Regulatory Effects Of Curcuma Longa On Reverse Cholesterol Transport And The Phenotypic Differentiation Of Vascular Smooth Muscle Cells

ObjectiveTo clarify the role of Curcuma longa L. in atherosclerosis, we observed the effect of Curcuma longa L. on serum lipid levels and vascular smooth muscle cell (VSMC) lipid metabolism. To explore the mechanism of Curcuma longa L. in prevention and treatment of vascular smooth muscle cell proliferation, we studied the regulation of curcumin on VSMC phenotype differentiation.Methods1. C57 mice and caveolin-1 knockout (cav-/-) mice were fed with normal diet or high fat diet and treatment with Curcuma longa L., the body weight, liver index and serum lipid levels were measured, and the expression of caveolin-1 was detected by western blot. Histopathological and lipid content of liver were observed by Hematoxylin-eosin staining.2. The cell proliferation and migration of rat primary VSMC and VSMC line were measured, and the cellular cholesterol content of these two kinds of cells was observed by oil red O staning and high performance liquid chromatography (HPLC). Rat primary VSMC and VSMC line were incubated with LDL, and treated with curcumin for 24h, HPLC was used to detected the cellular cholesterol content. Treated VSMC with different concentrations of curcumin and detected the expression of caveolin-1 and ABCA1 by western blot. Bioinformatics was used to analyze the regulatory mechanism of ABCA1 in VSMC. The expression of myocardin and miR-145 was detected after treatment of VSMC wit curcumin. Transfected the myocardin overexpressed or myocardin silenced VSMC with miR-145 mimic or miR-145 inhibitor, and detected the expression of ABCA1 and the cellular cholesterol content in VSMC3. Isolated the thoracic aortic rings from C57 mice and cav-/-mice, compared the contractile force by myograph. Incubated both aortic rings with curcumin, and measured the contractile force after curcumin incubation. Transfected VSMC with plasmid to up-regulate or silence caveolin-1 gene, and detected the expression of a-actin, SM22a, myocardin and NICD, and observed the effect of curcumin on VSMC proliferation..Results1. The liver index of cav-/-mice decreased compared to C57 mice, and restored after treatment with caveolin-1 high expression adenovirus. Curcuma longa L. treatment increased the liver index and liver caveolin-1 in C57 mice, but had little effect on cav-/-mice. Serum lipid level of cav-/-mice was significantly higher than that in C57 mice, and the serum lipid level reduced after infection of cav-/-mice with caveolin-1 high expression adenovirus. Curcuma longa L. treatment decreased the serum lipid level of C57 mice, but had little effect on cav-/-mice and those C57 mice with normal serum lipid level. Hematoxylin-eosin staining showed that the liver surface of C57 mice was greasy, and hepatic cell lipid vacuoles increased. Intrahepatic lipid droplet vacuoles increased further after Curcuma longa L. treatment, and also the liver tissue showed a slight injury. Cav-/-mice hepatic cell lipid vacuole reduced compared to C57 mice, and Curcuma longa L. had no obvious effect on cav-/-mice intrahepatic lipid droplet vacuoles. Hepatic cell lipid vacuoles of cav-/-mice increased significantly after intravenous injection of caveolin-1 high expression adenovirus, and the liver tissue damage more aggravated.2. Compared with rat primary VSMC, VSMC line showed strong proliferation, migration and lipid-loaded ability, but the contractile protein level was significantly reduced. Curcumin inhibited the expression of ABCA1, and prevented cholesterol spontaneous outflow from lipid-loaded VSMC. Bioinformatics analysis suggested that there may be a myocardin/ miR-145/ABCA1 pathway to regulate the level of ABCA1 in VSMC. The experimental results confirmed that curcumin induced the expression of myocardin and miR-145, myocardin and miR-145 both inhibited the expression of ABCA-1, and increased cholesterol levels within VSMC.3. The contractile response of cav-/-mice was weak compared to C57 mice, curcumin enhanced the contractility of vascular rings from C57 mice, but had little effect on cav-/-mice aortic rings. Intravenous injection of caveolin-1 high expression adenovirus promoted the expression of contractile proteinsa-actin and SM22?, and inhibited proliferation of VSMC.ConclusionsIn liver tissue, curcumin induced the expression of caveolin-1 and promoted the intake and metabolism of cholesterol by liver, which caused the reduction of serum lipid level.In VSMC, curcumin induced the expression of myocardin and inhibited the expression of ABCA1 through a myocardin/miR-145/ABCA1 pathway, which prevented ABCA1 mediated cholesterol efflux, resulting in lipid accumulation in VSMC. As a result, curcumin may play a role in serum lipid lowering at hyperlipemia stage, but has little effect on atherosclerotic plaque at atherosclerosis stage. Curcumin induced the expression of myocardin, and promoted differentiation of VSMC to contractile phenotype, which may contribute to prevention of vascular smooth muscle cell proliferation and intimal thickening.