Total organic acids from Cuscuta chinensis Lam. Modulate MDM2 to promote neurogenesis and alleviate depression

Abstract

Ethnopharmacological relevance

The seeds of Cuscuta chinensis Lam. (CCL) are commonly used in traditional Chinese medicine to strengthen kidney qi and alleviate mental fatigue as well as mood dysregulation and affective disturbances. Total organic acids, as major active constituents, have been reported to exert neuroprotective and mood-modulating effects, supporting their relevance to depression research.

Aim of the Study: Investigating the antidepressant effects and elucidating underlying molecular mechanisms of total organic acids from Cuscuta chinensis Lam. (Ora) on neurogenesis and neural plasticity through the MDM2 (E3 ubiquitin ligase)/FOXO3 (Forkhead box O3) ubiquitination regulatory pathway.

Materials and methods

Organic acids were extracted and isolated from Cuscuta chinensis Lam., and their major components were qualitatively identified by ultra-performance liquid chromatography coupled with LTQ-Orbitrap mass spectrometry (UPLC/LTQ-Orbitrap-MS) analysis. Subsequently, a chronic social defeat stress (CSDS) paradigm was established, and behavioral assessments were undertaken to delineate the influence of Ora in CSDS-exposed mice. Immunoblotting was used to quantify synaptic plasticity-associated proteins, and Golgi staining was subsequently applied to examine dendritic spine density. Immunofluorescence and immunohistochemistry were carried out to characterize neural stem/progenitor cell proliferation and differentiation both in vitro and in vivo, with Sholl analysis further providing an assessment of adult hippocampal neurogenesis. In addition, an integrative in silico strategy incorporating network-level analysis and ligand–target interaction modeling was applied to identify potential targets and delineate the mechanistic basis of Ora-mediated antidepressant activity. Subsequently, co-immunoprecipitation assay was performed to evaluate protein interactions and ubiquitination levels; additionally, the effect of MDM2 knockdown on the antidepressant efficacy of Ora was further examined.

Results

Ora alleviated CSDS-induced depressive behaviors, enhanced synaptic plasticity-associated protein expression, and increased dendritic spine density in hippocampal neurons. Moreover, Ora facilitated neural stem cell expansion and subsequent lineage commitment, thereby supporting hippocampal neurogenesis in adults. Furthermore, network pharmacology analysis revealed that CCL shares 387 common targets associated with depression, predominantly enriched in MDM2. Experimental validation demonstrated that Ora upregulated MDM2 expression, reduced FOXO3 levels, and enhanced FOXO3 ubiquitination to promote its degradation. Importantly, the therapeutic effects of Ora were markedly attenuated following MDM2 knockdown.

Conclusion

This study provides the first integrated evidence that Ora counteracts CSDS-associated depressive-like symptoms through MDM2/FOXO3-dependent regulation of ubiquitination, which in turn augments hippocampal neurogenesis and neural plasticity. Collectively, these observations provide a conceptual basis supporting the future translational exploration of this herbal agent.