Nitro-fatty acid metabolome: saturation, desaturation, beta-oxidation, and protein adduction.
Nitrated derivatives of fatty acids (NO2-FA) are pluripotent cell-signaling mediators that display anti-inflammatory properties. Current understanding of NO2-FA signal transduction lacks insight into how or if NO2-FA are modified or metabolized upon formation or administration in vivo. Here the disposition and metabolism of nitro-9-cis-octadecenoic (18:1-NO2) acid was investigated in plasma and liver after intravenous injection in mice. High performance liquid chromatography-tandem mass spectrometry analysis showed that no 18:1-NO2 or metabolites were detected under basal conditions, whereas administered 18:1-NO2 is rapidly adducted to plasma thiol-containing proteins and glutathione. NO2-FA are also metabolized via beta-oxidation, with high performance liquid chromatography-tandem mass spectrometry analysis of liver lipid extracts of treated mice revealing nitro-7-cis-hexadecenoic acid, nitro-5-cis-tetradecenoic acid, and nitro-3-cis-dodecenoic acid and corresponding coenzyme A derivatives of 18:1-NO2 as metabolites. Additionally, a significant proportion of 18:1-NO2 and its metabolites are converted to nitroalkane derivatives by saturation of the double bond, and to a lesser extent are desaturated to diene derivatives. There was no evidence of the formation of nitrohydroxyl or conjugated ketone derivatives in organs of interest, metabolites expected upon 18:1-NO2 hydration or nitric oxide (*NO) release. Plasma samples from treated mice had significant extents of protein-adducted 18:1-NO2 detected by exchange to added beta-mercaptoethanol. This, coupled with the observation of 18:1-NO2 release from glutathione-18:1-NO2 adducts, supports that reversible and exchangeable NO2-FA-thiol adducts occur under biological conditions. After administration of [3H]18:1-NO2, 64% of net radiolabel was recovered 90 min later in plasma (0.2%), liver (18%), kidney (2%), adipose tissue (2%), muscle (31%), urine (6%), and other tissue compartments, and may include metabolites not yet identified. In aggregate, these findings show that electrophilic FA nitroalkene derivatives (a) acquire an extended half-life by undergoing reversible and exchangeable electrophilic reactions with nucleophilic targets and (b) are metabolized predominantly via saturation of the double bond and beta-oxidation reactions that terminate at the site of acyl-chain nitration.
Rudolph
Volker
V
Department of Pharmacology & Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.
Schopfer
Francisco J
FJ
Khoo
Nicholas K H
NK
Rudolph
Tanja K
TK
Cole
Marsha P
MP
Woodcock
Steven R
SR
Bonacci
Gustavo
G
Groeger
Alison L
AL
Golin-Bisello
Franca
F
Chen
Chen-Shan
CS
Baker
Paul R S
PR
Freeman
Bruce A
BA
D000818:Animals; D005227:Fatty Acids / Q000378:metabolism* / Q000494:pharmacology*; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D008099:Liver / Q000378:metabolism*; D051379:Mice; D009574:Nitro Compounds / Q000378:metabolism* / Q000494:pharmacology*; D009928:Organ Specificity / Q000187:drug effects; D010084:Oxidation-Reduction / Q000187:drug effects; D010949:Plasma / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects
D005227:Fatty Acids; D009574:Nitro Compounds; D011506:Proteins; D005978:Glutathione