Antioxidants to prevent bovine neutrophil-induced mammary epithelial cell damage

Forsythiaside A attenuates lipopolysaccharide-induced mouse mastitis by activating autophagy and regulating gut microbiota and metabolism

Mastitis is an inflammatory disease of the mammary gland with a high incidence in lactating animals, significantly impacting their health and breastfeeding. Moreover, mastitis adversely affects milk quality and yield, resulting in substantial economic losses for the dairy farming industry. Forsythiaside A (FTA), a phenylethanol glycoside analog extracted from Forsythia, exhibits notable anti-inflammatory and antioxidant properties. However, its protective effects and specific mechanisms against mastitis remain unclear. In this study, a lipopolysaccharide (LPS)-induced mouse mastitis model was used to investigate the protective effect of FTA on LPS-induced mastitis and its potential mechanism using histological assays, Western blot, qRT-PCR, FITC-albumin permeability test, 16s rRNA gene sequencing analysis and non-targeted metabolomics assays to investigate the protective effect of FTA on LPS-induced mastitis model and its potential mechanism. The results demonstrated that FTA significantly mitigated LPS-induced mouse mastitis by reducing inflammation and apoptosis levels, modulating the PI3K/AKT/mTOR signaling pathways, inducing autophagy, and enhancing antioxidant capacity and the expression of tight junction proteins. Furthermore, FTA increased the abundance of beneficial microbiota while decreasing the levels of harmful microbiota in mice, thus counteracting the gut microbiota disruption induced by LPS stimulation. Intestinal metabolomics analysis revealed that FTA primarily regulated LPS-induced metabolite alterations through key metabolic pathways, such as tryptophan metabolism. This study confirms the anti-inflammatory and antioxidant effects of FTA on mouse mastitis, which are associated with key metabolic pathways, including the restoration of gut microbiota balance and the regulation of tryptophan metabolism. These findings provide a novel foundation for the treatment and prevention of mammalian mastitis using FTA.

Effects of Chestnut Hydrolysable Tannin on Intake, Digestibility, Rumen Fermentation, Milk Production and Somatic Cell Count in Crossbred Dairy Cows

This study was conducted to determine the effects of chestnut hydrolysable tannin (CHT) on intake, digestibility, rumen fermentation, milk yield and somatic cell count in crossbred dairy cows (>75% Holstein Friesian). Four crossbred dairy cows (467.6 ± 35.2 kg BW) were assigned to be supplemented with one of four levels of CHT according to a 4 × 4 Latin square design. Dietary treatments included the control (without CHT supplementation) and CHT treatments that consisted of supplementation with 3.15, 6.30 and 9.45 g CHT/day. Rice straw was given ad libitum. The results showed that increasing levels of CHT tended to quadratically decrease rice straw intake (p = 0.06). However, total dry matter intake (DMI) and other nutrients were not different (p > 0.05) among the dietary treatments. The apparent digestibility of DM, organic matter (OM) and crude protein (CP) in cows with CHT treatments were higher (p < 0.05) than those of control cows. Milk yield and milk composition were not different (p > 0.05) among treatments. Lactose yield tended to increase linearly (p = 0.09) as CHT supplementation increased. Ruminal pH and ammonia nitrogen (NH3-N) were not different (p > 0.05), but total volatile fatty acids (VFAs) increased linearly (p < 0.05) as CHT levels increased. The somatic cell count (SCC) and somatic cell score (SCS) in the CHT treatments were different (p < 0.01) than those in the control treatment. In conclusion, it appears that CHT supplementation improved feed utilization and influenced SCC in crossbred dairy cows. Long-term research is needed to confirm the benefit of CHT supplementation.

Inclusion of Sunflower Oil, Organic Selenium, and Vitamin E on Milk Production and Composition, and Blood Parameters of Lactating Cows

Simple Summary

Feeding sunflower oil, selenium, and vitamin E to lactating dairy cows has improved the nutritional profile of milk for human consumption and positively impacted animal performance. This may be attributed to the increased healthier fat components, i.e., “good fats”, and antioxidant substances in milk. This study evaluated the effects of supplementing sunflower oil, selenium, and vitamin E on milk production and composition, and the blood parameters of lactating dairy cows. Supplementing sunflower oil to lactating dairy cows provided beneficial effects on milk fatty acid profiles, increasing healthier fatty acids concentrations, which have been reported as important anticarcinogenic, antiatherogenic, and antidiabetic nutrients in human diet. However, this strategy reduced the milk fat content. Selenium and vitamin E supplementation improved milk production and provided higher selenium and vitamin E content in blood and milk. These compounds are important antioxidants and nutrients for animal and human health.

Abstract

Aiming to improve milk quality and animal health, the effects of the inclusion of sunflower oil with added organic selenium (Se) and vitamin E in the diets of lactating cows were evaluated. Twenty-four multiparous lactating Jersey cows were randomly enrolled into four treatments: CON (control); SEL [2.5 mg organic Se kg⁻¹ dry matter (DM) + 1000 IU vitamin E daily]; SUN (sunflower oil 3% DM); and SEL + SUN (sunflower oil 3% DM + 2.5 mg organic Se kg⁻¹ DM + 1000 IU vitamin E daily). The experimental period was 12 weeks with 14 days for acclimation. Cows were milked twice a day. Dry matter intake, milk production, and composition were measured daily and analyzed in a pooled 4-week sample. On day 84, white blood cell counts, as well as serum and milk Se and vitamin E levels, were assessed. Supplementation with selenium and vitamin E alone or combined with sunflower oil increased milk production, and increased the serum and milk concentrations of those nutrients. The inclusion of sunflower oil reduced fat content and DM intake but also altered the milk fatty acid profile, mainly increasing levels of trans 11 C18:1 (vaccenic) and cis 9 trans 11 conjugated linoleic acid (CLA). Our results indicate that supplementation with sunflower oil, Se and vitamin E provides beneficial effects on animal performance and milk composition, which could be an important source of CLA and antioxidants (Se and vitamin E) for human consumption.

Escherichia coli Mastitis in Dairy Cattle: Etiology, Diagnosis, and Treatment Challenges

Bovine mastitis is an inflammation of the udder tissue parenchyma that causes pathological changes in the glandular tissue and abnormalities in milk leading to significant economic losses to the dairy industry across the world. Mammary pathogenic Escherichia (E.) coli (MPEC) is one of the main etiologic agents of acute clinical mastitis in dairy cattle. MPEC strains have virulence attributes to resist the host innate defenses and thrive in the mammary gland environment. The association between specific virulence factors of MPEC with the severity of mastitis in cattle is not fully understood. Furthermore, the indiscriminate use of antibiotics to treat mastitis has resulted in antimicrobial resistance to all major antibiotic classes in MPEC. A thorough understanding of MPEC’s pathogenesis and antimicrobial susceptibility pattern is required to develop better interventions to reduce mastitis incidence and prevalence in cattle and the environment. This review compiles important information on mastitis caused by MPEC (e.g., types of mastitis, host immune response, diagnosis, treatment, and control of the disease) as well as the current knowledge on MPEC virulence factors, antimicrobial resistance, and the dilemma of MPEC as a new pathotype. The information provided in this review is critical to identifying gaps in knowledge that will guide future studies to better design diagnostic, prevent, and develop therapeutic interventions for this significant dairy disease.

Pistacia lentiscus extract enhances mammary epithelial cells' productivity by modulating their oxidative status

We assessed the potential of phenolic compounds from Pistacia lentiscus (lentisk) to enhance production of milk constituents in bovine mammary epithelial cells (MEC). MEC were exposed to 0 (control), 1 or 10 ppm of polyphenols from lentisk ethanolic extract (PLEE) for 24 h. PLEE were absorbed by the MEC plasma membrane, but also penetrated the cell to accumulate in and around the nucleus. PLEE increased triglyceride content in the cell and its secretion to the medium, and significantly increased intracellular lipid droplet diameter. Compared to control, PLEE increased dose-dependently the lactose synthesis, secretion of whey proteins, and contents of casein. To evaluate mitochondrial activity under pro-oxidant load, MEC were preincubated with PLEE and exposed for 2 h to H₂O₂. Exposure to H₂O₂ increased the proportion of cells with impaired mitochondrial membrane potential twofold in controls, but not in PLEE-pre-treated cells. Accordingly, proton leakage was markedly decreased by PLEE, and coupling efficiency between the respiratory chain and ATP production was significantly enhanced. Thus, lentisk polyphenols divert energy to production of milk fat, protein and lactose, with less energy directed to cellular damage control; alternatively, PLEE enables MEC to maintain energy and oxidative status under extreme metabolic rate required for milk production and secretion, and reduces the limitation on energy required to support production.

Bacterial Endotoxins and Their Role in Periparturient Diseases of Dairy Cows: Mucosal Vaccine Perspectives

During the periparturient period there is a significant increase in the incidence of multiple metabolic and infectious diseases in dairy cows. Dairy cows are fed high-grain diets immediately after calving to support production of large amounts of milk. Mounting evidence indicates these types of diets are associated with the release of high amounts of endotoxins in the rumen fluid. If infected, the udder and uterus additionally become important sources of endotoxins during the postpartum period. There is increasing evidence that endotoxins translocate from rumen, uterus, or udder into the systemic circulation and trigger chronic low-grade inflammatory conditions associated with multiple diseases including fatty liver, mastitis, retained placenta, metritis, laminitis, displaced abomasum, milk fever, and downer cow syndrome. Interestingly, endotoxin-related diseases are triggered by a bacterial component and not by a specific bacterium. This makes prevention of these type of diseases different from classical infectious diseases. Prevention of translocation of endotoxins into the host systemic circulation needs to take priority and this could be achieved with a new approach: mucosal vaccination. In this review article, we discuss all the aforementioned issues in detail and also report some of our trials with regards to mucosal vaccination of periparturient dairy cows.

Schisandrin A protects against lipopolysaccharide-induced mastitis through activating Nrf2 signaling pathway and inducing autophagy

Schisandrin A (Sch A), a dibenzocyclooctadiene lignan extracted from Schisandra chinensis (Turcz.) Baill., has anti-oxidant and anti-inflammatory effects, but the effect on masitits has not been studied. Therefore, we investigated the effect of Sch A in cell and mouse models of lipopolysaccharide (LPS)-induced mastitis. Studies in vivo showed that Sch A reduced LPS-induced mammary injury and the production of pro-inflammatory mediators. Sch A also decreased the levels of pro-inflammatory mediators and activated nuclear factor-E2 associated factor 2 (Nrf2) signaling pathway in mouse mammary epithelial cells (mMECs). The Nrf2 inhibitor partially abrogated the downregulation of Sch A on LPS-induced inflammatory response. In addition, LPS stimulation suppressed autophagy, while both Sch A and the autophagy inducer rapamycin activated autophagy in mMECs, which down-regulated inflammatory response. Sch A also restrained LPS-induced phosphorylation of mammalian target of rapamycin (mTOR) and activated AMP-activated protein kinase (AMPK) and unc-51 like kinase 1 (ULK1). In summary, these results suggest that Sch A exerts protective effects in LPS-induced mastitis models by activating Nrf2 signaling pathway and inducing autophagy and the autophagy is initiated by suppressing mTOR signaling pathway and activating AMPK-ULK1 signaling pathway.

Increasing Selenium and Vitamin E in Dairy Cow Milk Improves the Quality of the Milk as Food for Children

In this study, we investigated the beneficial effects of milk biofortified with antioxidants on the health of children. Two experiments were conducted: experiment one evaluated the milk of 24 Jersey dairy cows (450 ± 25 kg of body weight (BW); 60 ± 30 days in milk dry matter intake (DIM)) given different diet treatments (CON = control diet; COANT = diet with vitamin E and selenium as antioxidants; OIL = diet with sunflower oil; and OANT = diet with sunflower oil containing more vitamin E and selenium as antioxidants), and experiment two evaluated the effect of the milk produced in the first experiment on the health of children (CON = control diet; COANT = diet with vitamin E and selenium as antioxidants; OIL = diet with sunflower oil; OANT = diet with sunflower oil containing more vitamin E and selenium as antioxidants; and SM = skim milk). One hundred children (8 to 10 years old) were evaluated in the second experiment. Blood samples were collected at 0 days of milk intake and 28 and 84 days after the start of milk intake. The cows fed the COANT and OANT diets showed greater selenium and vitamin E concentrations in their milk (p = 0.001), and the children who consumed the milk from those cows had higher concentrations of selenium and vitamin E in their blood (p = 0.001). The platelet (p = 0.001) and lymphocyte (p = 0.001) concentrations were increased in the blood of the children that consumed milk from cows fed the OANT diet compared to those in the children that consumed SM (p = 0.001). The children who consumed milk from cows fed the OIL diet treatment had increased concentrations of low density lipoprotein (LDL) and total cholesterol in their blood at the end of the supplementation period compared to children who consumed SM. The results of this study demonstrate that the consumption of biofortified milk increases the blood concentrations of selenium and vitamin E in children, which may be beneficial to their health.

Influence of oxytetracycline susceptibility as a first-line antibiotic on the clinical outcome in dairy cattle with acute Escherichia coli mastitis

The purpose of this study was to clarify the therapeutic effects of oxytetracycline (OTC) as a first-line antibiotic in cattle with acute Escherichia coli mastitis and systemic signs. Drug susceptibility was determined by the minimum inhibitory concentration (MIC) of E. coli isolated from cows with acute E. coli mastitis (n=38). Cattle were divided into OTC-susceptible (S, n=30) and OTC-resistant (R, n=8) groups. They were further subdivided according to susceptibility to the antibiotic used as a second treatment, into susceptible-susceptible (SS, n=30), resistant-susceptible (RS, n=5), and resistant-resistant (RR, n=3) groups. Clinical signs on the day after initial treatment were compared between S and R groups as short-term indicators of treatment effects. The 28-day survival rate of cattle was then compared among SS, RS, and RR groups as a long-term indicator of treatment effects. There were no differences in clinical signs between S and R groups on the day after the first dose, but the 28-day survival rate was significantly greater in the SS group than in the RR group (P=0.04). The results demonstrated that an effective drug is essential for first-line treatment of acute coliform mastitis. However, anticipating the effectiveness of a first-line antibiotic based on clinical symptoms at the second day of treatment is impossible. It is important to build a picture of drug resistance trends in cattle herds for empirical selection of antibiotics to be administered.

Therapeutic effect of ginsenoside Rg1 on mastitis experimentally induced by lipopolysaccharide in lactating goats

Escherichia coli is a cause of subclinical and clinical mastitis in dairy cattle and goats, and sometimes causes severe clinical disease that may result in death of the animal. Previous investigation showed that ginsenoside Rg1 extracted from Panax ginseng C.A. Meyer (Araliaceae) has an anti-inflammatory effect on the sepsis induced by E. coli lipopolysaccharide via competitive binding to toll-like receptor 4. We hypothesized that intravenous injection of Rg1 had therapeutic effect on mastitis experimentally induced by intramammary infusion of lipopolysaccharide in lactating goats. In this study, 9 lactating goats were randomly assigned to 1 of the 3 groups: (1) lipopolysaccharide intramammary infusion + saline intravenous injection, (2) lipopolysaccharide intramammary infusion + Rg1 intravenous injection, and (3) saline intramammary administration + saline intravenous injection. Because no adverse clinical signs were observed after intramammary infusion of saline and intravenous injection of Rg1 in a preliminary experiment, and available qualified goats were limited in this study, this treatment was not included in this study. One udder half of each goat received intramammary infusion of lipopolysaccharide (50 μg/kg of body weight; groups 1 and 2) or saline solution (group 3), and the other half was infused with 2 mL of saline solution at h 0. Afterward, intravenous injections of saline solution (groups 1 and 3) or Rg1 (2.5 mg/kg of body weight; group 2) were administered at h 2 and 4 post-lipopolysaccharide challenge. Blood and milk samples were collected 3, 6, 9, 12, 15, 18, 21, 24, 48, and 72 h post-lipopolysaccharide challenge, and clinical signs were monitored hourly after lipopolysaccharide challenge within the first 10 h and at the same time points as blood samples. The results showed that Rg1 treatment downregulated rectal temperature, udder skin temperature, udder girth, milk somatic cell count, and N-acetyl-β-d-glucosaminidase and upregulated milk production, lactose, and recovered blood components, such as white blood cells, neutrophils, lymphocytes, total proteins, albumin, and globulin. Considering the positive therapeutic effect on lipopolysaccharide-induced mastitis in goats presented in this study as well as the anti-inflammatory activity found previously, the botanical Rg1 deserves further study as a therapeutic agent in the treatment of E. coli mastitis in dairy animals.

Performance and methane emissions in dairy cows fed oregano and green tea extracts as feed additives

Plant extracts have been proposed as substitutes for chemical feed additives due to their potential as rumen fermentation modifiers and because of their antimicrobial and antioxidant activities, possibly reducing methane emissions. This study aimed to evaluate the use of oregano (OR), green tea extracts (GT), and their association as feed additives on the performance and methane emissions from dairy between 28 and 87 d of lactation. Thirty-two lactating dairy cows, blocked into 2 genetic groups: 16 Holstein cows and 16 crossbred Holstein-Gir, with 522.6 ± 58.3 kg of body weight, 57.2 ± 20.9 d in lactation, producing 27.5 ± 5.0 kg/cow of milk and with 3.1 ± 1.8 lactations were evaluated (means ± standard error of the means). Cows were allocated into 4 treatments: control (CON), without plant extracts in the diet; oregano extract (OR), with the addition of 0.056% of oregano extract in the dry matter (DM) of the diet; green tea (GT), with the addition of 0.028% of green tea extract in the DM of the diet; and mixture, with the addition of 0.056% oregano extract and 0.028% green tea extract in the DM of the diet. The forage-to-concentrate ratio was 60:40. Forage was composed of corn silage (94%) and Tifton hay (6%); concentrate was based on ground corn and soybean meal. Plant extracts were supplied as powder, which was previously added and homogenized into 1 kg of concentrate in natural matter, top-dressed onto the total mixed diet. No treatment by day interaction was observed for any of the evaluated variables, but some block by treatment interactions were significant. In Holstein cows, the mixture treatment decreased gross energy and tended to decrease the total-tract apparent digestibility coefficient for crude protein and total digestible nutrients when compared with OR. During the gas measurement period, GT and OR increased the digestible fraction of the ingested DM and decreased CH₄ expressed in grams per kilogram of digestible DMI compared with CON. The use of extracts did not change rumen pH, total volatile fatty acid concentration, milk yield, or most milk traits. Compared with CON, oregano addition decreased fat concentration in milk. The use of plant extracts altered some milk fatty acids but did not change milk fatty acids grouped according to chain length (short or long), saturation (unsaturated or saturated), total conjugated linoleic acids, and n-3 and n-6 contents. Green tea and oregano fed separately reduced gas emission in cows during the first third of lactation and have potential to be used as feed additives for dairy cows.

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.

Mediation analysis to estimate direct and indirect milk losses associated with bacterial load in bovine subclinical mammary infections

Milk losses associated with mastitis can be attributed to either effects of pathogens per se (i.e. direct losses) or to effects of the immune response triggered by the presence of mammary pathogens (i.e. indirect losses). Test-day milk somatic cell counts (SCC) and number of bacterial colony forming units (CFU) found in milk samples are putative measures of the level of immune response and of the bacterial load, respectively. Mediation models, in which one independent variable affects a second variable which, in turn, affects a third one, are conceivable models to estimate direct and indirect losses. Here, we evaluated the feasibility of a mediation model in which test-day SCC and milk were regressed toward bacterial CFU measured at three selected sampling dates, 1 week apart. We applied this method on cows free of clinical signs and with records on up to 3 test-days before and after the date of the first bacteriological samples. Most bacteriological cultures were negative (52.38%), others contained either staphylococci (23.08%), streptococci (9.16%), mixed bacteria (8.79%) or were contaminated (6.59%). Only losses mediated by an increase in SCC were significantly different from null. In cows with three consecutive bacteriological positive results, we estimated a decreased milk yield of 0.28 kg per day for each unit increase in log2-transformed CFU that elicited one unit increase in log2-transformed SCC. In cows with one or two bacteriological positive results, indirect milk loss was not significantly different from null although test-day milk decreased by 0.74 kg per day for each unit increase of log2-transformed SCC. These results highlight the importance of milk losses that are mediated by an increase in SCC during mammary infection and the feasibility of decomposing total milk loss into its direct and indirect components.

Low-level laser therapy attenuates LPS-induced rats mastitis by inhibiting polymorphonuclear neutrophil adhesion

The aim of this study was to investigate the effects of low-level laser therapy (LLLT) on a rat model of lipopolysaccharide (LPS)-induced mastitis and its underlying molecular mechanisms. The rat model of mastitis was induced by inoculation of LPS through the canals of the mammary gland. The results showed that LPS-induced secretion of IL-1β and IL-8 significantly decreased after LLLT (650 nm, 2.5 mW, 30 mW/cm²). LLLT also inhibited intercellular adhesion molecule-1 (ICAM-1) expression and attenuated the LPS-induced decrease of the expression of CD62L and increase of the expression of CD11b. Moreover, LLLT also suppressed LPS-induced polymorphonuclear neutrophils (PMNs) entering the alveoli of the mammary gland. The number of PMNs in the mammary alveolus and the myeloperoxidase (MPO) activity were decreased after LLLT. These results suggested that LLLT therapy is beneficial in decreasing the somatic cell count and improving milk nutritional quality in cows with an intramammary infection.

Suppression of prolactin signaling by pyrrolidine dithiocarbamate is alleviated by N-acetylcysteine in mammary epithelial cells

Prolactin is the key hormone to stimulate milk synthesis in mammary epithelial cells. It signals through the Jak2-Stat5 pathway to induce the expression of β-casein, a milk protein which is often used as a marker for mammary differentiation. Here we examined the effect of pyrrolidine dithiocarbamate (PDTC) on prolactin signaling. Our results show that PDTC downregulates prolactin receptor levels, and inhibits prolactin-induced Stat5 tyrosine phosphorylation and β-casein expression. This is not due to its inhibitory action on NF-κB since application of another NF-κB inhibitor, BAY 11-7082, and overexpression of I-κBα super-repressor do not lead to the same results. Instead, the pro-oxidant activity of PDTC is involved as inclusion of the antioxidant N-acetylcysteine restores prolactin signaling. PDTC triggers great extents of activation of ERK and JNK in mammary epithelial cells. These do not cause suppression of prolactin signaling but confer serine phosphorylation of insulin receptor substrate-1, thereby perturbing insulin signal propagation. As insulin facilitates optimal β-casein expression, blocking insulin signaling by PDTC might pose additional impediment to β-casein expression. Our results thus imply that lactation will be compromised when the cellular redox balance is dysregulated, such as during mastitis.

Effect of reduction of milking frequency and supplementation of vitamin E and selenium above requirements on milk yield and composition in Assaf ewes

The aim of this research was to study the effect of milking frequency and supplementation with a vitamin-mineral complex above requirements on intake, body weight (BW), and milk yield and composition in high-yielding Assaf ewes. Sixteen lactating Assaf ewes were used in this study, separated into 4 groups of 4 ewes each. Animals in 2 of the groups (control groups) did not receive any extra vitamin-mineral supplement, whereas animals in the other 2 groups (supplement groups) received daily an oral dose of 1g of vitamin E (1,000 IU, DL-α-tocopherol acetate) and 0.4 mg of selenium (sodium selenite anhydrous). The experiment consisted of 2 consecutive periods of 3 wk (twice-daily milking in both mammary glands) and 8 wk (once-daily milking in one mammary gland and twice-daily milking in the other gland). Intake, BW, and milk composition were controlled weekly, and milk production was recorded 3 times a week. Administration of the vitamin-mineral supplement had no effect on dry matter intake, BW, or milk production and composition. The reduction of milking from twice to once a day caused a decrease in milk production and lactose concentration and a significant increase in protein concentration, total solids, and somatic cell count, without affecting the fat content. Administration of a vitamin E and Se supplement at the doses used in the present study does not seem to exert, in the short term, a noticeable effect on the mammary gland when milking frequency is reduced.

Effect of tea catechins on regulation of cell proliferation and antioxidant enzyme expression in H2 O2 -induced primary hepatocytes of goat in vitro

Tea catechins (TC) are polyphenols that have potent antioxidant activity. The objectives of this study were to determine the effects of TC on antioxidant status of hepatocytes challenged with H2 O2 . Primary hepatocytes of goat were exposed to 1 mm H2 O2 without or with 5, 50 and 500 μg/ml TC. The cells were harvested at 48 h post-treatment to determine effects of TC on proliferation, apoptotic features and membrane integrity of cells, and expression of genes and activities of antioxidant enzymes. H2 O2 exposure caused damage to cells (p < 0.001). A lower concentration of TC (5 μg/ml) displayed a protective effect by inhibiting exorbitant cell proliferation and DNA degradation. Both H2 O2 exposure and TC pre-incubation affected expression of antioxidant enzymes at mRNA and protein levels (p < 0.001). The activities of catalase (CAT) (p = 0.027), CuZn-superoxide dismutase (CuZn-SOD) (p < 0.001) and glutathione peroxidase (GPx) (p < 0.001) increased with TC pre-incubation followed by H2 O2 challenge. Changes of CuZn-SOD activity induced by H2 O2 and TC basically paralleled the changes in the corresponding mRNA and protein levels, but the correlation in CAT and GPx expression displayed slightly different patterns at different concentrations of TC. These findings infer that oxidative stress can induce deleterious cellular responses and this unfavourable condition may be alleviated by treatment with TC.

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.

Effects of intramammary infusion of cis-urocanic acid on mastitis-associated inflammation and tissue injury in dairy cows

OBJECTIVE

To evaluate the effects of cis-urocanic acid (cis-UCA) on mammary gland (MG) inflammation and injury associated with Escherichia coli-induced mastitis in dairy cows.

ANIMALS

12 lactating dairy cows (36 MGs).

PROCEDURES

At 7-week intervals, a different MG in each cow was experimentally inoculated with E coli. At 6-hour intervals from 6 to 36 hours after inoculation, the inoculated MG in each cow was infused with 40 mL of saline (0.9% NaCl) solution, 12.5mM cis-UCA, or 25mM cis-UCA (4 cows/group); ultimately, each cow received each treatment. Immediately prior to and at various time points after inoculation and treatment, milk samples were collected. Bacterial CFUs, somatic cell counts (SCCs), N-acetyl-beta-D-glucosaminidase (NAGase) and lactate dehydrogenase (LDH) activities, and concentrations of bovine serum albumin, tumor necrosis factor-alpha, and cis-UCA were quantified in each milk sample. Results-Compared with findings in saline solution-treated MGs, NAGase and LDH activities in milk samples from cis-UCA-treated MGs were lower. Cis-UCA had no effect on milk SCCs and milk concentrations of bovine serum albumin and tumor necrosis factor-alpha. Furthermore, cis-UCA had no adverse effect on bacterial clearance; CFUs of E coli in MGs treated with saline solution or cis-UCA were equivalent.

CONCLUSIONS AND CLINICAL RELEVANCE

In cows, milk NAGase and LDH activities were both lower in E coli-infected MGs infused with cis-UCA than in those infused with saline solution, which suggests that cis-UCA reduced mastitis-associated tissue damage. Furthermore, these data indicated that therapeutic concentrations of cis-UCA in milk can be achieved via intramammary infusion.

Neutrophils as one of the major haptoglobin sources in mastitis affected milk

The antioxidant haptoglobin (Hp) is an acute-phase protein responsive to infectious and inflammatory diseases. Hp and somatic cell counts (SCC) are sharply elevated in bovine milk following intramammary administration of endotoxin or bacteria. However, the sources of milk Hp responsible for such increases are not fully understood. The purpose of this study was to define the source of milk Hp from dairy cows with naturally occurring mastitis. Quarter milk samples selected from 50 dairy cows were separated into four groups according to SCC as group A: < 100 (n = 19); B: 100-200 (n = 10); C: 201-500 (n = 10); and D: > 500 x 10(3) (n = 11) cells/mL. Our results reveal that milk Hp concentrations were correlated with SCC (r = 0.742; P < 0.01), and concentrations in group D were approximately 10-fold higher than in group A. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis indicates that the milk somatic cells from group D were not only capable of synthesizing Hp but could also markedly increase Hp mRNA expression. Western blot, immunocytochemistry, double confocal immunofluorescence, and Hp releasing experiments demonstrate that neutrophils were associated with the biosynthesis and release of Hp in milk. It further shows that Hp was significantly elevated in the epithelium of mammary gland tissue with mastitis and was also expressed in the cultured mammary epithelial cells. We propose that neutrophils and epithelial cells may play an essential role in elevating milk Hp in addition to previous suggestions that Hp may be derived from mammary tissues and circulation.

Molecular analysis of tammar (Macropus eugenii) mammary epithelial cells stimulated with lipopolysaccharide and lipoteichoic acid

The immunological function of the metatherian mammary gland plays a crucial part in neonatal survival of the marsupial young. Marsupial pouch young do not develop adult like immune responses until just prior to leaving the pouch. The immune components of the maternal milk secretions are important during this vulnerable early post-partum period. In addition, infection of the mammary gland has not been recognized in metatherians, despite the ready availability of pathogens in the pouch. Regardless of which, little is known about the immunobiology of the mammary gland and the immune responses of mammary epithelial cells in metatherians. In this study, a molecular approach was utilized to examine the response of tammar (Macropus eugenii) mammary epithelial cells to Escherichia coli derived lipopolysaccharide (LPS) and Staphylococcus aureus derived lipoteichoic acid (LTA). Using custom-made cDNA microarrays, candidate genes were identified in the transciptome, which were involved in antigen presentation, inflammation, cell growth and proliferation, cellular damage and apoptosis. Quantification of mRNA expression of several of these candidate genes, along with seven other genes (TLR4, CD14, TNF-alpha, cathelicidin, PRDX1, IL-5 and ABCG2) associated with innate immunity in LPS and LTA challenged mammary epithelial cells and leukocytes, was assessed for up to 24 h. Differences in genes associated with cellular damage and pro-inflammatory cytokine production were seen between stimulated mammary epithelial cells and leukocytes. LTA challenge tended to result in lower level induction of pro-inflammatory cytokines, increased PRDX1 mRNA levels, suggesting increased oxidative stress, and increased CD14 expression, but in a non-TLR4-dependent manner. The use of functional genomic tools in the tammar identified differences in the response of tammar mammary epithelial cells (MEC) and leukocytes to challenge with LPS and LTA, and validates the utility of the approach. The results of this study are consistent with a model in which tammar mammary epithelial cells have the capacity to elicit a complex and robust immune response to pathogens.

Differential effects of alpha1-acid glycoprotein on bovine neutrophil respiratory burst activity and IL-8 production

During bacterial-mediated diseases, neutrophils (PMNs) play a critical role in defending the host against invading pathogens. PMN production of reactive oxygen species (ROS) contributes to the bactericidal capabilities of these cells. ROS are produced intracellularly and can be released extracellularly. The aberrant extracellular release of ROS, however, has been reported to induce injury to host tissues during mastitis and other inflammatory-mediated diseases of cattle. The acute phase response, which occurs shortly after infection or tissue injury, is characterized by the induction of a large number of plasma proteins referred to as acute phase proteins (APP). alpha1-Acid glycoprotein (AGP) is an APP that increases in response to infection or injury in cattle and humans. The precise function of AGP is unknown, but it has been reported to possess anti-inflammatory properties. The objective of this study was to evaluate the effects of bovine AGP on PMN pro-inflammatory responses, including respiratory burst activity and cytokine production. Bovine AGP dose-dependently inhibited zymosan-induced PMN extracellular release of superoxide anion and hydrogen peroxide without affecting the capacity of PMN to engulf and kill Staphylococcus aureus. Moreover, AGP exerted its effect on ROS production regardless of whether PMNs were exposed to AGP prior to or after activation. In contrast to respiratory burst activity, AGP enhanced PMN production of IL-8. The precise mechanism by which AGP regulates PMN functions remains unknown, but data presented in this study suggest that AGP may have a complex role by differentially regulating PMN pro-inflammatory activities.

Immunomodulatory activity of plant residues on ovine neutrophils

Neutrophils play an essential role in host defense and inflammation. Plants have long been used to improve the immune function, but for most of them specific investigations on animal health are lacking. In the present study, water and hydroethanolic extracts from 11 plant wastes have been screened on immune responses of ovine neutrophils. Eight sheep clinically healthy, not lactating, non-pregnant were selected and used for the experiment. Freshly isolated neutrophils were incubated with the extracts of the residues at increasing doses, and then they were tested for adhesion and superoxide production induced with PMA. The residues of Larix decidua, Thymus vulgaris, Salix alba, Sinupret, Helianthus annuus, Mangifera indica modulated the neutrophil immune functions, moreover, Larix decidua, Thymus vulgaris and Salix alba presented the highest anti-inflammatory activity.

Effect of cis-urocanic acid on bovine neutrophil generation of reactive oxygen species

Neutrophils play a fundamental role in the host innate immune response during mastitis and other bacterial-mediated diseases of cattle. One of the critical mechanisms by which neutrophils contribute to host innate immune defenses is through their ability to phagocytose and kill bacteria. The ability of neutrophils to kill bacteria is mediated through the generation of reactive oxygen species (ROS). However, the extracellular release of ROS can be deleterious to the host because ROS induce tissue injury. Thus, in diseases such as mastitis that are accompanied by the influx of neutrophils, the generation of large quantities of ROS may result in significant injury to the mammary epithelium. cis-Urocanic acid (cis-UCA), which is formed from the UV photoisomerization of the trans isoform found naturally in human and animal skin, is an immunosuppressive molecule with anti-inflammatory properties. Little is known about the effect of cis-UCA on neutrophils, although one report demonstrated that it inhibits human neutrophil respiratory burst activity. However, the nature of this inhibition remains unknown. Because of the potential therapeutic use that a molecule such as cis-UCA may have in blocking excessive respiratory burst activity that may be deleterious to the host, the ability of cis-UCA to inhibit bovine neutrophil production of ROS was studied. Further, because neutrophil generation of ROS is necessary for optimal neutrophil bactericidal activity, a response which is critical for the host innate immune defense against infection, the effects of cis-UCA on bovine neutrophil phagocytosis and bacterial killing were assayed. cis-Urocanic acid dose-dependently inhibited the respiratory burst activity of bovine neutrophils as measured by luminol chemiluminescence. Subsequently, the effect of cis-UCA on the production of specific oxygen radicals was investigated using more selective assays. Using 2 distinct assays, we established that cis-UCA inhibited the generation of extracellular superoxide. In contrast, cis-UCA had no effect on the generation of intracellular levels of superoxide or other ROS. At concentrations that inhibited generation of extracellular superoxide, bovine neutrophil phagocytosis and bacterial activity remained intact. Together, these data suggest that cis-UCA inhibits the tissue-damaging generation of extracellular ROS while preserving neutrophil bactericidal activity.

Mammary tissue damage during bovine mastitis: causes and control

Mastitis, an inflammatory reaction of the mammary gland that is usually caused by a microbial infection, is recognized as the most costly disease in dairy cattle. Decreased milk production accounts for approximately 70% of the total cost of mastitis. Mammary tissue damage reduces the number and activity of epithelial cells and consequently contributes to decreased milk production. Mammary tissue damage has been shown to be induced by either apoptosis or necrosis. These 2 distinct types of cell death can be distinguished by morphological, biochemical, and molecular changes in dying cells. Both bacterial factors and host immune reactions contribute to epithelial tissue damage. During infection of the mammary glands, the tissue damage can initially be caused by bacteria and their products. Certain bacteria produce toxins that destroy cell membranes and damage milk-producing tissue, whereas other bacteria are able to invade and multiply within the bovine mammary epithelial cells before causing cell death. In addition, mastitis is characterized by an influx of somatic cells, primarily polymorphonuclear neutrophils, into the mammary gland. With more immune cells migrating into the mammary gland and the breakdown of the blood-milk barrier, damage to the mammary epithelium worsens. It is well known that breakdown of the extracellular matrix can lead to death of the epithelial cells. Meanwhile, polymorphonuclear neutrophils can harm the mammary tissue by releasing reactive oxygen intermediates and proteolytic enzymes. In vitro and in vivo studies suggest that the use of antioxidants and other protective compounds in mastitis control programs is worth investigating, because they may aid in alleviating damage to secretory cells and thus reduce subsequent milk loss.

Evaluation of assays for the measurement of bovine neutrophil reactive oxygen species

During mastitis and other bacterial-mediated diseases of cattle, neutrophils play a critical role in the host innate immune response to infection. Neutrophils are among the earliest leukocytes recruited to the site of infection and contribute to host innate immune defenses through their ability to phagocytose and kill bacteria. The bactericidal activity of neutrophils is mediated, in part, through the generation of reactive oxygen species (ROS). Extracellular release of ROS can induce injury to host tissue as well, and aberrant release of ROS has been implicated in the pathogenesis of certain inflammatory-mediated diseases. Due to their essential role in bacterial clearance and implicated involvement in the pathogenesis of other diseases, there is much interest in the study of neutrophil-generated ROS. Several assays have been developed to measure ROS production, however, many of these have not been evaluated with bovine neutrophils. The objectives of the current study were to evaluate different assays capable of measuring bovine neutrophil ROS, and to compare the results of assays never previously tested with bovine neutrophils to those obtained from more well-established assays frequently used with these cells. Eight different assays were evaluated, including: luminol, isoluminol, and methyl cypridina luciferin analog (MCLA) chemiluminescence assays; Amplex Red, dihydroethidium (DHE), dichlorodihydrofluorescein diacetate (CM-H(2)DCFDA), and dihydrorhodamine 123 fluorescence assays; and the cytochrome c absorbance assay. The assays were evaluated in the context of their abilities to detect ROS produced in response to two agonists commonly used to induce neutrophil activation, phorbol 12-myristate, 13-acetate (PMA) and opsonized zymosan. Diphenyleneiodonium chloride, a NADPH oxidase inhibitor, was used to assess the specificity of the assays to detect ROS. The ability of these assays to discriminate between intra- and extracellular ROS and to specifically detect distinct ROS was evaluated using superoxide dismutase and catalase, which scavenge extracellular superoxide and hydrogen peroxide, respectively. With the exception of the DHE assay, all assays detected bovine neutrophil ROS generation elicited by PMA and zymosan. PMA, but not zymosan, was able to stimulate neutrophil generation of ROS at levels that were detectable with DHE. The MCLA chemiluminescence assay was the only assay that detected ROS produced in response to each of the lowest concentrations of PMA and zymosan tested. To our knowledge, this is the first study to evaluate DHE-, MCLA-, Amplex Red-, and isoluminol-based assays for the measurement of bovine neutrophil ROS, and the most comprehensive comparative study of ROS assays under similar experimental conditions.

Deferoxamine Reduces Tissue Damage During Endotoxin-Induced Mastitis in Dairy Cows

The protective effects of 3 antioxidants on polymorphonuclear neutrophil-induced damage to mammary cells were evaluated in vivo using an endotoxin-induced mastitis model. Fifteen healthy, midlactation cows with no history of clinical Escherichia coli mastitis were randomly assigned to 1 of the 3 treatment groups corresponding to each modulator to be evaluated, that is, deferoxamine, catechin, and glutathione ethyl ester. Each cow had 1 quarter infused with saline and 1 quarter infused with the selected modulator; a third quarter was infused with lipopolysaccharides (LPS), whereas the fourth quarter received a combination of LPS and the modulator. Infusion of LPS caused acute mastitis as determined by visual observations and by large increases in milk somatic cell count, BSA, and proteolytic activity. These parameters were not affected by antioxidant administration. The extent of cell damage was evaluated by measuring milk levels of lactate dehydrogenase and N-acetyl-beta-D-glucosaminidase activity. Levels of these parameters were several times higher after LPS administration. Intramammary infusions of catechin or glutathione ethyl ester did not exert any protective effect, whereas infusion of deferoxamine, a chelator of iron, decreased milk lactate dehydrogenase and NA-Gase activity, suggesting a protective effect against neutrophil-induced damage. The protective effect of deferoxamine was also evidenced by a lower milk level of haptoglobin. The proteolytic activity of mastitic milk was not influenced by the presence of deferoxamine. Overall, our results suggest that local infusion of deferoxamine may be an effective tool to protect mammary tissue against neutrophil-induced oxidative stress during bovine mastitis.