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Background: High density lipoprotein (HDL) has been proved to be a protective factor for coronary heart disease. Notably, HDL in atherosclerotic plaques can be nitrated (NO2-oxHDL) and chlorinated (Cl-oxHDL) by myeloperoxidase (MPO), likely compromising its cardiovascular protective effects. Method: Here we determined the effects of NO2-oxHDL and Cl-oxHDL on SMC migration using wound healing and transwell assays, proliferation using MTT and BrdU assays, and apoptosis using Annexin-V assay in vitro, as well as on atherosclerotic plaque stability in vivo using a coratid artery collar implantation mice model. Results: Our results showed that native HDL promoted SMC proliferation and migration, whereas NO2-oxHDL and Cl-oxHDL inhibited SMC migration and reduced capacity of stimulating SMC proliferation as well as migration, respectively. OxHDL had no significant influence on SMC apoptosis. In addition, we found that ERK1/2-phosphorylation was significantly lower when SMCs were incubated with NO2-oxHDL and Cl-oxHDL. Furthermore, transwell experiments showed that differences between native HDL, NO2-oxHDL and Cl-oxHDL was abolished after PD98059 (MAPK kinase inhibitor) treatment. In aortic SMCs from scavenger receptor BI (SR-BI) deficient mice, differences between migration of native HDL, NO2-oxHDL and Cl-oxHDL treated SMCs vanished, indicating SR-BI's possible role in HDL-associated SMC migration. Importantly, NO2-oxHDL and Cl-oxHDL induced neointima formation and reduced SMC positive staining cells in atherosclerotic plaque, resulting in elevated vulnerable index of atherosclerotic plaque. Conclusion: These findings implicate MPO-catalyzed oxidization of HDL may contribute to atherosclerotic plaque instability by inhibiting SMC proliferation and migration through MAPK-ERK pathway which was dependent on SR-BI. [ABSTRACT FROM AUTHOR]

Background: Hyperlipidemia plays a crucial role in the development and progression of coronary artery disease (CAD). Recent studies have identified that microRNAs (miRNAs) are important regulators of lipid metabolism, but little is known about the circulating levels of lipometabolism-related miRNAs and their relationship with the presence of CAD in patients with hyperlipidemia. Methods: In the present study, we enrolled a total of 255 hyperlipidemia patients with or without CAD and 100 controls with normal blood lipids. The plasma levels of four known lipometabolism-related miRNAs, miR-122, miR-370, miR-33a, and miR-33b were quantified by real-time quantitative PCR. Blood levels of total cholesterol (TC), triglyceride (TG), low density lipoprotein cholesterol (LDL-C), and high density lipoprotein cholesterol were determined. Furthermore, the severity of CAD was assessed with the Gensini score system based on the degree of luminal narrowing and its geographic importance. Results: Our results revealed for the first time that plasma levels of miR-122 and miR-370 were significantly increased in hyperlipidemia patients compared with controls, and the levels of miR-122 and miR-370 were positively correlated with TC, TG, and LDL-C levels in both hyperlipidemia patients and controls. Multiple logistic regression analysis demonstrated that the increased levels of miR-122 and miR-370 were associated with CAD presence, even after adjustment for other cardiovascular risk factors. Furthermore, miR-122 and miR-370 levels were positively correlated with the severity of CAD quantified by the Gensini score. However, both miR-33a and miR-33b were undetectable in plasma. Conclusions: Our results suggest that increased plasma levels of miR-122 and miR-370 might be associated with the presence as well as the severity of CAD in hyperlipidemia patients. [ABSTRACT FROM AUTHOR]