title: Oxidized LDL through LOX-1 modulates LDL-receptor expression in human coronary artery endothelial cells.
abstract: Experimental studies have shown that oxidized low-density lipoprotein (ox-LDL) up-regulates its receptor LOX-1. Both ox-LDL and LOX-1 are expressed in atherosclerotic plaques. Native LDL concentrations are elevated in atherosclerosis, suggesting a reduction in LDL-receptors. We hypothesized that ox-LDL via LOX-1 could influence the expression of LDL-receptors. This study was designed to examine the interaction between ox-LDL, LOX-1, and LDL-receptors in human coronary artery endothelial cells (HCAECs). HCAECs were incubated with ox-LDL (10-80 microg/ml) for 3-24h. Ox-LDL decreased the expression of LDL-receptor in a concentration- and time-dependent fashion. The effects of ox-LDL were mediated by its endothelial receptor LOX-1, since pretreatment of HCAECs with a blocking antibody to LOX-1 (JTX92, 10 microg/ml) prevented the effect of ox-LDL on LDL-receptor expression. The role of LOX-1 was further confirmed by the use of an antisense to LOX-1 mRNA, which also blocked the effect of ox-LDL in LDL-receptor expression. In other experiments, ox-LDL as expected induced superoxide anion generation; and pretreatment of HCAECs with the anti-oxidants trolox and alpha-tocopherol (each 10 microM) inhibited the formation of superoxide anions as well as the down-regulation of LDL-receptor in response to ox-LDL. These studies provide the first evidence that ox-LDL via LOX-1 modulates LDL-receptor expression in HCAECs. The generation of free radicals elicited by ox-LDL may be a key step in this process.
authors.affiliation: Department of Internal Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA.
authors.forename: Bo
authors.initials: B
authors.lastname: Hu
authors.forename: Dayuan
authors.initials: D
authors.lastname: Li
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Sawamura
authors.forename: Jawahar L
authors.initials: JL
authors.lastname: Mehta
mesh_terms: D000975:Antioxidants / Q000494:pharmacology; D002478:Cells, Cultured; D003331:Coronary Vessels / Q000166:cytology / Q000378:metabolism*; D015536:Down-Regulation; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D011973:Receptors, LDL / Q000378:metabolism* / Q000502:physiology; D051131:Receptors, Oxidized LDL; D051127:Scavenger Receptors, Class E
chemical_list: D000975:Antioxidants; D008077:Lipoproteins, LDL; C495137:OLR1 protein, human; D011973:Receptors, LDL; D051131:Receptors, Oxidized LDL; D051127:Scavenger Receptors, Class E; C099252:oxidized low density lipoprotein