The effect of citrus-derived oil on bovine blood neutrophil function and gene expression in vitro

The Effects of Sodium Acetate on the Immune Functions of Peripheral Mononuclear Cells and Polymorphonuclear Granulocytes in Postpartum Dairy Cows

Excessive lipid mobilization will snatch cell membrane lipids in postpartum dairy cows, which may impair the function of immune cells, including peripheral mononuclear cells (PBMCs) and polymorphonuclear granulocytes (PMNs). Acetate, as a precursor and the energy source of milk fat synthesis, plays a key role in lipid synthesis and the energy supply of dairy cows. However, there is little information about the effect of sodium acetate (NaAc) on the immune function of PBMC and PMN in postpartum dairy cows. Therefore, this study aimed to evaluate the effects of NaAc on the immune functions of PBMCs and PMNs in postpartum dairy cows. In this experiment, twenty-four postpartum multiparous Holstein cows were randomly selected and divided into a NaAc treatment group and a control group. Our results demonstrated that the dietary addition of NaAc increased (p < 0.05) the number of monocytes and the monocyte ratio, suggesting that these postpartum cows fed with NaAc may have better immunity. These expressions of genes (LAP, XBP1, and TAP) involved in the antimicrobial activity in PBMCs were elevated (p < 0.05), suggesting that postpartum dairy cows supplemented with NaAc had the ability of antimicrobial activity. In addition, the mRNA expression of the monocarboxylate transporters MCT1 and MCT4 in PBMCs was increased (p < 0.05) in diets supplemented with NaAc in comparison to the control. Notably, the expression of the XBP1 gene related to antimicrobial activity in PMN was upregulated with the addition of NaAc. The mRNA expression of genes (TLN1, ITGB2, and SELL) involved in adhesion was profoundly increased (p < 0.05) in the NaAc groups. In conclusion, our study provided a novel resolution strategy in which the use of NaAc can contribute to immunity in postpartum dairy cows by enhancing the ability of antimicrobial and adhesion in PBMCs and PMNs.

Heterologous Expression, Purification, and Immunomodulatory Effects of Recombinant Lipoprotein GUDIV-103 Isolated from Ureaplasma diversum

Ureaplasma diversum is a bacterial pathogen that infects cattle and can cause severe inflammation of the genital and reproductive systems. Lipid-associated membrane proteins (LAMPs), including GUDIV-103, are the main virulence factors in this bacterium. In this study, we heterologously expressed recombinant GUDIV-103 (rGUDIV-103) in Escherichia coli, purified it, and evaluated its immunological reactivity and immunomodulatory effects in bovine peripheral blood mononuclear cells (PBMCs). Samples from rabbits inoculated with purified rGUDIV-103 were analysed using indirect enzyme-linked immunosorbent assay and dot blotting to confirm polyclonal antibody production and assess kinetics, respectively. The expression of this lipoprotein in field isolates was confirmed via Western blotting with anti-rGUDIV-103 serum and hydrophobic or hydrophilic proteins from 42 U. diversum strains. Moreover, the antibodies produced against the U. diversum ATCC 49783 strain recognised rGUDIV-103. The mitogenic potential of rGUDIV-103 was evaluated using a lymphoproliferation assay in 5(6)-carboxyfluorescein diacetate succinimidyl ester−labelled bovine PBMCs, where it induced lymphocyte proliferation. Quantitative polymerase chain reaction analysis revealed that the expression of interleukin-1β, toll-like receptor (TLR)-α, TLR2, TLR4, inducible nitric oxide synthase, and caspase-3−encoding genes increased more in rGUDIV-103−treated PBMCs than in untreated cells (p < 0.05). Treating PBMCs with rGUDIV-103 increased nitric oxide and hydrogen peroxide levels. The antigenic and immunogenic properties of rGUDIV-103 suggested its suitability for immunobiological application.

Synergistic Activation of Bovine CD4+ T Cells by Neutrophils and IL-12

CD4+ T cell activation requires inflammatory cytokines to provide a third signal (3SI), such as interleukin-12 (IL-12). We recently reported that bovine neutrophils can enhance the activation of bovine CD4+ T cells. To explore the interactions between neutrophils and third signal cytokines in bovine CD4+ T cell activation, naïve CD4+ T cells were isolated from cattle lymph nodes and stimulated for 3.5 days with anti-bovine CD3 (first signal; 1SI), anti-bovine CD28 (second signal; 2SI), and recombinant human IL-12 (3SI) in the presence or absence of neutrophils harvested from the same animals. Indeed, the strongest activation was achieved in the presence of all three signals, as demonstrated by CD25 upregulation, IFNγ production in CD4+ T cells, and secretion of IFNγ and IL-2 in cell supernatants. More importantly, 1SI plus neutrophils led to enhanced CD25 expression that was further increased by IL-12, suggesting synergistic action by IL-12 and neutrophils. Consistently, neutrophils significantly increased IFNγ production in 1SI plus IL-12-stimulated CD4+ T cells. Our data suggest the synergy of neutrophils and IL-12 as a novel regulator on bovine CD4+ T cell activation in addition to three signals. This knowledge could assist the development of immune interventions for the control of infectious diseases in cattle.

NETosis of Peripheral Neutrophils Isolated From Dairy Cows Fed Olive Pomace

Neutrophils represent primary mobile phagocytes recruited to the site of infection, and their functions are essential to enhance animals' health performance. Neutrophils have an essential role in innate immunity and are able to kill the pathogens via the synthesis of neutrophil extracellular traps (NETs). The objective of the present work was the study of the in vitro NETosis of peripheral neutrophils isolated from dairy cows supplemented with olive pomace. Dairy cows (n = 16) balanced for parity (3.67 ± 1.5 for CON, 3.67 ± 1.9 for OP), milk yield (24.3 ± 4.5 kg d⁻¹for CON and 24.9 ± 1.7 kg d⁻¹ for OP), the number of days in milk (109 ± 83.5 for CON and 196 ± 51 for OP), and body weight (647 ± 44.3 kg for CON and 675 ± 70.7 kg for OP) were divided into two experimental groups fed with a control diet (CON) and supplemented with 6% of olive pomace (OP). Peripheral blood neutrophils were isolated and stimulated in vitro with phorbol-myristate-acetate (PMA) as a marker for activation and reactivity of the neutrophils. After isolation, both the viability and CD11b expression were analyzed by flow cytometry. Both NETosis by neutrophil elastase-DNA complex system and myeloperoxidase (MPO) activity were evaluated by ELISA. The specific antibodies against MPO and citrullination of Histone-H1 were used for investigating NETosis by immunofluorescence microscopy. The neutrophil elastase-DNA complexes produced during NETosis and MPO activity of neutrophil extracts were affected by OP supplementation. Furthermore, results from immunofluorescence analysis of NETosis depicted a similar result found by ELISA showing a higher expression of MPO and citrullination of Histone-H1 in OP than the CON neutrophils. In addition, all data showed that the OP diet resulted in a better response of neutrophils to PMA stimulation than the CON diet, which did not support the neutrophils' responses to PMA stimulation. Our results demonstrated that OP supplementation can enhance the neutrophil function in dairy cows leading to udder defense and inflammation response especially when an immunosuppression state can occur.

Overview of Research Development on the Role of NF-κB Signaling in Mastitis

Simple Summary

NF-κB signaling has been widely studied for its role in inflammatory and immunity-related diseases. Mastitis is considered one of the inflammatory and immunity associated diseases which are a serious threat to the global dairy industry. Having such a critical role in immunity and inflammation, NF-κB signaling is currently under target for therapeutic purposes in mastitis control research. The virulent factor, lipopolysaccharides (LPS), of bacteria after attachment with relevant Toll-like receptors (TLRs) on mammary epithelial cells starts its pathogenesis by using NF-κB signaling to cause mastitis. Several studies have proved that the blocking of NF-κB signaling could be a useful strategy for mastitis control.

Abstract

Mastitis is the inflammation of the mammary gland. Escherichia coli and Staphylococcus aureus are the most common bacteria responsible for mastitis. When mammary epithelial cells are infected by microorganisms, this activates an inflammatory response. The bacterial infection is recognized by innate pattern recognition receptors (PRRs) in the mammary epithelial cells, with the help of Toll-like receptors (TLRs). Upon activation by lipopolysaccharides, a virulent agent of bacteria, the TLRs further trigger nuclear factor-κB (NF-κB) signaling to accelerate its pathogenesis. The NF-κB has an essential role in many biological processes, such as cell survival, immune response, inflammation and development. Therefore, the NF-κB signaling triggered by the TLRs then regulates the transcriptional expression of specific inflammatory mediators to initiate inflammation of the mammary epithelial cells. Thus, any aberrant regulation of NF-κB signaling may lead to many inflammatory diseases, including mastitis. Hence, the inhibiting of NF-κB signaling has potential therapeutic applications in mastitis control strategies. In this review, we highlighted the regulation and function of NF-κB signaling in mastitis. Furthermore, the role of NF-κB signaling for therapeutic purposes in mastitis control has been explored in the current review.

The protective roles of tea tree oil extracts in bovine mammary epithelial cells and polymorphonuclear leukocytes

Background

Tea tree oil (TTO) plays an important role in antibacterial activity and alleviating the inflammatory responses. Bovine mammary epithelium and polymorphonuclear leukocytes (PMNL) can actively respond to bovine mastitis infection. However, regulatory effects of TTO extracts on the innate immune response of bovine mammary epithelial cells (BMECs) and PMNL remain not reported. Therefore, aim of the study was to evaluate the effects of TTO extracts on the mRNA levels of the genes involved in the innate immune response of BMECs and PMNL.

Results

Our results demonstrated that addition of 0.025% and 0.05% TTO increased the proliferation of BMECs, and significantly enhanced (P < 0.05) the viability of BMECs exposed to Staphylococcus aureus (S. aureus). An inhibitory effect was observed against the growth of S. aureus by TTO incubation. The 0.05% TTO reduced S. aureus biofilm formation, association and invasion of S. aureus to BMECs, and changed the morphological and structural features of S. aureus. The proinflammatory cytokines IL-1β, IL-6, and TNF-α were decreased (P < 0.001) by the incubation of TTO. Interestingly, the expression of IL-8 known for PMNL chemotactic function was elevated (P < 0.05) by 0.05% TTO treatment. Consistently, 0.05% TTO increased the migration of PMNL in S. aureus-exposed BMECs when compared with S. aureus treatment alone (P < 0.05). In addition, PMNL incubated with 0.05% TTO decreased the levels of NFKB inhibitor alpha (NFKBIA) and TNF-α.

Conclusions

Our results indicate that use of TTO can relieve the BMECs pro-inflammatory response caused by S. aureus and promote the migration of PMNL to mount the innate immune responses, and it may be novel strategy for the treatment of bovine mastitis caused by S. aureus.

Bovine mastitis: risk factors, therapeutic strategies, and alternative treatments - A review

Bovine mastitis, an inflammation of the mammary gland, is the most common disease of dairy cattle causing economic losses due to reduced yield and poor quality of milk. The etiological agents include a variety of gram-positive and gram-negative bacteria, and can be either contagious (e.g., Staphylococcus aureus, Streptococcus agalactiae, Mycoplasma spp.) or environmental (e.g., Escherichia coli, Enterococcus spp., coagulase-negative Staphylococcus, Streptococcus uberis). Improving sanitation such as enhanced milking hygiene, implementation of post-milking teat disinfection, maintenance of milking machines are general measures to prevent new cases of mastitis, but treatment of active mastitis infection is dependant mainly on antibiotics. However, the extensive use of antibiotics increased concerns about emergence of antibiotic-resistant pathogens and that led the dairy industries to reduce the use of antibiotics. Therefore, alternative therapies for prevention and treatment of bovine mastitis, particularly natural products from plants and animals, have been sought. This review provides an overview of bovine mastitis in the aspects of risk factors, control and treatments, and emerging therapeutic alternatives in the control of bovine mastitis.

Characterization of IL-10-producing neutrophils in cattle infected with Ostertagia ostertagi

IL-10 is a master regulator of immune responses, but its cellular source and function in cattle during the initial phase of immune priming have not been well established. Despite a massive B cell response in the abomasal draining lymph nodes in Ostertagia ostertagi (OO)-infected cattle, protective immunity is slow to develop, and partial protection requires years of repeated exposure. In addressing this problem, our initial hypothesis was that B cells produce IL-10 that downregulates the host protective immune response. However, our results showed that neutrophils made up the majority of IL-10-producing cells in circulation and in secondary lymphoid tissues, particularly the spleen (80%). Conversely, IL-10-producing B cells were rare. In addition, approximately 10% to 20% of the neutrophils in the blood and spleen expressed MHC II and were IL-10 negative, suggesting that neutrophils could also participate in antigen presentation. In vitro investigation of bovine neutrophils revealed that exposure thereof to OO extract increased IL-10 and MHC II expression in these cells in a dose-dependent manner, consistent with IL-10+/MHC II+ neutrophils detected in cattle shortly after experimental OO infection. Co-culture of untreated neutrophils with anti-CD3 antibody (Ab)-stimulated CD4+ T cells led to enhanced T cell activation; also, IL-10 depletion with neutralizing Ab enhanced the stimulatory function of neutrophils. OO extract depressed neutrophil stimulation of CD4+ T cells in the presence of IL-10-neutralizing Ab, suggesting that OO utilizes both IL-10-dependent and independent mechanisms to manipulate the bovine immune response. Finally, contact and viability were required for T cell-stimulatory neutrophil function. This report, to the best of our knowledge, is the first to demonstrate that neutrophil-derived IL-10 is directly involved in T cell regulation in cattle. Our data suggest that neutrophils and neutrophil-derived IL-10 are co-opted by nematode parasites and other pathogens to attenuate host immune responses and facilitate pathogen survival.

Bovine neutrophils form extracellular traps in response to the gastrointestinal parasite Ostertagia ostertagi

Ostertagia ostertagi (OO) is a widespread parasite that causes chronic infection in cattle and leads to annual losses of billions of dollars in the cattle industry. It remains unclear why cattle are unable to mount an effective immune response despite a large influx of immune cells to the infected abomasal mucosa and draining lymph nodes. Neutrophils, the immune system’s first responders, have the capacity to release neutrophil extracellular traps (NETs) to contain various pathogens, including some parasites. In the present study, the mechanisms by which O. ostertagi influences bovine NET formation were investigated. O. ostertagi larval soluble extract (OO extract) was able to induce typical NETs by purified neutrophils in vitro, confirmed by co-localization of extracellular DNA with typical NET-associated proteins histone and neutrophil elastase (NE). Consistent with existing literature, inhibition assays demonstrated that these OO extract-induced NETs were dependent upon the enzymes NADPH oxidase and myeloperoxidase (MPO). Live OO stage 4 larvae (L4) stimulated neutrophils to form NETs similar to those induced by OO extract. Bovine neutrophils also released NETs in response to Caenorhabditis elegans, a free-living soil nematode, suggesting that bovine NET production may be a conserved mechanism against a broad range of nematodes. This is the first report demonstrating O. ostertagi-induced NET formation by bovine neutrophils, a potentially underappreciated mechanism in the early immune response against nematode infections.

Choline Regulates the Function of Bovine Immune Cells and Alters the mRNA Abundance of Enzymes and Receptors Involved in Its Metabolism in vitro

Dietary choline can impact systemic immunity, but it remains unclear whether this is primarily via direct impacts on immune cells or secondary effects of altered metabolic function. To determine whether increased choline concentrations (3.2, 8.2, 13.2 μM) in cell culture alter the function of bovine innate and adaptive immune cells, we isolated cells from dairy cows in early and mid-lactation as models of immuno-compromised and competent cells, respectively. Phagocytic and killing capacity of isolated neutrophils were linearly diminished with increasing doses of choline. In contrast, lymphocyte proliferation was linearly enhanced with increasing doses of choline. Furthermore, increasing doses of choline increased the mRNA abundance of genes involved in the synthesis of choline products (betaine, phosphatidylcholine, and acetylcholine) as well as muscarinic and nicotinic acetylcholine receptors in a quadratic and linear fashion for neutrophils and monocytes, respectively. Phagocytic and killing capacity of neutrophils and proliferation of lymphocytes were not affected by stage of lactation or its interaction with choline or LPS. In neutrophils from early lactation cows, choline linearly increased the mRNA abundance of muscarinic and nicotinic cholinergic receptors, whereas choline-supplemented monocytes from mid-lactation cows linearly increased the mRNA abundance of several genes coding for choline metabolism enzymes. These data demonstrate that choline regulates the inflammatory response of immune cells and suggest that the mechanism may involve one or more of its metabolic products.

The protective effect of chlorogenic acid on bovine mammary epithelial cells and neutrophil function

Chlorogenic acid (CGA) is the ester of caffeic acid and quinic acid and plays an important role in antibacterial activity and anti-inflammatory properties. The objective of this study was to examine the effects of CGA on the growth of Staphylococcus aureus and the mRNA levels of the genes encoding the inflammatory response cytokines, κ-casein, and neutrophil function in bovine mammary epithelial cells (BMEC) exposed to S. aureus. Chlorogenic acid has important antibacterial, antioxidant, and anti-inflammatory functions; however, the effect of CGA on BMEC and neutrophils exposed to S. aureus has not been investigated previously. Our results demonstrated that 10, 20, and 30 μg/mL CGA had no cytotoxic effects on BMEC in culture, and that 20 μg/mL CGA enhanced the viability of BMEC exposed to S. aureus, whereas 30 μg/mL CGA reduced S. aureus growth after 9 h compared with controls. The rate of S. aureus invasion into BMEC was also attenuated by 30 μg/mL CGA compared with controls, whereas this treatment led to reduced abundance of IL6, IL8, and TLR2 mRNA in S. aureus-exposed BMEC. Migration of bovine polymorphonuclear leukocytes was significantly decreased in S. aureus-exposed BMEC with 10 and 20 μg/mL CGA treatment when compared with S. aureus treatment alone. In addition, incubation with 20 or 30 μg/mL CGA enhanced the phagocytic ability of polymorphonuclear leukocytes compared with the control group. Importantly, levels of κ-casein were enhanced by treatment of S. aureus-exposed BMEC with CGA. Our results suggest that the use of CGA may be a potent therapeutic tool against bovine mastitis caused by S. aureus.

Glucose supplementation has minimal effects on blood neutrophil function and gene expression in vitro

During early lactation, glucose availability is low and the effect of glucose supply on bovine polymorphonuclear leukocyte (PMNL) function is poorly understood. The objective of this study was to determine the effect of glucose supplementation on the function and transcriptomic inflammatory response of PMNL from cows in early and mid-lactation in vitro. Twenty Holstein cows in early (n=10; days in milk=17±3.1) and mid-lactation (n=10; days in milk=168±14.8) were used for this study. Jugular blood was analyzed for serum concentrations of nonesterified fatty acids, β-hydroxybutyrate, and glucose. Polymorphonuclear leukocytes were isolated and diluted using RPMI (basal glucose concentration was 7.2 mM) to different concentrations of PMNL/mL for phagocytosis, chemotaxis, gene expression, and medium analyses. Working solutions of glucose (0 or 4 mM of d-glucose) and lipopolysaccharide (0 or 50μg/mL) were added and tubes were incubated for 120 min at 37°C. Media were analyzed for concentrations of glucose and tumor necrosis factor-α (TNF-α). Data were analyzed in a randomized block (stage of lactation) design. Challenge with lipopolysaccharide increased the expression of the genes encoding for nuclear factor kappa B (NFKB1), IL-10 (IL10), IL1B, IL6, IL8, TNF-α (TNFA), glucose transporter 3 (SLC2A3), and the concentration of TNF-α in medium (147.3 vs. 72.5 pg/mL for lipopolysaccharide and control, respectively). Main effect of stage of lactation was minimal where the expression of IL10 increased for cows in early compared with cows in mid-lactation. After lipopolysaccharide challenge, cows in early lactation experienced more marked increases in the expression of IL6, TNFA, and IL8 when compared with cows in mid-lactation. Glucose supplementation had minimal effects on gene expression where glucose supplementation increased the expression of lysozyme (LYZ). Glucose supplementation increased PMNL phagocytosis but did not alter chemotaxis, morphology, or concentration of TNF-α in the medium. Under the conditions of the experiment, stage of lactation had minimal effects on PMNL response to glucose supply where only the expression of NFKB1 and the production of TNF-α were greater for cows in mid-lactation when compared with early lactation. Metabolic profiles for cows in early lactation did not parallel those for cows during the early postpartum period and may partly explain results for this study. Future studies investigating the effect of glucose supply on bovine PMNL function in vivo and how this may be altered by stage of lactation are warranted.

Peripartal rumen-protected methionine supplementation to higher energy diets elicits positive effects on blood neutrophil gene networks, performance and liver lipid content in dairy cows

BACKGROUND

Main objectives were to determine to what extent Smartamine M (SM) supplementation to a prepartal higher-energy diet could alter neutrophil (PMN) and liver tissue immunometabolic biomarkers, and whether those responses were comparable to those in cows fed a prepartal lower-energy diet (CON).

RESULTS

Twenty-eight multiparous Holstein cows were fed CON (NEL = 1.24 Mcal/kg DM) during d -50 to d -22 relative to calving. From d -21 to calving, cows were randomly assigned to a higher-energy diet (OVE, n = 9; NEL = 1.54 Mcal/kg DM), OVE plus SM (OVE + SM, n = 10; SM = 0.07 % of DM) or remained on CON (n = 9). All cows received the same basal lactation diet (NEL = 1.75 Mcal/kg DM). Supplementation of SM (OVE + SM) continued until 30 d postpartum. Liver biopsies were harvested at d -10, 7, and 21 relative to parturition. Blood PMN isolated at -10, 3, and 21 d relative to calving was used to evaluate gene expression. As expected, OVE increased liver lipid content postpartum; however, cows fed OVE + SM or CON had lower concentrations than OVE. Compared with OVE, cows in CON and OVE + SM had greater DMI postpartum and milk production. Furthermore, cows fed OVE + SM had the greatest milk protein and fat percentage and lowest milk SCC despite having intermediate PMN phagocytic capacity. Adaptations in PMN gene expression in OVE + SM cows associated with the lower SCC were gradual increases from -10 to 21 d in genes that facilitate migration into inflammatory sites (SELL, ITGAM), enzymes essential for reducing reactive oxygen metabolites (SOD1, SOD2), and a transcription factor(s) required for controlling PMN development (RXRA). The greater expression of TLR4 on d 3, key for activation of innate immunity due to inflammation, in OVE compared with CON cows suggests a more pronounced inflammatory state. Feeding OVE + SM dampened the upregulation of TLR4, despite the fact that these cows had similar expression of the pro-inflammatory genes NFKB1 and TNF as OVE. Cows in CON had lower overall expression of these inflammation-related genes and GSR, which generates reduced glutathione, an important cellular antioxidant.

CONCLUSIONS

Although CON cows appeared to have a less stressful transition into lactation, SM supplementation was effective in alleviating negative effects of energy-overfeeding. As such, SM was beneficial in terms of production and appeared to boost the response of PMN in a way that improved overall cow health.