Mast Cells, Neuroinflammation and Pain in Fibromyalgia Syndrome

Pharmacotherapeutic advances in fibromyalgia: what's new on the horizon?

INTRODUCTION

This review delves into Fibromyalgia Syndrome (FMS), a chronic pain condition demanding thorough understanding for precise diagnosis and treatment. Yet, a definitive pharmacological solution for FMS remains elusive.

AREAS COVERED

In this article, we systematically analyze various pharmacotherapeutic prospects for FMS treatment, organized into sections based on the stage of drug development and approval. We begin with an overview of FDA-approved drugs, discussing their efficacy in FMS treatment. Next, we delve into other medications currently used for FMS but still undergoing further study, including opioids and muscle relaxants. Further, we evaluate the evidence behind medications that are currently under study, such as cannabinoids and naltrexone. Lastly, we explore new drugs that are in phase II trials. Our research involved a thorough search on PUBMED, Google Scholar, and clinicaltrials.gov. We also discuss the action mechanisms of these drugs and their potential use in specific patient groups.

EXPERT OPINION

A focus on symptom-driven, combination therapy is crucial in managing FMS. There is also a need for ongoing research into drugs that target neuroinflammation, immunomodulation, and the endocannabinoid system. Bridging the gap between benchside research and clinical application is challenging, but it holds potential for more targeted and effective treatment strategies.

Schwann cell TRPA1 elicits reserpine-induced fibromyalgia pain in mice

BACKGROUND AND PURPOSE

Fibromyalgia is a complex clinical disorder with an unknown aetiology, characterized by generalized pain and co-morbid symptoms such as anxiety and depression. An imbalance of oxidants and antioxidants is proposed to play a pivotal role in the pathogenesis of fibromyalgia symptoms. However, the precise mechanisms by which oxidative stress contributes to fibromyalgia-induced pain remain unclear. The transient receptor potential ankyrin 1 (TRPA1) channel, known as both a pain sensor and an oxidative stress sensor, has been implicated in various painful conditions.

EXPERIMENTAL APPROACH

The feed-forward mechanism that implicates reactive oxygen species (ROS) driven by TRPA1 was investigated in a reserpine-induced fibromyalgia model in C57BL/6J mice employing pharmacological interventions and genetic approaches.

KEY RESULTS

Reserpine-treated mice developed pain-like behaviours (mechanical/cold hypersensitivity) and early anxiety-depressive-like disorders, accompanied by increased levels of oxidative stress markers in the sciatic nerve tissues. These effects were not observed upon pharmacological blockade or global genetic deletion of the TRPA1 channel and macrophage depletion. Furthermore, we demonstrated that selective silencing of TRPA1 in Schwann cells reduced reserpine-induced neuroinflammation (NADPH oxidase 1-dependent ROS generation and macrophage increase in the sciatic nerve) and attenuated fibromyalgia-like behaviours.

CONCLUSION AND IMPLICATIONS

Activated Schwann cells expressing TRPA1 promote an intracellular pathway culminating in the release of ROS and recruitment of macrophages in the mouse sciatic nerve. These cellular and molecular events sustain mechanical and cold hypersensitivity in the reserpine-evoked fibromyalgia model. Targeting TRPA1 channels on Schwann cells could offer a novel therapeutic approach for managing fibromyalgia-related behaviours.

Developments in targeting calcitonin gene-related peptide

INTRODUCTION

Calcitonin Gene-Related Peptide (CGRP)-targeted therapy has revolutionized migraine treatment since its first approval in 2018. CGRP-targeted therapy includes monoclonal antibodies (mAbs) and gepants, which modulate trigeminal nociceptive and inflammatory responses, alleviating pain sensitization involved in migraine pathogenesis. CGRP-targeted therapy is effective not only for migraine but also for other chronic headache disorders that share the CGRP pathway.

AREAS COVERED

The authors review the latest developments and evidence for CGRP-targeted therapy for episodic migraine and chronic migraine. In addition, the authors discuss the emerging evidence on response prediction, menstrual migraine, vestibular migraine, idiopathic intracranial hypertension, post-traumatic headache, and the relationship between selected migraine comorbidities and CGRP.

EXPERT OPINION

Since the launch of CGRP-targeted therapy, many practical issues have been raised. Generally, it's safe to combine CGRP-targeted mAbs and gepants; this is an excellent option for patients with partial response. When considering stopping CGRP-targeted therapy, although a disease-modifying effect is likely, the optimal time for discontinuation remains unknown. Finally, beyond migraine, CGRP-targeted therapy may be used for other chronic pain disorders and psychological comorbidities.

LC-MS/MS analysis of Shenghui decoction component and its effect on learning and memory and neuroprotection in sleep deprivation model mice

BACKGROUND

In recent years, sleep problems have emerged as a significant factor in the development of diseases that influence cognitive function. The inflammatory response may have a role in the neurobiological processes of sleep deprivation, resulting in impairment of memory and learning. Shenghui Decoction (SHD) is a classic formula in Chinese medicine used to treat forgetfulness and insomnia. However, it remains unclear whether the anti-inflammatory effects of SHD are specifically linked to the inhibition of P2X7R and p38MAPK.

METHODS

Analysis of chemical constituents of Shenghui Decoction based on UPLC-Q-TOF-MS / MS. The learning and memory competency of the mice was assessed using the new object recognition and Morris water maze tests. The morphology of hippocampus neurons was observed using HE staining, and the expression of inflammatory factors was measured using ELISA and immunofluorescence. The expression of P2X7R and p38MAPK in the hippocampus was analyzed via real-time PCR and Western blotting. Additionally, the components absorbed into the bloodstream of SHD were analyzed.

RESULTS

The study found that SHD contains 47 chemical constituents, including phenolic acids, flavonoids, iridoids, and triterpenoids. In addition, it was observed that SHD significantly improved the learning and memory abilities of the mice. SHD also improved the morphology of hippocampus neurons. The expression of inflammatory factors was decreased in the SHD-treated mice. Additionally, the expression of P2X7R and p38MAPK was decreased in the hippocampus of the SHD-treated mice. Fifteen prototype chemical constituents were detected in blood.

CONCLUSIONS

The study suggests that SHD could be a viable treatment for cognitive impairments associated with brain inflammation. The therapeutic effects of SHD are likely due to its chemical components, including phenolic acids, flavonoids, iridoids, and triterpenoids. SHD can improve learning and memory impairment caused by sleep deprivation through the P2X7R/p38MAPK inflammatory signaling pathways.

Mast cells in the autonomic nervous system and potential role in disorders with dysautonomia and neuroinflammation

Mast cells (MC) are ubiquitous in the body, and they are critical for not only in allergic diseases but also in immunity and inflammation, including having potential involvement in the pathophysiology of dysautonomias and neuroinflammatory disorders. MC are located perivascularly close to nerve endings and sites such as the carotid bodies, heart, hypothalamus, the pineal gland, and the adrenal gland that would allow them not only to regulate but also to be affected by the autonomic nervous system (ANS). MC are stimulated not only by allergens but also many other triggers including some from the ANS that can affect MC release of neurosensitizing, proinflammatory, and vasoactive mediators. Hence, MC may be able to regulate homeostatic functions that seem to be dysfunctional in many conditions, such as postural orthostatic tachycardia syndrome, autism spectrum disorder, myalgic encephalomyelitis/chronic fatigue syndrome, and Long-COVID syndrome. The evidence indicates that there is a possible association between these conditions and diseases associated with MC activation. There is no effective treatment for any form of these conditions other than minimizing symptoms. Given the many ways MC could be activated and the numerous mediators released, it would be important to develop ways to inhibit stimulation of MC and the release of ANS-relevant mediators.

Involvement of peripheral mast cells in a fibromyalgia model in mice

Fibromyalgia is a painful disorder of unknown aetiology that presents activation and recruitment of innate immune cells, including mast cells. Efforts have been made to understand its pathogenesis to manage it better. Thus, we explored the involvement of peripheral mast cells in an experimental model of fibromyalgia induced by reserpine. Reserpine (1 mg/kg) was subcutaneously (s.c.) injected once daily in the back of male Swiss mice for three consecutive days. We analysed mechanical and cold allodynia, muscle fatigue and number of mast cell in plantar tissue. The fibromyalgia induction produced mast cell infiltration (i.e., mastocytosis) in the mice's plantar tissue. The depletion of mast cell mediators with the compound 48/80 (0.5-4 mg/kg, intraperitoneal (i.p.)) or the mast cell membrane stabilizer ketotifen fumarate (10 mg/kg, oral route (p.o.) widely (80-90 %) and extensively (from 1 up to 10 days) prevented reserpine-induced mechanical and cold allodynia and muscle fatigue. Compound 48/80 also prevented the reserpine-induced mastocytosis. Finally, we demonstrated that PAR-2, 5-HT2A, 5-HT3, H1, NK1 and MrgprB2 receptors, expressed in neuronal or mast cells, seem crucial to mediate fibromyalgia-related cardinal symptoms since antagonists or inhibitors of these receptors (gabexate (10 mg/kg, s.c.), ENMD-1068 (10 mg/kg, i.p.), ketanserin (1 mg/kg, i.p.), ondansetron (1 mg/kg, p.o.), promethazine (1 mg/kg, i.p.), and L733,060 (5 mg/kg, s.c.), respectively) transiently reversed the reserpine-induced allodynia and fatigue. The results indicate that mast cells mediate painful and fatigue behaviours in this fibromyalgia model, representing potential therapy targets to treat fibromyalgia syndrome.

Valproate attenuates somatic hyperalgesia induced by orofacial inflammation combined with stress through inhibiting spinal IL-6 and STAT1 phosphorylation

Temporomandibular disorder (TMD) and fibromyalgia syndrome (FMS) may present as comorbid conditions, but treatment options are ineffective. The purpose of this study was to investigate whether valproate (VPA) attenuates somatic hyperalgesia induced by orofacial inflammation combined with stress, which represents a model of pain associated with TMD and FMS comorbidity, and to explore the potential mechanisms. The results showed that VPA inhibited somatic hyperalgesia induced by orofacial inflammation combined with stress, and down-regulated the interleukin-6 (IL-6) expression in the L4-L5 spinal dorsal horn of female rats. The anti-nociceptive effect of VPA was blocked by single or 5 consecutive day intrathecal administration of recombinant rat IL-6. Orofacial inflammation combined with stress up-regulated the ratio of phosphorylated signal transducer and activator of transcription 1 (p-STAT1) to STAT1 (p-STAT1/STAT1) in the spinal cord. VPA did not affect the STAT1 expression, while it down-regulated the ratio of p-STAT1/STAT1. The expression of STAT3 and the ratio of p-STAT3/STAT3 were not affected by orofacial inflammation combined with stress and VPA treatment. Intrathecal administration of exogenous IL-6 up-regulated the ratio of p-STAT1/STAT1. These data indicate that VPA attenuated somatic hyperalgesia induced by orofacial inflammation combined with stress via inhibiting spinal IL-6 in female rats, and the mechanism may involve the alteration of activation status of spinal STAT1. Thus, VPA may be a new candidate analgesic that targets IL-6 and STAT1 for the treatment of pain associated with the comorbidity of TMD and FMS.

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.

Mechanisms of transcranial direct current stimulation (tDCS) for pain in patients with fibromyalgia syndrome

Fibromyalgia syndrome (FMS) is a recurrent pain condition that can be challenging to treat. Transcranial direct current stimulation (tDCS) has become a promising non-invasive therapeutic option in alleviating FMS pain, but the mechanisms underlying its effectiveness are not yet fully understood. In this article, we discuss the most current research investigating the analgesic effects of tDCS on FMS and discuss the potential mechanisms. TDCS may exert its analgesic effects by influencing neuronal activity in the brain, altering cortical excitability, changing regional cerebral blood flow, modulating neurotransmission and neuroinflammation, and inducing neuroplasticity. Overall, evidence points to tDCS as a potentially safe and efficient pain relief choice for FMS by multiple underlying mechanisms. This article provides a thorough overview of our ongoing knowledge regarding the mechanisms underlying tDCS and emphasizes the possibility of further studies to improve the clinical utility of tDCS as a pain management tool.

Exploring the Relationship between Diamine Oxidase and Psychotropic Medications in Fibromyalgia Treatment, Finding No Reduction in Diamine Oxidase Levels and Activity except with Citalopram

Background: Histamine intolerance manifests when there is an imbalance between the production of histamine and the body's capacity to metabolise it. Within the gastrointestinal tract, diamine oxidase (DAO) plays a pivotal role in breaking down ingested histamine. Insufficient levels of DAO have been linked to various diseases affecting the respiratory, cardiovascular, nervous, muscular, and digestive systems; some of these symptoms are evidenced in fibromyalgia syndrome. This underscores the crucial role of DAO in maintaining the histamine balance and highlights its association with diverse physiological systems and health conditions. The management of fibromyalgia commonly involves the use of psychotropic medications; however, their potential interactions with DAO remain not fully elucidated. Methods: This study delved into the influence of various psychotropic medications on DAO activity through in vitro experiments. Additionally, we explored their impact on the human intestinal cell line Caco-2, examining alterations in DAO expression at both the mRNA and protein levels along with DAO activity. Results: Notably, the examined drugs-sertraline, pregabalin, paroxetine, alprazolam, and lorazepam-did not exhibit inhibitory effects on DAO activity or lead to reductions in DAO levels. In contrast, citalopram demonstrated a decrease in DAO activity in in vitro assays without influencing DAO levels and activity in human enterocytes. Conclusions: These findings imply that a collaborative approach involving psychotropic medications and DAO enzyme supplementation for individuals with fibromyalgia and a DAO deficiency could offer potential benefits for healthcare professionals in their routine clinical practice.

Dysregulated wound healing in the pathogenesis of urogynecologic mesh complications

To test the hypothesis that dysregulated wound healing is associated with Urogynecologic mesh complications, we collected vaginal cell secretions using vaginal swabs after polypropylene mesh implantation in patients with (N = 39) and without (N = 40) complication. A customized multiplex immunoassay measured markers of inflammation (MCP-1, IGFBP-1, IL-2, IL-10, IL-17, PDGF-BB, bFGF, IL-1b, IL-6, IL-12p70, TNF-α), neuroinflammation (IL-1RA, TGF-β, IL-15, IL-18, IL-3, M-CSF), angiogenesis (VEGF), and matrix proteins (fibronectin, tenasin c, thrombospondin-2, lumican) between groups. Patients with complications were younger, heavier, implanted with mesh longer, and more likely to be ever smokers. A 5 kg/m2 BMI increase and ever-smoking were associated with a 2.4-fold and sixfold increased risk of complication, respectively. Patients with the highest tertile of bFGF, fibronectin, thrombospondin-2, TNF-β, or VEGF had an odds ratio (OR) of 11.8 for having a mesh complication while ≥ 3 elevated had an OR of 237 while controlling for age, BMI, and smoking. The highest tertile of bFGF, thrombospondin-2, and fibronectin together perfectly indicated a complication (P < 0.0001). A receiver-operator curve for high bFGF, thrombospondin-2, and fibronectin showed excellent discrimination between complications and controls (AUC 0.87). These data provide evidence of dysregulated wound healing in mesh complications. Modifiable factors provide potential targets for patient counseling and interventions.

Fibromyalgia is associated with hypersensitivity but not with abnormal pain modulation: evidence from QST trials and spinal fMRI

Widespread pain and hyperalgesia are characteristics of chronic musculoskeletal pain conditions, including fibromyalgia syndrome (FM). Despite mixed evidence, there is increasing consensus that these characteristics depend on abnormal pain augmentation and dysfunctional pain inhibition. Our recent investigations of pain modulation with individually adjusted nociceptive stimuli have confirmed the mechanical and thermal hyperalgesia of FM patients but failed to detect abnormalities of pain summation or descending pain inhibition. Furthermore, our functional magnetic resonance imaging evaluations of spinal and brainstem pain processing during application of sensitivity-adjusted heat stimuli demonstrated similar temporal patterns of spinal cord activation in FM and HC participants. However, detailed modeling of brainstem activation showed that BOLD activity during "pain summation" was increased in FM subjects, suggesting differences in brain stem modulation of nociceptive stimuli compared to HC. Whereas these differences in brain stem activation are likely related to the hypersensitivity of FM patients, the overall central pain modulation of FM showed no significant abnormalities. These findings suggest that FM patients are hyperalgesic but modulate nociceptive input as effectively as HC.

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.

Hemokinin-1 is a mediator of chronic restraint stress-induced pain

The Tac4 gene-derived hemokinin-1 (HK-1) binds to the NK1 receptor, similarly to Substance P, and plays a role in acute stress reactions and pain transmission in mice. Here we investigated Tac4 mRNA expression in stress and pain-related regions and its involvement in chronic restraint stress-evoked behavioral changes and pain using Tac4 gene-deleted (Tac4-/-) mice compared to C57Bl/6 wildtypes (WT). Tac4 mRNA was detected by in situ hybridization RNAscope technique. Touch sensitivity was assessed by esthesiometry, cold tolerance by paw withdrawal latency from 0°C water. Anxiety was evaluated in the light-dark box (LDB) and open field test (OFT), depression-like behavior in the tail suspension test (TST). Adrenal and thymus weights were measured at the end of the experiment. We found abundant Tac4 expression in the hypothalamic-pituitary-adrenal axis, but Tac4 mRNA was also detected in the hippocampus, amygdala, somatosensory and piriform cortices in mice, and in the frontal regions and the amygdala in humans. In Tac4-/- mice of both sexes, stress-induced mechanical, but not cold hyperalgesia was significantly decreased compared to WTs. Stress-induced behavioral alterations were mild or absent in male WT animals, while significant changes of these parameters could be detected in females. Thymus weight decrease can be observed in both sexes. Higher baseline anxiety and depression-like behaviors were detected in male but not in female HK-1-deficient mice, highlighting the importance of investigating both sexes in preclinical studies. We provided the first evidence for the potent nociceptive and stress regulating effects of HK-1 in chronic restraint stress paradigm. Identification of its targets might open new perspectives for therapy of stress-induced pain.

Low-dose naltrexone's utility for non-cancer centralized pain conditions: a scoping review

BACKGROUND

At low doses, naltrexone (LDN) has been shown to modulate inflammation through the interruption of microglial cell activation within the central nervous system. One of the most likely contributors to centralized pain is changes in microglial cell processing. Therefore, it has been postulated that LDN can be used to manage patients with pain resulting from central sensitization due to this relationship. This scoping review aims to synthesize the relevant study data for LDN as a novel treatment strategy for various centralized pain conditions.

METHODS

A comprehensive literature search was conducted in PubMed, Embase, and Google Scholar, guided by the Scale for Assessment of Narrative Review Articles (SANRA) criteria.

RESULTS

Forty-seven studies related to centralized pain conditions were identified. Many of the studies were case reports/series and narrative reviews, but a few randomized control trials have been conducted. Overall, the body of evidence revealed improvement in patient-reported pain severity and in outcomes related to hyperalgesia, physical function, quality of life, and sleep. Variability in dosing paradigms and the time to patient response was present in the reviewed studies.

CONCLUSIONS

Evidence synthesized for this scoping review supports the ongoing use of LDN for the treatment of refractory pain in various centralized chronic pain conditions. Upon review of the currently available published studies, it is apparent that further high-quality, well-powered randomized control trials need to be conducted to establish efficacy, standardization for dosing, and response times. In summary, LDN continues to offer promising results in the management of pain and other distressing symptoms in patients with chronic centralized pain conditions.

Hemokinin-1 induces transcriptomic alterations in pain-related signaling processes in rat primary sensory neurons independent of NK1 tachykinin receptor activation

The tachykinin hemokinin-1 (HK-1) is involved in immunological processes, inflammation, and pain. Although the neurokinin 1 receptor (NK1R) is described as its main target, several effects are mediated by currently unidentified receptor(s). The role of HK-1 in pain is controversial, depending on the involvement of peripheral and central sensitization mechanisms in different models. We earlier showed the ability of HK-1 to activate the trigeminovascular system, but the mechanisms need to be clarified. Therefore, in this study, we investigated HK-1-induced transcriptomic alterations in cultured rat trigeminal ganglion (TRG) primary sensory neurons. HK-1 was applied for 6 or 24 h in 1 μM causing calcium-influx in these neurons, 500 nM not inducing calcium-entry was used for comparison. Next-generation sequencing was performed on the isolated RNA, and transcriptomic changes were analyzed to identify differentially expressed (DE) genes. Functional analysis was performed for gene annotation using the Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Reactome databases. NK1R and Neurokinin receptor 2 (NK2R) were not detected. Neurokinin receptor 3 (NK3R) was around the detection limit, which suggests the involvement of other NKR isoforms or other receptors in HK-1-induced sensory neuronal activation. We found protease-activated receptor 1 (PAR1) and epidermal growth factor receptor (EGFR) as DE genes in calcium signaling. The transmembrane protein anthrax toxin receptor 2 (ANTXR2), a potential novel pain-related target, was upregulated. Acid-sensing ion channel 1; 3 (Asic1,3), N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) glutamate receptors decreased, myelin production and maintenance related genes (Mbp, Pmp2, Myef2, Mpz) and GNDF changed by HK-1 treatment. Our data showed time and dose-dependent effects of HK-1 in TRG cell culture. Result showed calcium signaling as altered event, however, we did not detect any of NK receptors. Presumably, the activation of TRG neurons is independent of NK receptors. ANTXR2 is a potential new target, PAR-1 has also important role in pain, however their connection to HK-1 is unknown. These findings might highlight new targets or key mediators to solve how HK-1 acts on TRG.

Exogenous Supplementation with DAO Enzyme in Women with Fibromyalgia: A Double-Blind Placebo-Controlled Clinical Trial

Fibromyalgia (FM) is characterized by chronic musculoskeletal pain, muscle tension, joint mobility loss, and several psychological symptoms severely affecting patient well-being. Histamine is naturally degraded in the small intestine by diamine oxidase (DAO). Hereditary or acquired DAO deficiency causes extracellular histamine accumulation, leading to symptoms similar to those of individuals diagnosed with FM. Thus, this study aimed to assess the efficacy of adding DAO supplementation for 8 weeks to their standard therapy. We randomly assigned 100 women with FM (age: 33-61 years) to the supplementation and control groups. The Fibromyalgia Impact Questionnaire (FIQ), the Pain Catastrophizing Scale (PCS), and intensity scales were applied for a series of clinical symptoms together with the Bristol scale to assess the added value of DAO supplementation. Patients in both groups were receiving complete pharmacological support but some differences in the number of subjects receiving analgesics, antidepressants, and anxiolytics was noted. Patients in both study groups experienced favorable changes during the evaluation period as indicated by their final FIQ and PCS scores, particularly in the DAO group in the latter questionnaire. Qualitatively, the patients assigned to the DAO treatment group had lower scores for fatigue, anxiety, depression, burning and for rumination, magnification, and helplessness.

Fibromyalgia: Could hyperbaric oxygen therapy make the difference? Our experience

Fibromyalgia is a rare disease, difficult to diagnose and to treat. We think that hyperbaric oxygen therapy could improve its signs and symptoms although more evidences have to be accumulated.

Can the monocyte-to-HDL ratio be used as an inflammation marker in patients with fibromyalgia syndrome?

Background and Aim

The monocyte-to-high-density lipoprotein (HDL) ratio (MHR) may be used as a marker of inflammation and oxidative stress. This study aimed to evaluate the use of MHR and platelet markers in patients with fibromyalgia syndrome (FMS) and demonstrate MHR's relationship with inflammation, the Fibromyalgia Impact Questionnaire (FIQ), and quality of life.

Materials and Methods

Ninety FMS patients and 90 healthy controls, whose clinical and laboratory evaluations were performed simultaneously, were included in the study. The monocyte, platelet, HDL, MHR, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), mean platelet volume (MPV), and platelet distribution width (PDW) values of all patients were evaluated. The quality of life of the participants was assessed using the FIQ and their general health using the health assessment questionnaire (HAQ).

Results

Age, body mass index (BMI), and marital status distribution were similar in both groups. The FMS patients had a mean disease duration of 11.29 ± 2.62 months. The median monocyte, platelet, MPV, visual analog scale (VAS), FIQ, and HAQ values and the mean MHR of the FMS patients were significantly higher than the control group, while the mean HDL level was significantly lower (P < 0.05). There was a weak negative correlation between the MPV and HAQ score and the PDW and HAQ score (rs = -0.225, P = 0.042 and rs = -0.249, P = 0.024, respectively), whereas no correlation was detected between the MHR and the FIQ and HAQ scores in FMS patients. According to the receiver operating characteristic curve analysis, MHR had prediction of FMS (P = 0.002; sensitivity = 0.63, specificity = 0.50, cut-off point ≥8.4).

Conclusions

Our results suggest that the monocyte, platelet, HDL, MHR, and MPV parameters can be used in the evaluation of inflammation in FMS patients.

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.

A model for irritable bowel syndrome and anxiety comorbidities in relation to alcohol use disorders

About 95% of human body serotonin synthesis occurs in the gastrointestinal tract (GI). Lack of sufficient serotonin levels is thought to play a key role in mood disorders, including anxiety disorders. In this study, we looked at a disorder affecting the GI tract, irritable bowel syndrome (IBS), and aimed to determine whether IBS is differentially associated with anxiety disorders in 252 chronic pain patients in the presence of a history of alcohol use disorders (AUD) given that alcohol is an extremely aggressive substance for the GI mucosa. We found that while the prevalence of IBS was not affected by the presence of AUD in chronic pain patients, IBS had significantly higher comorbidity with anxiety disorders in chronic pain patients with comorbid alcohol use disorders. We argue that these findings highlight mechanistic differences in the comorbidity of anxiety disorders with chronic pain and AUD, implicating a central role for GI problems stemming from chronic alcohol use. The findings may have important implications for the treatment of IBS patients with AUD who commonly present with anxiety disorders which could motivate the continuation of problematic drinking and impede recovery success. We propose that addressing GI problems in patients with AUD may help manage AUD and recovery more effectively.

Stem cells therapeutic effect in a reserpine-induced fibromyalgia rat model: A possible NLRP3 inflammasome modulation with neurogenesis promotion in the cerebral cortex

Fibromyalgia is a chronic pain syndrome with a multifactorial pathophysiology affecting 2-8 % of the population.

AIMS

To investigate the therapeutic effects of bone marrow mesenchymal stem cells (BMSCs) against fibromyalgia-related cerebral cortex damage and the possible underlying mechanisms of action.

MATERIALS AND METHODS

Rats were randomly allocated into three groups; control, fibromyalgia and fibromyalgia treated with BMSCs groups. Physical and behavioural assessments were performed. Cerebral cortices were collected for biochemical and histological assessment.

KEY FINDINGS

Fibromyalgia group showed behavioural changes indicating presence of pain, fatigue, depression, and sleep disturbances. Moreover, biochemical biomarkers alterations were demonstrated by a significant decrease in brain monoamines and GSH levels, but MDA, NO, TNF-alpha, HMGB-1, NLRP3, and caspase-1 levels significantly increased. Furthermore, histological assessment revealed structural and ultrastructural alterations indicating neuronal and neuroglial degeneration with microglia activation, an increase in mast cell number and IL-1β immune-expression. Additionally, a significant decrease in Beclin-1 immune-expression, and blood brain barrier disruption were noticed. Interestingly, BMSCs administration significantly improved behavioural alterations, restored the reduced brain monoamines and oxidative stress markers, and reduced TNF-alpha, HMGB-1, NLRP3, and caspase-1 levels. Profoundly, cerebral cortices demonstrated improved histological structure, significant decrease in mast cell number and IL-1β immune-expression, besides a significant increase in Beclin-1 and DCX immune-expression.

SIGNIFICANCE

For the best of our knowledge, this is the first study showing ameliorative effects for BMSCs treatment in fibromyalgia-related cerebral cortical damage. The neurotherapeutic effects of BMSCs could be attributed to NLRP3 inflammasome signaling pathway inhibition, mast cell deactivation, and stimulation of neurogenesis and autophagy.

High overlap in patients diagnosed with hypermobile Ehlers-Danlos syndrome or hypermobile spectrum disorders with fibromyalgia and 40 self-reported symptoms and comorbidities

Background

Joint pain is a common symptom in patients with hypermobile Ehlers-Danlos Syndrome (hEDS), hypermobility spectrum disorders (HSD) and fibromyalgia. The goal of this study was to determine whether symptoms and comorbidities overlap in patients diagnosed with hEDS/HSD and/or fibromyalgia.

Methods

We retrospectively examined self-reported data from an EDS Clinic intake questionnaire in patients diagnosed with hEDS/HSD, fibromyalgia, or both vs. controls with an emphasis on joint issues.

Results

From 733 patients seen at the EDS Clinic, 56.5% (n = 414) were diagnosed with hEDS/HSD and fibromyalgia (Fibro), 23.8% (n = 167) hEDS/HSD, 13.3% (n = 98) fibromyalgia, or 7.4% (n = 54) none of these diagnoses. More patients were diagnosed with HSD (76.6%) than hEDS (23.4%). Patients were primarily White (95%) and female (90%) with a median age in their 30s (controls 36.7 [18.0, 70.0], fibromyalgia 39.7 [18.0, 75.0], hEDS/HSD 35.0 [18.0, 71.0], hEDS/HSD&Fibro 31.0 [18.0, 63.0]). There was high overlap in all 40 symptoms/comorbidities that we examined in patients diagnosed with fibromyalgia only or hEDS/HSD&Fibro, regardless of whether they had hEDS or HSD. Patients that only had hEDS/HSD without fibromyalgia had far fewer symptoms/comorbidities than patients with hEDS/HSD&Fibro. The top self-reported issues in patients that only had fibromyalgia were joint pain, hand pain when writing or typing, brain fog, joint pain keeping from daily activities, allergy/atopy and headache. Five issues that significantly and uniquely characterized patients diagnosed with hEDS/HSD&Fibro were subluxations (dislocations in hEDS patients), joint issues like sprains, the need to stop sports due to injuries, poor wound healing, and migraine.

Conclusion

The majority of patients seen at the EDS Clinic had a diagnosis of hEDS/HSD plus fibromyalgia that was associated with more severe disease. Our findings indicate that fibromyalgia should be routinely assessed in patients with hEDS/HSD and vis-a-versa to improve patient care.

Fibromyalgia patients with elevated levels of anti-satellite glia cell immunoglobulin G antibodies present with more severe symptoms

ABSTRACT

Transferring fibromyalgia patient immunoglobulin G (IgG) to mice induces pain-like behaviour, and fibromyalgia IgG binds mouse and human satellite glia cells (SGCs). These findings suggest that autoantibodies could be part of fibromyalgia pathology. However, it is unknown how frequently fibromyalgia patients have anti-SGC antibodies and how anti-SGC antibodies associate with disease severity. Here, we quantified serum or plasma anti-SGC IgG levels in 2 fibromyalgia cohorts from Sweden and Canada using an indirect immunofluorescence murine cell culture assay. Fibromyalgia serum IgG binding to human SGCs in human dorsal root ganglia tissue sections was also assessed by immunofluorescence. In the cell culture assay, anti-SGC IgG levels were increased in both fibromyalgia cohorts compared with control group. Elevated anti-SGC IgG was associated with higher levels of self-reported pain in both cohorts, and higher fibromyalgia impact questionnaire scores and increased pressure sensitivity in the Swedish cohort. Anti-SGC IgG levels were not associated with fibromyalgia duration. Swedish fibromyalgia (FM) patients were clustered into FM-severe and FM-mild groups, and the FM-severe group had elevated anti-SGC IgG compared with the FM-mild group and control group. Anti-SGC IgG levels detected in culture positively correlated with increased binding to human SGCs. Moreover, the FM-severe group had elevated IgG binding to human SGCs compared with the FM-mild and control groups. These results demonstrate that a subset of fibromyalgia patients have elevated levels of anti-SGC antibodies, and the antibodies are associated with more severe fibromyalgia symptoms. Screening fibromyalgia patients for anti-SGC antibodies could provide a path to personalized treatment options that target autoantibodies and autoantibody production.

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.

Activation of Mast Cells by Neuropeptides: The Role of Pro-Inflammatory and Anti-Inflammatory Cytokines

Mast cells (MCs) are tissue cells that are derived from bone marrow stem cells that contribute to allergic reactions, inflammatory diseases, innate and adaptive immunity, autoimmunity, and mental disorders. MCs located near the meninges communicate with microglia through the production of mediators such as histamine and tryptase, but also through the secretion of IL-1, IL-6 and TNF, which can create pathological effects in the brain. Preformed chemical mediators of inflammation and tumor necrosis factor (TNF) are rapidly released from the granules of MCs, the only immune cells capable of storing the cytokine TNF, although it can also be produced later through mRNA. The role of MCs in nervous system diseases has been extensively studied and reported in the scientific literature; it is of great clinical interest. However, many of the published articles concern studies on animals (mainly rats or mice) and not on humans. MCs are known to interact with neuropeptides that mediate endothelial cell activation, resulting in central nervous system (CNS) inflammatory disorders. In the brain, MCs interact with neurons causing neuronal excitation with the production of neuropeptides and the release of inflammatory mediators such as cytokines and chemokines. This article explores the current understanding of MC activation by neuropeptide substance P (SP), corticotropin-releasing hormone (CRH), and neurotensin, and the role of pro-inflammatory cytokines, suggesting a therapeutic effect of the anti-inflammatory cytokines IL-37 and IL-38.

The Cognitive and Emotional Aspect in Fibromyalgia: The Importance of the Orofacial Sphere

Fibromyalgia syndrome (FMS) is a systemic and multifactorial disease of unknown etiology. There are many co-morbidities that the patient presents, making the clinical picture not immediate. Cognitive decline and emotional alteration (anxiety and depression) are found in fibromyalgic patients, as well as temporomandibular joint arthrokinematic disorders, dental malocclusion, and periodontitis. There seems to be a biunivocal relationship between oral and psychiatric dysfunctions in fibromyalgia. The article reviews the information regarding oral health alterations with respect to the patient's cognitive and emotional response, as the most recent information we have raises new hypotheses about the diagnosis of FMS.

Could the fibromyalgia syndrome be triggered or enhanced by COVID-19?

Fibromyalgia (FM) is a complex disease with an uncertain aetiology and intricate pathophysiology. Although its genesis is not fully explained, potential environmental factors, such as viral infections might trigger FM or worsen patients' clinical outcomes. The SARS-CoV-2 virus may affect central and peripheral nervous systems, leading to musculoskeletal, neurological, and psychological disturbances. These symptoms might persist at least 12 months beyond the recovery, often referred to as post-COVID syndrome, which resembles FM syndrome. In this sense, we argued the potential consequences of COVID-19 exclusively on FM syndrome. First, we have described post-COVID syndrome and its painful symptoms. Afterwards, we argued whether FM syndrome could be triggered or enhanced by COVID-19 infection or by numerous and persistent stressors imposed daily by the pandemic setting (isolation, uncertainty, depression, mental stress, generalized anxiety, and fear of the virus). In addition, we have demonstrated similarities between pathophysiological mechanisms and cardinal symptoms of FM and COVID-19, speculating that SARS-CoV-2 might represent a critical mediator of FM or an exacerbator of its symptoms once both syndromes share similar mechanisms and complaints. Therefore, pharmacologic and non-pharmacological approaches commonly used to treat FM could serve as strategic therapies to attenuate painful and neurological manifestations of post-COVID syndrome. Although it is still theoretical, clinicians and researchers should be alert of patients who develop symptoms similar to FM or those who had their FM symptoms increased post-COVID to manage them better.

Role of SARS-CoV-2 Spike-Protein-Induced Activation of Microglia and Mast Cells in the Pathogenesis of Neuro-COVID

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus disease 2019 (COVID-19). About 45% of COVID-19 patients experience several symptoms a few months after the initial infection and develop post-acute sequelae of SARS-CoV-2 (PASC), referred to as "Long-COVID," characterized by persistent physical and mental fatigue. However, the exact pathogenetic mechanisms affecting the brain are still not well-understood. There is increasing evidence of neurovascular inflammation in the brain. However, the precise role of the neuroinflammatory response that contributes to the disease severity of COVID-19 and long COVID pathogenesis is not clearly understood. Here, we review the reports that the SARS-CoV-2 spike protein can cause blood-brain barrier (BBB) dysfunction and damage neurons either directly, or via activation of brain mast cells and microglia and the release of various neuroinflammatory molecules. Moreover, we provide recent evidence that the novel flavanol eriodictyol is particularly suited for development as an effective treatment alone or together with oleuropein and sulforaphane (ViralProtek®), all of which have potent anti-viral and anti-inflammatory actions.

Prevalence of Genetic Diamine Oxidase (DAO) Deficiency in Female Patients with Fibromyalgia in Spain

Diamine oxidase (DAO) is an enzyme that metabolizes intestinal histamine. Single nucleotide polymorphisms (SNPs) of the Amine Oxidase Copper Containing 1 (AOC1) gene can lead to low enzymatic activity or functionality in histamine metabolism. This study aimed to determine the prevalence of DAO deficiency for four variants of the AOC1 gene, p.Thr16Met (rs10156191), p.Ser332Phe (rs1049742), p.His664Asp (rs1049793), and c.691G > T (rs2052129), in 98 Spanish women with fibromyalgia between the ages of 33 and 60 years, and compare the distribution of allelic and genotypic frequencies with those of European population samples in Hardy–Weinberg equilibrium extracted from the Allele Frequency Aggregator (ALFA) database. The patients’ DNA was extracted, and analyzed using SNPE Multiplex (Single Nucleotide Primer Extension). The prevalence of genetic DAO deficiency was 74.5% based on the four variants of the AOC1 gene. SNP deficits were found at frequencies of 53.1% for p.Thr16Met, 49% for c.691G > T, 48% for p.His664Asp, and 19.4% for p.Ser332Phe. The allele and genotypic frequencies of the women with fibromyalgia did not differ from the European population. Variants of the AOC1 gene that are associated with genetic DAO deficiency could serve as a disruptive biomarker in patients with fibromyalgia. This study was registered in ClinicalTrials.gov Identifier: NCT05389761.

Calcitonin Gene-Related Peptide, Vascular Endothelial Growth Factor, and Clinical Manifestations in Women With Fibromyalgia

BACKGROUND

Fibromyalgia is a complex illness to diagnose and treat, which significantly impairs patients' quality of life.

OBJECTIVES

The study aims were to compare levels of calcitonin gene-related peptide and vascular endothelial growth factor between patients with fibromyalgia and healthy controls and to examine their relationship with the main clinical manifestations of fibromyalgia.

METHODS

This case-control study included 42 women diagnosed with fibromyalgia and 22 healthy women. Serum calcitonin gene-related peptide and vascular endothelial growth factor levels were spectrophotometrically analyzed by enzyme-linked immunosorbent assay. Clinical manifestations were assessed by means of self-administered questionnaires, including functional capacity in daily living activities, musculoskeletal pain, fatigue, anxiety, and sleep quality. The predictive value of these parameters in fibromyalgia was determined by receiver operating characteristic curve analysis.

RESULTS

Serum calcitonin gene-related peptide levels significantly increased in the fibromyalgia group in comparison to the control group. However, there were no significant differences in vascular endothelial growth factor levels between patients and controls. No significant correlations were found between calcitonin gene-related peptide and vascular endothelial growth factor and the symptoms analyzed.

DISCUSSION

Serum calcitonin gene-related peptide levels were dysregulated in women with fibromyalgia and may be a reliable parameter to help diagnose this complex syndrome.

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.

Distress as a mediator for pain and activities of daily living in older adults with fibromyalgia

Introduction

Pain, distress, and activities of daily living impact the lives of those with chronic pain. This study investigated distress (depressive symptoms, anxiety) on the relationship between pain (intensity and pain interference) and activities of daily living in individuals with fibromyalgia while controlling for age.

Methods

The current cross-sectional investigation focused on data from 123 men and women with fibromyalgia. Pain intensity, pain interference and anxiety were measured on 0-10 Likert type scales from the National Fibromyalgia Assessment Questionnaire. Depressive symptoms were assessed using the Beck Depression Inventory II. Activities of daily living (basic, instrumental) were measured with the Physical Activity Inventory Scale.

Results

It was hypothesized that the relationships between pain intensity and pain interference and activities of daily living in individuals with fibromyalgia would be mediated by the construct of distress while controlling for age. Mediation significantly occurred in both models as predicted. However, those who were older reported lower levels of pain intensity and distress than their younger counterparts, which may be related to time since diagnosis or other factors.

Discussion

Results of this study suggest that individuals with chronic pain conditions would benefit from treatment options which address distress, specifically depressive symptoms and anxiety.

Oxidative Stress in Fibromyalgia: From Pathology to Treatment

Fibromyalgia (FM) is characterized by chronic widespread musculoskeletal pain associated with sleep problems, fatigue, depression, and anxiety. The persistence of pain, impairment of cognitive function, and negative impact on the psychological state have caused a detrimental effect on the patients' quality of life. However, to date, the treatment and mechanisms of this disease are yet to be established. Oxidative stress might play a critical role in FM pathophysiology. Increased levels of prooxidative factors such as nitric oxide, lipid peroxidation, and mitophagy can cause pain sensitization in fibromyalgia. Numerous studies have supported the hypothesis of beneficial antioxidative effects in FM. Due to the lack of effective therapy for fibromyalgia, many treatments are sought to reduce pain and fatigue and improve patients' quality of life. This manuscript discusses the impact of various antioxidative procedures that can diminish fibromyalgia symptoms, such as hyperbaric oxygen therapy, modification of dietary habits, and physical activity.

Subcategories of Fibromyalgia: A New Concept

Fibromyalgia has previously been categorized as primary, secondary, and juvenile fibromyalgia. However, these definitions do not adequately explain the etiopathology of disease, nor do they help direct new specific therapies. Herein, we review the previously known categorizations of fibromyalgia. Based on common patient characteristics and previously studied pathophysiologies, we propose new subcategorizations of fibromyalgia that we have self-narrated, including hormonal fibromyalgia, neuroendocrine fibromyalgia, psychologic fibromyalgia, inflammatory fibromyalgia, and lastly, neuropathic fibromyalgia. Future research needs to be done to verify, add to, and fully describe these self-narrated categories of fibromyalgia that we have proposed.

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.

The Efficacy of Capsaicin on Sleep Quality and Fatigue in Fibromyalgia

Capsaicin is a topical pain reliever that has been evaluated by randomized controlled trials (RCTs) as a potential adjunctive therapy for treating unmitigated fibromyalgia. Therefore, a review of English articles using PubMed and Embase was conducted from January 1, 1990 to February 9, 2022 in order to evaluate the utility of capsaicin for improvement of sleep quality and fatigue associated with fibromyalgia. The search terms included: "fibromyalgia" and "capsaicin". Articles included were RCTs evaluating capsaicin in adult patients with fibromyalgia. Two studies met criteria and included 175 patients that received either capsaicin or placebo for an average total treatment length of 5 weeks. The treatment outcomes assessed were changes in quality of sleep and fatigue by several standardized modalities. These include visual analog scale (VAS) of sleep quality and fatigue, fatigue severity scale, Pittsburgh Sleep Quality Index (PSQI), and global subjective improvement. Both studies demonstrated no changes in sleep quality, but one study did find a significant difference in global subjective improvement. This same study also found a significant improvement in fatigue. Consequently, this existing evidence is insufficient to warrant recommending capsaicin as adjunctive therapy for improvement in sleep quality and fatigue. Future studies regarding capsaicin therapy for fibromyalgia are needed.

Hyper-connectivity between the left motor cortex and prefrontal cortex is associated with the severity of dysfunction of the descending pain modulatory system in fibromyalgia

Introduction

The association between descending pain modulatory system (DPMS) dysfunction and fibromyalgia has been previously described, but more studies are required on its relationship with aberrant functional connectivity (FC) between the motor and prefrontal cortices.

Objectives

The objective of this cross-sectional observational study was to compare the intra- and interhemispheric FC between the bilateral motor and prefrontal cortices in women with fibromyalgia, comparing responders and nonresponders to the conditioned pain modulation (CPM) test.

Methods

A cross-sectional sample of 37 women (23 responders and 14 nonresponders to the CPM test) with fibromyalgia diagnosed according to the American College of Rheumatology criteria underwent a standardized clinical assessment and an FC analysis using functional near-infrared spectroscopy. DPMS function was inferred through responses to the CPM test, which were induced by hand immersion in cold water (0–1°C). A multivariate analysis of covariance for main effects between responders and nonresponders was conducted using the diagnosis of multiple psychiatric disorders and the use of opioid and nonopioid analgesics as covariates. In addition, we analyzed the interaction between the CPM test response and the presence of multiple psychiatric diagnoses.

Results

Nonresponders showed increased FC between the left motor cortex (lMC) and the left prefrontal cortex (lPFC) (t = −2.476, p = 0.01) and right prefrontal cortex (rPFC) (t = −2.363, p = 0.02), even when both were considered as covariates in the regression analysis (lMC–lPFC: β = −0.127, t = −2.425, p = 0.021; lMC–rPFC: β = −0.122, t = −2.222, p = 0.033). Regarding main effects, a significant difference was only observed for lMC–lPFC (p = 0.035). A significant interaction was observed between the psychiatric disorders and nonresponse to the CPM test in lMC−lPFC (β = −0.222, t = −2.275, p = 0.03) and lMC−rPFC (β = −0.211, t = −2.2, p = 0.035). Additionally, a significant interaction was observed between the CPM test and FC in these two region-of-interest combinations, despite the psychiatric diagnoses (lMC−lPFC: β = −0.516, t = −2.447, p = 0.02; lMC−rPFC: β = −0.582, t = −2.805, p = 0.008).

Conclusions

Higher FC between the lMC and the bilateral PFC may be a neural marker of DPMS dysfunction in women with fibromyalgia, although its interplay with psychiatric diagnoses also seems to influence this association.

Role of Etanercept and Infliximab on Nociceptive Changes Induced by the Experimental Model of Fibromyalgia

Background: Fibromyalgia is a clinical condition that affects 1% to 5% of the population. No proper therapy has been currently found. It has been described that inflammation plays a central role in the nerve sensitizations that characterize the pathology. Methods: This paper aimed to evaluate the efficacy of etanercept and infliximab in the management of pain sensitization. Fibromyalgia was induced by three injections once a day of reserpine at the dose of 1 mg/kg. Etanercept (3 mg/kg) and infliximab (10 mg/kg) were administered the day after the last reserpine injection and then 5 days after that. Behavioral analyses were conducted once a week, and molecular investigations were performed at the end of the experiment. Results: Our data confirmed the major effect of infliximab administration as compared to etanercept: infliximab administration strongly reduced pain sensitization in thermal hyperalgesia and mechanical allodynia. From the molecular point of view, infliximab reduced the activation of microglia and astrocytes and the expression of the purinergic P2X7 receptor ubiquitously expressed on glia and neurons. Downstream of the P2X7 receptor, infliximab also reduced p38-MAPK overexpression induced by the reserpine administration. Conclusion: Etanercept and infliximab treatment caused a significant reduction in pain. In particular, rats that received infliximab showed less pain sensitization. Moreover, infliximab reduced the activation of microglia and astrocytes, reducing the expression of the purinergic receptor P2X7 and p38-MAPK pathway.

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.

Post-COVID-19 syndrome: persistent neuroimaging changes and symptoms 9 months after initial infection

A previously healthy and active middle-aged woman acquired COVID-19 as an occupational exposure with subsequent persistent post-COVID-19 symptoms including headache, dyspnoea on exertion, chest pressure, tachycardia, anosmia, parosmia, persistent myalgia, vertigo, cognitive decline and fatigue. She presented to a tertiary medical centre for further evaluation after 9 months of persistent symptoms and had a largely unremarkable workup with the exception of a persistently elevated monocyte chemoattractant protein 1, blunted cardiovagal response and non-specific scattered areas of low-level hypometabolism at the bilateral frontal, left precuneus, occipital and parietal regions on PET scan.

Varied Composition and Underlying Mechanisms of Gut Microbiome in Neuroinflammation

The human gut microbiome has been implicated in a host of bodily functions and their regulation, including brain development and cognition. Neuroinflammation is a relatively newer piece of the puzzle and is implicated in the pathogenesis of many neurological disorders. The microbiome of the gut may alter the inflammatory signaling inside the brain through the secretion of short-chain fatty acids, controlling the availability of amino acid tryptophan and altering vagal activation. Studies in Korea and elsewhere highlight a strong link between microbiome dynamics and neurocognitive states, including personality. For these reasons, re-establishing microbial flora of the gut looks critical for keeping neuroinflammation from putting the whole system aflame through probiotics and allotransplantation of the fecal microbiome. However, the numerosity of the microbiome remains a challenge. For this purpose, it is suggested that wherever possible, a fecal microbial auto-transplant may prove more effective. This review summarizes the current knowledge about the role of the microbiome in neuroinflammation and the various mechanism involved in this process. As an example, we have also discussed the autism spectrum disorder and the implication of neuroinflammation and microbiome in its pathogenesis.

Microglia and HPA axis in depression: An overview of participation and relationship

Objectives: This narrative review article provides an overview on the involvement of microglia and the hypothalamic-pituitary-adrenal (HPA) axis in the pathophysiology of depression, as well investigates the mutual relationship between these two entities: how microglial activation can contribute to the dysregulation of the HPA axis, and vice versa.Methods: Relevant studies and reviews already published in the Pubmed electronic database involving the themes microglia, HPA axis and depression were used to meet the objectives.Results: Exposition to stressful events is considered a common factor in the mechanisms proposed to explain the depressive disorder. Stress can activate microglial cells, important immune components of the central nervous system (CNS). Moreover, another system involved in the physiological response to stressors is the hypothalamic-pituitary-adrenal (HPA) axis, the main stress response system responsible for the production of the glucocorticoid hormone (GC). Also, mediators released after microglial activation can stimulate the HPA axis, inducing production of GC. Likewise, high levels of GCs are also capable of activating microglia, generating a vicious cycle.Conclusion: Immune and neuroendocrine systems seems to work in a coordinated manner and that their dysregulation may be involved in the pathophysiology of depression since neuroinflammation and hypercortisolism are often observed in this disorder.

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.

High-intensity interval training for chronic pain conditions: a narrative review

Chronic pain is defined as pain that persists past the normal healing time. Physical activity and exercise programs are increasingly being promoted and used for a variety of chronic pain conditions. Evidence suggests that physical exercise is an intervention with few adverse events that may improve pain severity and physical function, thus improving the quality of life. High-intensity interval training (HIIT) has been shown to improve physical outcome measures and to decrease disorder-related disability in people with chronic disorders. Since an overview of the benefits of HIIT on chronic pain conditions has not been published yet, this review aims to report the effects of HIIT alone or in combination with other forms of training on different kind of chronic pain conditions. A search in the main scientific electronic databases was performed. The results of the studies included in this review showed that HIIT is beneficial for several chronic pain conditions, improving pain and physical function. Since HIIT could represent a valid help to conventional drug therapies, it could improve the quality of life of these subjects. The actual quality of evidence remains very low, and further high evidence studies are needed to confirm the promising outcomes reported in this review.

Autism and chronic ill health: an observational study of symptoms and diagnoses of central sensitivity syndromes in autistic adults

BACKGROUND

Autistic adults, particularly women, are more likely to experience chronic ill health than the general population. Central sensitivity syndromes (CSS) are a group of related conditions that are thought to include an underlying sensitisation of the central nervous system; heightened sensory sensitivity is a common feature. Anecdotal evidence suggests autistic adults may be more prone to developing a CSS. This study aimed to investigate the occurrence of CSS diagnoses and symptoms in autistic adults, and to explore whether CSS symptoms were related to autistic traits, mental health, sensory sensitivity, or gender.

METHODS

The full sample of participants included 973 autistic adults (410 men, 563 women, mean age = 44.6) registered at the Netherlands Autism Register, who completed questionnaires assessing autistic traits, sensory sensitivity, CSS, physical and mental health symptoms. The reliability and validity of the Central Sensitization Inventory (CSI) in an autistic sample was established using exploratory and confirmatory factor analyses. Chi2 analyses, independent t-tests, hierarchical regression and path analysis were used to analyse relationships between CSS symptoms, autistic traits, measures of mental health and wellbeing, sensory sensitivity, age and gender.

RESULTS

21% of participants reported one or more CSS diagnosis, and 60% scored at or above the clinical cut-off for a CSS. Autistic women were more likely to report a CSS diagnosis and experienced more CSS symptoms than men. Sensory sensitivity, anxiety, age and gender were significant predictors of CSS symptoms, with sensory sensitivity and anxiety fully mediating the relationship between autistic traits and CSS symptoms.

LIMITATIONS

Although this study included a large sample of autistic adults, we did not have a control group or a CSS only group. We also could not include a non-binary group due to lack of statistical power.

CONCLUSIONS

CSS diagnoses and symptoms appear to be very common in the autistic population. Increased awareness of an association between autism and central sensitisation should inform clinicians and guide diagnostic practice, particularly for women where CSS are common and autism under recognised.

Post-HPV-Vaccination Mast Cell Activation Syndrome: Possible Vaccine-Triggered Escalation of Undiagnosed Pre-Existing Mast Cell Disease?

For nearly a decade, case reports and series have emerged regarding dysautonomias-particularly postural orthostatic tachycardia syndrome (POTS)-presenting soon after vaccination against human papilloma virus (HPV). We too have observed a number of such cases (all following vaccination with the Gardasil product), and have found several to have detectable mast cell activation syndrome (MCAS) as well as histories suggesting that MCAS was likely present long before vaccination. We detail 11 such cases here, posing a hypothesis that HPV vaccination (at least with the Gardasil product) may have triggered or exacerbated MCAS in teenagers previously not recognized to have it. Only recently recognized, MCAS is being increasingly appreciated as a prevalent and chronic multisystem disorder, often emerging early in life and presenting with inflammatory ± allergic phenomena following from known mast cell (MC) mediator effects. There is rising recognition, too, of associations of MCAS with central and peripheral neuropathic disorders, including autonomic disorders such as POTS. Given the recognized potential for many antigens to trigger a major and permanent escalation of baseline MC misbehavior in a given MCAS patient, we hypothesize that in our patients described herein, vaccination with Gardasil may have caused pre-existing (but not yet clinically recognized) MCAS to worsen to a clinically significantly degree, with the emergence of POTS and other issues. The recognition and management of MCAS prior to vaccinations in general may be a strategy worth investigating for reducing adverse events following HPV vaccinations and perhaps even other types of vaccinations.