Biomedical subjects

N Liu

Publications and source records attributed to N Liu.

At least 19 recordsLinked to original sources

PubMed2003

Investigations of 99mTc morpholino pretargeting in mice.

This laboratory is exploring the use of morpholinos (MORFs), synthetic DNA analogues, for nuclear medicine applications, including pretargeting. The anti-CEA antibody MN14 was conjugated with an 18 mer MORF and with diethylenetriaminepentaacetic acid (DTPA) for 111In labelling. In a dual label pretargeting study, tumour-bearing nude mice received different doses of (MN14-DTPA-111In+MN14-MORF) followed, at various times after i.v. injection, by 0.15 microg complementary MORF (cMORF) radiolabelled with 99mTc via MAG(3). Animals were killed 3 h thereafter and tissues were counted for both radionuclides. The 99mTc-cMORF was also administered to tumour bearing mice that, 2 days previously, had received different doses of unlabelled MN14-MORF IgG or, as control, unlabelled Sandoglobulin IgG-MORF (Sandoz-MORF). Tumour uptake was higher at all time points for the labelled antibody itself versus labelled cMORF (8-10 vs 1.3-2.3%ID/g, respectively) in part due to the rapid clearance of cMORF through the kidneys. However, target to non-target ratios were superior for pretargeting at all time points and in all tissue except blood and kidneys. By pretargeting alone, these ratios were highest in all tissues for 15 microg compared to higher MN14-MORF dosages and in all cases were superior to that of the Sandoz-MORF control. The superior target to non-target ratios for pretargeting can be partially explained through calculations based on both radiolabels: after 24 h, only 0-6% of MORF on MN14 was bound by 99mTc-cMORF in liver and spleen suggesting that the antibody is sequestered in these organs and 'invisible' to labelled MORF. Fortunately, this was not the case in tumours in which 50-60% was bound. It is concluded that pretargeting using MORFs provided encouraging results in one mouse model/anti-tumour antibody system. The advantages of pretargeting in this model were evident in the superior target to non-target ratios obtained over conventional imaging.

Animals↗

PubMed2002

Molecular cloning and functional characterization of Cynomolgus monkey (Macaca fascicularis) CC chemokine receptor, CCR3.

We have cloned and performed the first functional characterization of the chemokine receptor, CCR3, of Cynomolgus monkey (Macaca fascicularis). The deduced amino acid sequence of the cloned Cynomolgus CCR3 was found to be more similar to that of a previously-reported Rhesus (Macaca mulatta) CCR3 (99.4%) than that of a reported Cynomolgus CCR3 (98.0%). Stably-transfected Cynomolgus CCR3 bound human eotaxin (CCL11) with similar kinetics (Kd 240 pM) and was responsive to human CCR3 ligands (eotaxin [CCL11], eotaxin-2 [CCL24], and MCP4 [CCL13]) in Ca(2+) mobilization and chemotaxis assays, thus provides a useful alternative species model system for the analysis of modulators of eotaxin--CCR3 induced signaling and activation.

Amino Acid Sequence↗

PubMed2002

Hyaluronan metabolism in rat tail skin following blockage of the lymphatic circulation.

This study was undertaken to explore the effects of lymphatic blockage on the metabolism of hyaluronan in the skin. In initial experiments, [3H] hyaluronan was injected subcutaneously into the tail skin of rats that either had no surgical intervention (control) or into those that had their lymphatic drainage blocked two hours earlier (acute lymphedema) or after the lymphatics had been blocked for three months (chronic lymphedema). The removal of tritiated hyaluronan from the injection sites was determined by the appearance of [3H] in the plasma. The results showed that the clearance of injected hyaluronan was delayed in rats with lymphatic blockage. The half- life of injected hyaluronan in the controls was approximately 70-75 hr, compared with approximately 105-110 hr in the lymph blocking rats. The levels of radioactivity in the plasma from rats with both acute and chronically blocked lymphatics were lower than that of control rats during the entire follow up period. In addition, biochemical analysis revealed that there was a significant increased amount of hyaluronan in the tail skin three months after lymphatic blocking. These results suggest that lymph absorption is an important factor in the transport of hyaluronan from the interstitium. Blockage of regional draining lymphatics likely impairs the catabolism of hyaluronan, which stagnates in skin tissue.

Animals↗

PubMed2002

The influence of chain length and base sequence on the pharmacokinetic behavior of 99mTc-morpholinos in mice.

BACKGROUND: Despite in vivo use now over several years, in particular for nuclear medicine imaging, the influences on pharmacokinetics of chain length and base sequence of radiolabeled oligomers has not been investigated. METHODS: As test oligomer, morpholinos (MORFs), a DNA analogue, were radiolabeled with 99mTc via MAG3 and the pharmacokinetics in normal mice determined for 3 chain lengths (15, 18 and 25 mer) and 2 base sequences (MORF and its complement cMORF). In addition, LS174T-tumor bearing nude mice received the anti-CEA antibody MN14 (Immunomedics) conjugated either with MORF15 or MORF18 and subsequently received 99mTc-labeled cMORF15 or cMORF18 respectively in a pretargeting strategy. RESULTS: In normal mice, after 1 hr, regardless of chain length or sequence, all labeled MORFs and cMORFs accumulated only slightly in all tissues (e.g. at 3 hr <0.15 ID%/g) except in kidneys. Besides being excessive, the kidneys were the only tissue with levels dependent upon chain length (e.g. at 1 hr, 5, 7 and 22 ID%/g for MORF15, 18 and 25, respectively) and sequence (e.g. at 3 hrs 9 ID%/g for MORF25 and 21 ID%/g for cMORF25). Identical biodistribution trends were observed in tumored mice with all tissues including tumor showing levels independent of chain length or base sequence except for kidneys. Furthermore, while all other tissues cleared in the interval from 1-3 hrs, kidney levels remained constant in both normal and tumored animals. Largely because of these differences in kidneys, images obtained by pretargeting with 99mTc-cMORF15 were superior compared to 99mTc-cMORF18 (images of control animals not receiving the antibody showed no tumor at all). CONCLUSIONS: Judged by radiolabel accumulations in tissue, the pharmacokinetics of 99mTc labeled morpholinos were independent of chain length and base sequence. The only obvious exception was kidneys in which accumulations were significantly higher for the longer chain lengths and significantly different for cMORF vs MORF. These results show that chain length and base sequences may be varied to alter the pharmacokinetics of radiolabeled oligomers in nuclear medicine imaging studies.

Animals↗

PubMed2001

Phenotypic differentiation during migration of dopaminergic progenitor cells to the olfactory bulb.

A possible source for transplantable neurons in Parkinson's disease are adult olfactory bulb (OB) dopamine (DA) progenitors that originate in the anterior subventricular zone and reach the OB through the rostral migratory stream. We used adult transgenic mice expressing a lacZ reporter directed by an 8.9 kb tyrosine hydroxylase (TH) promoter to investigate the course of DAergic differentiation. Parallel transgene and intrinsic TH mRNA expression occurred during migration of DA interneurons through the mitral and superficial granule cell layers before these cells reached their final periglomerular position. Differential transgene and calcium-calmodulin-dependent protein kinase IV expression distinguished two nonoverlapping populations of interneurons. Transgenic mice carrying a TH8.9kb/lacZ construct with a mutant AP-1 site demonstrated that this element confers OB DA-specific TH gene regulation. These results indicate that DA phenotypic determination is specific to a subset of mobile OB progenitors.

Animals↗

PubMed2001

Hydrazinonaphthalene and azonaphthalene thrombopoietin mimics are nonpeptidyl promoters of megakaryocytopoiesis.

High-throughput screening for the induction of a luciferase reporter gene in a thrombopoietin (TPO)-responsive cell line resulted in the identification of 4-diazo-3-hydroxy-1-naphthalenesulfonic acids as TPO mimics. Modification of the core structure and adjustment of unwanted functionality resulted in the development of (5-oxo-1,5-dihydropyrazol-4-ylidene)hydrazines which exhibited efficacies equivalent to those of TPO in several cell-based assays designed to measure thrombopoietic activity. Furthermore, these compounds elicited biochemical responses in TPO-receptor-expressing cells similar to those in TPO itself, including kinase activation and protein phosphorylation. Potencies for the best compounds were high for such low molecular weight compounds (MW < 500) with EC(50) values in the region of 1-20 nM.

Animals↗

PubMed2001

Hyaluronan synthase 3 overexpression promotes the growth of TSU prostate cancer cells.

Hyaluronan synthase 3 (HAS3) is responsible for the production of both secreted and cell-associated forms of hyaluronan and is the most active of the three isoforms of this enzyme in adults. In this study, the cDNA for human HAS3 was cloned and characterized. The open reading frame consisted of 1659 bp coding for 553 amino acids with a deduced molecular weight of about 63,000 and isoelectric pH of 8.70. The sequence of human HAS3 displayed a 53% identity to HAS1 and a 67% identity to HAS2. It also contained a signal peptide and six potential transmembrane domains, suggesting that it was associated with the plasma membrane. To evaluate the physiological role of human HAS3, expression vectors for this protein were transfected into TSU cells (a prostate cancer cell line), and the phenotypic changes in these cells were examined. The enhanced expression of hyaluronan in the transfected cells was demonstrated by dot blot analysis and ELISA. These cells were found to differ from their vector-transfected counterparts with respect to the following: (a) they grew at a faster rate in high (but not low) density cultures; (b) conditioned media from these cells stimulated the proliferation and migration of endothelial cells; (c) when placed on the chorioallantoic membrane of chicken embryos, these cells formed large, dispersed xenografts, whereas the control transfectants formed compact masses; and (d) when injected s.c. into nude mice, the xenografts formed by HAS3 transfectants were bigger than those formed by control transfectants. Histological examination of these xenografts revealed the presence of extracellular hyaluronan that could act as conduits for the diffusion of nutrients. In addition, they had a greater number of blood vessels. However, the HAS3-transfected TSU cells did not display increased metastatic properties as judged by their ability to form lung masses after i.v. injection. These results suggested that the HAS3-induced overexpression of hyaluronan enhanced tumor cell growth, extracellular matrix deposition, and angiogenesis but was not sufficient to induce metastatic behavior in TSU cells.

Allantois↗

PubMed2001

A novel fluorometric oligonucleotide assay to measure O( 6)-methylguanine DNA methyltransferase, methylpurine DNA glycosylase, 8-oxoguanine DNA glycosylase and abasic endonuclease activities: DNA repair status in human breast carcinoma cells overexpressing methylpurine DNA glycosylase.

DNA repair status plays a major role in mutagenesis, carcinogenesis and resistance to genotoxic agents. Because DNA repair processes involve multiple enzymatic steps, understanding cellular DNA repair status has required several assay procedures. We have developed a novel in vitro assay that allows quantitative measurement of alkylation repair via O(6)-methylguanine DNA methyltransferase (MGMT) and base excision repair (BER) involving methylpurine DNA glycosylase (MPG), human 8-oxoguanine DNA glycosylase (hOGG1) and yeast and human abasic endonuclease (APN1 and APE/ref-1, respectively) from a single cell extract. This approach involves preparation of cell extracts in a common buffer in which all of the DNA repair proteins are active and the use of fluorometrically labeled oligonucleotide substrates containing DNA lesions specific to each repair protein. This method enables methylation and BER capacities to be determined rapidly from a small amount of starting sample. In addition, the stability of the fluorometric oligonucleotides precludes the substrate variability caused by continual radiolabeling. In this report this technique was applied to human breast carcinoma MDA-MB231 cells overexpressing human MPG in order to assess whether up-regulation of the initial step in BER alters the activity of selected other BER (hOGG1 and APE/ref-1) or direct reversal (MGMT) repair activities.

Alkylation↗

PubMed2001

Analysis of pancreatic development in living transgenic zebrafish embryos.

Using DNA constructs containing regulatory sequences of the zebrafish Pdx-1 and insulin genes, germline transgenic zebrafish expressing the green fluorescent protein (GFP) reporter gene in the pancreas were generated. For both constructs, the GFP expression patterns in transgenic embryos were consistent with the mRNA expression patterns detected by RNA in situ hybridization. A deletion promoter analysis revealed that positive and negative cis-acting elements were involved in regulation of insulin gene expression. Three-dimensional reconstructions imaged from living embryos using two-photon laser-scanning microscopy (TPLSM) demonstrated that the zebrafish pancreas is formed from a single dorsal pancreatic cell mass. This is in contrast to mammals where the pancreas derives from both dorsal and ventral anlage. These transgenic fish should be useful for in vivo studies of factors involved in specifying and regulating pancreatic development and function.

5' Untranslated Regions↗

PubMed2001

Induction of CYP1A by benzo[k]fluoranthene in human hepatocytes: CYP1A1 or CYP1A2?

While fresh human hepatocyte cultures are widely used to model hepatic cytochrome P450 (CYP) regulation and activity, their CYP1A subfamily composition induced by, e.g., polycyclic aromatic hydrocarbons is ambiguous. CYP1A1, CYP1A2, or both have been reported to be expressed, and their varied roles in chemical carcinogenesis makes resolution of which CYPs are expressed essential. We have used an immunoblot system with Bis-Tris-HCl-buffered polyacrylamide gel, which clearly resolves human CYP1A1 and CYP1A2, and polyclonal goat anti-human CYP1A1/CYP1A2 and rabbit anti-human CYP1A2 antibodies to probe the expressed CYP1A1 and CYP1A2 composition of seven individual human hepatocyte cultures induced with 5 microM benzo[k]fluoranthene (BKF) for 24 h. In six of the cultures only CYP1A1 was detected, and in the seventh both CYPs were detected. In most vehicle-treated hepatocyte cultures, neither CYP1A1 nor CYP1A2 was detected. In three additional hepatocyte cultures treated individually with BKF and 2,3,7,8,-tetrachlorodibenzo-p-dioxin (TCDD), the resultant induced CYP1A1/1A2 profiles were essentially not influenced by the nature of the inducing agents. To develop an activity-based assay to differentiate between CYP1A1 and CYP1A2 expression in human hepatocytes, our previously published R warfarin assay (Drug Metab. Disp. (1995) 23, 1339-1345) was applied to TCDD (10 nM)-treated hepatocyte culture. The low concentration of TCDD did not produce inhibition of the warfarin metabolism-such inhibition could confound the results. Based on the ratios of 6- to 8-hydroxywarfarin formed in two cultures, the ratios of CYP1A1/CYP1A2 expressed in these cultures were determined and they agreed with the ratios determined by immunoblot analysis. Thus each individual human hepatocyte culture must be characterized for induced CYP1A1 and CYP1A2 expression in studies of CYP1A activity. The warfarin assay provides a means of characterizing the cultures.

Adolescent↗

PubMed2001

RGD-Tachyplesin inhibits tumor growth.

Tachyplesin is an antimicrobial peptide present in leukocytes of the horseshoe crab (Tachypleus tridentatus). In this study, a synthetic tachyplesin conjugated to the integrin homing domain RGD was tested for antitumor activity. The in vitro results showed that RGD-tachyplesin inhibited the proliferation of both cultured tumor and endothelial cells and reduced the colony formation of TSU prostate cancer cells. Staining with fluorescent probes of FITC-annexin V, JC-1, YO-PRO-1, and FITC-dextran indicated that RGD-tachyplesin could induce apoptosis in both tumor and endothelial cells. Western blotting showed that treatment of cells with RGD-tachyplesin could activate caspase 9, caspase 8, and caspase 3 and increase the expression of the Fas ligand, Fas-associated death domain, caspase 7, and caspase 6, suggesting that apoptotic molecules related to both mitochondrial and Fas-dependent pathways are involved in the induction of apoptosis. The in vivo studies indicated that the RGD-tachyplesin could inhibit the growth of tumors on the chorioallantoic membranes of chicken embryos and in syngenic mice.

3T3 Cells↗

PubMed2001

2-Azabicyclo[2.1.1]hexanes. 2. Substitutent effects on the bromine-mediated rearrangement of 2-azabicyclo[2.2.0]hex-5-enes.

Methyl- and phenyl-substituted N-(ethoxycarbonyl)-2-azabicyclo[2.2.0]hex-5-enes 6 have been prepared by photoirradiation of appropriately substituted 1,2-dihydropyridines. Torquoselectivity is observed in the synthesis of the 3-endo-methyl- and 3-endo-phenyl-2-azabicyclo[2.2.0]hexenes 6c-e from 2-methyl- and 2-phenyl-1,2-dihydropyridines 5c-e. Products formed upon addition of bromine to 3-endo-, 4-, and 5-methyl- and 3-endo-phenyl-substituted N-(ethoxycarbonyl)-2-azabicyclo[2.2.0]hex-5-enes 6a-f were substituent dependent. For 6a,b, which lack substituents at C(3) or C(5), mixtures of unrearranged dibromides 8a,b and rearranged dibromides 9a,b were obtained. With the 3-endo-substituents in 6c-e, only rearranged dibromides 9c-e were formed; 5-methyl substitution afforded mainly unrearranged dibromide 8f and some allylic bromide 10. Both unrearranged 5-endo,6-exo-dibromo-2-azabicyclo[2.2.0]hexanes 8 and rearranged 5-anti-6-anti-dibromo-2-azabicyclo[2.1.1]hexanes 9 are formed stereoselectively. The dibromoazabicyclo[2.1.1]hexanes 9 have been reductively debrominated to afford the first reported 2-azabicyclo[2.1.1]hexanes 11 with alkyl or aryl substituents at C-3.

Bridged Bicyclo Compounds, Heterocyclic↗

PubMed2001

Synthesis of novel 2-azabicyclo[2.2.0]- and [2.1.1]hexanols.

Methyl- and phenyl-substituted N-(ethoxycarbonyl)-2-azabicyclo[2.2.0]hex-5-enes 6 were reacted with NBS in wet DMSO to afford bromohydrins. Mixtures of unrearranged 6-exo-bromo-5-endo-hydroxy-2-azabicyclo[2.2.0]hexanes 7a,b and rearranged 5-anti-bromo-6-anti-hydroxy-2-azabicyclo[2.1.1]hexanes 8a,b were formed stereoselectively from the parent alkene 6a and 4-methyl alkene 6b. The 5-methyl alkene 6c affords only unrearranged bromohydrin 7c and dibromohydrin 9. By contrast, solely rearranged 3-endo-substituted-2-azabicyclo[2.1.1]hexane bromohydrins 8d-f result from additions to 3-endo-methyl alkene 6d, 3-endo-4-dimethyl alkene 6e, and 3-endo-phenyl alkene 6f. As an alternative route to bromohydrins, the parent 5,6-exo-epoxide 10a and 5-endo-methyl-5,6-exo-epoxide 10b were ring opened with bromine/triphenylphosphine to afford unrearranged 5-endo-bromo-6-exo-hydroxy-2-azabicyclo[2.2.0]hexanes 11a,b, while the 3-endo-methyl epoxide 10c afforded solely the rearranged 5-anti-bromo-6-anti-hydroxy-3-exo-methyl-2-azabicyclo[2.1.1]hexane isomer 8g. Tributyltin hydride reduction of bromohydrins 7a,b and 11a afforded novel 2-azabicyclo[2.2.0]hexan-5-ols 13a,b and -6-ol 14, and bromohydrins 8a,b, 8d-g afforded new 2-azabicyclo[2.1.1]-hexan-5-ols 15a,b and 15d-g.

Journal Article↗

PubMed2001

A zebrafish forebrain-specific zinc finger gene can induce ectopic dlx2 and dlx6 expression.

Identification of the earliest forebrain-specific markers should facilitate the elucidation of molecular events underlying vertebrate forebrain determination and specification. Here we report the sequence and characterization of fez (forebrain embryonic zinc finger), a gene that is specifically expressed in the embryonic forebrain of zebrafish. Fez encodes a putative nuclear zinc finger protein that is highly conserved in Drosophila, zebrafish, Xenopus, mouse, and human. In zebrafish, the expression of fez becomes detectable at the anterior edge of the presumptive neuroectoderm by 70% epiboly. During the segmentation period, its expression is completely restricted to the rostral region of the prospective forebrain. At approximately 24 h postfertilization, fez expression is mostly confined to the telencephalon and the anterior-ventral region of the diencephalon. Although fez expression is present in one-eyed pinhead (oep) and cyclops (cyc) zebrafish mutants, the pattern is altered. Forced expression of fez induces ectopic expression of dlx2 and dlx6, two genes involved in brain development. Knockdown of fez function using a morpholino-based antisense oligo inhibited dlx2 expression in the ventral forebrain. Our studies indicate that fez is one of the earliest markers specific for the anterior neuroectoderm and it may play a role in forebrain development by regulating Dlx gene expression.

Amino Acid Sequence↗

PubMed2001

[Effects of vasoactive peptides on the development of restenosis].

OBJECTIVE: To investigate the effects of several vasoactive peptides on the development of restenosis. METHODS: The model of balloon angioplasty to the rat aorta was prepared and used to study the changes of endothelin (ET), angiotensin II (A II), calcitonin gene-related peptide (CGRP) and adrenomedullin (Adm) in the plasma and aorta tissues, with radioimmuno-assay. (3)H-TdR incorporation and intima/media ratio of aortic tissue were measured after angioplasty. In cultured vascular smooth muscle cells, effects of these peptides on the proliferation of VSMC were evaluated with (3)H-TdR incorporation. Effects of these peptides on the expression of hypertension-related gene (HRG-1) in aorta tissue and cultured VSMC from SHR and WKY rats were studied by semi-quantitative RT-PCR. RESULTS: After angioplasty, the levels of ET and A II in the plasma and/or aorta tissue were significantly increased, with VSMC proliferation. On day 10 after angioplasty, the levels of ET in the plasma and tissue were increased by 69% and 124% respectively, compared with the that in the control group (P < 0.01); and the levels of aortic A II were increased by 80% (P < 0.01). Antiserum against ET and angiotensin converting enzyme (ACE) inhibitors could obviously inhibit the proliferation of VSMC and neointima formation. Compared with the sham group on day 3 after angioplasty, the CGRP levels in plasma and aorta tissue were increased by 64% and 89% respectively (P < 0.01); the Adm levels in the plasma and aorta tissue were increased by 129% and 102% respectively (P < 0.01). On day 10, intravenous administration of CGRP significantly inhibited the proliferation of VSMC and neointima formation induced by balloon aortic injury with the inhibitory rate of 66% and 79%, respectively, (P < 0.01). ET and A II attenuated the expression of HRG-1 in the aorta, thus activating mitogen activated protein kinase (MAPK). CGRP and Adm potentiated the expression of HRG-1, thus inhibiting the activity of MAPK. CONCLUSIONS: ET and A II stimulate the proliferation of injured intima, and CGRP and Adm have an anti-hyperplasia effects after angioplasty. That these peptides are suggested to be involved in the regulation of proliferation of VSMC and to affect the developing of vascular restenosis, by means of regulating the expression of HRG-1 and MAPK activities.

Adrenomedullin↗

PubMed2001

Metastatin: a hyaluronan-binding complex from cartilage that inhibits tumor growth.

In this study, a hyaluronan-binding complex, which we termed Metastatin, was isolated from bovine cartilage by affinity chromatography and found to have both antitumorigenic and antiangiogenic properties. Metastatin was able to block the formation of tumor nodules in the lungs of mice inoculated with B16BL6 melanoma or Lewis lung carcinoma cells. Single i.v. administration of Metastatin into chicken embryos inhibited the growth of both B16BL6 mouse melanoma and TSU human prostate cancer cells growing on the chorioallantoic membrane. The in vivo biological effect may be attributed to the antiangiogenic activity because Metastatin is able to inhibit the migration and proliferation of cultured endothelial cells as well as vascular endothelial growth factor-induced angiogenesis on the chorioallantoic membrane. In each case, the effect could be blocked by either heat denaturing the Metastatin or premixing it with hyaluronan, suggesting that its activity critically depends on its ability to bind hyaluronan on the target cells. Collectively, these results suggest that Metastatin is an effective antitumor agent that exhibits antiangiogenic activity.

Allantois↗

PubMed2001

A duplication in chromosome 4q35 is associated with hereditary benign intraepithelial dyskeratosis.

Hereditary benign intraepithelial dyskeratosis (HBID) is an autosomal dominant disorder characterized by elevated epithelial plaques on the ocular and oral mucous membranes. It has been reported primarily, but not exclusively, in individuals of American Indian heritage in North Carolina. We have examined and obtained DNA on two large families affected by HBID. Using genetic linkage analysis we have localized the HBID gene to chromosome 4 (4q35) with a peak LOD score of 8.97. Molecular analysis of these data reveals that all individuals affected with HBID in both families demonstrate the presence of three alleles for two tightly linked markers, D4S1652 and D4S2390, which map to the telomeric region of 4q35. This suggests the presence of a duplication segregating with the disease phenotype that is most likely involved in its causation.

Alleles↗

PubMed2001

Effect of metals on polycyclic aromatic hydrocarbon induction of CYP1A1 and CYP1A2 in human hepatocyte cultures.

Environmental cocontamination by polycyclic aromatic hydrocarbons (PAHs) and metals could affect the carcinogenic consequences of PAH exposure by modifying PAH induction of PAH-bioactivating CYP1A. The effect of As, Pb, Hg, or Cd (ranked as the most hazardous environmental metals by EPA and ATSDR) on CYP1A1 and 1A2 induction by benzo[a]pyrene (BaP), benzo[b]fluoranthene (BbF), dibenzo[a,h]anthracene (DBahA), benzo[a]anthracene (BaA), and benzo[k]fluoranthene (BkF) has thus been investigated in fresh human hepatocyte cultures. Induction was probed by ethoxyresorufin-O-deethylase activity, by immunoblots, and by RT-PCR. Uptake of PAHs into the hepatocytes varied according to PAH and liver donor: 84% of 5 microM BaA and 25-40% of 5 microM DBahA was taken up in 24 h. Hepatocytes retained viability up to 1 microM Cd and 5 microM Pb, Hg, or As and 5 microM PAHs. PAH induction of CYP1A in hepatocytes was variable, some cultures expressed CYP1A1 and others CYP1A1 and 1A2, and to variable extents. Induction efficiency (relative to DMSO controls) at 2.5 microM PAH concentration was in the order BkF (7.6-fold) > DBahA (6.1 fold) > BaP (5.7 fold) > BbF (3.9-fold) > BaA (2.5-fold). All four metals (1-5 microM) decreased CYP1A1/1A2 induction by some of the PAHs with dose-, metal-, and PAH-dependency. Arsenic (5 microM) decreased induction by 47% for BaP, 68% for BaA, 45% for BbF, 79% for BkF, and 53% for DBahA. Induced CYP1A2 protein was much more extensively decreased than 1A1 protein, and CYP1A2 mRNA and, to variable extents, CYP1A1 mRNA were decreased by As. Thus the metals in PAH/metal mixtures could diminish PAH carcinogenicity by decreasing induction of their bioactivation by CYP1A1/1A2.

Arsenic↗