Upregulation of endothelial receptor for oxidized LDL (LOX-1) by oxidized LDL and implications in apoptosis of human coronary artery endothelial cells: evidence from use of antisense LOX-1 mRNA and chemical inhibitors.
A specific lectin-like endothelial receptor for oxidized low density lipoprotein (LOX-1), distinct from the scavenger receptor in monocytes/macrophages, has been identified and cloned. In this study, we examined the regulation of LOX-1 by oxidized low density lipoprotein (ox-LDL) and determined the role of LOX-1 in ox-LDL-induced apoptosis of cultured human coronary artery endothelial cells (HCAECs). Incubation of HCAECs with ox-LDL (40 microg/mL), but not native LDL, for 24 hours markedly increased LOX-1 expression (mRNA and protein). After 48 hours of preincubation of HCAECs with a specific antisense to LOX-1 mRNA (antisense LOX-1), ox-LDL-mediated upregulation of LOX-1 was suppressed (P<0.01). In contrast, treatment of HCAECs with sense LOX-1 had no effect. Ox-LDL also induced apoptosis (determined by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling and DNA laddering) of HCAECs in a concentration- and time-dependent fashion. LOX-1 played an important role in ox-LDL-mediated apoptosis of HCAECs because antisense LOX-1 inhibited this effect of ox-LDL. Polyinosinic acid and carrageenan, 2 different chemical inhibitors of LOX-1, also decreased ox-LDL-mediated apoptosis of HCAECs. Nuclear factor (NF)-kappaB was markedly activated in ox-LDL-treated HCAECs. The critical role of NF-kappaB activation became evident in experiments with antisense LOX-1, which abolished ox-LDL-mediated NF-kappaB activation. In this process, an NF-kappaB inhibitor, caffeic acid phenethyl ester, also inhibited ox-LDL-mediated apoptosis of HCAECs. These findings indicate that ox-LDL upregulates its own endothelial receptor. Ox-LDL-induced apoptosis is mediated by the action of LOX-1. In this process, NF-kappaB activation may play an important role as a signal transduction mechanism.
Li
D
D
Department of Medicine, University of Florida, Gainesville 32610, USA.
Mehta
J L
JL
D017209:Apoptosis; D002478:Cells, Cultured; D003331:Coronary Vessels / Q000166:cytology* / Q000378:metabolism; D053938:DNA Fragmentation; D004730:Endothelium, Vascular / Q000166:cytology* / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D020287:In Situ Nick-End Labeling; D008077:Lipoproteins, LDL / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011973:Receptors, LDL / Q000235:genetics*; D051131:Receptors, Oxidized LDL; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051127:Scavenger Receptors, Class E; D015398:Signal Transduction
D008077:Lipoproteins, LDL; D016328:NF-kappa B; C495137:OLR1 protein, human; D012333:RNA, Messenger; D011973:Receptors, LDL; D051131:Receptors, Oxidized LDL; D051127:Scavenger Receptors, Class E; C099252:oxidized low density lipoprotein