Fig. 5: PD-associated ImP induces mTORC1-dependent selective loss of dopaminergic neurons, inflammatory astrogliosis, and motor impairment.

a Schematic illustration of the experimental procedure showing systemic intraperitoneal (i.p.) administration of ImP (20 μg per mouse for three weeks). Created in BioRender. Kim, J. (https://BioRender.com/32jcwkt). b Representative anti-TH immunohistochemistry (Nissl counterstained) of ventral midbrain coronal sections from mice injected with ImP or vehicle (1% DMSO, Veh). Magnified images showing dopaminergic processes in the SNr are also presented on the right. Stereological counting of TH-positive dopaminergic neurons in the SNpc of each experimental mouse group is shown in the right panel (n = 5 mice per Veh group, n = 4 mice per ImP group). Scale bar = 400, and 100 μm for enlarged images, respectively. c, d Pole assessment of bradykinesia phenotype (c) and rotarod assessment of motor coordination (d) in mice injected with ImP or vehicle (1% DMSO) (n = 5 mice per Veh group, n = 4 mice per ImP group). e Schematic illustration of the experimental procedure showing intranigral stereotaxic injection of ImP (single injection of 7 μg of ImP in 2 μL) where rapamycin was injected intraperitoneally one day before ImP injection at 1 mg/kg per mouse daily for a total of four days. Created in BioRender. Kim, J. (https://BioRender.com/rxfm6ng). f Representative immunofluorescence images of pS6 and TH in the ventral midbrain coronal sections from mice with intranigral brain injections of PBS or ImP with or without mTORC1 inhibitor, rapamycin. Original red pS6 immunofluorescence signals are pseudocolored in white. Quantification of relative pS6 signal intensities in TH-positive dopamine neurons of the SNpc is shown in the right panel (n = 7 mice per group). Scale bar = 100. SNpc and SNr subregions of the VM are indicated by the white dashed line. g (Upper panel) Representative anti-TH immunohistochemistry images of ventral midbrains from mice with nigral ImP or PBS injections with or without rapamycin treatment. Magnified images showing dopaminergic processes in the SNr are also presented on the right. (Bottom panel) Stereological counts of TH-stained and Nissl-stained dopamine neurons in the lesioned hemisphere of the SNpc. Nissl-stained neuronal counts and TH fiber density in the SNr of the indicated experimental mouse group (n = 5 mice per group). Scale bar = 100 μm, and 50 μm for enlarged images, respectively. h Inflammatory astrogliosis in the ventral midbrains of the indicated experimental mouse groups determined by anti-GFAP immunohistochemistry. Quantified % area fraction of GFAP signals is shown below (n = 7 mice per group). Scale bar = 100 μm. i, j Pole assessment of bradykinesia (i) and rotarod assessment of motor coordination (j) in the indicated experimental groups (n = 7 mice per group). k Measurement of ImP concentrations in the plasma samples from patients with PD (n = 65) and age-matched neurologically healthy control participants (n = 65). Data transformed to log₁₀ scale and presented as box plots show minimum, 25% quartile, median, 75% quartile, maximum. Quantitative data are expressed as the mean ± S.E.M. *P < 0.05, **P < 0.01, ***P < 0.001; ns not significant. P values were determined using unpaired two-tailed Student’s t-tests (b–d), two-way ANOVA with Tukey’s post hoc test (f–j), and two-sided Wilcoxon rank-sum tests (k). Source data and test statistics are provided as a Source Data file. See also Supplementary Fig. 5.