The Thioredoxin System of Helicobacter pylori

Windle, Henry J.; Fox, Áine; Nı́Eidhin, Déirdre; Kelleher, Dermot

doi:10.1074/jbc.275.7.5081

Cited by 75 publications

(67 citation statements)

References 81 publications

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“…For host-generated oxidative stress to reach the pathogen DNA, it needs to overcome several barriers. Some of these are the stomach mucus layer itself, membrane lipids, and bacterial antioxidant enzymes such as superoxide dismutase, catalase, and thioredoxin reductase (33,34). Because the coculture with activated macrophages generates oxidative adducts in the bacterial DNA, we conclude that the bacterial antioxidant defenses are not sufficient to avoid oxidative DNA damage generated by a hostile environment.…”

Section: Discussionmentioning

confidence: 77%

Pathogen DNA as target for host-generated oxidative stress: Role for repair of bacterial DNA damage in Helicobacter pylori colonization

O’Rourke

Chevalier

Pinto

et al. 2003

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

122

110

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Helicobacter pylori elicits an oxidative stress during host colonization. This oxidative stress is known to cause lesions in the host DNA. Here we addressed the question as to whether the pathogen DNA is subject to lethal or mutational damage by the host-generated oxidative response. H. pylori Hpnth mutants unable to repair oxidized pyrimidines from the bacterial DNA were generated. H. pylori strains lacking a functional endonuclease III (HpNth) showed elevated spontaneous and induced mutation rates and were more sensitive than the parental strain to killing by exposure to oxidative agents or activated macrophages. Although under laboratory conditions the Hpnth mutant strain grows as well as the wild-type strain, in a mouse infection the stomach bacterial load gradually decreases while the population in the wild-type strain remains stable, showing that endonuclease III deficiency reduces the colonization capacity of the pathogen. In coinfection experiments with a wild-type strain, Hpnth cells are eradicated 15 days postinfection (p.i.) even when inoculated in a 1:9 wild-type:mutant strain ratio, revealing mutagenic lesions that are counterselected under competition conditions. These results show that the host effectively induces lethal and premutagenic oxidative DNA adducts on the H. pylori genome. The possible consequences of these DNA lesions on the adaptability of H. pylori strains to new hosts are discussed.

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Section: Discussionmentioning

confidence: 77%

Pathogen DNA as target for host-generated oxidative stress: Role for repair of bacterial DNA damage in Helicobacter pylori colonization

O’Rourke

Chevalier

Pinto

et al. 2003

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

122

110

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“…H. pylori cells were shown to be resistant to a high concentration (ϳ100 mM) of H 2 O 2 , and this resistance was abolished in katA Ϫ mutants (24). H. pylori AhpC is a major component of the AhpC-thioredoxin-thioredoxin reductase-dependent peroxiredoxin system that catalyzes the reduction of hydroperoxides including H 2 O 2 and organic hydroperoxides (22,25), as well as the reduction of peroxynitrite (26). It was extremely difficult to obtain an ahpC knock-out mutant (21,22), but the mutant was obtained eventually by screening transformants at a very low O 2 (1% partial pressure) condition (13).…”

mentioning

confidence: 99%

Role of a Bacterial Organic Hydroperoxide Detoxification System in Preventing Catalase Inactivation

Wang¹,

Conover

Benoit³

et al. 2004

Journal of Biological Chemistry

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In the gastric pathogen Helicobacter pylori, catalase (KatA) and alkyl hydroperoxide reductase (AhpC) are two highly abundant enzymes that are crucial for oxidative stress resistance and survival of the bacterium in the host. Here we report a connection unidentified previously between the two stress resistance enzymes. We observed that the catalase in ahpC mutant cells in comparison with the parent strain is inactivated partially (approximately 50%). The decrease of catalase activity is well correlated with the perturbation of the heme environment in catalase, as detected by electron paramagnetic resonance spectroscopy. To understand the reason for this catalase inactivation, we examined the inhibitory effects of hydroperoxides on H. pylori catalase (either present in cell extracts or added to the purified enzyme) by monitoring the enzyme activity and the EPR signal of catalase. H. pylori catalase is highly resistant to its own substrate, without the loss of enzyme activity by treatment with a molar ratio of 1:3000 H 2 O 2 . However, it is inactivated by lower concentrations of organic hydroperoxides (the substrate of AhpC). Treatment with a molar ratio of 1:400 t-butyl hydroperoxide resulted in an inactivation of catalase by approximately 50%. UV-visible absorption spectra indicated that the catalase inactivation by organic hydroperoxides is caused by the formation of a catalytically incompetent compound II species. To further support the idea that organic hydroperoxides, which accumulate in the ahpC mutant cells, are responsible for the inactivation of catalase, we compared the level of lipid peroxidation found in ahpC mutant cells with that found in wild type cells. The results showed that the total amount of extractable lipid hydroperoxides in the ahpC mutant cells is approximately three times that in the wild type cells. Our findings reveal a novel role of the organic hydroperoxide detoxification system in preventing catalase inactivation.

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“…No mixed disulfide bonds between Trx1 and His 6 -RocF were detected, and no evidence for contaminating proteins in purified His 6 -RocF or Trx1 was found. The oxidized form of Trx1 (Trx1 ox ) displays much lower fluorescence intensity at its emission maximum (A 340 ) than the reduced form (Trx1 red ) (9). If the cysteines of His 6 -RocF were being oxidized by Trx1 ox , resulting in Trx1 red , then an increase in the fluorescence emission of Trx1 ox would occur similar to that of Trx1 red alone.…”

Section: H Pylori Contains Anmentioning

confidence: 99%

“…Fluorescence Spectra of Trx1-Purified Trx1 was rendered fully oxidized or fully reduced, and its fluorescence emission at different times was determined in the presence or absence of purified His 6 -RocF using previously established procedures (9).…”

Section: Methodsmentioning

confidence: 99%

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Helicobacter pylori Thioredoxin Is an Arginase Chaperone and Guardian against Oxidative and Nitrosative Stresses

McGee

Kumar

Viator

et al. 2006

Journal of Biological Chemistry

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The gastric human pathogen Helicobacter pylori faces formidable challenges in the stomach including reactive oxygen and nitrogen intermediates. Here we demonstrate that arginase activity, which inhibits host nitric oxide production, is post-translationally stimulated by H. pylori thioredoxin (Trx) 1 but not the homologous Trx2. Trx1 has chaperone activity that renatures urea-or heat-denatured arginase back to the catalytically active state. Most reactive oxygen and nitrogen intermediates inhibit arginase activity; this damage is reversed by Trx1, but not Trx2. Trx1 and arginase equip H. pylori with a "renox guardian" to overcome abundant nitrosative and oxidative stresses encountered during the persistence of the bacterium in the hostile gastric environment.The gastric human pathogen Helicobacter pylori causes chronic gastritis and ulcers and has a strong link with gastric cancer. Despite enormous knowledge gleaned from two completely sequenced strains (1, 2), little is known about how this organism escapes the host innate and adaptive immune systems. The extensive inflammatory response observed in H. pylori-infected patients contributes to gastric damage; some of this damage is mediated by ROI/RNIs 3 such as NO and hydrogen peroxide. Arginase (RocF), which hydrolyzes L-arginine to urea and L-ornithine, inhibits macrophage NO production by directly competing with host nitric-oxide synthase for arginine availability (3). The urea can then be hydrolyzed by the copious H. pylori urease to yield carbon dioxide and ammonium, the latter of which neutralizes gastric acid. Indeed, acid treatment (pH 2) of H. pylori in the presence of arginine protects H. pylori in an arginase-dependent fashion (4). The arginase of H. pylori exhibits several unusual features, including optimal catalytic activity with cobalt, rather than manganese, and an acidic pH optimum (5). Furthermore, H. pylori arginase inhibits human T cell proliferation and T cell CD3 expression by siphoning arginine away from the host cell (6), potentially contributing to the inability of T cells to clear H. pylori infections. These findings point to a critical role for arginase in disarming two innate host defenses (acid and NO) and adaptive immunity (T cells), thereby disabling the two arms of the immune system. The critical questions remaining are: how is arginase modulated, and is arginase itself sensitive to ROI/RNIs? Here, we provide compelling evidence that H. pylori arginase is modulated at the post-translational level by thioredoxin 1 (Trx1) and that Trx1 protects arginase from ROI/RNIs and is an arginase chaperone.

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The Thioredoxin System of Helicobacter pylori

Cited by 75 publications

References 81 publications

Pathogen DNA as target for host-generated oxidative stress: Role for repair of bacterial DNA damage in Helicobacter pylori colonization

Pathogen DNA as target for host-generated oxidative stress: Role for repair of bacterial DNA damage in Helicobacter pylori colonization

Role of a Bacterial Organic Hydroperoxide Detoxification System in Preventing Catalase Inactivation

Helicobacter pylori Thioredoxin Is an Arginase Chaperone and Guardian against Oxidative and Nitrosative Stresses

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