Involvement of calcium regulating ion channels in contractility of human isolated urinary bladder

Inhibition of Contractility of Isolated Caprine Detrusor by the Calcium Channel Blocker Cilnidipine and Reversal by Calcium Channel Openers

Background

Cilnidipine is a fourth-generation calcium channel blocker that is clinically used to treat hypertension. It is a dihydropyridine that blocks L- and N-type calcium channels. The inhibitory effect of cilnidipine on isolated detrusor muscle contractility has not been studied. This study investigated the inhibitory effect of cilnidipine on isolated caprine (goat) detrusor muscle contractility and the reversal of the inhibition by calcium channel openers.

Methods

Fourteen caprine detrusor strips were made to contract using 80 mM potassium chloride before and after addition of three concentrations (20, 40, and 60 µM) of cilnidipine. Two reversal agents, the L-type calcium channel opener FPL64716, and the N-type calcium channel opener GV-58, were investigated for their ability to reverse the inhibitory effect of 40 µΜ cilnidipine on potassium chloride-induced detrusor contractility.

Results

Cilnidipine caused a dose-dependent and statistically significant inhibition of detrusor contractility at all concentrations of cilnidipine used (20, 40, and 60 µΜ). The inhibitory effect of 40 µM cilnidipine on detrusor contractility was significantly reversed by the addition of FPL64716 and GV-58.

Conclusions

Cilnidipine inhibits the contractility of the isolated detrusor by blocking L- and N-type calcium channels. Cilnidipine could be evaluated for treating clinical conditions requiring relaxation of the detrusor such as overactive bladder.

The role of intracellular calcium and Rho kinase pathways in G protein-coupled receptor-mediated contractions of urinary bladder urothelium and lamina propria

The influence of extracellular and intracellular calcium on smooth muscle contractile activity varies between organs. In response to G protein-coupled receptor (GPCR) stimulation, the urinary bladder detrusor muscle has shown a 70% dependence on extracellular calcium, whereas the urothelium and lamina propria (U&LP) has a 20%-50% dependence. However, as this only accounts for partial contractile activity, the contribution of intracellular calcium and calcium sensitization pathways remains unclear. This study assessed the role of intracellular signaling pathways on GPCR-mediated urinary bladder U&LP contraction. Porcine U&LP responses to activation of the G_q/11-coupled muscarinic, histamine, 5-hydroxytryptamine (serotonin), neurokinin, prostaglandin, and angiotensin II receptors were assessed with three selective inhibitors of store-released intracellular calcium, 2-aminoethyl diphenylborinate (2-APB), cyclopiazonic acid (CPA), and ruthenium red, and three Rho kinase inhibitors, fasudil, Y-27632, and GSK269962. There was no discernible impact on receptor agonist-induced contractions of the U&LP after blocking intracellular calcium pathways, suggesting that this tissue is more sensitive to alterations in the availability of extracellular calcium. However, an alternative mechanism of action for GPCR-mediated contraction was identified to be the activation of Rho kinase, such as when Y-27632 significantly reduced the GPCR-mediated contractile activity of the U&LP by approximately 50% (P < 0.05, n = 8). This suggests that contractile responses of the bladder U&LP do not involve a significant release of calcium from intracellular stores, but that G_q/11-coupled receptor activation causes calcium sensitization via Rho kinase. This study highlights a key role for Rho kinase in the urinary bladder, which may provide a novel target in the future pharmaceutical management of bladder contractile disorders.

Pharmacological Studies on the Ca2+ Influx Pathways in Platelet-Activating Factor (PAF)-Induced Mouse Urinary Bladder Smooth Muscle Contraction

Platelet-activating factor (PAF) not only acts as a mediator of platelet aggregation, inflammation, and allergy responses but also as a constrictor of various smooth muscle (SM) tissues, including gastrointestinal, tracheal/bronchial, and pregnancy uterine SMs. Previously, we reported that PAF induces basal tension increase (BTI) and oscillatory contraction (OC) in mouse urinary bladder SM (UBSM). In this study, we examined the Ca²⁺ influx pathways involved in PAF-induced BTI and OC in the mouse UBSM. PAF (10^-6 M) induced BTI and OC in mouse UBSM. However, the PAF-induced BTI and OC were completely suppressed by extracellular Ca²⁺ removal. PAF-induced BTI and OC frequencies were markedly suppressed by voltage-dependent Ca²⁺ channel (VDCC) inhibitors (verapamil (10^-5 M), diltiazem (10^-5 M), and nifedipine (10^-7 M)). However, these VDCC inhibitors had a minor effect on the PAF-induced OC amplitude. The PAF-induced OC amplitude in the presence of verapamil (10^-5 M) was strongly suppressed by SKF-96365 (3 × 10^-5 M), an inhibitor of receptor-operated Ca²⁺ channel (ROCC) and store-operated Ca²⁺ channel (SOCC), but not by LOE-908 (3 × 10^-5 M) (an inhibitor of ROCC). Overall, PAF-induced BTI and OC in mouse UBSM depend on Ca²⁺ influx and the main Ca²⁺ influx pathways in PAF-induced BTI and OC may be VDCC and SOCC. Of note, VDCC may be involved in PAF-induced BTI and OC frequency, and SOCC might be involved in PAF-induced OC amplitude.

Lansoprazole-induced osteoporosis via the IP3R- and SOCE-mediated calcium signaling pathways

Background

Many clinical studies have shown a correlation between proton pump inhibitors (PPIs) and osteoporosis or fractures. The purpose of this study was to establish a murine model of chronic oral PPI administration to verify whether PPIs caused bone metabolic impairment and investigate the relevant molecular mechanism underlying the effects of PPIs on MC3T3-E1 murine osteoblasts.

Methods

A lansoprazole-induced bone loss model was used to investigate the damaging effects of PPIs. In vivo, immunohistochemistry, Hematoxylin–Eosin (HE) staining, micro-CT analysis, and blood biochemical analyses were used to evaluate the effect of lansoprazole on bone injury in mice. In vitro, the effects of lansoprazole and related signaling pathways in MC3T3-E1 cells were investigated by CCK-8 assays, EdU assays, flow cytometry, laser confocal microscopy, patch clamping, reverse transcription-quantitative polymerase chain reaction and Western blotting.

Results

After 6 months of lansoprazole gavage in ICR mice, the micro-CT results showed that compared with that in the vehicle group, the bone mineral density (BMD) in the high-dose group was significantly decreased (P < 0.05), and the bone microarchitecture gradually degraded. Biochemical analysis of bone serum showed that blood calcium and phosphorus were both decreased (P < 0.01). We found that long-term administration of lansoprazole impaired skeletal function in mice. In vitro, we found that lansoprazole (LPZ) could cause calcium overload in MC3T3-E1 cells leading to apoptosis, and 2-APB, an inhibitor of IP3R calcium release channel and SOCE pathway, effectively blocked increase in calcium caused by LPZ, thus protecting cell viability.

Conclusions

Longterm administration of LPZ induced osteoporotic symptoms in mice, and LPZ triggered calcium increases in osteoblasts in a concentration-dependent manner. Intracellular calcium ([Ca²⁺]_i) persisted at a high concentration, thereby causing endoplasmic reticulum stress (ERS) and inducing osteoblast apoptosis.

Efficacy of resveratrol in male urogenital tract dysfunctions: an evaluation of pre-clinical data

Resveratrol is a polyphenol found naturally in fruits and plants. Recently, studies in humans and animal models have suggested beneficial properties of this polyphenol, such as improvements to metabolic and lipid profiles, along with antioxidant, anti-inflammatory and anti-proliferative effects. In the urogenital tract (UGT), resveratrol has also been tested clinically and experimentally as a therapeutic drug in several diseases; however, the translational efficacy of resveratrol, especially in UGT, is still a matter of debate. In the present review, we address the pre-clinical efficacy of resveratrol in UGT-related dysfunctions, focusing on lower urinary tract symptoms, non-cancerous prostatic disease (benign prostatic hyperplasia and prostatitis) and erectile dysfunction. In vitro studies indicate that resveratrol reduces inflammatory markers and oxidative stress, and improves endothelial function in UGT organs and cells isolated from humans and animals. Despite displaying low oral bioavailability, in vivo administration of resveratrol largely improves erectile dysfunction, benign prostatic hyperplasia, prostatitis and voiding impairments, as evidenced in different animal models. Resveratrol also acts as a microbiota modulator, which may explain some of its beneficial effects in vivo. In contrast to the large amount of pre-clinical data, there are insufficient clinical trials to establish resveratrol treatment efficacy in human UGT-related diseases. In summary, we provide an overview of the in vivo and in vitro efficacy of resveratrol in animal and human UGT dysfunctions, which may support future clinical trials.