Pharmacological studies of N,N-dimethylaminoethyl chloroacetate and N,N-dimethylaminoethyl acrylate as inhibitors of choline acetyltransferase in isolated skeletal and smooth muscle preparations

Discovery of novel choline acetyltransferase inhibitors using structure-based virtual screening

Alzheimer disease and related dementias are major challenges, demanding urgent needs for earliest possible diagnosis to optimize the success rate in finding effective therapeutic interventions. Mounting solid scientific premises point at the core acetylcholine-biosynthesizing cholinergic enzyme, ChAT as a legitimate in vivo target for developing positron emission tomography biomarker for early diagnosis and/or monitoring therapeutic responses in the neurodegenerative dementias. Up-to-date, no PET tracer ligands for ChAT are available. Here we report for the first time a novel hierarchical virtual screening approach on a commercial library of ~300,000 compounds, followed by in vitro screening of the hits by a new High-Throughput ChAT assay. We report detailed pharmacodynamic data for three identified selective novel ChAT ligands with IC₅₀ and K_i values ranging from ~7 to 26 µM. In addition, several novel selective inhibitors of the acetylcholine-degrading enzymes, AChE and BuChE were identified, with one of the compounds showing an IC₅₀-value of ~6 µM for AChE. In conclusion, this report provides an excellent starting platform for designing and optimizing potent and selective ChAT ligands, with high potential as PET-imaging probe for early diagnosis of AD, and related dementias, such as Down’s syndrome and Lewy body disorders.

In vivo effects of some tertiary alkylaminoethyl esters with choline acetyltransferase inhibitory properties

The tertiary nitrogen derivatives of two choline esters, chloroacetylcholine and acrylcholine, known to inhibit choline acetyltransferase (ChAc) in vitro, were tested for their effects in the whole animal, including peripheral and central cholinergic systems. These esters are N,N-dimethylaminoethyl chloroacetate (Cl-DMA) and N,N-dimethylaminoethyl acrylate (acryl-DMA). The peripheral preparations studied included a neuromuscular junction, a sympathetic ganglion and a postganglionic parasympathetic exocrine preparation. Both Cl-DMA and acryl-DMA blocked responses in these preparations when injected intravenously. The LD50 values for Cl-DMA and acryl-DMA were 640 mg/kg and 183 mg/kg, respectively. Cl-DMA and acryl-DMA were also able to inhibit brain ChAc when injected intravenously by 32% and 18.5%, respectively. The brain levels of acetylcholine (ACh) were significantly reduced by about 25% with Cl-DMA but not significantly with acryl-DMA when the animals were forced to exercise after injection. It is obvious that ChAc inhibition is not effective in decreasing ACh levels significantly under normal conditions.