Long-Term Exposure to Environmental Concentrations of Azoxystrobin Delays Sexual Development and Alters Reproduction in Zebrafish ( Danio rerio).

The strobilurin fungicide azoxystrobin (AZO) can induce adverse effects in aquatic organisms, but data are lacking on endpoints associated with sexual development and reproduction following chronic exposure to AZO. In this study, zebrafish embryos (F0) at 2-4 h postfertilization (hpf) were exposed to 0.2, 2.0, and 20.0 µg/L AZO until 120 d postfertilization (dpf). Decreased male ratio and increased intersex ratio were observed by 20.0 µg/L AZO at 42 and 60 dpf, but this effect disappeared at 120 dpf. AZO at 20.0 µg/L inhibited growth, retarded gonadal development, and disrupted sex hormone and vitellogenin in females at 60 and 120 dpf and in males at 42, 60, and 120 dpf. These effects were associated with altered expression of cyp19a, cyp19b, hsd3b, hsd17b, vtg1, and vtg2. Exposure to 2.0 µg/L AZO altered mRNA levels of these transcripts in females at 120 dpf and in males at 60 and 120 dpf. Reproduction ability was reduced by 20.0 µg/L AZO at 120 dpf. Developmental defects were observed after F1 embryos from exposed parents of 20.0 µg/L were reared in AZO-free water at 96 hpf. Overall, these data provide new understanding of fish sexual development and reproduction following chronic exposures to AZO.

Developmental neurotoxicity of maneb: Notochord defects, mitochondrial dysfunction and hypoactivity in zebrafish (Danio rerio) embryos and larvae.

Broad applications and exposure to the fungicide maneb can lead to toxicity in non-target organisms. Maneb is also associated with neurogenerative diseases such as Parkinson's disease (PD). The objectives of this study were to determine the acute toxicity of maneb to zebrafish by measuring mitochondrial bioenergetics, locomotor activity, and the expression of genes related to the oxidative damage response, as well as those related to dopamine signaling due to its association with PD. Zebrafish embryos at 6 h post-fertilization (hpf) were exposed to either solvent control (0.1% DMSO, v/v), or one dose of 0.1, 0.5, 1.0 and 10.0 µM maneb for 96 h. Maneb was moderately toxic to zebrafish embryos, and had a 96-h LC50 value of 4.29 µM (~ 1.14 mg/L). Maneb induced a dose-dependent increase in mortality, decreased hatching rate, and increased notochord deformity rate at both 1.0 and 10.0 µM after 72 and 96 h. Total body length was also significantly reduced with 1.0 µM maneb. A 50-60% decrease in mean basal oxygen consumption rate was also observed in embryos following a 24 hpf exposure to 10.0 µM maneb but oligomycin-induced ATP production and FCCP-induced maximum respiration remained unaffected. No change was detected in the expression levels of genes associated with oxidative stress (sod1 and sod2), nor those related to dopamine synthesis (th1), dopamine transporter (dat), dopamine receptors (drd1, drd2a, drd3, and drd4b). Thus, modifying the expression of these transcripts may not be a mechanism for maneb-induced developmental toxicity in zebrafish. To assess the potential for neurotoxicity, a dark photokinesis assay was conducted in larvae following 7 d exposure to 0.1, 0.5 and 1.0 µM maneb. Larvae exposed to 0.5 and 1.0 µM maneb showed signs related to hypoactivity, and this reduced activity is hypothesized to be associated with notochord defects as this deformity was prevalent at higher concentrations of maneb. Overall, these data demonstrate that maneb negatively affects embryonic development (i.e. notochord development), affects basal oxygen consumption rates of embryos, and induces hypoactivity in larval fish. This study improves understanding regarding the developmental neurotoxicity of the fungicide maneb to zebrafish.

Developmental toxicity and potential mechanisms of pyraoxystrobin to zebrafish (Danio rerio).

As a newly developed, highly efficient strobilurin fungicide, pyraoxystrobin has been reported to be highly toxic to some aquatic organisms. However, the toxicity of pyraoxystrobin to different life stages of fish and the potential underlying mechanisms are still unknown. Hence, in the present study, the acute toxicity of pyraoxystrobin to different life stages of zebrafish (embryo, larva, and adult) was assessed. The developmental toxicity of pyraoxystrobin to zebrafish embryos and its effects on gene transcription in the embryo were also investigated. The results showed that the 96-h LC50 values of pyraoxystrobin to embryos [2h post-fertilization (hpf)], 12h post-hatching (hph) larvae (84 hpf), 72 hph larvae (144 hpf), and adult zebrafish were 4.099, 1.069, 3.236, and 5.970µg/L, respectively. This suggests that pyraoxystrobin has very high toxicity to different life stages of zebrafish, while the newly hatched larvae constitute the most sensitive period of zebrafish to pyraoxystrobin. Decreased heart rate, hatching inhibition, growth regression, and morphological deformities were observed in zebrafish embryos after acute exposure to different concentrations of pyraoxystrobin. The rate of malformation increased in a time- and concentration-dependent manner in embryos, and the most pronounced abnormality was pericardial edema and yolk sac edema. Pyraoxystrobin (2 and 4µg/L) significantly altered the mRNA levels of genes related to mitochondrial respiratory chain and ATP synthesis (NDI, uqcrc, and ATPo6), oxidative stress (Mn-Sod, Cat, and Gpx), apoptosis (p53, Bcl2, Bax, and Cas3), and immune system (TNFα, IFN, and IL-1b) in zebrafish embryos. This result indicates that the alteration of these genes is a potential mechanism underlying the toxic effects of pyraoxystrobin on zebrafish.

Antioxidant and Anti-Aging Properties of Polyphenol-Polysaccharide Complex Extract from Hizikia fusiforme.

Hizikia fusiforme has a long history of consumption and medicinal use in China. It has been found that natural plants containing polyphenol-polysaccharide complexes have better activity compared with polyphenols and polysaccharides. Therefore, in this study on enzymatic hydrolysis and fractional alcohol precipitation, two kinds of polyphenol-polysaccharide complexes (PPC), PPC1 and PPC2, were initially obtained from Hizikia fusiforme, while the dephenolization of PPC1 and PPC2 produced PPC3 and PPC4. Through in vitro assays, PPC2 and PPC4 were found to have higher antioxidant activity, and thus were selected for testing the PPCs' anti-aging activity in a subsequent in vivo experiment with D-gal-induced aging in mice. The results indicated that PPCs could regulate the expressions of antioxidant enzymes and products of oxidation, elevate the expressions of genes and proteins related to the Nrf2 pathway in the mouse brain, enrich the gut microbiota species and increase the Bacteroidota-Firmicute (B/F) ratio. Above all, the Hizikia fusiforme polyphenol-polysaccharide complex has potential in the development of natural anti-aging drugs.

Urban Form and Function Optimization for Reducing Carbon Emissions Based on Crowd-Sourced Spatio-Temporal Data.

The low-carbon city has become an important global urban development-oriented goal. One important aspect of urban space is low-carbon urban planning, which has a vital role in urban carbon emissions. Which types of urban form and function allocations are conducive to reducing carbon emissions is therefore a key issue. In this study, the Futian and Luohu Districts of Shenzhen, Guangdong Province, China, are taken as an example to investigate this issue. Firstly, a "head/tail" breaks method based on the third fractal theory is adopted to obtain the minimum evaluation parcel of urban space. Then, the Landscape Shape Index (LSI), Fragmentation Index (C), Shannon's Diversity Index (SHDI), and Density of Public Facilities (Den) are used to evaluate the form and function allocation of each parcel. In addition, the CO2 concentration distribution in this study area is acquired from remote sensing satellite data. Finally, the relationships between urban form, function allocation, and CO2 concentration are obtained. The results show that the lower the urban form index or the higher the urban function index, the less the CO2 concentration. To verify this conclusion, three experiments are designed and carried out. In experiment A, the CO2 concentration of the tested area is reduced by 14.31% by decreasing the LSI and C by 6.1% and 9.4%, respectively. In experiment B, the CO2 concentration is reduced by 15.15% by increasing the SHDI and Den by 16.3% and 12.1%, respectively. In experiment C, the CO2 concentration is reduced by 27.72% when the urban form and function are adjusted in the same was as in experiments A and B.

Investigating mitochondria-immune responses in zebrafish, Danio rerio (Hamilton, 1822): A case study with the herbicide dinoseb.

The dinitrophenol herbicide dinoseb is an uncoupler of mitochondrial oxidative phosphorylation (OXPHOS). Studies in fish demonstrate impaired OXPHOS is associated with altered immune system responses and locomotor activity in fish. The objective of this study was to determine the effect of dinoseb on zebrafish (Danio rerio) during early stages of development. We measured oxygen consumption rates of embryos, transcripts related to OXPHOS, growth, and the immune system (cytokines and immune-signaling transcripts), and locomotor activity. We hypothesized that OXPHOS of fish would be impaired in vivo, leading to altered basal immune system expression and locomotor activity. Oxidative respiration assessments in embryos revealed that dinoseb decreased both mean basal respiration and oligomycin-induced ATP-linked respiration. Expression levels of cytochrome c oxidase complex IV, 3-hydroxyacyl-COA dehydrogenase and superoxide dismutase 1 were decreased in larvae following exposure to dinoseb while succinate dehydrogenase complex flavoprotein subunit A, insulin growth factor 1 (igf1) and igf2a mRNA were increased in abundance. Immune-related transcripts chemokine (C-X-C motif) ligand 1 and matrix metallopeptidase 9 (MMP-9) were decreased in expression levels while toll-like receptor 5a and 5b were increased in expression. In addition, a visual motor response test was conducted on both 6 and 7 dpf larvae to determine if dinoseb impaired locomotor activity. Dinoseb decreased locomotor activity in 7 dpf larvae but not 6 dpf. This study improves knowledge of toxicity mechanisms for dinoseb in early stages of fish development and demonstrates that mitochondrial toxicants may disrupt immune signaling in zebrafish.

Effects of Nano Aluminum Powder on the Mechanical Sensitivity of RDX-Based Explosives.

As nano-aluminum powder (NAP) can improve the detonation performance of aluminum-containing explosives, more and more explosives with NAP as the metal ingredient have been studied. It is believed that the mechanical sensitivity of explosives can be significantly enhanced by the added nano-sized aluminum powder. However, the mechanism for the enhancement has not been clarified. In order to illuminate the effects of NAP on the mechanical sensitivity of explosives, two RDX-based aluminum-containing explosives with the same weight ratio and preparation process were investigated despite the aluminum powders with different nano-size and micron-size. The morphology and surface atomic ratio of the two explosives were examined by scanning electron microscopy with energy dispersive spectroscopy tests. The contact angle and other microstructures properties of the explosives were calculated by Material Studio software. Results revealed that the impact and friction activity was determined by the aluminum particle sizes and explosive components. This paper clarified the mechanism for the increase in explosives sensitivity by the addition of NAP, which provide reference for the scientific and technical design of novel explosives.

The effects of a short-term exposure to propiconazole in zebrafish (Danio rerio) embryos.

Propiconazole (PCZ) is a widely used fungicide around the world and was frequently detected in surface waters, which would pose risk to aquatic organisms. Previous studies indicated that PCZ has high toxicity to different kinds of fish. However, most of the studies focus on the toxicity and mechanisms of PCZ to adult fish, the potential toxicity mechanism of PCZ to fish embryos is still poorly understood. The present study investigated the effects of PCZ on content of reactive oxygen species (ROS) and malondialdehyde (MDA); activities of superoxide dismutase (SOD), catalase (CAT), and Na+-K+-ATPase; and expression level of genes related to oxidative stress, cell apoptosis, and innate immune system in zebrafish embryos after 96-h exposure. The results showed that 5.0 mg/L PCZ induced oxidative damage in zebrafish embryos, as indicated by increased ROS and MDA content and alteration of antioxidative enzyme activity. The activity of Na+-K+-ATPase in zebrafish embryos was significantly inhibited after exposure to 0.5 mg/L PCZ. The expression levels of bax, p53, casp-3, casp-9, and apaf-1 were significantly increased, indicating that cell apoptosis was caused in embryos by 5.0 mg/L PCZ. The expression level of interleukin-1b (IL-1b) and IL-8 increased after exposure to 0.5 mg/L PCZ, but that of IL-1b, IL-8, and cxcl-c1c (chemokine (C-X-C motif) ligand 18b) decreased in 5.0-mg/L PCZ treatment group, indicating an immunotoxicity effect. Our results suggest that oxidative damage, cell apoptosis, and immunotoxicity would be induced in zebrafish embryos after short-term exposure to PCZ.

Developmental toxicity of the triazole fungicide cyproconazole in embryo-larval stages of zebrafish (Danio rerio).

Cyproconazole is a triazole fungicide used to protect a diverse range of fruits, vegetables, and grain crops. As such, it has the potential to enter aquatic environments and affect non-target organisms. The objective of this study was to assess the acute toxicity of the triazole fungicide cyproconazole to zebrafish embryos by assessing mortality, developmental defects, morphological abnormality, oxidative respiration, and locomotor activity following a 96-h exposure. Zebrafish embryos at 6-h post-fertilization (hpf) were exposed to either a solvent control (0.1% DMSO, v/v), or one dose of 10, 25, 50, 100, 250, and 500 µM cyproconazole for 96 h. Data indicated that cyproconazole exhibited low toxicity to zebrafish embryos, with a 96-h LC50 value of 90.6 µM (~ 26.4 mg/L). Zebrafish embryos/larvae displayed a significant decrease in spontaneous movement, hatching rate, and heartbeats/20 s with 50, 100, and 250 µM cyproconazole exposure. Malformations (i.e., pericardial edema, yolk sac edema, tail deformation, and spine deformation) were also detected in zebrafish exposed to ≥ 50 µM cyproconazole, with significant increases in cumulative deformity rate at 48, 72, and 96 hpf. In addition, a 20-30% decrease in basal and oligomycin-induced ATP respiration was observed after 24-h exposure to 500 µM cyproconazole in embryos. To determine if cyproconazole affected locomotor activity, a dark photokinesis assay was conducted in larvae following 7-day exposure to 1, 10, and 25 µM cyproconazole in two independent trials. Activity in the dark period was decreased for zebrafish exposed to 25 µM cyproconazole in the first trial, and hypoactivity was also observed in zebrafish exposed to 1 µM cyproconazole in a second trial, suggesting that cyproconazole can affect locomotor activity. These data improve understanding of the toxicity of cyproconazole in developing zebrafish and contribute to environmental risk assessments for the triazole fungicides on aquatic organisms. We report that, based on the overall endpoints assessed, cyproconazole exhibits low risk for developing fish embryos, as many effects were observed above environmentally-relevant levels.

Effects of penthiopyrad on the development and behaviour of zebrafish in early-life stages.

The agricultural use of succinate dehydrogenase inhibitor (SDHI) fungicides has increased dramatically in the US and Europe. As the SDHI fungicides, boscalid, flutolanil and thifluzamide had been reported to induce a series of toxic effects on zebrafish. However, the toxic effects of penthiopyrad on zebrafish have not been reported yet. This study aimed to assess the acute toxicity of penthiopyrad to zebrafish in early-life stages and investigate behavioural response of larvae and the effects on lipid metabolism and pigmentation under sub-lethal exposure of penthiopyrad. Based on results of the acute toxicity tests of zebrafish embryo and larvae, penthiopyrad had an acute toxicity to early-life stages of zebrafish and induced a series of deformities during development. Based on the results of sub-lethal exposure for 8 days, penthiopyrad resulted in significant decreases in swimming velocity, acceleration speed, distance moved and inactive time of larvae at 0.3, 0.6 and 1.2 mg/L. Penthiopyrad induced the disorders of lipid metabolism via affecting fatty acid synthesis and ß-oxidation, in accordance with remarkable changes in the content of triglycerides and cholesterol and the expression of key genes (hmgcrα, pparα1, srebf1, cyp51 and acca1) at 1.2 mg/L. In addition, the disorder of melanin synthesis and distribution was caused by penthiopyrad in larvae in accordance with changes in body colour and related gene expression at 8 dpe.

Mitochondrial dysfunction-based cardiotoxicity and neurotoxicity induced by pyraclostrobin in zebrafish larvae.

Pyraclostrobin is widely used to control crop diseases, and was reported to be highly toxic to aquatic organisms. The molecular target of pyraclostrobin to fungus is the mitochondrion, but its effect on mitochondria of aquatic organisms has rarely been investigated. In this study, zebrafish larvae at 4 days post fertilization (dpf) were exposed to a range of pyraclostrobin for 96 h to assess its acute toxicity and effects on mitochondria. Pyraclostrobin at 36 µg/L or higher concentrations caused significant influences on larval heart and brain including pericardial edema, brain damage malformations, histological and mitochondrial structural damage of the two organs. The results of RNA-Seq revealed that the transcripts of genes related to oxidative phosphorylation, cardiac muscle contraction, mitochondrion, nervous system development and glutamate receptor activity were significantly influenced by 36 µg/L pyraclostrobin. Further tests showed that pyraclostrobin at 18 and 36 µg/L reduced the concentrations of proteins related to cardiac muscle contraction, impaired cardiac function, inhibited glutamate receptors activities and suppressed locomotor behavior of zebrafish larvae. Negative changes in mitochondrial complex activities, as well as reduced ATP content were also observed in larvae treated with 18 and 36 µg/L pyraclostrobin. These results suggested that pyraclostrobin exposure caused cardiotoxicity and neurotoxicity in zebrafish larvae and mitochondrial dysfunction might be the underlying mechanism of pyraclostrobin toxicity.

Short-term developmental toxicity and potential mechanisms of the herbicide metamifop to zebrafish (Danio rerio) embryos.

Metamifop is a novel aryloxyphenoxy propionate (AOPP) herbicide that is widely applied in paddy fields, which will inevitably enter aquatic environments and pose a risk to aquatic organisms. However, the potential threat and toxicological mechanisms of metamifop in aquatic organisms are poorly understood. In this study, zebrafish embryos were used to investigate the potential developmental toxicity and mechanisms of metamifop. The results showed that metamifop exhibited high acute toxicity to zebrafish, with 96 h-LC50 values of 0.648 and 0.216 mg/L to embryos and larvae of 72 h post-hatching (hph), respectively. Decreased body lengths, heartbeat number, and hatching rates, and increased malformation rates of embryos were observed after 96 h of exposure to 0.38 mg/L or higher concentration of metamifop. Furthermore, oxidative stress was caused in embryos, with increased contents of reactive oxygen species (ROS) and malondialdehyde (MDA), and altered activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx). Metamifop exposure clearly triggered cell apoptosis in embryos, result in the increase of Caspase-3 and Caspase-9 activities and up-regulation of apoptosis-related genes (bax, p53, apaf1, caspase-3, and caspase-9). Additionally, the transcriptions of innate immune-related genes (il-8, il-1b, and ifn) were increased in the groups treated with 0.25 and 0.5 mg/L of metamifop. These results indicate that metamifop induced developmental toxicity in zebrafish, and the potential toxicological mechanisms were related to oxidative stress, cell apoptosis, and the innate immune responses in embryos.

Developmental toxicity of the fungicide ziram in zebrafish (Danio rerio).

Ziram is a broad spectrum pesticide that belongs to the class of dimethyl-dithiocarbamate (DTC) fungicides. The objectives of this study were to assess the effects of ziram in developing zebrafish. Ziram was highly toxic to zebrafish embryos, with a 96-h LC50 value of 1082.54 nM (∼0.33 mg/L). Zebrafish embryos at 6 h post-fertilization (hpf) were exposed to solvent control (0.1% DMSO), or one dose of 1, 10, 100, and 1000 nM ziram for 96 h. Ziram induced lethality in a dose-dependent manner, decreased hatching rate and heartbeat, and caused wavy deformities at 72 and 96 hpf at 100 and 1000 nM. Basal oxygen consumption rates of zebrafish at 24 hpf were decreased with 1000 nM, suggesting that ziram affects oxidative phosphorylation. We also measured the expression of transcripts associated with the oxidative stress response (sod1 and sod2) and dopamine receptor signaling at ∼96 h of exposure. There was no difference in the expression of genes related to oxidative stress, nor those related to the dopamine system. Locomotor activity was also assessed in larval zebrafish (7 dpf), and ziram increased total activity, the velocity in light zone, and total distance moved at 10 nM, while it decreased the mean time spent in the dark zone at 1 and 10 nM. Behavioral responses were dependent upon the time point and clutch examined. These data demonstrate that ziram negatively impacts embryonic development (i.e. mortality, hatching, heartbeat and notochord development) of zebrafish, decreases basal respiration of embryos, and alters behavioral responses in larvae.

Parental exposure to azoxystrobin causes developmental effects and disrupts gene expression in F1 embryonic zebrafish (Danio rerio).

The fungicide azoxystrobin induces reproductive toxicity in adult zebrafish. However, data are lacking regarding the impact of azoxystrobin in the F1 generation after parental exposure. To address this knowledge gap, parental zebrafish (F0) were exposed to 2, 20 and 200 µg/L azoxystrobin for 21 days. Following this, fertilized F1 embryos from the exposed parents were either exposed to the same concentration as their corresponding exposed parents (F0+/F1+) or were reared in clean water (F0+/F1-) for 96 h ("+", exposed; "-" unexposed). Likewise, F1 embryos from the non-exposed parents were either reared in clean water (F0-/F0-) as the control group or were exposed to 2, 20 and 200 µg/L azoxystrobin (F0-/F1+) for 96 h. Mortality, deformities, hatching rate, body length, and the expression of transcripts related to the endocrine system, oxidative stress, and apoptosis were measured. Increased mortality, higher malformation rate, decreased hatching rate, and a shorter total body length, as well as up-regulated cyp19b, vtg1, vtg2, p53, casp3, and casp9 mRNA and down-regulated sod1 and sod2 mRNA were detected in F1 embryos from the F0 and F1 exposure group at 20 and 200 µg/L azoxystrobin (F0+/F1+) when compared with the group from the F0 exposure alone (F0+/F1-). Interestingly, F1 exposure alone (F0-/F1+) did not induce mortality, developmental impairments, nor morphological deformations compared to the control group, but it did increase expression level of sod1, sod2, cat, p53, and casp9 at 200 µg/L azoxystrobin. Taken together, these data suggest that azoxystrobin affects survivability, development, and genes involved in the endocrine system, oxidative stress, and apoptosis in F1 embryos if their parents are initially exposed to this fungicide compared to embryos from non-exposed parents. Moreover, the effects are more severe if the offspring are continuously exposed to azoxystrobin similar to their parents.

Elucidating Conserved Transcriptional Networks Underlying Pesticide Exposure and Parkinson's Disease: A Focus on Chemicals of Epidemiological Relevance.

While a number of genetic mutations are associated with Parkinson's disease (PD), it is also widely acknowledged that the environment plays a significant role in the etiology of neurodegenerative diseases. Epidemiological evidence suggests that occupational exposure to pesticides (e.g., dieldrin, paraquat, rotenone, maneb, and ziram) is associated with a higher risk of developing PD in susceptible populations. Within dopaminergic neurons, environmental chemicals can have an array of adverse effects resulting in cell death, such as aberrant redox cycling and oxidative damage, mitochondrial dysfunction, unfolded protein response, ubiquitin-proteome system dysfunction, neuroinflammation, and metabolic disruption. More recently, our understanding of how pesticides affect cells of the central nervous system has been strengthened by computational biology. New insight has been gained about transcriptional and proteomic networks, and the metabolic pathways perturbed by pesticides. These networks and cell signaling pathways constitute potential therapeutic targets for intervention to slow or mitigate neurodegenerative diseases. Here we review the epidemiological evidence that supports a role for specific pesticides in the etiology of PD and identify molecular profiles amongst these pesticides that may contribute to the disease. Using the Comparative Toxicogenomics Database, these transcripts were compared to those regulated by the PD-associated neurotoxicant MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine). While many transcripts are already established as those related to PD (alpha-synuclein, caspases, leucine rich repeat kinase 2, and parkin2), lesser studied targets have emerged as "pesticide/PD-associated transcripts" [e.g., phosphatidylinositol glycan anchor biosynthesis class C (Pigc), allograft inflammatory factor 1 (Aif1), TIMP metallopeptidase inhibitor 3, and DNA damage inducible transcript 4]. We also compared pesticide-regulated genes to a recent meta-analysis of genome-wide association studies in PD which revealed new genetic mutant alleles; the pesticides under review regulated the expression of many of these genes (e.g., ELOVL fatty acid elongase 7, ATPase H+ transporting V0 subunit a1, and bridging integrator 3). The significance is that these proteins may contribute to pesticide-related increases in PD risk. This review collates information on transcriptome responses to PD-associated pesticides to develop a mechanistic framework for quantifying PD risk with exposures.

Short-term developmental effects and potential mechanisms of azoxystrobin in larval and adult zebrafish (Danio rerio).

Previous study indicated that azoxystrobin had high acute toxicity to zebrafish, and larval zebrafish were more sensitive to azoxystrobin than adult zebrafish. The objective of the present study was to investigate short-term developmental effects and potential mechanisms of azoxystrobin in larval and adult zebrafish. After zebrafish embryos and adults were exposed to 0.01, 0.05 and 0.20 mg/L azoxystrobin (equal to 25, 124 and 496 nM azoxystrobin, respectively) for 8 days, the lethal effect, physiological responses, liver histology, mitochondrial ultrastructure, and expression alteration of genes related to mitochondrial respiration, oxidative stress, cell apoptosis and innate immune response were determined. The results showed that there was no significant effect on larval and adult zebrafish after exposure to 0.01 mg/L azoxystrobin. However, increased ROS, MDA concentration and il1b in larval zebrafish, as well as increased il1b, il8 and cxcl-c1c in adult zebrafish were induced after exposure to 0.05 mg/L azoxystrobin. Reduced mitochondrial complex III activity and ATP concentration, increased SOD activity, ROS and MDA concentration, decreased cytb, as well as increased sod1, sod2, cat, il1b, il8 and cxcl-c1c were observed both in larval and adult zebrafish after exposure to 0.20 mg/L azoxystrobin; meanwhile, increased p53, bax, apaf1 and casp9, alteration of liver histology and mitochondrial ultrastructure in larval zebrafish, and alteration of mitochondrial ultrastructure in adult zebrafish were also induced. The results demonstrated that azoxytrobin induced short-term developmental effects on larval zebrafish and adult zebrafish, including mitochondrial dysfunction, oxidative stress, cell apoptosis and innate immune response. Statistical analysis indicated that azoxystrobin induced more negative effects on larval zebrafish, which might be the reason for the differences of developmental toxicity between larval and adult zebrafish caused by azoxystrobin. These results provided a new insight into potential mechanisms of azoxystrobin in larval zebrafish and adult zebrafish.

Developmental toxicity, oxidative stress and immunotoxicity induced by three strobilurins (pyraclostrobin, trifloxystrobin and picoxystrobin) in zebrafish embryos.

Strobilurins is the most widely used class of fungicides, but is reported highly toxic to some aquatic organisms. In this study, zebrafish embryos were exposed to a range concentrations of three strobilurins (pyraclostrobin, trifloxystrobin and picoxystrobin) for 96 h post-fertilization (hpf) to assess their aquatic toxicity. The 96-h LC50 values of pyraclostrobin, trifloxystrobin and picoxystrobin to embryos were 61, 55, 86 µg/L, respectively. A series of symptoms were observed in developmental embryos during acute exposure, including decreased heartbeat, hatching inhibition, growth regression, and morphological deformities. Moreover, the three fungicides induced oxidative stress in embryos through increasing reactive oxygen species (ROS) and malonaldehyde (MDA) contents, inhibiting superoxide dismutase (SOD) activity and glutathione (GSH) content as well as differently changing catalase (CAT) activity and mRNA levels of genes related to antioxidant system (Mn-sod, Cu/Zn-sod, Cat, Nrf2, Ucp2 and Bcl2). In addition, exposure to the three strobilurins resulted in significant upregulation of IFN and CC-chem as well as differently changed expressions of TNFa, IL-1b, C1C and IL-8, which related to the innate immune system, suggesting that these fungicides caused immunotoxicity during zebrafish embryo development. The different response of enzymes and genes in embryos exposed to the three fungicides might be the cause that leads to the difference of their toxicity. This work made a comparison of the toxicity of three strobilurins to zebrafish embryos on multi-levels and would provide a better understanding of the toxic effects of strobilurins on aquatic organisms.

Toxic effects of boscalid on the growth, photosynthesis, antioxidant system and metabolism of Chlorella vulgaris.

Boscalid is one of the most frequently detected pesticides in main coastal estuaries in California, with concentrations as high as 36 µg/L. However, ecotoxicology information about boscalid to aquatic organisms is scarce. To investigate toxic effects and mechanisms of boscalid on freshwater algae Chlorella vulgaris (C. vulgaris), C. vulgaris were exposed to a range of boscalid concentrations (0, 0.8, 1.6, 2.4 and 3.2 mg/L) for 96 h to study the changes in photosynthetic pigment contents, responses of the antioxidant enzyme system and alterations in endogenous substances. Results indicated that the growth of algae and the content of chlorophyll and carotenoids were significantly inhibited by 1.6 mg/L boscalid. Reactive oxygen species (ROS) and oxidative damage of C. vulgaris could be induced by boscalid, in accordance with significant changes in ROS levels and a series of antioxidant enzyme activities. Moreover, the alterations in endogenous substances showed that boscalid could affect photosynthesis and energy metabolism of C. vulgaris. These results demonstrated that boscalid could induce impacts on C. vulgaris mainly through disturbing the photosynthesis, oxidative damage and energy metabolism. The present study provided a better understanding of the negative effects and mechanisms of bosaclid in microalgae.

Biological impacts of organophosphates chlorpyrifos and diazinon on development, mitochondrial bioenergetics, and locomotor activity in zebrafish (Danio rerio).

The objectives of this study were to compare the biological responses in developing zebrafish to two organophosphate insecticides, chlorpyrifos (CPF) and diazinon (DZN). Zebrafish embryos were exposed to either solvent control (0.1% DMSO, v/v), or one dose of 0.1, 1.0, 10.0 and 25.0 µM CPF, as well as one dose of 0.1, 1.0, 10.0 and 100.0 µM DZN for 96 h. CPF at 10.0 and 25.0 µM caused 70-80% and 100% mortality in embryos after 96 h exposure, whereas embryos treated with 10.0 and 100.0 µM DZN showed 30-40% and 70-80% lethality. CPF at 10.0 µM significantly decreased cumulative hatching rate, whereas hatching rate was significantly reduced in embryos treated with 100.0 µM DZN. Spinal lordosis was primarily observed in larvae exposed to 1.0 and 10.0 µM CPF, whereas pericardial edema was mainly detected with 10.0 and 100.0 µM DZN exposure. Embryo exposed to 1.0, 10.0 and 25.0 µM CPF exhibited no mitochondrial dysfunction; exposure to 100.0 µM DZN significantly inhibited mitochondrial bioenergetics. To determine if CPF and DZN affected larval activity, dark photokinesis response was assessed in larvae following 7 days exposure to 0.1 and 1.0 µM CPF, as well as to 0.1 1.0, and 10.0 µM DZN. Larvae exposed to 1.0 µM CPF showed hypoactivity, whereas the activity in the dark was not overtly changed in larvae exposed to DZN. In summary, CPF showed higher developmental toxicity compared to DZN. Moreover, based on the types of morphological deformities noted, as well as differences in locomotor activity, we conclude that OPs have unique chemical-specific modes of action that can result in varied biological responses during early development.

Quizalofop-P-ethyl exposure increases estrogen axis activity in male and slightly decreases estrogen axis activity in female zebrafish (Danio rerio).

The herbicide Quizalofop-P-ethyl (QpE) exerts toxic effects in fish, but limited information is currently available on its effects on the endocrine system. In the current study, adult zebrafish (Danio rerio) were exposed to different concentrations (0, 2, 20, 200µg/L) of QpE for 30days. In males, QpE exposure significantly increased plasma estradiol (E2) and vitellogenin (VTG) levels, concomitant with up-regulation of hepatic esr1 and vtg gene expression. In females, plasma sex hormone levels and VTG concentrations were not altered significantly, but an increased expression of hepatic esr1 in addition to decreased expression of hepatic vtg, esr2a and esr2b was observed. Marked histological lesions were also observed in the gonads of both males and females. Moreover, QpE exposure significantly increased transcriptional profiles of some genes in the HPG axis and liver in males, while the majority of these genes were down-regulated in females. Docking studies showed QpE forming stable interactions with the ligand-binding domain (LBD) of zebrafish ESR1 and ESR2a, suggesting QpE may bind to estrogen receptors (ESRs). This study for the first time reveals QpE as an endocrine-disrupting chemical (EDC) disrupting the zebrafish endocrine system in a sex-specific manner, whereby it increases estrogen axis activity in males and slightly decreases estrogen axis activity in females, which may be accounted for by QpE regulating steroidogenesis and/or activating ESR(s).