Abstract
Our study aims to explore changes in bladder contractility and the phosphodiesterase type 5 (PDE5) signalling pathway in response to partial bladder outlet obstruction (PBOO). A surgically induced male rat PBOO model and human obstructed bladder tissues were used. Histological changes were examined by H&E and Masson's trichrome staining. Bladder strip contractility was measured via organ bath. The expressions of nitric oxide synthase (NOS) isoforms, PDE5, muscarinic cholinergic receptor (CHRM) isoforms and PDE4 isoforms in bladder were detected by RT-PCR and Western blotting. The immunolocalization of the PDE5 protein and its functional activity were also determined. PBOO bladder tissue exhibited significant SM hypertrophy and elevated responsiveness to KCl depolarization and the muscarinic receptor agonist carbachol. NOS isoforms, PDE5, CHRM2, CHRM3 and PDE4A were up-regulated in obstructed bladder tissue, whereas no change in PDE4B and PDE4D isoform expression was observed. With regard to PDE5, it was expressed in the SM bundles of bladder. Interestingly, obstructed bladder exhibited less relaxation responsiveness to sodium nitroprusside (SNP), but an exaggerated PDE5 inhibition effect. The up-regulation of PDE5 could contribute to the lack of effect on Qmax for benign prostatic hyperplasia/lower urinary tract symptom (BPH/LUTS) patients treated with PDE5 inhibitors. Moreover, PDE5 (with presence of NO) and PDE4 may serve as new therapeutic targets for bladder diseases such as BPH-induced LUTS and overactive bladder (OAB).