Endothelial Cd36 mediates endothelium stiffening and promotes barrier disruption in high-fat diet fed mice
Authors: Aguilar Victor , LeMaster Elizabeth , Paul Amit , Ahn Sang Joon , Lee James , Levitan Irena 
Published: May 2023

The impact of a Western-style high fat diet (HFD) on cardiovascular health is a chronic concern. Our previous studies showed that HFD results in significant endothelial cell (EC) stiffening, which was abrogated by the global deletion of scavenger receptor Cd36. Here we present studies into the role of endothelial Cd36 on EC stiffening and EC permeability in mice fed a short-term HFD of 6-8 weeks. Inducible EC-specific knockdown of Cd36 (EC-Cd36-KD) mice were generated by crossing EC-promoter Cre mice with Cd36fl/fl mice. Knockdowns were induced via tamoxifen injections at 8 weeks of age, after which mice were placed on HFD for 6-8 weeks (Cre-only and sham injected mice served as control groups). The efficiency and specificity of EC-Cd36-KD was verified through RT-qPCR and immunostaining. At the end of the study window, control and EC-Cd36-KD mice exhibited hallmarks of metabolic disease like significant increases in body weight and blood cholesterol (total and LDL-Chol). EC-Cd36-KD did not have an effect on these parameters. As described before, HFD results in significant endothelial stiffening in freshly-isolated intact aortas, assessed using atomic force microscopy. We show here that EC-Cd36-KD prevented HFD-induced EC stiffening. No effect was observed in EC-Cd36-KD mice fed low fat diet. In contrast no change was observed in vascular wall stiffness, assessed via pulse wave velocity analysis following Doppler echocardiography in the ventral short-axis. The EC stiffening effect was observed only in male mice, with female mice showing no EC stiffening and exhibiting lower levels of weight gain and blood cholesterol in comparison to males. EC permeability of the aorta was assessed by injecting Evans blue dye (EBD) into circulation and measuring its penetration into the vascular wall by fluorescent imaging. While HFD results in increased EC permeability, EC-Cd36-KD significantly reduced the penetration of EBD into the aortic wall indicating a protective barrier effect. Cre-only HFD-fed controls were unaffected. These results suggest that Cd36-depedent EC stiffening mediates EC permeability of the aorta. Mechanistically, we show that Cd36 is required for oxLDL-induced stiffening but not for the EC stiffening induced by 7-ketocholesterol and oxidized phospholipid PGPC, suggesting that these oxidized lipids induce endothelial stiffening downstream of Cd36. Finally, the knockdown of RhoGDI-1, an inactivator of RhoA, using siRNA prevents oxysterol-induced EC stiffening. We propose that oxidized lipids induce EC stiffening by uncoupling of RhoA from RhoGDI-1 leading to its activation. This work was supported by NHLBI grants HL141120, HL073965, HL083298 (IL), NHLBI trainee award T32HL144459 and an internal fellowship (VA). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.