Unmasking the Dynamic Interplay between Intestinal P-Glycoprotein and CYP3A4

Abstract

Drug efflux by intestinal P-glycoprotein (P-gp) is known to decrease the oral bioavailability of many CYP3A4 substrates. We hypothesized that the interplay occurring between P-gp and CYP3A4 at the apical membrane would increase the opportunity for drug metabolism. To define the roles of P-glycoprotein (P-gp) and CYP3A4 in controlling the extent of intestinal absorption and metabolism, two substrates were tested. The transport, metabolism, and intracellular levels of N-methyl piperazine-Phe-homoPhe-vinylsulfone phenyl (K77, a cysteine protease inhibitor; P-gp and CYP3A4 substrate) and felodipine (CYP3A4 substrate only) were measured across CYP3A4-transfected Caco-2 cells in the presence of an inhibitor of CYP3A4 and P-gp, cyclosporine (CsA), or an inhibitor of P-gp and not CYP3A4, GG918 (N-{4-[2-(1,2,3,4-tetrahydro-6,7-dimethoxy-2-isoquinolinyl)-ethyl]-phenyl}-9,10-dihydro-5-methoxy-9-oxo-4-acridine carboxamine). The extent of metabolism was measured by calculating the extraction ratio (ER) across the cells, while accounting for intracellular changes occurring with P-gp inhibition. The (A)pical to (B)asolateral and B3 A ERs for K77 were 0.33 and 0.06, respectively. These changed with GG918 to 0.14 and 0.12 and with CsA to 0.06 and 0.04. Felodipine ERs were similar in both directions, 0.26 and 0.24 (A3 B and B3 A), and were unchanged in the presence of GG918 but decreased with CsA (0.14 and 0.11). The K77 absorption rate was increased 5 and 4.2-fold in the presence of CsA and GG918, respectively, whereas no change was observed for felodipine absorption. The decreased A3 B ER and increased absorption of K77 with GG918 suggest that P-gp influences the extent of drug metabolism in the intestine via prolonging the access of drugs to CYP3A4 near the apical membrane and decreasing transport across the cells.Intestinal drug metabolism by cytochrome P450 3A (CYP3A) is increasingly being recognized as an important determinant in limiting drug bioavailability. CYP3A4 is the most prominent oxidative cytochrome P450 enzyme present in the human intestine (Watkins et al., 1987;Zhang et al., 1999), where it is localized to the columnar epithelial cells lining the intestinal lumen (Kolars et al., 1994). Despite the lower CYP3A4 content in the intestine relative to the liver, first-pass metabolism in the intestine by CYP3A has conclusively been shown to be important in the disposition of midazolam (Paine et al., 1996) and cyclosporine (CsA) (Kolars et al., 1991) from studies with anhepatic patients. Drug interaction studies performed with grapefruit juice [a suicide inhibitor of intestinal CYP3A (Schmiedlin-Ren et al., 1997a)] have also shown significant increases in the oral bioavailability of many CYP3A4 substrates including felodipine (Edgar et al., 1992).Drug absorption can also be hindered by efflux transporters in the intestine. P-glycoprotein (P-gp) is a plasma membrane-bound drug efflux protein found primarily in drugeliminating organs and presumably functions as a detoxifying transporter because it actively extrud...

Ligand Promiscuity between the Efflux Pumps Human P-Glycoprotein and S. aureus NorA

“…The SA-1199B strain contains a point mutation in grlA (topoisomerase IV A subunit gene) resulting in an amino acid substitution in GrlA (A116E), and it also overexpresses the NorA efflux pump (norA++) by way of a promoter up-mutation. 19,20 Compounds 3, 5, aripiprazole (7), ebastine (8), sertindole (9), and ziprasidone (10) demonstrate an inhibition of EtBr efflux in the SA-1199B strain of >70%, which is comparable to that of the reference compound, 1 (≥80%) ( Table 1). These six compounds were tested for their intrinsic antibacterial activity.…”

“…7,8 However, due to the key role played in the elimination and distribution of its substrates, Pgp inhibition is generally an unwanted property for therapeutics not employed in the oncologic field, since it might alter the pharmacokinetics parameters of coadministered drugs (for example transporter− enzyme interplay). 9 NorA is responsible for the phenomenon of MDR in some pathogenic strains S. aureus and is not considered to be an antitarget. Its inhibition is potentially beneficial, since when certain antimicrobials, including for example most fluoroquinolones, are being used as antibacterials against pump-related resistant strains, the inhibition of NorA by efflux pump inhibitors (EPIs) may restore the original efficacy of the compounds, unless some other resistance mechanism is also present.…”

The Interaction of Selected Phytochemicals, HIV Drugs, and Commercial-Source Herbal Teas and Capsules with Human Cytochrome P450 3A4 and P-glycoprotein

“…In general, the potential for clinically significant adverse reactions to occur is increased with concomitant NHP-drug use, due to the fact that there are numerous NHPs, phytochemicals, and drugs that can inhibit (or induce) CYP3A4, as well as influence P-gp-mediated efflux of coadministered substrates, because both CYP3A4 and P-gp have many common and overlapping substrate specificities (Cummins et al, 2001(Cummins et al, , 2002Kivistö et al, 2004;Mouly et al, 2004).…”

Lack of an effect of CYP3A4 and MDR1 gene polymorphisms on colchicine pharmacogenetics in the treatment of Familial Mediterranean fever

“…P-gp/MDR1 also mediates the counteracting active transport of drugs back to the lumen after passive absorption into the enterocytes (Cummins et al, 2002). The drug is continuously circulated between the lumen and enterocytes, allowing CYP3A constant access to the drug molecule.…”

“…There is a broad range of overlapping substrate specificities and tissue distribution for CYP3A and P-gp/MDR1 for what are known as CYP/P-gp substrates. P-gp/MDR1 and CYP3A act synergistically as a protective barrier in the bioavailability of orally administered colchicine (Cummins et al, 2002;Niel and Shermann, 2006). To date, more than 40 SNPs in CYP3A4 and more than 50 SNPs in P-gp/MDR1 have been identified (Hoffmeyer et al, 2000;Brinkmann and Eichelbaum, 2001;Marzolini et al, 2004;Du et al, 2006).…”