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Liu J, Zuo Z, Ewing M, Cao Q, Cao L, Li Q, Finkel T, Leppla SH, Liu S. ERK pathway reactivation prevents anthrax toxin lethality in mice. Nat Microbiol 2025; 10:1145-1155. [PMID: 40155776 DOI: 10.1038/s41564-025-01977-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2024] [Accepted: 03/03/2025] [Indexed: 04/01/2025]
Abstract
Lethal toxin (LT), the major virulence factor of Bacillus anthracis, proteolytically inactivates MEKs and disables downstream ERK, p38 and JNK pathway signalling leading to tissue damage and mortality. Therapies for LT-induced damage after host cell internalization of the toxin are lacking. Here we constructed MEK variants in which the LT proteolytic site was modified: MEK2(P10V/A11D), MEK3(I27D) and MEK6(I15D). These variants were resistant to proteolysis by LT. Expression in cells enabled sustained activation of ERK and p38 pathways and promoted cell survival upon LT treatment. Survival of LT- or B. anthracis-challenged MEK variant transgenic mice also increased compared with controls. We found that LT-mediated disruption of both ERK and p38 pathway is essential for anthrax pathogenesis. We show that engagement of upstream receptor tyrosine kinases reactivated the LT-disrupted ERK pathway, as did administering a cocktail of EGF, GM-CSF and FGF2 growth factors, which significantly increased survival of LT- or B. anthracis-challenged mice. These findings offer potential towards developing damage-limiting therapeutic strategies for anthrax.
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Affiliation(s)
- Jie Liu
- Aging Institute of University of Pittsburgh and University of Pittsburgh Medical Center, Pittsburgh, PA, USA
- Division of Cardiology, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Zehua Zuo
- Aging Institute of University of Pittsburgh and University of Pittsburgh Medical Center, Pittsburgh, PA, USA
| | - Michael Ewing
- Aging Institute of University of Pittsburgh and University of Pittsburgh Medical Center, Pittsburgh, PA, USA
| | - Qing Cao
- Aging Institute of University of Pittsburgh and University of Pittsburgh Medical Center, Pittsburgh, PA, USA
- Department of Environmental and Occupational Health, University of Pittsburgh School of Public Health, Pittsburgh, PA, USA
| | - Liu Cao
- Health Sciences Institute, China Medical University, Shenyang, China
| | - Qi Li
- Aging Institute of University of Pittsburgh and University of Pittsburgh Medical Center, Pittsburgh, PA, USA
| | - Toren Finkel
- Aging Institute of University of Pittsburgh and University of Pittsburgh Medical Center, Pittsburgh, PA, USA
- Division of Cardiology, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Stephen H Leppla
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Shihui Liu
- Aging Institute of University of Pittsburgh and University of Pittsburgh Medical Center, Pittsburgh, PA, USA.
- Division of Infectious Diseases, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
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2
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Liu J, Cao Q, Ewing M, Zuo Z, Kennerdell JR, Finkel T, Leppla SH, Liu S. ATP depletion in anthrax edema toxin pathogenesis. PLoS Pathog 2025; 21:e1013017. [PMID: 40168442 PMCID: PMC11977985 DOI: 10.1371/journal.ppat.1013017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2025] [Revised: 04/08/2025] [Accepted: 03/04/2025] [Indexed: 04/03/2025] Open
Abstract
Anthrax lethal toxin (LT) and edema toxin (ET) are two of the major virulence factors of Bacillus anthracis, the causative pathogen of anthrax disease. While the roles of LT in anthrax pathogenesis have been extensively studied, the pathogenic mechanism of ET remains poorly understood. ET is a calmodulin-dependent adenylate cyclase that elevates intracellular cAMP by converting ATP to cAMP. Thus, it was postulated that the ET-induced in vivo toxicity is mediated by certain cAMP-dependent events. However, mechanisms linking cAMP elevation and ET-induced damage have not been established. Cholera toxin is another bacterial toxin that increases cAMP. This toxin is known to cause severe intestinal fluid secretion and dehydration by cAMP-mediated activation of protein kinase A (PKA), which in turn activates cystic fibrosis transmembrane conductance regulator (CFTR). The cAMP-activated PKA phosphorylation of CFTR on the surface of intestinal epithelial cells leads to an efflux of chloride ions accompanied by secretion of H2O into the intestinal lumen, causing rapid fluid loss, severe diarrhea and dehydration. Due to similar in vivo effects, it was generally believed that ET and cholera toxin would exhibit a similar pathogenic mechanism. Surprisingly, in this work, we found that cAMP-mediated PKA/CFTR activation is not essential for ET to exert its in vivo toxicity. Instead, our data suggest that ET-induced ATP depletion may play an important role in the toxin's pathogenesis.
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Affiliation(s)
- Jie Liu
- Aging Institute of University of Pittsburgh and University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, United States of America
- Division of Cardiology, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Qing Cao
- Aging Institute of University of Pittsburgh and University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, United States of America
- PhD program, Department of Environmental and Occupational Health, University of Pittsburgh School of Public Health, Pittsburgh, Pennsylvania, United States of America
| | - Michael Ewing
- Aging Institute of University of Pittsburgh and University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, United States of America
| | - Zehua Zuo
- Aging Institute of University of Pittsburgh and University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, United States of America
| | - Jason R. Kennerdell
- Aging Institute of University of Pittsburgh and University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, United States of America
| | - Toren Finkel
- Aging Institute of University of Pittsburgh and University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, United States of America
- Division of Cardiology, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Stephen H. Leppla
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Shihui Liu
- Aging Institute of University of Pittsburgh and University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, United States of America
- Division of Infectious Diseases, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
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3
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Wang J, Yang D, Shen X, Wang J, Liu X, Lin J, Zhong J, Zhao Y, Qi Z. BPTES inhibits anthrax lethal toxin-induced inflammatory response. Int Immunopharmacol 2020; 85:106664. [PMID: 32521490 DOI: 10.1016/j.intimp.2020.106664] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Revised: 06/01/2020] [Accepted: 06/02/2020] [Indexed: 11/17/2022]
Abstract
Bacillus anthracis is a lethal agent of anthrax disease and the toxins are required in anthrax pathogenesis. The anthrax lethal toxin can trigger NLRP1b inflammasome activation and pyroptosis. Although the underlying mechanism is well understood, the medications targeting the NLRP1b inflammasome are not available in the clinic. Herein, we describe that BPTES, a known Glutaminase (GLS) inhibitor, is an effective NLRP1b inflammasome inhibitor. BPTES could effectively and specifically suppress NLRP1b inflammasome activation in macrophages but have no effects on NLRP3, NLRC4 and AIM2 inflammasome activation. Mechanistically, BPTES alleviated the UBR2 mediated proteasomal degradation pathway of the NLRP1b N terminus, thus blocking the release of the CARD domain for subsequent caspase-1 processing. Furthermore, BPTES could prevent disease progression in mice challenged with the anthrax lethal toxin. Taken together, our studies indicate that BPTES can be a promising pharmacological inhibitor to treat anthrax lethal toxin-related inflammatory diseases.
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Affiliation(s)
- Jinling Wang
- Department of Emergency, Zhongshan Hospital of Xiamen University, Xiamen 361005, China
| | - Daowei Yang
- Department of Emergency, Zhongshan Hospital of Xiamen University, Xiamen 361005, China.
| | - Xizi Shen
- Faculty of Medicine, The University of Queensland, Brisbane, Australia
| | - Junsheng Wang
- Department of Emergency, Zhongshan Hospital of Xiamen University, Xiamen 361005, China
| | - Xiaomei Liu
- Department of Emergency, Zhongshan Hospital of Xiamen University, Xiamen 361005, China
| | - Jinzhou Lin
- Department of Emergency, Zhongshan Hospital of Xiamen University, Xiamen 361005, China
| | - Jiaying Zhong
- Faculty of Medicine, Xiamen University, Xiamen, China
| | - Yilin Zhao
- Department of Oncology and Vascular Interventional Radiology, Zhongshan Hospital of Xiamen University, Xiamen, China
| | - Zhongquan Qi
- School of Medicine, Guangxi University, Nanning 530004, China.
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Farcasanu M, Wang AG, Uchański T, Bailey LJ, Yue J, Chen Z, Wu X, Kossiakoff A, Tang WJ. Rapid Discovery and Characterization of Synthetic Neutralizing Antibodies against Anthrax Edema Toxin. Biochemistry 2019; 58:2996-3004. [PMID: 31243996 DOI: 10.1021/acs.biochem.9b00184] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Anthrax, a lethal, weaponizable disease caused by Bacillus anthracis, acts through exotoxins that are primary mediators of systemic toxicity and also targets for neutralization by passive immunotherapy. The ease of engineering B. anthracis strains resistant to established therapy and the historic use of the microbe in bioterrorism present a compelling test case for platforms that permit the rapid and modular development of neutralizing agents. In vitro antigen-binding fragment (Fab) selection offers the advantages of speed, sequence level molecular control, and engineering flexibility compared to traditional monoclonal antibody pipelines. By screening an unbiased, chemically synthetic phage Fab library and characterizing hits in cell-based assays, we identified two high-affinity neutralizing Fabs, A4 and B7, against anthrax edema factor (EF), a key mediator of anthrax pathogenesis. Engineered homodimers of these Fabs exhibited potency comparable to that of the best reported neutralizing monoclonal antibody against EF at preventing EF-induced cyclic AMP production. Using internalization assays in COS cells, B7 was found to block steps prior to EF internalization. This work demonstrates the efficacy of synthetic alternatives to traditional antibody therapeutics against anthrax while also demonstrating a broadly generalizable, rapid, and modular screening pipeline for neutralizing antibody generation.
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Affiliation(s)
- Mara Farcasanu
- The Ben May Department for Cancer Research , The University of Chicago , Chicago , Illinois 60637 , United States
| | - Andrew G Wang
- The Ben May Department for Cancer Research , The University of Chicago , Chicago , Illinois 60637 , United States
| | - Tomasz Uchański
- Department of Biochemistry and Molecular Biology , The University of Chicago , Chicago , Illinois 60637 , United States
| | - Lucas J Bailey
- Department of Biochemistry and Molecular Biology , The University of Chicago , Chicago , Illinois 60637 , United States
| | - Jiping Yue
- The Ben May Department for Cancer Research , The University of Chicago , Chicago , Illinois 60637 , United States
| | - Zhaochun Chen
- National Institute of Allergy and Infection , National Institutes of Health , Bethesda , Maryland 20892 , United States
| | - Xiaoyang Wu
- The Ben May Department for Cancer Research , The University of Chicago , Chicago , Illinois 60637 , United States
| | - Anthony Kossiakoff
- Department of Biochemistry and Molecular Biology , The University of Chicago , Chicago , Illinois 60637 , United States
| | - Wei-Jen Tang
- The Ben May Department for Cancer Research , The University of Chicago , Chicago , Illinois 60637 , United States
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5
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In vivo dynamics of active edema and lethal factors during anthrax. Sci Rep 2016; 6:23346. [PMID: 26996161 PMCID: PMC4800402 DOI: 10.1038/srep23346] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Accepted: 02/26/2016] [Indexed: 01/21/2023] Open
Abstract
Lethal and edema toxins are critical virulence factors of Bacillus anthracis. However, little is known about their in vivo dynamics of production during anthrax. In this study, we unraveled for the first time the in vivo kinetics of production of the toxin components EF (edema factor) and LF (lethal factor) during cutaneous infection with a wild-type toxinogenic encapsulated strain in immuno-competent mice. We stratified the asynchronous infection process into defined stages through bioluminescence imaging (BLI), while exploiting sensitive quantitative methods by measuring the enzymatic activity of LF and EF. LF was produced in high amounts, while EF amounts steadily increased during the infectious process. This led to high LF/EF ratios throughout the infection, with variations between 50 to a few thousands. In the bloodstream, the early detection of active LF and EF despite the absence of bacteria suggests that they may exert long distance effects. Infection with a strain deficient in the protective antigen toxin component enabled to address its role in the diffusion of LF and EF within the host. Our data provide a picture of the in vivo complexity of the infectious process.
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6
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Kulshreshtha P, Tiwari A, Priyanka, Joon S, Sinha S, Bhatnagar R. Investigation of a panel of monoclonal antibodies and polyclonal sera against anthrax toxins resulted in identification of an anti-lethal factor antibody with disease-enhancing characteristics. Mol Immunol 2015; 68:185-93. [PMID: 26364143 DOI: 10.1016/j.molimm.2015.07.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Revised: 07/14/2015] [Accepted: 07/17/2015] [Indexed: 11/27/2022]
Abstract
Hybridomas were created using spleen of mice that were actively immunized with rLFn (recombinant N-terminal domain of lethal factor). Later on, separate group of mice were immunized with rLFn to obtain a polyclonal control for passive immunization studies of monoclonal antibodies. This led to the identification of one cohort of rLFn-immnized mice that harboured disease-enhancing polyclonal antibodies. At the same time, the monoclonal antibodies secreted by all the hybridomas were being tested. Two hybridomas secreted monoclonal antibodies (H10 and H8) that were cross-reactive with EF (edema factor) and LF (lethal factor), while the other two hybridomas secreted LF-specific antibodies (H7 and H11). Single chain variable fragment (LETscFv) was derived from H10 hybridoma. H11 was found to have disease-enhancing property. Combination of H11 with protective monoclonal antibodies (H8 and H10) reduced its disease enhancing nature. This in vitro abrogation of disease-enhancement provides the proof of concept that in polyclonal sera the disease enhancing character of a fraction of antibodies is overshadowed by the protective nature of the rest of the antibodies generated on active immunization.
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Affiliation(s)
- Parul Kulshreshtha
- Laboratory of Molecular Biology and Genetic Engineering, School of Biotechnology, Jawaharlal Nehru University, New Delhi 110067, India
| | - Ashutosh Tiwari
- Present address: Centre for Biodesign, Translational Health Science and Technology Institute, Gurgaon, India
| | - Priyanka
- Laboratory of Molecular Biology and Genetic Engineering, School of Biotechnology, Jawaharlal Nehru University, New Delhi 110067, India
| | - Shikha Joon
- Structural and Computational Biology Laboratory, Department Of Biotechnology, Netaji Subhas Institute of Technology, New Delhi 110078, India
| | | | - Rakesh Bhatnagar
- Laboratory of Molecular Biology and Genetic Engineering, School of Biotechnology, Jawaharlal Nehru University, New Delhi 110067, India.
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7
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Bouzianas DG. Potential biological targets ofBacillus anthracisin anti-infective approaches against the threat of bioterrorism. Expert Rev Anti Infect Ther 2014; 5:665-84. [PMID: 17678429 DOI: 10.1586/14787210.5.4.665] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The terrorist attacks of 2001 involving anthrax underscore the imperative that safe and effective medical countermeasures should be readily available. Vaccination appears to be the most effective form of mass protection against a biological attack, but the current vaccines have drawbacks that justify the enormous amount of effort currently being put into developing more effective vaccines and other treatment modalities. After providing a comprehensive overview of the organism Bacillus anthracis as a biological weapon and its pathogenicity, this review briefly summarizes the current knowledge vital to the management of anthrax disease. This knowledge has been acquired since 2001 as a result of the progress on anthrax research and focuses on the possible development of improved human anti-infective strategies targeting B. anthracis spore components, as well as strategies based on host-pathogen interactions.
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Affiliation(s)
- Dimitrios G Bouzianas
- Department of Medical Laboratories, Faculty of Health and Care Professions, University-level Technological Educational Institute of Thessaloniki, Greece.
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8
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Abstract
Bacillus anthracis, the causative agent of anthrax, has become an increasingly important scientific topic due to its potential role in bioterrorism. The lethal toxin (LT) of B. anthracis consists of lethal factor (LF) and a protective antigen (PA). This study investigated whether only lethal factor was efficient as a hepatotoxin in the absence of the PA. To achieve this aim, LF (100 µg/kg body weight, dissolved in sterile distilled water) or distilled water vehicle were intraperitoneally injected once into adult rats. At 24 h post-injection, the hosts were euthanized and their livers removed and tissue samples examined under light and electron microscopes. As a result of LF application, hepatic injury - including cytoplasmic and nuclear damage in hepatocytes, sinusoidal dilatation, and hepatocellular lysis - became apparent. Further, light microscopic analyses of liver sections from the LF-injected rats revealed ballooning degeneration and cytoplasmic loss within hepatocytes, as well as peri-sinusoidal inflammation. Additionally, an increase in the numbers of Kupffer cells was evident. Common vascular injuries were also found in the liver samples; these injuries caused hypoxia and pathological changes. In addition, some cytoplasmic and nuclear changes were detected within the liver ultrastructure. The results of these studies allow one to suggest that LF could be an effective toxicant alone and that PA might act in situ to modify the effect of this agent (or the reverse situation wherein LF modifies effects of PA) such that lethality results.
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Affiliation(s)
- Berrin Zuhal Altunkaynak
- Department of Histology and Embryology, Medical School, Ondokuz Mayıs University , Samsun , Turkey and
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Göttle M, Dove S, Seifert R. Bacillus anthracis edema factor substrate specificity: evidence for new modes of action. Toxins (Basel) 2012; 4:505-35. [PMID: 22852066 PMCID: PMC3407890 DOI: 10.3390/toxins4070505] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Revised: 06/15/2012] [Accepted: 06/27/2012] [Indexed: 12/20/2022] Open
Abstract
Since the isolation of Bacillus anthracis exotoxins in the 1960s, the detrimental activity of edema factor (EF) was considered as adenylyl cyclase activity only. Yet the catalytic site of EF was recently shown to accomplish cyclization of cytidine 5'-triphosphate, uridine 5'-triphosphate and inosine 5'-triphosphate, in addition to adenosine 5'-triphosphate. This review discusses the broad EF substrate specificity and possible implications of intracellular accumulation of cyclic cytidine 3':5'-monophosphate, cyclic uridine 3':5'-monophosphate and cyclic inosine 3':5'-monophosphate on cellular functions vital for host defense. In particular, cAMP-independent mechanisms of action of EF on host cell signaling via protein kinase A, protein kinase G, phosphodiesterases and CNG channels are discussed.
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Affiliation(s)
- Martin Göttle
- Department of Neurology, Emory University School of Medicine, 6302 Woodruff Memorial Research Building, 101 Woodruff Circle, Atlanta, GA 30322, USA
- Author to whom correspondence should be addressed; ; Tel.: +1-404-727-1678; Fax: +1-404-727-3157
| | - Stefan Dove
- Department of Medicinal/Pharmaceutical Chemistry II, University of Regensburg, D-93040 Regensburg, Germany;
| | - Roland Seifert
- Institute of Pharmacology, Medical School of Hannover, Carl-Neuberg-Str. 1, D-30625 Hannover, Germany;
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Lowe DE, Glomski IJ. Cellular and physiological effects of anthrax exotoxin and its relevance to disease. Front Cell Infect Microbiol 2012; 2:76. [PMID: 22919667 PMCID: PMC3417473 DOI: 10.3389/fcimb.2012.00076] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2012] [Accepted: 05/16/2012] [Indexed: 12/26/2022] Open
Abstract
Bacillus anthracis, the causative agent of anthrax, secretes a tri-partite exotoxin that exerts pleiotropic effects on the host. The purification of the exotoxin components, protective antigen, lethal factor, and edema factor allowed the rapid characterization of their physiologic effects on the host. As molecular biology matured, interest focused on the molecular mechanisms and cellular alterations induced by intoxication. Only recently have researchers begun to connect molecular and cellular knowledge back to the broader physiological effects of the exotoxin. This review focuses on the progress that has been made bridging molecular knowledge back to the exotoxin’s physiological effects on the host.
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Affiliation(s)
- David E Lowe
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia Health System, Charlottesville VA, USA
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11
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Abstract
The anthrax edema toxin (ET) of Bacillus anthracis is composed of the receptor-binding component protective antigen (PA) and of the adenylyl cyclase catalytic moiety, edema factor (EF). Uptake of ET into cells raises intracellular concentrations of the secondary messenger cyclic AMP, thereby impairing or activating host cell functions. We report here on a new consequence of ET action in vivo. We show that in mouse models of toxemia and infection, serum PA concentrations were significantly higher in the presence of enzymatically active EF. These higher concentrations were not caused by ET-induced inhibition of PA endocytosis; on the contrary, ET induced increased PA binding and uptake of the PA oligomer in vitro and in vivo through upregulation of the PA receptors TEM8 and CMG2 in both myeloid and nonmyeloid cells. ET effects on protein clearance from circulation appeared to be global and were not limited to PA. ET also impaired the clearance of ovalbumin, green fluorescent protein, and EF itself, as well as the small molecule biotin when these molecules were coinjected with the toxin. Effects on injected protein levels were not a result of general increase in protein concentrations due to fluid loss. Functional markers for liver and kidney were altered in response to ET. Concomitantly, ET caused phosphorylation and activation of the aquaporin-2 water channel present in the principal cells of the collecting ducts of the kidneys that are responsible for fluid homeostasis. Our data suggest that in vivo, ET alters circulatory protein and small molecule pharmacokinetics by an as-yet-undefined mechanism, thereby potentially allowing a prolonged circulation of anthrax virulence factors such as EF during infection.
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Dumetz F, Jouvion G, Khun H, Glomski IJ, Corre JP, Rougeaux C, Tang WJ, Mock M, Huerre M, Goossens PL. Noninvasive imaging technologies reveal edema toxin as a key virulence factor in anthrax. THE AMERICAN JOURNAL OF PATHOLOGY 2011; 178:2523-35. [PMID: 21641378 DOI: 10.1016/j.ajpath.2011.02.027] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2010] [Revised: 01/25/2011] [Accepted: 02/01/2011] [Indexed: 12/27/2022]
Abstract
Powerful noninvasive imaging technologies enable real-time tracking of pathogen-host interactions in vivo, giving access to previously elusive events. We visualized the interactions between wild-type Bacillus anthracis and its host during a spore infection through bioluminescence imaging coupled with histology. We show that edema toxin plays a central role in virulence in guinea pigs and during inhalational infection in mice. Edema toxin (ET), but not lethal toxin (LT), markedly modified the patterns of bacterial dissemination leading, to apparent direct dissemination to the spleen and provoking apoptosis of lymphoid cells. Each toxin alone provoked particular histological lesions in the spleen. When ET and LT are produced together during infection, a specific temporal pattern of lesion developed, with early lesions typical of LT, followed at a later stage by lesions typical of ET. Our study provides new insights into the complex spatial and temporal effects of B. anthracis toxins in the infected host, suggesting a greater role than previously suspected for ET in anthrax and suggesting that therapeutic targeting of ET contributes to protection.
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Affiliation(s)
- Fabien Dumetz
- Pathogenesis of Bacterial Toxi-Infections Laboratory, Pasteur Institute (Institut Pasteur), Paris, France
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Hicks CW, Cui X, Sweeney DA, Li Y, Barochia A, Eichacker PQ. The potential contributions of lethal and edema toxins to the pathogenesis of anthrax associated shock. Toxins (Basel) 2011; 3:1185-202. [PMID: 22069762 PMCID: PMC3202877 DOI: 10.3390/toxins3091185] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2011] [Revised: 09/08/2011] [Accepted: 09/09/2011] [Indexed: 12/22/2022] Open
Abstract
Outbreaks of Bacillus anthracis in the US and Europe over the past 10 years have emphasized the health threat this lethal bacteria poses even for developed parts of the world. In contrast to cutaneous anthrax, inhalational disease in the US during the 2001 outbreaks and the newly identified injectional drug use form of disease in the UK and Germany have been associated with relatively high mortality rates. One notable aspect of these cases has been the difficulty in supporting patients once shock has developed. Anthrax bacilli produce several different components which likely contribute to this shock. Growing evidence indicates that both major anthrax toxins may produce substantial cardiovascular dysfunction. Lethal toxin (LT) can alter peripheral vascular function; it also has direct myocardial depressant effects. Edema toxin (ET) may have even more pronounced peripheral vascular effects than LT, including the ability to interfere with the actions of conventional vasopressors. Additionally, ET also appears capable of interfering with renal sodium and water retention. Importantly, the two toxins exert their actions via quite different mechanisms and therefore have the potential to worsen shock and outcome in an additive fashion. Finally, both toxins have the ability to inhibit host defense and microbial clearance, possibly contributing to the very high bacterial loads noted in patients dying with anthrax. This last point is clinically relevant since emerging data has begun to implicate other bacterial components such as anthrax cell wall in the shock and organ injury observed with infection. Taken together, accumulating evidence regarding the potential contribution of LT and ET to anthrax-associated shock supports efforts to develop adjunctive therapies that target both toxins in patients with progressive shock.
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Affiliation(s)
- Caitlin W. Hicks
- Cleveland Clinic Lerner College of Medicine, Cleveland, OH 44195, USA;
- Howard Hughes Medical Institute-National Institutes of Health Research Scholar, National Institutes of Health, Bethesda, MD 20814, USA
| | - Xizhong Cui
- Critical Care Medicine Department, Clinical Center, National Institutes of Health, Bethesda, MD 20892, USA; (X.C.); (Y.L.); (A.B.)
| | - Daniel A. Sweeney
- Medical Intensivist Program, Washington Hospital, Fremont, CA 94538, USA;
| | - Yan Li
- Critical Care Medicine Department, Clinical Center, National Institutes of Health, Bethesda, MD 20892, USA; (X.C.); (Y.L.); (A.B.)
| | - Amisha Barochia
- Critical Care Medicine Department, Clinical Center, National Institutes of Health, Bethesda, MD 20892, USA; (X.C.); (Y.L.); (A.B.)
| | - Peter Q. Eichacker
- Critical Care Medicine Department, Clinical Center, National Institutes of Health, Bethesda, MD 20892, USA; (X.C.); (Y.L.); (A.B.)
- Author to whom correspondence should be addressed; ; Tel.: +1-301-496-9320; Fax: +1-301-402-1213
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14
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Guichard A, Nizet V, Bier E. New insights into the biological effects of anthrax toxins: linking cellular to organismal responses. Microbes Infect 2011; 14:97-118. [PMID: 21930233 DOI: 10.1016/j.micinf.2011.08.016] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2011] [Revised: 08/30/2011] [Accepted: 08/30/2011] [Indexed: 12/15/2022]
Abstract
The anthrax toxins lethal toxin (LT) and edema toxin (ET) are essential virulence factors produced by Bacillus anthracis. These toxins act during two distinct phases of anthrax infection. During the first, prodromal phase, which is often asymptomatic, anthrax toxins act on cells of the immune system to help the pathogen establish infection. Then, during the rapidly progressing (or fulminant) stage of the disease bacteria disseminate via a hematological route to various target tissues and organs, which are typically highly vascularized. As bacteria proliferate in the bloodstream, LT and ET begin to accumulate rapidly reaching a critical threshold level that will cause death even when the bacterial proliferation is curtailed by antibiotics. During this final phase of infection the toxins cause an increase in vascular permeability and a decrease in function of target organs including the heart, spleen, kidney, adrenal gland, and brain. In this review, we examine the various biological effects of anthrax toxins, focusing on the fulminant stage of the disease and on mechanisms by which the two toxins may collaborate to cause cardiovascular collapse. We discuss normal mechanisms involved in maintaining vascular integrity and based on recent studies indicating that LT and ET cooperatively inhibit membrane trafficking to cell-cell junctions we explore several potential mechanisms by which the toxins may achieve their lethal effects. We also summarize the effects of other potential virulence factors secreted by B. anthracis and consider the role of toxic factors in the evolutionarily recent emergence of this devastating disease.
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Affiliation(s)
- Annabel Guichard
- Section of Cell and Developmental Biology, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0349, USA
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15
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Inhibition of anthrax toxins with a bispecific monoclonal antibody that cross reacts with edema factor as well as lethal factor of Bacillus anthracis. Mol Immunol 2011; 48:1958-65. [PMID: 21704379 DOI: 10.1016/j.molimm.2011.05.024] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2011] [Revised: 05/26/2011] [Accepted: 05/26/2011] [Indexed: 01/29/2023]
Abstract
Bacillus anthracis overwhelms its victims by way of two toxins, namely edema toxin and lethal toxin. Lethal toxin is formed by the combination of protective antigen with lethal factor while edema toxin is formed by the combination of Protective Antigen with edema factor. Overlapping regions between edema factor and lethal factor have been reported in past. For the first time, this study reports characterization of a bispecific monoclonal antibody (mAb), H10, which showed high affinity interaction with both edema factor and lethal factor of B. anthracis. H10 mAb not only neutralized the adenylate cyclase activity of edema toxin but it could also neutralize the cytotoxic activity of lethal toxin. Passive immunization with this antibody gave 100% protection to mice from in vivo challenge with lethal toxin and edema toxin. The results of this study suggest future application of this bispecific monoclonal antibody as passive immunization prophylactics in cases of B. anthracis exposure and infection.
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16
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Glycogen synthase kinase 3 activation is important for anthrax edema toxin-induced dendritic cell maturation and anthrax toxin receptor 2 expression in macrophages. Infect Immun 2011; 79:3302-8. [PMID: 21576335 DOI: 10.1128/iai.05070-11] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Anthrax edema toxin (ET) is one of two binary toxins produced by Bacillus anthracis that contributes to the virulence of this pathogen. ET is an adenylate cyclase that generates high levels of cyclic AMP (cAMP), causing alterations in multiple host cell signaling pathways. We previously demonstrated that ET increases cell surface expression of the anthrax toxin receptors (ANTXR) in monocyte-derived cells and promotes dendritic cell (DC) migration toward the lymph node-homing chemokine MIP-3β. In this work, we sought to determine if glycogen synthase kinase 3 (GSK-3) is important for ET-induced modulation of macrophage and DC function. We demonstrate that inhibition of GSK-3 dampens ET-induced maturation and migration processes of monocyte-derived dendritic cells (MDDCs). Additional studies reveal that the ET-induced expression of ANTXR in macrophages was decreased when GSK-3 activity was disrupted with chemical inhibitors or with small interfering RNA (siRNA) targeting GSK-3. Further examination of the ET induction of ANTXR revealed that a dominant negative form of CREB could block the ET induction of ANTXR, suggesting that CREB or a related family member was involved in the upregulation of ANTXR. Because CREB and GSK-3 activity appeared to be important for ET-induced ANTXR expression, the impact of GSK-3 on ET-induced CREB activity was examined in RAW 264.7 cells possessing a CRE-luciferase reporter. As with ANTXR expression, the ET induction of the CRE reporter was decreased by reducing GSK-3 activity. These studies not only provide insight into host pathways targeted by ET but also shed light on interactions between GSK-3 and CREB pathways in host immune cells.
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17
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Kandadi MR, Hua Y, Ma H, Li Q, Kuo SR, Frankel AE, Ren J. Anthrax lethal toxin suppresses murine cardiomyocyte contractile function and intracellular Ca2+ handling via a NADPH oxidase-dependent mechanism. PLoS One 2010; 5:e13335. [PMID: 20967205 PMCID: PMC2954163 DOI: 10.1371/journal.pone.0013335] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2010] [Accepted: 09/22/2010] [Indexed: 01/10/2023] Open
Abstract
Objectives Anthrax infection is associated with devastating cardiovascular sequelae, suggesting unfavorable cardiovascular effects of toxins originated from Bacillus anthracis namely lethal and edema toxins. This study was designed to examine the direct effect of lethal toxins on cardiomyocyte contractile and intracellular Ca2+ properties. Methods Murine cardiomyocyte contractile function and intracellular Ca2+ handling were evaluated including peak shortening (PS), maximal velocity of shortening/ relengthening (± dL/dt), time-to-PS (TPS), time-to-90% relengthening (TR90), intracellular Ca2+ rise measured as fura-2 fluorescent intensity (ΔFFI), and intracellular Ca2+ decay rate. Stress signaling and Ca2+ regulatory proteins were assessed using Western blot analysis. Results In vitro exposure to a lethal toxin (0.05 – 50 nM) elicited a concentration-dependent depression on cardiomyocyte contractile and intracellular Ca2+ properties (PS, ± dL/dt, ΔFFI), along with prolonged duration of contraction and intracellular Ca2+ decay, the effects of which were nullified by the NADPH oxidase inhibitor apocynin. The lethal toxin significantly enhanced superoxide production and cell death, which were reversed by apocynin. In vivo lethal toxin exposure exerted similar time-dependent cardiomyocyte mechanical and intracellular Ca2+ responses. Stress signaling cascades including MEK1/2, p38, ERK and JNK were unaffected by in vitro lethal toxins whereas they were significantly altered by in vivo lethal toxins. Ca2+ regulatory proteins SERCA2a and phospholamban were also differentially regulated by in vitro and in vivo lethal toxins. Autophagy was drastically triggered although ER stress was minimally affected following lethal toxin exposure. Conclusions Our findings indicate that lethal toxins directly compromised murine cardiomyocyte contractile function and intracellular Ca2+ through a NADPH oxidase-dependent mechanism.
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Affiliation(s)
- Machender R. Kandadi
- Center for Cardiovascular Research and Alternative Medicine, University of Wyoming College of Health Sciences, Laramie, Wyoming, United States of America
| | - Yinan Hua
- Center for Cardiovascular Research and Alternative Medicine, University of Wyoming College of Health Sciences, Laramie, Wyoming, United States of America
| | - Heng Ma
- Center for Cardiovascular Research and Alternative Medicine, University of Wyoming College of Health Sciences, Laramie, Wyoming, United States of America
| | - Qun Li
- Center for Cardiovascular Research and Alternative Medicine, University of Wyoming College of Health Sciences, Laramie, Wyoming, United States of America
| | - Shu-ru Kuo
- Cancer Research Institute of Scott and White Memorial Hospital, Temple, Texas, United States of America
| | - Arthur E. Frankel
- Cancer Research Institute of Scott and White Memorial Hospital, Temple, Texas, United States of America
| | - Jun Ren
- Center for Cardiovascular Research and Alternative Medicine, University of Wyoming College of Health Sciences, Laramie, Wyoming, United States of America
- * E-mail:
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18
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Bouzianas DG. Current and future medical approaches to combat the anthrax threat. J Med Chem 2010; 53:4305-31. [PMID: 20102155 DOI: 10.1021/jm901024b] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Dimitrios G Bouzianas
- Laboratory of Molecular Endocrinology, Division of Endocrinology and Metabolism, AHEPA University Hospital, 1 S. Kyriakidi Street, P.C. 54636, Thessaloniki, Macedonia, Greece.
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19
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Neutralizing monoclonal antibody to edema toxin and its effect on murine anthrax. Infect Immun 2010; 78:2890-8. [PMID: 20385755 DOI: 10.1128/iai.01101-09] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Edema factor (EF) is a component of an anthrax toxin that functions as an adenylate cyclase. Numerous monoclonal antibodies (MAbs) have been reported for the other Bacillus anthracis toxin components, but relatively few to EF have been studied. We report the generation of six murine hybridoma lines producing two IgM and four IgG1 MAbs to EF. Of the six MAbs, only one IgM neutralized EF, as assayed by an increase in cyclic AMP (cAMP) production by Chinese hamster ovary (CHO) cells. Analysis of the variable gene elements revealed that the single neutralizing MAb had a different binding site than the others. There was no competition between the neutralizing IgM and the nonneutralizing IgG MAbs indicative of different specificity. MAb-based capture enzyme-linked immunosorbent assay (ELISA) detected EF in liver lysates from mice infected with B. anthracis Sterne 34F2. Administration of the neutralizing IgM MAb to A/JCr mice lethally infected with B. anthracis strain Sterne had no significant effect on median time to death, but mice treated with the MAb were more likely to survive infection. Combining the neutralizing IgM to EF with a subprotective dose of a neutralizing MAb to protective antigen (PA) prolonged mean time to death of infected mice, suggesting that neutralization of EF and PA could produce synergistic beneficial effects. In summary, the results from our study and literature observations suggest that the majority of Abs to EF are nonneutralizing, but the toxin has some epitopes that can be targeted by the humoral response to generate useful Abs that may contribute to defense against anthrax.
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20
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The major neutralizing antibody responses to recombinant anthrax lethal and edema factors are directed to non-cross-reactive epitopes. Infect Immun 2009; 77:4714-23. [PMID: 19720758 DOI: 10.1128/iai.00749-09] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Anthrax lethal and edema toxins (LeTx and EdTx, respectively) form by binding of lethal factor (LF) or edema factor (EF) to the pore-forming moiety protective antigen (PA). Immunity to LF and EF protects animals from anthrax spore challenge and neutralizes anthrax toxins. The goal of the present study is to identify linear B-cell epitopes of EF and to determine the relative contributions of cross-reactive antibodies of EF and LF to LeTx and EdTx neutralization. A/J mice were immunized with recombinant LF (rLF) or rEF. Pools of LF or EF immune sera were tested for reactivity to rLF or rEF by enzyme-linked immunosorbent assays, in vitro neutralization of LeTx and EdTx, and binding to solid-phase LF and EF decapeptides. Cross-reactive antibodies were isolated by column absorption of EF-binding antibodies from LF immune sera and by column absorption of LF-binding antibodies from EF immune sera. The resulting fractions were subjected to the same assays. Major cross-reactive epitopes were identified as EF amino acids (aa) 257 to 268 and LF aa 265 to 274. Whole LF and EF immune sera neutralized LeTx and EdTx, respectively. However, LF sera did not neutralize EdTx, nor did EF sera neutralize LeTx. Purified cross-reactive immunoglobulin G also failed to cross-neutralize. Cross-reactive B-cell epitopes in the PA-binding domains of whole rLF and rEF occur and have been identified; however, the major anthrax toxin-neutralizing humoral responses to these antigens are constituted by non-cross-reactive epitopes. This work increases understanding of the immunogenicity of EF and LF and offers perspective for the development of new strategies for vaccination against anthrax.
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21
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Moayeri M, Leppla SH. Cellular and systemic effects of anthrax lethal toxin and edema toxin. Mol Aspects Med 2009; 30:439-55. [PMID: 19638283 DOI: 10.1016/j.mam.2009.07.003] [Citation(s) in RCA: 175] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2009] [Accepted: 07/21/2009] [Indexed: 12/21/2022]
Abstract
Anthrax lethal toxin (LT) and edema toxin (ET) are the major virulence factors of anthrax and can replicate the lethality and symptoms associated with the disease. This review provides an overview of our current understanding of anthrax toxin effects in animal models and the cytotoxicity (necrosis and apoptosis) induced by LT in different cells. A brief reexamination of early historic findings on toxin in vivo effects in the context of our current knowledge is also presented.
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Affiliation(s)
- Mahtab Moayeri
- Bacterial Toxins and Therapeutics Section, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Building 33, Room 1W20B, Bethesda, MD 20892, USA.
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22
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Tang WJ, Guo Q. The adenylyl cyclase activity of anthrax edema factor. Mol Aspects Med 2009; 30:423-30. [PMID: 19560485 DOI: 10.1016/j.mam.2009.06.001] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2009] [Accepted: 06/19/2009] [Indexed: 02/08/2023]
Abstract
Bacillus anthracis, the etiologic agent for anthrax, secretes edema factor (EF) to disrupt intracellular signaling pathways. Upon translocation into host cells and association with a calcium sensor, calmodulin (CaM), EF becomes a highly active adenylyl cyclase (AC) that raises the intracellular concentration of cyclic AMP (cAMP). Growing evidence shows that EF plays a key role in anthrax pathogenesis by affecting cellular functions vital for host defense. This strategy is also used by Bordetella pertussis, a bacterium that causes whooping cough. Pertussis bacteria secrete the bifunctional toxin CyaA which raises the intracellular cAMP. Here, we discuss recent advances from structural analyses that reveal the molecular basis of the conserved mechanism of activation and catalysis of EF and CyaA by CaM even though these two toxins use the completely different sequences to bind CaM. Comparison of the biochemical and structural characteristics of these two AC toxins with host ACs reveal that they have diverse strategies of catalytic activation, yet use the same two-metal-ion catalytic mechanism.
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Affiliation(s)
- Wei-Jen Tang
- Ben-May Department for Cancer Research, The University of Chicago, 929 East 57th Street, GCIS W434, Chicago, IL 60637, USA.
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23
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Johnson SL, Chen LH, Barille E, Emdadi A, Sabet M, Yuan H, Wei J, Guiney D, Pellecchia M. Structure-activity relationship studies of a novel series of anthrax lethal factor inhibitors. Bioorg Med Chem 2009; 17:3352-68. [PMID: 19359184 PMCID: PMC2730741 DOI: 10.1016/j.bmc.2009.03.040] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2009] [Revised: 03/13/2009] [Accepted: 03/20/2009] [Indexed: 10/21/2022]
Abstract
We report on the identification of a novel small molecule inhibitor of anthrax lethal factor using a high-throughput screening approach. Guided by molecular docking studies, we carried out structure-activity relationship (SAR) studies and evaluated activity and selectivity of most promising compounds in in vitro enzyme inhibition assays and cellular assays. Selected compounds were further analyzed for their in vitro ADME properties, which allowed us to select two compounds for further preliminary in vivo efficacy studies. The data provided represents the basis for further pharmacology and medicinal chemistry optimizations that could result in novel anti-anthrax therapies.
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Affiliation(s)
- Sherida L. Johnson
- Burnham Institute for Medical Research, Cancer Research Center and Infectious and Inflammatory Disease Center, 10901 North Torrey Pines Rd, La Jolla, CA 92037
| | - Li-Hsing Chen
- Burnham Institute for Medical Research, Cancer Research Center and Infectious and Inflammatory Disease Center, 10901 North Torrey Pines Rd, La Jolla, CA 92037
| | - Elisa Barille
- Burnham Institute for Medical Research, Cancer Research Center and Infectious and Inflammatory Disease Center, 10901 North Torrey Pines Rd, La Jolla, CA 92037
| | - Aras Emdadi
- Burnham Institute for Medical Research, Cancer Research Center and Infectious and Inflammatory Disease Center, 10901 North Torrey Pines Rd, La Jolla, CA 92037
| | - Mojgan Sabet
- Department of Medicine, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Hongbin Yuan
- Burnham Institute for Medical Research, Cancer Research Center and Infectious and Inflammatory Disease Center, 10901 North Torrey Pines Rd, La Jolla, CA 92037
| | - Jun Wei
- Burnham Institute for Medical Research, Cancer Research Center and Infectious and Inflammatory Disease Center, 10901 North Torrey Pines Rd, La Jolla, CA 92037
| | - Donald Guiney
- Department of Medicine, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Maurizio Pellecchia
- Burnham Institute for Medical Research, Cancer Research Center and Infectious and Inflammatory Disease Center, 10901 North Torrey Pines Rd, La Jolla, CA 92037
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24
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Ratio of lethal and edema factors in rabbit systemic anthrax. Toxicon 2008; 52:824-8. [DOI: 10.1016/j.toxicon.2008.08.011] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2008] [Revised: 08/13/2008] [Accepted: 08/15/2008] [Indexed: 01/07/2023]
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25
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Bacillus anthracis edema toxin activates nuclear glycogen synthase kinase 3beta. Infect Immun 2008; 76:4895-904. [PMID: 18765729 DOI: 10.1128/iai.00889-08] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Bacillus anthracis edema toxin (ET) generates high levels of cyclic AMP and impacts a complex network of signaling pathways in targeted cells. In the current study, we sought to identify kinase signaling pathways modulated by ET to better understand how this toxin alters cell physiology. Using a panel of small-molecule inhibitors of mammalian kinases, we found that inhibitors of glycogen synthase kinase 3 beta (GSK-3beta) protected cells from ET-induced changes in the cell cycle. GSK-3beta inhibitors prevented declines in cellular levels of cyclin D1 and c-Jun following treatment of macrophages with ET. Strikingly, cell fractionation experiments and confocal immunofluorescence microscopy revealed that ET activates a compartmentalized pool of GSK-3beta residing in the nuclei, but not in the cytoplasm, of macrophages. To investigate the outcome of this event, we examined the cellular location and activation state of beta-catenin, a critical substrate of GSK-3beta, and found that the protein was inactivated within the nucleus following intoxication with ET. To determine if ET could overcome the effects of stimuli that inactivate GSK-3beta, we examined the impact of the toxin on the Wnt signaling pathway. The results of these experiments revealed that by targeting GSK-3beta residing in the nucleus, ET circumvents the upstream cytoplasmic inactivation of GSK-3beta, which occurs following exposure to Wnt-3A. These findings suggest ET arrests the cell cycle by a mechanism involving activation of GSK-3beta residing in the nucleus, and by using this novel mechanism of intoxication, ET avoids cellular systems that would otherwise reverse the effects of the toxin.
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26
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Bromberg-White JL, Duesbery NS. Biological and biochemical characterization of anthrax lethal factor, a proteolytic inhibitor of MEK signaling pathways. Methods Enzymol 2008; 438:355-65. [PMID: 18413261 DOI: 10.1016/s0076-6879(07)38025-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/07/2023]
Abstract
The secretion of factors that block critical intracellular signaling pathways is a common strategy used by pathogenic bacteria for disabling host defenses and causing disease. Anthrax lethal toxin (LeTx) has been shown to cleave and inactivate mitogen-activated protein kinase (MAPK) kinases (MKKs or MEKs) and to inhibit MKK signaling. Cleavage of MKKs by LeTx prevents activation of their downstream substrates, the MAPKs. Because MAPK pathways regulate a variety of crucial cellular functions including proliferation, survival, differentiation, adhesion, and motility, LeTx has become a focus of study as an investigative tool as well as for the treatment and prevention of diseases due to malfunctions in MAPK signaling. This chapter describes methods for expressing and purifying the components of LeTx and focuses on techniques available for assessing its activity.
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Affiliation(s)
- Jennifer L Bromberg-White
- Laboratory of Cancer and Developmental Cell Biology, Van Andel Research Institute, Grand Rapids, Michigan, USA
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27
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Watson LE, Kuo SR, Katki K, Dang T, Park SK, Dostal DE, Tang WJ, Leppla SH, Frankel AE. Anthrax toxins induce shock in rats by depressed cardiac ventricular function. PLoS One 2007; 2:e466. [PMID: 17520025 PMCID: PMC1867860 DOI: 10.1371/journal.pone.0000466] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2007] [Accepted: 05/01/2007] [Indexed: 12/05/2022] Open
Abstract
Anthrax infections are frequently associated with severe and often irreversible hypotensive shock. The isolated toxic proteins of Bacillus anthracis produce a non-cytokine-mediated hypotension in rats by unknown mechanisms. These observations suggest the anthrax toxins have direct cardiovascular effects. Here, we characterize these effects. As a first step, we administered systemically anthrax lethal toxin (LeTx) and edema toxin (EdTx) to cohorts of three to twelve rats at different doses and determined the time of onset, degree of hypotension and mortality. We measured serum concentrations of the protective antigen (PA) toxin component at various time points after infusion. Peak serum levels of PA were in the µg/mL range with half-lives of 10–20 minutes. With doses that produced hypotension with delayed lethality, we then gave bolus intravenous infusions of toxins to groups of four to six instrumented rats and continuously monitored blood pressure by telemetry. Finally, the same doses used in the telemetry experiments were given to additional groups of four rats, and echocardiography was performed pretreatment and one, two, three and twenty-four hours post-treatment. LeTx and EdTx each produced hypotension. We observed a doubling of the velocity of propagation and 20% increases in left ventricular diastolic and systolic areas in LeTx-treated rats, but not in EdTx-treated rats. EdTx-but not LeTx-treated rats showed a significant increase in heart rate. These results indicate that LeTx reduced left ventricular systolic function and EdTx reduced preload. Uptake of toxins occurs readily into tissues with biological effects occurring within minutes to hours of serum toxin concentrations in the µg/mL range. LeTx and EdTx yield an irreversible shock with subsequent death. These findings should provide a basis for the rational design of drug interventions to reduce the dismal prognosis of systemic anthrax infections.
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Affiliation(s)
- Linley E. Watson
- Division of Cardiology, Scott and White Memorial Hospital, Scott, Sherwood and Brindley Foundation, Temple, Texas, United States of America
- Department of Medicine, Texas A&M University System, Health Science Center College of Medicine, Temple, Texas, United States of America
- Division of Molecular Cardiology, Texas A&M University System, Health Science Center College of Medicine, and Central Texas Veterans Health Care System, Temple, Texas, United States of America
| | - Shu-ru Kuo
- Scott and White Cancer Research Institute, Temple, Texas, United States of America
| | - Khurshed Katki
- Department of Medicine, Texas A&M University System, Health Science Center College of Medicine, Temple, Texas, United States of America
| | - Tongyun Dang
- Scott and White Cancer Research Institute, Temple, Texas, United States of America
| | - Seong Kyu Park
- Scott and White Cancer Research Institute, Temple, Texas, United States of America
| | - David E. Dostal
- Department of Medicine, Texas A&M University System, Health Science Center College of Medicine, Temple, Texas, United States of America
- Division of Molecular Cardiology, Texas A&M University System, Health Science Center College of Medicine, and Central Texas Veterans Health Care System, Temple, Texas, United States of America
| | - Wei-Jen Tang
- Ben May Institute for Cancer Research, The University of Chicago, Chicago, Illinois, United States of America
| | - Stephen H. Leppla
- Bacterial Toxins and Therapeutics Section, National Institutes of Allergy and Infectious Diseases, Bethesda, Maryland, United States of America
| | - Arthur E. Frankel
- Department of Medicine, Texas A&M University System, Health Science Center College of Medicine, Temple, Texas, United States of America
- Scott and White Cancer Research Institute, Temple, Texas, United States of America
- * To whom correspondence should be addressed. E-mail:
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