In vivo assessment of the impact of efflux transporter on oral drug absorption using portal vein-cannulated rats

Gut microbiome modulates tacrolimus pharmacokinetics through the transcriptional regulation of ABCB1

BACKGROUND

Following solid organ transplantation, tacrolimus (TAC) is an essential drug in the immunosuppressive strategy. Its use constitutes a challenge due to its narrow therapeutic index and its high inter- and intra-pharmacokinetic (PK) variability. As the contribution of the gut microbiota to drug metabolism is now emerging, it might be explored as one of the factors explaining TAC PK variability. Herein, we explored the consequences of TAC administration on the gut microbiota composition. Reciprocally, we studied the contribution of the gut microbiota to TAC PK, using a combination of in vivo and in vitro models.

RESULTS

TAC oral administration in mice resulted in compositional alterations of the gut microbiota, namely lower evenness and disturbance in the relative abundance of specific bacterial taxa. Compared to controls, mice with a lower intestinal microbial load due to antibiotics administration exhibit a 33% reduction in TAC whole blood exposure and a lower inter-individual variability. This reduction in TAC levels was strongly correlated with higher expression of the efflux transporter ABCB1 (also known as the p-glycoprotein (P-gp) or the multidrug resistance protein 1 (MDR1)) in the small intestine. Conventionalization of germ-free mice confirmed the ability of the gut microbiota to downregulate ABCB1 expression in a site-specific fashion. The functional inhibition of ABCB1 in vivo by zosuquidar formally established the implication of this efflux transporter in the modulation of TAC PK by the gut microbiota. Furthermore, we showed that polar bacterial metabolites could recapitulate the transcriptional regulation of ABCB1 by the gut microbiota, without affecting its functionality. Finally, whole transcriptome analyses pinpointed, among others, the Constitutive Androstane Receptor (CAR) as a transcription factor likely to mediate the impact of the gut microbiota on ABCB1 transcriptional regulation.

CONCLUSIONS

We highlight for the first time how the modulation of ABCB1 expression by bacterial metabolites results in changes in TAC PK, affecting not only blood levels but also the inter-individual variability. More broadly, considering the high number of drugs with unexplained PK variability transported by ABCB1, our work is of clinical importance and paves the way for incorporating the gut microbiota in prediction algorithms for dosage of such drugs. Video Abstract.

Evaluation of the Herb-Drug Interaction (HDI) Potential of Zingiber officinale and Its Major Phytoconstituents

Ginger is currently one of the most popular herbs commonly added to diverse foods, beverages, and dietary supplements. We evaluated the ability of a well-characterized ginger extract, and several of its phytoconstituents, to activate select nuclear receptors as well as modulate the activity of various cytochrome P450s and ATP-binding cassette (ABC) transporters because phytochemical-mediated modulation of these proteins underlies many clinically relevant herb-drug interactions (HDI). Our results revealed ginger extract activated the aryl hydrocarbon receptor (AhR) in AhR-reporter cells and pregnane X receptor (PXR) in intestinal and hepatic cells. Among the phytochemicals investigated, (S)-6-gingerol, dehydro-6-gingerdione, and (6S,8S)-6-gingerdiol activated AhR, while 6-shogaol, 6-paradol, and dehydro-6-gingerdione activated PXR. Enzyme assays showed that ginger extract and its phytochemicals dramatically inhibited the catalytic activity of CYP3A4, 2C9, 1A2, and 2B6, and efflux transport capabilities of P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP). Dissolution studies with ginger extract conducted in biorelevant simulated intestinal fluid yielded (S)-6-gingerol and 6-shogaol concentrations that could conceivably exceed cytochrome P450 (CYP) IC50 values when consumed in recommended doses. In summary, overconsumption of ginger may disturb the normal homeostasis of CYPs and ABC transporters, which in turn, may elevate the risk for HDIs when consumed concomitantly with conventional medications.

Oral etoposide and zosuquidar bioavailability in rats: Effect of co-administration and in vitro-in vivo correlation of P-glycoprotein inhibition

P-glycoprotein inhibitors, like zosuquidar, have widely been used to study the role of P-glycoprotein in oral absorption. Still, systematic studies on the inhibitor dose-response relationship on intestinal drug permeation are lacking. In the present study, we investigated the effect of 0.79 nM-2.5 μM zosuquidar on etoposide permeability across Caco-2 cell monolayers. We also investigated etoposide pharmacokinetics after oral or IV administration to Sprague Dawley rats with co-administration of 0.063–63 mg/kg zosuquidar, as well as the pharmacokinetics of zosuquidar itself. Oral zosuquidar bioavailability was 2.6–4.2%, while oral etoposide bioavailability was 5.5 ± 0.9%, which increased with increasing zosuquidar doses to 35 ± 5%. The intestinal zosuquidar concentration required to induce a half-maximal increase in bioavailability was estimated to 180 μM. In contrast, the IC₅₀ of zosuquidar on etoposide permeability in vitro was only 5–10 nM, and a substantial in vitro-in vivo discrepancy of at least four orders of magnitude was thereby identified. Overall, the present study provides valuable insights for future formulation development that applies fixed dose combinations of P-glycoprotein inhibitors to increase the absorption of poorly permeable P-glycoprotein substrate drugs.

Dual Inhibition of P-gp and BCRP Improves Oral Topotecan Bioavailability in Rodents

P-glycoprotein (P-gp) inhibition has been studied to overcome multidrug resistance in cancer chemotherapy but failed in clinical trials due to low/toxic effects. Recently, a dual modulation of transporters and natural derivatives have been examined to surmount this limitation. We examined breast cancer resistance protein (BCRP) inhibition in vitro and in vivo by P-gp inhibitors derived from natural compounds in previous studies. P-gp inhibitors increased the accumulation of the anticancer drug, topotecan (TPT)-a substrate of P-gp and BCRP, albeit with higher affinity for BCRP-in BCRP-overexpressing cells, resulting in cell death. These dual inhibitors, when orally co-administered with TPT, enhanced TPT bioavailability with slightly reduced total oral clearance (Clt/F) in rats. In xenograft mice, they strengthened oral TPT-induced tumor reduction with no alterations in body weight. Moreover, we investigated the effects of an oral drug formulation (Cremophor® EL, Tween® 80, and polyethylene glycol 400) on the transporters function. The excipients increased TPT accumulation in P-gp- or BCRP-overexpressing cells. Oral TPT bioavailability was higher with the formulation than with a control, as shown by the increases in the maximum plasma concentration (Cmax) and the area under the plasma concentration-time curve from zero to infinity (AUCINF) (p< 0.01). Therefore, oral TPT bioavailability was enhanced by P-gp/BCRP dual inhibition, which resulted in a formulation-mediated increase in absorption and decrease in elimination, and a dual inhibitor-mediated decrease in elimination. These results suggest that the combination of dual inhibition by a natural derivative and the drug formulation can be a useful clinical approach.

Characterization of P-Glycoprotein Inhibitors for Evaluating the Effect of P-Glycoprotein on the Intestinal Absorption of Drugs

For developing oral drugs, it is necessary to predict the oral absorption of new chemical entities accurately. However, it is difficult because of the involvement of efflux transporters, including P-glycoprotein (P-gp), in their absorption process. In this study, we conducted a comparative analysis on the inhibitory activities of seven P-gp inhibitors (cyclosporin A, GF120918, LY335979, XR9576, WK-X-34, VX-710, and OC144-093) to evaluate the effect of P-gp on drug absorption. GF120918, LY335979, and XR9576 significantly decreased the basal-to-apical transport of paclitaxel, a P-gp substrate, across Caco-2 cell monolayers. GF120918 also inhibited the basal-to-apical transport of mitoxantrone, a breast cancer resistance protein (BCRP) substrate, in Caco-2 cells, whereas LY335979 hardly affected the mitoxantrone transport. In addition, the absorption rate of paclitaxel after oral administration in wild-type mice was significantly increased by pretreatment with LY335979, and it was similar to that in mdr1a/1b knockout mice. Moreover, the absorption rate of topotecan, a BCRP substrate, in wild-type mice pretreated with LY335979 was similar to that in mdr1a/1b knockout mice but significantly lower than that in bcrp knockout mice. These results indicate that LY335979 has a selective inhibitory activity for P-gp, and would be useful for evaluating the contribution of P-gp to drug absorption.

Optimization of dose and route of administration of the P-glycoprotein inhibitor, valspodar (PSC-833) and the P-glycoprotein and breast cancer resistance protein dual-inhibitor, elacridar (GF120918) as dual infusion in rats

Transporters can play a key role in the absorption, distribution, metabolism, and excretion of drugs. Understanding these contributions early in drug discovery allows for more accurate projection of the clinical pharmacokinetics. One method to assess the impact of transporters in vivo involves co‐dosing specific inhibitors. The objective of the present study was to optimize the dose and route of administration of a P‐glycoprotein (P‐gp) inhibitor, valspodar (PSC833), and a dual P‐gp/breast cancer resistance protein (BCRP) inhibitor, elacridar (GF120918), by assessing the transporters’ impact on brain penetration and absorption. A dual‐infusion strategy was implemented to allow for flexibility with dose formulation. The chemical inhibitor was dosed intravenously via the femoral artery, and a cassette of known substrates was infused via the jugular vein. Valspodar or elacridar was administered as 4.5‐hour constant infusions over a range of doses. To assess the degree of inhibition, the resulting ratios of brain and plasma concentrations, Kp's, of the known substrates were compared to the vehicle control. These data demonstrated that doses greater than 0.9 mg/hr/kg valspodar and 8.9 mg/hr/kg elacridar were sufficient to inhibit P‐gp‐ and BCRP‐mediated efflux at the blood‐brain barrier in rats without any tolerability issues. Confirmation of BBB restriction by efflux transporters in preclinical species allows for subsequent prediction in humans based upon the proteomic expression at rodent and human BBB. Overall, the approach can also be applied to inhibition of efflux at other tissues (gut absorption, liver clearance) or can be extended to other transporters of interest using alternate inhibitors.

The Impact of Breast Cancer Resistance Protein (BCRP/ABCG2) on Drug Transport Across Caco-2 Cell Monolayers

Breast cancer resistance protein (BCRP) is expressed on the apical membrane of small intestinal epithelial cells and functions as an efflux pump with broad substrate recognition. Therefore, quantitative evaluation of the contribution of BCRP to the intestinal permeability of new chemical entities is very important in drug research and development. In this study, we assessed the BCRP-mediated efflux of several model drugs in Caco-2 cells using WK-X-34 as a dual inhibitor of P-glycoprotein (P-gp) and BCRP and LY335979 as a selective inhibitor of P-gp. The permeability of daidzein was high with an apparent permeability coefficient for apical-to-basal transport (P _AB) of 20.3 × 10^-6 cm/s. In addition, its efflux ratio (ER) was 1.55, indicating that the contribution of BCRP to its transport is minimal. Estrone-3-sulfate and ciprofloxacin showed relatively higher ER values (>2.0), whereas their BCRP-related absorptive quotient (AQ _BCRP) was 0.21 and 0.3, respectively. These results indicate that BCRP does not play a major role in regulating the permeability of estrone-3-sulfate and ciprofloxacin in Caco-2 cells. Nitrofurantoin showed a P _AB of 1.8 × 10^-6 cm/s, and its ER was 7.6. However, the AQ _BCRP was 0.37, suggesting minimal contribution of BCRP to nitrofurantoin transport in Caco-2 cells. In contrast, topotecan, SN-38, and sulfasalazine had low P _AB values (0.81, 1.13, and 0.19 × 10^-6 cm/s, respectively), and each AQ _BCRP was above 0.6, indicating that BCRP significantly contributes to the transport of these compounds in Caco-2 cells. In conclusion, Caco-2 cells are useful to accurately estimate the contribution of BCRP to intestinal drug absorption. SIGNIFICANCE STATEMENT: We performed an in vitro assessment of the contribution of breast cancer resistance protein (BCRP) to the transport of BCRP and/or P-glycoprotein (P-gp) substrates across Caco-2 cell monolayers using absorptive quotient, which has been proposed to represent the contribution of drug efflux transporters to the net efflux. The present study demonstrates that the combined use of a BCRP/P-gp dual inhibitor and a P-gp selective inhibitor is useful to estimate the impact of BCRP and P-gp on the permeability of tested compounds in Caco-2 cells.

Impact of P-Glycoprotein on Intestinal Absorption of an Inhibitor of Apoptosis Protein Antagonist in Rats: Mechanisms of Nonlinear Pharmacokinetics and Food Effects

PURPOSE

This study was designed to investigate the effects of P-glycoprotein (P-gp) expressed in the intestine on the nonlinear pharmacokinetics (PK) of T-3256336, an inhibitor of apoptosis protein inhibitor, and food effects on its bioavailability in rats.

METHODS

To investigate the factors that contribute to nonlinear PK of T-3256336 in the intestine and liver, rats double-cannulated in the portal vein and femoral artery (PS rats) were used. F_aF_g (F_a, absorption ratio; F_g, intestinal availability) and hepatic availability (F_h) were simultaneously evaluated based on the difference between the portal and systemic blood area under the concentration-time curve (AUC). Elacridar was used as a P-gp inhibitor to assess the impact of P-gp on the intestinal absorption.

RESULTS

After oral administration of T-3256336 to PS rats at 3 and 30 mg/kg, F_aF_g value increased with dose escalation, whereas F_h value was nearly constant. Moreover, co-administration of elacridar resulted in a 5-fold increase in the F_aF_g value at 3 mg/kg. The AUC value of T-3256336 under fed conditions was 3-fold lower than that under fasted conditions. This food effect on the oral bioavailability (BA) was reduced by concomitant administration of elacridar.

CONCLUSION

P-gp expressed in the intestine would cause nonlinear PK and a food effect on BA of T-3256336 in rats.

Application of a Human Intestinal Epithelial Cell Monolayer to the Prediction of Oral Drug Absorption in Humans as a Superior Alternative to the Caco-2 Cell Monolayer

A human small intestinal epithelial cell (HIEC) monolayer was recently established in our laboratories as a novel system to evaluate the Papp (apparent permeability coefficient) of compounds during their absorption in humans. An effusion-based analysis using polyethylene glycol oligomers with molecular weights ranging from 194-898 indicated that HIEC and Caco-2 cell monolayers both had paracellular pores with 2 distinct radiuses (∼ 5 and 9-14 Å), whereas the porosity of large pores was 11-fold higher in the HIEC monolayer (44 × 10(-8)) than in the Caco-2 cells (4 × 10(-8)). A comparison between the fraction-absorbed (Fa) values observed in humans and those predicted from Papp values in both monolayers indicated that the HIEC monolayer had markedly higher precision to predict Fa values with root mean square error of 9.40 than the Caco-2 cells (root mean square error = 16.90) for 10 paracellularly absorbed compounds. Furthermore, the accuracy of the HIEC monolayer to classify the absorption of 23 test drugs with diverse absorption properties, including different pathways in the presence or absence of susceptibility to efflux transporters, was higher than that of the Caco-2 cell monolayer. In conclusion, the HIEC monolayer exhibited advantages over Caco-2 cells in the ranking and prediction of absorption of compounds in humans.

Pharmacokinetics of mangiferin and its metabolite-norathyriol, Part 2: Influence of UGT, CYP450, P-gp, and enterobacteria and the potential interaction in Rhizoma Anemarrhenae decoction with timosaponin B2 as the major contributor

The poor bioavailability of mangiferin (MGF) is a major obstacle on its further development. Aimed to illustrate the underlying mechanism and improve its poor exposure, the compared PK profiles of MGF and norathyriol (NTR) after different MGF preparation were performed: pure MGF, the Rhizoma Anemarrhenae (Zhi-mu) decoction, MGF, and timosaponin B2 (TB-2) combination. Furthermore, the potential contributing factors, including uridine diphosphoglucuronosyltransferase (UGT), cytochrome P450 (CYP450), P-gp, and enterobacterial were investigated by comparing the PK profiles with and without the corresponding inhibitors or in different rat models. After taking MGF, CYP450 and UGT inhibition could decrease MGF and NTR exposure; P-gp inhibition slightly enhanced (48%) MGF exposure, whereas more apparent for the improved NTR exposure (302%); enterobacterial inhibition almost completely stopped the NTR production, but no such effect was observed for MGF. Compared with the limited improvement by the abovementioned inhibition, the MGF and NTR exposure could significantly increase by 11.5- and 5.9-fold in the Zhi-mu decoction compared with the MGF treatment, probably contributed to TB-2 as an absorption enhancer because the MGF and TB-2 combination produced a similar level of improvement on the PK paremeters of MGF and NTR to the herb treatment. Likewise, most of the effects by UGT, CYP450, P-gp, and enterobacteria followed a similar variation tendency between them. Therefore, the poor bioavailability of MGF possibly mainly attributed to its poor membrane permeability, but not transporters or metabolic enzymes, and the compatibility of MGF and TB-2 could probably expand the prospective application of MGF by improving its bioavailability. © 2016 BioFactors, 42(5):545-555, 2016.

Absorption and cleavage of enalapril, a carboxyl ester prodrug, in the rat intestine: in vitro, in situ intestinal perfusion and portal vein cannulation models

In recent years prodrug strategy has been used extensively to improve the pharmacokinetic properties of compounds exhibiting poor bioavailability. Mechanistic understanding of the absorption and the role of intestine and liver in the activation of oral prodrugs is crucial. Enalapril, a carboxyl ester prodrug, is reported to be metabolized by human carboxylesterase-1 (CES1) but not by carboxylesterase-2 (CES2) to its active metabolite enalaprilat. Further, it has been reported that the small intestines of both rat and human contain mainly CES2. The objective of this work was to understand whether enalapril remains unchanged as it is absorbed through the intestine into the portal circulation. This was evaluated using different intestinal preparations, an in situ intestinal perfusion experiment and a portal vein cannulated rat model. No turnover of enalapril was seen with commercial rat intestinal S9 and microsomes, but reasonable turnover was observed with freshly prepared rat intestinal and mucosal homogenate and S9. In the intestinal perfusion study, both enalapril and enalaprilat were observed in the mesenteric plasma with the data suggesting 32% hydrolysis of enalapril in the intestine. In the portal vein cannulated rat, about 51% of enalapril absorbed into intestine was converted to enalaprilat. Overall, it was demonstrated that even though enalapril has been shown to be a specific substrate for CES1, it is converted to enalaprilat to a significant extent in the intestine. Such experimental techniques can be applied by other scientific groups who are working on prodrugs to determine the region and extent of activation. Copyright © 2015 John Wiley & Sons, Ltd.