Ken Iseki

Publications of Ken Iseki

• Regulation of human monocarboxylate transporter 4 in skeletal muscle cells: The role of protein kinase C (PKC).

  Authors: Katsuya Narumi, Masaki Kobayashi, Sho Otake, Ayako Furugen, Natsuko Takahashi, Jiro Ogura, Shirou Itagaki, Takeshi Hirano, Hiroaki Yamaguchi, Ken Iseki

  International journal of pharmaceutics. 03/2012; 428(1-2):25-32.

  In the present study, to clarify the role of protein kinase C (PKC) in the regulation of monocarboxylate transporter 4 (MCT4) expression, we examined the regulation mechanism of MCT4 expression inIn the present study, to clarify the role of protein kinase C (PKC) in the regulation of monocarboxylate transporter 4 (MCT4) expression, we examined the regulation mechanism of MCT4 expression in human rhabdomyosarcoma (RD) cells, an in vitro skeletal muscle model. Exposure of RD cells to PMA, a PKC activator, for 24h resulted in a two-fold increase in the amount of lactic acid in the growth medium. In parallel to an increase in lactic acid release from RD cells, the level of MCT4 mRNA and protein were also significantly increased in RD cells. A PKC inhibitory study indicated that PMA-induced stimulation of MCT4 expression can be mediated through a novel PKC isoform, especially PKCδ. Moreover, rottlerin, a selective PKCδ inhibitor, decreased PMA-induced MCT4 promoter activity. Deletion and mutational analysis suggested that the potential hypoxia-response elements (HREs) played a major role in the observed modulation of MCT4 expression by PMA. Furthermore, we found that small interfering RNA (siRNA)-mediated knockdown of hypoxia-inducible factor 1α (HIF-1α) significantly inhibited PMA-induced MCT4 promoter activity. Our results show that the effects of PMA on MCT4 expression are mediated through an indirect pathway partially involving PKCδ and HIF-1α transcription factor.

• A rapid and sensitive LC/ESI-MS/MS method for quantitative analysis of docetaxel in human plasma and its application to a pharmacokinetic study.

  Authors: Hiroaki Yamaguchi, Asuka Fujikawa, Hajime Ito, Nobuaki Tanaka, Ayako Furugen, Kazuaki Miyamori, Natsuko Takahashi, Jiro Ogura, Masaki Kobayashi, Takehiro Yamada, Nariyasu Mano, Ken Iseki

  Journal of chromatography. B, Analytical technologies in the biomedical and life sciences. 02/2012; 893-894:157-61.

  Docetaxel is a taxane family antineoplastic agent widely employed in cancer chemotherapy. We developed a liquid chromatography/tandem mass spectrometry method for the determination of docetaxel inDocetaxel is a taxane family antineoplastic agent widely employed in cancer chemotherapy. We developed a liquid chromatography/tandem mass spectrometry method for the determination of docetaxel in human plasma. Plasma samples were deproteinized by acetonitrile containing internal standard paclitaxel. Chromatographic separation was performed on a TSKgel ODS-100V 3μm (50mm×2.0mm i.d.) column using a mobile phase composed of acetonitrile-methanol-water-formic acid (50:5:45:0.1, v/v/v/v). Detection was performed on a triple-quadrupole tandem mass spectrometer with multiple reaction monitoring (MRM) mode via electrospray ionization (ESI) source. This method covered a linearity range of 5-5000ng/mL with the lower limit of quantification of 5ng/mL. The intra-day precision and inter-day precision (R.S.D.) of analysis were less than 6.7%, and the accuracy (R.E.) was within ±9.0% at the concentrations of 5, 20, 200, and 2000ng/mL. The total run time was 5.0min. This method was successfully applied for clinical pharmacokinetic investigation.

• Differential modulation of cytochrome P450 activity and the effect of 1-aminobenzotriazole on hepatic transport in sandwich-cultured human hepatocytes.

  Authors: Emi Kimoto, Robert Walsky, Hui Zhang, Yi-an Bi, Kevin M Whalen, Young-Sun Yang, Collette Linder, Yongling Xiao, Ken Iseki, Katherine S Fenner, Ayman F El-Kattan, Yurong Lai

  Drug metabolism and disposition: the biological fate of chemicals. 02/2012; 40(2):407-11.

  Sandwich-cultured human hepatocytes (SCHH) have been widely used for in vitro assessments of biliary clearance. However, the modulation of metabolism enzymes has not been fully evaluated in thisSandwich-cultured human hepatocytes (SCHH) have been widely used for in vitro assessments of biliary clearance. However, the modulation of metabolism enzymes has not been fully evaluated in this system. The present study was therefore undertaken to determine the activity of cytochrome P450 (P450) 1A2, 2C8, 2C9, 2C19, 2D6, and 3A and to evaluate the impact of 1-aminobenzotriazole (ABT) on hepatic uptake and biliary excretion in SCHH. The SCHH maintained integrity and viability as determined by lactate dehydrogenase release and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium assays conducted over the culture period. Although all assessed P450 activity decreased in day 2 SCHH, the extent of the decrease and the subsequent rebound in activity varied across the different isoforms. Day 5 CYP1A2 activity was approximately 2.5-fold higher than day 1 activity, whereas the CYP3A and CYP2C9 activities were 90 and 60% of the day 1 levels, respectively. In contrast, the initial CYP2C8, CYP2C19, and CYP2D6 activity losses did not rebound over the 5-day culture period. Furthermore, ABT was not found to have an effect, whether directly or indirectly as a P450 inactivator, with respect to the hepatic transport of rosuvastatin, atrovastatin, and midazolam in SCHH. Taken together, these results suggest that the SCHH model is a reliable tool to characterize hepatic uptake and biliary excretion. Due to the differential modulation of P450 activity, SCHH may not be considered a suitable tool for metabolic stability assessments with compounds predominantly cleared by certain P450 enzymes.

• NMDA receptor-mediated Ca(2+) influx triggers nucleocytoplasmic translocation of diacylglycerol kinase ζ under oxygen-glucose deprivation conditions, an in vitro model of ischemia, in rat hippocampal slices.

  Authors: Yusuke Suzuki, Yoshihiko Yamazaki, Yasukazu Hozumi, Masashi Okada, Toshiaki Tanaka, Ken Iseki, Nobuo Ohta, Masaru Aoyagi, Satoshi Fujii, Kaoru Goto

  Histochemistry and cell biology. 01/2012;

  Diacylglycerol kinase (DGK) plays a key role in pathophysiological cellular responses by regulating the levels of a lipid messenger diacylglycerol. Of DGK isozymes, DGKζ localizes to the nucleus inDiacylglycerol kinase (DGK) plays a key role in pathophysiological cellular responses by regulating the levels of a lipid messenger diacylglycerol. Of DGK isozymes, DGKζ localizes to the nucleus in various cells such as neurons. We previously reported that DGKζ translocates from the nucleus to the cytoplasm in hippocampal CA1 pyramidal neurons after 20 min of transient forebrain ischemia. In this study, we examined the underlying mechanism of DGKζ translocation using hippocampal slices exposed to oxygen-glucose deprivation (OGD) to simulate an ischemic model of the brain. DGKζ-immunoreactivity gradually changed from the nucleus to the cytoplasm in CA1 pyramidal neurons after 20 min of OGD and was never detected in the nucleus after reoxygenation. Intriguingly, DGKζ was detected in the nucleus at 10 min OGD whereas the following 60 min reoxygenation induced complete cytoplasmic translocation of DGKζ. Morphometric analysis revealed that DGKζ cytoplasmic translocation correlated with nuclear shrinkage indicative of an early process of neuronal degeneration. The translocation under OGD conditions was blocked by NMDA receptor (NMDAR) inhibitor, and was induced by activation of NMDAR. Chelation of the extracellular Ca(2+) blocked the translocation under OGD conditions. These results show that DGKζ cytoplasmic translocation is triggered by activation of NMDAR with subsequent extracellular Ca(2+) influx. Furthermore, inhibition of PKC activity under OGD conditions led to nuclear retention of DGKζ in about one-third of the neurons, suggesting that PKC activity partially regulates DGKζ cytoplasmic translocation. These findings provide clues to guide further investigation of glutamate excitotoxicity mechanisms in hippocampal neurons.

• Involvement of cholesterol membrane transporter niemann-pick c1-like 1 in the intestinal absorption of lutein.

  Authors: Yuki Sato, Risa Suzuki, Masaki Kobayashi, Shirou Itagaki, Takeshi Hirano, Toshihiro Noda, Satoshi Mizuno, Mitsuru Sugawara, Ken Iseki

  Journal of pharmacy & pharmaceutical sciences : a publication of the Canadian Society for Pharmaceutical Sciences, Société canadienne des sciences pharmaceutiques. 01/2012; 15(2):256-64.

  PURPOSE. Lutein is a carotenoid mainly found in green leafy vegetables and is located in the macula lutea in the human eye. Since humans cannot synthesize lutein de novo, it must be digested as food.PURPOSE. Lutein is a carotenoid mainly found in green leafy vegetables and is located in the macula lutea in the human eye. Since humans cannot synthesize lutein de novo, it must be digested as food. The physiological importance of an orally administered compound depends on its interaction with target tissues. It is therefore important to clarify the absorption mechanism in the intestine. Cholesterol membrane transporters Niemann-Pick C1 Like 1 (NPC1L1) and scavenger receptor class B type 1 (SR-B1) are involved in the intestinal absorption of highly lipophilic compounds including cholesterol. Ezetimibe, a selective inhibitor of intestinal NPC1L1, is the widespread lipid-lowering agent. It is important to investigate the possibility of food-drug interactions in order to prevent undesirable and harmful clinical consequences. The aim of this work was to determine whether NPC1L1, SR-B1 and other transporters are involved in absorption of lutein. METHODS. Caco-2 cells were used for accumulation and permeability study of lutein. Lutein concentration was determined by an HPLC system. The cDNA of transporters was isolated from total RNA of Caco-2 cells, and the expression of these transporters was confirmed by RT-PCR (reverse transcription - polymerase chain reaction). RESULTS. Ezetimibe inhibited up to 40% of lutein accumulation by Caco-2 cell monolayers. Block lipid transport 1 (BLT-1), a selective chemical inhibitor of SR-B1, also inhibited lutein accumulation by Caco-2 cells. On the other hand, ATP-depletion reagents (sodium fluoride and sodium azide or carbonyl cyanide m-chlorophenylhydrazone) did not influence the accumulation or permeation of lutein significantly. CONCLUSIONS. The results show that lutein absorption is, at least in part, mediated by influx transporters NPC1L1 and SR-B1 rather than mediated by efflux transporters such as ABC (ATP-binding cassette) transporters. This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.

• Intestinal Ischemia-Reperfusion Increases Efflux for Uric Acid Via Paracellular Route in the Intestine, but Decreases that Via Transcellular Route Mediated by BCRP.

  Authors: Jiro Ogura, Kaori Kuwayama, Atsushi Takaya, Yusuke Terada, Takashi Tsujimoto, Takahiro Koizumi, Hajime Maruyama, Asuka Fujikawa, Natsuko Takahashi, Masaki Kobayashi, Shirou Itagaki, Takeshi Hirano, Hiroaki Yamaguchi, Ken Iseki

  Journal of pharmacy & pharmaceutical sciences : a publication of the Canadian Society for Pharmaceutical Sciences, Société canadienne des sciences pharmaceutiques. 01/2012; 15(2):295-304.

  Purpose. Uric acid is thought to be one of the most important antioxidants in human biological fluids. Intestinal ischemia-reperfusion (I/R) is an important factor associated with high rates ofPurpose. Uric acid is thought to be one of the most important antioxidants in human biological fluids. Intestinal ischemia-reperfusion (I/R) is an important factor associated with high rates of morbidity and mortality. Reactive oxygen species (ROS) are responsible for intestinal I/R injury. The aim of this study was to clarify the efflux for uric acid from the intestine after intestinal I/R. Methods. We used intestinal ischemia-reperfusion (I/R) model rats. Serosal to mucosal flux for [14C]-uric acid was assessed by using Ussing-type diffusion chambers. BCRP/Bcrp expression was assessed by Western blot analysis. Caco-2 cells were used for a model of the intestinal epithelium, and rotenone was used as a mitochondrial dysfunction inducer. Results. Serosal to mucosal flux for uric acid was increased after intestinal I/R, and that for mannitol was also increased. Ko143, which is a BCRP inhibitor, did not affect the uric acid transport. The decreasing uric acid transport mediated by Bcrp was caused by decrease in the level of Bcrp homodimer, bridged by an S-S bond. The suppression of Bcrp S-S bond formation was associated with mitochondrial dysfunction. Moreover, BCRP S-S bond formation activity was decreased by rotenone in Caco-2 cells. Conclusions. Serosal to mucosal flux for uric acid is significantly increased via the paracelluler route, but that via the transcellular route mediated by Bcrp is decreased after intestinal I/R. The decreasing uric acid flux mediated by Bcrp is caused by suppression of Bcrp S-S bond formation. This suppression of Bcrp S-S bond formation may be related to mitochondrial dysfunction. This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.

• Quantification of intracellular and extracellular prostanoids stimulated by A23187 by liquid chromatography/electrospray ionization tandem mass spectrometry.

  Authors: Ayako Furugen, Hiroaki Yamaguchi, Nobuaki Tanaka, Hajime Ito, Kazuaki Miyamori, Asuka Fujikawa, Natsuko Takahashi, Jiro Ogura, Masaki Kobayashi, Takehiro Yamada, Nariyasu Mano, Ken Iseki

  Journal of chromatography. B, Analytical technologies in the biomedical and life sciences. 09/2011; 879(30):3378-85.

  Prostanoids are bioactive substances that contribute to various biological and pathological processes. To evaluate both extracellular and intracellular levels of prostanoids at the same time, weProstanoids are bioactive substances that contribute to various biological and pathological processes. To evaluate both extracellular and intracellular levels of prostanoids at the same time, we developed methods for quantification of extracellular and intracellular levels of prostanoids, including prostaglandin E(2) (PGE(2)), PGD(2), PGF(2α), 6-keto PGF(1α), and TXB(2), in cultured cells using liquid chromatography/tandem mass spectrometry (LC/MS/MS), and we validated the LC/MS/MS methods. A solid-phase extraction cartridge was used for extraction of prostanoids. The prostanoids were separated by a C(18) column with an isocratic flow of acetonitrile/water/acetic acid (40:60:0.1, v/v/v). Calibration curves of extracellular measurement for the prostanoids were linear in the range from 0.1 to 100 ng/mL (r(2)>0.999), and those of intracellular measurement were linear in the range from 0.05 to 50 ng (r(2)>0.999). Validation assessment showed that both methods of extracellular and intracellular measurements were highly reliable with good accuracy and precision. We also applied the methods to human airway epithelial Calu-3 cells and human lung adenocarcinoma epithelial A549 cells.

• Regulation mechanism of ABCA1 expression by statins in hepatocytes.

  Authors: Masaki Kobayashi, Keisuke Gouda, Ikumi Chisaki, Manami Ochiai, Shirou Itagaki, Ken Iseki

  European journal of pharmacology. 07/2011; 662(1-3):9-14.

  ATP-binding cassette transporter A1 (ABCA1) is predicted to be involved in the control of apolipoprotein AI-mediated cholesterol efflux: biosynthesis of high-density lipoprotein (HDL). However, theATP-binding cassette transporter A1 (ABCA1) is predicted to be involved in the control of apolipoprotein AI-mediated cholesterol efflux: biosynthesis of high-density lipoprotein (HDL). However, the effects of HMG-CoA reductase inhibitors (statins) on ABCA1 in the liver and the precise mechanisms of their actions have been obscure. The aims of this study were to determine whether statins (atorvastatin (Ato) and pitavastatin (Pit)) affect hepatic ABCA1 expression and to clarify the mechanisms of their actions using HepG2 cells and the rat liver. We examined alterations in mRNA and protein levels of ABCA1 and peroxisome proliferator-activated receptors (PPARs) by quantitative real-time polymerase chain reaction (PCR) and Western blot analysis, respectively. In vitro and in vivo studies suggested that Pit increases ABCA1 mRNA level, but not Ato. Pit greatly increased Abca1 mRNA level and also increased the amount of plasma HDL and the mRNA level of PPARα. Clofibrate (PPARα agonist) increased ABCA1 expression in HepG2 cells and rat primary hepatocytes more than did PPAR β/δ and γ agonists. Pit-induced ABCA1 expression alteration was blocked by GW6471 (PPARα antagonist) and by PPARα knockdown. In this study, we demonstrated that Pit affect ABCA1 expression via PPARα in hepatocytes. The strategy to target a PPARα agonist in the liver can lead to increases in ABCA1 expression and HDL level.

• Alteration of P-gp expression after intestinal ischemia-reperfusion following 16-h fasting in rats.

  Authors: Jiro Ogura, Asuka Fujikawa, Hajime Maruyama, Masaki Kobayashi, Shirou Itagaki, Ken Iseki

  Yakugaku zasshi : Journal of the Pharmaceutical Society of Japan. 03/2011; 131(3):453-62.

  Alteration of P-glycoprotein (P-gp) expression influences the pharmacokinetics of P-gp substrates after intestinal ischemia-reperfusion (I/R). Fasting before intestinal I/R affects intestinal I/RAlteration of P-glycoprotein (P-gp) expression influences the pharmacokinetics of P-gp substrates after intestinal ischemia-reperfusion (I/R). Fasting before intestinal I/R affects intestinal I/R injury. However, the effect of fasting on the alteration of P-gp expression after intestinal I/R has not been clarified. We previously reported that P-gp expression was altered after intestinal I/R following feeding. In the present study, we investigated the expression of P-gp after intestinal I/R following 16-h fasting. The mdr1a levels were decreased at 6 h in the jejunum, at 1 h in the ileum, at 6 and 24 h in the liver and at 6 h in the kidney. The mdr1b levels were decreased at 6 h in the ileum and at 1 and 6 h in the kidney. The mdr1b level in the liver was increased at 1 and 6 h. The expression of P-gp was decreased at 6 h in the jejunum, at 1, 6 and 24 h in the ileum, and at 6 h in the kidney. These alterations were different to those after intestinal I/R following feeding. In particular, the decrease in P-gp expression in the 16-h fasting I/R rats occurred at an early time during reperfusion compared with that in the feeding I/R rats. In conclusion, feeding condition affects the alteration of P-gp expression after intestinal I/R. Therefore, it is important to understand the patient's feeding condition for safe drug therapy.

• Pharmacokinetic properties of lutein emulsion after oral administration to rats and effect of food intake on plasma concentration of lutein.

  Authors: Yuki Sato, Masaki Kobayashi, Shirou Itagaki, Takeshi Hirano, Toshihiro Noda, Satoshi Mizuno, Mitsuru Sugawara, Ken Iseki

  Biopharmaceutics & drug disposition. 02/2011; 32(3):151-8.

  Lutein is a carotenoid found mainly in green leafy vegetables and is located in the macula lutea in the human eye. An intake of lutein as food is needed since humans cannot synthesize it de novo.Lutein is a carotenoid found mainly in green leafy vegetables and is located in the macula lutea in the human eye. An intake of lutein as food is needed since humans cannot synthesize it de novo. Although lutein has received much attention recently due to its antioxidant activities, little information about the pharmacokinetic properties of lutein is available. Lutein emulsion formulation was used and the pharmacokinetics of lutein emulsion after oral administration to rats was investigated. The bioavailability of lutein using this formulation was calculated to be 5.20%. It was found that a large amount of lutein was accumulated in the intestinal mucosa. The absorption of orally administered compounds in the intestine can be enhanced by interaction with food or food components. Thus, the effect of food intake on the intestinal absorption of lutein was investigated. The plasma concentration of lutein after oral administration of the emulsion formulation was improved significantly by food intake. It is possible that the absorption of lutein in the intestine is improved significantly by some food components. Bile acids may also play important roles in the intestinal absorption of lutein since the absorption of lipophilic compounds such as cholesterol is related to bile acids. The results of these studies should contribute to an improvement of lutein absorption and provide important information for obtaining more effective pharmacological effects of lutein.

• Multidrug resistance protein 2 implicates anticancer drug-resistance to sorafenib.

  Authors: Yoshihiko Shibayama, Kou Nakano, Hiroshi Maeda, Miyuki Taguchi, Ryuji Ikeda, Mitsuru Sugawara, Ken Iseki, Yasuo Takeda, Katsushi Yamada

  Biological & pharmaceutical bulletin. 01/2011; 34(3):433-5.

  Sorafenib and sunitinib is a small molecule inhibitor of certain receptor tyrosine kinases, and have improved outcomes for patients with advanced renal cell carcinoma. Inhibitory concentration of 50%Sorafenib and sunitinib is a small molecule inhibitor of certain receptor tyrosine kinases, and have improved outcomes for patients with advanced renal cell carcinoma. Inhibitory concentration of 50% cell growth of sorafenib significantly rose to 6.4-fold in a multidrug resistance protein 2 (MRP2) transfected cell line versus control cell line. The concentration of sorafenib was significantly decreased to 74% of control cells after 3 h treatment. In contrast, a tyrosine kinase inhibitor sunitinib did not show alteration of inhibitory concentration of 50% cell growth and accumulation into the cells of MRP2 transfected cells. The present study suggest that sorafenib is a substrate for MRP2, suggesting that MRP2 may implicate drug resistance to sorafenib.

• Effect of 5-fluorouracil treatment on SN-38 absorption from intestine in rats.

  Authors: Yoshihiko Shibayama, Yoshitaka Iwashita, Yoshimi Yoshikawa, Tomoko Kondo, Ryuji Ikeda, Yasuo Takeda, Takayuki Osada, Mitsuru Sugawara, Katsushi Yamada, Ken Iseki

  Biological & pharmaceutical bulletin. 01/2011; 34(9):1418-25.

  5-Fluorouracil (5-FU)-based chemotherapies with irinotecan have been applied for the treatment of cancers, and a common dose-limiting toxicity is neutropenia and diarrhea. In this study, we5-Fluorouracil (5-FU)-based chemotherapies with irinotecan have been applied for the treatment of cancers, and a common dose-limiting toxicity is neutropenia and diarrhea. In this study, we investigated the effect of 5-FU treatment on expression levels of drug transporters for SN-38 transportation and SN-38 absorption from the intestine following 5-FU treatment. Expression levels of several drug transporters and nuclear receptors in rats after 5-FU treatment were evaluated. SN-38 absorption from the intestine was evaluated by SN-38 concentration levels in serum following SN-38 injection into the intestine of 5-FU treated rats. The levels of renal multidrug resistance protein 2 (Mrp2) on day 4 after treatment (400 mg/kg) showed significant upregulation, 359.2 ± 33.2% (mean ± S.E.) of control. Mrp2 levels in the intestine were downregulated to 26.2 ± 8.4% of control. 5-FU treatment (400 mg/kg) also significantly downregurated expression levels of P-glycoprotein (P-gp) and breast cancer resistance protein (Bcrp) to 41.2 ± 14.7%, 15.7 ± 4.3% of control, respectively. To evaluate SN-38 absorption from the intestine, SN-38 was loaded in to the intestine on day 4 after 5-FU treatment. Pretreatment with 5-FU significantly increased SN-38 concentration in the blood 30, 60 and 90 min after SN-38 administration. The area under the curve for SN-38 in the 5-FU group was significantly higher than in vehicle groups. 5-FU treatment decreased expression levels of P-glycoprotein and Bcrp in intestine. The present study suggests that combination chemotherapy of 5-FU with irinotecan (CPT-11) may elevate SN-38 absorption from intestine.

• Protective effect of soy isoflavone genistein on ischemia-reperfusion in the rat small intestine.

  Authors: Yuki Sato, Shirou Itagaki, Setsu Oikawa, Jiro Ogura, Masaki Kobayashi, Takeshi Hirano, Mitsuru Sugawara, Ken Iseki

  Biological & pharmaceutical bulletin. 01/2011; 34(9):1448-54.

  Ischemia-reperfusion (I/R) injury of the intestine is an important factor associated with high rates of morbidity and mortality. Intestinal I/R is a common clinical problem in the settings of severeIschemia-reperfusion (I/R) injury of the intestine is an important factor associated with high rates of morbidity and mortality. Intestinal I/R is a common clinical problem in the settings of severe burns, circulatory shock and strangulation ileus. Intestinal I/R damages remote organs and promotes multi-organ failure. It has been shown that enteral feeding before ischemic insults is beneficial for reducing organ injury and improving survival after intestinal I/R. In that study, the authors used a standard complex enteral diet and they suggested that it is important to find new nutrient formulas. Since reactive oxygen species are responsible for intestinal I/R injury, we focused on a dietary polyphenol, the soy isoflavone genistein. Genistein has a wide spectrum of biochemical and pharmacological activities. However, the possibility of a protective effect of genistein as enteral nutrition on I/R injury has not been investigated. We therefore investigated the protective effect of genistein on oxidative injury using intestinal I/R model rats. We found that genistein, which has combined antioxidant activity from radical scavenging, xanthine oxidase inhibition and chain-breaking effects, exhibits a protective effect on intestinal I/R injury. The results suggest that genistein, a soy isoflavone, has the possibility as a new nutrient formula of enteral feeding.

• AMP-activated protein kinase regulates the expression of monocarboxylate transporter 4 in skeletal muscle.

  Authors: Ayako Furugen, Masaki Kobayashi, Katsuya Narumi, Meguho Watanabe, Sho Otake, Shirou Itagaki, Ken Iseki

  Life sciences. 11/2010; 88(3-4):163-8.

  The aim of this study was to determine the effect of 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR), an AMP-activated protein kinase (AMPK) activator, on monocarboxylate transporter 4The aim of this study was to determine the effect of 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR), an AMP-activated protein kinase (AMPK) activator, on monocarboxylate transporter 4 (MCT4) expression in rat skeletal muscle and a prototypic embryonal rhabdomyosarcoma cell line (RD cells). We examined the alteration in Glucose transporter 4 (GLUT4) and MCT4 mRNA levels by quantitative real-time PCR. Alteration in GLUT4 and MCT4 protein levels was examined by Western blotting. In an in vivo study, AICAR increased MCT4 mRNA and protein levels in a fiber-type specific manner. In an in vitro study, AICAR increased MCT4 mRNA and protein levels. Moreover, AICAR-induced MCT4 expression was blocked by Compound C, an AMPK inhibitor. In this study, we found that AMPK activation induced expression of MCT4 in RD cells and rat skeletal muscle in a fiber-type specific manner. These results indicate the possible involvement of an AMPK-mediated pathway associated with MCT4 expression in skeletal muscle.

• In vitro and in vivo antioxidant properties of chlorogenic acid and caffeic acid.

  Authors: Yuki Sato, Shirou Itagaki, Toshimitsu Kurokawa, Jiro Ogura, Masaki Kobayashi, Takeshi Hirano, Mitsuru Sugawara, Ken Iseki

  International journal of pharmaceutics. 10/2010; 403(1-2):136-8.

  Dietary polyphenols are thought to be beneficial for human health as antioxidants. Coffee beans contain a common polyphenol, chlorogenic acid. Chlorogenic acid is the ester of caffeic acid and quinicDietary polyphenols are thought to be beneficial for human health as antioxidants. Coffee beans contain a common polyphenol, chlorogenic acid. Chlorogenic acid is the ester of caffeic acid and quinic acid. Although these polyphenols have received much attention, there is little evidence indicating a relationship between the effect and the rate of absorption. In this study, we focused on the beneficial effects of chlorogenic acid and caffeic acid, a major metabolite of chlorogenic acid. We carried out in vitro and in vivo experiments. In the in vitro study, caffeic acid had stronger antioxidant activity than that of chlorogenic acid. The uptake of chlorogenic acid by Caco-2 cells was much less than that of caffeic acid. The physiological importance of an orally administered compound depends on its availability for intestinal absorption and subsequent interaction with target tissues. We then used an intestinal ischemia-reperfusion model to evaluate antioxidant activities in vivo. We found that both chlorogenic acid and caffeic acid had effects on intestinal ischemia-reperfusion injury. Since caffeic acid has a stronger antioxidant activity than that of chlorogenic acid and chlorogenic acid is hydrolyzed into caffeic acid in the intestine, it is possible that caffeic acid plays a major role in the protective effect of chlorogenic acid against ischemia-reperfusion injury.

• Pharmacokinetics of oral and intravenous administration of digoxin after intestinal ischemia-reperfusion.

  Authors: Jiro Ogura, Hajime Maruyama, Masaki Kobayashi, Shirou Itagaki, Ken Iseki

  Biological & pharmaceutical bulletin. 01/2010; 33(5):922-5.

  Intestinal ischemia-reperfusion (I/R) causes gut dysfunction characterized by decreased basement membrane integrity and decreased barrier function. Indeed, it has been reported that the absorption ofIntestinal ischemia-reperfusion (I/R) causes gut dysfunction characterized by decreased basement membrane integrity and decreased barrier function. Indeed, it has been reported that the absorption of several drugs is altered after intestinal I/R. Intestinal I/R also promotes multi-organ failure (MOF). The liver and kidney can be affected by MOF after intestinal I/R. However, little is known about the alteration of pharmacokinetics after intravenous administration in intestinal I/R injury. In the present study, we investigated pharmacokinetics of digoxin after oral administration and intravenous administration in intestinal I/R injury. Plasma digoxin concentration in I/R rats after oral administration was not significantly altered at any time compared with that in sham-operated rats. Plasma digoxin concentration in rats reperfused for 1 h after intravenous administration was significantly higher than that in sham-operated rats. Plasma digoxin concentrations in rats reperfused for 6 and 24 h were the same as those in sham-operated rats. The area under the concentration.time curve after intravenous administraion (AUC(i.v.)) and total clearance (CL(tot)) in rats reperfused for 1 h was 1.89- and 0.57-fold higher than that in sham-operated rats. However, elimination rate (k(e)) and half-life (t(1/2)) in rats reperfused for 1 h were not altered. Distribution volume (V(d)) in rats reperfused for 1 h was decreased than that in sham-operated rats, but there was not statistical difference. These results suggest that intestinal I/R affected the V(d) of digoxin, and plasma concentration of digoxin was increased. The present study suggests that understanding pharmacokinetics of drug after intravenous administration in intestinal I/R injury is important to provide valuable information for safe drug therapy for intestinal I/R patients.

• Regulation of monocarboxylate transporter 1 in skeletal muscle cells by intracellular signaling pathways.

  Authors: Katsuya Narumi, Ayako Furugen, Masaki Kobayashi, Sho Otake, Shirou Itagaki, Ken Iseki

  Biological & pharmaceutical bulletin. 01/2010; 33(9):1568-73.

  Skeletal muscle is the major producer of lactic acid in the body, but its oxidative fibers also use lactic acid as a respiratory fuel. Monocarboxylate transporter (MCT) 1 has been suggested to play aSkeletal muscle is the major producer of lactic acid in the body, but its oxidative fibers also use lactic acid as a respiratory fuel. Monocarboxylate transporter (MCT) 1 has been suggested to play a major role in influx of L-lactic acid for oxidation. The regulation mechanism of MCT1 was characterized utilizing rhabdomyosarcoma cells as an in vitro skeletal muscle model. The uptake of L-lactic acid via MCT1 was studied in the presence of various intracellular regulatory pathways, including pathways mediated by protein kinases A, C and G (PKA, PKC and PKG), protein tyrosine kinase (PTK), and Ca2+/calmodulin modulators. The results showed that PKG-, PTK-, and Ca2+/calmodulin-mediated regulatory pathways play no role in the regulation of L-lactic acid uptake, but a role for PKC- and PKA-mediated pathways was apparent. Uptake of L-lactic acid appeared to be stimulated by phorbol 12-myristate 13-acetate (PMA, a PKC activator) via an increase in Vmax of transport processes with no alteration in Km. In parallel, PMA treatment also resulted in an increase in the level of MCT1 expression. On the other hand, exposure to 8-Br-cAMP, a cAMP analog, and to forskolin, an adenylyl cyclase activator, resulted in a significant decrease in L-lactic acid uptake. Additionally, 8-Br-cAMP reduced Vmax but not Km values. Parallel to the decrease in Vmax of L-lactic acid uptake, the level of MCT1 expression was decreased in response to incubation with 8-Br-cAMP. These results indicate the possible involvement of a PKC- and PKA-mediated pathway associated with expression of MCT1 and lactate transport.

• [Approach to alternative therapies in community pharmacy]

  Authors: Toshihiro Noda, Kazuyuki Takaichi, Mineo Nakamura, Hidetaka Karasawa, Yasunori Okamoto, Satoshi Mizuno, Tomohito Kurihara, Toshiaki Makino, Takeshi Hirano, Ken Iseki

  Yakugaku zasshi : Journal of the Pharmaceutical Society of Japan. 12/2009; 129(12):1469-73.

  The growth of the dietary supplement in Japanese market suggests that the patient's need for assistance with self-care will also continue to grow. Patients' burgeoning acceptance and use ofThe growth of the dietary supplement in Japanese market suggests that the patient's need for assistance with self-care will also continue to grow. Patients' burgeoning acceptance and use of alternative therapies is another indication that patients seeking more from the health care system. The questionnaire showed that the most of them are expecting the pharmacists to provide their knowledge of dietary supplements. However, only limited amount of information is available. We founded the group Alterna in 2003, that compose the pharmacists working in community pharmacies accompanied with those in pharmaceutical universities. We have published the journal named "Alterna" that includes the information of dietary supplements, and it attained Vol. 9 in 2008. In the past studies, we evaluated the content and solubility of coenzyme Q10 dietary supplements in Japanese markets, some of which showed poor solubility. In others, we had taken up the information about vitamin and minerals, tea catechins, DHA and EPA, cooking oils to reduce body fat, collagen, etc. Findings in these studies present the opportunities for the pharmacists to provide the significant positive impact on health care outcomes and costs to patients.

• Liver X receptor regulates expression of MRP2 but not that of MDR1 and BCRP in the liver.

  Authors: Ikumi Chisaki, Masaki Kobayashi, Shirou Itagaki, Takeshi Hirano, Ken Iseki

  Biochimica et biophysica acta. 10/2009;

  Liver X receptors (LXRs) belong to the nuclear hormone receptor superfamily. Multidrug resistance-associated protein 2 (MRP2), multidrug resistance 1 (MDR1) and breast cancer resistance proteinLiver X receptors (LXRs) belong to the nuclear hormone receptor superfamily. Multidrug resistance-associated protein 2 (MRP2), multidrug resistance 1 (MDR1) and breast cancer resistance protein (BCRP) play an important role in the efflux of a broad range of endogenous and xenobiotic compounds from hepatocytes. Since the effects of LXR activation on there transporters have been obscure, we investigated the effects of LXR agonists, TO901317 and 25-hydroxychoresterol, on MRP2, MDR1, BCRP expression in HepG2 cells and the rat liver. In an in vitro study, TO901317 increased ABCA1, an LXR target gene, and MRP2 mRNA and protein levels. On the other hand, TO901317 had little effect on MDR1 and BCRP mRNA levels. In an in vivo study, Abca1 and Mrp2 mRNA and protein levels were increased by TO901317, but TO901317 had no effect on Mdr1a and Bcrp mRNA levels in the rat liver. Moreover, TO901317-induced MRP2 mRNA expression was blocked by LXRalpha knockdown. In this study, we demonstrated that LXR activation induced expression of MRP2 but not that of MDR1 and BCRP in hepatocytes. The results suggest that agonists for LXR activate transcription of the MRP2 gene in order to promote excretion of endogenous and xenobiotic compounds from hepatocytes into bile.

• Contribution of organic anion transporting polypeptide OATP2B1 to amiodarone accumulation in lung epithelial cells.

  Authors: Satoru Seki, Masaki Kobayashi, Shirou Itagaki, Takeshi Hirano, Ken Iseki

  Biochimica et biophysica acta. 04/2009;

  The accumulation mechanisms of amiodarone (AMD) involving transporters in lung alveolar epithelial type II cells were studied. The uptake of AMD was examined using human alveolar epithelial-derivedThe accumulation mechanisms of amiodarone (AMD) involving transporters in lung alveolar epithelial type II cells were studied. The uptake of AMD was examined using human alveolar epithelial-derived cell line A549 as a model. AMD was transported by the carrier-mediated system, and the apparent K(m) and V(max) values were 66.8+/-30.3 muM and 49.7+/-9.7 nmol/mg protein/5 min, respectively. The uptake of AMD by A549 cells was Na(+)-independent and was inhibited by substrates of human organic anion transporting polypeptide (OATP). The inhibition profiles were similar to the inhibitory effects of several compounds on OATP2B1-mediated E-3-S transport, and RT-PCR analysis showed mRNA expression of OATP2B1 and 1B3 in A549 cells. SiRNAs targeted to the OATP2B1 gene decreased the OATP2B1 mRNA expression level in A549 cells up to about 50% and reduced the uptake of AMD up to about 40%. These results indicate that AMD uptake mediated by carriers, including OATP2B1, might lead to accumulation of AMD in the lung and AMD-induced pulmonary toxicity (AIPT).