PURPOSE: Using rhodamine123 (RH123) cell exclusion. 17 clinically used compounds were screened for their inhibitory effect on P-glycoprotein (P-gp), which was compared with the drugs' inhibitory activity against CYP3A4. The same assay was used to study induction of P-gp activity. METHODS: P-gp inhibition was assessed using RH123 accumulation into LS180V cells as well as Rh123 transport across Caco-2 mono-layers. Inhibition of CYP3A4 was determined in human liver microsomes using triazolam-4-hydroxylation. Induction of P-gp expression and activity was measured using western blot analysis and RH123 accumulation into LS180V cells, respectively. RESULTS: The observed inhibition of RH123 cell exclusion ranged from little or no effect (digoxin, indinavir, fexofenadine) up to a nearly 10-fold increase in RH 123 accumulation (ivermectin, terfenadine). No correlation between P-gp and CYP3A4 inhibition was observed. The rank order in P-gp inhibitory potency for terfenadine, verapamil, ritonavir. and indomethacin was identical in both LS180V and Caco-2 models. Ritonavir and St. John's wort extract showed a concentration-dependent P-gp induction, with good correlation between western blot analysis and RH123 accumulation. CONCLUSIONS: The RH123 accumulation assay in LS180V cells can be used as a valuable screening tool to study both inhibition and induction of P-gp activity and expression. This assay has the potential to predict P-gp-mediated alterations in intestinal absorption of drugs.
PURPOSE: Using rhodamine123 (RH123) cell exclusion. 17 clinically used compounds were screened for their inhibitory effect on P-glycoprotein (P-gp), which was compared with the drugs' inhibitory activity against CYP3A4. The same assay was used to study induction of P-gp activity. METHODS:P-gp inhibition was assessed using RH123 accumulation into LS180V cells as well as Rh123 transport across Caco-2 mono-layers. Inhibition of CYP3A4 was determined in human liver microsomes using triazolam-4-hydroxylation. Induction of P-gp expression and activity was measured using western blot analysis and RH123 accumulation into LS180V cells, respectively. RESULTS: The observed inhibition of RH123 cell exclusion ranged from little or no effect (digoxin, indinavir, fexofenadine) up to a nearly 10-fold increase in RH 123 accumulation (ivermectin, terfenadine). No correlation between P-gp and CYP3A4 inhibition was observed. The rank order in P-gp inhibitory potency for terfenadine, verapamil, ritonavir. and indomethacin was identical in both LS180V and Caco-2 models. Ritonavir and St. John's wort extract showed a concentration-dependent P-gp induction, with good correlation between western blot analysis and RH123 accumulation. CONCLUSIONS: The RH123 accumulation assay in LS180V cells can be used as a valuable screening tool to study both inhibition and induction of P-gp activity and expression. This assay has the potential to predict P-gp-mediated alterations in intestinal absorption of drugs.
Authors: R B Kim; C Wandel; B Leake; M Cvetkovic; M F Fromm; P J Dempsey; M M Roden; F Belas; A K Chaudhary; D M Roden; A J Wood; G R Wilkinson Journal: Pharm Res Date: 1999-03 Impact factor: 4.200
Authors: C Cordon-Cardo; J P O'Brien; D Casals; L Rittman-Grauer; J L Biedler; M R Melamed; J R Bertino Journal: Proc Natl Acad Sci U S A Date: 1989-01 Impact factor: 11.205
Authors: M D Perloff; L L von Moltke; M H Court; T Kotegawa; R I Shader; D J Greenblatt Journal: J Pharmacol Exp Ther Date: 2000-02 Impact factor: 4.030
Authors: Xiaofeng Bao; Shuiyu Lu; Jeih-San Liow; Cheryl L Morse; Kacey B Anderson; Sami S Zoghbi; Robert B Innis; Victor W Pike Journal: Nucl Med Biol Date: 2012-08-14 Impact factor: 2.408