Oxygenation by COX-2 (cyclo-oxygenase-2) of 3-HETE (3-hydroxyeicosatetraenoic acid), a fungal mimetic of arachidonic acid, produces a cascade of novel bioactive 3-hydroxyeicosanoids.
Cyclo-oxygenases-1/2 (COX-1/2) catalyse the oxygenation of AA (arachidonic acid) and related polyunsaturated fatty acids to endoperoxide precursors of prostanoids. COX-1 is referred to as a constitutive enzyme involved in haemostasis, whereas COX-2 is an inducible enzyme expressed in inflammatory diseases and cancer. The fungus Dipodascopsis uninucleata has been shown by us to convert exogenous AA into 3(R)-HETE [3(R)-hydroxy-5Z,8Z,11Z,14Z-eicosatetraenoic acid]. 3R-HETE is stereochemically identical with AA, except that a hydroxy group is attached at its C-3 position. Molecular modelling studies with 3-HETE and COX-1/2 revealed a similar enzyme-substrate structure as reported for AA and COX-1/2. Here, we report that 3-HETE is an appropriate substrate for COX-1 and -2, albeit with a lower activity of oxygenation than AA. Oxygenation of 3-HETE by COX-2 produced a novel cascade of 3-hydroxyeicosanoids, as identified with EI (electron impact)-GC-MS, LC-MS-ES (electrospray) and LC-MS-API (atmospheric pressure ionization) methods. Evidence for in vitro production of 3-hydroxy-PGE2 (3-hydroxy-prostaglandin E2) was obtained upon infection of HeLa cells with Candida albicans at an MOI (multiplicity of infection) of 100. Analogous to interaction of AA and aspirin-treated COX-2, 3-HETE was transformed by acetylated COX-2 to 3,15-di-HETE (3,15-dihydroxy-HETE), whereby C-15 showed the (R)-stereochemistry. 3-Hydroxy-PGs are potent biologically active compounds. Thus 3-hydroxy-PGE2 induced interleukin-6 gene expression via the EP3 receptor (PGE2 receptor 3) in A549 cells, and raised cAMP levels via the EP4 receptor in Jurkat cells. Moreover, 3R,15S-di-HETE triggered the opening of the K+ channel in HTM (human trabecular meshwork) cells, as measured by the patch-clamp technique. Since many fatty acid disorders are associated with an 'escape' of 3-hydroxy fatty acids from the b-oxidation cycle, the production of 3-hydroxyeicosanoids may be critical in modulation of effects of endogenously produced eicosanoids.
Ciccoli
Roberto
R
Eicosanoid Research Division, Department of Gynecology, University Medical Centre, Benjamin Franklin, Free University Berlin, D-12200 Berlin, Germany.
Sahi
Shakti
S
Singh
Sandhya
S
Prakash
Hridayesh
H
Zafiriou
Maria-Patapia
MP
Ishdorj
Ganchimeg
G
Kock
Johan L F
JL
Nigam
Santosh
S
D000230:Adenocarcinoma / Q000201:enzymology; D000818:Animals; D002176:Candida albicans / Q000187:drug effects; D002460:Cell Line; D051545:Cyclooxygenase 1 / Q000378:metabolism; D051546:Cyclooxygenase 2 / Q000378:metabolism*; D004594:Electrophysiology; D006367:HeLa Cells; D006801:Humans; D006893:Hydroxyeicosatetraenoic Acids / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D007700:Kinetics; D018716:Molecular Mimicry; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D012756:Sheep; D013379:Substrate Specificity; D014129:Trabecular Meshwork / Q000378:metabolism
D006893:Hydroxyeicosatetraenoic Acids; C069265:3-hydroxy-5,8,11,14-eicosatetraenoic acid; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D010100:Oxygen