Characterization of phosphodiesterase type 5 expression and functional activity in the human male lower urinary tract.
BACKGROUND
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.


OBJECTIVE
To investigate PDE5 tissue distribution and activity in human LUT tissues (urethra, prostate, and bladder).


METHODS
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.
Andrology and Sexual Medicine Unit, Department of Clinical Physiopathology, University of Florence, Florence, Italy. m.maggi@dfc.unifi.it
Benedetta
B
Fibbi
Annamaria
A
Morelli
Linda
L
Vignozzi
Sandra
S
Filippi
Aravinda
A
Chavalmane
Giulia
G
De Vita
Mirca
M
Marini
Mauro
M
Gacci
Gabriella Barbara
GB
Vannelli
Peter
P
Sandner
Mario
M
Maggi
D000368:Aged; D002455:Cell Division / Q000187:drug effects; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5 / Q000235:genetics*; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D008297:Male; D009025:Morpholines / Q000494:pharmacology; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D011467:Prostate / Q000187:drug effects / Q000378:metabolism*; D011470:Prostatic Hyperplasia / Q000235:genetics / Q000473:pathology; D011743:Pyrimidines / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013450:Sulfones / Q000494:pharmacology; D014227:Triazines / Q000494:pharmacology; D014521:Urethra / Q000187:drug effects / Q000378:metabolism*; D001743:Urinary Bladder / Q000187:drug effects / Q000378:metabolism*; D000069058:Vardenafil Dihydrochloride; D014665:Vasodilator Agents / Q000494:pharmacology
C450679:BAY 41-8543; D007093:Imidazoles; D009025:Morpholines; D020030:Nitric Oxide Donors; D010879:Piperazines; D011743:Pyrimidines; D012333:RNA, Messenger; D013450:Sulfones; D014227:Triazines; D014665:Vasodilator Agents; D009599:Nitroprusside; D000069058:Vardenafil Dihydrochloride; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5