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The neuropeptide FF2 (NPFF) receptor, predominantly expressed in the central nervous system, plays an important role in the modulation of sensory input and opioid analgesia, as well as in locomotion, feeding, intestinal motility, reward, and the control of obesity. The NPFF receptor belongs to the RFamide peptide receptor family and to the G protein coupled receptor (GPCR) super family, but contrary to many other class A GPCRs, no 3D structure has been solved. Thus, it is essential to perform mutagenesis to gain information on the fine functioning of the NPFF receptor. In this study, we examined the role of aspartic acid (D) from the "D/ERY/F" motif found in the second intracellular loop (ICL2) and the role of the C-terminal end of the receptor in ligand binding and signal transduction. We found that mutation D3.49A does not impair binding capacities but inhibits G protein activation as well as adenylyl cyclase regulation. Truncation of the C terminal part of the receptor has different effects depending on the position of truncation. When truncation was realized downstream of the putative acylation site, ligand binding and signal transduction capabilities were not lost, contrary to total deletion of the C terminus, which totally impairs the activity of the receptor.
Learn More >The prototypical member of the receptor-inactivating kappa opioid receptor (KOR) antagonists norbinaltorphimine (norBNI) produces prolonged receptor inactivation by a cJun kinase mechanism. These antagonists have potential therapeutic utility in the treatment of stressdisorders, however additional preclinical characterization is necessary to understand important aspects of their action. In this study, we report that norBNI does not work as effectively in female mice as in males because of estrogen regulation of G-protein receptor kinase (GRK); pretreatment of ovary-intact female mice with the selective GRK2/3 inhibitor, CMPD101, made females equally sensitive to norBNI as males. Prior observations suggested that in vivo treatment with norBNI does not produce long-lasting inhibition of KOR regulation of dopamine release in the nucleus accumbens. We assessed the persistence of norBNI receptor inactivation in subcellular compartments. Fast-scan cyclic voltammetry recordings confirmed that presynaptic inhibition of dopamine release by the KOR agonist U69,593 was not blocked by in vivo pretreatment with norBNI under conditions that prevented KOR mediated aversion and analgesia. We employed a novel in vivo proxy sensor of KOR activation, AAV-DIO-HyPerRed and demonstrated that KOR activation stimulates JNK-dependent ROS production in somatic regions of VTA dopamine neurons, but did not activate ROS production in dopamine terminals. The compartment selective action helps explain how dopamine somatic, but not terminally expressed KORs are inactivated by norBNI. These results further elucidate molecular signaling mechanisms mediating receptor-inactivating KOR antagonist action and advance medication development for this novel class of stress-resilience medications. Kappa opioid receptor (KOR) antagonists are being developed as novel pro-resilience therapeutics for the treatment of mood and substance use disorders. This study showed that the long-acting KOR antagonists are affected by both the sex of the animal and the subcellular compartment in which the receptor is expressed.
Learn More >To assess the long-term safety, tolerability, and efficacy of fremanezumab, a fully humanized monoclonal antibody approved for the preventive treatment of migraine.
Learn More >Neuropathic pain is a debilitating public health concern for which novel non-narcotic therapeutic targets are desperately needed. Using unbiased transcriptomic screening of the dorsal horn spinal cord after nerve injury we have identified that Gpr183 (Epstein-Barr induced gene 2 [EBI2]) is upregulated after chronic constriction injury (CCI) in rats. GPR183 is a chemotactic receptor known for its role in the maturation of B cells and the endogenous ligand is the oxysterol, 7α,25-dihydroxycholesterol (7α,25-OHC). The role of GPR183 in the central nervous system is not well characterized and its role in pain is unknown. The profile of commercially available probes for GPR183 limits their use as pharmacological tools to dissect the roles of this receptor in pathophysiological settings. Using in silico modeling, we have screened a library of 5 million compounds to identify several novel small-molecule antagonists of GPR183 with nanomolar potency. These compounds are able to antagonize 7α,25-OHC-induced calcium mobilization in vitro with IC50 values below 50nM. In vivo intrathecal injections of these antagonists during peak pain after CCI surgery reversed allodynia in male and female mice. Acute intrathecal injection of the GPR183 ligand, 7α,25-OHC in naïve mice induced dose-dependent allodynia. Importantly, this effect was blocked using our novel GPR183 antagonists, suggesting spinal GPR183 activation as pro-nociceptive. These studies are the first to reveal a role for GPR183 in neuropathic pain and identify this receptor as a potential target for therapeutic intervention. We have identified several novel GPR183 antagonists with nanomolar potency. Using these antagonists, we have demonstrated that GPR183 signaling in the spinal cord is pro-nociceptive. These studies are the first to reveal a role for GPR183 in neuropathic pain and identify it as a potential target for therapeutic intervention.
Learn More >To evaluate the presence and characterization of chemotherapy-induced neuropathy (CIPN) and neuropathic pain 5 years after adjuvant chemotherapy with docetaxel or oxaliplatin. Patients from an ongoing prospective study, who had received adjuvant chemotherapy with docetaxel or oxaliplatin in 2011-2012 were invited to participate. The patients underwent a thorough examination with interview, neurological examination, questionnaires, assessment tools, nerve conduction studies (NCS), quantitative sensory testing, MScan motor unit number estimation (MUNE), and corneal confocal microscopy (CCM). Patients were divided into no, possible, probable, and confirmed CIPN. Out of the 132 eligible patients, 63 agreed to participate: 28 had received docetaxel and 35 had received oxaliplatin. Forty-one percent had confirmed CIPN, 34% possible or probable CIPN, and 22% did not have CIPN. The CIPN was characterized mainly by sensory nerve fiber loss, with a more pronounced large fiber than small fiber loss but also some motor fiber loss identified on NCS and MUNE. In general, patients had mild neuropathy with relatively low scores on assessment tools and no association with mood and quality of life. CCM was not useful as a diagnostic tool. Of the patients with probable or confirmed CIPN, 30% experienced pain, which was most often mild, but still interfered moderately with daily life in 20-25% and was associated with lower quality of life. CIPN was confirmed in 41% 5 years after chemotherapy. The neuropathy was generally mild, but in patients with neuropathic pain it was associated with lower quality of life. This article is protected by copyright. All rights reserved.
Learn More >Nalfurafine, a moderately selective kappa opioid receptor (KOR) agonist, is used in Japan for treatment of itch without causing dysphoria or psychotomimesis. Here we characterized pharmacology of compound 42B, a 3-dehydroxy analog of nalfurafine and compared with that of nalfurafine. Nalfurafine and 42B acted as full KOR agonists and partial opioid receptor (MOR) agonists, but 42B showed much lower potency for both receptors and lower KOR/MOR selectivity, different from previous reports. Molecular modeling revealed that water-mediated hydrogen-bond formation between 3-OH of nalfurafine and KOR accounted for its higher KOR potency than 42B. The higher potency of both at KOR over MOR may be due to hydrogen-bond formation between non-conserved Y7.35 of KOR and their carbonyl groups. Both showed modest G protein signaling biases. In mice, like nalfurafine, 42B produced antinociceptive and anti-scratch effects and did not cause conditioned place aversion (CPA) in the effective dose ranges. Unlike nalfurafine, 42B caused motor incoordination and hypolocomotion. As both agonists showed G protein biases, yet produced different effects on locomotor activity and motor incoordination, the findings and those in the literature suggest caution in correlating in vitro biochemical data with in vivo behavior effects. The factors contributing to the disconnect, including pharmacodynamic and pharmacokinetic issues, are discussed. In addition, our results suggest that among the KOR-induced adverse behaviors, CPA can be separated from motor incoordination and hypolocomotion.
Learn More >Opioid use, misuse, and risky use contribute to a critically important and complex crisis in current healthcare. Consequences of long-term opioid use, including opioid induced hyperalgesia, physical dependence, and opioid use disorder, can be considered iatrogenic, or partially iatrogenic, in cases where therapeutic opioid exposures were contributory. Research investigation and presumptive clinical action are needed to attenuate the iatrogenic component of the opioid crisis; treatment of individuals already suffering from opioid use disorder will not prevent incident cases. This work will be challenged by a remarkably high degree of complexity involving myriad and highly variable factors along the continuum from initial opioid exposure to long-term opioid use. An organized view of this complex problem should accelerate the pace of innovation and facilitate clinical implementation of research findings. Herein, we propose a theoretical framework and modern nomenclature for characterizing therapeutic opioid exposure and the degree to which it contributes iatrogenically to adverse outcomes. In doing so, we separate the role of exposure from other factors contributing to long-term opioid use, clarify the relationship between opioid exposure and outcomes, emphasize that exposure source is an important consideration for health services research and practice in the areas of pain treatment and opioid prevention, and recommend terminology necessary to quantify therapeutic opioid exposure separately from nonmedical exposure.
Learn More >Although opioids have been used as treatment of neuropathic pain, opioids have abuse potential in humans. Since soluble epoxide hydrolase (sEH) in the metabolism of polyunsaturated fatty acids plays a key role in the pain, sEH inhibitors would be promising new therapeutic drugs for neuropathic pain. In this study, we examined the effect of the sEH inhibitor TPPU on rewarding effects in mice using the conditioned place preference (CPP) paradigm.
Learn More >To explore the use of a multistate repeated, time-to-categorical event model describing the frequency, severity and duration of migraines.
Learn More >Dupilumab has demonstrated efficacy and acceptable safety in adults and children (aged 6-17 years) with moderate-to-severe atopic dermatitis (AD), but effective systemic therapy with a favorable risk-benefit profile in younger children remains a significant unmet need.
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