Identification of microRNAs involved in the modulation of pro-angiogenic factors in atherosclerosis by a polyphenol-rich extract from propolis.

New vessel formation plays a critical role in the progression and vulnerability of atherosclerotic lesions. It has been shown that polyphenols from propolis attenuate the progression of atherosclerosis and also exert inhibitory effects on angiogenic factors. However, the mechanisms underlying these effects are not completely understood. Thus, this study aimed to identify microRNAs (miRNAs) involved in the modulation of pro-angiogenic factors in the atherosclerotic plaques of LDL receptor gene knockout mice treated with a polyphenol-rich extract of Chilean propolis. The progression of the atherosclerotic lesions was significantly attenuated in treated mice compared with control mice. Using microarray analysis and a bioinformatic approach, we identified 29 differentially expressed miRNAs. Many of these miRNAs were involved in biological processes associated with angiogenesis, such as the cell cycle, cell migration, cell growth and proliferation. Among them, three miRNAs (miR-181a, miR-106a and miR-20b) were over-expressed and inversely related to the expression of Vegfa (vascular endothelial growth factor A) and Hif1a (hypoxia inducible factor 1 alpha). In addition, VEGF-A protein expression was attenuated in histological sections obtained from the aortic sinuses of treated mice. VEGFA is a key pro-angiogenic factor in atherosclerotic plaques, and Hif1a, which is expressed in the necrotic nucleus of the atheroma, is its main inducer. We found a correlation between the over-expression of miR-181a, miR-106a and miR-20b and their target genes, Hif1a and Vegfa, which is consistent with attenuation of the atherosclerotic lesion. In conclusion, our data analysis provides evidence that the anti-angiogenic effects of polyphenols from Chilean propolis can be modulated by miRNAs, in particular miR-181a, miR-106a and miR-20b.