title: Activation of Trpv4 reduces the hyperproliferative phenotype of cystic cholangiocytes from an animal model of ARPKD.
abstract: OBJECTIVE
  In polycystic liver diseases, cyst formation involves cholangiocyte hyperproliferation. In polycystic kidney (PCK) rats, an animal model of autosomal-recessive polycystic kidney disease (ARPKD), decreased intracellular calcium [Ca(2+)](i) in cholangiocytes is associated with hyperproliferation. We recently showed transient receptor potential vanilloid 4 (Trpv4), a calcium-entry channel, is expressed in normal cholangiocytes and its activation leads to [Ca(2+)](i) increase. Thus, we hypothesized that pharmacologic activation of Trpv4 might reverse the hyperproliferative phenotype of PCK cholangiocytes.
  
  
  METHODS
  Trpv4 expression was examined in liver of normal and PCK rats, normal human beings, and patients with autosomal-dominant polycystic kidney disease or ARPKD. Trpv4 activation effect on cell proliferation and cyst formation was assessed in cholangiocytes derived from normal and PCK rats. The in vivo effects of Trpv4 activation on kidney and liver cysts was analyzed in PCK rats.
  
  
  RESULTS
  Trpv4 was overexpressed both at messenger RNA (8-fold) and protein (3-fold) levels in PCK cholangiocytes. Confocal and immunogold electron microscopy supported Trpv4 overexpression in the livers of PCK rats and ARPKD or autosomal-dominant polycystic kidney disease patients. Trpv4 activation in PCK cholangiocytes increased [Ca(2+)](i) by 30%, inhibiting cell proliferation by approximately 25%-50% and cyst growth in 3-dimensional culture (3-fold). Trpv4-small interfering RNA silencing blocked effects of Trpv4 activators by 70%. Trpv4 activation was associated with Akt phosphorylation and beta-Raf and Erk1/2 inhibition. In vivo, Trpv4 activation induced a significant decrease in renal cystic area and a nonsignificant decrease in liver cysts.
  
  
  CONCLUSIONS
  Taken together, our in vitro and in vivo data suggest that increasing intracellular calcium by Trpv4 activation may represent a potential therapeutic approach in PKD.
authors.affiliation: Miles and Shirley Fiterman Center for Digestive Diseases, Division of Gastroenterology and Hepatology, Mayo Clinic College of Medicine, Rochester, Minnesota, USA.
authors.forename: Sergio A
authors.initials: SA
authors.lastname: Gradilone
authors.forename: Tatyana V
authors.initials: TV
authors.lastname: Masyuk
authors.forename: Bing Q
authors.initials: BQ
authors.lastname: Huang
authors.forename: Jesus M
authors.initials: JM
authors.lastname: Banales
authors.forename: Guillermo L
authors.initials: GL
authors.lastname: Lehmann
authors.forename: Brynn N
authors.initials: BN
authors.lastname: Radtke
authors.forename: Angela
authors.initials: A
authors.lastname: Stroope
authors.forename: Anatoliy I
authors.initials: AI
authors.lastname: Masyuk
authors.forename: Patrick L
authors.initials: PL
authors.lastname: Splinter
authors.forename: Nicholas F
authors.initials: NF
authors.lastname: LaRusso
mesh_terms: D000818:Animals; D001652:Bile Ducts / Q000166:cytology*; D002118:Calcium / Q000378:metabolism; D049109:Cell Proliferation; D004195:Disease Models, Animal; D048049:Extracellular Signal-Regulated MAP Kinases / Q000502:physiology; D006801:Humans; D007930:Leucine / Q000031:analogs & derivatives / Q000494:pharmacology; D010641:Phenotype; D010703:Phorbol Esters / Q000494:pharmacology; D017044:Polycystic Kidney, Autosomal Recessive / Q000473:pathology / Q000628:therapy*; D048493:Proto-Oncogene Proteins B-raf / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects; D013449:Sulfonamides / Q000494:pharmacology; D050916:TRPV Cation Channels / Q000502:physiology*
chemical_list: C530602:N-(1-((4-(2-(((2,4-dichlorophenyl)sulfonyl)amino)-3-hydroxypropanoyl)-1-piperazinyl)carbonyl)-3-methylbutyl)-1-benzothiophene-2-carboxamide; D010703:Phorbol Esters; D013449:Sulfonamides; D050916:TRPV Cation Channels; C416986:TRPV4 protein, human; C486577:Trpv4 protein, rat; C008876:phorbol-12,13-didecanoate; D048493:Proto-Oncogene Proteins B-raf; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D007930:Leucine; D002118:Calcium
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