Hippo/YAP Signaling Pathway Mitigates Blood-brain Barrier Disruption After Cerebral Ischemia/reperfusion Injury

【Objective】Ischemia/reperfusion(I/R)injuries commonly lead to breakdown of the blood-brain barrier(BBB).Restoration of the BBB can relieve neurologic damage caused by I/R injuries.The Hippo/YAP signaling pathway mediates cell proliferation,regulated cell death,and differentiation in various organisms and has been shown to participate in the restoration of the heart after I/R.In this study,we investigated whether the Hippo/YAP pathway plays a role in I/R injury in brain,especially in regard to I/R-induced BBB breakdown.【Method】Transient cerebral ischemia was induced by endovascular occlusion of the left middle cerebral artery.By withdrawning the monofilament,the ischemia/reperfusion(I/R)injury was induced.To interfere with the Hippo/YAP signaling pathway,we used YAP agonist dexamethasone(DXM).The experiment has two parts.One part was to explore whether Hippo/YAP signaling pathway was involved in the pathophysiological process of ischemia/reperfusion(I/R)injury.It was divided into five experimental groups,including sham group,I/R 3-h group,I/R 6-h group,I/R 12-h group and I/R 24-h group.The other part was divided into four groups to clarity whether the pathway could relieve BBB disruption,including sham group,I/R 3-h group,I/R 3-h +vehicle group,I/R 3-h+DXM group.Then we evaluated the neurological deficit score by Longa scoring system,water content of the rat brain through the dry wet weight method,the cerebral infarct volume by 2,3,5-triphenyltetrazoliumchloride(TTC)staining,the apoptotic cells by TUNEL staining,the expressions of targeted proteins by Western blot,the BBB permeability by Evans blue.【Result】The results of our study indicate that I/R injury led to an overall decrease in activity of the core proteins,YAP and TAZ,over a 24-h period.The most dramatic change was observed 1.5h after reperfusion.In rats that underwent 1.5h of reperfusion,intraperitoneal injection of YAP agonist DXM activated YAP and TAZ and led to improved neurologic function,smaller brain infarct sizes,increased levels of tight junction proteins,decreased BBB permeability,decreased cerebral edema,and less apoptosis.【Conclusion】This study demonstrated that Hippo/YAP signaling pathway exerts neuroprotective effects on the damaged brain that are likely related to restoration of the BBB.