P6289How and where aneurysms initiate: a study on angiotensin-II infused ApoE−/− mice
European Heart Journal
blockade on lipoprotein-induced oxidative stress and endothelial function and of AT1a/AT1b double knockout on oxidative stress is not well understood. Methods: We studied the impact of native and oxidized LDL (nLDL, oxLDL) on Ang II receptor expression and formation of reactive oxygen species in primary cultures of human umbilical arterial endothelial cells (HUAEC). Results: Native and oxLDL induced after 1 h AT1 (100 μg/mL, nLDL: 3.3-fold, oxLDL: 3.7-fold) and AT2 (100 μg/mL, nLDL: 1.8-fold,
... LDL: 2.8-fold) receptor mRNA expression in HUAEC. Increased AT1 and AT2 mRNA and protein expression could be observed after 3 for up to 24 h. Both lipoproteins increased intracellular AT1 receptor immunofluorescence in HUAEC. Native LDL and oxLDL activated MEK/ERK and p38 MAPK pathways in HUAEC. OxLDL induced oxLDL receptor LOX-1 expression in HUAEC (1.7-fold, RT-PCR, Western blot). Induction of both Ang II receptors by oxLDL was reduced by AT1 receptor antagonist candesartan. OxLDL induced in contrast to native LDL superoxide anion formation in HUAEC (1.7-fold vs. control, chemiluminescence). AT1 receptor blockade prevented lipoprotein-induced oxidative stress in HUAEC like SOD. AT1 blockade prevented impaired endothelial function (increase of log EC50 values to -6.696±0.093, P=0.897 vs. con and impaired max. relaxation by oxLDL in phenylephrine-preconstricted vessels). In aortic rings of wild-type mice, oxLDLinduced vascular superoxide anion formation was reduced by AT1 blockade. Deletion of AT1 receptor subtypes 1a and 1b in AT1a/AT1b double knockout mice resulted in the aorta in downregulation of protein expression of LOX-1 and Nox subunits Nox2, p47phox and p22phox to 60-70%, compared with wild-type mice. In conclusion, augmented vascular oxidative stress and endothelial dysfunction in response to lipoproteins involves induction of the AT1 receptor. Double knockout of AT1 receptors reduce LOX-1 and NADPH oxidase expression. Conclusion: Our data suggest an interaction between oxidized LDL, angiotensin II and oxidative stress after AT1 blockade and AT1a/AT1b double knockout.