title: Role of cytochrome P450-dependent transient receptor potential V4 activation in flow-induced vasodilatation.
abstract: OBJECTIVE
  Fluid shear stress elicits endothelium-dependent vasodilatation via nitric oxide and prostacyclin-dependent and -independent mechanisms. The latter includes the opening of Ca(2+)-operated potassium channels by cytochrome P450 (CYP) epoxygenase-derived epoxyeicosatrienoic acids (EETs) leading to endothelial hyperpolarization. We previously reported that EETs activate the transient receptor potential (TRP) V4 channel in vascular endothelial cells and that Ca(2+) influx in these cells in response to mechanical stimuli is dependent on the activation of CYP epoxygenases. We therefore hypothesized that the TRPV4 channel is involved in the flow-induced vasodilatation attributed to the endothelium-derived hyperpolarizing factor (EDHF).
  
  
  RESULTS
  In the presence of N(omega)-nitro-l-arginine methyl ester and diclofenac, precontracted mouse carotid arteries displayed a considerable vasodilatation in response to step-wise increases in luminal flow. The EDHF-mediated, flow-induced vasodilatation could be inhibited by the epoxygenase inhibitor MS-PPOH, was abolished after down-regulation of CYP epoxygenases in tissue culture, and could be restored by viral expression of CYP2C9 in the endothelium. The TRPV4-channel inhibitor ruthenium red (RuR) inhibited the EDHF-mediated flow response, but the combination of MS-PPOH and RuR had no further effect. RuR also inhibited the response in CYP2C9-overexpressing vessels. Moreover, TRPV4-deficient mice demonstrated a blunted EDHF-mediated response to increases in luminal flow in comparison to their wild-type littermates, and the addition of MS-PPOH was without effect in these mice (up to 38 +/- 3% in TRPV4(-/-) vs. 57 +/- 6% in TRPV4(+/+), P < 0.01). In cultured human endothelial cells, exposure to fluid shear stress induced the translocation of the TRPV4 channel from a perinuclear localization to the cell membrane.
  
  
  CONCLUSIONS
  We conclude that the TRPV4 channel is involved in flow-induced, endothelium-dependent vasodilatation of murine carotid arteries. Moreover, the activation of the TRPV4 channel by flow requires an active CYP epoxygenase and the translocation of the channel to the cell membrane.
authors.affiliation: Vascular Signalling Group, Institut für Kardiovaskuläre Physiologie, Goethe-Universität, Theodor-Stern-Kai 7, D-60590 Frankfurt am Main, Germany.
authors.forename: Annemarieke E
authors.initials: AE
authors.lastname: Loot
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Popp
authors.forename: Beate
authors.initials: B
authors.lastname: Fisslthaler
authors.forename: Joris
authors.initials: J
authors.lastname: Vriens
authors.forename: Bernd
authors.initials: B
authors.lastname: Nilius
authors.forename: Ingrid
authors.initials: I
authors.lastname: Fleming
mesh_terms: D015126:8,11,14-Eicosatrienoic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D000818:Animals; D001685:Biological Factors / Q000378:metabolism; D002339:Carotid Arteries / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D003577:Cytochrome P-450 Enzyme System / Q000502:physiology*; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism; D011464:Epoprostenol / Q000378:metabolism; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009569:Nitric Oxide / Q000378:metabolism; D012039:Regional Blood Flow / Q000502:physiology*; D050916:TRPV Cation Channels / Q000235:genetics / Q000502:physiology*; D014664:Vasodilation / Q000502:physiology*
chemical_list: D001685:Biological Factors; D050916:TRPV Cation Channels; C486576:Trpv4 protein, mouse; C067410:endothelium-dependent hyperpolarization factor; D009569:Nitric Oxide; C040776:5,6-epoxy-8,11,14-eicosatrienoic acid; D003577:Cytochrome P-450 Enzyme System; D011464:Epoprostenol; D015126:8,11,14-Eicosatrienoic Acid