Inhaled leukotrienes cause bronchoconstriction and neutrophil accumulation in horses.

The research primarily focuses on the effects of leukotrienes, a type of bioactive lipid that can cause inflammation, on horses. It was observed that inhaling different variants of leukotrienes caused constriction in bronchia and an increase in neutrophil accumulation, suggesting their potential contribution to the development of Chronic Obstructive Pulmonary Disease (COPD) in horses.

Methodology

• The researchers carried out independent studies where solutions of LTD4 and LTB4 leukotrienes were administered to the airways of healthy animals via nebulisation.
• They observed the changes in pleural pressure and rates of neutrophil accumulation in response to the inhalation of different types of leukotrienes.

Findings

• LTD4 was found to cause a dose-dependent increase in pleural pressure which peaked in three to four minutes and returned to baseline levels between 15 and 20 minutes.
• The potency of LTD4 was found to be significantly higher than methacholine, a bronchodilator used to diagnose bronchial asthma.
• On a molar basis, LTD4 was 305 to 970 times more potent than methacholine
• In contrast, LTB4 didn’t affect pleural pressure but induced an early accumulation of radiolabelled neutrophils in the lungs, which persisted for more than 5 hours in some cases.
• Neither LTD4 nor LTB4 affected the horse’s overall respiratory rate or peripheral blood leucocyte counts.

Conclusion

• The results of the study suggest that, if released during an antigen challenge, LTB4 and LTD4 could contribute to the pathogenesis of equine COPD.
• In a small segment of asymptomatic COPD horses, these leukotrienes appeared to cause similar, albeit smaller, changes in lung function and neutrophil recruitment, suggesting these horses may have reduced responsiveness to these bioactive lipids.