Allergen inhalation challenge induces decrease of serum neutral endopeptidase (NEP) in asthmatics

There is accumulating evidence that tachykinins are implicated in inflammation, including asthma. Therefore, we hypothesized that the neutral endopeptidase (NEP), under challenge conditions, could be affected. Serum from 21 asthmatics and six healthy volunteers was sampled before, 30, and 120 min after allergen challenge. NEP-IR was determined using an ELISA and was found in all subjects. Compared to prechallenge, no difference was seen between asthmatics and controls; however, under challenge conditions, NEP-IR in asthmatics was significantly lower (30 min, P = 0.058; 120 min, P = 0.0017, respectively). This finding supports indirectly the hypothesis that tachykinins are released during allergen exposure, and suggests a regulatory role of NEP.