Dysregulated polyamine metabolism in neurological disorders: molecular mechanisms and therapeutic opportunities.

Polyamines (PAs), principally putrescine (Put), spermidine (Spd), and spermine (Spm), are ubiquitous aliphatic polycations that regulate nucleic-acid interactions, ion-channel activity, autophagy, redox balance, proteostasis, and immune signaling. Growing genetic, multi-omics, and experimental evidence indicates that disruption of PA biosynthesis, catabolism, acetylation, and transport contributes to neurological disease. In Alzheimer's disease (AD), altered PA flux intersects with Tau and amyloid-β (Aβ) pathology, methylation imbalance, oxidative stress, and impaired autophagic clearance. In Parkinson's disease (PD), PA transport and interconversion are linked to lysosomal dysfunction, mitochondrial stress, and α-synuclein toxicity; ATP13A2-associated Kufor-Rakeb syndrome further illustrates the neurological consequences of defective lysosomal PA transport. PA dysregulation is also implicated in amyotrophic lateral sclerosis (ALS), diabetic retinopathy, Snyder-Robinson syndrome, epilepsy, Bachmann-Bupp syndrome, and cerebral ischemia. This review integrates disease-specific evidence with four interconnected mechanisms-autophagy, oxidative stress, proteostasis, and neuroinflammation-and discusses therapeutic approaches including direct Spd administration, modulation of PA-metabolic enzymes and transporters, and combination strategies. Because PAs can exert both protective and toxic effects depending on concentration, cellular compartment, and disease context, translation will require CNS-relevant biomarkers, dose and route optimization, and explicit consideration of blood-brain barrier constraints.