Imidazopyridine-Based 5-HT6 Receptor Neutral Antagonists: Impact of N1-Benzyl and N1-Phenylsulfonyl Fragments on Different Receptor Conformational States

J Med Chem. 2021 Jan 28;64(2):1180-1196. doi: 10.1021/acs.jmedchem.0c02009. Epub 2021 Jan 13.

Abstract

G-protein coupled receptors (GPCRs) exist in an equilibrium of multiple conformational states, including different active states, which depend on the nature of the bound ligand. In consequence, different conformational states can initiate specific signal transduction pathways. The study identified compound 7e, which acts as a potent 5-hydroxytryptamine type 6 receptor (5-HT6R) neutral antagonist at Gs and does not impact neurite growth (process controlled by Cdk5). MD simulations highlighted receptor conformational changes for 7e and inverse agonist PZ-1444. In cell-based assays, neutral antagonists of the 5-HT6R (7e and CPPQ), but not inverse agonists (SB-258585, intepirdine, PZ-1444), displayed glioprotective properties against 6-hydroxydopamine-induced and doxorubicin-induced cytotoxicity. These suggest that targeting the activated conformational state of the 5-HT6R with neutral antagonists implicates the protecting properties of astrocytes. Additionally, 7e prevented scopolamine-induced learning deficits in the novel object recognition test in rats. We propose 7e as a probe for further understanding of the functional outcomes of different states of the 5-HT6R.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Astrocytes / drug effects
  • Humans
  • Imidazoles / chemical synthesis*
  • Imidazoles / pharmacology*
  • Learning Disabilities / chemically induced
  • Learning Disabilities / prevention & control
  • Male
  • Molecular Conformation
  • Neurites / drug effects
  • Neuroglia / drug effects
  • Neuroprotective Agents / chemical synthesis
  • Neuroprotective Agents / pharmacology
  • Pyridines / chemical synthesis*
  • Pyridines / pharmacology*
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, G-Protein-Coupled / drug effects
  • Receptors, Serotonin / drug effects*
  • Serotonin Antagonists / chemical synthesis*
  • Serotonin Antagonists / pharmacology*
  • Serotonin Receptor Agonists / pharmacology
  • Structure-Activity Relationship

Substances

  • Imidazoles
  • Neuroprotective Agents
  • Pyridines
  • Receptors, G-Protein-Coupled
  • Receptors, Serotonin
  • Serotonin Antagonists
  • Serotonin Receptor Agonists
  • imidazopyridine
  • serotonin 6 receptor