title: Effect of botulinum toxin A on urothelial-release of ATP and expression of SNARE targets within the urothelium.
abstract: OBJECTIVE
  Botulinum neurotoxin serotype A (BoNT/A) has emerged as an effective treatment of urinary bladder overactivity. Intravesical lipotoxin (BoNT/A delivery using liposomes), which may target the urothelium, is effective in blocking acetic acid induced hyperactivity in animals. The objective of this study was to assess the possible site of toxin action within the urothelium.
  
  
  METHODS
  We examined expression of the toxin receptor (SV2) and its cleavage targets (SNAP-25 and SNAP-23) within urothelium as well as effects of the toxin on mechanically evoked release of ATP from cultured rat urothelial cells. ATP release was measured using the luciferin-luciferase assay; we examined expression of SNAP-23 and -25 in urothelial cells and mucosa of rat and human bladders.
  
  
  RESULTS
  BoNT/A (1.5 U; 1-3 hr) blocked hypotonic evoked release of urothelial ATP, without affecting morphology. The expression of protein targets for BoNT/A binding (SV2) was detected in human and rat bladder mucosa and catalytic action (SNAP-23, -25) in urothelial cells and mucosa (differed in intensity) from rat and human bladder. Incubation of cultured (rat) urothelial cells with BoNT/A decreased expression levels of both SNAP-23 (44%) and SNAP-25 (80%).
  
  
  CONCLUSIONS
  Our findings reveal that the bladder urothelium expresses the intracellular targets and the binding protein for cellular uptake of BoNT/A; and that the toxin is able to suppress the levels of these targets as well as hypotonic-evoked ATP release. These data raise the possibility that intravesical treatment with BoNT/A suppresses bladder reflex and sensory mechanisms by affecting a number of urothelial functions including release of transmitters.
authors.affiliation: Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
authors.forename: Ann T
authors.initials: AT
authors.lastname: Hanna-Mitchell
authors.forename: Amanda S
authors.initials: AS
authors.lastname: Wolf-Johnston
authors.forename: Stacey R
authors.initials: SR
authors.lastname: Barrick
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Kanai
authors.forename: Michael B
authors.initials: MB
authors.lastname: Chancellor
authors.forename: William C
authors.initials: WC
authors.lastname: de Groat
authors.forename: Lori A
authors.initials: LA
authors.lastname: Birder
mesh_terms: D065087:Acetylcholine Release Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D019274:Botulinum Toxins, Type A / Q000494:pharmacology* / Q000627:therapeutic use; D002478:Cells, Cultured; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D009419:Nerve Tissue Proteins / Q000378:metabolism; D051381:Rats; D050825:Synaptosomal-Associated Protein 25 / Q000378:metabolism; D001743:Urinary Bladder / Q000187:drug effects* / Q000378:metabolism; D053201:Urinary Bladder, Overactive / Q000188:drug therapy / Q000378:metabolism; D019459:Urothelium / Q000187:drug effects* / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000378:metabolism
chemical_list: D065087:Acetylcholine Release Inhibitors; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; C498858:Snap23 protein, rat; C494210:Snap25 protein, rat; C489618:Sv2a protein, rat; D050825:Synaptosomal-Associated Protein 25; D033921:Vesicular Transport Proteins; D000255:Adenosine Triphosphate; D019274:Botulinum Toxins, Type A
keywords: SNAP-23; SNAP-25; bladder mucosa; exocytosis