cis-9, trans-11-Conjugated Linoleic Acid Exerts an Anti-inflammatory Effect in Bovine Mammary Epithelial Cells after Escherichia coli Stimulation through NF-κB Signaling Pathway

The composition of linoleic acid and conjugated linoleic acid has potent synergistic effects on the growth and death of RAW264.7 macrophages: The role in anti-inflammatory effects

Linoleic acid (LA) is an omega-6 polyunsaturated fatty acid. Conjugated linoleic acid (CLA) is a family of LA isomers that includes both a trans fatty acid and a cis fatty acid. Both fatty acids play a nutritional role in maintaining health. Inflammation is critical in the pathogenesis of many diseases, including cancer. This study found that the combination of LA and CLA (LA/CLA), each of which had no effect, had a strong anti-synergistic effect on inflammatory macrophage RAW264.7 cells in vitro. Cells were cultured in a DMEM containing fetal bovine serum with or without either LA, CLA, or a combination of LA/CLA. The composition of LA and CLA at a comparatively lower concentration synergistically suppressed cell growth, resulting in a reduction in cell number. The underlying mechanism of this effect was based on reduced levels of Ras, PI3K, Akt, MAPK, and mTOR and elevated levels of p21, p53, and Rb, which are associated with cell growth. In addition, the combination of LA and CLA at a lower concentration stimulated potential cell death associated with increased caspase-3 and cleaved caspase-3 levels. Notably, this composition synergistically suppressed the production of TNF-α, IL-6, and PGE2, which are a major mediator of inflammation, with lipopolysaccharide stimulation in RAW264.7 cells This effect was associated with decreased levels of COX-1, COX-2, and NF-κB p65. This study may provide a useful tool for treating inflammatory conditions with the composition of LA and CLA.

Subacute ruminal acidosis induces pyroptosis via the mitophagy-mediated NLRP3 inflammasome activation in the livers of dairy cows fed a high-grain diet

High-grain (HG) feeding can trigger subacute ruminal acidosis (SARA) and subsequent liver tissue injury. This study investigated pyroptosis and NLRP3 inflammasome activation in SARA-induced liver injury, and the role of mitophagy during this process. Twelve mid-lactating Holstein cows equipped with rumen fistulas were randomly divided into 2 groups: a low-grain (LG) diet group (grain:forage = 4:6) and a HG diet group (grain:forage = 6:4). Each group had 6 cows. The experiment lasted for 3 wk. The ruminal fluid was collected through the rumen fistula on experimental d 20 and 21, and the pH immediately measured. At the end of the experiment, all animals were slaughtered, and peripheral blood and liver tissue were collected. The ruminal pH was lower in the HG group than that in the LG group at all time points. In addition, the ruminal pH in the HG group was lower than 5.6 at 3 consecutive time points after feeding (4, 6, and 8 h on d 20; 2, 4, and 6 h on d 21), indicating that HG feeding induced SARA. The content of lipopolysaccharide, IL-1β, and apoptosis-related cysteine protease 1 (caspase-1) and the activity of alanine aminotransferase and aspartate aminotransferase in the blood plasma of the HG group were all significantly increased. Hepatic caspase-1 activity was increased in the livers of the HG group. The increased expression levels of pyroptosis- and NLRP3 inflammasome-related genes IL1B, IL18, gasdermin D (GSDMD), apoptosis-associated speck-like protein containing a card (ASC), NLR family pyrin domain-containing 3 (NLRP3), and caspase-1 (CASP1) in liver tissue of the HG group were detected. Furthermore, western blot analysis showed that HG feeding led to increased expression of pyroptosis- and NLRP3 inflammasome-related proteins GSDMD N-terminal (GSDMD-NT), IL-1β, IL-18, cleaved-caspase-1, ASC, NLRP3, and cleaved-caspase-11 and upregulated expression of mitophagy-related proteins microtubule-associated protein 1 light chain 3 II (MAP1LC3-II), beclin 1 (BECN1), Parkin, and PTEN-induced kinase 1 (PINK1) in liver tissue. Collectively, our results revealed that SARA caused increased mitophagy and activated the NLRP3 inflammasome, causing pyroptosis and subsequent liver injury in dairy cows fed a HG diet.

In vitro model of human mammary gland microbial colonization (MAGIC) demonstrates distinctive cytokine response to imbalanced human milk microbiota

Despite the established concept of the human mammary gland (MG) as a habitat with its own microbiota, the exact mechanism of MG colonization is still elusive and a well-characterized in vitro model would reinforce studies of the MG microbiota development. We aimed to establish and characterize an in vitro cell model for studying MAmmary Gland mIcrobial Colonization (MAGIC) model. We used the immortalized cell line MCF10A, which expresses the strong polarized phenotype similar to MG ductal epithelium when cultured on a permeable support (Transwell). We analyzed the surface properties of the MAGIC model by gene expression analysis of E-cadherin, tight junction proteins, and mucins and by scanning electron microscopy. To demonstrate the applicability of the model, we tested the adhesion capability of the whole human milk (HM) microbial community and the cellular response of the model when challenged directly with raw HM samples. MCF10A on permeable supports differentiated and formed a tight barrier, by upregulation of CLDN8, MUC1, MUC4, and MUC20 genes. The surface of the model was covered with mucins and morphologically diverse with at least two cell types and two types of microvilli. Cells in the MAGIC model withstood the challenge with heat-treated HM samples and responded differently to the imbalanced HM microbiota by distinctive cytokine response. The microbial profile of the bacteria adhered on the MAGIC model reflected the microbiological profile of the input HM samples. The well-studied MAGIC model could be useful for studies of bacterial attachment to the MG and for in vitro studies of biofilm formation and microbiota development.IMPORTANCEThe MAGIC model may be particularly useful for studies of bacterial attachment to the surface of the mammary ducts and for in vitro studies of biofilm formation and the development of the human mammary gland (MG) microbiota. The model is also useful for immunological studies of the interaction between bacteria and MG cells. We obtained pioneering information on which of the bacteria present in the raw human milk (HM) were able to attach to the epithelium treated directly with raw HM, as well as on the effects of bacteria on the MG epithelial cells. The MAGIC cell model also offers new opportunities for research in other areas of MG physiology, such as the effects of bioactive milk components on microbial colonization of the MG, mastitis prevention, and studies of probiotic development. Since resident MG bacteria may be an important factor in breast cancer development, the MAGIC in vitro tool also offers new opportunities for cancer research.

Conjugated Linoleic Acid Ameliorates Hydrogen Peroxide-Induced Mitophagy and Inflammation via the DRP1-mtDNA-STING Pathway in Bovine Hepatocytes

Oxidative stress is tightly associated with liver dysfunction and injury in dairy cows. Previous studies have shown that cis-9, trans-11 conjugated linoleic acid (CLA) possesses anti-inflammatory and antioxidative abilities. In this study, the bovine hepatocytes were pretreated with CLA for 6 h, followed by treatment with hydrogen peroxide (H2O2) for another 6 h to investigate the antioxidative effect of CLA and uncover the underlying mechanisms. The results demonstrated that H2O2 treatment elevated the level of mitophagy, promoted mitochondrial DNA (mtDNA) leakage into the cytosol, and activated the stimulator of interferon genes (STING)/nuclear factor kappa B (NF-κB) signaling pathway to trigger an inflammatory response in bovine hepatocytes. In addition, the dynamin-related protein 1(DRP1)-mtDNA-STING-NF-κB axis contributed to the H2O2-induced oxidative injury of bovine hepatocytes. CLA could reduce mitophagy and the inflammatory response to attenuate oxidative damage via the DRP1/mtDNA/STING pathway in bovine hepatocytes. These findings offer a theoretical foundation for the hepatoprotective effect of CLA against oxidative injury in dairy cows.

Expression, Regulation, and Function of β-Defensins in the Bovine Mammary Glands: Current Knowledge and Future Perspectives

β-Defensins are cationic antimicrobial peptides (AMPs) that play an important role in the innate immune defense of bovines. They are constitutively expressed in mammary glands and induced differently in response to pathogens. Their expression is influenced by various factors, including hormones, plant-derived compounds, and dietary energy imbalance. The toll-like receptors (TLRs)/nuclear factor-kappa B (NF-κB) pathway plays a crucial role in β-defensin induction, while alternative pathways such as mitogen-activated protein kinase (MAPK) and epigenetic regulation also make substantial contributions. β-Defensins exhibit bactericidal activity against a wide range of pathogens, including two major mastitis pathogens, Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), primarily through membrane disruption. β-Defensins have low cytotoxicity to host cells and demonstrate immunomodulatory properties, and pathogens also display minimal resistance to these AMPs. Given the increasing concern in antimicrobial resistance, the potential of β-defensins as natural antimicrobials has garnered considerable attention. This article provides an overview of the characteristics of bovine β-defensins, their expression pathways, their mode of action, and factors influencing their expression in the mammary glands of cattle. Additionally, it identifies the current gaps in research within this field and suggests areas that require further investigation. Understanding the regulation and function of β-defensins offers valuable insights to develop effective strategies for strengthening the immune system of mammary glands, reducing the reliance on synthetic antimicrobials, and explore novel natural antimicrobial alternatives.

Glutamine alleviates Lipopolysaccharide-induced corneal epithelial inflammation and oxidative stress in dogs

Pseudomonas aeruginosa is a common pathogenic bacteria in canine ophthalmology. Lipopolysaccharide (LPS), a component in the cell wall of gram-negative bacteria, is released following bacterial lysis and causes pathology and inflammation of the cornea. Antibiotics are used to treat bacterial keratitis, and the reuse of antibiotics can easily cause bacterial resistance. Research has shown that glutamine (GLN) has anti-inflammatory and antioxidant biological functions. Herein, we explored the effects and underlying mechanisms of GLN and established an LPS-induced cornea inflammation model. Treatment groups comprised: control check (CK), LPS, LPS + GLN, and Sham groups. Topical GLN treatment alleviated corneal opacity, reduced corneal injury, and accelerated corneal wound healing. Furthermore, GLN treatment altered the uniform distribution of corneal epithelial cells and transformed the healing approach of these cells in the corneal wound from crawling to filling. The expression of Toll-like receptor 4 (TLR4), IL-6, TNF-α, and p-p65 and the activity of myeloperoxidase and superoxide dismutase decreased while the content of malondialdehyde increased in the LPS + GLN group compared with those in the LPS group. Thus, our study suggests that LPS-induced inflammation and oxidative stress may be suppressed via the TLR4/NF-κB signaling pathway by GLN and that GLN could be used as an adjunct therapy to reduce antibiotic use.

A high-concentrate diet induces mitochondrial dysfunction by activating the MAPK signaling pathway in the mammary gland of dairy cows

Subacute rumen acidosis can lead to mastitis in dairy cows. Mitochondrial dysfunction is closely related to the inflammatory response. This experiment was conducted to investigate the effects of a high-concentrate diet on mammary gland inflammation and mitochondrial damage in dairy cows. Twelve Holstein dairy cows in mid-lactation were randomly divided into 2 groups and fed a 40% concentrate (low concentrate, LC) diet or a 60% concentrate (high concentrate, HC) diet. Cows were fed individually, and the experiment lasted for 3 wk. After the experiment, mammary gland tissue, blood, and rumen fluid were collected. Compared with the LC diet, the HC diet significantly decreased rumen pH; the pH was <5.6 for more than 3 h. The HC diet also increased the concentration of LPS in the blood (7.17 ± 1.25 µg/mL vs. 12.12 ± 1.26 µg/mL), which indicated that feeding the HC diet successfully induced subacute rumen acidosis. The HC diet also increased the concentration of Ca2+ (34.80 ± 4.23 µg/g vs. 46.87 ± 7.24 µg/g) in the mammary gland and upregulated the expression of inflammatory factors IL-6 (1,128.31 ± 147.53 pg/g vs. 1,538.42 ± 241.38 pg/g), IL-1β (69.67 ± 5.86 pg/g vs. 90.13 ± 4.78 pg/g), and tumor necrosis factor-α (91.99 ± 10.43 pg/g vs. 131.75 ± 17.89 pg/g) in mammary venous blood. The HC diet also increased the activity of myeloperoxidase (0.41 ± 0.05 U/g vs. 0.71 ± 0.11 U/g) and decreased the content of ATP (0.47 ± 0.10 µg/mL vs. 0.32 ± 0.11 µg/mL) in the mammary gland. In addition, phosphorylation of JNK (1.00 ± 0.21 vs. 2.84 ± 0.75), ERK (1.00 ± 0.20 vs. 1.53 ± 0.31), and p38 (1.00 ± 0.13 vs. 1.47 ± 0.41) and protein expression of IL-6 (1.00 ± 0.22 vs. 2.21 ± 0.27) and IL-8 (1.00 ± 0.17 vs. 1.96 ± 0.26) were enhanced in cows of the HC group, indicating that the mitogen-activated protein kinase (MAPK) signaling pathway was activated. Compared with the LC diet, the HC diet reduced the protein expression of mitochondrial biogenesis-related proteins PGC-1α (1.00 ± 0.17 vs. 0.55 ± 0.12), NRF1 (1.00 ± 0.17 vs. 0.60 ± 0.10), TFAM (1.00 ± 0.10 vs. 0.73 ± 0.09), and SIRTI (1.00 ± 0.44 vs. 0.40 ± 0.10). The HC diet promoted mitochondrial fission and inhibited mitochondrial fusion by reducing protein expression of MFN1 (1.00 ± 0.31 vs. 0.49 ± 0.09), MFN2 (1.00 ± 0.19 vs. 0.69 ± 0.13), and OPA1 (1.00 ± 0.08 vs. 0.72 ± 0.07), and by increasing that of DRP1 (1.00 ± 0.09 vs. 1.39 ± 0.10), MFF (1.00 ± 0.15 vs. 1.89 ± 0.12), and TTC1/FIS1 (1.00 ± 0.08 vs. 1.76 ± 0.14), leading to mitochondrial dysfunction. The HC diet increased mitochondrial permeability by upregulating the protein expression of VDAC1 (1.00 ± 0.42 vs. 1.90 ± 0.44), ANT (1.00 ± 0.22 vs. 1.27 ± 0.17), and CYPD (1.00 ± 0.41 vs. 1.82 ± 0.43). Taken together, these results indicated that feeding the HC diet induced mitochondrial damage via the MAPK signaling pathway in the mammary gland of dairy cows.

Effects of conjugated linoleic acid and exercise on body composition and obesity: a systematic review and meta-analysis

CONTEXT

Conjugated linoleic acid (CLA) has been reported to have anti-obesity and antidiabetic effects. However, the benefits of CLA combined with exercise remain unclear, and studies report conflicting results.

OBJECTIVE

A systematic review and meta-analysis were performed to investigate the synergistic effect of CLA and exercise on body composition, exercise-related indices, insulin resistance, and lipid profiles; and of the safety of CLA supplements.

DATA SOURCES

In October 2021, the PubMed, Embase, and Cochrane Library databases were searched for reports on clinical trials of the combined intervention of CLA and exercise.

DATA EXTRACTION

A total of 18 randomized controlled trials and 2 crossover trials were included. The methodological quality assessment was performed using the revised Cochrane risk-of-bias tool. Pooled effect sizes were reported as standardized mean difference (SMD) for continuous data and risk ratio for dichotomous data with their corresponding 95% confidence intervals (CIs). Heterogeneity was tested using the I2 statistic.

DATA ANALYSIS

The combination of CLA and exercise resulted in significantly decreased body fat (SMD, -0.42 [95%CI, -0.70, -0.14]; P = 0.003; I2 = 65) and insulin resistance (SMD, -0.25 [95%CI, -0.44, -0.06]; P = 0.01; I2 = 0) than did exercise alone. In subgroup analysis, the following factors were associated with significant outcomes: (1) body mass index ≥25 kg/m2; (2) female sex; (3) follow-up time >4 weeks; and (4) intervention duration >4 weeks. Nevertheless, supplementation with CLA during exercise programs was not effective for body-weight control, exercise performance enhancement, or lipid-profile improvement. CLA in combination with exercise did not result in a higher risk of adverse events (risk ratio, 1.32 [95%CI, 0.94-1.84]; P > 0.05; I2 = 0).

CONCLUSION

CLA combined with exercise is generally safe and can lower body fat and insulin resistance but does not reduce body weight, enhance exercise performance, or improve lipid profiles.

Sodium butyrate pretreatment mitigates lipopolysaccharide-induced inflammation through the TLR4/NF-κB signaling pathway in bovine embryo trachea cells

The present study investigated the anti-inflammatory effects and potential mechanisms of sodium butyrate (SB) in bovine embryo tracheal cells (EBTr) stimulated with lipopolysaccharide (LPS). EBTr were exposed to either 1 mmol/L SB for 18 h for the SB group (SB) or to 0.4 μg/mL LPS for 6 h for the LPS group (LPS). PBS was added to EBTr for a control group (CON). EBTr were pretreated with SB for 18 h followed by 6 h of LPS stimulation for the LSB group (LSB). Results showed that with LPS stimulation, the gene expression of TLR4, NF-κB, IL6, and IL8, as well as cytokine production of IL6 and TNF-α, were significantly increased compared with the CON group. In contrast, protein expression of IL10 was decreased. However, these inflammatory effects induced by LPS were reversed in the LSB group. Compared with the CON group, protein expression of TLR4, phospho-NF-κB p65, phospho-IκBα, and IL1α were increased in the LPS group and these were decreased in the LSB group. Similarly, increased nuclear translocation of phospho-NF-κB p65 in the LPS group was suppressed with SB pretreatment. In conclusion, SB can reduce inflammation induced by LPS in EBTr, and this positive effect is mediated through the TLR4 and NF-κB signaling pathway.

Effects of Artemisinin on Escherichia coli–Induced Mastitis in Bovine Mammary Epithelial Cells and Mice

Simple Summary

Bovine mastitis is a persistent and inflammatory reaction of the udder tissue that is usually caused by microbial infection, which can result in substantial losses due to reduced milk yield. Escherichia coli is considered a causative environmental pathogen and has been reported as a common cause of bovine mastitis worldwide. Because of its pathogenicity, Escherichia coli is always an important problem to the dairy industry worldwide and also poses a threat to food safety and public health, and with the widespread use of antibiotics, the resistance of Escherichia coli is increasing. Despite considerable research on bovine mastitis, the disease still remains one of the most prevalent and costly diseases of the dairy industry. The need to control mastitis is driven by multiple considerations, including milk quality, reductions in antimicrobial use, and animal welfare. Artemisinin is an antimalarial drug that was developed from a Chinese traditional herb, Qinghao. In recent years, other effects of artemisinin (including antitumor, anti-inflammatory, antifungal, etc.) have been increasingly discovered and applied. In this study, we demonstrated that artemisinin possesses a protective effect toward Escherichia coli–induced mastitis, thus providing a practical approach for the clinical control of mastitis.

Abstract

Bovine mastitis is an important disease affecting dairy farming, and it causes large economic losses to the dairy industry. Escherichia coli (E. coli) is considered to be a causative environmental pathogen and frequently enters into mammary glands, causing inflammation. Artemisinin is a highly effective malaria remedy and is not easy to develop drug resistance to. In recent years, other effects of artemisinin (including antitumor, anti-inflammatory, antifungal, etc.) have been increasingly discovered and applied. The current study aimed to investigate whether artemisinin could attenuate E. coli–induced inflammation. Through the E. coli mastitis model in MAC-T cells and mice, the protective effects of artemisinin were analyzed by CCK-8 (Cell Counting Kit-8), Western blot, and RT-qPCR. The results showed that artemisinin reversed the decrease of cell viability and upregulated TLR4 (toll-like receptor 4)/NF-κB (nuclear factor κB) and MAPK (mitogen activated protein kinase)/p38 signaling pathways, as well as restrained the expression of TNF-α, IL-6, and IL-1β mRNA caused by E. coli. Meanwhile, artemisinin also alleviated mammary tissue damage, reduced inflammatory cells’ infiltration, and decreased the levels of inflammatory factors in a mice mastitis model. This study demonstrated that artemisinin alleviated the inflammatory response of mouse mastitis and MAC-T cells induced by E. coli, thus providing a practical approach for the clinical control of mastitis.

(-)-Epicatechin Ameliorates Monosodium Urate-Induced Acute Gouty Arthritis Through Inhibiting NLRP3 Inflammasome and the NF-κB Signaling Pathway

Background: Gouty arthritis is a common and complex inflammatory disease that will reduce the life quality of human beings (-)-Epicatechin (EC) is famous for antioxidant and anti-inflammatory activities. Thus, the aim of this study was to investigate the therapeutic effect of EC on gouty arthritis and its mechanisms. Methods and results: EC was added into a monosodium urate (MSU)-stimulated THP-1 cell that was induced by phorbol 12-myristate 13-acetate and lipopolysaccharide (LPS) in advance to establish a gout model in vitro. The efficiency of EC on acute gouty arthritis mice induced by MSU was further investigated. The results showed that EC concentration-dependently improved the cell viability of LPS and MSU stimulated THP-1 cells, and significantly alleviated MSU-induced ankle edema in mice in a dose-dependent manner. In addition, EC inhibited the infiltration of inflammatory cells and local cascular congestion in ankle joint tissue. Furthermore, the secretion of inflammatory cytokines (IL-1β, IL-18, IL-6, and TNF-α) activation of NLRP3 inflammasome and NF-κB signaling pathway were markedly suppressed by EC in vitro and in vivo. Conclusion: These results indicated that EC could effectively improve MSU-induced acute gouty arthritis via inhibiting NLRP3 inflammasome and the NF-κB signaling pathway in vitro and in vivo, which suggested that EC might be a promising active ingredient for the prevention and treatment of gouty arthritis.

Cis-9, Trans-11 CLA Alleviates Lipopolysaccharide-Induced Depression of Fatty Acid Synthesis by Inhibiting Oxidative Stress and Autophagy in Bovine Mammary Epithelial Cells

Lipopolysaccharide (LPS) is the dominating endotoxin of Gram-negative bacteria, which can cause mastitis. Bovine mammary epithelial cells (BMECs), as major components of the mammary gland, usually suffer LPS challenge. Cis-9, trans-11 conjugated linoleic acid (CLA) has been reported to have anti-inflammatory characteristics, while its anti-oxidative ability to maintain cellular homeostasis in BMECs under LPS challenge is limited. Therefore, we studied whether cis-9, trans-11 CLA can restore the disturbance of cellular homeostasis indicated by the redox status and autophagy level caused by LPS and have an effect on cellular function- milk fat metabolism. For oxidative stress, LPS challenge promoted the formation of reactive oxygen species (ROS) and thiobarbituric acid reactive substances (TBARS) and decreased the concentration of glutathione. Anti-oxidative signaling regulated by transcription factor nuclear factor, erythroid 2 like 2 (Nrf2) was also depressed by LPS at the mRNA and protein level. However, cis-9, trans-11 CLA pretreatment downregulated the formation of ROS and TBARS and upregulated the expression of antioxidative enzymes. As a part of innate immunity, autophagy was also motivated by LPS challenge, while CLA decreased the autophagy level. LPS and H₂O₂ inhibited milk fat synthesis-related transcription factor sterol regulatory element binding protein (SREBP1), peroxisome proliferator activated receptor gamma (PPARG) and their downstream enzymes. Furthermore, 50 uM cis-9, trans-11 CLA promoted the mRNA and protein abundance of milk fat synthesis-related genes and lipid droplet formation in BMECs. In conclusion, LPS challenge disturbed the cellular homeostasis and depressed milk fat synthesis in BMECs; while cis-9, trans-11 CLA alleviated oxidative stress and decreased autophagy level, thus promoting milk fat synthesis, which offers a natural therapeutic strategy for mastitis.

Lycium barbarum polysaccharides alleviate LPS-induced inflammatory responses through PPARγ/MAPK/NF-κB pathway in bovine mammary epithelial cells

As the main component of the gram-negative bacterial cell wall, lipopolysaccharide (LPS) is well-documented as an inducer of inflammation in bovine mammary cells. Lycium barbarum (goji) polysaccharides (LBP) have been used in non-ruminants as prebiotics to improve growth performance, immune ability and antioxidant capacity. We aimed to investigate the underlying effects of LBPs on pro-inflammatory responses in LPS-stimulated primary bovine mammary epithelial cells (bMECs). Cells were isolated from mammary tissue of 3 lactating Holstein cows without clinical disease (30.26 ± 3.1 kg/d of milk yield; 175 ± 6 DIM). For the pre-experimental treatment, bMECs were precultured with serum-free medium for 12 h. Treatments were as follows: pretreatment with culture medium devoid of LPS or LBP for 30 h (CON); CON for 24 h followed by challenge with 2 μg/mL LPS for 6 h (LPS); pretreatment with 100 μg/mL or 300 μg/mL LBP for 24 h followed by LPS challenge (2 μg/mL) for 6 h (LBP(100)+LPS; LBP(300)+LPS). To further determine if the effect of LBP on immune-regulation is PPARγ activation-dependent, an inhibitor of PPARγ, GW9662, at a concentration of 1 μM was used. Cells treated with LBP at 100, 300 and 500 μg/mL had upregulated protein abundance of PPARγ, while PGC1α had a higher expression only at 300 μg/mL of LBP treatment. Compared with CON, cells pretreated with LBP at 100 and 300 μg/mL had greater protein abundance of SCD1 and SREBP1. EdU staining and cell wound healing assays showed that the negative effect of LPS alone on cell proliferation was reversed by pretreatment with LBP at both 100 and 300 μg/mL. Upregulation of gene and protein abundance of proinflammatory factors and cytokines (COX-2, NLRP3, TNF-α, IL-1β and IL-6) induced by LPS stimulation were alleviated by LBP pretreatment at 300 μg/mL (more than 2-fold decrease). Compared with LPS challenge alone, phosphorylation of proteins involved in NF-κB (IκBα and p65) and MAPK (p38, JNK and ERK) pathways was downregulated following LBP treatment. Additionally, inhibition of PPARγ by GW9662 weakened the protective effect of LBP on LPS-induced protein abundance of phosphorylated p65, COX-2, IL-1β and TNF-α. These results indicated that the protective effect of LBP on LPS-induced bMECs inflammatory responses is PPARγ activation-dependent. As such, this knowledge might help design strategies for intervening against the detrimental effects of bovine mastitis.

Metformin Inhibits Lipoteichoic Acid-Induced Oxidative Stress and Inflammation Through AMPK/NRF2/NF-κB Signaling Pathway in Bovine Mammary Epithelial Cells

The objective of this research was to explore the effect of metformin on the lipoteichoic acid (LTA)–induced mastitis model using isolated primary bovine mammary epithelial cells (PBMECs). The PBMECs were exposed to either 3 mM metformin for 12 h as a metformin group (MET) or 100 μg/mL LTA for 6 h as LTA group (LTA). Cells pretreated with 3 mM metformin for 12 h followed by washing and 100 μg/mL LTA exposure for 6 h served as the MET + LTA group. Phosphate-buffered saline was added to cells as the control group. PBMECs pretreated with different metformin doses were analyzed by a flow cytometry (annexin V–fluorescein isothiocyanate assay) to detect the cell apoptotic rate. We performed quantitative reverse transcriptase–polymerase chain reaction and Western blot analysis to evaluate the inflammatory and oxidative responses to metformin and LTA by measuring cellular cytotoxicity, mRNA expression, and protein expression. Immunofluorescence was used to evaluate nuclear localization. The results showed that the gene expression of COX2, IL-1β, and IL-6 significantly increased in the cells challenged with LTA doses compared to control cells. In inflammatory PBMECs, metformin attenuated LTA-induced expression of inflammatory genes nuclear factor κB (NF-κB) p65, tumor necrosis factor α, cyclooxygenase 2, and interleukin 1β, as well as the nuclear localization and phosphorylation of NF-κBp65 protein, but increased the transcription of nuclear factor erythroid 2–related factor 2 (Nrf2) and Nrf2-targeted antioxidative genes heme oxygenase-1 (HO-1) and Gpx1, as well as the nuclear localization of HO-1 protein. Importantly, metformin-induced activation of Nrf2 is AMP-activated protein kinase (AMPK)–dependent; as metformin-pretreated PBMECs activated AMPK signaling via the upregulation of phosphorylated AMPK levels, cell pretreatment with metformin also reversed the translocation of Nrf2 that was LTA inhibited. This convergence between AMPK and Nrf2 pathways is essential for the anti-inflammatory effect of metformin in LTA-stimulated PBMECs. Altogether, our results indicate that metformin exerts anti-inflammation and oxidative stress through regulation of AMPK/Nrf2/NF-κB signaling pathway, which highlights the role of AMPK as a potential therapeutic strategy for treatment of bovine mastitis.

Metformin activated AMPK signaling contributes to the alleviation of LPS-induced inflammatory responses in bovine mammary epithelial cells

Background

Lipopolysaccharides (LPS) derived from gram-negative bacterial are often regarded as primary inducer of bovine mammary inflammation. This study evaluated the biological response of metformin activated AMPK signaling on LPS-induced inflammatory responses and metabolic changes in primary bovine mammary epithelial cells (pbMEC). The pbMEC were exposed to either 3 mmol/L Metf. for 12 h as Metf. group (Metf.) or 2 μg/mL LPS for 6 h as LPS group (LPS). Cells pretreated with 3 mmol/L metformin for 12 h followed by washing and 2 μg/mL LPS exposure for 6 h were served as ML group (ML). PBS was added to cells as the control group (Con.).

Results

Pre-incubation with Metf. inhibited LPS-induced expression of pro-inflammatory genes (TNF, IL1B, IL6, CXCL8, MYD88 and TLR4) and proteins (IL-1β, TNF-α, NLRP3, Caspase1, ASC) and was accompanied by increased activation of AMPK signaling. Compared with the LPS group, phosphorylation of p65 and IκBα in the ML group were decreased and accumulation of NF-κB in the nucleus was significantly reduced by pretreatment with metformin. Metformin protects the cells from the increase of LPS-induced binding activity of NF-κB on both TNFA and IL1B promoters. Compared with the LPS group, genes (G6PC, PCK2) and proteins (SREBP1, SCD1) related to lipogenesis and carbohydrate metabolism were downregulated while catabolic ones (PPARA, ACSL1, Glut1, HK1) were upregulated in the ML group. Furthermore, increased acetylation of H3K14 by LPS challenge was reversed by pretreatment with metformin.

Conclusion

Altogether, our results indicated that pretreatment with metformin dampens LPS-induced inflammatory responses mediated in part by AMPK/NF-κB/NLRP3 signaling and modification of histone H3K14 deacetylation and metabolic changes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-021-02797-x.

Bifidobacterium pseudocatenulatum Ameliorates DSS-Induced Colitis by Maintaining Intestinal Mechanical Barrier, Blocking Proinflammatory Cytokines, Inhibiting TLR4/NF-κB Signaling, and Altering Gut Microbiota

This study was designed to explore the effects and discrepancy of different CLA-producing Bifidobacterium pseudocatenulatum on relieving colitis and to investigate the potential mechanisms. B. pseudocatenulatum MY40C and CCFM680 were administered to mice with DSS-induced colitis. The content of tight junction proteins and mucin2 was significantly upregulated. TNF-α and IL-6 were downregulated, while IL-10 and PPAR-γ were upregulated. TLR4/NF-κB pathway activation was significantly inhibited. Moreover, each treated strain increased Allobaculum and decreased Sutterella, Bacteroides, and Oscillospira. The colonic conjugated linoleic acid (CLA) concentrations were significantly and positively correlated with the effectiveness of strain in relieving colitis. In conclusion, MY40C and CCFM680 supplementation alleviated DSS-induced colitis by protecting intestinal mechanical barrier, modulating gut microbiota, blocking proinflammatory cytokines, and inhibiting TLR4/NF-κB pathway. These results are conducive to promote clinical trials and product development of probiotics for colitis.

Bacteriophages isolated from dairy farm mitigated Klebsiella pneumoniae-induced inflammation in bovine mammary epithelial cells cultured in vitro

Background

Klebsiella pneumoniae, an environmental pathogen causing mastitis in dairy cattle, is often resistant to antibiotics. K. pneumoniae was used as the host bacteria to support bacteriophage replication; 2 bacteriophages, CM8-1 and SJT-2 were isolated and considered to have therapeutic potential. In the present study, we determined the ability of these 2 bacteriophages to mitigate cytotoxicity, pathomorphological changes, inflammatory responses and apoptosis induced by K. pneumoniae (bacteriophage to K. pneumoniae MOI 1:10) in bovine mammary epithelial cells (bMECs) cultured in vitro.

Results

Bacteriophages reduced bacterial adhesion and invasion and cytotoxicity (lactate dehydrogenase release). Morphological changes in bMECs, including swelling, shrinkage, necrosis and hematoxylin and eosin staining of cytoplasm, were apparent 4 to 8 h after infection with K. pneumoniae, but each bacteriophage significantly suppressed damage and decreased TNF-α and IL-1β concentrations. K. pneumoniae enhanced mRNA expression of TLR4, NF-κB, TNF-α, IL-1β, IL-6, IL-8, caspase-3, caspase-9 and cyt-c in bMECs and increased apoptosis of bMECs, although these effects were mitigated by treatment with either bacteriophage for 8 h.

Conclusions

Bacteriophages CM8-1 and SJT-2 mitigated K. pneumoniae-induced inflammation in bMECs cultured in vitro. Therefore, the potential of these bacteriophages for treating mastitis in cows should be determined in clinical trials.

Glutamine pretreatment protects bovine mammary epithelial cells from inflammation and oxidative stress induced by γ-d-glutamyl-meso-diaminopimelic acid (iE-DAP)

Glutamine (GLN) has many types of biological activity in rats, including anti-inflammatory, antioxidative stress, and anti-apoptosis effects. However, little is known about the effects of GLN on bovine mammary epithelial cells (BMEC). γ-d-Glutamyl-meso-diaminopimelic acid (iE-DAP) is a cell wall peptidoglycan component of gram-negative bacteria that can be recognized by the intracellular receptor nucleotide-binding oligomerization domain-containing protein 1 (NOD1) and can cause bovine mastitis. The goal of the present study was to investigate whether GLN protects BMEC from iE-DAP-induced inflammation, oxidative stress, and apoptosis. We cultured BMEC in a GLN-free medium for 24 h and then separated them into 4 groups: cells treated with 1× PBS for 26 or 32 h (control); cells stimulated by 10 μg/mL iE-DAP for 2 or 8 h (2- or 8-h iE-DAP); cells pretreated with 8 or 4 mM GLN for 24 h followed by 2 or 8 h of 1× PBS treatment (8 or 4 mM GLN); and cells pretreated with 8 or 4 mM GLN for 24 h followed by 2 or 8 h of iE-DAP treatment (DG). In the 2-h iE-DAP group, when levels of inflammation peaked, iE-DAP treatment increased both the mRNA and protein expression of NOD1, inhibitor of nuclear factor-κB (NFKBIA, IκB), and nuclear factor-κB subunit p65 (RELA, NF-κB p65), as well as the mRNA expression of IL6 and IL8 and levels of IL-6 and tumor necrosis factor-α in cell culture supernatants. In contrast, 8 mM GLN pretreatment inhibited the mRNA and protein expression of inflammatory-related factors by suppressing the NOD1/NF-κB pathway. In the 8-h iE-DAP group, iE-DAP treatment decreased the mRNA and protein expression of extracellular regulated kinase (Erk, ERK) and nuclear factor erythroid 2-associated factor2 (NFE2L2, Nrf2), as well as the mRNA expression of superoxide dismutase 1 (SOD1), catalase (CAT), coenzyme II oxidoreductase 1 (NQO1), and heme oxygenase 1 (HMOX1, HO1). In addition, iE-DAP treatment increased the expression of malondialdehyde in BMEC when oxidative stress levels peaked. Interestingly, 4 mM GLN pretreatment induced the mRNA and protein expression of antioxidative stress-related factors and inhibited the expression of reactive oxygen species in BMEC by promoting the ERK/Nrf2 pathway. Moreover, GLN reduced apoptosis caused by inflammation and oxidative stress in BMEC. This is the first report showing that GLN protects against iE-DAP-induced inflammation and oxidative stress via the NOD1/NF-κB and ERK/Nrf2 pathways in BMEC.

Sodium butyrate promotes lipopolysaccharide-induced innate immune responses by enhancing mitogen-activated protein kinase activation and histone acetylation in bovine mammary epithelial cells

The innate immune response plays a crucial role in recovery from infectious diseases by promoting the clearance of pathogens. Sodium butyrate (NaB) is an energy source for cellular processes with the potential to regulate the innate immune response. The present study aimed to evaluate the effect of NaB on the innate immune response in a bovine mammary alveolar cell line (MAC-T) initiated by lipopolysaccharides (LPS). Thus, treatments were conducted as follows: treated with 1× PBS for 24 h (control), pretreated with 1 mM NaB (optimized by cell viability assays and dose-dependent experiment) for 18 h followed by treatment of 1× PBS for 6 h (NaB), pretreated with 1× PBS for 18 h followed by stimulation with LPS (1 µg/mL) for 6 h (LPS), and pretreated with 1 mM NaB for 18 h followed by stimulation with LPS (1 µg/mL) for 6 h (NaB + LPS). Different inhibitors were also used to elucidate the underlying mechanism. Furthermore, cells were treated with NaB and heat-inactivated Escherichia coli to test the effect of NaB on transcription of genes related to the innate immune response triggered by the major causative pathogen of mastitis. Each treatment had 3 replicates and was repeated 3 times. Proinflammatory cytokines, chemokines, and β-defensins are crucial secretion factors in innate immunity, and transcription of these factors was increased by NaB during challenge with LPS or heat-inactivated E. coli in MAC-T cells. Acetylation of histone H3 protein, which promotes gene expression by affecting the structure of chromatin, was also upregulated by NaB in response to LPS stimulation. P38 mitogen-activated protein kinases (MAPK), JNK, and Erk 1 and 2 are key upstream regulators of the expression of proinflammatory cytokines, chemokines, and β-defensins, and their activity was enhanced by NaB during LPS stimulation. Furthermore, inhibitors were used to assess the role of MAPK signaling in the effects of NaB. The results showed that inhibitors of p38 MAPK, Erk, and JNK attenuated the NaB-induced upregulation of TNF and β-defensin 5 (DEFB5) transcription, and that the inhibitor of Erk attenuated the NaB-induced upregulation of IL1B transcription during LPS challenge. Enhanced transcription of CXCL8 by NaB was blocked by the inhibitor of Erk and p38 MAPK during LPS stimulation. Overall, NaB boosted the LPS-induced innate immune response by promoting the expression of proinflammatory cytokines, chemokines, and β-defensins, which was associated with enhanced MAPK signaling activation and histone H3 acetylation.

Selenomethionine Suppressed TLR4/NF-κB Pathway by Activating Selenoprotein S to Alleviate ESBL Escherichia coli-Induced Inflammation in Bovine Mammary Epithelial Cells and Macrophages

Inflammation is the hallmark of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli-induced bovine mastitis. Organic selenium can activate pivotal proteins in immune responses and regulate the immune system. The present study aimed to investigate whether selenomethionine (SeMet) attenuates ESBL E. coli-induced inflammation in bovine mammary epithelial cells (bMECs) and macrophages. Cells were treated with 0, 5/10, 10/20, 20/40, or 40/60 μM SeMet for 12 h and/or inoculated with ESBL-E. coli [multiplicity of infection (MOI) = 5] for 4/6 h, respectively. We assessed inflammatory responses, including selenoprotein S (SeS), Toll-like receptor 4 (TLR4), Ikappa-B (IκB), phospho-NF-κB p65 (Ser536), interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and lactate dehydrogenase (LDH) activities. Treatment with 40/60 μM SeMet promoted cell viability and inhibited LDH activities in both bMECs and macrophages. Inoculation with ESBL-E. coli reduced cell viability, which was attenuated by SeMet treatment in bMECs and macrophages. SeMet increased ESBL E. coli-induced downregulation of SeS and decreased LDH activities, TLR4, IκB, phospho-NF-κB p65 (Ser536), IL-1β, and TNF-α protein expressions in bMECs and macrophages. In addition, knockdown of SeS promoted protein expression of TLR4-mediated nuclear factor-kappa (NF-κB) pathway and BAY 11-708 inhibited TNF-α and IL-1β protein levels in bMECs and macrophages after ESBL-E. coli treatment. Moreover, ESBL-E. coli inoculation increased monocyte chemoattractant protein 1 (MCP-1), C-C motif ligand 3 (CCL-3), and CCL-5 mRNA expressions in bMECs. In conclusion, ESBL-E. coli induced expression of MCP-1, CCL-3, and CCL-5 in bMECs and then recruited and activated macrophages, whereas SeMet attenuated ESBL E. coli-induced inflammation through activated SeS-mediated TLR4/NF-κB signaling pathway in bMECs and macrophages.