miR-146a-3p drives major depressive disorder pathogenesis via BDNF suppression: a novel diagnostic and therapeutic...

Major depressive disorder (MDD) is a debilitating neuropsychiatric condition characterized by persistent low mood, affecting approximately 322 million individuals worldwide. With a staggering 15% mortality rate due to suicide among patients, MDD represents a critical global health challenge. Emerging evidence implicates microRNAs (miRNAs) in the pathogenesis of neuropsychiatric disorders; however, the role of miR-146a-3p in MDD-particularly its mechanistic involvement and potential as a diagnostic biomarker-remains unexplored. In this study, we integrated multi-database bioinformatics analyses with experimental validation to identify miR-146a-3p as a key regulator of MDD progression. Our computational screening revealed miR-146a-3p as a putative risk-associated non-coding RNA, alongside brain-derived neurotrophic factor (BDNF), a well-established MDD susceptibility gene. In vivo studies demonstrated a significant upregulation of miR-146a-3p and concurrent downregulation of BDNF in MDD model mice. Further bioinformatic predictions and dual-luciferase reporter assays confirmed a direct interaction between miR-146a-3p and BDNF mRNA, leading to post-transcriptional suppression of BDNF expression. Mechanistically, miR-146a-3p overexpression impaired synaptic plasticity, as evidenced by reduced levels of key synaptic proteins such as postsynaptic density protein 95 (PSD95) and synapsin (SYN-1), while in vitro transfection experiments validated its negative regulation of BDNF. Critically, intranasal delivery of a miR-146a-3p antagomir or exogenous BDNF protein rescued depressive-like behaviors in murine models, as assessed by open-field, forced swim, and tail suspension tests. These interventions restored synaptic protein expression and ameliorated behavioral deficits, suggesting a therapeutic avenue for MDD. Our findings establish miR-146a-3p as a pivotal epigenetic modulator of MDD pathogenesis, acting through direct suppression of BDNF-dependent synaptic plasticity. The reversibility of this pathway via antagomir inhibition highlights miR-146a-3p's dual potential as both a diagnostic biomarker and a therapeutic target. This study provides foundational insights for developing miRNA-based interventions in mood disorders.