The ribosome biogenesis pathway as an early target of benzyl butyl phthalate (BBP) toxicity in Chironomus riparius larvae

Insights into the molecular response of Dioithona rigida to selenium nanoparticles: de novo transcriptome assembly and differential gene expression analysis

The impact of contaminants on Copepod sp. and its molecular response is least explored, despite their abundance and dominance among invertebrates in aquatic environments. In the present investigation, Dioithona rigida, a cyclopoid zooplankton, was treated with selenium nanoparticles (SeNPs) to determine the associated biochemical changes, and the chronic exposure effects were recorded using transcriptomic analysis. It was found that, SeNPs were acutely toxic with a lethal dose 50% of 140.9 mg/L. The de novo assembled transcriptome of the copepod comprised 81,814 transcripts, which underwent subsequent annotations to biological processes (23,378), cellular components (21,414), and molecular functions (31,015). Comparison of the expressed transcripts against the treated sample showed that a total of 186 transcript genes were differentially expressed among the D. rigida treatments (control and SeNPs). The significant downregulated genes are coding for DNA repair, DNA-templated DNA replication, DNA integration, oxidoreductase activity and transmembrane transport. Similarly, significant upregulations were observed in protein phosphatase binding and regulation of membrane repolarization. Understanding the impact of SeNPs on copepods is crucial not only for aquatic ecosystem health but also for human health, as these organisms play a key role in marine food webs, ultimately affecting the fish consumed by humans. By elucidating the molecular responses and potential toxicological effects of SeNPs, this study provides key insights for risk assessments and regulatory policies, ensuring the safety of seafood and protecting human health from the unintended consequences of nanoparticle pollution.

Physiological and transcriptomic responses of silkworms to graphene oxide exposure

The growing use of nanomaterials has sparked significant interest in assessing the insect toxicities of nanoparticles. The silkworm, as an economically important insect, serves as a promising model for studying how insects respond to harmful substances. Here, we conducted a comprehensive investigation on the impact of graphene oxide (GO) on silkworms using a combination of physiological and transcriptome analyses. GO can enter the midguts and posterior silk glands of silkworms. High GO concentrations (> 25 mg/L) significantly (P < 0.01) inhibited larval growth. Additionally, GO (> 5 mg/L) significantly reduced the cocooning rate, and GO (> 15 mg/L) hindered oviduct development and egg laying in silkworms. GO increased the reactive oxygen species content and regulated catalase activity, suggesting that it may affect insect growth by regulating reactive oxygen detoxification. The transcriptome data analysis showed that 35 metabolism-related genes and 20 ribosome biogenesis-related genes were differentially expressed in response to GO, and their expression levels were highly correlated. Finally, we propose that a Ribosome biogenesis-Metabolic signaling network is involved in responses to GO. The research provides a new perspective on the molecular responses of insects to GO.

Phthalates contamination in sediments: A review of sources, influencing factors, benthic toxicity, and removal strategies

Sediments provide habitat and food for benthos, and phthalates (PAEs) have been detected in numerous river and marine sediments as a widely used plastic additive. PAEs in sediments is not only toxic to benthos, but also poses a threat to pelagic fish and human health through the food chain, so it is essential to comprehensively assess the contamination of sediments with PAEs. This paper presents a critical evaluation of PAEs in sediments, which is embodied in the analysis of the sources of PAEs in sediments from multiple perspectives. Biological production is indispensable, while artificial synthesis is the most dominant, thus the focus was on analyzing the industrial and commercial sources of synthetic PAEs. In addition, since the content of PAEs in sediments varies, some factors affecting the content of PAEs in sediments are summarized, such as the properties of PAEs, the properties of plastics, and environmental factors (sediments properties and hydrodynamic conditions). As endocrine disruptors, PAEs can produce toxicity to its direct contacts. Therefore, the effects of PAEs on benthos immunity, endocrinology, reproduction, development, and metabolism were comprehensively analyzed. In addition, we found that reciprocal inhibition and activation of the systems lead to genotoxicity and apoptosis. Finally, the paper discusses the feasible measures to control PAEs in wastewater and leachate from the perspective of source control, and summarizes the in-situ treatment measures for PAEs contamination in sediments. This paper provides a comprehensive review of PAEs contamination in sediments, toxic effects and removal strategies, and provides an important reference for reducing the contamination and toxicity of PAEs to benthos.

Alterations induced by Bisphenol A on cellular organelles and potential relevance on human health

Bisphenol A (BPA) is a chemical partially soluble in water and exists in a solid state. Its structural similarity with estrogen makes it an endocrine-disrupting chemical. BPA can disrupt signaling pathways at very low doses and may cause organellar stress. According to in vitro and in vivo studies, BPA interacts with various cell surface receptors to cause organellar stress, producing free radicals, cellular toxicity, structural changes, DNA damage, mitochondrial dysfunction, cytoskeleton remodeling, centriole duplication, and aberrant changes in several cell signaling pathways. The current review summarizes the impact of BPA exposure on the structural and functional aspects of subcellular components of cells such as the nucleus, mitochondria, endoplasmic reticulum, lysosome, ribosome, Golgi apparatus, and microtubules and its consequent impact on human health.

Differences of functionalized graphene materials on inducing chronic aquatic toxicity through the regulation of DNA damage, metabolism and oxidative stress in Daphnia magna

Graphene can be modified with functional groups when released into the environment. However, very little is known about molecular mechanisms of chronic aquatic toxicity induced by graphene nanomaterials with different surface functional groups. By using RNA sequencing, we investigated the toxic mechanisms of unfunctionalized graphene (u-G), carboxylated graphene (G-COOH), aminated graphene (G-NH₂), hydroxylated graphene (G-OH) and thiolated graphene (G-SH) to Daphnia magna during 21-day exposure. We revealed that alteration of ferritin transcription levels in the "mineral absorption" signaling pathway is a molecular initiating event leading to potential of oxidative stress in Daphnia magna by u-G, while toxic effects of four functionalized graphenes are related to several metabolic pathways including the "protein digestion and absorption" pathway and "carbohydrate digestion and absorption" pathway. The transcription and translation related pathways were inhibited by G-NH₂ and G-OH, which further affected the functions of proteins and normal life activities. Noticeably, detoxifications of graphene and its surface functional derivatives were promoted by increasing the gene expressions related to chitin and glucose metabolism as well as cuticle structure components. These findings demonstrate important mechanistic insights that can potentially be employed for safety assessment of graphene nanomaterials.

iTRAQ-based quantitative proteomic analysis in liver of Pomacea canaliculata induced by oleanolic acid stress

BACKGROUND

Triterpene acid is one of the typical active constituents of Eucalyptus bark, which is the main by-product of the Eucalyptus wood industry. Our studies have demonstrated that triterpene acid stress could inhibit climbing and increase mortality in Pomacea canaliculata (Lamarck). However, limited attention has been paid to the proteomic responses of this snail under triterpene acid stress.

RESULT

Using iTRAQ-based quantitative proteomics, we elucidated the regulatory mechanism in the livers of P. canaliculata held in chlorine-free water and exposed to 100 mg L^-1 oleanolic acid (OA) for 24 h. A total of 4308 proteins were identified, of which 274 were differentially expressed proteins (DEPs) including 168 (61.31%) differentially upregulated proteins and 106 (38.69%) differentially downregulated proteins. Bioinformatics analysis revealed that P. canaliculata responses to OA stress are mainly involved in glucose metabolism, energy synthesis, immune response, stress response, protein synthesis, and apoptosis. According to KEGG analysis, the 274 DEPs were mapped to 168 KEGG pathways and 10 KEGG pathways were significantly enriched (P < 0.05). Furthermore, qRT-PCR was performed for histone H4, catalase, isocitrate dehydrogenase, superoxide dismutase, ferritin, lipase, and tropomyosin to validate the iTRAQ results.

CONCLUSION

Proteomic analysis suggested that OA stress led to the disruption of glucose metabolism, energy synthesis, and protein synthesis, and triggered a series of molecular pathways containing many key proteins involved in the immune process, thereby helping P. canaliculata resist OA stress. © 2022 Society of Chemical Industry.

Effects of butyl benzyl phthalate exposure on Daphnia magna growth, reproduction, embryonic development and transcriptomic responses

Butyl benzyl phthalate (BBP) is widely used as a plasticizer to increase the plasticity and flexibility of plastic products. Although the potential health hazards of BBP have recently received extensive attention, its toxicological properties and mechanisms remain largely undefined. In the present work, growth, reproductive and developmental toxicity of BBP to Daphnia magna were evaluated, and the transcriptomic alteration of early embryos upon BBP exposure was analyzed. In a 21-day chronic toxicity test, reduced survival ratio, decreased body length, increased abnormal ratio, advanced time to first brood, and reduced offspring of D. magna were observed. BBP exposure inhibited expression of the vitellogenin gene. In addition, embryotoxicity of BBP was observed, which showed not only in the induction of abnormal neonates, but also in the shortened embryonic development cycle. RNA-Seq of early embryo treated with 0.1 mg/L BBP indicated that the pathways involved in signal transduction, cell communication, and embryonic development were significantly down-regulated, while those of biosynthesis, metabolism, cell homeostasis, redox homeostasis were remarkably up-regulated upon BBP exposure, which was consistent with the above phenotypic results. Taken together, our results highlight the toxic effects of BBP on the embryonic development and larval growth of D. magna.

iTRAQ and PRM-based comparative proteomic profiling in gills of white shrimp Litopenaeus vannamei under copper stress

Crustaceans are particularly sensitive to heavy metal pollution. Copper (Cu) is one of typical heavy metal pollutants in aquatic ecosystems. However, limited attention has been paid on the proteomic responses of shrimp under Cu stress. White shrimp Litopenaeus vannamei held in 5‰ seawater were exposed to 5 mg L^-1 Cu for 3 h, and the regulatory mechanism in the gills was elucidated using iTRAQ-based quantitative proteomics. The results showed that a total of 5034 proteins were identified, 385 differentially expressed proteins (DEPs), including 147 differentially up-regulated proteins (DUPs) and 238 differentially down-regulated proteins (DDPs) were found. Bioinformatics analysis indicated the DEPs responding to Cu stress mainly involved in cytoskeleton, immune response, stress response, protein synthesis, detoxification, ion homeostasis and apoptosis. Furthermore, we still performed PRM analysis on sarcoplasmic calcium binding protein (SCP), serine proteinase inhibitor B3 (SPIB3), C-type lectin 4 (CTL4), cathepsin L (CATHL), JHE-like carboxylesterase 1 (CXE1) and paramyosin (PMY), and biochemical analysis on Cu/Zn-superoxide dismutase (Cu/Zn-SOD) to validate the iTRAQ results, respectively. The present proteome analysis revealed that Cu stress disrupted the ion homeostasis and protein synthesis, and L.vannamei mainly regulates a series of molecular pathways which contained many key proteins involved in the immune process to protect the organism from Cu stress. Our data provides more insight about the underlying mechanisms that related to the stress response of Cu exposure in crustacean.

Multi-Level Gene Expression in Response to Environmental Stress in Aquatic Invertebrate Chironomids: Potential Applications in Water Quality Monitoring

In freshwater ecosystems, aquatic invertebrates are influenced continuously by both physical stress and xenobiotics. Chironomids (Diptera; Chironomidae), or non-biting midges, are the most diverse and abundant invertebrates in freshwater habitats. They are a fundamental link in food chains of aquatic ecosystems. Chironomid larvae tolerate stress factors in their environments via various physiological processes. At the molecular level, environmental pollutants induce multi-level gene responses in Chironomus that regulate cellular protection through the activation of defense processes. This paper reviews literature on the transcriptional responses of biomarker genes to environmental stress in chironomids at the molecular level, in studies conducted from 1991 to 2020 (120 selected literatures of 374 results with the keywords "Chironomus and gene expression" by PubMed search tool). According to these studies, transcriptional responses in chironomids vary depending on the type of stress factor and defensive responses associated with antioxidant activity, the endocrine system, detoxification, homeostasis and stress response, energy metabolism, ribosomal machinery, apoptosis, DNA repair, and epigenetics. These data could provide a comprehensive overview of how Chironomus species respond to pollutants in aquatic environments. Furthermore, the transcriptomic data could facilitate the development of genetic tools for water quality and environmental monitoring based on resident chironomid species.

Prodiamesa olivacea: de novo biomarker genes in a potential sentinel organism for ecotoxicity studies in natural scenarios

Along with traditional ecotoxicological approaches in model organisms, toxicological studies in non-model organisms are being taken into consideration in order to complement them and contribute to more robust approaches. This allows us to figure out the complexity of the exposures involved in natural ecosystems. In this context, in the present research we have used the model species Chironomus riparius (Chironomidae, Diptera) and the non-model species Prodiamesa olivacea (Chironomidae, Diptera) to assess the aquatic toxic effects of acute 4-h and 24-h exposures to 1 μgL^-1 of three common environmental pollutants: butyl benzyl phthalate (BBP), bisphenol A (BPA), and benzophenone 3 (BP3). Individuals of both species were collected from a contaminated river (Sar) in Galicia (Spain). Regarding Chironomus, there are four OECD standardized tests for the evaluation of water and sediment toxicity, in which different species in this genus can be used to assess classical toxicity parameters such as survival, immobilization, reproduction, and development. In contrast, Prodiamesa is rarely used in toxicity studies, even though it is an interesting toxicological species because it shares habitats with Chironomus but requires less extreme conditions (e.g., contamination) and higher oxygen levels. These different requirements are particularly interesting in assessing the different responses of both species to pollutant exposure. Quantitative real-time PCR was used to evaluate the transcriptional changes caused by xenobiotics in different genes of interest. Since information about P. olivacea in genomic databases is scarce, its transcriptome was obtained using de novo RNAseq. Genes involved in biotransformation pathways and the oxidative stress response (MnSOD, CAT, PHGPx, Cyp4g15, Cyp6a14-like and Cyp6a2-like) were de novo identified in this species. Our results show differential toxic responses depending on the species and the xenobiotic, being P. olivacea the dipteran that showed the most severe effects in most of the studied biomarker genes. This work represents a multi-species approach that allows us to deepen in the toxicity of BBP, BPA, and BP3 at the molecular level. Besides, it provides an assessment of the tolerance/sensitivity of natural populations of model and non-model insect species chronically exposed to complex mixtures of pollutants in natural scenarios. These findings may have important implications for understanding the adverse biological effects of xenobiotics on P. olivacea, providing new sensitive biomarkers of exposure to BBP, BPA, and BP3. It also highlights the suitability of Prodiamesa for ecotoxicological risk assessment, especially in aquatic ecosystems.

Genotoxic, metabolic, and biological responses of Chironomus sancticaroli Strixino & Strixino, 1981 (Diptera: Chironomidae) after exposure to BBP

Benzyl butyl phthalate (BBP), which is widely used in industrial production, reaches the aquatic environment, mainly owing to improper disposal of plastic products. In the water, it remains adsorbed to sedimentary particles causing toxic effects in aquatic invertebrates such as Chironomidae, which are important in maintaining ecosystem dynamics and are an important link in the food chain. However, the effects of BBP on Chironomidae are still poorly known. Thus, the toxic effects of BBP on Chironomus sancticaroli at acute (48 h), subchronic (8 d), and chronic (25 d) exposures of concentrations between 0.1 and 2000 μg·L^-1 were determined. Genotoxicity effects, changes in the oxidative stress pathway, and development and emergence of organisms were evaluated. Biochemical markers showed a reduction in cholinesterase (ChE) activity, indicating a neurotoxic effect on acute exposure (1-1000 μg·L^-1). The antioxidant pathway, glutathione S-transferase (GST) activity showed reduction on acute (0.1; 1-2000 μg·L^-1) and subchronic (1-2000 μg·L^-1) exposures and reduction in superoxide dismutase (SOD) activity at all evaluated concentrations, suggesting oxidative stress. In contrast, lipid peroxidation was not observed. DNA damage occurred on acute (10 μg·L^-1) and subchronic (10-2000 μg·L^-1) exposures, indicating genotoxic effects. At concentrations above 10 μg·L^-1, no emergence of adults occurred, while lower concentrations (0.1 and 1 μg·L^-1) showed a reduction in the number of adults, mainly males. The observed effects indicate that BBP is genotoxic and causes biochemical alterations presenting high toxicity at the population level.

Exposure to heavy metal-contaminated sediments disrupts gene expression, lipid profile, and life history traits in the midge Chironomus riparius

Despite the concern about anthropogenic heavy metal accumulation, there remain few multi-level ecotoxicological studies to evaluate their effects in fluvial ecosystems. The toxicity of field-collected sediments exhibiting a gradient of heavy metal contamination (Cd, Pb, and Zn) was assessed in Chironomus riparius. For this purpose, larvae were exposed throughout their entire life cycle to these sediments, and toxic effects were measured at different levels of biological organization, from the molecular (lipidomic analysis and transcriptional profile) to the whole organism response (respiration rate, shape markers, and emergence rate). Alterations in the activity of relevant genes, as well as an increase of storage lipids and decrease in membrane fluidity, were detected in larvae exposed to the most contaminated sediments. Moreover, reduced larval and adult mass, decrease of larval respiration rate, and delayed emergence were observed, along with increased mentum and mandible size in larvae and decreased wing loading in adults. This study points out the deleterious effects of heavy metal exposure at various levels of biological organization and provides some clues regarding the mode of toxic action. This integrative approach provides new insights into the multi-level effects on aquatic insects exposed to heavy metal mixtures in field sediments, providing useful tools for ecological risk assessment in freshwater ecosystems.

De novo transcriptome assembly and differential gene expression analysis of the calanoid copepod Acartia tonsa exposed to nickel nanoparticles

The calanoid copepod Acartia tonsa is a reference species in standardized ecotoxicology bioassay. Despite this interest, there is a lack of knowledge on molecular responses of A. tonsa to contaminants. We generated a de novo assembled transcriptome of A. tonsa exposed 4 days to 8.5 and 17 mg/L nickel nanoparticles (NiNPs), which have been shown to reduce egg hatching success and larval survival but had no effects on the adults. Aims of our study were to 1) improve the knowledge on the molecular responses of A. tonsa copepod and 2) increase the genomic resources of this copepod for further identification of potential biomarkers of NP exposure. The de novo assembled transcriptome of A. tonsa consisted of 53,619 unigenes, which were further annotated to nr, GO, KOG and KEGG databases. In particular, most unigenes were assigned to Metabolic and Cellular processes (34-45%) GO terms, and to Human disease (28%) and Organismal systems (23%) KEGG categories. Comparison among treatments showed that 373 unigenes were differentially expressed in A. tonsa exposed to NiNPs at 8.5 and 17 mg/L, with respect to control. Most of these genes were downregulated and took part in ribosome biogenesis, translation and protein turnover, thus suggesting that NiNPs could affect the copepod ribosome synthesis machinery and functioning. Overall, our study highlights the potential of toxicogenomic approach in gaining more mechanistic and functional information about the mode of action of emerging compounds on marine organisms, for biomarker discovering in crustaceans.

The BPA-substitute bisphenol S alters the transcription of genes related to endocrine, stress response and biotransformation pathways in the aquatic midge Chironomus riparius (Diptera, Chironomidae)

Bisphenol S (BPS) is an industrial alternative to the endocrine disruptor bisphenol A (BPA), and can be found in many products labeled “BPA-free”. Its use has grown in recent years, and presently it is considered a ubiquitous emerging pollutant. To date there is a lack of information on the effects of BPS on invertebrates, although they represent more than 95% of known species in the animal kingdom and are crucial for the structure and proper function of ecosystems. In this study, real-time RT-PCR was used to determine the early detrimental effects of BPS on the transcriptional rate of genes in the model species Chironomus riparius, specifically those related to the ecdysone pathway (EcR, ERR, E74, Vtg, cyp18a1) crucial for insect development and metamorphosis, stress and biotransformation mechanisms (hsp70, hsp40, cyp4g, GPx, GSTd3) that regulate adaptive responses and determine survival, and ribosome biogenesis (its2, rpL4, rpL13) which is essential for protein synthesis and homeostasis. While 24-hour exposure to 0.5, 5, 50, and 500 μg/L BPS had no effect on larval survival, almost all the studied genes were upregulated following a non-monotonic dose-response curve. Genes with the greatest increases in transcriptional activity (fold change relative to control) were EcR (3.8), ERR (2), E74 (2.4), cyp18a1 (2.5), hsp70 (1.7), hsp40 (2.5), cyp4g (6.4), GPx (1.8), and GST (2.1), while others including Vtg, GAPDH, and selected ribosomal genes remained stable. We also measured the transcriptional activity of these genes 24 hours after BPS withdrawal and a general downregulation compared to controls was observed, though not significant in most cases. Our findings showed that BPS exposure altered the transcriptional profile of these genes, which may have consequences for the hormone system and several metabolic pathways. Although further research is needed to elucidate its mode of action, these results raise new concerns about the safety of BPA alternatives.

Disrupting effects of antibiotic sulfathiazole on developmental process during sensitive life-cycle stage of Chironomus riparius

Antibiotics in the environment are a concern due to their potential to harm humans and interrupt ecosystems. Sulfathiazole (STZ), a sulfonamide antibiotic, is commonly used in aquaculture and is typically found in aquatic ecosystems. We evaluated the ecological risk of STZ by examining biological, molecular and biochemical response in Chironomus riparius. Samples were exposed to STZ for 12, 24 and 96 h, and effects of STZ were evaluated at the molecular level by analyzing changes in gene expression related to the endocrine system, cellular stress response and enzyme activity of genes on antioxidant and detoxification pathways. STZ exposure induced significant effects on survival, growth and sex ratio of emergent adults and mouthpart deformity in C. riparius. STZ caused concentration and time-dependent toxicity in most of the selected biomarkers. STZ exposure leads to significant heat-shock response of protein genes (HSP70, HSP40, HSP90 and HSP27) and to disruption by up-regulating selected genes, including the ecdysone receptor gene, estrogen-related receptors, ultraspiracle and E74 early ecdysone-responsive gene. Furthermore, STZ induced alteration of enzyme activities on antioxidant and detoxification responses (catalase, superoxide dismutase, glutathione peroxidase and peroxidase) in C. riparius. By inducing oxidative stress, antibiotic STZ disturbs the endocrine system and produces adverse effects in growth processes of invertebrates.

Genotoxic effects of vinclozolin on the aquatic insect Chironomus riparius (Diptera, Chironomidae)

Vinclozolin (Vz) is a pollutant found in aquatic environments whose antiandrogenic effects in reproduction are well known in mammals. Although its reproductive effects have been less studied in invertebrates, other effects, including genotoxicity, have been described. Therefore, in this work, we studied the genotoxic effects of Vz in the freshwater benthic invertebrate Chironomus riparius. DNA damage was evaluated with the comet assay (tail area, olive moment, tail moment and % DNA in tail), and the transcriptional levels of different genes involved in DNA repair (ATM, NLK and XRCC1) and apoptosis (DECAY) were measured by RT-PCR. Fourth instar larvae of C. riparius, were exposed to Vz for 24 h at 20 and 200 μg/L. The Vz exposures affected the DNA integrity in this organism, since a dose-response relationship occurred, with DNA strand breaks significantly increased with increased dose for tail area, olive moment and tail moment parameters. Additionally, the lower concentration of Vz produced a significant induction of the transcripts of three genes under study (ATM, NLK and XRCC1) showing the activation of the cellular repair mechanism. In contrast, the expression of these genes with the highest concentration were downregulated, indicating failure of the cellular repair mechanism, which would explain the higher DNA damage. These data report for the first time the alterations of Vz on gene transcription of an insect and confirm the potential genotoxicity of this compound on freshwater invertebrates.

Effects of tannery wastewater exposure on adult Drosophila melanogaster

Our aim was to evaluate the effects of exposure to tannery wastewater on mortality and/or antioxidant enzyme system in adult wild-type Canton-S Drosophila melanogaster. Exposure to tannery wastewater induced a concentration-dependent lethality in adult Canton-S flies. Tannery wastewater was able to alter antioxidant enzyme activities, specifically glutathione peroxidase-like and glutathione S-transferase, in adult Canton-S D. melanogaster. We conclude that D. melanogaster is a reliable model to evaluate the toxicity induced by tannery wastewater.

Transcriptional deregulation of genetic biomarkers in Chironomus riparius larvae exposed to ecologically relevant concentrations of di(2-ethylhexyl) phthalate (DEHP)

Di(2-ethylhexyl) phthalate (DEHP) is a ubiquitous environmental pollutant used worldwide as a plasticizer and solvent in many formulations. Based on available toxicological data, it has been classified as toxic for reproduction and as an endocrine disruptor. Despite this, ecotoxicological studies in aquatic wildlife organisms are still scarce. In the present work, the toxic molecular alterations caused by DEHP in aquatic larvae of the midge Chironomus riparius have been studied, by analyzing the transcriptional activity of genes related to some vital cellular pathways, such as the ribosomal machinery (rpL4, rpL13), the cell stress response (hsc70, hsp70, hsp40, hsp27), the ecdysone hormone pathway (EcR), the energy metabolism (GAPDH), and detoxication processes (CYP4G). Environmentally relevant concentrations (10-3 to 105 μg/L) and exposure conditions (24 to 96 h) have been tested, as well as the toxic effects after DEHP withdrawal. Although the compound caused no mortality, significant changes were detected in almost all the studied biomarkers: e.g. strong repression of hsp70; general inhibition of EcR; GAPDH activity loss in long exposures; among others. Our data show a general transcriptional downregulation that could be associated with an adaptive response to cell damage. Besides, the activity of the compound as an ecdysone antagonist and its delayed effects over almost all the biomarkers analyzed are described as novel toxic targets in insects.

Regulation of mRNA Translation Is a Novel Mechanism for Phthalate Toxicity

Phthalates are a group of plasticizers that are widely used in many consumer products and medical devices, thus generating a huge burden to human health. Phthalates have been known to cause a number of developmental and reproductive disorders functioning as endocrine modulators. They are also involved in carcinogenesis with mechanisms less understood. To further understand the molecular mechanisms of phthalate toxicity, in this study we reported a new effect of phthalates on mRNA translation/protein synthesis, a key regulatory step of gene expression. Butyl benzyl phthalate (BBP) was found to directly inhibit mRNA translation in vitro but showed a complicated pattern of affecting mRNA translation in cells. In human kidney embryonic cell (HEK-293T), BBP increased cap-dependent mRNA translation at lower concentrations but showed inhibitory effect at higher concentrations. Cap-independent translation was not affected. On the other hand, mono (2-ethylhexyl) phthalate (MEHP) as a major metabolite of another important phthalate di (2-ethylhexyl) phthalate (DEHP) inhibited both can-dependent and -independent mRNA translation in vivo. In contrast, BBP and MEHP exhibited an overall promoting effect on mRNA translation in cancer cells. Mechanistic studies identified that the level and phosphorylation of eIF4E-BP (eIF4E binding protein) and the amount of eIF4GI in eIF4F complex were altered in accordance with the effect of BBP on translation. BBP was also identified to directly bind to eIF4E, providing a further mechanism underlying the regulation of mRNA by phthalate. At the cellular level BBP inhibited normal cell growth but slightly promoted cancer cells (HT29) growth. Overall, this study provides the first evidence that phthalates can directly regulate mRNA translation as a novel mechanism to mediate their biological toxicities.