Article

Sirtuin 1 retards hyperphosphatemia-induced calcification of vascular smooth muscle cells.

Department of Geriatric Medicine, Graduate School of Medicine, University of Tokyo, Tokyo, Japan.
Arteriosclerosis Thrombosis and Vascular Biology (impact factor: 6.37). 06/2011; 31(9):2054-62. DOI:10.1161/ATVBAHA.110.216739
Source: PubMed

ABSTRACT Arterial calcification is associated with cardiovascular disease as a complication of advanced atherosclerosis. Aged vascular cells manifest some morphological features of a senescent phenotype. Recent studies have demonstrated that mammalian sirtuin 1 (SIRT1), a histone deacetylase, is an exciting target for cardiovascular disease management. Here, we investigated the role of SIRT1 in a calcification model of vascular smooth muscle cells (SMCs).
In adenine-induced renal failure rats with hyperphosphatemia, massive calcification was induced in the aortic media. Senescence-associated β-galactosidase (SAβ-gal) activity, a marker of cellular senescence, in medial SMCs was significantly increased, and its induction was positively associated with the degree of calcification. In cultured SMCs, inorganic phosphate (Pi) stimulation dose-dependently increased SAβ-gal-positive cells, and Pi-induced senescence was associated with downregulation of SIRT1 expression, leading to p21 activation. The activation via SIRT1 downregulation was blunted by inhibition of Pi cotransporter. Activation of SIRT1 by resveratrol significantly reduced the senescence-associated calcification. Conversely, SIRT1 knockdown by small interfering RNA accelerated the Pi-induced SMC senescence and subsequent calcification. In addition, SIRT1 knockdown induced phenotypic change from a differentiated state to osteoblast-like cells. The senescence-related SMC calcification was completely prevented by p21 knockdown. In addition to Pi-induced premature senescence, SMCs with replicative senescence were also more sensitive to Pi-induced calcification compared with young SMCs, and this finding was attributable to augmented p21 expression.
SIRT1 plays an essential role in preventing hyperphosphatemia-induced arterial calcification via inhibition of osteoblastic transdifferentiation. In addition, Pi-induced SMC calcification may be associated with both premature and replicative cellular senescence.

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Keywords

aortic media
 
Arterial calcification
 
augmented p21 expression
 
cardiovascular disease management
 
cultured SMCs
 
differentiated state
 
histone deacetylase
 
hyperphosphatemia-induced arterial calcification
 
mammalian sirtuin 1
 
medial SMCs
 
Pi cotransporter
 
Pi-induced calcification
 
Pi-induced SMC calcification
 
Senescence-associated β-galactosidase
 
senescence-related SMC calcification
 
SIRT1 downregulation
 
SIRT1 expression
 
subsequent calcification
 
vascular cells manifest
 
young SMCs