Abstract 14020: Effect of Endothelial Specific Overexpression of a Destabilized Endothelial Nitric Oxide Synthase Variant on Blood Pressure and Vascular Endothelial Function
Essential hypertension is associated with endothelial dysfunction and reactive oxygen species (ROS) are considered to play a role here. To investigate whether dysfunctional vascular eNOS might contribute to the regulation of blood pressure we overexpressed two different eNOS variants by the endothelial specific tie-2 promoter. Hence wildtype eNOS (eNOS-tg) or respectively a destabilized eNOS (C101A-eNOS-tg) were introduced into the vasculature of C57BL/6 mice. Destabilization of eNOS was induced via replacement of a cysteine residue by alanine resulting in impaired eNOS dimer stability, increased superoxide and decreased NO biavailability in stably transfected HEK cells. Western blot analysis e.g. in aortic tissue proved the vascular specific overexpression of eNOS in C101A-eNOS-tg (149.7±8%, n=8, p<0.05) and eNOS-tg (228.7±15%, n=6, p<0.05) compared to transgene negative littermates. Superoxide levels were increased in C101A-eNOS-tg (214.1±30%, n=5, p<0.05) but not in eNOS-tg (89.4±8%, n=6; both vs. controls) and this elevation was blunted by incubation with L-nitroarginine suggesting destabilized eNOS to be a source of ROS. Likewise peroxynitrite levels were increased in C101A-eNOS-tg (147.5±8%, n=7, p<0.05) but unchanged in eNOS-tg (103.1±12%, n=5). Protein kinase G activity was evaluated by VASP phosphorylation at Ser239 showing no difference in both strains vs. controls indicating a normal NO-cGMP pathway activation. Organ bath experiments revealed normal aortic reactivity to acetylcholine, phenylephrine and NO-donor SNAP in both strains vs. controls (n=5-7). As expected systolic blood pressure measured in awake mice by tail cuff method was significantly decreased in eNOS-tg (105.0±2mmHg, n=8, p<0.05). In striking contrast blood pressure was exactly the same in C101A-eNOS-tg (118.9±1mmHg, n=8) compared to controls (119.1±3mmHg, n=6) although dimer destabilization in C101A-eNOS-tg did reduce but not impair NO formation. These data suggest that a decrease of eNOS dimer stability associated with increased vascular oxidative stress might directly contribute to the regulation of blood pressure and the pathophysiology of essential hypertension.
- © 2012 by American Heart Association, Inc.