Abstract: Background – In horses, the proportion of neutrophils in bronchoalveolar lavage (BAL) is related to dust exposure. Dietary intake of omega-3 polyunsaturated fatty acids also affects BAL neutrophil proportions, presumably due to changes in the concentrations of specialized pro-resolving lipid mediators (SPM).
Hypothesis/Objectives – Plasma SPM concentrations are related to BAL neutrophil proportions and modulate the relationship between dust exposure and neutrophils in the airway.
Animals – Twenty-five Thoroughbred racehorses housed at the local racetrack.
Methods – As part of a feed trial, BAL cytology, dust exposure (PM2.5), and plasma SPM (ELISA) were measured at week-0 and week-6. We used univariate generalized linear mixed models (GLMM) to screen for the effect of each SPM on BAL neutrophil proportions. Any SPM identified as significantly related to neutrophil proportions was included in a multivariate GLMM of BAL neutrophil proportions that also included dust exposure and the interaction between SPM and dust exposure as explanatory variables. Significance was set at p< 0.05.
Results – Plasma resolvin D2 (RvD2) concentration was significantly related to BAL neutrophil proportions (p=0.0496). Multivariate analyses revealed a significant interaction between RvD2 concentration and PM2.5 exposure (p=0.0052). At the mean PM2.5 exposure (0.01 mg/m3), a 50 pg/ml increase in the RvD2 concentration resulted in a 15% reduction in the BAL neutrophil proportion.
Conclusions and clinical importance – In the horse, plasma RvD2 dampens the neutrophilic response of the airway to dust exposure. Diets or supplements that increase plasma RvD2 concentration may be beneficial in the management of neutrophilic airway inflammation.
