Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCB028

Poster Communications

Label-free analysis of the Na+/Ca2+-exchanger (NCX) isolated from iPSC-derived cardiomyocytes

M. Barthmes1, A. Bazzone1, U. Thomas1, A. Brüggemann1, M. George1, N. Fertig1, A. R. Obergrussberger1

1. Nanion Technologies GmbH, Munich, Bavaria, Germany.

  • Activation of NCX by Ca2+-containing buffer and subsequent block by Cd2+ recorded on the SURFE2R N1. The effect of Cd2+ was reversible upon washout.

The Sodium-Calcium Exchangers (NCX) play an important role in the cellular calcium homeostasis under physiological and pathological conditions. NCX has been of interest as a pharmacological target for many years, in particular because clinical trials involving inhibitors of the sodium-proton exchanger, NHE, have delivered mixed results. Inhibition of the reversed mode of NCX is thought to be beneficial in ischemia/reperfusion injury by reducing cardiac, neuronal and renal infarct areas. Moreover, inhibition of NCX is has been proposed to exhibit an anti-arrhythmic effect and therefore, may provide a novel target for the treatment of a variety of arrhythmic pathologies. So far, a number of studies have shown promising results but investigations are limited by the currently available NCX inhibitors such as KB-R7943, SEA-0400 and SN-6 which are only partially specific. To drive the progress in pharmacological NCX research, new methods to measure NCX function are needed. At the current time, functional investigation of NCX range from patch-clamp, calcium flux assays, Langendorff-perfused hearts to studies in whole animals. We have developed an electrophysiological method to investigate NCX function which is based on the solid supported membrane (SSM) technique. HEK cells overexpressing NCX were used on an automated SSM device recording from either 1 or 96 wells simultaneously. This vastly increases throughput which is a critical factor in screening of pharmacological agents for NCX activity. In addition, human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) were used on a single-well SSM electrophysiology device and NCX was recorded from these cells. NCX was activated using Ca2+ in the buffer and inhibited by Cd2+, and this inhibition was reversed upon washout of Cd2+. NCX was blocked by KB-R7943 with an IC50 of 10.7 µM. As expected, NCX recorded from hiPSC-CMs was blocked by the pro-arrhythmic compound, bepridil with an IC50 of 13 µM. Furthermore, the pro-arrhythmic effects of bepridil were investigated using electrical impedance and extracellular field potential (EFP) measurements in order to find out the effects of bepridil on contractility and electrophysiology of hiPSC-CMs in a beating monolayer.

Where applicable, experiments conform with Society ethical requirements