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

Genotoxicity of heterocyclic amines (HCAs) on freshly isolated human peripheral blood mononuclear cells (PBMC) and prevention by phenolic extracts derived from olive, olive oil and olive leaves

In this study we investigated the genotoxic potential of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, (PhIP); 2-amino-3-methyl-3H-imidazo[4,5-f]quinoline, (IQ); 2-amino-3,8-dimethyl-imidazo[4,5-f]quinoxaline, (MeIQx) and 2-amino-3,4,8-trimethyl-3H-imidazo[4,5-f]quinoxaline (DiMeIQx) on human freshly isolated peripheral blood mononuclear cells (PBMC) by the comet assay. The preventive ability of three different phenolic extracts derived from olive (O-PE), virgin olive oil (OO-PE) and olive leaf (OL-PE) on PhIP induced DNA damage was also investigated. PhIP and IQ induced a significant DNA damage at the lowest concentration tested (100 μM), while the genotoxic effect of MeIQx and DiMeIQx become apparent only in the presence of DNA repair inhibitors Cytosine b-D-arabinofuranoside and Hydroxyurea (AraC/HU). The inclusion of metabolic activation (S9-mix) in the culture medium increased the genotoxicity of all HCAs tested. All three phenolic extracts showed an evident DNA damage preventive activity in a very low concentration range (0.1-1.0 μM of phenols) which could be easily reached in human tissues "in vivo" under a regular intake of virgin olive oil. These data further support the observation that consumption of olive and virgin olive oil may prevent the initiation step of carcinogenesis. The leaf waste could be an economic and simple source of phenolic compounds to be used as food additives or supplements.

Occupational Exposure to Polycyclic Aromatic Hydrocarbons and Elevated Cancer Incidence in Firefighters

Cancer incidence appears to be higher amongst firefighters compared to the general population. Given that many cancers have an environmental component, their occupational exposure to products of carbon combustion such as polycyclic aromatic hydrocarbons (PAHs) is of concern. This is the first UK study identifying firefighters exposure to PAH carcinogens. Wipe samples were collected from skin (jaw, neck, hands), personal protective equipment of firefighters, and work environment (offices, fire stations and engines) in two UK Fire and Rescue Service Stations. Levels of 16 US Environmental Protection Agency (EPA) PAHs were quantified together with more potent carcinogens: 7,12-dimethylbenzo[a]anthracene, and 3-methylcholanthrene (3-MCA) (12 months post-initial testing). Cancer slope factors, used to estimate cancer risk, indicate a markedly elevated risk. PAH carcinogens including benzo[a]pyrene (B[a]P), 3-MCA, and 7,12-dimethylbenz[a]anthracene PAHs were determined on body surfaces (e.g., hands, throat), on PPE including helmets and clothing, and on work surfaces. The main exposure route would appear to be via skin absorption. These results suggest an urgent need to monitor exposures to firefighters in their occupational setting and conduct long-term follow-up regarding their health status.

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.

Lead Intoxication Synergies of the Ethanol-Induced Toxic Responses in Neuronal Cells--PC12

Lead (Pb)-induced neurodegeneration and its link with widespread neurobehavioral changes are well documented. Experimental evidences suggest that ethanol could enhance the absorption of metals in the body, and alcohol consumption may increase the susceptibility to metal intoxication in the brain. However, the underlying mechanism of ethanol action in affecting metal toxicity in brain cells is poorly understood. Thus, an attempt was made to investigate the modulatory effect of ethanol on Pb intoxication in PC12 cells, a rat pheochromocytoma. Cells were co-exposed to biological safe doses of Pb (10 μM) and ethanol (200 mM), and data were compared to the response of cells which received independent exposure to these chemicals at similar doses. Ethanol (200 mM) exposure significantly aggravated the Pb-induced alterations in the end points associated with oxidative stress and apoptosis. The finding confirms the involvement of reactive oxygen species (ROS)-mediated oxidative stress, and impairment of mitochondrial membrane potential, which subsequently facilitate the translocation of triggering proteins between cytoplasm and mitochondria. We further confirmed the apoptotic changes due to induction of mitochondria-mediated caspase cascade. These cellular changes were found to recover significantly, if the cells are exposed to N-acetyl cysteine (NAC), a known antioxidant. Our data suggest that ethanol may potentiate Pb-induced cellular damage in brain cells, but such damaging effects could be recovered by inhibition of ROS generation. These results open up further possibilities for the design of new therapeutics based on antioxidants to prevent neurodegeneration and associated health problems.

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.

Plasma microRNA expression and micronuclei frequency in workers exposed to polycyclic aromatic hydrocarbons

BACKGROUND

Ubiquitous polycyclic aromatic hydrocarbons (PAHs) have been shown to alter gene expression patterns and elevate micronuclei (MN) frequency, but the underlying mechanisms are largely unknown. MicroRNAs (miRNAs) are key gene regulators that may be influenced by PAH exposures and mediate their effects on MN frequency.

OBJECTIVES

We sought to identify PAH-associated miRNAs and evaluate their associations with MN frequency.

METHODS

We performed a two-stage study in healthy male coke oven workers to identify miRNAs associated with PAH exposures quantified using urinary monohydroxy-PAHs and plasma benzo[a]pyrene-r-7,t-8,c-10-tetrahydrotetrol-albumin (BPDE-Alb) adducts. In the discovery stage, we used Solexa sequencing to test differences in miRNA expression profiles between pooled plasma samples from 20 exposed workers and 20 controls. We then validated associations with eight selected miRNAs in 365 workers. We further evaluated associations between the PAH-associated miRNAs and MN frequency.

RESULTS

In the discovery stage, miRNA expression profiles differed between the exposed and control groups, with 68 miRNAs significantly down-regulated [fold change (FC) ≤ -5] and 3 miRNAs mildly up-regulated (+2 ≤ FC < +5) in the exposed group. In the validation analysis, urinary 4-hydroxyphenanthrene and/or plasma BPDE-Alb adducts were associated with lower miR-24-3p, miR-27a-3p, miR-142-5p, and miR-28-5p expression (p < 0.030). Urinary 1-hydroxynaphthalene, 2-hydroxynaphthalene, 2-hydroxyphenanthrene, and the sum of monohydroxy-PAHs were associated with higher miR-150-5p expression (p < 0.030). These miRNAs were associated with higher MN frequency (p < 0.005), with stronger associations in drinkers (pinteraction < 0.015).

CONCLUSIONS

Associations of PAH exposures with miRNA expression, and of miRNA expression with MN frequency, suggest potential mechanisms of adverse effects of PAHs that are worthy of further investigation.

Assessing cancer risk in China from γ-hexachlorocyclohexane emitted from Chinese and Indian sources

Three models, including an atmospheric transport model, a multimedia exposure model, and a risk assessment model, were used to assess cancer risk in China caused by γ-HCH (gamma-hexachlorocyclohexane) emitted from Chinese and Indian sources. Extensive model investigations revealed the contribution of different sources to the cancer risk in China. Cancer risk in Eastern China was primarily attributable to γ-HCH contamination from Chinese sources, whereas cancer risk in Western China was caused mostly by Indian emissions. The contribution of fresh use of lindane in India to the cancer risk in China was almost 1 order of magnitude higher than that of the reemission of γ-HCH from Indian soils. Of total population, 58% (about 0.79 billion) residents in China were found to live in the environment with high levels of cancer risk exceeding the acceptable cancer risk of 10(-6), recommended by the United States Environmental Protection Agency (U.S. EPA). The cancer risk in China was mostly induced by the local contamination of γ-HCH emitted from Chinese sources, whereas fresh use of lindane in India will become a significant source of the cancer risk in China if Indian emissions maintain their current levels.

Combinatory effects of PBDEs and 17β-estradiol on MCF-7 cell proliferation and apoptosis

In the present work, we analyzed whether polybrominated diphenyl ethers (PBDEs) (47, 99, 100 and 209) interfere with the effect of 17β-estradiol on the proliferation and apoptosis of the MCF-7 cell line. MCF-7 cells were cultured in DMEM without phenol red; upplemented with 5% charcoal-treated fetal bovine serum for 3 days with 10 nM 17β-estradiol; with 0.1 μM, 0.5 μM or 1 μM of the tested PBDE congeners; or with both 17β-estradiol and a congener. Cell proliferation was determined by measuring BrdU incorporation, and cell apoptosis was measured by caspase-9 activity. No PBDE congener had an effect on basal cell proliferation, but they all significantly decreased basal caspase-9 activity. An additive anti-apoptotic activity and ability to induce cell proliferation was observed in the presence of 17β-estradiol.

Differential effects of a complex organochlorine mixture on the proliferation of breast cancer cell lines

Organochlorine compounds (OCs) are a group of persistent chemicals that accumulate in fatty tissues with age. Although OCs has been tested individually for their capacity to induce breast cancer cell proliferation, few studies examined the effect of complex mixtures that comprise compounds frequently detected in the serum of women. We constituted such an OC mixture containing 15 different components in environmentally relevant proportions and assessed its proliferative effects in four breast cancer cell lines (MCF-7, T47D, CAMA-1, MDAMB231) and in non-cancerous CV-1 cells. We also determined the capacity of the mixture to modulate cell cycle stage of breast cancer cells and to induce estrogenic and antiandrogenic effects using gene reporter assays. We observed that low concentrations of the mixture (100 × 10(3) and 50 × 10(3) dilutions) stimulated the proliferation of MCF-7 cells while higher concentrations (10 × 10(3) and 5 × 10(3) dilutions) had the opposite effect. In contrast, the mixture inhibited the proliferation of non-hormone-dependent cell lines. The mixture significantly increased the number of MCF-7 cells entering the S phase, an effect that was blocked by the antiestrogen ICI 182,780. Low concentrations of the mixture also caused an increase in CAMA-1 cell proliferation but only in the presence estradiol and dihydrotestosterone (p<0.05 at the 50 × 10(3) dilution). DDT analogs and polychlorinated biphenyls all had the capacity to stimulate the proliferation of CAMA-1 cells in the presence of sex steroids. Reporter gene assays further revealed that the mixture and several of its constituents (DDT analogs, aldrin, dieldrin, β-hexachlorocyclohexane, toxaphene) induced estrogenic effects, whereas the mixture and several components (DDT analogs, aldrin, dieldrin and PCBs) inhibited the androgen signaling pathway. Our results indicate that the complex OC mixture increases the proliferation of MCF-7 cells due to its estrogenic potential. The proliferative effect of the mixture on CAMA-1 cells in the presence of sex steroids appears mostly due to the antiandrogenic properties of p,p'-DDE, a major constituent of the mixture. Other mixtures of contaminants that include emerging compounds of interest such as brominated flame retardants and perfluoroalkyl compounds should be tested for their capacity to induce breast cancer cell proliferation.

Monocrotophos induced apoptosis in PC12 cells: role of xenobiotic metabolizing cytochrome P450s

Monocrotophos (MCP) is a widely used organophosphate (OP) pesticide. We studied apoptotic changes and their correlation with expression of selected cytochrome P450s (CYPs) in PC12 cells exposed to MCP. A significant induction in reactive oxygen species (ROS) and decrease in glutathione (GSH) levels were observed in cells exposed to MCP. Following the exposure of PC12 cells to MCP (10⁻⁵ M), the levels of protein and mRNA expressions of caspase-3/9, Bax, Bcl₂, P⁵³, P²¹, GSTP1-1 were significantly upregulated, whereas the levels of Bclw, Mcl1 were downregulated. A significant induction in the expression of CYP1A1/1A2, 2B1/2B2, 2E1 was also observed in PC12 cells exposed to MCP (10⁻⁵ M), whereas induction of CYPs was insignificant in cells exposed to 10⁻⁶ M concentration of MCP. We believe that this is the first report showing altered expressions of selected CYPs in MCP-induced apoptosis in PC12 cells. These apoptotic changes were mitochondria mediated and regulated by caspase cascade. Our data confirm the involvement of specific CYPs in MCP-induced apoptosis in PC12 cells and also identifies possible cellular and molecular mechanisms of organophosphate pesticide-induced apoptosis in neuronal cells.

Sublethal genotoxicity and cell alterations by organophosphorus pesticides in MCF-7 cells: implications for environmentally relevant concentrations

Organophosphorus pesticide (OPP) toxicity is believed to be mediated through inhibition of acetylcholinesterase (AChE). Given their widespread distribution in aquatic systems and their ability to undergo chemical transformation, their environmental impacts at sublethal concentrations in nontarget organisms have become an important question. We conducted a number of mammalian-cell genotoxic and gene expression assays and examined cellular biochemical changes that followed low-dose exposure of MCF-7 cells to fenitrothion, diazinon, and the aqueous degradate of diazinon, 2-isopropyl-6-methyl-4-pyrimidinol (IMP). After exposure to the OPPs at low concentrations (10(-12) M to 10(-8) M), greater than twofold elevations in micronucleus formation were noted in MCF-7 cell cultures that went on to exhibit greater than 75% clonogenic survival; these levels of chromosomal damage were comparable to those induced by 10(-6) M benzo[a]pyrene, a known genotoxic agent. At this low concentration range, a fenitrothion-induced twofold elevation in B-cell leukemia/lymphoma-2 (BCL-2) and cytochrome P450 isoenzyme (CYP1A1) gene expressions was observed. Principal component analysis-linear discriminant analysis (PCA-LDA) of derived infrared (IR) spectra of vehicle control (nonexposed) and OPP-exposed cells highlighted that both fenitrothion and diazinon induced marked biochemical alterations in the lipid, protein, and DNA/RNA absorbance regions. Our findings demonstrate that the two OPP parent chemicals and IMP degradate can mediate a number of toxic effects or cellular alterations at very low concentrations. These are independent of just selective inhibition of AChE, with potential consequences for nontarget organisms exposed at environmentally relevant concentrations. Further assays on relevant aquatic organism cell lines are now recommended to understand the mechanistic low-dose toxicity of these chemicals present in aquatic systems.

Prenatal environmental exposures, epigenetics, and disease

This review summarizes recent evidence that prenatal exposure to diverse environmental chemicals dysregulates the fetal epigenome, with potential consequences for subsequent developmental disorders and disease manifesting in childhood, over the lifecourse, or even transgenerationally. The primordial germ cells, embryo, and fetus are highly susceptible to epigenetic dysregulation by environmental chemicals, which can thereby exert multiple adverse effects. The data reviewed here on environmental contaminants have potential implications for risk assessment although more data are needed on individual susceptibility to epigenetic alterations and their persistence before this information can be used in formal risk assessments. The findings discussed indicate that identification of environmental chemicals that dysregulate the prenatal epigenome should be a priority in health research and disease prevention.

Constitutive expression of bioactivating enzymes in normal human prostate suggests a capability to activate pro-carcinogens to DNA-damaging metabolites

BACKGROUND

The constitutive bioactivating capacity of human prostate may play a role in determining risk of adenocarcinoma developing in this tissue. Expression of candidate enzymes that convert exogenous and/or endogenous agents into reactive DNA-damaging species would suggest the potential to generate initiating events in prostate cancer (CaP).

METHODS

Normal prostate tissues from UK-resident Caucasians (n = 10) were collected following either radical retropubic prostatectomy (RRP) or cystaprostatectomy (CyP). An analysis of gene and protein expression of candidate metabolizing enzymes, including cytochrome P450 (CYP)1A1, CYP1A2, CYP1B1, N-acetyltransferase 1 (NAT1), sulfotransferase (SULT)1A1, SULT1A3, NAD(P)H:quinone oxidoreductase (NQO1), prostaglandin H synthase 1 (cyclooxygenase 1; COX1), and CYP oxidoreductase (POR) was carried out. Quantitative real-time reverse transcriptase polymerase chain reaction, Western blot, and immunohistochemical analysis were conducted.

RESULTS

Except for CYP1A1 and CYP1A2, the metabolizing enzymes examined appeared to be expressed with minimal inter-individual variation (in general, approximately two- to fivefold) in the expression levels. Enzymes such as CYP1B1 and NQO1 that are capable of bioactivating pro-carcinogens to reactive metabolites were readily identifiable in human prostate. Immunohistochemical analysis showed that although some expression is located in the stroma, the majority is localized to epithelial cells lining the glandular elements of the tissue; these are the cells from which CaP might arise.

CONCLUSION

Constitutive expression of bioactivating enzymes confers the potential to convert a range of exogenous and/or endogenous agents to reactive species capable of inducing DNA damaging events. These findings suggest an organ capability for pro-carcinogen activation that could play an important role in the etiology of human CaP.

Effects of cigarette smoking on reproduction

BACKGROUND Cigarette smoking is associated with lower fecundity rates, adverse reproductive outcomes and a higher risk of IVF failures. Over the last few decades, prevalence of smoking among women of reproductive age has increased. This review focuses on current knowledge of the potential effects of smoke toxicants on all reproductive stages and the consequences of smoke exposure on reproductive functions. METHODS We conducted a systematic review of the scientific literature on the impact of cigarette smoking and smoke constituents on the different stages of reproductive function, including epidemiological, clinical and experimental studies. We attempted to create hypotheses and find explanations for the deleterious effects of cigarette smoke observed in experimental studies. RESULTS Cigarette smoke contains several thousand components (e.g. nicotine, polycyclic aromatic hydrocarbons and cadmium) with diverse effects. Each stage of reproductive function, folliculogenesis, steroidogenesis, embryo transport, endometrial receptivity, endometrial angiogenesis, uterine blood flow and uterine myometrium is a target for cigarette smoke components. The effects of cigarette smoke are dose-dependent and are influenced by the presence of other toxic substances and hormonal status. Individual sensitivity, dose, time and type of exposure also play a role in the impact of smoke constituents on human fertility. CONCLUSIONS All stages of reproductive functions are targets of cigarette smoke toxicants. Further studies are necessary to better understand the deleterious effects of cigarette smoke compounds on the reproductive system in order to improve health care, help to reduce cigarette smoking and provide a better knowledge of the molecular mechanisms involved in reproductive toxicology.

Removal of the endocrine disrupter butyl benzyl phthalate from the environment

Butyl benzyl phthalate (BBP), an aryl alkyl ester of 1,2-benzene dicarboxylic acid, is extensively used in vinyl tiles and as a plasticizer in PVC in many commonly used products. BBP, which readily leaches from these products, is one of the most important environmental contaminants, and the increased awareness of its adverse effects on human health has led to a dramatic increase in research aimed at removing BBP from the environment via bioremediation. This review highlights recent progress in the degradation of BBP by pure and mixed bacterial cultures, fungi, and in sludge, sediment, and wastewater. Sonochemical degradation, a unique abiotic remediation technique, and photocatalytic degradation are also discussed. The degradation pathways for BBP are described, and future research directions are considered.

Transcriptional signature of human macrophages exposed to the environmental contaminant benzo(a)pyrene

Polycyclic aromatic hydrocarbons (PAHs) are widely distributed immunotoxic and carcinogenic environmental contaminants, known to affect macrophages. In order to identify their molecular targets in such cells, we have analyzed gene expression profile of primary human macrophages treated by the prototypical PAH benzo(a)pyrene (BaP), using pangenomic oligonucleotides microarrays. Exposure of macrophages to BaP for 8 and 24 h resulted in 96 and 1100 genes, differentially expressed by at least a twofold change factor, respectively. Some of these targets, including the chemokine receptor CXCR5, the G protein-coupled receptor 35 (GPR35), and the Ras regulator RASAL1, have not been previously shown to be affected by PAHs, in contrast to others, such as interleukin-1beta and the aryl hydrocarbon receptor (AhR) repressor. These BaP-mediated gene regulations were fully validated by reverse transcription-quantitative polymerase chain reaction assays for some selected genes. Their bioinformatic analysis indicated that biological functions linked to immunity, inflammation, and cell death were among the most affected by BaP in human macrophages and that the AhR and p53 signaling pathways were the most significant canonical pathways activated by the PAH. AhR and p53 implications were moreover fully confirmed by the prevention of BaP-related upregulation of some selected target genes by AhR silencing or the use of pifithrin-alpha, an inhibitor of PAH bioactivation-related DNA damage/p53 pathways. Overall, these data, through identifying genes and signaling pathways targeted by PAHs in human macrophages, may contribute to better understand the molecular basis of the immunotoxicity of these environmental contaminants.

Organophosphorus pesticides enhance the genotoxicity of benzo(a)pyrene by modulating its metabolism

Organophosphorus compounds (OPs) are widely used as pesticides. They act primarily as neurotoxins, but there is increasing evidence for secondary mechanisms of their toxicity. We have shown that the model OPs, methyl parathion (PT) and methyl paraoxon (PO), are genotoxic. Benzo(a)pyrene (BaP) is a widespread environmental genotoxin found in cigarette smoke, polluted air and grilled food. As people are constantly exposed to low concentrations of BaP and also to OPs, the aim of this study was to determine possible synergistic effects of PT and PO on BaP-induced genotoxicity. In the bacterial reverse mutation assay, PT and PO increased the number of BaP-induced mutations. The comet assay with human hepatoma HepG2 cells showed that BaP-induced DNA strand breaks were increased by PT but slightly decreased by PO. Using the acellular comet assay with UVC-induced DNA strand breaks, we observed a decrease in DNA migration, indicating that OPs cause cross-linking, thus interfering with comet assay results. In HepG2 cells the two OPs induced micronuclei formation at very low doses (0.01 microg/ml) and together with BaP, a more than additive increase of micronuclei was observed, confirming their co-genotoxic effect. We demonstrated for the first time that PT and PO modulate the metabolic activation of BaP. Addition of PT or PO increased aldo-keto reductase (AKR1C1/2) levels in the presence of BaP, while cytochrome 1A (CYP1A) mRNA expression and activity were decreased. Further, specific inhibition of CYP1A had no effect on BaP or OP+BaP-induced micronuclei, whereas inhibition of AKR1C dramatically decreased the number of micronuclei induced by BaP or OP+BaP. Based on these results we propose that co-genotoxicity results from OPs mediated modulation of BaP metabolism, favouring the induction of AKR1C enzymes known to catalyse the formation of DNA reactive BaP o-quinones and the production of reactive oxygen species.

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.