How Brain Iron Shapes Development, Aging, and Neurodegeneration

Iron is far more than a simple oxygen carrier in the brain — it is a master regulator of neural development, aging trajectories, and neurodegenerative disease risk. This comprehensive 2025 review from Wenzhou Medical University synthesizes the current understanding of brain iron metabolism and its implications across the human lifespan, with particular attention to clinical detection and therapeutic opportunities.

Iron crosses the blood-brain barrier primarily via the transferrin–transferrin receptor 1 (TFR1) system on brain microvascular endothelial cells, where Fe³⁺ is endocytosed, reduced to Fe²⁺, and exported into the brain parenchyma via ferroportin. Non-transferrin-bound iron (NTBI) provides a secondary transport route. Astrocytes, neurons, oligodendrocytes, and microglia each employ distinct uptake and efflux mechanisms — including DMT1, ZIP14, H-ferritin/Tim-2 receptors, and the FPN1/hephaestin pathway — with the iron regulatory protein (IRP)/iron response element (IRE) system providing post-transcriptional fine-tuning across all cell types.

During the first 1,000 days of life, iron is essential for neuronal dendritic arborization, mitochondrial ATP production, neural differentiation, oligodendrocyte maturation, and myelin synthesis. Iron deficiency — whether systemic or localized due to dysfunctional ceruloplasmin or DMT1 — impairs hippocampal neurogenesis, slows auditory nerve conduction, and reduces cortical dendritic complexity. These early deficits can translate into persistent memory, cognitive, and behavioral problems that extend into adulthood, underscoring the urgency of monitoring maternal and infant iron status.

In physiological aging, iron progressively and selectively accumulates in the basal ganglia, hippocampus, thalamus, and cortex. This redistribution promotes intracellular redox imbalance, lipid peroxidation via the Fenton reaction, and mitochondrial dysfunction, collectively accelerating cellular senescence. Elevated brain iron correlates with cognitive decline even in neurologically healthy older adults, and iron-sensitive MRI sequences such as quantitative susceptibility mapping (QSM) and R2* relaxometry can non-invasively track these changes, offering windows for early intervention.

In neurodegenerative disease, brain iron overload plays a central pathogenic role. In Alzheimer's disease, iron co-localizes with amyloid-beta plaques and tau tangles, catalyzing ROS production and ferroptosis. In Parkinson's disease, dopaminergic neurons of the substantia nigra accumulate iron, promoting alpha-synuclein aggregation and neuronal death. Huntington's disease features striatal iron accumulation linked to mitochondrial complex II dysfunction, while Friedreich's ataxia involves frataxin deficiency causing mitochondrial iron overload and oxidative damage in cerebellar and dorsal root ganglion neurons. Iron chelation strategies — including deferiprone, deferoxamine, and novel brain-penetrant agents — show therapeutic promise across these conditions, though clinical translation requires careful balancing of efficacy against the risk of systemic iron depletion.