TRV130 partial agonism and capacity to induce antinociceptive tolerance revealed through reducing available µ opioid receptor number

Samuel Singleton, Daniel T. Baptista-Hon, Emily Edelsten, Kirsty S. McCaughey, Ewan Camplisson, Tim G. Hales (Lead / Corresponding author)

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)
74 Downloads (Pure)

Abstract

Background and Purpose: β-Arrestin2 recruitment to μ-receptors may contribute to the development of opioid side effects. This possibility led to the development of TRV130 and PZM21, opioids reportedly biased against β-arrestin2 recruitment in favour of G-protein signalling. However, low efficacy β-arrestin2 recruitment by TRV130 and PZM21 may simply reflect partial agonism overlooked due to overexpression of μ-receptors.

Experimental Approach: Efficacies and apparent potencies of DAMGO, morphine, PZM21 and TRV130 as stimulators of β-arrestin2 recruitment and inhibitors of cAMP accumulation were assessed in CHO cells stably expressing μ-receptors. Receptor availability was depleted through prior exposure of cells to the irreversible antagonist, β-FNA. We also examined whether μ-receptor availability influences TRV130 anti-nociception and/or tolerance using the tail withdrawal assay in wild-type C57BL/6 and μ+/− mice

Key Results: Morphine, PZM21 and TRV130 were partial agonists in the β-arrestin2 recruitment assay. Only TRV130 exhibited partial agonism in the cAMP assay. Exposure to β-FNA to reduce μ-receptor availability further limited the efficacy of TRV130 and revealed morphine and PZM21 to be partial agonists. Despite having partial efficacy in vitro, TRV130 caused potent anti-nociception (ED 50: 0.33 mg·kg −1) in wild-type mice, without tolerance after daily administration for 10 days. TRV130 caused similar anti-nociception in μ+/− mice, with marked tolerance on day 4 of injections.

Conclusion and Implications: Our findings emphasise the importance of receptor reserve when characterising μ-receptor agonists. Reduced receptor availability reveals that TRV130 is a partial agonist capable of tolerance, despite having limited efficacy for β-arrestin2 recruitment to the μ-receptor.

Original languageEnglish
Pages (from-to)1855-1868
Number of pages14
JournalBritish Journal of Pharmacology
Volume178
Issue number8
Early online date8 Feb 2021
DOIs
Publication statusPublished - Apr 2021

Keywords

  • PZM21
  • TRV130
  • arrestin recruitment
  • morphine
  • opioid analgesia
  • receptor reserve
  • tolerance

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