Human-induced pluripotent stem cell-derived cardiomyocytes have limited I Ks for repolarization reserve as revealed by specific KCNQ1/KCNE1 blocker

Figures

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  Figure 1.. Effect of L-673 on KCNQ1/KCNE1 channels overexpressed in HEK293 cells. Example traces of whole-cell IKS currents (a), elicited with a voltage step, are superimposed during control condition and after addition of 10 nM L-673. The voltage-clamp protocol is shown above the current traces. The concentration dependence of KCNQ1/KCNE1 inhibition by L-673 (b) is quantified as the peak tail current amplitude measured at steady state for each concentration of L-673, normalized to the control tail current amplitude for each cell, expressed as % inhibition, and fitted with a Hill equation (solid line) to the data (n = 6–9).

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  Figure 2.. Representative impedance traces before and after L-673 addition. Panel (a) shows the pre-reads without external stimulation. Panel (b) is the pre-reads when paced at 1.2 Hz. Panel (c) shows the impedance traces 1 h after L-673 addition (from top to bottom: 0.1% DMSO, 1, 3, 10, 30, 100, 300, and 1000 nM L-673) without pacing. Panel (d) is the immediately following recordings but with external 1.2 Hz stimulation. Five second traces are shown in all panels.

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  Figure 3.. Effects of L-673 alone on hiPSC-CMs. Normalized changes on impedance amplitude, beating rate, and FPDcF or FPD of hiPSC-CMs at the presence of L-673 at different concentrations from 0.1 to 30000 nM as labeled in figure without pacing (a) or paced at 1.2 Hz (B). All data (n = 6) were normalized to 0.1% DMSO control at pre-read. *P<0.05, compared to time-matched 0.1% DMSO control (detailed in Experimental procedures).

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  Figure 4.. Impact of L-673 on the effects of cisapride. L-673 at 0.1, 0.3, or 1 nM was co-applied with cisapride at different concentrations (3, 10, or 30 nM) to hiPSC-CM for effects on impedance amplitude (a, no pacing; b, paced at 1.2 Hz), beating rate (c, no pacing; d, paced at 1.2 Hz), and FPDcF (e, no pacing) or FPD (f, paced at 1.2 Hz). All data (n = 6) were normalized to 0.1% DMSO control at pre-read. *P<0.05, compared to time-matched 0.1% DMSO control; #P<0.05, compared to time-matched, same concentration without L-673 (detailed in Experimental procedures).

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  Figure 5.. Impact of L-673 on the FPD prolongation effects of hERG blockers. L-673 at 0.1, 0.3, or 1 nM was co-applied with astemizole (a, no pacing; b, paced at 1.2 Hz), E-4031 (c, no pacing; d, paced at 1.2 Hz), and dofetilide (e, no pacing; f, paced at 1.2 Hz) for its impact on the FPD prolongation effects of these hERG blockers at different concentration as labeled. All data (n = 6) were normalized to 0.1% DMSO control at pre-read. *P<0.05, compared to time-matched 0.1% DMSO control; #P<0.05, compared to time-matched, corresponding test compound without L-673 (detailed in Experimental procedures).