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Ikeda M, Nakada A, Abukawa H, Yamazaki T, Maruyama I. Vibegron inhibits enhanced spontaneous contractions induced by anoxia/reoxygenation in isolated whole bladder from rats. Eur J Pharmacol 2022; 926:175017. [PMID: 35588870 DOI: 10.1016/j.ejphar.2022.175017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Revised: 04/12/2022] [Accepted: 05/04/2022] [Indexed: 11/16/2022]
Abstract
It has been recently proposed that repeated bladder ischemia/reperfusion induced by chronic pelvic ischemia may lead to detrusor overactivity, followed by lower urinary tract symptoms. Vibegron is a selective β3-adrenoceptor agonist approved for the treatment of overactive bladder. Several studies have tested β3-adrenoceptor agonists using animal models with detrusor overactivity related to bladder ischemia/reperfusion. However, whether β3-adrenoceptor agonists directly affect ischemia/reperfusion-evoked detrusor overactivity is unclear. Therefore, we examined whether bladder anoxia/reoxygenation could enhance spontaneous bladder contractions (SBCs) and investigated the effect of vibegron on enhanced SBCs. Isolated whole bladders from rats were incubated with Krebs solution aerated with 95% N2 + 5% CO2 for 5 h (anoxia). Subsequently, the bathing solution was replaced with an oxygen-saturated solution (reoxygenation). Anoxia/reoxygenation caused enhancement of the amplitude but not the frequency of SBC compared with that before reoxygenation. Vibegron (0.3-30 μM) inhibited this increase in SBC amplitude, but not the frequency, in a dose-dependent manner. The inhibitory effect of vibegron was not affected by pretreatment with the adenylyl cyclase inhibitor SQ22536 (100 μM) or protein kinase A inhibitor KT5720 (1 μM) and was not accompanied by considerable changes in cyclic adenosine monophosphate (cAMP) content in the bladder. In contrast, the large conductance potassium channel inhibitor iberiotoxin (100 nM) suppressed the inhibitory effect of vibegron. These results suggest that bladder ischemia/reperfusion induces SBC enhancement and vibegron directly inhibits detrusor overactivity via the large conductance potassium channel, which involves β3-adrenoceptor, rather than the cAMP signaling pathway.
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Affiliation(s)
- Makoto Ikeda
- Watarase Research Center, Kyorin Pharmaceutical Co, Ltd, 1848, Nogi, Nogi-machi, Shimotsuga-gun, Tochigi, 329-0114, Japan
| | - Akihiro Nakada
- Watarase Research Center, Kyorin Pharmaceutical Co, Ltd, 1848, Nogi, Nogi-machi, Shimotsuga-gun, Tochigi, 329-0114, Japan.
| | - Hayato Abukawa
- Watarase Research Center, Kyorin Pharmaceutical Co, Ltd, 1848, Nogi, Nogi-machi, Shimotsuga-gun, Tochigi, 329-0114, Japan.
| | - Takanobu Yamazaki
- Watarase Research Center, Kyorin Pharmaceutical Co, Ltd, 1848, Nogi, Nogi-machi, Shimotsuga-gun, Tochigi, 329-0114, Japan.
| | - Itaru Maruyama
- Central Research Laboratories, Kissei Pharmaceutical Co, Ltd, 4365-1, Kashiwabara, Hotaka, Azumino-city, Nagano, 399-8304, Japan.
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Zheng J, Zhou H, Yang M, Song S, Dai Q, Ji G, Zhou Z. Reduced Ca 2+ spark activity contributes to detrusor overactivity of rats with partial bladder outlet obstruction. Aging (Albany NY) 2020; 12:4163-4177. [PMID: 32112553 PMCID: PMC7093189 DOI: 10.18632/aging.102855] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2019] [Accepted: 01/28/2020] [Indexed: 12/19/2022]
Abstract
We tested whether or not altered Ca2+ spark activity accounted for detrusor overactivity (DO) of Wistar rats after partial bladder outlet obstruction (PBOO). We constructed a DO model through PBOO and studied the Ca2+ spark activity of detrusor. By way of using confocal microscopy and the patch-clamp technique, Ca2+ sparks and spontaneous transient outward currents (STOCs) in detrusor myocytes were measured respectively. Our results indicated that Ca2+ spark activity and STOCs were significantly reduced in the DO detrusor myocytes compared to unafflicted control cells, and both of these had levels that were remarkably increased by applications of caffeine (10 μM), a RyR agonist, in DO myocytes. In addition, measures of detrusor contractions were also recorded by using freshly isolated detrusor strips. These results indicated that the spontaneous contraction of DO detrusor was significantly enhanced, and that the effect of caffeine (10 μM) upon detrusor contractions was reversed by applications of iberiotoxin (100 nM) which is a BK channel blocker. Western blotting (WB) analyses indicated that the levels of expression of ryanodine receptor type 2 (RyR2) and FK506 binding protein 12.6 (FKBP12.6) in bladder muscle were respectively decreased and increased in the samples from DO rats. Thus, we considered in the rat DO model wherein PBOO, the reduced Ca2+ spark activity in detrusor myocytes partly contributed to overactive detrusor contractions. The impaired Ca2+ spark activity may have resulted from decreased RyR2 expression and increased FKBP12.6 expression. Such novel findings in our research might help to provide means for better treatment outcomes for patients afflicted by bladder dysfunction.
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Affiliation(s)
- Ji Zheng
- Department of Urology, Urological Surgery Research Institute, First Affiliated Hospital, Army Medical University (Third Military Medical University), Chongqing 400038, China
| | - Hao Zhou
- Department of Urology, Urological Surgery Research Institute, First Affiliated Hospital, Army Medical University (Third Military Medical University), Chongqing 400038, China
| | - Mengjun Yang
- Department of Urology, Urological Surgery Research Institute, First Affiliated Hospital, Army Medical University (Third Military Medical University), Chongqing 400038, China
| | - Siji Song
- Department of Urology, Urological Surgery Research Institute, First Affiliated Hospital, Army Medical University (Third Military Medical University), Chongqing 400038, China
| | - Qiang Dai
- Department of Urology, Urological Surgery Research Institute, First Affiliated Hospital, Army Medical University (Third Military Medical University), Chongqing 400038, China
| | - Guangju Ji
- Key Laboratory of Interdisciplinary Research, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100049, China
| | - Zhansong Zhou
- Department of Urology, Urological Surgery Research Institute, First Affiliated Hospital, Army Medical University (Third Military Medical University), Chongqing 400038, China
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He Q, Yu YL, Li GH, Chen S. The Dome Wall of Bladder Acts as a Pacemaker Site in Detrusor Instability in Rats. Med Sci Monit 2017; 23:2400-2407. [PMID: 28528343 PMCID: PMC5448627 DOI: 10.12659/msm.904406] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
BACKGROUND The aim of this study was to confirm that the interstitial cells of Cajal (ICCs) in the dome wall of the bladder are pacemaker cells, and that the dome wall of the bladder acts as a pacemaker site in the detrusor instability (DI) rat model. MATERIAL AND METHODS The model of DI in Wistar rats was established and urodynamic studies measuring the bladder volume and pressure were performed. The detrusor excitability was investigated using the amplitude and frequency of phasic contraction of strips. The localization and quantity of ICCs was identified by immunohistochemistry and c-KIT protein expression in the rat bladder. PCR assay and Western blot were used to assess the expression of HCN2 and Cx43. RESULTS The bladder capacity, residual volume, voiding volume, and maximum voiding pressure were significantly increased in the DI group. The contraction frequency and amplitude of the strips from the dome of the bladder in the DI group were higher than the triangle, body, and base parts. Both the concentration of c-KIT positive ICCs cells and expression of the c-KIT protein in the dome wall were higher than in other parts of the bladder. The expression of HCN2 and Cx43 in each part of the DI rat group were obviously higher than each part in the control group. Compared to the body, base, and triangle parts, the expression of HCN2 and Cx43 in the dome wall were obviously higher in the DI group. CONCLUSIONS The quantity of ICCs was higher in the dome wall and the dome wall of bladder acts as a pacemaker site in the DI rat model.
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Affiliation(s)
- Qian He
- Department of Urology, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, China (mainland)
| | - Yan-Lan Yu
- Department of Urology, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, China (mainland)
| | - Gong-Hui Li
- Department of Urology, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, China (mainland)
| | - Sheng Chen
- Department of Urology, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, China (mainland)
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Rosenberg J, Byrtus M, Stengl M. Original Research: Combined model of bladder detrusor smooth muscle and interstitial cells. Exp Biol Med (Maywood) 2016; 241:1853-64. [PMID: 27328937 DOI: 10.1177/1535370216655402] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Accepted: 05/26/2016] [Indexed: 11/15/2022] Open
Abstract
Although patients with lower urinary tract symptoms constitute a large and still growing population, understanding of bladder detrusor muscle physiology remains limited. Understanding the interactions between the detrusor smooth muscle cells and other bladder cell types (e.g. interstitial cells, IC) that may significantly contribute to coordinating and modulating detrusor contractions represents a considerable challenge. Computer modeling could help to elucidate some properties that are difficult to address experimentally; therefore, we developed in silico models of detrusor smooth muscle cell and interstitial cells, coupled through gap junctions. The models include all of the major ion conductances and transporters described in smooth muscle cell and interstitial cells in the literature. The model of normal detrusor muscle (smooth muscle cell and interstitial cells coupled through gap junctions) completely reproduced the experimental results obtained with detrusor strips in the presence of several pharmacological interventions (ryanodine, caffeine, nimodipine), whereas the model of smooth muscle cell alone (without interstitial cells) failed to reproduce the experimental results. Next, a model of overactive bladder, a highly prevalent clinical condition in both men and women with increasing incidence at older ages, was produced by modifying several processes as reported previously: a reduction of Ca(2+)-release through ryanodine receptors and a reduction of Ca(2+)-dependent K(+)-conductance with augmented gap junctional coupling. This model was also able to reproduce the pharmacological modulation of overactive bladder. In conclusion, a model of bladder detrusor muscle was developed that reproduced experimental results obtained in both normal and overactive bladder preparations. The results indicate that the non-smooth muscle cells of the detrusor (interstitial cells) contribute significantly to the contractile behavior of bladder detrusor muscle and should not be neglected. The model suggests that reduced Ca(2+)-release through ryanodine receptors and Ca(2+)-dependent K(+)-conductance together with augmented gap junctional coupling might play a major role in overactive bladder pathogenesis.
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Affiliation(s)
- Josef Rosenberg
- New Technologies Research Center, University of West Bohemia, Pilsen 30614, Czech Republic
| | - Miroslav Byrtus
- Department of Mechanics, University of West Bohemia, Pilsen 30614, Czech Republic
| | - Milan Stengl
- Department of Physiology, Faculty of Medicine in Pilsen, Charles University in Prague, Pilsen 32300, Czech Republic Biomedical Center, Faculty of Medicine in Pilsen, Charles University in Prague, Pilsen 32300, Czech Republic
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Ren Y, Zhu Y, Liu L, Yu T, Dong X. Ultrasound induces contraction of the bladder smooth muscle. Int Urol Nephrol 2016; 48:1229-1236. [PMID: 27262850 DOI: 10.1007/s11255-016-1298-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2016] [Accepted: 04/18/2016] [Indexed: 11/30/2022]
Abstract
PURPOSE To investigate whether the treatment of overt postpartum urinary retention (PUR) with low-intensity pulsed ultrasound (LIPUS) was clinically effective and whether LIPUS could accelerate bladder smooth muscle (BSM) contraction by opening the L-type calcium channels and activating the Ca(2+) signaling pathway. METHODS Records of 136 patients undergoing PUR were retrospectively reviewed in two different groups for LIPUS and neostigmine between from 2014 to July 2015. The rats BSM strips in vitro were irradiated by LIPUS. The contraction frequency and amplitude were recorded with BL-410F biological experimental system. The BSM cells were constructed and identified by α-actin-specific antibody staining, and the intracellular Ca(2+) concentration was analyzed by flow cytometry. RESULTS The clinical trial indicated that LIPUS had potential therapeutic effect on PUR (80.6 vs. 64.1 %, p < 0.05), and the BSM strip contractility was increased by LIPUS (p < 0.001), and the concentration of Ca(2+) was markedly enhanced by about twofold than that without LIPUS exposure (p < 0.01). Besides, nimodipine could suppress the contraction of BSM and the concentration of intracellular Ca(2+) which was caused by ultrasound. CONCLUSIONS The results suggested LIPUS had potential therapeutic effect on PUR and the Ca(2+) signaling pathway was involved in the mechanism. The ultrasound irradiation may provide a new method for PUR therapy.
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Affiliation(s)
- Yan Ren
- Department of Obstetrics and Gynecology, The Second Affiliated Hospital, Chongqing Medical University, 74 Linjiang Road, Yuzhong District, Chongqing, 400010, China
| | - Yi Zhu
- Department of Obstetrics and Gynecology, The Second Affiliated Hospital, Chongqing Medical University, 74 Linjiang Road, Yuzhong District, Chongqing, 400010, China
| | - Li Liu
- Department of Obstetrics and Gynecology, The Second Affiliated Hospital, Chongqing Medical University, 74 Linjiang Road, Yuzhong District, Chongqing, 400010, China
| | - Tinghe Yu
- Department of Obstetrics and Gynecology, The Second Affiliated Hospital, Chongqing Medical University, 74 Linjiang Road, Yuzhong District, Chongqing, 400010, China
| | - Xiaojing Dong
- Department of Obstetrics and Gynecology, The Second Affiliated Hospital, Chongqing Medical University, 74 Linjiang Road, Yuzhong District, Chongqing, 400010, China.
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Parajuli SP, Zheng YM, Levin R, Wang YX. Big-conductance Ca 2+-activated K + channels in physiological and pathophysiological urinary bladder smooth muscle cells. Channels (Austin) 2016; 10:355-364. [PMID: 27101440 DOI: 10.1080/19336950.2016.1180488] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Contraction and relaxation of urinary bladder smooth muscle cells (UBSMCs) represent the important physiological functions of the bladder. Contractile responses in UBSMCs are regulated by a number of ion channels including big-conductance Ca2+- activated K+ (BK) channels. Great progress has been made in studies of BK channels in UBSMCs. The intent of this review is to summarize recent exciting findings with respect to the functional interactions of BK channels with muscarinic receptors, ryanodine receptors (RyRs) and inositol triphosphate receptors (IP3Rs) as well as their functional importance under normal and pathophysiological conditions. BK channels are highly expressed in UBSMCs. Activation of muscarinic M3 receptors inhibits the BK channel activity, facilitates opening of voltage-dependent Ca2+ (CaV) channels, and thereby enhances excitability and contractility of UBSMCs. Signaling molecules and regulatory mechanisms involving RyRs and IP3Rs have a significant effect on functions of BK channels and thereby regulate cellular responses in UBSMCs under normal and pathophysiological conditions including overactive bladders. Moreover, BK channels may represent a novel target for the treatment of bladder dysfunctions.
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Affiliation(s)
- Shankar P Parajuli
- a Center for Cardiovascular Sciences, Albany Medical College , Albany , NY , USA
| | - Yun-Min Zheng
- a Center for Cardiovascular Sciences, Albany Medical College , Albany , NY , USA
| | - Robert Levin
- b Stratton VA Medical Center , Albany , NY , USA
| | - Yong-Xiao Wang
- a Center for Cardiovascular Sciences, Albany Medical College , Albany , NY , USA
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Petkov GV. Central role of the BK channel in urinary bladder smooth muscle physiology and pathophysiology. Am J Physiol Regul Integr Comp Physiol 2014; 307:R571-84. [PMID: 24990859 DOI: 10.1152/ajpregu.00142.2014] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The physiological functions of the urinary bladder are to store and periodically expel urine. These tasks are facilitated by the contraction and relaxation of the urinary bladder smooth muscle (UBSM), also known as detrusor smooth muscle, which comprises the bladder wall. The large-conductance voltage- and Ca(2+)-activated K(+) (BK, BKCa, MaxiK, Slo1, or KCa1.1) channel is highly expressed in UBSM and is arguably the most important physiologically relevant K(+) channel that regulates UBSM function. Its significance arises from the fact that the BK channel is the only K(+) channel that is activated by increases in both voltage and intracellular Ca(2+). The BK channels control UBSM excitability and contractility by maintaining the resting membrane potential and shaping the repolarization phase of the spontaneous action potentials that determine UBSM spontaneous rhythmic contractility. In UBSM, these channels have complex regulatory mechanisms involving integrated intracellular Ca(2+) signals, protein kinases, phosphodiesterases, and close functional interactions with muscarinic and β-adrenergic receptors. BK channel dysfunction is implicated in some forms of bladder pathologies, such as detrusor overactivity, and related overactive bladder. This review article summarizes the current state of knowledge of the functional role of UBSM BK channels under normal and pathophysiological conditions and provides new insight toward the BK channels as targets for pharmacological or genetic control of UBSM function. Modulation of UBSM BK channels can occur by directly or indirectly targeting their regulatory mechanisms, which has the potential to provide novel therapeutic approaches for bladder dysfunction, such as overactive bladder and detrusor underactivity.
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Affiliation(s)
- Georgi V Petkov
- Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, South Carolina
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Mukherjee S, Thomas NL, Williams AJ. A mechanistic description of gating of the human cardiac ryanodine receptor in a regulated minimal environment. ACTA ACUST UNITED AC 2012; 140:139-58. [PMID: 22802361 PMCID: PMC3409104 DOI: 10.1085/jgp.201110706] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Cardiac muscle contraction, triggered by the action potential, is mediated by the release of Ca2+ from the sarcoplasmic reticulum through ryanodine receptor (RyR)2 channels. In situ, RyR2 gating is modulated by numerous physiological and pharmacological agents, and altered RyR2 function underlies the occurrence of arrhythmias in both inherited and acquired diseases. To understand fully the mechanisms underpinning the regulation of RyR2 in the normal heart and how these systems are altered in pathological conditions, we must first gain a detailed knowledge of the fundamental processes of RyR2 gating. In this investigation, we provide key novel mechanistic insights into the physical reality of RyR2 gating revealed by new experimental and analytical approaches. We have examined in detail the single-channel gating kinetics of the purified human RyR2 when activated by cytosolic Ca2+ in a stringently regulated environment where the modulatory influence of factors external to the channel were minimized. The resulting gating schemes are based on an accurate description of single-channel kinetics using hidden Markov model analysis and reveal several novel aspects of RyR2 gating behavior: (a) constitutive gating is observed as unliganded opening events; (b) binding of Ca2+ to the channel stabilizes it in different open states; (c) RyR2 exists in two preopening closed conformations in equilibrium, one of which binds Ca2+ more readily than the other; (d) the gating of RyR2 when bound to Ca2+ can be described by a kinetic scheme incorporating bursts; and (e) analysis of flicker closing events within bursts reveals gating activity that is not influenced by ligand binding. The gating schemes generated in this investigation provide a framework for future studies in which the mechanisms of action of key physiological regulatory factors, disease-linked mutations, and potential therapeutic compounds can be described precisely.
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Affiliation(s)
- Saptarshi Mukherjee
- Institute of Molecular and Experimental Medicine, Wales Heart Research Institute, Cardiff University School of Medicine, Cardiff CF14 4XN, Wales, UK
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Petkov GV. Role of potassium ion channels in detrusor smooth muscle function and dysfunction. Nat Rev Urol 2011; 9:30-40. [PMID: 22158596 DOI: 10.1038/nrurol.2011.194] [Citation(s) in RCA: 126] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Contraction and relaxation of the detrusor smooth muscle (DSM), which makes up the wall of the urinary bladder, facilitates the storage and voiding of urine. Several families of K(+) channels, including voltage-gated K(+) (K(V)) channels, Ca(2+)-activated K(+) (K(Ca)) channels, inward-rectifying ATP-sensitive K(+) (K(ir), K(ATP)) channels, and two-pore-domain K(+) (K(2P)) channels, are expressed and functional in DSM. They control DSM excitability and contractility by maintaining the resting membrane potential and shaping the action potentials that determine the phasic nature of contractility in this tissue. Defects in DSM K(+) channel proteins or in the molecules involved in their regulatory pathways may underlie certain forms of bladder dysfunction, such as overactive bladder. K(+) channels represent an opportunity for novel pharmacological manipulation and therapeutic intervention in human DSM. Modulation of DSM K(+) channels directly or indirectly by targeting their regulatory mechanisms has the potential to control urinary bladder function. This Review summarizes our current state of knowledge of the functional role of K(+) channels in DSM in health and disease, with special emphasis on current advancements in the field.
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Affiliation(s)
- Georgi V Petkov
- Department of Pharmaceutical and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Coker Life Sciences Building, Room 609D, 715 Sumter Street, Columbia, SC 29208, USA.
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Urothelial/Lamina Propria Spontaneous Activity and the Role of M3 Muscarinic Receptors in Mediating Rate Responses to Stretch and Carbachol. Urology 2011; 78:1442.e9-15. [DOI: 10.1016/j.urology.2011.08.039] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Revised: 07/10/2011] [Accepted: 08/18/2011] [Indexed: 11/22/2022]
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Wang Y, Fang Q, Lu Y, Song B, Li W, Li L. Effects of mechanical stretch on interstitial cells of Cajal in guinea pig bladder. J Surg Res 2010; 164:e213-9. [PMID: 20828727 DOI: 10.1016/j.jss.2010.04.040] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2010] [Revised: 04/10/2010] [Accepted: 04/21/2010] [Indexed: 11/18/2022]
Abstract
OBJECTIVES C-kit positive interstitial cells of Cajal (ICCs) play an important role in the regulation of the smooth muscle motility. In this study, we investigated the mechanical sensitivity of ICCs in guinea pig bladder and their possible relationship with detrusor overactivity (DO). METHODS Stretch load was performed in vivo in DO models produced by 4 wk of partial bladder outlet obstruction (PBOO). Number and morphology of ICCs were examined using a specific ICC marker, c-kit, immunochemistry staining. The spontaneous and stretch-induced calcium transients (SICT) of ICCs were investigated in cells cultured onto flexible silicone membranes preloaded with the Ca(2+) indicator fluo-4AM in vitro. RESULTS C-kit positive ICCs were mainly located along and between bladder smooth muscle bundles. ICCs in DO bladders displayed more lateral branching with mutual connections. The number of c-kit positive bladder ICCs was increased in the DO group compared with the control group (n = 50, P < 0.05). Cultured ICCs from DO bladders showed spontaneous calcium waves with higher frequency and lower amplitude than those from control bladders (n = 15, P < 0.05). Significant SICT were detected in cultured bladder ICCs. SICT generated in ICCs from DO were more likely to transfer to adjacent smooth muscle cells through cell membrane connection than ICCs from control bladders. CONCLUSIONS Long-term overload tension following PBOO caused changes in morphology, quantity and spontaneous calcium transients of ICCs in guinea pig bladder. Mechanical sensitivity and interaction with SMC of ICCs may contribute to the mechanosensitive conductances in bladder regulation, and may play a role in the pathogenesis of DO.
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Affiliation(s)
- Yongquan Wang
- Center of Urology, Southwest Hospital, Third Military Medical University, Chongqing, China
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Abstract
The sarcoplasmic reticulum (SR) of smooth muscles presents many intriguing facets and questions concerning its roles, especially as these change with development, disease, and modulation of physiological activity. The SR's function was originally perceived to be synthetic and then that of a Ca store for the contractile proteins, acting as a Ca amplification mechanism as it does in striated muscles. Gradually, as investigators have struggled to find a convincing role for Ca-induced Ca release in many smooth muscles, a role in controlling excitability has emerged. This is the Ca spark/spontaneous transient outward current coupling mechanism which reduces excitability and limits contraction. Release of SR Ca occurs in response to inositol 1,4,5-trisphosphate, Ca, and nicotinic acid adenine dinucleotide phosphate, and depletion of SR Ca can initiate Ca entry, the mechanism of which is being investigated but seems to involve Stim and Orai as found in nonexcitable cells. The contribution of the elemental Ca signals from the SR, sparks and puffs, to global Ca signals, i.e., Ca waves and oscillations, is becoming clearer but is far from established. The dynamics of SR Ca release and uptake mechanisms are reviewed along with the control of luminal Ca. We review the growing list of the SR's functions that still includes Ca storage, contraction, and relaxation but has been expanded to encompass Ca homeostasis, generating local and global Ca signals, and contributing to cellular microdomains and signaling in other organelles, including mitochondria, lysosomes, and the nucleus. For an integrated approach, a review of aspects of the SR in health and disease and during development and aging are also included. While the sheer versatility of smooth muscle makes it foolish to have a "one model fits all" approach to this subject, we have tried to synthesize conclusions wherever possible.
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Affiliation(s)
- Susan Wray
- Department of Physiology, School of Biomedical Sciences, University of Liverpool, Liverpool, Merseyside L69 3BX, United Kingdom.
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Ekman M, Andersson KE, Arner A. Signal transduction pathways of muscarinic receptor mediated activation in the newborn and adult mouse urinary bladder. BJU Int 2009; 103:90-7. [DOI: 10.1111/j.1464-410x.2008.07935.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Hristov KL, Cui X, Brown SM, Liu L, Kellett WF, Petkov GV. Stimulation of beta3-adrenoceptors relaxes rat urinary bladder smooth muscle via activation of the large-conductance Ca2+-activated K+ channels. Am J Physiol Cell Physiol 2008; 295:C1344-53. [PMID: 18799656 DOI: 10.1152/ajpcell.00001.2008] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
We investigated the role of large-conductance Ca(2+)-activated K(+) (BK) channels in beta3-adrenoceptor (beta3-AR)-induced relaxation in rat urinary bladder smooth muscle (UBSM). BRL 37344, a specific beta3-AR agonist, inhibits spontaneous contractions of isolated UBSM strips. SR59230A, a specific beta3-AR antagonist, and H89, a PKA inhibitor, reduced the inhibitory effect of BRL 37344. Iberiotoxin, a specific BK channel inhibitor, shifts the BRL 37344 concentration response curves for contraction amplitude, net muscle force, and tone to the right. Freshly dispersed UBSM cells and the perforated mode of the patch-clamp technique were used to determine further the role of beta3-AR stimulation by BRL 37344 on BK channel activity. BRL 37344 increased spontaneous, transient, outward BK current (STOC) frequency by 46.0 +/- 20.1%. In whole cell mode at a holding potential of V(h) = 0 mV, the single BK channel amplitude was 5.17 +/- 0.28 pA, whereas in the presence of BRL 37344, it was 5.55 +/- 0.41 pA. The BK channel open probability was also unchanged. In the presence of ryanodine and nifedipine, the current-voltage relationship in response to depolarization steps in the presence and absence of BRL 37344 was identical. In current-clamp mode, BRL 37344 caused membrane potential hyperpolarization from -26.1 +/- 2.1 mV (control) to -29.0 +/- 2.2 mV. The BRL 37344-induced hyperpolarization was eliminated by application of iberiotoxin, tetraethylammonium or ryanodine. The data indicate that stimulation of beta3-AR relaxes rat UBSM by increasing the BK channel STOC frequency, which causes membrane hyperpolarization and thus relaxation.
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Affiliation(s)
- Kiril L Hristov
- Dept. of Pharmaceutical and Biomedical Sciences, South Carolina College of Pharmacy, Univ. of South Carolina, Coker Life Sciences Bldg., Rm. 709, 715 Sumter St., Columbia, SC 29208, USA
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Brown SM, Bentcheva-Petkova LM, Liu L, Hristov KL, Chen M, Kellett WF, Meredith AL, Aldrich RW, Nelson MT, Petkov GV. Beta-adrenergic relaxation of mouse urinary bladder smooth muscle in the absence of large-conductance Ca2+-activated K+ channel. Am J Physiol Renal Physiol 2008; 295:F1149-57. [PMID: 18701628 DOI: 10.1152/ajprenal.00440.2007] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In urinary bladder smooth muscle (UBSM), stimulation of beta-adrenergic receptors (beta-ARs) leads to activation of the large-conductance Ca2+-activated K+ (BK) channel currents (Petkov GV and Nelson MT. Am J Physiol Cell Physiol 288: C1255-C1263, 2005). In this study we tested the hypothesis that the BK channel mediates UBSM relaxation in response to beta-AR stimulation using the highly specific BK channel inhibitor iberiotoxin (IBTX) and a BK channel knockout (BK-KO) mouse model in which the gene for the pore-forming subunit was deleted. UBSM strips isolated from wild-type (WT) and BK-KO mice were stimulated with 20 mM K+ or 1 microM carbachol to induce phasic and tonic contractions. BK-KO and WT UBSM strips pretreated with IBTX had increased overall contractility, and UBSM BK-KO cells were depolarized with approximately 12 mV. Isoproterenol, a nonspecific beta-AR agonist, and forskolin, an adenylate cyclase activator, decreased phasic and tonic contractions of WT UBSM strips in a concentration-dependent manner. In the presence of IBTX, the concentration-response curves to isoproterenol and forskolin were shifted to the right in WT UBSM strips. Isoproterenol- and forskolin-mediated relaxations were enhanced in BK-KO UBSM strips, and a leftward shift in the concentration-response curves was observed. The leftward shift was eliminated upon PKA inhibition with H-89, suggesting upregulation of the beta-AR-cAMP pathway in BK-KO mice. These results indicate that the BK channel is a key modulator in beta-AR-mediated relaxation of UBSM and further suggest that alterations in BK channel expression or function could contribute to some pathophysiological conditions such as overactive bladder and urinary incontinence.
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Affiliation(s)
- Sean M Brown
- Department of Pharmaceutical and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Coker Life Sciences Bldg., Rm. 709, 715 Sumter St., Columbia, SC 29208, USA
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Xu L, Yu BP, Chen JG, Luo HS. Mechanisms mediating serotonin-induced contraction of colonic myocytes. Clin Exp Pharmacol Physiol 2007; 34:120-8. [PMID: 17201746 DOI: 10.1111/j.1440-1681.2007.04465.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
1. 5-Hydroxytryptamine (5-HT) has an important role in the pathogenesis of irritable bowel syndrome. To investigate the effects of 5-HT on the contractile activity of myocytes of the guinea-pig proximal colon, cell imaging before and after contraction was undertaken and images were analysed using image-analysis software. Ion currents and membrane potentials were measured. Cytoplasmic free Ca(2+) was recorded using a confocal microscope following loading of the cells with the fluorescent probe Fura-2AM. 2. 5-Hydroxytryptamine reduced cell length in a dose-dependent manner (EC(50) = 0.189 micromol/L). Under current clamp, 10 micromol/L 5-HT reduced action potential amplitude (measured as peak height) and decreased action potential duration, as well as depolarizing the resting potential from -68.4 +/- 3.6 to -22.96 +/- 4.65 mV. Iberiotoxin (1 micromol/L) blocked the effects of 5-HT in reducing the time to repolarization (T(90)) and nicardipine (5 micromol/L) blocked the effects of 5-HT in reducing action potential amplitude. 3. In the whole-cell mode, 5-HT enhanced L-type Ca(2+) currents, large conductance K(+) channel (BK(Ca)) currents and spontaneous transient outward currents (STOC). In addition, 5-HT increased intracellular Ca(2+) levels. Ondansetron (10 micromol/L) blocked the effects of 5-HT in enhancing L-type Ca(2+) currents, BK(Ca) currents and STOC. 4. In conclusion, 5-HT induces contraction of colonic myocytes, mostly as a result of Ca(2+) release from the sarcoplasmic reticulum (SR) following activation of 5-HT(3) receptors and the inositol 1,4,5-trisphosphate pathway. In addition, the effect of 5-HT in decreasing action potential amplitude is mediated by the release of Ca(2+) from the SR, as well as by enhanced L-type Ca(2+) current. 5-Hydroxytryptamine decreased action potential duration by enhancing BK(Ca) current.
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Affiliation(s)
- Long Xu
- Department of Gastroenterology, Renmin Hospital, Wuhan University, Wuhan, China
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Hotta S, Morimura K, Ohya S, Muraki K, Takeshima H, Imaizumi Y. Ryanodine receptor type 2 deficiency changes excitation-contraction coupling and membrane potential in urinary bladder smooth muscle. J Physiol 2007; 582:489-506. [PMID: 17363382 PMCID: PMC2075324 DOI: 10.1113/jphysiol.2007.130302] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The possibility that the ryanodine receptor type 2 (RyR2) can function as the major Ca(2+)-induced Ca(2+) release (CICR) channel in excitation-contraction (E-C) coupling was examined in smooth muscle cells (SMCs) isolated from urinary bladder (UB) of RyR2 heterozygous KO mice (RyR2+/-). RyR2 mRNA expression in UB from RyR2+/- was much lower than that in wild-type (RyR2+/+. In single UBSMCs from RyR2+/+, membrane depolarization under voltage clamp initially induced several local Ca(2+) transients (hot spots) in peripheral areas of the cell. Then, Ca(2+) waves spread from Ca(2+) hot spots to other areas of the myocyte. The number of Ca(2+) hot spots elicited by a short depolarization (< 20 ms) in UBSMCs of RyR2+/- was significantly smaller than in those of RyR2+/+. The force development induced either by direct electrical stimulation or by 10 microm acetylcholine in tissue segments of RyR2+/- was smaller than and comparable to those in RyR2+/+, respectively. The frequency of spontaneous transient outward currents in single myocytes and the membrane depolarization by 1 microm paxilline in tissue segments from RyR2+/- were significantly lower and smaller than those in RyR2+/+, respectively. The urination frequency and volume per voiding in RyR2+/- were significantly increased and reduced, respectively, compared with RyR2+/+. In conclusion, RyR2 plays a crucial role in the regulation of CICR during E-C coupling and also in the regulation of resting membrane potential, presumably via the modulation of Ca(2+)-dependent K(+) channel activity in UBSMCs and, thereby, has a pivotal role in the control of bladder activity.
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Affiliation(s)
- Shingo Hotta
- Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Science, Nagoya City University, 3-1 Tanabedori, Mizuhoku, Nagoya 467-8603, Japan
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Christ GJ, Hodges S. Molecular mechanisms of detrusor and corporal myocyte contraction: identifying targets for pharmacotherapy of bladder and erectile dysfunction. Br J Pharmacol 2006; 147 Suppl 2:S41-55. [PMID: 16465183 PMCID: PMC1751499 DOI: 10.1038/sj.bjp.0706627] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The Post-Genomic age presents many new challenges and opportunities for the improved understanding, diagnosis and treatment of human disease. The long-term goal is to identify molecular correlates of disease processes, and use this information to develop novel and more effective therapeutics. A major hurdle in this regard is ensuring that the molecular targets of interest are indeed relevant to the physiology and/or pathophysiology of the processes being studied, and, moreover, to determine if they are specific to the tissue/organ being investigated. As a first step in this direction, we have reviewed the literature pertaining to bladder and erectile physiology/pharmacology and dysfunction and attempted to summarize some of the critical molecular mechanisms regulating detrusor and corporal myocyte tone. Because of the vast amount of published data, we have limited the scope of this review to consideration of the calcium-mobilizing and calcium-sensitizing pathways in these cells. Despite obvious differences in phenotypic characteristics of the detrusor and corporal myocyte, there are some common molecular changes that may contribute to, for example, the increased myocyte contractility characteristic of bladder and erectile dysfunction (i.e. increased Rho kinase activity and decreased K(+) channel function). Of course, there are also some important distinctions in the pathways that modulate contractility in these two cell types (i.e. the contribution of ryanodine-sensitive calcium stores and the nitric oxide/cGMP pathways). This report highlights some of these similarities and distinctions in the hope that it will encourage scientific discourse and research activity in this area, eventually leading to an improved quality of life for those millions of individuals that are afflicted with bladder and erectile dysfunction.
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MESH Headings
- Animals
- Erectile Dysfunction/drug therapy
- Erectile Dysfunction/metabolism
- Erectile Dysfunction/physiopathology
- Humans
- Male
- Muscle Contraction
- Muscle, Smooth/innervation
- Muscle, Smooth/metabolism
- Muscle, Smooth, Vascular/innervation
- Muscle, Smooth, Vascular/metabolism
- Myocytes, Smooth Muscle/metabolism
- Penile Erection
- Penis/blood supply
- Penis/metabolism
- Signal Transduction
- Urinary Bladder/innervation
- Urinary Bladder/metabolism
- Urinary Bladder, Overactive/drug therapy
- Urinary Bladder, Overactive/metabolism
- Urinary Bladder, Overactive/physiopathology
- Urination
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Affiliation(s)
- George J Christ
- Wake Forest Institute for Regenerative Medicine, Wake Forest University Baptist Medical Center, Winston-Salem, NC 27157, USA.
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Yi CR, Wei ZQ, Deng XL, Sun ZY, Li XR, Tian CG. Effects of coffee and caffeine on bladder dysfunction in streptozotocin-induced diabetic rats. Acta Pharmacol Sin 2006; 27:1037-43. [PMID: 16867256 DOI: 10.1111/j.1745-7254.2006.00333.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
AIM To explore the effects and mechanisms of caffeine and coffee on bladder dysfunction in streptozotocin-induced diabetic rats. METHODS Sprague-Dawley male rats were divided randomly into 4 groups: control, diabetes mellitus (DM), DM with coffee treatment, and DM with caffeine treatment. The diabetic rat was induced by intraperitoneal injection of streptozotocin (60 mg/kg). After 7 weeks of treatment with coffee and caffeine, cystometrogram, contractile responses to electrical field stimulation (EFS) and acetylcholine (ACh), and cyclic AMP (cAMP) concentration of the bladder body and base were measured. RESULTS The bladder weight, volume threshold for micturition and post-void residual volume (PVR) in the diabetic rats were significantly higher compared to those in the control animals. Coffee or caffeine treatment significantly reduced the bladder weight, bladder capacity and PVR in the diabetic rats. DM caused significant decreases in cAMP concentration of the bladder and coffee and caffeine caused upregulation of cAMP content in the diabetic bladder. In addition, coffee and caffeine tended to normalize the altered detrusor contractile responses to EFS and ACh in the diabetic rats. CONCLUSION These results indicate that caffeine and coffee may have beneficial effects on bladder dysfunction in the early stage of diabetes by increasing cAMP content in the lower urinary tract, recovering the micturition reflex and improving the detrusor contractility.
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Affiliation(s)
- Chao-Ran Yi
- Department of Urology, the Affiliated Drum Tower Hospital, Nanjing University Medical School, Nanjing 210008, China.
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