title: In vitro potential modulation of baicalin and baicalein on P-glycoprotein activity and expression in Caco-2 cells and rat gut sacs.
abstract: Context Previous studies have shown that Scutellariae Radix, the dried root of Scutellaria baicalensis Georgi (Labiatae), has a certain inhibitory effect on P-glycoprotein (P-gp), but the effects of its main active constituents on P-gp are still ambiguous. Objectives In vitro studies were performed to investigate the effects of its main active constituents (baicalin and its aglycone, baicalein) on the activity and expression of P-gp in intestine using Caco-2 cells and rat gut sacs. Materials and methods In Caco-2 cell experiments, the effects of baicalin and baicalein on P-gp activity were investigated using a P-gp substrate, rhodamine 123 and non-substrate fluorescein Na, by determining their intracellular fluorescence accumulation, and their effects on P-gp expression were determined using flow cytometry. In addition, rat gut sac model was selected to investigate the effects of baicalin and baicalein on the transport of verapamil, a classical P-gp substrate. The gut sacs of male Sprague-Dawley rats were filled with 0.4 mL the test solution contained verapamil (0.2575 mg/mL) and the drugs [baicalin and baicalein, at concentrations of 1/8 IC50 (59.875, 41.5 μg/mL), 1/4 IC50 (119.75, 83 μg/mL) and 1/2 IC50 (239.5, 166 μg/mL)], and then incubated in Tyrode's solution for a period of time. After termination of the incubation, the incubated solution was processed for the subsequent detection. Results According to the results of MTT assay, the IC50 values of verapamil, baicalin and baicalein were 104, 479, 332 μg/mL, respectively. The obtained results from the two models were confirmed mutually. As a result, baicalin exhibited no obvious effect on intracellular accumulation of Rh-123, and almost had no effect on P-gp expression and verapamil transportation, while baicalein significantly increased intracellular accumulation of Rh-123 (p < 0.01), down-regulated P-gp expression (p < 0.01) and increased the transport of verapamil (p < 0.05). Discussion and conclusion The results indicated that baicalein may be a P-gp inhibitor, which presented obvious inhibitory effects on P-gp activity and expression level. A comparison of the structures of baicalin and baicalein indicates that the existence of glucosyl plays a decisive role in influencing the activity and expression of P-gp.
authors.affiliation: a School of Chinese Materia Medica , Beijing University of Chinese Medicine , Beijing , P.R. China ;
authors.forename: Qing
authors.initials: Q
authors.lastname: Miao
authors.affiliation: a School of Chinese Materia Medica , Beijing University of Chinese Medicine , Beijing , P.R. China ;
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Wang
authors.affiliation: a School of Chinese Materia Medica , Beijing University of Chinese Medicine , Beijing , P.R. China ;
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: a School of Chinese Materia Medica , Beijing University of Chinese Medicine , Beijing , P.R. China ;
authors.forename: Peipei
authors.initials: P
authors.lastname: Miao
authors.affiliation: a School of Chinese Materia Medica , Beijing University of Chinese Medicine , Beijing , P.R. China ;
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: a School of Chinese Materia Medica , Beijing University of Chinese Medicine , Beijing , P.R. China ;
authors.forename: Yujie
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: b National Institutes for Food and Drug Control , Beijing , P.R. China.
authors.forename: Shuangcheng
authors.initials: S
authors.lastname: Ma
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D000818:Animals; D018938:Caco-2 Cells; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D044950:Flavanones / Q000494:pharmacology*; D005419:Flavonoids / Q000494:pharmacology*; D019793:Fluorescein / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007408:Intestinal Absorption / Q000187:drug effects*; D007413:Intestinal Mucosa / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D015394:Molecular Structure; D010539:Permeability; D017207:Rats, Sprague-Dawley; D020112:Rhodamine 123 / Q000378:metabolism; D013329:Structure-Activity Relationship; D013997:Time Factors; D014700:Verapamil / Q000378:metabolism
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D044950:Flavanones; D005419:Flavonoids; D020112:Rhodamine 123; C038044:baicalin; C006680:baicalein; D014700:Verapamil; D019793:Fluorescein
keywords: Inhibitors; P-glycoprotein (P-gp); Scutellariae Radix; structure–activity relationship