Pon2^−/−mice have a pro-oxidant, proinflammatory, and dysfunctional endothelium. (A, left) Representative image of cryosectioned aortae form Pon2^−/− and WT mice, stained with dihydroethidium (DHE; red) for O₂⁻ and analyzed by confocal imaging (green, collagen autofluorescence; scale bar, 500 µm). (Right) Quantification of DHE-fluorescence intensities per area of aortic tissue (n = 19 sections of 3 mice each). *P = .0302; Student t test. (B) L-012 chemiluminescence signal of fresh aortic sections quantified over time for ROS formation (representative graph). Linear regression curve fits were calculated and slopes were analyzed for statistically significant differences. **P = .0053. (C) ROS level of aortic cells determined by H₂DCFDA flow cytometry (representative graph). A right shift of the peak indicates higher ROS levels. (D) Primary murine ECs were isolated from lungs, stained with CellRox-DeepRed, and quantified by confocal microscopy (n = 23-33 of 2-3 mice). ***P = .0001; Student t test. (E) mRNA expression of proinflammatory cytokines, chemokines, receptors, and coagulation-regulation factors in ECs isolated from lungs (n = 2-6 assays using 4-12 mice per group and target normalized against Gapdh and Polr2a). *P ≤ .0156; **P ≤ .007; ***P < .0001; Student t test. (F) Lung cells were stained with EC marker lectin and annexin V for quantification of endothelial PS exposure (n = 7-8). *P = .0277; Student t test. (G) Aortic rings of Pon2^−/− and WT mice were precontracted with norepinephrine and endothelium-dependent vasodilation induced by increasing concentrations of acetylcholine was measured (n = 6 rings of 3 mice). **P < .01; ***P < .001; 2-way ANOVA with Bonferroni multiple comparison for individual data points and nonlinear regression (R² = 0.84-0.97) with 95% confidence intervals (dotted lines) showed significant differences between curves.