Degradation of heparan sulfate proteoglycans enhances oxidized-LDL-mediated autophagy and apoptosis in human endothelial cells.
BACKGROUND
Cell surface heparan sulfate proteoglycans (HSPG) play an important role in atherogenesis. We hypothesized that degradation of HSPG may increase the binding of atherogenic oxidized low density lipoprotein (ox-LDL) to endothelial cells, and result in extensive HSPG degradation as well as autophagy and apoptosis.


METHODS
Primary human umbilical vein endothelial cells (HUVECs) were used to study the expression of lectin-like ox-LDL receptor-1 (LOX-1), HSPG, autophagy and apoptosis in response to ox-LDL and heparinase III (Hep III).


RESULTS
As expected, ox-LDL treatment resulted in LOX-1 expression, ox-LDL uptake and reactive oxygen species (ROS) generation. Ox-LDL treatment also resulted in a modest degradation of HSPG and increase in autophagy (expression of LC3, beclin-1 and Atg5) and apoptosis (enhanced expression of caspases and Bax, and reduced expression of Bcl-2 and Bcl-xL). The effects of ox-LDL were blocked by pretreatment of cells with LOX-1 antibody or apocynin, an NADPH oxidase inhibitor. Hep III alone caused HSPG degradation and slightly, but significantly, increased ROS generation, and induced autophagy and caspase expression. However, autophagy and apoptosis induced by Hep III were not affected by apocynin or LOX-1 antibody. Importantly, Hep III pretreatment of cells significantly enhanced ox-LDL-induced HSPG degradation, LOX-1 expression, ox-LDL uptake and ROS generation as well as autophagy and apoptosis.


CONCLUSIONS
These data demonstrate that Hep III enhances the pro-atherosclerotic characteristics in HUVECs induced by ox-LDL.
Central Arkansas Veterans Healthcare System and the Department of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR 72212, USA.
Zufeng
Z
Ding
Xianwei
X
Wang
Magomed
M
Khaidakov
Shijie
S
Liu
Yao
Y
Dai
Jawahar L
JL
Mehta
D000098:Acetophenones / Q000494:pharmacology; D017209:Apoptosis; D050197:Atherosclerosis / Q000139:chemically induced / Q000378:metabolism; D001343:Autophagy; D002478:Cells, Cultured; D019812:Heparan Sulfate Proteoglycans / Q000378:metabolism*; D061307:Human Umbilical Vein Endothelial Cells / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D008077:Lipoproteins, LDL / Q000378:metabolism* / Q000494:pharmacology; D011133:Polysaccharide-Lyases / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D051127:Scavenger Receptors, Class E / Q000096:biosynthesis
D000098:Acetophenones; D019812:Heparan Sulfate Proteoglycans; D008077:Lipoproteins, LDL; C495137:OLR1 protein, human; D017382:Reactive Oxygen Species; D051127:Scavenger Receptors, Class E; C099252:oxidized low density lipoprotein; C056165:acetovanillone; D011133:Polysaccharide-Lyases; C021349:heparitinsulfate lyase