title: Chlamydia species infect human vascular endothelial cells and induce procoagulant activity.
abstract: BACKGROUND
  Chlamydia pneumoniae infections have been linked with myocardial infarction, stroke, and the development of atherosclerosis by epidemiologic studies, immunohistochemical studies, and electron microscopic studies. The mechanisms underlying this association are unknown.
  
  
  METHODS
  Using cultured human venous endothelial cells, we investigated whether C pneumoniae, C trachomatis (types H and L2/434/BU) could infect these cells. The ability of infected cells to express procoagulant (tissue factor) activity was also measured using clotting and chromogenic substrate assays. Adhesion of platelets to chlamydia-infected cells was also quantitated.
  
  
  RESULTS
  We found that C pneumoniae, C trachomatis type H, and C trachomatis L2/434/BU could infect cultured human umbilical vein endothelial cells and stimulate a 4-fold increase in expression of tissue factor, which reached a peak 18 hours postinfection. Tissue factor expression was enhanced even in the presence of tetracycline, suggesting that the chlamydial factor responsible for stimulating synthesis of endothelial cell tissue factor was preformed. Platelet adhesion was significantly enhanced when endothelial cells were infected by chlamydia species.
  
  
  CONCLUSIONS
  These in vitro studies suggest possible pathogenic mechanisms that may explain the association of thrombotic events with C pneumoniae infection, including pathologically enhanced production of tissue factor by human endothelial cells and enhanced focal platelet deposition.
authors.affiliation: Division of Infectious Diseases, University of Utah Health Sciences Center, Salt Lake City 84132, USA.
authors.forename: R H
authors.initials: RH
authors.lastname: Fryer
authors.forename: E P
authors.initials: EP
authors.lastname: Schwobe
authors.forename: M L
authors.initials: ML
authors.lastname: Woods
authors.forename: G M
authors.initials: GM
authors.lastname: Rodgers
mesh_terms: D002478:Cells, Cultured; D002692:Chlamydia trachomatis / Q000302:isolation & purification / Q000502:physiology*; D016993:Chlamydophila pneumoniae / Q000302:isolation & purification / Q000502:physiology*; D004730:Endothelium, Vascular / Q000378:metabolism / Q000382:microbiology* / Q000473:pathology; D006801:Humans; D010973:Platelet Adhesiveness; D013925:Thromboplastin / Q000096:biosynthesis*; D013997:Time Factors; D014471:Umbilical Veins / Q000166:cytology
chemical_list: D013925:Thromboplastin