Stereoselective Inhibition of Renal Basolateral Human Organic Anion Transporter 3 by Lansoprazole Enantiomers

Contribution of human organic anion transporter 3-mediated transport of a major linezolid metabolite, PNU-142586, in linezolid-induced thrombocytopenia

Thrombocytopenia, a common adverse effect of linezolid, often occurs in patients lacking typical risk factors. In this study, we investigated the key risk factors for linezolid-induced thrombocytopenia using two real-world clinical databases and explored its underlying mechanism through in vitro and in vivo experiments. In a retrospective analysis of 150 linezolid-treated patients, multivariate analysis identified coadministration of lansoprazole, a proton pump inhibitor, as a significant independent risk factor for thrombocytopenia (odds ratio: 2.33, p = 0.034). Additionally, analysis of the Food and Drug Administration Adverse Event Reporting System database revealed a reporting odds ratio of thrombocytopenia for lansoprazole of 1.64 (95% CI: 1.25-2.16). In vitro studies showed that the uptake of PNU-142586, a major linezolid metabolite, was significantly higher in human organic anion transporter 3-expressing HEK293 (HEK-hOAT3) cells compared to HEK-pBK cells. The apparent IC50 value of lansoprazole against hOAT3-mediated transport of PNU-142586 was 0.59 ± 0.38 µM. In a pharmacokinetic study using rats, coadministration of linezolid with lansoprazole intravenously resulted in approximately a 1.7-fold increase in the area under the plasma concentration-time curve of PNU-142586, but not linezolid and PNU-142300. Moreover, PNU-142586, but not linezolid, exhibited concentration-dependent cytotoxicity in a human megakaryocytic cell line. These findings suggest that linezolid-induced thrombocytopenia should be due to delayed elimination of PNU-142586. Furthermore, delayed elimination of PNU-142586 due to renal failure and hOAT3-mediated transport inhibition by lansoprazole should exacerbate linezolid-induced thrombocytopenia.

Proton-Pump Inhibitors and Serum Concentrations of Uremic Toxins in Patients with Chronic Kidney Disease

Use of proton-pump inhibitors (PPIs) is common in patients with chronic kidney disease (CKD). PPIs and many uremic toxins (UTs) are eliminated by the kidney's tubular organic anion transporter system. In a cross-sectional study, we sought to evaluate the association between PPI prescription and serum concentrations of various UTs. We studied a randomly selected sub-group of participants in the CKD-REIN cohort (adult patients with a confirmed diagnosis of CKD and estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m²) with available frozen samples collected at baseline. PPI prescription was recorded at baseline. Serum concentrations of 10 UTs were measured using a validated liquid chromatography tandem mass spectrometry technique. Multiple linear regression was performed, with the log UT concentration as the dependent variable. Of the 680 included patients (median age: 68 years; median eGFR: 32 mL/min/1.73 m²), 31% had PPI prescriptions at baseline. Patients using PPIs had higher levels of certain UTs in comparison to other patients, including total and free indoxyl sulfate (IS), total and free p-cresylsulfate, total and free p-cresylglucuronide (PCG), phenylacetylglutamine (PAG), free kynurenine, and free hippuric acid. After adjustment for baseline co-morbidities, number of co-prescribed drugs, and laboratory data, including eGFR, associations between PPI prescription and elevated serum concentrations of free and total IS, free and total PCG, and PAG remained significant. Our results indicate that PPI prescription is independently associated with serum UT retention. These findings are interesting to better understand the factors that may modulate serum UT concentration in CKD patients, however, they will need to be confirmed by longitudinal studies.

Implication of human drug transporters to toxicokinetics and toxicity of pesticides

Human membrane drug transporters are recognized as major actors of pharmacokinetics. Pesticides also interact with human drug transporters, which may have consequences for pesticide toxicokinetics and toxicity. The present review summarizes key findings about this topic. In vitro assays have demonstrated that some pesticides, belonging to various chemical classes, modulate drug transporter activity, regulate transporter expression and/or are substrates, thus bringing the proof of concept for pesticide-transporter relationships. The expected low human concentration of pesticides in response to environmental exposure constitutes a key-parameter to be kept in mind for judging the in vivo relevance of such pesticide-transporter interactions and their consequences for human health. Existing data about interactions of pesticides with drug transporters remain, however, rather sparse; more extensive and systematic characterization of pesticide-transporter relationships, through the use of high throughput in vitro assays and/or in silico methods, is, therefore, required. In addition, consideration of transporter polymorphisms, pesticide mixture effects and physiological and pathological factors governing drug transporter expression may help to better define the in vivo relevance of pesticide-transporter interactions in terms of toxicokinetics and toxicity for humans. © 2019 Society of Chemical Industry.

Enantioselective Drug Recognition by Drug Transporters

Drug transporters mediate the absorption, tissue distribution, and excretion of drugs. The cDNAs of P-glycoprotein, multidrug resistance proteins (MRPs/ABCC), breast cancer resistance protein (BCRP/ABCG2), peptide transporters (PEPTs/SLC15), proton-coupled folate transporters (PCFT/SLC46A1), organic anion transporting polypeptides (OATPs/SLCO), organic anion transporters (OATs/SLC22), organic cation transporters (OCTs/SLC22), and multidrug and toxin extrusions (MATEs/SLC47) have been isolated, and their functions have been elucidated. Enantioselectivity has been demonstrated in the pharmacokinetics and efficacy of drugs, and is important for elucidating the relationship with recognition of drugs by drug transporters from a chiral aspect. Enantioselectivity in the transport of drugs by drug transporters and the inhibitory effects of drugs on drug transporters has been summarized in this review.