MiRNA Involves In Nerve Cell Damage Induced By Paraquat: The Role Of Transcription Factor Nrf2

Part Ⅰ Paraquat and MPTP induce alterations in the expression profiles ofmicoRNAs in Neuro-2a cellsRecent evidence indicates that microRNAs (miRNAs) play a key role inneurodegenerative diseases. However, little is known about how these miRNAscontribute to dopaminergic neuronal damage by paraquat (PQ) and1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). In the present study, weused microarray analysis to show that PQ and MPTP induce alterations of miRNAexpression in an in vitro cell model of Parkinson’s disease. The results reveal thattreatment with300μM PQ caused miRNA deregulation, such that60miRNAswere upregulated and228miRNAs were downregulated. Among the288miRNAsidentified, the levels of six miRNAs (miR-297b-5p, miR-497-5p, miR-503-5p,miR-374-5p, miR-135b-5p, and miR-669e-3p) changed more than1.2-fold.Following treatment with300μM MPTP, a total of576mRNAs were deregulated,of which506were upregulated and70were downregulated. Among the576miRNAs, miR-93-5p and miR-425-5p had a greater than1.2-fold change. Thesefindings showed that both PQ and MPTP alter miRNA expression, but each affectsa different set of miRNA targets. Alterations in the expressions of miR-17-5p,miR-93-5p, miR-210-3p, miR-374-5p, miR-378-3p, and miR-503-5p were verifiedby real-time quantitative reverse transcriptase polymerase chain reaction.Bioinformatics analysis indicated that aberrant expression of miR-17-5ppotentially contributes to PQ-induced neurotoxicity. Taken together, our studydemonstrates, for the first time, that characteristic changes in miRNA expression profiles occur after PQ and MPTP treatment, which suggests that miRNAs may beinvolved in the development of PQ-and MPTP-induced neurodegeneration.Part Ⅱ Nrf2involved in Paraquat and MPTP-induced nerve cell damageeffectsRecent evidence indicates that Nrf2plays a key role in oxidative stress andneurodegenerative diseases. However, little is known about how Nrf2contribute todopaminergic neuronal damage by paraquat (PQ) and1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). In the present study, we used immunohistochemicalanalysis to show that PQ and MPTP induce nerve cell damage in an mouse modelof Parkinson’s disease in vivo. Our results revealed that treatment with10mg/kgPQ and30mg/kg MPTP could lead to Nrf2(+/+) and Nrf2(-/-) ICR mousesubstantia nigra nerve cell damage, such that cell morphology change (nuclearcondensation, fragmentation), significant cell apoptosis and decline in the numberof DA neurons. To the number of DA neurons, when compared to the Nrf2(+/+)mice, the Nrf2(-/-) mice exhibited significantly decreased level (p<0.05) afterexposed to10mg/kg PQ, while significantly increased level (p<0.05) afterexposed to30mg/kg MPTP. Especially, Nrf2expression level was decreased in the5mg/kg PQ treatment group but increased in the10mg/kg PQ treatment group.Taken together, we successfully established Nrf2(+/+) and Nrf2(-/-) mice PDmodel induced by PQ and/or MPTP. Furthermore, this study demonstrated that10mg/kg PQ and30mg/kg MPTP could result in mouse substantia nigradopaminergic neurons damage and Nrf2could provide neuroprotective effect inPQ-induced neurotoxicity.Part Ⅲ The role of transcription factor Nrf2in alterations of microRNAexpression induced by paraquat, MPTP in mice substantia nigraPrevious studies suggest that microRNAs (miRNAs) and Nrf2plays a key role in neurodegenerative diseases. However, little is known about how the relationshipbetween miRNAs and Nrf2contribute to dopaminergic neuronal damage byparaquat (PQ) and1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). In thepresent study, we used microarray analysis to show that PQ and MPTP inducedalterations of miRNA expression in vivo in Nrf2(+/+) and Nrf2(-/-) mouse modelof Parkinson’s disease. We used miRNA array platforms as well as LNA-ISH tomeasure miRNA levels in wild-type (WT) versus Nrf2-null mice treated withsaline，PQ and MPTP. In vivo, PQ and MPTP exposure could change miRNAexpression profiles, which might be their neurotoxic mechanism. The changes ofmiRNA expression between them is distinguishing but related. MPTP mightchange miRNA expression profiling in substantia nigra through the interactionwith Nrf2, and then result in the change of miR-380-3p/Sp3mRNA pathway,which may be the mechanism of MPTP-induced neurotoxincity. Similarly, PQmight changes miRNA expression profiling in substantia nigra through theinteraction with Nrf2. However, this change showed difference with PQ dose.miR-495*, miR-154*, let-7b, miR-1983and miR-26a may play a role inneurotoxicity induced by10mg/kg PQ, while miR-669b may play a role inneurotoxicity induced by5mg/kg PQ. The result of target gene prediction analysisand mRNA microarray analysis suggested that Sp3mRNA may be the downstreamtarget genes of miRNA-380-3p. Taken together, this study demonstrated thattranscription factor Nrf2plays a role through miRNA expression alteration in micesubstantia nigra induced by PQ and/or MPTP.