Synergistic interactions between PBDEs and PCBs in human neuroblastoma cells.

Polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) are ubiquitous environmental pollutants. Exposure to these chemicals has been associated with developmental neurotoxicity, endocrine dysfunction, and reproductive disorders. Humans and wildlife are generally exposed to a mixture of these environmental pollutants, highlighting the need to evaluate the potential effects of combined exposures. In this study, we investigated the cytotoxic effects of the combined exposure to two PBDEs and two PCBs in a human neuronal cell line. 2,2',4,4'-Tetrabromodiphenyl ether, 2,2',4,4',5-pentabromodiphenyl ether, PCB-126 (3,3',4,4',5-pentachlorobiphenyl; a dioxin-like PCB), and PCB-153 (2,2',4,4',5,5'-hexachlorobiphenyl; a non-dioxin-like PCB) were chosen, because their concentrations are among the highest in human tissues and the environment. The results suggest that the nature of interactions is related to the PCB structure. Mixtures of PCB-153 and both PBDEs had a prevalently synergistic effect. In contrast, mixtures of each PBDE congener with PCB-126 showed additive effects at threshold concentrations, and synergistic effects at higher concentrations. These results emphasize the concept that the toxicity of xenobiotics may be affected by possible interactions, which may be of significance given the common coexposures to multiple contaminants.

[Non-invasive assessment of lung pathobiology in hairdressers]. / Valutazione non invasiva della patobiologia polmonare in una coorte di lavoratori del settore acconciatura.

BACKGROUND: Hairdressers are exposed to chemical agents with potentially irritant and sensitizing effects on airways. OBJECTIVES: To asses the presence of respiratory symptoms and biochemical and functional changes of the airways in a cohort of hairdressers. METHODS: Respiratory symptoms, lung function tests, fractional exhaled nitric oxide (FE(NO)50) and selected oxidative stress biomarkers [hydrogen peroxide (H2O2), malondialdehyde (MDA) and 4-hydroxynonenal (HNE)] in exhaled breath condensate (EBC) were assessed in 23 hairdressers on a rest day (Group 1); 12 workers (Group 2) were willing to perform the same tests at the beginning (BS) and at the end of a shift (ES) on the same working day. Eighteen subjects not occupationally exposed to airways irritants formed the control group. RESULTS: Most of the hairdressers reported respiratory symptoms during work; however, all (except one) showed normal spirometry indexes. FE(NO)50 levels were within the reference limits and did not change comparing BS vs. ES sampling. H2O2 and HNE values in EBC were higher in Group 1 (H2O2: 0,16 [0,05-0,19] microM; HNE: 0,94 [0,82-1,22] nM) than in controls (H2O2: 0,05 [0,02-0,09] microM; HNE: 0,61 [0,49-0,78] nM, p < 0,001). In Group 2, H2O2 and MDA levels were higher in EBC collected at ES (0,56 [0,23-3,62] mM and 5,21 [4,93-5,95] nM) in comparison with the BS values (0,11 [0,03-0,28] mM and 4,12 [3,46-5,16] nM, p < 0,001 and p < 0,02, respectively). CONCLUSIONS: Increased levels of oxidative stress biomarkers are detectable in EBC of hairdressers, without impairment in respiratory function. Exhaled biomarkers of oxidative stress may be sensitive end points for evaluating early biochemical changes in the airways of hairdressers.

Methylmercury at low doses modulates the toxicity of PCB153 on PC12 neuronal cell line in asynchronous combination experiments.

Me-Hg and PCB153 are known neurotoxic contaminants which tend to accumulate in food, particularly in fish. Aim of this study was to perform asynchronous and combined exposure to Me-Hg and PCB153 in a neuronal rat cell line (PC12) to better characterise the antagonism observed at some combination concentrations. PC12 cells were treated with three concentrations of Me-Hg (0.1-0.5-1.0 microM) and PCB153 at one concentration (175 microM) in single and combined asynchronous exposures, using viability (MTT assay) as end-point. At all concentrations used, a statistically significant antagonistic effect was observed when Me-Hg preceded PCB153 exposure, while effect was additive when PCB153 preceded Me-Hg exposure. The antagonism is particularly evident at low concentrations of Me-Hg (0.1 microM). In conclusion, combined asynchronous exposure showed that whereas Me-Hg can modulate PCB153 toxicity, the opposite seems not to be true. Therefore, the use of asynchronous exposure could be a promising approach to study the mechanisms of toxicity of binary mixtures.

[In vitro study of genotoxic and oxidative effects induced on human pulmonary cells by exposure to PAHs extracted from airborne particulate matter collected in a coke plant]. / Studio in vitro degli effetti genotossici ed ossidativi indotti su cellule polmonari umane dall'esposizione ad IPA estratti da matrici ambientali di una cokeria.

Genotoxic and oxidative effect of airborne particulate matter collected in a coke plant were evaluated on lung epithelial cells (A549). We aimed to clarify the mechanism of action of complex mixtures of PAHs and to identify biomarkers of effect of lung cancer. Particulate matter was analysed by GC/MS. Genotoxic and oxidative effects induced by the exposure to the extract were evaluated by Fpg comet assay. The cells were exposed for 30 min, 2h and 4h to 0.01%, 0.02% and 0.05% of the extract. We evaluated comet percentage and analysed tail moment values of exposed and unexposed cells treated with Fpg enzyme (TMenz) and untreated (TM) that indicate respectively oxidative and direct DNA damage. We found 0.328 ng/m3 of pyrene, 0.33 ng/m3 of benzo(a)anthracene, 1.073 ng/m3 of benzo(b)fluoranthene, 0.22 ng/m3 of benzo(k)fluoranthene, 0.35 ng/m3 of benzo(a)pyrene, 0.079 ng/m3 of dibenzo(a,h)anthracene and 0.40 ng/m3 of benzo(g,h,i)perylene. A dose-dependent increase, although not significant, of TM and TMenz in the exposed cells in respect to controls was found that indicates a slight increase of both direct and oxidative damage in exposed cells. A slight increase of comet percentage was found at the highest dose. We show the high sensibility of comet assay to measure early DNA damage also at low doses suggesting the use of such test on A549 to evaluate on target organ the effects of complex mixtures of genotoxic substances.

Antagonistic effects of methyl-mercury and PCB153 on PC12 cells after a combined and simultaneous exposure.

The study of interactions for those substances which tend to accumulate in food and affect the nervous system appears to be a fundamental point to characterize the combined exposure in vitro. In this study we included two food contaminants which are known neurotoxicants: methyl-mercury (Me-Hg) and the ortho-substituted PCB 153. PC12 cells were treated with Me-Hg (range 1e-7, 2e-6 M) and PCB153 (range 1e-5, 4e-4 M) in single and combined synchronous experiments and a mathematical model was set up according to the Loewe additivity criterion to evaluate the level of interaction between toxicants, using viability as end-point. At some concentrations (Me-Hg 5e-7 M and PCB153 1e-4 and 2e-4 M; Me-Hg 1e-6M and PCB153 5e-5 M; Me-Hg 1e-7 M and PCB153 4e-4 M), a statistically significant antagonist effect was observed. No interaction was observed for other combinations. The analysis of other toxicological parameters known to be modified in single exposure experiments (TBARS and intra-cellular dopamine) confirmed the viability results. The results of our work represent a starting point to generate novel information on the interactions between PCB153 and Me-Hg in vitro, as well as a new relevant experimental and mathematical approach useful to investigate the effects of different toxicant mixtures.

Analysis of oxidative stress in SK-N-MC neurons exposed to styrene-7,8-oxide.

Styrene-7,8-oxide (SO) is the main metabolite of styrene, a neurotoxic volatile organic compound used industrially. Here we report the novel observation that several markers of oxidative stress were affected in SK-N-MC cells exposed for 16 h to concentrations of SO that induce apoptotic cell death. The production of Thiobarbituric Acid Reactive Substances (TBARS), rose from 69.1 +/- 15.7 nmol/g protein (control) to 119.3 +/- 39.2 and 102.0 +/- 17.3 nmol/g protein after exposure to 0.3 and 1 mM SO, respectively. Carbonyl group levels were significantly enhanced by SO at both concentrations. The lower dose also decreased sulphydryl groups. SO caused a marked oxidative DNA damage, as shown by a fivefold increase in 8-hydroxy-2(')-deoxyguanosine (8-OHdG). In addition, SO exposure resulted in alterations of scavenging abilities, given the reduction of both glutathione (GSH) and glutathione-S-transferase (GST) activity. Induction of expression of the oxidative stress response gene heme-oxygenase-1 (HO-1) and an increased HO-1 activity were also observed. These data provide compelling evidence that oxidative stress significantly contributes to SO toxicity in neuronal cells.

[Definition of neurotoxic risk based on the benchmark dose in vitro: illustration with experimental models based on the use of known neurotoxic substances]. / Definizione del rischio neurotossico in base alla dose di riferimento ("benchmark dose") in vitro: esemplificazioni con modelli sperimentali basati sull'uso di sostanze neurotossiche note.

The BMD approach has been used to compare the cell viability (MTT assay) of different rat (C6 and PC12, glial and neuronal, respectively) and human cell lines (D384 and SK-N-MC, glial and neuronal, respectively) after 24-h exposure to the following neurotoxic substances: Manganese Chloride (MnCl2), Methyl-mercury (Me-Hg) and the enantiomers of Styrene Oxide (SO). For all rat and human cell lines, the potency of the examined compounds was: MnCl2 < S-SO < R-SO < Me-Hg. A preliminary comparison with in vivo toxicity data for these substances gave rise to consistent results. Whereas a reasonable agreement between in vitro and in vivo data has been found for Mn and styrene oxide, a wide scatter of LOAEL has been reported for Me-Hg and these appear to be either much higher or lower than the BMD for the MTT assay we observed in vitro.