Related Experiment Videos
A Chlamydia pneumoniae component that induces macrophage foam cell formation is chlamydial lipopolysaccharide
1Department of Medical Microbiology and Immunology, University of Wisconsin Medical School, Madison, Wisconsin 53706, USA.
Insights
Chlamydia pneumoniae infection may contribute to atherosclerosis. The study found that chlamydial lipopolysaccharide (cLPS) directly induces macrophage foam cell formation, a key step in atheroma development.
Area of Science:
- Microbiology
- Immunology
- Cardiovascular Disease
Background:
- Chlamydia pneumoniae infection is linked to atherosclerosis.
- The exact role of C. pneumoniae in atherogenesis remains unclear.
- Macrophage foam cell formation is a critical early event in atherosclerosis.
Purpose of the Study:
- To investigate the role of C. pneumoniae in macrophage foam cell formation.
- To identify specific components of C. pneumoniae involved in this process.
- To explore the mechanism by which C. pneumoniae contributes to atherogenesis.
Main Methods:
- Utilized the murine macrophage cell line RAW-264.7.
- Assessed cholesteryl ester accumulation in C. pneumoniae-infected macrophages.
- Examined the effect of modified C. pneumoniae and purified chlamydial lipopolysaccharide (cLPS).
- Investigated the role of LPS antagonist lipid X.
Main Results:
- C. pneumoniae-infected RAW cells accumulated cholesteryl esters when exposed to low-density lipoprotein.
- Treatment of C. pneumoniae with periodate, but not heat, reduced cholesteryl ester accumulation, implicating cLPS.
- Purified cLPS alone induced cholesteryl ester accumulation and foam cell formation.
- Lipid X inhibited both C. pneumoniae and cLPS-induced lipid uptake.
Conclusions:
- Chlamydial lipopolysaccharide (cLPS) is a key component of C. pneumoniae that induces macrophage foam cell formation.
- Chronic exposure to cLPS may lead to cholesterol accumulation in macrophages, contributing to atheroma development.
- These findings suggest a direct causal link between C. pneumoniae infection and atherogenesis via cLPS-mediated mechanisms.
Abstract:
Chlamydia pneumoniae infection is associated with atherosclerotic heart and vessel disease, but a causal relationship between this pathogen and the disease process has not been established. Recently, it was reported that C. pneumoniae induces human macrophage foam cell formation, a key event in early atheroma development, suggesting a role for the organism in atherogenesis. This study further examines C. pneumoniae-induced foam cell formation in the murine macrophage cell line RAW-264.7. Infected RAW cells accumulated cholesteryl esters when cultured in the presence of low-density lipoprotein in a manner similar to that described for human macrophages. Exposure of C. pneumoniae elementary bodies to periodate, but not elevated temperatures, inhibited cholesteryl ester accumulation, suggesting a role for chlamydial lipopolysaccharide (cLPS) in macrophage foam cell formation. Purified cLPS was found to be sufficient to induce cholesteryl ester accumulation and foam cell formation. Furthermore, the LPS antagonist lipid X inhibited C. pneumoniae and cLPS-induced lipid uptake. These data indicate that cLPS is a C. pneumoniae component that induces macrophage foam cell formation and suggest that infected macrophages chronically exposed to cLPS may accumulate excess cholesterol to contribute to atheroma development.