A pair of High Throughput Screening (HTS) assays suitable for identifying non-nicotine tobacco product compounds with activity at alpha3beta4 and alpha4beta2 nicotinic receptors is proposed.
Two Specific Aims are described: 1. HTS-ready assays will be established and optimized for a pair of existing, highly-functional, monoclonal cell lines. One is stably transfected with alpha3beta4-, the other with alpha4beta2- nicotinic acetylcholine receptors (nAChRs). Both membrane-potential and Ca2+ dye fluorescence approaches are suitable and the approach which can be refined to provide the most robust and reliable results will be adopted for Aim 2. 2. The optimized assays will be configured for HTS conditions. An overall screening workflow is proposed, and will be applied to each of the optimized alpha3beta4 and alpha4beta2 HTS-ready assays. This workflow incorporates secondary orthogonal- potency-, and selectivity-counter-screening protocols to identify and discard false positives, and to characterize confirmed candidates, from the initial screens. Already-available assays suitable for orthogonal- and counter-screening, using different activities than the primary screen, are described. We will generate proof-of-principle data for each fully-configured assay using a pilot screen of ~2400 structurally-diverse test compounds. Relevance of this proposal to PAR-12-266, and the Family Smoking Prevention and Tobacco Control Act (FSPTCA): As detailed in the Specific Aims, Significance and Innovation sections, this proposal will provide a set of validated assays targeting nAChR subtypes tied to use of, and dependence on, tobacco products. The resulting screens will produce impact by accelerating progress on two stated goals of PAR-12-266: 1) "Reducing Addiction - understanding ... other constituents and components beyond nicotine that affect addiction of combustible and non-combustible tobacco products." 2) "Diversity of Tobacco Products - understanding the constituents, components, ingredients, additives, and design features;... of conventional and new and emerging tobacco products." They will also address a specific research area of the FDA Center for Tobacco Products (www.fda.gov/downloads/TobaccoProducts/NewsEvents/UCM293998.pdf;#15;"What high-throughput screens can be developed and/or used to evaluate compounds in tobacco products and smoke that may affect addiction (e.g., act on nicotinic or dopaminergic receptors...etc.)?). Availability of this suite of screens will also advance priorities of the FSPTCA. Tobacco product components identified by such screens will be valuable leads for follow-up studies to understand their relevance to tobacco use and dependence, and their precise mechanisms of action. These studies would provide impact through new scientific insights and potentially by revealing novel tobacco-cessation therapeutic avenues/targets. Compounds identified by these screens may also be candidates for regulation under the FSPTCA.
This project is intended to develop and implement procedures (high-throughput screens) that may be used to rapidly test the large range of compounds found in the many existing and emerging forms of tobacco products. Testing will be for functional activity at nicotinic acetylcholine receptors of either the alpha3beta4* or alpha4beta2* subtypes (* indicates the possible presence of other subunits). These receptors, together with alpha6beta2* nicotinic subtypes, have been convincingly associated with tobacco product use and dependence (we have already developed an analogous screen for alpha6beta2* nicotinic receptors). The resulting screens will be made freely available to the research community, through NIH's MLPCN screening center program. This will accelerate progress on identifying non-nicotine components of tobacco products with activity at the set of nicotinic receptors with proven relevance to tobacco use and dependence. Such components may be candidates for regulation under the Family Smoking Prevention and Tobacco Control Act. Further studies of the same compounds could potentially also uncover novel tobacco-cessation approaches / targets.