Intravesical Suplatast Tosilate (IPD-1151T) Inhibits Experimental Bladder Inflammation

Purpose: Interstitial cystitis is a painful bladder disease characterized by urgency, frequency and variable inflammation but there is no curative therapy. Suplatast tosilate (IPD-1151T) is an immunoregulatory compound that decreases interstitial cystitis symptoms but to our knowledge its mechanism of action is unknown. We investigated the effect of intravesical IPD-1151T on mediator release from bladder explants in experimental cystitis. Materials and Methods: A catheter was inserted into the bladder of female mice. After urine was emptied normal saline, carbachol (100 nM) or lipopolysaccharide (10 mg/ml) was introduced with or without 10-minute pretreatment with IPD-1151T. Urine was removed after 45 minutes for histamine and tumor necrosis factor-α assays. The bladder was removed after 4 hours, minced into 1 mm² pieces and cultured with or without triggers overnight for mediator release. The effect of IPD-1151T was also tested on rat skin vascular permeability as well as on purified rat peritoneal mast cells and human cord blood derived mast cells. Results: Carbachol significantly increased histamine release in urine (61.3% in 8 preparations, p <0.05) but not in explant medium. IPD-1151T inhibited this effect by 77%. Lipopolysaccharide induced a 350% urine histamine increase in 9 preparations (p <0.05) and a 300% tumor necrosis factor-α increase in explant medium. IPD-1151T inhibited the lipopolysaccharide induced medium tumor necrosis factor-α increase by 95% in 5 preparations (p <0.05). IPD-1151T did not inhibit rat skin vascular permeability or purified rat peritoneal mast cell activation by compound 48/80 or human cord blood derived mast cells by anti-IgE. Conclusions: IPD-1151T inhibits bladder release of histamine and tumor necrosis factor-α through a mechanism that does not appear to involve direct mast cell inhibition. These findings may justify a beneficial effect of IPD-1151T in interstitial cystitis.