The formation of some antigenic epitopes in oxidized human low-density lipoprotein is inhibited by nitric oxide.
NO and NO-donors are able to inhibit the peroxidation of polyunsaturated fatty acids in human low-density lipoproteins (LDL) exposed to Cu+2. Here we report that 1-hydroxy-2-oxo-3,3-bis(3-aminoethyl)-1-triazene (NOC-18), a compound which releases NO at low rate in aqueous solutions, powerfully inhibits the peroxidation of polyunsaturated fatty acids, tryptophan loss, the formation of fluorescent aldehydic adducts in apo B100 and the increase of electrophoretic mobility in isolated LDL undergoing oxidation. The inhibitory effect is not restricted to Cu+2-induced peroxidation but is also detectable with other oxidizing conditions such as the free radical generator 2,2'-azobis-(2-amidino propane) hydrochloride (AAPH), the combination of horseradish peroxidase and H2O2 (HRP), and peroxynitrite (ONOO-). The recognition of Cu+2-, AAPH-, and ONOO(-)-modified LDL by specific autoantibodies present in serum of atherosclerotic patients is almost completely inhibited when the oxidation procedure is performed in the presence of NOC-18. However, NOC-18 is completely ineffective in preventing the formation of recognizable antigens in HRP-modified LDL. These findings suggest that NO may efficiently prevent the formation of some, but not all, the antigenic epitopes recognized by human autoantibodies and thus likely formed during in vivo LDL oxidation.
Seccia
M
M
Department of Medical Sciences, University of Torino, Novara, Italy.
Perugini
C
C
Bellomo
G
G
D001161:Arteriosclerosis / Q000209:etiology / Q000276:immunology / Q000378:metabolism; D001323:Autoantibodies / Q000097:blood; D001324:Autoantigens / Q000378:metabolism; D003300:Copper / Q000494:pharmacology; D000939:Epitopes / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D015227:Lipid Peroxidation / Q000187:drug effects; D008077:Lipoproteins, LDL / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism / Q000494:pharmacology*; D009603:Nitroso Compounds / Q000494:pharmacology; D010084:Oxidation-Reduction
D001323:Autoantibodies; D001324:Autoantigens; D000939:Epitopes; D008077:Lipoproteins, LDL; C093285:NOC 18; D009603:Nitroso Compounds; D009569:Nitric Oxide; D003300:Copper