title: The TRPV4 cation channel mediates stretch-evoked Ca2+ influx and ATP release in primary urothelial cell cultures.
abstract: Transient receptor potential channels have recently been implicated in physiological functions in a urogenital system. In this study, we investigated the role of transient receptor potential vanilloid 4 (TRPV4) channels in a stretch sensing mechanism in mouse primary urothelial cell cultures. The selective TRPV4 agonist, 4alpha-phorbol 12,13-didecanoate (4alpha-PDD) evoked Ca(2+) influx in wild-type (WT) urothelial cells, but not in TRPV4-deficient (TRPV4KO) cells. We established a cell-stretch system to investigate stretch-evoked changes in intracellular Ca(2+) concentration and ATP release. Stretch stimulation evoked intracellular Ca(2+) increases in a stretch speed- and distance-dependent manner in WT and TRPV4KO cells. In TRPV4KO urothelial cells, however, the intracellular Ca(2+) increase in response to stretch stimulation was significantly attenuated compared with that in WT cells. Stretch-evoked Ca(2+) increases in WT urothelium were partially reduced in the presence of ruthenium red, a broad TRP channel blocker, whereas that in TRPV4KO cells did not show such reduction. Potent ATP release occurred following stretch stimulation or 4alpha-PDD administration in WT urothelial cells, which was dramatically suppressed in TRPV4KO cells. Stretch-dependent ATP release was almost completely eliminated in the presence of ruthenium red or in the absence of extracellular Ca(2+). These results suggest that TRPV4 senses distension of the bladder urothelium, which is converted to an ATP signal in the micturition reflex pathway during urine storage.
authors.affiliation: Department of Urology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Yamanashi 409-3898, Japan.
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Mochizuki
authors.forename: Takaaki
authors.initials: T
authors.lastname: Sokabe
authors.forename: Isao
authors.initials: I
authors.lastname: Araki
authors.forename: Kayoko
authors.initials: K
authors.lastname: Fujishita
authors.forename: Koji
authors.initials: K
authors.lastname: Shibasaki
authors.forename: Kunitoshi
authors.initials: K
authors.lastname: Uchida
authors.forename: Keiji
authors.initials: K
authors.lastname: Naruse
authors.forename: Schuichi
authors.initials: S
authors.lastname: Koizumi
authors.forename: Masayuki
authors.initials: M
authors.lastname: Takeda
authors.forename: Makoto
authors.initials: M
authors.lastname: Tominaga
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008954:Models, Biological; D009130:Muscle, Smooth / Q000378:metabolism / Q000473:pathology*; D010703:Phorbol Esters / Q000378:metabolism; D012430:Ruthenium Red / Q000494:pharmacology; D050916:TRPV Cation Channels / Q000378:metabolism / Q000502:physiology*; D014554:Urination; D019459:Urothelium / Q000378:metabolism*
chemical_list: D010703:Phorbol Esters; D050916:TRPV Cation Channels; C486576:Trpv4 protein, mouse; D012430:Ruthenium Red; C008876:phorbol-12,13-didecanoate; D000255:Adenosine Triphosphate; D002118:Calcium