scholarly journals B. anthracisedema toxin increases cAMP levels and inhibits phenylephrine-stimulated contraction in a rat aortic ring model

2013 ◽  
Vol 305 (2) ◽  
pp. H238-H250 ◽  
Author(s):  
Yan Li ◽  
Xizhong Cui ◽  
Steven B. Solomon ◽  
Kenneth Remy ◽  
Yvonne Fitz ◽  
...  
Keyword(s):  
Protective Antigen ◽  
Lethal Factor ◽  
Aortic Ring ◽  
Contractile Force ◽  
Host Cells ◽  
Sprague Dawley ◽  
Adenyl Cyclase Activity ◽  
Ring Model ◽  
Arterial Relaxation ◽  
Rat Aortic Ring Model

B. anthracis edema toxin (ET) and lethal toxin (LT) are each composed of protective antigen (PA), necessary for toxin uptake by host cells, and their respective toxic moieties, edema factor (EF) and lethal factor (LF). Although both toxins likely contribute to shock during infection, their mechanisms are unclear. To test whether ET and LT produce arterial relaxation, their effects on phenylephrine (PE)-stimulated contraction in a Sprague-Dawley rat aortic ring model were measured. Rings were prepared and connected to pressure transducers. Their viability was confirmed, and peak contraction with 60 mM KCl was determined. Compared with PA pretreatment (control, 60 min), ET pretreatment at concentrations similar to those noted in vivo decreased the mean (±SE) maximum contractile force (MCF; percent peak contraction) in rings generated during stimulation with increasing PE concentrations (96.2 ± 7.0 vs. 57.3 ± 9.1) and increased the estimated PE concentration producing half the MCF (EC50; 10−7M, 1.1 ± 0.3 vs. 3.7 ± 0.8, P ≤ 0.002). ET inhibition with PA-directed monoclonal antibodies, selective EF inhibition with adefovir, or removal of the ring endothelium inhibited the effects of ET on MCF and EC50( P ≤ 0.02). Consistent with its adenyl cyclase activity, ET increased tissue cAMP in endothelium-intact but not endothelium-denuded rings ( P < 0.0001 and 0.25, respectively). LT pretreatment, even in high concentrations, did not significantly decrease MCF or increase EC50(all P > 0.05). In rings precontracted with PE compared with posttreatment with PA (90 min), ET posttreatment produced progressive reductions in contractile force and increases in relaxation in endothelium-intact rings ( P < 0.0001) but not endothelium-denuded rings ( P = 0.51). Thus, ET may contribute to shock by producing arterial relaxation.

Rat Aortic Ring Model to Assay Angiogenesis ex vivo

BIO-PROTOCOL ◽  
2015 ◽  
Vol 5 (20) ◽  
Author(s):  
Isabelle Ernens ◽  
B�n�dicte Lenoir ◽  
Yvan Devaux ◽  
Daniel Wagner
Keyword(s):  
Ex Vivo ◽  
Aortic Ring ◽  
Ring Model ◽  
Rat Aortic Ring Model

scholarly journals Injection of Staphylococcus aureus EDIN by the Bacillus anthracis Protective Antigen Machinery Induces Vascular Permeability

2009 ◽  
Vol 77 (9) ◽  
pp. 3596-3601 ◽  
Author(s):  
Monica Rolando ◽  
Patrick Munro ◽  
Caroline Stefani ◽  
Patrick Auberger ◽  
Gilles Flatau ◽  
...  
Keyword(s):  
Bacillus Anthracis ◽  
Vascular Permeability ◽  
Protective Antigen ◽  
Lethal Factor ◽  
Vascular Leakage ◽  
Host Cells ◽  
Mitogen Activated Protein Kinase ◽  
Systemic Injection ◽  
Pulmonary Endothelium ◽  
Endothelium Permeability

ABSTRACT Systemic injection of Bacillus anthracis lethal toxin (LT) produces vascular leakage and animal death. Recent studies suggest that LT triggers direct endothelial cell cytotoxicity that is responsible for the vascular leakage. LT is composed of heptamers of protective antigen (PA), which drives the endocytosis and translocation into host cells of the lethal factor (LF), a mitogen-activated protein kinase kinase protease. Here we investigated the consequences of injection of an endothelium-permeabilizing factor using LT as a “molecular syringe.” To this end, we generated the chimeric factor LE, corresponding to the PA-binding domain of LF (LF1-254) fused to EDIN exoenzyme. EDIN ADP ribosylates RhoA, leading to actin cable disruption and formation of transcellular tunnels in endothelial cells. We report that systemic injection of LET (LE plus PA) triggers a PA-dependent increase in the pulmonary endothelium permeability. We also report that native LT induces a progressive loss of endothelium barrier function. We established that there is a direct correlation between the extent of endothelium permeability induced by LT and the cytotoxic activity of LT. This suggests new ways to design therapeutic drugs against anthrax directed toward vascular permeability.

Manipulation of host signalling pathways by anthrax toxins

2007 ◽  
Vol 402 (3) ◽  
pp. 405-417 ◽  
Author(s):  
Benjamin E. Turk
Keyword(s):  
Protein Kinase ◽  
Pathogenic Bacteria ◽  
Protective Antigen ◽  
Lethal Factor ◽  
Cell Types ◽  
Host Cells ◽  
Mitogen Activated Protein Kinase ◽  
Signalling Pathways ◽  
Common Strategy ◽  
Mitogen Activated Protein

Infectious microbes face an unwelcoming environment in their mammalian hosts, which have evolved elaborate multicelluar systems for recognition and elimination of invading pathogens. A common strategy used by pathogenic bacteria to establish infection is to secrete protein factors that block intracellular signalling pathways essential for host defence. Some of these proteins also act as toxins, directly causing pathology associated with disease. Bacillus anthracis, the bacterium that causes anthrax, secretes two plasmid-encoded enzymes, LF (lethal factor) and EF (oedema factor), that are delivered into host cells by a third bacterial protein, PA (protective antigen). The two toxins act on a variety of cell types, disabling the immune system and inevitably killing the host. LF is an extraordinarily selective metalloproteinase that site-specifically cleaves MKKs (mitogen-activated protein kinase kinases). Cleavage of MKKs by LF prevents them from activating their downstream MAPK (mitogen-activated protein kinase) substrates by disrupting a critical docking interaction. Blockade of MAPK signalling functionally impairs cells of both the innate and adaptive immune systems and induces cell death in macrophages. EF is an adenylate cyclase that is activated by calmodulin through a non-canonical mechanism. EF causes sustained and potent activation of host cAMP-dependent signalling pathways, which disables phagocytes. Here I review recent progress in elucidating the mechanisms by which LF and EF influence host signalling and thereby contribute to disease.

scholarly journals Purified Anthocyanin Supplementation Improves Endothelial Function via NO-cGMP Activation in Hypercholesterolemic Individuals

2011 ◽  
Vol 57 (11) ◽  
pp. 1524-1533 ◽  
Author(s):  
Yanna Zhu ◽  
Min Xia ◽  
Yan Yang ◽  
Fengqiong Liu ◽  
Zhongxia Li ◽  
...  
Keyword(s):  
Endothelial Function ◽  
Hdl Cholesterol ◽  
Aortic Ring ◽  
Control Group ◽  
Short Term ◽  
Beneficial Effects ◽  
Ring Model ◽  
Vascular Adhesion ◽  
Rat Aortic Ring Model

BACKGROUND Anthocyanins have been shown to improve endothelial function in animal models. However, whether these compounds have similar beneficial effects in humans is largely unknown. METHODS In a short-term crossover study, 12 hypercholesterolemic individuals were given oral anthocyanins (320 mg) isolated from berries or placebo. Brachial artery flow-mediated dilation (FMD) was assessed before and after the intervention. In a long-term intervention trial (12 weeks), 150 hypercholesterolemic individuals were given anthocyanins (320 mg/day, n = 75) or placebo (n = 75), after which we measured FMD, plasma cGMP, and other serum biomarkers. Another short-term intervention was conducted in the presence of NO-cGMP inhibitors in 6 people and in a rat aortic ring model (n = 8). RESULTS Significant increases of FMD from 8.3% (0.6%) at baseline to 11.0% (0.8%) at 1 h and 10.1% (0.9%) at 2 h were observed after short-term anthocyanin consumption, concomitantly with increases of plasma anthocyanin concentrations (P &lt; 0.05). In the study participants who received long-term anthocyanin intervention, compared with the control group, we observed significant increases in the FMD (28.4% vs 2.2%), cGMP (12.6% vs −1.2%), and HDL-cholesterol concentrations, but decreases in the serum soluble vascular adhesion molecule-1 and LDL cholesterol concentrations (P &lt; 0.05). The changes in the cGMP and HDL cholesterol concentrations positively correlated with FMD in the anthocyanin group (P &lt; 0.05). In the presence of NO-cGMP inhibitors, the effects of anthocyanin on endothelial function were abolished in human participants and in a rat aortic ring model. CONCLUSIONS Anthocyanin supplementation improves endothelium-dependent vasodilation in hypercholesterolemic individuals. This effect involves activation of the NO-cGMP signaling pathway, improvements in the serum lipid profile, and decreased inflammation.

scholarly journals Anthrax toxins suppress T lymphocyte activation by disrupting antigen receptor signaling

2005 ◽  
Vol 201 (3) ◽  
pp. 325-331 ◽  
Author(s):  
Silvia Rossi Paccani ◽  
Fiorella Tonello ◽  
Raffaella Ghittoni ◽  
Mariarita Natale ◽  
Lucia Muraro ◽  
...  
Keyword(s):  
T Cell Activation ◽  
Cell Activation ◽  
Protective Antigen ◽  
Lethal Factor ◽  
Antigen Receptor ◽  
Lymphocyte Activation ◽  
Host Cells ◽  
Cytokine Gene Expression ◽  
Edema Factor ◽  
Human T Cell

Anthrax is an infection caused by pathogenic strains of Bacillus anthracis, which secretes a three-component toxic complex consisting of protective antigen (PA), edema factor (EF), and lethal factor (LF). PA forms binary complexes with either LF or EF and mediates their entry into host cells. Although the initial phases of bacterial growth occur in the lymph node, the host fails to mount an effective immune response. Here, we show that LT and ET are potent suppressors of human T cell activation and proliferation triggered through the antigen receptor. Both LT and ET inhibit the mitogen-activated protein and stress kinase pathways, and both toxins inhibit activation of NFAT and AP-1, two transcription factors essential for cytokine gene expression. These data identify a novel strategy of immune evasion by B. anthracis, based on both effector subunits of the toxic complex, and targeted to a key cellular component of adaptive immunity.

scholarly journals Modifications to the classical rat aortic ring model to allow vascular degeneration studies

2021 ◽  
Vol 2 (1) ◽  
pp. 100281
Author(s):  
Guillaume Blot ◽  
Thérèse-Marie Sartoris ◽  
Florian Sennlaub ◽  
Xavier Guillonneau
Keyword(s):  
Aortic Ring ◽  
Ring Model ◽  
Rat Aortic Ring Model

scholarly journals Green Synthesis of Silver Nanoparticles using Achillea biebersteinii Flower Extract and Its Anti-Angiogenic Properties in the Rat Aortic Ring Model

Molecules ◽  
2014 ◽  
Vol 19 (4) ◽  
pp. 4624-4634 ◽  
Author(s):  
Javad Baharara ◽  
Farideh Namvar ◽  
Tayebe Ramezani ◽  
Nasrin Hosseini ◽  
Rosfarizan Mohamad
Keyword(s):  
Silver Nanoparticles ◽  
Green Synthesis ◽  
Aortic Ring ◽  
Flower Extract ◽  
Ring Model ◽  
Achillea Biebersteinii ◽  
Rat Aortic Ring Model
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