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Cytochrome P450-dependent eicosapentaenoic acid metabolites are novel BK channel activators

Authors

  • B. Lauterbach
  • E. Barbosa-Sicard
  • M.H. Wang
  • H. Honeck
  • E. Kaergel
  • J. Theuer
  • M.L. Schwartzman
  • H. Haller
  • F.C. Luft
  • M. Gollasch
  • W.H. Schunck

Journal

  • Hypertension

Citation

  • Hypertension 39 (2): 609-613

Abstract

  • P450-dependent arachidonic acid (AA) metabolites regulate arterial tone by modulating calcium-activated (BK) potassium channels in vascular smooth muscle cells (VSMC), Because eicosapentaenoic acid (EPA) has been reported to improve vascular function, we tested the hypothesis that P450-dependent epoxygenation of EPA produces alternative vasoactive compounds. We synthesized the 5 regioisomeric epoxyeicosattrienoic acids (EETeTr) and examined them for effects on K+ currents in rat cerebral artery VSMCs with the patch-clamp technique. 11(R),12(S)-epoxyeicosatrienoic acid (50 nmol/L) was used for comparison and stimulated K+ currents 6-fold at +60 mV. However, 17(R),18(S)-EETeTr elicited a more than 14-fold increase, 17(S),18(R)-EET and the remaining four regioisomers were inactive. The effect of 17(R),18(S)-EETeTr was blocked by tetraethylammonium but not by 4-aminopyridine. VSMCs expressed P450s 4A1 and 4A3. Recombinant P450 4A1 hydroxylated EPA at C-19 and C-20 and epoxygenated the 17,18-double bond, yielding the R, S- and S, R-enantiomers in a ratio of 64:36. We conclude that 17(R),18(S)-EETeTr represents a novel, potent activator of BK potassium channels. Furthermore, this metabolite can be directly produced in VSMCs. We suggest that 17(R),18(S)-EETeTr may function as an important hyperpolarizing factor, particularly with EPA-rich diets.