Characterization of novel radicals from COX-catalyzed arachidonic acid peroxidation.
The peroxidation of arachidonic acid (AA) catalyzed by cyclooxygenase (COX) is a well-known free radical-mediated process that forms many bioactive products. Because of a lack of appropriate methodologies, however, no comprehensive structural evidence has been found previously for the formation of COX-mediated and AA-derived free radicals. Here we have used a combination of LC/ESR and LC/MS with a spin trap, alpha-[4-pyridyl-1-oxide]-N-tert-butylnitrone (POBN), to characterize the carbon-centered radicals formed from COX-catalyzed AA peroxidation in vitro, including cellular peroxidation in human prostate cancer cells (PC-3). Three types of radicals with numerous isomers were trapped by POBN as ESR-active peaks and MS-active ions of m/z 296, 448, and 548, all stemming from PGF(2)-type alkoxyl radicals. One of these was a novel radical centered on the carbon-carbon double bond nearest the PGF ring, caused by an unusual beta-scission of PGF(2)-type alkoxyl radicals. The complementary nonradical product was 1-hexanol, another novel beta-scission product, instead of the more common aldehyde. The characterization of these novel products formed from in vitro peroxidation provides a new mechanistic insight into COX-catalyzed AA peroxidation in cancer biology.
Yu
Qingfeng
Q
Department of Analytical Chemistry, China Pharmaceutical University, Nanjing 210009, China.
Purwaha
Preeti
P
Ni
Kunyi
K
Sun
Chengwen
C
Mallik
Sanku
S
Qian
Steven Y
SY
D016718:Arachidonic Acid / Q000378:metabolism*; D002853:Chromatography, Liquid; D051546:Cyclooxygenase 2 / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D015227:Lipid Peroxidation / Q000187:drug effects / Q000502:physiology*; D013058:Mass Spectrometry; D008954:Models, Biological; D011725:Pyridines / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D005609:Free Radicals; D011725:Pyridines; C043438:alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone; D016718:Arachidonic Acid; D051546:Cyclooxygenase 2