Chemokines: the link between inflammation, restenosis and atherosclerosis?

Shear Stress Enhances Chemokine Secretion from Chlamydia pneumoniae-infected Monocytes

Chlamydia pneumoniae is a common respiratory pathogen that is considered a highly likely risk factor for atherosclerosis. C. pneumoniae is disseminated from the lung into systemic circulation via infected monocytes and lodges at the atherosclerotic sites. During transit, C. pneumoniae-infected monocytes in circulation are subjected to shear stress due to blood flow. The effect of mechanical stimuli on infected monocytes is largely understudied in the context of C. pneumoniae infection and inflammation. We hypothesized that fluid shear stress alters the inflammatory response of C. pneumoniae-infected monocytes and contributes to immune cell recruitment to the site of tissue damage. Using an in vitro model of blood flow, we determined that a physiological shear stress of 7.5 dyn/cm² for 1 h on C. pneumoniae-infected monocytes enhances the production of several chemokines, which in turn is correlated with the recruitment of significantly large number of monocytes. Taken together, these results suggest synergistic interaction between mechanical and chemical factors in C. pneumoniae infection and associated inflammation.

Threonine for alanine substitution in the eotaxin (CCL11) gene and the risk of incident myocardial infarction

Recent studies suggest that the chemokine eotaxin may participate in atherosclerosis. Threonine (T) for alanine (A) substitution at amino acid 23 in the eotaxin gene (CCL11) has been associated with risk of developing allergic-inflammatory disorders. However, no genetic-epidemiological data are available on the risk of cardiovascular disease associated with this polymorphism. Using DNA samples collected at baseline in a prospective cohort of 14,916 initially healthy American men, we evaluated the A23T polymorphism among 523 individuals who subsequently developed myocardial infarction (MI) and among 2092 individuals who remained free of reported cardiovascular disease over a mean follow-up period of 13.2 years. The T23 allele was significantly associated with risk of myocardial infarction (odds ratio (OR) in an age and smoking adjusted recessive model of inheritance, 1.86; 95% confidence interval (CI), 1.15-3.01; P = 0.012). This risk effect remained statistically significant in analyses further controlling for body mass index, history of hypertension, the presence of diabetes, and randomized treatment assignment (OR, 1.95; 95% CI, 1.19-3.18; P = 0.008). In this cohort, a T for A substitution at amino acid 23 in the eotaxin gene is associated with increased risk for incident myocardial infarction. If confirmed in other cohorts, these data support the emerging hypothesis that eotaxin participates in atherosclerosis.