Neuroglobin in Neuronal Hypoxi and Cerebral Ischemia

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PROJECT SUMMARY/ABSTRACT Cerebral hypoxia and ischemia trigger endogenous protective mechanisms that can prevent or limit brain damage. Understanding these mechanisms may lead to new therapeutic strategies for stroke and related disorders. Neuroglobin (Ngb), a recently discovered monomeric globin that is distantly related to hemoglobin and myoglobin, is expressed predominantly in brain neurons, and appears to modulate hypoxic-ischemic brain injury. We have found that neuronal hypoxia and cerebral ischemia induce Ngb expression, that enhancing Ngb expression reduces and knocking down Ngb expression increases hypoxic neuronal injury in vitro and ischemic cerebral injury in vivo, and that Ngb-overexpressing transgenic mice are resistant to cerebral infarction from occlusion of the middle cerebral artery. However, the mechanisms that underlie hypoxic induction of an neuroprotection by Ngb are unknown. This application is based on the hypothesis that Ngb is a key mediator of endogenous neuroprotection from hypoxic-ischemic injury, and has the long-term goal of identifying new treatments for stroke. The specific aims of the proposed project are to: (1) Determine the role of hypoxia-inducible factor-1 (HIF-1) in hypoxic induction of Ngb expression in vitro; (2) Determine how Ngb protects neurons against hypoxia in vitro; and (3) Evaluate the extent to which mechanisms for hypoxic induction of Ngb and protection from hypoxia by Ngb in vitro are recapitulated during focal cerebral ischemia in vivo.