Dysregulated inflammation and oxidative stress are major underlying components of dairy cow diseases, such as mastitis, that negatively impact animal health, welfare, and production. These conditions are associated with increased reactive oxygen and nitrogen species (RONS) production, which can overwhelm antioxidant defenses and cause severe cellular damage. Indeed, damage to tissue components such as lipids is a defining feature of oxidative stress and leads to the generation of potent inflammatory mediators known as oxylipids. A special class of oxylipid, isoprostanes (IsoP), are highly sensitive and specific indicators of lipid damage and are thus considered the gold standard biomarker of oxidative stress in vivo. However, the ability to use IsoP measured at early mammary involution as biomarkers of oxidative stress and to predict postpartum disease in dairy cows was poorly characterized. To address this gap, we determined how oxylipids shift during this time and assess their utility as early biomarkers of disease risk. As the physiological role of IsoP is not fully elucidated, we then developed in vitro models of endothelial inflammation to determine how IsoP influence metabolic, transcriptomic, and proteomic responses to oxidant and endotoxin challenge in endothelial cells (EC) and macrophages. We found that different IsoP subtypes show differential expression patterns during times of oxidative stress in dairy cattle. Amongst the IsoP detected, 8-iso-PGA2 appeared to have the potential to indicate cows at-risk of developing postpartum disease. In our bovine endothelial inflammation model, IsoP have no influence over inflammatory outcomes such as cellular viability, apoptosis, RONS production, barrier integrity, and gene transcription networks. In RAW 264.7 macrophages, however, 15-F2t-IsoP promotes an anti-inflammatory phenotype. This work suggests that IsoP have the potential to be early indicators of postpartum disease risk in dairy cattle. Our data also provides evidence for a novel physiological action in which IsoP may support healing pathways in late-stage inflammation when they are elevated. Hence, IsoP represent an important biomarker of oxidative stress in dairy cows, especially at early mammary involution. Beyond their role as biomarkers, IsoP also serve as inflammatory modulators to help restore tissue homeostasis during acute inflammation. Establishing stronger associations between oxylipids measured at early mammary involution and specific postpartum diseases should be the focus of future studies. Additionally, further characterization of the mechanisms with which IsoP exert their effects, such as receptor targets, downstream signaling pathways, and functional consequences should be the basis of future work.
Read
