15-Hydroperoxyeicosapentaenoic acid, but not eicosapentaenoic acid, shifts arachidonic acid away from cyclooxygenase pathway into acyl-CoA synthetase pathway in rabbit kidney medulla microsomes.
Under physiological conditions, small amounts of free arachidonic acid (AA) are released from membrane phospholipids, and cyclooxygenase (COX) and acyl-CoA synthetase (ACS) competitively act on this fatty acid to form prostaglandins (PGs) and arachidonoyl-CoA (AA-CoA). In the present study, we investigated the effects of eicosapentaenoic acid (EPA) and 15-hydroperoxyeicosapentaenoic acid (15-HPEPE) on the PG and AA-CoA formations from high and low concentrations of AA (60 and 5 microM) in rabbit kidney medulla microsomes. The kidney medulla microsomes were incubated with 60 or 5 microM [(14)C]-AA in 0.1M Tris/HCl buffer (pH 8.0) containing cofactors of COX (reduced glutathione and hydroquinone) and cofactors of ACS (ATP, MgCl(2) and CoA). After incubation, PG (as total PGs), AA-CoA and residual AA were separated by selective extraction using petroleum ether and ethyl acetate. EPA reduced the PG and AA-CoA formations from both 60 and 5 microM AA. In contrast, 15-HPEPE decreased the PG formation without affecting the AA-CoA formation from 60 microM AA, and increased the AA-CoA formation at the expense of PG formation when 5 microM AA was used as substrate concentration. The experiments utilizing Fe(2+) and an electron spin resonance (ESR) revealed that 15-HPEPE elicits these effects in the form of hydroperoxy adduct. These results suggest that 15-HPEPE, but not EPA, has the potential to shift AA away from COX pathway into ACS pathway at low substrate concentration (close to the physiological concentration of AA).
Sakuma
Satoru
S
Laboratory of Physiological Chemistry, Osaka University of Pharmaceutical Sciences, Takatsuki, Osaka 569-1094, Japan. sakuma@gly.oups.ac.jp
Usa
Kumiko
K
Fujimoto
Yohko
Y
D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism*; D003066:Coenzyme A Ligases / Q000378:metabolism*; D015118:Eicosapentaenoic Acid / Q000031:analogs & derivatives / Q000494:pharmacology*; D004578:Electron Spin Resonance Spectroscopy; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007501:Iron / Q000494:pharmacology; D007679:Kidney Medulla / Q000187:drug effects* / Q000378:metabolism*; D008297:Male; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism*; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism*; D011817:Rabbits; D015398:Signal Transduction / Q000187:drug effects; D020122:tert-Butylhydroperoxide / Q000494:pharmacology
D016718:Arachidonic Acid; D020122:tert-Butylhydroperoxide; D015118:Eicosapentaenoic Acid; D006861:Hydrogen Peroxide; D007501:Iron; D011451:Prostaglandin-Endoperoxide Synthases; D003066:Coenzyme A Ligases