Eosinophilia is a feature of airway inflammation associated with asthma. Leukotriene antagonists provide therapeutic benefit in asthma, but their potential antiinflammatory actions have not been fully explored. We have examined the role of eosinophil-derived cysteinyl leukotrienes in the maintenance of eosinophil survival, and the involvement of leukotrienes in the paracrine stimulation of eosinophil survival by mast cells and lymphocytes. We obtained eosinophils and autologous lymphocytes from peripheral blood of asthmatic subjects. Leukotriene (LT)-B(4), LTC(4) and LTD(4), granulocyte-macrophage colony-stimulating factor (GM-CSF), and fibronectin promoted eosinophil survival. LTD(4) (10(-)(6) M) was as effective as GM-CSF (5 ng/ml) and fibronectin (400 ng/ml) in promoting survival. Lymphocytes and conditioned medium from a human mast cell line (HMC-1) induced eosinophil survival. Blockade of cysteinyl leukotriene receptors with SKF 104353 (pobilukast, 3 nM), and inhibition of 5-lipoxygenase (5-LO) with BW A4C (1 microM) and of 5-LO activating protein with MK 886 (1 microM), all increased basal rates of eosinophil apoptosis and reversed GM-CSF-induced eosinophil survival. Fifty percent reversal of GM-CSF- induced survival was achieved with SKF 104353 at 0.3 nM. The potency of SKF 104353 was two orders of magnitude greater than that of the LTB(4) receptor antagonist SB 201146. Mast cell- and lymphocyte-induced eosinophil survival were completely reversed by SB 201146, SKF 104353, BW A4C, and MK 886. These findings provide evidence for the involvement of an autocrine cysteinyl leukotriene pathway that supports eosinophil survival in response to a range of survival stimuli. They also suggest that LTB(4) could act as a paracrine stimulus of eosinophil survival.

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Persistent neutrophilia is a feature of chronic obstructive pulmonary disease (COPD). Leukotriene synthesis inhibitors and cysteinyl leukotriene receptor antagonists have shown efficacy in the treatment of asthma. Antagonism of leukotriene (LT)B(4) receptors is being considered as a mode of treating COPD. We examined the capacity for inhibition of leukotriene synthesis and LTB(4) receptor antagonism to reduce survival of neutrophils from patients with COPD and those from normal subjects. The basal apoptosis level of these cells was 55.4 +/- 2.4% (mean +/- SEM) of total cells. Separate exposure to lipopolysaccharide (LPS), granulocyte-macrophage colony-stimulating factor (GM-CSF), dexamethasone (DEX), and LTB(4) increased neutrophil survival (p < 0. 001). The LTB(4) receptor antagonist SB201146 abolished LPS-induced survival in a concentration-dependent manner (10 pmol to 0.1 microM), with an IC(50) of 1.9 nM. Combined exposure to SB201146 and to the cysteinyl leukotriene antagonist SKF104353 did not have a greater effect on survival than did exposure to SB201146 alone. Inhibition of 5-lipoxygenase (5-LO) with BWA4C and of 5-LO-activating protein (FLAP) with MK886 abolished GM-CSF- and DEX-induced neutrophil survival. BWA4C and MK886 abolished GM-CSF- induced neotrophil survival in a concentration-dependent manner (1 nM to 10 microM), with IC(50) values of 182.0 nM and 63.1 nM, respectively. These findings demonstrate reversal of LPS-, GM-CSF-, and DEX-induced neutrophil survival by LTB(4) receptor antagonism and inhibitors of 5-LO and FLAP. They also suggest a potential additional antiinflammatory mode of action of these compounds through reduction of cell survival.

Recent studies have suggested that theophylline, a nonspecific phospho-diesterase inhibitor, has useful anti-inflammatory actions in asthma. Phosphodiesterase 4 (PDE4) represents the predominant PDE isoenzyme present in inflammatory cells. PDE4 inhibitors might, therefore, have beneficial effects in asthma. Sideeffects, specifically nausea, have limited the use of existing agents. CDP840 is an orally active, potent and selective PDE4 inhibitor. We have examined the effect of CDP840 on the allergen-induced asthmatic response, its possible modes of action, and its tolerability at therapeutic doses.A total of 54 patients were recruited to three double-blind, placebo-controlled studies. The first study examined the effect of CDP840 (15 mg b.i.d. for 9.5 days) on the allergen-induced asthmatic response in patients with known dual response to allergen. A second study examined the effect of CDP840 (15 mg b.i.d. for 9.5 days) on airway responsiveness to histamine. A third study examined whether single dose CDP840 (15 and 30 mg) had significant bronchodilatory effects.In all studies, CDP840 was well-tolerated, with no patients reporting nausea. CDP840 did not lead to changes in baseline forced expiratory volume in one second (FEV1) as compared to placebo. The late asthmatic response (LAR) to allergen, expressed as area under the curve at 3-8 h (AUC3-8h), was inhibited by 30% (p=0.016), an effect which persisted to the end of the observation period. The early asthmatic response (EAR) was unaffected, and there was no bronchodilatory effect at the doses used. Treatment with CDP840 did not affect bronchial hyperresponsiveness to histamine.In conclusion, CDP840 significantly attenuated the late asthmatic response to allergen challenge in the absence of any bronchodilatory or histamine antagonist effect. This suggests that CDP840 may exert its effects via an anti-inflammatory mechanism.