Role for the Chlamydial Type III Secretion Apparatus in Host Cytokine Expression
- 1 January 2009
- journal article
- Published by American Society for Microbiology in Infection and Immunity
- Vol. 77 (1), 76-84
- https://doi.org/10.1128/iai.00963-08
Abstract
In many important human pathogens, such asShigellaandSalmonellaspp., the bacterial type III secretion (T3S) apparatus is required to initiate inflammation via activation of caspase-1- or NF-κB-dependent genes. Using an ex vivo infection model, the goal of the present study was to determine whether the chlamydial T3S apparatus also modulates the host inflammatory response. Infections of mouse peritoneal macrophages were performed withChlamydia muridarum, and the expression of inflammatory cytokines was monitored by quantitative reverse transcription-PCR and enzyme-linked immunosorbent assay. Since there is no current genetic system forChlamydiaspp., blockade of T3S was accomplished pharmacologically using a T3S inhibitor called INP0007. It has been previously shown that INP0007 also blocks chlamydial growth in vitro and that the addition of exogenous iron completely reverses this deficit. The addition of iron to INP0007-treatedC. muridarum-infected macrophages not only restored chlamydial growth deficit caused by INP0007 but also led to a multi-inclusion phenotype. Overall, T3S inhibition led to decreased interleukin-6 (IL-6), IL-1β, and CXCL10, whereas the tumor necrosis factor alpha levels were unchanged. Rescue of chlamydial growth by addition of iron sulfate did not restore cytokine production, implying that the decreased expression of many cytokines during infection was dependent on T3S and not solely on growth. In addition, the observation that the greatest effects of INP0007 were seen at late time points during infection suggests that a temporally regulated T3S effector protein(s) may be triggering the host cytokine response.Keywords
This publication has 50 references indexed in Scilit:
- Caspase-1 Activation in Macrophages Infected with Yersinia pestis KIM Requires the Type III Secretion System Effector YopJInfection and Immunity, 2008
- Iron depletion limits intracellular bacterial growth in macrophagesBlood, 2008
- Pseudomonas aeruginosa activates caspase 1 through IpafProceedings of the National Academy of Sciences of the United States of America, 2008
- Caspase-1 Contributes toChlamydia trachomatis-Induced Upper Urogenital Tract Inflammatory Pathologies without Affecting the Course of InfectionInfection and Immunity, 2008
- Immune recognition of Pseudomonas aeruginosa mediated by the IPAF/NLRC4 inflammasomeThe Journal of Experimental Medicine, 2007
- Reversal of the Antichlamydial Activity of Putative Type III Secretion Inhibitors by IronInfection and Immunity, 2007
- Inhibition of Type III Secretion inSalmonella entericaSerovar Typhimurium by Small-Molecule InhibitorsAntimicrobial Agents and Chemotherapy, 2007
- A small-molecule inhibitor of type III secretion inhibits different stages of the infectious cycle of Chlamydia trachomatisProceedings of the National Academy of Sciences of the United States of America, 2006
- Treatment of Chlamydia trachomatis with a small molecule inhibitor of the Yersinia type III secretion system disrupts progression of the chlamydial developmental cycleMolecular Microbiology, 2006
- Recognition of Cytosolic DNA Activates an IRF3-Dependent Innate Immune ResponseImmunity, 2006