The Roles Of SM22α In Vascular Inflammation

Objective: Chronic inflammation is involved in the development ofatherosclerosis. Endothelial injury-induced inflammatory response in vascularsmooth muscle cells (VSMC) is the main pathological basis of vascular injuryand intimal hyperplasia. Smooth muscle22alpha (SM22α), which is anactin-binding protein, is highly expressed in differentiated VSMCs. Recentreports have indicated that the disruption of SM22α induces vascular oxidativestress and inflammation. The aim of this study was to explore the role ofSM22α in TNF-α-induced inflammatory response of VSMCs.Methods and results:1TNF-α induces the expression of ICAM-1and VCAM-1in VSMCs.VSMCs were isolated from rat aorta and were cultured in DMEM med-ium containing10%FBS. The cells used for the experiment were passage3~5. VSMCs were grown to60%~70%confluence, and treated with TNF-α (10ng/ml) for different times (6,12,24h). Western blot assay showed that theexpression of ICAM-1and VCAM-1increased at6h and reached the peak at24h.2Overexpression of SM22α inhibits TNF-α-induced ICAM-1andVCAM-1expression in VSMCs.VSMCs were infected with GFP-SM22α recombinant adenovirus. AfterTNF-α stimulating for24hours, the expression of ICAM-1and VCAM-1wassignificantly reduced in GFP-SM22α-infected VSMCs compared with thecontrol.3Overexpression of SM22α inhibits TNF-α-induced p65acetylation.VSMCs were stimulated with TNF-α for different times (0-90min) and theacetylated p65was detected by immunoprecipitation analysis. FollowingTNF-α stimulation, the level of acetylated p65increased, and reached the peakat60min, However, the p65acetylation induced by TNF-α was significantly inhibited in Ad-GFP-SM22α-infected VSMCs, compared with Ad-GFP-infected cells. All these results showed that SM22α inhibits TNF-α inducedp65acetylation.4Balloon injury induces vascular intimal hyperplasia and the expressionof inflammatory factors.The sections of rat carotid arteries were prepared at day28after ballooninjury. The immunohistochemical staining results demonstrated that the levelof ICAM-1, VCAM-1, MMP-2and MMP-9in the model group was higherthan that in the sham group.5The enhancement of p65acetylation in neointimal cells.The results of immunohistochemical staining demonstrated that the levelof Ac-p65in the model group was higher than that in the sham group. Thepositive cells mainly distributed in the neointimal region. Similar results areobtained by western blot. The level of p65acetylation in the model groupincreased2folds compared with the sham group.6Down regulation of SM22α, SIRT1expression in the neointimal cells.To explore the relationship between the expression of SM22α and SIRT1and intimal hyperplasia, the immunohistochemical staining was performed.The results showed that SM22α positive cells in the balloon injury groupreduced significantly compared with the sham group. Similar results areobtained by western blot. The expression of SIRT1and SM22α decreased4.4and2.4folds, compared with the sham, respectively.Conclusions：1Overexpression of SM22α inhibits TNF-α-induced ICAM-1andVCAM-1expression in VSMCs.2Overexpression of SM22α inhibits TNF-α-induced p65acetylation.3Balloon injury induces vascular intimal hyperplasia4The acetylation of p65increases in neointimal cells. 5The expression of SM22α and SIRT1is downregul ated in theneointimal cells.