Sarsasapogenin Improves Pathological Phenotypes in MPTP/MPP+-Induced Parkinson's Disease Models: Synergistic Actions of Neurite Outgrowth, Neurotransmitter Modulation, and Anti-Inflammation.

Background

Parkinson's disease (PD) is a prevalent neurodegenerative disorder hallmarked by progressive loss of midbrain dopaminergic (DA) neurons, neurite atrophy, neurotransmitter imbalance, and motor dysfunction. Therapeutic strategies targeting neuronal integrity and neuroinflammation hold translational value beyond conventional symptomatic therapies for PD. Sarsasapogenin, a natural steroidal saponin, exhibits documented neuroprotective properties in multiple neurological diseases. However, its therapeutic potential and underlying mechanisms in PD remain to be elucidated.

Methods

The neuroprotective efficacy of sarsasapogenin was assessed in a subacute 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mouse PD model and 1-methyl-4-phenylpyridinium ion (MPP+)-insulted primary cortical and dopaminergic neuronal cultures. Motor function was evaluated via a variety of behavioral tests. Survival of dopaminergic neurons was quantified using tyrosine hydroxylase (TH) immunostaining. Levels of monoamine neurotransmitters and their metabolites were measured using high-performance liquid chromatography (HPLC), while serum proinflammatory cytokines were determined using enzyme-linked immunosorbent assay (ELISA). Neurite outgrowth and neuronal viability were examined under both preventive and therapeutic treatment regimens in vitro. Potential molecular targets of sarsasapogenin were screened and identified via Drug Affinity Responsive Target Stability (DARTS) coupled with molecular docking.

Results

Twenty-one-day sarsasapogenin intervention mitigated aberrant motor deficits in MPTP-treated mice, rescued TH+ dopaminergic neurons in the substantia nigra, restored homeostasis of dopamine and norepinephrine, normalized the turnover of monoamines, and decreased peripheral levels of the proinflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β). In primary neuronal cultures, sarsasapogenin significantly ameliorated MPP+-triggered neurite atrophy and neuronal loss in both cortical and ventral mesencephalic dopaminergic neurons. DARTS screening combined with molecular docking identified serpin family H member 1 (Serpin) H1 as a candidate binding protein of sarsasapogenin, with a favorable binding affinity of -8.6 kcal/mol.

Conclusions

Sarsasapogenin exerts comprehensive neuroprotective effects in preclinical PD models via synergistic modulation of dopaminergic neuronal survival, neurotransmitter balance, inflammatory inhibition, and neurite outgrowth. These findings highlight sarsasapogenin as a promising multi-target candidate for PD intervention, whereas the precise functional role of Serpin H1 in mediating its neuroprotective actions warrants further in-depth investigation.