CB2 cannabinoid receptor agonist enantiomers HU-433 and HU-308

An inverse relationship between binding affinity and biological potency

Reem Smoum, Saja Baraghithy, Mukesh Chourasia, Aviva Breuer, Naama Mussai, Malka Attar-Namdar, Natalya M. Kogan, Bitya Raphael, Daniele Bolognini, Maria Grazia Cascio, Pietro Marini, Roger Guy Pertwee, Avital Shurki, Raphael Mechoulam (Corresponding Author), Itai Bab

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

Activation of the CB2 receptor is apparently an endogenous protective mechanism. Thus, it restrains inflammation and protects the skeleton against age-related bone loss. However, the endogenous cannabinoids, as well as Δ9 -tetrahydrocannabinol, the main plant psychoactive constituent, activate both cannabinoid receptors, CB1 and CB2. HU-308 was among the first synthetic, selective CB2 agonists. HU-308 is antiosteoporotic and antiinflammatory. Here we show that the HU-308 enantiomer, designated HU-433, is 3–4 orders of magnitude more potent in osteoblast proliferation and osteoclast differentiation culture systems, as well as in mouse models, for the rescue of ovariectomy-induced bone loss and ear inflammation. HU-433 retains the HU-308 specificity for CB2, as shown by its failure
to bind to the CB1 cannabinoid receptor, and has no activity in CB2- deficient cells and animals. Surprisingly, the CB2 binding affinity of HU-433 in terms of [3 H]CP55,940 displacement and its effect on [35S]GTPγS accumulation is substantially lower compared with HU-308. A molecular-modeling analysis suggests that HU-433 and -308 have two different binding conformations within CB2, with one of them possibly responsible for the affinity difference, involving [35S]GTPγS and cAMP synthesis. Hence, different ligands may have different orientations relative to the same binding site. This situation questions the usefulness of universal radioligands for comparative binding studies. Moreover, orientation-targeted ligands have promising potential for the pharmacological activation of distinct processes.
Original languageEnglish
Pages (from-to)8774-8779
Number of pages6
JournalPNAS
Volume112
Issue number28
Early online date29 Jun 2015
DOIs
Publication statusPublished - 14 Jul 2015

Fingerprint

Cannabinoid Receptor Agonists
Cannabinoid Receptor CB2
Cannabinoid Receptor CB1
HU 308
Ligands
Otitis
Osteitis
Dronabinol
Cannabinoids
Ovariectomy
Osteoclasts
Osteoblasts
Skeleton
Osteoporosis
Anti-Inflammatory Agents
Binding Sites
Pharmacology

Keywords

  • endocannabinoids
  • osteoporosis
  • enantiomers
  • pose occupancy

Cite this

Smoum, R., Baraghithy, S., Chourasia, M., Breuer, A., Mussai, N., Attar-Namdar, M., ... Bab, I. (2015). CB2 cannabinoid receptor agonist enantiomers HU-433 and HU-308: An inverse relationship between binding affinity and biological potency. PNAS, 112(28), 8774-8779. https://doi.org/10.1073/pnas.1503395112

CB2 cannabinoid receptor agonist enantiomers HU-433 and HU-308 : An inverse relationship between binding affinity and biological potency. / Smoum, Reem; Baraghithy, Saja; Chourasia, Mukesh; Breuer, Aviva; Mussai, Naama; Attar-Namdar, Malka; Kogan, Natalya M.; Raphael, Bitya; Bolognini, Daniele; Cascio, Maria Grazia; Marini, Pietro; Pertwee, Roger Guy; Shurki, Avital; Mechoulam, Raphael (Corresponding Author); Bab, Itai.

In: PNAS, Vol. 112, No. 28, 14.07.2015, p. 8774-8779.

Research output: Contribution to journalArticle

Smoum, R, Baraghithy, S, Chourasia, M, Breuer, A, Mussai, N, Attar-Namdar, M, Kogan, NM, Raphael, B, Bolognini, D, Cascio, MG, Marini, P, Pertwee, RG, Shurki, A, Mechoulam, R & Bab, I 2015, 'CB2 cannabinoid receptor agonist enantiomers HU-433 and HU-308: An inverse relationship between binding affinity and biological potency', PNAS, vol. 112, no. 28, pp. 8774-8779. https://doi.org/10.1073/pnas.1503395112
Smoum, Reem ; Baraghithy, Saja ; Chourasia, Mukesh ; Breuer, Aviva ; Mussai, Naama ; Attar-Namdar, Malka ; Kogan, Natalya M. ; Raphael, Bitya ; Bolognini, Daniele ; Cascio, Maria Grazia ; Marini, Pietro ; Pertwee, Roger Guy ; Shurki, Avital ; Mechoulam, Raphael ; Bab, Itai. / CB2 cannabinoid receptor agonist enantiomers HU-433 and HU-308 : An inverse relationship between binding affinity and biological potency. In: PNAS. 2015 ; Vol. 112, No. 28. pp. 8774-8779.
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abstract = "Activation of the CB2 receptor is apparently an endogenous protective mechanism. Thus, it restrains inflammation and protects the skeleton against age-related bone loss. However, the endogenous cannabinoids, as well as Δ9 -tetrahydrocannabinol, the main plant psychoactive constituent, activate both cannabinoid receptors, CB1 and CB2. HU-308 was among the first synthetic, selective CB2 agonists. HU-308 is antiosteoporotic and antiinflammatory. Here we show that the HU-308 enantiomer, designated HU-433, is 3–4 orders of magnitude more potent in osteoblast proliferation and osteoclast differentiation culture systems, as well as in mouse models, for the rescue of ovariectomy-induced bone loss and ear inflammation. HU-433 retains the HU-308 specificity for CB2, as shown by its failureto bind to the CB1 cannabinoid receptor, and has no activity in CB2- deficient cells and animals. Surprisingly, the CB2 binding affinity of HU-433 in terms of [3 H]CP55,940 displacement and its effect on [35S]GTPγS accumulation is substantially lower compared with HU-308. A molecular-modeling analysis suggests that HU-433 and -308 have two different binding conformations within CB2, with one of them possibly responsible for the affinity difference, involving [35S]GTPγS and cAMP synthesis. Hence, different ligands may have different orientations relative to the same binding site. This situation questions the usefulness of universal radioligands for comparative binding studies. Moreover, orientation-targeted ligands have promising potential for the pharmacological activation of distinct processes.",
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AU - Smoum, Reem

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AU - Chourasia, Mukesh

AU - Breuer, Aviva

AU - Mussai, Naama

AU - Attar-Namdar, Malka

AU - Kogan, Natalya M.

AU - Raphael, Bitya

AU - Bolognini, Daniele

AU - Cascio, Maria Grazia

AU - Marini, Pietro

AU - Pertwee, Roger Guy

AU - Shurki, Avital

AU - Mechoulam, Raphael

AU - Bab, Itai

N1 - Acknowledgments Research in the R.M. laboratory was supported by the Kessler Family Foundation and by National Institute on Drug Abuse Grant DA-9789.

PY - 2015/7/14

Y1 - 2015/7/14

N2 - Activation of the CB2 receptor is apparently an endogenous protective mechanism. Thus, it restrains inflammation and protects the skeleton against age-related bone loss. However, the endogenous cannabinoids, as well as Δ9 -tetrahydrocannabinol, the main plant psychoactive constituent, activate both cannabinoid receptors, CB1 and CB2. HU-308 was among the first synthetic, selective CB2 agonists. HU-308 is antiosteoporotic and antiinflammatory. Here we show that the HU-308 enantiomer, designated HU-433, is 3–4 orders of magnitude more potent in osteoblast proliferation and osteoclast differentiation culture systems, as well as in mouse models, for the rescue of ovariectomy-induced bone loss and ear inflammation. HU-433 retains the HU-308 specificity for CB2, as shown by its failureto bind to the CB1 cannabinoid receptor, and has no activity in CB2- deficient cells and animals. Surprisingly, the CB2 binding affinity of HU-433 in terms of [3 H]CP55,940 displacement and its effect on [35S]GTPγS accumulation is substantially lower compared with HU-308. A molecular-modeling analysis suggests that HU-433 and -308 have two different binding conformations within CB2, with one of them possibly responsible for the affinity difference, involving [35S]GTPγS and cAMP synthesis. Hence, different ligands may have different orientations relative to the same binding site. This situation questions the usefulness of universal radioligands for comparative binding studies. Moreover, orientation-targeted ligands have promising potential for the pharmacological activation of distinct processes.

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