Astrocytic FKBP5 regulates neuroinflammation and cognitive outcomes in male mouse models of excitotoxic epilepsy.

FK506-binding protein 51 (FKBP51, encoded by FKBP5) is a multisignaling cochaperone that regulates cellular stress responses and inflammatory signaling through the NF-κB pathway. Although FKBP51 is upregulated in reactive astrocytes, its role in epilepsy and excitotoxic neuroinflammation remains unknown. Excessive astrogliosis and impaired glutamate transporter-1 (GLT-1)-mediated glutamate clearance promote excitotoxicity and increase seizure susceptibility. Here, we investigated how both global and astrocyte-specific Fkbp5 deletions influence seizure susceptibility, astrogliosis, neuroinflammation, and cognition in male mice subjected to a kainic acid (KA)-induced epilepsy mouse model. Global Fkbp5 knockout (Fkbp5-KO) presented lower seizure activity along with decreased neuronal loss and astrogliosis in the hippocampus compared with the wild-type mice. Astrocyte-specific Fkbp5 conditional knockout (aFkbp5-cKO) mice similarly attenuated seizure severity, decreased astrogliosis, improved novel object recognition, and preserved GLT-1 expression in hippocampal CA3. Glia-neuron mixed cultures derived from Fkbp5-KO brains showed reduced NMDA-induced neurotoxicity and astrogliosis, accompanied by decreased NF-κB p65 phosphorylation. Notably, overexpression of an Fkbp5 quadruple mutant that disrupts the FKBP51-NF-κB interaction inhibited proinflammatory lipopolysaccharide-induced astrogliosis and NF-κB activation. Transcriptomic analysis of Fkbp5-KO hippocampi further confirmed suppression of NF-κB-driven inflammatory pathways. In summary, astrocytic FKBP51 mediates reactive astrogliosis and GLT-1 downregulation, linking excitotoxic neuroinflammation with seizure susceptibility and cognitive impairment, and represents a potential intervention target for epilepsy.