Purpose: We investigated the functional expression of CLC-3 and CLCA4 chloride channels on bladder tissue in rats with cyclophosphamide (CYP)-induced overactive bladder (OAB).
Materials and Methods: A total of 96 adult male Wister rats (10–12 weeks) were divided into three groups (CYPc40, CYPc80 and control). CYP-induced OAB was provoked by four i.p injections in 7 days (CYPc40: 40 mg/kg and CYPc80: 80 mg/kg). Control rat received saline injections. The experiments were performed on day 7. We conducted a strategy involving: (1) Continuous infusion cystometry (CMG) under anaesthesia to record the basal pressure, threshold pressure, maximum bladder voiding pressure (MBVP) and intercontraction interval (ICI). (2) Urinary nerve growth factor (NGF) detection before CMG. (3) Western blot analysis and immunohistochemistry of CLC-3 and CLCA4 protein on rat bladder tissues. (4) Reverse transcription-polymerase chain reaction (RT-PCR) of the mRNA for CLC-3 and CLCA4 channels in normal and CYP-OAB bladder tissue. The CMG parameters, urine NGF level, molecular expressions of chloride channels are compared between rats in control, CYPc40 and CYPc80 groups.
Results: Repeated injection of low dose CYP (40 or 80 mg/kg) could successfully induce OAB like status in rats which was illustrated by CMG. In CYPc80 group, the bladder weight and urinary NGF increased significantly. In OAB rats (CYPc40 and CYPc80), the protein expressions of CLC-3 and CLCA4 chloride channels on bladder tissue (by western blotting) increased significantly in a dose dependent manner. The mRNA expression of CLC-3 and CLCA4 on bladder tissue (by Quantitative RT-PCR) also increased significantly in a dose dependent manner in OAB groups. Immunohistochemistry study revealed the CLC-3 and CLCA4 were located on both urothelium and smooth muscle layers of CYP-induced OAB bladder in rats. Moreover, the expression of CLC-3 and CLCA4 (both in protein and mRNA level) chloride channels on OAB rat bladder were strongly correlated with the NGF levels and CMG parameters.
Conclusion: Our results suggest that both the CLC-3 and CLCA4 chloride channels may play important roles in the pathogenesis of OAB and provide possible new therapeutic targets in treating OAB. Further studies are warranted.