Human Cardiomyocytes Pentamidine Pilsicainide

Evaluation of two hERG channel trafficking modulators, pentamidine and pilsicainide, on stably transfected cell line and human induced pluripotent stem cell-derived cardiomyocytes

R. Printemps1, S. Guilbot1, M. Morton2, M. Le Grand11 PhysioStim, Zone Industrielle de Brénas, 81440 Lautrec, France | 2ApconiX Ltd, 3F68 AlderleyPark, Cheshire, SK104TG, United Kingdom

hERG trafficking inhibition is known to be one of the mechanisms of indirect hERG inhibition, resulting in QT prolongation and lethal arrhythmia. An increasing number of drugs have been shown to interfere with hERG trafficking. Pilsicainide is a widely used antiarrhythmic agent (class Ic) especially for treating atrial fibrillation. This compound has been evaluated on hERG channel current expressed in stably transfected mammalian cell line as well as on human induced pluripotent stem cell derived cardiomyocytes (iPSC-CM) and compared to pentamidine, a well-known hERG trafficking inhibitor.

Method

Ion channel data

  • Electrophysiological recordings of hERG, Nav1.5 (peak), Ito and Iks currents were made from Chinese Hamster Ovary (CHO) cell lines while Cav1.2 currents were made from Human Embryonic Kidney (HEK-293) cell line. All cell lines stably expressed the full-length ion channel. Single cell ionic currents were measured in whole-cell configuration at room temperature (21-23⁰C) using a Patchliner (Nanion Technologies).
  • For acute study, cells were clamped at a holding potential of -80mV before a depolarizing step appropriate for each channel. Six Point concentration-response curves were generated by cumulative addition of compound and steady-state inhibition was achieved before the next concentration of compound was added.
  • During chronic exposure, hERG cells were exposed during 24h to different concentrations of pentamidine or pilsicainide and then hERG current amplitudes were recorded.
  • Data are expressed as Mean ± SEM. For acute study, experiments were replicated 4 times while during chronic exposition, the number of experiments ranged from 28 to 44 for pentamidine, and between 90 and 165 for pilsicainide.

Human Induced Pluripotent Stem cells derived cardiomyocytes (iPSC-CM)

  • iCell® Cardiomyocytes2 were supplied by Cellular Dynamics (a Fujifilm company) and seeded on 48 wells plate following manufacturers instruction and analyzed using the xCELLigence RTCA cardio ECR platform (simultaneous measurement of MEA and impedance).
  • 4 to 6 days after seeding, iCell2 cardiomyocytes were exposed during 48h to different concentrations of pentamidine and pilsicainide.
  • The following parameters were monitored: Cell Index (CI), Amplitude of contraction, Beat rate (BR) , Beating period (BP) , Individual Beating Duration (IBD), Field Potential Duration (FPD) and FPD corrected by Fridericia (FPDc), Spike amplitude, Beating Rhythm Irregularity (BRI).

Results

Ion channel experiments

Ion channel panel, acute exposition:

hERG channel

  • No acute effect of pentamidine on hERG, Nav1.5, Cav1.2, Iks and Ito.
  • Chronic exposition to pentamidine decrease the amplitude of hERG current (estimated IC50 = 9.0µM)
  • Acute effect of pilsicainide on hERG channel (estimated IC50 = 24.6µM) but no acute effects on Nav1.5, Cav1.2, Iks and Ito.
  • Chronic exposition to pilsicainide increase the amplitude of hERG current (≈+50%) whatever the concentration tested.

Ion channel panel, acute exposition:

iPSCs cardiomyocytes

Pentamidine

Pilsicainide

  • No acute effect of pentamidine on each parameter during the first 2 hours. From 6h to 24h, pentamidine 30 μM time-dependently ↓ amplitude of contraction, BR and CIand ↓ FPDc (+123% at 24h) and BRI (at 12h). After 48h, the cells stopped beating with pentamidine 30μM.
  • Acute effects of pilsicainide conduct to a concentration-dependent ↓ of BR (-28% at 10µM) and an ↑ of FPDc (+28% at 10µM) with maximum effect after 15 min and sustained through 48h. Pilsicainide from 1 to 10µM had no effect on amplitude of contraction and CI. The cells stopped beating immediately after pilsicainide 20µM addition.

conclusion

  • Absence of pentamidine’s acute effects on hERG current in CHO cells is confirmed in Human iPSC-CM. Indeed, no modification of FPDc was observed before 6h of treatment at the highest concentration tested (30 µM).
  • On the other hand, the increase of hERG trafficking observed on CHO cells by pilsicainide was not confirmed in iPSC-CM as FPDc was prolonged after short-term exposition and maintained during time.
  • This predictive and sensitive assay is particularly relevant for long-term cardiotoxicity assessment in Human iPSC derived cardiomyocytes.

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