Aryl hydrocarbon receptor-mediated activity of mutagenic polycyclic aromatic hydrocarbons determined using in vitro reporter gene assay

Activation of aryl hydrocarbon receptor (AhR) by 30 polycyclic aromatic hydrocarbons (PAHs) was determined in the chemical-activated luciferase expression (CALUX) assay, using two exposure times (6 and 24h), in order to reflect the metabolization of PAHs. AhR-inducing potencies of PAHs were expressed as induction equivalency factors (IEFs) relative to benzo[a]pyrene and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). In 24h exposure assay, the highest IEFs were found for benzo[k]fluoranthene, dibenzo[a,h]anthracene and dibenzo[a,k]fluoranthene (approximately three orders of magnitude lower than TCDD) followed by dibenzo[a,j]anthracene, benzo[j]fluoranthene, indeno[1,2,3-cd]pyrene, and naphtho[2,3-a]pyrene. The 6h exposure to PAHs led to a significantly higher AhR-mediated activity than the 24h exposure (generally by two orders of magnitude), probably due to the high rate of PAH metabolism. The strongest AhR inducers showed IEFs approaching that of TCDD. Several PAHs, including some strong mutagens, such as dibenzo[a,l]pyrene, cyclopenta[cd]pyrene, and benzo[a]perylene, elicited only partial agonist activity. Calculation of IEFs based on EC25 values and/or 6h exposure data is suggested as an alternative approach to estimation of toxic potencies of PAHs with high metabolic rates and/or the weak AhR agonists. The IEFs, together with the recently reported relative mutagenic potencies of PAHs [Mutat. Res. 371 (1996) 123; Mutat. Res. 446 (1999) 1] were combined with data on concentrations of PAHs in extracts of model environmental samples (river sediments) to calculate AhR-mediated induction equivalents and mutagenic equivalents. The highest AhR-mediated induction equivalents were found for benzo[k]fluoranthene and benzo[j]fluoranthene, followed by indeno[1,2,3-cd]pyrene, dibenzo[a,h]anthracene, benzo[a]pyrene, dibenzo[a,j]anthracene, chrysene, and benzo[b]fluoranthene. High mutagenic equivalents in the river sediments were found for benzo[a]pyrene, dibenzo[a,e]pyrene, and naphtho[2,3-a]pyrene and to a lesser extent also for benzo[a]anthracene, benzo[b]fluoranthene, indeno[1,2,3-cd]pyrene, benzo[j]fluoranthene, dibenzo[a,e]fluoranthene and dibenzo[a,i]pyrene. These data illustrate that AhR-mediated activity of PAHs, including the highly mutagenic compounds, occurring in the environment but not routinely monitored, could significantly contribute to their adverse effects.

Environmental xenobiotics and nuclear receptors--interactions, effects and in vitro assessment

A group of intracellular nuclear receptors is a protein superfamily including arylhydrocarbon AhR, estrogen ER, androgen AR, thyroid TR and retinoid receptors RAR/RXR as well as molecules with unknown function known as orphan receptors. These proteins play an important role in a wide range of physiological as well as toxicological processes acting as transcription factors (ligand-dependent signalling macromolecules modulating expression of various genes in a positive or negative manner). A large number of environmental pollutants and other xenobiotics negatively affect signaling pathways, in which nuclear receptors are involved, and these modulations were related to important in vivo toxic effects such as immunosuppression, carcinogenesis, reproduction or developmental toxicity, and embryotoxicity. Presented review summarizes current knowledge on major nuclear receptors (AhR, ER, AR, RAR/RXR, TR) and their relationship to known in vivo toxic effects. Special attention is focused on priority organic environmental contaminants and experimental approaches for determination and studies of specific toxicity mechanisms.

Estrogen-, androgen- and aryl hydrocarbon receptor mediated activities in passive and composite samples from municipal waste and surface waters

Passive and composite sampling in combination with in vitro bioassays and identification and quantification of individual chemicals were applied to characterize pollution by compounds with several specific modes of action in urban area in the basin of two rivers, with 400,000 inhabitants and a variety of industrial activities. Two types of passive samplers, semipermeable membrane devices (SPMD) for hydrophobic contaminants and polar organic chemical integrative samplers (POCIS) for polar compounds such as pesticides and pharmaceuticals, were used to sample wastewater treatment plant (WWTP) influent and effluent as well as rivers upstream and downstream of the urban complex and the WWTP. Compounds with endocrine disruptive potency were detected in river water and WWTP influent and effluent. Year-round, monthly assessment of waste waters by bioassays documented estrogenic, androgenic and dioxin-like potency as well as cytotoxicity in influent waters of the WWTP and allowed characterization of seasonal variability of these biological potentials in waste waters. The WWTP effectively removed cytotoxic compounds, xenoestrogens and xenoandrogens. There was significant variability in treatment efficiency of dioxin-like potency. The study indicates that the WWTP, despite its up-to-date technology, can contribute endocrine disrupting compounds to the river. Riverine samples exhibited dioxin-like, antiestrogenic and antiandrogenic potencies. The study design enabled characterization of effects of the urban complex and the WWTP on the river. Concentrations of PAHs and contaminants and specific biological potencies sampled by POCIS decreased as a function of distance from the city.

AhR-mediated and antiestrogenic activity of humic substances

Humic substances (HS) were for decades regarded as inert in the ecosystems with respect to their possible toxicity. However, HS have been recently shown to elicit various adverse effects generally attributed to xenobiotics. In our study, we used MVLN and H4IIE-luc cell lines stably transfected with luciferase gene under control of estrogen receptor (ER) and Ah receptor (AhR; receptor connected with so-called dioxin-like toxicity) for assessment of anti/estrogenic and AhR-mediated effects of 12 commercially available humic substances. Out of those, five humic acids were shown to induce AhR-mediated activity with relative potencies related to TCDD 2.6 x 10(-8)-7.4 x 10(-8). Organic extracts of HS solutions also elicited high activities what means that lipophilic molecules are responsible for a great part of effect. However, relatively high activity remaining in extracted solution suggests also presence of polar AhR-agonists. Contribution of persistent organic compounds to the observed effects was ruled out by H(2)SO(4) treatment. Eight out of twelve HS elicited significant antiestrogenic effects with IC(50) ranging from 40 to 164 mg l(-1). The possible explanations of the antiestrogenic effect include sorption of 17-beta-estradiol (E2) on HS, changes in membrane permeability for E2 or another specific mechanism.

Age dependency and mutual relations in T and B lymphocyte abnormalities in common variable immunodeficiency patients

Common variable immunodeficiency (CVID) is primary hypogammaglobulinaemia with an unknown aetiopathogenesis. Although various abnormalities of T and B cells have been described, their pathogenetic roles are unclear. We determined T and B lymphocyte subsets known to be abnormal in CVID in order to disclose possible relations between numerical abnormalities in those cells. Markers associated with B cell development (CD21, CD27, IgM, IgD) were determined on B lymphocytes (CD19+); T lymphocyte development (CD45RA, CD45RO, CD62L) and activation markers (CD25, CD27, CD28, CD29, CD38, CD57, HLA-DR) were determined on CD4+ and CD8+ T lymphocytes in 42 CVID patients and in 33 healthy controls. Abnormalities in CD4+ T lymphocyte activation markers (increase in CD29, HLA-DR, CD45RO, decrease in CD27, CD62L, CD45RA) were observed particularly in patients with a decreased number of memory (CD27+) and mature (CD21+) B cells (group Ia according to the Freiburg group's classification), while abnormalities observed in CD8+ cells (increase in CD27 and CD28 and decrease in HLA-DR, CD57 and CD38) did not depend upon grouping patients together according to B lymphocyte developmental subpopulations. We observed correlations between immature B cells (IgM+ CD21-) and expression of CD27, CD62L, CD45RA, CD45RO and HLA-DR on CD4+ T cells in CVID patients but not in the control group. The expression of CD27 and CD45RA on CD4+ T lymphocytes, such as the percentage of IgD+ CD27- and IgD+ CD27+ cells in B lymphocytes, showed age dependency to be more significant than in the control group. Our study demonstrates that T and B lymphocyte abnormalities in CVID are partially related to each other. Some of those abnormalities are not definite, but may evolve with age of the patient.

Effects of N-heterocyclic polyaromatic hydrocarbons on survival, reproduction, and biochemical parameters in Daphnia magna

N-heterocyclic polycyclic aromatic hydrocarbons (N-PAHs) belong among newly identified classes of environmental pollutants with relatively high toxic potential. N-PAHs have been detected in air, soil, marine environments, and freshwater sediments. The N-PAHs are present at lower concentrations than their nonsubstituted analogues but their greater solubility would lead to greater bioavailibity and potential for toxic effects. Here we present results of acute and chronic toxicity in traditional aquatic invertebrate ecotoxicological model (Daphnia magna) along with assessment of biochemical responses. Studied biomarkers in D. magna exposed to N-heterocyclic derivatives included glutathione levels and activities of detoxication and antioxidative enzymes glutathione S-transferase and glutathione peroxidase. Phenanthrene and 1,10-phenathroline were the most toxic of all tested compounds (EC50 < 6 microM after 48 h exposure) and all tested N-PAHs suppressed reproduction of Daphnia magna. The data suggest that N-PAHs can induce oxidative stress in D. magna. The significant decline of glutathione content was found in animals treated with acridine, 1,10-phenanthroline, benzo(h)quinoline, phenantridine, and phenazine. Significant decrease of GPx activities relative to controls was found for all tested compounds except of phenanthrene and phenazine. Activities of GST increased after exposure to phenanthridine, phenazine, and benzo(h)quinoline, and declined in D. magna treated with phenanthrene (significant at one concentration) or anthracene (not significant). Our results confirmed significant acute as well as chronic toxicities of N-PAHs as well as potential of biochemical parameters to be used as early warning signals of toxicity in Daphnia magna.

Estrogenic activity in extracts and exudates of cyanobacteria and green algae

Here is presented some of the first information on interactions of compounds produced by cyanobacteria and green algae with estrogen receptor signaling. Estrogenic potency of aqueous extracts and exudates (culture spent media with extracellular products) of seven species of cyanobacteria (10 different laboratory strains) and two algal species were assessed by use of in vitro trans-activation assays. Compounds produced by cyanobacteria and algae, and in particular those excreted from the cells, were estrogenic. Most exudates were estrogenic with potencies expressed at 50% of the maximum response under control of the estrogen receptor ranging from 0.2 to 7.2 ng 17β-estradiol (E(2)) equivalents (EEQ)/L. The greatest estrogenic potency was observed for exudates of Microcystis aerigunosa, a common species that forms water blooms. Aqueous extracts of both green algae, but only one species of cyanobacteria (Aphanizomenon gracile) elicited significant estrogenicity with EEQ ranging from 15 to 280 ng 17β-estradiol (E(2))/g dry weight. Scenedesmus quadricauda exudates and extracts of Aphanizomenon flos-aquae were antagonistic to the ER when coexposed to E(2). The EEQ potency was not correlated with concentrations of cyanotoxins, such as microcystin and cylindrospermopsin, which suggests that the EEQ was comprised of other compounds. The study demonstrates some differences between the estrogenic potency of aqueous extracts prepared from the same species, but of different origin, while the effects of exudates were comparable within species. The observed estrogenic potencies are important namely in relation to the possible mass expansion of cyanobacteria and release of the active compounds into surrounding water.

Simultaneous determination of reduced and oxidized glutathione in tissues by a novel liquid chromatography-mass spectrometry method: application in an inhalation study of Cd nanoparticles

The paper presents the development of an advanced extraction and fast analytical LC MS/MS method for simultaneous analyses of reduced and oxidized glutathione (GSH and GSSG, respectively) in different animal tissues. The simultaneous determination of GSH and GSSG is crucial because the amount and ratio of both GSH and GSSG may be altered in response to oxidative stress, an important mechanism of toxicity. The method uses the derivatization of free thiol groups in GSH. Its performance was demonstrated for less explored tissues (lung, brain, and liver) in mouse. The combined extraction and analytical method has very low variability and good reproducibility, maximum coefficients of variance for within-run and between-run analyses under 8 %, and low limits of quantification; for GSH and GSSG, these were 0.2 nM (0.06 ng/mL) and 10 nM (6 ng/mL), respectively. The performance of the method was further demonstrated in a model experiment addressing changes in GSH and GSSG concentrations in lung of mice exposed to CdO nanoparticles during acute 72 h and chronic 13-week exposures. Inhalation exposure led to increased GSH concentrations in lung. GSSG levels were in general not affected; nonsignificant suppression occurred only after the longer 13-week period of exposure. The developed method for the sensitive detection of both GSH and GSSG in very low tissue mass enables these parameters to be studied in cases where only a little sample is available, i.e. in small organisms or in small amounts of tissue.

Do predictions from Species Sensitivity Distributions match with field data?

Species Sensitivity Distribution (SSD) is a statistical model that can be used to predict effects of contaminants on biological communities, but only few comparisons of this model with field studies have been conducted so far. In the present study we used measured pesticides concentrations from streams in Germany, France, and Finland, and we used SSD to calculate msPAF (multiple substance potentially affected fraction) values based on maximum toxic stress at localities. We compared these SSD-based predictions with the actual effects on stream invertebrates quantified by the SPEARpesticides bioindicator. The results show that the msPAFs correlated well with the bioindicator, however, the generally accepted SSD threshold msPAF of 0.05 (5% of species are predicted to be affected) severely underestimated the observed effects (msPAF values causing significant effects are 2-1000-times lower). These results demonstrate that validation with field data is required to define the appropriate thresholds for SSD predictions.

In vitro modulation of intracellular receptor signaling and cytotoxicity induced by extracts of cyanobacteria, complex water blooms and their fractions

The biological activity of cyanobacteria and their chemical components have been widely studied due to their blooms in eutrophic waters worldwide. The primary goal of this study was to determine if individual cyanobacterial species and mixtures of cyanobacteria collected from the environment contain compounds with the potential for interaction with signaling pathways of the aryl hydrocarbon receptor (AhR), androgen receptor (AR), estrogen receptor (ER), glucocorticoid receptor (GR) and retinoid acid receptor (RAR). Cytotoxicity and specific toxic potencies of products of freshwater cyanobacteria were determined by use of in vitro reporter gene trans-activation assays. The testing included samples prepared from five selected single cyanobacterial species cultivated in laboratory and five complex cyanobacterial biomasses collected from blooms in surface waters in the Czech Republic. The results demonstrate estrogenic potencies of extracts of cyanobacterial biomasses. Among the laboratory single species, the extract of Planktothrix agardhii (intracellular metabolites) had a potency of estrogenic equivalents (EEQ) of 3.8 ng 17β-estradiol/g dw. The estimates of EEQs of samples prepared from complex cyanobacterial biomasses collected from freshwaters in the Czech Republic ranged from 19 to 2200 ng 17β-estradiol/g dw. Several samples prepared from the environmental cyanobacterial biomasses potentiated the androgenic potency of dihydrotestosterone. There was no dioxin-like, glucocorticoid or anti/retinoic activity observed for any of the extracts studied. Extracts of natural complex cyanobacterial biomasses exhibited greater and more frequent presence of compounds with specific modes of action, mainly estrogenic, and also greater cytotoxicity than extracts of single cyanobacterial species. The demonstrated estrogenic potency of the compounds present in complex cyanobacterial biomasses is of environmental relevance, and could potentially contribute to endocrine disruptive effects in aquatic ecosystems in case of great bloom densities.

Inhibitors of arachidonic acid metabolism potentiate tumour necrosis factor-alpha-induced apoptosis in HL-60 cells

We investigated whether and how could various modulators of arachidonic acid metabolism affect apoptosis induced by tumour necrosis factor-alpha (TNF-alpha) in human myeloid leukaemia HL-60 cells. These included arachinonyltrifluoromethyl ketone (AACOCF3; cytosolic phospholipase A2 inhibitor), indomethacin (cyclooxygenase inhibitor), MK-886 (3-[1-(4-chlorobenzyl)-3-t-butyl-thio-5-isopropylindol-2-yl]-2,2-dimethyl propanoic acid; 5-lipoxygenase-activating protein inhibitor), nordihydroguaiaretic acid (general lipoxygenase inhibitor), and arachidonic acid itself. Incubation of HL-60 cells with nordihydroguaiaretic acid resulted in apoptosis and it was characterised by mitochondria membrane depolarisation, release of cytochrome c from mitochondria into cytosol and activation of caspase-3. Indomethacin and nordihydroguaiaretic acid synergistically potentiated TNF-alpha-induced apoptosis, while arachidonic acid, AACOCF3 and MK-886 did not modulate its effects. Furthermore, indomethacin potentiated apoptosis in cells treated with a differentiating agent, all-trans retinoic acid, which induces resistance to TNF-alpha. However, the observed effects were probably not associated either with the cyclooxygenase- or lipoxygenase-dependent activities of indomethacin and nordihydroguaiaretic acid, respectively. Since indomethacin may reportedly activate peroxisome proliferator-activated receptors (PPARs), the effects of specific ligands of PPARs on apoptosis were studied as well. It was found that selective PPARs ligands had no effects on TNF-alpha-induced apoptosis. The findings suggest that arachidonic acid metabolism does not play a key role in regulation of apoptosis induced by TNF-alpha in the present model. Nevertheless, our data raise the possibility that indomethacin could potentially be used to improve the treatment of human myeloid leukaemia.

Assessment of non-derivatized β-N-methylamino-l-alanine (BMAA) neurotoxin in free form in urine of patients with nonspecific neurological symptoms

The beta-N-methylamino-l-alanine (BMAA) is a non-proteinogenic amino acid discussed to be produced by cyanobacteria forming harmful blooms. Since BMAA is suspected etiological agent in neurodegenerative diseases, there is a need to study and validate whether and in what concentrations can BMAA be present in human tissues. The aim of the present study was to validate analytical and extraction procedures for quantification of non-derivatized BMAA in the urine using liquid chromatography and commercial ELISA Kit. The study was focused on BMAA in different forms - dissolved, protein associated and total. The validated protocol included SPE followed by HILIC MS/MS for analyses of non-derivatized free form of BMAA with a limit of quantification 20 ng/mL. The methods for other BMAA forms (i.e. protein-associated and total) were also assessed but high matrix interferences did not allow their implementation. The method was used for analyses of free BMAA in 23 urine samples from healthy volunteers and psychiatric patients suffering from nonspecific neurological symptoms. Traces of BMAA were suspectedly detected in a single urine sample but they were not unequivocally proved according to all conservative analytical criteria. BMAA was also not confirmed in a repeatedly collected sample from the same person. The evaluated commercial BMAA ELISA Kit (Abraxis) was not suitable for determination of BMAA in extracted urine samples because of systematically highly false positive results. In agreement with recent findings, analyses of BMAA appear to methodologically challenging, and further research on BMAA in human tissues (or its precursors with potency to form BMAA under natural conditions or - eventually - during sample processing) is needed to clarify its potential ethiological role in neurodegenerative diseases.

Stimulation of nonspecific immunity, haemopoiesis and protection of mice against radiation injury by 1-adamantylamide-l-alanyl-d-isoglutamine incorporated in liposomes

1-Adamantylamide-L-alanyl-D-isoglutamine (adamantylamide dipeptide (AdDP)) belongs to a group of desmuramyl muramyl peptide derivatives which are able to protect an organism from some viral infections. Encapsulation of AdDP to egg phosphatidyl choline liposomes and the targeting of this drug to lymphatic node macrophages via subcutaneous (s.c.) administration proved to be the efficient way to protect mice against irradiation when administered s.c., 24 h prior to lethal gamma-irradiation (long-term survival rate in the range of 40% compared with 0% in saline or free drug control). Parameters characteristic for the recovery of haemopoiesis in the bone marrow (number of granulocyte-macrophage haemopoietic progenitor cells, granulocyte-macrophage colony forming cells (GM-CFC)) were significantly improved in comparison with the controls and free drug on day 10 after 6.5 Gy irradiation. The haemopoietic effect was observed in the broad application time window (72 h before and 48 h after irradiation). Very high radioprotective effect of s.c. administered liposomal AdDP (L-AdDP) can be explained (together with induction of haemopoiesis) by the effective and long-lasting activation of nonspecific immunity, which withholds the onset of septicemia in early days after irradiation. Induction of nonspecific immunity was proven in Candida albicans infectious model. L-AdDP significantly increased both the survival time and score (about 40% survival compared with 0% in controls and free drug). In conclusion, L-AdDP could be therapeutically beneficial to moderate the haemopoietic damage (undesirable effect of radiotherapy or chemotherapy) and induce the non-specific immunity to support the antimicrobial treatment of immunocompromised patients.

Endocrine effects of contaminated sediments on the freshwater snail Potamopyrgus antipodarum in vivo and in the cell bioassays in vitro

Lake Pilnok located in the black coal-mining region Ostrava-Karvina, Czech Republic, contains sediments highly contaminated with powdered waste coal. Moreover, population of the endangered species of narrow-clawed crayfish Pontastacus leptodactylus with high proportion of intersex individuals (18%) was observed at this site. These findings motivated our work that aimed to evaluate contamination, endocrine disruptive potency using in vitro assays and in vivo effects of contaminated sediments on reproduction of sediment-dwelling invertebrates. Chemical analyses revealed low concentrations of persistent chlorinated compounds and heavy metals but concentrations of polycyclic aromatic hydrocarbons (PAH) were high (sum of 16 PAHs 10 microg/g dw). Organic extracts from sediments caused significant in vitro AhR-mediated activity in the bioassay with H4IIE-luc cells, estrogenicity in MVLN cells and anti-androgenicity in recombinant yeast assay, and these effects could be attributed to non-persistent compounds derived from the waste coal. We have also observed significant in vivo effects of the sediments in laboratory experiments with the Prosobranchian euryhaline mud snail Potamopyrgus antipodarum. Sediments from Lake Pilnok as well as organic extracts of the sediments (externally added to the control sediment) significantly affected fecundity during 8 weeks of exposure. The effects were stimulations of fecundity at lower concentrations at the beginning of the experiment followed by inhibitions of fecundity and general toxicity. Our study indicates presence of chemicals that affected endocrine balance in invertebrates, and emphasizes the need for integrated approaches combining in vitro and in vivo bioassays with identification of chemicals to elucidate ecotoxicogical impacts of contaminated sediment samples.