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.