Entorhinal Cholecystokinin in Alzheimer’s Disease: Its Earliest Vulnerability and Rescue Effects across Different Disease Stages 

Abstract

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder characterized by cognitive decline. The entorhinal cortex (Ent) is among the earliest regions affected, and its neuropeptide cholecystokinin (CCK) supports neocortical-associated memory. Although previous work has demonstrated that CCK treatment rescues cognition and neuroplasticity in aged AD mice, the relationship between CCK expression, synaptic function, and cognitive decline during aging remains poorly understood.

Using 3xTg-AD mice (2-18 months of age), we performed histological and molecular analyses, together with design-based stereological volumetry, to evaluate brain volume changes, neuronal loss, glial responses, and gene expression. Cognitive function was assessed using the novel object recognition test (NOR), and motor learning was evaluated using the rotarod test. Synaptic integrity was measured by long-term potentiation (LTP) in acute neocortical and hippocampal slices. We also investigated the therapeutic potential of CCK-B receptor (CCK-BR) agonists on cognition and neuroplasticity across disease stages in this model.

In 3xTg-AD mice, the Ent exhibited considerable volume reduction and neuronal loss as early as 7 months of age, identifying it as one of the earliest and most severely affected regions in this model. Among the six synaptically relevant genes examined, CCK was the earliest and most selectively downregulated, with its reduction initially confined to the Ent at 7 months. Acute administration of cholecystokinin tetrapeptide (CCK-4), a preferential CCK-BR agonist, was associated with improved synaptic plasticity, recognition memory, and motor learning across multiple disease stages. Long-term treatment with HT-267, a stabilized CCK-4 analogue with an extended half-life, initiated in young adult 3xTg-AD mice, was associated with preserved cognitive and synaptic function.

These findings identify CCK downregulation as an early molecular change in the Ent of the 3xTg-AD mouse and provide evidence that pharmacological activation of CCK-BR can improve cognitive and synaptic function in this model. The ability of long-term CCK-4 analogue treatment to be associated with preserved functional outcomes suggests a potential avenue for early intervention in this preclinical context, though the relevance of these findings to human AD remains to be determined.

Date of Award	26 May 2026
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Jufang HE (Supervisor)