Lipid species profiling of bronchoalveolar lavage fluid cells of horses housed on two different bedding materials

Abstract

The lipidome of equine BALF cells has not been described. The objectives of this prospective repeated-measures study were to explore the BALF cells’ lipidome in horses and to identify lipids associated with progression or resolution of airway inflammation. BALF cells from 22 horses exposed to two bedding materials (Peat 1—Wood shavings [WS]—Peat 2) were studied by liquid chromatography-tandem mass spectrometry (LC–MS/MS). The effects of bedding on lipid class and species compositions were tested with rmANOVA. Correlations between lipids and cell counts were examined. The BALF cells’ lipidome showed bedding-related differences for molar percentage (mol%) of 60 species. Whole phosphatidylcholine (PC) class and its species PC 32:0 (main molecular species 16:0_16:0) had higher mol% after Peat 2 compared with WS. Phosphatidylinositol 38:4 (main molecular species 18:0_20:4) was higher after WS compared with both peat periods. BALF cell count correlated positively with mol% of the lipid classes phosphatidylserine, sphingomyelin, ceramide, hexosylceramide, and triacylglycerol but negatively with PC. BALF cell count correlated positively with phosphatidylinositol 38:4 mol%. In conclusion, equine BALF cells’ lipid profiles explored with MS-based lipidomics indicated subclinical inflammatory changes after WS. Inflammatory reactions in the cellular lipid species composition were detected although cytological responses indicating inflammation were weak.

Lipids in Equine Airway Inflammation: An Overview of Current Knowledge

“…This might indicate that both Cer and HexCer contribute to inflammation resolution in horse lungs. Contrary to the study of Christmann et al [ 22 ] on surfactant, Cer 18:1;O2/16:0 was lower and HexCer 18:1;O2/24:0 higher in the BALF cells after the bedding challenge in healthy horses [ 23 ]. Cer 18:1;O2/24:0 was consistently higher consistently in both surfactant [ 22 ] and BALF cells [ 23 ].…”

“…In our study on equine BALF cells [ 23 ], we found an increased mol% of PI 38:4 in the BALF cells from horses that were housed on wood shavings compared to peat bedding. This finding can be explained by the signalling role of arachidonic acid (20:4n-6) that is specifically released by PI 38:4 for the production of lipid mediators such as leukotrienes and prostaglandins (e.g., LTB4 and PGE2) [ 40 , 94 , 95 ].…”

“…In horses, plasma and cell-free surfactant samples have been the most common sample types investigated [ 11 , 22 , 88 ]. The BALF cell lipidome [ 23 ] and BALF EV FA profiles [ 24 ] have recently been investigated in healthy horses and during different stages of airway inflammation.…”

“…In a study by Christmann et al [ 22 ], proportions of Cer 18:1;O2/16:0, Cer 18:1;O2/24:0, Cer 18:0;O2/16:0, and hydroxy ceramide (OH-Cer) 18:1;O2/24:0 were elevated in crude surfactant pellets of clinical SEA cases of various horse breeds (four American Quarter Horses, one Thoroughbred, one Morgan, one Paint Horse, one Warmblood, one Tennessee Walking Horse, one Appaloosa, one Arab, and one mixed-breed). In a recent study by our research group [ 23 ], Cer and HexCer lipid classes in BALF cell pellets decreased together with BALF cell counts and neutrophil percentages after subclinical airway inflammation was induced with a bedding challenge. This might indicate that both Cer and HexCer contribute to inflammation resolution in horse lungs.…”

“…Lipidomics have been used to investigate mechanisms and treatments of asthma and other lung diseases in humans [ 9 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ], whilst studies in horses have included lipid and/or fatty acid (FA) compositions of plasma, surfactant [ 11 , 22 ], bronchoalveolar lavage fluid (BALF) cells [ 23 ], and BALF extracellular vesicles (EVs) [ 24 ] from horses affected by different types and severities of airway inflammation. The aim of this review article is to explore the basic concepts of biologically active lipids in the equine body, with special emphasis on the role of lipids in inflammation, and to collect and summarize the findings of recent lipidomic studies on equine airway inflammation.…”