title: Characterization of free radicals formed from COX-catalyzed DGLA peroxidation.
abstract: Like arachidonic acid (AA), dihomo-γ-linolenic acid (DGLA) is a 20-carbon ω-6 polyunsaturated fatty acid and a substrate of cyclooxygenase (COX). Through free radical reactions, COX metabolizes DGLA and AA to form well-known bioactive metabolites, namely, the 1 and 2 series of prostaglandins (PGs1 and PGs2), respectively. Unlike PGs2, which are viewed as proinflammatory, PGs1 possess anti-inflammatory and anticancer activities. However, the mechanisms linking the PGs to their bioactivities are still unclear, and radicals generated in COX-DGLA have not been detected. To better understand PG biology and determine whether different reactions occur in COX-DGLA and COX-AA, we have used LC/ESR/MS with a spin trap, α-(4-pyridyl-1-oxide)-N-tert-butyl nitrone (POBN), to characterize the carbon-centered radicals formed from COX-DGLA in vitro, including cellular peroxidation. A total of five types of DGLA-derived radicals were characterized as POBN adducts: m/z 266, m/z 296, and m/z 550 (same as or similar to COX-AA) and m/z 324 and m/z 354 (exclusively from COX-DGLA). Our results suggest that C-15 oxygenation to form PGGs occurs in both COX-DGLA and COX-AA; however, C-8 oxygenation occurs exclusively in COX-DGLA. This new finding will be further investigated for its association with various bioactivities of PGs, with potential implications for inflammatory diseases.
authors.affiliation: Department of Analytical Chemistry, China Pharmaceutical University, Nanjing 210009, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Xiao
authors.forename: Yan
authors.initials: Y
authors.lastname: Gu
authors.forename: Preeti
authors.initials: P
authors.lastname: Purwaha
authors.forename: Kunyi
authors.initials: K
authors.lastname: Ni
authors.forename: Benedict
authors.initials: B
authors.lastname: Law
authors.forename: Sanku
authors.initials: S
authors.lastname: Mallik
authors.forename: Steven Y
authors.initials: SY
authors.lastname: Qian
mesh_terms: D015126:8,11,14-Eicosatrienoic Acid / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D000893:Anti-Inflammatory Agents / Q000378:metabolism; D000970:Antineoplastic Agents / Q000378:metabolism; D016718:Arachidonic Acid / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D002384:Catalysis; D045744:Cell Line, Tumor; D002853:Chromatography, Liquid; D003110:Colonic Neoplasms / Q000737:chemistry / Q000201:enzymology*; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals / Q000378:metabolism; D006801:Humans; D013058:Mass Spectrometry; D010084:Oxidation-Reduction; D010545:Peroxides / Q000378:metabolism*; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism*; D011453:Prostaglandins / Q000032:analysis* / Q000737:chemistry; D011725:Pyridines / Q000378:metabolism; D019097:Spin Trapping
chemical_list: D000893:Anti-Inflammatory Agents; D000970:Antineoplastic Agents; D005609:Free Radicals; D010545:Peroxides; D011453:Prostaglandins; D011725:Pyridines; C043438:alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone; D016718:Arachidonic Acid; D011451:Prostaglandin-Endoperoxide Synthases; D015126:8,11,14-Eicosatrienoic Acid