Bacillus Calmette-Guerin induces long-term local formation of nitric oxidein the bladder via the induction of nitric oxide synthase activity in urothelial cells

Purpose: Bladder instillation of bacillus Calmette-Guerin (BCG) is effectiv e therapy for recurrent superficial bladder cancer and carcinoma in situ. B CG induces nitric oxide synthase activity in the bladder. Nitric oxide is f ormed from L-arginine by nitric oxide synthase. We investigated nitric oxid e formation and its localization in bladder cancer patients treated with in travesical BCG instillation. Materials and Methods: The L-citrulline conversion assay was done to assess nitric oxide synthase activity in BCG treated T24 human bladder cancer cel ls and cultured normal human urothelial cells. Nitrite and nitrate in cell culture medium, urine and plasma were measured by capillary electrophoresis . Nitric oxide formation in the bladder was measured by chemiluminescence. Results: A 24-hour treatment with BCG induced calcium independent nitric ox ide synthase activity in T24 cells in a dose dependent manner. Nitrite and nitrate production by T24 cells also increased in a dose dependent manner a fter 24-hour BCG treatment. BCG treatment of cultured normal human urotheli al cells resulted in the induction of calcium dependent and independent nit ric oxide synthase activity. Nitrite in the urine of patients receiving BCG for the first time was increased 5-fold 24 hours after instillation. Furth ermore, BCG increased luminal nitric oxide in the bladder. The increase was noted after a single treatment and sustained for 6 months. No changes in p lasma nitrite or nitrate were observed after BCG treatment. Conclusions: BCG induces the local formation of nitric oxide in the bladder , whereas no evidence for systemic nitric oxide formation was noted. Increa sed nitric oxide production in the bladder is likely due to the induction o f nitric oxide synthase activity in urothelial cells.