Neurotrophins are increased in bronchoalveolar lavage fluid after segmental allergen provocation

The mechanisms linking inflammation and airway hyperresponsiveness in allergic bronchial asthma are still not completely defined. Since neurotrophic factors increase nerve excitability and neurotransmitter synthesis and are produced by immunocompetent cells, they are likely candidates as mediators of inflammation and hyperresponsiveness. We tested the hypothesis that neurotrophin concentrations will increase in the bronchoalveolar lavage (BAL) fluid from patients with asthma after segmental allergen provocation. For this purpose an individually standardized dose of allergen or saline was instilled into different segments during bronchoscopy in eight subjects with mild allergic bronchial asthma. Segments were then lavaged 10 min and 18 h after allergen challenge or saline instillation. There was a significant increase in the neurotrophins nerve growth factor, brain-derived neurotrophic factor, and neurotrophin-3 in BAL fluids 18 h after allergen but not saline challenge. We conclude that neurotrophins are produced endobronchially following allergen provocation, suggesting a contribution to the pathogenesis of asthma.