 5-HT(2) receptor antagonist, suggesting the implication of other 5-HT receptors. Inhibitors of cyclooxygenase and antibody to PGE(2) abrogated the inhibitory and stimulatory effect of serotonin on TNF and IL-10 production, respectively, whereas NO synthase inhibitor eliminated serotonin-stimulated IL-10 increase. Furthermore, PGE(2) significantly increased AM IL-10 and NO production. These results suggest that serotonin alters the cytokine network in the lung through the production of PGE(2). The reduction of Th1-type cytokine by serotonin may contribute to asthma pathogenesis.

Inflammatory cells in asthma: mechanisms and implications for therapy

Recent clinical studies have brought asthma's complex inflammatory processes into clearer focus, and understanding them can help to delineate therapeutic implications. Asthma is a chronic airway inflammatory disease characterized by the infiltration of airway T cells, CD(+) (T helper) cells, mast cells, basophils, macrophages, and eosinophils. The cysteinyl leukotrienes also are important mediators in asthma and modulators of cytokine function, and they have been implicated in the pathophysiology of asthma through multiple mechanisms. Although the role of eosinophils in asthma and their contribution to bronchial hyperresponsiveness are still debated, it is widely accepted that their numbers and activation status are increased. Eosinophils may be targets for various pharmacologic activities of leukotriene receptor antagonists through their ability to downregulate a number of events that may be key to the effector function of these cells.

Leukotriene B4 production in human mononuclear phagocytes is modulated by interleukin-4-induced 15-lipoxygenase

The aim of this study was to evaluate the consequences of interleukin (IL)-4-induced 15-lipoxygenase (15-LO) expression on leukotriene B4 (LTB4) synthesis in human monocytes. Human monocytes incubated for 24, 48, and 72 h with IL-4 (10 ng/ml) were stimulated with Ca2+-ionophore A23187 (calcimycin; 5 microM) or opsonized zymosan. 15(S)-hydroxyeicosatetraenoic acid [15(S)-HETE], LTB4, and arachidonic acid (AA) release were measured by high-performance liquid chromatography/radioimmunoassay, liquid chromatography/tandem mass spectrometry (LC/MS/MS), or gas chromatography/mass spectrometry. 15-LO activity was evaluated in AA-treated monocytes. 15-LO, 5-lipoxygenase (5-LO) and 5-LO activating protein (FLAP) expression were analyzed by reverse transcription-polymerase chain reaction. Neutrophil chemotactic activity was evaluated using a microtaxis chamber assay. A23187-induced synthesis of 15(S)-HETE was significantly increased after treatment with IL-4 (10 ng/ml) for 48 and 72 h (p < 0.001). Concomitant decrease of LTB4 release was observed after 72 h of incubation with IL-4 (p < 0.001). LC/MS/MS analysis confirmed the production of 15(S)-HETE and the significant inhibition of LTB4 synthesis in IL-4-treated monocyte after challenge with opsonized zymosan. IL-4 treatment induced 15-LO enzymatic activity as well as 15-LO mRNA, but did not affect either 5-LO or FLAP mRNA expression in monocytes. Supernatant from IL-4-treated monocytes showed significantly lower neutrophil chemotactic activity than controls. 15(S)-HETE significantly inhibited LTB4 production induced by A23187-stimulated human monocytes without affecting AA release. IL-4-induced expression of 15-LO in monocytes caused a significant reduction of LTB4 production. Whereas this effect did not reflect changes in 5-LO and FLAP mRNA expression, synthetic 15(S)-HETE was able to significantly inhibit the synthesis of LTB4, without affecting AA release.

Assessing the evidence for remodelling of the airway in asthma

Asthma is now described as being characterized by reversible airflow obstruction, with bronchial inflammation and tissue remodelling of the airway wall. The description of remodelling has been usefully invoked to account for a component of airflow obstruction that is unresponsive to usual bronchodilator therapy. It is crucial to examine critically the evidence for this view, particularly the quantitation of specific changes in the epithelium, mucus glands, cell infiltrate, collagen, vessels and smooth muscle of the bronchial wall. The useful tools of immunohistochemistry and molecular biology combined with airway biopsy and well-designed clinical trials will be essential to determine the specific roles of cells and cytokines in airway remodelling in asthma.

15-Lipoxygenase expression and 15(S)-hydroxyeicoisatetraenoic acid release and reincorporation in induced sputum of asthmatic subjects

BACKGROUND

Recent evidence shows that 15(S)-hydroxy-eicoisatetraenoic acid (15[S]-HETE) can be released and rapidly reincorporated into cellular lipids. These mechanisms exert several immunoregulatory functions that may be relevant in airway inflammation.

OBJECTIVE

Our purpose was to evaluate the levels of both soluble and cell-associated 15(S)-HETE and to examine 15-lipoxygenase (15-LO) messenger RNA (mRNA) expression in sputum samples obtained from 10 control and 18 asthmatic subjects.

METHODS

Levels of 15(S)-HETE were measured by reverse-phase HPLC separation followed by RIA in supernatants and in cell membrane-extracted phospholipids after acid hydrolysis. 15-LO mRNA was evaluated by primed in situ hybridization (PRINS). Combined immunocytochemistry and PRINS was used to identify the phenotype of cells bearing 15-LO transcripts.

RESULTS

Levels of both soluble and cell-associated 15(S)-HETE were higher in asthmatic than in control subjects (P <.0001). The percentage of cells expressing 15-LO mRNA was higher in asthmatic than in control subjects (P <.01). On double staining for specific cell-type markers and 15-LO mRNA, macrophages were the major source for 15-LO.

CONCLUSION

This study shows that the induced sputum technique allows the evaluation of 15-LO activity and that soluble, cell-associated 15(S)-HETE and 15-LO levels are higher in asthmatic than in control subjects. In addition, this study indicates that, in induced sputum, airway macrophages are the major source of 15(S)-HETE in asthma.

IL-4 and IgE-anti-IgE modulation of 15(S)-hydroxyeicosatetraenoic acid release by mononuclear phagocytes

BACKGROUND

IL-4 modulates the synthesis of IgE, the expression of CD23, and the release of 15(S)-hydroxyeicosatetraenoic (15[S]-HETE).

OBJECTIVE

We evaluated the release of 15(S)-HETE by IL-4-stimulated monocytes and verified whether the observed increase in 15(S)-HETE release after passive sensitization and anti-IgE challenge of IL-4-treated monocytes was secondary to an increased CD23 expression.

METHODS

Human monocytes were incubated for 24, 48, and 72 hours with IL-4 (10 ng/mL) with or without an IgE-anti-IgE stimulation. We evaluated CD23 expression by immunocytochemistry and 15(S)-HETE release by HPLC and RIA. To prove that the increase in 15(S)-HETE release was due to the effect of IL-4 on CD23, we performed experiments with an anti-CD23 blocking mAb.

RESULTS

CD23 expression and 15(S)-HETE release were significantly increased by IL-4, reaching a peak after 72 hours (P <.02). After passive sensitization with human IgE and anti-IgE challenge, IL-4-stimulated monocytes released higher amounts of 15(S)-HETE than IL-4-unstimulated monocytes (P <.02). Pretreatment with the anti-human B-cell CD23 MHM6 mAb caused a dose-dependent inhibition of 15(S)-HETE release.

CONCLUSIONS

This study shows that immunologic challenge of IL-4-treated, passively sensitized monocytes results in a CD23-dependent additional increase of 15(S)-HETE release, indicating the presence of a synergistic effect of IL-4 on CD23 expression and 15(S)-HETE production.

Influence of interleukin 1alpha on superoxide anion, platelet activating factor release and phospholipase A2 activity of naive and sensitized guinea-pig alveolar macrophages

1. We studied the effect exerted by hr-interleukin-1alpha (IL-1alpha) on responsiveness of alveolar macrophages (AM) from naive and sensitized guinea-pigs, through O2.- production (by ferricytochrome C reduction), platelet-activating factor (PAF) release (by platelet aggregation), prostaglandin E2 (PGE2) release (by a radioimmunoassay), and cytosolic phospholipase A2 (cPLA2) activity (by hydrolysis of radioactive substrate). 2. In naive guinea-pig AM, 0.06 nM hr-IL-1alpha pretreatment decreased by 65% O2.- release stimulated with 10 nM fMLP. In contrast, O2.- production was not affected in sensitized guinea-pig AM. 3. O2.- release elicited by fMLP stimulation in both cell groups was affected by PLA2 inhibitors (10 microM bromophenacyl bromide, BPB or 10 microM methylprednisolone, MP). In contrast, 10 microM arachidonyl trifluoromethyl ketone (AACOCF3), a cPLA2 inhibitor, was ineffective. 4. In naive AM, PAF release was elicited by hr-IL-1alpha pretreatment and by separate fMLP-stimulation, but when the stimulus was added to hr-IL-1alpha-pretreated cells inhibition of PAF release was observed. In sensitized AM, PAF release was lower than that found in naive guinea-pig AM in both hr-IL-1alpha-pretreated and fMLP-stimulated cells. 5. PGE2 release was unaffected by hr-IL-1alpha pretreatment and it was decreased by fMLP in both naive and sensitized AMs. The latter released less PGE2 than naive cells in basal conditions and after fMLP treatment. 6. Sensitized AM showed a greater cPLA2 activity in all experimental conditions in comparison to naive cells. cPLA2 activity assayed in the cytosolic fraction was found to be enhanced by hr-IL-1alpha pretreatment and by fMLP stimulation in naive but not in sensitized AM. However, when the stimulus was added to hr-IL-1alpha-pretreated cells we observed a decrease in cPLA2 activity in the cytosol and an increase in the membranes, thus suggesting a translocation of enzymatic activity. 7. In conclusion, hr-IL-1alpha can modulate the responsiveness of AM from naive and sensitized guinea-pigs, as suggested by changes found in the release of PAF and O2.- and in cPLA2 activity; therefore, sensitization itself may affect cellular responsiveness.

Increased release of matrix metalloproteinase-9 in bronchoalveolar lavage fluid and by alveolar macrophages of asthmatics

In order to determine whether matrix metalloproteinases (MMPs) contribute to inflammation in asthma, we have examined the release of MMPs in bronchoalveolar lavage (BAL) fluids and their production and regulation by alveolar macrophages (AM), in short-term culture. BAL was collected from 38 asthmatic subjects (24 untreated and 14 treated with inhaled corticosteroids), 26 healthy nonsmokers, and 18 patients with chronic bronchitis used as a control group for another inflammation. The profile of MMPs present in BAL fluid and AM supernatant, determined by zymographic analysis, was found to be similar in all populations. The main enzyme released was identified immunologically as MMP-9, a potent collagenolytic and elastolytic enzyme. Its release, measured using enzyme immunoassay, was significantly enhanced in fluids and in AM supernatants from untreated asthmatics compared with those from the other populations. Enhanced MMP-9 levels, in asthma, could not be explained by a different sensitivity of AM to interleukin-4, interferon-gamma, or dexamethasone, compounds that have been shown to inhibit MMP-9. The phorbol ester phorbol 12-myristate 13-acetate (PMA), a protein kinase C (PKC) activator, significantly increased MMP-9 in AM from healthy control subjects but not in those from untreated asthmatics. Calphostin C and H7, PKC inhibitors, significantly reduced PMA-stimulated MMP-9 release in AM from healthy control subjects and spontaneous MMP-9 release in AM from untreated asthmatics. H8, a PKA inhibitor, was inactive in both populations. These data suggest that the stimulation of MMP-9 release in AM from untreated asthmatic patients occurs, at least partly, via signals activating PKC.

The effects of tachykinins on inflammatory and immune cells

The aim of this article is to provide an up-dated overview of the available information on the role played by tachykinins in recruiting/regulating the function of immune/inflammatory cells, an issue which has received considerable input from the recent availability of potent and selective antagonists for tachykinin receptors. It appears that NK1 receptors play a role in mediating the extravascular migration of granulocytes into inflamed tissues in response to various inflammatory stimuli, although this effect may not be due to the expression of NK1 receptors by granulocytes themselves. Several data also imply a role for NK1 and NK2 receptors in regulating immune function. No data are available to suggest the expression of NK3 receptors by inflammatory/immune cells. Mast cell degranulation by substance P appears to be a non-receptor dependent response which may take place in vivo during intense stimulation. An emerging concept in the field relates to the ability of certain immune cell types to synthesize and possibly release tachykinins. Immune cells could represent an additional source of tachykinins in inflamed tissues, providing a non-neurogenic tachykininergic contribution to the local inflammatory process.

Cyclic nucleotide phosphodiesterase isoenzyme activities in human alveolar macrophages

BACKGROUND

Alveolar macrophages and their precursors, the monocytes are involved in airway inflammation in asthma. An increase in intracellular cAMP by PDE inhibitors is known to suppress macrophage and monocyte functions. A comparison of the PDE-isoenzyme profiles of human alveolar macrophages from normal and atopic donors and of human peripheral blood monocytes might form a basis to differentially affect functions of these cells by PDE inhibitors.

OBJECTIVE

The study compares the PDE isoenzyme activity profiles of human alveolar macrophages from normal and atopic asthmatic donors and human peripheral blood monocytes. In addition, the effect of in vitro maturation of monocytes on their PDE isoenzyme profile is studied.

METHODS

Macrophages were purified (95-97%) by adherence to plastic, and blood monocytes were purified (88%) by counter-current elutriation. PDE isoenzyme activity profiles were investigated using isoenzyme selective inhibitors and activators.

RESULTS

In macrophages substantial PDE I activity, which was significantly higher than PDE III-V activity was detected and PDE II was absent. PDE III was membrane-bound whereas PDE I, IV and V were soluble. No difference was found between alveolar macrophages of normal donors and atopic asthmatics. Monocytes exclusively contained PDE IV but their in vitro maturation led to a PDE isoenzyme profile similar to that of alveolar macrophages.

CONCLUSION

These results indicate that human monocytes and alveolar macrophages are distinct targets for the effects of selective PDE inhibitors while alveolar macrophages from normal and atopic individuals appear to be equally sensitive.

Reduction in leukotriene B4 generation by bronchoalveolar lavage cells in asthma

BACKGROUND

Leukotrienes are inflammatory mediators implicated in the pathogenesis of asthma. The capacity of inflammatory cells within the airways to generate leukotrienes may be altered in asthma. This hypothesis was tested using bronchoalveolar lavage (BAL) to sample cells within the airways from atopic asthmatic and normal subjects, and by measuring their capacity to generate leukotriene B4 (LTB4) and leukotriene C4 (LTC4) in response to A23187, a potent stimulus of leukotriene generation.

METHODS

Bronchoalveolar lavage was performed in 12 mild asymptomatic atopic asthmatic patients and 12 normal subjects. Mixed BAL cell aliquots (approximately 80% alveolar macrophages) were incubated with 0-20 microM A23187 for 10 minutes and with 4 microM A23187 for 0-30 minutes, and leukotrienes were measured by radioimmunoassay and high performance liquid chromatography.

RESULTS

Mixed BAL cells from asthmatic subjects generated less LTB4 than cells from normal subjects in dose response and time course experiments (area under the curve 81.5 (0.0-228.5) ng.min.10(-6) cells in asthmatic subjects and 197.9 (13.9-935.6) ng.min.10(-6) cells in normal subjects. There were no differences in LTC4 generation between BAL cells from asthmatic and normal subjects.

CONCLUSIONS

Generation of LTB4 by BAL cells from atopic asthmatic subjects in response to A23187 was reduced. As the alveolar macrophage is the major source of LTB4 in BAL cells, these results probably reflect reduced generation of LTB4 by alveolar macrophages from asthmatic patients. This may be a consequence of monocyte migration into the lung, or altered alveolar macrophage function in asthma, or both.

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.

Assessment of inflammation in noninfectious chronic maxillary sinusitis

BACKGROUND AND AIM

Pathologic examination of the sinus mucosa and titration of inflammatory mediators in the sinus fluid were carried out to characterize inflammation in chronic sinusitis and determine whether patients with chronic allergic rhinitis (CAR) and sinusitis differ from patients with chronic nonallergic rhinitis (CNAR) and sinusitis.

METHODS

Nine control subjects (patients requiring ear, nose, and throat surgery not related to sinusitis), 12 patients with CAR and sinusitis, and 13 patients with CNAR and sinusitis were investigated. Eosinophil cationic protein, tryptase, myeloperoxidase, histamine, and prostaglandin D2 were measured in the sinus lavage fluids, and cells were enumerated. The cellular infiltrate was studied by immunohistochemistry with monoclonal antibodies against eosinophil cationic protein (eosinophils), tryptase (mast cells), neutrophil elastase (neutrophils), CD3 (lymphocytes), CD68 (macrophages), and proliferating cell nuclear antigens.

RESULTS

Neutrophils were not increased in sinusitis. In comparison with control subjects, patients with CAR and CNAR with sinusitis showed significant increases in eosinophils and macrophages in biopsy specimens and in eosinophil cationic protein in sinus lavage fluids. In comparison with patients with CNAR, patients with CAR had an increased number of intraepithelial mast cells and lymphocytes.

CONCLUSIONS

These findings suggest that patients with CNAR and sinusitis can be distinguished from patients with CAR and sinusitis, which resembles nonallergic rhinitis with eosinophilia syndrome.

Effects of parainfluenza type 3 virus on guinea pig pulmonary alveolar macrophage functions in vitro

The influence of parainfluenza type 3 (PI-3) virus on the release of inflammatory mediators by guinea pig pulmonary alveolar macrophages (PAMs) was investigated in vitro. Direct application of PI-3 virus dose-dependently stimulated the generation of chemiluminescence by PAMs and induced aggregation of PAMs. No significant effects of PI-3 virus on the release of linoleic acid metabolites by PAMs were detected. However, an increased release of the arachidonic acid metabolite thromboxane B2 (TxB2) was observed when PAMs were stimulated with PI-3 virus. PAMs were also cultured for 2 h or 18 h in the presence of PI-3 virus or control medium. The production of reactive oxygen species and the release of fatty acid metabolites by these PAMs were determined upon stimulation with opsonized zymosan particles or phorbol myristate acetate. The amounts of hydrogen peroxide and superoxide produced did not differ between virus- and control medium-incubated PAMs. However, the PI-3 virus-treated PAMs generated twice as much chemiluminescence when compared to PAMs incubated with control medium. The 2-h incubation period with PI-3 virus also resulted in a decreased release of TxB2 from the PAMs upon zymosan stimulation. The changes in the production of reactive oxygen species and the release of TxB2 by PAMs could account for damage to the airways and bronchial hyperresponsiveness often seen after viral infection.

Increased expression of adhesion molecules (ICAM-1 and LFA-1) on alveolar macrophages from asthmatic patients

In the airways inflammation observed in asthma, activated macrophages are present in increased numbers. Adhesion molecules are required for the cell:cell contacts between leukocytes and endothelial cells or other leukocytes, and they are induced by inflammatory stimuli. We studied the expression of two adhesion molecules (ICAM-1 and LFA-1) on alveolar macrophages recovered by bronchoalveolar lavage from 11 normal subjects and 13 asthmatic patients by using immunocytochemistry. Two specific monoclonal antibodies were used, and the reaction was revealed by the alkaline phosphatase-antialkaline phosphatase (APAAP) method. The percentage of cells expressing ICAM-1 or LFA-1 was significantly increased in asthmatic patients, as compared with normal subjects (P < 0.001 and P < 0.002, respectively; Mann-Whitney U test), and there was a significant correlation with the percentage of cells expressing both markers in asthma (P < 0.03, Spearman rank test). This study highlights the importance of macrophages in the inflammation of asthma and suggests that macrophage interactions with other cells play a role in this inflammation.

Inhaled substance P induces activation of alveolar macrophages and increases airway responses in the guinea-pig

Guinea-pigs pretreated with phosphoramidon or saline were treated with an aerosol of substance P (SP) or saline. 24 h later, the pulmonary inflation pressure (PIP) to substance P or to cumulative doses of acetylcholine or of histamine was recorded. The PIP response to SP itself was significantly enhanced in animals treated with phosphoramidon+SP as compared with phosphoramidon+saline (2.5-fold increase 1 min after the end of the inhalation, P < 0.001). The response to acetylcholine and to histamine was also significantly enhanced in phosphoramidon+substance P-treated as compared with phosphoramidon+saline-treated guinea-pigs (PC200 = 38.9 and 1.6 as compared with 77.6 and 3.9 micrograms/ml, P < 0.01 and P < 0.05 respectively). The production of superoxide anions by alveolar macrophages in response to f-MLP was also enhanced after treatment with phosphoramidon+SP as compared with phosphoramidon+saline (6.4 +/- 0.7 and 3.8 +/- 0.3 cpm, P < 0.001 respectively). In animals treated with saline+SP or saline+saline, the PIP responses and the production of superoxide anion were similar. Altogether these results suggest that SP contributes to the bronchial hyper-responsiveness in asthma and this probably through activation of alveolar macrophages.

Enhanced responsiveness of ovalbumin-sensitized guinea-pig alveolar macrophages to tachykinins

1. We have evaluated the ability of substance P (SP), neurokinin A (NKA) and the selective NK2 receptor agonist [beta-Ala8]-NKA(4-10) to induce superoxide anion (O2-) production and prostanoid (prostaglandin E2, thromboxane B2) release from alveolar macrophages (AMs) isolated from control or actively sensitized guinea-pigs. 2. The dose-response curves for NKA and SP were shifted to the left (three orders and one order of magnitude, respectively) in AMs isolated from sensitized animals, with no variation in maximal effects. 3. By evaluating the effects of [beta-Ala8]-NKA(4-10), we observed that not only was the concentration-response curve shifted to the left in both the functional parameters examined, but also maximal effects were significantly enhanced in AMs isolated from sensitized guinea-pigs. 4. This varied responsiveness seems to be specific for tachykinins, as it was not reproduced by another AM stimulant, the bacterial peptide N-formylmethionyl-leucyl-phenylalanine (fMLP). 5. Only small amounts of beta-glucuronidase were released following tachykinin or ovalbumin stimulation both in control and sensitized AMs. 6. These results indicate that AMs isolated from sensitized guinea-pigs show an increased responsiveness to NK2 receptor stimulation and further stress the role played by AMs in allergic lung diseases.

Is asthma curable?

The information reviewed here supports the concept that asthma is potentially curable. Reports of complete, durable remission of asthma can no longer be regarded as fortuitous occurrences, unrepresentative of asthma in general. Systematic studies of anti-inflammatory drug therapy designed to explore possible induction or remission of asthma clearly are warranted. Studies of aggressive anti-inflammatory drug therapy of asthma at the onset, to avoid establishment of chronic asthma, also are desirable. The current goals of therapy of asthma have been revised to include reduction of airway hyperreactivity with topical anti-inflammatory drugs, in addition to relief of current symptoms. This approach may provide valuable resistance to exacerbations in response to antigen exposures, infections, exercise, or irritants. Pathophysiologic mechanisms apparently essential to the establishment and perpetuation of chronic asthma have been identified. These processes may be vulnerable to eradication by combination therapy with existing pharmacologic agents such as cyclosporin A or FK-506 (to suppress cytokine production), gold, methotrexate, and other anti-inflammatory drugs, alone or in combination. Equally important, the vigorous anti-inflammatory therapy may be necessary only long enough to achieve a resolution of the chronic pulmonary inflammation. Systematic studies of the use of these agents to induce partial, or complete, stable remissions of asthma should be performed. In the past, remissions of asthma in children with neoplasia and the other patients presented herein were complete, durable, and welcome, but they were largely unexpected and unpredictable. For the future, there is increasing reason to believe that predictable pharmacologically induced remission of asthma will be feasible.

Leukotriene B4 level in stimulated blood neutrophils and alveolar macrophages from healthy and asthmatic subjects. Effect of beta-2 agonist therapy

Leukotriene B4 levels were measured after stimulation by calcium ionophore A23187: (i) in peripheral, neutrophils (PMN) from allergic asthmatics, rhinitis and healthy subjects; (ii) in macrophages collected by bronchoalveolar lavage. LTB4 levels in PMNs were significantly higher in non-treated allergic asthmatics and non-treated subjects with rhinitis compared to controls. Beta-2 agonist-treated asthmatics showed a significantly decreased LTB4 production which was not different from those of controls. In vitro, LTB4 production decreased significantly after PMN incubation with Salbutamol (10(-6) mol l-1). LTB4 produced by AM collected by BAL was measured in non-treated (n = 5) and treated (n = 11) asthmatics with inhaled beta-2 agonist. AM collected from all controls and non-treated asthmatics produced LTB4. By contrast, no production of LTB4 was observed in the treated group. LTB4 production decreased when normal AM were incubated in vitro with Salbutamol (10(-8) mol l-1). These results suggest that biochemical differences occur in PMN and macrophages from subjects treated with beta-2 agonist, presumably in changing the 5-lipoxygenase pathway.

Arachidonic acid metabolism in monocytes of aspirin-sensitive asthmatic patients before and after oral aspirin challenge

Aspirin and nonsteroidal antiinflammatory drugs induce bronchospastic reactions in patients with aspirin-sensitive respiratory disease. Although the mechanism of this reaction is unknown, all drugs that induce the respiratory reaction also inhibit the cyclooxygenase enzyme. The ensuing changes in arachidonate metabolism are presumed to play a role in the pathogenesis of the reaction. We measured generation of leukotrienes and thromboxane by calcium ionophore stimulated blood monocytes. Before aspirin challenge, monocytes released significantly more thromboxane B2 in patients with aspirin sensitivity than in patients without aspirin sensitivity or in healthy control subjects (p < 0.02). During aspirin-induced bronchospasm, release of leukotriene B4 increased significantly (45.5%, p = 0.018), whereas release of thromboxane B2 decreased (-46.9%, p = 0.028). Two hours after ingestion of 60 mg aspirin, normal monocyte release of thromboxane B2 did not drop, whereas leukotriene B4 release increased. Monocytes formed only minimal amounts of leukotriene C4. We conclude that the profile of released eicosanoids from aspirin-sensitive monocytes is distinct from non-aspirin-sensitive subjects, and that these differences could contribute to the development of bronchospasm after aspirin ingestion.

Adenosine-induced bronchoconstriction of isolated lung and trachea from sensitized guinea-pigs

1. The bronchoconstriction of airway-perfused lungs and contraction of superfused tracheal spirals from guinea-pigs in response to adenosine were examined. 2. In lungs from untreated animals, adenosine had little effect unless the perfusion pressure was raised with carbachol (1.1 microM), when it caused a fall in perfusion pressure. However, if removed from guinea-pigs sensitized with ovalbumin (5 mg and 10 mg i.p. 14 and 12 days before use), adenosine was bronchoconstrictor, exerting bronchodilator effects only at high (1 mg) doses. The constrictor response to adenosine (300 micrograms) was significantly greater than that in lungs from untreated or sham-injected animals. 3. In superfused trachea from untreated animals, adenosine exerted only relaxant responses. In tissues from ovalbumin-sensitized guinea-pigs adenosine produced contractile responses, with relaxation appearing only at high (1 mg) doses. 4. Thus sensitization by antigen challenge revealed a bronchoconstrictor response of isolated airway preparations to adenosine. This is related to the clinical situation where only asthmatic subjects respond to adenosine by bronchoconstriction and suggests that the sensitization may destabilize inflammatory cells for mediator release by adenosine. 5. The response to a second exposure to adenosine was consistently reduced (lungs) or converted to a relaxation (trachea) indicating tachyphylaxis and consistent with a mediator release mechanism. 6. The P1-purinoceptor antagonist, 8-phenyltheophylline (3.9 microM), antagonized the relaxant responses to higher doses of adenosine. However, it did not affect the contractile responses to lower doses of adenosine. Whether this is due to P,-purinoceptors not being involved in the contractile response, or whether preferential blockade of the relaxant response leaves the contraction unopposed and apparently unblocked, remains to be established.

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.

Quinacrine inhibits oxygen radicals release from human alveolar macrophages

We examined the effect of quinacrine, an anti-malarial drug which inhibits phospholipase A2, on phorbol myristate acetate (PMA) stimulated alveolar macrophage oxygen radical secretion. This drug suppressed 30% of radicals release, which was 70% of the amount inhibited by superoxide dismutase, a specific inhibitor of oxygen radicals. In addition, this reduction was at the same magnitude as dexamethasone. This and previous results on other inflammatory cells support the assumption that quinacrine may have a beneficial effect on bronchial asthma.

Animal models for testing anti-inflammatory drugs for treatment of bronchial hyperreactivity in asthma

In the first part of this review the important role played by the bronchial hyperreactivity caused by chronic bronchopulmonary inflammation in asthma is described. Deliberately, more emphasis is placed on the role of pro-inflammatory eosinophils, alveolar macrophages, lymphocytes and platelets rather than on mast cells and neutrophils or the numerous mediators. The reason for this is that, on account of the large number of mediators and their multitude of functions and interactions in asthma, antagonism of a specific mediator will probably not be clinically relevant for optimally effective curative treatment of asthma. Inhibition of the infiltration and activation of pro-inflammatory cells is likely to be a more successful approach. In the second part, various animal models of bronchial hyperreactivity, which could be suitable for testing anti-asthmatic drugs, are discussed. Most animal models pay too little attention to chronic bronchopulmonary inflammation as the cause of bronchial hyperreactivity in asthma. In various models the bronchial hyperreactivity is provoked by a single mediator and this leads to selection of specific antagonists which are unlikely to be of clinical benefit. Rats appear to have certain advantages over guinea-pigs as experimental animals for bronchial hyperreactivity.

Pathogenesis of asthma: therapeutic implications

The current knowledge of asthma, specifically an appreciation of the contributing mechanisms leading to its development as well as its clinical features, has increased vastly in recent years. A better understanding of asthma's inflammatory nature has resulted in wider use of antiinflammatory agents. Specific effects of available antiasthma medications have been better elucidated, thereby helping to focus the development of newer drugs and improve the use of currently available therapeutic agents. The purpose of this article is to further understanding of asthma by providing the pathologic and physiologic basis of this disease. This is vitally important information as it is shaping the directions of the therapeutic approach to asthma care.

Stimulation of airway ciliary motility by immunologically activated canine pulmonary macrophages: role of leukotrienes

To elucidate a possible interaction between alveolar macrophages and airway epithelial cells in allergic conditions, we studied the effect of immunologically stimulated macrophages on ciliary beat frequency (CBF) of cultured canine tracheal epithelium by a photoelectric method. Administration of supernatants from macrophages incubated with anti-dinitrophenyl (DNP) IgE antibody and anti-dinitrophenyl-human serum albumin dose-dependently increased ciliary beat frequency, the maximal increase from the baseline being 30.4 +/- 5.0% (mean +/- SE, P less than 0.01), an effect that was accompanied by the release of leukotriene (LT) C4 and leukotriene D4. This ciliostimulation was not affected by pretreatment of macrophages with indomethacin but was inhibited by that with nordihydroguaiaretic acid. Addition of FPL 55712 abolished the response of ciliary beat frequency to the stimulated macrophages, and exogenously administered leukotriene C4 and leukotriene D4 dose-dependently increased ciliary beat frequency. These results suggest that macrophages increase respiratory ciliary motility through the IgE-mediated release of leukotrienes and may modulate mucociliary transport function in the airway.

Inhibition of chemiluminescence in granulocytes and alveolar macrophages by azelastine

The effect of azelastine, an orally effective antiasthmatic antiallergic drug on the generation of oxygen-derived free radicals in phagocytes was investigated using different chemiluminescence-assays. The chemiluminescence (CL) of both human polymorphonuclear granulocytes (PMNL) and guinea-pig alveolar macrophages (AM) was induced either by phorbol myristate acetate (PMA) or zymosan and amplified either by lucigenin or DMNH (7-dimethylamino-naphthalene-1,2-dicarbonic-acidhydrazide). The inhibitory effect of azelastine was dependent on the inducer employed and the condition and type of cells used. Azelastine reduced PMA-induced CL concentration-dependently in both PMNL (IC30 = 3.9 microM) and AM (IC30 = 9.8 microM). In AM zymosan-induced CL was inhibited 21.7% by 10 microM azelastine, whereas in PMNL it remained unchanged up to 10 microM azelastine. Azelastine has a significantly stronger inhibitory effect (IC30 = 4.2 microM) on oxygen free radical generation in AM primed by fetal calf serum than in unprimed AM. Based on present results it is likely that azelastine inhibits oxygen-derived free radical generation by interaction with protein kinase C.

Eosinophilic inflammation in asthma

BACKGROUND AND METHODS

The importance of eosinophils in the pathogenesis of bronchial asthma is not established. In an attempt to evaluate the role of eosinophilic inflammation in asthma, we compared 10 normal subjects with 43 patients with chronic asthma, 19 of whom had severe disease as assessed by a clinical scoring method described by Aas and by pulmonary-function tests. Eosinophils were counted in peripheral blood and bronchoalveolar-lavage fluid, and in biopsy specimens obtained from the patients and post mortem from 8 subjects without asthma, but not from the 10 normal controls. Eosinophil cationic protein was titrated by radioimmunoassay in the bronchoalveolar-lavage fluid from all subjects and studied by immunohistochemistry in the biopsy specimens.

RESULTS

There was a significant increase in the number of peripheral-blood eosinophils in the patients that was correlated with the clinical severity of asthma (P less than 0.001) and pulmonary function (P less than 0.03). Levels of eosinophils and eosinophil cationic protein were increased in the bronchoalveolar-lavage fluid from the patients and were also correlated with the severity of asthma (P less than 0.001 and P less than 0.002, respectively). Hematoxylin-eosin staining of bronchial-biopsy specimens showed that intraepithelial eosinophils were present only in patients with asthma. Immunohistochemical analysis of eosinophil cationic protein revealed that normal subjects had only a few nondegranulated eosinophils deep in the submucosa, whereas all the patients had degranulated eosinophils beneath the basement membrane and among epithelial cells. In some patients there was a relation between the presence of degranulated eosinophils and epithelial damage.

CONCLUSIONS

Eosinophilic inflammation of the airways is correlated with the severity of asthma. These cells are likely to play a part in the epithelial damage seen in this disease.