Masaki Kobayashi

Hokkaido University, Sapporo, Hokkaidō, Japan

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Publications (76)183.42 Total impact

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    ABSTRACT: 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-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).
    Biochimica et Biophysica Acta 04/2009; 1788(5):911-7. · 4.66 Impact Factor
  • Rumi Takano, Takeshi Hirano, Chie Nakata, Kumiko Kasashi, Mituru Sugawara, Masaki Kobayashi, Shirou Itagaki, Ken Iseki
    Iryo Yakugaku (Japanese Journal of Pharmaceutical Health Care and Sciences). 01/2009; 35(4):247-253.
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    ABSTRACT: The aim of this study was to elucidate the effects of sex hormones on activity of the ABCG2 promoter in different cell lines. T47D cells and BeWo cells were used as models for ABCG2-expressing cell lines, and luciferase assays using ABCG2 promoter-luciferase constructs were performed. It was shown that progesterone increased the response of the ABCG2 promoter in T47D cells but not in BeWo cells. On the other hand, estradiol had no effect on response of the ABCG2 promoter in either cell line. However, response of the ABCG2 promoter was enhanced by overexpression of ERalpha in both T47D cells and BeWo cells. T47D cells had higher sensitivity to ERalpha than did BeWo cells. Furthermore, it was shown that the inductive effect of progesterone on the ABCG2 promoter was inhibited by addition of RU486 or mithramycin A. Therefore, it was thought that the ABCG2 promoter responded to stimulation of the progesterone receptor (PR)-Sp1 pathway in T47D cells. Furthermore, progesterone suppressed the response of the ABCG2 promoter by changing the expression levels of PR-A and PR-B in BeWo cells. These findings suggested that there are differences between cell lines in the regulation mechanism of ABCG2 expression by sex hormone treatment.
    Molecular Biology Reports 12/2008; 36(7):1889-96. · 1.96 Impact Factor
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    ABSTRACT: The aim of this study was to elucidate the mechanism of folate transport in the placenta over the course of pregnancy. We found that folate receptor alpha (FRalpha) and reduced folate carrier (RFC) localized on the apical side of human placental villi. Since folate binding to placental brush-border membrane vesicles (BBMVs) was strongly inhibited by phosphatidylinositol-specific phospholipase C (PI-PLC) treatment, it is possible that FRalpha, a glycosyl phosphatidylinositol linked glycoprotein, is a candidate for folate uptake from maternal blood to the placenta. Moreover, additional inhibitory effects of thiamine pyrophosphate (TPP) and hemin on folate uptake after PI-PLC treatment suggested that not only FRalpha but also RFC and heme carrier protein 1 (HCP1) are involved in the folate transport mechanism in the human placenta. It was also found that accumulation of folate after intravenous injection increased with the progress of gestation in the rat placenta and the fetus. Furthermore, increases in the expression levels of mRNA of rFRalpha, rRFC, and rHCP1 in the rat placenta during pregnancy were observed. These findings suggest that FRalpha, RFC, and HCP1 are important carriers of folate in the placenta during pregnancy. The results of this study suggest that increases in the expression levels of FRalpha, RFC, and HCP1 in the placenta play an important role in the response to increased need for folate for the placenta and fetus during development with the progress of gestation.
    Bioscience Biotechnology and Biochemistry 10/2008; 72(9):2277-84. · 1.27 Impact Factor
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    ABSTRACT: In clinical trials, patients usually take many kinds of drugs at the same time. Thus, drug-drug interactions can often directly affect the therapeutic safety and efficacy of many drugs. Oral delivery is the most desirable means of drug administration. Changes in the activity of drug transporters may substantially influence the absorption of administered drugs from the intestine. However, there have been a few studies on food-drug interactions involving transporters. It is important to be aware of the potential of food-drug interactions and to act in order to prevent undesirable and harmful clinical consequences. Coenzyme Q10 (CoQ10) is very widely consumed by humans as a food supplement because of its recognition by the public as an important nutrient in supporting human health. Since intestinal efflux transporter P-glycoprotein (P-gp) is one of the major factors in drug-drug interactions, we focused on this transporter. We report here for the first time that CoQ10, which is widely used as a food supplement, affects the transport activity of P-gp.
    Journal of Agricultural and Food Chemistry 08/2008; 56(16):6923-7. · 3.11 Impact Factor
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    ABSTRACT: Amiodarone (AMD)-induced pulmonary toxicity (AIPT) is the most life-threatening side-effect of AMD treatment. N-Monodesethylamiodarone (DEA), an active metabolite of AMD, also exhibits cytotoxicity and tends to accumulate in the lung more intensively than AMD. In this study, we characterized the mechanism of DEA accumulation using A549 cells as a model of the alveolar epithelium. Typical ATP-depletion compounds caused an approximately 30% increase in the accumulation of DEA in A549 cells, although these effects were less than those in Caco-2 cells. Triiodothyronine (T(3)), which exhibited an inhibitory effect on DEA efflux in Caco-2 cells, did not affect the accumulation of DEA in A549 cells. On the other hand, 100 microM AMD caused an approximately 200% increase in DEA content in A549 cells, although AMD accumulation was not affected by 100 microM DEA. Since the reducing effect of AMD on cellular ATP levels and that of FCCP were similar, the mechanism by which DEA accumulation is increased by AMD might be different from the ATP-dependent DEA efflux mechanism. The decrease in cell viability by DEA in the presence of AMD (IC(50) value of DEA for A549 cell viability: 25.4+/-2.4 microM) was more pronounced than that by DEA alone (IC(50) value: 11.5+/-3.0 microM). This further DEA accumulation by AMD might be a factor responsible for the greater accumulation of DEA than that of AMD in the lung in long-term AMD-treated patients.
    Biological & Pharmaceutical Bulletin 08/2008; 31(7):1449-52. · 1.78 Impact Factor
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    ABSTRACT: The present study was carried out in order to identify the changes in expression of multidrug resistance-associated protein (Mrp) 2 and P-glycoprotein (P-gp) in the intestine and remote organs after intestinal ischemia-reperfusion (I/R). Mrp2 expression in the jejunum and liver was decreased at 6 h after I/R. This decrease in Mrp2 expression was associated with an increase in the serum level of IL-6. These results suggest that the decreased Mrp2 expression after intestinal I/R was regulated by IL-6. The expression level of mdr1a in the ileum, which encodes P-gp, was decreased at 6 and 24 h after I/R, and the expression level of mdr1b, also encodes P-gp, was not altered at any time. P-gp protein expression in the ileum was decreased at 6 h after I/R. In the liver, mdr1a expression was decreased at 6 h after I/R, but mdr1b expression was increased at 6 h after I/R. P-gp protein was not altered at any time. In the kidney, mdr1a expression was decreased at 24 h after I/R, but mdr1b expression was not altered at any time. P-gp protein expression in the kidney was decreased at 24 h after I/R, as was mdr1a expression. These results suggest that P-gp expression after intestinal I/R differs in each organ. This is the first report to provide evidence that expression levels of transporters in remote organs are altered intestinal after I/R.
    Life Sciences 07/2008; 82(25-26):1242-8. · 2.30 Impact Factor
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    ABSTRACT: Breast cancer resistance protein (BCRP), the product of the ABCG2 gene, is a recently identified ATP binding cassette half-transporter. BCRP is expressed in a variety of tumor cells and many normal human tissues. In the small intestine, BCRP can limit the influx and facilitate the efflux to prevent intracellular accumulation of BCRP substrates. Ischemia-reperfusion (I/R) induces the release of reactive oxygen species, and organs are severely damaged by I/R. It has been shown that the expression of transporters was altered in the organ after I/R. The present study was undertaken to clarify the expression of BCRP after intestinal I/R. We showed that the expression level of Bcrp was significantly decreased at 1 h after I/R. Bcrp mRNA level was not altered at 1 h after I/R. These results suggest that Bcrp expression was regulated by a post-transcriptional regulation mechanism after intestinal I/R. Bcrp mRNA level was increased at 24 h after I/R, and the expression level of Bcrp protein was of the same level or slightly increased compared with sham operated-rats. Bcrp was slightly located at the intestinal membrane at 24 h after intestinal I/R. These results suggested that Bcrp was not translocated to the intestinal membrane after intestinal I/R. There is little information on post-transcriptional regulation compared with information on transcriptional regulation. In this study, it was shown that Bcrp expression is regulated by post-transcriptional regulation after intestinal I/R. These results of this study may provide important information for further studies aimed at revealing the biological function of Bcrp.
    Biological & Pharmaceutical Bulletin 06/2008; 31(5):1032-5. · 1.78 Impact Factor
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    ABSTRACT: In the present study, we examined the mechanisms underlying the cytotoxicity of pitavastatin, a new statin, and we compared the in vitro potencies of muscle cytotoxicity using a prototypic embryonal rhabdomyosarcoma cell line (RD cells), a typical side effect of statins and compared the cholesterol-lowering effects of statins using Hep G2 hepatoma cells. Pitavastatin reduced the number of viable cells and caused caspase-9 and -3/7 activation in a time- and concentration-dependent manner. The comparison of cytotoxities of statins showed that statins significantly reduced cell viability and markedly enhanced activity of caspase-3/7 in concentration-dependent manner. On the other hand, the effects of hydrophilic statins, pravastatin, rosuvastatin were very weak. The rank order of cytotoxicity was cerivastatin > simvastatin acid> fluvastatin > atorvastatin > lovastatin acid > pitavastatin > rosuvastatin, pravastatin. Statin-induced cytotoxicity is associated with these partition coefficients. On the other hand, the cholesterol-lowering effect of statins did not correlate with these partition coefficients and cytotoxicity. Thus, it is necessary to consider the association between risk of myopathy and cholesterol-lowering effect of a statin for precise use of statins.
    Life Sciences 04/2008; 82(17-18):969-75. · 2.30 Impact Factor
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    ABSTRACT: L-Carnitine plays an important role in lipid metabolism by facilitating the transport of long-chain fatty acids across the mitochondrial inner membrane followed by fatty acid beta-oxidation. It is known that members of the OCTN family play an important role in L-carnitine transport in the placenta. Investigation of drug-drug or drug-nutrient interaction in the placenta is important for establishment of safety drug medication during pregnancy. The aim of this study was to determine the effects of fluoroquinolones, inhibitors of OCTN2, on L-carnitine transport in the placenta which is known to have a high expression level of OCTN2. We investigated the inhibitory effect of five fluoroquinolones, ciprofloxacin (CPFX), gatifloxacin (GFLX), ofloxacin (OFLX), levofloxacin (LVFX) and grepafloxacin (GPFX), on L-carnitine transport mediated by OCTN2 in placental cell line BeWo cells. We found that all of the fluoroquinolones inhibited L-carnitine transport, GPFX being the strongest inhibitor. We also found that the inhibitory effects of LVFX and GPFX depended on their existence ratio of zwitterionic forms as, we reported previously. Furthermore, we elucidated the LVFX transport mechanism in BeWo cells. LVFX was transported actively by transporters. However, we found that LVFX transport was Na+-independent and l-carnitine had no inhibitory effect on LVFX transport, suggesting that LVFX acts as inhibitor of OCTN2, not as a substrate for OCTN2.
    International Journal of Pharmaceutics 04/2008; 351(1-2):113-8. · 3.79 Impact Factor
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    ABSTRACT: Although thalidomide was withdrawn due to teratogenicity and neuropathy, there is now growing clinical interest in this compound because of its immunomodulatory and anti-angiogenic properties. In 1998, thalidomide was approved by the U.S. Food and Drug Administration for the treatment of erythema nodosum leprosum (ENL), an inflammatory complication of Hansen's disease, through a restricted-use program. Thalidomide was approved for the treatment of relapsed or refractory multiple myeloma (MM) as an orphan drug in Japan. Direct deproteinization method was shown to be useful for quantitation of enantioselective thalidomide blood level. Stabilized blood was deproteinized with methanol and 2 M trichloroacetic acid. The supernatant was injected onto reverse-phase column (CHIRALPAK AD-RH). The mobile phase consisted of 10% acetonitrile, 70% methanol and 20% 0.025 m citrate buffer (pH 3.0), and the flow rate was 0.5 ml/min. Wavelength of detection was 220 nm. (-)-(S)-thalidomide and (+)-(R)-thalidomide were separated at 13.5 min and 17.6 min, respectively. The accuracy of this method was almost the same as that of the measurement technique with extraction and concentration. In clinical practice, MM patients usually take many kinds of drugs at the same time. Actually, this patient takes a lot of drugs with thalidomide. However, we found no interference of these drugs and thalidomide on the chromatogram. This simple and reliable HPLC determination method for both enantiomers of thalidomide is thought to be very useful for thalidomide studies.
    Biological & Pharmaceutical Bulletin 04/2008; 31(3):497-500. · 1.78 Impact Factor
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    ABSTRACT: The aim of this study was to elucidate the mechanism of folate transport in the placenta. A study of folate was carried out to determine which carriers transport folates in the human choriocarcinoma cell line BeWo, a model cell line for the placenta. We investigated the effects of buffer pH and various compounds on folate uptake. In the first part of the study, the expression levels of the mRNA of the folate receptor alpha (FRalpha), the reduced folate carrier (RFC), and heme carrier protein 1 (HCP1) were determined in BeWo cells by RT-PCR analysis. Folate uptake into BeWo cells was greater under an acidic buffer condition than under a neutral one. Structure analogs of folates inhibited folate uptake under all buffer pH conditions, but anion drugs (e.g., pravastatin) inhibited folate uptake only under an acidic buffer condition. Although thiamine pyrophosphate (TPP), a substrate of RFC, had no effect on folate uptake, hemin (a weak inhibitor of folate uptake via HCP1) decreased folate uptake to about 80% of the control level under an acidic buffer condition. Furthermore, kinetic analysis showed that hemin inhibited the low-affinity phase of folate uptake under an acidic buffer condition. We conclude that pH-dependent folate uptake in BeWo cells is mediated by at least two carriers. RFC is not involved in folate uptake, but FRalpha (high affinity phase) and HCP1 (low affinity phase) transport folate in BeWo cells.
    Bioscience Biotechnology and Biochemistry 03/2008; 72(2):329-34. · 1.27 Impact Factor
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    ABSTRACT: Various mechanisms can influence the intestinal absorption and oral bioavailability of drugs. The barrier effects of efflux transporters may be one of the critical factors limiting the bioavailability of certain drugs. It has been reported that multidrug resistance-associated protein 2 (Mrp2) is expressed in the mucosal membrane of the epithelium of the small intestine and secretes various drugs into the jejunum lumen. However, it is possible that total intestinal secretion of Mrp2 substrates is accounted for the contribution of Mrp2 and other transporter(s) to the intestinal secretion of Mrp2 substrates. In this study, we found that phenolsulfonphthalein and pravastatin, both Mrp2 substrates, are transported by different transport systems in the intestine. These results suggest that contribution of transporters to the drug transport may be a critical factor affecting drug disposition and drug-drug interaction. In addition to evaluating the substrate specificity of a transporter, it is important to be aware of the contribution of a transporter to drug disposition.
    Biological & Pharmaceutical Bulletin 02/2008; 31(1):146-8. · 1.78 Impact Factor
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    ABSTRACT: It has been reported that the transport function for organic anions on the kidney is maintained in multidrug resistance-associated protein 2 (Mrp2)-deficient rats. Different from Mrp2-deficient rats, Long-Evans Cinnamon (LEC) rats have impaired urinary excretion of Mrp2-substrate, phenolsulfonphthalein (PSP). PSP is transported by the potential-sensitive urate transport system in rat brush-border membranes. We analyzed the function of PSP transport system in LEC rats. Unlike Long-Evans Agouti (LEA) rats, the initial uptake of PSP and urate into the renal brush-border membrane vesicles of LEC rats were not significantly enhanced in the presence of positive intravesicular potential, suggesting that the potential-sensitive urate transport system is impaired in LEC rats. LEC rats should be useful for elucidating the potential-sensitive urate transport system in rats at the molecular level.
    Biochimica et Biophysica Acta 02/2008; 1778(1):270-5. · 4.66 Impact Factor
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    ABSTRACT: The aim of this study was to evaluate the bicarbonate-induced improvement of statins, cerivastatin, simvastatin acid and lovastatin acid -induced apoptosis using rat myoblast cell line (L6) as a model of in vitro skeletal muscle and of cerivastatin-induced muscle damage in vivo study. Statin-induced reduction of cell viability and apoptosis was measured by 3-(4,5-dimethylthiazol-2-yl)2,5-diphenyl tetrazolium bromide (MTT) assay and caspase assay. In vivo, we evaluated plasma creatine phosphokinase (CPK) level in cerivastatin-treated rat. Bicarbonate prevented cerivastatin-, simvastatin- acid and lovastatin acid -induced reduction of cell viability, morphological change and caspase activation in L6 cells. Moreover, in the in vivo study, bicarbonate prevented cerivastatin-induced increase in CPK concentrations. These results from in vitro and in vivo studies support that bicarbonate supplementation prevented statin-induced muscle damage.
    Journal of Pharmacy and Pharmaceutical Sciences 02/2008; 11(1):1-8. · 1.68 Impact Factor
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    ABSTRACT: Wilson's disease is an inherited, autosomal recessive disorder of copper accumulation and toxicity. Lifelong chelation therapy is essential in all Wilson's disease patients. Intestinal absorption of some compounds is limited partly because they are preferentially transported in the secretory direction. Several ATP-binding cassette (ABC) transporters are expressed in the apical membrane of the small intestine and secrete various drugs into the lumen. In this study, we investigated the characteristics of the intestinal efflux ABC transporters in LEC rats. We found that the expression of multidrug resistance-associated protein 2 (Mrp2) in the jejunum of Long-Evans Cinnamon (LEC) rats, an animal model for Wilson's disease, is decreased.
    Drug Metabolism and Pharmacokinetics 01/2008; 22(6):450-5. · 2.86 Impact Factor
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    ABSTRACT: The liver plays important roles in the detoxification of xenobiotics. Hepatobiliary transporters contribute to hepatic uptake and efflux processes of xenobiotecs. Expressions of these transporters may be modulated under the condition of hepatic failure. Long-Evans Cinnamon (LEC) rats provide a pertinent model for basic and clinical studies on hepatitis. However, only a few reports describing the properties of hepatobiliary transporters in LEC rats have appeared in the literature. We investigated the expression levels of hepatobiliary transporters in LEC rats by real-time RT-PCR. We found that hepatic expressions of three sinusoidal organic anion transporters, Ntcp, Oatp1a1 and Oatp1a4, were decreased in LEC rats. However, no significant difference of the expressions of Mrp2 and Bsep, organic anion transporters located on canalicular membrane, were found between Wistar rats and LEC rats.
    Drug Metabolism and Pharmacokinetics 11/2007; 22(5):387-90. · 2.86 Impact Factor
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    ABSTRACT: Coenzyme Q10 (CoQ10) is widely consumed as a food supplement because of its recognition as an important nutrient in supporting human health. Absorption of compounds from the gastrointestinal tract is one of the important determinants of oral bioavailability. However, the absorption of dietary CoQ10 is slow and limited due to its hydrophobicity and large molecular weight. The absorption of orally applied compounds can be enhanced by interactions with food or food components. Thus, we investigated the effect of food intake on the absorption of CoQ10 after oral supplementation. In this study, we demonstrated that food intake enhanced the intestinal absorption of CoQ10. In order to improve intestinal absorption of CoQ10 after oral supplementation, we developed an emulsion formulation. Intestinal absorption of CoQ10 after administration of the emulsion formulation was also enhanced by food intake. Moreover, the peak concentration and the extent of absorption after administration of the emulsion formulation were greater than those after administration of a suspension formulation. It is possible that administration of CoQ10 in an emulsion formulation enhances the pharmacological effects of CoQ10.
    Yakugaku zasshi journal of the Pharmaceutical Society of Japan 09/2007; 127(8):1251-4. · 0.31 Impact Factor
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    ABSTRACT: Amiodarone (AMD) is a benzofurane derivative with class III antiarrhythmic activity that is effective in controlling intractable cardiac arrhythmias. One of the most common and serious drug interactions in clinical practice is the interaction between digoxin and an antiarrhythmic agent. It has been reported that AMD and N-monodesethylamiodarone (DEA), the active metabolite of AMD, inhibit the P-glycoprotein (P-gp/MDR1)-mediated digoxin transport. However, the intestinal transport processes of AMD and DEA have not been fully revealed. In this study, we focused on the intestinal transport mechanism of DEA and characterized the intestinal transport of DEA using Caco-2 cells. Basal-to-apical transport of DEA by Caco-2 cells was greater than apical-to-basal transport. The relationship between concentration and basal-to-apical flux rate appeared to approach saturation. The uptake of DEA by Caco-2 cells was increased in the presence of typical ATP-depletion compounds and thyroid hormones. On the other hand, substrates for P-gp, multidrug resistance-associated proteins (MRPs/ABCCs) and breast cancer resistance protein (BCRP/ABCG2) had no effect on the efflux of DEA. These results suggest that an ATP-binding cassette (ABC) transporter, which is different from P-gp, MRPs and BCRP, mediates the efflux of DEA across the apical membrane in Caco-2 cells and that thyroid hormone inhibits this transporter.
    Drug Metabolism and Pharmacokinetics 09/2007; 22(4):307-12. · 2.86 Impact Factor
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    ABSTRACT: Although HMG-CoA reductase inhibitors such as statins are the most widely used cholesterol-lowering agents, there is a risk of myopathy or rhabdmyolysis occurring in patients taking these drugs. It has been reported that a number of lipophilic statins cause apoptosis in various cells, but it is still not clear whether intracellular acidification is involved in statin-induced apoptosis. There have been few studies aimed at identifying compounds that suppress statin-induced myotoxicity. In the present study, we examined the relationship between cerivastatin-induced apoptosis and intracellular acidification and the effect of bicarbonate on cerivastatin-induced apoptosis using an RD cell line as a model of in vitro skeletal muscle. Cerivastatin reduced the number of viable cells and caused dramatic morphological changes and DNA fragmentation in a concentration-dependent manner. Moreover, cerivastatin-induced apoptosis was associated with intracellular acidification and caspase-9 and -3/7 activation. On the other hand, bicarbonate suppressed cerivastatin-induced pH alteration, caspase activation, morphological change and reduction of cell viability. Accordingly, bicarbonate suppressed statin-induced apoptosis. The strategy to combine statins with bicarbonate can lead to reduction in the chance of the severe adverse events including myopathy or rhabdmyolysis.
    International Journal of Pharmaceutics 09/2007; 341(1-2):181-8. · 3.79 Impact Factor

Publication Stats

462 Citations
183.42 Total Impact Points


  • 2004–2014
    • Hokkaido University
      • • Laboratory of Clinical Pharmaceutics and Therapeutics
      • • Faculty of Pharmaceutical Sciences
      • • Graduate School of Pharmaceutical Sciences
      Sapporo, Hokkaidō, Japan