Dual targeting agents for Aβ plaque/P-glycoprotein and Aβ plaque/nicotinic acetylcholine α4β2* receptors—potential approaches to facilitate Aβ plaque removal in Alzheimer’s disease brain

Abstract

Alzheimer’s disease (AD) affects 10% of people older than 65 and is characterized by a progressive loss of cognitive function with an abnormal accumulation of amyloid β (Aβ) plaques and neurofibrillary tangles (NFT) in the brain. Efforts to reduce brain Aβ plaques continue to be investigated as a therapeutic approach for AD. We report here development of dual targeting agents with affinity for Aβ plaque/P-glycoprotein (Pgp) and Aβ plaque/α4β2* nicotinic acetylcholine receptors (nAChR). These novel dual agents may be able to efflux Aβ plaques via the paravascular (glymphatic) pathways. Ferulic acid (FA), ferulic acid ethyl ester (FAEE), and curcumin (CUR) were used for Aβ plaques, fexofenadine (FEX) was used as substrate for Pgp and nifrolidine (NIF) was used for α4β2* nAChRs. Aβ plaque/α4β2* nAChR dual agent, FA-NIF (GKS-007) exhibited IC₅₀ = 3–6 nM for α4β2* nAChRs in [³H]cytisine-radiolabeled thalamus and frontal cortex in rat brain slices. In postmortem human AD frontal cortex, Aβ plaques labeled with [³H]PIB, FEX-CUR showed a 35% reduction in gray matter (GM)/white matter (WM) [³H]PIB binding, while CUR alone showed a 50% reduction. In vivo biodistribution studies are required of the Aβ−Pgp and Aβ-α4β2* nAChRs dual targeting agents in order to evaluate their potential as therapeutic approaches for reducing brain Aβ plaques.