Pyroglutamylated amyloid-ß is associated with hyperphosphorylated tau and severity of Alzheimer's disease.

Pyroglutamylated amyloid-ß (pE(3)-Aß) has been suggested to play a major role in Alzheimer's disease (AD) pathogenesis as amyloid-ß (Aß) oligomers containing pE(3)-Aß might initiate tau-dependent cytotoxicity. We aimed to further elucidate the associations among pE(3)-Aß, full-length Aß and hyperphosphorylated tau (HP-τ) in human brain tissue. We examined 41 post mortem brains of both AD (n = 18) and controls. Sections from frontal and entorhinal cortices were stained with pE(3)-Aß, HP-τ and full-length Aß antibodies. The respective loads were assessed using image analysis and western blot analysis was performed in a subset of cases. All loads were significantly higher in AD, but when using Aß loads as independent variables only frontal pE(3)-Aß load predicted AD. In frontal and entorhinal cortices pE(3)-Aß load independently predicted HP-τ load while non-pE(3)-Aß failed to do so. All loads correlated with the severity of AD neuropathology. However, partial correlation analysis revealed respective correlations in the frontal cortex only for pE(3)-Aß load only while in the entorhinal cortex respective correlations were seen for both HP-τ and non-pE(3)-Aß loads. Mini Mental State Examination scores were independently predicted by entorhinal HP-τ load and by frontal pE(3)-Aß load. Here, we report an association between pE(3)-Aß and HP-τ in human brain tissue and an influence of frontal pE(3)-Aß on both the severity of AD neuropathology and clinical dementia. Our findings further support the notion that pE(3)-Aß may represent an important link between Aß and HP-τ, and investigations into its role as diagnostic and therapeutic target in AD are warranted.