Evaluation of 4-nonylphenol and bisphenol A toxicity using multiple molecular biomarkers in the water flea Daphnia magna

Exploring the impact of nonylphenol exposure on Litopenaeus vannamei at the histological and molecular levels

Nonylphenol (NP) is one of the common pollutants in the environment that have toxic effects on aquatic animals. Nevertheless, little is known about the possible toxicity mechanism of NP on the hepatopancreas of Litopenaeus vannamei. In the present study, the detrimental effects of NP on the hepatopancreas of the L. vannamei were explored at the histological and transcriptomic levels. The findings indicated that after NP exposed for 3, 12, and 48 h, the hepatopancreas histology was changed significantly. Transcriptomic analysis showed that a total of 4302, 3651, and 4830 differentially expressed genes (DEGs) were identified at 3, 12, and 48 h following NP exposure. All these DEGs were classified into 12 clusters according to the expression patterns at different time points. GO and KEGG enrichment analyses of DEGs were also performed, immunological, metabolic, and inflammatory related pathways, including arachidonic acid metabolism (ko00590), the PPAR signaling pathway (ko03320), and the regulation of TRP channels by inflammatory mediators (ko04750) were significantly enriched. Six DEGs were selected for validation by quantitative real-time PCR (qRT-PCR) and the results confirmed the reliability of transcriptome data. All results indicated that NP is toxic to L. vannamei by damaging the histopathological structure and disrupting the biological function. The findings would provide a theoretical framework for lowering or limiting the detrimental impacts of NP on aquaculture and help us to further study the molecular toxicity of NP in crustaceans.

Risk assessment of bisphenol analogues towards mortality, heart rate and stress-mediated gene expression in cladocerans Moina micrura

Bisphenol A (BPA) is a well-known endocrine-disrupting compound that causes several toxic effects on human and aquatic organisms. The restriction of BPA in several applications has increased the substituted toxic chemicals such as bisphenol F (BPF) and bisphenol S (BPS). A native tropical freshwater cladoceran, Moina micrura, was used as a bioindicator to assess the adverse effects of bisphenol analogues at molecular, organ, individual and population levels. Bisphenol analogues significantly upregulated the expressions of stress-related genes, which are the haemoglobin and glutathione S-transferase genes, but the sex determination genes such as doublesex and juvenile hormone analogue genes were not significantly different. The results show that bisphenol analogues affect the heart rate and mortality rate of M. micrura. The 48-h lethal concentration (LC₅₀) values based on acute toxicity for BPA, BPF and BPS were 611.6 µg L^-1, 632.0 µg L^-1 and 819.1 µg L^-1, respectively. The order of toxicity based on the LC₅₀ and predictive non-effect concentration values were as follows: BPA > BPF > BPS. Furthermore, the incorporated method combining the responses throughout the organisation levels can comprehensively interpret the toxic effects of bisphenol analogues, thus providing further understanding of the toxicity mechanisms. Moreover, the output of this study produces a comprehensive ecotoxicity assessment, which provides insights for the legislators regarding exposure management and mitigation of bisphenol analogues in riverine ecosystems.

Expression Profile of Hydroxysteroid Dehydrogenase-like 2 in Polychaete Perinereis aibuhitensis in Response to BPA

Hydroxysteroid dehydrogenases (HSDs) play an important role in the metabolism of steroids and xenobiotics. However, the function of HSDs in invertebrates is unclear. In this study, we cloned the hydroxysteroid dehydrogenase-like 2 (HSDL2) gene in Perinereis aibuhitensis, which is 1652 bp in length, encoding 400 amino acids. This sequence contains conserved short-chain dehydrogenase and sterol carrier protein-2 domain, and the alignment analysis showed its close relationship with other invertebrate HSDL2. Further, the tissue distribution analysis of the HSDL2 gene showed it is expressed strongly in the intestine. The expression level of HSDL2 after inducement with bisphenol A (BPA) was also detected both at transcriptional and translational levels. The results inferred that BPA exposure can induce HSDL2 expression, and the inductive effect was obvious in the high-concentration BPA group (100 μg/L). In summary, our results showed the detoxification function of HSDL2 in polychaetes.

Assessment of RNA extraction protocols from cladocerans

The usage of cladocerans as non-model organisms in ecotoxicological and risk assessment studies has intensified in recent years due to their ecological importance in aquatic ecosystems. The molecular assessment such as gene expression analysis has been introduced in ecotoxicological and risk assessment to link the expression of specific genes to a biological process in the cladocerans. The validity and accuracy of gene expression analysis depends on the quantity, quality and integrity of extracted ribonucleic acid (RNA) of the sample. However, the standard methods of RNA extraction from the cladocerans are still lacking. This study evaluates the extraction of RNA from tropical freshwater cladocerans Moina micrura using two methods: the phenol-chloroform extraction method (QIAzol) and a column-based kit (Qiagen Micro Kit). Glycogen was introduced in both approaches to enhance the recovery of extracted RNA and the extracted RNA was characterised using spectrophotometric analysis (NanoDrop), capillary electrophoresis (Bioanalyzer). Then, the extracted RNA was analysed with reverse transcription polymerase chain reaction (RT-PCR) to validate the RNA extraction method towards downstream gene expression analysis. The results indicate that the column-based kit is most suitable for the extraction of RNA from M. micrura, with the quantity (RNA concentration = 26.90 ± 6.89 ng/μl), quality (A260:230 = 1.95 ± 0.15, A280:230 = 1.85 ± 0.09) and integrity (RNA integrity number, RIN = 7.20 ± 0.16). The RT-PCR analysis shows that the method successfully amplified both alpha tubulin and actin gene at 33-35 cycles (i.e. Ct = 32.64 to 33.48). The results demonstrate that the addition of glycogen is only suitable for the phenol-chloroform extraction method. RNA extraction with high and comprehensive quality control assessment will increase the accuracy and reliability of downstream gene expression, thus providing more ecotoxicological data at the molecular biological level on other freshwater zooplankton species.

Hsp27, a potential EcR target, protects nonylphenol-induced cellular and organismal toxicity in Drosophila melanogaster

Deciphering the potential mechanism of chemical-induced toxicity enables us to alleviate the cellular and organismal dysfunction. The environmental presence of nonylphenol (endocrine disruptor) has a major health concern due to its widespread usage in our day-to-day life. The current study establishes a novel functional link among nonylphenol-induced oxidative stress, Heat shock protein 27 (Hsp27, member of stress protein family), and Ecdysone receptor (EcR, a nuclear receptor), which eventually coordinates the nonylphenol-induced sub-cellular and organismal level toxicity in a genetically tractable model Drosophila melanogaster. Drosophila larvae exposed to nonylphenol (0.05, 0.5 and 5.0 μg/mL) showed a significant decrease in Hsp27 and EcR mRNA levels in the midgut. In concurrence, reactive oxygen species (ROS) levels were increased with a corresponding decline in glutathione (GSH) level and Thioredoxin reductase (TrxR) activity. Increased lipid peroxidation (LPO), protein carbonyl (PC) contents, and cell death were also observed in a correlation with the nonylphenol concentrations. Sub-cellular toxicity poses a negative organismal response, which was evident by delayed larval development and reduced Drosophila emergence. Subsequently, a positive genetic correlation (p < 0.001) between EcR and Hsp27 revealed that nonylphenol-dependent EcR reduction is a possible link for the downregulation of Hsp27. Further, Hsp27 overexpression in midgut cells showed a reduction in nonylphenol-induced intracellular ROS, LPO, PC content, and cell death through the TrxR mediated regenerative pathway and reduced GSH level improving the organismal response to the nonylphenol exposure. Altogether, the study elucidates the potential EcR-Hsp27 molecular interactions in mitigating the nonylphenol-induced cellular and organismal toxicity.

Effects of nonylphenol exposure on histological changes, apoptosis and time-course transcriptome in gills of white shrimp Litopenaeus vannamei

Nonylphenol (NP) is considered as one of the persistent organic pollutants (POPs) in the environment. Pacific white shrimp Litopenaeus vannamei is the predominant species in China, which is frequently affected by environmental pollutants. However, potential toxicity mechanism of NP in shrimp has not been comprehensively studied. To explore the physiological changes and molecular mechanism involved in NP exposure of shrimp, we analyzed histological alterations, apoptosis and transcriptional responses of L.vannamei subjected to NP. Results indicated that significant changes in the histoarchitecture of the gills were observed after NP exposure for 3, 12 and 48 h. Apoptosis was also detected in a time-dependent manner. Numerous differentially expressed genes (DEGs) were obtained at 3 h, 12 h and 48 h after exposure. On the basis of the expression patterns over the time course, these DEGs were classified into 12 clusters. GO and KEGG enrichment analysis of these DEGs was carried out and a dynamic and global view was obtained in shrimp after NP exposure on a transcriptome level. In addition, 15 DEGs involved in immune response, apoptosis, DNA repair, osmoregulation etc. were selected for qRT-PCR validation. The expression patterns of these DEGs kept a well consistent with the high-throughput data at different timepoints, which confirmed the accuracy and reliability of the transcriptome data. All the results demonstrated that NP exposure might lead to impairments of biological functions in gills, alter immune and antioxidant response, compromise DNA repair and anti-apoptosis abilities of shrimp, cause severe histopathological changes and eventually trigger apoptosis. The present study enriched the information on the toxicity mechanism of crustaceans in response to NP exposure.

Acute toxicity of Bisphenol A (BPA) to tropical marine and estuarine species from different trophic groups

BPA is chemical pollutant of very high concern due to its toxicity to the environment and risks for human health. Environmental concern consists in BPA entrance into aquatic ecosystems due to acute and chronic toxicity to invertebrates and vertebrates. This study aimed to determine acute BPA toxicity to tropical estuarine-marine species of four trophic levels and integrate BPA toxicity values using species sensitivity distribution (SSD) analysis. Our hypothesis is that BPA toxicity increases towards higher trophic levels. Microalga (Tetraselmis sp.), zooplanktonic grazer (Artemia salina), deposit-feeder invertebrate (Heleobia australis), and omnivorous fish (Poecilia vivipara) were chosen as experimental models. Tetraselmis sp. showed the highest BPA tolerance, without a concentration-dependent response. Species sensitivity have increased from A. salina (LC_50,96h = 107.2 mg L^-1), followed by H. australis (LC_50,96h = 11.53.5 mg L^-1), to P. vivipara (LC_50,96h = 3.5 mg L^-1). Despite the toxicity hierarchy towards trophic levels, which partially supported our hypothesis, SSD did not evidence a clear pattern among estuarine-marine trophic groups. Our study disclosed the sensitivity of not yet investigated species to BPA and, in an integrative way, highlighted BPA toxic effects at different trophic levels. Although estimated acute hazardous concentration (HC5 = 1.18 mg L^-1) for estuarine and marine species was higher than environmentally relevant concentrations, sublethal adverse effects induced by BPA exposure may lead to unbalances in population levels and consequently affect the ecological functioning of tropical coastal systems.

BPA and its analogues (BPS and BPF) modify the expression of genes involved in the endocrine pathway and apoptosis and a multi drug resistance gene of the aquatic midge Chironomus riparius (Diptera)

Many countries are limiting the use of bisphenol A (BPA) because evidence shows it is dangerous to human health and wildlife. For the manufacturing of polycarbonate plastics, bisphenol S (BPS) and bisphenol F (BPF) are proposed as safer alternatives. They have already been released into the aquatic environment without previously available information about their potential adverse effects. In this study, we compared the effects of BPA, BPS and BPF exposure to the expression profile of genes involved in the endocrine pathway (EcR and E74), ecdysone metabolism (Cyp18a1 and Shadow), apoptosis (DRONC) and the multidrug resistance-associated protein 1 gene (MRP1) in the midge, Chironomus riparius (Diptera). The three toxicants increased Shadow expression, which is involved in ecdysone synthesis, but only BPF significantly altered Cyp18a1, which is implicated in ecdysone degradation. BPS and BPF modified EcR and E74 expression; BPF upregulated the effector caspase DRONC. Furthermore, BPA significantly increased MRP1 expression. This study provides insights into the action of bisphenols at the molecular level and highlights the potential risks of BPS and BPF as BPA alternatives.

Enhanced excretion of extracellular polymeric substances associated with nonylphenol tolerance in Dictyosphaerium sp

Dictyosphaerium sp. is tolerant to nonylphenol (NP); however, knowledge regarding the mechanisms involved in NP tolerance is limited. In this study, a batch of algal culture experiments were carried out to elucidate the underlying mechanisms by investigating the production and composition of extracellular polymeric substances (EPS) in algae exposed to NP. The excretion of EPS was significantly enhanced (P < 0.001) in algae exposed to 4 and 8 mg/L of NP. The polysaccharides in soluble EPS and the proteins in bound EPS were specifically overproduced. The three-dimensional excitation and emission matrix fluorescence spectra analyses indicated that tyrosine- and tryptophan-like substances were the main functional compositions in the proteins of EPS. In addition, enhanced EPS secretion significantly alleviated the toxicity of NP to the algae by the reduction of cell internalization, as indicated by the higher IC₅₀, biomass, and cell growth rate in the algae with EPS. These discoveries along with the characterizations by algal cell surface hydrophobicity analysis, scanning electron microscopy, and Fourier transform infrared spectra spectroscopy demonstrated the vital role of EPS in the algal resistance to NP.

Perfluorooctane sulfonate enhances mRNA expression of PPARγ and ap2 in human mesenchymal stem cells monitored by long-retained intracellular nanosensor

Perfluorooctane sulfonate (PFOS) has been widely used as a surface coating for household products. It still exists in living environments despite being restricted, due to its bioaccumulation and long half-life. Studies have shown that PFOS has the ability to induce adipogenic differentiation of human cells. Human mesenchymal stem cells (hMSCs) distributed within the adipose tissue might be a potential target of accumulated PFOS. However, traditional end-point toxicity assays failed to examine the subtle changes of cellular function exposed to low-dose persistent organic pollutants in real time. In the present work, highly sensitive and long-retained (more than 30 days) fluorescence based polymeric nanosensors were developed and employed for real-time assessment of cellular functions. hMSCs were engineered with sensor molecules encapsulated poly (lactic-co-glycolic acid) (PLGA) particles. Once internalized by hMSCs, PLGA particles continuously release and replenish sensor molecules to cytoplasm, resulting in prolonged fluorescence signal against photo bleaching and dilution by exocytosis. With this method, the dynamic changes of viability, ROS induction, and adipogenic differentiation related mRNA expression of hMSCs were monitored. PFOS with the concentration as low as 0.1 μM can induce cellular ROS and enhance the PPARγ and ap2 mRNA expression, suggesting the effect on promoting adipogenic differentiation of hMSCs.

Novel B-doped BiOCl nanosheets with exposed (001) facets and photocatalytic mechanism of enhanced degradation efficiency for organic pollutants

Novel B doped BiOCl nanocrystals (B-BiOCl) with exposed (001) facets were fabricated via a facile solvothermal route. The characterization methods of XRD, BET, SEM, TEM, UV-vis DRS, PL, EIS, ESR and photocurrent measurement were performed to investigate the physicochemical properties of the B-BiOCl samples. The results indicated that doping B into BiOCl could regulate and control the growth of (001) crystal facet, increase the specific surface areas and enhance the efficiency of charge separation. Hence, the optimal B_1.0-BiOCl (atomic ratio of Bi:O:Cl: B is around 27.41: 28.27:25.43:3.55) exhibited significant promoting effect for the degradation of phenol, bisphenol A and rhodamine B than that of pure of BiOCl. The results of radical capturing and ESR analysis confirmed that the O₂^- radicals played a fatal role in the degradation of organic pollutants. This work could be expected to offer a new insight into design and synthesis of highly efficient photocatalyst with specific exposed facets by doping non-metallic elements.