Estrogenic disruption effects and formation mechanisms of transformation products during photolysis of preservative parabens

The ubiquitous presence of emerging contaminants (ECs) in the environment and their associated adverse effects has raised concerns about their potential risks. The increased toxicity observed during the environmental transformation of ECs is often linked to the formation of their transformation products (TPs). However, comprehension of their formation mechanisms and contribution to the increased toxicity remains an unresolved challenge. To address this gap, by combining quantum chemical and molecular simulations with photochemical experiments in water, this study investigated the formation of TPs and their molecular interactions related to estrogenic effect using the photochemical degradation of benzylparaben (BZP) preservative as a representative example. A non-targeted analysis was carried out and three previously unknown TPs were identified during the transformation of BZP. Noteworthy, two of these novel TPs, namely oligomers BZP-o-phenol and BZP-m-phenol, exhibited higher estrogenic activities compared to the parent BZP. Their IC50 values of 0.26 and 0.50 μM, respectively, were found to be lower than that of the parent BZP (6.42 μM). The binding free energies (ΔGbind) of BZP-o-phenol and BZP-m-phenol (-29.71 to -23.28 kcal·mol-1) were lower than that of the parent BZP (-20.86 kcal·mol-1), confirming their stronger binding affinities toward the estrogen receptor (ER) α-ligand binding domain. Subsequent analysis unveiled that these hydrophobic residues contributed most favorably to ER binding, with van der Waals interactions playing a significant role. In-depth examination of the formation mechanisms indicated that these toxic TPs primarily originated from the successive cleavage of ester bonds (OCH2C6H5 and COO group), followed by their combination with BZP*. This study provides valuable insight into the mechanisms underlying the formation of toxic TPs and their binding interactions causing the endocrine-disrupting effects. It offers a crucial framework for elucidating the toxicological patterns of ECs with similar structures.

Aging increases the particulate- and leachate-induced toxicity of tire wear particles to microalgae

The toxic effects of tire wear particles (TWPs) on organisms have attracted widespread concerns over the past decade. However, the underlying toxicity mechanism of TWPs, especially aged TWPs to marine microalgae remains poorly understood. This study investigated the physiological and metabolic responses of Phaeodactylum tricornutum to different concentrations of TWPs (Experiment 1), virgin and differently aged TWPs (Experiment 2) as well as their leachates and leached particles (Experiment 3). Results demonstrated that TWPs promoted the growth of microalgae at low concentrations (0.6 and 3 mg L-1) and inhibited their growth at high concentrations (15 and 75 mg L-1). Moreover, aged TWPs induced more profound physiological effects on microalgae than virgin TWPs, including inhibiting microalgae growth, decreasing the content of Chla, promoting photosynthetic efficiency, and causing oxidative damage to algal cells. Untargeted metabolomics analysis confirmed that aged TWPs induced more pronounced metabolic changes than virgin TWPs. This study represented the first to demonstrate that both particulate- and leachate-induced toxicity of TWPs was increased after aging processes, which was confirmed by the changes in the surface morphology of TWPs and enhanced release of additives. Through the significant correlations between the additives and the microalgal metabolites, key additives responsible for the shift of microalgal metabolites were identified. These results broaden the understanding of the toxicity mechanism of aged TWPs to microalgae at the physiological and metabolic levels and appeal for considering the effects of long-term aging on TWP toxicity in risk assessment of TWPs.

A progress update on the biological effects of biodegradable microplastics on soil and ocean environment: A perfect substitute or new threat?

Conventional plastics are inherently difficult to degrade, causing serious plastic pollution. With the development of society, biodegradable plastics (BPs) are considered as an alternative to traditional plastics. However, current research indicated that BPs do not undergo complete degradation in natural environments. Instead, they may convert into biodegradable microplastics (BMPs) at an accelerated rate, thereby posing a significant threat to environment. In this paper, the definition, application, distribution, degradation behaviors, bioaccumulation and biomagnification of BPs were reviewed. And the impacts of BMPs on soil and marine ecosystems, in terms of physicochemical property, nutrient cycling, microorganisms, plants and animals were comprehensively summarized. The effects of combined exposure of BMPs with other pollutants, and the mechanism of ecotoxicity induced by BMPs were also addressed. It was found that BMPs reduced pH, increased DOC content, and disrupted the nitrification of nitrogen cycle in soil ecosystem. The shoot dry weight, pod number and root growth of soil plants, and reproduction and body length of soil animals were inhibited by BMPs. Furthermore, the growth of marine plants, and locomotion, body length and survival of marine animals were suppressed by BMPs. Additionally, the ecotoxicity of combined exposure of BMPs with other pollutants has not been uniformly concluded. Exposure to BMPs induced several types of toxicity, including neurotoxicity, gastrointestinal toxicity, reproductive toxicity, immunotoxicity and genotoxicity. The future calls for heightened attention towards the regulation of the degradation of BPs in the environment, and pursuit of interventions aimed at mitigating their ecotoxicity and potential health risks to human.

Toxic effects of combined exposure to homoyessotoxin and nitrite on the survival, antioxidative responses, and apoptosis of the abalone Haliotis discus hannai

Homoyessotoxin (homo-YTX) and nitrite (NO2-N), released during harmful dinoflagellate cell lysis adversely affect abalones. However, their toxicity mechanisms in shellfish remain unclear. This study investigated the economic abalone species Haliotis discus hannai exposed to varying concentrations of homo-YTX (0, 2, 5, and 10 µg L-1) and NO2-N (0, 3, and 6 mg L-1) on the basis of their 12 h LC50 values (5.05 µg L-1 and 4.25 mg L-1, respectively) and the environmentally relevant dissolved concentrations during severe dinoflagellate blooms, including mixtures. The test abalones were exposed to homo-YTX and NO2-N for 12 h. The mortality rate (D), reactive oxygen species (ROS) levels, antioxidant defense capabilities, and expression levels of antioxidant-related, Hsp-related, and apoptosis-related genes in abalone gills were assessed. Results showed that the combined exposure to homo-YTX and NO2-N increased the D and ROS levels and upregulated B-cell lymphoma-2 (BCL2)-associated X (BAX) and caspase3 (CASP3) expression levels while reducing glutathione peroxidase (GPx) activity and GPx, CuZnSOD, and BCL2 expression levels. High concentrations of homo-YTX (10 µg L-1) and NO2-N (6 mg L-1) solutions and the combinations of these toxicants inhibited the activities of superoxide dismutase (SOD) and catalase (CAT) and downregulated the expression levels of MnSOD, CAT, Hsp70, and Hsp90. The ROS levels were negatively correlated with the activities of SOD, CAT, and GPx and the expression levels of MnSOD, CuZnSOD, CAT, GPx, Hsp70, Hsp90, and BCL2. These results suggest that homo-YTX, in conjunction with NO2-N, induces oxidative stress, disrupts antioxidant defense systems, and triggers caspase-dependent apoptosis in the gills of abalone. ROS-mediated antioxidative and heat-shock responses and apoptosis emerge as potential toxicity mechanisms affecting the survival of H. discus hannai due to homo-YTX and NO2-N exposure.

Effect of long-term exposure of mixture of ZnO and CuO nanoparticles on Scenedesmus obliquus

The present study investigated the possible toxic effect of ZnO and CuO nanoparticles (NPs) on freshwater microalgae, Scenedesmus obliquus at environmentally- relevant nanoparticle concentration (1 mg/L) and high concentration (10 mg/L) in BG-11 medium under white light LED-illumination over 35 days. The effect of time on the stability of media, nanoparticles, and their relation to toxicity to algae was also studied. The transmission electron microscopy indicated structural damage to algae due to the presence of a mixture of nanoparticles (at 10 mg/L). FTIR (Fourier Transform infrared) analysis of a sample containing a mixture of nanoparticles showed an addition of bonds and a difference in the peak location and its intensity values. The inhibition time for biomass was observed between 14 days and 21 days at 10 mg/L NPs. At 1 mg/L, the order of toxicity of NPs to algae was found to be: CuO NPs (highest toxicity) > ZnO NPs>ZnO + CuO NPs (least toxicity). During exposure of algae cells to a mixture of NPs at 10 mg/L NP concentration, a smaller value of metal deposition was observed than that during exposure to individual NPs. Antagonistic toxic effects of two NPs on dry cell weight of algae was observed at both concentration levels. Future work is needed to understand the steps involved in toxicity due to mixture of NPs to algae so that environmental exposures of algae to NPs can be managed and minimized.

Ecotoxicity of a mixture of nanoparticles on algal species Scendesmus obliquus in OECD growth media, wastewater, and pond water

The possible impact of ZnO and CuO nanoparticles (NPs) (individually and in binary mixture) was investigated using the freshwater microalgae, Scenedesmus obliquus. The present study shows the effect of nanoparticles on algae in OECD growth media, wastewater, and pond water during a 96-h toxicity test. At 0.1 mg/L concentration of the mixture of NPs, the reduction in the chlorophyll a content was 13.61 ± 1.34% (OECD media), 28.83 ± 1.85% (wastewater), and 31.81 ± 2.23% (pond water). Values of reduction in biomass were observed to be 42.13 ± 1.38, 39.96 ± 1.03, and 33.10 ± 1.29% for OECD media, wastewater, and pond water, respectively. The highest increase in lipid values was observed in the case of pond water (6.3 ± 1.31%). A significant increase in the value of EPS-generated protein was observed in the wastewater sample. EPS-generated carbohydrate values were increased in OECD media but decreased in the wastewater matrix. The transmission electron microscope images showed structural damage to algae cells due to the exposure to a mixture of nanoparticles at higher concentrations. Fourier transform infrared analysis showed an addition of bonds and differences in the peak and its intensity during exposure to high concentrations of NPs. Overall, this study gives fundamental insights into the interaction and toxicity of a mixture of NPs to algal species in different water matrices.

Recent advances in metal-organic frameworks: Synthesis, application and toxicity

Metal-organic frameworks (MOFs) are a new class of crystalline porous hybrid materials with high porosity, large specific surface area and adjustable channel structure and biocompatibility, which are being investigated with increasing interest for energy storage and conversion, gas adsorption/separation, catalysis, sensing and biomedicine. However, the practical applications of MOFs make them release into the environment inevitable, posing a threat to humans and organisms. In this article, we cover advances in the currently available MOFs synthesis methods and the emerging applications of MOFs, especially in the biomedical field (therapeutic agents and bioimaging). Additionally, after evaluating the current status of main exposure routes and affecting factors in the field of MOFs-toxicity, the molecular mechanism is also clarified and identified. Knowledge gaps are identified from such a summarization and frontier development are explored for MOFs. Afterwards, we also present the limitations, challenges, and future perspectives in the study of the entire life cycle of MOFs. This review emphasizes the need for a more targeted discussion of the latest, widely used and effective versatile material class in order to exploit the full potential of high-performance and non-toxicity MOFs in the future.

Tire wear particles in different water environments: occurrence, behavior, and biological effects-a review and perspectives

As an important source of microplastics, the water ecological risk of tire wear particles (TWPs) has attracted widespread attention worldwide. However, the occurrence and behavior of TWPs and their biological effects in water environments have not been clearly analyzed. For example, most contemporary studies have focused on the evaluation of the aquatic toxicity of TWPs leachate, and little attention has been paid to the behavior process and potential risks of its surface properties in water environments. In addition, most studies rely on preparing TWPs under laboratory conditions or purchasing commercial TWPs for studying their water environmental behavior or exposure. These obviously cannot meet the requirements of accurate assessment of water ecological risks of TWPs. As thus, in addition to describing the occurrence, distribution, and (aging) transformation of TWPs in different water environments, we further tried to explain the potential water environment behavior process and multiple pathways leading to potential adverse impacts of TWPs on aquatic organisms from the perspectives of particle self-toxicity and release toxicity, as well as synergistic effects of TWPs and other substances are also discussed. The existing data, such as studies on the self-characteristics of TWPs, environmental factors, and subjects, are insufficient to comprehensively evaluate the recent changes in essential water ecosystem services and multifunctions caused by TWPs, implying that the impact of TWPs on water environmental health needs to be further evaluated, and the corresponding countermeasures should be recommended. In this context, the current review provides an outlook on future research on TWPs in aquatic environments.

Metabolomics and mass spectrometry imaging reveal the chronic toxicity of indoxacarb to adult zebrafish (Danio rerio) livers

Indoxacarb is a widely used insecticide in the prevention and control of agricultural pests, whereas its negative effects on non-target organisms remain largely unclear. Herein, we demonstrated the integrated metabolomics and mass spectrometry imaging (MSI) methods to investigate the chronic exposure toxicity of indoxacarb at environmentally relevant concentrations in adult zebrafish (Danio rerio) liver. Results showed that movement behaviors of zebrafish can be affected and catalase (CAT), glutamic oxalacetic transaminase (GOT), and glutamic pyruvic transaminase (GPT) activities were significantly increased after indoxacarb exposure for 28 days. Pathological analysis of zebrafish livers also showed that cavitation and pathological reactions occur. Metabolomics results indicated that metabolic pathways of zebrafish liver could be significantly affected by indoxacarb, such as tricarboxylic acid (TCA) cycle and various amino acid metabolisms. MSI results revealed the spatial differentiation of crucial metabolites involved in these metabolic pathways within zebrafish liver. Taken together, these integrated MSI and metabolomics results revealed that the toxicity of indoxacarb arises from metabolic pathways disturbance, which resulted in the decrease of liver detoxification ability. These findings will promote the current understanding of pesticide risks and metabolic disorders in zebrafish liver, which provide new insights into the environmental risk assessment of insecticides on aquatic organisms.

Effects of Micro(nano)plastics on the reproductive system: A review

Microplastics (100nm-5 mm) and nanoplastics (1-100 nm) are collectively referred to as micro(nano)plastics (MNPs), which are refractory to degradation, easy to migration, small in size, strong in adsorption, and can widely present in human living environment. A number of studies have confirmed that MNPs can be exposed to the human body through a variety of routes, and can penetrate various barriers to enter the reproductive system, suggesting that MNPs may pose potential harm to human reproductive health. Current studies most were limited to phenotypic studies and their subjects were basically lower marine organisms and mammals. Therefore, in order to provide theoretical base for further exploring the effects of MNPs on the human reproductive system, this paper searched the relevant literature at home and abroad, mainly analyzed rodent experiments, and concluded that the main exposure routes of MNPs are dietary intake, air inhalation, skin contact and medical plastics. After entering the reproductive system, MNPs produce reproductive toxicity mainly through oxidative stress, inflammation, metabolic disorders, cytotoxicity and other mechanisms. More work is required to comprehensively identify the exposure routes, improve the detection methods to evaluate the effective exposure and deeply study the specific mechanisms of toxic effects, withing the aim of conducting relevant studies at the population level in the next step.

Metagenomic analysis reveals the responses of microbial communities and nitrogen metabolic pathways to polystyrene micro(nano)plastics in activated sludge systems

Microplastics (MPs) and nanoplastics (NPs) are prevalent in sewage and pose a potential threat to nitrogen biotransformation in wastewater treatment systems. However, investigations on how MPs and NPs affect the microbial nitrogen conversion and metabolism of the activated sludge are still scanty. Herein, the responses of microbiomes and functional genes to polystyrene MPs and NPs in activated sludge systems were investigated by metagenomic analysis. Results indicated that 1 mg/L MPs and NPs had marginal impacts on the nitrogen removal performance of the activated sludge systems, whereas high concentrations of MPs and NPs (20 and 100 mg/L) decreased the total nitrogen removal efficiency (13.4%-30.6%) by suppressing the nitrogen transformation processes. Excessive reactive oxygen species induced by MPs and NPs caused cytotoxicity, as evidenced by impaired cytomembranes and decreased bioactivity. Metagenomic analysis revealed that MPs and NPs diminished the abundance of denitrifiers (e.g. Mesorhizobium, Rhodobacter and Thauera), and concurrently reduced the abundance of functional genes (e.g. napA, napB and nirS) encoding for key enzymes involved in the nitrogen transformations, as well as the genes (e.g. mdh) related to the electron donor production, thereby declining the nitrogen removal efficiency. Network analysis further clarified the attenuate association between denitrifiers and denitrification-related genes in the plastic-exposed systems, elucidating that MPs and NPs restrained the nitrogen removal by inhibiting the contributions of microorganisms to nitrogen transformation processes. This study provides vital insights into the responses of the microbial community structure and nitrogen conversion processes to micro(nano)plastics disturbance in activated sludge systems.

Using δFIP as a potential biomarker for risk assessment of environmental pollutants in aquatic ecosystem: A case study of marine cyanobacterium Synechococcus sp. PCC7002

Increased hazardous substances application causes more environmental pollution and risks for human health. Microalgae are the important biological groups in marine ecosystem, and considered to be sensitive to environmental pollutants. Therefore, toxicity test on marine microalgae could provide the most efficient method for aquatic toxicity assessment, and could also be used as the early warning signals in aquatic ecosystem. In view of this, our study aimed at investigating the toxicity potential of two typical organic compounds, and screening out novel photosynthetic indicators for the risk assessment of environmental pollutants. In this study, benzyl alcohol and 2-phenylethanol were chosen as the target organic compounds, and preliminary toxicity mechanism of these organic compounds on marine cyanobacterium Synechococcus sp. PCC7002 was investigated with chlorophyll fluorescence technology. Results showed that PCC7002 could be affected by benzyl alcohol or 2-phenylethanol stress, and the toxicity effect was concentration-dependent. And external benzyl alcohol and 2-phenylethanol stress damaged the oxygen evolving complex, and suppressed electron transport at the donor and receptor sides of photosystem II (PSII), influencing the absorption, transfer, and application of light energy. Furthermore, potential biomarkers were screened by half maximal inhibitory concentration (IC₅₀) on the basis of pearson correlation coefficient analysis, and fluorescence intensity difference between the I-step and P-step of OJIP curve (δF_IP) seems to be the most sensitive indicator for external stress. This study would be of significant interest to the biomarker community, and pave the way for the practical resource for marine pollution monitoring and assessment.

Cytotoxicity and cell injuries of flavored electronic cigarette aerosol and mainstream cigarette smoke: A comprehensive in vitro evaluation

INTRODUCTION

Although electronic cigarettes (e-cigarettes) have attracted much attention due to their claimed harm-reduction effects compared with conventional cigarettes, the adverse effects of e-cigarette aerosol exposure on human health are still unclear. In this work we compared the cytotoxic effects of combustion cigarettes with four commercially available flavored electronic cigarettes and their main components on ten cell lines. Cell injury mechanism of e-cigarette aerosol and combustible cigarette smoke was also explored using cellular models.

METHODS

Eleven kinds of e-cigarettes aerosol condensates (ECSCs) and cigarette smoke constituent's condensates (CSC) were collected by Cambridge filter pad, and the nicotine contents were determined by UPLC to provide an equivalent nicotine dosage. The CCK-8 assay was used to measure the cell viability differences between ECSC and CSC. Based on RNA-seq results, we compared the effects of ECSC and CSC on various cell injury pathways. Oxidative stress and inflammatory responses were further tested by Western Blot, immunofluorescence, and qRT-PCR assays.

RESULTS

CSC was found to be more cytotoxic than flavored ECSC and their main components, and BEAS-2B cell line was the most sensitive cells by comparing the IC50 value. With prolonged exposure duration and higher doses, ECSC began to exhibit cytotoxicity at and above 72 µg/mL. The IC50 values of ECSC were 15-fold higher than that of CSC. Transcriptome analyses indicated that cell injury-related processes were enriched after the treatment of CSC. CSC could significantly induce more oxidative stress and inflammatory signals than ECSC.

CONCLUSION

ECSCs and their components induced significantly less cytotoxicity than CSC under the laboratory exposure conditions, and CSC caused much severe cell injuries. Our study adds to the body of scientific evidence for a more comprehensive safety evaluation of e-cigarette products as compared to cigarettes.

Dimethyl phthalate inhibits the growth of Escherichia coli K-12 by regulating sugar transport and energy metabolism

Dimethyl phthalate (DMP) is one of the most widely used plasticizers, and it is easily released into the environment, posing a threat to microbes. In this study, the impact of DMP on the uptake and metabolism of sugars in E. coli K-12 was assessed using proteomics, computational simulation analysis, transcriptome analysis, and sugar utilization experiments. DMP contamination inhibited the growth of E. coli K-12 and downregulated the expression of proteins in ATP-binding cassette (ABC) transporters and the phosphotransferase (PTS) system of E. coli K-12, which are primarily involved in the transmembrane transport of sugars. DMP formed a stable complex with sugar transporters and changed the rigidity and stability of the proteins. Furthermore, DMP treatment decreased the utilization of L-arabinose, glucose, D-xylose, and maltose. Moreover, carbon metabolism and oxidative phosphorylation were also downregulated by DMP. Our study shows that DMP reduces the uptake of sugars and ATP production and subsequently inhibits the growth of E. coli K-12.

Pesticide responses of Arctic and temperate microalgae differ in relation to ecophysiological characteristics

Polar ecosystems play an important role in global primary production. Microalgae have adaptations that enable them to live under low temperature environments where irradiance and day length change drastically. Their adaptations, leading to different ecophysiological characteristics relative to temperate species, could also alter their sensitivity to pollutants such as pesticides. This study's objective was to understand how different ecophysiological characteristics influence the response of Arctic phytoplankton to pesticides in relation to the responses of their temperate counterparts. Ecophysiological endpoints were related to growth, cell biovolume, pigment content, photosynthetic activity, photoprotective mechanisms (NPQ, antioxidant enzyme activities), and reactive oxygen species (ROS) content. The Arctic species Micromonas polaris was more resistant to atrazine and simazine than its temperate counterpart Micromonas bravo. However, the other Arctic species Chaetoceros neogracilis was more sensitive to these herbicides than its temperate counterpart Chaetoceros neogracile. With respect to two other pesticide toxicity, both temperate microalgae were more sensitive to trifluralin, while Arctic microalgae were more sensitive to chlorpyrifos (insecticide). All differences could be ascribed to differences in the eco-physiological features of the two microalgal groups, which can be explained by cell size, pigment content, ROS content and protective mechanisms (NPQ and antioxidant enzymes).

Response of aerobic granular sludge under polyethylene microplastics stress: Physicochemical properties, decontamination performance, and microbial community

Microplastics are widely detected in sewage and sludge in wastewater treatment plants and can thereby influence biological processes. In this study, the overall impacts of polyethylene microplastics (PE MPs) and their toxicity mechanisms on aerobic granular sludge (AGS) were investigated. Particle structure, settling properties, particle size distribution, and extracellular polymeric substance characteristics of AGS were significantly affected by PE MPs with concentrations of 20 and 200 n/L. Increased relative contents of reactive oxygen species (ROS) (146.34% and 191.43%) and lactate dehydrogenase (LDH) (185.71% and 316.67%) under PE MPs (20 and 200 n/L) exposure resulted in disruption of cellular structure. The activities of enzymes related to denitrification and phosphorus removal were greatly decreased, while ammonia monooxygenase (AMO) was stable, supporting the high efficiency removal of ammonia nitrogen. High-throughput sequencing demonstrated that the relative abundance of nitrifying and denitrifying bacteria (Nitrospira, Thermomonas, Flavobacterium), and PAOs (Comamonas and Rhodocyclus) were significantly reduced from 4.47%, 3.57%, 2.02%, 9.38%, and 5.45%-2.95%, 2.88%, 1.77%, 8.01%, and 4.86% as the concentration of PE MPs increased from 0 to 200 n/L, respectively. Those findings were consistent with the deterioration in decontamination capability.

Mechanistic insights to lactic and formic acid toxicity on benthic oligochaete worm Tubifex tubifex

Lactic and formic acid are two commonly found monocarboxylic organic acids. Lactic acid is discharged into the water bodies as acidic industrial effluent from the food, cosmetic, chemical, and pharmaceutical industries, whereas formic acid is discharged from various paper, leather tanning, and textile processing industries. The present study investigated the toxicity of both organic acids upon the benthic oligochaete worm Tubifex tubifex. The 96-h median lethal concentration (LC₅₀) values for lactic and formic acid are determined as 143.81 mg/l and 57.99 mg/l respectively. The effects of two sublethal concentrations (10% and 30% of 96 h LC₅₀) of these acids on differential expression of oxidative stress enzymes are investigated. The comparative analysis of acute toxicity demonstrates that formic acid exposure is more detrimental to T. tubifex than lactic acid. The in silico structural analysis predicts that formic acid can interact with cytochrome c oxidase of the electron transport system and thereby inhibits its functionality and induces reactive oxygen species production. Integrated biomarker response (IBR) analysis illustrates that overall oxidative stress of formic acid to T. tubifex is significantly higher than that of lactic acid, which supports the structural analysis. It is concluded from this study that toxicokinetic-toxicodynamic and species sensitivity distributions studies are helpful for ecological risk management of environmental toxicants.

In-depth exploration of toxicity mechanism of nanoscale zero-valent iron and its aging products toward Escherichia coli under aerobic and anaerobic conditions

The bacteria toxicity of nanoscale zero-valent iron (nZVI) can be changed during its application in water treatment but the toxicity mechanism is still not well understood, particularly under anaerobic conditions. Here, the toxicity of nZVI and its aging products towards Escherichia coli (E. coli) and the mechanisms of extracellular and intracellular reactive oxygen species (ROS) damage were deeply probed in the presence and absence of oxygen in ultrapure water. Under aerobic conditions, the ROS damage primarily caused by the generation of extracellular free •OH can be a major contributor to the toxicity of nZVI to E. coli. By contrast, in anaerobic nZVI treatment system, the intracellular •OH can be quenched by benzoic acid which is a cell permeable quencher and the electron spin resonance (ESR) signals of 5,5-dimethy-1-pyrroline (DMPO)- •OH were evidently observed in system with the addition of F^- which could desorb the surface •OH into solution. It indicated that the intracellular •OH adsorbed on the particle surface can also play an indispensable role in inactivating cells under anaerobic conditions. Moreover, nZVI can steeply decline the membrane potential, causing severe membrane disruption and therefore resulting in the stronger toxicity in anaerobic conditions. Furthermore, the chemical composition transformation of nZVI and generation of benign iron corrosion products (e.g., Fe₃O₄, γ-Fe₂O₃, γ-FeOOH) are mainly responsible for the reduced toxicity with the increasing aging time. These results provide insights into the extracellular and intracellular ROS damage occurred in aerobic and anaerobic nZVI treatment systems, offering more perspective to the risk assessment of nZVI application.

Biological responses of alga Euglena gracilis to triclosan and galaxolide and the regulation of humic acid

Although the toxicity of triclosan (TCS) and galaxolide (HHCB) in freshwater has been reported, little study is shed light on their molecular toxicity mechanism and the regulation of humic acid (HA). In this work, freshwater algae E. gracilis was selected to explore these processes, and the molecular toxicity mechanism was analyzed by metabolomics. TCS was more toxic to E. gracilis than HHCB at 1 d exposure with the EC₅₀ value of 0.76 mg L^-1, but HHCB showed a higher toxicity as the exposure time prolonged. HA could alleviate the toxicity of TCS and HHCB, mainly due to the inhibition of TCS uptake and oxidative stress, respectively. The perturbations on a number of antioxidant defense-related metabolites in response to TCS or HHCB also indicated oxidative stress was a main toxicity mechanism. However, the exposure to HHCB resulted in more pronounced perturbations in the purine metabolism than TCS, implying that HHCB may pose a genetic toxicity on algae. It may explain the higher toxicity of HHCB to algae as the exposure time increased. These findings provide a comprehensive understanding on the ecological risks of TCS or HHCB in natural waters.

Reproductive toxicities of ofloxacin and norfloxacin on Caenorhabditis elegans with multi-generational oscillatory effects and trans-generational residual influences

The reproductive toxicities over generations are essential to assess the long-term impacts environmental fluoroquinolone antibiotics (FQs). In the present study, the multi-generational effects of ofloxacin (OFL) and norfloxacin (NOR) on reproduction were studied on Caenorhabditis elegans from 9 successive generations (F1-F9). Results showed that OFL showed no effects in F1, stimulation in F2 to F4, and inhibition F5 to F9. The effects of NOR also showed oscillation between stimulation and inhibition across generations. Further biochemical analysis demonstrated that the reproductive toxicities of OFL and NOR were more closely connected with total cholesterol (TCHO), progesterone (P) and testosterone (T), than major sperm protein (MSP) and vitellogenin (Vn). Moreover, OFL and NOR also showed significant trans-generational reproductive toxicities in T4 and T4', the great-grand-daughter of F1 and F9. Differences between T4 and T4' and between OFL and NOR, indicated influences of multi-generational exposure and urged more exploration on different mechanisms between FQs.

A comprehensive review on human health effects of chromium: insights on induced toxicity

The growing use of heavy metals in most industrial activities has led to it being considered as the most important environmental pollutant that may cause harm and toxicity to animals and humans. Chromium has been found in the environment in different oxidation states such as Cr⁰, Cr(III), and Cr(VI) and is released from a variety of anthropogenic and natural activities. At among, trivalent and hexavalent chromium are the most stable forms. Considerably, Cr(VI) is frequently more toxic than Cr(III) because of its particular solubility and high mobility. Chronic exposure and bioaccumulation of chromium, as a heavy metal, can cause toxicity and numerous pathophysiological defects, including allergic reactions, anemia, burns, and sores especially in the stomach and small intestine, damage to sperm along with the male reproductive system, and affect various biological systems. Chromium pollution can have severe consequences for water and the soil environment. This article reviews the toxicological effects of Cr(VI) and Cr(III) and their mechanisms of toxicity and carcinogenicity.

Application of ToxCast/Tox21 data for toxicity mechanism-based evaluation and prioritization of environmental chemicals: Perspective and limitations

In response to the need to minimize the use of experimental animals, new approach methodologies (NAMs) using advanced technology have emerged in the 21st century. ToxCast/Tox21 aims to evaluate the adverse effects of chemicals quickly and efficiently using a high-throughput screening and to transform the paradigm of toxicity assessment into mechanism-based toxicity prediction. The ToxCast/Tox21 database, which contains extensive data from over 1400 assays with numerous biological targets and activity data for over 9000 chemicals, can be used for various purposes in the field of chemical prioritization and toxicity prediction. In this study, an overview of the database was explored to aid mechanism-based chemical prioritization and toxicity prediction. Implications for the utilization of the ToxCast/Tox21 database in chemical prioritization and toxicity prediction were derived. The research trends in ToxCast/Tox21 assay data were reviewed in the context of toxicity mechanism identification, chemical priority, environmental monitoring, assay development, and toxicity prediction. Finally, the potential applications and limitations of using ToxCast/Tox21 assay data in chemical risk assessment were discussed. The analysis of the toxicity mechanism-based assays of ToxCast/Tox21 will help in chemical prioritization and regulatory applications without the use of laboratory animals.

Photosynthetic, antioxidative, and metabolic adjustments of a crop plant to elevated levels of La and Ce exposure

Rare earth elements (REEs) have been widely applied as fertilizers in farmland of China for decades to improve the yield and quality of crops. Unfortunately, adverse effects on plants have been observed due to overdosing with REEs. Until now, the toxicology of REEs was mainly evaluated based on phenotypic responses, but knowledge gaps still exist concerning their metabolic effects. Here, the physiological responses and nontargeted metabolomics studies were combined to systematically explore the potential effects of La and Ce on a crop plant, wheat Triticum aestivum. It was observed that REEs accumulated in the shoots of wheat, with significant reduction of the shoot biomass at higher exposure doses. The disturbance of photosynthesis and induced oxidative stress were identified by analyzing indicators of the photosynthetic (chlorophyll a/b, carotenoid and rubisco) and antioxidant systems (POD, CAT, SOD, GSH and MDA). Furthermore, the global metabolic profiles of REEs treatment groups and the non-exposed control group were screened and compared, and the metabolomic disturbance of REEs was dose-dependent. A high overlap of significantly changed metabolites and matched disturbed biological pathways was found between La and Ce treatments, indicating similarity of their toxicity mechanism in wheat shoots. Generally, the perturbed metabolomic pathways were mainly related to carbohydrate, amino acid and nucleotide/side metabolism, suggesting a disturbance of carbon and nitrogen metabolism, which finally affected the growth of wheat. We thus proved the potential adverse effect of inappropriate application of REEs in crop plants and postulated metabolomics as a feasible tool to identify the underlying toxicological mechanisms.

Systematic impacts of fluoride exposure on the metabolomics of rats

Fluoride is widely present in the environment. Excessive fluoride exposure leads to fluorosis, which has become a global public health problem and will cause damage to various organs and tissues. Only a few studies focus on serum metabolomics, and there is still a lack of systematic metabolomics associated with fluorosis within the main organs. Therefore, in the current study, a non-targeted metabolomics method using gas chromatography-mass spectrometry (GC-MS) was used to research the effects of fluoride exposure on metabolites in different organs, to uncover potential biomarkers and study whether the affected metabolic pathways are related to the mechanism of fluorosis. Male Sprague-Dawley rats were randomly divided into two groups: a control group and a fluoride exposure group. GC-MS technology was used to identify metabolites. Multivariate statistical analysis identified 16, 24, 20, 20, 24, 13, 7, and 13 differential metabolites in the serum, liver, kidney, heart, hippocampus, cortex, kidney fat, and brown fat, respectively, in the two groups of rats. Fifteen metabolic pathways were affected, involving toxic mechanisms such as oxidative stress, mitochondrial damage, inflammation, and fatty acid, amino acid and energy metabolism disorders. This study provides a new perspective on the understanding of the mechanism of toxicity associated with sodium fluoride, contributing to the prevention and treatment of fluorosis.

Toxic effects of glyphosate on the intestine, liver, brain of carp and on epithelioma papulosum cyprinid cells: Evidence from in vivo and in vitro research

Glyphosate (GLY) is the most widely used organophosphorus herbicide in agriculture. The present study aimed to analyze the comprehensive toxicological effects of GLY on juvenile common carp and an epithelioma papulosum cyprinid (EPC) cell line. In the in vivo experiments, exposure to GLY (5 and 15 mg/L) for 30 days induced liver inflammation and oxidative damage in common carp and changed the physical barrier of the intestine. Histopathological analysis of the intestine, liver, brain, and changes in oxidative stress biomarkers provided evidence of damage and immune system responses to GLY. Moreover, an inhibitory effect of 15 mg/L GLY on acetylcholinesterase (AChE) activity was found in the brain, which may be an important reason for the significant decrease in both swimming distance and average acceleration of common carp. Cell experiments showed that 0.65 and 3.25 mg/L GLY inhibited the viability of EPCs. Furthermore, oxidative DNA damage, mitochondrial dysfunction, and reactive oxygen species (ROS) production were observed in EPC cells following GLY exposure. Taken together, this study not only highlights the negative effects of GLY on common carp but also enriches the knowledge of the cytotoxicity mechanism to further clarify the comprehensive toxicity of GLY in common carp.

Toxicity mechanism of nanomaterials: Focus on endoplasmic reticulum stress

Over the years, although the broad application of nanomaterials has not brought convenience to people's life, growing concern surrounds their safety. Recently, much emphasis has been placed on exploring the toxicity mechanism of nanoparticles. Currently established toxic mechanisms include oxidative stress, inflammatory response, autophagy, and DNA damage. In recent years, endoplasmic reticulum stress (ERS) has gained widespread attention as another toxic mechanism of nanomaterials. It is widely acknowledged that the endoplasmic reticulum (ER) is an important site for protein synthesis, and lipids and Ca⁺ storage, playing an esseential role in the normal operation of the body functions. When the body's internal environment is damaged, the structure and function of the endoplasmic reticulum are destroyed, leading to a series of biological reactions called endoplasmic reticulum stress (ERS.) This paper reviews the mechanism of ERS in nanomaterial-associated toxicity. The process of ERS and its related unfolded protein response were briefly introduced, summarizing the factors affecting the nanoparticle ability to induce ERS and expounding on the changes of ER morphology after exposure to nanoparticles. Finally, the specific role and molecular mechanism of ERS under the action of different nanoparticles were comprehensively analyzed, including the relationship between ERS and inflammation, oxidative stress, lipid metabolism and apoptosis. This review provides a foothold for future studies on the toxic mechanism of nanoparticles, and provides novel insights into the safe application of nanoparticles and the treatment of diseases.

Biochemical toxicity and transcriptome aberration induced by dinotefuran in Bombyx mori

Dinotefuran is a third-generation neonicotinoid pesticide and is increasingly used in agricultural production, which has adverse effects on nontarget organisms. However, the research on the impact of dinotefuran on nontarget organisms is still limited. Here the toxic effects of dinotefuran on an important economic species and a model lepidopteran insect, Bombyx mori, were investigated. Exposure to different doses of dinotefuran caused physiological disorders or death. Cytochrome P450, glutathione S-transferase, carboxylesterase, and UDP glycosyl-transferase activities were induced in the fat body at early stages after dinotefuran exposure. By contrast, only glutathione S-transferase activity was increased in the midgut. To overcome the lack of sensitivity of the biological assays at the individual organism level, RNA sequencing was performed to measure differential expressions of mRNA from silkworm larvae after dinotefuran exposure. Differential gene expression profiling revealed that various detoxification enzyme genes were significantly increased after dinotefuran exposure, which was consistent with the upregulation of the detoxifying enzyme. The global transcriptional pattern showed that the physiological responses induced by dinotefuran toxicity involved multiple cellular processes, including energy metabolism, oxidative stress, detoxification, and other fundamental physiological processes. Many metabolism processes, such as carbon metabolism, fatty acid biosynthesis, pyruvate metabolism, and the citrate cycle, were partially repressed in the midgut or fat body. Furthermore, dinotefuran significantly activated the MAPK/CREB, CncC/Keap1, PI3K/Akt, and Toll/IMD pathways. The links between physiological, biochemical toxicity and comparative transcriptomic analysis facilitated the systematic understanding of the integrated biological toxicity of dinotefuran. This study provides a holistic view of the toxicity and detoxification metabolism of dinotefuran in silkworm and other organisms.

Microbial and physicochemical responses of anaerobic hydrogen-producing granular sludge to polyethylene micro(nano)plastics

Micro(nano)plastics is an emerging contaminant in wastewater that has showed significant impacts on various biological treatment processes. Nevertheless, the underlying effects of micro(nano)plastics with different concentrations and sizes on the anaerobic hydrogen-producing granular sludge (HPG) were still unclear. This work firstly attempted to illustrate the microbial and physicochemical responses of HPG to a shock load of polyethylene microplastics (PE-MPs) with varied concentrations and sizes. The results revealed that the PE-MPs inhibitory effect on hydrogen production by HPG was both concentration- and size-dependent. Specifically, the increase of PE-MPs concentration and the decline of PE-MPs size to nano-sized plastics (NPs) significantly decreased the hydrogen yield, downgraded to 79.9 ± 2.6% and 63.0 ± 3.9% (p = 0.001, and 0.0002) of control, respectively, at higher MPs concentration and the smaller MPs size (i.e., NPs). The higher PE-MPs concentration and PE-NPs also suppressed extracellular polymeric substances (EPS) generation more severely. The critical bio-processes involved in hydrogen production were disturbed by PE-MPs, with the extent of negative impacts depending on the dosage and size of PE-MPs. These adverse impacts further manifested as granule disintegration and loss of cellular activity. Mechanism analysis highlighted the roles of oxidative stress, leachate released from PE-MPs, interaction between PE-NPs and granules inducing physical crushing of HPG that led to possible direct contact between cells and toxic substances.

In vitro review of nanoparticles attacking macrophages: Interaction and cell death

In recent years, the wide application of nanoparticles (NPs) inevitably leads to environmental pollution and human exposure, and its safety has attracted more and more attention. Since macrophages are the cells most directly exposed to multi-pathway invading NPs in the body, it is necessary to assess of toxic effects of NPs in macrophages, clarify the potential mechanisms of NPs toxicity to improve our understanding about the interaction of NPs with macrophages in vivo, and avoid body damage. Currently, studies on the toxicity of NPs to macrophages are rare and mainly focused on in vitro, so this paper integrated the toxic effect of macrophages exposed to NPs and the macrophages cellular changes following the interaction with NPs, including NPs internalization, ROS production, cytokines alterations, DNA damage and cell death, and further explored the involved mechanisms. This review aims to provide some insights into the further toxicological studies of NPs.

Comparing the toxicity of iodinated X-ray contrast media on eukaryote- and prokaryote-based quantified microarray assays

This study compared the toxicity mechanisms of four X-ray-based iodinated contrast media (ICM) on Escherichia coli (E. coli) and yeast microarray assays, aiming to determine the diverse toxicity mechanisms among different exposed organisms and the relationship between toxicity and their physical and chemical characteristics. The conventional phenotypic endpoint cytotoxicity and the change in reactive oxygen species (ROS) level were employed in conjunction with toxicogenomics to quantify changes in the gene/protein biomarker level in the regulation of different damage/repair pathways. The results showed that molecular toxicity endpoints, named transcriptional effect level index (TELI) and protein effect level index (PELI) for E. coli and yeast, respectively, correlated well with the phenotypic endpoints. Temporal altered gene/protein expression profiles revealed dynamic and complex damage/toxic mechanisms. In particular, compared with E. coli cells, yeast cells exposed to ICM exhibited significantly higher stress intensity and diverse stress types, resulting in stress or damage to the organism. The toxic mechanisms of ICM are concentration/property-dependent and relevant to the cellular structure and defense systems in prokaryotes and eukaryotes. In particular, the toxicity of ionic ICM is higher than that of non-ionic ICM, and eukaryotes are more susceptible than prokaryotes to ICM exposure.

Application of Non-invasive Micro-test Technology (NMT) in environmental fields: A comprehensive review

Non-invasive Micro-test Technology (NMT) is a selective microelectrode technique which can detect the flux rates and three-dimensional motion directions of ions or molecules into and out of living organisms in situ without damaging the sample. It has the advantages of maintaining sample integrity, high temporal and spatial resolution, and being able to measure multiple sites simultaneously. In this paper we provide a comprehensive review on the development of NMT in recent years. Its principles, characteristics, and the differences with other microelectrode techniques are introduced. We discuss the applications of NMT in the field of phytoremediation, plant resistance, water quality monitoring, and toxicity mechanisms of heavy metals on organisms. Furthermore, the challenges and future prospects of NMT in the environmental field are presented.

Safety assessment of graphene oxide and microcystin-LR complex: a toxicological scenario beyond physical mixture

Background

Nanomaterials have been widely used in electrochemistry, sensors, medicine among others applications, causing its inevitable environmental exposure. A raising question is the “carrier” effect due to unique surface properties of nanomaterials, which may collectively impact the bioavailability, toxicokinetic, distribution and biological effects of classic toxicants. Noteworthy, this aspect of information remains largely unexplored.

Methods

Here, we deliberately selected two entities to mimic this scenario. One is graphene oxide (GO), which is made in ton quantity with huge surface-area that provides hydrophilicity and π–π interaction to certain chemicals of unique structures. The other is Microcystin-LR (MCLR), a representative double-bond rich liver-toxic endotoxin widely distributed in aquatic-system. Firstly, the adsorption of GO and MCLR after meeting under environmental conditions was explored, and then we focused on the toxicological effect and related mechanism of GO-MCLR complex on human skin cutin forming cells (HaCaT cells) and normal liver cells (L02 cells).

Results

Abiotically, our study demonstrated that GO could effectively adsorb MCLR through hydrogen bonding and π–π interaction, the oxidation degree of GO-MCLR decreased significantly and surface defect level raised. Compared to GO or MCLR, GO-MCLR was found to induce more remarkable apoptosis and ferroptosis in both HaCaT and L02 cells. The underlying mechanism was that GO-MCLR induced stronger intracellular reactive oxygen species (ROS) and mtROS generation, followed by Fe²⁺ accumulation, mitochondrial dysfunction and cytoskeletal damage.

Conclusions

These results suggest that the GO-MCLR complex formed by GO adsorption of MCLR may exhibit more toxic effects than the single material, which demonstrates the necessity for assessing nano-toxicant complexity. Our discovery may serve as a new toxicological paradigm in which nanomaterial mediated surface adsorption effects could impact the degree of cytotoxicity and toxicological mechanisms of classic toxins.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-022-00466-x.

Toxicity mechanism of Nylon microplastics on Microcystis aeruginosa through three pathways: Photosynthesis, oxidative stress and energy metabolism

Nylon has been widely used all over the world, and most of it eventually enters the aquatic environment in the form of microplastics (MPs). However, the impact of Nylon MPs on aquatic ecosystem remains largely unknown. Thus, the long-term biological effects and toxicity mechanism of Nylon MPs on Microcystis aeruginosa (M. aeruginosa) were explored in this study. Results demonstrated that Nylon MPs had a dose-dependent growth inhibition of M. aeruginosa at the initial stage, and the maximum inhibition rate reached to 47.62% at the concentration of 100 mg/L. Meanwhile, Nylon MPs could obstruct photosynthesis electron transfer, reduce phycobiliproteins synthesis, destroy algal cell membrane, enhance the release of extracellular polymeric substances, and induce oxidative stress. Furthermore, transcriptomic analysis indicated that Nylon MPs dysregulated the expression of genes involved in tricarboxylic acid cycle, photosynthesis, photosynthesis-antenna proteins, oxidative phosphorylation, carbon fixation in photosynthetic organisms, and porphyrin and chlorophyll metabolism. According to the results of transcriptomic and biochemical analysis, the growth inhibition of M. aeruginosa is inferred to be regulated by three pathways: photosynthesis, oxidative stress, and energy metabolism. Our findings provide new insights into the toxicity mechanism of Nylon MPs on freshwater microalgae and valuable data for risk assessment of MPs.

Structure-toxicity relationships, toxicity mechanisms and health risk assessment of food-borne modified deoxynivalenol and zearalenone: A comprehensive review

Mycotoxin, as one of the most common pollutants in foodstuffs, poses great threat to food security and human health. Specifically, deoxynivalenol (DON) and zearalenone (ZEN)-two mycotoxin contaminants with considerable toxicity widely existing in food products-have aroused broad public concerns. Adding to this picture, modified forms of DON and ZEN, have emerged as another potential environmental and health threat, owing to their higher re-transformation rate into parent mycotoxins inducing accumulation of mycotoxin in humans and animals. Given this, a better understanding of the toxicity of modified mycotoxins is urgently needed. Moreover, the lack of toxicity data means a proper risk assessment of modified mycotoxins remains challenging. To better evaluate the toxicity of modified DON and ZEN, we have reviewed the relationship between their structures and toxicities. The toxicity mechanisms behind modified DON and ZEN have also been discussed; briefly, these involve acute, subacute, chronic, and combined toxicities. In addition, this review also addresses the global occurrence of modified DON and ZEN, and summarizes novel methods-including in silico analysis and implementation of relative potency factors-for risk assessment of modified DON and ZEN. Finally, the health risk assessment of modified DON and ZEN has also been discussed comprehensively.

Application of transcriptomic analysis to unveil the toxicity mechanisms of fall armyworm response after exposure to sublethal chlorantraniliprole

The anthranilic diamide insecticide chlorantraniliprole is highly effective against Lepidoptera pests, but the underlying mechanisms of toxic effects of chlorantraniliprole exposures for adapting to the chemical environment are poorly known in fall armyworm (FAW), Spodoptera frugiperda (J.E.Smith). FAW being one of the most pests of maize in Latin America, suddenly appeared in China in 2019 and spread rapidly. In this study, using bioassay and transcriptomic and biochemical analyses, we comprehensively investigated gene expression changes of third instar larvae in response to different sublethal concentrations (LC10 and LC30) of chlorantraniliprole in this insect. Exposure to LC10 chlorantraniliprole (0.73 mg/L) causes 1266 differentially expressed genes (DEGs), of which 578 are up-regulated and 688 down-regulated. Exposure to LC30 (2.49 mg/L) causes differential expression of 3637 DEGs (1545 up-, 2092 down-regulated). Interestingly, the LC30 treatment led to a significant increase in the number of DEGs compared to that of the LC10, indicating a concentration effect manner. Moreover, enrichment analysis identified important DEGs belonging to specific categories, such as amino acid, carbohydrate, lipid, energy, xenobiotics metabolisms, signal transduction, and posttranslational modification pathways, and enzymes activities in enriched pathways were significantly altered at the LC10 and LC30, which matched transcriptome analysis to mediate toxic mechanisms. The DEGs encoding detoxification-related genes were identified and validated by quantitative real-time PCR (qRT-PCR), which correlated with the RNA-sequencing (RNA-seq) data. To our knowledge, these findings provide the first toxicity mechanisms for a better understanding of chlorantraniliprole action and detoxification in FAW and other insect pests at molecular level.

Difference in toxicity of Pd (II) and mechanism of action before and after reduction by Bacillus wiedmannii MSM

At present, there are many studies on microbial reduction of Pd (II), although few of these studies assess the bacterial toxicity of Pd (II) before and after reduction by microorganisms. In this study, the toxicity of Pd (II) to Bacillus wiedmannii MSM (B. wiedmannii MSM) was assessed before and after reduction by live B. wiedmannii MSM cells (referred to as "Pd (0)-loaded cells") and after biosorption by dead B. wiedmannii MSM cells (referred to as "Pd (II)-loaded cells"). B. wiedmannii MSM is a widely occurring, nonpathogenic aerobic bacterium. Compared with Pd (II), the EC₂₀, EC₅₀, and EC₈₀ of Pd (0)-loaded cells increased by 77.73-, 112.75-, and 163.91-fold, respectively, while the EC₂₀, EC₅₀, and EC₈₀ of Pd (II)-loaded cells increased by only 11.55-, 9.77-, and 8.29-fold, respectively. The sterilization contribution rates of the mechanisms of action of Pd (0)-loaded cells were ranked in the order of: remaining Pd (II) > oxidative stress > physical puncture. Pd (II) was found to increase cell membrane permeability, glutathione S-transferase (GST) enzyme activity, and reactive oxygen species levels in cells and decrease the cell membrane potential. XPS results indicated that Pd (II) increased the content of polysaccharides and peptides and decreased the content of hydrocarbons in cells. These findings reveal the bactericidal mechanism of toxicity of Pd (II) and Pd (0)-loaded cells on Bacillus wiedmannii MSM and provide an environmentally friendly and inexpensive method for Pd (II) detoxification.

Comprehensive analysis of metabolic changes in rats exposed to acrylamide

Acrylamide (ACR) is a widely used environmentally hazardous compound that is known to be neurotoxic, genotoxic, carcinogenic, and reproductive toxicity. It is widely present in soil, water, agents used in chemical industries, and food. It can be distributed to all organs and tissues, and can cause damage to various human systems and those of other animals. Previous metabolomics studies have mainly focused on metabolites in serum and urine, but have lacked comprehensive analysis of major organs and tissues. In the current study, a gas chromatography-massspectrometry method was used to investigate mechanisms underlying organ toxicity, in an effort to identify potentially sensitive biomarkers in the main target tissues of rats after ACR exposure. Male Sprague-Dawley rats were assigned to two groups; a control group and a group treated with 20 mg kg^-1 ACR intragastrically for 6 weeks. Metabolite changes in the two groups were statistically analyzed. The respective numbers of altered metabolites in the hippocampus, cortex, kidney, serum, heart, liver, and kidney fat were 21, 21, 17, 5, 15, 14, and 6. There were 14 metabolic pathways related to amino acid, fatty acid, purine, and energy metabolism, revealing that the toxic mechanism of ACR may involve oxidative stress, inflammation, and amino acid metabolism and energy disorders.

Enthralling the impact of engineered nanoparticles on soil microbiome: A concentric approach towards environmental risks and cogitation

Nanotechnology is an avant-garde field of scientific research that revolutionizes technological advancements in the present world. It is a cutting-edge scientific approach that has undoubtedly a plethora of functions in controlling environmental pollutants for the welfare of the ecosystem. However, their unprecedented utilization and hysterical release led to a huge threat to the soil microbiome. Nanoparticles(NPs) hamper physicochemical properties of soil along with microbial metabolic activities within rhizospheric soils.Here in this review shed light on concentric aspects of NP-biosynthesis, types, toxicity mechanisms, accumulation within the ecosystem. However, the accrual of tiny NPs into the soil system has dramatically influenced rhizospheric activities in terms of soil properties and biogeochemical cycles. We have focussed on mechanistic pathways engrossed by microbes to deal with NPs.Also, we have elaborated the fate and behavior of NPs within soils. Besides, a piece of very scarce information on NPs-toxicity towards environment and rhizosphere communities is available. Therefore, the present review highlights ecological perspectives of nanotechnology and solutions to such implications. We have comprehend certain strategies such as avant-garde engineering methods, sustainable procedures for NP synthesis along with vatious regulatory actions to manage NP within environment. Moreover, we have devised risk management sustainable and novel strategies to utilize it in a rationalized and integrated manner. With this background, we can develop a comprehensive plan about NPs with novel insights to understand the resistance and toxicity mechanisms of NPs towards microbes. Henceforth, the orientation towards these issues would enhance the understanding of researchers for proper recommendation and promotion of nanotechnology in an optimized and sustainable manner.

Dynamic and quantitative characterization of antagonism within disinfectant mixtures by a modified area-concentration ratio method

The coexistence of various typical disinfectant pollutants has the potential to produce toxicity interaction towards organisms in the environment. A suitable model is necessary to evaluate the interaction quantitatively. Hence, the area-concentration ratio (ACR) method was modified (MACR) by combing confidence intervals to dynamically and quantitatively evaluate the toxicity interactions within disinfectant mixture pollutants. Disinfectant mixtures were designed by the direct equipartition design ray method using three guanidine disinfectants, chlorhexidine diacetate (CD), chlorhexidine (CHL), and polyhexamethylene biguanidine (POL) and one chlorine-containing disinfectant calcium hypochlorite (CAL). The toxicities of the four disinfectants and their mixtures towards Vibrio qinghaiensis sp.-Q67 (Q67) were determined by the time-dependent toxicity microplate analysis method. And the toxicity mechanism was analyzed by determining the effects of four disinfectants and their binary mixtures on the structure of cell, DNA and proteins (Pro) for Q67. The results show that the toxicities of CD and CHL to Q67vary little with time, but POL and CAL show the obvious time-dependent toxicity. The toxicities of CD, CHL and POL to Q67 are significantly stronger than that of CAL at the same exposure time. The toxicities of three binary mixture systems don't have significant difference in different exposure time. MACR can dynamically, quantitatively and accurately characterize toxicity interactions compared with ACR. According to MACR, the antagonism intensity dynamically changes with the prolongation of exposure time for binary mixture rays of three guanidine disinfectants and CAL, and linearly correlates with the components' concentration ratios. Four disinfectants all can destroy cell membrane and cause desaturation DNA of test organism, and CAL even can destroy the structure of DNA and protein. The probably reason for the antagonism within binary mixtures is the reaction between guanidine group and ClO^-, which is called chemical antaogism.

Transcriptome analysis to elucidate the toxicity mechanisms of fenvalerate, sulfide gatifloxacin, and ridomil on the hepatopancreas of Procambarus clarkii

Most antibiotics, insecticides, and other chemicals used in agricultural and fishery production tend to persist in the environment. Fenvalerate, sulfide gatifloxacin, and ridomil are widely used in aquaculture as antibacterial, antifungal, and antiparasitic drugs; however, their toxicity mechanism remains unclear. Thus, we herein analyzed the effects of these three drugs on the hepatopancreas of Procambarus clarkii at the transcriptome level. Twelve normalized cDNA libraries were constructed using RNA extracted from P. clarkii after treatment with fenvalerate, sulfide gatifloxacin, or ridomil and from an untreated control group, followed by Kyoto Encyclopedia of Genes and Genomes pathway analysis. In the control vs fenvalerate and control vs sulfide gatifloxacin groups, 14 and seven pathways were significantly enriched, respectively. Further, the effects of fenvalerate and sulfide gatifloxacin were similar on the hepatopancreas of P. clarkii. We also found that the expression level of genes encoding senescence marker protein-30 and arylsulfatase A was downregulated in the sulfide gatifloxacin group, indicating that sulfide gatifloxacin accelerated the apoptosis of hepatopancreatocytes. The expression level of major facilitator superfamily domain containing 10 was downregulated, implying that it interferes with the ability of the hepatopancreas to metabolize drugs. Interestingly, we found that Niemann pick type C1 and glucosylceramidase-β potentially interact with each other, consequently decreasing the antioxidant capacity of P. clarkii hepatopancreas. In the fenvalerate group, the downregulation of the expression level of xanthine dehydrogenase indicated that fenvalerate affected the immune system of P. clarkii; moreover, the upregulation of the expression level of pancreatitis-associated protein-2 and cathepsin C indicated that fenvalerate caused possible inflammatory pathological injury to P. clarkii hepatopancreas. In the ridomil group, no pathway was significantly enriched. In total, 21 genes showed significant differences in all three groups. To conclude, although there appears to be some overlap in the toxicity mechanisms of fenvalerate, sulfide gatifloxacin, and ridomil, further studies are warranted.

Mechanism underlying the toxicity of the microplastic fibre transfer in the sea cucumber Apostichopus japonicus

Microscopic plastic particles (0.1 µm-5 mm) are widespread hazardous pollutants, and microfibres (MFs) are their dominant shape in habitats. Previous field and laboratory studies have demonstrated that MFs enter the coelomic fluid of sea cucumbers from the water through the respiratory tree. However, the possible mechanism underlying the toxicity of this process is not well understood. Herein, RNA-Seq was used to examine the responses of the respiratory tree during the MF transfer process in the sea cucumber Apostichopus japonicus. Polyester synthetic MFs were used, and the number of transferred MFs was controlled to the amount reported from the field. The results showed that the MFs altered gene expression as the transfer process increased. The top genes regulated by MF transfer were mainly related to metabolic processes and signal transduction pathways, with upregulated genes following low MF transfer and downregulated genes following high MF transfer. Functional enrichment analysis revealed the pathways in which differentially expressed genes were enriched under different MF transfer scenarios. The transcriptomic findings were further supported by histological observations, which revealed injury and loss of cell components. This study contributes to understanding the effects of MFs in a valuable echinoderm species through transcriptomic and histological examinations.

Hypothesis: Long non-coding RNA is a potential target of mycotoxins

The molecular target of mycotoxins is not fully understood. Extensive data derived from cell and animal experimental studies demonstrate that long non-coding RNAs (lncRNAs) play crucial roles in mycotoxin-induced toxicities. Mycotoxins stimulate the upregulation/downregulation of lncRNA expression, which further promote apoptosis, is related to the mTOR/FoxO signaling pathway, and contributes to tumor cell growth, death, and liver and chondrocyte damage. Moreover, lncRNA can establish interactions with NF-κB and cause immune evasion. These preliminary data suggest that lncRNAs are involved in potential upstream regulatory events and further regulate downstream apoptosis, oxidative stress, and anti-apoptotic events that affect cell death and survival. Therefore, we hypothesize that lncRNAs are potential targets of mycotoxins. Investigation of the expression of the potential target lncRNAs by mycotoxin-mediated stimulation, and exploration of the upstream and downstream relationship between lncRNA and the key proteins involved in mycotoxin toxicity, should be performed. This Hypothesis provides clues for further understanding of the molecular mechanisms of mycotoxins.

Approaches to Test the Neurotoxicity of Environmental Contaminants in the Zebrafish Model: From Behavior to Molecular Mechanisms

The occurrence of neuroactive chemicals in the aquatic environment is on the rise and poses a potential threat to aquatic biota of currently unpredictable outcome. In particular, subtle changes caused by these chemicals to an organism's sensation or behavior are difficult to tackle with current test systems that focus on rodents or with in vitro test systems that omit whole-animal responses. In recent years, the zebrafish (Danio rerio) has become a popular model organism for toxicological studies and testing strategies, such as the standardized use of zebrafish early life stages in the Organisation for Economic Co-operation and Development's guideline 236. In terms of neurotoxicity, the zebrafish provides a powerful model to investigate changes to the nervous system from several different angles, offering the ability to tackle the mechanisms of action of chemicals in detail. The mechanistic understanding gained through the analysis of this model species provides a good basic knowledge of how neuroactive chemicals might interact with a teleost nervous system. Such information can help infer potential effects occurring to other species exposed to neuroactive chemicals in their aquatic environment and predicting potential risks of a chemical for the aquatic ecosystem. In the present article, we highlight approaches ranging from behavioral to structural, functional, and molecular analysis of the larval zebrafish nervous system, providing a holistic view of potential neurotoxic outcomes. Environ Toxicol Chem 2021;40:989-1006. © 2020 SETAC.

Toxicity mechanism of silver nanoparticles to Chlamydomonas reinhardtii: photosynthesis, oxidative stress, membrane permeability, and ultrastructure analysis

Silver nanoparticles (Ag-NPs) are widely used in daily life and inevitably discharged into the aquatic environment, causing increasingly serious pollution. Research on the toxicity of Ag-NPs is still in infancy, little information is available on the relationships between oxidative stress and antioxidant, as well as damaging degrees of Ag-NPs to cellular structural components of Chlamydomonas reinhardtii (C. reinhardtiii). In the present study, we revealed the toxicity mechanism of C. reinhardtii under Ag-NPs stress using flow cytometry (FCM), metabolic methods, and transmission electron microscopy. The results showed that the chloroplasts were damaged and the synthesis of photosynthetic pigments was inhibited under Ag-NPs stress, which inhibited the growth of C. reinhardtii. Meanwhile, Ag-NPs also caused C. reinhardtii to produce excessive reactive oxygen species (ROS), increased malondialdehyde content and changed the permeability of cell membrane, resulting in the acceleration of internalization of Ag-NPs. The decrease of cell size and intracellular chlorophyll autofluorescence was observed with FCM. To deal with the induced excessive ROS that could lead to lethal and irreversible structure damage, C. reinhardtii activated antioxidant enzymes including superoxide dismutase and peroxidase. This study provides new information for better understanding the potential toxicity risks of Ag-NPs in the aquatic environment.

The cytotoxicity of core-shell or non-shell structure quantum dots and reflection on environmental friendly: A review

Quantum dots are widely applicated into bioindustry and research owing to its superior properties such as broad excitation spectra, narrow bandwidth emission spectra and high resistance to photo-bleaching. However, the toxicity of quantum dots should not be underestimated and aroused widespread concern. The surface properties and size of quantum dots are critical relevant properties on toxicity. Then, the core/shell structure becomes one common way to affect the activity of quantum dots such as enhance biocompatibility and stability. Except those toxicity it induced, the problem it brought into the environment such as the degradation of quantum dot similarly becomes a hot issue. This review initially took a brief scan of current research on the cytotoxicity of QDs and the mechanism behind that over the past five years. Mainly discussion concentrated on the diversity of structure on quantum dots whether played a key role on the cytotoxicty of quantum dots. It also discussed the role of different shells with metal or nonmetal cores and the influence on the environment.

Toxicity evaluation of cadmium-containing quantum dots: A review of optimizing physicochemical properties to diminish toxicity

Fluorescent quantum dots (QDs) have received extensive attention because of their excellent optical properties and wide utilization in biological and biomedical areas. Nonetheless, there have been intense concerns on the cytotoxicity assessment of cadmium-containing QDs due to free cadmium ions release and nano-size effects. This paper reviews the representative synthetic strategies for preparation of cadmium-containing QDs and their applications. Then the toxicity assessments of QDs from cell studies to animal models are discussed, which can aid in improving our understanding of the cytotoxicity of QDs, and the toxicity mechanism is proposed. Several critical physicochemical properties of QDs are discussed and suggestions are provided for optimizing QDs design in view of minimal cytotoxicity. Finally, accurate detection techniques and systematic methodologies for the toxicity assessment of QDs are expected to achieve further breakthroughs in the future, especially in-situ, real-time, and rapid quantitative analysis methods.

Effect of chronic exposure to microplastic fibre ingestion in the sea cucumber Apostichopus japonicus

Microplastics (MPs) in the form of microfibres (MFs) are of great concern because of their size and increasing abundance, which increase their potential to interact with or be ingested by aquatic organisms. Although MFs are the dominant shape of MPs ingested by sea cucumbers in habitats, their effect on sea cucumbers remains unclear. This study examined the effect of dietary exposure to MFs on the growth and physiological status of both juvenile and adult Apostichopus japonicus sea cucumbers. MFs were mixed into the diet of sea cucumbers for 60 d at environmentally relevant concentrations of 0.6 MFs g^-1, 1.2 MFs g^-1 and 10 MFs g^-1. Dietary exposure to MFs, with concentrations at or above those commonly found in the habitats, did not significantly affect the growth and faecal production rate of either juvenile or adult sea cucumbers. However, a disruption in immunity indices (acid phosphatase and alkaline phosphatase activity) and oxidative stress indices (total antioxidant capacity and malondialdehyde content) was observed in juvenile and adult sea cucumbers, indicating that these indices might be useful as potential biomarkers of the exposure to MF ingestion in sea cucumbers. This study provides insights into the toxicity mechanism of MF ingestion in a commercially and ecologically important species.

NOD-like receptor signaling pathway activation: A potential mechanism underlying negative effects of benzo(α)pyrene on zebrafish

Benzo(α)pyrene (BaP) is one of typical polycyclic aromatic hydrocarbons (PAHs) in aquatic environments and has been shown to cause toxic effects to aquatic animals. Although the negative effects of BaP have been investigated, the potential toxic mechanisms remain uncharacterized. To explore the potential mechanisms mediating the toxic effects of BaP, zebrafish (Danio rerio) were exposed to BaP for 15 days and the toxic effects of BaP in zebrafish liver were investigated using physiological and transcriptomic analyses. After 15-day BaP exposure, zebrafish liver exhibited abnormalities including increased cytoplasmic vacuolation, inflammatory cell infiltration, swelled nuclei and irregular pigmentation. BaP exposure also induced oxidative stress to the liver of zebrafish. Transcriptomic profiles revealed 5129 differentially expressed genes (DEGs) after 15-days of BaP exposure, and the vast majority of DEGs were up-regulated under BaP treatment. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses suggest that genes related to immune response were significantly dysregulated. Furthermore, the nucleotide-binding, oligomerization domain (NOD)-like receptor signaling pathway was significantly enriched and most of the genes in this pathway exhibited enhanced expression after BaP exposure. These results partially explained the mechanisms underlying the toxic effects of BaP on zebrafish liver. In conclusion, BaP has the potential to induce physiological responses in zebrafish liver through altering associated genes.

Comparative transcriptome reveals the response of oriental river prawn (Macrobrachium nipponense) to sulfide toxicity at molecular level

Aquatic environmental pollutants have various impacts on aquaculture. Specifically, sulfide has been established as being toxic to aquatic animals including the oriental river prawn Macrobrachium nipponense. In response, the hepatopancreas has been broadly studied, as it plays a pivotal role in arthropod nutrient digestion and absorption, energy supply, and organ development as well as in crustacean immunity. However, the underlying molecular mechanisms of hepatopancreas's response to sulfide toxicity are still poorly understand. Herein, we used Nova-seq 6000 platform to conduct a comparative transcriptome analysis of gene expression profiles in the hepatopancreas of M. nipponense, while it was under the influence of a semi-lethal sulfide concentration (3.20 mg/L at 48 h). A total of 139 million raw reads were obtained, in which 67,602 transcripts were clustered into 37,041 unigenes for further analysis. After constant sulfide exposure for 48 h, 235 differentially expressed genes, i.e., DEGs (151 up-regulated and 84 down-regulated) were identified in the sulfide treatment group (TGHP) compared with the control group (CGHP). We used GO and KEGG databases to annotate all the DEGs into 1180 functions and 123 pathways, respectively. The metabolic pathways included proximal tubule bicarbonate reclamation, sulfur metabolism, glycolysis and gluconeogenesis, and the TCA cycle; while immune-related pathways contained Ras, Rap1, focal adhesion and platelet activation. Additionally, apoptosis-involved pathways e.g., lysosome, also exhibited remarkable alteration in the presence of sulfide stress. Notably, responses to external stimuli and detoxification genes- such as GSKIP, CRT2, APOD, TRET1, CYP4C3 and HR39- were significantly altered by the sulfide stress, indicating that significant toxicity was transferred through energy metabolism, growth, osmoregulatory processes and immunity. Finally, we demonstrated that in the present of sulfide stress, M. nipponense altered the expression of detoxification- and extracellular stimulation-related genes, and displayed positive resistance via tight junction activation and lysosome pathways. The results of these novel experiments shed light on the hepatopancreas's molecular response to sulfide stress resistance and the corresponding adaptation mechanism; and enable us to identify several potential biomarkers for further studies.

Hydroxylated polychlorinated biphenyls (OH-PCBs) exert strong inhibitory effects towards human carboxylesterases (CESs)

Polychlorinated biphenyls (PCBs) have been reported to pose a severe risk towards human health, and hydroxylated polychlorinated biphenyls (OH-PCBs) were potential substances basis for PCBs' toxicity. This study aims to determine the inhibition of OH-PCBs towards human carboxylesterases (CESs), including CES1 and CES2. For phenotypic analysis of CES1 and CES2 activity, we used the hydrolysis metabolism of 2-(2-benzoyl3-methoxyphenyl) benzothiazole (BMBT) and fluorescein diacetate (FD) catalyzed by human liver microsomes (HLMs) as the probe reactions. Preliminary inhibition screening showed that the inhibition potential of OH-PCBs towards CES1 and CES2 increased with the increased numbers of chlorine atoms in OH-PCBs. Both 2'-OH-PCB61 and 2'-OH-PCB65 showed concentration-dependent inhibition towards both CES1 and CES2. Lineweaver-Burk plots showed that 2'-OH-PCB61 and 2'-OH-PCB65 exerted non-competitive inhibition towards CES1 and competitive inhibition towards CES2. The inhibition kinetics parameters (Ki) were 6.8 μM and 7.0 μM for 2'-OH-PCB61 and 2'-OH-PCB65 towards CES1, respectively. The inhibition kinetics parameters (Ki) were 1.4 μM and 1.0 μM for 2'-OH-PCB61 and 2'-OH-PCB65 towards CES2, respectively. In silico docking methods elucidate the contribution of hydrogen bonds and hydrophobic contacts towards the binding of 2'-OH-PCB61 and 2'-OH-PCB65 with CES1 and CES2. All these results will provide a new perspective for elucidation of toxicity mechanism of PCBs and OH-PCBs.