Impact of endocrine-active compounds on adrenal androgen production in pigs during neonatal period.

This study investigated the impact of neonatal exposure to endocrine-active compounds (EACs): flutamide (antiandrogen), 4-tert-octylphenol (an estrogenic compound), and methoxychlor (an organochlorine insecticide exhibiting estrogenic, antiestrogenic and antiandrogenic activities) on androgen production within porcine adrenal glands. The expression of genes related to androgen synthesis and the level of androgen production were analyzed (i) in the adrenal glands of piglets exposed to EACs during the first 10 days of life (in vivo study), and (ii) in adrenal explants from sow-fed or formula-fed 10-day-old piglets incubated with EACs (ex vivo study). EACs affected the expression of genes linked to adrenal androgen biosynthesis. The prominent effect of methoxychlor on downregulation of StAR, CYP11A1 and HSD3B and upregulation of CYP17A1 and SULT2A1 were demonstrated. Furthermore, our study revealed divergent response to EACs between sow-fed and formula-fed piglets, suggesting that natural feeding may provide protection against adverse EACs effects, particularly those interfering with estrogens action.

Pyrite-assisted degradation of methoxychlor by laccase immobilized on Fe3S4/earthworm-like mesoporous SiO2.

Laccase immobilized and cross-linked on Fe3S4/earthworm-like mesoporous SiO2 (Fe3S4/EW-mSiO2) was used to degrade methoxychlor (MXC) in aqueous environments. The effects of various parameters on the degradation of MXC were determined using free and immobilized laccase. Immobilization improved the thermal stability and reuse of laccase significantly. Under the conditions of pH 4.5, temperature 40 °C, and reaction time 8 h, the degradation rate of MXC by immobilized laccase reached a maximum value of 40.99% and remained at 1/3 of the original after six cycles. The excellent degradation performance of Fe3S4/EW-mSiO2 was attributable to the pyrite (FeS2) impurity in Fe3S4, which could act as an electron donor in reductive dehalogenation. Sulfide groups and Fe2+ reduced the activation energy of the system resulting in pyrite-assisted degradation of MXC. The degradation mechanism of MXC in aqueous environments by laccase immobilized on Fe3S4/EW-mSiO2 was determined via mass spectroscopy of the degradation products. This study is a new attempt to use pyrite to support immobilized laccase degradation.

Pesticides in surface water of the Ondas river watershed, western Bahia, Brazil: Spatial-seasonal distribution and risk assessment.

This study investigated the occurrence and seasonal distribution of different classes of pesticides in surface waters of the Ondas River Watershed, as well as potential risks to the aquatic health and human water consumption in the western region of Bahia state, Brazil. Two gas chromatography-mass spectrometry analytical methods were applied to monitor 34 pesticides in water samples collected during both the dry and rainy seasons at 17 sites. Upon individual analysis, only γ-HCH, methoxychlor, demeton-S, methyl parathion, fenitrothion, chlorpyrifos, and azoxystrobin exhibited statistically significant differences between seasons. During rainy season, concentration medians of residues were higher for γ-HCH (74.7 ng L-1), methoxychlor (25.1 ng L-1), and azoxystrobin (47.2 ng L-1), potentially linked to historical contamination or illegal use. Conversely, pesticides like methyl parathion, fenitrothion, and chlorpyrifos, belonging to the organophosphate class, showed higher concentration medians in the dry period, measuring 75.1, 5.50, and 10.8 ng L-1, respectively, probably due to region crop activities. The risk quotient (RQ) assessment for aquatic life indicated that 59.0% of the samples in the dry season and 76.0% in the rainy season had RQ values greater than one, signifying a critical scenario for species conservation. Regarding human consumption, elevated risks were observed for heptachlor in both sampling periods and for azoxystrobin during the rainy season, surpassing RQ levels above 1, indicating danger in untreated water ingestion. Additionally, 24.0% and 53.0% of the samples in the dry and rainy seasons, respectively, contained at least one pesticide exceeding the EU resolution limit (100 ng L-1). Therefore, considering this information, implementing mitigation measures to avoid the river's contamination becomes imperative.

Hydrolytic degradation of methoxychlor by immobilized cellulase on LDHs@Fe3O4 nanocomposites.

In this study, we synthesized Fe3O4 using the co-precipitation method and then prepared magnetic carrier LDHs@Fe3O4 by immobilizing layered double hydroxide on Fe3O4 by in situ growth method. Cellulase was immobilized on this magnetic carrier by using glutaraldehyde as a coupling agent, which can be used for degrading Methoxychlor (MXC). The results demonstrated the maximum MXC removal efficiency of 73.4% at 45 °C and pH = 6.0 with excellent reusability. Through kinetic analysis, it was found that the degradation reaction conforms to the Langmuir-Hinshelwood model and is a first-order reaction. Finally, according to the EPR analysis, the active radicals in the system were found to be OH· and the degradation mechanism was proposed in combination with LC-MS. This study provides a feasible method for degrading organochlorine pesticides, which can be used for groundwater purification.

Preparation of Fe3O4@Fe(0) immobilized enzyme to enhance the efficient degradation of methoxychlor.

The presence of methoxychlor (MXC) in soil and wastewater is considered a nonnegligible environmental threat. Herein, Fe3O4@Fe(0) was obtained by NaBH4 reduction of Fe3O4 nanoparticles and served as a carrier for laccase to construct catalyst. The catalyst was evaluated for the degradation of MXC in treated wastewater and soil with 2, 2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) being used as cocatalyst. The removal rate of MXC in wastewater and soil was found to be 89% and 88% in optimum conditions, and the influences of initial MXC concentration, pH, and temperature on the degradation rate were evaluated. The metabolites including 2-methylpentane, 3-methylpentane, and n-pentane of MXC were identified, and possible degradation mechanisms were proposed. Overall, this work successfully demonstrates not only the ability to degrade MXC in different circumstances but also provides a new idea for environmental remediation in the future.

Levels of pesticides and trace metals in water, sediment, and fish of a large, agriculturally-dominated river.

Basin land-use interacts with hydrology to deliver chemical contaminants to riverine environments. These chemicals are eventually taken up by aquatic organisms, where they can cause harmful effects. However, knowledge gaps related to the connections between hydrological, chemical, and biological processes currently limit our ability to forecast potential future changes in contaminant concentrations accurately. In this study, concentrations of three pesticide classes (organochlorines, organophosphates, and herbicides) and a standard suite of trace metals were analyzed in the South Saskatchewan River, Canada in 2020 and 2021 in water, sediments, and fishes. Organochlorine pesticides have been banned in Canada since the 1970s, yet there were some detections for methoxychlor and lindane, predominantly in sediment and fish samples, which could be attributed to legacy contamination. Except for malathion and parathion, organophosphate pesticides were scarcely detected in both sampling years in all matrices, and neonicotinoids were below detection in all samples. Conversely, the herbicides 2,4-D and dicamba were detected consistently throughout all locations in water samples for both sampling years. Overall, concentrations were 3 times higher in 2020 when river discharge was ∼2 times higher, suggesting run-off from the surrounding catchment or disturbance of contaminated sediments. Analysis for trace metals revealed that Cu and Zn exceeded sediment quality guidelines in some locations. Mercury concentrations exceeded the guidelines for about 18% of the samples (water and sediment) analyzed. These findings fill gaps in monitoring datasets and highlight key links between hydrology and chemistry that can be further explored in computational models to predict future contaminant trends in freshwater systems.

Long-Term Changes in Ovarian Follicles of Gilts Exposed Neonatally to Methoxychlor: Effects on Oocyte-Derived Factors, Anti-Müllerian Hormone, Follicle-Stimulating Hormone, and Cognate Receptors.

In this paper, we investigated the effects of neonatal exposure to methoxychlor (MXC), a synthetic organochlorine used as an insecticide with estrogenic, antiestrogenic, and antiandrogenic activities on ovarian follicles of adult pigs. Piglets were injected with MXC (20 µg/kg body weight) or corn oil (controls) from postnatal Day 1 to Day 10 (n = 5 per group). Then, mRNA expression, protein abundance and immunolocalization of growth and differentiation factor 9 (GDF9), bone morphogenetic protein 15 (BMP15), anti-Müllerian hormone (AMH) and cognate receptors (ACVR1, BMPR1A, BMPR1B, TGFBR1, BMPR2, and AMHR2), as well as FSH receptor (FSHR) were examined in preantral and small antral ovarian follicles of sexually mature gilts. The plasma AMH and FSH levels were also assessed. In preantral follicles, neonatal exposure to MXC increased GDF9, BMPR1B, TGFBR1, and BMPR2 mRNAs, while the levels of AMH and BMP15 mRNAs decreased. In addition, MXC also decreased BMP15 and BMPR1B protein abundance. Regarding small antral follicles, neonatal exposure to MXC upregulated mRNAs for BMPR1B, BMPR2, and AMHR2 and downregulated mRNAs for AMH, BMPR1A, and FSHR. MXC decreased the protein abundance of AMH, and all examined receptors in small antral follicles. GDF9 and BMP15 were immunolocalized in oocytes and granulosa cells of preantral follicles of control and treated ovaries. All analyzed receptors were detected in the oocytes and granulosa cells of preantral follicles, and in the granulosa and theca cells of small antral follicles. The exception, however, was FSHR, which was detected only in the granulosa cells of small antral follicles. In addition, MXC decreased the plasma AMH and FSH concentrations. In conclusion, the present study may indicate long-term effects of neonatal MXC exposure on GDF9, BMP15, AMH, and FSH signaling in ovaries of adult pigs. However, the MXC effects varied at different stages of follicular development. It seems that neonatal MXC exposure may result in accelerated initial recruitment of ovarian follicles and impaired cyclic recruitment of antral follicles.

Mass spectrometric determination of N7-HPTE-dG and N7-HPTE-Gua in mammalian cells and mice exposed to methoxychlor, an emergent persistent organic pollutant.

Methoxychlor (MXC) is an organopesticide classified as a "Proposed Persistent Organic Pollutant" in the Stockholm Convention, and recent studies revealed that MXC could induce DNA strand breaks, whereas its underlying mechanisms were underinvestigated. Here, we first reported that hydroxymethoxychlor (HPTE), one of MXC's active metabolites, could be oxidized in vivo to form quinone intermediate, which attacked N7 position of 2'-deoxyguanosine to form N7-HPTE-deoxyguanosine (N7-HPTE-dG), followed by depurination to produce N7-HPTE-guanine (N7-HPTE-Gua) in MXC-treated mammalian cells and tissues from mice fed with MXC, employing an ultra-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS/MS) method. We observed a positive correlation between the doses of MXC exposure and the levels of N7-HPTE-Gua and N7-HPTE-dG in cytoplasm and genomic DNA, respectively. Furthermore, after removal of exogenous MXC, the amount of genomic N7-HPTE-dG was significantly decreased during 24 h, while the level of cytoplasmic N7-HPTE-Gua was elevated during first 12 h, indicating the accumulation of the N7-HPTE-Gua in cells. Additionally, for animal experiment, genomic N7-HPTE-dG was observed in livers and cortexes from female C57BL/6 mice fed with MXC, suggesting a potential mechanism of its hepatoxicity and neurotoxicity. Overall, our study provides new understanding about the formation of MXC-induced DNA adducts in mammalian cells and animal models.

Effects of neonatal methoxychlor exposure on the ovarian transcriptome in piglets.

Methoxychlor (MXC) is a man-made organochlorine insecticide capable of disrupting endocrine functions due to its mixed steroidal properties (estrogenic, anti-estrogenic and/or anti-androgenic). Retarded follicle development was recently reported in neonatal pigs treated with MXC. The goal of the current study was to better understand the mechanism of MXC action in the ovary of newborn piglets. By employing RNA-Seq we studied the expression of protein coding (mRNA) and long non-coding RNA (lncRNA) transcripts in the ovary of the MXC-treated piglets. Piglets were injected (sc) daily with MXC (100 mg/kg body weight) or corn oil (controls) between postnatal Days 1 and 10 (n = 3 piglets/group). The ovaries excised from 11-day-old piglets were processed for total RNA isolation and subsequent RNA sequencing. Four hundred sixty differentially expressed genes (DEGs) and 143 differentially expressed lncRNAs (DELs) were identified in the ovaries of MXC-treated piglets (P-adjusted < 0.05; abs(log2FC) > 1). Functional enrichment analysis showed that MXC altered the expression of genes associated with intracellular and membrane transport, intra-ovarian signaling as well as cell-cell junction and communication. Moreover, positive and negative correlations determined between the identified DEGs and DELs suggest that some lncRNAs may mediate the MXC action in the ovary. The results support the hypothesis that MXC-induced changes in the expression of genes involved in neonatal ovarian folliculogenesis increase the risk of fertility problems in adults.

Effects of neonatal exposure to methoxychlor on corpus luteum in gilts: A transcriptomic analysis.

This study investigated the effects of neonatal exposure to methoxychlor (MXC), a synthetic organochlorine used as an insecticide with estrogenic, antiestrogenic, and antiandrogenic activities, on luteal function in pigs. Piglets were injected subcutaneously with MXC (20 µg/kg body weight) or corn oil (control) between postnatal Days 1 and 10 (N = 5/group). Corpora lutea from sexually mature gilts were examined for luteal steroid and prostaglandin concentrations and processed for total RNA isolation and subsequent RNA sequencing. Intra-luteal concentrations of androstenedione and prostaglandin E2 were greater, while that of estrone was lower when compared to control. Fifty-three differentially expressed (DE) microRNAS (miRNAs) (p-adjusted <.05 and log2(fold change) ≥.5) and 359 DE genes (p-adjusted <.05 and log2(fold change) ≥1) were identified in luteal tissue in response to neonatal MXC treatment. MXC was found to affect the expression of genes related to lipogenesis, steroidogenesis, membrane transport, immune response, cell signaling and adhesion. These results suggest an earlier onset of structural luteolysis in pigs caused by MXC actions in neonates. Since negative correlation analysis showed the potential interactions of miRNAs with specific messenger RNAs, we propose that these miRNAs are potential mediators of the long-term MXC effect on the CL function in pigs.

N-acetyl-l-cysteine mediated regulation of DNA fragmentation, an apoptotic event, against methoxychlor toxicity in the granulosa cells of ovarian antral follicles.

Methoxychlor (MXC), an organo-chlorine insecticide, is a reproductive toxicant in females, causing apoptosis-mediated follicular atresia. To elucidate the potentials of Methoxychlor as a geno-toxicant, granulosa cells of healthy antral follicles, exposed to MXC and antioxidant, N-acetyl-l-cysteine, were studied by the terminal deoxynucleotidyltransferase-dUTP nick end-labelling and single-cell gel electrophoresis (comet) assays. MXC caused DNA fragmentation, as revealed by the increased incidence of dark brown condensed TUNEL positive cells in contrast with lightly brown TUNEL negative cells with maximum TUNEL positive cells were observed in 100 µg/mL MXC treated groups. Quantitatively, maximum geno-toxicity was exhibited at highest MXC treatment with percent tail DNA as 17.87 ± 0.85, 41.16 ± 3.94, and 47.73 ± 3.71 in comparison with control (0.65 ± 0.03, 2.91 ± 0.27, and 7.16 ± 1.39) after 24, 48 and 72 h exposure duration, respectively. MXC treated groups exhibited Type 1-Type 3 comets as compared to Type 0 comets in control groups. Supplementation of NAC led to significant (p < 0.05) decline in geno-toxicity in MXC treated groups with maximum amelioration observed at 5 and 10 mM. Consequently, increased DNA damage attributed to the granulosa cells apoptosis in response to Methoxychlor exposure was significantly combated by NAC supplementation, preventing the geno-toxicity induced cyto-toxicity in GCs.

Perinatal Exposure to Methoxychlor Affects Reproductive Function and Sexual Behavior in Mice.

Numerous chemicals derived from human activity are now disseminated in the environment where their exert estrogenic endocrine disrupting effects, and therefore represent major health concerns. The present study explored whether Methoxychlor (MXC), an insecticide with xenoestrogens activities, given during the perinatal period (from gestational day 11 to postnatal day 8) and at an environmentally dose [20 µg/kg (body weight)/day], would affect reproductive physiology and sexual behavior of the offspring in mice. While MXC exposure did not induce any differences in the weight gain of animals from birth to 4 months of age, a clear difference (although in opposite direction according to the sexes) was observed on the anogenital distance between intact and exposed animals. A similar effect was also observed on preputial separation and vaginal opening, which reflects, respectively, in males and females, puberty occurrence. The advanced puberty observed in females was associated with an enhanced expression of kisspeptin cells in the anteroventral periventricular region of the medial preoptic area. Exposure to MXC did not induce in adult females changes in the estrous cycle or in the weight of the female reproductive tract. By contrast, males showed reduced weight of the epididymis and seminiferous vesicles associated with reduced testosterone levels and seminiferous tubule diameter. We also showed that both males and females showed deficits in mate preference tests. As a whole, our results show that MXC impacts reproductive outcomes.

In vivo assessment of respiratory burst inhibition by xenobiotic exposure using larval zebrafish.

Currently, assessment of the potential immunotoxicity of a given agent involves a tiered approach for hazard identification and mechanistic studies, including observational studies, evaluation of immune function, and measurement of susceptibility to infectious and neoplastic diseases. These studies generally use costly low-throughput mammalian models. Zebrafish, however, offer an excellent alternative due to their rapid development, ease of maintenance, and homology to mammalian immune system function and development. Larval zebrafish also are a convenient model to study the innate immune system with no interference from the adaptive immune system. In this study, a respiratory burst assay (RBA) was utilized to measure reactive oxygen species (ROS) production after developmental xenobiotic exposure. Embryos were exposed to non-teratogenic doses of chemicals and at 96 h post-fertilization, the ability to produce ROS was measured. Using the RBA, 12 compounds with varying immune-suppressive properties were screened. Seven compounds neither suppressed nor enhanced the respiratory burst; five reproducibly suppressed global ROS production, but with varying potencies: benzo[a]pyrene, 17ß-estradiol, lead acetate, methoxychlor, and phenanthrene. These five compounds have all previously been reported as immunosuppressive in mammalian innate immunity assays. To evaluate whether the suppression of ROS by these compounds was a result of decreased immune cell numbers, flow cytometry with transgenic zebrafish larvae was used to count the numbers of neutrophils and macrophages after chemical exposure. With this assay, benzo[a]pyrene was found to be the only chemical that induced a change in the number of immune cells by increasing macrophage but not neutrophil numbers. Taken together, this work demonstrates the utility of zebrafish larvae as a vertebrate model for identifying compounds that impact innate immune function at non-teratogenic levels and validates measuring ROS production and phagocyte numbers as metrics for monitoring how xenobiotic exposure alters the innate immune system.

Exploring the Environmental Exposure to Methoxychlor, α-HCH and Endosulfan-sulfate Residues in Lake Naivasha (Kenya) Using a Multimedia Fate Modeling Approach.

Distribution of pesticide residues in the environment and their transport to surface water bodies is one of the most important environmental challenges. Fate of pesticides in the complex environments, especially in aquatic phases such as lakes and rivers, is governed by the main properties of the contaminants and the environmental properties. In this study, a multimedia mass modeling approach using the Quantitative Water Air Sediment Interaction (QWASI) model was applied to explore the fate of organochlorine pesticide residues of methoxychlor, α-HCH and endosulfan-sulfate in the lake Naivasha (Kenya). The required physicochemical data of the pesticides such as molar mass, vapor pressure, air-water partitioning coefficient (KAW), solubility, and the Henry's law constant were provided as the inputs of the model. The environment data also were collected using field measurements and taken from the literature. The sensitivity analysis of the model was applied using One At a Time (OAT) approach and calibrated using measured pesticide residues by passive sampling method. Finally, the calibrated model was used to estimate the fate and distribution of the pesticide residues in different media of the lake. The result of sensitivity analysis showed that the five most sensitive parameters were KOC, logKow, half-life of the pollutants in water, half-life of the pollutants in sediment, and KAW. The variations of outputs for the three studied pesticide residues against inputs were noticeably different. For example, the range of changes in the concentration of α-HCH residue was between 96% to 102%, while for methoxychlor and endosulfan-sulfate it was between 65% to 125%. The results of calibration demonstrated that the model was calibrated reasonably with the R2 of 0.65 and RMSE of 16.4. It was found that methoxychlor had a mass fraction of almost 70% in water column and almost 30% of mass fraction in the sediment. In contrast, endosulfan-sulfate had highest most fraction in the water column (>99%) and just a negligible percentage in the sediment compartment. α-HCH also had the same situation like endosulfan-sulfate (e.g., 99% and 1% in water and sediment, respectively). Finally, it was concluded that the application of QWASI in combination with passive sampling technique allowed an insight to the fate process of the studied OCPs and helped actual concentration predictions. Therefore, the results of this study can also be used to perform risk assessment and investigate the environmental exposure of pesticide residues.

Assessing the Impacts of Methoxychlor Exposure on the Viability, Reproduction, and Locomotor Behavior of the Seminole Ramshorn Snail (Planorbella duryi).

In the present study, the effects of short-term methoxychlor exposure on the viability, reproduction, and locomotor behavior of adult seminole ramshorn snails (Planorbella duryi) was assessed. To examine impacts on viability and behavior, individuals were exposed to a water control, vehicle control, or 12.5, 50, 100, 250, 500, or 1000 µg/L of methoxychlor for 48 h; and differences in mortality and locomotor behavior assessed using the freely available ToxTrac software. To determine impacts on reproduction, pairs of snails were exposed to a vehicle control and 12.5, 25, 50, 100, and 250 µg/L of methoxychlor for 9 d; and the number of clutches and eggs laid quantified every 24 h. Methoxychlor concentrations in treatments were determined using gas chromatography. Complete mortality was observed in the 500 µg/L and 1000 µg/L treatments after 48 h and in the 250 µg/L treatment after 9 d. Decreases in the number of egg clutches were observed in all treatments, and the number of eggs laid decreased starting in the 25 µg/L treatment. Decreases in average speed, mobile speed, and total distance traveled, as well as a significant increase in frozen events, were also observed. Our results suggest that methoxychlor exposure causes detrimental effects on several nonlethal endpoints in a nonmodel aquatic invertebrate species and that the analysis of locomotor behaviors serves as a reliable, sensitive endpoint for ecotoxicology testing. Environ Toxicol Chem 2019;39:220-228. © 2019 SETAC.

Development of a Generic Physiologically Based Kinetic Model to Predict In Vivo Uterotrophic Responses Induced by Estrogenic Chemicals in Rats Based on In Vitro Bioassays.

The present study assessed the potential of a generic physiologically based kinetic (PBK) model to convert in vitro data for estrogenicity to predict the in vivo uterotrophic response in rats for diethylstibestrol (DES), ethinylestradiol (EE2), genistein (GEN), coumestrol (COU), and methoxychlor (MXC). PBK models were developed using a generic approach and in vitro concentration-response data from the MCF-7 proliferation assay and the yeast estrogen screening assay were translated into in vivo dose-response data. Benchmark dose analysis was performed on the predicted data and available in vivo uterotrophic data to evaluate the model predictions. The results reveal that the developed generic PBK model adequate defines the in vivo kinetics of the estrogens. The predicted dose-response data of DES, EE2, GEN, COU, and MXC matched the reported in vivo uterus weight response in a qualitative way, whereas the quantitative comparison was somewhat hampered by the variability in both in vitro and in vivo data. From a safety perspective, the predictions based on the MCF-7 proliferation assay would best guarantee a safe point of departure for further risk assessment although it may be conservative. The current study indicates the feasibility of using a combination of in vitro toxicity data and a generic PBK model to predict the relative in vivo uterotrophic response for estrogenic chemicals.

Characterization of enzyme-immobilized catalytic support and its exploitation for the degradation of methoxychlor in simulated polluted soils.

Chiral mesoporous silica (SiO2) with helical structure was synthesized by using anionic surfactants as template. Pre-prepared graphene oxide (GO) was then loaded onto SiO2 to synthesize composite carrier chial-meso-SiO2@GO for the immobilization of laccase. The enzyme activity, thermostability, acid stability, and repeatability of the immobilized enzyme were significantly improved after immobilization. The chial-meso-SiO2@GO-immobilized laccase was then used for the degradation of MXC in aqueous phase. The degradation conditions, including temperature, time, pH, MXC concentration, and the dose of immobilized enzyme for cellulosic hydrolysis, were optimized. The optimum conditions for degradation of methoxychlor were selected as pH 4.5, MXC concentration 30 mg/L, immobilized enzyme dose 0.1 g, the maximum MXC removal of over 85% and the maximum degradation rate of 50.75% were achieved after degradation time of six h at temperature of 45 °C. In addition, the immobilized cellulase was added into the immobilized laccase system to form chial-meso-SiO2@GO-immobilized compound enzyme with the maximum MXC degradation rate of 59.58%, higher than that of 50.75% by immobilized laccase. An assessment was made for the effect of chial-meso-SiO2@GO-immobilized compound enzyme on the degradation of MXC in soil phase. For three contaminated soils with MXC concentration of 25 mg/kg, 50 mg/kg, and 100 mg/kg, the MXC removals were 93.0%, 85.8%, and 65.1%, respectively. According to the GC-MS analyses, it was inferred that chial-meso-SiO2@GO-immobilized compound enzyme had a different degradation route with that of chial-meso-SiO2@GO-immobilized laccase. The hydrolysis by immobilized cellulase might attack at a weak location of the MXC molecule with its free radical OH and ultimately removed three chlorine atoms from MXC molecule, leading to generating small molecular amount of degradation product.

Bioaccumulation and toxicity of methoxychlor on Chinese mitten crab (Eriocheir sinensis).

Chinese mitten crab, a featured macrobenthos, has been one of the most important economical aquatic species in China. This study assessed the accumulation of an organochlorine pesticide methoxychlor (MXC) in Chinese mitten crab during exposure to 1 mg/L of MXC. The results showed the residual concentration of MXC in the ovary and hepatopancreas reached 55.07 ±â€¯2.64 ng/g and 34.51 ±â€¯2.35 ng/g, respectively. After exposure, tubular vacuolization of epithelial tissues, condensed egg cells and obvious intervals between egg cell wall and stroma were observed in the hepatopancreas and ovary, respectively. Significant changes of three key metabolic enzymes in hepatopancreas were observed upon exposure to MXC. Compared to the control, acetylcholinesterase level was significantly higher at day 7 (0.15 ±â€¯0.01 vs. 0.06 ±â€¯0.00 U/mgprot); glutathione S-transferase level was elevated at both day 4 (12.01 ±â€¯0.48 vs. 3.20 ±â€¯0.44 U/mgprot) and day 7 (12.84 ±â€¯1.01 vs. 8.22 ±â€¯0.81 U/mgprot); superoxide dismutase was sharply increased at day 4 (21.20 ±â€¯0.24 vs. 3.66 ±â€¯0.60 U/mgprot) but decreased at day 7 (3.74 ±â€¯0.12 vs. 9.44 ±â€¯0.85 U/mgprot). Overall, dissolved MXC accumulated in lipid-rich tissues could cause damages on epithelial cells and egg cells and change metabolic activities of enzymes involved in antioxidative stress and detoxification processes.

Effect of prenatal exposure to combined immunosuppressive agrochemicals in a mouse model of allergic airway inflammation.

The aim of this study is to identify the combined effect of multiple chemicals to the development of allergy. In this study, the effect of prenatal exposure to an organochlorine agent methoxychlor (MXC) and/or an organophosphate agent parathion (PARA) on trimellitic anhydride-induced allergic airway inflammation was examined in mice. Eosinophil infiltration in the bronchoalveolar lavage fluid (BALF) was significantly enhanced by MXC + PARA exposure compared to that of the control, MXC, and PARA groups. In the hilar lymph node, only slight increases in B-cell infiltration, as well as IL-6 and IL-9 secretions were observed in MXC + PARA group, and no effect was observed in the individual treatment groups. Our findings imply that prenatal exposure to some combinations of multiple chemicals may exacerbate the allergic inflammatory responses including eosinophils and cytokine production.

Methoxychlor and its metabolite HPTE inhibit rat neurosteroidogenic 3α-hydroxysteroid dehydrogenase and retinol dehydrogenase 2.

Methoxychlor is primarily used as an insecticide and it is widely present in the environment. The objective of the present study was to investigate the direct effects of methoxychlor and its metabolite hydroxychlor (HPTE) on rat neurosteroidogenic 3α-hydroxysteroid dehydrogenase (AKR1C14) and retinol dehydrogenase 2 (RDH2) activities. Rat AKR1C14 and RDH2 were cloned and expressed in COS-1 cells, and the effects of methoxychlor and HPTE on these enzymes were measured. HPTE was more potent to inhibit AKR1C14 and RDH2 activities than methoxychlor, with IC50 values of 2.602 ± 0.057 µM and 20.473 ± 0.049 µM, respectively, while those of methoxychlor were over 100 µM. HPTE competitively inhibited AKR1C14 and RDH2 when steroid substrates were used, while it showed a mode of mixed inhibition on these enzymes when NADPH/NAD+ were used. We elucidated the binding mode of methoxychlor and HPTE to the crystal structure of AKR1C14 by molecular docking and found that HPTE had higher affinity with the enzyme than methoxychlor. In conclusion, HPTE is more potent than methoxychlor to inhibit both AKR1C14 and RDH2.