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Genetic knockout or knockdown of fat-mass and obesity-associated protein (FTO), a demethylase that participates in RNA N-methyladenosine modification in injured dorsal root ganglion (DRG), has been demonstrated to alleviate nerve trauma-induced nociceptive hypersensitivities. However, these genetic strategies are still impractical in clinical neuropathic pain management. The present study sought to examine the effect of intrathecal administration of two specific FTO inhibitors, meclofenamic acid (MA) and N-CDPCB, on the development and maintenance of nociceptive hypersensitivities caused by unilateral L5 spinal nerve ligation (SNL) in rats. Intrathecal injection of either MA or N-CDPCB diminished dose-dependently the SNL-induced mechanical allodynia, heat hyperalgesia, cold hyperalgesia, and spontaneous ongoing nociceptive responses in both development and maintenance periods, without altering acute/basal pain and locomotor function. Intrathecal MA also reduced the SNL-induced neuronal and astrocyte hyperactivities in the ipsilateral L5 dorsal horn. Mechanistically, intrathecal injection of these two inhibitors blocked the SNL-induced increase in the histone methyltransferase G9a expression and rescued the G9a-controlled downregulation of mu opioid receptor and Kv1.2 proteins in the ipsilateral L5 DRG. These findings further indicate the role of DRG FTO in neuropathic pain and suggest potential clinical application of the FTO inhibitors for management of this disorder.
Learn More >Chronic low back pain (cLBP) rates among younger individuals are rising. Although pain and disability are often less severe, underlying changes in trunk behavior may be responsible for recurrence. We examine the biomarker capacity of a simple Trunk Compliance Index (TCI) to distinguish individuals with and without cLBP. A random subset (n = 49) of the RELIEF RCT were matched to healthy controls for sex, age, height and weight. We measured TCI (as displacement/ weight-normalized perturbation force) using anthropometrically-matched, suddenly-applied pulling perturbations to the trunk segment, randomized across three planes of motion (antero-posterior, medio-lateral, and rotational). Mean differences between cLBP, sex and perturbation direction were assessed with repeated-measures analysis of variance. Discriminatory accuracy of TCI was assessed using Receiver Operator Characteristic (ROC) analysis. Baseline characteristics between groups were equivalent (x̅ [range]): sex (57% female / group), age (23.0 [18-45], 22.8 [18-45]), height, cm (173.0 [156.5-205], 171.3 [121.2-197], weight, kg (71.8 [44.5-116.6], 71.7 [46.8-117.5]) with cLBP associated with significantly lower TCI for 5 of 6 directions (range mean difference, – 5.35: – 1.49, range 95% CI [- 6.46: – 2.18 to – 4.35: – 0.30]. Classification via ROC showed that composite TCI had high discriminatory potential (area under curve [95% CI], 0.90 [0.84-0.96]), driven by TCI from antero-posterior perturbations (area under curve [95% CI], 0.99 [0.97-1.00]). Consistent reductions in TCI suggests global changes in trunk mechanics that may go undetected in classic clinical examination. Evaluation of TCI in younger adults with mild pain and disability may serve as a biomarker for chronicity, leading to improved preventative measures in cLBP.Trial Registration and Funding RELIEF is registered with clinicaltrials.gov (NCT01854892) and funded by the NIH National Center for Complementary & Integrative Health (R01AT006978).
Learn More >ObjectiveTo determine whether the intravenous infusion of adrenomedullin, a potent vasodilator belonging to calcitonin family of peptides, provokes attacks of migraine in patients.MethodsTwenty migraine without aura patients participated in a placebo-controlled and double-blinded clinical study. In a randomized and crossover design the patients received an intravenous infusion of human adrenomedullin (19.9 picomole/kg/min) or placebo (saline) administrated via an automated intravenous pump (20 minutes). The patients participated in two study days with washout period of minimum of seven days. The primary outcome of the study was predefined as a difference in migraine incidence (0-12 h) and the secondary outcome were the headache intensity score's area under curve (AUC) and the (AUC ) for MAP, flushing and HR.ResultsEleven migraine without aura patients (55%) fulfilled migraine attacks criteria after adrenomedullin infusion in comparison to only three patients reported attack (15%) after placebo ( 0.039). We found that patients reported in a period of (0-12 hours) stronger headache intensity after adrenomedullin in comparison to placebo infusion ( 0.035). AUC for HR and, flushing ( < 0.05) were significant and MAP ( = 0.502) remain unchanged. Common adverse events reported were facial flushing, heat sensation and palpitation ( <0.001)ConclusionOur data implicate adrenomedullin in migraine pathogenesis. This suggests that adrenomedullin and/or its receptors are novel therapeutic targets for the treatment of migraine. However, we cannot discount for the possibility that adrenomedullin may be acting through the canonical CGRP receptor.
Learn More >C-C chemokine receptor 2 (CCR2) signaling plays a key role in pain associated with experimental murine osteoarthritis (OA) after destabilization of the medial meniscus (DMM). Here, we aimed to assess if CCR2 expressed by intra-articular sensory neurons contributes to knee hyperalgesia in the early stages of the model.
Learn More >(1) Background: Research has shown that thoughts about pain are important for the management of chronic pain in children. In order to monitor changes in thoughts about pain over time and evaluate the efficacy of treatments, we need valid and reliable measures. The aims of this study were to develop a questionnaire to assess a child's concept of pain and to evaluate its psychometric properties; (2) Methods: This is a cross-sectional, two-phase, mixed-method study. A total of 324 individuals aged 8 to 17 years old responded to the newly created questionnaire. The Conceptualization of Pain Questionnaire (COPAQ) was calibrated using the Rasch model. The chi-square test was used for the fit statistics. Underfit and overfit of the model were determined and a descriptive analysis of infit and outfit was conducted to identify who responded erratically. Internal consistency was measured using the Person Separation Index (PSI); (3) Results: Fit to the Rasch model was good. Suitable targeting indicated which items were simple to answer; Person Fit identified 9.56% children who responded erratically; PSI = 0.814; (4) Conclusions: The findings suggest that COPAQ is a measure of a child's concept of pain that is easy to administer and respond to. It has a good fit and a good internal consistency.
Learn More >The opioid crisis represents a major worldwide public health crisis that has accelerated the search for safer and more effective opioids. Over the past few years, the identification of biased opioid ligands capable of eliciting selective functional responses has provided an alternative avenue to develop novel therapeutics without the side effects of current opioid medications. However, whether biased agonism or other pharmacological properties, such as partial agonism (or low efficacy), account for the therapeutic benefits remains questionable. Here, we provide a summary of the current status of biased opioid ligands that target the μ- and κ-opioid receptors and highlight advances in preclinical and clinical trials of some of these ligands. We also discuss an example of structure-based biased ligand discovery at the μ-opioid receptor, an approach that could revolutionize drug discovery at opioid and other receptors. Last, we briefly discuss caveats and future directions for this important area of research.
Learn More >Overlap of pathways enriched by single nucleotide polymorphisms and DNA-methylation underlying chronic postsurgical pain (CPSP), prompted pilot study of CPSP-associated methylation quantitative trait loci (meQTL). Children undergoing spine-fusion were recruited prospectively. Logistic-regression for genome- and epigenome-wide CPSP association and DNA-methylation-single nucleotide polymorphism association/mediation analyses to identify meQTLs were followed by functional genomics analyses. CPSP (n = 20/58) and non-CPSP groups differed in pain-measures. Of 2753 meQTLs, DNA-methylation at 127 cytosine-guanine dinucleotides mediated association of 470 meQTLs with CPSP (p < 0.05). At PARK16 locus, CPSP risk meQTLs were associated with decreased DNA-methylation at and increased DNA-methylation at Corresponding blood eQTLs (GTEx) and cytosine-guanine dinucleotide-loci enrichment for histone marks, transcription factor binding sites and ATAC-seq peaks suggest altered transcription factor-binding. CPSP-associated meQTLs indicate epigenetic mechanisms mediate genetic risk. Clinical trial registration: NCT01839461, NCT01731873 (ClinicalTrials.gov).
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