Lactobacillus casei Zhang Counteracts Blood-Milk Barrier Disruption and Moderates the Inflammatory Response in Escherichia coli-Induced Mastitis

ALKBH5 Improves the Epithelial Cell Tight Junctions to Inhibit Escherichia coli-Induced Mastitis

Mastitis poses a severe threat to the global cattle industry, causing huge economic losses. Environmental mastitis is mainly induced by Escherichia coli (E. coli), and the current treatment is still using antibiotics, with problems such as drug resistance and food safety. ALKBH5 is an RNA m6A demethylase that plays an important role in various biological processes, while p65 is a key regulator of inflammatory responses. Therefore, studying the interaction between ALKBH5 and p65 in protecting the mammary epithelial barrier provides new insights into the pathogenesis of mastitis. This study revealed that E. coli-induced acute inflammation activated the NF-κB/p65 signaling pathway and disrupted mammary epithelial cell tight junctions. Knockdown of ALKBH5 promoted p65 phosphorylation and inhibited the expressions of the tight junction proteins TJP1, CDH1, and OCLN. Furthermore, motif analysis, CHIP-PCR, and dual luciferase assay confirmed that phosphorylated p65 inhibited TJP1 promoter activity, thereby inhibiting TJP1 expression. In addition, the mouse experiment further demonstrated that knockdown of ALKBH5 aggravated E. coli-induced acute mastitis and epithelial cell tight junction disruption, and promoted E. coli invasion and proliferation. Significantly, this study is the first to demonstrate the details of the interaction between p65 and TJP1 and to declare the molecular mechanism of ALKBH5 in improving the cell tight junction, which lays a potential target and theoretical foundation for the treatment of mastitis and other infectious diseases.

The preventive effect of probiotic Lactobacillus plantarum X86 isolated from raw milk on Staphylococcus aureus-induced mastitis in rats

Mastitis is the most common and challenging disease that affects dairy animal welfare and causes huge economic loss in dairy industry globally. Conventional antibiotic treatment of mastitis raised the drug resistance and unsuccessful therapy. As an alternative approach, probiotic lactobacilli had shown multifunctional effects against diseases. Lactobacillus strains against mastitis are worth screening and evaluating. In this study, milk-derived Lactobacillus spp. from Ningxia, China were screened in vitro and the anti-mastitis effect of a candidate strain was evaluated through a Staphylococcus aureus-induced rat mastitis model. The results showed that Lactobacillus plantarum X86 exhibited a high adhesion rate of MAC-T cells, presented the best probiotic properties, and demonstrated anti-S. aureus effects in vitro through comprehensive assessment. Furthermore, L. plantarum X86 alleviated pathological damage to the mammary gland, liver, and colon, inhibited the mRNA expression of pro-inflammatory cytokines factors IL-1β, IL-6, and TNF-α in mammary gland tissue; and increased the content of intestine SCFAs in a rat mastitis model induced by S. aureus. In conclusion, our results suggested that L. plantarum X86 could be a promising probiotic for the prevention and treatment of S. aureus-induced mastitis.

Hydroxy-selenomethionine helps cows to overcome heat stress by enhancing antioxidant capacity and alleviating blood-milk barrier damage

Heat stress can lead to decreased feed intake, apoptosis of mammary epithelial cells, and decreased milk yield and quality. Selenium is an important element in the composition of at least 25 selenoproteins. Hydroxy-selenomethionine (HMSeBA) is a novel organic selenium that has been shown to have a better deposition effect. However, whether HMSeBA alleviates damage to the mammary gland blood-milk barrier caused by heat stress and how this affects the performance of dairy cows remain largely unexplored. Therefore, 32 healthy Holstein cows with similar gestation days (150.41 ± 20.07 d), milk yield (36.15 ± 3.02 kg) and parity (3.25 ± 0.51) were selected and randomly divided into two total mixed rations with different selenium (Se) sources: sodium selenite (SSe) and HMSeBA. This study evaluated the outcomes of HMSeBA on antioxidant capacity, immunity, and blood-milk barrier damage in dairy cows during heat stress by collecting the samples of blood, rumen fluid and mammary gland biopsy. The experiment was conducted over 35 d, including a 5-day pre-feeding period and a 30-day experimental period. The temperature and humidity index (THI) were all above 80 throughout the experiment period. The results showed that HMSeBA decreased the respiratory rate (P < 0.001) and the content of inflammatory cytokines in the serum and increased the content of immune factors and antioxidant capacity (P < 0.05). In addition, HMSeBA reduced the expression of inflammatory cytokines and heat shock proteins in mammary gland (P < 0.05). Hematoxylin-eosin-stained pathological sections showed massive thickening of acinar walls and severe destruction of glandular structures in the SSe group, but the structure of the acinar mammary gland in the HMSeBA group was intact. Furthermore, HMSeBA promoted the expression of the phosphatidylinositol 3-kinase (PI3K, P < 0.001)/protein kinase B (AKT, P = 0.011)/mammalian target of rapamycin (mTOR, P = 0.008) pathway and improved the expression of zonula occludens-1 (ZO-1, P = 0.014) and occluding (OCLN, P = 0.012) in the mammary gland, suggesting less damage caused by heat stress to the blood-milk barrier. Our results demonstrated that HMSeBA can improve the antioxidant capacity and immunity of dairy cows and the expression of tight junction proteins in mammary gland to help alleviate the blood-milk barrier damage by heat stress, which could reduce the damage of heat stress on milk yield.

Ginsenoside Rg1 Alleviates Blood-Milk Barrier Disruption in Subclinical Bovine Mastitis by Regulating Oxidative Stress-Induced Excessive Autophagy

As a critical disease usually infected by Staphylococcus aureus, with a worldwide effect on dairy animals, subclinical mastitis is characterized by persistence and treatment resistance. During mastitis, the blood-milk barrier (BMB)'s integrity is impaired, resulting in pathogen invasion and milk quality decline. In this study, it was found that ginsenoside Rg1 (Rg1), a natural anti-inflammatory and antioxidant compound derived from ginseng, inhibited the onset of tight junction (TJ) dysfunction and ameliorated lipoteichoic acid (LTA)-induced BMB disruption inside and outside the organisms. According to subsequent mechanistic studies, Rg1 inhibited excessive autophagy and inactivated the NLRP3 inflammasome by blockading ROS generation, thereby alleviating TJ dysfunction. Peroxisome proliferator-activated receptor gamma (PPARγ) was identified as a potential target of Rg1 by means of molecular docking plus network pharmacology analysis. Furthermore, it was demonstrated that Rg1 inhibited the oxidative stress levels by activating PPARγ, and regulating the upstream autophagy-related AMPK/mTOR signaling pathway, thus decreasing excessive in vivo and in vitro autophagy. The ROS/autophagy/NLRP3 inflammasome axis was identified as a promising target for treating subclinical bovine mastitis in this study. In conclusion, Rg1 is proven to alleviate BMB disruption by activating PPARγ to inhibit oxidative stress and subsequent excessive autophagy in the case of subclinical bovine mastitis.

Functional Effects of Probiotic Lactiplantibacillus plantarum in Alleviation Multidrug-Resistant Escherichia coli-Associated Colitis in BALB/c Mice Model

Multidrug-resistant Escherichia coli (MDR-E. coli) is a global health concern. Lactic acid bacteria (LAB) are important probiotics that have beneficial effects on health, and in recent years, their influences in preventing foodborne pathogens-induced colitis have attracted much attention. Therefore, this study aimed to investigate the oral administration of Lactiplantibacillus plantarum NWAFU-BIO-BS29 as an emerging approach to alleviate MDR-E. coli-induced colitis in BALB/c mice model. To illustrate the mode of action of NWAFU-BIO-BS29 interventions with the gut microbiota and immune responses, the changes on the colonic mucosal barrier, regulatory of the gene expressions of inflammatory cytokines, re-modulating the intestinal microflora, and changes in physiological parameters were studied. The results indicated that daily supplementation of 200 µL fresh bacteria for 7 days had ameliorated the associated colitis and partially prevented the infection. The modes of action by ameliorating the inflammatory response, which destructed villous and then affected the intestinal barrier integrity, reducing the secretion of interleukins (6 and β) and tumor necrosis factor (TNF-α) in serum by 87.88-89.93%, 30.73-35.98%, and 19.14-22.32%, respectively, enhancing the expressions of some epithelial integrity-related proteins in the mouse mucous layer of mucins 2 and 3, Claudin-1, and Occludin by 130.00-661.85%, 27.64-57.35%, 75.52-162.51%, and 139.36-177.73%, respectively, and 56.09-73.58% for toll-like receptor (TLR4) in colon tissues. Notably, the mouse gut microbiota analysis showed an increase in the relative abundance of beneficial bacteria, including Lactobacillus, Bacteriodales bacterium, Candidatus Saccharimonas, Enterorhabdus, and Bacilli. Furthermore, the probiotic promoted the proliferation of epithelia and goblet cells by increasing short-chain fatty acids (SCFAs) levels by 19.23-31.39%. In conclusion, L. plantarum NWAFU-BIO-BS29 has potential applications and can be considered a safe dietary supplement to ameliorate the colitis inflammation symptoms of MDR-E. coli infection.

The preventive effects of Lactobacillus casei 03 on Escherichia coli-induced mastitis in vitro and in vivo

BACKGROUND

Lactobacillus casei possesses many kinds of bioactivities, such as anti-inflammation and anti-oxidant, and has been applied to treating multiple inflammatory diseases. However, its role in mastitis prevention has remained ambiguous.

METHODS

This study aimed to examine the mechanisms underlying the preventive effects of L. casei 03 against E. coli- mastitis utilizing bovine mammary epithelial cells (BMECs) and a mouse model.

RESULTS

In vitro assays revealed pretreatment with L. casei 03 reduced the apoptotic ratio and the mRNA expression levels of IL1β, IL6 and TNFα and suppressed phosphorylation of p65, IκBα, p38, JNK and ERK in the NF-κB signaling pathway and MAPK signaling pathway. Furthermore, in vivo tests indicated that intramammary infusion of L. casei 03 relieved pathological changes, reduced the secretion of IL1β, IL6 and TNFα and MPO activity in the mouse mastitis model.

CONCLUSIONS

These data suggest that L. casei 03 exerts protective effects against E. coli-induced mastitis in vitro and in vivo and may hold promise as a novel agent for the prevention and treatment of mastitis.

MicroRNA miR-223 modulates NLRP3 and Keap1, mitigating lipopolysaccharide-induced inflammation and oxidative stress in bovine mammary epithelial cells and murine mammary glands

Bovine mastitis, the most prevalent and costly disease in dairy cows worldwide, decreases milk quality and quantity, and increases cow culling. However, involvement of microRNAs (miRNAs) in mastitis is not well characterized. The objective was to determine the role of microRNA-223 (miR-223) in regulation of the nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3) inflammasome and kelch like ECH-associated protein 1 (Keap1)/nuclear factor erythroid 2-related factor 2 (Nrf2) oxidative stress pathway in mastitis models induced by lipopolysaccharide (LPS) treatment of immortalized bovine mammary epithelial cells (bMECs) and murine mammary glands. In bMECs cultured in vitro, LPS-induced inflammation downregulated bta-miR-223; the latter interacted directly with the 3' untranslated region (3' UTR) of NLRP3 and Keap1. Overexpression of bta-miR-223 in bMECs decreased LPS and Adenosine 5'-triphosphate (ATP)-induced NLRP3 and its mediation of caspase 1 and IL-1β, and inhibited LPS-induced Keap1 and Nrf2 mediated oxidative stress, whereas inhibition of bta-miR-223 had opposite effects. In an in vivo murine model of LPS-induced mastitis, increased miR-223 mitigated pathology in the murine mammary gland, whereas decreased miR-223 increased inflammatory changes and oxidative stress. In conclusion, bta-miR-223 mitigated inflammation and oxidative injury by downregulating the NLRP3 inflammasome and Keap1/Nrf2 signaling pathway. This study implicated bta-miR-223 in regulation of inflammatory responses, with potential as a novel target for treating bovine mastitis and other diseases.

In Vivo Functional Properties of Dairy Bacteria

This literature review aimed to collect investigations on the in vivo evidence for bacteria associated with fermented dairy foods to behave as probiotics with beneficial effects in the prevention and treatment of various diseases. All main bacterial groups commonly present in high numbers in fermented milks or cheeses were taken into account, namely starter lactic acid bacteria (SLAB) Lactobacillus delbrueckii subsp. bulgaricus and lactis, L. helveticus, Lactococcus lactis, Streptococcus thermophilus, non-starter LAB (NSLAB) Lacticaseibacillus spp., Lactiplantibacillus plantarum, dairy propionibacteria, and other less frequently encountered species. Only studies regarding strains of proven dairy origin were considered. Studies in animal models and clinical studies showed that dairy bacteria ameliorate symptoms of inflammatory bowel disease (IBD), mucositis, metabolic syndrome, aging and oxidative stress, cancer, bone diseases, atopic dermatitis, allergies, infections and damage caused by pollutants, mild stress, and depression. Immunomodulation and changes in the intestinal microbiota were the mechanisms most often involved in the observed effects. The results of the studies considered indicated that milk and dairy products are a rich source of beneficial bacteria that should be further exploited to the advantage of human and animal health.

Novel organic selenium source hydroxy-selenomethionine counteracts the blood-milk barrier disruption and inflammatory response of mice under heat stress

Heat stress (HS) in summer has caused huge economic losses to animal husbandry production recently. When mammary gland is exposed to high temperatures, it will cause blood-milk barrier damage. Hydroxy-selenomethionine (HMSeBA) is a new selenium source with better guarantee of animals' production performance under stress, but whether it has protective effect on heat stress-induced blood-milk damage is still unclear. We established mammary epithelial cells and mice heat stress injury models to fill this research gap, and hope to provide theoretical basis for using HMSeBA to alleviate heat stress damage mammary gland. The results showed that (1) Heat stress significantly decreases in vitro transepithelial electrical resistance (TEER) and cell viability (P < 0.01), and significantly decreases clinical score, histological score, and total alveoli area of mice mammary gland tissue (P < 0.01). (2) HMSeBA significantly increases TEER and fluorescein sodium leakage of HS-induced monolayer BMECs (P < 0.01), significantly improves the milk production and total area of alveoli (P < 0.01), and reduces clinical score, histological score, mRNA expression of heat stress-related proteins, and inflammatory cytokines release of heat-stressed mice (P < 0.01). (3) HMSeBA significantly improves tight junction structure damage, and significantly up-regulated the expression of tight junction proteins (ZO-1, claudin 1, and occludin) as well as signal molecules PI3K, AKT, and mTOR (P < 0.01) in heat-stressed mammary tissue. (4) HMSeBA significantly increases glutathione peroxidase (GSH-Px), total antioxidant capacity (T-AOC), and superoxide dismutase release (SOD) (P < 0.01) and significantly reduce malondialdehyde (MDA) expression (P < 0.01) in heat-stressed mammary tissue. In conclusion, this study implemented heat-stressed cell and mice model and showed that HMSeBA significantly regulate antioxidant capacity, inhibited inflammation, and regulate tight junction proteins expression in blood-milk barrier via PI3K/AKT/mTOR signaling pathway, so as to alleviate mammary gland damage and ensure its structure and function integrity.

Ethanol Extract of Artemisia Annua Prevents LPS-Induced Inflammation and Blood-Milk Barrier Disruption in Bovine Mammary Epithelial Cells

This experiment evaluated the pre-protective effect of AAE on inflammatory injury and tight junction disturbance in bMECs induced by LPS. The bMECs were treated with AAE (3, 6, 12 μg/mL) for 3 h and then incubated with 10 μg/mL lipopolysaccharide (LPS) for 12 h. Our results showed that LPS significantly increased the mRNA and protein expression of CD36, induced the phosphorylation of IκBα and p65 and elevated the levels of TNF-α, IL-1β and IL-6 mRNA, which further resulted in ultrastructural damage, disrupted the expression of tight junction proteins (occludin, zonula occludens (ZO-1) and claudin-1) and decreased the viability of bMECs (p < 0.05). More importantly, AAE pretreatment attenuated the expression of CD36, suppressed the activity of the NF-κB signaling pathway and down-regulated the levels of inflammatory factors in LPS-stimulated bMECs (p < 0.05). Therefore, AAE can effectively protect bMECs against inflammatory injury and tight junction dysfunction, which has important research value for the prevention of bovine mastitis.

Map of Enteropathogenic Escherichia coli Targets Mitochondria and Triggers DRP-1-Mediated Mitochondrial Fission and Cell Apoptosis in Bovine Mastitis

Bovine mastitis seriously affects bovine health and dairy product quality. Escherichia coli is the most important pathogen in the environment and dairy products. Enteropathogenic Escherichia coli (EPEC) is a zoonotic pathogen, which seriously threatens the health of people and dairy cows. We recently reported that E. coli can induce endogenous apoptosis in bovine mammary epithelial cells. However, the mechanism of EPEC-damaged mitochondria and -induced bovine mastitis is unclear. In this study, we found that EPEC can induce DRP-1-dependent mitochondrial fission and apoptosis. This was verified by the application of Mdivi, a DRP-1 inhibitor. Meanwhile, in order to verify the role of the Map virulence factor in EPEC-induced bovine mastitis, we constructed a map mutant, complementary strain, and recombinant plasmid Map_His. In the present study, we find that Map induced DRP-1-mediated mitochondrial fission, resulting in mitochondrial dysfunction and apoptosis. These inferences were further verified in vivo by establishing a mouse mastitis model. After the map gene was knocked out, breast inflammation and apoptosis in mice were significantly alleviated. All results show that EPEC targets mitochondria by secreting the Map virulence factor to induce DRP-1-mediated mitochondrial fission, mitochondrial dysfunction, and endogenous apoptosis in bovine mastitis.

Nisin Z attenuates lipopolysaccharide-induced mastitis by inhibiting the ERK1/2 and p38 mitogen-activated protein kinase signaling pathways

Nisin Z is a possible alternative for treating bovine mastitis by inhibiting mastitis-causing pathogens and having anti-inflammatory activity. However, the anti-inflammatory mechanism of nisin Z on mastitis is unknown. Our study aimed to investigate the mechanisms of nisin Z on mastitis. Our results showed that nisin Z inhibited the activation of the ERK1/2 and p38 mitogen-activated protein kinase (MAPK) signaling pathway, decreased the release of pro-inflammatory cytokines (i.e., tumor necrosis factor-α, IL-1β, and IL-6), and increased the anti-inflammatory cytokine (IL-10) in lipopolysaccharide (LPS)-induced MCF10A cells. After intraperitoneal injection, nisin Z significantly decreased inflammatory cell infiltration in the mammary gland, as well as decreased myeloperoxidase and pro-inflammatory cytokines in serum and mammary gland. Western blot analysis revealed that nisin Z also dramatically suppressed the activation of the ERK1/2 and p38 MAPK signaling pathways in LPS-induced mastitis mice. We also found that nisin Z treatment could enhance the blood-milk barrier. In summary, our study demonstrated that nisin Z exerted an anti-inflammatory effect by inhibiting the ERK1/2 and p38 MAPK signaling pathway and promoting the blood-milk barrier on LPS-induced mastitis.

N6-Methyladenosine Modification Profile in Bovine Mammary Epithelial Cells Treated with Heat-Inactivated Staphylococcus aureus

The symptoms of mastitis caused by Staphylococcus aureus (S. aureus) in dairy cows are not obvious and difficult to identify, resulting in major economic losses. N6-Methyladenosine (m6A) modification has been reported to be closely associated with the occurrence of many diseases. However, only a few reports have described the role of m6A modification in S. aureus-induced mastitis. In this study, after 24 h of treatment with inactivated S. aureus, MAC-T cells (an immortalized bovine mammary epithelial cell line) showed increased expression levels of the inflammatory factors IL-1β, IL-6, TNF-α, and reactive oxygen species. We found that the mRNA levels of METLL3, METLL14, WTAP, and ALKBH5 were also upregulated. Methylated RNA immunoprecipitation sequencing analysis revealed that 133 genes were m6A hypermethylated, and 711 genes were m6A hypomethylated. Biological functional analysis revealed that the differential m6A methylated genes were mainly related to oxidative stress, lipid metabolism, inflammatory response, and so on. In the present study, we also identified 62 genes with significant changes in m6A modification and mRNA expression levels. These findings elucidated the m6A modification spectrum induced by S. aureus in MAC-T cells and provide the basis for subsequent m6A research on mastitis.

An overview on mastitis-associated Escherichia coli: Pathogenicity, host immunity and the use of alternative therapies

Escherichia coli is one of the leading causes of bovine mastitis; it can cause sub-clinical, and clinical mastitis characterized by systemic changes, abnormal appearance of milk, and udder inflammation. E. coli pathogenicity in the bovine udder is due to the interaction between its virulence factors and the host factors; it was also linked to the presence of a new pathotype termed mammary pathogenic E. coli (MPEC). However, the presence of this pathotype is commonly debated. Its main virulence factor is the lipopolysaccharide (LPS) that is responsible for causing an endotoxic shock, and inducing a strong immune response by binding to the toll-like receptor 4 (TLR4), and stimulating the expression of chemokines (such as IL-8, and RANTES) and pro-inflammatory cytokines (such as IL-6, and IL-1β). This strong immune response could be used to develop alternative and safe approaches to control E. coli causing bovine mastitis by targeting pro-inflammatory cytokines that can damage the host tissue. The need for alternative treatments against E. coli is due to its ability to resist many conventional antibiotics, which is a huge challenge for curing ill animals. Therefore, the aim of this review was to highlight the pathogenicity of E. coli in the mammary gland, discuss the presence of the new putative pathotype, the mammary pathogenic E. coli (MPEC) pathotype, study the host's immune response, and the alternative treatments that are used against mastitis-associated E. coli.

Crosstalk between immune cells and bone cells or chondrocytes

The term "osteoimmunology" was coined to denote the bridge between the immune system and the skeletal system. Osteoimmunology is interdisciplinary, and a full understanding and development of this "bridge" will provide an in-depth understanding of the switch between body health and disease development. B lymphocytes can promote the maturation and differentiation of osteoclasts, and osteoclasts have a negative feedback effect on B lymphocytes. Different subtypes of T lymphocytes regulate osteoclasts in different directions. T lymphocytes have a two-way regulatory effect on osteoblasts, while B lymphocytes have minimal regulatory effects on osteoblasts. In contrast, osteoblasts can promote the differentiation and maturation of T lymphocytes and B lymphocytes. Different immune cells have different effects on chondrocytes; some cooperate with each other, while some antagonize each other. In a healthy adult body, bone resorption and bone formation are in a dynamic balance under the action of multiple mechanisms. In this review, we summarize the interactions and key signaling molecular mechanisms between each type of cell in the immune system and the skeletal system.