Search Results (93)

Organic anion-transporting polypeptides (OATPs) are key transporters of hepatic uptake for endogenous compounds and xenobiotics. Human OATP1B1 and OATP1B3 are well-studied due to their role in drug–drug interactions. In contrast, data on murine OATP1B2, the rodent orthologue of these transporters, are limited, despite its importance in early drug development. Here, we systematically compared the transport characteristics of mouse and rat OATP1B2 under identical experimental conditions. The K_m values for estrone-3-sulfate (E₁S) and taurocholate (TCA) were 242 and 73 µM for mOATP1B2 and 90 and 16 µM for rOATP1B2. Nine clinically relevant drugs were evaluated for inhibitory effects, showing strong correlation between species. Cyclosporine A, ritonavir, odevixibat, rosuvastatin, and rifampicin markedly inhibited uptake. Rifampicin demonstrated species-specific differences, with higher IC₅₀ values for mOATP1B2 (E₁S: 9.6 µM; TCA: 7.7 µM) than rOATP1B2 (E₁S: 1.1 µM; TCA: 2.4 µM). A comparison of the rodent data with the human orthologues revealed similar inhibition patterns but distinct substrate selectivity: hOATP1B1 showed high affinity for E₁S but negligible TCA uptake, while hOATP1B3 transported TCA weakly but not E₁S. This study provides insights into species-specific differences in OATP-mediated hepatic uptake and is therefore valuable for the interpretation of preclinical studies and their transfer to human pharmacology. Full article

Gut microbiota, through both its species composition and its metabolites, impacts expression and activity of intestinal drug transporters. This phenomenon directly affects absorption process of orally administered drugs and contributes to the observed inter-individual variability in pharmacotherapeutic responses. This review summarizes mechanistic evidence from in vitro and animal studies and integrates clinical observations in which alterations in gut microbiota are associated with changes in oral drug exposure, consistent with potential regulation of key intestinal drug transporters—such as P-glycoprotein (P-gp, ABCB1), Breast Cancer Resistance Protein (BCRP, ABCG2), MRP2/3 proteins (ABCC2/3), and selected Organic Anion-Transporting Polypeptides (OATPs, e.g., SLCO1A2, SLCO2B1)—by major bacterial metabolites including short-chain fatty acids (SCFAs), secondary bile acids, and tryptophan-derived indoles. The molecular mechanisms involved include activation of nuclear and membrane receptors (PXR, FXR, AhR, TGR5), modulation of transcriptional and stress-response pathways (Nrf2, AP-1) with simultaneous suppression of pro-inflammatory pathways (NF-κB), and post-translational modifications (e.g., direct inhibition of P-gp ATPase activity by Eggerthella lenta metabolites). The review also highlights the pharmacokinetic implications of, e.g., tacrolimus, digoxin, and metformin. In conclusion, the significance of “drug–transporter–microbiome” interactions for personalized medicine is discussed. Potential therapeutic interventions are also covered (diet, pre-/probiotics, fecal microbiota transplantation, modulation of PXR/FXR/AhR pathways). Considering the microbiota as a “second genome” enables more accurate prediction of drug exposure, reduction in toxicity, and optimization of dosing for orally administered preparations. Full article

Organic anion transporting polypeptide 1B1 (OATP1B1) is specifically expressed at the basolateral membrane of human liver cells and transports a wide range of endogenous compounds, toxins, and drugs, making it a crucial factor in determining the pharmacokinetics of many clinically important medications. Triptergium wilfordii Hook. f. (TWHF) is a traditional Chinese medicine known for its long history of therapeutic effects. A previous study conducted in our laboratory found that major components of TWHF, including wilforine (WFR), wilforgine (WFG), celastrol (CL), and triptolide (TPL), directly suppressed the function of OATP1B1. In the current study, we investigated the long-term (24 h) effects of these TWHF components on the transporter. It was found that TPL was the most potent compound exhibiting inhibitory effects. Mechanistically, TPL accelerated the degradation of OATP1B1, which is likely mediated by serum and glucocorticoid-induced kinase 1 (SGK1). TPL downregulated the mRNA expression of SGK1 and reduced the nuclear accumulation of nuclear factor kappa B (NFκB). Further analysis of the upstream sequence of SGK1 identified three potential binding sites for NFκB. Both luciferase activity assays and chromatin immunoprecipitation (ChIP) analyses confirmed the binding of NFκB to two specific sites located at −1015 bp~−1006 bp and −319 bp~−310 bp. Full article

Background/Objectives: Ochratoxin A (OTA) is a widespread foodborne mycotoxin linked to chronic kidney disease of unknown etiology. Despite evidence from animal models showing OTA accumulation in the kidney, the molecular mechanisms underlying its renal disposition in humans remain only partially understood. Here, we identify human renal transporters responsible for OTA kidney accumulation, elimination, and establish Michaelis–Menten kinetics under matched conditions to directly compare transport mechanisms. We also aim to identify inhibition potential of these transport mechanisms with common dietary polyphenols. Methods: Mammalian cells and membrane vesicles overexpressing human renal transporters were used to screen and profile the uptake and efflux of OTA. Miquelianin, (-)-Epicatechin-3-O-gallate, myricetin, luteolin, and caffeic acid were tested as potential concentration-dependent transporter inhibitors. Results: We demonstrate that OTA is a substrate for human organic anion transporter (hOAT) 1 (K_m: 2.10 ± 0.50 μM, V_max: 396.9 ± 27.0 pmol/mg/min), hOAT3 (K_m: 2.58 ± 0.83 μM, V_max: 141.4 ± 30.3 pmol/mg/min), hOAT4 (K_m: 6.38 ± 1.45 μM, V_max: 96.9 ± 18.8 pmol/mg/min), and human organic anion transporting polypeptide (hOATP) 1A2 (K_m: 37.3 ± 6.2 μM, V_max: 801.0 ± 133.9 pmol/mg/min). Among efflux transporters, OTA was transported only by human breast cancer resistance protein (hBCRP), which has minimal renal expression. While none of the uptake transporters were potently inhibited (>90%) by polyphenols at 10 μM, luteolin inhibited hBCRP-mediated transport of OTA with an IC₅₀ of 22 μM and caffeic acid stimulated hBCRP-mediated efflux with an EC₅₀ of 713.8 μM, both of which are physiologically relevant intestinal lumen concentrations. Conclusions: Our results confirm that exposure to OTA will lead to renal accumulation and increased health risks in affected populations, necessitating increased scrutiny of our food sources. Full article

Background/Objectives: Magnetic resonance imaging (MRI) is a powerful, non-invasive diagnostic tool capable of capturing detailed anatomical and physiological information. MRI contrast agents enhance image contrast but, especially linear gadolinium-based compounds, have been associated with safety concerns. This has prompted interest in alternative contrast agents. Manganese-based contrast agents offer a promising substitute, owing to manganese’s favorable magnetic properties, natural biological role, and strong T1 relaxivity. This review aims to critically assess the structure, mechanisms, applications, and challenges of manganese-based contrast agents in MRI. Methods: This review synthesizes findings from preclinical and clinical studies involving various types of manganese-based contrast agents, including small-molecule chelates, nanoparticles, theranostic platforms, responsive agents, and controlled-release systems. Special attention is given to pharmacokinetics, biodistribution, and safety evaluations. Results: Mn-based agents demonstrate promising imaging capabilities, with some achieving relaxivity values comparable to gadolinium compounds. Targeted uptake mechanisms, such as hepatocyte-specific transport via organic anion-transporting polypeptides, allow for enhanced tissue contrast. However, concerns remain regarding the in vivo release of free Mn²⁺ ions, which could lead to toxicity. Preliminary toxicity assessments report low cytotoxicity, but further comprehensive long-term safety studies should be carried out. Conclusions: Manganese-based contrast agents present a potential alternative to gadolinium-based MRI agents pending further validation. Despite promising imaging performance and biocompatibility, further investigation into stability and safety is essential. Additional research is needed to facilitate the clinical translation of these agents. Full article

Background: Baicalin (BG) has been used in the treatment of many diseases. However, the effect of hepatic insufficiency on its pharmacokinetics has not been reported, and there is a lack of clinical guidance for the use of BG in patients with hepatic impairment. Methods: Carbon tetrachloride (CCl₄)-induced rat models were used to simulate hepatic failure patients to assess the effect of hepatic impairment on the pharmacokinetics and distribution of BG. In vitro metabolism and transporter studies were employed to elucidate the potential mechanisms. Results: After intragastric administration of 10 mg/kg of BG, the peak plasma concentration and exposure (AUC_0–t) of BG decreased by 64.6% and 52.6%, respectively, in CCl₄-induced rats. After intravenous administration, the AUC_0–t decreased by 73.6%, and unlike in the control group, the second absorption peak of BG was not obvious in the concentration–time curve of CCl₄-induced rats. The cumulative excretion of BG in the feces increased, but that in the bile decreased. In vivo data indicated that the absorption and enterohepatic circulation of BG were affected. In vitro studies found that the hydrolysis of BG to the aglycone baicalein decreased significantly in the intestinal tissues and contents of the CCl₄-induced rats. And BG was identified as a substrate for multiple efflux and uptake transporters, such as breast cancer resistance protein (BCRP) and multidrug resistance-associated proteins (MRPs), organic anion transporting polypeptides (OATP1B1, 1B3, 2B1), and organic anion transporters (OATs). The bile acids accumulated by liver injury inhibited the uptake of BG by OATPs, especially that by OATP2B1. Conclusions: Hepatic impairment reduced BG hydrolysis by intestinal microflora and inhibited its transporter-mediated biliary excretion, which synergistically led to the attenuation of the enterohepatic circulation of BG, which altered its pharmacokinetics. Full article

Organic anion transporting polypeptide 1B1 (OATP1B1) is selectively expressed at the basolateral membrane of human hepatocytes and plays a crucial role in the absorption of various xenobiotic compounds, including many important clinical drugs. Oligomerization with regulatory proteins is a common mechanism for regulating membrane protein functions. In the present study, we found that knocking down the scaffold protein radixin, which is the major member of the ERM family expressed in the liver, significantly enhanced the uptake function of OATP1B1. On the other hand, the overexpression of the phospho-mimic form of radixin (radixin-D) reduced the uptake function and cell surface level of OATP1B1, while the wild-type and phospho-dormant form of radixin (radixin-A) did not exhibit the same effect. Further investigation revealed that radixin interacts with OATP1B1. Activation of protein kinase C (PKC), which our previous study showed accelerates the internalization of OATP1B1, was found to increase the phosphorylation level of radixin associated with OATP1B1. The knockdown of radixin significantly diminished the suppressive effect of PKC on the function and cell surface levels of OATP1B1. These results suggested that OATP1B1 forms complexes with radixin, which may be phosphorylated by PKC, leading to reduced cell surface expression and activity of the transporter. Full article

Drug interactions can have significant consequences for public health, especially given the growing importance of readily available dietary supplements. The same applies to the consumption of fruit and fruit juices, which are often praised for their health benefits, but which can generate drug interactions. These are well known and documented in the case of grapefruit, which should not be taken with certain medications. Grapefruit contains flavonoids and furanocoumarins, which are responsible for various interactions with the cytochrome P450 enzyme system. However, for young children and the elderly, fruit juices are often used to facilitate treatment. This review examines commonly used fruit juices, particularly from citrus, apple, and red fruits, and discusses potential interactions, disadvantages, and advantages, as well as the chemical structures involved in interactions with cytochromes P-450, P-glycoprotein, and organic anion transporter polypeptide (OATP), responsible for sometimes dangerous changes in bioavailability or potential accumulation of drugs in the body. Full article

S-nitrosoglutathione (GSNO) is the S-nitrosated derivative of glutathione (GSH). GSNO is an endogenous class of NO donors and a natural NO depot in biological systems. Organic anion transporting polypeptide 1B1 (OATP1B1) is an influx transporter that is expressed in the liver. OATP1B1 plays an important role in the transport of endogenous and exogenous substances. Various pathways for the regulation of OATP1B1 have been described. In the present study, the involvement of OATP1B1 in GSNO transport and the regulation of OATP1B1 by GSNO was examined. For HEK293-OATP1B1, it has been shown that GSNO is not a substrate of OATP1B1, but OATP1B1 can participate in the transport of GSH across the cell membrane. GSNO at concentrations of 1–100 μM and exposure for 3 h do not affect the expression and activity of OATP1B1, but exposure for 24 and 72 h stimulates the expression of the SLCO1B1 gene, OATP1B1, and transporter activity. Up-regulation of OATP1B1 by GSNO is carried out through the NO-cGMP signaling pathway, Nrf2, and LXRa. Full article

Background/Objectives: The increasing use of statins in people with cystic fibrosis (CF) necessitates the investigation of potential drug–drug interactions (DDI) of statins with cystic fibrosis transmembrane conductance regulator (CFTR) modulators, including elexacaftor, tezacaftor, and ivacaftor (ETI). The interactions may involve the potential inhibition of cytochrome P450 isoenzymes (CYPs), organic anion-transporting polypeptides (OATPs), and Breast Cancer Resistance Protein (BCRP) by ETI. This presents a therapeutic challenge in CF due to the potential for elevated statin levels, consequently heightening the risk of myopathy. This study aimed to predict potential DDIs between statins and ETI using a physiologically based pharmacokinetic (PBPK) modeling approach. Methods: We performed in vitro assays to measure the inhibitory potency of ETI against OATPs and CYP2C9 and incorporated these data into our PBPK models alongside published inhibitory parameters for BCRP and CYP3A4. Results: The PBPK simulation showed that atorvastatin had the highest predicted AUC ratio (3.27), followed by pravastatin (2.27), pitavastatin (2.24), and rosuvastatin (1.83). Conclusions: Based on these findings, rosuvastatin appears to exhibit a weak interaction with ETI, whereas other statins exhibited a moderate interaction, potentially requiring appropriate dose reductions. These data indicate potential clinically significant DDIs between ETI and certain statins, which warrants a clinical study to validate these findings. Full article

The involvement of drug-metabolizing enzymes and transporters in plasma clozapine (CLZ) dynamics has not been well examined in Japanese patients with treatment-resistant schizophrenia (TRS). Therefore, this clinical study investigated the relationship between single nucleotide polymorphisms (SNPs) of various pharmacokinetic factors (drug-metabolizing enzymes and transporters) and dynamic changes in CLZ. Additionally, we aimed to determine whether CLZ acts as a substrate for pharmacokinetic factors using in vitro assays and molecular docking calculations. We found that 6 out of 10 patients with TRS and with multiple organic anion transporting polypeptide (OATP) variants (OATP1B1: *1b, *15; OATP1B3: 334T>G, 699G>A; and OATP2B1: *3, 935G>A, 601G>A, 76_84del) seemed to be highly exposed to CLZ and/or N-desmethyl CLZ. A CLZ uptake study using OATP-expressing HEK293 cells showed that CLZ was a substrate of OATP1B1 with K_m and V_max values of 38.9 µM and 2752 pmol/mg protein/10 min, respectively. The results of molecular docking calculations supported the differences in CLZ uptake among OATP molecules and the weak inhibitory effect of cyclosporine A, which is a strong inhibitor of OATPs, on CLZ uptake via OATP1B1. This is the first study to show that CLZ is an OATP1B1 substrate and that the presence of SNPs in OATPs potentially alters CLZ pharmacokinetic parameters. Full article

Bempedoic acid is a new drug that improves the control of cholesterol levels, either as monotherapy or in combination with existing lipid-lowering therapies, and shows clinical efficacy in cardiovascular disease patients. Thus, patients with comorbidities and under multiple therapies may be eligible for bempedoic acid, thus facing the potential problem of drug–drug interactions (DDIs). Bempedoic acid is a prodrug administered orally at a fixed daily dose of 180 mg. The dicarboxylic acid is enzymatically activated by conjugation with coenzyme A (CoA) to form the pharmacologically active thioester (bempedoic acid–CoA). This process is catalyzed by very-long-chain acyl-CoA synthetase 1 (ACSVL1), expressed almost exclusively at the hepatic level. Bempedoic acid–CoA is a potent and selective inhibitor of ATP citrate lyase (ACL), a key enzyme in the biosynthetic pathway of cholesterol and fatty acids. The drug reduces low-density lipoprotein–cholesterol (LDL-C) (20–25%), non-high-density lipoprotein–cholesterol (HDL-C) (19%), apolipoprotein B (apoB) (15%), and total cholesterol (16%) in patients with hypercholesterolemia or mixed dyslipidemia. The drug has a favorable pharmacokinetics profile. Bempedoic acid and its metabolites are not substrates or inhibitors/inducers of cytochrome P450 (CYP450) involved in drug metabolism. On the other hand, bempedoic acid–glucuronide is a substrate for organic anion transporter 3 (OAT3). Bempedoic acid and its glucuronide are weak inhibitors of the OAT2, OAT3, and organic anion-transporting polypeptide 1B1 (OATP1B1) and 1B3 (OATP1B3). Thus, bempedoic acid could inhibit (perpetrator) the hepatic uptake of OATP1B1/3 substrate drugs and the renal elimination of OAT2 and OAT3 substrates and could suffer (victim) the effect of OAT3 transporter inhibitors, reducing its renal elimination. Based on these pharmacological characteristics, here, we describe the potential DDIs of bempedoic acid with concomitant medications and the possible clinical implications. Full article

Exposure to pesticides such as paraquat and 2,4-dichlorophenoxyacetic acid (2,4-D) has been linked to harmful health effects, including alterations in male reproduction. Both herbicides are widely used in developing countries and have been associated with reproductive alterations, such as disruption of spermatogenesis and steroidogenesis. The thyroid axis and Ca²⁺-permeable ion channels play a key role in these processes, and their disruption can lead to reproductive issues and even infertility. This study evaluated the short-term effects of exposure to commercial herbicides based on paraquat and 2,4-D on gene expression in rat testes. At the molecular level, exposure to paraquat increased the expression of the thyroid hormone transporters monocarboxylate transporter 8 (Mct8) and organic anion-transporting polypeptide 1C1 (Oatp1c1) and the thyroid receptor alpha (TRα), suggesting a possible endocrine disruption. However, it did not alter the expression of the sperm-associated cation channels (CatSper1-2) or vanilloid receptor-related osmotically activated channel (Trpv4) related to sperm motility. In contrast, exposure to 2,4-D reduced the expression of the Mct10 transporter, Dio2 deiodinase, and CatSper1, which could affect both the availability of T3 in testicular cells and sperm quality, consistent with previous studies. However, 2,4-D did not affect the expression of CatSper2 or Trpv4. Deregulation of gene expression could explain the alterations in male reproductive processes reported by exposure to paraquat and 2,4-D. These thyroid hormone-related genes can serve as molecular biomarkers to assess endocrine disruption due to exposure to these herbicides, aiding in evaluating the health risks of pesticides. Full article

Taurine can ameliorate hypercholesterolemia by facilitating cholesterol efflux and increasing cytochrome P450 7A1 (CYP7A1) without clear underlying molecular mechanisms. This study aims to elucidate the molecular action of taurine in diet-induced hypercholesterolemia. Male Wistar rats were fed a high cholesterol diet containing 5% taurine for 14 days. Three-dimensional primary hepatocytes from rats were exposed to 10 mM taurine for 24 h. Transcriptome analyses of both the liver and hepatocytes were performed using DNA microarray. Taurine significantly decreased serum cholesterol levels and increased hepatic CYP7A1 mRNA levels and transcription rates in rats. Taurine altered the expression of seventy-seven genes in the liver, involving lipid, drug, amino acid metabolism, and gluconeogenesis pathways. The small heterodimer partner (SHP), a transcription factor regulated by taurine, was suppressed. “Network analysis” revealed a negative correlation between the SHP and induction of CYP7A1 and cytochrome P450 8B1 (CYP8B1). However, CYP7A1 and CYP8B1 levels were not altered by taurine in 3D-primary hepatocytes. Venn diagram analyses of the transcriptomes in both hepatocytes and the liver indicated a consistent upregulation of organic anion transporting polypeptide 2 (OATP2) and betaine homocysteine methyltransferase (BHMT). Taurine ameliorated hypercholesterolemia in rats fed a high cholesterol diet by directly enhancing the hepatic expression of BHMT and OATP2, which modulated the SHP and induced CYP7A1 and CYP8B1, thereby promoting cholesterol catabolism and lowering blood cholesterol levels. Full article

Of the 450 cell membrane transporters responsible for shuttling substrates, nutrients, hormones, neurotransmitters, antioxidants, and signaling molecules, approximately nine are associated with clinically relevant drug–drug interactions (DDIs) due to their role in drug and metabolite transport. Therefore, a clinical study evaluating potential transporter DDIs is recommended if an investigational product is intestinally absorbed, undergoes renal or hepatic elimination, or is suspected to either be a transporter substrate or perpetrator. However, many of the transporter substrates and inhibitors administered during a DDI study also affect cytochrome P450 (CYP) activity, which can complicate data interpretation. To overcome these challenges, the assessment of endogenous biomarkers can help elucidate the mechanism of complex DDIs when multiple transporters or CYPs may be involved. This perspective article will highlight how creative study designs are currently being utilized to address complex transporter DDIs and the role of physiology-based -pharmacokinetic (PBPK) models can play. Full article