Hypoxia-inducible factor-1α: Dual roles in maintaining neuronal homeostasis and neuronal degeneration via regulation of oxidative stress, mitochondrial dynamics, and bioenergetics.

Hypoxia-inducible factor-1α (HIF-1α) is an oxygen-sensitive transcription factor with an inherently paradoxical biology: under mild-to-moderate hypoxic stress, it functions as a pro-survival regulator, yet under severe or prolonged hypoxia, the same signalling axis promotes apoptotic and autophagic cell death. This duality carries particular significance in neurons, where HIF-1α serves as a critical nexus among neuronal survival, metabolic adaptation, and mitochondrial integrity, and where the consequences of its dysregulation are most profound given their exceptional metabolic demands and limited regenerative capacity. This review examines the molecular determinants governing this protective-to-detrimental switch, integrating key interconnected dimensions: the context-dependent regulation of oxidative stress, the control of mitochondrial bioenergetics, dynamics, mitophagy, and axonal transport; the dual role of HIF-1α in Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and cerebral ischemia; and the therapeutic implications of precision-targeted HIF-1α modulation. Across all these contexts, a consistent pattern emerges: early or acute HIF-1α activation is broadly neuroprotective, while chronic or severe hypoxic stress converts the same pathway into a driver of neurodegeneration. Understanding the determinants of this switch, including hypoxia duration, severity, and cell-type specificity, provides a framework for designing temporally precise therapeutic interventions for hypoxia-related neurological disorders.