Background: The anti-chlamydial antibiotic, azithromycin, may improve outcome in patients who survive an acute coronary syndrome. The mechanisms are, however, poorly understood. The aims of this study were to define any relationship between Chlamydia pneumoniae seropositivity and levels of specific markers of endothelial activation (soluble cell adhesion molecules) and more general markers of inflammation (C-reactive protein [CRP] and interleukin-6 [IL-6]) and to assess whether azithromycin had any effect on such markers.
Methods: Patients who survived an acute coronary syndrome were randomized to receive treatment with azithromycin (n = 72) or placebo (n = 69) for 5 days. Before therapy, C pneumoniae IgA and IgG titers were checked, with serum levels of soluble intercellular adhesion molecule-1 (sICAM-1), soluble vascular cell adhesion molecule-1, soluble E-selectin (sE-selectin), soluble P-selectin, high-sensitivity CRP, and IL-6. They were rechecked 3 months later.
Results: There were no significant correlations between C pneumoniae titers and levels of CRP, IL-6, or soluble cell adhesion molecules. However, azithromycin treatment significantly reduced mean sICAM-1 levels (P =.006). This effect was more marked in patients with elevated titers of C pneumoniae IgA and IgG. Soluble E-selectin levels were also reduced in patients who were seropositive, but no effects were seen on other endothelial or inflammatory markers.
Conclusions: After an acute coronary syndrome, a 5-day course of azithromycin reduces levels of sICAM-1, a marker of endothelial cell activation. Although these data suggest a potentially beneficial role for azithromycin, they should be interpreted with caution.