Invited review: Cytochrome P450 enzyme involvement in health and inflammatory-based diseases of dairy cattle.

Dairy cattle are at the greatest risk of developing diseases around the time of calving because of compromised immune responses and the occurrence of oxidative stress. Both the development of compromised immunity and oxidative stress are influenced directly or indirectly by the metabolism of polyunsaturated fatty acids (PUFA) and fat-soluble vitamins. The cytochrome P450 (CYP450) family of enzymes is central to the metabolism of both classes of these compounds, but to date, the importance of CYP450 in the health of dairy cattle is underappreciated. As certain CYP450 isoforms metabolize both PUFA and fat-soluble vitamins, potential interactions may occur between PUFA and fat-soluble vitamins that are largely unexplored. For example, one CYP450 that generates anti-inflammatory oxylipids from arachidonic acid additionally contributes to the activation of vitamin D. Other potential substrate interactions between PUFA and vitamins A and E may exist as well. The intersection of PUFA and fat-soluble vitamin metabolism by CYP450 suggest that this enzyme system could provide an understanding of how immune function and oxidant status interconnect, resulting in increased postpartum disease occurrence. This review will detail the known contributions of bovine CYP450 to the regulation of oxylipids with a focus on enzymes that may also be involved in the metabolism of fat-soluble vitamins A, D, and E that contribute to antioxidant defenses. Although the activity of specific CYP450 is generally conserved among mammals, important differences exist in cattle, such as the isoforms primarily responsible for activation of vitamin D that makes their specific study in cattle of great importance. Additionally, a CYP450-driven inflammatory positive feedback loop is proposed, which may contribute to the dysfunctional inflammatory responses commonly found during the transition period. Establishing the individual enzyme isoform contributions to oxylipid biosynthesis and the regulation of vitamins A, D, and E may reveal how the CYP450 family of enzymes can affect inflammatory responses during times of increased susceptibility to disease. Determining the potential effect of each CYP450 on disease susceptibility or pathogenesis may allow for the targeted manipulation of the CYP450 pathways to influence specific immune responses and antioxidant defenses during times of increased risk for health disorders.

15-F2t-Isoprostane Concentrations and Oxidant Status in Lactating Dairy Cattle with Acute Coliform Mastitis.

BACKGROUND: Severe mammary tissue damage during acute coliform mastitis in cattle is partially caused by oxidative stress. Although considered a gold standard biomarker in some human conditions, the utility of 15-F2t-Isoprostanes (15-F2t-Isop) in detecting oxidative stress in dairy cattle has not been validated. HYPOTHESIS: Concentrations of 15-F2t-Isop in plasma, urine, and milk correlate with changes in oxidant status during severe coliform mastitis in cattle. ANIMALS: Eleven lactating Holstein-Friesian dairy cows in their 3rd-6th lactation. METHODS: A case-control study using cows with acute coliform mastitis and matched healthy controls were enrolled into this study. Measures of inflammation, oxidant status, and redox status in plasma and milk samples were quantified using commercial assays. Plasma, urine, and milk 15-F2t-Isop were quantified by liquid chromatography/tandem mass spectrometry (LC-MS/MS) and ELISA assays. Data were analyzed by Wilcoxon rank sum tests (α = 0.05). RESULTS: Plasma 15-F2t-Isop quantified by LC-MS/MS was positively correlated with systemic oxidant status (r = 0.83; P = .01). Urine 15-F2t-Isop quantified by LC-MS/MS did not correlate with systemic oxidant status, but was negatively correlated with redox status variables (r = -0.83; P = .01). Milk 15-F2t-Isop quantified by LC-MS/MS was negatively correlated (r = -0.86; P = .007) with local oxidant status. Total 15-F2t-Isop in milk quantified by a commercial ELISA (cbELISA) was positively correlated with oxidant status in milk (r = 0.98; P < .001). CONCLUSIONS AND CLINICAL IMPORTANCE: Free plasma 15-F2t-Isop quantified by LC-MS/MS and total milk 15-F2t-Isop quantified by cbELISA are accurate biomarkers of systemic and mammary gland oxidant status, respectively. Establishing reference intervals for free and total 15-F2t-Isops for evaluating oxidative stress in dairy cows should currently be based on the LC-MS/MS method.