Regulation of blood-brain barrier permeability by Salvinorin A via alleviating endoplasmic reticulum stress in brain endothelial cell after ischemia stroke

Inhibition of endoplasmic reticulum (ER) stress reduces blood-brain barrier (BBB) injury caused by ischemia/reperfusion (I/R), with indistinct mechanisms. Salvinorin A (SA) relieves I/R-induced BBB leakage; however, whether it is related to the suppression of ER stress is yet unclear. To address this question, we have used both a rat model of middle cerebral artery occlusion (MCAO) and human brain microvascular endothelial cells (HBMECs) with oxygen-glucose deprivation (OGD). SA was injected by tail vein at the terminal of ischemia; Norbinaltorphimine (NB), a kappa opioid antagonist, was administered 30 min prior to SA; 4-phenylbutyric acid (4-PBA), an ER stress inhibitor, was injected intraperitoneally after the onset of ischemia; adenylate-activated protein kinase (AMPK)-specific small interfering RNAs (siRNAs) were transfected to HBMECs before OGD. The assessment was as follows: infarct volume, brain water gain, Evans blue leakage, and modified neurological severity score (mNSS) after MCAO; HBMECs apoptosis rate and permeability, ER stress-related protein, and reactive oxygen species (ROS) and calcium levels after OGD. The results showed that SA significantly reduced the BBB leakage in vivo; SA relieved the apoptotic rates and ER stress in HBMECs, protected the permeability of HBMECs, and reduced ROS and calcium ion level after OGD. Moreover, the SA function was blocked by NB in vivo and AMPK- siRNAs in vitro. We conclude that SA mitigated BBB damage and HBMEC injury after I/R and alleviated ER stress in endothelial cells via AMPK pathway.