Netrin-1 protects blood-brain barrier (BBB) integrity after cerebral ischemia-reperfusion by activating the Kruppel-like factor 2 (KLF2)/occludin pathway

Ischemia/reperfusion (I/R)-induced neural damage and neuroinflammation have been associated with pathological progression during stroke. Netrin-1 is an important member of the family of laminin-related secreted proteins, which plays an important role in governing axon elongation. However, it is unknown whether Netrin-1 possesses a beneficial role in stroke. Here, we employed the middle cerebral artery occlusion (MCAO) model to study the function of Netrin-1 in alleviating brain injuries. Our results demonstrate that Netrin-1 rescued poststroke neurological deficits and inhibited production of the inflammatory cytokines such as interleukin 6 (IL-6) and endothelial chemokine (C-X-C motif) ligand 1 (Cxcl1). Importantly, Netrin-1 protected against MCAO-induced dysfunction of the blood-brain barrier (BBB) in mice and a reduction in the expression of the tight junction (TJ) protein occludin. Additionally, we report that Netrin-1 could ameliorate oxygen-glucose deprivation/reoxygenation (OGD/R)-induced injury and prevent aggravation in endothelial monolayer permeability in bEnd.3 human brain microvascular endothelial cells (HBMVECs). Mechanistically, Netrin-1 ameliorated OGD/R-induced decrease in occludin and Kruppel-like factor 2 (KLF2) in HBMVECs. Notably, silencing of KLF2 abolished the beneficial effects of Netrin-1 in protecting endothelial permeability and occludin expression, suggesting that these effects are mediated by KLF2. In conclusion, our findings suggest that Netrin-1 could constitute a novel therapeutic strategy for ischemic stroke. The expression of Netrin-1 is reduced in the brain cortex of experimental mice. Netrin-1 improved neurological dysfunction in the brain cortex of a MCAO model. Netrin-1 inhibited inflammatory response in the brain cortex of a MCAO model. Netrin-1 protected against MCAO-induced impairment of BBB. The effects of Netrin-1 in protecting BBB integrity are mediated by KLF2/occluding.image The expression of Netrin-1 is reduced in the brain cortex of experimental mice.Netrin-1 improved neurological dysfunction in the brain cortex of a MCAO model.Netrin-1 inhibited inflammatory response in the brain cortex of a MCAO model.Netrin-1 protected against MCAO-induced impairment of BBB.The effects of Netrin-1 in protecting BBB integrity are mediated by KLF2/occludin.