Association of HFE mutations with neurodegeneration and oxidative stress in Alzheimer's disease and correlation with APOE

Oxidative stress enhanced by transition metals such as iron forms an attractive hypothesis for neurodegeneration in Alzheimer's Disease (AD). Iron is increased in the brain in AD, but whether this is a primary abnormality or the result of secondary accumulation is unclear. Among several genetic loci associated with AD, the locus at chromosome 6p21 contains the hereditary hemochromatosis gene HFE. To determine whether a genetic predisposition to iron accumulation is associated with AD, we evaluated three hemochromatosis-assciated HFE mutations andAPOE in cognitively and histopathologically evaluated subjects with AD, mild cognitive impairment (MCI), non-demented controls with AD-like pathologic changes defined by Braak stage ≥ 3 (high pathology controls (HPC)), and non-demented controls without significant histologic changes (low-pathology controls (LPC)). In a subset, we examined ventricular (CSF) fluid F₂-isoprostane (F₂-IsoP) levels, a marker of lipid peroxidation. Seventeen subjects demonstrated homozygous or compound heterozygous HFE mutations, 13 (9.4%) in the AD/MCI group (P=0.019 vs. LPC) and four (20%) in the HPC group (P=0.006, P< 0.05 with Bonferroni correction vs. LPC). In contrast, the APOE4 allele frequency was increased only in the AD/MCI patients (P < 10-3 vs. HPC, P < 10 ^-6 vs. LPC). F₂-IsoP levels were increased in AD subjects with any HFE mutation versus wild type HFE (P = 0.027). Although confirmation is required, these findings suggest that HFE mutations are associated with increased oxidative stress and Braak stage, and that HFE and APOE genotypes are different between AD patients, high pathology and low pathology controls.