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Wray S, Arrowsmith S. Uterine Excitability and Ion Channels and Their Changes with Gestation and Hormonal Environment. Annu Rev Physiol 2020; 83:331-357. [PMID: 33158376 DOI: 10.1146/annurev-physiol-032420-035509] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We address advances in the understanding of myometrial physiology, focusing on excitation and the effects of gestation on ion channels and their relevance to labor. This review moves through pioneering studies to exciting new findings. We begin with the myometrium and its myocytes and describe how excitation might initiate and spread in this myogenic smooth muscle. We then review each of the ion channels in the myometrium: L- and T-type Ca2+ channels, KATP (Kir6) channels, voltage-dependent K channels (Kv4, Kv7, and Kv11), twin-pore domain K channels (TASK, TREK), inward rectifier Kir7.1, Ca2+-activated K+ channels with large (KCNMA1, Slo1), small (KCNN1-3), and intermediate (KCNN4) conductance, Na-activated K channels (Slo2), voltage-gated (SCN) Na+ and Na+ leak channels, nonselective (NALCN) channels, the Na K-ATPase, and hyperpolarization-activated cation channels. We finish by assessing how three key hormones- oxytocin, estrogen, and progesterone-modulate and integrate excitability throughout gestation.
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Affiliation(s)
- Susan Wray
- Department of Women's and Children's Health, University of Liverpool, Liverpool L69 3BX, United Kingdom;
| | - Sarah Arrowsmith
- Department of Women's and Children's Health, University of Liverpool, Liverpool L69 3BX, United Kingdom;
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Peng Y, Zheng X, Fan Z, Zhou H, Zhu X, Wang G, Liu Z. Paeonol alleviates primary dysmenorrhea in mice via activating CB2R in the uterus. PHYTOMEDICINE : INTERNATIONAL JOURNAL OF PHYTOTHERAPY AND PHYTOPHARMACOLOGY 2020; 68:153151. [PMID: 32058234 DOI: 10.1016/j.phymed.2019.153151] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2019] [Revised: 10/18/2019] [Accepted: 12/11/2019] [Indexed: 06/10/2023]
Abstract
BACKGROUND AND PURPOSE Primary dysmenorrhea is the most common gynaecologic problem in menstruating women and is characterized by spasmodic uterine contraction and pain symptoms associated with inflammatory disturbances. Paeonol is an active phytochemical component that has shown anti-inflammatory and analgesic effects in several animal models. The aim of this study was to explore whether paeonol is effective against dysmenorrhea and to investigate the potential mechanism of cannabinoid receptor signalling. EXPERIMENTAL APPROACH Dysmenorrhea was established by injecting oestradiol benzoate into female mice. The effects of paeonol on writhing time and latency, uterine pathology and inflammatory mediators were explored. Isolated uterine smooth muscle was used to evaluate the direct effect of paeonol on uterine contraction. KEY RESULTS The oral administration of paeonol reduced dysmenorrhea pain and PGE2 and TNF-α expression in the uterine tissues of mice, and paeonol was found to be distributed in lesions of the uterus. Paeonol almost completely inhibited oxytocin-, high potassium- and Ca2+-induced contractions in isolated uteri. Antagonists of CB2R (AM630) and the MAPK pathway (U0126), but not of CB1R (AM251), reversed the inhibitory effect of paeonol on uterine contraction. Paeonol significantly blocked L-type Ca2+ channels and calcium influx in uterine smooth muscle cells via CB2R. Molecular docking results showed that paeonol fits well with the binding site of CB2R. CONCLUSIONS AND IMPLICATIONS Paeonol partially acts through CB2R to restrain calcium influx and uterine contraction to alleviate dysmenorrhea in mice. These results suggest that paeonol has therapeutic potential for the treatment of dysmenorrhea.
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Affiliation(s)
- Yi Peng
- State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing, Jiangsu 210029, China
| | - Xiao Zheng
- State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing, Jiangsu 210029, China
| | - Zhiyi Fan
- Department of Pharmacy, Nanjing University of Chinese Medicine Affiliated Hospital, Nanjing, Jiangsu 210029, China
| | - Hongliang Zhou
- Department of Pharmacy, Nanjing University of Chinese Medicine Affiliated Hospital, Nanjing, Jiangsu 210029, China
| | - Xuanxuan Zhu
- Department of Pharmacy, Nanjing University of Chinese Medicine Affiliated Hospital, Nanjing, Jiangsu 210029, China
| | - Guangji Wang
- State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing, Jiangsu 210029, China.
| | - Zhihui Liu
- Department of Pharmacy, Nanjing University of Chinese Medicine Affiliated Hospital, Nanjing, Jiangsu 210029, China.
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Matthew A, Kupittayanant S, Burdyga T, Wray S. Characterization of Contractile Activity and Intracellular Ca2+ Signalling in Mouse Myometrium. ACTA ACUST UNITED AC 2016; 11:207-12. [PMID: 15120693 DOI: 10.1016/j.jsgi.2003.10.009] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
OBJECTIVE To characterize the contractile responses of mouse myometrium, the associated calcium (Ca2+) changes and the role of the sarcoplasmic reticulum (SR), and to better understand excitation contraction coupling in this tissue. METHODS Strips of longitudinal myometrium were used, and Ca2+ was measured after loading with Indo-1. RESULTS Intracellular Ca2+ transients, produced by Ca2+ entry, preceded phasic spontaneous contractions. Depolarization with high potassium concentration significantly increased the amplitude of the contractions and transformed the pattern of activity from phasic to tonic, with accompanying changes in intracellular Ca2+ concentration ([Ca2+]i). Oxytocin significantly stimulated contractile activity and [Ca2+]i above the level occurring spontaneously. Thus all forms of contractile activity were closely correlated with Ca2+. When the SR was emptied using a blocker of the SR calcium-adenosinetriphosphatase, cyclopiazonic acid, spontaneous Ca2+ and force transients increased greatly in frequency and amplitude. Ryanodine, a blocker of Ca(2+)-induced Ca2+ release (CICR), did not impair activity. In the absence of external Ca2+, oxytocin was able to release Ca2+ from the SR through IP3 but produced only a small increase in force, demonstrating a requirement for Ca2+ entry as part of the mechanism of agonist action. CONCLUSION Mouse myometrium, (1) produces contractile activity reflecting changes in [Ca2+]i irrespective of the stimulus, (2) has a significant SR Ca2+ content releasable by agonists but not CICR, (3) has an SR acting to inhibit spontaneous activity, and (4) behaves qualitatively similarly to human and rat myometrium in major aspects of excitation contraction coupling and is therefore a useful model tissue.
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Affiliation(s)
- A Matthew
- Department of Physiology, The University of Liverpool, United Kingdom
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Alotaibi M. The effect of cinnamon extract on isolated rat uterine strips. Reprod Biol 2015; 16:27-33. [PMID: 26952750 DOI: 10.1016/j.repbio.2015.12.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Revised: 11/24/2015] [Accepted: 12/05/2015] [Indexed: 11/13/2022]
Abstract
Cinnamon is a spice used by some populations as a traditional remedy to control blood pressure and thus hypertension. Cinnamon extract decreases contractility in some smooth muscles, but its effect on uterine smooth muscle is unknown. The aim of this study was to determine the physiological and pharmacological effects of cinnamon extract (CE) on the contractions of isolated rat uterine strips and to investigate its possible mechanism of action. Isolated longitudinal uterine strips were dissected from non-pregnant rats, mounted vertically in an organ bath chamber, and exposed to different concentrations of CE (10-20mg/mL). The effect of CE was investigated in the presence of each of the following solutions: 60mM KCl, 5nM oxytocin, and 1μM Bay K8644. CE significantly decreased the force of uterine contraction in a concentration-dependent manner and significantly attenuated the uterine contractions elicited by KCl and oxytocin. In addition, CE significantly decreased the contractile force elicited when L-type Ca(2+) channels were activated by Bay K8644. CE's major mechanism may be inhibition of L-type Ca(2+) channels, which limits calcium influx. These data demonstrate that CE can be a potent tocolytic that can decrease uterine activity regardless of how the force was produced, even when the uterus was stimulated by agonists. As a result, cinnamon may be used to alleviate menstrual pain associated with dysmenorrhoea or prevent unwanted uterine activity in early pregnancy.
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Affiliation(s)
- Mohammed Alotaibi
- Department of Physiology, College of Medicine, King Saud University and King Khalid University Hospital, P.O Box 2925, Riyadh 11461, Saudi Arabia.
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Wray S, Burdyga T, Noble D, Noble K, Borysova L, Arrowsmith S. Progress in understanding electro-mechanical signalling in the myometrium. Acta Physiol (Oxf) 2015; 213:417-31. [PMID: 25439280 DOI: 10.1111/apha.12431] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Revised: 11/11/2014] [Accepted: 11/17/2014] [Indexed: 11/30/2022]
Abstract
In this review, we give a state-of-the-art account of uterine contractility, focussing on excitation-contraction (electro-mechanical) coupling (ECC). This will show how electrophysiological data and intracellular calcium measurements can be related to more modern techniques such as confocal microscopy and molecular biology, to advance our understanding of mechanical output and its modulation in the smooth muscle of the uterus, the myometrium. This new knowledge and understanding, for example concerning the role of the sarcoplasmic reticulum (SR), or stretch-activated K channels, when linked to biochemical and molecular pathways, provides a clearer and better informed basis for the development of new drugs and targets. These are urgently needed to combat dysfunctions in excitation-contraction coupling that are clinically challenging, such as preterm labour, slow to progress labours and post-partum haemorrhage. It remains the case that scientific progress still needs to be made in areas such as pacemaking and understanding interactions between the uterine environment and ion channel activity.
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Affiliation(s)
- S. Wray
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Liverpool Women's Hospital; Liverpool UK
| | - T. Burdyga
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Liverpool Women's Hospital; Liverpool UK
| | - D. Noble
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Liverpool Women's Hospital; Liverpool UK
| | - K. Noble
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Liverpool Women's Hospital; Liverpool UK
| | - L. Borysova
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Liverpool Women's Hospital; Liverpool UK
| | - S. Arrowsmith
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Liverpool Women's Hospital; Liverpool UK
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Sukwan C, Wray S, Kupittayanant S. The effects of Ginseng Java root extract on uterine contractility in nonpregnant rats. Physiol Rep 2014; 2:2/12/e12230. [PMID: 25472610 PMCID: PMC4332211 DOI: 10.14814/phy2.12230] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Ginseng Java or Talinum paniculatum (Jacq.) Geartn has long been used in herbal recipes because of its various therapeutic properties. Ginseng Java is believed to be beneficial to the female reproductive system by inducing lactation and restoring uterine functions after the postpartum period. There are, however, no scientific data on verifying the effects on the uterus to support its therapeutic relevance. Therefore, the purpose of this study was to investigate the effects of Ginseng Java root extract and its possible mechanism(s) of action on uterine contractility. Female virgin rats were humanely killed by CO2 asphyxia and uteri removed. Isometric force was measured in strips of longitudinal myometrium. The effects of Ginseng Java root extract at its IC50 concentration (0.23 mg/mL) on spontaneous, oxytocin‐induced (10 nmol/L), and depolarized (KCl 40 mmol/L) contraction were investigated. After establishing regular phasic contractions, the application of Java root extract significantly inhibited spontaneous uterine contractility (n =5). The extract also significantly inhibited the contraction induced by high KCl solution (n =5) and oxytocin (n =5). The extract also inhibited oxytocin‐induced contraction in the absence of external Ca entry (n =7) and the tonic force induced by oxytocin in the presence of high KCl solution. Taken together, the data demonstrate a potent and consistent ability of extract from Ginseng Java root to reduce myometrial contractility. The tocolytic effects were demonstrated on both spontaneous and agonist‐induced contractions. The fact that force was inhibited in depolarized conditions suggests that the possible mechanisms may be blockade of Ca influx via L‐type Ca channels. The data in Ca‐free solutions suggest that the extract also reduces IP3‐induced Ca release from the internal store. These tocolytic effects do not support the use of ginseng to help with postpartum contractility, but instead suggest it may be helpful in reducing inappropriate uterine contractions, such as in threatened preterm delivery. The data demonstrate a potent and consistent ability of extract from Ginseng Java root to reduce myometrial contractility. The tocolytic effects were demonstrated on both spontaneous and agonist‐induced contractions.
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Affiliation(s)
- Catthareeya Sukwan
- Agricultural Program, Faculty of Science and Technology, Nakhon Ratchasima Rajabhat University, Nakhon Ratchasima, Thailand
| | - Susan Wray
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, U.K
| | - Sajeera Kupittayanant
- School of Physiology, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima, Thailand
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Loftus FC, Shmygol A, Richardson MJE. Fine spatiotemporal activity in contracting myometrium revealed by motion-corrected calcium imaging. J Physiol 2014; 592:4447-63. [PMID: 25085893 PMCID: PMC4280886 DOI: 10.1113/jphysiol.2014.275412] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Successful childbirth depends on the occurrence of precisely coordinated uterine contractions during labour. Calcium indicator fluorescence imaging is one of the main techniques for investigating the mechanisms governing this physiological process and its pathologies. The effective spatiotemporal resolution of calcium signals is, however, limited by the motion of contracting tissue: structures of interest in the order of microns can move over a hundred times their width during a contraction. The simultaneous changes in local intensity and tissue configuration make motion tracking a non-trivial problem in image analysis and confound many of the standard techniques. This paper presents a method that tracks local motion throughout the tissue and allows for the almost complete removal of motion artefacts. This provides a stabilized calcium signal down to a pixel resolution, which, for the data examined, is in the order of a few microns. As a byproduct of image stabilization, a complete kinematic description of the contraction–relaxation cycle is also obtained. This contains novel information about the mechanical response of the tissue, such as the identification of a characteristic length scale, in the order of 40–50 μm, below which tissue motion is homogeneous. Applied to our data, we illustrate that the method allows for analyses of calcium dynamics in contracting myometrium in unprecedented spatiotemporal detail. Additionally, we use the kinematics of tissue motion to compare calcium signals at the subcellular level and local contractile motion. The computer code used is provided in a freely modifiable form and has potential applicability to in vivo calcium imaging of neural tissue, as well as other smooth muscle tissue.
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Affiliation(s)
- Fiona C Loftus
- Warwick Systems Biology Centre, University of Warwick, Coventry, UK Division of Translational and Systems Medicine, Warwick Medical School, University of Warwick, Coventry, UK Warwick Systems Biology Doctoral Training Centre, University of Warwick, Coventry, UK
| | - Anatoly Shmygol
- Division of Translational and Systems Medicine, Warwick Medical School, University of Warwick, Coventry, UK
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Pehlivanoğlu B, Bayrak S, Doğan M. A close look at the contraction and relaxation of the myometrium; the role of calcium. J Turk Ger Gynecol Assoc 2013; 14:230-4. [PMID: 24592112 DOI: 10.5152/jtgga.2013.67763] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Accepted: 08/12/2013] [Indexed: 11/22/2022] Open
Abstract
The function and regulation of the myometrium, especially during pregnancy, labour and birth are important in reproductive physiology. It is crucial to understand the mechanisms that generate and modulate uterine contractility in order to be able to prevent and/or treat the problems related with the myometrium. A limited understanding of the cellular and molecular events underlying these phenomena complicates the situation. Various agonists, hormones, transmitters and/or chemicals are related to the regulation of the functions of the myometrium. Although notable advances regarding the key steps in receptor signalling explaining the actions of these factors have been achieved, a good deal of information is still necessary to understand this vital process. A better comprehension of myometrium physiology and the translation of research findings to clinical settings will help progress in women's health. In this review, we attempt to present a critical overview of myometrial functions and focus specifically on the role of calcium.
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Affiliation(s)
- Bilge Pehlivanoğlu
- Department of Physiology, Hacettepe University Faculty of Medicine, Ankara, Turkey
| | - Sibel Bayrak
- Department of Physiology, Hacettepe University Faculty of Medicine, Ankara, Turkey
| | - Murat Doğan
- Department of Physiology, Hacettepe University Faculty of Medicine, Ankara, Turkey
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Lecarpentier ER, Claes VA, Timbely O, Arsalane A, Wipff JA, Hébert JLM, Michel FY, Lecarpentier YC. Mechanics and energetics of myosin molecular motors from nonpregnant human myometrium. J Appl Physiol (1985) 2011; 111:1096-105. [PMID: 21778420 DOI: 10.1152/japplphysiol.00414.2011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mechanical properties of spontaneously contracting isolated nonpregnant human myometrium (NPHM) were investigated throughout the whole continuum of load from zero load up to isometry. This made it possible to assess the three-dimensional tension-velocity-length (T-V-L) relationship characterizing the level of contractility and to determine crossbridge (CB) kinetics of myosin molecular motors. Seventy-seven muscle strips were obtained from hysterectomy in 42 nonpregnant patients. Contraction and relaxation parameters were measured during spontaneous mechanical activity. The isotonic tension-peak velocity (T-V) relationship was hyperbolic in 30 cases and nonhyperbolic in 47 cases. When the T-V relationship was hyperbolic, the Huxley formalism could be used to calculate CB kinetics and CB unitary force. At the whole muscle level and for a given isotonic load level, part of the V-L phase plane showed a common pathway, so that a given instantaneous length corresponded to only one possible instantaneous velocity, independent of time and initial length. At the molecular level, rate constants for CB attachment and detachment were dramatically low, ∼100 times lower than those of striated muscles, and ∼5 to 10 times lower than those of other smooth muscles. The CB unitary force was ∼1.4 ± 0.1 pN. NPHM shared similar basic contractile properties with striated muscles, reflected in the three-dimensional T-V-L relationship characterizing the contractile level. Low CB attachment and detachment rate constants made it possible to generate normal CB unitary force and normal muscle tension in NPHM, even though it contracted extremely slowly compared with other muscles.
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Abstract
The sarcoplasmic reticulum (SR) of smooth muscles presents many intriguing facets and questions concerning its roles, especially as these change with development, disease, and modulation of physiological activity. The SR's function was originally perceived to be synthetic and then that of a Ca store for the contractile proteins, acting as a Ca amplification mechanism as it does in striated muscles. Gradually, as investigators have struggled to find a convincing role for Ca-induced Ca release in many smooth muscles, a role in controlling excitability has emerged. This is the Ca spark/spontaneous transient outward current coupling mechanism which reduces excitability and limits contraction. Release of SR Ca occurs in response to inositol 1,4,5-trisphosphate, Ca, and nicotinic acid adenine dinucleotide phosphate, and depletion of SR Ca can initiate Ca entry, the mechanism of which is being investigated but seems to involve Stim and Orai as found in nonexcitable cells. The contribution of the elemental Ca signals from the SR, sparks and puffs, to global Ca signals, i.e., Ca waves and oscillations, is becoming clearer but is far from established. The dynamics of SR Ca release and uptake mechanisms are reviewed along with the control of luminal Ca. We review the growing list of the SR's functions that still includes Ca storage, contraction, and relaxation but has been expanded to encompass Ca homeostasis, generating local and global Ca signals, and contributing to cellular microdomains and signaling in other organelles, including mitochondria, lysosomes, and the nucleus. For an integrated approach, a review of aspects of the SR in health and disease and during development and aging are also included. While the sheer versatility of smooth muscle makes it foolish to have a "one model fits all" approach to this subject, we have tried to synthesize conclusions wherever possible.
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Affiliation(s)
- Susan Wray
- Department of Physiology, School of Biomedical Sciences, University of Liverpool, Liverpool, Merseyside L69 3BX, United Kingdom.
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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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Burdyga T, Borisova L, Burdyga AT, Wray S. Temporal and spatial variations in spontaneous Ca events and mechanical activity in pregnant rat myometrium. Eur J Obstet Gynecol Reprod Biol 2009; 144 Suppl 1:S25-32. [PMID: 19282086 DOI: 10.1016/j.ejogrb.2009.02.017] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
OBJECTIVES The aim of this study was to investigate the temporal and spatial characteristics of spontaneous Ca signals in pregnant rat myometrium. STUDY DESIGN Confocal imaging of longitudinal strips of 21-day pregnant rats loaded with the Ca sensitive indicator Fluo-4, was combined with measurements of mechanical activity in uterine smooth muscle cells, in situ and freshly isolated. RESULTS Our results show that the Ca transients in pregnant uterine tissue are composed of Ca spikes, which are associated with the spike-like action potentials. There is large variation in the pattern of spontaneous activity in myometrium, ranging from non-propagating Ca spikes confined to individual smooth muscle cells, through to regional and global propagating Ca spikes. Irrespective of the pattern of activity displayed, the Ca signals were always in the form of Ca spikes, singularly or in bursts. These Ca spikes did not show fixed initiations sites, propagated in longitudinal and transverse directions from the initiation regions, and had a variable pattern of propagation in preparations which were not synchronously active. In preparations which showed synchronous activity, Ca spikes singularly or bursts propagated mainly in the transverse direction from the initiation regions. The amplitude of force generated by single spikes was dependent on the number of bundles recruited by the propagating Ca spike within the strip, and was about 30-40% of the maximal force produced by carbachol or high-K stimulation. If Ca spikes appeared in the form of bursts they generated longer lasting fused contractions, the amplitudes of which were dependent on the number and the frequency of Ca spikes in the burst. CONCLUSIONS Longitudinal myometrium from pregnant rats generates spontaneous Ca spikes which vary in their initiation sites, spatial spread and frequency and are associated with the spike-like action potentials. They are sensitive to the L-type Ca channel blocker, nifedipine. Contractile activity was dependent on the spatial spread of individual Ca spikes and when fully synchronized, produced single submaximal phasic contraction. The number and frequency of bursts of Ca spikes controlled the amplitude and duration of contraction.
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Affiliation(s)
- Theodor Burdyga
- Department of Physiology, School of Biomedical Sciences, University of Liverpool, Crown Street, Liverpool L693BX, UK.
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Noble K, Matthew A, Burdyga T, Wray S. A review of recent insights into the role of the sarcoplasmic reticulum and Ca entry in uterine smooth muscle. Eur J Obstet Gynecol Reprod Biol 2009; 144 Suppl 1:S11-9. [PMID: 19285773 DOI: 10.1016/j.ejogrb.2009.02.010] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The uterine sacroplasmic reticulum (SR) takes up and stores calcium [Ca], using an ATPase (SERCA) and the Ca-buffering proteins, calsequestrin and calreticulin. This stored Ca can be released via IP(3)-gated Ca channels. Decreases in luminal Ca concentration [Ca] have been directly measured following agonist stimulation. During spontaneous contractions however, there appears to be no involvement of the SR, as Ca entry and efflux across the plasma membrane account for these phasic contractions. After over-viewing current knowledge concerning SR structure and function, we highlight three areas of research which suggest new ways of looking at the role of the SR in the uterus, although they may be controversial or speculative at the moment. Firstly, we review the evidence for the function, if any, of Ca-induced SR Ca release channels, the ryanodine receptor (RyR) and the lack of Ca sparks (the elemental release events from RyRs), in the uterus. Secondly, we ask does regulation of SERCA by the accessory protein, phospholamban, occur in the uterus and what is the effect of knocking out phospholamban on uterine activity? Thirdly, we address the question of when and how store-operated Ca entry occurs in the myometrium. By analogy with other, usually less excitable tissues, is there a mechanism that links store Ca depletion to plasma membrane Ca entry in smooth muscle cells within intact uterus and is it physiologically relevant and regulated? Are the recently described proteins ORAI and STIM-1 involved in uterine store-operated Ca entry? We end the review by integrating these new insights with previous data to present a new working model of the SR in the uterus.
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Affiliation(s)
- Karen Noble
- Department of Physiology, School of Biomedical Sciences, University of Liverpool, Crown Street, Liverpool L693BX, UK
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Camello-Almaraz C, Macias B, Gomez-Pinilla PJ, Alcon S, Martin-Cano FE, Baba A, Matsuda T, Camello PJ, Pozo MJ. Developmental changes in Ca2+ homeostasis and contractility in gallbladder smooth muscle. Am J Physiol Cell Physiol 2009; 296:C783-91. [PMID: 19211915 DOI: 10.1152/ajpcell.00452.2008] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Relatively little is known about the contribution of Ca(2+)-dependent and -independent mechanisms in the contractility of neonatal gastrointestinal smooth muscle. We therefore studied Ca(2+) homeostasis and Ca(2+) sensitization mechanisms in 10-day-old and adult guinea pig gallbladder smooth muscle to elucidate developmental changes in these processes. Gallbladder contractility was evaluated by isometrical tension recordings from strips, intracellular Ca(2+) concentration was estimated by epifluorescence microscopy of fura-2-loaded isolated cells, and protein expression and phosphorylation were assessed by Western blot analysis. The neonatal gallbladder contracted significantly less to CCK than adult tissue, but this correlated with an increased Ca(2+) mobilization, suggesting immaturity of Ca(2+) sensitization mechanisms. The enhanced Ca(2+) release in the newborn gallbladder was the result of the increase in the size of the releasable Ca(2+) pool. Moreover, in neonatal smooth muscle cells, neither the plasma membrane Ca(2+) pump nor the Na(+)/Ca(2+) exchanger collaborate in the extrusion of Ca(2+). In contrast, in these cells, there is an increase in phospholamban phosphorylation, which could drive to an overactivity of the sarco(endo)plasmic reticulum Ca(2+)-ATPase pump. The reduced Ca(2+) sensitivity in neonatal tissues was demonstrated by the lack of effect to Y-27362, an inhibitor of Rho kinase (ROCK), and GF-109203X, an inhibitor of PKC, on agonist-induced contraction. In addition, the neonatal gallbladder showed lower levels of RhoA, ROCK, PKC, and two effectors [C-kinase-dependent inhibitor of 17 kDa (CPI-17) and myosin phosphatase targetting 1 (MYPT1)] as well as an absence of CPI-17 and MYPT1 phosphorylation in response to agonists. In conclusion, our results indicate that the main mechanisms involved in smooth muscle contractility are under developmental regulation.
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Wray S, Burdyga T, Noble K. Calcium signalling in smooth muscle. Cell Calcium 2008; 38:397-407. [PMID: 16137762 DOI: 10.1016/j.ceca.2005.06.018] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2005] [Accepted: 06/28/2005] [Indexed: 11/26/2022]
Abstract
Calcium signalling in smooth muscles is complex, but our understanding of it has increased markedly in recent years. Thus, progress has been made in relating global Ca2+ signals to changes in force in smooth muscles and understanding the biochemical and molecular mechanisms involved in Ca2+ sensitization, i.e. altering the relation between Ca2+ and force. Attention is now focussed more on the role of the internal Ca2+ store, the sarcoplasmic reticulum (SR), global Ca2+ signals and control of excitability. Modern imaging techniques have shown the elaborate SR network in smooth muscles, along with the expression of IP3 and ryanodine receptors. The role and cross-talk between these two Ca(2+) release mechanisms, as well as possible compartmentalization of the SR Ca2+ store are discussed. The close proximity between SR and surface membrane has long been known but the details of this special region to Ca2+ signalling and the role of local sub-membrane Ca2+ concentrations and membrane microdomains are only now emerging. The activation of K+ and Cl- channels by local Ca2+ signals, can have profound effects on excitability and hence contraction. We examine the evidence for both Ca2+ sparks and puffs in controlling ion channel activity, as well as a fundamental role for Ca2+ sparks in governing the period of inexcitability in smooth muscle, i.e. the refractory period. Finally, the relation between different Ca2+ signals, e.g. sparks, waves and transients, to smooth muscle activity in health and disease is becoming clearer and will be discussed.
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Affiliation(s)
- Susan Wray
- Department of Physiology, The University of Liverpool, Liverpool L69 3BX, UK.
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Wray S, Noble K. Sex hormones and excitation-contraction coupling in the uterus: the effects of oestrous and hormones. J Neuroendocrinol 2008; 20:451-61. [PMID: 18266942 DOI: 10.1111/j.1365-2826.2008.01665.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In this review, we examine how far the increased understanding that we have of the events in excitation contraction can explain the effects of the oestrous cycle and sex hormones on uterine function. Observational studies of electrical and mechanical activity in the rat myometrium have shown a relative quiescence during pro-oestrous, with little propagation of any electrical events. Thus, uterine activity can be said to approximately inversely reflect plasma 17beta-oestradiol concentrations. We show that Ca(2+) signalling and mechanical activity are greatest in metoestrous and dioestrous compared to pro-oestrous and oestrous. These data are discussed in terms of hormonal effects on Ca(2+) and K(+) channels. Finally, the influence of sex hormones on lipid rafts and caveolae are considered and discussed in relation to recent findings on their role in uterine signalling and contractility, and cholesterol levels and obesity.
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Affiliation(s)
- S Wray
- The Physiological Department, School of Biomedical Sciences, University of Liverpool, Liverpool, UK.
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Abstract
A better understanding of the mechanisms that generate and modulate uterine contractility is needed if progress is to be made in the prevention or treatment of problems in labour. Dysfunctional labour describes the condition when uterine contractility is too poor to dilate the cervix, and it is the leading cause of emergency Caesarean sections. Recently, insight has been gained into a possible causal mechanism for dysfunctional labour. Study of the physiological mechanisms that produce excitation in the uterus, the subsequent Ca(2)(+) signals and biochemical pathway leading to contraction has underpinned this progress. In this review, I give an account of excitation-contraction signalling in the myometrium and explore the implications of recent findings concerning lipid rafts for these processes. I also discuss how changes of pH are fundamentally enmeshed in uterine activity and biochemistry and explore the effect that pH changes will have on human myometrium. Finally, I present the evidence that acidification of the myometrium is correlated with dysfunctional labour and suggest the processes by which it is occurring. It is only by gaining a better understanding of uterine physiology and pathophysiology that progress will be made and research findings translated into clinical benefit for women and their families.
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Affiliation(s)
- Susan Wray
- Department of Physiology, University of Liverpool, Crown Street, Liverpool L69 3BX, UK.
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Wray S, Shmygol A. Role of the calcium store in uterine contractility. Semin Cell Dev Biol 2007; 18:315-20. [PMID: 17601757 DOI: 10.1016/j.semcdb.2007.05.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2007] [Accepted: 05/03/2007] [Indexed: 11/19/2022]
Abstract
This article assesses the nature of the sarcoplasmic reticulum (SR) in uterine smooth muscle. Modern imagining techniques have revealed new information about the location and density of Ca storage and release. Release mechanisms, including IP(3) and Ca itself, via ryanodine receptors (RyR), as well as possible roles for cyclic ADP ribose, and the contribution of the SR to relaxation are detailed. The role of the SR Ca-ATPase in both decay of the Ca transient and maintaining Ca homeostasis is reviewed. Recent data on the role of local Ca signals from the SR in contributing to membrane excitability and contractility are discussed, along with interactions with ion channels in lipid microdomains.
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Affiliation(s)
- Susan Wray
- University of Liverpool, Department of Physiology, Crown Street, Liverpool L69 3BX, United Kingdom.
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Burdyga T, Wray S, Noble K. In Situ Calcium Signaling: No Calcium Sparks Detected in Rat Myometrium. Ann N Y Acad Sci 2007; 1101:85-96. [PMID: 17303831 DOI: 10.1196/annals.1389.002] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Controlled uterine smooth muscle activity is essential for our reproductive health. While we understand reasonably well the steps that produce contraction following a rise in intracellular [Ca], the mechanism controlling excitability and thus the rise of Ca, is less well understood. Here we examine the role of the internal Ca sore, the sarcoplasmic reticulum (SR), and its relation to surface membrane ion channels. We show that despite having a well-developed SR, the rat uterus does not produce the elemental and local Ca signals, known as Ca sparks. This in turn has consequences for excitability, as the negative feedback loop between these Ca signals and Ca-activated K (BK) channels on the surface membrane is lost. This may be important for producing the powerful long-lasting contractions of the uterus required during labor.
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Affiliation(s)
- Theodor Burdyga
- Department of Physiology, The University of Liverpool, Crown Street, Liverpool, L69 3BX, UK.
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Noble K, Zhang J, Wray S. Lipid rafts, the sarcoplasmic reticulum and uterine calcium signalling: an integrated approach. J Physiol 2005; 570:29-35. [PMID: 16239270 PMCID: PMC1464295 DOI: 10.1113/jphysiol.2005.098475] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The pathways involved in Ca2+ signalling in the uterus remain incompletely understood, impairing our ability to prevent preterm and difficult labours. In this review we focus on two elements in the pathway of Ca2+ signalling that have recently emerged as playing important roles: membrane lipid rafts and the sarcoplasmic reticulum. We examine the evidence for lipid rafts in the uterus and discuss their functional role. We suggest that the increases in cytosolic [Ca2+] and contractility that occur with raft disruption are due, at least in part, to effects on large conductance Ca2+-activated K+ (BK) channels that are localized to rafts. The role of the SR in contributing to subsarcolemmal cytosolic microdomains in uterus is evaluated, along with its interactions with ion channels on the plasma membrane. Thus, signalling microdomains play an important, but incompletely understood, role in the uterus, and integrating them into other Ca2+ signalling pathways is a challenge for further research. We suggest that the role of the SR changes in pregnancy, from promoting quiescence via BK channels or SR Ca2+ uptake, to promoting Ca2+ entry and contractility at term, and relate data on lipid rafts to clinical outcome in obese pregnant women.
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Affiliation(s)
- Karen Noble
- Department of Physiology, University of Liverpool, Crown Street, Liverpool, L69 3BX, UK
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