The mechanistic role of natural antimicrobials in preventing Staphylococcus aureus invasion of MAC-T cells using an in vitro mastitis model

BACKGROUND

Starting primarily as an inflammation of the mammary gland, mastitis is frequently driven by infectious agents such as Staphylococcus aureus. Mastitis has a large economic impact globally, which includes diagnostic, treatment, and the production costs not to mention the potential milk contamination with antimicrobial residues. Currently, mastitis prevention and cure depends on intramammary infusion of antimicrobials, yet, their overuse risks engendering resistant pathogens, posing further threats to livestock.

METHODS

In our study we aimed to investigate, in vitro, using bovine mammary epithelial cells (MAC-T), the efficacy of the AuraShield an antimicrobial mixture (As) in preventing S. aureus attachment, internalisation, and inflammation. The antimicrobial mixture (As) included: 5% maltodextrin, 1% sodium chloride, 42% citric acid, 18% sodium citrate, 10% silica, 12% malic acid, 9% citrus extract and 3% olive extract (w/w).

RESULTS AND DISCUSSION

Herein we show that As can significantly reduce both adherence and invasion of MAC-T cells by S. aureus, with no impact on cell viability at all concentrations tested (0.1, 0.2, 0.5, 1%) compared with untreated controls. The anti-apoptotic effect of As was achieved by significantly reducing cellular caspase 1, 3 and 8 activities in the infected MAC-T cells. All As concentrations were proven to be subinhibitory, suggesting that Ac can reduce S. aureus virulence without bacterial killing and that the effect could be dual including a host modulation effect. In this context, we show that As can reduce the expression of S. aureus clumping factor (ClfB) and block its interaction with the host Annexin A2 (AnxA2), resulting in decreased bacterial adherence in infection of MAC-T cells. Moreover, the ability of As to block AnxA2 had a significant decreasing effect on the levels of pro inflammatory cytokine released upon S. aureus interaction with MAC-T cells.

CONCLUSION

The results presented in this study indicate that mixtures of natural antimicrobials could potentially be considered an efficient alternative to antibiotics in treating S. aureus induced mastitis.

Association of pro-fibrinolytic receptor AnnexinA2 with tissue plasminogen activator/Inhibitor-1 in pre-eclampsia

Background

The clinical manifestations of pre-eclampsia are related to placental anti-angiogenic factor alteration. These variations are mainly due to the alteration of plasminolytic components. The study aims to compare the expression of plasminolytic components in the placenta of women with and without pre-eclampsia.

Material and Methods

The study included pregnant women with pre-eclampsia as PE group (n = 30) and without pre-eclampsia as a control group (n = 30). Placental bed biopsy tissues were collected. AnxA2, tPA, PAI-1 expression in the placental villous tissue was quantitatively evaluated using immunohistochemistry, western blot, and real time-PCR analysis.

Results

The results of the study showed a significant decrease in the expression of ANXA2 and increased expression of tPA and PAI-1 in PE group compared to control group (p<0.005). AnxA2 expression showed positive correlation with tPA (r=+0.895, p=0.002) and negative correlation with PAI-1(r=-0.905, p=0.020) in control group whereas in the PE group AnxA2 expression was negatively correlated with tPA ((r=-0.801, p=0.016) and PAI-1 (R=-0.831, P=0.010).

Conclusion

Decreased AnxA2 with increased expression of PAI-1 and tPA may be responsible for the altered fibrinolytic activity and play a significant role in pre-eclampsia pathogenesis.

TRIM59 attenuates ox-LDL-induced endothelial cell inflammation, apoptosis, and monocyte adhesion through AnxA2

Background

Atherosclerosis (AS), a chronic inflammatory vascular disease, is a cause of heart attack and ischemic stroke. Tripartite motif-containing protein 59 (TRIM59), a member of the tripartite motif family, has been reported to be involved in inflammatory diseases. This study was to investigate the role of TRIM59 in oxidized low-density lipoprotein (ox-LDL)-induced endothelial cells and examine the mechanism of TRIM59.

Methods

To simulate a cellular model of AS in vitro, varying concentrations of ox-LDL (i.e., 20, 40, 60, 80, and 100 µg/mL) were used to treat the human umbilical vein endothelial cells (HUVECs) for 24 h. The messenger ribonucleic acid (RNA) and protein levels of TRIM59, lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), and annexin 2 (AnxA2) were examined by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot. The transfection efficacy of overexpression (Ov)-TRIM59 and small-interfering RNA-AnxA2 was examined by RT-qPCR and western blot. Cell counting kit-8 assays, lactate dehydrogenase (LDH) assays, enzyme-linked immunosorbent assays, and terminal-deoxynucleotidyl transferase mediated nick end labeling staining were used to examine viability, LDH expression, inflammation, and apoptosis in HUVECs. The protein levels of B-cell lymphoma 2, Bcl-2-associated X (BAX), cleaved caspase3, intercellular adhesion molecule 1, and vascular cell adhesion molecule 1 were assessed by western blot. Additionally, the adhesion of THP-1 to ox-LDL-induced HUVECs was detected using monocyte adhesion assays and the binding of TRIM59 and AnxA2 was verified by co-immunoprecipitation.

Results

This study showed that TRIM59 expression was decreased in the ox-LDL-induced HUVECs while LOX-1 expression was increased. After transfection with Ov-TRIM59, TRIM59 in ox-LDL-induced HUVECs was increased, and TRIM59 overexpression alleviated the viability damage, inflammation, and apoptosis of the ox-LDL-induced HUVECs. In addition, THP-1 adhesion to the ox-LDL-induced HUVECs was also suppressed by TRIM59 overexpression. This study also showed that TRIM59 could bind to AnxA2 and promote AnxA2 expression in ox-LDL-stimulated HUVECs. Moreover, the rescue experiments revealed that TRIM59 suppressed the viability damage, inflammation, apoptosis, and monocyte adhesion of the ox-LDL-induced HUVECs via AnxA2.

Conclusions

TRIM59 protected against ox-LDL-induced AS by binding to AnxA2.

Implicative role of epidermal growth factor receptor and its associated signaling partners in the pathogenesis of Alzheimer's disease

Epidermal growth factor receptor (EGFR) plays a pivotal role in early brain development, although its expression pattern declines in accordance with the maturation of the active nervous system. However, recurrence of EGFR expression in brain cells takes place during neural functioning decline and brain atrophy in order to maintain the homeostatic neuronal pool. As a consequence, neurotoxic lesions such as amyloid beta fragment (Aβ_1-42) formed during the alternative splicing of amyloid precursor protein in Alzheimer's disease (AD) elevate the expression of EGFR. This inappropriate peptide deposition on EGFR results in the sustained phosphorylation of the downstream signaling axis, leading to extensive Aβ_1-42 production and tau phosphorylation as subsequent pathogenesis. Recent reports convey that the pathophysiology of AD is correlated with EGFR and its associated membrane receptor complex molecules. One such family of molecules is the annexin superfamily, which has synergistic relationships with EGFR and is known for membrane-bound signaling that contributes to a variety of inflammatory responses. Besides, Galectin-3, tissue-type activated plasminogen activator, and many more, which lineate the secretion of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6, and IL-18) result in severe neuronal loss. Altogether, we emphasized the perspectives of cellular senescence up-regulated by EGFR and its associated membrane receptor molecules in the pathogenesis of AD as a target for a therapeutical alternative to intervene in AD.

The interaction of smoking habit, SLPI and AnxA2 in HPV associated head and neck and other cancers

Six own studies confirm a correlation between smoking, expression of the secretory leukocyte protease inhibitor (SLPI, an antileukoproteinase) and expression of Annexin A2 (AnxA2), and their influence on human papilloma virus (HPV)-infections. SLPI and HPV are ligands of AnxA2. This correlation was tested on 928 tissue samples from 892 patients in six independent studies [squamous cell carcinoma of the head and neck (HNSCC), n = 522; non-neoplastic tonsils n = 214; clinically normal mucosa, n = 93 (of these n = 57 were obtained from patients treated for non-malignant diseases and n = 36 were obtained from HNSCC-patients) and vulvar squamous cell carcinoma (VSCC) n = 99]. HPV-DNA-status was determined by GP5+/GP6+-PCR, followed in case of HPV-positivity by Sanger sequencing and RT-PCR using HPV-type specific primers. SLPI- and AnxA2-gene-expression was determined by RT-q-PCR; SLPI-protein-expression was additionally determined by immunohistochemistry (IHC); the data were correlated with each other and with patient characteristics. Smoking results in increased SLPI-gene- and protein- and AnxA2-gene-expression with significantly higher SLPI- than AnxA2-gene-expression. SLPI is decreased in non-smokers with a continuous AnxA2-surplus. HPV-status correlates with smoking habit, with smokers being mostly HPV-negative and non-smokers HPV-positive. We hypothesize that smoking leads to SLPI-overexpression with SLPI-binding to AnxA2. Thus, HPV cannot bind to AnxA2 but this seems pivotal for HPV-cell-entry. Smoking favors SLPI-expression resulting in HPV-negative carcinomas, while HPV-positive carcinomas are more common in non-smokers possibly due to a surplus of unbound AnxA2. In addition, the hypothesis may contribute to understand why smokers show increased oral HPV-prevalence in natural history studies but do not necessarily develop HPV-associated lesions.

Cell surface interaction of annexin A2 and galectin-3 modulates epidermal growth factor receptor signaling in Her-2 negative breast cancer cells

Overexpression and activation of tyrosine kinase receptors like EGFR and Src regulate the progression and metastasis of Her-2 negative breast cancer. Recently we have reported the role of cell membrane interaction of phospholipid-binding protein annexin A2 (AnxA2) and EGFR in regulating cellular signaling in the activation of angiogenesis, matrix degradation, invasion, and cancer metastasis. Beta-galactoside-specific animal lectin galectin-3 is an apoptosis inhibitor, and cell surface-associated extracellular galectin-3 also has a role in cell migration, cancer progression, and metastasis. Similar expression pattern and membrane co-localization of these two proteins made us to hypothesize in the current study that galectin-3 and AnxA2 interaction is critical for Her-2 negative breast cancer progression. By various experimental analyses, we confirm that glycosylated AnxA2 at the membrane surface interacts with galectin-3. N-linked glycosylation inhibitor tunicamycin treatment convincingly blocked AnxA2 membrane translocation and its association with galectin-3. To analyze whether this interaction has any functional relevance, we tried to dissociate this interaction with purified plant lectin from chickpea (Cicer arietinum agglutinin). This highly specific 30 kDa plant lectin could dissociate AnxA2 from endogenous lectin galectin-3 interaction at the cell surface. This dissociation could down-regulate Bcl-2 family proteins, cell proliferation, and migration simultaneously triggering cell apoptosis. Targeting this interaction of membrane surface glycoprotein and its animal lectin in Her-2 negative breast cancer may be of therapeutic value.

Protein interactions between surface annexin A2 and S100A10 mediate adhesion of breast cancer cells to microvascular endothelial cells

Annexin A2 (AnxA2) and S100A10 are known to form a molecular complex. Using fluorescence-based binding assays, we show that both proteins are localised on the cell surface, in a molecular form that allows mutual interaction. We hypothesized that binding between these proteins could facilitate cell-cell interactions. For cells that express surface S100A10 and surface annexin A2, cell-cell interactions can be blocked by competing with the interaction between these proteins. Thus an annexin A2-S100A10 molecular bridge participates in cell-cell interactions, revealing a hitherto unexplored function of this protein interaction.