Simvastatin, a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, has been shown to improve atherosclerosis (AS) via its anti-inflammatory activity. Recently, several studies have reported the involvement of macrophages in chronic inflammation associated with AS. However, it is unknown whether macrophages participate in the anti-inflammatory activity of simvastatin in AS. This study was designed to investigate the roles and underlying mechanisms of simvastatin in LPS-stimulated RAW264.7 macrophages. First, we examined the anti-inflammatory effects of simvastatin on LPS-treated macrophage RAW264.7 cells using an enzyme-linked immunosorbent assay (ELISA) and a quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). Then, a microarray assay was used to analyze the microRNA (miRNA) expression profile in RAW264.7 cells incubated with or without simvastatin in the presence of LPS. MicroRNA-22 (miR-22) with the highest change was validated independently by qRT-PCR. Luciferase reporter assays were conducted to determine the association between miR-22 and the cysteine-rich protein 61 (Cyr61). Subsequently, we investigated the molecular mechanism by which miR-22 functions in the anti-inflammation of simvastatin in LPS-stimulated macrophages. We found that simvastatin treatment could significantly inhibit inflammation by modulating the expression of mediators, such as IL-1β, TNF-α and IL-6, whose expression were increased remarkably in the activated RAW264.7 cells. miR-22 was found to be one of the most significantly upregulated miRNAs in LPS-stimulated RAW264.7 macrophages after treatment with simvastatin. Pre-treatment of simvastatin in LPS-stimulated RAW264.7 macrophages enhanced miR-22 expression in a dose dependent manner. Interestingly, Cyr61, a novel pro-inflammatory factor involved in the pathogenesis of atherosclerosis (AS), was identified as a direct target of miR-22. Overexpression of miR-22 enhanced the anti-inflammatory effects of simvastatin, whereas inhibition of miR-22 had an opposite effect. More importantly, further study demonstrated that the knockdown of Cyr61 by siRNA could attenuate the inhibitory effects of miR-22 inhibition on anti-inflammatory activities of simvastatin. The results clearly show that simvastatin inhibits the inflammation response in LPS-stimulated RAW264.7 macrophages through the miR-22/Cyr61 axis and suggests that targeting the miR-22/Cyr61 axis may be a promising molecular target for AS therapy.
Keywords: Atherosclerosis; RAW264.7 macrophages; inflammation; miR-22/Cyr61 axis; simvastatin.
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