Stimulation of airway neutrophils following dexamethasone administration and equid herpesvirus-2 challenge in horses.

This study investigates the effects of induced airway inflammation in horses, specifically looking at neutrophil stimulation. It found that administering dexamethasone and equid herpesvirus-2 (EHV-2) significantly activated and degranulated neutrophils in the trachea, with noticeable changes also seen in the lower airways.

Research Context and Objective

• The study was set out to explore the impact of experimentally-induced airway inflammation on healthy horses, specifically the stimulation of a type of white blood cell called neutrophils.
• The researchers aimed to use two interventions – administration of a corticosteroid named dexamethasone and inoculation with equid herpesvirus-2 (EHV-2), a virus known to affect horses.

Methodology

• Six horses were administered dexamethasone, a medication often used to treat inflammation. Of these, four were then inoculated with EHV-2 to see whether this would have any additional impact.
• The researchers observed and recorded any changes in neutrophil levels and behavior in the trachea and lower airways of the horses for up to 14 days following the interventions.

Findings

• The results indicated a significant increase in neutrophil count (neutrophilia) in the tracheal wash (a diagnostic procedure where the trachea is washed with saline and the return fluid is analysed) and bronchoalveolar lavage fluid (a similar procedure carried out in the lungs) of the horses for up to 6 days following the interventions.
• Levels of neutrophil elastase (NE) and myeloperoxidase (MPO) – markers for neutrophil activity – were shown to increase notably for up to 14 days in the tracheal washes. Both markers were found to strongly correlate with neutrophil counts.
• No significant changes were observed in the serum levels of surfactant protein D, a molecule of interest in lung disease research, throughout the study period.

Conclusion

• The study suggests that the administration of dexamethasone, with or without EHV-2 inoculation, is associated with a long-lasting activation and degranulation (release of cellular substances) of neutrophils in the horse’s trachea.
• Moderate changes in the same parameters were also observed in the lower airways.
• This research provides insights into airway inflammation in horses, which could inform future treatments for equine respiratory conditions.