Chlamydia pneumoniae and Cardiovascular Disease

Induction of tissue factor expression and release as microparticles in ECV304 cell line by Chlamydia pneumoniae infection

The association between Chlamydia pneumoniae (C. pneumoniae) infection and the onset and progression of atherosclerosis has become apparent recently. Moreover, increased expression of tissue factor (TF) as a result of C. pneumoniae infection has been previously demonstrated. We have examined the expression of TF on the surface of endothelial cells and the release of TF-containing cell-derived microparticles, over seven days. Additionally, using cells expressing a procoagulantly active EGFP-TF hybrid protein, we examined the kinetics of TF trafficking on the cells and incorporation into shed microparticles. Finally, in an attempt to associate this with the activation of NFkappaB, we used a luciferase reporter to measure the duration of the activation of this transcription factor. TF-containing microparticles were released within 24h of infection and continued for up to 7 days. Moreover, the initial release of TF containing microparticles was associated with NFkappaB activation and was suppressed on inclusion of an NFkappaB inhibitor, pyrrolidinedithiocarbamate ammonium. Moreover, persistent dissemination of TF-containing microparticles at later stages of infection was associated with the release of the infective C. pneumoniae elementary bodies. The released procoagulant, cellular microparticles are known to be strongly atherogenic and therefore we suggest a mechanism for the involvement of C. pneumoniae in the onset and progression of vascular disease.

Infections and their role in atherosclerotic vascular disease

BACKGROUND

Complications of atherosclerosis are the leading cause of mortality in developed countries, and infections may play a role in the pathogenesis. Numerous studies have addressed this issue in the past decade.

TYPES OF STUDIES REVIEWED

The author examined peer-reviewed studies and reviews on the role of microbes or infections in atherosclerosis, cardiovascular disease and cerebrovascular disease. He included selected articles on epidemiology, pathology, in vitro experiments, animal models and clinical studies.

RESULTS

Cross-sectional and retrospective studies have shown an association between Chlamydia pneumoniae antibodies and cardiovascular disease, but prospective studies have not been as convincing. Studies on the association between cardiovascular disease and periodontal disease or loss of teeth have produced conflicting results. Cytomegalovirus infection is associated mainly with accelerated arteriosclerosis after cardiac transplantation. Infectious agents can induce biological mechanisms important for atherogenesis. Mice and rabbit studies have indicated that C. pneumoniae is capable of initiating or accelerating the progression of atherosclerosis. Limited studies on cytomegalovirus also suggest the ability to induce early changes of atherosclerosis in a rodent model. Preliminary clinical trials of treatment for C. pneumoniae infection suggest a possible short-term benefit, but larger randomized trials for longer periods are in progress.

CONCLUSION AND CLINICAL IMPLICATIONS

Infectious agents may play an important role in atherogenesis, but currently the jury is not in. Further management of cardiovascular disease could change radically if this concept were proven.