Restoring mitochondria–endoplasmic reticulum–synapse axis: a proteomic dissection of Rhein’s multi-pathway antidepressant mechanism

Depression is a heterogeneous psychiatric disorder with limited treatment efficacy, as 30-50% of patients exhibit inadequate responses to conventional monoaminergic antidepressants. Rhein, a bioactive anthraquinone derived from Rheum palmatum, exhibits rapid and sustained antidepressant effects in both acute and chronic social defeat stress (CSDS) mouse models. Using quantitative proteomics on prefrontal cortex (PFC) samples from control, CSDS, Rhein-treated, and imipramine-treated cohorts, we identified differentially expressed proteins that revealed Rhein's multi-target regulatory profile. Functional enrichment and clustering analyses indicated that Rhein predominantly restores dysregulated pathways related to lipid metabolism, ribosomal translation, mitochondrial and endoplasmic reticulum (ER) function, and synaptic plasticity, forming a coherent mechanistic axis underlying its therapeutic effects. Comparative analysis with imipramine-treated mice further highlighted Rhein's distinct capacity to modulate organelle homeostasis and synaptic remodeling with greater breadth. Parallel reaction monitoring (PRM) and Western Blotting validated key proteins involved in mitochondrial functions (BNIP1, PISD, MRPL42, MRPS30, LRBA, IGHM), ER homeostasis (ACBD5, APOA4, RPL14), and synaptic plasticity (HDAC1, FAM3C, SSU72). These molecular findings suggest that Rhein exerts its antidepressant effects by restoring the functional integrity of mitochondria and the ER, thereby reprogramming synaptic plasticity. We inferred that this organelle-centered regulation further reinforces its potent modulation through multiple mechanisms and signaling pathways of synaptic plasticity, enabling Rhein to exert antidepressant effects through a coordinated, multi-layered mechanism. Collectively, our findings provide a systems-level mechanistic framework for Rhein's antidepressant efficacy and support its potential as a multi-pathway natural therapeutic, particularly for metabolic subtypes of depression.