Caveolae and caveolin-1 mediate endocytosis and transcytosis of oxidized low density lipoprotein in endothelial cells

Abstract

Aim: To explore the mechanisms involved in ox-LDL transcytosis across endothelial cells and the role of caveolae in this process. Methods: An in vitro model was established to investigate the passage of oxidized low density lipoprotein (ox-LDL) through a tight monolayer of human umbilical vein endothelial cells (HUVEC) cultured on a collagen-coated filter. Passage of DiI-labeled ox-LDL through the monolayer was measured using a fluorescence spectrophotometer. The uptake and efflux of ox-LDL by HUVEC were determined using fluorescence microscopy and HPLC. Results: Caveolae inhibitors -carrageenan (250 μg/mL), filipin (5 μg/mL), and nocodazole (33 μmol/L)-decreased the transport of ox-LDL across the monolayer by 48.9%, 72.4%, and 79.8% as compared to the control group. In addition, they effectively decreased ox-LDL uptake and inhibited the efflux of ox-LDL. Caveolin-1 and LOX-1 were up-regulated by ox-LDL in a time-dependent manner and decreased gradually after depletion of ox-LDL (P<0.05). After treatment HUVEC with ox-LDL and silencing caveolin-1, NF-κB translocation to the nucleus was blocked and LOX-1 expression decreased (P<0.05). Conclusion: Caveolae can be a carrier for ox-LDL and may be involved in the uptake and transcytosis of ox-LDL by HUVEC.Keywords: caveolae; caveolin-1; oxidized low density lipoprotein; atherosclerosis; transcytosis; human umbilical vein endothelial cells Acta Pharmacologica Sinica (2010Sinica ( ) 31: 1336Sinica ( -1342 doi: 10.1038/aps.2010 published online 13 Sep 2010 Original Article * To whom correspondence should be addressed. E-mail dfliao66@yahoo.com.cn (Duan-fang LIAO); tchaoke@yahoo.com.cn (Chao-ke TANG) Received 2010-03-09 Accepted 2010-06-03 the vessel lumen and the arterial wall, and the control may be disturbed in arteriosclerotic blood vessels. Understanding the mechanisms of lipoprotein translocation, especially from arterial wall to vessel lumen, will be beneficial to the therapy of cardiovascular disorders. Caveolae are distinctive, flaskshaped invaginations of the plasma membrane generated in the Golgi complex. These organelles have a characteristic lipid composition and are associated with a 22 kDa protein called caveolin-1. Zhang reported that two ox-LDL receptors, CD36 and the related receptor SR-B1, localize to caveolae [4,5] . Several human studies have indicated transcytosis of macromolecules by means of caveolae in endothelial cells [6][7][8][9][10][11] . We hypothesized that ox-LDL may internalize and transcytose in this way. Bruneau described a model to study the passage of macromolecules through a monolayer of INT-407 cells [12] . We used this model to investigate the characteristics and mechanism of ox-LDL passage. LOX-1 is the major receptor for ox-LDL in endothelial cells [13] . [14] . Caveolin-1 is the main structural protein of caveolae, and it plays a crucial role in the formation of these invaginations of the plasma membrane. Caveolin-1 is a cholesterolbinding protein. Hu and Wu demonstrated the correlation between caveolin-1 and cellular choles...

AMP-dependent Kinase Inhibits Oxidative Stress-induced Caveolin-1 Phosphorylation and Endocytosis by Suppressing the Dissociation between c-Abl and Prdx1 Proteins in Endothelial Cells

“…Using fibroblasts derived from c-Abl or Src knock-out mice, Sanguinetti and Mastick (19) showed that c-Abl phosphorylates caveolin-1 independently of Src. In contrast, in pulmonary microvascular endothelial cells, Sun et al (2,20,38) reported that c-Abl activation and subsequent caveolin-1 phosphorylation is in part dependent on Src activity. They further mentioned that the c-Abl pathway becomes more important particularly when higher concentrations of H 2 O 2 are used to stimulate caveolin-1 phosphorylation.…”

oxLDL induces injury and defenestration of human liver sinusoidal endothelial cells via LOX1

“…CAV1 potentially plays an important positive role in the regulation of LSEC tubular formation (Yokomori et al 2009). Recent studies demonstrate that CAV1 expression increases oxLDL uptake by hepatic cells and mediates oxLDL endocytosis and transcytosis by ECs (Truong et al 2009, Sun et al 2010. Furthermore, oxLDL upregulates CAV1 expression and downregulates eNOS expression at the mRNA and protein levels in HUVECs (Ma et al 2012).…”

A novel model of cholesterol efflux from lipid-loaded cells

“…Recently, we found that caveolae and caveolin-1 mediate the endocytosis and transcytosis of oxidized low-density lipoprotein (ox-LDL) in endothelial cells [10] . Caveolae in the plasma membrane may invaginate and form caveolar vesicles that contain cholesterol or lipoprotein.…”