Characterization of Phosphodiesterase Type 5 Expression and Functional Activity in the Human Male Lower Urinary Tract

Abstract

Introduction Phosphodiesterase type 5 (PDE5) inhibitors ameliorate low urinary tract (LUT) symptoms in men with ED and symptomatic benign prostatic hyperplasia (BPH). PDE5 is highly expressed in rat and human bladder, where it regulates cyclic guanosine monophosphate (cGMP) degradation, muscle tone, and proliferation. Aim To investigate PDE5 tissue distribution and activity in human LUT tissues (urethra, prostate, and bladder). Main Outcome Measures PDE5 expression and activity were analyzed and compared within the same BPH patient in LUT tissues and in smooth muscle cells (SMCs) cultured from urethra, prostate, and bladder. Methods In LUT tissues, PDE5 was localized by immunohistochemistry and mRNA expression by quantitative real-time polymerase chain reaction. Proliferation assay was used as readout of PDE5 activity, evaluated as ability of vardenafil to increase the antiproliferative effect of different nitric oxide (NO)/cGMP pathway activators [the PDE5-resistant cGMP analog Sp-8-Br-PET-cGMPS, the NO donor sodium nitroprusside (SNP), and the soluble guanylate cyclase (sGC) stimulator BAY 41-8543]. Results In all the LUT tissues, PDE5 was immunolocalized in blood vessels and in muscular fibres, but not in epithelium. PDE5 mRNA expression was higher in urethra and bladder than in prostate SMC. The antiproliferative effect of Sp-8-Br-PET-cGMPS was similar in all LUT SMC. In prostatic SMC, SNP and BAY 41-8543 show a dose-dependent antiproliferative effect that resulted marginally enhanced by vardenafil. Conversely, in urethra and bladder SMC the antiproliferative effect of SNP and BAY 41-8543 was lower than in prostatic SMC, but it was significantly enhanced by vardenafil. In urethral and bladder cells vardenafil half-maximal response inhibiting concentration was in the subnanomolar range, whereas in prostate cells it resulted significantly higher. Conclusions The highest expression and biological activity of PDE5 was found in bladder. However, a consistent PDE5 expression and activity was also found in prostatic urethra. In contrast, the prostate gland showed the lowest PDE5 abundance and cultures derived from this tissue were less sensitive to vardenafil.

Cyclic GMP signaling in rat urinary bladder, prostate, and epididymis: tissue-specific changes with aging and in response to Leydig cell depletion

“…Our findings are in apparent disagreement with previous data showing high abundance of PDE5 mRNA in the human prostate (Morelli et al 2004) and question the view that androgendependent upregulation leads to generally enhanced PDE5 expression in organs of the male genital tract (Morelli et al 2004). Compatible with our results, however, a recent characterization of PDE5 mRNA distribution in human male lower-urinary tract tissues also revealed lowest abundance in the prostate gland (Fibbi et al 2010). Thus, the weak expression of PDE5 (and probably the other cGMP signaling proteins) in the prostate may not represent a rat-specific phenomenon.…”

“…Compared with lung, where high PDE5 provided a molecular basis for treatment of pulmonary hypertension (Corbin et al 2005), cytosolic PDE5 abundance is similar and membrane concentrations are even higher in the bladder. Immunohistochemical data localized PDE5 to the bladder smooth muscle (Fibbi et al 2010), and both NO donors and PDE5 inhibitors were found to reduce the muscle tonus in experiments with rat and human bladder tissues (Sandner et al 2009), although cAMPmediated pathways appear to play a predominant role for direct detrusor muscle relaxation (Andersson & Arner 2004). Tension release during the bladder filling phase is crucial and requires robust mechanisms to generate smooth muscle relaxation.…”

“…Local roles for cGMP signaling comprise the regulation of muscle contractions and micturition sensations in the bladder (Persson et al 2000, Andersson & Arner 2004, Sandner et al 2009, Caremel et al 2010, the relaxation of stromal smooth muscle and control of cell proliferation in the prostate (Gradini et al 1999, Sandner et al 2009, Fibbi et al 2010, Zenzmaier et al 2010, and regulation of peristalsis and secretory epithelial cell functions in the epididymis (Mewe et al 2006, Shum et al 2008. Although certain factors implicated in cGMP pathways have been demonstrated by immunohistochemical, RT-PCR, and functional approaches, the cGMP signaling system in these organs is still poorly characterized.…”

Antiinflammatory effect of androgen receptor activation in human benign prostatic hyperplasia cells

“…The prostate is an immunocompetent organ, not only because it is populated by resident inflammatory cells, including T-and B-lymphocytes, macrophages, and mast cells (De Marzo et al 2007, Fibbi et al 2010a, but also because stromal prostatic cells can secrete several proinflammatory cytokines and are able to recruit and activate CD4…”

“…Primary human prostatic smooth muscle cells (hBPH) were obtained and cultured as previously described (Crescioli et al 2000, Fibbi et al 2010a. Briefly, six different hBPH cell preparations were obtained from prostate tissues derived from six patients who underwent TURP or suprapubic adenomectomy for BPH after informed consent.…”