Tauroursodeoxycholic acid prevents ER stress-induced apoptosis and improves cerebral and vascular function in mice subjected to subarachnoid hemorrhage

Early brain injury (EBI) has been recognized as a major cause of poor clinical outcomes in patients with spontaneous subarachnoid hemorrhage (SAH). Endoplasmic reticulum (ER) stress contributes to EBI, but its impact on cerebrovascular function following SAH remains poorly defined. We tested the hypothesis that blocking ER stress by the inhibitor Tauroursodeoxycholic acid (TUDCA) attenuates EBI, which is associated with the rescue of cerebrovascular function defined by local cerebral blood flow and vascular permeability and ER-stress mediated-apoptosis in mouse models. We first preconditioned mice with TUDCA (500 mg/kg/d x 3 days) before SAH and evaluated them for cerebrovascular function by analyzing cerebral cortical perfusion and blood-brain-barrier (BBB) permeability, unfolded protein response (UPR), ER stress-mediated apoptosis and neurological function after SAH. We found that SAH induced a rapidly reduction in cerebral blood flow and an elevated level of ER stress, which lasted for 24 h. The level of neurological deficits was closely associated with the reduction of cerebral blood flow and excessive ER stress. TUDCA improved cerebral blood flow, reduced BBB permeability, inhibited the ER stress through the PERK/eIF2 alpha/ATF4/CHOP signaling pathway, blocked the Caspase-12-dependent ER-stress mediated apoptosis, resulting in significantly improved neurological function of mice subjected to SAH. These data suggest that blocking ER stress prevents EBI and improves the outcome of mice subjected to experimental SAH. These beneficial effects are associated with the restoration of SAH-associated cerebrovascular dysfunction and reduction of the ER-stress induced apoptosis, but additional signaling pathways of ER stress may also be involved.