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Phosphodiesterase-4 inhibition alters gene expression and improves isoniazid-mediated clearance of Mycobacterium tuberculosis in rabbit lungs.

ABSTRACT: Tuberculosis (TB) treatment is hampered by the long duration of antibiotic therapy required to achieve cure. This indolent response has been partly attributed to the ability of subpopulations of less metabolically active Mycobacterium tuberculosis (Mtb) to withstand killing by current anti-TB drugs. We have used immune modulation with a phosphodiesterase-4 (PDE4) inhibitor, CC-3052, that reduces tumor necrosis factor alpha (TNF-?) production by increasing intracellular cAMP in macrophages, to examine the crosstalk between host and pathogen in rabbits with pulmonary TB during treatment with isoniazid (INH). Based on DNA microarray, changes in host gene expression during CC-3052 treatment of Mtb infected rabbits support a link between PDE4 inhibition and specific down-regulation of the innate immune response. The overall pattern of host gene expression in the lungs of infected rabbits treated with CC-3052, compared to untreated rabbits, was similar to that described in vitro in resting Mtb infected macrophages, suggesting suboptimal macrophage activation. These alterations in host immunity were associated with corresponding down-regulation of a number of Mtb genes that have been associated with a metabolic shift towards dormancy. Moreover, treatment with CC-3052 and INH resulted in reduced expression of those genes associated with the bacterial response to INH. Importantly, CC-3052 treatment of infected rabbits was associated with reduced ability of Mtb to withstand INH killing, shown by improved bacillary clearance, from the lungs of co-treated animals compared to rabbits treated with INH alone. The results of our study suggest that changes in Mtb gene expression, in response to changes in the host immune response, can alter the responsiveness of the bacteria to antimicrobial agents. These findings provide a basis for exploring the potential use of adjunctive immune modulation with PDE4 inhibitors to enhance the efficacy of existing anti-TB treatment.

SUBMITTER: Subbian S

PROVIDER: S-EPMC3174258 | biostudies-literature | 2011 Sep

REPOSITORIES: biostudies-literature

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Phosphodiesterase-4 inhibition alters gene expression and improves isoniazid-mediated clearance of Mycobacterium tuberculosis in rabbit lungs.

Subbian Selvakumar S Tsenova Liana L O'Brien Paul P Yang Guibin G Koo Mi-Sun MS Peixoto Blas B Fallows Dorothy D Dartois Veronique V Muller George G Kaplan Gilla G

PLoS pathogens 20110915 9

Tuberculosis (TB) treatment is hampered by the long duration of antibiotic therapy required to achieve cure. This indolent response has been partly attributed to the ability of subpopulations of less metabolically active Mycobacterium tuberculosis (Mtb) to withstand killing by current anti-TB drugs. We have used immune modulation with a phosphodiesterase-4 (PDE4) inhibitor, CC-3052, that reduces tumor necrosis factor alpha (TNF-α) production by increasing intracellular cAMP in macrophages, to ex ...[more]

PMID: 21949656

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Project description:Tuberculosis kills nearly 2 million people through out the world, every year. The outcome of M. tuberculosis infection is determined by the host and bacterial factors. A strong host immune response controls the growth of the bacilli effectively. However, in a host with suboptimal immune response, the bacilli grows and mounts disease. Activation of immune response following M. tuberculosis infection affects the expression of many host genes that are involved in the production of immune system molecules such as cytokines, chemokines, surface receptors and transcriptional regulators that manifest in the change of subsequent cellular events, including chemotaxis and proliferation of effector cells. The infecting bacilli counteracts the bactericidal activities of the host immune cells, primarily by modifying their gene expression. However, the specific nature of the host-pathogen interactions and the outcome of Mtb infection are not fully understood. Tumor necrosis factor-alpha (TNF-a), produced by the immune cells, is an important cytokine in protecting the host against Mtb infection. However, excessive TNF-a production leads to severe inflammation and host cell destruction. In fact, pharmacologic inhibition of TNF-a production has been considered as a therapeutic modality in inflammatory diseases. Interestingly, inhibitors of host phosphodiesterase-4 (PDE4) have been shown to reduce TNF-a production and dampen inflammation without complete immune suppression of the host. In this study, we have explored the use of one of the PDE4 inhibitors, CC-3052, as an adjunct immune modulatory drug, in combination with isoniazid (INH) treatment in rabbit pulmonary tuberculosis. We hypothesize that reducing TNF-a levels during Mtb infection would reduce the environmental pressure on the bacteria, rendering them more amenable to killing by INH. Mtb infected rabbits were treated with CC-3052 or INH or both and the lung tissue were harvested after 4 and 8 weeks of treatment. Lung bacterial load, histologic changes and host and bacterial gene expression were determined for each timepoint and compared between various treatment groups. The results of our study provides data to support the idea that combining anti-TB drugs with an adjunctive immune modulator may enhance the efficacy of current TB therapy regimens and shorten the duration of treatment if applied appropriately to humans. The microarray experiments involves 2 comparison groups. 1) Changes in rabbit gene expression between Mtb infected and uninfected animals; 2). Changes in rabbit gene expression between CC-3052 treated and untreated animals during Mtb infection at 4,8 and 12 weeks post infection. New Zealand White rabbits were infected with Mtb HN878 at 3.2log10 (on day 0). At 4 weeks post infection, one group of infected rabbits were treated with a phosphodiesterase-4 (PDE4) inhibitor, CC-3052, and the treatment was continued up to 12 weeks post infection. The compound was used at 25mg/kg body weight, dissolved in distilled water and administered through gavage five days a weeks. Lung tissue from Uninfected, Mtb-infected and Untreated or CC-3052 treated rabbits were isolated at Day0, 4,8 and 12 weeks post infection and used for total RNA extraction. Only the 8 and 12 week timepoints correspond to the associated publication.

Dataset Information

Phosphodiesterase-4 inhibition alters gene expression and improves isoniazid-mediated clearance of Mycobacterium tuberculosis in rabbit lungs.

Publications

Phosphodiesterase-4 inhibition alters gene expression and improves isoniazid-mediated clearance of Mycobacterium tuberculosis in rabbit lungs.

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