Docking Analysis of Drugs Used in the Treatment of Alzheimer’s Disease, Using Cell Membrane Receptors and Enzymes of the Kynurenine Pathway: A Pilot Study

Molecular docking in silico techniques were used to assess the interactions between several drugs used in the treatment of Alzheimer’s disease (AlzD) with neuronal receptors and with tryptophan and glycolytic pathway enzymes. AlzD drugs believed to act by inhibiting acetylcholinesterase (AChE) docked to that enzyme, whereas other drugs did not. No docking was observed to the nicotinic acetylcholine receptor (α-7-nAChR). All the drugs tested docked to the kainic acid receptor for glutamate, whereas donepezil, galantamine, tropisetron and N-acetylcysteine docked to the glutamate-NMDA receptor, but none docked to the glutamate-AMPA receptor. Two compounds docked to GABA receptors. Since the kynurenine pathway of tryptophan metabolism has been linked to AlzD, docking was examined with its various enzymes. Docking to tryptophan-2,3-dioxygenase (TDO2), indoleamine-2,3-dioxygenase-1 (IDO1) and 2-amino-3-carboxymuconic acid-6-semialdehyde decarboxylase was seen with most of the AlzD drugs. Donepezil docked to kynurenine monooxygenase, while rivastigmine, memantine and tropisetron docked to kynurenine aminotransferase-2. There was limited docking to the aryl hydrocarbon receptor and glycolytic enzymes, whereas most drugs docked to phosphoenolpyruvate carboxykinase (PEPCK). Despite their strong docking ability to IDO1 and TDO, none of the compounds tested inhibited their enzyme activity in an assay of kynurenine production. This pilot study highlights the varied pharmacological profile of drugs used in AlzD and suggests that a detailed examination of their functional effects should be considered to assist understanding of their different profiles at on- and off- target sites in human treatment.