A combination of secondhand cigarette smoke and Chlamydia pneumoniae accelerates atherosclerosis

Abstract Objective Secondhand smoke (SS) induces chronic infection of endothelial cells by Chlamydia pneumoniae (Cpn) in vitro . We investigated the in vivo effect on atherosclerosis following exposure to SS and infection with Cpn both independently and in combination in ApoE−/− mice. Methods and results Plaques were largest in the combined SS+Cpn-exposed mice with 12–57% greater cross-sectional area compared with all other groups ( P P P P Conclusions The combination of SS exposure and Cpn infection enhanced atherosclerosis more than either variable did independently by activating inflammatory cells and by promoting growth and maturation of lesions via defective phagocytic clearance and accumulation of apoptotic cells.