Assessment of Toll-like Receptor 4, Glycogen Synthase Kinase-3 Beta, and Oxidative Stress in Parkinsonism Mice Model Treated with Metformin

Background: Parkinson’s disease is a progressive neurological disorder that affects the substantia nigra, a brain region responsible for controlling body movement. In Parkinson's disease, the death of dopaminergic neurons is thought to result, at least in part, from a neuroinflammatory state that originates from the activation of toll-like receptor-4 (TLR4) and glycogen synthase kinase-3 beta (GSK3β), among other contributing mechanisms. Objective: To assess the neuroprotective role of metformin, alone or in combination with levodopa/carbidopa, against rotenone-induced Parkinsonism in male albino mice. Methods: Thirty healthy male albino mice weighing 25-30 grams were randomly assigned to six experimental groups (n = 5 per group). The total duration of the experiment was 47 days. The neuroprotective and therapeutic effects were evaluated by measuring serum levels of GSK3β, malondialdehyde (MDA), and superoxide dismutase (SOD) using enzyme-linked immunosorbent assay kits. Additionally, quantitative real-time polymerase chain reaction was performed to evaluate the messenger ribonucleic acid expression of TLR4 specifically in the substantia nigra region. Results: Rotenone administration led to a significant elevation in GSK3β and MDA levels, a reduction in SOD activity, and upregulation of TLR4 expression in the substantia nigra, indicating its strong neurotoxic effect. Preventive administration of metformin effectively restored these molecular and oxidative stress markers to normal levels, demonstrating a clear protective role. Moreover, therapeutic intervention with metformin, whether administered alone or in combination with levodopa/carbidopa, significantly improved the biochemical and inflammatory profiles associated with rotenone exposure. Conclusions: Metformin showed neuroprotective activity in the rotenone-induced model, potentially by modulating oxidative stress and inflammation.