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Yoshinao Kobayashi

Publications and source records attributed to Yoshinao Kobayashi.

At least 19 recordsLinked to original sources

Physicochemical and pharmacokinetic characterization of highly potent recombinant L-methionine gamma-lyase conjugated with polyethylene glycol as an antitumor agent.

A highly potent recombinant L-methionine gamma-lyase (METase) conjugated with polyethylene glycol (PEG) was characterized physicochemically and pharmacokinetically in vivo and in vitro. Pegylated METase (PEG-METase), which contains pyridoxal 5'-phosphate (PLP) as a cofactor in the molecule, is a potent anticancer agent that can deplete L-methionine from plasma. Although pegylation decreased its specific activity, dithiothreitol (DTT) treatment increased it over three times with the detachment of one PEG moiety modified with a cysteine residue. We can produce DTT-treated PEG-METase on a large scale in sufficient quality for therapeutic use. The superiority of DTT-treated PEG-METase was confirmed by the enhancement of L-methionine depletion and amelioration of pharmacokinetics in mice. The holoenzyme of DTT-treated PEG-METase gave a several times larger area under the plasma concentration curve than that of DTT-untreated PEG-METase, not because of an increase of the half-life but because of high specific activity. Conversely, simultaneous PLP infusion led to a greatly increased half-life of the holoenzyme. DTT-treated PEG-METase administration with PLP infusion was the most useful combination for maximizing the potency of the enzyme. We showed that serum albumin interfered with holoenzyme activity in vitro. The decrease of holoenzyme activity was dependent on the type of serum albumin. We concluded that PLP was released from PEG-METase by serum albumin in vivo and in vitro. The deleterious effect of PLP dissociation from PEG-METase could be improved by supplementing PLP and oleic acid. Their synergistic effect in preventing a decrease of the holoenzyme activity was also observed.

Animals↗

Role of transferrin receptor 2 in hepatic accumulation of iron in patients with chronic hepatitis C.

BACKGROUND AND AIM: Iron deposition in the liver is a common finding in patients with chronic hepatitis C (CH-C). The mechanism of this hepatic accumulation of iron is not completely understood. This study assessed if the protein expression of transferrin receptor 2 (TfR2) is upregulated in the liver of patients with CH-C and if TfR2 protein mediates iron accumulation during hepatitis C virus (HCV) infection. METHOD: Liver specimens from patients with CH-C that underwent interferon (IFN) therapy (n=23) and from patients with CH-B (n=18) were evaluated. Hepatic expression of TfR2 protein was analyzed by immunohistochemistry. Total hepatic iron score (THIS) was evaluated by Prussian blue staining. RESULTS: TfR2 protein was expressed in the cell membrane and cytosol of hepatocytes. Cytosol TfR2 protein was found to co-localize with Tf. THIS (P=0.0198) and hepatic TfR2 (P=0.0047) expression were significantly higher in CH-C than in CH-B. The change in THIS values (rho=0.580, P=0.0079) and the grade of histological activity (rho=0.444, P=0.0373) were significantly correlated with changes in TfR2 expression after IFN therapy. CONCLUSIONS: The protein expression of TfR2 is significantly associated with iron deposition in the liver in patients with CH-C. HCV infection may affect the hepatic expression of TfR2, leading to iron accumulation in the liver.

Adult↗

Improvement of regional cerebral blood flow after oral intake of branched-chain amino acids in patients with cirrhosis.

AIM: To evaluate the effect of oral intake of branched-chain amino acids (BCAA) on brain perfusion in patients with liver cirrhosis. METHODS: Single photon emission computed tomography scans were performed in 43 patients with cirrhosis and in 15 age-matched healthy subjects. Twenty-nine out of forty-three patients were randomly treated with either BCAA granules or placebo, and single photon emission computed tomography was performed before and after the treatment. We measured the regional cerebral blood flow values using a three-dimensional stereotaxic region of interest template. RESULTS: Cirrhotic patients had regions of significant hypoperfusion in the bilateral central (right P=0.039, P<0.05; left P=0.006 P<0.01), parietal (right P=0.018, P<0.05; left P=0.009, P<0.01), angular (right P=0.039, P<0.05; left P 0.008, P<0.01), and left pericallosal segments (P=0.038 P<0.05) as compared with healthy subjects. A significant increase in cerebral perfusion was observed 70 min after the oral intake of BCAA in the angular (right P=0.012, P<0.05; left P=0.049, P<0.05), temporal (right P=0.012, P<0.05; left P=0.038, P<0.05), pericallosal segments (right P=0.025, P<0.05; left P=0.049, P<0.05) and left precentral (P=0.044, P<0.05), parietal (P=0.040, P<0.05) and thalamus (P=0.033, P<0.05). No significant change in perfusion was observed in the placebo group. CONCLUSION: Administration of BCAA rapidly improves cerebral perfusion.

Administration, Oral↗

Polymorphism of UDP-glucuronosyltransferase 1A7 gene: a possible new risk factor for lung cancer.

UDP-glucuronosyltransferase (UGT) 1A7 detoxifies hydroxylated benzo-(alpha)-pyrenes and 2-hydroxyamino-1-methyl-6-phenylimidazo (4,5-beta) pyridine. The purpose of this study was to evaluate whether UGT1A7 polymorphisms are risk factors for lung cancer. A total of 113 Japanese patients with lung cancer and 178 healthy individuals were enrolled in this study. Genomic DNA was isolated from leukocytes. Exon 1 of UGT1A7 was sequenced. Homozygous UGT1A7*3/3 was observed in 17 (15%) of patients with lung cancer, and this incidence was significantly increased compared with the control group (4.5%, P=0.0036). Multivariate logistic regression analysis demonstrated a significant association of lung cancer with Brinkmann index (odds ratio=4.577, P=0.0004) and homozygous UGT1A7*3 (odds ratio=4.020, P=0.0037). The presence of UGT1A7 polymorphisms was associated with lung cancer. Homozygous UGT1A7*3 is a possible risk factor for lung cancer, at least in the Japanese population. Thus, determination of UGT1A7 polymorphisms may provide an important clue to preventive measures against lung cancer.

Adult↗

Accumulation of 8-nitroguanine in the liver of patients with chronic hepatitis C.

BACKGROUND/AIMS: Nucleic acid damage by reactive nitrogen and oxygen species may contribute to inflammation-related carcinogenesis. To investigate the extent of nucleic acid damage in hepatitis C virus infection and its change after interferon treatment, we measured 8-nitroguanine and 8-hydroxy-2'-deoxyguanosine (8-OHdG) in the liver of patients with chronic hepatitis C (CHC) before and after interferon therapy. METHODS: Hepatic accumulation of 8-nitroguanine and 8-OHdG was immunohistochemically evaluated in 20 CHC patients and 7 control patients with non-alcoholic fatty liver. RESULTS: Immunoreactivities of 8-nitroguanine and 8-OHdG were strongly detected in the liver from patients with CHC, but not in control livers. 8-Nitroguanine accumulation was found not only in infiltrating inflammatory cells, but also hepatocytes particularly in the periportal area. The accumulation of 8-nitroguanine and 8-OHdG increased with inflammatory grade (8-nitroguanine; P = 0.0019, 8-OHdG; P = 0.0009). In the sustained virological responder group after interferon therapy, 8-nitroguanine and 8-OHdG accumulation were markedly decreased in the liver (8-nitroguanine; P = 0.018, 8-OHdG; P = 0.018). CONCLUSIONS: In this study, we demonstrated for the first time that 8-nitroguanine accumulated in the liver of patients with CHC. 8-Nitroguanine is a useful biomarker to evaluate the severity of HCV-induced chronic inflammation in relation to hepatocellular carcinoma.

8-Hydroxy-2'-Deoxyguanosine↗

Upregulation of transferrin receptor 2 and ferroportin 1 mRNA in the liver of patients with chronic hepatitis C.

BACKGROUND: Iron accumulation has been reported to be associated with progression of liver injury. The mechanism of iron accumulation in the liver is not known. In the present study, hepatic messenger RNA (mRNA) expression of transferrin receptor (TfR)1, TfR2, and ferroportin (FP)1 was measured in patients with chronic hepatitis (CH). METHODS: Eleven patients with CH-B and 43 patients with CH-C were enrolled. All patients underwent liver biopsy. Hepatic expression of TfR1, TfR2 and FP1 mRNA was analyzed using a real-time polymerase chain reaction. Total hepatic iron score (THIS) was evaluated by Prussian blue staining. RESULTS: Serum ferritin concentration is significantly higher in CH-C than in CH-B. Values of THIS of >/=5 were observed only in CH-C patients (44% of CH-C patients). The expression level of TfR2 mRNA was 10-26-fold higher than the TfR1 mRNA expression level. The TfR2 and FP1 mRNA expression was significantly higher in CH-C than in CH-B patients. Hepatic expression of TfR2 and FP1 mRNA was well correlated with THIS. CONCLUSIONS: Hepatic iron accumulation is more severe in patients with CH-C. Upregulation of hepatic iron transporters may contribute to the hepatic iron accumulation in CH-C.

Adult↗

Transfecting the multidrug resistance protein 2 gene improves transcellular organic anion transport.

Eisai hyperbilirubinuria rats (EHBRs) lack functionally active multidrug resistance protein 2 (Mrp2), which causes impaired biliary excretion of numerous organic anions. We previously reported that Mrp3 expression is enhanced while organic anion transporting polypeptide 1 (Oatp1) or Oatp2 expression is reduced in the liver of EHBRs. Mrp3 mediates basolateral efflux of organic anions but not canalicular export. In this study, we transfected the human MRP2 gene into the liver of EHBRs and evaluated whether its transfection improves transcellular transport of organic anions in hepatocytes of EHBRs. The protein expression vector (pDEST26) including the full-length human MRP2 cDNA was developed. This vector was mixed with the hemagglutinating virus of Japan (HJV) envelope protein and transfected into the liver of EHBRs via the portal vein. Expression of Mrp3, Oatp1 and Oatp2 was evaluated by reverse transcription-polymerase chain reaction and Western blot analysis. mRNA and protein expression of MRP2 were detected in hepatocytes from transfected EHBRs. The serum-conjugated bilirubin level in EHBRs decreased to a normal level (35.7 to 6.4 micromol/l) with the expression of human MRP2. The change in expression of Mrp3, Oatp1 and Oatp2 in the liver of EHBRs was normalized by transfecting MRP2. Transfection of human MRP2 was performed using the HJV envelope protein. Transfection of MRP2 is useful for improving the transcellular transport of organic anions in the livers of EHBRs.

ATP Binding Cassette Transporter, Subfamily B↗

PEGylation confers greatly extended half-life and attenuated immunogenicity to recombinant methioninase in primates.

Methionine depletion by recombinant methioninase (rMETase) has been demonstrated previously to be highly effective in tumor-bearing mouse models. However, the therapeutic potential of rMETase has been limited by its short plasma half-life and immunologic effects, including high antibody production in mice and monkeys and anaphylactic reactions in monkeys. To overcome these limits of rMETase, the enzyme has been coupled to methoxypolyethylene glycol succinimidyl glutarate (MEGC-PEG-5000). In this study, we evaluated the pharmacokinetics, antigenicity and toxicity of MEGC-PEG-rMETase in Macaca fascicularis monkeys using an escalating-dose strategy. Dose ranging studies at 1,000, 4,000, and 8,000 units/kg i.v. determined that a single dose of 4,000 units/kg was sufficient to reduce plasma methionine to <5 micromol/L for 12 hours. Pharmacokinetic analysis with the single 4,000 units/kg dose showed that MEGC-PEG-rMETase holoenzyme activity was eliminated with a biological half-life of 1.3 hours, and the MEGC-PEG-rMETase apoenzyme was eliminated with a biological half-life of 90 hours, an approximately 36-fold increase compared with non-PEGylated rMETase. A single dose at 2,000 units/kg of MEGC-PEG-rMETase resulted in an apoenzyme half-life of 143 hours. A seven-day i.v. administration of 4,000 units/kg every 12 hours resulted in a steady-state depletion of plasma methionine to <5 micromol/L. The only manifest toxicity was decreased food intake and slight weight loss. Red cell values and hemoglobin declined transiently during treatment but recovered after cessation of treatment. Subsequent challenges on days 29, 50 and, 71 did not result in any immunologic reactions. This result is in contrast to non-PEGylated rMETase, which elicited anaphylactic reactions in monkeys. Anti-MEGC-PEG-rMETase antibodies (at 10(-2)) were found on day 29, and these increased to 10(-3) to 10(4) on day 71, 100 to 1,000-fold less than antibodies elicited by naked rMETase. Although anti-MEGC-PEG-rMETase antibodies were produced, no neutralizing antibody was identified, and each challenge dose was effective in depleting plasma methionine levels. The results of the present study demonstrate that PEGylation greatly prolongs serum half-life of the rMETase apoenzyme and eliminated anaphylactic reactions. The results indicate a profile with respect to serum half-life, toxicity, and antigenicity that suggest clinical potential of MEGC-PEG-rMETase.

Animals↗

Circulating half-life of PEGylated recombinant methioninase holoenzyme is highly dose dependent on cofactor pyridoxal-5'-phosphate.

Recombinant methioninase (rMETase) has been shown to target the elevated methionine (MET) dependence of tumor cells and arrest their growth as well as make tumors more sensitive to standard chemotherapy agents. Polyethylene glycol (PEG)-modified rMETase (PEG-rMETase) has reduced antigenicity compared with unmodified rMETase. However, PEG-rMETase has a limited active circulating half-life due to rapid in vivo dissociation of its cofactor pyridoxal-5'-phosphate (PLP), a surprising finding, because PLP is tightly bound to PEG-rMETase in buffer. The question asked in the current study was on the effect of increasing doses of PLP to extend the circulating half-life of active PEG-rMETase holoenzyme in vivo. rMETase was conjugated with methoxypolyethylene glycol succinimidyl glutarate 5000 (MEGC-PEG). Miniosmotic pumps containing various concentrations of PLP were implanted in BALB-C mice. PLP-infused mice were then injected with a single dose of 4000 or 8000 units/kg PEG-rMETase. Mice infused with 5, 50, 100, 200, and 500 mg/ml PLP-containing miniosmotic pumps increased plasma PLP to 7, 24, 34, 60, and 95 microm, respectively, from the PLP baseline of 0.3 microm. PLP increased the half-life of MEGC-PEG-rMETase holoenzyme in a dose-dependent manner. Pumps containing 500 mg/ml PLP increased the half-life of MEGC-PEG-rMETase holoenzyme 4.5-fold from 1.5 to 7 h. Infused PLP did not extend the half-life of MEGC-PEG-rMETase apoenzyme. With a dose of 4000 units/kg MEGC-PEG-rMETase in the mice infused with 5, 50, 200, and 500 mg/ml PLP, plasma MET was depleted from 50 microm to < or = 5 microm for 8, 24, 72, and 72 h, respectively. Thus, PLP infusion could extend the period of MET depletion by MEGC-PEG-rMETase by approximately 10-fold in a dose-dependent manner. The mice given 8000 units/kg MEGC-PEG-rMETase showed a similar plasma MET depletion time course, indicating that the limiting factor for MEGC-PEG-rMETase-mediated MET depletion in vivo was PLP. The extended time of MET depletion by MEGC-PEG-rMETase was due to the maintenance of active MEGC-PEG-rMETase holoenzyme by infused PLP. The infused PLP either bound to apo-MEGC-PEG-rMETase and/or inhibited dissociation of PLP from holo-PEG-rMETase, thereby maintaining the holoenzyme form of MEGC-PEG-rMETase in vivo. The combination of MEGC-PEG-rMETase treatment with PLP infusion suggests an effective clinical strategy for long-term MET depletion to arrest cancer growth.

Animals↗

Dubin-Johnson-like black liver with normal bilirubin level.

Black liver is a common finding in Dubin-Johnson syndrome (DJS), which is caused by the lack of multidrug resistance-associated protein 2 (MRP2). Impaired excretion of epinephrine metabolites is believed to be a cause of black liver in DJS. Recently, we experienced a patient with black liver whose serum bilirubin level was normal. Coarse brown granules were observed in the hepatocytes, and this finding closely resembled that observed in DJS. However, the granules were negative for Schmorl staining. The MRP2 gene did not show any mutation. Immunostaining study demonstrated MRP2 protein expression in the liver, and it was localized in the canalicular membranes of hepatocytes. This case illustrates for the first time that DJS is not the only cause of black liver.

Adult↗

Modulation of organic anion transporting polypeptide 1 and multidrug resistance protein 3 expression in the liver and kidney of Gunn rats.

Background: Gunn rat is an animal model of Crigler-Najjar syndrome (CNS) type I that develops jaundice due to defect of bilirubin conjugation. Bilirubin UDP-glucuronosyltransferase (UGT1A1), which plays a critical role in bilirubin glucuronidation, has been reported to be deficient in CNS type 1. On the other hand, little is known about the expression of organic anion transporters in Gunn rats. In the present study, we evaluated expressions of organic anion transporting polypeptide (oatp) 1 and 2, multidrug resistance-associated protein (mrp) 2 and mrp3 in the liver and kidney of Gunn rats. Methods: Serum samples, liver and kidney tissues were obtained from Gunn rats and normal SD rats ( [Formula: see text], in each group). Semi-quantitative mRNA expression of oatp1, oatp2, mrp2, and mrp3 mRNA was evaluated by constructed reverse transcription-polymerase chain reaction (RT-PCR). Protein expressions were determined by Western blotting and by immunohistochemistry. Results: Marked elevation of serum unconjugated bilirubin concentration ( [Formula: see text] micromol/l) was observed in Gunn rats. Hepatic expression of oatp1 and oatp2 mRNA was 44% ( [Formula: see text] ) and 35% ( [Formula: see text] ) lower in Gunn rats than in SD rats, respectively. Hepatic oatp1 protein expression was 37% ( [Formula: see text] ) lower in Gunn rats than in SD rats. In contrast to oatp1, hepatic expression of mrp3 mRNA and protein was 76% ( [Formula: see text] ) and 557% ( [Formula: see text] ) higher in Gunn rats than in SD rats, respectively. Hepatic expression of oatp2 and mrp2 protein was not significantly different between Gunn rats and SD rats. Like the Western blot analysis, immunohistochemical staining disclosed decrease of oatp1 and increase of mrp3 protein expressions in the liver of Gunn rats. Decrease of oatp1 and increase of mrp3 expressions were also observed in the kidney of Gunn rats. Conclusion: Decreased expression of oatp1 and increased expression of mrp3 were observed in the liver and kidney of Gunn rats. Deficient UGT1A1 activity-associated retention of unconjugated bilirubin in the hepatocytes may modulate the expressions of these transporters in Gunn rats.

Journal Article↗

Efficacy of long-term dietary restriction of total calories, fat, iron, and protein in patients with chronic hepatitis C virus.

OBJECTIVES: A diet restrictive in total calories, fat, iron, and protein intake reduces serum alanine aminotransferase levels in patients with long-term hepatitis C virus infection. However, whether long-term dietary therapy causes adverse effects such as malnutrition and anemia due to a shortage of energy intake is not clear. We evaluated the balance of energy intake and changes in physical and hematologic indices of nutrition after a long-term dietary therapy. METHODS: Twenty-two patients with long-term hepatitis C virus infection that did not respond to or who were able or unwilling to take interferon therapy were enrolled in this study. Our prescriptions included 7 mg/d or less of iron, 30 kcal. kg(-1). d(-1) of energy, 1.1 to 1.2 g. kg(-1). d(-1) of protein, and a fat energy fraction of 20%. Patients were followed for 24 mo. RESULTS: Mean body fat percentage was 24.6% at entry and was significantly reduced after the diet prescription. Mean serum ferritin decreased significantly from 376 ng/mL at entry to 141 ng/mL after 24 mo. Mean serum alanine aminotransferase levels decreased significantly from 66 to 49 IU/L. Mean levels of hemoglobin, serum albumin, and cholinesterase did not change significantly during the follow-up period. CONCLUSIONS: These results suggest that restriction of energy, fat, iron, and protein intakes is safely tolerated, so its long-term use should be recommended to patients with long-term infection with hepatitis C virus.

Adipose Tissue↗

Increased hepatic and renal expressions of multidrug resistance-associated protein 3 in Eisai hyperbilirubinuria rats.

BACKGROUND AND AIM: Eisai hyperbilirubinuria rats (EHBR) are animal models of Dubin-Johnson syndrome, which suffer from jaundice due to impaired biliary excretion of bilirubin glucuronides. In EHBR, deficiency of multidrug resistance-associated protein 2 (mrp2) causes defective biliary excretion of numerous organic anions. However, little is known about the expression of other organic anion transporters in this mrp2-deficient model. The aim of the present study was to investigate adaptive expressions of mrp1, mrp3, mrp6, organic anion transporting polypeptide 1 (oatp1) and oatp2 in liver and kidney of EHBR. METHODS: For the present study, EHBR (n = 5) were used. Hepatic and renal mRNA expression of the aforementioned transporters was determined by constructed semiquantitative reverse transcription polymerase chain reaction assay. Their protein expression was determined by western blotting. Localization of hepatic and renal mrp3 was confirmed by immunohistochemistry. Sprague-Dawley (SD) rats (n = 5) were used as normal controls. RESULTS: Deficiency of mrp2 protein was confirmed in EHBR. Hepatic and renal expression of mrp3 mRNA was 53.6% (P < 0.001) and 82.9% (P < 0.001), and its protein expression was 298.9% (P < 0.001) and 245.0% (P = 0.001) higher in EHBR than in SD rats, respectively. Hepatic and renal expression of mrp1 and mrp6 mRNA was not significantly different between EHBR and SD rats. The mrp1 and mrp6 proteins were expressed in very low amounts in the liver and kidney of both EHBR and SD rats. In contrast to mrp3, hepatic expression of oatp1 and oatp2 mRNA was 33.9% (P = 0. 001) and 38.6% (P < 0.001), and their protein expression was 57.4% (P < 0.05) and 51.0% (P < 0.01) lower in EHBR than in SD rats, respectively. Hepatic and renal mrp3 protein was localized at the basolateral membrane. CONCLUSIONS: Mrp3 plays an important role in the compensation of mrp2 deficiency in liver and kidney of EHBR. Hepatic expressions of mrp3, oatp1 and oatp2 changed adaptively in this animal model. This is a compensatory mechanism for reducing injury to hepatocytes from cytotoxic materials that increase in mrp2 deficiency.

ATP Binding Cassette Transporter, Subfamily B↗

Genetic polymorphisms of bilirubin uridine diphosphate-glucuronosyltransferase gene in Japanese patients with Crigler-Najjar syndrome or Gilbert's syndrome as well as in healthy Japanese subjects.

BACKGROUND AND AIM: Numerous mutations of bilirubin uridine diphosphate-glucuronosyltransferase gene (UGT1A1) have been reported in patients with familial unconjugated hyperbilirubinemia. The UGT1A1 mutation appears to be considerably different among ethnic groups. To clarify the incidence of this gene mutation in the Japanese population, the presence of UGT1A1 mutation was investigated in a group of Japanese patients with Crigler-Najjar syndrome type 2 (CNS2) and Gilbert's syndrome (GS), as well as in healthy anicteric subjects. METHODS: Four patients with CNS2, 63 patients with GS, and 71 healthy subjects were enrolled in the study. The promoter and coding regions of UGT1A1 were amplified by polymerase chain reaction (PCR) from genomic DNA isolated from leukocytes. The PCR products were directly sequenced by a dye terminating method. The UGT1A1 enzyme activity was determined in COS7 cells transfected with wild or P364L (1091 C > T) mutant DNA. RESULTS: Homozygous Y486D was observed in all four patients with CNS2. The GS patients had UGT1A1 mutations with 13 different genotypes in the promoter and coding region. Homozygous TA insertion in the TATA box (TA7) of the promoter region (TA7/7; 33%), homozygous G71R (9%), and combination of TA7/6 and heterozygous G71R (17%) were the most frequent findings in GS patients. Homozygous or heterozygous Y486D (8%) and P229Q (8%) were also observed in GS. A novel mutation, heterozygous P364L, was also identified in a GS patient. In addition to GS patients, homozygous or heterozygous TA7, G71R, and heterozygous Y486D were also observed in healthy subjects. The allele frequency of G71R and TA7 was 0.183 and 0.113 in healthy subjects, respectively. The P364L UGT1A1 enzyme activity was 64.4% lower than the wild-type enzyme activity. CONCLUSIONS: Polymorphisms in the coding region of UGT1A1 were commonly observed in Japanese patients with GS and in healthy subjects. The genetic basis of hyperbilirubinemia appears to be different between the Japanese and Caucasian populations.

Adult↗