EFFECTS OF COLCHICINE ON IGE-MEDIATED EARLY AND LATE AIRWAY REACTIONS

Background: The pathogenesis of bronchial asthma is thought to involve elements of both acute and chronic inflammation. Hence, there is growing interest in the potential of immunomodulatory drugs in asthma therapy. This study examines the effects of the anti-inflammatory compound colchicine on early and late allergen-induced, IgE-mediated airway reactions. Methods: Nine mildly allergic asthmatic subjects were evaluated in a single-blind, two-way crossover study designed to examine the effects of colchicine and placebo on early and late airway reactions to ragweed allergen and related changes in nonspecific responsiveness to methacholine. Results: Compared with placebo, colchicine provided 19% (p=0.036) and 40% (p=0.004) inhibition of early and late airway reactions to allergen, respectively. Allergen-induced increases in methacholine responsiveness were observed with both types of treatment, although there was a trend toward a smaller increase after administration of colchicine (p=0.13). We also found that methacholine responsiveness per se was not directly altered by colchicine (n=7). In 6 subjects, we found suppression of neutrophil leukotriene B-4 generation after colchicine treatment, suggesting that the colchicine dose (0.6 mg twice daily) was sufficient to produce an anti-inflammatory effect. Further in vitro studies using purified human lung tissue mast cells failed to demonstrate inhibition of mediator release at concentrations corresponding to achievable tissue or blood levels during the in vivo trial. Conclusion: Colchicine partially inhibits IgE-mediated early and late airway reactions at conventional clinical doses. This inhibitory effect may be mediated via suppression of some cell species other than the lung tissue mast cell. Controlled studies to examine the benefits of colchicine in clinically evidenced asthma are warranted.