Detection of muscarinic receptor subtypes in human urinary bladder mucosa: age and gender-dependent modifications

Practical solutions for including sex as a biological variable (SABV) in preclinical neuropsychopharmacological research

Recently, many funding agencies have released guidelines on the importance of considering sex as a biological variable (SABV) as an experimental factor, aiming to address sex differences and avoid possible sex biases to enhance the reproducibility and translational relevance of preclinical research. In neuroscience and pharmacology, the female sex is often omitted from experimental designs, with researchers generalizing male-driven outcomes to both sexes, risking a biased or limited understanding of disease mechanisms and thus potentially ineffective therapeutics. Herein, we describe key methodological aspects that should be considered when sex is factored into in vitro and in vivo experiments and provide practical knowledge for researchers to incorporate SABV into preclinical research. Both age and sex significantly influence biological and behavioral processes due to critical changes at different timepoints of development for males and females and due to hormonal fluctuations across the rodent lifespan. We show that including both sexes does not require larger sample sizes, and even if sex is included as an independent variable in the study design, a moderate increase in sample size is sufficient. Moreover, the importance of tracking hormone levels in both sexes and the differentiation between sex differences and sex-related strategy in behaviors are explained. Finally, the lack of robust data on how biological sex influences the pharmacokinetic (PK), pharmacodynamic (PD), or toxicological effects of various preclinically administered drugs to animals due to the exclusion of female animals is discussed, and methodological strategies to enhance the rigor and translational relevance of preclinical research are proposed.

Efficacy and Safety of DA-8010, a Novel M3 Antagonist, in Patients With Overactive Bladder: A Randomized, Double-Blind Phase 2 Study

Purpose: DA-8010 is a novel muscarinic M3 receptor antagonist with significant selectivity for bladder over salivary gland in preclinical studies. We evaluated the clinical efficacy and safety of DA-8010 in overactive bladder (OAB) patients.Methods: This phase 2, randomized, double-blind, parallel-group, active reference- and placebo-controlled trial was conducted at 12 centers in South Korea (NCT03566134). Patients aged ≥19 years with OAB symptoms for ≥3 months were enrolled. Three hundred six patients (30.07% male) were randomized to 12 weeks of treatment among 4 groups; 2 experimental groups (DA-8010 2.5 or 5 mg), an active reference group (solifenacin 5 mg), and a placebo group. The change from the baseline of (=∆) 24-hour frequency at 12 weeks (primary endpoint), episodes of urgency, overall/urgency urinary incontinence, average/ maximum voided volume, nocturia, and patients’ subjective responses were analyzed.Results: In the full analysis set, the mean (standard deviation) [median] values for ∆ 24-hour frequency at 12 weeks were -1.01 (2.44) [-1.33] for placebo, -1.22 (2.05) [-1.33] for DA-8010 2.5 mg, and -1.67 (2.25) [-1.67] for DA-8010 5 mg; DA-8010 5 mg showed a significant decrease compared with placebo (P=0.0413). At 4 and 8 weeks, both DA-8010 2.5 mg (P=0.0391 at 4 weeks, P=0.0335 at 8 weeks) and DA-8010 5 mg (P=0.0001 at 4 weeks, P=0.0210 at 8 weeks) showed significant decrease in ∆ 24-hour frequency compared with placebo. DA-8010 5 mg achieved a significant decrease in ∆ number of urgency episodes, compared with placebo at 4 (P=0.0278) and 8 (P=0.0092) weeks. Adverse drug reactions (ADRs) were observed in 3.95% of placebo, 6.67% of DA-8010 2.5 mg, 18.42% of DA-8010 5 mg, and 17.33% of solifenacin 5 mg groups. No serious ADRs were observed in any patient.Conclusions: Both DA-8010 2.5 mg and 5 mg showed therapeutic efficacy for OAB without serious ADRs. Therefore, both dosages of DA-8010 can advance to a subsequent large-scale phase 3 trial.

The Urothelium: Life in a Liquid Environment

The urothelium, which lines the renal pelvis, ureters, urinary bladder, and proximal urethra, forms a high-resistance but adaptable barrier that surveils its mechanochemical environment and communicates changes to underlying tissues including afferent nerve fibers and the smooth muscle. The goal of this review is to summarize new insights into urothelial biology and function that have occurred in the past decade. After familiarizing the reader with key aspects of urothelial histology, we describe new insights into urothelial development and regeneration. This is followed by an extended discussion of urothelial barrier function, including information about the roles of the glycocalyx, ion and water transport, tight junctions, and the cellular and tissue shape changes and other adaptations that accompany expansion and contraction of the lower urinary tract. We also explore evidence that the urothelium can alter the water and solute composition of urine during normal physiology and in response to overdistension. We complete the review by providing an overview of our current knowledge about the urothelial environment, discussing the sensor and transducer functions of the urothelium, exploring the role of circadian rhythms in urothelial gene expression, and describing novel research tools that are likely to further advance our understanding of urothelial biology.

Gender specific pharmacokinetic and pharmacodynamic considerations for antimuscarinic drugs for overactive bladder treatment

Introduction: Overactive bladder (OAB) has a heterogeneous presentation that varies between individuals and by gender. Treatment with antimuscarinic medications is standard first line pharmacotherapy for most patients with OAB. However, gender specific differences in the pharmacokinetics and pharmacodynamics of antimuscarinic therapy are often overlooked and not discussed.Areas covered: This review will explore differences by gender between the presentation and treatment of OAB. We will discuss the differences between sexes in terms of lower urinary tract anatomy, muscarinic receptors, and hormone variation. The effect of antimuscarinics on males and females as well as adherence and persistence patterns will be reviewed in order to fully review all available literature on the gender specific pharmacokinetic and pharmacodynamic considerations for antimuscarinic use in the treatment of OAB.Expert opinion: Despite extensive research into various antimuscarinic formulations and therapeutic regimens for the treatment of OAB, identification of gender specific pharmacokinetic and pharmacodynamics considerations remains scant. As our knowledge and understanding of OAB, muscarinic receptors, and antimuscarinic medications evolve, we will hopefully be better able to understand and implement gender-specific and genomic-sprecific treatment regimens and considerations for improved clinical outcomes.

The efficacy of mirabegron in the treatment of urgency and the potential utility of combination therapy

Urgency is the prevalent and most bothersome symptom of overactive bladder (OAB) and the treatment of urgency is the primary objective in the management of OAB. Urgency has a major impact on other symptoms of OAB and culminates in an increased frequency of micturition and reduced volume voided, which may contribute to shorter intervals between the need to void. Antimuscarinic agents and mirabegron, a β3-adrenoceptor agonist, constitute the main oral pharmacotherapeutic options for the treatment of urgency and other OAB symptoms. The reduction of urgency and other OAB symptoms significantly improve health-related quality of life. This review will explore the distinct mechanisms of action and effects of antimuscarinic agents and mirabegron, in relation to their effect on the pathophysiology of urgency. The review will also provide an overview of the various validated measurements of urgency and the numerous clinical trials regarding antimuscarinic agent monotherapy, mirabegron monotherapy, or combination treatment with mirabegron added on to the antimuscarinic agent solifenacin. A narrative review of the literature relating to pathophysiology of urgency, the validated measurements of urgency, and clinical trials relating to the pharmacological treatment of urgency. Antimuscarinic agent monotherapy, mirabegron monotherapy, or combination treatment with mirabegron added on to the antimuscarinic agent solifenacin statistically significantly reduce the symptoms of urgency compared with placebo. Combination therapy with mirabegron added on to solifenacin also statistically significantly reduces the symptoms of severe urgency compared with antimuscarinic agent monotherapy. A critique of the clinical benefits of combination therapy is also provided. Combination therapy provides an alternative treatment in patients with OAB that includes urgency who respond poorly to first-line monotherapy and who may otherwise often move on to more invasive treatments.

Different muscarinic receptor subtypes modulate proliferation of primary human detrusor smooth muscle cells via Akt/PI3K and map kinases

While acetylcholine (ACh) and muscarinic receptors in the bladder are mainly known for their role in the regulation of smooth muscle contractility, in other tissues they are involved in tissue remodelling and promote cell growth and proliferation. In the present study we have used primary cultures of human detrusor smooth muscle cells (HDSMCs), in order to investigate the role of muscarinic receptors in HDSMC proliferation. Samples were obtained as discarded tissue from men >65 years undergoing radical cystectomy for bladder cancer and cut in pieces that were either immediately frozen or placed in culture medium for the cell culture establishment. HDSMCs were isolated from samples, propagated and maintained in culture. [(3)H]-QNB radioligand binding on biopsies revealed the presence of muscarinic receptors, with a Kd of 0.10±0.02nM and a Bmax of 72.8±0.1fmol/mg protein. The relative expression of muscarinic receptor subtypes, based on Q-RT-PCR, was similar in biopsies and HDSMC with a rank order of M2≥M3>M1>M4>M5. The cholinergic agonist carbachol (CCh, 1-100μM) concentration-dependently increased [(3)H]-thymidine incorporation (up to 46±4%). This was concentration-dependently inhibited by the general muscarinic receptor antagonist atropine and by subtype-preferring antagonists with an order of potency of darifenacin >4-DAMP>AF-DX 116. The CCh-induced cell proliferation was blocked by selective PI-3 kinase and ERK activation inhibitors, strongly suggesting that these intracellular pathways mediate, at least in part, the muscarinic receptor-mediated cell proliferation. This work shows that M2 and M3 receptors can mediate not only HDSM contraction but also proliferation; they may also contribute bladder remodelling including detrusor hypertrophy.

Urothelial signaling

The urothelium, which lines the inner surface of the renal pelvis, the ureters, and the urinary bladder, not only forms a high-resistance barrier to ion, solute and water flux, and pathogens, but also functions as an integral part of a sensory web which receives, amplifies, and transmits information about its external milieu. Urothelial cells have the ability to sense changes in their extracellular environment, and respond to chemical, mechanical and thermal stimuli by releasing various factors such as ATP, nitric oxide, and acetylcholine. They express a variety of receptors and ion channels, including P2X3 purinergic receptors, nicotinic and muscarinic receptors, and TRP channels, which all have been implicated in urothelial-neuronal interactions, and involved in signals that via components in the underlying lamina propria, such as interstitial cells, can be amplified and conveyed to nerves, detrusor muscle cells, and ultimately the central nervous system. The specialized anatomy of the urothelium and underlying structures, and the possible communication mechanisms from urothelial cells to various cell types within the bladder wall are described. Changes in the urothelium/lamina propria ("mucosa") produced by different bladder disorders are discussed, as well as the mucosa as a target for therapeutic interventions.

Sex differences in the physiology and pharmacology of the lower urinary tract

Sexual dimorphism is not only noticed in the prevalence of many diseases, but also in multiple physiological functions in the body. This review has summarized findings from published literature on the sex differences of the pathophysiology and pharmacology of the lower urinary tract (LUT) of humans and animals. Sex differences have been found in several key areas of the LUT, such as overactive bladder, expression and function of neurotransmitter receptors in the bladder and urethra, and micturition patterns in humans and animals. It is anticipated that this review will not only evoke renewed interest for further research on the mechanism of sex differences in the pathophysiology of the LUT (especially for overactive bladder), but might also open up the possibilities for gender-based drug development by pharmaceutical industries in order to find separate cures for men and women with diseases of the LUT.

Nervous network for lower urinary tract function

Traditionally, sensory signaling in the urinary bladder has been largely attributed to direct activation of bladder afferents. There is substantive evidence that sensory systems can be influenced by non-neuronal cells, such as the urothelium, which are able to respond to various types of stimuli that can include physiological, psychological and disease-related factors. The corresponding release of chemical mediators (through activation of a number of receptors/ion channels) can initiate signaling mechanisms between and within urothelial cells, as well as other cell types within the bladder wall including bladder nerves. However, the mechanisms underlying how various cell types in the bladder wall respond to normal filling and emptying, and are challenged by a variety of stressors (physical and chemical) are still not well understood. Alterations or defects in signaling mechanisms are likely to contribute to the pathophysiology of bladder disease with symptoms including urinary urgency, increased voiding frequency and pain. This review will discuss some of the components involved in control of lower urinary tract function, with an emphasis on the sensor and transducer roles of the urothelium.

Neurotransmitter influence on human meibomian gland epithelial cells

PURPOSE

A striking characteristic of the human meibomian gland is its rich sensory, sympathetic, and parasympathetic innervation, yet the functional relevance of these nerve fibers remains unknown. Acting on the hypothesis that neurotransmitters are released in the vicinity of the gland, act on glandular receptors, and influence the production, secretion, and/or delivery of meibomian gland secretions to the ocular surface, the goal in this study was to begin to determine whether neurotransmitters influence the meibomian gland.

METHODS

Immortalized human meibomian gland epithelial (SLHMG) cells were examined for the presence of vasoactive intestinal peptide (VIP) and muscarinic acetylcholine (mACh) receptor transcripts and proteins. Cells were also exposed to VIP, carbachol, forskolin, and/or 3-isobutyl-1-methylxanthine (IBMX) to determine whether these agents, alone or in combination, modulate the adenylyl cyclase pathway, the accumulation of intracellular free calcium ([Ca2+]i), or cell proliferation.

RESULTS

Results demonstrate that SLHMG cells transcribe and translate VIP and mACh receptors; VIP, with either IBMX or forskolin, activates the adenylyl cyclase pathway, and the effect of VIP and forskolin together is synergistic; both VIP and carbachol increase intracellular [Ca2+] in SLHMG cells; and VIP with forskolin stimulates SLHMG cell proliferation.

CONCLUSIONS

This study shows that parasympathetic neurotransmitters and their agonists influence the function of human meibomian gland epithelial cells. It remains to be determined whether this action alters the production, secretion, and/or delivery of meibum to the ocular surface.

Molecular and pharmacological detection of dopaminergic receptors in the human male urinary tract

AIMS

Evidence indicates that dopamine (DA) and DA receptors play a role in the central nervous system (CNS) control of micturition; however, while the central DAergic role in the micturition physiology has been extensively investigated, the expression and the function of DA receptors in the urinary tract are still under investigation. Here, we studied the distribution of DA receptor subtypes in different parts of the human male urinary tract.

METHODS

Fragments were collected from 34 men. The mRNAs encoding DA receptors were assessed by RT-PCR, followed by densitometric analysis. Adenylyl cyclase (AC) activity was evaluated using a commercially available RIA kit. Statistical analysis was carried out using one-way ANOVA, with the Bonferroni's post hoc test.

RESULTS

Results obtained indicated that RT-PCR products of D(1), D(4), and D(5) subtypes were obtained in each part studied, while no signal was observed for the D(2) and D(3) receptor subtypes. The pharmacological characterization demonstrated that the expressed DA receptors were linked to AC.

CONCLUSIONS

DA receptors were expressed throughout the human male urinary tract, from the ureter to the prostatic urethra. In particular, we observed a distinctive DA receptor subtype distribution, with evidence of the presence of mRNA encoding both subtypes of the D(1)-like DA receptor family (D(1) and D(5)), while the D(4) receptors were the only expressed subtype of the D(2)-like family. These results suggested that DAergic drugs used for the treatment of a number of diseases may influence the micturition physiology not only in the CNS, but at the peripheral level as well.

Lack of specificity of commercially available antisera: better specifications needed

The ideal antiserum for immunohistochemical (IHC) applications contains monospecific high-affinity antibodies with little nonspecific adherence to sections. Many commercially available antibodies are "affinity" purified, but it is unknown if they meet "hard" specificity criteria, such as absence of staining in tissues genetically deficient for the antigen or a staining pattern that is identical to that of an antibody raised against a different epitope on the same protein. Reviewers, therefore, often require additional characterization. Although the affinity-purified antibodies used in our study on the distribution of muscarinic receptors produced selective staining patterns on sections, few passed the preabsorption test, and none produced bands of the anticipated size on Western blots. More importantly, none showed a difference in staining pattern on sections or Western blots between wild-type and knockout mice. Because these antibodies were used in most studies published thus far, our findings cast doubts on the validity of the extant body of morphological knowledge of the whole family of muscarinic receptors. We formulate requirements that antibody-specification data sheets should meet and propose that journals for which IHC is a core technique facilitate consumer rating of antibodies. "Certified" antibodies could avoid fruitless and costly validation assays and should become the standard of commercial suppliers.