Novel imaging of the prostate reveals spontaneous gland contraction and excretory duct quiescence together with different drug effects

The oxytocin antagonist cligosiban reduces human prostate contractility: Implications for the treatment of benign prostatic hyperplasia

BACKGROUND AND PURPOSE

With increasing life expectancy, benign prostatic hyperplasia (BPH) consequently affects more ageing men, illustrating the urgent need for advancements in BPH therapy. One emerging possibility may be the use of oxytocin antagonists to relax smooth muscle cells in the prostate, similar to the currently used (although often associated with side effects) α1-adrenoceptor blockers.

EXPERIMENTAL APPROACH

For the first time we used live-imaging, combined with a novel image analysis method, to investigate the multidirectional contractions of the human prostate and determine their changes in response to oxytocin and the oxytocin antagonists atosiban and cligosiban. Human prostate samples were obtained and compared from patients undergoing prostatectomy due to prostate cancer as well as from patients with transurethral resection of prostate tissue due to severe BPH.

KEY RESULTS

The two cohorts of tissue samples showed spontaneous multidirectional contractions, which significantly increased after the addition of oxytocin. Different to atosiban, which showed ambiguous effects of short duration, only long-acting cligosiban reliably prevented, as well as counteracted, any contractile oxytocin effect. Furthermore, cligosiban visibly reduced not only oxytocin-induced contractions, but also showed intrinsic activity to relax prostatic tissue.

CONCLUSION AND IMPLICATIONS

Thus, the oxytocin antagonist cligosiban could be an interesting candidate in the search for novel BPH treatment options.

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.

Treatment of benign prostatic hyperplasia and abnormal ejaculation: live imaging reveals tamsulosin - but not tadalafil - induced dysfunction of prostate, seminal vesicles and epididymis

In brief

One of the most commonly prescribed benign prostatic hyperplasia (BPH) pharmacotherapies, the alpha1-adrenergic blocker tamsulosin, is frequently discontinued, especially by younger patients due to ejaculatory disorders, often without feedback to the attending physician. Using a newly developed ex vivo system simulating sympathetic effects on the most relevant structures for the emission phase of ejaculation, that is seminal vesicles, prostate and the most distal part of the cauda epididymidis, we elucidated that tamsulosin fundamentally disturbed the obligatory noradrenaline-induced contractions in each of these structures which differed to an alternative pharmacotherapy, the PDE5 inhibitor tadalafil.

Abstract

Structures responsible for the emission phase of ejaculation are the seminal vesicles, the most distal part of the cauda epididymidis and the newly characterized prostate excretory ducts. The emission phase is mainly regulated by the sympathetic nervous system through alpha1-adrenergic receptor activation by noradrenaline at the targeted organs. BPH treatment with alpha1A-adrenergic antagonists such as tamsulosin is known to result in ejaculation dysfunction, often leading to discontinuation of therapy. Mechanisms of this disturbance remain unclear. We established a rodent model system to predict drug responses in tissues involved in the emission phase of ejaculation. Imitating the therapeutic situation, prostate ducts, seminal vesicles and the distal cauda epididymal duct were pre-incubated with the smooth muscle cell-relaxing BPH drugs tadalafil, a novel BPH treatment option, and tamsulosin in an ex vivo time-lapse imaging approach. Afterwards, noradrenergic responses in the relevant structures were investigated to simulate sympathetic activation. Noradrenaline-induced strong contractions ultimately lead to secretion in structures without pre-treatment. Contractions were abolished by tamsulosin in prostate ducts and seminal vesicles and significantly decreased in the epididymal duct. Such effects were not observed with tadalafil pre-treatment. Data visualized a serious dysfunction of each organ involved in emission by affecting alpha1-adrenoceptors localized at the relevant structures but not by targeting smooth muscle cell-localized PDE5 by tadalafil. Our model system reveals the mechanism of tamsulosin resulting in adverse effects during ejaculation in patients treated for BPH. These adverse effects on contractility do not apply to tadalafil treatment. This new knowledge translates directly to clinical medicine.

Tadalafil and Steroid Hormones Interactions in Adipose, Bone and Prostate Tissues: Focus on Translational Perspectives

Tadalafil is a selective phosphodiesterase type-5 (PDE5) inhibitor that is approved for the treatment of men with erectile dysfunction (ED) and/or benign prostate hyperplasia (BPH) -associated symptoms. Besides its classical actions on PDE5 within the genitourinary tract, where the specific enzyme expression is maximal, it may exert different systemic effects. This is mainly due to the pleiotropic distribution of PDE5 enzyme throughout the human (and animal) body, where it can exert protective effects in different clinical conditions. Recently, it has been demonstrated that tadalafil may display novel actions on androgen receptor (AR) expression and activity and cytochrome P19a1 (Cyp19a1) and estrogen receptor β (ERβ) expression in different in vitro systems, such as adipose, bone and prostate cancer cells, where it can act as a selective modulator of steroid hormone production. This may determine novel potential mechanism(s) of control in pathophysiologic pathways. In this review, we summarize basic research and translational results applicable to the use of tadalafil in the treatment of obesity, bone loss and prostate cancer.

Tissue clearing to examine tumour complexity in three dimensions

The visualization of whole organs and organisms through tissue clearing and fluorescence volumetric imaging has revolutionized the way we look at biological samples. Its application to solid tumours is changing our perception of tumour architecture, revealing signalling networks and cell interactions critical in tumour progression, and provides a powerful new strategy for cancer diagnostics. This Review introduces the latest advances in tissue clearing and three-dimensional imaging, examines the challenges in clearing epithelia - the tissue of origin of most malignancies - and discusses the insights that tissue clearing has brought to cancer research, as well as the prospective applications to experimental and clinical oncology.

Phosphodiesterase Type-5 Inhibitor Tadalafil Modulates Steroid Hormones Signaling in a Prostate Cancer Cell Line

Background: The androgen receptor (AR) plays a key role in normal prostate homeostasis and in prostate cancer (PCa) development, while the role of aromatase (Cyp19a1) is still unclear. We evaluated the effects of a treatment with Tadalafil (TAD) on both these proteins. Methods: Androgen-sensitive human PCa cell line (LnCAP) was incubated with/without TAD (10⁻⁶ M) and bicalutamide (BCT) (10⁻⁴ M) to evaluate a potential modulation on cell proliferation, protein and mRNA expression of Cyp19a, AR and estrogen receptor-β (ERβ), respectively. Results: TAD increased early AR nuclear translocation (p < 0.05, after 15 min of exposure), and increased AR transcriptional activity (p < 0.05) and protein expression (p < 0.05) after 24 h. Moreover, after 24 h this treatment upregulated Cyp19a1 and ERβ mRNA (p < 0.05 and p < 0.005 respectively) and led to an increase in protein expression of both after 48 h (p < 0.05). Interestingly, TAD counteracted Cyp19a1 stimulation induced by BCT (p < 0.05) but did not alter the effect induced by BCT on the AR protein expression. Conclusion: We demonstrate for the first time that TAD can significantly modulate AR expression and activity, Cyp19a1 and ERβ expression in PCa cells, suggesting a specific effect of these proteins. In addition, TAD potentiates the antiproliferative activity of BCT, opening a new clinical scenario in the treatment of PCa.

Cohesive cancer invasion of the biophysical barrier of smooth muscle

Smooth muscle is found around organs in the digestive, respiratory, and reproductive tracts. Cancers arising in the bladder, prostate, stomach, colon, and other sites progress from low-risk disease to high-risk, lethal metastatic disease characterized by tumor invasion into, within, and through the biophysical barrier of smooth muscle. We consider here the unique biophysical properties of smooth muscle and how cohesive clusters of tumor use mechanosensing cell-cell and cell-ECM (extracellular matrix) adhesion receptors to move through a structured muscle and withstand the biophysical forces to reach distant sites. Understanding integrated mechanosensing features within tumor cluster and smooth muscle and potential triggers within adjacent adipose tissue, such as the unique damage-associated molecular pattern protein (DAMP), eNAMPT (extracellular nicotinamide phosphoribosyltransferase), or visfatin, offers an opportunity to prevent the first steps of invasion and metastasis through the structured muscle.