8-iso-prostaglandin F2alpha as a marker of tissue oxidative damage in bovine retained placenta

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

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

Role of lipid mediators in the regulation of oxidative stress and inflammatory responses in dairy cattle

Periparturient dairy cows experience an increased incidence and severity of several inflammatory-based diseases such as mastitis and metritis. Factors associated with the physiological adaptation to the onset of lactation can impact the efficiency of the inflammatory response at a time when it is most needed to eliminate infectious pathogens that cause these economically important diseases. Oxidative stress, for example, occurs when there is an imbalance between the production of oxygen radicals during periods of high metabolic demand and the reduced capabilities of the host's antioxidant defenses. The progressive development of oxidative stress in early lactation cows is thought to be a significant underlying factor leading to dysfunctional inflammatory responses. Reactive oxygen species (ROS) are also produced by leukocytes during inflammation resulting in positive feedback loops that can further escalate oxidative stress during the periparturient period. During oxidative stress, ROS can modify polyunsaturated fatty acids (PUFA) associated with cellular membranes, resulting in the biosynthesis of oxidized products called oxylipids. Depending on the PUFA substrate and oxidation pathway, oxylipids have the capacity of either enhancing or resolving inflammation. In mediating their effects, oxylipids can directly or indirectly target sites of ROS production and thus control the degree of oxidative stress. This review discusses the evidence supporting the roles of oxylipids in the regulation of oxidative stress and the subsequent development of uncontrolled inflammatory responses. Further, the utility of some of the oxylipids as oxidative stress markers that can be exploited in developing and monitoring therapies for inflammatory-based diseases in dairy cattle is discussed. Understanding of the link between some oxylipids and the development or resolution of oxidative stress could provide novel therapeutic targets to limit immunopathology, reduce antibiotic usage, and optimize the resolution of inflammatory-based diseases in periparturient dairy cows.

The bovine placenta in vivo and in vitro

The gross anatomic features (cotyledonary type) and histologic classification (synepitheliochorial) of the bovine placenta have been known for many years. Thorough ultrastructural analysis as well as a variety of descriptive studies dealing with the localization of cytoskeletal filaments, extracellular matrix, growth factor systems, steroid hormone receptors, and major histocompatibility complex have contributed further significant knowledge. However, this knowledge was not sufficient to solve clinical placenta-based problems, such as retained fetal membranes. Owing to the complexity of the fetomaternal interface in vitro, culture systems have been developed. As trophoblast giant cells (TGC) are thought to be key players in the cattle placenta, most cell culture models attempt to overcome the pitfall of losing the entire TGC population in vitro. Nevertheless, distinct cell line-based in vitro systems such as cell monolayers or 3-dimensional (co-culture) spheroids were generated for the fetal (trophoblast) and maternal (uterine epithelium) placental compartments. Monolayers have been used to study for example, growth factor or hormonal signaling and TGC formation, whereas spheroids served as models for, for example, trophoblast attachment, uterine epithelium depolarization, and also TGC formation. In the future, the use of more improved culture models might lead to better treatments of retained fetal membranes and increased prevention of embryonic loss. In addition, the in vitro models could shed more light on the mechanisms of the differentiation of uninucleate trophoblast into TGC.

Comparison of antioxidative/oxidative profiles in blood plasma of cows with and without retained fetal placental membranes

Ante- and postpartum antioxidative/oxidative profiles in blood plasma of cows with and without retained placental membranes (RFM) were investigated. Twenty-two healthy pregnant cows were included in the study. Seven animals out of 22 suffered from RFM. Blood samples were obtained at 4, 3, 2, 1 weeks and 5 days antepartum (a.p.), at parturition and 1, 3, and 5 weeks postpartum. The following antioxidative parameters were measured using spectrophotometric methods: total antioxidant activity (TAC), β-carotene, vitamin A, vitamin C, and ceruloplasmin. The oxidative profile was based on the content of intermediates and end products of lipid and protein peroxidative processes which were measured by spectrophotometric and spectrofluorimetric methods. The examined parameters revealed a dynamic profile within the experimental period. The highest antioxidant and oxidant activity was noted at 2 and 1 week a.p. with a drop towards parturition suggesting the presence of oxidative stress during this time period and an apparent appropriate metabolic response of the macroorganism. Except for TAC and vitamin A, the contents of oxidative and antioxidative blood constituents did not differ between cows with and without RFM. A TAC and vitamin A by time interaction indicated higher antepartal concentrations of TAC and vitamin A in cows without RFM than in cows with RFM suggesting a possible role of antioxidative/oxidative imbalances in the aetiology of RFM.

Measurement of urinary F2-isoprostanes as markers of in vivo lipid peroxidation: a comparison of enzyme immunoassays with gas chromatography-mass spectrometry in domestic animal species

F(2)-isoprostanes are useful markers for assessing oxidant injury; however, the validity of measuring urinary 15-F(2t)-isoprostane concentration by enzyme-linked immunosorbent assay (ELISA) has not been evaluated in veterinary species. The current study assesses the agreement between 2 commercially available urinary isoprostane kits and gas chromatography and negative ion chemical ionization-mass spectrometry (GC/NICI-MS). The results indicate that only feline urinary isoprostane measurement by glucuronidase (GL)-ELISA has acceptable agreement with GC/NICI-MS. Urinary isoprostane concentration was highly variable in critically ill animals, but there were too many variations between healthy and critically ill animals to draw meaningful conclusions. Currently, GC/NICI-MS is the only method that can be recommended for the assessment of urinary isoprostanes in dogs, cattle, and horses. Feline urinary isoprostanes can be assessed by GL-ELISA, but caution is still warranted when comparing data from manuscripts using different methods given the relatively low Spearman rank correlation coefficient. Future studies may require large sample sizes or focused inclusion criteria to account for variability in isoprostane concentration.

Messenger RNA expression of angiotensin-converting enzyme, endothelin, cyclooxygenase-2 and prostaglandin synthases in bovine placentomes during gestation and the postpartum period

The bovine placenta contains local vasoactive-related systems, including angiotensin-converting enzyme (ACE), endothelin-1 (ET-1), ET-A receptor (ETAR) and ET-B receptor (ETBR), as well as arachidonic acid (AA) cascade-related enzymes, such as cyclooxygenase-2 (Cox-2), prostaglandin E-synthase (PGES) and prostaglandin F-synthase (PGFS). The mRNA expression of these molecules was examined in bovine placentomes (caruncles and cotyledons) collected immediately (0 h) and 6h after spontaneous parturition from 15 cows with early (fetal membranes released within 6 h of parturition) or late (fetal membranes released 6-12 h after parturition) detachment, as well as from 15 pregnant cows at a slaughterhouse. Significant differences were observed in expression of ET-1, ETAR and ETBR mRNAs between gestation and the postpartum period in both caruncles and cotyledons. Significant differences were also found between 0 and 6 h postpartum in the expression of ETBR mRNA in the early detachment group and PGES mRNA in the early and late detachment groups. Compared to PGFS, both Cox-2 and PGES exhibited opposite mRNA expression patterns during gestation and the postpartum period. The vasoactive-related peptide systems and AA cascade-related enzymes may mediate placental development and fetal membrane detachment after parturition in cattle.

Total antioxidant capacity of bovine spontaneously released and retained placenta

Exposure of living organisms to a constant generation of reactive oxygen species (ROS) resulted in the development of antioxidative defence systems which protect cells and tissues against their harmful effects. The retention of fetal membranes (RFM) in cows is hypothesized to be connected with the imbalance between production and neutralization of ROS. The efficiency of enzymatic and non-enzymatic antioxidative systems can be detected by the determination of single components of this system or by so-called total antioxidant capacity (TAC). In the present study, total antioxidant capacity was compared with previously measured parameters of antioxidative defence mechanisms in placental tissues of cows with respect to time of fetal membranes expulsion and mode of delivery. Placental samples were divided into: (A) caesarian section before term (272-277 days of pregnancy) without RFM (n=9), (B) caesarian section before term with RFM (n=14), (C) caesarian section at term (282-288 days of pregnancy) without RFM (n=12), (D) caesarian section at term with RFM (n=16), (E) spontaneous delivery at term without RFM (n=8), (F) spontaneous delivery at term with RFM (n=8). TAC was measured spectrophotometrically at 593nm by use of 2,4,6-tri-pyridyl-s-triazine in homogenates of maternal and fetal part of placenta and expressed as mumol/g protein (mean+/-S.E.M.). The values of TAC were significantly higher (P</=0.05) in the fetal than in maternal part in preterm samples (A - maternal: 27.24+/-4.17mumol/g prot, fetal: 63.67+/-18.16, B - maternal: 49.80+/-5.11, fetal: 70.96+/-13.23). The opposite relationship was noticed in term samples. Significantly higher values were observed in retained than in not retained placental tissues (C - maternal: 32.40+/-6.12, fetal: 16.29+/-3.97, D - maternal: 48.17+/-6.91, fetal: 27.92+/-4.72, E - maternal: 40.55+/-2.66, fetal: 27.90+/-1.23, F - maternal: 45.85+/-6.40, fetal: 43.50+/-4.61). Values of TAC are comparable with previously determined single parameters of antioxidative defence mechanisms in placental tissues and may be of clinical importance. Whether they reflect plasma values as well requires further evaluation.

Is poly(ADP-ribose) polymerase involved in bovine placental retention?

Poly(ADP-ribose) polymerase (PARP) is the enzyme which utilises NAD to synthesise poly(ADP-ribose) polymers. This process appears in response to DNA lesions. Oxidative stress, which might be involved in bovine placental retention, is the reason for oxidative DNA injury. In this mini-review, the relationship between PARP activity and bovine placental retention is discussed. The results of our experiments on PARP activity in placental tissues showed that the enzyme of 113 kDa and its cleavage products were present in retained as well as released fetal membranes. Western blotting technique showed different intensities in the staining of bands which might suggest different activities of the enzyme.