Lipoprotein lipase is nitrated in vivo after lipopolysaccharide challenge.
Lipopolysaccharide (LPS) administration down-regulates lipoprotein lipase (LPL) activity at the posttranscriptional level. Hypertriglyceridemia is the main metabolic consequence of this fall in LPL activity and is presumably involved in the innate immune response to infection. Nitric oxide (NO) has been implicated in LPS-induced down-regulation of LPL activity, but whether its effects are direct or indirect remains unclear. Here we examined the potential nitration of LPL in vivo in response to LPS challenge in rats. We found hypertriglyceridemia, iNOS expression, NO overproduction, and a generalized decrease in LPL activity in tissues 6 h after LPS administration. LPL sensitivity to nitration was first explored by in vitro exposure of bovine LPL to peroxynitrite, a reactive nitrogen species (RNS). Nitration was confirmed by anti-nitrotyrosine Western blot and subsequent identification of specific nitrotyrosine-containing LPL sequences by tandem mass spectrometry. Further analysis by targeted mass spectrometry revealed three in vivo-nitrated tyrosine residues in heart LPL from LPS-challenged rats. This is the first study to identify nitrated tyrosine residues in LPL, both in vitro and in vivo, and it demonstrates that LPL is a target for RNS in endotoxemia. These results indicate that LPL nitration may be a new mechanism of LPL activity regulation in vivo.
Casanovas
Albert
A
Departament de Bioquímica i Biologia Molecular, Facultat de Biologia, Universitat de Barcelona, E-08028 Barcelona, Spain.
Carrascal
Montserrat
M
Abián
Joaquín
J
López-Tejero
M Dolores
MD
Llobera
Miquel
M
D000818:Animals; D002417:Cattle; D019446:Endotoxemia / Q000139:chemically induced / Q000201:enzymology* / Q000276:immunology; D015228:Hypertriglyceridemia / Q000209:etiology / Q000378:metabolism; D008070:Lipopolysaccharides / Q000008:administration & dosage / Q000378:metabolism*; D008071:Lipoprotein Lipase / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D008297:Male; D009206:Myocardium / Q000201:enzymology* / Q000276:immunology; D009569:Nitric Oxide / Q000737:chemistry / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000096:biosynthesis / Q000235:genetics; D018384:Oxidative Stress; D030421:Peroxynitrous Acid / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D053719:Tandem Mass Spectrometry; D014443:Tyrosine / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism
D008070:Lipopolysaccharides; D030421:Peroxynitrous Acid; D009569:Nitric Oxide; C002744:3-nitrotyrosine; D014443:Tyrosine; D052247:Nitric Oxide Synthase Type II; D008071:Lipoprotein Lipase