Monoacylglycerol Lipase Inhibition Using JZL184 Attenuates Paw Inflammation and Functional Deficits in a Mouse Model of Inflammatory Arthritis.

Background: Patients with rheumatoid arthritis (RA) experience joint swelling and cartilage destruction resulting in chronic pain, functional disability, and compromised joint function. Current RA treatments, including glucocorticoid receptor agonists, produce adverse side effects and lack prolonged treatment efficacy. Cannabinoids (i.e., cannabis-like signaling molecules) exert anti-inflammatory and analgesic effects with limited side effects compared to traditional immunosuppressants, making them excellent targets for the development of new arthritic therapeutics. Monoacylglycerol lipase (MAGL) inhibition reduces inflammation in mouse models of acute inflammation, through cannabinoid receptor dependent and independent pathways. The current study investigated the efficacy of inhibiting synthetic and catabolic enzymes that regulate the endocannabinoid 2-arachidonoylglycerol (2-AG) in blocking paw inflammation, pain-related behaviors, and functional loss caused by collagen-induced arthritis (CIA). Methods: Male DB1A mice subjected to CIA were administered the glucocorticoid agonist dexamethasone (DEX), MAGL inhibitor JZL184 (8 or 40 mg/kg, s.c.), alone or in combination, or diacylglycerol lipase ß (DAGLß) inhibitor KT109 (40 mg/kg, s.c.). CIA-induced deficits were assayed by arthritic clinical scoring, paw thickness measurements, and behavioral tests of pain and paw function. Results: DEX or dual administration with JZL184 reduced paw thickness and clinical scores, and JZL184 dose-dependently attenuated grip strength and balance beam deficits caused by CIA. Traditional measures of pain-induced behaviors (hyperalgesia and allodynia) were inconsistent. The antiarthritic effects of JZL184 (40 mg/kg) were largely blocked by coadministration of the CB2 antagonist SR144528, and the DAGLß inhibitor KT109 had no effect on CIA, indicating that these effects likely occurred through CB2 activation. Conclusions: MAGL inhibition reduced paw inflammation and pain-depressed behavioral signs of arthritis, likely through an endocannabinoid mechanism requiring CB2. These data support the development of MAGL as a target for therapeutic treatment of inflammatory arthritis.

Role of mu-opioid agonist efficacy on antinociceptive interactions between mu agonists and the nociceptin opioid peptide agonist Ro 64-6198 in rhesus monkeys.

Mu-opioid receptor agonists are clinically effective analgesics, but also produce undesirable effects that limit their clinical utility. The nociceptin opioid peptide (NOP) receptor system also modulates nociception, and NOP agonists might be useful adjuncts to enhance the analgesic effects or attenuate the undesirable effects of mu-opioid agonists. The present study determined behavioral interactions between the NOP agonist (-)-Ro 64-6198 and mu-opioid ligands that vary in mu-opioid receptor efficacy (17-cyclopropylmethyl-3,14ß-dihyroxy-4,5α-epoxy-6α-[(3 ́-isoquinolyl)acetamindo]morphinan (NAQ) < buprenorphine < nalbuphine < morphine = oxycodone < methadone) in male rhesus monkeys. For comparison, Ro 64-6198 interactions were also examined with the kappa-opioid receptor agonist nalfurafine. Each opioid ligand was examined alone and following fixed-dose Ro 64-6198 pretreatments in assays of thermal nociception (n = 3-4) and schedule-controlled responding (n = 3). Ro 64-6198 alone failed to produce significant antinociception up to doses (0.32 mg/kg, IM) that significantly decreased rates of responding. All opioid ligands, except NAQ and nalfurafine, produced dose- and thermal intensity-dependent antinociception. Ro 64-6198 enhanced the antinociceptive potency of buprenorphine, nalbuphine, methadone, and nalfurafine. Ro 64-6198 enhancement of nalbuphine antinociception was NOP antagonist SB-612111 reversible and occurred under a narrow range of dose and time conditions. All opioid ligands, except NAQ and buprenorphine, produced dose-dependent decreases in rates of responding. Ro 64-6198 did not significantly alter mu-opioid ligand rate-decreasing effects. Although these results suggest that NOP agonists may selectively enhance the antinociceptive vs. rate-suppressant effects of some mu-opioid agonists, this small enhancement occurred under a narrow range of conditions dampening enthusiasm for NOP agonists as candidate "opioid-sparing" adjuncts.

Additive and subadditive antiallodynic interactions between µ-opioid agonists and N-methyl D-aspartate antagonists in male rhesus monkeys.

µ-Opioid agonists are clinically effective analgesics, but also produce undesirable effects such as sedation and abuse potential that limit their clinical utility. Glutamatergic systems also modulate nociception and N-methyl D-aspartate (NMDA) receptor antagonists have been proposed as one useful adjunct to enhance the therapeutic effects and/or attenuate the undesirable effects of µ-opioid agonists. Whether NMDA antagonists enhance the antiallodynic effects of µ-agonists in preclinical models of thermal hypersensitivity (i.e. capsaicin-induced thermal allodynia) are unknown. The present study determined the behavioral effects of racemic ketamine, (+)-MK-801, (-)-nalbuphine, and (-)-oxycodone alone and in fixed proportion mixtures in assays of capsaicin-induced thermal allodynia and schedule-controlled responding in rhesus monkeys. Ketamine, nalbuphine, and oxycodone produced dose-dependent antiallodynia. MK-801 was inactive up to doses that produced undesirable effects. Ketamine, but not MK-801, enhanced the potency of µ-agonists to decrease rates of operant responding. Ketamine and nalbuphine interactions were additive in both procedures. Ketamine and oxycodone interactions were additive or subadditive depending on the mixture. Furthermore, oxycodone and MK-801 interactions were subadditive on antiallodynia and additive on rate suppression. These results do not support the broad clinical utility of NMDA receptor antagonists as adjuncts to µ-opioid agonists for thermal allodynic pain states.

Development of a Clinically Viable Heroin Vaccine.

Heroin is a highly abused opioid and incurs a significant detriment to society worldwide. In an effort to expand the limited pharmacotherapy options for opioid use disorders, a heroin conjugate vaccine was developed through comprehensive evaluation of hapten structure, carrier protein, adjuvant and dosing. Immunization of mice with an optimized heroin-tetanus toxoid (TT) conjugate formulated with adjuvants alum and CpG oligodeoxynucleotide (ODN) generated heroin "immunoantagonism", reducing heroin potency by >15-fold. Moreover, the vaccine effects proved to be durable, persisting for over eight months. The lead vaccine was effective in rhesus monkeys, generating significant and sustained antidrug IgG titers in each subject. Characterization of both mouse and monkey antiheroin antibodies by surface plasmon resonance (SPR) revealed low nanomolar antiserum affinity for the key heroin metabolite, 6-acetylmorphine (6AM), with minimal cross reactivity to clinically used opioids. Following a series of heroin challenges over six months in vaccinated monkeys, drug-sequestering antibodies caused marked attenuation of heroin potency (>4-fold) in a schedule-controlled responding (SCR) behavioral assay. Overall, these preclinical results provide an empirical foundation supporting the further evaluation and potential clinical utility of an effective heroin vaccine in treating opioid use disorders.

Neurotensin NTS1 and NTS2 receptor agonists produce anxiolytic-like effects in the 22-kHz ultrasonic vocalization model in rats.

Neurotensin is a neuropeptide neurotransmitter that interacts with multiple neurotransmitter systems, including those regulating amygdalar function, via NTS1 and NTS2 receptors. Both receptors are expressed in the amygdala and agonists for NTS1 or NTS2 receptors have exhibited anxiolytic effects in animal models. Systemic adminstration of NTS1 receptor agonist PD149163 was recently shown to reduce footshock conditioned 22-kHz ultrasonic vocalizations in rats, suggesting that PD149163 produced an anxiolytic effect. The effects that neurotensin may have or a selective NTS2 receptor agonist may have on 22-kHz vocalizations has yet to be examined. The current study evaluated the effects of intracerebroventricularly administered neurotensin (0.1-10.0µg), PD149163 (0.1-10.0ng), or the NTS2 receptor agonist JMV-431 (0.1-1.0µg) on footshock conditioned 22-kHz vocalizations in male Wistar rats. Neurotensin, PD149163, and JMV-431 all significantly reduced the number 22-kHz calls. No changes in call duration were found, suggesting that non-specific drug effects do not account for the reductions in 22-kHz calls. These data support anxiolytic effects produced by activation of NTS1 or NTS2 receptors, and suggest that neurotensin plays a natural role in the expression of conditioned USVs. These data suggest that both receptor subtypes are putative pharmacologic targets.