Novel halogenated derivates of JWH-018: Behavioral and binding studies in mice
Introduction
JWH-018 (1-pentyl-3-(1-naphthoyl)indole) is a synthetic cannabinoid agonist developed in the early 1990's (Huffman et al., 1994) from a computational melding of the chemical structural features of Δ9-tetrahydrocannabinol (Δ9-THC) with the prototypic aminoalkylindole WIN 55,212-2 (D'Ambra et al., 1992). JWH-018 binds and activates the CB1 (Ki = 9 nM) and CB2 (Ki = 3 nM) receptors in the low nanomolar range (Huffman et al., 1994, Wiley et al., 1998), showing approximately a four-fold increased activity at the CB1 and about a ten-fold affinity at the CB2 receptor compared with Δ9-THC (Auwarter et al., 2009). This aminoalkylindole is the first synthetic cannabinoid ever reported through the Early Warning System (EMCDDA, 2009, Uchiyama et al., 2010). JWH-018 mixtures are marketed as “Spice” and “herbal blend” for their psychoactive effects similar to those produced by cannabis. However, in addition to the “desired” psychoactive action, clinical data reported that JWH-018 induces significant psychiatric and physical adverse effects in consumers. The most common psychiatric effects reported were anxiety, psychosis, hallucinations and alterations in cognitive abilities, while physical effects reported ranged in severity from nausea to more serious sympathomimetic-like symptoms such as psychomotor agitation, diaphoresis, palpitations, tachycardia, tachyarrhythmia, hyperreflexia and generalized convulsions (Auwarter et al., 2009, Hermanns-Clausen et al., 2013, Seely et al., 2012).
In vivo animal studies revealed that JWH-018 reproduces the typical “tetrad” effects of Δ9-THC such as hypothermia, analgesia, hypolocomotion, akinesia (Brents et al., 2011, Macri et al., 2013, Wiebelhaus et al., 2012, Wiley et al., 2012) when delivered both via inhalation (Poklis et al., 2012, Wiebelhaus et al., 2012) or systemic injection (Fantegrossi et al., 2014, Wiley et al., 1998). In fact no differences were found in the final “tetrad” symptoms between the two routes of administration (Marshell et al., 2014). Moreover, JWH-018 produces anxiolysis and depressive-related behavior in mice (Macri et al., 2013), sensorimotor and cardio-respiratory alterations (Marti et al., 2013b, Marti, 2014) and impaired working memory in adult mice more potently than Δ9-THC (Marti et al., 2013a). In particular, the cannabinoid “tetrad” (Compton et al., 1992) has been extremely useful in the characterization of the biological activity of natural and synthetic agonists at CB1 receptors. Ligands that fully activate cannabinoid receptors which produce maximal effects in a given system (i.e. “tetrad”) are referred to as high efficacy agonists. In contrast, agonists that result in reduced maximal effects when compared to full agonists are designated as low efficacy agonists. Interestingly, Δ9-THC, which is a partial agonist both in vitro (Govaerts et al., 2004) and in vivo (Paronis et al., 2012), tends to elicit tetrad effects of similar magnitude to higher efficacy cannabinoids such as WIN-55,212-2 and CP-55,940 (Fan et al., 1994).
In the last year, the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) reported the seizure of plant material containing halogenated derivatives (N-(5-chloro-pentyl)- and N-(5-bromo-pentyl)) of JWH-018 to the Italian National Early Warning System (NEWS) (Fig. 1). The discovery of these new halogenated derivatives of JWH-018 on the illegal market and the lack of pharmacological and toxicological information suggested the need to rapidly study their in vitro and in vivo pharmacological profile to understand their main adverse effects. In fact, it is well known that halogenation of cannabinoid structures may lead to significant changes in compound potency and affinities for the CB1 receptors (Nikas et al., 2004, Wiley et al., 2014) as well as potential changes in pharmacokinetic properties.
The present study was aimed at investigating the effects of acute exposure to JWH-018, JWH-018 Cl and JWH-018 Br on primary neurological changes, core and surface body temperature, modulation of acute thermal and mechanical pain stimuli and motor activity in CD-1 mice. Moreover, in vitro competition binding experiments were carried out to determine the selectivity and potency of the halogenated compounds for the CB1 receptor. To better understand the behavioral profile of the JWH-018-R compounds, Δ9-THC was used as a reference molecule and the effects were monitored for over 5 h.
Section snippets
Animals
Male ICR (CD-1®) mice, 25–30 gr (Harlan Italy; S. Pietro al Natisone, Italy), were group-housed (8–10 mice per cage; floor area per animal was 80 cm2; minimum enclosure height was 12 cm) on a reverse 12:12-h light–dark cycle, temperature of 20–22 °C, humidity of 45–55% and were provided ad libitum access to food (Diet 4RF25 GLP; Mucedola, Settimo Milanese, Milan, Italy) and water. The experimental protocols performed in the present study were in accordance with the new European Communities
Affinity and potency of JWH-018 Cl and JWH-018 Br in comparison with JWH-018
In human CB1 receptor expressing cell membranes, competition binding experiments resulted in Ki values in the nanomolar range for JWH-018 Cl and JWH-018 Br (Table 1). The affinity value of the reference compound JWH-018 (9.53 ± 0.88 nM; Table 1) was similar to those found for the novel halogenated derivatives with JWH-018 Cl showing a slightly higher affinity than the other examined compounds (3.92 ± 0.31 nM; Table 1). Tested compounds were also able to bind human CB2 receptors with high
Discussion
The present study investigates for the first time the in vitro and in vivo activity of two novel synthetic halogenated cannabinoids, JWH-018 Cl and JWH-018 Br. These compounds are currently available on the European internet market (EMCDDA–Europol, 2012). The discovery of these compounds in products seized by law enforcement has placed an urgency for their rapid study since the halogenation on the terminal portion of the pentylic side chain of JWH-018 could potentiate its effects. This is
Conclusion
The present data, together with preliminary evidence (Marti et al., 2013b), shows that JWH-018 Cl and JWH-018 Br alter the sensorimotor response in mice similar to JWH-018 but with fewer adverse effects on motor skills and neurologic functions (convulsions). These observations allow us to hypothesize that the halogenated derivatives (in particular JWH-018 Br) may have been placed on the illegal market to try to replace JWH-018 because of its severe side effects (convulsions) that have limited
Acknowledgments
This research has been funded by the Drug Policies Department, Presidency of the Council of Ministers, Italy (project NS-Drugs to M Marti). The authors would like to thank Dott. Omar S. Mabrouk for his support in the preparation of the manuscript.
References (59)
- et al.
Role of ionotropic cannabinoid receptors in peripheral antinociception and antihyperalgesia
Trends Pharmacol. Sci.
(2009) - et al.
Cannabinoid receptor agonists are mitochondrial inhibitors: a unified hypothesis of how cannabinoids modulate mitochondrial function and induce cell death
Biochem. Biophys. Res. Commun.
(2007) - et al.
‘Spice’ and other herbal blends: harmless incense or cannabinoid designer drugs?
J. Mass Spectrom.
(2009) - et al.
Cellular and molecular mechanisms of pain
Cell
(2009) - et al.
Monohydroxylated metabolites of the K2 synthetic cannabinoid JWH-073 retain intermediate to high cannabinoid 1 receptor (CB1R) affinity and exhibit neutral antagonist to partial agonist activity
Biochem. Pharmacol.
(2012) - et al.
Phase I hydroxylated metabolites of the K2 synthetic cannabinoid JWH-018 retain in vitro and in vivo cannabinoid 1 receptor affinity and activity
PLoS One
(2011) - et al.
Pharmacological characterization of the nociceptin receptor mediating hyperalgesia in the mouse tail withdrawal assay
Br. J. Pharmacol.
(1998) - et al.
Pharmacological profile of a series of bicyclic cannabinoid analogs: classification as cannabimimetic agents
J. Pharmacol. Exp. Ther.
(1992) - et al.
Conformationally restrained analogues of pravadoline: nanomolar potent, enantioselective, (aminoalkyl)indole agonists of the cannabinoid receptor
J. Med. Chem.
(1992) Understanding the ‘Spice’ Phenomenon
(2009)
Annual Report on the Implementation of Council Decision 2005/387/JHA (New Drugs in Europe, 2012)
Development of cross-tolerance between delta 9-tetrahydrocannabinol, CP 55,940 and WIN 55,212
J. Pharmacol. Exp. Ther.
Distinct pharmacology and metabolism of K2 synthetic cannabinoids compared to delta(9)-THC: mechanism underlying greater toxicity?
Life Sci.
Changes in body temperature and oxygen consumption rate of conscious mice produced by intrahypothalamic and intracerebroventricular injections of delta 9-tetrahydrocannabinol
Br. J. Pharmacol.
Enhanced withdrawal responses to heat and mechanical stimuli following intraplantar injection of capsaicin in rats
Pain
Comparison of cannabinoid ligands affinities and efficacies in murine tissues and in transfected cells expressing human recombinant cannabinoid receptors
Eur. J. Pharm. Sci.
‘Crazy Monkey’ poisons man and dog: human and canine seizures due to PB-22, a novel synthetic cannabinoid
Clin. Toxicol. (Phila)
Cannabinoid CB2 receptors: a therapeutic target for the treatment of inflammatory and neuropathic pain
Br. J. Pharmacol.
Acute toxicity due to the confirmed consumption of synthetic cannabinoids: clinical and laboratory findings
Addiction
Cannabinoid suppression of noxious heat-evoked activity in wide dynamic range neurons in the lumbar dorsal horn of the rat
J. Neurophysiol.
Role of alpha2C-adrenoceptors in the reduction of skin blood flow induced by local cooling in mice
Br. J. Pharmacol.
Design, synthesis and pharmacology of cannabimimetic indoles
Bioorg. Med. Chem. Lett.
Comprehensive observational assessment: Ia. A systematic, quantitative procedure for assessing the behavioral and physiologic state of the mouse
Psychopharmacologia
Severe toxicity following synthetic cannabinoid ingestion
Clin. Toxicol. (Phila)
The directive 2010/63/EU on animal experimentation may skew the conclusions of pharmacological and behavioural studies
Sci. Rep.
Morphine has an antinociceptive effect through activation of the okadaic-acid-sensitive Ser/Thr protein phosphatases PP 2 A and PP5 estimated by tail-pinch test in mice
Brain Res.
In vivo effects of synthetic cannabinoids JWH-018 and JWH-073 and phytocannabinoid Delta-THC in mice: inhalation versus intraperitoneal injection
Pharmacol. Biochem. Behav.
Blockade of nociceptin/orphanin FQ transmission attenuates symptoms and neurodegeneration associated with Parkinson's disease
J. Neurosci.
Blockade of nociceptin/orphanin FQ receptor signaling in rat substantia nigra pars reticulata stimulates nigrostriatal dopaminergic transmission and motor behavior
J. Neurosci.
Cited by (77)
Immune and glial cell alterations in the rat brain after repeated exposure to the synthetic cannabinoid JWH-018
2024, Journal of NeuroimmunologyInfluence of structural characteristics on the binding of synthetic cannabinoids from the JWH family to the CB1 receptor: A computational study
2024, Journal of Molecular Graphics and ModellingEffects of cannabinoid agonists and antagonists in male rats discriminating the synthetic cannabinoid AM2201
2023, European Journal of PharmacologyAcute toxic effects of new synthetic cannabinoid on brain: Neurobehavioral and Histological: Preclinical studies
2023, Chemico-Biological Interactions