Dietary Long‐chain PUFAs Enrich Porcine Alveolar Macrophages and Alter Prostaglandin E2 Production Following LPS Challenge

Abstract

The US swine industry experiences severe production and profit losses from respiratory infections despite the wide spread use of vaccines and antibiotics. Long‐chain PUFAs can modulate immune cell function through the production of eicosanoids, such as prostaglandin E2 (PGE2) which is capable of stimulating both inflammation and inflammatory resolution upon infection. The aim of this study was to determine the effects of dietary arachidonic acid (ARA) and eicosapentaenoic acid (EPA) on cultured porcine alveolar macrophages stimulated with LPS. Day‐old pigs (n=60) were fed milk replacer for 21d. Diets contained 0.5% ARA (control), 2.5% ARA or 3.5% EPA of total fatty acids. Alveolar macrophages were isolated via bronchoalveolar lavage, cultured and stimulated with LPS for 24h. Total fatty acids in alveolar macrophages and lung tissue were analyzed via gas chromatography‐mass spectrometry (GC‐MS). Alveolar macrophages were cultured and stimulated with 10ng/mL LPS or unstimulated (control). Concentrations of PGE2 in tissue culture media were measured via competitive enzyme‐linked immunosorbent assay (ELISA) kits. Average body weight and clinical hematology were unaffected by diet treatments (P >0.5). Concentration of ARA (% of fatty acids, w/w) in alveolar macrophages from pigs fed 2.5% ARA had an 82% increase in ARA compared to controls, and the concentration was decreased 21% in pigs fed 3.5% EPA compared to control (P < 0.01). Lung parenchymal tissue showed a similar enrichment pattern; tissue was enriched by 39% in pigs fed 2.5% ARA, while pigs fed the 3.5% EPA diet had a 45% decrease in ARA compared to control (P < 0.002). Media concentration of PGE2 was increased following LPS stimulation of alveolar macrophages. The increase in PGE2 concentration was greater in macrophages enriched in ARA, exceeding that from control cells by 187% and that from EPA‐enriched cells by 191% (P < 0.05). These data demonstrate that dietary supplementation of LC‐PUFAs can effectively alter lung tissue and alveolar macrophage fatty acid composition. Furthermore, these data validate that increased dietary ARA is an effective means to increase eicosanoid production by LPS‐stimulated immune cells.Support or Funding InformationUSDA Animal Health Funds