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Inhibition of Chlamydia pneumoniae Replication in Human Dendritic cells by TNF-alpha-Induced Indoleamine 2,3-Dioxygenase

ABSTRACT: Infection with Chlamydia pneumoniae, a human respiratory pathogen, has been associated with various chronic diseases such as asthma, coronary heart disease and importantly atherosclerosis. Possibly because the pathogen can exist in a persistent form. TNF-a has been reported to induce chlamydial persitence in epithelial cell lines, however the mechanism of TNF-a-induced persistence has not been reported. Moreover, C. pneumoniae persistently infect human dendritic cells (DCs) and activate DCs to produce cytokines including TNF-a. Induction of chlamydial persistence by other cytokines such as IFN-g is known to be due to indoleamine 2,3-dioxygenase (IDO) activity. The present study therefore, investigated whether C. pneumoniae infection can induce IDO activity in dendritic cells, and whether the restriction of chlamydial growth in the DCs by TNF-a is IDO-dependent. Our data indicate that infection of DCs with C. pneumoniae resulted in the induction of IDO expression. Reporting on our use of anti-TNF-a antibody adalimumab and varying concentrations of TNF-a, we further demonstrate that IDO induction following infection of DCs with C. pneumoniae is TNF-a-dependent. The anti-chlamydial activity induced by TNF-a and the expression of chlamydial 16S rRNA gene, euo, groEL1, ftsk and tal genes was correlated with the induction of IDO. Addition of excess amounts of tryptophan to the DC cultures resulted in abrogation of the TNF-a-mediated chlamydial growth restriction. These findings suggest that infection of DCs by C. pneumoniae induces production of functional IDO, which subsequently causes depletion of tryptophan. This may represent a potential mechanism for DCs to restrict bacterial growth in chlamydial infections. Keywords: Chlamydia pneumoniae, Dendritic cells, TNF-a, Indoleamine 2,3-dioxygenase

ORGANISM(S): Homo sapiens

PROVIDER: GSE12806 | GEO | 2009/08/21

SECONDARY ACCESSION(S): PRJNA111111

REPOSITORIES: GEO

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Project description:Infection with Chlamydia pneumoniae, a human respiratory pathogen, has been associated with various chronic diseases such as asthma, coronary heart disease and importantly atherosclerosis. Possibly because the pathogen can exist in a persistent form. TNF-a has been reported to induce chlamydial persitence in epithelial cell lines, however the mechanism of TNF-a-induced persistence has not been reported. Moreover, C. pneumoniae persistently infect human dendritic cells (DCs) and activate DCs to produce cytokines including TNF-a. Induction of chlamydial persistence by other cytokines such as IFN-g is known to be due to indoleamine 2,3-dioxygenase (IDO) activity. The present study therefore, investigated whether C. pneumoniae infection can induce IDO activity in dendritic cells, and whether the restriction of chlamydial growth in the DCs by TNF-a is IDO-dependent. Our data indicate that infection of DCs with C. pneumoniae resulted in the induction of IDO expression. Reporting on our use of anti-TNF-a antibody adalimumab and varying concentrations of TNF-a, we further demonstrate that IDO induction following infection of DCs with C. pneumoniae is TNF-a-dependent. The anti-chlamydial activity induced by TNF-a and the expression of chlamydial 16S rRNA gene, euo, groEL1, ftsk and tal genes was correlated with the induction of IDO. Addition of excess amounts of tryptophan to the DC cultures resulted in abrogation of the TNF-a-mediated chlamydial growth restriction. These findings suggest that infection of DCs by C. pneumoniae induces production of functional IDO, which subsequently causes depletion of tryptophan. This may represent a potential mechanism for DCs to restrict bacterial growth in chlamydial infections. Experiment Overall Design: Human monocyte-derived DCs from five heathy donors were infected with C. pneumoniae at multiplicity of infection of 5 for 72 h. Mock-infected (uninfected) DCs were used as a control for the infection. Total RNA from 72 h chlamydiae-infected or mock-infected DCs was isolated with RNeasy Mini Kit (Qiagen, Hilden, Germany) and DNA contamination was removed with RQ1 DNase (Promega). Total RNA from all donors was pooled and the samples were processed and analyzed at the array facility of Helmholtz center for infection biology, Braunschweig. The integrity of the RNA was verified on the Agilent Bioanalyzer system. We used the Affymetrix Gene Chip Human Genome U133 2.0 Plus. Data were processed using Affymetrix software and signal intensity measured was normalized by the Affymetrix MAS5 algorithm. Data were filtered to exclude genes at background levels (non-expressors, signal intensity at 100).

Project description:Myeloid dendritic cells (DC) and macrophages play an important role in pathogen sensing and antimicrobial defense. Recently we demonstrated that infection of human DC with intracellular bacterium Listeria monocytogenes (L.monocytogenes) leads to the induction of the immunoinhibitory enzyme indoleamine 2,3-dioxygenase (Popov et al., J Clin Invest, 2006), while in the previous studies L.monocytogenes infection was associated with a rather stimulatory DC phenotype. To clarify this discrepancy we performed comparative microarray analysis of immature mo-DC (immDC), mature stimulatory mo-DC (matDC) and mature inhibitory DC either stimulated with prostaglandin E2 (PGE2-DC) or infected with L.monocytogenes (infDC). Studying infection of human myeloid DC with Listeria monocytogenes, we found out, that infected DC are modified by the pathogen to express multiple inhibitory molecules, including indoleamine 2,3-dioxygenase (IDO), cyclooxygenase-2, interleukin 10 and CD25, which acts on DC as IL-2 scavenger. All these inhibitory molecules, expressed on regulatory DC (DCreg), are strictly TNF-dependent and are in concert suppressing T-cell responses. Moreover, only DCreg can efficiently control the number of intracellular listeria, mostly by IDO-mediated mechanisms and by other factors, remaining to be identified. Analyzing publicly acessible data of transcriptional changes in DC and macrophages, infected by various pathogens and parasites (GEO, GSE360), we noticed that infection of these cells with Mycobacterium tuberculosis causes transcriptional response, comparable with the one caused by listeria in human DC. In fact, granuloma in tuberculosis and listeriosis in vivo are enriched for myeloid DC and macrophages characterized by regulatory phenotype. In summary, regulatory myeloid DC and macrophages may play a dual role during life-threatening granulomatous infections, such as tuberculosis: on one hand, regulatory myeloid cells promote pathogen containment by efficiently killing intracellular bacteria, on the other hand these cells inhibit granuloma-associated T cells and thereby might be involved in the retention of TNF-controlled granuloma integrity protecting the host from granuloma break-down and pathogen dissemination. Experiment Overall Design: Transcriptional profiles of immature mo-DC (immDC, n=3), mature stimulatory mo-DC (matDC, n=3) and mature inhibitory mo-DC either stimulated with prostaglandin E2 (PGE2-DC, n=3) or infected with L.monocytogenes (infDC, n=3) were compared on Affymetrix HG-U133A platform. All samples represent biological replicates and were processed separately throughout the experiment.

Project description:Myeloid dendritic cells (DC) and macrophages play an important role in pathogen sensing and antimicrobial defense. Recently we demonstrated that infection of human DC with intracellular bacterium Listeria monocytogenes (L.monocytogenes) leads to the induction of the immunoinhibitory enzyme indoleamine 2,3-dioxygenase (Popov et al., J Clin Invest, 2006), while in the previous studies L.monocytogenes infection was associated with a rather stimulatory DC phenotype. To clarify this discrepancy we performed comparative microarray analysis of immature mo-DC (immDC), mature stimulatory mo-DC (matDC) and mature inhibitory DC either stimulated with prostaglandin E2 (PGE2-DC) or infected with L.monocytogenes (infDC). Studying infection of human myeloid DC with Listeria monocytogenes, we found out, that infected DC are modified by the pathogen to express multiple inhibitory molecules, including indoleamine 2,3-dioxygenase (IDO), cyclooxygenase-2, interleukin 10 and CD25, which acts on DC as IL-2 scavenger. All these inhibitory molecules, expressed on regulatory DC (DCreg), are strictly TNF-dependent and are in concert suppressing T-cell responses. Moreover, only DCreg can efficiently control the number of intracellular listeria, mostly by IDO-mediated mechanisms and by other factors, remaining to be identified. Analyzing publicly acessible data of transcriptional changes in DC and macrophages, infected by various pathogens and parasites (GEO, GSE360), we noticed that infection of these cells with Mycobacterium tuberculosis causes transcriptional response, comparable with the one caused by listeria in human DC. In fact, granuloma in tuberculosis and listeriosis in vivo are enriched for myeloid DC and macrophages characterized by regulatory phenotype. In summary, regulatory myeloid DC and macrophages may play a dual role during life-threatening granulomatous infections, such as tuberculosis: on one hand, regulatory myeloid cells promote pathogen containment by efficiently killing intracellular bacteria, on the other hand these cells inhibit granuloma-associated T cells and thereby might be involved in the retention of TNF-controlled granuloma integrity protecting the host from granuloma break-down and pathogen dissemination. Keywords: Cell type comparison, response to infection

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Inhibition of Chlamydia pneumoniae Replication in Human Dendritic cells by TNF-alpha-Induced Indoleamine 2,3-Dioxygenase

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