Aluminum oxide nanoparticles induce neurodegeneration via oxidative stress, amyloidogenic pathway activation, and BDNF suppression in rat brain.

Abstract

Aluminum oxide nanoparticles (Al₂O₃NPs) are used across industrial and consumer sectors, raising concerns about their potential neurotoxic effects. Despite growing application, the mechanisms underlying Al₂O₃NP-induced neurodegeneration remain poorly understood. This study investigated the mechanistic pathways of Al₂O₃NP neurotoxicity in adult male Sprague-Dawley rats exposed intraperitoneally to 15, 30, or 60 mg/kg Al₂O₃NPs for 60 days. Comprehensive analyses included hematological profiling, serum biochemistry, oxidative stress markers (MDA, Nrf2/Keap1), neurotransmitter assays (dopamine, acetylcholine, AChE), quantitative PCR of APP, BACE1, and BDNF, inductively coupled plasma spectroscopy for brain aluminum levels, histopathology, immunohistochemistry (caspase-3, BCL2), and ultrastructural examination by transmission electron microscopy. Al₂O₃NP exposure induced dose-dependent anemia, disrupted iron and calcium homeostasis, and triggered oxidative stress, evidenced by elevated MDA and suppressed Nrf2/Keap1 signaling. Neurochemical analyses revealed marked dopamine and acetylcholine depletion alongside diminished AChE activity. Molecular assays showed significant upregulation of amyloidogenic markers (APP, BACE1) and severe BDNF suppression, indicating impaired neurotrophic support. Brain histopathology revealed progressive neuronal shrinkage, Purkinje cell loss, astrogliosis, and perivascular edema, while immunohistochemistry demonstrated heightened caspase-3 activation and reduced BCL2 expression. TEM confirmed ultrastructural axonal degeneration, demyelination, and necrotic neuronal profiles. Notably, aluminum bioaccumulation increased 116-fold at the highest dose, tightly correlating with neurodegeneration severity. These findings demonstrate that subchronic Al₂O₃NP exposure promotes neurodegeneration via a multifaceted oxidative stress mechanism, activating the amyloidogenic pathway, synaptic dysfunction, neurotrophic impairment, and apoptosis. This work underscores the urgent need for rigorous safety assessments of nanoparticle exposure in biomedical and environmental settings.