Neuroprotective effects of donepezil through inhibition of GSK‐3 activity in amyloid‐β‐induced neuronal cell death

Abstract

Acetylcholinesterase inhibitors (AChE‐inhibitors) are used for the treatment of Alzheimer’s disease. Recently, the AChE‐inhibitor donepezil was found to have neuroprotective effects. However, the protective mechanisms of donepezil have not yet been clearly identified. We investigated the neuroprotective effects of donepezil and other AChE‐inhibitors against amyloid‐β1–42 (Aβ42)‐induced neurotoxicity in rat cortical neurons. To evaluate the neuroprotective effects of AChE‐inhibitors, primary cultured cortical neurons were pre‐treated with several concentrations of AChE‐inhibitors for 24 h and then treated with 20 μM Aβ42 for 6 h. In addition to donepezil, other AChE‐inhibitors (galantamine and huperizine A) also showed increased neuronal cell viability against Aβ42 toxicity in a concentration‐dependent manner. However, we demonstrated that donepezil has a more potent effect in inhibiting glycogen synthase kinase‐3 (GSK‐3) activity compared with other AChE‐inhibitors. The neuroprotective effects of donepezil were blocked by LY294002 (10 μM), a phosphoinositide 3 kinase inhibitor, but only partially by mecamylamine (10 μM), a blocker of nicotinic acetylcholine receptors. Additionally, donepezil’s neuroprotective mechanism was related to the enhanced phosphorylation of Akt and GSK‐3β and reduced phosphorylation of tau and glycogen synthase. These results suggest that donepezil prevents Aβ42‐induced neurotoxicity through the activation of phosphoinositide 3 kinase/Akt and inhibition of GSK‐3, as well as through the activation of nicotinic acetylcholine receptors.

Effect of triptolide on estradiol release from cultured rat granulosa cells

“…Cell viability was assessed using the ELISA plate reader at 450 nm. All results were normalized to OD values measured from an identically conditioned well without cell culture [27]. For MTT method, 20 μL of MTT (5 mg/mL in PBS) was incubated for 4 h with cells from each sample, then the medium was replaced with 150 μL dimethyl sulfoxide (DMSO) and plates were rotated gently for 10 min to allow dissolution of the formazan.…”

Neuroprotective Effects of Citidine-5-diphosphocholine on Impaired Spatial Memory in a Rat Model of Cerebrovascular Dementia

“…Donepezil powerfully inhibits acetylcholinesterase (17) and elevates acetylcholine concentration in the synapse, which results in increased cholinergic transmission. Previous studies have suggested the donepezil has neuroprotective effects aside from its acetylcholinesterase-inhibiting action through up-regulation of Bcl-2, an anti-apoptotic protein (18), stimulation of nicotinic acetylcholine receptors (19), and inhibition of glycogen synthase kinase-3 (GSK-3) activity (20). It is unknown whether donepezil exerts its neuroprotective effect in rats subjected to repeated cerebral ischemia.…”

“…It is unknown whether donepezil exerts its neuroprotective effect in rats subjected to repeated cerebral ischemia. Induction of the neuroprotective effects of donepezil via the nicotinic acetylcholine receptor in rats subjected to repeated cerebral ischemia may require a higher concentration and/or long-term treatment because the concentration of donepezil showing neuroprotection is higher than the concentration needed to exhibit acetylcholinesterase-inhibiting action in vitro (17,19,20).…”

Triptolide Improves Early Survival of Mesenchymal Stem Cells Transplanted into Rat Myocardium

“…Ten microliters of kit reagent were added to each well and incubated for an additional 2 h. The optical density values were measured using a microplate reader at 450 nm every day. All results were normalized to the optical density values measured from an identically treated well without cells [23]. All the experiments were performed in triplicate, and the average optical density values were used for the longitudinal growth curve.…”