Female-biased astrocytic priming shapes early locus coeruleus vulnerability in an Aβ oligomer milieu.

INTRODUCTION

The locus coeruleus (LC) is an early site of Alzheimer's disease (AD) pathology, yet the role of brainstem astrocytes in early, sex-dependent vulnerability remains unclear.

METHODS

In 2- to 3-month-old APP/PS1 mice, we combined in vivo proton magnetic resonance spectroscopy (MRS) of the brainstem with region-resolved molecular analyses, including quantitative real-time polymerase chain reaction, amyloid beta 42 (Aβ42) oligomers enzyme-linked immunosorbent assay, lactate assay, immunohistochemistry, immunoblotting, astrocyte isolation, and 3D structural assessment. Environmental enrichment (EE) served as a non-pharmacologic intervention.

RESULTS

Females exhibited higher brainstem Aβ42 oligomers and an astrocyte-weighted MRS profile. Pontine glial fibrillary acidic protein (GFAP), complement component 3, and nuclear factor kappa-light-chain-enhancer of activated B cells were selectively upregulated without pan-reactive astrocytic and microglial markers. LC-restricted GFAP elevation occurred without changes in astrocyte counts or morphology, indicating a "primed" state. Females also showed higher lactate levels, increased monocarboxylate transporter 2 expression, and elevations in selected oxidative phosphorylation-associated transcripts, and reduced astrocytic alpha 2A-adrenergic receptor expression. EE normalized noradrenergic and pontine astrocytic changes.

DISCUSSION: Female-biased, LC-centric astrocytic priming emerges early in this amyloid-driven model and is modifiable.