Multifunctional opioid receptor agonism and antagonism by a novel macrocyclic tetrapeptide prevents reinstatement of morphine‐seeking behaviour

Abstract

Background and Purpose: The macrocyclic tetrapeptide natural product CJ-15,208 (cyclo[Phe-D-Pro-Phe-Trp]) is a multifunctional μ-opioid receptor and κ-opioid receptor agonist and κ-opioid receptor antagonist that produces antinociception and prevents stress-induced reinstatement of extinguished cocaine-conditioned place preference (CPP). We hypothesized that an analogue of CJ-15,208, cyclo[Pro-Sar-Phe-D-Phe], would demonstrate multifunctional μ-opioid receptor and κ-opioid receptor ligand activity, producing potent antinociception with fewer liabilities than selective μ-opioid receptor agonists, while preventing both drug-and stress-induced reinstatement of morphine-induced CPP. Experimental Approach: The opioid receptor agonist and antagonist activity of cyclo [Pro-Sar-Phe-D-Phe] was characterized after i.c.v. and i.p. administration to C57BL/6J or transgenic opioid receptor "knockout" mice using the 55 C warm-water tail-withdrawal assay. Liabilities of locomotor coordination, respiration and spontaneous ambulation, and direct rewarding or aversive properties were assessed. Finally, the ability of cyclo[Pro-Sar-Phe-D-Phe] to block morphine-and stress-induced reinstatement of extinguished CPP was determined. Key Results: cyclo[Pro-Sar-Phe-D-Phe] demonstrated dose-dependent, short-lasting antinociception, with an ED 50 (and 95% confidence interval) of 0.15 (0.05-0.21) nmol i.c.v. and 1.91 (0.40-3.54) mgÁkg −1 i.p., mediated by μand κ-opioid receptors. The macrocyclic tetrapeptide also demonstrated potent dose-dependent κ-opioid receptor antagonist-like activity at 2.5, but not at 4.5, h after administration. cyclo[Pro-Sar-Phe-D-Phe] displayed reduced liabiities compared with morphine, attributed to its additional activity at κ-receptors. Pretreatment with cyclo[Pro-Sar-Phe-D-Phe] prevented stress-and drug-induced reinstatement of extinguished morphine-place preference responses in a time-dependent manner.

Phenylalanine Stereoisomers of CJ-15,208 and [d-Trp]CJ-15,208 Exhibit Distinctly Different Opioid Activity Profiles

“…Mice place conditioned with either isomer demonstrated no significant preference or aversion for their respective drug-paired chamber. These results are consistent with earlier tests of multifunctional macrocyclic tetrapeptides [ 9 , 19 ] and could reflect the counteracting effects of agonism at multiple opioid receptors such as MOR and KOR [ 9 , 10 ]. In contrast to 5 , isomer 3 did not demonstrate significant MOR-mediated agonism, but rather KOR- and DOR-mediated antinociception.…”

“…The lack of significant decreases in respiratory rates for all three CJ-15,208 isomers was very promising. We have previously shown that the multifunctional macrocyclic tetrapeptide cyclo [Pro-Sar-Phe- d -Phe] exhibits reduced liabilities, particularly respiratory effects, and that the peptide’s KOR agonist activity appears to offset respiratory depression mediated by MOR [ 9 ]. In contrast, treatment with [ d -Trp]CJ-15,208 isomers 4 and 5 decreased respiratory rates; this effect of 4 was surprising, given the lack of MOR agonist activity by this isomer.…”

“…injections performed as described previously [ 26 ]. This concentration of DMSO was not observed to have antinociceptive or behavioral effects in previous use [ 9 , 19 , 21 ]. For per os (p.o.)…”

“…The stereoisomers were tested for their possible impairment of locomotor coordination in the rotarod assay as described previously [ 9 , 21 ]. Locomotor activity was recorded using an automated, computer-controlled rotarod apparatus (San Diego Instruments, San Diego, CA, USA).…”

“…Co-administration of either KOR [ 6 , 7 ] or DOR [ 8 ] agonists enhanced the antinociceptive effects of MOR-selective agonists. Some multifunctional opioids also produce reduced side effects [ 9 ], a profile attributed to simultaneous modulation of more than one opioid receptor that may counter their individual adverse effects [ 10 ]. For example, KOR agonism offsets MOR-mediated reinforcement [ 11 ] and respiratory depression [ 12 ], while DOR antagonism may slow the development of MOR agonist analgesic tolerance [ 13 , 14 ].…”