Hydroxytyrosol, the phenolic compound of olive oil protects human PBMC against oxidative stress and DNA damage mediated by 2,3,7,8-TCDD

The protective effect of hydroxytyrosol (HT), a strong antioxidant compound from extra virgin olive oil, against TCDD induced toxicity was investigated in human peripheral blood mononuclear cells (PBMC). PBMC (1 × 10⁶ cells mL⁻¹) were divided into four groups and were incubated in a CO₂ incubator (5% CO₂) for 12 h with vehicle, TCDD (10 nM), TCDD + HT (10 nM + 100 μM) and HT alone (100 μM) respectively. To clarify the role of HT against TCDD induced cytotoxicity, oxidative stress and the levels of antioxidant enzymes were assessed. Incubation of PBMC with TCDD significantly decreased cell viability, catalase (CAT) and glutathione peroxidase (GPx) and increased the levels of superoxide dismutase (SOD), glutathione reductase (GR) and oxidative stress markers such as lipid peroxidation products (LPO), protein carbonyl content (PCC) and reactive oxygen species (ROS). Whereas, HT had an effective antioxidant property as observed by the increased cell viability, normalization of antioxidant enzymes and decreased levels of LPO, PCC and ROS in PBMC co-treated with HT and TCDD. Apoptosis detection and comet assay results shows that HT, by acting as an antioxidant, prevents the damage to DNA induced by TCDD. In addition light microscopic and histopathological observations revealed that the cells are apoptotic and degenerated during TCDD treatment, whereas cells showed intact morphology during co-treatment with HT. On the whole, the results reveal that HT exerts a promising antioxidant potential in protecting the PBMC against TCDD induced oxidative stress, which might be due to the presence of catechol moiety in its structure.     

Induction to oxidative stress by saxitoxin investigated through lipid peroxidation in Neuro 2A cells and Chlamydomonas reinhardtii alga

Saxitoxin (STX) is a cyanotoxin, which can cause neurotoxic effects and induce ecological changes in aquatic environments, a potential risk to public and environmental health. Many studies of cytotoxicity on animal cells and algae have been performed, although few compare the toxic effects between the two models. In this sense, we investigated the oxidative stress induced by STX (0.4-3.0 nM) in two different cellular models: Neuro-2A (N2A) cells and Chlamydomonas reinhardtii alga by quantification of malondialdehyde (MDA) levels as indicative of lipid peroxidation (LPO). Also was evaluated the antioxidant defense of these cells systems after exposure to STX by the addition of antioxidants in N2A cells culture, and by the measure of antioxidants enzymes activity in C. reinhardtii cells. The MDA levels of N2A cells increased from 15% to 113% for 0.4 and 3.0 nM of STX, respectively, as compared to control. Superoxide-dismutase and catalase did not appear to protect the cell from STX effect while, in cells treated with vitamin E, the rates of MDA production decreased significantly, except for higher concentrations of STX. No MDA productions were observed in algal cells however some effects on antioxidant enzymes activity were observed when algae were exposed to 3.0 nM STX. Our results indicate that the concentrations of STX that may induce oxidative stress through LPO are different in animal and phytoplankton communities. A combination of algal and animal bioassays should be conducted for reliable assessment of oxidative stress induced by STX.     

Screening for antioxidant and detoxification responses in Perna canaliculus Gmelin exposed to an antifouling bioactive intended for use in aquaculture

Polygodial is a drimane sesquiterpene dialdehyde derived from certain terrestrial plant species that potently inhibits ascidian metamorphosis, and thus has potential for controlling fouling ascidians in bivalve aquaculture. The current study examined the effects of polygodial on a range of biochemical biomarkers of oxidative stress and detoxification effort in the gills of adult Perna canaliculus Gmelin. Despite high statistical power and the success of positive controls, the antioxidant enzymes glutathione reductase (GR), glutathione peroxidase (GPOX), catalase (CAT), and superoxide dismutase (SOD); thiol status, as measured by total glutathione (GSH-t), glutathione disulphide (GSSG), and GSH-t/GSSG ratio; end products of oxidative damage, lipid hydroperoxides (LHPO) and protein carbonyls; and detoxification pathways, represented by GSH-t and glutathione S-transferase (GST), were unaffected in the gills of adult P. canaliculus exposed to polygodial at 0.1 or 1 × the 99% effective dose in fouling ascidians (IC₉₉). Similarly, GR levels, thiol status, and detoxification activities were unaffected in mussels exposed to polygodial at 10 × the IC₉₉, although GPOX, CAT, and SOD activities increased. However, the increases were small relative to positive controls, no corresponding oxidative damage was detected, and this concentration greatly exceeds effective doses required to inhibit fouling ascidians in aquaculture. These findings compliment a previous study that established the insensitivity to polygodial of P. canaliculus growth, condition, and mitochondrial functioning, providing additional support for the suitability of polygodial for use as an antifouling agent in bivalve aquaculture.     

Growth, photosynthesis and antioxidant responses of two microalgal species, Chlorella vulgaris and Selenastrum capricornutum, to nonylphenol stress

The effect of nonylphenol (NP) on growth, photochemistry and biochemistry of two green microalgae, Chlorella vulgaris and Selenanstrum capricornutum, and their ability to degrade NP were compared. The 96 h EC₅₀ of C. vulgaris and S. capricornutum were greater than 4.0 and 1.0 mg L⁻¹ NP, respectively, suggesting that the former species was more tolerant to NP. Both microalgae acclimated to NP stress through down-regulating their photosynthetic activities, including antenna size (chlorophyll a content), maximal photochemistry (Fv/Fm) and the light absorbed by PSII (ABS/CS₀), but the dissipation of energy from reaction centres (DI₀/RC) increased with the increase of NP concentrations. In C. vulgaris, the changes of these parameters were more significant than in S. capricornutum and recovered completely after a 96 h exposure. The antioxidant responses, such as GSH content, CAT and POD activities in C. vulgaris increased with the increase of NP concentrations after a 24 h exposure, but these changes disappeared with exposure time and recovered to the control levels after 96 h. In S. capricornutum, although GSH content, CAT and POD activities also increased when exposed to low- to moderate-NP concentrations, these values were significantly reduced at a high concentration (4 mg L⁻¹) even after a 96 h exposure, indicating its antioxidant responses were significantly delayed. It is clear that the more NP-tolerant species, C. vulgaris, acclimated better with a faster recovery of its photosynthetic activity from the NP-induced damage, and exhibited more efficient and rapid responses to NP-induced oxidative stress. C. vulgaris also had a higher NP degradation ability than S. capricornutum.     

The short-term effects of air pollution on adolescent lung function in Taiwan

A mass screening of lung function associated with air pollutants for children is limited. This study assessed the association between air pollutants exposure and the lung function of junior high school students in a mass screening program in Taipei city, Taiwan. Among 10,396 students with completed asthma screening questionnaires and anthropometric measures, 2919 students aged 12-16 received the spirometry test. Forced vital capacity (FVC) and forced expiratory flow in 1 s (FEV₁) in association with daily ambient concentrations of particulate matter with diameter of 10 μm or less (PM₁₀), sulfur dioxide (SO₂), carbon monoxide (CO), nitrogen dioxide (NO₂), and ozone (O₃) were assessed by regression models controlling for the age, gender, height, weight, student living districts, rainfall and temperature. FVC, had a significant negative association with short-term exposure to O₃ and PM₁₀ measured on the day of spirometry testing. FVC values also were reversely associated with means of SO₂, O₃, NO₂, PM₁₀ and CO exposed 1 d earlier. An increase of 1-ppm CO was associated with the reduction in FVC for 69.8 mL (95% CI: −115, −24.4 mL) or in FEV₁ for 73.7 mL (95% CI: −118, −29.7 mL). An increase in SO₂ for 1 ppb was associated with the reductions in FVC and FEV₁ for 12.9 mL (95% CI: −20.7, −5.09 mL) and 11.7 mL (95% CI: −19.3, −4.16 mL), respectively. In conclusion, the short-term exposure to O₃ and PM₁₀ was associated with reducing FVC and FEV₁. CO and SO₂ exposure had a strong 1-d lag effect on FVC and FEV₁.     

PCDD/Fs-induced oxidative damage and antioxidant system responses in tobacco cell suspension cultures

Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) are ubiquitous contaminants and can be considerably accumulated by natural plants. In order to elucidate the biochemical and physiological responses of plant to PCDD/Fs, tobacco Bright Yellow-2 (BY-2) cells were selected as model plant and treated with time- and concentration-dependent PCDD/Fs. The toxic effect and oxidative stress caused by PCDD/Fs were evident, which could be indicted by the reduction in fresh mass, the increase in malondialdehyde (MDA) content, and the damage of tobacco cell ultrastructure. PCDD/Fs tolerance was correlated with changes in antioxidant system and hormones of tobacco cells. Superoxide dismutase (SOD) and peroxidase (POD) exhibited peak enzyme activities at the PCDD/Fs concentration of 1000 ng WHO₉₈-TEQ g⁻¹ fresh weight. Glutathione reductase (GR) enzyme activity increased monotonically at high level PCDD/Fs, but the activity of catalase (CAT) was only slightly affected at all treatment. Meanwhile, the exposure to PCDD/Fs resulted in the changes of hormones content. With the increase of exposure concentration of PCDD/Fs, the levels of indole-3-acetic acid (IAA) and abscisic acid (ABA) increased, whereas the concentration of jasmonates (JAs) decreased. The above results suggest that tobacco cells had the ability to cope with the oxidative stress induced by low concentration of PCDD/Fs through increasing the activities of antioxidant enzymes and alternating plant hormones levels. However, oxidative stress and toxicity would burst out when plant cells were exposed to the high levels of PCDD/Fs.     

Removal of Rhodamine B under visible irradiation in the presence of Fe⁰, H₂O₂, citrate and aeration at circumneutral pH

A new Vis-Fe⁰-H₂O₂-citrate-O₂ system comprising zero-valent iron, hydrogen peroxide, citrate anion and aeration at circumneutral pH under visible irradiation was studied. 21 μmol L⁻¹ of Rhodamine B (RhB) was chosen as the substrate to be tested. Experiments were conducted under conditions of 2.9 mmol L⁻¹ of H₂O₂, 12.6 g of Fe⁰ and 1.0 mmol L⁻¹ of citrate at pH 7.5. Results showed that, in 1 h reaction, 54% of RhB was removed with corresponding 26% of COD reduced. Meanwhile, the amount of released dissolved irons from Fe⁰ surface was found to be at a very low level as <5.4 μmol L⁻¹. Extinguishing tests with isopropanol suggested that RhB oxidation by hydroxyl radicals was the main process taken place in Vis-Fe⁰-H₂O₂-citrate-O₂ system, which accounted for 75% of substrate removal in 3 h reaction. Control and factor influencing experiments showed that the prohibitive extents of individual factor importance on RhB removal followed a decreasing order of Fe⁰ > H₂O₂ > citrate > Vis > O₂. This study showed an excellent system that could remove refractory organic compounds from water in laboratory researches, and also provided a good idea to reduce secondary contamination by dissolved irons in future investigations.     

Fate of citalopram during water treatment with O3, ClO2, UV and Fenton oxidation

In the present study we investigate the fate of citalopram (CIT) at neutral pH using advanced water treatment technologies that include O₃, ClO₂ oxidation, UV irradiation and Fenton oxidation. The ozonation resulted in 80% reduction after 30 min treatment. Oxidation with ClO₂ removed >90% CIT at a dosage of 0.1 mg L⁻¹. During UV irradiation 85% reduction was achieved after 5 min, while Fenton with addition of 14 mg L⁻¹ (Fe²⁺) resulted in 90% reduction of CIT. During these treatment experiments transformation products (TPs) were formed from CIT, where five compounds were identified by using high resolution and tandem mass spectrometry. Among these desmethyl-citalopram and citalopram N-oxide have been previously identified as human metabolites, while three are novel and published here for the first time. The three TPs are a hydroxylated dimethylamino-side chain derivative, a butyrolactone derivative and a defluorinated derivative of CIT.     

Effect of humic acids on physicochemical property and Cd(II) sorption of multiwalled carbon nanotubes

Zinc pyrithione is used as an antifouling agent. However, the environmental impacts of zinc pyrithione have recently been of concern. Zinc induces diverse actions during oxidative stress; therefore, we examined the effect of zinc pyrithione on rat thymocytes suffering from oxidative stress using appropriate fluorescent probes. The cytotoxicity of zinc pyrithione was not observed when the cells were incubated with 3 μM zinc pyrithione for 3 h. However, zinc pyrithione at nanomolar concentrations (10 nM or more) significantly increased the lethality of cells suffering from oxidative stress induced by 3 mM H₂O₂. The application of zinc pyrithione alone at nanomolar concentrations increased intracellular Zn²⁺ level and the cellular content of superoxide anions, and decreased the cellular content of nonprotein thiols. The simultaneous application of nanomolar zinc pyrithione and micromolar H₂O₂ synergistically increased the intracellular Zn²⁺ level. Therefore, zinc pyrithione at nanomolar concentrations may exert severe cytotoxic action on cells simultaneously exposed to chemicals that induce oxidative stress. If so, zinc pyrithione leaked from antifouling materials into surrounding environments would be a risk factor for aquatic ecosystems. Alternatively, zinc pyrithione under conditions of oxidative stress may become more potent antifouling ingredient.     

Susceptibility of epigeic earthworm Eisenia fetida to agricultural application of six insecticides

Ecotoxicological risks of agricultural application of six insecticides to soil organisms were evaluated by acute toxicity tests under laboratory condition following OECD guidelines using the epigeic earthworm Eisenia fetida as the test organism. The organochlorine insecticide endosulfan (LC₅₀ - 0.002 mg kg⁻¹) and the carbamate insecticides aldicarb (LC₅₀ - 9.42 mg kg⁻¹) and carbaryl (LC₅₀ - 14.81 mg kg⁻¹) were found ecologically most dangerous because LC₅₀ values of these insecticides were lower than the respective recommended agricultural dose (RAD). Although E. fetida was found highly susceptible to the pyrethroid insecticide cypermethrin (LC₅₀ - 0.054 mg kg⁻¹), the value was higher than its RAD. The organophosphate insecticides chlorpyrifos (LC₅₀ - 28.58 mg kg⁻¹), and monocrotophos (LC₅₀ - 39.75 mg kg⁻¹) were found less toxic and ecologically safe because the LC₅₀ values were much higher than their respective RAD.     

Impact of nano-CuO stress on rice (Oryza sativa L.) seedlings

Indiscriminate release of metal oxide nanoparticles (NPs) into the environment due to anthropogenic activities has become a serious threat to the ecological system including plants. The present study assesses the toxicity of nano-CuO on rice (Oryza sativa cv. Swarna) seedlings. Three different levels of stress (0.5 mM, 1.0 mM and 1.5 mM suspensions of copper II oxide, <50 nm particle size) were imposed and seedling growth performance was studied along control at 7 and 14 d of experiment. Modulation of ascorbate–glutathione cycle, membrane damage, in vivo ROS detection, foliar H₂O₂ and proline accumulation under nano-CuO stress were investigated in detail to get an overview of nano-stress response of rice. Seed germination percentage was significantly reduced under stress. Higher uptake of Evans blue by nano-CuO stressed roots over control indicates loss of root cells viability. Presence of dark blue and deep brown spots on leaves evident after histochemical staining with NBT and DAB respectively indicate severe oxidative burst under nano-copper stress. APX activity was found to be significantly increased in 1.0 and 1.5 mM CuO treatments. Nevertheless, elevated APX activity might be insufficient to scavenge all H₂O₂ produced in excess under nano-CuO stress. That may be the reason why stressed leaves accumulated significantly higher H₂O₂ instead of having enhanced APX activity. In addition, increased GR activity coupled with isolated increase in GSH/GSSG ratio does not seem to prevent cells from oxidative damages, as evident from higher MDA level in leaves of nano-CuO stressed seedlings over control. Enhanced proline accumulation also does not give much protection against nano-CuO stress. Decline in carotenoids level might be another determining factor of meager performance of rice seedlings in combating nano-CuO stress induced oxidative damages.     

Impact of biochar application to a Mediterranean wheat crop on soil microbial activity and greenhouse gas fluxes

Biochar has been recently proposed as a management strategy to improve crop productivity and global warming mitigation. However, the effect of such approach on soil greenhouse gas fluxes is highly uncertain and few data from field experiments are available. In a field trial, cultivated with wheat, biochar was added to the soil (3 or 6 kg m⁻²) in two growing seasons (2008/2009 and 2009/2010) so to monitor the effect of treatments on microbial parameters 3 months and 14 months after char addition. N₂O, CH₄ and CO₂ fluxes were measured in the field during the first year after char addition. Biochar incorporation into the soil increased soil pH (from 5.2 to 6.7) and the rates of net N mineralization, soil microbial respiration and denitrification activity in the first 3 months, but after 14 months treated and control plots did not differ significantly. No changes in total microbial biomass and net nitrification rate were observed. In char treated plots, soil N₂O fluxes were from 26% to 79% lower than N₂O fluxes in control plots, excluding four sampling dates after the last fertilization with urea, when N₂O emissions were higher in char treated plots. However, due to the high spatial variability, the observed differences were rarely significant. No significant differences of CH₄ fluxes and field soil respiration were observed among different treatments, with just few exceptions. Overall the char treatments showed a minimal impact on microbial parameters and GHG fluxes over the first 14 months after biochar incorporation.     

Biosafety assessment of titanium dioxide nanoparticles in acutely exposed nematode Caenorhabditis elegans with mutations of genes required for oxidative stress or stress response

We used Caenorhabditis elegans to investigate whether acute exposure to TiO₂-NPs at the concentration of 20 μg L⁻¹ reflecting predicted environmental relevant concentration and 25 mg L⁻¹ reflecting concentration in food can cause toxicity on nematodes with mutations of susceptible genes. Among examined mutants associated with oxidative stress and stress response, we found that genes of sod-2, sod-3, mtl-2, and hsp-16.48 might be susceptible for TiO₂-NPs toxicity. Mutations of these genes altered functions of both possible primary and secondary targeted organs in nematodes exposed to 25 mg L⁻¹ of TiO₂-NPs for 24-h. Mutations of these genes caused similar expression patterns of genes required for oxidative stress in TiO₂-NPs exposed mutant nematodes, implying their similar mechanisms to form the susceptible property. Nevertheless, acute exposure to 20 μg L⁻¹ of TiO₂-NPs for 24-h and 25 mg L⁻¹ of TiO₂-NPs for 0.48-h or 5.71-h did not influence functions of both possible primary and secondary targeted organs in sod-2, sod-3, mtl-2, and hsp-16.48 mutants. Therefore, our results suggest the relatively safe property of acute exposure to TiO₂-NPs with certain durations at predicted environmental relevant concentrations or concentrations comparable to those in food in nematodes with mutations of some susceptible genes.     

Interactive effects of cadmium and hypoxia on metabolic responses and bacterial loads of eastern oysters Crassostrea virginica Gmelin

Pollution by toxic metals including cadmium (Cd) and hypoxia are important stressors in estuaries and coastal waters which may interactively affect sessile benthic organisms, such as oysters. We studied metabolic responses to prolonged hypoxic acclimation (2 weeks at 5% O₂) in control and Cd-exposed (30 d at 50 μg L⁻¹ Cd) oysters Crassostrea virginica, and analyzed the effects of these stressors on abundance of Vibrio spp. in oysters. Hypoxia-acclimated oysters retained normal standard metabolic rates (SMR) at 5% O₂, in contrast to a decline of SMR observed during acute hypoxia. However, oysters spent more time actively ventilating in hypoxia than normoxia resulting in enhanced Cd uptake and 2.7-fold higher tissue Cd burdens in hypoxia. Cd exposure led to a significant decrease in tissue glycogen stores, increase in free glucose levels and elevated activity of glycolytic enzymes (hexokinase and aldolase) indicating a greater dependence on carbohydrate catabolism. A compensatory increase in activities of two key mitochondrial enzymes (citrate synthase and cytochrome c oxidase) was found during prolonged hypoxia in control oysters but suppressed in Cd-exposed ones. Cd exposure also resulted in a significant increase in abundance of Vibrio parahaemolyticus and Vibrio vulnificus levels during normoxia and hypoxia, respectively. Overall, Cd- and hypoxia-induced changes in metabolic profile, Cd accumulation and bacterial flora of oysters indicate that these stressors can synergistically impact energy homeostasis, performance and survival of oysters in polluted estuaries and have significant consequences for transfer of Cd and bacterial pathogens to the higher levels of the food chain.     

Nano-TiO2 enhances the toxicity of copper in natural water to Daphnia magna

The acute toxicity of engineered nanoparticles (NPs) in aquatic environments at high concentrations has been well-established. This study demonstrates that, at a concentration generally considered to be safe in the environment, nano-TiO₂ remarkably enhanced the toxicity of copper to Daphnia magna by increasing the copper bioaccumulation. Specifically, at 2 mg L⁻¹ nano-TiO₂, the (LC₅₀) of Cu²⁺ concentration observed to kill half the population, decreased from 111 μg L⁻¹ to 42 μg L⁻¹. Correspondingly, the level of metallothionein decreased from 135 μg g⁻¹ wet weight to 99 μg g⁻¹ wet weight at a Cu²⁺ level of 100 μg L⁻¹. The copper was found to be adsorbed onto the nano-TiO₂, and ingested and accumulated in the animals, thereby causing toxic injury. The nano-TiO₂ may compete for free copper ions with sulfhydryl groups, causing the inhibition of the detoxification by metallothioneins.     

Gene expression responses of paper birch (Betula papyrifera) to elevated CO2 and O3 during leaf maturation and senescence

Gene expression responses of paper birch (Betula papyrifera) leaves to elevated concentrations of CO₂ and O₃ were studied with microarray analyses from three time points during the summer of 2004 at Aspen FACE. Microarray data were analyzed with clustering techniques, self-organizing maps, K-means clustering and Sammon's mappings, to detect similar gene expression patterns within sampling times and treatments. Most of the alterations in gene expression were caused by O₃, alone or in combination with CO₂. O₃ induced defensive reactions to oxidative stress and earlier leaf senescence, seen as decreased expression of photosynthesis- and carbon fixation-related genes, and increased expression of senescence-associated genes. The effects of elevated CO₂ reflected surplus of carbon that was directed to synthesis of secondary compounds. The combined CO₂ + O₃ treatment resulted in differential gene expression than with individual gas treatments or in changes similar to O₃ treatment, indicating that CO₂ cannot totally alleviate the harmful effects of O₃.     

Lethal effects of abamectin on the aquatic organisms Daphnia similis, Chironomus xanthus and Danio rerio

Abamectin is used as an acaricide and insecticide for fruits, vegetables and ornamental plants, as well as a parasiticide for animals. One of the major problems of applying pesticides to crops is the likelihood of contaminating aquatic ecosystems by drift or runoff. Therefore, toxicity tests in the laboratory are important tools to predict the effects of chemical substances in aquatic ecosystems. The aim of this study was to assess the potential hazards of abamectin to the freshwater biota and consequently the possible losses of ecological services in contaminated water bodies. For this purpose, we identified the toxicity of abamectin on daphnids, insects and fish. Abamectin was highly toxic, with an EC₅₀ 48 h for Daphnia similis of 5.1 ng L⁻¹, LC₅₀ 96 h for Chironomus xanthus of 2.67 μg L⁻¹ and LC₅₀ 48 h for Danio rerio of 33 μg L⁻¹.     

Plant steroid hormones produced under Ni stress are involved in the regulation of metal uptake and oxidative stress in Brassica juncea L

Brassinosteroids (BRs) are involved in the amelioration of various biotic and abiotic stresses. With an aim to explore the role of BRs under heavy metal stress, plants of Brassica juncea L. were grown in pots. The plants were subjected to various concentrations of Nickel metal (0.0, 0.2, 0.4 and 0.6 mM) and harvested on 60th day in order to observe the expression of these hormones. The isolated BRs from the leaves of Brassica plants characterized by GC-MS include 24-Epibrassinolide (24-EBL), Castasterone, Dolicholide and Typhasterole. The effect of isolated 24-EBL was studied on Ni metal uptake and antioxidative defense system in 60 d old plants of Brassica. It was observed that 24-EBL significantly increased the activities of stress ameliorating enzymes and lowered the metal uptake in plants. This is the first report in B. juncea L. plants showing the expression of BRs under metal treatments and effect of the isolated 24-EBL on metal uptake and in oxidative stress management.