Orexin-A alleviates cerebral ischemia-reperfusion injury by inhibiting endoplasmic reticulum stress-mediated apoptosis

Orexin-A (OXA) protects neurons against cerebral ischemia-reperfusion injury (CIRI). Endoplasmic reticulum stress (ERS) induces apoptosis after CIRI by activating caspase-12 and the CHOP pathway. The present study aimed to determine whether OXA mitigates CIRI by inhibiting ERS-induced neuronal apoptosis. A model of CIRI was established, in which rats were subjected to middle cerebral artery occlusion with ischemic intervention for 2 h, followed by reperfusion for 24 h. Neurological deficit examination and 2,3,5-triphenyltetrazolium chloride staining were performed to assess the level of CIRI and neuroprotection by OXA. Expression levels of ERS-related proteins and cleaved caspase-3 were measured via western blotting, while the rate of neuronal apoptosis in the cortex was determined using a TUNEL assay. OXA treatment decreased the infarct volume of rats after CIRI and attenuated neuron apoptosis. Furthermore, administration of OXA decreased the expression levels of GRP78, phosphorylated (p)-PERK, p-eukaryotic initiation factor-2α, p-inositol requiring enzyme 1α, p-JNK, cleaved caspase-12, CHOP and cleaved caspase-3, all of which were induced by CIRI. Collectively, these findings suggested that OXA attenuated CIRI by inhibiting ERS-mediated apoptosis, thus clarifying the mechanism underlying its neuroprotective effect and providing a novel therapeutic direction for the treatment of CIRI.