An efficient screening approach for anti-Microcystis compounds based on knowledge of aquatic microbial ecosystem

To improve the efficiency of screening for anti-Microcystis compounds, we planned to use algae-lysing bacteria that kill the organisms of water blooms. A two step-screening process was carried out, i.e., the screening of algae-lysing bacteria and the selection of anti-Microcystis producers from the bacteria. Sources for the isolation of the bacteria were a co-cultivated fluid of a water sample with axenic Microcystis viridis, a water sample collected in a water bloom season, and a water bloom sample. The water bloom sample was the best source for the isolation of the algae-lysing bacteria and such bacteria were shown to exhibit potent activity. Seventeen strains out of 20 isolated algae-lysing bacteria produced anti-Microcystis activities, and one of the principles was the previously reported argimicin A. These results indicate that algae-lysing bacteria in water blooms may be good sources for potent and selective anticyanobacterial compounds.

Rat cytochrome p450 1A and 3A enzymes involved in bioactivation of tegafur to 5-fluorouracil and autoinduced by tegafur in liver microsomes

Tegafur, an anticancer prodrug, is reported to be bioactivated to 5-fluorouracil (5-FU) by cytochrome P450 (P450) enzymes. Liver microsomal P450 enzymes involved in the biotransformation of tegafur into 5-FU in rats and the effect of tegafur in vivo on P450 levels in rats were investigated. Of 12 cDNA-expressed rat P450 enzymes tested, CYP1A2, CYP3A1, and CYP2C11 had high 5-FU formation rates from 100 microM and 1.0 mM tegafur concentrations. The contributions of CYP1A, CYP2C, and CYP3A enzymes to 5-FU formation in male rat liver microsomes were supported by immunoinhibition studies. 5-FU formation from tegafur, at substrate concentrations of 100 microM and 1.0 mM, was increased by intraperitoneal treatment of tegafur (50 mg/kg for 5 days) as well as by beta-naphthoflavone, phenobarbital, and dexamethasone. Orally administered tegafur (100 mg/kg daily for 20 days) caused the induction of CYP2B (5-fold) and of CYP1A and CYP3A (approximately 2-fold) and of 5-FU formation (approximately 2-fold) in rat liver microsomes. These results suggest that CYP1A and CYP3A enzymes, autoinduced by tegafur, have important roles in 5-FU formation from tegafur in rat liver microsomes. Coadministration of tegafur and P450-inducing drugs could markedly enhance the biotransformation of tegafur into 5-FU via P450 induction.

High frequency of circulating HBcAg-specific CD8 T cells in hepatitis B infection: a flow cytometric analysis

Viral antigen-specific T cells are important for virus elimination. We studied the hepatitis B virus (HBV)-specific T cell response using flow cytometry. Three phases of HBV infection were studied: Group A, HBeAg (+) chronic hepatitis; Group B, HBeAb (+) HBV carrier after seroconversion; and Group C, HBsAb (+) phase. Peripheral T cells were incubated with recombinant HB core antigen (HBcAg), and intracytoplasmic cytokines were analysed by flow cytometry. HBcAg-specific CD4 and CD8 T cells were identified in all three groups and the number of IFN-gamma-positive T cells was greater than TNF-alpha-positive T cells. The frequency of IFN-gamma-positive CD4 and CD8 T cells was highest in Group C, compared with Groups A and B. No significant difference in the HBcAg-specific T cell response was observed between Group A and Group B. The HBcAg-specific CD8 T cell response was diminished by CD4 depletion, addition of antibody against human leucocyte antigen (HLA) class I, class II or CD40L. Cytokine-positive CD8 T cells without HBcAg stimulation were present at a high frequency (7 of 13 cases) in Group B, but were rare in other groups. HBcAg-specific T cells can be detected at high frequency by a sensitive flow cytometric analysis, and these cells are important for controlling HBV replication.

Effect of dilazep dihydrochloride on urinary albumin excretion in patients with autosomal dominant polycystic kidney disease

Proteinuria and microalbuminuria occur with a highly variable severity and are associated with progression of autosomal dominant polycystic kidney disease (ADPKD). Dilazep dihydrochloride, an antiplatelet drug, is effective in patients with immunoglobulin A nephropathy or diabetic nephropathy. We studied whether dilazep dihydrochloride affects the urinary albumin excretion (UAE) in normotensive and hypertensive patients with ADPKD. Twelve normotensive ADPKD patients with microalbuminuria were randomly assigned to two groups: a dilazep (300 mg/day) treatment group (n = 6, group A) and a placebo group (n = 6, group B). In addition, 10 hypertensive ADPKD patients with microalbuminuria were randomly assigned to two groups: a dilazep (300 mg/day) treatment group (n = 5, group C) and a placebo group (n = 5, group D). Treatment with dilazep was continued for a period of 6 months, at the end of which the UAE was reduced form 130 +/- 52 to 46 +/- 26 microg/min (p < 0.01) in group A. There was no reduction in group C. There were no changes in UAE in placebo groups B and D. These results suggest that dilazep dihydrochloride may be effective in reducing UAE in normotensive ADPKD patients with microalbuminuria.

Cooperativity of alpha-naphthoflavone in cytochrome P450 3A-dependent drug oxidation activities in hepatic and intestinal microsomes from mouse and human

1. The effects of several CYP3A substrates (alpha-naphthoflavone (alphaNF), terfenadine, midazolam, erythromycin) on nifedipine oxidation and testosterone 6beta-hydroxylation activities were investigated in hepatic and intestinal microsomes from mouse and human. 2. alphaNF (10 microM) and terfenadine (100 microM) inhibited nifedipine oxidation activities (at substrate concentration of 100 microM) in mouse hepatic microsomes to approximately 50%, but not in mouse intestinal microsomes. alphaNF (30 microM) stimulated nifedipine oxidation activities in mouse and human intestinal microsomes and in human hepatic microsomes to approximately 1.3-1.8-fold. Inhibitory potencies (50% inhibition concentration, IC50) of midazolam and erythromycin for nifedipine oxidations were calculated to be approximately 90 microM in human intestinal microsomes. In contrast, testosterone (100 microM) stimulated the nifedipine oxidation activities approximately 1.5-fold in hepatic and intestinal microsomes from mouse and human. 3. alphaNF showed different effects on the kinetic parameters including the Hill coefficients of nifedipine oxidation and testosterone 6beta-hydroxylation catalysed by hepatic and intestinal microsomes from mouse and human. Cooperativity in nifedipine oxidation was increased by the addition of alphaNF to pooled human hepatic microsomes, but little effects of alphaNF could be observed in individual human intestinal microsomes. 4. These results suggest that CYP3A enzymes in liver and intestine might have different characteristics and that observations from hepatic microsomes should not be directly applicable to intestine metabolism in some cases. Studies of drug-drug interactions of CYP3A substrates are recommended to be performed using intestinal samples.

Effect of troglitazone on urinary albumin excretion and serum type IV collagen concentrations in Type 2 diabetic patients with microalbuminuria or macroalbuminuria

AIMS

Troglitazone, a newly developed thiazolidinedione derivative, has been shown to ameliorate microalbuminuria in diabetic animal model and in human diabetic nephropathy in short-term studies. The aim of the present study was to determine whether troglitazone or sulphonylurea affect micro- albuminuria, macroalbuminuria, or serum type IV collagen concentrations in patients with diabetic nephropathy.

METHODS

We studied 32 normotensive patients with type 2 diabetes mellitus associated with microalbuminuria (n = 16) or macroalbuminuria (n = 16) and 20 healthy controls. The patients were randomly assigned to one of two groups: those treated with glibenclamide (5.0 mg/day) (n = 8) and those treated with troglitazone (400 mg/day) (n = 8). They received the drug regimen for 12 months. Serum type IV collagen was measured with sandwich enzyme immunoassay.

RESULTS

Type IV collagen concentrations in macroalbuminuric patients were higher than those in microalbuminuric patients (P < 0.05) and healthy controls (P < 0.01). Troglitazone reduced urinary albumin excretion (UAE) in micro-albuminuric patients from 126 microg/min (range 58--180 microg/min) to 42 microg/min (range 14--80 microg/min) (P < 0.01) and also reduced serum type IV collagen levels gradually at 3, 6 and 12 months after treatment (P < 0.05). However, glibenclamide did not affect UAE and type IV collagen levels in micro- albuminuric diabetes patients. In addition, neither troglitazone nor gliben- clamide changed UAE and type IV collagen levels in macroalbuminuric patients.

CONCLUSIONS

These data suggest that troglitazone is an effective treatment for renal injury in patients with early diabetic nephropathy.

Decreases in phenytoin hydroxylation activities catalyzed by liver microsomal cytochrome P450 enzymes in phenytoin-treated rats

Phenytoin, 5,5-diphenylhydantoin, is a widely used anticonvulsant agent with a variety of toxicities, including drug interactions. The formation of four oxidative metabolites, 4'-hydroxylated (4'-HPPH), 3'-hydroxylated (3'-HPPH), a catechol (3',4'-diHPPH), and the 3',4'-dihydrodiol form of phenytoin was examined in rat liver microsomes. In 11 cDNA-expressed rat P450 enzymes tested, CYP2C6 had the highest activities in 4'- and 3'-HPPH formation from phenytoin, followed only by CYP2C11. In contrast, CYP2C11 had high activity for 3',4'-diHPPH formation from 4'-HPPH, followed by CYP2C6. The rates of 4'-HPPH and 3',4'-diHPPH formation from phenytoin in liver microsomes in the presence of NADPH were significantly decreased by oral administration of phenytoin (300 mg/kg for 20 days) to rats, despite the increase in P450 contents. However, the cumene hydroperoxide-supported formation of 3',4'-dihydrodiol and 4'-HPPH from phenytoin was induced by phenytoin administration. Hydrogen peroxide formation in reaction mixtures with NADPH was induced by the administration of phenytoin; however, the coupling ratio of phenytoin oxidation was decreased in phenytoin-induced liver microsomal P450 systems. These results suggested that phenytoin could not stimulate its own apparent oxidative metabolism by liver P450s induced with phenytoin administration. The increase of unmetabolized phenytoin and byproducts of oxygen generated in the phenytoin-induced liver microsomal P450 system may be involved in phenytoin-related drug toxicity.

Synthesis, structural characterization and antimicrobial activities of 4- and 6-coordinate nickel(II) complexes with three thiosemicarbazones and semicarbazone ligands

To investigate the relationship between antimicrobial activities and the molecular structures of nickel(II) complexes with thiosemicarbazone and semicarbazone ligands, nickel(II) complexes with ligands Hmtsc, Hatsc, Hasc and H2dmtsc, were prepared and characterized by elemental analysis, FT-IR, 1H and 13C NMR spectroscopies, magnetic susceptibility measurements, UV-Vis absorption spectra, TG/DTA and single-crystal X-ray analysis. Their antimicrobial activities were evaluated by the MIC against four bacteria (B. subtilis, S. aureus, E. coli and P. aeruginosa), two yeasts (C. albicans and S. cerevisiae) and two molds (A. niger and P. citrinum). The 4-coordinate, diamagnetic nickel(II) complexes showed antimicrobial activities which were different from those of free ligands or the starting nickel(II) compounds; [Ni(mtsc)(OAc)] 1 showed selective and effective antimicrobial activities against two Gram-positive bacteria (B. subtilis and S. aureus) and modest activities against a yeast (S. cerevisiae), [Ni(mtsc)Cl] 3 exhibited moderate activities against a Gram-positive bacterium (S. aureus), and [Ni(atsc)(OAc)] 5 showed modest activities against two Gram-positive bacteria (B. subtilis and S. aureus). On the other hand, the 6-coordinate, paramagnetic nickel(II) complexes with two protonated or deprotonated ligands ([Ni(mtsc)2] 2, [Ni(atsc)(mtsc)] 4, [Ni(atsc)2] 6, [Ni(Hatsc)2](NO3)(2)7, [Ni(Hatsc)2]Cl(2)8 and [Ni(Hasc)2](OAc)(2)9) and the sterically crowded 4-coordinate, diamagnetic nickel(II) complex ([Ni(dmtsc)] 10) did not inhibit the growth of the test organisms. The structure-activity correlation in this series of nickel(II) complexes was discussed based on their ligand-replacement abilities.

Laparoscopic findings in primary sclerosing cholangitis

BACKGROUND AND STUDY AIMS

Primary sclerosing cholangitis (PSC) is a cholestatic disease characterized by segmental narrowing and dilatation of bile ducts. Few studies have been performed on the laparoscopic findings associated with this disease, and the present study was intended to assess the usefulness of laparoscopy for the diagnosis and staging of PSC.

PATIENTS AND METHODS

Six patients were examined by laparoscopy with liver biopsy. Repeated laparoscopy was performed in three patients.

RESULTS

Laparoscopy revealed coarse surface irregularity and discoloration. Surface irregularity was classified into four grades: smooth, shallowly depressed, undulated, and nodular. The affected area showed whitish yellow discoloration. The discolored area was demonstrated as a poorly stained area by intravenous injection of indocyanine green (ICG). Lobular markings became apparent because of the yellow color change in the portal tract, resulting in a leopardskin-like appearance. Lymph-vessel dilatation was seen in advanced stages. Repeated laparoscopy of a patient without treatment demonstrated a progression from a smooth surface to a shallow depression with leopardskin-like markings. On the other hand, the two patients treated with immunosuppressive agents showed improvement of liver swelling and disappearance of the leopardskin-like markings and lymph-vessel dilatation.

CONCLUSIONS

Laparoscopy may provide useful information for the diagnosis and staging of PSC.

In vitro/in vivo scaling of alprazolam metabolism by CYP3A4 and CYP3A5 in humans

We attempted to predict the in vivo metabolic clearance of alprazolam from in vitro metabolic studies using human liver microsomes and human CYP recombinants. Good correlations were observed between the intrinsic clearance (CL(int)) for 4-hydroxylation and CYP3A4 content and between the CL(int) for alpha-hydroxylation and CYP3A5 content in ten human liver microsomal samples. Using the recombinant CYP isoforms expressed in insect cells, the CL(int) for CYP3A4 was about 2-fold higher than the CL(int) for CYP3A5 in the case of 4-hydroxylation. However, the CL(int) for CYP3A5 was about 3-fold higher than the CL(int) for CYP3A4 in the case of alpha-hydroxylation. The metabolic rates for 4- and alpha-hydroxylation increased as the added amount of cytochrome b(5) increased, and their maximum values were 3- to 4-fold higher than those without cytochrome b(5). The values of CL(int), in vivo predicted from in vitro studies using human liver microsomes and CYP3A4 and CYP3A5 recombinants were within 2.5 times of the observed value calculated from literature data. The average CL(int) value (sum of 4- and alpha-hydroxylation) obtained using three human liver microsomal samples was 4-fold higher than that obtained using three small intestinal microsomal samples from the same donors, indicating the minor contribution of intestinal metabolism to alprazolam disposition. The area under the plasma concentration-time curve (AUC) of alprazolam is reported to increase following co-administration of ketoconazole and the magnitude of the increase predicted from the in vitro K(i) values and reported pharmacokinetic parameters of ketoconazole was 2.30-2.45, which is close to the value observed in vivo (3.19). A quantitative prediction of the AUC increase by cimetidine was also successful (1.73-1.79 vs 1.58-1.64), considering the active transport of cimetidine into the liver. In conclusion, we have succeeded in carrying out an in vitro/in vivo scaling of alprazolam metabolism using human liver microsomes and human CYP3A4 and CYP3A5 recombinants.

Involvement of microsomal cytochrome P450 and cytosolic thymidine phosphorylase in 5-fluorouracil formation from tegafur in human liver

Recently, we have reported that tegafur, an anticancer agent, is biotransformed into active drug 5-fluorouracil (5-FU) by cytochromes P450 1A2, 2A6, and 2C8 in human liver microsomes (T. Komatsu et al., Drug Metab. Dispos, 28: 1457-1463, 2000). Because the conversion of tegafur into 5-FU has also been reported to be catalyzed by cytosolic thymidine phosphorylase (dThdPase), the involvement of human liver microsomes and cytosol and individual differences in 5-FU formation from tegafur were investigated. In 14 human samples, the mean rates of 5-FU formation in liver microsomes were 5-fold and 2-fold higher than those in liver cytosol at substrate concentrations of 100 microM and 1 mM tegafur, respectively. In the presence of 5-chloro-2,4-dihydroxypyridine, a dihydropyrimidine dehydrogenase inhibitor, the rates of 5-FU formation by the combination of liver microsomes and cytosol showed 5- and 3-fold interindividual differences at 100 microM and 1 mM tegafur, respectively. Kinetic analysis of human liver cytosolic 5-FU formation indicated an apparent higher Km value (16 +/- 4 mM) than that of liver microsomes (1.8 +/- 0.3 mM) with similar Vmax values. Human liver cytosolic 5-FU formation was confirmed to be catalyzed by dThdPase with correlation and chemical inhibition studies. These results suggested that 5-FU formation from tegafur in human liver was mainly catalyzed by microsomal P450 at low concentrations of tegafur, but the contribution of cytosolic 5-FU formation by dThdPase would be important at high concentrations.

Effect of high amniotic fluid pressure on fetal circulation

The purpose of this study was to investigate the effects of high amniotic fluid pressure (AFP) created by amnioinfusion on fetal circulation. Five pregnant goats whose fetuses had a mean gestational age of 131 +/- 2 days (term 145 days) were used. After a 30 minute control period, 1500 ml of warm saline was infused to the amniotic cavity over a period of 30 minutes. The AFP gradually increased during amnioinfusion and remained 2-3 mmHg above the control level for 3 hours after amnioinfusion. Fetal arterial pH (FpH) tended to decrease, and there was a significant negative correlation between the FpH and AFP (r = -0.723). Fetal arterial pO2 also tended to decrease and negatively correlated to the AFP (r = -0.59). On the other hand, fetal arterial pCO2 tended to increase and positively correlated with the AFP (r = 0.75). Although amnioinfusion is useful for improving the status of a distressed fetus, the fetal condition may be jeopardized at the same time. Therefore, careful monitoring of the AFP and fetal status is recommended during amnioinfusion.

Aberrant expression of cytokeratin 7 as a histological marker of progression in primary biliary cirrhosis

AIM

We evaluated the aberrant expression of cytokeratin 7 (CK-7) in hepatocytes as a marker of cholestasis and progression in primary biliary cirrhosis (PBC).

PATIENTS AND METHODS

The expression of CK-7 was studied by immunohistochemistry in 83 cases of PBC. This expression was compared with biochemical data, the deposition of copper-associated protein, and previous histological classifications.

RESULTS

In normal liver, CK-7 was expressed exclusively in bile duct epithelial cells (BDE). In PBC, the expression was also observed in hepatocytes. The expression pattern was classified as follows: Grade 0, BDE as in normal; Grade 1, proliferated bile ductules; Grade 2, periportal hepatocytes in addition to proliferated bile ductules; Grade 3, intralobular hepatocytes; Grade 4, the majority of hepatocytes. The grades correlated with serum bilirubin levels but not with serum levels of biliary enzymes. A discrepancy between the CK-7 grading and Ludwig's classification was noted in cases with Stage 1 of the CK-7 grading who were considered Stage 2 or 3 in Ludwig's classification, suggesting that cholestasis and inflammatory activity might be independent events.

CONCLUSIONS

These results suggest that the aberrant expression of CK-7 in hepatocytes may be a marker of chronic cholestasis and progression in PBC.

Role of CYP2C19 in stereoselective hydroxylation of mephobarbital by human liver microsomes

The 4-hydroxylation of mephobarbital enantiomers was investigated by using human liver microsomes from the extensive metabolizers (EM) and poor metabolizers of CYP2C19. The 4-hydroxylase activity of R-mephobarbital in the EM microsomes was >10 times higher than that of S-mephobarbital. In the poor metabolizer microsomes, the 4-hydroxylase activity of R-mephobarbital was much lower than that in the EM microsomes, and the ratio of 4-hydroxylase activity of R-mephobarbital to that of S-mephobarbital was also lower than that in the EM microsomes. Moreover, the 4-hydroxylase activity of R-mephobarbital showed a high correlation (r = 0.985, p<0.001) with the 4'-hydroxylase activity of S-mephenytoin in a panel of nine human liver microsomes. Anti-CYP2C antibody inhibited R-mephobarbital 4-hydroxylase activity by 85% of the control activity. R-Mephobarbital competitively inhibited S-mephenytoin 4'-hydroxylase activity (K(i) = 34 microM), while S-mephenytoin inhibited R-mephobarbital 4-hydroxylase activity (K(i) = 103 microM). Among the seven cDNA-expressed CYPs studied, only CYP2C19 catalyzed R-mephobarbital 4-hydroxylation. These findings suggest that the 4-hydroxylation of mephobarbital catalyzed by CYP2C19 is preferential for R-enantiomer in human liver microsomes.

Bioactivation of diesel exhaust particle extracts and their major nitrated polycyclic aromatic hydrocarbon components, 1-nitropyrene and dinitropyrenes, by human cytochromes P450 1A1, 1A2, and 1B1

The genotoxicities of four samples of diesel exhaust particle (DEP) extracts (DEPE) and nine nitroarenes found in DEPE were investigated after activation catalyzed by human cytochrome P450 (P450) family 1 enzymes co-expressed with NADPH-cytochrome P450 reductase (NPR) in Escherichia coli membranes. The DEPE samples induced umu gene expression in Salmonella typhimurium TA1535/pSK1002 without any P450 system and were further activated by human P450 1B1/NPR membranes. Moderate activation of the DEPE sample by P450 1A2/NPR membranes was also observed, but not by either P450 1A1/NPR or NPR membranes. 1-Nitropyrene (1-NP) was strongly activated by human P450 1B1/NPR membranes. 1,8-Dinitropyrene (1,8-DNP) was most highly activated by P450 1A1 and 1B1 systems for the three DNPs tested. In contrast, 1, 3-DNP was inactivated by P450 1A1/NPR, 1A2/NPR, and 1B1/NPR systems and slightly activated by NPR membranes. 2-Nitrofluoranthene (2-NF) and 3-nitrofluoranthene (3-NF) showed activities similar to 1-NP after bioactivation by P450 1B1/NPR membranes. However, the genotoxicities of 6-nitrochrysene, 7-nitrobenz[a]anthracene, and 6-nitrobenzo[a]pyrene were all weak in the present assay system. Apparent genotoxic activities of DEPE were very low compared with standard nitroarenes in the presence of P450s, possibly because unknown component(s) of DEPE had inhibitory effects on the bioactivation of 1-NP and 1,8-DNP catalyzed by human P450 1B1. These results suggest that environmental chemicals existing in airborne DEP, in addition to 1-NP, 1,6-DNP, 1,8-DNP, 2-NF, and 3-NF, can be activated by human P450 1B1. Biological actions of air pollutants such as nitroarenes to human extrahepatic tissues may be of concern in tissues in which P450 1B1 is expressed.

Induction of isoflavonoid pathway in the model legume Lotus japonicus: molecular characterization of enzymes involved in phytoalexin biosynthesis

Treatment of the seedlings of Lotus japonicus, a model legume for molecular genetic studies, with reduced glutathione (GSH) resulted in the accumulation of an isoflavan phytoalexin, vestitol. Using PCR strategies based on the conserved amino acid sequences, full length P450 cDNAs were obtained from GSH-treated seedling roots. When the clones, LjCYP-1 (CYP93C family) and LjCYP-2 (CYP81E family), were heterologously expressed in yeast, the proteins exhibited 2-hydroxyisoflavanone synthase (IFS) and isoflavone 2'-hydroxylase (I2'H) activities, respectively. The transcription levels of LjCYP-1, LjCYP-2 and isoflavone reductase, which are all involved in vestitol biosynthesis, coordinately increased upon elicitation. Genomic Southern blot analysis indicated that the IFS gene forms a small gene family and a single copy of the I2'H gene is present in the L. japonicus genome. Molecular biological aspects of P450s involved in the isoflavonoid pathway and the genomic approach to flavonoid metabolism in this unique plant are discussed.

Roles of cytochromes P450 1A2, 2A6, and 2C8 in 5-fluorouracil formation from tegafur, an anticancer prodrug, in human liver microsomes

Tegafur, an anticancer prodrug, is bioactivated to 5-fluorouracil (5-FU) mainly by cytochrome P450 (P450) enzymes. The conversion from tegafur into 5-FU catalyzed by human liver microsomal P450 enzymes was investigated. In fourteen cDNA-expressed human P450 enzymes having measurable activities, CYP1A2, CYP2A6, CYP2E1, and CYP3A5 were highly active in catalyzing 5-FU formation at a tegafur concentration of 100 microM. Kinetic analysis revealed that CYP1A2 had the highest V(max)/K(m) value and that the V(max) value of CYP2A6 was high in 5-FU formation. In human liver microsomes, the activities of 5-FU formation from 10 microM, 100 microM, and 1 mM tegafur were significantly correlated with both coumarin 7-hydroxylation (r = 0.83, 0.86, and 0.74) and paclitaxel 6 alpha-hydroxylation (r = 0.77, 0.62, and 0.85) activities, respectively. Coumarin efficiently inhibited the 5-FU formation activities from 100 microM and 1 mM tegafur catalyzed by human liver microsomes that had high coumarin 7-hydroxylation activity. On the other hand, furafylline, fluvoxamine, and quercetin, as well as coumarin, showed inhibitory effects in liver microsomes that had high catalytic activities of 5-FU formation. The other P450 inhibitors examined showed weak or no inhibition in human liver microsomes. Polyclonal anti-CYP1A2 antibody, monoclonal anti-CYP2A6, and anti-CYP2C8 antibodies inhibited 5-FU formation activities to different extents in those two microsomal samples. These results suggest that CYP1A2, CYP2A6, and CYP2C8 have important roles in human liver microsomal 5-FU formation and that the involvement of these three P450 forms differs among individual humans.

A significant role of human cytochrome P450 2C8 in amiodarone N-deethylation: an approach to predict the contribution with relative activity factor

Human cytochrome P450 (CYP) isoforms involved in amiodarone N-deethylation were identified, and the relative contributions of these CYP isoforms were evaluated in different human liver microsomes. The mean K(M) and V(max) values of amiodarone N-deethylation in microsomes from six human livers were 31.6 +/- 7.5 microM and 1.2 +/- 0.7 pmol/min/pmol of CYP, respectively. Ketoconazole and anti-CYP3A antibodies strongly inhibited amiodarone N-deethylase activity in human liver microsomes at a substrate concentration of 50 microM. Of 15 recombinant human CYP enzymes (19 preparations), CYP1A1, CYP3A4, CYP1A2, CYP2D6, CYP2C8, and CYP2C19 catalyzed amiodarone N-deethylation. The amiodarone N-deethylase activity at a substrate concentration of 5 microM was significantly correlated with the paclitaxel 6alpha-hydroxylase activity (r = 0.84, P <.05) in the human liver microsomes, whereas the amiodarone N-deethylase activity at 100 microM was significantly correlated with the testosterone 6beta-hydroxylase activity (r = 0.94, P <.005). According to the concept of relative activity factor, it was clarified that CYP2C8 as well as CYP3A4 were significantly involved in amiodarone N-deethylation in human livers at clinically significant concentrations and that the contributions of CYP1A2, CYP2C19, and CYP2D6 were relatively minor. However, there was a large interindividual variability in the contribution of each CYP isoform to amiodarone N-deethylase activity in human liver; the relevance of these enzymes would be dependent on the content of the respective isoforms and on the amiodarone concentration in the liver.

Metalloproteinase-9 mRNA expression in monocytes from patients with chronic renal failure

Long-term dialysis patients suffer from various complications including atherosclerosis. It has been suggested that metalloproteinases (MMPs) contribute to vascular remodeling during the development and progression of human atherosclerosis. Activated human monocytes have been demonstrated to secrete MMPs. In the present study, we measured levels of MMP mRNA in peripheral blood monocytes obtained from patients on continuous ambulatory peritoneal dialysis (CAPD) or hemodialysis (HD) and chronic-renal-failure patients not undergoing dialysis. Twenty patients with chronic renal failure were not undergoing dialysis, 20 patients were on CAPD, 40 patients were on chronic HD and 20 healthy volunteers served as controls. We used cDNA probes encoding for MMP-1, MMP-2, MMP-3 and MMP-9 and glyceraldehyde phosphate dehydrogenase. Higher levels of MMP-9 mRNA in the peripheral blood monocytes were observed in HD patients than in CAPD patients, undialyzed chronic renal failure patients or healthy controls. MMP-9 mRNA levels at the end of HD were not significantly higher than those at the start of HD. MMP-9 mRNA levels from HD patients did not differ among the types of membranes. We could detect minimal MMP-1, MMP-2 and MMP-3 mRNA expression in monocytes from all groups. Serum gelatinase activity was detectable in all samples; however, no significant differences existed among the groups. In summary, MMP-9 mRNA expression is enhanced in monocytes from HD and CAPD patients, and the enhancement may be, in part, associated with cardiovascular complications, including atherosclerosis, in dialysis patients. This increase in monocyte MMP-9 mRNA levels is lower in CAPD patients that it is in HD patients.