Allergen-induced synthesis of F-2-isoprostanes in atopic asthmatics - Evidence for oxidant stress

It is thought that reactive oxygen species (ROS) participate in the inflamm ation which characterizes asthma, but the evidence supporting this contenti on is incomplete. F-2-isoprostanes (F-2-IsoPs) are arachidonate products fo rmed on membrane phospholipids by the action of ROS and thereby represent a quantitative measure of oxidant stress in vivo. Using a mass spectrometric assay we measured urinary release of F-2-IsoPs in 11 patients with mild at opic asthma after inhaled allergen challenge. The excretion of F-2-IsoPs in creased at 2 h after allergen (1.5 +/- 0.2 versus 2.6 +/- 0.3 ng/mg creatin ine) and remained significantly elevated in all urine collections for the 8 -h period of the study (analysis of variance [ANOVA]). The measured compoun ds were of noncyclooxygenase origin because neither aspirin nor indomethaci n given before challenge suppressed them. Urinary F-2-IsoPs remained unchan ged after inhaled methacholine challenge. In nine atopic asthmatics, F-2-Is oPs were quantified in bronchoalveolar lavage fluid (BALF) at baseline valu es and in a separate segment 24 h after allergen instillation. F-2-IsoPs we re elevated late in the BALF (0.9 +/- 0.2 versus 11.4 +/- 3.0 pg/ml, baseli ne versus allergen, respectively, p = 0.007). The increase was inhibited by pretreatment of the subjects with inhaled corticosteroids. These findings provide a new evidence for a role for ROS and lipid peroxidation in allerge n-induced airway inflammation.