Nasal hyperosmolar challenge with a dry powder of mannitol in patients with allergic rhinitis. Evidence for epithelial cell involvement

Background The responses to airway hyperosmolar challenges probably involve various inflammatory mediators. However, it is not fully understood which cell type/types are the source of these mediators. Potential cell types inc lude mast cell, epithelial cell and the sensory c-fibre nerve cell. Objective To clarify which cell types are involved with the mediator respon se to hyperosmolarity in the human airway. Methods Ten healthy subjects, 11 patients with nonactive allergic rhinitis, and nine with active allergic rhinitis were challenged intranasally with m annitol powder, and with sham provocation, on separate days. Symptoms were assessed by visual analogue scales and nasal patency by measuring the nasal peak inspiratory flow (nPIF). Nasal lavage fluid levels of alpha (2)-macro globulin (an index of plasma extravasation), substance P (an index of senso ry nerve cell activation), tryptase (an index of mast cell activation) and 15-hydroxyeicosatetraenoic acid (15-HETE, an index of epithelial cell activ ation) were analysed. Results Immediate, although transient burning was the most prominent sympto m in all groups whereas only the patients with active rhinitis experienced a fall in nPIF. Mannitol significantly increased the nasal lavage fluid 15- HETE levels in the allergic patients (P<0.01 vs the sham challenge), but no t in the healthy subjects. The increase in 15-HETE correlated with nasal sy mptoms for itching (r(s) = 0.65, P = 0.019) and burning (r(s) = 0.72, P = 0 .009). Detectable levels of tryptase was found only in five allergic subjec ts. Lavage levels of substance P and <alpha>(2)-macroglobulin did not not c hange. Conclusion Epithelial cell seems to be involved with the mediator response to airway hyperosmolar challenge. The roles of sensory c-fibre nerve cell a nd mast cell remained less clear.