Evidence of central inflammation in fibromyalgia-increased cerebrospinal fluid interleukin-8 levels

Association Between Systemic Neuroinflammation, Pain Perception and Clinical Status in Fibromyalgia Patients: Cross-Sectional Study

BACKGROUND

Fibromyalgia (FM) is characterized by chronic pain and a complex array of symptoms, with neuroinflammation implicated in its pathophysiology.

METHODS

This study aimed to explore the association between neuroinflammation, measured through interleukin levels (IL-1, IL-6, IL-8), and clinical outcomes in FM patients. Using a cross-sectional study design, blood levels of these interleukins were correlated with pain severity and disability, assessed via the Fibromyalgia Impact Questionnaire (FIQ) and pain measures.

RESULTS

Results indicated that IL-6 and IL-8 may particularly serve as biomarkers for pain severity and disability in FM patients, showing significant associations with worse clinical outcomes. Elevated IL-8 levels, for instance, correlated strongly with increased pain perception and higher disability scores.

CONCLUSIONS

These findings suggest that specific interleukins are not only elevated in FM but are actively involved in the modulation of pain and disability, underscoring the role of systemic neuroinflammation in the clinical severity of FM. This study contributes to a deeper understanding of the inflammatory mechanisms in FM and underscores the potential of targeting interleukins in therapeutic strategies.

Unraveling the neuroimmune interface in chronic pain-the association between cytokines in the cerebrospinal fluid and pain in patients with lumbar disk herniation or degenerative disk disease

ABSTRACT

Recent evidence highlights the importance of the neuroimmune interface, including periphery-to-central nervous system (CNS) neuroimmune crosstalk, in chronic pain. Although neuroinflammatory processes have been implicated in central sensitization for a long time, their potential neuroprotective and analgesic effects remain relatively elusive. We have explored the relationships between cytokine expression and symptom severity, and candidates for periphery-to-CNS crosstalk. Patients with degenerative disk disease (DDD) (nociceptive pain) or patients with lumbar disk herniation (LDH) with radiculopathy (predominantly neuropathic pain) completed questionnaires regarding pain and functional disability, underwent quantitative sensory testing, and provided blood and cerebrospinal fluid (CSF) samples. Proximity extension assay (PEA) was used to measure the levels of 92 inflammatory proteins in the CSF and serum from a total of 160 patients and controls, and CSF/serum albumin quotients was calculated for patients with DDD and patients with LDH. We found signs of neuroimmune activation, in the absence of systemic inflammation. Regarding periphery-to-CNS neuroimmune crosstalk, there were significant associations between several cytokines and albumin quotient, despite the latter being primarily at subclinical levels. The cytokines CCL11, CD5, IL8, and MMP-10 were elevated in the CSF, had positive correlations between CSF and serum levels, and associated in a nonlinear manner with back, but not leg, pain intensity in the LDH, but not the DDD, group. In conclusion, we found evidence for neuroimmune activation in the CNS of both patient groups in the absence of systemic inflammation and signs of a communication between CSF and serum. Complex and disease-specific associations were found between cytokines in CSF and back pain intensity.

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.

Fibromyalgia Animal Models Using Intermittent Cold and Psychological Stress

Fibromyalgia (FM) is a chronic pain condition characterized by widespread musculoskeletal pain and other frequent symptoms such as fatigue, sleep disturbance, cognitive impairment, and mood disorder. Based on the view that intermittent stress would be the most probable etiology for FM, intermittent cold- and intermittent psychological stress-induced generalized pain (ICGP and IPGP) models in mice have been developed and validated as FM-like pain models in terms of the patho-physiological and pharmacotherapeutic features that are shared with clinical versions. Both models show long-lasting and generalized pain and female-predominant sex differences after gonadectomy. Like many other neuropathic pain models, ICGP and IPGP were abolished in lysophosphatidic acid receptor 1 (LPAR1) knock-out mice or by LPAR1 antagonist treatments, although deciding the clinical importance of this mechanism depends on waiting for the development of a clinically available LPAR1 antagonist. On the other hand, the nonsteroidal anti-inflammatory drug diclofenac with morphine did not suppress hyperalgesia in these models, and this is consistent with the clinical findings. Pharmacological studies suggest that the lack of morphine analgesia is associated with opioid tolerance upon the stress-induced release of endorphins and subsequent counterbalance through anti-opioid NMDA receptor mechanisms. Regarding pharmacotherapy, hyperalgesia in both models was suppressed by pregabalin and duloxetine, which have been approved for FM treatment in clinic. Notably, repeated treatments with mirtazapine, an α2 adrenergic receptor antagonist-type antidepressant, and donepezil, a drug for treating Alzheimer's disease, showed potent therapeutic actions in these models. However, the pharmacotherapeutic treatment should be carried out 3 months after stress, which is stated in the FM guideline, and many preclinical studies, such as those analyzing molecular and cellular mechanisms, as well as additional evidence using different animal models, are required. Thus, the ICGP and IPGP models have the potential to help discover and characterize new therapeutic medicines that might be used for the radical treatment of FM, although there are several limitations to be overcome.

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.

Characteristics of pain and their relationship to disease activity in UK patients with Behçet's syndrome: a prospective cohort study

Background

Behçet's syndrome (BS) is a rare multi-systemic vasculitis of unknown aetiology. Fibromyalgia syndrome (FMS) is more prevalent in rheumatological conditions such-as BS, than the general population. However, there is limited research into the aetiology and characteristics of pain in BS.

Objectives

To describe the pain characteristics and incidence of FMS in people with BS and investigate their relationship with BS disease activity.

Methods

A cohort study of BS patients attending the Liverpool Behçet's Centre between February 2017 and March 2019. BS was defined using the International Study Group Criteria. BS severity was assessed using the Behçet's Disease Current Activity Form. FMS was determined from consultant diagnosis. Assessments of pain included: Pain Visual Analogue Scale (PVAS), Pain Mannequin, Brief Pain Inventory, EQ-5D-3L and Short Form McGill. Pain and FMS prevalence were compared between high and low disease activity.

Results

90% reported moderate-severe pain with a median PVAS score of 68/100 [38, 81]. 35.6% of participants had FMS and 46.5% experienced generalized pain. 76% of participants with high disease activity reported severe pain, compared to 39.1% with low disease activity (p = .003). Pain was more generalised in high disease activity (72%) compared to low disease activity (37.7%) (p = .003). FMS was more prevalent in the high disease activity group (52%) than the low disease activity group (29%) (p = .04).

Conclusions

This is the first study to explore pain in participants with BS in the United Kingdom. The majority of BS patients experience moderate-severe widespread pain. Severe widespread pain is more prevalent in those with high disease activity. We have demonstrated a relationship between high disease activity, worse pain intensity, and FMS. This paper contributes to the understanding of two conditions which remain to be fully understood, FMS and BS, and generates new hypotheses to describe the interplay between.

Links between brain neuroimaging and blood inflammatory markers in urological chronic pelvic pain syndrome

Urological chronic pelvic pain syndrome (UCPPS) is a debilitating painful condition with unclear etiology. Prior researchers have indicated that compared to healthy controls, patients with UCPPS demonstrated altered brain activity. Researchers have also shown that in UCPPS, several blood inflammatory markers relate to clinical variables of pain, fatigue, and pain widespreadness. However, how altered brain function in patients with UCPPS relates to blood inflammation remains unknown. To extend and connect prior findings of altered brain function and inflammatory factors in UCPPS, we conducted a secondary analysis of data from a cohort of UCPPS patients (N = 29) and healthy controls (N = 31) who provided both neuroimaging and blood data (National Institute of Health MAPP Research Network publicly available dataset). In our present study, we aimed to evaluate relationships between a priori-defined brain neuroimaging markers and inflammatory factors of interest and their relationships to pain-psychological variables. We hypothesized that two brain alterations of interest (i.e., PCC - left hippocampus functional connectivity and PCC - bilateral amygdala functional connectivity) would be correlated with four cytokine markers of interest: interleukin (IL) - 6, tumor necrosis factor-alpha (TNF-a), IL-8, and granulocyte-macrophage colony-stimulating factor (GM-CSF). In the UCPPS cohort, we identified a significant PCC - left hippocampus functional connectivity relationship with IL-6 (p = 0.0044). Additionally, in the UCPPS cohort, we identified a PCC - amygdala functional connectivity relationship with GM-CSF which did not meet our model's threshold for statistical significance (p = 0.0665). While these data are preliminary and cross-sectional, our findings suggest connections between brain function and levels of low-grade systemic inflammation in UCPPS. Thus, while further study is needed, our data indicate the potential for advancing the understanding of how brain functional circuits may relate to clinical symptoms and systemic inflammation.

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.

Non-invasive brain stimulation for fibromyalgia: current trends and future perspectives

Fibromyalgia, a common and enduring pain disorder, ranks as the second most prevalent rheumatic disease after osteoarthritis. Recent years have witnessed successful treatment using non-invasive brain stimulation. Transcranial magnetic stimulation, transcranial direct current stimulation, and electroconvulsion therapy have shown promise in treating chronic pain. This article reviews the literature concerning non-invasive stimulation for fibromyalgia treatment, its mechanisms, and establishes a scientific basis for rehabilitation, and discusses the future directions for research and development prospects of these techniques are discussed.

How Can Experimental Endotoxemia Contribute to Our Understanding of Pain? A Narrative Review

The immune system and the central nervous system exchange information continuously. This communication is a prerequisite for adaptive responses to physiological and psychological stressors. While the implicate relationship between inflammation and pain is increasingly recognized in clinical cohorts, the underlying mechanisms and the possibilities for pharmacological and psychological approaches aimed at neuro-immune communication in pain are not fully understood yet. This calls for preclinical models which build a bridge from clinical research to laboratory research. Experimental models of systemic inflammation (experimental endotoxemia) in humans have been increasingly recognized as an approach to study the direct and causal effects of inflammation on pain perception. This narrative review provides an overview of what experimental endotoxemia studies on pain have been able to clarify so far. We report that experimental endotoxemia results in a reproducible increase in pain sensitivity, particularly for pressure and visceral pain (deep pain), which is reflected in responses of brain areas involved in pain processing. Increased levels of blood inflammatory cytokines are required for this effect, but cytokine levels do not always predict pain intensity. We address sex-dependent differences in immunological responses to endotoxin and discuss why these differences do not necessarily translate to differences in behavioral measures. We summarize psychological and cognitive factors that may moderate pain sensitization driven by immune activation. Together, studying the immune-driven changes in pain during endotoxemia offers a deeper mechanistic understanding of the role of inflammation in chronic pain. Experimental endotoxemia models can specifically help to tease out inflammatory mechanisms underlying individual differences, vulnerabilities, and comorbid psychological problems in pain syndromes. The model offers the opportunity to test the efficacy of interventions, increasing their translational applicability for personalized medical approaches.

Evidence of neuroinflammation in fibromyalgia syndrome: a [ 18 F]DPA-714 positron emission tomography study

ABSTRACT

This observational study aimed to determine whether individuals with fibromyalgia (FM) exhibit higher levels of neuroinflammation than healthy controls (HCs), as measured with positron emission tomography using [ 18 F]DPA-714, a second-generation radioligand for the translocator protein (TSPO). Fifteen women with FM and 10 HCs underwent neuroimaging. Distribution volume (V T ) was calculated for in 28 regions of interest (ROIs) using Logan graphical analysis and compared between groups using multiple linear regressions. Group (FM vs HC) was the main predictor of interest and TSPO binding status (high- vs mixed-affinity) was added as a covariate. The FM group had higher V T in the right postcentral gyrus ( b = 0.477, P = 0.033), right occipital gray matter (GM; b = 0.438, P = 0.039), and the right temporal GM ( b = 0.466, P = 0.042). The FM group also had lower V T than HCs in the left isthmus of the cingulate gyrus ( b = -0.553, P = 0.014). In the subgroup of high-affinity binders, the FM group had higher V T in the bilateral precuneus, postcentral gyrus, parietal GM, occipital GM, and supramarginal gyrus. Group differences in the right parietal GM were associated with decreased quality of life, higher pain severity and interference, and cognitive problems. In support of our hypothesis, we found increased radioligand binding (V T ) in the FM group compared with HCs in several brain regions regardless of participants' TSPO binding status. The ROIs overlapped with prior reports of increased TSPO binding in FM. Overall, increasing evidence supports the hypothesis that FM involves microglia-mediated neuroinflammation in the brain.

Micro-inflammation related gene signatures are associated with clinical features and immune status of fibromyalgia

BACKGROUND

Fibromyalgia (FM) is a multifaceted disease. Along with the genetic, environmental and neuro-hormonal factors, inflammation has been assumed to have role in the pathogenesis of FM. The aim of the present study was to explore the differences in clinical features and pathophysiology of FM patients under different inflammatory status.

METHODS

The peripheral blood gene expression profile of FM patients in the Gene Expression Omnibus database was downloaded. Differentially expressed inflammatory genes were identified, and two molecular subtypes were constructed according to these genes used unsupervised clustering analysis. The clinical characteristics, immune features and pathways activities were compared further between the two subtypes. Then machine learning was used to perform the feature selection and construct a classification model.

RESULTS

The patients with FM were divided into micro-inflammation and non-inflammation subtypes according to 54 differentially expressed inflammatory genes. The micro-inflammation group was characterized by more major depression (p = 0.049), higher BMI (p = 0.021), more active dendritic cells (p = 0.010) and neutrophils. Functional enrichment analysis showed that innate immune response and antibacterial response were significantly enriched in micro-inflammation subtype (p < 0.050). Then 5 hub genes (MMP8, ENPP3, MAP2K3, HGF, YES1) were screened thought three feature selection algorithms, an accurate classifier based on the 5 hub DEIGs and 2 clinical parameters were constructed using support vector machine model. Model scoring indicators such as AUC (0.945), accuracy (0.936), F1 score (0.941), Brier score (0.079) and Hosmer-Lemeshow goodness-of-fit test (χ2 = 4.274, p = 0.832) proved that this SVM-based classifier was highly reliable.

CONCLUSION

Micro-inflammation status in FM was significantly associated with the occurrence of depression and activated innate immune response. Our study calls attention to the pathogenesis of different subtypes of FM.

Melatonin as a Coadjuvant in the Treatment of Patients with Fibromyalgia

Fibromyalgia syndrome (FMS) is a chronic widespread pain syndrome that is accompanied by fatigue, sleep disturbances, anxiety, depression, lack of concentration, and neurocognitive impairment. As the currently available drugs are not completely successful against these symptoms and frequently have several side effects, many scientists have taken on the task of looking for nonpharmacological remedies. Many of the FMS-related symptoms have been suggested to be associated with an altered pattern of endogenous melatonin. Melatonin is involved in the regulation of several physiological processes, including circadian rhythms, pain, mood, and oxidative as well as immunomodulatory balance. Preliminary clinical studies have propounded that the administration of different doses of melatonin to patients with FMS can reduce pain levels and ameliorate mood and sleep disturbances. Moreover, the total antioxidant capacity, 6-sulfatoxymelatonin and urinary cortisol levels, and other biological parameters improve after the ingestion of melatonin. Recent investigations have proposed a pathophysiological relationship between mitochondrial dysfunction, oxidative stress, and FMS by looking at certain proteins involved in mitochondrial homeostasis according to the etiopathogenesis of this syndrome. These improvements exert positive effects on the quality of life of FMS patients, suggesting that the use of melatonin as a coadjuvant may be a successful strategy for the management of this syndrome.

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.

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.

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.

The effects of a 15-week physical exercise intervention on pain modulation in fibromyalgia: Increased pain-related processing within the cortico-striatal- occipital networks, but no improvement of exercise-induced hypoalgesia

Dysfunctional top-down pain modulation is a hallmark of fibromyalgia (FM) and physical exercise is a cornerstone in FM treatment. The aim of this study was to explore the effects of a 15-week intervention of strengthening exercises, twice per week, supervised by a physiotherapist, on exercise-induced hypoalgesia (EIH) and cerebral pain processing in FM patients and healthy controls (HC). FM patients (n = 59) and HC (n = 39) who completed the exercise intervention as part of a multicenter study were examined at baseline and following the intervention. Following the exercise intervention, FM patients reported a reduction of pain intensity, fibromyalgia severity and depression. Reduced EIH was seen in FM patients compared to HC at baseline and no improvement of EIH was seen following the 15-week resistance exercise intervention in either group. Furthermore, a subsample (Stockholm site: FM n = 18; HC n = 19) was also examined with functional magnetic resonance imaging (fMRI) during subjectively calibrated thumbnail pressure pain stimulations at baseline and following intervention. A significant main effect of exercise (post > pre) was observed both in FM patients and HC, in pain-related brain activation within left dorsolateral prefrontal cortex and caudate, as well as increased functional connectivity between caudate and occipital lobe bordering cerebellum (driven by the FM patients). In conclusion, the results indicate that 15-week resistance exercise affect pain-related processing within the cortico-striatal-occipital networks (involved in motor control and cognition), rather than directly influencing top-down descending pain inhibition. In alignment with this, exercise-induced hypoalgesia remained unaltered.

A Link Between Inflammatory Mechanisms and Fibromyalgia

Fibromyalgia (FM) is a condition characterized by chronic widespread pain, which has traditionally been considered psychogenic in nature due to lack of known underlying organic pathophysiology. In more recent years, inflammation of the nervous system has become increasingly recognized as a sign of neuropsychiatric conditions, and this association may enhance our knowledge of conditions such as FM. Emerging evidence has suggested inflammation, particularly neuroinflammation, as a potential contributor underlying the etiology of FM. Studies have searched for linked biomarkers with mixed results, though the literature is beginning to point to increased systemic levels of pro-inflammatory cytokines such as IL-6 and IL-8 in patients with FM relative to healthy controls. A multicenter imaging study has also reported results suggestive of microglial activation related to the presence of FM. Given the consistency in neuroinflammatory effects implicated in "sickness behavior" characteristic of chronic systemic inflammatory conditions such as cancer or rheumatic diseases, therein springs the hypothesis for a connection between FM and neuroinflammation as discussed in this chapter.

Emotion regulation and the salience network: a hypothetical integrative model of fibromyalgia

Fibromyalgia is characterized by widespread pain, fatigue, sleep disturbances and other symptoms, and has a substantial socioeconomic impact. Current biomedical and psychosocial treatments are unsatisfactory for many patients, and treatment progress has been hindered by the lack of a clear understanding of the pathogenesis of fibromyalgia. We present here a model of fibromyalgia that integrates current psychosocial and neurophysiological observations. We propose that an imbalance in emotion regulation, reflected by an overactive 'threat' system and underactive 'soothing' system, might keep the 'salience network' (also known as the midcingulo-insular network) in continuous alert mode, and this hyperactivation, in conjunction with other mechanisms, contributes to fibromyalgia. This proposed integrative model, which we term the Fibromyalgia: Imbalance of Threat and Soothing Systems (FITSS) model, should be viewed as a working hypothesis with limited supporting evidence available. We hope, however, that this model will shed new light on existing psychosocial and biological observations, and inspire future research to address the many gaps in our knowledge about fibromyalgia, ultimately stimulating the development of novel therapeutic interventions.

Online Questionnaire with Fibromyalgia Patients Reveals Correlations among Type of Pain, Psychological Alterations, and Effectiveness of Non-Pharmacological Therapies

Fibromyalgia (FM) is a chronic pain syndrome with an unclear etiology. In addition to pain, FM patients suffer from a diverse array of symptoms and comorbidities, encompassing fatigue, cognitive dysfunction, mood disorders, sleep deprivation, and dizziness. Due to the complexity of FM, the diagnosis and treatment of it are highly challenging. The aim of the present work was to investigate some clinical and psychological characteristics of FM patients, and to uncover possible correlations with pharmacological and non-pharmacological therapies. We conducted a cross-sectional, questionnaire-based study aimed at evaluating pain, psychological traits, and the self-perceived effectiveness of pharmacological and non-pharmacological treatments in an Italian population of FM patients. Descriptive statistics, correlation, and inference analyses were performed. We found a prevalence of a neuropathic/nociplastic type of pain, which correlated with psychological traits such as anxiety, low mood, psychophysical discomfort, and the inability to relax. The pain type and psychological traits proved to play a role in determining the self-perceived effectiveness of therapeutic interventions. Patients revealed a better response to non-pharmacological therapies, particularly dietary interventions, relaxation techniques, and psychotherapy rather than pharmacological interventions. The sum of our data indicates that for better outcomes, the type of pain and psychological traits should be considered for tailor-made treatments considering non-pharmacological protocols as a complement to the use of drugs.

Protocatechuic acid counteracts oxidative stress and inflammation in carrageenan-induced paw edema in mice

Protocatechuic acid (PCA), a phenolic compound found in teas, fruits, and vegetables, is widely recognized with its antioxidant and anti-inflammatory activities. Here, we verified the protective role of PCA on carrageenan (CGN)-induced paw edema in mice. Forty-five male Swiss albino mice were assigned into five groups: control group, CGN-injected group (1% w/v), PCA (25 mg/kg) + CGN group. PCA (50 mg/kg) + CGN group and diclofenac sodium (20 mg/kg) + CGN group. PCA and diclofenac sodium were administered orally for 5 consecutive days prior to the CGN injection. PCA pretreatment notably decreased the volume of the developed edema and alleviated the histopathological alterations induced by carrageenan. Additionally, PCA administration enhanced the cellular antioxidant capacity as demonstrated by the increased levels of catalase, superoxide dismutase, and reduced glutathione, in addition to the decreased malondialdehyde level in the edematous tissue. Interestingly, PCA administration was able significantly to suppress the developed inflammatory response upon carrageenan injection as indicated by the decreased levels and expression of pro-inflammatory cytokines and mediators including tumor necrosis factor alpha, interleukin-1 beta, interleukin-6, inducible nitric oxide synthase, nitric oxide, cyclooxygenase-II, prostaglandin E2, monocyte chemoattractant protein-1, myeloperoxidase and nuclear factor kappa B. These results collectively confirm the protective effect of PCA against carrageenan-induced paw edema owing to its antioxidant and anti-inflammatory characteristics.

Thalamocortical bistable switch as a theoretical model of fibromyalgia pathogenesis inferred from a literature survey

Fibromyalgia (FM) is an unsolved central pain processing disturbance. We aim to provide a unifying model for FM pathogenesis based on a loop network involving thalamocortical regions, i.e., the ventroposterior lateral thalamus (VPL), the somatosensory cortex (SC), and the thalamic reticular nucleus (TRN). The dynamics of the loop have been described by three differential equations having neuron mean firing rates as variables and containing Hill functions to model mutual interactions among the loop elements. A computational analysis conducted with MATLAB has shown a transition from monostability to bistability of the loop behavior for a weakening of GABAergic transmission between TRN and VPL. This involves the appearance of a high-firing-rate steady state, which becomes dominant and is assumed to represent pathogenic pain processing giving rise to chronic pain. Our model is consistent with a bulk of literature evidence, such as neuroimaging and pharmacological data collected on FM patients, and with correlations between FM and immunoendocrine conditions, such as stress, perimenopause, chronic inflammation, obesity, and chronic dizziness. The model suggests that critical targets for FM treatment are to be found among immunoendocrine pathways leading to GABA/glutamate imbalance having an impact on the thalamocortical system.

Microstructural Evidence of Neuroinflammation for Psychological Symptoms and Pain in Patients with Fibromyalgia

Objective

In patients with fibromyalgia (FM), the brain shows altered structure and functional connectivity, but the mechanisms underlying these changes remain unclear. This study investigated the associated changes in brain microstructures and neuroinflammation of patients with FM.

Methods

We recruited 14 patients with FM and 14 healthy controls. Visual analog scale (VAS), Beck's Anxiety Inventory (BAI), and Beck's Depression Inventory-II (BDI-II) were used for assessing their pain, anxiety, and depression levels, respectively. Diffusion kurtosis imaging (DKI) was used to visualize microstructural alterations associated with neuroinflammation in specific brain regions. The biomarkers for the neuron damage, including serum tau and amyloid β protein fragment 1-42 (Aβ1-42) levels, were assessed. Spearman correlation of DKI parameters with VAS, BAI, and BDI-II scores and tau and Aβ1-42 levels were assessed.

Results

The patients with FM had significantly higher levels of Aβ1-42 levels compared with the controls. Compared with the controls, the patients showed significantly lower DKI parameters in the bilateral dorsal–lateral prefrontal cortex and orbital–frontal cortex. The patients showed a significant correlation between the axial kurtosis values of the amygdala and VAS scores (left: rho = -0.603, p = 0.022; right: rho = -7.04, p = 0.005).

Conclusion

To the best of our knowledge, this is the first study to use DKI to examine the brain of FM patients. We noted significant DKI changes at specific areas associated with neuroinflammation in patients with FM. Our results provide valuable information on brain neuroinflammation and pathophysiological changes in patients with FM.

Hepatocyte growth factor, colony-stimulating factor 1, CD40, and 11 other inflammation-related proteins are associated with pain in diabetic neuropathy: exploration and replication serum data from the Pain in Neuropathy Study

ABSTRACT

One in 5 patients with diabetes suffers from chronic pain with neuropathic characteristics, but the pathophysiological mechanisms underlying the development of neuropathic pain in patients with diabetic distal symmetrical polyneuropathy (DSP) are poorly understood. Systemic low-grade inflammation has been implicated, but there is still a considerable knowledge gap concerning its scope and meaning in this context. The aim of the study was to establish the broad inflammatory signature of painful diabetic DSP in serum samples from the Pain in Neuropathy Study, an observational cross-sectional multicentre study in which participants underwent deep phenotyping. In the present two cohorts exploration-replication study (180 participants in each cohort), serum samples from Pain in Neuropathy Study participants were analyzed with the Olink INFLAMMATION panel (Olink Bioscience, Uppsala, Sweden) that enables the simultaneous measurement of 92 inflammation-related proteins (mainly cytokines, chemokines, and growth factors). In both the exploration and the replication cohort, we identified a high-inflammation subgroup where 14 inflammation-related proteins in particular were associated with more neuropathy and higher pain intensity. The top 3 proteins were hepatocyte growth factor, colony-stimulating factor 1, and CD40 in both cohorts. In the exploratory cohort, additional clinical data were available, showing an association of inflammation with insomnia and self-reported psychological distress. Hence, this cross-sectional exploration-replication study seems to confirm that low-grade systemic inflammation is related to the severity of neuropathy and neuropathic pain in a subgroup of patients with diabetic DSP. The pathophysiological relevance of these proteins for the development of neuropathic pain in patients with diabetic DSP must be explored in more depth in future studies.

Noninvasive intracranial pressure monitoring in women with migraine

This cross-sectional study aimed to compare the waveform morphology through noninvasive intracranial pressure (ICP-NI) measurement between patients with migraine and controls, and to analyze the association with clinical variables. Twenty-nine women with migraine, age 32.4 (11.2) years and headache frequency of 12.6 (7.5) days per month and twenty-nine women without headache, age 32.1 (9.0) years, were evaluated. Pain intensity, migraine disability, allodynia, pain catastrophizing, central sensitization and depression were evaluated. The ICP-NI monitoring was performed by a valid method consisting of an extracranial deformation sensor positioned in the patients’ scalp, which allowed registration of intracranial pressure waveforms. Heart rate and blood pressure measurements were simultaneously recorded during 20 min in the supine position. The analyzed parameter was the P2/P1 ratio based on mean pulse per minute which P1 represents the percussion wave related to the arterial blood pression maximum and P2 the tidal wave, middle point between the P1 maximum and the dicrotic notch. There was no between-groups difference in the P2/P1 ratio (mean difference: 0.04, IC95%: -0.07 to 0.16, p = 0.352, F (1,1) = 0.881) adjusted by body mass index covariable. The Multiple Linear Regression showed non-statistical significance [F (5,44) = 1.104; p = 0.372; R² = 0.11)] between the P2/P1 ratio and body mass index, presence of migraine, central sensitization, pain catastrophizing and depression. We found no correlation (p > 0.05) between P2/P1 ratio and migraine frequency, migraine onset, pain intensity, pain intensity at day of examination, disability, allodynia. Migraine patients did not present alterations in the waveform morphology through ICP-NI compared to women without headache and no association with clinical variables was found.

The translocator protein gene is associated with endogenous pain modulation and the balance between glutamate and γ-aminobutyric acid in fibromyalgia and healthy subjects: a multimodal neuroimaging study

ABSTRACT

A cerebral upregulation of the translocator protein (TSPO), a biomarker of glial activation, has been reported in fibromyalgia subjects (FMS). The TSPO binding affinity is genetically regulated by the Ala147Thr polymorphism in the TSPO gene (rs6971) and allows for a subject classification into high affinity binders (HABs) and mixed/low affinity binders (MLABs). The aim of the present multimodal neuroimaging study was to examine the associations of the TSPO polymorphism with: (1) conditioned pain modulation, (2) expectancy-modulated pain processing assessed during functional magnetic resonance imaging, and (3) the concentration and balance of glutamate and γ-aminobutyric acid in the rostral anterior cingulate cortex and thalamus using proton magnetic resonance spectroscopy in FMS (n = 83) and healthy controls (n = 43). The influence of TSPO on endogenous pain modulation presented in the form of TSPO HABs, as opposed to MLABs, displaying less efficient descending pain inhibition and expectancy-induced reduction of pain. Translocator protein HABs in both groups (FM and healthy controls) were found to have higher thalamic glutamate concentrations and exhibit a pattern of positive correlations between glutamate and γ-aminobutyric acid in the rostral anterior cingulate cortex, not seen in MLABs. Altogether, our findings point to TSPO-related mechanisms being HAB-dependent, brain region-specific, and non-FM-specific, although in FMS the disadvantage of an aberrant pain regulation combined with an HAB genetic set-up might hamper pain modulation more strongly. Our results provide evidence for an important role of TSPO in pain regulation and brain metabolism, thereby supporting the ongoing drug development targeting TSPO-associated mechanisms for pain relief.

Evaluation of Endothelial Dysfunction and Autophagy in Fibromyalgia-Related Vascular and Cerebral Cortical Changes and the Ameliorative Effect of Fisetin

Fibromyalgia (FM) is a common chronic pain syndrome that affects 1% to 5% of the population. We aimed to investigate the role of endothelial dysfunction and autophagy in fibromyalgia-related vascular and cerebral cortical changes in a reserpine-induced rat model of fibromyalgia at the histological and molecular levels and to study the ameliorative effect of fisetin. Forty adult female albino rats were divided into four groups (10 each): two control groups, the reserpine-induced fibromyalgia group, and the fisetin-treated group. The carotid arteries and brains of the animals were dissected. Frozen tissue samples were used for total RNA extraction and qPCR analysis of eNOS, caspase-3, Bcl-2, LC-3, BECN-1, CHOP, and TNF-α expression. Histological, immunohistochemical (eNOS), and ultrastructure studies were conducted. The carotid arteries revealed excessive autophagy and endothelial, vascular, and apoptotic changes. The cerebral cortex showed similar findings apart from endoplasmic reticulum stress. Additionally, there was decreased gene expression of eNOS and Bcl-2 and increased expression of caspase-3, LC-3, BECN-1, CHOP, and TNF-α. In the fisetin-treated rats, improvements in the histological and molecular results were detected. In conclusion, oxidative stress, enhanced apoptosis, and excessive autophagy are fundamental pathophysiologic mechanisms of reserpine-induced fibromyalgia. Moreover, fisetin has an ameliorative effect against fibromyalgia.

The evaluation of nailfold capillaroscopy pattern in patients with fibromyalgia

Objectives

This study aims to evaluate nailfold capillaroscopic pattern in patents with fibromyalgia and to assess the relation of capillaroscopic parameters with clinical variables and disease-related measures.

Patients and methods

This cross-sectional, case-control study included 60 participants (4 males, 56 females; mean age: 44.0±8.2 years; range, 26 to 64 years) between August 2019 and November 2019. All participants were divided into two groups as the primary fibromyalgia group (n=30) who met the 2016 modified American College of Rheumatology Diagnostic Criteria for Fibromyalgia and the control group (n=30) consisting of age- and sex-matched healthy individuals. Nailfold capillaroscopy was performed by a digital microscope under a magnification of 200X. Capillary density, capillary loop diameter, number of dilated, giant and neoangiogenic capillaries, capillary shape, number of avascular areas, micro-aneurysms and micro-hemorrhages were evaluated by an assessor who was blind to the group allocation. In the fibromyalgia group, Widespread Pain Index, Symptom Severity Scale scores, and Fibromyalgia Severity scores were calculated. Health status and presence of benign joint hypermobility syndrome (BJHS) were evaluated using the Fibromyalgia Impact Questionnaire (FIQ) and revised Brighton criteria, respectively.

Results

Of the capillaroscopic parameters, the mean capillary loop diameter, number of micro-aneurysms, avascular areas, and neoangiogenic capillaries were significantly higher in the patient group compared to the controls (p<0.001, p=0.016, p=0.038, and p=0.04, respectively). Nailfold capillaroscopic findings did not significantly differ between the patients with (n=16) and without concomitant BJHS (n=14). Of the disease-related measures, only FIQ score showed a weak correlation with the number of dilated capillaries (p=0.324).

Conclusion

Patients with fibromyalgia have distinct capillaroscopic patterns than healthy population. Capillaroscopic features, in general, are not related to clinical variables and disease-related measures.

Diagnostic Challenges and Management of Fibromyalgia

The World Health Organization regards chronic pain to be a public health concern. In clinical medicine, fibromyalgia (FM) is the most prevalent chronic widespread pain disease. In terms of impairment, consumption of health and social resources, and impact on primary and speciality care systems, it has reached worrisome proportions. This disease is frequently managed by primary care providers. Because of its intricacy, fibromyalgia diagnosis and treatment can be difficult. Fibromyalgia is a controversial condition. It might appear ill-defined in comparison to other pain conditions, with no clear knowledge of pathophysiology and hence no particular targeted therapy. This invariably sparks debates and challenges. There is no obvious cut-off point that distinguishes FM from non-FM. The diagnosis of fibromyalgia has been complicated by several factors, including patients' health-seeking behaviour, symptom identification, and physician labelling of the disease. Fibromyalgia is currently considered a centralized pain condition, according to research that has improved our understanding of its etiopathology. A multidisciplinary strategy combining pharmacological and non-pharmacological therapies based on a biopsychosocial paradigm can result in effective therapy. Cultural and psychosocial variables appear to be a recent development in fibromyalgia, and they appear to have a larger influence on physician diagnosis than severe symptom levels in FM patients. Although physicians rely on FM criteria as the only way to classify FM patients in research and clinical settings, some crucial elements of the diagnostic challenge of fibromyalgia remain unsolved - invalidation, psychosocial variables, and diverse illness manifestation are some examples. Beyond the existing constructional scores, physicians' judgment gained in real communicative contexts with patients, appears to be the only dependable route for a more accurate diagnosis for fibromyalgia. We have performed an exhaustive review of the literature using the keywords "Fibromyalgia", "challenges" and "diagnosis" in PubMed and Google Scholar indexes up to September 2021. This article aims to examine the causes, diagnosis, and current treatment protocols of FM, as well as discuss some continuing debates and diagnostic challenges which physicians face in accurately diagnosing fibromyalgia.

Impaired Lymphatic Drainage and Interstitial Inflammatory Stasis in Chronic Musculoskeletal and Idiopathic Pain Syndromes: Exploring a Novel Mechanism

A normal functioning lymphatic pump mechanism and unimpaired venous drainage are required for the body to remove inflammatory mediators from the extracellular compartment. Impaired vascular perfusion and/or lymphatic drainage may result in the accumulation of inflammatory substances in the interstitium, creating continuous nociceptor activation and related pathophysiological states including central sensitization and neuroinflammation. We hypothesize that following trauma and/or immune responses, inflammatory mediators may become entrapped in the recently discovered interstitial, pre-lymphatic pathways and/or initial lymphatic vessels. The ensuing interstitial inflammatory stasis is a pathophysiological state, created by specific pro-inflammatory cytokine secretion including tumor necrosis factor alpha, interleukin 6, and interleukin 1b. These cytokines can disable the local lymphatic pump mechanism, impair vascular perfusion via sympathetic activation and, following transforming growth factor beta 1 expression, may lead to additional stasis through direct fascial compression of pre-lymphatic pathways. These mechanisms, when combined with other known pathophysiological processes, enable us to describe a persistent feed-forward loop capable of creating and maintaining chronic pain syndromes. The potential for concomitant visceral and/or vascular dysfunction, initiated and maintained by the same feed-forward inflammatory mechanism, is also described.

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

Objectives

The aetiology of primary chronic pain syndromes (CPS) is highly disputed. We performed a systematic review and meta-analysis aiming to assess differences in circulating cytokine levels in patients with diffuse CPS (fibromyalgia) vs healthy controls (HC).

Methods

Human studies published in English from the PubMed, MEDLINE/Scopus and Cochrane databases were systematically searched from inception up to January 2020. We included full text cross-sectional or longitudinal studies with baseline cytokine measurements, reporting differences in circulating cytokine levels between fibromyalgia patients and HC. Random-effects meta-analysis models were used to report pooled effects and 95% CIs. This study is registered with PROSPERO (CRD42020193774).

Results

Our initial search yielded 324 papers and identified 29 studies (2458 participants) eligible for systematic review and 22 studies (1772 participants) suitable for meta-analysis. The systematic analysis revealed reproducible findings supporting different trends of cytokine levels when fibromyalgia patients were compared with HC, while the chemokine eotaxin, was consistently raised in fibromyalgia. Meta-analysis showed significantly increased TNF-α [standardized mean difference (SMD) = 0.36, 95% CI: 0.12, 0.60, P = 0.0034; I² = 71%, Q²P = 0.0002], IL-6 (SMD = 0.15, 95% CI: 0.003, 0.29, P = 0.045; I² = 39%, Q²P = 0.059), IL-8 (SMD = 0.26, 95% CI: 0.05, 0.47, P = 0.01; I² = 61%, Q²P = 0.005) and IL-10 (SMD = 0.61, 95% CI: 0.34, 0.89, P < 0.001; I² = 10%, Q²P = 0.34) in fibromyalgia patients compared with HC.

Conclusion

We found evidence of significant differences in the peripheral blood cytokine profiles of fibromyalgia patients compared with HC. However, the distinctive profile associated with fibromyalgia includes both pro-inflammatory (TNF-α, IL-6, IL-8) and anti-inflammatory (IL-10) cytokines in pooled analysis, as well as chemokine (eotaxin) signatures. Further research is required to elucidate the role of cytokines in fibromyalgia.

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.

The Italian Society for Rheumatology clinical practice guidelines for the diagnosis and management of fibromyalgia Best practices based on current scientific evidence

Fibromyalgia or fibromyalgia syndrome (FMS) is defined as a central sensitization syndrome characterized by the dysfunction of neurocircuits detecting, transmitting and processing nociceptive stimuli; the prevalent manifestation is musculoskeletal pain. In addition to pain, there are multiple accompanying symptoms, in common with other algo-dysfunctional syndromes, which are reflected in a broad spectrum of somatic, neurocognitive and neuro-vegetative manifestations. An evidence-based approach is essential in FMS management, in order to improve patient health and to reduce its social burden. Since in the last ten years new international guidelines for clinical practice (Clinical Practice Guidelines or CPGs) concerning FMS diagnosis and pharmacological/ non-pharmacological management have been published, the Italian Society of Rheumatology (SIR) has decided to adapt them to the Italian national setting. The framework of the Guidelines International Network Adaptation Working Group was adopted to identify, appraise (AGREE II), synthesize, and customize the most recent CPGs on FMS to the needs of the Italian healthcare context. A working group of rheumatologists from SIR epidemiology unit and FMS experts identified relevant clinical questions to guide the systematic review of the literature. The target audience of these CPGs included physicians and healthcare professionals who manage FMS. The adapted recommendations were finally assessed by an external multidisciplinary panel. From the systematic search in databases (Pubmed/Medline, Embase) and grey literature, 6 CPGs were selected and appraised by two independent raters. The combination of the scientific evidence underlying the original CPGs with expert opinion lead to the development of 17 recommendations. The quality of evidence for each recommendation was reported and their potential impact on clinical practice was assessed. These SIR recommendations are expected to be a valuable aid in the diagnosis and treatment of FMS, as they will contribute to disseminate the best practice on the basis of the current scientific evidence.

Thalamic neurometabolite alterations in patients with knee osteoarthritis before and after total knee replacement

ABSTRACT

The weak association between disability levels and "peripheral" (ie, knee) findings suggests that central nervous system alterations may contribute to the pathophysiology of knee osteoarthritis (KOA). Here, we evaluated brain metabolite alterations in patients with KOA, before and after total knee arthroplasty (TKA), using 1H-magnetic resonance spectroscopy (MRS). Thirty-four presurgical patients with KOA and 13 healthy controls were scanned using a PRESS sequence (TE = 30 ms, TR = 1.7 seconds, voxel size = 15 × 15 × 15 mm). In addition, 13 patients were rescanned 4.1 ± 1.6 (mean ± SD) weeks post-TKA. When using creatine (Cr)-normalized levels, presurgical KOA patients demonstrated lower N-acetylaspartate (NAA) (P < 0.001), higher myoinositol (mIns) (P < 0.001), and lower Choline (Cho) (P < 0.05) than healthy controls. The mIns levels were positively correlated with pain severity scores (r = 0.37, P < 0.05). These effects reached statistical significance also using water-referenced concentrations, except for the Cho group differences (P ≥ 0.067). Post-TKA patients demonstrated an increase in NAA (P < 0.01), which returned to the levels of healthy controls (P > 0.05), irrespective of metric. In addition, patients demonstrated postsurgical increases in Cr-normalized (P < 0.001), but not water-referenced mIns, which were proportional to the NAA/Cr increases (r = 0.61, P < 0.05). Because mIns is commonly regarded as a glial marker, our results are suggestive of a possible dual role for neuroinflammation in KOA pain and post-TKA recovery. Moreover, the apparent postsurgical normalization of NAA, a putative marker of neuronal integrity, might implicate mitochondrial dysfunction, rather than neurodegenerative processes, as a plausible pathophysiological mechanism in KOA. More broadly, our results add to a growing body of literature suggesting that some pain-related brain alterations can be reversed after peripheral surgical treatment.

Differential expression of cerebrospinal fluid neuroinflammatory mediators depending on osteoarthritis pain phenotype

Supplemental Digital Content is Available in the Text.

Distinct cerebrospinal fluid neuroinflammatory profiles may be associated with different objective characteristics of persistent pain in osteoarthritis patients undergoing total hip arthroplasty.

Neuroinflammation is implicated in the development and maintenance of persistent pain states, but there are limited data linking cerebrospinal fluid (CSF) inflammatory mediators with neurophysiological pain processes in humans. In a prospective observational study, CSF inflammatory mediators were compared between patients with osteoarthritis (OA) who were undergoing total hip arthroplasty due to disabling pain symptoms (n = 52) and pain-free comparison controls (n = 30). In OA patients only, detailed clinical examination and quantitative sensory testing were completed. Cerebrospinal fluid samples were analyzed for 10 proinflammatory mediators using Meso Scale Discovery platform. Compared to controls, OA patients had higher CSF levels of interleukin 8 (IL-8) (P = 0.002), intercellular adhesion molecule 1 (P = 0.007), and vascular cell adhesion molecule 1 (P = 0.006). Osteoarthritis patients with central sensitization possibly indicated by arm pressure pain detection threshold <250 kPa showed significantly higher CSF levels of Fms-related tyrosine kinase 1 (Flt-1) (P = 0.044) and interferon gamma-induced protein 10 (IP-10) (P = 0.024), as compared to subjects with PPDT above that threshold. In patients reporting pain numerical rating scale score ≥3/10 during peripheral venous cannulation, Flt-1 was elevated (P = 0.025), and in patients with punctate stimulus wind-up ratio ≥2, CSF monocyte chemoattractant protein 1 was higher (P = 0.011). Multiple logistic regression models showed that increased Flt-1 was associated with central sensitization, assessed by remote-site PPDT and peripheral venous cannulation pain, and monocyte chemoattractant protein-1 with temporal summation in the area of maximum pain. Multiple proinflammatory mediators measured in CSF are associated with persistent hip OA-related pain. Pain phenotype may be influenced by specific CSF neuroinflammatory profiles.

Vegetarian and Vegan Diet in Fibromyalgia: A Systematic Review

Fibromyalgia (FM) is a chronic non-degenerative disease characterized by the presence of multiple symptoms such as chronic pain, which negatively influence the quality of life of sufferers, most of whom are women. Currently, there is no effective treatment to limit the impact of these symptoms. The aim of this research is to review the scientific evidence on the effect of following a vegetarian or vegan diet on fibromyalgia patients. A systematic review included the original articles that answered the research question. These articles were in 2021 in the PubMed, Web of Science and Scopus databases. The research used the PRISMA (preferred reporting items for systematic reviews and meta-analyses) guidelines. No time restriction was applied, and grey literature was not included. The evaluation of the methodological quality of the articles was carried out using the following different scales: STROBE (strengthening the reporting of observational studies in epidemiology), PEDro (Physiotherapy Evidence Database), and MMAT (Mixed Methods Appraisal Tool) scales. A total of 88 studies were analyzed, of which 6 investigations were included in this systematic review (n = 4 clinical trials and n = 2 cohort studies). These investigations show significant improvements in biochemical parameters, quality of life, quality of sleep, pain at rest and general health status when following mainly plant-based dietary patterns. In conclusion, these findings are promising but interpretation of the findings is limited due to the methodological quality of the studies. Well-designed clinical trials are needed to consolidate these dietary recommendations in FM patients.

Fibromyalgia: Pathogenesis, Mechanisms, Diagnosis and Treatment Options Update

Fibromyalgia is a syndrome characterized by chronic and widespread musculoskeletal pain, often accompanied by other symptoms, such as fatigue, intestinal disorders and alterations in sleep and mood. It is estimated that two to eight percent of the world population is affected by fibromyalgia. From a medical point of view, this pathology still presents inexplicable aspects. It is known that fibromyalgia is caused by a central sensitization phenomenon characterized by the dysfunction of neuro-circuits, which involves the perception, transmission and processing of afferent nociceptive stimuli, with the prevalent manifestation of pain at the level of the locomotor system. In recent years, the pathogenesis of fibromyalgia has also been linked to other factors, such as inflammatory, immune, endocrine, genetic and psychosocial factors. A rheumatologist typically makes a diagnosis of fibromyalgia when the patient describes a history of pain spreading in all quadrants of the body for at least three months and when pain is caused by digital pressure in at least 11 out of 18 allogenic points, called tender points. Fibromyalgia does not involve organic damage, and several diagnostic approaches have been developed in recent years, including the analysis of genetic, epigenetic and serological biomarkers. Symptoms often begin after physical or emotional trauma, but in many cases, there appears to be no obvious trigger. Women are more prone to developing the disease than men. Unfortunately, the conventional medical therapies that target this pathology produce limited benefits. They remain largely pharmacological in nature and tend to treat the symptomatic aspects of various disorders reported by the patient. The statistics, however, highlight the fact that 90% of people with fibromyalgia also turn to complementary medicine to manage their symptoms.

Efficacy of Posidonia oceanica Extract against Inflammatory Pain: In Vivo Studies in Mice

Posidonia oceanica (L.) Delile is traditionally used for its beneficial properties. Recently, promising antioxidant and anti-inflammatory biological properties emerged through studying the in vitro activity of the ethanolic leaves extract (POE). The present study aims to investigate the anti-inflammatory and analgesic role of POE in mice. Inflammatory pain was modeled in CD-1 mice by the intraplantar injection of carrageenan, interleukin IL-1β and formalin. Pain threshold was measured by von Frey and paw pressure tests. Nociceptive pain was studied by the hot-plate test. POE (10–100 mg kg⁻¹) was administered per os. The paw soft tissue of carrageenan-treated animals was analyzed to measure anti-inflammatory and antioxidant effects. POE exerted a dose-dependent, acute anti-inflammatory effect able to counteract carrageenan-induced pain and paw oedema. Similar anti-hyperalgesic and anti-allodynic results were obtained when inflammation was induced by IL-1β. In the formalin test, the pre-treatment with POE significantly reduced the nocifensive behavior. Moreover, POE was able to evoke an analgesic effect in naïve animals. Ex vivo, POE reduced the myeloperoxidase activity as well as TNF-α and IL-1β levels; further antioxidant properties were highlighted as a reduction in NO concentration. POE is the candidate for a new valid strategy against inflammation and pain.

Application of Salivary Biomarkers in the Diagnosis of Fibromyalgia

Fibromyalgia (FM) is a highly prevalent syndrome that impairs the quality of life of the patients; however, its diagnosis is complex and mainly centered on pain symptoms. The study of salivary biomarkers has proven highly useful for the diagnosis and prognosis of numerous diseases. The objective of this review was to gather published data on the utilization of salivary biomarkers to facilitate and complement the diagnosis of FM. Salivary biomarkers used in FM diagnosis include cortisol; calgranulin; and the enzymes α-amylase, transaldolase, and phosphoglycerate mutase. Increased serum levels of C-reactive protein, cytokines interleukin 1-β, interleukin 6, interleukin 8, interleukin 10, interleukin 17, tumor necrosis factor α, and various chemokines may serve as salivary biomarkers, given observations of their increased serum levels in patients with FM. Further research is warranted to study in depth the role and performance of biomarkers currently used in FM diagnosis/prognosis and to identify novel salivary biomarkers for this disease.

Relationship Between Blood Cytokine Levels, Psychological Comorbidity, and Widespreadness of Pain in Chronic Pelvic Pain

Background: Low-grade inflammation has been implicated in the etiology of depression, long-term fatigue and chronic pain. TNFα and IL-6 are perhaps the most studied pro-inflammatory cytokines in the field of psychoneuroimmunology. The purpose of our study was to further investigate these relationships in patients with chronic pelvic pain specifically. Using plasma samples from a large, well-described cohort of patients with pelvic pain and healthy controls via the Multidisciplinary Approach to the Study of Chronic Pelvic Pain (MAPP) Research Network, we examined the relationship between TNFα and IL-6 and comorbid psychological symptoms. We also investigated the relationship between IL-8 and GM-CSF, and widespreadness of pain. Methods: We included baseline blood samples in the analyses, 261 patients (148 women) and 110 healthy controls (74 women). Fourteen pro- and anti-inflammatory or regulatory cytokines were analyzed in a Luminex^® xMAP^® high-sensitivity assay. We used regression models that accounted for known factors associated with the outcome variables to determine the relationship between cytokine levels and clinical measures. Results: There were no statistical differences in cytokine levels between patients and healthy controls when controlling for age. In patients, TNFα was significantly associated with levels of fatigue (p = 0.026), but not with pain intensity or depression. IL-6 was not significantly related to any of the outcome variables. Women with pelvic pain showed a negative relationship between IL-8 and widespreadness of pain, while men did not (p = 0.003). For both sexes, GM-CSF was positively related to widespreadness of pain (p = 0.039). Conclusion: Our results do not suggest low-grade systemic inflammation in chronic pelvic pain. Higher TNFα blood levels were related to higher fatigue ratings, while higher systemic GM-CSF levels predicted more widespread pain. Our study further suggests a potentially protective role of IL-8 with regard to with regard to the widepreadness of pain in the body, at least for women.

Elevated inflammatory proteins in cerebrospinal fluid from patients with painful knee osteoarthritis are associated with reduced symptom severity

Neuroinflammation and periphery-to-CNS neuroimmune cross-talk in patients with painful knee osteoarthritis (OA) are poorly understood. We utilized proximity extension assay to measure the level of 91 inflammatory proteins in CSF and serum from OA patients and controls. The patients had elevated levels of 48 proteins in CSF indicating neuroinflammation. Ten proteins were correlated between CSF and serum and potentially involved in periphery-to-CNS neuroimmune cross-talk. Seven CSF proteins, all with previously reported neuroprotective effects, were associated with lower pain intensity and milder knee-related symptoms. Our findings indicate that neuroinflammation in OA could be protective and associated with less severe symptoms.

The Neuroimmunology of Chronic Pain: From Rodents to Humans

Chronic pain, encompassing conditions, such as low back pain, arthritis, persistent post-surgical pain, fibromyalgia, and neuropathic pain disorders, is highly prevalent but remains poorly treated. The vast majority of therapeutics are directed solely at neurons, despite the fact that signaling between immune cells, glia, and neurons is now recognized as indispensable for the initiation and maintenance of chronic pain. This review highlights recent advances in understanding fundamental neuroimmune signaling mechanisms and novel therapeutic targets in rodent models of chronic pain. We further discuss new technological developments to study, diagnose, and quantify neuroimmune contributions to chronic pain in patient populations.

Significant correlation between plasma proteome profile and pain intensity, sensitivity, and psychological distress in women with fibromyalgia

Fibromyalgia (FM) is a complex pain condition where the pathophysiological and molecular mechanisms are not fully elucidated. The primary aim of this study was to investigate the plasma proteome profile in women with FM compared to controls. The secondary aim was to investigate if plasma protein patterns correlate with the clinical variables pain intensity, sensitivity, and psychological distress. Clinical variables/background data were retrieved through questionnaires. Pressure pain thresholds (PPT) were assessed using an algometer. The plasma proteome profile of FM (n = 30) and controls (n = 32) was analyzed using two-dimensional gel electrophoresis and mass spectrometry. Quantified proteins were analyzed regarding group differences, and correlations to clinical parameters in FM, using multivariate statistics. Clear significant differences between FM and controls were found in proteins involved in inflammatory, metabolic, and immunity processes. Pain intensity, PPT, and psychological distress in FM had associations with specific plasma proteins involved in blood coagulation, metabolic, inflammation and immunity processes. This study further confirms that systemic differences in protein expression exist in women with FM compared to controls and that altered levels of specific plasma proteins are associated with different clinical parameters.

Key Milestones Contributing to the Understanding of the Mechanisms Underlying Fibromyalgia

The promulgation of the American College of Rheumatology (ACR) 1990 criteria for fibromyalgia (FM) classification has significantly contributed to an era of increased research into mechanisms that underlie the disorder. The previous emphasis on putative peripheral nociceptive mechanisms has advanced to identifying of changes in central neural networks that modulate pain and other sensory processes. The influences of psychosocial factors on the dynamic and complex neurobiological mechanisms involved in the fibromyalgia clinical phenotype are now better defined. This review highlights key milestones that have directed knowledge concerning the fundamental mechanisms contributing to fibromyalgia.

Anti-inflammatory and anti-hyperalgesic effects of milnacipran in inflamed rats: involvement of myeloperoxidase activity, cytokines and oxidative/nitrosative stress

BACKGROUND

Many injuries cause pain and inflammation, which are one of the major challenges for physicians. In this study, the analgesic and the anti-inflammatory effects of milnacipran were investigated on carrageenan-induced nociception and inflammation in male rats.

METHODS

Pain and inflammation were induced by injection of λ-carrageenan (1% v/v) into the hind paw. Indomethacin (10 mg/kg: ip) or milnacipran (10, 20 and 40 mg/kg: ip) were administered 30 min before carrageenan. Analgesia and inflammation were measured by hot plate and plethysmometer. Finally, lipid peroxidation, tumor necrosis factor alpha (TNF-α), Interleukin 1 beta (IL-1β), Interleukin 6 (IL-6), myeloperoxidase (MPO) activity, nitric oxide (NO) and total antioxidant capacity (TAC) status evaluated in the hind paw tissue.

RESULTS

The results showed that carrageenan caused hyperalgesia and inflammation in the hind paw tissue. Milnacipran (20 and 40 mg/kg) significantly and dose-dependently attenuated (65 ± 3.2%; p ≤0.01 and 42 ± 6.2%; p ≤ 0.001, respectively) carrageenan-induced inflammation and significantly increased (p ≤ 0.001) nociception threshold. Also, milnacipran (20 and 40 mg/kg) significantly suppressed levels of malondialdehyde (MDA), NO (p ≤ 0.05), MPO activity, TNF-α, IL-1β and IL-6 (p ≤ 0.001) following carrageenan injection. Additionally, milnacipran (10, 20 and 40 mg/kg) significantly augmented (p ≤ 0.05) TAC status following carrageenan in the hind paw tissue.

CONCLUSION

In the present study, milnacipran showed anti-nociceptive and anti-inflammatory effects on carrageenan-induced hyperalgesia and inflammation in a dose-dependent manner. Milnacipran reduced inflammatory edema and increased the paw withdrawal threshold probably through suppression of MDA, NO, TNF-α, IL-1β, IL-6 and MPO activity, and increase of TAC status in the hind paw tissue. Therefore, milnacipran holds important potential as an anti-inflammatory and anti-nociceptive drug. Although, further clinical trials to confirm this issue, is required.

Fibromyalgia interferes with disease activity and biological therapy response in inflammatory rheumatic diseases

Fibromyalgia is one of the numerous comorbidities that may accompany inflammatory rheumatic diseases. Concomitant fibromyalgia in inflammatory rheumatic conditions can interfere with symptomatology, disease activity and overall management plan. The aim of the present narrative review article was to discuss the current evidence on (i) the prevalence/frequency of comorbid fibromyalgia in inflammatory rheumatic conditions, (ii) the role of fibromyalgia on disease activity, (iii) the impact of concomitant fibromyalgia on biological disease-modifying antirheumatic treatment outcomes and (iv) potential effectiveness of biological disease-modifying antirheumatic drugs on fibromyalgia-related symptoms among patients with inflammatory rheumatic diseases. A literature search was conducted through PubMed/MEDLINE Cochrane and Web of Science databases by using relevant keywords and their combinations. Studies representing different geographical areas of the world revealed that frequency rates of fibromyalgia are higher in inflammatory rheumatic diseases than those in the general population. Comorbid fibromyalgia interferes not only with the disease activity scores but also with the treatment outcomes and management plan. Further evidence is warranted in order to determine the potential benefits of biological disease-modifying antirheumatic drugs on fibromyalgia-related symptoms in patients with inflammatory rheumatic diseases.

T Cell Subpopulations in the Physiopathology of Fibromyalgia: Evidence and Perspectives

Fibromyalgia is one of the most important “rheumatic” disorders, after osteoarthritis. The etiology of the disease is still not clear. At the moment, the most defined pathological mechanism is the alteration of central pain pathways, and emotional conditions can trigger or worsen symptoms. Increasing evidence supports the role of mast cells in maintaining pain conditions such as musculoskeletal pain and central sensitization. Importantly, mast cells can mediate microglia activation through the production of proinflammatory cytokines such as IL-1β, IL-6, and TNFα. In addition, levels of chemokines and proinflammatory cytokines are enhanced in serum and could contribute to inflammation at systemic level. Despite the well-characterized relationship between the nervous system and inflammation, the mechanism that links the different pathological features of fibromyalgia, including stress-related manifestations, central sensitization, and dysregulation of the innate and adaptive immune responses is largely unknown. This review aims to provide an overview of the current understanding of the role of adaptive immune cells, in particular T cells, in the physiopathology of fibromyalgia. It also aims at linking the latest advances emerging from basic science to envisage new perspectives to explain the role of T cells in interconnecting the psychological, neurological, and inflammatory symptoms of fibromyalgia.

Immune System Sex Differences May Bridge the Gap Between Sex and Gender in Fibromyalgia

The fibromyalgia syndrome (FMS) is characterized by chronic widespread pain, sleep disturbances, fatigue, and cognitive alterations. A limited efficacy of targeted treatment and a high FMS prevalence (2–5% of the adult population) sums up to high morbidity. Although, altered nociception has been explained with the central sensitization hypothesis, which may occur after neuropathy, its molecular mechanism is not understood. The marked female predominance among FMS patients is often attributed to a psychosocial predisposition of the female gender, but here we will focus on sex differences in neurobiological processes, specifically those of the immune system, as various immunological biomarkers are altered in FMS. The activation of innate immune sensors is compatible with a neuropathy or virus-induced autoimmune diseases. Considering sex differences in the immune system and the clustering of FMS with autoimmune diseases, we hypothesize that the female predominance in FMS is due to a neuropathy-induced autoimmune pathophysiology. We invite the scientific community to verify the autoimmune hypothesis for FMS.