Akinobu Hamada

Publications of Akinobu Hamada

• Effects of genetic variants in SLC22A2 organic cation transporter 2 and SLC47A1 multidrug and toxin extrusion 1 transporter on cisplatin-induced adverse events.

  Authors: Kazufumi Iwata, Keiji Aizawa, Saori Kamitsu, Sachiko Jingami, Eiko Fukunaga, Minoru Yoshida, Misato Yoshimura, Akinobu Hamada, Hideyuki Saito

  Clinical and experimental nephrology. 05/2012;

  BACKGROUND: Susceptibility to cisplatin (CDDP) nephrotoxicity is known to vary between individuals, but the basis of this variation has not been fully elucidated. In the kidney, CDDP is taken up intoBACKGROUND: Susceptibility to cisplatin (CDDP) nephrotoxicity is known to vary between individuals, but the basis of this variation has not been fully elucidated. In the kidney, CDDP is taken up into the renal proximal tubular cells mainly via SLC22A2 organic cation transporter 2 (OCT2) and secreted into lumen via other transporters including SLC47A1 multidrug and toxin extrusion 1 (MATE1). Here, we explore the effect of single-nucleotide polymorphisms (SNPs) at 808G>T in OCT2 and at rs2289669 G>A in MATE1 on CDDP-induced adverse events. METHODS: Fifty-three patients who had been treated with CDDP were enrolled. The plasma concentration of CDDP was measured on days 4 and 7 after treatment. The grade of hematology and nephrotoxicity was evaluated by Common Terminology Criteria for Adverse Events. RESULTS: In the first treatment cycle, serum creatinine (SCr) levels in the patients with OCT2 808GG and 808GT were increased by 1.43- and 1.19-fold, respectively. In the total treatment cycles, 12 patients (27 %) with 808GG experienced over grade 2 SCr elevation, whereas those with 808GT did not show any apparent nephrotoxicity. The hematological toxicity and plasma concentrations of CDDP showed no difference between patients in both groups. The rs2289669 G>A SNP in MATE1 was not associated with adverse effects and disposition of CDDP. CONCLUSION: The 808G>T SNP in OCT2 ameliorated CDDP-induced nephrotoxicity without alteration of disposition, whereas the rs2289669 G>A SNP in MATE1 had no effect on CDDP toxicity.

• Association of ABCB1 polymorphisms with erlotinib pharmacokinetics and toxicity in Japanese patients with non-small-cell lung cancer.

  Authors: Akinobu Hamada, Ji-Ichiro Sasaki, Sho Saeki, Norihiro Iwamoto, Megumi Inaba, Sunao Ushijima, Maki Urata, Hiroto Kishi, Shinji Fujii, Hiroshi Semba, Kosuke Kashiwabara, Yukari Tsubata, Yuki Kai, Takeshi Isobe, Hirotsugu Kohrogi, Hideyuki Saito

  Pharmacogenomics. 04/2012; 13(5):615-24.

  Aims: We analyzed the association of ABCB1 polymorphisms with erlotinib-induced toxicity and the pharmacokinetics in patients with non-small-cell lung cancer. Materials & methods: After erlotinib 150Aims: We analyzed the association of ABCB1 polymorphisms with erlotinib-induced toxicity and the pharmacokinetics in patients with non-small-cell lung cancer. Materials & methods: After erlotinib 150 mg was administered to 50 patients, ABCB1 polymorphisms were analyzed via either TaqMan(®) assays or direct nucleotide sequencing. Plasma concentrations were measured by HPLC. Results: The trough concentration at steady state in patients with the ABCB1 1236TT-2677TT-3435TT genotype was higher compared with others groups (p = 0.021) and patients carrying this genotype had a higher risk of developing higher grade 2 toxicity (p = 0.012). Conclusion: The present study suggested that the ABCB1 1236TT-2677TT-3435TT genotype was associated with higher plasma concentration and the risk of developing higher toxicity in patients treated with erlotinib. Original submitted 5 August 2011; Revision submitted 30 November 2011.

• Erlotinib-induced acute interstitial lung disease associated with extreme elevation of the plasma concentration in an elderly non-small-cell lung cancer patient.

  Authors: Yukari Tsubata, Akinobu Hamada, Akihisa Sutani, Takeshi Isobe

  Journal of cancer research and therapeutics. 01/2012; 8(1):154-6.

  We herein describe a case of drug-induced interstitial lung disease (ILD) following treatment with erlotinib. The plasma trough concentration of erlotinib at the time of the ILD diagnosis wasWe herein describe a case of drug-induced interstitial lung disease (ILD) following treatment with erlotinib. The plasma trough concentration of erlotinib at the time of the ILD diagnosis was extremely elevated compared with the plasma maximum concentration on day 1. We hypothesized that this phenomenon was associated with the pharmacodynamic interaction with a concomitant drug. The present case indicates that erlotinib-induced ILD was associated with a high plasma concentration of erlotinib. Oncologists should be aware of the possibility of ILD induced by erlotinib, especially for patients with co-morbidities.

• Genetic polymorphisms in metabolic and cellular transport pathway of methotrexate impact clinical outcome of methotrexate monotherapy in Japanese patients with rheumatoid arthritis.

  Authors: Tomomi Kato, Akinobu Hamada, Shunsuke Mori, Hideyuki Saito

  Drug metabolism and pharmacokinetics. 11/2011;

  The aim of this study was to investigate the impact of genetic polymorphisms in metabolic and cellular transport pathway of methotrexate (MTX) on the clinical outcome of MTX monotherapy in JapaneseThe aim of this study was to investigate the impact of genetic polymorphisms in metabolic and cellular transport pathway of methotrexate (MTX) on the clinical outcome of MTX monotherapy in Japanese rheumatoid arthritis (RA) patients. Fifty-five patients were treated with MTX monotherapy at a dose of 4-10 mg/week. The total concentration of MTX-polyglutamates (MTX-PGs) was measured at steady-state in red blood cells (RBCs) by high performance liquid chromatography. The genotype at 16 polymorphic sites in 11 genes (ABCB1, ABCG2, ABCC2, RFC1, PCFT, SLCO1B1, MTHFR, GGH, ATIC, MTR, MTRR) was analyzed. No significant association between the total concentration of MTX-PGs in RBCs and clinical outcome was found. However, patients with the ABCB1 3435TT genotype had significantly lower mean disease activity score (DAS) 28 than did patients with the ABCB1 3435CC genotype (p = 0.02). Similarly, patients with the ABCB1 2677AA/AT/TT genotypes had significantly lower mean DAS28 than did patients with the ABCB1 2677GG/GA/GT genotypes (p = 0.04). The patients with the MTHFR 1298AA genotype had a significantly lower mean DAS28 than those with the MTHFR 1298AC/CC genotypes (p = 0.04). In conclusion, the ABCB1 3435C>T, ABCB1 2677G>A/T, MTHFR 1298A>C polymorphisms influenced the efficacy of MTX monotherapy.

• Alleviation of cisplatin-induced acute kidney injury using phytochemical polyphenols is accompanied by reduced accumulation of indoxyl sulfate in rats.

  Authors: Masahiro Kusumoto, Hiroki Kamobayashi, Daisuke Sato, Megumi Komori, Misato Yoshimura, Akinobu Hamada, Yukimasa Kohda, Kimio Tomita, Hideyuki Saito

  Clinical and experimental nephrology. 08/2011; 15(6):820-30.

  Polyphenols such as quercetin have been reported to prevent cisplatin-induced acute kidney injury (AKI). Indoxyl sulfate (IS), a uremic toxin generated in the liver, is increased in cisplatin AKI.Polyphenols such as quercetin have been reported to prevent cisplatin-induced acute kidney injury (AKI). Indoxyl sulfate (IS), a uremic toxin generated in the liver, is increased in cisplatin AKI. The present study examined the effect of phytochemical polyphenols on serum and renal accumulations of IS in association with cisplatin AKI. Sprague-Dawley rats were treated with cisplatin (10 mg/kg body weight) by intraperitoneal injection. Polyphenols were orally administered at -24, -1, 24 and 48 h before or after cisplatin injection. Serum levels of IS, cisplatin, serum creatinine (SCr), blood urea nitrogen (BUN) and electrolytes were measured. By using an in vitro assay system with rat liver S9 fraction, the inhibitory potencies of several compounds on IS production were determined. Injection of cisplatin in rats markedly elevated the SCr and BUN levels, which were accompanied by tubular injuries and the expression of kidney injury molecule-1 (Kim-1). By contrast, quercetin significantly suppressed the SCr and BUN levels in the cisplatin-treated rats and protected them against renal injury with the decreased expression of Kim-1. Quercetin had no effect on serum and renal levels of cisplatin. In addition, quercetin had no effect on cisplatin-induced renal accumulation of malondialdehyde. IS concentrations in serum, kidney, liver, intestine and lung were markedly elevated by cisplatin treatment, whereas quercetin suppressed the serum and tissue IS levels. An in vitro kinetic assay revealed that quercetin displayed a potent inhibitory effect on hepatic production of IS. Inhibition of IS accumulation by oral administration of quercetin alleviates cisplatin-induced AKI.

• Association of genetic polymorphisms in the influx transporter SLCO1B3 and the efflux transporter ABCB1 with imatinib pharmacokinetics in patients with chronic myeloid leukemia.

  Authors: Yuji Yamakawa, Akinobu Hamada, Reiko Nakashima, Misato Yuki, Chie Hirayama, Tatsuya Kawaguchi, Hideyuki Saito

  Therapeutic drug monitoring. 02/2011; 33(2):244-50.

  This study explored the association of 14 single nucleotide polymorphisms in three genes coding for influx transporters (SLC22A1, SLCO1B1, and SLCO1B3), two genes coding for efflux transportersThis study explored the association of 14 single nucleotide polymorphisms in three genes coding for influx transporters (SLC22A1, SLCO1B1, and SLCO1B3), two genes coding for efflux transporters (ABCB1 and ABCG2), and four genes coding for enzymes (CYP2C9, CYP2C19, CYP2D6, and CYP3A5) with the pharmacokinetics of imatinib in Japanese patients with chronic myeloid leukemia. Pharmacokinetic parameters were estimated by a population pharmacokinetic analysis based on 622 plasma samples from 34 patients at steady state. Approximately 4.6-fold variability in individual clearance was observed (range, 3.4-15.5 L/hr). The individual estimated clearance was significantly increased in patients with the SLCO1B3 334GG genotype (median value ± standard deviation, 9.5 ± 3.1 L/hr; n = 19) compared with SLCO1B3 334TT and TG genotypes (7.0 ± 3.1 L/hr; n = 15) (P = 0.019). Patients with the ABCB1 3435CC genotype had significantly higher imatinib clearance (12.7 ± 3.0 L/hr; n = 7) compared with patients with ABCB1 3435CT and TT genotypes (7.9 ± 2.7 L/hr; n = 27) (P = 0.035). In conclusion, the present study suggests that single nucleotide polymorphisms of the influx transporter SLCO1B3 and the efflux transporter ABCB1 were functionally associated with individual variability of imatinib pharmacokinetics in Japanese patients with chronic myeloid leukemia.

• Association of SLCO1B3 polymorphism with intracellular accumulation of imatinib in leukocytes in patients with chronic myeloid leukemia.

  Authors: Takeru Nambu, Akinobu Hamada, Reiko Nakashima, Misato Yuki, Tatsuya Kawaguchi, Hiroaki Mitsuya, Hideyuki Saito

  Biological & pharmaceutical bulletin. 01/2011; 34(1):114-9.

  Intracellular concentration of imatinib in leukemic cells is thought to affect the clinical efficacy of this drug in patients with chronic myeloid leukemia (CML); however, there is no report thatIntracellular concentration of imatinib in leukemic cells is thought to affect the clinical efficacy of this drug in patients with chronic myeloid leukemia (CML); however, there is no report that directly indicates the relationship between intracellular concentration and clinical outcome and/or, plasma concentration. In addition, the impacts of genetic variations of drug transporters, which mediate leukocyte concentration of imatinib, are unknown. In the present study, we investigated the correlation between intracellular imatinib concentrations in leukocytes, plasma imatinib levels, and genotypes of drug transporters, including ATP binding cassette B1 (ABCB), ABCG2, solute carrier 22A1 (SLC22A1), solute carrier organic anion transporter family members 1B1 (SLCO1B1) and SLCO1B3. The imatinib levels in leukocytes were determined using HPLC in 15 patients with chronic phase CML. No significant correlation between intracellular and plasma concentrations of imatinib was observed. The intracellular concentration was comparable in both patients with or without complete cytogenetic response. The intracellular imatinib concentration was significantly higher in patients with SLCO1B3 334TT than in those with 334TG/GG (p=0.0188). Plasma concentrations were similar in both SLCO1B3 genotypes (p=0.860), thereby resulting in the intracellular to plasma concentration ratio being higher in patients with SLCO1B3 334TT than those with 334 TG/GG (p=0.0502). These results suggested that the SLCO1B3 334T>G polymorphism could have a significant impact on the intracellular concentration of imatinib in leukocytes as a promising biomarker for personalized treatment of CML patients.

• High-performance liquid chromatographic assay for the determination of nilotinib in human plasma.

  Authors: Misato Yuki, Yuji Yamakawa, Takashi Uchida, Takeru Nambu, Tatsuya Kawaguchi, Akinobu Hamada, Hideyuki Saito

  Biological & pharmaceutical bulletin. 01/2011; 34(7):1126-8.

  A precise and convenient high-performance liquid chromatography (HPLC) method has been established to assay nilotinib in human plasma. Chromatographic separation of nilotinib was performed on aA precise and convenient high-performance liquid chromatography (HPLC) method has been established to assay nilotinib in human plasma. Chromatographic separation of nilotinib was performed on a LiChrosphere(®)100 RP-18(e) column (250 mm×4.0 mm, 5 µm) using a mixture of acetonitrile and 0.01 M phosphate buffer (pH 3.0) (42 : 58, v/v) under isocratic conditions at a flow rate of 1.0 ml/min with ultraviolet (UV) detection at 266 nm. The calibration curve showed linearity at concentrations between 250 ng/ml and 5000 ng/ml (r(2)>0.999). The mean±S.D. absolute recovery of nilotinib from plasma was 99.2±3.3%. The coefficients of variation of both intra- and inter-day precision were below 9.1%. These results indicate that this new HPLC-based quantification may be useful for therapeutic drug monitoring of nilotinib to help manage treatment in patients with chronic myeloid leukemia in clinical practice.

• The relationship between treatment time of gemcitabine and development of hematologic toxicity in cancer patients.

  Authors: Kazufumi Iwata, Keiji Aizawa, Saori Sakai, Sachiko Jingami, Eiko Fukunaga, Minoru Yoshida, Akinobu Hamada, Hideyuki Saito

  Biological & pharmaceutical bulletin. 01/2011; 34(11):1765-8.

  Although gemcitabine is frequently used in the treatment of cancer, it is associated with myelosuppression. An animal study showed that the tolerability of gemcitabine varied with changes inAlthough gemcitabine is frequently used in the treatment of cancer, it is associated with myelosuppression. An animal study showed that the tolerability of gemcitabine varied with changes in treatment time; however, no clinical data have verified this finding. The purpose of this study was to determine the relationship between treatment time and development of hematologic toxicity in patients treated with gemcitabine. Gemcitabine-induced hematologic toxicity was retrospectively investigated in 77 patients. Patients were divided into two treatment-time groups: 9:00 and 15:00. Hematologic toxicity was evaluated on day 8 and 15 after treatment. On day 8 and 15, the changing count of white blood cells was significantly reduced in patients treated at 15:00 compared with those treated at 9:00 (p<0.01 and p<0.05, respectively). On days 8 and 15, the changing count of platelet was significantly reduced in patients treated at 15:00 compared with those treated at 9:00 (p<0.05). The incident of over common terminology criteria for adverse events (CTCAE) grade 2 white blood cell decreased was significantly reduced in patients treated at 15:00 compared with those treated at 9:00 (p=0.048, odds ratio=2.92). In conclusion, this cohort study demonstrated that gemcitabine-induced hematologic toxicity could be alleviated by treating patients at 9:00.

• Prospective evaluation of pharmacokinetically guided dosing of carboplatin in Japanese patients with cancer.

  Authors: Tomoya Shimokata, Yuichi Ando, Yoshinari Yasuda, Akinobu Hamada, Kenji Kawada, Hideyuki Saito, Seiichi Matsuo, Masashi Kondo, Kazuyoshi Imaizumi, Yoshinori Hasegawa

  Cancer science. 12/2010; 101(12):2601-5.

  The Calvert formula, that is, carboplatin dose (mg) = target area under the concentration versus time curve (AUC) × (glomerular filtration rate [GFR] + 25), has not been validated in JapaneseThe Calvert formula, that is, carboplatin dose (mg) = target area under the concentration versus time curve (AUC) × (glomerular filtration rate [GFR] + 25), has not been validated in Japanese subjects in whom the GFR was accurately measured. The purpose of this study is to evaluate the validity of this formula for Japanese patients with cancer and modify it for this population. The GFR was measured on the basis of inulin clearance, which is considered to reflect the accurate GFR. Inulin clearance was measured in 28 patients with cancer. The adjusted 24-h creatinine clearance (24-h Ccr) was unbiased (mean prediction error [MPE] ± SE = -2.3 ± 4.5%) and acceptably precise (root mean squared error = 23.7%) for GFR assessment. The pharmacokinetics of carboplatin were analyzed in 21 patients with a GFR of 17.2-91.4 mL/min. The original Calvert formula overestimated carboplatin clearance, resulting in an MPE of 14.3%. When we revised the Calvert formula for Japanese patients by substituting a non-renal clearance of 15 for 25, that is, dose = target AUC × (GFR + 15), the MPE decreased to -0.1% (P < 0.001). We conclude that the adjusted 24-h Ccr is acceptably precise for GFR assessment, and the non-renal clearance of carboplatin is suggested to be lower in Japanese patients with cancer than in their Western counterparts.

• P-glycoprotein mediates efflux transport of darunavir in human intestinal Caco-2 and ABCB1 gene-transfected renal LLC-PK1 cell lines.

  Authors: Hiromi Fujimoto, Maiko Higuchi, Hiroshi Watanabe, Yasuhiro Koh, Arun K Ghosh, Hiroaki Mitsuya, Naomi Tanoue, Akinobu Hamada, Hideyuki Saito

  Biological & pharmaceutical bulletin. 10/2009; 32(9):1588-93.

  Darunavir (DRV) is a nonpeptidic protease inhibitor (PI) approved for the treatment of human immunodeficiency virus (HIV) infection. DRV displays potent activity against HIV strains resistant toDarunavir (DRV) is a nonpeptidic protease inhibitor (PI) approved for the treatment of human immunodeficiency virus (HIV) infection. DRV displays potent activity against HIV strains resistant to other available PIs. Coadministration with ritonavir (RTV) improves the oral bioavailability of DRV. Inhibition of cytochrome P450 by RTV has been proposed as a mechanism for enhanced DRV bioavailability. However, interaction of these drugs with intestinal transporters has not been elucidated. This study was performed to explore the involvement of P-glycoprotein in transcellular DRV transport in monolayers of human intestinal Caco-2 and in ABCB1 multidrug resistance 1, (MDR1) gene-transfected renal LLC-PK1 (L-MDR1) cell lines. Transepithelial transport of DRV in Caco-2 cell monolayers was 2-fold greater in the basal-to-apical direction compared to that in the opposite direction. RTV had a significant inhibitory effect on the efflux transport of DRV in Caco-2 cells. The apical-to-basal DRV transport was enhanced by P-glycoprotein inhibitors, cyclosporin A and verapamil, as well as multidrug resistance-related protein (MRP/ABCC) inhibitors, probenecid and MK571. Using the L-MDR1 cell line, basal-to-apical DRV transport was much greater than in the opposite direction. Furthermore, cyclosporin A markedly inhibited the basal-to-apical DRV transport. RTV significantly increased the apical-to-basal transport of DRV in L-MDR1 cells, but reduced transport in the opposite direction. DRV inhibited P-glycoprotein-mediated efflux of calcein-acetoxymethyl ester in L-MDR1 cells with the inhibitory potency of 121 microM. These findings suggest that DRV is a substrate of P-glycoprotein and MRP, most likely MRP2. RTV appeared to inhibit P-glycoprotein, thereby enhancing the absorptive transport of DRV.

• Co-administration of irinotecan decreases the plasma concentration of an active metabolite of amrubicin, amrubicinol in rats.

  Authors: Yukiko Maeda, Akinobu Hamada, Emiko Sanematsu, Ji-Ichro Sasaki, Koji Yokoo, Asumi Hira, Hideyuki Saito

  Cancer chemotherapy and pharmacology. 09/2009;

  PURPOSE: This study examined the pharmacokinetics of irinotecan (CPT-11), active metabolite 7-ethyl-10-hydroxycamptothecin (SN-38), SN-38 glucuronide (SN-38G) amrubicin (AMR), and active metabolitePURPOSE: This study examined the pharmacokinetics of irinotecan (CPT-11), active metabolite 7-ethyl-10-hydroxycamptothecin (SN-38), SN-38 glucuronide (SN-38G) amrubicin (AMR), and active metabolite amrubicinol (AMR-OH) after intravenous administration of this combination therapy in rats. METHODS: Male Sprague-Dawley rats were treated with 10 mg/kg CPT-11 with 10 mg/kg AMR. AMR, AMR-OH, CPT-11, SN-38 and SN-38G were measured in plasma, bile, and tissues using high-performance liquid chromatography. RESULTS: Co-administration of CPT-11 resulted in a significant decrease in plasma concentrations and area under the curves (AUC) of AMR-OH compared with treatment with AMR alone. On the other hand, co-administration of AMR resulted in a slight increase in the initial plasma concentration of SN-38; however, there were no differences in AUC values in CPT-11 and SN-38. The cumulative biliary excretion curves of AMR, CPT-11, and their active metabolites were not changed. CPT-11 inhibited the conversion of AMR to AMR-OH in rat cytosolic fractions. CONCLUSIONS: CPT-11 did not affect the pharmacokinetic of AMR but decreased the plasma concentration of AMR-OH and might affect the formation of AMR-OH from AMR in hepatocytes.

• Contribution of BCR-ABL-independent activation of ERK1/2 to acquired imatinib resistance in K562 chronic myeloid leukemia cells.

  Authors: Takeru Nambu, Norie Araki, Aiko Nakagawa, Akihiko Kuniyasu, Tatsuya Kawaguchi, Akinobu Hamada, Hideyuki Saito

  Cancer science. 09/2009;

  BCR-ABL tyrosine kinase, generated from the reciprocal chromosomal translocation t(9;22), causes chronic myeloid leukemia (CML). BCR-ABL is inhibited by imatinib; however, several mechanisms ofBCR-ABL tyrosine kinase, generated from the reciprocal chromosomal translocation t(9;22), causes chronic myeloid leukemia (CML). BCR-ABL is inhibited by imatinib; however, several mechanisms of imatinib resistance have been proposed that account for loss of imatinib efficacy in patients with CML. Previously, we showed that overexpression of the efflux drug transporter P-glycoprotein partially contributed to imatinib resistance in imatinib-resistant K562 CML cells having no BCR-ABL mutations. To explain an additional mechanism of drug resistance, we established a subclone (K562/R) of the cells and examined the BCR-ABL signaling pathway in these and wild-type K562 (K562/W) cells. We found the K562/R cells were 15 times more resistant to imatinib than their wild-type counterparts. In both cell lines, BCR-ABL and its downstream signaling molecules, such as ERK1/2, ERK5, STAT5, and AKT, were phosphorylated in the absence of imatinib. In both cell lines, imatinib effectively reduced the phosphorylation of all the above, except ERK1/2, whose phosphorylation was, interestingly, only inhibited in the wild-type cells. We then observed that phospho-ERK1/2 levels decreased in the presence of siRNA targeting BCR-ABL, again, only in the K562/W cells. However, using an ERK1/2 inhibitor, U0126, we found that we could reduce phospho-ERK1/2 levels in K562/R cells and restore their sensitivity to imatinib. Taken together, we conclude that the BCR-ABL-independent activation of ERK1/2 contributes to imatinib resistance in K562/R cells, and that ERK1/2 could be a target for the treatment of CML patients whose imatinib resistance is due to this mechanism. (Cancer Sci 2009).

• Enhanced renal accumulation of cisplatin via renal organic cation transporter deteriorates acute kidney injury in hypomagnesemic rats.

  Authors: Koji Yokoo, Risa Murakami, Takanobu Matsuzaki, Kanako Yoshitome, Akinobu Hamada, Hideyuki Saito

  Clinical and experimental nephrology. 08/2009;

  BACKGROUND: This study aimed to explore the effects of hypomagnesemia on cisplatin (CDDP)-induced acute kidney injury (AKI) in rats and the relation of hypomagnesemia to the regulation of organicBACKGROUND: This study aimed to explore the effects of hypomagnesemia on cisplatin (CDDP)-induced acute kidney injury (AKI) in rats and the relation of hypomagnesemia to the regulation of organic cation transporters and renal accumulation of CDDP. METHODS: Sprague-Dawley rats were given an Mg-deficient diet starting 7 days before treatment with CDDP. CDDP was administered intravenously to rats in the normal Mg-diet group and Mg-deficient-diet group at 3 mg/kg via the left jugular vein. At the specified periods after injection of CDDP, the amount of platinum in blood and organ samples was determined using inductively coupled plasma-mass spectrometry. Protein expression levels of renal organic cation transporters were determined. Uptake of tetraethylammonium (TEA) bromide in renal slices of rats was measured. RESULTS: Rats fed a Mg-deficient diet showed a significant body weight decrease and a marked decrease in serum Mg levels compared with control rats fed an adequate Mg diet. Serum blood urea nitrogen and creatinine levels were unaltered after CDDP treatment in control rats, whereas these levels were markedly elevated in hypomagnesemic rats. Immunoblotting revealed up-regulation of the organic cation transporter rOCT2 in hypomagnesemic rats before CDDP administration, but not of rOCT1 or rat multidrug and toxin-extrusion 1. TEA uptake by renal slices from hypomagnesemic rats was significantly higher compared with that of control rats. Renal accumulation of CDDP was markedly increased in hypomagnesemic rats. CONCLUSION: These results suggest that hypomagnesemia could cause dehydration and up-regulation of rOCT2, enhancing renal accumulation of CDDP and the deterioration of AKI.

• Effects of Oral Administration of S-1 on the Pharmacokinetics of SN-38, Irinotecan Active Metabolite, in Patients With Advanced Colorectal Cancer.

  Authors: Koji Yokoo, Akinobu Hamada, Kensuke Tazoe, Yutaka Sasaki, Hideyuki Saito

  Therapeutic drug monitoring. 06/2009;

  Previous studies have assessed the efficacy and safety of combined treatment with irinotecan (7-ethyl-10-[4-[1-piperidino]-1-piperidino]carbonyloxycamptothecin, CPT-11) and S-1, containing tegafur, aPrevious studies have assessed the efficacy and safety of combined treatment with irinotecan (7-ethyl-10-[4-[1-piperidino]-1-piperidino]carbonyloxycamptothecin, CPT-11) and S-1, containing tegafur, a prodrug of 5-fluorouracil, in the treatment of colorectal and gastric cancer. The objective of this study was to describe the interaction between CPT-11 and S-1 in 4 patients with colorectal cancer. Coadministration of S-1 changed the pharmacokinetic behavior of CPT-11 and its metabolites. In particular, maximum plasma concentration (Cmax) and area under the plasma concentration curve (AUC) of 7-ethyl-10-hydroxycampothecin (SN-38) was markedly decreased by coadministration of S-1. For SN-38, the median ratio of Cmax and AUC with S-1 to those without S-1 was median 0.34 (range 0.24-0.78) and 0.56 (range 0.23-0.68), respectively. A markedly difference in drug interaction among individual patients was observed. We conclude that the plasma concentration of SN-38 was decreased by oral administration of S-1 in patients with colorectal cancer. This observation might be important for clinical decisions regarding combination therapy.

• Relationship between an effective dose of imatinib, body surface area, and trough drug levels in patients with chronic myeloid leukemia.

  Authors: Tatsuya Kawaguchi, Akinobu Hamada, Chie Hirayama, Reiko Nakashima, Takeru Nambu, Yuji Yamakawa, Hiroshi Watanabe, Kentaro Horikawa, Hiroaki Mitsuya, Hideyuki Saito

  International journal of hematology. 05/2009;

  The standard dose of imatinib for the treatment of chronic-phase chronic myeloid leukemia (CML) is 400 mg/day. Some patients receive reduced doses of imatinib because of serious adverse effects.The standard dose of imatinib for the treatment of chronic-phase chronic myeloid leukemia (CML) is 400 mg/day. Some patients receive reduced doses of imatinib because of serious adverse effects. Recently, the effective plasma threshold for trough imatinib levels was demonstrated to be 1,002 ng/mL. In this study, we evaluated the association of an imatinib dose with trough plasma concentrations and clinical outcomes in 31 patients with chronic-phase CML who were treated at Kumamoto University Hospital. Twenty-seven patients were optimally treated with various doses of imatinib. The mean (+/-SD) trough plasma concentrations of imatinib were 1.40 +/- 0.57 mug/mL in 13 patients receiving 400 mg/day and 1.15 +/- 0.44 mug/mL in 9 patients receiving 300 mg/day as an effective dose. Mean trough levels of the two groups were not significantly different and exceeded the effective plasma threshold. Body surface area (BSA) was significantly smaller in patients receiving the reduced dose compared with those receiving the standard dose (p = 0.001). The effective imatinib dose was associated with age and gender as well as BSA. A reduced dose of 300 mg/day of imatinib may be sufficient for the treatment of CML patients with smaller body size, particularly when intolerability arises.

• Metabolic dysfunction and circadian rhythm abnormalities in adolescents with sleep disturbance.

  Authors: Akemi Tomoda, Junko Kawatani, Takako Joudoi, Akinobu Hamada, Teruhisa Miike

  NeuroImage. 03/2009;

  BACKGROUND: Sleep disturbance attributable to circadian rhythm abnormalities frequently occurs in previously healthy children and adolescents who often complain of gastrointestinal discomfort afterBACKGROUND: Sleep disturbance attributable to circadian rhythm abnormalities frequently occurs in previously healthy children and adolescents who often complain of gastrointestinal discomfort after meals. METHODS: Glucose metabolism, autonomic function, and human clock gene expression in whole blood cells were investigated in 18 adolescent patients with circadian rhythm sleep disorder. RESULTS: Glucose tolerance was significantly lower in the patients than in normal controls: the mean sigma blood glucose level was significantly higher (P<0.05) and the insulinogenic index was significantly lower (P<0.05) in the patient group than in controls. Messenger ribonucleic acid level of hPer2 was significantly higher at 6:00 in the control subjects, but in only 3 of the 18 patients. Component analysis of cardiographic R-R interval revealed that high-frequency component peaks were suppressed significantly in the patient group compared to the controls (P<0.001). CONCLUSIONS: Metabolic and endocrine dysfunctions were identified in adolescents with sleep disturbance as decreased glucose tolerance and absence of human clock gene regulation in whole blood cells. Their brain dysfunction attributable to sleep disturbances might cause such peripheral autonomic imbalance and carbohydrate metabolic dysfunction.

• Regulation of Renal Organic Ion Transporters in Cisplatin-Induced Acute Kidney Injury and Uremia in Rats.

  Authors: Takafumi Morisaki, Takanobu Matsuzaki, Koji Yokoo, Masahiro Kusumoto, Kazufumi Iwata, Akinobu Hamada, Hideyuki Saito

  Pharmaceutical research. 08/2008;

  PURPOSE: The purpose of this study was to examine the regulation of renal organic ion transporters in cisplatin-induced acute kidney injury (AKI) and its relation with indoxyl sulfate (IS), a uremicPURPOSE: The purpose of this study was to examine the regulation of renal organic ion transporters in cisplatin-induced acute kidney injury (AKI) and its relation with indoxyl sulfate (IS), a uremic toxin. METHODS: The IS concentrations in the serum and kidney were monitored by high-performance liquid chromatography. Uptake of p-aminohippuric acid, estrone-3-sulfate and tetraethylammonium were examined using renal slices. Real-time PCR and immunoblotting were performed to examine the mRNA and protein expression of rOATs, rOCTs and rMATE1 in the kidney, respectively. RESULTS: The serum and renal IS levels were markedly elevated in cisplatin-treated rats. However, this effect was largely reversed by administration of AST-120, an oral charcoal adsorbent. The functions of renal basolateral organic anion and cation transporters were reduced in cisplatin-treated rats. The levels of mRNA and protein corresponding to rOAT1, rOAT3, rOCT2 and rMATE1, but not rOCT1, were depressed in the kidney of cisplatin-treated rats. Administration of AST-120 to cisplatin-treated rats partially restored the function and expression level of these transporters. CONCLUSIONS: Cisplatin-induced AKI causes down-regulation of renal organic ion transporters accompanied by accumulation of serum and renal IS. IS could be involved in the mechanism of down-regulation of rOAT1, rOAT3 and rMATE1 under cisplatin-induced AKI.

• Altered pharmacokinetics of cationic drugs caused by down-regulation of renal rat organic cation transporter 2 (Slc22a2) and rat multidrug and toxin extrusion 1 (Slc47a1) in ischemia/reperfusion-induced acute kidney injury.

  Authors: Takanobu Matsuzaki, Takafumi Morisaki, Wakako Sugimoto, Koji Yokoo, Daisuke Sato, Hiroshi Nonoguchi, Kimio Tomita, Tomohiro Terada, Ken-ichi Inui, Akinobu Hamada, Hideyuki Saito

  Drug metabolism and disposition: the biological fate of chemicals. 05/2008; 36(4):649-54.

  In the proximal tubules of rat (r) kidney, the polyspecific organic cation transporters (OCTs), rOCT1 and rOCT2, mediate the baso-lateral uptake of various organic cations, including many drugs,In the proximal tubules of rat (r) kidney, the polyspecific organic cation transporters (OCTs), rOCT1 and rOCT2, mediate the baso-lateral uptake of various organic cations, including many drugs, toxins, and endogenous compounds, and the apical type of H(+)/ organic cation antiporter, rat multidrug and toxin extrusion 1 (rMATE1), mediate the efflux of organic cations. Renal clearances of H(2) receptor antagonists, including famotidine, were reported to be decreased in patients with kidney disease. Therefore, acute kidney injury (AKI) could influence renal excretion and disposition of organic cations accompanied by the regulation of organic cation transporters. The aim of this study was to investigate the pharmacokinetic alteration of cationic drugs and the expression of tubular organic cation transporters, rOCT1, rOCT2, and rMATE1, in ischemia/reperfusion (I/R)-induced AKI rats. I/R-induced AKI increased the plasma concentration of i.v. administrated famotidine, a substrate for rOCT1 and rOCT2, or tetraethylammonium (TEA), a substrate for rOCT1, rOCT2, and rMATE1. The areas under the plasma concentration curves for famotidine and TEA were 2- and 6-fold higher in I/R rats than in sham-operated rats, respectively. The accumulation of TEA into renal slices was significantly decreased, suggesting that organic cation transport activity at the basolateral membranes was reduced in I/R rat kidney. The protein expressions of basolateral rOCT2 and luminal rMATE1 were down-regulated in I/R rat kidneys. These data suggest that the urinary secretion of cationic drugs via epithelial organic cation transporters is decreased in AKI.

• Constitutive overexpression of P-glycoprotein, rather than breast cancer resistance protein or organic cation transporter 1, contributes to acquisition of imatinib-resistance in K562 cells.

  Authors: Chie Hirayama, Hiroshi Watanabe, Reiko Nakashima, Takeru Nanbu, Akinobu Hamada, Akihiko Kuniyasu, Hitoshi Nakayama, Tatsuya Kawaguchi, Hideyuki Saito

  Pharmaceutical research. 05/2008; 25(4):827-35.

  PURPOSE: The purpose of this study was to investigate the contribution of drug transporters in acquired imatinib-resistance. Specifically, we focused on the efflux transporters, P-glycoprotein (P-gp)PURPOSE: The purpose of this study was to investigate the contribution of drug transporters in acquired imatinib-resistance. Specifically, we focused on the efflux transporters, P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP), and an influx transporter, organic cation transporter 1 (OCT1). MATERIALS AND METHODS: We established imatinib-resistant K562 cells (K562/IM). Real-time PCR or Western blot analyses were performed to examine the mRNA or protein levels. Alamar blue method was used in the cytotoxicity assay. The transport activities and intracellular imatinib levels were measured by flow cytometry and HPLC, respectively. RESULTS: K562/IM displayed a 47-fold increase in resistance to imatinib over the parent K562 cells. Both P-gp and BCRP were overexpressed in K562/IM relative to K562. Furthermore, the intracellular imatinib level was markedly reduced in K562/IM. Interestingly, cyclosporin A, a P-gp inhibitor, but not fumitremorgin C, a BCRP inhibitor, restored both imatinib-sensitivity and the intracellular imatinib level. By contrast, no significant difference in the expression and function of OCT1 was observed between K562/IM and K562. CONCLUSIONS: P-gp, rather than BCRP or OCT1, is partially responsible for the development of imatinib-resistance due to constitutive and functional overexpression, leading to reduced intracellular accumulation of imatinib in K562/IM.