Are we getting close to an MOA? Who can provide a layman's explanation of the very last sentence?
It seems to say that anatabine flat out KILLS cells that were deliberately "transfected" with pro-inflammatory cytokines.
From Neuroscience 2013
Program#/Poster#: 702.07/C9
Presentation Title: Biphasic effects of anatabine on nicotinic receptors and NFkB signaling
Location: Halls B-H
Presentation time: Wednesday, Nov 13, 2013, 10:00 AM -11:00 AM
Topic: ++B.02.b. Nicotinic acetylcholine receptors: trafficking and signaling
Authors: *R. H. LORING, Y. SZETO, L. GUO, M. PIRES, R. PAPKE;
1. Pharmaceut. Sci., Northeastern Univ., Boston, MA;
2. Dept. of Pharmacol. and Therapeut., Univ. of Florida, Gainesville, FL
Abstract: Anatabine, a minor alkaloid in tobacco and other Solanacea plants, is structurally similar to nicotine. Marketed as a “nutraceutical” for smoking cessation and anti-inflammation (CigRx® and Anatabloc®, Rock Creek Pharmaceuticals), anatabine directly blocks the pro-inflammatory transcription factor NF-?B (Paris et al., Eur J Pharmacol, 670:384, 2011). However, anatabine binds to nicotinic a3ß4 receptors (Maciuk et al., J Pharm Biomed Anal, 48:238, 2008), which may also have anti-inflammatory effects when activated. We find that 30 µM racemic anatabine (Cayman Chemicals) is a very weak agonist or partial agonist on a3ß4, and a1ß1?d nicotinic receptors expressed in frog oocytes, a relatively efficacious agonist for a7 and a relatively potent partial agonist for HS a4ß2 receptors (IC50 for acetylcholine ~ 40 µM and a Imax of ~ 13% that of acetylcholine). To further investigate the anti-inflammatory effects of anatabine, we repeated experiments of Paris et al. using HEK-293 cells lacking nicotinic receptors transfected with an NF-?B-driven secreted alkaline phosphatase (AP) reporter gene. HEK reporter cells treated with the pro-inflammatory cytokine TNFa (10 ng/ml) increased AP activity >10x, but anatabine decreased NF-?B-driven signaling with an IC50 of approximately 1 mM, similar to effects found by Paris et al. using a NF-?B-driven luciferase reporter. However, anatabine killed reporter HEK cells as measured by an MTS cell-viability assay (Promega) with an LD50 of approximately 1 mM. Nicotine had no effect over a similar concentration range. Anatabine’s toxic effects closely resemble other NF-?B inhibitors such as Bay 11-7082, pyrrolidine dithiocarbamate, and parthenolide, but these compounds are effective at 1-10 µM. Reporter HEK cells are only partially protected from 1-4 mM anatabine by the pan-caspase inhibitor Z-VAD-FMK (20 µM), suggesting that anatabine causes both apoptosis and necrosis. We propose that anatabine has biphasic effects, acting on nicotinic receptors at µM concentrations but directly blocking NF-?B at mM concentrations, which depending on context, may lead to cell death.
Disclosures: R.H. Loring: None. Y. Szeto: None. L. Guo: None. M. Pires: None. R. Papke: None.
Keyword(s):
APOPTOSIS
NICOTINIC AGONIST
TRANSCRIPTION FACTOR
Support: Supported in part by GM57481
AI
