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Difluoromethylornithine is a novel inhibitor of Helicobacter pylori growth, CagA translocation, and interleukin-8 induction.

Barry DP, Asim M, Leiman DA, de Sablet T, Singh K, Casero RA, Chaturvedi R, Wilson KT - PLoS ONE (2011)

Bottom Line: We found that DFMO significantly reduced the growth rate of H. pylori in a polyamine-independent manner.H. pylori exposed to DFMO were significantly shorter in length than those untreated and they contained greater internal levels of ATP, suggesting severe effects on bacterial metabolism.These findings suggest that DFMO has effects on H. pylori that may contribute to its effectiveness in reducing gastritis and colonization and may be a useful addition to anti-H. pylori therapies.

View Article: PubMed Central - PubMed

Affiliation: Division of Gastroenterology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America.

ABSTRACT
Helicobacter pylori infects half the world's population, and carriage is lifelong without antibiotic therapy. Current regimens prescribed to prevent infection-associated diseases such as gastroduodenal ulcers and gastric cancer can be thwarted by antibiotic resistance. We reported that administration of 1% D,L-α-difluoromethylornithine (DFMO) to mice infected with H. pylori reduces gastritis and colonization, which we attributed to enhanced host immune response due to inhibition of macrophage ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine biosynthesis. Although no ODC has been identified in any H. pylori genome, we sought to determine if DFMO has direct effects on the bacterium. We found that DFMO significantly reduced the growth rate of H. pylori in a polyamine-independent manner. Two other gram-negative pathogens possessing ODC, Escherichia coli and Citrobacter rodentium, were resistant to the DFMO effect. The effect of DFMO on H. pylori required continuous exposure to the drug and was reversible when removed, with recovery of growth rate in vitro and the ability to colonize mice. H. pylori exposed to DFMO were significantly shorter in length than those untreated and they contained greater internal levels of ATP, suggesting severe effects on bacterial metabolism. DFMO inhibited expression of the H. pylori virulence factor cytotoxin associated gene A, and its translocation and phosphorylation in gastric epithelial cells, which was associated with a reduction in interleukin-8 expression. These findings suggest that DFMO has effects on H. pylori that may contribute to its effectiveness in reducing gastritis and colonization and may be a useful addition to anti-H. pylori therapies.

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DFMO affects H. pylori 60190, but has no effect on two other Gram-negative bacteria.(A) Growth rates of H. pylori 60190 cultured in the absence or presence of 1% DFMO were compared as described in Figure 1B. Dashed lines indicate exponential curve regressions for each data set and are labeled with generation time and goodness of fit (n = 3; *, p<0.05). (B) E. coli DH5α were grown in control broth or broth supplemented with 1% or 2% DFMO and growth was monitored for 8 h. (C) C. rodentium were grown in control broth or broth supplemented with 1% or 2% DFMO and growth was monitored for 8 h.
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pone-0017510-g003: DFMO affects H. pylori 60190, but has no effect on two other Gram-negative bacteria.(A) Growth rates of H. pylori 60190 cultured in the absence or presence of 1% DFMO were compared as described in Figure 1B. Dashed lines indicate exponential curve regressions for each data set and are labeled with generation time and goodness of fit (n = 3; *, p<0.05). (B) E. coli DH5α were grown in control broth or broth supplemented with 1% or 2% DFMO and growth was monitored for 8 h. (C) C. rodentium were grown in control broth or broth supplemented with 1% or 2% DFMO and growth was monitored for 8 h.

Mentions: As our experiments to this point utilized a single strain of H. pylori, SS1, and the H. pylori species is known to exhibit an extreme degree of genetic diversity [37], we next investigated the growth inhibitory effect of DFMO on a second strain of H. pylori, 60190, that has been extensively used in laboratory studies [38], [39]. When we tested the effect of 1% DFMO on the growth of strain 60190 we observed a similar outcome, with generation time increasing from 3.6 h to 7.8 h (Figure 3A). We then explored whether the effect of DFMO was more universal and could be seen in other bacterial species. We selected E. coli and C. rodentium, which are Gram-negative bacteria of the same phylum as H. pylori (Proteobacteria). Neither of these species were affected by 1% DFMO, nor was there an effect when we doubled the concentration to 2% (Figures 3B and 3C). The fact that no inhibition of growth was observed using E. coli or C. rodentium, close relatives of H. pylori that do express ODC, suggests that the effect may be species-specific and is not simply due to toxicity, and that the mechanism is likely polyamine-independent.


Difluoromethylornithine is a novel inhibitor of Helicobacter pylori growth, CagA translocation, and interleukin-8 induction.

Barry DP, Asim M, Leiman DA, de Sablet T, Singh K, Casero RA, Chaturvedi R, Wilson KT - PLoS ONE (2011)

DFMO affects H. pylori 60190, but has no effect on two other Gram-negative bacteria.(A) Growth rates of H. pylori 60190 cultured in the absence or presence of 1% DFMO were compared as described in Figure 1B. Dashed lines indicate exponential curve regressions for each data set and are labeled with generation time and goodness of fit (n = 3; *, p<0.05). (B) E. coli DH5α were grown in control broth or broth supplemented with 1% or 2% DFMO and growth was monitored for 8 h. (C) C. rodentium were grown in control broth or broth supplemented with 1% or 2% DFMO and growth was monitored for 8 h.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3046249&req=5

pone-0017510-g003: DFMO affects H. pylori 60190, but has no effect on two other Gram-negative bacteria.(A) Growth rates of H. pylori 60190 cultured in the absence or presence of 1% DFMO were compared as described in Figure 1B. Dashed lines indicate exponential curve regressions for each data set and are labeled with generation time and goodness of fit (n = 3; *, p<0.05). (B) E. coli DH5α were grown in control broth or broth supplemented with 1% or 2% DFMO and growth was monitored for 8 h. (C) C. rodentium were grown in control broth or broth supplemented with 1% or 2% DFMO and growth was monitored for 8 h.
Mentions: As our experiments to this point utilized a single strain of H. pylori, SS1, and the H. pylori species is known to exhibit an extreme degree of genetic diversity [37], we next investigated the growth inhibitory effect of DFMO on a second strain of H. pylori, 60190, that has been extensively used in laboratory studies [38], [39]. When we tested the effect of 1% DFMO on the growth of strain 60190 we observed a similar outcome, with generation time increasing from 3.6 h to 7.8 h (Figure 3A). We then explored whether the effect of DFMO was more universal and could be seen in other bacterial species. We selected E. coli and C. rodentium, which are Gram-negative bacteria of the same phylum as H. pylori (Proteobacteria). Neither of these species were affected by 1% DFMO, nor was there an effect when we doubled the concentration to 2% (Figures 3B and 3C). The fact that no inhibition of growth was observed using E. coli or C. rodentium, close relatives of H. pylori that do express ODC, suggests that the effect may be species-specific and is not simply due to toxicity, and that the mechanism is likely polyamine-independent.

Bottom Line: We found that DFMO significantly reduced the growth rate of H. pylori in a polyamine-independent manner.H. pylori exposed to DFMO were significantly shorter in length than those untreated and they contained greater internal levels of ATP, suggesting severe effects on bacterial metabolism.These findings suggest that DFMO has effects on H. pylori that may contribute to its effectiveness in reducing gastritis and colonization and may be a useful addition to anti-H. pylori therapies.

View Article: PubMed Central - PubMed

Affiliation: Division of Gastroenterology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America.

ABSTRACT
Helicobacter pylori infects half the world's population, and carriage is lifelong without antibiotic therapy. Current regimens prescribed to prevent infection-associated diseases such as gastroduodenal ulcers and gastric cancer can be thwarted by antibiotic resistance. We reported that administration of 1% D,L-α-difluoromethylornithine (DFMO) to mice infected with H. pylori reduces gastritis and colonization, which we attributed to enhanced host immune response due to inhibition of macrophage ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine biosynthesis. Although no ODC has been identified in any H. pylori genome, we sought to determine if DFMO has direct effects on the bacterium. We found that DFMO significantly reduced the growth rate of H. pylori in a polyamine-independent manner. Two other gram-negative pathogens possessing ODC, Escherichia coli and Citrobacter rodentium, were resistant to the DFMO effect. The effect of DFMO on H. pylori required continuous exposure to the drug and was reversible when removed, with recovery of growth rate in vitro and the ability to colonize mice. H. pylori exposed to DFMO were significantly shorter in length than those untreated and they contained greater internal levels of ATP, suggesting severe effects on bacterial metabolism. DFMO inhibited expression of the H. pylori virulence factor cytotoxin associated gene A, and its translocation and phosphorylation in gastric epithelial cells, which was associated with a reduction in interleukin-8 expression. These findings suggest that DFMO has effects on H. pylori that may contribute to its effectiveness in reducing gastritis and colonization and may be a useful addition to anti-H. pylori therapies.

Show MeSH
Related in: MedlinePlus