Abstract 14488: p66Shc Drives Persistent Oxidative Stress and Inflammation in the Diabetic Heart: Insights for the Progression of Cardiovascular Complications Despite Intensive Glycemic Control
Introduction: Hyperglycemia causes subtle myocardial damage and is associated with an increased risk of cardiac events. Normalization of glucose levels has recently failed to improve cardiovascular outcomes in subjects with diabetes. The mitochondrial adaptor p66Shc, critically involved in reactive oxygen species production, participates to the phenotype of diabetic cardiomyopathy.
Hypothesis: To investigate p66Shc role in maintaining cardiac oxidative stress and inflammation despite glycemic control in diabetic mice.
Methods: Diabetes was induced in 129sv mice (4-6 months) by streptozotocin. Mice were randomized as follows: 1) controls; 2) diabetics; 3) diabetics treated with insulin, 4) diabetics receiving insulin plus p66Shc or 5) scrambled siRNA (n=6-7/group). Insulin implants were placed 3 weeks after diabetes induction for the following 3 weeks. Silencing of p66Shc was obtained by i.v administration every 5 days. Cardiac mitochondria were used for measurement of superoxide anion (O2-) by ESR spectroscopy and swelling assay. Immunoprecipitation was performed to show p66Shc-cytochrome c interaction. NF-kB activity was assessed as p65 nuclear translocation and binding activity. p66Shc epigenetic changes were investigated by chromatin immunoprecipitation (ChIP).
Results: Mitochondrial O2- production and swelling were significantly increased in the diabetic hearts and glycemic control did not revert this phenomenon. These findings squared with persistent p66Shc upregulation and mitochondrial translocation as well as its interaction with cytochorme c. Cardiac expression of pro-inflammatory genes IL-6, TNF-α, MCP-1, and VCAM-1 increased in diabetics and was not affected by normoglycemia restoration. Interestingly, in vivo knockdown of p66Shc, in the context of glucose normalization restored mitochondrial integrity, blunted ROS production, and abolished myocardial inflammation by inhibiting NF-kB. Acetylation of histone 3 binding p66Shc promoter is the mechanism whereby p66Shc transcription continues despite glycemic control.
Conclusions: p66Shc is a key mediator of persistent oxidative stress and inflammation in the diabetic heart.
- © 2012 by American Heart Association, Inc.