Evaluation of phenanthrene toxicity on earthworm (Eisenia fetida): an ecotoxicoproteomics approach

Decoding the biological toxicity of phenanthrene on intestinal cells of Eisenia fetida: Effects, toxicity pathways and corresponding mechanisms

Phenanthrene is frequently detected and exists extensively in the soil environment, and its residues inevitably impose a significant threat to soil organisms. Exposure to and toxicity of phenanthrene on earthworms has been extensively studied before, however, the possible mechanisms and related pathways associated with phenanthrene-triggered toxicity at the intestinal cell level remain unclear. Herein, primary intestinal cells isolated from Eisenia fetida (Annelida, Oligochaeta) intestine were used as targeted receptors to probe the molecular mechanisms involved in ROS-mediated damaging effects and the potential pathways of phenanthrene-induced toxicity at cellular and sub-cellular levels. Results indicated that phenanthrene exposure induced oxidative stress by activating intracellular ROS (elevated O2-, H2O2, and OH- content) bursts in E. fetida intestinal cells, causing various oxidative damage effects, including lipid peroxidation (increased MDA content), protein oxidation (enhanced PCO levels), and DNA damage (enhanced 8-OHdG levels). The enzymatic and non-enzymatic strategies in earthworm cells were activated to mitigate these detrimental effects by regulating ROS-mediated pathways involving defense regulation. Also, phenanthrene stress destroyed the cell membrane of E. fetida intestinal cells, resulting in cellular calcium homeostasis disruption and cellular energetic alteration, ultimately causing cytotoxicity and cell apoptosis/death. More importantly, the mitochondrial dysfunction in E. fetida cells was induced by phenanthrene-caused mitochondrial membrane depolarization, which in turn caused un-controlled ROS burst and induced apoptosis through mitochondria-mediated caspase-3 activation and ROS-mediated mitochondrial-dependent pathway. Furthermore, exposure to phenanthrene activated an abnormal mRNA expression profile associated with defense regulation (e.g., Hsp70, MT, CRT, SOD, CAT, and GST genes) in E. fetida intestinal cells, resulting in various cellular dysfunctions and pathological conditions, eventually, apoptotic cell death. Taken together, this study offers valuable insights for probing the toxic effects and underlying mechanisms posed by phenanthrene at the intestinal cell level, and is of great significance to estimate the detrimental side effects of phenanthrene on soil ecological health.

Mechanistic insights into phenanthrene-triggered oxidative stress-associated neurotoxicity, genotoxicity, and behavioral disturbances toward the brandling worm (Eisenia fetida) brain: The need for an ecotoxicological evaluation

In this study, earthworm (Eisenia fetida) brain was chosen as targeted receptors to probe the mechanisms of oxidative stress-related neurotoxicity, genotoxicity, and behavioral disturbances triggered by PHE. Results showed that PHE stress can initiate significant amounts of ROS, thus triggering oxidative stress in E. fetida brain. These effects were accompanied by a significant increase of damage to macromolecules DNA and lipids, resulting in severe oxidative effects. PHE exposure can induce AChE inhibition by ROS-induced injury and the accumulation of excess ACh at the nicotinic post-synaptic membrane, thus inducing aggravated neurological dysfunction and neurotoxicity of E. fetida through an oxidative stress pathway. Moreover, the burrowing behavior of earthworms was disturbed by oxidative stress-induced neurotoxicity after exposure to PHE. Furthermore, the abnormal mRNA expression profiles of oxidative stress- and neurotoxicity-related genes in worm brain were induced by PHE stress. The IBR results suggested that E. fetida brain was suffered more serious damage caused by PHE under higher doses and long-term exposure. Taken together, PHE exposure can trigger oxidative stress-mediated neurotoxicity and genotoxicity in worm brain and behavioral disorder through ROS-induced damage. This study is of great significance to evaluate the harmful effects of PHE and its mechanisms on soil ecological health.

Study on the enantioselective bioaccumulation and dissipation of uniconazole enantiomers in earthworm-soil microcosm through supercritical fluid chromatography-tandem mass spectrometry (SFC-MS/MS)

In this work, the enantioselective bioaccumulation and dissipation of uniconazole enantiomers in earthworm-soil microcosm were studied. A fast enantioseparation method of uniconazole through supercritical fluid chromatography-tandem mass spectrometry (SFC-MS/MS) was established. The CHIRALCEL OZ-3 column and a mixture of CO₂ and methanol (80:20, v/v) were used within 1.0 min to separate uniconazole enantiomers. The recoveries of uniconazole enantiomers in earthworm and soil samples ranged from 83.3 to 113%, and the intra-day and inter-day relative standard deviation values were lower than 11%. In earthworms, the bioaccumulation concentrations of uniconazole enantiomers increased with time and reached the maximum on the 7th day and then decreased. The elimination of uniconazole enantiomers in earthworms followed the first-order kinetics equation, and the elimination half-lives were approximately 7 days. In artificial soil, the dissipation of uniconazole enantiomers was slow, and the dissipation half-lives were both 25.7 days. No enantioselectivity occurred in the earthworm-soil microcosm. These results may reduce the uncertainty of environmental risk assessment for uniconazole.

Multi-omics analysis reveals copper-induced growth inhibition mechanisms of earthworm (Eisenia fetida)

Exposure to high concentrations of copper can cause toxic effects on the growth and development of organisms, but the relevant toxic mechanisms are far from fully understood. This study investigated the changes of metabolites, genes, and gut microorganisms in earthworms (Eisenia fetida) exposed to 0 (control), 67.58 (low), 168.96 (medium), and 337.92 (high) mg/kg of Cu in soil for 60 days. Differentially expressed genes (DEGs) and differential metabolites (DMs) at the low-, medium-, and high-level Cu exposure groups were identified and introduced into Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Integrated metabolomic and transcriptomic analysis revealed that amino acid metabolism, lipid metabolism, and carbohydrate metabolism are the major metabolic pathways disturbed by Cu exposure. Furthermore, Cu exposure significantly decreased the diversity of the intestinal bacterial community and affected the relative abundance (increased or decreased) of intestinal colonizing bacteria. This resulted in high energy expenditure, inhibited nutrient absorption and fatty acid synthesis, and weakened antioxidant and detoxification abilities, ultimately inhibiting the growth of E. fetida. These findings offer important clues and evidence for understanding the mechanism of Cu-induced growth and development toxicity in E. fetida and provide further data for risk assessment in terrestrial ecosystems.

Toxic mechanism on phenanthrene-triggered cell apoptosis, genotoxicity, immunotoxicity and activity changes of immunity protein in Eisenia fetida: Combined analysis at cellular and molecular levels

Phenanthrene (PHE) is a harmful organic contaminant and exists extensively in the soil environment. The accumulation of PHE would potentially threaten soil invertebrates, including earthworms, and the toxicity is also high. Currently, the possible mechanisms underlying apoptotic pathways induced by PHE and its immunotoxicity and genotoxicity in earthworms remain unclear. Thus, Eisenia fetida coelomocytes and immunity protein lysozyme (LYZ) were chosen as targeted receptors to reveal the apoptotic pathways, genotoxicity, and immunotoxicity triggered by PHE and its binding mechanism with LYZ, using cellular, biochemical, and molecular methods. Results indicated that PHE exposure can cause cell membrane damage, increase cell membrane permeability, and ultimately trigger mitochondria-mediated apoptosis. Increased 8-hydroxy-2-deoxyguanosine (8-OHdG) levels indicated PHE had triggered DNA oxidative damage in cells after PHE exposure. Occurrence of detrimental effects on the immune system in E. fetida coelomocytes due to decreased phagocytic efficacy and destroyed the lysosomal membrane. The LYZ activity in coelomocytes after PHE exposure was consistent with the molecular results, in which the LYZ activity was inhibited. After PHE binding, the protein structure (secondary structure and protein skeleton) and protein environment (the micro-environment of aromatic amino acids) of LYZ were destroyed, forming a larger particle size of the PHE-LYZ complex, and causing a significant sensitization effect on LYZ fluorescence. Molecular simulation indicated the key residues Glu 35, Asp 52, and Trp 62 for protein function located in the binding pocket, suggesting PHE preferentially binds to the active center of LYZ. Additionally, the primary driving forces for the binding interaction between PHE and LYZ molecule are hydrophobicity forces and hydrogen bonds. Taken together, PHE exposure can induce apoptosis by mitochondria-mediated pathway, destroy the normal immune system, and trigger DNA oxidative damage in earthworms. Besides, this study provides a comprehensive evaluation of phenanthrene toxicity to earthworms on molecular and cellular level.

Toxic mechanism on phenanthrene-induced cytotoxicity, oxidative stress and activity changes of superoxide dismutase and catalase in earthworm (Eisenia foetida): A combined molecular and cellular study

Phenanthrene (PHE) is an important organic compound, which is widespread in the soil environment and exhibits potential threats to soil organisms. Toxic effects of PHE to earthworms have been extensively studied, but toxic mechanisms on PHE-induced cytotoxicity and oxidative stress at the molecular and cellular levels have not been reported yet. Therefore, we explored the cytotoxicity and oxidative stress caused by PHE in earthworm coelomocytes and the interaction mechanism between PHE and the major antioxidant enzymes SOD/CAT. It was shown that high-dose PHE exposure induced the intracellular reactive oxygen species (ROS) generation, mediated lipid peroxidation, reduced total antioxidant capacity (T-AOC) in coelomocytes, and triggered oxidative stress, thus resulted in a strong cytotoxicity at higher concentrations (0.6-1.0 mg/L). The intracellular SOD/CAT activity in cells after PHE exposure were congruent with that in molecular levels, which the activity of SOD enhanced and CAT inhibited. Spectroscopic studies showed the SOD/CAT protein skeleton and secondary structure, as well as the micro-environment of aromatic amino acids were changed after PHE binding. Molecular docking indicated PHE preferentially docked to the surface of SOD. However, the key residues Tyr 357, His 74, and Asn 147 for activity were in the binding pocket, indicating PHE more likely to dock to the active center of CAT. In addition, H-bonding and hydrophobic force were the primary driving force in the binding interaction between PHE and SOD/CAT. This study indicates that PHE can induce cytotoxicity and oxidative damage to coelomocytes and unearthes the potential effects of PHE on earthworms.

Species-specific Cd-detoxification mechanisms in lumbricid earthworms Eisenia andrei, Eisenia fetida and their hybrids

Hermaphroditic lumbricid Eisenia sp. earthworms are ubiquitous and highly resistant to a variety of environmental stressors, including heavy metals. Among the progeny of laboratory mated inter-specific pairs of Eisenia fetida (Ea) and Eisenia andrei (Ef) there are fertile Ha hybrids derived from Ea ova fertilized by Ef spermatozoa and very rare sterile Hf hybrids from Ef ova fertilized by Ea spermatozoa. The aim of the first part of the experiment was to compare the life traits and whole body accumulation of cadmium in adult earthworms from genetically defined Ea, Ef and their hybrids (Ha) exposed for four weeks to commercial soil either unpolluted (control) or cadmium-spiked leading to moderate (M) or high (H) soil pollution (M = 425 and H = 835 mg kg^-1 dry soil weight). Such exposure impaired cocoon production but not affected earthworm viability despite the massive Cd bioaccumulation in the whole earthworm bodies reaching at M and H groups 316-454, 203-338, 114-253, and 377-309 mg kg^-1 dry body weights of Ea, Ef1, Ef2, and Ha, respectively, surprisingly reaching maximum accumulation quantities in hybrids. The second part of the experiment aimed to investigate cadmium-related defense mechanisms at transcriptomic level in coelomocytes non-invasively extruded from coelomic cavities of the new sets of Ea, Ef, Ha, and Hf earthworms exposed to Cd in microcosms for 0 days (control), 2 days, and 7 days (M = 425 mg kg^-1). Expression level of stress-induced Cd-metallothionein (mt) and superoxide dismutase (sod) were gradually up-regulated, while the immune-connected lysenin (lys) was rapidly down-regulated; the expression of glutathione S-transferase (gst) and phytochelatin synthase (pcs) remained unaffected. Mt and sod gene up-regulation and lys gene down-regulation were especially pronounced in Ea-derived hybrids. In sum, capacity of cadmium bioaccumulation and detoxification mechanisms is more efficient in interspecific hybrids than in the pure Ea and Ef species.

Single and joint oxidative stress of cadmium and phenanthrene on the Bivalve Anadara subcrenata

Single and joint oxidative stress of cadmium (Cd) and phenanthrene (Phe) on Anadara subcrenata were investigated under laboratory conditions with biomarkers such as reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD) and total antioxidant capacity (TAOC). The results indicated that the ROS level in Anadara subcrenata exposed to Cd and Phe significantly (P < 0.05) increased during the early exposure stage, and the TAOC level and SOD activity were induced as the response of the antioxidant defense system, and this followed a damage, recovery or acclimation event. The MDA content was negatively correlated with SOD activity. As the time went on, the ROS level decreased gradually and was close to that in the control after 9 days; the TAOC level decreased accordingly, but the recovery rate of the SOD activity was slower than that of the TAOC level. High concentrations of Cd or Phe had a stronger oxidative stress effect on Anadara subcrenata. Phe had a stronger effect on the SOD activity of Anadara subcrenata. The joint effects of Cd and Phe on the levels of ROS and TAOC, SOD activity and MDA content in Anadara subcrenata are dependent on their concentration combination, which were called the double-dose dependent effects and time-dependent effects, respectively. The binary mixture treatments of 477.33 μg/L Cd and 48.08 μg/L Phe had the highest oxidative stress on Anadara subcrenata.

Transcriptomic analyses of human bronchial epithelial cells BEAS-2B exposed to brominated flame retardant (tetrabromobisphenol A)

Brominated flame retardants (BFRs) are supposed to act as disruptors of cell signaling, but the underlying mechanisms remain less clear. Human bronchial epithelial cells (BEAS-2B) were used to investigate the toxic effect and gene expression changes induced by tetrabromobisphenol A (TBBPA). By genome-wide approaches with Illumina RNA-seq, 87 genes were identified to exhibit ≥1.5-fold changes in expression after treatment by TBBPA for 48 h, among which, 79 were upregulated and 8 were downregulated. Gene ontology (GO) annotation enriched unigenes were divided into three clusters: biological process (BP), cellular component (CC) and molecular function (MF). Pathway analysis showed that NF-κB, TNF signaling, toll-like receptor, MAPK signaling and B-cell receptor were the most prominent pathways affected by TBBPA, which play key roles in regulating cell proliferation and cell differentiation, inflammatory response. Finally, for verifying the accuracy of microarray analysis, qRT-PCR was used to analyze the transcription level of key genes in the above signaling pathways, and ELISA assay confirmed the effect of TBBPA on the levels of CXCL-2, CCL-3, CCL-4, IL-1β, TNF-α, and IL-6. These findings provided important information for further exploitation of the mechanisms under-lying BFR-induced adverse health effects.

Effects of novel brominated flame retardant TBBPA on human airway epithelial cell (A549) in vitro and proteome profiling

The cellular toxicity response of human airway epithelial cells (A549) to tetrabromobisphenol (TBBPA) was assessed in vitro. Cell viability, levels of intracellular reactive oxygen species (ROS), lipid peroxidation (MDA), and caspase-3 activity were determined after A549 treated with varying concentrations of TBBPA. A comparative proteomic analysis was performed in cells treated with different concentrations of TBBPA (0, 10, and 40 μg/mL). Two-way anova analysis showed that cell viability was significantly decreased after treatment by TBBPA with a concentration of 16 μg/mL for 48 hr, however, the caspase-3 activities, ROS generation, and MDA content increased. Ultrastructural observation revealed that the cell was morphological damaged after exposure to 64 μg/mL TBBPA, with mitochondria seriously injured and the smooth endoplasmic reticulum dilated. There was a good correlation between ROS generation and mitochondrial dysfunction. Seventeen differentially expressed proteins involved in various biological processes were identified. These findings provide a basis for understanding the mechanisms of cell dysfunction and perturbation of antioxidant status induced by additive flame retardant on airway epithelial cells.

Lethal Toxicity and Sublethal Metabolic Interference Effects of Sulfoxaflor on the Earthworm ( Eisenia fetida)

Testing for effects of pesticides on nontarget organisms is an integral part of ecological risk assessment. In the present study, the acute toxicity of sulfoxaflor to earthworms was evaluated using an artificial soil toxicity test, and sublethal effects were assessed through oxidative stress and metabolomics. Sulfoxaflor is a supertoxic pollutant to earthworms that easily bioaccumulates in earthworms, and contains LC₂, LC₁₀, and LC₅₀ values of 0.08 (0.04-0.13), 0.19 (0.11-0.25), and 0.54 (0.45-0.65) mg/kg, respectively. Sublethal doses of sulfoxaflor resulted in oxidative damage to earthworms in which antioxidant enzymatic activities including SOD, CAT, and GST were significantly inhibited and MDA content accumulated. Metabolomics analysis suggested that the energy metabolism and the urea cycle in earthworms were significantly activated, while nucleotide metabolism was depressed, which could cause DNA damage. The results suggest earthworms have the potential to be a new entry point for sulfoxaflor into the wildlife food chain. Since earthworms significantly contribute to soil function and ecosystems, the high safety risks of sulfoxaflor to the earthworm could extend to the environment. In view of these findings, more attention should be given to the risks sulfoxaflor poses to the environment through its effects on earthworms.

Earthworms, Rice Straw, and Plant Interactions Change the Organic Connections in Soil and Promote the Decontamination of Cadmium in Soil

The joint effects of earthworms and crop straw on toxic metal speciation are not clear, and very limited information is available regarding the effects of their interaction on Cd mobility in Cd contaminated soil or in remediation processes involving plants. This study evaluated their impacts on Cd mobile form changes in soil and their effects on Cd uptake by plants. Treatments included both planted and unplanted-Cd-contaminated soil with or without rice straw and/or earthworms. The results revealed that earthworms, rice straw, and plant interactions change the Cd mobile forms in soil. The order of Cd concentration of different chemical forms was as follows: exchangeable > residual > bound to Fe-Mn oxide > bound to organic matter for earthworms, and exchangeable > bound to organic matter > residual > bound to Fe-Mn oxide for rice straw treatment, with a recovery rate of 96 ± 3%. The accumulation of Cd in plants increased in the presence of earthworms and decreased in the presence of rice straw. FT-IR spectra indicated that the degradation of rice straw increases C⁻O, C⁻O⁻H, C⁻H, and O⁻H functional groups which could complex with Cd ions. These findings highlighted that earthworms' activities and crop straw can modify soil properties and structure and promote the remediation of heavy metal. This study suggests that the ecological context of remediation instead of being limiting on soil-earthworms-plant interaction, should integrate the natural resources forsaken which can provide a positive influence on both plant health and the remediation of heavy metal in contaminated soil.

Phenanthrene Mitigates Cadmium Toxicity in Earthworms Eisenia fetida (Epigeic Specie) and Aporrectodea caliginosa (Endogeic Specie) in Soil

In classical toxicology studies, the interaction of combined doses of chemicals with dissimilar modes of toxic action in soil is complex and depending on the end point investigated and the experimental protocol employed. This study was used to examine the interactive effect of phenanthrene and Cadmium on two ecologically different species of earthworms; Eisenia. fetida and Aporrectodea. caliginosa. This interactive effect was scrutinized by using the acute toxicity test with the concentrations of 2.51 mg kg⁻¹ and 3.74 mg kg⁻¹, respectively, being lethal for 50% of E. fetida and A. caliginosa. The results showed that in the mixture treatment, phenanthrene at 5, 10, 15 and 20 mg kg⁻¹ significantly mitigated both earthworms species mortality and body-mass loss. Moreover, the factor of Cd accumulated in E. fetida and A. caliginosa tissues was significantly decreased by about 12% and 16%, respectively. Linear regression correlation coefficient revealed that the reduction of both earthworm species mortality was negatively and significantly correlated (r² = 0.98 ± 0.40 and 1 ± 3.9 p < 0.001) with phenanthrene concentration in soil. However, over 20 mg kg⁻¹ of phenanthrene, both organisms mortality rate increased again, as was the Bioaccumulation factor of phenanthrene. Thus, this study proposes that the antagonistical effect of phenanthrene on Cd at a degree of concentration can be used to mitigate Cd effect on soil living organisms. However, as an implication of these results, the interpretation of standardized toxicity bioassays, including whole effluent toxicity tests and single-compound toxicity tests, should be performed with caution. In addition, risk assessment protocols for environment pollution by a mixture of metals and polycyclic aromatic hydrocarbons should include robust methods that can detect possible interactive effects between contaminants to optimize environmental protection.

An integrative omics approach to unravel toxicity mechanisms of environmental chemicals: effects of a formulated herbicide

The use of integrative molecular approaches can aid in a comprehensive understanding of the effects of toxicants at different levels of biological organization, also supporting risk assessment. The present study aims to unravel the toxicity mechanisms of a widely used herbicide to the arthropod Folsomia candida exposed in a natural soil, by linking effects on reproduction, proteomics and genome-wide gene expression. The EC50 effects on reproduction over 4 weeks was 4.63 mg glyphosate/kg of soil. The formulation included a polyethoxylated tallowamine as an adjuvant, which at 50% effect on reproduction had an estimated concentration of 0.87-1.49 mg/kg of soil. No effects were observed on survival and reproduction when using the isolated active substance, pointing the toxicity of the formulated product to the co-formulant instead of the active ingredient, glyphosate. RNA sequencing and shotgun proteomics were applied to assess differential transcript and protein expressions between exposed and control organisms in time, respectively. Specific functional categories at protein and transcriptome levels were concordant with each other, despite overall limited correlations between datasets. The exposure to this formulation affected normal cellular respiration and lipid metabolism, inducing oxidative stress and leading to impairment in biological life cycle mechanisms such as molting and reproduction.

Exposure to lethal levels of benzo[a]pyrene or cadmium trigger distinct protein expression patterns in earthworms (Eisenia fetida)

Different pollutants induce distinct toxic responses in earthworms (Eisenia fetida). Here, we used proteomics techniques to compare the responses of E. fetida to exposure to the 10% lethal concentration (14d-LC₁₀) of benzo[a]pyrene (BaP) or cadmium (Cd) in natural red soil (China). BaP exposure markedly induced the expression of oxidation-reduction proteins, whereas Cd exposure mainly induced the expression of proteins involved in transcription- and translation-related processes. Furthermore, calmodulin-binding proteins were differentially expressed upon exposure to different pollutants. The calcium (Ca²⁺)-binding cytoskeletal element myosin was down-regulated upon BaP treatment, whereas the Ca²⁺-binding cytoskeletal element tropomyosin-1 was up-regulated upon Cd treatment. Some proteins exhibited opposite responses to the two pollutants. For instance, catalase (CAT) and heat shock protein 70 were up-regulated upon BaP treatment and down-regulated upon Cd treatment. A significant (p<0.05, one-way ANOVA with least-significant difference (LSD) test) increase in the level of reactive oxygen species (ROS) and CAT activity further showed that BaP mainly induces oxidative stress. Real-time PCR analysis showed that mRNA expression often did not correlate well with protein expression in earthworms subjected to Cd or BaP treatment. In addition, the expression of the gene encoding the protein metallothionein, which was not detected in the protein analysis, was induced upon Cd treatment, but slightly reduced upon BaP treatment. Therefore, BaP and Cd have distinct effects on the protein profile of E. Fetida with BaP markedly inducing ROS activity, and Cd mainly triggering genotoxicity.

CAPSULE SUMMARY

Distinct patterns of protein expression are induced in earthworms upon exposure to different pollutants; BaP markedly induces high levels of ROS, while Cd resultes in genotoxicity.

Biomarkers indicate mixture toxicities of fluorene and phenanthrene with endosulfan toward earthworm (Eisenia fetida)

α-Endosulfan and some polycyclic aromatic compounds (PAHs) are persistent in the environment and can reach crop products via contaminated agricultural soils. They may even be present as mixtures in the soil and induce mixture toxicity in soil organisms such as earthworms. In this study, the combined toxicities of PAHs with α-endosulfan were determined in Eisenia fetida adults using an artificial soil system. α-Endosulfan and five PAHs were tested for their acute toxicity toward E. fetida in artificial soils. Only α-endosulfan, fluorene, and phenanthrene showed acute toxicities, with LC₅₀ values of 9.7, 133.2, and 86.2 mg kg^-1, respectively. A mixture toxicity assay was conducted using α-endosulfan at LC₁₀ and fluorene or phenanthrene at LC₅₀ in the artificial soils. Upon exposure to the mixture of fluorene and α-endosulfan, earthworms were killed in increasing numbers owing to their synergistic effects, while no other mixture showed any additional toxicity toward the earthworms. Along with the acute toxicity results, the biochemical and molecular changes in the fluorene- and phenanthrene-treated earthworms with or without α-endosulfan treatment demonstrated that enhancement of glutathione S-transferase activity was dependent on the addition of PAH chemicals, and the HSP70 gene expression increased with the addition of α-endosulfan. Taken together, these findings contribute toward understanding the adverse effects of pollutants when present separately or in combination with other types of chemicals.

Proteomics study revealed altered proteome of Dichogaster curgensis upon exposure to fly ash

Fly ash is toxic and its escalating use as a soil amendment and disposal by dumping into environment is receiving alarming attention due to its impact on environment. Proteomics technology is being used for environmental studies since proteins respond rapidly when an organism is exposed to a toxicant, and hence soil engineers such as earthworms are used as model organisms to assess the toxic effects of soil toxicants. This study adopted proteomics technology and profiled proteome of earthworm Dichogaster curgensis that was exposed to fly ash, with main aim to elucidate fly ash effects on cellular and metabolic pathways. The functional classification of identified proteins revealed carbohydrate metabolism (14.36%), genetic information processing (15.02%), folding, sorting and degradation (10.83%), replication and repair (3.95%); environmental information processing (2.19%), signal transduction (9.61%), transport and catabolism (17.27%), energy metabolism (6.69%), etc. in the proteome. Proteomics data and functional assays revealed that the exposure of earthworm to fly ash induced protein synthesis, up-regulation of gluconeogenesis, disturbed energy metabolism, oxidative and cellular stress, and mis-folding of proteins. The regulation of ubiquitination, proteasome and modified alkaline comet assay in earthworm coelomocytes suggested DNA-protein cross link affecting chromatin remodeling and protein folding.

Determination of biomarkers for polycyclic aromatic hydrocarbons (PAHs) toxicity to earthworm (Eisenia fetida)

Polycyclic aromatic hydrocarbon (PAH) compounds are persistent, carcinogenic, and mutagenic. When PAHs enter agricultural soils through sewage sludge, they pose an environmental risk to soil organisms, including earthworms. Therefore, we aimed to determine the toxic effects of PAHs on earthworms. Five PAHs were used: fluorene, anthracene, phenanthrene, fluoranthene, and pyrene. Only fluorene and phenanthrene exhibited toxicity (LC50 values 394.09 and 114.02 g L(-1), respectively) against the earthworm Eisenia fetida. None of the other PAHs tested in this study enhanced the mortality of adult earthworm until the concentrations reached to 1000 g L(-1). After exposure to PAHs, acetylcholinesterase (AChE) activity in E. fetida decreased in a concentration-dependent manner, and phenanthrene exhibited the strongest inhibitory effect on AChE, followed by fluorene. Activity of a representative detoxifying enzyme, carboxylesterase, was dramatically reduced in E. fetida exposed to all tested PAHs in comparison with that observed in the control test. The remaining glutathione S-transferase activity significantly decreased in E. fetida after exposure to PAHs. To profile small proteins <20 kDa, SELDI-TOF MS with Q10 ProteinChips was used, and 54 proteins were identified as being significantly different from the control (p = 0.05). Among them, the expressions of three proteins at 4501.8, 4712.4, and 4747.9 m/z were only enhanced in E. fetida exposed to anthracene and pyrene. One protein with 16,174 m/z was selectively expressed in E. fetida exposed to fluorene, phenanthrene, and fluoranthene. These proteins may be potential biomarkers for the five PAHs tested in E. fetida.

Redox proteomics changes in the fungal pathogen Trichosporon asahii on arsenic exposure: identification of protein responses to metal-induced oxidative stress in an environmentally-sampled isolate

Trichosporon asahii is a yeast pathogen implicated in opportunistic infections. Cultures of an isolate collected from industrial wastewater were exposed for 2 days to 100 mg/L sodium arsenite (NaAsO₂) and cadmium (CdCl₂). Both metals reduced glutathione transferase (GST) activity but had no effect on superoxide dismutase or catalase. NaAsO₂ exposure increased glutathione reductase activity while CdCl₂ had no effect. Protein thiols were labeled with 5-iodoacetamido fluorescein followed by one dimensional electrophoresis which revealed extensive protein thiol oxidation in response to CdCl₂ treatment but thiol reduction in response to NaAsO₂. Two dimensional electrophoresis analyses showed that the intensity of some protein spots was enhanced on treatment as judged by SameSpots image analysis software. In addition, some spots showed decreased IAF fluorescence suggesting thiol oxidation. Selected spots were excised and tryptic digested for identification by MALDI-TOF/TOF MS. Twenty unique T. asahii proteins were identified of which the following proteins were up-regulated in response to NaAsO₂: 3-isopropylmalate dehydrogenase, phospholipase B, alanine-glyoxylate aminotransferase, ATP synthase alpha chain, 20S proteasome beta-type subunit Pre3p and the hypothetical proteins A1Q1_08001, A1Q2_03020, A1Q1_06950, A1Q1_06913. In addition, the following showed decreased thiol-associated fluorescence consistent with thiol oxidation; aconitase; aldehyde reductase I; phosphoglycerate kinase; translation elongation factor 2; heat shock protein 70 and hypothetical protein A1Q2_04745. Some proteins showed both increase in abundance coupled with decrease in IAF fluorescence; 3-hydroxyisobutyryl- CoA hydrolase; homoserine dehydrogenase Hom6 and hypothetical proteins A1Q2_03020 and A1Q1_00754. Targets implicated in redox response included 10 unique metabolic enzymes, heat shock proteins, a component of the 20S proteasome and translation elongation factor 2. These data suggest extensive proteomic alterations in response to metal-induced oxidative stress in T. asahii. Amino acid metabolism, protein folding and degradation are principally affected.