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Role of Quercetin in Modulating Chloride Transport in the Intestine

View Article: PubMed Central - PubMed

ABSTRACT

Epithelial chloride channels provide the pathways for fluid secretion in the intestine. Cystic fibrosis transmembrane conductance regulator (CFTR) and calcium-activated chloride channels (CaCCs) are the main chloride channels in the luminal membrane of enterocytes. These transmembrane proteins play important roles in many physiological processes. In this study, we have identified a flavonoid quercetin as a modulator of CaCC chloride channel activity. Fluorescence quenching assay showed that quercetin activated Cl− transport in a dose-dependent manner, with EC50 ~37 μM. Short-circuit current analysis confirmed that quercetin activated CaCC-mediated Cl− currents in HT-29 cells that can be abolished by CaCCinh-A01. Ex vivo studies indicated that application of quercetin to mouse ileum and colon on serosal side resulted in activation of CFTR and CaCC-mediated Cl− currents. Notably, we found that quercetin exhibited inhibitory effect against ANO1 chloride channel activity in ANO1-expressing FRT cells and decreased mouse intestinal motility. Quercetin-stimulated short-circuit currents in mouse ileum was multi-component, which included elevation of Ca2+ concentration through L-type calcium channel and activation of basolateral NKCC, Na+/K+-ATPase, and K+ channels. In vivo studies further revealed that quercetin promoted fluid secretion in mouse ileum. The modulatory effect of quercetin on CaCC chloirde channels may therefore represent a potential therapeutic strategy for treating CaCC-related diseases like constipation, secretory diarrhea and hypertension. The inverse effects of quercetin on CaCCs provided evidence that ANO1 and intestinal epithelial CaCCs are different calcium-activated chloride channels.

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Inhibition of quercetin-induced short-circuit currents by basolateral ion channel and transporter inhibitors. (A) Traces showing the inhibition of quercetin-induced short-circuit currents by ouabain, bumetanide and clotrimazole. (B) Comparison of the inhibitory effect of different inhibitors on quercetin-induced short-circuit currents. Data are the means ± SEs from four experiments. “**” indicate significantly difference from control at the P < 0.01 levels.
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Figure 7: Inhibition of quercetin-induced short-circuit currents by basolateral ion channel and transporter inhibitors. (A) Traces showing the inhibition of quercetin-induced short-circuit currents by ouabain, bumetanide and clotrimazole. (B) Comparison of the inhibitory effect of different inhibitors on quercetin-induced short-circuit currents. Data are the means ± SEs from four experiments. “**” indicate significantly difference from control at the P < 0.01 levels.

Mentions: Transepithelial Cl− secretion can be promoted by activated chloride channel, as well as the accumulation of Cl− in the epithelial cells. Therefore, it was important to determine whether transporters and ion channels in the basolateral membrane would participate in quercetin-activated short-circuit currents. Ouabain applied at 1 mM can inhibit 61% of the quercetin (200 μM)-activated short-circuit current when applied to mouse ileum on the serosal side, whereas bumetanide and clotrimazole given at 100 and 50 μM, respectively, completely abolished the short-circuit currents stimulated by quercetin (Figures 7A,B). These results suggested that Na+/K+-ATPase, NKCC, and K+ channels could participate in quercetin-induced Cl− currents.


Role of Quercetin in Modulating Chloride Transport in the Intestine
Inhibition of quercetin-induced short-circuit currents by basolateral ion channel and transporter inhibitors. (A) Traces showing the inhibition of quercetin-induced short-circuit currents by ouabain, bumetanide and clotrimazole. (B) Comparison of the inhibitory effect of different inhibitors on quercetin-induced short-circuit currents. Data are the means ± SEs from four experiments. “**” indicate significantly difference from control at the P < 0.01 levels.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5120089&req=5

Figure 7: Inhibition of quercetin-induced short-circuit currents by basolateral ion channel and transporter inhibitors. (A) Traces showing the inhibition of quercetin-induced short-circuit currents by ouabain, bumetanide and clotrimazole. (B) Comparison of the inhibitory effect of different inhibitors on quercetin-induced short-circuit currents. Data are the means ± SEs from four experiments. “**” indicate significantly difference from control at the P < 0.01 levels.
Mentions: Transepithelial Cl− secretion can be promoted by activated chloride channel, as well as the accumulation of Cl− in the epithelial cells. Therefore, it was important to determine whether transporters and ion channels in the basolateral membrane would participate in quercetin-activated short-circuit currents. Ouabain applied at 1 mM can inhibit 61% of the quercetin (200 μM)-activated short-circuit current when applied to mouse ileum on the serosal side, whereas bumetanide and clotrimazole given at 100 and 50 μM, respectively, completely abolished the short-circuit currents stimulated by quercetin (Figures 7A,B). These results suggested that Na+/K+-ATPase, NKCC, and K+ channels could participate in quercetin-induced Cl− currents.

View Article: PubMed Central - PubMed

ABSTRACT

Epithelial chloride channels provide the pathways for fluid secretion in the intestine. Cystic fibrosis transmembrane conductance regulator (CFTR) and calcium-activated chloride channels (CaCCs) are the main chloride channels in the luminal membrane of enterocytes. These transmembrane proteins play important roles in many physiological processes. In this study, we have identified a flavonoid quercetin as a modulator of CaCC chloride channel activity. Fluorescence quenching assay showed that quercetin activated Cl&minus; transport in a dose-dependent manner, with EC50 ~37 &mu;M. Short-circuit current analysis confirmed that quercetin activated CaCC-mediated Cl&minus; currents in HT-29 cells that can be abolished by CaCCinh-A01. Ex vivo studies indicated that application of quercetin to mouse ileum and colon on serosal side resulted in activation of CFTR and CaCC-mediated Cl&minus; currents. Notably, we found that quercetin exhibited inhibitory effect against ANO1 chloride channel activity in ANO1-expressing FRT cells and decreased mouse intestinal motility. Quercetin-stimulated short-circuit currents in mouse ileum was multi-component, which included elevation of Ca2+ concentration through L-type calcium channel and activation of basolateral NKCC, Na+/K+-ATPase, and K+ channels. In vivo studies further revealed that quercetin promoted fluid secretion in mouse ileum. The modulatory effect of quercetin on CaCC chloirde channels may therefore represent a potential therapeutic strategy for treating CaCC-related diseases like constipation, secretory diarrhea and hypertension. The inverse effects of quercetin on CaCCs provided evidence that ANO1 and intestinal epithelial CaCCs are different calcium-activated chloride channels.

No MeSH data available.