Native low-density lipoprotein increases endothelial cell nitric oxide synthase generation of superoxide anion.
To examine mechanisms by which native low-density lipoprotein (n-LDL) perturbs endothelial cell (EC) release of superoxide anion (O2-) and nitric oxide (NO), ECs were incubated with n-LDL at 240 mg cholesterol per deciliter for 4 days with media changes every 24 hours. n-LDL increases EC release of O2- by more than fourfold and increases nitrite production by 57%. In the conditioned media from day-4 incubations, n-LDL increases total nitrogen oxides 20 times control EC (C-EC) levels. However, n-LDL did not alter EC NO synthase (eNOS) enzyme activity as measured by the [3H]citrulline assay. N omega-Nitro-L-arginine methyl ester, a specific inhibitor of eNOS activity, increases C-EC release of O2- by > 300% but decreases LDL-treated EC (LDL-EC) release by > 95%. L-Arginine inhibits the release of O2- from LDL-ECs by > 95% but did not effect C-EC release of O2-. Indomethacin and SKF 525A partially attenuate LDL-induced increases in O2- production by approximately 50% and 30%, respectively. Thus, n-LDL increases O2- and NO production, which increases the likelihood of the formation of peroxynitrite (ONOO-), a potent oxidant. n-LDL increases the levels of nitrotyrosine, a stable oxidation product of ONOO-, and tyrosine by approximately 50%. In spite of this increase in oxidative metabolism, analysis of thiobarbituric acid substances reveals that no significant changes in the oxidation of n-LDL occur during the 24-hour incubations with ECs.(ABSTRACT TRUNCATED AT 250 WORDS)
Pritchard
K A
KA
Department of Pathology, Medical College of Wisconsin, Milwaukee 53226, USA.
Groszek
L
L
Smalley
D M
DM
Sessa
W C
WC
Wu
M
M
Villalon
P
P
Wolin
M S
MS
Stemerman
M B
MB
D000594:Amino Acid Oxidoreductases / Q000502:physiology*; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D019331:NG-Nitroarginine Methyl Ester; D009569:Nitric Oxide / Q000502:physiology; D019001:Nitric Oxide Synthase; D013481:Superoxides / Q000378:metabolism*
D008077:Lipoproteins, LDL; D013481:Superoxides; D009569:Nitric Oxide; D001120:Arginine; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases; D019331:NG-Nitroarginine Methyl Ester