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Ferreira JJ, Kent LN, McCarthy R, Butler A, Ma X, Peramsetty N, Amazu C, Zhang A, Whitter GC, England SK, Santi CM. SLO2.1/NALCN Functional Complex Activity in Mouse Myometrial Smooth Muscle Cells During Pregnancy. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.29.596465. [PMID: 38853884 PMCID: PMC11160795 DOI: 10.1101/2024.05.29.596465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2024]
Abstract
At the end of pregnancy, the uterus transitions from a quiescent to a highly contractile state. This is partly due to depolarization of the resting membrane potential in uterine (myometrial) smooth muscle cells (MSMCs). Experiments with human MSMCs showed that the membrane potential is regulated by a functional complex between the sodium (Na+)-activated potassium (K+) channel SLO2.1 and the Na+ Leak Channel Non-Selective (NALCN). In human MSMCs, Na+ entering through NALCN activates SLO2.1, leading to K+ efflux, membrane hyperpolarization (cells become more negative inside), and reduced contractility. Decreased SLO2.1/NALCN activity results in reduced K+ efflux, leading to membrane depolarization, Ca2+ influx via voltage-dependent calcium channels, and increased MSMC contractility. However, all of these experiments were performed with MSMCs isolated from women at term, so the role of the SLO2.1/NALCN complex early in pregnancy was speculative. To address this question here, we examined the role of the SLO2.1/NALCN complex in regulating mouse MSMC membrane potential across pregnancy. We report that Slo2.1 and Nalcn expression change along pregnancy, being more highly expressed in MSMCs from non-pregnant and early pregnant mice than in those from late-pregnant mice. Functional studies revealed that SLO2.1 channels mediate a significant portion of the K+ current in mouse MSMCs, particularly in cells from non-pregnant and early pregnant mice. Activation of SLO2.1 by Na+ influx through NALCN led to membrane hyperpolarization in MSMCs from early pregnancy but not in MSMCs from later pregnancy. Moreover, we found that the NALCN/SLO2.1 complex regulates intracellular Ca2+ responses more in MSMCs from non-pregnant and early pregnancy mice than in MSMCs from late pregnancy. Together, these findings reveal that the SLO2.1/NALCN functional complex is conserved between mouse and humans and functions throughout pregnancy. This work could open avenues for targeted pharmacological interventions in pregnancy-related complications.
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Affiliation(s)
| | | | - Ronald McCarthy
- Department of Obstetrics and Gynecology, Center for Reproductive Health Sciences, Washington University in St. Louis, School of Medicine, 425 S. Euclid Avenue, CB 8064, St. Louis, MO 63110, USA
| | - Alice Butler
- Department of Obstetrics and Gynecology, Center for Reproductive Health Sciences, Washington University in St. Louis, School of Medicine, 425 S. Euclid Avenue, CB 8064, St. Louis, MO 63110, USA
| | - Xiaofeng Ma
- Department of Obstetrics and Gynecology, Center for Reproductive Health Sciences, Washington University in St. Louis, School of Medicine, 425 S. Euclid Avenue, CB 8064, St. Louis, MO 63110, USA
| | - Nikita Peramsetty
- Department of Obstetrics and Gynecology, Center for Reproductive Health Sciences, Washington University in St. Louis, School of Medicine, 425 S. Euclid Avenue, CB 8064, St. Louis, MO 63110, USA
| | - Chinwendu Amazu
- Department of Obstetrics and Gynecology, Center for Reproductive Health Sciences, Washington University in St. Louis, School of Medicine, 425 S. Euclid Avenue, CB 8064, St. Louis, MO 63110, USA
| | - Alexander Zhang
- Department of Obstetrics and Gynecology, Center for Reproductive Health Sciences, Washington University in St. Louis, School of Medicine, 425 S. Euclid Avenue, CB 8064, St. Louis, MO 63110, USA
| | - Grace C. Whitter
- Department of Obstetrics and Gynecology, Center for Reproductive Health Sciences, Washington University in St. Louis, School of Medicine, 425 S. Euclid Avenue, CB 8064, St. Louis, MO 63110, USA
| | - Sarah K. England
- Department of Obstetrics and Gynecology, Center for Reproductive Health Sciences, Washington University in St. Louis, School of Medicine, 425 S. Euclid Avenue, CB 8064, St. Louis, MO 63110, USA
| | - Celia M. Santi
- Department of Obstetrics and Gynecology, Center for Reproductive Health Sciences, Washington University in St. Louis, School of Medicine, 425 S. Euclid Avenue, CB 8064, St. Louis, MO 63110, USA
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Clinical Importance of the Human Umbilical Artery Potassium Channels. Cells 2020; 9:cells9091956. [PMID: 32854241 PMCID: PMC7565333 DOI: 10.3390/cells9091956] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 08/21/2020] [Accepted: 08/24/2020] [Indexed: 02/06/2023] Open
Abstract
Potassium (K+) channels are usually predominant in the membranes of vascular smooth muscle cells (SMCs). These channels play an important role in regulating the membrane potential and vessel contractility-a role that depends on the vascular bed. Thus, the activity of K+ channels represents one of the main mechanisms regulating the vascular tone in physiological and pathophysiological conditions. Briefly, the activation of K+ channels in SMC leads to hyperpolarization and vasorelaxation, while its inhibition induces depolarization and consequent vascular contraction. Currently, there are four different types of K+ channels described in SMCs: voltage-dependent K+ (KV) channels, calcium-activated K+ (KCa) channels, inward rectifier K+ (Kir) channels, and 2-pore domain K+ (K2P) channels. Due to the fundamental role of K+ channels in excitable cells, these channels are promising therapeutic targets in clinical practice. Therefore, this review discusses the basic properties of the various types of K+ channels, including structure, cellular mechanisms that regulate their activity, and new advances in the development of activators and blockers of these channels. The vascular functions of these channels will be discussed with a focus on vascular SMCs of the human umbilical artery. Then, the clinical importance of K+ channels in the treatment and prevention of cardiovascular diseases during pregnancy, such as gestational hypertension and preeclampsia, will be explored.
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Djokic V, Jankovic-Raznatovic S, Novakovic R, Kostic M, Rajkovic J, Labudovic-Borovic M, Rakocevic J, Stanisic J, Djuric M, Gojkovic-Bukarica L. Effect of gestational diabetes mellitus and pregnancy-induced hypertension on human umbilical vein smooth muscle K ATP channels. Exp Mol Pathol 2019; 111:104323. [PMID: 31669131 DOI: 10.1016/j.yexmp.2019.104323] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 09/03/2019] [Accepted: 10/21/2019] [Indexed: 01/25/2023]
Abstract
Gestational diabetes mellitus (GDM) and pregnancy-induced hypertension (PIH) can jeopardize mother and/or fetus. Vascular ATP-sensitive potassium (KATP) channels most likely participate in the processes of diabetes and hypertension. The aim of this research was to examine whether GDM and PIH cause changes in the expression and function of KATP channels in vascular smooth muscle of human umbilical vein (HUV). Western blot and immunohistochemistry detected significantly decreased expression of Kir6.1 subunit of KATP channels in GDM and PIH, while the expression of SUR2B was unchanged. In GDM, a K+ channel opener, pinacidil caused reduced relaxation of the endothelium-denuded HUVs compared to normal pregnancy. However, its effects in HUVs from PIH subjects were similar to normal pregnancy. In all groups KATP channel blocker glibenclamide antagonized the relaxation of HUV induced by pinacidil without change in the maximal relaxations indicating additional KATP channel-independent mechanisms of pinacidil action. Iberiotoxin, a selective antagonist of large-conductance calcium-activated potassium channels, inhibited the relaxant effect of pinacidil in PIH, but not in normal pregnancy and GDM. Experiments performed in K+-rich solution confirmed the existence of K+-independent effects of pinacidil, which also appear to be impaired in GDM and PIH. Thus, the expression of KATP channels is decreased in GDM and PIH. In GDM, vasorelaxant response of HUV to pinacidil is reduced, while in PIH it remains unchanged. It is very likely that KATP channels modulation and more detailed insight in KATP channel-independent actions of pinacidil may be precious in the therapy of pathological pregnancies.
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Affiliation(s)
- Vladimir Djokic
- Department of Pharmacology, Clinical Pharmacology and Toxicology, Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia.
| | - Svetlana Jankovic-Raznatovic
- Department of Obstetrics and Gynecology "Narodni front", Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia
| | - Radmila Novakovic
- Department of Pharmacology, Clinical Pharmacology and Toxicology, Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia
| | - Milan Kostic
- Vinca Institute of Nuclear Sciences, 11000 Belgrade, Serbia
| | - Jovana Rajkovic
- Department of Pharmacology, Clinical Pharmacology and Toxicology, Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia
| | - Milica Labudovic-Borovic
- Institute of Histology and Embryology "Aleksandar Dj. Kostic", Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia
| | - Jelena Rakocevic
- Institute of Histology and Embryology "Aleksandar Dj. Kostic", Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia
| | | | - Milos Djuric
- Department of Pharmacology, Clinical Pharmacology and Toxicology, Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia
| | - Ljiljana Gojkovic-Bukarica
- Department of Pharmacology, Clinical Pharmacology and Toxicology, Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia
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Ferreira JJ, Butler A, Stewart R, Gonzalez-Cota AL, Lybaert P, Amazu C, Reinl EL, Wakle-Prabagaran M, Salkoff L, England SK, Santi CM. Oxytocin can regulate myometrial smooth muscle excitability by inhibiting the Na + -activated K + channel, Slo2.1. J Physiol 2018; 597:137-149. [PMID: 30334255 DOI: 10.1113/jp276806] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Accepted: 10/17/2018] [Indexed: 01/05/2023] Open
Abstract
KEY POINTS At the end of pregnancy, the uterus transitions from a quiescent state to a highly contractile state. This transition requires that the uterine (myometrial) smooth muscle cells increase their excitability, although how this occurs is not fully understood. We identified SLO2.1, a potassium channel previously unknown in uterine smooth muscle, as a potential significant contributor to the electrical excitability of myometrial smooth muscle cells. We found that activity of the SLO2.1 channel is negatively regulated by oxytocin via Gαq-protein-coupled receptor activation of protein kinase C. This results in depolarization of the uterine smooth muscle cells and calcium entry, which may contribute to uterine contraction. These findings provide novel insights into a previously unknown mechanism by which oxytocin may act to modulate myometrial smooth muscle cell excitability. Our findings also reveal a new potential pharmacological target for modulating uterine excitability. ABSTRACT During pregnancy, the uterus transitions from a quiescent state to a more excitable contractile state. This is considered to be at least partly a result of changes in the myometrial smooth muscle cell (MSMC) resting membrane potential. However, the ion channels controlling the myometrial resting membrane potential and the mechanism of transition to a more excitable state have not been fully clarified. In the present study, we show that the sodium-activated, high-conductance, potassium leak channel, SLO2.1, is expressed and active at the resting membrane potential in MSMCs. Additionally, we report that SLO2.1 is inhibited by oxytocin binding to the oxytocin receptor. Inhibition of SLO2.1 leads to membrane depolarization and activation of voltage-dependent calcium channels, resulting in calcium influx. The results of the present study reveal that oxytocin may modulate MSMC electrical activity by inhibiting SLO2.1 potassium channels.
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Affiliation(s)
- Juan J Ferreira
- Washington University School of Medicine, Department of Obstetrics and Gynecology, St Louis, MO, USA
| | - Alice Butler
- Washington University School of Medicine, Department of Neuroscience, St Louis, MO, USA
| | - Richard Stewart
- Washington University School of Medicine, Department of Neuroscience, St Louis, MO, USA
| | - Ana Laura Gonzalez-Cota
- Washington University School of Medicine, Department of Obstetrics and Gynecology, St Louis, MO, USA
| | - Pascale Lybaert
- Washington University School of Medicine, Department of Obstetrics and Gynecology, St Louis, MO, USA.,Present address: Laboratoire de Physiologie et Pharmacologie (LAPP), Faculté de Médecine, Université Libre de Bruxelles, Bruxelles, Belgium
| | - Chinwendu Amazu
- Washington University School of Medicine, Department of Obstetrics and Gynecology, St Louis, MO, USA
| | - Erin L Reinl
- Washington University School of Medicine, Department of Obstetrics and Gynecology, St Louis, MO, USA.,Present address: Pharmacology Department, School of Medicine, University of Maryland, Baltimore, MD, USA
| | - Monali Wakle-Prabagaran
- Washington University School of Medicine, Department of Obstetrics and Gynecology, St Louis, MO, USA
| | - Lawrence Salkoff
- Washington University School of Medicine, Department of Neuroscience, St Louis, MO, USA
| | - Sarah K England
- Washington University School of Medicine, Department of Obstetrics and Gynecology, St Louis, MO, USA
| | - Celia M Santi
- Washington University School of Medicine, Department of Obstetrics and Gynecology, St Louis, MO, USA.,Washington University School of Medicine, Department of Neuroscience, St Louis, MO, USA
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Arrowsmith S, Keov P, Muttenthaler M, Gruber CW. Contractility Measurements of Human Uterine Smooth Muscle to Aid Drug Development. J Vis Exp 2018. [PMID: 29443077 PMCID: PMC5841565 DOI: 10.3791/56639] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Discovery and characterization of novel pharmaceutical compounds or biochemical probes rely on robust and physiologically relevant assay systems. We describe methods to measure ex vivo myometrium contractility. This assay can be used to investigate factors and molecules involved in the modulation of myometrial contraction and to determine their excitatory or inhibitory actions, and hence their therapeutic potential in vivo. Biopsies are obtained from women undergoing cesarean section delivery with informed consent. Fine strips of myometrium are dissected, clipped and attached to a force transducer within 1 mL organ baths superfused with physiological saline solution at 37 °C. Strips develop spontaneous contractions within 2-3 h under set tension and remain stable for many hours (>6 h). Strips can also be stimulated to contract such as by the endogenous hormones, oxytocin and vasopressin, which cause concentration-dependent modulation of contraction frequency, force and duration, to more closely resemble contractions in labor. Hence, the effect of known and novel drug leads can be tested on spontaneous and agonist-induced contractions. This protocol specifically details how this assay can be used to determine the potency of known and novel agents by measuring their effects on various parameters of human myometrial contraction. We use the oxytocin- and V1a receptor antagonists, atosiban and SR49059 as examples of known compounds which inhibit oxytocin- and vasopressin-induced contractions, and demonstrate how this method can be used to complement and validate pharmacological data obtained from cell-based assays to aid drug development. The effects of novel agonists in comparison to oxytocin and vasopressin can also be characterized. Whilst we use the example of the oxytocin/ vasopressin system, this method can also be used to study other receptors and ion channels that play a role in uterine contraction and relaxation to advance the understanding of human uterine physiology and pathophysiology.
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Affiliation(s)
- Sarah Arrowsmith
- Harris-Wellbeing Preterm Birth Research Centre, Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool;
| | - Peter Keov
- School of Biomedical Sciences, The University of Queensland
| | - Markus Muttenthaler
- Faculty of Chemistry, Institute of Biological Chemistry, University of Vienna; Institute for Molecular Bioscience, University of Queensland
| | - Christian W Gruber
- School of Biomedical Sciences, The University of Queensland; Center for Physiology and Pharmacology, Medical University of Vienna;
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Abstract
In the United States, the generally accepted indication for tocolytic therapy centers on suppression of preterm labor. This may be in the form of preventative therapy with progesterone in women with prior spontaneous preterm birth or as an acute intervention to suppress established uterine contractions associated with cervical change occurring at less than 37 weeks gestation. This article seeks to apply this perspective to tocolytic therapy. Here, we provide a review of current tocolytic options and what the last decade of discovery has revealed about the regulation of myometrial excitability and quiescence. Moving forward, we must incorporate the emerging molecular data that is amassing in order to develop novel and effective tocolytic therapeutic options to prevent preterm labor and spontaneous preterm birth (sPTB).
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Affiliation(s)
| | | | - George Gallos
- Department of Anesthesia, Columbia University Medical Center, New York, NY.
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7
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Crankshaw DJ, Crosby DA, Morrison JJ. Effects of the KIR7.1 Blocker VU590 on Spontaneous and Agonist-Induced Contractions of Human Pregnant Myometrium. Reprod Sci 2017; 24:1402-1409. [PMID: 28071357 DOI: 10.1177/1933719116687657] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
KIR7.1, an inwardly rectifying K+ channel, plays a critical role in regulating uterine excitability during pregnancy and has been suggested as a potential new target for the treatment of conditions arising from dysfunctional uterine contractility, for example, atonic postpartum hemorrhage. The aim of this study was to investigate the effects of the selective KIR7.1 blocker, VU590, on both spontaneous and agonist-stimulated contractions of human pregnant myometrium in vitro. At a concentration of 20 µmol/L, VU590 significantly increased the mean contractile force and the frequency of spontaneous contractions ( P < 0.05) when compared to vehicle-treated tissues. However, there was a significant ( P < 0.0001) monoexponential decay in amplitude with time of exposure. When VU590 was coadministered with EC50 concentration of the uterotonics oxytocin, ergometrine, or carboprost, the only significant changes were an immediate decrease in the amplitude of oxytocin- and carboprost-induced contractions and a delayed reduction in amplitude and an increase in the frequency of ergometrine-induced contractions. Amplitude to all 3 agents in the presence of VU590 showed a monoexponential decay with time of exposure ( P < 0.0001). We conclude that VU590 modifies the contractility of pregnant human myometrium in support of a role for KIR7.1 in regulating that process. However, VU590 in vitro does not produce the types of contraction, either alone or in combination with other uterine stimulants that would suggest its usefulness as a first- or second-line clinical uterotonic agent.
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Affiliation(s)
- Denis J Crankshaw
- 1 Department of Obstetrics and Gynaecology, Lambe Institute for Translational Research, National University of Ireland Galway, Galway, Ireland
| | - David A Crosby
- 1 Department of Obstetrics and Gynaecology, Lambe Institute for Translational Research, National University of Ireland Galway, Galway, Ireland
| | - John J Morrison
- 1 Department of Obstetrics and Gynaecology, Lambe Institute for Translational Research, National University of Ireland Galway, Galway, Ireland
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Myorelaxant action of fluorine-containing pinacidil analog, flocalin, in bladder smooth muscle is mediated by inhibition of L-type calcium channels rather than activation of KATP channels. Naunyn Schmiedebergs Arch Pharmacol 2016; 389:585-92. [PMID: 26976335 DOI: 10.1007/s00210-016-1228-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Accepted: 03/07/2016] [Indexed: 10/22/2022]
Abstract
Flocalin (FLO) is a new ATP-sensitive K(+) (KATP) channel opener (KCO) derived from pinacidil (PIN) by adding fluorine group to the drug's structure. FLO acts as a potent cardioprotector against ischemia-reperfusion damage in isolated heart and whole animal models primarily via activating cardiac-specific Kir6.2/SUR2A KATP channels. Given that FLO also confers relaxation on several types of smooth muscles and can partially inhibit L-type Ca(2+) channels, in this study, we asked what is the mechanism of FLO action in bladder detrusor smooth muscle (DSM). The actions of FLO and PIN on contractility of rat and guinea pig DSM strips and membrane currents of isolated DSM cells were compared by tensiometry and patch clamp. Kir6 and SUR subunit expression in rat DSM was assayed by reverse transcription PCR (RT-PCR). In contrast to PIN (10 μM), FLO (10 μM) did not produce glibenclamide-sensitive DSM strips' relaxation and inhibition of spontaneous and electrically evoked contractions. However, FLO, but not PIN, inhibited contractions evoked by high K(+) depolarization. FLO (40 μM) did not change the level of isolated DSM cell's background K(+) current, but suppressed by 20 % L-type Ca(2+) current. Determining various Kir6 and SUR messenger RNA (mRNA) expressions in rat DSM by RT-PCR indicated that dominant KATP channel in rat DSM is of vascular type involving association of Kir6.1 and SUR2B subunits. Myorelaxant effects of FLO in bladder DSM are explained by partial blockade of L-type Ca(2+) channel-mediated Ca(2+) influx rather than by hyperpolarization associated with increased K(+) permeability. Thus, insertion of fluorine group in PIN's structure made the drug more discriminative between Kir6.2/SUR2A cardiac- and Kir6.1/SUR2B vascular-type KATP channels and rendered it partial L-type Ca(2+) channel-blocking potency.
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McCloskey C, Rada C, Bailey E, McCavera S, van den Berg HA, Atia J, Rand DA, Shmygol A, Chan YW, Quenby S, Brosens JJ, Vatish M, Zhang J, Denton JS, Taggart MJ, Kettleborough C, Tickle D, Jerman J, Wright P, Dale T, Kanumilli S, Trezise DJ, Thornton S, Brown P, Catalano R, Lin N, England SK, Blanks AM. The inwardly rectifying K+ channel KIR7.1 controls uterine excitability throughout pregnancy. EMBO Mol Med 2015; 6:1161-74. [PMID: 25056913 PMCID: PMC4197863 DOI: 10.15252/emmm.201403944] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Abnormal uterine activity in pregnancy causes a range of important clinical disorders, including preterm birth, dysfunctional labour and post-partum haemorrhage. Uterine contractile patterns are controlled by the generation of complex electrical signals at the myometrial smooth muscle plasma membrane. To identify novel targets to treat conditions associated with uterine dysfunction, we undertook a genome-wide screen of potassium channels that are enriched in myometrial smooth muscle. Computational modelling identified Kir7.1 as potentially important in regulating uterine excitability during pregnancy. We demonstrate Kir7.1 current hyper-polarizes uterine myocytes and promotes quiescence during gestation. Labour is associated with a decline, but not loss, of Kir7.1 expression. Knockdown of Kir7.1 by lentiviral expression of miRNA was sufficient to increase uterine contractile force and duration significantly. Conversely, overexpression of Kir7.1 inhibited uterine contractility. Finally, we demonstrate that the Kir7.1 inhibitor VU590 as well as novel derivative compounds induces profound, long-lasting contractions in mouse and human myometrium; the activity of these inhibitors exceeds that of other uterotonic drugs. We conclude Kir7.1 regulates the transition from quiescence to contractions in the pregnant uterus and may be a target for therapies to control uterine contractility.
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Affiliation(s)
- Conor McCloskey
- Division of Reproductive Health, Clinical Sciences Research Laboratories, Warwick Medical School University of Warwick, Coventry, UK
| | - Cara Rada
- Division of Basic Science Research, Department of Obstetrics and Gynecology, School of Medicine Washington University in St. Louis,, St. Louis, MO, USA
| | - Elizabeth Bailey
- Division of Reproductive Health, Clinical Sciences Research Laboratories, Warwick Medical School University of Warwick, Coventry, UK
| | - Samantha McCavera
- Division of Reproductive Health, Clinical Sciences Research Laboratories, Warwick Medical School University of Warwick, Coventry, UK
| | - Hugo A van den Berg
- Warwick Systems Biology & Mathematics Institute University of Warwick, Coventry, UK
| | - Jolene Atia
- Division of Reproductive Health, Clinical Sciences Research Laboratories, Warwick Medical School University of Warwick, Coventry, UK
| | - David A Rand
- Warwick Systems Biology & Mathematics Institute University of Warwick, Coventry, UK
| | - Anatoly Shmygol
- Division of Reproductive Health, Clinical Sciences Research Laboratories, Warwick Medical School University of Warwick, Coventry, UK
| | - Yi-Wah Chan
- Division of Reproductive Health, Clinical Sciences Research Laboratories, Warwick Medical School University of Warwick, Coventry, UK
| | - Siobhan Quenby
- Division of Reproductive Health, Clinical Sciences Research Laboratories, Warwick Medical School University of Warwick, Coventry, UK
| | - Jan J Brosens
- Division of Reproductive Health, Clinical Sciences Research Laboratories, Warwick Medical School University of Warwick, Coventry, UK
| | - Manu Vatish
- Division of Reproductive Health, Clinical Sciences Research Laboratories, Warwick Medical School University of Warwick, Coventry, UK
| | - Jie Zhang
- Division of Reproductive Health, Clinical Sciences Research Laboratories, Warwick Medical School University of Warwick, Coventry, UK
| | - Jerod S Denton
- Vanderbilt Institute of Chemical Biology, Vanderbilt Institute for Global Health Vanderbilt University School of Medicine Medical Center North, Nashville, TN, USA
| | - Michael J Taggart
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, UK
| | | | - David Tickle
- Centre for Therapeutics and Discovery, Medical Research Council Technologies, London, UK
| | - Jeff Jerman
- Centre for Therapeutics and Discovery, Medical Research Council Technologies, London, UK
| | - Paul Wright
- Centre for Therapeutics and Discovery, Medical Research Council Technologies, London, UK
| | - Timothy Dale
- BioPark, Essen BioScience Ltd, Welwyn Garden City, Hertfordshire, UK
| | | | - Derek J Trezise
- BioPark, Essen BioScience Ltd, Welwyn Garden City, Hertfordshire, UK
| | | | - Pamela Brown
- MRC Centre for Reproductive Health (CRH), Queen's Medical Research Institute University of Edinburgh, Edinburgh, UK
| | - Roberto Catalano
- MRC Centre for Reproductive Health (CRH), Queen's Medical Research Institute University of Edinburgh, Edinburgh, UK
| | - Nan Lin
- Department of Mathematics, Washington University, St. Louis, MO, USA
| | - Sarah K England
- Division of Basic Science Research, Department of Obstetrics and Gynecology, School of Medicine Washington University in St. Louis,, St. Louis, MO, USA
| | - Andrew M Blanks
- Division of Reproductive Health, Clinical Sciences Research Laboratories, Warwick Medical School University of Warwick, Coventry, UK
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Novakovi R, Radunovi N, Markovi -Lipkovski J, irovi S, Beleslin- oki B, Ili B, Ivkovi B, Heinle H, ivanovi V, Gojkovi -Bukarica L. Effects of the polyphenol resveratrol on contractility of human term pregnant myometrium. Mol Hum Reprod 2015; 21:545-51. [DOI: 10.1093/molehr/gav011] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Accepted: 03/02/2015] [Indexed: 12/27/2022] Open
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11
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Crankshaw DJ, Walsh JM, Morrison JJ. The effects of methyl palmitate, a putative regulator from perivascular fat, on the contractility of pregnant human myometrium. Life Sci 2014; 116:25-30. [DOI: 10.1016/j.lfs.2014.08.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Revised: 08/05/2014] [Accepted: 08/27/2014] [Indexed: 12/11/2022]
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12
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Waite SL, Gandhi SV, Khan RN, Chapman NR. The effect of trichostatin-A and tumor necrosis factor on expression of splice variants of the MaxiK and L-type channels in human myometrium. Front Physiol 2014; 5:261. [PMID: 25076912 PMCID: PMC4097961 DOI: 10.3389/fphys.2014.00261] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Accepted: 06/20/2014] [Indexed: 01/30/2023] Open
Abstract
The onset of human parturition is associated with up-regulation of pro-inflammatory cytokines including tumor necrosis factor (TNF) as well as changes in ion flux, principally Ca2+ and K+, across the myometrial myocytes membrane. Elevation of intra-cellular Ca2+ from the sarcoplasmic reticulum opens L-type Ca2+ channels (LTCCs); in turn this increased calcium level activates MaxiK channels leading to relaxation. While the nature of how this cross-talk is governed remains unclear, our previous work demonstrated that the pro-inflammatory cytokine, TNF, and the histone deacetylase inhibitor, Trichostatin-A (TSA), exerted opposing effects on the expression of the pro-quiescent Gαs gene in human myometrial cells. Consequently, in this study we demonstrate that the different channel splice variants for both MaxiK and LTCC are expressed in primary myometrial myocytes. MaxiK mRNA expression was sensitive to TSA stimulation, this causing repression of the M1, M3, and M4 splice variants. A small but not statistically significantly increase in MaxiK expression was also seen in response to TNF. In contrast to this, expression of LTCC splice variants was seen to be influenced by both TNF and TSA. TNF induced overall increase in total LTCC expression while TSA stimulated a dual effect: causing induction of LTCC exon 8 expression but repressing expression of other LTCC splice variants including that encoding exons 30, 31, 33, and 34, exons 30–34 and exons 40–43. The significance of these observations is discussed herein.
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Affiliation(s)
- Sarah L Waite
- Academic Unit of Reproductive and Developmental Medicine, Department of Human Metabolism, University of Sheffield Sheffield, UK
| | - Saurabh V Gandhi
- Department of Obstetrics and Gynaecology, Sheffield Teaching Hospitals NHS Foundation Trust Sheffield, UK
| | - Raheela N Khan
- Division of Medical Sciences and Graduate Entry Medicine, School of Medicine, Royal Derby Hospital, University of Nottingham Derby, UK
| | - Neil R Chapman
- Academic Unit of Reproductive and Developmental Medicine, Department of Human Metabolism, University of Sheffield Sheffield, UK
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Corriveau S, Pasquier JC, Blouin S, Bellabarba D, Rousseau É. Chronic levothyroxine and acute T3 treatments enhance the amplitude and time course of uterine contractions in human. Am J Physiol Endocrinol Metab 2013; 304:E478-85. [PMID: 23249699 DOI: 10.1152/ajpendo.00346.2012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study compares the functional consequences of levothyroxine (T4) treatment during pregnancy as well as the acute affects of triiodothyronine (T3) on spontaneous uterine contractile activities observed in vitro. Uterine biopsies were obtained from consenting women undergoing elective caesarean at term (n = 28). Spontaneous contractile activities from T4-treated pregnant women (n = 8) were compared with control patients (n = 20) by isometric tension measurements. Effects of acute T3 and T4 on control tissues were also monitored. Area under the curve, amplitude, time to peak, duration, and frequency were quantified. In uterine strips from women treated for hypothyroidism, phasic uterine contractions of larger amplitude (+77%) were observed, with a prolonged duration at 90% relaxation (+138%) and reduced frequency (-55%) compared with values of the control group. The addition of exogenous T3 in vitro on control strips induced a significant increase in the duration of the contractions and a significant decrease in frequency (P < 0.05), which partially mimics the results obtained in strips from T4-treated women. Significant modifications of contractile properties were observed in strips from pregnant women treated with levothyroxine, consistent with those observed with the addition of exogenous T3. Clinical practices of modern obstetrics should take into account the effect of thyroid hormones on uterine contractions' time course to ensure a tighter followup at the end of pregnancy to achieve safer delivery.
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Affiliation(s)
- Stéphanie Corriveau
- Department of Obstetrics and Gynecology, Université de Sherbrooke, Sherbrooke, Quebec, Canada
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Rosenbaum ST, Larsen T, Joergensen JC, Bouchelouche PN. Relaxant effect of a novel calcium-activated potassium channel modulator on human myometrial spontaneous contractility in vitro. Acta Physiol (Oxf) 2012; 205:247-54. [PMID: 22099068 DOI: 10.1111/j.1748-1716.2011.02384.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIM To investigate the effect of 4,5-dichloro-1,3-diethyl-1,3-dihydro-benzoimidazol-2-one (NS4591), a novel SK/IK channels positive modulator, on human myometrial activity. METHODS Organ bath studies were performed on myometrial preparations obtained from women undergoing elective caesarean section at term (N = 11) or hysterectomy (N = 11). NS4591 was added cumulatively in the concentration range of 0.3-30 μm. In separate experiments, the effects of pre-incubation of muscle preparation with the SK or IK channel blockers apamin (1 μm) and TRAM34 (10 μm) on the outcomes of NS4591 were evaluated. Simultaneous vehicle controls were performed for all experiments. The effects of drugs were studied on spontaneous contractions. RESULTS NS4591 exerted an inhibitory effect on myometrial contractions in muscle strips from non-pregnant and pregnant women. The contractility in non-pregnant and pregnant myometrium was reduced to the following values respectively: amplitude 20.65 ± 7.38% (P < 0.001) and 42.85 ± 11.04% (P < 0.05) and area under the curve 11.72 ± 7.39% (P < 0.001) and 34.84 ± 10.50% (P < 0.001) and are reflective of 30 μm NS4591 compared to vehicle control. In non-pregnant tissue, apamin partially reduced the inhibitory effects of NS4591, but we observed relaxation mediated by NS4591 despite pre-incubation with TRAM34. In contrast, in pregnant tissue, neither apamin nor TRAM34 could reverse the relaxatory effects of NS4591. CONCLUSION Our findings imply that SK/IK channels are present and functional in myometrium from pregnant and non-pregnant women. The SK/IK channel-positive modulator NS4591 exerts relaxation of human myometrium in vitro, and this may have implications for the clinical management of preterm labour.
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Affiliation(s)
- S T Rosenbaum
- Department of Gynecology and Obstetrics, Holbaek Hospital, Holbaek, Denmark.
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15
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Distribution, expression and functional effects of small conductance Ca-activated potassium (SK) channels in rat myometrium. Cell Calcium 2009; 47:47-54. [PMID: 19969350 DOI: 10.1016/j.ceca.2009.11.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2009] [Accepted: 11/05/2009] [Indexed: 11/21/2022]
Abstract
Calcium-activated potassium channels are important in a variety of smooth muscles, contributing to excitability and contractility. In the myometrium previous work has focussed on the large conductance channels (BK), and the role of small conductance channels (SK) has received scant attention, despite the finding that over-expression of an SK channel isoform (SK3) results in uterine dysfunction and delayed parturition. This study therefore characterises the expression of the three SK channel isoforms (SK1-3) in rat myometrium throughout pregnancy and investigates their effect on cytosolic [Ca] and force and compares this with that of BK channels. Consistent expression of all SK isoform transcripts and clear immunostaining of SK1-3 was found. Inhibition of SK1-3 channels (apamin, scyllatoxin) significantly inhibited outward current, caused membrane depolarisation and elicited action potentials in previously quiescent cells. Apamin or scyllatoxin increased the amplitude of [Ca] and force in spontaneously contracting myometrial strips throughout gestation. The functional effect of SK inhibition was larger than that of BK channel inhibition. Thus we show for the first time that SK1-3 channels are expressed and translated throughout pregnancy and contribute to outward current, regulate membrane potential and hence Ca signals in pregnant rat myometrium. They contribute more to quiescence that BK channels.
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Shih HC, Hsu CS, Yang LL. In vitro study of the tocolytic effect of oroxylin A from Scutellaria baicalensis root. J Biomed Sci 2009; 16:27. [PMID: 19272127 PMCID: PMC2656494 DOI: 10.1186/1423-0127-16-27] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2009] [Accepted: 03/04/2009] [Indexed: 12/04/2022] Open
Abstract
Scutellariae Radix is one of the well-known tocolytic Chinese herbs. Oroxylin A is isolated from the root of Scutellaria baicalensis. The main syndrome of preterm birth is caused by uterus contractions from excitatory factors. Administration of tocolytic agents is a strategy to prevent the occurrence of preterm births. The aim of this study was to investigate the effects of oroxylin A on contractions of uterine strips isolated from non-pregnant female Wistar rats (250~350 g). Contractions of the uterus were induced with acetylcholine (Ach) (1 μM), PGF2α (0.1 μM), oxytocin (10-3 U/ml), KCl (56.3 mM), tetraethylammonium (TEA; 1 and 10 mM), 4-aminopyridine (4-AP; 5 mM), glipizide (30 μM), a nitric oxide synthase (NOS) inhibitor (LNNA; 10-3M), a β-receptor blocker (propranolol; 10 μM), and a cyclooxygenase inhibitor (indomethacin; 60 μM). The inhibitory effects of the amplitude and frequency of spontaneous contractions by oroxylin A were antagonized with Ach (IC50 22.85 μM), PGF2α (IC5027.28 μM), oxytocin (IC50 12.34 μM), TEA; 1 and 10 mM (IC50 52.73 and 76.43 μM), 4-AP (IC50 67.16 μM), and glipizide (IC5027.53 μM), but oroxylin A was not influenced by Ca2+-free medium, LNNA, propranolol, or indomethacin. Otherwise, oroxylin A-mediated relaxation of the rat uterus might occur through opening of uterine calcium-dependent potassium channels or adenosine triphosphate potassium channel activation. This suggests that oroxylin A is the tocolytic principle constituent of Scutellariae Radix, and oroxylin A may provide a lead compound for new tocolytic drug development in the future.
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Affiliation(s)
- Huey-Chuan Shih
- School of Pharmacy, College of Pharmacy, Taipei Medical University, 250 Wu-Hsing Street, Taipei 110, Taiwan.
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17
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Novakovic R, Milovanovic S, Protic D, Djokic J, Heinle H, Gojkovic-Bukarica L. The effect of potassium channel opener pinacidil on the non-pregnant rat uterus. Basic Clin Pharmacol Toxicol 2008; 101:181-6. [PMID: 17697038 DOI: 10.1111/j.1742-7843.2007.00096.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The effects of the K(+) channel opener, pinacidil on the spontaneous rhythmic contractions and contractions provoked by electrical field stimulation (50 Hz) or by oxytocin were investigated in the isolated uterus of the non-pregnant rat in oestrus. Pinacidil produced more potent inhibition of oxytocin-elicited contractions than of spontaneous rhythmic contractions or electrical field stimulation-induced contractions. Glibenclamide, a selective blocker of adenosine triphosphate (ATP)-sensitive K(+) (K(ATP)) channels, antagonized the pinacidil-induced inhibition of contractions elicited by oxytocin in a competitive manner. However, the pinacidil-induced inhibition of electrical field stimulation-elicited contractions and spontaneous rhythmic contractions was antagonized non-competitively by glibenclamide. In the uterine strips pre-contracted with 80 mM K(+), the pinacidil-induced maximal relaxation was not affected. The present data show that pinacidil exhibits potent relaxant properties in the rat non-pregnant uterus in oestrus and therefore should be taken into account as a possible agent for treatment of dysmenorrhoea. Based on glibenclamide affinity, it appears that the inhibitory response to pinacidil involves K(ATP )channels. We need further investigations to explain why the interaction between glibenclamide and pinacidil in this experimental model depends on the nature of contractions. The ability of pinacidil to completely relax the rat non-pregnant uterus pre-contracted with K(+)-rich solution suggests that K(+) channel-independent mechanism(s) also play a part in its relaxant effect.
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Affiliation(s)
- Radmila Novakovic
- Department of Clinical Pharmacology, Pharmacology and Toxicology, Faculty of Medicine, University of Belgrade, Belgrade, Serbia
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18
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Doheny HC, O'Reilly MJ, Sexton DJ, Morrison JJ. THG113.31, a specific PGF2alpha receptor antagonist, induces human myometrial relaxation and BKCa channel activation. Reprod Biol Endocrinol 2007; 5:10. [PMID: 17367527 PMCID: PMC1831777 DOI: 10.1186/1477-7827-5-10] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2007] [Accepted: 03/16/2007] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND PGF2alpha exerts a significant contractile effect on myometrium and is central to human labour. THG113.31, a specific non-competitive PGF2alpha receptor (FP) antagonist, exerts an inhibitory effect on myometrial contractility. The BKCa channel is ubiquitously encountered in human uterine tissue and plays a significant role in modulating myometrial cell membrane potential and excitability. The objective of this study was to investigate potential BKCa channel involvement in the response of human myometrium to THG113.31. METHODS Single and whole-cell electrophysiological BKCa channel recordings from freshly dispersed myocytes, were investigated in the presence and absence of THG113.31. Functional studies investigated the effects of THG113.31 on isolated spontaneous myometrial contractions, in the presence and absence of the BKCa channel blocker, iberiotoxin. RESULTS Single channel recordings identified the BKCa channel as a target of THG113.31. THG113.31 significantly increased the open state probability of these channels [control 0.023+/-0.006; 10 microM THG113.31 0.087+/-0.012 (P = 0.009); and 50 microM THG113.31 0.1356+/-0.018 (P = 0.001)]. In addition, THG113.31 increased whole-cell BKCa currents over a range of membrane potentials, and this effect was reversed by 100 nanoM IbTX. Isometric tension studies demonstrated that THG113.31 exerted a significant concentration-dependent relaxant effect on human myometrial tissue and pre-incubation of strips with IbTX abolished this effect on spontaneously occurring contractions. CONCLUSION These data suggests that activation of the BKCa channel may contribute, at least partially, to the uterorelaxant effect of THG113.31.
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Affiliation(s)
- Helen C Doheny
- Department of Obstetrics & Gynaecology, National University of Ireland Galway, Clinical Science Institute, University College Hospital Galway, Newcastle Road, Galway, Ireland
| | - Michael J O'Reilly
- Department of Obstetrics & Gynaecology, National University of Ireland Galway, Clinical Science Institute, University College Hospital Galway, Newcastle Road, Galway, Ireland
| | - Donal J Sexton
- Department of Obstetrics & Gynaecology, National University of Ireland Galway, Clinical Science Institute, University College Hospital Galway, Newcastle Road, Galway, Ireland
| | - John J Morrison
- Department of Obstetrics & Gynaecology, National University of Ireland Galway, Clinical Science Institute, University College Hospital Galway, Newcastle Road, Galway, Ireland
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Doheny HC, Lynch CM, Smith TJ, Morrison JJ. Functional coupling of beta3-adrenoceptors and large conductance calcium-activated potassium channels in human uterine myocytes. J Clin Endocrinol Metab 2005; 90:5786-96. [PMID: 16014404 DOI: 10.1210/jc.2005-0574] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT Beta3-adrenoreceptor modulation in human myometrium during pregnancy is linked functionally to myometrial inhibition. Maxi-K+ channels (BK(Ca)) play a significant role in modulating cell membrane potential and excitability. OBJECTIVE This study was designed to investigate the potential involvement of BK(Ca) channel function in the response of human myometrium to beta3-adrenoceptor activation. DESIGN Single and whole-cell electrophysiological BK(Ca) channel recordings from freshly dispersed myocytes were obtained in the presence and absence of BRL37344, a specific beta3-adrenoreceptor agonist. The in vitro effects of BRL37344 on isolated myometrial contractions, in the presence and absence of the specific BK(Ca) channel blocker, iberiotoxin (IbTX), were investigated. SETTING The study was carried out at the Clinical Science Institute. PATIENTS OR OTHER PARTICIPANTS Myometrial biopsies were obtained at elective cesarean delivery. INTERVENTION No intervention was applied. MAIN OUTCOME MEASURES Open state probability of single channel recordings, whole cell currents, and myometrial contractile activity were measured. RESULTS Single-channel recordings identified the BK(Ca) channel as a target of BRL37344. BRL37344 significantly increased the open state probability of this channel in a concentration-dependent manner (control 0.031 +/- 0.004; 50 microM BRL37344 0.073 +/- 0.005 (P < 0.001); and 100 microM BRL37344 0.101 +/- 0.005 (P < 0.001). This effect was completely blocked after preincubation of the cells with 1 microM bupranolol, a nonspecific beta-adrenoreceptor blocker, or 100 nM SR59230a, a specific beta3-adrenoreceptor antagonist. In addition, BRL37344 increased whole-cell currents over a range of membrane potentials, and this effect was reversed by 100 nM IbTX. In vitro isometric tension studies demonstrated that BRL37344 exerted a significant concentration-dependent relaxant effect on human myometrial tissue (P < 0.05), and preincubation of these strips with IbTX attenuated this effect on both spontaneous and oxytocin-induced contractions (44.44 and 57.84% at 10(-5) M, respectively). CONCLUSIONS These findings outline that activation of the BK(Ca) channel may explain the potent uterorelaxant effect of beta3-adrenoreceptor agonists.
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Affiliation(s)
- Helen C Doheny
- Department of Obstetrics and Gynecology, National University of Ireland Galway, Clinical Science Institute, University College Hospital Galway, Galway, Ireland.
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20
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Chanrachakul B, Broughton Pipkin F, Warren AY, Arulkumaran S, Khan RN. Progesterone enhances the tocolytic effect of ritodrine in isolated pregnant human myometrium. Am J Obstet Gynecol 2005; 192:458-63. [PMID: 15695987 DOI: 10.1016/j.ajog.2004.07.077] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVE To evaluate the effect of natural progesterone on the relaxant effect of ritodrine on pregnant human oxytocin-induced myometrial contractility. STUDY DESIGN Isometric tension recordings were performed under physiologic conditions on isolated myometrial strips taken from low-risk term pregnant women undergoing elective cesarean section. Cumulative effects of natural progesterone (10 (-11) to 10 (-5) mol/L) on oxytocin-induced myometrial contractility were evaluated. Contractile activity following ritodrine exposure was also investigated in myometrium pretreated with natural progesterone. RESULTS Natural progesterone alone exerted a concentration-dependent relaxant effect on myometrial contractions. The concentration-response curve for ritodrine from natural progesterone pretreated myometrium was shifted to the left with a significant reduction ( P < .01) of 50% of the maximal response, contraction amplitude ( P < .05), and frequency ( P < .05). However, there was no significant difference in the mean maximal inhibition achieved ( P = .95). CONCLUSION Natural progesterone increased the relaxant effect of ritodrine by reducing 50% of the maximal response, amplitude, and frequency of myometrial contraction, most likely through nongenomic actions. These results suggest that natural progesterone may be beneficial for preventing preterm birth in a low-risk population.
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Affiliation(s)
- Boonsri Chanrachakul
- Academic Division of Obstetrics and Gynaecology, Derby City General Hospital, University of Nottingham, Derby, DE22 3DT, United Kingdom
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Chanrachakul B, Broughton Pipkin F, Khan RN. Contribution of coupling between human myometrial beta2-adrenoreceptor and the BK(Ca) channel to uterine quiescence. Am J Physiol Cell Physiol 2004; 287:C1747-52. [PMID: 15329337 DOI: 10.1152/ajpcell.00236.2004] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The beta(2)-adrenergic receptor (beta(2)-AR) and the large-conductance Ca(2+)-activated K(+) (BK(Ca)) channel have been shown, separately, to be involved in mediating uterine relaxation. Our recent studies reveal that the levels of both beta(2)-AR and BK(Ca) channel proteins in pregnant human myometrium decrease by approximately 50% after the onset of labor. We present direct evidence in support of a structural and functional association between the beta(2)-AR and the BK(Ca) channel in pregnant human myometrium. Localization of both proteins is predominantly plasmalemmal, with 60% of beta(2)-AR colocalizing with the BK(Ca) channel. Coimmunoprecipitation studies indicate that BK(Ca) and beta(2)-AR are structurally linked by direct protein-protein interactions. Functional correlation was confirmed by experiments of human myometrial contractility in which the BK(Ca) channel blocker, paxilline, significantly antagonized the relaxant effect of the beta(2)-AR agonist ritodrine. These novel findings provide an insight into the coupling between the beta(2)-AR and BK(Ca) channel and may have utility in the application of this signaling cascade for therapeutic potential in the management of preterm labor.
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Affiliation(s)
- Boonsri Chanrachakul
- Center for Reproduction and Early Life, Institute of Clinical Research, University of Nottingham, Academic Division of Obstetrics and Gynaecology, The Medical School, Derby City General Hospital, Uttoxeter New Road, Derby DE22 3DT, UK
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Takeuchi K, Fukuda A, Kanayama N. Effect of urinary trypsin inhibitor on potassium currents: fetus modulates membrane excitability by production of UTI. Acta Obstet Gynecol Scand 2003; 83:6-11. [PMID: 14678080 DOI: 10.1111/j.1600-0412.2004.00268.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND Amniotic fluid contains a significant level of urinary trypsin inhibitor (UTI). Previously, we reported that UTI inhibits calcium influx of myometrium and it is effective in preventing uterine contraction. This study examined the effects of UTI upon potassium channels, which is important for membrane excitability. METHODS Whole-cell patch-clamp recordings were performed in fibroblasts derived from human fetal skin. Potassium currents were recorded and the effects of exogenous UTI and/or cadmium determined. RESULTS Tetraethylammonium sensitive potassium currents were elicited by step or ramp stimulations at depolarized membrane potentials (over +30 mV). Administration of 1 micro M UTI significantly increased these potassium currents by 16.9%. When calcium channels were blocked by the administration of cadmium, UTI increased the rest of the potassium currents by 4.8%. This indicates that UTI increased calcium-dependent potassium currents by 94.8% but only increased voltage-dependent potassium currents by 4.8%. CONCLUSIONS Urinary trypsin inhibitor is a physiological substance of fetal origin that modulates calcium-dependent and voltage-dependent potassium channels. These data suggest that UTI is capable of regulating the membrane properties of the fetal and myometrial cells in contact with amniotic fluid.
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Affiliation(s)
- Kinya Takeuchi
- Department of Obstetrics and Gynecology, Hamamatsu University School of Medicine, 1-20-1 Handayama, Hamamatsu, Shizuoka 431-3192, Japan.
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Matharoo-Ball B, Ashford MLJ, Arulkumaran S, Khan RN. Down-regulation of the alpha- and beta-subunits of the calcium-activated potassium channel in human myometrium with parturition. Biol Reprod 2003; 68:2135-41. [PMID: 12606455 DOI: 10.1095/biolreprod.102.010454] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Large-conductance, calcium-dependent potassium (BKCa) channels are implicated in maintaining uterine quiescence during pregnancy. The mechanisms whereby calcium sensitivity of the BKCa channel is dramatically removed at parturition remain unknown. The aim of the present study was to investigate whether this loss of calcium sensitivity of the BKCa channel with the onset of labor is associated with changes in the protein expression of the alpha- and/or beta-subunit or arises from a physical dissociation of the alpha-subunit from the beta-subunit. The beta-subunit is a key determinant of BKCa-channel Ca2+ sensitivity. Western blot analysis, using alpha- and beta-subunit-specific antibodies, detected bands of 110-125 and 36 kDa, respectively. Protein expression levels of the alpha-subunit in term labor myometrium were significantly reduced compared with term pregnancy without labor. Furthermore, alpha-subunit levels at term pregnancy were significantly increased relative to the nonpregnant state, whereas levels at preterm gestations were unchanged. Densitometric analysis demonstrated significantly decreased beta-subunit levels in term and preterm labor samples compared with term nonlabor samples. Immunoprecipitation studies revealed the presence of both the alpha- and beta-subunits in samples taken before or after the onset of labor. We conclude that during labor, the alpha-subunit is not physically uncoupled from the beta-subunit, but a decline occurs in the level of beta-subunit protein, which may underlie the loss of calcium and voltage sensitivity of the BKCa channel with labor. Furthermore, reduced beta-subunit protein in preterm labor myometrium implies that ion channels may also contribute to pathophysiological labor.
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Affiliation(s)
- B Matharoo-Ball
- Academic Division of Obstetrics & Gynaecology, University of Nottingham, Derby City General Hospital, Derby DE22 3NE, United Kingdom
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Carvajal JA, Thompson LP, Weiner CP. Chorion-induced myometrial relaxation is mediated by large-conductance Ca2+-activated K+ channel opening in the guinea pig. Am J Obstet Gynecol 2003; 188:84-91. [PMID: 12548200 DOI: 10.1067/mob.2003.102] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
OBJECTIVE We previously demonstrated that chorion releases a factor that inhibits both spontaneous and oxytocin-stimulated myometrial contractility. Here, we investigate the mechanism of action of this unidentified substance. STUDY DESIGN Myometrial strips from pregnant guinea pigs were mounted in an organ bath and contractility stimulated with oxytocin. RESULTS Guinea pig chorion produced a time-dependent decrease in oxytocin-induced myometrial contractility. The ability of the chorion to reduce contractility was unaltered by inhibiting chorionic synthesis of either nitric oxide (N [omega]-nitro-L-arginine), carbon monoxide (tin-protoporphyrin), prostaglandins (indomethacin), or the myometrial cyclic guanosine monophosphate pathway (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalime-1-one and Rp-8Br-cGMP). In contrast, iberiotoxin, an inhibitor of large conductance Ca(2+)-activated K(+) channels reduced the quiescent effect of chorion by 40%; in contrast, inhibition of adenosine triphosphate-sensitive (glibenclamide) and voltage-gated K(+) channels (4amynopyridine) had no effect. CONCLUSION Chorion-induced relaxation of oxytocin-stimulated myometrial contraction is, in great part, the product of a paracrine substance that opens myometrial large conductance Ca(2+)-activated K(+) channels.
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Affiliation(s)
- Jorge A Carvajal
- Department of Obstetrics, Gynecology and Reproductive Sciences, University of Maryland Baltimore, School of Medicine, Baltimore, MD 21201, USA
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25
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Slattery MM, O'leary MJ, Morrison JJ. Effect of parathyroid hormone-related peptide on human and rat myometrial contractility in vitro. Am J Obstet Gynecol 2001; 184:625-9. [PMID: 11262463 DOI: 10.1067/mob.2001.110695] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
OBJECTIVES The aims of this study were primarily to investigate the effects of parathyroid hormone-related peptide (human fragment 1-34) on human nonpregnant and pregnant (nonlabor and labor) myometrial contractility in vitro and secondarily to compare these effects with those of parathyroid hormone-related peptide on rat myometrial contractility. STUDY DESIGN Isometric tension recording was performed under physiologic conditions in isolated myometrial strips obtained at hysterectomy and cesarean delivery and from Sprague-Dawley rats. The effect of cumulative additions of parathyroid hormone-related peptide (1, 10, and 100 nmol/L) on myometrial contractility was measured and the significance of results was assessed by 2-way analysis of variance. RESULTS Parathyroid hormone-related peptide exerted a statistically significant net relaxant effect on myometrial contractility in human nonpregnant myometrium (34.71%; P<.01), in human pregnant myometrium obtained before (18.27%; P <.05) but not after (10.32%; P>.05) the onset of labor, and in rat tissue (31.60%; P<.01). CONCLUSIONS Parathyroid hormone-related peptide exerts a relaxant effect on human and rat myometrial tissue. In human myometrium, sensitivity to parathyroid hormone-related peptide is reduced in pregnancy and abolished by the onset of labor.
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Affiliation(s)
- M M Slattery
- Department of Obstetrics and Gynaecology, National University of Ireland Galway, and the Clinical Science Institute, University College Hospital Galway, Ireland
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Buxton IL, Crow W, Mathew SO. Regulation of uterine contraction: mechanisms in preterm labor. AACN CLINICAL ISSUES 2000; 11:271-82. [PMID: 11235436 DOI: 10.1097/00044067-200005000-00010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Preterm labor (PTL) is defined as uterine irritability accompanied by cervical dilation and/or effecement that occurs before 37 weeks gestation. In most cases, PTL becomes preterm delivery (PTD), accounting for 8% to 10% of births in the United States. Fetuses born before 37 weeks' gestation are at risk for a multitude of health and developmental problems. Most perinatal morbidity and mortality in the United States are caused by PTL. It is a costly problem, in both monetary and human terms. Although some risk factors have been identified, they by no means identify, in advance, every case of PTL and PTD. Despite the understandable emphasis on attempts to find and test risk factors that predict PTL, the ultimate benefit--preventing PTD--will come only from an understanding of the physiologic mechanisms of parturition and how to halt those processes when they occur too early. This article reviews current approaches to preventing PTD, describes the biology of myometrial contraction, and discusses recent progress from several laboratories including the authors' that may shed light on approaches to inhibit uterine contractility in the setting of PTL.
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Affiliation(s)
- I L Buxton
- Department of Pharmacology, University of Nevada School of Medicine, Howard Research Bldg., Laboratory Suite 216, Reno, NV 89557, USA.
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Knock GA, Smirnov SV, Aaronson PI. Voltage-gated K+ currents in freshly isolated myocytes of the pregnant human myometrium. J Physiol 1999; 518 ( Pt 3):769-81. [PMID: 10420013 PMCID: PMC2269461 DOI: 10.1111/j.1469-7793.1999.0769p.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/1998] [Accepted: 04/21/1999] [Indexed: 11/29/2022] Open
Abstract
1. Voltage-gated K+ currents in human myometrium are not well characterized, and were therefore investigated, using the whole-cell patch clamp technique, in freshly isolated myometrial smooth muscle cells from pregnant women at term. 2. Three types of voltage-gated K+ currents were identified. IK1 was a 4-aminopyridine-insensitive current with a negative half-inactivation (V0.5 = -61 to -67 mV) and negative activation characteristics (threshold between -60 and -40 mV) and slow kinetics. IK2 was a 4-aminopyridine-sensitive current (half-maximal block at approximately 1 mM) with relatively positive half-inactivation (V0.5 = -30 mV) and activation characteristics (threshold between -40 and -30 mV) and faster kinetics. IK,A was a 4-aminopyridine-sensitive current with a negative inactivation and very fast inactivation kinetics. 3. Both IK1 and IK2 were sensitive to high concentrations of tetraethylammonium (half-maximal block at approximately 3 mM) and low concentrations of clofilium (half-maximal block by 3-10 microM). 4. IK1 and IK2 were unevenly distributed between myometrial cells, most cells possessing either IK1 (30 cells) or IK2 (24 cells) as the predominant current. 5. The characteristics of these currents suggest a possible function in the control of membrane potentials and smooth muscle quiescence in the pregnant human myometrium.
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Affiliation(s)
- G A Knock
- London Myometrial Group and Division of Pharmacology and Therapeutics, King's College London, St Thomas' Campus, Lambeth Palace Road, London SE1 7EH, UK
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Chien EK, Zhang Y, Furuta H, Hara M. Expression of adenosine triphosphate-sensitive potassium channel subunits in female rat reproductive tissues: overlapping distribution of messenger ribonucleic acid for weak inwardly rectifying potassium channel subunit 6.1 and sulfonylurea-binding regulatory subunit 2. Am J Obstet Gynecol 1999; 180:1121-6. [PMID: 10329865 DOI: 10.1016/s0002-9378(99)70604-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
OBJECTIVE Potassium channel activation has been shown to decrease uterine tone and is a target for inhibition of uterine activity in the treatment of preterm labor. In addition, potassium channel activation also appears to be involved in oocyte maturation. The specific potassium channels responsible for these channel currents have not been identified but are known to be responsive to such agents as pinacidil and to be inhibited by glibenclamide. These findings suggest the presence of an adenosine triphosphate-sensitive potassium channel that is a complex of a weak inwardly rectifying potassium channel subunit 6.1 or 6.2 and sulfonylurea-binding regulatory subunit 1 or 2. STUDY DESIGN The technique of reverse transcriptase-polymerase chain reaction was used to detect the presence of messenger ribonucleic acid for sulfonylurea-binding regulatory subunit 1 and 2 and weak inwardly rectifying potassium channel subunit 6.1 and 6.2 in the ovary and myometrium of the pregnant rat. In situ hybridization histochemical analysis was used to identify the specific cell types expressing each messenger ribonucleic acid. RESULTS Reverse transcriptase-polymerase chain reaction analysis found expression of messenger ribonucleic acid for sulfonylurea-binding regulatory subunits 1 and 2B and messenger ribonucleic acid for weak inwardly rectifying potassium channel subunit 6.1 in rat myometrium and ovary during gestation. There was no evidence for expression of weak inwardly rectifying potassium channel subunit 6.2 messenger ribonucleic acid in the ovary or the myometrium of the pregnant rat. In situ hybridization histochemical examination localized expression of messenger ribonucleic acid for sulfonylurea-binding regulatory subunit 2B and messenger ribonucleic acid for weak inwardly rectifying potassium channel subunit 6.1 to uterine myocytes and granulosa cells of the corpus luteum. The cells expressing sulfonylurea-binding regulatory subunit 1 messenger ribonucleic acid could not be identified because of the scarcity of this messenger ribonucleic acid. Messenger ribonucleic acid for sulfonylurea-binding regulatory subunit 1, messenger ribonucleic acid for sulfonylurea-binding regulatory subunit 2B, and messenger ribonucleic acid for weak inwardly rectifying potassium channel subunit 6.1 were also observed in the placenta by in situ hybridization histochemical examination. CONCLUSION The results suggest that the major adenosine triphosphate-sensitive potassium channel expressed in the myometrium and the corpus luteum during pregnancy is a complex of sulfonylurea-binding regulatory subunit 2B and weak inwardly rectifying potassium channel subunit 6.1.
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Affiliation(s)
- E K Chien
- Departments of Obstetrics and Gynecology and Medicine and the Howard Hughes Medical Institute, The University of Chicago, Illinois, USA
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