CULTURED NEURONS EXPRESSING PHOSPHORYLATED-TAU ARE MORE RESISTANT TO APOPTOSIS INDUCED BY NMDA OR SERUM DEPRIVATION

Apoptosis is a programmed cell death that occurs during the developmen t of the nervous system and in neurodegenerative disorders. Tau protei n is a cytoskeletal component that promotes microtubule polymerization and stabilization. Apoptosis was induced in primary neuronal cultures by a prolonged exposure (16 h) to the NMDA (N-methyl-D-aspartate 20 m u M) or by serum deprivation. The percentages of apoptotic neurons exp ressing phosphorylated tau (AT8) immunoreactivity are comparable in co ntrol and NMDA-exposed cultures (7.5 +/- 1.9 and 6.9 +/- 1.9%, respect ivelly). At the opposite, the percentage of apoptotic neurons expressi ng de-phosphorylated tau (tau1) immunolabellings is dramatically incre ased in NMDA-treated cultures (x2.3 of controls). Similar results were also observed 48 h after serum deprivation. These results demonstrate in vitro that under these conditions, resistant and sensitive cortica l neurons to apoptosis can be partly differentiated according to their phosphorylated tau immunoreactivities.