Effect of fentanyl and remifentanil on neuron damage and oxidative stress during induction neurotoxicity.

Opioids can be used for medical and non-medical purposes. Chronic pain such as cancer, as well as the frequent use of such drugs in places such as operating rooms and intensive care units, and in non-medical areas like drug abuse the effects and side effects of these drugs need to be examined in more detail. For this purpose, the effects of fentanyl and remifentanil drugs on neuroinflammation, oxidative stress and cholinesterase metabolism were investigated. Neuron cells (CRL-10742) were used for the evaluation of the toxicity of fentanyl and remifentanil. MTT, PON1 activity and total thiol levels for its effect on oxidative stress, AChE and BChE activities for its effect on the cholinergic system, and TNF, IL-8 and IL-10 gene levels for its neuroinflammation effect were determined. The highest neurotoxic dose of fentanyl and remifentanil was determined as 10 µg/mL. It was observed that the rate of neuron cells in this dose has decreased by up to 61.80% and 56.89%, respectively. The IL-8 gene expression level in both opioids was down-regulated while IL 10 gene level was up-regulated in a dose-dependent manner compared to the control. In our results, the TNF gene expression level differs between the two opioids. In the fentanyl group, it was seen to be up-regulated in a dose-dependent manner compared to the control. Fentanyl and remifentanil showed an inhibitory effect against PON1, while remifentanil showed an increase in total thiol levels. PON1, BChE and total thiol activities showed similarity with MTT.

Trajectories of prescription opioid tapering in patients with chronic non-cancer pain: a retrospective cohort study, 2015-2020.

OBJECTIVE: To identify common opioid tapering trajectories among patients commencing opioid taper from long-term opioid therapy for chronic non-cancer pain and to examine patient-level characteristics associated with these different trajectories. DESIGN: A retrospective cohort study. SETTING: Australian primary care. SUBJECTS: Patients prescribed opioid analgesics between 2015 and 2020. METHODS: Group-based trajectory modeling and multinomial logistic regression analysis were conducted to determine tapering trajectories and to examine demographic and clinical factors associated with the different trajectories. RESULTS: A total of 3369 patients commenced a taper from long-term opioid therapy. Six distinct opioid tapering trajectories were identified: low dose / completed taper (12.9%), medium dose / faster taper (12.2%), medium dose / gradual taper (6.5%), low dose / noncompleted taper (21.3%), medium dose / noncompleted taper (30.4%), and high dose / noncompleted taper (16.7%). A completed tapering trajectory from a high opioid dose was not identified. Among patients prescribed medium opioid doses, those who completed their taper were more likely to have higher geographically derived socioeconomic status (relative risk ratio [RRR], 1.067; 95% confidence interval [CI], 1.001-1.137) and less likely to have sleep disorders (RRR, 0.661; 95% CI, 0.463-0.945) than were those who didn't complete their taper. Patients who didn't complete their taper were more likely to be prescribed strong opioids (eg, morphine, oxycodone), regardless of whether they were tapered from low (RRR, 1.444; 95% CI, 1.138-1.831) or high (RRR, 1.344; 95% CI, 1.027-1.760) doses. CONCLUSIONS: Those prescribed strong opioids and high doses appear to be less likely to complete tapering. Further studies are needed to evaluate the clinical outcomes associated with the identified trajectories.

A Progressive Build-up of Perineuronal Nets in the Somatosensory Cortex Is Associated with the Development of Chronic Pain in Mice.

Chronic pain is sustained by a maladaptive form of neuronal plasticity occurring in all stations of the pain neuraxis, including cortical regions of the pain matrix. We report that chronic inflammatory pain induced by unilateral injection of complete Freund's adjuvant (CFA) in the hindpaw of male mice was associated with a progressive build-up of perineuronal nets (PNNs) in the contralateral somatosensory cortex (SSC), medial prefrontal cortex (mPFC), and reticular thalamic nucleus. In the SSC, the density of PNNs labeled by Wisteria floribunda agglutinin (WFA) was increased at both 3 and 7 d following CFA injection, but only after 7 d in the mPFC. The number of parvalbumin (PV)-positive interneurons enwrapped by WFA+/PNNs was also increased in all three brain regions of mice injected with CFA. Remarkably, PNN degradation induced by intracortical infusion of chondroitinase-ABC significantly reduced mechanical and thermal pain, and also reversed the increased frequency of IPSCs recorded in layer 5 pyramidal neurons of the contralateral SSC in CFA-injected mice. These findings suggest a possible relationship between cortical PNNs and nociceptive sensitization, and support the hypothesis that PNNs maintain their plasticity in the adult life and regulate cortical responses to sensory inputs.SIGNIFICANCE STATEMENT The brain extracellular matrix not only provides structural support, but also regulates synapse formation and function, and modulates neuronal excitability. We found that chronic inflammatory pain in mice enhances the density of perineuronal nets (PNNs) in the somatosensory cortex and medial prefrontal cortex. Remarkably, enzymatic degradation of PNNs in the somatosensory cortex caused analgesia and reversed alterations of inhibitory synaptic transmission associated with chronic pain. These findings disclose a novel mechanism of nociceptive sensitization and support a role for PNNs in mechanisms of neuronal plasticity in the adult brain.

Anti-inflammatory and analgesic effect of Forsythiaside B on complete Freund's adjuvant-induced inflammatory pain in mice.

Chronic pain is frequently reported in clinical practice. Therefore, it is important to identify effective therapy to relieve pain. In this work, we selected Forsythoside B (FB), a phenylethanoid glycoside isolated from Forsythia suspensa (Thunb.) Vahl, to evaluate its effect in modulating inflammatory pain induced by complete Freund's adjuvant (CFA) and the involved mechanisms. We discovered that FB could attenuate inflammatory pain triggered by CFA injection and exert anti-anxiety effects. In detail, proinflammatory cytokines, consisting of IL-6 and TNF-α, were decreased after FB administration in the CFA-injected mice. Furthermore, the FB application ameliorated the activation of ionized calcium-binding adaptor molecule 1 (Iba-1) and glial fibrillary acidic protein (GFAP), the microglia and astrocytes markers respectively. Therefore, our findings indicate that FB could be a promising treatment for chronic inflammatory pain.

CDC Clinical Practice Guideline for Prescribing Opioids for Pain - United States, 2022.

This guideline provides recommendations for clinicians providing pain care, including those prescribing opioids, for outpatients aged ≥18 years. It updates the CDC Guideline for Prescribing Opioids for Chronic Pain - United States, 2016 (MMWR Recomm Rep 2016;65[No. RR-1]:1-49) and includes recommendations for managing acute (duration of <1 month), subacute (duration of 1-3 months), and chronic (duration of >3 months) pain. The recommendations do not apply to pain related to sickle cell disease or cancer or to patients receiving palliative or end-of-life care. The guideline addresses the following four areas: 1) determining whether or not to initiate opioids for pain, 2) selecting opioids and determining opioid dosages, 3) deciding duration of initial opioid prescription and conducting follow-up, and 4) assessing risk and addressing potential harms of opioid use. CDC developed the guideline using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) framework. Recommendations are based on systematic reviews of the scientific evidence and reflect considerations of benefits and harms, patient and clinician values and preferences, and resource allocation. CDC obtained input from the Board of Scientific Counselors of the National Center for Injury Prevention and Control (a federally chartered advisory committee), the public, and peer reviewers. CDC recommends that persons with pain receive appropriate pain treatment, with careful consideration of the benefits and risks of all treatment options in the context of the patient's circumstances. Recommendations should not be applied as inflexible standards of care across patient populations. This clinical practice guideline is intended to improve communication between clinicians and patients about the benefits and risks of pain treatments, including opioid therapy; improve the effectiveness and safety of pain treatment; mitigate pain; improve function and quality of life for patients with pain; and reduce risks associated with opioid pain therapy, including opioid use disorder, overdose, and death.

Should We Use COMM (Current Opioid Misuse Measure) to Screen for Opioid Abuse in Patients With Cancer Pain?

BACKGROUND: Growing concerns about opioid use disorder (OUD) and the resulting decrease in opioid availability for patients with cancer pain highlight the need for reliable screening tools to identify the subset of patients at increased risk for aberrant opioid use. Our study examines the utility of Current Opioid Misuse Measure (COMM) recommended by the NCCN Clinical Practice Guidelines in Oncology for Adult Cancer Pain. PATIENTS AND METHODS: We analyzed prospectively collected patient-reported outcomes of 444 consecutive patients with cancer seen in pain clinics of a cancer center at 2 time points within 100 days. The relationship of COMM to other OUD screening tools, pain, opioid doses, patient demographics, and mortality was examined using univariate and multivariable logistic regression. We also examined individual items of COMM for face validity. RESULTS: Among 444 patients who completed pain surveys at 2 time points, 157 (35.4%) did not complete COMM surveys. Using a COMM cutoff of ≥13, a total of 84 patients (29.3%; 84/287) scored positive for aberrant drug use. As patients remained on opioids for 49 to 100 days, the likelihood of improving COMM score (turning from positive to negative) was 6.1 times greater than the reverse. The number of patients with COMM ≥13 was 3.8 times higher than the number of patients with CPT diagnostic codes for OUD, 5.3 times higher than those with a positive urine drug screening, and 21 times higher than those with a positive CAGE (Cut Down, Annoyed, Guilty, Eye-Opener Questionnaire) score. COMM ≥13 was not associated with pain relief response (worst pain intensity score ≥2 points on the Brief Pain Inventory), opioid doses, gender, or age. Contrary to the intended use of COMM to identify aberrant opioid use, COMM ≥13 predicted mortality: patients with COMM ≥13 were 1.9 times more likely to die within 12 months. CONCLUSIONS: Our study found that using COMM in a cancer population may significantly overestimate the risk of opioid misuse. Using COMM without modifications can create an additional barrier to cancer pain management, such as limiting appropriate opioid use.

Pain, Opioid Analgesics, and Cognition: A Conceptual Framework in Older Adults.

Chronic pain is highly prevalent in older adults and is associated with poor functional outcomes. Furthermore, opioid analgesics are commonly utilized for the treatment of pain in older adults despite well-described adverse effects. Importantly, both chronic pain and opioid analgesics have been linked with impairments in cognitive function, though data are limited. In this manuscript we summarize the evidence and critical knowledge gaps regarding the relationships between pain, opioid analgesics, and cognition in older adults. Furthermore, we provide a conceptual framework to guide future research in the development, implementation, and evaluation of strategies to optimize analgesic outcomes in older adults while minimizing deleterious effects on cognition.

Myth and Truth in Opioid Consumption with Intrathecal Morphine Pump Implantation in Chronic Pain: A Retrospective Cohort Study with Claims Database in South Korea.

OBJECTIVE: To investigate the opioid consumption and the healthcare resource utilization in patients with the intrathecal drug delivery system (IDDS) therapy and the comprehensive medical management (CMM) alone. DESIGN: A retrospective cohort study with a customized claims database. SETTING: In a university-based hospital. SUBJECTS: Patients with complex regional pain syndrome, post-laminectomy syndrome, and fibromyalgia. METHODS: Using propensity score matching (1:3), we selected patients with morphine infusion through IDDS (IDDS group) and CMM alone (CMM group). The primary endpoints were comparisons of average morphine equivalents daily dosages (MEDD, mg/day) for 6 and 12 months from an index date. The number of emergency room (ER) visits and hospitalizations and the total medical expenditures were compared as secondary outcomes. RESULTS: In total, 82 patients (N = 23 in the IDDS group and N = 59 in the CMM group) were analyzed. Although a 6-month average MEDD did not reach statistical significance, a 12-month average MEDD was significantly decreased in the IDDS group compared to the CMM group (53.2 ± 46.3 vs 123.9 ± 176.4, respectively; P = 0.008). ER visits were more frequent in the IDDS group than the CMM group at baseline (5.4 vs 0.5, respectively; P = .002), which was maintained for 12 months (P < 0.001). Otherwise, the number of hospitalization and the medical expenditures for pain management were not different between the groups for 12 months. CONCLUSIONS: The combined IDDS therapy had some benefits in reducing opioid consumption for 1-year follow-up compared to the CMM alone in chronic noncancer pain patients.

Long-term opioid therapy and mental health comorbidity in patients with chronic pain.

OBJECTIVES: Evidence suggests that patients with chronic pain and mental illness are more likely to receive long-term opioid therapy (LTOT) and at higher doses but are also at increased risk of experiencing opioid-related harm. This study investigates LTOT and its relationship to mental illness in the setting of a university-based outpatient pain clinic with liaison psychiatric care. METHODS: Retrospective analysis of patients with chronic pain admitted between 2011 and 2015. After a 1-year treatment period, patients with non-opioid treatment, guideline-recommended LTOT, and high-dose LTOT were compared, and multiple regression analysis was performed to identify predictors of higher opioid dosage. RESULTS: Of 769 patients, 46% received LTOT (opioids for >90 consecutive days), 13% at high dosage (>120 oral morphine milligram equivalents [MME] / day). Two thirds of all patients had mental illness. The prevalence of psychiatric diagnoses and prescription rate of psychotropic medication did not significantly differ between groups. Pain chronicity stages, use of antidepressants, and sex significantly predicted MME/day but explained only a minor part of the variance. The association with antidepressants can be attributed to the prescription of antidepressants for analgesic purposes rather than for treating depression. No association with any other type of psychiatric disorders was observed. CONCLUSION: This study shows that mental health comorbidity is highly prevalent but that the prescribed opioid dosage is independent of it in the clinical setting of this study. The concept of liaison psychiatric care might have essentially contributed to the "detachment" of opioid prescription and psychiatric conditions but cannot be isolated from other potentially contributing factors within this single-center observational study.

Analgesic Effect of Buprenorphine for Chronic Noncancer Pain: A Systematic Review and Meta-analysis of Randomized Controlled Trials.

BACKGROUND: Buprenorphine is a partial agonist at the µ-opioid receptor and an antagonist at the delta and kappa opioid receptors. It has high affinity and low intrinsic activity at the µ-opioid receptor. Buprenorphine demonstrates no ceiling effect for clinical analgesia, but demonstrates this for respiratory depression and euphoria. It may provide effective analgesia while producing less adverse effects, making it a promising opioid analgesic. A systematic review and meta-analysis were performed to examine the analgesic efficacy of buprenorphine for patients with chronic noncancer pain. METHODS: PubMed, MEDLNE, Embase, and the Cochrane Library were searched up to January 2022. Randomized controlled trials were included if they compared buprenorphine versus placebo or active analgesic in patients with chronic noncancer pain, where pain score was an outcome. Nonrandomized controlled trials, observational studies, qualitative studies, case reports, and commentaries were excluded. Two investigators independently performed the literature search, study selection, and data collection. A random-effects model was used. The primary outcome was the effect of buprenorphine on pain intensity in patients with chronic noncancer pain based on standardized mean difference (SMD) in pain score. Quality of evidence was assessed using the Grade of Recommendations Assessment, Development, and Evaluation (GRADE) approach. RESULTS: Two separate literature searches were conducted for patients with and without opioid use disorder (OUD). Only one study met the search criteria for those with OUD. Fourteen randomized controlled trials were included for those without OUD. Buprenorphine was associated with reduced pain score (SMD = -0.368, P < .001, I 2 = 89.37%) compared to placebo or active analgesic. Subgroup meta-analyses showed statistically significant differences in favor of buprenorphine versus placebo (SMD = -0.404, P < .001), for chronic low back pain (SMD = -0.383, P < .001), when administered via the transdermal route (SMD = -0.572, P = .001), via the buccal route (SMD = -0.453, P < .001), with length of follow-up lasting <12 weeks (SMD = -0.848, P < .05), and length of follow-up lasting 12 weeks or more (SMD = -0.415, P < .001). There was no significant difference when compared to active analgesic (SMD = 0.045, P > .05). Quality of evidence was low to moderate. CONCLUSIONS: Buprenorphine was associated with a statistically significant and small reduction in pain intensity compared to placebo. Both the transdermal and buccal routes provided pain relief. There was more evidence supporting its use for chronic low back pain.

Patients' Perspectives on the Development of Prescription Opioid Use Disorder in Patients with Chronic Non-Cancer Pain.

INTRODUCTION: In the past decade, prescription opioid use increased exponentially and concomitantly opioid use disorders (OUD) are becoming more common. Several risk factors for developing OUD have been identified, but little is known regarding the patients' perspective on developing a prescription OUD. METHODS: We recruited 25 adults undergoing treatment for prescription OUD. In-depth, semi-structured interviews focussed on experiences with long-term opioid use, knowledge and attitudes regarding opioids, and access to opioids. A directed content analysis was conducted on the transcribed interviews using NVivo. RESULTS: Participants showed that the development of an OUD is affected by various factors which could be grouped into three themes: (1) experiences driving initiation, (2) experiences driving continuation, and (3) experiences with prescription OUD. Besides the need for pain management, the dynamics of patient-provider communication, care coordination, provider vigilance, and environmental support all contributed to the way patients used their opioids. CONCLUSION: Patients' experiences illustrate that the first stage of the development of prescription OUD differs from the development of other substance addictions. Negative reinforcement might play a more prominent role in the early phase of prescription opioid use. Patients expressed a lack of guidance, both at the start of use and long-term use, easy access to new prescriptions and a lack of monitoring as main drivers of the development. Poorly controlled pain and subjective stress fuelled continuous opioid use.

Opioid-Induced Esophageal Dysmotility (OIED) - A Case Report.

Recent studies have shown that chronic opioid use is associated with an increased risk of symptomatic esophageal motility disorders. Opioid-induced esophageal dysfunction (OIED) is most often identified in patients taking high doses of opioids. This condition is associated with poorer treatment outcomes than primary motility disorders and management of these cases is further complicated by the presence of chronic pain, opioid addiction, and physical and psychological comorbidity.We present the case of a 68-year-old Caucasian woman with OIED, induced by the chronic intake of low-dose Fentanyl and Tramadol prescribed to treat severe back pain. The clinical course highlights the sometimes difficult diagnosis and management of this recently recognized condition.

Association between sustained opioid prescription and frequent emergency department use: a cohort study.

BACKGROUND: Chronic non-cancer pain (CNCP) is common among frequent emergency department (ED) users, although factors underlying this association are unclear. This study estimated the association between sustained opioid use and frequent ED use among patients with CNCP. METHODS: Retrospective cohort study using a Canadian provincial health insurer database (Régie d'Assurance Maladie du Québec). The database included adults with both ≥1 chronic condition and ≥ 1 ED visit in 2012 or 2013. Inclusion in the study further required a CNCP diagnosis, public drug insurance coverage and 1-year survival after the first ED visit in 2012 or 2013 (index visit). Multivariable logistic regression was used to derive ORs of frequent ED use (≥5 visits in the year following the index visit) subsequent to sustained opioid use (≥60 days opioids prescription within 90 days preceding the index visit), adjusting for important covariables. RESULTS: From 576 688 patients in the database, 58 237 were included in the study. Of these, 4109 (7.1%) had received a sustained opioid prescription and 4735 (8.1%) were frequent ED users in the follow-up year. Sustained opioid use was not associated with frequent ED use in the multivariable model (OR: 1.06, 95% CI 0.94 to 1.19). Novel associated covariables were benzodiazepine prescription (OR: 1.21, 95% CI 1.12 to 1.30) and polypharmacy (OR: 1.23, 95% CI 1.13 to 1.34). CONCLUSIONS: Due to confounding by social and medical vulnerability, patients with CNCP with sustained opioid use appear to have a higher propensity for frequent ED use in unadjusted models. However, sustained opioid use was not associated with frequent ED use in these patients after adjustment.

Pharmacogenetic Guided Opioid Therapy Improves Chronic Pain Outcomes and Comorbid Mental Health: A Randomized, Double-Blind, Controlled Study.

Interindividual variability in analgesic response is at least partly due to well-characterized polymorphisms that are associated with opioid dosing and adverse outcomes. The Clinical Pharmacogenetics Implementation Consortium (CPIC) has put forward recommendations for the CYP2D6 phenotype, but the list of studied drug-gene pairs continues to grow. This clinical trial randomized chronic pain patients (n = 60), referred from primary care to pain unit care into two opioid prescribing arms, one guided by CYP2D6, µ-opioid receptor (OPRM1), and catechol-O-methyl transferase (COMT) genotypes vs. one with clinical routine. The genotype-guided treatment reduced pain intensity (76 vs. 59 mm, p < 0.01) by improving pain relief (28 vs. 48 mm, p < 0.05), increased quality of life (43 vs. 56 mm p < 0.001), and lowered the incidence of clinically relevant adverse events (3 [1-5] vs. 1 [0-2], p < 0.01) and 42% opioid dose (35 [22-61] vs. 60 [40-80] mg/day, p < 0.05) as opposed to usual prescribing arm. The final health utility score was significantly higher (0.71 [0.58-0.82] vs. 0.51 [0.13-0.67] controls, p < 0.05) by improving sleepiness and depression comorbidity, with a significant reduction of 30-34% for headache, dry mouth, nervousness, and constipation. A large-scale implementation analysis could help clinical translation, together with a pharmaco-economic evaluation.

Effectiveness and Tolerability of Dronabinol Use in Patients with Chronic Pain: A Retrospective Analysis of 12-Week Open-Label Real-World Data Provided by the German Pain e-Registry.

OBJECTIVE: To evaluate the effectiveness of Δ9-tetrahydrocannabinol (dronabinol [DRO]) as an add-on treatment in patients with refractory chronic pain (CP). METHODS: An exploratory retrospective analysis of 12-week data provided by the German Pain e-Registry on adult patients with treatment refractory CP who received DRO. RESULTS: Between March 10, 2017, and June 30, 2019, the German Pain e-Registry collected information on 89,095 patients with pain, of whom 1,145 patients (1.3%) received DRO (53.8% female, mean ± standard deviation age: 56.9 ± 10.6 years), and 70.0% documented use for the entire 12-week evaluation period. The average DRO daily dose was 15.8 ± 7.5 mg, typically in three divided doses (average DRO dose of 5.3 ± 2.1 mg). Average 24-hour pain intensity decreased from 46.3 ± 16.1 to 26.8 ± 18.7 mm on a visual analog scale (absolute visual analog scale difference: -19.5 ± 17.3; P < 0.001). Among patients who completed follow-up, an improvement from baseline of at least 50% was documented for pain (46.5%), activities of daily living (39%), quality of life (31.4%), and sleep (35.3%). A total of 536 patients (46.8%) reported at least one of 1,617 drug-related adverse events, none of which were serious, and 248 patients (21.7%) stopped treatment. Over the 12-week period, 59.0% of patients reported a reduction of other pain treatments, and 7.8% reported a complete cessation of any other pharmacological pain treatments. CONCLUSION: Add-on treatment with DRO in patients with refractory CP was well tolerated and associated with a significant improvement.

Intention to get naloxone among patients prescribed opioids for chronic pain.

BACKGROUND: Prescription opioids have been increasingly prescribed for chronic pain while the opioid-related death rates grow. Naloxone, an opioid antagonist, is increasingly recommended in these patients, yet there is limited research that investigates the intention to get naloxone. This study aimed to investigate intention toward getting naloxone in patients prescribed opioids for chronic pain and to assess the predictive utility of the theory of reasoned action (TRA) constructs in explaining intention to get naloxone. METHODS: This was a cross-sectional study of a panel of U.S. adult patients prescribed opioids for chronic pain using a Qualtrics®XM survey. These patients participated in the study during February to March 2020. The online internet survey assessed the main outcome of intention to get naloxone and constructs of TRA (attitudes and subjective norms); additional measures assessed the characteristics of patients' opioid overdose risk factors, knowledge of naloxone, and their demographics. The relationship between TRA constructs, namely, attitudes and subjective norms, and the intention variable was examined using logistic regression analyses with the intention outcome contrasted as follows: high intention (scores ≥ 5) and non-high intention (scores < 5). RESULTS: A total of 549 participants completed the survey. Most of them were female (53.01%), White or Caucasian (83.61%), non-Hispanic (87.57%) and had a mean age of 44.16 years (SD = 13.37). Of these, 167 (30.42%) had high intention to get naloxone. The TRA construct of subjective norm was significantly associated with increased likelihood of higher intentions to get naloxone (OR 3.04, 95% CI 2.50-3.70, P < 0.0001). CONCLUSIONS: Our study provides empirical support of the TRA in predicting intention to get naloxone among chronic pain patients currently taking opioids. Subjective norms significantly predicted intention to get naloxone in these patients. The interventions targeting important reference groups of these patients would have greater impact on increasing intention to get naloxone in this population. Future studies should test whether theory-based interventions focusing on strengthening subjective norms increase intention to get naloxone in this population.

Granulocyte-Macrophage Colony Stimulating Factor As an Indirect Mediator of Nociceptor Activation and Pain.

The interaction between the immune system and the nervous system has been at the center of multiple research studies in recent years. Whereas the role played by cytokines as neuronal mediators is no longer contested, the mechanisms by which cytokines modulate pain processing remain to be elucidated. In this study, we have analyzed the involvement of granulocyte-macrophage colony stimulating factor (GM-CSF) in nociceptor activation in male and female mice. Previous studies have suggested GM-CSF might directly activate neurons. However, here we established the absence of a functional GM-CSF receptor in murine nociceptors, and suggest an indirect mechanism of action, via immune cells. We report that GM-CSF applied directly to magnetically purified nociceptors does not induce any transcriptional changes in nociceptive genes. In contrast, conditioned medium from GM-CSF-treated murine macrophages was able to drive nociceptor transcription. We also found that conditioned medium from nociceptors treated with the well established pain mediator, nerve growth factor, could also modify macrophage gene transcription, providing further evidence for a bidirectional crosstalk.SIGNIFICANCE STATEMENT The interaction of the immune system and the nervous system is known to play an important role in the development and maintenance of chronic pain disorders. Elucidating the mechanisms of these interactions is an important step toward understanding, and therefore treating, chronic pain disorders. This study provides evidence for a two-way crosstalk between macrophages and nociceptors in the peripheral nervous system, which may contribute to the sensitization of nociceptors by cytokines in pain development.

ZEB1 Induces Ddr1 Promoter Hypermethylation and Contributes to the Chronic Pain in Spinal Cord in Rats Following Oxaliplatin Treatment.

Application of chemotherapeutic oxaliplatin represses gene transcription through induction of DNA methylation, which may contribute to oxaliplatin-induced chronic pain. Here, Ddr1, which showed an increased methylation in the promoter, was screened from the SRA methylation database (PRJNA587622) after oxaliplatin treatment. qPCR and MeDIP assays verified that oxaliplatin treatment increased the methylation in Ddr1 promoter region and decreased the expression of DDR1 in the neurons of spinal dorsal horn. In addition, overexpression of DDR1 by intraspinal injection of AAV-hSyn-Ddr1 significantly alleviated the mechanical allodynia induced by oxaliplatin. Furthermore, we found that oxaliplatin treatment increased the expression of DNMT3b and ZEB1 in dorsal horn neurons, and promoted the interaction between DNMT3b and ZEB1. Intrathecal injection of ZEB1 siRNA inhibited the enhanced recruitment of DNMT3b and the hypermethylation in Ddr1 promoter induced by oxaliplatin. Finally, ZEB1 siRNA rescued the DDR1 downregulation and mechanical allodynia induced by oxaliplatin. In conclusion, these results suggested that the ZEB1 recruited DNMT3b to the Ddr1 promoter, which induced the DDR1 downregulation and contributed to the oxaliplatin-induced chronic pain.

Validity and responsiveness of EQ-5D-5L and SF-6D in patients with health complaints attributed to their amalgam fillings: a prospective cohort study of patients undergoing amalgam removal.

BACKGROUND: Evidence of health utility changes in patients who suffer from longstanding health complaints attributed to dental amalgam fillings are limited. The change in health utility outcomes enables calculating quality-adjusted life-year (QALY) and facilitates the comparison with other health conditions. The purpose of this study was to estimate the validity and responsiveness of the EQ-5D-5L and SF-6D utilities following removal of dental amalgam fillings in patients with health complaints attributed to their amalgam fillings, and examine the ability of these instruments to detect minimally important changes over time. METHODS: Patients with medically unexplained physical symptoms, which they attributed to dental amalgam restorations, were recruited to a prospective cohort study in Norway. Two health state utility instruments, EQ-5D-5L and SF-6D, as well as self-reported general health complaints (GHC-index) and visual analogue scale (EQ-VAS) were administered to all patients (n = 32) at baseline and at follow-up. The last two were used as criteria measures. Concurrent and predictive validities were examined using correlation coefficients. Responsiveness was assessed by the effect size (ES), standardized response mean (SRM), and relative efficiency. Minimally important change (MIC) was examined by distribution and anchor-based approaches. RESULTS: Concurrent validity of the EQ-5D-5L was similar to that of SF-6D utility. EQ-5D-5L was more responsive than SF-6D: the ES were 0.73 and 0.58 for EQ-5D-5L and SF-6D, respectively; SRM were 0.76 and 0.67, respectively. EQ-5D-5L was more efficient than SF-6D in detecting changes, but both were less efficient compared to criteria-based measures. The estimated MIC of EQ-5D-5L value set was 0.108 and 0.118 based on distribution and anchor-based approaches, respectively. The corresponding values for SF-6D were 0.048 and 0.064, respectively. CONCLUSIONS: In patients with health complaints attributed to dental amalgam undergoing amalgam removal, both EQ-5D-5L and SF-6D showed reasonable concurrent and predictive validity and acceptable responsiveness. The EQ-5D-5L utility appears to be more responsive compared to SF-6D. Trial registration The research was registered at ClinicalTrials.gov., NCT01682278. Registered 10 September 2012, https://clinicaltrials.gov/ct2/show/NCT01682278 .

TRPV1 Responses in the Cerebellum Lobules VI, VII, VIII Using Electroacupuncture Treatment for Chronic Pain and Depression Comorbidity in a Murine Model.

Depression is a prominent complex psychiatric disorder, usually complicated through expression of comorbid conditions, with chronic pain being among the most prevalent. This comorbidity is consistently associated with a poor prognosis and has been shown to negatively impact patient outcomes. With a global rise in this condition presenting itself, the importance of discovering long-term, effective, and affordable treatments is crucial. Electroacupuncture has demonstrated renowned success in its use for the treatment of pain and is a widely recognized therapy in clinical practice for the treatment of various psychosomatic disorders, most notably depression. Our study aimed to investigate the effects and mechanisms of Acid-Saline (AS) inducing states of chronic pain and depression comorbidity in the cerebellum, using the ST36 acupoint as the therapeutic intervention. Furthermore, the role of TRPV1 was relatedly explored through the use of TRPV1-/- mice (KO). The results indicated significant differences in the four behavioral tests used to characterize pain and depression states in mice. The AS and AS + SHAM group showed significant differences when compared to the Control and AS + EA groups in the von Frey and Hargreaves's tests, as well as the Open-Field and Forced Swimming tests. This evidence was further substantiated in the protein levels observed in immunoblotting, with significant differences between the AS and AS + SHAM groups when compared to the AS + EA and AS + KO groups being identified. In addition, immunofluorescence visibly served to corroborate the quantitative outcomes. Conclusively these findings suggest that AS-induced chronic pain and depression comorbidity elicits changes in the cerebellum lobules VI, VII, VIII, which are ameliorated through the use of EA at ST36 via its action on TRPV1 and related molecular pathways. The action of TRPV1 is not singular in CPDC, which would suggest other potential targets such as acid-sensing ion channel subtype 3 (ASIC3) or voltage-gated sodium channels (Navs) that could be explored in future studies.