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Y Oda

Publications and source records attributed to Y Oda.

At least 37 records · Page 2Linked to original sources
PubMed2003

Vitamin D regulated keratinocyte differentiation: role of coactivators.

1,25 Dihydroxyvitamin D (1,25(OH)(2)D) regulates the differentiation of keratinocytes. 1,25(OH)(2)D raises intracellular free calcium (Cai) as a necessary early step toward stimulating differentiation. 1,25(OH)(2)D induces the calcium sensing receptor (CaR) in keratinocytes and enhances the calcium response of these cells. Activation of the CaR by calcium increases intracellular free calcium by a mechanism involving phospholipase C (PLC) cleavage of phosphatidylinositolbisphosphate into inositoltrisphosphate (IP(3)) and diacylglycerol (DG). 1,25(OH)(2)D induces the family of PLCs. PLC-gamma1 has a DR6 VDRE in its promoter which binds and is activated by VDR/RAR rather than VDR/RXR. The involucrin gene, which encodes a critical component of the cornified envelope, contains a DR3 VDRE in its promoter that acts in conjunction with a nearby AP-1 site. The sequential regulation of these genes is critical for the differentiation process. In undifferentiated keratinocytes, the VDR binds preferentially to the DRIP complex of coactivators. However, with differentiation DRIP 205 is no longer produced, and the VDR switches partners to the SRC family (SRC2 and 3). These studies suggest that at least part of the sequential activation of genes required during keratinocyte differentiation is regulated by the change (availability) of these different coactivator complexes.

Animals↗
PubMed2003

Wear resistance of experimental Ti-Cu alloys.

After using cast titanium prostheses in clinical dental practice, severe wear of titanium teeth has been observed. This in vitro study evaluated the wear behavior of teeth made with several cast titanium alloys containing copper (CP Ti+3.0 wt% Cu; CP Ti+5.0 wt% Cu; Ti-6Al-4V +1.0 wt% Cu; Ti-6Al-4V+4.0 wt% Cu) and compared the results with those for commercially pure (CP) titanium, Ti-6Al-4V, and gold alloy. Wear testing was performed by repeatedly grinding upper and lower teeth under flowing water in an experimental testing apparatus. Wear resistance was assessed as volume loss (mm(3)) at 5kgf (grinding force) after 50,000 strokes. Greater wear was found for the six types of titanium than for the gold alloy. The wear resistance of the experimental CP Ti+Cu and Ti-6Al-4V+Cu alloys was better than that of CP titanium and Ti-6Al-4V, respectively. Although the gold alloy had the best wear property, the 4% Cu in Ti-6Al-4V alloy exhibited the best results among the titanium metals. Alloying with copper, which introduced the alpha Ti/Ti(2)Cu eutectoid, seemed to improve the wear resistance.

Alloys↗
PubMed2003

p53 Mutation and MDM2 amplification in inflammatory myofibroblastic tumours.

AIMS: The pathogenic mechanism and predictive indicators of biological behaviour of inflammatory myofibroblastic tumour are poorly understood. We investigated molecular abnormalities of p53 and MDM2 in order to assess whether these play an important role in pathogenesis, and whether they also contribute to clinicopathological aggressive phenotype in inflammatory myofibroblastic tumour. METHODS AND RESULTS: We compared the immunohistochemical expression of calponin, h-caldesmon, ALK, and p53 gene mutation and MDM2 gene amplification with clinicopathological findings in 15 cases of inflammatory myofibroblastic tumour. Histologically, cellular atypia was observed in five (33.3%) out of 15 cases. Local recurrences were observed in two (14.3%) of 14 informative cases, but no distant metastasis was observed. The expression of calponin (9/14; 64%) but not h-caldesmon (0/14; 0%) was seen, which suggested myofibroblastic differentiation. ALK expression was seen in eight (53.3%) out of 15 cases, particularly in patients under 40 years old. Nuclear expression of p53 protein was recognized in only one (6.7%) of 15 cases, and polymerase chain reaction single-strand conformation polymorphism followed by direct sequencing revealed p53 gene missense mutations in two (13.3%) of 15 cases. Nuclear expression of MDM2 was seen in four (26.7%) of 15 cases, and the MDM2 gene amplification was observed in two of the four cases. CONCLUSION: Inflammatory myofibroblastic tumour shows a wide spectrum of cellular atypia and biological behaviour with p53 and MDM2 expression. However, the alterations in the p53 pathway seem not to play a major role in the pathogenesis of inflammatory myofibroblastic tumour.

Adult↗
PubMed2003

Dose-response studies on the induction of liver cytochromes P4501A1 and 1B1 by polycyclic aromatic hydrocarbons in arylhydrocarbon-responsive C57BL/6J mice.

1. To determine the biological effects of 23 polycyclic aromatic hydrocarbons (PAHs) and 3,4,3',4'-tetrachlorobiphenyl, the dose-response studies of the induction of CYP1-dependent xenobiotic oxidation activities by these chemicals in liver microsomes of C57BL/6J mice were studied. 2. In arylhydrocarbon-responsive C57BL/6J mice, the liver microsomal xenobiotic oxidation with substrates of 7-ethoxyresorufin, 7-ethoxycoumarin, (+/-)-benzo[a]pyrene-7,8-diol, dibenzo[a, pyrene-11,12-diol and 2-amino-3,5-dimethylimidazo[4,5-f]quinoline increased by increasing the doses of PAHs to mice, particularly when the PAHs that have been reported to be carcinogenic in experimental animals were used. In arylhydrocarbon receptor-knockout mice, there were no increases in liver microsomal 7-ethoxyresorufin O-deethylation activities nor in liver mRNA levels of CYP1A1, 1A2 and 1B1 by these chemicals. 3. Of the chemicals examined, benzo[k]fluoranthene, benzo[b]fluoranthene, benzo[j]-fluoranthene, 3-methylcholanthrene, dibenz[a,h]anthracene, dibenz[a,c]anthracene and 3,4,3',4'-tetrachlorobiphenyl were potent inducers of the induction of liver microsomal 7-ethoxyresorufin O-deethylation in mice. 4. Other PAHs such as 5-methylchrysene, benzo[a]pyrene, dibenzo[a,l]pyrene, dibenz[a,j]acridine, benzo[a]anthracene and 7,12-dimethylbenz[a]anthracene moderately induced 7-ethoxyresorufin O-deethylation activities in mice. PAHs reported to be weak or less carcinogenic in experimental animals did not induce the xenobiotic oxidation activities of CYP1A1 and 1B1 in the mice. 5. The results suggest that induction of liver microsomal CYP1-dependent xenobiotic oxidation activities is a good tool in determining the potencies of carcinogenic PAHs in arylhydrocarbon-responsive C57BL/6J mice.

Animals↗
PubMed2003

Spatial distribution of Rhodopseudomonas palustris ecotypes on a local scale.

The number, spatial distribution, and significance of genetically distinguishable ecotypes of prokaryotes in the environment are poorly understood. Oda et al. (Y. Oda, B. Star, L. A. Huisman, J. C. Gottschal, and L. J. Forney, Appl. Environ. Microbiol. 69:xxx-xxx, 2003) have shown that Rhodopseudomonas palustris ecotypes were lognormally distributed along a 10-m transect and that multiple strains of the species could coexist in 0.5-g sediment samples. To extend these observations, we investigated the clonal diversity of R. palustris in 0.5-g samples taken from the corners and center of a 1-m square. A total of 35 or 36 clones were recovered by direct plating from each sample and were characterized by BOX A1R repetitive element-PCR genomic DNA fingerprinting. Isolates with fingerprint images that were >/=80% similar to each other were defined as the same genotype. Among the 178 isolates studied, 32 genotypes were identified, and each genotype contained between 1 and 40 isolates. These clusters were consistent with minor variations found in 16S rRNA gene sequences. The Shannon indices of the genotypic diversity within each location ranged from 1.08 (5 genotypes) to 2.18 (13 genotypes). Comparison of the rank abundance of genotypes found in pairs of locations showed that strains from three locations were similar to each other, with Morisita-Horn similarity coefficients ranging from 0.59 to 0.71. All comparisons involving the remaining two locations resulted in coefficients between 0 and 0.12. From these results we inferred that the patterns of ecotype diversity at the sampling site are patchy at a 1-m scale and postulated that factors such as mixing, competitive interactions, and microhabitat variability are likely to be responsible for the maintenance of the similarities between some locations and the differences between others.

DNA Fingerprinting↗
PubMed2003

Dedifferentiation and decreased expression of adhesion molecules, E-cadherin and ZO-1, in colorectal cancer are closely related to liver metastasis.

Carcinoma cells with high metastatic potential often show a dedifferentiated phenotype at the primary site. In this study, a total of 48 cases (24 primary tumors of colorectal cancer (Pr-CRC) with liver metastasis, 24 without) were examined for E-cadherin and ZO-1 expression by immunohistochemical staining, and for their dedifferentiated phenotype. The expression levels of E-cadherin and ZO-1 were markedly decreased in the cancer cells of tumors with liver metastasis. Moreover, dedifferentiation of cancer cells, which was evaluated by the modified Gleason score, was also related to liver metastasis. However, none of the conventional clinicopathologic parameters of invasion, except lymph node metastasis, showed any relationship with liver metastasis. These results indicate that dedifferentiation and a decreased expression of E-cadherin and ZO-1 are closely related to liver metastasis.

Cadherins↗
PubMed2002

Bone response to calcium phosphate-coated and bisphosphonate-immobilized titanium implants.

Thin calcium phosphate (Ca-P) coatings have been introduced to overcome the shortcomings of plasma-sprayed Ca-P coatings. In our previous experiments, thin Ca-P coatings also enabled the immobilization of bisphosphonate, which is a drug used to treat osteoporosis. The present study was designed to evaluate the bone response to titanium implants treated with a thin Ca-P coating and bisphosphonate. Forty cylindrical commercially pure titanium implants with a length of 7 mm and a diameter of 3 mm were used as test implant fixtures. Three groups of surface-treated implants were prepared: (1) blasted with titanium powder and etched with a solution of 10% HF + 5% HNO3 (control); (2) modified with 0.5-microm thick Ca-P coatings and rapid heat-treating, and (3) immobilized with bisphosphonate by immersion in pamidronate disodium solution (10(-2) M) for 24 h at 37 degrees C. These surface-treated implants were inserted into edentulous areas in the mandibular molar region of five beagle dogs. After implantation periods of 4 and 12 weeks, the bone implant interface was evaluated histologically and histomorphometrically. All measurements were statistically evaluated using a one-way ANOVA and Fisher PLSD test for multiple comparisons among the means. Four weeks after the implantation, higher percentage of bone contact was found around the thin Ca-P-coated implants compared to that of the control group. The highest percentage of bone contact was found around the bisphosphonate-immobilized implants after 12 weeks of implantation. These data suggest that a thin coating of calcium phosphate followed by bisphosphonate-immobilization is effective in the promotion of osteogenesis on surfaces of dental implants.

Animals↗
PubMed2002

Matrix metalloproteinase-2 expression correlates with morphological and immunohistochemical epithelial characteristics in synovial sarcoma.

AIMS: Synovial sarcoma is a unique mesenchymal tumour characterized by the presence of epithelial differentiation, although the mechanism involved in the epithelial morphology is still unclear. The aim of this study was to evaluate the function of matrix metalloproteinase-2 (MMP-2) in synovial sarcoma, in order to assess whether MMP-2 expression plays an important role in epithelial differentiation, or whether it contributes to a poor clinical outcome. METHODS AND RESULTS: Immunohistochemical stainings for MMP-2, cytokeratins (CKs) 7, 8, 18 and 19, and E-cadherin were performed for 58 (44 monophasic and 14 biphasic) cases of synovial sarcoma, and we compared the expression of these proteins with the histological and clinical findings. MMP-2 and E-cadherin expression was observed in 43 cases (74.1%) and in 18 cases (31.0%), respectively. Expression of these proteins was preferentially observed in the glandular components of biphasic tumours or the epithelioid areas of monophasic tumours. Statistically significant correlations were recognized between MMP-2 expression and E-cadherin expression of biphasic subtype. Moreover, there were statistically significant correlations between monophasic tumours with epithelioid areas and MMP-2 expression or E-cadherin expression. MMP-2 expression was correlated with epithelial differentiation as assessed by CK immunoreactivity. The expression of MMP-2 did not affect the overall survival rate in synovial sarcoma. CONCLUSIONS: MMP-2 expression seemed to have an important role to play in the epithelial differentiation of tumour cells in synovial sarcoma, through remodelling of the extracellular matrix and by changing the cytoskeletal interaction between the extracellular matrix and tumour cells.

Cadherins↗
PubMed2002

Clinicopathological prognostic factors in soft tissue leiomyosarcoma: a multivariate analysis.

AIMS: Prognostic factors affecting survival in cases of leiomyosarcoma of soft parts were investigated in this study. METHODS AND RESULTS: A retrospective study of 267 patients was carried out. This group comprised 142 females (53%) and 125 males (47%), whose ages ranged from 7 to 95 years (median 58 years). One hundred and five cases were superficially situated (arising from the skin or subcutis), while the remaining 162 cases were deeply situated (subfacial). Nineteen were cases of pleomorphic leiomyosarcoma where the diagnosis had been amended from malignant fibrous histiocytoma to leiomyosarcoma whilst under review. Of the 167 patients with follow-up data, 83 died of leiomyosarcoma. In univariate analysis, depth, tumour size (>or=50 mm), mitotic rate of >20 per 10 high-power fields (HPF), tumour necrosis of >50% and a high stage according to the most recent American Joint Committee on Cancer (AJCC) staging for soft tissue sarcoma were found to lessen significantly the rate of survival (log rank test; P < 0.05). However, in multivariate analysis (Cox's proportional hazards model), tumour size and high AJCC stage were the only factors that were correlated independently with decreased survival. CONCLUSIONS: This study indicates that the most reliable prognostic parameters are tumour size and AJCC stage in leiomyosarcoma.

Adolescent↗
PubMed2002

Renal cell carcinoma with rhabdoid features: an aggressive neoplasm.

AIMS: Only a few reports on renal cell carcinoma with rhabdoid features have been published. This study was performed to investigate the clinicopathological characteristics of renal cell carcinomas with rhabdoid features. METHODS AND RESULTS: Among 253 cases of renal cell carcinoma in adults, eight cases with rhabdoid features were detected. Rhabdoid areas ranged from 10% to 90% of each of the cases. Seven of the eight cases were TNM stage III or IV, and four of the eight cases died within 8 months of surgery. Immunohistochemically, the rhabdoid areas were positive for CAM 5.2 (4/8), AE1/AE3 (6/8), epithelial membrane antigen (6/8) and vimentin (8/8), and negative for myogenetic markers (0/8). The mean MIB-1 labelling index in the rhabdoid areas was higher than that in the definite carcinomatous areas. Ultrastructurally, perinuclear whorls of intermediate filaments were demonstrated in three of the eight cases using paraffin-embedded blocks. CONCLUSIONS: The rhabdoid areas in renal cell carcinoma have histological, immunohistochemical and ultrastructural similarities to malignant rhabdoid tumours. Renal cell carcinoma with rhabdoid features is a highly aggressive neoplasm and its malignant behaviour may be due to the high cell-proliferative activity of the rhabdoid areas. Rhabdoid features in renal cell carcinoma may represent the endpoint of clonal evolution of renal cell carcinoma (especially in clear cell type cases).

Aged↗
PubMed2002

Effect of HEMA on bonding of Er:YAG laser-irradiated bovine dentine and 4-META/MMA-TBB resin.

The purpose of this study was to evaluate the priming effect of 2-hydroxyethylmetaclirate (HEMA) following acid treatment on resin bonding to prototype Er:YAG laser-irradiated dentine. Extracted bovine dentine following laser irradiation was acid treated by aqueous solution of 10% citric acid (10-0) or 10% citric acid/3% ferric chloride (10-3), and additionally treated with 35% HEMA. Pre-treated dentines were bonded to the polymethyl-methacrylate (PMMA) rod with 4-META/MMA-TBB resin (Super Bond C & B) and miniaturized dumbbell-shaped bonded specimens were prepared. These specimens profiled for tensile bond testing and fractured surfaces were observed by scanning electron microscopy (SEM). Cross-sections of resin-dentine interface were also examined. The HEMA treatment following acid conditioned by 10-3 or 10-0 for both laser-irradiated and non-irradiated dentines was significantly higher than that without HEMA treatment. SEM view of a fractured specimen showed some cohesive failure in cured resin, but almost all of the fractured surface shows boundary failure between the penetrated resin and underlying dentine. A cross-sectional view of the interface showed a very thick hybrid layer between the hybridized dentine and underlying dentine. It was concluded that HEMA treatment following acid conditioning provided a slightly higher bond strength for both the Er:YAG laser-irradiated and non-irradiated dentines. However, the bond strength of Er:YAG laser irradiated dentine was significantly lower than that of the non-irradiated dentine.

Animals↗
PubMed2002

The ENaC channel is required for normal epidermal differentiation.

Ionic fluxes are important for critical aspects of keratinocyte differentiation, including synthesis of differentiation-specific proteins, enzymatic catalysis of protein cross-linking, post-transcriptional processing of profilaggrin, and lipid secretion. The epithelial sodium channel is expressed in epidermis and the expression of its alpha and beta subunits is enhanced as keratinocytes differentiate. In order to ascertain the role of the epithelial sodium channel in epidermal differentiation, we examined skin of mice in which the epithelial sodium channel alpha subunit had been deleted. Newborn -/- mice, in which the alpha subunit had been completely inactivated, demonstrated epithelial hyperplasia, abnormal nuclei, premature secretion of lipids, and abnormal keratohyaline granules. In addition, immunohistochemistry demonstrated that expression of the differentiation markers K1, K6, and involucrin were abnormal. These data suggest that the epithelial sodium channel modulates ionic signaling for specific aspects of epidermal differentiation, such as synthesis or processing of differentiation- specific proteins, and lipid secretion.

Animals↗
PubMed2002

Clinicopathological study of involvement of granulocyte colony stimulating factor and granulocyte-macrophage colony stimulating factor in non-lymphohematopoietic malignant tumors accompanied by leukocytosis.

Involvement of granulocyte colony stimulating factor (G-CSF) and granulocyte-macrophage colony stimulating factor (GM-CSF) in non-lymphohematopoietic malignant tumors accompanied by leukocytosis was clinicopathologically investigated. Among 1,778 autopsy cases in the last 20 years, 485 lesions of 439 cases with non-lymphohematopoietic malignant tumors accompanied by leukocytosis with a white blood cell count of 10,000/mm3 or greater during the course were immunohistologically examined for G-CSF and GM-CSF. Three (0.7%) and two cases (0.5%) were G-CSF- and GM-CSF-positive, respectively. GM-CSF mRNA was confirmed by using non-fixed cryopreserved tumor tissues in one case positive for GM-CSF. G-CSF-positive cases were large cell carcinoma of the lung, adenocarcinoma of the colon, and adenocarcinoma of the stomach, and GM-CSF-positive cases were spindle cell carcinoma of the lung and malignant thymoma. In the case with stomach carcinoma, the primary lesion showing moderately differentiated adenocarcinoma was negative, but the lung metastatic lesion showing less differentiated adenocarcinoma was G-CSF-positive. The survival period was six months or less in four out of five positive cases. The highest white blood cell count in five CSF-positive cases was markedly elevated: 29,400-103,500/mm3 (mean: 59,700/mm3). In four cases, excluding one case which may have been markedly affected by chemotherapy, the bone marrow showed hyperplasia, and the number of the granulocyte series cells significantly increased. There were three cases (0.7%) negative for both G-CSF and GM-CSF, although they showed marked leukocytosis (60,000/mm3 or higher) which were higher than the mean count of CSF-positive cases and was not observed in autopsy cases with non-tumorous diseases. Other stimulating factors may be involved in the development of leukocytosis in such cases.

Bone Marrow↗
PubMed2001

Protective effects of baicalein and wogonin against benzo[a]pyrene- and aflatoxin B(1)-induced genotoxicities.

To evaluate the protective effects of baicalein and wogonin against benzo[a]pyrene- and aflatoxin (AF) B(1)-induced toxicities, the effects of these flavonoids on the genotoxicities and oxidation of benzo[a]pyrene and AFB(1) were studied in C57BL/6J mice. Baicalein and wogonin reduced benzo[a]pyrene and AFB(1) genotoxicities as monitored by the umuC gene expression response in Salmonella typhimurium TA1535/pSK1002. Baicalein added in vitro decreased liver microsomal benzo[a]pyrene hydroxylation (AHH) activity with an ic(50) of 33.9 +/- 1.4 microM at 100 microM benzo[a]pyrene. Baicalein also inhibited AFQ(1) and AFB(1)-epoxide formation from AFB(1) (50 microM) oxidation (AFO) with ic(50) values of 22.8 +/- 1.4 and 5.3 +/- 0.8 microM, respectively. However, the in vitro inhibitory effects of wogonin on AHH and AFO activities in liver microsomes were less than those of baicalein as inhibition by 500 microM wogonin was only about 51-65%. Treatment of mice with liquid diets containing 5 mM baicalein and wogonin resulted in 22 and 49% decreases in hepatic AHH activities, respectively. Baicalein treatment resulted in 39 and 32% decreases in AFQ(1) and AFB(1)-epoxide formation from liver microsomal AFO, respectively. Wogonin treatment resulted in 39 and 47% decreases in AFQ(1) and AFB(1)-epoxide formation, respectively. A 1-week pretreatment with wogonin significantly decreased hepatic DNA adduct formation in mice treated with 200 mg/kg of benzo[a]pyrene via gastrogavage. These in vitro and in vivo effects suggested that baicalein and wogonin might have beneficial effects against benzo[a]pyrene- and AFB(1)-induced hepatic toxicities and that wogonin had a stronger protective effect in vivo.

Aflatoxin B1↗
PubMed2001

Specific distribution of sialic acids in animal tissues as examined by LC-ESI-MS after derivatization with 1,2-diamino-4,5-methylenedioxybenzene.

Simultaneous analysis of sialic acids has been a challenging target, because sialic acids having N- or O-acetyl, glycolyl, and sulfonic acid ester groups are labile during their release from carbohydrate chains and analytical procedures. In the present paper, we propose a method using high-performance liquid chromatography coupled with eletrospray ionization mass spectrometry (HPLC-ESI-MS). The method was evaluated by applying to the analysis of sialic acids in various tissues, especially digestive organs in mice and rats. The method was based on the in situ precolumn derivatization of sialic acids after releasing them by hydrolysis. The sialic acids were derivatized with 1,2-diamino-4,5-methylenedioxybenzene to form highly fluorescent quinoxaline derivatives. By using two different hydrolysis conditions (i.e., with 2 M acetic acid and with 0.1 M hydrochloric acid), both total sialic acids and sialic acid distributions were easily determined. We found that sialic acids showed characteristic distributions in the tissues of mice and rats. Further, HPLC-ESI-MS revealed that all the tissues examined in mice and rats commonly contained highly acetylated sialic acids and 8-O-sulfated N-acetylneuraminic acid.

Animals↗
PubMed2001

Calponin and h-caldesmon expression in atypical fibroxanthoma and superficial leiomyosarcoma.

To evaluate smooth muscle differentiation, myogenic markers [desmin, alpha-smooth muscle actin (SMA), and muscle-specific actin (HHF35)] have been widely used. Calponin and h-caldesmon, which are cytoskeleton-associated actin-binding proteins, have been reported to be more specific myogenic markers, especially since myofibroblasts express a small amount of h-caldesmon. Atypical fibroxanthoma (AFX) occurs in the sun-exposed skin of the elderly and follows a benign clinical course. Histologically, AFX, which is a pleomorphic spindle cell tumor and considered to be a superficial variant of malignant fibrous histiocytoma, also mimics leiomyosarcoma. AFX has been thought to differentiate along pathways with fibrohistiocytic and myofibroblastic phenotypes. AFX ( n=10), superficial leiomyosarcoma (S-LMS) ( n=17) and benign fibrous histiocytoma (BFH) ( n=17) were analyzed for myofibroblastic and smooth muscle differentiation immunohistochemically from the viewpoint of comparison. AFX and BFH showed immunoreactivities respectively for calponin (3/10, 11/17), desmin (3/10, 1/17), SMA (3/10, 13/17), and HHF35 (1/10, 5/17), but failed to express h-caldesmon (0/10, 0/17). S-LMS had a high immunoreactive rate of calponin (17/17), desmin (13/17), SMA (16/17), and HHF35 (16/17), while also expressing caldesmon (11/17). The results reveal that AFX and BFH have immunoreactivities for several myogenic markers, with myofibroblastic differentiation (calponin: +/-, h-caldesmon: -), but without the smooth muscle differentiation seen in S-LMS (calponin:+, h-caldesmon: +/-). In addition, calponin and h-caldesmon are considered to be useful markers for distinguishing AFX from S-LMS.

Adolescent↗
PubMed2001

Metabolic activation of carcinogenic 1-nitropyrene by human cytochrome P450 1B1 in Salmonella typhimurium strain expressing an O-acetyltransferase in SOS/umu assay.

Metabolic activation of 1-nitropyrene (1-NP) by human cytochrome P450 (P450) family 1 enzymes co-expressed with NADPH-cytochrome P450 reductase (NPR) in Escherichia coli membranes was investigated. 1-NP induced umu gene expression in Salmonella typhimurium TA1535/pSK1002 in the absence of any P450 system, but the activities were influenced by the levels of bacterial O-acetyltransferase (OAT) and nitroreductase. Metabolic activation of 1-NP by human P450 1B1/NPR membranes was observed and was influenced by the levels of OAT levels in tester strains. Metabolic activation of 1-NP (0.3microM) by P450 1B1 was 750 umu units/min/nmol P450 1B1 in an OAT-overexpressing strain NM2009. The metabolic activation of 1-NP (3-30microM) was similar (approximately 300 umu units/min/nmol P450 1B1) using TA1535/pSK1002 or OAT-deficient strain NM2000. P450 1B1 had the highest catalytic activities among P450 family 1 enzymes for the activation of 1-aminopyrene (1-AP) in the OAT-overexpressing strain NM2009, suggesting nitrenium ion formation via N-hydroxylation/O-acetylation. High-performance liquid chromatography (HPLC) analyses revealed the formation of 1-nitropyrene-6-ol and also 1-nitropyrene-3-ol, 1-nitropyrene-8-ol, and trans-4,5-dihydroxy-4,5-diol-1-nitropyrene from 1-NP (10microM), catalyzed by P450 1B1. These results indicate that 1-NP can be activated by human P450 1B1 to a genotoxic agent by nitroreduction/O-acetylation at low substrate concentrations and probably by epoxidation (independent of OAT) at high concentrations.

Acetyltransferases↗