Characterization of Acetylcholinesterase-Inhibition by Itopride

Abstract

ABSTRACT-Itopride is a gastroprokinetic benzamide derivative. This agent inhibited both electric eel acetylcholinesterase (AChE) and horse serum butyrylcholinesterase (BuChE). The IC50 of itopride with AChE (2.04±0.27 pM) was, however, 100-fold less than that with BuChE, whereas in the case of neostigmine with AChE (11.3±3.4 nM), it was 10-fold less. The recovery of AChE activity inhibited by 10-7 M neostigmine was partial, but that inhibited by upto 3 x 10-5 M itopride was complete when the reaction mix ture was subjected to ultrafiltration. Double reciprocal plots of the experimental data showed that both Km and Vmax were affected by itopride, suggesting that the inhibition is a "mixed" type, although primarily being an uncompetitive one. The inhibitory effect of itopride on cholinesterase (ChE) activity in guinea pig gastrointestine was much weaker than that on pure AChE. However, in the presence of a low dose of diisopropyl fluorophosphate, just enough to inhibit BuChE but not AChE, the IC50s of itopride against ChE activities were found to be about 0.5 1tM. In conclusion, itopride exerts reversible and a "mixed" type of inhibition preferably against AChE. The IC50 of itopride for electric eel and guinea pig gastrointestinal AChE inhibition was 200 times and 50 times as large as that of neostigmine, respectively.

Rapid and label-free screening of enzyme inhibitors using segmented flow electrospray ionization mass spectrometry

“…Neostigmine resulted in two IC 50 values, 50 Ϯ 25 M and 38 Ϯ 10 nM, based on two-site competition fitting. These numbers generally agreed well with previously reported values (eserine 72-109 nM [34], malathion 370 M [35], edrophonium 5.4 M [36], and neostigmine 11.3 nM [37]; however, direct comparison of these numbers might not be appropriate because the experimental conditions were not identical (e.g., use of surrogate substrates and different AchE in other assays).…”

Stimulatory Action of Itopride Hydrochloride on Colonic Motor Activity in Vitro and in Vivo

“…Itopride did not cause any adverse effects such as salivation, snivel, vomiting, and diarrhea based on anti-AChE action throughout our experiments. The inhibitory action of itopride on AChE was 100 times stronger than that on butyrylcholinesterase, whereas the inhibitory action of neostigmine on AChE was 10 times stronger than that on butyrylcholinesterase (Iwanaga et al, 1994). The selectivity on AChE seems a cause of the differences of safety window.…”

“…Itopride has antiacetylcholinesterase (AChE) activity as well as dopamine D 2 receptor antagonist activity and is used for the symptomatic treatment of functional dyspepsia (Iwanaga et al, 1990(Iwanaga et al, , 1994. It is well established that the M 3 receptor exists on the smooth muscle layer throughout the whole gut and that acetylcholine released from the enteric nerve endings stimulates the contraction of smooth muscle through the M 3 receptor.…”

“…Although stimulation of gastrointestinal motility by itopride is ascribed to activation of the cholinergic drive based on D 2 receptor blocking and anti-AChE activity (Iwanaga et al, 1990(Iwanaga et al, , 1994, the stimulatory action on colonic motility seems mainly due to anti-AChE activity. Because gastrointestinal smooth muscle is directly stimulated by ACh through the activation of the M 3 receptor irrespective of the gastrointestinal site and animal species, it is apparent that itopride can stimulate colonic contractions as well as antral contractions in all species.…”

Effects of nizatidine and itopride hydrochloride on esophageal motor function

“…Nizatidine, a histamine H 2 receptor antagonist, has been demonstrated to inhibit acetylcholine esterase, with a resulting increment of acetylcholine in the cholinergic nervous systems [6][7][8]. Itopride hydrochloride is a prokinetic agent acting both as a dopamine D2 receptor antagonist and acetylcholine esterase inhibitor [9,10]. Administration of nizatidine and itopride hydrochloride has been reported to augment gastric motor function [7,9,11].…”