Importance of nitric oxide synthase in the control of infection by Bacillus anthracis.
The spore-forming, gram-positive bacterium Bacillus anthracis, the causative agent of anthrax, has achieved notoriety due to its use as a bioterror agent. In the environment, B. anthracis exists as a dormant endospore. Upon infection, germination of endospores occurs during their internalization within the phagocyte, and the ability to survive exposure to antibacterial killing mechanisms, such as O2*-, NO*, and H2O2, is a key initial event in the infective process. Macrophages generate NO* from the oxidative metabolism of L-arginine, using an isoform of nitric oxide synthase (NOS 2). Exposure of murine macrophages (RAW264.7 cells) to B. anthracis endospores up-regulated the expression of NOS 2 12 h after exposure, and production of NO* was comparable to that achieved following other bacterial infections. Spore-killing assays demonstrated a NO*-dependent bactericidal response that was significantly decreased in the presence of the NOS 2 inhibitor L-N6-(1-iminoethyl)lysine and in L-arginine-depleted media. Interestingly, we also found that B. anthracis bacilli and endospores exhibited arginase activity, possibly competing with host NOS 2 for its substrate, L-arginine. As macrophage-generated NO* is an important pathway in microbial killing, the ability of endospores of B. anthracis to regulate production of this free radical has important implications in the control of B. anthracis-mediated infection.
Raines
Kimberly W
KW
Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, 725 West Lombard Street, Baltimore, MD 21201, USA.
Kang
Tae Jin
TJ
Hibbs
Stephen
S
Cao
Guan-Liang
GL
Weaver
John
J
Tsai
Pei
P
Baillie
Les
L
Cross
Alan S
AS
Rosen
Gerald M
GM
D000818:Animals; D000881:Anthrax / Q000201:enzymology* / Q000382:microbiology*; D001119:Arginase / Q000378:metabolism; D001408:Bacillus anthracis / Q000472:pathogenicity* / Q000648:ultrastructure; D002460:Cell Line; D004790:Enzyme Induction / Q000235:genetics; D007527:Isoenzymes / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D008264:Macrophages / Q000201:enzymology* / Q000382:microbiology / Q000648:ultrastructure; D051379:Mice; D009569:Nitric Oxide / Q000096:biosynthesis / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D010587:Phagocytosis / Q000502:physiology; D013171:Spores, Bacterial / Q000502:physiology; D013379:Substrate Specificity / Q000235:genetics
D007527:Isoenzymes; D009569:Nitric Oxide; C496319:NOS2 protein, human; D052247:Nitric Oxide Synthase Type II; D001119:Arginase