Luteolin Improves <scp>BBB</scp> Integrity Following Ischemic Stroke Injury by Downregulating the Expression of <scp>LRP1</scp> and <scp>MMP9</scp>

Ischemic stroke is a prevalent neurological disorder often resulting in brain tissue injury and blood-brain barrier (BBB) damage. Luteolin (LUT), a natural polyphenolic compound in grape skin, wine, and other plants, has neuroprotective properties against ischemic stroke. However, it remains unclear whether its protective effect involves alterations in BBB integrity. This study aimed to examine the BBB-protective impact of LUT in a photothrombotic (PT) mouse model and oxygen-glucose deprivation (OGD) cell model and investigate its underlying mechanism. First, we used neurofunctional scoring, 2,3,5-triphenyltetrazolium chloride staining, Nissl staining, and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) to evaluate the neuroprotective effects of LUT in ischemic stroke. Furthermore, we assessed the impact of LUT on BBB permeability using Evans Blue staining, brain water content, transendothelial electrical resistance, FITC, and flow cytometry techniques. We also examined the expression of tight junction (TJ) proteins related to BBB integrity using Western blotting. Finally, we validated the potential mechanism of action of LUT using short hairpin RNA (shRNA) technology. LUT alleviated the cerebral infarct area and neuronal apoptosis in the PT mouse model, reduced brain water content and Evans Blue leakage, decreased bEnd.3 cell apoptosis in the OGD model, increased transmembrane resistance, and reduced FITC leakage. LUT also counteracted the degradation of TJ proteins and decreased the expression of MMP9. Furthermore, the improvement was weakened when LRP1 was interfered with using shRNA. Our study suggests that LUT has the potential to improve BBB damage and exert neuroprotective effects following ischemic stroke. The mechanism of action may involve the inhibition of LRP1 and subsequent reduction in MMP9 expression.