Temporal changes in metabolites of prostanoids in milk of heifers after intramammary infusion of Escherichia coli organisms

cis-9, trans-11-Conjugated Linoleic Acid Exerts an Anti-inflammatory Effect in Bovine Mammary Epithelial Cells after Escherichia coli Stimulation through NF-κB Signaling Pathway

The anti-inflammatory effects of cis-9, trans-11-conjugated linoleic acid ( cis-9, trans-11-CLA) in diverse cells have been demonstrated in recent studies. The present study was conducted to observe the anti-inflammatory effects and involved mechanisms of CLA in bovine mammary epithelial cells (BMECs) exposed to Escherichia coli. According to the gene expression of IL-6, to optimize the treatment period and dose of CLA, 50 and 100 μM CLA were chosen to pretreat the cells for a period of 48 h. BMECs were exposed to 1 × 10⁷ /mL E. coli for 6 h (ECO group), and cells were pretreated with 50 and 100 μM CLA for 48 h followed by E. coli challenge (C50 and C100 groups). After E. coli challenge, compared with that in the CON group (control group), the gene expressions of pro-inflammatory cytokines (IL-1β and IL-6), chemokines (IL-8 and CCL-20), and antimicrobial peptide BNBD5 were increased, while the gene expression of the anti-inflammatory cytokine IL-10 was decreased significantly; CLA reversed this inflammation effect. Pretreatment with CLA also repressed the secretion of IL-6, IL-8, and TNF-α from BMECs in the culture medium following E. coli challenge. Therefore, cis-9, trans-11-CLA exerted anti-inflammatory effects in BMECs. The cells that were pretreated with CLA expressed remarkably lower levels of phospho-p65, phospho-IκB, and TLR4 and a higher level of PPARγ after E. coli challenge at the gene and protein levels. Compared to that in the ECO group, the nuclear translocation of phospho-p65 was suppressed when CLA was added. Combined with the above results, 50 μM CLA showed a better anti-inflammatory effect. In conclusion, CLA can reduce inflammation caused by E. coli in bovine mammary epithelial cells, and this effect is mediated through the TLR4-NF-κB pathway and PPARγ participation.

Lipopolysaccharides, cytokines, and nitric oxide affect secretion of prostaglandins and leukotrienes by bovine mammary gland during experimentally induced mastitis in vivo and in vitro

The aim of the study was to determine the effects of lipopolysaccharide (LPS), tumor necrosis factor alpha (TNF), interleukin-1-alpha (IL-1α), and nitric oxide donor (NONOate) on both in vivo and in vitro secretion of prostaglandin (PG)E2, PGF2α, leukotriene (LT)B4, and LTC4 by the bovine mammary gland. In the first experiment, tissues isolated from the teat cavity and lactiferous sinus were treated in vitro with LPS (10 ng/mL), TNF (10 ng/mL), IL-1α (10 ng/mL), NONOate (10(-4) M), and the combination of TNF + IL-1α + NONOate for 4 or 8 h. PGE2 or PGF2α secretion was stimulated by all treatments (P < 0.05) excepting NONOate alone, which did not stimulate PGF2α secretion. Moreover, all factors increased LTB4 and LTC4 secretion (P < 0.05). In the second experiment, mastitis was experimentally mimicked in vivo by repeated (12 h apart) intramammary infusions (5 mL) of (1) sterile saline; (2) 250-μg LPS; (3) 1-μg/mL TNF; (4) 1-μg/mL IL-1α; (5) 12.8-μg/mL NONOate; and (6) TNF + IL-1α + NONOate into 2 udder quarters. All infused factors changed PGE2, 13,14-dihydro,15-keto-PGF2α, and LT concentrations in blood plasma collected from the caudal vena cava, the caudal superficial epigastric (milk) vein, the jugular vein, and the abdominal aorta (P < 0.05). In summary, LPS and other inflammatory mastitis mediators modulate PG and LT secretion by bovine mammary gland in both in vivo and in vitro studies.

Lipopolysaccharides, cytokines, and nitric oxide affect secretion of prostaglandins and leukotrienes by bovine mammary gland epithelial cells

The aims of this study were to determine the effects of lipopolysaccharides (LPS), tumor necrosis factor (TNF), interleukin 1 alpha (IL-1α), nitric oxide donor (NONOate), or the combination of TNF + IL-1α + NONOate on the following: (i) secretion of prostaglandin (PG)-F(2α), PGE(2), leukotriene (LT)-B(4), and LTC(4) by epithelial cells of the teat cavity and lactiferous sinus of bovine mammary gland; (ii) messenger RNA (mRNA) transcription of enzymes responsible for arachidonic acid (AA) metabolism (prostaglandin-endoperoxide synthase 2 [PTGS2], prostaglandin E synthase [PTGES], prostaglandin F synthase [PGFS], and arachidonate 5-lipooxygenase [ALOX5]); and (iii) proliferation of the cells. The cells were stimulated for 24 h. Prostaglandins and LT were measured by enzyme immunoassay, mRNA transcription of enzymes was determined by real-time reverse transcription polymerase chain reaction, and the cell viability was measured by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide. All factors increased PG secretion, but the highest stimulation was observed after TNF and IL-1α (P < 0.001). Tumor necrosis factor, NONOate, and TNF + IL-1α + NONOate increased LTB(4) production (P < 0.01), whereas LTC(4) was increased by LPS, TNF, and IL-1α (P < 0.01). Lipopolysaccharides, TNF, IL-1α, and the reagents combination increased PTGS2, PTGES, and PGFS mRNA transcription (P < 0.01), whereas ALOX5 mRNA transcription was increased only by TNF (P < 0.001). Lipopolysaccharides, TNF, IL-1α, NONOate, and the combination of reagents increased the cell number (P < 0.001). Mediators of acute-clinical Escherichia coli mastitis locally modulate PG and LT secretion by the epithelial cells of the teat cavity and lactiferous sinus, which might be a useful first line of defense for the bovine mammary gland. Moreover, the modulation of PG and LT secretion and the changing ratio of luteotropic (PGE(2), LTB(4)) to luteolytic (PGF(2α), LTC(4)) metabolites may contribute to disorders in reproductive functions.

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.

Variation of inflammatory dynamics and mediators in primiparous cows after intramammary challenge with Escherichia coli

The objective of the current study was to investigate (i) the outcome of experimentally induced Escherichia coli mastitis in primiparous cows during early lactation in relation with production of eicosanoids and inflammatory indicators, and (ii) the validity of thermography to evaluate temperature changes on udder skin surface after experimentally induced E. coli mastitis. Nine primiparous Holstein Friesian cows were inoculated 24 ± 6 days (d) after parturition in both left quarters with E. coli P4 serotype O32:H37. Blood and milk samples were collected before and after challenge with E. coli. The infrared images were taken from the caudal view of the udder following challenge with E. coli. No relationship was detected between severity of mastitis and changes of thromboxane B2 (TXB2), leukotriene B4 (LTB4) and lipoxin A4 (LXA4). However, prostaglandin E2 (PGE2) was related to systemic disease severity during E. coli mastitis. Moreover, reduced somatic cell count (SCC), fewer circulating basophils, increased concentration of tumor necrosis factor-α (TNF-α) and higher milk sodium and lower milk potassium concentrations were related to systemic disease severity. The thermal camera was capable of detecting 2-3°C temperature changes on udder skin surface of cows inoculated with E. coli. Peak of udder skin temperature occurred after peak of rectal temperature and appearance of local signs of induced E. coli mastitis. Although infrared thermography was a successful method for detecting the changes in udder skin surface temperature following intramammary challenge with E. coli, it did not show to be a promising tool for early detection of mastitis.

Effect of treatment with the nonsteroidal antiinflammatory meloxicam on milk production, somatic cell count, probability of re-treatment, and culling of dairy cows with mild clinical mastitis

It was hypothesized that treatment of clinical mastitis with a combination of a nonsteroidal antiinflammatory treatment (meloxicam) and a parenteral antibiotic (penethamate hydriodide) would result in lower somatic cell counts (SCC), reduced milk yield losses, improved clinical outcomes, and reduced culling rates compared with antibiotic therapy alone. Cows in 15 herds with clinical mastitis during the first 200 d of lactation (median = 13 d) were treated with 5 g of penethamate hydriodide daily for 3 d, and one-half these cows were treated with 250 mg of the nonsteroidal antiinflammatory drug meloxicam (n = 361 cows), whereas the other half (n = 366 cows) were treated with the vehicle (control group). Milk samples for bacteriology were collected from clinically affected glands before treatment, and samples were collected at 7 (+/-3), 14 (+/-3), and 21 (+/-3) d after commencement of treatment for SCC determination. Additionally, the rectal temperature, udder edema score, California Mastitis Test score, and milk clot score were determined before treatment and daily milk yield data were collected across the lactation. There were no differences between the treatment groups in calving date, days in milk, age, breed, rectal temperature, California Mastitis Test score, clot score, udder edema score, or bacterial pathogens isolated before treatment. There was no difference between treatment groups in the number of cows that were defined as treatment failures (i.e., re-treated within 24 d of initial treatment, died, or the treated gland stopped producing milk); 79 (21.9%) vs. 92 (25.1%) cows in the meloxicam and control groups failed, respectively. The SCC was lower in the meloxicam-treated group compared with the control group after treatment [550 +/- 48 vs. 711 +/- 62 geometric mean (x1,000/mL) +/- standard error of the mean SCC for quarters after treatment with meloxicam vs. control, respectively]. There was no difference in milk yield for the cows treated with meloxicam compared with the control cows within 28 or 200 d after treatment. Fewer meloxicam-treated than control cows were removed (culled) from the herds [39/237 (16.4%) vs. 67/237 (28.2%) for meloxicam vs. control cows, respectively; odds ratio = 0.42, 95% confidence interval = 0.26 to 0.68]. It was concluded that treatment of cows with clinical mastitis with a combination of meloxicam and penethamate resulted in a lower SCC and a reduced risk of removal from the herd (culling) compared with treatment with penethamate alone.

Pathogen-dependent induction of cytokines and other soluble inflammatory mediators during intramammary infection of dairy cows

Mastitis is a highly prevalent and costly disease of dairy cows that is commonly caused by intramammary bacterial infection. The innate immune response to bacterial penetration of the mammary gland is evoked within hours of infection, and the rapidity and magnitude of this response have been demonstrated to influence the resolution of this disease. Cytokines and other mediators of inflammation are known to play critical roles in the innate immune response to intramammary infection. The objectives of this review are to summarize the current understanding of the cytokine response to intramammary infection, highlight recent findings identifying differences in the cytokine response to various bacterial pathogens, and discuss future research directions that will increase our knowledge of the role of inflammatory mediators in predicting and governing the outcome of mastitis.

Effect of Carprofen Treatment Following Experimentally Induced Escherichia coli Mastitis in Primiparous Cows

Acute Escherichia coli mastitis is one of the major sources of economic loss in the dairy industry due to reduced milk production, treatment costs, discarded milk, and occasional fatal disease. Nonsteroidal anti-inflammatory drugs (NSAIDs) are frequently used as adjunctive therapy to antibiotics. The objective of the current study was to evaluate the effect of carprofen treatment following infusion of Escherichia coli into the mammary glands of primiparous cows during the periparturient period. Severity of mastitis was scored based on the average milk production in the uninfected quarters on d +2 postinoculation and a clinical severity score. Carprofen was administered intravenously at 9 h postchallenge, when clinical signs of mastitis appeared. In previous work, efficacy of NSAIDs was mainly evaluated using clinical symptoms. In the present study, the effect of carprofen on innate immune response was also assessed by quantification of inflammatory mediators. All primiparous cows reacted as moderate responders throughout the experimental period. Primiparous cows were intramammarily inoculated with 1 x 10(4) cfu of E. coli P4:O32 in 2 left quarters. Analysis of blood and milk parameters, including IL-8, complement component C5a, lipopolysaccharide-binding protein (LBP), soluble CD14, prostaglandin E2, and thromboxane B2 was performed from d 0 to d +6 relative to intramammary inoculation. Rectal temperature in carprofen-treated animals was lower than in control animals at 3 and 6 h posttreatment. Treatment also restored the decreased reticulorumen motility that occurs during E. coli mastitis to preinfection levels faster than in control animals. Carprofen treatment resulted in an earlier normalization of the clinical severity score. Eicosanoid (prostaglandin E2 and thromboxane B2) production in milk tended to be inhibited by carprofen. No significant differences in the kinetic patterns of somatic cell count, IL-8, complement component C5a, LBP, and soluble CD14 were observed. In conclusion, carprofen treatment improved general clinical condition by effective antipyrexia and restoration of reticulorumen motility but did not significantly inhibit eicosanoid production. Carprofen treatment did not result in a significant decrease of chemotactic inflammatory mediators, IL-8 and C5a, and early innate immune molecules, sCD14 and LBP. Therefore, major modulatory effects from NSAID administration were not observed in this mastitis model, although a larger study might confirm some apparent trends obtained in the present results.

Immunity in the mammary gland

The ruminant mammary gland is an extremely important economic organ in that it provides a major nutrition source for a significant portion of the world's human population. The ruminant mammary gland is also responsible for providing protective immunity to neonates and for defending itself from invading pathogens. A wide array of humoral and cellular immune mechanisms are present in the mammary gland and actively participate in providing immunity to newborns and the mammary gland per se. The acute inflammatory response is essential in determining the outcome of intramammary challenge, and factors affecting innate and adaptive immunity in the context of mammary health are reviewed in detail. The ruminant mammary gland is also unique in that lymphocyte trafficking, which is essential to adaptive immunity, is shared with the peripheral immune system rather than the common mucosal immune system.