Inhibiting PI3K/Akt-Signaling Pathway Improves Neurobehavior Changes in Anti-NMDAR Encephalitis Mice by Ameliorating Blood–Brain Barrier Disruption and Neuronal Damage

The disruption of the blood–brain barrier (BBB) is hypothesized to be involved in the progression of anti- N -methyl- d -aspartate receptor (NMDAR) encephalitis, but its mechanism is still unclear. Recently, the phosphatidylinositol 3-kinase (PI3K)/threonine kinase (Akt) pathway is involved in the regulation of the BBB in various diseases. This study is aimed to investigate the mechanism of BBB damage and neurobehavior changes in anti-NMDAR encephalitis mice. Female C57BL/6J mice were actively immunized to establish an anti-NMDAR encephalitis mouse model and evaluate the neurobehavior changes of mice. To study its potential mechanism, LY294002 (PI3K inhibitor, 8 mg/kg) and Recilisib (PI3K agonist, 10 mg/kg) were treated by intraperitoneal injection, respectively. Anti-NMDAR encephalitis mice showed neurological deficits, increased BBB permeability, open endothelial tight junctions (TJs), and decreased expression of TJ-related proteins zonula occludens (ZO)-1 and Claudin-5. However, administration of PI3K inhibitor significantly reduced the expression of p-PI3K and p-Akt, improved neurobehavior function, decreased BBB permeability, and upregulated the expressions of ZO-1 and Claudin-5. Furthermore, PI3K inhibition reversed the decline of NMDAR NR1 in the membranes of hippocampal neurons, which reduced the loss of neuron-specific nucleoprotein (NeuN) and microtubule-associated protein 2 (MAP2). In contrast, administration of the PI3K agonist Recilisib showed a tendency to exacerbate BBB breakdown and neurological deficits. Our results showed that the activation of PI3K/Akt, along with the changes in TJ-related proteins ZO-1 and Claudin-5, may be closely related to BBB damage and neurobehavior changes in anti-NMDAR encephalitis mice. PI3K inhibition attenuates BBB disruption and neuronal damage in mice, thereby improving neurobehavior.