Iron on trial: recasting the role of iron in neurodegeneration

Iron is critical for numerous neurophysiological functions, while its dysregulation is potentially hazardous for neurodegeneration through oxidative stress and ferroptosis. For decades, elevated brain iron levels observed in neurodegenerative diseases such as Alzheimer's, Parkinson's and amyotrophic lateral sclerosis was presumed to drive disease progression; a hypothesis that propelled clinical trials of strong iron chelators like deferiprone. Results from these trials, however, have challenged this paradigm, with deferiprone markedly worsening outcomes in patients with Alzheimer's disease and, in certain contexts, patients with Parkinson's disease. These findings underscore the vital role of iron for brain health and suggest functional compensatory mechanisms that could become deleterious at the extremes of iron distribution (both low and high levels). Here, we outline an evolving understanding of iron's role in neurodegeneration, and we explore pathways for therapeutic development strategies that mitigate potential iron-mediated damage, while preserving its essential functions in the brain.