Dual-Acting Cholinesterase–Human Cannabinoid Receptor 2 Ligands Show Pronounced Neuroprotection in Vitro and Overadditive and Disease-Modifying Neuroprotective Effects in Vivo

We have designed
and synthesized a series of 14 hybrid molecules
out of the cholinesterase (ChE) inhibitor tacrine and a benzimidazole-based
human cannabinoid receptor subtype 2 (hCB2R) agonist and
investigated them in vitro and in vivo. The compounds are potent ChE
inhibitors, and for the most promising hybrids, the mechanism of human
acetylcholinesterase (hAChE) inhibition as well as their ability to
interfere with AChE-induced aggregation of β-amyloid (Aβ),
and Aβ self-aggregation was assessed. All hybrids were evaluated
for affinity and selectivity for hCB1R and hCB2R. To ensure that the hybrids retained their agonist character, the
expression of cAMP-regulated genes was quantified, and potency and
efficacy were determined. Additionally, the effects of the hybrids
on microglia activation and neuroprotection on HT-22 cells were investigated.
The most promising in vitro hybrids showed pronounced neuroprotection
in an Alzheimer’s mouse model at low dosage (0.1 mg/kg, i.p.),
lacking hepatotoxicity even at high dose (3 mg/kg, i.p.).