Pulmonary arterial oxidative stress is mediated by gp91phox NADPH oxidase. (a and b) Microtopography revealed significantly increased superoxide levels in PAs from triple-embolised mice as compared to PAs from control mice or after IVC ligation. IHC (c) and qPCR (d) revealed a significantly increased NOX2/gp91phox expression in PAs after pulmonary embolism as compared to PAs from control mice or after IVC ligation. (e) qPCR of PAI-1 mRNA in PAs. Ctrl: control mice; AF: autofluorescence; DHE: dihydroethidium (a); gp91phox: antibody against gp91phox NADPH oxidase; DAPI: 4′,6-diamidin-2-phenylindol; IVCL: IVC ligated mice; APE: mice with recurrent acute PE. 5 animals per group; data are presented as mean and SEM. 1-way ANOVA and Bonferroni’s multiple comparison test.