Reduced infarct size in neuroglobin-null mice after experimental stroke in vivo

Using neuroglobin-null mice, we estimated the infarct volume 24 hours after permanent middle cerebral artery occlusion using Cavalieri’s Principle, and compared the infarct volume in neuroglobin-null and wild-type mice. Neuroglobin antibody staining was used to examine neuroglobin expression in the infarct area of wild-type mice.Infarct volumes 24 hours after permanent middle cerebral artery occlusion were significantly smaller in neuroglobin-null mice than in wild-types (p？<？0.01). Neuroglobin immunostaining of the penumbra area revealed no visible up-regulation of neuroglobin protein in ischemic wild-type mice when compared to uninjured wild-type mice. In uninjured wild-type mice, neuroglobin protein was seen throughout cortical layer II and sparsely in layer V. In contrast, no neuroglobin-immunoreactive neurons were observed in the aforementioned layers of the ischemia injured cortical area, or in the surrounding penumbra of ischemic wild-type mice. This suggests no selective sparing of neuroglobin expressing neurons in ischemia.Neuroglobin-deficiency resulted in reduced tissue infarction, suggesting that, at least at endogenous expression levels, neuroglobin in itself is non-protective against ischemic injury.Neurons are particularly sensitive to hypoxia- and ischemia-related stress due to the very high metabolic demand of the brain [1] and were believed to lack an endogenous oxygen storage/diffusion system. In 2000 Burmester and co-workers discovered a neuronal specific heme-globin, Neuroglobin (Ngb), in the mouse brain [2]. Due to structural similarity with hemoglobin and myoglobin, and ability to bind oxygen, Ngb was suggested to function as global oxygen provider or reactive oxygen species (ROS) scavenger in the brain [3-6]. Ngb was therefore proposed to be a novel pharmacological target in combating neurodegenerative disorders [7] (for review see Dietz 2011 [8]). A number of in vitro and in vivo studies have addressed the role of Ngb in neuroprotection and