title: Role of epoxyeicosatrienoic acids as autocrine metabolites in glutamate-mediated K+ signaling in perivascular astrocytes.
abstract: Epoxyeicosatrienoic acids (EETs), synthesized and released by astrocytes in response to glutamate, are known to play a pivotal role in neurovascular coupling. In vascular smooth muscle cells (VSMC), EETs activate large-conductance, Ca(2+)-activated K(+) (BK) channels resulting in hyperpolarization and vasodilation. However, the functional role and mechanism of action for glial-derived EETs are still to be determined. In this study, we evaluated the effect of the synthetic EET analog 11-nonyloxy-undec-8(Z)-enoic acid (NUD-GA) on outward K(+) currents mediated by calcium-activated K(+) channels. Addition of NUD-GA significantly increased intracellular Ca(2+) and outward K(+) currents in perivascular astrocytes. NUD-GA-induced currents were significantly inhibited by BK channel blockers paxilline and tetraethylammonium (TEA) (23.4 ± 2.4%; P < 0.0005). Similarly, NUD-GA-induced currents were also significantly inhibited in the presence of the small-conductance Ca(2+)-activated K(+) channel inhibitor apamin along with a combination of blockers against glutamate receptors (12.8 ± 2.70%; P < 0.05). No changes in outward currents were observed in the presence of the channel blocker for intermediate-conductance K(+) channels TRAM-34. Blockade of the endogenous production of EETs with N-methylsulfonyl-6-(2-propargyloxyphenyl)hexanamide (MS-PPOH) significantly blunted (dl)-1-aminocyclopentane-trans-1,3-dicarboxylic acid (t-ACPD)-induced outward K(+) currents (P < 0.05; n = 6). Both NUD-GA and t-ACPD significantly increased BK channel single open probability; the later was blocked following MS-PPOH incubation. Our data supports the idea that EETs are potent K(+) channel modulators in cortical perivascular astrocytes and further suggest that these metabolites may participate in NVC by modulating the levels of K(+) released at the gliovascular space.
authors.affiliation: Department of Physiology, Medical College of Georgia, Augusta, Georgia 30912, USA.
authors.forename: Haruki
authors.initials: H
authors.lastname: Higashimori
authors.forename: Víctor M
authors.initials: VM
authors.lastname: Blanco
authors.forename: Vengopal Raju
authors.initials: VR
authors.lastname: Tuniki
authors.forename: John R
authors.initials: JR
authors.lastname: Falck
authors.forename: Jessica A
authors.initials: JA
authors.lastname: Filosa
mesh_terms: D000577:Amides / Q000378:metabolism; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics / Q000378:metabolism; D001253:Astrocytes / Q000166:cytology / Q000378:metabolism*; D019898:Autocrine Communication / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D000072467:Cytochrome P450 Family 2; D004537:Eicosanoic Acids / Q000737:chemistry / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000378:metabolism*; D011720:Pyrazoles / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000502:physiology*; D039181:Steroid 16-alpha-Hydroxylase / Q000235:genetics / Q000378:metabolism
chemical_list: D000577:Amides; D004537:Eicosanoic Acids; C121756:N-methylsulfonyl-6-(2-propargyloxyphenyl)hexanamide; D015221:Potassium Channels; D011720:Pyrazoles; C411671:TRAM 34; D018698:Glutamic Acid; D001189:Aryl Hydrocarbon Hydroxylases; C450279:CYP2C11 protein, rat; D000072467:Cytochrome P450 Family 2; D039181:Steroid 16-alpha-Hydroxylase; D002118:Calcium