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Abstract
Oxidative stress is a major mediator of neurodegeneration. In this study, we tested
the effects of oxidative stress induced by a brief exposure to hydrogen peroxide (H(2)O(2))
on the phosphorylation state of the tau protein in oligodendrocytes (OL). Primary
oligodendrocyte cultures prepared from newborn rat brains were exposed to millimolar
concentrations of H(2)O(2) for up to 15 min, and then incubated in normal medium for
up to 12 h. The treatment caused morphological degeneration of OL characterized by
the loss of cellular processes apparent approximately 3 h after H(2)O(2) exposure.
The morphological degeneration was preceded by a profound dephosphorylation of tau
protein revealed by immunoblot using monoclonal tau-1 antibody that recognizes the
dephosphorylated epitope. The dephosphorylated form increased dramatically during
H(2)O(2) exposure, peaked after 2 h of post-exposure, and returned to the baseline
level within 12 h. Total tau protein levels were not changed in the course of the
experiment as judged by immunoblotting with phosphorylation-insensitive tau-5 and
46-1 monoclonal antibodies. Our finding demonstrates that oxidative stress induces
a rapid but transient dephosphorylation of tau protein that may underlie morphological
degeneration of OL.