Abstract 18091: Role of Endothelial Expression of ABCA1 and SR-BI Genes in HDL Metabolism, Cholesterol Trafficking and Protection Against Atherosclerosis.
The transfer of cholesterol (C) across endothelial cells (EC) is critical in the pathogenesis of atherosclerosis (AC). To examine the role of ABCA1 and SR-BI genes in this function, we created transgenic mice specifically expressing either human ABCA1 or mouse SR-BI in EC, using the Tie2 promoter. We have previously shown that when ABCA1 was expressed in EC in mice, it increased plasma HDL-C and protected against TD90221 diet-induced AC. In the current study, we found that ABCA1 transgene was expressed in EC of most tissues except the liver at a level comparable or higher than expression of the endogenous mouse Abca1 gene. Furthermore, expression of ABCA1 in EC enhanced apoA1-mediated C efflux from primary cultures of transgenic aortic EC by 2.6±0.5 fold (p<0.01), and increased the level of expression of eNOS in the aorta of transgenic mice by 2.2±0.5 fold (p<0.04). In addition, aortas from ABCA1 transgenic mice kept for 3 month on TD90221 high fat diet had gene expression changes consistent with deceased inflammation and apoptosis: expression of Ace and Tfpi was higher that in aortas from control mice on the same diet, respectively, in 1.9±0.06 and 1.5±0.1, whereas expression of Casp6, Cxc11, Pecam1, Ripk1, Sod1 and Tnfsf10 genes was significantly decreased (in 1.5±0.1; 3.6±0.2; 1.5±0.1; 1.4±0.1; 1.4±0.0; 2.1±0.2 folds; p<0.05). Tie2-SR-BI transgenic mice expressed the transgene in EC at a level comparable with expression of mouse Sr-bI. Increased expression of SR-BI in EC led to decreased en face surface of aortic lesions in mice with C57BL/6 background kept 6 months on TD90221 diet (4.2±0.7% in transgenic vs. 6.8±.7% in control, p<0.02). Using polarized SVEC4-10 EC grown on Transwell filters, we found that the rate of transfer of HDL through EC from the apical to basolateral compartment was 3.8±0.5 fold faster than from the basolateral to apical direction (p<0.001). Polarized EN showed selective uptake of cholesteryl esters from HDL 3.1±0.2 fold faster from basolateral than from apical side (p<0.01). In contrast, efflux of free C to HDL from apical membrane of polarized EC was 3.4±0.3 faster than from basolateral side (p<0.0003). In summary, ABCA1 and SR-BI play major roles in C trafficking and homeostasis in EC, which was associated with decreased AC.
- © 2010 by American Heart Association, Inc.