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.
METHODS AND RESULTS: We conducted a retrospective study to establish a diverse mouse cohort resembling large human studies. We sequenced the V4 region of the 16S rRNA gene from 538 samples across the gastrointestinal tract of 303 male and female C57BL/6J mice randomized into sham or angiotensin II treatment from different genotypes, diets, animal facilities, and age groups. Analysing over 17 million sequencing reads, we observed that angiotensin II treatment influenced α-diversity (P = 0.0137) and β-diversity (i.e. composition of the microbiome, P < 0.001). Bacterial abundance analysis revealed patterns consistent with a reduction in short-chain fatty acid producers, microbial metabolites that lower blood pressure. Furthermore, animal facility, genotype, diet, age, sex, intestinal sampling site, and sequencing batch had significant effects on both α- and β-diversity (all P < 0.001). Sampling site (6.8%) and diet (6%) had the largest impact on the microbiome, while angiotensin II and sex had the smallest effect (each 0.4%).
CONCLUSION: Our large-scale data confirmed findings from small-scale studies that angiotensin II impacted the gut microbiome. However, this effect was modest relative to most of the other factors studied. Accounting for these factors in future pre-clinical hypertensive studies will increase the likelihood that microbiome findings are replicable and translatable.