Fig. 8

Rifabutin reduces α-synuclein oligomers and nigrostriatal dopaminergic neurodegeneration in an AAV-based α-synuclein rat model. (a) Dopaminergic neuron loss was induced by stereotactic injection of human A53T α-synuclein-expressing AAV in the unilateral SN. For vehicle treated animals, the number of dopaminergic (TH+) cells in the injected SN was only 57% of the non-injected SN versus 93% for rifabutin treated animals (n = 8 animals per treatment group, two-tailed t-test, ****p < 0.0001). (b) Representative images of TH staining of the SN injected with AAV-A53T α-synuclein and the contralateral non-injected SN from rats treated with vehicle or rifabutin. Scale bars are 200 μm. (c) Striatal levels of dopamine (DA) and its metabolites, DOPAC and HVA, were higher for rifabutin treated animals compared to vehicle treated animals (n = 8 animals per treatment group, two-tailed t-test, *p < 0.05). (d) Analyses of immunofluorescent images demonstrated that animals treated with rifabutin exhibited less dopaminergic (TH+) cell death in the injected SN compared to vehicle treated animals. Levels of α-synuclein oligomers and total human α-synuclein were lower in the surviving TH+ cells in the SN of rifabutin treated animals versus vehicle treated animals (n = 7–8 animals per treatment group, two-tailed t-test, *p < 0.05). (e) Representative images of immunofluorescent staining with anti-TH antibodies (to detect dopaminergic neurons), Syn-O2 (to detect α-synuclein oligomers), or Syn211 (to detect total human α-synuclein) in SN injected with AAV-A53T α-synuclein from rats treated with vehicle or rifabutin. Scale bars are 200 μm. (f) RT-QuIC spectra of CSF from 7 animals treated with vehicle and 8 animals treated with rifabutin. The dotted black line represents the threshold (mean background fluorescence + 5 SD) defining the positive and negative cases. Four vehicle treated cases were positive (coloured spectra) and 3 vehicle treated cases were negative (gray spectra). All 8 rifabutin treated cases were negative (gray spectra)