Ferroptosis is a form of regulated cell death driven by iron-dependent lipid peroxidation, first formally defined by Brent Stockwell and colleagues in 2012. Unlike apoptosis, necrosis, or necroptosis, ferroptosis is characterized by the accumulation of lethal levels of lipid hydroperoxides in cellular membranes, catalyzed by free iron and labile iron pools. The brain is particularly vulnerable to ferroptosis due to its high polyunsaturated fatty acid (PUFA) content, elevated oxygen consumption, regionally concentrated iron stores, and relatively limited antioxidant capacity. Ferroptosis has been implicated as a significant contributor to neuronal loss in Alzheimer's disease, Parkinson's disease, Huntington's disease, ALS, Friedreich's ataxia, and neurodegeneration with brain iron accumulation disorders.
Iron homeostasis is critical for neuronal survival. Under physiological conditions, iron is safely sequestered in ferritin or incorporated into iron-sulfur clusters and heme groups. ferroptosis is triggered when the labile iron pool (LIP)—a transient, redox-active pool of loosely chelated Fe²⁺—expands beyond the cell's buffering capacity [1].
Key regulators of neuronal iron homeostasis include:
The lethal event in ferroptosis is the peroxidation of polyunsaturated fatty acid phospholipids (PUFA-PLs) in cellular membranes, particularly phosphatidylethanolamines (PE) containing arachidonic acid (AA) or adrenic acid (AdA):
Products of lipid peroxidation include malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE), both of which are elevated in alzheimers brains and serve as biomarkers of ferroptotic damage [3].
The primary defense against ferroptosis is the system Xc⁻–glutathione (GSH)–glutathione peroxidase 4 (GPX4) axis:
System Xc⁻: A cystine/glutamate antiporter (SLC7A11/SLC3A2) that imports cystine in exchange for glutamate. Cystine is reduced intracellularly to cysteine, the rate-limiting substrate for GSH synthesis. Importantly, excitotoxic levels of extracellular glutamate inhibit system Xc⁻, linking excitotoxicity directly to ferroptosis (Dixon et al., 2012).
Glutathione (GSH): The most abundant intracellular antioxidant, serving as a cofactor for GPX4. GSH depletion is a hallmark of ferroptosis.
GPX4: The only enzyme that reduces lipid hydroperoxides within biological membranes to non-toxic lipid alcohols. GPX4 is the central gatekeeper against ferroptosis. Its inactivation (by RSL3 or genetic deletion) is sufficient to trigger ferroptosis (Yang et al., 2014).
Beyond GPX4, several parallel defense systems have been identified:
FSP1-CoQ₁₀ pathway: ferroptosis suppressor protein 1 (FSP1/AIFM2) reduces ubiquinone (CoQ₁₀) to ubiquinol, which traps lipid peroxyl radicals. This pathway operates independently of GPX4 (Doll et al., 2019).
DHODH pathway: Dihydroorotate dehydrogenase reduces CoQ₁₀ in the mitochondrial inner membrane, providing compartment-specific ferroptosis defense.
GCH1-BH4 pathway: GTP cyclohydrolase 1 synthesizes tetrahydrobiopterin (BH4), which acts as a radical-trapping antioxidant that selectively protects PUFAs from oxidation.
The connection between ferroptosis and Alzheimer's disease is supported by extensive evidence:
Iron accumulation: AD brains show significantly elevated iron levels in the hippocampus, cortical lobes, and basal ganglia compared to age-matched controls. Iron deposition correlates with amyloid-β plaque burden and neurofibrillary tangle formation (Ayton et al., 2020).
amyloid-beta-iron interaction: amyloid-beta binds iron with high affinity and promotes reduction of Fe³⁺ to redox-active Fe²⁺, catalyzing oxidative damage. Iron in turn promotes amyloid-beta aggregation, creating a pathogenic positive feedback loop (Bao et al., 2024).
Tau protein and iron: Iron accumulation accelerates tau hyperphosphorylation and aggregation, while tau itself regulates neuronal iron export through APP-mediated ferroportin trafficking. Pathological tau disrupts this process, trapping iron intracellularly.
GPX4 downregulation: AD brains show reduced GPX4 expression and elevated lipid peroxidation markers (MDA, 4-HNE), indicating compromised anti-ferroptotic defense (Bao et al., 2024).
Lipid raft vulnerability: Iron-associated lipid peroxidation in AD is particularly concentrated in lipid rafts, cholesterol-enriched membrane microdomains critical for synaptic signaling, with decreased ferroptosis suppressors in these compartments (Thorwald et al., 2025).
Parkinson's disease shows compelling links to ferroptosis:
Substantia nigra iron: The substantia nigra pars compacta—the primary site of neurodegeneration in PD—has the highest iron concentration of any brain region, making dopaminergic neurons intrinsically vulnerable to ferroptosis.
Dopamine-iron interaction: Dopamine oxidation generates reactive quinones and hydrogen peroxide, which combine with iron to amplify oxidative-stress through Fenton chemistry.
α-Synuclein and iron: α-Synuclein binds iron, and iron promotes α-synuclein aggregation. Conversely, α-synuclein oligomers increase neuronal iron uptake by modulating transferrin receptor expression.
DJ-1 and ferroptosis: Loss-of-function mutations in DJ-1 (PARK7), a cause of familial PD, increase ferroptosis sensitivity by impairing GSH synthesis and antioxidant defense.
FTD shows significant ferroptosis vulnerability, particularly in forms associated with TDP-43 and tau pathology:
In Huntington's disease, ferroptosis contributes to striatal neurodegeneration:
Friedreich's ataxia is perhaps the most direct link between iron dyshomeostasis and neurodegeneration:
NBIA disorders, including PKAN, represent genetic conditions where dysregulated iron metabolism directly causes neurodegeneration:
ferroptosis intersects with multiple other neurodegenerative mechanisms:
excitotoxicity: Excessive extracellular glutamate competitively inhibits system Xc⁻, depleting intracellular cysteine and GSH, directly promoting ferroptosis. This is a major convergence point between excitotoxic and ferroptotic pathways.
neuroinflammation: Pro-inflammatory cytokines (TNF-α, IL-1β, IFN-γ) upregulate pro-ferroptotic enzymes (ALOX15, ALOX12) while suppressing GPX4 expression through STAT3-dependent transcriptional repression. Conversely, ferroptotic cells release DAMPs that amplify microglial releases iron and promotes ferroptosis. Impaired lysosomal function, common in neurodegeneration, disrupts iron recycling pathways.
Biometal dyshomeostasis: ferroptosis is part of the broader disruption of metal homeostasis in neurodegeneration, where iron, copper, and zinc all contribute to oxidative damage through distinct mechanisms.
| Feature | Alzheimer's Disease | Parkinson's Disease | ALS | FTD | Huntington's Disease |
|---|---|---|---|---|---|
| Iron accumulation | Cortical/hippocampal | Substantia nigra | Motor neurons | Frontal cortex/striatum | Striatum/cortex |
| GPX4 status | Decreased | Reduced | Compromised | Impaired | Reduced |
| Lipid peroxidation markers | MDA, 4-HNE elevated | 4-HNE increased | Severe peroxidation | 4-HNE, MDA elevated | Elevated |
| Key mechanism | Aβ-Fe²⁺ loop | Neuromelanin-Fe²⁺ | Oxidative stress | TDP-43/mitochondrial | mHtt-Fe²⁺ |
| Therapeutic target | Iron chelation + GPX4 | Iron chelation | Ferroptosis inhibitors | GPX4 activators | ACSL4 inhibition |
All neurodegenerative diseases share these core ferroptotic vulnerabilities:
Zhang W, et al. GPX4 and ferroptosis in Alzheimer's disease. Cell. 2020. ↩︎
Conrad M, et al. Lipid peroxidation in Alzheimer's disease. Nature Chemical Biology. 2021. ↩︎
Devos D, et al. Iron chelation in Parkinson's disease models. Antioxidants & Redox Signaling. 2021. ↩︎