Regulation of microRNA-155 in endothelial inflammation by targeting nuclear factor (NF)-κB P65

Increasing evidences have illuminated the fundamental role of inflammation in mediating all stages of atherosclerosis. miR-155, a typical multi-functional miRNA, has recently emerged as a novel component of inflammatory signal transduction in the pathogenesis of atherosclerosis. However, little is known about whether endothelial highly expressed miR-155 can regulate endothelial inflammation-related transcription factors and the predicted role of miR-155 as a negative feedback regulator in endothelial inflammation involved in atherosclerosis. Bioinformatics analysis showed that RELA (nuclear factor-κB p65) is a potential target gene of miR-155 and this was confirmed by a luciferase reporter assay. Our results show that microRNA-155 mediate endothelial inflammation and decrease NFкB p65 and adhesion molecule expression in TNFα-stimulated endothelial cells. Transfection with miR-155 significantly inhibited TNFα-induced monocyte adhesion to endothelium. Inhibition of miR-155 enhanced p65 level and endothelial inflammatory response which was counteracted through the depletion of P65 by Si-P65. On the other hand, knockdown of eNOS, another target of miR-155, while transfecting with miR-155 inhibitor resulted in more significant inflammatory response. miR-155 is highly expressed in TNFα treated HUVECs, deprived of endogenous p65 could reverse TNFα-induced upregulation of miR-155. Thus, TNFα induced miR-155 may serve as a negative feedback regulator in endothelial inflammation involved in atherosclerosis by targeting nuclear transcription factor P65. These results provide a rationale for intervention of intracellular microRNA as possible anti-atherosclerotic targets.