FP40-5 Cross-Talk between Oxidized LDL, Angiotensin II and Oxidative Stress after AT1 Blockade and AT1a/AT1b double knockout

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: FP40-Renin-Angiotensin-Aldosterone System/Endocrine Hypertension
Monday, June 17, 2013: 10:45 AM-11:15 AM
Presentation Start Time: 11:05 AM
Room 135 (Moscone Center)

Poster Board MON-724
Henning Morawietz*1, Rusan A. Catar2, Claudia Goettsch1, Ashraf Taye1, Anja Hofmann1, Coy Brunssen1, Gregor Muller1, Susann Lehmann1, Undine Schubert1, Barbara Ludwig1, Christian G Ziegler1, Stefan Richard Bornstein1, Alexander Wolfgang Krug3 and Thomas Walther4
1University Hospital Carl Gustav Carus, Dresden, Germany, 2Charite Berlin, 3Brigham and Women's Hospital, Chestnut Hill, MA, 4University of Hull, Hull, United Kingdom
Oxidized low-density-lipoprotein (oxLDL) and angiotensin II (Ang II) can increase formation of reactive oxygen species in endothelial cells. However, the potential cross-talk between both risk factors, the impact of Ang II receptor 1 (AT1) receptor blockade on lipoprotein-induced oxidative stress and endothelial function and of AT1a/AT1b double knockout on oxidative stress is currently not well understood. First, 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). Native and oxLDL induced already after 1 h AT1 (100 µg/mL, nLDL: 3.3-fold, oxLDL: 3.7-fold) and AT2 (100 µg/mL, nLDL: 1.8-fold, oxLDL: 2.8-fold) receptor mRNA expression in HUAEC. Increased AT1 and AT2 mRNA and protein expression could also be observed after 3 for up to 24 h. Both lipoproteins increased intracellular AT1 receptor immunofluorescence in HUAEC. Next, we studied the impact of lipoproteins on signal transduction. Native LDL and oxLDL activated MEK/ERK and p38 MAPK pathways (ELISA, Western blot) in HUAEC. OxLDL induced oxLDL receptor LOX-1 expression in HUAEC (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 (chemiluminescence). AT1 receptor blockade prevented lipoprotein-induced oxidative stress in HUAEC like SOD. Furthermore, AT1 blockade prevented impaired endothelial function (increase of log EC50 values and impaired max. relaxation by oxLDL in phenylephrine-preconstricted vessels). In aortic rings of wild-type mice, oxLDL-induced vascular superoxide anion formation was reduced by AT1 blockade. Finally, deletion of AT1 receptor subtypes 1a and 1b in AT1a/AT1b double knockout mice resulted in the aorta in significant downregulation of protein expression of LOX-1, Nox subunits Nox2, p47phox and p22phox, 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. Our data suggest a cross-talk between oxidized LDL, angiotensin II and oxidative stress after AT1 blockade and AT1a/AT1b double knockout.

Nothing to Disclose: HM, RAC, CG, AT, AH, CB, GM, SL, US, BL, CGZ, SRB, AWK, TW

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