The relationship between erectile dysfunction and lower urinary tract symptoms and the role of phosphodiesterase type 5 inhibitors

Prophylactic effect of tadalafil on bladder function in a rat model of chronic bladder ischemia

PURPOSE

We investigated the effect of tadalafil on chronic ischemia related bladder dysfunction.

MATERIALS AND METHODS

Adult male Sprague-Dawley® rats were divided into control, arterial endothelial injury and arterial endothelial injury with tadalafil treatment groups. The arterial injury and arterial injury-tadalafil groups underwent endothelial injury of the iliac arteries and received a 2% cholesterol diet after injury. Arterial injury-tadalafil rats received tadalafil (2 mg/kg per day) orally for 8 weeks after injury. The control group received a regular diet. At 8 weeks urodynamic investigation was performed. Bladder tissue was harvested for pharmacological studies, and histological examination of the iliac arteries and bladders was performed.

RESULTS

Iliac arteries from arterial injury and arterial injury-tadalafil rats showed neointimal formation and luminal occlusion. In the arterial injury group the micturition interval was significantly shorter (mean ± SEM 5.4 ± 0.5 vs 11.1 ± 1.1 minutes), and bladder capacity and voided volume were less than in controls. Contractile responses of bladder strips to KCl, electrical field stimulation and carbachol were significantly less after arterial injury than in controls. The arterial injury group showed a significantly increased percent of collagen compared with controls (mean 37.4% ± 1.8% vs 21.5% ± 1.8%). In the arterial injury-tadalafil group intimal formation and luminal occlusion were not prevented. However, there were significant improvements in all functional and morphological parameters compared with the arterial injury group.

CONCLUSIONS

Arterial occlusive disease may lead to chronic bladder ischemia and bladder hyperactivity. Chronic treatment with tadalafil protects bladder function and morphology, resulting in decreased bladder hyperactivity. If valid for humans, the data support phosphodiesterase 5 inhibition as treatment for chronic ischemia related bladder dysfunction.

Les inhibiteurs de la phosphodiestérase de type 5 : une révolution dans le traitement des symptômes du bas appareil urinaire?

Contexte

L’incidence des symptômes du bas appareil urinaire (SBAU) liés à une hypertrophie bénigne de prostate (HBP) augmente avec l’âge puisqu’ils touchent 50 % des patients âgés de plus de 50 ans et 90 % de ceux âgés de plus de 80 ans. La prévalence et la sévérité de la dysfonction érectile (DE) augmentent également avec l’âge. Sa prévalence est évaluée à 31,6 % dans une population générale d’adultes âgés de plus de 40 ans. Les SBAU comme la DE altèrent de façon significative la qualité de vie (QdV) des patients et de leur partenaire. Plusieurs études ont montré que les SBAU constituent un facteur de risque de DE indépendant de l’âge et des autres comorbidités. La sévérité des SBAU est corrélée à celle de la DE. Les hypothèses physiopathologiques pour expliquer le lien entre SBAU et DE sont : une augmentation du tonus sympathique, une altération du système NO/cGMP, une altération du système rho-kinase et une athéromatose pelvienne.

Objectif

Évaluer les résultats et comprendre le mécanisme d’action de l’administration d’un inhibiteur de la phosphodiestérase de type 5 (IPDE 5) sur les SBAU liés à une HBP.

Matériels et méthodes

Une revue de la littérature a été réalisée à partir des articles originaux et des articles de synthèse déjà disponibles, sélectionnés par le moteur de recherche Pubmed de la National Library of Medecine. Les mots clés utilisés pour cette recherche ont été : benign prostatic hyperplasia; cyclic nucleotide phosphodiesterase type 5; LUTS; erectile dysfunction.

Résultats

Cette revue de la littérature montre que l’administration d’un inhibiteur de la phosphodiestérase de type 5 améliore les SBAU de manière significative dans 12 essais cliniques randomisés, avec un bénéfice également sur la DE et l’absence d’effets secondaires indésirables graves rapportés.

Conclusion

Le traitement des SBAU par les IPDEs 5 semble très prometteur, même s’il ne dispose pas d’une AMM dans cette indication en France. Récemment, le tadalafil à la posologie de 5 mg a été approuvé aux États-Unis par la FDA dans les troubles mictionnels liés à l’HBP, avec ou sans DE.

Testosterone regulates smooth muscle contractile pathways in the rat prostate: emphasis on PDE5 signaling

Testosterone (T) plays a permissive role in the development of benign prostatic hyperplasia (BPH), and phosphodiesterase 5 inhibitors (PDE5is) have been found to be effective for BPH and lower urinary tract symptoms (LUTS) in clinical trials. This study investigated the effect of T on smooth muscle (SM) contractile and regulatory signaling pathways, including PDE5 expression and functional activity in prostate in male rats (sham-operated, surgically castrated, and castrated with T supplementation). In vitro organ bath studies, real-time RT-PCR, Western blot analysis, and immunohistochemistry were performed. Castration heavily attenuated contractility, including sensitivity to phenylephrine with SM myosin immunostaining revealing a disrupted SM cell arrangement in the stroma. PDE5 was immunolocalized exclusively in the prostate stroma, and orchiectomy signficantly reduced PDE5 immunopositivity, mRNA, and protein expression, along with nNOS and ROKβ mRNA, whereas it increased eNOS plus α(1a) and α(1b) adrenoreceptor expression in castrated animals. The PDE5i zaprinast significantly increased prostate strip relaxation to the nitric oxide donor sodium nitroprusside (SNP) in control but not castrated rats. But SNP alone was more effective on castrated rats, comparable with sham treated with SNP plus zaprinast. T supplementation prevented or restored all above changes, including SNP and zaprinast in vitro responsiveness. In conclusion, our data show that T positively regulates PDE5 expression and functional activities in prostate, and T ablation not only suppresses prostate size but also reduces prostatic SM contractility, with several potential SM contraction/relaxation pathways implicated. Zaprinast findings strongly suggest a major role for PDE5/cGMP in this signaling cascade. PDE5 inhibition may represent a novel mechanism for treatment of BPH.

Effects of testosterone on the lower urinary tract go beyond the prostate: New insights, new treatment options

The traditional assumption that the prostate is an organ exquisitely sensitive to androgen action still holds true, but with lower-than-normal circulating levels of testosterone, all androgen receptors are saturated and a further increase in circulating levels of testosterone has no effect on the prostate (saturation model). Prostate disease (prostate cancer and benign prostatic hyperplasia, BPH) usually occur at an age when circulating levels of testosterone are declining, so it is unlikely that they are to be attributed to an excess of testosterone. The bother of BPH is presently subsumed under ‘pathology of the lower urinary tract’. Surprisingly, these structures have androgen receptors, and depend for their relaxation on nitric oxide, for which the mechanism, in turn, is aided by androgens. This explains why phosphodiesterase type-5 inhibitors also benefit erectile function and symptoms of the lower urinary tract. Normalisation of testosterone in hypogonadal men favours this action. During the development of the prostate, epithelium and mesenchyme are under the control of testicular androgens, and interact to form an organised secretory organ. Furthermore, many of the disease processes of the prostate have been attributed to androgen action, and consequently, therapies have been aimed at manipulating androgen activity.

Phosphodiesterase type 5 inhibitors in the management of non-neurogenic male lower urinary tract symptoms: critical analysis of current evidence

CONTEXT

A large body of epidemiologic data suggests a causal relationship between lower urinary tract symptoms (LUTS) and erectile dysfunction (ED). Recently reported studies on phosphodiesterase type 5 inhibitors (PDE5-Is) and LUTS have further contributed to the understanding of mechanisms involved in this relationship and of potential treatment options.

OBJECTIVE

A nonsystematic descriptive review was performed to summarize the literature concerning the role of PDE5-Is in men with LUTS, particularly looking at data derived from clinical trials in relation to the different PDE5-Is or their association with α-blockers.

EVIDENCE ACQUISITION

A comprehensive electronic search was conducted in October 2010 using the Medline database to identify all publications relating to ED and BPH and treatment with sildenafil, vardenafil, tadalafil, udenafil, UK-369003, and combination therapy with alfuzosin and tamsulosin.

EVIDENCE SYNTHESIS

In studies in which either ED or LUTS was the entry criterion, sildenafil appears to improve both erectile function and LUTS in subjects with ED. Placebo-controlled trials of tadalafil and vardenafil showed improvement of LUTS secondary to benign prostatic hyperplasia (BPH), but none of the studies showed a significant effect on urodynamic measures. Exploratory studies with UK-369003 showed improvements in LUTS and ED. Sildenafil or tadalafil associated with alfuzosin or tamsulosin showed greater benefits for the combination therapy for both LUTS and ED. The coadministration of udenafil and an α-blocker in patients with BPH and ED also appeared to improve both LUTS and ED severity.

CONCLUSIONS

Consistent evidence of improvements in LUTS has been shown with PDE5-Is, either alone or in combination with α-blockers. However, effects on urodynamics or objective measures of urinary flow are lacking. Further areas of research include investigation of mechanism of PDE5-Is, urodynamic studies, identification of new efficacy end points, head-to-head comparison with standard of care, potential benefit of add-on treatment, and long-term outcomes.

Tadalafil for the treatment of lower urinary tract symptoms secondary to benign prostatic hyperplasia: pathophysiology and mechanism(s) of action

BACKGROUND

The PDE5 inhibitor tadalafil is investigation for the treatment of lower urinary tract symptoms (LUTS) in men with benign prostatic hyperplasia (BPH). Several clinical studies of tadalafil and other PDE5 inhibitors have reported significant symptom reduction but limited urinary flow rate improvement. This manuscript reviews the published literature describing the pathophysiology of male LUTS, with an emphasis on mechanisms that may be modulated or improved by phosphodiesterase type 5 (PDE5) inhibition.

METHODS

Literature (through March 2010) was obtained via Medline searches and from the individual reviewers files. Articles were selected for review based on describing in vitro, preclinical, or clinical studies of pathological processes contributing to LUTS, or possible effects of PDE5 inhibition in the lower urinary tract.

RESULTS

Major mechanisms contributing to LUTS include: reduced nitric oxide/cyclic guanosine monophosphate signaling; increased RhoA kinase pathway activity; autonomic overactivity; increased bladder afferent activity; and pelvic ischemia. Tadalafil and other PDE5 inhibitors have demonstrated beneficial effects on smooth muscle relaxation, smooth muscle and endothelial cell proliferation, nerve activity, and tissue perfusion that may impact LUTS in men.

CONCLUSIONS

The pathophysiology of male LUTS is complex and not completely understood. LUTS may occur independently of BPH or secondary to BPH but in both cases involve obstructive or irritative mechanisms with substantial pathophysiological overlap. While the precise mechanism remains unclear, inhibition of PDE5 seems to have an effect on several pathways that may impact LUTS.

Impact of lower urinary tract symptoms/benign prostatic hyperplasia treatment with tamsulosin and solifenacin combination therapy on erectile function

PURPOSE

To examine the effects on erectile function of concomitant treatment with an alpha-blocker (tamsulosin) and an antimuscarinic agent (solifenacin) in patients with lower urinary tract symptoms (LUTS)/benign prostatic hyperplasia (BPH).

MATERIALS AND METHODS

Fifty-seven male patients with LUTS/BPH were assessed for the degree of LUTS and erectile function. In group 1 (tamsulosin) and group 2 (tamsulosin and solifenacin), changes in the International Prostate Symptom Score [IPSS: total scores, storage symptoms (ST), voiding symptoms (VD), and quality of life (QoL)], prostate-specific antigen, trans-rectal ultrasonography, urine flowmetry, residual urine, and a 5-item version of the International Index of Erectile Function (IIEF-5) were assessed after a 3-month treatment period. In both groups, it was determined whether treatment was associated with changes in LUTS and erectile function and whether improvement in the IPSS was correlated with the IIEF-5. Comparative analysis was also done to examine the linear relationship between improved IPSS scores and IIEF-5 scores.

RESULTS

A comparison of the degree of improvement in all the parameters indicated that both groups showed significant improvement in total IPSS, IPSS-ST, IPSS-VD, and IPSS-QoL (p<0.05). A comparison of the degree of improved sexual function associated with improved LUTS in each patient showed significant improvement in the IIEF-5 score associated with the degree of improvement in the IPSS-ST domain in group 1, but no significant associations were found in group 2. In cases in which tamsulosin was administered, the IIEF-5 score significantly improved as the IPSS-ST domain score improved. In the group in which tamsulosin and solifenacin were concomitantly administered, improvement of the IPSS-ST domain score had no significant effect on the IIEF-5 score.

CONCLUSIONS

In patients with LUTS/BPH, tamsulosin and solifenacin combination therapy was effective for LUTS, but erectile function was not significantly improved. Therefore, although effective for improving LUTS, combination therapy with an alpha-blocker and an antimuscarinic agent was not effective for improving erectile function.

Activity of phosphodiesterase type 5 inhibitors in patients with lower urinary tract symptoms due to benign prostatic hyperplasia

OBJECTIVE

• To evaluate the impact and distribution of a single phosphodiesterase type 5 inhibitor (PDE5 I) dose (udenafil or tadalafil) in prostate tissue and plasma in patients with benign prostatic hyperplasia (BPH).

PATIENTS AND METHODS

• Thirty BPH patients complaining of erectile dysfunction along with moderate-to-severe lower urinary tract symptoms (LUTS) who underwent transurethral resection of the prostate (TURP) were enrolled in the present study. • The patients were randomly divided into the three groups: group 1, TURP without PDE5 Is; group 2, 200 mg of udenafil given 1 h before TURP; and group 3, 20 mg of tadalafil given 1 h before TURP. • We evaluated the concentrations of PDE5-I, cAMP and cGMP in prostate tissues and plasma, and calculated the prostate tissue-to-plasma (T/P) ratio.

RESULTS

• The concentration of udenafil in prostate tissue and plasma was 2028.6 ± 360.8 ng/g and 463.7 ± 39.1 ng/mL, respectively, and the resulting T/P ratio was 4.4. The tadalafil concentration in prostate tissue and plasma was 385.7 ± 83.8 ng/g and 305.8 ± 41.1 ng/mL, respectively, and the T/P ratio was 1.3. • Udenafil and tadalafil significantly increased the cAMP and cGMP levels in plasma and prostate tissues.

CONCLUSIONS

• Udenafil and tadalafil significantly increased cAMP and cGMP levels and were more highly distributed in the prostate than plasma. The T/P ratio of udenafil was higher than tadalafil. • These findings may help in the assessment of the feasibility of using PDE5 Is to concurrently treat both LUTS and erectile dysfunction.

Prevalence and factors associated with uncomplicated storage and voiding lower urinary tract symptoms in community-dwelling Australian men

PURPOSE

To determine the prevalence of, and associated risk factors for, voiding and storage lower urinary tract symptoms (LUTS) in a population-based sample of Australian men.

METHODS

Data were collected from 1,103 men randomly selected, community-dwelling men, as part of the Florey Adelaide Male Ageing Study, after exclusion of men with prostate or bladder cancer or prior surgery to either organ. The presence of LUTS was assessed using the International Prostate Symptom Score. Urine flow was measured via flow meter. Demographic, clinical, and bio-psychosocial data were collected by questionnaire.

RESULTS

The prevalence of total, storage, and voiding LUTS was 18.1, 28.0 and 12.6%, respectively. The most common storage symptoms were frequency (12.3%), nocturia (9.9%) and urgency (8.1%), and voiding symptoms were weak stream (8.5%), intermittency (5.4%), incomplete emptying (5.1%) and straining (2.4%). There were linear associations between storage LUTS and increased abdominal fat mass, plasma glucose and low HDL cholesterol (components of the metabolic syndrome), obstructive sleep apnoea (OSA) risk, and retirement. Voiding symptoms were associated with a previous diagnosis of benign prostatic enlargement (BPH), mean peak urine flow, total energy intake, elevated risk of OSA, erectile dysfunction, physician-diagnosed thyroid dysfunction and higher household income.

CONCLUSIONS

The close association of storage LUTS with the metabolic syndrome, and of both storage and voiding LUTS with OSA, suggest that these conditions should be considered in men presenting with LUTS.

Attenuated proliferation and trans-differentiation of prostatic stromal cells indicate suitability of phosphodiesterase type 5 inhibitors for prevention and treatment of benign prostatic hyperplasia

Benign prostatic hyperplasia (BPH) is characterized by tissue overgrowth and stromal reorganization primarily due to cellular proliferation and fibroblast-to-myofibroblast trans-differentiation. To evaluate the potential of phosphodiesterase type 5 (PDE5) inhibitors like tadalafil for prevention and treatment of BPH, we analyzed the role of the nitric oxide/cyclic GMP (cGMP)/PDE5 pathway for cellular proliferation and TGFbeta1-induced fibroblast-to-myofibroblast trans-differentiation in primary prostate stromal cells. Inhibition by tadalafil of PDE5, which is mainly expressed in the stromal compartment of the prostate, reduced proliferation of primary prostate stromal cells and to a lesser extent of primary prostate basal epithelial cells. Attenuated proliferation due to elevated intracellular cGMP levels was confirmed by inhibition of the cGMP-dependent protein kinase G by its inhibitor KT2358. Moreover, tadalafil strongly attenuated TGFbeta1-induced fibroblast-to-myofibroblast trans-differentiation. The inhibitory effect on trans-differentiation was also observed after small interfering RNA-mediated PDE5 knockdown. As confirmed by the MAPK kinase 1 inhibitor PD98059, this effect was mediated via MAPK kinase 1 signaling. We conclude that BPH patients might benefit from adjuvant therapies with PDE5 inhibitors that inhibit stromal enlargement due to cell proliferation, as well as TGFbeta1-induced trans-differentiation processes.

Effects of tadalafil on lower urinary tract symptoms secondary to benign prostatic hyperplasia in men with or without erectile dysfunction

OBJECTIVES

To compare the safety and efficacy of the daily erectogenic therapy, tadalafil, on lower urinary tract symptoms secondary to benign prostatic hyperplasia (BPH-LUTS) in men with or without comorbid erectile dysfunction (ED).

METHODS

Following a 4-week placebo run-in period, men with moderate-to-severe BPH-LUTS were randomized to placebo or tadalafil 2.5, 5, 10, or 20 mg once daily for 12 weeks. International Prostate Symptom Scores (IPSS), IPSS quality of life, and BPH Impact Index were measured every 4 weeks. Safety was mainly assessed via spontaneous reports of adverse events. Data from men with (n=716) or without (n=340) ED at baseline were compared in posthoc analyses.

RESULTS

Men with ED were older and had more frequent hypertension, hyperlipidemia, coronary artery disease, and diabetes at baseline compared with men without ED. After 12 weeks, changes in IPSS in men with ED (least squares mean change from baseline, placebo: -2.4; tadalafil 2.5, 5, 10, 20 mg: -4.3, -4.8, -5.3, -5.6) and without ED (-2.4, -3.2, -5.3, -5.1, -4.5) were not significantly different (subgroup/interaction P values: .352/.644). Similar effects were observed for IPSS quality of life (with ED: -0.6, -0.9, -0.9, -1.0, -1.1; without ED: -0.6, -0.7, -0.9, -0.8, -0.8; 0.090/0.773) and BPH Impact Index (with ED: -0.7, -0.9, -1.3, -1.3, -1.4; without ED: -1.0, -0.7, -1.3, -1.3, -1.2; 0.753/0.852). Tadalafil was generally well tolerated, and men with or without ED had similar tolerability profiles.

CONCLUSIONS

Changes in BPH-LUTS after 12 weeks of treatment with placebo or various doses of once daily tadalafil were similar in men with or without comorbid ED.

PDE5 inhibitors for LUTS

To review the current literature regarding the relationship between lower urinary tract symptoms (LUTS) and erectile dysfunction (ED), and the role of phosphodiesterase-5 (PDE5) inhibitors for the treatment of LUTS. Review of recently published (1990-2009) data regarding epidemiologic and pathophysiologic mechanisms are involved in LUTS-ED, focusing on PDE5 inhibitors particularly evidenced from level 1 clinical trials. Search terms included phosphodiesterase inhibitors, nitric oxide, autonomic hyperactivity, Rho-kinase, atherosclerosis, LUTS, benign prostatic hypertrophy, and ED. Results of several epidemiologic studies show a possible causal relationship between LUTS and ED. Four possible mechanisms have been proposed to explain this association. Multiple large clinical trials have shown a benefit in LUTS after PDE5-inhibitors treatment. PDE5 inhibitors show promise as a future treatment for LUTS, either in conjunction with existing therapies or as a primary treatment.