Antioxidant enzyme activity in Daphnia magna under microscopic observation and shed carapace length as an alternative growth endpoint

Toxicity of antimony to Daphnia magna: Influence of environmental factors, development of biotic ligand approach and biochemical response at environmental relevant concentrations

Acute toxicity of antimony pentavalent to neonatal Daphnia magna and the influence of water quality parameters were investigated, and enzymatic activities of organisms at environmentally relevant levels of antimony were determined. EC50 values of antimony to neonatal D. magna were 90.3 and 63.8 mg/L at 24 and 48 h of exposure, respectively. Dissolved organic matter (FA and HA) and cation (Ca2+, Mg2+ or Na+) had significant protective effects on D. magna against antimony toxicity. With increasing pH in the range from 7.4 to 8.5, increase of EC50 were observed due to the competition of OH- on biotic ligands. Based on the biotic ligand model (BLM) concept, stability constants for the binding of Sb(OH)6- and OH- to the biotic ligand were estimated, and the Log [Formula: see text] - and LogKXOH- were 3.137 and 2.859, respectively. Moreover, antimony exposure in low concentrations significantly increased MDA levels and maybe exert oxidative stress to the organisms. Antimony can also induce toxicity in D. magna by affecting oxidative stress and neurotransmitter systems. The relatively comprehensive toxicological data can contribute to the toxicity prediction and ecological risk assessments of antimony.

Developmental toxicity in Daphnia magna induced by environmentally relevant concentrations of carbon black: From the perspective of metabolomics and symbiotic bacteria composition

The level of carbon black (CB) pollution in the environment is rapidly increasing, owing to the increase in natural and industrial emissions. The water environment has become an important sink for CB. However, studies on CB mainly focused on its impact on air pollution and phytoremediation applications, and the toxicity mechanism of CB in aquatic organisms is relatively limited. Thus, Daphnia magna was used as a model organism to explore the developmental toxicity of environmentally relevant concentrations of CB under a full life-cycle exposure. The toxicity mechanism of CB in aquatic organisms was investigated based on metabolomic and symbiotic microbial analyses. It was found that compared with the control group, the body length of exposed D. magna decreased, while the mortality and intestinal inflammation increased with increasing concentration of CB. The normal reproductive regularity of D. magna was disturbed, and the deformity and body length of the offspring increased and decreased, respectively, after CB exposure. Metabolomic analysis showed that the urea cycle metabolic pathway of exposed D. magna was increased significantly, suggesting a perturbation of N metabolism. In addition, two eicosanoids were increased, suggesting possible inflammation in D. magna. The levels of seven phospholipid metabolites decreased that might be responsible for offspring malformations. Microbiological analysis showed that the composition of the symbiotic microbial community of D. magna was disturbed, including microorganisms involved in carbon cycling, nitrogen cycling, and biodegradation of pollutants, as well as pathogenic microorganisms. Overall, this study found that the inflammatory related metabolites and symbiotic bacterial, as well as reproductive related metabolites, were disrupted after D. magna exposed to different concentrations of CB, which revealed a possible developmental toxicity mechanism of CB in D. magna. These findings provide a scientific basis for analyzing the risks of CB in aquatic environments.

In vitro assembly of the trehalose bi-enzyme complex with artificial scaffold protein

Introduction: Trehalose is a significant rare sugar known for its stable properties and ability to protect biomolecules from environmental factors. Methods: In this study, we present a novel approach utilizing a scaffold protein-mediated assembly method for the formation of a trehalose bi-enzyme complex. This complex consists of maltooligosyltrehalose synthase (MTSase) and maltooligosyltrehalose trehalohydrolase (MTHase), which work in tandem to catalyze the substrate and enhance the overall catalytic efficiency. Utilizing the specific interaction between cohesin and dockerin, this study presents the implementation of an assembly, an analysis of its efficiency, and an exploration of strategies to enhance enzyme utilization through the construction of a bi-enzyme complex under optimal conditions in vitro. Results and Discussion: The bi-enzyme complex demonstrated a trehalose production level 1.5 times higher than that of the free enzyme mixture at 40 h, with a sustained upward trend. Compared to free enzyme mixtures, the adoption of a scaffold protein-mediated bi-enzyme complex may improve cascade reactions and catalytic effects, thus presenting promising prospects.

Study on the role of AlOOH in fluorescence correction and depth purification of Cyclops water

Protein-like substances produced by biochemical reactions after disinfection of Zooplankton like Cyclops and humic substances in natural water are the main components of NOM (Natural organic matter). To eliminate early warning interference in the fluorescence detection of organic matter in natural water, a clustered flower-like AlOOH (aluminum oxide hydroxide) sorbent was prepared. HA (humic acid) and amino acids were selected as mimics of humic substances and protein-like substances in natural water. The results demonstrate that the adsorbent can selectively adsorb HA from the simulated mixed solution and restore the fluorescence properties of tryptophan and tyrosine. Based on these results, a stepwise fluorescence detection strategy was developed and used in natural water rich in zooplanktonic Cyclops. The results show that the established stepwise fluorescence strategy can well overcome the interference caused by fluorescence quenching. The sorbent was also used for water quality control to enhance coagulation treatment. Finally, trial runs of the water plant demonstrated its effectiveness and suggested a potential control method for early warning and monitoring of water quality.

Advances in the Utilization of Zebrafish for Assessing and Understanding the Mechanisms of Nano-/Microparticles Toxicity in Water

A large amount of nano-/microparticles (MNPs) are released into water, not only causing severe water pollution, but also negatively affecting organisms. Therefore, it is crucial to evaluate MNP toxicity and mechanisms in water. There is a significant degree of similarity between the genes, the central nervous system, the liver, the kidney, and the intestines of zebrafish and the human body. It has been shown that zebrafish are exceptionally suitable for evaluating the toxicity and action mechanisms of MNPs in water on reproduction, the central nervous system, and metabolism. Providing ideas and methods for studying MNP toxicity, this article discusses the toxicity and mechanisms of MNPs from zebrafish.

Adverse effects of polystyrene nanoplastic and its binary mixtures with nonylphenol on zebrafish nervous system: From oxidative stress to impaired neurotransmitter system

Micro(nano)plastics generally co-exist with other chemicals in the environment, resulting in inevitable interaction and combined toxic effects on biota. Nevertheless, little is known regarding the interaction of nanoplastics (NPs) with other co-occurring insults. Hereby, we investigated single and combined effects of chronic exposure (45 days) to polystyrene nanoplastic particulates (PS-NPs) and nonylphenol (4-NP) on zebrafish nervous system. Multiple biomarkers concerning with oxidative-stress [catalase (CAT) activity and reduced glutathione (GSH) level], cholinergic system [Acetylcholinesterase (AchE) activity], glutamatergic system [glutamine synthetase (GS) and glutamate dehydrogenase (GDH) activities], energy metabolism [a-ketoglutarate dehydrogenase (a-KGDH) activity], and histological alterations were assessed. Both single and binary exposure to PS-NPs and 4-NP induced oxidative stress through reducing CAT activity and GSH level, in which a more sever effect was noticed in combined exposure. The AchE activity was significantly inhibited only in single treatment groups demonstrating antagonistic interaction between PS-NPs and 4-NP. Effects on GS activity was also alleviated in binary exposure as compared with single exposure to each contaminant. In addition, an increase in GDH activity was noticed in PS-NPs at 10 and 100 μg/L, and simultaneous presence of PS-NPs and 4-NP with a greater response were observed in combined treatments. PS-NPs and 4-NP either in separate or binary mixtures disrupted energy metabolism by deficiency of α-KGDH activity; however, co-exposure to PS-NPs and 4-NP induced more intense adverse impacts on this parameter. Furthermore, histological analysis revealed that 4-NP and PS-NPs, alone or in combination, reduced neural cells. These findings provide new insight into the neurotoxic effects of binary exposure to PS-NPs and 4-NP at environmentally relevant concentrations. Overall, our findings raise concerns about the presence and toxicity of nano-scale plastic particulates and highlight the importance of investigating the interaction of Micro(nano)plastics with other environmental irritants.

Metabolomic analysis predicted changes in growth rate in Daphnia magna exposed to acetaminophen

As urbanization and the global population increases, pollutants associated with municipal wastewater such as pharmaceuticals are becoming more prevalent in aquatic environments. Acetaminophen (paracetamol) is a widely used drug worldwide and one of the most frequently detected pharmaceuticals in freshwater ecosystems. This study investigated the impact of acetaminophen on the metabolite profile of Daphnia magna at two life stages; and used these metabolomic findings to hypothesize a potential impact at a higher organismal level which was subsequently tested experimentally. Targeted polar metabolite analysis by liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to measure changes in the concentration of 51 metabolites in the neonate (> 24 h old) and adult (8 day-old) daphnids following a 48-h exposure to sub-lethal concentrations of acetaminophen. The impact of acetaminophen on the metabolic profile of neonates was widely different from adults. Also, acetaminophen exposure perturbed the abundance of nucleotides more extensively than other metabolites. The acute metabolomic experimental results led to the hypotheses that exposure to sub-lethal concentrations of acetaminophen upregulates protein synthesis in D. magna and subsequently increases growth during early life stages and has an opposite impact on adults. Accordingly, a 10 day growth rate experiment indicated that exposure to acetaminophen elevated biomass production in neonates but not in adults. These novel findings demonstrate that a targeted analysis and interpretation of the changes in the polar metabolic profile of organisms in response to environmental stressors could be used as a tool to predict changes at higher biological levels. As such, this study further emphasizes the incorporation of molecular-level platforms as critical and robust tools in environmental assessment frameworks and biomonitoring of aquatic ecosystems.

Behavior and toxicity assessment of copper nanoparticles in aquatic environment: A case study on red swamp crayfish

With the wide use of copper nanoparticles (CuNPs) in various industrial and commercial applications, they inevitably enter the aquatic environment. However, their behavior in the aquatic environment and potential toxicity to aquatic organisms remain little known. In this study, we investigated the behavior of CuNPs in freshwater, as well as the toxicity and bioaccumulation of CuNPs and copper sulfate (CuSO₄), used as a positive control for copper ions toxicity, in red swamp crayfish (Procambarus clarkii). The results showed that CuNPs released copper ions into freshwater and aggregated rapidly in freshwater, and their release of copper ions and aggregation slowed down at a higher concentration of CuNPs. The calculated 72-h LC₅₀ values for crayfish were 1.18 and 0.54 mg/L for CuNPs and CuSO₄, respectively. Cu accumulation in the gill and hepatopancreas from CuSO₄ treatments was significantly higher than that from CuNPs, and the highest Cu bioaccumulation level in crayfish was found in the gill, followed by hepatopancreas and muscle with the exposure of copper. The activities of the antioxidative enzymes in the crayfish significantly decreased after exposure to CuNPs for 48 h, compared to the control (without CuNPs or CuSO₄). Histological examination revealed that there was no significant alteration of hepatopancreas in the crayfish exposed to CuNPs. Meanwhile, the growth of crayfish was not significantly inhibited by CuNPs. These results suggested that CuNPs exposure can induce oxidative stress in the crayfish, gill is the main tissue for their accumulation, and their toxicity is mainly caused by the released copper ions.

Effect of Copper Nanoparticles and Ions on Epididymis and Spermatozoa Viability of Chinese Soft-Shelled Turtles Pelodiscus sinensis

Copper nanoparticles (CuNPs) have been widely used in various industrial and commercial applications, which become a potential threat to aquatic organisms. Nevertheless, their potential toxicity to the epididymis and sperm remains little known. In this study, we evaluated the effect of CuNPs and copper ions (CuSO4) on the spermatozoa viability, epididymal structure, antioxidant enzyme activity, and inflammatory cytokines in cauda epididymis of the Chinese soft-shelled turtle. Results showed that the spermatozoa viability of Chinese soft-shelled turtles decreased significantly with an increase in CuNPs or Cu ions concentrations. The epithelial cells of the epididymal duct of the Chinese soft-shelled turtles with the treatment of 5 mg kg−1 CuNPs were slightly swollen, and the connective tissue between the epididymal ducts was loose. The epithelial structure of the epididymal tube was severely damaged with an increase in Cu ion concentrations. Compared to the control, the antioxidative enzymes activities and the expression of IL-1β, TNF-α, and IL-6 mRNA in the epididymis significantly increased with the treatment of CuNPs or CuSO4. The present study revealed that Cu ions exert more harmful effect on the epididymis and spermatozoa viability of Chinese soft-shelled turtles than copper nanoparticles.