Vitamin B3-Based Biologically Active Compounds as Inhibitors of Human Cholinesterases

Abstract

We evaluated the potential of nine vitamin B3 scaffold-based derivatives as acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitors, as a starting point for the development of novel drugs for treating disorders with cholinergic neurotransmission-linked pathology. As the results indicate, all compounds reversibly inhibited both enzymes in the micromolar range pointing to the preference of AChE over BChE for binding the tested derivatives. Molecular docking studies revealed the importance of interactions with AChE active site residues Tyr337 and Tyr124, which dictated most of the observed differences. The most potent inhibitor of both enzymes with K_i of 4 μM for AChE and 8 μM for BChE was the nicotinamide derivative 1-(4'-phenylphenacyl)-3-carbamoylpyridinium bromide. Such a result places it within the range of several currently studied novel cholinesterase inhibitors. Cytotoxicity profiling did not classify this compound as highly toxic, but the induced effects on cells should not be neglected in any future detailed studies and when considering this scaffold for drug development.

Keywords: AChE; Alzheimer’s; BChE; cytotoxicity; neurodegenerative; nicotinamide.

Figure 1

Chemical structures of tested vitamin B3-derivatives 1-9 (nicotinamide form) and known ChE acting drugs (reversible inhibitors).

Figure 2

Physicochemical characteristics (molecular weight (M), number of hydrogen bond donors and acceptors (HBD and HBA), number of rotating bonds (RB), lipophilicity (logP) and topological polar surface area (TPSA)) of nicotinamide derivatives in relation to the reference values set for blood–brain barrier (BBB) acting drugs presented here by the red dotted line [46].

Figure 3

Close-up of AChE and BChE active site from model complexes with compounds 6 (a,c) and 8 (b,d). Hydrogen bonds are shown in dashed magenta lines.

Figure 4

Time and dose-dependent cytotoxicity of selected nicotinamide derivatives on SH-SY5Y and HEK293 cells after 1-, 4- and 24-h treatment. Experimental data was presented as a mean of at least three experiments.

Figure 5

Time-dependent effects of nicotinamide derivatives on intracellular signalling in HEK293 cells. Serum-starved HEK293 cells were treated with 100 μM 3, 4, 5 or 8 for 10 or 30 min as indicated. Immunoblotting was used to estimate (a) phospho-AMPK (Thr172), (b) phospho-ACC (Ser79), (c) phospho-Akt (Ser473), (d) phospho-S6RP (Ser235/236), (e) phospho-ERK1/2 (Thr202/Tyr204), (f) HIF-1α. Results are presented as means ± SD (n = 6). * p < 0.05 vs. Basal (ANOVA followed by Dunnett’s post hoc test).