Thiyl radicals in biosystems: inhibition of the prostaglandin metabolism by the cis-trans-isomerization of arachidonic acid double bonds.
This paper describes parallel and comparative experiments on the enzymatic cyclooxygenase (COX) driven conversion of arachidonic acid (AA, all-cis-5,8,11,14-eicosatetraenoic acid) into prostaglandins by using pure arachidonic acid and AA samples containing relatively small amounts of thiyl radical induced trans-isomers. The experiments were performed in a liquid aqueous model system using COX-1 as well as by the in vitro feeding of VD(3)-differentiated and LPS-stimulated promyelocytic HL-60 cells using the cell's own COX-2. In the model solution, all the different test methods used (oxygen consumption, ROS induced luminescence, and TMPD oxidation) indicated the greatly disproportionate, non-stoichiometric inhibition of the prostaglandin metabolism by the trans-isomers. Accordingly, measurements performed in the cell system gave comparable results: both luminescence ROS detection and the ELISA test on PGE(2) expression resulted in the strong inhibition of the prostaglandin metabolism. We interpret these findings as enzyme blocking caused by just one mono-trans-isomerized double bond of AA.
Kratzsch
Susanne
S
Institute of Zoology, University of Leipzig, Permoserstrasse 15, 04303 Leipzig, Germany.
Drössler
Karl
K
Sprinz
Helmut
H
Brede
Ortwin
O
D016718:Arachidonic Acid / Q000737:chemistry / Q000378:metabolism*; D051545:Cyclooxygenase 1; D016861:Cyclooxygenase Inhibitors / Q000737:chemistry / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D005609:Free Radicals / Q000737:chemistry; D018922:HL-60 Cells / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D008565:Membrane Proteins; D011451:Prostaglandin-Endoperoxide Synthases / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism*; D011453:Prostaglandins / Q000096:biosynthesis* / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism; D013237:Stereoisomerism; D013438:Sulfhydryl Compounds / Q000737:chemistry / Q000494:pharmacology*
D016861:Cyclooxygenase Inhibitors; D005609:Free Radicals; D007527:Isoenzymes; D008565:Membrane Proteins; D011453:Prostaglandins; D013438:Sulfhydryl Compounds; D016718:Arachidonic Acid; D051545:Cyclooxygenase 1; C496511:PTGS1 protein, human; D011451:Prostaglandin-Endoperoxide Synthases