Frieß, J. L.

Heselich, A.

Layer, P. G.

Ritter, S.

Thielemann, C.

GSI Repository

Combined effects of ionizing radiation and cardio-active drugs on human iPSC-derived cardiomyocytes* J. L. Frieß1, A. Heselich2, S. Ritter2, P. G. Layer3 and C. Thielemann1 1University of Applied Sciences Aschaffenburg, biomems lab, Germany;  2GSI, Biophysics, Darmstadt, Germany;     3TU Darmstadt, Developmental Biology and Neurogenetics, Darmstadt, Germany Motivation There are multiple cardio-active pharmaceuticals avail-able on the market, extracting various electrophysiologi-cal effects upon the human heart. These effects are well known and well characterized [1]. However, there is vir-tually no information on the combined effects of applied heart pharmaceuticals in conjunction with ionizing radia-tion. A deeper insight in these effects, however, is of great interest for occupationally exposed groups, heart patients receiving radiation treatments, as well as astronauts. Therefore we examined the influence of X-rays on drug-treated human induced pluripotent stem cell (hiPSC)-derived cardiomyocyte cultures. As a test substance iso-proterenol, an analogon of the stress hormone adrenaline, was applied. The applied X-ray dose was 2 Gy. Electro-physiological parameters of the cultures were measured using microelectrode array (MEA) technology for 7 days after radiation exposure. Our results show an increase in the beat rate enhancing property of isoproterenol one day after irradiation. Direct radiation effects on the drug itself could be excluded. This poses many questions on the combined effects of ionizing radiation and stress re-sponse.  Materials&Methods Human induced pluripotent stem cell (hiPSC) –derived cardiomyocytes (Cellular Dynamics, Madison, WI, USA) were cultured on microelectrode array chips (Multichan-nel Systems, Reutlingen, Germany) for 5 days prior to the experiment (Figure 1). Electrophysiological properties of the cell cultures were measured before and after exposure. Cardiac signals could be recorded for 7 days after treat-ment and were analyzed in terms of beat rate, conduction velocity, field action potential duration and general spike shape, using the MATLAB-based software DrCell [2]. X-irradiation was performed with 250 kV at 16 mA at a dose rate of 2 Gy/min. First only culture medium supplemented with 500 nM isoproterenol was irradiated with 2 and 7 Gy of X-ray and subsequently applied to the cardiomyocytes. Effects of the irradiated chemical on the cells were moni-tored for one day. Then cultures were treated with 500 nM of isoproterenol and subsequently irradiated with 2 Gy X-rays. Electrophysiology was then monitored for another 7 days. Figure 1: Human induced pluripotent stem cell-derived cardiomyocytes cultured on a microelectrode array at a 100× magnification. Myosin heavy chains are genetically marked with red fluorescent protein. Microelectrodes have a diame-ter of 30 µm. APPA-HEALTH-37 GSI SCIENTIFIC REPORT 2014330 DOI:10.15120/GR-2015-1-APPA-HEALTH-37Results In a study performed by Guo et al., it was shown that isoproterenol, has a beat rate enhancing effect on hiPSC-derived cardiomyocytes [3]. To examine if ionizing radia-tion alters the effectiveness of isoproterenol, culture me-dium containing 500 nM isoproterenol was irradiated with 2 and 7 Gy, respectively. These irradiated media were administered to the cultures and electrophysiology was monitored for 1 day. The experiments showed that irradia-tion with up to 7 Gy X-rays had only minor effects on the beat rate enhancing property of the pharmaceutical, 1 day after application (Figure 2).  After exclusion of possible radiation-induced effects on the chemical, cardiomyocyte cultures were first treated with isoproterenol and subsequently irradiated with 2 Gy X-rays. The cultures were measured daily for seven days after exposure. One day after treatment, the beat rate of samples exposed to 2 Gy X-ray and 500 nM isoproterenol increases above all other samples (Figure 3).  Figure 2: The beat rate enhancing property of isopro-terenol is only marginally affected by X-irradiation, 1 day after administration. Data represent medians normalized to the controls before treatment. Error bars represent standard error. Ncontrols = 6; Nisoproterenol 0; 2; 7 Gy = 3 (sta-tistics were performed by two-tailed unpaired t-test, CI = 95%, **P < 0.01). Figure 3: X-irradiation further enhances the beat rate of cardiomyocytes treated with 500 nM isoproterenol, one day after irradiation. Data represent medians normalized to the controls before treatment. Error bars represent standard error. N = 5 (statistics were performed by two-tailed unpaired t-test, CI = 95%, *P < 0.05).  Summary Our data indicate that the exposure to ionizing radiation of cardiomyocytes pre-treated with isoproterenol may further increase the enhanced beat rate of cardiomyocytes. This effect possibly harbours yet unknown threats to peo-ple occupationally exposed to ionizing radiation and are either taking heart pharmaceuticals or are exposed to stress, as isoproterenol chemically resembles the stress hormone adrenaline. References [1] M. Reppel, P. Igelmund, U. Egert, F. Juchelka, J. Hescheler, I. Drobinskaya, Effect of cardioactive drugs on action potential generation and propagation in embryonic stem cell-derived cardiomyocytes, Cellular Physiology and Biochemistry, 19 (2007) 213-224. [2] C. Nick, M. Goldhammer, R. Bestel, F. Steger, A. Daus, C. Thielemann, DrCell – A Software Tool for the Analysis of Cell Signals recorded with Extracellular Microelectrodes, Signal Processing: An International Journal (SPIJ), (2013) 96-109. [3] L. Guo, R.M. Abrams, J.E. Babiarz, J.D. Cohen, S. Kameoka, M.J. Sanders, E. Chiao, K.L. Kolaja, Estimating the risk of drug-induced proarrhythmia using human induced pluripotent stem cell-derived cardiomyocytes, Toxicological sciences : an official journal of the Society of Toxicology, 123 (2011) 281-289. __________________________________________________________________________________________ * This work is supported by the DLR and ESA in the frame of the ESA IBER-10 program. Grant #: 50WB1226 And in parts by the German federal ministry of education and research (BMBF). Grant#: 02NUK037A.GSI SCIENTIFIC REPORT 2014 APPA-HEALTH-37DOI:10.15120/GR-2015-1-APPA-HEALTH-37 331

Combined effects of ionizing radiation and cardio-active drugs on human iPSC-derived cardiomyocytes

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Combined effects of ionizing radiation and cardio-active drugs on human iPSC-derived cardiomyocytes

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