Cerebral ischemic preconditioning refers to a transient, sublethal ischemic event that results in tolerance to subsequent lethal cerebral ischemia. IPC is believed to trigger an intrinsic neuroprotective mechanism. Most studies of brain ischemic preconditioning in vivo and in vitro have been limited to neurons. However, astrocytes comprise the majority of brain cells in mammals and play an important role in the brain��s repair and inflammatory responses by producing various cytokines and growth factors. They are essential to preserving neural tissue and restricting inflammation after brain injury. Neurons cannot survive in the brain if adjacent astrocytes are damaged during ischemia or other brain insults. Nonetheless, it remains unknown whether IPC affects astrocyte cell death outcomes after simulated ischemia. TLR4 activation in response to cerebral ischemia leads to an excessive inflammatory response that plays a deleterious role in cerebral ischemic injury. However, evidence suggests that TLR4 might also be involved in IPC-induced ischemic tolerance. Studies suggest that preconditioning with TLR4 ligand lipopolysaccharide enhances TLR4 signaling through the MyD88-independent pathway, thereby suppressing the ischemia-induced inflammatory response. Unlike TLR4, TLR3 signals exclusively through the MyD88- independent pathway. Interestingly, deletion of TLR3 in mice did not alter infarction volume after stroke compared with that in wild-type mice. Additionally, Bsibsi et al. reported that medium from human astrocytes conditioned with TLR3 ligand polyinosinic:polycytidylic acid improved neuronal survival in human brain slice cultures and that Poly I:C freshly added to control medium promoted neuronal survival equally well. It was also reported that acute treatment of primary mouse cortical cells with Poly I:C protects against oxygen-glucose deprivation -induced cell death. Moreover, Poly I:C induces protracted resistance of human astrocytes to H2O2 SC 66 toxicity, whereas TLR3 contributes to ischemic injury in the gut. In our study, we examined the protective potential of IPC in vivo and in vitro to clarify the role of astrocytes in IPC-induced cerebral ischemia tolerance. Our results showed that IPC in vivo with three brief episodes of bilateral carotid artery occlusion reduced brain SCH 23390 hydrochloride damage in a permanent focal cerebral ischemia model and that IPC in vitro with transient OGD reduced post-injurious OGD induced damage to astrocytes.