Concentration-dependent effects of lithium on Daphnia magna: Life-history profiles and integrated biomarker response implementation

The growing use of lithium (Li) in industrial and energy applications and increasing demand worldwide has inevitably resulted in its wide dispersal, representing a significant threat to aquatic systems. Unfortunately, as a ubiquitous emerging contaminant, the comprehensive toxicological information regarding Li at multifarious levels is limited. To diminish this gap, this work was focused to explore Li-induced cascading effects on Daphnia magna as a key species in freshwater ecosystems. Specifically, the organisms were chronically exposed to gradient Li concentrations with emphasis on characterizing life-history traits from individual to population scale, primarily as observed by a markedly concentration-dependent decrease along exposure gradients. In parallel, a robust set of biomarkers relating to energy reserves, antioxidant and biotransformation enzymes, cellular damage, ionoregulation and neurotoxicity were assayed for further understanding potential underlying mechanisms. As a result, biomarker alterations were characterized by significant decreases in energy storage and enzymatic profiles of antioxidant and biotransformation systems, not only triggering an imbalance between reactive oxygen species (ROS) generation and elimination under Li exposure, but compromising the fecundity fitness of phenotypical costs. In contrast, malondialdehyde (MDA) levels were remarkably enhanced as a consequence of inefficient antioxidant and biotransformation capacity leading to lipid peroxidation (LPO). Additionally, Li exerted a dose-dependent biphasic effect on the activities of superoxide dismutase (SOD), Na+,K+-ATPase and acetylcholinesterase (AChE) by interfering with inherent balance. In terms of responsive patterns and dose-effect trends, the integrated biomarker response indices (IBRv2) and star plots were consistent with the differences in biomarker profiles, not only presenting comprehensively biological effects in a visualized form, but signaling the importance of progressive induced changes in an integrative way. Overall, these findings highlighted the need for elucidating Li-produced impacts from a comprehensive perspective, providing valuable insights into better understanding the toxicity of Li in relation to aquatic ecosystem functioning and ecological relevance.

Integrated biomarker responses: a further improvement of IBR and IBRv2 indexes to preserve data variability in statistical analyses

In biomonitoring and laboratory studies, it is typical to measure a battery of molecular, biochemical, and cytogenetic biomarkers to evaluate the effects of xenobiotics in biota. However, summarizing the results of several biomarkers to inform laypersons and environmental agencies is still a challenge for researchers and environmental specialists. To address this issue, researchers have developed indexes such as the Integrated Biomarker Responses (IBR) and Integrated Biomarker Response version 2 (IBRv2) to summarize all biomarkers responses into a single value. Unfortunately, these indexes do not preserve the original biological variability, which hampers subsequent statistical analyses. In this study, we created new versions of IBR and IBRv2, which preserve individual data variability and can be used in typical statistical analyses. The new Integrated Biomarker Responses individual (IBRi), Integrated Biomarker Responses version 2 individual (IBRv2i) and Weighted Integrated Biomarker Responses version 2 individual (Weighted IBRv2i) indexes correlated with the original IBR and IBRv2 indexes and were able to detect differences among experimental groups in a simulated and case studies. Using the IBRi, IBRv2i, or Weighted IBRv2i indexes is advantageous because they maintain the data variability of the experimental groups and can be analyzed using hypothesis testing statistics like any other parameter. Additionally, this approach can help translate technical scientific terminology into a more accessible language suitable for environmental governmental agencies and decision-makers.

Responses and detoxification mechanisms of earthworm Amynthas hupeiensis to metal contaminated soils of North China

Metal contamination is widespread, but only a few studies have evaluated the toxicological risks of metals (Cd, Cu, and Pb) in earthworms from farmlands in North China (Hebei province). Amynthas hupeiensis, the dominant species in the study area, was used to determine the responses and detoxification mechanisms of uncontaminated (CK), and low (LM)-, and high (HM)-metal-contaminated soils following 7-, 14-, and 28-days exposure. Metal toxicity in LM and HM soils inhibited the biomass of A. hupeiensis. The concentrations of Cd in A. hupeiensis bodies indicated accumulated Cd appeared to remain steady with prolonged exposure, while Cu/Pb increased significantly with soil levels. Bioaccumulation occurred in the order Cd > Pb > Cu in LM soil, and in the order Cd > Cu ≈ Pb in HM soil, which was attributed to differences in available fractions between LM and HM soils. Physiological levels of biomarkers in A. hupeiensis were determined, including total protein (TP), glutathione (GSH), glutathione peroxidase (GPx), acetylcholinesterase (AChE), and malondialdehyde (MDA). Deviations in GSH, GPx, and AChE were considered to denote sensitive biomarkers using the IBRv2 index. Metabolomics data (1H nuclear magnetic resonance-based) revealed changes in metabolites following 28-days exposure to LM and HM soils. Differences in metabolism in A. hupeiensis following exposure to LM and HM were related to energy metabolism, amino acid biosynthesis, glycerophospholipid metabolism, inositol phosphate metabolism, and glutathione metabolism. Metal stress from LM and HM soils disturbed osmoregulation, resulting in oxidative stress, destruction of cell membranes and inflammation, and altered levels of amino acids required for energy by A. hupeiensis. These findings provide biochemical insights into the physiological and metabolic mechanisms underlying the ability of A. hupeiensis to resist metal stress, and for assessing the environmental risks of metal-contaminated soils in farmland in North China.

Metabolism toxicity and susceptibility of decabromodiphenyl ether (BDE-209) exposure on BRL cells with insulin resistance

Type 2 diabetes mellitus (T2DM) is a metabolic disease characterized by insulin resistance (IR) and has attracted worldwide attention due to its high prevalence. As a typical persistent organic pollutant, decabromodiphenyl ether (BDE-209) has been detected in food and human samples, and the concentration trends increase year by year. In addition, it has been proved to have the potential to increase the risk of IR, but it is rarely reported whether it could aggravate IR in T2DM. Therefore, in this study, the IR-BRL (buffalo rat liver cells with IR) model was applied to study the metabolism toxicity and susceptibility of BDE-209. Results showed that BDE-209 could inhibit glucose absorption and increase the levels of serum total cholesterol (TC) and triglyceride (TG), ultimately leading to the disorder of glucolipid metabolism in IR-BRL cells. Besides, it also could cause cell damage by increasing the levels of aspartate transaminase (AST), alanine aminotransferase (ALT), and malondialdehyde (MDA) in cells. Moreover, its potential mechanisms were to: (1) affect the transport of glucose, synthesis of glycogen and fatty acid via IRS-1/GLUT4 and IRS-1/PI3K/AKT/GSK-3β pathways; (2) impact the proliferation and differentiation by regulating the expression of Mek1/2, Erk1/2, and mTOR proteins and genes. Furthermore, susceptibility analysis showed that there was a significant synergism interaction between IR and BDE-209, which suggested that IR-BRL cells were more susceptible to the metabolism toxicity induced by BDE-209.

Spatial distribution of benthic toxicity and sediment-bound metals and arsenic in Guangzhou urban waterways: Influence of land use

The effects of land use on pollutant loads in sediments have been well documented; however, its influence on spatial variations in sediment toxicity remains largely unknown. In the present study, the toxicological effects of 17 sediments collected from Guangzhou waterways were evaluated using two benthic invertebrates (Chironomus dilutus and Hyalella azteca), along with quantification of heavy metals and arsenic in the sediments. The impacts of land-use configuration on sediment toxicity and occurrence of heavy metals and arsenic were analyzed. The sediments presented moderate lethality (<40 %) in the two test species and significantly altered their enzymatic activity, including the activities of oxidative stress biomarkers and acetylcholine esterase. Metals (Ag, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) and arsenic were detected in all the sediments, with total concentrations ranging from 238 to 1019 mg/kg of dry weight. Both the toxicity and chemical results displayed spatially dependent patterns but were related to different land use types. Toxicity was most influenced by agricultural and aquacultural activities, while metal and arsenic pollution was most influenced by urban land areas. The present findings are expected to provide essential knowledge for developing strategies that reduce the chemical pollution and ecotoxicological risk in sediments.

Effects of short-term exposure to tralopyril on physiological indexes and endocrine function in turbot (Scophthalmus maximus)

Tralopyril is an emerging marine antifouling agent with potential toxic effects on non-target aquatic organisms. To evaluate the toxicity of tralopyril, to turbot (Scophthalmus maximus), we assessed biomarkers, including oxidative stress, neurotoxicity, and osmotic homeostasis regulation enzymes, after a 7-day exposure to tralopyril (5 μg/L, 15 μg/L, 30 μg/L). Superoxide dismutase activity was significantly decreased at 30 μg/L, and Ca²⁺-Mg²⁺-ATPase activity in the gills was significantly increased at 15 μg/L and 30 μg/L. No statistically significant differences in the responses of acetylcholinesterase and nitric oxide were detected. In addition, 15 μg/L and 30 μg/L tralopyril induced hyperthyroidism, reflected by significantly increased of T3 levels. The expression levels of hypothalamus-pituitary-thyroid axis-related genes were also upregulated. The molecular docking results showed that the thyroid system disruption was not caused by competitive binding to the receptor. In addition, the integrated biomarker response index showed that 15 μg/L tralopyril had the greatest effect on turbot. In general, tralopyril caused oxidative damage, affected energy metabolism, and interfered with the endocrine system. These findings could provide reference data for assessing the ecological risk of tralopyril in marine environments.

Short-term exposure of decabromodiphenyl ether in female adult Balb/c mice: Immune toxicity and self-recovery

As a typical persistent organic pollutant, decabromodiphenyl ether (BDE-209) is associated with various health risks, especially on immune system, which is sensitive to environmental pollutants. In addition, there is a problem of multi-index estimation and lack of comprehensive evaluation in immune toxicity study. In this study, the immunotoxicity of BDE-209 was systematically estimated from the aspects of immunopathology, humoral immunity, cellular immunity and non-specific immunity, etc., and integrated biomarker responses (IBR) combined with principal component analysis was applied to comprehensively evaluate the immunotoxicity of BDE-209 and its self-recovery after discontinuation. Results showed that BDE-209 exposure could cause immunotoxicity. This response seems to depend on (1) atrophying immune organs (thymus and spleen), hepatomegaly accompanied by increasing aspartate aminotransferase and oxidative stress;(2) changing humoral (immunoglobulins) and cellular (lymphocyte proliferation and cytokine secretion) immunity indices; (3) altering related expressions of genes, and further leading to imbalance of Th1/Th2 (Th, helper T cell). Integrated biomarker responses (IBR) companied with principal component analysis selected five biomarkers (mRNA expression of GATA-3, malondialdehyde level in thymus, count of white blood cell, serum IgG and lipopolysaccharide-induced splenic lymphocyte proliferation) to clarify the immunotoxicity induced by BDE-209. Furthermore, IBR combined with factorial analysis revealed that the effect of BDE-209 could be dose-dependently reduced after withdrawal of BDE-209. Overall results suggested that BDE-209 has immunotoxicity on adult Balb/c mice, whereas this immunotoxicity could be reduced by the self-regulation of organisms to some extent.

Evaluating environmental impact of STP effluents on receiving water in Beijing by the joint use of chemical analysis and biomonitoring

To evaluate the environmental impact of receiving water from the Qinghe River sewage treatment plant (STP) effluents in Beijing, we collected sediments and Bellamya aeruginosa (Up-site, Discharge-site, and Down-site) both in 2017 and 2018 and analyzed the samples via chemical analysis, biological responses and transcriptomics. In two years of data, our biological results showed that AChE activities presented different degrees of influence on B. aeruginosa captured at sampling points of the STP compared to control sites (P < 0.05). Additionally, indicators of the antioxidant system (e.g., SOD, CAT, GST, EROD activity) and MDA content were significantly increased in the whole tissue at the Up-site of the STP. Integration of the assessed biomarkers using the integrated biomarker response (IBR) index ranked the environmental impact at sites as Up-site > Discharge-site > Down-site. In terms of the transcriptome data, B. aeruginosa collected from the Discharge-site of the STP showed greater transcriptomic response than it did from all other sites. KEGG pathway analysis revealed that sewage significantly altered the expression of genes involved in xenobiotics by cytochrome P450, drug metabolism-cytochrome P450, glutathione metabolism, oxidative phosphorylation, citrate (TCA) cycle, glycolysis/gluconeogenesis, apoptotic and Parkinson's disease. The concentrations of 34 organic pollutants (17 PAHs, 10 PAEs, 7 EDCs) were measured. The chemical concentrations of pollutants decreased from Up-site to Down-site and were well correlated with enzyme activity, IBR, and transcriptomic results. Our results demonstrated that the combined use of chemical analysis, biological responses and transcriptome data is necessary to validate the efficacy of a battery of biomarkers chosen to detect environmental stress due to pollution.

A multilevel response approach reveals the Asian clam Corbicula largillierti as a mirror of aquatic pollution

The endobenthic bivalves are widely used as a bioindicators since they inhabit the sediment-water interface and are able to accumulate a different kind of contaminants. In the present work, we evaluated wild Corbicula largillierti (Phillippi, 1844) as a bioindicator of water quality in the central region of Argentina. The responses at different levels of the biological organization were used. We measured organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) levels in water and clams tissues. The biomarkers selected were enzymatic activities (Glutathione S-Transferase, Catalase, Acetyl-, Butyryl-cholinesterase, and Carboxylesterase) morphometry of the digestive gland, condition index and morphology of valves. In order to integrate all the responses a multivariate analysis and integrated stress index were applied. Our results showed the presence of contaminants along the studied river and the ability of C. largillierti to bioaccumulate them. All the biomarkers selected varied according to the water quality gradient, although there was no specific correlation with OCPs and PCBs levels. At the most polluted sites, the detoxification and oxidative stress enzymes, the morphometric analysis of the digestive gland and the variation in the morphology of the valves indicated the water quality degradation. The multivariate analyses allowed to discriminate the sites according to the different biomarker responses. The IBR index also showed a variation pattern according to the environmental quality gradient along the basin. According to the responses shown by C. largillierti we suggest this species as an useful bioindicator of aquatic pollution.

Heavy metal accumulation, risk assessment and integrated biomarker responses of local vegetables: A case study along the Le'an river

In this research, Ganzhou Chinese Cabbage (Brassica rapa pekinensis), Native Purple Garlic (Allium sativum L) and Leping Radish (Raphanus sativus L) widely planted and distributed along the Le'an River were chosen in the present study. Soil physical-chemical properties, nutrients contents as well as heavy metals elements accumulated in both soils and vegetables collected from 24 sites were analyzed by lab analysis combined with statistical method which was also used for calculation of contamination factor, pollution indexes and hazardous index. Heavy metals accumulation in soils were revealed with higher level, and copper and cadmium exceeded the background values by 8.82 and 16.73 times on average, which were also significantly related with the distribution of nonferrous metal processing enterprises. Heavy metal elements accumulated in vegetables were fully consistent with the finding of pollution characteristics in soils. Peroxidase biomarkers in vegetables, including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), reduced glutathione (GSH) and lipoperoxidation (as TBARS), as well as integrated biomarker responses (IBR) were determined to give a reliable response after exposing of contaminants. Heavy metals accumulation ability and biomarker responses for three vegetables were usually determined in the following decrease trend: Ganzhou Chinese Cabbage > Native Purple Garlic > Leping Radish. Compared with peroxidase biomarkers activities or contents of control site, all the measured biomarkers in polluted sites showed significantly responses, indicating potential relationship between pollutants stresses and biomarker responses. This study also revealed that the IBR values were coordinated well with the pollutants concentrations.