Reduced Nerve Growth Factor (NGF) Mediates Arsenic-Induced Mitochondrial Dynamics Imbalance and Neuronal Damage Both in Vivo and in Vitro

Arsenic exposure is known to cause cognitive deficits, although the underlying mechanisms are yet to be explored. In this study, we investigated the role of nerve growth factor (NGF), a neuroprotective factor, in arsenic-induced cognitive impairment. In mouse models exposed to 25 and 50 mg/L sodium arsenite (NaAsO2), we observed neuronal damage accompanied by the downregulation of NGF, decreased phosphorylation of phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT), reduced phosphorylation of the mitochondrial fission protein dynamin-related protein 1 (Drp1), and downregulation of the mitochondrial fusion protein optic atrophy 1 (OPA1). Similarly, the downregulation of NGF, inactivation of the PI3K/AKT signaling pathway, mitochondrial dynamics imbalance (dysregulation of mitochondrial fission and fusion processes), and increased apoptosis were observed in HT-22 cells exposed to 4 µmol/L NaAsO2. NGF overexpression mitigated these arsenic-induced alterations, while the protective effect of NGF against arsenic toxicity was reduced by LY294002, a PI3K/AKT pathway inhibitor. These findings suggest that a decrease in NGF mediates the arsenic-disrupted mitochondrial dynamics via inhibiting the PI3K/AKT pathway, ultimately impairing cognitive function.