ORIGINAL RESEARCH
Phosphodiesterase Type 5 Expression in Human and Rat Lower Urinary Tract Tissues and the Effect of Tadalafil on Prostate Gland Oxygenation in Spontaneously Hypertensive Rats

https://doi.org/10.1111/j.1743-6109.2011.02416.xGet rights and content

ABSTRACT

Introduction

In humans, prostate phosphodiesterase type 5 inhibitors (PDE5) expression was prominently localized in the endothelial and smooth muscle cells of the vascular bed, suggesting a possible action of PDE5 inhibitors (PDE5i) on prostate blood flow.

Aim

To investigate PDE5 expression in human and rat lower urinary tract (LUT) tissues, including vasculature, and determine the effects of PDE5 inhibition with tadalafil on prostatic blood perfusion.

Main Outcome Measures

Human vesicular‐deferential arteries (which originate from the inferior vesical artery, the main arterial source of blood supply to the bladder and prostate) were analyzed for PDE5 expression and activity. The effects of tadalafil on prostate oxygenation were studied in spontaneously hypertensive rats (SHR), characterized by ischemia/hypoxia of the genitourinary tract.

Methods

PDE5 expression was evaluated by quantitative reverse transcription‐polymerase chain reaction and immunohistochemistry. SHR were treated with tadalafil (2 mg/kg/day) for 1, 7, or 28 days and compared with untreated SHR and the unaffected counterpart Wistar‐Kyoto (WKY) rats. Prostate oxygenation was detected by Hypoxyprobe‐1 and hypoxia markers (hypoxia‐inducible factor‐1α[HIF‐1α] and endothelin‐1 type B [ETB]) immunostaining.

Results

Human vesicular‐deferential artery expressed high levels of PDE5, similar to corpora cavernosa, immunolocalized in the endothelial and smooth muscle layer. In these arteries, tadalafil inhibited cyclic guanosine monophosphate breakdown (half maximal inhibitory concentration (IC50) in the low nanomolar range, as in corpora cavernosa) and increased the relaxant response to sodium nitroprusside. SHR prostate resulted markedly hypoxic (hypoxyprobe immunopositivity) and positive for HIF‐1α and ETB, while tadalafil treatment restored oxygenation to WKY level at each time point. The mRNA expression of the HIF‐1α target gene, BCL2/adenovirus E1B 19 kDa interacting protein 3, was significantly increased in SHR prostate and partially restored to WKY level by tadalafil.

Conclusion

Human vesicular‐deferential artery is characterized by a high expression and activity of PDE5, which was inhibited by tadalafil in vitro. In SHR, tadalafil increases prostate tissue oxygenation, thus suggesting a possible mechanism through which PDE5i exert beneficial effects on LUT symptoms. Morelli A, Sarchielli E, Comeglio P, Filippi S, Mancina R, Gacci M, Vignozzi L, Carini M, Vannelli GB, and Maggi M. Phosphodiesterase type 5 expression in human and rat lower urinary tract tissues and the effect of tadalafil on prostate gland oxygenation in spontaneously hypertensive rats. J Sex Med 2011;8:2746–2760.

Introduction

In the last few years, phosphodiesterase type 5 (PDE5) inhibitors (PDE5i)—the approved, gold standard, therapy for erectile dysfunction (ED)—have gained much interest in urology research for the treatment of lower urinary tract (LUT) symptoms (LUTS), secondary to benign prostatic hyperplasia (BPH), another common condition affecting the aging male. Accordingly, several clinical studies showed a clear effect of all the three PDE5i (vardenafil, sildenafil, and tadalafil) in improving LUTS in men with or without ED 1, 2, 3, 4, 5, 6, 7, 8, 9

It is well known that PDE5 inhibition improves erectile function through the amplification of the relaxing pathway mediated by nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) in penile musculature. However, the mechanism of action of PDE5i in LUT remains to be fully elucidated. Several evidences have been collected in different species, including humans, about a physiological role of NO/cGMP in LUT, regulating smooth muscle tone of bladder, prostate, and prostatic urethra, as well as prostate glandular secretion, and local blood flow 10, 11, 12. Indeed, the cGMP hydrolyzing activity of PDE5 strongly limits relaxation in bladder musculature [11], most probably by decreasing the activity of the RAS homologue of small G‐protein A (RhoA)/Rho‐kinase contractile signaling through a cGMP‐protein kinase (PKG)‐dependent phosphorylation of RhoA, which remains docked into the cytoplasm in an inactive state [13]. Moreover, it has been demonstrated that in human LUT and penis, PDE5 is present not only in the muscular wall but also in the endothelial and smooth muscle cells of the vascular bed 11, 12, 14. When PDE5 expression and activity were analyzed in human smooth muscle cells isolated from LUT tissues, it was found that prostate exhibited the lowest amount and functional activity in comparison with bladder and urethra [12]. In human prostate, PDE5 expression was predominantly localized in the endothelial cells of vascular bed [12], thus suggesting a possible action of PDE5i on prostate blood flow. The functional significance of PDE5 expression in prostate vasculature is still unclear.

The spontaneous hypertensive rat (SHR) is a rat strain characterized by an excessive neuroendocrine activity (sympathetic overactivity) and a commonly used model to study both LUT (such as BPH and overactive bladder) and EDs 15, 16, 17, 18, 19. This genetically selected rat strain is characterized by a reduced pelvic blood flow to the genitourinary tract, when compared with its control strain, Wistar‐Kyoto (WKY) rats [20]. In SHR, ischemia/hypoxia in the LUT leads to morphological/structural alterations, such as prostate and bladder fibrosis, increased prostate and bladder contractions, and an increase in urethral resistance 21, 22. Accordingly, we recently demonstrated in SHR the presence of bladder hypoxia that was ameliorated by acute treatment with the PDE5i vardenafil, administered 90 minutes before the sacrifice [23]. We also previously demonstrated the ability of both short‐ (1, 5, and 10 days) and long‐term (12 weeks) PDE5 inhibition (sildenafil and tadalafil, respectively) in improving penile oxygenation in a rat model of penile hypoxia induced by bilateral cavernous neurotomy 24, 25, 26. Hence, it is possible that PDE5 inhibition might lead to increased blood supply and oxygenation also in other vascular districts.

The present study had two main objectives: (i) to investigate the expression and activity of PDE5 in human and rat LUT tissues, including the supporting vasculature, and (ii) to determine the effect of PDE5 inhibition with tadalafil on prostate oxygenation in SHR.

Section snippets

Human Tissues

Human tissues, including bladder, corpora cavernosa (CC), urethra, prostate, epididymis, testis, and vas deferens, were collected during surgery for benign diseases, after signed informed consent. In particular, bladder, urethra, and prostate samples were collected during open transvesical simple prostatectomy for large BPH, CC during penile surgery for Peyronie's disease, while testis, epididymis, and vas deferens during post‐traumatic orchiectomy.

The main arterial supply to the LUT, including

PDE5 Expression and Activity in Human Vesicular‐Deferential Artery and Other LUT Tissues

Figure1 shows the absolute expression of PDE5 mRNA in a panel of tissues from the human urogenital tract, using a previously validated quantitativeRT‐PCR method [14]. In vesicular‐deferential artery, the PDE5 mRNA was expressed similarly to CC (29 ± 9 × 106 and 22 ± 5 × 106 molecules/µg total RNA, respectively). CC is known to be the human tissue expressing the highest amount of PDE5 [14]. A lower PDE5 abundance was found in other portions of the male urogenital tract, including bladder

Discussion

In this report, we confirm [12] that human prostate expresses PDE5 mostly in the vascular bed and show for the first time that human vesicular‐deferential artery (one of the small arterial branches arising from the main artery that provides blood flow to prostate gland and bladder) expresses high levels of PDE5 (as in CC), which is immunolocalized in the endothelial cells and smooth muscle layer. Accordingly, human vesicular‐deferential artery homogenates catabolyzes cGMP, as CC does. In

Acknowledgment

This study was funded by Eli Lilly and Company.

Conflict of Interest

None.

Category 1

  • (a)

    Conception and Design

    Annamaria Morelli; Sandra Filippi; Mauro Gacci; Mario Maggi

  • (b)

    Acquisition of Data

    Annamaria Morelli; Erica Sarchielli; Paolo Comeglio; Sandra Filippi; Rosa Mancina; Gabriella B. Vannelli

  • (c)

    Analysis and Interpretation of Data

    Annamaria Morelli; Erica Sarchielli; Paolo Comeglio; Sandra Filippi; Rosa Mancina; Linda Vignozzi; Marco Carini; Gabriella B. Vannelli; Mario Maggi

Category 2

  • (a)

    Drafting the Article

    Annamaria Morelli; Erica Sarchielli; Paolo Comeglio; Sandra Filippi; Rosa Mancina; Mario Maggi

  • (b)

References (54)

  • M. Yono et al.

    Effects of doxazosin on blood flow and mRNA expression of nitric oxide synthase in the spontaneously hypertensive rat genitourinary tract

    Life Sci

    (2007)
  • K.T. McVary

    Erectile dysfunction and lower urinary tract symptoms secondary to BPH

    Eur Urol

    (2005)
  • A. Morelli et al.

    Acute vardenafil administration improves bladder oxygenation in spontaneously hypertensive rats

    J Sex Med

    (2010)
  • L. Vignozzi et al.

    Effect of chronic tadalafil administration on penile hypoxia induced by cavernous neurotomy in the rat

    J Sex Med

    (2006)
  • L. Vignozzi et al.

    Cavernous neurotomy in the rat is associated with the onset of an overt condition of hypogonadism

    J Sex Med

    (2009)
  • P. Medina et al.

    Contractile responses of human deferential artery and vas deferens to vasopressin

    Eur J Pharmacol

    (1996)
  • C. Martínez et al.

    The human deferential artery: Endothelium‐mediated contraction in response to adrenergic stimulation

    Eur J Pharmacol

    (1994)
  • G. D'Amati et al.

    Type 5 phosphodiesterase expression in the human vagina

    Urology

    (2002)
  • G.M. Pinggera et al.

    Sildenafil citrate causes a 3‐fold increase in periurethral prostatic blood fow

    J Urol

    (2004)
  • K.M. Azadzoi et al.

    Chronic ischemia increases prostatic smooth muscle contraction in the rabbit

    J Urol

    (2003)
  • B.M. Tsai et al.

    Differential effects of phosphodiesterase‐5 inhibitors on hypoxic pulmonary vasoconstriction and pulmonary artery cytokine expression

    Ann Thorac Surg

    (2006)
  • G.L. Semenza

    Hypoxia‐inducible factor 1: Oxygen homeostasis and disease pathophysiology

    Trends Mol Med

    (2001)
  • S. Uckert et al.

    Characterization and functional relevance of cyclic nucleotide phosphodiesterase isoenzymes of the human prostate

    J Urol

    (2001)
  • S. Uckert et al.

    Update on phosphodiesterase (PDE) isoenzymes as pharmacologic targets in urology: Present and future

    Eur Urol

    (2006)
  • S. Uckert et al.

    Effects of phosphodiesterase inhibitors on tension induced by norepinephrine and accumulation of cyclic nucleotides in isolated human prostatic tissue

    Urology

    (2008)
  • S. Oger et al.

    Combination of alfuzosin and tadalafil exerts an additive relaxant effect on human detrusor and prostatic tissues in vitro

    Eur Urol

    (2010)
  • C.G. Roehrborn et al.

    Changes in peak urinary flow and voiding efficiency in men with signs and symptoms of benign prostatic hyperplasia during once daily tadalafil treatment

    BJU Int

    (2010)
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