Innate immune response of bovine mammary gland to pathogenic bacteria responsible for mastitis

Lactobacillus casei BL23 modulates the innate immune response in Staphylococcus aureus-stimulated bovine mammary epithelial cells

Probiotics have been adopted to treat and prevent various diseases in humans and animals. They were notably shown to be a promising alternative to prevent mastitis in dairy cattle. This inflammation of the mammary gland is generally of infectious origin and generates extensive economic losses worldwide. In a previous study, we found that Lactobacillus casei BL23 was able to inhibit the internalisation of Staphylococcus aureus, one of the major pathogens involved in mastitis, into bovine mammary epithelial cells (bMEC). In this study, we further explored the capacity of this strain to modulate the innate immune response of bovine mammary epithelial cells during S. aureus infection. L. casei BL23 was able to decrease the expression of several pro-inflammatory cytokines, including interleukins 6, 8, 1α and 1β and tumour necrosis factor alpha, in S. aureus-stimulated bMEC, 8 h post-infection. On the other hand, L. casei did not impair the induction of defensins, such as lingual antimicrobial peptide and defensin β1 in the presence of S. aureus, and even slightly increased the induction of tracheal antimicrobial peptide during S. aureus infection. Finally, this strain did not alter the expression of the pattern recognition receptor nucleotide-binding oligomerisation domain proteins (NOD2). This study demonstrates that L. casei BL23 displayed anti-inflammatory properties on S. aureus-stimulated bMEC. These results open the way to further characterisation of the BL23 probiotic potential in a bovine mammary gland context and to a better understanding of how all these beneficial properties combine in vivo to combat mastitis pathogens.

DNA methylation rather than single nucleotide polymorphisms regulates the production of an aberrant splice variant of IL6R in mastitic cows

Interleukin-6 receptor-alpha (IL6R) interacts with IL6 and forms a ligand-receptor complex, which can stimulate various cellular responses, such as cell proliferation, cell differentiation, and activation of inflammatory processes. Both genetic mutation and epigenetic modification regulate gene transcription. We identified a novel splice variant of bovine IL6R, designated as IL6R-TV, which is characterized by the skipping of exon 2 of the NCBI-referenced IL6R gene (IL6R-reference). The expression levels of IL6R-TV and IL6R-reference transcripts were lower in normal mammary gland tissues. These transcripts play a potential role during inflammatory infection. We also detected two putative functional SNPs (g.19711 T > C and g.19731 G > C) located within the upstream 100 bp of exon 2. These SNPs formed two haplotypes (T-G and C-C). Two mutant pSPL3 exon-trapping plasmids (pSPL3-T-G and pSPL3-C-C) were transferred into the bovine mammary epithelial cells (MAC-T) and human embryonic kidney 293 T cells (HEK293T) to investigate the relationship between the two SNPs and the aberrant splicing of IL6R. DNA methylation levels of the alternatively spliced exon in normal and mastitis-infected mammary gland tissues were quantified through nested bisulfate sequencing PCR (BSP) and cloning sequencing. We found that DNA methylation regulated IL6R transcription. The DNA methylation level was high in mastitis-infected mammary gland tissues and stimulated IL6R expression, thereby promoting the inclusion of the alternatively spliced exon. The upregulated expression of the two transcripts was due to DNA methylation modification rather than genetic mutations.

Relationships among quarter milk leukocyte proportions and cow and quarter-level variables under different intramammary infection statuses

The use of milk leukocyte differential (MLD) test has been proposed as a complement to somatic cell count (SCC) to assess the presence and the severity of intramammary infection. However, detailed information regarding the behavior of MLD under different physiological or pathological stages of the cow is nonexistent. The objective was to analyze the association between milk leukocyte proportions provided by a commercial automated MLD test and multiple cow and quarter-level variables. The study population consisted of 104 Holstein cows (32 primiparous and 72 multiparous) in one farm. Cows were categorized by days in milk as early (<50 DIM; n=29), middle (50–250 DIM; n=25), and late lactation (>250 DIM; n = 50). Milk from 416 quarters was collected and analyzed for lymphocytes (LYM), neutrophils (NEU), and macrophages (MAC) counts using an automated milk fluorescence microscopy system. Concurrently, a sterile composite milk sample was collected from each cow for pathogen identification through microbiological culture. Culture results were classified as no growth (NOG), gram-negative (GN), gram-positive (GP), or other (OTH). Milk leukocyte proportions varied depending on the level of total leukocyte counts (TLC; P < 0.001). Similarly, leukocyte ratios (NEU:LYM, NEU:MAC, and phagocyte:LYM) were different for multiple TLC categories (P < 0.05). There was no association between parity number and MLD; however, cows in early lactation had the greatest proportions of NEU and LYM. Leukocyte ratios varied depending on parity number and stage of lactation. Cows in the medium milk-yield category had the smallest proportions of NEU and LYM, and there was significant variation in leukocyte ratios, depending on the level of milk yield. In healthy quarters, MLD were not associated with quarter position; however, the NEU:MAC ratio was greater in rear quarters than in front quarters. In quarters with TLC >100,000, NEU% was greater in rear quarters than in front quarters (P = 0.03). For quarters with pathogen growth, TLC was greatest for GN followed by OTH and GP (P < 0.001). Milk LD depended on the isolated pathogen group, although the magnitudes of the differences were small. Although the changes in the proportions of leukocytes in milk were associated with categories of TLC, levels of milk yield, and mastitis-causing pathogen groups, the deviations were small in magnitude. Additional research is necessary to determine the potential applications for this methodology.

The Mammary Microenvironment in Mastitis in Humans, Dairy Ruminants, Rabbits and Rodents: A One Health Focus

The One Health concept promotes integrated evaluation of human, animal, and environmental health questions to expedite advances benefiting all species. A recognition of the multi-species impact of mastitis as a painful condition with welfare implications leads us to suggest that mastitis is an ideal target for a One Health approach. In this review, we will evaluate the role of the mammary microenvironment in mastitis in humans, ruminants and rabbits, where appropriate also drawing on studies utilising laboratory animal models. We will examine subclinical mastitis, clinical lactational mastitis, and involution-associated, or dry period, mastitis, highlighting important anatomical and immunological species differences. We will synthesise knowledge gained across different species, comparing and contrasting disease presentation. Subclinical mastitis (SCM) is characterised by elevated Na/K ratio, and increased milk IL-8 concentrations. SCM affecting the breastfeeding mother may result in modulation of infant mucosal immune system development, whilst in ruminants notable milk production losses may ensue. In the case of clinical lactational mastitis, we will focus on mastitis caused by Staphylococcus aureus and Escherichia coli. Understanding of the pathogenesis of involution-associated mastitis requires characterization of the structural and molecular changes occurring during involution and we will review these changes across species. We speculate that milk accumulation may act as a nidus for infection, and that the involution 'wound healing phenotype' may render the tissue susceptible to bacterial infection. We will discuss the impact of concurrent pregnancy and a 'parallel pregnancy and involution signature' during bovine mammary involution.

Invited review: Low milk somatic cell count and susceptibility to mastitis

An enduring controversy exists about low milk cell counts and susceptibility to mastitis. The concentration of milk leukocytes, or somatic cell count (SCC), is a well-established direct indicator of mammary gland inflammation that is highly correlated with the presence of a mammary infection. The SCC is also used as a trait for the selection of dairy ruminants less prone to mastitis. As selection programs favor animals with less SCC, and as milk cells contribute to the defense of the mammary gland, the idea that susceptibility to mastitis could possibly be increased in the long term has been put forward and is still widely debated. Epidemiological and experimental studies aimed at relating SCC to susceptibility to mastitis have yielded results that seem contradictory at first sight. Nevertheless, by taking into account the immunobiology of milk and mammary tissue cells and their role in the defense against infection, along with recent studies on SCC-based divergent selection of animals, the issue can be settled. Apparent SCC-linked susceptibility to mastitis is a phenotypic trait that may be linked to immunomodulation but not to selection.

The effect of the SNP g.18475 A>G in the 3'UTR of NCF4 on mastitis susceptibility in dairy cattle

Neutrophil cytosolic factor 4 (NCF4) is a member of the nicotinamide adenine dinucleotide phosphate oxidase subunit. This protein functions as an essential factor in the host defense against the progression of bacterial infection. To explore the variability of the NCF4 gene and the susceptibility of cows to mastitis, NCF4 functional single nucleotide polymorphism (SNP) of the 3' untranslated region (3'UTR) and its targeted microRNA (miRNA) were identified. One SNP g.18475 A>G in the 3'UTR of NCF4 was found within the binding seed region of bta-miR-2426. We constructed two recombinant pMIR-REPORT™ vectors with the A or G allele in the g.18475 locus and transiently co-transfected the vectors in human embryo kidney 293T (HEK 293T) cells, along with bta-miR-2426 mimics. A luciferase assay indicated that this SNP affects the binding of NCF4 and bta-miR-2426. In addition, the association analysis results showed that cows with the GG genotype in SNP g.18475 A>G had a relatively lower SCS value than cows with the AA genotype. Finally, quantitative real-time PCR (RT-qPCR) results showed that the cows with genotype GG had a relatively higher expression of NCF4 mRNA compared to the cows with genotype AA. NCF4 expression was regulated by the miRNA-mRNA interaction mechanism, and an important role for NCF4 in mastitis susceptibility in dairy cow was suggested.

Rapid baso-apical translocation of Mycobacterium avium ssp. paratuberculosis in mammary epithelial cells in the presence of Escherichia coli

Infection of mammary gland cells with bacterial pathogens begins with adhesion, invasion, and persistence within the cells or systemic distribution. Some bacteria, such as Escherichia coli, are known to causes bovine mastitis, resulting in acute proinflammatory responses in the mammary tissue. Mycobacterium avium ssp. paratuberculosis (MAP), the etiological agent of paratuberculosis, is able to spread to distant organs after crossing intestinal cells, reaching the mammary gland and potentially being released in milk, infecting calves during suckling. Its exit from systemic sites may be influenced by preexisting inflammation such as that caused by E. coli mastitis. Interactions between E. coli and MAP in mammary epithelial cells have not yet been described. In this study, we posited that E. coli-infected bovine mammary epithelial cells would facilitate baso-apical translocation of MAP in an ex vivo model. We showed that the presence of E. coli in a bovine mammary epithelial cell line (MAC-T) increased baso-apical translocation of MAP to the apical side of the cells. Levels were significantly higher 30 min post-infection and decreased at 120 min post-infection. Cells previously infected with E. coli and MAP or with E. coli alone showed a significant increase in IL1B mRNA expression at 120 min. We detected no significant expression of p38 mitogen-activated protein kinase (mapkp38) or IL10, regardless of treatment. Thereby, the presence of E. coli in MAC-T cells alters the translocation of MAP through epithelial cells, enabling its rapid translocation to the cellular surface. Expression of IL1B was shown to influence the apical-basal translocation of MAP at 120 min. Findings from the current study suggest that MAP translocation into milk is likely enhanced by inflammatory states such as those induced during E. coli mastitis. This is the first report demonstrating the effect of E. coli under MAP coinfection in bovine mammary epithelial cells under experimental conditions.

Association of leptin, toll-like receptor 4, and chemokine receptor of interleukin 8 C-X-C motif single nucleotide polymorphisms with fertility traits in Czech Fleckvieh cattle

Objective

The use of genetic markers can help to enhance reproduction in cattle, which is a very important trait for profitability in dairy production systems. This study evaluated the association between genotypes of leptin (LEP), toll-like receptor 4 (TLR4), and chemokine receptor of interleukin 8 C-X-C motif (CXCR1) genes and fertility traits in Czech Fleckvieh cattle.

Methods

Phenotypic data from 786 Czech Fleckvieh cows raised on 5 farms in the Czech Republic were used, along with information from the 1st three parities. To determine genotype, the polymerase chain reaction– restriction fragment length polymorphism method was used.

Results

Except for LEP g.-963C>T, all studied genotype frequencies of single nucleotide polymorphisms (SNPs) were distributed according to the Hardy-Weinberg equilibrium. Two LEP SNPs (g.-963C>T and c.357C>T) were associated with the age at the 1st calving, days open (DO), pregnancy rate after 1st service (PR), and calving interval (CLI). In LEP g.-963C>T the TT genotype heifers firstly calved 24 days earlier than CC genotype and the CT genotype cow showed a tendency for shorter DO and higher PR. In LEP c.357C>T we observed longer CLI and DO period in TT cows. In general, we can propose the TT genotype of g.-963C>T as favorable and the TT genotype of c.357C>T as unfavorable for a cow’s fertility. Heterozygotes in TLR4 c.-226C>G were significantly associated with shorter CLI, and presented a nonsignificant tendency to be associated with higher PR. In CXCR1 c.777 C>G, we did not observe any relationship of this SNP with reproduction.

Conclusion

Overall, the results showed that LEP could be an effective marker for improving reproduction in Czech Fleckvieh cattle. This study also provides novel insights into the relationship between TLR4 and CXCR1 SNPs and reproduction in dual-purpose cattle.

Domestic water buffaloes: Access to surface water, disease prevalence and associated economic losses

Given the shortage and non-availability of freshwater in Pakistan, wastewater is being used for bathing water buffaloes; however, this has a negative impact on animal welfare. Although there is a vast literature on indirect linkages between wastewater and animal productivity, studies focusing on the direct impacts of water buffaloes bathing in wastewater on animal productivity and economic losses are rare. Therefore, using 360 domestic water buffalo farms, this study examines the expenditure and production losses associated with bathing (in wastewater and freshwater) and non-bathing water buffaloes by employing partial budgeting and resource adjustment component techniques. Furthermore, it investigates the prevalence of animal diseases and associated economic effects using correlation analysis and propensity score matching techniques, respectively. The findings reveal that compared to their counterparts (freshwater bathing and non-bathing water buffaloes), buffaloes bathing in wastewater are at increased risk of clinical mastitis, foot and mouth disease (FMD) and tick infestation. Moreover, the use of wastewater for bathing buffaloes also leads to higher economic and production losses by affecting milk productivity, causing premature culling, and reducing slaughter value. The findings of the double-log model show that economic losses are higher if buffaloes bathe in wastewater within 30 min after milking, as there are more chances that those buffaloes would be exposed to bacterial penetration in the teat ducts, which may result in intramammary infection. According to the propensity score matching method, the higher economic damages per month are associated with buffaloes bathing in wastewater and freshwater, 155 and 110 USD per farm, respectively. The study findings reference the need for policies to restrict wastewater access by water buffaloes, and a regular check of and access to cool clean water wallows for bathing during hot summer days, to reduce excess heat and economic losses, and thus improve animal welfare.

Evaluation of milk sample fractions for characterization of milk microbiota from healthy and clinical mastitis cows

Amplicon sequencing technique has been increasingly applied to the clinical setting as a sensitive diagnostic tool. Therefore, it is of great importance to develop a DNA extraction method that accurate isolates DNA from complex host-associated microbiota. Given the multifactorial etiology of clinical mastitis and the diversified lifestyle of bacterial species harboring in milk, here four distinct milk sample fractions: raw whole milk, milk fat, casein-pellet, and casein-pellet + fat from healthy cows and cows with clinical mastitis, were subjected to bead-beating DNA extraction, followed by high-throughput sequencing. We aimed to identify the best approach for characterization of the milk microbiota and detection of mastitis pathogens (Klebsiella spp., Streptococcus spp. and Escherichia coli). DNA from each milk fraction tested was extracted by two commercial kits, which include physical, mechanical and chemical lysis; in total 280 DNA samples from 35 cows were analyzed. Milk-health-status were categorized into four groups (healthy group; E. coli-mastitis group; Klebsiella spp.-mastitis group; and Streptococcus spp.–mastitis group). Bacterial phyla and families were described for each milk-health-status group across milk sample fractions and DNA extraction kits. For the mastitis groups the relative abundance of f__Enterobacteriaceae and f__Streptococcaceae were compared to determine the efficacy of procedures in detecting the mastitis pathogens. The four milk fractions used allowed efficiently and uniformly detection of the causative agent of mastitis. Only 27% of the families detected in healthy milk were shared among the samples extracted from all fractions of milk samples; followed by 3, 4, and 12% for the samples from E. coli-mastitis, Klebsiella spp.-mastitis and Streptococcus spp-mastitis, respectively. However, the shared families comprised a mean relative abundance greater than 85%, regardless of milk-health-status, milk fraction and DNA isolation method. Taxonomic data at the family level showed that sequences from mastitis milk samples cultured positive for E. coli and Klebsiella spp. were predominantly affiliated with f__Enterobacteriaceae, while for Streptococcus spp. were dominated by f__Streptococcacea, followed by f__Pseudomonadaceae and f__Enterococcaceae. Microbial community analysis revealed that most of the microbial community composition corresponded to milk bacterial species irrespective of the DNA isolation method and milk fraction evaluated.

Subclinical mastitis (SCM) and proinflammatory cytokines are associated with mineral and trace element concentrations in human breast milk

The possibility that either subclinical mastitis (SCM), an inflammatory condition of the breast, or elevations in breast milk proinflammatory cytokines alter breast milk mineral and trace element composition in humans has not been investigated. In this cross-sectional study, breast milk samples (n=108) were collected from Guatemalan Mam-Mayan mothers at one of three stages of lactation (transitional, early and established), and categorized as SCM (Na:K >0.6) or non-SCM (Na:K ≤0.6). Milk concentrations of 12 minerals (calcium, copper, iron, magnesium, manganese, phosphorus, potassium, rubidium, selenium, sodium, strontium, and zinc) and 4 proinflammatory cytokines (IL-1β, IL-6, IL-8, TNF-α) were measured by inductively coupled plasma mass spectrometry (ICP-MS), Lachat analyzer or Luminex multiplex bead cytokine assay. SCM was more prevalent during transitional (30%) than early (15.6%) and established (8.9%) lactation. Analysis of variance revealed that breast milk minerals differed by stage of lactation and SCM status. Breast milk minerals with the exception of magnesium were lower in established lactation, whereas SCM was associated with higher selenium and lower phosphorus. Regression models that controlled for lactation stage also confirmed that SCM was associated with lower milk phosphorus and higher milk selenium concentrations. Furthermore, cytokine concentrations were independently associated with several mineral concentrations: IL-1β with higher phosphorus and iron, IL-6 with higher calcium, magnesium, copper and manganese, IL-8 with higher calcium and zinc, and TNF-α with lower iron and manganese. We conclude that milk mineral and trace element concentrations are affected not only by the presence of SCM but also by proinflammatory cytokines in breast milk.

CYP1A1 Relieves Lipopolysaccharide-Induced Inflammatory Responses in Bovine Mammary Epithelial Cells

The expression of cytochrome P4501A1 (CYP1A1) enzyme is changed in various organs during the host response to inflammation or infection, leading to alterations in the metabolism of endogenous and exogenous compounds. Results of this study showed that CYP1A1 expression was significantly downregulated in the mammary tissue of bovine with mastitis, in inflammatory epithelial cells (INEs) extracted from the tissue, and in lipopolysaccharide- (LPS-) induced INEs compared with their corresponding counterparts. Overexpression of CYP1A1 in bovine mammary epithelial cells alleviated the LPS-induced inhibition of epithelial proliferation, abated the LPS-induced increase of gene expression and protein secretion of inflammatory cytokine tumor necrosis factor-α and interleukin-6, and attenuated the LPS-induced activation of NF-κB signaling. These findings suggest that CYP1A1 has immense potential in the regulation of inflammatory responses in bovine mammary epithelial cells during mastitis and may serve as a useful therapeutic target in mitigating injuries caused by inflammatory overreaction.

Inhibition of histone deacetylase reduces lipopolysaccharide-induced-inflammation in primary mammary epithelial cells by regulating ROS-NF-кB signaling pathways

Histone deacetylase 6 (HDAC6) is the sole member of the HDAC family, that is predominantly located in the cytoplasm and has substrate specificity for nonhistone proteins, such as α-Tubulin. Although an increasing number of studies have shown that HDAC6 is involved in inflammatory diseases, but little is known about the participation of HDAC6 in the transcriptional regulation of inflammatory cytokines. Here, we examined the effects of Tubastatin (Tub), a highly selective HDAC6 inhibitor, on lipopolysaccharide (LPS)-stimulated primary bovine mammary epithelial cells (bMECs). The specific inhibition of HDAC6 using Tub significantly decreased the release of pro-inflammatory cytokines, such as TNF-α and IL-1β, which was associated with increased α-Tubulin acetylation. HDAC6 overexpression significantly induced reactive oxygen species (ROS) generation via upregulation of NADPH oxidase activity. Administration of Tub dose-dependently inhibited ROS production and NADPH oxidase activity. In addition, inhibition of HDAC6 led to suppression of the NF-κB signaling pathway. Thus, we report herein that HDAC6 is involved in ROS-NF-κB signaling pathway related to pro-inflammatory cytokine expression and that selective HDAC6 inhibition by Tub is a potent approach for preventing LPS-mediated inflammation.

Glycogen Synthase Kinase 3α Is the Main Isoform That Regulates the Transcription Factors Nuclear Factor-Kappa B and cAMP Response Element Binding in Bovine Endothelial Cells Infected with Staphylococcus aureus

Glycogen synthase kinase 3 (GSK3) is a constitutive enzyme implicated in the regulation of cytokine expression and the inflammatory response during bacterial infections. Mammals have two GSK3 isoforms named GSK3α and GSK3β that plays different but often overlapping functions. Although the role of GSK3β in cytokine regulation during the inflammatory response caused by bacteria is well described, GSK3α has not been found to participate in this process. Therefore, we tested if GSK3α may act as a regulatory isoform in the cytokine expression by bovine endothelial cells infected with Staphylococcus aureus because this bacterium is one of the major pathogens that cause tissue damage associated with inflammatory dysfunction. Interestingly, although both isoforms were phosphorylated–inactivated, we consistently observed a higher phosphorylation of GSK3α at Ser21 than that of GSK3β at Ser9 after bacterial challenge. During a temporal course of infection, we characterized a molecular switch from pro-inflammatory cytokine expression (IL-8), promoted by nuclear factor-kappa B (NF-κB), at an early stage (2 h) to an anti-inflammatory cytokine expression (IL-10), promoted by cAMP response element binding (CREB), at a later stage (6 h). We observed an indirect effect of GSK3α activity on NF-κB activation that resulted in a low phosphorylation of CREB at Ser133, a decreased interaction between CREB and the co-activator CREB-binding protein (CBP), and a lower expression level of IL-10. Gene silencing of GSK3α and GSK3β with siRNA indicated that GSK3α knockout promoted the interaction between CREB and CBP that, in turn, increased the expression of IL-10, reduced the interaction of NF-κB with CBP, and reduced the expression of IL-8. These results indicate that GSK3α functions as the primary isoform that regulates the expression of IL-10 in endothelial cells infected with S. aureus.

lncRNA H19 is involved in TGF-β1-induced epithelial to mesenchymal transition in bovine epithelial cells through PI3K/AKT Signaling Pathway

Increased levels of long noncoding RNA H19 (H19) have been observed in many inflammatory and organ fibrosis diseases including ulcerative colitis, osteoarthritis, liver fibrosis, renal fibrosis and pulmonary fibrosis. However, the role of H19 in bovine mastitis and mastitis-caused fibrosis is still unclear. In our study, H19 was characterized as a novel regulator of EMT induced by transforming growth factor-β1 (TGF-β1) in bovine mammary alveolar cell-T (MAC-T) cell line. We found that H19 was highly expressed in bovine mastitis tissues and inflammatory MAC-T cells induced by virulence factors of pathogens. TGF-β1 was also highly expressed in inflammatory MAC-T cells, and exogenous TGF-β1 could induce EMT, enhance extracellular matrix protein expression, and upregulate H19 expression in epithelial cells. Stable expression of H19 significantly promotes EMT progression and expression of ECM protein induced by TGF-β1 in MAC-T cells. Furthermore, by using a specific inhibitor of the PI3K/AKT pathway, we demonstrated that TGF-β1 upregulated H19 expression through PI3K/AKT pathway. All these observations imply that the lncRNA H19 modulated TGF-β1-induced epithelial to mesenchymal transition in bovine epithelial cells through PI3K/AKT signaling pathway, which suggests that mammary epithelial cells might be one source for myofibroblasts in vivo in the mammary glands under an inflammatory condition, thereby contributing to mammary gland fibrosis.

Exfoliation rate of mammary epithelial cells in milk on bovine mastitis caused by Staphylococcus aureus is associated with bacterial load

The exfoliation rate of mammary epithelial cells (MECs) in milk is affected by physiological, breeding and environmental factors. Little is known about the relationship between the MEC exfoliation into milk and mammary-infected Staphylococcus aureus (S. aureus) load on bovine mastitis caused by S. aureus. The aim of this study was to investigate the relationship between S. aureus load and the proportion of MEC exfoliation in milk using five substantial bovine mastitis models. In 64 randomly extracted milk samples from udders at 3-21 days after S. aureus infusion, there were various samples with different numbers of S. aureus counts and somatic cell counts. No significant correlations were found between the S. aureus counts and somatic cell count (r = 0.338). In contrast, a significant correlation was noted between S. aureus counts and the proportion of cytokeratin-positive cells in the milk from the infused udders (r = 0.734, P < 0.01). In conclusion, the increasing MEC exfoliation rate in milk from mastitis udders caused by S. aureus may contribute to reduced milk yield.

Bifunctional role of ephrin A1-Eph system in stimulating cell proliferation and protecting cells from cell death through the attenuation of ER stress and inflammatory responses in bovine mammary epithelial cells

Structural and functional development of the mammary gland is constant in the mammary gland life cycle. Eph receptors and their ligands, ephrins, control events through cell-to-cell interactions during embryonic development, and adult tissue homeostasis; however, little information on participation of ephrin A1, a representative ligand of the Eph receptor, in the development and function of normal mammary glands is known. In this study, we demonstrated functional effects of the ephrin A1-Eph system and mechanisms of its action on bovine mammary epithelial (MAC-T) cells. The in vitro cultured MAC-T cells expressed the ephrin A1 ligand and EphA1, A2, A4, A7, and A8 among the eight members of the Eph A family. Our results revealed that ephrin A1 induced MAC-T cell cycle progression and stimulated cell proliferation with abundant expression of nucleic PCNA and cyclin D1 proteins. Additionally, ephrin A1 induced activation of intracellular signaling molecules involved in PI3 K/AKT and MAPK signaling, and the proliferation-stimulating effect of ephrin A1 was mediated by activation of these pathways. Furthermore, ephrin A1 influenced expression and activation of various ER stress-related proteins and protected MAC-T cells from stress-induced cell death. Finally, ephrin A1 alleviated LPS-induced cell death through down-regulation of inflammatory cytokines. In conclusion, the results of this study suggest that the Eph A-ephrin A1 system is a positive factor in the increase and maintenance of epithelial cells in mammary glands of cows; the signaling system contributes to development, remodeling, and functionality of normal mammary glands and could overcome mastitis in cows and other mammals.

Structure, chaperone-like activity and allergenicity profile of bovine caseins upon peroxynitrite modification: New evidences underlying mastitis pathomechanisms

Mastitis, an inflammatory reaction frequently develops in response to intra-mammary bacterial infection‌‌, may induce the generation of peroxynitrite (PON)‌ which is a highly potent reactive oxygen and nitrogen species. Caseins as the intrinsically unfolded proteins seem feasible substrates to react with PON. Therefore, in the current study, structural and functional aspects of both β-casein (β-CN) and whole casein fraction (WCF) were evaluated after PON modification, using a variety of techniques. Modification of the bovine caseins with PON results in an important enhancement in the carbonyl, nitrotryptophan, nitrotyrosine and dityrosine content of these proteins‌. The results of fluorescence and far UV-CD assessments suggested significant structural alteration of caseins upon PON-modification. The chaperone-like activity of β-casein was significantly altered after PON modification. The results of scanning electron microscopy suggest that bovine caseins display unique morphological features after treatment with PON. Also, the PON-modified caseins preserved their allergenicity profile and displayed partial resistance against digestion by the pancreatic proteases. Ascorbic acid, an important antioxidant component of milk, was also capable to significantly prevent the PON-induced structural damages in bovine milk caseins. In conclusion, our results suggest that PON may have significant role in the structural and functional alteration of milk caseins. Also, the PON-induced structural damaging effects of caseins might be effectively prevented by a sufficient level of milk antioxidant components particularly by ascorbic acid.

Transcriptome profiling of Staphylococci-infected cow mammary gland parenchyma

BACKGROUND

Genome-wide gene expression profiling allows for identification of genes involved in the defense response of the host against pathogens. As presented here, transcriptomic analysis and bioinformatics tools were applied in order to identify genes expressed in the mammary gland parenchyma of cows naturally infected with coagulase-positive and coagulase-negative Staphylococci.

RESULTS

In cows infected with coagulase-positive Staphylococci, being in 1st or 2nd lactation, 1700 differentially expressed genes (DEGs) were identified. However, examination of the 3rd or 4th lactations revealed 2200 DEGs. Gene ontology functional classification showed the molecular functions of the DEGs overrepresented the activity of cytokines, chemokines, and their receptors. In cows infected with coagulase-negative Staphylococci, in the 1st or 2nd lactations 418 DEGs, while in the 3rd or 4th lactations, 1200 DEGs were identified that involved in molecular functions such as protein, calcium ion and lipid binding, chemokine activity, and protein homodimerization. Gene network analysis showed DEGs associated with inflammation, cell migration, and immune response to infection, development of cells and tissues, and humoral responses to infections caused by both types of Staphylococci.

CONCLUSION

A coagulase-positive Staphylococci infection caused a markedly stronger host response than that of coagulase-negative, resulting in vastly increased DEGs. A significant increase in the expression of the FOS, TNF, and genes encoding the major histocompatibility complex proteins (MHC) was observed. It suggests these genes play a key role in the synchronization of the immune response of the cow's parenchyma against mastitis-causing bacteria. Moreover, the following genes that belong to several physiological pathways (KEGG pathways) were selected for further studies as candidate genes of mammary gland immune response for use in Marker Assisted Selection (MAS): chemokine signaling pathway (CCL2, CXCL5, HCK, CCR1), cell adhesion molecules (CAMs) pathway (BOLA-DQA2, BOLA-DQA1, F11R, ITGAL, CD86), antigen processing and presentation pathway (CD8A, PDIA3, LGMN, IFI30, HSPA1A), and NOD-like receptor signaling pathway (TNF, IL8, IL18, NFKBIA).

Intramammary inoculation of Panax ginseng plays an immunoprotective role in Staphylococcus aureus infection in a murine model

The immunoprotective effect of Panax ginseng (Pg) extract was investigated in a mouse mastitis model. Lactating female mice were intramammarily inoculated with Pg or placebo, and then were challenged with S. aureus, while other group was inoculated with S. aureus alone. The number of bacteria recovered from mammary glands was significantly lower in Pg-treated S. aureus-infected mice (group I) compared with placebo-treated S. aureus-infected mice (group II) and S. aureus-infected mice (group III). The mRNA expression of TLR2, TLR4, IL-1α and TNF-α was influenced by treatment; being the transcript levels for all genes higher in group I compared with group II and III. Activation of NF-κB and the number of monocytes-macrophages in mammary gland tissue was significantly increased in group I compared with group II and III. Pg extract was able to trigger an adequate immune response to confront an infection demonstrating its protective effect and potential for preventing bovine intramammary infections.

Bivariate threshold models for genetic evaluation of susceptibility to and ability to recover from mastitis in Danish Holstein cows

Mastitis in dairy cows is an unavoidable problem and genetic variation in recovery from mastitis, in addition to susceptibility, is therefore of interest. Genetic parameters for susceptibility to and recovery from mastitis were estimated for Danish Holstein-Friesian cows using data from automatic milking systems equipped with online somatic cell count measuring units. The somatic cell count measurements were converted to elevated mastitis risk, a continuous variable [on a (0-1) scale] indicating the risk of mastitis. Risk values >0.6 were assumed to indicate that a cow had mastitis. For each cow and lactation, the sequence of health states (mastitic or healthy) was converted to a weekly transition: 0 if the cow stayed within the same state and 1 if the cow changed state. The result was 2 series of transitions: one for healthy to diseased (HD, to model mastitis susceptibility) and the other for diseased to healthy (DH, to model recovery ability). The 2 series of transitions were analyzed with bivariate threshold models, including several systematic effects and a function of time. The model included effects of herd, parity, herd-test-week, permanent environment (to account for the repetitive nature of transition records from a cow) plus two time-varying effects (lactation stage and time within episode). In early lactation, there was an increased risk of getting mastitis but the risk remained stable afterwards. Mean recovery rate was 45% per lactation. Heritabilities were 0.07 [posterior mean of standard deviations (PSD) = 0.03] for HD and 0.08 (PSD = 0.03) for DH. The genetic correlation between HD and DH has a posterior mean of -0.83 (PSD = 0.13). Although susceptibility and recovery from mastitis are strongly negatively correlated, recovery can be considered as a new trait for selection.

Differential somatic cell count-A novel method for routine mastitis screening in the frame of Dairy Herd Improvement testing programs

Somatic cell count (SCC) is used as key indicator in mastitis screening programs typically applied in the frame of Dairy Herd Improvement (DHI) testing programs. However, mastitis is still causing tremendous economic losses to the dairy industry. Hence, new biomarkers are needed that can be used for enhanced management of mastitis on dairy farms. Besides the determination of SCC, differentiation of cells has been described to be beneficial for a more definite description of the actual udder health status of dairy cows. The aim of this study was to develop a new method for rapid and simultaneous determination of SCC and a new parameter, differential somatic cell count (DSCC), in individual cow milk samples using flow cytometry. The method is sought to be applied in central milk testing laboratories, so that existing DHI infrastructures can be used. The DSCC represents the combined proportion of polymorphonuclear leukocytes (PMN) and lymphocytes expressed in percentage. The proportion of macrophages can be calculated by subtracting DSCC from 100%. Our research revealed increasing proportions of PMN, but decreasing proportions of macrophages as SCC increased. However, lymphocytes occurred fairly constantly with low proportions across the entire SCC range. Hence, the DSCC parameter reflects the antidromic trend of PMN and macrophages. Fluorescence microscopy was used to evaluate the specificity of the new Foss DSCC method in terms of DSCC and a high correlation was found. Apart from that, the accuracy of cell differentiation using the Foss DSCC method was confirmed in a cell sorting trial. Total SCC could be determined equally well using the new method as compared with existing methods. The new method was further proven to be robust toward a range of method and milk-sample-related factors. In an initial field trial, regular DHI samples of a local dairy herd were analyzed. The DSCC values occurred in a broad range from 34 to 79% in samples with <400,000 cells/mL. Higher DSCC values (53-89%) were found in samples with >400,000 cells/mL. In conclusion, the new Foss DSCC method allows reliable, repeatable, fast, robust, and accurate determination of both DSCC and SCC at low cost. This, in turn, provides more accurate information on the actual udder health status of dairy cows. The practical application of DSCC in the frame of DHI testing programs, however, needs further investigation.

The correlation between inflammatory injury induced by LPS and RAS in EpH4-Ev cells

Renin-angiotensin system (RAS) plays an important role of regulating inflammatory injury. However, it is not clear about the correlation between renin-angiotensin system (RAS) and inflammation induced by LPS in mammary gland cells. So immunofluorescence was performed to verify the ACE2 expression in mammary gland cells. MTT assay was performed to detect cell viability. ELISA was performed to detect cytokines in cell supernatant. Western Blot was performed to analyze RAS levels and ACE2 level change was observed by immunofluorescence. The TLR4 level and p65 phosphorylation were detected by Western Blot. The ACE2 protein intensively located on the cell membrane. According to the results of MTT assay and TNF-α level, the injury was evidently induced by high concentration LPS after 9h. The TNF-α, IL-6, IL-8, ACE, AT1R and AngII had an increasing expression with the rise of cell injury. In contrast, the MasR, Ang1-7 and ACE2 had a declining expression with the increase of cell injury degree. The TLR4 level and p65 phosphorylation in high concentration LPS group was significantly higher than that of control group. These results suggest that a valid inflammatory injury was induced after the cells were treated by high concentration of LPS for 9h. Meanwhile, the ACE/AngII/AT1R axis was activated and the ACE2/Ang1-7/MasR axis was depressed.

The bovine colostrum microbiome and its association with clinical mastitis

In an effort to characterize colostrum microbial diversity and its potential associations with early-lactation clinical mastitis, we used high-throughput sequencing of the 16S rRNA gene to investigate the bovine colostrum microbiome. A prospective observational study was conducted that included 70 Holstein cows; colostrum samples were collected from all 4 mammary gland quarters. Colostrum samples were categorized according to whether the quarter was diagnosed (CMC) or not diagnosed (NCMC) with clinical mastitis during the first 30 d postpartum. Colostrum samples were dominated by Firmicutes, Bacteroidetes, Proteobacteria, Actinobacteria, Fusobacteria, and Tenericutes phyla, with the 6 most common taxa [order (o), family (f), and genus (g)] being g_Staphylococcus, g_Prevotella, f_Ruminococcaceae, o_Bacteroidales, o_Clostridiales, and g_Pseudomonas. The colostrum microbiota of primiparous cows was significantly richer (higher number of bacterial species) than that of multiparous cows, and differences in colostrum taxonomic structure between parities were also observed. The microbial community of NCMC samples of primiparous cows was significantly more diverse than that of CMC samples, and the relative abundances of the Tenericutes and Fusobacteria phyla as well as the Mycoplasma and Fusobacterium genera were significantly higher in NCMC than in CMC samples of primiparous cows. The colostrum core microbiome, defined as the bacterial taxa common to all colostrum samples examined, was composed of 20 taxa and included bacterial genera already known to be associated with mastitis (e.g., Staphylococcus, Mycoplasma, and Streptococcus spp.). Our results indicate that the colostrum microbiome of primiparous cows differs from that of multiparous cows, and it harbors some diversity and taxonomic markers of mammary gland health specific to primiparous cows only.

Genome-Wide Transcriptional and Post-transcriptional Regulation of Innate Immune and Defense Responses of Bovine Mammary Gland to Staphylococcus aureus

Staphylococcus aureus (S. aureus) is problematic for lactating mammals and public health. Understanding of mechanisms by which the hosts respond to severe invasion of S. aureus remains elusive. In this study, the genome-wide expression of mRNAs and miRNAs in bovine mammary gland cells were interrogated at 24 h after intra-mammary infection (IMI) with high or low concentrations of S. aureus. Compared to the negative control quarters, 194 highly-confident responsive genes were identified in the quarters with high concentration (10⁹ cfu/mL) of S. aureus, which were predominantly implicated in pathways and biological processes pertaining to innate immune system, such as cytokine-cytokine receptor interaction and inflammatory response. In contrast, only 21 highly-confident genes were significantly differentially expressed in face of low concentration (10⁶ cfu/mL) of S. aureus, which slightly perturbed the cell signaling and invoked corresponding responses like vasoconstriction, indicating limited perturbations and immunological evading. Additionally, the significant up-regulations of bta-mir-223 and bta-mir-21-3p were observed in the quarters infected by high concentration of S. aureus. Network analysis suggested that the two miRNAs' pivotal roles in defending hosts against bacterial infection probably through inhibiting CXCL14 and KIT. The significant down-regulation of CXCL14 was also observed in bovine mammary epithelial cells at 24 h post-infection of S. aureus (10⁸ cfu/mL) in vitro. Integrated analysis with QTL database further suggested 28 genes (e.g., CXCL14, KIT, and SLC4A11) as candidates of bovine mastitis. This study first systematically revealed transcriptional and post-transcriptional responses of bovine mammary gland cells to invading S. aureus in a dosage-dependent pattern, and highlighted a complicated responsive mechanism in a network of miRNA-gene-pathway interplay.

Mammary inflammatory gene expression was associated with reproductive stage and regulated by docosahexenoic acid: in vitro and in vivo studies

Background

Periparturient mastitis is the most prevalent disease affecting lactating animals. However, it has long been relied on antibiotics to deal with mastitis, leading to a potential threat to food safety. This study was aimed to investigate the expression of pro-inflammatory cytokines in mammary glands of sows around parturition when mastitis and oxidative stress usually occur, and evaluate the anti-inflammatory effect of docosahexenoic acid (DHA) in porcine mammary epithelial cells (PMEC) challenged by lipopolysaccharide (LPS).

Methods

Mammary tissues and blood samples were collected from seven pregnant sows at different reproductive stages. Primarily cultured PMEC at passage 4 were assigned to four treatments: basal medium (control), basal medium with LPS (10 μg/mL) (LPS treatment), basal medium with LPS (10 μg/mL) and DHA (100 or 200 μM) (LPS + DHA treatments), and cell samples were harvested after 24 h incubation. The measurements included oxidative stress markers in blood samples and gene expression in mammary tissues and PMEC samples.

Results

Serum α-tocopherol concentration was lower at parturition than at day 90 of gestation and day 28 post parturition, while serum malondialdehyde concentration was higher at day 28 post parturition than at day 90 of gestation. Higher interleukin (IL)-1β mRNA abundance while lower LPS binding protein mRNA abundance in mammary tissues were observed at day 90 of gestation compared with that at parturition and at day 28 and 35 post parturition. Mammary tumor necrosis factor (TNF)-α mRNA abundance were lower at parturition than at day 90 of gestation and day 28 and 35 post parturition, whereas mammary IL-8 mRNA abundance were lower at parturition than at day 35 post parturition. In the PMEC experiment, compared with the control, increased mRNA abundances of Toll-like receptor (TLR)-4 downstream target, myeloid differentiation factor 88 (MyD88), IL-6 and IL-8 were observed in LPS treatment, whereas DHA appeared to decrease mRNA abundances of MyD88, IL-6 and IL-8 induced by LPS.

Conclusions

The down-regulated expression of pro-inflammatory cytokines in mammary tissues and aggravated systemic oxidative stress at parturition suggest that sows are in a vulnerable status during periparturient period. DHA appears to attenuate inflammatory responses in LPS-challenged PMEC through modulation of TLR4 signalling pathway.

Exogenous β-mannanase improves feed conversion efficiency and reduces somatic cell count in dairy cattle

Exogenous fibrolytic enzymes have been shown to be a promising way to improve feed conversion efficiency (FCE). β-Mannanase is an important enzyme digesting the polysaccharide β-mannan in hemicellulose. Supplementation of diets with β-mannanase to improve FCE has been more extensively studied in nonruminants than in ruminants. The objective of this study was to investigate the effects of β-mannanase supplementation on nutrient digestibility, FCE, and nitrogen utilization in lactating Holstein dairy cows. Twelve post-peak-lactation multiparous Holstein cows producing 45.5±6.6kg/d of milk at 116±19.0d in milk were randomly allotted to 1 of 3 treatments in a 3×3 Latin square design with 3 periods of 18d (15d for adaptation plus 3d for sample collection). All cows were fed the same basal diet and the 3 treatments differed only by the β-mannanase dose: 0% dry matter (DM; control), 0.1% of DM (low supplement, LS), and 0.2% of DM (high supplement, HS) supplemented to the basal diet. Supplementation of β-mannanase enzyme at the LS dose reduced dry matter intake (DMI) but did not affect milk yield or milk composition. Cows receiving LS produced 90g more milk per kg of DMI compared with control cows. Somatic cell count (SCC) in milk was lower for cows fed the LS diet compared with cows fed control diets. Cows fed LS diet had lower DM, organic matter and crude protein digestibility compared with cows fed control diets. Starch, neutral detergent fiber, and acid detergent fiber digestibility were not affected by LS. Milk yield, DMI, SCC, and nutrient digestibility did not change for HS. Despite the reduced crude protein digestibility, reduced N intake led to similar fecal N excretions in LS cows and control cows (234 vs. 235g/cow per day). Urinary N excretions remained similar between enzyme-fed and control cows (~190g/cow per day), although the percentage of N intake partitioned to urinary N tended to be greater in LS than in control cows (31 vs. 27%). Cows fed LS significantly improved the percentage of apparently absorbed N partitioned to milk protein N (42 vs. 38%). When supplemented at 0.1% of dietary DM, β-mannanase can improve FCE and lower the SCC of dairy cows without affecting milk yield, milk composition, or total manure N excretions of dairy cows.

Variant innate immune responses of mammary epithelial cells to challenge by Staphylococcus aureus, Escherichia coli and the regulating effect of taurine on these bioprocesses

Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) are important pathogens causing subclinical and clinical bovine mastitis, respectively. Taurine, an organic acid found in animal tissues, has been used for the treatment of various superficial infections and chronic inflammations. We challenged a bovine mammary epithelial cell (MEC) line (MAC-T) or a mouse mammary epithelial cell line (EpH4-Ev) with either E. coli or S. aureus and compared the responses of MECs to these 2 pathogens. We also examined the regulatory effects of taurine on these responses. Receptor analyses showed that both TLR2 and TLR4 are upregulated upon exposure to either E. coli or S. aureus. Taurine pre-treatment dampened upregulation to some extent. E. coli and S. aureus stimulated comparable levels of ROS, which could be inhibited by taurine pre-treatment. E. coli infection elicited a dramatic change in iNOS expression. Taurine significantly decreased iNOS expression in the S. aureus challenged group. Protein microarray demonstrated that 32/40 and 8/40 inflammatory molecules/mediators were increased after E. coli or S. aureus challenge, respectively. The fold changes of most molecules were higher in the E. coli infection group than that in the S. aureus infection group. Taurine negatively regulated the inflammatory profile in both bacterial infections. Pro-inflammatory cytokines (such as TNF-α) connected with TLR activation were down-regulated by taurine pre-treatment. The influence of TAK-242 and OxPAPC on cytokine/molecule expression profiles to E. coli challenge are different than to S. aureus. Some important factors (MyD88, TNF-α, IL-1β, iNOS and IL-6) mediated by TLR activation were suppressed either in protein microarray or special assay (PCR/kits) or both. TAK-242 restrained ROS production and NAGase activity similar to the effect of taurine in E. coli challenge groups. The detection of 3 indices (T-AOC, SOD and MDA) reflecting oxidative stress in vivo, showed that taurine improved the antioxidant ability of cells. We conclude that taurine can regulate the inflammatory response during infection with E. coli and prevent cell damage by affecting the signaling pathways mediated by TLRs and by improving the antioxidant ability of cells. In S. aureus infections, taurine's antioxidant ability may be the primary means of resistance to inflammation. This study provides a better understanding of the inflammatory mechanisms of E. coli and S. aureus mastitis, and it provides a putative strategy for the prevention of this disease.

Mastites em ruminantes no Brasil

Resumo: A mastite é uma doença complexa e considerada uma das principais causas de perdas à indústria leiteira mundial. Objetivou-se com esta revisão compilar informações dos últimos dez anos sobre a mastite em ruminantes no Brasil. A prevalência da mastite subclínica chega a 48,64% na espécie bovina, 30,7% na espécie caprina, 31,45% na espécie ovina e 42,2% na espécie bubalina, destacando-se a etiologia por Staphylococcus spp. Os fatores de risco associados à ocorrência de mastite estão relacionados a problemas no saneamento ambiental e ao manejo dos animais. As bactérias isoladas do leite mastítico apresentam maior percentual de resistência a penicilina, ampicilina, amoxicilina e neomicina e a utilização de técnicas moleculares no diagnóstico dos agentes causadores de mastites no país, ainda é escassa o que dificulta a obtenção de um diagnóstico mais rápido, sensível e específico.

Stromal fibroblasts derived from mammary gland of bovine with mastitis display inflammation-specific changes

Fibroblasts are predominant components of mammary stromal cells and play crucial roles in the development and involution of bovine mammary gland; however, whether these cells contribute to mastitis has not been demonstrated. Thus, we have undertaken biological and molecular characterization of inflammation-associated fibroblasts (INFs) extracted from bovine mammary glands with clinical mastitis and normal fibroblasts (NFs) from slaughtered dairy cows because of fractured legs during lactation. The functional contributions of INFs to normal epithelial cells were also investigated by using an in vitro co-culture model. We present evidence that the INFs were activated fibroblasts and showed inflammation-related features. Moreover, INFs significantly inhibited the proliferation and β-casein secretion of epithelial cells, as well as upregulated the expression of tumor necrosis factor-α and interleukin-8 in epithelial cells. These findings indicate that functional alterations can occur in stromal fibroblasts within the bovine mammary gland during mastitis, demonstrating the importance of stromal fibroblasts in bovine mastitis and its treatment.

Reproductive stage associated changes in plasma fatty acid profile and proinflammatory cytokine expression in rat mammary glands

Mastitis is a common disease for mammals all around the world. Figuring out why mastitis mainly occurs around parturition may be helpful for dealing with the disease. Lipolytic activity and oxidative stress take place around parturition, which may leads to alteration in fatty acids profile and proinflammatory cytokine expression. Thus, the aim of the present study was to further our understanding about the high incidence of mastitis around parturition by comparison of plasma fatty acid profile and mammary inflammation indicators at different reproductive stages. A total of 47 female rats were included in the present study. After mating, all the pregnant and non-pregnant rats began to receive the same experimental diet. Blood samples were collected at day 1 and 14 of gestation as well as day 3 postpartum. Mammary samples were collected at day 14 of gestation and day 3 postpartum from pregnant and non-pregnant rats. The results showed that rats at d 3 postpartum had greater (P < 0.05) plasma concentrations of non-esterified fatty acids (NEFA), arachidonic acid (ARA) and docosahexaenoic acid (DHA) as well as ARA: eicosapentaenoic acid (EPA) ratio than those at d 14 of gestation. The mRNA abundances of interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), IL-8 and xanthine oxidoreductase (XOR) in mammary of the pregnant rats were greater (P < 0.05) than those in age-matched non-pregnant rats. Rats at d 3 postpartum had higher (P < 0.05) protein expression levels of IL-1β and TNF-α as well as meloperoxidase (MPO) activity and polymorphonuclear neutrophils (PMN) prevalence than those at d 1 of gestation. The rats at d 3 postpartum also had greater (P < 0.05) IL-1β and MPO activity than those at d 14 of gestation. The results indicated that elevated mammary expression of proinflammatory cytokines and XOR as well as altered fatty acid profile around parturition might facilitate the recruitment of neutrophils into mammary glands.

The cell wall component lipoteichoic acid of Staphylococcus aureus induces chemokine gene expression in bovine mammary epithelial cells

Staphylococcus aureus (SA) is a major cause of bovine mastitis, but its pathogenic mechanism remains poorly understood. To evaluate the role of lipoteichoic acid (LTA) in the immune or inflammatory response of SA mastitis, we investigated the gene expression profile in bovine mammary epithelial cells stimulated with LTA alone or with formalin-killed SA (FKSA) using cap analysis of gene expression. Seven common differentially expressed genes related to immune or inflammatory mediators were up-regulated under both LTA and FKSA stimulations. Three of these genes encode chemokines (IL-8, CXCL6 and CCL2) functioning as chemoattractant molecules for neutrophils and macrophages. These results suggest that the initial inflammatory response of SA infection in mammary gland may be related with LTA induced chemokine genes.

Defensin γ-thionin from Capsicum chinense has immunomodulatory effects on bovine mammary epithelial cells during Staphylococcus aureus internalization

β-Defensins are members of the antimicrobial peptide superfamily that are produced in various species from different kingdoms, including plants. Plant defensins exhibit primarily antifungal activities, unlike those from animals that exhibit a broad-spectrum antimicrobial action. Recently, immunomodulatory roles of mammal β-defensins have been observed to regulate inflammation and activate the immune system. Similar roles for plant β-defensins remain unknown. In addition, the regulation of the immune system by mammalian β-defensins has been studied in humans and mice models, particularly in immune cells, but few studies have investigated these peptides in epithelial cells, which are in intimate contact with pathogens. The aim of this work was to evaluate the effect of the chemically synthesized β-defensin γ-thionin from Capsicum chinense on the innate immune response of bovine mammary epithelial cells (bMECs) infected with Staphylococcus aureus, the primary pathogen responsible for bovine mastitis, which is capable of living within bMECs. Our results indicate that γ-thionin at 0.1 μg/ml was able to reduce the internalization of S. aureus into bMECs (∼50%), and it also modulates the innate immune response of these cells by inducing the mRNA expression (∼5-fold) and membrane abundance (∼3-fold) of Toll-like receptor 2 (TLR2), as well as by inducing genes coding for the pro-inflammatory cytokines TNF-α and IL-1β (∼14 and 8-fold, respectively) before and after the bacterial infection. γ-Thionin also induces the expression of the mRNA of anti-inflammatory cytokine IL-10 (∼12-fold). Interestingly, the reduction in bacterial internalization coincides with the production of other antimicrobial products by bMECs, such as NO before infection, and the secretion into the medium of the endogenous antimicrobial peptide DEFB1 after infection. The results from this work support the potential use of β-defensins from plants as immunomodulators of the mammalian innate immune response.