Sodium Acetate and Sodium Butyrate Differentially Upregulate Antimicrobial Component Production in Mammary Glands of Lactating Goats

Effect of sodium butyrate treatment at the basolateral membranes on the tight junction barrier function via a monocarboxylate transporter in goat mammary epithelial cells

In lactating mammary glands, tight junctions (TJs) prevent blood from mixing with milk and maintain epithelial cell polarity, which is important for milk production. This study aimed to investigate the effect of sodium acetate and sodium butyrate (SB) stimulation direction on the TJ barrier function, which is measured with regard to transepithelial electrical resistance and fluorescein flux, in goat mammary epithelial cells. The expression and localization of the TJ proteins claudin-3 and claudin-4 were examined using Western blotting and immunofluorescence. SB treatment in the lower chamber of cell culture inserts adversely affected the TJ barrier function, whereas sodium acetate barely had any effect, regardless of stimulation direction. In addition, SB treatment in the lower chamber significantly upregulated claudin-3 and claudin-4, whereas TJ proteins showed intermittent localization. Moreover, SB induced endoplasmic reticulum (ER) stress. ARC155858, a monocarboxylate transporter-1 inhibitor, alleviated the adverse impact of SB on TJs and the associated ER stress. Interestingly, sodium β-hydroxybutyrate, a butyrate metabolite, did not affect the TJ barrier function. Our findings indicate that sodium acetate and SB influence the TJ barrier function differently, and excessive cellular uptake of SB can disrupt TJs and induce ER stress.

Effect of milking time on yield, composition, and antimicrobial components of milk in lactating goats

Various studies have attempted to improve the milk yield and composition in dairy animals. However, no study has examined the effects of milking at different times on milk yield and composition. Therefore, this study aimed to compare the yield, composition, and antimicrobial components of milk obtained from milking at different times in lactating goats. Eight goats were milked once daily at different times for three consecutive weeks (first week: 06:00 h; second week: 09:00 h; and third week: 12:00 h). The light ranged from 06:30 to 19:00 h. Milk and blood samples were collected once a day during milking time. Milking at 09:00 h resulted in a significantly higher milk yield than that obtained after milking at 06:00 and 12:00 h. Prolactin levels in plasma and the fat, Na+, β-defensin, and S100A7 (antimicrobial component) levels in milk were the lowest in the 09:00 h milking. These results indicate that milk yield, composition, and antimicrobial components can be affected by milking time, which may be related to the altered concentration of prolactin in the blood. These findings provide a rational basis for achieving maximal milk production with strong immunity by changing to a more effective milking time.

Effect of intramammary lipopolysaccharide challenge after repeated intrauterine infusion of lipopolysaccharide on the inflammation status of goat mammary glands

Previous studies have shown that a single infusion of lipopolysaccharide (LPS) into the uterus induces mammary gland inflammation. However, repeated LPS infusions return the mammary glands to their basal state of inflammation. To confirm that this is a state of tolerance to LPS, we examined whether tolerance induced by repeated intrauterine LPS infusions limits mammary gland inflammation following subsequent intramammary LPS infusions. In the first experiment, three goats were treated with repeated intrauterine infusions of LPS dissolved in black ink for 5 consecutive days. Blood and milk samples were collected at 2, 4, 6, 12, 24, 48, 72, 96, and 120 h and smeared on glass slides to confirm the translocation of LPS from the uterus to the mammary gland. Black particles were detected in the blood and milk samples more than 2 h after the first infusion and in the connective tissue of the mammary gland after day 5. In the second experiment, goats were divided into two groups: an intrauterine infusion group (IU; n = 7) and a control group (CON; n = 6). The IU group received an intrauterine infusion of 100 μg of LPS in saline for 5 days. Subsequently, LPS was infused into the mammary glands of both groups to examine the effect of intrauterine treatment on the mammary inflammatory response after intramammary LPS infusion. Blood and milk samples were collected at 6, 12, and 24 h, and then daily until 7 d after the intramammary LPS challenge. Interestingly, a significant increase in the milk somatic cell count (SCC), IL-8, IL-1β, and TNF-α concentrations were observed in the CON group compared to the IU group. This suggests that pretreatment with repeated intrauterine infusions of LPS suppresses the inflammatory responses to subsequent intramammary LPS challenges.

The Relationship between Mastitis and Antimicrobial Peptide S100A7 Expression in Dairy Goats

S100A7 is an inflammation-related protein and plays an essential role in host defenses, yet there is little research about the relationship between mastitis and S100A7 expression in dairy goats. Here, according to the clinical diagnosis of udders, SCC, and bacteriological culture (BC) of milk, 84 dairy goats were grouped into healthy goats (n = 25), subclinical mastitis goats (n = 36), and clinical mastitis goats (n = 23). The S100A7 concentration in subclinical mastitis goats was significantly upregulated than in healthy dairy goats (p = 0.0056) and had a limited change with clinical mastitis dairy goats (p = 0.8222). The relationship between log10 SCC and S100A7 concentration in milk was positive and R = 0.05249; the regression equation was Y = 0.1446 × X + 12.54. According to the three groups, the log10 SCC and S100A7 were analyzed using the receiver operating characteristics (ROC) curve; in subclinical mastitis goats, the area under the ROC curve (AUC) of log10 SCC was 0.9222 and p < 0.0001, and the AUC of S100A7 concentration was 0.7317 and p = 0.0022, respectively; in clinical mastitis goats, the AUC of log10 SCC was 0.9678 and p < 0.0001, and the AUC of S100A7 concentration was 0.5487 and p = 0.5634, respectively. In healthy goats, S100A7 was expressed weakly in the alveolus of the mammary gland of healthy goats while expressed densely in the collapsed alveolus of mastitis goats. Moreover, S100A7 expression increased significantly in mastitis goats than in healthy dairy goats. In this research, results showed the effects of mastitis on the S100A7 expression in the mammary gland and S100A7 concentration in milk and the limited relationship between SCC and mastitis, which provided a new insight into S100A7's role in the host defenses of dairy goats.

Potential effects of gingerol topical application on components of the innate immunity in lactating goat mammary glands

In the mammary glands, production of antimicrobial components and formation of less-permeable tight junctions (TJs) are important for safe milk production. Previously, we reported that local heat treatment of udders using disposable heating pad enhances the components of innate immunity in lactating goat mammary glands. Gingerol is a polyphenol present in ginger that can induce heat-like effects. However, oral administration of polyphenols causes a decrease in biological activity through conjugation and metabolic conversion. Here, we investigated the effects of gingerol on antimicrobial components and TJs by topically applying it to lactating goat udders. Gingerol application increased the somatic cell count, cathelicidin-2 concentration, and proportion of polymorphonuclear cells in the milk and interleukin-8 production. Moreover, gingerol treatment enhanced β-defensin-1 production in milk, cultured mammary epithelial cells, and cultured somatic cells. Contrastingly, gingerol treatment did not affect the concentrations of blood-derived components (Na+, albumin, and IgG) in the milk or the TJ barrier function of cultured mammary epithelial cells. These findings suggest that the topical application of gingerol, similar to local heat treatment, to udders enhances the components of innate immunity in mammary glands. These findings may be useful for the prevention of mastitis in milk-producing animals and, hence, safe and stable dairy production.

Valine Treatment Enhances Antimicrobial Component Production in Mammary Epithelial Cells and the Milk of Lactating Goats Without Influencing the Tight Junction Barrier

The production of antimicrobial components and the formation of less-permeable tight junctions (TJs) are important in the defense system of lactating mammary glands and for safe dairy production. Valine is a branched-chain amino acid that is actively consumed in the mammary glands and promotes the production of major milk components like β-casein; additionally, branched-chain amino acids stimulate antimicrobial component production in the intestines. Therefore, we hypothesized that valine strengthens the mammary gland defense system without influencing milk production. We investigated the effects of valine in vitro using cultured mammary epithelial cells (MECs) and in vivo using the mammary glands of lactating Tokara goats. Valine treatment at 4 mM increased the secretion of S100A7 and lactoferrin as well as the intracellular concentration of β-defensin 1 and cathelicidin 7 in cultured MECs. In addition, an intravenous injection of valine increased S100A7 levels in the milk of Tokara goats without influencing milk yield and milk components (i.e., fat, protein, lactose, and solids). In contrast, valine treatment did not affect TJ barrier function either in vitro or in vivo. These findings indicate that valine enhances antimicrobial component production without influencing milk production and TJ barrier function in lactating mammary glands; thus, valine contributes to safe dairy production.

Effect of repeated intrauterine infusion of lipopolysaccharides on mastitis in goats

A single infusion of lipopolysaccharide (LPSs) into the uterus induces inflammation in the mammary gland. This indicates that LPS can translocate from the uterus to the mammary gland. Natural endometritis is characterized by continuous intrauterine inflammation. The aim of the present study was to determine the effect of repeated intrauterine infusion of two different types of LPSs obtained from Escherichia coli O111:B4 (LPS-O111) and O55:B5 (LPS-O55) on the inflammatory status of the mammary glands of goats. Goats were assigned to three groups: LPS-O111, LPS-O55, and saline (control). Saline with (LPS-O111 and 55 groups) and without (control) 100 μg LPS was infused into the uterus continuously for 7 days. Decreased milk yield was detected in both LPS-O111 and LPS-O55 groups 2 days after the first LPS infusion. While somatic cell count (SCC) was significantly increased in all groups 1 day after the first LPS infusion, both LPS infusions further increased SCC 2 days after the first infusion and showed a significantly higher SCC than that in the control group. Plasma LPS-binding protein (LBP) was significantly higher in both LPS groups than in the control group during the days after infusion. In addition, pro-inflammatory cytokines, interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and IL-8, were significantly increased in both LPS infusion groups compared with those in the control group. The LPS-O111 infusion resulted in higher SCC, LBP, TNF-α, and IL-8 concentrations than those in the LPS-O55 group. These results suggest that repeated LPS infusion into the uterus can induce more severe mammary gland inflammation than a single infusion. Interestingly, the mammary tissues recovered from inflammation even though the LPS intrauterine infusion was continued.