Novel Action of the Chalcone Isoliquiritigenin as a Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Inhibitor: Potential Therapy for Cholera and Polycystic Kidney Disease

Abstract

Abstract. Overstimulation of cAMP-activated Cl− secretion can cause secretory diarrhea. Isoliquiritigenin (ISLQ) is a plant-derived chalcone that has a wide range of biological activities. The present study thus aimed to investigate the effect of ISLQ on cAMP-activated Cl − secretion in human intestinal epithelium, especially the underlying mechanism and therapeutic application. Short-circuit current analysis of human intestinal epithelial (T84) cell monolayers revealed that ISLQ dose-dependently inhibited cAMP-activated Cl − secretion with an IC 50 of approximately 20 μM. ISLQ had no effect on either basal short-circuit current or Ca 2+ -activated Cl − secretion. Apical Cl − current analysis of T84 cell monolayers indicated that ISLQ blocked mainly the cystic fibrosis transmembrane conductance regulator (CFTR) Cl − channels, but not other unidentified cAMPdependent Cl − channels. ISLQ did not affect intracellular cAMP levels or cell viability. ISLQ completely abolished the cholera toxin-induced transepithelial Cl − secretion in T84 cells and reduced the cholera toxin-induced intestinal fluid secretion in mouse closed loop models by 90%. Similarly, ISLQ completely inhibited the cAMP-activated apical Cl − current across monolayers of Madin-Darby Canine Kidney (MDCK) cells and retarded cyst growth in MDCK cyst models by 90%. This study reveals a novel action of ISLQ as a potent CFTR inhibitor with therapeutic potential for treatment of cholera and polycystic kidney disease.

Hydroxyxanthone as an inhibitor of cAMP-activated apical chloride channel in human intestinal epithelial cell

“…A recent study by Hoque et al (2010) raises a possibility that CFTR and IRC equally contribute to cAMP-activated Cl − secretion in T84 cells (Hoque et al, 2010). However, using a CFTR-specific CFTR inhibitor isoliquiritigenin (ISLQ), we recently found that cAMP-induced Cl − secretion in T84 cell monolayers was completely inhibited by ISLQ, suggesting the sole contribution of CFTR to the cAMP-activated Cl − secretion (Muanprasat et al, 2012). In addition, IRC-mediated apical Cl − current during cAMP stimulation was observed only after CFTR was inhibited by CFTR inh - 172 (Muanprasat et al, 2012).…”

“…However, using a CFTR-specific CFTR inhibitor isoliquiritigenin (ISLQ), we recently found that cAMP-induced Cl − secretion in T84 cell monolayers was completely inhibited by ISLQ, suggesting the sole contribution of CFTR to the cAMP-activated Cl − secretion (Muanprasat et al, 2012). In addition, IRC-mediated apical Cl − current during cAMP stimulation was observed only after CFTR was inhibited by CFTR inh - 172 (Muanprasat et al, 2012). This data suggest that CFTR inhibition alone may not be sufficient to completely inhibit intestinal fluid secretion in cholera, since cholera toxin-induced apical Cl − efflux could escape CFTR blockage by using IRC as an alternative route.…”

“…Polyphenols are abundantly found in several kinds of plants and have been reported to possess a wide range of biological activities such as anti-oxidation, anti-inflammation and anti-cancer (Visioli et al, 2011). Interestingly, polyphenols including flavonols, flavone, flavanols, chalcones and tannins have been shown to inhibit cAMP-activated Cl − secretion in human intestinal epithelial cells (Muanprasat et al, 2012;Schuier et al, 2005;Wongsamitkul et al, 2010). Furthermore, structure-activity analysis of plant-derived flavonoids has suggested that phenolic groups are responsible for the inhibitory effect of flavonoids on cAMP-activated Cl − secretion (Illek et al, 2000).…”

Characteristics and Pharmacological Regulation of Epithelial Na+ Channel (ENaC) and Epithelial Na+ Transport

“…The activation of the NSC channel by catecholamine is not directly mediated by PKA (71). cAMP, the concentration of which is increased by catecholamine, activates K + and Cl − channels directly and also indirectly via a PKA-mediated pathway (10,121,122) (Fig. 1).…”

Activation of AMP-Activated Protein Kinase by a Plant-Derived Dihydroisosteviol in Human Intestinal Epithelial Cell

“…3,4) CFTR inhibitors have been shown to effectively inhibit fluid loss in rodent models of cholera and to reduce renal cyst progression in mouse models of polycystic kidney disease. 5,6) CFTR exists in a macromolecular complex consisted of several interacting partners including regulatory proteins such as protein kinase A (PKA) and adenosine monophosphate (AMP)-activated protein kinase (AMPK). 7,8) Activation of a cAMP-dependent PKA stimulates CFTR activity via phosphorylation at a regulatory (R) domain.…”