Suppression of NoxA1 expression decreases thrombin-induced ROS production. A, Wild-type mouse aortic VSMC were infected with retroviruses encoding either scrambled shRNA or NoxA1 shRNA. NoxA1 protein levels were determined by Western blot analysis using anti-NoxA1 antibody. β-tubulin levels were used as loading controls. B, VSMC expressing scrambled or NoxA1 shRNA were treated without or with thrombin (1 U/mL) after pretreatment with DPI. ROS levels were determined by measuring DCF fluorescence (mean ± SEM, n=4; *P<0.001 vs respective controls; **P<0.01 vs thrombin-treated scrambled shRNA expressing cells). C, ROS levels in the above mentioned VSMC were determined by measuring L012 chemiluminescence (mean ± SEM, n=4; *P<0.001 vs respective controls; **P<0.01 vs thrombin-treated scrambled shRNA expressing cells). D, VSMC expressing scrambled or NoxA1 shRNA were treated with or without thrombin and ROS production was detected by DHE staining.