Chemokine associations with blood cerebrospinal fluid (CSF) barrier permeability and delirium

Delirium is a highly prevalent neuropsychiatric syndrome characterised by acute and fluctuating impairments in attention and cognition. Mechanisms driving delirium are poorly understood but it has been suggested that blood cytokines and chemokines cross the blood brain barrier during delirium, directly impairing brain function. It is not known whether these molecules reach higher brain levels when the blood cerebrospinal fluid barrier (BCSFB) is impaired. Here, in human hip-fracture patients, we tested the influence of BCSFB integrity on CSF levels of chemokines and assessed their association with delirium. CSF levels of IP-10, eotaxin, eotaxin 3 and TARC showed weak to moderate correlations with BCSFB permeability, as measured by the Q_albumin ratio, while MCP1, IL-8, MIP1α and MIP1β showed no significant correlation. Chemokines were not associated with delirium in univariate analysis or when stratified on dementia status, but exploratory analyses showed that elevated Eotaxin (CCL11) and MIP1α (CCL3) were associated with prevalent delirium. Modelling acute systemic inflammation, we used bacterial LPS (250 μg/kg) or sterile laparotomy surgery in mice to demonstrate de novo synthesis of chemokines at the choroid plexus (CP) and microvasculature. Gene expression data showed CP-enriched expression of Il1b, Tnfa, Cxcl1 and Ccl3 in both models and immunohistochemistry showed cytokine and chemokine synthesis in CP stromal (IL-1β, CCL2/MCP1) or epithelial cells (CXCL10/IP-10) cells and at the microvasculature. Larger studies are required to confirm these human findings on chemokine associations with BCSFB permeability and prevalent delirium. Preclinical studies are warranted to determine whether chemokines might play a role in the pathophysiology of delirium.