AUTHOR=Alzamora Rodrigo , O'Mahony Fiona , Ko Wing-Hung , Yip Tiffany W., Carter Derek , Irnaten Mustapha , Harvey Brian J. TITLE=Berberine Reduces cAMP-Induced Chloride Secretion in T84 Human Colonic Carcinoma Cells through Inhibition of Basolateral KCNQ1 Channels JOURNAL=Frontiers in Physiology VOLUME=2 YEAR=2011 URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2011.00033 DOI=10.3389/fphys.2011.00033 ISSN=1664-042X ABSTRACT=

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.