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Papers: 27 Nov 2021 - 3 Dec 2021

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Association of Genetic Variant at Chromosome 12q23.1 With Neuropathic Pain Susceptibility.

Neuropathic pain (NP) has important clinical and socioeconomic consequences for individuals and society. Increasing evidence indicates that genetic factors make a significant contribution to NP, but genome-wide association studies (GWASs) are scant in this field and could help to elucidate susceptibility to NP.

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Decreased dopaminergic inhibition of pyramidal neurons in anterior cingulate cortex maintains chronic neuropathic pain.

Pyramidal neurons in the anterior cingulate cortex (ACC), a prefrontal region involved in processing the affective components of pain, display hyperexcitability in chronic neuropathic pain conditions, and their silencing abolishes hyperalgesia. We show that dopamine, through D1 receptor (D1R) signaling, inhibits pyramidal neurons of mouse ACC by modulation of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels. Activation of G-coupled D1R by dopamine induces the opening of HCN channels at physiological membrane potentials, driving a significant decrease in input resistance and excitability. Systemic L-DOPA in chronic neuropathic mice rescues HCN channel activity, normalizes pyramidal excitability in ACC, and blocks mechanical and thermal allodynia. Moreover, microinjection of a selective D1R agonist in the ACC relieves the aversiveness of ongoing neuropathic pain, while an ACC D1R antagonist blocks gabapentin- and lidocaine-evoked antinociception. We conclude that dopaminergic inhibition via D1R in ACC plays an analgesic role in physiological conditions and is decreased in chronic pain.

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Implanted spinal neuromodulation interventions for chronic pain in adults.

Implanted spinal neuromodulation (SNMD) techniques are used in the treatment of refractory chronic pain. They involve the implantation of electrodes around the spinal cord (spinal cord stimulation (SCS)) or dorsal root ganglion (dorsal root ganglion stimulation (DRGS)), and a pulse generator unit under the skin. Electrical stimulation is then used with the aim of reducing pain intensity.

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Morphine resistance in spinal cord injury-related neuropathic pain in rats is associated with alterations in dopamine and dopamine-related metabolomics.

Opioids are not universally effective for treating neuropathic pain following spinal cord injury (SCI), a finding that we previously demonstrated in a rat model of SCI. The aim of this study was to determine analgesic response of morphine-responsive and nonresponsive SCI rats to adjunct treatment with dopamine modulators and to establish if the animal groups expressed distinct metabolomic profiles. Thermal thresholds were tested in female Long Evans rats (N = 45) prior to contusion SCI, after SCI and following injection of morphine, morphine combined with dopamine modulators, or dopamine modulators alone. Spinal cord and striatum samples were processed for metabolomics and targeted mass spectrometry. Morphine provided analgesia in 1/3 of SCI animals. All animals showed improved analgesia with morphine + pramipexole (D3 receptor agonist). Only morphine nonresponsive animals showed improved analgesia with the addition of SCH 39166 (D1 receptor antagonist). Metabolomic analysis identified three distinct clusters related to the tyrosine pathway that corresponded to uninjured, SCI morphine-responsive and SCI morphine-nonresponsive groups. Mass spectrometry showed matching differences in dopamine levels in striatum and spinal cord between these groups. The data suggest an overall benefit of the D3 system in improving analgesia, and an association between morphine responsiveness and metabolomic changes in the tyrosine/dopamine pathways in striatum and spinal cord. Perspective: Spinal cord injury (SCI) leads to opioid-resistant neuropathic pain that is associated with changes in dopamine metabolomics in the spinal cord and striatum of rats. We present evidence that adjuvant targeting of the dopamine system may be a novel pain treatment approach to overcome opioid desensitization and tolerance after SCI.

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Research Recommendations Following the Discovery of Pain Sensitising IgG Autoantibodies in Fibromyalgia Syndrome.

Fibromyalgia syndrome (FMS) is the most common chronic widespread pain condition in rheumatology. Until recently, no clear pathophysiological mechanism for fibromyalgia had been established, resulting in management challenges. Recent research has indicated that serum IgGs may play a role in FMS. We undertook a research prioritisation exercise to identify the most pertinent research approaches that may lead to clinically implementable outputs.

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The effectiveness of interventions and intervention components for increasing physical activity and reducing sedentary behaviour in people with persistent musculoskeletal pain: a systematic review and meta-analysis.

This systematic review and meta-analysis investigated the effectiveness of physical activity (PA) and sedentary behaviour (SB) interventions on PA and SB levels in people with persistent musculoskeletal pain. We explored the effectiveness of behaviour change techniques (BCTs), the use of behaviour change theory and non-PA/SB outcomes. Randomised controlled trials of PA or SB interventions for people with persistent musculoskeletal pain were eligible. Twenty-three studies were included. Quality of evidence was assessed using the GRADE approach. Meta-analysis demonstrated a small effect for PA post-intervention (Hedge's g = 0.321, CI 0.136 to 0.507, p = 0.001, very low-quality evidence). There was no effect for longer-term follow-up PA (low quality evidence) or SB outcomes (very low-quality evidence). There was a small effect for studies with low risk-of-bias at longer-term follow-up PA. Self-report PA outcomes, PA and education interventions, non-self-selected PA, a combination of supervised and unsupervised PA and a combination of individual and group-based interventions had larger effects. Heterogeneity was moderate to considerable. Risk-of-bias, assessed using Cochrane risk-of-bias tool (version two), was generally low. Five promising BCTs were identified: 'adding objects to the environment', 'goal setting (outcome)', 'action planning', 'monitoring outcome(s) of behaviour by others without feedback' and 'feedback on outcome(s) of behaviour'. In conclusion, there is evidence for a modest benefit for PA interventions immediately post-intervention, however the quality of evidence is very low. There was no evidence for longer-term follow-up PA or SB. Higher quality studies of PA and SB interventions that use objective measures are needed. PROSPERO registration: CRD42020180260.

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Exploring Patient Preference Heterogeneity for Pharmacological Treatments for Chronic Pain: A Latent Class Analysis.

Several pharmaceutical treatments for chronic pain caused by osteoarthritis (OA) and chronic low back pain (CLBP) are available or currently under development, each associated with different adverse events (AEs) and efficacy profiles. It is therefore important to understand what trade-offs patients are willing to make when choosing between treatments.

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Intrathecal IGF2 siRNA injection provides long-lasting anti-allodynic effect in a spared nerve injury rat model of neuropathic pain.

Previous studies have shown an increase of insulin-like growth factor-2 (IGF2) in animal models of neuropathic pain. We aimed to examine the hypothesis that reducing the expression of IGF2 using intrathecal IGF2 small-interfering RNA (siRNA) would attenuate the development of neuropathic pain in rats after spared nerve injury (SNI). Male Wistar rats were divided into three groups: sham-operated group, in which surgery was performed to cut the muscles without injuring the nerves; SNI group, in which SNI surgery was performed to sever the nerves; and SNI + siRNA IGF2 group, in which SNI surgery was performed, and IGF2-siRNA was administered intrathecally 1 day after SNI. The rats were assessed for mechanical allodynia and cold allodynia 1 day before surgery (baseline), and at 2, 4, 6, 8, and 10 days after siRNA treatment. The rat spinal cord was collected for quantitative polymerase chain reaction and western blot analysis. Compared with the SNI group, rats that received IGF2 siRNA showed a significantly increased SNI-induced paw-withdrawal threshold to metal filament stimulation from Day 4 to Day 10 after SNI surgery. IGF2 siRNA significantly decreased the response duration from the acetone test from Day 2 to Day 10 following SNI surgery. SNI increased IGF2 mRNA expression on Day 2 and increased IGF2 protein expression on Day 8 and Day 10 in the spinal cord of the SNI rats. However, the above-mentioned effects of IGF2 mRNA and protein expression were significantly inhibited in the SNI + IGF2 siRNA group. We demonstrated that intrathecal administration of IGF2 siRNA provided significant inhibition of SNI-induced neuropathic pain via inhibition of IGF2 expression in the spinal cord. The analgesic effect lasted for 10 days. Further exploration of intrathecal IGF2 siRNA administration as a potential therapeutic strategy for neuropathic pain is warranted.

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The Genomic and Phenotypic Landscape of Ichthyosis: An Analysis of 1000 Kindreds.

Ichthyoses are clinically and genetically heterogeneous disorders characterized by scaly skin. Despite decades of investigation identifying pathogenic variants in more than 50 genes, clear genotype-phenotype associations have been difficult to establish.

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Proto-oncogene tyrosine-protein kinase SRC (Src) inhibition in microglia relieves neuroinflammation in neuropathic pain mouse models.

Chronic neuroinflammation is an important factor in the development of neuropathic pain (NP). Excess microglia activation releases a mass of pro-inflammatory cytokines during neuroinflammation process, leading to a constant painful irritation of the sensory nerve. Src belongs to a non-receptor tyrosine kinase associated with sarcoma, whereas the role of Src in neuropathic pain is controversial. We designed to testify the inflammation-regulatory role of Src in the lipopolysaccharide (LPS)-induced BV2 microglia line and the mouse model of neuropathic pain by partial sciatic nerve ligation (PNL). In BV2 microglia, Src expression was inhibited using a Src family kinase inhibitor PP2 after LPS induced inflammatory response. , the neuropathic pain in mice was induced by PNL surgery and then treated with PP2. The neuroinflammation level was detected by enzyme-linked immunosorbent assay (ELISA), immunofluorescence (IF), trans-well and Western blotting (WB) assays, was examined in PNL mice using immunohistochemistry (IHC) and IF. Finally, mechanical allodynia and thermal hyperalgesia assays were used to access the functional evaluation. Inhibition of Src was decreased microglial inflammation and migration after LPS stimuli. Mechanistically, the expression of nuclear factor kappa B (NF-κB) pathway decreased after Src inhibition. The data showed that the decrease expression of Src reduced neuroinflammation and the amount of microglia in spinal dorsal horn (SDH), the mechanical allodynia of mice thereby attenuated after Src inhibition. These results indicated that the inhibition of Src took a protective effect in neuropathic pain mouse models reducing microglia-induced neuroinflammation.

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The associations between sleep disturbance, psychological dysfunction, pain intensity, and pain interference in children with chronic pain.

This study aimed to better understand the associations between both sleep disturbance and psychological dysfunction (i.e., anxiety and depressive symptoms, and anger), and pain intensity and pain interference, in a sample of children with chronic pain.

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Inhibition of SYK and cSrc kinases can protect bone and cartilage in preclinical models of osteoarthritis and rheumatoid arthritis.

The pathophysiology of osteoarthritis (OA) includes the destruction of subchondral bone tissue and inflammation of the synovium. Thus, an effective disease-modifying treatment should act on both of these pathogenetic components. It is known that cSrc kinase is involved in bone and cartilage remodeling, and SYK kinase is associated with the inflammatory component. Thus the aim of this study was to characterize the mechanism of action and efficacy of a small molecule multikinase inhibitor MT-SYK-03 targeting SYK and cSrc kinases among others in different in vitro and in vivo arthritis models. The selectivity of MT-SYK-03 kinase inhibition was assayed on a panel of 341 kinases. The compound was evaluated in a set of in vitro models of OA and in vivo OA and RA models: surgically-induced arthritis (SIA), monosodium iodoacetate-induced arthritis (MIA), collagen-induced arthritis (CIA), adjuvant-induced arthritis (AIA). MT-SYK-03 inhibited cSrc and SYK with IC of 14.2 and 23 nM respectively. Only five kinases were inhibited > 90% at 500 nM of MT-SYK-03. In in vitro OA models MT-SYK-03 reduced hypertrophic changes of chondrocytes, bone resorption, and inhibited SYK-mediated inflammatory signaling. MT-SYK-03 showed preferential distribution to joint and bone tissue (in rats) and revealed disease-modifying activity in vivo by halving the depth of cartilage erosion in rat SIA model, and increasing the pain threshold in rat MIA model. Chondroprotective and antiresorptive effects were shown in a monotherapy regime and in combination with methotrexate (MTX) in murine and rat CIA models; an immune-mediated inflammation in rat AIA model was decreased. The obtained preclinical data support inhibition of cSrc and SYK as a viable strategy for disease-modifying treatment of OA. A Phase 2 clinical study of MT-SYK-03 is to be started.

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PROTEOMIC QUANTITATIVE STUDY OF DORSAL ROOT GANGLIA AND SCIATIC NERVE IN TYPE 2 DIABETIC MICE.

Peripheral neuropathy is the most common and debilitating complication of type 2 diabetes leading to sensory loss, dysautonomia, hyperalgesia and spontaneous noxious sensations. Despite clinical and economic burden of diabetic neuropathy, no effective treatment is available. Thus, more preclinical research must be conducted to gain further understanding of the aetiology of the disease and elucidate new therapeutic targets.

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A Dyadic Investigation of Depressed Affect and Interspousal Behavior in Couples With Chronic Back Pain.

Depression and marital discord are characteristic not only of individuals with chronic low back pain (ICPs) but also of their spouses.

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Synthesis and evaluation of antioxidant, anti-edematogenic and antinociceptive properties of new selenium-sulfa compounds.

We describe here results for the synthesis and synthetic application of 4-amino-3-(arylselanyl)benzenesulfonamides, and preliminary evaluation of antioxidant, anti-edematogenic and antinociceptive properties. This class of compounds was synthesized in good yields by a reaction of commercially available sulfanilamide and diorganyl diselenides in the presence of 10 mol% of I 2 . Furthermore, the synthesized compound 3a was evaluated on complete Freund's adjuvant (CFA)-induced acute inflammatory pain. Dose and time-response curves of antinociceptive effect of compound 3a were performed using this experimental model. Also, compound 3a effect was tested in hot-plate test to evaluate the acute non-inflammatory antinociception. The open field test was performed to evaluate the locomotor and exploratory behaviors of mice. Oxidative stress markers, such as glutathione peroxidase activity; reactive species, non-protein thiols, and lipid peroxidation levels were performed to investigate the antioxidant action of compound 3a . Our findings suggest that the antioxidant effect of compound 3a may contribute to reducing the nociception and suppress the signaling pathways of inflammation on the local injury induced by CFA. Thus, compound 3a reduced the paw edema as well as the hyperalgesic behavior in mice, being a promising therapeutic agent for the treatment of painful conditions.

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The PPARγ agonist pioglitazone produces a female-predominant inhibition of hyperalgesia associated with surgical incision, peripheral nerve injury, and painful diabetic neuropathy.

Pioglitazone, an agonist at peroxisome proliferator-activated receptor gamma, is FDA-approved for the treatment of insulin resistance in type 2 diabetes. Numerous studies in male rodents suggest that pioglitazone inhibits inflammatory and neuropathic pain, but few included female subjects. To address this gap, we compared the effects of pioglitazone in both sexes in the intraplantar methylglyoxal model (MG) model of chemical pain and painful diabetic neuropathy (PDN), the plantar incision model (PIM) of postoperative pain, the spared nerve injury (SNI) model of traumatic nerve injury, and the ZDF rat and db/db mouse models of PDN. We administered pioglitazone by one-time intrathecal or intraperitoneal injection or by adding it to chow for 6 weeks, followed by measurement of hypersensitivity to non-noxious mechanical, noxious mechanical, heat, and/or cold stimuli. In all mouse models, injection of pioglitazone decreased pain-like behaviors with greater potency and/or efficacy in females as compared to males: heat and mechanical hypersensitivity in the MG model (0.1-10 mg/kg); mechanical hypersensitivity in the PIM model (10 μg); mechanical and cold hypersensitivity in the SNI model (100 mg/kg); and heat hypersensitivity in the db/db model (100 mg/kg). Furthermore, co-administration of low doses of morphine (1 mg/kg) and pioglitazone (10 mg/kg) decreased SNI-induced mechanical and cold hypersensitivity in female but not male mice. In the ZDF rat, pioglitazone (100 mg/kg) decreased heat and mechanical hypersensitivity with no sex difference. In the db/db model, pioglitazone had no effect when given into chow for 6 weeks at 0.3, 3 or 30 mg/kg doses. We conclude that females exhibit greater anti-hyperalgesic responses to pioglitazone in mouse models of chemical-induced nociception, postsurgical pain, neuropathic pain, and PDN. These findings set the stage for clinical trials to determine whether pioglitazone has analgesic properties across a broad spectrum of chronic pain conditions, particularly in women.

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A green-lipped mussel reduces pain behavior and chondrocyte inflammation and attenuated experimental osteoarthritis progression.

The green-lipped mussel (GLM) contains novel omega-3 polyunsaturated fatty acids, which exhibit anti-inflammatory and joint-protecting properties. Osteoarthritis (OA) is a degenerative joint disease characterized by a progressive loss of cartilage; oxidative stress plays a role in the pathogenesis of OA. The objectives of this study were to investigate the in vivo effects of the GLM on pain severity and cartilage degeneration using an experimental rat OA model, and to explore the mode of action of GLM. OA was induced in rats by intra-articular injection of monosodium iodoacetate (MIA) into the knee. Oral GLM was initiated on the day after 3dyas of MIA injection. Limb nociception was assessed by measuring the paw withdrawal latency and threshold. Samples were analyzed both macroscopically and histologically. Immunohistochemistry was used to investigate the expression of interleukin-1β (IL-1β), IL-6, nitrotyrosine, and inducible nitric oxide synthase (iNOS) in knee joints. Also, the GLM was applied to OA chondrocyte, and the expression on catabolic marker and necroptosis factor were evaluated by real-time polymerase chain reaction. Administration of the GLM improved pain levels by preventing cartilage damage and inflammation. GLM significantly attenuated the expression levels of mRNAs encoding matrix metalloproteinase-3 (MMP-3), MMP-13, and ADAMTS5 in IL-1β-stimulated human OA chondrocytes. GLM decreased the expression levels of the necroptosis mediators RIPK1, RIPK3, and the mixed lineage kinase domain-like protein (MLKL) in IL-1β-stimulated human OA chondrocytes. Thus, GLM reduced pain and cartilage degeneration in rats with experimentally induced OA. The chondroprotective properties of GLM included suppression of oxidative damage and inhibition of catabolic factors implicated in the pathogenesis of OA cartilage damage. We suggest that GLM may usefully treat human OA.

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Metformin effect in models of inflammation is associated with activation of ATP-dependent potassium channels and inhibition of tumor necrosis factor-α production.

Metformin is an oral hypoglycemic drug widely used in the management of type 2 diabetes mellitus. We have recently demonstrated that metformin exhibits activity in models of nociceptive and neuropathic pain. However, little is known about its effects in experimental models of inflammation and inflammatory pain. Thus, the present study aimed to evaluate the activity of metformin in experimental models of inflammation and inflammatory pain in mice, as well as the underlying mechanisms. Previous (1 h) per os (p.o.) administration of metformin (250, 500 or 1000 mg/kg) inhibited the mechanical allodynia and paw edema induced by intraplantar (i.pl.) injection of carrageenan (600 μg) and also the pleurisy induced by this stimulus (200 μg, intrapleural). In the model of mechanical allodynia and paw edema induced by carrageenan, metformin also exhibited activity when administered after (1 h) the inflammatory stimulus. Metformin (1000 mg/kg) reduced the production of tumor necrosis factor-α induced by i.pl. injection of carrageenan. Metformin antiallodynic effect was not affected by previous administration of naltrexone (5 or 10 mg/kg, intraperitoneal) or cyproheptadine (5 or 10 mg/kg, p.o). However, this effect was abolished by previous administration of glibenclamide (20 or 40 mg/kg, p.o). In conclusion, the results demonstrate the activity of metformin in models of inflammation and inflammatory pain. In addition, the results indicate that the activity of metformin may be mediated by activation of ATP-sensitive potassium channels and reduction of production of inflammatory mediators. Altogether, these results stimulate the conduction of studies aiming to evaluate whether metformin may be repositioned in the treatment of patients with painful and inflammatory disorders.

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Psychometric Properties of a Healthcare Provider Burden Scale: Preliminary Results.

Measures are lacking of the clinical burden that healthcare providers perceive in treating chronic conditions. This study presents a preliminary psychometric evaluation of a novel self-report measure of provider burden in the treatment of chronic pain. Data for eight burden items were available from vignette studies examining the effects of patient pain severity and medical evidence on clinical burden and judgments for chronic pain. Participants (N = 922) were 109 physicians and 813 non-physicians, all acting in the role of physician (232 community members without chronic pain, 105 community members with chronic pain, and 476 American Chronic Pain Association members with chronic pain). Factor analyses of burden items yielded one-factor solutions in all samples, with high factor loadings and adequate explained variance. Internal consistency reliability was uniformly high (≥ .87). Burden scores were significantly higher among physicians compared to non-physicians; non-physician groups did not differ on any burden score. Significant correlations of burden score with indicators of psychosocial complications in patient care supported scale validity. Burden score was not associated with gender, age, or education. Results provide initial support for the psychometric properties of a Healthcare Provider Burden Scale (HPBS). Research utilizing larger and representative healthcare provider groups is needed.

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A scoping review of the diurnal variation in the intensity of neuropathic pain.

Recent studies suggest that neuropathic pain exhibit a daily diurnal pattern with peak levels usually in the late afternoon to evening and trough in the morning hours, although literature on this topic has been sparse. This scoping review examines current evidence on the chronobiology of neuropathic pain in both animal models and in humans with neuropathic pain.

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Core outcome set for preventive intervention trials in chronic and episodic migraine (COSMIG): an international, consensus-derived and multistakeholder initiative.

Typically, migraine prevention trials focus on reducing migraine days. This narrow focus may not capture all that is important to people with migraine. Inconsistency in outcome selection across trials limits the potential for data pooling and evidence synthesis. In response, we describe the development of core outcome set for migraine (COSMIG).

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Vulnerable Dispositional Traits and Chronic Pain: Predisposing but not Predetermining.

Dispositional traits can be protective or contribute to increased vulnerability in individuals with chronic pain. This study aims to evaluate the association between two dispositional trait measures, affect balance style and multi-domain trait groups, with psychosocial measures, clinical pain, functional pain, and experimental pain at two years in individuals with chronic knee pain. The study is a prospective analysis of 168 community dwelling individuals aged 45-85 years old with knee pain with or at risk for knee osteoarthritis. At baseline, affect balance style and multi-domain trait groups were associated with psychosocial measures, clinical pain, and functional status. At the two-year time point, the multi-domain trait groups were associated with the clinical pain measures. Interestingly, individuals with previously demonstrated vulnerable traits showed more variability in dispositional trait status at the two-year time point compared to those with dispositional traits previously demonstrated as more protective. Findings reiterate that dispositional traits are predisposing but are not predetermining regarding pain-related experiences. PERSPECTIVE: Vulnerable and protective dispositional traits are positively and negatively associated with clinical pain and functional limitations respectively. Although considered relatively stable, a 30-50% shift in dispositional traits was indicated over a two-year period. Findings highlight that dispositional traits are modifiable and thus, predisposing but not predetermining for persisting chronic pain.

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Commentary: Intergenerational Associations in Pediatric Chronic Pain: Validity of an Adapted Unified Multifactorial Model of Parental Factors in Pediatric Chronic Pain.

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Mini-Review: Dissecting receptor-mediated stimulation of TRPV4 in nociceptive and inflammatory pathways.

Transient Receptor Potential Vanilloid 4 (TRPV4) is a polymodal, non-selective cation channel that detects thermal, mechanical, and environmental cues and contributes to a range of diverse physiological processes. The effects of chronic TRPV4 stimulation and gain-of-function genetic mutations suggest that TRPV4 may also be a valuable therapeutic target for pathophysiological events including neurogenic inflammation, peripheral neuropathies, and impaired wound healing. There has been significant interest in defining how and where TRPV4 may promote inflammation and pain. Endogenous stimuli such as osmotic stress and lipid binding are established TRPV4 activators. The TRP channel family is also well-known to be controlled by 'receptor-operated' pathways. For example, G protein-coupled receptors (GPCRs) expressed by primary afferent neurons or other cells in inflammatory pathways utilize TRPV4 as an effector protein to amplify nociceptive and inflammatory signaling. Contributing to disorders including arthritis, neuropathies, and pulmonary edema, GPCRs such as the protease-activated receptor PAR2 mediate activation of kinase signaling cascades to increase TRPV4 phosphorylation, resulting in sensitization and enhanced neuronal excitability. Phospholipase activity also leads to production of polyunsaturated fatty acid lipid mediators that directly activate TRPV4. Consistent with the contribution of TRPV4 to disease, pharmacological inhibition or genetic ablation of TRPV4 can diminish receptor-mediated inflammatory events. This review outlines how receptor-mediated signaling is a major endogenous driver of TRPV4 gating and discusses key signaling pathways and emerging TRPV4 modulators such as the mechanosensitive Piezo1 ion channel. A collective understanding of how endogenous stimuli can influence TRPV4 function is critical for future therapeutic endeavors to modulate this channel.

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Dose-Related Inhibition of Capsaicin Responses by Cannabinoids CBG, CBD, THC and their Combination in Cultured Sensory Neurons.

The analgesic effects of are mediated by ∆ tetrahydrocannabinol (THC), but the contributions of other bioactive complex components, including cannabigerol (CBG) and cannabidiol (CBD), are unclear. We describe the individual and combined effects of CBG, CBD and THC, on blocking capsaicin responses in dorsal root ganglion (DRG) neurons, in an in vitro model of nociceptor hypersensitivity.

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Antinociceptive and chondroprotective effects of prolonged β-caryophyllene treatment in the animal model of osteoarthritis: Focus on tolerance development.

Osteoarthritis (OA) is a chronic joint disease in which cartilage degeneration leads to chronic pain. The endocannabinoid system has attracted attention as an emerging drug target for OA. However, the therapeutic potential of cannabinoids is limited by psychoactive side-effects related to CB1 activation and tolerance development for analgesic effects. β-Caryophyllene (BCP) is a low-efficacy natural agonist of CB2 and a common constituent of human diet with well-established anti-inflammatory properties. The results presented herein show the anti-nociceptive and chondroprotective potential of BCP in an animal model of OA induced by intra-articular injection of monoiodoacetate (MIA). Behavioural assessment included pressure application measurement and kinetic weight bearing tests. Histological assessment of cartilage degeneration was quantified using OARSI scoring. Experiments established the dose-response effects of BCP and pharmacological mechanisms of the antinociceptive action dependent on CB2 and opioid receptors. Chronic BCP treatment was able to hamper cartilage degeneration without producing tolerance for the analgesic effects. The data presented herein show that BCP is able to produce both acute and prolonged antinociceptive and chondroprotective effects. Together with the safety profile and legal status of BCP, these results indicate a novel and promising disease-modifying strategy for treating OA.

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Mini-Review: Two Brothers in Crime – The Interplay of TRESK and TREK in Human Diseases.

TWIK-related spinal cord potassium (TRESK) and TWIK-related potassium (TREK) channels are both subfamilies of the two-pore domain potassium (K2P) channel group. Despite major structural, pharmacological, as well as biophysical differences, emerging data suggest that channels of these two subfamilies are functionally more closely related than previously assumed. Recent studies, for instance, indicate an assembling of TRESK and TREK subunits, leading to the formation of heterodimeric channels with different functional properties compared to homodimeric ones. Formation of tandems consisting of TRESK and TREK subunits might thus multiply the functional diversity of both TRESK and TREK activity. Based on the involvement of these channels in the pathophysiology of migraine, we here highlight the role as well as the impact of the interplay of TRESK and TREK subunits in the context of different disease settings. In this regard, we focus on their involvement in migraine and pain syndromes, as well as on their influence on (neuro-)inflammatory processes. Furthermore, we describe the potential implications for innovative therapeutic strategies that take advantage of TRESK and TREK modulation as well as obstacles encountered in the development of therapies related to the aforementioned diseases.

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Preventing progression from chronic to widespread pain and its impact on health-related quality of life: a historical cohort study of osteopathic medical care.

It is generally acknowledged that osteopathic physicians take a holistic approach to patient care. This style may help prevent the progression of painful musculoskeletal conditions, particularly if combined with osteopathic manipulative treatment (OMT).

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Comment on “The value of interdisciplinary treatment for sickness absence in chronic pain: A nationwide register-based cohort study”.

We have read the article "The value of interdisciplinary treatment for sickness absence in chronic pain: A nationwide register-based cohort study" by LoMartire et al (1) with great interest but also great concern. We, a group of experienced specialists, clinicians and scientists in Pain Medicine, welcome well-designed good quality studies on the treatment of chronic pain, a major health problem. Valid evidence on the benefits of interventions is of great importance for healthcare and Society. A critical appraisal of current standard of care methods is certainly warranted in order to promote continuous improvement. However, the present study has in our opinion several critical issues to which we would like to draw your attention.

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Effectiveness of non-opioid interventions to reduce opioid withdrawal symptoms in patients with chronic pain: a systematic review.

Dealing with the opioid crisis, medical doctors are keen to learn how to best treat opioid dependency in patients with chronic non-cancer pain. Opioid replacement therapy is commonly used, but success rates vary widely. Since many patients still experience severe withdrawal symptoms, additional interventions are necessary.

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Analgesia Prescribing in Patients with Inflammatory Arthritis in England: An Observational Study Using Electronic Healthcare Record Data.

International data suggest inflammatory arthritis (IA) pain management frequently involves opioid prescribing, despite little evidence of efficacy, and potential harms. We evaluated analgesia prescribing in English National Health Service-managed patients with IA.

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Disease-modifying therapeutic strategies in osteoarthritis: current status and future directions.

Osteoarthritis (OA) is the most common form of arthritis. It is characterized by progressive destruction of articular cartilage and the development of chronic pain and constitutes a considerable socioeconomic burden. Currently, pharmacological treatments mostly aim to relieve the OA symptoms associated with inflammation and pain. However, with increasing understanding of OA pathology, several potential therapeutic targets have been identified, enabling the development of disease-modifying OA drugs (DMOADs). By targeting inflammatory cytokines, matrix-degrading enzymes, the Wnt pathway, and OA-associated pain, DMOADs successfully modulate the degenerative changes in osteoarthritic cartilage. Moreover, regenerative approaches aim to counterbalance the loss of cartilage matrix by stimulating chondrogenesis in endogenous stem cells and matrix anabolism in chondrocytes. Emerging strategies include the development of senolytic drugs or RNA therapeutics to eliminate the cellular or molecular sources of factors driving OA. This review describes the current developmental status of DMOADs and the corresponding results from preclinical and clinical trials and discusses the potential of emerging therapeutic approaches to treat OA.

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