Inhibition of oxidized low-density lipoprotein-induced apoptosis in endothelial cells by nitric oxide. Peroxyl radical scavenging as an antiapoptotic mechanism.
Proatherogenic oxidized low-density lipoprotein (oxLDL) induces endothelial apoptosis. We investigated the anti-apoptotic effects of intracellular and extracellular nitric oxide (*NO) donors, iron chelators, cell-permeable superoxide dismutase (SOD), glutathione peroxidase mimetics, and nitrone spin traps. Peroxynitrite (ONOO-)-modified oxLDL induced endothelial apoptosis was measured by DNA fragmentation, TUNEL assay, and caspase-3 activation. Results indicated the following: (i) the lipid fraction of oxLDL was primarily responsible for endothelial apoptosis. (ii) Endothelial apoptosis was potently inhibited by *NO donors and lipophilic phenolic antioxidants. OxLDL severely depleted Bcl-2 levels in endothelial cells and *NO donors restored Bcl-2 protein in oxLDL-treated cells. (iii) The pretreatment of a lipid fraction derived from oxLDL with sodium borohydride or potassium iodide completely abrogated apoptosis in endothelial cells, suggesting that lipid hydroperoxides induce apoptosis. (iv) Metalloporphyrins dramatically inhibited oxLDL-induced apoptosis in endothelial cells. Neither S-nitrosation of caspase-3 nor induction of Hsp70 appeared to play a significant role in the antiapoptotic mechanism of *NO in oxLDL-induced endothelial apoptosis. We propose that cellular lipid peroxyl radicals or lipid hydroperoxides induce an apoptotic signaling cascade in endothelial cells exposed to oxLDL, and that *NO inhibits apoptosis by scavenging cellular lipid peroxyl radicals.
Biophysics Research Institute and Free Radical Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
S
S
Kotamraju
N
N
Hogg
J
J
Joseph
L K
LK
Keefer
B
B
Kalyanaraman
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D001011:Aorta; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002374:Catalase / Q000494:pharmacology; D002417:Cattle; D002463:Cell Membrane Permeability; D002478:Cells, Cultured; D053938:DNA Fragmentation; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D004789:Enzyme Activation; D005979:Glutathione Peroxidase / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D020287:In Situ Nick-End Labeling; D007502:Iron Chelating Agents / Q000494:pharmacology; D007700:Kinetics; D008077:Lipoproteins, LDL / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D008954:Models, Biological; D009566:Nitrates / Q000494:pharmacology*; D009569:Nitric Oxide / Q000494:pharmacology / Q000502:physiology*; D020030:Nitric Oxide Donors / Q000494:pharmacology*; D016877:Oxidants / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism / Q000494:pharmacology
D000975:Antioxidants; D018840:HSP70 Heat-Shock Proteins; D007502:Iron Chelating Agents; D008077:Lipoproteins, LDL; D009566:Nitrates; D020030:Nitric Oxide Donors; D016877:Oxidants; D019253:Proto-Oncogene Proteins c-bcl-2; C099252:oxidized low density lipoprotein; C039642:peroxynitric acid; D009569:Nitric Oxide; D002374:Catalase; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase; D053148:Caspase 3; D020169:Caspases