Therapeutic effect of formononetin in 6-OHDA induced Parkinson disease in rats

Preclinical models of Parkinson's disease (PD) have been developed using intracerebroventricular (i.c.v.) injection of 6-hydroxydopamine (6-OHDA) to induce neurodegeneration and motor dysfunction. Formononetin, a phytoestrogen with known anti-aging and anti-apoptotic properties, was investigated for its potential neuroprotective effects against 6-OHDA-induced toxicity. In this study, the rats received a single i.c.v. injection of 6-OHDA and were then treated with formononetin at doses of 25, 50, and 100 mg/kg orally for 21 days. Motor coordination, grip strength, and gait were evaluated using the rotarod test, gait analysis, and pole test. Biochemical assessments measured oxidative stress markers [superoxide dismutase (SOD), catalase, and glutathione (GSH)], proinflammatory cytokines (TNFα, IL-6, and IL-1β), and brain monoamines [dopamine (DA) and acetylcholine (ACh)]. Immunohistochemistry was performed to assess α-synuclein and B-cell lymphoma 2 (BCl2) protein expression. The results showed that formononetin significantly improved motor coordination, gait, and grip strength. It also enhanced antioxidant defenses by increasing SOD, catalase, and GSH activities, while reducing neuroinflammation by lowering IL-1β, TNFα, and IL-6 levels. Furthermore, formononetin alleviated DA depletion and reduced ACh levels, indicating its protective effect on dopaminergic neurons. The immunohistochemical analysis revealed that formononetin decreased α-synuclein aggregation and upregulated BCl2 expression, highlighting its neuroprotective and antioxidative properties. In conclusion, formononetin, at doses of 25, 50, and 100 mg/kg, exhibited significant neuroprotective effects in the 6-OHDA-induced PD rat model. By improving motor function, reducing oxidative stress, and attenuating neuroinflammation, formononetin holds promise as a potential therapeutic agent for PD.