Background: Platelets are involved in the pathogenesis of aspirin-induced asthma (AIA). AIA patients suffer from an active disease despite avoidance of aspirin, and it has been suggested that administration of aspirin to these patients increases the generation of immediate oxygen products of arachidonic acid, 12-hydroperoxyeicosatetraenoic acid (12-HPETE), in their platelets. 12-HPETE further activates the 5-lipoxygenase of leukotriene B4-producing inflammatory macrophages precipitating an acute asthmatic attack. Glutathione peroxidase (GPX) has the antioxidant capacity to reduce 12-HPETE, and thus modulate the arachidonic acid metabolic cascade. There is evidence that selenium (Se) nutrition can influence asthma but Se status in AIA patients has not received much attention. Methods: We measured Se concentrations and GPX activities in platelets and plasma from 13 patients with AIA. Age-and sex-matched healthy individuals served as the control group. Results: Patients with AIA had significantly higher median platelet Se concentration (102 ng/mg platelet protein) when compared with controls (49 ng/mg platelet protein, P ¼ 0.003). Plasma Se concentrations in patients with AIA and controls were not significantly different (P ¼ 0.59). Median platelet GPX activity was significantly higher in patients with AIA (102.7 mU/mg platelet protein) than in controls (66 mU/mg protein) (P ¼ 0.05). The patient and control groups when combined showed weak, but significant correlation between platelet Se concentration and platelet GPX activity (r ¼ 0.44; P ¼ 0.03). Conclusion: It is proposed that the higher platelet Se concentration observed in AIA patients contributed to the higher platelet GPX activity seen in these patients. Such an enhanced antioxidant defence system might represent an adaptive response to protect against increasing free radical production by inflammatory cells in AIA and help decelerate ongoing respiratory hypersensitivity.

Aspirin and other inhibitors of cyclo-oxygenase precipitate acute bronchospasm in about 10% of adult asthmatics. It has been assumed that cyclo-oxygenase is involved in the pathogenesis of bronchospasm, but the precise mechanism remains poorly understood. The oxygenation products of arachidonic acid include hydroperoxyeicosatetraenoic acid and cyclic endoperoxides. Glutathione peroxidase (GPX) reduces semi-stable hydroperoxides to less reactive alcohols and removes H(2)O(2) involved in inflammation. GPX could, therefore, modulate oxidation of arachidonic acid in the cyclo-oxygenase and lipoxygenase pathways, but the involvement of GPX in the pathogenesis of asthma has received little attention. We measured GPX activity in platelets, peripheral blood lymphocytes (PBL), red blood cells (RBC) and plasma from 13 patients with aspirin-induced asthma (AIA). Age- and sex-matched healthy individuals served as the comparison group. The patients had significantly higher GPX activity in platelets (P = 0.05) and tended to have high GPX activity (P = 0.08) in plasma but not in RBC or PBL. The results suggest that the increased GPX activity may be an adaptive advantage in AIA to protect against increased free radical production by inflammatory cells. That the higher GPX activity was not evident in all cell types studied may indicate a differential role played by them as effector cells in the pathogenesis of AIA.