1,2-Dichloroethane causes anxiety and cognitive dysfunction in mice by disturbing GABA metabolism and inhibiting the cAMP-PKA-CREB signaling pathway.

1,2-Dichloroethane (1,2-DCE) is a powerfully toxic neurotoxin, which is a common environmental pollutant. Studies have indicated that 1,2-DCE long-term exposure can result in adverse effects. Nevertheless, the precise mechanism remains unknown. In this study, behavioral results revealed that 1,2-DCE long-term exposure could cause anxiety and learning and memory ability impairment in mice. The contents of γ-aminobutyric acid (GABA) and glutamine (Gln) in mice's prefrontal cortex decreased, whereas that of glutamate (Glu) increased. With the increase in dose, the activities of glutamate decarboxylase (GAD) decreased and those of GABA transaminase (GABA-T) increased. The protein and mRNA expressions of GABA transporter-3 (GAT-3), vesicular GABA transporter (VGAT), GABA A receptor α2 (GABAARα2), GABAARγ2, K-Cl cotransporter isoform 2 (KCC2), GABA B receptor 1 (GABABR1), GABABR2, protein kinase A (PKA), cAMP-response element binding protein (CREB), p-CREB, brain-derived neurotrophic factor (BDNF), c-fos, c-Jun and the protein of glutamate dehydrogenase (GDH) and PKA-C were decreased, while the expression levels of GABA transporter-1 (GAT-1) and Na-K-2Cl cotransporter isoform 1 (NKCC1) were increased. However, there was no significant change in the protein content of succinic semialdehyde dehydrogenase (SSADH). The expressions of adenylate cyclase (AC) and cyclic adenosine monophosphate (cAMP) contents were also reduced. In conclusion, the results of this study show that exposure to 1,2-DCE could lead to anxiety and cognitive impairment in mice, which may be related to the disturbance of GABA metabolism and its receptors along with the cAMP-PKA-CREB pathway.

Factors ameliorate pro-inflammatory microglia polarization through inhibition of reactive astrocytes induced by 2-chloroethanol.

Our previous studies have demonstrated that the crosstalk between astrocytes and microglia may trigger and amplify the neuroinflammatory response and, in turn, cause brain edema in 1,2-dichloroethane (1,2-DCE)-intoxicated mice. Moreover, findings from our in vitro studies showed that astrocytes are more sensitive to 2-chloroethanol (2-CE), an intermediate metabolite of 1,2-DCE, than microglia, and 2-CE-induced reactive astrocytes (RAs) can promote microglia polarization through releasing the pro-inflammatory mediators. Therefore, it is essential to explore therapeutic agents that may ameliorate microglia polarization through inhibition of 2-CE-induced RAs, which remains unclear till now. Results of this study revealed that exposure to 2-CE could induce RAs with pro-inflammatory effects, and fluorocitrate (FC), GIBH-130 (GI) and diacerein (Dia) pretreatment could all abolish the pro-inflammatory effects of 2-CE-induced RAs. FC and GI pretreatment might suppress 2-CE-induced RAs through inhibition of p38 mitogen-activated protein kinase (p38 MAPK)/activator protein-1 (AP-1) and nuclear factor-kappaB (NF-κB) signaling pathways, but Dia pretreatment might only inhibit p38 MAPK/NF-κB signaling pathway. FC, GI, and Dia pretreatment could all suppress the pro-inflammatory microglia polarization through inhibition of 2-CE-induced RAs. Meanwhile, GI and Dia pretreatment could also restored the anti-inflammatory microglia polarization via inhibition of 2-CE-induced RAs. However, FC pretreatment could not affect the anti-inflammatory polarization of microglia through inhibition of 2-CE-induced RAs. Taken together, findings from the present study demonstrated that FC, GI, and Dia might be the potential candidates with different characteristic for therapeutic use in 1,2-DCE poisoning.

Comparison of speciated arsenic levels in the liver and brain of mice between arsenate and arsenite exposure at the early life.

The aim of this study was to compare the risk from exposure to arsenate (iAs(V) ) or arsenite (iAs(III) ) at the early life. Mother mice were exposed to equimolar dose of iAs(V) and iAs(III) via drinking water during gestation and lactation. Their offspring continually drank the same water after weaning. Levels of speciated arsenic in both liver and brain were analyzed by hydride generation of volatile arsines and atomic absorption spectrophotometry (HG-AAS). In the liver, inorganic arsenic (iAs) levels significantly increased from postnatal day (PND) 15, and those on PND 35 were significantly higher than on PND 15 and 21 in iAs(III) exposed mice, but iAs levels did not significantly differ until PND 35 in iAs(V) exposed mice; Furthermore, all speciated arsenic levels on PND 35 and dimethylarsinic acid (DMA) levels on PND 1 were significantly higher in iAs(III) exposed mice than those in iAs(V) exposed mice. In the brain, iAs levels increased significantly on PND 21, but those declined sharply on PND 35 in either iAs(III) or iAs(V) exposed mice, however the mean difference between the two exposure groups was not significant; whereas DMA levels in iAs(III) exposed mice were significantly higher than those in iAs(V) exposed mice on both PND 1 and 35. In conclusion, findings from this study suggested that iAs(III) was preferentially accumulated into liver, and expected to result in more efficient methylation capacity than iAs(V) ; either iAs(V) or iAs(III) might be accumulated in the brain readily, when immature blood brain barrier can not limit it into brain. Hence, exposure to either iAs(V) or iAs(III) at the early life may increase the risk of iAs exposure in the brain.

Synergistic effects of combined treatment of 1,2-dichloroethane and high-dose ethanol on liver damage in mice and the related mechanisms.

Our previous studies have shown that the metabolism of 1,2-dichloroethane (1,2-DCE) mediated by CYP2E1 could result in oxidative damage in the liver of mice. In the current study, we further investigated the effects of combined treatment with 1,2-DCE and high dose ethanol on liver and the mechanisms since both of them can be metabolized by CYP2E1 in the liver. There are several novel findings in the current study. First, combined treatment of mice with 1,2-DCE and high-dose ethanol could synergistically upregulate both protein and mRNA levels of CYP2E1, which might aggravate liver damage through CYP2E1-mediated oxidative stress. Second, the combined treatment could also synergistically trigger NLRP3 inflammasome activation and inflammatory responses in the liver. Third, the combined treatment synergistically upregulated the antioxidant defence systems in response to oxidative stress, however the compensatory mechanisms of antioxidant defence systems appeared to be insufficient to protect liver damage in the mice. Finally, the upregulated CYP2E1 expression was confirmed by using its specific inhibitor to play the crucial roles in liver damage in the mice during the combined treatment.

Effects of exogenous methionine on arsenic burden and NO metabolism in brain of mice exposed to arsenite through drinking water.

The aim of this study was to explore the effects of exogenous methionine (Met) on arsenic burden and metabolism of nitric oxide (NO) in the brain of mice exposed to arsenite via drinking water. Mice were exposed to sodium arsenite through drinking water contaminated with 50 mg/L arsenic for four consecutive weeks, and treated intraperitoneally with saline solution, 100 mg/kg body weight (b.w), 200 mg/kg b.w or 400 mg/kg b.w of Met, respectively at the fourth week. Levels of inorganic arsenic (iAs), monomethylarsenic acid (MMAs), and dimethylarsenic acid (DMAs) in the liver, blood and brain were determined by method of hydride generation coupled with atomic absorption spectrophotometry. Nitric oxide synthase (NOS) activities and NO levels in the brain were determined by colorimetric method. Compared with mice exposed to arsenite alone, administration of Met increased significantly the primary methylation ratio in the liver, which resulted in decrease of percent iAs and increase of percent DMAs in the liver, and decrease of iAs, MMAs and total arsenic levels (TAs) in the blood and DMAs and TAs in the brain. NOS activities and NO levels in the brain of mice exposed to arsenite alone were significantly lower than those in control, however administration of Met could increase significantly NO levels. Findings from this study suggested that exogenous Met could benefit the primary arsenic methylation in the liver, which might increase the production of methylated arsenicals and facilitate arsenic excretion. As a consequence, arsenic burden in both blood and brain was reduced, and toxic effects on NO metabolism in the brain were ameliorated.

Disturbance of glutamate metabolism and inhibition of CaM-CaMKII-CREB signaling pathway in the hippocampus of mice induced by 1,2-dichloroethane exposure.

1,2-Dichloroethane (1,2-DCE) is a highly toxic neurotoxicity, and the brain tissue is the main target organ. At present, long-term exposure to 1,2-DCE has been shown to cause cognitive dysfunction in some studies, but the mechanism is not clear. The results of this study showed that long-term 1,2-DCE exposure decreased learning and memory abilities in mice and impaired the structure and morphology of neurons in the hippocampal region. Moreover, except for the mRNA level of PAG, the enzymatic activities and protein levels of GS and PAG, as well as the mRNA level of GS were inhibited. With increasing dose of exposure, the protein and mRNA expression of GLAST and GLT-1 also decreased. Contrarily, there were protein and mRNA expression upregulation of GluN1, GluN2A and GluN2B in the hippocampus, as well as increased levels of extracellular Glu and intracellular Ca2+. In addition, 1,2-DCE exposure also downregulated the protein expression levels of CaM, CaMKII and CREB. Taken together, our results suggest that long-term 1,2-DCE exposure impairs the learning and memory capacity in mice, which may be attributed to the disruption of Glu metabolism and the inhibition of CaM- CaMKII-CREB signaling pathway in the hippocampus.

Effects of exogenous glutathione on arsenic burden and NO metabolism in brain of mice exposed to arsenite through drinking water.

Chronic exposure to inorganic arsenic (iAs) is associated with neurotoxicity. Studies to date have disclosed that methylation of ingested iAs is the main metabolic pathway, and it is a process relying on reduced glutathione (GSH). The aim of this study was to explore the effects of exogenous GSH on arsenic burden and metabolism of nitric oxide (NO) in the brain of mice exposed to arsenite via drinking water. Mice were exposed to sodium arsenite through drinking water contaminated with 50 mg/L arsenic for 4 weeks and treated intraperitoneally with saline solution, 200 mg/kg body weight (b.w), 400 mg/kg b.w, or 800 mg/kg b.w GSH, respectively, at the 4th week. Levels of iAs, monomethylarsenic acid, and dimethylarsenic acid (DMAs) in the liver, blood, and brain were determined by method of hydride generation coupled with atomic absorption spectrophotometry. Activities of nitric oxide synthase (NOS) and contents of NO in the brain were determined by colorimetric method. Compared with mice exposed to arsenite alone, administration of GSH increased dose-dependently the primary and secondary methylation ratio in the liver, which caused the decrease in percent iAs and increase in percent DMAs in the liver, as a consequence, resulted in significant decrease in iAs levels in the blood and total arsenic levels in both blood and brain. NOS activities and NO levels in the brain of mice in iAs group were significantly lower than those in control; however, administration of GSH could increase significantly activities of NOS and contents of NO. Findings from this study suggested that exogenous GSH could promote both primary and secondary arsenic methylation capacity in the liver, which might facilitate excretion of arsenicals, and consequently reduce arsenic burden in both blood and brain and furthermore ameliorate the effects of arsenicals on NO metabolism in the brain.

Roles of Crosstalk between Astrocytes and Microglia in Triggering Neuroinflammation and Brain Edema Formation in 1,2-Dichloroethane-Intoxicated Mice.

We have previously reported that the activation of astrocytes and microglia may lead to the overproduction of proinflammatory mediators, which could induce neuroinflammation and cause brain edema in 1,2-dichloroethane (1,2-DCE)-intoxicated mice. In this research, we further hypothesized that astrocyte-microglia crosstalk might trigger neuroinflammation and contribute to brain edema in 1,2-DCE-intoxicated mice. The present research revealed, for the first time, that subacute intoxication with 1,2-DCE might provoke the proinflammatory polarization of microglia, and pretreatment with minocycline, a specific inhibitor of microglial activation, may attenuate the enhanced protein levels of ionized calcium-binding adapter molecule1 (Iba-1), cluster of differentiation 11b (CD11b), glial fibrillary acidic protein (GFAP), soluble calcium-binding protein 100B (S100B), tumor necrosis factor α (TNF-α), interleukin 6 (IL-6), inducible nitric oxide synthase (iNOS), vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), matrix metalloproteinase-9 (MMP-9), Toll-like receptor 4 (TLR4), MyD88, and p-p65, and ameliorate the suppressed protein expression levels of occludin and claudin 5; we also observed changes in water content and made pathological observations on edema in the brains of 1,2-DCE-intoxicated mice. Moreover, pretreatment with fluorocitrate, an inhibitor of reactive astrocytes, could also reverse the alteration in protein expression levels of GFAP, S100B, Iba-1, CD11b, TNF-α, IL-6, iNOS, VCAM-1, ICAM-1, MMP-9, occludin, and claudin 5 in the brain of 1,2-DCE intoxicated mice. Furthermore, pretreatment with melatonin, a well-known anti-inflammatory drug, could also attenuate the above-mentioned changes in the brains of 1,2-DCE-intoxicated mice. Altogether, the findings from this research indicated that microglial activation might play an important role in triggering neuroinflammation, and hence may contribute to brain edema formation; additionally, the findings suggested that molecular crosstalk between reactive astrocytes and activated microglia may amplify the neuroinflammatory reaction, which could induce secondary brain injury in 1,2-DCE-intoxicated mice.

Reactive astrocytes induced by 2-chloroethanol modulate microglia polarization through IL-1ß, TNF-α, and iNOS upregulation.

The synthetic organic chemical, 1,2-dichloroethane (1,2-DCE), can cause brain edemas under subacute poisoning. Our previous studies indicated that neuroinflammation could be induced due to astrocytes and microglia activation during brain edemas in 1,2-DCE-intoxicated mice. However, the crosstalk between these two glial cells in 1,2-DCE-induced neuroinflammation remained unclear. In this study, primary cultured rat astrocytes and microglia, as well as an immortalized microglia cell line were employed to study the effects of 2-chloroethanol (2-CE, a 1,2-DCE intermediate metabolite in vivo) treated astrocytes on microglia polarization. Our current results revealed that 2-CE treated rat astrocytes were activated through p38 mitogen-activated protein kinase (p38 MAPK)/nuclear factor-κB (NF-κB), and activator protein-1 (AP-1) signaling pathways. Theses pathways were triggered by reactive oxygen species (ROS) produced during 2-CE metabolism. Also, astrocytes were more sensitive to 2-CE effects than microglia. Interleukin-1ß (IL-1ß), tumor necrosis factor-α (TNF-α), and inducible nitric oxide synthase (iNOS) expressions were upregulated in 2-CE-induced reactive astrocytes, enhancing IL-1ß, TNF-α, and nitric oxide (NO) excretions, which stimulated microglia polarization. Therefore, the neuroinflammation induced by 1,2-DCE in mice's brains is probably triggered by reactive astrocytes.

Frondoside A Inhibits an MYC-Driven Medulloblastoma Model Derived from Human-Induced Pluripotent Stem Cells.

Medulloblastoma (MB) is the most common malignant pediatric brain tumor. MYC-driven MBs, commonly found in the group 3 MB, are aggressive and metastatic with the worst prognosis. Modeling MYC-driven MB is the foundation of therapeutic development. Here, we applied a synthetic mRNA-driven strategy to generate neuronal precursors from human-induced pluripotent stem cells (iPSCs). These neuronal precursors were transformed by the MYC oncogene combined with p53 loss of function to establish an MYC-driven MB model recapitulating the histologic and transcriptomic hallmarks of group 3 MB. We further show that the marine compound Frondoside A (FA) effectively inhibits this MYC-driven MB model without affecting isogenic neuronal precursors with undetectable MYC expression. Consistent results from a panel of MB models support that MYC levels are positively correlated with FA's antitumor potency. Next, we show that FA suppresses MYC expression and its downstream gene targets in MB cells, suggesting a potential mechanism underlying FA's inhibitory effects on MYC-driven cancers. In orthotopic xenografts of MYC-driven MB, intratumoral FA administration potently induces cytotoxicity in tumor xenografts, significantly extends the survival of tumor-bearing animals, and enhances the recruitment of microglia/macrophages and cytotoxic T lymphocytes to tumors. Moreover, we show that MYC levels also predict FA potency in glioblastoma and non-small cell lung cancer cells. Taken together, this study provides an efficient human iPSC-based strategy for personalizable cancer modeling, widely applicable to mechanistic studies (e.g., genetic predisposition to cancer) and drug discovery. Our preclinical results justify the clinical translation of FA in treating MYC-driven MB and other human cancers.

Distribution of speciated arsenicals in mice exposed to arsenite at the early life.

The aim of this study was to explore distribution of speciated arsenicals in mice exposed to arsenite at early developmental stages. Levels of speciated arsenicals in both liver and brain of mice were analyzed by hydride generation of volatile arsines, and determined by atomic absorption spectrophotometry (HG-AAS). In the liver, levels of inorganic arsenic (iAs) increased on postnatal day (PND) 15, and monomethylarsonic acid (MMA) increased on PND 21, however, levels of dimethylarsinic acid (DMA) in newborn mice were significantly higher than those on PND 10 and 15. In the brain, levels of iAs on PND 21 were the highest; iAs levels on PND 15 were also significantly higher than those on PND 35. Our results suggested transplacental transfer of arsenicals from pregnant mice into their fetus was relatively efficient, lactational transfer from mother mice into their offspring was inefficient, and transfer of iAs from blood into brain at early developmental stages was efficient.

Effects of exogenous GSH and methionine on methylation of inorganic arsenic in mice exposed to arsenite through drinking water.

We hypothesized that chronic exposure to arsenic would deplete the reduced glutathione (GSH) and methionine in vivo, thereby impair the methylation capacity of inorganic arsenic (iAs) ingested. Our experiment was designed to explore the effects of exogenous GSH and methionine on arsenic methylation in mice exposed to arsenite via drinking water. Levels of iAs, monomethylarsenic acid (MMAs), and dimethylarsenic acid (DMAs) in the liver and blood were determined by the method of hydride generation coupled with atomic absorption spectrophotometry. Compared with mice exposed to arsenite alone, administration of GSH or methionine increased the secondary methylation index in the liver and primary methylation index in the blood, which resulted in the consequent increase of DMAs percent and decrease of iAs percent in the blood. Moreover, administration of GSH resulted in the increase of DMAs percent in the liver and total arsenic in the blood. Increase of total arsenic in the blood was mainly due to the increase of DMAs. Findings from the present study suggested that administration of GSH or methionine might potentiate the methylation capacity of arsenic in both liver and extrahepatic tissues, which may facilitate the excretion of arsenic and decrease arsenic related toxicities in the body.

Alterations of NMDA and AMPA receptors and their signaling apparatus in the hippocampus of mouse offspring induced by developmental arsenite exposure.

Loss of cognitive function due to arsenic exposure is a serious health concern in many parts of the world, including China. The present study aims to determine the molecular mechanism of arsenic-induced neurotoxicity and its consequent effect on downstream signaling pathways of mouse N-methyl-D-aspartate receptors (NMDARs) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs). Drinking water containing 0, 25, 50 or 100 mg/L arsenite was provided each day to mother mice throughout gestation period until postnatal day (PND) 35 to expose the newborn mice to arsenite during early developmental period. The effect of arsenite in the expressions of different components of NMDAR (NR1, NR2A, NR2B) and AMPAR (GluR1, GluR2, GluR3), including calcium/calmodulin-dependent protein kinase II (CaMKII) and phosphorylated-CaMKII (p-CaMKII), at PND 7, 14, 21 and 35 was estimated and analyzed from the hippocampus of mice. A significant inhibition in the protein and mRNA expressions of NR1, NR2A, NR2B and GluR1 was observed in mice exposed to 50 mg/L arsenite since PND 7. Down regulation of GluR2 and GluR3 both at mRNA and protein levels was observed in mice exposed to 50 mg/L arsenite till PND 14. Moreover, both CaMKII as well as p-CaMKII expressions were significantly limited since PND 7 in 50 mg/L arsenite exposed mice group. Findings form this study suggested that the previously reported impairment in learning and memorizing abilities in later stage due to early life arsenite exposure is associated with the alterations of NMDARs, AMPARs, CaMKII and p-CaMKII expressions.

Upregulation of CYP2E1 expression causes oxidative damage induced by 2-chloroethanol in primary cultured rat astrocytes.

Brain edema caused by subacute poisoning with 1,2-dichloroethane (1,2-DCE) has gained much attention during recent years, but its underlying mechanism is poorly understood. As an intermediate metabolite of 1,2-DCE in vivo, 2-chloroethanol (2-CE) can be transformed into chloroacetaldehyde and reactive oxygen species (ROS) through cytochrome P450 2E1 (CYP2E1) mediated metabolism. In previous studies, it was found that CYP2E1 expression is enhanced in the brain of mice treated with 1,2-DCE. This study was designed to verify the roles of CYP2E1 overexpression in 2-CE induced cytotoxicity in rat astrocytes, and the contribution of specific signaling molecules to the upregulation of CYP2E1 expression caused by 2-CE. The results of this study demonstrate that treatment with 2-CE can enhance CYP2E1 protein and mRNA levels, cause an increase in ROS and MDA levels, and higher percentages of apoptotic cells in rat astrocytes. Pretreatment with either diallyl sulfide or vitamin C, the inhibitor of CYP2E1 or scavenger of ROS, respectively, can suppress the levels of CYP2E1 expression, ROS and MDA, ameliorate cell apoptosis, and attenuate phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) in these cells. Additionally, pretreatment with the inhibitor of either ERK1/2 or transcriptional factor specificity protein 1 (SP1) can suppress the CYP2E1 expression, and alleviate the oxidative damage caused to these cells. In conclusion, our findings demonstrate that CYP2E1 overexpression plays a crucial role in 2-CE induced oxidative damage of rat astrocytes, and that CYP2E1 expression is upregulated partially through the activation of the ERK1/2 and SP1 signaling pathways by ROS generated during CYP2E1-mediated 2-CE metabolism. This study provides novel information that can be used in elucidating the mechanism by which 1,2-DCE induces brain edema.

Neuroinflammatory Reactions in the Brain of 1,2-DCE-Intoxicated Mice during Brain Edema.

We previously reported that expression of matrix metalloproteinase-9 (MMP-9) mRNA and protein was upregulated during 1,2-dichloroethane (1,2-DCE) induced brain edema in mice. We also found that the p38 mitogen-activated protein kinase (p38 MAPK) signaling pathway resulted in MMP-9 overexpression and nuclear factor-κB (NF-κB) activation in mice treated with 1,2-DCE. In this study, we further hypothesized that inflammatory reactions mediated by the p38 MAPK/ NF-κB signaling pathway might be involved in MMP-9 overexpression, blood-brain barrier (BBB) disruption and edema formation in the brain of 1,2-DCE-intoxicated mice. Our results revealed that subacute poisoning by 1,2-DCE upregulates protein levels of glial fibrillary acidic protein (GFAP), ionized calcium-binding adapter molecule 1 (Iba-1), interleukin-1ß (IL-1ß), vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), inducible nitric oxide synthase (iNOS) and p-p65 in mouse brains. Pretreatment with an inhibitor against p38 MAPK attenuates these changes. Moreover, pretreatment with an inhibitor against NF-κB attenuates alterations in brain water content, pathological indications notable in brain edema, as well as mRNA and protein expression on levels of MMP-9, VCAM-1, ICAM-1, iNOS, and IL-1ß, tight junction proteins (TJs), GFAP and Iba-1 in the brain of 1,2-DCE-intoxicated mice. Furthermore, pretreatment with an inhibitor against MMP-9 obstructs the decrease of TJs in the brain of 1,2-DCE-intoxicated mice. Lastly, pretreatment with an antagonist against the IL-1ß receptor also attenuates changes in protein levels of p-p38 MAPK, p-p65, p-IκB, VCAM -1, ICAM-1, IL-1ß, and Iba-1 in the brain of 1,2-DCE-intoxicated-mice. Taken together, findings from the current study indicate that the p38 MAPK/ NF-κB signaling pathway might be involved in the activation of glial cells, and the overproduction of proinflammatory factors, which might induce inflammatory reactions in the brain of 1,2-DCE-intoxicated mice that leads to brain edema.

Involvement of CYP2E1 in the Course of Brain Edema Induced by Subacute Poisoning With 1,2-Dichloroethane in Mice.

This study was designed to explore the role of cytochrome P4502E1 (CYP2E1) expression in the course of brain edema induced by subacute poisoning with 1,2-dichloroethane (1,2-DCE). Mice were randomly divided into five groups: the control group, the 1,2-DCE poisoned group, and the low-, medium- and high-dose diallyl sulfide (DAS) intervention groups. The present study found that CYP2E1 expression levels in the brains of the 1,2-DCE-poisoned group were upregulated transcriptionally; in contrast, the levels were suppressed by DAS pretreatment in the intervention groups. In addition, the expression levels of both Nrf2 and HO-1 were also upregulated transcriptionally in the brains of the 1,2-DCE-poisoned group, while they were suppressed dose-dependently in the intervention groups. Moreover, compared with the control group, MDA levels and water contents in the brains of the 1,2-DCE-poisoned group increased, whereas NPSH levels and tight junction (TJ) protein levels decreased significantly. Conversely, compared with the 1,2-DCE- poisoned group, MDA levels and water contents in the brains of the intervention groups decreased, and NPSH levels and TJ protein levels increased significantly. Furthermore, pathological changes of brain edema observed in the 1,2-DCE-poisoned group were markedly improved in the intervention groups. Collectively, our results suggested that CYP2E1 expression could be transcriptionally upregulated in 1,2-DCE-poisoned mice, which might enhance 1,2-DCE metabolism in vivo, and induce oxidative damage and TJ disruption in the brain, ultimately leading to brain edema.

Disruption of Intracellular ATP Generation and Tight Junction Protein Expression during the Course of Brain Edema Induced by Subacute Poisoning of 1,2-Dichloroethane.

The aim of this study was to explore changes in intracellular ATP generation and tight junction protein expression during the course of brain edema induced by subacute poisoning of 1,2-dichloroethane (1,2-DCE). Mice were exposed to 1.2 g/m3 1,2-DCE for 3.5 h per day for 1, 2, or 3 days, namely group A, B, and C. Na+-K+-ATPase and Ca2+-ATPase activity, ATP and lactic acid content, intracellular free Ca2+ concentration and ZO-1 and occludin expression in the brain were measured. Results of present study disclosed that Ca2+-ATPase activities in group B and C, and Na+/K+-ATPase activity in group C decreased, whereas intracellular free Ca2+ concentrations in group B and C increased significantly compared with control. Moreover, ATP content decreased, whereas lactic acid content increased significantly in group C compared with control. On the other hand, expressions of ZO-1 and occludin at both the protein and gene levels in group B and C decreased significantly compared with control. In conclusion, findings from this study suggest that calcium overload and depressed expression of tight junction associated proteins, such as ZO-1 and occludin might play an important role in the early phase of brain edema formation induced by subacute poisoning of 1,2-DCE.

Involvement of the p38 MAPK signaling pathway in overexpression of matrix metalloproteinase-9 during the course of brain edema in 1,2-dichloroethane-intoxicated mice.

Accumulated data have revealed that subacute poisoning of 1,2-dichloroethane (1,2-DCE), an industrial solvent used in some countries can cause encephalopathy, in which brain edema is the main pathological change. However, the underlying mechanisms are unclear. In the present study, we hypothesized that the p38 MAPK (p38) signaling pathway could be activated in 1,2-DCE-intoxicated mice, which in turn stimulates transcription factors, such as nuclear factor-κB (NF-κB) and activator protein-1 (AP-1), and then enhances the expression of proinflammatory factors, including matrix metalloproteinase-9 (MMP-9), finally leading to blood-brain barrier (BBB) disruption and brain edema formation. Our results revealed that brain water content and BBB permeability increased significantly in the intoxicated mice. Meanwhile, the levels of phosphorylated p38 (p-p38) and inhibitory κBα (p-IκB), as well as the expression levels of MMP-9, c-jun, c-fos, and p65, also increased markedly in the brains of intoxicated mice. Conversely, the protein levels of ZO-1, occludin and claudin-5 in these mice decreased markedly, but their JAM-1 protein levels increased dramatically. Our results revealed that p-p38 levels in the brains of intoxicated mice were suppressed by pretreatment with a p38 inhibitor. In response to suppressed p-p38 levels, the brain water contents and DNA binding activities of NF-κB and AP-1, as well as the expression levels of MMP-9, c-jun, c-fos, p65, p-IκB and JAM-1, decreased, whereas the protein levels of ZO-1, occludin and claudin-5 increased markedly. Taken together, our findings indicated that the p38 signaling pathway might be activated and involved in the course of brain edema in 1,2-DCE-intoxicated mice.

Association of NF-κB and AP-1 with MMP-9 Overexpression in 2-Chloroethanol Exposed Rat Astrocytes.

Subacute poisoning of 1,2-dichloroethane (1,2-DCE) has become a serious occupational problem in China, and brain edema is its main pathological consequence, but little is known about the underlying mechanisms. As the metabolite of 1,2-DCE, 2-chloroethanol (2-CE) is more reactive, and might play an important role in the toxic effects of 1,2-DCE. In our previous studies, we found that matrix metalloproteinases-9 (MMP-9) expression was enhanced in mouse brains upon treatment with 1,2-DCE, and in rat astrocytes exposed to 2-CE. In the present study, we analyzed the association of nuclear factor kappa B (NF-κB) and activator protein-1 (AP-1) with MMP-9 overexpression in astrocytes treated with 2-CE. MMP-9, p65, c-Jun, and c-Fos were significantly upregulated by 2-CE treatment, which also enhanced phosphorylation of c-Jun, c-Fos and inhibitor of κBα (IκBα), and nuclear translocation of p65. Furthermore, inhibition of IκBα phosphorylation and AP-1 activity with the specific inhibitors could attenuate MMP-9 overexpression in the cells. On the other hand, inhibition of p38 mitogen-activated protein kinase (p38 MAPK) signaling pathway suppressed the activation of both NF-κB and AP-1 in 2-CE-treated astrocytes. In conclusion, MMP-9 overexpression induced by 2-CE in astrocytes could be mediated at least in part through the p38 signaling pathway via activation of both NF-κB and AP-1. This study might provide novel clues for clarifying the mechanisms underlying 1,2-DCE associated cerebral edema.

Effects of developmental arsenite exposure on hippocampal synapses in mouse offspring.

Arsenic exposure through drinking water can impair the learning and memory ability of children in China and other countries. Synaptic plasticity plays a key role in the process of learning and memory. Alterations in the expression of presynaptic and postsynaptic proteins can be used to evaluate synaptic plasticity, and further to evaluate impairment in learning and memory ability. Thereby, the aim of this study was to explore the mechanisms underlying arsenic neurotoxicity by focusing on alterations in the hippocampal synapses of mouse offspring induced by developmental arsenite exposure. Mother mice and their offspring were exposed to 0, 25, 50 or 100 mg L-1 arsenite via drinking water from the first day of gestation until postnatal day (PND) 35. The spatial learning and memory ability of PND 35 mice was evaluated using a Morris water maze. The levels of speciated arsenicals in the brain of PND 7, 14, 21 and 35 mice were analyzed by hydride generation coupled with atomic absorption spectrophotometry. Synaptic structure and protein expression of postsynaptic density protein-95 (PSD-95) and synaptophysin (SYP) in the hippocampus of PND 7, 14, 21 and 35 mice were examined. The findings from this study disclosed that the spatial learning ability of mice could be impaired by exposure to 25 mg L-1 arsenite; however spatial memory ability could not be impaired until exposure to 100 mg L-1 arsenite. The thickness of the postsynaptic density (PSD) decreased, whereas the width of the synaptic cleft widened significantly in arsenite exposure groups. Moreover, protein expression of both PSD-95 and SYP decreased significantly in arsenite exposure groups. In conclusion, the results of this study demonstrated that developmental arsenite exposure could depress the expression of synaptic proteins, subsequently cause alteration in synaptic structures, and finally contribute to arsenite-induced deficits in spatial learning and memory ability in mouse offspring.