Graduate Student Literature Review: Systemic mediators of inflammation during mastitis and the search for mechanisms underlying impaired lactation

Modulatory Effects of Regulated Cell Death: An Innovative Preventive Approach for the Control of Mastitis

Mastitis is a common disease worldwide that affects the development of the dairy industry due to its high incidence and complex etiology. Precise regulation of cell death and survival plays a critical role in maintaining internal homeostasis, organ development, and immune function in organisms, and regulatory abnormalities are a common mechanism of various pathological changes. Recent research has shown that regulated cell death (RCD) plays a crucial role in mastitis. The development of drugs to treat cell death and survival abnormalities that can be widely used in mastitis treatment has important clinical significance. This paper will review the molecular mechanisms of apoptosis, autophagy, pyroptosis, ferroptosis, and necroptosis and their regulatory roles in mastitis to provide a new perspective for the targeted treatment of mastitis.

Polyphenols and Lactation: Molecular Evidence to Support the Use of Botanical Galactagogues

Botanicals and herbal supplements contain a diverse array of polyphenols that may affect mammary gland function and promote galactagogue activity. This scoping review is conducted to identify scientific literature elucidating how polyphenols affect mammary gland biology and cellular mechanisms critical for lactation. A literature search of PubMed and Medline reviews relevant studies in dairy animals, rodent models, and cultured mammary epithelial cells that are published from January 2010 until July 2023, to ascertain effects of polyphenols on mechanisms regulating milk production and composition. The PRISMA-ScR (Preferred Reporting Items for Systematic Reviews and Meta-Analyses for Scoping Review) strategy is applied and 80 studies on polyphenols and their implications on milk production and composition are included in this review. Limited information delineating effects of polyphenols on the molecular pathways that affect lactation are found, although available information suggests modulation of Stat5 signaling/differentiation, Stat3 signaling/remodeling, mTOR and insulin signaling/energy production, and nuclear factor kappa beta (NFκβ) signaling/oxidative stress and inflammation may play roles. A profound lack of mechanistic information underscores the critical need for further research to understand the impact of botanical supplements and polyphenols on milk production and composition in humans to establish maternal nutritional guidelines to support lactation and breastfeeding goals.

Comparison of the gastrointestinal bacterial microbiota between dairy cows with and without mastitis

Mastitis causes significant losses in the global dairy industry, and the health of animals has been linked to their intestinal microbiota. To better understand the relationship between gastrointestinal microbiota and mastitis in dairy cows, we collected blood, rumen fluid, and fecal samples from 23 dairy cows, including 13 cows with mastitis and 10 healthy cows. Using ELISA kit and high-throughput sequencing, we found that cows with mastitis had higher concentrations of TNF-α, IL-1, and LPS than healthy cows (p < 0.05), but no significant differences in microbiota abundance or diversity (p > 0.05). Principal coordinate analysis (PCOA) revealed significant differences in rumen microbial structure between the two groups (p < 0.05), with Moryella as the signature for rumen in cows with mastitis. In contrast, fecal microbial structure showed no significant differences (p > 0.05), with Aeriscardovia, Lactococcus, and Bacillus as the signature for feces in healthy cows. Furthermore, the results showed distinct microbial interaction patterns in the rumen and feces of cows with mastitis compared to healthy cows. Additionally, we observed correlations between the microbiota in both the rumen and feces of cows and blood inflammatory indicators. Our study sheds new light on the prevention of mastitis in dairy cows by highlighting the relationship between gastrointestinal microbiota and mastitis.

The inhibition effect of caffeic acid on NOX/ROS-dependent macrophages M1-like polarization contributes to relieve the LPS-induced mice mastitis

The mammary gland is an adipose tissue containing not only adipocytes but also epithelial, endothelial, and immune cells. Epithelial cells and macrophages, as the integral components of the immune system, are on the front line of defense against infection. Our preliminary work proved that caffeic acid (CA) can effectively inhibit the inflammatory cascade of bovine mammary epithelial cells (BMEC) induced by lipopolysaccharide (LPS) and maintain cellular integrity and viability. Here, we investigated the therapeutic effect of CA on LPS-induced mice mastitis and explored its regulatory mechanism on macrophage inflammatory response induced by LPS in vitro. Firstly, the mice mastitis model was established by intramammary injection with 10 μg LPS, after which different CA doses (5, 10, 15 mg/kg) were administered. Then, the pathological section, myeloperoxidase (MPO) activity, proinflammatory factors and chemokines releasement, and redox state of mammary tissues were assessed, confirming CA's effectiveness on mice mastitis. In vitro, we validated the therapeutic relevance of CA in relieving LPS-induced RAW264.7 inflammatory and oxidative stress responses. Moreover, we further provided evidence that CA significantly reduced LPS-induced reactive oxygen species (ROS) generation via NADPH oxidase (NOX), which improved the imbalance relationship between nuclear factor kappa-B (NF-κB) and NF-E2 p45-related factor 2 (Nrf2) and led to a marked weakening of M1 polarization. The NOX-ROS signal inhibited by CA weakened the oxidative burst and neutrophil chemotaxis of macrophages, thus alleviating the immune cascade in mammary gland tissue and reducing the LPS-induced inflammatory damage. Collectively, CA would be a potential candidate or antibacterial synergist for curbing mastitis.

Maslinic acid alleviates LPS-induced mice mastitis by inhibiting inflammatory response, maintaining the integrity of the blood-milk barrier and regulating intestinal flora

Mastitis occurs frequently in breastfeeding women and not only affects the women's health but also hinders breastfeeding. Maslinic acid is a type of pentacyclic triterpenoid widely found in olives that has good anti-inflammatory activity. This study aims to discuss the protective function of maslinic acid against mastitis and its underlying mechanism. For this, mice models of mastitis were established using lipopolysaccharide (LPS). The results revealed that maslinic acid reduced the pathological lesions in the mammary gland. In addition, it reduced the generation of pro-inflammatory factors and enzymes (IL-6, IL-1β, TNF-α, iNOS, and COX2) in both mice mammary tissue and mammary epithelial cells. The high-throughput 16S rDNA sequencing of intestinal flora showed that in mice with mastitis, maslinic acid treatment altered β-diversity and regulated microbial structure by increasing the abundance of probiotics such as Enterobacteriaceae and downregulating harmful bacteria such as Streptococcaceae. In addition, maslinic acid protected the blood-milk barrier by maintaining tight-junction protein expression. Furthermore, maslinic acid downregulated mammary inflammation by inhibiting the activation of NLRP3 inflammasome, AKT/NF-κB, and MAPK signaling pathways. Thus, in a mice model of LPS-induced mastitis, maslinic acid can inhibit the inflammatory response, protect the blood-milk barrier, and regulate the constitution of intestinal flora.

Feeding citrus flavonoid extracts decreases bacterial endotoxin and systemic inflammation and improves immunometabolic status by modulating hindgut microbiome and metabolome in lactating dairy cows

The objectives of this study were to determine the effects of dietary supplementation with citrus flavonoid extracts (CFE) on milk performance, serum biochemistry parameters, fecal volatile fatty acids, fecal microbial community, and fecal metabolites in dairy cows. Eight multiparous lactating Holstein cows were used in a replicated 4 × 4 Latin square design (21-day period). Cows were fed a basal diet without addition (CON) or basal diet with added CFE at 50 (CFE50), 100 (CFE10), and 150 g/d (CFE150). Feeding CFE up to 150 g/d increased milk yield and milk lactose percentage. Supplementary CFE linearly decreased milk somatic cell count. Serum cytokines interleukin-1β (IL-1β), IL-2, IL-6, and tumor necrosis factor-α (TNF-α) concentrations decreased linearly as the levels of CFE increased. Cows in CFE150 had lower serum lipopolysaccharide and lipopolysaccharide binding protein compared with CON. These results indicate feeding CFE decreased systemic inflammation and endotoxin levels in dairy cows. Furthermore, feeding CFE linearly increased the concentrations of total volatile fatty acids, acetate, and butyrate in feces. The relative abundances of beneficial bacteria Bifidobacterium spp., Clostridium coccoides-Eubacterium rectale group, and Faecalibacterium prausnitzii in feces increased linearly with increasing CFE supplementation. The diversity and community structure of fecal microbiota were unaffected by CFE supplementation. However, supplementing CFE reduced the relative abundances of genera Ruminococcus_torques_group, Roseburia, and Lachnospira, but increased genera Bacteroides and Phascolarctobacterium. Metabolomics analysis showed that supplementary CFE resulted in a significant modification in the fecal metabolites profile. Compared with CON, fecal naringenin, hesperetin, hippuric acid, and sphingosine concentrations were greater in CFE150 cows, while fecal GlcCer(d18:1/20:0), Cer(d18:0/24:0), Cer(d18:0/22:0), sphinganine, and deoxycholic acid concentrations were less in CFE150 cows. Predicted pathway analysis suggested that "sphingolipid metabolism" was significantly enriched. Overall, these results indicate that citrus flavonoids could exert health-promoting effects by modulating hindgut microbiome and metabolism in lactating cows.

Transcriptomic changes underlying glucocorticoid-induced suppression of milk production by dairy cows

Milk production by dairy cows is sensitive to increased levels of stress hormones such as glucocorticoids (GC) that also regulate the transcription of several genes required for milk synthesis. Whereas previous studies identified that an exogenous GC such as dexamethasone (DEX) transiently suppresses milk yield in several species without any pronounced effect on milk protein or fat percentage, the mechanism underlying this effect has not been established. In this study we sought to establish changes within the mammary glands of non-pregnant dairy cows in their second lactation (n = 3-4; 648-838 kg) following a single dose of exogenous DEX. Changes in the udder were monitored by serial biopsy of alternating quarters, concurrent with quarter-level monitoring of milk yield and composition. Dexamethasone increased serum glucose levels from 12-36 h (p <0 .05), reduced milk yield from 12-48 h (p <0 .05), increased % milk protein content at 24 h post-DEX, and transiently decreased both milk lactose and α-lactalbumin content, while not altering the level of milk fat. After 72 h, all aspects of milk production had returned to pre-treatment levels. Transcriptomic changes in the mammary glands in response to DEX were identified by RNA sequencing followed by differential gene expression analysis. Coincident with the milk yield and composition changes was the differential expression of 519 and 320 genes at 12 and 24 h after DEX (adjusted p <0 .05), respectively, with the return of all gene expression to baseline levels by 72 h. Among the transcriptomic changes in response to DEX, there was notable downregulation of elements in the lactose synthesis pathway, specifically AQP3, GALE and LALBA (α-lactalbumin) at 12 h, and sustained downregulation of LALBA at 24 h. One gene in the pathway, UGP2, was upregulated at 12-24 h post-DEX. This work supports the hypothesis that there is a direct relationship between the response to DEX and the concurrent suppression of milk yield due to the reduced synthesis of α-lactalbumin and lactose by the mammary epithelium. The ability of glucocorticoids to modulate the homeorrhetic requirements for glucose during stressful states concurrent with immune activation bears significance for dairy animals as well as a broad range of lactating mammals.

Inflammatory pathophysiological mechanisms implicated in postpartum depression

Postpartum Depression (PPD) is a serious psychiatric disorder of women within the first year after delivery. It grievously damages women's physical and mental health. Inflammatory reaction theory is well-established in depression, and also has been reported associated with PPD. This review summarized the inflammatory pathophysiological mechanisms implicated in PPD, including decreased T cell activation, increased proinflammatory cytokines secretion, active kynurenine pathway, and initiated NLRP3 inflammasome. Clinical and preclinical research are both gathered. Potential therapeutical alternatives targeting the inflammatory mechanisms of PPD were introduced. In addition, this review briefly discussed the differences of inflammatory mechanisms between PPD and depression. The research of inflammation in PPD is limited and seems just embarking, which indicates the direction we can further study. As a variety of risky factors contribute to PPD collectively, therapy for women with PPD should be comprehensive, and clinical heterogeneity should be taken into consideration. As PPD has a predictability, early clinical screening and interventions are also needed. This review aims to help readers better understand the inflammatory pathological mechanisms in PPD, so as to identify biomarkers and potential therapeutic targets in the future.

Preliminary Investigation of the Effects of Rosemary Extract Supplementation on Milk Production and Rumen Fermentation in High-Producing Dairy Cows

Rosemary extract (RE) has been used as an antioxidant in cosmetics and food additives, indicating its potential as a feed additive to improve adaptation in high-producing dairy cows. Here, we investigated the effects of RE supplementation on lactation performance and rumen fermentation in high-producing dairy cows. Thirty multiparous cows were blocked into 15 groups based on milk production and were randomly assigned to one of two treatments: 0 or 28 g/d of RE supplementation to the basic diet per cow. The experiment was conducted over a 74-day period, which included an initial two-week adaptation period. We observed significant increases in milk and milk lactose yields following RE supplementation. Somatic cell count tended to decrease by treatment. Additionally, superoxide dismutase concentration significantly increased and malonaldehyde level decreased after RE supplementation. Sequencing of 16S rRNA revealed that RE supplementation significantly affected the microbial composition and decreased the richness of the microbiota. Specifically, the abundance of the genus Prevotella was significantly decreased by RE supplementation and was correlated with volatile fatty acids in the Mantel test, whereas no significant correlation was found for other genera. Our findings provide fundamental information on the potential for RE as a feed additive for dairy cows to improve antioxidant status and enhance propionate generation.