Activity of sEH and Oxidant Status during Systemic Bovine Coliform Mastitis

Abstract

Bovine coliform mastitis presents treatment challenges because of systemic inflammation and oxidative stress. Soluble epoxide hydrolase (sEH) is a promising therapeutic target in conditions characterized by inflammation and oxidative stress but has not been evaluated in cattle. We compared sEH activity and oxidant status in healthy Holstein dairy cows to those with systemic coliform mastitis (n = 5/group) using complementary approaches. First, the activity of sEH on [³H]-trans-diphenyl-propene oxide (tDPPO) was assessed ex vivo using tissue homogenates (mammary, liver, and kidney). Second, the concentrations of sEH substrates and metabolites in plasma, milk, and urine were determined as an index of in vivo sEH activity. Oxidant status was assessed in serum and milk. Data were analyzed by non-parametric methods. Metabolism of tDPPO was greater in mammary tissues from cows with coliform mastitis compared to controls. In contrast, ratios of sEH substrates and metabolites predicted lower sEH activity in cows with coliform mastitis than controls. Milk oxidant status showed greater prooxidant levels in coliform mastitis cows. Cows with coliform mastitis exhibit increased sEH activity in mammary tissue; at the same time, milk oxidant status is increased. Future studies should characterize sEH activity and oxidant status patterns and explore therapies targeting sEH during coliform mastitis.

Keywords: cytochrome P450; inflammation; mastitis; oxidative stress; oxylipids; soluble epoxide hydrolase.

Figure 1

Soluble epoxide hydrolase enzymatic activity based on the metabolism of [³H]-trans-diphenyl-propene oxide (t-DPPO) (median and range) in the mammary gland (A), liver (B), and kidney (C) tissues from healthy control (Cont) dairy cows (open circles, n = 5) and those with systemic coliform mastitis (Mast) (filled black squares, n = 5). Data were analyzed with Wilcoxon rank-sum tests (α = 0.05). * p < 0.05, NS—not significant.

Figure 2

Relative expression of soluble epoxide hydrolase (sEH) mRNA (median and range) in tissues: (A) mammary gland, (B) kidney, (C) liver from dairy cows with systemic coliform mastitis (n = 5) and matched control dairy cows with no overt clinical disease (n = 5). Data were analyzed with Wilcoxon rank-sum tests (α = 0.05). * p < 0.05, ** p < 0.01, **** p < 0.0001.

Figure 3

Relative expression of cyclooxygenase (COX2) mRNA (median and range) in tissues (A) mammary gland, (B) kidney, (C) liver from dairy cows with systemic coliform mastitis (n = 5) and matched control dairy cows with no overt clinical disease (n = 5). Data were analyzed with Wilcoxon rank-sum tests (α = 0.05). * p < 0.05, NS—not significant.

Figure 4

IHC staining intensity for soluble epoxide hydrolase protein (Median and Range, graphs) in the mammary gland (A), liver (B), kidney (C) in cows with mastitis (Mast) and healthy controls (Cont) (1 representative mastitis case and a matched control). IHC, immunohistochemistry, bar—25 µm.