Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2021 Apr 20;118(16):e2000017118.
doi: 10.1073/pnas.2000017118.

Positive allosteric modulation of the mu-opioid receptor produces analgesia with reduced side effects

Ram Kandasamy  1   2 , Todd M Hillhouse  1   3 , Kathryn E Livingston  1 , Kelsey E Kochan  1 , Claire Meurice  1 , Shainnel O Eans  4 , Ming-Hua Li  5 , Andrew D White  6 , Bernard P Roques  7 , Jay P McLaughlin  4 , Susan L Ingram  5 , Neil T Burford  8 , Andrew Alt  1   8   9 , John R Traynor  10   6
Affiliations

Positive allosteric modulation of the mu-opioid receptor produces analgesia with reduced side effects

Ram Kandasamy et al. Proc Natl Acad Sci U S A. .

Abstract

Positive allosteric modulators (PAMs) of the mu-opioid receptor (MOR) have been hypothesized as potentially safer analgesics than traditional opioid drugs. This is based on the idea that PAMs will promote the action of endogenous opioid peptides while preserving their temporal and spatial release patterns and so have an improved therapeutic index. However, this hypothesis has never been tested. Here, we show that a mu-PAM, BMS-986122, enhances the ability of the endogenous opioid Methionine-enkephalin (Met-Enk) to stimulate G protein activity in mouse brain homogenates without activity on its own and to enhance G protein activation to a greater extent than β-arrestin recruitment in Chinese hamster ovary (CHO) cells expressing human mu-opioid receptors. Moreover, BMS-986122 increases the potency of Met-Enk to inhibit GABA release in the periaqueductal gray, an important site for antinociception. We describe in vivo experiments demonstrating that the mu-PAM produces antinociception in mouse models of acute noxious heat pain as well as inflammatory pain. These effects are blocked by MOR antagonists and are consistent with the hypothesis that in vivo mu-PAMs enhance the activity of endogenous opioid peptides. Because BMS-986122 does not bind to the orthosteric site and has no inherent agonist action at endogenously expressed levels of MOR, it produces a reduced level of morphine-like side effects of constipation, reward as measured by conditioned place preference, and respiratory depression. These data provide a rationale for the further exploration of the action and safety of mu-PAMs as an innovative approach to pain management.

Keywords: allostery; analgesia; endogenous opioid peptides; mu-opioid receptor; signaling bias.

PubMed Disclaimer

Conflict of interest statement

Competing interest statement: N.T.B. and A.A. have a patent related to this work: “Positive allosteric modulators and silent allosteric modulators of the μ-opioid receptor.” Publication number: WO2014/107344 A1. Publication date: July 10, 2014.

Figures

Fig. 1.
Fig. 1.
BMS-986122 (BMS) enhances activity of orthosteric agonists in vitro. (A–C) BMS increased the activity of (A) DAMGO, (B) morphine, and (C) methadone in the [35S]GTPγS binding assay in whole brain homogenates from C57BL/6 mice. (D) Potency of Met-Enk to stimulate [35S]GTPγS binding in homogenates of PAG from C57BL/6 mice increased in the presence of BMS. (E). The effect of BMS on Met-Enk-stimulation of [35S]GTPγS in CHO cell membranes expressing hMOR. (F) The effect of BMS on β-arrestin recruitment in Pathunter CHO cells expressing hMOR. All [35S]GTPγS data (A–E) are from at least three separate experiments in duplicate. β-arrestin data are from four separate experiments in triplicate. (G) BMS-986122 affords a sixfold increase in the potency of Met-Enk to inhibit presynaptic GABA release, measured as mIPSCs, in rat PAG slices (n = 4 to 9). (H) BMS alone did not alter mIPSC frequency, F[11,11] = 2.337, P = 0.17. (I) Representative traces showing increased inhibition by Met-Enk (ME) in the presence of BMS.
Fig. 2.
Fig. 2.
Antinociceptive activity of BMS-986122 (BMS) in the hot-plate test in C57BL/6 mice. (A) Enhanced antinociceptive effect of methadone (3 µg, i.c.v.) with coadministration of BMS (i.c.v). Interaction: F(6,51) = 52.01, P < 0.0001, n = 6. ***P < 0.001, **P < 0.001 versus methadone alone. (B) Enhancement of a 5.6 mg/kg systemic (i.p.) dose of methadone coadministered with 0.15 nmol BMS (i.c.v.). Interaction: F(9,60) = 19.12, P < 0.0001, n = 6. ****P < 0.0001. ***P < 0.001 compared with methadone alone. (C) Administration of 1.5 nmol BMS (i.c.v.) enhances the antinociceptive effects of 32 mg/kg morphine. Interaction: F(9,60) = 14.47, P < 0.0001], n = 6. ****P < 0.0001, **P < 0.01, and *P < 0.05 compared with morphine alone. (D) Dose- and time-dependent effects of BMS (i.c.v): F(8,54) = 17.15, P < 0.0001, n = 6 to 8. ****P < 0.0001, *P < 0.05 compared with vehicle. (E) Pretreatment (24 h; 5.0 mg/kg) with the irreversible antagonist β-FNA prevented the effect of BMS (1.5 nmol, i.c.v.). Interaction: F(2,30) = 63.34, P < 0.0001, n = 6. ****P < 0.0001, ***P < 0.001 versus β-FNA–treated mice. (F) Enhanced antinociceptive effects of the enkephalinase inhibitor RB-101 (50 μg, i.c.v.) by BMS (0.15 nmol, i.c.v.) given simultaneously. Interaction: F(6,42) = 27.51, P < 0.0001, n = 6 to 7. ****P < 0.0001 compared with RB101 alone or BMS alone. (G) BMS (0.15 to 1.5 nmol, i.c.v.) administered 15 min before the swim significantly improved the antinociceptive effects of swim stress. Interaction: F(4,40) = 10.9 P < 0.0001, n = 6. ***P < 0.001, *P < 0.05 compared with vehicle; #the effect was prevented by 10 mg/kg naloxone (NLX; i.p.), P < 0.0001 versus 1.5 nmol BMS. y-axis labels in A and D refer to all figures in the row; 1 nmol BMS = 447 ng; 50 μg RB101 = 86 nmol.
Fig. 3.
Fig. 3.
BMS-986122 (BMS) produces antinociception in 129S1/SvlmJ mice in the warm water tail-withdrawal test. (A) Antinociception produced by increasing doses of BMS. Interaction: F(15,135) = 7.170, P < 0.0001, n = 6. ****P < 0.0001 compared with vehicle. The dotted line indicates the mean basal response before treatment. (B) Inhibition of BMS-induced antinociception by 10 mg/kg naloxone (NLX). Interaction: F(18,144) = 6.533, P < 0.0001, n = 6. ****P < 0.0001, ***P < 0.001, and *P < 0.05 compared with BMS with NLX; NLX alone was not different from vehicle. Time indicates minutes after BMS injection. (C) Tail-withdrawal latencies after one and three administrations (i.p., over 2 d) of BMS or morphine. Interaction: F(4,30) = 15.94, P < 0.0001, n = 6. BMS produced antinociception after one but not three injections. Morphine was effective at both one and three injections; ****P < 0.00001 compared with vehicle. (D) Antinociceptive effect of BMS is lost after three injections of either vehicle or BMS. Interaction: F(2,30) = 4.30, P = 0.023, n = 6. ***P < 0.001 compared with vehicle. In C and D, data were not collected after the second injection.
Fig. 4.
Fig. 4.
BMS-986122 (BMS) produces antinociception against inflammatory pain in 129S1/Svlmj mice. Paw withdrawal thresholds were assessed in the right hindpaw 30 min after BMS (10 mg/kg, i.p.). Mice received either bilateral (A) or unilateral (B) intraplantar injections of carrageenan, and mechanical allodynia was assessed in the right hindpaw by sensitivity to von Frey filaments. Carrageenan produced robust mechanical allodynia in the right hindpaw 24 h after injection, compared with preinjury baseline (BL), after both unilateral [main effect of treatment: F(3,50) = 22.07, P < 0.0001, n = 6 ****P < 0.0001] and bilateral injections [main effect of treatment: F(3,46) = 19.05, P < 0.0001, n =6, ****P < 0.0001]. A single systemic injection of BMS reversed allodynia in mice with bilateral inflammation (*P < 0.05, n = 6) in a naloxone (NLX) reversible manner (#P < 0.05). (C) Sustained antiallodynic effects of BMS against CFA-induced unilateral inflammation after twice daily injections for 3 d. Main effect of treatment: F(1,10) = 69.51, P < 0.0001; n = 6. **P < 0.01, ***P < 0.001. (D) Reversal of pain-depressed nesting behavior following i.p. injections of BMS. i.p. injection of dilute acetic acid depressed nesting, which was restored by BMS. Main effect of treatment: F(2,16) = 24.58, P < 0.0001, n = 6. ****P < 0.0001 versus vehicle or morphine.
Fig. 5.
Fig. 5.
BMS-986122 (BMS) produces a reduced level of MOR-mediated side effects compared with morphine in 129S1/Svlmj mice. (A) The number of fecal boli deposited 2 h following i.p. administration of 10 mg/kg BMS or morphine. Main effect of treatment: F(2,22) = 13.10, P = 0.0002; n = 6. *P < 0.05 versus BMS or vehicle. (B) CPP of 10 mg/kg BMS compared with 10 mg/kg morphine following 5 d of conditioning. CPP score refers to the difference in time spent on the drug-paired side on test day compared with preconditioning. Animals conditioned with morphine showed significant preference for the drug-paired chamber compared with animals conditioned with either vehicle or BMS. Main effect of treatment: F(2,15) = 7.65, P = 0.005, n = 6. *P < 0.05 versus BMS or vehicle. (C) Respiration was assessed immediately after i.p. injection of morphine or BMS. Interaction: F(69,1,012) = 10.75, P < 0.0001, n = 12. Respiratory depression was seen with morphine (****P < 0.0001) and 10 mg/kg BMS (**P < 0.01), but the effect of morphine was significantly greater than BMS (###P < 0.001). The effect of BMS was reversed by naloxone (NLX).
See this image and copyright information in PMC

Comment in

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Valentino R. J., Volkow N. D., Untangling the complexity of opioid receptor function. Neuropsychopharmacology 43, 2514–2520 (2018). - PMC - PubMed
    1. Mansour A., Fox C. A., Thompson R. C., Akil H., Watson S. J., mu-Opioid receptor mRNA expression in the rat CNS: Comparison to mu-receptor binding. Brain Res. 643, 245–265 (1994). - PubMed
    1. Burford N. T., et al. ., Discovery of positive allosteric modulators and silent allosteric modulators of the μ-opioid receptor. Proc. Natl. Acad. Sci. U.S.A. 110, 10830–10835 (2013). - PMC - PubMed
    1. Livingston K. E., Traynor J. R., Disruption of the Na+ ion binding site as a mechanism for positive allosteric modulation of the mu-opioid receptor. Proc. Natl. Acad. Sci. U.S.A. 111, 18369–18374 (2014). - PMC - PubMed
    1. Livingston K. E., et al. ., Pharmacologic evidence for a putative conserved allosteric site on opioid receptors. Mol. Pharmacol. 93, 157–167 (2018). - PMC - PubMed

Publication types

MeSH terms