Intravesical Botulinum Toxin A Administration Inhibits COX-2 and EP4 Expression and Suppresses Bladder Hyperactivity in Cyclophosphamide-Induced Cystitis in Rats

BackgroundCyclooxygenase 2 (COX-2) elevation and subsequent prostaglandin E2 (PGE2) production play a major role in bladder inflammation and hyperactivity. EP4 receptor, a subtype of PGE2 receptors, mediates tissue inflammation and hypersensitivity.ObjectiveTo investigate the effect of intravesical botulinum toxin A (BoNT-A) on COX-2 and EP4 expression in cyclophosphamide (CYP)-induced cystitis in rats.Design, setting, and participantsExperimental (N = 40) and control animals (N = 20) were injected with CYP (75mg/kg intraperitoneally) or saline on days 1, 4, and 7. BoNT-A (1 ml, 20 unit/ml) or saline were administered into the bladder and retained for 1 h on day 2.InterventionWaking cystometrograms (CMGs) were performed. Bladder and L6 and S1 spinal cord were harvested on day 8.MeasurementsCMG parameters, histology, and COX-2 and EP4 expression by immunostaining or western blotting were measured.Results and limitationsCYP induced increased bladder inflammatory reaction, bladder hyperactivity, and COX-2 and EP4 expression in the bladder and spinal cord. The CYP effects were suppressed by BoNT-A treatment. BoNT-A treatment decreased inflammatory reaction (56.5% decrease), COX-2 expression (77.8%, 61.7%, and 54.8% decrease for bladder, L6, and S1 spinal cord, respectively), EP4 expression (56.8%, 26.9%, and 84.2% decrease for bladder, L6, and S1 spinal cord, respectively), and suppressed bladder hyperactivity (intercontraction interval, 107% increase and contraction amplitude, 43% decrease).ConclusionsCYP injection activated COX2 and EP4 expression in the bladder and spinal cord and induced bladder inflammation and hyperactivity, which effects were suppressed by BoNT-A treatment. These findings suggest a potential benefit of EP4-targeted pharmacotherapy and BoNT-A treatment for bladder inflammatory conditions.