Gene expression profile changes in Eisenia fetida chronically exposed to PFOA

How do different arsenic species affect the joint toxicity of perfluorooctanoic acid and arsenic to earthworm Eisenia fetida: A multi-biomarker approach

Perfluorooctanoic acid (PFOA) and arsenic are widely distributed pollutants and can coexist in the environment. However, no study has been reported about the effects of different arsenic species on the joint toxicity of arsenic and PFOA to soil invertebrates. In this study, four arsenic species were selected, including arsenite (As(III)), arsenate (As(V)), monomethylarsonate (MMA), and dimethylarsinate (DMA). Earthworms Eisenia fetida were exposed to soils spiked with sublethal concentrations of PFOA, different arsenic species, and their binary mixtures for 56 days. The bioaccumulation and biotransformation of pollutants, as well as eight biomarkers in organisms, were assayed. The results indicated that the coexistence of PFOA and different arsenic species in soils could enhance the bioavailability of arsenic species while reducing the bioavailability of PFOA, and inhibit the arsenic biotransformation process in earthworms. Responses of most biomarkers in joint treatments of PFOA and As(III)/As(V) showed more significant variations compared with those in single treatments, indicating higher toxicity to the earthworms. The Integrated Biomarker Response (IBR) index was used to integrate the multi-biomarker responses, and the results also exhibited enhanced toxic effects in combined treatments of inorganic arsenic and PFOA. In comparison, both the biomarker variations and IBR values were lower in joint treatments of PFOA and MMA/DMA. Then the toxic interactions in the binary mixture systems were characterized by using a combined method of IBR and Effect Addition Index. The results revealed that the toxic interactions of the PFOA/arsenic mixture in earthworms depended on the different species of arsenic. The combined exposure of PFOA with inorganic arsenic led to a synergistic interaction, while that with organic arsenic resulted in an antagonistic response. Overall, this study provides new insights into the assessment of the joint toxicity of perfluoroalkyl substances and arsenic in soil ecosystems.

Phytoremediation prospects of per- and polyfluoroalkyl substances: A review

Extensive use of per- and polyfluoroalkyl substances (PFASs) in various industrial activities and daily-life products has made them ubiquitous contaminants in soil and water. PFAS-contaminated soil acts as a long-term source of pollution to the adjacent surface water bodies, groundwater, soil microorganisms, and soil invertebrates. While several remediation strategies exist to eliminate PFASs from the soil, strong ionic interactions between charged groups on PFAS with soil constituents rendered these PFAS remediation technologies ineffective. Pilot and field-scale data from recent studies have shown a great potential of PFAS to bio-accumulate and distribute within plant compartments suggesting that phytoremediation could be a potential remediation technology to clean up PFAS contaminated soils. Even though several studies have been performed on the uptake and translocation of PFAS by different plant species, most of these studies are limited to agricultural crops and fruit species. In this review, the role of both aquatic and terrestrial plants in the phytoremediation of PFAS was discussed highlighting different mechanisms underlying the uptake of PFASs in the soil-plant and water-plant systems. This review further summarized a wide range of factors that influence the bioaccumulation and translocation of PFASs within plant compartments including both structural properties of PFASs and physiological properties of plant species. Even though phytoremediation appears to be a promising remediation technique, some limitations that reduced the feasibility of phytoremediation in the practical application have been emphasized in previous studies. Additional research directions are suggested, including advanced genetic engineering techniques and endophyte-assisted phytoremediation to upgrade the phytoremediation potential of plants for the successful removal of PFASs.

Ecotoxicological effects of per- and polyfluoroalkyl substances (PFAS) and of a new PFAS adsorbing organoclay to immobilize PFAS in soils on earthworms and plants

A novel adsorptive organoclay (Intraplex A®) was developed for the in situ immobilization of per- and polyfluoroalkyl substances (PFAS) in the vadose zone. We provide the first evaluation of the effects of Intraplex A® on earthworms and plants in a PFAS-contaminated soil. Ecotoxicological tests were carried out on control soil with and without Intraplex A® (C + I and C, respectively) and PFAS-contaminated soil with and without Intraplex A® (PFAS + I and PFAS, respectively). We investigated the acute ecotoxicological effects of PFAS and Intraplex A® on the growth, reproduction and survival of earthworms (Eisenia fetida) and on plant growth (oat - Avena sativa and turnip - Brassica rapa L. silvestris). Earthworm lethality was 7.6 lower in PFAS + I than in PFAS soil. Earthworms avoided 100% C + I and PFAS + I soils, and reduced earthworms' reproduction was observed in both these soils. For both plant species, the PFAS + I soil yielded less fresh and dry shoot biomass than the PFAS soil, while root growth remained unaffected (all tests: p < 0.05). Soils with Intraplex A® had some negative effects on plants and earthworms, which must be balanced with its benefits as an in situ PFAS adsorbent.

Evaluation of single and joint toxicity of perfluorooctanoic acid and arsenite to earthworm (Eisenia fetida): A multi-biomarker approach

Perfluorooctanoic acid (PFOA) and arsenic are ubiquitous environmental contaminants and could co-exist in soil. However, data on their possible combined toxic effects on terrestrial organisms are still lacking. In this study, we exposed earthworm Eisenia fetida to artificial soil spiked with different sub-lethal levels of PFOA, arsenite (As(III)) or their mixture for 28 days. The bioaccumulation and multi-biomarker responses in the earthworms were measured. Results showed that the co-existence of PFOA and As(III) in soil enhanced the bioaccumulation of arsenic while reduced the bioaccumulation of PFOA. Most selected biomarkers exhibited significant responses at higher exposure levels and indicated oxidative damages. Biomarker Response Index (BRI) was used to integrate the multi-biomarker responses and the results showed significant dose-effect relationships between biological health status and exposure levels. Moreover, variation analysis of multi-biomarkers and BRI proved that As(III) exhibited more toxicity than PFOA to the earthworms. Based on BRI results, Effect Addition Index (EAI) was calculated to evaluate the joint effects of the two toxicants. According to EAI, the joint toxicity of PFOA and As(III) was related to exposure concentration, changing from synergism to slight antagonism with the increase of exposure level. These results provide valuable toxicological information for the risk assessment of co-exposure to PFOA and arsenic in the soil environment. Moreover, this study proved that BRI is an effective tool to integrate multi-biomarker responses, and its combination with EAI provides a useful combined approach to evaluate the joint effects of mixed contamination systems.

PFOA regulate adenosine receptors and downstream concentration-response cAMP-PKA pathway revealed by integrated omics and molecular dynamics analyses

As an important pollutant, perfluorooctane acid (PFOA) has been widely concerned and reported by thousands of times, while less is known about the concentration-response pathway of PFOA. The aim of the present work was to reveal the concentration-response mechanism of PFOA in human cells. Omics results showed that calcium-related pathways play key roles in PFOA injury mechanisms. The results of GO and KEGG analyses showed that the cAMP signaling pathway was presented as the top one in all of the regulatory patterns and concentrations groups of PFOA. In the cAMP signaling pathway, the adenosine A₁ receptor (ADORA1) recognized the low concentration of PFOA and induced pathway "G_i-cAMP-PKA" to decrease the concentration of cAMP. This indicated that the low concentration of PFOA may promote breast hyperplasia and inhibit lactation. While adenosine A_2A receptor (ADORA2A) recognized the high concentration of PFOA and induced pathway "G_S-AC-cAMP-RKA" to increase the concentration of cAMP, induce cell damage and may lead to the deterioration of breast cancer. The results of molecular dynamics simulation showed that PFOA could bind to ADORA1 and ADORA2A, thus cause subsequent signal transduction. Furthermore, considering the strong binding ability of PFOA with ADORA1, PFOA tends to bind to ADORA1 at a low concentration. On the other side, PFOA at high concentration will continue to bind to another receptor protein, ADORA2A, and activate subsequent signaling pathways. Combined analyses of transcriptomic and proteomic revealed that different concentrations of PFOA regulate cellular calcium-related pathways. The cAMP pathway showed a concentration-response effect of PFOA. After treatment with different concentrations of PFOA, ADORA1 and ADORA2A were activated respectively, showing opposite cellular effects, leading to kinds of breast lesions. In the nervous system, PFOA might induce a variety of nervous system diseases. The present work was an exploration on the toxicological mechanism of PFOA, providing important information on the health impacts of PFOA in humans.

A review of responses of terrestrial organisms to perfluorinated compounds

Perfluorinated compounds (PFCs) are a class of persistent organic pollutants with widespread distribution in the environment. Since the soil environment has become a significant sink for PFCs, the toxicological assessment about their potential effects on terrestrial organisms is necessary. This review compiles the toxicity researches of regular and emerging PFCs on classical terrestrial biota i.e. microorganisms, earthworms, and plants. In the soil environment, the bioavailability of PFCs much depends on their adsorption in soil, which is affected by soil properties and PFCs structure. By the exploration of bacterial community richness and structure, the gene expression, the influences of PFCs on soil microorganisms were revealed; while the plants and earthworms manifested the PFCs disruption not only through macroscopic indicators, but also from molecular and metabolite responses. Basically, the addition of PFCs would accelerate the production of reactive oxygen species (ROS) in terrestrial organisms, while the excessive ROS could not be eliminated by the defense system causing oxidative damage. Nowadays, the PFCs toxic mechanisms discussed are limited to a single strain, Escherichia coli; thus, the complexity of the soil environment demands further in-depth researches. This review warrants studies focus on more potential quantitative toxicity indicators, more explicit elaboration on toxicity influencing factors, and environmentally relevant concentrations to obtain a more integrated picture of PFCs toxicity on terrestrial biota.

Persistence of the parabens in soil and their potential toxicity to earthworms

Due to their antimicrobial activity, parabens are commonly used as preservatives in a variety of consumer goods including cosmetics, pharmaceuticals, and personal care products. During the production, usage and disposal of these products, parabens are released into the environment. In this study, the persistence of three widely used parabens; methyl-, propyl-, and butyl paraben in soil and their toxic effects on the soil invertebrate, Eisenia fetida was investigated. The results of this study indicate that selected parabens do not negatively affect the survival, growth, and reproduction of Eisenia fetida up to 1000 mg Kg^-1 concentration. Further, these parabens (0-1000 mg Kg^-1) exhibited a low persistence in soil with more than 90 % disappearing within three days. In contrast, only 16-54 % degradation of parabens occurred in frozen soil suggesting a microbial role in parabens degradation. This study demonstrates that methyl-, propyl-, and butyl parabens degrade rapidly in the terrestrial environment and therefore, are unlikely to pose a threat to species such as Eisenia fetida. To our knowledge, this is the first report on the toxicity of parabens to earthworms.

Assessing the Ecological Risks of Per- and Polyfluoroalkyl Substances: Current State-of-the Science and a Proposed Path Forward

Per- and poly-fluoroalkyl substances (PFAS) encompass a large, heterogenous group of chemicals of potential concern to human health and the environment. Based on information for a few relatively well-understood PFAS such as perfluorooctane sulfonate and perfluorooctanoate, there is ample basis to suspect that at least a subset can be considered persistent, bioaccumulative, and/or toxic. However, data suitable for determining risks in either prospective or retrospective assessments are lacking for the majority of PFAS. In August 2019, the Society of Environmental Toxicology and Chemistry sponsored a workshop that focused on the state-of-the-science supporting risk assessment of PFAS. The present review summarizes discussions concerning the ecotoxicology and ecological risks of PFAS. First, we summarize currently available information relevant to problem formulation/prioritization, exposure, and hazard/effects of PFAS in the context of regulatory and ecological risk assessment activities from around the world. We then describe critical gaps and uncertainties relative to ecological risk assessments for PFAS and propose approaches to address these needs. Recommendations include the development of more comprehensive monitoring programs to support exposure assessment, an emphasis on research to support the formulation of predictive models for bioaccumulation, and the development of in silico, in vitro, and in vivo methods to efficiently assess biological effects for potentially sensitive species/endpoints. Addressing needs associated with assessing the ecological risk of PFAS will require cross-disciplinary approaches that employ both conventional and new methods in an integrated, resource-effective manner. Environ Toxicol Chem 2021;40:564-605. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Antioxidant defense system responses, lysosomal membrane stability and DNA damage in earthworms (Eisenia fetida) exposed to perfluorooctanoic acid: an integrated biomarker approach to evaluating toxicity

Perfluorooctanoic acid (PFOA) is one of the most representative perfluoroalkyl substances and has garnered intense human and ecological health concerns due to its ubiquity in the environment, bio-accumulative nature and potential toxicological effects. In this study, an artificial soil containing PFOA was used to evaluate the biological toxicity of PFOA to earthworms Eisenia fetida. Six kinds of oxidative stress biomarkers, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST), reduced glutathione (GSH) and lipid peroxidation (LPO), as well as lysosomal membrane stability (LMS) and DNA damage in earthworms were detected after exposure to 0, 10, 20, 40, 80 and 120 mg kg⁻¹ PFOA in the soil for 3, 7, 14, 28, and 42 days. The results of multi-biomarker responses indicated that PFOA can induce various adverse effects on earthworms, including growth inhibition, oxidative stress and genotoxicity, resulting in lipid membrane peroxidation, decreased lysosomal membrane stability and DNA damage. LPO, LMS and DNA damage all presented dose- and time-dependent relationships. An integrated biomarker response (IBR) index was applied to summarize the multi-biomarker responses to star plots, and the IBR value was calculated as the area of the plots to indicate the integrated stress of PFOA on earthworms. The IBR index showed that the integrated stress induced by PFOA increased markedly throughout the exposure period, exhibiting a concentration-related and exposure time-related effect. The graphical changing trend of the IBR star plots, along with the multi-biomarker responses, suggested that the biomarkers of the antioxidant defense system in earthworms are sufficiently sensitive for short-term PFOA biomonitoring programs, while the bioindicators that indicate actual damage in organisms are more suitable to be employed in long-term monitoring programs for the risk assessment of PFOA. This is the first study evaluating the biological toxicity of PFOA by using an integrated biomarker approach. Our results showed that PFOA can potentially damage soil ecosystems, which provides valuable information for chemical risk assessment of PFOA in the soil environment and early warning bioindicators of soils contaminated by PFOA.

The integrated biomarker response (IBR) index was calculated to evaluate the integrated toxicological effects of PFOA on earthworm Eisenia fetida.

Ecological risk assessment for perfluorooctanoic acid in soil using a species sensitivity approach

Perfluorooctanoic acid (PFOA) is one of the persistent organic pollutants that has been listed in Annex A of the Stockholm Convention and has attracted attention owing to its endocrine-disrupting properties. However, there is currently little information available regarding the soil ecotoxicity of PFOA and the associated ecological risks. Accordingly, in this study, we sought to assess the soil ecological risk of PFOA based on a probabilistic approach using data obtained from multispecies bioassays and soil toxicity assessments, from which we generated soil species sensitivity distributions and estimated soil protective concentrations for PFOA. Using the latter distributions, we also undertook a probabilistic ecological risk assessment. On the basis of acute and chronic toxicity estimates obtained from bioassays involving eight soil-associated organisms from six diverse taxonomic groups, we could deduce that PFOA poses a negligible risk to soil ecosystems. However, we also found that this chemical may be more toxic than some of the established endocrine-disrupting chemicals such as bisphenol A, nonylphenol, and methylparaben, thereby indicating that further in-depth studies would be necessary to obtain a better understanding of the toxic potential of this chemical in the soil environment.

Annotation of nerve cord transcriptome in earthworm Eisenia fetida

In annelid worms, the nerve cord serves as a crucial organ to control the sensory and behavioral physiology. The inadequate genome resource of earthworms has prioritized the comprehensive analysis of their transcriptome dataset to monitor the genes express in the nerve cord and predict their role in the neurotransmission and sensory perception of the species. The present study focuses on identifying the potential transcripts and predicting their functional features by annotating the transcriptome dataset of nerve cord tissues prepared by Gong et al., 2010 from the earthworm Eisenia fetida. Totally 9762 transcripts were successfully annotated against the NCBI nr database using the BLASTX algorithm and among them 7680 transcripts were assigned to a total of 44,354 GO terms. The conserve domain analysis indicated the over representation of P-loop NTPase domain and calcium binding EF-hand domain. The COG functional annotation classified 5860 transcript sequences into 25 functional categories. Further, 4502 contig sequences were found to map with 124 KEGG pathways. The annotated contig dataset exhibited 22 crucial neuropeptides having considerable matches to the marine annelid Platynereis dumerilii, suggesting their possible role in neurotransmission and neuromodulation. In addition, 108 human stem cell marker homologs were identified including the crucial epigenetic regulators, transcriptional repressors and cell cycle regulators, which may contribute to the neuronal and segmental regeneration. The complete functional annotation of this nerve cord transcriptome can be further utilized to interpret genetic and molecular mechanisms associated with neuronal development, nervous system regeneration and nerve cord function.

Toxicity of perfluorooctanoic acid towards earthworm and enzymatic activities in soil

Perfluorooctanoic acid (PFOA) is a widespread persistent organic contaminant in the environment that has recently raised much of regulatory and public concern. Therefore, assessment of its ecological risk is a top priority research. Hence, this study investigated the toxicity of PFOA to beneficial microbial processes in the soil such as activities of dehydrogenase, urease and potential nitrification in addition to earthworm survival, weight loss and PFOA bioaccumulation in two contrasting soils. In general, PFOA caused inhibition of all the measured microbial processes in a dose-dependent manner and the inhibition was higher in Williamtown (WT) soil than Edinburgh (EB) soil. Thus, WT soil being sandy in nature with low clay content showed higher PFOA bioavailability and hence showed higher toxicity. There was no mortality in earthworms exposed up to 100 mg PFOA/kilogram soil in both the soils; however, there was a significant weight loss from 25 mg/kg onwards. This study clearly demonstrates that soil contamination of PFOA can lead to adverse effects on soil health.