Chlamydia pneumoniae induces tissue factor expression in mouse macrophages via activation of Egr-1 and the MEK-ERK1/2 pathway.
Recent studies have suggested that infection with Chlamydia pneumoniae (C pneumoniae) may contribute to the instability of atherosclerotic plaques and thrombosis and is associated with acute coronary events. Tissue factor (TF), a potent prothrombotic molecule, is expressed by macrophages and other cell types within atherosclerotic lesions and plays an essential role in thrombus formation after plaque rupture. Therefore the effects of C pneumoniae on induction of TF expression in macrophages were investigated. Infection of RAW mouse macrophages with C pneumoniae induced a time-dependent increase in procoagulant activity, expression of TF protein, and TF mRNA. C pneumoniae infection stimulated increased binding of nuclear proteins to the consensus DNA sequence for Egr-1, a key response element within the TF promoter, and increased the expression of Egr-1 protein. Transient transfections of RAW cells with mutated TF promoter constructs showed that the Egr-1 binding region is an important transcriptional regulator of C pneumoniae-induced TF expression. Furthermore, C pneumoniae-stimulated phosphorylation of ERK1/2 and Elk-1 and pharmacological inhibition of mitogen-activated protein kinase activity reduced the expression of TF and Egr-1. Antibody and polymyxin B blocking of the Toll-like receptor 4 (TLR4) partially reduced the C pneumoniae-induced expression of TF and Egr-1. In conclusion, the C pneumoniae-induced increase in TF expression in macrophages is mediated in part by Egr-1, signaling through TLR4, and activation of the MEK-ERK1/2 pathway.
Bea
Florian
F
Department of Pathobiology, University of Washington, Seattle, Wash 98195, USA.
Puolakkainen
Mirja H
MH
McMillen
Timothy
T
Hudson
Francesca N
FN
Mackman
Nigel
N
Kuo
Cho Chou
CC
Campbell
Lee Ann
LA
Rosenfeld
Michael E
ME
D000818:Animals; D001665:Binding Sites / Q000235:genetics; D015153:Blotting, Western; D002460:Cell Line; D016993:Chlamydophila pneumoniae / Q000254:growth & development*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D051766:Early Growth Response Protein 1; D024202:Electrophoretic Mobility Shift Assay; D017874:Immediate-Early Proteins; D020935:MAP Kinase Signaling System; D008264:Macrophages / Q000378:metabolism* / Q000382:microbiology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D010766:Phosphorylation; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013925:Thromboplastin / Q000096:biosynthesis* / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D004268:DNA-Binding Proteins; D051766:Early Growth Response Protein 1; C486109:Egr1 protein, mouse; D017874:Immediate-Early Proteins; D009687:Nuclear Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; D013925:Thromboplastin; D017346:Protein Serine-Threonine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases