METHODOLOGY: A total of 80 adult zebrafish were divided into 4 groups namely control, paraquat-treated, pre-hMT2-treated, and post-hMT2-treated groups. Fish were treated with paraquat intraperitoneally every 3 days for 15 days. hMT2 were injected intracranially on day 0 (pre-treated group) and day 16 (post-treated group). Fish were sacrificed on day 22 and the brains were collected for qPCR, ELISA and immunohistochemistry analysis.
RESULTS: qPCR analysis showed that paraquat treatment down-regulated the expression of genes related to dopamine activity and biosynthesis (dat and th1) and neuroprotective agent (bdnf). Paraquat treatment also up-regulated the expression of the mt2, smtb and proinflammatory genes (il-1α, il-1β, tnf-α and cox-2). hMT2 treatment was able to reverse the effects of paraquat. Lipid peroxidation decreased in the paraquat and pre-hMT2-treated groups. However, lipid peroxidation increased in the post-hMT2-treated group. Paraquat treatment also led to a reduction of dopaminergic neurons while their numbers showed an increase following hMT2 treatment.
CONCLUSION: Paraquat has been identified as one of the pesticides that can cause the death of dopaminergic neurons and affect dopamine biosynthesis. Treatment with exogenous hMT2 could reverse the effects of paraquat in the zebrafish brain.
METHODS: We obtained sequencing data sets (SUB12404730, SUB12422862, and SUB12421357) and transcriptome sequencing data sets (GSE111708, GSE108925, and GSE18981) from mouse models of schizophrenia using the Sequence Read Archive and the Gene Expression Omnibus databases, respectively. We performed differential expression analysis on mRNA to identify differentially expressed genes. We conducted Gene Ontology (GO) functional and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses to determine differentially expressed genes. Subsequently, we determined the intersection of differentially expressed microRNAs in plasma exosomes and in prefrontal cortex tissue. We retrieved downstream target genes of mmu-miR-146a-5p from TargetScan and used Cytoscape to visualize and map the microRNA-target gene regulatory network. We conducted in vivo experiments using MK-801-induced mouse schizophrenia models and in vitro experiments using cultured mouse neurons. The role of plasma exosomal miR-146a-5p in schizophrenia was validated using a cell counting kit, detection of lactate dehydrogenase, dual-luciferase assay, quantitative reverse transcription polymerase chain reaction, and Western blot analysis.
RESULTS: Differential genes were mainly enriched in synaptic regulation-related functions and pathways and were associated with neuronal degeneration. We found that mmu-miR-146a-5p was highly expressed in both prefrontal cortical tissue and plasma exosomes, which may be transferred to lobe cortical vertebral neurons, leading to the synergistic dysregulation of gene network functions and, therefore, promoting schizophrenia development. We found that mmu-miR-146a-5p may inhibit the Notch signalling pathway-mediated synaptic activity of mouse pyramidal neurons in the lobe cortex by targeting NOTCH1, which in turn could promote the onset and development of schizophrenia in mice.
LIMITATIONS: The study's findings are based on animal models and in vitro experiments, which may not fully replicate the complexity of human schizophrenia.
CONCLUSION: Our findings suggest that mmu-miR-146a-5p in plasma-derived exosomes may play an important role in the pathogenesis of schizophrenia. Our results provide new insights into the underlying molecular mechanisms of the disease.