Endothelial stiffening induced by CD36-mediated lipid uptake leads to endothelial barrier disruption and contributes to atherosclerotic lesions

BackgroundTo determine the impact of endothelial stiffening induced by CD36-mediated lipid uptake in the disruption of aortic endothelial barrier and development of atherosclerosis in mouse models of obesity and hypercholesterolemia. Approach and ResultsEndothelial-specific inducible downregulation of CD36 results in abrogating the stiffening of aortic endothelium induced by a short-term (6-8 weeks) high-fat Western diet in intact freshly isolated mouse aortas of Cdh5.CreERT2CD36fl/fl mice, as assessed by atomic force microscopy. No effect was observed on the stiffness of aortic vascular wall assessed in the same groups of mice by echocardiography. Prevention of WD-induced endothelial stiffening by the downregulation of endothelial CD36 was associated with a protective effect against endothelial barrier disruption, assessed by morphological analysis of VE-cadherin junctions and penetration of Evans blue dye into the aortic wall. These protective effects were independent of the changes in the serum lipid profiles. Furthermore, endothelial specific downregulation of CD36 in hypercholesterolemic Cdh5.CreERT2CD36fl/flLDLR-/- mice also led to significant decrease in endothelial stiffening after 4-5 months of high fat diet and a significant decrease in the areas of atherosclerotic lesion. In both models, significant endothelial stiffening was observed specifically in male mice, while female mice exhibited less endothelial stiffening and less severe atherosclerosic phenotype, consistent with endothelial stiffening playing an important role in aortic vascular disease in a sex-dependent way. Mechanistically, we show in vitro that CD36-mdiated uptake of long chain saturated fatty acids, particularly palmitic acid, induces endothelial stiffening via activation of RhoA/ROCK pathway. Moreover, palmitic acid-induced endothelial stiffening critically depends on the expression of a RhoA inhibitory protein, Rho-GDI-1. ConclusionsWe conclude that stiffening of the aortic endothelium by CD36-mediated uptake of fatty acids contributes significantly to WD-induced vascular dysfunction and atherosclerosis. We further propose that fatty acids may activate RhoA by inducing its dissociation from Rho-GDI-1.