Clinical Aspects of Transporter-Mediated Drug-Drug Interactions

The Competitive Counterflow Assay for Identifying Drugs Transported by Solute Carriers: Principle, Applications, Challenges/Limits, and Perspectives

The identification of substrates for solute carriers (SLCs) handling drugs is an important challenge, owing to the major implication of these plasma membrane transporters in pharmacokinetics and drug-drug interactions. In this context, the competitive counterflow (CCF) assay has been proposed as a practical and less expensive approach than the reference functional uptake assays for discriminating SLC substrates and non-substrates. The present article was designed to summarize and discuss key-findings about the CCF assay, including its principle, applications, challenges and limits, and perspectives. The CCF assay is based on the decrease of the steady-state accumulation of a tracer substrate in SLC-positive cells, caused by candidate substrates. Reviewed data highlight the fact that the CCF assay has been used to identify substrates and non-substrates for organic cation transporters (OCTs), organic anion transporters (OATs), and organic anion transporting polypeptides (OATPs). The performance values of the CCF assay, calculated from available CCF study data compared with reference functional uptake assay data, are, however, rather mitigated, indicating that the predictability of the CCF method for assessing SLC-mediated transportability of drugs is currently not optimal. Further studies, notably aimed at standardizing the CCF assay and developing CCF-based high-throughput approaches, are therefore required in order to fully precise the interest and relevance of the CCF assay for identifying substrates and non-substrates of SLCs.

Inhibition of human drug transporter activities by succinate dehydrogenase inhibitors

Succinate dehydrogenase inhibitors (SDHIs) are widely-used fungicides, to which humans are exposed and for which putative health risks are of concern. In order to identify human molecular targets for these environmental chemicals, the interactions of 15 SDHIs with activities of main human drug transporters implicated in pharmacokinetics were investigated in vitro. 5/15 SDHIs, i.e., benzovindiflupyr, bixafen, fluxapyroxad, pydiflumetofen and sedaxane, were found to strongly reduce activity of the renal organic anion transporter (OAT) 3, in a concentration-dependent manner (with IC50 values in the 1.0-3.9 μM range), without however being substrates for OAT3. Moreover, these 5/15 SDHIs decreased the membrane transport of estrone-3 sulfate, an endogenous substrate for OAT3, and sedaxane was predicted to inhibit in vivo OAT3 activity in response to exposure to the acceptable daily intake (ADI) dose. In addition, pydiflumetofen strongly inhibited the renal organic cation transporter (OCT) 2 (IC50 = 2.0 μM) and benzovindiflupyr the efflux pump breast cancer resistance protein (BCRP) (IC50 = 3.9 μM). Other human transporters, including organic anion transporting polypeptide (OATP) 1B1 and OATP1B3 as well as multidrug and toxin extrusion protein (MATE) 1 and MATE2-K were moderately or weakly inhibited by SDHIs, whereas P-glycoprotein, multidrug resistance-associated protein (MRP), OCT1 and OAT1 activities were not or only marginally impacted. Then, some human drug transporters, especially OAT3, constitute molecular targets for SDHIs. This could have toxic consequences, notably with respect to levels of endogenous compounds and metabolites substrates for the considered transporters or to potential SDHI-drug interactions. This could therefore contribute to putative health risk of these fungicides.

Utilising Endogenous Biomarkers in Drug Development to Streamline the Assessment of Drug-Drug Interactions Mediated by Renal Transporters: A Pharmaceutical Industry Perspective

The renal secretion of many drugs is facilitated by membrane transporters, including organic cation transporter 2, multidrug and toxin extrusion protein 1/2-K and organic anion transporters 1 and 3. Inhibition of these transporters can reduce renal excretion of drugs and thereby pose a safety risk. Assessing the risk of inhibition of these membrane transporters by investigational drugs remains a key focus in the evaluation of drug-drug interactions (DDIs). Current methods to predict DDI risk are based on generating in vitro data followed by a clinical assessment using a recommended exogenous probe substrate for the individual drug transporter. More recently, monitoring plasma-based and urine-based endogenous biomarkers to predict transporter-mediated DDIs in early phase I studies represents a promising approach to facilitate, improve and potentially avoid conventional clinical DDI studies. This perspective reviews the evidence for use of these endogenous biomarkers in the assessment of renal transporter-mediated DDI, evaluates how endogenous biomarkers may help to expand the DDI assessment toolkit and offers some potential knowledge gaps. A conceptual framework for assessment that may complement the current paradigm of predicting the potential for renal transporter-mediated DDIs is outlined.

Tofacitinib uptake by patient-derived intestinal organoids predicts individual clinical responsiveness

Background & Aims

Despite increasing therapeutic options in the treatment of ulcerative colitis (UC), achieving disease remission remains a major clinical challenge. Nonresponse to therapy is common and clinicians have little guidance in selecting the optimal therapy for an individual patient. This study examined whether patient-derived materials could predict individual clinical responsiveness to the Janus kinase (JAK) inhibitor, tofacitinib, prior to treatment initiation.

Method

In 48 patients with UC initiating tofacitinib, we longitudinally collected clinical covariates, stool, and colonic biopsies to analyze the microbiota, transcriptome, and exome variations associated with clinical responsiveness at week 24. We established patient-derived organoids (n = 23) to determine how their viability upon stimulation with proinflammatory cytokines in the presence of tofacitinib related to drug responsiveness in patients. We performed additional biochemical analyses of organoids and primary tissues to identify the mechanism underlying differential tofacitinib sensitivity.

Results

The composition of the gut microbiota, rectal transcriptome, inflammatory biomarkers, and exome variations were indistinguishable among UC patients prior to tofacitinib treatment. However, a subset of patient-derived organoids displayed reduced sensitivity to tofacitinib as determined by the ability of the drug to inhibit STAT1 phosphorylation and loss of viability upon cytokine stimulation. Remarkably, sensitivity of organoids to tofacitinib predicted individual clinical patient responsiveness. Reduced responsiveness to tofacitinib was associated with decreased levels of the cationic transporter MATE1, which mediates tofacitinib uptake.

Conclusions

Patient-derived intestinal organoids predict and identify mechanisms of individual tofacitinib responsiveness in UC. Specifically, MATE1 expression predicted clinical response to tofacitinib.

Performance and Sensitivity of [99mTc]Tc-sestamibi Compared with Positron Emission Tomography Radiotracers to Measure P-glycoprotein Function in the Kidneys and Liver

P-glycoprotein (P-gp, encoded in humans by the ABCB1 gene and in rodents by the Abcb1a/b genes) is a membrane transporter that can restrict the intestinal absorption and tissue distribution of many drugs and may also contribute to renal and hepatobiliary drug excretion. The aim of this study was to compare the performance and sensitivity of currently available radiolabeled P-gp substrates for positron emission tomography (PET) with the single-photon emission computed tomography (SPECT) radiotracer [99mTc]Tc-sestamibi for measuring the P-gp function in the kidneys and liver. Wild-type, heterozygous (Abcb1a/b(+/-)), and homozygous (Abcb1a/b(-/-)) Abcb1a/b knockout mice were used as models of different P-gp abundance in excretory organs. Animals underwent either dynamic PET scans after intravenous injection of [11C]N-desmethyl-loperamide, (R)-[11C]verapamil, or [11C]metoclopramide or consecutive static SPECT scans after intravenous injection of [99mTc]Tc-sestamibi. P-gp in the kidneys and liver of the mouse models was analyzed with immunofluorescence labeling and Western blotting. In the kidneys, Abcb1a/b() mice had intermediate P-gp abundance compared with wild-type and Abcb1a/b(-/-) mice. Among the four tested radiotracers, renal clearance of radioactivity (CLurine,kidney) was significantly reduced (-83%) in Abcb1a/b(-/-) mice only for [99mTc]Tc-sestamibi. Biliary clearance of radioactivity (CLbile,liver) was significantly reduced in Abcb1a/b(-/-) mice for [11C]N-desmethyl-loperamide (-47%), [11C]metoclopramide (-25%), and [99mTc]Tc-sestamibi (-79%). However, in Abcb1a/b(+/-) mice, CLbile,liver was significantly reduced (-47%) only for [99mTc]Tc-sestamibi. Among the tested radiotracers, [99mTc]Tc-sestamibi performed best in measuring the P-gp function in the kidneys and liver. Owing to its widespread clinical availability, [99mTc]Tc-sestamibi represents a promising probe substrate to assess systemic P-gp-mediated drug-drug interactions and to measure renal and hepatic P-gp function under different (patho-)physiological conditions.

Tissue Distribution, Pharmacokinetics, and Effect of Hematological and Biochemical Parameters of Acute Intravenous Administration of Silver Nanoparticles in Rats

The widespread biomedical and commercial applications of silver nanoparticles (AgNPs) have increased their potential for human and environmental exposure and toxicity to human health. The bio-distribution and toxicity of AgNPs in rodents following inhalation, intratracheal instillation, and oral ingestion are well documented; however, little is known about the bio-distribution of intravenously (IV)-administered AgNPs and their organ-specific pathophysiological effects. Here, we investigate the pharmacokinetic pattern and tissue distribution of AgNPs in male rats following IV administration. The animals were humanely sacrificed after 10 min, 1 h, 6 h, 12 h, 24 h, and 168 h of AgNP administration, and the silver (Ag) content was measured from blood samples and various tissues following acid digestion. The AgNPs were readily absorbed and subsequently distributed into most organs predominantly in the colon, small intestine, kidney, and heart after 6 h; however, they were the highest in the spinal cord after 168 h. White blood cells (WBCs) were significantly increased (42-60%) in AgNP-administered animals at all time points except 10 min. Regarding platelets, all AgNP-administered animals showed counts 7.8-39.2% lower, with the lowest count at 168 h post-administration. In the case of lymphocytes (LYMs), the AgNP-treated animals exhibited a count 19.5-41% lower at 10 min and 1 h post-administration; however, the animals at 168 h post-administration showed a count 30.5% more. The mean corpuscular hemoglobin (MCH) counts from the AgNP-treated animals were decreased by 50-62%. The concentrations of aspartate transaminase (AST), urea, and creatinine were increased in the AgNP-treated animals. Taken together, the results suggest that the acute IV administration of AgNPs alters metabolic and hematological parameters in animals and may pose a health risk to humans.

Study Models of Drug-Drug Interactions Involving P-Glycoprotein: The Potential Benefit of P-Glycoprotein Modulation at the Kidney and Intestinal Levels

P-glycoprotein (P-gp) is a crucial membrane transporter situated on the cell's apical surface, being responsible for eliminating xenobiotics and endobiotics. P-gp modulators are compounds that can directly or indirectly affect this protein, leading to changes in its expression and function. These modulators can act as inhibitors, inducers, or activators, potentially causing drug-drug interactions (DDIs). This comprehensive review explores diverse models and techniques used to assess drug-induced P-gp modulation. We cover several approaches, including in silico, in vitro, ex vivo, and in vivo methods, with their respective strengths and limitations. Additionally, we explore the therapeutic implications of DDIs involving P-gp, with a special focus on the renal and intestinal elimination of P-gp substrates. This involves enhancing the removal of toxic substances from proximal tubular epithelial cells into the urine or increasing the transport of compounds from enterocytes into the intestinal lumen, thereby facilitating their excretion in the feces. A better understanding of these interactions, and of the distinct techniques applied for their study, will be of utmost importance for optimizing drug therapy, consequently minimizing drug-induced adverse and toxic effects.

A Metabolomic Analysis of Sensitivity and Specificity of 23 Previously Proposed Biomarkers for Renal Transporter-Mediated Drug-Drug Interactions

Endogenous biomarkers are discussed as tools for detection of drug-drug interactions (DDIs) mediated by renal transport proteins, such as organic cation transporter 2 (OCT2), multidrug and toxin extrusion proteins (MATE1 and MATE2-K) and organic anion transporters (OAT1 and OAT3). Whereas sensitivity of some endogenous biomarkers against at least one clinical transporter inhibitor has frequently been shown, intra-study comparisons of the extent of effects of inhibitors on different biomarkers are frequently lacking. Moreover, in vivo specificity of such discussed biomarkers has frequently not been studied. We therefore investigated changes of 10 previously described putative biomarkers for inhibition of OCT2/MATEs, as well as 15 previously described putative biomarkers for OATs in human plasma and urine samples of healthy volunteers in response to treatment with 4 inhibitors of transport proteins [verapamil (P-glycoprotein), rifampin (organic anion transporting polypeptides), cimetidine (OCT2/MATEs), and probenecid (OATs)]. Two of the putative biomarkers had been suggested for both OCT2/MATEs and OATs. All substances were unequivocally identified in an untargeted metabolomics assay. The OCT2/MATE biomarkers choline and trimethylamine N-oxide were both sensitive and specific (median log2-fold changes -1.18 in estimated renal elimination and -0.85 in urinary excretion, respectively). For renal OATs, indoleacetyl glutamine and indoleacetic acid (median log2-fold changes -3.77 and -2.85 in estimated renal elimination, respectively) were the candidates for sensitive and specific biomarkers with the most extensive change, followed by taurine, indolelactic acid, and hypoxanthine. This comprehensive study adds further knowledge on sensitivity and specificity of 23 previously described biomarkers of renal OCT2/MATE- and OAT-mediated DDIs.

Inhibitory interaction of flavonoids with organic cation transporter 2 and their structure-activity relationships for predicting nephroprotective effects

Organic cation transporter 2 (OCT2) is mainly responsible for the renal secretion of various cationic drugs, closely associated with drug-induced acute kidney injury (AKI). Screening and identifying potent OCT2 inhibitors with little toxicity in natural products in reducing OCT2-mediated AKI is of great value. Flavonoids are enriched in various vegetables, fruits, and herbal products, and some were reported to produce transporter-mediated drug-drug interactions. This study aimed to screen potential inhibitors of OCT2 from 96 flavonoids, assess the nephroprotective effects on cisplatin-induced kidney injury, and clarify the structure-activity relationships of flavonoids with OCT2. Ten flavonoids exhibited significant inhibition (>50%) on OCT2 in OCT2-HEK293 cells. Among them, the six most potent flavonoid inhibitors, including pectolinarigenin, biochanin A, luteolin, chrysin, 6-hydroxyflavone, and 6-methylflavone markedly decreased cisplatin-induced cytotoxicity. Moreover, in cisplatin-induced renal injury models, they also reduced serum blood urea nitrogen (BUN) and creatinine levels to different degrees, the best of which was 6-methylflavone. The pharmacophore model clarified that the aromatic ring, hydrogen bond acceptors, and hydrogen bond donors might play a vital role in the inhibitory effect of flavonoids on OCT2. Thus, our findings would pave the way to predicting the potential risks of flavonoid-containing food/herb-drug interactions in humans and optimizing flavonoid structure to alleviate OCT2-related AKI.

Novel drug transporter substrates identification: An innovative approach based on metabolomic profiling, in silico ligand screening and biological validation

Solute carrier (SLC) transport proteins are fundamental for the translocation of endogenous compounds and drugs across membranes, thus playing a critical role in disease susceptibility and drug response. Because only a limited number of transporter substrates are currently known, the function of a large number of SLC transporters is elusive. Here, we describe the proof-of-concept of a novel strategy to identify SLC transporter substrates exemplarily for the proton-coupled peptide transporter (PEPT) 2 (SLC15A2) and multidrug and toxin extrusion (MATE) 1 transporter (SLC47A1), which are important renal transporters of drug reabsorption and excretion, respectively. By combining metabolomic profiling of mice with genetically-disrupted transporters, in silico ligand screening and in vitro transport studies for experimental validation, we identified nucleobases and nucleoside-derived anticancer and antiviral agents (flucytosine, cytarabine, gemcitabine, capecitabine) as novel drug substrates of the MATE1 transporter. Our data confirms the successful applicability of this new approach for the identification of transporter substrates in general, which may prove particularly relevant in drug research.

Preincubation Time-Dependent, Long-Lasting Inhibition of Drug Transporters and Impact on the Prediction of Drug-Drug Interactions

Transporter-mediated drug-drug interaction (DDI) is of clinical concern, and the quantitative prediction of DDIs is an indispensable part of drug development. Cell-based inhibition assays, in which a representative probe substrate and a potential inhibitor are coincubated, are routinely performed to assess the inhibitory potential of new molecular entities on drug transporters. However, the inhibitory effect of cyclosporine A (CsA) on organic anion transporting polypeptide (OATP) 1B1 is substantially potentiated with CsA preincubation, and this effect is both long-lasting and dependent on the preincubation time. This phenomenon has also been reported with transporters other than OATP1Bs, but it is considered more prevalent among OATP1Bs and organic cation transporters. Regulatory agencies have also noted this preincubation effect and have recommended that pharmaceutical companies consider inhibitor preincubation when performing in vitro OATP1B1 and OATP1B3 inhibition studies. Although the underlying mechanisms responsible for the preincubation effect are not fully understood, a trans-inhibition mechanism was recently demonstrated for OATP1B1 inhibition by CsA, in which CsA inhibited OATP1B1 not only extracellularly (cis-inhibition) but also intracellularly (trans-inhibition). Furthermore, the trans-inhibition potency of CsA was much greater than that of cis-inhibition, suggesting that trans-inhibition might be a key driver of clinical DDIs of CsA with OATP1B substrate drugs. Although confidence in transporter-mediated DDI prediction is generally considered to be low, the predictability might be further improved by incorporating the trans-inhibition mechanism into static and dynamic models for preincubation-dependent inhibitors of OATP1Bs and perhaps other transporters. SIGNIFICANCE STATEMENT: Preincubation time-dependent, long-lasting inhibition has been observed for OATP1B1 and other solute carrier transporters in vitro. Recently, a trans-inhibition mechanism for the preincubation effect of CsA on OATP1B1 inhibition was identified, with the trans-inhibition potency being greater than that of cis-inhibition. The concept of trans-inhibition may allow us to further understand the mechanism of transporter-mediated DDIs not only for OATP1B1 but also for other transporters and to improve the accuracy and confidence of DDI predictions.

Progress in the Quantitative Assessment of Transporter-Mediated Drug-Drug Interactions Using Endogenous Substrates in Clinical Studies

Variations in drug transporter activities, caused by genetic polymorphism and drug-drug interactions (DDIs), alter the systemic exposure of substrate drugs, leading to differences in drug responses. Recently, some endogenous substrates of drug transporters, particularly the solute carrier family transporters such as OATP1B1, OATP1B3, OAT1, OAT3, OCT1, OCT2, MATE1, and MATE2-K, have been identified to investigate variations in drug transporters in humans. Clinical data obtained support their performance as surrogate probes in terms of specificity and reproducibility. Pharmacokinetic parameters of the endogenous biomarkers depend on the genotypes of drug transporters and the systemic exposure to perpetrator drugs. Furthermore, the development of physiologically based pharmacokinetic models for the endogenous biomarkers has enabled a top-down approach to obtain insights into the effect of perpetrators on drug transporters and to more precisely simulate the DDI with victim drugs, including probe drugs. The endogenous biomarkers can address the uncertainty in the DDI prediction in the preclinical and early phases of clinical development and have the potential to fulfill regulatory requirements. Therefore, the endogenous biomarkers should be able to predict disease effects on the variations in drug transporter activities observed in patients. This mini-review focuses on recent progress in the identification and use of the endogenous drug transporter substrate biomarkers and their application in drug development. SIGNIFICANCE STATEMENT: Advances in analytical methods have enabled the identification of endogenous substrates of drug transporters. Changes in the pharmacokinetic parameters (Cmax, AUC, or CLR) of these endogenous biomarkers relative to baseline values can serve as a quantitative index to assess variations in drug transporter activities during clinical studies and thereby provide more precise DDI predictions.

Beneficial herb-drug interaction of rhein in Jinhongtang and Imipenem/Cilastatin mediated by organic anion transporters

ETHNOPHARMACOLOGICAL RELEVANCE

Jinhongtang as a traditional Chinese medicine (TCM) formula, has been widely used as a clinical adjuvant in the treatment of acute abdominal diseases and sepsis. Clinical benefits of the concurrent use of Jinhongtang and antibiotics have been observed, however, the mechanism has not been fully understood.

AIM OF THE STUDY

The present study aimed to explore the effect of Jinhongtang on the antibacterial activity of Imipenem/Cilastatin and to clarify the underlying mechanism of herb-drug interaction (HDI).

MATERIALS AND METHODS

A mouse model of sepsis induced by Staphylococcus aureus (S. aureus) was used to evaluate the pharmacodynamic interaction in vivo. In vitro antibacterial activity of Imipenem/Cilastatin was studied by determining minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). Pharmacokinetic interaction was investigated by pharmacokinetic studies in rats and uptake assays using OAT1/3-HEK293 cells. The main constituents ingested into blood of rats were qualitatively identified by UHPLC-Q-TOF-MS.

RESULTS

Mice treated by Imipenem/Cilastatin and Jinhongtang exhibited higher survival rate, lower bacteria load and less inflammation in blood and lung tissues, compared with those treated by Imipenem/Cilastatin alone after injection of S. aureus. However, MIC and MBC of Imipenem/Cilastatin against S. aureus in vitro were not significantly changed in the presence of Jinhongtang. On the contrary, Jinhongtang increased the plasma concentration of Imipenem and decreased its urinary excretion in rats. CL_r of Imipenem was reduced by 58.5%, while its half-life (t_1/2) was prolonged for approximate 1.2 times after coadministered Jinhongtang. Furthermore, the extracts of Jinhongtang, single herb in the prescription, and main absorbable constituents inhibited cellular uptake of probe substrates and Imipenem by OAT1/3-HEK293 cells to different extents. Among them, rhein exhibited the strongest inhibition capacity with IC₅₀ values of 0.08 ± 0.01 μM (OAT1) and 2.86 ± 0.28 μM (OAT3). Moreover, coadministration of rhein also significantly enhanced the antibacterial activity of Imipenem/Cilastatin in sepsis mice.

CONCLUSION

Concomitant administration of Jinhongtang enhanced antibacterial activity of Imipenem/Cilastatin in sepsis mice induced by S. aureus through reducing renal elimination of Imipenem via inhibition of OATs. Our investigation provided the insight of Jinhongtang as an effective supplement to enhance the antibacterial activity of Imipenem/Cilastatin and can be useful for future clinical studies.

Interaction between Changan Granule and its main components in the plasma and CYP450 enzymes

ETHNOPHARMACOLOGICAL RELEVANCE

Changan Granule (CAG) is a Chinese patent drug developed based on an empirical prescription in accordance with the formulation theory of Traditional Chinese Medicine. The prescription is composed of eight herbal drugs which have been traditionally used by Chinese people for a long history. It has effects of invigorating spleen and supplementing qi, as well as regulating liver and ceasing diarrhea, and is indicated for the treatment of irritable bowel syndrome (IBS).

AIM OF THE STUDY

This study was aimed to investigate the interaction between CAG and its main components and cytochrome P450 (CYP450) enzymes so as to characterize the major metabolites and metabolic enzymes and evaluate the safety concerns to its clinical use.

MATERIALS AND METHODS

Both in vivo and in vitro experiments using such as diarrhea-predominant IBS (IBS-D) rat model, HepG2 cells, and human liver microsomes (HLM) were carried out to investigate the interaction between CAG and its main components and CYP450 enzymes. Real-time quantitative PCR (qPCR), ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), and cocktail probes were employed to qualitatively or quantitatively measure the metabolites and metabolic enzymes.

RESULTS

CAG inhibited the enzyme activities of CYP1A2, CYP2E1, CYP2D6, CYP2C9, and CYP3A4 and the mRNA expressions of CYP2E1, CYP2C9, CYP3A4, and CYP2D6 in vitro. CAG down-regulated the increased expression of CYP1A2 and up-regulated the decreased expression of CYP3A1 in vivo. Twenty-two metabolites were characterized from the main components of CAG after incubation with HLM in vitro. CYP2D6, CYP2E1, CYP3A4 and CYP2C9 were identified as the characteristic metabolic enzymes.

CONCLUSIONS

This study provides a reference for clinical application of CAG in safety. CAG and CYP450 enzymes are interacted. CAG is mainly metabolized by CYP2E1 and CYP2D6. The expression of CYP2E1 and CYP2D6 are more susceptible to be influenced by CAG in comparison with that of CYP3A4, CYP2C9 and CYP1A2. It implies the potential risk of interaction when CAG is taken together with the drugs metabolized by CYP2E1 and CYP2D6.

Substrate binding and lipid-mediated allostery in the human organic anion transporter 1 at the atomic-scale

The Organic Anion Transporter 1 is a membrane transporter known for its central role in drug elimination by the kidney. hOAT1 is an antiporter translocating substrate in exchange for a-ketoglutarate. The understanding of hOAT1 structure and function remains limited due to the absence of resolved structure of hOAT1. Benefiting from conserved structural and functional patterns shared with other Major Facilitator Superfamily transporters, the present study intended to investigate fragments of hOAT1 transport function and modulation of its activity in order to make a step forward the understanding of its transport cycle. μs-long molecular dynamics simulation of hOAT1 were carried out suggesting two plausible binding sites for a typical substrate, adefovir, in line with experimental observations. The well-known B-like motif binding site was observed in line with previous studies. However, we here propose a new inner binding cavity which is expected to be involved in substrate translocation event. Binding modes of hOAT1 co-substrate α-ketoglutarate were also investigated suggesting that it may bind to highly conserved intracellular motifs. We here hypothesise that α-ketoglutarate may disrupt the pseudo-symmetrical intracellular charge-relay system which in turn may participate to the destabilisation of OF conformation. Investigations regarding allosteric communications along hOAT1 also suggest that substrate binding event might modulate the dynamics of intracellular charge relay system, assisted by surrounding lipids as active partners. We here proposed a structural rationalisation of transport impairments observed for two single nucleotide polymorphisms, p.Arg50His and p.Arg454Gln suggesting that the present model may be used to transport dysfunctions arising from hOAT1 mutations.

Positron Emission Tomography-Based Pharmacokinetic Analysis To Assess Renal Transporter-Mediated Drug-Drug Interactions of Antimicrobial Drugs

Transporter-mediated drug-drug interactions (DDIs) are of concern in antimicrobial drug development, as they can have serious safety consequences. We used positron emission tomography (PET) imaging-based pharmacokinetic (PK) analysis to assess the effect of different drugs, which may cause transporter-mediated DDIs, on the tissue distribution and excretion of [18F]ciprofloxacin as a radiolabeled model antimicrobial drug. Mice underwent PET scans after intravenous injection of [18F]ciprofloxacin, without and with pretreatment with either probenecid (150 mg/kg), cimetidine (50 mg/kg), or pyrimethamine (5 mg/kg). A 3-compartment kidney PK model was used to assess the involvement of renal transporters in the examined DDIs. Pretreatment with probenecid and cimetidine significantly decreased the renal clearance (CLrenal) of [18F]ciprofloxacin. The effect of cimetidine (-86%) was greater than that of probenecid (-63%), which contrasted with previously published clinical data. The kidney PK model revealed that the decrease in CLrenal was caused by inhibition of basal uptake transporters and apical efflux transporters in kidney proximal tubule cells. Changes in the urinary excretion of [18F]ciprofloxacin after pretreatment with probenecid and cimetidine resulted in increased blood and organ exposure to [18F]ciprofloxacin. Our results suggest that multiple membrane transporters mediate the tubular secretion of ciprofloxacin, with possible species differences between mice and humans. Concomitant medication inhibiting renal transporters may precipitate DDIs, leading to decreased urinary excretion and increased blood and organ exposure to ciprofloxacin, potentially exacerbating adverse effects. Our study highlights the strength of PET imaging-based PK analysis to assess transporter-mediated DDIs at a whole-body level.

The Use of Antibiotics and Antimicrobial Resistance in Veterinary Medicine, a Complex Phenomenon: A Narrative Review

As warned by Sir Alexander Fleming in his Nobel Prize address: “the use of antimicrobials can, and will, lead to resistance”. Antimicrobial resistance (AMR) has recently increased due to the overuse and misuse of antibiotics, and their use in animals (food-producing and companion) has also resulted in the selection and transmission of resistant bacteria. The epidemiology of resistance is complex, and factors other than the overall quantity of antibiotics consumed may influence it. Nowadays, AMR has a serious impact on society, both economically and in terms of healthcare. This narrative review aimed to provide a scenario of the state of the AMR phenomenon in veterinary medicine related to the use of antibiotics in different animal species; the impact that it can have on animals, as well as humans and the environment, was considered. Providing some particular instances, the authors tried to explain the vastness of the phenomenon of AMR in veterinary medicine due to many and diverse aspects that cannot always be controlled. The veterinarian is the main reference point here and has a high responsibility towards the human–animal–environment triad. Sharing such a burden with human medicine and cooperating together for the same purpose (fighting and containing AMR) represents an effective example of the application of the One Health approach.

Glycochenodeoxycholate and glycodeoxycholate 3-O-glucuronides, but not hexadecanedioate and tetradecanedioate, detected weak inhibition of OATP1B caused by GDC-0810 in humans

Endogenous biomarkers of drug transporters are promising tools to evaluate in vivo transporter function and potential alterations in the pharmacokinetics of their substrates. We have previously reported that coproporphyrin I/III captured the weak inhibition of OATP1B transporters by GDC-0810. In this study, we measured plasma concentrations of additional biomarkers, namely fatty acids, bile acids and their sulphate or glucuronide conjugates in the presence and absence of GDC-0810. Concentrations of hexadecanedioate and tetradecanedioate did not increase in the presence of GDC-0810. Among bile acids and their conjugates, glycochenodeoxycholate and glycodeoxycholate 3-O-glucuronides (GCDCA-3G and GDCA-3G) showed C_max increases with geometric mean ratio (95% confidence interval) of 1.58 (1.13-2.22) and 1.49 (1.21-1.83), consistent with previous reports from low-dose rifampin co-administration and pharmacogenetic studies. These results suggest that GCDCA-3G and GDCA-3G are two more promising biomarkers that may capture weak OATP1B inhibition in addition to coproporphyrin I/III.

Novel inhibitors of breast cancer resistance protein (BCRP, ABCG2) among marketed drugs

Drug-drug interactions (DDIs) are a major concern for the safe use of medications. Breast cancer resistance protein (BCRP) is a clinically relevant ATP-binding cassette (ABC) transporter for drug disposition. Inhibition of BCRP increases the plasma concentrations of BCRP substrate drugs, which potentially could lead to adverse drug reactions. The aim of the present study was to identify BCRP inhibitors amongst a library of 232 commonly used drugs and anticancer drugs approved by the United States Food and Drug Administration (FDA). BCRP inhibition studies were carried out using the vesicular transport assay. We found 75 drugs that reduced the relative transport activity of BCRP to less than 25% of the vehicle control and were categorized as strong inhibitors. The concentration required for 50% inhibition (IC₅₀) was determined for 13 strong inhibitors that were previously poorly characterized for BCRP inhibition. The IC₅₀ ranged from 1.1 to 11 µM, with vemurafenib, dabigatran etexilate and everolimus being the strongest inhibitors. According to the drug interaction guidance documents from the FDA and the European Medicines Agency (EMA), in vivo DDI studies are warranted if the theoretical intestinal luminal concentration of a drug exceeds its IC₅₀ by tenfold. Here, the IC₅₀ values for eight of the drugs were 100-fold lower than their theoretical intestinal luminal concentration. Moreover, a mechanistic static model suggested that vemurafenib, bexarotene, dabigatran etexilate, rifapentine, aprepitant, and ivacaftor could almost fully inhibit intestinal BCRP, increasing the exposure of concomitantly administered rosuvastatin over 90%. Therefore, clinical studies are warranted to investigate whether these drugs cause BCRP-mediated DDIs in humans.

Polypharmazie – Interaktionen bei älteren Menschen

Thrombozytenaggregationshemmer und Antikoagulanzien sind wichtige Standardmedikationen in der Prophylaxe und Therapie kardiovaskulärer Erkrankungen. Die oft multiple Medikation und durch zusätzliche Begleiterkrankungen notwendige weitere Medikation birgt besonders bei älteren Patienten ein hohes Risiko von Arzneimittelwechselwirkungen. Diese können das Blutungsrisiko oder im Fall des Wirkungsverlusts das Risiko thromboembolischer Ereignisse erhöhen. In diesem Artikel werden klinisch relevante Interaktionen von COX-Hemmern (COX: Cyclooxygenase) und Adenosinrezeptorantagonisten sowie von Vitamin-K-Antagonisten und direkten oralen Antikoagulanzien (DOAK) wie auch Strategien zur Vermeidung unerwünschter Wirkungen diskutiert.

ABCG2 and SLCO1B1 gene polymorphisms in the Croatian population

BACKGROUND

Organic anion-transporting polypeptide 1B1 (OATP1B1) and the ATP-binding cassette subfamily G member 2, ABCG2, are important transporters involved in the transport of endogenous substrates and xenobiotics, including drugs. Genetic polymorphisms of these transporters have effect on transporter activity. There is significant interethnic variability in the frequency of allele variants.

AIM

To determined allele and genotype frequencies of ABCG2 and SLCO1B1 genes in Croatian populations of European descent.

SUBJECTS AND METHODS

A total of 905 subjects (482 women) were included. Genotyping for ABCG2 c.421C > A (rs2231142) and for SLCO1B1 c.521T > C (rs4149056), was performed by real-time polymerase chain reaction (PCR) using TaqMan^® DME Genotyping Assays.

RESULTS

For ABCG2 c.421C > A, the frequency of CC, CA and AA genotypes was 81.4%, 17.8% and 0.8% respectively. The frequency of variant ABCG2 421 A allele was 9.7%. For SLCO1B1 c.521T > C, the frequency of TT, TC and CC genotypes was 61.7%, 34.8% and 3.5% respectively. The frequency of variant SLCO1B1 521 C allele was 20.9%.

CONCLUSION

The frequency of the ABCG2 and SLCO1B1 allelic variants and genotypes in the Croatian population is in accordance with other European populations. Pharmacogenetic analysis can serve to individualise drug therapy and minimise the risk of developing adverse drug reactions.

A Metabolomics Approach for Predicting OATP1B-Type Transporter-Mediated Drug–Drug Interaction Liabilities

In recent years, various endogenous compounds have been proposed as putative biomarkers for the hepatic uptake transporters OATP1B1 and OATP1B3 that have the potential to predict transporter-mediated drug–drug interactions (DDIs). However, these compounds have often been identified from top–down strategies and have not been fully utilized as a substitute for traditional DDI studies. In an attempt to eliminate observer bias in biomarker selection, we applied a bottom–up, untargeted metabolomics screening approach in mice and found that plasma levels of the conjugated bile acid chenodeoxycholate-24-glucuronide (CDCA-24G) are particularly sensitive to deletion of the orthologous murine transporter Oatp1b2 (31-fold increase vs. wild type) or the entire Oatp1a/1b(−/−)cluster (83-fold increased), whereas the humanized transgenic overexpression of hepatic OATP1B1 or OATP1B3 resulted in the partial restoration of transport function. Validation studies with the OATP1B1/OATP1B3 inhibitors rifampin and paclitaxel in vitro as well as in mice and human subjects confirmed that CDCA-24G is a sensitive and rapid response biomarker to dose-dependent transporter inhibition. Collectively, our study confirmed the ability of CDCA-24G to serve as a sensitive and selective endogenous biomarker of OATP1B-type transport function and suggests a template for the future development of biomarkers for other clinically important xenobiotic transporters.

Reimagining the Framework Supporting the Static Analysis of Transporter Drug Interaction Risk; Integrated Use of Biomarkers to Generate Pan‐Transporter Inhibition Signatures

Solute carrier (SLC) transporters present as the loci of important drug-drug interactions (DDIs). Therefore, sponsors generate in vitro half-maximal inhibitory concentration (IC₅₀ ) data and apply regulatory agency-guided "static" methods to assess DDI risk and the need for a formal clinical DDI study. Because such methods are conservative and high false-positive rates are likely (e.g., DDI study triggered when liver SLC R value ≥ 1.04 and renal SLC maximal unbound plasma (C_max,u )/IC₅₀ ratio ≥ 0.02), investigators have attempted to deploy plasma- and urine-based SLC biomarkers in phase I studies to de-risk DDI and obviate the need for drug probe-based studies. In this regard, it was possible to generate in-house in vitro SLC IC₅₀ data for various clinically (biomarker)-qualified perpetrator drugs, under standard assay conditions, and then estimate "% inhibition" for each SLC and relate it empirically to published clinical biomarker data (area under the plasma concentration vs. time curve (AUC) ratio (AUCR, AUC_inhibitor /AUC_reference ) and % decrease in renal clearance (ΔCL_renal )). After such a "calibration" exercise, it was determined that only compounds with high R values (> 1.5) and C_max,u /IC₅₀ ratios (> 0.5) are likely to significantly modulate liver (AUCR > 1.25) and renal (ΔCL_renal  > 25%) biomarkers and evoke DDI risk. The % inhibition approach supports integration of liver and renal SLC data and allows one to generate pan-SLC inhibition signatures for different test perpetrators (e.g., SLC % inhibition ranking). In turn, such signatures can guide the selection of the most appropriate individual (or combinations of) biomarkers for testing in phase I studies.

Gene Expression and Protein Abundance of Nuclear Receptors in Human Intestine and Liver: A New Application for Mass Spectrometry-Based Targeted Proteomics

Background: Unwanted drug-drug interactions (DDIs), as caused by the upregulation of clinically relevant drug metabolizing enzymes and transporter proteins in intestine and liver, have the potential to threaten the therapeutic efficacy and safety of drugs. The molecular mechanism of this undesired but frequently occurring scenario of polypharmacy is based on the activation of nuclear receptors such as the pregnane X receptor (PXR) or the constitutive androstane receptor (CAR) by perpetrator agents such as rifampin, phenytoin or St. John’s wort. However, the expression pattern of nuclear receptors in human intestine and liver remains uncertain, which makes it difficult to predict the extent of potential DDIs. Thus, it was the aim of this study to characterize the gene expression and protein abundance of clinically relevant nuclear receptors, i.e., the aryl hydrocarbon receptor (AhR), CAR, farnesoid X receptor (FXR), glucocorticoid receptor (GR), hepatocyte nuclear factor 4 alpha (HNF4α), PXR and small heterodimer partner (SHP), in the aforementioned organs. Methods: Gene expression analysis was performed by quantitative real-time PCR of jejunal, ileal, colonic and liver samples from eight human subjects. In parallel, a targeted proteomic method was developed and validated in order to determine the respective protein amounts of nuclear receptors in human intestinal and liver samples. The LC-MS/MS method was validated according to the current bioanalytical guidelines and met the criteria regarding linearity (0.1–50 nmol/L), within-day and between-day accuracy and precision, as well as the stability criteria. Results: The developed method was successfully validated and applied to determine the abundance of nuclear receptors in human intestinal and liver samples. Gene expression and protein abundance data demonstrated marked differences in human intestine and liver. On the protein level, only AhR and HNF4α could be detected in gut and liver, which corresponds to their highest gene expression. In transfected cell lines, PXR and CAR could be quantified. Conclusions: The substantially different expression pattern of nuclear receptors in human intestinal and liver tissue may explain the different extent of unwanted DDIs in the dependence on the administration route of drugs.

Repositioning of Lansoprazole as a Protective Agent Against Cisplatin-Induced Ototoxicity

Cisplatin (CDDP) is a well-known chemotherapeutic drug approved for various cancers. However, CDDP accumulates in the inner ear cochlea via organic cation transporter 2 (OCT2) and causes ototoxicity, which is a major clinical limitation. Since lansoprazole (LPZ), a proton pump inhibitor, is known to inhibit OCT2-mediated transport of CDDP, we hypothesized that LPZ might ameliorate CDDP-induced ototoxicity (CIO). To test this hypothesis, we utilized in vivo fluorescence imaging of zebrafish sensory hair cells. The fluorescence signals in hair cells in zebrafish treated with CDDP dose-dependently decreased. Co-treatment with LPZ significantly suppressed the decrease of fluorescence signals in zebrafish treated with CDDP. Knockout of a zebrafish homolog of OCT2 also ameliorated the reduction of fluorescence signals in hair cells in zebrafish treated with CDDP. These in vivo studies suggest that CDDP damages the hair cells of zebrafish through oct2-mediated accumulation and that LPZ protects against CIO, possibly inhibiting the entry of CDDP into the hair cells via oct2. We also evaluated the otoprotective effect of LPZ using a public database containing adverse event reports. The analysis revealed that the incidence rate of CIO was significantly decreased in patients treated with LPZ. We then retrospectively analyzed the medical records of Mie University Hospital to examine the otoprotective effect of LPZ. The incidence rate of ototoxicity was significantly lower in patients co-treated with LPZ compared to those without LPZ. These retrospective findings suggest that LPZ is also protective against CIO in humans. Taken together, co-treatment with LPZ may reduce the risk of CIO.

Inflammatory-Dependent Bidirectional Effect of Bile Acids on NLRP3 Inflammasome and Its Role in Ameliorating CPT-11-Induced Colitis

Irinotecan (CPT-11) in combination with 5-fluorouracil and leucovorin is a first-line chemotherapy regimen for the treatment of colorectal cancer; however, its clinical application is limited by the dose-limiting gastrointestinal toxicity of colitis. In our previous studies, several bile acids (BAs) were found significantly elevated in the colon of the CPT-11-induced rat colitis model. On the other hand, NLRP3 inflammasome has been reported to play important roles in mediating colitis. Interestingly, BA was stated to activate the NLRP3 inflammasome in some studies, while in some other reports, it showed an inhibitory effect. We assumed that the inflammatory status in different circumstances might have contributed to the controversial findings. In this study, we first discovered, under non-inflammatory conditions, that supplementing BA could activate the NLRP3 inflammasome in THP-1-differentiated macrophages and promote inflammation. In lipopolysaccharide (LPS)-induced inflammatory macrophages, however, BA inhibited the NLRP3 inflammasome and reduced inflammation. Further experiments demonstrated that Takeda G protein-coupled receptor 5 (TGR5) is essential in mediating the inhibitory effect of BA, while phospho-SP1 (p-SP1) is key to the activation. Furthermore, we applied the above findings to ameliorate CPT-11-caused colitis in rats by inhibiting SP1 with mithramycin A (MitA) or activating TGR5 using oleanolic acid (OA). Our findings may shed light on the discovery of effective interventions for reducing dose-limiting chemotherapy-induced colitis.

Physiologically based pharmacokinetic combined JAK2 occupancy modelling to simulate PK and PD of baricitinib with kidney transporter inhibitors and in patients with hepatic/renal impairment

PURPOSE

Our aim is to build a physiologically based pharmacokinetic and JAK2 occupancy model (PBPK-JO) to simultaneously predict pharmacokinetic (PK) and pharmacodynamic (PD) changes of baricitinib (BAR) in healthy humans when co-administrated with kidney transporters OAT3 and MATE2-K inhibitors, and in patients with hepatic and renal impairment.

METHODS

Probenecid and vandetanib were selected as OAT3 and MATE2-K competitive inhibitors, respectively. The PBPK-JO model was built using physicochemical and biochemical properties of BAR, and then verified by observed clinical PK. Finally, the model was applied to determine optimal dosing regimens in various clinical situations.

RESULTS

Here, we have successfully simulated PK and JAK2 occupancy profiles in humans by PBPK-JO model. Moreover, this modelling reproduced every observed PK data, and every mean relative deviation (MRD) was below 2. The simulation suggested that PK of BAR had a significant change (2.22-fold increase), however PD only had a slight increase of 1.14-fold. Additionally, the simulation also suggested that vandetanib was almost unlikely to affect the PK and PD of BAR. In simulations of hepatic and renal impairment patients, the predictions suggested that significant changes in the PK and PD of BAR occurred. However, there was a lower fold increase in JAK2 occupancy than in PK in patients relative to healthy individuals.

CONCLUSION

Administration dose adjustment of BAR when co-administrated with OAT3 inhibitors or in patients with hepatic or renal impairment should combine PK and PD changes of BAR, instead of only considering PK alteration.

Interactions between meropenem and renal drug transporters

BACKGROUND

Meropenem is a carbapenem antibiotic and commonly used with other antibiotics for the treatment of bacterial infections. It is primarily eliminated renally by glomerular filtration and renal tubular secretion.

OBJECTIVE

To evaluate the roles of renal uptake and efflux transporters in the excretion of meropenem and potential drug interactions mediated by renal drug transporters.

METHOD

Uptake and inhibition studies were conducted in human embryonic kidney 293 cells stably transfected with organic anion transporter (OAT) 1, OAT3, multidrug and toxin extrusion protein (MATE) 1 and MATE2K, as well as membrane vesicles containing breast cancer resistance-related protein (BCRP), multidrug resistance protein 1 (MDR1) and multidrug resistance-associated protein 2 (MRP2). Probenecid and piperacillin were used to assess potential drug interactions with meropenem in rats.

RESULTS

We observed that meropenem was a low-affinity substrate of OAT1/3 and had a weak inhibitory effect on OAT1/3 and MATE2K. BCRP, MDR1, MRP2, MATE1 and MATE2K could not mediate renal excretion of meropenem. Moreover, meropenem was not an inhibitor of BCRP, MDR1, MRP2 or MATE1. Among five tested antibiotics, moderate inhibition on OAT3-mediated meropenem uptake was observed for linezolid (IC50 value was 69.2 μM), weak inhibition was observed for piperacillin, benzylpenicillin and tazobactam (IC50 values were 282.2, 308.0 and 668.1 μM, respectively), and no inhibition was observed for sulbactam. Although piperacillin had a relatively high drug-drug interaction index (ratio of maximal unbound plasma concentration to IC50 was 1.42) in vitro, it had no meaningful impact on the pharmacokinetics of meropenem in rats.

CONCLUSION

Our results indicate that clinically significant interactions between meropenem and these five antibiotics are low.

Regulation of Drug Transport Proteins-From Mechanisms to Clinical Impact: A White Paper on Behalf of the International Transporter Consortium

Membrane transport proteins are involved in the absorption, disposition, efficacy, and/or toxicity of many drugs. Numerous mechanisms (e.g., nuclear receptors, epigenetic gene regulation, microRNAs, alternative splicing, post‐translational modifications, and trafficking) regulate transport protein levels, localization, and function. Various factors associated with disease, medications, and dietary constituents, for example, may alter the regulation and activity of transport proteins in the intestine, liver, kidneys, brain, lungs, placenta, and other important sites, such as tumor tissue. This white paper reviews key mechanisms and regulatory factors that alter the function of clinically relevant transport proteins involved in drug disposition. Current considerations with in vitro and in vivo models that are used to investigate transporter regulation are discussed, including strengths, limitations, and the inherent challenges in predicting the impact of changes due to regulation of one transporter on compensatory pathways and overall drug disposition. In addition, translation and scaling of in vitro observations to in vivo outcomes are considered. The importance of incorporating altered transporter regulation in modeling and simulation approaches to predict the clinical impact on drug disposition is also discussed. Regulation of transporters is highly complex and, therefore, identification of knowledge gaps will aid in directing future research to expand our understanding of clinically relevant molecular mechanisms of transporter regulation. This information is critical to the development of tools and approaches to improve therapeutic outcomes by predicting more accurately the impact of regulation‐mediated changes in transporter function on drug disposition and response.

Potential Role of Ginger (Zingiber officinale Roscoe) in the Prevention of Neurodegenerative Diseases

Ginger is composed of multiple bioactive compounds, including 6-gingerol, 6-shogaol, 10-gingerol, gingerdiones, gingerdiols, paradols, 6-dehydrogingerols, 5-acetoxy-6-gingerol, 3,5-diacetoxy-6-gingerdiol, and 12-gingerol, that contribute to its recognized biological activities. Among them, the major active compounds are 6-shogaol and 6-gingerol. Scientific evidence supports the beneficial properties of ginger, including antioxidant and anti-inflammatory capacities and in contrast, a specific and less studied bioactivity is the possible neuroprotective effect. The increase in life expectancy has raised the incidence of neurodegenerative diseases (NDs), which present common neuropathological features as increased oxidative stress, neuroinflammation and protein misfolding. The structure-activity relationships of ginger phytochemicals show that ginger can be a candidate to treat NDs by targeting different ligand sites. Its bioactive compounds may improve neurological symptoms and pathological conditions by modulating cell death or cell survival signaling molecules. The cognitive enhancing effects of ginger might be partly explained via alteration of both the monoamine and the cholinergic systems in various brain areas. Moreover, ginger decreases the production of inflammatory related factors. The aim of the present review is to summarize the effects of ginger in the prevention of major neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease and multiple sclerosis.

Toxicity induced by ciprofloxacin and enrofloxacin: oxidative stress and metabolism

Ciprofloxacin (CIP) (human use) and enrofloxacin (ENR) (veterinary use) are synthetic anti-infectious medications that belong to the second generation of fluoroquinolones. They have a wide antimicrobial spectrum and strong bactericidal effects at very low concentrations via enzymatic inhibition of DNA gyrase and topoisomerase IV, which are required for DNA replication. They also have high bioavailability, rapid absorption with favorable pharmacokinetics and excellent tissue penetration, including cerebral spinal fluid. These features have made them the most applied antibiotics in both human and veterinary medicine. ENR is marketed exclusively for animal medicine and has been widely used as a therapeutic veterinary antibiotic, resulting in its residue in edible tissues and aquatic environments, as well as the development of resistance and toxicity. Estimation of the risks to humans due to antimicrobial resistance produced by CIP and ENR is important and of great interest. Moreover, in rare cases due to their overdose and/or prolonged administration, the development of CIP and ENR toxicity may occur. The toxicity of these fluoroquinolones antimicrobials is mainly related to reactive oxygen species (ROS) and oxidative stress (OS) generation, besides metabolism-related toxicity. Therefore, CIP is restricted in pregnant and lactating women, pediatrics and elderly similarly ENR do in the veterinary field. This review manuscript aims to identify the toxicity induced by ROS and OS as a common sequel of CIP and ENR. Furthermore, their metabolism and the role of metabolizing enzymes were reported.

The Role of Uptake and Efflux Transporters in the Disposition of Glucuronide and Sulfate Conjugates

Glucuronidation and sulfation are the most typical phase II metabolic reactions of drugs. The resulting glucuronide and sulfate conjugates are generally considered inactive and safe. They may, however, be the most prominent drug-related material in the circulation and excreta of humans. The glucuronide and sulfate metabolites of drugs typically have limited cell membrane permeability and subsequently, their distribution and excretion from the human body requires transport proteins. Uptake transporters, such as organic anion transporters (OATs and OATPs), mediate the uptake of conjugates into the liver and kidney, while efflux transporters, such as multidrug resistance proteins (MRPs) and breast cancer resistance protein (BCRP), mediate expulsion of conjugates into bile, urine and the intestinal lumen. Understanding the active transport of conjugated drug metabolites is important for predicting the fate of a drug in the body and its safety and efficacy. The aim of this review is to compile the understanding of transporter-mediated disposition of phase II conjugates. We review the literature on hepatic, intestinal and renal uptake transporters participating in the transport of glucuronide and sulfate metabolites of drugs, other xenobiotics and endobiotics. In addition, we provide an update on the involvement of efflux transporters in the disposition of glucuronide and sulfate metabolites. Finally, we discuss the interplay between uptake and efflux transport in the intestine, liver and kidneys as well as the role of transporters in glucuronide and sulfate conjugate toxicity, drug interactions, pharmacogenetics and species differences.

Pharmacokinetic drug interactions of integrase strand transfer inhibitors

The integrase strand transfer inhibitor (INSTI)-containing regimens are currently considered as the first-line treatment of human immunodeficiency virus (HIV) infection. Although possessing a common mechanism of action to inhibit HIV integrase irreversibly to stop HIV replication cycle, the INSTIs, including raltegravir, elvitegravir, dolutegravir, and bictegravir, differ in pharmacokinetic characteristics. While raltegravir undergoes biotransformation by the UDP-glucuronosyltransferases (UGTs), elvitegravir is primarily metabolized by cytochrome P450 (CYP) 3A4 and co-formulated with cobicistat to increase its plasma exposure. The metabolism pathways of dolutegravir and bictegravir are similar, both including CYP3A and UGT1A1, and both agents are substrates to different drug transporters. Because of their differences in metabolism, INSTIs interact with other medications differently through CYP enzymes and transporters as inducers or inhibitors. These drug interactions may become an important consideration in the long-term clinical use because the life expectancy of people with HIV (PWH) approaches to that of the general population. Also, common geriatric challenges such as multimorbidity and polypharmacy have been increasingly recognized in PWH. This review provides a summary of pharmacokinetic interactions with INSTIs and future perspectives in implications of INSTI drug interactions.

Plumbagin and Plumbago indica Differentially Modulated Cytochrome P450 and Transporter Profiles in BeWo and HepG2 Cells

<b>Background and Objective:</b> The medicinal herb <i>Plumbago indica</i> (PI) and its major constituent plumbagin have reported pharmacological properties but there is a lack of information about their herb-drug interactions. The effects of methanolic (PI-MeOH) and ethanolic (PI-EtOH) crude extracts of PI and plumbagin on the expression of cytochrome P450s (<i>CYP1A2</i>, <i>CYP2E1</i> and <i>CYP3A4</i>) and transporters (<i>ABCC1</i>, <i>ABCG2</i> and <i>SLC22A11</i>) were investigated in BeWo and HepG2 cells. <b>Materials and Methods:</b> BeWo or HepG2 cells were treated with 0.5-5 μM plumbagin or 25-500 μg mL<sup>1</sup> of PI-MeOH or PI-EtOH for 24 hrs. Total RNA was extracted and mRNA expression of CYPs and transporters were determined using RT-qPCR. <b>Results:</b> PI and plumbagin affected mRNA expression differently in the two tested cell types. In BeWo cells, all concentrations of PI-MeOH induced <i>CYP2E1</i>, 100 and 500 μg Ml<sup>1</sup> PI-MeOH and PI-EtOH up-regulated <i>CYP1A2</i>, <i>CYP3A4 </i>and <i>ABCG2 </i>and 500 μg mL<sup>1</sup> PI-EtOH induced <i>ABCG2</i> expression. Plumbagin suppressed <i>CYP1A2</i> and induced <i>SLC22A11 </i>expression at the highest concentration, 5 μM. In HepG2 cells, 5 μM plumbagin and 500 μg Ml<sup>1</sup> PI-EtOH suppressed <i>CYP3A4 </i>expression and 500 μg mL<sup>1</sup> PI-MeOH and PI-EtOH up-regulated <i>CYP1A2</i> and <i>CYP2E1 </i>expression. <i>ABCC1</i> expression was induced by all treatments while <i>ABCG2</i> and <i>SLC22A11 </i>were induced only by 500 μg mL<sup>1</sup> PI-MeOH and PI-EtOH. <b>Conclusion:</b> The use of PI or plumbagin supplements in large quantities or for long periods should be carefully considered due to the risk of herbal drug interactions via modulated expression of CYPs and transporters.

Evaluation of potential herb-drug interactions based on the effect of Suxiao Jiuxin Pill on CYP450 enzymes and transporters

ETHNOPHARMACOLOGY RELEVANCE

Suxiao jiuxin pill (SJP) is a Chinese medical drug with anti-inflammatory, anti-apoptotic, and vasodilatory function. It is widely used in combination with other drugs for the treatment of coronary heart disease (CHD) and angina. Nevertheless, the effect of SJP on Cytochrome P450 (CYP450) enzymes and transporters' activity related to drug metabolism is rarely studied.

OBJECTIVE

The aim of this study was to investigate the effect of SJP on the activity of drug-metabolizing enzyme CYP450 and transporters.

MATERIALS AND METHODS

Human primary hepatocytes were used in present study. Probe substrates of CYP450 enzymes were incubated in human liver microsomes (HLMs) with and without SJP while IC₅₀ values were calculated. The inhibitory effect of SJP on the activity of CYP1A2, 2B6, 2C8, 2C9, 2C19, 2D6 and 3A4 was evaluated. The inducing effect of SJP on the activity of CYP1A2, 2B6 and 3A4 was accessed. The inhibition of SJP on human OATP1B1 was investigated through cell-based assay. The inhibition of SJP on human MDR1 and BCRP was also estimated by means of the vesicles assay.

RESULTS

The results showed that the SJP under the concentration of 1000 μg/mL could inhibit the activity of CYP1A2, 2B6, 2C19, and 3A4, with IC₅₀ values of 189.7, 308.2, 331.2 and 805.7 μg/mL, respectively. There was no inhibitory effect found in the other 3 liver drug enzyme subtypes. In addition, SJP showed no induction effect on CYP1A2, 2B6 and 3A4, however it had a significant inhibitory effect on human-derived OATP1B1 at the concentration of 100 and 1000 μg/mL, with the IC₅₀ value of 21.9 μg/mL. Simultaneously, the SJP inhibited BCRP at high concentration of 1000 μg/mL but did not affect human MDR1.

CONCLUSIONS

Based on these research results above, it is suggested that the SJP can affect some of the CYP450 enzymes and transporters' activity. When used in combination with related conventional drugs, potential herb-drug interactions should be considered.

Folium Sennae Increased the Bioavailability of Methotrexate through Modulation on MRP 2 and BCRP

Folium Sennae (FS), a popular laxative (Senna), contains polyphenolic anthranoids, whose conjugation metabolites are probable modulators of multidrug resistance-associated proteins (MRPs) and breast cancer resistance protein (BCRP). We suspected that the combined use of FS might alter the pharmacokinetics of various medicines transported by MRPs or BCRP. This study investigated the effect of FS on the pharmacokinetics of methotrexate (MTX), an anticancer drug and a probe substrate of MRPs/BCRP. Rats were orally administered MTX alone and with two dosage regimens of FS in a parallel design. The results show that 5.0 g/kg of FS significantly increased the AUC_0–2880, AUC_720–2880 and MRT of MTX by 45%, 102% and 42%, and the seventh dose of 2.5 g/kg of FS significantly enhanced the AUC_720–2880 and MRT by 78% and 42%, respectively. Mechanism studies indicated that the metabolites of FS (FSM) inhibited MRP 2 and BCRP. In conclusion, the combined use of FS increased the systemic exposure and MRT of MTX through inhibition on MRP 2 and BCRP.

Bis-thiobarbiturates as Promising Xanthine Oxidase Inhibitors: Synthesis and Biological Evaluation

Xanthine oxidase (XO) is the enzyme responsible for the conversion of endogenous purines into uric acid. Therefore, this enzyme has been associated with pathological conditions caused by hyperuricemia, such as the disease commonly known as gout. Barbiturates and their congeners thiobarbiturates represent a class of heterocyclic drugs capable of influencing neurotransmission. However, in recent years a very large group of potential pharmaceutical and medicinal applications have been related to their structure. This great diversity of biological activities is directly linked to the enormous opportunities found for chemical change off the back of these findings. With this in mind, sixteen bis-thiobarbiturates were synthesized in moderate to excellent reactional yields, and their antioxidant, anti-proliferative, and XO inhibitory activity were evaluated. In general, all bis-thiobarbiturates present a good antioxidant performance and an excellent ability to inhibit XO at a concentration of 30 µM, eight of them are superior to those observed with the reference drug allopurinol (Allo), nevertheless they were not as effective as febuxostat. The most powerful bis-thiobarbiturate within this set showed in vitro IC₅₀ of 1.79 μM, which was about ten-fold better than Allo inhibition, together with suitable low cytotoxicity. In silico molecular properties such as drug-likeness, pharmacokinetics, and toxicity of this promising barbiturate were also analyzed and herein discussed.

Validation of a Drug Transporter Probe Cocktail Using the Prototypical Inhibitors Rifampin, Probenecid, Verapamil, and Cimetidine

Background and Objective

A novel cocktail containing four substrates of key drug transporters was previously optimized to eliminate mutual drug–drug interactions between the probes digoxin (P-glycoprotein substrate), furosemide (organic anion transporter 1/3), metformin (organic cation transporter 2, multidrug and toxin extrusion protein 1/2-K), and rosuvastatin (organic anion transporting polypeptide 1B1/3, breast cancer resistance protein). This clinical trial investigated the effects of four commonly employed drug transporter inhibitors on cocktail drug pharmacokinetics.

Methods

In a randomized open-label crossover trial in 45 healthy male subjects, treatment groups received the cocktail with or without single oral doses of rifampin, verapamil, cimetidine or probenecid. Concentrations of the probe drugs in serial plasma samples and urine fractions were measured by validated liquid chromatography-tandem mass spectrometry assays to assess systemic exposure.

Results

The results were generally in accordance with known in vitro and/or clinical drug–drug interaction data. Single-dose rifampin increased rosuvastatin area under the plasma concentration–time curve up to the last quantifiable concentration (AUC_0–tz) by 248% and maximum plasma concentration (C_max) by 1025%. Probenecid increased furosemide AUC_0–tz by 172% and C_max by 23%. Cimetidine reduced metformin renal clearance by 26%. The effect of single-dose verapamil on digoxin systemic exposure was less than expected from multiple-dose studies (AUC_0–tz unaltered, C_max + 22%).

Conclusions

Taking all the interaction results together, the transporter cocktail is considered to be validated as a sensitive and specific tool for evaluating transporter-mediated drug–drug interactions in drug development.

Clinical Trial Registration

EudraCT number 2017-001549-29.

Electronic supplementary material

The online version of this article (10.1007/s40262-020-00907-w) contains supplementary material, which is available to authorized users.

Endogenous Biomarkers for SLC Transporter-Mediated Drug-Drug Interaction Evaluation

Membrane transporters play an important role in the absorption, distribution, metabolism, and excretion of xenobiotic substrates, as well as endogenous compounds. The evaluation of transporter-mediated drug-drug interactions (DDIs) is an important consideration during the drug development process and can guide the safe use of polypharmacy regimens in clinical practice. In recent years, several endogenous substrates of drug transporters have been identified as potential biomarkers for predicting changes in drug transport function and the potential for DDIs associated with drug candidates in early phases of drug development. These biomarker-driven investigations have been applied in both preclinical and clinical studies and proposed as a predictive strategy that can be supplanted in order to conduct prospective DDIs trials. Here we provide an overview of this rapidly emerging field, with particular emphasis on endogenous biomarkers recently proposed for clinically relevant uptake transporters.

Gold Nanoparticles Modified With Polyethyleneimine Disturbed the Activity of Drug-Metabolic Enzymes and Induced Inflammation-Mediated Liver Injury in Mice

Gold nanoparticles (GNPs) have been used as a potential bioactive platform for drug delivery due to their unique optical and thermal characteristics. Liver is the main organ in orchestrating physiological homeostasis through metabolization of drugs and detoxification of exogenous substances. Therefore, it is crucial to deeply understand the mechanism of nanoparticle–liver interaction and the potential hepatic effects of GNPs in vivo. In this study, we studied the hepatic impacts of the intravenously injected polyethyleneimine (PEI)-modified GNPs (PEI-GNPs) on the expression of hepatic drug-metabolic enzymes and sterol responsive element binding protein 1c (SREBP-1c)-mediated de novo lipogenesis in mice for 24 h and 1 week. PEI-GNP accumulation in the liver is associated with increased liver inflammation, as evidenced by the gene expression of pro-inflammatory cytokines. Moreover, the GNP-induced hepatotoxicity in mice is partly due to liver inflammation–triggered disruption in the function of drug-metabolic enzymes, including hepatic uptake and efflux transporters, cytochrome P450 (CYP450), and UDP-glucuronosyltransferases (UGTs). The study provides evidence that it is necessary to consider the nanomaterial–liver interaction and manipulate the surface chemistry of GNPs prior to biomedical application of nanoparticles.

Role of organic anion transporter 3 in the renal excretion of biapenem and potential drug-drug interactions

Biapenem is a carbapenem antibiotic. It is excreted predominantly through the kidney as unchanged forms. However, the molecular mechanism of renal excretion of biapenem and potential drug-drug interactions (DDIs) were still unknown. In the present study, the role of organic anion transporters (OAT) 1/3 and organic cation transporters (OCT) 2 in the renal excretion of biapenem, and the potential DDIs between biapenem and six clinical commonly prescribed antibiotics and antiviral drugs that acted as substrates or inhibitors of OAT3 were evaluated in vitro. Further, the effect of probenecid on the pharmacokinetics of biapenem was explored in the rats. We observed that biapenem could not inhibit the transport activities of OAT1 or OCT2, while mildly inhibited OAT3 (IC₅₀ >500 μM). Among the tested antibiotics and antiviral drugs, the relatively high DDI index values (maximal unbound plasma concentration over IC₅₀, I_max,u/IC₅₀) were found for piperacillin, linezolid and benzylpenicillin, which were 2.84, 1.7 and 0.62, respectively. Although probenecid had the highest DDI index (27.1) in vitro, no significant impact of it on the pharmacokinetics of biapenem was observed in the rats. Our results indicated that biapenem was primarily eliminated by the glomerular filtration, while OAT3-mediated renal tubular secretion was a minor route. Biapenem is not a clinically relevant substrate or inhibitor because of its low affinity to OAT3. According to current results, it would be safe to use biapenem with other antibiotics and antiviral drugs that acted as substrates or inhibitors of OAT3.

In Vitro Inhibition of Renal OCT2 and MATE1 Secretion by Antiemetic Drugs

The organic cation transporter 2 (OCT2) and multidrug and toxin extrusion protein 1 (MATE1) mediate the renal secretion of drugs. Recent studies suggest that ondansetron, a 5-HT₃ antagonist drug used to prevent nausea and vomiting, can inhibit OCT2- and MATE1-mediated transport. The purpose of this study was to test the ability of five 5-HT₃ antagonist drugs to inhibit the OCT2 and MATE1 transporters. The transport of the OCT2/MATE1 probe substrate ASP⁺ was assessed using two models: (1) HEK293 kidney cells overexpressing human OCT2 or MATE1, and (2) MDCK cells transfected with human OCT2 and MATE1. In HEK293 cells, the inhibition of ASP⁺ uptake by OCT2 listed in order of potency was palonosetron (IC₅₀: 2.6 μM) > ondansetron > granisetron > tropisetron > dolasetron (IC₅₀: 85.4 μM) and the inhibition of ASP⁺ uptake by MATE1 in order of potency was ondansetron (IC₅₀: 0.1 μM) > palonosetron = tropisetron > granisetron > dolasetron (IC₅₀: 27.4 μM). Ondansetron (0.5–20 μM) inhibited the basolateral-to-apical transcellular transport of ASP⁺ up to 64%. Higher concentrations (10 and 20 μM) of palonosetron, tropisetron, and dolasetron similarly reduced the transcellular transport of ASP⁺. In double-transfected OCT2-MATE1 MDCK cells, ondansetron at concentrations of 0.5 and 2.5 μM caused significant intracellular accumulation of ASP⁺. Taken together, these data suggest that 5-HT₃ antagonist drugs may inhibit the renal secretion of cationic drugs by interfering with OCT2 and/or MATE1 function.

Downregulated expression of organic anion transporting polypeptide (Oatp) 2b1 in the small intestine of rats with acute kidney injury

The expression of transporters on the apical and basal membranes of renal tubular cells is modulated under acute kidney injury (AKI). However, little is known about alterations in non-renal transporters in the tissues other than the kidney under AKI situation. This study aimed to assess the modulation of organic anion transporting polypeptide (Oatp) 1a2 and Oatp2b1 expression/function in the small intestine of rats with drug-induced AKI. AKI was induced by intraperitoneal administration of cisplatin at a dose of 5 mg/kg. On day 3 after cisplatin administration, morphological changes in the small intestine, Oatp1a2 and Oatp2b1 expression, and absorption of pravastatin and theophylline were evaluated. Non-negligible atrophy was observed in the jejunum and ileum of the AKI rats. However, the absorption of theophylline was not affected. While intestinal Oatp2b1 expression was markedly decreased in the AKI rats, no alteration was observed in Oatp1a2 expression. The plasma levels of pravastatin after intraluminal administration declined significantly in the AKI rats. However, no such decline was observed after intravenous administration. This study suggested that the responses of intestinal Oatps to experimentally induced AKI was not unidirectional and that pravastatin absorption was governed more potently by Oatp2b1 than by Oatp1a2 in the rat intestine.

Update on drug-drug interaction at organic cation transporters: mechanisms, clinical impact, and proposal for advanced in vitro testing

Introduction: Organic cation transporters collectively called OCTs belong to three gene families (SLC22A1 OCT1, SLC22A2 OCT2, SLC22A3 OCT3, SLC22A4 OCTN1, SLC22A5 OCTN2, SLC29A4 PMAT, SLC47A1 MATE1, and SLC47A1 MATE2-K). OCTs transport structurally diverse drugs with overlapping selectivity. Some OCTs were shown to be critically involved in pharmacokinetics and therapeutic efficacy of cationic drugs. Drug-drug interactions at individual OCTs were shown to result in clinical effects. Procedures for in vitro testing of drugs for interaction with OCT1, OCT2, MATE1, and MATE2-K have been recommended.Areas covered: An overview of functional properties, cation selectivity, location, and clinical impact of OCTs is provided. In addition, clinically relevant drug-drug interactions in OCTs are compiled. Because it was observed that the half maximal concentration of drugs to inhibit transport by OCTs (IC₅₀) is dependent on the transported cation and its concentration, an advanced protocol for in vitro testing of drugs for interaction with OCTs is proposed. In addition, it is suggested to include OCT3 and PMAT for in vitro testing.Expert opinion: Research on clinical roles of OCTs should be reinforced including more transporters and drugs. An improvement of the in vitro testing protocol considering recent data is imperative for the benefit of patients.