Association of APOE with tau-tangle pathology with and without beta-amyloid

This study tested the hypothesis that the association of apolipoprotein E (APOE) with paired helical filament tau (PHF-tau) tangle pathology differs in brains with and without beta-amyloid. Participants were 1056 autopsied individuals from 2 clinical-pathologic cohort studies of aging and Alzheimer's disease (AD), the Religious Orders Study, and the Rush Memory and Aging Project. Neuropathologic measures were obtained using immunohistochemistry targeting beta-amyloid and PHF-tau tangles in 8 brain regions. Linear regression was used to compare the relation of APOE epsilon 4 and epsilon 2 to PHF-tau-tangle density in persons with beta-amyloid relative to persons without beta-amyloid. We found an interaction between APOE epsilon 4 carriers and presence of beta-amyloid (beta = -0.968, p = 0.013) such that the association of APOE epsilon 4 with PHF-tau tangles was much stronger in brains with beta-amyloid. Stratified analysis shows that the association of APOE epsilon 4 with PHF-tau tangles was considerably stronger among those with beta-amyloid (beta = 0.757, p = 1.1 x 10(-15)) compared to those without beta-amyloid which was not significant (beta = -0.201, p = 0.424). Separately, APOE epsilon 2 was associated with fewer tangles in brains with beta-amyloid (beta = -0.425, p = 7.6 x 10(-4)) compared to those without beta-amyloid which was not significant (beta = -0.102, p = 0.506). Thus, the presence of APOE epsilon 4 and epsilon 2 alleles was not associated with PHF-tau tangles in the absence of beta-amyloid. The data provide additional evidence that PHF-tau tangles in the absence of beta-amyloid may reflect a pathologic process distinct from Alzheimer's disease. (C) 2016 Elsevier Inc. All rights reserved.