Effect of Shaoyao Gancao Tang on function and expression of P-glycoprotein in Caco-2 cells / 中国中药杂志

<p><b>OBJECTIVE</b>To investigate the effect of Shao Yao-Gan Cao-Tang on function and expression of P-glycoprotein (P-gp) in Caco-2 cells.</p><p><b>METHOD</b>3H-digoxin (Dig), a substrate of P-glycoprotein, was used as a probe to measure the P-gp-mediated drug efflux transport, which indicated the function of P-gp in Caco-2 cells, while Verapamil (Ver) was used as a positive P-gp inhibitor. P-gp expression in Caco-2 cells was tested by immunohistochemistry staining. Inhibition effect of SGT on P-gp-mediated drug efflux transport and P-gp expression were investigated.</p><p><b>RESULT</b>Dig was shown a positive absorption mode in Caco-2 cell monolayer, characterized as the ratio of apparent permeabilities (Papp) from basolateral side to apical side Papp (BL-->AP) and from apical side to basolateral side Papp (AP-->BL) of Dig was 27.07. Addition of Ver into Dig transport media significantly inhibited P-gp activity which was indicated by increasing the Papp (AP-->BL) of Dig by 3.82 times, whereas Ver had no significant effect on Papp (BL-->AP). SGT (at the concentrations of 1/25 IC5, 1/5 IC5, IC,) could promote Papp (AP-->BL) of Dig by 159.83%, 217.95% ,160.26%. Papp (AP-->BL) of Dig was mildly increased by 59.16%, 50.73% by SGT at 1/25 IC5, 1/5 IC, respectively. Immunohistochemistry staining showed that SGT inhibited the expression of P-gp of Caco-2 cells.</p><p><b>CONCLUSION</b>SGT showed the potential inhibition to the function and expression of P-gp, leading to the increase absorption of P-gp's substrates.</p>

Potent in vitro inhibition of CYP3A4 and P-glycoprotein by Rhodiola rosea.

Six clones of RHODIOLA ROSEA, obtained from plants originating from widely different areas in Norway, were investigated for their IN VITRO inhibitory potential on CYP3A4-mediated metabolism and P-gp efflux transport activity. Presumed active constituents in the ethanol extracts of the different clones were quantified. C-DNA baculovirus expressed CYP3A4 and Caco-2 cells were used for inhibitory assays, and as positive control inhibitors ketoconazole and verapamil were applied, respectively. A validated HPLC methodology was used to quantify the formation of 6-beta-OH-testosterone and scintillation counting was used to quantify the transport of (3)H-digoxin in Caco-2 cells. All clones showed potent inhibition of CYP3A4 and P-gp activities, with IC (50) values ranging from 1.7 to 3.1 microg/mL and from 16.7 to 51.7 microg/mL, respectively, being below that reported for other herbs and some known classic drug inhibitors, such as St. John's wort and fluoxetine. RHODIOLA ROSEA might thus be a candidate for clinically relevant drug interactions. The concentration of presumed biologically active constituents in the different clones varied considerably, but this variation was not related to the clones' inhibitory potential on CYP3A4 or P-gp activities. Other constituents might thus be responsible for the observed inhibitory properties. The place of origin seemed to be of minor importance for CYP3A4 or P-gp inhibition.