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Chlamydia pneumoniae--induced macrophage foam cell formation is mediated by Toll-like receptor 2

Fei Cao1, Antonio Castrillo, Peter Tontonoz

  • 1Department of Molecular Sciences, University of Tennessee Health Science Center, Memphis, TN 38163, USA.

Infection and Immunity
|December 6, 2006
PubMed

Insights

Chlamydia pneumoniae infection promotes foam cell formation in macrophages, a key step in atherosclerosis. This process primarily involves Toll-like receptor 2 (TLR2) and can be modulated by liver X receptor (LXR) activation.

Area of Science:

  • Immunology
  • Cardiovascular Research
  • Microbiology

Background:

  • Macrophage foam cell formation is a critical early event in atherosclerosis.
  • Chlamydia pneumoniae infection is implicated in cardiovascular disease pathogenesis.
  • Toll-like receptors (TLRs) are key mediators of innate immunity and inflammation.

Purpose of the Study:

  • To investigate the role of Toll-like receptor 2 (TLR2) and Toll-like receptor 4 (TLR4) in Chlamydia pneumoniae-induced macrophage foam cell formation.
  • To explore the potential of liver X receptor (LXR) activation in mitigating TLR-mediated atherogenic processes.

Main Methods:

  • Murine macrophage cell lines (RAW 264.7, TLR2(-/-), TLR4-deficient GG2EE) were used.
  • Cells were infected with C. pneumoniae or treated with TLR2 (Pam) and TLR4 (LPS) ligands.
  • Foam cell formation was assessed by Oil Red O staining and cholesteryl ester (CE) content measurement.
  • The effect of LXR agonist GW3965 on CE content was evaluated.

Main Results:

  • C. pneumoniae, Pam, and LPS induced foam cell formation and increased CE content in macrophages co-cultured with LDL.
  • C. pneumoniae-induced foam cell formation was dependent on TLR2, as it was impaired in TLR2(-/-) macrophages but occurred in TLR4-deficient cells.
  • Conversely, LPS induced foam cells via TLR4, while Pam induced them via TLR2.
  • LXR agonist GW3965 significantly reduced CE content in cells treated with C. pneumoniae, Pam, or LPS.

Conclusions:

  • Chlamydia pneumoniae primarily induces macrophage foam cell formation through TLR2 activation.
  • TLR signaling pathways play a significant role in C. pneumoniae-associated atherogenesis.
  • Activation of the LXR signaling pathway presents a potential therapeutic strategy to counteract TLR-mediated atherogenic processes.

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