Naringin preserved cognitive function through modulation of cholinergic dysfunction, oxidative stress, and synaptic...

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by memory loss and cognitive decline. The cholinergic hypothesis remains central to its framework, suggesting that the degeneration of cholinergic neurons and resulting neurotransmission disruption play a major role in cognitive impairment. Naringin, a potent polyphenolic compound abundant in citrus fruits, has gained attention for its antioxidant, anti-inflammatory, and neuroprotective properties. This study aims to investigate naringin's neuroprotective potential in a scopolamine-induced amnesia model, focusing on the BDNF/GAP-43 signaling pathway and markers of synaptic plasticity.

A total of 42 male Wistar albino rats were divided into six groups: Saline, Scopolamine (Sco; 1 mg/kg/day), Sco + Naringin (50, 100, and 200 mg/kg), and Sco + Donepezil (3 mg/kg). Following a 21-day treatment period, cognitive and emotional behaviors were assessed using the Morris Water Maze (MWM) and Elevated Plus Maze (EPM) tests. Hippocampal tissues were analyzed for acetylcholinesterase (AChE) activity and oxidative/nitrosative stress markers (MDA, Peroxynitrite, NO, NOS). BDNF and GDNF mRNA expression was quantified by RT-qPCR, and the protein levels of BDNF, GAP-43, PSD-95, SYP, GFAP, SIRT1, KEAP1, Nrf2, and HO-1 were evaluated by Western blot. PSD-95, SYP, GFAP, and NeuN were further examined by confocal imaging.

Scopolamine administration induced significant impairments in spatial learning and memory, alongside anxiogenic-like behaviors. Biochemical analyses revealed a marked increase in AChE activity and oxidative/nitrosative stress in the Sco group. Additionally, scopolamine caused a profound reduction in BDNF, GDNF, GAP-43, PSD-95, and SYP levels, while increasing GFAP expression. Naringin treatment effectively attenuated these deficits by lowering AChE activity, reducing oxidative damage, and suppressing neuroinflammation. Notably, naringin preserved the expression of synaptic proteins, in association with upregulation of the BDNF/GAP-43 pathway and maintaining pre- and post-synaptic protein levels (SYP and PSD-95).

These findings demonstrate that naringin exerts significant neuroprotective effects against scopolamine-induced cholinergic amnesia. These findings are consistent with the possibility that naringin preserves synaptic plasticity, enhances neurotrophic support, and mitigates inflammatory responses, suggesting that it may represent a promising natural therapeutic candidate for Alzheimer-like neurodegeneration.