Cultured Bladder Smooth Muscle Cells Research Articles

Injecting RNA interference lentiviruses targeting the muscarinic 3 receptor gene into the bladder wall inhibits neurogenic detrusor overactivity in rats with spinal cord injury.

To investigate the effects of injecting RNA interference (RNAi) lentiviruses targeting the muscarinic 3 (M3 ) receptor gene into the bladder wall on bladder activity in rats with spinal cord injury (SCI). Four M3 RNAi lentiviruses were constructed and used to infect primary cultured bladder smooth muscle cells (BSMCs). Western blotting and quantitative reverse transcription polymerase chain reaction (qRT-PCR) were performed to determine the optimal RNAi lentivirus with the highest interference efficiency. Female Wistar rats were subjected spinal cord transection at T9-10 and randomly divided into three groups (n = 8), namely, blank control, negative control, and experimental groups, and injected into the bladder wall with saline, negative control shRNA, and M3 RNAi lentiviruses, respectively, 1 week after spinal cord transection. The normal rats were used as normal control group. Urodynamic parameters and bladder tissues were evaluated in the different groups. An M3 RNAi lentivirus with the highest interference efficiency (78.9%) was constructed and identified. Three weeks after injecting M3 RNAi lentiviruses into the bladder wall, Western blotting and qRT-PCR showed that the M3 receptor was significantly downregulated in the experimental group. Cystometric evaluation suggested that downregulating M3 receptor expression could substantially decrease basal pressure, residual volume, and non-voiding contraction number, increase intercontraction interval, and significantly improve bladder compliance in rats with SCI. Injecting RNAi lentiviruses targeting the M3 receptor gene into the bladder wall could effectively inhibit neurogenic detrusor overactivity (NDO) due to SCI. Thus, this approach may be a potential treatment for NDO in SCI.

AB295. SPR-22 Functional relevance of purinergic P2X4R in bladder smooth muscle

ObjectiveUnder physiologic conditions in animals and pathologic conditions in humans, purinergic mechanisms contribute significantly to detrusor contractions. Although the activation of P2X1 receptors (P2X1R) accounts for the largest portion of bladder smooth muscle (BSM) responses to ATP, previous reports have shown that P2X1R antagonists do not completely abolish the purinergic component of neurogenic contractions, suggesting the presence of other P2XR subtypes on BSM. P2X4R has been identified in bladder tissue, however whether this receptor is functionally relevant warrants investigation. The aim of this study was to examine the extent of P2X4R expression in BSM tissue and to investigate its pharmacological contribution to ATP-mediated detrusor contractions.MethodsP2X4R mRNA and protein expression was investigated in mouse bladder tissue (without mucosa) and in cultured BSM cells by real-time RT-PCR and western blotting respectively. In vitro isometric tension studies were performed in mouse BSM strips without mucosa. Purinergic detrusor contractions were elicited by administration of α-β-methylene-ATP (αβmATP), and the purinergic component of neurogenic contractions induced by electrical field stimulations (EFS) was isolated by pre-treatment with the muscarinic receptor antagonist atropine. The inhibitory effect of two P2X4R selective antagonists, 5-BDBD and BX430, on the αβmATP- and EFS-induced contractions was investigated in the presence of P2X1R antagonist NF449. In addition, the effect of the P2X4R positive modulator ivermectin (IVC) on αβmATP responses was investigated. Data were analyzed by a repeated measures analysis of variance.ResultsP2X4R mRNA was detected in smooth muscle from both bladder tissue and cultured BSM cells, although its expression was significantly lower than P2X1R expression. Immunoreactivity for P2X4R was detected in lysates from both mouse BSM tissue and smooth muscle cells. Functional studies indicated that although P2X1R activation is predominantly responsible for purinergic contractions in mouse detrusor, a significant portion of the contractile response to both αβmATP (22.3±7%) and EFS (27.5±4% of purinergic component of EFS) was resistant to P2X1R inhibition. This NF449-resistant component was abolished by administration of P2X4R antagonists 5-BDBD or BX430. In addition, responses to αβmATP increased significantly upon administration of IVC.ConclusionsThe expression of P2X4R in detrusor smooth muscle together with the identification of a P2X4R-sensitive component of bladder contractions suggest that the activation of this P2X receptor subtype could significantly contribute to ATP-mediated BSM responses. P2X4R may thus potentially represent a novel target for the management of detrusor dysfunctions associated with alterations in purinergic signaling.Funding Source(s)Department of Veterans Affairs, Research Service BX001790; BX002806

Menthol inhibits detrusor contractility independently of TRPM8 activation.

Agonists such as icilin and menthol can activate the cool temperature-sensitive ion channel TRPM8. However, biological responses to menthol may occur independently of TRPM8 activation. In the rodent urinary bladder, menthol facilitates the micturition reflex but inhibits muscarinic contractions of the detrusor smooth muscle. The site(s) of TRPM8 expression in the bladder are controversial. In this study we investigated the regulation of bladder contractility in vitro by menthol. Bladder strips from wild type and TRPM8 knockout male mice (25–30 g) were dissected free and mounted in organ baths. Isometric contractions to carbachol (1 nM–30 µM), CaCl2 (1 µM to 100 mM) and electrical field stimulation (EFS; 8, 16, 32 Hz) were measured. Strips from both groups contracted similarly in response to both carbachol and EFS. Menthol (300 µM) or nifedipine (1 µM) inhibited carbachol and EFS-induced contractions in both wild type and TRPM8 knockout bladder strips. Incubation with the sodium channel blocker tetrodotoxin (1 µM), replacement of extracellular sodium with the impermeant cation N-Methyl-D-Glucamine, incubation with a cocktail of potassium channel inhibitors (100 nM charybdotoxin, 1 µM apamin, 10 µM glibenclamide and 1 µM tetraethylammonium) or removal of the urothelium did not affect the inhibitory actions of menthol. Contraction to CaCl2 was markedly inhibited by either menthol or nifedipine. In cultured bladder smooth muscle cells, menthol or nifedipine abrogated the carbachol or KCl-induced increases in [Ca2+]i. Intravesical administration of menthol increased voiding frequency while decreasing peak voiding pressure. We conclude that menthol inhibits muscarinic bladder contractions through blockade of L-type calcium channels, independently of TRPM8 activation.

PTHrP Is Endogenous Relaxant for Spontaneous Smooth Muscle Contraction in Urinary Bladder of Female Rat

Acute bladder distension causes various morphologic and functional changes, in part through altered gene expression. We aimed to investigate the physiologic role of PTHrP, which is up-regulated in an acute bladder distension model in female rats. In the control Empty group, bladders were kept empty for 6 hours, and in the Distension group, bladders were kept distended for 3 hours after an artificial storing-voiding cycle for 3 hours. In the Distention group bladder, up-regulation of transcripts was noted for 3 genes reported to be up-regulated by stretch in the cultured bladder smooth muscle cells in vitro. Further transcriptome analysis by microarray identified PTHrP as the 22nd highest gene up-regulated in Distension group bladder, among more than 27,000 genes. Localization of PTHrP and its functional receptor, PTH/PTHrP receptor 1 (PTH1R), were analyzed in the untreated rat bladders and cultured bladder cells using real-time RT-PCR and immunoblotting, which revealed that PTH1R and PTHrP were more predominantly expressed in smooth muscle than in urothelium. Exogenous PTHrP peptide (1-34) increased intracellular cAMP level in cultured bladder smooth muscle cells. In organ bath study using bladder strips, the PTHrP peptide caused a marked reduction in the amplitude of spontaneous contraction but caused only modest suppression for carbachol-induced contraction. In in vivo functional study by cystometrogram, the PTHrP peptide decreased voiding pressure and increased bladder compliance. Thus, PTHrP is a potent endogenous relaxant of bladder contraction, and autocrine or paracrine mechanism of the PTHrP-PTH1R axis is a physiologically relevant pathway functioning in the bladder.

276 MECHANOSENSITIVITY OF THE HUMAN DETRUSOR IN RESPONSE TO STRETCH IS REGULATED BY STRETCH-ACTIVATED TWO-PORE DOMAIN POTASSIUM CHANNELS

You have accessJournal of UrologyBladder and Urethra: Anatomy, Physiology and Pharmacology (I)1 Apr 2013276 MECHANOSENSITIVITY OF THE HUMAN DETRUSOR IN RESPONSE TO STRETCH IS REGULATED BY STRETCH-ACTIVATED TWO-PORE DOMAIN POTASSIUM CHANNELS Qi Lei, Xiao-Qing Pan, Stanley Malkowicz, Thomas Guzzo, and Anna Malykhina Qi LeiQi Lei Glenolden, PA More articles by this author , Xiao-Qing PanXiao-Qing Pan Glenolden, PA More articles by this author , Stanley MalkowiczStanley Malkowicz Philadelphia, PA More articles by this author , Thomas GuzzoThomas Guzzo Philadelphia, PA More articles by this author , and Anna MalykhinaAnna Malykhina Glenolden, PA More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2013.02.1660AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Mechanosensitivity of the detrusor is defined as the ability of smooth muscle cells to generate mechanical activity independent of external stimuli. The mechanisms of bladder mechanosensitivity due to detrusor wall stretch are poorly understood. Animal data suggest that stretch-activated two-pore domain (K2P) K+ channels play a critical role in bladder response to filling. The objective of this study was to characterize the function of stretch-activated K+ channels in the human bladder and determine their physiological role in bladder mechanosensitivity. METHODS Full thickness bladder specimens were obtained from patients without symptoms of detrusor overactivity who underwent cystectomy for early stages of bladder cancer (T1-T2,N0-N1). Expression of mechanosensitive K2P channels was determined by immunohistochemistry (IHC) and Western blotting. Functional characterization and biophysical properties of the predominantly expressed member of K2P family, TREK-1 channel, were performed using path-clamp technique. RESULTS Western blot analysis evaluated protein expression of mechanosensitive channels TREK-1, TREK-2, and TRAAK in the human bladder, and established that TREK-1 is the predominantly expressed member of K2P family. IHC staining of the full thickness bladder wall identified TREK-1 expression in the urothelium, on single cells located in the lamina propria, and on bladder smooth muscle cells. Electrophysiological recordings from single smooth muscle cells established that TREK-1 channels are directly activated by mechanical stretch of the cell membrane. We next tested the effects of TREK-1 channel opener arachidonic acid (10 μM) in a whole cell patch clamp mode. Arachidonic acid caused a 5-fold increase in the current amplitude. Additionally, we performed IHC staining of cultured bladder smooth muscle cells with TREK-1 antibodies before and after treatment with Lantrunculin A, an agent which disrupts actin polymerization. Treatment with Lantrunculin A caused an increase in TREK-1 staining in bladder smooth muscle cells suggesting that these channels are linked to the cell cytoskeleton. CONCLUSIONS The results of our study provide direct evidence that the response of the human detrusor to mechanical stretch during bladder filling is regulated by TREK-1 channels. Impaired mechanosensation and mechanotransduction associated with changes in stretch-activated K2P channels may underlie overactive bladder disorders in humans. © 2013 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 189Issue 4SApril 2013Page: e112-e113 Advertisement Copyright & Permissions© 2013 by American Urological Association Education and Research, Inc.MetricsAuthor Information Qi Lei Glenolden, PA More articles by this author Xiao-Qing Pan Glenolden, PA More articles by this author Stanley Malkowicz Philadelphia, PA More articles by this author Thomas Guzzo Philadelphia, PA More articles by this author Anna Malykhina Glenolden, PA More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

GATA-6 and NF-κB Activate CPI-17 Gene Transcription and Regulate Ca2+ Sensitization of Smooth Muscle Contraction

Protein kinase C (PKC)-potentiated inhibitory protein of 17 kDa (CPI-17) inhibits myosin light chain phosphatase, altering the levels of myosin light chain phosphorylation and Ca(2+) sensitivity in smooth muscle. In this study, we characterized the CPI-17 promoter and identified binding sites for GATA-6 and nuclear factor kappa B (NF-κB). GATA-6 and NF-κB upregulated CPI-17 expression in cultured human and mouse bladder smooth muscle (BSM) cells in an additive manner. CPI-17 expression was decreased upon GATA-6 silencing in cultured BSM cells and in BSM from NF-κB knockout (KO) mice. Moreover, force maintenance by BSM strips from KO mice was decreased compared with the force maintenance of BSM strips from wild-type mice. GATA-6 and NF-κB overexpression was associated with CPI-17 overexpression in BSM from men with benign prostatic hyperplasia (BPH)-induced bladder hypertrophy and in a mouse model of bladder outlet obstruction. Thus, aberrant expression of NF-κB and GATA-6 deregulates CPI-17 expression and the contractile function of smooth muscle. Our data provide insight into how GATA-6 and NF-κB mediate CPI-17 transcription, PKC-mediated signaling, and BSM remodeling associated with lower urinary tract symptoms in patients with BPH.

Platelet‐derived growth factor‐BB increases expression of connexin 43 in an extracellular‐regulated protein kinase‐dependent manner in bladder smooth muscle cells

To investigate whether platelet-derived growth factor-BB induces the upregulation of connexin 43 in bladder smooth muscle cells and to examine the involved signaling pathway. Bladder smooth muscle cells were exposed to platelet-derived growth factor-BB in the presence or absence of p38 mitogen-activated protein kinase, c-jun amino-terminal kinase or extracellular-regulated protein kinase inhibitors. Transfection of bladder smooth muscle cells with specific small interference ribonucleic acid against platelet-derived growth factor receptor-β gene expression was also carried out to investigate whether platelet-derived growth factor receptor-β was involved in the signaling pathway. Expression of messenger ribonucleic acid and protein for connexin 43 was measured by real time polymerase chain reaction and western blot. The addition of platelet-derived growth factor-BB in cultured bladder smooth muscle cells caused the significant upregulation of connexin 43, and the activation of extracellular-regulated protein kinase, c-jun amino-terminal kinase and p38 mitogen-activated protein kinase compared with the control group. This action of platelet-derived growth factor-BB could be abolished by the pretreatment of bladder smooth muscle cells with the extracellular-regulated protein kinase inhibitor PD98059, whereas p38 mitogen-activated protein kinase and c-jun amino-terminal kinase inhibitors did not have any effect on this. Platelet-derived growth factor-BB could induce the activation of platelet-derived growth factor receptor-β. Transfection of bladder smooth muscle cells with small interference ribonucleic acid specific for platelet-derived growth factor receptor-β gene resulted in the potent suppression of gene expression and inhibition of extracellular-regulated protein kinase activation, as well as upregulation of connexin 43 induced by platelet-derived growth factor-BB. Platelet-derived growth factor-BB upregulates connexin 43 expression through the activation of extracellular-regulated protein kinase and platelet-derived growth factor receptor-β signaling pathways. This finding suggests that this signaling pathway might provide a potential target to manipulate detrusor overactivity.

Inhibition of TNF-α Improves the Bladder Dysfunction That Is Associated With Type 2 Diabetes

Diabetic bladder dysfunction (DBD) is common and affects 80% of diabetic patients. However, the molecular mechanisms underlying DBD remain elusive because of a lack of appropriate animal models. We demonstrate DBD in a mouse model that harbors hepatic-specific insulin receptor substrate 1 and 2 deletions (double knockout [DKO]), which develops type 2 diabetes. Bladders of DKO animals exhibited detrusor overactivity at an early stage: increased frequency of nonvoiding contractions during bladder filling, decreased voided volume, and dispersed urine spot patterns. In contrast, older animals with diabetes exhibited detrusor hypoactivity, findings consistent with clinical features of diabetes in humans. The tumor necrosis factor (TNF) superfamily genes were upregulated in DKO bladders. In particular, TNF-α was upregulated in serum and in bladder smooth muscle tissue. TNF-α augmented the contraction of primary cultured bladder smooth muscle cells through upregulating Rho kinase activity and phosphorylating myosin light chain. Systemic treatment of DKO animals with soluble TNF receptor 1 (TNFRI) prevented upregulation of Rho A signaling and reversed the bladder dysfunction, without affecting hyperglycemia. TNFRI combined with the antidiabetic agent, metformin, improved DBD beyond that achieved with metformin alone, suggesting that therapies targeting TNF-α may have utility in reversing the secondary urologic complications of type 2 diabetes.

Caldesmon is necessary for maintaining the actin and intermediate filaments in cultured bladder smooth muscle cells

Caldesmon (CaD), a component of microfilaments in all cells and thin filaments in smooth muscle cells, is known to bind to actin, tropomyosin, calmodulin, and myosin and to inhibit actin-activated ATP hydrolysis by smooth muscle myosin. Thus, it is believed to regulate smooth muscle contraction, cell motility and the cytoskeletal structure. Using bladder smooth muscle cell cultures and RNA interference (RNAi) technique, we show that the organization of actin into microfilaments in the cytoskeleton is diminished by siRNA-mediated CaD silencing. CaD silencing significantly decreased the amount of polymerized actin (F-actin), but the expression of actin was not altered. Additionally, we find that CaD is associated with 10 nm intermediate-sized filaments (IF) and in vitro binding assay reveals that it binds to vimentin and desmin proteins. Assembly of vimentin and desmin into IF is also affected by CaD silencing, although their expression is not significantly altered when CaD is silenced. Electronmicroscopic analyses of the siRNA-treated cells showed the presence of myosin filaments and a few surrounding actin filaments, but the distribution of microfilament bundles was sparse. Interestingly, the decrease in CaD expression had no effect on tubulin expression and distribution of microtubules in these cells. These results demonstrate that CaD is necessary for the maintenance of actin microfilaments and intermediate-sized filaments in the cytoskeletal structure. This finding raises the possibility that the cytoskeletal structure in smooth muscle is affected when CaD expression is altered, as in smooth muscle de-differentiation and hypertrophy seen in certain pathological conditions.

Biocompatibility evaluation of vessel extracellular matrix as a matrix for urethral reconstruction

The objective of this study was to evaluate the biocompatibility of vessel extracellular matrix (VECM) from rabbit and to discuss the feasibility of vessel extracellular matrix as a matrix for urethral reconstruction. Primary cultured bladder smooth muscle cells isolated from New Zealand rabbits were implanted on VECM.The effects of VECM on rabbit bladder smooth muscle cells (RBSMCs) metabolic activity, attachment, proliferation were monitored in vitro with the aid of an inverted light microscope and a scanning electron microscope. The cell viability was monitored by MTT(methythiazolye tetrazolium bromide) after 1, 3, 5 days seeding. The in vivo tissue response to VECM was investigated by implanting them into the subcutaneous of rabbits. VECM exhibited a nontoxic and bioactive effect on RBSMCs. RBSMCs could be attached to and proliferated on VECM and maintained their morphologies. MTT assay showed RBSMCs cultured with the extracts of VECM were not significantly different from those of negative controls. In vivo, VECM demonstrated a favorable tissue compatibility without tissue necrosis, fibrosis and other abnormal response. VECM exhibited nontoxic and bioactive effects on RBSMC. It is a suitable material for urethral reconstruction.

Biocompatibility of compounds of extracellular matrix and thermally reversible hydrogel

A new scaffold material composed of extracellular matrix (ECM) and thermal sensitive hydrogel (HG), and evaluated its biocompatibility were investigated. We cultured bladder smooth muscle cells with this compound material, and then observed with phase contrast microscopy and scanning electron microscope (SEM) to assess the cell growth and morphology. The cell adhesion and proliferation were detected with MTT assay and cell count. Results show the ECM/HG compounds appeared as a net-like and red-stained construction with enough meshes and without any cellular fragments. 6 h after implantation, cells were observed adhere on the compounds and extend spurious along the fibers 12 h later. Under SEM even some ECM was observed to be secreted. MTT assay shows there was obvious statistic difference among 3 groups (P<0.05). ECM/HG compound materials show a good biocompatibility, which confirms that it would be an ideal tissue engineering scaffolds.

Differentially expressed gene networks in cultured smooth muscle cells from normal and neuropathic bladder

Neuropathic bladder dysfunction results from abnormal development of the spine, spinal cord injuries, or diseases such as diabetics. Patients with neuropathic bladders often require surgical intervention such as bladder reconstruction to improve incontinence and prevent renal damage. Tissue engineering with ex-vivo cultured bladder cells has been suggested as one means for improving bladder function. However, we previously demonstrated that cultured bladder smooth muscle cells (SMCs) derived from neuropathic bladder exhibit and maintain altered pathologic phenotypes in culture. To identify genes that are responsible for the abnormal neuropathic phenotypes specifically elevated cell proliferation, the expression levels of 1,185 genes were compared between cultured SMCs derived from normal and neuropathic bladders using a cDNA array consisting of well-annotated genes. The expression data were analyzed using several methods to identify differentially expressed genes. The resulting sets of differentially expressed genes were examined by pathway analysis to identify the networks that remain abnormal in the culture-stable phenotype of neuropathic SMCs. A total of 18 genes that are differentially expressed between cultured normal and neuropathic bladder SMCs were identified. Of these 17 were up-regulated greater than 2-fold in neuropathic bladder SMCs, six of them along with one gene that was not up-regulated greater than 2-fold in cultured neuropathic bladder SMCs were confirmed and identified by more stringent analysis methods including significance analysis of microarrays, class comparison, and class prediction analyses. The major dysregulated pathways include fibroblast growth factor signaling, PTEN signaling, and integrin signaling. Our results further suggest that altered neuropathic bladder SMC phenotypes is stable in the culture environments and that SMCs derived from diseased bladders may not be appropriate for tissue engineering purpose without modification of pathologically altered genes expression.

Involvement of STAT3 in bladder smooth muscle hypertrophy following bladder outlet obstruction.

We examined the involvement of the signal transducer and activator of transcription 3 (STAT3) in bladder outlet obstruction (BOO)-induced bladder smooth muscle hypertrophy using a rat in vivo and in vitro study. BOO induced increases in bladder weight and bladder smooth muscle thickness 1 week after the operation. By using antibody microarrays, 64 of 389 proteins blotted on the array met our selection criteria of an INR value between > or = 2.0 and < or = 0.5. This result revealed up-regulation of transcription factors, cell cycle regulatory proteins, apoptosis-associated proteins and so on. On the other hand, down-regulation (INR value < or = 0.5) of proteins was not found. In a profiling study, we found an increase in the expression of STAT3. A significant increase in nuclear phosphorylated STAT3 expression was confirmed in bladder smooth muscle tissue by immunohistochemistry and Western blot analysis. Cyclical stretch-relaxation (1 Hz) at 120% elongation significantly increased the expression of STAT3 and of alpha-smooth muscle actin in primary cultured bladder smooth muscle cells. Furthermore, the blockade of STAT3 expression by the transfection of STAT3 small interfering RNA (siRNA) significantly prevented the stretch-induced increase in alpha-smooth muscle actin expression. These results suggest that STAT3 has an important role in the induction of bladder smooth muscle hypertrophy.

Activity and expression of nitric oxide synthase in the hypertrophied rat bladder and the effect of nitric oxide on bladder smooth muscle growth.

We investigated the expression and activity of nitric oxide synthase (NOS) and the localization of cyclic guanosine monophosphate (cGMP) in hypertrophied rat bladder. We also examined whether nitric oxide (NO) has a growth inhibitory effect in bladder smooth muscle cells. The urethra was partly ligated and the bladder was removed 3 days, 3 or 6 weeks after obstruction. NOS activity was determined as the conversion of L-[14C]citrulline from L-[14C]arginine (Amersham Life Science, Solna, Sweden). Neuronal NOS (nNOS) expression was studied with Western blot analysis and immunohistochemistry. The expression of inducible NOS (iNOS) and cGMP was evaluated by immunohistochemistry. The effect of NO on isolated bladder smooth muscle cell growth was assessed as protein and DNA synthesis by [3H]-leucine and [3H]-thymidine (NEN Life Science Products, Zaventem, Belgium) incorporation, respectively. Ca independent iNOS activity increased after short-term obstruction. Immunohistochemical studies in obstructed bladders demonstrated iNOS expression primarily in urothelial and inflammatory cells. Ca dependent nNOS activity decreased after obstruction, as confirmed by Western blot analysis. The cGMP immunoreactive cells were mainly found within the serosal layer of obstructed bladders. The NO donor DETA-NONOate (Alexis Biochemicals, Lausen, Switzerland) (300 microM.) reduced [3H]-leucine and [ H]-thymidine incorporation by a mean of 29% +/- 2% and 95% +/- 2%, respectively, in cultured bladder smooth muscle cells. Bladder obstruction caused a small increase in iNOS activity and a decrease in nNOS activity. NO was found to have a growth inhibitory effect in bladder smooth muscle cells, suggesting that changes in NOS activity may influence the progress of bladder hypertrophy.

Phenotypic modulation of cultured bladder smooth muscle cells and the expression of inducible nitric oxide synthase

Phenotypic modulation of smooth muscle is associated with various pathological conditions, including bladder dysfunction. Cytoskeletal dynamics modulate the cell phenotype and were recently shown to be involved in regulation of inducible nitric oxide synthase (iNOS). We tested the hypothesis that the cell differentiation status affects iNOS expression, and that iNOS is preferentially expressed in immature dedifferentiated bladder smooth muscle cells (BSMC). Isolated at BSMC were put into different stages of differentiation by serum deprivation on laminin-coated plates in the presence of IGF-I and by interaction with Rho signaling and actin polymerization. iNOS and smooth muscle-myosin heavy chain (SM-MHC) protein expression were investigated with Western blot analysis. Our results showed iNOS protein in BSMC exposed to interleukin-1 beta (2 ng/ml) + TNF-alpha (50 ng/ml). Growth of BSMC in serum-free medium on laminin in the presence of IGF-I increased SM-MHC expression, whereas cytokine-induced iNOS was inhibited. Disruption of F-actin with latrunculin B (0.5 microM) potentiated iNOS expression and decreased SM-MHC expression. Rho inhibition with C3 (2.5 microg/ml) increased iNOS expression, whereas SM-MHC expression was slightly decreased. Rho-kinase inhibition with Y-27632 (10 microM) mediated a decrease in iNOS and a slight increase in SM-MHC expression. In conclusion, the capacity of BSMC to express iNOS was negatively correlated to differentiation status measured as SM-MHC expression. Actin cytoskeletal dynamics and Rho signaling are involved in regulation of cytokine-induced iNOS expression in BSMC. Phenotypic changes and impairment in actin cytoskeleton formation may potentiate cytokine activation and in turn increase nitric oxide production in the bladder during disease.

Calcineurin Mediates Bladder Smooth Muscle Hypertrophy After Bladder Outlet Obstruction

Bladder outlet obstruction (BOO) leads to compensatory bladder hypertrophy. However, the hypertrophy mechanism remains elusive. We report that calcineurin (Cn) is involved in bladder hypertrophy. Partial BOO was surgically induced in 10-week-old female Wistar rats. The bladder was excised 2, 4 and 6 weeks following surgery in 9 rats each. Histological study was performed at each time point. Cn expression was examined by Western blot analysis. Myosin heavy chain expression was evaluated on gels stained with Coomassie blue. Primary cultured bladder smooth muscle cells were infected with recombinant adenoviruses encoding a constitutive active form of CnA (DeltaCnA), CnB and lacZ, and cell size was measured. In histological findings bladder smooth muscle hypertrophy was observed 2 and 4 weeks after surgery. However, the thickened muscles became thinner 6 weeks after BOO. CnA expression 2 weeks after BOO increased 3.2-fold compared with that of controls. Expression significantly decreased 4 and 6 weeks after surgery. In contrast, CnB expression was unchanged throughout hypertrophy development. Changes in myosin heavy chain expression correlated with changes in CnA. We observed significant hypertrophy in DeltaCnA and CnB over expressing smooth muscle cells. Moreover, FK506, which is a potent inhibitor of Cn, blocked hypertrophy in DeltaCnA and CnB over expressing smooth muscle cells. These data suggest that Cn has an important role in the induction of bladder smooth muscle hypertrophy.

Expression of members of the S100 Ca 2+-binding protein family in guinea-pig smooth muscle

The calcium-binding proteins of the S100 family show tissue-specific expression. In this study, the mRNA and protein expression of five S100 calcium-binding proteins was investigated in different guinea-pig smooth muscle preparations. Transcripts of cDNA of S100A1, S100A4, S100A6 and S100A10 were amplified from smooth muscle RNA of neonatal and adult urinary bladder, ileum, aorta and from freshly isolated and cultured urinary bladder smooth muscle cells. S100B was not detectable in smooth muscle RNA, but was seen in control RNA isolated from brain. The pattern of S100 mRNA expression did not change during postnatal development and cell culture of smooth muscle. The structural homology of guinea-pig S100 proteins reverse transcription–polymerase chain reaction (RT–PCR) sequences compared to other species was 85–93% (human), 83–88% (rat) and 81–87% (mouse). Protein expression of S100A4, S100A6 and S100A10 was investigated in aorta, ileum, bladder and cultured bladder smooth muscle cells by Western blot analysis using polyclonal antibodies against guinea-pig-specific S100 immunogenic peptide sequences raised in rabbits. The results show that the proteins S100A4, S100A6 and S100A10 are expressed in the smooth muscle of ileum, bladder and aorta. S100A4 and S100A6 proteins are also expressed in cultured smooth muscle cells. The results of this study suggest that the calcium-binding proteins S100A1, S100A4, S100A6 and S100A10, but not S100B, are expressed in guinea-pig smooth muscle, and could be potentially involved in the regulation of cytoplasmic Ca 2+-concentration and/or in signal transduction in smooth muscle.

Activity and Expression of Nitric Oxide Synthase in the Hypertrophied Rat Bladder and the Effect of Nitric Oxide on Bladder Smooth Muscle Growth

We investigated the expression and activity of nitric oxide synthase (NOS) and the localization of cyclic guanosine monophosphate (cGMP) in hypertrophied rat bladder. We also examined whether nitric oxide (NO) has a growth inhibitory effect in bladder smooth muscle cells. The urethra was partly ligated and the bladder was removed 3 days, 3 or 6 weeks after obstruction. NOS activity was determined as the conversion of L-[14C]citrulline from L-[14C]arginine (Amersham Life Science, Solna, Sweden). Neuronal NOS (nNOS) expression was studied with Western blot analysis and immunohistochemistry. The expression of inducible NOS (iNOS) and cGMP was evaluated by immunohistochemistry. The effect of NO on isolated bladder smooth muscle cell growth was assessed as protein and DNA synthesis by [3H]-leucine and [3H]-thymidine (NEN Life Science Products, Zaventem, Belgium) incorporation, respectively. Ca independent iNOS activity increased after short-term obstruction. Immunohistochemical studies in obstructed bladders demonstrated iNOS expression primarily in urothelial and inflammatory cells. Ca dependent nNOS activity decreased after obstruction, as confirmed by Western blot analysis. The cGMP immunoreactive cells were mainly found within the serosal layer of obstructed bladders. The NO donor DETA-NONOate (Alexis Biochemicals, Lausen, Switzerland) (300 microM.) reduced [3H]-leucine and [ H]-thymidine incorporation by a mean of 29% +/- 2% and 95% +/- 2%, respectively, in cultured bladder smooth muscle cells. Bladder obstruction caused a small increase in iNOS activity and a decrease in nNOS activity. NO was found to have a growth inhibitory effect in bladder smooth muscle cells, suggesting that changes in NOS activity may influence the progress of bladder hypertrophy.

AUGMENTED STRETCH ACTIVATED ADENOSINE TRIPHOSPHATE RELEASE FROM BLADDER UROEPITHELIAL CELLS IN PATIENTS WITH INTERSTITIAL CYSTITIS

Extracellular adenosine triphosphate (ATP) has been shown to mediate inflammation and nociception and, therefore, it may have a role in symptoms associated with interstitial cystitis. We theorized that the bladder uroepithelium releases ATP in response to stretch and, furthermore, this process is augmented in interstitial cystitis. We quantitated ATP using the luciferin-luciferase assay. Urinary ATP levels were compared in 35 patients with interstitial cystitis and in 33 normal controls after pH correction. Cultured interstitial cystitis and normal urothelial cells from the bladder biopsies of 5 patients each were stretched with the Flexcell 2000 machine (Flexcell International Corp., McKeesport, Pennsylvania) and supernatant ATP concentrations were measured. Mean urinary ATP plus or minus standard error of mean was significantly higher in patients with interstitial cystitis than in controls (L value 985 +/- 161 versus 377 +/- 27, p = 0.0007). Supernatant ATP released by stretched interstitial cystitis cells was stretch intensity dependent when comparing 0%, 10% and 20% elongation, and was also significantly higher in stretched interstitial cystitis than in stretched normal cells. Adenosine triphosphate was significantly elevated in the urine of individuals with interstitial cystitis and the stretch activated release of ATP was augmented in interstitial cystitis urothelium. Increased extracellular ATP may have a role in mechanosensory transduction and to our knowledge it represents a novel hypothesis.

Regulation of Cyr61 gene expression by mechanical stretch through multiple signaling pathways.

The cysteine-rich protein 61 (Cyr61) is a signaling molecule with functions in cell migration, adhesion, and proliferation. This protein is encoded by an immediate early gene whose expression is mainly induced by serum growth factors. Here we show that Cyr61 mRNA levels increase sharply in response to cyclic mechanical stretch applied to cultured bladder smooth muscle cells. Stretch-induced changes of Cyr61 transcripts were transient and accompanied by an increase of the encoded protein that localized mainly to the cytoplasm and nucleus of the cells. With the use of pharmacological agents that interfere with known signaling pathways, we show that transduction mechanisms involving protein kinase C and phosphatidylinositol 3-kinase activation partly blocked stretch-induced Cyr61 gene expression. Selective inhibition of Rho kinase pathways altered this stretch effect as well. Meanwhile, using inhibitors of the actin cytoskeleton, we show that Cyr61 gene expression is sensitive to mechanisms that sense actin dynamics. These results establish the regulation of Cyr61 gene by mechanical stretch and provide clues to the key signaling molecules involved in this process.