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Regulation of P2X1 receptors by modulators of the cAMP effectors PKA and EPAC. Proc Natl Acad Sci U S A 2021; 118:2108094118. [PMID: 34508006 DOI: 10.1073/pnas.2108094118] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/12/2021] [Indexed: 11/18/2022] Open
Abstract
P2X1 receptors are adenosine triphosphate (ATP)-gated cation channels that are functionally important for male fertility, bladder contraction, and platelet aggregation. The activity of P2X1 receptors is modulated by lipids and intracellular messengers such as cAMP, which can stimulate protein kinase A (PKA). Exchange protein activated by cAMP (EPAC) is another cAMP effector; however, its effect on P2X1 receptors has not yet been determined. Here, we demonstrate that P2X1 currents, recorded from human embryonic kidney (HEK) cells transiently transfected with P2X1 cDNA, were inhibited by the highly selective EPAC activator 007-AM. In contrast, EPAC activation enhanced P2X2 current amplitude. The PKA activator 6-MB-cAMP did not affect P2X1 currents, but inhibited P2X2 currents. The inhibitory effects of EPAC on P2X1 were prevented by triple mutation of residues 21 to 23 on the amino terminus of P2X1 subunits to the equivalent amino acids on P2X2 receptors. Double mutation of residues 21 and 22 and single mutation of residue 23 also protected P2X1 receptors from inhibition by EPAC activation. Finally, the inhibitory effects of EPAC on P2X1 were also prevented by NSC23766, an inhibitor of Rac1, a member of the Rho family of small GTPases. These data suggest that EPAC is an important regulator of P2X1 and P2X2 receptors.
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Malysz J, Petkov GV. Urinary bladder smooth muscle ion channels: expression, function, and regulation in health and disease. Am J Physiol Renal Physiol 2020; 319:F257-F283. [PMID: 32628539 PMCID: PMC7473901 DOI: 10.1152/ajprenal.00048.2020] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 06/21/2020] [Accepted: 06/28/2020] [Indexed: 12/17/2022] Open
Abstract
Urinary bladder smooth muscle (UBSM), also known as detrusor smooth muscle, forms the bladder wall and ultimately determines the two main attributes of the organ: urine storage and voiding. The two functions are facilitated by UBSM relaxation and contraction, respectively, which depend on UBSM excitability shaped by multiple ion channels. In this review, we summarize the current understanding of key ion channels establishing and regulating UBSM excitability and contractility. They include excitation-enhancing voltage-gated Ca2+ (Cav) and transient receptor potential channels, excitation-reducing K+ channels, and still poorly understood Cl- channels. Dynamic interplay among UBSM ion channels determines the overall level of Cav channel activity. The net Ca2+ influx via Cav channels increases global intracellular Ca2+ concentration, which subsequently triggers UBSM contractility. Here, for each ion channel type, we describe UBSM tissue/cell expression (mRNA and protein) profiles and their role in regulating excitability and contractility of UBSM in various animal species, including the mouse, rat, and guinea pig, and, most importantly, humans. The currently available data reveal certain interspecies differences, which complicate the translational value of published animal research results to humans. This review highlights recent developments, findings on genetic knockout models, pharmacological data, reports on UBSM ion channel dysfunction in animal bladder disease models, and the very limited human studies currently available. Among all gaps in present-day knowledge, the unknowns on expression and functional roles for ion channels determined directly in human UBSM tissues and cells under both normal and disease conditions remain key hurdles in the field.
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Affiliation(s)
- John Malysz
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee
| | - Georgi V Petkov
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee
- Department of Pharmacology, College of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee
- Department of Urology, College of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee
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Ocampo-Néstor AL, López-Mayorga RM, Castillo-Henkel EF, Padilla-Martínez II, Trujillo-Ferrara JG, Soriano-Ursúa MA. Design, synthesis and in vitro evaluation of a Dopa-organoboron compound that acts as a bladder relaxant through non-catecholamine receptors. Mol Divers 2019; 23:361-370. [PMID: 30284107 DOI: 10.1007/s11030-018-9883-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Accepted: 09/25/2018] [Indexed: 02/07/2023]
Abstract
Bladder relaxation through drug administration is an interesting topic in medicinal and combinatorial chemistry. In fact, compounds targeting catecholamine receptors [dopamine receptors and beta-adrenergic receptors (βAR) expressed in the bladder] are among the compounds commonly employed for this purpose. In particular, recent investigations have tended to focus on the β3-adrenoceptor (β3AR) as a target in the treatment of urinary incontinence and other disorders. However, organoboron compounds have been suggested as potent and efficient agents on these drug targets. In this work, through a docking study, we identified the parameters that induce a theoretical improvement in the affinity and activity of the organoboron compounds on the catecholamine receptors expressed in the bladder. Then, the identified potential drug, a boron-containing dopa-derivative named DPBX-L-Dopa, was synthesized and characterized. This compound induces a relaxation on the smooth muscle of the rat bladder, behaving as a weak relaxant compared to isoproterenol but with similar efficacy to BRL377, a selective β3AR agonist. However, unexpectedly, this effect was not blocked by propranolol or haloperidol at the concentrations at which they are able to block the catecholamine receptors in bladder tissue. In view of these results, the effect of DPBX-L-Dopa compound on the alpha 1 adrenergic receptors (α1AR) of aorta of the rats was also explored; however, no response of the tissue to this compound was obtained. The possible mechanisms of the action of this compound were explored and are discussed further.
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Affiliation(s)
- Ana L Ocampo-Néstor
- Departamento de Fisiología, Laboratorio de Investigación en Bioquímica y Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, Plan de San Luis y Díaz Mirón, 11340, México, Mexico
| | - Ruth M López-Mayorga
- Departamento de Fisiología, Laboratorio de Investigación en Bioquímica y Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, Plan de San Luis y Díaz Mirón, 11340, México, Mexico
| | - Enrique F Castillo-Henkel
- Departamento de Fisiología, Laboratorio de Investigación en Bioquímica y Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, Plan de San Luis y Díaz Mirón, 11340, México, Mexico
| | - Itzia I Padilla-Martínez
- Unidad Profesional Interdisciplinaria de Biotecnología, Instituto Politécnico Nacional, Avenida Acueducto s/n, Barrio La Laguna Ticomán, 07340, México, Mexico
| | - José G Trujillo-Ferrara
- Departamento de Fisiología, Laboratorio de Investigación en Bioquímica y Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, Plan de San Luis y Díaz Mirón, 11340, México, Mexico.
| | - Marvin A Soriano-Ursúa
- Departamento de Fisiología, Laboratorio de Investigación en Bioquímica y Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, Plan de San Luis y Díaz Mirón, 11340, México, Mexico.
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Fong Z, Griffin CS, Hollywood MA, Thornbury KD, Sergeant GP. β 3-Adrenoceptor agonists inhibit purinergic receptor-mediated contractions of the murine detrusor. Am J Physiol Cell Physiol 2019; 317:C131-C142. [PMID: 31042424 DOI: 10.1152/ajpcell.00488.2018] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
β3-Adrenoceptor (β3-AR) agonists are used to treat overactive bladder syndrome; however, their mechanism of action has not been determined. The aims of this study were to compare the effects of β3-AR agonists on cholinergic versus purinergic receptor-mediated contractions of the detrusor and to examine the mechanisms underlying inhibition of the purinergic responses by β3-AR agonists. Isometric tension recordings were made from strips of murine detrusor and whole cell current recordings were made from freshly isolated detrusor myocytes using the patch-clamp technique. Transcriptional expression of exchange protein directly activated by cAMP (EPAC) subtypes in detrusor strips was assessed using RT-PCR and real-time quantitative PCR. The β3-AR agonists BRL37344 and CL316243 (100 nM) inhibited cholinergic nerve-mediated contractions of the detrusor by 19 and 23%, respectively, but did not reduce contractions induced by the cholinergic agonist carbachol (300 nM). In contrast, BRL37344 and CL316243 inhibited purinergic nerve-mediated responses by 55 and 56%, respectively, and decreased the amplitude of contractions induced by the P2X receptor agonist α,β-methylene ATP by 40 and 45%, respectively. The adenylate cyclase activator forskolin inhibited purinergic responses, and these effects were mimicked by a combination of the PKA activator N6-monobutyryl-cAMP and the EPAC activator 8-pCPT-2'-O-methyl-cAMP-AM (007-AM). Application of ATP (1 μM) evoked reproducible P2X currents in isolated detrusor myocytes voltage-clamped at -60 mV. These responses were reduced in amplitude in the presence of BRL37344 and also by 007-AM. This study demonstrates that β3-AR agonists reduce postjunctional purinergic responses in the detrusor via a pathway involving activation of the cAMP effector EPAC.
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Affiliation(s)
- Zhihui Fong
- Smooth Muscle Research Centre, Dundalk Institute of Technology , Dundalk , Ireland
| | - Caoimhín S Griffin
- Smooth Muscle Research Centre, Dundalk Institute of Technology , Dundalk , Ireland
| | - Mark A Hollywood
- Smooth Muscle Research Centre, Dundalk Institute of Technology , Dundalk , Ireland
| | - Keith D Thornbury
- Smooth Muscle Research Centre, Dundalk Institute of Technology , Dundalk , Ireland
| | - Gerard P Sergeant
- Smooth Muscle Research Centre, Dundalk Institute of Technology , Dundalk , Ireland
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Ocampo-Néstor AL, López-Mayorga RM, Castillo-Henkel EF, Padilla-Martínez II, Trujillo-Ferrara JG, Soriano-Ursúa MA. Design, synthesis and in vitro evaluation of a Dopa-organoboron compound that acts as a bladder relaxant through non-catecholamine receptors. Mol Divers 2018. [PMID: 30284107 DOI: 10.1007/s11030-018-9883-7.] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/29/2022]
Abstract
Bladder relaxation through drug administration is an interesting topic in medicinal and combinatorial chemistry. In fact, compounds targeting catecholamine receptors [dopamine receptors and beta-adrenergic receptors (βAR) expressed in the bladder] are among the compounds commonly employed for this purpose. In particular, recent investigations have tended to focus on the β3-adrenoceptor (β3AR) as a target in the treatment of urinary incontinence and other disorders. However, organoboron compounds have been suggested as potent and efficient agents on these drug targets. In this work, through a docking study, we identified the parameters that induce a theoretical improvement in the affinity and activity of the organoboron compounds on the catecholamine receptors expressed in the bladder. Then, the identified potential drug, a boron-containing dopa-derivative named DPBX-L-Dopa, was synthesized and characterized. This compound induces a relaxation on the smooth muscle of the rat bladder, behaving as a weak relaxant compared to isoproterenol but with similar efficacy to BRL377, a selective β3AR agonist. However, unexpectedly, this effect was not blocked by propranolol or haloperidol at the concentrations at which they are able to block the catecholamine receptors in bladder tissue. In view of these results, the effect of DPBX-L-Dopa compound on the alpha 1 adrenergic receptors (α1AR) of aorta of the rats was also explored; however, no response of the tissue to this compound was obtained. The possible mechanisms of the action of this compound were explored and are discussed further.
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Affiliation(s)
- Ana L Ocampo-Néstor
- Departamento de Fisiología, Laboratorio de Investigación en Bioquímica y Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, Plan de San Luis y Díaz Mirón, 11340, México, Mexico
| | - Ruth M López-Mayorga
- Departamento de Fisiología, Laboratorio de Investigación en Bioquímica y Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, Plan de San Luis y Díaz Mirón, 11340, México, Mexico
| | - Enrique F Castillo-Henkel
- Departamento de Fisiología, Laboratorio de Investigación en Bioquímica y Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, Plan de San Luis y Díaz Mirón, 11340, México, Mexico
| | - Itzia I Padilla-Martínez
- Unidad Profesional Interdisciplinaria de Biotecnología, Instituto Politécnico Nacional, Avenida Acueducto s/n, Barrio La Laguna Ticomán, 07340, México, Mexico
| | - José G Trujillo-Ferrara
- Departamento de Fisiología, Laboratorio de Investigación en Bioquímica y Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, Plan de San Luis y Díaz Mirón, 11340, México, Mexico.
| | - Marvin A Soriano-Ursúa
- Departamento de Fisiología, Laboratorio de Investigación en Bioquímica y Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, Plan de San Luis y Díaz Mirón, 11340, México, Mexico.
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Griffin CS, Bradley E, Hollywood MA, McHale NG, Thornbury KD, Sergeant GP. β3-adrenoceptor agonists inhibit carbachol-evoked Ca 2+ oscillations in murine detrusor myocytes. BJU Int 2018; 121:959-970. [PMID: 29211339 DOI: 10.1111/bju.14090] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
OBJECTIVE To test if carbachol (CCh)-evoked Ca2+ oscillations in freshly isolated murine detrusor myocytes are affected by β3-adrenoceptor (β-AR) modulators. MATERIALS AND METHODS Isometric tension recordings were made from strips of murine detrusor, and intracellular Ca2+ measurements were made from isolated detrusor myocytes using confocal microscopy. Transcriptional expression of β-AR sub-types in detrusor strips and isolated detrusor myocytes was assessed using reverse transcriptase-polymerase chain reaction (RT-PCR) and real-time quantitative PCR (qPCR). Immunocytochemistry experiments, using a β3-AR selective antibody, were performed to confirm that β3-ARs were present on detrusor myocytes. RESULTS The RT-PCR and qPCR experiments showed that β1-, β2- and β3-AR were expressed in murine detrusor, but that β3-ARs were the most abundant sub-type. The selective β3-AR agonist BRL37344 reduced the amplitude of CCh-induced contractions of detrusor smooth muscle. These responses were unaffected by addition of the BK channel blocker iberiotoxin. BRL37344 also reduced the amplitude of CCh-induced Ca2+ oscillations in freshly isolated murine detrusor myocytes. This effect was mimicked by CL316,243, another β3-AR agonist, and inhibited by the β3-AR antagonist L748,337, but not by propranolol, an antagonist of β1- and β2-ARs. BRL37344 did not affect caffeine-evoked Ca2+ transients or L-type Ca2+ current in isolated detrusor myocytes. CONCLUSION Inhibition of cholinergic-mediated contractions of the detrusor by β3-AR agonists was associated with a reduction in Ca2+ oscillations in detrusor myocytes.
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Affiliation(s)
- Caoimhin S Griffin
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, Co Louth, Ireland
| | - Eamonn Bradley
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, Co Louth, Ireland
| | - Mark A Hollywood
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, Co Louth, Ireland
| | - Noel G McHale
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, Co Louth, Ireland
| | - Keith D Thornbury
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, Co Louth, Ireland
| | - Gerard P Sergeant
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, Co Louth, Ireland
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On the Site and Mechanism of Action of β 3-Adrenoceptor Agonists in the Bladder. Int Neurourol J 2017; 21:6-11. [PMID: 28361520 PMCID: PMC5380826 DOI: 10.5213/inj.1734850.425] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 03/10/2017] [Indexed: 12/20/2022] Open
Abstract
The clinical success of mirabegron as the first β3-adrenoceptor (AR) agonist for treatment of the overactive bladder (OAB) syndrome, has resulted in substantial interest in its site and mechanism of action. Even if the adrenergic innervation of the bladder and urethra has been well studied, the location(s) of β3-ARs in different structures within the bladder wall and urethra, and the mode(s) of action of β3-AR stimulation have still not been established. The recent demonstration of β3-ARs on cholinergic nerve terminals with no immunoreactivity in urothelium or detrusor smooth muscle, is not in agreement with previous morphological studies, and functional data strongly suggest that β3-ARs can be found these structures. However, recent studies suggest that the β3-ARs on detrusor smooth muscle may not be the functionally most relevant. The assumption that β3-AR activation during bladder filling inhibits acetylcholine release from parasympathetic neurons by a prejunctional mechanism and that this decreases bladder micromotions that generate afferent activity, is an attractive hypothesis. It does not exclude that other mechanisms may be contributing, and supports combined approaches to reduce afferent activity for treatment of the OAB syndrome.
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Michel MC, Korstanje C. β3-Adrenoceptor agonists for overactive bladder syndrome: Role of translational pharmacology in a repositioning clinical drug development project. Pharmacol Ther 2016; 159:66-82. [PMID: 26808167 DOI: 10.1016/j.pharmthera.2016.01.007] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
β3-Adrenoceptor agonists were originally considered as a promising drug class for the treatment of obesity and/or type 2 diabetes. When these development efforts failed, they were repositioned for the treatment of the overactive bladder syndrome. Based on the example of the β3-adrenoceptor agonist mirabegron, but also taking into consideration evidence obtained with ritobegron and solabegron, we discuss challenges facing a translational pharmacology program accompanying clinical drug development for a first-in-class molecule. Challenges included generic ones such as ligand selectivity, species differences and drug target gene polymorphisms. Challenges that are more specific included changing concepts of the underlying pathophysiology of the target condition while clinical development was under way; moreover, a paucity of public domain tools for the study of the drug target and aspects of receptor agonists as drugs had to be addressed. Nonetheless, a successful first-in-class launch was accomplished. Looking back at this translational pharmacology program, we conclude that a specifically tailored and highly flexible approach is required. However, several of the lessons learned may also be applicable to translational pharmacology programs in other indications.
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Affiliation(s)
- Martin C Michel
- Department of Pharmacology, Johannes Gutenberg University, Mainz, Germany.
| | - Cees Korstanje
- Department of Drug Discovery Science & Management-Europe, Astellas Pharma Europe R&D, Leiden, The Netherlands
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Andersson KE. Drug therapy of overactive bladder--what is coming next? Korean J Urol 2015; 56:673-9. [PMID: 26495067 PMCID: PMC4610893 DOI: 10.4111/kju.2015.56.10.673] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Accepted: 09/03/2015] [Indexed: 01/25/2023] Open
Abstract
After the approval and introduction of mirabegron, tadalafil, and botulinum toxin A for treatment of lower urinary tract symptoms/overactive bladder, focus of interest has been on their place in therapy versus the previous gold standard, antimuscarinics. However, since these agents also have limitations there has been increasing interest in what is coming next - what is in the pipeline? Despite progress in our knowledge of different factors involved in both peripheral and central modulation of lower urinary tract dysfunction, there are few innovations in the pipe-line. Most developments concern modifications of existing principles (antimuscarinics, β3-receptor agonists, botulinum toxin A). However, there are several new and old targets/drugs of potential interest for further development, such as the purinergic and cannabinoid systems and the different members of the transient receptor potential channel family. However, even if there seems to be good rationale for further development of these principles, further exploration of their involvement in lower urinary tract function/dysfunction is necessary.
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Affiliation(s)
- Karl-Erik Andersson
- Institute for Regenerative Medicine, Wake Forest University School of Medicine, Winston Salem, NC, USA. ; Aarhus Institute for Advanced Sciences, Aarhus University, Aarhus, Denmark
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Cernecka H, Kersten K, Maarsingh H, Elzinga CR, de Jong IJ, Korstanje C, Michel MC, Schmidt M. β3-Adrenoceptor-mediated relaxation of rat and human urinary bladder: roles of BKCa channels and Rho kinase. Naunyn Schmiedebergs Arch Pharmacol 2015; 388:749-59. [PMID: 25956403 PMCID: PMC4475246 DOI: 10.1007/s00210-015-1128-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Accepted: 03/23/2015] [Indexed: 12/18/2022]
Abstract
Previous studies suggest that the large-conductance Ca(2+)-activated K(+) (BKCa) channel and Rho-kinase play major roles in the control of urinary bladder tone. Here, we investigated their involvement in β-adrenoceptor (AR)-mediated relaxation of rat and human bladder. Concentration-response curves of isoprenaline and mirabegron-induced bladder relaxation were generated against passive tension and KCl- and carbachol-induced tone, in the absence or presence of the BKCa channel inhibitor iberiotoxin (100 nM) or the Rho-kinase inhibitor Y27,632 (1 μM). Myosin light chain (MLC) phosphorylation was studied by Western blot. In rat, iberiotoxin only slightly altered isoprenaline- and mirabegron-induced relaxation against KCl-induced tone but attenuated relaxation by both agonists against carbachol-induced tone. Y27,632 enhanced isoprenaline- or mirabegron-induced relaxation only against carbachol-induced tone. In humans, iberiotoxin slightly enhanced relaxation by both agonists against carbachol-induced pre-contraction. Y27,632 did not change isoprenaline-induced relaxation but enhanced that by mirabegron. Under passive tension, MLC phosphorylation was markedly reduced by both β-AR agonists, an effect insensitive to Y27,632. In the presence of carbachol, both β-AR agonists increased MLC phosphorylation, an effect reduced by Y27,632 only in the presence of 1 μM carbachol. These results indicate that the extent of BKCa channel and Rho-kinase involvement in relaxation induced by β-AR agonists depends on pre contractile stimulus and species.
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Affiliation(s)
- Hana Cernecka
- Department of Molecular Pharmacology, University of Groningen, Antonius Deusinglaan 1, 9713 AV, Groningen, The Netherlands,
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D' Agostino G, Maria Condino A, Calvi P. Involvement of β3-adrenoceptors in the inhibitory control of cholinergic activity in human bladder: Direct evidence by [(3)H]-acetylcholine release experiments in the isolated detrusor. Eur J Pharmacol 2015; 758:115-22. [PMID: 25861936 DOI: 10.1016/j.ejphar.2015.03.074] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Revised: 03/24/2015] [Accepted: 03/25/2015] [Indexed: 01/25/2023]
Abstract
Bladder overactivity (OAB) is a multifactorial bladder disorder that requires therapeutics superior to the current pharmacological treatment with muscarinic antagonists. β3-adrenoceptor (β3-ADR) agonists represent a novel promising approach that differently addresses the parasympathetic pathway, but the clinical efficacy of these drugs has not been fully elucidated to date. Therefore, we aimed to study the pharmacological mechanisms activated by β3-ADR agonists at muscular and neural sites in the isolated human bladder. Detrusor smooth muscle strips obtained from male patients undergoing total cystectomy were labelled with tritiated choline and stimulated with electrical field stimulation (EFS). EFS produced smooth muscle contraction and simultaneous acetylcholine ([(3)H]-ACh) release, which mostly reflects the neural origin of acetylcholine. Isoprenaline (INA), BRL37344 and mirabegron inhibited the EFS-evoked contraction and [(3)H]-ACh release in a concentration-dependent manner, yielding concentration-response curves (CRCs) that were shifted to the right by the selective β3-ADR antagonists L-748,337 and SR59230A. Based on the agonist potency estimates (pEC50) and apparent affinities (pKb) of antagonists evaluated from the CRCs of agonists, our data confirm the occurrence of β3-ADRs at muscle sites. Moreover, our data are consistent with the presence of inhibitory β3-ADRs that are functionally expressed at the neural site. Taken together, these findings elucidate the mechanisms activated by β3-ADR agonists because neural β3-ADRs participate in the inhibition of detrusor motor drive by reducing the amount of acetylcholine involved in the cholinergic pathway.
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Affiliation(s)
- Gianluigi D' Agostino
- Department of Drug Science, Experimental Pharmacology Unit, University of Pavia, Italy.
| | - Anna Maria Condino
- Department of Drug Science, Experimental Pharmacology Unit, University of Pavia, Italy
| | - Paolo Calvi
- Urological Unit, Santa Rita Clinic Hospital, Vercelli, Italy
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12
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Bayrak S, Balkanci ZD, Pehlivanoğlu B, Karabulut İ, Karaismailoğlu S, Erdem A. Does hypercholesterolemia affect the relaxation of the detrusor smooth muscle in rats? In vitro and in vivo studies. Naunyn Schmiedebergs Arch Pharmacol 2014; 388:761-71. [PMID: 25344203 DOI: 10.1007/s00210-014-1060-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Accepted: 10/13/2014] [Indexed: 12/22/2022]
Abstract
To evaluate the effects of hypercholesterolemia on the relaxation function of the urinary bladder, we examined the physiological mechanisms involved in the isoproterenol-induced relaxation in isolated detrusor strips in vitro and voiding behavior in vivo in rats. Adult male Sprague-Dawley rats were fed standard (control, N = 16) or 4 % cholesterol diet (hypercholesterolemia, N = 17) for 4 weeks. Concentration-response curves for isoproterenol-induced relaxations in carbachol-precontracted detrusor muscle strips were recorded. The contributions of β2- and β3-adrenoceptors and ATP-dependent and Ca(2+)-dependent potassium channels to the relaxation response were investigated by using selective adrenergic agonists salbutamol and BRL 37344 and specific potassium channel inhibitors glibenclamide and charybdotoxin, respectively. Cystometrography was performed to assess bladder function. Hypercholesterolemic rats had higher serum cholesterol and low- and high-density lipoprotein levels than the controls with no sign of atherosclerosis. Isoproterenol-induced relaxation was significantly enhanced in the hypercholesterolemia group. Preincubation with the M2 receptor antagonist attenuated the relaxation response in both groups. The relaxation responses to isoproterenol and salbutamol were similar in both groups, while BRL 37344 appeared to produce a greater relaxant effect in the hypercholesterolemic rats. Also, the inhibitory effects of potassium channel inhibitors on relaxation responses were comparable among the groups. The cystometric findings revealed that threshold and basal pressure values were higher in the hypercholesterolemia group compared with controls. We showed that hypercholesterolemia leads to greater relaxation responses to isoproterenol, appears to impair the braking function of M2 cholinergic receptors on adrenoceptor-induced relaxations in the isolated detrusor muscle, and affects the voiding function in rats.
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Affiliation(s)
- Sibel Bayrak
- Department of Physiology, Faculty of Medicine, Hacettepe University, 39, 06100, Sihhiye, Ankara, Turkey,
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Petkov GV. Central role of the BK channel in urinary bladder smooth muscle physiology and pathophysiology. Am J Physiol Regul Integr Comp Physiol 2014; 307:R571-84. [PMID: 24990859 DOI: 10.1152/ajpregu.00142.2014] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The physiological functions of the urinary bladder are to store and periodically expel urine. These tasks are facilitated by the contraction and relaxation of the urinary bladder smooth muscle (UBSM), also known as detrusor smooth muscle, which comprises the bladder wall. The large-conductance voltage- and Ca(2+)-activated K(+) (BK, BKCa, MaxiK, Slo1, or KCa1.1) channel is highly expressed in UBSM and is arguably the most important physiologically relevant K(+) channel that regulates UBSM function. Its significance arises from the fact that the BK channel is the only K(+) channel that is activated by increases in both voltage and intracellular Ca(2+). The BK channels control UBSM excitability and contractility by maintaining the resting membrane potential and shaping the repolarization phase of the spontaneous action potentials that determine UBSM spontaneous rhythmic contractility. In UBSM, these channels have complex regulatory mechanisms involving integrated intracellular Ca(2+) signals, protein kinases, phosphodiesterases, and close functional interactions with muscarinic and β-adrenergic receptors. BK channel dysfunction is implicated in some forms of bladder pathologies, such as detrusor overactivity, and related overactive bladder. This review article summarizes the current state of knowledge of the functional role of UBSM BK channels under normal and pathophysiological conditions and provides new insight toward the BK channels as targets for pharmacological or genetic control of UBSM function. Modulation of UBSM BK channels can occur by directly or indirectly targeting their regulatory mechanisms, which has the potential to provide novel therapeutic approaches for bladder dysfunction, such as overactive bladder and detrusor underactivity.
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Affiliation(s)
- Georgi V Petkov
- Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, South Carolina
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