Supra-additive expression of interleukin-6, interleukin-8 and basic fibroblast growth factor in vascular smooth muscle cells following coinfection with Chlamydia pneumoniae and cytomegalovirus as a novel link between infection and atherosclerosis

BACKGROUND: Chlamydia pneumoniae and human cytomegalovirus (HCMV) may be involved in the pathogenesis of atherosclerosis. Prospective studies indicate an increased risk for cardiovascular events in patients with evidence of multiple infections. OBJECTIVE: To determine whether there is a synergistic effect of coinfection with C pneumoniae and HCMV on expression of selected growth factors and cytokines. METHODS: The production of interleukin (IL)-6, IL-8, basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF), and 'regulated on activation normal T-cell expressed and secreted' (RANTES) was measured in coinfected aortic smooth muscle cells (AoSMC). RESULTS: Using reverse transcription polymerase chain reaction and immunoassays, it was demonstrated that the expression of IL-6, IL-8, RANTES and bFGF was stimulated in a dose-and time-dependent fashion in C pneumoniae and also in HCMV-infected cultures. In contrast, the expression of PDGF-AA was only stimulated following HCMV infection. Coinfection with C pneumoniae and HCMV resulted in a supra-additive stimulation of IL-6 (30% increased expression, P <= 0.05) at 48 h, IL-8 (137% increased expression, P <= 0.001) at 24 h and bFGF (209% increased expression, P <= 0.01) at 48 h following infection. CONCLUSIONS: The findings of the present study show that C pneumoniae and HCMV are able to act in synergy in coinfected AoSMC. The supra-additive induction of AoSMC growth factors and cytokines indicates a novel molecular link between infection and vascular disease development.