High salt loading induces urinary storage dysfunction via upregulation of epithelial sodium channel alpha in the bladder epithelium in Dahl salt-sensitive rats

Mechanotransduction in the urothelium: ATP signalling and mechanoreceptors

The urothelium, which covers the inner surface of the bladder, is continuously exposed to a complex physical environment where it is stimulated by, and responds to, a wide range of mechanical cues. Mechanically activated ion channels endow the urothelium with functioning in the conversion of mechanical stimuli into biochemical events that influence the surface of the urothelium itself as well as suburothelial tissues, including afferent nerve fibres, interstitial cells of Cajal and detrusor smooth muscle cells, to ensure normal urinary function during the cycle of filling and voiding. However, under prolonged and abnormal loading conditions, the urothelial sensory system can become maladaptive, leading to the development of bladder dysfunction. In this review, we summarize developments in the understanding of urothelial mechanotransduction from two perspectives: first, with regard to the functions of urothelial mechanotransduction, particularly stretch-mediated ATP signalling and the regulation of urothelial surface area; and secondly, with regard to the mechanoreceptors present in the urothelium, primarily transient receptor potential channels and mechanosensitive Piezo channels, and the potential pathophysiological role of these channels in the bladder. A more thorough understanding of urothelial mechanotransduction function may inspire the development of new therapeutic strategies for lower urinary tract diseases.

Reduced salt intake partially restores the circadian rhythm of bladder clock genes in Dahl salt-sensitive rats

AIMS

To examine the circadian expression changes in bladder clock genes in Dahl salt-sensitive rats following high salt intake.

MAIN METHODS

Eighteen rats were divided into three groups: the high-salt diet group (HS group), the normal-salt diet group (NS group), and the salt-load interruption group (from a 4 % salt diet to a normal diet; salt-load interruption group [SI group]). Each rat was placed in an individual metabolic cage for 24 h twice weekly. Water intake, urine production, voiding frequency, and voided volume per micturition were recorded. Furthermore, 108 control rats were prepared. Bladders were harvested every 4 h at six time points. Furthermore, the mRNA expression of clock genes and mechanosensors was analyzed.

KEY FINDINGS

In the HS group, the bladder clock genes showed lower mRNA levels than in the NS group. The amplitude of circadian expression changes in bladder clock genes in the HS group was lower than that in the NS group. However, after changing from a 4 % salt diet to a normal diet, the waveforms of the clock gene expression in the SI group were closer to those of the NS group. The 24-hour water intake and urinary volume of the SI group decreased to levels comparable to those of the NS group.

SIGNIFICANCE

Reduced salt intake partially restored the circadian rhythms of bladder clock genes.

Gosha-Jinki-Gan Improved Erectile Dysfunction Caused by Anti-Cancer Agent Oxaliplatin by Decreasing Transcriptional Expression of Phosphodiesterase-5 in Rats

Background

A platinum-containing anti-cancer agent, oxaliplatin (L-OHP), is known to induce peripheral neuropathy, including erectile dysfunction (ED) as a side effect, while Gosha-jinki-gan (GJG) is a traditional Japanese herbal medicine mainly used for peripheral neuropathy.

Aim

To investigate the effect of GJG on L-OHP-induced ED in rats.

Methods

Twelve-week-old male Wister/ST rats were categorized into the following groups: Sham, Sham+GJG, L-OHP, and L-OHP+GJG (each n = 10). The L-OHP and L-OHP+GJG groups were injected intravenously with L-OHP (4 mg/kg) for 2 consecutive days in the first week. Statistical significance was determined using Bonferroni's multiple comparison test.

Outcomes

At the end of the study period, erectile function was evaluated by measuring intracavernosal pressure (ICP) and mean arterial pressure (MAP) after cavernous nerve stimulation. Western blot analysis was used to assess the neuronal nitric oxide synthase (nNOS) and endothelial nitric oxide synthase (eNOS) levels, and quantitative polymerase chain reaction was used to assess the expression of phosphodiesterase-5 (PDE-5) and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-1.

Results

The ICP/MAP ratio of L-OHP rats (0.34 ± 0.06) was significantly lower than that of Sham rats (0.67 ± 0.03, P < .01), however, the ICP/MAP ratio of L-OHP+GJG rats (0.55 ± 0.01) was significantly higher than that of L-OHP rats (P < .01). There were no significant differences in the nNOS and eNOS protein expression between both groups (P > .05). GJG administration significantly decreased PDE-5 and NADPH oxidase-1 messenger RNA expressions in the L-OHP+GJG group.

Clinical Translation

This animal model study suggests that GJG might be effective for erectile function in cancer survivors.

Strengths & limitations

Our study identified that GJG had no notable side effects in the treated group. Further investigation of the cavernous nerve would also help elucidate the mechanism of GJG effect, which is a limitation of this study.

Conclusion

We found that GJG administration improved L-OHP-induced ED by improving transcriptional PDE-5 expression.

Kataoka T, Kawaki Y, Kito Y, et al. Gosha-Jinki-Gan Improved Erectile Dysfunction Caused by Anti-Cancer Agent Oxaliplatin by Decreasing Transcriptional Expression of Phosphodiesterase-5 in Rats. Sex Med 2022;10:100484.

Oxaliplatin, an Anticancer Agent, Causes Erectile Dysfunction in Rats due to Endothelial Dysfunction

BACKGROUND

Chemotherapeutics, one of the standard treatment options for cancer worldwide, have various adverse effects, including erectile dysfunction (ED).

AIM

To investigate erectile function in an animal model after administration of the anticancer agent oxaliplatin (L-OHP).

METHODS

Male Wistar/ST rats were divided into 2 groups: L-OHP rats (n = 21), which were intravenously administered L-OHP (4 mg/kg; twice a week for 4 weeks), and Control rats (n = 21), which were injected with the same volume of 5% glucose solution, using the same dosing schedule. At the end of the study period, erectile function was evaluated by measuring intracavernous pressure (ICP) and mean arterial pressure (MAP) after cavernous nerve stimulation (n = 9-10). Endothelial function was evaluated with an isometric tension study using corpus cavernosum strips (n = 11). Western blot analysis was used to assess neuronal nitric oxide (nNOS) and endothelial NO synthase (eNOS) protein levels (n = 7). Real-time quantitative polymerase chain reaction (qRT-PCR) was used to assess the expression of inflammation- and oxidative stress-related markers (nicotinamide adenine dinucleotide phosphate oxidase-1, p22^phox, interleukin [IL]-6, and nuclear factor-kappa B) (n = 6). Statistical significance was determined using the Student's t-test.

OUTCOMES

The L-OHP group had a significantly lower ICP:MAP ratio than the control group (P < .05). Compared to the Control group, the L-OHP group exhibited significantly lower responses to ACh and eNOS protein levels and significantly higher inflammatory biomarker levels.

CLINICAL TRANSLATION

The results based on this animal model indicate that use of the anticancer agent L-OHP should be considered as a risk factor for ED occurring via reduction of NO bioavailability in humans; our results provide possible treatment strategies for maintaining the erectile function of cancer survivors.

STRENGTHS AND LIMITATIONS

Our study showed that the anticancer agent L-OHP has the propensity to cause ED in rats. A major limitation of this study is the lack of an established cure for ED associated with L-OHP and the lack of clinical evidence.

CONCLUSIONS

L-OHP causes ED in rats via reduction of NO bioavailability caused by endothelial dysfunction. Kataoka T, Mori T, Suzuki J, et al. Oxaliplatin, an Anticancer Agent, Causes Erectile Dysfunction in Rats due to Endothelial Dysfunction. J Sex Med 2021;18:1337-1345.

Association between female urinary urgency and aponeurotic ptosis: Results from a community-based cross-sectional study in Japan

AIMS

To investigate the relationship between urinary urgency (UU) and aponeurotic ptosis (AP) in a health promotion project.

METHODS

This cross-sectional study analyzed 658 women in Aomori, Japan. The presence of UU was evaluated using the Overactive Bladder Symptom Score. The distance from the light reflex on the cornea to the upper eyelid (margin reflex distance-1 [MRD-1]) was measured. AP was defined as MRD-1 of less than 2.0 mm. The daily salt intake amount was estimated using the dietary questionnaire. Daily salt intake was defined as excessive if it was 10 g/day or higher. Independent factors of UU and AP were analyzed via multivariable logistic regression model.

RESULTS

The number of women with UU and AP was 193 and 65, respectively. Similar background differences were observed in age, cardiovascular disease history, renal function, hypertension, diabetes mellitus, dyslipidemia, and daily salt intake between participants with UU and those with AP. Participants with UU had a higher prevalence of AP (19% vs. 6.2%) than those without. Moreover, more than 50% of the women with AP experienced UU. Multivariable logistic analysis on UU showed that age (≥65 years), diabetes mellitus, daily salt intake (≥10 g/day), and AP (odds ratio, 2.07, p = .014) were independent factors. Multivariable analysis on AP revealed that age (≥65 years), hypertension, daily salt intake (≥10 g/day), and UU were independent factors.

CONCLUSIONS

AP was an independent indicator of UU, in addition to excessive daily salt intake. Women with AP may tend to intake excessive salt and experience UU.

Efficacy of salt reduction for managing overactive bladder symptoms: a prospective study in patients with excessive daily salt intake

This study aimed to investigate the efficacy of salt intake restriction on overactive bladder (OAB) symptoms in patients with excessive salt intake. Patients received a brochure on nutritional guidance regarding salt intake reduction and received health education every 4 weeks for 12 weeks. Data from overactive bladder symptom score (OABSS) questionnaires and frequency volume charts (FVCs) were evaluated. The daily salt intake was estimated by determining the urinary sodium and creatinine concentrations using spot urine samples. Of the 98 patients included, 71 (72.4%) successfully restricted their daily salt intake after 12 weeks (salt restricted [R] group), while 27 (27.6%) did not (salt non-restricted [N-R] group). The scores to each OABSS question and the resulting total score improved significantly in the R group; however, the individual scores remained unchanged and the total score increased in the N-R group. The FVC data indicated improved voided volumes in the R group as compared to in the N-R group. Ultimately, 17 (23.9%) patients in the R group no longer fulfilled the OAB diagnostic criteria after salt intake reduction. Thus, salt intake reduction improved urinary symptoms in patients with OAB and may be a therapeutic option for OAB in patients with excessive daily salt intakes.

Effects of High Salt Intake on Detrusor Muscle Contraction in Dahl Salt-Sensitive Rats

High salt intake has been reported as a risk factor for urinary storage symptoms. However, the association between high salt intake and detrusor muscle contraction is not clear. Therefore, we investigated the effects of high salt intake on the components of detrusor muscle contraction in rats. Six-week-old male Dahl salt-resistant (DR; n = 5) and Dahl salt-sensitive (DS; n = 5) rats were fed a high salt (8% NaCl) diet for one week. The contractile responses of the detrusor muscle to the cumulative administration of carbachol and electrical field stimulation (EFS) with and without suramin and atropine were evaluated via isometric tension study. The concentration-response curves of carbachol were shifted more to the left in the DS group than those in the DR group. Contractile responses to EFS were more enhanced in the DS group than those in the DR group (p < 0.05). Cholinergic component-induced responses were more enhanced in the DS group than those in the DR group (p < 0.05). High salt intake might cause urinary storage symptoms via abnormalities in detrusor muscle contraction and the enhancement of cholinergic signals. Excessive salt intake should be avoided to preserve bladder function.

Impairment of accessory nerves around major pelvic ganglion leading to overflow urinary incontinence in rats

AIMS

To investigate the relationship between lower urinary tract function and the accessory nerve (ACN) arising from the major pelvic ganglion (MPG).

METHODS

Ten-week-old male Wistar/ST rats were randomly divided into eight groups according to the type of treatment (sham or bilateral accessory nerve injury [BACNI]) and the duration of observation (3 days, 1 week, 2 weeks, or 4 weeks: Sham-3d, Sham-1w, Sham-2w, Sham-4w, BACNI-3d, BACNI-1w, BACNI-2ws, and BACNI-4w. BACNI was induced in the following manner: the ACN was crushed for 1 min (2 mm away from the MPG) using reverse-action tweezers. The same procedure was performed on both sides. On the last day of each observation period, the bladder function was measured by awake cystometry, and histological evaluation was performed.

RESULTS

All rats in the Sham groups micturated normally. In the BACNI-3d and BACNI-1w groups, all rats showed symptoms of overflow urinary incontinence (OUI). This OUI improved gradually over time. The bladder's size in the BACNI group was significantly larger than that in the Sham group (p < .01). In addition, fibrosis was observed in the subserosa of the bladder of rats in BACNI groups.

CONCLUSION

The BACNI model rats exhibited OUI, suggesting that ACN is involved in the lower urinary tract function. It might be possible that ACN controls the function of either the bladder, the urethra, or both.

The Correlation amongst Salty Taste Preference and Overactive Bladder Symptoms in Female Individuals

Sodium intake could have an indirect effect on storage symptoms as it is an established fact that it has a correlation to hypertension (HTN). However, clinical support for the correlation of sodium intake to STORAGE symptom remains scarce. Therefore, the present work sought to determine how sodium intake and OAB symptom seriousness were correlated in female individuals based on a cross-sectional research design. Data from 115,578 respondents chosen from 228,921 individuals enrolled in the Korean Community Health Survey (KCHS) were subjected to cross-sectional analysis. The correlation amongst sodium intake and STORAGE symptom was assessed on the basis of estimates of the incidence rate ratio (IRR) with 95% confidence interval (CI). Furthermore, joint correspondence analysis (JCA) was conducted to investigate how a predilection for salty taste was associated with several factors, including STORAGE symptom, socio-economic factors, comorbidities, and dietary habits. By comparison to respondents indicating a neutral predilection for salty taste, those who indicated a predilection for bland and salty taste were 7.1% (IRR = 1.071, p < 0.001, 95% CI = 1.045–1.097) and 20.5% (IRR = 1.205, p < 0.001, 95% CI = 1.177–1.234) more probable to experience severe STORAGE symptom, within an adjusted model with multiple variables. JCA confirmed the existence of a correlation between predilection for salty taste and STORAGE symptom. A close correlation was established to exist between predilection for salty taste and lower urinary tract symptoms (LUTS), such as voiding and storage symptoms and nocturia. Moreover, sodium intake was found to be a risk factor for LUTS seriousness in both excessive and deficient amount.

Genome-Wide Association Meta-Analysis of Individuals of European Ancestry Identifies Suggestive Loci for Sodium Intake, Potassium Intake, and Their Ratio Measured from 24-Hour or Half-Day Urine Samples

BACKGROUND

Excess sodium intake and insufficient potassium intake are risk factors for hypertension, but there is limited knowledge regarding genetic factors that influence intake. Twenty-hour or half-day urine samples provide robust estimates of sodium and potassium intake, outperforming other measures such as spot urine samples and dietary self-reporting.

OBJECTIVE

The aim of this study was to investigate genomic regions associated with sodium intake, potassium intake, and sodium-to-potassium ratio measured from 24-h or half-day urine samples.

METHODS

Using samples of European ancestry (mean age: 54.2 y; 52.3% women), we conducted a meta-analysis of genome-wide association studies in 4 cohorts with 24-h or half-day urine samples (n = 6,519), followed by gene-based analysis. Suggestive loci (P < 10-6) were examined in additional European (n = 844), African (n = 1,246), and Asian (n = 2,475) ancestry samples.

RESULTS

We found suggestive loci (P < 10-6) for all 3 traits, including 7 for 24-h sodium excretion, 4 for 24-h potassium excretion, and 4 for sodium-to-potassium ratio. The most significant locus was rs77958157 near cocaine- and amphetamine-regulated transcript prepropeptide (CARTPT) , a gene involved in eating behavior and appetite regulation (P = 2.3 × 10-8 with sodium-to-potassium ratio). Two suggestive loci were replicated in additional samples: for sodium excretion, rs12094702 near zinc finger SWIM-type containing 5 (ZSWIM5) was replicated in the Asian ancestry sample reaching Bonferroni-corrected significance (P = 0.007), and for potassium excretion rs34473523 near sodium leak channel (NALCN) was associated at a nominal P value with potassium excretion both in European (P = 0.043) and African (P = 0.043) ancestry cohorts. Gene-based tests identified 1 significant gene for sodium excretion, CDC42 small effector 1 (CDC42SE1), which is associated with blood pressure regulation.

CONCLUSIONS

We identified multiple suggestive loci for sodium and potassium intake near genes associated with eating behavior, nervous system development and function, and blood pressure regulation in individuals of European ancestry. Further research is needed to replicate these findings and to provide insight into the underlying genetic mechanisms by which these genomic regions influence sodium and potassium intake.

Anagliptin, a dipeptidyl peptidase-4 inhibitor, improved bladder function and hemodynamics in rats with bilateral internal iliac artery ligation

AIMS

To investigate the effect of anagliptin (Ana), a dipeptidyl peptidase-4 (DPP-4) inhibitor, on acute ischemia-induced bladder dysfunction in rats.

METHODS

Eight-week-old female Wistar-ST rats were randomly assigned into four groups: (a) sham; (b) ligation (Lig); (c) Lig + Ana; and (d) Lig + Liraglutide (a glucagon-like peptide-1 [GLP-1] receptor agonist; Lira). Rats in the Lig, Lig + Ana, and Lig + Lira groups underwent ligature of the bilateral internal iliac arteries. Ana was orally administered mixed with the CE-2 diet. Lira was subcutaneously administered once a day. Blood glucose levels, plasma dipeptidyl peptidase 4 (DPP-4) activity, GLP-1 levels, and bladder function were measured in all groups. Bladder blood flow was measured in the sham, Lig, and Lig + Ana groups, 4 weeks postsurgery.

RESULTS

No differences in blood glucose levels among the groups were observed. DPP-4 activity decreased in the Lig + Ana group (P < .01). GLP-1 levels in the Lig + Ana and Lig + Lira groups were higher than those in the sham and Lig groups (P < .01). Intercontraction intervals (ICIs) were longer in the Lig and Lig + Lira groups than in the sham group (P < .05), but similar to those observed in the Lig + Ana and sham groups. The Lig group exhibited reduced bladder blood flow relative to the sham group (P < .01); however, this measure improved in the Lig + Ana group (P < .01).

CONCLUSIONS

Ana administration improved ICIs and bladder blood flow after acute bladder ischemia through a GLP-1 receptor-independent signaling pathway, without altering the blood glucose levels. Therefore, Ana dosing might be useful to prevent ischemia-induced bladder dysfunctions.

Association between sodium intake and lower urinary tract symptoms: does less sodium intake have a favorable effect or not?

Background

Sodium intake is known to be related with hypertension (HTN), which could impact lower urinary tracts symptoms (LUTS) indirectly. To date, only limited clinical evidences exist upon the association between sodium preference and LUTS. This cross-sectional study analyzed the association between sodium preference and the severity of LUTS in men.

Methods

A cross-sectional analysis has been performed and a total of 86,637 participants among total registered population of 229,226 in Korean Community Health Survey (KCHS) were included for final analysis. The adjusted odds ratio (OR) or coefficient with 95% confidence interval (CI) estimates were described to show the association between sodium preference and LUTS using negative binomial regression (for the IPSS total, IPSS voiding, and IPSS storage symptoms), ordinal logistic regression (for the IPSS grade), and binomial logistic regression (for the IPSS nocturia symptoms).

Results

Preference of salty taste group (high sodium preference) were significantly associated with higher IPSS total score (Coef =0.31; 95% CI: 0.27, 0.35), increased risk of severe IPSS grade (OR =1.46; 95% CI: 1.35, 1.57), higher IPSS voiding score (Coef =0.38; 95% CI: 0.32, 0.44), higher IPSS storage score (Coef =0.25; 95% CI: 0.22, 0.29), and increased risk of having IPSS nocturia symptoms (OR =1.21; 95% CI: 1.16, 1.27) compared to subjects with neutral group (normal sodium preference). Prediction of IPSS score according to salty taste preference showed u shaped distribution.

Conclusions

Sodium preference for taste were significantly associated with LUTS including voiding symptom, storage symptom and nocturia. Both higher and lower intake of sodium could be unfavorable factor for severity of LUTS.

Sodium plays an important role in the absorption of intravesical fluid

OBJECTIVES

To investigate the role of sodium in intravesical absorption of water in the bladder and the sodium pathway in the urothelium.

METHODS

Adult female Sprague-Dawley rats received either saline or a 5% glucose solution injection into their bladders. The changes in intravesical fluid volume; concentrations of sodium and chlorine and osmolality; and expression of aquaporin-2, epithelial sodium channel, and claudins were compared after 3 hours.

RESULTS

Intravesical volume decreased significantly in the saline group compared to that in the 5% glucose solution group. The expression of claudin-3 and -6 was higher in the saline group than in the glucose group. There was a significant correlation between changes in the intravesical saline volume and the concentration of sodium and chlorine. Intravesical administration of amiloride did not affect changes in the fluid volume and concentration of sodium.

CONCLUSIONS

The presence of sodium is important for the absorption of intravesical fluid through aquaporin-2 in the urinary bladders of rats. Claudin-3 and -6 may be associated with the transport of sodium through the bladder urothelium.

Bone marrow mesenchymal stem cells encapsulated thermal-responsive hydrogel network bridges combined photo-plasmonic nanoparticulate system for the treatment of urinary bladder dysfunction after spinal cord injury

Spinal cord injury (SCI) is a distressing injury and an irretrievable dramatic event that can debilitate victims for lifespan. Recovery and treatment of SCI is critical challenges for medicine, to overcome the hurdles stem cells and hydrogel scaffolds implantation is a boon for SCI recovery. In this regard, we reported the synthesis of Gold nanoparticles (Au NPs) loaded Agarose/Poly (N-isopropylacrylamide) (PNIPAM) as promising materials for SCI treatment. Herein, Au NPs was synthesized by well-established citrate reduction method and the prepared materials were characterised by UV-visible spectroscopy (UV-vis), Transmission electron microscopy (TEM), Fourier- transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), and EDAX analysis. The microscopic images showed an elliptical or ovoid porous structure nature of hydrogel, and successful and homogenous loading of photo plasmonic nanoparticles into the hydrogel structure. The in vitro cell viability and inflammation analyses data exhibited that prepared hydrogels have no toxic to the cells and displayed high anti-regenerative ability with bone marrow Mesenchymal stem cells (MSCs) and macrophages cells. The in vivo analysis study demonstrated that the treated materials with encapsulated MSCs have greater nerve tissue regeneration efficacy which was confirmed by the results of BBB scores. The hind limb locomotion of treated model animals was totally vanished after post-operational surgery. It's established that implanted nano-hydrogel materials combined with MSCs have quicker recovery of motor function after post-operative surgery, when compared to the other implanted animal groups.

Effect of salt intake reduction on nocturia in patients with excessive salt intake

AIMS

To assess the efficacy of salt reduction for improving nocturia in patients with high salt intake.

METHODS

Changes in lower urinary symptoms and frequency volume chart by salt intake (men: 8 g/day; women: ≥7 g/day) were analyzed in this prospective study. Patients were instructed to use a brochure for salt intake restriction via interview once every four weeks. The daily salt intake was estimated by using spot urine samples.

RESULTS

Two-hundred twenty-three (69.5%) patients were successful in reducing their daily salt intake (S group), whereas 98 (30.5%) patients failed to reduce their salt intake (F group). In the S group, nocturia improved from 2.3 ± 0.9 to 1.4 ± 1.0, and nocturnal polyuria index (NPi) improved from 30.2 ± 7.5 to 27.7 ± 7.3% (P < 0.001). In the Core Lower Urinary Tract Symptom Score (CLSS) of the S group, Q3 (urgency) improved from 1.0 ± 1.0 to 0.9 ± 1.0 (P = 0.001); Q1 (diurnal frequency) (P < 0.001), and Q2 (nocturia) also improved (P < 0.001). Moreover, the quality of life parameter improved significantly (P < 0.001). The patients in the F group did not have improvements in any symptom during the study period.

CONCLUSIONS

Patients with nocturia who also have high salt intake should be advised to reduce their salt intake, as a lifestyle modification. Our results support the importance of randomized clinical trials with larger populations and the appropriate inclusion/exclusion criteria to conclude the clinical usefulness of salt reduction in this patient cohort.