EP2 and EP4 in Alzheimer’s Disease: Cell-Dependent Signalling and Implications for Selective Targeting

Prostaglandin E2 (PGE2) signalling influences amyloid-β (Aβ) processing, myeloid function, and neuronal injury in Alzheimer’s disease (AD). Although EP2 and EP4 share Gs–cyclic adenosine monophosphate (cAMP) signalling, their cellular effects differ. This review integrates genetic, pharmacological, ageing, and AD-model evidence to assess receptor-selective targeting. EP2 deletion enhances myeloid Aβ handling and reduces microglia-mediated neuronal injury in experimental systems, providing a rationale for selective EP2 inhibition. In aged mice, PGE2–EP2 signalling redirects glucose towards glycogen storage and restricts myeloid mitochondrial respiration; benefits from a predominantly peripheral antagonist suggest that some age-related outcomes may improve without high brain exposure. Chronic antagonist studies in AD models, however, show variable effects on inflammation, amyloid burden, and behaviour. EP4 exhibits contrasting cell-dependent actions: activation supports microglial Aβ uptake and inflammatory control, whereas signalling in some amyloid precursor protein (APP)-expressing cells promotes APP internalisation and Aβ production. Human AD evidence remains mainly tissue-based; EP2 antagonist testing has involved healthy volunteers, not patients with AD. These findings indicate that receptor selectivity alone is insufficient to predict therapeutic outcomes. Further studies should combine cell-specific receptor manipulation, measurements of central and peripheral exposure, and separate assessments of Aβ production, clearance, tissue injury, and functional outcomes.