Oxidized LDL promotes vascular endothelial cell pinocytosis via a prooxidation mechanism

Abstract

Human low density lipoprotein (LDL) is prepared in the presence of antioxidants and is oxidized to different levels (measured by thiobarbituric acid reactive substance) with copper ion. The effects of unoxidized LDL and oxidized LDL (ox-LDL) on stress fiber formation, cell membrane ruffling, and pinocytosis (measured by [14C]sucrose uptake) in cultured human umbilical cord vein endothelial cells (EC) are compared. We show that at a concentration range of 100 to 200 microg cholesterol/ml, both unoxidized LDL and ox-LDL promote EC elongation and stress fiber formation, but the effect by the latter is more prominent when compared at the same dose range. In addition, ox-LDL also induces EC membrane ruffling and promotes pinocytosis. These effects are positively correlated with the extent of LDL oxidation and depend on the dose of ox-LDL. Ox-LDL-promoted membrane ruffling and pinocytosis are effectively blocked by brief preexposure of the cells to antioxidants. In contrast, stress fiber formation is not affected by antioxidant pretreatment. Although unoxidized LDL also promotes [14C]sucrose uptake, it is less potent than ox-LDL and significantly higher concentrations are required to produce a detectable effect. Unlike ox-LDL, unoxidized LDL-enhanced pinocytosis is not accompanied by the appearance of membrane ruffling; therefore, they may act via different mechanisms. Elevated pinocytosis may increase transcytotic activity of the endothelium, leading to an increased influx of plasma components such as LDL into the subendothelial space.

Association of αB-Crystallin, a Small Heat Shock Protein, with Actin: Role in Modulating Actin Filament Dynamics in Vivo

“…Stress fiber formation and membrane ruffling are associated with increased pinocytosis, an essential cellular function. 47,48 We have investigated the effect of heat stress and cytochalasin B in the pinocytotic process. We find that unstressed, cytochalasin Btreated cells show dramatically reduced pinocytosis compared to heat-preconditioned, cytochalasin Btreated cells as reflected by FITC-dextran particle uptake ( Figure 9).…”

Oxidized LDL activates fas-mediated endothelial cell apoptosis.

“…Interestingly, OxLDL-treated endothelial cells protected from death by anti-FasL antibody still attained a distinctive elongated cell morphology (27) (Fig. 2 A ), indicating that other actions of OxLDL are not blocked by the neutralizing anti-FasL antibody.…”

Resveratrol attenuates oxLDL-stimulated NADPH oxidase activity and protects endothelial cells from oxidative functional damages

“…EC were isolated from human umbilical cord vein with 0.1% type IV collagenase. The cells were cultured in medium MCDB107 supplemented with 2% FBS and a FGF-enriched fraction of porcine brain extract (1 g/ml) (7).…”