Impact And Molecular Mechanisms Of Vascular Smooth Muscle Cell Migration. Sirt1

Target-To investigate the effects of Sirtl on TNF-a-induced VSMC migration and further elucidate the possible underlying mechanisms.Background- Sirtl (Sirtuinl), which belongs to classⅢhistone deacetylase (HDAC), is the closest homology to yeast Sir2 in the seven members of human classⅢHDAC. Human Sirtl plays important roles in embryonic development, differentiation, metabolic regulation and stress resistance. As a deacetylase, Sirtl exerts its protective function in apoptosis, stress resistance, cell senescence and inflammation through deacetylating a broad array of targets, including histones (H3, H4), many important transcription factors (p53, FOXO, Ku70, NF-KBp65) and transcription coactivators such as p300, NcoR, PGC-1αand so on.Vascular remodeling presents a complicated dynamic process, including the vascular alteration of capacity, components, configuration and elasticity; and comprising vascular smooth muscle cell proliferation, migration, apoptosis and matrix synthesis, degradation and rearrangement. The biologic process of vascular remodeling may be divided into the following steps:the detection of signals due to changes in hemodynamic conditions and humoral factors (sensors); the relay of signals within the cell and to adjacent cells (transducers); the synthesis and release or activation of substances that influence cell growth, death, or migration or the composition of the extracellular matrix (mediators); and the resultant structural changes in the vessel wall (both cellular and noncellular components). Inappropriate vascular remodeling underlies the pathogenesis of major cardiovascular diseases, such as atherosclerosis, pulmonary hypertension, systemic hypertension, abdominal aneurysm and restenosis after angioplasty. Matrix metalloproteinases (MMPs) potentially participate the vascular remodeling evolve and change through degradation and reorganization of the extracellular matrix (ECM) scaffold of the vessel wall, and regulation VSMCs proliferation and migration. Among them, MMP-9 plays a pivotal role in vascular migration. There is so little MMP-9 expression in quiescent condition, however, the major drivers of vascular remodeling, hemodynamics, injury, inflammation, and oxidative stress, increase MMP-9 expression and activity severely.Methods-Using luciferase reporter assay, immunofluorescence,immunohistochemistry, RT-PCR and Western blotting, we examined the expression of Sirtl in VSMCs incubated with and without TNF-a and in rat carotid artery with balloon injury. Following that we observed the effects of Sirtl on VSMCs migration capability through wound closure and transwell migration assays. Using immunoprecipitation, immunofluorescence, luciferase reporter assay, Western blotting and ChIP, we identified the deacetylase function of Sirtl to c-Jun/c-Fos (AP-1), further more, examined the effect of Sirtl on MMP-9, one of classic AP-1 target genes. Using Western blotting and immunohistochemistry we further detected the effects of Sirtl on MMP-9 expression and activity in VSMC -specific Sirtl transgenic mice subjected carotid artery ligation injury.Results-Sirtl is up-regulated in carotid artery balloon injury model or in VSMCs treated with TNF-a. Overexpression of Sirtl represses VSMCs migration capability in basic or TNF-a-induced state and vice versa. Sirtl interacts with and deacetylates c-Jun/c-Fos (two subunits of AP-1), and decreases the transcriptional activity of AP-1. The expression of MMP-9, a typical AP-1 target gene, is inhibited in VSMCs transfected with adenovirus-mediaced Sirtl, The similar findings are also observed in VSMC -specific Sirtl transgenic mice subjected carotid artery ligation injury.Conclusion- To our knowledge, this report demonstrates for the first time that Sirtl is up-regulated in TNF-a-induced VSMCs and artery under injury. VSMCs migration capability is repressed by Sirtl. Sirtl can interact with and deacetylate c-Jun/c-Fos. to regulate its transcriptional activity and its target gene MMP-9 in VSMCs and mice model. We conclude that Sirtl exerts its protective role through inhibiting the expression of MMP-9 in VSMC migration which may ameliorate the impairment of inappropriate vascular remodeling.