Abstract 15990: Disturbed Shear Stress Facilitates Caveolae-Mediated oxLDL Uptake Leading to Increased Endothelial Stiffness
Introduction: Oxidized low density lipoprotein (oxLDL) is a key risk factor in the formation of atherosclerotic plaques, which are primarily located at vessel bifurcations that exhibit bidirectional recirculating disturbed shear stress (DSS) patterns. It is also well known that while DSS patterns are pro-atherogenic, laminar shear stress (LSS) is atheroprotective.
Hypothesis: OxLDL uptake into endothelial cells (ECs) is caveolin-1 (Cav-1) protein dependent and increases under DSS conditions leading to increased cellular stiffness.
Methods: To address these questions, a microfluidic channel with a step barrier was designed, tested and fabricated to generate both unidirectional LSS and recirculating DSS patterns onto an endothelial monolayer for 48 hours. EC stiffness was assessed using atomic force microscopy.
Results: Our results show a 40% increase in endothelial oxLDL uptake in DSS vs. LSS regions (n=4, p<0.05), which was significantly diminished (50% less) in cells lacking Cav-1, the main protein in caveolae (n=4, p<0.05). There was no observable difference in oxLDL uptake in the LSS and DSS regions in Cav-1 knockout (KO) ECs. The mechanism of differential oxLDL uptake in LSS vs. DSS regions was further investigated using ECs lacking endothelial nitric oxide synthase (eNOS), which was shown previously to regulate caveolae-mediated endocytosis. Our experiments revealed that indeed eNOS is also required for increased oxLDL uptake in DSS regions (n=3). Furthermore, we observed that the increase in oxLDL uptake in DSS regions results in a 60% increase in EC stiffness compared to ECs from LSS regions (n=3, p<0.05). This data is further supported by ex vivo stiffness measurements of intact vessels from wild type (WT) mice which showed a 50% increase in EC stiffness in the DSS regions of the aortic arch as compared to the LSS regions of the descending aorta (DA) (n=5, p<0.05). In Cav-1 KO mice, EC stiffness was markedly reduced (n=5, p<0.05) and no differences in stiffness were observed between the DA and arch.
Conclusion: Taken together, this study suggests that DSS-induced increase in oxLDL uptake is mediated by caveolae and plays a significant role in increasing localized EC stiffness which in turn is expected to impair endothelial barrier function.
Author Disclosures: E. LeMaster: None. S. Sun: None. D. Eddington: None. M. Cho: None. R. Minshall: None. I. Levitan: None.
- © 2014 by American Heart Association, Inc.