Neurotrophins in the lower urinary tract: becoming of age

Effects of oral administration of nonselective Trk inhibitor on bladder overactivity in rodent models of prostatic inflammation

BACKGROUND

Our research focused on the assessment of the impact of systemic inhibition of Trk receptors, which bind to nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), on bladder hypersensitivity in two distinct rodent models of prostatic inflammation (PI).

METHODS

Male Sprague-Dawley rats were divided into three groups (n = 6 each): the control group (no PI, vehicle administration), the untreated group (PI, vehicle administration), and the treated group (PI, nonselective Trk inhibitor, GNF 5837, administration). PI in rats was induced by a intraprostatic injection of 5% formalin. Posttreatment, we carried out conscious cystometry and a range of histological and molecular analyses. Moreover, the study additionally evaluated the effects of a nonselective Trk inhibitor on bladder overactivity in a mouse model of PI, which was induced by prostate epithelium-specific conditional deletion of E-cadherin.

RESULTS

The rat model of PI showed upregulations of NGF and BDNF in both bladder and prostate tissues in association with bladder overactivity and inflammation in the ventral lobes of the prostate. GNF 5837 treatment effectively mitigated these PI-induced changes, along with reductions in TrkA, TrkB, TrkC, and TRPV1 mRNA expressions in L6-S1 dorsal root ganglia. Also, in the mouse PI model, GNF 5837 treatment similarly improved bladder overactivity.

CONCLUSIONS

The findings of our study suggest that Trk receptor inhibition, which reduced bladder hypersensitivity and inflammatory responses in the prostate, along with a decrease in overexpression of Trk and TRPV1 receptors in sensory pathways, could be an effective treatment strategy for male lower urinary tract symptoms associated with PI and bladder overactivity.

Neurobiological insights into lower urinary tract dysfunction: evaluating the role of brain-derived neurotrophic factor

Lower urinary tract dysfunction (LUTD) encompasses a range of debilitating conditions that affect both sexes and different age groups. Understanding the underlying neurobiological mechanisms contributing to LUTD has emerged as a critical avenue for the development of targeted therapeutic strategies. Brain-derived neurotrophic factor (BDNF), a prominent member of the neurotrophin family, has attracted attention due to its multiple roles in neural development, plasticity, and maintenance. This review examines the intricate interplay between neurobiological factors and LUTD, focusing on the central involvement of BDNF. The review emphasizes the bidirectional relationship between LUTD and BDNF and explores how LUTD-induced neural changes may affect BDNF dynamics and vice versa. Growth factor therapy and the combined administration of controlled release growth factors and stem cells are minimally invasive treatment strategies for neuromuscular injury. Among the many growth factors and cytokines, brain-derived neurotrophic factor (BDNF) plays a prominent role in neuromuscular repair. As an essential neurotrophin, BDNF is involved in the modulation of neuromuscular regeneration through tropomyosin receptor kinase B (TrkB). Increasing BDNF levels facilitates the regeneration of the external urethral sphincter and contributes to the regulation of bladder contraction. Treatments targeting the BDNF pathway and sustained release of BDNF may become novel treatment options for urinary incontinence and other forms of lower urinary tract dysfunction. This review discusses the applications of BDNF and the theoretical basis for its use in the treatment of lower urinary tract dysfunction, including urinary incontinence (UI), overactive bladder (OAB), and benign prostatic hyperplasia (BPH), and in the clinical diagnosis of bladder dysfunction.

Development and validation of brain-derived neurotrophic factor measurement in human urine samples as a non-invasive effect biomarker

Background

Brain-derived neurotrophic factor (BDNF), a neurotrophic growth factor mainly expressed in the brain, has been proposed as a potential effect biomarker; that is, as a measurable biomarker whose values could be associated with several diseases, including neurological impairments. The European Human Biomonitoring Initiative (HBM4EU) has also recognized effect biomarkers as a useful tool for establishing link between exposure to environmental pollutants and human health. Despite the well-establish protocol for measuring serum BDNF, there is a need to validate its assessment in urine, a non-invasive sample that can be easily repeated over time. The aim of this study was to develop, standardize and validate a methodology to quantify BDNF protein levels in urine samples before its implementation in biomonitoring studies.

Methods

Different experimental conditions and non-competitive commercial enzyme-linked immunosorbent assay (ELISA) kits were tested to determine the optimal analytical procedure, trying to minimize the shortcomings of ELISA kits. The fine-tune protocol was validated in a pilot study using both upon awakening (n = 150) and prior to sleeping (n = 106) urine samples from the same Spanish adolescent males in a well-characterized study population (the Spanish INMA-Granada cohort).

Results

The best results were obtained in 0.6 ml of urine after the acidification and extraction (pre-concentration) of samples. The highest reproducibility was obtained with the ELISA kit from Raybiotech. Urinary BDNF concentrations of adolescent males were within the previously reported range (morning = 0.047-6.801 ng/ml and night = 0.047-7.404 ng/ml). Urinary BDNF levels in the awakening and pre-sleep samples did not follow a normal distribution and were not correlated.

Conclusion

The developed methodology offers good sensitivity and reproducibility. Having reliable markers in urine may facilitate both diagnosis and monitoring possible diseases (and treatment). Further studies are needed to implement urinary BDNF in biomonitoring studies to further elucidate its usefulness and biological significance for neurological impairments.

Effects of pharmacological neurotrophin receptor inhibition on bladder function in female mice with cyclophosphamide-induced cystitis

Interstitial cystitis/bladder pain syndrome is a chronic inflammatory pelvic pain syndrome of unknown etiology characterized by a number of lower urinary tract symptoms, including increased urinary urgency and frequency, bladder discomfort, decreased bladder capacity, and pelvic pain. While its etiology remains unknown, a large body of evidence suggests a role for changes in neurotrophin signaling, particularly that of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF). Here, we evaluated the effects of pharmacological inhibition of the NGF receptor TrkA, BDNF receptor TrkB, and pan-neurotrophin receptor p75NTR on bladder function in acute (4-hour) and chronic (8-day) mouse models of cyclophosphamide (CYP)-induced cystitis. TrkA inhibition via ARRY-954 significantly increased intermicturition interval and bladder capacity in control and acute and chronic CYP-treatment conditions. TrkB inhibition via ANA-12 significantly increased intermicturition interval and bladder capacity in acute, but not chronic, CYP-treatment conditions. Interestingly, intermicturition interval and bladder capacity significantly increased following p75NTR inhibition via LM11A-31 in the acute CYP-treatment condition, but decreased in the chronic condition, potentially due to compensatory changes in neurotrophin signaling or increased urothelial barrier dysfunction in the chronic condition. Our findings demonstrate that these receptors represent additional potent therapeutic targets in mice with cystitis and may be useful in the treatment of interstitial cystitis and other inflammatory disorders of the bladder.

Prevalence, Risk Factors, Pathophysiology, Potential Biomarkers and Management of Feline Idiopathic Cystitis: An Update Review

Feline idiopathic cystitis is a widespread disease in small animal clinics, which mainly presents with urinary signs like dysuria, stranguria, hematuria, pollakiuria, and periuria. The etiopathogenesis of the disease may involve interactions between the environmental stressors, neuroendocrine system and bladder of affected cats. Diagnostic biomarkers have not been tested in clinical studies though they are theoretically feasible, and since the clinical signs of the disease assemble those of other feline lower urinary diseases, its diagnosis is a procedure of exclusion. The primary treatment of the disease is long-term multimodal environmental modification (or enrichment) while anti-anxiety drugs and nutritional supplements are recommended for chronic recurrent cases. Still, many medicines need to be evaluated for their efficacy and safety. This review aims to provide readers with a comprehensive understanding of feline idiopathic cystitis by summarizing and updating studies concerning the prevalence, risk factors, etiological hypotheses, diagnostic procedures, possible treatments, and prognosis of the disease.

Neurophysiological control of urinary bladder storage and voiding-functional changes through development and pathology

The effective storage of urine and its expulsion relies upon the coordinated activity of parasympathetic, sympathetic, and somatic innervations to the lower urinary tract (LUT). At birth, all mammalian neonates lack the ability to voluntary regulate bladder storage or voiding. The ability to control urinary bladder activity is established as connections to the central nervous system (CNS) form through development. The neural regulation of the LUT has been predominantly investigated in adult animal models where comparatively less is known about the neonatal and postnatal neurophysiological development that facilitate urinary continence. Furthermore, congenital neurological or anatomical defects can adversely affect both storage and voiding functions through postnatal development and into adulthood, leading to secondary conditions including vesicoureteral reflux, chronic urinary tract infections, and end-stage renal disease. Therefore, the aim of the review is to provide the current knowledge available on neurophysiological regulation of the LUT through pre- to postnatal development of human and animal models and the consequences of congenital anomalies that can affect LUT neural function.

Asiatic Acid, a Natural Compound that Exerts Beneficial Effects on the Cystometric and Biochemical Parameters in the Retinyl Acetate-Induced Model of Detrusor Overactivity

Scientists have been constantly looking for new synthetic and natural compounds that could have beneficial effects in bladder overactivity. Our attention was drawn by asiatic acid that influences a number of molecules and signaling pathways relevant for the proper functioning of the urinary tracts in humans. In the present project we wanted to check whether asiatic acid would have positive effects in the confirmed animal model of detrusor overactivity (DO) and whether it would affect the bladder blood flow, urothelium thickness, inflammatory and oxidative stress markers, neurotrophic and growth factors, and other parameters important for the activity of the urinary bladder. The outcomes of our study showed that a 14-day administration of asiatic acid (30 mg/kg/day) by oral gavage normalizes the cystometric parameters corresponding to DO and reduces the accompanying oxidative stress (measured by the levels of malondialdehyde–61,344 ± 24,908 pg/ml vs. 33,668 ± 5,071 pg/ml, 3-nitrotyrosine–64,615 ± 25,433 pg/ml vs. 6,563 ± 1,736 pg/ml, and NOS2–2,506 ± 411.7 vs. 3,824 ± 470.1 pg/ml). Moreover, it decreases the urinary secretion of neurotrophins (BDNF–304.4 ± 33.21 pg/ml vs. 119.3 ± 11.49 pg/ml and NGF–205.5 ± 18.50 vs. 109.7 ± 15.94 pg/ml) and prevents the changes in a range of biomarkers indicating the dysfunction of the urinary bladder, CGRP (421.1 ± 56.64 vs. 108.1 ± 11.73 pg/ml), E-Cadherin (773.5 ± 177.5 pg/ml vs. 1,560 ± 154.5 pg/ml), OCT3 (3,943 ± 814.6 vs. 1,018 ± 97.07 pg/ml), SNAP-23 (6,763 ± 808.9 pg/ml vs. 3,455 ± 554.5 pg/ml), SNAP-25 (2,038 ± 162.7 pg/ml vs. 833.3 ± 65.48), substance P (171.7 ± 16.86 pg/ml vs. 65.07 ± 8.250 pg/ml), SV2A (1,927 ± 175.3 pg/ml vs. 1,154 ± 254.9 pg/ml), tight junction protein 1 (360.1 ± 95.05 pg/ml vs. 563.4 ± 65.43 pg/ml), VAChT (16,470 ± 2,419 pg/ml vs. 7,072 ± 1,339 pg/ml), VEGFA (318.3 ± 37.89 pg/ml vs. 201.5 ± 22.91 pg/ml). The mentioned parameters are associated with smooth muscle contractions, urothelial barrier, transportation and release of transmitters, or bladder compensation. Thus, the presented findings allow to suggest a possible future role of asiatic acid in the prevention of conditions accompanied by DO, such as overactive bladder.

O-1602, an Agonist of Atypical Cannabinoid Receptors GPR55, Reverses the Symptoms of Depression and Detrusor Overactivity in Rats Subjected to Corticosterone Treatment

In view of the fact that GPR55 receptors are localized in brain areas implicated in the pathophysiology of depression, GPR55 gene expression is reduced in the dorsolateral prefrontal cortex of suicide victims, and GPR55 receptor agonism exerts an anxiolytic-like effect, GPR55 receptors have drawn our attention as a potential target in the treatment of mood disorders. Therefore, in the present study, we wanted to check whether a 7-day intravenous administration of O-1602 (0.25 mg/kg/day) – a phytocannabinoid-like analogue of cannabidiol that belongs to the agonists of GPR55 receptors, was able to reverse the corticosterone-induced depressive-like behavior accompanied by detrusor overactivity in female Wistar rats. Additionally, we tried to determine the influence of GPR55 stimulation on the bladder, hippocampal and urine levels of several biomarkers that play a role in the functioning of the urinary bladder and/or the pathophysiology of depression. Our experiments showed that O-1602 therapy improved signs of depression (measured by the forced swim test) and detrusor contractility (measured by conscious cystometry) in animals exposed to the corticosterone treatment. Moreover, the treatment reduced the oxidative damage in the urinary bladder and neuroinflammation (observed as the reduction of elevated levels of 3-NIT, MAL, and IL-1β, TNF-α, CRF, respectively). The O-1602 treatment also reversed the abnormal changes in the bladder, hippocampal or urine values of CGRP, OCT3, VAChT, BDNF, and NGF. The above-mentioned findings allow to suggest that in the future the modulation of atypical cannabinoid receptors GPR55 could have a potential role in the treatment of depression and overactive bladder.

Urinary Biomarkers in Overactive Bladder: Revisiting the Evidence in 2019

CONTEXT

In overactive bladder (OAB), after an initial outbreak of research, it is more consensual that biomarkers may be better used to phenotype patients. Herein, we revisit this topic, including some of the most promising biomarkers.

OBJECTIVE

To provide a comprehensive analysis of the actual role of biomarkers in OAB.

EVIDENCE ACQUISITION

A PubMed-based literature search was conducted, including the most relevant articles published in the last 15 yr, on nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), adenosine triphosphate (ATP), genomics, and microbiota as OAB biomarkers. Articles with no full text available or not written in English were excluded. Additional reviews were included.

EVIDENCE SYNTHESIS

Urinary NGF, BDNF, and ATP are increased in many OAB patients. These biomarkers can help identify OAB phenotypes and select the ideal candidates for new therapies directed to neurotrophic and purinergic pathways. Circulating urinary miRNA may be useful for establishing the ideal moment for bladder outlet obstruction relief and will eventually lead to the development of therapeutic agents that inhibit or reverse fibrotic pathways in the bladder. Urinary microbiota seems to be related to OAB symptoms, in particular urgency urinary incontinence, and may have strong implications in the prevention, diagnosis, and treatment of OAB.

CONCLUSIONS

In the future, physicians may consider the use of biomarkers to identify distinct OAB phenotypes, with distinct causal mechanisms, selecting patients for specific target therapies with expected better outcomes.

PATIENT SUMMARY

Overactive bladder biomarkers can be useful for phenotype patients and for selecting more effective target therapies.

PACAP/Receptor System in Urinary Bladder Dysfunction and Pelvic Pain Following Urinary Bladder Inflammation or Stress

Complex organization of CNS and PNS pathways is necessary for the coordinated and reciprocal functions of the urinary bladder, urethra and urethral sphincters. Injury, inflammation, psychogenic stress or diseases that affect these nerve pathways and target organs can produce lower urinary tract (LUT) dysfunction. Numerous neuropeptide/receptor systems are expressed in the neural pathways of the LUT and non-neural components of the LUT (e.g., urothelium) also express peptides. One such neuropeptide receptor system, pituitary adenylate cyclase-activating polypeptide (PACAP; Adcyap1) and its cognate receptor, PAC1 (Adcyap1r1), have tissue-specific distributions in the LUT. Mice with a genetic deletion of PACAP exhibit bladder dysfunction and altered somatic sensation. PACAP and associated receptors are expressed in the LUT and exhibit neuroplastic changes with neural injury, inflammation, and diseases of the LUT as well as psychogenic stress. Blockade of the PACAP/PAC1 receptor system reduces voiding frequency in preclinical animal models and transgenic mouse models that mirror some clinical symptoms of bladder dysfunction. A change in the balance of the expression and resulting function of the PACAP/receptor system in CNS and PNS bladder reflex pathways may underlie LUT dysfunction including symptoms of urinary urgency, increased voiding frequency, and visceral pain. The PACAP/receptor system in micturition pathways may represent a potential target for therapeutic intervention to reduce LUT dysfunction.

Decrease of urinary nerve growth factor but not brain-derived neurotrophic factor in patients with interstitial cystitis/bladder pain syndrome treated with hyaluronic acid

Aims

To investigate urinary nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) levels in interstitial cystitis/bladder pain syndrome (IC/BPS) patients after hyaluronic acid (HA) therapy.

Methods

Thirty-three patients with IC/BPS were prospectively studied; a group of 45 age-matched healthy subjects served as controls. All IC/BPS patients received nine intravesical HA instillations during the 6-month treatment regimen. Urine samples were collected for measuring urinary NGF and BDNF levels at baseline and 2 weeks after the last HA treatment. The clinical parameters including visual analog scale (VAS) of pain, daily frequency nocturia episodes, functional bladder capacity (FBC) and global response assessment (GRA) were recorded. Urinary NGF and BDNF levels were compared between IC/BPS patients and controls at baseline and after HA treatment.

Results

Urinary NGF, NGF/Cr, BDNF, and BDNF/Cr levels were significantly higher in IC/BPS patients compared to controls. Both NGF and NGF/Cr levels significantly decreased after HA treatment. Urinary NGF and NGF/Cr levels significantly decreased in the responders with a VAS pain reduction by 2 (both p < 0.05) and the GRA improved by 2 (both p < 0.05), but not in non-responders. Urinary BDNF and BDNF/Cr did not decrease in responders or non-responders after HA therapy.

Conclusions

Urinary NGF, but not BDNF, levels decreased significantly after HA therapy; both of these factors remained higher than in controls even after HA treatment. HA had a beneficial effect on IC/BPS, but it was limited. The reduction of urinary NGF levels was significant in responders, with a reduction of pain and improved GRA.

CB1 cannabinoid receptor agonist prevents NGF-induced sensitization of TRPV1 in sensory neurons

The transient receptor potential vanilloid type 1 channel (TRPV1) and nerve growth factor (NGF) are important mediators of inflammatory pain. NGF released during inflammation sensitizes TRPV1 in afferent nerve endings of peripheral nociceptors, increasing pain sensation. Cannabinoids, by activating CB1 G protein-coupled receptors, produce analgesia in a variety of pain models, though the exact mechanisms are not known. We tested the hypothesis that activation of the CB1 receptor by cannabinoids attenuates NGF-induced TRPV1 sensitization. TRPV1-mediated currents were measured in acutely isolated primary sensory neurons with the whole-cell patch clamp technique using capsaicin (100 nM) as the agonist. After the first capsaicin application, during which the baseline current was measured, cells were exposed to NGF (100 ng/mL), and the capsaicin application was repeated after 5 min. NGF sensitized TRPV1 in 31.0% of cells (13 of 42), with a mean (±SE) increase in the capsaicin-induced current of 262 ± 47% over the baseline current. When the cannabinoid agonist ACEA (arachidonoyl-2'-chloroethylamide; 10nM) was given before NGF, only 10.8% of cells (4 of 37) were sensitized (p<0.05). Neither this rate, nor the magnitude of the sensitization (198 ± 63% of baseline) were different from that seen in cells not treated with NGF (3 of 25 cells sensitized (12.0%), 253 ± 70% of baseline). Pretreatment with the CB1 antagonist AM-251 (100 nM) prevented the effect of ACEA on NGF-induced sensitization. These results support the hypothesis that cannabinoids, acting through CB1 receptors, may produce analgesia in part by preventing NGF-induced sensitization of TRPV1 in afferent nociceptor nerve endings.

Repeated variate stress in male rats induces increased voiding frequency, somatic sensitivity, and urinary bladder nerve growth factor expression

Stress exacerbates symptoms of functional lower urinary tract disorders including interstitial cystitis (IC)/bladder pain syndrome (BPS) and overactive bladder (OAB) in humans, but mechanisms contributing to symptom worsening are unknown. These studies address stress-induced changes in the structure and function of the micturition reflex using an animal model of stress in male rats. Rats were exposed to 7 days of repeated variate stress (RVS). Target organ (urinary bladder, thymus, adrenal gland) tissues were collected and weighed following RVS. Evans blue (EB) concentration and histamine, myeloperoxidase (MPO), nerve growth factor (NGF), brain-derived neurotropic factor (BDNF), and CXCL12 protein content (ELISA) were measured in the urinary bladder, and somatic sensitivity of the hindpaw and pelvic regions was determined following RVS. Bladder function was evaluated using continuous, open outlet intravesical infusion of saline in conscious rats. Increases in body weight gain were significantly (P ≤ 0.01) attenuated by day 5 of RVS, and adrenal weight was significantly (P ≤ 0.05) increased. Histamine, MPO, NGF, and CXCL12 protein expression was significantly (P ≤ 0.01) increased in the urinary bladder after RVS. Somatic sensitivity of the hindpaw and pelvic regions was significantly (P ≤ 0.01) increased at all monofilament forces tested (0.1-4 g) after RVS. Intercontraction interval, infused volume, and void volume were significantly (P ≤ 0.01) decreased after RVS. These studies demonstrate increased voiding frequency, histamine, MPO, NGF, and CXCL12 bladder content and somatic sensitivity after RVS suggesting an inflammatory component to stress-induced changes in bladder function and somatic sensitivity.