Inter-individual differences in the ability of human milk-fat extracts to enhance the genotoxic potential of the procarcinogen benzo[a]pyrene in MCF-7 breast cells

Using 3D MCF-7 mammary spheroids to assess the genotoxicity of mixtures of the food-derived carcinogens benzo[a]pyrene and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine

Genotoxic carcinogens are present in the human diet, and two important examples are benzo[a]pyrene (BaP) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). BaP is a polycyclic aromatic hydrocarbon generated by incomplete combustion of organic substances, thus contaminating numerous foodstuffs, and PhIP is a heterocyclic amine formed when meat is cooked. Genotoxicity testing of chemical carcinogens has focussed largely on individual chemicals, particularly in relation to diet, despite mixtures representing a more realistic exposure scenario. We have previously shown that exposure of MCL-5 cells to BaP-PhIP mixtures produces a TK mutation dose response that differs from the predicted additive response, using traditional regulatory-like two-dimensional (2D) cell culture. There is a large gap between 2D cell culture and the whole animal, and three-dimensional (3D) cell culture, shown to better represent in vivo tissue structure, may bridge the gap. The aim of the current study was to use 3D spheroids to characterise the DNA damage response following exposure to mixtures of the mammary carcinogens BaP and PhIP. Mammary MCF-7 cells were grown in 3D spheroids, exposed (24 h) to BaP (10^-10 to 10^-5 M) or PhIP (10^-9 to 10^-4 M) individually or in mixtures and DNA damage assessed by micronucleus (MN) formation. A dose-dependent increase in MN was observed for the individual chemicals in 3D cell culture. In line with our previous 2D TK mutation data, 3D mixture exposures gave a modified DNA damage profile compared to the individual chemicals, with a potent response at low dose combinations and a decrease in MN with higher concentrations of BaP in the mixture. Ethoxyresorufin-O-deethylase (CYP1A) activity increased with increasing concentration of BaP in the mixture, and for combinations with 10 μM BaP, CYP1A1 mRNA induction was sustained up to 48 h. These data suggest mixtures of genotoxic chemicals give DNA damage responses that differ considerably from those produced by the chemicals individually, and that 3D cell culture is an appropriate platform for DNA damage assays.

Genetic damage in coal miners evaluated by buccal micronucleus cytome assay

During coal mining activities, large quantities of coal dust, ashes, polycyclic aromatic hydrocarbons and metals are released into the environment. This complex mixture presents one of the most important occupational hazards for health of workers. The aim of the present study was to evaluate the genetic damage together with the presence of inorganic elements, in an exposed workers population to coal mining residues of Guajira-Colombia. Thus, 100 exposed workers and 100 non-exposed control individuals were included in this study. To determine genetic damage we assessed the micronucleus (MN) frequencies and nuclear buds in buccal mucosa samples (BMCyt) assay, which were significantly higher in the exposed group than non-exposed control group. In addition, karyorrhectic and karyolytic cells were also significantly higher in the exposed group (cell death). No significant difference was observed between the exposed groups engaged in different mining activities. No correlation between age, alcohol consumption, time of service and MN assay data were found in this study. However, the content of inorganic elements in blood samples analyzed by a Particle-induced X-ray emission technique (PIXE) showed higher values of silicon (Si) and aluminum (Al) in the exposed group. In this study we discuss the possibility of DNA damage observed in the mine workers cells be a consequence of oxidative damage.

Effects of decabrominated diphenyl ether (PBDE-209) in regulation of growth and apoptosis of breast, ovarian, and cervical cancer cells

BACKGROUND

Polybrominated diphenyl ethers (PBDEs), commonly used in building materials, electronics, plastics, polyurethane foams, and textiles, are health hazards found in the environment.

OBJECTIVE

In this study we investigated the effects of PBDE-209, a deca-PBDE, on the regulation of growth and apoptosis of breast, ovarian, and cervical cancer cells as well as the underlying protein alterations.

METHODS

We used MCF-7 and MCF-7/ADR (multidrug-resistant MCF-7) breast cancer cell lines, the HeLa cervical cancer cell line, the OVCAR-3 ovarian cancer cell line, and the normal CHO (Chinese hamster ovary) cell line to assess the effects of PBDE-209 using cell viability, immunofluorescence, and flow cytometric assays. Western blot assays were used to detect changes in protein expression. To assess the effects of PBDE-209 on apoptosis, we used the protein kinase Cα (PKCα) inhibitor Gö 6976, the extracellular signal-regulated kinase (ERK) inhibitor PD98059, and tamoxifen.

RESULTS

Our data indicate that PBDE-209 increased viability and proliferation of the tumor cell lines and in CHO cells in a dose- and time-dependent manner. PBDE-209 also altered cell cycle distribution by inducing the S phase or G2/M phase. Furthermore, PBDE-209 partially suppressed tamoxifen-induced cell apoptosis in the breast cancer cell lines (MCF-7 and MCF-7/ADR) but suppressed Gö 6976- and PD98059-induced apoptosis in all cell lines. At the molecular level, PBDE-209 enhanced PKCα and ERK1/2 phosphorylation in the cell lines.

CONCLUSIONS

Our data demonstrate that PBDE-209 is able to promote proliferation of various cancer cells from the female reproductive system and normal ovarian CHO cells. Furthermore, it reduced tamoxifen, PKCα, and ERK inhibition-induced apoptosis. Finally, PBDE-209 up-regulated phosphorylation of PKCα and ERK1/2 proteins in tumor cells and in CHO cells.

Polybrominated diphenyl ether-associated alterations in cell biochemistry as determined by attenuated total reflection Fourier-transform infrared spectroscopy: a comparison with DNA-reactive and/or endocrine-disrupting agents

Whether polybrominated diphenyl ethers (PBDEs) induce effects in target cells is increasingly important given that their environmental burdens are rising. Attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy can be used to biochemically signature cells based on the notion that a detailed "biochemical-cell fingerprint" in the form of an infrared (IR) spectrum is derived. By employing subsequent computational approaches such as principal component analysis (PCA) and/or linear discriminant analysis (LDA), data reduction is achieved to allow for the identification of wavenumber-related biomarkers of effect Clustering of similar spectra (or scores) away from dissimilar ones highlights the variance responsible for discriminating classes. Discriminating biomarkers might include protein conformational changes, structural alterations to DNA/RNA, glycogen content, or protein phosphorylation. Employing this approach, we investigated in MCF-7 cells the dose-related effects of PBDEs (congeners 47, 153, 183, and 209), benzo[a]pyrene (B[a]P), 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PHIP), 17beta-Oestradiol (E2), or lindane (gamma-hexachlorocyclohexane). Cultures concentrated in G0/G1- or S-phases were treated for 24 h. Following treatment MCF-7 cells were fixed and applied to IR reflective Low-E windows for interrogation using ATR-FTIR spectroscopy. At concentrations as low as 10(-12) M in culture, significant separation (P < or = 0.05) of PBDE-treated and vehicle control cell populations was noted. In some cases this was associated with alterations in lipid or the secondary structure of proteins; with DNA-reactive compounds (e.g., B[a]P), variance was primarily noted in the DNA/RNA region. This study points to a novel nondestructive approach capable of identifying contaminant effects at environmental concentrations in target cells.

Exposure of HepG2 cells to low levels of PAH-containing extracts from contaminated soils results in unpredictable genotoxic stress responses

Contaminated soil is a serious environmental problem, constituting a risk to humans and the environment. Polycyclic aromatic hydrocarbons (PAHs) are often present at contaminated sites. However, risk levels are difficult to estimate because of the complexity of contaminants present. Here, we compare cellular effects of extracts from contaminated soils collected at six industrial settings in Sweden. Chemical analysis showed that all soils contained complex mixtures of PAHs and oxy-PAHs. Western blotting and immunocytochemistry were used to investigate DNA damage signaling in HepG2 cells exposed to extracts from these soils. The effects on phosphorylated Mdm2, p53, Erk, H2AX, 53BP1, and Chk2, cell cycle regulating proteins (cyclin D1 and p21), and cell proliferation were compared. We found that most soil extracts induced phosphorylation of Mdm2 at the 2A10 epitope at low concentrations. This is in line with previous studies suggesting that this endpoint reflects readily repaired DNA-damage. However, we found concentration- and time-dependent gammaH2AX and 53BP1 responses that were sustained for 48 hr. These endpoints may reflect the presence of different types of persistent DNA-damage. High concentrations of soil extracts decreased cyclin D1 and increased p21 response, indicating cell cycle arrest. Phosphorylation of Mdm2 at Ser166, which attenuates the p53 response and is induced by many tumor promoters, was induced in a time-dependent manner and was associated with Erk phosphorylation. Taken together, the PAH extracts elicited unpredictable signaling responses that differed between samples. More polar compounds, i.e., oxy-PAHs, also contributed to the complexity.

ATR-FTIR spectroscopy detects alterations induced by organotin(IV) carboxylates in MCF-7 cells at sub-cytotoxic/-genotoxic concentrations

The environmental impact of metal complexes such as organotin(IV) compounds is of increasing concern. Genotoxic effects of organotin(IV) compounds (0.01 mug/ml, 0.1 mug/ml or 1.0 mug/ml) were measured using the alkaline single-cell gel electrophoresis (comet) assay to measure DNA single-strand breaks (SSBs) and the cytokinesis-block micronucleus (CBMN) assay to determine micronucleus formation. Biochemical-cell signatures were also ascertained using attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy. In the comet assay, organotin(IV) carboxylates induced significantly-elevated levels of DNA SSBs. Elevated micronucleus-forming activities were also observed. Following interrogation using ATR-FTIR spectroscopy, infrared spectra in the biomolecular range (900 cm-1 - 1800 cm-1) derived from organotin-treated MCF-7 cells exhibited clear alterations in their biochemical-cell fingerprint compared to control-cell populations following exposures as low as 0.0001 mug/ml. Mono-, di- or tri-organotin(IV) carboxylates (0.1 mug/ml, 1.0 mug/ml or 10.0 mug/ml) were markedly cytotoxic as determined by the clonogenic assay following treatment of MCF-7 cells with >/= 1.0 mug/ml. Our results demonstrate that ATR-FTIR spectroscopy can be applied to detect molecular alterations induced by organotin(IV) compounds at sub-cytotoxic and sub-genotoxic concentrations. This biophysical approach points to a novel means of assessing risk associated with environmental contaminants.PACS codes: 87.15.-v, 87.17.-d, 87.18.-h.

Enhanced micronucleus formation and modulation of BCL-2:BAX in MCF-7 cells after exposure to binary mixtures

BACKGROUND

Within mixtures, interactions between different xenobiotics may occur to give rise to additive, synergistic, inhibitory and/or stimulatory effects in target cells. The role that xenobiotics individually or in mixtures, and at environmental concentrations, play in the etiology of common human diseases often remains obscure.

METHODS

In the presence or absence of lindane, chromosomal aberrations were detected in MCF-7 cells after 24-hr treatment with benzo[a]pyrene (B[a]P) or 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) using the cytokinesis-block micronucleus assay. Micronuclei were scored in 1,000 binucleate cells/treatment. We investigated intracellular responses using quantitative gene expression analyses of cyclin-dependent kinase inhibitor 1A [CDKN1A (P21(WAF1/CIP1))], B-cell leukemia/lymphoma 2 (BCL-2), BCL-2-associated X (BAX), and isoforms of cytochrome P450 (CYP), CYP1A1, CYP1A2, and CYP1B1. Immunocytochemical analyses of p53, p21(Waf1/Cip1), Bcl-2 and Bax protein expression in MCF-7 cells were also carried out.

RESULTS

After exposure to binary mixtures of B[a]P plus lindane or PhIP plus lindane, a 10-fold increase in micronucleus formation resulted; these test agents individually induced 2- to 5-fold increases. Lindane increased the ratio of Bcl-2:Bax, as did 17beta-estradiol (E(2)). Although treatment with B[a]P alone was found to elevate expression of P21(WAF1/CIP1)and CYP isoenzymes, it reduced the ratio of BCL-2:BAX mRNA transcripts. Treatment with a binary mixture of 10(-8) M B[a]P plus 10(-12) M lindane or 10(-10) M E(2) reversed B[a]P-induced reductions in the ratio of Bcl-2- to Bax-positive cells. In contrast, treatments with PhIP (known to possess hormonelike properties) plus lindane or E(2) resulted in profound reductions in Bcl-2:Bax ratio.

CONCLUSIONS

Our results suggest that low-dose treatments (i.e., close to environmental levels) may increase DNA damage while influencing survival in exposed cells and that these effects may depend on the endocrine activity of test agents.

Complex mixtures that may contain mutagenic and/or genotoxic components: a need to assess in vivo target-site effect(s) associated with in vitro-positive(s)

A battery of short-term in vitro assays and/or in vivo protocols to evaluate single-agent mutagenicity and/or genotoxicity is available. However, a protocol to assess the effect(s) of complex mixtures in vivo following a positive test finding in vitro remains difficult. Complex interactions may occur in vivo because component pharmacokinetics increases the unpredictability of pharmacodynamic outcomes. The question arises as to whether in vitro mutagenic component(s) of a complex mixture, probably unidentified, reach target organ(s) in vivo at a sufficient concentration. To address the issue of an in vitro positive, standard in vivo chromosome damage assays to test both mixtures and fractions could be conducted but, to assess site-of-contact effects, the alkaline single cell-gel electrophoresis ("comet") assay or DNA reactivity (e.g., (32)P-postlabelling of DNA adducts) might be employed. A newer approach may be the derivation of a "biochemical-cell fingerprint" of potential target sites using infrared microspectroscopy. There is interest in platforms such as gene expression, proteomics, epigenomics or metabolomics as biomarkers of signature genotoxic or non-genotoxic mechanisms. One still needs to address whether a mutagenic and/or genotoxic component reaches a target organ. An approach to track levels of target-organ exposure may be to radio-label components with a short-lived positron-emitting radionuclide. The parent compound retains its physicochemical properties whilst allowing non-invasive in vivo tissue-specific imaging. However, determining target-organ concentration(s) and effect(s) in vivo remains a difficult challenge.

Infrared spectral analysis of MCF-7 cells treated with serum-lipid extracts segregates predominantly brominated flame retardant-exposed subjects from those with mainly organochlorine exposures

We set out to determine whether infrared (IR) spectra of treated MCF-7 cells derived using attenuated total reflection Fourier-transform IR (ATR) microspectroscopy could be used to signature different exposures. Serum-lipid samples from residents living in an electronics waste (e-waste) dismantling region (Region E, n = 26) in the south of P.R. China or from a nearby region (Region S, n = 20) associated with the fishing industry were obtained. Following extraction, estrogen receptor-positive MCF-7 cells were treated for 24 h with < or = 5-mg lipid equivalent of individual extracts prior to ethanol fixation; subsequently, IR spectra of treated-cell populations were obtained using ATR microspectroscopy. Levels of organochlorinated and brominated compounds in parallel extracts were also determined. Principal component analysis (PCA) was employed to ascertain whether IR-spectral scores would cluster according to particular cohort. Scores plots following PCA highlighted significant clustering dependent on with which set of extracts MCF-7 cells were treated. This suggests marked differences in the cell-biochemical modulating effects induced by either set of extracts. Analysis of contaminant profiles in the extracts showed that polybrominated diphenyl ethers (PBDEs) accounted for 46.0% of total organohalogens and were higher than dichloro-diphenyl-trichloroethanes (DDTs) in Region E; DDTs were the major contaminants (85.2% of total contaminant load) compared to PBDEs (8.7%) in Region S. These results suggest that ATR microspectroscopy can segregate cell-biochemical effects as a consequence of very different exposure paradigms.

Polybrominated diphenyl ethers in South China maternal and fetal blood and breast milk

Twenty-one-paired human fetal and maternal serum and 27 breast milk samples at South China were analyzed for concentrations of polybrominated diphenyl ethers (PBDEs). Seven PBDE congeners (BDE-28, -47, -99, -100, -153, -154, and -183) were quantified using gas chromatography/mass spectrometry (GC/MS). This is the first report to present the residue levels of PBDEs in human samples of China. The concentrations of total PBDEs ranged from 1.5 to 17 ng/g in the samples and were within the range reported in European samples for a similar population, but lower than human tissue levels in North America. BDE-47 and -153 were the dominant PBDE congeners in all samples and accounted for 60% of the total PBDEs. Further research is needed to determine the exposure route of PBDEs and their health effects.

Organohalogen chemicals in human blood from the United Kingdom

Blood serum from 154 volunteers at 13 UK locations in 2003 were analysed for a range of PCBs, organochlorine pesticides and PBDEs. HCB, p,p'-DDE and p,p'-DDT and beta-HCH were the dominant organochlorine pesticides in most samples. BDEs 47, 99, 100, 153, 154 and 183 were the most regularly detected PBDEs. This study is the first report of BDE209 in UK human blood (found in 11 samples, range < 15-240 ng/g lipid). Concentration and age correlated for the less easily metabolised PCBs, p,p'-DDT and p,p'-DDE, HCB and HCHs. With increasing age females tended to have lower concentrations of the more chlorinated PCBs than males. Similar PBDE concentrations, and distributions, to those reported in the general population in Sweden in 2002 were found, despite differences in historical PBDE production and usage. There is increasing regulation to control persistent and bioaccumulative chemicals, and establishing human exposure will help to identify substances which should be urgently phased out.

Large-scale evaluation of the current level of polybrominated diphenyl ethers (PBDEs) in breast milk from 13 regions of Japan

Polybrominated diphenyl ethers (PBDEs) were measured in 2004 in 105 breast milk samples collected from 13 regions of Japan (Hokkaido, Akita, Miyagi, Tokyo, Gifu, Fukui, Kyoto, Hyogo, Wakayama, Shimane, Yamaguchi, Kochi and Okinawa). Six congeners (BDE-28, BDE-47, BDE-99, BDE-100, BDE-153 and BDE-154) were determined by gas chromatography /mass spectrometry (GC/MS). Total PBDE levels ranged from 0.01 to 23.0 ng/g lipid (geometric mean (GM), 1.34 ng/g lipid). BDE-47 (GM, 0.66 ng/g lipid, 59% of sigmaPBDE) was the most abundant congener present in breast milk and was detected in 99% of the samples. Total PBDE levels were higher in northern Japan than in other regions. We analyzed the effects of occupation, age, smoking status, alcohol consumption and number of deliveries on total PBDE levels. None of these factors were significantly associated with the level of PBDEs. The present study revealed that the current level of exposure to PBDEs in Japan is lower than that in the USA or Sweden. GMs (ng/g lipid) (GSD, geometric standard deviation) and medians (ng/g lipid) of PBDE levels in each district are as follows: Hokkaido 2.70 (1.70), 2.74; Akita 4.49 (2.19), 5.44; Miyagi 1.77 (4.37), 1.11; Tokyo 1.39 (2.09), 1.63, Gifu 2.83 (4.79), 2.23; Fukui 1.05 (2.34), 1.18; Kyoto 1.31 (2.95), 1.33; Hyogo 1.02 (2.69), 0.88; Wakayama 1.33 (3.80), 1.70; Shimane 0.83 (2.51), 0.66; Yamaguchi 1.74 (2.82), 1.76; Kochi 0.50 (2.69), 0.74 and Okinawa 1.91 (2.75), 1.22. This is the first large-scale study of current PBDE levels in breast milk in Japan.

Risk migration and scientific advance: the case of flame-retardant compounds

It is a common experience that attempts to mitigate a risk lead to new risks, and that risks formerly thought to be of one kind become another kind as technical knowledge evolves. This phenomenon of risk migration suggests that we should take processes over time, rather than specific risks or specific technologies, as a unit of analysis. Several of our existing models of the social management of risks-such as that of social risk amplification-are process models of a kind but are still oriented around the playing out of a particular event or issue. A case study of risk in a group of flame-retardant compounds was used as the basis of a grounded, exploratory analysis of migration processes, the phenomena that influence them, and their consequences. This illustrated how migration naturally occurs from risks that are understood, in which risk bearers have at least some agency, to risks that are not understood and not capable of being influenced by risk bearers. It illustrated how the simultaneous improvement in measuring technology, which detects potential toxins at increasingly small concentrations, combines with intuitive models that ignore concentration to produce conditions likely to generate anxiety. And it illustrated how pressure groups and commercial interests exploit this effect. It also showed how migration makes precautionary action problematic, and how more generally it tends to undermine a society's capacity to cope with risk.