title: Hydroxyzine inhibits neurogenic bladder mast cell activation.
abstract: OBJECTIVE
  Increased numbers of activated mast cells have been documented close to substance P (SP) containing nerve endings in the bladders of patients with interstitial cystitis (IC), a painful, sterile bladder disorder occurring primarily in females. Many of these patients also suffer from allergies, but common antihistamines do not help. In line with the fact that IC symptoms worsen under stress, we recently showed that bladder mast cells could be activated by the stable acetylcholine (Ach) analogue carbachol and by immobilization stress. Preliminary data from open label studies indicated that the heterocyclic histamine-1 receptor antagonist (H-1r alpha) hydroxyzine reduces IC symptoms. We, therefore, investigated whether hydroxyzine could inhibit carbachol-induced bladder mast cell activation.
  
  
  METHODS
  Bladder pieces from male Sprague-Dawley rats were perfused with 10(-5) M carbachol, 10(-5) M SP, or 100 microg/ml compound 48/80 (C48/80), with or without preincubation with the designated concentrations of the H-1r alpha. Mast cell activation was assessed by release of exogenous 3H-serotonin and morphological evidence of secretion by light microscopy.
  
  
  RESULTS
  Carbachol at 10(-5) M triggered rat bladder mast cell serotonin release which represented a 65% increase over control. Equimolar concentrations of SP caused a 32% increase, while C48/80 had no effect. The heterocyclic piperazine H-1r alpha hydroxyzine reduced carbachol-induced serotonin release by 25% at 10(-6) M and 34% at 10(-5) M, both of which were statistically significant (P < 0.05). On the contrary, the well known H-1r alpha diphenhydramine had no inhibitory effect, while the mixed H-1r alpha and 5-hydroxytryptamine-receptor antagonist (5-HTr alpha) azatadine actually caused an 11% increase.
  
  
  CONCLUSIONS
  Hydroxyzine reduced carbachol-induced serotonin release from rat bladder in vitro through a mechanism which was unrelated to its H-1 receptor antagonistic properties. The ability of hydroxyzine to inhibit bladder mast cell activation by neurogenic stimuli along with its anticholinergic, anxiolytic and analgesic properties, may explain the clinical efficacy of this drug in reducing IC symptoms. Other, nonsedating, hydroxyzine analogues able to inhibit bladder mast cell activation may provide potentially new therapeutic approaches for IC.
authors.affiliation: Department of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, New England Medical Center, Boston, MA 02111, USA.
authors.forename: P
authors.initials: P
authors.lastname: Minogiannis
authors.forename: M
authors.initials: M
authors.lastname: El-Mansoury
authors.forename: J A
authors.initials: JA
authors.lastname: Betances
authors.forename: G R
authors.initials: GR
authors.lastname: Sant
authors.forename: T C
authors.initials: TC
authors.lastname: Theoharides
mesh_terms: D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D006634:Histamine H1 Antagonists / Q000494:pharmacology*; D006919:Hydroxyzine / Q000031:analogs & derivatives / Q000494:pharmacology*; D008297:Male; D008407:Mast Cells / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000378:metabolism*; D001743:Urinary Bladder / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism
chemical_list: D006634:Histamine H1 Antagonists; D006919:Hydroxyzine; D012701:Serotonin; D002217:Carbachol