PFOA and PFOS interact with superoxide dismutase and induce cytotoxicity in mouse primary hepatocytes: A combined cellular and molecular methods

Per- and polyfluoroalkyl substances in environment and potential health impacts: Sources, remediation treatment and management, policy guidelines, destructive technologies, and techno-economic analysis

Per- and polyfluoroalkyl Substances (PFAS), also known as forever chemicals and ubiquitous persistence, pose significant public health challenges due to their potential toxicity, particularly in drinking water and soil contamination. However, PFAS occurrence and their concentrations in different environmental matrices vary globally, but factors influencing trends, transport, fate, toxicity, and interactions with co-contaminants remain largely unexplored. Therefore, this review critically examines the state-of-the-art worldwide PFAS sources, distribution, and pathways, and evaluates how PFASs are processed in wastewater treatment, generally, which causes severe problems with the quality and safety of drinking water. Importantly, the review also underscores health issues due to PFAS consumption and recent research trends on developing effective treatment strategies to manage PFAS contamination. Potential effects of PFAS were linked to urban land use and the proportion of wastewater effluent in streamflow. Besides, major emphasis was provided on challenges for conventional treatment, destructive technologies, environmental accumulation, precursor transformation, and cost-investment related to PFAS removal technologies. To combat PFAS contamination, this review proposes a framework that promotes the comprehensive identification of prevalent compounds, with a focus on their eradication through knowledge-based and targeted analysis. Additionally, it explores the ongoing debate surrounding PFAS laws and legal frameworks, offering ideas for enhancing contamination management. Lastly, this review provides a strategic plan for improving response and preparedness, serving as a foundation for addressing future environmental challenges and informing health risk assessments.

Research Progress in Current and Emerging Issues of PFASs' Global Impact: Long-Term Health Effects and Governance of Food Systems

Per- and polyfluoroalkyl substances (PFASs) are found everywhere, including food, cosmetics, and pharmaceuticals. This review introduces PFASs comprehensively, discussing their nature and identifying their interconnection with microplastics and their impacts on public health and the environment. The human cost of decades of delay, cover-ups, and mismanagement of PFASs and plastic waste is outlined and briefly explained. Following that, PFASs and long-term health effects are critically assessed. Risk assessment is then critically reviewed, mentioning different tools and models. Scientific research and health impacts in the United States of America are critically analyzed, taking into consideration the Center for Disease Control (CDC)'s PFAS Medical Studies and Guidelines. PFAS impact and activities studies around the world have focused on PFAS levels in food products and dietary intake in different countries such as China, European countries, USA and Australia. Moreover, PFASs in drinking water and food are outlined with regard to risks, mitigation, and regulatory needs, taking into account chemical contaminants in food and their impact on health and safety. Finally, PFAS impact and activities briefings specific to regions around the world are discussed, referring to Australia, Vietnam, Canada, Europe, the United States of America (USA), South America, and Africa. The PFAS crisis is a multifaceted issue, exacerbated by mismanagement, and it is discussed in the context of applying the following problem-solving analytical tools: the Domino Effect Model of accident causation, the Swiss Cheese Theory Model, and the Ishikawa Fish Bone Root Cause Analysis. Last but not least, PFASs' impacts on the Sustainable Development Goals (SDGs) of 2030 are rigorously discussed.

Critical new insights into the interactions of hexafluoropropylene oxide-dimer acid (GenX or HFPO-DA) with albumin at molecular and cellular levels

A key characteristic to be elucidated, to address the harmful health risks of environmental perfluorinated alkyl substances (PFAS), is their binding modes to serum albumin, the most abundant protein in blood. Hexafluoropropylene oxide-dimer acid (GenX or HFPO-DA) is a new industrial replacement for the widespread linear long-chain PFAS. However, the detailed interaction of new-generation short-chain PFAS with albumin is still lacking. Herein, the binding characteristics of bovine serum albumin (BSA) to GenX were explored at the molecular and cellular levels. It was found that this branched short-chain GenX could bind to BSA with affinity lower than that of legacy linear long-chain perfluorooctanoic acid (PFOA). Site marker competitive study and molecular docking simulation revealed that GenX interacted with subdomain IIIA to form BSA-GenX complex. Consistent with its weaker affinity to albumin protein, the cytotoxicity of branched short-chain GenX was less susceptible to BSA binding compared with that of the linear long-chain PFOA. In contrast to the significant effects of strong BSA-PFOA interaction, the weak affinity of BSA-GenX binding did not influence the structure of protein and the cytotoxicity of GenX. The detailed characterization and direct comparisons of serum albumin interaction with new generation short-chain GenX will provide a better understanding for the toxicological properties of this new alternative.

Protective Effects of Resveratrol Against Perfluorooctanoic Acid-Induced Testicular and Epididymal Toxicity in Adult Rats Exposed During Their Prepubertal Period

The antioxidant properties of resveratrol (RES) against oxidative toxicity induced by testicular toxicants are well documented. The current study aimed to investigate the probable beneficial role of RES on male reproduction in adult rats following prepubertal exposure to perfluorooctanoic acid (PFOA). Healthy rats of the Wistar strain (23 days old) were allocated into four groups. Rats in group I did not receive any treatment, while rats in groups II, III, and IV received RES, PFOA, and RES + PFOA, respectively, between days 23 and 56 and were monitored for up to 90 days. Exposure to PFOA resulted in a significant reduction in spermiogram parameters, testicular 3β- and 17β-HSD activity levels, and circulatory levels of testosterone. A significant elevation in LPx, PCs, H2O2, and O2-, associated with a concomitant reduction in SOD, CAT, GPx, GR, and GSH, was noticed in the testes, as well as region-specific changes in pro- and antioxidants in the epididymides of exposed rats compared to controls. A significant increase in serum FSH and LH, testicular cholesterol levels, and caspase-3 activity was observed in PFOA-exposed rats compared to controls. Histological analysis revealed that the integrity of the testes was deteriorated in PFOA-exposed rats. Transcriptomic profiling of the testes and epididymides revealed 98 and 611 altered genes, respectively. In the testes, apoptosis and glutathione pathways were disrupted, while in the epididymides, glutathione and bile secretion pathways were altered in PFOA-exposed rats. PFOA exposure resulted in the down-regulation in the testes of 17β-HSD, StAR, nfe2l2, ar, Lhcgr, and mRNA levels, associated with the up-regulation of casp3 mRNA, and down-regulation of alpha 1 adrenoceptor, muscarinic choline receptor 3, and androgen receptor in the epididymides of exposed rats compared to the controls. These events might lead to male infertility in PFOA-exposed rats. In contrast, restoration of selected reproductive variables was observed in RES plus PFOA-exposed rats compared to rats exposed to PFOA alone. Taken together, we postulate that prepubertal exposure to PFOA triggered oxidative damage and altered genes in the testes and epididymides, leading to suppressed male reproductive health in adult rats, while RES, with its steroidogenic, antiapoptotic, and antioxidant effects, restored PFOA-induced fertility potential in rats.

Perfluorooctanoic Acid Induces Ferroptosis in Hepatocytes via Oxidative Stress and AKT/GSK3β/β-Catenin Pathway Disruption

Perfluorooctanoic acid (PFOA), a typical environmental contaminant, has been observed in tissue samples of various diseases, including liver cancer. PFOA can lead to hepatotoxicity, but the underlying molecular mechanism remains unclear. Our results showed that PFOA significantly inhibited HL-7702 (L02) and MIHA cell viability in a time- and dose-dependent manner. Furthermore, PFOA could cause oxidative stress, mitochondrial injury, and ferroptosis. In addition, PFOA upregulated the levels of malondialdehyde and glutathione/oxidized glutathione and downregulated the expressions of SLC7A11 and GPX4, which refer to typical phenotypes of ferroptosis. PFOA suppressed phosphorylation of signaling cascades AKT/GSK3β/β-catenin, indicating the signal pathway might be related to ferroptosis. In order to prove the above hypothesis, the Wnt signaling pathway activator chir99021 was used and the result revealed that PFOA-induced inhibition of p-AKT and its downstream effectors p-GSK3β, SLC7A11, and GPX4 was counteracted. On the other hand, the inhibitor of p-AKT, Ly294002, strengthened PFOA's regulatory actions on these factors. Overall, our results suggest that PFOA can lead to liver cell injury by inducing oxidative stress and ferroptosis. The effects are conferred through the regulation of the AKT/GSK3β/β-catenin signaling cascades.

Understanding the effects of perfluorobutane sulfonate in zebrafish larvae model (Danio rerio): Insights into potential ecotoxicological risks and human health

Perfluorobutane sulfonate (PFBS) is a synthetic organic molecule that belongs to the per and polyfluoroalkyl substances family. Due to its unique physicochemical characteristics, PFBS has been extensively used in consumer products and industries. However, its increasing usage and chemical stability cause environmental pollution and bioaccumulation. The toxicological effects of PFBS were not well studied. In this study, the impact of PFBS on zebrafish embryos was evaluated. PFBS (1000-1500 μM) exposure exhibited increased mortality and malformation in a concentration-dependent manner. After 96 hour post-fertilization of PFBS exposure, the LC50 was estimated to be 1378 μM. Furthermore, PFBS (1.4, 14, 140, 1400 μM) exposure significantly increases oxidative stress by suppressing antioxidant levels. Locomotor behavior analysis revealed that PFBS exposure caused locomotor changes in zebrafish larvae. Acetylcholine esterase activity was also reduced in the PFBS-exposed groups. Gene expression study showed that PFBS exposure downregulated the antioxidant gene expression in zebrafish larvae. Overall, the current study reveals that PFBS can trigger oxidative stress-induced apoptosis by reducing antioxidant activity in zebrafish larvae.

New mechanistic insights into soil ecological risk assessment of arsenite (III) and arsenate (V)：Cellular and molecular toxicity responses in Eisenia fetida

Inorganic arsenic (iAs) is a persistent bioaccumulation carcinogen that is most abundant in soils in the form of arsenite-As (III) and arsenate-As (V). However, there is currently very little explicit evidence about cytotoxicity of As on soil organisms. Moreover, toxicological data for iAs and proteotoxicity is shortage. The purpose of the present work is to elucidate the cytotoxicity mechanism of As (III) and As (V) to earthworms, a soil ecological sentinel species, and the molecular mechanisms by which As (III)/As (V) directly bind to antioxidative enzyme Cu/Zn-superoxide dismutase (Cu/Zn-SOD). Results indicate that iAs triggered cell membrane injury and genotoxicity. As (V) (56.15 %) induced lower cell viability than As (III) (61.88 %). Higher ROS and lipid peroxidation level in As (V) support greater cytotoxicity. Differences in cellular uptake due to valence induced diverse levels of oxidative stress and cytotoxicity. At the molecular level, As (III) (129.33 %) induced higher Cu/Zn-SOD activity than As (V) (110.75 %). Changes in backbone, secondary structure, amino acid microenvironment and particle size of Cu/Zn-SOD further revealed the mechanisms of differential molecular toxicity of As (III) and As (V). Binding reactions with Cu/Zn-SOD explain differences in molecular toxicity. Collective research showed that iAs-induced oxidative stress and binding reactions determine the difference of SOD activity between As (III) and As (V) at the cellular level. This work offers new insights into the health risk assessment of As.

SAP130 mediates crosstalk between hepatocyte ferroptosis and M1 macrophage polarization in PFOS-induced hepatotoxicity

Perfluorooctane sulfonate (PFOS) is a persistent organic pollutant widely utilized in industrial manufacturing and daily life, leading to significant environmental accumulation and various public health issues. This study aims to characterize spliceosome-associated protein 130 (SAP130) as a key mediator of crosstalk between hepatocytes and macrophages, elucidating its role in PFOS-induced liver inflammation. The data demonstrate that PFOS exposure induces ferroptosis in mouse liver and AML12 cells. During ferroptosis, SAP130 is released from injured hepatocytes into the microenvironment, binding to macrophage-inducible C-type lectin (Mincle) and activating the Mincle/Syk signaling pathway in macrophages, ultimately promoting M1 polarization and exacerbating liver injury. Treatment with the ferroptosis inhibitor Ferrostatin-1 reduces SAP130 release, inhibits Mincle/Syk signaling activation, and mitigates inflammatory response. Furthermore, siSAP130 suppresses the activation of the Mincle signaling pathway and M1 polarization in BMDM cells. Conversely, treatment with the ferroptosis agonist Erastin enhances paracrine secretion of SAP130 and exacerbates inflammation. These findings emphasize the significance of hepatocyte-macrophage crosstalk as a critical pathway for PFOS-induced liver injury in mice while highlighting SAP130 as a pivotal regulator of ferroptosis and inflammation, thereby elucidating the potential mechanism of PFOS-induced liver injury.

Integrated non-targeted metabolomics and lipidomics reveal mechanisms of fluorotelomer sulfonates-induced toxicity in human hepatocytes

Fluorotelomer sulfonates (FTSs) are widely used as novel substitutes for perfluorooctane sulfonate, inevitably leading to FTSs accumulation in various environmental media and subsequent exposure to humans. This accumulation eventually poses environmental hazards and health risks. However, their toxicity mechanisms remain unclear. Herein, the mechanisms of two FTSs (6:2 and 8:2 FTS) induced toxicity in human hepatocellular carcinoma cells were investigated via non-targeted metabolomics and lipidomics based on liquid chromatography-high resolution mass spectrometry. Our results revealed that amino acid, purine, acylcarnitine and lipid levels were significantly perturbed by 6:2 and 8:2 FTS exposure. The effects of 8:2 FTS exposure were largely characterized by up-regulation of pyruvate metabolism pathway and down-regulation of purine metabolism pathway, whereas the opposite trends were induced by 6:2 FTS exposure. The opposite trends were confirmed by the mRNA expression levels of four key genes (glyoxalase 1, adenylosuccinate lyase, inosine monophosphate dehydrogenase 1 (IMPDH1) and IMPDH2) determined by real-time PCR. Common lipid perturbations included significantly increased ceramide/sphingomyelin ratios, and obvious accumulation of hexosylceramides and lysoglycerophospholipids. 6:2 FTS exposure induced sharp accumulation of glycerides, including monoglycerides, diglycerides and triglycerides. 8:2 FTS exposure induced decreased levels of acylcarnitines and fatty acids. Both of 6:2 and 8:2 FTS exposure induced increased levels of intracellular reactive oxygen species, an imbalance in energy metabolism homeostasis, and mitochondrial dysfunction. The results of integrated omics analysis are expected to serve as valuable information for the health risk assessment of 6:2 FTS and 8:2 FTS.

Combined environmental relevant exposure to perfluorooctanoic acid and zinc sulfate enhances apoptosis through binding with endogenous antioxidants in Daphnia magna

Perfluorooctanoic acid (PFOA) is a long-chain legacy congener of the per- and polyfluoroalkyl substances (PFAS) family, notorious as a "forever chemical" owing to its environmental persistence and toxic nature. Essential elements such as zinc (Zn) can cause toxic effects when they change their metal speciation and become bioavailable, such as zinc sulfate (ZnSO4). Combined toxicity assessment is a realistic approach and a challenging task to evaluate chemical interactions and associated risks. Therefore, the present study aims to elucidate the acute mixture toxicity (12-48 h) of PFOA and ZnSO4 in Daphnia magna at environment-relevant concentrations (ERCs, low dose: PFOA 10 μg/L ZnSO4 20 μg/L; high dose: PFOA 20 μg/L ZnSO4 50 μg/L) in terms of developmental impact, apoptosis induction, and interaction with major endogenous antioxidants. Our results showed that deformity rates significantly increased (p < 0.05) with increasing exposure duration and exposure concentrations, compared to the control group. Further, lack of antenna, tale degeneration, and carapace alterations were the most commonly observed deformities following combined exposure to PFOA and ZnSO4, and these malformations were particularly pronounced after 48 h of exposure. Acridine orange (AO) staining was employed to examine apoptosis in D. magna, and apoptotic cells in terms of bright green fluorescence were detected in the abdominal claw carapace, heart, and post-abdominal area following exposure to a high dose of PFOA and ZnSO4. The molecular docking results revealed that both PFOA and ZnSO4 showed strong binding affinities with endogenous antioxidants CAT and GST, where PFOA was more strongly bound with CAT and GST with higher docking scores of -9.59 kcal/mol and -7.49 kcal/mol than those with ZnSO4 (-6.70 kcal/mol and -6.55 kcal/mol, respectively). In conclusion, the mixture exposure to PFOA and ZnSO4 at the environmental level induce developmental impacts and apoptosis through binding with major endogenous antioxidants in D. magna.

Identification of sanguinarine as a novel antagonist for perfluorooctanoate/perfluorooctane sulfonate-induced senescence of hepatocytes: An integrated computational and experimental analysis

Perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS), two prominent per- and polyfluoroalkyl substances (PFASs), are potentially harmful to many human organs. However, there only exist limited methods to mitigate their health hazards. The aim of this study is to combine a bioinformatics analysis with in vitro experiments to discover small molecules that can alleviate liver damage caused by PFOA/PFOS. We identified 192 and 82 key genes related to hepatocytes exposed to PFOA and PFOS, respectively. The functional enrichment analysis of key genes suggested cellular senescence may be important in PFOA/PFOS-induced hepatotoxicity. The in vitro models revealed that PFOA/PFOS led to hepatocyte senescence by increasing the activity of SA-β-gal, inducing mitochondrial dysfunction, impacting cell cycle arrest, and elevating the expressions of p21, p53, IL-1β, and SASP-related cytokines. The drug-target gene set enrichment analysis method was employed to compare the transcriptome data from the Gene Expression Omnibus database (GEO), Comparative Toxicogenomics Database (CTD), and the high-throughput experiment- and reference-guided database (HERB), and 21 traditional Chinese medicines (TCMs) were identified that may alleviate PFOA/PFOS-induced liver aging. The experimental results of co-exposure to PFOA/PFOS and TCMs showed that sanguinarine has particular promise in alleviating cellular senescence caused by PFOA/PFOS. Further investigations revealed that the mTOR-p53 signaling pathway was involved in PFOA/PFOS-mediated hepatic senescence and can be blocked using sanguinarine.

Chronic environmental level exposure to perfluorooctane sulfonate overshadows graphene oxide to induce apoptosis through activation of the ROS-p53-caspase pathway in marine medaka Oryzias melastigma

The widespread occurrence of perfluorooctane sulfonate (PFOS) and the mass production and application of graphene oxide (GO) lead to their inevitable release and interaction in the environment, which may enhance associated toxic impacts on aquatic organisms. This study elucidates the induction of apoptosis by 60-day chronic single and mixture exposures to environmentally relevant levels of PFOS (0.5 μg/L and 5 μg/L) and GO (1 mg/L) in adult marine medaka Oryzias melastigma. Results showed a significant increase (p < 0.05) in reactive oxygen species (ROS) levels, the apoptotic positive rate in livers, and activities of caspases 3, 8, and 9 in all treated groups compared to the control. PFOS individual and PFOS-GO combined exposures significantly impacted fish growth, upregulated expressions of six apoptosis-related genes including p53, apaf1, il1b, tnfa, bcl2l1, bax, as well as enriched cell cycle and p53 signaling pathways (transcriptomic analysis) related to apoptosis compared to control group. Besides higher ROS production, GO also had a higher binding affinity to proteins than PFOS, especially to caspase 8 as revealed by molecular docking. Overall, PFOS induced ROS-p53-caspase apoptosis pathway through multi-gene regulation during single or mixture exposure, while GO single exposure induced apoptosis through tissue damage and ROS-caspase pathway activation and direct docking with caspase 8 to activate the caspase cascade. Under co-exposure, the PFOS-induced apoptotic pathway overshadowed the GO-induced pathway, due to competition for limited active sites on caspases. These findings will contribute to a better understanding of the apoptosis mechanism and ecological risks of nanomaterials and per- and polyfluoroalkyl substances in marine ecosystems.

Itaconic Acid Alleviates Perfluorooctanoic Acid-Induced Oxidative Stress and Intestinal Damage by Regulating the Keap1/Nrf2/Ho-1 Pathway and Reshaping the Gut Microbiota

Itaconic acid (IA) is recognized for its potential application in treating intestinal diseases owing to the anti-inflammatory and antioxidant properties. Perfluorooctanoic acid (PFOA) can accumulate in animals and result in oxidative and inflammatory damages to multi-tissue and organ, particularly in the intestinal tract. This study aimed to explore whether IA could mitigate intestinal damage induced by PFOA exposure in laying hens and elucidate its potential underlying mechanisms. The results showed that IA improved the antioxidant capacity of laying hens and alleviated the oxidative damage induced by PFOA, as evidenced by the elevated activities of T-SOD, GSH-Px, and CAT, and the decreased MDA content in both the jejunum and serum. Furthermore, IA improved the intestinal morphological and structural integrity, notably attenuating PFOA-induced villus shedding, length reduction, and microvillus thinning. IA also upregulated the mRNA expression of ZO-1, Occludin, Claudin-1, and Mucin-2 in the jejunum, thereby restoring intestinal barrier function. Compared with the PF group, IA supplementation downregulated the gene expression of Keap1 and upregulated the HO-1, NQO1, SOD1, and GPX1 expression in the jejunum. Meanwhile, the PF + IA group exhibited lower expressions of inflammation-related genes (NF-κB, IL-1β, IFN-γ, TNF-α, and IL-6) compared to the PF group. Moreover, IA reversed the PFOA-induced imbalance in gut microbiota by reducing the harmful bacteria such as Escherichia-Shigella, Clostridium innocuum, and Ruminococcus torques, while increasing the abundance of beneficial bacteria like Lactobacillus. Correlation analysis further revealed a significant association between gut microbes, inflammatory factors, and the Keap1/Nrf2/HO-1 pathway expression. In conclusion, dietary IA supplementation could alleviate the oxidative and inflammatory damage caused by PFOA exposure in the intestinal tract by reshaping the intestinal microbiota, modulating the Keap1/Nrf2/HO-1 pathway and reducing oxidative stress and inflammatory response, thereby promoting intestinal homeostasis.

Associations of perfluoroalkyl substances with metabolic-associated fatty liver disease and non-alcoholic fatty liver disease: NHANES 2017-2018

OBJECTIVES

This study investigated the potential effects of perfluoroalkyl substance (PFAS) in serum on MAFLD, NAFLD, and liver fibrosis.

METHODS

Our sample included 696 participants (≥ 18 years) from the 2017-2018 NHANES study with available serum PFASs, covariates, and outcomes. Using the first quartile of PFAS as the reference group, we used weighted binary logistic regression and multiple ordered logistic regression used to analyze the relationship between PFAS and MAFLD, NAFLD, and liver fibrosis and multiple ordinal logistic regression to investigate the relationship between PFAS and MAFLD, NAFLD, and liver fibrosis and calculated the odds ratio (OR) and 95% confidence interval for each chemical. Finally, stratified analysis and sensitivity analysis were performed according to gender, age, BMI, and serum cotinine concentration.

RESULTS

A total of 696 study subjects were included, including 212 NAFLD patients (weighted 27.03%) and 253 MAFLD patients (weighted 32.65%). The quartile 2 of serum PFOA was positively correlated with MAFLD and NAFLD (MAFLD, OR 2.29, 95% CI 1.05-4.98; NAFLD, OR 2.37, 95% CI 1.03-5.47). PFAS were not significantly associated with liver fibrosis after adjusting for potential confounders in MAFLD and NAFLD. Stratified analysis showed that PFOA was strongly associated with MAFLD, NAFLD, and liver fibrosis in males and obese subjects. In women over 60 years old, PFHxS was also correlated with MAFLD, NAFLD, and liver fibrosis.

CONCLUSION

The serum PFOA was positively associated with MAFLD and NAFLD in US adults. After stratified analysis, the serum PFHxS was correlated with MFALD, NAFLD, and liver fibrosis.

The size-dependent effects of nanoplastics in mouse primary hepatocytes from cells to molecules

Nanoplastics (NPs) are easily ingested by organisms and their major accumulation organ was determined to be liver. To date, the size-dependent cytotoxicity of NPs on mammalian hepatocytes remains unclear. This study utilized mouse primary hepatocytes and catalase (CAT) as specific receptors to investigate the toxicity of NPs from cells to molecules, focusing on size-dependent effects. Results showed that the larger the particle size of NP at low doses (≤50 mg/L), the most pronounced inhibitory effect on hepatocyte viability. 20 nm NPs significantly inhibit cell viability only at high doses (100 mg/L). Larger NP particles (500 nm and 1000 nm) resulted in a massive release of lactate dehydrogenase (LDH) from the cell (cell membrane damage). Reactive oxygen species (ROS), superoxide dismutase (SOD) and CAT tests suggest that NPs disturbed the cellular antioxidant system. 20 nm NPs show great strength in oxidizing lipids and disrupting mitochondrial function compared to NPs of other particle sizes. The degree of inhibition of CAT activity by different sized NPs was coherent at the cellular and molecular levels, and NP-500 had the most impact. This suggests that the structure and microenvironment of the polypeptide chain in the vicinity of the CAT active site is more susceptible to proximity and alteration by NP-500. In addition, the smaller NPs are capable of inducing relaxation of CAT backbone, disruption of H-bonding and reduction of α-helix content, whereas the larger NPs cause contraction of CAT backbone and increase in α-helix content. All NPs induce CAT fluorescence sensitization and make the chromophore microenvironment hydrophobic. This study provides new insights for NP risk assessment and applications.

Impact of perfluorooctanoic acid (PFOA) and perfluorobutanoic acid (PFBA) on oxidative stress and metabolic biomarkers in human neuronal cells (SH-SY5Y)

Perfluorinated alkyl substances (PFAS) are pervasive environmental contaminants that have attracted considerable attention due to their widespread utilization, resilient characteristics, adverse health implications, and regulatory scrutiny. Despite documented toxicity in living organisms, the precise molecular mechanisms governing the induced adverse effects remain unclear. This study aims to elucidate mechanisms of toxic action by collecting empirical data sets along oxidative stress and metabolic disruption pathways. We investigated the impact of long-chain PFAS (perfluorooctanoic acid (PFOA)) and its short-chain analog (perfluorobutanoic acid (PFBA)) on human neuronal cells (SH-SY5Y). The functionalities of enzymes associated with oxidative stress (catalase and glutathione reductase) and cellular metabolism (lactate dehydrogenase and pyruvate dehydrogenase) were also characterized. Our results reveal that a 24-hour exposure to PFOA and PFBA generated significant levels of reactive oxygen species. Correspondingly, there was a notable decline in catalase and glutathione reductase activities, with PFBA demonstrating a more pronounced effect. High concentrations of PFOA and PFBA reduced metabolic activity. Lactate dehydrogenase activity was only impacted by a high concentration of PFBA, while pyruvate dehydrogenase activity was decreased with PFBA exposure and increased with PFOA exposure. The findings from this study contribute to the knowledge of PFAS and cell interactions and reveal the potential underlying mechanisms of PFAS-induced toxicity.

Perfluorooctane Sulfonamide Induced Autotoxic Effects on the Zebrafish Immune System

Perfluorooctane sulfonamide (PFOSA) is an immediate perfluorooctanesulfonate (PFOS) precursor (PreFOS). Previous studies have shown PFOSA to induce stronger toxic responses compared to other perfluorinated compounds (PFCs). However, the specific nature of PFOSA-induced toxicity, whether autonomous or mediated by its metabolite PFOS, has not been fully elucidated. This study systematically investigates the immunomodulatory effects of PFOSA and PFOS in zebrafish (Danio rerio). Exposure to PFOSA compromised the zebrafish's ability to defend against pathogenic infections, as evidenced by increased bacterial adhesion to their skin and reduced levels of the biocidal protein lysozyme (LYSO). Moreover, PFOSA exposure was associated with disruptions in inflammatory markers and immune indicators, along with a decrease in immune cell counts. The findings from this study suggest that the immunotoxicity effects of PFOSA are primarily due to its own toxicity rather than its metabolite PFOS. This conclusion was supported by dose-dependent responses, the severity of observed effects, and multivariate analysis. In addition, our experiments using NF-κB-morpholino knock-down techniques further confirmed the role of the Nuclear factor-κappa B pathway in mediating PFOSA-induced immunotoxicity. In conclusion, this study reveals that PFOSA impairs the immune system in zebrafish through an autotoxic mechanism, providing valuable insights for assessing the ecological risks of PFOSA.

Persistent organic pollutants dysregulate energy homeostasis in human ovaries in vitro

Exposure to persistent organic pollutants (POPs), such as dichlorodiphenyltrichloroethane (DDT) and polychlorinated biphenyls (PCBs), has historically been linked to population collapses in wildlife. Despite international regulations, these legacy chemicals are still currently detected in women of reproductive age, and their levels correlate with reduced ovarian reserve, longer time-to-pregnancy, and higher risk of infertility. However, the specific modes of action underlying these associations remain unclear. Here, we examined the effects of five commonly occurring POPs - hexachlorobenzene (HCB), p,p'-dichlorodiphenyldichloroethylene (DDE), 2,3,3',4,4',5-hexachlorobiphenyl (PCB156), 2,2',3,4,4',5,5'-heptachlorobiphenyl (PCB180), perfluorooctane sulfonate (PFOS) - and their mixture on human ovaries in vitro. We exposed human ovarian cancer cell lines COV434, KGN, and PA1 as well as primary ovarian cells for 24 h, and ovarian tissue containing unilaminar follicles for 6 days. RNA-sequencing of samples exposed to concentrations covering epidemiologically relevant levels revealed significant gene expression changes related to central energy metabolism in the exposed cells, indicating glycolysis, oxidative phosphorylation, fatty acid metabolism, and reactive oxygen species as potential shared targets of POP exposures in ovarian cells. Alpha-enolase (ENO1), lactate dehydrogenase A (LDHA), cytochrome C oxidase subunit 4I1 (COX4I1), ATP synthase F1 subunit alpha (ATP5A), and glutathione peroxidase 4 (GPX4) were validated as targets through qPCR in additional cell culture experiments in KGN. In ovarian tissue cultures, we observed significant effects of exposure on follicle growth and atresia as well as protein expression. All POP exposures, except PCB180, decreased unilaminar follicle proportion and increased follicle atresia. Immunostaining confirmed altered expression of LDHA, ATP5A, and GPX4 in the exposed tissues. Moreover, POP exposures modified ATP production in KGN and tissue culture. In conclusion, our results demonstrate the disruption of cellular energy metabolism as a novel mode of action underlying POP-mediated interference of follicle growth in human ovaries.

Investigating the toxic mechanism of iron oxide nanoparticles-induced oxidative stress in tadpole (Duttaphrynus melanostictus): A combined biochemical and molecular study

Metal oxide nanomaterials have toxicity towards aquatic organisms, especially microbes and invertebrates, but little is known about their impact on amphibians. We conducted a study on Duttaphrynus melanostictus (D. melanostictus) tadpoles to explore the chronic toxicity effects of iron oxide nanoparticles (IONPs) and the underlying mechanisms of IONPs-induced oxidative stress. IONPs exposure led to increased iron accumulation in the blood, liver, and kidneys of tadpoles, significantly affecting blood parameters and morphology. Higher IONPs concentrations (10 and 50 mg L-1) triggered reactive oxygen species generation, resulting in lipid peroxidation, oxidative stress, and pronounced toxicity in tadpoles. The activity levels of antioxidant enzymes/proteins (SOD, CAT, albumin, and lysozyme) decreased after IONPs exposure, and immunological measures in the blood serum were significantly reduced compared to the control group. Molecular docking analysis revealed that IONPs primarily attached to the surface of SOD/CAT/albumin/lysozyme through hydrogen bonding and hydrophobic forces. Overall, this study emphasizes the ability of IONPs to induce oxidative damage by decreasing immunological profiles such as ACH50 (34.58 ± 2.74 U mL-1), lysozyme (6.94 ± 0.82 U mL-1), total Ig (5.00 ± 0.35 g dL-1), total protein (1.20 ± 0.17 g dL-1), albumin (0.52 ± 0.01 g dL-1) and globulin (0.96 ± 0.01 g dL-1) and sheds light on their potential toxic effects on tadpoles.

Integrated evidence of transcriptional, metabolic, and intestinal microbiota changes in Ruditapes philippinarum due to perfluorooctanoic acid-induced immunotoxicity

Perfluorooctanoic acid (PFOA) is a toxic pollutant that bioaccumulates and is a significant public health concern due to its ubiquitous and persistent occurrence in global environments. Few studies have evaluated the adverse effects of PFOA on immune system, and this is particularly true for mollusks. Here, the PFOA-associated effects on immune system were evaluated in Ruditapes philippinarum using integrated analysis of metabolomes, microbiomes, and transcriptomes, providing evidence for possible mechanisms related to immunotoxicity. PFOA exposure caused clear variation in several important metabolites related to immune regulatory function within the haemolyph from R. philippinarum, while also altering key metabolic pathways, including those of lipids, unsaturated fatty acids (UFAs), and bile acids (BAs). After exposure to PFOAs, intestinal bacterial communities also clearly changed, with the predominant microflora becoming Mycoplasma and Bacteroidetes that are related to intestinal inflammation. Molecular analyses provided consistent results, wherein the expression of immune-related genes was significantly altered. Integration of the multi-'omics' analyses suggested that the TLR/MyD88/NF-kB pathway, along with PI3K-Akt-mTOR pathway, PPAR-mediated lipid metabolism and the autophagy signaling pathway, likely play important roles in initiating immunotoxic effects in R. philippinarum after PFOA exposure. These results provide further evidence that PFOA exposure can lead to immunologic dysfunction and also provide new insights into the mechanisms of PFAS alteration of bivalve immune function.

The combined effects of polystyrene nanoplastics with nickel on oxidative stress and related toxic effects to earthworms from individual and cellular perspectives

Nanoplastics may adsorb other pollutants in the environment due to their high specific surface area and small size. We used earthworms as experimental organisms to evaluate the ecotoxicity of NPs and Ni combined pollution at the individual and cellular levels. The results showed that when only 20 mg/L Ni2+ was added to the combined pollution system, the antioxidant system of earthworm coelomocytes was destroyed to a certain extent, the ROS level increased, the cell viability decreased significantly, and the redox balance was destroyed. With the introduction of PS-NPs and the increase of concentration, the oxidative damage in the coelomocytes of earthworms gradually increased, and finally tended to be stable when the maximum concentration of 50 mg/L PS-NPs and Ni were exposed together. At the animal level, the activities of CAT and SOD decreased within 28 days of exposure, and the combined pollution showed a synergistic effect. At the same time, it promoted the synthesis of GST in earthworms, improved their detoxification ability and reduced oxidative damage. The changes of T-AOC and MDA showed that the combined pollution caused the accumulation of ROS and caused more serious toxicological effects. With the increase of exposure time, the antioxidant system of earthworms was continuously destroyed, and the oxidative damage was serious, which induced more serious lipid peroxidation and caused the damage of earthworm body wall structure.

Novel evidence on iodoacetic acid-induced immune protein functional and conformational changes: Focusing on cellular and molecular aspects

Elevated levels of iodide occur in raw water in certain regions, where iodination disinfection byproducts are formed during chloramine-assisted disinfection of naturally iodide-containing water. Iodoacetic acid (IAA) is one of the typical harmful products. The mechanisms underlying IAA-induced immunotoxicity and its direct effects on biomolecules remained unclear in the past. Cellular, biochemical, and molecular methods were used to investigate the mechanism of IAA-induced immunotoxicity and its binding to lysozyme. In the presence of IAA, the cell viability of coelomocytes was significantly reduced to 70.8 %, as was the intracellular lysozyme activity. Upon binding to IAA, lysozyme underwent structural and conformational changes, causing elongation and unfolding of the protein due to loosening of the backbone and polypeptide chains. IAA effectively quenched the fluorescence of lysozyme and induced a reduction in particle sizes. Molecular docking revealed that the catalytic residue, Glu 35, which is crucial for lysozyme activity, resided within the docking range, suggesting the preferential binding of IAA to the active site of lysozyme. Moreover, electrostatic interaction emerged as the primary driving force behind the interaction between IAA and lysozyme. In conclusion, the structural and conformational changes induced by IAA in lysozyme resulted in impaired immune protein function in coelomocytes, leading to cellular dysfunction.

Sodium p-perfluorous nonenoxybenzene sulfonate induces ROS-mediated necroptosis by directly targeting catalase in HepG2 cells

Sodium p-perfluorous nonenoxybenzene sulfonate (OBS) has been widely used as a substitute for perfluorooctane sulfonic acid (PFOS) because of its high surface activity and low cost, but the knowledge of its biological effects is still limited. In this study, we compared the toxic effects of OBS and PFOS on human hepatoma cells (HepG2). OBS resulted in lower cell viability, higher ROS levels, and more severe necrosis than PFOS, indicating that OBS caused higher cytotoxicity than PFOS. In this process, OBS induced a burst of ROS and downregulation of catalase (CAT). OBS-induced oxidative stress was recovered after the CAT overexpression, but the CAT levels were not reversed after N-acetylcysteine (NAC) pretreatment. This indicates that the downregulated CAT is an upstream signal of the ROS burst. Moreover, drug affinity targeting assay, spectroscopic analysis and molecular docking were conducted, showing that OBS directly targeted CAT and therefore downregulated CAT. In addition, we found that OBS-induced necrosis is RIP1/RIP3-dependent programmed necroptosis. In summary, OBS directly targets CAT to reduce CAT levels and induces oxidative stress and necroptosis. Our findings are helpful to understand the toxicity of OBS and to evaluate the safety of OBS as a substitute for PFOS.

New strategies for evaluating imidacloprid-induced biological consequences targeted to Eisenia fetida species and the corresponding mechanisms of its toxicity

Imidacloprid (IMI), a neonicotinoid insecticide, has a wide variety of applications in both agriculture and horticulture. As a result of it massive and repeated use, its traces remained in soil pose severe damage to soil invertebrates, particularly earthworms. Limited information is available regarding the underlying mechanisms of IMI toxicity toward earthworms at the molecular, transcriptional, and cellular levels. Here, Eisenia fetida coelomocytes and key defensive proteins were selected as targeted receptors to explore the toxic mechanisms of oxidative stress-mediated cytotoxicity, genotoxicity, and antioxidant responses induced by IMI stress and the molecular mechanisms underlying the binding of IMI and superoxide dismutase (SOD)/catalase (CAT). Results showed that IMI exposure destroyed the cell membrane integrity of earthworm cells, causing cell damage and cytotoxicity. The intracellular levels of ROS, including ·O2- and H2O2 were induced by IMI exposure, thereby triggering oxidative stress and damage. Moreover, IMI exposure attenuated the antioxidative stress responses (reduced antioxidant capacity and CAT/SOD activities) and caused deleterious effects (enhanced DNA damage, lipid peroxidation (LPO), and protein carbonylation (PCO)) through ROS-mediated oxidative stress pathway. Aberrant gene expression associated with oxidative stress and defense regulation, including CAT, CRT, MT, SOD, GST, and Hsp70 were induced after IMI exposure. Concentration-dependent conformational and structural alterations of CAT/SOD were observed when IMI binding. Also, direct binding of IMI resulted in significant inhibition of CAT/SOD activities in vitro. Molecular simulation showed that IMI preferred to bind to CAT active center through its direct binding with the key residue Tyr 357, while IMI bound more easily to the connecting cavity of two subunits away from SOD active center. In addition, hydrogen bonds and hydrophobic force are the main driving force of IMI binding with CAT/SOD. These findings have implications for comprehensive evaluation of IMI toxicity to soil eco-safety and offer novel strategies to elucidate the toxic mechanisms and pathways of IMI stress.

Perfluorooctanoic acid (PFOA) inhibits steroidogenesis and mitochondrial function in bovine granulosa cells in vitro

Perfluorooctanoic acid (PFOA) is a persistent environmental contaminant. Due to the ubiquitous presence of PFOA in the environment, the impacts of PFOA exposure not only affect human reproductive health but may also affect livestock reproductive health. The focus of this study was to determine the effects of PFOA on the physiological functions of bovine granulosa cells in vitro. Primary bovine granulosa cells were exposed to 0, 4, and 40 μM PFOA for 48 and 96 h followed by analysis of granulosa cell function including cell viability, steroidogenesis, and mitochondrial activity. Results revealed that PFOA inhibited steroid hormone secretion and altered the expression of key enzymes required for steroidogenesis. Gene expression analysis revealed decreases in mRNA transcripts for CYP11A1, HSD3B, and CYP19A1 and an increase in STAR expression after PFOA exposure. Similarly, PFOA decreased levels of CYP11A1 and CYP19A1 protein. PFOA did not impact live cell number, alter the cell cycle, or induce apoptosis, although it reduced metabolic activity, indicative of mitochondrial dysfunction. We observed that PFOA treatment caused a loss of mitochondrial membrane potential and increases in PINK protein expression, suggestive of mitophagy and mitochondrial damage. Further analysis revealed that these changes were associated with increased levels of reactive oxygen species. Expression of autophagy related proteins phosphoULK1 and LAMP2 were increased after PFOA exposure, in addition to an increased abundance of lysosomes, characteristic of increased autophagy. Taken together, these findings suggest that PFOA can negatively impact granulosa cell steroidogenesis via mitochondrial dysfunction.

Environmental impacts, exposure pathways, and health effects of PFOA and PFOS

Per- and polyfluoroalkyl substances (PFAS) are synthetic chemicals that have been widely utilized in various industries since the 1940s, and have now emerged as environmental contaminants. In recent years, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) have been restricted and replaced with several alternatives. The high persistence, bioaccumulation, and toxicity of these substances have contributed to their emergence as environmental contaminants, and several aspects of their behavior remain largely unknown and require further investigation. The trace level of PFAS makes the development of a monitoring database challenging. Additionally, the potential health issues associated with PFAS are not yet fully understood due to ongoing research and inadequate evidence (experimental and epidemiological studies), especially with regard to the combined effects of exposure to PFAS mixtures and human health risks from drinking water consumption. This in-depth review offers unprecedented insights into the exposure pathways and toxicological impacts of PFAS, addressing critical knowledge gaps in their behaviors and health implications. It presents a comprehensive NABC-Needs, Approach, Benefits, and Challenges-analysis to guide future strategies for the sustainable monitoring and management of these pervasive environmental contaminants.

Serum albumin mitigated perfluorooctane sulfonate-induced cytotoxicity by affecting the cellular responses

During the wide applications of perfluorinated materials such as perfluorooctane sulfonate (PFOS) in commercial and industrial products, the potential toxicity of these engineered compounds has attracted more and more attention. As a typical environmental pollutant, PFOS could preferentially bind to albumin protein in vivo. However, the role of protein-PFOS interactions in the cytotoxicity of PFOS was not stressed enough. Herein, we investigated the interactions of PFOS with human serum albumin (HSA, the most abundant protein in human plasma) using both experimental and theoretical approaches. It was demonstrated that PFOS could mainly bind to the Sudlow site I of HSA to generate HSA-PFOS complex through hydrogen bonds and van der Waals forces. Toxicity assays with endothelial cells illustrated that the binding of HSA could significantly attenuate the intracellular uptake and subcellular distribution of PFOS, thereby inhibiting the formation of reactive oxygen species and toxicity for those HSA-bound PFOS. Similarly, the presence of fetal bovine serum in the cell culture media greatly reduced PFOS-caused cytotoxicity. Conclusively, our study reveals that the binding of albumin protein to PFOS could mitigate its toxicity by the modulation of cellular responses. The formation of protein-complexed contaminants would significantly reduce the bioavailability of these chemicals and subsequently mitigate their environmental toxicology to the human health.

Molecular interaction mechanisms and cellular response of superoxide dismutase and catalase to fluoranthene

As an important raw material and intermediate product of the petrochemical industry, fluoranthene (Fla) can be emitted with industrial activities and has become a typical polycyclic aromatic hydrocarbon enriched in the Chinese topsoil layer, posing a significant threat to sensitive soil biota. Here, multispectral tools and molecular simulation techniques were integrated to elucidate the molecular mechanism of Fla interaction with key antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) at the molecular level. Meanwhile, we further revealed the cellular responses of SOD and CAT and the associated redox states in earthworm (Eisenia fetida) coelomocytes based on the molecular-level results. Our results showed that the exposure to Fla affected the backbone structure of SOD and CAT molecules and resulted in the formation of Fla-SOD polymers as well as an overall reduction in the size of the Fla-CAT binding system. Fla altered the microenvironment around Tyr residues in the SOD molecule and quenched the endogenous fluorescence of Tyr within the CAT molecule. In earthworm coelomocytes, Fla at 60 and 80 μM resulted in a significant elevation of CAT and SOD activities by 114% (p = 0.032) and 6.09% (p = 0.013), respectively. Molecular simulation results suggested that Fla-induced changes in the structure and conformation of SOD and CAT may be the key reason for their altered activities. The related redox homeostasis detection in earthworm coelomocytes indicated that high concentrations (80 μM) of Fla led to a significant accumulation of intracellular ROS (p = 0.018) and resulted in the development of lipid peroxidation. Our work contributes to an in-depth understanding of the biological effect of Fla to sensitive soil fauna, thus providing new ideas for Fla ecological risk prevention and control.

Binding of serum albumin to perfluorooctanoic acid reduced cytotoxicity

With the ubiquitous applications of perfluorinated compounds such as perfluorooctanoic acid (PFOA) in industrial and commercial products, the toxicity of these engineered materials in environmental and public health is received growing attention. As a typical organic pollutant, PFOA has been extensively found in wildlife and human bodies, and can preferentially bind to serum albumin in vivo. However, the importance of protein-PFOA interactions on the cytotoxicity of PFOA could not be stressed enough. In this study, we used both experimental and theoretical approaches, to investigate the interactions of PFOA with bovine serum albumin (BSA, the most abundant protein in blood). It was found that PFOA could mainly interact with Sudlow site I of BSA to form BSA-PFOA complex, in which van der Waals forces and hydrogen bonds played dominant roles. Moreover, the strong binding of BSA could greatly alter the cellular uptake and distribution of PFOA in human endothelial cells, and result in the decreases of reactive oxygen species formation and cytotoxicity for these BSA-coated PFOA. Consistently, the addition of fetal bovine serum into cell culture medium also significantly mitigated PFOA-induced cytotoxicity, which was attributed to the extracellular complexation between PFOA and serum proteins. Altogether, our study demonstrates that the binding of serum albumin to PFOA could reduce its toxicity by affecting the cellular responses.

Study on the binding of polystyrene microplastics with superoxide dismutase at the molecular level by multi-spectroscopy methods

Microplastics are harmful pollutants that widely exist worldwide and pose a severe threat to all types of organisms. The effects of polystyrene microplastics (PS-MPs) on organisms have been extensively studied, but the interaction mechanism between PS-MPs and superoxide dismutase (SOD) at the molecular level has not been reported yet. Therefore, based on multiple spectroscopic methods and enzyme activity measurements, the molecular mechanism of the interaction between PS-MPs and SOD was investigated. The multispectral results showed that the protein skeleton and secondary structure of SOD were altered by PS-MPs, resulting in decreased α-helix and β-sheet content. After PS-MPs exposure, fluorescence sensitization occurred, and micelles were formed, along with the enhanced hydrophobicity of aromatic amino acids in SOD. Moreover, the resonance light scattering (RLS) spectra result suggested that the PS-MPs and SOD combined to form a larger complex. Eventually, the activity of SOD was increased due to these structural changes, and the concentration of PS-MPs is positively correlated with SOD activity. This study can provide experimental support for studying the toxicological effects of PS-MPs.

Probing the toxic effect of quinoline to catalase and superoxide dismutase by multispectral method

Quinoline is a common nitrogen heterocyclic aromatic hydrocarbon with high water solubility. Studies have shown that quinoline can be teratogenic, carcinogenic and mutagenic. And Hepatocytes are the target cell of quinoline, which contain a large number of mitochondria and are related to cell function and the balance of reactive oxygen species (ROS). However, the research on the effect of quinoline on hepatocyte damage and anti-oxidation system is still unclear. Through the means of multispectral experiments, it is concluded that quinoline can affect the catalase (CAT) and superoxide dismutase (SOD), change their structure and affect their activity. The binding mode and binding site of quinoline to CAT/SOD were analyzed by isothermal calorimetric titration (ITC) and Molecular Operating Environment (MOE). In molecular docking simulation, the binding site of quinoline-CAT system is close to the active site, and affect the microenvironment of Tyr 357. This may be the reason why quinoline affects CAT activity and synchronous fluorescence (Δλ = 15 nm). This study demonstrated that quinoline has a great effect on CAT, which may affect the intracellular ROS balance and become a potential way to cause hepatocyte damage.

Perfluoroalkyl substances promote breast cancer progression via ERα and GPER mediated PI3K/Akt and MAPK/Erk signaling pathways

Perfluoroalkyl substances (PFASs) are a classic environmental endocrine disruptor with carcinogenic risk. Epidemiological studies have shown that PFASs contamination is associated with breast cancer development, but the mechanism remains largely unknown. This study first obtained complex biological information about PFASs-induced breast cancer through the comparative toxicogenomics database (CTD). The Protein-Protein Interaction (PPI) network, Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) analysis were utilized to investigate molecular pathways. The ESR1 and GPER expression levels at different pathological stages and the prognosis of Breast Cancer patients were confirmed using the Cancer Genome Atlas (TCGA) database. Furthermore, we verified this by cellular experiments and the results showed breast cancer cell migration and invasion were promoted by PFOA. Two estrogen receptors (ER), ERα and G protein-coupled estrogen receptor (GPER), mediated the promoting effects of PFOA by activating MAPK/Erk and PI3K/Akt signaling pathways. These pathways were regulated by ERα and GPER in MCF-7 cells or independently by GPER in MDA-MB-231 cells. Overall, our study provides a better overview of the mechanisms associated with PFASs-induced breast cancer development and progression.

Ecotoxicological evaluation of oxidative stress-mediated neurotoxic effects, genetic toxicity, behavioral disorders, and the corresponding mechanisms induced by fluorene-contaminated soil targeted to earthworm (Eisenia fetida) brain

Fluorene is a commonly identified PAH pollutant in soil and exhibits various worrisome hazardous effects to soil organisms. Currently, the toxicity profiles of fluorene on earthworm brain are rare, and the mechanisms and their corresponding pathways involved in fluorene-triggered neurotoxicity, genotoxicity, and behavior changes have not been reported hitherto. Herein, earthworm (Eisenia fetida) brain was chosen as targeted receptor to explore the neurotoxic effects, genetic toxicity, behavioral disorders, and related mechanisms caused by fluorene-induced oxidative stress pathways. The results showed excess fluorene initiated the release of excessive quantities of ROS in earthworm brain, which have caused oxidative stress and accompanied by serious oxidative effects, including LPO (lipid peroxidation) and DNA injury. To minimize the damage effects, the antioxidant defense mechanisms (antioxidant enzymes and non-enzymatic antioxidants) were activated, and entailed a decrease of the antioxidant capacity in E. fetida brain, which, in turn, causes further ROS-induced ROS release. Exposure of fluorene induced the abnormal mRNA expression of genes relevant to oxidative stress (e.g., GST, SOD, CAT, GPx, MT, and Hsp70) and neurotoxicity (e.g., H02, C04, D06, and E08) in E. fetida brain. Specifically, fluorene can bind directly to AChE, destroying the conformation of this protein, and even affecting its physiological functions. This occurrence caused the inhibition of AChE activity and excess ACh accumulation at the nicotinic post-synaptic membrane, finally triggering neurotoxicity by activation of pathways related to oxidative stress. Moreover, the avoidance responses and burrowing behavior were obviously disturbed by oxidative stress-induced neurotoxicity after exposure to fluorene. The results form IBR suggested more severe poisoning effects to E. fetida brain initiated by high-dose and long-term exposure of fluorene. Among, oxidative stress injury and genotoxic potential are more sensitive endpoint than others. Collectively, fluorene stress can provoke potential neurotoxicity, genotoxicity, and behavioral disturbances targeted to E. fetida brain through the ROS-mediated pathways involving oxidative stress. These findings are of great significance to estimate the detrimental effects of fluorene and the corresponding mechanisms on soil eco-safety.

Short-chain per- and polyfluoralkyl substances (PFAS) effects on oxidative stress biomarkers in human liver, kidney, muscle, and microglia cell lines

Long-chain per- and polyfluoralkyl substances (PFAS) are ubiquitous contaminants implicated in the induction of intracellular reactive oxygen species (ROS), compromising antioxidant defense mechanisms in vitro and in vivo. While a handful of studies have assessed oxidative stress effects by PFAS, few specifically address short-chain PFAS. We conducted an evaluation of oxidative stress biomarkers in vitro following exposures to low (1 nM) and high (1 μM) concentrations of five short-chain PFAS compounds: perfluorobutanesulfonic acid (PFBS), perfluorohexanoic acid (PFHxA), [undecafluoro-2-methyl-3-oxahexanoic acid (HFPO-DA)], 6:2 fluorotelomer alcohol (6:2 FTOH) and perfluorohexanesulfonic acid (PFHxS). We conducted experiments in human kidney (HEK293-hTLR2), liver (HepaRG), microglia (HMC-3), and muscle (RMS-13) cell lines. Fluorescence microscopy measurements in HepaRG cells indicated ROS generation in cells exposed to PFBS and PFHxA for 24 h. Antioxidant enzyme activities were determined following 24 h short-chain PFAS exposures in HepaRG, HEK293-hTLR2, HMC-3, and RMS-13. Notably, exposure to PFBS for 24 h increased the activity of GPX in all four cell types at 1 μM and 1 nM in HepaRG and RMS-13 cells. Every short-chain PFAS evaluated, except for PFHxS, increased the activity of at least one antioxidant enzyme. To our knowledge, this is the first study of its kind to explore antioxidant defense alterations to microglia and muscle cell lines by PFAS. The findings of this study hold great potential to contribute to the limited understanding of short-chain PFAS mechanisms of toxicity and provide data necessary to inform the human health risk assessment process.

The culprits of superoxide dismutase inactivation under size-dependent stress of ultrafine carbon black: Superoxide anion, genotoxicity and protein corona

As a critical component of atmospheric ultrafine particulates, ultrafine carbon black (UFCB) brings great exposure risk to organisms. At present, the action pathway and activity regulation mechanism of UFCB on functional proteins in vivo are not clear, and the size-dependent effects of UFCB during this process need to be elucidated. Superoxide dismutase (SOD), one of the most applied biomarkers to assess the environmental impact of pollutants, plays crucial roles in resistance to oxidative stress. Here, based on the inactivation of SOD (84.79 %, 86.81 % and 91.70 %) in primary mouse hepatocytes exposed to UFCB (13 nm, 50 nm and 95 nm), oxidative stress, genotoxicity and protein molecular studies were employed to elucidate the inactivation mechanisms. Results showed that inhibition of UFCB-mediated superoxide anion (O₂^-) contributed to a decrease in SOD activity. Furthermore, the significant increase in 8-hydroxy-2-deoxyguanosine content and the comet tail formation indicated the occurrence of DNA damage, supporting that concomitant aberrant transcriptional and protein translational under gene regulation should be responsible for SOD inactivation. At the molecular level, the constricted backbone, reduced content of α-helix and fluorescence sensitization all demonstrated that the attachment-type binding of SOD on UFCB to form the 'protein corona' disrupted protein structure. Enzyme activity assays indicated that SOD backbone tightening and helix decay resulted in decreased activity, which should be another reason for intracellular SOD inactivation. More importantly, the particle sizes of UFCB exert powerful influences on SOD inactivation mechanisms. Smaller UFCB (13 nm) induced more severe O₂^- inhibition and DNA damage, while UFCB_50nm with the best dispersity bound more SOD and induced stronger molecular toxicity, which are their different strengths in stressing SOD inactivation in hepatocytes. Our findings provide novel insights for exploring functional proteins activity and underscore a potentially size-dependent risk of nanoparticles.

Consideration of pathways for immunotoxicity of per- and polyfluoroalkyl substances (PFAS)

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are of public health concern, because of their ubiquitous and extremely persistent occurrence, and depending on their structure, their bio-accumulative, mobile and toxic properties. Human health effects associated with exposure to PFAS include adverse effects on the immune system. In 2020, EFSA (the European Food Safety Authority) defined adverse effects on the immune system as the most critical effect for human health risk assessment, based on reduced antibody responses to childhood vaccines and similar effects observed in experimental animal studies. Likewise, the U.S. EPA (Environmental Protection Agency) considers PFAS-induced immunotoxicity, especially in children, as the critical effect for risk assessment. However, the mechanisms by which antibody concentrations are impacted are not completely understood. Furthermore, other targets of the immune system functions have been reported in the literature.

OBJECTIVE

The aim of this review is to explore PFAS-associated immune-related effects. This includes, relevant mechanisms that may underlie the observed effects on the immune system, immunosuppression as well as immunoenhancement, such as i) modulation of cell signalling and nuclear receptors, such as NF-κB and PPARs; ii) alteration of calcium signalling and homoeostasis in immune cells; iii) modulation of immune cell populations; iv) oxidative stress and v) impact on fatty acid metabolism & secondary effects on the immune system.

METHODS

A literature research was conducted using three databases (Web of Science, PubMed, and Scopus), which were searched in July 2021 for relevant studies published in the time frame from 2018 to 2021. In total, 487 publications were identified as potentially eligible and following expert-based judgement, articles relevant for mechanisms of PFAS induced immunotoxicity are discussed.

CONCLUSIONS

Taken together, we show that there is substantial evidence from both in vitro and in vivo experimental as well as epidemiological studies, supporting that various PFAS, not only PFOA and PFOS, affect multiple aspects of the immune system. Timing of exposure is critical, because the developing immune system is especially vulnerable to toxic insults, resulting in a higher risk of particularly adverse immune effects but also other organs later in life.

Cytotoxicity and Oxidative Stress Effects of Indene on Coelomocytes of Earthworm (Eisenia foetida): Combined Analysis at Cellular and Molecular Levels

Indene (IND) is a kind of important aromatic hydrocarbon that is extracted from coal tar and has important applications in industry and biology. In the process of production and utilization, it is easy to enter the soil and produce toxic effects on the soil or organisms. The earthworm is an important organism in the soil. The toxicity of indene on earthworm coelomocytes is rarely studied, and the oxidative stress effects of IND on earthworm coelomocytes remain unclear. In this study, coelomocytes from earthworms and antioxidant enzymes were selected as the research targets. In addition, IND caused oxidative stress, and its related toxic effects and mechanisms were systematically studied and evaluated at the cellular and molecular levels. The results showed that IND destroyed the redox balance in earthworm coelomocytes, and the large accumulation of reactive oxygen species (ROS) significantly inhibited the activities of the antioxidant system, including superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH), and caused lipid peroxidation and membrane permeability changes, resulting in a decrease in cell viability to 74.5% of the control group. At the molecular level, IND was bound to SOD by the arene-H bond, and the binding constant was 4.95 × 10³. IND changed the secondary structure of the SOD and led to a loosening of the structure of the SOD peptide chain. Meanwhile, IND caused SOD fluorescence sensitization, and molecular simulation showed that IND was mainly bound to the junction of SOD subunits. We hypothesized that the changes in SOD structure led to the increase in SOD activity. This research can provide a scientific basis for IND toxicity evaluation.

Response pathways of superoxide dismutase and catalase under the regulation of triclocarban-triggered oxidative stress in Eisenia foetida: Comprehensive mechanism analysis based on cytotoxicity and binding model

Triclocarban (TCC) is an emerging environmental contaminant, posing potential ecological risks. Displaying a high accumulation effect and 120-day half-life in the soil environment, the toxic effects of TCC to soil organisms have been widely reported. Previous studies have confirmed that TCC can induce the oxidative stress and changes in superoxide dismutase (SOD) and catalase (CAT) activities in earthworms, but the underlying mechanisms of oxidative stress and disorder in antioxidant enzyme activities induced by TCC have not yet been elucidated. Here, we explored the multiple response mechanisms of SOD and CAT under the regulation of oxidative stress induced by TCC. Results indicated that higher-dose (0-2.0 mg/L) TCC exposure triggered the overproduction of ROS in Eisenia foetida coelomocytes, causing oxidative damage and a decrease in cell viability that was response to ROS accumulation. The TCC-induced inhibition of intracellular SOD/CAT activity was found under the regulation of oxidative stress (SOD: 29.2 %; CAT: 18.5 %), and this effect was blunted by antioxidant melatonin. At the same time, the interaction between antioxidative enzymes and TCC driven by various forces (SOD: electrostatic interactions; CAT: van der Waals forces and hydrogen bonding) led to inhibited SOD activity (9.84 %) and enhanced CAT activity (17.5 %). Then, to elucidate the binding mode of TCC, we explored the changes in SOD and CAT structure (protein backbone and secondary structure), the microenvironment of aromatic amino acids, and aggregation behavior through multispectral techniques. Molecular docking results showed that TCC inhibited SOD activity in a substrate competitive manner and enhanced CAT activity by the stabilizing effects of TCC on the heme groups. Collectively, this study reveals the response mechanisms of SOD/CAT under the regulation of TCC-triggered oxidative stress and shed a new light on revealing the toxic pathways of exogenous pollutants on antioxidant-related proteins function.

Toxic effects and transcriptional responses in zebrafish liver cells following perfluorooctanoic acid exposure

As a typical type of persistent organic pollutant, perfluorooctanoic acid (PFOA) is pervasive in the environment. Multiple studies have found that PFOA has hepatotoxicity, but the mechanism remains poorly understood. In this study, the toxic effects of different concentrations of PFOA on zebrafish liver cells were systematically assessed by recording cell survival, ultrastructural observations, and transcriptome analyses. The results showed that the inhibition of cell viability and the massive accumulation of autophagic vacuoles were observed at 400 µM PFOA, while transcriptomic changes occurred with treatments of 1 and 400 µM PFOA. The transcription levels of 1055 (977 up- and 78 down-regulated genes) and 520 (446 up- and 74 down-regulated genes) genes were significantly changed after treatment with 1 and 400 µM PFOA, respectively. Based on Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis, significant expression changes were observed in autophagy, tight junction, signal transduction, immune system, endocrine system, and metabolism-related pathways, indicating that such processes were greatly affected by PFOA exposure. The findings of this study will provide a scientific basis for the toxic effects and potential toxic mechanisms of PFOA on zebrafish, and provide information for ecological risk assessments.

Size-dependent effects of nanoplastics on structure and function of superoxide dismutase

The ubiquitous existence of nano-plastics (NPs) has attracted widespread concern. Currently, the uptake of NPs by organisms and cells has been reported. However, knowledge about the interaction between NPs and protein is still limited, and there is a gap in research on the size-dependent toxicity of NPs toward protein. In this study, multi-spectroscopic techniques and enzyme activity determination were used to explore the structure and function changes of the main antioxidant enzyme superoxide dismutase (SOD), caused by the binding of NPs with different particle sizes. Results indicated NPs with different sizes can directly interact with SOD. NPs with smaller sizes result in looser skeletons of SOD, while the larger lead to tighter peptide chains. In addition, NPs can bind with SOD to form complexes, and the smaller the NPs are easier to be induced to coalesce by SOD. The surface curvature of 100 nm NPs was more conducive to varying the secondary structure of SOD. NPs of 100 nm and 500 nm can cause greater sensitization of SOD endogenous fluorescence, and increase the polarity around tyrosine residue. The enzyme activity assay further revealed the functional differences caused by the size-dependent effects of NPs. NPs of 100 nm and 20 nm induced a more significant change in SOD activity (increased by 20% and 8%, respectively), while NPs of 500 nm and 1000 nm had a little impact on it. Together, smaller NPs have a greater impact on the structure and function of SOD. This study revealed the size-dependent toxicity of NPs to protein, which provided a rationale for the necessary avoidance and substitution of NPs in engineering applications.

Toxicity of dibutyl phthalate to pakchoi (Brassica campestris L.): Evaluation through different levels of biological organization

Dibutyl phthalate (DBP) is a typical persistent organic pollutant with a high load in the agricultural soils of vegetable crops. Currently, studies on the toxicity of DBP in vegetable crops are limited. Therefore, in this study, pakchoi (Brassica campestris L.), a typical vegetable crop, was used to evaluate the toxic effects of DBP. Pakchoi was exposed to DBP for 24 d at three doses (2, 20, and 200 mg/kg), and the phenotypic, biochemical, and molecular indicators were determined. The results revealed that DBP could reduce the emergence of pakchoi and inhibit plant height, root length, fresh weight, and leaf area. At the biochemical level, DBP exposure could reduce the content of three typical photosynthetic pigments (chlorophyll a and b and carotenoids). The effects of DBP exposure on the quality of pakchoi were primarily through reduced soluble sugar and increased proline contents. In addition, O₂·^- and H₂O₂ levels increased after DBP stress, and the corresponding antioxidant enzymes (SOD, POD, and CAT) were activated to resist oxidative damage. The dose- and time-dependent toxicities of DBP to pakchoi were demonstrated using an integrated biological response index. Finally, the molecular-level results on Day 24 showed that the three antioxidant enzyme genes (sod, pod, and cat) were significantly downregulated, and the antioxidant enzyme genes were more sensitive biomarkers than the enzyme activities. However, the expression level of enzyme genes was opposite to that of enzyme activity (SOD and POD); thus, DBP might directly interact with these enzymes. Molecular docking showed that DBP could stably bind near the SOD/POD active center through intermolecular interaction forces. This study provides essential information on the risk of DBP toxicity to vegetable crops.

Ferric ions release from iron-binding protein: Interaction between acrylamide and human serum transferrin and the underlying mechanisms of their binding

Acrylamide (ACR) is a surprisingly common chemical due to its widespread use in industry and various other applications. However, its toxicity is a matter of grave concern for public health. Even worse, ACR is frequently detected in numerous fried or baked carbohydrate-rich foods due to the Maillard browning reaction. Herein, this study intends to delineate the underlying molecular mechanisms of Fe ions released from iron-binding protein transferrin (TF) after acrylamide binding by combining multiple methods, including multiple complementary spectroscopic techniques (UV-Vis, fluorescence, and circular dichroism spectroscopy), isothermal titration calorimetry, ICP-MS measurements, and modeling simulations. Results indicated that free Fe was released from TF only under high-dose ACR exposure (>100 μM). Acrylamide binding induced the loosening and unfolding of the backbone and polypeptide chain and destroyed the secondary structure of TF, thereby leading to protein misfolding and denaturation of TF and forming a larger size of TF agglomerates. Of which, H-binding and van der Waals force are the primary driving force during the binding interaction between ACR and TF. Further modeling simulations illustrated that ACR prefers to bind to the hinge region connecting the C-lobe and N-lobe, after that it attaches to the Fe binding sites of this protein, which is the cause of free Fe release from TF. Moreover, ACR interacted with the critical fluorophore residues (Tyr, Trp, and Phe) in the binding pocket, which might explain such a phenomenon of fluorescence sensitization. The two binding sites (Site 2 and Site 3) located around the Fe (III) ions with low-energy conformations are more suitable for ACR binding. Collectively, our study demonstrated that the loss of iron in TF caused by acrylamide-induced structural and conformational changes of transferrin.

Identification of molecular initiating events and key events leading to endocrine disrupting effects of PFOA: Integrated molecular dynamic, transcriptomic, and proteomic analyses

Perfluorooctanoic acid (PFOA) can rapidly activate signaling pathways independent of nuclear hormone receptors through membrane receptor regulation, which leads to endocrine disrupting effects. In the present work, the molecular initiating event (MIE) and the key events (KEs) which cause the endocrine disrupting effects of PFOA have been explored and determined based on molecular dynamics simulation (MD), fluorescence analysis, transcriptomics, and proteomics. MD modeling and fluorescence analysis proved that, on binding to the G protein-coupled estrogen receptor-1 (GPER), PFOA could induce a conformational change in the receptor, turning it into an active state. The results also indicated that the binding to GPER was the MIE that led to the adverse outcome (AO) of PFOA. In addition, the downstream signal transduction pathways of GPER, as regulated by PFOA, were further investigated through genomics and proteomics to identify the KEs leading to thr endocrine disrupting effects. Two pathways (Endocrine resistance, ERP and Estrogen signaling pathway, ESP) containing GPER were regulated by different concentration of PFOA and identified as the KEs. The knowledge of MIE, KEs, and AO of PFOA is necessary to understand the links between PFOA and the possible pathways that lead to its negative effects.

Perfluorooctanoic acid affects mouse brain and liver tissue through oxidative stress

The aim of this study was to investigate oxidative stress induced by perfluorooctanoic acid (PFOA) in the brain and liver tissues of Balb/c mice as well as protective effects of taurine and coenzyme Q₁₀ (CoQ₁₀) in both organs. For this purpose, animals were treated with PFOA (15 and 30 mg/kg) orally and their lipid peroxidation, total glutathione levels (GSH), and antioxidant enzyme activities measured and both tissues analysed for histopathological changes. Our results showed a dose-dependent decrease in body weight and increase in relative brain and liver weights, PFOA-induced lipid peroxidation and reduced glutathione peroxidase (GPx) activity in the brain tissue, and changes in GSH levels, GPx, superoxide dismutase (Cu-Zn SOD), and catalase (CAT) activities in the liver tissue. Pre-treatment with taurine or CoQ₁₀ provided protection against PFOA-induced Cu-Zn SOD reduction in the liver tissue. Our findings evidence the depleting effect of PFOA on antioxidative systems and confirm that PFOA exerts its (neuro)toxicity through oxidative stress, but further research is needed to identify the exact toxicity mechanisms, especially in the brain.

Effects of benzo[a]pyrene exposure on oxidative stress and apoptosis of gill cells of Chlamys farreri in vitro

As a common pollutant in marine environment, benzo[a]pyrene (B[a]P) has high toxicity to economic shellfish. In order to explore the mechanism of oxidative stress and apoptosis, the effects of 0, 2, 4, 8 μg/mL B[a]P on gill cells of C. farreri at 12 and 24 h were studied. The results showed that B[a]P decreased the activity of gill cells, increased the content of reactive oxygen species (ROS) and the expression of antioxidant defense genes. Besides, B[a]P could induce oxidative damage to nucleus and mitochondria. The gene expression and enzyme activity of apoptosis pathway related factors were changed. In conclusion, these results showed that B[a]P could cause oxidative stress and oxidative damage in gill cells of C. farreri, and mediate gill cell apoptosis through mitochondrial pathway and death receptor pathway. This article provides a theoretical basis for clarifying the molecular mechanism of PAHs-included oxidative stress and apoptosis in bivalves.

Response of earthworm coelomocytes and catalase to pentanone and hexanone: a revelation of the toxicity of conventional solvents at the cellular and molecular level

Organic solvents like 2-pentanone and 2-hexanone which are widely used in industrial production make up a large proportion of the source of chemical pollution. What is worrisome is that the cellular and molecular toxicity of 2-pentanone and 2-hexanone has not been reported yet. Based on this, earthworms and catalase (CAT) were chosen as target receptors for the toxicity studies. The cytotoxicity of 2-pentanone and 2-hexanone was revealed by measuring the multiple intracellular indicators of oxidative stress. At the molecular level, changes in the structure and function of CAT were characterized in vitro by the spectroscopy and molecular docking. The results show that 2-pentanone and 2-hexanone that induced the accumulation of reactive oxygen species can eventually reduce coelomocytes viability, accompanying by the regular changes of antioxidant activity and lipid peroxidation level. In addition, the exposure of 2-pentanone and 2-hexanone can shrink the backbone structure of CAT, quench the fluorescence, and misfold the secondary structure. The decrease in enzyme activity should be attributed to the structural changes induced by surface binding. This study discussed the toxicological effects and mechanisms of conventional solvents at the cellular and molecular level, which creatively proposed a joint research method.

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

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

A Critical Review and Meta-Analysis of Impacts of Per- and Polyfluorinated Substances on the Brain and Behavior

Per- and polyfluoroalkyl substances (PFAS) are a class of structurally diverse synthetic organic chemicals that are chemically stable, resistant to degradation, and persistent in terrestrial and aquatic environments. Widespread use of PFAS in industrial processing and manufacturing over the last 70 years has led to global contamination of built and natural environments. The brain is a lipid rich and highly vascularized organ composed of long-lived neurons and glial cells that are especially vulnerable to the impacts of persistent and lipophilic toxicants. Generally, PFAS partition to protein-rich tissues of the body, primarily the liver and blood, but are also detected in the brains of humans, wildlife, and laboratory animals. Here we review factors impacting the absorption, distribution, and accumulation of PFAS in the brain, and currently available evidence for neurotoxic impacts defined by disruption of neurochemical, neurophysiological, and behavioral endpoints. Emphasis is placed on the neurotoxic potential of exposures during critical periods of development and in sensitive populations, and factors that may exacerbate neurotoxicity of PFAS. While limitations and inconsistencies across studies exist, the available body of evidence suggests that the neurobehavioral impacts of long-chain PFAS exposures during development are more pronounced than impacts resulting from exposure during adulthood. There is a paucity of experimental studies evaluating neurobehavioral and molecular mechanisms of short-chain PFAS, and even greater data gaps in the analysis of neurotoxicity for PFAS outside of the perfluoroalkyl acids. Whereas most experimental studies were focused on acute and subchronic impacts resulting from high dose exposures to a single PFAS congener, more realistic exposures for humans and wildlife are mixtures exposures that are relatively chronic and low dose in nature. Our evaluation of the available human epidemiological, experimental, and wildlife data also indicates heightened accumulation of perfluoroalkyl acids in the brain after environmental exposure, in comparison to the experimental studies. These findings highlight the need for additional experimental analysis of neurodevelopmental impacts of environmentally relevant concentrations and complex mixtures of PFAS.

[Bmim]FeCl4 mediated inhibition and toxicity during anaerobic digestion: Dose-response kinetics, biochar-dependent detoxification and microbial resistance

[Bmim]FeCl₄, or 1‑butyl‑3-methylimidazolium tetrachloroferrate, is a typical ionic liquid (IL). Its recyclable, magnetic, multicomponent, and solvent-free nature makes it a particularly attractive ionic liquid for use in industrial processes. Despite its widespread use, the potential hazards that [Bmim]FeCl₄ might pose to the environment, including productive microorganisms, have not been explored. In this study, the dose-response of [Bmim]FeCl₄ in anaerobic digestion (AD) was investigated to assess the potential toxification and biochar-dependent detoxification in microbial communities, including enzymatic activity and molecule docking dynamics. Our results showed that methane production (31.52 mL_max/gVS) was sharply inhibited following [Bmim]FeCl₄ treatment. Moreover, increasing the dosage of [Bmim]FeCl₄ caused more dissolved organic matter (DOM) to be generated. Interestingly, 0.4 g/L of [Bmim]FeCl₄ could stimulate the high activity of microbial hydrolase and ATPase. However, a higher concentration of 2.65 g/L prevented these enzymatic processes from continuing. At the cellular level, higher concentration of [Bmim]FeCl₄ (>0.4 g/L) increased malondialdehyde (MDA) levels, leading to a higher cell lethal rate and weakening of the secondary structures of protein (especially, the amide I region). At the molecular level, the competitive H-bonding in the active sites caused low activity and consummated more energy. At the community level, structural equation modeling (SEM) revealed that [Bmim]FeCl₄ and biochar were the main drivers for microbial community succession. For instance, high [Bmim]FeCl₄ (8 g/L) benefited the growth of Clostridium sensu_stricto (from ≤1% to 27%). It is worth mentioning that biochar reversed the inhibition with high α-diversity, which caused a resurgence in the activity of previously inhibited ATPase and hydrolase. H₂-trophic methanogens (Methanolinea and Methaofastidisoum) were sensitive to [Bmim]FeCl₄ and decreased linearly while acetoclastic methanogens (Methanosaeta) were unchanged. These findings were consistent with the short-term activity tests and further verified by functional analysis.