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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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Inhibitory effect of quercetin on ANO1-mediated Cl− transport. (A) Short-circuit current induced by Eact following DMSO addition in apical or basolateral side (upper panel). Partial inhibition of ANO1-mediated short-circuit current by apical or basolateral pre-treatment of 100 μM quercetin (lower panel). (B) Magnitudes of short-circuit current inhibition generated by apical vs. basolateral application of quercetin. Data are the means ± SEs from four determinations. “*” and “**” indicate significantly difference from control at the P < 0.05 and P < 0.01 levels.
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Figure 4: Inhibitory effect of quercetin on ANO1-mediated Cl− transport. (A) Short-circuit current induced by Eact following DMSO addition in apical or basolateral side (upper panel). Partial inhibition of ANO1-mediated short-circuit current by apical or basolateral pre-treatment of 100 μM quercetin (lower panel). (B) Magnitudes of short-circuit current inhibition generated by apical vs. basolateral application of quercetin. Data are the means ± SEs from four determinations. “*” and “**” indicate significantly difference from control at the P < 0.05 and P < 0.01 levels.

Mentions: Short-circuit current experiment was further performed to investigate whether quercetin act as a blocker of ANO1 chloride channel activity in ANO1-expressed FRT cells. Pre-treatment of both the apical and basolateral sides of FRT cells with 100 μM quercetin partially blocked the Cl− current induced by Eact, yielding an inhibition rate of ~20 and 65%, respectively for apical and basolateral sides compared to the control (Figure 4).


Role of Quercetin in Modulating Chloride Transport in the Intestine
Inhibitory effect of quercetin on ANO1-mediated Cl− transport. (A) Short-circuit current induced by Eact following DMSO addition in apical or basolateral side (upper panel). Partial inhibition of ANO1-mediated short-circuit current by apical or basolateral pre-treatment of 100 μM quercetin (lower panel). (B) Magnitudes of short-circuit current inhibition generated by apical vs. basolateral application of quercetin. Data are the means ± SEs from four determinations. “*” and “**” indicate significantly difference from control at the P < 0.05 and P < 0.01 levels.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC5120089&req=5

Figure 4: Inhibitory effect of quercetin on ANO1-mediated Cl− transport. (A) Short-circuit current induced by Eact following DMSO addition in apical or basolateral side (upper panel). Partial inhibition of ANO1-mediated short-circuit current by apical or basolateral pre-treatment of 100 μM quercetin (lower panel). (B) Magnitudes of short-circuit current inhibition generated by apical vs. basolateral application of quercetin. Data are the means ± SEs from four determinations. “*” and “**” indicate significantly difference from control at the P < 0.05 and P < 0.01 levels.
Mentions: Short-circuit current experiment was further performed to investigate whether quercetin act as a blocker of ANO1 chloride channel activity in ANO1-expressed FRT cells. Pre-treatment of both the apical and basolateral sides of FRT cells with 100 μM quercetin partially blocked the Cl− current induced by Eact, yielding an inhibition rate of ~20 and 65%, respectively for apical and basolateral sides compared to the control (Figure 4).

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.