The blood-brain barrier (BBB) acts as a specialized structure separating the brain from peripheral blood circulation and plays an important role in brain function. Following an ischaemic stroke or cerebral ischaemia, the BBB is damaged leading to degraded proteins being released into blood circulation. However, little is known about cerebral ischaemia and reperfusion (I/R) induced BBB damage and changes in circulatory biomarkers. This study aims to use both immunohistochemistry and western blotting (WB) to examine neuronal death, glial cell alterations and changes in BBB tight junction (TJ) proteins such as zonula occludens-1 (ZO-1), Occludin and Claudin-5 in the hippocampus in a murine model of cerebral I/R. The changes in these proteins in the blood serum of this model were assessed by enzyme-linked immunosorbent assay. The results showed neuronal death and a significant increase in glial fibrillary acidic protein (GFAP), a protein primarily expressed in astrocytes and a significant decrease in TJ proteins, ZO-1, Occludin and Claudin-5 in the hippocampus of occluded mice as compared to sham-operated mice. These changes are associated with an increased level of these proteins in blood serum in ischaemic mice, suggesting that these proteins can be used as potential biomarkers for determining ischaemic stroke.

Background: Stroke is one of the leading causes of death and disability worldwide. The diagnosis of stroke remains largely clinical, yet widely used stroke scoring systems and brain imaging do not satisfactorily allow distinction of ischaemic stroke (IS) patients from stroke mimics (SM). Blood biomarkers are promising tools that could facilitate clinical triage. Methods: This study recruited 66 patients with IS and 24 SM. The levels of Glial fibrillary acidic protein (GFAP), Neuron-specific enolase (NSE), Neurofilament light chain (NfL) and blood-brain barrier (BBB) proteins [Occludin (OCLN), Zonula occludens 1 (ZO-1), Claudin-5] in blood serum were measured by enzyme-linked immunosorbent assay technique. Biomarker levels in IS patients and SM was compared using the Mann–Whitney U test. Multivariable logistic regression analysis was used to evaluate the diagnostic performance of biomarkers in combination with the National Institutes of Stroke Scale (NIHSS) score. Results: Significant differences in circulating GFAP, NfL, OCLN, ZO-1, and Claudin-5 but not NSE in IS patients compared to SM. The combination of circulating ZO-1, Claudin-5, and OCLN with NIHSS score gives the highest diagnostic accuracy, sensitivity, and specificity. Conclusion: A prediction model with Circulating BBB proteins in combination with NIHSS score differentiates between IS patients and SM.