Antagonism of the EP2 Receptor Reveals Sex-Specific Protection in a Two-Hit Mouse Model of Alzheimer's Disease

Neuroinflammation is evident in Alzheimer's disease (AD) brains, exacerbating the pathology and ensuing cognitive deficits in patients. The prostaglandin-E2 receptor EP2 emerged as a neuroinflammatory target in several neurodegenerative diseases, including AD. Antagonism of EP2 mitigates neuroinflammation and cognitive deficits in status epilepticus and stroke models. Here, we investigated the efficacy of a potent and selective EP2 antagonist TG11-77.HCl on the cognitive behavior and neuroinflammation in a two-hit 5xFAD mouse model of AD. We exposed adult 5xFAD mice on B6SJL genetic background and their nontransgenic littermates to a low dose of lipopolysaccharide and administered TG11-77.HCl or the vehicle in the drinking water for 12 weeks. Mice were subjected to Morris water maze and Y-maze testing during their last week of drug treatment. Blood samples were subjected to complete blood count (CBC) analysis and brain tissues were processed to examine the levels of inflammatory transcripts and glial marker expression (mRNA), followed by the quantification of congophilic amyloid deposition and microglial activation (IBA⁺) in the brain by immunohistochemistry. TG11-77.HCl treatment enhanced the spatial memory performance and ameliorated mRNA expression of proinflammatory mediators, chemokines, and cytokines in the neocortex of 5xFAD males only and attenuated astroglia and microglia activation in both male and female 5xFAD mice and the congophilic amyloid load in 5xFAD males only. CBC analysis revealed no changes in peripheral inflammation, irrespective of sex, on treatment with TG11-77.HCl. This study reveals sex-specific protection of selective EP2 antagonism in a two-hit mouse model of AD and supports a prudent therapeutic strategy against neuroinflammation and associated cognitive impairment in AD.