MAPT and Alzheimer disease: Excessive iron accumulation in CNS injuries drives divergent mechanisms: nigral iron excess in PD promotes LP via Fenton reactions (Ayton and Lei, 2014; You et al., 2015), while AD demonstrates co-localized hippocampal iron deposition with tau/Aβ pathology (Van San et al., 2023; Zhou et al., 2024), and stroke or TBI liberates free iron to amplify oxidative stress (Toro-Urrego et al., 2019; Liu D. et al., 2024).