Berberine is a plant alkaloid with multiple pharmacological actions, including antidiarrhoeal activity and has been shown to inhibit Cl− secretion in distal colon. The aims of this study were to determine the molecular signaling mechanisms of action of berberine on Cl− secretion and the ion transporter targets. Monolayers of T84 human colonic carcinoma cells grown in permeable supports were placed in Ussing chambers and short-circuit current measured in response to secretagogues and berberine. Whole-cell current recordings were performed in T84 cells using the patch-clamp technique. Berberine decreased forskolin-induced short-circuit current in a concentration-dependent manner (IC50 80 ± 8 μM). In apically permeabilized monolayers and whole-cell current recordings, berberine inhibited a cAMP-dependent and chromanol 293B-sensitive basolateral membrane K+ current by 88%, suggesting inhibition of KCNQ1 K+ channels. Berberine did not affect either apical Cl− conductance or basolateral Na+–K+-ATPase activity. Berberine stimulated p38 MAPK, PKCα and PKA, but had no effect on p42/p44 MAPK and PKCδ. However, berberine pre-treatment prevented stimulation of p42/p44 MAPK by epidermal growth factor. The inhibitory effect of berberine on Cl− secretion was partially blocked by HBDDE (∼65%), an inhibitor of PKCα and to a smaller extent by inhibition of p38 MAPK with SB202190 (∼15%). Berberine treatment induced an increase in association between PKCα and PKA with KCNQ1 and produced phosphorylation of the channel. We conclude that berberine exerts its inhibitory effect on colonic Cl− secretion through inhibition of basolateral KCNQ1 channels responsible for K+ recycling via a PKCα-dependent pathway.
Keywords: berberine, KCNQ1 K+ channels, CFTR, chloride secretion, colon ion transport, T84 cells
Citation: Alzamora R, O’Mahony F, Ko W-H, Yip TW-N, Carter D, Irnaten M and Harvey BJ (2011) Berberine reduces cAMP-induced chloride secretion in T84 human colonic carcinoma cells through inhibition of basolateral KCNQ1 channels. Front. Physio. 2:33. doi: 10.3389/fphys.2011.00033
Received: 13 May 2011; Paper pending published: 04 June 2011;
Accepted: 18 June 2011; Published online: 30 June 2011.
Edited by:Ali Mobasheri, The University of Nottingham, UK
Reviewed by:Richard Barrett-Jolley, University of Liverpool, UK
Copyright: © 2011 Alzamora, O’Mahony, Ko, Yip, Carter, Irnaten and Harvey. This is an open-access article subject to a non-exclusive license between the authors and Frontiers Media SA, which permits use, distribution and reproduction in other forums, provided the original authors and source are credited and other Frontiers conditions are complied with.
*Correspondence: Brian Joseph Harvey, Department of Molecular Medicine, Education and Research Centre, Royal College of Surgeons in Ireland, Beaumont Hospital PO Box 9063, Dublin 9, Ireland. e-mail: firstname.lastname@example.org