title: Role of caspases in Ox-LDL-induced apoptotic cascade in human coronary artery endothelial cells.
abstract: Oxidized low-density lipoprotein (ox-LDL) induces apoptosis in endothelial cells. However, steps leading to ox-LDL-induced apoptosis remain unclear. We examined the role of ox-LDL and its newly described receptor LOX-1 in the expression of intracellular pro- and antiapoptotic proteins and caspase pathways in human coronary artery endothelial cells (HCAECs). Cells were cultured and treated with different concentrations (10 to 80 microg/mL) of ox-LDL for different times (2 to 24 hours). Ox-LDL induced apoptosis in HCAECs in a concentration- and time-dependent manner. Ox-LDL also activated caspase-9 and caspase-3, but not caspase-8. After ox-LDL treatment, there was a significant release of activators of caspase-9, including cytochrome c and Smac from mitochondria to cytoplasmic compartment, and their release was not affected by treatment of cells with inhibitors of either caspase-8 or caspase-9. Ox-LDL also decreased expression of antiapoptotic proteins Bcl-2 and c-IAP (inhibitory apoptotic protein)-1, which are involved in the release of cytochrome c and Smac and activation of caspase-9, in a concentration- and time-dependent manner. On the other hand, ox-LDL did not change the expression of Fas-associated death domain-like interleukin-1beta-converting enzyme-inhibitory protein (FLIP) and proapoptotic protein Fas, which are required for the activation of caspase-8. Further, ox-LDL did not cause the truncation of Bid, which implies the activation of caspase-8. In other experiments, pretreatment of HCAECs with the caspase-9 inhibitor z-LEHD-fmk, but not the caspase-8 inhibitor z-IETD-fmk, blocked ox-LDL-induced activation of caspase-3 and apoptosis. As expected, pretreatment with the caspase-3 inhibitor DEVD-CHO inhibited ox-LDL-induced activation of caspase-3 and resultant apoptosis. The proapoptotic effects of ox-LDL were mediated by its receptor LOX-1, because pretreatment of HCAECs with antisense-LOX-1, but not sense-LOX-1, blocked these effects of ox-LDL. These findings suggest that ox-LDL through its receptor LOX-1 decreases the expression of antiapoptotic proteins Bcl-2 and c-IAP-1. This is followed by activation of apoptotic signaling pathway, involving release of cytochrome c and Smac and activation of caspase-9 and then caspase-3.
authors.affiliation: Department of Internal Medicine, University of Arkansas for Medical Sciences and Central Arkansas Veterans Healthcare System, Little Rock, AR 72205, USA. lidayuan@uams.edu
authors.forename: Jiawei
authors.initials: J
authors.lastname: Chen
authors.forename: Jawahar L
authors.initials: JL
authors.lastname: Mehta
authors.forename: Nezam
authors.initials: N
authors.lastname: Haider
authors.forename: Xingjian
authors.initials: X
authors.lastname: Zhang
authors.forename: Jagat
authors.initials: J
authors.lastname: Narula
authors.forename: Dayuan
authors.initials: D
authors.lastname: Li
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins / Q000378:metabolism; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D002478:Cells, Cultured; D003331:Coronary Vessels / Q000166:cytology; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D045304:Cytochromes c / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D042783:Endothelial Cells / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D006801:Humans; D020287:In Situ Nick-End Labeling; D051034:Inhibitor of Apoptosis Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000378:metabolism; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology; D011506:Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011973:Receptors, LDL / Q000235:genetics / Q000502:physiology; D051131:Receptors, Oxidized LDL; D051127:Scavenger Receptors, Class E; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors
chemical_list: D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; C412403:DIABLO protein, human; D051034:Inhibitor of Apoptosis Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008077:Lipoproteins, LDL; D024101:Mitochondrial Proteins; C495137:OLR1 protein, human; D016376:Oligonucleotides, Antisense; D009842:Oligopeptides; D011506:Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011973:Receptors, LDL; D051131:Receptors, Oxidized LDL; D051127:Scavenger Receptors, Class E; C108637:aspartyl-glutamyl-valyl-aspartal; C403754:benzyloxycarbonyl-leucyl-glutamyl-histidyl-aspartic acid fluoromethyl ketone; C099252:oxidized low density lipoprotein; D045304:Cytochromes c; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases