Gram Negative Bacterial Inflammation Ameliorated by the Plasma Protein Beta 2-Glycoprotein I

Domain 5 of Beta 2 glycoprotein I: Friend or foe in health? Context matters

Beta 2 glycoprotein I (β2GPI) is the major autoantigen in the antiphospholipid syndrome, an autoimmune disorder characterized by thrombotic and obstetric complications. The autoantibodies that target beta 2 glycoprotein I are pathogenic and contribute to disease pathogenesis. The β2GPI molecule is composed of 5 domains that are numbered 1 through to 5. Autoantibodies bind mainly to domain 1 whereas the majority of the biological functions of the β2GPI molecule in diverse processes such as apoptotic cell clearance, complement regulation, lipopolysaccharide clearance and anticoagulation have been localised to domain 5 and its unique biochemistry, reviewed in this article. The role of purified domain 5 peptide as a potential therapeutic agent in APS and ischemia reperfusion injury is discussed.

The protective effect of apolipoprotein H in paediatric sepsis

BACKGROUND

Sepsis is a severe condition characterized by acute organ dysfunction resulting from an imbalanced host immune response to infections. Apolipoprotein H (APOH) is a critical plasma protein that plays a crucial role in regulating various biological processes. However, the precise role of APOH in the immunopathology of paediatric sepsis remains unclear.

METHODS

In this study, we evaluated the concentration of APOH in paediatric patients with sepsis and healthy individuals. In an experimental sepsis model of caecal ligation and puncture (CLP), the impact of APOH on survival, organ injury, and inflammation was measured. Furthermore, the anti-inflammatory effects of APOH were investigated across diverse immune cell types, encompassing peripheral blood mononuclear cells (PBMCs), peritoneal macrophages (PMs), bone marrow-derived macrophages (BMDMs), and RAW 264.7 macrophages.

RESULTS

In the pilot cohort, the relative abundance of APOH was found to be decreased in patients with sepsis (2.94 ± 0.61) compared to healthy controls (1.13 ± 0.84) (p < 0.001), non-survivors had lower levels of APOH (0.50 ± 0.37) compared to survivors (1.45 ± 0.83) (p < 0.05). In the validation cohort, the serum concentration of APOH was significantly decreased in patients with sepsis (202.0 ± 22.5 ng/ml) compared to healthy controls (409.5 ± 182.9 ng/ml) (p < 0.0001). The application of recombinant APOH protein as a therapeutic intervention significantly lowered the mortality rate, mitigated organ injury, and suppressed inflammation in mice with severe sepsis. In contrast, neutralizing APOH with an anti-APOH monoclonal antibody increased the mortality rate, exacerbated organ injury, and intensified inflammation in mice with non-severe sepsis. Intriguingly, APOH exhibited minimal effects on the bacterial burden, neutrophil, and macrophage counts in the sepsis mouse model, along with negligible effects on bacterial phagocytosis and killing during Pseudomonas aeruginosa infection in PMs, RAW 264.7 cells, and PBMCs. Mechanistic investigations in PMs and RAW 264.7 cells revealed that APOH inhibited M1 polarization in macrophages by suppressing toll-like receptor 4 (TLR4)/nuclear factor-κB (NF-κB) signalling pathway.

CONCLUSION

This proof-of-concept study demonstrated that APOH has a protective role in the host defense response to sepsis, highlighting the potential therapeutic value of APOH in sepsis treatment.

Interaction of the antiphospholipid syndrome autoantigen beta-2 glycoprotein I with DNA and neutrophil extracellular traps

Beta-2 glycoprotein I (β2GPI) is a phospholipid-binding plasma protein and prominent autoantigen in antiphospholipid syndrome (APS). Here, we tested the hypothesis that β2GPI might bind to not only phospholipids, but also cell-free DNA and neutrophil extracellular traps (NETs). We report that β2GPI interacts with cell-free DNA from different species, as well as NETs, in a dose-dependent manner, retarding their migration in an agarose-gel electrophoretic mobility shift assay. We confirm the direct binding interaction of β2GPI with DNA and NETs by ELISA. We also demonstrate that β2GPI colocalizes with NET strands by immunofluorescence microscopy. Finally, we provide evidence that β2GPI-DNA complexes can be detected in the plasma of APS patients, where they positively correlate with an established biomarker of NET remnants. Taken together, our findings indicate that β2GPI interacts with DNA and NETs, and suggest that this interaction may play a role as a perpetuator and/or instigator of autoimmunity in APS.

Interplay between Systemic Glycemia and Neuroprotective Activity of Resveratrol in Modulating Astrocyte SIRT1 Response to Neuroinflammation

The flow of substances between the blood and the central nervous system is precisely regulated by the blood-brain barrier (BBB). Its disruption due to unbalanced blood glucose levels (hyper- and hypoglycemia) occurring in metabolic disorders, such as type 2 diabetes, can lead to neuroinflammation, and increase the risk of developing neurodegenerative diseases. One of the most studied natural anti-diabetic, anti-inflammatory, and neuroprotective compounds is resveratrol (RSV). It activates sirtuin 1 (SIRT1), a key metabolism regulator dependent on cell energy status. The aim of this study was to assess the astrocyte SIRT1 response to neuroinflammation and subsequent RSV treatment, depending on systemic glycemia. For this purpose, we used an optimized in vitro model of the BBB consisting of endothelial cells and astrocytes, representing microvascular and brain compartments (MC and BC), in different glycemic backgrounds. Astrocyte-secreted SIRT1 reached the highest concentration in hypo-, the lowest in normo-, and the lowest in hyperglycemic backgrounds. Lipopolysaccharide (LPS)-induced neuroinflammation caused a substantial decrease in SIRT1 in all glycemic backgrounds, as observed earliest in hyperglycemia. RSV partially counterbalanced the effect of LPS on SIRT1 secretion, most remarkably in normoglycemia. Our results suggest that abnormal glycemic states have a worse prognosis for RSV-therapy effectiveness compared to normoglycemia.

Antioxidant and Antineuroinflammatory Mechanisms of Kaempferol-3-O-β-d-Glucuronate on Lipopolysaccharide-Stimulated BV2 Microglial Cells through the Nrf2/HO-1 Signaling Cascade and MAPK/NF-κB Pathway

Aglycone- and glycoside-derived forms of flavonoids exist broadly in plants and foods such as fruits, vegetables, and peanuts. However, most studies focus on the bioavailability of flavonoid aglycone rather than its glycosylated form. Kaempferol-3-O-β-d-glucuronate (K3G) is a natural flavonoid glycoside obtained from various plants that have several biological activities, including antioxidant and anti-inflammatory effects. However, the molecular mechanism related to the antioxidant and antineuroinflammatory activity of K3G has not yet been demonstrated. The present study was designed to demonstrate the antioxidant and antineuroinflammatory effect of K3G against lipopolysaccharide (LPS)-stimulated BV2 microglial cells and to evaluate the underlying mechanism. Cell viability was determined by MTT assay. The inhibition rate of reactive oxygen species (ROS) and the production of pro-inflammatory mediators and cytokines were measured by DCF-DA assay, Griess assay, enzyme-linked immunosorbent assay (ELISA), and western blotting. K3G inhibited the LPS-induced release of nitric oxide, interleukin (IL)-6, and tumor necrosis factor-α (TNF-α) as well as the expression of prostaglandin E synthase 2. Additionally, K3G reduced the expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and nuclear factor-kappa B (NF-κB) related proteins. Mechanistic studies found that K3G downregulated phosphorylated mitogen-activated protein kinases (MAPKs) and upregulated the Nrf2/HO-1 signaling cascade. In this study, we demonstrated the effects of K3G on antineuroinflammation by inactivating phosphorylation of MPAKs and on antioxidants by upregulating the Nrf2/HO-1 signaling pathway through decreasing ROS in LPS-stimulated BV2 cells.

Microbial and metabolic characterization of organic artisanal sauerkraut fermentation and study of gut health-promoting properties of sauerkraut brine

Sauerkraut is a traditionally fermented cabbage, and recent evidence suggests that it has beneficial properties for human health. In this work, a multi-disciplinary approach was employed to characterize the fermentation process and gut health-promoting properties of locally produced, organic sauerkraut from two distinct producers, SK1 and SK2. 16S rRNA metataxonomics showed that bacterial diversity gradually decreased as fermentation progressed. Differences in sauerkraut microbiota composition were observed between the two producers, especially at the start of fermentation. Lactic acid bacteria (LAB) dominated the microbiota after 35 days, with Lactiplantibacillus being the dominant genus in both sauerkraut products, together with Leuconostoc and Paucilactobacillus in SK1, and with Pediococcus, Levilactibacillus, and Leuconostoc in SK2. LAB reached between 7 and 8 Log CFU/mL brine at the end of fermentation (35 days), while pH lowering happened within the first week of fermentation. A total of 220 LAB strains, corresponding to 133 RAPD-PCR biotypes, were successfully isolated. Lactiplantibacillus plantarum and Lactiplantibacillus pentosus accounted for 67% of all SK1 isolates, and Lactiplantibacillus plantarum/paraplantarum and Leuconostoc mesenteroides represented 72% of all the isolates from SK2. ¹H-NMR analysis revealed significant changes in microbial metabolite profiles during the fermentation process, with lactic and acetic acids, as well as amino acids, amines, and uracil, being the dominant metabolites quantified. Sauerkraut brine did not affect trans-epithelial electrical resistance through a Caco-2 cell monolayer as a measure of gut barrier function. However, significant modulation of inflammatory response after LPS stimulation was observed in PBMCs-Caco-2 co-culture. Sauerkraut brine supported a robust inflammatory response to endotoxin, by increasing TNF-α and IL-6 production while also stimulating the anti-inflammatory IL-10, therefore suggesting positive resolution of inflammation after 24 h and supporting the potential of sauerkraut brine to regulate intestinal immune function.

A H2O2-responsive theranostic platform for chemiluminescence detection and synergistic therapy of tumor

Chemiluminescence substances that respond to hydrogen peroxide (H2O2) in the tumor microenvironment have the potential to achieve accurate tumor imaging. Here, Pluronic F-127 (PF127) and polymers containing oxalate ester (POE)...

The Secretome Deregulations in a Rat Model of Endotoxemic Shock

Introduction

Septic shock is a systemic inflammatory response syndrome associated with organ failures. Earlier clinical diagnosis would be of benefit to a decrease in the mortality rate. However, there is currently a lack of predictive biomarkers. The secretome is the set of proteins secreted by a cell, tissue, or organism at a given time and under certain conditions. The plasma secretome is easily accessible from biological fluids and represents a good opportunity to discover new biomarkers that can be studied with nontargeted “omic” strategies.

Aims

To identify relevant deregulated proteins (DEP) in the secretome of a rat endotoxemic shock model.

Methods

Endotoxemic shock was induced in rats by intravenous injection of lipopolysaccharides (LPS, S. enterica typhi, 0.5 mg/kg) and compared to controls (Ringer Lactate, iv). Under isoflurane anesthesia, carotid cannulation allowed mean arterial blood pressure (MAP) and heart rate (HR) monitoring and blood sampling at different time points (T0 and T50 or T0 and T90, with EDTA and protease inhibitor). Samples were prepared for large-scale tandem mass spectrometry (MS-MS) based on a label-free quantification to allow identification of the proteins deregulated upon endotoxemic conditions. A Gene Ontology (GO) analysis defined several clusters of biological processes (BP) in which the DEP are involved.

Results

Ninety minutes after shock induction, the LPS group presents a reduction in MAP (-45%, p < 0.05) and increased lactate levels (+27.5%, p < 0.05) compared to the control group. Proteomic analyses revealed 10 and 33 DEP in the LPS group, respectively, at 50 and 90 minutes after LPS injection. At these time points, GO-BP showed alterations in pathways involved in oxidative stress response and coagulation.

Conclusion

This study proposes an approach to identify relevant DEP in septic shock and brings new insights into the understanding of the secretome adaptations upon sepsis.

Protein Deimination and Extracellular Vesicle Profiles in Antarctic Seabirds

Pelagic seabirds are amongst the most threatened of all avian groups. They face a range of immunological challenges which seem destined to increase due to environmental changes in their breeding and foraging habitats, affecting prey resources and exposure to pollution and pathogens. Therefore, the identification of biomarkers for the assessment of their health status is of considerable importance. Peptidylarginine deiminases (PADs) post-translationally convert arginine into citrulline in target proteins in an irreversible manner. PAD-mediated deimination can cause structural and functional changes in target proteins, allowing for protein moonlighting in physiological and pathophysiological processes. PADs furthermore contribute to the release of extracellular vesicles (EVs), which play important roles in cellular communication. In the present study, post-translationally deiminated protein and EV profiles of plasma were assessed in eight seabird species from the Antarctic, representing two avian orders: Procellariiformes (albatrosses and petrels) and Charadriiformes (waders, auks, gulls and skuas). We report some differences between the species assessed, with the narrowest EV profiles of 50-200 nm in the northern giant petrel Macronectes halli, and the highest abundance of larger 250-500 nm EVs in the brown skua Stercorarius antarcticus. The seabird EVs were positive for phylogenetically conserved EV markers and showed characteristic EV morphology. Post-translational deimination was identified in a range of key plasma proteins critical for immune response and metabolic pathways in three of the bird species under study; the wandering albatross Diomedea exulans, south polar skua Stercorarius maccormicki and northern giant petrel. Some differences in Gene Ontology (GO) biological and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways for deiminated proteins were observed between these three species. This indicates that target proteins for deimination may differ, potentially contributing to a range of physiological functions relating to metabolism and immune response, as well as to key defence mechanisms. PAD protein homologues were identified in the seabird plasma by Western blotting via cross-reaction with human PAD antibodies, at an expected 75 kDa size. This is the first study to profile EVs and to identify deiminated proteins as putative novel plasma biomarkers in Antarctic seabirds. These biomarkers may be further refined to become useful indicators of physiological and immunological status in seabirds-many of which are globally threatened.

Resveratrol inhibits LPS-induced inflammation through suppressing the signaling cascades of TLR4-NF-κB/MAPKs/IRF3

Resveratrol (Res) is a natural compound that possesses anti-inflammatory properties. However, the protective molecular mechanisms of Res against lipopolysaccharide (LPS)-induced inflammation have not been fully studied. In the present study, RAW264.7 cells were stimulated with LPS in the presence or absence of Res, and the subsequent modifications to the LPS-induced signaling pathways caused by Res treatment were examined. It was identified that Res decreased the mRNA levels of Toll-like receptor 4 (TLR4), myeloid differentiation primary response protein MyD88, TIR domain-containing adapter molecule 2, which suggested that Res may inhibit the activation of the TLR4 signaling pathway. It suppressed the expression levels of total and phosphorylated TLR4, NF-κB inhibitor, p38 mitogen-activated protein kinase (MAPK), c-Jun N-terminal kinase, extracellular signal-regulated kinase 1/2 and interferon (IFN) regulatory factor 3 (IRF3) proteins. Following treatment with Res or specific inhibitors, the production of pro-inflammatory mediators including tumor necrosis factor-α, interleukin (IL)-6, IL-8 and IFN-β were decreased and the expression of anti-inflammatory mediator IL-10 was increased. These results suggested that Res may inhibit the signaling cascades of NF-κB, MAPKs and IRF3, which modulate pro-inflammatory cytokines. In conclusion, Res exhibited a therapeutic effect on LPS-induced inflammation through suppression of the TLR4-NF-κB/MAPKs/IRF3 signaling cascades.

Reduced β2GPI Inhibiting Glomerular Mesangial Cells VEGF-NO Axis Uncoupling Induced by High Glucose

VEGF-NO axis uncoupling is an important pathogenesis for DN. Reduced β2GPI could play a part in VEGF signaling pathway and has a protective effect on diabetic vascular disease. This study investigates the effect of reduced β2GPI on glomerular mesangial cells VEGF-NO axis uncoupling induced by high glucose. Compared to control group, glomerular mesangial cell line HBZY-1 cells treated with high glucose expressed higher levels of VEGF mRNA and protein and produced more ROS but less NO. The related proteins related to VEGF-NO axis were assayed. High glucose could significantly increase the expression of the level of VEGFR2 and obviously increase phosphorylation of Akt and eNOS but significantly decrease the expression of GTP cyclohydrolase 1 (GCH-1), reducing the production of eNOS dimer. Both β2GPI and reduced β2GPI partly reverse these effects caused by high glucose. Reduced β2GPI had stronger effect than β2GPI. GCH-1 is the speed limit of tetrahydrobiopterin (BH4) synthesis enzyme. As the key part of eNOS cofactors, BH4 could partly restore eNOS dimer induced by high glucose. Our results indicated that high glucose could interfere with eNOS dimer formation. β2GPI and reduced β2GPI can partly reverse the VEGF-NO axis uncoupling by restoring the GCH-1 expression level and then promote eNOS dimer formation.

The purification of reduced β2-glycoprotein I showed its native activity in vitro

Background

New evidence has shown that reduced β2-glycoprotein I (β2GPI) has anti-oxidative stress and anti-inflammatory activity. However, the details are still poorly understood. This study aims to prepare stable reduced β2GPI with its native bioactivity in vitro.

Methods

Human β2GPI was purified from plasma first with perchloric acid precipitation and then purified with a series of chromatography methods including Sephadex G-25 desalting, SP HP, AF-heparin HC-650 M, and Sephacryl S-200. The purified human β2GPI was reduced with thioredoxin-1 (TRX-1) activated by DL-dithiothreitol (DTT). Glutathione (GSH) was selected to block the free thiols in reduced β2GPI. LC/MS was used to verify the location of free thiols. Western blot analysis was used to detect β2GPI immunoreactivity. MTS and flow cytometry were conducted to investigate its biological effect on oxidative-stress-induced death of human umbilical vein endothelial cells (HUVECs). The levels of tumour necrosis factor-alpha (TNF-α),interleukin-6 (IL-6) interleukin-10 (IL-10),interleukin-12P70 (IL-12P70),interferon-gamma (IFN-γ) and monocyte chemoattractant protein −1(MCP-1) in mouse serum were quantified to assess its anti-inflammatory activity in lipopolysaccharide (LPS)-mediated systemic inflammation.

Results

We obtained approximately 10 mg β2GPI (purity 98.7%) from 200 ml plasma. The protein yield was 0.05 mg/ml plasma. β2GPI was then reduced by TRX-1/DTT in vitro; the free thiols were detected on Cys288 and Cys326 in domain V of β2GPI. The GSH blockage stabilized the reduced β2GPI in vitro. This reduced β2GPI can be recognized by the anti-β2GPI antibody, can significantly reduce the death of HUVECs after H₂O₂ treatment and can significantly decrease the levels of TNF-α, IL-6,IFN-γ and MCP-1 in mice upon LPS stimulation.

Conclusion

Stable reduced β2GPI can be obtained in vitro by TRX-1 deoxidation followed by the blockage of thiols with GSH. This reduced β2GPI maintains the same immunological activity as oxidized β2GPI and has the ability to counter the oxidative stress induced by H₂O₂ in HUVECs and inflammation in LPS-mediated inflammation in mice.

Βeta 2-glycoprotein I protects mice against gram-negative septicaemia in a sexually dimorphic manner

The immune responses of males and females to bacterial infections display differences. The mechanisms that underlie this sexual dimorphism are multifactorial. Lipopolysaccharide (LPS) contributes to the pathogenesis of endotoxaemia. We have previously demonstrated that the plasma protein beta-2 glycoprotein-1 (β2GPI) reduces LPS-induced inflammation in male mice. In the present study using a more robust infection model of septicaemia the role of β2GPI is examined in both male and female wild type (WT) and β2GPI deficient (β2GPI^-/-) mice challenged with Escherichia coli (E. coli) intravenously. β2GPI deficiency led to an increase of E. coli colony forming units (CFU) in the circulation of both male and female mice. In male β2GPI^-/- mice this was associated with a worse clinical severity score. This difference was not observed between female β2GPI^-/- and female WT mice. Male WT mice had decreased levels of total and increased levels of free thiol β2GPI following administration of LPS or E. coli. This pattern of sexual dimorphic response was also observed in our cohort of humans with sepsis. These findings support a role for β2GPI in modulating the sex-specific susceptibility to gram-negative septicaemia.