Cellular Signaling Mechanisms Underlying Pharmacological Action of Bak Foong Pills on Gastrointestinal Secretion

Abstract

Bak Foong Pills (BFP, also known as Bai Feng Wan) is an over-the-counter traditional Chinese medicine that has long been used for treating gynecological disorders and improving overall body functions, including gastrointestinal (GI) function. However, the cellular signaling mechanism underlying BFP action, especially on the GI tract, has not been elucidated. In the present study, the human colonic epithelia cell line T₈₄ was used as a model to investigate the effect of BFP ethanol extract on ion transport in conjunction with the short-circuit current (I_SC) technique. The results showed that the apical addition of BFP extract produced a concentration-dependent (10-1,000 μg/ml, EC₅₀ = 120 μg/ml) increase in I_SC. The maximal response was observed at 500 μg/ml with an increase in I_SC of 24.4 ± 2.3 μA/cm² and apical conductance. The BFP-induced I_SC was not observed when extracellular Cl⁻ was replaced or when treated with Bumetanide (100 μM), an inhibitor of the Na⁺-K⁺-2Cl⁻ cotransporter. The BFP-induced I_SC was insensitive to the Na⁺ channel blocker, amiloride, but partially inhibited by the Cl⁻ channel blocker, DIDS (100 μM), and completely blocked by DPC (2 mM) or glibenclamide (1 mM) with a significant reduction in the apical conductance. The BFP-induced I_SC could be mimicked by forskolin (10 μM), but inhibited by a pretreatment of the cells with adenylate cyclase inhibitor, MDL-12330A (10 μM). Pretreatment with EGTA (5 mM) and thapsigargin (10 μM) decreased the BFP-induced I_SC by 10%. These results demonstrated that BFP ethanol extract exerted a stimulatory effect on gastrointestinal Cl⁻ secretion by predominantly activating adenylate cyclase and apical cAMP-dependent Cl⁻ channels, with minor contributions from calcium-dependent Cl⁻ channels. The effect of BFP may be explored to treat GI disorders such as constipation.