Is fibromyalgia associated with a unique cytokine profile? A systematic review and meta-analysis

Deciphering nociplastic pain: clinical features, risk factors and potential mechanisms

Nociplastic pain is a mechanistic term used to describe pain that arises or is sustained by altered nociception, despite the absence of tissue damage. Although nociplastic pain has distinct pathophysiology from nociceptive and neuropathic pain, these pain mechanisms often coincide within individuals, which contributes to the intractability of chronic pain. Key symptoms of nociplastic pain include pain in multiple body regions, fatigue, sleep disturbances, cognitive dysfunction, depression and anxiety. Individuals with nociplastic pain are often diffusely tender - indicative of hyperalgesia and/or allodynia - and are often more sensitive than others to non-painful sensory stimuli such as lights, odours and noises. This Review summarizes the risk factors, clinical presentation and treatment of nociplastic pain, and describes how alterations in brain function and structure, immune processing and peripheral factors might contribute to the nociplastic pain phenotype. This article concludes with a discussion of two proposed subtypes of nociplastic pain that reflect distinct neurobiological features and treatment responsivity.

Characterization of pain-related behaviors in a rat model of acute-to-chronic low back pain: single vs. multi-level disc injury

Introduction

Low back pain is the most common type of chronic pain. We examined pain-related behaviors across 18 weeks in rats that received injury to one or two lumbar intervertebral discs (IVD) to determine if multi-level disc injuries enhance/prolong pain.

Methods

Twenty-three Sprague-Dawley adult female rats were used: 8 received disc puncture (DP) of one lumbar IVD (L5/6, DP-1); 8 received DP of two lumbar IVDs (L4/5 & L5/6, DP-2); 8 underwent sham surgery.

Results

DP-2 rats showed local (low back) sensitivity to pressure at 6- and 12-weeks post-injury, and remote sensitivity to pressure (upper thighs) at 12- and 18-weeks and touch (hind paws) at 6, 12 and 18-weeks. DP-1 rats showed local and remote pressure sensitivity at 12-weeks only (and no tactile sensitivity), relative to Sham DP rats. Both DP groups showed reduced distance traveled during gait testing over multiple weeks, compared to pre-injury; only DP-2 rats showed reduced distance relative to Sham DP rats at 12-weeks. DP-2 rats displayed reduced positive interactions with a novel adult female rat at 3-weeks and hesitation and freezing during gait assays from 6-weeks onwards. At study end (18-weeks), radiological and histological analyses revealed reduced disc height and degeneration of punctured IVDs. Serum BDNF and TNFα levels were higher at 18-weeks in DP-2 rats, relative to Sham DP rats, and levels correlated positively with remote sensitivity in hind paws (tactile) and thighs (pressure).

Discussion

Thus, multi-level disc injuries resulted in earlier, prolonged and greater discomfort locally and remotely, than single-level disc injury. BDNF and TNFα may have contributing roles.

Plasma and peritoneal fluid cytokine profiles in patient with Essure® implant: Towards a molecular signature?

OBJECTIVE(S)

Many patients with Essure® implant may experience adverse events related to the device. Although local inflammation does not appear to be the pathophysiological mechanism underlying the symptoms, systemic inflammation could play a role. In the present study, as cytokines are involved in the inflammatory process, we proposed to investigate the profile of circulating and peritoneal cytokines.

STUDY DESIGN

In this retrospective study, we evaluated the levels of cytokines in peritoneal fluid (PF) as well as in plasma sample from three different groups: Essure® group, endometriosis group (known to be associated with immune dysregulation), and control group.

RESULTS

There were 60 symptomatic patients with Essure® device, 30 patients with endometriosis and a control group of 30 patients. The PF levels of Interleukin-10 (IL-10), Interleukin-6 (IL-6), and Monocyte chemoattractant protein-1 (MCP-1) were statistically higher in endometriosis group than in Essure® group and control group. The plasma level of MCP-1 was higher in Essure® group than in endometriosis group and control group. The plasma level of TNF-α was higher in Essure® group than in control group.

CONCLUSIONS

The chemokine MCP-1 as well as the pro-inflammatory TNF-α, are known to be increased in patients with fibromyalgia and chronic fatigue syndrome. Since patients with Essure® may exhibit symptoms similar to fibromyalgia, MCP-1 and TNF-α may be relevant markers in symptomatic patients with Essure®. Because of the lack of longitudinal data (no evaluation of postoperative cytokine profile and no assessment of the level of clinical improvement), other studies are needed to confirm these preliminary results.

Manual therapy and exercise effects on inflammatory cytokines: a narrative overview

Background

Matching disease and treatment mechanisms is a goal of the Precision Medicine Initiative. Pro- and anti-inflammatory cytokines (e.g., Tumor Necrosis Factor-alpha, Transforming Growth Factor-beta, and Interleukin-2, 10, and 12) have gained a significant amount of interest in their potential role in persistent pain for musculoskeletal (MSK) conditions. Manual therapy (MT) and exercise are two guideline-recommended approaches for treating MSK conditions. The objective of this narrative overview was to investigate of the effects of MT and exercise on pro- and anti-inflammatory cytokines and determine the factors that lead to variability in results.

Methods

Two reviewers evaluated the direction and variabilities of MT and exercise literature. A red, yellow, and green light scoring system was used to define consistencies.

Results

Consistencies in responses were seen with acute and chronic exercise and both pro- and anti-inflammatory cytokines. Chronic exercise is associated with a consistent shift towards a more anti-inflammatory cytokine profile (Transforming Growth Factor-beta, and Interleukin-2 and 13, whereas acute bouts of intense exercise can transiently increase pro-inflammatory cytokine levels. The influence of MT on cytokines was less commonly studied and yielded more variable results.

Conclusion

Variability in findings is likely related to the subject and their baseline condition or disease, when measurement occurs, and the exercise intensity, duration, and an individual's overall health and fitness.

Pharmacological Evidence of Eugenia Brasiliensis Leaves in a Reserpine-Induced Fibromyalgia Model: Antinociceptive, Emotional, Anti-Inflammatory, and Neurotrophic Effects

Fibromyalgia (FM) is a painful chronic condition that significantly impacts the quality of life, posing challenges for clinical management. Given the difficulty of understanding the pathophysiology and finding new therapeutics, this study explored the effects of a medicinal plant, E. brasiliensis, in an FM model induced by reserpine in Swiss mice. Animals were treated with saline 0.9% (vehicle), duloxetine 10 mg/kg (positive control), or hydroalcoholic extract of E. brasiliensis leaves 300 mg/kg (HEEb). Nociceptive parameters, as well as locomotion, motor coordination, strength, anxiety, and depressive-like behaviors, were evaluated for 10 days. After that, the brain and blood were collected for further analysis of cytokines (interleukin 1? and interleukin 6), brain-derived neurotrophic factor (BDNF), and the immunocontents of total and phosphorylated Tropomyosin receptor kinase B (TrkB). The results demonstrated that the acute and prolonged treatment with HEEb was able to reduce both mechanical and thermal nociception. It was also possible to observe an increase in the strength, without changing locomotion and motor coordination parameters. Interestingly, treatment with HEEb reduces anxious and depressive-like behaviors. Finally, we observed a reduction in inflammatory cytokines in the hippocampus of animals treated with HEEb, while an increase in BDNF was observed in the prefrontal cortex (PFC). However, no alterations related to total and phosphorylated TrkB receptor expression were found. Our study demonstrated the antinociceptive and emotional effects of HEEb in mice, possibly acting on neuroinflammatory and neurotrophic mechanisms. These data provide initial evidence about the E. brasiliensis potential for treating chronic pain.

Online Questionnaire with Fibromyalgia Patients Shows Negative Correlations between Disease Severity and Adherence to Mediterranean Diet

Fibromyalgia (FM) is a multidimensional disorder in which intense chronic pain is accompanied by a variety of psychophysical symptoms that impose a burden on the patients' quality of life. Despite the efforts and the recent advancement in research, FM pathogenesis and effective treatment remain unknown. Recently, the possible role of dietary patterns and/or components has been gaining attention. The current study aimed to investigate a potential correlation between adherence to the Mediterranean diet (MedDiet) and FM severity in a sample of Italian FM patients. An online survey was designed, composed of customized questions and validated questionnaires with the aim of investigating the intensity and type of pain, the presence of other psychophysical symptoms, the overall impact of FM, general food and lifestyle habits, and adherence to the MedDiet. The collected responses were analyzed for descriptive statistics, linear regression, and propensity score analyses. The results show that, despite considerable use of pharmaceuticals and supplements, FM participants suffered from a high-severity grade disease. However, those with good adherence to the MedDiet experienced a lower pain intensity and overall FM impact. A propensity score analysis indicates a positive influence of the MedDiet against FM severity, thus unveiling the need for well-designed intervention studies to evaluate the therapeutic potential of different dietary patterns.

C-Reactive Protein (CRP) is Associated With Chronic Pain Independently of Biopsychosocial Factors

Inflammation is linked with chronic pain but the extent to which this relationship is associated with biopsychosocial factors is not known. We investigated relationships between blood C-reactive protein (CRP) and regional chronic pain conditions adjusting for a large range and number of potential confounders. We performed cross-sectional analyses using the UK Biobank (N = 415,567) comparing CRP in people reporting any of 9 types of regional chronic pain with pain-free controls. Using logistic regression modelling, we explored relationships between CRP and the presence of chronic pain, with demographic, socioeconomic, psychological/lifestyle factors, and medical comorbidities as covariates. CRP was higher in chronic pain at any site compared with controls (Females: median [interquartile range] 1.60 mg/L [2.74] vs 1.17 mg/L [1.87], P < .001; Males: 1.44 mg/L [2.12] vs 1.15 mg/L [1.65], P < .001). In males, associations between CRP and all types of chronic pain were attenuated but remained significant after adjustment for biopsychosocial covariates (OR range 1.08-1.49, P ≤ .001). For females, adjusted associations between CRP and pain remained significant for most chronic pain types (OR range 1.07-1.34, P < .001) except for facial pain (OR 1.04, P = .17) and headache (OR 1.02, P = .07)-although these non-significant findings may reflect reduced sample size. The significant association between CRP and chronic pain after adjustment for key biopsychosocial confounders implicates an independent underlying biological mechanism of inflammation in chronic pain. The presence of yet unknown or unmeasured confounding factors cannot be ruled out. Our findings may inform better-targeted treatments for chronic pain. PERSPECTIVE: Using a large-scale dataset, this article investigates associations between chronic pain conditions and blood C-reactive protein (CRP), to evaluate the confounding effects of a range of biopsychosocial factors. CRP levels were higher in those with chronic pain versus controls after adjusting for confounders-suggesting a possible independent biological mechanism.

Psoriasis and Fibromyalgia: A Systematic Review

Psoriasis is a chronic inflammatory cutaneous condition characterized by several comorbidities, including musculoskeletal disorders. While the association with psoriatic arthritis has been widely addressed in literature, the aim of the present systematic review was to identify all available evidence on the relationship between psoriasis and fibromyalgia, a musculoskeletal syndrome primarily characterized by chronic widespread pain. We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, and MedLine and Web of Science (WOS) databases were searched for literature up to March 2023. After the removal of duplicate records, a total of 11 articles were deemed eligible for inclusion in a qualitative synthesis. Our results suggested that psoriatic patients had a higher prevalence of fibromyalgia (8-30%), with a very high impact on symptoms of psoriasis. Moreover, fibromyalgic patients had a slightly increased prevalence of psoriasis (2.2-6.7%) compared to the control groups. Finally, several studies demonstrated the substantial impact of fibromyalgia on psoriatic outcome measures in patients with concomitant psoriatic arthritis. In conclusion, available data support a potential interplay between psoriasis and fibromyalgia, but further research is encouraged in this area.

Pain and the biochemistry of fibromyalgia: patterns of peripheral cytokines and chemokines contribute to the differentiation between fibromyalgia and controls and are associated with pain, fat infiltration and content

Objectives

This explorative study analyses interrelationships between peripheral compounds in saliva, plasma, and muscles together with body composition variables in healthy subjects and in fibromyalgia patients (FM). There is a need to better understand the extent cytokines and chemokines are associated with body composition and which cytokines and chemokines differentiate FM from healthy controls.

Methods

Here, 32 female FM patients and 30 age-matched female healthy controls underwent a clinical examination that included blood sample, saliva samples, and pain threshold tests. In addition, the subjects completed a health questionnaire. From these blood and saliva samples, a panel of 68 mainly cytokines and chemokines were determined. Microdialysis of trapezius and erector spinae muscles, phosphorus-31 magnetic resonance spectroscopy of erector spinae muscle, and whole-body magnetic resonance imaging for determination of body composition (BC)-i.e., muscle volume, fat content and infiltration-were also performed.

Results

After standardizing BC measurements to remove the confounding effect of Body Mass Index, fat infiltration and content are generally increased, and fat-free muscle volume is decreased in FM. Mainly saliva proteins differentiated FM from controls. When including all investigated compounds and BC variables, fat infiltration and content variables were most important, followed by muscle compounds and cytokines and chemokines from saliva and plasma. Various plasma proteins correlated positively with pain intensity in FM and negatively with pain thresholds in all subjects taken together. A mix of increased plasma cytokines and chemokines correlated with an index covering fat infiltration and content in different tissues. When muscle compounds were included in the analysis, several of these were identified as the most important regressors, although many plasma and saliva proteins remained significant.

Discussion

Peripheral factors were important for group differentiation between FM and controls. In saliva (but not plasma), cytokines and chemokines were significantly associated with group membership as saliva compounds were increased in FM. The importance of peripheral factors for group differentiation increased when muscle compounds and body composition variables were also included. Plasma proteins were important for pain intensity and sensitivity. Cytokines and chemokines mainly from plasma were also significantly and positively associated with a fat infiltration and content index.

Conclusion

Our findings of associations between cytokines and chemokines and fat infiltration and content in different tissues confirm that inflammation and immune factors are secreted from adipose tissue. FM is clearly characterized by complex interactions between peripheral tissues and the peripheral and central nervous systems, including nociceptive, immune, and neuroendocrine processes.

Altered response to Toll-like receptor 4 activation in fibromyalgia: A low-dose, human experimental endotoxemia pilot study

In this pilot study, a human intravenous injection of low-dose endotoxin (lipopolysaccharide, LPS) model was used to test if fibromyalgia is associated with altered immune responses to Toll-like receptor 4 (TLR4) activation. Eight women with moderately-severe fibromyalgia and eight healthy women were administered LPS at 0.1 ng/kg in session one and 0.4 ng/kg in session two. Blood draws were collected hourly to characterize the immune response. The primary analytes of interest, leptin and fractalkine, were assayed via commercial radioimmunoassay and enzyme-linked immunosorbent assay kits, respectively. Exploratory analyses were performed on 20 secreted cytokine assays by multiplex cytokine panels, collected hourly. Exploratory analyses were also performed on testosterone, estrogen, and cortisol levels, collected hourly. Additionally, standard clinical complete blood counts with differential (CBC-D) were collected before LPS administration and at the end of the session. The fibromyalgia group demonstrated enhanced leptin and suppressed fractalkine responses to LPS administration. In the exploratory analyses, the fibromyalgia group showed a lower release of IFN-γ, CXCL10, IL-17A, and IL-12 and higher release of IL-15, TARC, MDC, and eotaxin than the healthy group. The results of this study suggest that fibromyalgia may involve an altered immune response to TLR4 activation.

The crosstalk of the pathophysiologic models in fibromyalgia

Fibromyalgia (FM) is a heterogeneous condition with various mechanisms (endotype) and manifestations (phenotypes). Many worthy endeavors have been dedicated to exploring the main trajectories of FM pathogenesis, depicted as the models of FM development. The Imbalance of Threat and Soothing Systems (FITSS) model, which is an advancing psychosocial form of the "central sensitization" model, and autonomic nervous system (ANS) model, besides new discoveries of potential pathways for FM development such as autoimmunity, small fiber pathology, and gut-brain axis currently comprise all our knowledge assets about FM pathogenesis. The pathophysiology of fibromyalgia is too complex to justify with one model, one main loop of pathogenesis, and one terminator. It appears that the variable FM models could justify some phenotypes of FM. Currently, our knowledge about FM pathogenesis and trying to match the different pathways and links mimic solving a puzzle in the hands of beginners. Until unraveling many missed interconnections and formulas between numerous scrambled pieces of the FM puzzle, proposing an integrated model seems not possible. This review focuses on the main trajectories of FM pathogenesis proposed thus far and tries to illuminate the crosstalking between them. We also propose the subgrouping FM into more homogenous categories based on the endotype-phenotype characteristics. It could provide a more pragmatic approach toward understanding of the diverse network of FM pathogenesis as well as the personalized stratification of FM. Key Points • The disentangled nature of FM pathogenesis escapes from embracing under one integrated model. • There appears to be no way for formulizing FM pathogenesis except the acknowledgment of the different pathways and their crosstalk explored as yet. • Acknowledging the different endotypes/phenotypes of FM spectrum and classifying them into more homogenous groups can help to the pragmatic approach to FM.

The role of inflammatory markers in Temporomandibular Myalgia: A systematic review

Approximately 10 % of the general population is affected by temporomandibular disorder (TMD) pain. Diagnosis of myogenous TMD pain (i.e., TM myalgia) may be challenging, while an adequate assessment of this pain is crucial to establish an adequate management strategy. We aim to analyze if there is a relation between inflammation and TM myalgia, and if we can identify and measure inflammatory markers in patients suffering from this condition. An electronic literature search was conducted from inception up to July 14 2022 through the databases PubMed, Cochrane Library, Web of Science, and Embase in collaboration with a medical information specialist. Studies on patients with masticatory muscle inflammation and/or pain were included. After a screening procedure, only nine full-text articles met the criteria for inclusion. In the included studies 9-131 patients showed TM myalgia, and presence of inflammation was reported with analysis of interleukines IL-1, IL-6, IL-10, tumor necrosis factor alpha, and prostaglandins from blood, saliva, and extracellular fluid of masseter muscle using microdialysis. Our results contributed to the identification of the relation between inflammation and TM myalgia and established that measurement of inflammatory cytokines may be a valid diagnostic tool, which is an essential step towards finding a better treatment.

Anti-satellite glia cell IgG antibodies in fibromyalgia patients are related to symptom severity and to metabolite concentrations in thalamus and rostral anterior cingulate cortex

Recent translational work has shown that fibromyalgia might be an autoimmune condition with pathogenic mechanisms mediated by a peripheral, pain-inducing action of immunoglobulin G (IgG) antibodies binding to satellite glia cells (SGC) in the dorsal root ganglia. A first clinical assessment of the postulated autoimmunity showed that fibromyalgia subjects (FMS) had elevated levels of antibodies against SGC (termed anti-SGC IgG) compared to healthy controls and that anti-SGC IgG were associated with a more severe disease status. The overarching aim of the current study was to determine whether the role of anti-SGC IgG in driving pain is exclusively through peripheral mechanisms, as indirectly shown so far, or could be attributed also to central mechanisms. To this end, we wanted to first confirm, in a larger cohort of FMS, the relation between anti-SGC IgG and pain-related clinical measures. Secondly, we explored the associations of these autoantibodies with brain metabolite concentrations (assessed via magnetic resonance spectroscopy, MRS) and pressure-evoked cerebral pain processing (assessed via functional magnetic resonance imaging, fMRI) in FMS. Proton MRS was performed in the thalamus and rostral anterior cingulate cortex (rACC) of FMS and concentrations of a wide spectrum of metabolites were assessed. During fMRI, FMS received individually calibrated painful pressure stimuli corresponding to low and high pain intensities. Our results confirmed a positive correlation between anti-SGC IgG and clinical measures assessing condition severity. Additionally, FMS with high anti-SGC IgG levels had higher pain intensity and a worse disease status than FMS with low anti-SGC IgG levels. Further, anti-SGC IgG levels negatively correlated with metabolites such as scyllo-inositol in thalamus and rACC as well as with total choline and macromolecule 12 in thalamus, thus linking anti-SGC IgG levels to the concentration of metabolites in the brain of FMS. However, anti-SGC IgG levels in FMS were not associated with the sensitivity to pressure pain or the cerebral processing of evoked pressure pain. Taken together, our results suggest that anti-SGC IgG might be clinically relevant for spontaneous, non-evoked pain. Our current and previous translational and clinical findings could provide a rationale to try new antibody-related treatments in FMS.

Can open label placebos improve pain and gluten tolerance via open label placebos in fibromyalgia patients? A study protocol for a randomised clinical trial in an outpatient centre

INTRODUCTION

Fibromyalgia syndrome (FMS) is defined as a medical condition with chronic widespread musculoskeletal pain accompanied by mood disorders, fatigue and sleep disturbances. Treatment of this condition can often be challenging. As nutrition in general and nutritional interventions in the context of illness management become more and more important, current research also focuses on the relevance of diets for FMS, including gluten as field of interest. To date, there is no clear evidence that a gluten-free diet or other nutritional interventions are significantly important for the reduction of pain in the context of FMS. Only a very few studies show that FMS patients respond to a gluten-free diet and that cytokine production (also in FMS) can be reduced through the change. However, these studies have not investigated whether and to what extent cognitive factors, such as the expectation of symptom reduction triggered by diet, play a role. Recent research shows that treatment expectation plays an important role in the course of the disease and in the effectiveness of treatment approaches. For example, there are promising pain treatment options using open-label placebos (OLPs), which show that expectation alone, rather than the pharmacological substance of medication, can reduce pain experience. In our study protocol, we hypothesise that treatment expectation can be positively influenced by the given information regarding the placebos, resulting in improved treatment outcomes for pain and indigestions.

METHODS AND ANALYSIS

In this trial, patients with FMS will undergo a food challenge and take an OLP (patients will be informed about the placebo), followed by a 3-week OLP treatment. The subjects will be randomised into four groups: (a) gluten-free porridge+neutral OLP instructions; (b) gluten-free porridge+positive OLP instructions; (c) gluten-containing porridge+neutral OLP instructions and (d) gluten-containing porridge+positive OLP instructions. Patients will be recruited via different institutions and support groups in Hamburg. The inclusion criteria are (a) diagnosed FMS, (b) absence of wheat allergy, coeliac disease or pain-related red flags and (c) being a minimum age of 18 years. The study requires 100 subjects to assess the primary outcomes: pain intensity and occurence of indigestion. Secondary outcomes are functional capacity, treatment expectation, and different pain-related and inflammation-related blood parameters. The measure time points will be before and after the food challenge and before and after the 3-week OLP treatment.

ETHICS AND DISSEMINATION

Ethical approval was obtained in October 2021 from the Hamburg Medical Ethics Council. The results of the study will be disseminated through publications, presentations and conference meetings.

TRIAL REGISTRATION NUMBER

German Clinical Trials Register (DRKS; DRKS00027130).

Pain Biomarkers in Fibromyalgia Syndrome: Current Understanding and Future Directions

Fibromyalgia is a complex and heterogeneous clinical syndrome, mainly characterized by the presence of widespread pain, possibly associated with a variety of other symptoms. Fibromyalgia can have an extremely negative impact on the psychological, physical and social lives of people affected, sometimes causing patients to experience dramatically impaired quality of life. Nowadays, the diagnosis of fibromyalgia is still clinical, thus favoring diagnostic uncertainties and making its clear identification challenging to establish, especially in primary care centers. These difficulties lead patients to undergo innumerable clinical visits, investigations and specialist consultations, thus increasing their stress, frustration and even dissatisfaction. Unfortunately, research over the last 25 years regarding a specific biomarker for the diagnosis of fibromyalgia has been fruitless. The discovery of a reliable biomarker for fibromyalgia syndrome would be a critical step towards the early identification of this condition, not only reducing patient healthcare utilization and diagnostic test execution but also providing early intervention with guideline-based treatments. This narrative article reviews different metabolite alterations proposed as possible biomarkers for fibromyalgia, focusing on their associations with clinical evidence of pain, and highlights some new, promising areas of research in this context. Nevertheless, none of the analyzed metabolites emerge as sufficiently reliable to be validated as a diagnostic biomarker. Given the complexity of this syndrome, in the future, a panel of biomarkers, including subtype-specific biomarkers, could be considered as an interesting alternative research area.

Genetic impact of blood C-reactive protein levels on chronic spinal & widespread pain

PURPOSE

Causal mechanisms underlying systemic inflammation in spinal & widespread pain remain an intractable experimental challenge. Here we examined whether: (i) associations between blood C-reactive protein (CRP) and chronic back, neck/shoulder & widespread pain can be explained by shared underlying genetic variants; and (ii) higher CRP levels causally contribute to these conditions.

METHODS

Using genome-wide association studies (GWAS) of chronic back, neck/shoulder & widespread pain (N = 6063-79,089 cases; N = 239,125 controls) and GWAS summary statistics for blood CRP (Pan-UK Biobank N = 400,094 & PAGE consortium N = 28,520), we employed cross-trait bivariate linkage disequilibrium score regression to determine genetic correlations (rG) between these chronic pain phenotypes and CRP levels (FDR < 5%). Latent causal variable (LCV) and generalised summary data-based Mendelian randomisation (GSMR) analyses examined putative causal associations between chronic pain & CRP (FDR < 5%).

RESULTS

Higher CRP levels were genetically correlated with chronic back, neck/shoulder & widespread pain (rG range 0.26-0.36; P ≤ 8.07E-9; 3/6 trait pairs). Although genetic causal proportions (GCP) did not explain this finding (GCP range - 0.32-0.08; P ≥ 0.02), GSMR demonstrated putative causal effects of higher CRP levels contributing to each pain type (beta range 0.027-0.166; P ≤ 9.82E-03; 3 trait pairs) as well as neck/shoulder pain effects on CRP levels (beta [S.E.] 0.030 [0.021]; P = 6.97E-04).

CONCLUSION

This genetic evidence for higher CRP levels in chronic spinal (back, neck/shoulder) & widespread pain warrants further large-scale multimodal & prospective longitudinal studies to accelerate the identification of novel translational targets and more effective therapeutic strategies.

Neurophysiological and Psychosocial Mechanisms of Fibromyalgia: A Comprehensive Review and Call for An Integrative Model

Research into the neurobiological and psychosocial mechanisms involved in fibromyalgia has progressed remarkably in recent years. Despite this, current accounts of fibromyalgia fail to capture the complex, dynamic, and mutual crosstalk between neurophysiological and psychosocial domains. We conducted a comprehensive review of the existing literature in order to: a) synthesize current knowledge on fibromyalgia; b) explore and highlight multi-level links and pathways between different systems; and c) build bridges connecting disparate perspectives. An extensive panel of international experts in neurophysiological and psychosocial aspects of fibromyalgia discussed the collected evidence and progressively refined and conceptualized its interpretation. This work constitutes an essential step towards the development of a model capable of integrating the main factors implicated in fibromyalgia into a single, unified construct which appears indispensable to foster the understanding, assessment, and intervention for fibromyalgia.

Fibromyalgia - etiology, diagnosis and treatment including perioperative management in patients with fibromyalgia

Fibromyalgia (FM) is considered a multifactorial disorder/syndrome with not fully understood etiology. Chronic generalized pain is the main symptom. A broad spectrum of factors is proposed to explain the etiology. Its multifactorial nature is inherently associated with challenges in diagnosis and therapy. Various evidence of etiology has been evaluated with the aim of establishing a novel therapeutic approach. The main issue in the diagnosis and management is to focus on the evaluation of strict diagnostic criteria to minimize under- and overdiagnosis. Fibromyalgia is a challenge for perioperative management because of the increased risk of possible complications and poorer outcomes, including postoperative pain chronification. The authors have proposed an up-to-date evaluation of perioperative management considering the current guidelines. Multimodal analgesia combined with tailored perioperative care is the most appropriate assessment. Interdisciplinary research with special interest in pain management, including perioperative medicine, seems to be the main theme for the future.

The immunomodulatory effects of ethosuximide and sodium butyrate on experimentally induced fibromyalgia: The interaction between IL-4, synaptophysin, and TGF-β1/NF-κB signaling

BACKGROUND AND AIMS

Fibromyalgia is a widespread chronic pain syndrome associated with several comorbid conditions that affect the quality of patients' life. Its pathogenesis is complex, and the treatment strategies are limited by partial efficacy and potential adverse effects. So, our aim was to investigate the possible ameliorative effects of ethosuximide and sodium butyrate on fibromyalgia and compare their effects to pregabalin.

MATERIALS AND METHODS

In a mouse model of reserpine induced fibromyalgia, the effect of ethosuximide, sodium butyrate, and pregabalin was investigated. Evaluation of mechanical allodynia, cold hypersensitivity, anxiety, cognitive impairment, and depression was performed. Also, the brain and spinal cord tissue serotonin, dopamine and glutamate in addition to the serum levels of interleukin (IL)-4 and transforming growth factor beta 1 (TGF-β1) were assayed. Moreover, the expression of nuclear factor kappa B (NF-κB) synaptophysin was immunoassayed in the hippocampal tissues.

KEY FINDINGS

Ethosuximide and sodium butyrate restored the behavioral tests to the normal values except for the antidepressant effect which was evident only with ethosuximide. Both drugs elevated the levels of the anti-inflammatory cytokines IL-4 and TGF-β1, reduced the hippocampal NF-κB, and increased synaptophysin expression with superiority of sodium butyrate. Ethosuximide reduced only spinal cord and brain glutamate while improved brain dopamine while sodium butyrate elevated spinal cord dopamine and serotonin with no effect on glutamate. Also, sodium butyrate elevated brain serotonin and reduced glutamate with no effect on brain dopamine.

SIGNIFICANCE

Each of sodium butyrate and ethosuximide would serve as a promising therapeutic modality for management of fibromyalgia and its comorbid conditions.

“Long COVID-19” and viral “fibromyalgia-ness”: Suggesting a mechanistic role for fascial myofibroblasts (Nineveh, the shadow is in the fascia)

The coronavirus pandemic has led to a wave of chronic disease cases; “Long COVID-19” is recognized as a new medical entity and resembles “fibromyalgia” which, likewise, lacks a clear mechanism. Observational studies indicate that up to 30%–40% of convalescent COVID-19 patients develop chronic widespread pain and fatigue and fulfill the 2016 diagnostic criteria for “fibromyalgia.” A recent study suggested a theoretical neuro-biomechanical model (coined “Fascial Armoring”) to help explain the pathogenesis and cellular pathway of fibromyalgia, pointing toward mechanical abnormalities in connective tissue and fascia, driven by contractile myo/fibroblasts and altered extracellular matrix remodeling with downstream corresponding neurophysiological aberrations. This may help explain several of fibromyalgia’s manifestations such as pain, distribution of pain, trigger points/tender spots, hyperalgesia, chronic fatigue, cardiovascular abnormalities, metabolic abnormalities, autonomic abnormalities, small fiber neuropathy, various psychosomatic symptoms, lack of obvious inflammation, and silent imaging investigations. Pro-inflammatory and pro-fibrotic pathways provide input into this mechanism via stimulation of proto/myofibroblasts. In this hypothesis and theory paper the theoretical model of Fascial Armoring is presented to help explain the pathogenesis and manifestations of “long COVID-19” as a disease of immuno-rheumo-psycho-neurology. The model is also used to make testable experimental predictions on investigations and predict risk and relieving factors.

Cytokines in primary headache disorders: a systematic review and meta-analysis

BACKGROUND

The role of inflammation and cytokines in the pathophysiology of primary headache disorders is uncertain. We performed a systematic review and meta-analysis to synthesise the results of studies comparing peripheral blood cytokine levels between patients with migraine, tension-type headache, cluster headache, or new daily persistent headache (NDPH), and healthy controls; and in migraine between the ictal and interictal stages.

METHODS

We searched PubMed/Medline and Embase from inception until July 2022. We included original research studies which measured unstimulated levels of any cytokines in peripheral blood using enzyme-linked immunosorbent assay or similar assay. We assessed risk of bias using the Newcastle-Ottawa Quality Assessment Scale. We used random effects meta-analysis with inverse variance weighted average to calculate standardised mean difference (SMD), 95% confidence intervals, and heterogeneity for each comparison. This study is registered with PROSPERO (registration number CRD42023393363). No funding was received for this study.

RESULTS

Thirty-eight studies, including 1335 patients with migraine (32 studies), 302 with tension-type headache (nine studies), 42 with cluster headache (two studies), and 1225 healthy controls met inclusion criteria. Meta-analysis showed significantly higher interleukin (IL)-6 (SMD 1.07, 95% CI 0.40-1.73, p = 0.002), tumour necrosis factor (TNF)-α (SMD 0.61, 95% CI 0.14-1.09, p = 0.01), and IL-8 (SMD 1.56, 95% CI 0.03-3.09, p = 0.04), in patients with migraine compared to healthy controls, and significantly higher interleukin-1β (IL-1β) (SMD 0.34, 95% CI 0.06-0.62, p = 0.02) during the ictal phase of migraine compared to the interictal phase. Transforming growth factor (TGF)-β (SMD 0.52, 95% CI 0.18-0.86, p = 0.003) and TNF-α (SMD 0.64, 95% CI 0.33-0.96, p = 0.0001) were both higher in patients with tension-type headache than controls.

CONCLUSIONS

The higher levels of the proinflammatory cytokines IL-6, IL-8 and TNF-α in migraine compared to controls, and IL-1β during the ictal stage, suggest a role for inflammation in the pathophysiology of migraine, however prospective studies are required to confirm causality and investigate the mechanisms for the increase in cytokine levels identified. Cytokines may also have a role in tension-type headache. Due a lack of data, no conclusions can be made regarding cluster headache or NDPH.

IL-1 Mediates Chronic Stress-Induced Hyperalgesia Accompanied by Microglia and Astroglia Morphological Changes in Pain-Related Brain Regions in Mice

Chronic stress causes several pain conditions including fibromyalgia. Its pathophysiological mechanisms are unknown, and the therapy is unresolved. Since the involvement of interleukin-1 (IL-1) has been described in stress and inflammatory pain but no data are available regarding stress-induced pain, we studied its role in a chronic restraint stress (CRS) mouse model. Female and male C57Bl/6J wild-type (WT) and IL-1αβ-deficient (knock-out: IL-1 KO) mice were exposed to 6 h of immobilization/day for 4 weeks. Mechanonociception, cold tolerance, behavioral alterations, relative thymus/adrenal gland weights, microglia ionized calcium-binding adaptor molecule 1 (IBA1) and astrocyte glial fibrillary acidic protein (GFAP) integrated density, number and morphological transformation in pain-related brain regions were determined. CRS induced 15–20% mechanical hyperalgesia after 2 weeks in WT mice in both sexes, which was significantly reduced in female but not in male IL-1 KOs. Increased IBA1+ integrated density in the central nucleus of amygdala, primary somatosensory cortex hind limb representation part, hippocampus cornu ammonis area 3 (CA3) and periaqueductal gray matter (PAG) was present, accompanied by a cell number increase in IBA1+ microglia in stressed female WTs but not in IL-1 KOs. CRS induced morphological changes of GFAP+ astrocytes in WT but not in KO mice. Stress evoked cold hypersensitivity in the stressed animals. Anxiety and depression-like behaviors, thymus and adrenal gland weight changes were detectable in all groups after 2 but not 4 weeks of CRS due to adaptation. Thus, IL-1 mediates chronic stress-induced hyperalgesia in female mice, without other major behavioral alterations, suggesting the analgesic potentials of IL-1 in blocking drugs in stress-related pain syndromes.

Analysis of the Influence of IL-6 and the Activation of the Jak/Stat3 Pathway in Fibromyalgia

Background: Fibromyalgia is a medical condition that affects a small percentage of the population, with no known effective treatment. There is evidence to suggest that inflammation is a key factor in the nerve sensitization that characterizes the disorder. Therefore, this paper concentrates on the role of IL-6 in fibromyalgia and the related pain-like symptoms. Methods: This work aimed to evaluate Sprague–Dawley rats, which were injected for three consecutive days with 1 mg/kg of reserpine; IL-6-R Ab was intraperitoneally injected at 1.5 mg/kg seven days after the first reserpine injection. Behavioral analyses were conducted at the beginning of the experiment and at seven and twenty-one days from the first reserpine injection. At this timepoint, the animals were sacrificed, and tissues were collected for molecular and histological analysis. Results: Our data showed the analgesic effect of IL-6-R-Ab administration on mechanical allodynia and thermal hyperalgesia. Additionally, the reserpine + IL-6-R-Ab group showed a reduced expression of the pain-related mediators cFOS and NFG and reduced levels of pro-inflammatory cytokines (TNF-α, IL-1β and IL-6) and chemokines (Cxcl5, Cxcl10 and Cx3cl1). From the molecular point of view, the IL-6-R-Ab administration reduced the gp130 phosphorylation and the activation of the Jak/STAT3 pathway. Additionally, the IL-6-R Ab reduced the activation of neuroinflammatory cells. Conclusions: Our study showed that IL-6 plays a crucial role in fibromyalgia by triggering the Jak/STAT3 pathway, leading to an increase in chemokine levels and activating glial cells.

Regulatory T-cells and IL-5 mediate pain outcomes in a preclinical model of chronic muscle pain

Fibromyalgia (FM) is a chronic musculoskeletal pain disorder primarily diagnosed in women. Historically, clinical literature focusing on cytokines and immune cells has been inconsistent. However, recent key studies show several layers of immune system dysfunction in FM. Preclinically, studies of the immune system have focused on monocytes with little focus on other immune cells. Importantly, T-cells are implicated in the development and resolution of chronic pain states, particularly in females. Our previous work showed that monocytes from women with FM produced more interleukin 5 (IL-5) and systemic treatment of IL-5 reversed mechanical hypersensitivity in a preclinical model of FM. Typically, IL-5 is produced by T_H2-cells, so in this study we assessed T-cell populations and cytokine production in female mice using the acid-induced chronic muscle pain model of FM before and after treatment with IL-5. Two unilateral injections of pH4.0 saline, five days apart, into the gastrocnemius muscle induce long-lasting widespread pain. We found that peripheral (blood) regulatory T_helper-cells (CD4⁺ FOXP3+) are downregulated in pH4.0-injected mice, with no differences in tissue (lymph nodes) or CD8⁺ T-cell populations. We tested the analgesic properties of IL-5 using a battery of spontaneous and evoked pain measures. Interestingly, IL-5 treatment induced place preference in mice previously injected with pH4.0 saline. Mice treated with IL-5 show limited changes in T-cell populations compared to controls, with a rescue in regulatory T-cells which positively correlates with improved mechanical hypersensitivity. The experiments in this study provide novel evidence that downregulation of regulatory T-cells play a role in chronic muscle pain pathology in the acidic saline model of FM and that IL-5 signaling is a promising target for future development of therapeutics.

The Vastus Lateralis Muscle Interstitium Proteome Changes after an Acute Nociception in Patients with Fibromyalgia Compared to Healthy Subjects-A Microdialysis Study

Fibromyalgia (FM) is a complex disorder and a clinical challenge to diagnose and treat. Microdialysis is a valuable tool that has been used to investigate the interstitial proteins and metabolites of muscle in patients with fibromyalgia. The implantation of the catheter in the muscle causes acute tissue trauma and nociception. The aim of this study was to investigate acute proteome changes in the vastus lateralis muscle in women fibromyalgia patients (FM) and healthy subjects (CON). A further aim was to study if a 15-week resistance exercise program in FM had any influence on how chronic painful muscle responds to acute nociception. Twenty-six women patients with FM and twenty-eight CON were included in this study. A microdialysis catheter (100 kilo Dalton cut off, membrane 30 mm) was inserted in the vastus lateralis muscle, and samples were collected every 20 min. Subjects rated pain before catheter insertion, directly after, and every 20 min of sample collection. Dialysate samples from time points 0-120 were pooled and considered trauma samples due to the catheter insertion. The samples were analyzed with nano-liquid chromatography-tandem mass spectrometry (nLC-MS/MS). Advanced multivariate data analysis was used to investigate protein profile changes between the groups. Multivariate data analysis showed significant (CV-ANOVA p = 0.036) discrimination between FM and CON based on changes in 26 proteins. After the 15-week exercise intervention, the expression levels of the 15 proteins involved in muscle contraction, response to stimulus, stress, and immune system were increased to the same expression levels as in CON. In conclusion, this study shows that microdialysis, in combination with proteomics, can provide new insights into the interstitial proteome in the muscle of FM. In response to acute nociception, exercise may alter the innate reactivity in FM. Exercise may also modulate peripheral muscle proteins related to muscle contraction, stress, and immune response in patients with FM.

Swedish Chronic Pain Biobank: protocol for a multicentre registry and biomarker project

INTRODUCTION

About 20% of the adult population have chronic pain, often associated with psychological distress, sick leave and poor health. There are large variations in the clinical picture. A biopsychosocial approach is used in investigation and treatment. The concept of personalised medicine, that is, optimising medication types and dosages for individual patients based on biomarkers and other patient-related factors, has received increasing attention in different diseases but used less in chronic pain. This cooperative project from all Swedish University Hospitals will investigate whether there are changes in inflammation and metabolism patterns in saliva and blood in chronic pain patients and whether the changes correlate with clinical characteristics and rehabilitation outcomes.

METHODS AND ANALYSIS

Patients at multidisciplinary pain centres at University Hospitals in Sweden who have chosen to participate in the Swedish Quality Registry for Pain Rehabilitation and healthy sex-matched and age-matched individuals will be included in the study. Saliva and blood samples will be collected in addition to questionnaire data obtained from the register. From the samples, proteins, lipids, metabolites and micro-RNA will be analysed in relation to, for example, diagnosis, pain characteristics, psychological distress, body weight, pharmacological treatment and clinical rehabilitation results using advanced multivariate data analysis and bioinformatics.

ETHICS AND DISSEMINATION

The study is approved by the Swedish Ethical Review Authority (Dnr 2021-04929) and will be conducted in accordance with the declaration of Helsinki.The results will be published in open access scientific journals and in popular scientific relevant journals such as those from patient organisations. Data will be also presented in scientific meetings, meeting with healthcare organisations and disseminated in different lecturers at the clinics and universities.

Plasma proteins from several components of the immune system differentiate chronic widespread pain patients from healthy controls - an exploratory case-control study combining targeted and non-targeted protein identification

Chronic widespread pain (CWP), including fibromyalgia (FM), is characterized by generalized musculoskeletal pain and hyperalgesia. Plasma proteins from proteomics (non-targeted) and from targeted inflammatory panels (cytokines/chemokines) differentiate CWP/FM from controls. The importance of proteins obtained from these two sources, the protein-protein association network, and the biological processes involved were investigated. Plasma proteins from women with CWP (n = 15) and CON (n = 23) were analyzed using two-dimensional gel electrophoresis analysis and a multiplex proximity extension assay for analysis of cytokines/chemokines. Associations between the proteins and group were multivarietly analyzed. The protein-protein association network and the biological processes according to the Gene Ontology were investigated. Proteins from both sources were important for group differentiation; the majority from the two-dimensional gel electrophoresis analysis. 58 proteins significantly differentiated the two groups (R2 = 0.83). A significantly enriched network was found; biological processes were acute phase response, complement activation, and innate immune response. As with other studies, this study shows that plasma proteins can differentiate CWP from healthy subjects. Focusing on cytokines/chemokines is not sufficient to grasp the peripheral biological processes that maintain CWP/FM since our results show that other components of the immune and inflammation systems are also highly significant.

Fatigue and Pain Severity in Gulf War Illness Is Associated With Changes in Inflammatory Cytokines and Positive Acute Phase Proteins

OBJECTIVE

The aim of the study is to investigate relationships between inflammatory analytes and symptoms of pain and fatigue in Gulf War illness (GWI).

METHODS

In this preliminary study, 12 male veterans meeting GWI criteria provided daily blood samples and symptom ratings over 25 days. Linear mixed models were used to analyze associations between symptoms and sera concentrations of cytokines, acute phase proteins, insulin, and brain-derived neurotropic factor.

RESULTS

Analyses included 277 days with both blood draws and self-reports. Days with worse fatigue severity were associated with higher C-reactive protein and serum amyloid A, and lower eotaxin 1. Muscle pain and joint pain were associated with leptin, monocyte chemoattractant protein 1, and interferon γ-induced protein. Joint pain was further associated with serum amyloid A and eotaxin 3.

CONCLUSIONS

Gulf War illness involves fatigue and pain associated with inflammation. Conventional and novel anti-inflammatories should be further explored for the treatment of GWI.

Direct-Acting Antiviral Drugs Reduce Fibromyalgia Symptoms in Patients with Chronic Hepatitis C

Background Fibromyalgia (FM) is a complex disorder characterized by chronic widespread pain and significant patient burden. Patients with chronic hepatitis C are reportedly predisposed to the development of FM. Direct-acting antiviral drugs (DAA) achieved a remarkable therapeutic efficacy in CHC patients. We therefore investigated the impact of DAA on FM symptoms in CHC patients. Methods We enrolled consecutive CHC patients who received DAA. FM symptoms were evaluated based on the 2016 American College of Rheumatology (ACR) fibromyalgia scale at baseline and 12 and 24 weeks after cessation of DAA therapy. Logistic regression was performed to determine the influence of HCV on FM at baseline. We also recruited individuals who underwent a health checkup examination as the control group, and calculated the standardized prevalence ratio of FM in CHC patients. Comparisons of fibromyalgia in different time points were undertaken using the Wilcoxon signed-rank test. Results A total of 33 CHC patients (15 males and 18 females) and 402 controls were recruited. All CHC patients achieved sustained virological response. Two (6%) patients and two (0.5%) controls fulfilled the diagnostic criteria for FM, and the standardized prevalence ratio was 23.9 in CHC patients. Logistic regression also showed increased odds for FM in CHC patients after adjusting for age and sex (OR: 14.4; 95%CI: 1.6, 128.0). In addition, their fibromyalgianess scale decreased at 12 and 24 weeks after DAA therapy. In conclusion, CHC patients were more likely to develop FM. Implementation of DAA therapy might improve FM symptoms in these patients.

Gentle Touch Therapy, Pain Relief and Neuroplasticity at Baseline in Fibromyalgia Syndrome: A Randomized, Multicenter Trial with Six-Month Follow-Up

Background: Fibromyalgia (FM) is considered a stress-related disorder characterized mainly by chronic widespread pain. Its pathogenesis is unknown, but cumulative evidence points at dysfunctional transmitter systems and inflammatory biomarkers that may underlie the major symptoms of the condition. This study aimed to evaluate pain scores (primary outcome), quality of life, inflammatory biomarkers and neurotransmitter systems in women with FM (secondary outcomes) subjected to gentle touch therapy (GTT) or placebo. Methods: A total of 64 female patients with FM were randomly assigned to two groups, namely GTT (n = 32) or Placebo (n = 32). Clinical assessments were conducted at baseline and post-intervention with six-month follow-up. We measured serum catecholamines (dopamine), indolamines and intermediary metabolites (serotonin or 5-hydroxyindolacetic acid (5-HIAA)), as well as tetrahydrobiopterin (BH4), which is a cofactor for the synthesis of neurotransmitters and inflammatory biomarkers in women with FM. A group of healthy individuals with no intervention (control group) was used to compare biochemical measurements. Intervention effects were analyzed using repeated measures (RM) two-way ANOVA followed by Bonferroni post hoc test and mixed ANCOVA model with intention to treat. Results: Compared to placebo, the GTT group presented lower pain scores and brain-derived neurotrophic factor (BDNF) levels without altering the quality of life of women with FM. Changes in BDNF had a mediating role in pain. Higher baseline serum BDNF and 5-HIAA or those with a history of anxiety disorder showed a higher reduction in pain scores across time. However, women with higher serum dopamine levels at baseline showed a lower effect of the intervention across the observation period revealed by an ANCOVA mixed model. Conclusions: In conclusion, lower pain scores were observed in the GTT group compared to the placebo group without altering the quality of life in women with FM. Reductions in BDNF levels could be a mechanism of FM pain status improvement. In this sense, the present study encourages the use of these GTT techniques as an integrative and complementary treatment of FM.

The Role of Neuro-Immune Interaction in Chronic Pain Conditions; Functional Somatic Syndrome, Neurogenic Inflammation, and Peripheral Neuropathy

Functional somatic syndromes are increasingly diagnosed in chronically ill patients presenting with an array of symptoms not attributed to physical ailments. Conditions such as chronic fatigue syndrome, fibromyalgia syndrome, or irritable bowel syndrome are common disorders that belong in this broad category. Such syndromes are characterised by the presence of one or multiple chronic symptoms including widespread musculoskeletal pain, fatigue, sleep disorders, and abdominal pain, amongst other issues. Symptoms are believed to relate to a complex interaction of biological and psychosocial factors, where a definite aetiology has not been established. Theories suggest causative pathways between the immune and nervous systems of affected individuals with several risk factors identified in patients presenting with one or more functional syndromes. Risk factors including stress and childhood trauma are now recognised as important contributors to chronic pain conditions. Emotional, physical, and sexual abuse during childhood is considered a severe stressor having a high prevalence in functional somatic syndrome suffers. Such trauma permanently alters the biological stress response of the suffers leading to neuroexcitatory and other nerve issues associated with chronic pain in adults. Traumatic and chronic stress results in epigenetic changes in stress response genes, which ultimately leads to dysregulation of the hypothalamic-pituitary axis, the autonomic nervous system, and the immune system manifesting in a broad array of symptoms. Importantly, these systems are known to be dysregulated in patients suffering from functional somatic syndrome. Functional somatic syndromes are also highly prevalent co-morbidities of psychiatric conditions, mood disorders, and anxiety. Consequently, this review aims to provide insight into the role of the nervous system and immune system in chronic pain disorders associated with the musculoskeletal system, and central and peripheral nervous systems.

Nociplastic pain concept, a mechanistic basis for pragmatic approach to fibromyalgia

Nociplastic pain (NP), as a mechanistic term, denotes pain arising from altered nociception without clear evidence of tissue or somatosensory damage. Fibromyalgia (FM), a prototypical NP condition, incorporates a broad continuum of phenotypes with a distinct neurobiological signature and shared NP attributes. The nociplastic concept may provide a new opportunity for early diagnosis of FM by identifying the characteristic NP features before a state of pain generalization and symptoms clustering. In this approach, even individual symptoms associated with NP features are worthy of attention to denote FM. It may provide a timely diagnosis of FM before clinical progression to a severe and hard-to-manage condition. Furthermore, collecting all various FM phenotypes under the nociplastic concept and not delimiting FM to the only typical presentation allows investigators to identify FM subgroups reflecting potentially distinct pathophysiologic mechanisms and biomarkers. This viewpoint can be served in future studies to develop individualized management. In this review, we postulate a novel approach to early FM diagnosis and management based on NP conceptualization and phenotype recognition. Key Points • FM as a NP condition represents overlapping clinical phenotypes and incomplete presentations especially in early stage of illness. • The mechanistic approach based on the NP features of FM can be implicated in the timely diagnosis and management of FM. • The NP-based approach to FM provides a broader viewpoint beyond FM delimitation to pain generalization and polysymptomatic complaints.

Utilization of Mind–Body Intervention for Integrative Health Care of COVID-19 Patients and Survivors

Recent findings suggest a correlation between COVID-19 and diabetes, although the underlying causes are still little understood. COVID-19 infection tends to induce severe symptoms in patients with underlying diabetes, increasing their mortality rate. Moreover, COVID-19 itself appears to be a diabetogenic factor. In addition, mental health conditions, such as depression due to lockdown and anxiety about infection, were found to affect glycemic control and immunity, highlighting the importance of mental health care during the pandemic. Mind–Body Intervention (MBI), which includes meditation, yoga, and qigong, has emerged as a tool for mental health management due to its effects on stress reduction and the promotion of mental and physical well-being. Here, we review the latest randomized controlled trials to determine the effects of MBI on glycemic control and the immune system and discuss the underlying mechanisms by which MBI facilitates the virtuous cycle of stress management, glycemic control, and immune modulation. Furthermore, we examine the actual utilization of MBI during the COVID-19 pandemic era through recent studies. With proper online education, non-pharmacological MBI may be more widely used as an important tool for self-health care that complements the usual treatment of COVID-19 patients and survivors.

Inflammation and Interferon Signatures in Peripheral B-Lymphocytes and Sera of Individuals With Fibromyalgia

Fibromyalgia (FM) is an idiopathic chronic disease characterized by widespread musculoskeletal pain, hyperalgesia and allodynia, often accompanied by fatigue, cognitive dysfunction and other symptoms. Autoimmunity and neuroinflammatory mechanisms have been suggested to play important roles in the pathophysiology of FM supported by recently identified interferon signatures in affected individuals. However, the contribution of different components in the immune system, such as the B-lymphocytes, in the progression to FM are yet unknown. Furthermore, there is a great need for biomarkers that may improve diagnostics of FM. Herein, we investigated the gene expression profile in peripheral B-cells, as well as a panel of inflammatory serum proteins, in 30 FM patients and 23 healthy matched control individuals. RNA sequence analysis revealed 60 differentially expressed genes when comparing the two groups. The group of FM patients showed increased expression of twenty-five interferon-regulated genes, such as S100A8 and S100A9, VCAM, CD163, SERPINA1, ANXA1, and an increased interferon score. Furthermore, FM was associated with elevated levels of 19 inflammatory serum proteins, such as IL8, AXIN1, SIRT2 and STAMBP, that correlated with the FM severity score. Together, the results shows that FM is associated with an interferon signature in B-cells and increased levels of a set of inflammatory serum proteins. Our findings bring further support for immune activation in the pathogenesis of FM and highlight candidate biomarkers for diagnosis and intervention in the management of FM.

Altered Plasma Proteins in Myogenous Temporomandibular Disorders

The aims of this study were (1) to compare the levels and interactions of several plasma proteins in patients with myogenous temporomandibular disorders (TMDM) compared to healthy and pain-free controls, (2) to compare the levels and interactions in two TMDM subgroups, myalgia (MYA) and myofascial pain (MFP), and (3) to explore associations between the proteins and clinical data. Thirty-nine patients with TMDM (MFP, n = 25, MYA, n = 14), diagnosed according to the diagnostic criteria for TMD (DC/TMD), aged 38 years, and sex-matched pain-free controls completed an extended DC/TMD Axis II questionnaire and the plasma concentration of 87 biomarkers were analyzed. Nine proteins separated TMDM from controls (p = 0.0174) and 12 proteins separated MYA from MFP (p = 0.019). Pain duration, characteristic pain intensity, pain catastrophizing, perceived stress, and insomnia severity were significantly associated with protein markers (p < 0.001 to p < 0.022). In conclusion, several plasma proteins were upregulated in TMDM and either upregulated or downregulated in MYA compared to MFP. Some proteins in TMDM were associated with pain variables, sleep disturbance, and emotional function. These results show that systemic differences in protein expression exist in patients with TMDM and that altered levels of specific plasma proteins are associated with different clinical variables.

Distinct CholinomiR Blood Cell Signature as a Potential Modulator of the Cholinergic System in Women with Fibromyalgia Syndrome

Fibromyalgia syndrome (FMS) is a heterogeneous chronic pain syndrome characterized by musculoskeletal pain and other key co-morbidities including fatigue and a depressed mood. FMS involves altered functioning of the central and peripheral nervous system (CNS, PNS) and immune system, but the specific molecular pathophysiology remains unclear. Anti-cholinergic treatment is effective in FMS patient subgroups, and cholinergic signaling is a strong modulator of CNS and PNS immune processes. Therefore, we used whole blood small RNA-sequencing of female FMS patients and healthy controls to profile microRNA regulators of cholinergic transcripts (CholinomiRs). We compared microRNA profiles with those from Parkinson’s disease (PD) patients with pain as disease controls. We validated the sequencing results with quantitative real-time PCR (qRT-PCR) and identified cholinergic targets. Further, we measured serum cholinesterase activity in FMS patients and healthy controls. Small RNA-sequencing revealed FMS-specific changes in 19 CholinomiRs compared to healthy controls and PD patients. qRT-PCR validated miR-182-5p upregulation, distinguishing FMS patients from healthy controls. mRNA targets of CholinomiRs bone morphogenic protein receptor 2 and interleukin 6 signal transducer were downregulated. Serum acetylcholinesterase levels and cholinesterase activity in FMS patients were unchanged. Our findings identified an FMS-specific CholinomiR signature in whole blood, modulating immune-related gene expression.

The Female-Predominant Persistent Immune Dysregulation of the Post-COVID Syndrome

OBJECTIVE

To describe the clinical data from the first 108 patients seen in the Mayo Clinic post-COVID-19 care clinic (PCOCC).

METHODS

After Institutional Review Board approval, we reviewed the charts of the first 108 patients seen between January 19, 2021, and April 29, 2021, in the PCOCC and abstracted from the electronic medical record into a standardized database to facilitate analysis. Patients were grouped into phenotypes by expert review.

RESULTS

Most of the patients seen in our clinic were female (75%; 81/108), and the median age at presentation was 46 years (interquartile range, 37 to 55 years). All had post-acute sequelae of SARS-CoV-2 infection, with 6 clinical phenotypes being identified: fatigue predominant (n=69), dyspnea predominant (n=23), myalgia predominant (n=6), orthostasis predominant (n=6), chest pain predominant (n=3), and headache predominant (n=1). The fatigue-predominant phenotype was more common in women, and the dyspnea-predominant phenotype was more common in men. Interleukin 6 (IL-6) was elevated in 61% of patients (69% of women; P=.0046), which was more common than elevation in C-reactive protein and erythrocyte sedimentation rate, identified in 17% and 20% of cases, respectively.

CONCLUSION

In our PCOCC, we observed several distinct clinical phenotypes. Fatigue predominance was the most common presentation and was associated with elevated IL-6 levels and female sex. Dyspnea predominance was more common in men and was not associated with elevated IL-6 levels. IL-6 levels were more likely than erythrocyte sedimentation rate and C-reactive protein to be elevated in patients with post-acute sequelae of SARS-CoV-2 infection.

Scoping review and interpretation of myofascial pain/fibromyalgia syndrome: An attempt to assemble a medical puzzle

BACKGROUND

Myofascial Pain Syndrome (MPS) is a common, overlooked, and underdiagnosed condition and has significant burden. MPS is often dismissed by clinicians while patients remain in pain for years. MPS can evolve into fibromyalgia, however, effective treatments for both are lacking due to absence of a clear mechanism. Many studies focus on central sensitization. Therefore, the purpose of this scoping review is to systematically search cross-disciplinary empirical studies of MPS, focusing on mechanical aspects, and suggest an organic mechanism explaining how it might evolve into fibromyalgia. Hopefully, it will advance our understanding of this disease.

METHODS

Systematically searched multiple phrases in MEDLINE, EMBASE, COCHRANE, PEDro, and medRxiv, majority with no time limit. Inclusion/exclusion based on title and abstract, then full text inspection. Additional literature added on relevant side topics. Review follows PRISMA-ScR guidelines. PROSPERO yet to adapt registration for scoping reviews.

FINDINGS

799 records included. Fascia can adapt to various states by reversibly changing biomechanical and physical properties. Trigger points, tension, and pain are a hallmark of MPS. Myofibroblasts play a role in sustained myofascial tension. Tension can propagate in fascia, possibly supporting a tensegrity framework. Movement and mechanical interventions treat and prevent MPS, while living sedentarily predisposes to MPS and recurrence.

CONCLUSIONS

MPS can be seen as a pathological state of imbalance in a natural process; manifesting from the inherent properties of the fascia, triggered by a disrupted biomechanical interplay. MPS might evolve into fibromyalgia through deranged myofibroblasts in connective tissue ("fascial armoring"). Movement is an underemployed requisite in modern lifestyle. Lifestyle is linked to pain and suffering. The mechanism of needling is suggested to be more mechanical than currently thought. A "global percutaneous needle fasciotomy" that respects tensegrity principles may treat MPS/fibromyalgia more effectively. "Functional-somatic syndromes" can be seen as one entity (myofibroblast-generated-tensegrity-tension), sharing a common rheuma-psycho-neurological mechanism.

Evaluating the construct validity and internal consistency of the Sickness Questionnaire in a Swedish sample of adults with longstanding pain

OBJECTIVES

Low-grade inflammation is a possible contributing factor in the development and persistence of chronic primary pain syndromes. Related to inflammatory activity is sickness behavior, a set of behavioral responses including increased pain sensitivity, fatigue, malaise, fever, loss of appetite, as well as depressive behavior and anhedonia. To capture these behavioral responses and their relation to longstanding pain, psychometrically sound self-report questionnaires are needed. The Sickness Questionnaire (SicknessQ) was developed to assess self-reported sickness behavior based on studies on acute immune activation while maintaining relevance for persistent conditions. The aim of the current study was to evaluate aspects of the validity and reliability of the SicknessQ in a Swedish sample of persons with longstanding pain.

METHODS

Aspects of construct validity were evaluated by means of performing a confirmatory factor analysis (CFA) (testing structural validity) and by relevant hypothesis testing i.e., that ratings of sickness behavior in combination with other related factors (e.g., depression and anxiety) would be significantly related to ratings of avoidance. Reliability was evaluated by means of analyzing the internal consistency of items.

RESULTS

Following the CFA, a non-significant Chi-Square test (χ2 [32, N=190] = 42.95, p=0.094) indicated perfect model fit. Also, the relative fit indices supported adequate model fit (CFI = 0.978; TLI = 0.969; RMSEA = 0.0430). Sickness behavior (p<0.0001), depression (p<0.05) and pain duration (p<0.05) significantly contributed to the regression model, explaining 45% of the total variance in avoidance. Internal consistency was adequate, as indicated by a Cronbach's α value of 0.82 for the entire questionnaire.

CONCLUSIONS

Results indicate that the SicknessQ has adequate structural validity as well as adequate internal consistency, and is significantly associated with avoidance. The SicknessQ appears to have utility as a self-report questionnaire to assess symptoms of sickness behavior for adults with longstanding pain.

Comment on Siracusa et al. Fibromyalgia: Pathogenesis, Mechanisms, Diagnosis and Treatment Options Update. Int. J. Mol. Sci. 2021, 22, 3891

We have read the study by Siracusa et al. [...].

MAO-A Inhibition by Metaxalone Reverts IL-1β-Induced Inflammatory Phenotype in Microglial Cells

Experimental and clinical studies have suggested that several neurological disorders are associated with the occurrence of central nervous system neuroinflammation. Metaxalone is an FDA-approved muscle relaxant that has been reported to inhibit monoamine oxidase A (MAO-A). The aim of this study was to investigate whether metaxalone might exert antioxidant and anti-inflammatory effects in HMC3 microglial cells. An inflammatory phenotype was induced in HMC3 microglial cells through stimulation with interleukin-1β (IL-1β). Control cells and IL-1β-stimulated cells were subsequently treated with metaxalone (10, 20, and 40 µM) for six hours. IL-1β stimulated the release of the pro-inflammatory cytokines tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6), but reduced the anti-inflammatory cytokine interleukin-13 (IL-13). The upstream signal consisted of an increased priming of nuclear factor-kB (NF-kB), blunted peroxisome proliferator-activated receptor gamma (PPARγ), and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) expression. IL-1β also augmented MAO-A expression/activity and malondialdehyde levels and decreased Nrf2 mRNA expression and protein levels. Metaxalone decreased MAO-A activity and expression, reduced NF-kB, TNF-α, and IL-6, enhanced IL-13, and also increased PPARγ, PGC-1α, and Nrf2 expression. The present experimental study suggests that metaxalone has potential for the treatment of several neurological disorders associated with neuroinflammation.

Brain-Derived Neurotrophic Factor and Immune Cells in Osteoarthritis, Chronic Low Back Pain, and Chronic Widespread Pain Patients: Association with Anxiety and Depression

Background and Objectives: Musculoskeletal dysfunction can induce several types of chronic pain syndromes. It is of particular interest to elucidate the pathomechanism of different forms of chronic pain. It is possible that patients who have developed chronic widespread pain (CWP) may endure different pathomechanisms as compared to those who suffer from local pain (osteoarthritis, OA) and regional pain (chronic low back pain, cLBP), especially with regard to pain regulation and its related biomediators. The aim of this study was to determine the differences in pathomechanisms among these patients by measuring pain-related biomediators, particularly brain-derived neurotrophic factor (BDNF). Additionally, subpopulations of immune cells were determined in parallel. Materials and Methods: Patients and healthy subjects (HSs) were recruited (age and gender-matched). BDNF was measured from serum samples of patients and HSs and the data of body composition parameters were recorded. Additionally, both patients and HSs were asked to fill in questionnaires related to pain intensity, anxiety, and depression. Results: Our results highlight that the levels of both free and total BDNF are significantly lower in pain patients compared to HSs, with p values of 0.041 and 0.024, respectively. The number of CD3- CD56bright natural killer (NK) cells shows significant differences between the groups. Comparing all chronic pain patients with HSs reveals a significantly lower number of CD4+ CD8+ T cells (p = 0.031), CD3- CD56bright NK cells (p = 0.049) and CD20+ CD3- cells (p = 0.007). Conclusions: To conclude, it seems that a general conformity between the pathomechanisms of different chronic pain diseases exists, although there are unique findings only in specific chronic pain patients.