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On the action of methotrexate and 6-mercaptopurine on M. avium subspecies paratuberculosis.

ABSTRACT: BACKGROUND: Clinical improvement in inflammatory bowel disease (IBD) treated with methotrexate and 6-mercaptopurine (6-MP) is associated with a decrease in pro-inflammatory cytokines. This has been presumed to indicate the mechanism of action of methotrexate and 6-MP. Although controversial, there are increasingly compelling data that Mycobacterium avium subspecies paratuberculosis (MAP) may be an etiological agent in some or all of IBD. We hypothesized that the clinical efficacy of methotrexate and 6-MP in IBD may be to simply inhibit the growth of MAP. METHODOLOGY: The effect on MAP growth kinetics by methotrexate and 6-MP were evaluated in cell culture of two strains each of MAP and M. avium using a radiometric ((14)CO(2) BACTEC detection system that quantifies mycobacterial growth as arbitrary "growth index units" (GI). Efficacy data are presented as "percent decrease in cumulative GI" (% -DeltacGI). PRINCIPAL FINDINGS: The positive control antibiotic (clarithromycin) has >or=85% -DeltacGI at a concentration of 0.5 microg/ml. The negative control (ampicillin) has minimal inhibition at 64 microg/ml. MAP ATCC 19698 shows >or=80% -DeltacGI for both agents by 4 microg/ml. With the other three isolates, although more effective than ampicillin, 6-MP is consistently less effective than methotrexate. CONCLUSIONS: We show that methotrexate and 6-MP inhibit MAP growth in vitro. Each of the four isolates manifests different % -DeltacGI. These data are compatible with the hypothesis that the clinical improvement in patients with IBD treated with methotrexate and 6-MP could be due to treating a MAP infection. The decrease in pro-inflammatory cytokines, thought to be the primary mechanism of action, may simply be a normal, secondary, physiological response. We conclude that henceforth, in clinical studies that evaluate the effect of anti-MAP agents in IBD, the use of methotrexate and 6-MP should be excluded from any control groups.

SUBMITTER: Greenstein RJ

PROVIDER: S-EPMC1779805 | biostudies-literature | 2007

REPOSITORIES: biostudies-literature

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On the action of methotrexate and 6-mercaptopurine on M. avium subspecies paratuberculosis.

Greenstein Robert J RJ Su Liya L Haroutunian Vahram V Shahidi Azra A Brown Sheldon T ST

PloS one 20070124 1

<h4>Background</h4>Clinical improvement in inflammatory bowel disease (IBD) treated with methotrexate and 6-mercaptopurine (6-MP) is associated with a decrease in pro-inflammatory cytokines. This has been presumed to indicate the mechanism of action of methotrexate and 6-MP. Although controversial, there are increasingly compelling data that Mycobacterium avium subspecies paratuberculosis (MAP) may be an etiological agent in some or all of IBD. We hypothesized that the clinical efficacy of metho ...[more]

PMID: 17252054

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Project description:BACKGROUND:Antibiotic therapy targeting chronic mycobacterial disease is often ineffective due to problems with the emergence of drug resistance and non-replicating persistent intracellular antibiotic resistant phenotypes. Strategies which include agents able to enhance host cell killing mechanisms could represent an alternative to conventional methods with the potential for host clearance if active against dormant phenotypes. Investigations of agents with potential activity against non-replicating mycobacteria however are restricted due to a need for assays that can assess bacterial viability without having to culture. RESULTS:This study describes the development and use of a pre16S ribosomal gene RNA/DNA ratio viability assay which is independent of the need for culture, supported by a novel thin layer accelerated mycobacterial colony forming method for determining viability and culturability of MAP in intracellular environments. We describe the use of these tools to demonstrate intracellular killing activity of a novel rhodanine agent (D157070) against the intracellular pathogen Mycobacterium avium subspecies paratuberculosis (MAP) and show that the culturability of MAP decreases relative to its viability on intracellular entry suggesting the induction of a non-culturable phenotype. We further demonstrate that D157070, although having no direct activity against the culturability of extracellular MAP, can bind to cultured MAP cells and has significant influence on the MAP transcriptome, particularly with respect of delta(L )associated genes. D157070 is shown to be taken up by bovine and human cells and able to enhance host cell killing, as measured by significant decreases in both culturability and viability of intracellular MAP. CONCLUSIONS:This work suggests that pre16srRNA gene ratios represent a viable method for studying MAP viability. In addition, the rhodanine agent D157070 tested is non-toxic and enhances cell killing activity against both growing and latent MAP phenotypes.

Dataset Information

On the action of methotrexate and 6-mercaptopurine on M. avium subspecies paratuberculosis.

Publications

On the action of methotrexate and 6-mercaptopurine on M. avium subspecies paratuberculosis.

Similar Datasets

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