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

Bang, Iel Soo; Liu, Limin; Vázquez‐Torres, Andrés; Crouch, Marie Laure V; Stamler, Jonathan S.; Fang, Ferric C.

doi:10.1074/jbc.m605174200

Cited by 169 publications

(208 citation statements)

References 62 publications

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“…Hmp has been identified as important for protection of non-pathogenic E. coli against NOmediated killing by human macrophages [17]. Furthermore Hmp was required for Salmonella virulence in mice [48]. However, so far no studies have addressed the significance of Hmp in urovirulence.…”

Section: Discussionmentioning

confidence: 99%

Role of flavohemoglobin in combating nitrosative stress in uropathogenic Escherichia coli – Implications for urinary tract infection

Svensson

Poljakovic

Säve

et al. 2010

Microbial Pathogenesis

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Role of flavohemoglobin in combating nitrosative stress in uropathogenic Escherichia coliimplications for urinary tract infection. During the course of urinary tract infection (UTI) nitric oxide (NO) is generated as part of host response. The aim of this study was to investigate the significance of the NO-detoxifying enzymes flavohemoglobin (Hmp) and flavorubredoxin (Norv) in protection of uropathogenic Escherichia coli (UPEC) against nitrosative stress. Hmp (J96∆hmp) and norV (J96∆norV) knockout mutants of UPEC strain J96 were constructed using a single-gene deletion strategy. Bacterial tolerance and expression of hmp and norV in response to the NO-donor DETA/NO was evaluated in Luria broth and urine from healthy volunteers. Bacterial NO consumption and respiratory inhibition were assessed when exposed to NO. Expression of hmp and norV from E. coli originating from patients with UTI was evaluated using real-time PCR. The colonizing ability of J96 wild-type (wt) compared to an hmp-deficient mutant was assessed using a competition-based mouse UTI model. The viability of J96∆hmp and J96∆norV was significantly reduced compared to the wildtype strain after exposure to DETA/NO. The hmp expression in DETA/NO-exposed cultures was similar in J96wt and J96∆norV, while J96∆hmp showed an increased norV expression compared to J96wt. The NO consumption in J96∆hmp, but not in J96∆norV, was significantly impaired compared to J96wt. An up-regulation of hmp expression was found in E. coli isolated from all UTIpatients while norV expression increased in 50% of the patients. In the mouse UTI model, the hmp-mutant strain was significantly out-competed by the wild-type strain in the bladder and kidney. Hmp and NorV contribute to the protection of UPEC against NOmediated toxicity in vitro. Screening UPEC isolates from UTI patients revealed an increased hmp expression in all patients which confirms that hmp expression occurs in vivo in the infected human urinary tract. The ability to colonize the mouse urinary tract was impaired in the hmp-deficient mutant compared to the wild-type strain. NO-detoxification by Hmp is suggested to be an important characteristic for UPEC in protection against nitrosative stress and may be a virulence-facilitating factor.

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Section: Discussionmentioning

confidence: 99%

Role of flavohemoglobin in combating nitrosative stress in uropathogenic Escherichia coli – Implications for urinary tract infection

Svensson

Poljakovic

Säve

et al. 2010

Microbial Pathogenesis

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“…Salmonella lacking Hmp experienced three times more N 2 O 3 in resting macrophages than in wild-type controls, resulting in comparable reductions in SPI2 expression and intracellular survival. Because SPI2 is critical for intracellular survival of Salmonella in a variety of phagocytic and nonphagocytic cells and is essential for the development of systemic salmonellosis (Ochman et al, 1996;Shea et al, 1996;Vazquez-Torres et al, 2000b), protection of SPI2 transcription against NO toxicity represents a novel mechanism by which Hmp may contribute to Salmonella virulence (Bang et al, 2006). It should be noted, nonetheless, that SPI2-dependent survival in resting macrophages was not completely abrogated in hmpAdeficient Salmonella.…”

Section: Discussionmentioning

confidence: 99%

“…Hmp is the most important antinitrosative defense of Salmonella (Bang et al, 2006). We calculated the degree by which Hmp protects SPI2 expression against nitrosative stress and the extent of hmpA expression during innate and acquired responses of macrophages.…”

Section: Quantification Of Hmpa Expression By Intracellular Salmonellamentioning

confidence: 99%

N2O3 enhances the nitrosative potential of IFNγ-primed macrophages in response to Salmonella

et al. 2008

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We show here that the nitric oxide (NO)-detoxifying Hmp flavohemoprotein increases by 3-fold the transcription of the Salmonella pathogenicity island 2 (SPI2) in macrophages expressing a functional inducible NO synthase (iNOS). However, Hmp does not prevent NO-related repression of SPI2 transcription in IFNγ-primed phagocytes, despite preserving intracellular transcription of sdhA sdhB subunits of Salmonella succinate dehydrogenase within both control and IFNγ-primed phagocytes. To shed light into the seemingly paradoxical role that Hmp plays in protecting intracellular SPI2 expression in various populations of macrophages, N 2 O 3 was quantified as an indicator of the nitrosative potential of Salmonella-infected phagocytes in different states of activation. Hmp was found to prevent the formation of 300 nM N 2 O 3 /h/bacteria in IFNγ-primed macrophages, accounting for about a 60% reduction of the nitrosative power of activated phagocytes. Utilization of the vacuolar ATPase inhibitor bafilomycin indicates that a fourth of the ~200 nM N 2 O 3 /h sustained by IFNγ-primed macrophages is generated in endosomal compartments via condensation of HNO 2 . In sharp contrast, control macrophages infected with wild-type Salmonella produce as little N 2 O 3 as iNOS-deficient controls. Collectively, these findings indicate that the NOmetabolizing activity of Salmonella Hmp is functional in both control and IFNγ-primed macrophages. Nonetheless, a substantial amount of the NO generated by IFNγ-primed macrophages gives rise to N 2 O 3 , a species that not only enhances the nitrosative potential of activated phagocytes but also avoids detoxification by Salmonella Hmp.

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“…A suspension of 100 μL of bacteria was transferred to a 200-well plate with 100 μL them to replenish cytosolic thiol groups, alter metal homeostasis and activate specific DNA repair mechanisms. [25][26][27] Additionally, Gram-negative bacteria such as E. coli, K. pneumoniae and P. aeruginosa synthesize flavohemoglobins (Hmp), enzymes that neutralize NO and therefore counteract nitrosative stress. 28 Under aerobic conditions, Hmp are upregulated in the presence of NO acting as a denitrosylase that downgrade NO to a harmless NO 3 -ion.…”

mentioning

confidence: 99%

Susceptibility of Gram-positive and -negative bacteria to novel nitric oxide-releasing nanoparticle technology

Friedman¹,

Blecher²,

Sanchez³

et al. 2011

Virulence

122

100

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

Cited by 169 publications

References 62 publications

Role of flavohemoglobin in combating nitrosative stress in uropathogenic Escherichia coli – Implications for urinary tract infection

Role of flavohemoglobin in combating nitrosative stress in uropathogenic Escherichia coli – Implications for urinary tract infection

N2O3 enhances the nitrosative potential of IFNγ-primed macrophages in response to Salmonella

Susceptibility of Gram-positive and -negative bacteria to novel nitric oxide-releasing nanoparticle technology

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