C.pneumoniae infection increases NADPH oxidase activity in vascular smooth muscle cells

Abstract

Up‐regulation of NADPH oxidases, leading to increased reactive oxygen species (ROS) formation and oxidative stress is a key feature of atherogenesis. Chlamydia pneumoniae has been detected in human atheromas including vascular smooth muscle cells (VSMCs), suggesting a link between the bacteria and atherosclerosis. We examined whether C.pneumoniae induces NADPH oxidase activity in VSMCs. The mouse VSMC cell line, MOVAS, was infected with C.pneumoniae (104‐106 inclusion forming units) and superoxide production (L‐012 chemiluminescence), expression of NADPH oxidase subunit p47phox (immunoblotting), and C.pneumoniae inclusion counts (immunostaining) was assessed. C.pneumoniae caused a dose‐ and time‐dependent increase in superoxide production over 72 hours (n=6, p<0.001). This response was significantly reduced by superoxide scavengers SOD, PEG SOD and tempol (p<0.001, n=6), as well as the NADPH oxidase inhibitor, apocynin (p<0.05, n=6). In preliminary studies (n=2), infection appeared to have no effect on expression of p47phox, suggesting it is not essential for C.pneumoniae‐induced superoxide production. PEG SOD, SOD and the hydrogen peroxide scavenger, catalase, reduced Chlamydia inclusion counts in VSMCs (by 19%, 25%, and 35% respectively). These data suggest that C.pneumoniae increases NADPH oxidase activity in VSMCs and that ROS may promote bacterial growth in these cells. (NHMRC 436825)