Takahiro Nii

Immune system is regulated by circadian rhythms, which promote inflammation and facilitate pathogen elimination. Antimicrobial peptides secreted by milk so

Osmotic and hydrostatic (intramammary pressure) pressures within the mammary gland may stimulate mammary epithelial cells and leukocytes, which alter milk production and immune functions. We aimed to clarify the effects of different volumes and concentrations of NaCl solution on milk and antimicrobial substance production in lactating goats. Intramammary infusions of different NaCl solution concentrations (0.9% and 2.7%) at different volumes (50 mL or until full in the udder) were carried out; milk samples were collected for 5 days after infusion. The infusions resulted in significant daily effects on milk yield, somatic cell count (SCC), sodium ion (Na ⁺ ) and potassium ion (K ⁺ ), milk amyloid A (MAA), S100A7, and lactoferrin (LF) concentrations. Sodium and potassium ions, SCC, and MAA levels differed depending on the infused volume, whereas those of S100A7 and LF differed according to the NaCl concentration. These results suggest that short‐term increases in hydrostatic and osmotic pressures modulate milk production and stimulate antimicrobial factor production in the mammary glands. Hence, they highlight a potential approach toward enhancing innate immune function in the udder.

Mastitis is a major cause of economic losses in dairy production; however, its prevention and treatment remain challenging. Under field conditions, antimicrobial drugs are frequently administered when somatic cell counts (SCCs) are elevated and signs of inflammation are observed, even in the absence of detectable pathogens in milk. As antimicrobial therapy may be unnecessary during the healing phase of inflammation, improved indicators of the mastitis stage are required. Therefore, this study aimed to determine whether changes in milk antimicrobial component (AMC) concentrations could serve as indicators of the inflammatory stage, thereby supporting judicious antimicrobial use. Lactating Tokara goats received an intramammary infusion of lipopolysaccharide (LPS) to induce experimental mastitis, with saline‐infused quarters serving as controls. Milk samples were collected for up to 120 h post‐infusion to measure SCC and the concentrations of lactoferrin (LF), goat β‐defensin 1 (GBD1), cathelicidin‐7, S100A8, and milk amyloid A (MAA). SCC peaked at 10 h, whereas GBD1 tended to peak at 4 h, indicating early inflammation. In contrast, LF, S100A8, and MAA, together with the increasing tendency of Cath‐7 levels, peaked later (36–84 h) as SCC declined, suggesting an association with the recovery phase. These findings demonstrate that temporal patterns of milk AMCs can be used to stage mastitis progression.

A previous study found that repeated intrauterine infusions of lipopolysaccharide (LPS) followed by an LPS infusion into the mammary glands attenuated the mammary inflammatory response. This suggests that repeated LPS infusion into the uterus promotes endotoxin tolerance (ET) in the mammary gland. However, the specific changes in mammary glands under ET conditions remain unclear. We hypothesized that ET affects leukocyte function in milk. This study aimed to investigate leukocyte function in milk under ET conditions induced through repeated LPS infusions into the uterus for three days followed by LPS infusion into the mammary glands of goats. Goats in the IU group (n = 17) received an infusion of 100 μg LPS in 5 ml saline into the uterus for three consecutive days (d −3, −2, and −1), whereas the goats in the control group did not receive this infusion (n = 19). On d 0, 1 μg LPS in 5 ml saline was infused into the mammary glands of both groups. Milk was collected 0, 4, 8, 12, 24, 48, 72, and 120 h after LPS intramammary infusion. The IU group decreased cytokine production (interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and IL-1Ra) in milk following intramammary LPS infusion. Moreover, leukocyte activation, measured by phagocytic activity and CD11b expression, was higher in the IU group than in the control group. These findings suggest that goats exhibit enhanced leukocyte function in mammary glands under ET conditions, induced by repeated intrauterine infusion of LPS.

Aging and inflammation of the intestinal and oviductal mucosa reduce egg production in laying hens. In mammals, microbiota changes in the intestine and reproductive mucosa are linked to aging and mucosal inflammation, but this relationship remains unclear in hens. The present study aimed to investigate the impact of aging on microbiota and inflammation in the intestinal and oviductal mucosa of hens. Sixteen White Leghorn hens aged ~280 days (young) and ~730 days (aged) were used. Bacterial DNA was extracted from feces and vaginal swabs for 16S rRNA amplicon sequencing. Intestinal (ileum and cecum) and oviductal (uterus and vagina) tissues were processed for histological analysis. Real-time PCR was performed to profile pro- and anti-inflammatory cytokines, tight junction-related molecules, and calbindin in the uterus. Whereas microbial diversity and composition in the vagina did not change with age; alpha-diversity of intestinal bacteria was lower in the aged group, as suggested by 46 genera showing a decrease and five an increase. The morphology of the ileum mucosa deteriorated, with transforming growth factor (TGF)β3 being upregulated and claudin (CLA)3 being downregulated in the intestine of the aged group. Finally, fibrosis progressed with age in the uterine mucosa, along with overexpression of IL-1β, TGFβ3, TGFβ4, and CLA1, but downregulation of calbindin in the oviductal mucosa. These results suggest that aging may impair intestinal and oviductal health through mucosal inflammation in both the intestine and oviduct of laying hens. This change may be related to alterations in the intestinal microbiota but appears less evident in the vagina.

Interleukin‐1 receptor antagonist (IL‐1ra) is an anti‐inflammatory cytokine, whose balance with pro‐inflammatory cytokines affects the susceptibility to and severity of udder mastitis. In this study, we aimed to investigate the IL‐1ra dynamics in the mammary gland immune system. Lipopolysaccharide (LPS group) or saline (control group) were infused into mammary gland of goats. Milk samples were collected 0–72 h after intramammary infusion. The results indicated that LPS infusion increased the somatic cell count and serum amyloid A level in milk, compared to those in the control group. The IL‐1ra concentration in milk decreased after LPS infusion and was significantly lower at 4 h in the LPS group compared to that in the control group. The number of IL‐1ra‐positive cells significantly increased from 8 to 12 h in the LPS group. Immunohistochemistry revealed IL‐1ra‐positive cells in the alveolar connective tissue. Notably, the number of phagocytic cells and IL‐1ra mRNA expression did not change significantly after LPS infusion. Overall, these results suggest that IL‐1ra mRNA is expressed and synthesized in leukocytes, but is not secreted into milk for at least 72 h after intramammary LPS infusion. Furthermore, these findings highlight the role of IL‐1ra in controlling inflammation in the mammary glands.