kjpp The Korean Journal of Physiology & Pharmacology Korean J Physiol Pharmacol 1226-4512 2093-3827 Korean J Physiol Pharmacol 10.4196/kjpp.2008.12.3.111 kjpp-12-111 Original Article (–)-Epigallocatechin Gallate Inhibits the Pacemaker Activity of Interstitial Cells of Cajal of Mouse Small Intestine KimKweon Young 1 ChoiSoo Jin 2 JangHyuk Jin 3 ZuoDong Chuan 4 ShahiPawan Kumar 4 ParajuliShankar Prasad 4 YeumCheol Ho 4 YoonPyung Jin 4 ChoiSeok 4 JunJae Yeoul 4 Department of Rehabilitation, College of Medicine, Chosun University, Gwangju 501-759, Korea Department of Radiology, Gacheon University Gil Medical Center, Incheon 405-760, Korea Department of Psychiatry, College of Medicine, Chosun University, Gwangju 501-759, Korea Department of Physiology, College of Medicine, Chosun University, Gwangju 501-759, Korea Corresponding to: Jea Yeoul Jun, Department of Physiology, College of Medicine, Chosun University, 375, Seosuk-dong, Gwangju 501-759, Korea. (Tel) 82-62-230-6412, (Fax) 82-62-232-4943, (E-mail) jyjun@chosun.ac.kr 062008 17062008 12 3 111115 Copyright © 2008 Korean J Physiol Pharmacol 2008 This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

The effects of (–)-epigallocatechin gallate (EGCG) on pacemaker activities of cultured interstitial cells of Cajal (ICC) from murine small intestine were investigated using whole-cell patch-clamp technique at 30°C and Ca2+ image analysis. ICC generated spontaneous pacemaker currents at a holding potential of −70 mV. The treatment of ICC with EGCG resulted in a dose-dependent decrease in the frequency and amplitude of pacemaker currents. SQ-22536, an adenylate cyclase inhibitor, and ODQ, a guanylate cyclase inhibitor, did not inhibit the effects of EGCG. EGCG-induced effects on pacemaker currents were not inhibited by glibenclamide, an ATP-sensitive K+ channel blocker and TEA, a Ca2+-activated K+ channel blocker. Also, we found that EGCG inhibited the spontaneous [Ca2+]i oscillations in cultured ICC. In conclusion, EGCG inhibited the pacemaker activity of ICC and reduced [Ca2+]i oscillations by cAMP-, cGMP-, ATP-sensitive K+ channel-independent manner.

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Effects of catechins on pacemaker currents recorded in cultured ICC from mouse small intestine (A) Pacemaker currents of ICC recorded at a holding potential of −70 mV, when exposed to polyphenon 60 (200μM). (B) Pacemaker currents of ICC recorded at a holding potential of −70 mV when exposed to epicatechin gallate (200μM). (C) Pacemaker currents of ICC recorded at a holding potential of −70 mV which were exposed to epigallocatechin gallate (200μM). Vertical solid line scales amplitude of pacemaker current and horizontal solid line scales duration of recording (s) pacemaker currents. ECG: (–)-epicatechin gallate, EGCG: (–)-epigallocatechin gallate.

Dose-dependent effects of (–)-epigallocatechin gallate on pacemaker currents in cultured ICC of mouse small intestine. (A), (B), and (C) show pacemaker currents of ICC exposed to (–)-epigallocatechin gallate (50, 100, or 200 μM respectively) at a holding potential of −70 mV. Vertical solid line scales amplitude of pacemaker current and horizontal solid line scales duration of recording (s) pacemaker currents. (–)-epigallocatechin gallate at 100 and 200 μM concentrations inhibited spontaneous pacemaker currents of ICC. (D), (E), and (F) summarize the inhibitory effects of (–)-epigallocatechin gallate on pacemaker currents in ICC. Bars represents means±SE (n=5/group). ∗Asterisks mean significantly different from the controls (p<0.05). EGCG: (–)-epigallocatechin gallate, CON: control.

Effects of SQ-22536, an inhibitor of adenylate cyclase, and ODQ, an inhibitor of guanylate cyclase, on (–)-epigallocatechin gallate-induced response in cultured ICC from mouse small intestine. (A) Pretreatment with SQ-22536 (10μM) did not affect the inhibitory effects of (–)-epigallocatechin gallate (200μM) on spontaneous inward currents. (B) Pretreatment with ODQ (10μM) did not affect the inhibitory effects of (–)-epigallocatechin gallate (200μM) on spontaneous inward currents. Vertical solid line scales amplitude of pacemaker current and horizontal solid line scales duration of recording (s) pacemaker currents. EGCG: (–)-epigallocatechin gallate.

Effects of tetraethylammonium chloride, a Ca2+-activated K+ channel blocker, and glibenclamide, an ATP-sensitive K+ channel blocker, on (–)-epigallocatechin gallate-induced response in cultured ICC from mouse small intestine. (A) Pretreatment with tetraethylammonium chloride (2 mM) did not affect the inhibitory effects of (–)-epigallocatechin gallate (200 μM) on spontaneous inward currents. (B) Pretreatment with glibenclamide (10 μM) did not affect the inhibitory effects of (–)-epigallocatechin gallate (200 μM) on spontaneous inward currents. Vertical solid line scales amplitude of pacemaker current and horizontal solid line scales duration of recording (s) pacemaker currents. EGCG: (–)-epigallocatechin gallate, TEA: tetraethylammonium chloride.

Effects of (–)-epigallocatechin gallate on intrcellular Ca2+ oscillation in cultured ICC from mouse small intestine. (A) Sequential fluorescence intensity images of fluo-3-loaded cultured ICC in control condition. (B) Sequential fluorescence intensity images of fluo-3-loaded cultured ICC in the presence of (–)-epigallocatechin gallate (200 μM). The images of basal (1 and 2) and peak (1 and 2) in (A) and (B) acquired from indicators in (B). (C) Fluorescence intensity change plotted in (A) and (B) red marker.