Impact of clozapine on the expression of miR-675-3p in plasma exosomes derived from patients with schizophrenia

Objectives Recently, the expression changes of microRNAs (miRNAs) in the serum exosomes (EXO) of schizophrenia (SCZ) have been reported. The aim of this study was to investigate the global expression changes of miRNA derived from the plasma EXO of patients with treatment-resistant schizophrenia (TRS) and the effects of clozapine on miRNA expression. Methods Global miRNA expression changes in plasma EXO between TRS and controls were studied using microarray analysis. Then, miRNA expressions among TRS, non-TRS, and controls were confirmed with quantitative qPCR experiments. We also studied changes in EXO miRNA expression with in-vitro SH-SY5Y cells. Results A microarray for miRNA expression analysis (nine controls vs. nine patients with TRS) revealed 13 up- and 18 downregulated miRNAs that were relevant to neuronal and brain development based on gene ontology analysis. Of those, upregulated miR-675-3p expression was successfully validated in the same cohort by qPCR experiments. Conversely, miR-675-3p expression levels were significantly decreased in the non-TRS cohort (50 controls vs. 50 patients without TRS without clozapine treatment). Conclusions We identified global miRNA changes in plasma EXO derived from patients with SCZ that were relevant to neuronal functions, among which, hsa-miR-675-3p expression was upregulated by clozapine treatment.