Effects of Phosphodiesterase Inhibitors on the Contractile Responses of Isolated Human Seminal Vesicle Tissue to Adrenergic Stimulation

Commonality and heterogeneity of pacemaker mechanisms in the male reproductive organs

During emission, the first phase of ejaculation, smooth muscle in organs of the male reproductive tract (MRT) vigorously contract upon sympathetic nerve excitation to expel semen consisting of sperm and seminal plasma. During inter-ejaculation phases, the epididymis, seminal vesicles and prostate undergo spontaneous phasic contractions (SPCs), this transporting and maintaining the quality of sperm and seminal plasma. Recent studies have revealed platelet-derived growth factor receptor α-expressing (PDGFRα+) subepithelial interstitial cells in seminal vesicles subserve the role of pacemaker cells that electrically drive SPCs in this organ. PDGFRα+ smooth muscle cells in the epididymis also appear to function as pacemaker cells implicating PDGFRα as a potential signature molecule in MRT pacemaking. The dominant mechanism driving pacemaking in these organs is the cytosolic Ca2+ oscillator. This operates through entrainment of the release-refill cycle of Ca2+ stores, the released Ca2+ ions opening Ca2+-activated chloride channels, including in some cases ANO1 (TMEM16A), with the resultant pacemaker potential activating L-type voltage-dependent Ca2+ channels in the smooth muscle causing contraction (viz. SPCs). A second pacemaker mechanism, namely the membrane oscillator also has a role in specific cases. Further investigations into the commonality and heterogeneity of MRT pacemakers will open an avenue for understanding the pathogenesis of male infertility associated with deterioration of seminal plasma.

Network Pharmacology-Based Strategy to Investigate Pharmacological Mechanisms of Qiaoshao Formula for Treatment of Premature Ejaculation

Background

Qiaoshao (QS) formula, a traditional Chinese medicine (TCM) comprising seven herbs, has been clinically proven to have a favorable treatment effect on premature ejaculation (PE). However, its underlying pharmacological mechanisms in the treatment of PE need to be further clarified.

Methods

In the present study, a network pharmacology-based strategy was adopted. The active compounds of QS formula were obtained from the Chinese medicine database, and the potential targets of these compounds were collected from the DrugBank database to construct compound-compound targets network. PE-related targets were identified from human disease databases and used to construct the protein-protein interaction (PPI) networks. Compound-disease target PPI network was constructed by merging the PPI network of disease-targets and compound-targets. Cluster and enrichment analyses were performed on the PPI network of disease targets and compound-disease targets. The influence of QS formula on serum 5-HT, NO, oxytocin, and thyroid hormones of PE patients was verified.

Results

Four primary pharmacological networks of QS formula were constructed, including the compound-compound targets network, PPI network of PE-related targets and compound-disease targets, and the QS-PE mechanism network. The module and pathway enrichment analyses revealed that the QS formula had the potential to affect varieties of biological process and pathways, such as nitric oxide biosynthetic process, oxytocin, thyroid hormone, TNF, PI3K-Akt, and the HIF-1 signaling pathway, that play an important role in the pathogenesis of PE. Meanwhile, the QS formula has been clinically confirmed to regulate the serum level of 5-HT, NO, oxytocin, and TT in PE patients.

Conclusion

This study preliminarily discovered the potential targets and pathways of QS formula in the treatment of PE, which laid a good foundation for further experimental research.

Skills Vs. Pills: Comparative Effectiveness for Low Sexual Desire in Women

This study compared the effectiveness of a skill-based bibliotherapy intervention and a placebo pill intervention purported to be efficacious in increasing women's sexual desire. Forty-five participants were randomized into the two groups after completing pretest measures of sexual desire and functioning. After completing their interventions, participants completed 6-week posttest and 12-week follow-up measures. Results demonstrated that when compared to the placebo pill group, the bibliotherapy group made statistically greater gains from pretest to follow-up in sexual desire and satisfaction. Nevertheless, the placebo pill group evidenced short-term improvements in sexual desire over time. Findings have implications for future research and current treatments for low sexual desire in women.

Phosphodiesterase Inhibitors (PDE Inhibitors) and Male Reproduction

The nonspecific PDE inhibitors, particularly the methylxanthines: caffeine, pentoxifylline (PTX), and theophylline, are known to stimulate sperm motility in vitro and have been used to treat sperm prior to insemination. The in vivo effects are less dramatic. A beneficial effect of caffeine, which is a constituent of some medications, remains controversial. Very high doses of caffeine do have negative effects on fertility endpoints in men and experimental species. The specific PDE5 inhibitors, particularly sildenafil and tadalafil, are prescribed for erectile dysfunction, as well as pulmonary hypertension, lower urinary tract symptoms, and premature ejaculation. PDE5 is expressed throughout the contractile tissues of the male reproductive tract, generally increasing contractility. Some PDE5 inhibitors tend to increase circulating testosterone levels somewhat. For short-term exposure consistent with use prior to intercourse, there appears to be minimal effects on semen quality. Several large, randomized controlled trials (RCTs) in healthy men have not found adverse effects of long-term use of these drugs on semen quality. RCTs in infertile men have demonstrated a modest increase in semen quality. Animal studies at human equivalent doses (HED) have produced similar results in young males, but a study in aging male rats found progressive decreases in epididymal sperm quality accompanied by consistent degeneration of the seminal tubules suggesting that studies in older men might be warranted. A concerning study in mice found lower fertilization rates in males treated with HED of sildenafil and mated the next day to untreated females than for control males. Fertility studies in humans are needed.

Physiology and Pharmacology of Ejaculation

Ejaculation is the final stage of coitus in mammalian male and is mandatory for natural procreation. Two synchronized phases, emission and expulsion, form the ejaculatory response and involve specific organs and anatomical structures. The peripheral events leading to ejaculation are commanded by autonomic (sympathetic and parasympathetic) and somatic divisions of the nervous system. The autonomic and somatic motor efferents originate in spinal nuclei located in thoracolumbar and lumbosacral segments. Co-ordinated activation of autonomic and somatic spinal nuclei is orchestrated by a group of lumbar spinal interneurons defined as the spinal generator of ejaculation. The generator of ejaculation together with the autonomic and somatic spinal nuclei constitutes a spinal network that is under the strong influence of stimulating or inhibiting genital sensory and supraspinal inputs. A brain circuitry dedicated to ejaculation has been delineated that is part of a more global network controlling other aspects of the sexual response. This circuitry includes discrete neuronal populations distributed in all divisions of the brain. The corollary to the expanded CNS network is the variety of neurotransmitter systems participating in the ejaculatory process. Among them, serotonin neurotransmission plays a key role and its targeting led to the development of the first registered pharmacological treatment of premature ejaculation in human beings. Critical gaps remain in the understanding of neurophysiopharmacology of ejaculation and management of ejaculatory disorders in human beings needs improvement. Because the ejaculatory response in laboratory animals and in human beings shares many similarities, the use of animal models will certainly provide further advances in the field.

First Pharmacological Therapy for Hypoactive Sexual Desire Disorder in Premenopausal Women

Objective: To review data regarding flibanserin, a recently approved therapy for hypoactive sexual desire disorder (HSDD). Data Sources: Literature search of MEDLINE (September 1995 to November 2015) was performed using the search term flibanserin. Reference lists from included articles were reviewed for pertinent citations. Study Selection and Data Extraction: We included phase-3 trials of flibanserin as a treatment for HSDD. Four reports of phase-3 trials were included. One extension study of four phase-3 trials and one phase-2 pharmacokinetic trial were also included. Data Synthesis: Though a strong placebo response was demonstrated, flibanserin consistently, yet marginally, showed improvement (compared with placebo) in the number of satisfying sexual events per month. The most common adverse events were dizziness (11.4%), somnolence (11.2%), nausea (10.4%), fatigue (9.2%), insomnia (4.9%), and dry mouth (2.4%). Conclusions: Flibanserin is effective in the treatment of HSDD. Flibanserin should be administered at bedtime to limit the risk for hypotension/syncope, accidental injury, and central nervous system (CNS) depression. Concomitant alcohol use contributes to significant CNS depression and hypotension/syncope with flibanserin and should be avoided according to the boxed warning. Careful patient assessment prior to the diagnosis of HSDD and the use of flibanserin is needed for safe use. Prescribing guidelines recommend discontinuing flibanserin at 8 weeks in the absence of benefit. Sexual dysfunction should be addressed in a patient-specific manner. Providers should exercise shared decision making in prescribing flibanserin for HSDD and discuss flibanserin’s benefits and alternative options.

Peripheral arterial tonometry to measure the effects of vardenafil on sympathetic tone in men with lifelong premature ejaculation

To elucidate whether adrenergic overtone is involved in the pathophysiology of men with lifelong (LL) premature ejaculation (PE), we investigated differences in reactive hyperemia index (RHI) responses by using peripheral arterial tonometry (PAT). 20 men with LL-PE (18-40 years) were enrolled in an 8-week, double-blind, placebo-controlled, crossover study and compared with 10 age-matched controls without LL-PE. Primary endpoints were PAT modifications induced by vardenafil 10 mg on demand. Secondary endpoints were the improvement in intravaginal ejaculatory latency time (IELT) as measured by the stopwatch technique and variations in anxiety scores at Stai-X1 for state-anxiety and Stai-X2 for trait-anxiety. At baseline, men with LL-PE showed higher RHI variation (P < 0.001), Stai-X1 and Stai X2 scores (P < 0.0001, resp.), and prolactin levels (P < 0.05) compared with controls. Vardenafil treatment markedly reduced RHI variation in men with LL-PE (P < 0.01) when compared with placebo. Mean changes in geometric IELT were higher after taking vardenafil (0.6 ± 0.3 versus 4.5 ± 1.1 min, P < 0.01) when compared with placebo. STAI-X1 and STAI-X2 scores fell within the normal range after treatment with vardenafil (P < 0.01). Vardenafil was an effective treatment in men with LL-PE; improvements of IELT may be due to increased NO production which is able to reduce adrenergic overactivity and anxiety levels.

Seminal vesicles and diabetic neuropathy: ultrasound evaluation after prolonged treatment with a selective phosphodiesterase-5 inhibitor

We have previously reported that infertile patients with diabetes mellitus (DM) have a particular ultrasound features of the seminal vesicles (SV) characterized by higher fundus-to-body ratio and lower pre- and post-ejaculatory difference in body antero-posterior diameter (APD). Based on these premises the aim of the present study was to investigate possible ultrasound SV changes in infertile patients with DM and diabetic neuropathy (DN), after prolonged administration of tadalafil (TAD) (a specific phosphodiesterase-5 inhibitor). To accomplish this, 20 infertile patients with symptomatic DN and erectile dysfunction were selected and arbitrarily divided into two groups which were assigned to: daily administration of 5 mg TAD for 3 months (Group A) (n = 10) and administration of placebo (Group B) (n = 10). All patients underwent to scrotal and prostate-vesicular transrectal ultrasound evaluation and semen analysis (Laboratory Manual for the Examination and Processing of Human Semen, WHO, 2010) before and after treatment. The following SV US parameters were recorded: (i) body APD; (ii) fundus APD; (iii) parietal thickness of the right and left SVs; and (iv) number of polycyclic areas within both SVs. We then calculated the following parameters: (i) fundus/body (F/B) ratio; (ii) difference of the parietal thickness between the right and the left SV and (iii) pre- and post-ejaculatory APD difference. In addition, we also evaluated the SV ejection fraction. Group A patients showed a significant reduction in F/B ratio and higher pre- and post-ejaculatory body SV APD difference compared with baseline or Group B after 3 months. These patients showed also a significant increase in SV ejection fraction and a significant improvement of the total sperm count, progressive motility, seminal levels of fructose, leucocytes and ejaculate volume. In conclusion, these results suggest that infertile DM patients with DN and erectile dysfunction had an improvement of ultrasound features suggestive of diabetic neuropathy after daily treatment with low doses of TAD.

Flibanserin: A Potential Treatment for Hypoactive Sexual Desire Disorder in Premenopausal Women

Hypoactive Sexual Desire Disorder (HSDD) is defined as a persistent or recurrent deficiency of sexual fantasies and desire for sexual activity, which causes marked personal distress or interpersonal difficulty, and is not better accounted for by another psychiatric disorder or the direct physiological effects of a substance (e.g., a medication) or medical condition. HSDD is believed to be the most common form of Female Sexual Dysfunction and is associated with emotional distress and relationship problems. No pharmacologic therapy is approved for the treatment of HSDD in premenopausal or naturally postmenopausal women. Flibanserin is a 5-HT1A agonist/5-HT2A antagonist that is under investigation as a treatment for HSDD in women. The aim of this article is to present an overview of the pharmacology, clinical efficacy and safety of flibanserin. Flibanserin is an investigational drug that is not licensed for any indication in any country.

Characterization of the effects of various drugs likely to affect smooth muscle tension on isolated human seminal vesicle tissue

OBJECTIVES

To investigate the effects of different classes of drugs on the isometric tension of isolated human seminal vesicle (SV) tissue. The contractility of human SV contributes to the process of seminal emission during ejaculation. Different endogenous compounds, such as serotonin (5-HT), adenosine triphosphate (ATP), and nitric oxide, have been suggested to be involved in the control of contraction and relaxation of human SV smooth muscle. However, only limited data are available regarding the effects of compounds known to affect smooth musculature on SV contractile activity.

METHODS

Using the organ bath technique, the effects of increasing concentrations (10 nm-1 microm/10 microm) of norepinephrine (NE), phenylephrine, endothelin 1, ATP, and 5-HT on human SV tissue at basal tension were studied. In another set-up, SV strip preparations were preincubated with prazosin (alpha-adrenergic blocker), nifedipine and verapamil (Ca(2+)-channel blockers), 2-aminoethoxydiphenyl borate [inositol 1,4,5-trisphosphate (IP(3)) antagonist], cromakalim (K(+)-channel opener), or Y-27632 (ROK inhibitor) (1 microm each, for 10 minutes), followed by the application of NE (0.1 microM, 1 microM, and 10 microm).

RESULTS

SV smooth muscle was most effectively contracted by NE (mean = 75% of calibrated scale), phenylephrine (mean = 82% of calibrated scale), and endothelin 1 (mean = 70% calibrated scale), whereas only minor responses to ATP (mean = 10.65% calibrated scale) and 5-HT (mean = 6.3% calibrated scale) were observed. The contraction induced by NE was significantly inhibited after pre-exposure of the tissue to prazosin (-92.4%), cromakalim (-83.7%), 2-aminoethoxydiphenyl borate (-43.1%), Y-27632 (-42.8%), and nifedipine (-32.7%).

CONCLUSIONS

alpha-adrenoceptor antagonism, activation of potassium channels, and inhibition of Rho-kinase decrease the sympathetic contraction of SV smooth muscle. This might be of significance with regard to the identification of new pharmacologic avenues to affect the male ejaculatory system.

Effects of vardenafil administration on intravaginal ejaculatory latency time in men with lifelong premature ejaculation

Premature ejaculation (PE) is thought to be the most common male sexual dysfunction; however, the prevalence of lifelong (LL)-PE is relatively low. The aim of this study was to investigate the effects of on-demand vardenafil (10 mg) to modify the intravaginal ejaculatory latency time (IELT) in men with LL-PE without erectile dysfunction. Forty-two men (18-35 years) were enrolled in a 16-week, double-blind, placebo-controlled, cross-over study. Primary end point was the modification from baseline of IELT assessed by stopwatch technique; secondary end points were post-ejaculatory refractory time (PERT) and variations of scores at the Index of Premature Ejaculation questionnaire. The changes in geometric mean IELT were superior after taking vardenafil (0.6+/-0.3 vs 4.5+/-1.1 min, P<0.01), compared with placebo (0.7+/-0.3 vs 0.9+/-1.0 min, ns). PERT dropped significantly after vardenafil (16.7+/-2.0 vs 4.3+/-0.9 min, P<0.001), compared with placebo (15.3+/-2.2 vs 15.8+/-2.3 min). Patients who took vardenafil (vs placebo) reported significantly (P<0.01) increased ejaculatory control (6+/-2 vs 16+/-2), improved overall sexual satisfaction (7+/-2 vs 15+/-1) and distress (4+/-1 vs 8+/-1) scores, respectively. Multiple regression analysis (r(2)=0.86) for IELT by the number of attempts at sexual intercourse showed significant differences between the slopes of lines for placebo and vardenafil (P<0.0001). The most common adverse events for vardenafil (vs placebo) were headache (10 vs 3%), flushing (12 vs 0%) and dyspepsia (10 vs 0%), which tended to disappear over the time. In conclusion, in our study, vardenafil increased IELT and reduced PERT in men with LL-PE. Besides, improvements in confidence, perception of ejaculatory control and overall sexual satisfaction were reported.