scholarly journals Bacillus anthracis Edema Toxin Inhibits Efferocytosis in Human Macrophages and Alters Efferocytic Receptor Signaling

2019 ◽  
Vol 20 (5) ◽  
pp. 1167 ◽  
Author(s):  
Zijian Pan ◽  
Eric Dumas ◽  
Christina Lawrence ◽  
Lance Pate ◽  
Sherri Longobardi ◽  
...  
Keyword(s):  
Bacillus Anthracis ◽  
Protective Antigen ◽  
Apoptotic Cell ◽  
Systemic Infection ◽  
Cyclic Adenosine Monophosphate ◽  
Protein S ◽  
Adenosine Monophosphate ◽  
Receptor Signaling ◽  
Human Macrophages ◽  
Edema Toxin

The Bacillus anthracis Edema Toxin (ET), composed of a Protective Antigen (PA) and the Edema Factor (EF), is a cellular adenylate cyclase that alters host responses by elevating cyclic adenosine monophosphate (cAMP) to supraphysiologic levels. However, the role of ET in systemic anthrax is unclear. Efferocytosis is a cAMP-sensitive, anti-inflammatory process of apoptotic cell engulfment, the inhibition of which may promote sepsis in systemic anthrax. Here, we tested the hypothesis that ET inhibits efferocytosis by primary human macrophages and evaluated the mechanisms of altered efferocytic signaling. ET, but not PA or EF alone, inhibited the efferocytosis of early apoptotic neutrophils (PMN) by primary human M2 macrophages (polarized with IL-4, IL-10, and/or dexamethasone) at concentrations relevant to those encountered in systemic infection. ET inhibited Protein S- and MFGE8-dependent efferocytosis initiated by signaling through MerTK and αVβ5 receptors, respectively. ET inhibited Rac1 activation as well as the phosphorylation of Rac1 and key activating sites of calcium calmodulin-dependent kinases CamK1α, CamK4, and vasodilator-stimulated phosphoprotein, that were induced by the exposure of M2(Dex) macrophages to Protein S-opsonized apoptotic PMN. These results show that ET impairs macrophage efferocytosis and alters efferocytic receptor signaling.

scholarly journals Murine Innate Immune Response to Virulent Toxigenic and Nontoxigenic Bacillus anthracis Strains

2007 ◽  
Vol 75 (4) ◽  
pp. 1757-1764 ◽  
Author(s):  
Melissa Drysdale ◽  
Gwyneth Olson ◽  
Theresa M. Koehler ◽  
Mary F. Lipscomb ◽  
C. Rick Lyons
Keyword(s):  
Bacillus Anthracis ◽  
Protective Antigen ◽  
Lethal Factor ◽  
Systemic Infection ◽  
Neutrophil Recruitment ◽  
Cell Recruitment ◽  
Edema Factor ◽  
Edema Toxin ◽  
Neutrophil Depletion ◽  
Intravenous Inoculation

ABSTRACT Effective treatment of anthrax is hampered by our limited understanding of the pathophysiology of Bacillus anthracis infection. We used a genetically complete (pXO1+ pXO2+) virulent B. anthracis strain and four isogenic toxin-null mutants to determine the effects of the anthrax edema toxin (ET; edema factor [EF] plus protective antigen [PA]) and lethal toxin (LT; lethal factor [LF] plus PA) on the host innate response during systemic infection. Using the spleen as an indicator for host response, we found that intravenous inoculation of LT-deficient mutants into C57BL/6 mice significantly increased production of several cytokines over that observed after infection with the parent strain or an EF-deficient mutant. Bacteria producing one or both of the toxins were capable of inducing significant apoptosis of cells present in spleens, whereas apoptosis was greatly reduced in mice infected with nontoxigenic mutants. Mice infected with toxin-producing strains also showed increased splenic neutrophil recruitment compared to mice infected with nontoxigenic strains and neutrophil depletion prior to infection with toxin-producing strains, leading to decreased levels of apoptosis. Together, these studies indicate that anthrax LT suppresses cytokine secretion during infection, but both EF and LF play roles in inducing neutrophil recruitment and enhancing apoptosis. Interestingly, in the absence of LF the effect of EF-induced cell recruitment is further enhanced, perhaps because LF so effectively suppresses the secretion of chemokines.

Theophylline synergizes with chlorambucil in inducing apoptosis of B- chronic lymphocytic leukemia cells

Blood ◽  
1996 ◽  
Vol 88 (6) ◽  
pp. 2172-2182 ◽  
Author(s):  
F Mentz ◽  
MD Mossalayi ◽  
F Ouaaz ◽  
S Baudet ◽  
F Issaly ◽  
...  
Keyword(s):  
B Cells ◽  
Chronic Lymphocytic Leukemia ◽  
Apoptotic Cell ◽  
Protein A ◽  
Phosphodiesterase Inhibitor ◽  
Cyclic Adenosine Monophosphate ◽  
Adenosine Monophosphate ◽  
Lymphocytic Leukemia ◽  
Interleukin 4 ◽  
Induced Apoptosis

We tested the effects of theophylline, a phosphodiesterase inhibitor inducing intracellular accumulation of cyclic adenosine monophosphate (cAMP), on malignant B cells from 15 patients with B-chronic lymphocytic leukemia (B-CLL). We observed a large increase in apoptotic cell numbers (mean, 90% v 20% in medium alone) in the presence of theophylline (100 micrograms/mL) or chlorambucil (10 mumol/L) after 72 hours of incubation. Maximal apoptosis (90%) was reached after 36 hours when the two drugs were used together at fourfold lower concentrations, indicating a synergistic effect; no effect was observed with normal B cells, suggesting that the combination might have therapeutic interest. Chlorambucil induced intracellular Ca+2 influx, pointing to the involvement of two signaling pathways that might explain its synergy with theophylline through their effects on oncogenes. The expression of bcl-2 protein, a proto-oncogene inhibiting apoptosis, decreased after incubation with the drugs, while c-myc, recently described as having a potent role in apoptosis, was overexpressed. For p53 we observed an overexpression in the presence of chlorambucil or both theophylline- chlorambucil and a decrease after theophylline incubation. Chlorambucil- and theophylline-induced apoptosis was partially inhibited by interleukin-4 (IL-4), which also abrogated the effects on oncogene expression. These results provide insight into the mechanisms underlying B-CLL apoptosis and suggest that the theophylline- chlorambucil combination may be of therapeutic value in this setting.

scholarly journals Contributions of Histamine, Prostanoids, and Neurokinins to Edema Elicited by Edema Toxin from Bacillus anthracis

2007 ◽  
Vol 75 (4) ◽  
pp. 1895-1903 ◽  
Author(s):  
Jeffrey Tessier ◽  
Candace Green ◽  
Diana Padgett ◽  
Wei Zhao ◽  
Lawrence Schwartz ◽  
...  
Keyword(s):  
Bacillus Anthracis ◽  
Protective Antigen ◽  
Cell Types ◽  
Vascular Leakage ◽  
Target Cells ◽  
Edema Factor ◽  
Edema Toxin ◽  
Neurokinin 1

ABSTRACT Bacillus anthracis edema toxin (ET), composed of protective antigen and an adenylate cyclase edema factor (EF), elicits edema in host tissues, but the target cells and events leading from EF-mediated cyclic-AMP production to edema are unknown. We evaluated the direct effect of ET on several cell types in vitro and tested the possibility that mediators of vascular leakage, such as histamine, contribute to edema in rabbits given intradermal ET. ET increased the transendothelial electrical resistance of endothelial monolayers, a response that is mechanistically inconsistent with the in vivo vascular leakage induced by ET. Screening of several drugs by intradermal treatment prior to toxin injection demonstrated reduced ET-induced vascular leakage with a cyclo-oxygenase inhibitor (indomethacin), agents that interfere with histamine (pyrilamine or cromolyn), or a neurokinin antagonist (spantide). Systemic administration of indomethacin or celecoxib (cyclo-oxygenase inhibitors), pyrilamine, aprepitant (a neurokinin 1 receptor antagonist), or indomethacin with pyrilamine significantly reduced vascular leakage associated with ET. Although the effects of pyrilamine, cromolyn, or aprepitant on ET-induced vascular leakage suggest a possible role for mast cells (MC) and sensory neurons in ET-induced edema, ET did not elicit degranulation of human skin MC or substance P release from NT2N cells in vitro. Our results indicate that ET, acting indirectly or directly on a target yet to be identified, stimulates the production/release of multiple inflammatory mediators, specifically neurokinins, prostanoids, and histamine. These mediators, individually and through complex interactions, increase vascular permeability, and interventions directed at these mediators may benefit hosts infected with B. anthracis.

scholarly journals Bacillus anthracis Edema Toxin Impairs Neutrophil Actin-Based Motility

2009 ◽  
Vol 77 (6) ◽  
pp. 2455-2464 ◽  
Author(s):  
Sarah E. Szarowicz ◽  
Russell L. During ◽  
Wei Li ◽  
Conrad P. Quinn ◽  
Wei-Jen Tang ◽  
...  
Keyword(s):  
Bacillus Anthracis ◽  
Protective Antigen ◽  
Fold Increase ◽  
Polymorphonuclear Neutrophil ◽  
Actin Assembly ◽  
Anthrax Lethal Toxin ◽  
Edema Factor ◽  
Low Concentrations ◽  
Inhalation Anthrax ◽  
Edema Toxin

ABSTRACT Inhalation anthrax results in high-grade bacteremia and is accompanied by a delay in the rise of the peripheral polymorphonuclear neutrophil (PMN) count and a paucity of PMNs in the infected pleural fluid and mediastinum. Edema toxin (ET) is one of the major Bacillus anthracis virulence factors and consists of the adenylate cyclase edema factor (EF) and protective antigen (PA). Relatively low concentrations of ET (100 to 500 ng/ml of PA and EF) significantly impair human PMN chemokinesis, chemotaxis, and ability to polarize. These changes are accompanied by a reduction in chemoattractant-stimulated PMN actin assembly. ET also causes a significant decrease in Listeria monocytogenes intracellular actin-based motility within HeLa cells. These defects in actin assembly are accompanied by a >50-fold increase in intracellular cyclic AMP and a >4-fold increase in the phosphorylation of protein kinase A. We have previously shown that anthrax lethal toxin (LT) also impairs neutrophil actin-based motility (R. L. During, W. Li, B. Hao, J. M. Koenig, D. S. Stephens, C. P. Quinn, and F. S. Southwick, J. Infect. Dis. 192:837-845, 2005), and we now find that LT combined with ET causes an additive inhibition of PMN chemokinesis, polarization, chemotaxis, and FMLP (N-formyl-met-leu-phe)-induced actin assembly. We conclude that ET alone or combined with LT impairs PMN actin assembly, resulting in paralysis of PMN chemotaxis.

scholarly journals A Monoclonal Antibody to Bacillus anthracis Protective Antigen Defines a Neutralizing Epitope in Domain 1

2006 ◽  
Vol 74 (7) ◽  
pp. 4149-4156 ◽  
Author(s):  
Johanna Rivera ◽  
Antonio Nakouzi ◽  
Nareen Abboud ◽  
Ekaterina Revskaya ◽  
David Goldman ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Monoclonal Antibodies ◽  
Bacillus Anthracis ◽  
Protective Antigen ◽  
Lethal Factor ◽  
Proteolytic Digestion ◽  
Potential Mechanism ◽  
Host Protection ◽  
Edema Toxin

ABSTRACT Antibody (Ab) responses to Bacillus anthracis toxins are protective, but relatively few protective monoclonal antibodies (MAbs) have been reported. Protective antigen (PA) is essential for the action of B. anthracis lethal toxin (LeTx) and edema toxin. In this study, we generated two MAbs to PA, MAbs 7.5G and 10F4. These MAbs did not compete for binding to PA, consistent with specificities for different epitopes. The MAbs were tested for their ability to protect a monolayer of cultured macrophages against toxin-mediated cytotoxicity. MAb 7.5G, the most-neutralizing MAb, bound to domain 1 of PA and reduced LeTx toxicity in BALB/c mice. Remarkably, MAb 7.5G provided protection without blocking the binding of PA or lethal factor or the formation of the PA heptamer complex. However, MAb 7.5G slowed the proteolytic digestion of PA by furin in vitro, suggesting a potential mechanism for Ab-mediated protection. These observations indicate that some Abs to domain 1 can contribute to host protection.

scholarly journals Therapeutic targeting of the pathological triad of extrasynaptic NMDA receptor signaling in neurodegenerations

2017 ◽  
Vol 214 (3) ◽  
pp. 569-578 ◽  
Author(s):  
Hilmar Bading
Keyword(s):  
Nmda Receptor ◽  
Nmda Receptors ◽  
Histone Deacetylases ◽  
Cyclic Adenosine Monophosphate ◽  
Adenosine Monophosphate ◽  
Cell Loss ◽  
Nuclear Accumulation ◽  
Receptor Signaling ◽  
Element Binding Protein ◽  
Responsive Element

Activation of extrasynaptic N-methyl-d-aspartate (NMDA) receptors causes neurodegeneration and cell death. The disease mechanism involves a pathological triad consisting of mitochondrial dysfunction, loss of integrity of neuronal structures and connectivity, and disruption of excitation–transcription coupling caused by CREB (cyclic adenosine monophosphate–responsive element-binding protein) shut-off and nuclear accumulation of class IIa histone deacetylases. Interdependency within the triad fuels an accelerating disease progression that culminates in failure of mitochondrial energy production and cell loss. Both acute and slowly progressive neurodegenerative conditions, including stroke, Alzheimer’s disease, amyotrophic lateral sclerosis, and Huntington’s disease, share increased death signaling by extrasynaptic NMDA receptors caused by elevated extracellular glutamate concentrations or relocalization of NMDA receptors to extrasynaptic sites. Six areas of therapeutic objectives are defined, based on which a broadly applicable combination therapy is proposed to combat the pathological triad of extrasynaptic NMDA receptor signaling that is common to many neurodegenerative diseases.

scholarly journals Noncapsulated Toxinogenic Bacillus anthracis Presents a Specific Growth and Dissemination Pattern in Naive and Protective Antigen-Immune Mice

2007 ◽  
Vol 75 (10) ◽  
pp. 4754-4761 ◽  
Author(s):  
Ian J. Glomski ◽  
Jean-Philippe Corre ◽  
Michèle Mock ◽  
Pierre L. Goossens
Keyword(s):  
Immune Responses ◽  
Bacillus Anthracis ◽  
Bacterial Growth ◽  
Protective Antigen ◽  
Host Immune Responses ◽  
Edema Toxin ◽  
In Vivo Bioluminescence Imaging ◽  
Mammalian Genetic ◽  
Draining Lymph Nodes

ABSTRACTBacillus anthracisis a spore-forming bacterium that causes anthrax.B. anthracishas three major virulence factors, namely, lethal toxin, edema toxin, and a poly-γ-d-glutamic acid capsule. The toxins modulate host immune responses, and the capsule inhibits phagocytosis. With the goal of increasing safety, decreasing security concerns, and taking advantage of mammalian genetic tools and reagents, mouse models ofB. anthracisinfection have been developed using attenuated bacteria that produce toxins but no capsule. While these models have been useful in studying both toxinogenic infections and antitoxin vaccine efficacy, we questioned whether eliminating the capsule changed bacterial growth and dissemination characteristics. Thus, the progression of infection by toxinogenic noncapsulatedB. anthraciswas analyzed and compared to that by previously reported nontoxinogenic capsulated bacteria, using in vivo bioluminescence imaging. The influence of immunization with the toxin component protective antigen (PA) on the development of infection was also examined. The toxinogenic noncapsulated bacteria were initially confined to the cutaneous site of infection. Bacteria then progressed to the draining lymph nodes and, finally, late in the infection, to the lungs, kidneys, and frequently the gastrointestinal tract. There was minimal colonization of the spleen. PA immunization reduced bacterial growth from the outset and limited infection to the site of inoculation. These in vivo observations show that dissemination by toxinogenic noncapsulated strains differs markedly from that by nontoxinogenic capsulated strains. Additionally, PA immunization counters bacterial growth and dissemination in vivo from the onset of infection.

Effects of Glycosaminoglycan from Urechis Unicinctus on the P2Y12 Receptor Signaling Pathway in Rat Platelets

2019 ◽  
Author(s):  
Chunying Yuan ◽  
Fei Miao ◽  
Jinghong Li ◽  
Qingman Cui
Keyword(s):  
Signaling Pathway ◽  
Cyclic Adenosine Monophosphate ◽  
Adenosine Monophosphate ◽  
P2y12 Receptor ◽  
Enzyme Linked Immunosorbent Assay ◽  
Receptor Signaling ◽  
Urechis Unicinctus ◽  
Camp Content ◽  
Receptor Signaling Pathway ◽  
Rat Platelets

This study aims to investigate the effects of glycosaminoglycan (GAG) from Urechis unicinctus on the P2Y12 receptor signaling pathway in rat platelets. The concentrations of cyclic adenosine monophosphate (cAMP), thromboxane B2 (TXB2) and glycoprotein IIb/IIIa (GPIIb/IIIa) in rat platelets were determined using enzyme-linked immunosorbent assay (ELISA) kits. The phosphorylation levels of protein kinase A (PKA) and vasodilator-stimulated phosphoprotein (VASP) in rat platelets were detected through Western blot. The expression of P2Y12 gene in rat platelets was analyzed via real-time fluorescence quantitative PCR and reverse-transcription PCR. It was observed that GAG significantly increased the cAMP content (plessthan 0.05, plessthan 0.01) and decreased the TXB2 and GPIIb/IIIa concentrations (plessthan 0.05,plessthan 0.01) in rat platelets. GAG significantly enhanced the phosphorylation levels of PKA and VASP in rat platelets plessthan 0.01) and had a synergistic effect with the P2Y12 receptor blocker. GAG significantly reduced the expression level of P2Y12 gene in rat platelets (plessthan 0.01). We speculated that GAG from U. unicinctus inhibited platelet aggregation in rats through the P2Y12 receptor signaling pathway.

scholarly journals Expression of either Lethal Toxin or Edema Toxin by Bacillus anthracis Is Sufficient for Virulence in a Rabbit Model of Inhalational Anthrax

2012 ◽  
Vol 80 (7) ◽  
pp. 2414-2425 ◽  
Author(s):  
Julie A. Lovchik ◽  
Melissa Drysdale ◽  
Theresa M. Koehler ◽  
Julie A. Hutt ◽  
C. Rick Lyons
Keyword(s):  
Bacillus Anthracis ◽  
Protective Antigen ◽  
Lethal Factor ◽  
Rabbit Model ◽  
Lethal Toxin ◽  
Content Type ◽  
Edema Factor ◽  
Systemic Dissemination ◽  
Edema Toxin ◽  
Ames Strain

ABSTRACTThe development of therapeutics against biothreats requires that we understand the pathogenesis of the disease in relevant animal models. The rabbit model of inhalational anthrax is an important tool in the assessment of potential therapeutics againstBacillus anthracis. We investigated the roles ofB. anthraciscapsule and toxins in the pathogenesis of inhalational anthrax in rabbits by comparing infection with the Ames strain versus isogenic mutants with deletions of the genes for the capsule operon (capBCADE), lethal factor (lef), edema factor (cya), or protective antigen (pagA). The absence of capsule or protective antigen (PA) resulted in complete avirulence, while the presence of either edema toxin or lethal toxin plus capsule resulted in lethality. The absence of toxin did not influence the ability ofB. anthracisto traffic to draining lymph nodes, but systemic dissemination required the presence of at least one of the toxins. Histopathology studies demonstrated minimal differences among lethal wild-type and single toxin mutant strains. When rabbits were coinfected with the Ames strain and the PA− mutant strain, the toxin produced by the Ames strain was not able to promote dissemination of the PA− mutant, suggesting that toxigenic action occurs in close proximity to secreting bacteria. Taken together, these findings suggest that a major role for toxins in the pathogenesis of anthrax is to enable the organism to overcome innate host effector mechanisms locally and that much of the damage during the later stages of infection is due to the interactions of the host with the massive bacterial burden.

Protein-Protein Interactions of Phosphodiesterases

2019 ◽  
Vol 19 (7) ◽  
pp. 555-564 ◽  
Author(s):  
Mayasah Y. Al-Nema ◽  
Anand Gaurav
Keyword(s):  
Protein Interactions ◽  
Second Messengers ◽  
Cyclic Adenosine Monophosphate ◽  
Protein S ◽  
Adenosine Monophosphate ◽  
Specific Protein ◽  
Guanosine Monophosphate ◽  
Protein Protein Interactions ◽  
Specific Mechanism

Background: Phosphodiesterases (PDEs) are enzymes that play a key role in terminating cyclic nucleotides signalling by catalysing the hydrolysis of 3’, 5’- cyclic adenosine monophosphate (cAMP) and/or 3’, 5’ cyclic guanosine monophosphate (cGMP), the second messengers within the cell that transport the signals produced by extracellular signalling molecules which are unable to get into the cells. However, PDEs are proteins which do not operate alone but in complexes that made up of a many proteins. Objective: This review highlights some of the general characteristics of PDEs and focuses mainly on the Protein-Protein Interactions (PPIs) of selected PDE enzymes. The objective is to review the role of PPIs in the specific mechanism for activation and thereby regulation of certain biological functions of PDEs. Methods: Methods The article discusses some of the PPIs of selected PDEs as reported in recent scientific literature. These interactions are critical for understanding the biological role of the target PDE. Results: The PPIs have shown that each PDE has a specific mechanism for activation and thereby regulation a certain biological function. Conclusion: Targeting of PDEs to specific regions of the cell is based on the interaction with other proteins where each PDE enzyme binds with specific protein(s) via PPIs.

Sign in / Sign up

Export Citation Format

Share Document