Local coagulation activation following bronchial instillation of house dust mite allergen (HDM) and HDM/Lipopolysaccharide (LPS) in mild asthmatics

Rationale: Exposure to house dust, containing HDM and LPS, is associated with exacerbations of allergic asthma. In patients with asthma, the hemostatic balance in the lungs is often instable. We hypothesized that adding LPS to bronchial provocation with HDM increases activation of coagulation and complement pathways in asthmatics while on maintenance treatment with inhalation corticosteroids (ICS). Aim: To assess the activation of coagulation in bronchoalveolar lavage fluid (BALF) induced by provocation with HDM +/- LPS. Methods: We included 32 mild asthmatic patients with HDM allergy. After 2 weeks run-in with fluticasone 100μg bid, subjects underwent bronchoscopy for segmental instillation of saline in one lung followed by instillation of HDM +/- LPS in the contralateral lung. Six hours later, BAL was performed. Statistical comparisons were made by univariate analysis. Results: Additional instillation of LPS to HDM resulted in a significant increase in levels of thrombin-antithrombin complexes (TATc) (p = 0.015) and complement 4b (p = 0.007) in BALF. Conclusion: Additional instillation of LPS to a provocation with HDM in mild asthma increases pulmonary activation of coagulation and activation of the complement system. This suggests that coagulation contributes to environmentally-induced airway responses in asthma.