Revealing the therapeutic targets, mechanisms, and heterogeneity of Huatan Jieyu Granules for Parkinson's disease through single-cell sequencing.

Background: The incidence of Parkinson's disease (PD) increases with age. Previous pharmacological studies have shown the potential of Huatan Jieyu Granules (HGs) for the treatment of PD, but the exact mechanisms remain unclear. This study aimed to explore the effects of herbal treatment on PD using mouse models and single-cell sequencing.

Methods: In this study, we established in vivo 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD models in mice. Motor function was assessed through behavioral tests. Immunofluorescence was used to examine dopaminergic neuron loss. Single-cell sequencing was performed on mice from the blank, PD model and medication groups. After quality control and dimensionality reduction of the single-cell data, cells were clustered, and different cell types were identified. We then identified the intersection of differentially expressed genes (DEGs1) in the blank and model groups and DEGs2 in the model and medication groups, yielding intersected DEGs. Key drug targets were identified by intersecting these DEGs with the drug targets of active ingredients in TCM. Topological analysis of the PPI network was used to identify key genes. Cell types exhibiting high expression of these genes were designated as key cells. These key cells were subjected to cellular communication analysis and temporal analysis, after which they were classified into subtypes.

Results: HGs significantly improved motor function and prevented dopaminergic neuronal loss in the substantia nigra (SN) of MPTP-treated mice. A total of 34 cell clusters were delineated, with 9 cell types identified, including oligodendrocytes (oligo), neurons, and T cells. We identified 758 intersected DEGs and 13 key drug targets, including Egfr, Ntrk2, Grm5, Htr2c, Bcl2l1. Oligo and neuronal cells were identified as key cells due to higher expression levels of these key genes. In the cellular communication analysis, oligo-neuronal interactions in the blank and model groups, and oligo-OPC and oligo-T cell interactions in the medication group, exhibited the most receptor-ligand interactions. In temporal analysis, both oligo and neuronal cells were differentiated into 9 states, with C1 being the most differentiated.

Conclusion: HGs demonstrate neuroprotective effects in MPTP-treated mice. Using single-cell sequencing, we identified five key genes (Egfr, Ntrk2, Grm5, Htr2c, Bcl2l1) and two key cell types (oligo and neuronal) related to HGs in PD. These findings provided a foundation for understanding the molecular mechanisms by which HGs treat PD.