Science Note / Ferroptosis
The Polyamine Paradox: Polyamines as Regulators of Ferroptosis
Polyamines: Abundant and Multifunctional
Polyamines are ubiquitous, evolutionarily conserved cations containing multiple amine groups. Their dysregulation has pleiotropic implications in aging and pathology1, 2. Present at millimolar concentration ranges in cells, polyamines have been documented to contribute to many essential cellular processes, including:
Novel Interactions Between Polyamines and Ferroptosis
Recent work6, 7 revealed a previously uncharacterized role for polyamines: direct chelation of labile Fe2+. Sharma et al. designed a CRISPR screen to identify genetic sensitizers to polyamine depletion. Among the top hits, they identified the central ferroptosis suppressor, GPX4.
Through careful dissection of the ferroptosis pathway, investigation of known polyamine functions, in vitro Fe2+ binding assays, and in vivo imaging, the authors demonstrated that polyamine depletion increases labile iron pools. The authors propose that direct Fe2+ buffering by polyamines may explain the lethal interaction between polyamine depletion and GPX4 knockout.
Polyamine Paradox: Ferroptosis Suppression or Sensitization?
A previous study also implicated polyamines in ferroptosis, however, this investigation identified an inverse role: sensitization8. Earlier observations by Bi et al. showed enhanced sensitivity of A549 and HT1080 cells upon exogenous treatment with ferroptosis inducers and polyamines8. Their investigation identified polyamine catabolism as the mechanism for this stimulus-interaction.
Cells maintain multiple mechanisms to stabilize polyamine levels. Upon polyamine overload, the enzymes PAOX and SMOX can disassemble spermine and spermidine leaving H2O2 and aldehydes as toxic byproducts1 which may sensitize cells to ferroptosis.
In agreement, Sharma et al. observed a concentration-dependent rescue of polyamine-depleted GPX4 knockout cells, with only moderate spermine and spermidine concentrations rescuing the conditional phenotype7. Likewise, Li et al. showed that exogenous spermine supplementation plays a suppressive role, potentially through direct Fe2+ buffering, when polyamine catabolism is inhibited or knocked out6.
Together, these studies highlight a novel, complex, and quasi-paradoxical role of polyamines in the regulation of ferroptosis depending on their concentrations and metabolic context.
← Previous Science NoteResearch Highlights
Polyamines buffer labile iron to suppress ferroptosis
A CRISPR screen identified the key ferroptosis suppressor, GPX4, as a sensitizer to polyamine depletion. Their investigation demonstrated that spermine and spermidine act as key buffers for the labile iron pool potentially through direct coordination of cellular Fe2+.
Highlighted Techniques
Sharma et al. showed coordination of Fe2+ by polyamines suppressed reactivity with FerroOrange, a Fe2+ specific probe. In combination with competitive Ferrozine binding assays and Mössbauer spectroscopy these provided compelling in vitro data to demonstrate direct, polyamine coordination of Fe2+.
Polyamine-mediated ferroptosis amplification acts as a targetable vulnerability in cancer
The authors showed polyamine catabolism by PAOX and SMOX acts as a sensitizer to ferroptosis
Highlighted Techniques
Using DCFH-DA, the authors showed that polyamine supplementation induced ROS accumulation dependent on PAOX and SMOX. Polyamine pretreatment followed by ferroptosis induction increased cytotoxicity and ROS accumulation compared with either treatment alone.
Experimental Workflow
Dissecting the Ferroptosis Pathway
From treatment validation to subcellular labile iron detection and lipid peroxidation
Cellular Iron
Measure the labile iron abundance and subcellular localization using fluorescent probes to verify ferroptosis in your treatment.
- Measure total cellular iron
- Quantify the labile iron pool at the cellular and organelle level, including mitochondria and lysosomes
Monitor expression and accumulation of iron chelators
Lipid Peroxidation
Measure accumulation of lipid peroxidation products to confirm ferroptosis is occurring in your treatment
- Quantify intracellular ROS
- Monitor lipid peroxidation,
lipid radical, and lipid peroxide accumulation - Measure cellular glutathione
- Measure malondialdehyde (MDA) accumulation
Cell Viability
Confirm ferroptosis suppressors or inducers are having a measurable impact on cell viability/cytotoxicity
Application Note
Real experimental data, practical readouts①–⑥ indicate measurement targets corresponding to the kits and probes listed under Products in Use.
A549 cells in MEM, incubated at 37°C for 3 h.
Control, 0 μmol/l erastin. Treatment, 100 μmol/l erastin.
In each microscopy row, control is on the left and erastin treatment is on the right.
Experimental Example
Induction of Ferroptosis via System Xc− Inhibition
We investigated the transition of cellular metabolisms in A549 cells treated with erastin, a known ferroptosis inducer. Our results revealed the following.
Results
- The inhibition of cystine uptake by erastin led to a depletion of cysteine, which in turn increased the compensatory uptake of other amino acids.
- The depletion of cysteine resulted in a decrease in glutathione levels and an increase in Fe2+, ROS, and lipid peroxides, all of which are recognized markers of ferroptosis.
- Cell Line
- A549
- Incubation Conditions
- MEM, 37°C, 3 h
0 or 100 μmol/l erastin
- Readouts
- Amino acid uptake
Cystine uptake
Glutathione
Fe2+
Total ROS
Lipid peroxides
Products in Use
- ① Amino Acid Uptake
Amino Acid Uptake Assay Kit - ② Cystine Uptake
Cystine Uptake Assay Kit - ③ Intracellular glutathione
GSSG/GSH Quantification Kit - ④ Intracellular labile Fe
FerroOrange - ⑤ Intracellular total ROS
ROS Assay Kit -Highly Sensitive DCFH-DA- - ⑥ Lipid Peroxides
Liperfluo
References
- 1. Casero and Pegg (2010). Polyamine catabolism and disease. Biochem J. DOI: 10.1042/BJ20090598
- 2. Schibalski et al. (2024). The role of polyamine metabolism in cellular function and physiology. Am J Physiol Cell Physiol. DOI: 10.1152/ajpcell.00074.2024
- 3. Lee et al. (2019). Promotion of homology-directed DNA repair by polyamines. Nat Commun. DOI: 10.1038/s41467-018-08011-1
- 4. Cooper et al. (1983). Identification of the hypusine-containing protein hy+ as translation initiation factor eIF-4D. PNAS. DOI: 10.1073/pnas.80.7.1854.
- 5. Dhara et al. (2020). Polyamine regulation of ion channel assembly and implications for nicotinic acetylcholine receptor pharmacology. Nat Commun. DOI: 10.1038/s41467-020-16629-3
- 6. Li et al. (2026). Spermine is an endogenous iron chelator that inhibits ferroptosis. Nature. DOI: 10.1038/s41586-026-10597-2
- 7. Sharma et al. (2026). Polyamines buffer labile iron to suppress ferroptosis. Cell. DOI: 10.1016/j.cell.2026.07.040
- 8. Bi et al. (2024). Polyamine-mediated ferroptosis amplification acts as a targetable vulnerability in cancer. Nat Commun. DOI: 10.1038/s41467-024-46776-w.
