Identification of 5-keto-(7E,9E,11Z,14Z)-eicosatetraenoic acid as a novel nonenzymatic rearrangement product of leukotriene A4.
Leukotriene A4 (LTA4), the reaction product of 5-lipoxygenase in human polymorphonuclear (PMN) leukocytes, is transformed both to LTB4 and a mixture of 5,6- and 5,12-dihydroxy-eicosatetraenoic acids (diHETE) via nonenzymatic hydrolysis. Evidence has been obtained that LTA4 is also converted to 5-keto-(7E,9E,11Z,14Z)-eicosatetraenoic acid (5-oxo-ETE). The compound was isolated from the products of the 5-lipoxygenase reaction and its structure elucidated by UV spectroscopy, LC-MS, two-dimensional [1H]NMR spectroscopy and chemical reduction to the corresponding alcohol. The 5-oxo-ETE represented about 14% of the LTA4 hydrolysis products as compared to 72 and 14% for the 5,12-diHETE and 5,6-diHETE, respectively. A similar profile of hydrolysis products was obtained after incubation of synthetic LTA4 in aqueous buffer. Human PMN leukocytes produced 5-oxo-ETE in an arachidonic acid-dependent and MK-886-inhibitable manner. The 5-oxo-ETE caused 50% inhibition of 5-lipoxygenase activity at 1 microM. These results demonstrate that the nonenzymatic conversion of LTA4, in addition to the previously described hydrolysis products, yields 5-oxo-ETE during both the 5-lipoxygenase reaction and arachidonic acid oxidation by human PMN leukocytes. They indicate that allylic epoxides can rearrange in aqueous media at physiological pH to spontaneously form beta,gamma-unsaturated ketones.
Gravel
J
J
Biochemistry Department, Merck Frosst Centre for Therapeutic Research, Kirkland, Québec, Canada.
Falgueyret
J P
JP
Yergey
J
J
Trimble
L
L
Riendeau
D
D
D000818:Animals; D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism*; D016718:Arachidonic Acid / Q000097:blood; D001095:Arachidonic Acids / Q000378:metabolism / Q000494:pharmacology; D002460:Cell Line; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007313:Insecta; D007700:Kinetics; D017572:Leukotriene A4 / Q000737:chemistry* / Q000378:metabolism; D020024:Leukotriene Antagonists; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet; D014162:Transfection; D002722:Chlorobenzenes
D001094:Arachidonate 5-Lipoxygenase; D016718:Arachidonic Acid; D001095:Arachidonic Acids; D007211:Indoles; D017572:Leukotriene A4; D020024:Leukotriene Antagonists; D011994:Recombinant Proteins; C060893:MK-886; D002722:Chlorobenzenes; C083764:5-ketoeicosatetraenoic acid