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Bacillus anthracis genomic DNA enhances lethal toxin–induced cytotoxicity through TNF-α production

BACKGROUND: Bacillus anthracis is the etiological agent of anthrax. Lethal toxin (LT) produced by B. anthracis is a well-known key virulence factor for anthrax because of its strong cytotoxic activity. However, little is known about the role of B. anthracis genomic DNA (BAG) in anthrax pathogenesis....

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Autores principales: Jeon, Jun Ho, Kim, Yeon Hee, Choi, Min Kyung, Kim, Kyung Ae, Lee, Hae-Ri, Jang, Jeyoun, Kim, Yu-Ri, Chun, Jeong-Hoon, Eo, Seong Kug, Kim, Tae Sung, Rhie, Gi-eun
Formato: Online Artículo Texto
Lenguaje:English
Publicado: BioMed Central 2014
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4267052/
https://www.ncbi.nlm.nih.gov/pubmed/25472474
http://dx.doi.org/10.1186/s12866-014-0300-9
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author Jeon, Jun Ho
Kim, Yeon Hee
Choi, Min Kyung
Kim, Kyung Ae
Lee, Hae-Ri
Jang, Jeyoun
Kim, Yu-Ri
Chun, Jeong-Hoon
Eo, Seong Kug
Kim, Tae Sung
Rhie, Gi-eun
author_facet Jeon, Jun Ho
Kim, Yeon Hee
Choi, Min Kyung
Kim, Kyung Ae
Lee, Hae-Ri
Jang, Jeyoun
Kim, Yu-Ri
Chun, Jeong-Hoon
Eo, Seong Kug
Kim, Tae Sung
Rhie, Gi-eun
author_sort Jeon, Jun Ho
collection PubMed
description BACKGROUND: Bacillus anthracis is the etiological agent of anthrax. Lethal toxin (LT) produced by B. anthracis is a well-known key virulence factor for anthrax because of its strong cytotoxic activity. However, little is known about the role of B. anthracis genomic DNA (BAG) in anthrax pathogenesis. RESULTS: We examined the effect of BAG on TNF-α production and LT-mediated cytotoxicity during B. anthracis spore infection in mouse macrophage cell lines (RAW264.7 cells and J774A.1) and BALB/c mice. Infection of RAW264.7 cells with B. anthracis spores induced TNF-α expression in a multiplicity of infection (MOI)-dependent manner, and this enhancement was attenuated by the toll-like receptor (TLR) 9 inhibitor oligodeoxynucleotide (ODN)2088. BAG led to TNF-α expression in a dose- and time-dependent manner when applied to RAW264.7 cells. TNF-α expression induced by BAG was reduced by either pretreatment with TLR9 inhibitors (ODN2088 and chloroquine (CQ)) or transfection with TLR9 siRNA. Furthermore, BAG-induced TNF-α production in TLR9(+/+) macrophages was completely abrogated in TLR9(−/−) macrophages. BAG enhanced the phosphorylation of mitogen-activated protein kinases (MAPK), and BAG-induced TNF-α expression was attenuated by pretreatment with MAPK inhibitors. A reporter gene assay and confocal microscopy demonstrated that BAG increased NF-κB activation, which is responsible for TNF-α expression. Treatment with BAG alone showed no cytotoxic activity on the macrophage cell line J774A.1, whereas LT-mediated cytotoxicity was enhanced by treatment with BAG or TNF-α. Enhanced LT-induced lethality was also confirmed by BAG administration in mice. Furthermore, LT plus BAG-mediated lethality was significantly recovered by administration of Infliximab, an anti-TNF-α monoclonal antibody. CONCLUSIONS: Our results suggest that B. anthracis DNA may contribute to anthrax pathogenesis by enhancing LT activity via TLR9-mediated TNF-α production. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12866-014-0300-9) contains supplementary material, which is available to authorized users.
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spelling pubmed-42670522014-12-17 Bacillus anthracis genomic DNA enhances lethal toxin–induced cytotoxicity through TNF-α production Jeon, Jun Ho Kim, Yeon Hee Choi, Min Kyung Kim, Kyung Ae Lee, Hae-Ri Jang, Jeyoun Kim, Yu-Ri Chun, Jeong-Hoon Eo, Seong Kug Kim, Tae Sung Rhie, Gi-eun BMC Microbiol Research Article BACKGROUND: Bacillus anthracis is the etiological agent of anthrax. Lethal toxin (LT) produced by B. anthracis is a well-known key virulence factor for anthrax because of its strong cytotoxic activity. However, little is known about the role of B. anthracis genomic DNA (BAG) in anthrax pathogenesis. RESULTS: We examined the effect of BAG on TNF-α production and LT-mediated cytotoxicity during B. anthracis spore infection in mouse macrophage cell lines (RAW264.7 cells and J774A.1) and BALB/c mice. Infection of RAW264.7 cells with B. anthracis spores induced TNF-α expression in a multiplicity of infection (MOI)-dependent manner, and this enhancement was attenuated by the toll-like receptor (TLR) 9 inhibitor oligodeoxynucleotide (ODN)2088. BAG led to TNF-α expression in a dose- and time-dependent manner when applied to RAW264.7 cells. TNF-α expression induced by BAG was reduced by either pretreatment with TLR9 inhibitors (ODN2088 and chloroquine (CQ)) or transfection with TLR9 siRNA. Furthermore, BAG-induced TNF-α production in TLR9(+/+) macrophages was completely abrogated in TLR9(−/−) macrophages. BAG enhanced the phosphorylation of mitogen-activated protein kinases (MAPK), and BAG-induced TNF-α expression was attenuated by pretreatment with MAPK inhibitors. A reporter gene assay and confocal microscopy demonstrated that BAG increased NF-κB activation, which is responsible for TNF-α expression. Treatment with BAG alone showed no cytotoxic activity on the macrophage cell line J774A.1, whereas LT-mediated cytotoxicity was enhanced by treatment with BAG or TNF-α. Enhanced LT-induced lethality was also confirmed by BAG administration in mice. Furthermore, LT plus BAG-mediated lethality was significantly recovered by administration of Infliximab, an anti-TNF-α monoclonal antibody. CONCLUSIONS: Our results suggest that B. anthracis DNA may contribute to anthrax pathogenesis by enhancing LT activity via TLR9-mediated TNF-α production. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12866-014-0300-9) contains supplementary material, which is available to authorized users. BioMed Central 2014-12-04 /pmc/articles/PMC4267052/ /pubmed/25472474 http://dx.doi.org/10.1186/s12866-014-0300-9 Text en © Jeon et al.; licensee BioMed Central Ltd. 2014 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
spellingShingle Research Article
Jeon, Jun Ho
Kim, Yeon Hee
Choi, Min Kyung
Kim, Kyung Ae
Lee, Hae-Ri
Jang, Jeyoun
Kim, Yu-Ri
Chun, Jeong-Hoon
Eo, Seong Kug
Kim, Tae Sung
Rhie, Gi-eun
Bacillus anthracis genomic DNA enhances lethal toxin–induced cytotoxicity through TNF-α production
title Bacillus anthracis genomic DNA enhances lethal toxin–induced cytotoxicity through TNF-α production
title_full Bacillus anthracis genomic DNA enhances lethal toxin–induced cytotoxicity through TNF-α production
title_fullStr Bacillus anthracis genomic DNA enhances lethal toxin–induced cytotoxicity through TNF-α production
title_full_unstemmed Bacillus anthracis genomic DNA enhances lethal toxin–induced cytotoxicity through TNF-α production
title_short Bacillus anthracis genomic DNA enhances lethal toxin–induced cytotoxicity through TNF-α production
title_sort bacillus anthracis genomic dna enhances lethal toxin–induced cytotoxicity through tnf-α production
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4267052/
https://www.ncbi.nlm.nih.gov/pubmed/25472474
http://dx.doi.org/10.1186/s12866-014-0300-9
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