Flavonoids with Novel Nicotinic Activity as Potential Pharmacotherapies to Treat Ethanol-Induced Neurotoxicity

OF DISSERTATION FLAVONOIDS WITH NOVEL NICOTINIC ACTIVITY AS POTENTIAL PHARMACOTHERAPIES TO TREAT ETHANOL-INDUCED NEUROTOXICITY Ethanol causes neurotoxicity via several mechanisms at different points in the cycle of dependence, including neuroinflammation and oxidative stress during ethanol exposure as well as excitotoxicity during ethanol withdrawal. The primary therapeutic implication is that ethanol-induced neurotoxicity requires multifunctional pharmacotherapies which reduce all mechanisms. Using an innovative pharmacological high throughput screening method on a large plant extract library we discovered flavonoids with alpha7 nicotinic acetylcholine receptor (nAChR) activity. In addition to their well-known anti-inflammatory and antioxidant properties, this novel activity means they can potentially reduce excitotoxicity and therefore makes them ideal for inhibition of ethanol-induced neurotoxicity. Rhamnetin, the candidate compound, was first found to inhibit lipopolysaccharide induced inflammation in immortalized BV2 microglia, in part, via alpha7 nAChRs. We then established an in vitro model of ethanol inducedneurotoxicity using organotypic hippocampal slice cultures which incorporated both neuroinflammatory and excitotoxic components. Neuroinflammation enhanced excitotoxicity under control conditions but the reverse was observed during ethanol withdrawal. Both mechanisms are important but their interaction is not simple. Finally, rhamnetin was evaluated in this model and found to reduce neuroinflammation and excitotoxicity associated with ethanol withdrawal. In conclusion, the studies herein provide strong evidence for alpha7 nAChRs selective flavonoids as potential pharmacotherapies for the treatment of ethanol-induced neurotoxicity and further implicate neuroinflammation, excitotoxicity, and their interaction as critical mechanisms in this pathology.