title: Shear stress, SIRT1, and vascular homeostasis.
abstract: Shear stress imposed by blood flow is crucial for maintaining vascular homeostasis. We examined the role of shear stress in regulating SIRT1, an NAD(+)-dependent deacetylase, and its functional relevance in vitro and in vivo. The application of laminar flow increased SIRT1 level and activity, mitochondrial biogenesis, and expression of SIRT1-regulated genes in cultured endothelial cells (ECs). When the effects of different flow patterns were compared in vitro, SIRT1 level was significantly higher in ECs exposed to physiologically relevant pulsatile flow than pathophysiologically relevant oscillatory flow. These results are in concert with the finding that SIRT1 level was higher in the mouse thoracic aorta exposed to atheroprotective flow than in the aortic arch under atheroprone flow. Because laminar shear stress activates AMP-activated protein kinase (AMPK), with subsequent phosphorylation of endothelial nitric oxide synthase (eNOS) at Ser-633 and Ser-1177, we studied the interplay of AMPK and SIRT1 on eNOS. Laminar flow increased SIRT1-eNOS association and eNOS deacetylation. By using the AMPK inhibitor and eNOS Ser-633 and -1177 mutants, we demonstrated that AMPK phosphorylation of eNOS is needed to prime SIRT1-induced deacetylation of eNOS to enhance NO production. To verify this finding in vivo, we compared the acetylation status of eNOS in thoracic aortas from AMPKalpha2(-/-) mice and their AMPKalpha2(+/+) littermates. Our finding that AMPKalpha2(-/-) mice had a higher eNOS acetylation indicates that AMPK phosphorylation of eNOS is required for the SIRT1 deacetylation of eNOS. These results suggest that atheroprotective flow, via AMPK and SIRT1, increases NO bioavailability in endothelium.
authors.affiliation: Division of Biomedical Sciences, Biochemistry and Molecular Biology Graduate Program, University of California, Riverside, CA 92521-0121, USA.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Chen
authors.forename: I-Chen
authors.initials: IC
authors.lastname: Peng
authors.forename: Xiaopei
authors.initials: X
authors.lastname: Cui
authors.forename: Yi-Shuan
authors.initials: YS
authors.lastname: Li
authors.forename: Shu
authors.initials: S
authors.lastname: Chien
authors.forename: John Y-J
authors.initials: JY
authors.lastname: Shyy
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D000107:Acetylation; D019943:Amino Acid Substitution; D000818:Animals; D001011:Aorta / Q000502:physiology; D001483:Base Sequence; D001808:Blood Vessels / Q000502:physiology*; D002478:Cells, Cultured; D017931:DNA Primers / Q000235:genetics; D042783:Endothelial Cells / Q000502:physiology; D004789:Enzyme Activation; D018056:Hemorheology; D006706:Homeostasis; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008928:Mitochondria / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000235:genetics / Q000378:metabolism; D011673:Pulsatile Flow; D034741:RNA, Small Interfering / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D056564:Sirtuin 1 / Q000378:metabolism*; D013314:Stress, Mechanical
chemical_list: D017931:DNA Primers; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; D009569:Nitric Oxide; C496314:NOS3 protein, human; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse; C534978:Prkaa2 protein, mouse; D055372:AMP-Activated Protein Kinases; C447939:SIRT1 protein, human; C470545:Sirt1 protein, mouse; D056564:Sirtuin 1