Drug Repurposing Strategy Targeting The Human 5-Ht3a Receptor

Abstract

Drug repurposing strategies offer a rational approach to reducing the time and costs associated with new therapies. In this study, piperazine (PZE) and hydroxyzine (HZE) were tested as novel modulators of the human 5-HT3A receptor. This receptor belongs to the pentameric ligand-gated ion channel family and is emerging as a pharmacological target for neurological, psychiatric and gastrointestinal disorders. PZE is an anthelmintic drug that acts through nematode GABA and MOD-1 receptors while HZE, a derivative of PZE, is a first- generation H1 receptor antagonist used for skin allergies and shows mild anxiolytic, sedative, and antiemetic effects. By whole cell recordings, we observed that the preincubation with PZE inhibited 5-HT-evoked currents of 5- HT3A receptors. The co-application of PZE and 5-HT did not alter the peak current, suggesting a non-competitive inhibition. PZE caused an increase in the EC50 value and a decrease in the maximum response to 5-HT, further supporting the proposed inhibitory mechanism. Molecular docking of PZE into the 5-HT3A receptor suggested two major binding sites, distinct from the 5-HT binding site, reinforcing that PZE may act as a negative allosteric modulator. Candidate residues at these sites, located at the interface between the transmembrane (TMD) and the extracellular domains, and at the top of the TMD were mutated to confirm their contribution. Regarding HZE, our electrophysiological studies demonstrated that the preincubation with this drug in the low micromolar concentration range strongly decreased macroscopic responses of 5-HT3A. Thus, the 5-HT3A receptor may mediate several effects observed with HZE and could represent an important pharmacological target. By identifying new targets and mechanisms, our drug repositioning strategy facilitates the discovery of novel therapeutic applications for clinically approved drugs in a rational and efficient manner.