Substrate-Dependent Trans-Stimulation of Organic Cation Transporter 2 Activity

The search of substrates for solute carriers (SLCs) constitutes a major issue, owing notably to the role played by some SLCs, such as the renal electrogenic organic cation transporter (OCT) 2 (SLC22A2), in pharmacokinetics, drug–drug interactions and drug toxicity. For this purpose, substrates have been proposed to be identified by their cis-inhibition and trans-stimulation properties towards transporter activity. To get insights on the sensitivity of this approach for identifying SLC substrates, 15 various exogenous and endogenous OCT2 substrates were analysed in the present study, using 4-(4-(dimethylamino)styryl)-N-methylpyridinium iodide (DiASP) as a fluorescent OCT2 tracer substrate. All OCT2 substrates cis-inhibited DiASP uptake in OCT2-overexpressing HEK293 cells, with IC50 values ranging from 0.24 µM (for ipratropium) to 2.39 mM (for dopamine). By contrast, only 4/15 substrates, i.e., acetylcholine, agmatine, choline and metformin, trans-stimulated DiASP uptake, with a full suppression of the trans-stimulating effect of metformin by the reference OCT2 inhibitor amitriptyline. An analysis of molecular descriptors next indicated that trans-stimulating OCT2 substrates exhibit lower molecular weight, volume, polarizability and lipophilicity than non-trans-stimulating counterparts. Overall, these data indicated a rather low sensitivity (26.7%) of the trans-stimulation assay for identifying OCT2 substrates, and caution with respect to the use of such assay may therefore be considered.

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Wedelolactone protects against cisplatin-induced nephrotoxicity in mice via inhibition of organic cation transporter 2

Human & Experimental Toxicology ◽

10.1177/09603271211047915 ◽

2021 ◽

pp. 096032712110479

Author(s):

Guangju Wang ◽

Yajuan Bi ◽

Hui Xiong ◽

Tongwei Bo ◽

Lifeng Han ◽

...

Keyword(s):

Natural Compound ◽

Organic Cation ◽

Kidney Injury ◽

Organic Cation Transporter ◽

Competitive Inhibitor ◽

Hek293 Cells ◽

Cytotoxicity Studies ◽

Organic Cation Transporter 2 ◽

Uptake Assay ◽

Noncompetitive Inhibitor

The balance of cisplatin uptake and efflux, mediated mainly by organic cation transporter 2 (OCT2) and multidrug and toxin extrusion 1 (MATE1), respectively, determines the renal accumulation and nephrotoxicity of cisplatin. Using transporter-mediated cellular uptake assay, we identified wedelolactone (WEL), a medicinal plant-derived natural compound, is a competitive inhibitor of OCT2 and a noncompetitive inhibitor of MATE1. Wedelolactone showed a selectivity to inhibit OCT2 rather than MATE1. Cytotoxicity studies revealed that wedelolactone alleviated cisplatin-induced cytotoxicity in OCT2-overexpressing HEK293 cells, whereas it did not alter the cytotoxicity of cisplatin in various cancer cell lines. Additionally, wedelolactone altered cisplatin pharmacokinetics, reduced kidney accumulation of cisplatin, and ameliorated cisplatin-induced acute kidney injury in the Institute of Cancer Research mice. In conclusion, these findings suggest a translational potential of WEL as a natural therapy for preventing cisplatin-induced nephrotoxicity and highlight the need for drug–drug interaction investigations of WEL with other treatments which are substrates of OCT2 and/or MATE1.

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The Affinity of the Organic Cation Transporter rOCT1 Is Increased by Protein Kinase C-Dependent Phosphorylation

Journal of the American Society of Nephrology ◽

10.1681/asn.v1171216 ◽

2000 ◽

Vol 11 (7) ◽

pp. 1216-1224 ◽

Cited By ~ 5

Author(s):

THOMAS MEHRENS ◽

SILKE LELLECK ◽

IBRAHIM ÇETINKAYA ◽

MARION KNOLLMANN ◽

HELGE HOHAGE ◽

...

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Tyrosine Kinases ◽

Organic Cation ◽

Organic Cation Transporter ◽

Hek293 Cells ◽

Substrate Uptake ◽

Fluorescence Measurements ◽

Kinase C ◽

Stimulation Of

Abstract. Members of the organic cation transporter (OCT) family are mainly expressed in kidney, liver, intestine, and brain. The regulation of the OCT type 1 from rat (rOCT1) stably transfected in HEK293 cells was examined using a fluorimetric technique, 1-[3H]methyl-4-phenylpyridinium uptake studies, and fast-whole-cell patch-clamp recordings. For the fluorescence measurements, the cation 4-(4-(dimethylamino)styryl)-N-methylpyridinium iodide (ASP+) was used as substrate. Uptake of ASP+via rOCT1 was electrogenic, and its inhibition by other organic cations was consistent with previously reported radioactive tracer flux measurements. The inhibitor quinine was not translocated by the organic cation transporter in contrast to tetraethylammonium. Stimulation of diacyl glycerol-dependent protein kinase C (PKC) bysn-1,2-dioctanoyl glycerol (1 μM) resulted in an increase in initial ASP+uptake rate by 216 ± 28% (n= 29). The effect was completely antagonized by the PKC inhibitor tamoxifen (20 μM,n= 22). Forskolin (1 μM), which activates adenylate cyclase and thereby protein kinase A (PKA), stimulated the initial rate of ASP+accumulation by 51 ± 6% (n= 19). This effect was inhibited by the specific PKA inhibitor KT5720 (1 μM,n= 12). Inhibition of tyrosine kinases by aminogenestein (10 μM) reduced ASP+uptake by 63 ± 7% (n= 7), while genestein or tyrphostin AG1295 (each 10 μM) were without significant effects. Incubation of the cells withsn-1,2-dioctanoyl glycerol (1 μM) increased the affinities of the transporter to tetraethylammonium, tetrapenthylammonium, and quinine by a factor of 58, 14.5, and 2.4, respectively. Western blot analysis revealed that rOCT1 protein was phosphorylated at a serine residue upon stimulation of PKC. In conclusion, it has been demonstrated that the organic cation transport by rOCT1 is stimulated by PKC, PKA, and endogenous tyrosine kinase activation. The PKC phosphorylates rOCT1 and leads to a conformational change at the substrate binding site.

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The conditional stimulation of rat organic cation transporter 2, but not its human ortholog, by mesoridazine: the possibility of the involvement of the high-affinity binding site of the transporter in the stimulation

Journal of Pharmacy and Pharmacology ◽

10.1111/jphp.12799 ◽

2017 ◽

Vol 69 (11) ◽

pp. 1513-1523 ◽

Cited By ~ 2

Author(s):

Sungwoo Hyung ◽

Wonji Pyeon ◽

Ji Eun Park ◽

Yoo-Kyung Song ◽

Suk-Jae Chung

Keyword(s):

Binding Site ◽

Organic Cation ◽

Organic Cation Transporter ◽

Affinity Binding ◽

High Affinity Binding ◽

High Affinity ◽

High Affinity Binding Site ◽

Organic Cation Transporter 2 ◽

Human Ortholog ◽

Stimulation Of

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

International Journal of Molecular Sciences ◽

10.3390/ijms22126439 ◽

2021 ◽

Vol 22 (12) ◽

pp. 6439

Author(s):

Blessy George ◽

Xia Wen ◽

Edgar A. Jaimes ◽

Melanie S. Joy ◽

Lauren M. Aleksunes

Keyword(s):

Organic Cation ◽

Mdck Cells ◽

Organic Cation Transporter ◽

Hek293 Cells ◽

Intracellular Accumulation ◽

Renal Secretion ◽

Transcellular Transport ◽

Antiemetic Drugs ◽

Organic Cation Transporter 2

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.

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