Tau maturation in clinicopathological spectrum of Lewy body and Alzheimer’s disease

Abstract

AbstractBackgroundIn Alzheimer’s disease neuropathologic change (ADNC), maturation of neurofibrillary tangles and tau pathology are characterized by posttranslational modifications of tau. ANDC and Lewy body disease (LBD) commonly co‐exist in aging brains and there are overlapping clinical syndromes and heterogeneity in clinical features among cases with mixed ADNC and LBD pathology. Given this clinical and pathological overlap, we examined the postmortem expression of tau conformational epitopes that mark various stages of tangle maturation in clinicopathologic spectrum of Alzheimer’s disease (AD) and LBD.MethodAutopsy‐confirmed cases with diffuse neocortical LBD with/without ADNC (n = 59) were selected (Table1). We used digital histology methods to measure percent area occupied (%AO) with pathology in three regions (middle frontal, anterior cingulate, and superior temporal cortices) immunohistochemically stained with MJF‐R13 (α‐synuclein), NAB228 (beta‐amyloid), and tau monoclonal antibodies marking phosphorylated (AT8), early conformational (MC1, preferentially reactive in pre‐tangles), and C‐terminally truncated tau epitopes (TauC3, preferentially reactive in mature intracellular and ghost tangles). Linear models tested the group comparisons, and correlation between α‐synuclein or beta‐amyloid with outcome of average neocortical tau. In models, %AO were log‐transformed, and age and sex were included as covariates.Resultα‐synuclein was strongly correlated with early tau epitopes labelled with AT8 (β = 1.37, p<0.001) and MC1 (β = 1.20, p<0.001), but not with mature tau epitopes detected by TauC3 (p = 0.38). There were significant positive correlations between all tau epitopes and beta‐amyloid, including TauC3 immunoreactive tau (p≤0.013) (Figure1). In the mixed pathology group, those with clinical LBD had a positive association between α‐synuclein and MC1 (β = 1.61, p = 0.014) and AT8 (β = 1.67, p = 0.005) positive tau, while those with clinical AD had no correlation between α‐synuclein and tau epitopes. There was greater MC1 (β = 3.40, p<0.001), AT8 (β = 3.59, p<0.001), and TauC3 (β = 1.43, p = 0.005) pathology in patients with clinical AD compared to clinical LBD.ConclusionIn LBD, higher α‐synuclein is associated with greater phosphorylated and early tau conformations, but not later conformation of mature tau, which was selectively associated with beta‐amyloid pathology. Our findings suggest that tau pathology may modify the clinical expression of synucleinopathies and C‐terminal truncation of tau may be more closely related to AD pathophysiology than synucleinopathy.