Abstract 17947: The Role of Endothelial Dicer in Atherosclerosis
Increased monocyte adhesion to endothelial cells (ECs) orchestrated by chemokines is a characteristic feature of vascular inflammation, which promotes the development of atherosclerosis. Non-coding, small microRNAs (Mirs) generated by the endonuclease Dicer in ECs augment angiogenesis. However, the role of the endothelial Mir network in monocyte adhesion during atherosclerosis remains unclear.
To study the effect of Dicer-dependent Mirs in ECs on atherosclerosis, VE-Cadherin-CreT+/Dicerflox/Apoe-/- (EC-DicerKO) mice and VE-Cadherin-CreT+/DicerWT/Apoe-/- (EC-DicerWT) mice were treated with tamoxifen and fed with a high fat diet (HFD) for 4 or 12 weeks. Dicer mRNA expression was reduced in the aorta of EC-DicerKO mice after tamoxifen treatment by 58% as determined by qRT-PCR (n=4; p<0.05). The adhesion of monocytes and the expression of CXCL1, CX3CL1 and CCL2 was inhibited in carotid arteries of EC-DicerKO mice after 4 weeks HFD determined by ex vivo perfusion assays and qRT-PCR, respectively (n=5; p<0.05). Atherosclerosis in the aortic roots (by 58%) and lipid depositions in thoracoabdominal aortas (by 41%) were decreased in EC-DicerKO compared to EC-DicerWT mice after 12 weeks of a HFD analyzed by staining of aortic root sections with Elastic van Gieson stain and en face prepared aortas with Oil red O, respectively (n=8-12; p<0.05). In arteries of EC-DicerKO mice, consistent down-regulation of Mir103, 301b, 433, and 652 was found after 4 and 12 weeks of a HFD by qRT-PCR miRNA array (n=3; p<0.05). In ECs of normal and atherosclerotic arteries, prominent expression of Mir103 was detectable by in situ PCR. Inhibition of Mir103 in human aortic ECs (HAoECs) suppressed the expression of CXCL1, CX3CL1 and CCL2 (studied by qRT-PCR), reduced monocyte adhesion (studied by flow adhesion assays) and increased the expression of its target KLF4 at the protein, but not at the RNA level (n=3-5; p<0.05). In contrast to Mir103, silencing of KLF4 in HAoEC induced the chemokine expression as determined by qRT-PCR (n=5; p<0.05).
In conclusion, endothelial Dicer promotes atherosclerosis most likely by enhanced chemokine-mediated monocyte recruitment. This effect of endothelial Dicer may be due to suppression of the anti-inflammatory transcription factor KLF4 by Mir103.
- © 2013 by American Heart Association, Inc.