Improvement of lower urinary tract dysfunction by a monoacylglycerol lipase inhibitor in mice with spinal cord injury.

AIMS: Activation of the endocannabinoid system by monoacylglycerol lipase (MAGL) blockade may affect the lower urinary tract function. We investigated the effect of an MAGL inhibitor, MJN110, on neurogenic lower urinary tract dysfunction (LUTD) in the mouse model of spinal cord injury (SCI). METHODS: Female C57BL/6 mice that underwent spinal cord transection at T8-10 level were divided into three groups consisting of (1) vehicle-treated SCI mice, (2) 5 mg/kg, or (3) 10 mg/kg of MJN110-treated SCI mice. MJN110 and vehicle were administered intraperitoneally for 7 days from 4 weeks after spinal cord transection. We then conducted awake cystometrograms and compared urodynamic parameters between three groups. The expression of cannabinoid (CB) receptors, TRP receptors, and inflammatory cytokines in L6-S1 dorsal root ganglia (DRG) or the bladder mucosa were evaluated and compared among three groups. Changes in the level of serum 2-arachidonoylglycerol (2-AG) and bladder MAGL were also evaluated. RESULTS: In the cystometrogram, detrusor overactivity (DO) parameters, such as the number of nonvoiding contraction (NVC), a ratio of time to the 1st NVC to intercontraction interval (ICI), and NVC integrals were improved by MJN110 treatment, and some effects were dose dependent. Although MJN110 did not improve voiding efficiency, it decreased bladder capacity, ICI, and residual urine volume compared to vehicle injection. MJN110 treatment groups had lower CB2, TRPV1, TRPA1, and inflammatory cytokines mRNA levels in DRG and bladder mucosa. Serum 2-AG was increased, and bladder MAGL was decreased after MAGL inhibitor treatment. CONCLUSIONS: MAGL inhibition improved LUTD including attenuation of DO after SCI. Thus, MAGL can be a therapeutic target for neurogenic LUTD after SCI.

The NADPH oxidase inhibitor diphenyleneiodonium suppresses Ca2+ signaling and contraction in rat cardiac myocytes.

Diphenyleneiodonium (DPI) has been widely used as an inhibitor of NADPH oxidase (Nox) to discover its function in cardiac myocytes under various stimuli. However, the effects of DPI itself on Ca2+ signaling and contraction in cardiac myocytes under control conditions have not been understood. We investigated the effects of DPI on contraction and Ca2+ signaling and their underlying mechanisms using video edge detection, confocal imaging, and whole-cell patch clamp technique in isolated rat cardiac myocytes. Application of DPI suppressed cell shortenings in a concentration-dependent manner (IC50 of ≅0.17 µM) with a maximal inhibition of ~70% at ~100 µM. DPI decreased the magnitude of Ca2+ transient and sarcoplasmic reticulum Ca2+ content by 20%-30% at 3 µM that is usually used to remove the Nox activity, with no effect on fractional release. There was no significant change in the half-decay time of Ca2+ transients by DPI. The L-type Ca2+ current (ICa) was decreased concentration-dependently by DPI (IC50 of ≅40.3 µM) with ≅13.1%-inhibition at 3 µM. The frequency of Ca2+ sparks was reduced by 3 µM DPI (by ~25%), which was resistant to a brief removal of external Ca2+ and Na+. Mitochondrial superoxide level was reduced by DPI at 3-100 µM. Our data suggest that DPI may suppress L-type Ca2+ channel and RyR, thereby attenuating Ca2+-induced Ca2+ release and contractility in cardiac myocytes, and that such DPI effects may be related to mitochondrial metabolic suppression.

Exercise Causes Arrhythmogenic Remodeling of Intracellular Calcium Dynamics in Plakophilin-2-Deficient Hearts.

BACKGROUND: Exercise training, and catecholaminergic stimulation, increase the incidence of arrhythmic events in patients affected with arrhythmogenic right ventricular cardiomyopathy correlated with plakophilin-2 (PKP2) mutations. Separate data show that reduced abundance of PKP2 leads to dysregulation of intracellular Ca2+ (Ca2+i) homeostasis. Here, we study the relation between excercise, catecholaminergic stimulation, Ca2+i homeostasis, and arrhythmogenesis in PKP2-deficient murine hearts. METHODS: Experiments were performed in myocytes from a cardiomyocyte-specific, tamoxifen-activated, PKP2 knockout murine line (PKP2cKO). For training, mice underwent 75 minutes of treadmill running once per day, 5 days each week for 6 weeks. We used multiple approaches including imaging, high-resolution mass spectrometry, electrocardiography, and pharmacological challenges to study the functional properties of cells/hearts in vitro and in vivo. RESULTS: In myocytes from PKP2cKO animals, training increased sarcoplasmic reticulum Ca2+ load, increased the frequency and amplitude of spontaneous ryanodine receptor (ryanodine receptor 2)-mediated Ca2+ release events (sparks), and changed the time course of sarcomeric shortening. Phosphoproteomics analysis revealed that training led to hyperphosphorylation of phospholamban in residues 16 and 17, suggesting a catecholaminergic component. Isoproterenol-induced increase in Ca2+i transient amplitude showed a differential response to ß-adrenergic blockade that depended on the purported ability of the blockers to reach intracellular receptors. Additional experiments showed significant reduction of isoproterenol-induced Ca2+i sparks and ventricular arrhythmias in PKP2cKO hearts exposed to an experimental blocker of ryanodine receptor 2 channels. CONCLUSIONS: Exercise disproportionately affects Ca2+i homeostasis in PKP2-deficient hearts in a manner facilitated by stimulation of intracellular ß-adrenergic receptors and hyperphosphorylation of phospholamban. These cellular changes create a proarrhythmogenic state that can be mitigated by ryanodine receptor 2 blockade. Our data unveil an arrhythmogenic mechanism for exercise-induced or catecholaminergic life-threatening arrhythmias in the setting of PKP2 deficit. We suggest that membrane-permeable ß-blockers are potentially more efficient for patients with arrhythmogenic right ventricular cardiomyopathy, highlight the potential for ryanodine receptor 2 channel blockers as treatment for the control of heart rhythm in the population at risk, and propose that PKP2-dependent and phospholamban-dependent arrhythmogenic right ventricular cardiomyopathy-related arrhythmias have a common mechanism.

Structural and Functional Characterization of a Nav1.5-Mitochondrial Couplon.

RATIONALE: The cardiac sodium channel NaV1.5 has a fundamental role in excitability and conduction. Previous studies have shown that sodium channels cluster together in specific cellular subdomains. Their association with intracellular organelles in defined regions of the myocytes, and the functional consequences of that association, remain to be defined. OBJECTIVE: To characterize a subcellular domain formed by sodium channel clusters in the crest region of the myocytes and the subjacent subsarcolemmal mitochondria. METHODS AND RESULTS: Through a combination of imaging approaches including super-resolution microscopy and electron microscopy we identified, in adult cardiac myocytes, a NaV1.5 subpopulation in close proximity to subjacent subsarcolemmal mitochondria; we further found that subjacent subsarcolemmal mitochondria preferentially host the mitochondrial NCLX (Na+/Ca2+ exchanger). This anatomic proximity led us to investigate functional changes in mitochondria resulting from sodium channel activity. Upon TTX (tetrodotoxin) exposure, mitochondria near NaV1.5 channels accumulated more Ca2+ and showed increased reactive oxygen species production when compared with interfibrillar mitochondria. Finally, crosstalk between NaV1.5 channels and mitochondria was analyzed at a transcriptional level. We found that SCN5A (encoding NaV1.5) and SLC8B1 (which encode NaV1.5 and NCLX, respectively) are negatively correlated both in a human transcriptome data set (Genotype-Tissue Expression) and in human-induced pluripotent stem cell-derived cardiac myocytes deficient in SCN5A. CONCLUSIONS: We describe an anatomic hub (a couplon) formed by sodium channel clusters and subjacent subsarcolemmal mitochondria. Preferential localization of NCLX to this domain allows for functional coupling where the extrusion of Ca2+ from the mitochondria is powered, at least in part, by the entry of sodium through NaV1.5 channels. These results provide a novel entry-point into a mechanistic understanding of the intersection between electrical and structural functions of the heart.

Regulation of Survival Motor Neuron Gene Expression by Calcium Signaling.

Spinal muscular atrophy (SMA) is caused by homozygous survival of motor neurons 1 (SMN1) gene deletion, leaving a duplicate gene, SMN2, as the sole source of SMN protein. However, a defect in SMN2 splicing, involving exon 7 skipping, results in a low level of functional SMN protein. Therefore, the upregulation of SMN protein expression from the SMN2 gene is generally considered to be one of the best therapeutic strategies to treat SMA. Most of the SMA drug discovery is based on synthetic compounds, and very few natural compounds have been explored thus far. Here, we performed an unbiased mechanism-independent and image-based screen of a library of microbial metabolites in SMA fibroblasts using an SMN-specific immunoassay. In doing so, we identified brefeldin A (BFA), a well-known inhibitor of ER-Golgi protein trafficking, as a strong inducer of SMN protein. The profound increase in SMN protein was attributed to, in part, the rescue of the SMN2 pre-mRNA splicing defect. Intriguingly, BFA increased the intracellular calcium concentration, and the BFA-induced exon 7 inclusion of SMN2 splicing, was abrogated by the depletion of intracellular calcium and by the pharmacological inhibition of calcium/calmodulin-dependent kinases (CaMKs). Moreover, BFA considerably reduced the expression of Tra2-ß and SRSF9 proteins in SMA fibroblasts and enhanced the binding of PSF and hnRNP M to an exonic splicing enhancer (ESE) of exon 7. Together, our results demonstrate a significant role for calcium and its signaling on the regulation of SMN splicing, probably through modulating the expression/activity of splicing factors.

Distinct shear-induced Ca2+ signaling in the left and right atrial myocytes: Role of P2 receptor context.

Atrial myocytes are continuously exposed to shear stress during cardiac cycles. Previous reports have shown that shear stress induces two different types of global Ca2+ signaling in atrial myocytes-longitudinal Ca2+ waves (L-waves) and action potential-involved transverse waves (T-waves), and suggested an underlying role of the autocrine activation of P2 receptors. We explored the correlations between ATP release and Ca2+ wave generation in atrial myocytes and investigated why the cells develop two Ca2+-wave types during the same shear force. We examined whether ATP release correlates with different shear-stress (~16 dyn/cm2)-mediated Ca2+ signaling by simultaneous measurement of local Ca2+ and ATP release in individual atrial myocytes using two-dimensional confocal imaging and sniffer patch techniques, respectively. Functional P2X7-receptor-expressing HEK293 cells were established as sniffer cells, which generated currents in real time in response to ATP released from a closely positioned atrial myocyte. Both shear-stress-induced L- and T-waves were preceded by sniffer currents with no difference in the current magnitude. Left atrial (LA) myocytes had two- to three-fold larger sniffer currents than right atrial (RA) cells, as was confirmed by ATP chemiluminescence assay. Shear-stress-induced ATP release was eliminated by connexin (Cx) 43 hemichannel inhibition using La3+, Gap19, or knock-down of Cx43 expression. The level of phosphorylated Cx43 at Ser386 (p-Cx43Ser368), but not total Cx43, was higher in LA versus RA myocytes. Most LA cells (~70%) developed L-waves, whereas most RA myocytes (~80%) presented T-waves. Shear-stress-induced T-waves were completely removed by inhibition of P2X4R, which were most abundant in rat atrial cells. Expression of P2X4R was higher in RA than LA myocytes, whereas expression of P2Y1R, the mediator of L-waves, was higher in LA than RA myocytes. ATP release mainly triggers L-waves in LA myocytes and T-waves in RA myocytes under the same shear force, partly because of the differential expression of P2Y1R and P2X4R between LA and RA myocytes. Higher ATP release in LA myocytes under shear stress may not contribute to determination of the wave pattern.

Disruption of Ca2+i Homeostasis and Connexin 43 Hemichannel Function in the Right Ventricle Precedes Overt Arrhythmogenic Cardiomyopathy in Plakophilin-2-Deficient Mice.

BACKGROUND: Plakophilin-2 (PKP2) is classically defined as a desmosomal protein. Mutations in PKP2 associate with most cases of gene-positive arrhythmogenic right ventricular cardiomyopathy. A better understanding of PKP2 cardiac biology can help elucidate the mechanisms underlying arrhythmic and cardiomyopathic events consequent to PKP2 deficiency. Here, we sought to capture early molecular/cellular events that can act as nascent arrhythmic/cardiomyopathic substrates. METHODS: We used multiple imaging, biochemical and high-resolution mass spectrometry methods to study functional/structural properties of cells/tissues derived from cardiomyocyte-specific, tamoxifen-activated, PKP2 knockout mice (PKP2cKO) 14 days post-tamoxifen injection, a time point preceding overt electrical or structural phenotypes. Myocytes from right or left ventricular free wall were studied separately. RESULTS: Most properties of PKP2cKO left ventricular myocytes were not different from control; in contrast, PKP2cKO right ventricular (RV) myocytes showed increased amplitude and duration of Ca2+ transients, increased Ca2+ in the cytoplasm and sarcoplasmic reticulum, increased frequency of spontaneous Ca2+ release events (sparks) even at comparable sarcoplasmic reticulum load, and dynamic Ca2+ accumulation in mitochondria. We also observed early- and delayed-after transients in RV myocytes and heightened susceptibility to arrhythmias in Langendorff-perfused hearts. In addition, ryanodine receptor 2 in PKP2cKO-RV cells presented enhanced Ca2+ sensitivity and preferential phosphorylation in a domain known to modulate Ca2+ gating. RNAseq at 14 days post-tamoxifen showed no relevant difference in transcript abundance between RV and left ventricle, neither in control nor in PKP2cKO cells. Instead, we found an RV-predominant increase in membrane permeability that can permit Ca2+ entry into the cell. Connexin 43 ablation mitigated the membrane permeability increase, accumulation of cytoplasmic Ca2+, increased frequency of sparks and early stages of RV dysfunction. Connexin 43 hemichannel block with GAP19 normalized [Ca2+]i homeostasis. Similarly, protein kinase C inhibition normalized spark frequency at comparable sarcoplasmic reticulum load levels. CONCLUSIONS: Loss of PKP2 creates an RV-predominant arrhythmogenic substrate (Ca2+ dysregulation) that precedes the cardiomyopathy; this is, at least in part, mediated by a Connexin 43-dependent membrane conduit and repressed by protein kinase C inhibitors. Given that asymmetric Ca2+ dysregulation precedes the cardiomyopathic stage, we speculate that abnormal Ca2+ handling in RV myocytes can be a trigger for gross structural changes observed at a later stage.

Alterations of Ca2+ signaling and Ca2+ release sites in cultured ventricular myocytes with intact internal Ca2+ storage.

Although cultured adult cardiac myocytes in combination with cell-level genetic modifications have been adopted for the study of protein function, the cellular alterations caused by the culture conditions themselves need to be clarified before we can interpret the effects of genetically altered proteins. We systematically compared the cellular morphology, global Ca2+ signaling, elementary Ca2+ release (sparks), and arrangement of ryanodine receptor (RyR) clusters in short-term (2 days)-cultured adult rat ventricular myocytes with those of freshly isolated myocytes. The transverse (t)-tubules were remarkably decreased (to ∼25%) by culture, and whole-cell capacitance was reduced by ∼35%. The magnitude of depolarization-induced Ca2+ transients decreased to ∼50%, and Ca2+ transient decay was slowed by culture. The culture did not affect sarcoplasmic reticulum (SR) Ca2+ loading. Therefore, fractional Ca2+ release was attenuated by culture. In the cultured cells, the L-type Ca2+ current (ICa) was smaller (∼50% of controls) and its inactivation was slower. In cultured myocytes, there were significantly fewer (∼50% of control) Ca2+ sparks, the local Ca2+ releases through RyR clusters, compared with in freshly isolated cells. Amplitude and kinetics (duration and time-to-peak) of individual sparks were similar, but they showed greater width in cultured cells. Immunolocalization analysis revealed that the cross-striation of RyRs distribution became weaker and less organized, and that the density of RyR clusters decreased in cultured myocytes. Our data suggest that the loss of t-tubules and generation of compromised Ca2+ transients and ICa in short-term adult ventricular cell culture are independent of SR Ca2+ loading status. In addition, the deteriorated arrangement of the RyR-clusters and their decreased density after short-term culture may be partly responsible for fewer Ca2+ sparks and a decrease in global Ca2+ release.

A multicenter prospective study for overactive bladder patient treatment satisfaction with mirabegron after being unsatisfied with antimuscarinic therapy (FAVOR study).

AIM: We investigated the satisfaction and efficacy of mirabegron in patients with overactive bladder (OAB) symptoms who were unsatisfied with previous antimuscarinic treatment. METHODS: This was a 12-week, open-label study of adults with OAB who had been treated with antimuscarinics within 2 years of screening and expressed dissatisfaction over poor efficacy or adverse events of antimuscarinics. All enrolled patients have received mirabegron 50 mg once daily for 12 weeks. The primary outcome was the percentage of patients reporting treatment satisfaction questions (TSQ) at week 12 ("very satisfied" or "somewhat satisfied"). Patients completed voiding diaries, Overactive Bladder Questionnaire short form (OAB-q-SF), Overactive Bladder Symptom Score (OABSS), and the global response assessment (GRA) at baseline, Week 4, and Week 12. At 12-weeks, patients were assessed for willingness to continue treatment. RESULTS: The response rate of treatment satisfaction at 12 weeks was 69.3% (275/397) (95% confidence interval 64.7-73.8). Significant improvements from baseline to weeks 4 and 12 were observed in the frequency, urgency due to urinary incontinence, and urgency episodes per 24 h (all p < .0001). Both OAB-q-SF and OABSS were significantly improved compared to baseline. At 4 and 12 weeks, 27.5% and 41.8% of patients, respectively, responded to the GRA as being moderately or markedly improved. At 12 weeks, 80.8% of patients were willing to continue mirabegron. CONCLUSIONS: Mirabegron improved the rates of treatment satisfaction and symptoms in patients with OAB who were unsatisfied with prior antimuscarinic treatment.

Clinical guidelines for interstitial cystitis/bladder pain syndrome.

The clinical guidelines for interstitial cystitis and related symptomatic conditions were revised by updating our previous guidelines. The current guidelines define interstitial cystitis/bladder pain syndrome as a condition with chronic pelvic pain, pressure or discomfort perceived to be related to the urinary bladder accompanied by other urinary symptoms, such as persistent urge to void or urinary frequency in the absence of confusable diseases. The characteristic symptom complex is collectively referred as hypersensitive bladder symptoms. Interstitial cystitis/bladder pain syndrome is divided into Hunner-type interstitial cystitis and bladder pain syndrome; Hunner-type interstitial cystitis and bladder pain syndrome represent interstitial cystitis/bladder pain syndrome with Hunner lesions and interstitial cystitis/bladder pain syndrome without Hunner lesions, respectively. So-called non-Hunner-type interstitial cystitis featured by glomerulations or bladder bleeding after distension is included in bladder pain syndrome. The symptoms are virtually indistinguishable between Hunner-type interstitial cystitis and bladder pain syndrome; however, Hunner-type interstitial cystitis and bladder pain syndrome should be considered as a separate entity of disorder. Histopathology totally differs between Hunner-type interstitial cystitis and bladder pain syndrome; Hunner-type interstitial cystitis is associated with severe inflammation of the urinary bladder accompanied by lymphoplasmacytic infiltration and urothelial denudation, whereas bladder pain syndrome shows little pathological changes in the bladder. Pathophysiology would also differ between Hunner-type interstitial cystitis and bladder pain syndrome, involving interaction of multiple factors, such as inflammation, autoimmunity, infection, exogenous substances, urothelial dysfunction, neural hyperactivity and extrabladder disorders. The patients should be treated differently based on the diagnosis of Hunner-type interstitial cystitis or bladder pain syndrome, which requires cystoscopy to determine the presence or absence Hunner lesions. Clinical studies are to be designed to analyze outcomes separately for Hunner-type interstitial cystitis and bladder pain syndrome.

Shear stress enhances Ca2+ sparks through Nox2-dependent mitochondrial reactive oxygen species generation in rat ventricular myocytes.

Shear stress enhances diastolic and systolic Ca2+ concentration in ventricular myocytes. Here, using confocal Ca2+ imaging in rat ventricular myocytes, we assessed the effects of shear stress (~16dyn/cm2) on the frequency of spontaneous Ca2+ sparks and explored the mechanism underlying shear-mediated Ca2+ spark regulation. The frequency of Ca2+ sparks was immediately increased by shear stress (by ~80%), and increased further (by ~150%) during prolonged exposure (20s). The 2-D size and duration of individual sparks were increased by shear stimulation. Inhibition of nitric oxide synthase (NOS) only partially attenuated the prolonged shear-mediated enhancement in spark frequency. Pretreatment with antioxidants significantly attenuated the short- and long-term effects of shear on spark frequency. Microtubule or nicotinamide adenine dinucleotide phosphate oxidase 2 (Nox2) inhibition abolished the immediate shear-induced increase in spark frequency and suppressed the effects of prolonged exposure to shear stress by ~70%. Scavenging of mitochondrial reactive oxygen species (ROS) and mitochondrial uncoupling also abolished the effect of short-term shear on spark occurrence, and markedly reduced (by ~80%) the effects of prolonged shear. Mitochondrial ROS levels increased under shear; this was eliminated by blocking Nox2. Sarcoplasmic reticulum Ca2+ content was increased only by prolonged shear. Our data suggest that shear stress enhances ventricular spark frequency mainly via ROS generated from mitochondria through Nox2, and that NOS and higher sarcoplasmic reticulum Ca2+ concentrations may also contribute to the enhancement of Ca2+ sparks under shear stress. This article is part of a Special Issue entitled: ECS Meeting edited by Claus Heizmann, Joachim Krebs and Jacques Haiech.

Ca2+ Signaling Triggered by Shear-Autocrine P2X Receptor Pathway in Rat Atrial Myocytes.

BACKGROUND/AIMS: The atrium is exposed to high shear stress during heart failure and valvular diseases. We aimed to understand atrial shear-induced Ca2+ signaling and its underlying mechanisms. METHODS: Pressurized micro-flow was applied to single rat atrial myocytes, and Ca2+ signal, membrane potential, and ATP release were assessed using confocal imaging, patch clamp technique, and luciferin-luciferase assay, respectively. RESULTS: Shear stress (∼16 dyn/cm2) induced global Ca2+ waves (∼0.1 events/s) from the periphery to the center of cells in a transverse direction ("T-wave"; ∼145 µm/s). Pharmacological interventions and simultaneous recording of membrane potential and Ca2+ demonstrated that shear-induced T-waves resulted from action potential (AP)-triggered Ca2+ release from the sarcoplasmic reticulum. T-waves were not sensitive to inhibitors of known shear signaling mechanisms except connexin hemichannels and ATP release. Shear stress caused ATP release from these myocytes (∼1.1x10-17 moles/unit membrane, µm2); ATP release was increased by enhancement of connexin hemichannels and suppressed by inhibition of the hemichannels, but not affected by inhibitors of other ATP release pathways. Blockade of P2X receptor, but not pannexin or the Na+-Ca2+ exchanger, eliminated shear-induced T-wave initiation. CONCLUSION: Our data suggest that shear stress triggers APs and concomitant Ca2+ signaling via activation of P2X receptors by connexin hemichannel-mediated ATP release in atrial myocytes.

Role of inositol 1,4,5-trisphosphate receptor type 1 in ATP-induced nuclear Ca2+ signal and hypertrophy in atrial myocytes.

Inositol 1,4,5-trisphosphate receptor type 1 (IP3R1) is expressed in atrial muscle, but not in ventricle, and they are abundant in the perinucleus. We investigated the role of IP3R1 in the regulations of local Ca2+ signal and cell size in HL-1 atrial myocytes under stimulation by IP3-generating chemical messenger, ATP. Assessment of nuclear and cytosolic Ca2+ signal using confocal Ca2+ imaging revealed that IP3 generation by ATP (1 mM) induced monophasic nuclear Ca2+ increase, followed by cytosolic Ca2+ oscillation. Genetic knock-down (KD) of IP3R1 eliminated the monophasic nuclear Ca2+ signal and slowed the cytosolic Ca2+ oscillation upon ATP exposure. Prolonged application of ATP as well as other known hypertrophic agonists (endothelin-1 and phenylephrine) increased cell size in wild-type cells, but not in IP3R1 KD cells. Our data indicate that IP3R1 mediates sustained elevation in nuclear Ca2+ level and facilitates cytosolic Ca2+ oscillation upon external ATP increase, and further suggests possible role of nuclear IP3R1 in atrial hypertrophy.

Regulation of cardiac calcium by mechanotransduction: Role of mitochondria.

Myocardium is subjected to a variety of forces with each contraction, such as stretch, afterload, and shear stress, and adapts to those mechanical stimuli. These mechanical stimuli increase in heart failure, valvular heart disease and hypertension that are clinically associated with arrhythmia and myocyte remodeling. To understand cellular and molecular basis of mechanical stress-mediated cardiac dysfunction and remodeling, several experimental approaches have been successfully used in single cardiac myocytes. In this review, we will briefly summarize the current knowledge about the responses of cardiac myocytes to mechanical stimuli and underlying mechanisms in the context of Ca2+ signaling, with focusing on the role of mitochondria in these mechanotransductions. Recent evidence suggests that mechanotransduction, associated with mitochondrial metabolism, significantly alters Ca2+ signaling and ionic homeostasis in cardiac myocytes under shear stress or prolonged stretch, and that it may play a key role in the pathogenesis of heart failure.

Signaling Pathway for Endothelin-1- and Phenylephrine-Induced cAMP Response Element Binding Protein Activation in Rat Ventricular Myocytes: Role of Inositol 1,4,5-Trisphosphate Receptors and CaMKII.

BACKGROUND/AIMS: Endothelin-1 (ET-1) and the α₁-adrenoceptor agonist phenylephrine (PE) activate cAMP response element binding protein (CREB), a transcription factor implicated in cardiac hypertrophy. The signaling pathway involved in CREB activation by these hypertrophic stimuli is poorly understood. We examined signaling pathways for ET-1- or PE-induced cardiac CREB activation. METHODS: Western blotting was performed with pharmacological and genetic interventions in rat ventricular myocytes. RESULTS: ET-1 and PE increased CREB phosphorylation, which was inhibited by blockade of phospholipase C, the extracellular-signal-regulated kinase 1/2 (ERK1/2) pathway, protein kinase C (PKC) or Ca2+-calmodulin-dependent protein kinase II (CaMKII). Intracellular Ca2+ buffering decreased ET-1- and PE-induced CREB phosphorylation by ≥80%. Sarcoplasmic reticulum Ca2+ pump inhibitor, inositol 1,4,5-trisphosphate receptor (IP₃R) blockers, or type 2 IP₃R (IP₃R2) knock-out abolished ET-1- or PE-induced CREB phosphorylation. ET-1 and PE increased phosphorylation of CaMKII and ERK1/2, which was eliminated by IP₃R blockade/knock-out or PKC inhibition. Activation of CaMKII, but not ERK1/2, by these agonists was sensitive to Ca2+ buffering or to Gö6976, the inhibitor of Ca2+-dependent PKC and protein kinase D (PKD). CONCLUSION: CREB phosphorylation by ET-1 and PE may be mainly mediated by IP₃R2/Ca2+-PKC-PKD-CaMKII signaling with a minor contribution by ERK1/2, linked to IP₃R2 and Ca2+-independent PKC, in ventricular myocytes.

Changes in Adenosine Triphosphate and Nitric Oxide in the Urothelium of Patients with Benign Prostatic Hyperplasia and Detrusor Underactivity.

PURPOSE: We investigated changes in the levels of adenosine triphosphate and nitric oxide in the urothelium of men with detrusor underactivity and benign prostatic hyperplasia. MATERIALS AND METHODS: We prospectively enrolled in study 30 men who planned to undergo surgical treatment for benign prostatic hyperplasia. The 15 patients with a bladder contractility index less than 100 were assigned to the detrusor underactivity group while the 15 with a bladder contractility index more than 100 were assigned to the no detrusor underactivity group. Bladder mucosal specimens were collected at surgical prostate resection, and adenosine triphosphate and endothelial nitric oxide synthase were analyzed in these specimens. The levels of adenosine triphosphate and endothelial nitric oxide synthase were compared between the 2 groups. The correlation of urodynamic parameters with adenosine triphosphate and endothelial nitric oxide synthase was assessed in all patients. RESULTS: Mean ± SEM endothelial nitric oxide synthase did not significantly differ between the detrusor underactivity and no underactivity groups (3.393 ± 0.969 vs 1.941 ± 0.377 IU/ml, p = 0.247). However, the mean level of adenosine triphosphate in the detrusor underactivity group was significantly lower than in the no detrusor underactivity group (1.289 ± 0.320 vs 9.262 ± 3.285 pmol, p = 0.011). In addition, in all patients adenosine triphosphate positively correlated with the bladder contractility index (r = 0.478, p = 0.018) and with detrusor pressure on maximal flow (r = 0.411, p = 0.046). CONCLUSIONS: Adenosine triphosphate was significantly decreased in the urothelium in men with detrusor underactivity and benign prostatic hyperplasia, reflecting the change in detrusor function.

Efficacy and Safety of Desmopressin Add-On Therapy for Men with Persistent Nocturia on α-Blocker Monotherapy for Lower Urinary Tract Symptoms: A Randomized, Double-Blind, Placebo Controlled Study.

PURPOSE: We investigated the efficacy and safety of desmopressin add-on therapy for men with persistent nocturia on α-blocker for lower urinary tract symptoms in this placebo controlled study. MATERIALS AND METHODS: The study included men 40 to 65 years old with lower urinary tract symptoms and persistent nocturia despite α-blocker therapy for at least 8 weeks. Patients were randomized to once daily placebo or desmopressin 0.2 mg for 8 weeks. The primary end point was to assess changes in the mean number of nocturia episodes from baseline to the final assessment. Other secondary end points and adverse events were evaluated. RESULTS AND LIMITATION: A total of 86 patients were randomized to treatment, including placebo in 39 and desmopressin 0.2 mg in 47. Baseline characteristics were similar in the 2 groups. The desmopressin add-on group was significantly superior to placebo in terms of the change from baseline in the mean number of nocturia episodes (-1.13 ± 0.92 vs -0.68 ± 0.79, p = 0.034), the changes in nocturnal urine volume (p <0.001), total I-PSS (International Prostate Symptom Score) (p = 0.041), the nocturnal polyuria index (p = 0.001) and ICIQ-N (International Consultation on Incontinence Questionnaire-Nocturia) (p = 0.001), and the willingness to continue (p = 0.025). The incidence of adverse events in the desmopressin add-on group was similar to that in the placebo group. Most adverse events were mild. CONCLUSION: Desmopressin add-on therapy in men 40 to 65 years old with persistent nocturia on α-blocker monotherapy for lower urinary tract symptoms is effective and well tolerated.

Expressions of vaginal endothelial nitric oxide synthase and phosphodiesterase 5 in female sexual dysfunction: a pilot study.

INTRODUCTION AND HYPOTHESIS: The objective was to investigate the expression of endothelial nitric oxide synthase (eNOS) and phosphodiesterase (PDE) 5 in vaginal tissue of premenopausal women experiencing stress urinary incontinence (SUI) with and without sexual dysfunction. METHODS: Women presenting for treatment of SUI were screened using the Female Sexual Function Index (FSFI) and 10 were selected who met the criteria for female sexual dysfunction (FSD) and 10 asymptomatic controls. Vaginal tissue specimens were obtained from those premenopausal women aged ≥40 years who had had sexual activity ≥2 times every month for the last 6 months and who were scheduled to undergo surgery for SUI. FSD criteria was FSFI scores <18 and arousal domain scores <3. The control group had FSFI scores ≥26 and individual domain scores ≥4. The expressions of eNOS and PDE 5 were compared in the two groups using immunofluorescence staining and western blotting. RESULTS: The mean total FSFI scores were 30.4 ± 2.6 and 15.3 ± 2.3 in the control and FSD groups respectively. In immunofluorescence staining, eNOS and PDE5 were localized in the vaginal epithelium. In western blotting, the expressions of eNOS and PDE5 were significantly lower in the FSD group than in the control group (p = 0.003 and p = 0.038 respectively). CONCLUSIONS: eNOS and PDE5 in the vagina may play important roles in the pathophysiology of FSD.

Expression of cannabinoid 1 and, 2 receptors and the effects of cannabinoid 1 and, 2 receptor agonists on detrusor overactivity associated with bladder outlet obstruction in rats.

BACKGROUND: This study investigated changes in the expression of cannabinoid (CB) receptors and the effects of CB1 and CB2 agonists on detrusor overactivity (DO) associated with bladder outlet obstruction (BOO) in rats. METHODS: Male Sprague Dawley rats were randomly assigned to four groups (n = 10) in each group. The control group comprised sham-operated rats. A animals in the BOO, CB1 agonist and CB2 agonist groups all underwent BOO surgery. Three weeks postoperatively, cystometrography (CMG) was performed on all rats. After confirming the presence of DO in the CB1 and CB2 agonist groups, a CB1 agonist (WIN 55,212-2) and a CB2 agonist (CB65) were instilled intravesically, and CMG was repeated. CMG parameters, including the contraction interval (CI) and contraction pressure (CP) were then analyzed. The bladders of rats in all four groups were excised following CMG. Immunofluorescence staining and Western blotting were performed to localize CB1 and CB2 and measure their expression levels in the urothelium and detrusor muscle. RESULTS: The CI was significantly longer and the CP was significantly lower in the CB1 agonist group than in the BOO group. CI and CP in the CB2 agonist group showed the same results. CB1 receptor immunofluorescence staining signals and immunoreactive bands in Western blotting were increased in the BOO group compared with results in the control group. Similarly, results for the CB2 receptor were also increased in the BOO group, although this difference was not significant. The CMG parameters in the BOO group were significantly improved by the inhibitory effects of CB1 and CB2 agonists on BOO-associated DO. The expression of CB1 was significantly increased in the urothelium and detrusor muscle in BOO-associated DO, but no significant change in CB2 expression was observed. CONCLUSIONS: CB1 and CB2 receptors, especially CB1, play a role in the pathophysiology of BOO-associated DO, and could serve as therapeutic targets.

Tailoring pharmacotherapy for male lower urinary tract symptoms: A prospective, multicenter, observational trial.

OBJECTIVES: The aim of this study was to evaluate the pattern of tailoring and efficacy of several types of pharmacotherapy in male LUTS. METHODS: Prospectively 404 male subjects were included who were over 40 years old, had at least 3 months symptom duration, and 12 or higher international prostate symptom score (IPSS). Subjects were treated with several types of pharmacotherapy for 6 months and were evaluated with IPSS/QoL at every follow-up. Subjects were subdivided into storage (44%), nocturia (18.5%), and voiding symptom (37.5%) groups according to the most bothersome symptom. RESULTS: At 6 months, 188 subjects (46.5%) completed the study. The mean age was 64.2±8.5 years, and symptom duration was 30.6±32.6 months. PSA was 2.98±7.96 ng/mL, and prostate size was 32.8±14.2 cc. IPSS continually decreased from baseline (18.7) to last follow-up (10.8). Combination therapy increased from 33.0% to 52.7% at last follow-up (P=.006). However, there was no difference of IPSS changes between combination and monotherapy groups (P>.05). Only antimuscarinic prescription significantly increased from 15.4% to 28.2% (P=.004). Mean number of visits to the clinic was 3.6±1.3 and the number of treatment changes was 0.31±0.47. The nocturia (0.47±0.51) group changed treatment more than voiding group (0.21±0.41, P=.003). However, the voiding group (-9.4) had significantly more improvement than e storage (-6.4) and nocturia (-7.8) groups (P=.011). CONCLUSIONS: Male LUTS continually improved over 6 months with customised treatment. Pharmacotherapy for male LUTS should be tailored by symptom type and alteration of symptoms during treatment.