The poly-γ-d-glutamic acid capsule surrogate of the Bacillus anthracis capsule induces nitric oxide production via the platelet activating factor receptor signaling pathway.
The poly-γ-d-glutamic acid (PGA) capsule, a major virulence factor of Bacillus anthracis, confers protection of the bacillus from phagocytosis and allows its unimpeded growth in the host. PGA capsules released from B. anthracis are associated with lethal toxin in the blood of experimentally infected animals and enhance the cytotoxic effect of lethal toxin on macrophages. In addition, PGA capsule itself activates macrophages and dendritic cells to produce proinflammatory cytokine such as IL-1β, indicating multiple roles of PGA capsule in anthrax pathogenesis. Here we report that PGA capsule of Bacillus licheniformis, a surrogate of B. anthracis capsule, induces production of nitric oxide (NO) in RAW264.7 cells and bone marrow-derived macrophages. NO production was induced by PGA in a dose-dependent manner and was markedly reduced by inhibitors of inducible NO synthase (iNOS), suggesting iNOS-dependent production of NO. Induction of NO production by PGA was not observed in macrophages from TLR2-deficient mice and was also substantially inhibited in RAW264.7 cells by pretreatment of TLR2 blocking antibody. Subsequently, the downstream signaling events such as ERK, JNK and p38 of MAPK pathways as well as NF-κB activation were required for PGA-induced NO production. In addition, the induced NO production was significantly suppressed by treatment with antagonists of platelet activating factor receptor (PAFR) or PAFR siRNA, and mediated through PAFR/Jak2/STAT-1 signaling pathway. These findings suggest that PGA capsule induces NO production in macrophages by triggering both TLR2 and PAFR signaling pathways which lead to activation of NF-kB and STAT-1, respectively.
Division of High-Risk Pathogen Research, Center for Infectious Diseases, Korea National Institute of Health, Cheongju-si, Chungcheongbuk-do 363-951, South Korea.
Hae-Ri
HR
Lee
Division of High-Risk Pathogen Research, Center for Infectious Diseases, Korea National Institute of Health, Cheongju-si, Chungcheongbuk-do 363-951, South Korea.
Jun Ho
JH
Jeon
Division of High-Risk Pathogen Research, Center for Infectious Diseases, Korea National Institute of Health, Cheongju-si, Chungcheongbuk-do 363-951, South Korea.
Ok-Kyu
OK
Park
Division of High-Risk Pathogen Research, Center for Infectious Diseases, Korea National Institute of Health, Cheongju-si, Chungcheongbuk-do 363-951, South Korea.
Jeong-Hoon
JH
Chun
Department of Bioscience and Biotechnology, Yongin 449-791, South Korea; Protein Research Center for Bioindustry, Hankuk University of Foreign Studies, Yongin 449-791, South Korea.
Jungchan
J
Park
Division of High-Risk Pathogen Research, Center for Infectious Diseases, Korea National Institute of Health, Cheongju-si, Chungcheongbuk-do 363-951, South Korea. Electronic address: gerhie@nih.go.kr.
Gi-Eun
GE
Rhie
D000818:Animals; D057134:Antibodies, Neutralizing / Q000494:pharmacology; D001407:Bacillus / Q000737:chemistry* / Q000276:immunology; D001408:Bacillus anthracis / Q000737:chemistry / Q000276:immunology; D016667:Bacterial Capsules / Q000737:chemistry / Q000276:immunology; D002460:Cell Line; D004306:Dose-Response Relationship, Immunologic; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005786:Gene Expression Regulation; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000276:immunology; D016328:NF-kappa B / Q000235:genetics / Q000276:immunology; D009569:Nitric Oxide / Q000819:agonists* / Q000096:biosynthesis; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000276:immunology*; D010980:Platelet Membrane Glycoproteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000276:immunology*; D011099:Polyglutamic Acid / Q000031:analogs & derivatives* / Q000302:isolation & purification / Q000494:pharmacology; D061251:Primary Cell Culture; D034741:RNA, Small Interfering / Q000235:genetics / Q000276:immunology; D043562:Receptors, G-Protein-Coupled / Q000037:antagonists & inhibitors / Q000235:genetics / Q000276:immunology*; D050794:STAT1 Transcription Factor / Q000235:genetics / Q000276:immunology; D015398:Signal Transduction; D051195:Toll-Like Receptor 2 / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics / Q000276:immunology*
D057134:Antibodies, Neutralizing; D004791:Enzyme Inhibitors; D016328:NF-kappa B; D010980:Platelet Membrane Glycoproteins; D034741:RNA, Small Interfering; D043562:Receptors, G-Protein-Coupled; D050794:STAT1 Transcription Factor; C494080:Stat1 protein, mouse; C493486:Tlr2 protein, mouse; D051195:Toll-Like Receptor 2; C039351:platelet activating factor receptor; C511775:poly(gamma-glutamic acid); D011099:Polyglutamic Acid; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D020928:Mitogen-Activated Protein Kinases
Bacillus anthracis; Macrophages; Nitric oxide; Platelet activating factor receptor (PAFR); Poly-γ-d-glutamic acid (PGA) capsule