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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] [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, Ca 2+ 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 Ca 2+ 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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Monteil A, Guérineau NC, Gil-Nagel A, Parra-Diaz P, Lory P, Senatore A. New insights into the physiology and pathophysiology of the atypical sodium leak channel NALCN. Physiol Rev 2024; 104:399-472. [PMID: 37615954 DOI: 10.1152/physrev.00014.2022] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Revised: 07/13/2023] [Accepted: 08/15/2023] [Indexed: 08/25/2023] Open
Abstract
Cell excitability and its modulation by hormones and neurotransmitters involve the concerted action of a large repertoire of membrane proteins, especially ion channels. Unique complements of coexpressed ion channels are exquisitely balanced against each other in different excitable cell types, establishing distinct electrical properties that are tailored for diverse physiological contributions, and dysfunction of any component may induce a disease state. A crucial parameter controlling cell excitability is the resting membrane potential (RMP) set by extra- and intracellular concentrations of ions, mainly Na+, K+, and Cl-, and their passive permeation across the cell membrane through leak ion channels. Indeed, dysregulation of RMP causes significant effects on cellular excitability. This review describes the molecular and physiological properties of the Na+ leak channel NALCN, which associates with its accessory subunits UNC-79, UNC-80, and NLF-1/FAM155 to conduct depolarizing background Na+ currents in various excitable cell types, especially neurons. Studies of animal models clearly demonstrate that NALCN contributes to fundamental physiological processes in the nervous system including the control of respiratory rhythm, circadian rhythm, sleep, and locomotor behavior. Furthermore, dysfunction of NALCN and its subunits is associated with severe pathological states in humans. The critical involvement of NALCN in physiology is now well established, but its study has been hampered by the lack of specific drugs that can block or agonize NALCN currents in vitro and in vivo. Molecular tools and animal models are now available to accelerate our understanding of how NALCN contributes to key physiological functions and the development of novel therapies for NALCN channelopathies.
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Affiliation(s)
- Arnaud Monteil
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
- LabEx "Ion Channel Science and Therapeutics," Montpellier, France
- Department of Physiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
| | - Nathalie C Guérineau
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
- LabEx "Ion Channel Science and Therapeutics," Montpellier, France
| | - Antonio Gil-Nagel
- Department of Neurology, Epilepsy Program, Hospital Ruber Internacional, Madrid, Spain
| | - Paloma Parra-Diaz
- Department of Neurology, Epilepsy Program, Hospital Ruber Internacional, Madrid, Spain
| | - Philippe Lory
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
- LabEx "Ion Channel Science and Therapeutics," Montpellier, France
| | - Adriano Senatore
- Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada
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Zangeneh FZ, Hantoushzadeh S. The physiological basis with uterine myometrium contractions from electro-mechanical/hormonal myofibril function to the term and preterm labor. Heliyon 2023; 9:e22259. [PMID: 38034762 PMCID: PMC10687101 DOI: 10.1016/j.heliyon.2023.e22259] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Revised: 11/07/2023] [Accepted: 11/07/2023] [Indexed: 12/02/2023] Open
Abstract
Background Most labor-related problems can be attributed to the uterine myometrium muscle, as this irritable tissue must suppress its irritability potential during pregnancy. Unfortunately, fewer studies have investigated the causes of this lack of suppression in preterm labor. Methods We conducted a scoping narrative review using three online databases (PubMed, Scopus, and Science Direct). Results The review focused on ion channel functions in the myometrium, including sodium channels [Na K-ATPase, Na-activated K channels (Slo2), voltage-gated (SCN) Na+, Na+ leaky channels, nonselective (NALCN) channels], potassium 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), intermediate (KCNN4) conductance], and calcium channels [L-Type and T-type Ca2+ channels, calcium-activated chloride channels (CaCC)], as well as hyperpolarization-activated cation channels. These channels' functions are associated with hormonal effects such as oxytocin, estrogen/progesterone, and local prostaglandins. Conclusion Electromechanical/hormonal activity and environmental autocrine factors can serve as the primary practical basis for premature uterine contractions in term/preterm labor. Our findings highlight the significance of.1.the amplitude rate of hyperpolarization and the frequency of contractions,2.changes in the estrogen/progesterone ratio,3.Prostaglandins E/F involvement in initiating potential spikes and the increase of intracytoplasmic Ca2+.This narrative study highlights the range of hyperpolarization and the frequency of myometrium contractions as crucial factors. The synchronized complex progress of estrogen to progesterone ratio and prostaglandins plays a significant role in initiating potential spikes and increasing intracytoplasmic Ca2+, which further influences the contraction process during labor. Insights into myometrium physiology gained from this study may pave the way for much-needed new treatments to reduce problems associated with normal and preterm labor.
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Affiliation(s)
- Farideh Zafari Zangeneh
- Vali-E-Asr Reproductive Health Research Center, Family Health Research Institute, Imam Khomeini Hospital, Tehran University of Medical Sciences, Tehran, Iran
| | - Sedighe Hantoushzadeh
- Department of Fetal-Maternal Medicine, Tehran University of Medical Sciences, Imam Khomeini Hospital, Tehran, Iran
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Arrowsmith S. Multiple pregnancies, the myometrium and the role of mechanical factors in the timing of labour. Curr Res Physiol 2023; 6:100105. [PMID: 38107788 PMCID: PMC10724211 DOI: 10.1016/j.crphys.2023.100105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 07/17/2023] [Accepted: 08/23/2023] [Indexed: 12/19/2023] Open
Abstract
Multiple pregnancy remains a relatively common occurrence, but it is associated with increased risks of adverse outcomes for the mother and her babies and presents unique challenges to healthcare providers. This review will briefly discuss multiple pregnancies, their aetiology and their problems, including preterm birth, before reviewing the processes leading to normal labour onset and how they may be different in a multiple pregnancy. The mechanisms by which mechanical factors i.e., uterine distension or 'stretch' contribute to uterine excitability and the timing of labour onset will be the major focus, and how over distention may pre-dispose multiple pregnancies to preterm birth. This includes current thinking around the role of mechano (stretch) sensitive ion channels in the myometrium and changes to other important regulators of excitability and contraction which have been identified from studies using in vitro and in vivo models of uterine stretch. Physiological stimuli arising from the fetus(es) and placenta(s) will also be discussed. In reviewing what we know about the myometrium in multiple pregnancy in humans, the focus will be on twin pregnancy as it is the most common type of multiple pregnancy and has been the most studied.
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Affiliation(s)
- Sarah Arrowsmith
- Department of Life Sciences, Manchester Metropolitan University, John Dalton Building, Chester Street, Manchester, M1 5GD, UK
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Wray S, Prendergast C, Arrowsmith S. Calcium-Activated Chloride Channels in Myometrial and Vascular Smooth Muscle. Front Physiol 2021; 12:751008. [PMID: 34867456 PMCID: PMC8637852 DOI: 10.3389/fphys.2021.751008] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Accepted: 09/24/2021] [Indexed: 11/24/2022] Open
Abstract
In smooth muscle tissues, calcium-activated chloride channels (CaCC) provide the major anionic channel. Opening of these channels leads to chloride efflux and depolarization of the myocyte membrane. In this way, activation of the channels by a rise of intracellular [Ca2+], from a variety of sources, produces increased excitability and can initiate action potentials and contraction or increased tone. We now have a good mechanistic understanding of how the channels are activated and regulated, due to identification of TMEM16A (ANO1) as the molecular entity of the channel, but key questions remain. In reviewing these channels and comparing two distinct smooth muscles, myometrial and vascular, we expose the differences that occur in their activation mechanisms, properties, and control. We find that the myometrium only expresses “classical,” Ca2+-activated, and voltage sensitive channels, whereas both tonic and phasic blood vessels express classical, and non-classical, cGMP-regulated CaCC, which are voltage insensitive. This translates to more complex activation and regulation in vascular smooth muscles, irrespective of whether they are tonic or phasic. We therefore tentatively conclude that although these channels are expressed and functionally important in all smooth muscles, they are probably not part of the mechanisms governing phasic activity. Recent knockdown studies have produced unexpected functional results, e.g. no effects on labour and delivery, and tone increasing in some but decreasing in other vascular beds, strongly suggesting that there is still much to be explored concerning CaCC in smooth muscle.
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Affiliation(s)
- Susan Wray
- Department of Women and Children's Health, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, United Kingdom
| | - Clodagh Prendergast
- Department of Women and Children's Health, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, United Kingdom
| | - Sarah Arrowsmith
- Department of Life Sciences, Manchester Metropolitan University, Manchester, United Kingdom
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Ferreira JJ, Amazu C, Puga-Molina LC, Ma X, England SK, Santi CM. SLO2.1/NALCN a sodium signaling complex that regulates uterine activity. iScience 2021; 24:103210. [PMID: 34746693 PMCID: PMC8551532 DOI: 10.1016/j.isci.2021.103210] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 07/29/2021] [Accepted: 09/29/2021] [Indexed: 01/05/2023] Open
Abstract
Depolarization of the myometrial smooth muscle cell (MSMC) resting membrane potential is necessary for the uterus to transition from a quiescent state to a contractile state. The molecular mechanisms involved in this transition are not completely understood. Here, we report that a coupled system between the Na+-activated K+ channel (SLO2.1) and the non-selective Na+ leak channel (NALCN) determines the MSMC membrane potential. Our data indicate that Na+ entering through NALCN acts as an intracellular signaling molecule that activates SLO2.1. Potassium efflux through SLO2.1 hyperpolarizes the membrane. A decrease in SLO2.1/NALCN activity induces membrane depolarization, triggering Ca2+ entry through voltage-dependent Ca2+ channels and promoting contraction. Consistent with functional coupling, our data show that NALCN and SLO2.1 are in close proximity in human MSMCs. We propose that these arrangements of SLO2.1 and NALCN permit these channels to functionally regulate MSMC membrane potential and cell excitability and modulate uterine contractility.
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Affiliation(s)
- Juan J. Ferreira
- 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
- Department of Neuroscience, Washington University in St. Louis, School of Medicine, 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
| | - Lis C. Puga-Molina
- 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
| | - 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
- Department of Neuroscience, Washington University in St. Louis, School of Medicine, St. Louis, MO 63110, USA
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Dodds KN, Travis L, Beckett EAH, Spencer NJ. Identification of a novel distension-evoked motility pattern in the mouse uterus. Am J Physiol Regul Integr Comp Physiol 2021; 321:R317-R327. [PMID: 34287078 DOI: 10.1152/ajpregu.00327.2020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The dynamic changes in uterine contractility in response to distension are incompletely understood. Rhythmic, propagating contractions of nonpregnant uterine smooth muscle occur in the absence of nerve activity (i.e., myogenic), events that decline during pregnancy and reemerge at parturition. We therefore sought to determine how myogenic contractions of the nonpregnant uterus are affected by distension, which might provide mechanistic clues underlying distension-associated uterine conditions such as preterm birth. Uteri isolated from nulliparous adult female mice in proestrus were video imaged to generate spatiotemporal maps, and myoelectrical activity simultaneously recorded using extracellular suction electrodes. Motility patterns were examined under basal conditions and following ramped intraluminal distension with fluid to 5 and 10 cmH2O. Intraluminal distension caused pressure-dependent changes in the frequency, amplitude, propagation speed, and directionality of uterine contractions, which reversed upon pressure release. Altered burst durations of underlying smooth muscle myoelectric events were concurrently observed, although action potential spike intervals were unchanged. Voltage-gated sodium channel blockade [tetrodotoxin (TTX); 0.6 µM] attenuated both the amplitude of contractions and burst duration of action potentials, whereas all activity was abolished by L-type calcium channel blockade (nifedipine; 1 µM). These data suggest that myogenic motility patterns of the nonpregnant mouse uterus are sensitive to changes in intraluminal pressure and, at high pressures, may be modulated by voltage-gated sodium channel activity. Future studies may investigate whether similar distension-evoked changes occur in the pregnant uterus and the possible pathophysiological role of such activity in the development of preterm birth.
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Affiliation(s)
- Kelsi N Dodds
- College of Medicine & Public Health, Flinders Health & Medical Research Institute, Flinders University of South Australia, Bedford Park, South Australia, Australia
| | - Lee Travis
- College of Medicine & Public Health, Flinders Health & Medical Research Institute, Flinders University of South Australia, Bedford Park, South Australia, Australia
| | - Elizabeth A H Beckett
- Discipline of Physiology, Adelaide Medical School, The University of Adelaide, Adelaide, South Australia, Australia
| | - Nick J Spencer
- College of Medicine & Public Health, Flinders Health & Medical Research Institute, Flinders University of South Australia, Bedford Park, South Australia, Australia
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Malik M, Roh M, England SK. Uterine contractions in rodent models and humans. Acta Physiol (Oxf) 2021; 231:e13607. [PMID: 33337577 PMCID: PMC8047897 DOI: 10.1111/apha.13607] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 12/07/2020] [Accepted: 12/11/2020] [Indexed: 12/18/2022]
Abstract
Aberrant uterine contractions can lead to preterm birth and other labour complications and are a significant cause of maternal morbidity and mortality. To investigate the mechanisms underlying dysfunctional uterine contractions, researchers have used experimentally tractable small animal models. However, biological differences between humans and rodents change how researchers select their animal model and interpret their results. Here, we provide a general review of studies of uterine excitation and contractions in mice, rats, guinea pigs, and humans, in an effort to introduce new researchers to the field and help in the design and interpretation of experiments in rodent models.
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Affiliation(s)
- Manasi Malik
- Center for Reproductive Health Sciences Department of Obstetrics and Gynecology Washington University School of Medicine St. Louis MO USA
| | - Michelle Roh
- Center for Reproductive Health Sciences Department of Obstetrics and Gynecology Washington University School of Medicine St. Louis MO USA
| | - Sarah K. England
- Center for Reproductive Health Sciences Department of Obstetrics and Gynecology Washington University School of Medicine St. Louis MO USA
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9
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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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10
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Kuijsters NPM, Sammali F, Ye X, Blank C, Xu L, Mischi M, Schoot BC, Rabotti C. Propagation of spontaneous electrical activity in the ex vivo human uterus. Pflugers Arch 2020; 472:1065-1078. [PMID: 32691139 PMCID: PMC7376519 DOI: 10.1007/s00424-020-02426-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2020] [Revised: 05/21/2020] [Accepted: 06/26/2020] [Indexed: 12/18/2022]
Abstract
Contractions of the non-pregnant uterus play a key role in fertility. Yet, the electrophysiology underlying these contractions is poorly understood. In this paper, we investigate the presence of uterine electrical activity and characterize its propagation in unstimulated ex vivo human uteri. Multichannel electrohysterographic measurements were performed in five freshly resected human uteri starting immediately after hysterectomy. Using an electrode grid externally and an electrode array internally, measurements were performed up to 24 h after hysterectomy and compared with control. Up to 2 h after hysterectomy, we measured biopotentials in all included uteri. The median root mean squared (RMS) values of the external measurements ranged between 3.95 μV (interquartile range (IQR) 2.41–14.18 μV) and 39.4 μV (interquartile range (IQR) 10.84–105.64 μV) and were all significantly higher than control (median RMS of 1.69 μV, IQR 1.13–3.11 μV), consisting of chicken breast meat. The RMS values decreased significantly over time. After 24 h, the median RMS (1.27 μV, IQR 0.86–3.04 μV) was comparable with the control (1.69 μV, IQR 1.13–3.11 μV, p = 0.125). The internal measurements showed a comparable pattern over time, but overall lower amplitude. The measured biopotentials propagated over the uterine surface, following both a plane-wave as well as an erratic pattern. No clear pacemaker location nor a preferred propagation direction could be identified. These results show that ex vivo uteri can spontaneously generate propagating biopotentials and provide novel insight contributing to improving our understanding of the electrophysiology of the human non-pregnant uterus.
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Affiliation(s)
- Nienke P M Kuijsters
- Department of Electrical Engineering (Signal Processing Systems: Biomedical Diagnostics), Eindhoven Technical University, Post box 513, 5600 MB, Eindhoven, the Netherlands. .,Department of Obstetrics and Gynaecology, Catharina Hospital, Michelangelolaan 2, 5623 EJ, Eindhoven, the Netherlands.
| | - Federica Sammali
- Department of Electrical Engineering (Signal Processing Systems: Biomedical Diagnostics), Eindhoven Technical University, Post box 513, 5600 MB, Eindhoven, the Netherlands
| | - Xin Ye
- Department of Electrical Engineering (Signal Processing Systems: Biomedical Diagnostics), Eindhoven Technical University, Post box 513, 5600 MB, Eindhoven, the Netherlands
| | - Celine Blank
- Department of Electrical Engineering (Signal Processing Systems: Biomedical Diagnostics), Eindhoven Technical University, Post box 513, 5600 MB, Eindhoven, the Netherlands.,Department of Obstetrics and Gynaecology, University Hospital (UZ) Gent, C. Heymanslaan 10, 9000, Ghent, Belgium
| | - Lin Xu
- School of Information Science and Technology, ShanghaiTech University, Shanghai, China
| | - Massimo Mischi
- Department of Electrical Engineering (Signal Processing Systems: Biomedical Diagnostics), Eindhoven Technical University, Post box 513, 5600 MB, Eindhoven, the Netherlands
| | - Benedictus C Schoot
- Department of Electrical Engineering (Signal Processing Systems: Biomedical Diagnostics), Eindhoven Technical University, Post box 513, 5600 MB, Eindhoven, the Netherlands.,Department of Obstetrics and Gynaecology, Catharina Hospital, Michelangelolaan 2, 5623 EJ, Eindhoven, the Netherlands.,Department of Obstetrics and Gynaecology, University Hospital (UZ) Gent, C. Heymanslaan 10, 9000, Ghent, Belgium
| | - Chiara Rabotti
- Department of Electrical Engineering (Signal Processing Systems: Biomedical Diagnostics), Eindhoven Technical University, Post box 513, 5600 MB, Eindhoven, the Netherlands
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Montero-Nava JE, Pliego-Carrillo AC, Ledesma-Ramírez CI, Peña-Castillo MÁ, Echeverría JC, Pacheco-López G, Reyes-Lagos JJ. Analysis of the fetal cardio-electrohysterographic coupling at the third trimester of gestation in healthy women by Bivariate Phase-Rectified Signal Averaging. PLoS One 2020; 15:e0236123. [PMID: 32649719 PMCID: PMC7351174 DOI: 10.1371/journal.pone.0236123] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Accepted: 06/29/2020] [Indexed: 11/18/2022] Open
Abstract
INTRODUCTION The fetal cardio-electrohysterographic coupling (FCEC) is defined as the influence of the uterine electrical activity on fetal heart rate. FCEC has been mainly evaluated by visual analysis of cardiotocographic data during labor; however, this physiological phenomenon is poorly explored during the antenatal period. Here we propose an approach known as Bivariate Phase-Rectified Signal Averaging analysis (BPRSA) to assess such FCEC in the late third trimester of low-risk pregnancies. We hypothesized that BPRSA is a more reliable measure of FCEC than visual analysis and conventional measures such as cross-correlation, coherence, and cross-sample entropy. Additionally, by using BPRSA it is possible to detect FCEC even from the third trimester of pregnancy. MATERIAL AND METHODS Healthy pregnant women in the last third trimester of pregnancy (36.6 ± 1.8 gestational weeks) without any clinical manifestation of labor were enrolled in the Maternal and Childhood Research Center (CIMIGen), Mexico City (n = 37). Ten minutes of maternal electrohysterogram (EHG) and fetal heart rate (FHR) data were collected by a transabdominal non-invasive device. The FCEC was quantified by the coefficient of coherence, the maximum normalized cross-correlation, and the cross-sample entropy obtained either from the EHG and FHR raw signals or from the corresponding BPRSA graphs. RESULTS We found that by using BPRSA, the FCEC was detected in 92% cases (34/37) compared to 48% cases (18/37) using the coefficient of coherence between the EHG and FHR raw signals. Also, BPRSA indicated FCEC in 82% cases (30/37) compared to 30% cases (11/37) using the maximum normalized cross-correlation. By comparing the analyses, the BPRSA evidenced higher FCEC in comparison to the coupling estimated from the raw EHG and FHR signals. CONCLUSIONS Our results support the consideration that in the third trimester of pregnancy, the fetal heart rate is also influenced by uterine activity despite the emerging manifestation of this activity before labor. To quantify FCEC, the BPRSA can be applied to FHR and EHG transabdominal signals acquired in the third trimester of pregnancy.
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Affiliation(s)
| | | | | | - Miguel Ángel Peña-Castillo
- Metropolitan Autonomous University (UAM), Campus Iztapalapa, Basic Sciences and Engineering Division, Mexico City, Mexico
| | - Juan Carlos Echeverría
- Metropolitan Autonomous University (UAM), Campus Iztapalapa, Basic Sciences and Engineering Division, Mexico City, Mexico
| | - Gustavo Pacheco-López
- Metropolitan Autonomous University (UAM), Campus Lerma, Biological and Health Sciences Division, Lerma, Mexico
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Amazu C, Ma X, Henkes C, Ferreira JJ, Santi CM, England SK. Progesterone and estrogen regulate NALCN expression in human myometrial smooth muscle cells. Am J Physiol Endocrinol Metab 2020; 318:E441-E452. [PMID: 31935111 PMCID: PMC7191408 DOI: 10.1152/ajpendo.00320.2019] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
During pregnancy, the uterus transitions from a quiescent state to an excitable, highly contractile state to deliver the fetus. Two important contributors essential for this transition are hormones and ion channels, both of which modulate myometrial smooth muscle cell (MSMC) excitability. Recently, the sodium (Na+) leak channel, nonselective (NALCN), was shown to contribute to a Na+ leak current in human MSMCs, and mice lacking NALCN in the uterus had dysfunctional labor. Microarray data suggested that the proquiescent hormone progesterone (P4) and the procontractile hormone estrogen (E2) regulated this channel. Here, we sought to determine whether P4 and E2 directly regulate NALCN. In human MSMCs, we found that NALCN mRNA expression decreased by 2.3-fold in the presence of E2 and increased by 5.6-fold in the presence of P4. Similarly, E2 treatment decreased, and P4 treatment restored NALCN protein expression. Additionally, E2 significantly inhibited, and P4 significantly enhanced an NALCN-dependent leak current in MSMCs. Finally, we identified estrogen response and progesterone response elements (EREs and PREs) in the NALCN promoter. With the use of luciferase assays, we showed that the PREs, but not the ERE, contributed to regulation of NALCN expression. Our findings reveal a new mechanism by which NALCN is regulated in the myometrium and suggest a novel role for NALCN in pregnancy.
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Affiliation(s)
- Chinwendu Amazu
- Department of Obstetrics Gynecology, Washington University in St. Louis, School of Medicine, St. Louis, Missouri
- Center for Reproductive Health Sciences, Washington University in St. Louis, School of Medicine, St. Louis, Missouri
| | - Xiaofeng Ma
- Department of Obstetrics Gynecology, Washington University in St. Louis, School of Medicine, St. Louis, Missouri
- Center for Reproductive Health Sciences, Washington University in St. Louis, School of Medicine, St. Louis, Missouri
| | - Clara Henkes
- Department of Obstetrics Gynecology, Washington University in St. Louis, School of Medicine, St. Louis, Missouri
- Center for Reproductive Health Sciences, Washington University in St. Louis, School of Medicine, St. Louis, Missouri
| | - Juan J Ferreira
- Department of Obstetrics Gynecology, Washington University in St. Louis, School of Medicine, St. Louis, Missouri
- Center for Reproductive Health Sciences, Washington University in St. Louis, School of Medicine, St. Louis, Missouri
- Department of Neuroscience, Washington University in St. Louis, School of Medicine, St. Louis, Missouri
| | - Celia M Santi
- Department of Obstetrics Gynecology, Washington University in St. Louis, School of Medicine, St. Louis, Missouri
- Center for Reproductive Health Sciences, Washington University in St. Louis, School of Medicine, St. Louis, Missouri
- Department of Neuroscience, Washington University in St. Louis, School of Medicine, St. Louis, Missouri
| | - Sarah K England
- Department of Obstetrics Gynecology, Washington University in St. Louis, School of Medicine, St. Louis, Missouri
- Center for Reproductive Health Sciences, Washington University in St. Louis, School of Medicine, St. Louis, Missouri
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14
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Trying to keep calm in troubled times: The role of K channels in uterine physiology. CURRENT OPINION IN PHYSIOLOGY 2020. [DOI: 10.1016/j.cophys.2019.07.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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16
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The Regulation of Uterine Function During Parturition: an Update and Recent Advances. Reprod Sci 2020; 27:3-28. [DOI: 10.1007/s43032-019-00001-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Accepted: 03/19/2019] [Indexed: 12/13/2022]
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Ducza E, Csányi A, Szőke É, Pohóczky K, Hajagos-Tóth J, Kothencz A, Tiszai Z, Gáspár R. Significance of transient receptor potential vanilloid 4 and aquaporin 5 co-expression in the rat uterus at term. Heliyon 2019; 5:e02697. [PMID: 31687520 PMCID: PMC6820280 DOI: 10.1016/j.heliyon.2019.e02697] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Revised: 09/13/2019] [Accepted: 10/16/2019] [Indexed: 12/15/2022] Open
Abstract
Aims Aquaporins (AQPs) are channel proteins that facilitate the rapid passive movement of water. In our studies it was proved that the decreased AQP5 expression is followed by the increase of uterine contractility. The transient receptor potential vanilloid 4 (TRPV4) is a calcium channel, which is activated in response to osmotic changes. Our aim was to determine the possible role of AQP5 in this osmotic regulation of TRPV4, thus in pregnant uterine contraction. Main methods We used RT-PCR and Western blot techniques for the detection of the TRPV4 expression during pregnancy in rat uterus. The localization of AQP5 and TRPV4 was determined by immunohistochemical studies. The role of TRPV4 in uterus contraction was investigated in an isolated organ bath system. In vitro uterus contractions were stimulated with KCl and its effect was investigated with the selective TRPV4 agonist (RN1747) and antagonist (RN1734). Key findings The TRPV4 expression continuously increased from day 18 to the last day of pregnancy. The co-expression of TRPV4 and AQP5 in the myometrium and endometrium was determined in the late pregnant uterus. The TRPV4 antagonist and agonist significantly decreased and increased uterine contraction, respectively, especially on the last day of pregnancy. Significance We presume the decreased AQP5 expression triggers hypertonic stress, which activates TRPV4 and increases uterus contraction on the day of labor. Based on these findings, we suppose the TRPV4 effect on uterus contraction is AQP5 control, which could be a new target in preterm birth therapy.
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Affiliation(s)
- Eszter Ducza
- Department of Pharmacodynamics and Biopharmacy, University of Szeged, Hungary
- Corresponding author.
| | - Adrienn Csányi
- Department of Pharmacodynamics and Biopharmacy, University of Szeged, Hungary
| | - Éva Szőke
- Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, Pécs, Hungary
- János Szentágothai Research Center & Centre for Neuroscience, University of Pécs, Hungary
| | - Krisztina Pohóczky
- Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, Pécs, Hungary
- János Szentágothai Research Center & Centre for Neuroscience, University of Pécs, Hungary
- Department of Pharmacology, Faculty of Pharmacy, University of Pécs, Pécs, Hungary
| | - Judit Hajagos-Tóth
- Department of Pharmacodynamics and Biopharmacy, University of Szeged, Hungary
- Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, Hungary
| | - Anna Kothencz
- Department of Pharmacodynamics and Biopharmacy, University of Szeged, Hungary
- Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, Hungary
| | - Zita Tiszai
- Department of Pharmacodynamics and Biopharmacy, University of Szeged, Hungary
| | - Róbert Gáspár
- Department of Pharmacodynamics and Biopharmacy, University of Szeged, Hungary
- Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, Hungary
- Corresponding author.
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18
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The Myometrium: From Excitation to Contractions and Labour. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1124:233-263. [PMID: 31183830 DOI: 10.1007/978-981-13-5895-1_10] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/06/2022]
Abstract
We start by describing the functions of the uterus, its structure, both gross and fine, innervation and blood supply. It is interesting to note the diversity of the female's reproductive tract between species and to remember it when working with different animal models. Myocytes are the overwhelming cell type of the uterus (>95%) and our focus. Their function is to contract, and they have an intrinsic pacemaker and rhythmicity, which is modified by hormones, stretch, paracrine factors and the extracellular environment. We discuss evidence or not for pacemaker cells in the uterus. We also describe the sarcoplasmic reticulum (SR) in some detail, as it is relevant to calcium signalling and excitability. Ion channels, including store-operated ones, their contributions to excitability and action potentials, are covered. The main pathway to excitation is from depolarisation opening voltage-gated Ca2+ channels. Much of what happens downstream of excitability is common to other smooth muscles, with force depending upon the balance of myosin light kinase and phosphatase. Mechanisms of maintaining Ca2+ balance within the myocytes are discussed. Metabolism, and how it is intertwined with activity, blood flow and pH, is covered. Growth of the myometrium and changes in contractile proteins with pregnancy and parturition are also detailed. We finish with a description of uterine activity and why it is important, covering progression to labour as well as preterm and dysfunctional labours. We conclude by highlighting progress made and where further efforts are required.
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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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20
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Zhang M, La Rosa PS, Eswaran H, Nehorai A. Estimating uterine source current during contractions using magnetomyography measurements. PLoS One 2018; 13:e0202184. [PMID: 30138376 PMCID: PMC6121809 DOI: 10.1371/journal.pone.0202184] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 05/29/2018] [Indexed: 11/28/2022] Open
Abstract
Understanding the uterine source of the electrophysiological activity of
contractions during pregnancy is of scientific interest and potential clinical
applications. In this work, we propose a method to estimate uterine source
currents from magnetomyography (MMG) temporal course measurements on the
abdominal surface. In particular, we develop a linear forward model, based on
the quasistatic Maxwell’s equations and a realistic four-compartment volume
conductor, relating the magnetic fields to the source currents on the uterine
surface through a lead-field matrix. To compute the lead-field matrix, we use a
finite element method that considers the anisotropic property of the myometrium.
We estimate the source currents by minimizing a constrained least-squares
problem to solve the non-uniqueness issue of the inverse problem. Because we
lack the ground truth of the source current, we propose to predict the
intrauterine pressure from our estimated source currents by using an
absolute-value-based method and compare the result with real abdominal
deflection recorded during contractile activity. We test the feasibility of the
lead-field matrix by displaying the lead fields that are generated by putative
source currents at different locations in the myometrium: cervix and fundus,
left and right, front and back. We then illustrate our method by using three
synthetic MMG data sets, which are generated using our previously developed
multiscale model of uterine contractions, and three real MMG data sets, one of
which has simultaneous real abdominal deflection measurements. The numerical
results demonstrate the ability of our method to capture the local contractile
activity of human uterus during pregnancy. Moreover, the predicted intrauterine
pressure is in fair agreement with the real abdominal deflection with respect to
the timing of uterine contractions.
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Affiliation(s)
- Mengxue Zhang
- Preston M. Green Department of Electrical and Systems Engineering,
Washington University in Saint Louis, Saint Louis, Missouri, United States of
America
| | - Patricio S. La Rosa
- Geospatial Analytics, Global IT Analytics, Monsanto Company, Saint Louis,
Missouri, United States of America
| | - Hari Eswaran
- Department of Obstetrics and Gynecology, University of Arkansas for
Medical Sciences, Little Rock, Arkansas, United States of America
| | - Arye Nehorai
- Preston M. Green Department of Electrical and Systems Engineering,
Washington University in Saint Louis, Saint Louis, Missouri, United States of
America
- * E-mail:
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21
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Testrow CP, Holden AV, Shmygol A, Zhang H. A computational model of excitation and contraction in uterine myocytes from the pregnant rat. Sci Rep 2018; 8:9159. [PMID: 29904075 PMCID: PMC6002389 DOI: 10.1038/s41598-018-27069-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Accepted: 05/24/2018] [Indexed: 12/17/2022] Open
Abstract
Aberrant uterine myometrial activities in humans are major health issues. However, the cellular and tissue mechanism(s) that maintain the uterine myometrium at rest during gestation, and that initiate and maintain long-lasting uterine contractions during delivery are incompletely understood. In this study we construct a computational model for describing the electrical activity (simple and complex action potentials), intracellular calcium dynamics and mechanical contractions of isolated uterine myocytes from the pregnant rat. The model reproduces variant types of action potentials - from spikes with a smooth plateau, to spikes with an oscillatory plateau, to bursts of spikes - that are seen during late gestation under different physiological conditions. The effects of the hormones oestradiol (via reductions in calcium and potassium selective channel conductance), oxytocin (via an increase in intracellular calcium release) and the tocolytic nifedipine (via a block of L-type calcium channels currents) on action potentials and contractions are also reproduced, which quantitatively match to experimental data. All of these results validated the cell model development. In conclusion, the developed model provides a computational platform for further investigations of the ionic mechanism underlying the genesis and control of electrical and mechanical activities in the rat uterine myocytes.
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Affiliation(s)
- Craig P Testrow
- The University of Manchester, School of Physics and Astronomy, Manchester, M13 9PL, UK
| | - Arun V Holden
- The University of Leeds, School of Biomedical Sciences, Leeds, LS2 9JT, UK
| | - Anatoly Shmygol
- United Arab Emirates University, College of Medicine and Health Sciences, Department of Physiology, Al-Ain, P.O. Box 17666, Emirates, UAE
| | - Henggui Zhang
- The University of Manchester, School of Physics and Astronomy, Manchester, M13 9PL, UK.
- School of Computer Science and Technology, Harbin Institute of Technology (HIT), Harbin, 150001, China.
- Space Institute of Southern China, Shenzhen, 518117, China.
- Key laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease/Institute of Cardiovascular Research, Southwest Medical University, Luzhou, 646000, China.
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22
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Lutton EJ, Lammers WJEP, James S, van den Berg HA, Blanks AM. Identification of uterine pacemaker regions at the myometrial-placental interface in the rat. J Physiol 2018; 596:2841-2852. [PMID: 29704394 PMCID: PMC6046083 DOI: 10.1113/jp275688] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Accepted: 04/19/2018] [Indexed: 12/16/2022] Open
Abstract
KEY POINTS Coordinated contraction of the uterine smooth muscle is essential to parturition. Histologically and physiologically defined pacemaker structures have not been identified in uterine smooth muscle. Here we report combined electrophysiological and histological evidence of zones associated with pacemaker activity in the rat myometrium. Our method relies crucially on the integration of histological and electrophysiological data in an in silico three-dimensional reconstruction of the rat myometrium at 10 μm resolution. We find that myometrial/placental pacemaking zones are closely related with placental sites and the area of disruptive myometrial remodelling surrounding such sites. If analogues of the myometrial/placental pacemaking zone are present in the human, defining their histology and physiology will be important steps towards treatment of pre-term birth, pre-eclampsia, and postpartum haemorrhage. ABSTRACT Coordinated uterine contractions are essential for delivering viable offspring in mammals. In contrast to other visceral smooth muscles, it is not known where excitation within the uterus is initiated, and no defined pacemaking region has hitherto been identified. Using multi-electrode array recordings and high-resolution computational reconstruction of the three-dimensional micro-structure of late pregnant rat uterus, we demonstrate that electrical potentials are initiated in distinct structures within the placental bed of individual implantation sites. These previously unidentified structures represent modified smooth muscle bundles that are derived from bridges between the longitudinal and circular layers. Coordinated implantation and encapsulation by invading trophoblast give rise to isolated placental/myometrial interface bundles that directly connect to the overlying longitudinal smooth muscle layer. Taken together, these observations imply that the anatomical structure of the uterus, combined with site-specific implantation, gives rise to emergent patterns of electrical activity that drive effective contractility during parturition.
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Affiliation(s)
- E Josiah Lutton
- Cell and Developmental Biology, Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, CV4 7AL, UK
| | - Wim J E P Lammers
- Bioengineering Institute, Auckland University, Auckland, New Zealand.,Department of Physiology, College of Medicine and Health Sciences, UAE University, Al Ain, United Arab Emirates
| | - Sean James
- Department of Pathology, University Hospitals Coventry and Warwickshire (UHCW), NHS Trust, Coventry, CV2 2DX, UK
| | | | - Andrew M Blanks
- Cell and Developmental Biology, Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, CV4 7AL, UK
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23
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Young RC. The uterine pacemaker of labor. Best Pract Res Clin Obstet Gynaecol 2018; 52:68-87. [PMID: 29866432 DOI: 10.1016/j.bpobgyn.2018.04.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Accepted: 04/10/2018] [Indexed: 10/17/2022]
Abstract
The laboring uterus is generally thought to initiate contractions much similar to the heart, with a single, dedicated pacemaker. Research on human and animal models over decades has failed to identify such pacemaker. On the contrary, data indicate that instead of being fixed at a site similar to the sinoatrial node of the heart, the initiation site for each uterine contraction changes during time, often with each contraction. The enigmatic uterine "pacemaker" does not seem to fit the standard definition of what a pacemaker should be. The uterine pacemaker must also mesh with the primary physiological function of the uterus - to generate intrauterine pressure. This requires that most areas of the uterine wall contract in a coordinated, or synchronized, manner for each contraction of labor. It is not clear whether the primary mechanism of the uterine pacemaker is a slow-wave generator or an impulse generator. Slow waves in the gut initiate localized smooth muscle contractions. Because the uterus and the gut have somewhat similar cellular and tissue structure, it is reasonable to consider if uterine contractions are paced by a similar mechanism. Unfortunately, there is no convincing experimental verification of uterine slow waves. Similarly, there is no convincing evidence of a cellular mechanism for impulse generation. The uterus appears to have multiple widely dispersed mechanically sensitive functional pacemakers. It is possible that the coordination of organ-level function occurs through intrauterine pressure, thus creating wall stress followed by activation of many mechanosensitive electrogenic pacemakers.
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24
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Nair SV, Sharma V, Sharma A, Nakade UP, Jaitley P, Mathesh K, Choudhury S, Garg SK. The functional and molecular studies on involvement of hydrogen sulphide in myometrial activity of non-pregnant buffaloes (Bubalus bubalis). BMC Vet Res 2017; 13:379. [PMID: 29207994 PMCID: PMC5717829 DOI: 10.1186/s12917-017-1288-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Accepted: 11/17/2017] [Indexed: 01/23/2023] Open
Abstract
Background Hydrogen sulphide (H2S), a member of the gasotransmitters family, is known to play patho-physiological role in different body systems including during pregnancy. But its involvement in myometrial spontaneity and associated signalling pathways in uterus in non-pregnant animals is yet to be studied. Present study describes the effect of L-cysteine, an endogenous H2S donor, on isolated myometrial strips of non-pregnant buffaloes and the underlying signaling mechanism(s). Results L-cysteine (10 nM-30 mM) produced concentration-dependent contractile effect on buffalo myometrium which was extracellular Ca2+ and L-type calcium channels-dependent. Significant rightward shift of dose-response curve of L-cysteine was observed with significant decrease in maxima in the presence of amino-oxyacetic acid (AOAA; 100 μM) and d, l-propargylglycine (PAG; 100 μM), the specific blockers of cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE), respectively. Existence of CBS enzyme of 63 kDa and CSE of 45 kDa molecular weights was confirmed by western blot using specific antibodies and also by immunohistochemistry. Conclusions Endogenous H2S along with its biosynthetic enzymes (CBS and CSE) is evidently present in uteri of non-pregnant buffaloes and it regulates spontaneity in uteri of non-pregnant buffaloes and this effect is dependent on extracellular Ca2+ influx through nifedipine-sensitive L-type calcium channels. Thus H2S-signalling pathway may be a potential target to alter the uterine activities in physiology and patho-physiolgical states.
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Affiliation(s)
- Sooraj V Nair
- Experimental and Molecular Pharmacology Laboratory, Department of Pharmacology & Toxicology, College of Veterinary Science and Animal Husbandry, U.P. Pandit Deen Dayal Upadhyaya Pashu Chikitsa Vigyan Vishwavidyalaya Evam Go-Anusandhan Sansthan (DUVASU), Mathura, 281001, India
| | - Vipin Sharma
- Experimental and Molecular Pharmacology Laboratory, Department of Pharmacology & Toxicology, College of Veterinary Science and Animal Husbandry, U.P. Pandit Deen Dayal Upadhyaya Pashu Chikitsa Vigyan Vishwavidyalaya Evam Go-Anusandhan Sansthan (DUVASU), Mathura, 281001, India
| | - Abhishek Sharma
- Experimental and Molecular Pharmacology Laboratory, Department of Pharmacology & Toxicology, College of Veterinary Science and Animal Husbandry, U.P. Pandit Deen Dayal Upadhyaya Pashu Chikitsa Vigyan Vishwavidyalaya Evam Go-Anusandhan Sansthan (DUVASU), Mathura, 281001, India
| | - Udayraj P Nakade
- Experimental and Molecular Pharmacology Laboratory, Department of Pharmacology & Toxicology, College of Veterinary Science and Animal Husbandry, U.P. Pandit Deen Dayal Upadhyaya Pashu Chikitsa Vigyan Vishwavidyalaya Evam Go-Anusandhan Sansthan (DUVASU), Mathura, 281001, India
| | - Pooja Jaitley
- Experimental and Molecular Pharmacology Laboratory, Department of Pharmacology & Toxicology, College of Veterinary Science and Animal Husbandry, U.P. Pandit Deen Dayal Upadhyaya Pashu Chikitsa Vigyan Vishwavidyalaya Evam Go-Anusandhan Sansthan (DUVASU), Mathura, 281001, India
| | - Karikalan Mathesh
- Centre for Wildlife Conservation Management and Disease Surveillance, Indian Veterinary Research Institute (ICAR-IVRI), Izatnagar, Bareilly, U.P, 243 122, India
| | - Soumen Choudhury
- Experimental and Molecular Pharmacology Laboratory, Department of Pharmacology & Toxicology, College of Veterinary Science and Animal Husbandry, U.P. Pandit Deen Dayal Upadhyaya Pashu Chikitsa Vigyan Vishwavidyalaya Evam Go-Anusandhan Sansthan (DUVASU), Mathura, 281001, India
| | - Satish Kumar Garg
- Experimental and Molecular Pharmacology Laboratory, Department of Pharmacology & Toxicology, College of Veterinary Science and Animal Husbandry, U.P. Pandit Deen Dayal Upadhyaya Pashu Chikitsa Vigyan Vishwavidyalaya Evam Go-Anusandhan Sansthan (DUVASU), Mathura, 281001, India.
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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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26
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Myers KM, Elad D. Biomechanics of the human uterus. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2017; 9. [PMID: 28498625 DOI: 10.1002/wsbm.1388] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Revised: 02/23/2017] [Accepted: 03/01/2017] [Indexed: 12/15/2022]
Abstract
The appropriate biomechanical function of the uterus is required for the execution of human reproduction. These functions range from aiding the transport of the embryo to the implantation site, to remodeling its tissue walls to host the placenta, to protecting the fetus during gestation, to contracting forcefully for a safe parturition and postpartum, to remodeling back to its nonpregnant condition to renew the cycle of menstruation. To serve these remarkably diverse functions, the uterus is optimally geared with evolving and contractile muscle and tissue layers that are cued by chemical, hormonal, electrical, and mechanical signals. The relationship between these highly active biological signaling mechanisms and uterine biomechanical function is not completely understood for normal reproductive processes and pathological conditions such as adenomyosis, endometriosis, infertility and preterm labor. Animal studies have illuminated the rich structural function of the uterus, particularly in pregnancy. In humans, medical imaging techniques in ultrasound and magnetic resonance have been combined with computational engineering techniques to characterize the uterus in vivo, and advanced experimental techniques have explored uterine function using ex vivo tissue samples. The collective evidence presented in this review gives an overall perspective on uterine biomechanics related to both its nonpregnant and pregnant function, highlighting open research topics in the field. Additionally, uterine disease and infertility are discussed in the context of tissue injury and repair processes and the role of computational modeling in uncovering etiologies of disease. WIREs Syst Biol Med 2017, 9:e1388. doi: 10.1002/wsbm.1388 For further resources related to this article, please visit the WIREs website.
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Affiliation(s)
- Kristin M Myers
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - David Elad
- Department of Biomedical Engineering, Tel Aviv University, Tel Aviv, Israel.,Department of Biomedical Engineering, Columbia University, New York, NY, USA
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Functional involvement of protein kinase C, Rho-kinase and TRPC3 decreases while PLC increases with advancement of pregnancy in mediating oxytocin-induced myometrial contractions in water buffaloes ( Bubalus bubalis ). Theriogenology 2017; 92:176-189. [DOI: 10.1016/j.theriogenology.2016.12.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Revised: 12/06/2016] [Accepted: 12/06/2016] [Indexed: 11/20/2022]
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Alotaibi M, Kahlat K, Nedjadi T, Djouhri L. Effects of ZD7288, a hyperpolarization-activated cyclic nucleotide-gated (HCN) channel blocker, on term-pregnant rat uterine contractility in vitro. Theriogenology 2017; 90:141-146. [DOI: 10.1016/j.theriogenology.2016.11.022] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2016] [Revised: 11/22/2016] [Accepted: 11/24/2016] [Indexed: 12/01/2022]
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Sharma A, Nakade UP, Choudhury S, Yadav RS, Garg SK. Extra and intracellular calcium signaling pathway(s) differentially regulate histamine-induced myometrial contractions during early and mid-pregnancy stages in buffaloes (Bubalus bubalis). Anim Reprod Sci 2017; 179:10-19. [PMID: 28228338 DOI: 10.1016/j.anireprosci.2017.01.011] [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] [Received: 07/08/2016] [Revised: 01/18/2017] [Accepted: 01/25/2017] [Indexed: 10/20/2022]
Abstract
This study examines the differential role of calcium signaling pathway(s) in histamine-induced uterotonic action during early and mid-pregnancy stages in buffaloes. Compared to mid pregnancy, tonic contraction, amplitude and mean-integral tension were significantly increased by histamine to produce myometrial contraction during early pregnancy with small effects on phasic contraction and frequency. Although uterotonic action of histamine during both stages of pregnancy is sensitive to nifedipine (a L-type Ca2+ channels blocker) and NNC55-0396 (T-type Ca2+ channels blocker), the role of extracellular calcium seems to be more significant during mid-pregnancy as in this stage histamine produced only 9.38±0.96% contraction in Ca2+ free-RLS compared to 21.60±1.45% in uteri of early pregnancy stage. Intracellular calcium plays major role in histamine-induced myometrial contraction during early pregnancy as compared to mid pregnancy, as in the presence of cyclopiazonic acid (CPA) Ca2+-free RLS, histamine produced significantly higher contraction in myometrial strips of early-pregancy in comparison to mid-pregnancy (10.59±1.58% and 3.13±0.46%, respectively). In the presence of U-73122, the DRC of histamine was significantly shifted towards right with decrease in maximal effect (Emax) only in early pregnancy suggesting the predominant role of phospholipase-C (PL-C) in this stage of pregnancy.
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Affiliation(s)
- Abhishek Sharma
- Experimental Pharmacology Laboratory, Department of Pharmacology and Toxicology, College of Veterinary Science and Animal Husbandry, UP Pandit Deen Dayal Upadhyaya Pashu Chikitsa Vigyan Vishwavidyalaya Evam Go-Anusandhan Sansthan, Mathura, U.P., 281 001, India
| | - Udayraj P Nakade
- Experimental Pharmacology Laboratory, Department of Pharmacology and Toxicology, College of Veterinary Science and Animal Husbandry, UP Pandit Deen Dayal Upadhyaya Pashu Chikitsa Vigyan Vishwavidyalaya Evam Go-Anusandhan Sansthan, Mathura, U.P., 281 001, India
| | - Soumen Choudhury
- Experimental Pharmacology Laboratory, Department of Pharmacology and Toxicology, College of Veterinary Science and Animal Husbandry, UP Pandit Deen Dayal Upadhyaya Pashu Chikitsa Vigyan Vishwavidyalaya Evam Go-Anusandhan Sansthan, Mathura, U.P., 281 001, India
| | - Rajkumar Singh Yadav
- Experimental Pharmacology Laboratory, Department of Pharmacology and Toxicology, College of Veterinary Science and Animal Husbandry, UP Pandit Deen Dayal Upadhyaya Pashu Chikitsa Vigyan Vishwavidyalaya Evam Go-Anusandhan Sansthan, Mathura, U.P., 281 001, India
| | - Satish Kumar Garg
- Experimental Pharmacology Laboratory, Department of Pharmacology and Toxicology, College of Veterinary Science and Animal Husbandry, UP Pandit Deen Dayal Upadhyaya Pashu Chikitsa Vigyan Vishwavidyalaya Evam Go-Anusandhan Sansthan, Mathura, U.P., 281 001, India.
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Bafor EE, Rowan EG, Edrada-Ebel R. Toward Understanding Myometrial Regulation: Metabolomic Investigation Reveals New Pathways of Oxytocin and Ritodrine Activity on the Myometrium. Reprod Sci 2016; 24:691-705. [DOI: 10.1177/1933719116667224] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Affiliation(s)
- Enitome E. Bafor
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, Scotland, United Kingdom
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, University of Benin, Benin, Edo State, Nigeria
| | - Edward G. Rowan
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, Scotland, United Kingdom
| | - RuAngelie Edrada-Ebel
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, Scotland, United Kingdom
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Ruttner Z, Ivanics T, Slaaf DW, Reneman RS, Toth A, Ligeti L. In Vivo Monitoring of Intracellular Free Calcium Changes During Uterine Activation By Prostaglandin F2α and Oxytocin. ACTA ACUST UNITED AC 2016. [DOI: 10.1177/107155760200900507] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Zoltan Ruttner
- Semmelweis University, Faculty of Medicine, Institute of Human Physiology and Clinical Experimental Research, Budapest, Hungary; Departments of Biophysics and Physiology, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands
| | | | | | | | | | - Laszló Ligeti
- Semmelweis University, Faculty of Medicine, Institute of Human Physiology and Clinical Experimental Research, Budapest, Hungary; Departments of Biophysics and Physiology, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands
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Abstract
While still experimental, measurement of external uterine electromyographic (EMG) activity is a more sensitive and noninvasive method for measuring uterine contractility in human labor than the methods currently used in clinical practice. Hydrotherapy is purported to improve contractility in labor, yet there have been no reports of abdominal uterine EMG activity measured during immersion. To test telemetric EMG equipment and different waterproofing techniques under dry and immersed conditions, the authors recorded surface EMG activity from the abdominal muscles of 11 healthy, nonpregnant women, 22 to 51 years of age. After attaching one pair of electrodes to the skin on either side of the umbilicus and applying the waterproofing material, the authors tested the signal by asking participants to perform a short series of leg lifts while seated in a chair to evoke abdominal muscle contractions. They were then immersed to the chest in a hydrotherapy tub while performing two to three leg lifts over 60 s every 5 min for 60 min with 20 lb of weight suspended from their ankles to counteract the buoyancy effect of water. EMG activity was continuously recorded. They then repeated the dry-measures sequence. While waterproofing remained intact, EMG signals were essentially unchanged between dry and wet conditions. Of the 11 waterproofing applications tested, 10 failed at some point. In the data from the successful application, EMG signals in both channels exhibited stable baselines throughout and an absence of low-frequency artifact. The development of this technique allows for the recording of external uterine EMG activity during hydrotherapy. The authors have begun using it to investigate the effects of hydrotherapy on uterine contractility during human labor.
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Atia J, McCloskey C, Shmygol AS, Rand DA, van den Berg HA, Blanks AM. Reconstruction of Cell Surface Densities of Ion Pumps, Exchangers, and Channels from mRNA Expression, Conductance Kinetics, Whole-Cell Calcium, and Current-Clamp Voltage Recordings, with an Application to Human Uterine Smooth Muscle Cells. PLoS Comput Biol 2016; 12:e1004828. [PMID: 27105427 PMCID: PMC4841602 DOI: 10.1371/journal.pcbi.1004828] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Accepted: 02/23/2016] [Indexed: 11/28/2022] Open
Abstract
Uterine smooth muscle cells remain quiescent throughout most of gestation, only generating spontaneous action potentials immediately prior to, and during, labor. This study presents a method that combines transcriptomics with biophysical recordings to characterise the conductance repertoire of these cells, the ‘conductance repertoire’ being the total complement of ion channels and transporters expressed by an electrically active cell. Transcriptomic analysis provides a set of potential electrogenic entities, of which the conductance repertoire is a subset. Each entity within the conductance repertoire was modeled independently and its gating parameter values were fixed using the available biophysical data. The only remaining free parameters were the surface densities for each entity. We characterise the space of combinations of surface densities (density vectors) consistent with experimentally observed membrane potential and calcium waveforms. This yields insights on the functional redundancy of the system as well as its behavioral versatility. Our approach couples high-throughput transcriptomic data with physiological behaviors in health and disease, and provides a formal method to link genotype to phenotype in excitable systems. We accurately predict current densities and chart functional redundancy. For example, we find that to evoke the observed voltage waveform, the BK channel is functionally redundant whereas hERG is essential. Furthermore, our analysis suggests that activation of calcium-activated chloride conductances by intracellular calcium release is the key factor underlying spontaneous depolarisations. A well-known problem in electrophysiologal modeling is that the parameters of the gating kinetics of the ion channels cannot be uniquely determined from observed behavior at the cellular level. One solution is to employ simplified “macroscopic” currents that mimic the behavior of aggregates of distinct entities at the protein level. The gating parameters of each channel or pump can be determined by studying it in isolation, leaving the general problem of finding the densities at which the channels occur in the plasma membrane. We propose an approach, which we apply to uterine smooth muscle cells, whereby we constrain the list of possible entities by means of transcriptomics and chart the indeterminacy of the problem in terms of the kernel of the corresponding linear transformation. A graphical representation of this kernel visualises the functional redundancy of the system. We show that the role of certain conductances can be fulfilled, or compensated for, by suitable combinations of other conductances; this is not always the case, and such “non-substitutable” conductances can be regarded as functionally non-redundant. Electrogenic entities belonging to the latter category are suitable putative clinical targets.
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Affiliation(s)
- Jolene Atia
- Division of Reproductive Health, Warwick Medical School, University of Warwick, Coventry, United Kingdom
| | - Conor McCloskey
- Division of Reproductive Health, Warwick Medical School, University of Warwick, Coventry, United Kingdom
| | - Anatoly S. Shmygol
- Division of Reproductive Health, Warwick Medical School, University of Warwick, Coventry, United Kingdom
| | | | | | - Andrew M. Blanks
- Division of Reproductive Health, Warwick Medical School, University of Warwick, Coventry, United Kingdom
- * E-mail:
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Zhang M, Tidwell V, La Rosa PS, Wilson JD, Eswaran H, Nehorai A. Modeling Magnetomyograms of Uterine Contractions during Pregnancy Using a Multiscale Forward Electromagnetic Approach. PLoS One 2016; 11:e0152421. [PMID: 27019202 PMCID: PMC4809542 DOI: 10.1371/journal.pone.0152421] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Accepted: 03/14/2016] [Indexed: 01/22/2023] Open
Abstract
Understanding the mechanisms of uterine contractions during pregnancy is especially important in predicting the onset of labor and thus in forecasting preterm deliveries. Preterm birth can cause serious health problems in newborns, as well as large financial burdens to society. Various techniques such as electromyography (EMG) and magnetomyography (MMG) have been developed to quantify uterine contractions. However, no widely accepted method to predict labor based on electromagnetic measurement is available. Therefore, developing a biophysical model of EMG and MMG could help better understand uterine contractions, interpret real measurements, and detect labor. In this work, we propose a multiscale realistic model of uterine contractions during pregnancy. At the cellular level, building on bifurcation theory, we apply generalized FitzHugh-Nagumo (FHN) equations that produces both plateau-type and bursting-type action potentials. At the tissue level, we introduce a random fiber orientation model applicable to an arbitrary uterine shape. We also develop an analytical expression for the propagation speed of transmembrane potential. At the organ level, a realistic volume conductor geometry model is provided based on magnetic resonance images of a pregnant woman. To simulate the measurements from the SQUID Array for Reproductive Assessment (SARA) device, we propose a sensor array model. Our model is able to reproduce the characteristics of action potentials. Additionally, we investigate the sensitivity of MMG to model configuration aspects such as volume geometry, fiber orientation, and pacemaker location. Our numerical results show that fiber orientation and pacemaker location are the key aspects that greatly affect the MMG as measured by the SARA device. We conclude that sphere is appropriate as an approximation of the volume geometry. The initial step towards validating the model against real MMG measurement is also presented. Our results show that the model is flexible to mimic the limited-propagation magnetic signature during the emergence and decay of a uterine contraction.
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Affiliation(s)
- Mengxue Zhang
- Department of Electrical and Systems Engineering, Washington University in Saint Louis, Saint Louis, Missouri, United States of America
| | - Vanessa Tidwell
- Department of Electrical and Systems Engineering, Washington University in Saint Louis, Saint Louis, Missouri, United States of America
| | - Patricio S. La Rosa
- Research & Development/Technology Pipeline Solutions, Monsanto Company, Saint Louis, Missouri, United States of America
- Joint Undergraduate Engineering Program - University of Missouri and Washington University in Saint Louis, Saint Louis, Missouri, United States of America
| | - James D. Wilson
- Graduate Institute of Technology, University of Arkansas at Little Rock, Little Rock, Arkansas, United States of America
| | - Hari Eswaran
- Department of Obstetrics and Gynecology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States of America
| | - Arye Nehorai
- Department of Electrical and Systems Engineering, Washington University in Saint Louis, Saint Louis, Missouri, United States of America
- * E-mail:
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35
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A Hypothesis for Self-Organization and Symmetry Reduction in the Synchronization of Organ-Level Contractions in the Human Uterus during Labor. Symmetry (Basel) 2015. [DOI: 10.3390/sym7041981] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Sheldon RE, Mashayamombe C, Shi SQ, Garfield RE, Shmygol A, Blanks AM, van den Berg HA. Alterations in gap junction connexin43/connexin45 ratio mediate a transition from quiescence to excitation in a mathematical model of the myometrium. J R Soc Interface 2015; 11:20140726. [PMID: 25401181 DOI: 10.1098/rsif.2014.0726] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The smooth muscle cells of the uterus contract in unison during delivery. These cells achieve coordinated activity via electrical connections called gap junctions which consist of aggregated connexin proteins such as connexin43 and connexin45. The density of gap junctions governs the excitability of the myometrium (among other factors). An increase in gap junction density occurs immediately prior to parturition. We extend a mathematical model of the myometrium by incorporating the voltage-dependence of gap junctions that has been demonstrated in the experimental literature. Two functional subtypes exist, corresponding to systems with predominantly connexin43 and predominantly connexin45, respectively. Our simulation results indicate that the gap junction protein connexin45 acts as a negative modulator of uterine excitability, and hence, activity. A network with a higher proportion of connexin45 relative to connexin43 is unable to excite every cell. Connexin45 has much more rapid gating kinetics than connexin43 which we show limits the maximum duration of a local burst of activity. We propose that this effect regulates the degree of synchronous excitation attained during a contraction. Our results support the hypothesis that as labour approaches, connexin45 is downregulated to allow action potentials to spread more readily through the myometrium.
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37
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Hanley JA, Weeks A, Wray S. Physiological increases in lactate inhibit intracellular calcium transients, acidify myocytes and decrease force in term pregnant rat myometrium. J Physiol 2015. [PMID: 26223765 PMCID: PMC4606541 DOI: 10.1113/jp270631] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Key points Lactate is increased in myometrial capillary blood from women in slow or non‐progressive labour (dystocia), suggesting that it is detrimental to uterine contractions. There are no studies of the effect of lactate on the myometrium. In the present study, we have investigated its effects and mechanism of action on myometrial strips from term pregnant rats. We show that lactate significantly decreased spontaneous contractility. Lactatedecreased pHi and inhibited Ca2+ transients. Nulling the decrease in pHi abolished the effects of lactate effects. If Ca2+ entry was enhanced, the effects of lactate were abolished. The present study suggests that the accumulation of extracellular lactate could contribute to labour dystocia.
Abstract Lactate is increased in myometrial capillary blood from women in slow or non‐progressive labour (dystocia), suggesting that it is detrimental to uterine contractions. There are, however, no studies of the effect of lactate on the myometrium. We therefore investigated its effects and mechanism of action on myometrial strips from term pregnant rats. The effects on spontaneous and oxytocin‐induced contractility in response to sodium lactate and other weak acids (1–20 mM) were studied. In some experiments, simultaneous force and intracellular Ca2+ or pH (pHi) were measured with Indo‐1 or Carboxy‐SNARF, respectively. Statistical differences were tested using non‐parametric tests. Lactate significantly decreased spontaneous contractility with an EC50 of 3.9 mM. Propionate, butyrate and pyruvate also reduced contractions with similar potency. The effects of lactate were reduced in the presence of oxytocin but remained significant. Lactate decreased pHi and nulling the decrease in pHi abolished its effects. We also show that lactate inhibited Ca2+ transients, with these changes mirroring those produced on force. If Ca2+ entry was enhanced by depolarization (high KCl) or applying the Ca2+ channel agonist, Bay K 4644, the effects of lactate were abolished. Taken together, these data show that lactate in the physiological range potently decreases myometrial contractility as a result of its inhibition of Ca2+ transients, which can be attributed to the induced acidification. The present study suggests that the accumulation of extracellular lactate will reduce myometrial contractions and could therefore contribute to labour dystocia.
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Affiliation(s)
| | - Andrew Weeks
- Women's and Children's Health, Institute of Translational Medicine, University of Liverpool, Liverpool, UK
| | - Susan Wray
- Departments of Cellular and Molecular Physiology
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Reinl EL, Cabeza R, Gregory IA, Cahill AG, England SK. Sodium leak channel, non-selective contributes to the leak current in human myometrial smooth muscle cells from pregnant women. Mol Hum Reprod 2015; 21:816-24. [PMID: 26134120 DOI: 10.1093/molehr/gav038] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Accepted: 06/26/2015] [Indexed: 01/25/2023] Open
Abstract
Uterine contractions are tightly regulated by the electrical activity of myometrial smooth muscle cells (MSMCs). These cells require a depolarizing current to initiate Ca(2+) influx and induce contraction. Cationic leak channels, which permit a steady flow of cations into a cell, are known to cause membrane depolarization in many tissue types. Previously, a Gd(3+)-sensitive, Na(+)-dependent leak current was identified in the rat myometrium, but the presence of such a current in human MSMCs and the specific ion channel conducting this current was unknown. Here, we report the presence of a Na(+)-dependent leak current in human myometrium and demonstrate that the Na(+)-leak channel, NALCN, contributes to this current. We performed whole-cell voltage-clamp on fresh and cultured MSMCs from uterine biopsies of term, non-laboring women and isolated the leak currents by using Ca(2+) and K(+) channel blockers in the bath solution. Ohmic leak currents were identified in freshly isolated and cultured MSMCs with normalized conductances of 14.6 pS/pF and 10.0 pS/pF, respectively. The myometrial leak current was significantly reduced (P < 0.01) by treating cells with 10 μM Gd(3+) or by superfusing the cells with a Na(+)-free extracellular solution. Reverse transcriptase PCR and immunoblot analysis of uterine biopsies from term, non-laboring women revealed NALCN messenger RNA and protein expression in the myometrium. Notably, ∼90% knockdown of NALCN protein expression with lentivirus-delivered shRNA reduced the Gd(3+)-sensitive leak current density by 42% (P < 0.05). Our results reveal that NALCN, in part, generates the leak current in MSMCs and provide the basis for future research assessing NALCN as a potential molecular target for modulating uterine excitability.
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Affiliation(s)
- Erin L Reinl
- Department of Obstetrics and Gynecology, Basic Science Division, Washington University in St. Louis School of Medicine, St. Louis, MO 63110, USA
| | - Rafael Cabeza
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52442, USA
| | - Ismail A Gregory
- Department of Obstetrics and Gynecology, Basic Science Division, Washington University in St. Louis School of Medicine, St. Louis, MO 63110, USA
| | - Alison G Cahill
- Department of Obstetrics and Gynecology, Basic Science Division, Washington University in St. Louis School of Medicine, St. Louis, MO 63110, USA
| | - Sarah K England
- Department of Obstetrics and Gynecology, Basic Science Division, Washington University in St. Louis School of Medicine, St. Louis, MO 63110, USA
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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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The role of cellular coupling in the spontaneous generation of electrical activity in uterine tissue. PLoS One 2015; 10:e0118443. [PMID: 25793276 PMCID: PMC4368634 DOI: 10.1371/journal.pone.0118443] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Accepted: 01/16/2015] [Indexed: 11/19/2022] Open
Abstract
The spontaneous emergence of contraction-inducing electrical activity in the uterus at the beginning of labor remains poorly understood, partly due to the seemingly contradictory observation that isolated uterine cells are not spontaneously active. It is known, however, that the expression of gap junctions increases dramatically in the approach to parturition, by more than one order of magnitude, which results in a significant increase in inter-cellular electrical coupling. In this paper, we build upon previous studies of the activity of electrically excitable smooth muscle cells (myocytes) and investigate the mechanism through which the coupling of these cells to electrically passive cells results in the generation of spontaneous activity in the uterus. Using a recently developed, realistic model of uterine muscle cell dynamics, we investigate a system consisting of a myocyte coupled to passive cells. We then extend our analysis to a simple two-dimensional lattice model of the tissue, with each myocyte being coupled to its neighbors, as well as to a random number of passive cells. We observe that different dynamical regimes can be observed over a range of gap junction conductances: at low coupling strength, corresponding to values measured long before delivery, the activity is confined to cell clusters, while the activity for high coupling, compatible with values measured shortly before delivery, may spread across the entire tissue. Additionally, we find that the system supports the spontaneous generation of spiral wave activity. Our results are both qualitatively and quantitatively consistent with observations from in vitro experiments. In particular, we demonstrate that the increase in inter-cellular electrical coupling observed experimentally strongly facilitates the appearance of spontaneous action potentials that may eventually lead to parturition.
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Loftus FC, Richardson MJE, Shmygol A. Single-cell mechanics and calcium signalling in organotypic slices of human myometrium. J Biomech 2015; 48:1620-4. [PMID: 25702249 PMCID: PMC4503816 DOI: 10.1016/j.jbiomech.2015.01.046] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Accepted: 01/31/2015] [Indexed: 11/29/2022]
Abstract
Elucidation of cellular mechanisms regulating myometrial contractility is crucial for improvement in management of many obstetric abnormalities, such as premature delivery, uterine dystocia and post-partum haemorrhage. Myometrial contractions are triggered by periodic synchronous rises in intracellular calcium concentration ([Ca(2+)]i) elicited by spontaneously generated action potentials propagating throughout the entire myometrium. During labour, hormones like oxytocin and prostaglandins potentiate uterine contractions by increasing their duration, strength and frequency. The most informative approach to studying the mechanisms underlying hormonal modulation of uterine contractility is to record [Ca(2+)]i responses to hormones in intact myometrial samples that have not been subjected to enzymatic treatment for cell isolation or cell culture conditions. However, the spatio-temporal resolution of such recording is limited due to the motion artifacts occurring in contracting tissue. Here we describe the application of our newly developed motion correction algorithm to investigate the [Ca(2+)]i dynamics in control and oxytocin stimulated slices of human myometrium on a cellular level. We present evidence that oxytocin induces asynchronous [Ca(2+)]i oscillations in individual myocytes within intact myometrium which are similar to those observed in cultured cells. The oscillations occur between synchronous action potential-driven [Ca(2+)]i transients but appear to be unrelated to contractions. Furthermore, the oxytocin-triggered [Ca(2+)]i oscillations wane within 30-50min of hormone application, while the action potential induced [Ca(2+)]i transients remain augmented. We conclude that oxytocin-induced [Ca(2+)]i oscillations are not relevant to the acute regulation of myometrial contractility but may play a role in longer-term regulatory processes, for example, by triggering gene expression.
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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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Wright PD, Kanumilli S, Tickle D, Cartland J, Bouloc N, Dale T, Tresize DJ, McCloskey C, McCavera S, Blanks AM, Kettleborough C, Jerman JC. A High-Throughput Electrophysiology Assay Identifies Inhibitors of the Inwardly Rectifying Potassium Channel Kir7.1. ACTA ACUST UNITED AC 2015; 20:739-47. [PMID: 25656238 DOI: 10.1177/1087057115569156] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 12/31/2014] [Indexed: 11/17/2022]
Abstract
Kir7.1 is an inwardly rectifying potassium channel that has been implicated in controlling the resting membrane potential of the myometrium. Abnormal uterine activity in pregnancy plays an important role in postpartum hemorrhage, and novel therapies for this condition may lie in manipulation of membrane potential. This work presents an assay development and screening strategy for identifying novel inhibitors of Kir7.1. A cell-based automated patch-clamp electrophysiology assay was developed using the IonWorks Quattro (Molecular Devices, Sunnyvale, CA) system, and the iterative optimization is described. In total, 7087 compounds were tested, with a hit rate (>40% inhibition) of 3.09%. During screening, average Z' values of 0.63 ± 0.09 were observed. After chemistry triage, lead compounds were resynthesized and activity confirmed by IC50 determinations. The most potent compound identified (MRT00200769) gave rise to an IC50 of 1.3 µM at Kir7.1. Compounds were assessed for selectivity using the inwardly rectifying potassium channel Kir1.1 (ROMK) and hERG (human Ether-à-go-go Related Gene). Pharmacological characterization of known Kir7.1 inhibitors was also carried out and analogues of VU590 tested to assess selectivity at Kir7.1.
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Affiliation(s)
- Paul D Wright
- MRC Technology, Center for Therapeutics Discovery, London, UK
| | | | - David Tickle
- MRC Technology, Center for Therapeutics Discovery, London, UK
| | - Jamie Cartland
- MRC Technology, Center for Therapeutics Discovery, London, UK
| | - Nathalie Bouloc
- MRC Technology, Center for Therapeutics Discovery, London, UK
| | - Timothy Dale
- Essen BioScience Ltd, Welwyn Garden City, Hertfordshire, UK
| | | | - Conor McCloskey
- Division of Reproductive Health, Warwick Medical School, Clinical Sciences Research Laboratory, Coventry, UK
| | - Samantha McCavera
- Division of Reproductive Health, Warwick Medical School, Clinical Sciences Research Laboratory, Coventry, UK
| | - Andrew M Blanks
- Division of Reproductive Health, Warwick Medical School, Clinical Sciences Research Laboratory, Coventry, UK
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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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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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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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Store-operated Ca²⁺ entry and depolarization explain the anomalous behaviour of myometrial SR: effects of SERCA inhibition on electrical activity, Ca²⁺ and force. Cell Calcium 2014; 56:188-94. [PMID: 25084623 PMCID: PMC4169181 DOI: 10.1016/j.ceca.2014.07.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Revised: 07/03/2014] [Accepted: 07/09/2014] [Indexed: 11/23/2022]
Abstract
SERCA pump inhibition by CPA caused membrane depolarization, activation of action potentials, Ca2+ spikes and force. Depletion of Ca2+ store by agonists leads to membrane depolarization and activation of electrical and mechanical activity. Ca2+ release/Ca2+ entry coupling is playing a key role in control of spontaneous electrical and mechanical activity in rat pregnant myometrium.
In the myometrium SR Ca2+ depletion promotes an increase in force but unlike several other smooth muscles, there is no Ca2+ sparks-STOCs coupling mechanism to explain this. Given the importance of the control of contractility for successful parturition, we have examined, in pregnant rat myometrium, the effects of SR Ca2+-ATPase (SERCA) inhibition on the temporal relationship between action potentials, Ca2+ transients and force. Simultaneous recording of electrical activity, calcium and force showed that SERCA inhibition, by cyclopiazonic acid (CPA 20 μM), caused time-dependent changes in excitability, most noticeably depolarization and elevations of baseline [Ca2+]i and force. At the onset of these changes there was a prolongation of the bursts of action potentials and a corresponding series of Ca2+ spikes, which increased the amplitude and duration of contractions. As the rise of baseline Ca2+ and depolarization continued a point was reached when electrical and Ca2+ spikes and phasic contractions ceased, and a maintained, tonic force and Ca2+ was produced. Lanthanum, a non-selective blocker of store-operated Ca2+ entry, but not the L-type Ca2+ channel blocker nifedipine (1–10 μM), could abolish the maintained force and calcium. Application of the agonist, carbachol, produced similar effects to CPA, i.e. depolarization, elevation of force and calcium. A brief, high concentration of carbachol, to cause SR Ca2+ depletion without eliciting receptor-operated channel opening, also produced these results. The data obtained suggest that in pregnant rats SR Ca2+ release is coupled to marked Ca2+ entry, via store operated Ca2+ channels, leading to depolarization and enhanced electrical and mechanical activity.
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Diminished hERG K+ channel activity facilitates strong human labour contractions but is dysregulated in obese women. Nat Commun 2014; 5:4108. [PMID: 24937480 DOI: 10.1038/ncomms5108] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Accepted: 05/13/2014] [Indexed: 01/01/2023] Open
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Mijušković A, Oreščanin-Dušić Z, Nikolić-Kokić A, Slavić M, Spasić MB, Spasojević I, Blagojević D. Comparison of the effects of methanethiol and sodium sulphide on uterine contractile activity. Pharmacol Rep 2014; 66:373-9. [DOI: 10.1016/j.pharep.2013.12.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Revised: 11/04/2013] [Accepted: 12/19/2013] [Indexed: 01/13/2023]
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Sharma A, Choudhury S, Nakade UP, Yadav RS, Garg SK. Calcium influx and release mechanism(s) in histamine-induced myometrial contraction in buffaloes. Anim Reprod Sci 2014; 146:157-64. [PMID: 24631173 DOI: 10.1016/j.anireprosci.2014.02.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Revised: 02/02/2014] [Accepted: 02/15/2014] [Indexed: 01/10/2023]
Abstract
The present study was undertaken to characterize the presence of histamine H1R using molecular biology tools and unravel the influx and release mechanism(s) involved in calcium signalling cascades in histamine-induced myometrial contraction in buffaloes. The presence of H1R mRNA transcript and immunoreactive membrane protein in buffalo myometrium was confirmed by RT-PCR and Western blot analysis. Further, histamine produced concentration-dependent (1nM-10μM) contraction in buffalo myometrium with a potency of 7.13±0.11. When myometrial strips were pre-incubated either with Ca(2+) free solution or with nifedipine, a L-type Ca(2+) channel blocker, dose response curve (DRC) of histamine was significantly (P<0.05) shifted towards right with decline in maximal contraction (Emax). Reduction in Emax of histamine in the presence of nifedipine (55.75±3.10%) was significantly (P<0.001) greater than that in the presence of ruthenium red (93.61±3.43%), a blocker of IP3-gated and RyR-sensitive Ca(2+) channels. Moreover, histamine produced only 26.87±1.99% of the maximum contraction in the presence of both nifedipine and CPA (blocker of sarco-endoplasmic reticulum Ca(2+)-ATPase). Interestingly, following concurrent exposure to U-73122 (a PL-C inhibitor) and nifedipine, the DRC of histamine was significantly (P<0.05) shifted towards left with increase in maximal contraction (126.30±3.36%). Our findings in buffalo uterus thus suggest that influx of extracellular calcium plays a major role in histamine-induced myometrial contraction, while release of intracellular calcium through calcium-release channels of sarcoplasmic reticulum has a minor role. A possible involvement of non-selective cation channels in histamine-induced myometrial contraction cannot be ruled out, and therefore requires further investigations.
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Affiliation(s)
- Abhishek Sharma
- Department of Pharmacology & Toxicology, College of Veterinary Science and Animal Husbandry, U.P. Pandit Deen Dayal Upadhyaya Pashu Chikitsa Vigyan Vishwavidyalaya Evam Go-Anusandhan Sansthan, Mathura 281001, India
| | - Soumen Choudhury
- Department of Pharmacology & Toxicology, College of Veterinary Science and Animal Husbandry, U.P. Pandit Deen Dayal Upadhyaya Pashu Chikitsa Vigyan Vishwavidyalaya Evam Go-Anusandhan Sansthan, Mathura 281001, India
| | - Udayraj P Nakade
- Department of Pharmacology & Toxicology, College of Veterinary Science and Animal Husbandry, U.P. Pandit Deen Dayal Upadhyaya Pashu Chikitsa Vigyan Vishwavidyalaya Evam Go-Anusandhan Sansthan, Mathura 281001, India
| | - Rajkumar Singh Yadav
- Department of Pharmacology & Toxicology, College of Veterinary Science and Animal Husbandry, U.P. Pandit Deen Dayal Upadhyaya Pashu Chikitsa Vigyan Vishwavidyalaya Evam Go-Anusandhan Sansthan, Mathura 281001, India
| | - Satish Kumar Garg
- Department of Pharmacology & Toxicology, College of Veterinary Science and Animal Husbandry, U.P. Pandit Deen Dayal Upadhyaya Pashu Chikitsa Vigyan Vishwavidyalaya Evam Go-Anusandhan Sansthan, Mathura 281001, India.
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Bru-Mercier G, Gullam JE, Thornton S, Blanks AM, Shmygol A. Characterization of the tissue-level Ca2+ signals in spontaneously contracting human myometrium. J Cell Mol Med 2014; 16:2990-3000. [PMID: 22947266 PMCID: PMC4393727 DOI: 10.1111/j.1582-4934.2012.01626.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Accepted: 08/28/2012] [Indexed: 11/30/2022] Open
Abstract
In the labouring uterus, millions of myocytes forming the complex geometrical structure of myometrium contract in synchrony to increase intrauterine pressure, dilate the cervix and eventually expel the foetus through the birth canal. The mechanisms underlying the precise coordination of contractions in human myometrium are not completely understood. In the present study, we have characterized the spatio-temporal properties of tissue-level [Ca(2+)](i) transients in thin slices of intact human myometrium. We found that the waveform of [Ca(2+)](i) transients and isotonic contractions recorded from thin slices was similar to the waveform of isometric contractions recorded from the larger strips in traditional organ bath experiments, suggesting that the spatio-temporal information obtained from thin slices is representative of the whole tissue. By comparing the time course of [Ca(2+)](i) transients in individual cells to that recorded from the bundles of myocytes we found that the majority of myocytes produce rapidly propagating long-lasting [Ca(2+)](i) transients accompanied by contractions. We also found a small number of cells showing desynchronized [Ca(2+)](i) oscillations that did not trigger contractions. The [Ca(2+)](i) oscillations in these cells were insensitive to nifedipine, but readily inhibited by the T-type Ca(2+) channel inhibitor NNC55-0396. In conclusion, our data suggest that the spread of [Ca(2+)](i) signals in human myometrium is achieved via propagation of long-lasting action potentials. The propagation was fast when action potentials propagated along bundles of myocytes and slower when propagating between the bundles of uterine myocytes.
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