Petter Hedlund

Pharmacologic perspective on the physiology of the lower urinary tract.

Myogenic activity, distention of the detrusor, and signals from the urothelium may initiate voiding. In the bladder, afferent nerves have been identified not only in the detrusor, but also suburothelially, where they form a plexus that lies immediately beneath the epithelial lining. Extracellular adenosine triphosphate (ATP) has been found to mediate excitation of small-diameter sensory neurons via P2X3 receptors, and it has been shown that bladder distention causes release of ATP from the urothelium. In turn, ATP can activate P2X3 receptors on suburothelial afferent nerve terminals to evoke a neural discharge. However, most probably, not only ATP but also a cascade of inhibitory and stimulatory transmitters and mediators are involved in the transduction mechanisms underlying the activation of afferent fibers during bladder filling. These mechanisms may be targets for future drugs. The central nervous control of micturition involves many transmitter systems, which may be suitable targets for pharmacologic intervention. gamma-Aminobutyric acid, dopamine, enkephalin, serotonin, and noradrenaline receptors and mechanisms are known to influence micturition, and potentially, drugs that affect these systems could be developed for clinical use. However, a selective action on the lower urinary tract may be difficult to obtain. Most drugs currently used for treatment of detrusor overactivity have a peripheral site of action, mainly the efferent (cholinergic) neurotransmission and/or the detrusor muscle itself. In the normal bladder, muscarinic receptor stimulation produces the main part of detrusor contraction, but evidence is accumulating that in disease states, such as neurogenic bladders, outflow obstruction, idiopathic detrusor instability, and interstitial cystitis, as well as in the aging bladder, a noncholinergic activation via purinergic receptors may occur. If this component of activation is responsible not only for part of the bladder contractions, but also for the symptoms of the overactive bladder, it should be considered an important target for therapeutic interventions.

CHOLINERGIC NERVES IN HUMAN CORPUS CAVERNOSUM AND SPONGIOSUM CONTAIN NITRIC OXIDE SYNTHASE AND HEME OXYGENASE

PURPOSE To characterize the distribution of cholinergic nerves in the human corpus cavernosum (CC) and spongiosum (CS) using antibodies to the vesicular acetylcholine transporter (VAChT), and to compare this distribution to those of other transmitters/mediators or transmitter/mediator generating enzymes (heme oxygenases: HO-1 and HO-2; neuronal and endothelial NO synthases: nNOS and eNOS; vasoactive intestinal polypeptide: VIP; and tyrosine hydroxylase: TH), and to investigate NO- and carbon monoxide (CO)-mediated effects. MATERIALS AND METHODS Immunocytochemistry, confocal laser scanning microscopy, radioimmunoassay, and functional in vitro studies. RESULTS Along strands of smooth muscle in the CC and CS, rich numbers of VAChT-, nNOS-, VIP-, TH-, and very few HO-1-immunoreactive (-IR) nerve fibers were observed. Immunoreactivities for VAChT and nNOS, VAChT and VIP, and nNOS and VIP, were generally found in the same varicose nerve terminals. TH-IR nerve fibers or terminals did not contain immunoreactivities for VAChT, NOS or VIP. In the endothelium lining penile arteries, immunoreactivities for eNOS, HO-1, and HO-2 were detected. Single endothelial cells, lining the sinusoidal walls of the CC and CS, were found also to contain eNOS and HO-immunoreactivities. Noradrenaline (NA)-contracted preparations of CC and CS were relaxed by NO, CO, carbachol and by electrical stimulation of nerves. Inhibition of NO synthesis abolished electrically- and carbachol-induced relaxation. In NA-activated strips, relaxation induced by exogenously applied NO, but not those by CO, were accompanied by increases in intracellular levels of cyclic GMP. CONCLUSIONS VAChT, NOS and VIP are found in the same nerve terminals within the human CC and CS, suggesting that these terminals comprise a distinct population of parasympathetic, cholinergic nerves. Endothelially derived NO and the HO/CO system may have a complementary role in penile erection.

Heme oxygenase and NO-synthase in the human prostate – relation to adrenergic, cholinergic and peptide-containing nerves

In the human prostate, the distribution of heme oxygenase (HO-1 and HO-2)-, nitric oxide synthase (NOS)-, and tyrosine hydroxylase (TH)-immunoreactive (IR), acetylcholine-esterase (AChE)-positive, and some peptidergic nerve structures was investigated. Cell bodies and nerve fibers within coarse nerve trunks expressed HO-1-, HO-2-, NOS-, TH-, and vasoactive intestinal polypeptide (VIP)-immunoreactivities, and were AChE-positive, but, as revealed by confocal microscopy. HO- and NOS-immunoreactivities were found in separate nerves. Along strains of smooth muscle, intraglandular septa, and around acini, HO-1-, NOS-, and VIP-IR nerves, and AChE-positive fibers were observed. Double immunostaining showed that NOS- and VIP-immunoreactivities were generally co-localized in varicose nerve terminals. Some TH-IR terminals had profiles that were similar, but not identical, to those of NOS-, HO-1-, or VIP-IR terminals. NPY-IR nerves were similarly distributed as VIP- and NOS-IR fibers, and were found in rich amounts. Calcitonin gene-related peptide (CGRP)-IR nerves were few compared to other nerve populations studies. NOS- and CGRP-IR terminals had similar profiles, but the immunoreactivities were not co-localized. Nitric oxide and electrical stimulation of nerves relaxed noradrenaline-contracted preparations of prostatic stroma. Inhibition of synthesis of nitric oxide abolished the electrically induced relaxations. VIP had small relaxant effects, whereas carbon monoxide was without effect on noradrenaline-contracted strips. The innervation pattern and the functional effects suggest that the L-arginine/nitric oxide pathway may have a role in the control of human prostatic smooth muscle activity and/or in secretory neurotransmission. A physiological role of carbon monoxide in the prostate remains to be established.

NO synthase in cholinergic nerves and NO-induced relaxation in the rat isolated corpus cavernosum

In the rat corpus cavernosum (CC), the distribution of immunoreactivity for neuronal and endothelial NO synthase (nNOS and eNOS), and the pattern of NOS‐immunoreactive (‐IR) nerves in relation to some other nerve populations, were investigated. Cholinergic nerves were specifically immunolabelled with antibodies to the vesicular acetylcholine transporter protein (VAChT). In the smooth muscle septa surrounding the cavernous spaces, and around the central and helicine arteries, the numbers of PGP‐ and tyrosine hydroxylase (TH)‐IR terminals were large, whereas neuropeptide Y (NPY)‐, VAChT‐, nNOS‐, and vasoactive intestinal polypeptide (VIP)‐IR terminals were found in few to moderate numbers. Double immunolabelling revealed that VAChT‐ and nNOS‐IR terminals, VAChT‐ and VIP‐IR terminals, nNOS‐IR and VIP‐IR terminals, and TH‐ and NPY‐IR terminals showed coinciding profiles, and co‐existence was verified by confocal laser scanning microscopy. TH immunoreactivity was not found in VAChT‐, nNOS‐, or VIP‐IR nerve fibres or terminals. An isolated strip preparation of the rat CC was developed, and characterized. In this preparation, cumulative addition of NO to noradrenaline (NA)‐contracted strips, produced concentration‐dependent, rapid, and almost complete relaxations. Electrical field stimulation of endothelin‐1‐contracted preparations produced frequency‐dependent responses: a contractile twitch followed by a fast relaxant response. After cessation of stimulation, there was a slow relaxant phase. Inhibition of NO synthesis, or blockade of guanylate cyclase, abolished the first relaxant phase, whereas the second relaxation was unaffected. The results suggest that in the rat CC, nNOS, VAChT‐, and VIP‐immunoreactivities can be found in the same parasympathetic cholinergic neurons. Inhibitory neurotransmission involves activation of the NO‐system, and the release of other, as yet unknown, transmitters.

Intratunical injection of human adipose tissue-derived stem cells prevents fibrosis and is associated with improved erectile function in a rat model of Peyronie's disease.

BACKGROUND Peyronies disease (PD) is a connective tissue disorder of the tunica albuginea (TA). Currently, no gold standard has been developed for the treatment of the disease in its active phase. OBJECTIVE To test the effects of a local injection of adipose tissue-derived stem cells (ADSCs) in the active phase of a rat model of PD on the subsequent development of fibrosis and elastosis of the TA and underlying erectile tissue. DESIGN, SETTING, AND PARTICIPANTS A total of 27 male 12-wk-old Sprague-Dawley rats were divided in three equal groups and underwent injection of vehicle (sham), 0.5-μg [corrected] transforming growth factor (TGF)-β1 in a 50-μl vehicle in either a PD or a PD plus ADSC group in the dorsal aspect of the TA. INTERVENTION The sham and PD groups were treated 1 d after TGF-β1 injection with intralesional treatment of vehicle, and the PD plus ADSC group received 1 million human-labeled ADSCs in the 50-μl vehicle. Five weeks after treatment, six rats per group underwent erectile function measurement. Following euthanasia, penises were harvested for histology and Western blot. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS The ratio of intracavernous pressure to mean arterial pressure (ICP/MAP) upon cavernous nerve stimulation, elastin, and collagen III protein expression and histomorphometric analysis of the penis. Statistical analysis was performed by analysis of variance followed by the Tukey-Kramer test for post hoc comparisons or the Mann-Whitney test when applicable. RESULTS AND LIMITATIONS Erectile function significantly improved after ADSC treatment (ICP/MAP 0.37 in PD vs 0.59 in PD plus ADSC at 5-V stimulation; p=0.03). PD animals developed areas of fibrosis and elastosis with a significant upregulation of collagen III and elastin protein expression. These fibrotic changes were prevented by ADSC treatment. CONCLUSIONS This study is the first to test stem cell therapy in an animal model of PD. Injection of ADSCs into the TA during the active phase of PD prevents the formation of fibrosis and elastosis in the TA and corpus cavernosum.

The role of the transient receptor potential (TRP) superfamily of cation-selective channels in the management of the overactive bladder

• The pathophysiology of lower urinary tract symptoms (LUTS), detrusor overactivity (DO), and the overactive bladder (OAB) syndrome is multifactorial and remains poorly understood.

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

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.

Phasic non-micturition contractions in the bladder of the anaesthetized and awake rat

To characterize the contractile activity that occurs in the bladder during the filling phase of the micturition cycle (non‐micturition contractions, NMCs), which generate transient rises in intravesical pressure not associated with urine flow.

Nerve-sparing approach during radical prostatectomy is strongly associated with the rate of postoperative urinary continence recovery

Urinary incontinence and erectile dysfunction are the most bothersome sequelae affecting health‐related quality of life in patients treated with radical prostatectomy for prostate cancer. While it has been widely reported that a nerve‐sparing approach significantly improves postoperative erectile function, the impact of neurovascular bundle preservation on urinary continence recovery is still a matter of controversy. Our study clearly demonstrates that patients treated with nerve‐sparing radical prostatectomy have higher chances of recovering full continence after surgery. The results indicate that, when technically and oncologically feasible, an attempt at a nerve‐sparing approach should be planned in order to increase the probability of achieving full continence after radical prostatectomy.

Transient receptor potential A1 (TRPA1) activity in the human urethra--evidence for a functional role for TRPA1 in the outflow region.

BACKGROUND A role for the transient receptor potential (TRP) A1 ion channel in rat lower urinary tract (LUT) sensation and disease has been proposed, but in the human LUT no information on TRPA1 activity is available. OBJECTIVES To investigate the distribution of TRPA1 in the human urethra and to study the effect of TRPA1 agonists on isolated urethral strip preparations. DESIGN, SETTINGS, AND PARTICIPANTS Urethral specimens were obtained preoperatively from 10 patients and were freshly prepared for Western blot, immunohistochemistry, and functional in vitro investigations. MEASUREMENTS The expression patterns of TRPA1 were studied with Western blot and immunohistochemistry. The effects of allyl isothiocyanate (AI), cinnamaldehyde (CA), and NaHS (donor of H(2)S) on tension of urethral strips were investigated in tissue baths. RESULTS AND LIMITATIONS TRPA1 immunoreactivity (-IR) was found in nerve fibres in the suburothelial space and was also located to nerve fibres of the muscle layer. Single TRPA1-IR nerves extended into the urothelium. A majority, but not all TRPA1-IR nerves also expressed immunoreactivity for CGRP or TRPV1. In the urothelium, TRPV1 was located to the outer layers whereas TRPA1 was observed in basal urothelial cells. Interspersed between strands of smooth muscle cells of the urethral wall, TRPA1- and vimentin-IR cells containing central nuclei and slender cytoplasmatic extensions were observed. In functional experiments, TRPA1-agonists had no contractile effect in urethral preparations. After precontraction with phenylephrine, AI, CA, and NaHS caused concentration-dependent relaxations of urethral strip preparations. CONCLUSIONS The localization of TRPA1 to nerves that also express TRPV1 and CGRP, and in urothelial cells and interstitial cells, as well as the findings that TRPA1 agonists can modify tone of urethral preparations, propose a role for TRPA1 in afferent and efferent sensory signaling of the human outflow region.