Analysis of lipid mediator profiles in the blood of horses with equine asthma using UPLC-MS/MS

Equine asthma (EA) is a chronic inflammatory disease of the lower respiratory tract in horses, which is mainly triggered by dusty hay. EA is becoming increasingly acknowledged as a valuable animal model for studying human asthma. Research on the pathogenesis of EA has primarily focused on the associated cells and cytokines involved. However, the role of inflammation-related lipid mediators (LM) in the development and progression of equine asthma remains elusive. LMs are categorized into pro-inflammatory arachidonic acid (AA)-derived leukotrienes (LTs) and prostaglandins (PGs), as well as inflammation-resolving LMs derived from omega-3 fatty acids, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). In this study, targeted liquid chromatography-tandem mass spectrometry-based metabololipidomics was employed to analyze LM profiles from serum and stimulated whole blood samples collected from 30 healthy horses and from 30 horses with EA. We found that the levels of free fatty acids, as well as their metabolomes, vary substantially among individual horses in serum. In this regard, we observed no significant differences between healthy horses and those with EA, highlighting the complexity of the pathogenesis of respiratory disease in horses. In detail, we detected 12-hydroxyeicosatetraenoic acid (HETE) as the most abundant LM in serum and stimulated whole blood. Furthermore, we found that the levels of LMs decrease with increasing age of the horses. Conclusively, this study presents the comprehensive assessment of LM profiles in serum and stimulated whole blood from horses, which can serve as scientific basis for transferring findings from equine to human asthma.