Enolase1 Alleviates Cerebral Ischemia-Induced Neuronal Injury via Its Enzymatic Product Phosphoenolpyruvate

Stroke is a leading cause of disability and the second leading cause of death among adults worldwide, while the mechanisms underlying neuronal death and dysfunction remain poorly understood. Here, we investigated the differential proteomic profiles of mouse brain homogenate with 3 h of middle cerebral artery occlusion (MCAO) ischemia, or sham, using Coomassie Brilliant Blue staining, followed by mass spectrometry. We identified enolase1 (ENO1), a key glycolytic enzyme, as a potential mediator of neuronal injury in MCAO ischemic model. Reverse transcription polymerase chain reaction and western blotting data showed that ENO1 was ubiquitously expressed in various tissues, distinct regions of brain, and different postnatal age. Immunohistochemical analysis revealed that ENO1 is localized in neuronal cytoplasm and dendrites. Interestingly, the expression level of ENO1 was significantly increased in the early stage, but dramatically decreased in the late stage, of cerebral ischemia in vivo. This dynamic change was consistent with our finding in cultured hippocampal neurons treated with oxygen/glucose deprivation (OGD) in vitro. Importantly, ENO1 overexpression in cultured neurons alleviated dendritic and spinal loss caused by OGD treatment. Furthermore, the enzymatic product of ENO1, phosphoenolpyruvate (PEP), was also synchronously changed along with the dynamic ENO1 level. The neuronal injury caused by OGD treatment in vitro or ischemia in vivo was mitigated by the application of PEP. Taken together, our data revealed that ENO1 plays a novel and protective role in cerebral ischemia-induced neuronal injury, highlighting a potential of ENO1 as a therapeutic target of neuronal protection from cerebral ischemia.