The adenosine A 2A receptor alleviates postoperative delirium‐like behaviors by restoring blood cerebrospinal barrier permeability in rats

Postoperative delirium (POD) is a common post-operative complication in elderly patients that is associated with increased morbidity and mortality. However, the neuropathogenesis of this complication remains unknown. The blood-cerebrospinal fluid barrier (BCB) and brain-blood barrier (BBB) are composed of tight junctions between cells that form physical barriers, and BBB damage plays an important role in the neuropathogenesis of POD. Nevertheless, the role of BCB in POD remains to be elucidated. Herein, we investigated the effect of adenosine A2A receptor (A2A R), a key regulator of the permeability of barriers, on surgery-induced increased permeability of BCB and POD-like behaviors. Open field, buried food, and Y maze tests were used to evaluate behavioral changes in rats after surgery. Levels of tight junction proteins, adherens junction proteins, A2A R, GTP-RhoA, and ROCK2 in the choroid plexus were assessed by western blotting. The concentrations of NaFI and FITC-dextran in the cerebrospinal fluid (CSF) were detected by fluorescence spectrophotometry. Transmission electron microscopy was applied to observe the ultrastructure of the choroid plexus. Surgery/anesthesia decreased the levels of tight junction (e.g., ZO-1, occludin, and claudin1) proteins, increased concentrations of NaFI and FITC-dextran in CSF, damaged the ultrastructure of choroid plexus, and induced POD-like behaviors in rats. An A2A R antagonist alleviated POD-like behaviors in rats. Furthermore, the A2A R antagonist increased the levels of tight junction proteins and restored the permeability of BCB in rats with POD. Fasudil, a selective Rho-associated protein kinase 2 (ROCK2) inhibitor, ameliorated POD-like behaviors induced by A2A R activation. Moreover, fasudil also abolished the increased levels of GTP-RhoA/ROCK2, decreased levels of tight junction proteins, and increased permeability of BCB caused by A2A R activation. Our findings demonstrate that A2A R might participate in regulating BCB permeability in rats with POD via the RhoA/ROCK2 signaling pathway, which suggests the potential of A2A R as a therapeutic target for POD.