Hypochlorite-oxidized low density lipoproteins reduce production and bioavailability of nitric oxide in RAW 264.7 macrophages by distinct mechanisms.
Oxidative modification of low density lipoproteins is thought to play a pivotal role in the development and exacerbation of atherosclerosis and atherogenesis, and is believed to be closely associated with alterations in the vascular production of nitric oxide (NO). Previous work has shown that several products emerging from lipid peroxidation (e.g. lipid hydroperoxides, lysophospholipids, oxidized cholesterol) are able to reduce NO production in macrophages. The naturally occurring oxidant hypochlorite has been shown to be responsible for the in vivo formation of hypochlorite-oxidized LDL and such OxLDL are known to lack lipid peroxidation products. In this work we demonstrate that hypochlorite-oxidized LDL mediate profound effects on lipopolysaccharide-induced nitric oxide production in RAW 264.7 macrophages. By means of the membrane-permeable NO indicator 4,5-diaminofluorescein diacetate, we are able to show decreased levels of intracellular authentic nitric oxide following incubation with hypochlorite-oxidized LDL. The observed effects are dose-dependent and comparable to results obtained in the presence of the NOS inhibitor NG-monomethyl-L-arginine. This marked reduction of intracellular NO is accompanied by a dose-dependent inhibition of inducible nitric oxide synthase (iNOS) protein and mRNA expression. Furthermore, hyp-OxLDL lead to the generation of peroxynitrite, thereby also reducing bioavailability of NO. By mediating these effects on production and bioavailability of NO, hyp-OxLDL might also contribute to atherogenesis by reducing the antiatherogenic effects of nitric oxide.
Center for Physiology and Pathophysiology, Institute of Physiology, Medical University of Vienna, and Department of Urology, Rudolfstiftung Hospital, Vienna, Austria. werner.schmid@meduniwien.ac.at
Werner
W
Schmid
Alexander
A
Lee
Jinhi
J
Son
Elisabeth
E
Koller
Ivo
I
Volf
D000818:Animals; D002460:Cell Line; D015536:Down-Regulation; D006801:Humans; D006997:Hypochlorous Acid / Q000494:pharmacology*; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D051379:Mice; D009569:Nitric Oxide / Q000096:biosynthesis / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D016877:Oxidants / Q000494:pharmacology*; D030421:Peroxynitrous Acid / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism
D008077:Lipoproteins, LDL; D009573:Nitrites; D016877:Oxidants; D012333:RNA, Messenger; C099252:oxidized low density lipoprotein; D030421:Peroxynitrous Acid; D009569:Nitric Oxide; D006997:Hypochlorous Acid; D052247:Nitric Oxide Synthase Type II