Neuroglobin is a monomeric globin protein expressed predominantly in brain neurons that functions as an endogenous neuroprotectant under hypoxic and ischemic stress. The protein contains a bis-histidyl six-coordinate heme-iron atom that binds dioxygen, carbon monoxide, and nitric oxide. Although neuroglobin's low tissue concentration and high oxygen affinity argue against a primary oxygen-transport role, it contributes to neuroprotection through multiple mechanisms: in its deoxygenated state, it exhibits nitrite reductase activity to produce nitric oxide, and acts as a guanine nucleotide dissociation inhibitor (GDI) toward G-protein alpha subunits to facilitate cell survival signaling in response to hypoxia and oxidative stress 12. Neuroglobin expression is upregulated by cerebral ischemia and hypoxia, and overexpression reduces hypoxic neuronal injury and ischemic brain damage in vivo, whereas knockdown exacerbates injury 13. Recent evidence suggests neuroglobin protects dopaminergic neurons in Parkinson's disease models through direct interaction with mitochondrial complex I subunit NDUFA10, restoring Complex I activity and suppressing apoptosis 4. Neuroglobin also shows protective effects in Alzheimer disease and guards against oxidative stress-induced injury 5. However, neuroglobin overexpression paradoxically facilitates survival of cancer cells, positioning it as a switch point between cell death and survival across different disease contexts 5.