QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: jpet.108.144717v1 328/1/351    most recent Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Godlewski, G. Articles by Kunos, G. Search for Related Content PubMed PubMed Citation Articles by Godlewski, G. Articles by Kunos, G.

CARDIOVASCULAR

The Endogenous Brain Constituent N-Arachidonoyl L-Serine Is an Activator of Large Conductance Ca²⁺-Activated K⁺ Channels

Laboratories of Physiologic Studies (G.G., L.O., D.O.-H., F.M.M., J.H.-W., J.L., P.P., P.M., G.K.) and Integrative Neuroscience (M.I.D., L.Z., D.M.L.), National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland; Organix, Inc., Woburn, Massachusetts (R.K.R.); and Department of Medicinal Chemistry, Hebrew University, Jerusalem, Israel (G.M.)

The novel endocannabinoid-like lipid N-arachidonoyl L-serine (ARA-S) causes vasodilation through both endothelium-dependent and -independent mechanisms. We have analyzed the vasorelaxant effect of ARA-S in isolated vascular preparations and its effects on Ca²⁺-activated K⁺ currents in human embryonic kidney cells stably transfected with the -subunit of the human, large conductance Ca⁺-activated K⁺ (BK_Ca) channel [human embryonic kidney (HEK) 293hSlo cells]. ARA-S caused relaxation of rat isolated, intact and denuded, small mesenteric arteries preconstricted with (R)-(-)-1-(3-hydroxyphenyl)-2-methylaminoethanol hydrochloride (pEC₅₀, 5.49 and 5.14, respectively), whereas it caused further contraction of vessels preconstricted with KCl (pEC₅₀, 5.48 and 4.82, respectively). Vasorelaxation by ARA-S was inhibited by 100 nM iberiotoxin. In human embryonic kidney cells stably transfected with the -subunit of the human BK_Ca channel cells, ARA-S and its enantiomer, N-arachidonoyl-D-serine, enhanced the whole-cell outward K⁺ current with similar potency (pEC₅₀, 5.63 and 5.32, respectively). The potentiation was not altered by the β₁ subunit or mediated by ARA-S metabolites, stimulation of known cannabinoid receptors, G proteins, protein kinases, or Ca²⁺-dependent processes; it was lost after patch excision or after membrane cholesterol depletion but was restored after cholesterol reconstitution. BK_Ca currents were also enhanced by N-arachidonoyl ethanolamide (pEC₅₀, 5.27) but inhibited by another endocannabinoid, O-arachidonoyl ethanolamine (pIC₅₀, 6.35), or by the synthetic cannabinoid O-1918 [(-)-1,3-dimethoxy-2-(3-3,4-trans-p-menthadien-(1,8)-yl)-orcinol] (pIC₅₀, 6.59), which blocks ARA-S-induced vasodilation. We conclude the following. 1) ARA-S directly activates BK_Ca channels. 2) This interaction does not involve cannabinoid receptors or cytosolic factors but is dependent on the presence of membrane cholesterol. 3) Direct BK_Ca channel activation probably contributes to the endothelium-independent component of ARA-S-induced mesenteric vasorelaxation. 4) O-1918 is a BK_Ca channel inhibitor.

Address correspondence to: Grzegorz Godlewski, National Institute on Alcohol Abuse and Alcoholism, 5625 Fishers Lane, Bethesda, MD 20892-9413. E-mail: godlewskig{at}mail.nih.gov