Evaluation of antioxidant and proinflammatory gene expression in bovine mammary tissue during the periparturient period

The incidence and severity of mastitis can be high during the period of transition from pregnancy to lactation when dairy cattle are susceptible to oxidative stress. Oxidative stress may contribute to the pathogenesis of mastitis by modifying the expression of proinflammatory genes. The overall goal of this study was to determine the relationship between critical antioxidant defense mechanisms and proinflammatory markers in normal bovine mammary tissue during the periparturient period. Mammary tissue samples were obtained from 12 cows at 35, 20, and 7 d before expected calving and during early lactation (EL, 15 to 28 d in milk). Enzyme activities for cytosolic glutathione peroxidase and phospholipid hydroperoxide glutathione peroxidase were relatively low during the dry period, but increased during EL, whereas activity of thioredoxin reductase 1 did not change significantly as a function of time. In contrast, gene expression for these antioxidant selenoproteins and for heme oxygenase-1 gradually decreased as parturition approached and then increased during EL. The expression of intercellular vascular adhesion molecule-1 and vascular cell adhesion molecule-1 followed a similar trend where mRNA abundance gradually declined as parturition approached with a slight rebound in EL. Gene expression of the pro-oxidant, 15-lipoxygenase 1, which is known to increase during times of oxidative stress, also increased dramatically in mammary tissue from EL cows. Expression of the proinflammatory cytokines, IL-1beta, IL-6, and IL-8 did not change significantly during the periparturient period. Strong positive correlations were found between several antioxidant enzymes (cytosolic glutathione peroxidase, thioredoxin reductase 1, and heme oxygenase-1) and vascular adhesion molecules (intercellular vascular adhesion molecule-1, vascular cell adhesion molecule-1) suggesting a protective response of these antioxidants to an enhanced proinflammatory state. Ability to control oxidative stress through manipulation of key antioxidant enzymes in the future may modify the proinflammatory state of periparturient cows and reduce incidence and severity of some diseases such as mastitis.

Shifts in Thioredoxin Reductase Activity and Oxidant Status in Mononuclear Cells Obtained from Transition Dairy Cattle

Measures of oxidative status were examined in 14 dairy cows during the transition period. Blood samples were obtained approximately 21 d before expected calving, at calving, and again at 21 d in milk (DIM). Plasma samples were used to determine lipid hydroperoxide concentrations. Total white blood cells were used to determine the oxidative status of glutathione. Peripheral blood mononuclear cell (PBMC) lysates were used to determine the total antioxidant potential and enzymatic activities of glutathione peroxidase (GPX) and thioredoxin reductase (TrxR1). Both plasma lipid hydroperoxide concentrations and GPX activity in PBMC increased at calving and during the first 21 DIM when compared with prepartum samples. Conversely, the total antioxidant potential and TrxR activity declined in PBMC during the first 21 DIM, even though both GPX activity and the glutathione-to-GSSG ratio remained elevated during this time period. Results from this study support previous findings that report increased GPX activity when reactive oxygen metabolites, including lipid hydroperoxides, increase in transition dairy cows. The significant decrease in TrxR activity with a concomitant decrease in total antioxidant potential in PBMC during this same stage of lactation, however, would suggest that this selenoprotein is not able to rebound during periods of oxidative stress to the same extent as GPX1. This study shows for the first time that TrxR may be an important antioxidant defense mechanism in PBMC that is compromised during the periparturient period.

Relationship of body condition score and oxidant stress to tumor necrosis factor expression in dairy cattle

The relationship between body condition score (BCS) with measures of oxidative status and TNF-alpha production was examined in 16 mid-lactation dairy cows. Cows were selected based on either a normal (2.5-2.7) or a high (> or =3.5) BCS using the standard five-point scaling system. The metabolic status of all cows was determined by plasma nonesterified fatty acid levels (NEFA). Plasma samples or white blood cell lysates also were analyzed for indices of oxidant stress and for the expression of TNF-alpha. Cows with a high BCS had significantly lower NEFA levels when compared to normal BCS cows and the over-conditioned animals were not in a state of negative energy balance. No significant changes in lipid hydroperoxide levels, glutathione peroxidase activity, or the ratio of reduced (GSH) to oxidized (GSSG) glutathione was detected with respect to BCS. However, high BCS cows did have a significantly lower overall antioxidant potential and reduced TrxR activities when compared with the normal BCS cows. Changes in the oxidative state of over-conditioned cows were accompanied by a significantly higher expression of TNF-alpha. Results from this study suggest that cows with a high BCS can experience oxidant stress in the absence of altered energy status. Increased TNF-alpha expression may be related to the pro-oxidant state of over-conditioned cows and possibly be a contributing factor to the enhanced susceptibility to disease in high BCS dairy cattle.

Glucose transporter and hypoxia-associated gene expression in the mammary gland of transition dairy cattle

Glucose is an important energy substrate, especially needed by dairy cows postpartum to support the onset of lactation. The prioritization and regulation of glucose uptake is accomplished, in part, by changes in expression of cellular glucose transport molecules (GLUT) within the mammary gland. The objectives of this study were to (1) evaluate the expression and cell-type specific localization of GLUT and hypoxia-associated genes that may regulate GLUT expression over the transition period and through lactation in bovine mammary tissue and (2) determine functionality of GLUT on primary bovine mammary endothelial cells (BMEC). Mammary tissue biopsies were taken from cows at 15 d before calving and again at 1, 15, 30, 60, 120, and 240 d post-parturition for quantitative real-time PCR analysis of GLUT and hypoxia-associated genes. Additional mammary tissue samples were used to localize GLUT within the cells of the lobulo-alveolar system via fluorescence microscopy. Cultures of primary bovine mammary endothelial cells were used to confirm the functionality of GLUT with a fluorescent glucose analog uptake assay. Significant increases in GLUT1 gene expression were observed during early lactation, whereas both GLUT3 and GLUT4 gene expression increased during late lactation. The gene expression for 2 receptors of vascular endothelial growth factor increased significantly during early lactation and remained increased throughout lactation when compared with gene expression during the transition period. All GLUT were detected on cultured BMEC and were capable of internalizing glucose through GLUT-mediated mechanisms. These data suggest mammary vascular tissues express GLUT during lactation and BMEC express functional glucose transporters. A better understanding of glucose uptake at the endothelial level may prove to be critical to improve glucose absorption from the blood for utilization by mammary epithelial cells.

Selenium inhibits 15-hydroperoxyoctadecadienoic acid-induced intracellular adhesion molecule expression in aortic endothelial cells

Increased intracellular adhesion molecule 1 (ICAM-1) expression and enhanced monocyte recruitment to the endothelium are critical steps in the early development of atherosclerosis. The 15-lipoxygenase 1 (15-LOX1) pathway can generate several proinflammatory eicosanoids that are known to enhance ICAM-1 expression within the vascular endothelium. Oxidative stress can exacerbate endothelial cell inflammatory responses by modifying arachidonic acid metabolism through the 15-LOX1 pathway. Because selenium (Se) influences the oxidant status of cells and can modify the expression of eicosanoids, we investigated the role of this micronutrient in modifying ICAM-1 expression as a consequence of enhanced 15-LOX1 activity. Se supplementation reduced ICAM-1 expression in bovine aortic endothelial cells, an effect that was reversed with 15-LOX1 overexpression or treatment with exogenous 15-hydroperoxyoctadecadienoic acid (15-HPETE). ICAM-1 expression increased proportionately when intracellular15-HPETE levels were allowed to accumulate. However, changes in intracellular 15-HETE levels did not seem to affect ICAM-1 expression regardless of Se status. Our results indicate that Se supplementation can reduce 15-HPETE-induced expression of ICAM-1 by controlling the intracellular accumulation of this fatty acid hydroperoxide in endothelial cells.

Ethyl pyruvate diminishes the inflammatory response to lipopolysaccharide infusion in horses

REASONS FOR PERFORMING THE STUDY

Endotoxaemia contributes to morbidity and mortality in horses with colic due to inflammatory cascade activation. Effective therapeutic interventions are limited for these horses. Ethyl pyruvate (EP), an anti-inflammatory agent that alters the expression of proinflammatory cytokines, improved survival and organ function in sepsis and gastrointestinal injury in rodents and swine. Therapeutic efficacy of EP is unknown in endotoxaemic horses.

OBJECTIVES

Determine the effects of EP on signs of endotoxaemia and expression of proinflammatory cytokines following administration of lipopolysaccharide (LPS) in horses.

METHODS

Horses received 30 ng/kg bwt LPS in saline to induce signs of endotoxaemia. Next, horses received lactated Ringer's solution (LRS), (n = 6), 150 mg/kg bwt EP in LRS, (n = 6), or 1.1 mg/kg bwt flunixin meglumine (FM), (n = 6). Controls received saline followed by LRS (n = 6). Physical examinations, behaviour pain scores and blood for clinical pathological testing and gene expression were obtained at predetermined intervals for 24 h.

RESULTS

Lipopolysaccharide infusion produced clinical and clinicopathological signs of endotoxaemia and increased expression of tumour necrosis factor alpha (TNFα), interleukin 6 (IL-6) and IL-8 (P<0.001) compared with controls. Leucopenia and neutropenia occurred in all horses that received LPS. Horses treated with EP and FM had significantly (P<0.0001) reduced pain scores compared with horses receiving LPS followed by LRS. Flunixin meglumine was significantly more effective at ameliorating fever compared with EP. Both EP and FM significantly diminished TNFα expression. Ethyl pyruvate significantly decreased, but FM significantly increased, IL-6 expression. Neither EP nor FM altered IL-8 expression.

CONCLUSIONS AND POTENTIAL RELEVANCE

Ethyl pyruvate administered following LPS diminished the clinical effects of endotoxaemia and decreased proinflammatory gene expression in horses. Ethyl pyruvate suppressed expression of proinflammatory cytokines better than FM. However, FM was a superior anti-pyretic compared with EP. Ethyl pyruvate may have therapeutic applications in endotoxaemic horses.

Differences in the Oxylipid Profiles of Bovine Milk and Plasma at Different Stages of Lactation

Mastitis is caused by a bacterial infection of the mammary gland, which reduces both milk quality and quantity produced for human consumption. The incidence and severity of bovine mastitis are greatest during the periparturient period that results from dysfunctional inflammatory responses and causes damage to milk synthesizing tissues. Oxylipids are potent fatty acid-derived mediators that control the onset and resolution of the inflammatory response. The purpose of this study was to investigate how oxylipid profiles change in bovine milk at different stages of the lactation cycle. Results showed significantly lower concentrations of both milk polyunsaturated fatty acid content and total oxylipid biosynthesis during early lactation when compared to mid- or late-lactation. The only oxylipid that was higher during early lactation was 20-hydroxyeicosatetraenoic acid (HETE), which is often associated with inflammatory-based diseases. Milk oxylipid profiles during the different stages of lactation differed from plasma profiles. As such, plasma fatty acid and oxylipid concentrations are not a proxy for local changes in the mammary gland during the lactation cycle.

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‐F_2t‐Isoprostanes (15‐F_2t‐Isop) in detecting oxidative stress in dairy cattle has not been validated.

Hypothesis

Concentrations of 15‐F_2t‐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‐F_2t‐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‐F_2t‐Isop quantified by LC‐MS/MS was positively correlated with systemic oxidant status (r = 0.83; P = .01). Urine 15‐F_2t‐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‐F_2t‐Isop quantified by LC‐MS/MS was negatively correlated (r = −0.86; P = .007) with local oxidant status. Total 15‐F_2t‐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‐F_2t‐Isop quantified by LC‐MS/MS and total milk 15‐F_2t‐Isop quantified by cbELISA are accurate biomarkers of systemic and mammary gland oxidant status, respectively. Establishing reference intervals for free and total 15‐F_2t‐Isops for evaluating oxidative stress in dairy cows should currently be based on the LC‐MS/MS method.

Platelet activating factor production and proinflammatory gene expression in endotoxin-challenged bovine mammary endothelial cells

The bovine mammary gland responds to gram-negative pathogens by stimulating the production of cytokines and other proinflammatory mediators that orchestrate the migration of leukocytes into tissues. Platelet activating factor (PAF), interleukin 1 beta (IL-1 beta), IL-8, and intercellular adhesion molecule 1 (ICAM1) are among the several inflammatory factors involved in the early activation and migration of leukocytes into the mammary gland during the initial stages of coliform mastitis. Several different cell types within the mammary gland are capable of expressing these potent pro-inflammatory mediators. The objective of this study was to characterize the expression profile of vascular-derived inflammatory molecules that may play a role in the pathogenesis of bovine coliform mastitis. Isolated bovine mammary gland endothelial cells were stimulated in culture for up to 12 h with endotoxin obtained from Escherichia coli, and the temporal expression of proinflammatory cytokines and adhesion molecules relative to endogenous PAF biosynthesis was evaluated. Results from the in vitro time course experiment showed that vascular-derived PAF biosynthesis began as early as 30 min and peaked at 1 h following endotoxin challenge. The biosynthesis of PAF preceded the endotoxin-induced IL-1 beta, IL-8, and ICAM1 mRNA expression that increased after 1 h and reached peak expression between 4 and 12 h following stimulation. Inhibiting the effects of endogenous PAF with a receptor antagonist suggests that vascular-derived PAF is an early proinflammatory mediator that plays at least a partial role in the subsequent expression of IL-1 beta, IL-8, and ICAM1 during endotoxin challenge. Furthermore, endotoxin-induced PAF biosynthesis by bovine mammary gland endothelial cells is regulated to some extent by phospholipase D activity and phosphatidic acid production. The results from this study support the contention that mammary gland endothelial cells can contribute to the production of important proinflammatory mediators that are typically associated with coliform mastitis.

Predictive models for early lactation diseases in transition dairy cattle at dry-off

During the transition period, dairy cattle undergo tremendous metabolic and physiological changes to prepare for milk synthesis and secretion. Failure to sufficiently regulate these changes may lead to metabolic stress, which increases risk of transition diseases. Metabolic stress is defined as a physiological state consisting of 3 components: aberrant nutrient metabolism, oxidative stress, and inflammation. Current monitoring methods to detect cows experiencing metabolic stress involve measuring biomarkers for nutrient metabolism. However, these biomarkers, including non-esterified fatty acids, beta-hydroxybutyrate, and calcium are typically measured a few weeks before to a few days after calving. This is a retroactive approach, because there is little time to integrate interventions that remediate metabolic stress in the current cohort. Our objective was to determine if biomarkers of metabolic stress measured at dry-off are predictive of transition disease risk. We designed a prospective cohort study carried out on 5 Michigan dairy farms (N = 277 cows). We followed cows from dry-off to 30 days post-calving. Diseases and adverse outcomes were grouped in an aggregate outcome that included mastitis, metritis, retained placenta, ketosis, lameness, pneumonia, milk fever, displaced abomasum, abortion, and death of the calf or the cow. We used best subsets selection to select candidate models for four different sets of models: one set for each component of metabolic stress (nutrient metabolism, oxidative stress, and inflammation), and a combined model that included all 3 components. We used model averaging to obtain averaged predicted probabilities across each model set. We hypothesized that the averaged predictions from the combined model set with all 3 components of metabolic stress would be more effective at predicting disease than each individual component model set. The area under the curve estimated using receiver operator characteristic curves for the combined model set (0.93; 95% confidence interval [CI] = 0.90-0.96) was significantly higher compared with averaged predictions from the inflammation (0.87; 95% CI = 0.83-0.91), oxidative stress (0.78; 95% CI = 0.72-0.84), and nutrient metabolism (0.73; 95% CI = 0.67-0.79) model sets (p < 0.05). Our results indicate that it may be possible to detect cattle at risk for some transition diseases as early as dry-off. This has important implications for disease prevention, as earlier identification of cows at risk of health disorders will allow for earlier implementation of intervention strategies. A limitation of the current study is that we did not perform external validation. Future validation studies are needed to confirm our findings.

Effect of infection with bovine leukosis virus on lymphocyte proliferation and apoptosis in dairy cattle

OBJECTIVE

To determine effects of infection with bovine leukosis virus (BLV) on lymphocyte proliferation and apoptosis in dairy cattle.

ANIMALS

27 adult Holstein cows.

PROCEDURES

Peripheral blood mononuclear cells (PBMCs) were isolated from whole blood from lactating Holstein cows seronegative for BLV (n = 9 cows), seropositive for BLV and aleukemic (aleukemic; 9), and seropositive for BLV and persistently lymphocytotic (PL; 9). Isolated PBMCs were assayed for mitogen-induced proliferation and were analyzed by means of flow cytometry. The PBMCs from a subset of each group were assayed for apoptosis, caspase-9 activity, and expression of selected genes related to apoptosis.

RESULTS

PL cows had significantly higher total lymphocyte counts and significantly lower proportions of T-lymphocyte populations than did BLV-negative and aleukemic cows. Both groups of BLV-infected cows had significantly higher proportions of B cells and major histocompatibility complex II-expressing cells than did BLV-negative cows. Proliferation with concanavalin A was significantly lower for PL cows, compared with proliferation for BLV-negative cows. Pokeweed mitogen-induced proliferation was significantly higher for aleukemic and PL cows than for BLV-negative cows. Gene expression of apoptosis-inhibitory proteins BCL2 and BCL2L1 was significantly higher for aleukemic cows and expression of BCL2 was significantly higher for PL cows than for BLV-negative cows.

CONCLUSIONS AND CLINICAL RELEVANCE

Cattle infected with BLV had marked changes in PBMC populations accompanied by alterations in proliferation and apoptosis mechanisms. Because the relative distribution and function of lymphocyte populations are critical for immune competence, additional studies are needed to investigate the ability of BLV-infected cattle to respond to infectious challenge.

Production of 15-F2t-isoprostane as an assessment of oxidative stress in dairy cows at different stages of lactation

Oxidative stress contributes to dysfunctional immune responses and predisposes dairy cattle to several metabolic and inflammatory-based diseases. Although the negative effects of oxidative stress on transition cattle are well established, biomarkers that accurately measure oxidative damage to cellular macromolecules are not well defined in veterinary medicine. Measuring 15-F_2t-isoprostane, a lipid peroxidation product, is the gold standard biomarker for quantifying oxidative stress in human medicine. The aim of our study was to determine whether changes in 15-F_2t-isoprostane concentrations in plasma and milk could accurately reflect changes in oxidant status during different stages of lactation. Using liquid chromatography-tandem mass spectrometry, 15-F_2t-isoprostane concentrations were quantified in milk and plasma of 12 multiparous Holstein-Friesian cows that were assigned to 3 different sampling periods, including the periparturient period (1-2 d in milk; n = 4), mid lactation (80-84 d in milk; n = 4), and late lactation (183-215 d in milk; n = 4). Blood samples also were analyzed for indicators of oxidant status, inflammation, and negative energy balance. Our data revealed that 15-F_2t-isoprostane concentrations changed at different stages of lactation and coincided with changes in other gauges of oxidant status in both plasma and milk. Interestingly, milk 15-F_2t-isoprostane concentrations and other indices of oxidant status did not follow the same trends as plasma values at each stage of lactation. Indeed, during the periparturient period, systemic 15-F_2t-isoprostane increased significantly accompanied by an increase in the systemic oxidant status index. Milk 15-F_2t-isoprostane was significantly decreased during the periparturient period compared with other lactation stages in conjunction with a milk oxidant status index that trended lower during this period. The results from this study indicate that changes in 15-F_2t-isoprostane concentrations in both milk and plasma may be strong indicators of an alteration in redox status both systemically and within the mammary gland.

Evaluation of natural plant extracts as antioxidants in a bovine in vitro model of oxidative stress

Oxidative stress contributes to many inflammatory-based diseases of dairy cattle especially during periods of increased metabolic activity such as around calving. Endothelial cells play a key role in maintaining normal inflammatory responses, but they are especially susceptible to macromolecule damage during times of oxidative stress. Therefore, bovine aortic endothelial cells (BAEC) were used to study the effect of natural tannin-based extracts on oxidative stress that may improve health and well-being of cattle. Tannins are secondary metabolites in plants with potent antioxidant activity that have been used as natural feed additives for food-producing animals. However, there is little information on how tannin-rich plant extracts may affect oxidative stress in dairy cattle. The objective of this study was to evaluate the antioxidant effect of pomegranate (Punica granatum; PMG), tara (Caesalpinia spinosa; TA), chestnut (Castanea sativa; CH), and gambier (Uncaria gambir; GM) natural extracts using an in vitro BAEC model of oxidative stress. Natural extracts were tested at a concentration of 80 μg/mL. Viability, apoptosis, intracellular reactive oxygen species, and isoprostanes were determined on cultured BAEC treated with different plant natural extracts. No changes in cell viability was detected following PMG and GM treatments. In contrast, there was a 30% reduction of BAEC viability following treatment with CH or TA extracts. Intracellular reactive oxygen species production was significantly less abundant in cells treated with natural extracts than with the lipopolysaccharide control. Moreover, antioxidant activity varied according to the tested extract, showing a reduction of 63, 45, 51, and 27% in PMG, GM, CH, and TA, respectively. The formation of isoprostanes as a consequence of lipid peroxidation after induction of oxidative stress also were significantly decreased in PMG-treated cells when compared with the untreated cells. Theses findings suggest that PMG extract has the potential to mitigate oxidative stress without detrimental effects on cell viability. Further in vitro and in vivo research is warranted to explore the antioxidant potential of PMG extract as a dietary supplement to control oxidative stress in dairy cattle.

Preliminary safety and biological efficacy studies of ethyl pyruvate in normal mature horses

REASONS FOR PERFORMING THE STUDY

Endotoxaemia causes substantial morbidity and mortality in horses with colic and sepsis. Ethyl pyruvate is a novel anti-inflammatory medication that improved survival in preclinical models of severe sepsis endotoxaemia and intestinal ischaemia and reperfusion in rodents, swine, sheep and dogs and may be a useful medication in horses.

HYPOTHESIS

Ethyl pyruvate has no adverse effects in normal horses and is biologically active based on suppression of proinflammatory gene expression in endotoxin stimulated whole blood, in vitro.

METHODS

Physical and neurological examinations, behaviour scores, electrocardiograms and clinicopathological tests were performed on 5 normal healthy horses receiving 4 different doses of ethyl pyruvate. Doses included 0, 50, 100 and 150 mg/kg bwt administered in a randomised crossover design with a 2 week washout period between doses. Biological efficacy was assessed by stimulating whole blood with endotoxin from the horses that received ethyl pyruvate prior to and 1 and 6 h after drug infusion. Gene expression for TNFα, IL-1β and IL-6 was assessed.

RESULTS

There were no effects of drug or dose (0, 50, 100 or 150 mg/kg bwt) on any of the physical or neurological examination, behaviour factors, electrocardiogram or clinical pathological results collected from any of the horses. All parameters measured remained within the normal reference range. There was a significant reduction in TNFα, IL-1β and IL-6 gene expression in endotoxin stimulated whole blood from horses 6 h after receiving 150 mg/kg bwt ethyl pyruvate. There were no detectable effects on gene expression of any of the other doses of ethyl pyruvate tested.

CONCLUSION

We were unable to detect any detrimental effects of ethyl pyruvate administration in normal horses. Ethyl pyruvate significantly decreased proinflammatory gene expression in endotoxin stimulated blood 6 h after drug administration.

CLINICAL RELEVANCE

Ethyl pyruvate may be a safe, effective medication in endotoxaemic horses.

Serum vitamin D concentrations at dry-off and close-up predict increased postpartum urine ketone concentrations in dairy cattle

Vitamin D is commonly supplemented to dairy cows as vitamin D₃ to support calcium homeostasis and in times of low sunlight exposure. Vitamin D has beneficial immunomodulatory and anti-inflammatory properties. Serum 25-hydroxyvitamin D [25(OH)D] concentrations fluctuated during lactation, with the lowest concentrations measured in healthy cows within 7 d of calving. However, it is unknown if serum 25(OH)D concentrations measured during the previous lactation are associated with transition diseases or health risk factors in dairy cattle. We collected serum samples from 279 dairy cattle from 5 commercial dairy herds in Michigan at dry-off, close-up, and 2-10 d in milk (DIM). Vitamin D concentrations were determined by measuring serum 25(OH)D by radioimmunoassay. Total serum calcium was measured by colorimetric methods. Body condition scores (BCS) were assigned at the time of blood collection. Clinical disease incidence was monitored until 30 d postparturition. Separate bivariable logistic regression analyses were used to determine if serum 25(OH)D at dry-off, close-up, and 2-10 DIM was associated with various clinical diseases including mastitis, lameness, and uterine disorders (classified as metritis, retained placenta, or both) and increased urine ketone concentrations at P < 0.05. Among all significant bivariable analyses, multivariable logistic regression analyses were built to adjust for potential confounding variables including parity, BCS, season, and calcium. Receiver operator characteristic (ROC) curve analyses were used to determine optimal concentrations of serum 25(OH)D. We found that higher serum 25(OH)D concentrations at dry-off and close-up predicted increased urine ketone concentrations in early lactation, even after adjustment for confounders. Alternatively, we found that lower serum 25(OH)D at 2-10 DIM was associated with uterine diseases. Optimal concentrations for serum 25(OH)D at dry-off and close-up for lower risk of increased urine ketone concentrations were below 103.4 and 91.1 ng/mL, respectively. The optimal concentration for serum 25(OH)D at 2-10 DIM for uterine diseases was above 71.4 ng/mL. These results indicate that serum 25(OH)D at dry-off and close-up may be a novel predictive biomarker for increased urine ketone concentrations during early lactation. Increased urine ketone concentrations are not necessarily harmful or diagnostic for ketosis but do indicate development of negative energy balance, metabolic stress, and increased risk of early lactation diseases. Predicting that dairy cattle are at increased risk of disease facilitates implementation of intervention strategies that may lower disease incidence. Future studies should confirm these findings and determine the utility of serum 25(OH)D concentrations as a predictive biomarker for clinical and subclinical ketosis.

20-hydroxyeicosatetraenoic acid alters endothelial cell barrier integrity independent of oxidative stress and cell death

Unregulated inflammation during bovine mastitis is characterized by severe mammary tissue damage with systemic involvement. Vascular dysfunction underlies tissue pathology because of concurrent oxidative stress mediated by several inflammatory mediators. We recently demonstrated increased production of 20-hydroxyeicosatetraenoic acid (20-HETE), a cytochrome P450-derived (CYP) oxylipid that correlated with oxidative stress during severe bovine coliform mastitis. The hypothesis for this study was that 20-HETE-induced oxidative stress disrupts barrier function of endothelial cells. Primary endothelial cells from the bovine aorta were utilized to investigate the effects of 20-HETE on barrier integrity in an in-vitro model of oxidative stress. The effects of various antioxidants on modulating the 20-HETE barrier integrity effects also were investigated. Our results showed that 20-HETE decreased endothelial barrier integrity, which was associated with increased reactive metabolite production and decreased total glutathione. The antioxidant, vitamin E, partially delayed the loss of endothelial resistance upon exposure to 20-HETE but did not prevent complete loss of barrier integrity. The decrease in barrier resistance due to 20-HETE was neither associated with oxidative stress as assessed by oxidative protein or lipid damage nor endothelial cell apoptosis; however, selenium supplementation conferred resistance to loss of barrier integrity suggesting a role for shifts in redox status. Specific mechanisms by which 20-HETE alters vascular barrier integrity require further investigation to identify targets for therapy during inflammatory conditions with enhanced CYP450 activity.

Duration of in vivo endotoxin tolerance in horses

Endotoxemia models are used to study mechanisms and treatments of early sepsis. Repeated endotoxin exposures induce periods of endotoxin tolerance, characterized by diminished proinflammatory responses to lipopolysaccharide (LPS) and modulated production of proinflammatory cytokines. Repeated measure designs using equine endotoxemia models are rarely performed, despite the advantages associated with reduced variability, because the altered responsiveness would confound study results and because the duration of equine endotoxin tolerance is unknown. We determined the interval of endotoxin tolerance, in vivo, in horses based on physical, clinicopathologic, and proinflammatory gene expression responses to repeated endotoxin exposures. Six horses received 30 ng/kg LPS in saline infused over 30 min. Behavior pain scores, physical examination parameters, and blood for complete blood count and proinflammatory gene expression were obtained at predetermined intervals for 24h. Horses received a total of 3 endotoxin exposures. The first exposure was LPS 1, followed 7 days later by LPS 7 or 14-21 days later by LPS 14-21. Lipopolysaccharide exposures were allocated in a randomized, crossover design. Lipopolysaccharide produced clinical and clinicopathologic signs of endotoxemia and increased expression of tumor necrosis factor alpha (TNFα), interleukin (IL)-6 and IL-8, P<0.001. Horses exhibited evidence of endotoxin tolerance following LPS 7 but not following LPS 14-21. Horses had significantly lower pain scores, heart rates, respiratory rates and duration of fever, after LPS 7 compared to LPS 1 and LPS 14-21, P<0.001, and expression of TNFα was lower in the whole blood of horses after LPS 7, P=0.05. Clinical parameters and TNFα gene expression were similar or slightly increased in horses following LPS 14-21 compared to measurements made in horses following LPS 1, suggesting that endotoxin tolerance had subsided. A minimum of 3 weeks between experiments is warranted if repeated measures designs are used to assess in vivo response to endotoxin in horses.

Cohort-level disease prediction by extrapolation of individual-level predictions in transition dairy cattle

Dairy cattle experience metabolic stress during the transition from late gestation to early lactation resulting in higher risk for several economically important diseases (e.g. mastitis, metritis, and ketosis). Metabolic stress is described as a physiological state composed of 3 processes: nutrient metabolism, oxidative stress, and inflammation. Current strategies for monitoring transition cow nutrient metabolism include assessment of plasma non-esterified fatty acids and beta-hydroxybutyrate concentrations around the time of calving. Although this method is effective at identifying cows with higher disease risk, there is often not enough time to implement intervention strategies to prevent health disorders from occurring around the time of calving. Previously, we published predictive models for early lactation diseases at the individual cow level at dry-off. However, it is unknown if predictive probabilities from individual-level models can be aggregated to the cohort level to predict cohort-level incidence. Therefore, our objective was to test different data aggregation methods using previously published models that represented the 3 components of metabolic stress (nutrient metabolism, oxidative stress, and inflammation). We included 277 cows from five Michigan dairy herds for this prospective cohort study. On each farm, two to four calving cohorts were formed, totaling 18 cohorts. We measured biomarker data at dry-off and followed the cows until 30 days post-parturition for cohort disease incidence, which was defined as the number of cows: 1) having one or more clinical transition disease outcome, and/or 2) having an adverse health event (abortion or death of calf or cow) within each cohort. We tested three different aggregation methods that we refer to as the p-central, p-dispersion, and p-count methods. For the p-central method, we calculated the averaged predicted probability within each cohort. For the p-dispersion method, we calculated the standard deviation of the predicted probabilities within a cohort. For the p-count method, we counted the number of cows above a specified threshold of predicted probability within each cohort. We built four sets of models: one for each aggregation method and one that included all three aggregation methods (p-combined method). We found that the p-dispersion method was the only method that produced viable predictive models. However, these models tended to overestimate incidence in cohorts with low observed counts and underestimate risk in cohorts with high observed counts.

Postpartum meloxicam administration alters plasma haptoglobin, polyunsaturated fatty acid, and oxylipid concentrations in postpartum ewes

Background

Postpartum inflammation is a natural and necessary response; however, a dysfunctional inflammatory response can be detrimental to animal productivity. The objective of this study was to determine the effects of a non-steroidal anti-inflammatory drug (meloxicam) on ewe postpartum inflammatory response, ewe plasma polyunsaturated fatty acid and oxylipid concentrations, and lamb growth.

Results

After lambing, 36 Hampshire and Hampshire × Suffolk ewes were sequentially assigned within type of birth to control (n = 17) or meloxicam orally administered on d 1 and 4 of lactation (MEL; 90 mg, n = 19). Milk and blood samples were collected on d 1 (prior to treatment) and d 4. Milk glucose-6-phosphate was not affected by MEL. Plasma haptoglobin (Hp) concentrations were less for MEL ewes; control ewes with greater d 1 Hp concentrations had elevated Hp on d 4, but this was not the case for MEL-treated ewes. Treatment with MEL increased plasma arachidonic acid concentration by more than 4-fold in ewes rearing singles but decreased concentrations of 9,10-dihydroxyoctadecenoic acid, prostaglandin F_2α, 8-iso-prostaglandin E₂, and 8,9-dihydroxyeicosatetraenoic acid. Nine oxylipids in plasma had interactions of treatment with d 1 Hp concentration, all of which revealed positive associations between d 1 Hp and d 4 oxylipid concentrations for CON, but neutral or negative relationships for MEL. MEL decreased 13-hydroxyoctadecadienoic acid:13-oxooctadecadienoic acid ratio and tended to increase 9-hydroxyoctadecadienoic acid:9-oxooctadecadienoic acid ratio (both dependent on d 1 values), indicating progressive metabolism of linoleic acid-derived oxylipids occurred by enzymatic oxidation after MEL treatment. Meloxicam reduced oxylipids generated across oxygenation pathways, potentially due to an improved redox state.

Conclusions

Postpartum MEL treatment of ewes decreased plasma concentrations of Hp and several oxylipids, with the greatest impact in ewes with biomarkers reflecting a greater inflammatory state before treatment. Anti-inflammatory strategies may help resolve excessive postpartum inflammation in some dams.

Peripheral markers of oxidative stress in Labrador retrievers with copper-associated hepatitis

OBJECTIVES

To evaluate biomarkers of oxidative stress in dogs with copper-associated hepatitis (CAH) as compared with healthy controls, and to evaluate if these markers correlate with hepatic copper concentrations and hepatic histopathologic features.

MATERIALS AND METHODS

Prospective study. Plasma reactive metabolite concentrations, plasma antioxidant potential, and plasma and urine isoprostane concentrations were determined in Labrador retrievers with copper-associated hepatitis (n=9) as well as in breed- and sex-matched (n=9) and age- and sex-matched (n=9) healthy control populations. Possible correlations between markers of oxidative stress and hepatic histopathological features also were investigated.

RESULTS

Reactive metabolites (median, range) were over twofold greater in dogs with copper-associated hepatitis (87.2 RFU/μL, 60.9 to 185.6 RFU/μL) as compared to breed- and sex-matched (38.2 RFU/μL, 22.4 to 116.8 RFU/μL) and age- and sex-matched controls (32.0 RFU/μL, 18.5 to 127.4 RFU/μL). Antioxidant potential was decreased in copper-associated hepatitis dogs (6.5 TE/μL, 5.1 to 7.7 TE/μL) as compared to breed- and sex-matched controls (8.2 TE/μL, 5.3 to 11.8 TE/μL). Both reactive metabolite concentrations and the reactive metabolite to antioxidant potential ratio were positively correlated with hepatic copper concentrations. Plasma and urine isoprostanes were variable and not significantly different between populations.

CLINICAL SIGNIFICANCE

Labrador retrievers with copper-associated hepatitis have altered oxidant status. Plasma reactive metabolite concentrations and the reactive metabolite to antioxidant potential ratio could be useful biomarkers. However, neither plasma nor urine isoprostanes were useful biomarkers for copper-associated hepatitis.

Oxylipids are associated with higher disease risk in postpartum cows

Postpartum diseases are a major animal welfare and economic concern for dairy producers. Dysregulated inflammation, which may begin as soon as the cessation of lactation, contributes to the development of postpartum diseases. The ability to regulate inflammation and mitigate postpartum health diseases relies, in part, on the production of inflammatory mediators known as oxylipids. The objective of this study was to examine associations between oxylipids and postpartum diseases. Plasma samples were collected from 16 cattle via coccygeal venipuncture at the following time points: 6 d before dry-off; dry-off (d 0); 1, 2, 6, and 12 d after dry-off; 14 ± 3 d before the expected calving date; and 7 ± 2 d after calving. After calving, cows were grouped according to if clinical disease was undetected throughout the sampling period (n = 7) or if they developed a disease postpartum (n = 9). Liquid chromatography-tandem mass spectrometry was used to analyze plasma concentrations of 63 oxylipid species. Of the 32 oxylipids detected, concentrations of 7 differed between cows with no detected disease and diseased cows throughout the sampling period. Thus, a variable oxylipid profile was demonstrated through 2 major physiological transitions of a lactation cycle. Further, the information gained from this pilot study using a small number of animals with diverse diseases from a single herd suggests that it may be possible to use oxylipids at early mammary involution to alert dairy producers of cows at risk for disease after calving. Future studies should be performed in larger populations of animals, including cows from diverse geographies and dairying styles, and focus on specific diseases to evaluate the utility of oxylipids as biomarkers. Furthermore, it is important to determine the clinical implications of variable oxylipid concentrations throughout the lactation cycle and if the oxylipid profile can be modulated to improve inflammatory outcomes.

Peripheral biomarkers of oxidative stress in dogs with acute pancreatitis

BACKGROUND

Oxidative stress is considered a pathomechanism of acute pancreatitis (AP), but no studies have extensively characterized oxidant status in dogs with naturally-occurring AP.

HYPOTHESIS OR OBJECTIVES

Evaluate measures of oxidant status in dogs with AP and explore whether these measures correlate with AP severity.

ANIMALS

Fifteen dogs with AP and 9 control dogs.

METHODS

Prospective, controlled observational study. Plasma reactive metabolite (RM) concentrations, antioxidant potential (AOP), and urinary F₂ isoprostane concentrations were measured in AP dogs and healthy controls. Severity of AP was assessed by length of hospitalization and 3 disease severity indices: canine acute pancreatitis severity (CAPS), modified canine activity index (M-CAI), and the acute patient physiologic and laboratory evaluation score (APPLE_full ).

RESULTS

Reactive metabolite (RM) concentrations (median, 65 relative fluorescent units [RFU]/μL; range, 20-331 RFU/μL) and RM:AOP (median, 7; range, 4-109) were higher in AP dogs than healthy controls (median RM, 25 RFU/μL; range, 16-41 RFU/μL; median RM:AOP, 4; range, 2-7; P < .001 for both comparisons). Reactive metabolite (r_S  = 0.603, P = .08) and RM:AOP (r_S  = 0.491, P = .06) were not correlated with the duration of hospitalization or disease severity indices evaluated. However, disease severity indices did not predict mortality in our study. Normalized urine 2,3-dinor-8-iso-prostaglandin F2α concentrations were correlated with C-reactive protein (CRP; r_S  = 0.491, P = .03), canine specific pancreatic lipase (Spec cPL; r_S  = 0.746, P = .002), and CAPS (r_S  = 0.603, P = .02).

CONCLUSIONS AND CLINICAL IMPORTANCE

Oxidant status is altered in dogs with naturally occurring AP, but the clinical relevance of this finding is unknown.