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 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.
Neuronal hypoxia and brain ischemia activate protective mechanisms, and understanding these mechanisms may lead to new treatments for stroke. Neuroglobin (Ngb), a recently discovered protein related to blood hemoglobin and muscle myoglobin, is found primarily in the brain. In previous work, we found that hypoxia and ischemia increase Ngb expression, that this reduces hypoxic and ischemic neuronal injury, and that mice overexpressing Ngb are resistant to experimental stroke. In this application, we propose to investigate the mechanisms involved in the induction of Ngb expression and in Ngb's protective effects, concentrating on the roles of hypoxia-inducible factor-1 and nitric oxide synthases. The goal of this research is to find new ways to treat stroke and related neurological disorders.
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