Ginsenoside compound K ameliorates depressive-like behaviors by targeting kynurenine 3-monooxygenase

Background

With its high prevalence, frequent recurrence, and significant disability rates, depression has emerged as a major global health burden. Ginsenosides, the primary components of the herbal medicine ginseng, demonstrate antidepressant effects.

Methods

Drug affinity-responsive target stability (DARTS) and lipid chromatography-mass spectrometry were employed to identify the potential targets of ginsenosides. Active components were characterized through biolayer interferometry (BLI), molecular docking, and site-directed mutagenesis assays to assess binding affinity and interaction sites. RNAscope in situ hybridization and tissue clearing were used to visualize the expression pattern of kynurenine 3-monooxygenase (KMO) and the distribution of ginsenoside metabolite compound K (CK) in brain. In corticosterone-induced depressive mouse models, behavioral phenotyping, viral-mediated gene manipulations, and bulk RNA sequencing with Mfuzz clustering were performed to explore the roles of KMO and ginsenosides in vivo.

Results

DARTS-based screening identified KMO as a critical binding target of ginsenosides. Among the components, CK showed the strongest direct binding to KMO, as confirmed by BLI. Molecular docking and mutations of candidate residues (I309 and G316) validated the specificity of the KMO-CK interaction. Spatial visualization via tissue clearing revealed colocalization of KMO and CK in the brain, with notable enrichment of KMO in thalamic neurons. Importantly, CK exerts antidepressant effects in a KMO-dependent pattern: it alleviated corticosterone-induced depressive-like behaviors and counteracted the associated upregulation of KMO expression. Furthermore, CK restored the neuroactive kynurenine pathway balance by modulating the quinolinic acid/kynurenic acid ratio.

Conclusions

KMO serves as a direct target of ginsenosides in the brain. CK acts as a novel brain-penetrant KMO inhibitor that confers antidepressant activity. The enrichment of KMO in thalamic neurons—as opposed to cortical microglia—offers new insights into the neuroanatomical basis of KMO function and the mechanism of antidepressant interventions.