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Chen H, Wu A, Zeidel ML, Yu W. Smooth Muscle Insulin Receptor Deletion Causes Voiding Dysfunction: A Mechanism for Diabetic Bladder Dysfunction. Diabetes 2022; 71:2197-2208. [PMID: 35876633 PMCID: PMC9501730 DOI: 10.2337/db22-0233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2022] [Accepted: 07/20/2022] [Indexed: 01/03/2023]
Abstract
Diabetic bladder dysfunction (DBD) is the most common complication in diabetes. Myogenic abnormalities are common in DBD; however, the underlying mechanisms leading to these remain unclear. To understand the importance of smooth muscle insulin receptor (IR)-mediated signaling in the pathogenesis of DBD, we conditionally deleted it to achieve either heterozygous (SMIR+/-) or homozygous (SMIR-/-) deletion in smooth muscle cells. Despite impaired glucose and insulin tolerance seen with SMIR-/- mice, both SMIR+/- and SMIR-/- mice exhibited normal blood glucose and plasma insulin levels. Interestingly, these mice had abnormal voiding phenotypes, that included urinary frequency and small voids, and bladder smooth muscle (BSM) had significantly diminished contraction force. Morphology revealed a dilated bladder with thinner BSM layer, and BSM bundles were disorganized with penetrating interstitial tissue. Deletion of IR elevated FoxO and decreased mTOR protein expression, which further decreased the expression of Chrm3, P2x1, Sm22, and Cav1.2, crucial functional proteins for BSM contraction. Furthermore, we determined the expression of adiponectin in BSM, and deletion of IR in BSM inhibited adiponectin-mediated signaling. In summary, disruption of IR-mediated signaling in BSM caused abnormalities in proliferation and differentiation, leading to diminished BSM contractility and a voiding dysfunction phenotype that recapitulates human DBD.
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Affiliation(s)
| | | | | | - Weiqun Yu
- Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA
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2
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Yu W. Reviving Cav1.2 as an attractive drug target to treat bladder dysfunction. FASEB J 2022; 36:e22118. [PMID: 34939692 PMCID: PMC9841550 DOI: 10.1096/fj.202101475r] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 12/06/2021] [Accepted: 12/08/2021] [Indexed: 01/18/2023]
Abstract
Inhibition of bladder contraction with antimuscarinics is a common approach to treat bladder hyperactivity, and the L-type voltage-gated calcium channel α1C (Cav1.2) is crucial for bladder contractility. Therefore, strategies aimed at inhibiting Cav1.2 appear warranted. However, multiple clinical trials that attempted to treat bladder overactivity with calcium channel blockers (CCBs) have been unsuccessful, creating an unsolved mystery. In contrast, cardiologists and epidemiologists have reported strong associations between CCB use and bladder hyperactivity, opposing expectations of urologists. Recent findings from our lab offer a potential explanation. We have demonstrated that ketamine which can cause cystitis, functions, like nifedipine, as a Cav1.2 antagonist. We also show that a Cav1.2 agonist which potentiates muscle contraction, rather than antagonizing it, can increase the volume of voids and reduce voiding frequency. This perspective will discuss in detail the unsuccessful urological trials of CCBs and the promise of Cav1.2 agonists as potential novel therapies for bladder dysfunctions.
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Affiliation(s)
- Weiqun Yu
- Department of Medicine Beth Israel Deaconess Medical Center and Harvard Medical School Boston Massachuesetts USA
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3
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Kennedy C. ATP as a cotransmitter in sympathetic and parasympathetic nerves - another Burnstock legacy. Auton Neurosci 2021; 235:102860. [PMID: 34340045 DOI: 10.1016/j.autneu.2021.102860] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2021] [Revised: 07/09/2021] [Accepted: 07/21/2021] [Indexed: 12/19/2022]
Abstract
Geoff Burnstock created an outstanding scientific legacy that includes identification of adenosine 5'-triphosphate (ATP) as an inhibitory neurotransmitter in the gut, the discovery and characterisation of a large family of purine and uridine nucleotide-sensitive ionotropic P2X and metabotropic P2Y receptors and the demonstration that ATP is as an excitatory cotransmitter in autonomic nerves. The evidence for cotransmission includes that: 1) ATP is costored with noradrenaline in synaptic vesicles in postganglionic sympathetic nerves innervating smooth muscle tissues, including the vas deferens and most arteries. 2) When coreleased with noradrenaline, ATP acts at postjunctional P2X1 receptors to elicit depolarisation, Ca2+ influx, Ca2+ sensitisation and contraction. 3) ATP is also coreleased with acetylcholine from postganglionic parasympathetic nerves innervating the urinary bladder, where it stimulates postjunctional P2X1 receptors, and a second, as yet unidentified site to evoke contraction of detrusor smooth muscle. In both systems membrane-bound ecto-enzymes and soluble nucleotidases released from postganglionic nerves dephosphorylate ATP and so terminate its neurotransmitter actions. Currently, the most promising potential area of therapeutic application relating to cotransmission is treatment of dysfunctional urinary bladder. This family of disorders is associated with the appearance of a purinergic component of neurogenic contractions. This component is an attractive target for drug development and targeting it may be a rewarding area of research.
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Affiliation(s)
- Charles Kennedy
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE, United Kingdom.
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4
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Maeda K, Hotta Y, Kawata R, Kataoka T, Kimura K. Detrusor underactivity causes neurogenic voiding dysfunction in a rat bilateral accessory nerve-injury model. J Pharmacol Sci 2021; 146:116-119. [PMID: 33941322 DOI: 10.1016/j.jphs.2021.03.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Revised: 03/22/2021] [Accepted: 03/29/2021] [Indexed: 01/03/2023] Open
Abstract
We aimed to investigate detrusor function in a previously developed rat neurogenic voiding dysfunction model that we have developed previously. We performed sham or bilateral accessory nerve injury (BACNI) surgeries on ten-week-old male Wistar/ST rats. One week after surgery, we evaluated detrusor contractility in the bladder using isometric tension and mRNA expression assays. Cholinergic contraction was attenuated in the injury model, whereas carbachol-evoked contraction was enhanced, and mRNA expression of the cholinergic receptor increased. These findings suggest that there was a reduction in neurotransmitter release causing detrusor underactivity.
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Affiliation(s)
- Kotomi Maeda
- Department of Hospital Pharmacy, Nagoya City University Graduate School of Pharmaceutical Sciences, 3-1 Tanabe-dori, Mizuho-ku, Nagoya-shi, Aichi-ken 467-8603, Japan.
| | - Yuji Hotta
- Department of Hospital Pharmacy, Nagoya City University Graduate School of Pharmaceutical Sciences, 3-1 Tanabe-dori, Mizuho-ku, Nagoya-shi, Aichi-ken 467-8603, Japan.
| | - Ryoya Kawata
- Department of Hospital Pharmacy, Nagoya City University Graduate School of Pharmaceutical Sciences, 3-1 Tanabe-dori, Mizuho-ku, Nagoya-shi, Aichi-ken 467-8603, Japan.
| | - Tomoya Kataoka
- Department of Clinical Pharmaceutics, Nagoya City University, Graduate School of Medical Sciences, 1-Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya-shi, Aichi-ken 467-8601, Japan.
| | - Kazunori Kimura
- Department of Hospital Pharmacy, Nagoya City University Graduate School of Pharmaceutical Sciences, 3-1 Tanabe-dori, Mizuho-ku, Nagoya-shi, Aichi-ken 467-8603, Japan; Department of Clinical Pharmaceutics, Nagoya City University, Graduate School of Medical Sciences, 1-Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya-shi, Aichi-ken 467-8601, Japan.
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5
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Babou Kammoe RB, Kauffenstein G, Pelletier J, Robaye B, Sévigny J. NTPDase1 Modulates Smooth Muscle Contraction in Mice Bladder by Regulating Nucleotide Receptor Activation Distinctly in Male and Female. Biomolecules 2021; 11:biom11020147. [PMID: 33498759 PMCID: PMC7911947 DOI: 10.3390/biom11020147] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 01/17/2021] [Accepted: 01/20/2021] [Indexed: 12/20/2022] Open
Abstract
Nucleotides released by smooth muscle cells (SMCs) and by innervating nerve terminals activate specific P2 receptors and modulate bladder contraction. We hypothesized that cell surface enzymes regulate SMC contraction in mice bladder by controlling the concentration of nucleotides. We showed by immunohistochemistry, enzymatic histochemistry, and biochemical activities that nucleoside triphosphate diphosphohydrolase-1 (NTPDase1) and ecto-5′-nucleotidase were the major ectonucleotidases expressed by SMCs in the bladder. RT-qPCR revealed that, among the nucleotide receptors, there was higher expression of P2X1, P2Y1, and P2Y6 receptors. Ex vivo, nucleotides induced a more potent contraction of bladder strips isolated from NTPDase1 deficient (Entpd1−/−) mice compared to wild type controls. The strongest responses were obtained with uridine 5′-triphosphate (UTP) and uridine 5′-diphosphate (UDP), suggesting the involvement of P2Y6 receptors, which was confirmed with P2ry6−/− bladder strips. Interestingly, this response was reduced in female bladders. Our results also suggest the participation of P2X1, P2Y2 and/or P2Y4, and P2Y12 in these contractions. A reduced response to the thromboxane analogue U46619 was also observed in wild type, Entpd1−/−, and P2ry6−/− female bladders showing another difference due to sex. In summary, NTPDase1 modulates the activation of nucleotide receptors in mouse bladder SMCs, and contractions induced by P2Y6 receptor activation were weaker in female bladders.
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Affiliation(s)
- Romuald Brice Babou Kammoe
- Centre de Recherche du CHU de Québec, Université Laval, Québec City, QC G1V 4G2, Canada; (R.B.B.K.); (G.K.); (J.P.)
- Département de Microbiologie-Infectiologie et d’immunologie, Faculté de Médecine, Université Laval, Québec City, QC G1V 0A6, Canada
| | - Gilles Kauffenstein
- Centre de Recherche du CHU de Québec, Université Laval, Québec City, QC G1V 4G2, Canada; (R.B.B.K.); (G.K.); (J.P.)
- Département de Microbiologie-Infectiologie et d’immunologie, Faculté de Médecine, Université Laval, Québec City, QC G1V 0A6, Canada
- UMR INSERM 1260, Centre de Recherche en Biomédecine de Strasbourg, Université de Strasbourg, 67084 Strasbourg, France
| | - Julie Pelletier
- Centre de Recherche du CHU de Québec, Université Laval, Québec City, QC G1V 4G2, Canada; (R.B.B.K.); (G.K.); (J.P.)
| | - Bernard Robaye
- Institut de Recherche Interdisciplinaire en Biologie Humaine et Moléculaire, Université Libre de Bruxelles, 10 rue Adrienne Bolland, 6041 Gosselies, Belgium;
| | - Jean Sévigny
- Centre de Recherche du CHU de Québec, Université Laval, Québec City, QC G1V 4G2, Canada; (R.B.B.K.); (G.K.); (J.P.)
- Département de Microbiologie-Infectiologie et d’immunologie, Faculté de Médecine, Université Laval, Québec City, QC G1V 0A6, Canada
- Correspondence: ; Tel.: +1-418-525-4444 (ext. 46319); Fax: +1-418-654-2765
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Dalghi MG, Montalbetti N, Carattino MD, Apodaca G. The Urothelium: Life in a Liquid Environment. Physiol Rev 2020; 100:1621-1705. [PMID: 32191559 PMCID: PMC7717127 DOI: 10.1152/physrev.00041.2019] [Citation(s) in RCA: 85] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Revised: 03/02/2020] [Accepted: 03/14/2020] [Indexed: 02/08/2023] Open
Abstract
The urothelium, which lines the renal pelvis, ureters, urinary bladder, and proximal urethra, forms a high-resistance but adaptable barrier that surveils its mechanochemical environment and communicates changes to underlying tissues including afferent nerve fibers and the smooth muscle. The goal of this review is to summarize new insights into urothelial biology and function that have occurred in the past decade. After familiarizing the reader with key aspects of urothelial histology, we describe new insights into urothelial development and regeneration. This is followed by an extended discussion of urothelial barrier function, including information about the roles of the glycocalyx, ion and water transport, tight junctions, and the cellular and tissue shape changes and other adaptations that accompany expansion and contraction of the lower urinary tract. We also explore evidence that the urothelium can alter the water and solute composition of urine during normal physiology and in response to overdistension. We complete the review by providing an overview of our current knowledge about the urothelial environment, discussing the sensor and transducer functions of the urothelium, exploring the role of circadian rhythms in urothelial gene expression, and describing novel research tools that are likely to further advance our understanding of urothelial biology.
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Affiliation(s)
- Marianela G Dalghi
- Department of Medicine, Renal-Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Nicolas Montalbetti
- Department of Medicine, Renal-Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Marcelo D Carattino
- Department of Medicine, Renal-Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Gerard Apodaca
- Department of Medicine, Renal-Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
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7
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The Role of Purinergic Receptors in the Circadian System. Int J Mol Sci 2020; 21:ijms21103423. [PMID: 32408622 PMCID: PMC7279285 DOI: 10.3390/ijms21103423] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Revised: 04/30/2020] [Accepted: 05/06/2020] [Indexed: 12/24/2022] Open
Abstract
The circadian system is an internal time-keeping system that synchronizes the behavior and physiology of an organism to the 24 h solar day. The master circadian clock, the suprachiasmatic nucleus (SCN), resides in the hypothalamus. It receives information about the environmental light/dark conditions through the eyes and orchestrates peripheral oscillators. Purinergic signaling is mediated by extracellular purines and pyrimidines that bind to purinergic receptors and regulate multiple body functions. In this review, we highlight the interaction between the circadian system and purinergic signaling to provide a better understanding of rhythmic body functions under physiological and pathological conditions.
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Su MS, Xu L, Gu SG, Huang N, Ren XK, Cai XH, Li CC. Therapeutic effects and modulatory mechanism of Alpiniae oxyphyllae Fructus in chronic intermittent hypoxia induced enuresis in rats. Sleep Breath 2020; 24:329-337. [PMID: 31898190 DOI: 10.1007/s11325-019-01983-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Revised: 10/25/2019] [Accepted: 11/20/2019] [Indexed: 12/15/2022]
Abstract
OBJECTIVE The objective of this study was to explore the effect of Alpiniae oxyphyllae Fructus (AOF) on a rat model of chronic intermittent hypoxia (CIH)-induced enuresis. Findings of this study may help identify therapeutic targets in children with nocturnal enuresis (NE). METHODS Female rats were randomly divided into a control group (saline gavage, 4 weeks of normal air), CIH group (saline gavage, 4 weeks of CIH), and AOF group (AOF gavage, 4 weeks of CIH). The variables measured in this study included water intake, urine output, bladder leak point pressure (BLPP), malondialdehyde (MDA) levels, and superoxide dismutase (SOD) activity. The expression levels of the purinergic P2X3 receptor, muscarinic M3 receptor, and ß3-adrenergic receptor (ß3-AR) in the bladder were also measured. The bladder was subjected to haematoxylin and eosin (HE) and Weigert staining, and histological changes were observed under a light microscope to evaluate the morphological changes in the bladder in each group. RESULTS Compared with the control group, urine output was increased, and the BLPP was decreased in the CIH group, but AOF administration decreased urine output and increased BLPP. In addition, the serum MDA level increased and the SOD activity decreased in the CIH group compared with the control group. Administration of AOF decreased the MDA level and increased the SOD activity. Additionally, compared with the control group, HE and Weigert staining in the CIH group showed that the bladder detrusor muscle bundles were disordered and loose, some muscle bundles were broken, the content of collagen fibres in the gap was reduced, and the gap was significantly widened. However, following the administration of AOF, the bladder detrusor muscle bundles were neatly arranged, and the content of collagen fibres in the gap was increased. Furthermore, compared with the control group, the purinergic P2X3 receptor and muscarinic M3 receptor were expressed at higher levels, and ß3-AR was expressed at lower levels in the CIH group, but AOF administration decreased the expression of the purinergic P2X3 receptor and muscarinic M3 receptor and increased the expression of the ß3-AR. CONCLUSIONS AOF improves enuresis by inhibiting oxidative stress and regulating the expression of the purinergic P2X3 receptor, muscarinic M3 receptor, and ß3 adrenergic receptor.
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Affiliation(s)
- Miao-Shang Su
- Department of Pediatric Respiratory Medicine and Sleep Medicine, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, People's Republic of China
| | - Li Xu
- Department of Pediatric Respiratory Medicine and Sleep Medicine, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, People's Republic of China
| | - Shu-Ge Gu
- Department of Pediatric Respiratory Medicine and Sleep Medicine, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, People's Republic of China
| | - Nan Huang
- Department of Pediatric Respiratory Medicine and Sleep Medicine, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, People's Republic of China
| | - Xi-Kai Ren
- Department of Pediatric Respiratory Medicine and Sleep Medicine, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, People's Republic of China
| | - Xiao-Hong Cai
- Department of Pediatric Respiratory Medicine and Sleep Medicine, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, People's Republic of China
| | - Chang-Chong Li
- Department of Pediatric Respiratory Medicine and Sleep Medicine, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, People's Republic of China.
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Hao Y, Wang L, Chen H, Hill WG, Robson SC, Zeidel ML, Yu W. Targetable purinergic receptors P2Y12 and A2b antagonistically regulate bladder function. JCI Insight 2019; 4:122112. [PMID: 31434806 DOI: 10.1172/jci.insight.122112] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Accepted: 07/26/2019] [Indexed: 12/21/2022] Open
Abstract
Abnormalities in purine availability or purinergic receptor density are commonly seen in patients with lower urinary tract symptoms (LUTS), but the underlying mechanisms relating altered receptor function to LUTS are unknown. Here we provide extensive evidence for the reciprocal interplay of multiple receptors responding to ATP, ADP (adenosine diphosphate), and adenosine, agonists that regulate bladder function significantly. ADP stimulated P2Y12 receptors, causing bladder smooth muscle (BSM) contraction, whereas adenosine signaling through potentially newly defined A2b receptors, actively inhibited BSM purinergic contractility. The modulation of adenylyl cyclase-cAMP signaling via A2b and P2Y12 interaction actively regulated bladder contractility by modulating intracellular calcium levels. KO mice lacking the receptors display diametrically opposed bladder phenotypes, with P2Y12-KO mice exhibiting an underactive bladder (UAB) phenotype with increased bladder capacity and reduced voiding frequency, whereas A2b-KO mice have an overactive bladder (OAB), with decreased capacity and increased voiding frequency. The opposing phenotypes in P2Y12-KO and A2b-KO mice not only resulted from dysregulated BSM contractility, but also from abnormal BSM cell growth. Finally, we demonstrate that i.p. administration of drugs targeting P2Y12 or A2b receptor rescues these abnormal phenotypes in both KO mice. These findings strongly indicate that P2Y12 and A2b receptors are attractive therapeutic targets for human patients with LUTS.
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Affiliation(s)
- Yuan Hao
- Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
| | - Lu Wang
- Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA.,Chongqing University, Chongqing, China
| | - Huan Chen
- Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
| | - Warren G Hill
- Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
| | - Simon C Robson
- Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
| | - Mark L Zeidel
- Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
| | - Weiqun Yu
- Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
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10
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Tykocki NR, Heppner TJ, Dalsgaard T, Bonev AD, Nelson MT. The K V 7 channel activator retigabine suppresses mouse urinary bladder afferent nerve activity without affecting detrusor smooth muscle K + channel currents. J Physiol 2018; 597:935-950. [PMID: 30536555 DOI: 10.1113/jp277021] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Accepted: 12/06/2018] [Indexed: 01/20/2023] Open
Abstract
KEY POINTS KV 7 channels are a family of voltage-dependent K+ channels expressed in many cell types, which open in response to membrane depolarization to regulate cell excitability. Drugs that target KV 7 channels are used clinically to treat epilepsy. Interestingly, these drugs also cause urinary retention, but it was unclear how. In this study, we focused on two possible mechanisms by which retigabine could cause urinary retention: by decreasing smooth muscle excitability, or by decreasing sensory nerve outflow. Urinary bladder smooth muscle had no measurable KV 7 channel currents. However, the KV 7 channel agonist retigabine nearly abolished sensory nerve outflow from the urinary bladder during bladder filling. We conclude that KV 7 channel activation likely affects urinary bladder function by blocking afferent nerve outflow to the brain, which is key to sensing bladder fullness. ABSTRACT KV 7 channels are voltage-dependent K+ channels that open in response to membrane depolarization to regulate cell excitability. KV 7 activators, such as retigabine, were used to treat epilepsy but caused urinary retention. Using electrophysiological recordings from freshly isolated mouse urinary bladder smooth muscle (UBSM) cells, isometric contractility of bladder strips, and ex vivo measurements of bladder afferent activity, we explored the role of KV 7 channels as regulators of murine urinary bladder function. The KV 7 activator retigabine (10 μM) had no effect on voltage-dependent K+ currents or resting membrane potential of UBSM cells, suggesting that these cells lacked retigabine-sensitive KV 7 channels. The KV 7 inhibitor XE-991 (10 μM) inhibited UBSM K+ currents; the properties of these currents, however, were typical of KV 2 channels and not KV 7 channels. Retigabine inhibited voltage-dependent Ca2+ channel (VDCC) currents and reduced steady-state contractions to 60 mM KCl in bladder strips, suggesting that reduction in VDCC current was sufficient to directly affect UBSM function. To determine if retigabine altered ex vivo bladder sensory outflow, we measured afferent activity during simulated transient contractions (TCs) of the bladder wall. Simulated TCs caused bursts of afferent activity that were nearly abolished by retigabine. The effects of retigabine were blocked by co-incubation with XE-991, suggesting specific activation of KV 7 channels on afferent nerves. These results indicate that retigabine primarily affects urinary bladder function by inhibiting TC generation and afferent nerve activity, which are key to sensing bladder fullness. Any direct inhibition of UBSM contractility is likely to be from non-specific effects on VDCCs and KV 2 channels.
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Affiliation(s)
- Nathan R Tykocki
- Department of Pharmacology, University of Vermont, Burlington, VT, 05405, USA
| | - Thomas J Heppner
- Department of Pharmacology, University of Vermont, Burlington, VT, 05405, USA
| | | | - Adrian D Bonev
- Department of Pharmacology, University of Vermont, Burlington, VT, 05405, USA
| | - Mark T Nelson
- Department of Pharmacology, University of Vermont, Burlington, VT, 05405, USA.,Institute of Cardiovascular Sciences, University of Manchester, Manchester, UK
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11
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Shang Z, Jia C, Yan H, Cui B, Wu J, Wang Q, Gao W, Cui X, Li J, Ou T. Injecting RNA interference lentiviruses targeting the muscarinic 3 receptor gene into the bladder wall inhibits neurogenic detrusor overactivity in rats with spinal cord injury. Neurourol Urodyn 2018; 38:615-624. [DOI: 10.1002/nau.23894] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2018] [Accepted: 10/22/2018] [Indexed: 12/16/2022]
Affiliation(s)
- Zhenhua Shang
- Department of UrologyXuanwu Hospital Capital Medical UniversityXuanwu DistrictBeijingChina
| | - Chunsong Jia
- Department of UrologyXuanwu Hospital Capital Medical UniversityXuanwu DistrictBeijingChina
| | - Hao Yan
- Department of UrologyXuanwu Hospital Capital Medical UniversityXuanwu DistrictBeijingChina
| | - Bo Cui
- Department of UrologyXuanwu Hospital Capital Medical UniversityXuanwu DistrictBeijingChina
| | - Jiangtao Wu
- Department of UrologyXuanwu Hospital Capital Medical UniversityXuanwu DistrictBeijingChina
| | - Qi Wang
- Department of UrologyXuanwu Hospital Capital Medical UniversityXuanwu DistrictBeijingChina
| | - Wei Gao
- Department of UrologyXuanwu Hospital Capital Medical UniversityXuanwu DistrictBeijingChina
| | - Xin Cui
- Department of UrologyXuanwu Hospital Capital Medical UniversityXuanwu DistrictBeijingChina
| | - Jin Li
- Department of UrologyXuanwu Hospital Capital Medical UniversityXuanwu DistrictBeijingChina
| | - Tongwen Ou
- Department of UrologyXuanwu Hospital Capital Medical UniversityXuanwu DistrictBeijingChina
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12
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Mahapatra C, Brain KL, Manchanda R. A biophysically constrained computational model of the action potential of mouse urinary bladder smooth muscle. PLoS One 2018; 13:e0200712. [PMID: 30048468 PMCID: PMC6061979 DOI: 10.1371/journal.pone.0200712] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 07/02/2018] [Indexed: 11/19/2022] Open
Abstract
Urinary incontinence is associated with enhanced spontaneous phasic contractions of the detrusor smooth muscle (DSM). Although a complete understanding of the etiology of these spontaneous contractions is not yet established, it is suggested that the spontaneously evoked action potentials (sAPs) in DSM cells initiate and modulate the contractions. In order to further our understanding of the ionic mechanisms underlying sAP generation, we present here a biophysically detailed computational model of a single DSM cell. First, we constructed mathematical models for nine ion channels found in DSM cells based on published experimental data: two voltage gated Ca2+ ion channels, an hyperpolarization-activated ion channel, two voltage-gated K+ ion channels, three Ca2+-activated K+ ion channels and a non-specific background leak ion channel. The ion channels' kinetics were characterized in terms of maximal conductances and differential equations based on voltage or calcium-dependent activation and inactivation. All ion channel models were validated by comparing the simulated currents and current-voltage relations with those reported in experimental work. Incorporating these channels, our DSM model is capable of reproducing experimentally recorded spike-type sAPs of varying configurations, ranging from sAPs displaying after-hyperpolarizations to sAPs displaying after-depolarizations. The contributions of the principal ion channels to spike generation and configuration were also investigated as a means of mimicking the effects of selected pharmacological agents on DSM cell excitability. Additionally, the features of propagation of an AP along a length of electrically continuous smooth muscle tissue were investigated. To date, a biophysically detailed computational model does not exist for DSM cells. Our model, constrained heavily by physiological data, provides a powerful tool to investigate the ionic mechanisms underlying the genesis of DSM electrical activity, which can further shed light on certain aspects of urinary bladder function and dysfunction.
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Affiliation(s)
- Chitaranjan Mahapatra
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, Maharashtra, India
| | - Keith L. Brain
- School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, England, United Kingdom
| | - Rohit Manchanda
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, Maharashtra, India
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13
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Doyle C, Cristofaro V, Sack BS, Mahmood F, Sullivan MP, Adam RM. The role of the mucosa in modulation of evoked responses in the spinal cord injured rat bladder. Neurourol Urodyn 2018; 37:1583-1593. [PMID: 29427331 PMCID: PMC6086770 DOI: 10.1002/nau.23512] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Accepted: 01/09/2018] [Indexed: 11/27/2022]
Abstract
Aims Mounting evidence indicates that a variety of factors released from the urothelium or suburothelium can modulate smooth muscle activity. Although the relationship between the mucosa and smooth muscle has been investigated, little is known about the pathophysiologic changes in detrusor‐mucosa interactions in neurogenic bladders. The goal of the study was to determine the impact of the mucosa on evoked responses in spinal cord injured (SCI) bladders. Methods Urinary bladders were obtained from 6wk SCI rats or age‐matched uninjured controls. Ex vivo isometric tension studies were performed and muscarinic receptor expression was measured in bladder tissue with and without mucosa. Results The magnitude and area of nerve evoked responses in SCI tissue with mucosa was higher than without mucosa. The duration and decay time of nerve‐evoked responses were longer in SCI than control tissue irrespective of the mucosa. The level of the muscarinic M2 receptor was decreased in the mucosa of SCI bladders. Conclusions Detrusor‐mucosa interactions are substantially altered in the neurogenic bladder. After spinal cord injury, an excitatory modulation of smooth muscle contraction by the mucosa emerges, and could be targeted via intravesical treatment in the context of neurogenic bladder dysfunction.
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Affiliation(s)
- Claire Doyle
- Urological Diseases Research Center, Boston Children's Hospital, Boston, Massachusetts.,Department of Surgery, Harvard Medical School, Boston, Massachusetts
| | - Vivian Cristofaro
- Department of Surgery, Harvard Medical School, Boston, Massachusetts.,Division of Urology, VA Boston Healthcare System, Boston, Massachusetts.,Department of Surgery, Brigham and Women's Hospital, Boston, Massachusetts
| | - Bryan S Sack
- Urological Diseases Research Center, Boston Children's Hospital, Boston, Massachusetts.,Department of Surgery, Harvard Medical School, Boston, Massachusetts
| | - Fabliha Mahmood
- Urological Diseases Research Center, Boston Children's Hospital, Boston, Massachusetts
| | - Maryrose P Sullivan
- Department of Surgery, Harvard Medical School, Boston, Massachusetts.,Division of Urology, VA Boston Healthcare System, Boston, Massachusetts.,Department of Surgery, Brigham and Women's Hospital, Boston, Massachusetts
| | - Rosalyn M Adam
- Urological Diseases Research Center, Boston Children's Hospital, Boston, Massachusetts.,Department of Surgery, Harvard Medical School, Boston, Massachusetts
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14
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Yu W, Hill WG, Robson SC, Zeidel ML. Role of P2X 4 Receptor in Mouse Voiding Function. Sci Rep 2018; 8:1838. [PMID: 29382907 PMCID: PMC5789870 DOI: 10.1038/s41598-018-20216-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Accepted: 01/16/2018] [Indexed: 01/16/2023] Open
Abstract
Purinergic signalling plays an important role in the regulation of bladder smooth muscle (BSM) contractility, and P2X4 receptor is expressed in the bladder wall, where it may act by forming heteromeric receptors with P2X1, the major purinergic force-generating muscle receptor. To test this hypothesis, we examined mouse BSM contractile properties in the absence and presence of selective P2X1 (NF449 & NF279) and P2X4 antagonists (5-BDBD). These drugs inhibited BSM purinergic contraction only partially, suggesting the possibility of a heteromeric receptor. However, carefully controlled co-immunoprecipitation experiments indicated that P2X1 and P2X4 do not form physically linked heteromers. Furthermore, immunofluorescence staining showed that P2X4 is not present in mouse BSM per se, but in an unknown cellular structure among BSM bundles. To investigate whether deletion of P2X4 could impact voiding function in vivo, P2X4 null mice were characterized. P2X4 null mice had normal bladder weight and morphology, normal voiding spot size and number by voiding spot assay, normal voiding interval, pressure and compliance by cystometrogram, and normal BSM contractility by myography. In conclusion, these data strongly suggest that P2X4 is not present in mouse BSM cells, does not affect smooth muscle contractility and that mice null for P2X4 exhibit normal voiding function.
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Affiliation(s)
- Weiqun Yu
- Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachuesetts, USA.
| | - Warren G Hill
- Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachuesetts, USA
| | - Simon C Robson
- Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachuesetts, USA
| | - Mark L Zeidel
- Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachuesetts, USA
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15
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Electrical Activity of the Bladder Is Attenuated by Intravesical Inhibition of P2X2/3 Receptors During Micturition in Female Rats. Int Neurourol J 2017; 21:259-269. [PMID: 29298472 PMCID: PMC5756821 DOI: 10.5213/inj.1734998.499] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Accepted: 11/27/2017] [Indexed: 01/23/2023] Open
Abstract
Purpose To simultaneously monitor electrical discharges in various bladder regions and the external urethral sphincter (EUS) during voiding contractions, and to assess the functional role of myogenic modulation of the lower urinary tract (LUT) by ionotropic purinergic receptors containing the P2X3 subunit. Methods Female Sprague-Dawley rats were anesthetized with urethane, and implanted with a suprapubic catheter for open cystometry. Flexible microelectrodes were placed ventrally in the bladder dome, upper bladder, lower bladder, and bladder base, along with the middle section of the exposed EUS. Intravesical P2X3-containing receptors were blocked with AF-323, a specific P2X3-P2X2/3 receptor antagonist. A digital electrophysiology amplifier was used to record electrical and cystometric signals throughout the LUT. Results Electrical activity in the LUT started before effective voiding contractions. Bladder pressure and electrical waveforms showed consistent out-of-phase activity when compared with the recordings made at the EUS. This pattern was also observed during voiding contractions in the presence of AF-353, supporting the hypothesis that during bladder distension, activation of P2X3-containing receptors is required for voiding contractions. Furthermore, the inhibition of P2X3-containing receptors significantly decreased the amplitude of electrical signals in the urinary bladder, but not the base or EUS. Conclusions Our results provide novel information about the regulation of the micturition process by P2X3-containing receptors located in the inner layers of the bladder.
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16
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Chai TC, Kudze T. New therapeutic directions to treat underactive bladder. Investig Clin Urol 2017; 58:S99-S106. [PMID: 29279882 PMCID: PMC5740036 DOI: 10.4111/icu.2017.58.s2.s99] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Accepted: 11/18/2017] [Indexed: 11/18/2022] Open
Abstract
Underactive bladder (UAB) is a term used to describe a constellation of symptoms that is perceived by patients suggesting bladder hypocontractility. Urodynamic measurement that suggest decreased contractility of the bladder is termed detrusor underactivity (DUA). Regulatory approved specific management options with clinically proven ability to increase bladder contractility do not currently exist. While DUA specific treatments presumably will focus on methods to increase efficiency of bladder emptying capability relying on augmenting the motor pathway in the micturition reflex, other approaches include methods to augment the sensory (afferent) contribution to the micturition reflex which could result in increased detrusor contractility. Another method to induce more efficient bladder emptying could be to induce relaxation of the bladder outlet. Using cellular regenerative techniques, the detrusor smooth muscle can be targeted so the result is to increase detrusor smooth muscle function. In this review, we will cover areas of potential new therapies for DUA including: drug therapy, stem cells and regenerative therapies, neuromodulation, and urethral flow assist device. Paralleling development of new therapies, there also needs to be clinical studies performed that address how DUA relates to UAB.
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Affiliation(s)
- Toby C Chai
- Department of Urology, Yale University School of Medicine, New Haven, CT, USA
| | - Tambudzai Kudze
- Department of Urology, Yale University School of Medicine, New Haven, CT, USA
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17
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Provence A, Angoli D, Petkov GV. K V7 Channel Pharmacological Activation by the Novel Activator ML213: Role for Heteromeric K V7.4/K V7.5 Channels in Guinea Pig Detrusor Smooth Muscle Function. J Pharmacol Exp Ther 2017; 364:131-144. [PMID: 29084816 DOI: 10.1124/jpet.117.243162] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Accepted: 10/20/2017] [Indexed: 01/12/2023] Open
Abstract
Voltage-gated KV7 channels (KV7.1 to KV7.5) are important regulators of the cell membrane potential in detrusor smooth muscle (DSM) of the urinary bladder. This study sought to further the current knowledge of KV7 channel function at the molecular, cellular, and tissue levels in combination with pharmacological tools. We used isometric DSM tension recordings, ratiometric fluorescence Ca2+ imaging, amphotericin-B perforated patch-clamp electrophysiology, and in situ proximity ligation assay (PLA) in combination with the novel compound N-(2,4,6-trimethylphenyl)-bicyclo[2.2.1]heptane-2-carboxamide (ML213), an activator of KV7.2, KV7.4, and KV7.5 channels, to examine their physiologic roles in guinea pig DSM function. ML213 caused a concentration-dependent (0.1-30 µM) inhibition of spontaneous phasic contractions in DSM isolated strips; effects blocked by the KV7 channel inhibitor XE991 (10 µM). ML213 (0.1-30 µM) also reduced pharmacologically induced and nerve-evoked contractions in DSM strips. Consistently, ML213 (10 µM) decreased global intracellular Ca2+ concentrations in Fura-2-loaded DSM isolated strips. Perforated patch-clamp electrophysiology revealed that ML213 (10 µM) caused an increase in the amplitude of whole-cell KV7 currents. Further, in current-clamp mode of the perforated patch clamp, ML213 hyperpolarized DSM cell membrane potential in a manner reversible by washout or XE991 (10 µM), consistent with ML213 activation of KV7 channel currents. Preapplication of XE991 (10 µM) not only depolarized the DSM cells, but also blocked ML213-induced hyperpolarization, confirming ML213 selectivity for KV7 channel subtypes. In situ PLA revealed colocalization and expression of heteromeric KV7.4/KV7.5 channels in DSM isolated cells. These combined results suggest that ML213-sensitive KV7.4- and KV7.5-containing channels are essential regulators of DSM excitability and contractility.
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Affiliation(s)
- Aaron Provence
- Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, South Carolina (A.P., D.A., G.V.P.); and Department of Pharmaceutical Sciences, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee (G.V.P.)
| | - Damiano Angoli
- Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, South Carolina (A.P., D.A., G.V.P.); and Department of Pharmaceutical Sciences, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee (G.V.P.)
| | - Georgi V Petkov
- Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, South Carolina (A.P., D.A., G.V.P.); and Department of Pharmaceutical Sciences, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee (G.V.P.)
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18
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Biophysical Processes in a Urinary Bladder Detrusor Smooth Muscle Cell during Rehabilitation Stimulation of Parasympathetic Efferents: a Simulation Study. NEUROPHYSIOLOGY+ 2016. [DOI: 10.1007/s11062-016-9583-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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19
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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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20
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Kochenov AV, Korogod SM. Impact of the Ratio of Metabotropic and Ionotropic Components of Parasympathetic Action on the Excitability of a Urinary Bladder Smooth Muscle Cell: a Simulation Study. NEUROPHYSIOLOGY+ 2016. [DOI: 10.1007/s11062-016-9562-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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21
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Ehrhardt A, Wang B, Yung AC, Wang Y, Kozlowski P, van Breemen C, Schrader JW. Urinary Retention, Incontinence, and Dysregulation of Muscarinic Receptors in Male Mice Lacking Mras. PLoS One 2015; 10:e0141493. [PMID: 26516777 PMCID: PMC4627820 DOI: 10.1371/journal.pone.0141493] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Accepted: 10/07/2015] [Indexed: 12/20/2022] Open
Abstract
Here we show that male, but not female mice lacking expression of the GTPase M-Ras developed urinary retention with distention of the bladder that exacerbated with age but occurred in the absence of obvious anatomical outlet obstruction. There were changes in detrusor morphology in Mras-/- males: Smooth muscle tissue, which exhibited a compact organization in WT mice, appeared disorganized and became increasingly ‘layered’ with age in Mras-/- males, but was not fibrotic. Bladder tissue near the apex of bladders of Mras-/- males exhibited hypercontractility in response to the cholinergic agonist carbachol in in vitro, while responses in Mras-/- females were normal. In addition, spontaneous phasic contractions of detrusors from Mras-/- males were increased, and Mras-/- males exhibited urinary incontinence. We found that expression of the muscarinic M2 and M3 receptors that mediate the cholinergic contractile stimuli of the detrusor muscle was dysregulated in both Mras-/- males and females, although only males exhibited a urinary phenotype. Elevated expression of M2R in young males lacking M-Ras and failure to upregulate M3R with age resulted in significantly lower ratios of M3R/M2R expression that correlated with the bladder abnormalities. Our data suggests that M-Ras and M3R are functionally linked and that M-Ras is an important regulator of male bladder control in mice. Our observations also support the notion that bladder control is sexually dimorphic and is regulated through mechanisms that are largely independent of acetylcholine signaling in female mice.
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MESH Headings
- Acetylcholine/physiology
- Aging/genetics
- Aging/physiology
- Animals
- Female
- Gene Expression Regulation
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Monomeric GTP-Binding Proteins/deficiency
- Monomeric GTP-Binding Proteins/genetics
- Monomeric GTP-Binding Proteins/physiology
- Muscle Contraction
- Muscle, Smooth/metabolism
- Phenotype
- Proteinuria/genetics
- Proteinuria/physiopathology
- RNA, Messenger/biosynthesis
- Receptor, Muscarinic M2/biosynthesis
- Receptor, Muscarinic M2/genetics
- Receptor, Muscarinic M2/physiology
- Receptor, Muscarinic M3/biosynthesis
- Receptor, Muscarinic M3/genetics
- Receptor, Muscarinic M3/physiology
- Sex Characteristics
- Urinary Bladder/metabolism
- Urinary Bladder/pathology
- Urinary Bladder, Overactive/genetics
- Urinary Bladder, Overactive/physiopathology
- Urinary Incontinence/genetics
- Urinary Incontinence/physiopathology
- Urinary Retention/genetics
- Urinary Retention/physiopathology
- Urination/physiology
- ras Proteins
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Affiliation(s)
- Annette Ehrhardt
- The Biomedical Research Centre, The University of British Columbia, 2222 Health Sciences Mall, Vancouver, British Columbia, Canada
| | - Bin Wang
- The Biomedical Research Centre, The University of British Columbia, 2222 Health Sciences Mall, Vancouver, British Columbia, Canada
| | - Andrew C. Yung
- The University of British Columbia MRI Research Centre, Life Sciences Centre, 2350 Health Sciences Mall, Vancouver, British Columbia, Canada
| | - Yanni Wang
- The Biomedical Research Centre, The University of British Columbia, 2222 Health Sciences Mall, Vancouver, British Columbia, Canada
| | - Piotr Kozlowski
- The University of British Columbia MRI Research Centre, Life Sciences Centre, 2350 Health Sciences Mall, Vancouver, British Columbia, Canada
- The University of British Columbia, Departments of Radiology and Urologic Sciences, 818 West 10th Ave., Vancouver, British Columbia, Canada
| | - Cornelis van Breemen
- The University of British Columbia, Department of Pharmacology and Therapeutics, 2176 Health Sciences Mall, Vancouver, British Columbia, Canada
| | - John W. Schrader
- The Biomedical Research Centre, The University of British Columbia, 2222 Health Sciences Mall, Vancouver, British Columbia, Canada
- * E-mail:
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Cardoso AM, Schetinger MRC, Correia-de-Sá P, Sévigny J. Impact of ectonucleotidases in autonomic nervous functions. Auton Neurosci 2015; 191:25-38. [PMID: 26008223 DOI: 10.1016/j.autneu.2015.04.014] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2014] [Revised: 04/28/2015] [Accepted: 04/29/2015] [Indexed: 01/05/2023]
Abstract
Adenine and uracil nucleotides play key functions in the autonomic nervous system (ANS). For instance, ATP acts as a neurotransmitter, co-transmitter and neuromodulator in the ANS. The purinergic system encompasses (1) receptors that respond to extracellular purines, which are designated as P1 and P2 purinoceptors, (2) purine release and uptake, and (3) a cascade of enzymes that regulate the concentration of purines near the cell surface. Ectonucleotidases and adenosine deaminase (ADA) are enzymes responsible for the hydrolysis of ATP (and other nucleotides such as ADP, UTP, UDP, AMP) and adenosine, respectively. Accordingly, these enzymes are expected to play an important role in the control of neuro-effector transmission in tissues innervated by both the sympathetic and parasympathetic divisions of the ANS. Indeed, ectonucleotidases have the ability to either terminate P2 receptor responses initiated by nucleoside triphosphates (ATP and UTP), and/or to favor the activation of ADP (e.g. P2Y1,12,13) and UDP (e.g. P2Y6) and/or adenosine (P1) specific receptors. In addition, ectonucleotidases can also importantly protect some P2 receptors from desensitization (e.g. P2X1, P2Y1). In this review, we present the (putative) roles of ectonucleotidases and ADA in the ANS with a focus on their regulatory activity at neuro-effector junctions in the following tissues: heart, vas deferens, urinary bladder, salivary glands, blood vessels and the intestine. We also present their implication in nociceptive transmission.
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Affiliation(s)
- Andréia Machado Cardoso
- Post-Graduation Program in Toxicological Biochemistry, Department of Biochemistry and Molecular Biology of the Center of Natural and Exact Sciences of the Federal University of Santa Maria, Santa Maria Rio Grande do Sul, Brazil; Département de Microbiologie-Infectiologie et d'Immunologie, Faculté de Médecine, Université Laval, Québec City, Québec G1V 0A6, Canada; Centre de Recherche du CHU de Québec - Université Laval, Québec G1V 4G2, Canada.
| | - Maria Rosa Chitolina Schetinger
- Post-Graduation Program in Toxicological Biochemistry, Department of Biochemistry and Molecular Biology of the Center of Natural and Exact Sciences of the Federal University of Santa Maria, Santa Maria Rio Grande do Sul, Brazil
| | - Paulo Correia-de-Sá
- Laboratório de Farmacologia e Neurobiologia, MedInUP, Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto (UP), 4050-313 Porto, Portugal
| | - Jean Sévigny
- Département de Microbiologie-Infectiologie et d'Immunologie, Faculté de Médecine, Université Laval, Québec City, Québec G1V 0A6, Canada; Centre de Recherche du CHU de Québec - Université Laval, Québec G1V 4G2, Canada.
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Fernandes VS, Xin W, Petkov GV. Novel mechanism of hydrogen sulfide-induced guinea pig urinary bladder smooth muscle contraction: role of BK channels and cholinergic neurotransmission. Am J Physiol Cell Physiol 2015; 309:C107-16. [PMID: 25948731 DOI: 10.1152/ajpcell.00021.2015] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 05/02/2015] [Indexed: 12/13/2022]
Abstract
Hydrogen sulfide (H2S) is a key signaling molecule regulating important physiological processes, including smooth muscle function. However, the mechanisms underlying H2S-induced detrusor smooth muscle (DSM) contractions are not well understood. This study investigates the cellular and tissue mechanisms by which H2S regulates DSM contractility, excitatory neurotransmission, and large-conductance voltage- and Ca(2+)-activated K(+) (BK) channels in freshly isolated guinea pig DSM. We used a multidisciplinary experimental approach including isometric DSM tension recordings, colorimetric ACh measurement, Ca(2+) imaging, and patch-clamp electrophysiology. In isolated DSM strips, the novel slow release H2S donor, P-(4-methoxyphenyl)-p-4-morpholinylphosphinodithioic acid morpholine salt (GYY4137), significantly increased the spontaneous phasic and nerve-evoked DSM contractions. The blockade of neuronal voltage-gated Na(+) channels or muscarinic ACh receptors with tetrodotoxin or atropine, respectively, reduced the stimulatory effect of GYY4137 on DSM contractility. GYY4137 increased ACh release from bladder nerves, which was inhibited upon blockade of L-type voltage-gated Ca(2+) channels with nifedipine. Furthermore, GYY4137 increased the amplitude of the Ca(2+) transients and basal Ca(2+) levels in isolated DSM strips. GYY4137 reduced the DSM relaxation induced by the BK channel opener, NS11021. In freshly isolated DSM cells, GYY4137 decreased the amplitude and frequency of transient BK currents recorded in a perforated whole cell configuration and reduced the single BK channel open probability measured in excised inside-out patches. GYY4137 inhibited spontaneous transient hyperpolarizations and depolarized the DSM cell membrane potential. Our results reveal the novel findings that H2S increases spontaneous phasic and nerve-evoked DSM contractions by activating ACh release from bladder nerves in combination with a direct inhibition of DSM BK channels.
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Affiliation(s)
- Vítor S Fernandes
- Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, South Carolina
| | - Wenkuan Xin
- Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, South Carolina
| | - 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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Abstract
The role of adenosine 5'-triphosphate (ATP) as a major intracellular energy source is well-established. In addition, ATP and related nucleotides have widespread extracellular actions via the ionotropic P2X (ligand-gated cation channels) and metabotropic P2Y (G protein-coupled) receptors. Numerous experimental techniques, including myography, electrophysiology and biochemical measurement of neurotransmitter release, have been used to show that ATP has several major roles as a neurotransmitter in peripheral nerves. When released from enteric nerves of the gastrointestinal tract it acts as an inhibitory neurotransmitter, mediating descending muscle relaxation during peristalsis. ATP is also an excitatory cotransmitter in autonomic nerves; 1) It is costored with noradrenaline in synaptic vesicles in postganglionic sympathetic nerves innervating smooth muscle preparations, such as the vas deferens and most arteries. When coreleased with noradrenaline, ATP acts at postjunctional P2X1 receptors to evoke depolarisation, Ca(2+) influx, Ca(2+) sensitisation and contraction. 2) ATP is also coreleased with acetylcholine from postganglionic parasympathetic nerves innervating the urinary bladder and again acts at postjunctional P2X1 receptors, and possibly also a P2X1+4 heteromer, to elicit smooth muscle contraction. In both cases the neurotransmitter actions of ATP are terminated by dephosphorylation by extracellular, membrane-bound enzymes and soluble nucleotidases released from postganglionic nerves. There are indications of an increased contribution of ATP to control of blood pressure in hypertension, but further research is needed to clarify this possibility. More promising is the upregulation of P2X receptors in dysfunctional bladder, including interstitial cystitis, idiopathic detrusor instability and overactive bladder syndrome. Consequently, these roles of ATP are of great therapeutic interest and are increasingly being targeted by pharmaceutical companies.
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Affiliation(s)
- Charles Kennedy
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE, United Kingdom.
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25
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Ferguson AC, Sutton BW, Boone TB, Ford AP, Munoz A. Inhibition of urothelial P2X3 receptors prevents desensitization of purinergic detrusor contractions in the rat bladder. BJU Int 2015; 116:293-301. [DOI: 10.1111/bju.13003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
| | | | - Timothy B. Boone
- Houston Methodist Research Institute; Houston TX USA
- Houston Methodist Hospital Department of Urology; Houston TX USA
| | | | - Alvaro Munoz
- Houston Methodist Research Institute; Houston TX USA
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26
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Jespersen B, Tykocki NR, Watts SW, Cobbett PJ. Measurement of smooth muscle function in the isolated tissue bath-applications to pharmacology research. J Vis Exp 2015:52324. [PMID: 25650585 PMCID: PMC4354551 DOI: 10.3791/52324] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
Abstract
Isolated tissue bath assays are a classical pharmacological tool for evaluating concentration-response relationships in a myriad of contractile tissues. While this technique has been implemented for over 100 years, the versatility, simplicity and reproducibility of this assay helps it to remain an indispensable tool for pharmacologists and physiologists alike. Tissue bath systems are available in a wide array of shapes and sizes, allowing a scientist to evaluate samples as small as murine mesenteric arteries and as large as porcine ileum - if not larger. Central to the isolated tissue bath assay is the ability to measure concentration-dependent changes to isometric contraction, and how the efficacy and potency of contractile agonists can be manipulated by increasing concentrations of antagonists or inhibitors. Even though the general principles remain relatively similar, recent technological advances allow even more versatility to the tissue bath assay by incorporating computer-based data recording and analysis software. This video will demonstrate the function of the isolated tissue bath to measure the isometric contraction of an isolated smooth muscle (in this case rat thoracic aorta rings), and share the types of knowledge that can be created with this technique. Included are detailed descriptions of aortic tissue dissection and preparation, placement of aortic rings in the tissue bath and proper tissue equilibration prior to experimentation, tests of tissue viability, experimental design and implementation, and data quantitation. Aorta will be connected to isometric force transducers, the data from which will be captured using a commercially available analog-to-digital converter and bridge amplifier specifically designed for use in these experiments. The accompanying software to this system will be used to visualize the experiment and analyze captured data.
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Affiliation(s)
- Brian Jespersen
- Department of Pharmacology and Toxicology, Michigan State University
| | - Nathan R Tykocki
- Department of Pharmacology, University of Vermont College of Medicine
| | - Stephanie W Watts
- Department of Pharmacology and Toxicology, Michigan State University;
| | - Peter J Cobbett
- Department of Pharmacology and Toxicology, Michigan State University
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Afeli SAY, Rovner ES, Petkov GV. BRL37344, a β3-adrenergic receptor agonist, decreases nerve-evoked contractions in human detrusor smooth muscle isolated strips: role of BK channels. Urology 2013; 82:744.e1-7. [PMID: 23890664 PMCID: PMC3758792 DOI: 10.1016/j.urology.2013.05.027] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Revised: 04/29/2013] [Accepted: 05/28/2013] [Indexed: 11/16/2022]
Abstract
OBJECTIVE To investigate the mechanism by which BRL37344, a β3-adrenergic receptor (β3-ARs) agonist, facilitates the inhibition of nerve-evoked contractions in human detrusor smooth muscle (DSM) isolated strips and to identify the role of large-conductance Ca(2+)-activated K(+) (BK) channels in this process. METHODS Human DSM specimens were obtained from open bladder surgeries on patients without preoperative history of overactive bladder symptoms. Isometric DSM tension recordings were conducted using force-displacement transducers and thermostatically controlled tissue baths. Nerve-evoked contractions were generated by electrical field stimulation (EFS). RESULTS BRL37344, a β3-AR agonist, significantly decreased the amplitude, muscle force, and duration of the DSM contractions induced by 20 Hz EFS, in a concentration-dependent manner. This BRL37344-mediated inhibition of the amplitude and muscle force of the nerve-evoked DSM contraction was significantly reduced by iberiotoxin, a highly selective inhibitor of the BK channel, revealing a role for BK channels in the β3-AR-induced inhibition of human DSM nerve-evoked contractions. We further used atropine, α,β-methylene-ATP, and suramin to separate the cholinergic and purinergic components of human DSM nerve-evoked contractions. We found that the β3-AR agonist, BRL37344, inhibited both components of the EFS-induced (0.5-50 Hz) DSM contractions. CONCLUSION This study supports the concept that β3-AR agonists inhibit nerve-evoked contractions in human DSM. We have further revealed that BK channels play a critical role in BRL37344-mediated relaxation of nerve-evoked contractions in human DSM. The study suggests that in addition to β3-ARs, BK channels may also represent promising pharmacologic targets in the treatment of urinary bladder dysfunction.
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Affiliation(s)
- Serge A. Y. Afeli
- Department of Drug Discovery & Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, SC-29208
| | - Eric S. Rovner
- Medical University of South Carolina, Charleston, SC-29425
| | - Georgi V. Petkov
- Department of Drug Discovery & Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, SC-29208
- Medical University of South Carolina, Charleston, SC-29425
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Afeli SAY, Petkov GV. Functional BK channels facilitate the β3-adrenoceptor agonist-mediated relaxation of nerve-evoked contractions in rat urinary bladder smooth muscle isolated strips. Eur J Pharmacol 2013; 711:50-6. [PMID: 23643998 DOI: 10.1016/j.ejphar.2013.04.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Revised: 04/17/2013] [Accepted: 04/18/2013] [Indexed: 10/26/2022]
Abstract
The large-conductance voltage- and Ca(2+)-activated K(+) (BK) channel is a major regulator of detrusor smooth muscle (DSM) contractility thus facilitating urinary bladder function. Recent findings suggest that activation of β3-adrenoceptors causes DSM relaxation. However, it is unknown whether the β3-adrenoceptor-mediated DSM relaxation is BK channel-dependent during nerve-evoked contractions. To test this hypothesis, we induced nerve-evoked contractions in rat DSM isolated strips by using a tissue bath system equipped with platinum electrodes for electrical field stimulation (EFS). (±)-(R(*),R(*))-[4-[2-[[2-(3-chlorophenyl)-2-hydroxyethyl]amino]propyl]phenoxy] acetic acid sodium hydrate (BRL37344), a β3-adrenoceptor agonist, significantly decreased the amplitude and muscle force of the 20 Hz EFS-induced DSM contractions in a concentration-dependent manner. The BRL37344 inhibitory effect was significantly antagonized by 1-(2-ethylphenoxy)-3-[[(1S)-1,2,3,4-tetrahydro-1-naphthalenyl]amino]-(2S)-2-propanol hydrochloride (SR59230A), a β3-adrenoceptor antagonist. We further isolated the cholinergic from the purinergic component of the 0.5-50 Hz EFS-induced DSM contractions by using selective inhibitors, atropine as well as suramin and α,β-methylene-ATP. We found that BRL37344 inhibited both the purinergic and cholinergic components of the nerve-evoked contractions in rat DSM isolated strips. The pharmacological blockade of the BK channels with iberiotoxin, a selective BK channel inhibitor, increased the amplitude and muscle force of the 20 Hz EFS-induced contractions in rat DSM isolated strips. In the presence of iberiotoxin, there was a significant reduction in the BRL37344-induced inhibition of the 20 Hz EFS-induced contractions in rat DSM isolated strips. These latter findings suggest that BK channels play a critical role in the β3-adrenoceptor-mediated inhibition of rat DSM nerve-evoked contractions.
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Affiliation(s)
- Serge A Y Afeli
- Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, SC 29208, USA
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Kullmann FA, Wells GI, McKenna DG, Thor KB. Exogenous activation of muscarinic receptors decreases subsequent non-muscarinic bladder contractions in vivo in the female rat. Life Sci 2013; 92:733-9. [DOI: 10.1016/j.lfs.2013.01.030] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2012] [Revised: 01/25/2013] [Accepted: 01/30/2013] [Indexed: 01/23/2023]
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Yu W, Sun X, Robson SC, Hill WG. Extracellular UDP enhances P2X-mediated bladder smooth muscle contractility via P2Y(6) activation of the phospholipase C/inositol trisphosphate pathway. FASEB J 2013; 27:1895-903. [PMID: 23362118 DOI: 10.1096/fj.12-219006] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Bladder dysfunction characterized by abnormal bladder smooth muscle (BSM) contractions is pivotal to the disease process in overactive bladder, urge incontinence, and spinal cord injury. Purinergic signaling comprises one key pathway in modulating BSM contractility, but molecular mechanisms remain unclear. Here we demonstrate, using myography, that activation of P2Y6 by either UDP or a specific agonist (MRS 2693) induced a sustained increase in BSM tone (up to 2 mN) in a concentration-dependent manner. Notably, activation of P2Y6 enhanced ATP-mediated BSM contractile force by up to 45%, indicating synergistic interactions between P2X and P2Y signaling. P2Y6-activated responses were abolished by phospholipase C (PLC) and inositol trisphosphate (IP3) receptor antagonists U73122 and xestospongin C, demonstrating involvement of the PLC/IP3 signal pathway. Mice null for Entpd1, an ectonucleotidase on BSM, demonstrated increased force generation on P2Y6 activation (150%). Thus, in vivo perturbations to purinergic signaling resulted in altered P2Y6 activity and bladder contractility. We conclude that UDP, acting on P2Y6, regulates BSM tone and in doing so selectively maximizes P2X1-mediated contraction forces. This novel neurotransmitter pathway may play an important role in urinary voiding disorders characterized by abnormal bladder motility.
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Affiliation(s)
- Weiqun Yu
- Laboratory of Voiding Dysfunction, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA
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31
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Burnstock G. Purinergic signalling in the lower urinary tract. Acta Physiol (Oxf) 2013; 207:40-52. [PMID: 23176070 DOI: 10.1111/apha.12012] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Revised: 12/22/2011] [Accepted: 09/10/2012] [Indexed: 02/01/2023]
Abstract
The aim of this review is to describe the conceptual steps contributing to our current knowledge of purinergic signalling and to consider its involvement in the physiology and pathophysiology of the lower urinary tract. The voiding reflex involves ATP released as a cotransmitter with acetylcholine from parasympathetic nerves supplying the bladder and ATP released from urothelial cells during bladder distension to initiate the voiding reflex via P2X3 receptors on suburothelial low threshold sensory nerve fibres. This mechanosensory transduction pathway also participates, via high threshold sensory nerve fibres, in the initiation of pain in bladder and ureter. Treatment of prostate and bladder cancer with ATP is effective against the primary tumours in animal models and human cell lines, via P2X5 and P2X7 receptors, and also improves the systemic symptoms associated with advanced malignancy. Acupuncture is widely used for the treatment of urinary disorders, and a purinergic hypothesis is discussed for the underlying mechanism.
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Affiliation(s)
- G. Burnstock
- Autonomic Neuroscience Centre; University College Medical School; London; UK
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Suson KD, Stec AA, Shimoda LA, Gearhart JP. Initial Characterization of Exstrophy Bladder Smooth Muscle Cells in Culture. J Urol 2012; 188:1521-7. [DOI: 10.1016/j.juro.2012.02.028] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Indexed: 10/28/2022]
Affiliation(s)
- Kristina D. Suson
- Division of Pediatric Urology, the Brady Urological Institute, The Johns Hopkins School of Medicine, Baltimore, Maryland
| | - Andrew A. Stec
- Department of Urology, Medical University of South Carolina, Charleston, South Carolina
| | - Larissa A. Shimoda
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, The Johns Hopkins School of Medicine, Baltimore, Maryland
| | - John P. Gearhart
- Division of Pediatric Urology, the Brady Urological Institute, The Johns Hopkins School of Medicine, Baltimore, Maryland
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Xin W, Soder RP, Cheng Q, Rovner ES, Petkov GV. Selective inhibition of phosphodiesterase 1 relaxes urinary bladder smooth muscle: role for ryanodine receptor-mediated BK channel activation. Am J Physiol Cell Physiol 2012; 303:C1079-89. [PMID: 22992675 DOI: 10.1152/ajpcell.00162.2012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The large conductance voltage- and Ca(2+)-activated K(+) (BK) channel is a major regulator of detrusor smooth muscle (DSM) excitability and contractility. Recently, we showed that nonselective phosphodiesterase (PDE) inhibition reduces guinea pig DSM excitability and contractility by increasing BK channel activity. Here, we investigated how DSM excitability and contractility changes upon selective inhibition of PDE type 1 (PDE1) and the underlying cellular mechanism involving ryanodine receptors (RyRs) and BK channels. PDE1 inhibition with 8-methoxymethyl-3-isobutyl-1-methylxanthine (8MM-IBMX; 10 μM) increased the cAMP levels in guinea pig DSM cells. Patch-clamp experiments on freshly isolated DSM cells showed that 8MM-IBMX increased transient BK currents and the spontaneous transient hyperpolarization (STH) frequency by ∼2.5- and ∼1.8-fold, respectively. 8MM-IBMX hyperpolarized guinea pig and human DSM cell membrane potential and significantly decreased the intracellular Ca(2+) levels in guinea pig DSM cells. Blocking BK channels with 1 μM paxilline or inhibiting RyRs with 30 μM ryanodine abolished the STHs and the 8MM-IBMX inhibitory effects on the DSM cell membrane potential. Isometric DSM tension recordings showed that 8MM-IBMX significantly reduced the spontaneous phasic contraction amplitude, muscle force integral, duration, frequency, and tone of DSM isolated strips. The electrical field stimulation-induced DSM contraction amplitude, muscle force integral, and duration were also attenuated by 10 μM 8MM-IBMX. Blocking BK channels with paxilline abolished the 8MM-IBMX effects on DSM contractions. Our data provide evidence that PDE1 inhibition relaxes DSM by raising cellular cAMP levels and subsequently stimulates RyRs, which leads to BK channel activation, membrane potential hyperpolarization, and decrease in intracellular Ca(2+) levels.
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Affiliation(s)
- Wenkuan Xin
- Department of Pharmaceutical and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Coker Life Sciences Bldg., Rm. 609D, 715 Sumter St, Columbia, SC 29208, USA
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Tsai MH, Kamm KE, Stull JT. Signalling to contractile proteins by muscarinic and purinergic pathways in neurally stimulated bladder smooth muscle. J Physiol 2012; 590:5107-21. [PMID: 22890701 DOI: 10.1113/jphysiol.2012.235424] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Urinary bladder smooth muscle contraction is triggered by parasympathetic nerves, which release ATP and acetylcholine (ACh) that bind to purinergic and muscarinic receptors, respectively. Neuronal signalling may thus elicit myosin regulatory light chain (RLC) phosphorylation and contraction through the combined, but distinct contributions of these receptors. Both receptors mediate Ca2+ influx whereas muscarinic receptors may also recruit Ca2+-sensitization mechanisms. Using transgenic mice expressing calmodulin sensor myosin light chain kinase (MLCK) in smooth muscles, the effects of suramin/α,β-methylene ATP (α,β-meATP) (purinergic inhibition) or atropine (muscarinic inhibition) on neurally stimulated elevation of [Ca2+]i, MLCK activation, force and phosphorylation of RLC, myosin light chain phosphatase (MLCP) targeting subunit MYPT1 and MLCP inhibitor protein CPI-17 were examined. Electric field stimulation (EFS) increased [Ca2+]i, MLCK activation and concomitant force in a frequency-dependent manner. The dependence of force on [Ca2+]i and MLCK activation decreased with time suggesting increased Ca2+ sensitization in the late contractile phase. RLC and CPI-17 phosphorylation increased upon stimulation with maximal responses at 20 Hz; both responses were attenuated by atropine, but only RLC phosphorylation was inhibited by suramin/α,β-meATP. Antagonism of purinergic receptors suppressed maximal MLCK activation to a greater extent in the early contractile phase than in the late contractile phase; atropine had the opposite effect. A frequency- and time-dependent increase in MLCK phosphorylation explained the desensitization of MLCK to Ca2+, since MLCK activation declined more rapidly than [Ca2+]i. EFS elicited little or no effect on MYPT1 Thr696 or 850 phosphorylation. Thus, purinergic Ca2+ signals provide the initial activation of MLCK with muscarinic receptors supporting sustained responses. Activation of muscarinic receptors recruits CPI-17, but not MYPT1-mediated Ca2+ sensitization. Furthermore, nerve-released ACh also initiates signalling cascades leading to phosphorylation-dependent desensitization of MLCK.
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Affiliation(s)
- Ming-Ho Tsai
- Department of Physiology, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX 75390-9040, USA
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Xin W, Cheng Q, Soder RP, Petkov GV. Inhibition of phosphodiesterases relaxes detrusor smooth muscle via activation of the large-conductance voltage- and Ca²⁺-activated K⁺ channel. Am J Physiol Cell Physiol 2012; 302:C1361-70. [PMID: 22322973 DOI: 10.1152/ajpcell.00432.2011] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Detrusor smooth muscle (DSM) exhibits increased spontaneous phasic contractions under pathophysiological conditions such as detrusor overactivity (DO). Our previous studies showed that activation of cAMP signaling pathways reduces DSM contractility by increasing the large-conductance voltage- and Ca(2+)-activated K(+) (BK) channel activity. Here, we tested the hypothesis whether inhibition of phosphodiesterases (PDEs) can reduce guinea pig DSM excitability and contractility by increasing BK channel activity. Utilizing isometric tension recordings of DSM isolated strips and the perforated patch-clamp technique on freshly isolated DSM cells, we examined the mechanism of DSM relaxation induced by PDE inhibition. Inhibition of PDEs by 3-isobutyl-1-methylxanthine (IBMX), a nonselective PDE inhibitor, significantly reduced DSM spontaneous and carbachol-induced contraction amplitude, frequency, duration, muscle force integral, and tone in a concentration-dependent manner. IBMX significantly reduced electrical field stimulation-induced contractions of DSM strips. Blocking BK channels with paxilline diminished the inhibitory effects of IBMX on DSM contractility, indicating a role for BK channels in DSM relaxation mediated by PDE inhibition. IBMX increased the transient BK currents (TBKCs) frequency by ∼3-fold without affecting the TBKCs amplitude. IBMX increased the frequency of the spontaneous transient hyperpolarizations by ∼2-fold and hyperpolarized the DSM cell resting membrane potential by ∼6 mV. Blocking the BK channels with paxilline abolished the IBMX hyperpolarizing effects. Under conditions of blocked Ca(2+) sources for BK channel activation, IBMX did not affect the depolarization-induced steady-state whole cell BK currents. Our data reveal that PDE inhibition with IBMX relaxes guinea pig DSM via TBKCs activation and subsequent DSM cell membrane hyperpolarization.
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Affiliation(s)
- Wenkuan Xin
- Department of Pharmaceutical and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, South Carolina 29208, USA
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Amobi NIB, Guillebaud J, Smith ICH. Perspective on the role of P2X-purinoceptor activation in human vas deferens contractility. Exp Physiol 2012; 97:583-602. [PMID: 22227201 DOI: 10.1113/expphysiol.2011.063206] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The contractile actions of α,β-methylene ATP (α,β-meATP) and ATP and the effects of K(+) channel blockers in longitudinal and circular muscles of human vas deferens were investigated with a view to clarifying the functional importance of P2X(1)-purinoceptor activation and K(+) channels in modulating contractility of the tissues. The results provide an experiment-based perspective for resolving differing reports on purinergic activation of the tissues and uncertain roles of large-conductance Ca(2+)-activated K(+) (BK(Ca)) and voltage-gated delayed rectifier K(+) (K(V)) channels. α,β-Methylene ATP (3-100 μm) evoked suramin-sensitive contractions of longitudinal muscle but rarely of circular muscle. ATP (0.1-3 mm) less reliably activated only longitudinal muscle contractions. These were enhanced by ARL 67156 (100 μm), but a different ectonucleotidase inhibitor, POM 1, was ineffective. Both muscle types were unresponsive to ADP-βS (100 μm), a P2Y-purinoceptor agonist. Longitudinal muscle contractions in response to α,β-meATP were enhanced by FPL 64176 (1 μm), an L-type Ca(2+) agonist, TEA (1 mm), a non-specific K(+) channel blocker, 4-aminopyridine (0.3 mm), a selective blocker of K(V) channels, and iberiotoxin (0.1 μm), a selective blocker of BK(Ca) channels. Quiescent circular muscles responded to α,β-meATP reliably in the presence of FPL 64176 or iberiotoxin. Apamin (0.1 μm), a selective blocker of small conductance Ca(2+)-activated K(+) (SK(Ca)) channels had no effect in both muscle types. Y-27632 (1-10 μm) reduced longitudinal muscle contractions in response to α,β-meATP, suggesting involvement of Rho-kinase-dependent contractile mechanisms. The results indicate that P2X(1)-purinoceptor stimulation elicits excitatory effects that: (a) lead to longitudinal muscle contraction and secondary activation of 4-aminopyridine-sensitive (K(V)) and iberiotoxin-sensitive (BK(Ca)) K(+) channels; and (b) are subcontractile in circular muscle due to ancillary activation of BK(Ca) channels. The novel finding of differential action by P2X(1)-purinoceptor agonists in the muscle types has functional implication in terms of the purinergic contribution to overall contractile function of human vas deferens. The modulatory effects of K(V) and BK(Ca) channels following P2X(1)-purinoceptor activation may be pivotal in providing the crucial physiological mechanism that ensures temporal co-ordination of longitudinal and circular muscle contractility.
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Meng E, Chang HY, Chang SY, Sun GH, Yu DS, Cha TL. Involvement of Purinergic Neurotransmission in Ketamine Induced Bladder Dysfunction. J Urol 2011; 186:1134-41. [PMID: 21784472 DOI: 10.1016/j.juro.2011.04.102] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Indexed: 11/16/2022]
Affiliation(s)
- En Meng
- Division of Urology, Department of Surgery, Tri-Service General Hospital and Department and Institute of Biochemistry (HYC), National Defense Medical Center, Taipei, Taiwan, Republic of China
| | - Han-Yu Chang
- Division of Urology, Department of Surgery, Tri-Service General Hospital and Department and Institute of Biochemistry (HYC), National Defense Medical Center, Taipei, Taiwan, Republic of China
| | - Sun-Yran Chang
- Division of Urology, Department of Surgery, Tri-Service General Hospital and Department and Institute of Biochemistry (HYC), National Defense Medical Center, Taipei, Taiwan, Republic of China
| | - Guang-Huan Sun
- Division of Urology, Department of Surgery, Tri-Service General Hospital and Department and Institute of Biochemistry (HYC), National Defense Medical Center, Taipei, Taiwan, Republic of China
| | - Dah-Shyong Yu
- Division of Urology, Department of Surgery, Tri-Service General Hospital and Department and Institute of Biochemistry (HYC), National Defense Medical Center, Taipei, Taiwan, Republic of China
| | - Tai-Lung Cha
- Division of Urology, Department of Surgery, Tri-Service General Hospital and Department and Institute of Biochemistry (HYC), National Defense Medical Center, Taipei, Taiwan, Republic of China
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Hill-Eubanks DC, Werner ME, Heppner TJ, Nelson MT. Calcium signaling in smooth muscle. Cold Spring Harb Perspect Biol 2011; 3:a004549. [PMID: 21709182 DOI: 10.1101/cshperspect.a004549] [Citation(s) in RCA: 136] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Changes in intracellular Ca(2+) are central to the function of smooth muscle, which lines the walls of all hollow organs. These changes take a variety of forms, from sustained, cell-wide increases to temporally varying, localized changes. The nature of the Ca(2+) signal is a reflection of the source of Ca(2+) (extracellular or intracellular) and the molecular entity responsible for generating it. Depending on the specific channel involved and the detection technology employed, extracellular Ca(2+) entry may be detected optically as graded elevations in intracellular Ca(2+), junctional Ca(2+) transients, Ca(2+) flashes, or Ca(2+) sparklets, whereas release of Ca(2+) from intracellular stores may manifest as Ca(2+) sparks, Ca(2+) puffs, or Ca(2+) waves. These diverse Ca(2+) signals collectively regulate a variety of functions. Some functions, such as contractility, are unique to smooth muscle; others are common to other excitable cells (e.g., modulation of membrane potential) and nonexcitable cells (e.g., regulation of gene expression).
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Affiliation(s)
- David C Hill-Eubanks
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, Vermont 05405, USA
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Heppner TJ, Layne JJ, Pearson JM, Sarkissian H, Nelson MT. Unique properties of muscularis mucosae smooth muscle in guinea pig urinary bladder. Am J Physiol Regul Integr Comp Physiol 2011; 301:R351-62. [PMID: 21632849 PMCID: PMC3154705 DOI: 10.1152/ajpregu.00656.2010] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2010] [Accepted: 05/27/2011] [Indexed: 11/22/2022]
Abstract
The muscularis mucosae, a type of smooth muscle located between the urothelium and the urinary bladder detrusor, has been described, although its properties and role in bladder function have not been characterized. Here, using mucosal tissue strips isolated from guinea pig urinary bladders, we identified spontaneous phasic contractions (SPCs) that appear to originate in the muscularis mucosae. This smooth muscle layer exhibited Ca(2+) waves and flashes, but localized Ca(2+) events (Ca(2+) sparks, purinergic receptor-mediated transients) were not detected. Ca(2+) flashes, often in bursts, occurred with a frequency (∼5.7/min) similar to that of SPCs (∼4/min), suggesting that SPCs are triggered by bursts of Ca(2+) flashes. The force generated by a single mucosal SPC represented the maximal force of the strip, whereas a single detrusor SPC was ∼3% of maximal force of the detrusor strip. Electrical field stimulation (0.5-50 Hz) evoked force transients in isolated detrusor and mucosal strips. Inhibition of cholinergic receptors significantly decreased force in detrusor and mucosal strips (at higher frequencies). Concurrent inhibition of purinergic and cholinergic receptors nearly abolished evoked responses in detrusor and mucosae. Mucosal SPCs were unaffected by blocking small-conductance Ca(2+)-activated K(+) (SK) channels with apamin and were unchanged by blocking large-conductance Ca(2+)-activated K(+) (BK) channels with iberiotoxin (IbTX), indicating that SK and BK channels play a much smaller role in regulating muscularis mucosae SPCs than they do in regulating detrusor SPCs. Consistent with this, BK channel current density in myocytes from muscularis mucosae was ∼20% of that in detrusor myocytes. These findings indicate that the muscularis mucosae in guinea pig represents a second smooth muscle compartment that is physiologically and pharmacologically distinct from the detrusor and may contribute to the overall contractile properties of the urinary bladder.
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Affiliation(s)
- Thomas J Heppner
- Department of Pharmacology, University of Vermont, Burlington, Vermont 05405, USA.
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Expression and distribution of ectonucleotidases in mouse urinary bladder. PLoS One 2011; 6:e18704. [PMID: 21533188 PMCID: PMC3077397 DOI: 10.1371/journal.pone.0018704] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2011] [Accepted: 03/08/2011] [Indexed: 11/30/2022] Open
Abstract
Background Normal urinary bladder function requires bidirectional molecular communication between urothelium, detrusor smooth muscle and sensory neurons and one of the key mediators involved in this intercellular signaling is ATP. Ectonucleotidases dephosphorylate nucleotides and thus regulate ligand exposure to P2X and P2Y purinergic receptors. Little is known about the role of these enzymes in mammalian bladder despite substantial literature linking bladder diseases to aberrant purinergic signaling. We therefore examined the expression and distribution of ectonucleotidases in the mouse bladder since mice offer the advantage of straightforward genetic modification for future studies. Principal Findings RT-PCR demonstrated that eight members of the ectonucleoside triphosphate diphosphohydrolase (NTPD) family, as well as 5′-nucleotidase (NT5E) are expressed in mouse bladder. NTPD1, NTPD2, NTPD3, NTPD8 and NT5E all catalyze extracellular nucleotide dephosphorylation and in concert achieve stepwise conversion of extracellular ATP to adenosine. Immunofluorescent localization with confocal microscopy revealed NTPD1 in endothelium of blood vessels in the lamina propria and in detrusor smooth muscle cells, while NTPD2 was expressed in cells localized to a region of the lamina propria adjacent to detrusor and surrounding muscle bundles in the detrusor. NTPD3 was urothelial-specific, occurring on membranes of intermediate and basal epithelial cells but did not appear to be present in umbrella cells. Immunoblotting confirmed NTPD8 protein in bladder and immunofluorescence suggested a primary localization to the urothelium. NT5E was present exclusively in detrusor smooth muscle in a pattern complementary with that of NTPD1 suggesting a mechanism for providing adenosine to P1 receptors on the surface of myocytes. Conclusions Ectonucleotidases exhibit highly cell-specific expression patterns in bladder and therefore likely act in a coordinated manner to regulate ligand availability to purinergic receptors. This is the first study to determine the expression and location of ectonucleotidases within the mammalian urinary bladder.
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Abstract
The pharmacological concept of specifically targeting purinoceptors (receptors for ATP and related nucleotides) has emerged over the last two decades in the quest for novel, differentiated therapeutics. Investigations from many laboratories have established a prominent role for ATP in the functional regulation of most tissue and organ systems, including the urinary tract, under normal and pathophysiological conditions. In the particular case of the urinary tract, ATP signaling via P2X1 receptors participates in the efferent control of detrusor smooth muscle excitability, and this function may be heightened in disease and aging. Perhaps of greater interest, ATP also appears to be involved in bladder sensation, operating via activation of P2X3-containing receptors on sensory afferent neurones, both on peripheral terminals within the urinary tract tissues (e.g., ureters, bladder) and on central synapses in the dorsal horn of the spinal cord. Such findings are based on results from classical pharmacological and localization studies in nonhuman and human tissues, gene knockout mice, and studies using recently identified pharmacological antagonists - some of which have progressed as candidate drug molecules. Based on recent advances in this field, it is apparent that the development of selective antagonists for these receptors will occur that could lead to therapies offering better relief of storage, voiding, and sensory symptoms for patients, while minimizing the systemic side effects that curb the clinical effectiveness of current urologic medicines.
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Hill-Eubanks DC, Werner ME, Nelson MT. Local elementary purinergic-induced Ca2+ transients: from optical mapping of nerve activity to local Ca2+ signaling networks. ACTA ACUST UNITED AC 2010; 136:149-54. [PMID: 20660658 PMCID: PMC2912073 DOI: 10.1085/jgp.201010402] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Cho YR, Jang HS, Kim W, Park SY, Sohn UD. P2X and P2Y Receptors Mediate Contraction Induced by Electrical Field Stimulation in Feline Esophageal Smooth Muscle. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2010; 14:311-6. [PMID: 21165330 DOI: 10.4196/kjpp.2010.14.5.311] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2010] [Revised: 10/07/2010] [Accepted: 10/20/2010] [Indexed: 11/15/2022]
Abstract
It is well-known that electrical field stimulation (EFS)-induced contraction is mediated by a cholinergic mechanism and other neurotransmitters. NO, ATP, calcitonin gene-related peptide (CGRP), and substance P are released by EFS. To investigate the purinergic mechanism involved in the EFS-induced contraction, purinegic receptors antagonists were used. Suramine, a non-selective P2 receptor antagonist, reduced the contraction induced by EFS. NF023 (10(-7)~10(-4) M), a selective P2X antagonist, inhibited the contraction evoked by EFS. Reactive blue (10(-6)~10(-4) M), selective P2Y antagonist, also blocked the contraction in a dose-dependent manner. In addition, P2X agonist α,β-methylene 5'-adenosine triphosphate (αβMeATP, 10(-7)~10(-5) M) potentiated EFS-induced contraction in a dose-dependent manner. P2Y agonist adenosine 5'-[β-thio]diphosphate trilithium salt (ADPβS, 10(-7)~10(-5) M) also potentiated EFS-induced contractions in a dose-dependent manner. Ecto-ATPase activator apyrase (5 and 10 U/ml) reduced EFS-induced contractions. Inversely, 6-N,N-diethyl-D-β,γ-dibromomethylene 5'-triphosphate triammonium (ARL 67156, 10(-4) M) increased EFS-induced contraction. These data suggest that endogenous ATP plays a role in EFS-induced contractions which are mediated through both P2X-receptors and P2Y-receptors stimulation in cat esophageal smooth muscle.
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Affiliation(s)
- Young Rae Cho
- Department of Pharmacology, College of Pharmacy, Chung-Ang University, Seoul 156-756, Korea
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Nausch B, Heppner TJ, Nelson MT. Nerve-released acetylcholine contracts urinary bladder smooth muscle by inducing action potentials independently of IP3-mediated calcium release. Am J Physiol Regul Integr Comp Physiol 2010; 299:R878-88. [PMID: 20573989 DOI: 10.1152/ajpregu.00180.2010] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Nerve-released ACh is the main stimulus for contraction of urinary bladder smooth muscle (UBSM). Here, the mechanisms by which ACh contracts UBSM are explored by determining Ca(2+) and electrical signals induced by nerve-released ACh. Photolysis of caged inositol 1,4,5-trisphosphate (IP(3)) evoked Ca(2+) release from the sarcoplasmic reticulum. Electrical field stimulation (20 Hz) induced Ca(2+) waves within the smooth muscle that were present only during stimulus application. Ca(2+) waves were blocked by inhibition of muscarinic ACh receptors (mAChRs) with atropine and depletion of sarcoplasmic reticulum Ca(2+) stores with cyclopiazonic acid (CPA), and therefore likely reflect activation of IP(3) receptors (IP(3)Rs). Electrical field stimulation also increased excitability to induce action potentials (APs) that were accompanied by Ca(2+) flashes, reflecting Ca(2+) entry through voltage-dependent Ca(2+) channels (VDCCs) during the action potential. The evoked Ca(2+) flashes and APs occurred as a burst with a lag time of approximately 1.5 s after onset of stimulation. They were not inhibited by blocking IP(3)-mediated Ca(2+) waves, but by blockers of mAChRs (atropine) and VDCCs (diltiazem). Nerve-evoked contractions of UBSM strips were greatly reduced by blocking VDCCs, but not by preventing IP(3)-mediated Ca(2+) signaling with cyclopiazonic acid or inhibition of PLC with U73122. These results indicate that ACh released from nerve varicosities induces IP(3)-mediated Ca(2+) waves during stimulation; but contrary to expectations, these signals do not appear to participate in contraction. In addition, our data provide compelling evidence that UBSM contractions evoked by nerve-released ACh depend on increased excitability and the resultant Ca(2+) entry through VDCCs during APs.
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Affiliation(s)
- Bernhard Nausch
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, VT 05405, USA
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Layne JJ, Nausch B, Olesen SP, Nelson MT. BK channel activation by NS11021 decreases excitability and contractility of urinary bladder smooth muscle. Am J Physiol Regul Integr Comp Physiol 2009; 298:R378-84. [PMID: 19923353 DOI: 10.1152/ajpregu.00458.2009] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Large-conductance Ca(2+)-activated potassium (BK) channels play an important role in regulating the function and activity of urinary bladder smooth muscle (UBSM), and the loss of BK channel function has been shown to increase UBSM excitability and contractility. However, it is not known whether activation of BK channels has the converse effect of reducing UBSM excitability and contractility. Here, we have sought to investigate this possibility by using the novel BK channel opener NS11021. NS11021 (3 microM) caused an approximately threefold increase in both single BK channel open probability (P(o)) and whole cell BK channel currents. The frequency of spontaneous action potentials in UBSM strips was reduced by NS11021 from a control value of 20.9 + or - 5.9 to 10.9 + or - 3.7 per minute. NS11021 also reduced the force of UBSM spontaneous phasic contractions by approximately 50%, and this force reduction was blocked by pretreatment with the BK channel blocker iberiotoxin. NS11021 (3 microM) had no effect on contractions evoked by nerve stimulation. These findings indicate that activating BK channels reduces the force of UBSM spontaneous phasic contractions, principally through decreasing the frequency of spontaneous action potentials.
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Affiliation(s)
- Jeffrey J Layne
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, VT 05405, USA
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