BACKGROUND: Cytochromes P450 are major drug-metabolizing enzymes involved in the biotransformation of diverse xenobiotics and endogenous chemicals. Persistent organic pollutants (POPs) are toxic hydrophobic compounds that cause serious environmental problems because of their poor degradability. This calls for rational design of enzymes capable of catalyzing their biotransformation. Cytochrome P450 1A1 isoforms catalyze the biotransformation of some POPs, and constitute good starting points for the design of biocatalysts with tailored substrate specificity. METHODS: We rationalized the activities of wild type and mutant forms of rat cytochrome P450 1A1 towards 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD) and 3,3',4,4'-tetrachlorobiphenyl (PCB77) using experiments and molecular dynamics simulations. RESULTS: We showed that the enhanced activity of the CYP1A1 mutant towards TCDD was due to more efficient binding of the substrate in the active site even though the mutated site was over 2.5nm away from the catalytic center. Moreover, this mutation reduced activity towards PCB77. GENERAL SIGNIFICANCE: Amino acids that affect substrate access channels can be viable targets for rational enzyme design even if they are located far from the catalytic site.
- MeSH
- adukty DNA účinky léků MeSH
- biotransformace účinky léků MeSH
- cytochrom P-450 CYP1A1 chemie genetika MeSH
- katalytická doména účinky léků MeSH
- katalýza * MeSH
- krysa rodu rattus MeSH
- látky znečišťující životní prostředí chemie toxicita MeSH
- lidé MeSH
- metabolická inaktivace účinky léků genetika MeSH
- mutace MeSH
- polychlorované bifenyly chemie toxicita MeSH
- polychlorované dibenzodioxiny chemie toxicita MeSH
- substrátová specifita MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Using pine needles as a bio-sampler of atmospheric contamination is a relatively cheap and easy method, particularly for remote sites. Therefore, pine needles have been used to monitor a range of semi-volatile contaminants in the air. In the present study, pine needles were used to monitor polychlorinated biphenyls (PCBs) in the air at sites with different land use types in Sweden (SW), Czech Republic (CZ), and Slovakia (SK). Spatiotemporal patterns in levels and congener profiles were investigated. Multivariate analysis was used to aid source identification. A comparison was also made between the profile of indicator PCBs (ind-PCBs-PCBs 28, 52, 101, 138, 153, and 180) in pine needles and those in active and passive air samplers. Concentrations in pine needles were 220-5100 ng kg(-1) (∑18PCBs - ind-PCBs and dioxin-like PCBs (dl-PCBs)) and 0.045-1.7 ng toxic equivalent (TEQ) kg(-1) (dry weight (dw)). Thermal sources (e.g., waste incineration) were identified as important sources of PCBs in pine needles. Comparison of profiles in pine needles to active and passive air samplers showed a lesser contribution of lower molecular weight PCBs 28 and 52, as well as a greater contribution of higher molecular weight PCBs (e.g., 180) in pine needles. The dissimilarities in congener profiles were attributed to faster degradation of lower chlorinated congeners from the leaf surface or metabolism by the plant.
- MeSH
- borovice lesní chemie metabolismus MeSH
- dioxiny chemie metabolismus MeSH
- listy rostlin chemie MeSH
- monitorování životního prostředí metody MeSH
- polychlorované bifenyly chemie metabolismus MeSH
- polychlorované dibenzodioxiny chemie metabolismus MeSH
- spalování odpadů MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Evropa MeSH
Consensus toxicity factors (CTFs) were developed as a novel approach to establish toxicity factors for risk assessment of dioxin-like compounds (DLCs). Eighteen polychlorinated dibenzo-p-dioxins, dibenzofurans (PCDD/Fs), and biphenyls (PCBs) with assigned World Health Organization toxic equivalency factors (WHO-TEFs) and two additional PCBs were screened in 17 human and rodent bioassays to assess their induction of aryl hydrocarbon receptor-related responses. For each bioassay and compound, relative effect potency values (REPs) compared to 2,3,7,8-tetrachlorodibenzo-p-dioxin were calculated and analyzed. The responses in the human and rodent cell bioassays generally differed. Most notably, the human cell models responded only weakly to PCBs, with 3,3',4,4',5-pentachlorobiphenyl (PCB126) being the only PCB that frequently evoked sufficiently strong responses in human cells to permit us to calculate REP values. Calculated REPs for PCB126 were more than 30 times lower than the WHO-TEF value for PCB126. CTFs were calculated using score and loading vectors from a principal component analysis to establish the ranking of the compounds and, by rescaling, also to provide numerical differences between the different congeners corresponding to the TEF scheme. The CTFs were based on rat and human bioassay data and indicated a significant deviation for PCBs but also for certain PCDD/Fs from the WHO-TEF values. The human CTFs for 2,3,4,7,8-pentachlorodibenzofuran, 1,2,3,4,7,8-hexachlorodibenzofuran, 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin, and 1,2,3,4,7,8,9-heptachlorodibenzofuran were up to 10 times greater than their WHO-TEF values. Quantitative structure-activity relationship models were used to predict CTFs for untested WHO-TEF compounds, suggesting that the WHO-TEF value for 1,2,3,7,8-pentachlorodibenzofuran could be underestimated by an order of magnitude for both human and rodent models. Our results indicate that the CTF approach provides a powerful tool for condensing data from batteries of screening tests using compounds with similar mechanisms of action, which can be used to improve risk assessment of DLCs.
- MeSH
- benzofurany chemie toxicita MeSH
- hlodavci MeSH
- krysa rodu rattus MeSH
- kvantitativní vztahy mezi strukturou a aktivitou MeSH
- lidé MeSH
- počítačová simulace MeSH
- polychlorované bifenyly chemie toxicita MeSH
- polychlorované dibenzodioxiny analogy a deriváty chemie toxicita MeSH
- receptory aromatických uhlovodíků fyziologie MeSH
- techniky in vitro MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Dissolved organic matter (DOM) in freshwaters is present at concentrations ranging from 0.5 to 50 mg L⁻¹, and consists of various organic compounds, including humic substances (HS). HS exert a variety of direct and indirect biological effects, including interaction with the aryl hydrocarbon receptor (AhR). AhR is a cytosolic receptor that binds various hydrophobic organic compounds (HOCs) and mediates some of their toxic effects. In vitro effects of binary mixtures of various DOM (mainly HS) with various HOCs on AhR-mediated responses were studied by use of H4IIE-luc cells. Six out of 12 DOM activated the AhR even at environmentally relevant concentrations (17 mg L⁻¹). In simultaneous exposures of H4IIE-luc cells to DOM (17 mg L⁻¹) and each of the model compounds, 2,3,7,8-TCDD, PCB126, PCB169, benzo[a]pyrene, benzo[a]anthracene, dibenz[a,h]anthracene, fluoranthene, a mixture of persistent organic pollutants (POPs), a mixture of polycyclic aromatic hydrocarbons (PAHs), and a mixture of all HOCs, either significant additive or facilitative effects were observed when compared to activities of single HOCs. No significant decrease of effects due to possible sorption of HOCs to DOM was observed, even in subsequent experiments when HOCs+DOM mixtures were preincubated for six days before exposure to H4IIE-luc. Thus, DOM does not seem to protect organisms against AhR-mediated toxic effects of HOCs (as usually predicted due to sorption of HOCs on DOM), but it can actually enhance their potency for AhR-mediated effects in some situations.
- MeSH
- anthraceny chemie metabolismus toxicita MeSH
- benzopyren chemie metabolismus toxicita MeSH
- fluoreny chemie metabolismus toxicita MeSH
- huminové látky analýza MeSH
- hydrofobní a hydrofilní interakce MeSH
- krysa rodu rattus MeSH
- látky znečišťující životní prostředí chemie metabolismus toxicita MeSH
- nádorové buněčné linie MeSH
- organické látky chemie metabolismus toxicita MeSH
- polychlorované dibenzodioxiny chemie metabolismus toxicita MeSH
- polycyklické aromatické uhlovodíky chemie metabolismus toxicita MeSH
- receptory aromatických uhlovodíků metabolismus MeSH
- sladká voda chemie MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Problém s dioxinem začal v roce 1991, když U.S. Environmental Protection Agency (EPA) oznámila, že na základě nových vědeckých poznatků je nutné přehodnotit zdravotní riziko expozice 2,3,7,8 tetrachlorodibenzo-p-dioxinem (TCDD) a jemu chemicky podobným látkám, které označujeme jako dioxin. Tyto látky byly nalezeny ve všech kompartmentech životního prostředí a protože jsou velmi stálé a rozpouští se v tucích, mají schopnost akumulovat se v organismech vyšších živočichů - včetně člověka. . TCDD jako všudypřítomný polutant je vysoce toxický a představuje vážný zdravotní problém. Již velmi nízké koncentrace TCDD mohou mít negativní vliv na životní prostředí a lidské zdraví a nejvíce ohroženy jsou děti. Protože problém dioxinu je velmi často medializován a ne všechny informace o něm jsou správně vykládány, považujeme za nutné informovat zájemce o současných znalostech jeho biologické aktivity a zdravotního rizika.
The problem with dioxin began in 1991, when U.S. Environmental Protection Agency (EPA) announced that it would conduct a scientific reassessment of the health risks resulting from exposure to 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD) and chemically similar compounds collectively known as dioxin. They are found in all environmental compartments, are persistent and, being fat soluble, they tend to accumulate in higher animals - including humans. TCDD like a ubiquitous pollutant is highly toxic and represents serious health problem. Even very small TCDD concentrations can cause negative effects on the environment and on human health, in particular on the most vulnerable groups like children. Since the problem of dioxin is published very often and not all of information is right interpreted, we treat necessary to inform interested persons about recent knowledge of its biological activity and health risk.
