The effect EGCG (epigallocatechin 3-gallate) and quercetin on outward in hUC-MSCs. hUC-MSCs were voltage-clamped under whole cell configuration at -80 mV. Voltage steps of 200 ms duration were then applied from -40 mV to 50 mV in 10-mV increments every 10 s, showing outward currents a rapidly activating current with noisy oscillation, similar to large conductance Ca²⁺ activated K⁺ current (BK_Ca). The pipette solution consisted of 140 mM KCl, 1 mM MgCl₂, 5 mM Mg-ATP and 2 mM EGTA; the bath solution contained 143 mM NaCl, 5.4 mM KCl, 0.5 mM NaH₂PO₄, 0.5 mM MgCl₂, 1.8 mM CaCl₂, 5 mM HEPES and 10 mM glucose. (A) Membrane currents were recorded in the presence of EGCG. (A-1) The current-voltage relationship (I-V relationship) was plotted from A. Current-voltage relationship showed in the control (■), 50 µM EGCG (●) and wash (▲). (B) Quercetin increased outward current in hUC-MSCs. (B-1) The current-voltage relationship (I-V relationship) was plotted from B. I-V relationships showed in the control (■), 100 µM quercetin (●) and wash (▲).

Effect of extracellular quercetin on the outward current in hUC-MSCs. (A) Ramp pulse was applied from -120 to 60 mV for 250 ms at a holding potential of -80 mV and the pulse was applied at every 10 s. The x-axis shows time and the y-axis shows current. The outward current was activated by quercetin. Currents were reached a stable level in 2 min after the application of quercetin (100 µM) and recovered after washing with quercetin-free solution. (A-1) Quercetin -induced typical outward-rectifying current vs. voltage. (B) Dose dependence of quercetin-induced outward current in hUC-MSC using the whole cell patch configuration. Currents were measured at 50 mV and IC₅₀ was 19.9 µM. (n=3 cells per concentration).

The effect of intracellular quercetin on large conductance Ca²⁺ activated K⁺ channels (BK_Ca) using single channel recording in hUC-MSCs. Data were obtained from estimates of relative channel activity. (A) The trace shown the effect of intracellular Ca²⁺. Single channel currents recorded at +40mV from an inside-out patch configuration. Pipette solution contained 150 mM KCl, 1 mM MgCl₂, 5 mM EGTA, and 10 mM HEPES. The bath solution consisted of 150 mM KCl 150 mM KCl, 1 mM MgCl₂, 5 mM EGTA, and 10 mM HEPES and 0 µM, 1 µM CaCl₂. The channel activity was increased by [Ca²⁺]_i dependently. The letter “a” and “b” show an expanded scale of the A. Current amplitude of 1 main peak is about 12 pA. (B) The traces were showed the effect of quercetin on BK_Ca channels. The channel activity was increased by intracellular application of quercetin (30 µM). The letter “a” and “b” show an expanded scale of the A. The recording potential was +60mV. Current amplitude of 1 main peak is about 15 pA. The letter “close” represents the closed channel level and the letter “open” represents the open channel level. Abbreviations: min, minutes; ms, milliseconds; pA, picoampere.

Effect of quercetin and Iberiotoxin (IBX, a blocker of large conductance Ca²⁺-activated K⁺ current) on BK_Ca in hUC-MSCs. (A) Current traces are shown for 200-ms depolarization pulses from -40 mV to +50 mV (in 10-mV increments) from a holding potential of -80mV. Quercetin activates noisy outward currents in hUC-MSCs. Currents were recorded before (control), after the exposure to quercetin (100 µM) reached a stable level (3 min) and after application with quercetin and IBX solution. (B) The current-voltage relationship (I-V relationship) was plotted from A. I-V relationships of currents showed in the control (■), 100 µM quercetin (●) and 100 µM quercetin with 100 nM iberiotoxin (▲).