Nasal corticosteroid treatment reduces substance P levels in tear fluid in allergic rhinoconjunctivitis

Abstract

Background: The mechanisms underlying conjunctival symptom reduction by nasal corticosteroids in allergic rhinoconjunctivitis are unknown. A naso-ocular reflex may be present.

Objective: To study the effects of nasal fluticasone furoate (FF) on conjunctival symptoms and substance P and histamine levels in tear fluid after nasal grass pollen provocation (GPP).

Methods: A double-blind placebo-controlled study was performed in 26 grass pollen-allergic patients. A selective GPP was performed during the grass pollen season after 2 weeks of FF or placebo treatment. Nasal and conjunctival symptoms were scored using a visual analog scale (VAS), and tear fluid was collected for measuring substance P and histamine using an enzyme-linked immunosorbent assay.

Results: Compared with placebo, FF reduced conjunctival symptom scores during the pollen season (-1.75 [-2.75, 0.20] vs 0.0 [0.0, 0.0]; P = .01) and after GPP at 15 minutes (0.05 [-0.42, 1.52] vs 2.05 [0.62, 3.62]; P < .001) and 1 hour (-0.45 [-1.75, 0.1] vs 0.05 [-0.97, 1.85]; P < .01). Treatment with FF decreased substance P levels in tear fluid (44.11 [32.81, 61.02] vs 65.26 [48.62, 79.73] pg/mg protein; P = .0098). Histamine levels in tear fluid showed a GPP-induced increase in the placebo group (7.26 [3.12, 9.69] vs 5.71 [2.05, 7.00] ng/mg protein; P = .02), but not in the FF group (6.77 [3.43, 13.00] vs 5.24 [3.18, 7.06] ng/mg protein; P = .08).

Conclusion: FF nasal spray reduced conjunctival symptoms in grass pollen-allergic patients in parallel with lower substance P levels in tear fluid. These data help in understanding the reduction of conjunctival symptoms by intranasal anti-inflammatory therapy.