論文 - 米澤　淳

Cisplatin and oxaliplatin, but not carboplatin and nedaplatin, are substrates for human organic cation transporters (SLC22A1-3 and multidrug and toxin extrusion family)

Yonezawa A., Masuda S., Yokoo S., Katsura T., Inui K.

Journal of Pharmacology and Experimental Therapeutics （Journal of Pharmacology and Experimental Therapeutics）  319 （ 2 ） 879 - 886 2006年11月

研究論文（学術雑誌）, 共著, 筆頭著者, 査読有り,  ISSN  00223565

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We have examined the role of the human organic cation transporters [hOCTs and human novel organic cation transporter (hOCTN); SLC22A1-5] and apical multidrug and toxin extrusion (hMATE) in the cellular accumulation and cytotoxicity of platinum agents using the human embryonic kidney (HEK) 293 cells transiently transfected with the transporter cDNAs. Both the cytotoxicity and accumulation of cisplatin were enhanced by the expression of hOCT2 and weakly by hOCT1, and those of oxaliplatin were also enhanced by the expression of hOCT2 and weakly by hOCT3. The hOCT-mediated uptake of tetraethylammonium (TEA) was markedly decreased in the presence of cisplatin in a concentration-dependent manner. However, oxaliplatin showed almost no influence on the TEA uptakes in the HEK293 cells expressing hOCT1, hOCT2, and hOCT3. The hMATE1 and hMATE2-K, but not hOCTN1 and OCTN2, mediated the cellular accumulation of cisplatin and oxaliplatin without a marked release of lactate dehydrogenase. Oxaliplatin, but not cisplatin, markedly decreased the hMATE2-K-mediated TEA uptake. However, the inhibitory effect of cisplatin and oxaliplatin against the hMATE1-mediated TEA uptake was similar. The release of lactate dehydrogenase and the cellular accumulation of carboplatin and nedaplatin were not found in the HEK293 cells transiently expressing these seven organic cation transporters. These results indicate that cisplatin is a relatively good substrate of hOCT1, hOCT2, and hMATE1, and oxaliplatin is of hOCT2, hOCT3, hMATE1, and hMATE2-K. These transporters could play predominant roles in the tissue distribution and anticancer effects and/or adverse effects of platinum agent-based chemotherapy. Copyright © 2006 by The American Society for Pharmacology and Experimental Therapeutics.

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Identification and functional characterization of a new human kidney-specific H⁺/organic cation antiporter, kidney-specific multidrug and toxin extrusion 2

Masuda S., Terada T., Yonezawa A., Tanihara Y., Kishimoto K., Katsura T., Ogawa O., Inui K.

Journal of the American Society of Nephrology （Journal of the American Society of Nephrology）  17 （ 8 ） 2127 - 2135 2006年08月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  10466673

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A cDNA coding a new H+/organic cation antiporter, human kidney-specific multidrug and toxin extrusion 2 (HMATE2-K), has been isolated from the human kidney. The hMATE2-K cDNA had an open reading frame that encodes a 566-amino acid protein, which shows 94, 82, 52, and 52% identity with the hMATE2, hMATE2-B, hMATE1, and rat MATE1, respectively. Reverse transcriptase-PCR revealed that hMATE2-K mRNA but not hMATE2 was expressed predominantly in the kidney, and hMATE2-B was ubiquitously found in all tissues examined except the kidney. The immunohistochemical analyses revealed that the HMATE2-K as well as the hMATE1 was localized at the brush border membranes of the proximal tubules. HEK293 cells that were transiently transfected with the hMATE2-K cDNA but not hMATE2-B exhibited the H+ gradient-dependent antiport of tetraethylammonium (TEA). Transfection of hMATE2-B had no affect on the hMATE2-K-mediated transport of TEA. hMATE2-K also transported cimetidine, 1-methyl-4-phenylpyridinium (MPP), procainamide, metformin, and N 1-methylnicotinamide. Kinetic analyses demonstrated that the Michaelis-Menten constants for the hMATE2-K-mediated transport of TEA, MPP, cimetidine, metformin, and procainamide were 0.83 mM, 93.5 μM, 0.37 mM, 1.05 mM, and 4.10 mM, respectively. Ammonium chloride-induced intracellular acidification significantly stimulated the hMATE2-K-dependent transport of organic cations such as TEA, MPP, procainamide, metformin, N1- methylnicotinamide, creatinine, guanidine, quinidine, quinine, thiamine, and verapamil. These results indicate that hMATE2-K is a new human kidney-specific H+/organic cation antiporter that is responsible for the tubular secretion of cationic drugs across the brush border membranes. Copyright © 2006 by the American Society of Nephrology.

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Up-regulation of nicotinic acetylcholine receptors by central-type acetylcholinesterase inhibitors in rat cortical neurons

Kume T., Sugimoto M., Takada Y., Yamaguchi T., Yonezawa A., Katsuki H., Sugimoto H., Akaike A.

European Journal of Pharmacology （European Journal of Pharmacology）  527 （ 1-3 ） 77 - 85 2005年12月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  00142999

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We previously reported that donepezil, a central-type acetylcholinesterase inhibitor, showed neuroprotective action via α4-and α7-nicotinic acetylcholine receptors against glutamate neurotoxicity in rat cortical culture. The present study was performed to investigate whether the neuroprotective action of acetylcholinesterase inhibitors is accompanied by the alteration of expression and function of nicotinic receptors. Four days treatment with acetylcholinesterase inhibitors (10 μM) enhanced the nicotine-induced increase of the intracellular calcium concentration. Immunoblot analysis revealed that donepezil increased both α4 and α7 subunit proteins. Donepezil and galanthamine increased the number of cells expressing α4- and α7-nicotinic receptors in immunocytochemical analysis. We examined whether up-regulation of nicotinic receptors affected the neuroprotective action of acetylcholinesterase inhibitors. Under up-regulating conditions, donepezil and galanthamine exerted neuroprotective action at lower concentrations. These results suggest that donepezil and galanthamine up-regulate nicotinic receptors in cortical neurons, and that the up-regulation of nicotinic receptors may make cortical neurons more sensitive to the neuroprotective action of donepezil and galanthamine. © 2005 Elsevier B.V. All rights reserved.

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Association between tubular toxicity of cisplatin and expression of organic cation transporter rOCT2 (Slc22a2) in the rat

Yonezawa A., Masuda S., Nishihara K., Yano I., Katsura T., Inui K.

Biochemical Pharmacology （Biochemical Pharmacology）  70 （ 12 ） 1823 - 1831 2005年12月

研究論文（学術雑誌）, 共著, 筆頭著者, 査読有り,  ISSN  00062952

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Cisplatin is an effective anticancer drug, but has its severe adverse effects, especially nephrotoxicity. The molecular mechanism of cisplatin-induced nephrotoxicity is still not clear. In the present study, we examined the role of rat (r)OCT2, an organic cation transporter predominantly expressed in the kidney, in the tubular toxicity of cisplatin. Using HEK293 cells stably expressing rOCT2 (HEK-rOCT2), we evaluated the cisplatin-induced release of lactate dehydrogenase and the uptake of cisplatin. The release of lactate dehydrogenase and the accumulation of platinum were greater in HEK-rOCT2 cells treated with cisplatin than in mock-transfected cells. Moreover, cimetidine and corticosterone, OCT2 inhibitors, inhibited the cytotoxicity and the transport of cisplatin in HEK-rOCT2 cells. Pharmacokinetics of cisplatin was investigated in male and female rats because the renal expression level of rOCT2 was higher in male than female rats. The renal uptake clearance of cisplatin was greater in male than female rats, while the hepatic uptake clearance was similar between the sexes. In addition, glomerular filtration rate and liver function were unchanged, but N-acetyl-β-d-glucosaminidase activity in the bladder urine and the urine volume were markedly increased 2 days after the administration of 2 mg/kg of cisplatin in male rats. Moreover, cisplatin did not induce the elevation of urinary N-acetyl-β-d-glucosaminidase activity in the castrated male rats whose renal rOCT2 level was lower than that of the sham-operated rats. In conclusion, the present results indicated that renal rOCT2 expression was the major determinant of cisplatin-induced tubular toxicity. © 2005 Elsevier Inc. All rights reserved.

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Lansoprazole-Tacrolimus Interaction in Japanese Transplant Recipient with CYP2C19 Polymorphism

Takahashi K., Motohashi H., Yonezawa A., Okuda M., Ito N., Yamamoto S., Ogawa O., Inui K.I.

Annals of Pharmacotherapy （Annals of Pharmacotherapy）  38 （ 5 ） 791 - 794 2004年05月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  10600280

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OBJECTIVE: To report a patient with a high tacrolimus blood concentration after lansoprazole administration and assess the potential interaction between tacrolimus and lansoprazole. CASE SUMMARY: A 34-year-old Japanese man underwent a living-donor kidney transplantation having received tacrolimus, mycophenolate mofetil, and prednisolone for immunosuppression. Lansoprazole was administered from postoperative day 4 as prophylaxis of ulcers. The trough concentration of tacrolimus increased markedly after the introduction of lansoprazole, while results of liver function tests were within normal limits. Lansoprazole was stopped on day 15 and was replaced with famotidine on day 17. The trough concentration of tacrolimus returned to the therapeutic range after administration of lansoprazole ceased. Genetic analysis revealed a heterozygous mutation at exon 5 of the CYP2C19 gene (CYP2C19*1/*2) in this patient. DISCUSSION: Lansoprazole is metabolized by 2 enzymes, CYP2C19 and CYP3A4. Since tacrolimus is also metabolized by CYP3A4, the blood concentration of tacrolimus in this patient who had a CYP2C19 gene mutation may have been elevated by decreased hepatic elimination of lansoprazole. An objective causality assessment revealed that this interaction was probable. CONCLUSIONS: Trough concentrations of tacrolimus should be monitored closely for optimizing the dosage regimen in patients receiving concomitant lansoprazole.

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Nicotinic acetylcholine receptor-mediated neuroprotection by donepezil against glutamate neurotoxicity in rat cortical neurons

Takada Y., Yonezawa A., Kume T., Katsuki H., Kaneko S., Sugimoto H., Akaike A.

Journal of Pharmacology and Experimental Therapeutics （Journal of Pharmacology and Experimental Therapeutics）  306 （ 2 ） 772 - 777 2003年08月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  00223565

　概要を見る

Donepezil is a potent and selective acetylcholinesterase (AChE) inhibitor developed for the treatment of Alzheimer's disease. To elucidate whether donepezil shows neuroprotective action in addition to amelioration of cognitive deficits, we examined the effects of donepezil on glutamate-induced neurotoxicity using primary cultures of rat cortical neurons. A 10-min exposure of cultures to glutamate followed by a 1-h incubation with glutamate-free medium caused a marked loss of viability, as determined by Trypan blue exclusion. Glutamate neurotoxicity was prevented by 24-h pretreatment of donepezil in a concentration-dependent manner. Among AChE inhibitors examined, donepezil and certain AChE inhibitors such as tacrine and galanthamine showed potent neuroprotective action, although physostigmine did not affect glutamate neurotoxicity. Neuroprotective action of donepezil was antagonized by mecamylamine, a nicotinic acetylcholine receptor (nAChR) antagonist, but not by scopolamine, a muscarinic acetylcholine receptor antagonist. Furthermore, both dihydro-β-erythroidine, an α4β2-neuronal nAChR antagonist, and methyllycaconitine, an α7-nAChR antagonist, each also significantly antagonized the effect of donepezil. Next, we examined the effects of donepezil on glutamate-induced apoptosis. Exposure of 100 μM glutamate to cortical neurons for 24 h induced apoptotic neuronal death and nuclear fragmentation. Donepezil for 24 h before and 24 h during glutamate exposure prevented nuclear fragmentation and glutamate-induced apoptosis. These results suggest that donepezil not only protects cortical neurons against glutamate neurotoxicity via α4β2- and α7-nAChRs but also prevents apoptotic neuronal death.

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