Orexin receptor agonist Yan 7874 is a weak agonist of orexin/hypocretin receptors and shows orexin receptor-independent cytotoxicity

PLoS One. 2017 Jun 2;12(6):e0178526. doi: 10.1371/journal.pone.0178526. eCollection 2017.

Abstract

Two promising lead structures of small molecular orexin receptor agonist have been reported, but without detailed analyses of the pharmacological properties. One of them, 1-(3,4-dichlorophenyl)-2-[2-imino-3-(4-methylbenzyl)-2,3-dihydro-1H-benzo[d]imidazol-1-yl]ethan-1-ol (Yan 7874), is commercially available, and we set out to analyze its properties. As test system we utilized human OX1 and OX2 orexin receptor-expressing Chinese hamster ovary (CHO) K1 cells as well as control CHO-K1 and neuro-2a neuroblastoma cells. Gq-coupling was assessed by measurement of intracellular Ca2+ and phospholipase C activity, and the coupling to Gi and Gs by adenylyl cyclase inhibition and stimulation, respectively. At concentrations above 1 μM, strong Ca2+ and low phospholipase C responses to Yan 7874 were observed in both OX1- and OX2-expressing cells. However, a major fraction of the response was not mediated by orexin receptors, as determined utilizing the non-selective orexin receptor antagonist N-biphenyl-2-yl-1-{[(1-methyl-1H-benzimidazol-2-yl)sulfanyl]acetyl}-L-prolinamide (TCS 1102) as well as control CHO-K1 cells. Yan 7874 did not produce any specific adenylyl cyclase response. Some experiments suggested an effect on cell viability by Yan 7874, and we thus analyzed this. Within a few hours of exposure, Yan 7874 markedly changed cell morphology (shrunken, rich in vacuoles), reduced growth, promoted cell detachment, and induced necrotic cell death. The effect was equal in cells expressing orexin receptors or not. Thus, Yan 7874 is a weak partial agonist of orexin receptors. It also displays strong off-target effects in the same concentration range, culminating in necrotic cell demise. This makes Yan 7874 unsuitable as orexin receptor agonist.

MeSH terms

  • Adenylyl Cyclases / metabolism
  • Animals
  • Benzimidazoles / pharmacology*
  • CHO Cells
  • Calcium / metabolism
  • Cell Death / drug effects
  • Cell Line, Tumor
  • Cricetinae
  • Cricetulus
  • Humans
  • Imines / pharmacology*
  • Orexin Receptors / agonists*
  • Type C Phospholipases / metabolism

Substances

  • 1-(3,4-dichlorophenyl)-2-(2-imino-3-(4-methylbenzyl)-2,3-dihydro-1H-benzo(d)imidazol-1-yl)ethan-1-ol
  • Benzimidazoles
  • Imines
  • Orexin Receptors
  • Type C Phospholipases
  • Adenylyl Cyclases
  • Calcium

Grants and funding

Support was provided by the Academy of Finland, Gustav Boije af Gennäs, grant number 257685 [http://www.aka.fi/en/]; Finnish Cultural Foundation, Ainoleena Turku [https://skr.fi/en]; University of Helsinki Research Funds, Henri Xhaard [https://www.helsinki.fi/en/studying/during-your-studies/apply-for-a-grant]; Magnus Ehrnrooth Foundation, Dan Lindholm, Jyrki Kukkonen [http://www.magnusehrnroothinsaatio.fi/en/]; Waldemar von Frenckell Foundation, Gustav Boije af Gennäs [http://www.foundationweb.net/frenckell/]; Liv & Hälsa Foundation, Dan Lindholm, Jyrki Kukkonen [http://www.livochhalsa.fi/].