Accumulation of tau induced in neurites by microglial proinflammatory mediators

Aggregated fibrillary microtubule-associated protein tau is the major component of neurofibrillary tangles in Alzheimer’s disease. The exact molecular mechanism of tau aggregation is unknown. Microglial cell activation and migration toward amyloid-β plaques precede the appearance of dysmorphic neurites and formation of neurofibrillary tangles. Here, we analyzed the accumulation of tau at a distance range of expected spontaneous aggregation by fluorescence lifetime-based Forster resonance energy transfer in cultured primary murine neurons cotransfected with the human tau gene tagged to the green fluorescent protein variants Citrine (tau-Citrine) and Cerulean (tau-Cerulean). No spontaneous accumulation of cotransfected tau-Citrine and tau-Cerulean was detected in untreated neurons. Coculture of neurons with activated microglia induced aggregation of tau in neurites. Treatment of neurons with tumor necrosis factor-α (TNF-α) stimulated reactive oxygen species generation and resulted in the accumulation of tau...