Genotoxicity and Estrogenic Activity of 3,3′-Dinitrobisphenol A in Goldfish

Formation of nitro(so) and chlorinated products and toxicity alteration during the UV/monochloramine treatment of phenol

The UV/monochloramine (UV/NH₂Cl) process is an emerging advanced oxidation process (AOP) to remove organic contaminants in water treatment with radicals including hydroxyl radicals (HO^•), reactive chlorine species (RCS) and reactive nitrogen species (RNS). This study investigated the formation of nitro(so) and chlorinated products and toxicity alteration during the UV/NH₂Cl treatment of phenol. RNS and/or RCS induced the formation of nitro(so), chlorinated and polymeric compounds during phenol transformation by UV/NH₂Cl. These compounds dramatically increased the cytotoxicity to Chinese hamster ovary cells after 20 min UV/NH₂Cl treatment, which was 10 times higher than that after 24 h chloramination. The increase of cytotoxicity in UV/NH₂Cl was primarily attributable to 4-nitrosophenol, and the cytotoxicity followed the order of 4-nitrosophenol >> 4-nitrophenol > 2,4,6-trichlorophenol > 2,4-dichlorophenol > phenol. 4-Nitrosophenol was significantly generated by the combination of ^•NO and phenoxy radical, where the maximum conversion rates of phenol to 4-nitrosophenol increased from 4.9% to 62.4% when pH increased from 5 to 10. The highest conversion rate was at pH 10 because the ^•NO concentration increased with increasing pH from 5 to 10 in UV/NH₂Cl, as verified by the electron paramagnetic resonance (EPR) analysis. Nitrophenols were also detected at much lower concentrations than 4-nitrosophenol, which were mainly formed by the oxidation of 4-nitrosophenol and the combination of ^•NO₂ with phenoxy radicals. RCS was responsible for the formation of chlorinated products mainly through Cl^• addition and the reactions of Cl^•/Cl₂^•- with phenoxy radicals. Also, RCS and RNS significantly enhanced the formation of carbonaceous (i.e., chloroform and chloral hydrate) and nitrogenous disinfection byproducts (i.e., chloropicrin and dichloroacetonitrile) in UV/NH₂Cl. This study indicates that the UV/NH₂Cl treatment significantly increased toxicity and validates the roles of RNS and RCS in producing toxic nitro(so) and chlorinated products.

Comparative Study for Interactions of Sulfate Radical and Hydroxyl Radical with Phenol in the Presence of Nitrite

Sulfate radical (SO₄^•-)- and hydroxyl radical (HO^•)-based advanced oxidation processes (AOPs) are effective for the removal of organic pollutants in water treatment. This study compared the interactions of SO₄^•- and HO^• for the transformation of phenol in UV/peroxydisulfate (PDS) and UV/H₂O₂ with the presence of NO₂^-, which is widely present in aquatic environments and transforms SO₄^•- and HO^• to ^•NO₂. By using laser flash photolysis, the products of phenol reacting with SO₄^•- and HO^• were demonstrated to be phenoxy radical and phenol-HO-adduct radical, respectively. This result, along with density functional theory (DFT) calculations, indicate that the predominant reaction mechanisms of phenol with SO₄^•- and HO^• with phenol are electron transfer and addition, respectively. The different mechanisms induced the much higher formation of nitrophenols by SO₄^•- than HO^• in the presence of NO₂^- through the fast combination of phenoxy radicals and ^•NO₂. The conversion yields of phenol to nitrophenols (including 2-nitrophenol and 4-nitrophenol), were 47.5% by SO₄^•- versus 5.3% by HO^• at the experimental conditions. Increasing PDS/H₂O₂ dosages from 0.2 to 1 mM resulted in a 61.9% increase of nitrophenol conversion yield in UV/PDS/NO₂^- but a 35.4% decrease of that in UV/H₂O₂/NO₂^-. In addition, the significant formation of phenoxy radicals by SO₄^•- also induced many nitrated polymers in UV/PDS/NO₂^-, while those induced in UV/H₂O₂/NO₂^- were negligible. The significant formation of nitrophenols and nitrated polymers increased the mutagenicity by 860.5% when the removal rate of phenol was 98% by UV/PDS/NO₂^-. This is the first study to demonstrate the different mechanisms of phenol transformation by SO₄^•- and HO^• in the presence of NO₂^-.

Development of a lipovitellin-based goldfish (Carassius auratus) vitellogenin ELISA for detection of environmental estrogens

The susceptibility of vitellogenin (Vtg) to degradation is a major problem affecting the robustness of enzyme-linked immunosorbent assay (ELISA) for goldfish (Carassius auratus) Vtg. In this study, a phospholipoglycoprotein with molecular mass of ∼420kDa was purified from goldfish egg extracts and it produced a single band corresponding to ∼112kDa in SDS-polyacrylamide gel electrophoresis (SDS-PAGE). Additionally, the amino acid composition of the purified protein was comparable to that of lipovitellin (Lv) from other fish species. Thus, the purified protein was identified as goldfish Lv. Purified Lv and anti-Lv polyclonal antiserum were used to develop an ELISA with a detection range between 31.25 and 1000ngmL(-)(1). The intra- and inter-assay coefficients of variation were 6.45% and 7.08%, respectively. The immunological similarity between goldfish Vtg and Lv was confirmed by immunoelectrophoresis and Western blot. Goldfish Lv showed higher stability than Vtg after -80°C storage, multiple freeze/thaw cycles, and heat treatment. Moreover, the use of treated Lv in the ELISA did not change the slopes of standard curves. Parallelism between the Lv standard curve and plasma dilution curves of vitellogenic females confirmed the validity of the assay for quantifying plasma Vtg. The Lv-based Vtg ELISA was further applied to evaluate the estrogenic activity of monocrotophos pesticide.

Preparation of a polyclonal antibody against goldfish (Carassius auratus) vitellogenin and its application to detect the estrogenic effects of monocrotophos pesticide

Goldfish (Carassius auratus) represents a good model to detect the estrogenic effects of chemicals, and vitellogenin (Vtg) is a vital indicator of estrogenic activity. The heterologous anti-carp Vtg antibody has previously been used for goldfish Vtg detection. Here, we report the preparation of an anti-goldfish Vtg antibody to improve the sensitivity and specificity of goldfish Vtg immunoassays. Vtg was purified from the plasma of 17β-estradiol (E2)-induced goldfish by gel filtration followed by anion-exchange chromatography. It was characterized as a phospholipoglycoprotein with an apparent molecular weight of ~460 kDa and separated into three major polypeptides corresponding to ~130, ~106, and ~81 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). A polyclonal antibody against goldfish Vtg was raised in rabbits and found to be specific for goldfish Vtg through immunoelectrophoresis and Western blot. A sensitive sandwich enzyme-linked immunosorbent assay (ELISA) was developed for the quantification of plasma Vtg, with a detection limit of 3.6 ng/mL and a detection range from 7.8 to 250 ng/mL. The intra- and inter-assay coefficients of variations were 2.4-6.8% and 6.7-10.8%, respectively. Additionally, we qualitatively and quantitatively detected the induction of Vtg in male fish exposed to 0.01, 0.01, and 1.00 mg/L monocrotophos pesticide by Western blot and ELISA. The homologous sandwich ELISA based on the anti-goldfish Vtg antibody could provide a valuable tool for the study of estrogenic effects of exogenous chemicals on goldfish.

Comparisons between abiotic nitration and biotransformation reactions of phenolic micropollutants in activated sludge

The transformation of selected phenolic substances was investigated during biological wastewater treatment. A main emphasis was put on the relevance of abiotic processes leading to toxic nitrophenolic transformation products (TPs). Due to their environmental relevance, the antiseptic ortho-phenylphenol (OPP), the plastics additive bisphenol A (BPA) and the psychoactive drug dextrorphan have been studied. Batch experiments confirmed that nitro- and nitroso-phenolic TPs can be formed under acidic conditions when nitrite is present. HNO2, N2O3 and NO and NO2 radicals are likely involved in the abiotic process. It was found that the process was promoted by the freezing of water samples, since this can lead to an unexpected pH drop. However, under conditions present at wastewater treatment plants (neutral pH, low nitrite concentrations), the formation of appreciable concentrations is rather unlikely through this process, since HNO2 concentrations are extremely low and NO and NO2 radicals will also react with other wastewater constituents. Thus, the transformation of phenolic substances such as OPP and BPA is mainly caused by biotic transformation. In addition to hydroxylation as a common reaction under aerobic conditions, the formation of sulfate conjugates was detected with the original compounds as well as with nitrophenolic TPs. Therefore, even when nitro-phenolic substances are formed it is likely that they are further transformed to sulfate conjugates. In raw wastewater and WWTP effluent nitrated BPA and NO2-dextrorphan were not detected. Only nitro-OPP was found in the influent of a WWTP with 2.3 ng/L, but it was not identified in the WWTP effluents. The concentrations of dextrorphan increased slightly during WWTP passage, possibly due to the cleavage of the glucuronide-conjugate, its human metabolite form, or demethylation of the prodrug dextromethorphan.

Formaldehyde induces toxic effects and regulates the expression of damage response genes in BM-MSCs

In this study, we assessed the toxic effects of formaldehyde (FA) on mouse bone marrow mesenchymal stem cells (BM-MSCs). Cytotoxicity was measured by using MTT assay. DNA strand breakage was detected by standard alkaline comet assay and comet assay modified with proteinase K (PK). DNA-protein crosslinks (DPCs) were detected by KCl-SDS precipitation assay. We found that FA at a concentration from 75 to 200 μM inhibited cell survival and induced DPCs over 125 μM. The PK-modified comet assay showed that FA-induced DNA strand breakage was increased in a dose-dependent manner from 75 to 200 μM. On the other hand, standard alkaline comet assay showed that DNA strand breakage was decreased with FA concentration over 125 μM. We confirmed by using Pearson correlation that there was a negative linear correlation between DPCs and survival rate (r = -0.987, P < 0.01) and positive linear relationships between DPCs and (i) sister chromatid exchange and (ii) micronucleus (r = 0.995, P < 0.01; r = 0.968, P < 0.01). DNA damage RT(2) profiler polymerase chain reaction array was used to investigate the changes in the expression of damage response genes. Xpa and Xpc of the nucleotide excision repair pathway and Brca2, Rad51, and Xrcc2 of the homologous recombination pathway were all up-regulated in both 75 and 125 μM FA. However, the same genes were down-regulated with 175 μM FA. The expressions of Chek1 and Hus1, which are involved in cell cycle regulation, were altered in the same manner with 75, 125, and 175 μM FA. These results indicated that Xpa, Xpc, Brca2, Rad51, Xrcc2, Chek1, and Hus1 were essential for the BM-MSCs to counteract the effects of FA.

In vivo examination of the genotoxicity of the urban air and surface soil pollutant, 3,6-dinitrobenzo[e]pyrene, with intraperitoneal and intratracheal administration

3,6-Dinitrobenzo[e]pyrene (3,6-DNBeP) was identified as a new potent mutagen toward Salmonella strains in surface soil and airborne particles. Because data of in vivo examination of the genotoxicity of 3,6-DNBeP are limited, micronucleus test was performed in peripheral blood and bone marrow, and comet assay in the lungs of mice treated with 3,6-DNBeP. In male ICR mice intraperitoneally (i.p.) injected with 3,6-DNBeP, the frequency of micronuclated polychromatic erythrocytes (MNPCEs) was increased in the peripheral blood and bone marrow after 24 h in a dose-dependent manner. Compared to controls, the highest dose of 3,6-DNBeP (40 mg/kg B.W.) induced 7.3- and 8.7-fold increases of MNPCE frequency in the peripheral blood and bone marrow, respectively. Furthermore, when 3,6-DNBeP was intratracheally (i.t.) instilled to male ICR mice, 3,6-DNBeP at the highest dose of 0.1 mg/kg body exhibited 3.1-fold increase of DNA tail moment in the lungs at 3 h after the instillation compared to controls. The values of DNA tail moment at 9 and 24 h after the instillation were increased up to 3.5 and 4.2-fold, respectively. These data indicate that 3,6-DNBeP is genotoxic to mammalians in in vivo and suggest that 3,6-DNBeP may be a carcinogenic compound present in the human environment.

An evaluation of the combined effects of phenolic endocrine disruptors on vitellogenin induction in goldfish Carassius auratus

Phenolic compounds are widely distributed in the natural environment, typically existing as a mixture at the nanogram or microgram per liter level. Among the phenolic compounds, 4-nonylphenol, 4-t-octylphenol, bisphenol A and 2,4-dichlorophenol attract the most concern due to their abundance and risks within the natural environment. The former three chemicals are known as endocrine disruptors causing feminization in various organisms, whereas the latter one requires further clarification concerning its feminization effect. This study aims to evaluate the combined effects of these chemicals using vitellogenin protein induction in male juvenile goldfish Carassius auratus as an endpoint after 15 days of exposure. The results showed that all these chemicals can induce vitellogenin with a relative potency of 4-t-octylphenol > bisphenol A > 4-nonylphenol ≫ 2,4-dichlorophenol. 2,4-dichlorophenol showed a very weak estrogenic effect with an induction of vitellogenin concentration of <1 % of positive control, and it is therefore omitted in further tests to evaluate their combined effect. The other three chemicals were mixed in two ways, at an equipotent ratio and at an equal environmental level ratio, and their combined effects were evaluated with both the toxicity units method and concentration addition model. The resulting effect of exposure to both mixtures showed that these chemicals generally exhibited an additive effect. The ecological risk of phenolic chemicals may therefore be underestimated if based on the presence of single chemicals whereas their combined effects warrant further consideration.

3,3'-Dinitro-bis-phenol A

The title compound [systematic name: 2,2′-dinitro-4,4′-(propane-2,2-di­yl)diphenol], C₁₅H₁₄N₂O₆, crystallizes with two mol­ecules in the asymmetric unit. Both have a trans conformation for their OH groups, and in each, the two aromatic rings are nearly orthogonal, with dihedral angles of 88.30 (3) and 89.62 (2)°. The nitro groups are nearly in the planes of their attached benzene rings, with C—C—N—O torsion angles in the range 1.21 (17)–4.06 (17)°, and they each accept an intra­molecular O—H⋯O hydrogen bond from their adjacent OH groups. One of the OH groups also forms a weak inter­molecular O—H⋯O hydrogen bond.

Environmentally induced oxidative stress in aquatic animals

Reactive oxygen species (ROS) are an unenviable part of aerobic life. Their steady-state concentration is a balance between production and elimination providing certain steady-state ROS level. The dynamic equilibrium can be disturbed leading to enhanced ROS level and damage to cellular constituents which is called "oxidative stress". This review describes the general processes responsible for ROS generation in aquatic animals and critically analyses used markers for identification of oxidative stress. Changes in temperature, oxygen levels and salinity can cause the stress in natural and artificial conditions via induction of disbalance between ROS production and elimination. Human borne pollutants can also enhance ROS level in hydrobionts. The role of transition metal ions, such as copper, chromium, mercury and arsenic, and pesticides, namely insecticides, herbicides, and fungicides along with oil products in induction of oxidative stress is highlighted. Last years the research in biology of free radicals was refocused from only descriptive works to molecular mechanisms with particular interest to ones enhancing tolerance. The function of some transcription regulators (Keap1-Nrf2 and HIF-1α) in coordination of organisms' response to oxidative stress is discussed. The future directions in the field are related with more accurate description of oxidative stress, the identification of its general characteristics and mechanisms responsible for adaptation to the stress have been also discussed. The last part marks some perspectives in the study of oxidative stress in hydrobionts, which, in addition to classic use, became more and more popular to address general biological questions such as development, aging and pathologies.

Genotoxicity of nano/microparticles in in vitro micronuclei, in vivo comet and mutation assay systems

BACKGROUND

Recently, manufactured nano/microparticles such as fullerenes (C60), carbon black (CB) and ceramic fiber are being widely used because of their desirable properties in industrial, medical and cosmetic fields. However, there are few data on these particles in mammalian mutagenesis and carcinogenesis. To examine genotoxic effects by C60, CB and kaolin, an in vitro micronuclei (MN) test was conducted with human lung cancer cell line, A549 cells. In addition, DNA damage and mutations were analyzed by in vivo assay systems using male C57BL/6J or gpt delta transgenic mice which were intratracheally instilled with single or multiple doses of 0.2 mg per animal of particles.

RESULTS

In in vitro genotoxic analysis, increased MN frequencies were observed in A549 cells treated with C60, CB and kaolin in a dose-dependent manner. These three nano/microparticles also induced DNA damage in the lungs of C57BL/6J mice measured by comet assay. Moreover, single or multiple instillations of C60 and kaolin, increased either or both of gpt and Spi- mutant frequencies in the lungs of gpt delta transgenic mice. Mutation spectra analysis showed transversions were predominant, and more than 60% of the base substitutions occurred at G:C base pairs in the gpt genes. The G:C to C:G transversion was commonly increased by these particle instillations.

CONCLUSION

Manufactured nano/microparticles, CB, C60 and kaolin, were shown to be genotoxic in in vitro and in vivo assay systems.

Estrogenic effects of monocrotophos evaluated by vitellogenin mRNA and protein induction in male goldfish (Carassius auratus)

Monocrotophos (MCP) is listed as a Prior Informed Consent chemical, and it is still used extensively in developing countries. It has been seen that MCP shows high toxicity in fish and aquatic ecosystems. To confirm whether MCP shows estrogenic effects on fish, the induction of vitellogenin (VTG) in male goldfish (Carassius auratus) following a 21 day exposure to 0.01, 0.10 and 1.00 mg x L(-1) 40% MCP pesticide in a semi-static exposure system was evaluated by hepatic mRNA and plasma protein. Real-time reverse transcriptase polymerase chain reaction assay showed that MCP significantly increased hepatic mRNA expression of VTG in male goldfish in a dose-dependent manner. Western blot analysis revealed the presence of two VTG subunits with molecular masses of 134 kDa and 110 kDa in the plasma of the exposure groups, which were not observed in that of the control males, indicating the induction of VTG protein synthesis and secretion by MCP in male goldfish. Furthermore, the levels of plasma VTG protein in the control group and the 0.01, 0.10 and 1.00 mg x L(-1) 40% MCP pesticide exposure groups were quantified by enzyme-linked immunoassay, and revealed concentrations of 53.8+/-5.6 ng x mL(-1), 285.5+/-5.0 ng x mL(-1), 972.9+/-7.4 ng x mL(-1) and 678.4+/-38.0 ng x mL(-1), respectively. The overlapping results of VTG mRNA and protein indicated that MCP had significant estrogenic properties and was thus a potential endocrine disruptor.