Abstract 178: Cytosolic Phospholipase A2a in Brain Subfornical Organ is Critical for Angiotensin II-induced ER and Oxidative Stress and Hypertension
Angiotensin (Ang) II activates group IV cytosolic phospholipase A2α (cPLA2α) and releases arachidonic acid (AA) that is metabolized into pro-and antihypertensive eicosanoids. Ang II is also known to increase blood pressure via enhanced ER and oxidative stress in brain subfornical organ (SFO). These observations and our recent finding that Ang II-induced hypertension and associated cardiovascular dysfunction is ameliorated in cPLA2α knockout mice (cPLA2α-/-) led us to investigate the contribution of SFO cPLA2α in Ang II-induced ER and oxidative stress and hypertension. Ang II infusion (700ng/kg/min, s.c.) for 14 days increased systolic blood pressure (SBP) measured by tail cuff, in wild type (cPLA2α+/+) but not cPLA2α-/- mice (122 ± 2 to 177 ± 2 mmHg vs. 119 ± 4 to 125 ±1 mmHg, respectively, P<0.05). Ang II increased cPLA2 activity, determined by immunohistochemistry using phospho-Ser505 antibody, in SFO of cPLA2α+/+ but not cPLA2α-/- mice. Ang II also increased in SFO of cPLA2α+/+ mice reactive oxygen species (ROS) production measured by dihydroethidium staining (5.09 ± 0.31 AU to 8.99 ± 0.33 AU, P<0.05), and expression of ER stress markers measured by RT-PCR (AU) GRP78 and CHOP (1.00 vehicle vs. 1.31 ± 0.09 and 1.79 ± 0.17 Ang II, respectively, P<0.05), but not in cPLA2α-/- mice. Transduction in cPLA2α-/- mice of SFO with adenovirus (Ad) (1x 1012 pfu/0.5 μL) expressing Ad-enhanced fluorescence protein (ECFP) cPLA2α DNA but not control Ad-green fluorescence protein (GFP) DNA, restored the effect of Ang II to increase SBP and ROS production (121 ± 3.45 to 173 ± 2.54 mmHg and 4.40 ± 0.31 to 7.66 ± 0.47 AU with Ad-ECFP cPLA2α DNA vs. 121 ± 1 to 125 ± 4.07 mmHg and 4.04 ± 0.35 to 4.56 ± 0.19 AU with Ad-GFP, respectively, P<0.05). In contrast, in cPLA2α+/+ mice transduction of SFO with Ad-cPLA2α shRNA but not its control Ad-shRNA inhibited cPLA2 expression and its activity, and prevented Ang II to increase SBP (124 ± 4.03 mmHg Ad-cPLA2α shRNA vs. 170 ± 5.32 mmHg Ad-control shRNA, P<0.05). These observations and our finding that the inhibitor of AA metabolism, 5, 8, 11, 14-eicosatetraynoic acid, prevents Ang II-induced hypertension suggest that AA released by cPLA2α via one or more of its metabolites increases ER and oxidative stress in SFO that promotes development of hypertension.
- © 2013 by American Heart Association, Inc.