Role of prostaglandin I₂ in the bronchoconstriction-triggered cough response in guinea pigs

Purpose/Aim of the study: Methacholine chloride (MCh) inhalation causes bronchoconstriction and cough. Following MCh-induced bronchoconstriction, metabolic products of prostaglandin I₂ (PGI₂) increase in bronchoalveolar lavage fluid (BALF), suggesting that PGI₂ plays a role in the cough response. Accordingly, we used an experimental guinea pig model to evaluate the role of PGI₂ in the bronchoconstriction-triggered cough response.

Materials and methods: Experiment 1: The concentration of PGF_1α, a stable metabolite of PGI₂, in BALF was assessed in animals exposed to nebulized MCh and animals exposed to nebulized saline. Experiment 2: Bronchoconstriction and cough were assessed in 3 groups of animals after MCh inhalation (a saline group, low-dose PGI₂ group, and high-dose PGI₂ group). Enhanced pause (Penh) was used as a measure of bronchoconstriction. Experiment 3: Bronchoconstriction and cough were assessed in 3 groups of animals (groups administered saline, a low dose of a specific antagonist of the PGI₂ receptor (IP antagonist), and a high dose of a specific IP antagonist).

Results: The PGF_1α concentration in BALF was significantly higher in the bronchoconstriction group than in the control group. In animals administered high-dose PGI₂, the MCh-induced increase in Penh was significantly suppressed, and the number of coughs induced by bronchoconstriction was significantly decreased. In animals treated with a high dose of an IP antagonist, the MCh-induced increase in Penh was not affected, and the number of coughs increased.

Conclusions: Our results suggest that PGI₂ ameliorates a bronchoconstriction-triggered cough. The measurement and administration of PGI₂ may assist in the diagnosis and treatment, respectively, of the cough response triggered by bronchoconstriction.