Reduction of dioxin-like toxicity in effluents by additional wastewater treatment and related effects in fish.

Efficiency of advanced wastewater treatment technologies to reduce micropollutants which mediate dioxin-like toxicity was investigated. Technologies compared included ozonation, powdered activated carbon and granular activated carbon. In addition to chemical analyses in samples of effluents, surface waters, sediments, and fish, (1) dioxin-like potentials were measured in paired samples of effluents, surface waters, and sediments by use of an in vitro biotest (reporter gene assay) and (2) dioxin-like effects were investigated in exposed fish by use of in vivo activity of the mixed-function, monooxygenase enzyme, ethoxyresorufin O-deethylase (EROD) in liver. All advanced technologies studied, based on degradation or adsorption, significantly reduced dioxin-like potentials in samples and resulted in lesser EROD activity in livers of fish. Results of in vitro and in vivo biological responses were not clearly related to quantification of targeted analytes by use of instrumental analyses.

Endocrine, teratogenic and neurotoxic effects of cyanobacteria detected by cellular in vitro and zebrafish embryos assays.

Cyanobacteria contain various types of bioactive compounds, which could cause adverse effects on organisms. They are released into surface waters during cyanobacterial blooms, but there is little information on their potential relevance for effects in vivo. In this study presence of bioactive compounds was characterized in cyanobacteria Microcystis aeruginosa (Chroococcales), Planktothrix agardhii (Oscillatoriales) and Aphanizomenon gracile (Nostocales) with selected in vitro assays. The in vivo relevance of detected bioactivities was analysed using transgenic zebrafish embryos tg(cyp19a1b-GFP). Teratogenic potency was assessed by analysis of developmental disorders and effects on functions of the neuromuscular system by video tracking of locomotion. Estrogenicity in vitro corresponded to 0.95-54.6 ng estradiol equivalent(g dry weight (dw))(-1). In zebrafish embryos, estrogenic effects could not be detected potentially because they were masked by high toxicity. There was no detectable (anti)androgenic/glucocorticoid activity in any sample. Retinoid-like activity was determined at 1-1.3 µg all-trans-retinoic acid equivalent(g dw)(-1). Corresponding to the retinoid-like activity A. gracile extract also caused teratogenic effects in zebrafish embryos. Furthermore, exposure to biomass extracts at 0.3 gd wL(-1) caused increase of body length in embryos. There were minor effects on locomotion caused by 0.3 gd wL(-1)M. aeruginosa and P. agardhii extracts. The traditionally measured cyanotoxins microcystins did not seem to play significant role in observed effects. This indicates importance of other cyanobacterial compounds at least towards some species or their developmental phases. More attention should be paid to activity of retinoids, estrogens and other bioactive substances in phytoplankton using in vitro and in vivo bioassays.

Dioxins and dioxin-like compounds in composts and digestates from European countries as determined by the in vitro bioassay and chemical analysis.

Aerobic composting and anaerobic digestion plays an important role in reduction of organic waste by transforming the waste into humus, which is an excellent soil conditioner. However, applications of chemical-contaminated composts on soils may have unwanted consequences such as accumulation of persistent compounds and their transfer into food chains. The present study investigated burden of composts and digestates collected in 16 European countries (88 samples) by the compounds causing dioxin-like effects as determined by use of an in vitro transactivation assay to quantify total concentrations of aryl hydrocarbon receptor-(AhR) mediated potency. Measured concentrations of 2,3,7,8-Tetrachlorodibeno-p-dioxin (2,3,7,8-TCDD) equivalents (TEQbio) were compared to concentrations of polycyclic aromatic hydrocarbons (PAHs) and selected chlorinated compounds, including polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs), co-planar polychlorinated biphenyls (PCBs), indicator PCB congeners and organochlorine pesticides (OCPs). Median concentrations of TEQbio (dioxin-like compounds) determined by the in vitro assay in crude extracts of various types of composts ranged from 0.05 to 1.2 with a maximum 8.22µg (TEQbio)kg(-1) dry mass. Potencies were mostly associated with less persistent compounds such as PAHs because treatment with sulfuric acid removed bioactivity from most samples. The pan-European investigation of contamination by organic contaminants showed generally good quality of the composts, the majority of which were in compliance with conservative limits applied in some countries. Results demonstrate performance and added value of rapid, inexpensive, effect-based monitoring, and points out the need to derive corresponding effect-based trigger values for the risk assessment of complex contaminated matrices such as composts.

The effects of PAHs and N-PAHs on retinoid signaling and Oct-4 expression in vitro.

Polycyclic aromatic hydrocarbons (PAHs) and their N-heterocyclic analogs (N-PAHs) are important environmental contaminants with negative effects in living organisms, including teratogenicity and embryotoxicity. Though most studies linked their embryotoxicity with aryl hydrocarbon receptor (AhR) and cytochrome P450 activation, the exact mechanism is not known. Other mechanisms such as disruption of retinoid signaling were recently suggested to be of importance. This study investigated PAHs and N-PAHs interference with retinoid signaling in vitro by modulating all-trans retinoic acid (ATRA) mediated response in a reporter gene assay using P19/A15 cell line. Further, effects on pluripotency and differentiation processes were evaluated by measuring octamer-4 (Oct-4), an important pluripotency marker and master differentiation factor. Two of the studied compounds, benz[a]anthracene and benz[c]acridine significantly up-regulated ATRA-mediated response in the co-exposure with a range of ATRA concentrations. Another structural N-PAH variant, 1,7-phenanthroline, downregulated ATRA-mediated response at most of tested ATRA concentrations and exposure times. Interesting concentration-dependent biphasic effects (i.e. downregulation with subsequent up-regulation to control levels) were observed at co-exposures of ATRA and parent PAH phenanthrene. Non significant Oct-4 modulation in co-exposure with ATRA was observed at compounds, which potentiated ATRA-mediated effects in the reporter gene assay. On the other hand, 1,7-phenanthroline and phenanthrene significantly suppressed Oct-4 levels in higher tested concentrations. Our results further extend the knowledge of PAH and N-PAH in vitro effects and indicate that these environmental toxicants may have influence on differentiation process and embryonic development by interfering with ATRA signaling and by modulating levels of Oct-4.

Interference of PAHs and their N-heterocyclic analogs with signaling of retinoids in vitro.

Retinoids are dietary hormones acting through nuclear receptors for retinoic acid, important especially during embryonic development. This study focuses on the disruption of signaling pathways of retinoids by polycyclic aromatic hydrocarbons (PAHs) and their N-heterocyclic analogs (N-PAHs), important environmental contaminants with numerous biological effects. In vitro test with P19/A15 cell line stably transfected with luciferase reporter gene under control of retinoic acid-responsive elements was used to investigate both direct activation of retinoic acid receptors and modulation of response induced by natural ligand all-trans retinoic acid (ATRA) by 26 PAHs and N-PAHs. While none of individual compounds alone activated retinoic acid receptors, many of them modulated ATRA-mediated activity both after 6 h and 24 h exposure. Majority of compounds active after 6h downregulated ATRA-mediated activity (most effective were two analogs of dibenz[a,h]anthracene with LOECs about 185 nM), while most compounds active after 24h upregulated the effects of ATRA (most effective benz[a]acridine and dibenz[a,i]acridine caused 400% induction of ATRA response). Quantitative structure-activity relationship analysis identified molecular volume and dipole moment as the most important descriptors of inhibitory effects after 6h, while length, total molecular energy, gap-HOMO/LUMO and Van der Waals energy are important descriptors for stimulatory effects of PAHs and N-PAHs. This study demonstrates those abundant pollutants such as PAHs and their analogs interfere in vitro with retinoid signaling, which could play role in some in vivo effects of these organic contaminants such as teratogenicity.

Disruption of retinoid transport, metabolism and signaling by environmental pollutants.

Although the assessment of circulatory levels of retinoids has become a widely used biomarker of exposure to environmental pollutants, the adverse effects caused by imbalance of the retinoid metabolism and signaling in wildlife are not known in detail. Retinoids play an important role in controlling such vital processes as morphogenesis, development, reproduction or apoptosis. Unlike other signaling molecules, retinoids are not strictly endogenous but they are derived from dietary sources of vitamin A or its precursors and thus they are sometimes referred to as 'dietary' hormones. Some environmental pollutants that affect embryogenesis, immunity or epithelial functions were also shown to interfere with retinoid metabolism and signaling in animals. This suggests that at least some of their toxic effects may be related to interaction with the retinoid metabolism, transport or signal transduction. This review summarizes in vivo and in vitro studies on interaction of environmental complex samples, pesticides, polychlorinated dioxins, polychlorinated biphenyls, polycyclic aromatic compounds and other organic pollutants with physiology of retinoids. It sums up contemporary knowledge about levels of interaction and mechanisms of action of the environmental contaminants.

Interference of contaminated sediment extracts and environmental pollutants with retinoid signaling.

Retinoids are known to regulate important processes such as differentiation, development, and embryogenesis. Some effects, such as malformations in frogs or changes in metabolism of birds, could be related to disruption of the retinoid signaling pathway by exposure to organic contaminants. A new reporter gene assay has been established for evaluation of the modulation of retinoid signaling by individual chemicals or environmental samples. The bioassay is based on the pluripotent embryonic carcinoma cell line P19 stably transfected with the firefly luciferase gene under the control of a retinoic acid-responsive element (clone P19/ A15). The cell line was used to characterize the effects of individual chemicals and sediments extracts on retinoid signaling pathways. The extracts of sediments from the River Kymi, Finland, which contained polychlorinated dioxins and furans and polycyclic aromatic hydrocarbons (PAHs), significantly increased the potency of all-trans retinoic acid (ATRA), while no effect was observed with the extract of the sediment from reference locality. Considerable part of the effect was caused by the labile fraction of the sediment extracts. Also, several individual PAHs potentiated the effect of ATRA; on the other hand, 2,3,7,8-tetrachlorodibenzo-p-dioxin and several phthalates showed slightly inhibiting effect. These results suggest that PAHs could be able to modulate the retinoid signaling pathway and that they could be responsible for a part of the proretinoid activity observed in the sediment extracts. However, the effects of PAHs on the retinoic acid signaling pathways do not seem to be mediated directly by crosstalk with aryl hydrocarbon receptor.