Integrating network pharmacology with molecular docking and dynamics to uncover therapeutic targets and signaling mechanisms of vitamin D3 in Parkinson's disease.

Parkinson's disease (PD) is a chronic neurodegenerative disorder marked by dopaminergic neuron degeneration in the substantia nigra. Emerging evidence suggests vitamin D3 (VD) plays a therapeutic role in PD, but its precise molecular mechanisms remain unclear. This study employed network pharmacology and bioinformatics to identify VD's hub targets and related pathways. We identified 24 VD's anti-PD targets, with estrogen receptor 1, estrogen receptor 2 (ESR2), sodium-dependent norepinephrine transporter, and insulin-like growth factor 1 receptor emerging as hub targets. Gene enrichment analysis elucidated that VD's anti-PD mechanism is closely related to the estrogen signaling pathway. Additionally, two-sample Mendelian randomization suggested a positive causal relationship between 25-hydroxyvitamin D and estrogen levels in vivo. To verify the interaction between VD and the hub drug targets, we performed molecular docking and kinetic simulations, finding the strongest interaction between VD and ESR2. Further Mendelian randomization analysis of drug targets confirmed the significant effect of the ESR2 drug target on PD risk. Single-cell nuclear sequencing of dopaminergic neurons, coupled with GSEA analysis, indicated that ESR2 activation upregulates the neuroactive ligand-receptor interaction signaling pathway and downregulates the Parkinson's disease pathway, thereby exerting a neuroprotective effect. In summary, our findings suggest that VD supplementation can not only elevate estradiol levels in humans but also directly activate ESR2, thereby modulating the estrogen signaling pathway in PD patients and providing neuroprotection. These predictive biological targets offer promising avenues for future clinical applications in Parkinson's disease treatment.