Abstract 11918: Endothelial NO-Synthase-Induced Vascular Oxidative Stress Does Not Impair Endothelial Function and Vascular Remodelling
We aimed to investigate a role of O2•- and ONOO- generated by genetically destabilized eNOS for the development of endothelial dysfunction and neointima formation. Transgenic mice carrying a mutant of eNOS in which cysteine 101 was replaced by alanine (C101A) resulting in decreased eNOS dimer stability have been generated on a C57Bl/6 background using the endothelium-specific tie-2 promoter. By breeding these mice with eNOS knockouts (eNOS-KO), mice that express eNOS-C101A exclusively in the endothelium (C101A-eNOS-Tg/eNOS-KO) were obtained. Unilateral common carotid artery ligation was performed in C57Bl/6, eNOS-KO, and C101A-eNOS-Tg/eNOS-KO to study a role of eNOS dimer stability for vascular lesion formation. Western blot analysis revealed eNOS expression in aorta (37±8%), skeletal muscle (45±5%) and myocardium (17±5%) of C101A-eNOS-Tg/eNOS-KO (n=8-10, p<0.05, vs C57Bl/6). Destabilization of eNOS was confirmed on native gel by reduced eNOS dimer/monomer ratio in C101A-eNOS-Tg/eNOS-KO. C101A-eNOS-Tg/eNOS-KO showed 2.3-3.7-fold increase in O2•- and ONOO- formation in the aorta and the myocardium, which was blunted by NOS-inhibitor L-NAME (P<0.05, n=6-8). Surprisingly, endothelial expression of C101A-eNOS almost completely restored aortic endothelium-dependent relaxation. Experiments with L-NAME, soluble guanylyl cyclase inhibitor ODQ, PEG-catalase and NO-scavenger Fe(DETC)2 indicated that endothelium-dependent relaxation in eNOS-KO/eNOS-C101A-Tg is NO-mediated. Neointima formation, media thickening and luminal narrowing were observed in the ligated arteries of all studied genotypes (n=4-7, P<0.05). Neointimal hyperplasia was greatly accelerated in eNOS-KO, but not in C101A-eNOS-Tg/eNOS-KO despite significantly increased vascular oxidative stress. These data indicate that increased vascular O2•- and ONOO- generated by C101A-eNOS did not induce endothelial dysfunction and had negligible effect on neointima formation indicating that the loss of endothelial NO production seems to be more important for vascular remodelling then vascular oxidative stress. This finding might contribute to explain the lack of effect of antioxidants observed in large clinical trials.
- © 2012 by American Heart Association, Inc.