Enhanced protein-metabolite correlation analysis: To investigate the association between Staphylococcus aureus mastitis and metabolic immune pathways.

Mastitis is a disease characterized by congestion, swelling, and inflammation of the mammary gland and usually caused by infection with pathogenic microorganisms. Furthermore, the development of mastitis is closely linked to the exogenous pathway of the gastrointestinal tract. However, the regulatory mechanisms governing the gut-metabolism-mammary axis remain incompletely understood. The present study revealed alterations in the gut microbiota of mastitis rats characterized by an increased abundance of the Proteobacteria phylum. Plasma analysis revealed significantly higher levels of L-isoleucine and cholic acid along with 7-ketodeoxycholic acid. Mammary tissue showed elevated levels of arachidonic acid metabolites and norlithocholic acid. Proteomic analysis showed increased levels of IFIH1, Tnfaip8l2, IRGM, and IRF5 in mastitis rats, which suggests that mastitis triggers an inflammatory response and immune stress. Follistatin (Fst) and progesterone receptor (Pgr) were significantly downregulated, raising the risk of breast cancer. Extracellular matrix (ECM) receptors and focal adhesion signaling pathways were downregulated, while blood-milk barrier integrity was disrupted. Analysis of protein-metabolic network regulation revealed that necroptosis, protein digestion and absorption, and arachidonic acid metabolism were the principal regulatory pathways involved in the development of mastitis. In short, the onset of mastitis leads to changes in the microbiota and alterations in the metabolic profiles of various biological samples, including colonic contents, plasma, and mammary tissue. Key manifestations include disturbances in bile acid metabolism, amino acid metabolism, and arachidonic acid metabolism. At the same time, the integrity of the blood-milk barrier is compromised while inflammation is promoted, thereby reducing cell adhesion in the mammary glands. These findings contribute to a more comprehensive understanding of the metabolic status of mastitis and provide new insights into its impact on the immune system.

Hesperetin regulates the intestinal flora and inhibits the TLR4/NF-κB signaling axis to protect the blood-milk barrier and prevent mastitis.

The World Health Organization recommends breastfeeding for 6 months, but mastitis, a common disease during lactation, presents a major obstacle to fulfilling this recommendation. Maternal nutrient intake during lactation has been shown to be related to mastitis. Therefore, this study aimed to explore the effect of hesperetin, a phytonutrient, on mastitis. The oral administration of hesperetin to lipopolysaccharide (LPS)-induced mastitis mice alleviated their pathological damage, reduced the secretion of pro-inflammatory cytokines, and maintained the integrity of their blood-milk barrier. Moreover, our results showed that oral administration of hesperetin regulates the composition of the intestinal flora of mice. Fecal microbial transplantation (FMT) from the mice of hesperetin group alleviated LPS-induced mastitis in recipient mice. In additional, hesperetin attenuated the inflammatory response and increased the expression of tight junction proteins (TJs) in LPS-stimulated mouse mammary epithelial cells (mMECs). Through network pharmacological analysis and further research, we demonstrated hesperetin inhibits the expression of TLR4 and the activation of NF-κB signaling. In conclusion, hesperetin protects the blood-milk barrier and improve mastitis by regulating intestinal flora and inhibiting the activation of TLR4/NF-κB signaling axis. This study provides a theoretical basis for lactating females to consume hesperetin as a supplement to prevent mastitis and maintain mammary health.

Bilateral plasma cell mastitis simulating breast cancer: a case report and literature review.

Plasma cell mastitis (PCM) is a chronic inflammatory disease of the breast. It is a benign entity mainly found in nonpregnant and nonlactating women. PCM presents with symptoms of inflammation, breast erythema, masses, and indurations. We herein describe a 26-year-old woman with a 2-year history of right breast swelling and a 1-year history of left breast swelling during pregnancy and lactation. She was clinically diagnosed with bilateral breast cancer, but a biopsy specimen revealed PCM. During pregnancy and lactation, PCM can present as bilateral lesions. Early presentation and diagnosis are crucial because PCM, a benign disease, can lead to remarkable morbidity if allowed to progress to an advanced stage.

[Breast tuberculosis. Report of two cases]. / Tuberculosis mamaria. Reporte de dos casos.

Two cases of mammary tuberculosis (TB) are presented, one of them with additional pleural and lymph node involvement. Both were HIV-negative, with no history of previous TB, with long-standing breast lesions. Both presented a successful outcome with antituberculosis treatment. Breast TB is a very rare pathology that is difficult to diagnose. The cases are presented to consider their differential diagnosis in patients with chronic mastitis and/or nodular or ulcerated lesions of the breast. Multidisciplinary management is recommended.

Se presentan los casos de dos pacientes con tuberculosis (TB) mamaria, una de ellas también con compromiso pleural y ganglionar. Ambas HIV negativas, sin antecedentes de TB previa, con lesiones mamarias de largo tiempo de evolución. Las dos presentaron buena evolución con tratamiento antifímico. La TB mamaria es una afección muy poco frecuente de difícil diagnóstico. Se presentan los casos con el fin de plantear su diagnóstico diferencial en pacientes con mastitis crónicas y/o lesiones nodulares o ulceradas de la mama. Se recomienda el manejo multidisciplinario.

Retinoic acid ameliorates low-grade endotoxemia-induced mastitis by limiting inflammatory responses in mice.

Mastitis is a serious disease for humans and animals, which causes huge economic losses in the dairy industry and is hard to prevent due to the complex and unclear pathogenesis. Subacute ruminal acidosis (SARA) has contributed to the development of mastitis by inducing ruminal dysbiosis and subsequent low-grade endotoxemia (LGE), however, how ruminal metabolic changes regulate this progress is still unclear. Our previous study revealed that cows with SARA had increased ruminal retinoic acid (RA) levels, a metabolic intermediate of vitamin A that plays an essential role in mucosal immune responses. Hence, the aim of this study was to investigate the protective effect of RA on LGE-induced mastitis and the underlying mechanisms in mice. The results showed that RA alleviated LGE-induced mastitis, as evidenced by RA significantly reduced the increase in mammary proinflammatory cytokines and improved blood-milk barrier injury caused by LGE. In addition, RA increased the expression of tight junction proteins, including ZO-1, occludin and claudin-3. Furthermore, we found that RA limited the mammary inflammatory responses by inhibiting the activation of NF-κB and NLRP3 signaling pathways. These findings suggest that RA effectively alleviates LGE-induced mastitis and implies a potential strategy for the treatment and prevention of mastitis and other diseases.

A mimicker of inflammatory breast carcinoma: Lupus mastitis and evolving imaging features.

Rare case of lupus mastitis in a 58-year-old female with discoid lupus erythematosus presented with fever, left breast swelling, and painful palpable lesion. Accurate imaging and histopathologic evaluation allowed for appropriate management and regression of breast findings with hydroxychloroquine treatment, emphasizing the need to avoid unnecessary biopsies and surgeries.

A Retrospective Analysis of the Clinicopathological Features of Patients with Tuberculous Mastitis: A Single Institution's Experience.

INTRODUCTION: Tuberculosis remains a global health burden, especially in low- and middle-income countries. Breast tuberculosis is a rare disease with minimal research available. This disease produces a diagnostic challenge as the clinical presentation is variable, and diagnosis often requires additional investigations. This study was undertaken to determine the efficacy of cytology and histology, together with ancillary studies, in diagnosing tuberculous mastitis. METHODS: This retrospective study was conducted in a Johannesburg Hospital over 5 years. Thirty-two patients with confirmed tuberculous mastitis were included. The patients were considered positive for tuberculous mastitis if histological or cytological findings were confirmed with either a positive tuberculosis culture, Ziehl-Neelsen stain, or polymerase chain reaction examination/GeneXpert. RESULTS: This case series comprises 3 males and 29 females with a mean age of 35.66. A breast mass was the most common presentation. Over these 5 years, more biopsies were performed on inflammatory breast lesions than fine needle aspirations. There was a higher confirmation rate for cytology diagnoses compared to histology diagnoses. CONCLUSION: This study supports using fine needle aspiration combined with GeneXpert as the primary diagnostic modality in diagnosing tuberculous mastitis. This test combination is advantageous in resource- and financially constrained environments as it is relatively simple to perform, cost-effective, and has a rapid turnaround time.

Lupus mastitis and antiphospholipid syndrome treated with anticoagulation and immunosuppression: a case report.

BACKGROUND: Systemic lupus erythematosus is an autoimmune disease that can have cutaneous and systemic manifestations. Lupus panniculitis, also known as lupus mastitis, is a subset of chronic cutaneous lupus erythematosus that involves inflammation of the subcutaneous fat. The pathogenesis of lupus mastitis is not fully understood. Diagnosis involves a combination of skin manifestations, imaging, and pathologic confirmation. Treatment typically includes steroids and antimalarials, with more severe disease requiring additional immunosuppressive medications. This report highlights a case of lupus mastitis treated with rituximab and a possible relationship between this disease process and thrombotic disease. CASE PRESENTATION: A 48-year-old African American female with systemic lupus erythematosus and antiphospholipid syndrome presented with new breast lesion. Mammography revealed calcifications and increased density with coarse trabecular pattern. Breast biopsy showed features of cutaneous lupus and occlusive vasculopathy. The patient was diagnosed with lupus mastitis and treated with anticoagulation, rituximab, mycophenolate mofetil, and quinacrine with resolution of her symptoms. CONCLUSION: This patient experienced improvement in her breast symptoms with combination therapy including rituximab. There are only two other cases reported in literature of patients with lupus mastitis responding to rituximab, highlighting the possible role of B cell depleting therapy for those who have contraindications to standard treatments for lupus mastitis. While the pathophysiology of lupus mastitis is thought to be immune driven, some literature suggests that associated thrombosis commonly seen may be due to a physiologic overlap similar to antiphospholipid syndrome. The possible relationship between antiphospholipid syndrome and lupus mastitis and the use of antiplatelet and anticoagulation therapy is discussed and may warrant further investigation.

An herbal drug combination identified by knowledge graph alleviates the clinical symptoms of plasma cell mastitis patients: A nonrandomized controlled trial.

Background: Plasma cell mastitis (PCM) is a nonbacterial breast inflammation with severe and intense clinical manifestation, yet treatment methods for PCM are still rather limited. Although the mechanism of PCM remains unclear, mounting evidence suggests that the dysregulation of immune system is closely associated with the pathogenesis of PCM. Drug combinations or combination therapy could exert improved efficacy and reduced toxicity by hitting multiple discrete cellular targets. Methods: We have developed a knowledge graph architecture toward immunotherapy and systematic immunity that consists of herbal drug-target interactions with a novel scoring system to select drug combinations based on target-hitting rates and phenotype relativeness. To this end, we employed this knowledge graph to identify an herbal drug combination for PCM and we subsequently evaluated the efficacy of the herbal drug combination in clinical trial. Results: Our clinical data suggests that the herbal drug combination could significantly reduce the serum level of various inflammatory cytokines, downregulate serum IgA and IgG level, reduce the recurrence rate, and reverse the clinical symptoms of PCM patients with improvements in general health status. Conclusions: In summary, we reported that an herbal drug combination identified by knowledge graph can alleviate the clinical symptoms of PCM patients. We demonstrated that the herbal drug combination holds great promise as an effective remedy for PCM, acting through the regulation of immunoinflammatory pathways and improvement of systematic immune level. In particular, the herbal drug combination could significantly reduce the recurrence rate of PCM, a major obstacle to PCM treatment. Our data suggests that the herbal drug combination is expected to feature prominently in future PCM treatment. Funding: C. Liu's lab was supported by grants from the Public Health Science and Technology Project of Shenyang (grant: 22-321-32-18); Y. Yang's laboratory was supported by the National Natural Science Foundation of China (grant: 81874301), the Fundamental Research Funds for Central University (grant: DUT22YG122), and the Key Research project of 'be Recruited and be in Command' in Liaoning Province (2021JH1/10400050). Clinical trial number: NCT05530226.

CDK5RAP3, a key defender of udder, modulates NLRP3 inflammasome activation by regulating autophagolysosome degradation in S. agalactiae-infected mastitis.

Streptococcus agalactiae, as one of the main pathogens of clinical and subclinical mastitis, affects animal welfare and leads to huge economic losses to farms due to the sharp decline in milk yield. However, both the real pathogenic mechanisms of S. agalactiae-induced mastitis and the regulator which controls the inflammation and autophagy are largely unknown. Served as a substrate of ubiquitin-like proteins of E3 ligase, CDK5RAP3 is widely involved in the regulation of multiple signaling pathways. Our findings revealed that CDK5RAP3 was significantly down-regulated in mastitis infected by S. agalactiae. Surprisingly, inflammasome activation was triggered by CDK5RAP3 knockdown: up-regulated NLRP3, IL1ß and IL6, and cleaved caspase1 promoting by NF-κB, thereby resulting in pyroptosis. Additionally, the accumulation of autophagy markers (LC3B and p62) after CDK5RAP3 knockdown suggested that the autophagolysosome degradation pathway was inhibited, thereby activating the NF-κB pathway and NLRP3 inflammasome. Hence, our findings suggest that downregulation or ablation of CDK5RAP3 inhibits autophagolysosome degradation, causes inflammation by activating the NF-κB /NLRP3 inflammasome, and triggers cell death. In conclusion, CDK5RAP3 holds the key to understanding the interaction between autophagy and immune responses, its anti-inflammatory role in this study will throw new light on the clinical drug discovery to cure S. agalactiae mastitis.

Unilateral lupus mastitis.

Lupus mastitis is a rare clinical manifestation associated with systemic lupus erythematosus or discoid lupus erythematosus. It is necessary to make a correct diagnosis to differentiate it from inflammatory breast cancer. The histological study shows involvement of the adipose tissue of the breast with histopathological findings of cutaneous lupus erythematosus. Direct immunofluorescence detects the lupus band at the dermal-epidermal junction. The treatment of choice is hydroxychloroquine. We present a case of unilateral lupus mastitis in a patient with no previous diagnosis of lupus with complete remission after the use of hydroxychloroquine and topical corticosteroids.

Phenotypic evaluation of mast cells in bovine mammary tissue and mastitis in the context of fibrosis.

This research paper addresses the hypothesis that mast cells (MCs) contribute to the formation of mammary fibrosis. MCs are important immune regulatory and immune modulatory cells that play major roles in the inflammatory process. Since there is no detailed knowledge, this research study aimed to comparatively investigate the presence, localization, and immunophenotypes of MCs in healthy and mastitic mammary tissues. A total of 264 mammary samples were evaluated for the examination of mast cells and fibrosis. The mean mast cell number in both acute and chronic mastitis samples were very significantly higher than the control group P < 0.001). A 7.9-fold increase in the number of mast cells was found when the chronic mastitis group was compared with the control (healthy) group. Immunohistochemistry revealed presence of all three immune phenotypes in control and mastitic mammary samples (tryptase + (MCT), chymase + (MCC) and both chymase and tryptase + (MCTC). The mean MCT, MCC, and MCTC numbers in the chronic mastitis group were found to be significantly higher than the control (P < 0.001 for all three phenotypes) but did not differ significantly between control and acute mastitis samples. When the mean numbers of MCT, MCC, and MCTC in the control group and chronic mastitis group were compared, a 10.5, 7.8, and a 4.1-fold increase was observed, respectively. The amount of connective tissue was strongly increased in tissues with chronic mastitis and a 3.01-fold increase was detected compared to the control group. A statistically significant relation was also found between the amount of fibrosis and the increased number of total MCs (P < 0.001).

Image-guided fine-needle aspiration cytology or core biopsy - A key to definitive diagnosis of tuberculous mastitis.

Despite advances in the treatment, tuberculosis (TB) is still a global health problem. The diagnosis of extrapulmonary TB in their primary form is very challenging. Breast TB is very uncommon and accounts for < 0.1% of all breast lesions. Due to rarity of the disease and difficulty in diagnosis, we report a case of a 40-year-old female who had a hard lump in the right breast. Full-field digital mammography suggested the lesion as American College of Radiology Breast Imaging Reporting and Data System-5 (ACR BIRADS-5) (highly suggestive of carcinoma). Histopathological examination of multiple cores of the breast tissue showed lymphocytic inflammatory infiltrates confined to breast lobules. Fungal stains and Ziehl-Neelsen (ZN) stain were negative. A diagnosis of chronic mastitis with the possibility of autoimmune lobular mastitis was suggested. Subsequent image-guided fine needle aspiration smears showed epithelioid granulomas mixed with lymphocytes. Areas of amorphous-to-granular eosinophilic material (caseous necrosis) were seen at places. ZN stain showed acid-fast bacilli. A diagnosis of tuberculous mastitis was given.

Vitexin Mitigates Staphylococcus aureus-Induced Mastitis via Regulation of ROS/ER Stress/NF-κB/MAPK Pathway.

Mastitis, caused by a variety of pathogenic microorganisms, seriously threatens the safety and economic benefits of the dairy industry. Vitexin, a flavone glucoside found in many plant species, has been widely reported to have antioxidant, anti-inflammatory, antiviral, anticancer, neuroprotective, and cardioprotective effects. However, few studies have explored the effect of vitexin on mastitis. This study is aimed at exploring whether the antioxidant and anti-inflammatory functions of vitexin can improve Staphylococcus aureus-induced mastitis and its possible molecular mechanism. The expression profiles of S. aureus-infected bovine mammary epithelial cells and gland tissues from the GEO data set (GSE94056 and GSE139612) were analyzed and found that DEGs were mainly involved in immune signaling pathways, apoptosis, and ER stress through GO and KEGG enrichment. Vitexin blocked the production of ROS and increased the activity of antioxidant enzymes (SOD, GSH-PX, and CAT) via activation of PPARγ in vivo and in vitro. In addition, vitexin reduced the production of inflammatory cytokines (TNF-α, IL-1ß, and IL-6) and inhibited apoptosis in MAC-T cells and mouse mammary tissues infected with Staphylococcus aureus. Moreover, vitexin decreased the expression of PDI, Ero1-Lα, p-IRE1α, PERK, p-eIF2α, and CHOP protein but increased BiP in both mammary gland cells and tissues challenged by S. aureus. Western blot results also found that the phosphorylation levels of JNK, ERK, p38, and p65 were reduced in vitexin-treated tissues and cells. Vitexin inhibited the production of ROS through promoting PPARγ, increased the activity of antioxidant enzymes, and reduced inflammatory cytokines and apoptosis by alleviating ER stress and inactivation MAPKs and NF-κB signaling pathway. Vitexin maybe have great potential to be a preventive and therapeutic agent for mastitis.

Hydrogen helps to ameliorate Staphylococcus aureus-induced mastitis in mice.

Many studies have shown that hydrogen has anti-inflammatory and anti-oxidant effects. Because of its ability to quickly pass through cell membranes, hydrogen has become a hot spot in the research of inflammatory diseases. Vitamin E glycerin (VEG) and hydrogen-rich Vitamin E glycerin (HR-VEG) were prepared, aiming to explore their anti-inflammatory activities in mice mastitis induced by Staphylococcus aureus (S. aureus). In the early part of this study, the prepared vitamin E medium (VEM) and hydrogen-rich vitamin E medium (HR-VEM) were added to mammary epithelial cells infected with S. aureus. HR-VEM was found to be more effective in reducing the phosphorylation of p65 and p38 and in reducing the production of interleukin-1 beta (IL-1ß) than VEM. Whereafter, the mice model of mastitis was established by injecting S. aureus from the mammary duct. Then VEG and HR-VEG were applied to the mammary gland for seven consecutive days. After that, the clinical symptoms, histopathology, bacterial load, inflammatory factors, as well as the related pathway were analyzed. The results showed that HR-VEG can more significantly alleviate the damage of mammary tissue than VEG, and reduce the production of tumor necrosis factor-alpha (TNF-α), IL-1ß and interleukin 6 (IL-6). In addition, HR-VEG inhibited the TLR2 and Nod2 signaling pathways and reduced the phosphorylation level of MAPK and NF-κB signaling pathways in S. aureus-induced murine mastitis. This study indicates that hydrogen helps to ameliorate S. aureus-induced mastitis in mice through attenuating TLR2 and Nod2 mediated NF-κB and MAPK activation.

Pathology of the Mammary Gland in Sheep and Goats.

The recognition of lesions of the mammary gland in small ruminants is a useful diagnostic procedure that can aid in the identification of several udder diseases. This article reviews the main pathological lesions in this organ in sheep and goats. Mastitis is, by far, the most commonly diagnosed change. Acute clinical mastitis is associated with bacterial infections, mainly Staphylococcus aureus or Mannheimia haemolytica. Lesions related to subclinical and chronic mastitis are also described, either as localized cases or as a part of systemic diseases such as contagious agalactia, maedi-visna or tuberculosis. Neoplasia is rare in the mammary gland of sheep and goats with sporadic mammary adenocarcinomas most commonly reported. Teat lesions, including those due to trauma, orf virus infection or papillomas, are predisposing factors for the subsequent development of mastitis.

Ultrasonic multimodality imaging features and the classification value of nonpuerperal mastitis.

OBJECTIVE: To explore the value of ultrasonic multimodality imaging for characterizing nonpuerperal mastitis (NPM) lesions and feasibility of distinguishing different subtypes. METHODS: Thirty-eight NPM lesions were assessed using conventional ultrasonography (US), strain elastography (SE), and contrast-enhanced ultrasound (CEUS). The lesions were confirmed pathologically and classified as granulomatous lobular mastitis (GLM), plasma cell mastitis (PCM), or nonspecific mastitis (NSM). Furthermore, diagnostic indicators were evaluated. The diagnostic performances of the modalities were compared using the area under the receiver operating characteristic curve (AUC). RESULTS: The overall morphological features on US differed significantly between the GLM and PCM groups (p = 0.002). Lesion size (≤10 mm) (p = 0.003) and mean SE score (p = 0.001) differed significantly between the PCM and NSM groups. The frequent NPM characteristic on CEUS was hyperenhancement with (or without) increased lesion size; intergroup differences were not significant. Breast Imaging Reporting and Data System > 3 was considered to indicate malignancy; accordingly, the accuracy of US alone, US with CEUS, and US with SE was 10.5%, 21.1%, and 65.8%, respectively. Moreover, the AUC for US with SE for classifying GLM and PCM was 0.616. CONCLUSION: CEUS cannot accurately classify NPM subtypes, while US and SE are valuable for classification.

Formononetin Protects LPS-Induced Mastitis Through Suppressing Inflammation and Enhancing Blood-Milk Barrier Integrity via AhR-Induced Src Inactivation.

Formononetin (FOR), a natural flavonoid derived from Radix Astragali, has been reported to have anti-inflammatory and anti-oxidative effects. However, its protective mechanism against mastitis is still unknown. Nuclear factor kappa-B (NF-κB) signaling pathway plays an important role in inflammation, especially mastitis. Aryl hydrocarbon receptor (AhR) is involved in inflammatory regulation and defense against diseases. We investigated the protective effect of FOR on LPS-induced mastitis in mice and the effect of Ahr and NF-κB signaling pathways on the development of mastitis. In this study, mastitis model was induced by LPS injection through the nipple duct. Protective effect of FOR on LPS-induced mastitis was assessed by FOR pretreatment. The protective mechanism of FOR against mastitis was further investigated using LPS stimulation on mouse mammary epithelial cells EpH4-Ev. The results showed that LPS-induced mammary histological injury was inhibited by FOR. FOR significantly inhibited LPS-induced MPO activity. FOR administration enhanced the integrity of blood-milk barrier. In vitro and in vivo experiments showed that FOR inhibited LPS-induced NF-κB signaling pathway activation and the production of inflammatory factors TNF-α and IL-1ß. Moreover, FOR increased the expression of tight junction protein and enhanced blood-milk barrier integrity. LPS activated AhR and Src expression. But FOR induced significant increase in AhR inhibited Src phosphorylation to exert anti-inflammatory effects. In addition, AhR antagonist CH223191 reversed the inhibition of FOR on Src expression. And the inhibition of FOR on NF-κB activation and inflammatory cytokine production were reversed by AhR antagonist CH223191. In conclusion, FOR had protective effects against LPS-induced mastitis via suppressing inflammation and enhancing blood-milk barrier integrity via AhR-induced Src inactivation.

Diverse myeloid cells are recruited to the developing and inflamed mammary gland.

The immune system plays fundamental roles in the mammary gland, shaping developmental processes and controlling inflammation during infection and cancer.Here, we reveal unanticipated heterogeneity in the myeloid cell compartment duringdevelopment of virgin, pregnant, lactating and involuting mouse mammary glands,and in milk. We investigate the functional consequences of individual and compoundchemokine receptor deficiency on cell recruitment. Diverse myeloid cell recruitmentwas also shown in models of sterile inflammation and bacterial infection.Strikingly, we have shown that inflammation and infection can alter the abundanceof terminal end buds, a key developmental structure, within the pubertal mammarygland. This previously unknown effect of inflammatory burden during puberty couldhave important implications for understanding pubertal development.

Escherichia coli and Staphylococcus aureus Differentially Regulate Nrf2 Pathway in Bovine Mammary Epithelial Cells: Relation to Distinct Innate Immune Response.

Escherichia coli and Staphylococcus aureus are major mastitis causing pathogens in dairy cattle but elicit distinct immune and an inflammatory response in the udder. However, the host determinants responsible for this difference remains largely unknown. Our initial studies focused on the global transcriptomic response of primary bovine mammary epithelial cells (pbMECs) to heat-killed E. coli and S. aureus. RNA-sequencing transcriptome analysis demonstrates a significant difference in expression profiles induced by E. coli compared with S. aureus. A major differential response was the activation of innate immune response by E. coli, but not by S. aureus. Interestingly, E. coli stimulation increased transcript abundance of several genes downstream of Nrf2 (nuclear factor erythroid 2-related factor 2) that were enriched in gene sets with a focus on metabolism and immune system. However, none of these genes was dysregulated by S. aureus. Western blot analysis confirms that S. aureus impairs Nrf2 activation as compared to E. coli. Using Nrf2-knockdown cells we demonstrate that Nrf2 is necessary for bpMECs to mount an effective innate defensive response. In support of this notion, nuclear Nrf2 overexpression augmented S. aureus-stimulated inflammatory response. We also show that, unlike E. coli, S. aureus disrupts the non-canonical p62/SQSTM1-Keap1 pathway responsible for Nrf2 activation through inhibiting p62/SQSTM1 phosphorylation at S349. Collectively, our findings provide important insights into the contribution of the Nrf2 pathway to the pathogen-species specific immune response in bovine mammary epithelial cells and raise a possibility that impairment of Nrf2 activation contributes to, at least in part, the weak inflammatory response in S. aureus mastitis.