High Affinity Staining for Histological Immunoreactivity revealed phosphorylated tau within amyloid-cored plaques in the brain of AD model mice.

Abstract

The historical pathology of the brain in Alzheimer's disease (AD) is characterized by the amyloid cascade hypothesis, in which amyloid β protein accumulates in the extracellular parenchyma as senile plaque and triggers phosphorylation of microtubule-associated protein tau for forming neurofibrillary tangle in the human neurons. Whether these protein existences differed in the brain parenchyma, the relationship of these proteins of accumulation mechanisms is unknown. In the case of brain pathological analysis, the level of phosphorylation for tau has been decreased in the paraffin-embedded sections compared with biochemical analysis. Here, we have established and developed a method to highlight phosphorylated proteins including tau with frozen sections, as the HIGh Affinity Staining Histological Immunoreactivity (HIGASHI) method. Using this HIGASHI method, hyper-phosphorylated tau could be detected in the mossy fiber on the frozen brain sections of wild-type mice under hypothermia conditions. Here, we attempted the HIGASHI method to detect senile plaque and phosphorylated tau in the AD model mouse brains. Phosphorylated tau was found in the center of senile plaques in the mice brain parenchyma. Additionally, these senile plaques colocalized with microglia cells in the center of senile plaques. Interestingly, senile plaques have been made in the tau knock-out mice brains expressing human amyloid precursor protein. Thus, senile plaques have been composed of Aβ and phosphorylated tau in the brain, but tau isn't necessary for bearing senile plaques.