Exposure of LS-180 Cells to Drugs of Diverse Physicochemical and Therapeutic Properties Up-regulates P-glycoprotein Expression and Activity

Abstract

Purpose Drug transporters are increasingly recognized as important determinants of variability in drug disposition and therapeutic response, both in pre-clinical and clinical stages of drug development process. The role P-glycoprotein (P-gp) plays in drug interactions via its inhibition is well established. However, much less knowledge is available about drugs effect on P-gp up-regulation. The objective of this work was to in vitro investigate and rank commonly used drugs according to their potencies to up-regulate P-gp activity utilizing the same experimental conditions. Methods The in vitro potencies of several drugs of diverse physicochemical and therapeutic properties including rifampicin, dexamethasone, caffeine, verapamil, pentylenetetrazole, hyperforin, and β-estradiol over broad concentration range to up-regulate P-gp expression and activity were examined. For dose-response studies, LS-180 cells were treated with different concentrations of the selected drugs followed by P-gp protein and gene expressions analyses. P-gp functionality was determined by uptake studies with rhodamine 123 as a P-gp substrate, followed by Emax/EC50 evaluation. Results The results demonstrated a dose-dependent increase in P-gp expression and activity following treatments. At 50 μM concentration (hyperforin, 0.1 μM), examined drugs increased P-gp protein and gene expressions by up to 5.5 and 6.2-fold, respectively, while enhanced P-gp activity by 1.8–4-fold. The rank order of these drugs potencies to up-regulate P-gp activity was as following: hyperforin ⋙ dexamethasone ≈ β-estradiol > caffeine > rifampicin ≈ pentylenetetrazole > verapamil. Conclusions These drugs have the potential to be involved in drug interactions when administered with other drugs that are P-gp substrates. Further studies are needed to in vivo evaluate these drugs and verify the consequences of such induction on P-gp activity for in vitro-in vivo correlation purposes.

Enhanced Brain Amyloid-β Clearance by Rifampicin and Caffeine as a Possible Protective Mechanism Against Alzheimer's Disease

“…Although this finding is in line with previous results obtained from in vitro [32] and in vivo [42] studies, a previous study reported that the induction of P-gp by rifampicin is associated with increased pregnane X receptor (PXR) activity in humans and rats but not mice PXR [39]. While this discrepancy could be related to differences in administered dose, treatment duration, and/or mice strain [42], the above results suggest that rifampicin may have an alternative pathway(s) for P-gp upregulation other than PXR activation in mouse brain endothelial cells, and demonstrate that, regardless of the mechanism, rifampicin upregulates P-gp expression and activity in both the human [32] and mouse origin cell lines. Mechanistic studies to investigate P-gp upregulation is beyond the scope of this study.…”

“…According to our western blot results, confirmed by RT-PCR and fluorescent imaging, it is clear that caffeine upregulated P-gp but not LRP1 expression in both bEnd3 cells and in the isolated microvessels. These results in bEnd3 cells are consistent with those obtained using cell line of human origin [32] suggesting that caffeine effect on P-gp and LRP1 in humans and mice is comparable. Such increase in P-gp expression by caffeine has been obtained from 40mg/kg/day, a dose which is lower than that reported by Arendash et al that is associated with cognitive protective effect and reduction in mice brain Aβ levels [47].…”

“…In addition, several studies, including ours, have demonstrated both drugs as potent P-gp inducers [17, 32]. In this study, we further investigated the effect of either drug on LRP1 where rifampicin treatment upregulated LRP1 but not caffeine.…”

“…Cells were allowed to grow up to 50% confluence and then treated with rifampicin, caffeine, or control (DMSO, 0.1%). Stock solutions of rifampicin and caffeine were diluted to a final concentration of 50 µM in growth medium before use [17, 32]. Vehicle and drug containing media were added to the respective treatment cells and were then incubated for 72 h at 37°C/5% CO2.…”

“…In addition to their established protective effect, both drugs have been reported as potent inducers of P-gp [17,32]; however, studies investigating rifampicin and caffeine as LRP1 inducers are still lacking. Collectively, in the current study we have hypothesized that enhanced Aβ clearance from the brain across the BBB of wild-type mice treated with rifampicin or caffeine is caused by both drugs potential to upregulate LRP1 and/or P-gp at the BBB, thus exhibiting their protective effect against AD.…”