title: Dose-limiting inhibition of acetylcholinesterase by ladostigil results from the rapid formation and fast hydrolysis of the drug-enzyme complex formed by its major metabolite, R-MCPAI.
abstract: Ladostigil is a pseudo reversible inhibitor of acetylcholinesterase (AChE) that differs from other carbamates in that the maximal enzyme inhibition obtainable does not exceed 50-55%. This could explain the low incidence of cholinergic adverse effects induced by ladostigil in rats and human subjects. The major metabolite, R-MCPAI is believed to be responsible for AChE inhibition by ladostigil in vivo. Therefore we determined whether the ceiling in AChE inhibition resulted from a limit in the metabolism of ladostigil to R-MCPAI by liver microsomal enzymes, or from the kinetics of enzyme inhibition by R-MCPAI. Ladostigil reduces TNF-α in lipopolysaccharide-activated microglia. In vivo, it may also reduce pro-inflammatory cytokines by inhibiting AChE and increasing the action of ACh on macrophages and splenic lymphocytes. We also assessed the contribution of AChE inhibition in the spleen of LPS-injected mice to the anti-inflammatory effect of ladostigil. As in other species, AChE inhibition by ladostigil in spleen, brain and plasma did not exceed 50-55%. Since levels of R-MCPAI increased with increasing doses of ladostigil we concluded that there was no dose or rate limitation of metabolism. The kinetics of enzyme inhibition by R-MCPAI are characterized by a rapid formation of the drug-enzyme complex and fast hydrolysis which limits the attainable degree of AChE inhibition. Ladostigil and its metabolites (1-100 nM) decreased TNF-α in lipopolysaccharide-activated macrophages. Ladostigil (5 and 10mg/kg) also reduced TNF-α in the spleen after injection of lipopolysaccharide in mice. However, AChE inhibition contributed to the anti-inflammatory effect only at a dose of 10mg/kg.
authors: Institute of Drug Research, The Hebrew University of Jerusalem, Jerusalem, Israel.
authors: Dorit
authors: D
authors: Moradov
authors: Institute of Drug Research, The Hebrew University of Jerusalem, Jerusalem, Israel.
authors: Efrat
authors: E
authors: Finkin-Groner
authors: Institute of Drug Research, The Hebrew University of Jerusalem, Jerusalem, Israel.
authors: Corina
authors: C
authors: Bejar
authors: Institute of Drug Research, The Hebrew University of Jerusalem, Jerusalem, Israel.
authors: Priyashree
authors: P
authors: Sunita
authors: Institute of Drug Research, The Hebrew University of Jerusalem, Jerusalem, Israel.
authors: Donna
authors: D
authors: Schorer-Apelbaum
authors: Institute of Drug Research, The Hebrew University of Jerusalem, Jerusalem, Israel.
authors: Dinorah
authors: D
authors: Barasch
authors: Institute of Drug Research, The Hebrew University of Jerusalem, Jerusalem, Israel.
authors: Alina
authors: A
authors: Nemirovski
authors: Institute of Drug Research, The Hebrew University of Jerusalem, Jerusalem, Israel.
authors: Marganit
authors: M
authors: Cohen
authors: Institute of Drug Research, The Hebrew University of Jerusalem, Jerusalem, Israel. Electronic address: martar@ekmd.huji.ac.il.
authors: Marta
authors: M
authors: Weinstock
mesh_terms: D000110:Acetylcholinesterase / Q000187:drug effects*; D000818:Animals; D001921:Brain / Q000378:metabolism; D002800:Cholinesterase Inhibitors / Q000493:pharmacokinetics / Q000494:pharmacology*; D002853:Chromatography, Liquid; D006868:Hydrolysis; D007189:Indans / Q000493:pharmacokinetics / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008813:Mice, Inbred ICR; D013154:Spleen / Q000378:metabolism; D053719:Tandem Mass Spectrometry
chemical_list: C423264:(N-propargyl-(3R) aminoindan-5-yl)-ethyl methyl carbamate; D002800:Cholinesterase Inhibitors; D007189:Indans; D000110:Acetylcholinesterase
keywords: Acetylcholinesterase inhibition, Brain, Spleen, LC–MS, Ladostigil metabolites; BW284C51 (PubChem CID: 9820); Kinetics of enzyme inhibition; Ladostigil tartrate (PubChem CID: 6918440); Mecamylamine HCl (PubChem CID: 13221); Rivastigmine tartrate (PubChem CID: 6918078)