Oxidized LDL promotes the mitogenic actions of Chlamydia pneumoniae in vascular smooth muscle cells

  • Chahine M
  • Deniset J
  • Dibrov E
 et al. 
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AIMS: The atherogenic actions of Chlamydia pneumoniae (C. pneumoniae), a common respiratory pathogen, are dependent upon a high-cholesterol environment in vivo. It is possible that oxidized low-density lipoprotein (oxLDL) is responsible for promoting the atherogenic effects of C. pneumoniae through a stimulation of cell proliferation. This study determined whether oxLDL can enhance the mitogenic action of C. pneumoniae in vascular smooth muscle cells (VSMCs) and the involvement of mitogen-activated protein kinase (MAPK) pathways and heat shock protein 60 (HSP60) in these mechanisms.

METHODS AND RESULTS: Primary rabbit VSMCs were treated with live C. pneumoniae, heat-inactivated C. pneumoniae or infection medium, and subsequently incubated for up to 48 h in the presence or absence of oxLDL. Chlamydia pneumoniae infection alone stimulated cell proliferation and the addition of oxLDL significantly amplified this proliferative effect. This proliferation was accompanied by extracellular signal-regulated kinase-1 and -2 (ERK1/2) activation and an up-regulation of HSP60 expression. Changes in proliferation and HSP60 expression were attenuated by the inhibition of ERK1/2.

CONCLUSION: These results indicate a novel role for oxLDL in promoting the mitogenic actions of C. pneumoniae in the vasculature. ERK1/2 is an important factor in the stress-mediated response and HSP60 up-regulation in VSMC. These data provide mechanistic evidence that C. pneumoniae may stimulate atherogenesis.

Author-supplied keywords

  • Atherosclerosis
  • Heat shock protein
  • Infection
  • Mitogen-activated protein kinase
  • Oxidized low-density lipoprotein

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  • Mirna N. Chahine

  • Justin Deniset

  • Elena Dibrov

  • Satoru Hirono

  • David P. Blackwood

  • Jose Alejandro Austria

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