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Differential Effects of Quercetin and Quercetin Glycosides on Human α7 Nicotinic Acetylcholine Receptor-Mediated Ion Currents.

Lee BH, Choi SH, Kim HJ, Jung SW, Hwang SH, Pyo MK, Rhim H, Kim HC, Kim HK, Lee SM, Nah SY - Biomol Ther (Seoul) (2016)

Bottom Line: Quercetin is a flavonoid usually found in fruits and vegetables.Quercetin glycosides mediated an inhibition of IACh, which increased when they were pre-applied and the inhibitory effects were concentration dependent.These results show that quercetin and quercetin glycosides regulate the α7 nAChR in a differential manner.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, College of Veterinary Medicine and BioMolecular Informatics Center, Konkuk University, Seoul 05029, Republic of Korea.

ABSTRACT
Quercetin is a flavonoid usually found in fruits and vegetables. Aside from its antioxidative effects, quercetin, like other flavonoids, has a various neuropharmacological actions. Quercetin-3-O-rhamnoside (Rham1), quercetin-3-O-rutinoside (Rutin), and quercetin- 3-(2(G)-rhamnosylrutinoside (Rham2) are mono-, di-, and tri-glycosylated forms of quercetin, respectively. In a previous study, we showed that quercetin can enhance α7 nicotinic acetylcholine receptor (α7 nAChR)-mediated ion currents. However, the role of the carbohydrates attached to quercetin in the regulation of α7 nAChR channel activity has not been determined. In the present study, we investigated the effects of quercetin glycosides on the acetylcholine induced peak inward current (IACh) in Xenopus oocytes expressing the α7 nAChR. IACh was measured with a two-electrode voltage clamp technique. In oocytes injected with α7 nAChR copy RNA, quercetin enhanced IACh, whereas quercetin glycosides inhibited IACh. Quercetin glycosides mediated an inhibition of IACh, which increased when they were pre-applied and the inhibitory effects were concentration dependent. The order of IACh inhibition by quercetin glycosides was Rutin≥Rham1>Rham2. Quercetin glycosides-mediated IACh enhancement was not affected by ACh concentration and appeared voltage-independent. Furthermore, quercetin-mediated IACh inhibition can be attenuated when quercetin is co-applied with Rham1 and Rutin, indicating that quercetin glycosides could interfere with quercetin-mediated α7 nAChR regulation and that the number of carbohydrates in the quercetin glycoside plays a key role in the interruption of quercetin action. These results show that quercetin and quercetin glycosides regulate the α7 nAChR in a differential manner.

No MeSH data available.


Concentration-dependent effects of quercetin and its glycosides on IACh. (A) The representative trace of quercetin- or quercetin gly-coside- (30 μM each) mediated effects on IACh. IACh in oocytes expressing the α7 nAChR was elicited at a holding potential of −80 mV for 30 s in the presence of 200 μM ACh. Quercetin and its glycosides were pre-applied 30 s before ACh application. (B) The representative trace of quercetin- and quercetin glycoside- (300 μM each) mediated effects on IACh. IACh in oocytes expressing the α7 nAChRs was elicited at a holding potential of −80 mV for 30 s in the presence of 200 μM ACh. Quercetin and its glycosides were pre-applied 30 s before ACh application. Traces represent six separate oocytes from three different batches of frogs. (C–D) Concentration-dependent effects of quercetin and quercetin glycosides on IACh. The solid lines were fit using the Hill equation. Each point represents the mean ± S.E.M. (n=9–12/group).
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f3-bt-24-410: Concentration-dependent effects of quercetin and its glycosides on IACh. (A) The representative trace of quercetin- or quercetin gly-coside- (30 μM each) mediated effects on IACh. IACh in oocytes expressing the α7 nAChR was elicited at a holding potential of −80 mV for 30 s in the presence of 200 μM ACh. Quercetin and its glycosides were pre-applied 30 s before ACh application. (B) The representative trace of quercetin- and quercetin glycoside- (300 μM each) mediated effects on IACh. IACh in oocytes expressing the α7 nAChRs was elicited at a holding potential of −80 mV for 30 s in the presence of 200 μM ACh. Quercetin and its glycosides were pre-applied 30 s before ACh application. Traces represent six separate oocytes from three different batches of frogs. (C–D) Concentration-dependent effects of quercetin and quercetin glycosides on IACh. The solid lines were fit using the Hill equation. Each point represents the mean ± S.E.M. (n=9–12/group).

Mentions: In concentration-dependent experiments with quercetin, pre-application with quercetin for 30 s enhanced IACh in a con centration-dependent manner in oocytes expressing α7 nA ChRs (Fig. 3C). Pre-application of quercetin at 3, 10, 30, 100, and 300 μM increased IACh by 5.9 ± 0.9, 23.1 ± 3.0, 52.9 ± 4.2, 98.7 ± 7.3, and 113.4 ± 11.9% in oocytes expressing α7 AChRs, respectively. Thus, the apparent EC50 of IACh for quercetin pre-application was 35.1 ± 3.8 μM (n=10–11, with samples taken from three different frogs for each point; Fig. 3C). In concentration-dependent experiments with quercetin glycosides, pre-application with quercetin glycosides for 30 s inhibited IACh in a concentration-dependent manner in oocytes expressing α7 nAChRs (Fig. 3D). For instance, pre-application of Rham1 inhibited IACh by 1.2 ± 0.3, 6.8 ± 0.8, 16.2 ± 1.1, 41.9 ± 3.5, and 53.9 ± 4.1% at 3, 10, 30, 100, and 300 μM in oocytes expressing α7 AChRs, respectively. Pre-application of Rutin inhibited IACh by 2.9 ± 0.9, 8.9 ± 0.8, 21.8 ± 1.8, 45.7 ± 3.7 and 63.1 ± 4.6% at 3, 10, 30, 100, and 300 μM in oocytes expressing α7 AChRs, respectively. Pre-application of Rham2 inhibited IACh by 0.7 ± 0.3, 1.3 ± 0.4, 4.1 ± 1.1, 16.3 ± 1.9 and 23.2 ± 2.6% at 3, 10, 30, 100, and 300 μM in oocytes expressing α7 AChRs, respectively. The apparent IC50s of IACh were 56.4 ± 8.4, 70.4 ± 3.6, 71.3 ± 6.7 μM for Rham1, Rutin, and Rham2 pre-application in oocytes expressing the α7 AChR receptor, respectively (n=10–11, with samples taken from three different frogs for each point; Fig. 3D). These results indicate that quercetin and quercetin glycosides regulate α7 nAChR channel activity in a differential manner.


Differential Effects of Quercetin and Quercetin Glycosides on Human α7 Nicotinic Acetylcholine Receptor-Mediated Ion Currents.

Lee BH, Choi SH, Kim HJ, Jung SW, Hwang SH, Pyo MK, Rhim H, Kim HC, Kim HK, Lee SM, Nah SY - Biomol Ther (Seoul) (2016)

Concentration-dependent effects of quercetin and its glycosides on IACh. (A) The representative trace of quercetin- or quercetin gly-coside- (30 μM each) mediated effects on IACh. IACh in oocytes expressing the α7 nAChR was elicited at a holding potential of −80 mV for 30 s in the presence of 200 μM ACh. Quercetin and its glycosides were pre-applied 30 s before ACh application. (B) The representative trace of quercetin- and quercetin glycoside- (300 μM each) mediated effects on IACh. IACh in oocytes expressing the α7 nAChRs was elicited at a holding potential of −80 mV for 30 s in the presence of 200 μM ACh. Quercetin and its glycosides were pre-applied 30 s before ACh application. Traces represent six separate oocytes from three different batches of frogs. (C–D) Concentration-dependent effects of quercetin and quercetin glycosides on IACh. The solid lines were fit using the Hill equation. Each point represents the mean ± S.E.M. (n=9–12/group).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4930285&req=5

f3-bt-24-410: Concentration-dependent effects of quercetin and its glycosides on IACh. (A) The representative trace of quercetin- or quercetin gly-coside- (30 μM each) mediated effects on IACh. IACh in oocytes expressing the α7 nAChR was elicited at a holding potential of −80 mV for 30 s in the presence of 200 μM ACh. Quercetin and its glycosides were pre-applied 30 s before ACh application. (B) The representative trace of quercetin- and quercetin glycoside- (300 μM each) mediated effects on IACh. IACh in oocytes expressing the α7 nAChRs was elicited at a holding potential of −80 mV for 30 s in the presence of 200 μM ACh. Quercetin and its glycosides were pre-applied 30 s before ACh application. Traces represent six separate oocytes from three different batches of frogs. (C–D) Concentration-dependent effects of quercetin and quercetin glycosides on IACh. The solid lines were fit using the Hill equation. Each point represents the mean ± S.E.M. (n=9–12/group).
Mentions: In concentration-dependent experiments with quercetin, pre-application with quercetin for 30 s enhanced IACh in a con centration-dependent manner in oocytes expressing α7 nA ChRs (Fig. 3C). Pre-application of quercetin at 3, 10, 30, 100, and 300 μM increased IACh by 5.9 ± 0.9, 23.1 ± 3.0, 52.9 ± 4.2, 98.7 ± 7.3, and 113.4 ± 11.9% in oocytes expressing α7 AChRs, respectively. Thus, the apparent EC50 of IACh for quercetin pre-application was 35.1 ± 3.8 μM (n=10–11, with samples taken from three different frogs for each point; Fig. 3C). In concentration-dependent experiments with quercetin glycosides, pre-application with quercetin glycosides for 30 s inhibited IACh in a concentration-dependent manner in oocytes expressing α7 nAChRs (Fig. 3D). For instance, pre-application of Rham1 inhibited IACh by 1.2 ± 0.3, 6.8 ± 0.8, 16.2 ± 1.1, 41.9 ± 3.5, and 53.9 ± 4.1% at 3, 10, 30, 100, and 300 μM in oocytes expressing α7 AChRs, respectively. Pre-application of Rutin inhibited IACh by 2.9 ± 0.9, 8.9 ± 0.8, 21.8 ± 1.8, 45.7 ± 3.7 and 63.1 ± 4.6% at 3, 10, 30, 100, and 300 μM in oocytes expressing α7 AChRs, respectively. Pre-application of Rham2 inhibited IACh by 0.7 ± 0.3, 1.3 ± 0.4, 4.1 ± 1.1, 16.3 ± 1.9 and 23.2 ± 2.6% at 3, 10, 30, 100, and 300 μM in oocytes expressing α7 AChRs, respectively. The apparent IC50s of IACh were 56.4 ± 8.4, 70.4 ± 3.6, 71.3 ± 6.7 μM for Rham1, Rutin, and Rham2 pre-application in oocytes expressing the α7 AChR receptor, respectively (n=10–11, with samples taken from three different frogs for each point; Fig. 3D). These results indicate that quercetin and quercetin glycosides regulate α7 nAChR channel activity in a differential manner.

Bottom Line: Quercetin is a flavonoid usually found in fruits and vegetables.Quercetin glycosides mediated an inhibition of IACh, which increased when they were pre-applied and the inhibitory effects were concentration dependent.These results show that quercetin and quercetin glycosides regulate the α7 nAChR in a differential manner.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, College of Veterinary Medicine and BioMolecular Informatics Center, Konkuk University, Seoul 05029, Republic of Korea.

ABSTRACT
Quercetin is a flavonoid usually found in fruits and vegetables. Aside from its antioxidative effects, quercetin, like other flavonoids, has a various neuropharmacological actions. Quercetin-3-O-rhamnoside (Rham1), quercetin-3-O-rutinoside (Rutin), and quercetin- 3-(2(G)-rhamnosylrutinoside (Rham2) are mono-, di-, and tri-glycosylated forms of quercetin, respectively. In a previous study, we showed that quercetin can enhance α7 nicotinic acetylcholine receptor (α7 nAChR)-mediated ion currents. However, the role of the carbohydrates attached to quercetin in the regulation of α7 nAChR channel activity has not been determined. In the present study, we investigated the effects of quercetin glycosides on the acetylcholine induced peak inward current (IACh) in Xenopus oocytes expressing the α7 nAChR. IACh was measured with a two-electrode voltage clamp technique. In oocytes injected with α7 nAChR copy RNA, quercetin enhanced IACh, whereas quercetin glycosides inhibited IACh. Quercetin glycosides mediated an inhibition of IACh, which increased when they were pre-applied and the inhibitory effects were concentration dependent. The order of IACh inhibition by quercetin glycosides was Rutin≥Rham1>Rham2. Quercetin glycosides-mediated IACh enhancement was not affected by ACh concentration and appeared voltage-independent. Furthermore, quercetin-mediated IACh inhibition can be attenuated when quercetin is co-applied with Rham1 and Rutin, indicating that quercetin glycosides could interfere with quercetin-mediated α7 nAChR regulation and that the number of carbohydrates in the quercetin glycoside plays a key role in the interruption of quercetin action. These results show that quercetin and quercetin glycosides regulate the α7 nAChR in a differential manner.

No MeSH data available.