Abstract 470: Redox Rgulation of SIRTUIN1 in Endothelium-Dependent Vascular Function

• Published in: Arteriosclerosis, thrombosis, and vascular biology Vol. 32; no. suppl_1
• Main Authors: Kim, Cuk-Seong, Jung, Saet-Byel, Hoffman, Timothy A, Narqvi, Asma, Irani, Kaikobad
• Format: Journal Article
• Language: English
• Published: 01.05.2012
• ISSN: 1079-5642; 1524-4636
• DOI: 10.1161/atvb.32.suppl_1.A470

Abstract only Objective: The DNA repair enzyme/reducing protein Apurinic/Apyrmidinic Endonuclease 1/Redox Factor-1 (APE/Ref-1) maintains normal endothelial function, as mice heterozygous for APE1/Ref-1 (+/-) have impaired endothelium-dependent vasorelaxation and are hypertensive. APE1/Ref-1 maintains many redox sensitive transcription factors in their reduced active form. The SIRTUIN1 (SIRT1) protein deacetylase also promotes endothelial nitric oxide (NO) production and endothelium-dependent vasorelaxation. Although SIRT1 activity is subject to redox regulation, whether it is governed by APE1/Ref-1 is not known. The purpose of this study is to determine if APE1/Ref-1 governs the redox state and activity of SIRT1, and whether SIRT1 mediates the effect of APE1/Ref-1 on endothelium-dependent vascular function. Methods and results: In endothelial cells APE1/Ref-1 maintains cysteine (thiol) residues in SIRT1 in the reduced (free) form and is obligatory for endothelial SIRT1 activity. In vitro APE1/Ref-1 increases the free thiol content of SIRT1, targeting functionally critical cysteine residues in the catalytic domain of SIRT1 for reduction, and activates SIRT1. Cysteine residues in the N-terminal redox domain of APE1/Ref-1 are essential for activating SIRT1 and for increasing free thiol content of SIRT1. APE1/Ref-1 protects endothelial SIRT1 from hydrogen peroxide-induced oxidation and inactivation. Moreover, APE1/Ref-1 stimulates lysine deacetylation of nitric oxide synthase, a target of SIRT1 in endothelial cells. When compared to wild-type mice, APE1/Ref-1(+/-) mice have lower free thiol content of SIRT1, and diminished SIRT1 activity in tissues. Overexpression of SIRT1 in aortas of APE1/Ref-1 (+/-) mice restores endothelium-dependent vasorelaxation and vascular bioavailable NO to levels similar to those observed in wild-type mice. Conclusions: APE1/Ref-1 maintains endothelial SIRT1 in the reduced form, and is required for maintaining SIRT1 activity. This relationship between SIRT1 and APE1/Ref-1 is an important mechanism responsible for APE1/Ref-1-stimulated endothelium-dependent vasorelaxation.