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

Oxylipins biosynthesis and the regulation of bovine postpartum inflammation

Uncontrolled or dysregulated inflammation has adverse effects on the reproduction, production and health of animals, and is a major pathological cause of increased incidence and severity of infectious and metabolic diseases. To achieve successful transition from a non-lactation pregnant state to a non-pregnant lactation state, drastic metabolic and endocrine alteration have taken place in dairy cows during the periparturient period. These physiological changes, coupled with decreased dry matter intake near calving and sudden change of diet composition after calving, have the potential to disrupt the delicate balance between pro- and anti-inflammation, resulting in a disordered or excessive inflammatory response. In addition to cytokines and other immunoregulatory factors, most oxylipins formed from polyunsaturated fatty acids (PUFAs) via enzymatic and nonenzymatic oxygenation pathways have pro- or anti-inflammatory properties and play a pivotal role in the onset, development and resolution of inflammation. However, little attention has been paid to the possibility that oxylipins could function as endogenous immunomodulating agents. This review will provide a detailed overview of the main oxylipins derived from different PUFAs and discuss the regulatory role that oxylipins play in the postpartum inflammatory response in dairy cows. Based on the current research, much remains to be illuminated in this emerging field. Understanding the role that oxylipins play in the control of postpartum inflammation and inflammatory-based disease may improve our ability to prevent transition disorders via Management, pharmacological, genetic selection and dietary intervention strategies.

Selenium and Selenoproteins in Health

Selenium is a trace mineral that is essential for health. After being obtained from food and taken up by the liver, selenium performs various physiological functions in the body in the form of selenoproteins, which are best known for their redox activity and anti-inflammatory properties. Selenium stimulates the activation of immune cells and is important for the activation of the immune system. Selenium is also essential for the maintenance of brain function. Selenium supplements can regulate lipid metabolism, cell apoptosis, and autophagy, and have displayed significant alleviating effects in most cardiovascular diseases. However, the effect of increased selenium intake on the risk of cancer remains unclear. Elevated serum selenium levels are associated with an increased risk of type 2 diabetes, and this relationship is complex and nonlinear. Selenium supplementation seems beneficial to some extent; however, existing studies have not fully explained the influence of selenium on various diseases. Further, more intervention trials are needed to verify the beneficial or harmful effects of selenium supplementation in various diseases.

Gene network expression of whole blood leukocytes in dairy cows with different milk yield at dry-off

Dairy cows at dry-off undergo several management and physiological changes, resulting in alterations in plasma biomarkers of inflammation, oxidative stress, and immune system. High milk yield at the end of lactation exacerbates these responses. The underlying mechanism of these changes has yet to be elucidated. We hypothesized altered leukocyte gene expression after dry-off and different responses in cows with different milk yield. Thirteen Holstein dairy cows were sampled at the turn of dry-off to investigated whole blood leukocyte gene expression and were grouped according to the average milk yield during the last week of lactation: low (< 15 kg/d) and high milk yield (> 15 kg/d). Blood samples were collected in PAXgene tubes (Preanalytix, Hombrechtikon, Switzerland) at -7, 7, and 34 days from dry-off (DFD) to measure mRNA abundance of 37 genes. Normalized gene abundance data were subjected to MIXED model ANOVA (SAS Institute Inc., Cary, NC). Compared with -7 DFD, at 7 DFD RNA abundance of lipoxygenase genes (ALOX5, ALOX15) and myeloperoxidase (MPO) increased, and that of the antioxidant gene (SOD2) decreased. Meanwhile, genes related to recognition and immune mediation (CD16, MYD88, TLR2), migration and cell adhesion (CX3CR1, ITGAL, ITGB2, TLN1), and the antimicrobial gene MMP9 were downregulated at 7 or 34 DFD, whereas the antimicrobial IDO1 gene was upregulated. Compared with low-producing cows, cows with high milk yield at dry-off cows had upregulated expression of the pro-inflammatory cytokines IL8 and IL18 and a greater reduction in transcript abundance of the toll-like receptor (TLR) recognition-related gene TLR2. Overall, the dry-off confirmed to be a phase of intense changes, triggering an inflammatory response and somewhat suppressing leukocyte immune function. In cows with high milk yield during the week before dry-off, the inflammatory response was exacerbated.

Serum Vitamin D Is Associated with Antioxidant Potential in Peri-Parturient Cows

Dairy cows experience increased oxidative stress during periods of transition such as at the cessation of lactation and around the periparturient period, thus increasing disease risk. Despite routine supplementation of transition cow diets with certain vitamins in an attempt to mitigate oxidative stress, there is no currently available data directly linking vitamin supplementation with antioxidant potential (AOP) in transition cows. The objective of this study was to determine the association between serum vitamins and biomarkers of oxidative stress in healthy cows. Blood samples were collected from 240 cows at dry off (DO), close up (CU), and 2-10 days post-calving (DIM2-10). Blood samples were analyzed for vitamins (A, D, E), β-carotene, reactive oxygen species (ROS), and AOP. Spearman correlations and mixed linear regression models were used to assess associations between vitamins and measures of oxidant status. Vitamin D concentrations were positively associated with AOP at the CU and DIM2-10. Based on the positive association with AOP, additional in-vitro studies were conducted that showed vitamin D mitigated barrier integrity loss in endothelial cells during oxidative stress. These results indicate for the first time that vitamin D may have a role in promoting antioxidant potential in transition dairy cows.

Protective Effect of Se-Methylselenocysteine on Elaidic Acid-Induced Inflammation in Human Arterial Endothelial Cells

This study was designed to investigate the anti-inflammatory effect of Se-methylselenocysteine (MSC) on elaidic acid (9t18:1, EA) induced human arterial endothelial cells (HAECs). MTT and flow cytometry were used to determine cell viability and cell apoptosis respectively. Western blotting was used to assess protein expression of intercellular adhesion molecular 1 (ICAM-1), E-selectin, interleukin-8 (IL-8), endothelial nitric oxide synthase (e-NOS) and phospholipases A2 (PLA2), while enzyme-linked immunosorbent assay (ELISA) was performed to examine the secretion level of nitric oxide (NO). In the cell viability assay, EA significantly decreased cell viability when compared with negative control (NC) group, and MSC effectively reversed this adverse effect, especially at the concentration of 200 μmol/L with 24 h incubation. Also, the same concentration of MSC prevented HAECs cell apoptosis induced by EA. In addition, we found that the expression of ICAM-1, E-selectin, IL-8 and PLA2 were significantly increased and e-NOS decreased in EA group compared with NC group. Inhibition of PLA2 promoted ICAM-1, E-slectin and IL-8 expression in HAECs induced by EA. And MSC down-regulated the secretion of NO level in EA-induced HAECs. Based on these results, we concluded that MSC activated PLA2 which regulated the expression of ICAM-1, E-selectin and IL-8 to protect inflammation induced by EA in HEACs.

MicroRNA-223 triggers inflammation in porcine aorta by activating NLRP3 inflammasome under selenium deficiency

Selenium (Se) is an essential trace element in organism. Se deficiency can cause many diseases, including vascular disease. Studies have shown that inflammation is the main inducement of vascular disease, microRNA (miRNA) can influence inflammation in various ways, and Se deficiency can affect miRNAs expression. To study the mechanism of aorta damage caused by Se deficiency, we constructed a Se deficiency porcine aorta model and found that Se deficiency can significantly inhibit miR-223, which downregulates the expression of nucleotide-binding oligomerization domain-like receptor family 3 (NLRP3). Subsequently, we found that in Se deficiency group, NLRP3, and its downstream (caspase-1, apoptosis-related spot-like protein [ASC], IL-18, IL-1β) expression was significantly increased. In vitro, we cultured pig iliac endothelium cell lines, and constructed miR-223 knockdown and overexpression models. NLRP3 messenger RNA and protein levels were significant increased in the knockdown group, and decreased in the overexpression group. The results of this study show that Se deficiency in porcine arteries can induce inflammation through miR-223/NLRP3.

Role of oxylipins generated from dietary PUFAs in the modulation of endothelial cell function

Oxylipins, which are circulating bioactive lipids generated from polyunsaturated fatty acids (PUFAs) by cyclooxygenase, lipooxygenase and cytochrome P450 enzymes, have diverse effects on endothelial cells. Although studies of the effects of oxylipins on endothelial cell function are accumulating, a review that provides a comprehensive compilation of current knowledge and recent advances in the context of vascular homeostasis is lacking. This is the first compilation of the various in vitro, ex vivo and in vivo reports to examine the effects and potential mechanisms of action of oxylipins on endothelial cells. The aggregate data indicate docosahexaenoic acid-derived oxylipins consistently show beneficial effects related to key endothelial cell functions, whereas oxylipins derived from other PUFAs exhibit both positive and negative effects. Furthermore, information is lacking for certain oxylipin classes, such as those derived from α-linolenic acid, which suggests additional studies are required to achieve a full understanding of how oxylipins affect endothelial cells.

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.

Selenium and selenoproteins: from endothelial cytoprotection to clinical outcomes

The role of the vascular endothelium in inflammation was demonstrated experimentally through biomarkers of endothelial dysfunction and cytoprotection. Selenium is a trace element essential for cell protection against oxidative lesions triggered by reactive oxygen species or inflammatory responses. Preclinical studies have demonstrated a relationship between adhesion molecules as biomarkers of endothelial dysfunction and selenoproteins as biomarkers of selenium status under conditions that mimic different diseases. Most studies in humans indicate an association between selenium deficiency and increased risk of morbidity and mortality, yet the pathophysiology of selenium in endothelial activation remains unknown. Here, we summarize selenium-dependent endothelial function evaluation techniques and focus on the role of selenium in endothelial cytoprotection according to current scientific knowledge. Most studies on the role of selenium in endothelial processes show selenium-dependent endothelial functions and explain how cells and tissues adapt to inflammatory insults. Taken together, these studies show an increase in adhesion molecules and a decrease in the expression of selenoproteins following a decreased exposure to selenium. Few clinical trials have enough methodological quality to be included in meta-analysis on the benefits of selenium supplementation. Furthermore, the methodology adopted in many studies does not consider the relevant findings on the pathophysiology of endothelial dysfunction. Preclinical studies should be more frequently integrated into clinical studies to provide clearer views on the role of selenium status in endothelial cytoprotection.

Maternal late-gestation metabolic stress is associated with changes in immune and metabolic responses of dairy calves

Metabolic stress in periparturient dairy cows is characterized by excessive lipid mobilization, inflammation, and oxidative stress that is associated with immune dysfunction. Thus, metabolic stress around the time calving is linked to the development of various early-lactation health disorders. Maternal status during late pregnancy can have carryover effects on several health and production variables of neonatal calves. However, the effects of metabolic stress during gestation on metabolic and immune responses of newborn calves remain unknown. Thus, we aimed to investigate whether metabolic stress in late-gestation dairy cows is associated with changes in the metabolic and immune responses of their offspring during the first month of life. Holstein-Friesian cows (n = 12) were blood sampled at 28 and 15 d before expected calving. The average between these 2 sampling points in the serum concentrations of nonesterified fatty acids (NEFA), haptoglobin (Hp), and oxidant status index (OSi)-defined as the ratio between reactive oxygen and nitrogen species and total antioxidant potential-were calculated as indicators of the degree of lipid mobilization, inflammation, and oxidant status (OS), respectively. Calves were subsequently divided into groups (n = 6 each) according to their dams' high or low degree of lipid mobilization, inflammation, and OS. The metabolic responses of calves in each of these groups were compared weekly throughout their first month of life by assessing serum concentration of NEFA, Hp, and OSi. Additionally, whole blood was obtained from calves at each sampling period and subjected to a lipopolysaccharide (LPS)-stimulated tumor necrosis factor-α (TNF-α) production assay to assess cell-mediated innate immunity against induced inflammatory responses, using high (5 μg/mL of blood) and low (10 ng/mL) concentrations of LPS. Calves born to cows with higher NEFA or OSi showed lower body weight at birth and throughout the study, whereas no association between any of the maternal groups and average daily gain at 4 wk of age was identified. Serum concentrations of reactive oxygen and nitrogen species were higher in calves exposed to higher maternal NEFA concentrations or OSi when compared with calves born to cows with lower values of these biomarkers. Calves exposed to high maternal OS also had higher circulating concentrations of Hp and TNF-α, indicating greater basal inflammatory responses when compared with calves born to cows with a lower OSi. In contrast, LPS-induced inflammatory responses were less robust in calves exposed to higher maternal biomarkers of inflammation or OS, suggesting compromised immune responses to microbial agonists. Collectively, these data suggest that prenatal exposure to maternal parameters of metabolic stress may adversely affect some metabolic and inflammatory responses of the offspring that could influence disease susceptibility.

Selenium in the prevention of atherosclerosis and its underlying mechanisms

Atherosclerosis and related cardiovascular diseases (CVDs) represent the greatest threats to human health worldwide. Selenium, an essential trace element, is incorporated into selenoproteins that play a crucial role in human health and disease. Although findings from a limited number of randomized trials have been inconsistent and cannot support a protective role of Se supplementation in CVDs, prospective observational studies have generally shown a significant inverse association between selenium or selenoprotein status and CVD risk. Furthermore, a benefit of selenium supplementation in the prevention of CVDs has been seen in population with low baseline selenium status. Evidence from animal studies shows consistent results that selenium and selenoproteins might prevent experimental atherosclerosis, which can be explained by the molecular and cellular effects of selenium observed both in animal models and cell cultures. Selenoproteins of particular relevance to atherosclerosis are glutathione peroxidases, thioredoxin reductase 1, selenoprotein P, selenoprotein S. The present review is focusing on the existing evidence that supports the concept that optimal selenium intake can prevent atherosclerosis. Its underlying mechanisms include inhibiting oxidative stress, modulating inflammation, suppressing endothelial dysfunction, and protecting vascular cells against apoptosis and calcification. However, the benefit of selenium supplementation in the prevention of atherosclerosis remains insufficiently documented so far. Future studies with regard to the effects of selenium supplementation on atherosclerosis should consider many factors, especially the baseline selenium status, the dose and forms of selenium supplementation, and the selenoprotein genotype. Additionally, much more studies are needed to confirm the roles of selenoproteins in atherosclerosis prevention and clarify the underlying mechanisms.

Nutritional strategies to optimize dairy cattle immunity

Dairy cattle are susceptible to increased incidence and severity of both metabolic and infectious diseases during the periparturient period. A major contributing factor to increased health disorders is alterations in bovine immune mechanisms. Indeed, uncontrolled inflammation is a major contributing factor and a common link among several economically important infectious and metabolic diseases including mastitis, retained placenta, metritis, displaced abomasum, and ketosis. The nutritional status of dairy cows and the metabolism of specific nutrients are critical regulators of immune cell function. There is now a greater appreciation that certain mediators of the immune system can have a reciprocal effect on the metabolism of nutrients. Thus, any disturbances in nutritional or immunological homeostasis can provide deleterious feedback loops that can further enhance health disorders, increase production losses, and decrease the availability of safe and nutritious dairy foods for a growing global population. This review will discuss the complex interactions between nutrient metabolism and immune functions in periparturient dairy cattle. Details of how either deficiencies or overexposure to macro- and micronutrients can contribute to immune dysfunction and the subsequent development of health disorders will be presented. Specifically, the ways in which altered nutrient metabolism and oxidative stress can interact to compromise the immune system in transition cows will be discussed. A better understanding of the linkages between nutrition and immunity may facilitate the design of nutritional regimens that will reduce disease susceptibility in early lactation cows.

The etiology of oxidative stress in the various species of animals, a review

Oxidative stress is the consequence of an imbalance of pro-oxidants and antioxidants leading to cell damage and tissue injury. The exhaustion of antioxidant systems is one of the reasons for the occurrence of oxidative stress, which results in avalanche production of reactive oxygen species (ROS) or free radicals. High oxidative stress is common in organs and tissues with high metabolic and energy demands, including skeletal and heart muscle, liver and blood cells. Stress arises in animals in response to unavoidable or adverse environmental conditions. In the external environment, which affects the body of the cow, there are four main groups of stressors: physical, chemical, biological and psychological. Physical stressors include fluctuations in ambient temperature as well as mechanical injuries. High ambient temperature is one of the factors affecting the productivity of cows. Biological stressors are conditioned by errors and irregularities in habits. Both of these phenomena have an adverse impact on both the resistance of animals and fertility and are the etiological agent of oxidative stress. Various mechanisms may be responsible for metal-induced oxidative stress: direct or indirect generation of ROS, depletion of glutathione and inhibition of antioxidant enzymes are well known for all redox-active and redox-inactive metals.

Role of endothelial cells in bovine mammary gland health and disease

The bovine mammary gland is a dynamic and complex organ composed of various cell types that work together for the purpose of milk synthesis and secretion. A layer of endothelial cells establishes the blood–milk barrier, which exists to facilitate the exchange of solutes and macromolecules necessary for optimal milk production. During bacterial challenge, however, endothelial cells divert some of their lactation function to protect the underlying tissue from damage by initiating inflammation. At the onset of inflammation, endothelial cells tightly regulate the movement of plasma components and leukocytes into affected tissue. Unfortunately, endothelial dysfunction as a result of exacerbated or sustained inflammation can negatively affect both barrier integrity and the health of surrounding extravascular tissue. The objective of this review is to highlight the role of endothelial cells in supporting milk production and regulating optimal inflammatory responses. The consequences of endothelial dysfunction and sustained inflammation on milk synthesis and secretion are discussed. Given the important role of endothelial cells in orchestrating the inflammatory response, a better understanding of endothelial function during mastitis may support development of targeted therapies to protect bovine mammary tissue and mammary endothelium.

NEFAs activate the oxidative stress-mediated NF-κB signaling pathway to induce inflammatory response in calf hepatocytes

Non-esterified fatty acids (NEFAs) are important induction factors of inflammatory responses in some metabolic diseases. High plasma levels of NEFAs and oxidative stress exist in the dairy cows with ketosis. The aim of this study was to investigate whether high levels of NEFAs can induce inflammatory response and the specific molecular mechanism in the hepatocytes of dairy cow. In vitro, primary cultured bovine hepatocytes were treated with different concentrations of NEFAs, PDTC (an NF-κB inhibitor) and NAC (an antioxidant). NEFAs significantly activated NF-κB pathway. Activated NF-κB upregulated the release of pro-inflammatory cytokines, thereby inducing inflammatory response in bovine hepatocytes. When PDTC was added, activation of NF-κB-mediated inflammatory response induced by NEFAs was inhibited. NEFAs treatment results in the overproduction of the markers of oxidative stress, reactive oxygen species (ROS) and malondialdehyde (MDA), which were ameliorated by NAC treatment. These increased ROS and MDA were caused by decreasing activity of antioxidant system, including glutathione peroxidase, superoxide dismutase and catalase, in bovine hepatocytes treated with NEFAs. NAC also ameliorated NEFAs-mediated NF-κB activation and the release of pro-inflammatory cytokines. These results indicate that high concentrations of NEFAs can induce cattle hepatocytes inflammatory response through activating the oxidative stress-mediated NF-κB signaling pathway.

Effect of Selenium-Enriched Garlic Oil against Cytotoxicity Induced by OX-LDL in Endothelial Cells

Objective. To detect the effect of selenium-enriched garlic oil (Se-garlic oil) against cytotoxicity induced by ox-LDL in endothelial cells. Methods. Se-garlic oil was extracted by organic solvent extraction. High performance liquid chromatography (HPLC) was used to detect the content of allicin in the Se-garlic oil. Hydride generation atomic fluorescence spectrometry (HG-AFS) was used to detect the content of Se in the Se-garlic oil. ECV-304 cells were separated into five groups (blank, ox-LDL, and low-, medium-, and high-dose Se-garlic oil). Methyl thiazolyl tetrazolium (MTT) assay was used to detect the cytoactivity of each cell group after culturing for 24, 48, and 72 hours. Flow cytometry (FCM) stained with annexin V-FITC/PI was used to detect the apoptosis of the cells from the blank, Se-garlic oil, ox-LDL, and Se-garlic oil + ox-ldl groups after 48 hours of incubation. Results. The amount of allicin in Se-garlic oil was 142.66 mg/ml, while, in Se, it was 198 mg/kg. When ox-LDL was added to low-, medium-, and high-dose Se-garlic oil, the cell viability rates of ECV-304 cells treated in the three groups were all higher, while the apoptosis rates were significantly lower than those of the ox-LDL group (P < 0.05). However, there was no significant difference between the apoptosis rates of the blank, Se-garlic oil, and Se-garlic oil + ox-LDL groups (P > 0.05). Conclusion. Se-garlic oil could inhibit the cytotoxic effect induced by ox-LDL in endothelial cells.

Reduced macrophage selenoprotein expression alters oxidized lipid metabolite biosynthesis from arachidonic and linoleic acid

Uncontrolled inflammation is an underlying etiology for multiple diseases and macrophages orchestrate inflammation largely through the production of oxidized fatty acids known as oxylipids. Previous studies showed that selenium (Se) status altered the expression of oxylipids and magnitude of inflammatory responses. Although selenoproteins are thought to mediate many of the biological effects of Se, the direct effect of selenoproteins on the production of oxylipids is unknown. Therefore, the role of decreased selenoprotein activity in modulating the production of biologically active oxylipids from macrophages was investigated. Thioglycollate-elicited peritoneal macrophages were collected from wild-type and myeloid-cell-specific selenoprotein knockout mice to analyze oxylipid production by liquid chromatography/mass spectrometry as well as oxylipid biosynthetic enzyme and inflammatory marker gene expression by quantitative real-time polymerase chain reaction. Decreased selenoprotein activity resulted in the accumulation of reactive oxygen species, enhanced cyclooxygenase and lipoxygenase expression and decreased oxylipids with known anti-inflammatory properties such as arachidonic acid-derived lipoxin A₄ (LXA₄) and linoleic acid-derived 9-​oxo-octadecadienoic acid (9-oxoODE). Treating RAW 264.7 macrophages with LXA₄ or 9-oxoODE diminished oxidant-induced macrophage inflammatory response as indicated by decreased production of TNFα. The results show for the first time that selenoproteins are important for the balanced biosynthesis of pro- and anti-inflammatory oxylipids during inflammation. A better understanding of the Se-dependent control mechanisms governing oxylipid biosynthesis may uncover nutritional intervention strategies to counteract the harmful effects of uncontrolled inflammation due to oxylipids.

Regulation of inflammation by selenium and selenoproteins: impact on eicosanoid biosynthesis

Uncontrolled inflammation is a contributing factor to many leading causes of human morbidity and mortality including atherosclerosis, cancer and diabetes. Se is an essential nutrient in the mammalian diet that has some anti-inflammatory properties and, at sufficient amounts in the diet, has been shown to be protective in various inflammatory-based disease models. More recently, Se has been shown to alter the expression of eicosanoids that orchestrate the initiation, magnitude and resolution of inflammation. Many of the health benefits of Se are thought to be due to antioxidant and redox-regulating properties of certain selenoproteins. The present review will discuss the existing evidence that supports the concept that optimal Se intake can mitigate dysfunctional inflammatory responses, in part, through the regulation of eicosanoid metabolism. The ability of selenoproteins to alter the biosynthesis of eicosanoids by reducing oxidative stress and/or by modifying redox-regulated signalling pathways also will be discussed. Based on the current literature, however, it is clear that more research is necessary to uncover the specific beneficial mechanisms behind the anti-inflammatory properties of selenoproteins and other Se metabolites, especially as related to eicosanoid biosynthesis. A better understanding of the mechanisms involved in Se-mediated regulation of host inflammatory responses may lead to the development of dietary intervention strategies that take optimal advantage of its biological potency.

A prospective study of selenium concentration and risk of preeclampsia in pregnant Iranian women: a nested case-control study

Preeclampsia remains a leading cause of maternal and perinatal mortality and morbidity worldwide; however, its specific etiology still remains obscure. Some studies implicate poor maternal selenium status predisposing the mother to preeclampsia. This study was designed to determine changes in plasma selenium levels in women having preeclampsia as compared with those with normal pregnancy. In a nested case-control study, 650 normal primigravida in their first 24-28 weeks participated in the study. After 3 months of follow-up of all subjects, blood selenium levels were measured in 38 women presenting consecutively with preeclampsia and in 38 women having a normal pregnancy by atomic absorption spectrophotometry. Birth outcomes were recorded, such as gestational age at delivery, height, weight, birth head circumflex and 1-min Apgar score. Preeclampsia affects about 5.84 % of pregnancies, and in our study, there were no significant differences in age, anthropometric indices, and family history of preeclampsia between the preeclamptic and control groups. The selenium concentrations in plasma in women with preeclampsia were significantly lower as compared with those in women with normal pregnancy (70.63 ± 21.41 versus 82.03 ± 15.54 μg/L, p < 0.05). Being in the bottom tertile of selenium concentration (less than 62.2 μg/L) was associated with greater risk of preeclampsia in pregnant women. The reduced selenium in the maternal circulations observed in the preeclamptic mothers support the hypothesis that insufficient selenium concentration may be a contributing factor to the pathophysiological mechanisms associated with preeclampsia, and optimizing the dietary selenium intake through supplementation could produce demonstrable clinical benefits.

Significance of metabolic stress, lipid mobilization, and inflammation on transition cow disorders

The incidence and severity of disease in cows is greatest during the transition period, when immune functions are impaired. Intense lipid mobilization is associated with both metabolic and infectious diseases in the transition cow. Significant increases in plasma nonesterified fatty acids contribute to oxidative stress and uncontrolled inflammatory responses. A dysfunctional inflammatory response is the common link between metabolic and infectious diseases around the time of calving. Intervention strategies that can reduce lipid mobilization may improve inflammatory responses and reduce the economic losses associated with health disorders during the transition period.

Nonesterified fatty acids modify inflammatory response and eicosanoid biosynthesis in bovine endothelial cells

Intense lipid mobilization during the transition period in dairy cows is associated with increased disease susceptibility. The potential impact of altered plasma nonesterified fatty acids (NEFA) concentrations and composition on host inflammatory responses that may contribute to disease incidence and severity are not known. The objective of this study was to evaluate if increased NEFA concentrations could modify vascular inflammatory responses in vitro by changing the expression of important inflammatory mediators that are important in the pathogenesis of infectious diseases of transition cows such as mastitis and metritis. Bovine aortic endothelial cells (BAEC) were cultured with different concentrations of a NEFA mixture that reflected the plasma NEFA composition during different stages of lactation. The expression of cytokines, adhesion molecules, and eicosanoids were measured to assess changes in BAEC inflammatory phenotype. Addition of NEFA mixtures altered the fatty acid profile of BAEC by increasing the concentration of stearic acid (C18:0) and decreasing the content of arachidonic acid (C20:4n6c) and other long-chain polyunsaturated fatty acids in the phospholipid fraction. A significant increase also occurred in mRNA expression of cytokine and adhesion molecules that are associated with increased inflammatory responses during the transition period. Expression of cyclooxygenase 2, an important enzyme associated with eicosanoid biosynthesis, was increased in a NEFA concentration-dependent manner. The production of linoleic acid-derived eicosanoids 9- and 13-hydroxyoctadecadienoic acids also was increased significantly after treatment with NEFA mixtures. This research described for the first time specific changes in vascular inflammatory response during in vitro exposure to NEFA mixtures that mimic the composition and concentration found in cows during the transition period. These findings could explain, in part, alterations in inflammatory responses observed during intense lipid mobilization stages such as in the transition period of dairy cows. Future studies should analyze specific mechanisms by which high NEFA concentrations induce a vascular proinflammatory phenotype including the effect of 9 and 13-hydroxyoctadecadienoic acids and other lipid mediators.

Selenium-dependent regulation of oxidative stress and immunity in periparturient dairy cattle

Uncontrolled or impaired immune and inflammatory responses in periparturient dairy cows are associated with increased incidence and severity of infectious diseases. The progressive development of oxidative stress during the transition from late gestation to peak lactation is thought to be a significant underlying factor leading to dysfunctional immune cell responses. Certain trace minerals, such as selenium (Se), can ameliorate oxidative stress and reduce the severity of several economically important diseases in dairy cattle including mastitis and metritis. Many of the health benefits of Se can be attributed to the antioxidant functions of selenoproteins. Changes in selenoprotein activity as a consequence of Se nutritional status can directly alter a number of critical cellular functions involved in the inflammatory response. A better understanding of how Se can optimize immune cell responses may facilitate the design of nutritional regimes that will reduce health disorders during the periparturient period.

Immunopathology of mastitis: insights into disease recognition and resolution

Mastitis is an inflammation of the mammary gland commonly caused by bacterial infection. The inflammatory process is a normal and necessary immunological response to invading pathogens. The purpose of host inflammatory responses is to eliminate the source of tissue injury, restore immune homeostasis, and return tissues to normal function. The inflammatory cascade results not only in the escalation of local antimicrobial factors, but also in the increased movement of leukocytes and plasma components from the blood that may cause damage to host tissues. A precarious balance between pro-inflammatory and pro-resolving mechanisms is needed to ensure optimal bacterial clearance and the prompt return to immune homeostasis. Therefore, inflammatory responses must be tightly regulated to avoid bystander damage to the milk synthesizing tissues of the mammary gland. The defense mechanisms of the mammary gland function optimally when invading bacteria are recognized promptly, the initial inflammatory response is adequate to rapidly eliminate the infection, and the mammary gland is returned to normal function quickly without any noticeable clinical symptoms. Suboptimal or dysfunctional mammary gland defenses, however, may contribute to the development of severe acute inflammation or chronic mastitis that adversely affects the quantity and quality of milk. This review will summarize critical mammary gland defense mechanisms that are necessary for immune surveillance and the rapid elimination of mastitis-causing organisms. Situations in which diminished efficiency of innate or adaptive mammary gland immune responses may contribute to disease pathogenesis will also be discussed. A better understanding of the complex interactions between mammary gland defenses and mastitis-causing pathogens should prove useful for the future control of intramammary infections.

Ethyl pyruvate diminishes the endotoxin-induced inflammatory response of bovine mammary endothelial cells

The endotoxin-induced inflammatory response during coliform mastitis is difficult to control with the currently available therapeutics. Endothelial cells are among the first cell type to be engaged in the inflammatory response and can modulate the severity of inflammation by producing proinflammatory mediators upon endotoxin exposure. Ethyl pyruvate, an ethyl ester of pyruvic acid, can ameliorate endotoxin-induced inflammatory responses by inhibiting the production of proinflammatory mediators in several in vitro and in vivo endotoxemia models. The objective of this study was to determine the effect of ethyl pyruvate on the production of vascular proinflammatory mediators that are associated with the pathogenesis of coliform mastitis. The ability of ethyl pyruvate to reduce the expression of proinflammatory mediators was evaluated in cultured bovine mammary endothelial cells (BMEC) stimulated with endotoxin. Treatment of endotoxin-stimulated BMEC with ethyl pyruvate significantly reduced gene expression of IL-6, IL-8, and intercellular adhesion molecule 1 as well as expression of eicosanoid-producing enzymes, including cyclooxygenase 2 and 15-lipoxygenase 1. This is the first time that the effect of ethyl pyruvate was evaluated in an in vitro BMEC model of coliform mastitis. The ability of ethyl pyruvate to effectively inhibit gene and protein expression of potent vascular proinflammatory mediators in vitro warrants further investigations to assess in vivo efficacy. Ethyl pyruvate is safe for human consumption, and it may be an attractive candidate as a therapeutic in ameliorating the severe pathogenesis associated with coliform mastitis.

Dipetalodipin, a novel multifunctional salivary lipocalin that inhibits platelet aggregation, vasoconstriction, and angiogenesis through unique binding specificity for TXA2, PGF2alpha, and 15(S)-HETE

Dipetalodipin (DPTL) is an 18 kDa protein cloned from salivary glands of the triatomine Dipetalogaster maxima. DPTL belongs to the lipocalin superfamily and has strong sequence similarity to pallidipin, a salivary inhibitor of collagen-induced platelet aggregation. DPTL expressed in Escherichia coli was found to inhibit platelet aggregation by collagen, U-46619, or arachidonic acid without affecting aggregation induced by ADP, convulxin, PMA, and ristocetin. An assay based on incubation of DPTL with small molecules (e.g. prostanoids, leukotrienes, lipids, biogenic amines) followed by chromatography, mass spectrometry, and isothermal titration calorimetry showed that DPTL binds with high affinity to carbocyclic TXA(2), TXA(2) mimetic (U-46619), TXB(2), PGH(2) mimetic (U-51605), PGD(2,) PGJ(2), and PGF(2α). It also interacts with 15(S)-HETE, being the first lipocalin described to date to bind to a derivative of 15-lipoxygenase. Binding was not observed to other prostaglandins (e.g. PGE(1), PGE(2), 8-iso-PGF(2α), prostacyclin), leukotrienes (e.g. LTB(4), LTC(4), LTD(4), LTE(4)), HETEs (e.g. 5(S)-HETE, 12(S)-HETE, 20-HETE), lipids (e.g. arachidonic acid, PAF), and biogenic amines (e.g. ADP, serotonin, epinephrine, norepinephrine, histamine). Consistent with its binding specificity, DPTL prevents contraction of rat uterus stimulated by PGF(2α) and induces relaxation of aorta previously contracted with U-46619. Moreover, it inhibits angiogenesis mediated by 15(S)-HETE and did not enhance inhibition of collagen-induced platelet aggregation by SQ29548 (TXA(2) antagonist) and indomethacin. A 3-D model for DPTL and pallidipin is presented that indicates the presence of a conserved Arg(39) and Gln(135) in the binding pocket of both lipocalins. Results suggest that DPTL blocks platelet aggregation, vasoconstriction, and angiogenesis through binding to distinct eicosanoids involved in inflammation.

Selenoprotein P protects cells from lipid hydroperoxides generated by 15-LOX-1

Reactive lipid hydroperoxides formed by lipoxygenases and cyclooxygenases can contribute to disease through cellular oxidative damage. Several selenoproteins have lipid hydroperoxidase activity, including glutathione peroxidase 4, thioredoxin reductase, and selenoprotein P (SelP). SelP is an extracellular glycoprotein that functions both in selenium distribution and has an antioxidant activity. The major objective of this study was to determine if an SelP, at physiological concentrations and in selenium replete media, possessed hydroperoxidase activity directed at lipid hydroperoxides generated from the metabolism of arachidonic acid by 15-lipoxygenase-1 (15-LOX-1). An SelP displayed in vitro lipid hydroperoxidase activity of 15-hydroperoxyeicosatetraenoic acid (15-HpETE), attenuated 15-HpETE oxidation in cellular assays, and in transcellular assay when 15-LOX-1 is metabolically active. These results suggest that an SelP can function as an antioxidant enzyme against reactive lipid intermediates formed during inflammation, but an SelP has modest activity. Nevertheless, this effect may help protect cells against the oxidative damage induced by these lipid metabolites.

Metabolic factors affecting the inflammatory response of periparturient dairy cows

Dairy cattle are susceptible to increased incidence and severity of disease during the periparturient period. Increased health disorders have been associated with alterations in bovine immune mechanisms. Many different aspects of the bovine immune system change during the periparturient period, but uncontrolled inflammation is a dominant factor in several economically important disorders such as metritis and mastitis. In human medicine, the metabolic syndrome is known to trigger several key events that can initiate and promote uncontrolled systemic inflammation. Altered lipid metabolism, increased circulating concentrations of non-esterified fatty acids and oxidative stress are significant contributing factors to systemic inflammation and the development of inflammatory-based diseases in humans. Dairy cows undergo similar metabolic adaptations during the onset of lactation, and it was postulated that some of these physiological events may negatively impact the magnitude and duration of inflammation. This review will discuss how certain types of fatty acids may promote uncontrolled inflammation either directly or through metabolism into potent lipid mediators. The relationship of increased lipid metabolism and oxidative stress to inflammatory dysfunction will be reviewed as well. Understanding more about the underlying cause of periparturient health disorders may facilitate the design of nutritional regimens that will meet the energy requirements of cows during early lactation and reduce the susceptibility to disease as a function of compromised inflammatory responses.

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.