Interaction of Natural Dietary and Herbal Anionic Compounds and Flavonoids with Human Organic Anion Transporters 1 (SLC22A6), 3 (SLC22A8), and 4 (SLC22A11)

Abstract

Active components of complementary/alternative medicines and natural supplements are often anionic compounds and flavonoids. As such, organic anion transporters (OATs) may play a key role in their pharmacokinetic and pharmacological profiles, and represent sites for adverse drug-drug interactions. Therefore, we assessed the inhibitory effects of nine natural products, including flavonoids (catechin and epicatechin), chlorogenic acids (1,3- and 1,5-dicaffeoylquinic acid), phenolic acids (ginkgolic acids (13 : 0), (15 : 1), and (17 : 1)), and the organic acids ursolic acid and 18 β -glycyrrhetinic acid, on the transport activity of the human OATs, hOAT1 (SLC22A6), hOAT3 (SLC22A8), and hOAT4 (SLC22A11). Four compounds, 1,3- and 1,5-dicaffeoylquinic acid, ginkgolic acid (17 : 1), and 18 β -glycyrrhetinic acid, significantly inhibited hOAT1-mediated transport (50 μ M inhibitor versus 1 μ M substrate). Five compounds, 1,3- and 1,5-dicaffeoylquinic acid, ginkgolic acids (15 : 1) and (17 : 1), and epicatechin, significantly inhibited hOAT3 transport under similar conditions. Only catechin inhibited hOAT4. Dose-dependency studies were conducted for 1,3-dicaffeoylquinic acid and 18 β -glycyrrhetinic acid on hOAT1, and IC50 values were estimated as 1.2 ± 0.4 μ M and 2.7 ± 0.2 μ M, respectively. These data suggest that 1,3-dicaffeoylquinic acid and 18 β -glycyrrhetinic acid may cause significant hOAT1-mediated DDIs in vivo; potential should be considered for safety issues during use and in future drug development.

Figure 1

Chemical structures of compounds investigated in this study. MW: molecular weight.

Figure 2

Inhibitory effects of the nine test compounds on hOAT1-mediated PAH uptake. Ten-minute uptake of [³H]PAH (1 μM) was measured in CHO-hOAT1 cells in the absence and presence of test compounds (50 μM) or probenecid (1000 μM). Data represent hOAT1-mediated transport specifically, that is, data have been corrected for background PAH accumulation measured in empty vector transfected cells. Values are mean ± S.D. of triplicate values from a representative experiment. ** denotes  P < 0.01, and *** denotes  P < 0.001 as determined by one-way ANOVA followed by Dunnett's t-test.

Figure 3

Dose-response effects for 1,3-dicaffeoylquinic acid and 18β-glycyrrhetinic acid on hOAT1-mediated PAH transport. One-minute uptake of [³H]PAH (1 μM) in CHO-hOAT1 cells was measured in the presence of increasing concentrations (10⁻⁷ to 5 × 10⁻⁴  M) of test compounds. Data were corrected by subtracting background PAH accumulation measured in empty vector transfected cells. IC₅₀ values were determined with nonlinear regression and the “log(inhibitor) versus response” model using GraphPad Prism software. Experiments were repeated three times with triplicate samples and graphs shown are from representative experiments with values plotted as mean ± S.D. (n = 3). The data were used to generate mean IC₅₀ ± S.E.M. estimates.

Figure 4

Inhibitory effects of the nine test compounds on hOAT3-mediated ES uptake. Ten-minute uptake of [³H]ES (1 μM) was measured in HEK-hOAT3 cells in the absence and presence of test compounds (50 μM) or probenecid (1000 μM). Data represent hOAT3-mediated transport specifically, that is, data have been corrected for background ES accumulation measured in empty vector transfected cells. Values are mean ± S.D. of triplicate values from a representative experiment. * denotes  P < 0.05, ** denotes  P < 0.01, and ***  denotes  p < 0.001 as determined by one-way ANOVA followed by Dunnett's t-test.

Figure 5

Inhibitory effects of the nine test compounds on hOAT4-mediated ES uptake. Ten minute uptake of [³H]ES (1 μM) was measured in CHO-hOAT4 cells in the absence and presence of test compounds (50 μM) or ES (1000 μM for self-inhibition). Data represent hOAT4-mediated transport specifically, that is, data have been corrected for background ES accumulation measured in empty vector transfected cells. Values are mean ± S.D. of triplicate values from a representative experiment. * denotes  P < 0.05, and *** denotes  P < 0.001 as determined by one-way ANOVA followed by Dunnett's t-test.