Effects of low doses Trichlorfon exposure on Rana chensinensis tadpoles

Lead promoted bile acid deconjugation by modulating gut bacteria encoding bile salt hydrolase (BSH) in Rana chensinensis tadpoles

Bile salt hydrolase (BSH) is produced by gut bacteria and is responsible for deconjugating amino acids from the aliphatic side chains of conjugated bile acids (BAs), initiating the critical first step in BAs metabolism. Lead (Pb) is known to cause gut microbial dysbiosis, but whether it affects BAs profiles by reshaping the gut microbiota remains elusive. Here, using targeted BAs metabolomics and metagenomics sequencing, we found that 200 μg/L Pb treatment led to a significant increase in the abundance of BSH-producing microbiota (e.g., Eubacterium and Yersinia), thus promoting the deconjugation of taurocholic acid (TCA) and taurochenodeoxycholic acid (TCDCA). Consequently, the accumulation of relatively hydrophobic BAs cholic acid (CA) and chenodeoxycholic acid (CDCA) may cause damage to enterocytes (e.g., reduced microvilli and enterocyte heights), which attenuated tadpole digestion and ultimately led to significant reductions in morphological parameters. The inhibition of tadpole growth by Pb toxicity may negatively affect their survival and even increase their risk of death. Overall, these results revealed for the first time the toxicological mechanism by which Pb reshapes the gut microbiota and thus disrupts the BAs profile, shedding new insights into the detrimental effects of Pb toxicity on amphibian growth.

Study on low concentration deltamethrin toxicity mediated by phospholipase D in Chinese mitten crab (Eriocheir sinensis) ovary

This study evaluates the impact of environmentally relevant, low-concentration deltamethrin exposure to Eriocheir sinensis ovaries. Our findings revealed that even at a concentration of 0.05 µg/L, deltamethrin exposure can induce significant ovarian toxicity through a 5-day exposure, with gradual amplification detected with time, demonstrating the toxicity amplification effect. Hematoxylin and Eosin staining revealed that low-concentration deltamethrin exposure produces pathological damage consistent with acute toxicity-yolk granules were dissolved and oocyte membranes were ruptured. High-throughput RNA-sequencing data indicated that the acute and low-concentration exposure groups involved completely different pathways and molecular functions, suggesting distinct mechanisms for their toxic effects. Following the identification of phospholipase D (PLD) as a potential core factor regulating the toxicity amplification effect of low concentration deltamethrin, we delved into subsequent mechanism studies using quantitative real-time PCR, immunofluorescence and enzyme-linked immunosorbent assay. Through the GnRH signaling pathway, increased PLD indirectly stimulates augmented estradiol secretion, subsequently inducing apoptosis by upregulating Cathepsin D, which can activate the key executioners of apoptosis-caspases (CASP3 and CASP7). In conclusion, low-concentration deltamethrin exposures can induce significant ovarian damage through apoptosis mediated by the upregulation of PLD in the ovaries of Eriocheir sinensis at environmentally relevant concentrations, which lays the preliminary theoretical groundwork for further elucidating the mechanism of toxicity amplification effect of pesticide exposure at low concentrations.

Changes in thermal sensitivity of Rhinella arenarum tadpoles (Anura: Bufonidae) exposed to sublethal concentrations of different pesticide fractions (Lorsban® 75WG)

The intensive use of agrochemicals and the rapid increase of global temperatures have modified the thermal conditions of aquatic environments, thus increasing amphibians' vulnerability to global warming and positioning them at great risk. Commercial formulations of chlorpyrifos (COM) are the pesticides most widely used in agricultural activities, with a high toxic potential on amphibians. However, little is known about the separate effects of the active ingredient (CPF) and adjuvants (AD). We studied the thermal sensitivity at different concentrations and pesticide fractions in Rhinella arenarum tadpoles, on thermal tolerance limits (CTmax = Critical thermal maximum and CTmin = Critical thermal minimum), swimming speed (Ss), Optimum temperature (Top), and Thermal breadth 50 (B50). Our results demonstrate that the pesticide active ingredient, the adjuvants, and the commercial formulation of chlorpyrifos differentially impair the thermal sensitivity of R. arenarum tadpoles. The pesticide fractions affected the heat and the cold tolerance (CTmax and CTmin), depending on the concentrations they were exposed to. The locomotor performance (Ss, Top, and B50) of tadpoles also varied among fractions, treatments, and environmental temperatures. In the context of climate change, the outcomes presented are particularly relevant, as mean temperatures are increasing at unprecedented rates, which suggests that tadpoles inhabiting warming and polluted ponds are currently experiencing deleterious conditions. Considering that larval stages of amphibians are the most susceptible to changing environmental conditions and the alarming predictions about environmental temperatures in the future, it is likely that the synergism between high temperatures and pesticide exposure raise the threat of population deletions in the coming years.

Dynamics of dominant rhizospheric microbial communities responsible for trichlorfon absorption and translocation in maize seedlings

In this study, the available phosphorus (AP) and TCF concentrations in soils and maize (Zea mays) seedling tissues were measured in response to escalating TCF concentrations during 216 hr of culture. Maize seedlings growth considerably enhanced soil TCF degradation, reaching the highest of 73.2% and 87.4% at 216 hr in 50 and 200 mg/kg TCF treatments, respectively, and increased AP contents in all the seedling tissues. Soil TCF was majorly accumulated in seedling roots, reaching maximum concentration of 0.017 and 0.076 mg/kg in TCF-50 and TCF-200, respectively. The hydrophilicity of TCF might hinder its translocation to the aboveground shoot and leaf. Using bacterial 16 S rRNA gene sequencing, we found that TCF addition drastically lessened bacterial community interactions and hindered the complexity of their biotic networks in rhizosphere than in bulk soils, leading to the homogeneity of bacterial communities that were resistant or prone to TCF biodegradation. Mantel test and redundancy analysis suggested a significant enrichment of dominant species Massilia belonging to Proteobacteria phyla, which in turn affecting TCF translocation and accumulation in maize seedling tissues. This study provided new insight into the biogeochemical fate of TCF in maize seedling and the responsible rhizobacterial community in soil TCF absorption and translocation.

Cytochrome P450 superfamily in spotted sea bass: Genome-wide identification and expression profiles under trichlorfon and environmental stresses

Cytochrome P450s (CYPs), as one of the most diverse enzyme superfamilies in nature, play critical functions in antioxidant reactions against endogenous and exogenous compounds. In this study, we performed genome-wide characterization of CYP superfamily members and analyzed their expression patterns under several abiotic stresses in spotted sea bass, which is known as an economically important fish species in the Chinese aquaculture industry. A total of 55 CYP genes were identified and divided into 17 families within 10 clans. The analysis of phylogeny, gene structure, and syntenic relationships provided evidence for the evolution of CYP genes and confirmed their annotation and orthology. The expression of CYP genes was examined in the liver during trichlorfon stress using quantitative real-time PCR. The results showed that 20 tested CYP genes displayed significant mRNA expression changes, indicating that they may play crucial roles in the metabolism of trichlorfon and can be potential biomarkers for trichlorfon pollution. Moreover, by screening transcriptomic databases, 10, 3 and 19 CYP genes exhibited differential expression patterns in response to hypoxia, alkalinity and heat stress, respectively. Taken together, this study provided insights into the regulation of CYP genes by toxicological and environmental stresses, laid basis for extensive functional studies of the CYP superfamily in spotted sea bass and other teleost species.

Effects of waterborne Pb/Cu mixture on Chinese toad, Bufo gargarizans tadpoles: morphological, histological, and intestinal microbiota assessment

Coexistence of heavy metals in aquatic environments exert complex effects on amphibians. Here, the adverse effects of Pb (0.14 μM) combined with Cu at concentrations of 0, 0.25, and 1.0 μM were investigated in Bufo gargarizans tadpoles. Tadpoles were chronically exposed from Gosner stage (Gs) 26 to Gs 38, and morphology of tadpoles as well as intestinal histology and bacterial community were assessed. Our results indicated that Pb+Cu1.0 exposure induced significant retardation of somatic mass, total length, intestine mass, and intestine length as well as intestinal histological alterations. Pb+Cu0.25 and Pb+Cu1.0 exposure were associated with the loss of gut bacterial diversity. Proteobacteria and Bacteroidetes were two dominant phyla in tadpoles independently of heavy metal exposure, but the abundance of Proteobacteria increased significantly in Pb+Cu1.0 group and Bacteroidetes decreased significantly in all treatment groups. Furthermore, functional prediction indicated that metabolic disorders were associated with Pb+Cu0.25 and Pb+Cu1.0 exposure. Overall, relative limited shifts in intestinal bacterial diversity, composition, and functionality caused by Pb+Cu0 exposure, while coexistence of Pb and Cu induced gut dysbiosis and might further cause disturbance of metabolic homeostasis. The findings of this study provide insights into the effects of Pb and Cu coexistence on the health of amphibians.

Effects of isolated and combined exposures of Boana curupi (Anura: Hylidae) tadpoles to environmental doses of trichlorfon and ultraviolet radiation

The biodiversity collapse strongly affects the amphibian group and many factors have been pointed out as catalytic agents. It is estimated that several events in the amphibian population decline worldwide may have been caused by the interaction of multiple drivers. Thus, this study aimed to evaluate the stressful effects of the exposure to environmental doses of trichlorfon (TCF) pesticide (0.5 μg/L; and an additional 100-fold concentration of 50 µg/L) and ultraviolet radiation (UV) (184.0 kJ/m² of UVA and 3.4 kJ/m² of UVB, which correspond to 5% of the daily dose) in tadpoles of the Boana curupi species (Anura: Hylidae). The isolated and combined exposures to TCF happened within 24 h of acute treatments under laboratory-controlled conditions. In the combined treatments, we adopted three different moments (M) of tadpole irradiation from the beginning of the exposures to TCF (0 h - M1; 12 h - M2; and 24 h - M3). Then, we evaluated tadpole survival, change in morphological characters, induction of apoptotic cells, lipid peroxidation (LPO), protein carbonyl content (PCC), glutathione S-transferase (GST), non-protein thiols (NPSH), and acetylcholinesterase (AChE), as well as the induction of genomic DNA (gDNA) damage. UVB treatment alone resulted in high mortality, along with a high level of apoptosis induction. Both UVA, UVB, and TCF increased LPO, PC, and AChE, while decreased GST activity. Regarding co-exposures, the most striking effect was observed in the interaction between UVB and TCF, which surprisingly decreased UVB-induced tadpole mortality, apoptosis, and gDNA damage. These results reinforce the B. curupi sensitivity to solar UVB radiation and indicate a complex response in face of UVB interaction with TCF, which may be related to activation of DNA repair pathways and/or inhibition of apoptosis, decreasing UVB-induced tadpole mortality.

Manipulation of cadmium and diethylhexyl phthalate on Rana chensinensis tadpoles affects the intestinal microbiota and fatty acid metabolism

Gastrointestinal tract and intestine microbiota can both have deep effects on the lipid metabolism and immune function of amphibians. Additionally, the composition and structure of the microbial community are influenced by environmental pollutions. It is noteworthy that environmental compounds such as Cd and DEHP are pervasive in the aquatic environment and do not exist in isolation, and single exposure experiments cannot well explain the effects of unpredictable interactions between co-existing compounds on amphibians. In this study, we calculated the parameters of morphological and histological indices of Rana chensinensis tadpoles after treated with Cd and/or DEHP. The 16S rRNA gene sequencing technology was used to assess the relative abundance of intestinal microbial community among tadpoles from each treatment groups. We also examined the mRNA expression levels of lipid digestion and absorption and SCFAs related-genes. Our results indicated that all morphological and histological indices were significantly declined in the Cd treatment group, while the mixed treatment group was similar to the control group. Compared with the control group, the relative abundances of Firmicutes, Proteobacteria and Verrucomicrobia exhibited distinctive differences in Cd and/or DEHP treatment groups. Further, RT-qPCR results revealed that the expression levels of lipid metabolism and SCFAs related-genes were also significantly altered among the treatment groups. Taken together, the present study highlighted a new evidence that the alterations in intestinal microbial community and mRNA expression levels of larval amphibians after exposure to Cd and/or DEHP may impair lipid storage and transport, as well as reduce anti-inflammatory capacity, which may ultimately lead to a decline in amphibian populations.

Nicosulfuron, a sulfonylurea herbicide, alters embryonic development and oxidative status of hatchlings at environmental concentrations in an amphibian species

The widespread use of agrochemicals for controlling pests and diseases of crops is recognized as a main threat to biodiversity. Sulfonylurea herbicides are being increasingly used and display low levels of degradation in water which suggest that they might affect non-target organisms. In a common garden experiment, eggs of a widespread amphibian (Bufo spinosus) were exposed to sublethal environmentally relevant concentrations of a widely used sulfonylurea herbicide, nicosulfuron, during the whole embryonic development. We assessed development-related traits (i.e., development duration, hatching success, hatchling size and occurrence of malformation) as well as antioxidant markers in response to contamination (i.e., SOD, GPx, catalase, thiols and relevant ratios thereof). We found that sublethal concentrations of nicosulfuron increased embryonic development duration, increased hatchling size and tended to increase malformations. Embryos exposed to nicosulfuron displayed decreased thiols and increased catalase activity suggesting alteration of oxidative status. We did not find any effect of nicosulfuron on SOD and GPx levels. Interestingly, higher catalase activity was linked to higher proportion of malformed individuals, suggesting that exposure to nicosulfuron induced teratogenic effects. Our results suggest that alteration of antioxidant levels might be one physiological mechanism through which nicosulfuron might cause detrimental effects on amphibian embryos. Sublethal effects of pesticides at environmentally relevant concentrations have been overlooked and require further investigations, especially in non-target taxa occurring in agricultural landscapes.

Effectiveness of UV/SO32- advanced reduction process for degradation and mineralization of trichlorfon pesticide in water: identification of intermediates and toxicity assessment

This study aimed to investigate the degradability, mineralization, proposed decomposition pathway, intermediate products, and toxicity of effluent from trichlorfon (TCF) degradation in water by UV/sulfite-advanced reduction process (UV/S-ARP). This study was experimentally performed in a photochemical reactor as a batch operation. The source of light was a UV lamp. Sulfite ion was used as the reducing agent. After the treatment, the residual concentration of TCF was measured by liquid chromatography equipped with tandem mass spectrometry (LC-MS/MS). UV/S-ARP had the highest performance at an initial pH of 7, a sulfite ion concentration of 120 mg/L, a contact time of 60 min, and a TCF concentration of 10 mg/L. Under such conditions, the degradation efficiency of TCF was 96.0%, and the amount of mineralization based on the removal of TOC and COD was 74.6% and 79.5%, respectively. The results of the degradation mechanism showed that eaq- and SO3•- have played the greatest role in dechlorination and transformation of TCF. Based on the identified intermediates, more complex compounds are transformed into compounds with simpler structures by UV/S-ARP. Evaluating the toxicity of TCF by-products via ECOSAR bioassay showed that as-generated intermediates do not have acute and chronic adverse effects on fish. The results of our study indicated that the advanced reduction process could be an effective process for the purification of TCF-contaminated water.

Transcriptome analysis reveals the molecular mechanism of long-term exposure of Eriocheir sinensis to low concentration of trichlorfon

Trichlorphon, a common organophosphorus pesticide (OPs), is widely used in aquaculture to prevent aquatic insects from infecting cultured objects as well as to control the excessive proliferation of plankton in water bodies. However, its repeated use time can contaminate water bodies and impart direct/indirect toxicity to beneficial aquatic species. However, the underlying mechanism regarding toxicity and cellular metabolism remains unclear. Understanding the mechanism would enable the standardized use and management of OPs and their use in the aquatic environment. Here, low concentration of trichlorphon (5 × 10^-5 g/L) was used to construct a hepatopancreatic transcriptional library 30 d, 60 d and 90 d after exposure using RNA-Seq. We detected 649, 148, and 2949 DEGs in the hepatopancreas of E. sinensis for the Tri01 vs. Ctr01, Tri02 vs. Ctr02 and Tri03 vs. Ctr03 library, respectively. The results of KEGG pathway enrichment analysis showed that DEGs were mainly enriched in signal transduction, carbohydrate metabolism, transport and catabolism, endocrine system, and digestive system. Also, under trichlorfon stress, DEGs of E. sinensis were enriched in thyroid hormone signaling pathways, protein digestion and absorption, cancer pathways, etc. The significant DEGs were mainly related to metabolism and the apoptosis and autophagy pathways. This study lays a foundation for further revealing the effects of long-term trichlorfon stress on E. sinensis as well as the potential physiological toxicity. The relevant transcriptome data could provide a reference for the molecular toxicological evaluation of trichlorfon in aquaculture.

Protective role of rutin dietary supplementation mediated by purinergic signaling in spleen of silver catfish Rhamdia quelen exposed to organophosphate pesticide trichlorfon

Evidence suggests the involvement of purinergic signaling, a mechanism mediated by extracellular nucleotides and nucleosides, with the impairment of immune and inflammatory responses in silver catfish (Rhamdia quelen) exposed to trichlorfon. Plant-derived substances have been considered potent anti-inflammatory agents due to effects on the purinergic system, such as the use of the flavonoid rutin. The aim of this study was to determine whether a diet containing rutin is able to prevent or reduce trichlorfon-induced impairment of immune responses through alteration of the purinergic pathway. Spleen adenosine triphosphate (ATP) levels were significantly higher in silver catfish exposed to 11 mg/L trichlorfon for 48 h compared to the control group, while adenosine (Ado) levels were significantly lower. Spleen ectonucleoside triphosphate diphosphohydrolase (NTPDase) activity was significantly lower in silver catfish exposed to trichlorfon compared to control group, while adenosine deaminase activity was significantly higher. Spleen metabolites of nitric oxide, interleukin-1, and IL-6 were significantly higher in silver catfish exposed to trichlorfon compared to control group. Diet with 3 mg rutin/kg diet was able to prevent all the alterations elicited by trichlorfon, except restoring spleen ATP levels. The purinergic exposure signaling is involved in impairment of immune and inflammatory responses in fish exposed to trichlorfon due to reduction in ATP hydrolyses and by an increase in Ado deamination, leading to release of pro-inflammatory mediators. Use of rutin-added diet exerted an essential role in protecting the silver catfish spleen from trichlorfon-induced impairment on immune and inflammatory responses, preventing all alterations on splenic purinergic signaling.

Chronic trichlorfon stress induces differential transcriptome expression and interferes with multifunctional pathways in the brain of Rana chensinensis

Trichlorfon is widely used to control pest insects and various parasitic infestations in agriculture, aquaculture and human medicine. However, the long-term widespread use and overuse of trichlorfon poses risks to public and environmental health. Thus, the aim of this study was to evaluate the interference of trichlorfon on gene transcription patterns in the brain of Rana chensinensis with 4 weeks treatment under control conditions and 0.1 mg/L exposure. In total, 102,013 unigenes were obtained from the brain tissue of R. chensinensis, and 874 differentially expressed genes (DEGs) were identified. Functional annotation indicated that out of 118,643 unigenes, 45,600 (44.7%) were annotated in the Nr, Nt, the Swiss-Prot, KEGG, COG, and GO databases. The differential expression patterns of 4 genes associated with neural activity were selected and validated by quantitative polymerase chain reaction (qPCR). The results revealed that except for the canonical cholinesterase-based mechanism, trichlorfon could act on other receptors and alter certain types of neuronal ion channels as the major target sites. All of these effects ultimately cause disorders of multifunctional pathways and other neurotransmitter pathways in the host. The results further our understanding of the mechanisms underlying nontarget effects of organophosphate insecticides (OPs) through multitargets studies.

Preparation of a Sensor Based on Biomass Porous Carbon/Covalent-Organic Frame Composites for Pesticide Residues Detection

In this work, a covalent-organic framework with high carbon and nitrogen content microstructures (named COF-LZU1), assisted by 3D nitrogen-containing kenaf stem composites (represented as COF-LZU1/3D-KSCs), was constructed. Moreover, it was utilized for immobilizing acetylcholinesterase (AChE) for identifying trichlorfon, a commonly applied organophosphorus (OP) pesticide. The development of COF-LZU1/3D-KSC was affirmed by SEM, PXRD, and EDXS. The findings confirmed that COF-LZU1 microstructures were uniformly developed on 3D-KSC holes using a one-step synthesis approach, which can substantially enhance the effective surface area. Also, the COF-LZU1/3D-KSC composite contains not only the nitrogen element in COF-LZU1 but also the nitrogen element in 3D-KSC, which will greatly improve the biocompatibility of the material. The AChE/COF-LZU1/3D-KSC integrated electrode was fabricated by directly fixing a large amount of AChE on the composite. At the same time, the integrated electrode had good detection efficiency for trichlorfon. Improved stabilization, a wide-linear-range (0.2–19 ng/mL), and a lower detection limit (0.067 ng/mL) have been displayed by the sensor. Therefore, this sensor can be used as an important platform for the on-site detection of OP residue.

Impact of chronic exposure to trichlorfon on intestinal barrier, oxidative stress, inflammatory response and intestinal microbiome in common carp (Cyprinus carpio L.)

Trichlorfon is an organic phosphorus pesticide used to control different parasitic infections in aquaculture. The repeated, excessive use of trichlorfon can result in environmental pollution, thus affecting human health. This study aimed to determine the effects of different concentrations of trichlorfon (0, 0.1, 0.5 and 1.0 mg/L) on the intestinal barrier, oxidative stress, inflammatory response and intestinal microbiome of common carp. Trichlorfon exposure significantly reduced the height of intestinal villus and decreased the expression levels of tight junction genes, such as claudin-2, occludin and ZO-1, in common carp. Moreover, the activities of antioxidant enzymes, such as CAT, SOD and GSH-Px, exhibited a decreasing trend with increasing trichlorfon concentrations, while the contents of MDA and ROS elevated in the intestinal tissues of common carp. The mRNA and protein levels of pro-inflammatory cytokines TNF-α and IL-1β were significantly upregulated by trichlorfon exposure. The level of anti-inflammatory cytokine TGF-β was remarkably higher in 1.0 mg/L trichlorfon treatment group compared to control group. In addition, the results demonstrated that trichlorfon exposure could affect the microbiota community composition and decreased the community diversity in the gut of common carp. Notably, the proportions of some probiotic bacteria, namely, Lactobacillus, Bifidobacterium and Akkermansia, were observed to be reduced after trichlorfon exposure. In summary, the findings of this study indicate that exposure to different concentrations of trichlorfon can damage intestinal barrier, induce intestinal oxidative damage, trigger inflammatory reaction and alter gut microbiota structure in common carp.

Toxicity, Biodegradation, and Metabolic Fate of Organophosphorus Pesticide Trichlorfon on the Freshwater Algae Chlamydomonas reinhardtii

This study investigated the toxicity of trichlorfon (TCF) to the freshwater algae Chlamydomonas reinhardtii, as well as its biodegradation and metabolic fate. The growth of C. reinhardtii decreased with increasing TCF concentration, and the maximum inhibition ratio was 51.3% at 200 mg L^-1 TCF compared to the control. Analyses of pigment content, chlorophyll fluorescence, and antioxidant enzymes indicated that C. reinhardtii can produce resistance and acclimatize to the presence of TCF. The variations in pH during cultivation suggested that photosynthetic microalgae have innate advantages over bacteria and fungi in remediating TCF. A 100% biodegradation rate was achieved at a maximum concentration of 100 mg L^-1 TCF. Ten metabolites were identified by GC-MS, and the degradation pathways of TCF by the algae were proposed. This research demonstrated that C. reinhardtii is highly tolerant to and can efficiently degrade TCF. Thus, C. reinhardtii can be used to remove traces of TCF from natural water environments and to treat TCF-contaminated wastewater.