Combined toxic effects of fluxapyroxad and multi-walled carbon nanotubes in Xenopus laevis larvae.

Carbon nanomaterials rarely exist in isolation in the natural environment, and their combined effects cannot be ignored. Multi-walled carbon nanotubes (MWCNTs) have shown tremendous potential applications in diverse fields, including pollution remediation, biomedicine, energy, and smart agriculture. However, the combined toxicities of MWCNTs and pesticides on non-target organisms, particularly amphibians, are often overlooked. Fluxapyroxad (FLX), a significant succinate dehydrogenase inhibitor fungicide, has been extensively utilized for the protection of food and cash crops and control of fungi. This raises the possibility of coexistence of MWCNTs and FLX. The objective of this study was to explore the individual and combined toxic effects of FLX and MWCNTs on the early life stages of Xenopus laevis. Embryos were exposed to varying concentrations of FLX (0, 5, and 50 µg/L) either alone or in combination with MWCNTs (100 µg/L) for a duration of 17 days. The findings indicated that co-exposure to FLX and MWCNTs worsened the inhibition of growth, liver damage, and dysregulation of enzymatic activity in tadpoles. Liver transcriptomic analysis further revealed that the presence of MWCNTs exacerbated the disturbances in glucose and lipid metabolism caused by FLX. Additionally, the combined exposure groups exhibited amplified alterations in the composition and function of the gut microflora. Our study suggests that it is imperative to pay greater attention to the agricultural applications, management and ecological risks of MWCNTs in the future, considering MWCNTs may significantly enhance the toxicity of FLX.

The thalamic reticular nucleus orchestrates social memory.

Social memory has been developed in humans and other animals to recognize familiar conspecifics and is essential for their survival and reproduction. Here, we demonstrated that parvalbumin-positive neurons in the sensory thalamic reticular nucleus (sTRNPvalb) are necessary and sufficient for mice to memorize conspecifics. sTRNPvalb neurons receiving glutamatergic projections from the posterior parietal cortex (PPC) transmit individual information by inhibiting the parafascicular thalamic nucleus (PF). Mice in which the PPCCaMKII→sTRNPvalb→PF circuit was inhibited exhibited a disrupted ability to discriminate familiar conspecifics from novel ones. More strikingly, a subset of sTRNPvalb neurons with high electrophysiological excitability and complex dendritic arborizations is involved in the above corticothalamic pathway and stores social memory. Single-cell RNA sequencing revealed the biochemical basis of these subset cells as a robust activation of protein synthesis. These findings elucidate that sTRNPvalb neurons modulate social memory by coordinating a hitherto unknown corticothalamic circuit and inhibitory memory engram.

Uncovering hidden dangers: The combined toxicity of abamectin and lambda-cyhalothrin on honey bees.

Studying the toxic effects of pesticides on bees has consistently been a prominent area of interest for researchers. Nonetheless, existing research has predominantly concentrated on individual toxicity assessments, leaving a gap in our understanding of mixed toxicity. This study delves into the individual and combined toxic effects of abamectin (ABA) and lambda-cyhalothrin (LCY) on honey bees (Apis mellifera) in laboratory settings. We discovered that ABA (96 h-LC50 value of 0.079 mg/L) exhibited greater acute toxicity to honey bees compared to LCY (96 h-LC50 value of 9.177 mg/L). Moreover, the mixture of ABA and LCY presented an acute antagonistic effect on honey bees. Additionally, our results indicated that exposure to LCY, at medium concentration, led to a reduction in the abundance of gut core bacterium Snodgrassella. However, an increase in the abundance of Bifidobacterium was noted when exposed to a medium concentration of LCY and its mixture with ABA. Transcriptomic analysis revealed significant regulation of certain genes in the medium concentration of all three treatments compared to the control group, primarily enriching in metabolism and immune-related pathways. Following chronic exposure to field-relevant concentrations of ABA, LCY, and their mixture, there were significant alterations in the activities of immunity-related enzyme polyphenol oxidase (PPO) and detoxification enzymes glutathione S-transferase (GST) and carboxylesterase (CarE). Additionally, the expression of four genes (abaecin, cyp9e2, cyp302a1, and GstD1) associated with immune and detoxification metabolism was significantly altered. These findings suggest a potential health risk posed by the insecticides ABA and LCY to honey bees. Despite exhibiting acute antagonistic effect, mixed exposure still induced damage to bees at all levels. This study advances our knowledge of the potential adverse effects of individual or combined exposure to these two pesticides on non-target pollinators and offers crucial guidance for the use of insecticides in agricultural production.

Metabolic perturbations in zebrafish (Danio rerio) larvae exposed to sulfentrazone and imidacloprid.

The intensive and widespread application of pesticides in agroecosystems can lead to the simultaneous exposure of non-target aquatic organisms to insecticides and herbicides. However, the underlying mechanisms through which aquatic organisms undergo metabolic reprogramming to withstand the combined effects of the insecticide imidacloprid (IMI) and herbicide sulfentrazone (SUL) remain poorly elucidated. This study employs metabolomics to investigate the effects of individual and combined exposures to IMI and SUL on zebrafish (Danio rerio), aiming to simulate complex environmental conditions. Metabolomics analysis revealed extensive metabolic reprogramming in larvae induced by the selected agrochemicals. Both individual and combined exposures disrupted nucleotide metabolism, inhibited glycolysis, and led to the accumulation of acetylcholine through the shared modulation of differential metabolites. Notably, individual exposure exhibited a unique mode of action. Larvae exposed to IMI alone showed mitochondrial dysfunction, potentially stemming from interference with the electron transport chain, while SUL-induced disruptions were associated with glycerophospholipid accumulation, marking it as a critical target. Additionally, calculations of the metabolic effect level index indicated antagonistic interactions between SUL and IMI mixtures at an overall metabolic level. The results obtained through investigating the lethal and sub-lethal effects also revealed that the simultaneous application of SUL and IMI may have the potential to diminish acute and developmental toxicity in zebrafish. This study underscores the significance of metabolomics as a valuable and effective strategy for deciphering the toxicity and interactions of agrochemical mixtures.

Evaluation of the toxic effects of fluindapyr, a novel SDHI fungicide, to the earthworms Eisenia fetida.

The emergence of resistance to existing succinate dehydrogenase inhibitor fungicides (SDHIs) calls for the urgent innovation of novel formulations, but also results in an increase information gap on the ecological risks of novel SDHIs especially to non-target organisms. Herein, the environmental behavior and toxicological effects of a novel SDHI, fluindapyr (FIP), were evaluated using earthworm as model non-target organism. Results showed that FIP had a relatively shorter half-live (about 28 days) in artificial soil compared with traditional SDHIs. Besides, FIP exhibited a rapid uptake and bioaccumulation trend in earthworms. For the toxicological effects, FIP suppressed earthworm growth (≥ 5 mg/kg) and reproduction (≥ 1 mg/kg) whereas no lethal effects were observed up to the highest tested concentration of 25 mg/mg. FIP of high exposure concentrations also induced serious epidermis and intestines damage as well as oxidative stress to earthworms after 28-day exposure. In addition, expression of oxidative damage related genes (CAT, CRT, GST, HSP70, SOD) was further verified after FIP exposure. The earthworm Tier 1 RQ also indicated a potential risk for earthworm reproduction. Data presented here may be useful for the risk assessments of FIP in soil ecosystems and help to set appropriate precautions to ensure protection against novel SDHIs.

Adverse effects and potential mechanisms of fluxapyroxad in Xenopus laevis on carbohydrate and lipid metabolism.

Fungicides are one of significant contributing factors to the rapid decline of amphibian species worldwide. Fluxapyroxad (FLX), an effective and broad-spectrum succinate dehydrogenase inhibitor fungicide, has attracted major concerns due to its long-lasting in the environment. However, the potential toxicity of FLX in the development of amphibians remains mostly unknown. In this research, the potential toxic effects and mechanisms of FLX on Xenopus laevis were investigated. In the acute toxicity test, the 96 h median lethal concentration (LC50) of FLX in X. laevis tadpoles was 1.645 mg/L. Based on the acute toxicity result, tadpoles at the stage 51 were exposed to 0, 0.00822, 0.0822, and 0.822 mg/L FLX during 21 days. Results demonstrated that FLX exposure led to an apparent delay in the growth and development of tadpoles and associated with severe liver injury. Additionally, FLX induced glycogen depletion and lipid accumulation in the liver of X. laevis. The biochemical analysis of plasma and liver indicated that FLX exposure could perturb liver glucose and lipid homeostasis by altering enzyme activity related to glycolysis, gluconeogenesis, fatty acid synthesis, and oxidation. Consistent with the biochemical result, FLX exposure altered the liver transcriptome profile, and the enrichment analysis of differential expression genes highlighted the adverse effects of FLX exposure on steroid biosynthesis, PPAR signaling pathway, glycolysis/gluconeogenesis, and fatty acid metabolism in the tadpole liver. Overall, our study was the first to reveal that sub-lethal concentrations of FLX could induce liver damage and produce obvious interference effects on carbohydrate and lipid metabolism of Xenopus, providing new insight into the potential chronic hazards of FLX for amphibians.

Prostaglandin Metabolome Profiles in Zebrafish (Danio rerio) Exposed to Acetochlor and Butachlor.

Prostaglandins (PGs) are critically important signaling molecules that play key roles in normal and pathophysiological processes. Many endocrine-disrupting chemicals have been found to suppress PG synthesis; however, studies about the effects of pesticides on PGs are limited. The effects of two known endocrine disrupting herbicides, acetochlor (AC) and butachlor (BC), on PG metabolites in zebrafish (Danio rerio) females and males were studied using widely targeted metabolomics analysis based on ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). In total, 40 PG metabolites were detected in 24 zebrafish samples, including female and male samples, with and without exposure to AC or BC at the sub-lethal concentration of 100 µg/L for 96 h. Among them, 19 PGs significantly responded to AC or BC treatment, including 18 PGs that were upregulated. The enzyme-linked immunosorbent assay (ELISA) test in zebrafish showed BC could cause significant upregulation of an isoprostane metabolite, 5-iPF2a-VI, which is positively related to the elevated level of reactive oxygen species (ROS). The present study guides us to conduct a further study to determine whether PG metabolites, including isoprostanes, could be potential biomarkers for chloracetamide herbicides.

Dysregulation of prefrontal parvalbumin interneurons leads to adult aggression induced by social isolation stress during adolescence.

Social isolation during the juvenile stage results in structural and functional impairment of the brain and deviant adult aggression. However, the specific subregions and cell types that underpin this deviant behavior are still largely unknown. Here, we found that adolescent social isolation led to a shortened latency to attack onset and extended the average attack time, accompanied by anxiety-like behavior and deficits in social preference in adult mice. However, when exposed to social isolation during adulthood, the mice did not show these phenotypes. We also found that the structural plasticity of prefrontal pyramidal neurons, including the dendritic complexity and spine ratio, was impaired in mice exposed to adolescent social isolation. The parvalbumin (PV) interneurons in the prefrontal infralimbic cortex (IL) are highly vulnerable to juvenile social isolation and exhibit decreased cell numbers and reduced activation in adulthood. Moreover, chemogenetic inactivation of IL-PV interneurons can mimic juvenile social isolation-induced deviant aggression and social preference. Conversely, artificial activation of IL-PV interneurons significantly attenuated deviant aggression and rescued social preference during adulthood in mice exposed to adolescent social isolation. These findings implicate juvenile social isolation-induced damage to IL-PV interneurons in long-term aggressive behavior in adulthood.

Precise control of embolic stroke with magnetized red blood cells in mice.

Precise embolism control in immature brains can facilitate mechanistic studies of brain damage and repair after perinatal arterial ischemic stroke (PAIS), but it remains a technical challenge. Microhemorrhagic transformation is observed in one-third of infant patients who have suffered PAIS, but the underlying mechanism remains elusive. Building on an established approach that uses magnetic nanoparticles to induce PAIS, we develop a more advanced approach that utilizes magnetized erythrocytes to precisely manipulate de novo and in situ embolus formation and reperfusion in perinatal rodent brains. This approach grants spatiotemporal control of embolic stroke without any transarterial delivery of pre-formed emboli. Transmission electron microscopy revealed that erythrocytes rather than nanoparticles are the main material obstructing the vessels. Both approaches can induce microbleeds as an age-dependent complication; this complication can be prevented by microglia and macrophage depletion. Thus, this study provides an animal model mimicking perinatal embolic stroke and implies a potential therapeutic strategy for the treatment of perinatal stroke.

Effect of short-chain chlorinated paraffins on metabolic profiling of male SD rats.

The toxic effect of high-dose of short-chain chlorinated paraffins (SCCPs) has been extensively studied, however the possible health risks induced by SCCPs at low-dose remain largely unknown. In this study, a comprehensive toxicology analysis of SCCPs was conducted with the exposure levels from the environmental dose to the Lowest Observed Adverse Effect Level (LOAEL) of 100 mg/kg/day. General toxicology analysis revealed inconspicuous toxicity of the environmental dose of SCCPs, high dose SCCP exposure inhibited the growth rate and increased the liver weight of rat. Metabolomics analysis indicated that SCCP-induced toxicity was triggered at environmentally relevant doses. First, inhibition of energy metabolism was observed with the decrease in blood glucose and the dysfunction of TCA cycle, which may have contributed to lower body weight gain in rats exposed to a high dose of SCCPs. Second, the increase of free fatty acids indicated the acceleration of lipid metabolism to compensate for the energy deficiency caused by hypoglycemia. Lipid oxidative metabolism inevitably leads to oxidative stress and stimulates the up-regulation of antioxidant metabolites such as GSH and GSSH. The up-regulation of polyunsaturated fatty acids (PUFAs) and phospholipids composed of arachidonic acid indicates the occurrence of inflammation. Dysfunction of lipid metabolism can be an indicator of SCCP-induced liver injury.

Methane attenuates lung ischemia-reperfusion injury via regulating PI3K-AKT-NFκB signaling pathway.

Objective: This study aims to investigate the protective effects and possible mechanism of methane-rich saline (MS) on lung ischemia-reperfusion injury (LIRI) in rats.Methods: MS (2 ml/kg and 20 ml/kg) was injected intraperitoneally in rats after LIRI. Lung injury was assayed by Hematoxylin-eosin (HE) staining and wet-to-dry weight (W/D). The cells in the bronchoalveolar lavage fluid (BALF) and blood were counted. Oxidative stress was examined by the level of malondialdehyde (MDA) and superoxide dismutase (SOD). Inflammatory factors including tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß), and interleukin-10 (IL-10) were determined by ELISA. Lung tissue apoptosis was detected by TUNEL staining and western blotting of Bcl-2, Bax, and caspase-3. The expressions of IкBα, p38, PI3K, AKT, and NF-κB were analyzed with Western blotting.Results: MS effectively decreased the lung W/D ratio as well as the lung pathological damage and reduced the localized infiltration of inflammatory cells. Methane suppressed the expression of the PI3K-AKT-NFκB signaling pathway during the lung IR injury, which inhibited the activation of NF-kB and decreased the level of inflammatory cytokines, such as TNF-α, IL-1ß, and IL-10. Moreover, we found that MS treatment relieved reactive oxygen species (ROS) damage by downregulating MDA and upregulating SOD. MS treatment also regulated apoptosis-related proteins, such as Bcl-2, Bax, and caspase-3.Conclusions: MS could repair LIRI and reduce the release of oxidative stress, inflammatory cytokines, and cell apoptosis via the PI3K-AKT-NFκB signaling pathway, which may provide a novel and promising strategy for the treatment of LIRI.

Integration of metabolomics and transcriptomics reveals short-chain chlorinated paraffin-induced hepatotoxicity in male Sprague-Dawley rat.

BACKGROUND: Short-chain chlorinated paraffins (SCCPs) used in various industrial applications have been listed as new POPs. Previous studies based on high-dose exposures indicate their hepatotoxicity. However, their mechanisms of toxicity or adverse outcome pathways and health risks remain largely unknown. OBJECTIVES: This study aimed to evaluate metabolic consequences of chronic dietary exposure to SCCPs at low doses and reveal the molecular mechanisms underlying hepatotoxicity of SCCPs. METHODS: A combination of transcriptomics and metabolomics, together with general pathophysiological tests were performed to assess the hepatic response of male rats exposed to SCCPs. RESULTS: Our results highlight two major modes of action: Inhibition of energy metabolism and activation of the peroxisome proliferator-activated receptor α (PPARα). Exposure to SCCPs suppressed oxidative phosphorylation, glycolysis, gluconeogenesis and turnover of ATP-ADP-AMP and thus results in deficiencies of amino acids and nucleotides in liver of the rat. Exposure to SCCPs affected expression levels of 13 genes downstream of PPARα that encode proteins associated with metabolism of fatty acids. As a result, peroxisomal and mitochondrial fatty acid ß-oxidation, microsomal fatty acid ω-oxidation, and lipogenesis were accelerated. CONCLUSIONS: Results of this work strongly support the conclusion that low-dose exposure to SCCPs can result in adverse outcomes in the rat model. Significant SCCP-induced inhibition of energy metabolism occurs at environmentally relevant dosages, which suggests that SCCPs exhibit metabolic toxicity. Interactions of SCCPs with PPARα signaling pathway can explain the disruption of lipids and amino acids metabolism.

Comparing the disrupting effects of short-, medium- and long-chain chlorinated Paraffins on cell viability and metabolism.

With the phasing out of short-chain chlorinated paraffins (SCCPs), the production and emissions of medium- and long-chain chlorinated paraffins (MCCPs and LCCPs) are expected to increase. In this study, cell viability assay and pseudotargeted metabolomics approach were adopted to define and compare the toxic effects induced by SCCPs, MCCPs and LCCPs. The dose response curves indicated that three CP mixtures with comparable chlorine contents produced similar inhibitory effects on cell viability. At exposure concentration of 100 µg/L, three CP mixtures all induced significant increases in levels of reactive oxygen species (ROS) and malondialdehyde (MDA) and a significant reduction in level of adenosine triphosphate production (ATP), and produced similar impact intensities on overall metabolism. A stronger perturbation in phospholipid and fatty acid metabolism was observed in all CP exposure groups. In comparison with SCCPs and MCCPs, LCCPs produced a stronger suppressive effect on amino acid transport across cell membrane and induced an opposite effect on purine metabolism. Furthermore, the toxicity mechanism and possible health risks of the three types of CPs were discussed. MCCPs shared the most similar cytotoxicity and metabolic perturbation with SCCPs, suggesting that there should be concern about using MCCPs as alternatives to SCCPs.

Dummy molecularly imprinted solid phase extraction of climbazole from environmental water samples.

Dummy molecularly imprinted polymer (DMIP) for climbazole (CBZ) was synthesized for the first time employing miconazole (MNZ) as the dummy template together with methacrylic acid (MAA) monomer, ethylene glycol dimethacrylate (EGDMA) cross-linker and acetonitrile (ACN) porogen. The selectivity and capacity of the prepared MNZ-DMIP was estimated for CBZ by high-performance liquid chromatography (HPLC) and equilibrium binding experiments. Imprinting factor (IF) with a value of 7.0 was achieved, much higher than the CBZ templated MIP (IF = 3.5). Heterogeneous binding sites were found in the MNZ-DMIP, the corresponding saturation capacity and dissociation constant for the high and low affinity binding sites were 6.761 µmol g-1 and 0.3027 mmol L-1, 43.60 µmol g-1 and 4.055 mmol L-1, respectively. High efficient method based on dummy molecularly imprinted solid phase extraction (DMISPE) coupled with HPLC was established for the selective enrichment of CBZ in river and tap water using MNZ-DMIP as sorbent. DMISPE conditions including sample loading pH/volume, selective washing and elution solvents were carefully optimized. The developed method showed good recoveries (82.3-96.2%) and repeatability (RSDs 0.6-4.9%, n = 5) for samples spiked at three different concentration levels (0.2, 1.0 and 5.0 µg L-1). The detection limit was determined as 0.012 µg L-1. The results demonstrated good potential of this method for sample pretreatment of CBZ in environmental water samples.

Developmental toxicity of kresoxim-methyl during zebrafish (Danio rerio) larval development.

Kresoxim-methyl (KM) is a broad spectrum strobilurin fungicide that has been used widely on crops around the world. In the present study, we aimed to investigate the toxic effects of KM using various sublethal endpoints during zebrafish (Danio rerio) larval development. Results showed that the LC50 values of KM to zebrafish at multiple life stages (embryo, larvae, juvenile and adult) were 0.340, 0.224, 0.328 and 0.436 mg/L, respectively. The transcription patterns of 45 genes involved in hypothalamic-pituitary-thyroid/gonadal (HPT/HPG) axis, oxidative stress and apoptosis revealed KM could affect zebrafish larval development at multiple pathways. The activities of aromatase, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), caspase 3 (Cas3) and caspase 9 (Cas9), and the levels of estradiol (E2), vitellogenin (VTG), thyroid hormones (T3 and T4), reactive oxygen species (ROS) and ATP after embryos exposed to KM for 3 d, 6 d and 10 d were correlated well with the transcription of the corresponding molecules involved in these pathways. In addition to providing the first description of the toxic effects induced by KM during larval development, the results of present study also provided the potential mechanisms of KM on multi-level biomarker responses in larval zebrafish.

Short term exposure to oxycodone alters the survival, proliferation and differentiation of rat embryonic neural stem cell in vitro.

As one of several opioids, oxycodone has been widely used, particularly in postoperative analgesia in children and cesarean section. However, the effect of oxycodone on developing brain still remains to be seen. Since there is a link between anesthetics exposure and long-term behavioral or cognitive dysfunction in young children, in the current study, the direct effect of oxycodone on neural stem cells (NSCs) biological behaviors was investigated. After exposed to a high dose of oxycodone (10 µg/mL) for 48 h, NSCs survival and proliferation were significantly reduced, while NSCs apoptosis and differentiation were enhanced. These effects were significantly weaker than that when exposed to same dose of morphine. No significant difference was observed regarding to above biological behaviors when exposed to lower doses (0.1 µg/mL and 1.0 µg/mL) of oxycodone. The antagonist of opioid receptor, nalmefene, successfully reversed the influence of oxycodone. Taken together, our results indicated that short term exposure to oxycodone in low dose might be allowed for developing brain.

HIF-1α/Beclin1-Mediated Autophagy Is Involved in Neuroprotection Induced by Hypoxic Preconditioning.

Hypoxic preconditioning (HPC) exerts a protective effect against hypoxic/ischemic brain injury, and one mechanism explaining this effect may involve the upregulation of hypoxia-inducible factor-1 (HIF-1). Autophagy, an endogenous protective mechanism against hypoxic/ischemic injury, is correlated with the activation of the HIF-1α/Beclin1 signaling pathway. Based on previous studies, we hypothesize that the protective role of HPC may involve autophagy occurring via activation of the HIF-1α/Beclin1 signaling pathway. To test this hypothesis, we evaluated the effects of HPC on oxygen-glucose deprivation/reperfusion (OGD/R)-induced apoptosis and autophagy in SH-SY5Y cells. HPC significantly attenuated OGD/R-induced apoptosis, and this effect was suppressed by the autophagy inhibitor 3-methyladenine and mimicked by the autophagy agonist rapamycin. In control SH-SY5Y cells, HPC upregulated the expression of HIF-1α and downstream molecules such as BNIP3 and Beclin1. Additionally, HPC increased the LC3-II/LC3-I ratio and decreased p62 levels. The increase in the LC3-II/LC3-I ratio was inhibited by the HIF-1α inhibitor YC-1 or by Beclin1-short hairpin RNA (shRNA). In OGD/R-treated SH-SY5Y cells, HPC also upregulated the expression levels of HIF-1α, BNIP3, and Beclin1, as well as the LC3-II/LC3-I ratio. Furthermore, YC-1 or Beclin1-shRNA attenuated the HPC-mediated cell viability in OGD/R-treated cells. Taken together, our results demonstrate that HPC protects SH-SY5Y cells against OGD/R via HIF-1α/Beclin1-regulated autophagy.

Short-chain chlorinated paraffins (SCCPs) induced thyroid disruption by enhancement of hepatic thyroid hormone influx and degradation in male Sprague Dawley rats.

Short-chain chlorinated paraffins (SCCPs) are known to disturb thyroid hormone (TH) homeostasis in rodents. However, the mechanism remains to be fully characterized. In this study, male Sprague Dawley rats received SCCPs (0, 1, 10, or 100mg/kg/day) via gavage once a day for consecutive 28days. Plasma and hepatic TH concentrations, thyrocyte structure, as well as thyroid and hepatic mRNA and protein levels of genes associated with TH homeostasis were examined. Moreover, we performed molecular docking to predict interactions between constitutive androstane receptor (CAR), a key regulator in xenobiotic-induced TH metabolism, with different SCCP molecules. Exposure to SCCPs significantly decreased the circulating free thyroxine (T4) and triiodothyronine (T3) levels, but increased thyroid-stimulating hormone (TSH) levels by a feedback mechanism. Decreased hepatic T4 and increased hepatic T3 levels were also seen after 100mg/kg/day SCCPs exposure. SCCPs didn't show any significant effects on the expression of thyroid TH synthesis genes or thyrocyte structure. However, stimulation effects were observed for mRNA and protein levels of hepatic uridine diphosphoglucuronosyl transferase (UGT) 1A1 and organic anion transporter 2, suggesting an accelerated TH metabolism in rat liver. The increased cytochrome P450 2B1 but not 1A1 mRNA and protein levels indicated that the CAR signaling was activated by SCCPs exposure. According to docking analysis, SCCPs form hydrophobic interactions with CAR and the binding affinity shows dependency on chlorine content. Overall, our data showed that CAR implicated enhancement of hepatic TH influx and degradation could be the main cause for SCCPs induced TH deficiency in male rats.

Developmental and metabolic responses of zebrafish (Danio rerio) embryos and larvae to short-chain chlorinated paraffins (SCCPs) exposure.

Short-chain chlorinated paraffins (SCCPs) are highly toxic to aquatic organisms, but their toxicity is yet not well characterized. In this study, the developmental toxicity of SCCPs to zebrafish embryos/larvae was evaluated, and a metabolomics approach was adopted to explore the impact of SCCPs exposure on the metabolism in zebrafish embryos. Exposure to SCCPs at concentrations of 1-200µg/L did not produce an observable effect on the hatching rate and morphological deformities of zebrafish embryos/larvae. However, the survival rate of zebrafish larvae in SCCPs exposure groups decreased in a concentration-dependent manner. The 13-day 50% lethal concentration (LC50) value of SCCPs was calculated to be 34.4µg/L. Exposure to SCCPs induced a significant change of overall metabolism, even at environmentally relevant concentrations (1-5µg/L). The most relevant pathways affected by SCCPs exposure were glycerophospholipid metabolism, fatty acid metabolism and purine metabolism. Exposure to SCCPs at concentrations of 1-5µg/L had begun to accelerate the ß-oxidation of unsaturated fatty acids and very long chain fatty acids, and affect the transformation of guanine to xanthine in the pathway of purine metabolism. Furthermore, when the exposure concentrations of SCCPs were increased to 50-200µg/L, the levels of phospholipids and amino acids were significantly raised; whereas the levels of fatty acids, carnitines and inosine were significantly decreased. In view of the significant effect on metabolism, the sub-chronic and chronic toxicity of SCCPs to fish should be concerned.

A metabolomics strategy to assess the combined toxicity of polycyclic aromatic hydrocarbons (PAHs) and short-chain chlorinated paraffins (SCCPs).

The combined toxicity of mixed chemicals is usually evaluated according to several specific endpoints, and other potentially toxic effects are disregarded. In this study, we provided a metabolomics strategy to achieve a comprehensive understanding of toxicological interactions between mixed chemicals on metabolism. The metabolic changes were quantified by a pseudotargeted analysis, and the types of combined effects were quantitatively discriminated according to the calculation of metabolic effect level index (MELI). The metabolomics strategy was used to assess the combined effects of polycyclic aromatic hydrocarbons (PAHs) and short-chain chlorinated paraffins (SCCPs) on the metabolism of human hepatoma HepG2 cells. Our data suggested that exposure to a combination of PAHs and SCCPs at human internal exposure levels could result in an additive effect on the overall metabolism, whereas diverse joint effects were observed on various metabolic pathways. The combined exposure could induce a synergistic up-regulation of phospholipid metabolism, an additive up-regulation of fatty acid metabolism, an additive down-regulation of tricarboxylic acid cycle and glycolysis, and an antagonistic effect on purine metabolism. SCCPs in the mixture acted as the primary driver for the acceleration of phospholipid and fatty acid metabolism. Lipid metabolism disorder caused by exposure to a combination of PAHs and SCCPs should be an important concern for human health.