Unilateral intranigral administration of beta-sitosterol beta-D-glucoside triggers pathological alpha-synuclein spreading and bilateral nigrostriatal dopaminergic neurodegeneration in the rat.

The spreading and accumulation of alpha-synuclein and dopaminergic neurodegeneration, two hallmarks of Parkinson's disease (PD), have been faithfully reproduced in rodent brains by chronic, oral administration of beta-sitosterol beta-D-glucoside (BSSG). We investigated whether a single injection of BSSG (6 mug BSSG/muL DMSO) in the left substantia nigra of Wistar rats causes the same effects. Mock DMSO injections and untreated rats formed control groups. We performed immunostainings against the pathological alpha-synuclein, the dopaminergic marker tyrosine hydroxylase (TH), the neuroskeleton marker beta-III tubulin, the neurotensin receptor type 1 (NTSR1) as non-dopaminergic phenotype marker and Fluro-Jade C (F-J C) label for neurodegeneration. Using beta-galactosidase (beta-Gal) assay and active caspase-3 immunostaining, we assessed cell death mechanisms. Golgi-Cox staining was used to measure the density and types of dendritic spines of striatal medium spiny neurons. Motor and non-motor alterations were also evaluated. The study period comprised 15 to 120 days after the lesion. In the injured substantia nigra, BSSG caused a progressive alpha-synuclein aggregation and dopaminergic neurodegeneration caused by senescence and apoptosis. The alpha-synuclein immunoreactivity was also present within microglia cells. Decreased density of dopaminergic fibers and dendritic spines also occurred in the striatum. Remarkably, all the histopathological changes also appeared on the contralateral nigrostriatal system, and alpha-synuclein aggregates were present in other brain regions. Motor and non-motor behavioral alterations were progressive. Our data show that the stereotaxic BSSG administration reproduces PD alpha-synucleinopathy phenotype in the rat. This approach will aid in identifying the spread mechanism of alpha-synuclein pathology and validate anti-synucleinopathy therapies.