Yinghuan Wang

Bioaccumulation and enantioselectivity of type I and type II pyrethroid pesticides in earthworm

In this study, the bioavailability and enantioselectivity differences between bifenthrin (BF, typeⅠpyrethroid) and lambad-cyhalothrin (LCT, type Ⅱ pyrethroid) in earthworm (Eisenia fetida) were investigated. The bio-soil accumulation factors (BSAFs) of BF was about 4 times greater than that of LCT. LCT was degraded faster than BF in soil while eliminated lower in earthworm samples. Compound sorption plays an important role on bioavailability in earthworm, and the soil-adsorption coefficient (K(oc)) of BF and LCT were 22 442 and 42 578, respectively. Metabolic capacity of earthworm to LCT was further studied as no significant difference in the accumulation of LCT between the high and low dose experiment was found. 3-phenoxybenzoic acid (PBCOOH), a metabolite of LCT produced by earthworm was detected in soil. The concentration of PBCOOH at high dose exposure was about 4.7 times greater than that of in low dose level at the fifth day. The bioaccumulation of BF and LCT were both enantioselective in earthworm. The enantiomer factors of BF and LCT in earthworm were approximately 0.12 and 0.65, respectively. The more toxic enantiomers ((+)-BF and (-)-LCT) had a preferential degradation in earthworm and leaded to less toxicity on earthworm for racemate exposure. In combination with other studies, a liner relationship between Log BSAF(S) and Log K(ow) was observed, and the Log BSAF(S) decreased with the increase of Log K(ow).

Stereoselective degradation and toxic effects of benalaxyl on blood and liver of the Chinese lizard Eremias argus

Benalaxyl as a xylem-systemic fungicide is usually direct sprayed on the soil surface, which is potential harm to the animals lived in the soil. However, the stereoselectivity of benalaxyl in reptiles have rarely been studied. In this study, Chinese lizards (Eremias argus) were firstly used to evaluate the stereoselectivity in biodegradation and toxicity of racemate and individual enantiomers of benalaxyl. A method for determining residues of the two enantiomers of benalaxyl in lizard blood and liver by high-performance liquid chromatography coupled with triple quadrupole mass spectrometry (HPLC-MS/MS) was developed. The degradation followed pseudo first-order kinetics and the degradation of the (S)-(+)-benalaxyl was faster than its antipode in blood and liver (Half-time t1/2 of (R)-(-)-benalaxyl and (S)-(+)-benalaxyl were 5.08 h and 3.75 h in blood, 6.21 h and 4.45 h in liver, separately). Moreover, antioxidant defenses consisting of activities of superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST) and lipid peroxide malondialdehyde (MDA) were determined in 24h acute exposure. Enantioselectivity of acute toxicity depended on the concentration and form of benalaxyl. In addition, cellular degeneration, decrease of cell number, clustering phenomena of cell nuclei and preliminary liver fibrosis were observed in pathological detection at the termination of 21-d subchronic exposure (20 mg/kg(-bw) of racemate and individual enantiomers of benalaxyl). The enantiomer fractions (EFs) in racemate and individual enantiomer groups were approached both in blood and liver caused by the chiral conversion. The chiral conversion from (R)-(-)-benalaxyl to (S)-(+)-benalaxyl and (S)-(+)-benalaxyl to (R)-(-)-benalaxyl were the primary cause for no remarkable differences in toxicity between the enantiomers of benalaxyl.

A New Acyl-homoserine Lactone Molecule Generated by Nitrobacter winogradskyi.

It is crucial to reveal the regulatory mechanism of nitrification to understand nitrogen conversion in agricultural systems and wastewater treatment. In this study, the nwiI gene of Nitrobacter winogradskyi was confirmed to be a homoserine lactone synthase by heterologous expression in Escherichia coli that synthesized several acyl-homoserine lactone signals with 7 to 11 carbon acyl groups. A novel signal, 7, 8-trans-N-(decanoyl) homoserine lactone (C10:1-HSL), was identified in both N. winogradskyi and the recombined E. coli. Furthermore, this novel signal also triggered variances in the nitrification rate and the level of transcripts for the genes involved in the nitrification process. These results indicate that quorum sensing may have a potential role in regulating nitrogen metabolism.

Toxicity and bioaccumulation of ethofumesate enantiomers in earthworm Eisenia fetida

Earthworms represent an important food source for many vertebrates and as a result, predators may encounter toxic effects via the food chain from consumption of contaminated worms. Therefore, including an assessment of xenobiotic to worms in risk assessment procedures is advisable. Here we studied the acute toxicity, bioaccumulation and elimination of ethofumesate enantiomers in earthworm, Eisenia fetida, in a soil. A slight difference in toxicity to earthworm between two enantiomers was found, and the calculated LC50 values for (+)-, rac- and (-)-ethofumesate were 4.51, 5.93 and 7.98 μg/cm(2), respectively, indicating that the acute toxicity of ethofumesate enantiomers was enantioselective. Earthworm can uptake ethofumesate but the bioaccumulation curve did not reach the steady state. In the elimination experiment, the concentrations of ethofumesate in earthworm declined following a first-order decay model with a short half life of 1.8d. The bioaccumulation and elimination of ethofumesate in earthworm were both nonenantioselective. In combination with other studies, a linear relationship between Log BSAFs and Log Kow was observed, and the Log BSAFs increased with increasing Log Kow. But the elimination rate did not show any correlation with the Kow value.

Unraveling the different toxic effect of flufenoxuron on the thyroid endocrine system of the Mongolia racerunner (Eremias Argus) at different stages

Flufenoxuron is a widely used pesticide to inhibit the synthesis of chitin during insect development and its effect on the growth of lizards has been little addressed. The hypothalamus-pituitary-thyroid (HPT) axis plays an important role on the development of lizards. In this study, the lizards at different development stages (proliferation and resting stages) were exposed to flufenoxuron for 21 days. The plasma thyroid hormone levels, thyroid gland histopathology and expression profiles of thyroid hormone receptors (trα, trβ), deiodinases (dio1, dio2), and transthyretin (ttr) genes were measured to evaluated the toxic effect of flufenoxuron on the HPT axis at different stages. The flufenoxuron exposure showed more seriously effect on the triiodothyronine (T3) level at resting phase than that at proliferation stage. The follicle epithelium cell height in the thyroid was only significantly increased when the exposed male lizards were at proliferation stage. The alteration of HPT axis-related genes expression was gender and tissue dependent after flufenoxuron treatment. The lizards exposed to flufenoxuron showed that the trα, trβ, dio1, dio2, and ttr genes in the female liver were more sensitive at the proliferation stage than that at the resting stage. In the male brain, the expressions of trα, trβ, dio1, and dio2 gene were significant decreased at proliferation stage while significant increased at resting stage after flufenoxuron exposure. Therefore, the thyroid endocrine system of lizards could be affected by the flufenoxuron exposure and the different development stage should also be considered when study the toxic effect of contaminants on the lizards.

The body burden and thyroid disruption in lizards ( Eremias argus ) living in benzoylurea pesticides-contaminated soil

Dermal exposure is regarded as a potentially significant but understudied route for pesticides uptake in terrestrial reptiles. In this study, a native Chinese lizard was exposed to control, diflubenzuron or flufenoxuron contaminated soil (1.5 mg kg-1) for 35 days. Tissue distribution, liver lesions, thyroid hormone levels and transcription of most target genes were examined. The half-lives of diflubenzuron and flufenoxuron in the soil were 118.9 and 231.8 days, respectively. The accumulation of flufenoxuron in the liver, brain, kidney, heart, plasma and skin (1.4-35.4 mg kg-1) were higher than that of diflubenzuron (0-1.7 mg kg-1) at all time points. The skin permeability factor of flufenoxuron was more than 20-fold greater than that of diflubenzuron at the end of exposure. However, the liver was more vulnerable in the diflubenzuron exposure group. The alterations of triiodothyronine (T3) and thyroxine (T4) level after diflubenzuron or flufenoxuron exposure were accompanied with the changes in the transcription of target genes involved not only in hypothalamus-pituitary-thyroid (HPT) axis (sult, dio2, trα and udp) but also in metabolism system (cyp1a and ahr). These results indicated that flufenoxuron produced greater body burdens to lizards through dermal exposure, whereas both diflubenzuron and flufenoxuron have the potential to disturb metabolism and thyroid endocrine system.

The Metabolism Distribution and Effect of Thiamethoxam After Oral Exposure in Mongolian racerunner (Eremias argus)

Systematic evaluation of the metabolism, distribution, and effect of thiamethoxam in Mongolian racerunner ( Eremias argus) was carried out after oral exposure. HPLC equipped with Q Exactive focus was used for identification and concentration analysis of thiamethoxam and its metabolites. Percutaneous and urine excretions were the primary ways for the elimination of thiamethoxam and its metabolites, and the limiting factor was urine output. Demethylated thiamethoxam and clothianidin were the main metabolites of thiamethoxam in lizards. CYP3A4, CYP3A7, and CYP2C9 played a crucial role in the metabolism process. Aldehyde oxidase only dominated the nitro-reduction process of demethylated thiamethoxam and clothianidin. Glutathione S-transferase might be related to the clearance process of thiamethoxam and its metabolites. The findings indicated that thiamethoxam might pose potential carcinogenic and hepatic injury risk to lizards. The results enrich and supplement the knowledge of the environmental fate of thiamethoxam in reptiles.

The metabolism distribution and effect of imidacloprid in chinese lizards (Eremias argus) following oral exposure

Systematically evaluation of the metabolism, distribution and effect of imidacloprid in Chinese lizards (Eremias argus) were carried out following oral exposure. Imidacloprid-olefin-guanidine was prone to accumulate in the brain and caused potential neurotoxicity. Percutaneous and excretory excretions were the primary ways for the elimination of imidacloprid and its metabolites. Liver was the main site for hydroxy reduction and nitro-reduction metabolism of imidacloprid. The metabolism of imidacloprid was a complex process in which many metabolic enzymes participated. Aldehyde oxidase and CYP2C9 were the key enzymes in nitro-reduction process. CYP3A4 dominated the process of hydroxylation and desaturation. The increase in Glutathione S-transferase expression may be related to the removal of imidacloprid, but also related to the oxidative stress reaction that imidacloprid may cause in tissues, especially in the kidney. The findings enrich and supplement the knowledge of the environmental fate of imidacloprid in reptiles.

The metabolism distribution and effect of dinotefuran in Chinese lizards (Eremias argus)

The Chinese lizards (Eremias argus) were used to evaluate the metabolism, distribution and effect of dinotefuran following oral exposed. The HPLC equipped with Q Exactive focus was used for metabolite identification and concentration analysis. After single oral administration, the time-concentration curves of dinotefuran and its metabolites were tissue-dependent. The liver and kidney were the major metabolic organs. Percutaneous and urinary excretions were the main ways for lizards to eliminate dinotefuran, and the urine output was the limiting factor. Nitro-reduction was an important process of the metabolism of dinotefuran that was dominated by aldehyde oxidase, and P450 enzymes were involved. The CYP3A4 and CYP2C19 played a crucial role in the other metabolic pathways of dinotefuran. The mRNA expressions of GST family were severely inhibited in liver, which showed dinotefuran might pose a risk of damaging the oxidative stress system in liver. Prolonged residuals of dinotefuran and its demethylation metabolite might enhance the risk of dinotefuran to brain. The results enrich and supplement the knowledge of the environmental fate of dinotefuran in reptiles.

Tissue distribution and metabolism of triadimefon and triadimenol enantiomers in Chinese lizards (Eremias argus)

Triadimefon (TF, S-(+)-TF, R-(-)-TF) and its metabolite triadimenol (TN, TN-A1, A2 and TN-B1, B2) are two systemic fungicides and both of them are chiral pharmaceuticals which are widely used in agricultural industry. Many researches focused on the toxicity effects of triadimefon on mammals, while the ecotoxicological data of tiradimefon on reptiles is limited. In order to understand the toxicity mechanism of triadimefon in reptiles, the current study administrated S-(+)-TF or R-(-)-TF traidimefon (50mg/kgbw) to Chinese lizards (Eremias argus) respectively, the absorption, distribution of triadimefon and the formation of triadimenol were analysed at different sampling times. The metabolic pathways were demonstrated through relative gene expression using quantitative real-time PCR reaction. During the experiment time, triadimefon was quickly peaked to the maximum concentration within 12h in liver, brain, kidney, and plasma, eliminated slowly. The biotransformation in kidney was the lowest and fat possessed the worst degradation ability among others. The metabolite, triadimenol was detected in blood in 2h and reached to a plateau at about 12h in most organs (fat excepted), while the process of metabolism is stereoselective. The mainly metabolite in R-(-)-TF treated group was TN-B1, and TN-A2 in S-(+)-TF group which showed the selective metabolism to other species caused by environmental conditions, differences in the animal models and concentration of TF. The related gene expression of cyp1a1, cyp3a1 and hsd11β mRNA level in lizards showed different metabolic pathways in the liver and brain. Both P450s enzymes and 11β-hydroxysteroid dehydrogenase participated in metabolic reaction in liver, while no 11β-hydroxysteroid dehydrogenase pathway observed in brain. This diversity in liver and brain may cause different degradation rate and ecotoxicological effect in different organs.