[Show abstract][Hide abstract] ABSTRACT: Ethnopharmacological relevance:
People living in the tropical rain forest of South-Western Nigeria use Rinorea dentata (P. Beauv.) Kuntze (Violaceae) in ethno-veterinary medicine to facilitate parturition. There are no evidence-based pharmacological investigations for the uterotonic activity of this plant. Aims of study (i) Collection of data about the ethnopharmacological uses of R. dentata and evaluation of its uses and applications in health care; (ii) determining potential uterotonic effects in vitro, and (iii) chemical characterization of R. dentata, which is a member of the Violaceae family known to express circular cystine-knot peptides, called cyclotides. Materials and Methods The ethnopharmacological use of R. dentata in settlement camps within the area J4 of Omo forest has been investigated by semi-structured questionnaires and open interviews. Use index analysis has been performed by seven quantitative statistical models. Respondents' claim on the beneficial ethno-veterinary application of the plant to aid parturition has been investigated in vitro by myometrial contractility organ bath assays. The bioactive plant extract was screened by chemical derivatization and mass spectrometry-based peptidomics using reversed-phase HPLC fractionation and MALDI-TOF/TOF analysis. Results Based on the survey analysis, medicinal preparations of R. dentata have been used for anti-microbial and anti-malaria purpose in humans, and for aiding parturition in farm animals. The latter application was mentioned by one out of six respondents who claimed to use this plant for any medicinal purpose. The plant extract exhibited a weak uterotonic effect using organ bath studies. The plant contains cyclotides and the peptide riden A has been identified by de novo amino acid sequencing using mass spectrometry. Conclusion Few dwellers around the settlement camps of the tropical forest of Omo (Nigeria) use R. dentata for various health problems in traditional veterinary and human medicine. The weak uterotonic effect of the cyclotide-rich extract is in agreement with the low use value index obtained for this plant. Cyclotides have been reported in the genus Rinorea confirming the ubiquitous expression of these stable bioactive plant peptides within the family of Violaceae.
Full-text · Article · Feb 2016 · Journal of ethnopharmacology
[Show abstract][Hide abstract] ABSTRACT: Aim: Magnesium sulphate (MgSO4) is currently used in obstetrics for treatment of seizures in women with preeclampsia. It is also used for neonatal protection and given to women who are anticipated to deliver
before 32 weeks of gestation. The use of MgSO4 as a tocolytic is however questioned. The aim of this study was to assess in vitro the inhibitory effects of MgSO4 in term pregnant and non-pregnant mice myometrium.
Methods: Myometrial strips obtained from term pregnant (18 days) and non-pregnant mice were superfused in physiological saline solution at pH 7.4 and 37 °C. After steady contractions were achieved, the effect of different concentrations of MgSO4 (2 –12 mM) was examined on spontaneous and oxytocin induced (0.5 nM) myometrial contractions.
Results: MgSO4 had an inhibitory effect on mouse myometrium. Compared with controls (100%),10mM MgSO4 produced a significant (P <0.001) decrease in force integral of spontaneous (6.14 ± 3.18%, n=9) and oxytocin-induced (50.5 ± 3.93%, n=11) contracting pregnant myometrium, mean ± SEM. 50% reduction of force integral was achieved in spontaneous and oxytocin induced contractions at 4mM and 10mM respectively. In non-pregnant myometrium, the effect of MgSO4 was less than that observed in pregnant, 50% reduction was seen at 8 and 10mM of spontaneous and oxytocin induced contractions respectively and further decreased with increased concentrations.
Conclusion: Our in vitro data demonstrated that MgSO4 had a dose dependent inhibitory effect on pregnant and non-pregnant mouse myometrial contractility. Oxytocin decreases its effectiveness which may affect its tocolytic ability in vivo.
[Show abstract][Hide abstract] ABSTRACT: Advances in molecular, genetic and "omic" technologies are fuelling the thirst to better understand the uterus, and then apply this information to problems in pregnancy and labour. Progress has, however, been limited while we still have an incomplete understanding of some of the basic physiology of uterine smooth muscle (myometrium). In this review and opinion piece I will explore some of the fascinating findings from selected recent studies and see how these may provide new avenues for physiological and clinical research. It is also the case however that there is still limited mechanistic understanding about physiological and pathophysiological processes in the myometrium. This lack of understanding limits the usefulness of some finding from genomic and allied studies. By focussing on some key recent findings and relating these to two important clinical problems in childbirth that involve myometrial activity; preterm delivery and difficult labours, the interplay between our physiological knowledge and information provided by newer technologies will be explored. My opinion is that physiology has provided much more new mechanistic insight into difficult births and that the newer technologies may lead to breakthroughs in preterm birth research, but that this has not happened yet. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
No preview · Article · Aug 2015 · Experimental physiology
[Show abstract][Hide abstract] 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 have 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 investigated. In some experiments simultaneous force and intracellular Ca or pH (pHi ) were measured with Indo-1 or carboxy-Snarf respectively. Statistical differences were tested using non-parametric tests and significance taken as P<0.05. Lactate significantly decreased spontaneous contractility with an IC50 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 fall of pHi abolished its effects. We also show that lactate inhibited Ca transients and these changes mirrored those produced on force. If Ca entry was enhanced by depolarization (high KCl) or applying the Ca channel agonist, Bayk4644, the effects of lactate were abolished. Together these data show that lactate in the physiological range potently decreases myometrial contractility, due to its inhibition of Ca transients, which can be attributed to the induced acidification. This study suggests accumulation of extracellular lactate will reduce myometrial contractions and could therefore contribute to labour dystocia. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
No preview · Article · Jul 2015 · The Journal of Physiology
[Show abstract][Hide abstract] ABSTRACT: For successful birth, contractions need to become progressively stronger. The underlying mechanisms are unknown, however. We have found that a novel mechanism, hypoxia-induced force increase (HIFI), is switched on selectively, at term, and is essential to strengthening contractions. HIFI is initiated as contractions cyclically reduce blood flow and produce repeated hypoxic stresses, with associated metabolic and transcriptomic changes. The increases in contractility are a long-lasting, oxytocin-independent, intrinsic mechanism present only in the full-term pregnant uterus. HIFI is inhibited by adenosine receptor antagonism and blockade of cyclooxygenase-2 signaling, and partially reproduced by brief episodes of acidic (but not alkalotic) pH. HIFI explains how labor can progress despite paradoxical metabolic challenge, and provides a new mechanistic target for the 1 in 10 women suffering dysfunctional labor because of poor contractions.
No preview · Article · Jul 2015 · Proceedings of the National Academy of Sciences
[Show abstract][Hide abstract] ABSTRACT: Introduction
Increasing evidence suggests obesity has its origins prior to birth. There is clear correlation between maternal obesity, high birthweight and offspring risk of obesity in later life. It is also clear that women who are obese during pregnancy are at greater risk of adverse outcomes, including gestational diabetes and stillbirth. The mechanism(s) by which obesity causes these problems is unknown, although hyperglycaemia and insulin resistance are strongly implicated. We present a protocol for a study to test the hypothesis that metformin will improve insulin sensitivity in obese pregnant women, thereby reducing the incidence of high birthweight babies and other pregnancy complications.
Methods and analysis
The Efficacy of Metformin in Pregnant Obese Women, a Randomised controlled (EMPOWaR) trial is a double-masked randomised placebo-controlled trial to determine whether metformin given to obese (body mass index >30 kg/m2) pregnant women from 16 weeks’ gestation until delivery reduces the incidence of high birthweight babies. A secondary aim is to test the mechanism(s) of any effect. Obese women with a singleton pregnancy and normal glucose tolerance will be recruited prior to 16 weeks’ gestation and prescribed study medication, metformin or placebo, to be taken until delivery. Further study visits will occur at 28 and 36 weeks’ gestation for glucose tolerance testing and to record anthropometric measurements. Birth weight and other measurements will be recorded at time of delivery. Anthropometry of mother and baby will be performed at 3 months postdelivery. As of January 2014, 449 women had been randomised across the UK.
Ethics and dissemination
The study will be conducted in accordance with the principles of Good Clinical Practice. A favourable ethical opinion was obtained from Scotland A Research Ethics Committee, reference number 10/MRE00/12. Results will be disseminated at conferences and published in peer-reviewed journals.
Trial registration number
[Show abstract][Hide abstract] 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.This article is protected by copyright. All rights reserved.
Full-text · Article · Nov 2014 · Acta Physiologica
[Show abstract][Hide abstract] ABSTRACT: Apolipoprotein-E knockout (ApoE−/−) mice develop hypercholesterolemia and are a useful model of atherosclerosis. Hypercholesterolemia alters intracellular Ca2+ signalling in vascular endothelial cells but our understanding of these changes, especially in the early stages of the disease process, is limited. We therefore determined whether carbachol-mediated endothelial Ca2+ signals differ in plaque-prone aortic arch compared to plaque-resistant thoracic aorta, of wild-type and ApoE−/− mice, and how this is affected by age and the presence of hypercholesterolemia. The extent of plaque development was determined using en-face staining with Sudan IV. Tissues were obtained from wild-type and ApoE−/− mice at 10 weeks (pre-plaques) and 24 weeks (established plaques). We found that even before development of plaques, significantly increased Ca2+ responses were observed in arch endothelial cells. Even with aging and plaque formation, ApoE−/− thoracic responses were little changed, however a significantly enhanced Ca2+ response was observed in arch, both adjacent to and away from lesions. In wild-type mice of any age, 1–2% of cells had oscillatory Ca2+ responses. In young ApoE−/− and plaque-free regions of older ApoE−/−, this is unchanged. However a significant increase in oscillations (~13–15%) occurred in thoracic and arch cells adjacent to lesions in older mice. Our data suggest that Ca2+ signals in endothelial cells show specific changes both before and with plaque formation, that these changes are greatest in plaque-prone aortic arch cells, and that these changes will contribute to the reported deterioration of endothelium in atherosclerosis.
[Show abstract][Hide abstract] ABSTRACT: In the myometrium SR Ca(2+) depletion promotes an increase in force but unlike several other smooth muscles, there is no Ca(2+) 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 Ca(2+)-ATPase (SERCA) inhibition on the temporal relationship between action potentials, Ca(2+) transients and force. Simultaneous recording of electrical activity, calcium and force showed that SERCA inhibition, by cyclopiazonic acid (CPA 20μM), caused time-dependent changes in excitability, most noticeably depolarization and elevations of baseline [Ca(2+)]i and force. At the onset of these changes there was a prolongation of the bursts of action potentials and a corresponding series of Ca(2+) spikes, which increased the amplitude and duration of contractions. As the rise of baseline Ca(2+) and depolarization continued a point was reached when electrical and Ca(2+) spikes and phasic contractions ceased, and a maintained, tonic force and Ca(2+) was produced. Lanthanum, a non-selective blocker of store-operated Ca(2+) entry, but not the L-type Ca(2+) channel blocker nifedipine (1-10μM), 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 Ca(2+) depletion without eliciting receptor-operated channel opening, also produced these results. The data obtained suggest that in pregnant rats SR Ca(2+) release is coupled to marked Ca(2+) entry, via store operated Ca(2+) channels, leading to depolarization and enhanced electrical and mechanical activity.
[Show abstract][Hide abstract] ABSTRACT: Oxytocin is a nonapeptide hormone that has a central role in the regulation of parturition and lactation. In this review, we address oxytocin receptor (OTR) signalling and its role in the myometrium during pregnancy and in labour. The OTR belongs to the rhodopsin-type (Class 1) of the G-protein coupled receptor (GPCR) superfamily and is regulated by changes in receptor expression, receptor desensitisation and local changes in oxytocin concentration. Receptor activation triggers a number of signalling events to stimulate contraction, primarily by elevating intracellular calcium (Ca). This includes; inositol-tris-phosphate-mediated store calcium release, store-operated Ca entry and voltage-operated Ca entry. We discuss each mechanism in turn and also discuss Ca-independent mechanisms such as Ca sensitisation. Since oxytocin induces contraction in the myometrium, both the activation and the inhibition of its receptor have long been targets in the management of dysfunctional and preterm labours respectively.. We discuss current and novel OTR agonists and antagonists and their use and potential benefit in obstetric practice. In this regard, we highlight the following clinical scenarios: dysfunctional labour, postpartum haemorrhage and preterm birth.This article is protected by copyright. All rights reserved.
Full-text · Article · Apr 2014 · Journal of Neuroendocrinology
[Show abstract][Hide abstract] ABSTRACT: Little is known about how hypercholesterolemia affects Ca2+ signalling in the vasculature of ApoE−/− mice, a model of atherosclerosis. Our objectives were therefore to determine (i) if hypercholesterolemia alters Ca2+ signalling in aortic endothelial cells before overt atherosclerotic lesions occur, (ii) how Ca2+ signals are affected in older plaque-containing mice, and (iii) whether Ca2+ signalling changes were translated into contractility differences. Using confocal microscopy we found agonist-specific Ca2+ changes in endothelial cells. ATP responses were unchanged in ApoE−/− cells and methyl-β-cyclodextrin, which lowers cholesterol, was without effect. In contrast, Ca2+ signals to carbachol were significantly increased in ApoE−/− cells, an effect methyl-β-cyclodextrin reversed. Ca2+ signals were more oscillatory and store-operated Ca2+ entry decreased as mice aged and plaques formed. Despite clearly increased Ca2+ signals, aortic rings pre-contracted with phenylephrine had impaired relaxation to carbachol. This functional deficit increased with age, was not related to ROS generation, and could be partially rescued by methyl-β-cyclodextrin. In conclusion, carbachol-induced calcium signalling and handling are significantly altered in endothelial cells of ApoE−/− mice before plaque development. We speculate that reduction in store-operated Ca2+ entry may result in less efficient activation of eNOS and thus explain the reduced relaxatory response to CCh, despite the enhanced Ca2+ response.
[Show abstract][Hide abstract] ABSTRACT: In this short review we discuss how recent insights into myometrial physiology may be taken forward and translated into much needed novel therapies for problems associated with labour. We consider excitation-contraction coupling in the myometrium and how this relates to our understanding of the changes that occur to produce myometrial contractions and successful labour. We then discuss how this information has already been used in the development of drugs to either stimulate or relax the myometrium, to address the needs of women with either slow (dystocic) labours or threatened preterm labours, respectively. We next present the data showing how basic physiological findings pertaining to hypoxia and lactate production, have been taken and translated into a tool for predicting and hence better managing difficult labours. We then highlight examples of where physiological research has started to provide mechanistic insight into clinical problems associated with labour and parturition (obesity, diabetes, advanced maternal age, postdate and twin pregnancies) and suggest how these findings could be translated into new therapies for difficult labours.
No preview · Article · Dec 2013 · Experimental physiology
[Show abstract][Hide abstract] ABSTRACT: This report summarizes work on investigating the effects of some medicinal plants on uterine contraction. As there is a clinical need to find better drugs to help control uterine activity, and novel compounds are sought, the mechanisms whereby the medicinal plants exerted their effects along with their major compounds are discussed. By identifying the plants, major constituents and mechanisms, this review will also illustrate where new drugs may be next developed so that better ways to treat uterine disorders will be available to women worldwide.
No preview · Article · Nov 2013 · Experimental physiology
[Show abstract][Hide abstract] ABSTRACT: Cyclotides are plant peptides comprising a circular backbone and three conserved disulfide bonds that confer them with exceptional stability. They were originally discovered in Oldenlandia affinis based on their use in traditional African medicine to accelerate labor. Recently, cyclotides have been identified in numerous plant species of the coffee, violet, cucurbit, pea, potato, and grass families. Their unique structural topology, high stability, and tolerance to sequence variation make them promising templates for the development of peptide-based pharmaceuticals. However, the mechanisms underlying their biological activities remain largely unknown; specifically, a receptor for a native cyclotide has not been reported hitherto. Using bioactivity-guided fractionation of an herbal peptide extract known to indigenous healers as "kalata-kalata," the cyclotide kalata B7 was found to induce strong contractility on human uterine smooth muscle cells. Radioligand displacement and second messenger-based reporter assays confirmed the oxytocin and vasopressin V1a receptors, members of the G protein-coupled receptor family, as molecular targets for this cyclotide. Furthermore, we show that cyclotides can serve as templates for the design of selective G protein-coupled receptor ligands by generating an oxytocin-like peptide with nanomolar affinity. This nonapeptide elicited dose-dependent contractions on human myometrium. These observations provide a proof of concept for the development of cyclotide-based peptide ligands.
Full-text · Article · Nov 2013 · Proceedings of the National Academy of Sciences