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Endocannabinoids are showing great promise as effective mediators for controlling joint inflammation and pain. One strategy that could be harnessed to promote endogenous cannabinoid function is to inhibit the enzymatic break down of endocannabinoids locally in the joint. KML29 is an inhibitor of monoacylglycerol lipase (MAGL) activity which has been shown to promote increased 2-arachodonylglycerol (2-AG) levels in the circulation and in peripheral tissues. It is also known that 2-AG can be metabolised via the cyclo-oxygenase-2 (COX-2) pathway leading to the production of pro-inflammatory prostaglandins, which may counteract the effects of 2-AG. Therefore, this study examined the effect of KML29 alone as well as in combination with low-dose celecoxib (CXB) on joint pain and inflammation in the monoiodoacetate (MIA) model of osteoarthritis (OA) pain.
Learn More >This cross-sectional study examined, for the first time, a large cohort of patients with trigeminal neuralgia, to ascertain the occurrence of familial cases, providing a systematic description of clinical features of familial disease. Since there is evidence linking hyperexcitability of trigeminal ganglion neurons to trigeminal neuralgia, we also carried out an exploratory genetic analysis of the neuronal electrogenisome in these patients.
Learn More >Children's experience of chronic pain is influenced by the psychological and behavioural responses of their parents. However, the vast majority of research has been cross-sectional, precluding examination of how these dynamic relationships unfold over time. This study used a micro-longitudinal design to examine the daily relationships between parent mood and protective responses and child chronic pain. We also examined the moderating roles of child and parent pain catastrophizing to determine how the affective-motivational context may alter the influence of parent factors. Participants included 95 youth with idiopathic chronic pain (Mage=14.08; 71.6% female) and their parents. At baseline, parents and youth reported on their catastrophic thinking about child pain. For 7 consecutive days, parents completed daily assessments of their mood and protective responses, while youth completed assessments of their pain intensity, unpleasantness, and interference. Multi-level path analyses were conducted. At a daily level, greater parent protectiveness significantly predicted higher youth pain unpleasantness, interference, and intensity; more negative parent mood significantly predicted higher youth pain intensity and unpleasantness. Higher baseline youth pain catastrophizing predicted a stronger daily association between parent mood and youth pain unpleasantness and intensity. Higher baseline parent pain catastrophizing predicted a weaker daily association between parent protectiveness and youth pain interference. Findings suggest that parent mood and protective responses are dynamic, daily predictors of child pain. Findings also underscore the importance of addressing parents' daily mental health and protectiveness, among youth with chronic pain, and suggest different intervention targets depending on levels of child and parent catastrophizing.
Learn More >N-methyladenosine (mA) modification in RNA has been implicated in diverse biological processes. However, very little is currently known about its role in nociceptive modulation. Here, we found that the level of spinal mA modification was significantly increased in a mouse model of Complete Freund's Adjuvant (CFA)-induced chronic inflammatory pain, which was accompanied with the augmentation of methyltransferase-like 3 (METTL3) expression in the spinal cord. Knockdown of spinal METTL3 prevented and reversed CFA-induced pain behaviors and spinal neuronal sensitization. In contrast, overexpression of spinal METTL3 produced pain behaviors and neuronal sensitization in naive mice. Moreover, we found that METTL3 positively modulated the pri-miR-65-3p processing in a microprocessor protein DiGeorge critical region 8-dependent manner. Collectively, our findings reveal an important role of METTL3-mediated mA modification in nociceptive sensitization and provide a novel perspective on mA modification in the development of pathological pain.
Learn More >Sensory neurons and immune cells share a common microenvironmental niche for surveying tissue integrity. The immune and nervous systems both sense deviations in homeostasis and initiate protective responses and, upon malfunction, also jointly contribute to disease. Barrier tissues are heavily innervated by nociceptors, the sensory neurons that detect noxious stimuli, leading to pain and itch. The same tissues are also home to diverse immune cells that respond to infections and injury. The physical proximity of nociceptors and immune cells allows for direct local interactions between the two, independent of the CNS. We discuss in this study their ligand-receptor-based interactions and propose the need to shift from studying individual neuroimmune interactions to exploring the reciprocal neuroimmune interaction network in its entirety: the "neuroimmune interactome." Identification of the nature of the interactome in health and its plasticity in disease will unravel the functional consequences of interactions between nociceptors and immune cells.
Learn More >Recent research has shown that placebos can be effective even if they are openly prescribed to participants. Yet, it is unclear how such "open-label placebos" (OLPs) compare to deceptive placebo (DP) and what the mechanisms of actions are. In this study, we therefore compared 2 versions of OLP to DP and no treatment (NT).
Learn More >The evolution of peripheral and central changes following a peripheral nerve injury imply the onset of afferent signals that affect the brain. Changes to inflammatory processes may contribute to peripheral and central alterations such as altered psychological state and are not well characterized in humans. We focused on four elements that change peripheral and central nervous systems following ankle injury in 24 adolescent patients and 12 age-sex matched controls. Findings include (a) Changes in tibial, fibular, and sciatic nerve divisions consistent with neurodegeneration; (b) Changes within the primary motor and somatosensory areas as well as higher order brain regions implicated in pain processing; (c) Increased expression of fear of pain and pain reporting; and (d) Significant changes in cytokine profiles relating to neuroinflammatory signaling pathways. Findings address how changes resulting from peripheral nerve injury may develop into chronic neuropathic pain through changes in the peripheral and central nervous system.
Learn More >To review the effect of patient decision aids for adults making treatment decisions regarding the management of chronic musculoskeletal pain.
Learn More >Fluorescent probes have been used as effective methods for profiling proteins in biological system because of their high selectivity, sensitivity and temporal-spatial resolution. A specific fluorescent probe for understanding the function of the transient receptor potential ankyrin 1 (TRPA1) channel that is closely related with various diseases like persistent pain, respiratory and chronic itch syndromes, however, is still lacking. Here, we report a "turn-on" fluorescent probe (A1CA) for visualizing TRPA1 channels in the plasma membrane of live cells based on a photochromic ligand derived from 4-(phenylazo)benzenamine. Evaluating of the specificity and sensitivity of A1CA by electrophysiology and confocal imaging showed that A1CA probe displays higher affinity and selectivity to TRPA1 channel versus all other ion channels including TRPV1, TRPV3, Nav1.4, Nav1.5 and hERG. Based on the supporting evidence, A1CA has great potential as a molecular imaging probe for high-throughput screening of novel TRPA1 agonists.
Learn More >Accumulating evidence suggests that epigenetic mechanisms may hold great potential in the field of pain. We systematically reviewed the literature exploring epigenetic mechanisms in people with pain. Four databases have been interrogated: MEDLINE, The Cochrane Central Register of Controlled Trial, Scopus, and Web of Science, following PRISMA guidelines in conducting study selection and assessment. Thirty-seven studies were included. Studies explored epigenetics in conditions such as fibromyalgia, CRPS, neuropathies, or osteoarthritis. Research focussed on genome-wide and gene-specific DNA methylation, and miRNA expression. Bioinformatics analyses exploring miRNA-associated molecular pathways were also performed. Several genes already known for their role in pain (BDNF, HDAC4, PRKG1, IL-17, TNFRSF13B, etc.), and several miRNAs linked to inflammatory regulation, nociceptive signalling and protein kinases functions have been found to differ significantly between people with chronic pain and healthy controls. Although the studies included were cross-sectional in nature, and no conclusion on causal links between epigenetic changes and pain could be drawn, we summarised the large amount of data available in literature on the topic, highlighting results that have been replicated by independent investigations. The field of pain epigenetics appears very exciting and has all the potential to lead to remarkable scientific advances. However, high-quality, well-powered, longitudinal studies are warranted. Perspective: Though more high-quality research is needed, available research exploring epigenetic mechanisms or miRNAs in people with pain shows that genes regulating synaptic plasticity and excitability, protein kinases, and elements of the immune system might hold great potential in understanding the pathophysiology of different conditions.
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