Degradation of multiple PAHs and co-contaminants by microbial consortia and their toxicity assessment

The anthropogenic activities toward meeting the energy requirements have resulted in an alarming rise in environmental pollution levels. Among pollutants, polycyclic aromatic hydrocarbons (PAHs) are the most predominant due to their persistent and toxic nature. Amidst the several pollutants depuration methods, bioremediation utilizing biodegradation is the most viable alternative. This study investigated the biodegradation efficacy using developed microbial consortium PBR-21 for 2-4 ringed PAHs named naphthalene (NAP), anthracene (ANT), fluorene (FLU), and pyrene (PYR). The removal efficiency was observed up to 100 ± 0.0%, 70.26 ± 4.2%, 64.23 ± 2.3%, and 61.50 ± 2.6%, respectively, for initial concentrations of 400 mg L-1 for NAP, ANT, FLU, and PYR respectively. Degradation followed first-order kinetics with rate constants of 0.39 d-1, 0.10 d-1, 0.08 d-1, and 0.07 d-1 and half-lifet 1 / 2  of 1.8 h, 7.2 h, 8.5 h, and 10 h, respectively. The microbial consortia were found to be efficient towards the co-contaminants with 1 mM concentration. Toxicity examination indicated that microbial-treated PAHs resulted in lesser toxicity in aquatic crustaceans (Artemia salina) than untreated PAHs. Also, the study suggests that indigenous microbial consortia PBR-21 has the potential to be used in the bioremediation of PAH-contaminated environment.

Endogenous IAA affected fluoranthene accumulation by regulating H+-ATPase and SOD activity in ryegrass

This study explores the role of endogenous indole-3-acetic acid (IAA) in modulating plant responses to pollution stress and its effect on pollutant accumulation, with a focus on fluoranthene (Flu) in ryegrass. To elucidate the mechanism, we employed an IAA promoter (α-aminobutyric acid [α-AB]) and an IAA inhibitor (naphthylphthalamic acid [NPA]) to regulate IAA levels and analyze Flu uptake characteristics. The experimental setup included a Flu treatment group (ryegrass with Flu addition) and a control group (ryegrass without Flu). Our findings demonstrate that Flu treatment enhanced IAA content and plant growth in ryegrass compared to the control. The Flu+AB treatment further enhanced these effects, while the Flu+NPA treatment exhibited a contrasting trend. Moreover, Flu+AB treatment led to increased Flu accumulation, in contrast to the inhibitory effect observed with Flu+NPA treatment. Flu treatment also enhanced the activities of key antioxidant enzymes (SOD, POD, CAT) and increased soluble sugar and protein levels, indicative of enzymatic and nonenzymatic defense responses, respectively. The Flu+AB treatment amplified these responses, whereas the Flu+NPA treatment attenuated them. Significantly, Flu treatment raised H+-ATPase activity compared to the control, an effect further elevated by Flu+AB treatment and diminished by Flu+NPA treatment. A random forest analysis suggested that Flu accumulation dependency varied under different treatments: it relied more on H+-ATPase activity under Flu+AB treatment and more on SOD activity under Flu+NPA treatment. Additionally, Flu+AB treatment boosted the transpiration rate in ryegrass, thereby increasing the Flu translocation factor, a trend reversed by Flu+NPA treatment. This research highlights crucial factors influencing Flu accumulation in ryegrass, offering potential new avenues for controlling the gathering of contaminants within plant systems.

The toxicity response of the electrochemical signal of the cell to the drug metabolized by the S9 system

The electrochemical detection method of cytotoxicity using intracellular purines as biomarkers has shown great potential for in vitro drug toxicity evaluation. However, no electrochemical detection system based on an in vitro drug metabolism mechanism has been devised. In this paper, electrochemical voltammetry was used to investigate the effect of the S9 system on the electrochemical behavior of HepG2 cells, and benzo[a]pyrene, fluoranthene, and pyrene were employed to investigate the sensitivity of electrochemical signals of cells to the cytotoxicity of drugs metabolized by the S9 system. The results showed that, within 8 h of exposure to the S9 system, the electrochemical signal of HepG2 cells at 0.7 V did not alter noticeably. The levels of xanthine, guanine, hypoxanthine, and adenine in the cells were not significantly altered. Compared with the absence of S9 system metabolism, benzo[a]pyrene and fluoranthene processed by the S9 system decreased the electrochemical signal of the cells in a dose-dependent manner, while pyrene did not change it appreciably. HPLC also revealed that benzo[a]pyrene and fluoranthene metabolized by the S9 system decreased the intracellular purine levels, whereas pyrene had no effect on them before and after S9 system metabolism. The cytotoxicity results of the three drugs examined by electrochemical voltammetry and MTT assay showed a strong correlation and good agreement. The S9 system had no effect on the intracellular purine levels or the electrochemical signal of cells. When the drug was metabolized by the S9 system, variations in cytotoxicity could be precisely detected by electrochemical voltammetry.

Fluorene-induced stress in the benthic oligochaete Tubifex tubifex: A multi-biomarker assessment of toxicological pathways and mechanisms under acute and subchronic exposures

This study examined the multifaceted impacts of fluorene exposure on Tubifex tubifex, encompassing acute (survival analysis and behavioral responses) and subchronic exposure regimens (antioxidant enzyme response and histopathology), molecular docking studies, and generalized read-across analysis. Survival analysis revealed concentration-dependent increases in toxicity over varying time intervals, with LC50 values decreasing from 30.072 mg/L at 24 h to 12.365 mg/L at 96 h, emphasizing the time-sensitive and concentration-responsive nature of the stressor. Behavioral responses were both concentration- and duration-dependent. While Erratic Movement and Clumping Tendency exhibited earlier responses (within 24 h) at lower concentrations, the wrinkling effect and mucus secretion) exhibited delayed onset, suggesting intricate regulatory mechanisms underlying adaptability to environmental challenges; moreover, the wrinkling effect was consistently induced at higher concentrations, indicating greater sensitivity to the toxic effects of fluorene. With sublethal environmentally relevant concentrations-1.24 mg/l and 2.47 mg/L i.e., 10% and 20% 96 h, respectively-the antioxidant enzyme response (i.e., upregulation of SOD, CAT, and GST) with increasing fluorene concentration, revealing a nonlinear, hormetic response, suggested adaptive protection at lower doses but inhibition at higher concentrations. Histopathological examination indicated that higher fluorene concentrations caused cellular proliferation, inflammation, and severe tissue damage in the digestive tract and body wall. Molecular docking studies demonstrated robust interactions between fluorene and major stress biomarker enzymes, disrupting their functions and inducing oxidative stress. Interactions with cytochrome c oxidase suggested interference with cellular energy production. Generalized Read-Across (GenRA) analysis unveiled shared toxicity mechanisms among fluorene and its analogs, involving the formation of reactive epoxides and the influence of cytochrome P450 enzymes. The diverse functional groups of these analogs, particularly chlorine-containing compounds, were implicated in toxicity through lipid peroxidation and membrane damage. Adverse outcome pathways and broader consequences for aquatic ecosystem health are discussed.

Tricyclic hydrocarbon fluorene attenuates ventricular ionic currents and pressure development in the navaga cod

The release of polycyclic aromatic hydrocarbons (PAHs) into the environment due to oil and diesel fuel spills is a serious threat to Arctic fish populations. PAHs produce multiple toxic effects in fish, but disturbance of electrical and contractile activity of the heart seems to be the most negative effect. Our study focused on the effects of fluorene, a tricyclic PAH resembling the well-investigated tricyclic phenanthrene, on major ionic currents and action potential (AP) waveform in isolated ventricular myocytes and on contractile activity in isolated whole hearts of polar navaga cod (Eleginus nawaga). Among the studied currents, the repolarizing rapid delayed rectifier K+ current IKr demonstrated the highest sensitivity to fluorene with IC50 of 0.54 μM. The depolarizing inward currents, INa and ICaL, were inhibited with 10 μM fluorene by 20.2 ± 2.8 % and 27.9 ± 8.4 %, respectively, thereby being much less sensitive to fluorene than IKr. Inward rectifier IK1 current was insensitive to fluorene (up to 10 μM). While 3 μM fluorene prolonged APs, 10 μM also slowed the AP upstroke. Resting membrane potential was not affected by any tested concentrations. In isolated heart experiments 10 μM fluorene caused modest depression of ventricular contractile activity. Thus, we have demonstrated that fluorene, a tricyclic PAH present in high quantities in crude oil, strongly impacts electrical activity with only slight effects on contractile activity in the heart of the polar fish, the navaga cod.

The multifaceted effects of fluoranthene and polystyrene on the taxonomic composition and associated functional traits of marine meiofauna, by using single and mixture applications

The current experiment measured the multifaceted effects of polystyrene and fluoranthene, acting alone or in a mixture on marine meiofauna, but with a special focus on nematodes' morphological and functional traits. The results showed changes in the abundances for all tested concentrations of both compounds. The nematode communities exposed to the highest concentrations of fluoranthene (30 ng.g-1 Dry Weight (DW)) and polystyrene (100 mg.kg-1 DW) alone or in a mixture, were significantly less diverse compared to control and were associated with significant changes in the percentage of taxonomic composition and feeding-guilds. The most sensitive taxa to fluoranthene comprised epistratum feeders, whereas the nematodes mostly affected by polystyrene were omnivores-carnivores. A new functional tool, the Index of Sensitivity (IOS), proved to be reliable in depicting the changes that occurred in the taxonomic and functional features of the nematofauna.

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.

Reproductive Toxicity and Teratogenicity of Fluorene-9-bisphenol on Chinese Medaka (Oryzias sinensis): A Study from Laboratory to Field

Fluorene-9-bisphenol (BHPF), a bisphenol A (BPA) substitute, has been increasingly used as a material in syntheses of polymers that are widely used in road markings, artificial tracks, coating floors, building paints, etc., increasing the likelihood of BHPF contamination in the aquatic environment due to its release from the products. However, to date, it is unknown whether it may have actual impacts on fish in real environments. In this study, a 105-day exposure experiment of BHPF at various concentrations (0.01, 0.1, 1, and 10 μg/L) on Chinese medaka (Oryzias sinensis) was performed under laboratory conditions and found decreased fecundity, such as lower egg qualities and quantities, retarded oogenesis, and atretic follicles in the fish and deformed eyes and bodies in its F1 generation. Toxico-transcriptome analyses showed that estrogen-responsive genes were significantly suppressed by BHPF, indicating that antagonist properties of BHPF on estrogen receptors might be causes for the decreased fecundity. Field investigations (Beijing) demonstrated that BHPF was detectable in 60% surface waters, with a mean concentration of 10.49 ± 6.33 ng/L, by gas chromatography-mass spectrometry, and similar effects in wild Chinese medaka were also observed, some of which the parameters were found to be obviously correlated with the BHPF levels in corresponding waters.

Comparison of the sensitivity between indigenous and exotic aquatic species for fluoranthene and derivation of water quality criteria (WQC)

Fluoranthene (FLU) has shown relatively high toxicity to aquatic life as a priority polycyclic aromatic hydrocarbon (PAH). Considering the toxic effects of FLU on aquatic organisms and its high detection frequency in the aquatic environment, it is necessary and critical to derive FLU water quality criteria (WQC) for the protection of aquatic organisms and ecological risk assessment. However, due to the lack of toxicity data at different classification levels, there has been no research about the WQC of FLU. In this study, nine acute and three chronic toxicity tests were carried out on 9 Chinese indigenous aquatic species from different classification levels to obtain toxicity data. According to the US EPA guidelines, the criterion maximum concentration of 0.570 mg/L and the criterion continuous concentration of 0.174 mg/L were developed. There is no significant difference when comparing the species sensitivity distributions between indigenous and exotic species. Therefore, it is possible to use toxicity data from organisms in different areas for ecological risk assessment of FLU. CAPSULE: We compared the sensitivity between indigenous and exotic aquatic species for fluoranthene and derived its water quality criteria.

Evaluation of fluorene-caused ecotoxicological responses and the mechanism underlying its toxicity in Eisenia fetida: Multi-level analysis of biological organization

Fluorene is an important toxic chemical that exists ubiquitously in the environment, and it has also been suggested to exert potential deleterious effects on soil invertebrates. However, knowledge about the toxic effects of fluorene and its underlying mechanisms of the effects on key soil organism earthworms remains limited. From this view point, this study was undertaken to explore the potential effects of fluorene and its underlying mechanisms in Eisenia fetida at the level of experimental animals, tissue, cell, and molecule. It was concluded that fluorene exerted lethal activity to adult E. fetida on day 14 with the LC₅₀ determined to be 88.61 mg/kg. Fluorene-induced ROS caused oxidative stress in E. fetida, resulting in DNA damage, protein carbonylation, and lipid peroxidation. Moreover, changed antioxidative enzymatic activities, non-enzymatic antioxidative activities, and total antioxidative capacity in E. fetida by fluorene stress are associated with antioxidative and protective effects. High-dose fluorene (> 2.5 mg/kg) exposure significantly caused histopathological lesions including the microstructure of body wall, intestine, and seminal vesicle of earthworms. Also, the reproductive system of E. fetida was clearly disrupted by fluorene stress, leading to poor reproduction ability (decreased cocoon and juvenile production) in earthworms. It is found that E. fetida growth was significantly inhibited when treated with high-dose fluorene, thereby causing normal growth disorders. Additionally, fluorene stress triggered the abnormal mRNA expression related to oxidative stress (e.g., metallothionein and heat shock protein 70), growth (translationally controlled tumour protein), reproduction (annetocin precursor) in E. fetida. Together, both high-dose and long-term exposure elicited more severe poisoning effects on earthworms using the Integrated Biological Response (IBR) index, and E. fetida coelomocyte DNA was the most negatively affected by fluorene stress. This study comprehensively evaluated fluorene-induced toxicity in E. fetida, and its underlying molecular mechanisms mediating the toxic responses have been elucidated. These findings provide valuable data for assessing potential ecological risks posed by fluorene-contaminated soil.

Antiestrogenic property of 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene (BPEF) and its effects on female development in CD-1 mice

Identifying chemicals with endocrine disrupting properties linked to disease outcomes is a key concern, as stated in the WHO-UNEP 2012 report on endocrine-disrupting chemicals. The chemical 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene (BPEF) is widely and increasingly applied in synthesizing fluorene-based cardo polymers with superior optical, thermal and mechanical properties for various uses. However, little toxicological information is available regarding its safety. Here, we studied the endocrine disrupting property of BPEF by multiple toxicological tools and investigated its effects on female development in adolescent mice. Using the yeast two-hybrid bioassay, BPEF showed strong antiestrogenicity which was similar to that of tamoxifen, an effective antiestrogenic drug. In adolescent CD-1 mice, BPEF significantly decreased the uterine weight at relatively low doses and induced marked endometrial atrophy. Immunohistochemical staining and transcriptome analyses of the mice uteri revealed that BPEF could repressed the expressions of estrogen-responsive genes. Molecular simulation indicated that BPEF could be docked into the antagonist pocket of human estrogen receptor α, and the formation of hydrogen bonds and hydrophobic interactions between BPEF and the active site of receptor maintained their strong binding. All of the data demonstrated that BPEF possessed strong antiestrogenic property and might disrupt female development, suggesting it should be avoided in making products that might directly expose to people, particularly immature women.

Effects of fluoranthene on digestive enzymes activity and relative growth rate of larvae of lepidopteran species, Lymantria dispar L. and Euproctis chrysorrhoea L

Fluoranthene is one of the most abundant polycyclic aromatic hydrocarbon pollutants in the environment and it may accumulate in plant leaves which are the main food source for phytophagous insect species. The aim of this study was to establish the effects of dietary fluoranthene on specific activities of digestive enzymes and expression of their isoforms in the midgut, and the relative growth rates of Lymantria dispar and Euproctis chrysorrhoea larvae. Exposure to fluoranthene led to significantly decreased trypsin activity in the midgut of larvae of both species. Leucine aminopeptidase activity decreased significantly in the midgut of L. dispar larvae exposed to the lower concentration of fluoranthene, but that enzyme activity showed the opposite trend in E. chrysorrhoea larvae. There was no pollutant induced changes in lipase activity in L. dispar, while elevated enzyme activity was recorded in the midgut of E. chrysorrhoea larvae exposed to the lower concentration of fluoranthene. Different patterns of expression of enzyme isoforms were noticed. Relative growth rates of both species significantly decreased in fluoranthene treated larvae. These responses indicate to the significance of relationships between physiological changes and fitness-related traits in L. dispar and E. chrysorrhoea larvae affected by pollutant, and contribute to understanding the mechanisms of their adjustment to stressful conditions.

Hepatic toxicity of fluorene-9-bisphenol (BHPF) on CD-1 mice

Fluorene-9-bisphenol (BHPF), a substitute for bisphenol A (BPA), has been widely used in the synthesis of polyester polymers. Studies have reported multiple BHPF toxicities but its effect on the liver remains unknown. In this study, we performed short-term and subchronic toxicity tests, as well as primary hepatocyte experiments, to investigate the hepatic toxicity of BHPF using CD-1 mice. And microarray was used to analyze the changes of global gene expression in the liver of mice treated with BHPF. The results showed that the liver coefficient and the activities of serum aminotransferases were obviously elevated by BHPF at doses of 27.8 mg/kg body weight (bw)/day or higher in mice treated for 10 days. Histological analysis showed obvious changes, including narrowed hepatic sinuses, dilated central vein, leucocyte infiltration, and cytoplasmic vacuolation, in the livers of mice treated with BHPF at dosages of 2 mg/kg bw/3-day and higher for 36 days. Microarray analyses revealed 2623 differentially expressed genes (DEGs) in the livers of mice treated with 50 mg/kg bw/day of BHPF for 3 days, which could be enriched in GO terms of T cell activation, leukocyte migration, and leukocyte chemotaxis and KEGG pathways of natural killer cell-mediated cytotoxicity and autoimmune thyroid disease. The top 10 hub DEGs, including LTF and MMP8, were observed in the protein-protein interaction network obtained via STRING database analysis, and are proposed as potential biomarkers for liver injury studies. Primary hepatocyte experiments demonstrated the hepatotoxicity of BHPF at concentrations of 10^-6 M and higher. This study indicates that BHPF could cause liver injury at relatively low levels, suggesting that the risk of human BHPF exposure should be of concern.

Enzymatic pathway involved in the degradation of fluoranthene by microalgae Chlorella vulgaris

In the present study, the potential of a microalga, Chlorella vulgaris, was assessed for the bioremediation of fluoranthene (FLT), a four ring polycyclic aromatic hydrocarbon (PAH). With an initial cell density of C. vulgaris (OD₆₈₀ = 0.100), 54-58% of 25 μM FLT was removed from the growth medium within 3 days and almost 90-94% after 7 days of incubation. Enzymatic studies confirmed that the enzyme involved in FLT metabolism was catechol 2,3, dioxygenase (C2,3D) which increased almost 2 times in 5 μM FLT and 2.4 times in 25 μM FLT inoculated culture. Activity of dehydrogenase and superoxide dismutase (SOD) was significantly reduced, while peroxidase (POD) activity was induced very prominently in FLT inoculated cultures. Changes in growth, physiological parameters and biochemical compositions of the algae with 5 μM and 25 μM FLT were also analyzed and compared to control. The analysis showed that parameters including growth rate, biomass, chlorophyll, carbohydrate and protein contents, were negatively affected by the higher concentration of FLT, whereas the lipid and carotenoids content significantly increased. To our knowledge, this is the first report to suggest the role of C2,3D pathway for the metabolism of FLT in a eukaryotic algae.

Synthesis of glutathione as a central aspect of PAH toxicity in liver cells: A comparison between phenanthrene, Benzo[b]Fluoranthene and their mixtures

Polycyclic Aromatic Hydrocarbons (PAH) are a class of organic pollutants normally found as mixtures with effects often hard to predict, which poses a major challenge for risk assessment. In this study, we address the effects of Phenanthrene (Phe), benzo[b]fluoranthene (B[b]F) and their mixtures (2 Phe:1 B[b]F; 1 Phe: 1 B[b]F; 1 Phe: 2 B[b]F) over glutathione (GSH) synthesis and function in HepG2 cells. We analyzed the effects on cellular viability, ROS production, glutathione (GSH) levels, protein-S-glutathionylation (PSSG), the activity of glutathione peroxidase (GPx), glutathione-S-transferases (GST) and glutathione reductase (GR). Transcript (mRNA) levels of glutathione synthesis enzymes - glutathione cysteine ligase catalytical (GCLC) and modifying (GCLM) sub-units and glutathione synthetase (GS) - and Nrf2 translocation to the nucleus were analyzed. Phe showed a higher cytotoxicity (IC₅₀ = 130 µM after 24 h) than B[b]F related to a higher ROS production (up-to 50% for Phe). In agreement, GSH levels were significantly increased (up-to 3-fold) by B[b]F and were accompanied by an increase in the levels of PSSG, which is a mechanism that protect proteins from oxidative damage. The upregulation of GSH was the consequence of Nrf2 signaling activation and increased levels of GCLC, GCLM and GS mRNA observed after exposure to B[b]F, but not during exposure to Phe. Most interestingly, all mixtures showed higher cytotoxicity than individual compounds, but intriguingly it was the 1 Phe: 1B[b]F mixture showing the highest cytotoxicity and ROS production. GSH levels were not significantly upregulated not even in the mixture enriched in B[b]F. These results point to the role of GSH as a central modulator of PAH toxicity and demonstrate the idiosyncratic behavior of PAH mixtures even when considering only two compounds in varying ratios.

Acute toxicities of fluorene, fluorene-1-carboxylic acid, and fluorene-9-carboxylic acid on zebrafish embryos (Danio rerio): Molecular mechanisms of developmental toxicities of fluorene-1-carboxylic acid

In this study, fluorene (FL), FL-1-carboxylic acid (FC-1), and FL-9-carboxylic acid (FC-9) were investigated to understand their acute toxicity by measuring inhibitory effects on hatching rates and developmental processes of zebrafish embryos (Danio rerio). For exposure concentrations up to 3000 μg/L, FC-1 alone showed acute toxicity at 1458 μg/L for LC₅₀ value. FC-1 caused yolk sac and spinal deformities, and pericardial edema. Molecular studies were undertaken to understand FC-1 toxicity examining 61 genes after exposure to 5 μM (equivalent to LC₂₀ value of FC-1) in embryos. In the FC-1-treated embryos, the expression of the cyp7a1 gene, involved in bile acid biosynthesis, was dramatically decreased, while the expression of the Il-1β gene involved in inflammation was remarkably increased. In addition to these findings, in FC-1-treated embryos, the expression of nppa gene related to the differentiation of the myocardium was 3-fold increased. On the other hand, cyp1a, cyp3a, ugt1a1, abcc4, mdr1, and sult1st1 responsible for detoxification of xenobiotics were upregulated in FC-9-treated embryos. Taken together, carboxylation on carbon 1 of FL increased acute toxicity in zebrafish embryos, and its toxicity might be related to morphological changes with modification of normal biological functions and lowered defense ability.

Microplastic-associated trophic transfer of benzo(k)fluoranthene in a limnic food web: Effects in two freshwater invertebrates (Daphnia magna, Chironomus riparius) and zebrafish (Danio rerio)

The continuously growing plastic production and incomplete recycling processes open manifold entry routes for microplastic particles (MPs) into the environment. Since knowledge on trophic transfer of contaminants sorbed to MPs is still insufficient for freshwater systems, the transfer of the model pollutant benzo(k)fluoranthene (BkF) sorbed to polymethyl methacrylate (PMMA) particles in a limnic food web was investigated: Two freshwater invertebrates (Daphnia magna and Chironomus riparius larvae) were selected and either left untreated, exposed to pristine PMMA, PMMA-associated BkF, or exposed to dissolved BkF (BkF_aq). As second-level consumers, zebrafish (Danio rerio) were fed twice daily with pre-treated invertebrates over two days. Induction of hepatic cytochrome P450 by BkF was determined as 7-ethoxy-O-resorufin deethylase (EROD) activity. Both invertebrate species readily ingested PMMA particles, tracked via fluorescence microscopy and accumulated BkF_aq, measured via GC-MS. Fluorescence signals in gastrointestinal tracts of zebrafish were quantified with confocal laser scanning microscopy (CLSM). The fluorescence signal in gastrointestinal tracts of zebrafish was not altered, whereas, EROD activity was significantly induced when zebrafish were fed with Chironomus riparius, pre-exposed to BkF_aq. Trophic exposure scenarios with BkF sorbed to PMMA did not result in any alterations of investigated endpoints in both invertebrate species and zebrafish compared to controls. Given that BkF amounts were in the low ng-range, as detected by GC-MS, the transport of MP-sorbed BkF to zebrafish was less effective than direct exposure to waterborne BkF_aq, and the potential threat of trophic transfer of substances such as BkF in limnic food webs may have been overestimated.

Acute fluorene-9-bisphenol exposure damages early development and induces cardiotoxicity in zebrafish (Danio rerio)

Fluorene-9-bisphenol (BHPF) is a substitute for bisphenol A (BPA), which is widely used to manufacture plastic products. Previous studies indicate that BHPF has an anti-estrogenic effect and induces cytotoxicity in mice oocytes. However, the effects of acute BHPF exposure on the aquatic organism obtain little attention. In this study, a series of BHPF concentrations (1 μM, 2 μM, 5 μM, 10 μM, 20 μM) was used to exposed zebrafish embryos from 2 h post-fertilization (hpf). The results showed the LC₅₀ at 96hpf was 2.88 μM (1.01 mg/L). Acute exposure induced malformation in morphology, and retarded epiboly rate at 10hpf, increased apoptosis. Moreover, acute BHPF exposure led cardiotoxicity, by impeding cardiac looping, decreasing cardiac contractility (reducing the stroke volume and cardiac output, decreasing fractional shortening of ventricle). Besides that, BHPF exposure altered the expression of cardiac transcriptional regulators and development related genes. In conclusion, acute BHPF exposure induced developmental abnormality, retarded cardiac morphogenesis and injured the cardiac contractility. This study indicated BHPF would be an unneglected threat for the safety of aquatic organisms.

Toxicity assessment of Fluoranthene, Benz(a)anthracene and its mixed pollution in soil: Studies at the molecular and animal levels

An increasing amount of Fluoranthene (Fla) and Benz(a)anthracene (BaA) is being produced and used, eventually entering the soil sediments. The accumulation of Fla and BaA will cause poisoning to typical enzymes (α-Amylase) and organisms (Eisenia fetida) in soil. However, the studies about exploring and comparing the different effects of Fla, BaA and their joint effect at different levels are rarely reported. In this paper, the different effects of Fla, BaA and their mixed pollutant on α-Amylase were evaluated and compared at the molecular level, and the effect of Fla-BaA to the antioxidant system of earthworm (Eisenia fetida) was investigated from the aspects of concentration and exposure time at the animal level. The results showed that Fla-BaA had the greatest influence on the skeleton structure and the microenvironment of amino acid residue of α-Amylase compared to Fla and BaA, and in the mixed pollutant system, the joint effect mode was additive mode. The inhibitory effect of Fla-BaA on the activity of α-Amylase was also stronger than that of the system alone. The assays at the animal level showed that low concentrations (below 5 mg/kg) of Fla-BaA increased the activity of GSH-Px and SOD while high concentrations inhibited their activity. The POD that was activated throughout the experiment period suggested its key role in the earthworm antioxidant system. Changes in T-AOC and MDA showed that long-term and high-dose of Fla-BaA exposure inhibited the antioxidant capacity of Eisenia fetida, causing lipid peroxidation and damage to cells.

Differential responses in the biotransformation systems of the oyster Crassostrea gigas (Thunberg, 1789) elicited by pyrene and fluorene: Molecular, biochemical and histological approach - Part II

Pyrene (PYR) and fluorene (FLU) are among the sixteen priority Polycyclic Aromatic Hydrocarbons (PAH) of the United States Environmental Protection Agency and are both frequently detected in contaminated sites. Due to the importance of bivalve mollusks in biomonitoring programs and the scarce information on the biotransformation system in these organisms, the aim of this study was to investigate the effect of PYR and FLU at the transcriptional level and the enzymatic activities of some biotransformation systems in the Pacific oyster Crassostrea gigas, and to evaluate the histological effects in their soft tissues. Oysters C. gigas were exposed for 24 h and 96 h to PYR (0.25 and 0.5 μM) and FLU (0.6 and 1.2 μM). After exposure, transcript levels of cytochrome P450 coding genes (CYP1-like, CYP2-like, CYP2AU2, CYP356A1, CYP17α-like), glutathione S tranferase genes (omega GSTO-like and microsomal, MGST-like) and sulfotransferase gene (SULT-like), and the activity of ethoxyresorufin O-deethylase (EROD), Glutathione S-transferase (GST) and microssomal GST (MGST) were evaluated in gills. Histologic changes were also evaluated after the exposure period. PYR and FLU bioconcentrated in oyster soft tissues. The half-life time of PYR in water was lower than fluorene, which is in accordance to the higher lipophilicity and bioconcentration of the former. EROD activity was below the limit of detection in all oysters exposed for 96 h to PYR and FLU. The reproductive stage of the oysters exposed to PYR was post-spawn. Exposure to PYR caused tubular atrophy in digestive diverticula, but had no effect on transcript levels of biotransformation genes. However, the organisms exposed for 96 h to PYR 0.5 μM showed higher MGST activity, suggesting a protective role against oxidative stress in gills of oysters under higher levels of PYR in the tissues. Increased number of mucous cells in mantle were observed in oysters exposed to the higher FLU concentration, suggesting a defense mechanisms. Oysters exposed for 24 h to FLU 1.2 μM were in the ripe stage of gonadal development and showed higher transcript levels of CYP2AU2, GSTO-like and SULT-like genes, suggesting a role in the FLU biotransformation. In addition, after 96 h of exposure to FLU there was a significant increase of mucous cells in the mantle of oysters but no effect was observed on the EROD, total GST and MGST activities. These results suggest that PAH have different effects on transcript levels of biotransformation genes and enzyme activities, however these differences could also be related to the reproductive stage.

Aryl Hydrocarbon Receptor Mediates Larval Zebrafish Fin Duplication Following Exposure to Benzofluoranthenes

The aryl hydrocarbon receptor (AHR) mediates developmental toxicity of several xenobiotic classes including polycyclic aromatic hydrocarbons. Using embryonic zebrafish, we previously identified 4 polycyclic aromatic hydrocarbons that caused a novel phenotype among AHR ligands-growth of a lateral, duplicate caudal fin fold. The window of sensitivity to the most potent inducer of this phenotype, benzo[k]fluoranthene (BkF), was prior to 36 h postfertilization (hpf), although the phenotype was not manifest until 60 hpf. AHR dependency via Ahr2 was demonstrated using morpholino knockdown. Hepatocyte ablation demonstrated that hepatic metabolism of BkF was not required for the phenotype, nor was it responsible for the window of sensitivity. RNA sequencing performed on caudal trunk tissue from BkF-exposed animals collected at 48, 60, 72, and 96 hpf showed upregulation of genes associated with AHR activation, appendage development, and tissue patterning. Genes encoding fibroblast growth factor and bone morphogenic protein ligands, along with retinaldehyde dehydrogenase, were prominently upregulated. Gene Ontology term analysis revealed that upregulated genes were enriched for mesoderm development and fin regeneration, whereas downregulated genes were enriched for Wnt signaling and neuronal development. MetaCore (Clarivate Analytics) systems analysis of orthologous human genes predicted that R-SMADs, AP-1, and LEF1 regulated the expression of an enriched number of gene targets across all time points. Our results demonstrate a novel aspect of AHR activity with implications for developmental processes conserved across vertebrate species.

The benzo[b]fluoranthene in the atmospheric fine particulate matter induces mouse glomerular podocytes injury via inhibition of autophagy

BACKGROUND

Evidence shows that individuals who are under long-term exposure to environmental PM_2.5 are at increased risk of chronic kidney disease. Various laboratory experiments also suggest several mechanistic links between PM_2.5 exposure and kidney injury. Polycyclic aromatic hydrocarbons (PAHs) are common organic chemicals existing in PM_2.5. However, whether benzo [b]fluoranthene (BbF), the most potent carcinogens and the highest content of PAHs, plays an important role in podocyte injury via reducing autophagy, have not been reported.

METHODS

Podocytes were exposed to different concentrations and times of BbF. Cell viability was assessed by using CCK-8. Morphological phenotypes were detected by using optical microscopy. Cytoskeletons were detected by using immunofluorescence assay. Expression of podocyte injury markers were determined by Western blot. Podocytes were observed under TEM, autophagic activity was evaluated by Western blot analysis and immunofluorescence assay. A possible effect of an inhibitor (CQ, chloroquine) or an inducer (rapamycin) of autophagy on BbF-induced podocyte injury also was examined.

RESULTS

BbF changed cellular morphology, decreased cell viability and rearranged cytoskeleton. The proteins' expression level of autophagy and the numbers of autophagosomes under TEM was decreased and the proteins' expression level of slit diaphragm was increased in a dose- and time-dependent manner. In addition, BbF-induced podocyte injury was enhanced by inhibition of autophagy and inhibited by activation of autophagy in podocytes.

CONCLUSIONS

Taken together, our data suggest that BbF is toxic to podocytes, as well as reduce autophagy. Furthermore, inhibition of autophagy plays a regulatory role in BbF-induced podocyte injury.

Fluorescent conjugated polymer nanovector for in vivo tracking and regulating the fate of stem cells for restoring infarcted myocardium

Stem cell therapy holds great promise for cardiac regeneration. However, the lack of ability to control stem cell fate after in vivo transplantation greatly restricts its therapeutic outcomes. MicroRNA delivery has emerged as a powerful tool to control stem cell fate for enhanced cardiac regeneration. However, the clinical translation of therapy based on gene-transfected stem cells remains challenging, due to the unknown in vivo behaviors of stem cells. Here, we developed a nano-platform (i.e., PFBT@miR-1-Tat NPs) that can achieve triggered release of microRNA-1 to promote cardiac differentiation of mesenchymal stem cells (MSCs), and long-term tracking of transplanted MSCs through bright and ultra-stable fluorescence of conjugated polymer poly(9,9-dioctylfluorene-alt-benzothiadiazole) (PFBT). We found that PFBT@miR-1-Tat NP-treated MSCs significantly restored the infarcted myocardium by promoting stem cell cardiac differentiation and integration with the in situ cardiac tissues. Meanwhile, MSCs without gene delivery improved the infarcted heart functions mainly through a paracrine effect and blood vessel formation. The developed conjugated polymer nanovector should be a powerful tool for manipulating as well as revealing the fate of therapeutic cells in vivo, which is critical for optimizing the therapeutic route of gene and cell combined therapy and therefore for accelerating clinical translation. STATEMENT OF SIGNIFICANCE: The lack of controllability in stem cell fate and the unclear in vivo cellular behaviors restrict the therapeutic outcomes of stem cell therapy. Herein, we engineered fluorescent conjugated polymer nanoparticles as gene delivery nanovectors with controlled release and high intracellular delivery capability to harness the fate of mesenchymal stem cells (MSCs) in vivo, meanwhile to reveal the cellular mechanism of gene-treated stem cell therapy. As compared with only MSC treatment that improves infarcted myocardium functions through paracrine effect, treatment with conjugated polymer nanovector-treated MSCs significantly restored infarcted myocardium through enhancing MSC cardiac differentiation and integration with the in-situ cardiac tissues. These findings demonstrate that the conjugated polymer nanovector would be a powerful tool in optimizing gene and cell combined therapy.

Development of a paper-based microanalysis device doped with multi-walled carbon nanotubes for in vitro evaluation of fluorene cytotoxicity

Developing a cost-effective and simple micro-analysis tool has long been an important objective in the toxicological detection of fluorene. In this study, a disposable paper-based micro-analysis device (μ-PAD) was designed using graphite doped with multi-walled carbon nanotubes (MWCNTs) to hand draw the electrode (MWCNTs/μ-PAD). We investigated the feasibility of the designed MWCNTs/μ-PAD as a cell-sensing platform using voltammetry measurements. Its application for evaluating the cytotoxicity of fluorene was studied based on the electrochemical determination of human breast cancer cells induced by fluorene. The results showed a dose-dependent toxicity effect of fluorene on cellular activity. The measurements were comparable with those obtained using a methyl-thiazolyl-tetrazolium assay. The detection limit of the MWCNTs/μ-PAD for human breast cancer cells was as low as 4.00 × 10³ cells·mL^-1 owing to the enhanced catalytic activity of the MWCNTs. Notably, the MWCNTs/μ-PAD-which had a diameter of 7.00 mm-allowed a sampling volume of 10.0 μL, which is 50.0 times less than the sampling volume required with a conventional electrode (500 μL). Advantages such as the simplicity of manufacture, low consumption, low cost, rapid detection, and disposability, suggest that the MWCNTs/μ-PAD could provide new opportunities and directions for in vitro microanalysis.

Ecological risk assessment of petroleum hydrocarbons on aquatic organisms based on multisource data

From the perspective of ecological risk, this study uses a multisource data method to search for global data, uses the acute and chronic ratio method to process the data, uses the species-sensitive distribution method to evaluate the ecological risk that petroleum hydrocarbons pose to aquatic organisms, and evaluates the ecological risk of the water environment in five Chinese water bodies. The results are as follows. First, in an aquatic ecosystem, the toxicological effects of petroleum hydrocarbons were found to be more obvious on consumers, and the sensitivity of fish was found to be higher than that of crustaceans. Second, the acutely lethal effects of petroleum hydrocarbons, fluorene, and benzo [a] pyrene on aquatic ecosystems were fitted by using the documentary method of multisource data collection and a Log-logistic curve. Third, in the case study evaluation of five Chinese water bodies, the ecological risks of polycyclic aromatic hydrocarbons were ranked (from low to high) as fluorene < benzo [a] pyrene. The ecological risk values of benzo [a] pyrene were all greater than 1. These risks should not be underestimated, and prevention and control work should be performed.

Role of Human N-Acetyltransferase 2 Genetic Polymorphism on Aromatic Amine Carcinogen-Induced DNA Damage and Mutagenicity in a Chinese Hamster Ovary Cell Mutation Assay

Carcinogenic aromatic amines such as 4-aminobiphenyl (ABP) and 2-aminofluorene (AF) require metabolic activation to form electrophilic intermediates that mutate DNA leading to carcinogenesis. Bioactivation of these carcinogens includes N-hydroxylation catalyzed by CYP1A2 followed by O-acetylation catalyzed by arylamine N-acetyltransferase 2 (NAT2). To better understand the role of NAT2 genetic polymorphism in ABP- and AF-induced mutagenesis and DNA damage, nucleotide excision repair-deficient (UV5) Chinese hamster ovary (CHO) cells were stably transfected with human CYP1A2 and either NAT2*4 (rapid acetylator) or NAT2*5B (slow acetylator) alleles. ABP and AF both caused significantly (P < 0.001) greater mutagenesis measured at the hypoxanthine phosphoribosyl transferase (hprt) locus in the UV5/CYP1A2/NAT2*4 acetylator cell line compared to the UV5, UV5/CYP1A2, and UV5/CYP1A2/NAT2*5B cell lines. ABP- and AF-induced hprt mutant cDNAs were sequenced and over 80% of the single-base substitutions were at G:C base pairs. DNA damage also was quantified by γH2AX in-cell western assays and by identification and quantification of the two predominant DNA adducts, N-(deoxyguanosin-8-yl)-4-aminobiphenyl (dG-C8-ABP) and N-(deoxyguanosin-8-yl)-2-aminofluorene (dG-C8-AF) by liquid chromatography-mass spectrometry. DNA damage and adduct levels were dose-dependent, correlated highly with levels of hprt mutants, and were significantly (P < 0.0001) greater in the UV5/CYP1A2/NAT2*4 rapid acetylator cell line following treatment with ABP or AF as compared to all other cell lines. Our findings provide further clarity on the importance of O-acetylation in CHO mutagenesis assays for aromatic amines. They provide evidence that NAT2 genetic polymorphism modifies aromatic amine-induced DNA damage and mutagenesis that should be considered in human risk assessments following aromatic amine exposures. Environ. Mol. Mutagen. 61:235-245, 2020. © 2019 Wiley Periodicals, Inc.

Differential responses in the biotransformation systems of the oyster Crassostrea gasar (Adanson, 1757) elicited by pyrene and fluorene: molecular, biochemical and histological approach - Part I

Polycyclic aromatic hydrocarbons (PAHs) are among the main contaminants in aquatic environments. PAHs can affect organisms due to their carcinogenic, mutagenic and/or teratogenic characteristics. Depending on the PAHs, concentration, and period of exposure, biological damage can occur leading to histopathologic alterations. This study aimed to evaluate the molecular, biochemical and histological responses of the oyster Crassostrea gasar exposed to pyrene (0.25 and 0.5 μM) and fluorene (0.6 and 1.2 μM), after exposure for 24 and 96 h. Concentrations of both PAHs were quantified in the water and in oyster tissues. Transcript levels of phase I (CYP3475C1, CYP2-like, CYP2AU1 and CYP356A) and phase II (GSTO-like, MGST-like and SULT-like) biotransformation-related genes and the activities of ethoxyresorufin-O-deethylase (EROD), total and microsomal glutathione S-transferase (GST and MGST) were evaluated in the gills. Also, histological changes and localization of mRNA transcripts CYP2AU1 in gills, mantle, and digestive diverticula were evaluated. Both PAHs accumulated in oyster tissues. Pyrene half-life in water was significantly lower than fluorene. Transcript levels of all genes were higher in oysters exposed to of pyrene 0.5 μM (24 h). Only CYP2AU1 gene was up-regulated by fluorene exposure. EROD and MGST activities were higher in oysters exposed to pyrene. Tubular atrophy in the digestive diverticula and an increased number of mucous cells in the mantle were observed in oysters exposed to pyrene. CYP2AU1 transcripts were observed in different tissues of pyrene-exposed oysters. A significant correlation was observed between tubular atrophy and the CYP2AU1 hybridization signal in oysters exposed to pyrene, suggesting the sensibility of the species to this PAH. These results suggest an important role of biotransformation-related genes and enzymes and tissue alterations associated to pyrene metabolism but not fluorene. In addition, it reinforces the role of CYP2AU1 gene in the biotransformation process of PAHs in the gills of C. gasar.

Effect of fluoranthene on antioxidative defense in different tissues of Lymantria dispar and Euproctis chrysorrhoea larvae

This study examined the effect of long-term exposure to environmentally relevant concentrations of dietary fluoranthene (6.7 and 67 ng / g dry food weight) on defense mechanisms of the polyphagous forest insects Lymantria dispar L. and Euproctis chrysorrhoea L. The activities and expression of isoforms of superoxide dismutase (SOD) and catalase (CAT), the activities of glutathione S-transferase (GST) and glutathione reductase (GR), and total glutathione content (GSH) were determined in the whole midgut and midgut tissue, while SOD and CAT activities were assessed in hemolymph of the larvae. The results showed significant changes of enzyme activities, with more pronounced responses in larval midgut tissues, and between-species differences in patterns of response. Significantly increased activity of SOD was recorded in the whole midgut and midgut tissue of L. dispar larvae, as well as in midgut tissue of E. chrysorrhoea larvae. Fluoranthene increased CAT activity in midgut tissue of L. dispar larvae, and in the whole midgut and midgut tissue of E. chrysorrhoea larvae. Different expression patterns were detected for enzyme isoforms in tissues of larvae exposed to dietary fluoranthene. Total GSH content and GST activity increased in E. chrysorrhoea larval midgut tissue. Significantly decreased SOD activity in hemolymph of L. dispar larvae, and opposite changes in CAT activity were recorded in the hemolymph of larvae of two insect species. The tissue-specific responses of enzymes to dietary fluoranthene, recorded in each species, enabled the larvae to overcome the pollutant induced oxidative stress, and suggest further assessment of their possible use as early-warning signals of environmental pollution.

Fluorene-9-bisphenol exposure induces cytotoxicity in mouse oocytes and causes ovarian damage

Fluorene-9-bisphenol (BHPF), a substitute for bisphenol A, is a chemical component of plastics for industrial production. There is evidence that BHPF exerts an antioestrogenic effect on mice, induces endometrial atrophy and leads to adverse pregnancy outcomes. However, the effects of BHPF on oocyte maturation and ovary development as well as its possible mechanisms remain unclear. The objective of this study was to investigate the toxicity and mechanism of BHPF exposure in mouse oocytes in vitro and in vivo. Our results showed that BHPF could inhibit the maturation of oocytes in vitro by reducing the protein level of p-MAPK and destroying the meiotic spindle. We found that in vitro, BHPF-treated oocytes showed increased ROS levels, DNA damage, mitochondrial dysfunction, and expression of apoptosis- and autophagy-related genes, such as Bax, cleaved-caspase 3, LC 3 and Atg 12. In addition, in vivo experiments showed that BHPF exposure could induce the expression of oxidative stress genes (Cat, Gpx 3 and Sod 2) and apoptosis genes (Bax, Bcl-2 and Cleaved-caspase 3) and increase the number of atresia follicles in the ovaries. Our data showed that BHPF exposure affected the first polar body extrusion of oocytes, increased oxidative stress, destroyed spindle assembly, caused DNA damage, altered mitochondrial membrane potentials, induced apoptosis and autophagy, and affected ovarian development.

Highly Biocompatible Nanoparticles of Au@Fluorescent Polymers as Novel Contrast Agent for In Vivo Bimodality NIR Fluorescence/CT Imaging

In this work, one kind of biocompatible and all-in-one dual-modal nanoprobe, based on Au nanoparticles and NIR emissive semiconducting fluorescence polymers, was developed by the one-step solvent-mediated self-assembly method for in vivo X-ray computed tomography (CT) and fluorescence bioimaging for the first time. After preparation, a series of comprehensive evaluations were performed, and the nanoprobe exhibited smart size and modification, good compatibility, inducement of autophagy, long blood circulation, unconspicuous in vivo toxicity, and excellent fluorescence/CT imaging effects. Overall, the studies in this work assuredly indicate that the synthesized Au@FP nanoparticles as a noninvasive contrast agent is suitable for in vivo fluorescence/X-ray CT bimodality biomedical imaging and diagnosis.

Distribution, toxicity, and origins of polycyclic aromatic hydrocarbons in soils in Ulsan, South Korea

This study was conducted to investigate the concentrations, distributions, toxicities, and sources of polycyclic aromatic hydrocarbons (PAHs) in the soils from different areas in Ulsan, South Korea. Samples were collected from 41 sites, including a waste treatment facilities area (WA), traffic facilities area (TA), child playground area (CA), industrial area (IA), railroad facilities area (RA), ore and iron scraps fields area (OA), and residential area (ReA). Ulsan was chosen for research area because it used to be an environmental hot spot in South Korea, and 16 PAHs in the US EPA priority pollutant list were selected. The concentration of total PAHs (t-PAHs) ranged from 61.7 to 12,421 μg/kg, and the average concentration of t-PAHs was 706.9 μg/kg. The distribution of PAHs by ring number indicated that the portion followed the order of 4 rings > 5 rings > 3 rings > 6 rings > 2 rings. According to PAH origin indices, LMW/HMW (low molecular weight 2-3 ring PAHs over high molecular weight 4-6-ring PAHs), phenanthrene/anthracene ratio and fluoranthene/pyrene ratio, benzo(g,h,i)perylene/indeno (1,2,3-c,d)pyrene ratio, vehicular emissions, and the combustion of fossil fuel were the sources of PAHs. The strong correlation (R² = 0.995) between t-PAHs and total carcinogenic PAHs (t-PAH_carc) indicated that the concentration of t-PAH_carc increased in proportion with that of t-PAHs. The toxic equivalent concentrations (TEQs) of PAHs in the soils ranged from 44.0 to 1929.9 μg TEQ/kg. It is imperative to set regulatory levels for PAHs for periodic monitoring and rapid remediation action of contaminated soils, because there are no national standards in South Korea for 15 PAHs with the exception of benzo(a)pyrene.

A Petri Net Approach to Physiologically Based Toxicokinetic Modeling

Physiologically based toxicokinetic (PBTK) modeling enables researchers to predict internal tissue concentrations for various species exposed to exogenous compounds through different routes at varying concentrations without having to run in vivo experiments for each scenario. Parameters for the models may be gathered from in vivo or in vitro measurements, cross-species or cross-chemical extrapolations, literature reviews, or other models. The PBTK models, described using ordinary differential equations (ODEs), are then simulated using these parameters for a given compound/exposure/species scenario. Although they are potentially useful for regulatory toxicology, the complexity of ODE programming and simulation remains a barrier for many would-be researchers. Petri nets, a graphical modeling framework, offers a more intuitive approach to PBTK modeling. To demonstrate their utility and ease of use, we present a model of waterborne fluoranthene exposure to rainbow trout (Oncorhynchus mykiss) written and simulated in Snoopy, a graphical Petri net development and simulation software package. We converted an existing ODE PBTK model and evaluated the Petri net model against the ODE model results. The simulated tissue concentrations of the Petri net model closely mirrored the simulated concentrations of the ODE model. To convert the ODE model to a Petri net model, we introduced a new parameter, blood volume (V _BLOOD ). Sensitivity analysis found V _BLOOD to be very robust when varied over an order of magnitude. The resulting Petri net PBTK model has a number of advantages over ODE models, while maintaining equivalent predictive functionality. Environ Toxicol Chem 2019;00:1-10. © 2019 SETAC.

Effects of Acute Fluorene-9-Bisphenol Exposure on Mouse Oocyte in vitro Maturation and Its Possible Mechanisms

Fluorene-9-bisphenol (BHPF), a substitute of bisphenol A (BPA) used in the production of the so-called "BPA-free" plastics, has now been shown to be released from commercial plastic bottles into drinking water and has strong anti-estrogenic activity in mice, which suggests that BHPF is also an environmental toxin. However, whether BHPF exposure has effects on mouse oocyte development is unknown. In this study, the influence of acute exposure to BHPF (50-150 μM, 12 hr) on mouse oocyte maturation and its possible mechanisms were investigated. Of note, 50-μM BHPF had no effects on the maturation of mouse oocytes, whereas 100- and 150-μM BHPF significantly blocked germinal vesicle breakdown and led to the failure of first polar body extrusion. Particularly, 100-μM BHPF exposure severely decreased the cellular adenosine triphosphate in a time-dependent manner, which finally brought out the loss of spindles. In addition, the actin cytoskeleton was also impaired. The defective mitochondrial dynamics and decreased mitochondrial DNA implied the damage of mitochondria in BHPF-treated oocytes. Increased PINK1, Beclin1, and LC3B protein level and decreased TOMM20 and TOMM17A protein level illustrated that mitophagy was induced, which also confirmed that BHPF exposure impaired the cellular mitochondria. Moreover, BHPF induced reactive oxygen species accumulation and early apoptosis. Oocyte quality was also impaired by BHPF exposure through altering histone modifications evidenced by increased H3K9me3 and H3K27me3 levels. Collectively, our results indicated that BHPF exposure disrupted mouse oocyte maturation and reduced oocyte quality through affecting cytoskeleton architecture, mitochondrial function, oxidative stress, apoptosis, and histone modifications. Environ. Mol. Mutagen. 60:243-253, 2019. © 2018 Wiley Periodicals, Inc.

iTRAQ-based comparative proteomic analysis of differentially expressed proteins in Rhodococcus sp. BAP-1 induced by fluoranthene

To reveal the molecular mechanism at the level of regulation of proteins in Rhodococcus sp. BAP-1 induced by fluoranthene comparative proteomic analysis was performed on proteins extracted from fluoranthene-exposed cells on 1 d, 3 d, 6 d and 8 d compared with control cells using isobaric tags for relative and absolute quantization (iTRAQ) labeling and LC-MS/MS analysis to access differentially expressed proteins. As a result, we detected a total of 897 significantly differentially expressed proteins, including 30 shared proteins in four comparison clusters. We were able to short-list 190, 329, 101 and 90 proteins that were over-represented, and 394, 234, 65 and 49 under-represented proteins, in 1d/control, 3d/control, 6d/control and 8d/control comparisons, respectively. Functional analysis relied on Clusters of Orthologous Groups (COG), gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) revealed that fluoranthene significantly altered the expression of proteins involved in metabolic and biosynthesis processes. Furthermore, BAP-1 up-regulates aldehyde dehydrogenase, cytochrome c oxidase, and oligopeptide transport ATP-binding protein, while down-regulates several other proteins in order to adapt to fluoranthene exposure. These findings provide important clues to reveal fluoranthene degradation mechanism in BAP-1 and promote its bioremediation applications.

Effects of dietary fluoranthene on nymphs of Blaptica dubia S. (Blattodea: Blaberidae)

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants which exert detrimental effects on living beings. Considering the health risk associated with exposure to these pollutants, their presence in food increases efforts to establish early-warning indicators of pollution. We aimed to examine the effects of environmentally relevant concentrations of fluoranthene (0.2 ng and 18 ng/g dry weight of diet) on the activities of midgut antioxidant and detoxification enzymes in Blaptica dubia. Significant changes of superoxide dismutase and catalase activities, recorded at the higher fluoranthene concentration regardless of the exposure time, suggest that they may be used as biomarkers of PAH pollution. Increased GST activity and decreased total GSH content, detected upon acute exposure to the lower concentration, indicate processes of detoxification. Reorganization of B. dubia mechanisms of defense in response to oxidative stress caused by exposure to dietary PAH point to the necessity for further examination of fluoranthene actions.

Melatonin protects embryonic development and maintains sleep/wake behaviors from the deleterious effects of fluorene-9-bisphenol in zebrafish (Danio rerio)

Environmental endocrine chemicals have various adverse effects on the development of vertebrates. Fluorene-9-bisphenol (BHPF), a substitute of bisphenol A (BPA), is widely used in commercial production. The effects of BHPF on development and behavior are unclear. Melatonin plays a protective role under many unfavorable conditions. In this study, we investigated the effects of BHPF on the development and behaviors of zebrafish and whether melatonin reverses effects induced by BHPF. Zebrafish embryos were exposed to 0.1, 10, or 1000 nmol/L BHPF with or without 1 μmol/L melatonin from 2 hours postfertilization to 6 days postfertilization. The results showed that 0.1 and 10 nmol/L BHPF had little effect on development. High-dose BHPF (1000 nmol/L) delayed the development, increased mortality and surface tension of embryonic chorions, caused aberrant expression of the key genes (ntl, shh, krox20, pax2, cmlc2) in early development detected by in situ hybridization, and damaged the CaP motor neurons, which were associated with locomotion ability detected by immunofluorescence. Melatonin addition reversed or weakened these adverse effects of BHPF on development, and melatonin alone increased surface tension as the effects of high-dose BHPF. However, all groups of BHPF exposure triggered insomnia-like behaviors, with increased waking activity and decreased rest behaviors. BHPF acted on the hypocretin (hcrt) system and upregulated the expression of sleep/wake regulators such as hcrt, hcrt receptor (hcrtr), arylalkylamine N-acetyltransferase-2 (aanat2). Melatonin recovered the alternation of sleep/wake behaviors induced by BHPF and restored abnormal gene expression to normal levels. This study showed that high-dose BHPF had adverse effects on early development and induced behavioral alternations. However, melatonin prevented BHPF-induced aberrant development and sleep/wake behaviors.

Effects of combined exposures of fluoranthene and polyethylene or polyhydroxybutyrate microplastics on oxidative stress biomarkers in the blue mussel (Mytilus edulis)

A growing interest in developing and commercialization of new eco-friendly plastic polymers is occurring attributed to the impact of marine plastics debris and microplastics that result from the degradation of oil-based polymers as these substances adversely affect ecosystem health. Recently, polyhydroxybutyrate (PHB) has become of interest due to its biodegradability and physicochemical properties. However, biological consequences resulting from bioplastics exposure remain to be determined. Further, few data are apparently available regarding the potential for bioplastics to act as a vector for exogenous chemicals in the environment. The aim of the study was to compare the effects of polyethylene (PE MPs) and polyhydroxybutyrate (PHB MPs) microplastics administered alone or in combination with fluoranthene (Flu) on detoxifying enzymes in digestive glands and gills of Mytilus edulis. Blue mussels were exposed for 96h to eight experimental groups: control, Flu-only, PE MPs-only, PHB MPs-only, PE MPs-Flu co-exposure, PHB MPs-Flu co-exposure, Flu-incubated PE MPs, and Flu-incubated PHB MPs. Activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidases (GPx), glutathione S-transferase (GST), and glutathione reductase (GR) were found to be significantly susceptible to Flu and plastics in both tissues. Interestingly, a single exposure to PHB MPs led to decreased activity levels of CAT and GST in gills, SOD in digestive glands and SeGPx in both tissues. In co-exposure and incubation treatments, biochemical responses were generally comparable with those exerted by PE MPs or PHB MPs only, suggesting an apparent absence of combined effects of microplastics with the pollutant. Data demonstrated the ecotoxicological impact of bioplastics materials on digestive glands and gills of Mytilus edulis.

Single contaminant and combined exposures of polyethylene microplastics and fluoranthene: accumulation and oxidative stress response in the blue mussel, Mytilus edulis

The microplastic "vector effect" has received increasing attention. The aim of this study was to investigate the influence of polyethylene microplastic beads (PE MP) on accumulation and associated oxidative stress responses attributed to fluoranthene (Flu) in blue mussels, Mytilus edulis. Blue mussels were exposed for 96 h to four treatment groups: Flu-only, MP-only, Flu and MP coexposure, and Flu-incubated MP. Treatments were conducted at a low and high concentration (50 μg/L and 100  Flu μg/L and 100, and 1000 MP/mL). Results demonstrated that in both the gill and digestive gland, coexposure did not markedly affect Flu uptake, but this treatment significantly decreased tissue Flu concentrations. Antioxidant responses including activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidases (GPx), and levels of total glutathione (GSH) in both gills and digestive glands were significantly altered suggesting a perturbation of redox state induced by the exposure conditions. Although individual biomarkers varied, the biomarker profile enabled certain generalizations to be made. Antioxidant responses occurred more likely in gill tissue than in digestive gland. Individual contaminant exposures to Flu or MP led to varying responses, but coexposures and incubated exposures did not result in additive or synergistic effects. Exposure concentrations (i.e., low or high treatments) were not a consistent a predictor of response; and the internal Flu dose did not consistently predict outcome of various biomarkers. Importantly, MP-only exposure appeared to be capable of eliciting direct effects on the oxidative stress system as demonstrated by the activities of CAT and GPx. These findings warrant further investigation.

Adaptive changes in global gene expression profile of lung carcinoma A549 cells acutely exposed to distinct types of AhR ligands

Exposure to persistent ligands of aryl hydrocarbon receptor (AhR) has been found to cause lung cancer in experimental animals, and lung adenocarcinomas are often associated with enhanced AhR expression and aberrant AhR activation. In order to better understand the action of toxic AhR ligands in lung epithelial cells, we performed global gene expression profiling and analyze TCDD-induced changes in A549 transcriptome, both sensitive and non-sensitive to CH223191 co-treatment. Comparison of our data with results from previously reported microarray and ChIP-seq experiments enabled us to identify candidate genes, which expression status reflects exposure of lung cancer cells to TCDD, and to predict processes, pathways (e.g. ER stress, Wnt/β-cat, IFNɣ, EGFR/Erbb1), putative TFs (e.g. STAT, AP1, E2F1, TCF4), which may be implicated in adaptive response of lung cells to TCDD-induced AhR activation. Importantly, TCDD-like expression fingerprint of selected genes was observed also in A549 cells exposed acutely to both toxic (benzo[a]pyrene, benzo[k]fluoranthene) and endogenous AhR ligands (2-(1H-Indol-3-ylcarbonyl)-4-thiazolecarboxylic acid methyl ester and 6-formylindolo[3,2-b]carbazole). Overall, our results suggest novel cellular candidates, which could help to improve monitoring of AhR-dependent transcriptional activity during acute exposure of lung cells to distinct types of environmental pollutants.

Environmentally prevalent polycyclic aromatic hydrocarbons can elicit co-carcinogenic properties in an in vitro murine lung epithelial cell model

Low molecular weight (LMW) polycyclic aromatic hydrocarbons (PAH) are the most abundant PAHs environmentally, occupationally, and are in cigarette smoke; however, little is known about their carcinogenic potential. We hypothesized that LMW PAHs act as co-carcinogens in the presence of a known carcinogen (benzo[a]pyrene (B[a]P)) in a mouse non-tumorigenic type II cell line (C10 cells). Gap junctions are commonly suppressed and inflammation induced during tumor promotion, while DNA-adduct formation is observed during the initiation stage of cancer. We used these endpoints together as markers of carcinogenicity in these lung adenocarcinoma progenitor cells. LMW PAHs (1-methylanthracene and fluoranthene, 1-10 µM total in a 1:1 ratio) were used based on previous studies as well as B[a]P (0-3 µM) as the classic carcinogen; non-cytotoxic doses were used. B[a]P-induced inhibition of gap junctional intercellular communication (GJIC) was observed at low doses and further reduced in the presence of the LMW PAH mixture (P < 0.05), supporting a role for GJIC suppression in cancer development. Benzo[a]pyrene diol-epoxide (BPDE)-DNA adduct levels were significantly induced in B[a]P-treated C10 cells and additionally increased with the LMW PAH mixture (P < 0.05). Significant increases in cyclooxygenase (Cox-2) were observed in response to the B[a]P/LMW PAH mixture combinations. DNA adduct formation coincided with the inhibition of GJIC and increase in Cox-2 mRNA expression. Significant cytochrome p4501b1 increases and connexin 43 decreases in gene expression were also observed. These studies suggest that LMW PAHs in combination with B[a]P can elicit increased carcinogenic potential. Future studies will further address the mechanisms of co-carcinogenesis driving these responses.

Individual and combined effects of fluoranthene, phenanthrene, mannitol and sulfuric acid on marigold (Calendula officinalis)

A study was conducted to characterize marigold stress response to polycyclic aromatic hydrocarbons (PAHs) (oxidative stress inducers) with and without sulfuric acid (S.Acid; pH 3) (acid-stress inducer), and to evaluate reactive oxygen species (ROS) scavenging activity of mannitol (Mann). Marigold (Calendula officinalis) seedlings were grown in a greenhouse and fumigated with fluoranthene (FLU), phenanthrene (PHE), Mann, and S.Acid individually and in various combinations for 40 days. Various physiological and biochemical parameters among others were analyzed using standard methods. The results revealed that fumigation of FLU induced oxidative stress to the plants via ROS generation leading to negative effects on photosynthesis at near saturating irradiance (A_max), stomatal conductance (G_s), internal carbon dioxide concentration (C_i), leaf water relations and chlorophyll pigments. Significant per cent inhibition of A_max (54%), G_s (86%) and C_i (32%), as well as per cent reductions in chlorophyll a (Chl.a) (33%), Chl.b (34%), and total chlorophyll (Tot. Chl) (48%) contents were recorded in FLU fumigated treatment in comparison to control. Combination of Mann with FLU scavenged the generated ROS and substantially lowered the oxidative stress on the plants hence all the measured parameters were not significantly different from control. PHE fumigation had varied effects on marigold plants and was not as deleterious as FLU. Combined fumigation of S.Acid with both the PAHs had significant negative effect on leaf water relations, and positive effect on fresh and turgid weight of the plants but had no effect on the other measured parameters. The lowest proline contents and highest catalase and ascorbate peroxidase activities in FLU fumigated plants further confirmed that oxidative stress was imposed via the generation of ROS. From the results, it is evident that Mann could be an efficient scavenger of ROS-generated by FLU in the marigold plants. We recommend Mann to be widely used for the protection of higher plants from FLU-generated stress in the urban areas.

Biomass burning particles in the Brazilian Amazon region: Mutagenic effects of nitro and oxy-PAHs and assessment of health risks

Emissions from burning of biomass in the Amazon region have adverse effects on the environment and human health. Herein, particulate matter (PM) emitted from biomass burning in the Amazon region during two different periods, namely intense and moderate, was investigated. This study focused on: i) organic characterization of nitro- and oxy-polycyclic aromatic hydrocarbons (PAHs); ii) assessment of the excess lifetime cancer risk (LCR); and iii) assessment of the in vitro mutagenic effects of extractable organic matter (EOM). Further, we compared the sensitivity of two mutagenicity tests: Salmonella/microsome test and cytokinesis-block micronucleus (CBMN) with human lung cells. Among the nitro-PAHs, 2-nitrofluoranthene, 7-nitrobenz[a]anthracene, 1-nitropyrene, and 3-nitrofluoranthene showed the highest concentrations, while among oxy-PAHs, 2-metylanthraquinone, benz[a]anthracene-7,12-dione, and 9,10-anthraquinone were the most abundant. The LCR calculated for nitro-PAH exposure during intense biomass burning period showed a major contribution of 6-nitrochrysene to human carcinogenic risk. The EOM from intense period was more mutagenic than that from moderate period for both TA98 and YG1041 Salmonella strains. The number of revertants for YG1041 was 5-50% higher than that for TA98, and the most intense responses were obtained in the absence of metabolic activation, suggesting that nitroaromatic compounds with direct-acting frameshift mutagenic activity are contributing to the DNA damage. Treatment of cells with non-cytotoxic doses of EOM resulted in an increase in micronuclei frequencies. The minimal effective dose showed that Salmonella/microsome test was considerably more sensitive in comparison with CBMN mainly for the intense burning period samples. This was the first study to assess the mutagenicity of EOM associated with PM collected in the Amazon region using Salmonella/microsome test. The presence of compounds with mutagenic effects, particularly nitro- and oxy-PAHs, and LCR values in the range of 10^-5 indicate that the population is potentially exposed to an increased risk of DNA damage, mutation, and cancer.

Effects of in ovo exposure to benzo[k]fluoranthene (BkF) on CYP1A expression and promoter methylation in developing chicken embryos

Polycyclic aromatic hydrocarbons (PAHs) are toxic environmental pollutants that are potent teratogens. Recent research suggests that early life exposure to PAHs can affect health outcomes later in life. Some of these latent responses may be mediated by epigenetic mechanisms such as DNA methylation. The role of DNA methylation in regulating responses to PAHs in birds is currently unknown. Here, we assess the effect of in ovo exposure to the model PAH, benzo[k]fluoranthene (BkF), on aryl hydrocarbon receptor (AHR) mediated cytochrome P4501A (CYP1A) gene expression and promoter methylation in chicken embryos. Fertilized chicken eggs were injected with BkF (0-100μg/kg) prior to incubation. BkF exposure was associated with an increase in CYP1A4 and CYP1A5 mRNA levels at mid-incubation (embryonic day 10), which dropped to baseline levels towards the end of the incubation period (embryonic day 19). The transient induction in CYP1A expression was accompanied by small but significant increases in CYP1A promoter methylation, which persisted until after shortly after hatching. Methylation within the CYP1A promoter was correlated with levels of CYP1A5, but not CYP1A4 mRNA. Characterization of the role of DNA methylation in the AHR response pathway may increase our understanding of the effects of early life exposure to PAHs in birds.

A non-destructive BFCOD assay for in vivo measurement of cytochrome P450 3A (CYP3A) enzyme activity in fish embryos and larvae

There is increasing interest in quantifying the exposure and effects of anthropogenic contaminants in fish. Determination of exposures in wild fish is routinely performed, but methods to investigate potential effects are less established. One of the most relevant approaches would be the use of in vivo assays, but existing assays are often limited to in vitro determination of enzyme activity. Many pharmaceuticals and some persistent pollutants activate, and are metabolized by cytochrome P4503A (CYP3A), which make it a relevant and desirable target for biomarker research. We altered the established 7-benzyloxy-4-trifluoromethylcoumarin-O-debenzylation (BFCOD) in vitro protocol for CYP3A activity determination, developing a rapid and inexpensive method to measure in vivo (and in ovo) CYP3A activity in two fish systems: Gulf killifish (Fundulus grandis) and zebrafish (Danio rerio) early life stages. Even with very low concentrations of 7-benzyloxy-4-trifluoromethyl coumarin (BFC, 0.06 µM or 20 µg/L), we were able to detect significant induction in CYP3A activity in embryos of F. grandis, as well as in larvae of D. rerio in response to benzo[a]pyrene (BaP) and fluoranthene (FL) exposures. Because of concerns regarding the possible contribution of CYP1A to BFCOD activity from previous research, we have used a CYP1A post-translational inhibitor (FL) in order to calculate the contribution of CYP1A to the BFCOD assay. We also dosed with benzo[k]fluoranthene (BkF) and showed significant induction of CYP1A activity, with no concurrent increase in CYP3A activity. In this paper, we have taken an established in vitro CYP3A activity assay, and utilized the reaction in a novel way to allow for the non-destructive determination of CYP3A. In summary, we describe a sensitive, cheap, fast and easy modified BFCOD assay for in ovo and in vivo determination of CYP3A activity for use in moderate throughput early-life-stage fish experiments.

Combination of polycyclic aromatic hydrocarbons and temperature exposure: In vitro effects on immune response of European clam (Ruditapes decussatus)

Marine organisms are subjected to various biotic and abiotic factors such as changes of temperature and pollutants [e.g. polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and heavy metals, which may affect their defense mechanisms. In this context, the aim was to evaluate the combined effects of temperature (20 and 30 °C) and PAHs (fluorene, phenanthrene and pyrene) at two concentrations (10^-5 and 10^-3 mg mL^-1) on the immune responses of the European clam Ruditapes decussatus were after 24 h of in vitro exposure. Total haemocyte count, cell viability, phenoloxidase, lysozyme, alkaline phosphatase, esterase, antibacterial and agglutinating activities were measured. Exposure to high temperatures resulted in lower phosphatase alkaline activity and higher haemocyte viability and antibacterial and haemagglutinating activities, compared with the values recorded for clams maintained at low temperature. Only pyrene induced a significant decrease in haemocyte lysozyme (at 20 and 30 °C) and esterase (at 30 °C) activities. The total haemocyte count was increased by phenanthrene and pyrene at 20 °C and at 30 °C, respectively. Alkaline phosphatase activity increased when haemocytes were exposed to pyrene at 30 °C but decreased in the presence of fluorene at 20 °C. Furthermore, haemocyte viability was low in the presence of pyrene and fluorene at 20 °C and 30 °C, respectively, but was unaffected by phenanthrene. Antibacterial activity was significantly increased and no-significantly affected by the presence of pyrene and fluorene at 20 °C and 30 °C, respectively. The present study demonstrates the strong effect of PAHs and high temperature on haemocyte viability and other important immune functions, including phosphatase alkaline and antibacterial activities. Furthermore, changes in the immune parameters of European clam resulting from high temperatures may modulate the effects of PAHs and vice versa.

Biomarkers indicate mixture toxicities of fluorene and phenanthrene with endosulfan toward earthworm (Eisenia fetida)

α-Endosulfan and some polycyclic aromatic compounds (PAHs) are persistent in the environment and can reach crop products via contaminated agricultural soils. They may even be present as mixtures in the soil and induce mixture toxicity in soil organisms such as earthworms. In this study, the combined toxicities of PAHs with α-endosulfan were determined in Eisenia fetida adults using an artificial soil system. α-Endosulfan and five PAHs were tested for their acute toxicity toward E. fetida in artificial soils. Only α-endosulfan, fluorene, and phenanthrene showed acute toxicities, with LC₅₀ values of 9.7, 133.2, and 86.2 mg kg^-1, respectively. A mixture toxicity assay was conducted using α-endosulfan at LC₁₀ and fluorene or phenanthrene at LC₅₀ in the artificial soils. Upon exposure to the mixture of fluorene and α-endosulfan, earthworms were killed in increasing numbers owing to their synergistic effects, while no other mixture showed any additional toxicity toward the earthworms. Along with the acute toxicity results, the biochemical and molecular changes in the fluorene- and phenanthrene-treated earthworms with or without α-endosulfan treatment demonstrated that enhancement of glutathione S-transferase activity was dependent on the addition of PAH chemicals, and the HSP70 gene expression increased with the addition of α-endosulfan. Taken together, these findings contribute toward understanding the adverse effects of pollutants when present separately or in combination with other types of chemicals.

Never deem lightly the "less harmful" low-molecular-weight PAH, NPAH, and OPAH - Disturbance of the immune response at real environmental levels

The upcoming energy structure optimization and the implementation of strict emissions control will effectively alleviated the pollution of high-molecular-weight (HMW) polycyclic aromatic hydrocarbons (PAHs) in the atmosphere. Compared to HMW PAHs, the immune response to low-molecular-weight (LMW) PAHs is recognized as "less harmful", despite the high proportions of these substances. The present study intends to investigate the effects of several of the most abundant LMW PAHs on macrophages RAW264.7 at environmentally relevant doses. The data assembled herein showed that Fluoranthene (Fluo, PAH) formed a π-π interaction with the Phe12 residue of AhR while inhibiting the transcription of CYP1A1 and CYP1B1, and ultimately induced the inflammatory cytokines in RAW264.7. The 1-Nitropyrene (1-Nitro, NPAH) formed both a π-π interaction and a hydrogen bond with AhR, stimulated CYP1A1transcription, while suppressed the cytokine levels. Additionally, the inflammation potency caused by TPAHs was highly correlated with the cytotoxic potency rather than the oxidative stress potency. When stimulated by LPS, the transcription of IL-6 was inhibited by Fluo, and 1-Nitro suppressed both IL-6 and TNFα transcription. Furthermore, only 1-Nitro gave a significant inhibition on phagocytosis. The effects of 9-Fluorenone (9-Fluo, OPAH) on macrophages remained insignificant throughout the study since the low affinity for AhR, which resulted in low cytotoxicity. Collectively, this study suggested that LMW PAHs tended to cause mild inflammation when they bind without activating AhR. During infection, AhR ligands caused immunosuppression and this potency for TPAHs may be higher in AhR activator than that in AhR inactivator.

A bioenergetics assay for studying the effects of environmental stressors on mitochondrial function in vivo in zebrafish larvae

Mitochondria, an integral component of cellular energy metabolism and other key functions, are extremely vulnerable to damage by environmental stressors. Although methods to measure mitochondrial function in vitro exist, sensitive, medium- to high-throughput assays that assess respiration within physiologically-relevant whole organisms are needed to identify drugs and/or chemicals that disrupt mitochondrial function, particularly at sensitive early developmental stages. Consequently, we have developed and optimized an assay to measure mitochondrial bioenergetics in zebrafish larvae using the XF^e24 Extracellular Flux Analyzer. To prevent larval movement from confounding oxygen consumption measurements, we relied on MS-222-based anesthetization. We obtained stable measurement values in the absence of effects on average oxygen consumption rate and subsequently optimized the use of pharmacological agents for metabolic partitioning. To confirm assay reproducibility we demonstrated that triclosan, a positive control, significantly decreased spare respiratory capacity. We then exposed zebrafish from 5 hours post-fertilization (hpf) to 6days post-fertilization (dpf) to three polycyclic aromatic hydrocarbons (PAHs) - benzo(a)pyrene (BaP), phenanthrene (Phe), and fluoranthene (FL) - and measured various fundamental parameters of mitochondrial respiratory chain function, including maximal respiration, spare respiratory capacity, mitochondrial and non-mitochondrial respiration. Exposure to all three PAHs decreased spare respiratory capacity and maximal respiration. Additionally, Phe exposure increased non-mitochondrial respiration and FL exposure decreased mitochondrial respiration and increased non-mitochondrial respiration. Overall, this whole organism-based assay provides a platform for examining mitochondrial dysfunction in vivo at critical developmental stages. It has important implications in biomedical sciences, toxicology and ecophysiology, particularly to examine the effects of environmental chemicals and/or drugs on mitochondrial bioenergetics.

Using In Vitro High-Throughput Screening Data for Predicting Benzo[k]Fluoranthene Human Health Hazards

Today there are more than 80,000 chemicals in commerce and the environment. The potential human health risks are unknown for the vast majority of these chemicals as they lack human health risk assessments, toxicity reference values, and risk screening values. We aim to use computational toxicology and quantitative high-throughput screening (qHTS) technologies to fill these data gaps, and begin to prioritize these chemicals for additional assessment. In this pilot, we demonstrate how we were able to identify that benzo[k]fluoranthene may induce DNA damage and steatosis using qHTS data and two separate adverse outcome pathways (AOPs). We also demonstrate how bootstrap natural spline-based meta-regression can be used to integrate data across multiple assay replicates to generate a concentration-response curve. We used this analysis to calculate an in vitro point of departure of 0.751 μM and risk-specific in vitro concentrations of 0.29 μM and 0.28 μM for 1:1,000 and 1:10,000 risk, respectively, for DNA damage. Based on the available evidence, and considering that only a single HSD17B4 assay is available, we have low overall confidence in the steatosis hazard identification. This case study suggests that coupling qHTS assays with AOPs and ontologies will facilitate hazard identification. Combining this with quantitative evidence integration methods, such as bootstrap meta-regression, may allow risk assessors to identify points of departure and risk-specific internal/in vitro concentrations. These results are sufficient to prioritize the chemicals; however, in the longer term we will need to estimate external doses for risk screening purposes, such as through margin of exposure methods.

The mutagenic assessment of an electronic-cigarette and reference cigarette smoke using the Ames assay in strains TA98 and TA100

Salmonella typhimurium strains TA98 and TA100 were used to assess the mutagenic potential of the aerosol from a commercially available, rechargeable, closed system electronic-cigarette. Results obtained were compared to those for the mainstream smoke from a Kentucky reference (3R4F) cigarette. Two different test matrices were assessed. Aerosol generated from the e-cigarette was trapped on a Cambridge filter pad, eluted in DMSO and compared to cigarette smoke total particulate matter (TPM), which was generated in the same manner for mutagenicity assessment in the Salmonella assay. Fresh e-cigarette and cigarette smoke aerosols were generated on the Vitrocell® VC 10 smoking robot and compared using a modified scaled-down 35mm air agar interface (AAI) methodology. E-cigarette aerosol collected matter (ACM) was found to be non-mutagenic in the 85mm plate incorporation Ames assay in strains TA98 and TA100 conducted in accordance with OECD 471, when tested up to 2400μg/plate. Freshly generated e-cigarette aerosol was also found to be negative in both strains after an AAI aerosol exposure, when tested up to a 1L/min dilution for up to 3h. Positive control responses were observed in both strains, using benzo[a]pyrene, 2-nitrofluorene, sodium azide and 2-aminoanthracene in TA98 and TA100 in the presence and absence of metabolic activation respectively. In contrast, cigarette smoke TPM and aerosol from 3R4F reference cigarettes were found to be mutagenic in both tester strains, under comparable test conditions to that of e-cigarette exposure. Limited information exists on the mutagenic activity of captured e-cigarette particulates and whole aerosol AAI approaches. With the lower toxicant burden of e-cigarette aerosols compared to cigarette smoke, it is clear that a more comprehensive Ames package of data should be generated when assessing e-cigarettes, consisting of the standard OECD-five, TA98, TA100, TA1535, TA1537 (or TA97) and E. coli (or TA102). In addition, TA104 which is more sensitive to the carbonyl based compounds found in e-cigarette aerosols under dry-wicking conditions may also prove a useful addition in a testing battery. Regulatory standard product testing approaches as used in this study will become important when determining whether e-cigarette aerosols are in fact less biologically active than cigarette smoke, as this study suggests. Future studies should be supported by in vitro dosimetry approaches to draw more accurate comparisons between cigarette smoke, e-cigarette aerosol exposure and human use.