The monoacylglycerol lipase inhibitor KML29 with gabapentin synergistically produces analgesia in mice.

BACKGROUND AND PURPOSE: Gabapentin is commonly prescribed for nerve pain but may also cause dizziness, sedation and gait disturbances. Similarly, inhibition of the endogenous cannabinoid enzyme monoacylglycerol lipase (MAGL) has antinociceptive and anti-inflammatory properties but also induces sedation in mice at high doses. To limit these side effects, the present study investigated the analgesic effects of coadministering a MAGL inhibitor with gabapentin. EXPERIMENTAL APPROACH: Mice subjected to the chronic constriction injury model of neuropathic pain were administered the MAGL inhibitor KML29 (1-40 mg·kg-1 , i.p.), gabapentin (1-50 mg·kg-1 , i.p.) or both compounds. Mice were tested for mechanical and cold allodynia. The function and expression of cannabinoid CB1 receptors in whole brain homogenates and lipid profile of spinal cords were assessed after repeated drug administration. KEY RESULTS: The combination of low-dose KML29:gabapentin additively attenuated mechanical allodynia and synergistically reduced cold allodynia. The CB1 antagonist, rimonabant, partially reversed the anti-allodynic effects of KML29:gabapentin in mechanical allodynia but not cold allodynia. The anti-allodynic effects of KML29:gabapentin did not undergo tolerance in mechanical allodynia after repeated administration but produced mild tolerance in cold allodynia. High dose KML29 alone reduced CB1 receptor expression and function, but KML29:gabapentin reduced the density of CB1 receptors but did not alter their function. KML29:gabapentin influenced additional signalling pathways (including fatty acids) other than the pathways activated by a higher dose of either drug alone. CONCLUSION AND IMPLICATIONS: These data support the strategy of combining MAGL inhibition with a commonly prescribed analgesic as a therapeutic approach for attenuating neuropathic pain.

Evaluation of Analgesia, Tolerance, and the Mechanism of Action of Morphine-6-O-Sulfate Across Multiple Pain Modalities in Sprague-Dawley Rats.

BACKGROUND: Morphine-6-O-sulfate (M6S) is a mixed µ/δ-opioid receptor (OR) agonist and potential alternative to morphine for treatment of chronic multimodal pain. METHODS: To provide more support for this hypothesis, the antinociceptive effects of M6S and morphine were compared in tests that access a range of pain modalities, including hot plate threshold (HPT), pinprick sensitivity threshold (PST) and paw pressure threshold tests. RESULTS: Acutely, M6S was 2- to 3-fold more potent than morphine in HPT and PST tests, specifically, derived from best-fit analysis of dose-response relationships of morphine/M6S half-effective dose (ED50) ratios (lower, upper 95% confidence interval [CI]) were 2.8 (2.0-5.8) in HPT and 2.2 (2.1, 2.4) in PST tests. No differences in analgesic drug potencies were detected in the PPT test (morphine/M6S ED50 ratio 1.2 (95% CI, 0.8-1.4). After 7 to 9 days of chronic treatment, tolerance developed to the antinociceptive effects of morphine, but not to M6S, in all 3 pain tests. Morphine-tolerant rats were not crosstolerant to M6S. The antinociceptive effects of M6S were not sensitive to κ-OR antagonists. However, the δ-OR antagonist, naltrindole, blocked M6S-induced antinociception by 55% ± 4% (95% CI, 39-75) in the HPT test, 94% ± 4% (95% CI, 84-105) in the PST test, and 5% ± 17% (95% CI, -47 to 59) or 51% ± 14% (95% CI, 14-84; 6 rats per each group) in the paw pressure threshold test when examined acutely or after 7 days of chronic treatment, respectively. CONCLUSIONS: Activity via δ-ORs thus appears to be an important determinant of M6S action. M6S also exhibited favorable antinociceptive and tolerance profiles compared with morphine in 3 different antinociceptive assays, indicating that M6S may serve as a useful alternative for rotation in morphine-tolerant subjects.

The K2/Spice phenomenon: emergence, identification, legislation and metabolic characterization of synthetic cannabinoids in herbal incense products.

In 2008, the European Monitoring Center for Drugs and Drug Addiction (EMCDDA) detected unregulated, psychoactive synthetic cannabinoids (SCBs) in purportedly all-natural herbal incense products (often known as K2 or Spice) that were being covertly abused as marijuana substitutes. These drugs, which include JWH-018, JWH-073 and CP-47,497, bind and activate the cannabinoid receptors CB1R and CB2R with remarkable potency and efficacy. Serious adverse effects that often require medical attention, including severe cardiovascular, gastrointestinal and psychiatric sequelae, are highly prevalent with SCB abuse. Consequently, progressively restrictive legislation in the US and Europe has banned the distribution, sale and use of prevalent SCBs, initiating cycles in which herbal incense manufacturers replace banned SCBs with newer unregulated SCBs. The contents of the numerous, diverse herbal incense products was unknown when SCB abuse first emerged. Furthermore, the pharmacology of the active components was largely uncharacterized, and confirmation of SCB use was hindered by a lack of known biomarkers. These knowledge gaps prompted scientists across multiple disciplines to rapidly (1) monitor, identify and quantify with chromatography/mass spectrometry the ever-changing contents of herbal incense products, (2) determine the metabolic pathways and major urinary metabolites of several commonly abused SCBs and (3) identify active metabolites that possibly contribute to the severe adverse effect profile of SCBs. This review comprehensively describes the emergence of SCB abuse and provides a historical account of the major case reports, legal decisions and scientific discoveries of the "K2/Spice Phenomenon". Hypotheses concerning potential mechanisms SCB adverse effects are proposed in this review.

Differential drug-drug interactions of the synthetic Cannabinoids JWH-018 and JWH-073: implications for drug abuse liability and pain therapy.

Marijuana substitutes often contain blends of multiple psychoactive synthetic cannabinoids (SCBs), including the prevalent SCBs (1-pentyl-1H-indole-3-yl)-1-naphthalenyl-methanone (JWH-018) and (1-butyl-1H-indole-3-yl)-1-naphthalenyl-methanone (JWH-073). Because SCBs are frequently used in combinations, we hypothesized that coadministering multiple SCBs induces synergistic drug-drug interactions. Drug-drug interactions between JWH-018 and JWH-073 were investigated in vivo for Δ(9)-tetrahydrocannabinol (Δ(9)-THC)-like discriminative stimulus effects, analgesia, task disruption, and hypothermia. Combinations (JWH-018:JWH-073) of these drugs were administered to mice in assays of Δ(9)-THC discrimination, tail-immersion, and food-maintained responding, and rectal temperatures were measured. Synergism occurred in the Δ(9)-THC discrimination assay for two constant dose ratio combinations (1:3 and 1:1). A 1:1 and 2:3 dose ratio induced additivity and synergy, respectively, in the tail-immersion assay. Both 1:1 and 2:3 dose ratios were additive for hypothermia, whereas a 1:3 dose ratio induced subadditive suppression of food-maintained responding. In vitro drug-drug interactions were assessed using competition receptor-binding assays employing mouse brain homogenates and cannabinoid 1 receptor (CB1R)-mediated inhibition of adenylyl cyclase activity in Neuro2A wild-type cells. Interestingly, synergy occurred in the competition receptor-binding assay for two dose ratios (1:5 and 1:10), but not in the adenylyl cyclase activity assay (1:5). Altogether, these data indicate that drug-drug interactions between JWH-018 and JWH-073 are effect- and ratio-dependent and may increase the relative potency of marijuana substitutes for subjective Δ(9)-THC-like effects. Combinations may improve the therapeutic profile of cannabinoids, considering that analgesia but not hypothermia or task disruption was potentiated. Importantly, synergy in the competition receptor-binding assay suggests multiple CB1R-SCB binding sites.

Betulinic acid targets YY1 and ErbB2 through cannabinoid receptor-dependent disruption of microRNA-27a:ZBTB10 in breast cancer.

Treatment of ErbB2-overexpressing BT474 and MDA-MB-453 breast cancer cells with 1 to 10 µmol/L betulinic acid inhibited cell growth, induced apoptosis, downregulated specificity protein (Sp) transcription factors Sp1, Sp3, and Sp4, and decreased expression of ErbB2. Individual or combined knockdown of Sp1, Sp3, Sp4 by RNA interference also decreased expression of ErbB2 and this response was because of repression of YY1, an Sp-regulated gene. Betulinic acid-dependent repression of Sp1, Sp3, Sp4, and Sp-regulated genes was due, in part, to induction of the Sp repressor ZBTB10 and downregulation of microRNA-27a (miR-27a), which constitutively inhibits ZBTB10 expression, and we show for the first time that the effects of betulinic acid on the miR-27a:ZBTB10-Sp transcription factor axis were cannabinoid 1 (CB1) and CB2 receptor-dependent, thus identifying a new cellular target for this anticancer agent.

Marijuana-based drugs: innovative therapeutics or designer drugs of abuse?

The principal psychoactive component of marijuana, Δ(9)-tetrahydrocannabinol (THC), activates CB1 cannabinoid receptors (CB1Rs). Unfortunately, pharmacological research into the design of effective THC analogs has been hampered by psychiatric side effects. THC-based drug design of a less academic nature, however, has led to the marketing of "synthetic marijuana," labeled as K2 or "Spice," among other terms, which elicits psychotropic actions via CB1R activation. Because of structural dissimilarity to THC, the active ingredients of K2/Spice preparations are widely unregulated. The K2/Spice "phenomenon" provides a context for considering whether marijuana-based drugs will truly provide innovative therapeutics or merely perpetuate drug abuse.

Agonist-directed trafficking of response by endocannabinoids acting at CB2 receptors.

This study examined the ability of the endocannabinoids 2-arachidonoyl glycerol (2-AG) and noladin ether as well as the synthetic cannabinoid CP-55,940 [(-)-cis-3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-trans-4-(3-hydroxypropyl) cyclohexanol] to regulate three intracellular effectors via CB2 receptors in transfected Chinese hamster ovary cells. Although the three agonists regulate all effectors with equivalent efficacy, the rank order of potencies differs depending on which effector is evaluated. Noladin ether and CP-55,940 most potently inhibit adenylyl cyclase, requiring higher concentrations to stimulate the extracellular signal-regulated kinase subgroup of the mitogen-activated protein kinases (extracellular signal-regulated kinase-mitogen-activated protein kinase; ERK-MAPK) and Ca(2+)-transients. In contrast, 2-AG most potently activates ERK-MAPK, necessitating greater concentrations to inhibit adenylyl cyclase and even higher amounts to stimulate Ca(2+)-transients. Endocannabinoids also seem to be more "efficient" agonists at CB2 receptors relative to synthetic agonists. 2-AG and noladin ether require occupancy of less than one-half the number of receptors to produce comparable regulation of adenylyl cyclase and ERK-MAPK, relative to the synthetic cannabinoid CP-55,940. The CB2 antagonist 6-iodo-2-methyl-1-[2-(4-morpholinyl)-ethyl]-1H-indol-3-yl](4-methoxyphenyl)-methanone (AM630) reverses the actions of all agonists except Ca(2+)-transient stimulation by 2-AG. However, the effect of 2-AG on Ca(2+)-transients is attenuated by a second CB2 antagonist N-[(1S)-endo-1,3,3-trimethylbicyclo[2.2.1]heptan-2-yl]-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)-1-pyrazole-3-carboxamide (SR144528). This suggests that 2-AG stimulates Ca(2+)-transients by binding to sites on CB2 receptors distinct from those occupied by AM630 and the other cannabinoids examined. Agonists produce no effects in pertussis toxin-treated cells. In summary, cannabinoid agonists distinctly bind to CB2 receptors and display different rank order of potencies and fractional receptor occupancies for regulation of intracellular effectors. These data provide direct evidence for agonist-directed trafficking of response by endocannabinoids acting at CB2 receptors.