Proceedings of The Physiological Society

Physiology 2016 (Dublin, Ireland) (2016) Proc Physiol Soc 37, PCB312

Poster Communications

KV7 channel activators inhibit pregnant mouse myometrium uterine contractility and delay RU486 induced preterm birth

Y. T. Mansour1, R. Patel1, I. A. Greenwood2, S. K. England3, P. Taylor1, R. M. Tribe1

1. Women's Health, King's College London, London, United Kingdom. 2. Vascular Biology Research Centre, St George's University of London, London, United Kingdom. 3. Obstetrics & Gynecology, School of Medicine, Washington University in St Louis, St Louis, Missouri, United States.

Introduction: This study focussed on the potential of KV7 channel activators as a new class of tocolytics. Building upon our previous work demonstrating KV7 channels (alpha subunits KCNQ1-5 and auxiliary proteins KCNE1-5 genes) are expressed in myometrium from women at term and preterm gestations, and functional in pregnant human myometrium, our aim was to assess the function of KV7 channels and determine whether KV7 activators could delay birth in in murine model of preterm birth. Methods: Myometrium was isolated on day 16 of gestation from C57BL/6J pregnant mice treated with RU486 to induce preterm labour (PTL, 150 µg S.C., day 15) or DMSO (preterm not in labour, PTNL) (n=6 per group). Tissues were used for isometric organ bath studies (% of baseline mean integral tension) with KV7 channel activators retigabine and ML213 (5-20 µM) or stored (-80°C) for analysis (qPCR). CCTV recording used to determine the onset of labour and time gestation length (delivery of first pup) following a maximum of six doses (given once an hour) of either retigabine or ML213 (20 mg/kg P.O) or vehicle. In vivo uterine telemetry determined the impact of acute doses (2 doses P.O.) of retigabine on intrauterine pressure (IUP). Data are mean ± S.E.M. or median [interquartile range] and assessed using Kruskal-Wallis test with Dunn's multiple comparison post hoc test or Mann-Whitney U test (significance, P<0.05) Results: mRNA for KCNQ1-5 and KCNE 1-5 mRNA were detected in PTNL and PTL mouse myometrium (n=4-6, expression profile KCNQ1=Q5>Q4>Q2>Q3). mRNA expression for KCNQ4 and KCNQ5 slightly decreased after labour onset (P <0.05). KCNE expression profiles in PTL myometrium (E4>E3>E2>E5>E1) differed slightly to those in PTNL (E4>E2>E3>E5>E1) due to a reduction in KCNE2 expression in labour. Retigabine and ML213 suppressed myometrium contractions in vitro in PTL at all concentrations studied (e.g. MIT: retigabine at 5 µM, 32.7 ± 4.5% versus DMSO 79.2 ± 4.5%, p<0.05; ML213 at 5 µM 11.9 ± 3.6% versus DMSO 75.8 ± 4.5% p<0.05, n=6). In vivo, acute doses of retigabine transiently reduced IUP when analysed relative to time of labour, but did not increase gestation length. However, both retigabine and ML213 when given in 6 repeated doses caused significant 6 and 3 hour delays in preterm labour onset respectively compared to the KV7 activator vehicle (p<0.01). Conclusions: KV7 channels are present and functional in myometrium from the RU486 mouse model of preterm birth, and treatment in vivo with KV7 channel activators can delay preterm birth. Taken together with our previous in vitro human myometrium data this suggests that KV7 channels are a viable tocolytic target. Development of activators that target the predominant myometrium KV7 channel isoforms should be pursued.

Where applicable, experiments conform with Society ethical requirements