Flavohemoglobin Hmp Protects<i>Salmonella enterica</i>Serovar Typhimurium from Nitric Oxide-Related Killing by Human Macrophages

Stevanin, Tânia M.; Poole, Robert K.; Demoncheaux, Eric; Read, Robert C.

doi:10.1128/iai.70.8.4399-4405.2002

Cited by 150 publications

(122 citation statements)

References 44 publications

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“…By demonstrating an unequivocal contribution of Hmp to Salmonella virulence, we have been able to expand significantly upon an earlier report that Hmp modestly enhances Salmonella survival in cultured macrophages (50). Moreover, our finding that Hmp is required for persistent infection of Salmonella in mice suggests that host-derived RNS are important during microbial persistence as well as acute infection.…”

Section: Discussionsupporting

confidence: 58%

Maintenance of Nitric Oxide and Redox Homeostasis by the Salmonella Flavohemoglobin Hmp

Bang

Liu

Vázquez‐Torres

et al. 2006

Journal of Biological Chemistry

169

191

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Intracellular pathogens must resist the antimicrobial actions of nitric oxide (NO⅐) produced by host cells. To this end pathogens possess several NO⅐-metabolizing enzymes. Here we show that the flavohemoglobin Hmp is the principal enzyme responsible for aerobic NO⅐ metabolism by Salmonella enterica serovar typhimurium. We further show that Hmp is required for Salmonella virulence in mice, in contrast to S-nitrosoglutathione reductase, flavorubredoxin, or cytochrome c nitrite reductase. Abrogation of murine-inducible NO⅐ synthase restores virulence to hmp mutant bacteria. In the presence of nitrosative stress, Hmp-deficient Salmonella exhibits reduced NO⅐ consumption, impaired growth, increased protein S-nitrosylation, and filamentous morphology. However, under aerobic conditions in the absence of nitrosative stress, elevated hmp expression increases S. typhimurium susceptibility to hydrogen peroxide. Both the heme binding and flavoreductase domains are required for resistance to NO⅐, whereas the flavoreductase domain is responsible for iron-dependent susceptibility to oxidative stress. This provides a rationale for the regulation of hmp expression by the transcriptional repressor NsrR in response to both nitrosative stress and intracellular free iron concentration. The Hmp flavohemoglobin plays a central role in the response of Salmonella to nitrosative stress but requires precise regulation to avoid the exacerbation of oxidative stress that can result if electrons are shuttled to extraneous iron.

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Section: Discussionsupporting

confidence: 58%

Maintenance of Nitric Oxide and Redox Homeostasis by the Salmonella Flavohemoglobin Hmp

Bang

Liu

Vázquez‐Torres

et al. 2006

Journal of Biological Chemistry

169

191

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“…Considering that macrophages produce a large amount of NO to control infection (18)(19)(20) our seemingly paradoxical results can be rationalized if NO production by bacteria and macrophages is separated in time, leading to opposite outcomes. Indeed, it is well established that superoxide generation begins immediately after phagocytosis of bacteria.…”

Section: No From B Anthracis Is An Essential Virulence Factormentioning

confidence: 99%

Bacillus anthracis -derived nitric oxide is essential for pathogen virulence and survival in macrophages

Shatalin

Gusarov

Avetissova

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

192

182

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Phagocytes generate nitric oxide (NO) and other reactive oxygen and nitrogen species in large quantities to combat infecting bacteria. Here, we report the surprising observation that in vivo survival of a notorious pathogen-Bacillus anthracis-critically depends on its own NO-synthase (bNOS) activity. Anthrax spores (Sterne strain) deficient in bNOS lose their virulence in an A/J mouse model of systemic infection and exhibit severely compromised survival when germinating within macrophages. The mechanism underlying bNOS-dependent resistance to macrophage killing relies on NO-mediated activation of bacterial catalase and suppression of the damaging Fenton reaction. Our results demonstrate that pathogenic bacteria use their own NO as a key defense against the immune oxidative burst, thereby establishing bNOS as an essential virulence factor. Thus, bNOS represents an attractive antimicrobial target for treatment of anthrax and other infectious diseases.anthrax ͉ bacterial NO-synthase ͉ oxidative stress T he spore-producing Gram-positive soil organism, Bacillus anthracis, is the causative agent of anthrax, an acute lifethreatening infection in humans and domestic animals. Inhalation of B. anthracis spores results in a high rate of mortality, because effective treatment must be provided within a very short time after exposure (1). Deliberate dispersal of anthrax spores through the United States Postal Service in 2001 emphasized the importance of developing effective treatments to combat this potential biological scourge.Although the innate immune response is the first line of defense against B. anthracis, its spores survive, germinate, and proliferate in macrophages, eventually bursting them to produce a lethal titer of infectious particles. The mechanism by which B. anthracis evades immune attack is not fully understood. Most studies have been focused on major virulence factors found on two plasmids (pXO1 and pXO2) that are responsible for exotoxins, capsule formation, and spore germination (2). These plasmid-borne virulence factors have been the prime candidates for anti-anthrax drug design. However, the ability of pathogens such as B. anthracis to survive in phagocytes also depends critically on the state of their oxidative stress defense system. Reactive oxygen species (ROS) play essential roles in innate immunity against many types of microorganisms (3-5). The antibacterial effects of ROS have been largely attributed to DNA and protein damage mediated by the Fenton reaction (6). This process generates hydroxyl radicals that react with DNA bases, sugar moieties, and amino acid side chains, causing various types of lesions (7). We showed that nonpathogenic B. subtilis utilizes its own nitric oxide (NO) to gain rapid protection against sudden oxidative damage (8). The mechanism of protection does not rely on transcriptional gene induction but rather on rapid suppression of DNA damage by preventing the Fenton reaction and direct activation of catalase (8). Here, we describe the key role of NO-synthase (bNOS)-derived ...

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“…Specifically, both S. typhimurium and Escherichia coli produce NO (10,11), although the physiological significance of this is unclear. In E. coli, it has been reported that periplasmic nitrite reductase (NrfA; pentaheme periplasmic cytochrome c nitrite reductase) has a dual role in NO homeostasis; not only is it responsible for production of NO (11) but is also capable of detoxification of NO to NH 4 ϩ or N 2 O anaerobically (12,13). However, the major role of NrfA in E. coli is as a catalyst of the 6-electron reduction of NO 2 Ϫ to NH 4 ϩ (14).…”

mentioning

confidence: 99%

“…Enterobacteria possess several NO-detoxifying mechanisms, the most prominent being the flavohemoglobin Hmp (3)(4)(5)(6) and the flavorubredoxin NorV (7). These enzymes detoxify incoming NO both aerobically (Hmp) and anoxically (NorV), converting the toxic gas to NO 3 Ϫ or N 2 O, respectively (8).…”

mentioning

confidence: 99%

“…In E. coli, it has been reported that periplasmic nitrite reductase (NrfA; pentaheme periplasmic cytochrome c nitrite reductase) has a dual role in NO homeostasis; not only is it responsible for production of NO (11) but is also capable of detoxification of NO to NH 4 ϩ or N 2 O anaerobically (12,13). However, the major role of NrfA in E. coli is as a catalyst of the 6-electron reduction of NO 2 Ϫ to NH 4 ϩ (14). Expression of NrfA is positively regulated at the transcriptional level by FNR under anaerobic conditions and is further enhanced by the presence of NO 3 Ϫ and NO 2 Ϫ via the NarL and NarP regulators.…”

mentioning

confidence: 99%

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Nitric Oxide Homeostasis in Salmonella typhimurium

Gilberthorpe

Poole

2008

Journal of Biological Chemistry

Self Cite

113

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Nitric oxide (NO) is generated in biological systems primarily via the activity of NO synthases and nitrate and nitrite reductases. Here we show that Salmonella enterica serovar Typhimurium (S. typhimurium) grown anaerobically with nitrate is capable of generating polarographically detectable NO after nitrite (NO 2 ؊ ) addition. NO accumulation is sensitive to the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide. Neither an fnr mutant nor an fnr hmp double mutant produces NO, indicating the involvement in NO evolution from NO 2 ؊ of protein(s) positively regulated by FNR. Contrary to previous findings in Escherichia coli, we demonstrate that neither the periplasmic nitrite reductase (NrfA) nor the cytoplasmic nitrite reductase (NirB) is involved in NO production in S. typhimurium. However, mutant cells lacking the membrane-bound nitrate reductase, NarGHI, and membranes derived from these cells are unable to produce NO, demonstrating that, in wild-type S. typhimurium, this enzyme is responsible for NO production. Membrane terminal oxidases cannot account for the NO levels measured. The nitrate reductase inhibitor, azide, abrogates NO evolution by Salmonella, and production of NO occurs only in the absence from the assays of nitrate; both features reveal a marked similarity between the NO-generating activities of this bacterium and plants. Unlike the situation in E. coli, an S. typhimurium hmp mutant produces NO both aerobically and anaerobically. Under aerobic conditions, when a functional flavohemoglobin is present, no NO is detectable. We propose a homeostatic mechanism in S. typhimurium, in which NO produced from NO 2 ؊ by nitrate reductase derepresses Hmp expression (via FNR and NsrR) and NorV expression (via NorR) and thus limits NO toxicity.

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Flavohemoglobin Hmp ProtectsSalmonella entericaSerovar Typhimurium from Nitric Oxide-Related Killing by Human Macrophages

Cited by 150 publications

References 44 publications

Maintenance of Nitric Oxide and Redox Homeostasis by the Salmonella Flavohemoglobin Hmp

Maintenance of Nitric Oxide and Redox Homeostasis by the Salmonella Flavohemoglobin Hmp

Bacillus anthracis -derived nitric oxide is essential for pathogen virulence and survival in macrophages

Nitric Oxide Homeostasis in Salmonella typhimurium

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