"Oxidative stress contributes to the pathology of several inflammatory-based diseases of humans and animals. In acute inflammation, the production of metabolites with prooxidant effects occurs rapidly, overwhelming the protective mechanism resulting in acute cellular damage. A major challenge has been identifying ways of effective controlling oxidative stress to improve responses to therapies for the conditions characterized by oxidative stress such as sepsis. Despite decades of research and the equivocal success associated with use of antioxidants, the control of oxidative stress continues to be problematic. Among many reasons, the inability to deliver antioxidants to specific subcellular sites where they may be most beneficial may explain some of the disappointing results of antioxidants during disease. As such, renewed interest focused at improving antioxidant delivery to sites of prooxidant metabolite formation is critical. Another alternative is to target the specific pathways involved in the formation of reactive metabolites such as those involved in lipid metabolism. To determine which lipid metabolizing pathways maybe most relevant, we utilized the severe coliform mastitis disease as a model for oxidative stress to evaluate the extent of lipid metabolism during severe inflammation. The hypothesis for Chapter 2 therefore, was that oxylipid biosynthesis in severe acute inflammation is influenced by substrate availability, metabolism pathway, and the activities of key metabolic enzymes. Results of that study showed an extensive profile of lipid oxygenation products (oxylipids) broader than previously reported. In addition, increased substrate availability as evidenced by greater polyunsaturated fatty acids (PUFA) concentrations, involvement of multiple biosynthetic pathways, and various degrees of metabolism accounted for the variety in the oxylipid profiles detected. Follow up studies evaluated the concurrent oxidative stress during changes observed for the oxylipid profiles. The hypothesis for that work reported in Chapter 3 was that a specific oxylipid produced during bovine coliform mastitis would reliably detect the concurrent severe oxidative stress. This work showed that a specific biomarker of oxidative stress frequently used in human diseases, 15-F2t-isoprostane correlated positively with several biomarkers of oxidative stress. The same oxidative stress biomarkers, including 15-F2t-isoprostane, correlated with an oxylipid from the cytochrome P450 pathway known as 20-HETE. Human observational studies on diseases such as hypertension and laboratory disease models showed that 20-HETE was shown to potently induce inflammation and oxidative stress. Many of these conditions are associated with vascular dysfunction. Therefore, we hypothesized that 20-HETE contributes to the pathology that occurs during severe coliform mastitis of dairy cattle by inducing oxidative stress-dependent endothelial cell death thus disrupting vascular barrier integrity. Utilizing a primary bovine endothelial cell culture system, the effects of direct exposure to 20-HETE on the barrier integrity were evaluated through determining the development of oxidative stress and the functional consequence on barrier integrity. Results support a role of 20-HETE in mediating changes related to oxidative stress as inducing the disruption of barrier integrity, and supports the idea of targeting this pathway in modulating the oxidative stress responses during diseases in which there is enhanced 20-HETE biosynthesis. Further work should focus on characterizing the sources of 20-HETE biosynthesis and the mechanisms of its regulation to facilitate the development of targeted and specific therapies that modulate 20-HETE biosynthesis."--Pages ii-iii.
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