Abstract 5037: Phosphorylation of eNOS Corrects Diabetic Vascular Dysfunction and Improves Outcome to Stroke
Background: While diabetes is associated with diminished vascular NO levels, the precise mechanisms of diabetic endothelial dysfunction are not known. We hypothesized that deficient eNOS S1179 phosphorylation plays a key role in diabetic vascular abnormalities, and that increasing S1179 phosphorylation may improve endothelial function. To test this hypothesis, we created eNOS knock-in mice that carry a S1179D mutation in the eNOS gene, resulting in the generation of a phosphomimetic form of eNOS with increased enzymatic activity and NO generation. We bred these animals to db/db mice to obtain S1179D-db/db mice to test whether modulation of the S1179 phosphorylation site could overcome diabetic vascular dysfunction, and whether this could affect stroke size in vivo.
Experimental Procedures: Adult male mice were anesthetized by 30 % oxygen, 70 % nitrous oxide, and 1.5 % isoflurane. Body temperature was maintained at 36–37°C. Vessel reactivity studies were performed on isolated pressurized carotid arteries. For stroke studies we used the middle cerebral artery occlusion with subsequent reperfusion by filament with Laser Doppler cortical blood flow monitoring. Mice were examined for neurologic deficits 24 hours after stroke. Infarct sizes were determined by the indirect method by 2,3,5-triphenyltetrazolium chloride staining. Statistical analysis was performed with t-test.
Results: Db/db mice showed normal levels of total eNOS, while S1179 phospho-eNOS was diminished. Db/db mice are hypertensive compared with wild-type (WT) mice (116±4 vs 93±3 mm Hg, mean± SEM). The eNOS S1179D mutation normalizes the blood pressure of db/db mice (92±5 mmHg). Carotid artery vasodilation to ACh was impaired in db/db mice (EC50 43.4±6.1 nM) compared with WT mice (16.3±2.9 nM) and S1179D-db/db mice (26.6±4.2 nM). Db/db mice show a larger stroke (100±7 mm3) than do WT (65±7 mm3) and S1179D-db/db mice (80±4 mm3, P<0.05). This was associated with a functional improvement in the neurologic deficit.
Conclusion: Our results establish eNOS phosphorylation as an important cause of vascular dysfunction in db/db mice, and suggest eNOS phosphorylation as a novel target for the treatment and prevention of diabetic vascular disease and stroke.
This research has received full or partial funding support from the American Heart Association, National Center.