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Epidemiological studies have revealed that environmentally relevant low levels of paraquat (PQ) exposure is listed on the etiology of neurological disorders such as Parkinson's disease (PD). The behavioral effects of PQ are of current interest, especially when exposure occurs in the period of early stage of life. To characterize whether and how age affects neurobehavioral performances of mice after PQ exposure, 21 days postnatal (PN21) and adult male C57BL/6 mice were daily administrated by oral gavage with 0 mg/kg (saline, control), 5 mg/kg or 10 mg/kg of PQ for 28 consecutive days. Survival rate and body weight were analyzed. Subsequently, mice were subjected to Morris water maze tests (MWM). The results showed that mice exposed to PQ had significantly longer latencies than those in the control group, with a dose-dependent manner. Furthermore, PN21 mice tended to have longer latencies than adult mice in the same dose group. Our data suggested that PQ exposure induced significant learning and memory impairment and more severely in PN21 mice when compared with adult mice.

Paraquat (PQ) exposure influences central nervous system and results in serious neurotoxicity in vitro and in vivo. However, the role of PQ exposure in the development of CNS remains unclear. In present study, we investigated microRNAs (miRNAs) expression profiling and cell differential status following PQ treatment in human neural progenitor cells (hNPCs) as well as involved mechanism. Microarray profiling of miRNAs expression of PQ treated cell line and their corresponding control was determined. Differentially expression miRNAs were confirmed by quantitative real time PCR. Neural cell differentiation was performed with immunocytochemical analysis. Predicated target of miRNA was identified with luciferase reports and quantitatively analyzed using western blotting. Our results found PQ dramatically suppressed neural cell differentiation ability. 43 differentially expressed miRNAs were identified in PQ treated cells. The expression levels were over expressed in 25 miRNAs, whereas 18 miRNAs were suppressed. More importantly, we observed that miR-200a expression level to be lower in PQ treated cells. Luciferase assay and protein expression results confirmed the direct binding effect between CTNNB1 and miR-200a following PQ exposure. Collectively, our data suggested that down regulation of miR-200a in the PQ treated neural stem cell significantly participated in the differentiation processes and subsequently resulting in decreased cell viability, increased epithelial-mesenchymal transition process and the inhibited differential through CTNNB1 pathway., (Copyright © 2016. Published by Elsevier B.V.)

Compelling evidences have shown that diverse environmental insults arising during early life can either directly lead to a reduction in the number of dopaminergic neurons or cause an increased susceptibility to neurons degeneration with subsequent environmental insults or with aging alone. Oxidative stress is considered the main effect of neurotoxins exposure. In this study, we investigated the oxidative stress effect of Paraquat (PQ) on immortalized human embryonic neural progenitor cells by treating them with various concentrations of PQ. We show that PQ can decrease the activity of SOD and CAT but increase MDA and LDH level. Furthermore, the activities of Cyc and caspase-9 were found increased significantly at 10 μM of PQ treatment. The cytoplasmic Nrf2 protein expressions were upregulated at 10 μM but fell back at 100 μM. The nuclear Nrf2 protein expressions were upregulated as well as the downstream mRNA expressions of HO-1 and NQO1 in a dose-dependent manner. In addition, the proteins expression of PKC and CKII was also increased significantly even at 1 μM. The results suggested that Nrf2/ARE pathway is involved in mild to moderate PQ-induced oxidative stress which is evident from dampened Nrf2 activity and low expression of antioxidant genes in PQ induced oxidative damage.

Aberration during the development of the central nervous system (CNS) due to environmental factors underlies a variety of adverse developmental outcomes. Paraquat (PQ) is a widely studied neurotoxicant that perturbs the normal structure/function of adult CNS. Yet, the impacts of PQ exposure on the developing CNS remain unclear. miRNAs represent a class of small non-coding RNA molecules involved in the regulation of neural development. Thus in the present study, we analyzed the impacts of PQ on the miRNome of human neural progenitor cells (hNPCs) during proliferation by using the Exiqon miRCURY™ LNA Array. A total of 66 miRNAs were identified as differentially expressed in proliferating hNPCs upon PQ treatment. miRTarBase prediction identified 1465 mRNAs, including several genes (e.g., nestin, sox1, ngn1) previously proved to be associated with the neural proliferation and differentiation, as target genes of PQ-induced differentially expressed miRNAs. The database for annotation, visualization and integrated discovery (DAVID) bioinformatics analysis showed that target genes were enriched in regulation of cell proliferation and differentiation, cell cycle and apoptosis as well as tumor protein 53 (p53), Wnt, Notch and mitogen-activated protein kinases (MAPK) signaling pathways (p < 0.001). These findings were confirmed by real-time RT-PCR. Based on our results we conclude that PQ-induced impacts on the miRNA profiling of hNPCs undergoing proliferation may underlie the developmental neurotoxicity of PQ.

Objective: To investigate the effects of paraquat on microRNA expressions in PCl2 cells, and to explore the regulatory mechanism of bcl-2., Methods: We used PC12 cells as a popular in vitro cell model system for characterizing the dopaminergic neuron. After 24 h treatment with different concentrations of PQ (0, 62.5 ümol/L), expression difference of microRNA was detected by microarray and examined by real-time quantitative PCR (RT-PCR). Cell apoptosis was analyzed with flow cytometry (FCM) and the relative levels of miR-34a, miR-Let-7e were measured by RT-RCR following the PCl2 cells treatment with 0, 62.5, 125, 250, 500, 1000 ümol/L PQ. Meanwhile, the protein expression of bcl-2 was evaluated by western blot according to forecasting targets analysis databases., Results: Cell viability decreased and cell apoptosis increased with increasing PQ concentrations (from 125 to 1000 ümol/L) in a dose-dependent manner (P < 0.05 or P < 0.01). MiRNA microarray showed that after 62.5 ümol/L PQ treatment, 11 miRNAs were significantly up-regulated while 8 miRNAs were down-regulated compared with control (P < 0.01). We chose miR-34a, miR-Let-7e which appeared most remarkable changes in microarray to examine by RT-PCR. It revealed that the level of miR-34a gradually ascended while miR-Let-7e declined after PQ treatment, which are accordant to the microarray results. The protein expression of bcl-2 treated with PQ significantly decreased compared with control and presented a negative correlation with the expression of miR-34a (P < 0.05 or P < 0.01)., Conclusion: The alteration of miRNAs expression may be involved in the neurotoxicity of PQ. Especially, mir-34a negatively regulated the level of bcl-2, and thus plays a key role in PQ-induced cell apoptosis.

Paraquat (PQ) is one of the most widely used herbicides in the world. Although available evidence indicates that people exposed to PQ have a higher risk of developing Parkinson's disease, adverse effects of PQ on neural progenitor cells have not been investigated yet. In this study, we investigated the in vitro effect of PQ on immortalized human embryonic neural progenitor cells (hNPCs) by treating them with various concentrations of PQ (0, 0.1, 1, 10 and 100 μM) for 24h. We show that PQ treatment reduces the cell viability and proliferation and induces reactive oxygen species (ROS) production in a dose-dependent manner. In addition, apoptosis induced by PQ was significantly increased at a concentration of as low as 1 μM. To illustrate the underlying molecular mechanisms, we examined the caspase-3 activity, intracellular calcium level, the NF-κB activity, as well as expression of p21, p53 and metallothionein-III mRNA. PQ significantly increased caspase-3 activity at the concentration of 100 μM. Similarly, PQ triggered intracellular Ca(2+) releases and activation of NF-κB was observed after exposure of hNPCs at low concentrations of PQ (1 μM). Meanwhile, p53 and p21 mRNA transcripts were significantly up-regulated at 10 μM and 1 μM of PQ, respectively. MT-III mRNA and protein expression was significantly up-regulated at 1 μM of PQ and reached peak at 10 μM. These results suggest that PQ could reduce viability of hNPCs by inducing oxidative stress and apoptosis., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

Abstract: The broad application of paraquat (PQ) has given rise to wide public concern over its potential to damage the nigrostriatal dopaminergic system because its chemical structure closely resembles that of the well-known dopaminergic neurotoxicant MPP+. However, little is known about the relevance of dopamine homeostasis changes in response to PQ exposure as the underlying mechanism of the neurotoxicity. We used the PC12 cell, a popular in vitro cell model system for characterizing the dopaminergic neuron to examine the effects of PQ on dopamine homeostasis. After 24h treatment with different concentrations of PQ (from 0 to 1000μmol/l), MTT tests showed that cell viability decreased with increasing PQ concentrations. Flow cytometry analysis also showed that PQ induced cell apoptosis in a dose-dependent manner. An enzyme-linked immunosorbent assay revealed that the intracellular dopamine content increased after PQ treatment. The mRNA expression of genes associated with dopamine synthesis (TH), storage (VMAT2), transportation (DAT and D2R) and degradation (MAO) was assessed using real-time PCR. Results showed that the expression of TH and COMT were unaffected while the expression of MAO was suppressed after PQ treatment. In addition, exposure to PQ reduced the expression of VMAT2 but up-regulated the expression of D2R. Moreover, the expression of DAT was up-regulated at a lower dose of PQ, and then decreased at a higher dose. These alterations of gene expression of MAO, D2R and DAT are consistent with an increase of intracellular dopamine content. Together, these findings suggest that PQ exposure can influence dopamine homeostasis, which may be partly related to the neurotoxicity of PQ. [Copyright &y& Elsevier]