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BioMed Research International
Volume 2014, Article ID 902842, 13 pages
http://dx.doi.org/10.1155/2014/902842
Research Article

Oxidative Stress Induces Endothelial Cell Senescence via Downregulation of Sirt6

1Department of Ophthalmology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
2Department of Ophthalmology and Visual Sciences, The University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555, USA
3Center for Biomedical Engineering, The University of Texas Medical Branch, Galveston, TX, USA
4Internal Medicine, Division of Endocrinology and Stark Diabetes Center, The University of Texas Medical Branch, Galveston, TX, USA
5Neuroscience and Cell Biology, The University of Texas Medical Branch, Galveston, TX, USA

Received 15 June 2014; Accepted 13 July 2014; Published 5 August 2014

Academic Editor: Mohamed Al-Shabrawey

Copyright © 2014 Rong Liu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Accumulating evidence has shown that diabetes accelerates aging and endothelial cell senescence is involved in the pathogenesis of diabetic vascular complications, including diabetic retinopathy. Oxidative stress is recognized as a key factor in the induction of endothelial senescence and diabetic retinopathy. However, specific mechanisms involved in oxidative stress-induced endothelial senescence have not been elucidated. We hypothesized that Sirt6, which is a nuclear, chromatin-bound protein critically involved in many pathophysiologic processes such as aging and inflammation, may have a role in oxidative stress-induced vascular cell senescence. Measurement of Sirt6 expression in human endothelial cells revealed that H2O2 treatment significantly reduced Sirt6 protein. The loss of Sirt6 was associated with an induction of a senescence phenotype in endothelial cells, including decreased cell growth, proliferation and angiogenic ability, and increased expression of senescence-associated -galactosidase activity. Additionally, H2O2 treatment reduced eNOS expression, enhanced p21 expression, and dephosphorylated (activated) retinoblastoma (Rb) protein. All of these alternations were attenuated by overexpression of Sirt6, while partial knockdown of Sirt6 expression by siRNA mimicked the effect of H2O2. In conclusion, these results suggest that Sirt6 is a critical regulator of endothelial senescence and oxidative stress-induced downregulation of Sirt6 is likely involved in the pathogenesis of diabetic retinopathy.