Characterisation of Organic Cation Transport across the Apical Membrane of Proximal Tubular Cells with the Fluorescent Dye 4-Di-1-ASP

Hereditary hypophosphatemic rickets with hypercalciuria results from mutations of the renal type IIc Na-Pi cotransporter gene, suggesting that the type IIc transporter plays a prominent role in renal phosphate handling. The goal of the present study was to investigate the regulation of the type IIc Na-Pi cotransporter by parathyroid hormone (PTH). Type IIc Na-Pi cotransporter levels were markedly increased in thyroparathyroidectomized (TPTX) rats. Four hours after administration of PTH, type IIc transporter protein levels were markedly decreased in the apical membrane fraction but recovered to baseline levels at 24 h. Immunohistochemical analyses demonstrated the presence of the type IIc transporter in the apical membrane and subapical compartments in the proximal tubular cells in TPTX animals. After administration of PTH, the intensity of immunoreactive signals in apical and subapical type IIc transporter decreased in the renal proximal tubular cells in TPTX rats. Colchicine completely blocked the internalization of the type IIc transporter. In addition, leupeptin prevented the PTH-mediated degradation of the type IIa transporter in lysosomes but had no effect on PTH-mediated degradation of the lysosomal type IIc transporter. In PTH-treated TPTX rats, the internalization of the type IIc transporter occurred after administration of PTH(1–34) (PKA and PKC activator) or PTH(3–34) (PKC activator). Thus the present study demonstrated that PTH is a major hormonal regulator of the type IIc Na-Pi cotransporter in renal proximal tubules.

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Transport characteristics of L-citrulline in renal apical membrane of proximal tubular cells

Biopharmaceutics & Drug Disposition ◽

10.1002/bdd.653 ◽

2009 ◽

Vol 30 (3) ◽

pp. 126-137 ◽

Cited By ~ 13

Author(s):

Keisuke Mitsuoka ◽

Yoshiyuki Shirasaka ◽

Akimasa Fukushi ◽

Masanobu Sato ◽

Toshimichi Nakamura ◽

...

Keyword(s):

Apical Membrane ◽

Proximal Tubular Cells ◽

Tubular Cells ◽

Proximal Tubular

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Rat Kidney Slices for Evaluation of Apical Membrane Transporters in Proximal Tubular Cells

Journal of Pharmaceutical Sciences ◽

10.1016/j.xphs.2019.03.031 ◽

2019 ◽

Vol 108 (8) ◽

pp. 2798-2804 ◽

Cited By ~ 2

Author(s):

Hiroshi Arakawa ◽

Hikaru Kubo ◽

Ikumi Washio ◽

Angelina Yukiko Staub ◽

Shiho Nedachi ◽

...

Keyword(s):

Apical Membrane ◽

Rat Kidney ◽

Membrane Transporters ◽

Proximal Tubular Cells ◽

Tubular Cells ◽

Kidney Slices ◽

Proximal Tubular

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Farnesoid X Receptor Activation Stimulates Organic Cations Transport in Human Renal Proximal Tubular Cells

International Journal of Molecular Sciences ◽

10.3390/ijms21176078 ◽

2020 ◽

Vol 21 (17) ◽

pp. 6078

Author(s):

Teerasak Wongwan ◽

Varanuj Chatsudthipong ◽

Sunhapas Soodvilai

Keyword(s):

Organic Cation ◽

Organic Cation Transporter ◽

Receptor Activation ◽

Farnesoid X Receptor ◽

Organic Cations ◽

Proximal Tubular Cells ◽

Tubular Cells ◽

Proximal Tubular ◽

Renal Proximal Tubular Cells ◽

Renal Proximal Tubular

Farnesoid X receptor (FXR) is a ligand-activated transcription factor highly expressed in the liver and kidneys. Activation of FXR decreases organic cation transporter (OCT) 1-mediated clearance of organic cation compounds in hepatocytes. The present study investigated FXR regulation of renal clearance of organic cations by OCT2 modulation and multidrug and toxin extrusion proteins (MATEs). The role of FXR in OCT2 and MATEs functions was investigated by monitoring the flux of 3H–MPP+, a substrate of OCT2 and MATEs. FXR agonists chenodeoxycholic acid (CDCA) and GW4064 stimulated OCT2-mediated 3H–MPP+ uptake in human renal proximal tubular cells (RPTEC/TERT1 cells) and OCT2-CHO-K1 cells. The stimulatory effect of CDCA (20 µM) was abolished by an FXR antagonist, Z-guggulsterone, indicating an FXR-dependent mechanism. CDCA increased OCT2 transport activity via an increased maximal transport rate of MPP+. Additionally, 24 h CDCA treatment increased MATEs-mediated 3H-MPP+ uptake. Moreover, CDCA treatment increased the expression of OCT2, MATE1, and MATE2-K mRNA compared with that of the control. OCT2 protein expression was also increased following CDCA treatment. FXR activation stimulates renal OCT2- and MATE1/2-K-mediated cation transports in proximal tubules, demonstrating that FXR plays a role in the regulation of OCT2 and MATEs in renal proximal tubular cells.

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Kidney Transporters and Drug-Induced Injury in Drug Development

Toxicologic Pathology ◽

10.1177/0192623320937012 ◽

2020 ◽

Vol 48 (6) ◽

pp. 721-724

Author(s):

Zaher A. Radi

Keyword(s):

Drug Development ◽

Drug Disposition ◽

Apical Membrane ◽

Basolateral Membrane ◽

Efflux Transporters ◽

Pharmaceutical Drugs ◽

Proximal Tubular Cells ◽

Drug Induced ◽

Tubular Cells ◽

Proximal Tubular

Influx and efflux kidney tubular transporters are major determinants of the disposition of xenobiotics, including pharmaceutical drugs. On the basolateral membrane of proximal tubular cells, there are influx transporters, such as organic cation transporters. On the apical membrane of proximal tubular cells, there are efflux transporters, such as multidrug and toxin extrusion proteins. The secretion process across the apical membrane into the lumen occurs via efflux transporters which plays an important role in serum creatinine (sCr) elimination in urine. The interference of a pharmaceutical drug with transporters can lead to changes in sCr with no alterations in biomarkers or light microscopic evidence indicative of renal injury. Identification of transporters that influence drug disposition, toxicity, and overall nonclinical safety assessment is important in drug discovery and development programs. This mini review describes some key aspects of kidney tubular transporters and drug-induced renal toxicities in safety risk assessment and drug development.

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Organic Cation Transporter 2 Overexpression May Confer an Increased Risk of Gentamicin-Induced Nephrotoxicity

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00907-16 ◽

2016 ◽

Vol 60 (9) ◽

pp. 5573-5580 ◽

Cited By ~ 23

Author(s):

Zhibo Gai ◽

Michele Visentin ◽

Christian Hiller ◽

Evelin Krajnc ◽

Tongzhou Li ◽

...

Keyword(s):

Protein Expression ◽

Organic Cation ◽

Obese Patients ◽

Organic Cation Transporters ◽

Proximal Tubular Cells ◽

Tubular Cells ◽

Drug Concentrations ◽

Increased Risk ◽

Proximal Tubular ◽

Cation Transporters

ABSTRACTNephrotoxicity is a relevant limitation of gentamicin, and obese patients have an increased risk for gentamicin-induced kidney injury. This damage is thought to depend on the accumulation of the drug in the renal cortex. Obese rats showed substantially higher levels of gentamicin in the kidney than did lean animals. This study characterized the role of organic cation transporters (OCTs) in gentamicin transport and elucidated their possible contribution in the increased renal accumulation of gentamicin in obesity. The mRNA and protein expression levels of the organic cation transporters Oct2 (Slc22a2) and Oct3 (Slc22a3) were increased in kidney samples from obese mice fed a high-fat diet. Similarly, OCT2 (∼2-fold) and OCT3 (∼3-fold) showed increased protein expression in the kidneys of obese patients compared with those of nonobese individuals. Using HEK293 cells overexpressing the different OCTs, human OCT2 was found to transport [3H]gentamicin with unique sigmoidal kinetics typical of homotropic positive cooperativity (autoactivation). In mouse primary proximal tubular cells, [3H]gentamicin uptake was reduced by approximately 40% when the cells were coincubated with the OCT2 substrate metformin. The basolateral localization of OCT2 suggests that gentamicin can enter proximal tubular cells from the blood side, probably as part of a slow tubular secretion process that may influence intracellular drug concentrations and exposure time. Increased expression of OCT2 may explain the higher accumulation of gentamicin, thereby conferring an increased risk of renal toxicity in obese patients.

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Germacrone Reduces Cisplatin-Induced Toxicity of Renal Proximal Tubular Cells via Inhibition of Organic Cation Transporter

Biological and Pharmaceutical Bulletin ◽

10.1248/bpb.b20-00392 ◽

2020 ◽

Vol 43 (11) ◽

pp. 1693-1698

Author(s):

Sirima Soodvilai ◽

Paranee Meetam ◽

Lawan Siangjong ◽

Ratchanaporn Chokchaisiri ◽

Apichart Suksamrarn ◽

...

Keyword(s):

Organic Cation ◽

Organic Cation Transporter ◽

Proximal Tubular Cells ◽

Tubular Cells ◽

Proximal Tubular ◽

Renal Proximal Tubular Cells ◽

Renal Proximal Tubular

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Pharmacokinetics and Toxicokinetics Roles of Membrane Transporters at Kidney Level

Journal of Pharmacy & Pharmaceutical Sciences ◽

10.18433/jpps30865 ◽

2020 ◽

Vol 23 ◽

pp. 333-356

Author(s):

Jéssica Veiga-Matos ◽

Fernando Remião ◽

Ana Motales

Keyword(s):

Renal Damage ◽

Organic Cation ◽

Organic Anion ◽

Efflux Transporters ◽

Cancer Resistance ◽

Proximal Tubular Cells ◽

Tubular Cells ◽

Proximal Tubular ◽

Resistance Protein ◽

Uptake Transporters

Transporters are large membrane proteins, which control the passage of various compounds through biological membranes. These proteins are divided into uptake and efflux transporters and play an important role in the toxicokinetics of many endobiotics and xenobiotics. The uptake transporters facilitate the absorption of these compounds from the blood into the proximal tubular cells, while the efflux transporters eliminate these compounds into tubular fluid (urine). Overall, the uptake is performed by the superfamily solute carrier (SLC) transporters, which are, mostly, located in the basolateral membrane. The organic anion transporters (OATs; SLC22), the organic cation transporters (OCTs; SLC22), the organic cation/carnitine transporters (OCTNs), and the organic anion transporting polypeptides (OATP; SLC21/SLCO) are some examples of uptake transporters of the SLC superfamily. On the other hand, the superfamily ATP-binding cassette (ABC) transporters carry out the elimination of the substances through the apical membrane of the proximal tubular cells. The multidrug resistance proteins 1 (MDR; ABCB), the multi resistance protein (MRP2; ABCC) and the breast cancer resistance protein (BCRP, ABCG) along with the multidrug and toxin extrusion (MATE), which is an SLC transporter, carry out the substance efflux of the cell, However, uptake transporters seem to be more efficient than efflux transporters, leading to an accumulation of compounds in proximal tubular cells and, consequently, to renal damage. The accumulation of compounds can also occur due to variations in the number of transporters that exist due to differences in sex, age, genetic polymorphisms and epigenetics. Furthermore, some substances can inhibit, induce or, eventually, activate these transporters, with consequent drug-drug interactions (DDIs) as a result of alterations on the toxicokinetics of xenobiotics, leading to an increase of their accumulation and, consequently, to renal damage. These compounds may be exogenous, such as antibiotics, antivirals, cisplatin, metals, herbicides, mycotoxins and drugs; or endogenous, like uric acid, bile acids, bilirubin conjugates and conjugated steroids. Thus, in this review, we will focus on the accumulation of exogenous compounds due to variations on renal transporters and the consequent biological effects caused by them.

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