A CONSORT‐guided, randomized controlled clinical trial of nebulized administration of dexamethasone and saline on lower airway cytokine mRNA expression in horses with moderate asthma

Abstract Background Nebulized administration of dexamethasone on cytokine regulation in horses with moderate asthma has not been investigated. Objective To investigate the changes in expression of inflammatory cytokine mRNA after nebulized administration of dexamethasone treatment of horses with moderate asthma. Animals Horses with naturally occurring moderate asthma (n = 16) and healthy control horses (n = 4). All horses were kept in a dusty environment during the study. Methods Prospective, parallel, randomized, controlled, blinded clinical trial. Blood endogenous cortisol, tracheal mucus, and bronchoalveolar lavage (BAL) were sampled before and after 13 days treatment with either nebulized administration of dexamethasone (15 mg once daily) or 0.9% saline (3 mL). Treatment groups were randomly allocated via randomization function (Microsoft Excel). Amplification of target mRNA in BAL fluid (IL‐1β, IL‐4, IL‐5, IL‐6, IL‐8, IL‐10, IL‐12, IL‐17, IL‐23, IFN‐γ, Eotaxin‐2, and TNF‐α) was achieved by qPCR, and the relative expression software tool was used to analyze BAL inflammatory cytokine mRNA. Results Horses treated with nebulized administration of dexamethasone had increased relative expression of IL‐5 (1.70‐fold), IL‐6 (1.71‐fold), IL‐17 (3.25‐fold), IL‐12 (1.66‐fold), and TNF‐α (1.94‐fold), and decreased relative expression of IL‐23 (1.76‐fold; P = .04) in samples collected on Day 14, in comparison to samples collected on Day 0 (all P .05). Conclusions and Clinical Importance Nebulized administration of dexamethasone was associated with increased expression of inflammatory cytokine mRNA. There was no improvement in inflammatory airway cytology associated with either dexamethasone or saline treatment.