Gentisic acid confers multimodal neuroprotection in experimental Alzheimer's disease by targeting oxidative stress, neuroinflammation, and protein aggregation.
BACKGROUND: Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by cognitive decline associated with oxidative stress, neuroinflammation, cholinergic dysfunction, and accumulation of amyloid-β (Aβ) and hyperphosphorylated tau (p-tau). Given the multifactorial nature of AD, phytochemicals with multi-target pharmacological properties are of growing therapeutic interest. Gentisic acid (GA; 2,5-dihydroxybenzoic acid) possesses established antioxidant and anti-inflammatory activities; however, its potential relevance in AD has not been comprehensively evaluated. PURPOSE: This study investigated the neuroprotective potential of gentisic acid against Alzheimer-like pathology using integrated in vitro and in vivo experimental models. STUDY DESIGN: A preclinical experimental study combining cell-based assays and an aluminium chloride (AlCl3) and D-galactose (D-Gal)-induced rat model of AD-like neurodegeneration was conducted. METHODS: Blood-brain barrier (BBB) permeability of GA was assessed using a PAMPA-BBB assay. Neuroprotective effects were examined in AlCl₃-exposed SH-SY5Y cells. In vivo, Wistar rats received AlCl₃ and D-Gal to induce cognitive and biochemical alterations, followed by oral GA treatment. Behavioral paradigms such as open field, Morris water maze, novel object recognition, elevated plus maze and Y-maze tests were employed to assess spatial learning, recognition memory, and anxiety-like behavior. Oxidative stress markers, antioxidant enzymes, acetylcholinesterase activity, monoaminergic neurotransmitters, brain-derived neurotrophic factor (BDNF), pro-inflammatory cytokines, amyloid beta, and hyperphosphorylated tau protein levels were quantified. Histopathological evaluation of hippocampal and cortical regions was performed. RESULTS: GA demonstrated adequate BBB permeability and concentration-dependent protection against AlCl₃-induced cytotoxicity in SH-SY5Y cells. In the rat model, GA (10, 30, and 100 mg/kg, per oral (p.o.) improved cognitive performance and attenuated anxiety-like behavior. Treatment with GA reduced lipid peroxidation (malondialdehyde), restored antioxidant defenses (superoxide dismutase, catalase and reduced glutathione), inhibited acetylcholinesterase activity, and normalized monoaminergic neurotransmitters (serotonin and dopamine). GA further elevated BDNF levels and suppressed pro-inflammatory cytokines (tumor necrosis factor-alpha and interleukin-1 beta). Notably, GA decreased cerebral Aβ and p-tau accumulation and preserved hippocampal and cortical architecture. CONCLUSION: Gentisic acid exerts multi-modal neuroprotective effects, including antioxidant, anti-inflammatory, anti-cholinesterase, and anti-amyloidogenic actions, in experimental models of AD. These findings support its potential as a phytochemical candidate for further development in the prevention or adjunctive management of AD.