The Role of Neuroglobin in the Neuroprotection of Limb Ischemic Preconditioning in Rats

Recent evidence suggests that limb ischemic preconditioning (LIP) protects neurons against cerebral ischemia-reperfusion injury. However, the mechanisms of LIP are not well understood. Neuroglobin (Ngb) is a recently discovered globin that affords protection against hypoxic/ischemic brain injury. This study was performed to investigate the role of Ngb in the neuroprotection of LIP against brain ischemia and the involvements of mitochondria in the process. The rat global brain ischemic model was used, and the CA1 hippocampus was selected as the observational target. Ngb expression was investigated by RT-PCR and Western blot. Neuropathological evaluation was performed by thionin staining. Mitochondrial membrane potential (Delta psi m), Na+-K+-ATPase activity, and ultrastructure were examined by flow cytometry, spectrophotometry, and transmission electron microscopy, respectively. We also used Ngb antisense oligodeoxynucleotides (AS-ODNs) and Ngb inducer hemin to inhibit or mimic the effect of LIP. We found that LIP significantly up-regulated Ngb expression and protected neurons against ischemia. Furthermore, LIP effectively improved deterioration in the Delta psi m, mitochondrial Na+-K+-ATPase activity, and ultrastructure induced by cerebral ischemia. These effects of LIP were inhibited partly by Ngb AS-ODNs and mimicked by hemin. It could be concluded that up-regulation of Ngb expression played an important role in the neuroprotection induced by LIP, and the Ngb-mediated neuroprotection of LIP was, at least partly, associated with mitochondria.