Abstract 10075: Mechanisms of Endothelial Dysfunction in Amyloid-β Precursor Protein Transgenic Mice
The amyloid-β precursor protein (APP) is a precursor of amyloid-β, an essential culprit of neurovascular pathology of Alzheimer's disease. Recent evidence suggests that APP may play a role in pathogenesis of atherosclerosis. However, the exact molecular mechanisms underlying the effects of APP on vascular function are not completely understood. In the present study, we used the 5 months old APP transgenic mice (Tg2576 mouse model of Alzheimer's disease) and their wild-type littermates (WT). Vascular reactivity of isolated aortas was studied in-vitro. Levels of tetrahydrobiopterin (BH4) and superoxide anion production were measured in the aorta using HPLC. Western blot analyses of normal wild-type mice aortas with and without endothelium provided evidence that 63% of total APP protein is present in vascular endothelial cells. Protein expression of APP was increased 3.5-fold and endothelium-dependent relaxations to acetylcholine (10-9-10-5M) were significantly impaired in aortas of Tg2576 mice (77±6%; P<0.05 vs. WT: 97±3% for maximal relaxation; n=6). Furthermore, phosphorylation of endothelial nitric oxide synthase (eNOS) at Ser1177 was reduced two-fold in Tg2576 mice aortas (P<0.05; n=6). In contrast, endothelium-independent relaxations to nitric oxide-donor DEA-NONOate were unchanged. HPLC analysis revealed that levels of BH4 were significantly reduced in Tg2576 mice (3.2±0.4 pmol/mg; P<0.05 vs. WT: 6.1±0.8 pmol/mg; n=10) while the oxidative product of BH4, 7,8-dihydrobiopterin, was significantly increased (P<0.05). Furthermore, production of superoxide anion was significantly increased in APP transgenic mice aortas (0.34±0.07 nmol 2-hydroxyethidium/mg; P<0.05 vs. wild-type mice: 0.18±0.02 nmol/mg; n=5). We also detected significantly decreased protein expression of copper- and zinc-containing superoxide dismutase and extracellular superoxide dismutase in Tg2576 mice aortas (P<0.05; n=6). Our results suggest that in Tg2576 mice impairment of endothelial function is caused by increased production of superoxide anion, reduced antioxidant capacity and loss of nitric oxide. We also provide evidence that oxidation of BH4 and subsequent uncoupling of eNOS may contribute to endothelial dysfunction in APP transgenic mice.
- © 2011 by American Heart Association, Inc.