CELL-TYPE-SPECIFIC ALTERATIONS IN HIPPOCAMPAL CHOLINERGIC SIGNALING IN APOE4 MICE

Cholinergic dysfunction is a central feature of cognitive decline in Alzheimer’s disease (AD), with the APOE4 allele conferring vulnerability to basal forebrain cholinergic neurons. Although the hippocampus is a major target of cholinergic input and undergoes significant degeneration in AD, the impact of disrupted cholinergic signalling on hippocampal circuitry remains unclear. This study examines age-related changes in hippocampal neuronal populations and their association with α7 nicotinic acetylcholine receptor (α7 nAChR) expression, given its interaction with amyloid-β.

Hippocampal brain sections from APOE3 and APOE4 mice at multiple ages were analyzed using immunofluorescence staining for neuronal subtype markers, including β-calretinin and glutamate decarboxylase 67 (GAD67), as well as pathological markers such as amyloid-β and NLRP3. RNAscope in situ hybridization was used to detect nicotinic acetylcholine receptor expression. Images were acquired using a Zeiss confocal microscope and analyzed with Imaris 11.0 software for three-dimensional reconstruction, segmentation, fluorescence intensity measurement, and neuronal quantification.

Preliminary findings reveal distinct expression patterns of β-calretinin and GAD67 across hippocampal subregions, including the dentate gyrus, CA1, and CA3, in APOE3 versus APOE4 mice. These observations suggest that specific neuronal subpopulations exhibit differential vulnerability to cholinergic loss. Ongoing analyses of α7 nAChR and NLRP3 expression aim to delineate the contribution of α7 nAChR to cell-type-specific neuronal vulnerability and neuroinflammatory responses.

This work refines the cellular characterization of cholinergic signalling within the hippocampus and provides insight into APOE4-associated neuronal vulnerability. Identification of cell-type-specific alterations may inform the development of early biomarkers and targeted neuroprotective strategies for Alzheimer’s disease.