Dynamics of oxylipin biosynthesis in systemic inflammation: Insights from a large animal model of endotoxemia

Madison N. Myers^1*Miguel Chirivi¹Jose M. dos Santos Neto²Jair Parales-Girón²Lynn C. Worden²Adam L. Lock²Andres Contreras^1*

• ¹Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, United States
• ²Department of Animal Science, College of Agriculture and Natural Resources, Michigan State University, East Lansing, Michigan, United States

Endotoxemia, characterized by the presence of bacterial endotoxins such as lipopolysaccharide (LPS) in blood, triggers acute inflammation linked to mortality and chronic disease across species. LPS stimulates the release of free fatty acids (FA) and activation of oxidative enzymes (COX, LOX, and CYP450), which synthesize bioactive lipid mediators known as oxylipins (OXL). Our study sought to characterize the impact of LPS on OXL release in plasma and by adipocytes using a bovine model. Mature Holstein cows received an intravenous infusion of LPS or sterile saline (SAL). Plasma samples were collected immediately before infusions (PRE), 2 h after (+2H), and 12 h after (+12H). Cows that received LPS exhibited classical signs of endotoxemia, including tachycardia, fever, and tachypnea. Plasma OXL profiles were characterized via LC-MS/MS, revealing significant shifts in arachidonic acid (AA)-and eicosapentaenoic acid (EPA)-based pathways. LPS-treated cows exhibited persistent elevations in COX-and LOX-derived OXL, including pro-inflammatory, AA-based thromboxane B2 and hydroxyeicosatetraenoic acids, alongside transient increases in docosahexaenoic acid (DHA)-and EPA-based pro-resolving mediators. In vitro, LPS triggers transient increases in adipocytes' release of AA-based 5-HETE, 6-keto-PGF1α, LA-based 13-HODE, and DHA-based 19,20-DiHDPA. These findings suggest that OXL may contribute to acute yet incomplete activation of resolving pathways, potentially exacerbating inflammation. Our results provide insight into systemic and adipocyte-specific OXL responses during endotoxemia, laying an initial foundation for the use of OXL as biomarkers and targets for modulation of inflammation.