The effect of adding oral dexamethasone to feed alterations on the airway cell inflammatory gene expression in stabled horses affected with recurrent airway obstruction.
Authors: DeLuca L, Erb H N, Young J C, Perkins G A, Ainsworth D M
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary Recurrent airway obstruction (RAO) in stabled horses involves excessive inflammatory chemokine production in the airways, and whilst switching from hay to pelleted feed offers some clinical benefit, the question remained whether adding systemic anti-inflammatory therapy could enhance outcomes. DeLuca and colleagues conducted a randomised cross-over study in 12 RAO-affected horses, comparing feed modification alone against feed modification plus a 21-day tapering course of oral dexamethasone, measuring inflammatory gene expression (IL-8, CXCL2, IL-1β, IL-6 and pattern-recognition receptors) in bronchoalveolar lavage cells and bronchial epithelium using quantitative PCR. Both interventions reduced airway neutrophilia and respiratory effort, yet dexamethasone combination therapy produced substantially greater suppression of key inflammatory mediators in lavage fluid—IL-8, CXCL2 and IL-1β expression dropped 3.3-, 2.5- and 4.7-fold respectively compared with diet change alone—whilst also achieving fewer treatment failures and more consistent clinical improvement. The results suggest that for horses requiring continued stabling, oral dexamethasone administered alongside environmental and nutritional modifications provides superior short-term control of the RAO inflammatory cascade, though practitioners should note that neither intervention altered IL-1 receptor or Toll-like receptor expression in the epithelium itself, indicating incomplete resolution of the underlying pathophysiology.
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Practical Takeaways
- •For stabled RAO horses, switching from hay to pelleted feed improves lung function, but adding a 21-day dexamethasone course provides significantly greater reduction in airway inflammation and more reliable clinical response
- •If stabling cannot be avoided, the combination approach is worth discussing with clients as it produces faster results and fewer treatment failures than diet modification alone
- •Feed changes reduce some inflammatory markers in the airway epithelium equally well as dexamethasone, suggesting environmental management should always be the foundation of RAO treatment
Key Findings
- •Both feed alterations (pellets vs hay) and dexamethasone reduced airway neutrophilia and breathing efforts in stabled RAO-affected horses
- •Dexamethasone combined with feed changes reduced IL-8, CXCL2, and IL-1beta expression in BALF cells by 3.3-, 2.5-, and 4.7-fold respectively compared to feed changes alone
- •Both treatments equally reduced IL-8 and CXCL2 expression in airway epithelium, but neither altered IL-1R2 and TLR4 expression
- •Combined dexamethasone and feed alterations showed fewer treatment failures and more rapid, consistent improvement in pulmonary function than feed changes alone