Corticosteroid suppression of lipoxin A4 and leukotriene B4from alveolar macrophages in severe asthma

<p>Abstract</p> <p>Background</p> <p>An imbalance in the generation of pro-inflammatory leukotrienes, and counter-regulatory lipoxins is present in severe asthma. We measured leukotriene B₄(LTB₄), and lipoxin A₄(LXA₄) production by alveolar macrophages (AMs) and studied the impact of corticosteroids.</p> <p>Methods</p> <p>AMs obtained by fiberoptic bronchoscopy from 14 non-asthmatics, 12 non-severe and 11 severe asthmatics were stimulated with lipopolysaccharide (LPS,10 μg/ml) with or without dexamethasone (10^-6M). LTB₄and LXA₄were measured by enzyme immunoassay.</p> <p>Results</p> <p>LXA₄biosynthesis was decreased from severe asthma AMs compared to non-severe (p < 0.05) and normal subjects (p < 0.001). LXA₄induced by LPS was highest in normal subjects and lowest in severe asthmatics (p < 0.01). Basal levels of LTB₄were decreased in severe asthmatics compared to normal subjects (p < 0.05), but not to non-severe asthma. LPS-induced LTB₄was increased in severe asthma compared to non-severe asthma (p < 0.05). Dexamethasone inhibited LPS-induced LTB₄and LXA₄, with lesser suppression of LTB₄in severe asthma patients (p < 0.05). There was a significant correlation between LPS-induced LXA₄and FEV₁(% predicted) (r_s= 0.60; p < 0.01).</p> <p>Conclusions</p> <p>Decreased LXA₄and increased LTB₄generation plus impaired corticosteroid sensitivity of LPS-induced LTB₄but not of LXA₄support a role for AMs in establishing a pro-inflammatory balance in severe asthma.</p