Inhibition of Src phosphorylation reduces damage to the blood- brain barrier following transient focal cerebral ischemia in rats

The disruption of the blood-brain barrier (BBB) caused by cerebral ischemia determines the extent of injury and patient prognosis. Inhibitors of Src can markedly minimize the infarct size and preserve neurological function. The Src protein tyrosine kinase (PTK) inhibitor, PP2, protects the rat brain against ischemic injury, possibly through the reduction of vascular endothelial growth factor A (VEGFA) expression and the upregulation of claudin-5 expression, which preserves the integrity of the BBB. In this study, the expression levels of phosphorylated (p)-Src, VEGFA and claudin-5 were determined to investigate the changes occurring in the levels of these proteins and to determine the benefits of PP2 treatment following cerebral ischemia/reperfusion (I/R). Our study included a sham-operated group, an I/R group, a vehicle-treated group (V) and a PP2-treated group (PP2). We found that the rats in the PP2 group exhibited greater preservation of neurological function and reduced VEGFA and p-Src protein expression compared with the rats in the I/R and V groups. Moreover, the mRNA and protein levels of claudin-5 were markedly higher in the PP2 group than in the I/R group or the V group after 3 days of reperfusion. Immunofluorescence staining revealed that the co-localized immunostaining of fibrinogen and claudin-5 was reduced in the PP2 group, which suggests that the exudation of fibrinogen in this group was less than that in the I/R and V groups. Furthermore, the reduced co-localization of immunostaining of glial fibrillary acidic protein (GFAP) and claudin-5 indicated that the rats in the PP2 group had only a slight disruption of the BBB. These findings suggested that PP2 treatment attenuated the disruption of the BBB following ischemia and minimized the neurological deficit; these effects were associated with a decreased VEGFA expression and an increased claudin-5 expression. Members of the Src PTK family may be critical targets for the protection of the BBB following cerebral ischemia.