Many studies demonstrate an inverse correlation between tobacco use and the risk of Parkinson’s disease. This inadvertent therapeutic effect of tobacco may be caused by the upregulation of neuronal nicotinic acetylcholine receptors (nAChRs) by nicotine. Compounds causing targeted nAChR upregulation are therefore potential drugs for treating PD. Building on this hypothesis, the project describes the development and validation of a fluorescence-based screening assay to identify subtype-specific nAChR upregulators for the treatment of PD.
Our laboratory has previously characterized fluorescently tagged nAChR subunits. These first-generation fluorescent receptor subunits are visualized using fluorescence microscopy, and their pharmacological properties resemble those of untagged receptors. Now, nAChR subunits will be engineered to contain optimized fluorophores. These second-generation constructs will then be incorporated into stably expressing fluorescent nAChR cell lines. The cell lines will be subjected to a variety of fluorescence microscopy-based and electrophysiological techniques for detecting and quantifying receptor upregulation in the presence of nicotine itself. Finally, a panel of chemicals with known pharmacological effects on nAChRs will be tested to validate the assay and to identify chemical upregulators of nAChRs.
Relevance to Diagnosis/Treatment of Parkinson’s Disease:
Nicotine demonstrates significant neuroprotective effects in animal models of PD, but adverse off-target effects preclude its therapeutic use. This project develops powerful tools to identify candidate compounds that selectively upregulate nAChRs with minimal off-target effects. These compounds can be used in conjunction with L-dopa, consequently attenuating the advent of motor symptoms and tolerance. Identified nAChR upregulators could also slow disease progression at early stages of PD, providing a dual benefit for the treatment of PD.
If successfully executed, the project will develop powerful tools and techniques for the discovery of novel drugs upregulating nAChRs. In addition, candidate compounds that cause receptor upregulation will be further tested in animal models of PD, both to further understand the role of nAChR.
Dr. Srinivasan developed an assay to measure upregulation of nicotinic receptors in cultured cells and demonstrated the ability of nicotine and other compounds to upregulate these receptors. The assay could be used in future screens to define drugs with selective ability to upregulate this class of receptor or to understand the cell-delimited aspects of nicotine's protective effects.