Abstract 12438: Vascular Hyperglycemic Memory is Abolished by in-vivo Silencing of the Mitochondrial Adaptor p66Shc
Introduction: Upregulation of the adaptor p66Shc determines increased ROS production, mitochondrial swelling and cellular death. Expression of p66Shc is increased in human and experimental diabetes and triggers endothelial dysfunction (ED). However, it is not known whether p66Shc maintains vascular damage despite glucose normalization, and, hence, contributes to the “hyperglycaemic memory”. Such phenomenon is emerging as a putative major determinant of diabetic cardiovascular complications.
Hypothesis: To assess the role of p66Shc in perpetuating hyperglycemia-induced ED despite glycemic control.
Methods: Diabetes was induced in wild-type 129sv male mice (4-6 months old) by a single i.p dose of streptozocin. Mice were divided into 5 experimental groups: 1) controls; 2) diabetics; 3) diabetics treated with insulin, 4) diabetics concomitantly receiving insulin and p66Shc siRNA or 5) scrambled siRNA (n=6-7/group). Slow release insulin implants were placed subcutaneously after 3 weeks of diabetes for the following 3 weeks. Silencing of p66Shc was obtained by i.v administration of selective siRNA every 5 days. Animals were euthanized and p66Shc protein expression levels were assessed in aortic lysates. Western blot results are shown as percentages of control. Endothelium-dependent relaxations to acetylcholine (Ach, 10-9-10-6 mol/L) were determined by organ chamber experiments.
Results: In vivo delivery of p66Shc siRNA abolished p66Shc expression compared to scrambled siRNA (24±1 vs 93±4%, p<0.01). Endothelium-dependent relaxations were significantly impaired in diabetic mice compared to control (max relaxations: 40±1 vs 80±8%, p<0.01). Glycemic control with insulin did not improve Ach relaxations (47±1 vs 40±1% for groups 3 and 2, respectively , p=NS) whereas superoxide dismutase pretreatment (150 U/mL) abolished ED, indicating ROS-induced hyperglycemic memory (74±3%). Interestingly, silencing of p66Shc in mice receiving insulin restored ED (70±2 vs 44±1% in group 5, p<0.01).
Conclusions: Our findings suggest that p66Shc maintains ROS-induced ED even after glucose normalization. Targeting molecular mechanisms underlying “hyperglycaemic memory” may represent the best option to reduce diabetes cardiovascular health burden.
- © 2011 by American Heart Association, Inc.