Suppression of Astrocytic <scp>PirB</scp> Alleviates Aβ‐Induced Excitotoxicity and Cognitive Deficits via <scp>EAAT</scp> Expression

Glutamate-mediated neurotoxicity is a key factor in the pathogenesis of Alzheimer's disease, yet its regulatory mechanism and connection to the amyloid β (Aβ) cascade remain unclear. This study examined the role of the astrocytic Aβ receptor, PirB, on glutamate reuptake, excitotoxic neuronal death, and cognition. In vitro, primary astrocytes were treated with soluble PirB extracellular peptide (PEP), the PirB inhibitor Fluspirilene, or lentiviral vectors encoding PirB or shPirB. We measured excitatory amino acid transporter (EAAT) expression, intracellular glutamate levels, and calcium influx in astrocytes. We also evaluated neuronal apoptosis in neuron-astrocyte co-cultures. PirB inhibition (via PEP or Fluspirilene) significantly increased EAAT1 and EAAT2 expression and activated the mTOR signaling. This was accompanied by elevated astrocytic glutamate levels, decreased intracellular calcium, as well as reduced neuronal apoptosis, whereas PirB overexpression had the opposite effects. In vivo, mice with astrocyte-specific PirB conditional knockout (cKO) were injected with Aβ oligomers into the hippocampus and subjected to cognitive behavioral assays. Hippocampal neuronal loss and apoptosis were evaluated through Nissl and TUNEL staining. PirB cKO mice showed enhanced exploratory behavior, improved working memory, and higher EAAT expression, along with higher Bcl-2/Bax ratios, mTOR activation, and reduced neuronal apoptosis compared with Aβ-injected PirB^flox/flox mice. Overall, our findings identify astrocytic PirB as a key driver of Aβ-triggered glutamate-mediated neurotoxicity and suggest that suppressing the PirB-mTOR-EAAT pathway could be a promising therapeutic strategy for mitigating Aβ-related cognitive impairment.