PubMed Health⌕ Search

Biomedical subjects

E Bresnick

Publications and source records attributed to E Bresnick.

At least 55 records · Page 3Linked to original sources
PubMed1989

The effect of diets enriched in cabbage and collards on murine pulmonary metastasis.

Feeding mice with diets enriched in dried cruciferous vegetables (cabbage and collards) resulted in a significant decrease in the number of pulmonary metastases after the animals were injected intravenously with mammary tumor cells. No differences in weight gain or calorie consumption were seen between the mice fed the different diets. These results support other evidence that diets high in cruciferous vegetables may be beneficial in cancer prevention.

Animals↗
PubMed1988

The 4S binding protein acts as a trans-regulator of the polycyclic hydrocarbon-inducible cytochrome P450.

A model has been proposed for the induction of cytochrome P450c in liver by polycyclic hydrocarbons such as benzo(a)pyrene (BaP) and 3-methylcholanthrene (3MC). The polycyclic hydrocarbon interacts in specific, saturable, and high-affinity fashion with a rat liver cytosolic 4s binding protein. The latter enters the nucleus, complexes to 5' upstream regions of the cytochrome P450c gene, and stimulates the transcription. The 4s binding protein has been purified from rat liver and its substrate specificity has been determined. The affinity for 3MC or BaP is 1-2 mM. The binding protein has been demonstrated to complex with specific 5'-upstream regions of the P450c gene by using a filtration assay as well as exonuclease footprinting. In addition, the binding protein stimulates in vitro transcription with upstream regions of the P450c gene as template; these data confirm the hypotheses.

Animals↗
PubMed1987

Interaction of the 4 S polycyclic aromatic hydrocarbon-binding protein with the cytochrome P-450c gene.

The induction of cytochrome P-450c, the isozyme most closely associated with aryl hydrocarbon hydroxylase activity in the rat, is mediated through a cytosolic polycyclic aromatic hydrocarbon (PAH)-binding protein(s). We have reported on the purification and characterization of a 4 S protein that interacts in a specific and saturable manner with [3H]benzo[a]pyrene and other PAHs. (W. H. Houser et al. (1985) Biochemistry 24, 7839-7845). We have also reported on the specific and saturable interaction of the 4 S protein with a plasmid containing 1.9 kbp of cloned rat P-450c sequence including exon 1, the 5' half of intron 1, and approximately 882 bp upstream information. Our investigations now show that incubation of this protein with a portion of the rat P-450c gene, followed by digestion with either lambda exonuclease or exonuclease III, tentatively identified two protected regions at -225 and -455 bp 5' from exon 1. To further study the significance of these protected regions, a 3.4-kbp fragment containing cytochrome P-450c promoter and 5'-upstream sequences (-882 to +2545) was fused to the chloramphenicol acetyl transferase (CAT) reporter gene and transfected into either rat epithelial RL-PR-C cells or rat hepatoma H-4-II-E cells. Both cell lines expressed CAT activity in response to induction by 3-methylcholanthrene (3MC), indicating that important regulatory regions responsive to 3MC are present in these constructs. However, neither cell line expressed CAT activity in response to 3MC when transfected with plasmids containing deletions (-95 to -724 or -240 to -720) in the regions shown to be protected by our footprinting studies. These results corroborate previous studies which indicated that the 4 S PAH-binding protein interacts in a specific manner with regions of the rat cytochrome P-450c gene. We conclude that the 4 S protein may play an important role in the regulation of expression of cytochrome P-450c in the rat.

Animals↗
PubMed1987

Synergy of phenobarbital and 3-methylcholanthrene in "superinduction" of cytochrome P-450c mRNA but not enzyme activity.

The combination of phenobarbital and 3-methylcholanthrene in the inductive process of the rat hepatic cytochrome P-450c gene was evaluated. Daily injections of phenobarbital (80 mg/kg, i.p.) had little or no effect on the amount of poly (A)+ RNA encoding cytochrome P-450c, whereas a single injection of 3-methylcholanthrene (25 mg/kg, i.p.) produced a significant accumulation at 15 hr in cytosolic mRNA coding for cytochrome P-450c. Four daily injections of phenobarbital followed by a single dose of 3-methylcholanthrene produced 5-24 times more poly (A)+ RNA coding for P-450c than 3-methylcholanthrene treatment alone. This superinduction of RNA transcripts was also observed for a species coding for cytochrome P-450d, which was increased 3-6 times over 3-methylcholanthrene treatment alone. However, the elevated concentration of transcripts for both the P-450d and P-450c RNA species did not result in an increase in the marker enzyme activity for cytochrome P-450c, 7-ethoxyresorufin O-deethylase. These data implicate a regulatory step in the induction of cytochrome P-450c enzyme activity which must occur at a level beyond transcription.

Animals↗
PubMed1987

Multiple constitutive but phenobarbital-inducible rat hepatic nuclear RNA species homologous to a novel cytochrome P-450 cDNA.

A cDNA clone, pPB8, representing partial information for a phenobarbital-inducible rat hepatic cytochrome P-450, immunochemically related to cytochrome P-450b and/or P-450e, hybridized to multiple hepatic nuclear RNA species. In addition to the 3.7 +/- 0.2 kb mRNA encoding this novel cytochrome P-450 isozyme, pPB8 hybridized to nuclear RNAs of 4.9 +/- 0.3, 5.4, 5.7 +/- 0.2, and 6.3 +/- 0.1 kb. These nuclear RNAs were constitutively expressed and were inducible to various extents by phenobarbital administration. The time course of induction of these nuclear RNA components suggested product-precursor relationships. A "full-length" cDNA clone, pPB8/7, synthesized from poly(A)+ RNA homologous to pPB8, detected two mRNA species of 4.6 and 1.8 kb. The 4.6 kb nuclear RNA was inducible by 3-methylcholanthrene, Aroclor 1254, and phenobarbital, while the 1.8 kb nuclear RNA was not appreciably affected. It is suggested that pPB8 and pPB8/7 were synthesized from distinct mRNAs that share homology in their 3' regions.

Animals↗
PubMed1987

Aflatoxin B1-4-hydroxylase is associated with cytochrome P3-450 in C57BL/6 mouse liver.

Messenger RNA from the livers of Aroclor 1254 treated mice was used to produce a cDNA library. cDNA clones corresponding to cytochromes P1-450 and P3-450 were isolated from this library by screening with a probe for the rat cytochrome P-450c gene. Specific non-cross hybridizing probes for P1-450 and P3-450 were prepared from unique restriction fragments. The radiolabeled probes were hybridized to RNA from mice treated with a low (15 mg/kg) and high (150 mg/kg, 400 mg/kg) doses of beta-naphthoflavone. The low dose of beta-naphthoflavone was found to induce only P3-450 mRNA, whereas higher doses induced both P1-450 and P3-450 mRNA. Similarly, a low dose of beta-naphthoflavone induced aflatoxin B1-4-hydroxylase, whereas higher doses induced both aflatoxin B1-4-hydroxylase and aryl hydrocarbon hydroxylase activities. These results suggest that P3-450 mRNA codes for the cytochrome that is associated with aflatoxin B1-4-hydroxylase activity.

Animals↗
PubMed1987

Structural details of the human cytochrome P-450c gene.

Aryl hydrocarbon hydroxylase activity is most closely associated with cytochrome P-450c in the rat and cytochrome P1-450 in the mouse. The sequence for the orthologous human gene coding for this enzymatic activity has been determined from several sources: cytochrome P-450c isolated from human embryonic DNA [K. Kawajiri, J. Watanabe, O. Gotoh, Y. Tagashiri, K. Sogawa, and Y. Fujii-Kuriyama (1986) Eur. J. Biochem. 139, 219-225], human lymphocytes in our own laboratory, and cytochrome P1-450 isolated from the established human breast carcinoma cell line, MCF-7 [A.K. Jaiswal, F. J. Gonzalez, and D. W. Nebert (1985) Nucleic Acids Res. 13, 4503-4520]. The data from our laboratory agree well with the sequence derived from human embryonic DNA, but differs significantly from that reported for the gene isolated from MCF-7 cells. Among these differences are a 320-bp insert and a 650-bp deletion in intron 1 relative to the sequence derived from the established cell line. We observe two mRNA species that hybridize to cytochrome P-450c probes, one expected at 2.7 kb and an additional 2.0-kb species. Finally, we note additional hybridization bands in 11% of the population examined by Southern blot analysis, representing either a second rare allele or, more likely, a duplication of at least a portion of the cytochrome P-450c gene.

Base Sequence↗
PubMed1987

Metabolism of 6-nitrobenzo[a]pyrene in rat lung preparations.

6-Nitrobenzo[alpha]pyrene (6-NBaP) occurs in our environment. Since human exposure to environmental contaminants may occur via the inhalation route, we examined the metabolites of 6-NBaP formed in lung preparations, and compared the metabolite profile to that which was found with liver. The metabolites formed in both liver and lung preparations consisted of ring-hydroxylated 6-NBaP, 6-hydroxybenzo[a]pyrene (6-OHBaP) and small amounts of benzo[a]pyrene. In the lung experiments, 6-OHBaP most frequently oxidized to quinones. The mechanism for the formation of 6-OHBaP from 6-NBaP remains to be elucidated.

Animals↗
PubMed1987

Enhanced pancreatic and skin tumorigenesis in cabbage-fed hamsters and mice.

Studies were conducted to evaluate the ability of dietary dried cabbage supplements to inhibit pancreatic carcinogenesis in hamsters and skin tumorigenesis in mice. Pancreatic cancer was induced by treatment with 40 mg/kg body wt N-nitrosobis-(2-oxopropyl)amine (BOP). Cabbage was fed from before carcinogen treatment in low fat diet and, beginning 1 week after BOP treatment, cabbage was given in low fat and high fat diets in comparison with the respective non-cabbage-containing diets. Dried cabbage was incorporated at 9 and 11% levels into the low and high fat diets. Feeding cabbage in the high fat diet elevated the yield of BOP-induced pancreatic ductular carcinoma (1.6 carcinomas/effective animal) in comparison with that observed in hamsters fed cabbage in a low fat diet or in those given a high fat diet without cabbage, 0.6-0.8 carcinomas/effective animal (P less than 0.05). Furthermore, the incidence of BOP-induced gall bladder adenocarcinoma was elevated in cabbage-fed hamsters irrespective of dietary fat intake. Effects of dietary fat and cabbage on food consumption, body weight, and serum T3 and T4 values are described. Skin tumorigenesis was induced in SENCAR mice by 10 nmol 7,12 dimethylbenz[a]anthracene (DMBA) and promoted beginning 1 week later with twice weekly applications of 2 micrograms 12-O-tetradecanoyl-13-phorbol acetate (TPA). Dried cabbage was incorporated into AIN semi-purified diets from before DMBA treatment and throughout TPA treatment. Skin papilloma yield was elevated in DMBA-initiated TPA-promoted mice that were fed diets containing 10% cabbage. Mice fed cabbage developed an average of 8.45 papillomas per mouse following 22 weeks of promotion while mice given control diet developed 7.25 papillomas per mouse (P less than 0.001). Cabbage feeding did not influence survival, food consumption or body weight of the mice. These results suggest the need for further research on the use of cabbage as a chemopreventive measure.

Animals↗
PubMed1987

Ring oxidation of 6-nitrobenzo (a) pyrene by female mouse liver.

6-Nitrobenzo (a) pyrene (6-NBaP) is an environmental contaminant. In bacterial mutagenesis assays, 6-NBaP requires rat liver S9 enzymes for its activity. Chemical characterization of metabolites of 6-NBaP produced by male rat liver microsomes showed them to be ring-hydroxylated (both mono- and dihydroxy) derivatives. Thus, metabolic activation of 6-NBaP may occur via ring oxidation. It has been shown by others that when injected intraperitoneally into newborn mice, 6-NBaP was carcinogenic to male, but not to female, mouse liver. The nitro-hydrocarbon was not carcinogenic to the lungs of either sex. We have examined the metabolism of 6-NBaP by the liver of a non-susceptible female mouse and observed the formation of ring-hydroxylated metabolites of 6-NBaP. In view of this observation, we suggest that ring hydroxylation alone may not be sufficient in explaining the carcinogenicity of 6-NBaP in male and not in female mice.

Acetylation↗
PubMed1986

Northern hybridization analysis of RNA using diethylpyrocarbonate-treated nonfat milk.

A simple and relatively inexpensive method for hybridizing RNA that is immobilized on nitrocellulose to a radioactive DNA probe is presented. The procedure, a modification of the Bovine Lacto Transfer Technique Optimizer method of Johnson et al. (1984) Gene Anal. Tech. 1, 3-8, uses nonfat milk which has been treated with the RNase inhibitor, diethylpyrocarbonate (DEPC), to saturate nonspecific binding sites on nitrocellulose paper, and to wash off unbound radioactivity. The DEPC-nonfat milk hybridization technique is faster, less costly, and more reliable than standard Northern blot hybridization conditions, yielding sharp, clear bands of RNA on autoradiographs with virtually no background reactivity.

Animals↗
PubMed1986

Further characterization of the polycyclic aromatic hydrocarbon binding properties of the 4S protein.

A 4-S protein which specifically binds [3H]benzo(a)pyrene and other polycyclic aromatic hydrocarbons has been investigated in the rat using a hydroxylapatite assay and sucrose gradient analysis. Although there was significant interanimal variation, the specific polycyclic aromatic hydrocarbon binding activity appeared to be highest in 4-week-old male rats and declined with age. The specific [3H]benzo(a)pyrene binding activity was induced after pretreatment with either phenobarbital or isosafrole as evidenced by a 72 and 61% increase, respectively, over untreated controls. No apparent increase in specific binding activity was observed after pretreatment of animals with 3-methylcholanthrene. Pretreatment with either phenobarbital or isosafrole also resulted in the appearance of a small, nonspecific, benzo(a)pyrene binding peak at the 8- to 9-S region in the sucrose density gradients. This 8-S peak was not seen in untreated control animals and represented low affinity, high capacity binding sites. In contrast to the 8-S protein, the 4-S binding protein had low affinity for polychlorinated aromatic compounds such as tetrachlorodibenzodioxin and tetrachlorodibenzofuran. The addition of a 200-fold excess of tetrachlorodibenzofuran to incubations did not displace [3H]benzo(a)pyrene from the 4-S protein. The addition of sodium molybdate to isolation buffers, known to stabilize certain hormone receptors, did not alter the sedimentation coefficient or the specific binding activity of the 4-S protein. These experiments indicate that the 4-S protein does not appear to be a subunit of the 8-S protein. We conclude that in the rat the 4-S protein is distinct from the 8-S protein and the 4-S species may regulate the polycyclic aromatic hydrocarbon-induced expression of aryl hydrocarbon hydroxylase activity.

Age Factors↗
PubMed1986

Regulation of cytochrome P-450c by glucocorticoids and polycyclic aromatic hydrocarbons in cultured fetal rat hepatocytes.

The actions of polycyclic aromatic hydrocarbons and glucocorticoids to regulate the synthesis of cytochrome P-450c (the major isozyme induced by polycyclic aromatic hydrocarbons) were investigated in fetal rat hepatocytes maintained in primary monolayer culture. Treatment of hepatocytes in culture with 1,2-benzanthracene resulted in a 50-fold increase in 7-ethoxycoumarin O-deethylase activity. The level of P-450c increased in the cells in a time-dependent fashion as determined by immunoelectrophoretic analysis. The inductive effect of BA was potentiated approximately 1.6- to 2.3-fold when 1 microM dexamethasone was included in the culture medium. However, dexamethasone alone had little or no effect on the induction of P-450c. The rate of synthesis of P-450c was examined by immunoisolation of the specific isozyme from total cellular proteins radiolabeled with [35S]methionine and from the protein products formed during in vitro translation of the isolated mRNA. In addition, the amount of mRNA specific for cytochrome P-450c was determined by Northern blot analysis of RNA extracted from cultured cells. The changes in the rates of synthesis and mRNA levels were found to parallel the changes in enzyme activity. The concentration of dexamethasone required to cause a half-maximal increase in P-450c content in the presence of 1,2-benzanthracene was between 10(-8) and 10(-7) M. It is concluded that glucocorticoids act synergistically with polycyclic aromatic hydrocarbons to increase the levels of P-450c expressed in the fetal rat liver, and that this action is likely mediated by the classical type II glucocorticoid receptor.

Animals↗
PubMed1986

6-Nitrobenzo[a]pyrene can be denitrated during mammalian metabolism.

Nitropolycyclic aromatic hydrocarbons (nitroarenes), including 6-nitrobenzo[a]pyrene (6-NBap), occur in our environment and are mutagenic in bacterial mutagenesis assays. The mutagenicity of 6-NBaP is enhanced when rat liver S9 is added. To investigate the cause of this increased activity, the metabolism of 6-NBaP was carried out with a total rat liver homogenate obtained from 3-methylcholanthrene- (MC-) induced rats, a 9000 X g supernatant enzyme, and with both unwashed and washed microsomes. Ring-hydroxylated 6-NBaP was detected. On the basis of retention times for known standards in a high-performance liquid chromatographic system, benzo[a]pyrene (BaP) and 6-acetoxy-BaP (6-OAcBaP) were isolated as products. BaP was further characterized via ultraviolet (UV) and mass spectra and 6-OAcBaP by UV, mass, and nuclear magnetic resonance (NMR) spectra. 6-HydroxyBaP (6-OHBaP) was also detected by UV and mass spectra. It is suggested that BaP is formed via a nitroanion radical of 6-NBaP and undergoes metabolism, while the 6-OHBaP is acetylated to form 6-OAcBaP. The acetyl donor remains to be identified.

Animals↗
PubMed1986

Anti-mutagenesis and anti-promotion by apigenin, robinetin and indole-3-carbinol.

We assessed the anti-mutagenic and anti-promotion properties of two flavones, apigenin and robinetin, and of indole-3-carbinol, because these compounds have been reported in vegetables, the consumption of which has been associated with reduced rates of cancer. However, the active components of these foods and their effects on carcinogenesis have not been established. Anti-mutagenicity was determined in the Salmonella typhimurium assay by measuring the effects of the test compounds on bacterial mutagenesis induced by methyl-nitrosourea (MNU), methyl-n-nitro-N-nitrosoguanidine (MNNG), benzo[a]pyrene (BaP) or 2-aminoanthracene (2-AA). Inclusion of apigenin resulted in a 62% and a 43% inhibition of mutagenicity with 13 nmol of 2-AA and 30 nmol BaP respectively. Robinetin caused an 87% inhibition of mutagenicity by 2-AA, but indole-3-carbinol had little or no effect on the mutagenicity of any of the compounds. None of the three compounds inhibited mutagenesis by MNU or MNNG and none were mutagenic or toxic when tested in the absence of mutagenic compounds at doses up to 20 micrograms/plate. Anti-promotion properties were assessed by measuring the effects of apigenin, robinetin and indole-3-carbinol on induction of ornithine decarboxylase activity (ODC) in mouse epidermis by 17 nmol 12-O-tetradecanoyl phorbol-13-acetate (TPA). Pretreatment of the skin half an hour before TPA with apigenin, robinetin, butylated hydroxyanisole, 13-cis-retinoic acid (all at 50 mumol) or di-fluoromethylornithine (1.6 mumol) inhibited ODC induction at 6 h after TPA by 67-80%. Pretreatment with 50 mumol indole-3-carbinol caused a 78% elevation in the TPA induction at this time. Dose response measurements were conducted with apigenin, indole-3-carbinol and robinetin. Inhibition by 30-90% of TPA-induced ODC was observed at 6 h after TPA in mice pretreated with 12.5-100 mumol apigenin. Pretreatment with 37.5 or 50 mumol indole-3-carbinol or 0.5, 12.5 or 25 mumol robinetin resulted in elevated induction of epidermal ODC by TPA at 6 h after TPA. However, treatment with 50 or 100 mumol robinetin diminished ODC induction at 6 h after TPA. Treatment with 100 mumol apigenin or 50 or 100 mumol indole-3-carbinol in non-TPA-treated mouse skin caused elevations in epidermal ODC. In comparing the time course of ODC induction, indole-3-carbinol (50 mumol) pretreatment shifted the induction of epidermal ODC to earlier times, in addition to elevating ODC induction by TPA.(ABSTRACT TRUNCATED AT 400 WORDS)

2-Acetylaminofluorene↗
PubMed1985

Implication of the "4S" polycyclic aromatic hydrocarbon binding protein in the transregulation of rat cytochrome P-450c expression.

A protein which specifically binds [3H]benzo[a]pyrene and other polycyclic aromatic hydrocarbons has been purified over 6000-fold from rat hepatic cytosol by using ion-exchange, gel permeation, and hydrophobic interaction chromatography. The binding protein differs from the 9S binding protein characterized in other laboratories. A Stokes radius of 2.75 nm was determined by gel filtration on Sephadex G-100. A sedimentation coefficient of 3.3 S was determined by using sucrose gradient analysis. The ability of this protein to bind total rat liver DNA as well as subclones containing portions of the rat cytochrome P-450c gene was investigated. Under high stringency conditions, this binding protein was found to interact in a specific and saturable manner with several subclones of the rat cytochrome P-450c gene containing 5'-upstream sequences, as well as portions of intron 1. Binding was not observed to the coding portions of the gene. These data implicate the "4S" binding protein in the transregulation of rat cytochrome P-450c expression.

Animals↗
PubMed1985

3-Methylcholanthrene-induced expression of the cytochrome P-450c gene.

Transcriptional control of 3-methylcholanthrene-dependent cytochrome P-450c nuclear RNA induction was directly observed in an in vitro rat liver nuclear transcription system. Mercurated and radiolabeled ribonucleotides were incorporated into nuclear RNA transcribed in vitro, which was then isolated using thiopropyl-Sepharose 6B affinity chromatography. Dot hybridization experiments were carried out using bacteriophage M13 subclones of pRSA57 (a cDNA clone for rat serum albumin), pEB339 (a cDNA clone for rat cytochrome P-450c), and clone 46 (a cDNA clone for mouse cytochrome P1-450). The results of these studies demonstrate that 3-methylcholanthrene does not significantly influence the transcription of the rat serum albumin gene, but does increase the transcription of the cytochrome P-450c gene. Nuclear RNA precursors to the cytochrome P-450c mRNA were characterized by Northern blot analysis. Clone 46 hybridized to nuclear RNA species of 6.7 and 4.0 kb, in addition to the 3.0-kb cytochrome P-450c mRNA. pA8 (a genomic clone for rat cytochrome P-450c), hybridized to the same nuclear RNA species in addition to nuclear RNA species of 4.3, 3.4, and 2.2 kb. M13pd15 (a genomic clone containing information for the first intron of the cytochrome P-450c gene) hybridized to nuclear RNA species of 6.7 and 4.3 kb. All of these nuclear RNA species are polyadenylated. The mRNA coding for cytochrome P-450c was induced maximally in hepatic nuclei at 3 h following 3-methylcholanthrene administration. Maximal accumulation of cytochrome P-450c mRNA in hepatic cytosol has been previously shown to occur at approximately 15 h following 3-methylcholanthrene administration (Bresnick, E., Brosseau, M., Levin, W., Reik, L., Ryan, D. E., and Thomas, P. E. (1981) Proc. Natl. Acad. Sci. USA 78, 4083-4087). These data implicate a possible role of nuclear RNA transport in the regulation of induction of cytochrome P-450c, although further investigations are indicated.

Animals↗