Paraquat and MPTP induce alteration in the expression profile of long noncoding RNAs in the substantia nigra of mice: Role of the transcription factor Nrf2.

Parkinson's disease (PD) is a common age-related degenerative disease of the central nervous system caused mainly by hereditary, pesticides, metals, and polychlorinated biphenyls. Paraquat (PQ), a widely used herbicide, causes PD. Long noncoding RNAs (lncRNAs) are nonprotein-coding transcripts, expressed in the brain and play irreplaceable roles in neurodegenerative diseases. NF-E2-related factor-2 (Nrf2) is an important genetic transcription regulator in oxidative stress. We aimed to discover novel PQ or 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-Nrf2-related lncRNAs and explore their association with PD. 17157 lncRNAs and 13707 mRNAs (fold change ≥2, P < 0.05) were identified by Microarray. And the expressions of six lncRNAs were confirmed by using qRT-PCR and two by FISH. Coding-noncoding analysis and qRT-PCR were applied to discover the functions of lncRNAs and predict the targeted genes. In mice, PQ and MPTP exposure caused alteration of the lncRNA expression profile, suggesting lncRNAs may be involved in PQ- and MPTP-induced neurotoxicity. The changes in their lncRNA expression were distinct but related. PQ caused lncRNA expression profiling alteration in the substantia nigra (SN) through an interaction with Nrf2, thus changing the NR_027648/Zc3h14/Cybb and NR_030777/Zfp326/Cpne5 mRNA pathways. Similarly, MPTP caused lncRNA expression profiling alteration in SN through an interaction with Nrf2. Nrf2 may be involved in the development of neurodegeneration induced by PQ and MPTP via interaction with lncRNAs as the molecular mechanism. Our findings indicate the potential roles of lncRNAs in the development of PD by PQ or MPTP and provide positive insights into future mechanism studies.

Paraquat and MPTP alter microRNA expression profiles, and downregulated expression of miR-17-5p contributes to PQ-induced dopaminergic neurodegeneration.

Recent evidence indicates that microRNAs (miRNAs) play a key role in neurodegenerative diseases. However, the toxic effects of paraquat (PQ) and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on miRNA expression profiles in dopaminergic neurons have not been investigated. In the present study, we used microarray analysis to show that PQ and MPTP induce alterations of miRNA expression in neuro-2a cells. The results reveal that treatment with 300 µm PQ caused miRNA deregulation, such that 60 miRNAs were upregulated and 228 miRNAs were downregulated. Following treatment with 300 µm MPTP, a total of 576 miRNAs were dysregulated, of which 506 were upregulated and 70 were downregulated. Alterations in the expression of miR-17-5p, miR-210-3p, miR-374-5p, miR-378-3p and miR-503-5p were verified by real-time quantitative reverse transcriptase polymerase chain reaction. Moreover, overexpression of miR-17-5p in Neuro-2a cells enhanced cell proliferation, suppressed apoptosis and promoted S phase transition of the cell cycle after PQ treatment. Taken together, our study demonstrates that characteristic changes in miRNA expression profiles occur after PQ and MPTP treatment, which suggests that miRNAs may be involved in the development of PQ- and MPTP-induced neurodegeneration. Downregulated miR-17-5p expression contributes to PQ-induced dopaminergic neurodegeneration.

Paraquat and MPTP induce neurodegeneration and alteration in the expression profile of microRNAs: the role of transcription factor Nrf2.

Both transcription factors (TFs) and microRNAs (miRNAs) can exert a widespread impact on gene expression. In the present study, we investigated the role of Nrf2 in paraquat-induced intracorporeal neurodegeneration and miRNA expression by exposing Nrf2 wild-type and knockout mice to paraquat (PQ) or 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Exposure to 10 mg/kg PQ or 30 mg/kg MPTP caused damage to nerve cells in the substantia nigra (SN) in both Nrf2 (+/+) and Nrf2 (-/-) ICR mice, which included cell morphological changes, detectable apoptosis and a significant reduction in the number of dopaminergic (DA) neurons. When mice were exposed to the same PQ dose of 10 mg/kg, significant fewer tyrosine hydroxylase (TH)-positive DA neurons were observed in the Nrf2 (-/-) mice than that in the Nrf2 (+/+) mice. Both Nrf2 deficiency and PQ or MPTP exposure could alter miRNA expression profile in the SN, suggesting the potential involvement of Nrf2 in the PQ-induced or MPTP-induced miRNA expression alteration. The expression of miR-380-3p was altered by the Nrf2-MPTP interaction effect. miR-380-3p/Sp3-mRNA pathway is likely part of the mechanism of MPTP-induced neurodegeneration. Collectively, our results corroborated the protective role of Nrf2 and also demonstrated the essential interaction of Nrf2 with miRNAs in intracorporal neurodegeneration induced by neurotoxicants.

Neuroprotective effects of tert-butylhydroquinone on paraquat-induced dopaminergic cell degeneration in C57BL/6 mice and in PC12 cells.

The present study was aimed at determining the role of paraquat (PQ) in the activation of the NF-E2-related factor 2 (Nrf2)/heme oxygenase 1 (HO-1) pathway and the possible neuroprotective effects of tert-butylhydroquinone (tBHQ) pretreatment on PQ-induced neurodegeneration in vivo and in vitro. 7 mg/kg PQ treatment of male C57BL/6 mice caused decreased spontaneous locomotor activity, decreased tyrosine hydroxylase (TH)-positive neurons, increased terminal deoxynucleotidyl transferase-mediated dUTP biotin nick end-labeling (TUNEL)-positive cells in the substantia nigra, as well as increased protein levels of both nuclear Nrf2 and HO-1. In PQ-treated mice, pretreatment with 1 % tBHQ (w/w) significantly attenuated impairments in behavioral performance, decreased TH-positive neurons, and increased TUNEL-positive cells in the substantia nigra, as well as increased protein expression of both nuclear Nrf2 and HO-1. Pretreatment with 40 µM tBHQ protected PC12 cells against 100 and 300 µM PQ-mediated cytotoxicity. The dual-luciferase reporter gene also revealed that the transcriptional activation of HO-1 gene expression of the antioxidant responsive element via Nrf2 occurred as a consequence of 100 and 300 µM PQ exposure. Collectively, these results clearly indicated for the first time that the Nrf2/HO-1 pathway in the substantia nigra was activated by PQ, and pretreatment with tBHQ conferred neuroprotection against PQ-induced Parkinsonism presumably by increasing Nrf2 and HO-1 expression.

[Antagonism of tert-butylhydroquinone on neurotoxicity and oxidative stress induced by paraquat in PC12].

OBJECTIVE: To investigate the protective effects of the tert-butylhydroquinone (tBHQ) pretreatment on neurotoxicity and oxidative stress induced by paraquat (PQ) in PC12 cells. METHODS: Cytotoxicity of PC12 cells was measured by MTT assay, following the PC12 cells treatment with different concentrations of 100, 300 micromol/L PQ for 24 h and 48 h. PC12 cells were pretreated with or without 40 micromol/L tBHQ for 4 h, PC12 cells were exposed to PQ at the doses of 0, 100, 300 micromol/L for 24 h and 48 h, respectively. The viability of PC12 cells was measured by MTT assay, the apoptosis rates of PC12 cells were detected by flow cytometry (FCM) and the malondialdehyde (MDA) levels of PC12 cells were examine by thiobarbituric acid (TBA) method. RESULTS: When the exposure doses of PQ were 100 and 300 micromol/L for 24 h, the viability of PC12 cells pretreated with tBHQ was significantly higher than that of PC12 cells only exposed to PQ (P < 0.05 or P < 0.01). When the exposure dose of PQ was 100 micromol/L for 48 h, the viability of PC12 cells pretreated with tBHQ was significantly higher than that of PC12 cells only exposed to PQ (P < 0.01). When the exposure doses of PQ were 100 and 300 micromol/L for 24 h, the apoptosis rates and MDA levels of PC12 cells pretreated with tBHQ were significantly lower than those of PC12 cells only exposed to PQ (P < 0.05 or P < 0.01). CONCLUSIONS: tBHQ pretreatment can reduce the cytotoxicity, apoptosis and oxidative stress induced by PQ in PC12 cells.