Tau Mislocation in Glucocorticoid-Triggered Hippocampal Pathology.

Area of Science:

• Neuroscience
• Cellular Biology
• Endocrinology

Background:

• High glucocorticoid (GC) exposure causes neuronal atrophy and cognitive deficits.
• Mechanisms of GC-induced dendritic remodeling and spine loss are not fully understood.
• Sustained GC elevations are linked to neurodegeneration via Tau hyperphosphorylation and mislocation, relevant to Alzheimer's disease (AD).

Purpose of the Study:

• To investigate the impact of prolonged GC treatment on Tau intracellular localization and phosphorylation in different cellular compartments.
• To elucidate the cellular mechanisms underlying GC-associated synaptic damage and neuronal disconnection.

Main Methods:

• Biochemical analysis of Tau protein in rat hippocampus.
• Ultrastructural analysis of neuronal and synaptic morphology.
• Monitoring Tau phosphorylation status at specific epitopes (Ser396/404, Thr231, Ser262).

Main Results:

• Prolonged GC administration caused cytosolic and dendritic Tau accumulation in rat hippocampus.
• GC treatment led to Tau hyperphosphorylation at specific sites (Ser396/404, Thr231, Ser262).
• Chronic GC exposure increased synaptic Tau levels, with altered phosphorylation patterns at the synapse (increased Ser396/404, decreased Thr231), paralleled by reduced synaptic scaffolding proteins (PSD-95, Shank) and spine loss.

Conclusions:

• GC-induced Tau missorting and hyperphosphorylation contribute to synaptic atrophy and neuronal disconnection.
• These findings reveal Tau's role in GC-evoked synaptic damage, independent of AD pathology.
• This study deepens the understanding of GC neurotoxicity mechanisms.