CHARACTERIZATION AND FUNCTIONAL RELEVANCE OF CYCLIC NUCLEOTIDE PHOSPHODIESTERASE ISOENZYMES OF THE HUMAN PROSTATE:

Are age, anthropometry and components of metabolic syndrome-risk factors interrelated with lower urinary tract symptoms in patients with erectile dysfunction? A prospective study

AIM

To evaluate the effects of metabolic profiles on lower urinary tract symptoms (LUTS) in men with erectile dysfunction (ED).

METHODS

A total of 75 impotent men aged 25-75 years old (mean 58.1 years) were included in the study on a prospective basis. Patients were evaluated with a complete history, physical examination, anthropometry and metabolic profiles. LUTS were assessed using the International Prostate Symptom Score (IPSS).

RESULTS

Overall, there was no correlation between the IPSS and continuous parameters. However, when continuous variables were categorized, some parameters were significantly associated with LUTS. Patients with triglyceride level of 150 mg/dL or higher had more severe symptoms than those with triglyceride levels less than 150 mg/dL (19.4 +/- 2.4 vs. 14.3 +/- 1.1, P = 0.033). When 40 mg/dL was chosen as the high-density lipoprotein (HDL)-cholesterol cut-off level, the IPSS was significantly different between the two groups divided by 40 mg/dL (19.4 +/- 2.6 for HDL-cholesterol < 40 mg/dL vs. 14.4 +/- 1.0 for HDL-cholesterol = or > 40 mg/dL, P = 0.042). The area under the receiver operating characteristic curve (AUROCC) of triglyceride was 65.7% (95% confidence interval [CI], 52.6%-82.3%; P = 0.034) for severe LUTS. However, the AUROCC for 'HDL-cholesterol' was not significant (area, 65.4%; 95% CI, 48.2%-82.7%; P = 0.062). No other factors were determined to be significant in this regard.

CONCLUSION

The results of the present study indicate that some metabolic profiles might influence LUTS in men with ED.

Pre-clinical evidence for the use of phosphodiesterase-5 inhibitors for treating benign prostatic hyperplasia and lower urinary tract symptoms

OBJECTIVE

To evaluate the potential of sildenafil, vardenafil and tadalafil, all phosphodiesterase-5 (PDE-5) inhibitors used for treating erectile dysfunction, for treating benign prostatic hyperplasia (BPH) and lower urinary tract symptoms (LUTS).

MATERIALS AND METHODS

The mRNA expression of the PDE-5 was determined in rat LUT tissues. The PDE-5 inhibitors were also tested in organ-bath experiments and in a partial bladder outlet obstruction (BOO) rat model in vivo.

RESULTS

The highest PDE-5 mRNA expression was in the bladder, followed by the urethra and prostate. PDE-5 inhibitors dose-dependently reduced the contraction of the isolated bladder, urethral and prostate strips. The rank order of potency was vardenafil > sildenafil > tadalafil. In human prostate stromal cells vardenafil inhibited cell proliferation and was more effective than tadalafil and sildenafil. In the BOO model, there was a reduction in the non-voiding contractions after bolus intravenous administration of 3 mg/kg sildenafil and vardenafil.

CONCLUSION

These results show that PDE-5 is expressed in LUT tissues. PDE-5 inhibitors induced significant relaxation of these tissues, inhibited the proliferation of human prostate stromal cells and reduced the irritative symptoms of BPH/LUTS in vivo. Therefore, PDE-5 inhibitors could be used as an effective treatment for BPH/LUTS.

Phosphodiesterase 5 inhibitors in the treatment of premature ejaculation

To date, there is no FDA-approved therapy for premature ejaculation (PE). Recently, phosphodiesterase 5 inhibitors (PDE5-Is) have been demonstrated to have encouraging results in the treatment of PE by a few studies. The aim of this review was to assess the updated manuscripts and thereafter present the practical recommendations and possible mechanisms concerning PDE5-Is for treating PE. Using MEDLINE, we searched and assessed the peer manuscripts published from 1 January 1996 to 1 September 2005 about PDE5-Is for treating PE. The results show that the number of patients in all the reports is very few and most of the studies do not employ double-blinded and placebo-controlled tests, though they are prospective and randomized. Therefore, the results and conclusions might be biased. PDE5-Is are suggested to be used in PE with old age or associated with erectile dysfunction (ED), or to be employed alone or in combination with selective-serotonin reuptake inhibitors (SSRIs) when SSRIs fail to treat PE; behavioural therapy is proposed to be used for preventing the recurrence of PE following withdrawal of PDE5-Is. In addition, for the PE patient with a definite aetiological cause, the aetiology should be cured first, if PE still exists, followed by PDE-Is prescription. Possible mechanisms that are involved include relaxing the smooth muscles of vas deferens, seminal vesicle, prostate and urethra; decreasing the central sympathetic output; inducing peripheral analgesia; prolonging the duration of erection; and increasing confidence, the perception of ejaculatory control, overall sexual satisfaction, and decreasing the post-orgasmic refractory time to achieve a second erection after ejaculation. Well-designed multicentre studies are urgently warranted to further elucidate the efficacies and safety as well as mechanisms of PDE5-Is in the treatment of PE.

Phosphodiesterase 5 in the female pig and human urethra: morphological and functional aspects

OBJECTIVE

To characterize the distribution of phosphodiesterase 5 (PDE-5), cGMP and cGMP-dependent protein kinase I (PKG1), and to evaluate the effect of pharmacological inhibition of PDE-5 in isolated preparations of pig and human urethra, as the nitric oxide (NO)/cGMP pathway generates the main inhibitory signals to reduce resistance in the bladder outlet and urethra during emptying of the bladder.

MATERIALS AND METHODS

After obtaining ethics committee approval, urethral specimens were obtained from three female patients during cystectomy, and from young female pigs. The specimens were prepared for immunohistochemical investigations and for functional studies in organ baths. Effects of sildenafil, vardenafil and tadalafil (1 nm to 30 microm) were studied in l-noradrenaline (1 microm)-activated or spontaneously contracted preparations, and on relaxations induced by electrical-field stimulation (EFS). Levels of cGMP were determined by radioimmunoassay.

RESULTS

After stimulation with the NO donor, DETA NONO-ate (1 mm), there was greater cGMP-immunoreactivity (IR) in urethral and vascular smooth muscles. There was a wide distribution of cGMP- and vimentin-positive interstitial cells between pig urethral smooth muscle bundles. There was also cGMP-IR within NO-synthase-IR endothelium. There was PDE-5 IR within the urethral and vascular smooth muscle cells, but also in vascular endothelial cells that expressed cGMP-IR. In pig and human sections, there was strong PKG1-IR in alpha-actin-IR urethral smooth muscle cells that also contained IR for cGMP. Sildenafil, vardenafil and tadalafil caused mean (sem) concentration-dependent relaxations of the pig urethra which, at 30 microm, were 80 (3)% (11 samples), 81 (5)% (12 samples) and 64 (4)% (10 samples) of the spontaneous tone. The relaxation of L-noradrenaline-contracted female human urethra was 100% in response to 10 microm sildenafil, and 85 (15)% and 47 (13)% for 30 microm of vardenafil and tadalafil, respectively (three samples). Vardenafil or sildenafil (30 microm) doubled cGMP levels in pig specimens. There were no effects on cGMP levels with tadalafil. EFS (1-32 Hz) caused l-NG-nitroarginine-sensitive relaxations of pig urethral muscle that were increased in amplitude and duration by PDE-5 inhibition. At 0.1 microm, sildenafil, vardenafil or tadalafil significantly prolonged the mean (sem) duration of the relaxation at 4 Hz by 55 (19)%, 45 (14)% and 51 (12)%, respectively.

CONCLUSIONS

PDE-5-, cGMP- and PKG1-IR is widely distributed in human and pig urethral tissues. Nerve-induced relaxations of urethral preparations were enhanced at low concentrations of sildenafil, vardenafil and tadalafil, whereas there were direct smooth muscle-relaxant actions of the PDE-5 inhibitors at high concentrations. Inhibition of PDE-5 might be an interesting option to facilitate cGMP-mediated relaxation of the outflow region.

Lower urinary tract symptoms and sexual dysfunction: epidemiology and pathophysiology

There is ample evidence from many epidemiological studies that lower urinary tract symptoms (LUTS) and sexual dysfunction are strongly linked, independently of age and comorbidities such as hypertension, diabetes, dyslipidaemia and coronary heart disease. However, a causal link between both conditions is not yet established. Four pathophysiological mechanisms currently support the relationship between LUTS and erectile dysfunction (ED): (i) The nitric oxide synthase (NOS)/NO theory; there is a reduction in NOS-containing nerves in the prostate and bladder/urethra in patients with bladder outlet obstruction (BOO), and that lack of NO or loss of protein kinase G causes ED; (ii) The autonomic hyperactivity and metabolic syndrome hypothesis: benign prostatic hyperplasia (BPH) may be part of the metabolic syndrome, which includes cardiovascular diseases (e.g. hypertension, ischaemic heart disease) and diabetes mellitus, known risk factors for ED. Hypertension, obesity, and hyperinsulinaemia have all been claimed to be associated with an increased sympathetic activity. Increased sympathetic activity is involved in LUTS/BPH and may have a role in ED/sexual dysfunction, with noradrenaline and alpha1-adrenoceptors representing a common link; (iii) the Rho-kinase activation/endothelin pathway; there can be increased Rho-kinase activity, and consequently calcium sensitivity of the contractile machinery, in prostate smooth muscle in BPH, the detrusor in BOO, corpora cavernosa in ED, and in the resistance vessels in hypertension. The actions of several factors beside noradrenaline (e.g. endothelin-1, angiotensin II), possibly involved in the increased smooth muscle activity found in both LUTS/BPH and sexual dysfunction, are dependent on Rho-kinase activity. Thus increased Rho-kinase activity might represent a common link between LUTS and sexual dysfunction; (iv) Pelvic atherosclerosis; animal models mimicking pelvic ischaemia and hypercholesterolaemia show similar smooth muscle alterations of the detrusor and corpora. Pelvic ischaemia may induce the biological modifications described above and may thus represent as well a common link between LUTS and sexual dysfunction. Studies treating one condition (e.g. ED) and measuring the impact on the other (e.g. LUTS) should further contribute to support this common link.

Alpha-adrenoceptors are a common denominator in the pathophysiology of erectile function and BPH/LUTS - implications for clinical practice

A literature search of PubMed documented publications and abstracts from proceedings of scientific meetings was made to review the available data on benign prostatic hyperplasia/lower urinary tract symptoms (BPH/LUTS) and erectile dysfunction (ED) with a special focus on the role of alpha-adrenoceptors as critical mediators of pathophysiology. The reader is introduced to clinical results on the therapeutic potential of alpha-blockers alone and in combination with phosphodiesterase type 5 (PDE-5) inhibitors in the treatment of ED associated with LUTS/BPH. Epidemiological studies clearly show that an association exists between ED and LUTS/BPH. The severity of LUTS is correlated with the risk for ED. A significant number of LUTS/BPH patients are nonresponsive to the common ED treatment with PDE-5 inhibitors. As smooth muscle contractility is regulated by adrenoceptors in the corpus cavernosum, prostate and detrusor, the alpha-adrenoceptor system may be considered a common pathophysiological mediator in the development of ED and LUTS/BPH. Blockade of alpha-adrenoceptors for the treatment of BPH/LUTS may have the potential of improving sexual function. Conversely, PDE-5 inhibitors may exhibit positive effects in LUTS patients. Pilot studies on combination regimens of alpha-adrenoceptor antagonists and PDE-5 inhibitors have yielded encouraging results in LUTS patients with persistent ED. On the basis of pharmacological and clinical evidence, it is established that the alpha-adrenoceptor system plays an important role in the pathophysiology of ED and LUTS secondary to BPH. Larger trials on the combination of alpha-adrenoceptor antagonists with PDE-5 inhibitors are necessary to develop an integrated treatment approach for BPH/LUTS patients with comorbid ED.

The female partner's satisfaction with sildenafil citrate treatment of erectile dysfunction

BACKGROUND

Data on female partners' satisfaction are scarce, although there have been many articles on patient satisfaction after sildenafil citrate treatment. The aim of this study was to evaluate the satisfaction of female partners of patients receiving sildenafil citrate for their erectile dysfunction (ED) and to assess the female partners' sexual function.

METHODS

Ninety-eight patients with ED were treated. Their female partners were asked to answer a questionnaire we have prepared to evaluate the efficacy of treatment, sexual satisfaction and changes in quality of life. It also included a question about female sexual function. From the results, the relationship between their female partner's satisfaction and efficacy of treatment, as well as female sexual function, were assessed.

RESULTS

Thirty (31%) questionnaires were returned to us for analysis. Effectiveness of the treatment was acknowledged by 90% of the partners. An improvement in their partner's quality of life was noticed by 60% of the women. The majority (66.7%) of the female partners were satisfied with sildenafil citrate treatment and 20% were disappointed. Moreover, 20% of the female partners were concerned about adverse events. Regarding female sexual function, some form of sexual dysfunction affected 46.7% of the women. Furthermore, a significant number (P = 0.0230) of the female partners disappointed with the treatment had some kind of sexual dysfunction.

CONCLUSIONS

The results indicated that female partners reported relatively high levels of treatment satisfaction. Female partners' sexual function and anxiety regarding adverse events should be evaluated when their satisfaction with sildenafil citrate treatment is poor despite an improvement of erectile function.