Stimulation of airway neutrophils following dexamethasone administration and equid herpesvirus-2 challenge in horses.
Authors: Richard Eric A, Pitel Pierre-Hugues, Lemaitre Laurent, Jas Dominique, Lekeux Pierre, Pronost Stéphane, Fortier Guillaume
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary Dexamethasone administration—with or without subsequent equid herpesvirus-2 (EHV-2) challenge—triggers a prolonged neutrophilic response in the equine respiratory tract, characterised by significant elevations in tracheal neutrophil counts persisting for up to 6 days post-treatment, alongside markedly elevated neutrophil elastase and myeloperoxidase concentrations that remain significantly elevated for 14 days. This 2014 experimental study involving six horses examined the inflammatory cascade following steroid exposure and viral challenge by collecting samples via tracheal wash and bronchoalveolar lavage, finding that neutrophil degranulation markers correlated strongly with absolute neutrophil counts, suggesting active cellular activation rather than passive recruitment alone. The sustained elevation of these protease markers in the trachea—particularly elastase, which degrades structural proteins—indicates tissue-damaging potential that extends considerably beyond the initial neutrophilic infiltration phase. Notably, serum surfactant protein D remained unchanged, implying that systemic markers may not reflect lower airway inflammation adequately. For practitioners managing horses with viral respiratory infections or those receiving corticosteroid therapy, these findings underscore the risk of secondary airway inflammation and tissue damage, suggesting that post-treatment respiratory monitoring and support may warrant extension beyond the visible clinical resolution window to mitigate long-term airway remodelling effects.
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Practical Takeaways
- •Dexamethasone treatment in horses may trigger sustained neutrophil activation in airways lasting 1-2 weeks, with potential implications for horses with concurrent respiratory infections
- •Tracheal wash neutrophil counts and elastase/myeloperoxidase levels can serve as markers for monitoring airway neutrophil activation and degranulation in clinical cases
- •Systemic biomarkers (serum surfactant protein D) may not reliably reflect lower airway inflammation, necessitating direct sampling via bronchoalveolar lavage for accurate assessment
Key Findings
- •Dexamethasone administration with or without EHV-2 inoculation induced significant neutrophilia in tracheal wash and bronchoalveolar lavage fluid persisting up to 6 days
- •Neutrophil elastase and myeloperoxidase concentrations increased significantly compared to baseline for up to 14 days in tracheal washes
- •Neutrophil elastase and myeloperoxidase were significantly correlated with neutrophil counts, indicating active neutrophil degranulation
- •Serum surfactant protein D levels remained unchanged throughout the study despite airway inflammation