Altered IRF1-miR-20a-5p Regulatory Axis in the Hippocampus of Patients with Major Depressive Disorder.

AIM:Neuroinflammation has been implicated in the pathogenesis of major depressive disorder (MDD), with interferon regulatory factor 1 (IRF1) playing a potential role. MicroRNAs (miRs) are also involved in MDD through posttranscriptional regulation of gene expression. This study investigated whether miR-20a-5p regulates IRF1 in MDD. METHODS:IRF1 mRNA and miR-20a-5p expression levels were measured by qPCR in postmortem hippocampi from 14 MDD subjects and 14 controls, and in chronic social defeat stress (CSDS) mice. Their regulatory relationship was examined in HEK293 cells using miR-20a-5p overexpression and a dual-luciferase assay. Neuro2a cells treated with DMSO were used to evaluate the effects of cellular stress on Irf1 and miR-20a-5p expression. RESULTS:IRF1 mRNA and miR-20a-5p expression levels were significantly increased in both MDD hippocampi and CSDS mice. Luciferase assays showed that miR-20a-5p directly targeted the conserved seed sequence within the IRF1 3'-UTR and suppressed IRF1 expression. During the early phase of cellular stress, Irf1 mRNA was upregulated, whereas miR-20a-5p was downregulated, suggesting that stress initially induces Irf1 expression, followed by secondary regulation of miR-20a-5p. CONCLUSION:IRF1 mRNA expression was increased in the hippocampus of both MDD subjects and CSDS mice. Moreover, miR-20a-5p directly targeted the IRF1 3'-UTR, supporting a potential miR-20a-5p-IRF1 regulatory axis involved in inflammatory signaling in MDD. However, its functional significance in vivo remains to be determined.