title: Role of β-catenin in regulating microvascular endothelial cell hyperpermeability.
abstract: BACKGROUND
  Paracellular microvascular hyperpermeability occurs mainly because of the disruption of the endothelial adherens junction complex. Vascular endothelial-cadherin that consists of an extracellular and intracellular domain to confer cell-cell contact is linked to the actin cytoskeletal assembly through β-catenin. Our objective was to determine the functional role of β-catenin during paracellular hyperpermeability and to evaluate whether exogenous β-catenin would protect against vascular leak.
  
  
  METHODS
  β-Catenin siRNA (2.5 μg/mL) was administered to Sprague-Dawley rats through tail vein. FITC-albumin extravasation of the mesenteric postcapillary venules was evaluated after 48 hours using intravital microscopy. Parallel studies using rat lung microvascular endothelial cell monolayers were transfected with β-catenin siRNA, and hyperpermeability was determined using monolayers after 48 hours. The effectiveness of β-catenin siRNA was tested using immunofluorescence and Western blot. To study the protective effect of β-catenin, rat lung microvascular endothelial cell monolayers were transfected with a β-catenin gene expression construct for 48 hours or a recombinant β-catenin protein (1 μg/mL) for 2 hours, followed by transfection with proapoptotic BAK peptide (5 μg/mL), a known inducer hyperpermeability.
  
  
  RESULTS
  β-Catenin siRNA induced a significant increase in vascular hyperpermeability in vivo (p<0.05) and monolayer permeability (in vitro; p<0.05). β-Catenin siRNA significantly altered the adherens junction complex and decreased β-catenin protein levels. β-Catenin gene expression construct or recombinant β-catenin protein attenuated BAK-induced monolayer hyperpermeability significantly (p<0.05).
  
  
  CONCLUSIONS
  Posttranscriptional gene silencing of β-catenin leads to vascular hyperpermeability in vivo and monolayer hyperpermeability in vitro. The enhancement of β-catenin gene expression at the adherens junction or exogenous introduction of β-catenin protein shows protection against vascular hyperpermeability.
authors.affiliation: Department of Surgery, Texas A&M University Health Science Center College of Medicine and Scott & White Memorial Hospital, Temple, Texas 76508, USA.
authors.forename: Devendra A
authors.initials: DA
authors.lastname: Sawant
authors.forename: Binu
authors.initials: B
authors.lastname: Tharakan
authors.forename: Felicia A
authors.initials: FA
authors.lastname: Hunter
authors.forename: W Roy
authors.initials: WR
authors.lastname: Smythe
authors.forename: Ed W
authors.initials: EW
authors.lastname: Childs
mesh_terms: D022005:Adherens Junctions / Q000378:metabolism; D000818:Animals; D002199:Capillary Permeability / Q000187:drug effects / Q000502:physiology*; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D015870:Gene Expression / Q000187:drug effects / Q000235:genetics; D008297:Male; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000494:pharmacology; D014162:Transfection / Q000379:methods; D051176:beta Catenin / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*
chemical_list: D034741:RNA, Small Interfering; D011994:Recombinant Proteins; D051176:beta Catenin