Changes in the concentrations of amino acids in the cerebrospinal fluid that correlate with pain in patients with fibromyalgia: implications for nitric oxide pathways

Nociplastic pain mechanisms and toll-like receptors as promising targets for its management

ABSTRACT

Nociplastic pain, characterized by abnormal pain processing without an identifiable organic cause, affects a significant portion of the global population. Unfortunately, current pharmacological treatments for this condition often prove ineffective, prompting the need to explore new potential targets for inducing analgesic effects in patients with nociplastic pain. In this context, toll-like receptors (TLRs), known for their role in the immune response to infections, represent promising opportunities for pharmacological intervention because they play a relevant role in both the development and maintenance of pain. Although TLRs have been extensively studied in neuropathic and inflammatory pain, their specific contributions to nociplastic pain remain less clear, demanding further investigation. This review consolidates current evidence on the connection between TLRs and nociplastic pain, with a specific focus on prevalent conditions like fibromyalgia, stress-induced pain, sleep deprivation-related pain, and irritable bowel syndrome. In addition, we explore the association between nociplastic pain and psychiatric comorbidities, proposing that modulating TLRs can potentially alleviate both pain syndromes and related psychiatric disorders. Finally, we discuss the potential sex differences in TLR signaling, considering the higher prevalence of nociplastic pain among women. Altogether, this review aims to shed light on nociplastic pain, its underlying mechanisms, and its intriguing relationship with TLR signaling pathways, ultimately framing the potential therapeutic role of TLRs in addressing this challenging condition.

Predictive Ability of Serum Amino Acid Levels to Differentiate Fibromyalgia Patients from Healthy Subjects

BACKGROUND

Fibromyalgia is a complex illness to diagnose and treat.

OBJECTIVES

To evaluate a broad range of circulating free amino acid (AA) levels in fibromyalgia patients as well as the ability of the AAs to differentiate fibromyalgia patients from healthy subjects.

DESIGN

We carried out a case-control study to evaluate AA levels in 62 patients with fibromyalgia and 78 healthy subjects. This study adheres to the STROBE guidelines.

METHODS

AAs content was assayed by HPLC in serum samples. The predictive value of AA levels in fibromyalgia was determined by receiver operating characteristic (ROC) curve and forward binary logistic regression analyses.

RESULTS

Fibromyalgia patients showed higher serum levels of aspartic acid, glutamic acid, aminoadipic acid, asparagine, histidine, 3-methyl-histidine, 5-methyl-histidine, glycine, threonine, taurine, tyrosine, valine, methionine, isoleucine, phenylalanine, leucine, ornithine, lysine, branched chain AAs (BCAAs), large neutral AAs, essential AAs (EAAs), non-essential AAs (NEAAs), basic AAs, EAAs/NEAAs ratio, phenylalanine/tyrosine ratio, and global arginine bioavailability ratio than the controls. Serum alanine levels were lower in patients than in controls. According to ROC analysis, most of these AAs may be good markers for differentiating individuals with fibromyalgia from healthy subjects. Results of logistic regression showed that the combination of glutamic acid, histidine, and alanine had the greatest predictive ability to diagnose fibromyalgia.

CONCLUSIONS

Our results show an imbalance in serum levels of most AAs in patients with fibromyalgia, which suggest a metabolic disturbance. The determination of serum levels of these AAs may aid in the diagnosis of fibromyalgia, in combination with clinical data of the patient.

Combined metabolomics and transcriptomics analysis of rats under neuropathic pain and pain-related depression

Neuropathic pain often leads to negative emotions, which in turn can enhance the sensation of pain. This study aimed to investigate the molecular mechanisms mediating neuropathic pain and negative emotions. Chronic constriction injury (CCI) rats were used as model animals and behavioral tests were conducted to assess pain and negative emotions. Then, the rat anterior cingulate cortex (ACC) was analyzed using UPLC-MS/MS and subsequently integrated with our previously published transcriptome data. Metabolomics analysis revealed that 68 differentially expressed metabolites (DEMs) were identified, mainly in amino acid metabolites and fatty acyls. Combined with our previously published transcriptome data, we predicted two genes that potentially exhibited associations with these metabolites, respectively Apolipoprotein L domain containing 1 (Apold1) and WAP four-disulfide core domain 1 (Wfdc1). Taken together, our results indicated that peripheral nerve injury contributing to neuropathic pain and pain-related depression may be associated with these metabolites and genes. This research provides new insights into the molecular regulatory mechanism, which could serve as a reference for the treatment of neuropathic pain and pain-related depression.

Serum paraoxonase activities, nitric oxide, and malondialdehyde levels are altered in patients with primary fibromyalgia syndrome

BACKGROUND

Fibromyalgia patients who are exposed to extreme oxidative stress may face more severe clinical features or oxidative stress may be increased by the severity of the disease.

AIM

The purpose of these investigation were to determine serum paraoxonase activities (PON-1) and nitric oxide (NO) activities and malondialdehyde (MDA) level in fibromyalgia and whether there were any associations between these enzymes activities, MDA level, and clinical parameters.

METHODS

The study groups were consisted of 30 primer fibromyalgia patients and 30 healthy subjects. Clinical findings, pain severity, functional disability, general health status, anxiety, and depression assessed, and serum PON-1 activity, MDA, and NO levels were measured.

RESULTS

The primer fibromyalgia group had significantly higher MDA, low density lipoprotein-cholesterol (LDL-C), and decreased PON-1 activity, NO, and high density lipoprotein-cholesterol (HDL-C) with respect to controls. The paraoxonase activity was negatively correlated with MDA, LDL-C, Visual Analog Scale (VAS), Fibromyalgia Impact Questionnaire score (FIQ score), tender point score, age, and BDI score, while positively correlated with NO and HDL-C. MDA level was positively correlated with VAS, FIQ score, tender point score, age, and negatively correlated with NO level.

CONCLUSION

These results suggest that FMS patients have an alteration in levels of MDA, NO, and PON-1 activities. We think that impaired oxidant/antioxidant status may affect the symptoms of the disease. Also, they may be of importance in the complex physiopathologic mechanism behind the development of FMS.

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.

Pharmacological treatments of fibromyalgia in adults; overview of phase IV clinical trials

Background: Fibromyalgia is a chronic neurological condition characterized by widespread pain. The effectiveness of current pharmacological treatments is limited. However, several medications have been approved for phase IV trials in order to evaluate them.

Aim: To identify and provide details of drugs that have been tested in completed phase IV clinical trials for fibromyalgia management in adults, including the primary endpoints and treatment outcomes. This article was submitted to Neuropharmacology, a section of the journal Frontiers in Pharmacology.

Method: Publicly available and relevant phase IV trials registered at ClinicalTrials.gov were analyzed. The uses of the trialed drugs for fibromyalgia were reviewed.

Results: As of 8 August 2022, a total of 1,263 phase IV clinical trials were identified, of which 121 were related to fibromyalgia. From these, 10 clinical trials met the inclusion criteria for the current study. The drugs used in phase IV trials are milnacipran, duloxetine, pregabalin, a combination of tramadol and acetaminophen, and armodafinil. The effectiveness of the current pharmacological treatments is apparently limited.

Conclusion: Due to its complexity and association with other functional pain syndromes, treatment options for fibromyalgia only are limited and they are designed to alleviate the symptoms rather than to alter the pathological pathway of the condition itself. Pain management specialists have numerous pharmacologic options available for the management of fibromyalgia.

Metabolomics of Synovial Fluid and Infrapatellar Fat Pad in Patients with Osteoarthritis or Rheumatoid Arthritis

Osteoarthritis (OA) and autoimmune-driven rheumatoid arthritis (RA) are inflammatory joint diseases with complex and insufficiently understood pathogeneses. Our objective was to characterize the metabolic fingerprints of synovial fluid (SF) and its adjacent infrapatellar fat pad (IFP) obtained during the same surgical operation from OA and RA knees. Non-targeted metabolite profiling was performed for 5 non-inflammatory trauma controls, 10 primary OA (pOA) patients, and 10 seropositive RA patients with high-resolution mass spectrometry-based techniques, and metabolites were matched with known metabolite identities. Groupwise differences in metabolic features were analyzed with the univariate Welch’s t-test and the multivariate linear discriminant analysis (LDA) and principal component analysis (PCA). Significant discrimination of metabolite profiles was discovered by LDA for both SF and IFP and by PCA for SF based on diagnosis. In addition to a few drug-derived substances, there were 16 and 13 identified metabolites with significant differences between the diagnoses in SF and IFP, respectively. The pathways downregulated in RA included androgen, bile acid, amino acid, and histamine metabolism, and those upregulated included biotin metabolism in pOA and purine metabolism in RA and pOA. The RA-induced downregulation of androgen and bile acid metabolism was observed for both SF and IFP. The levels of 11 lipid metabolites, mostly glycerophospholipids and fatty acid amides, were also altered by these inflammatory conditions. The identified metabolic pathways could be utilized in the future to deepen our understanding of the pathogeneses of OA and RA and to develop not only biomarkers for their early diagnosis but also therapeutic targets.

Systematic Review of the Use of Intravenous Ketamine for Fibromyalgia

Background: Fibromyalgia, a complex disorder that affects 1% to 5% of the population, presents as widespread chronic musculoskeletal pain without physical or laboratory signs of any specific pathologic process. The mechanism, while still being explored, suggests central sensitization and disordered pain regulation at the spinal cord and supraspinal levels, with a resulting imbalance between excitation and inhibition that may alter central nervous system nociceptive processing. Nociceptive hypersensitivity results from activity of the N-methyl-D-aspartate receptor (NMDAR)-mediated glutamatergic synaptic transmission in the spinal cord and brain. Because ketamine, an NMDAR antagonist, may reduce induction of synaptic plasticity and maintenance of chronic pain states, the study of its use in intravenous form to treat fibromyalgia has increased. Methods: We conducted a literature search with the objectives of examining the effect of intravenous ketamine administration on pain relief, identifying side effects, and highlighting the need for clinical studies to evaluate ketamine infusion treatment protocols for patients with fibromyalgia. We used the keywords "fibromyalgia," "chronic pain," "ketamine," "intravenous," and "infusion" and found 7 publications that included 118 patients with fibromyalgia who met inclusion criteria. Results: Clinical studies revealed a short-term reduction-only for a few hours after the infusions-in self-reported pain intensity with single, low-dose, intravenous ketamine infusions, likely attributable to nociception-dependent central sensitization in fibromyalgia via NMDAR blockade. Case studies suggest that increases in the total dose of ketamine and longer, more frequent infusions may be associated with more effective pain relief and longer-lasting analgesia. Another neurotransmitter release may be contributing to this outcome. Conclusion: This systematic review suggests a dose response, indicating potential efficacy of intravenous ketamine in the treatment of fibromyalgia.

Enhanced sensory conduction in primary fibromyalgia: a case–control pilot study

Background

This study aimed to test the changes in the conduction properties of peripheral nerves in patients with primary fibromyalgia (FM). Thirty patients with FM and sixteen healthy controls participated in this study. Visual analogue scale (VAS) for pain severity, pain duration, Widespread Pain Index (WPI), Symptom Severity (SS) scale, Hamilton depression rating scale, Taylor’s manifest anxiety scale, and Fibromyalgia Impact Questionnaire (FIQR) were used for measurement of psychiatric comorbidities and quality of life for each patient. Routine motor and sensory nerve conduction studies of both median, ulnar, common peroneal, posterior tibial, and sural nerves were measured for all study participants.

Results

We found statistically significant increase in Sensory Conduction Velocity (SCV), Sensory Nerve Action Potential (SNAP) amplitude, and decrease in Sensory Latency (SL) in patients with FM compared to controls. There were no significant changes in motor nerve conduction between patients and controls. Regression analysis showed a significant relation between WPI and both SCV and SL especially in nerves of upper limbs. However, no significant relation between SCV and SL and other presumed predictors including VAS for pain severity, pain duration, SS scale, FIQR, and psychiatric comorbidities. Patients with FM suffered more depression and anxiety than controls.

Conclusions

We found enhanced conductivity of the sensory rather than the motor nerves in patients with FM. To our knowledge, this is the first study to describe these sensory changes which may add further evidence of peripheral sensitization in patients with FM.

The Role of Nutrient Supplementation in the Management of Chronic Pain in Fibromyalgia: A Narrative Review

INTRODUCTION

The multifaceted clinical presentation of fibromyalgia (FM) supports the modern understanding of the disorder as a more global condition than one simply affecting pain sensation. The main pharmacologic therapies used clinically include anti-epileptics and anti-depressants. Conservative treatment options include exercise, myofascial release, psychotherapy, and nutrient supplementation.

METHODS

Narrative review.

RESULTS

Nutrient supplementation is a broadly investigated treatment modality as numerous deficiencies have been linked to FM. Additionally, a proposed link between gut microbiome patterns and chronic pain syndromes has led to studies investigating probiotics as a possible treatment. Despite positive results, much of the current evidence regarding this topic is of poor quality, with variable study designs, limited sample sizes, and lack of control groups.

CONCLUSIONS

The etiology of FM is complex, and has shown to be multi-factorial with genetics and environmental exposures lending influence into its development. Preliminary results are promising, however, much of the existing evidence regarding diet supplementation is of poor quality. Further, more robust studies are needed to fully elucidate the potential of this alternative therapeutic option.

Determination of amino acids in human biological fluids by high-performance liquid chromatography: critical review

The quantitation and qualification of amino acids are most commonly used in clinical and epidemiological studies, and provide an excellent way of monitoring compounds in human fluids which have not been monitored previously, to prevent some diseases. Because of this, it is not surprising that scientific interest in evaluating these compounds has resurfaced in recent years and has precipitated the development of a multitude of new analytical techniques. This review considers recent developments in HPLC analytics on the basis of publications from the last few years. It helps to update and systematize knowledge in this area. Particular attention is paid to the progress of analytical methods, pointing out the advantages and drawbacks of the various techniques used for the preparation, separation and determination of amino acids. Depending on the type of sample, the preparation conditions for HPLC analysis change. For this reason, the review has focused on three types of samples, namely urine, blood and cerebrospinal fluid. Despite time-consuming sample preparation before HPLC analysis, an additional derivatization technique should be used, depending on the detection technique used. There are proposals for columns that are specially modified for amino acid separation without derivatization, but the limit of detection of the substance is less beneficial. In view of the fact that amino acid analyses have been performed for years and new solutions may generate increased costs, it may turn out that older proposals are much more advantageous.

Metabolomics and psychological features in fibromyalgia and electromagnetic sensitivity

Fibromyalgia (FM) as Fibromyalgia and Electromagnetic Sensitivity (IEI-EMF) are a chronic and systemic syndrome. The main symptom is represented by strong and widespread pain in the musculoskeletal system. The exact causes that lead to the development of FM and IEI-EMF are still unknown. Interestingly, the proximity to electrical and electromagnetic devices seems to trigger and/or amplify the symptoms. We investigated the blood plasma metabolome in IEI-EMF and healthy subjects using ¹H NMR spectroscopy coupled with multivariate statistical analysis. All the individuals were subjected to tests for the evaluation of psychological and physical features. No significant differences between IEI-EMF and controls relative to personality aspects, Locus of Control, and anxiety were found. Multivariate statistical analysis on the metabolites identified by NMR analysis allowed the identification of a distinct metabolic profile between IEI-EMF and healthy subjects. IEI-EMF were characterized by higher levels of glycine and pyroglutamate, and lower levels of 2-hydroxyisocaproate, choline, glutamine, and isoleucine compared to healthy subjects. These metabolites are involved in several metabolic pathways mainly related to oxidative stress defense, pain mechanisms, and muscle metabolism. The results here obtained highlight possible physiopathological mechanisms in IEI-EMF patients to be better defined.

Nitric oxide, lipid peroxidation products, and antioxidants in primary fibromyalgia and correlation with disease severity

Background

Fibromyalgia syndrome (FMS) is characterized by altered pain perception with chronic, widespread musculoskeletal pain. The relationship between nitric oxide, oxidative stress and the severity of FMS has not been studied. This study evaluated NO levels in plasma, LPO products and antioxidants in Red Cell lysate in patients of FMS and correlated it with disease severity.

Methods

105 FMS patients who fulfilled 1990 ACR Criteria and 105 age- and sex-matched healthy controls were recruited over two years from 2013 to 2015. Antioxidative enzyme activity was assessed by the estimation of catalase, glutathione peroxidase (GPx) and glutathione reductase (GR) and superoxide dismutase (SOD). Nitric oxide in plasma, MDA marker of lipid per - oxidation (LPO) in the lysate was donen for estimating oxidative stress. FIQR was used to assess the severity of fibromyalgia.

Results

The catalase, superoxide dismutase, glutathione reductase and glutathione peroxidase levels were significantly low in patients than controls (p<0.001). Plasma NO levels and LPO were also significantly high (p<0.05). NO and LPO levels showed a significant positive correlation with FIQR (r: 0.57, 0.8 and p: <0.001) whereas a negative correlation was observed between antioxidants (Cat, GR and GPx, but not SOD) and FIQR.

Conclusions

Low antioxidants and raised LPO in RBC lysate in patients with FM together with high plasma NO correlated with the severity of FMS.

Metabolomic Differentials in Women With and Without Fibromyalgia

A nontargeted plasma metabolomic analysis was conducted to compare differentially expressed metabolites in women with and without fibromyalgia (FM) using data and samples collected from two parent studies in women with FM (n = 20) and comparative data collected from newly recruited age‐matched women (n = 20). Blood plasma samples were analyzed for metabolite content using liquid chromatography mass spectrometry. Consolidation of positive and negative ion mode metabolomics data with fold change (>2 or <0.5) and variable importance of projection scores ≥1 revealed statistically significant metabolites comparing samples from women with and without FM. Metabolite profiles in patients with FM differed from the comparison group in energy, lipid and amino acid metabolites reflecting heightened oxidative stress, inflammation, and tryptophan degradation in patients with FM. Study results may contribute to further identification of unique metabolomic profiles enhancing understanding of the pathophysiology of FM and for the development of effective therapeutic options.

The gadolinium hypothesis for fibromyalgia and unexplained widespread chronic pain

Fibromyalgia (FM) is a chronic, painful, heterogeneous, and common disorder carrying a substantial socio-economical burden. It lacks effective cures and its aetiology is still unknown. There exists evidence for central and peripheral neurological contribution to the symptoms but grasping the real source of abnormal nervous system sensitization remains an ongoing challenge. There exists an association between an injury/trauma and the onset of the symptoms, but a causal relationship has not been yet sufficiently supported by scientific evidence. I postulate a role for gadolinium-based contrast agents and retention of gadolinium in the body. This conjecture breaks the hypothesis of a direct role for a physical injury/trauma per se in favour of an indirect one by the subsequent diagnostic procedures. It creates a new link between retention of gadolinium in the body and painful conditions as FM and unexplained chronic widespread pain reported after a trauma, surgery, or medical illness. Experimental evidence demonstrates possible retention of gadolinium species in human body, still lacking conclusive answers on their pathological consequences. Notwithstanding, there exist some initial data that report unexplained chronic widespread pain and symptoms of FM in those patients: they are suggestive for pathological consequences associated with gadolinium retention. Besides clear compelling symptoms overlapping, biochemical findings are provided to sustain the hypothesis of a role for gadolinium in the disease process focusing on neurotransmitters, endogenous metal cations, cytokines, and muscle tissue. Experimental findings strongly support the hypothesis of impairment at the cellular, intracellular, and systemic levels in FM. And these data are highly compatible with collateral effects associated with the interference of the gadolinium ion and its pharmaceutical chelates into biochemical pathways in vivo. The hypothesis presented in this article, along with the support of scientific evidence, links FM and unexplained chronic widespread pain reported after a trauma, surgery, or medical illness to retention of gadolinium in the body. If the hypothesis is confirmed, it could improve diagnosis and prevention, while providing a ground for development of new treatments.

Hyperbaric oxygen and aerobic exercise in the long-term treatment of fibromyalgia: A narrative review

Chronic pain is one of the most common clinical presentations in the primary care settings. In the US, Fibromyalgia (FM) affects about 1-3% of adults and commonly occurs in adults between the ages of 40-50 years. FM causes widespread muscular pain and tenderness with hyperalgesia and allodynia and may be associated with other somatic complaints. Hyperbaric oxygen therapy (HBOT) has been utilized and has recently shown promising effects in the management of FM and other chronic pain disorders. In HBOT, the intermittent breathing of 100% oxygen in a pressurized chamber where the pressure is higher than 1 atmosphere absolute (ATA) has been utilized. HBOT exhibits a significant anti-inflammatory effect through reducing production of glial cells and inflammatory mediators which results in pain alleviation in different chronic pain conditions. HBOT can also influence neuroplasticity and affects the mitochondrial mechanisms resulting in functional brain changes. In addition to that, HBOT stimulates nitric oxide (NO) synthesis which helps in alleviating hyperalgesia and NO-dependent release of endogenous opioids which seemed to be the primary HBOT mechanism of antinociception. Moreover, aerobic exercise and meditative movement therapies (MMT) have gained attention for their role in pain alleviation through different anti-inflammatory and antioxidant mechanisms. In this review, we aim to elucidate the different mechanisms of HBOT and aerobic exercise in attenuating pain as adjuvant therapy in the multidisciplinary treatment strategy of chronic pain, and more particularly fibromyalgia.

Neuroinflammation and Central Sensitization in Chronic and Widespread Pain

Chronic pain is maintained in part by central sensitization, a phenomenon of synaptic plasticity, and increased neuronal responsiveness in central pain pathways after painful insults. Accumulating evidence suggests that central sensitization is also driven by neuroinflammation in the peripheral and central nervous system. A characteristic feature of neuroinflammation is the activation of glial cells, such as microglia and astrocytes, in the spinal cord and brain, leading to the release of proinflammatory cytokines and chemokines. Recent studies suggest that central cytokines and chemokines are powerful neuromodulators and play a sufficient role in inducing hyperalgesia and allodynia after central nervous system administration. Sustained increase of cytokines and chemokines in the central nervous system also promotes chronic widespread pain that affects multiple body sites. Thus, neuroinflammation drives widespread chronic pain via central sensitization. We also discuss sex-dependent glial/immune signaling in chronic pain and new therapeutic approaches that control neuroinflammation for the resolution of chronic pain.

Measuring Glutamate Levels in the Brains of Fibromyalgia Patients and a Potential Role for Glutamate in the Pathophysiology of Fibromyalgia Symptoms: A Systematic Review

OBJECTIVES

The aim of this study was to systematically review the literature concerning proton magnetic resonance spectroscopy (H-MRS) measured glutamate levels in specific brain regions of fibromyalgia (FM) patients to determine if there is a correlation between raised glutamate levels and the presentation of FM.

MATERIALS AND METHODS

The electronic databases-MEDLINE, EMBASE Classic+Embase, PsychINFO, Cochrane Database of Systematic Reviews, Cochrane Database of Abstracts of Reviews of Effect, Cochrane Central Register of Controlled Trials-were searched to find original studies that used H-MRS to measure glutamate concentrations in the brains of FM patients.

RESULTS

Nine studies with a total of 482 participants were selected for inclusion in the review. Seven of the 8 studies that investigated an association between cerebral glutamate levels and FM, showed a positive association. Brain regions identified as having increased glutamate levels include the posterior cingulate gyrus, posterior insula, ventrolateral prefrontal cortex, and amygdala. One study reported a decrease in glutamate levels in the hippocampus of FM patients compared with healthy controls. Seven of the 8 studies that analyzed the correlations between cerebral glutamate levels and FM symptoms, found a significant positive correlation.

DISCUSSION

Although the cause of FM remains inconclusive, there is converging data in favor of a dysregulation of pain processing in the central nervous system of FM patients, particularly associated with an increase in cerebral glutamate levels. Furthermore, there is evidence to support an association between increased glutamate levels and an increase in FM symptoms.

Effects of pregabalin and duloxetine on neurotransmitters in the dorsal horn of the spinal cord in a rat model of fibromyalgia

Dysfunction of the monoamine systems in the nervous system is associated with the clinical symptoms of fibromyalgia. Reserpine-induced myalgia (RIM) rats are a putative model of fibromyalgia in which muscle pressure thresholds and monoamine content is reduced in the brain and spinal cord. We examined the effects of pregabalin and duloxetine, drugs approved for fibromyalgia treatment, on the levels of extracellular neurotransmitters in the dorsal horn of the spinal cord in RIM rats using microdialysis. Male SD rats were used for all experiments. To generate RIM rats, reserpine was injected at 1 mg/kg subcutaneously once daily for three consecutive days. The pressure threshold of the mid-gastrocnemius muscle was measured using a Randall-Selitto apparatus. Norepinephrine, dopamine, and serotonin were detected using high-performance liquid chromatography with electrochemical detection, and glutamate and γ-aminobutyric acid (GABA) were detected using liquid chromatography-mass spectrometry. The muscle pressure threshold in RIM rats was significantly lower than that in normal rats. While the levels of monoamines and glutamate were lower in the spinal cord of RIM rats than in normal rats, levels of GABA did not markedly differ. Duloxetine increased the levels of all three monoamines in normal and RIM rats in a dose-dependent manner. In contrast, pregabalin only increased norepinephrine levels in RIM rats. These results indicate that while both pregabalin and duloxetine ameliorate muscle pressure thresholds in RIM rats, their effects on the levels of extracellular neurotransmitters in the spinal cord differ considerably.

New insights into the genetics of fibromyalgia

Although debate on the concept of fibromyalgia (FM) has been vigorous ever since the classification criteria were first published, FM is now better understood and has become recognized as a disorder. Recently, FM has come to be considered a major health problem, affecting 1% to 5% of the general population. As familial aggregations have been observed among some FM patients, genetic research on FM is logical. In fact, genome-wide association studies and linkage analysis, and studies on candidate genes, have uncovered associations between certain genetic factors and FM. Genetic susceptibility is now considered to influence the etiology of FM. At the same time, novel genetic techniques, such as microRNA analysis, have been used in attempts to improve our understanding of the genetic predisposition to FM. In this article, we review recent advances in, and continuing challenges to, the identification of genes contributing to the development of, and symptom severity in, FM.

Microvascular functions in patients with fibromyalgia syndrome: effects of physical exercise

Objectives

This study aims to evaluate the current state of microvascular function and to investigate the effect of supervised aerobic exercise on microvascular control mechanisms and health outcomes in women with fibromyalgia syndrome (FMS).

Patients and methods

Forty female patients (mean age 51±11 years) with a diagnosis of FMS according to the American College of Rheumatology criteria and 20 healthy female controls (mean age 52±9 years) were included in the study. Microvascular blood flow was measured using a laser Doppler flowmeter (LDF) at the volar skin site of the forearm. Pain severity and FMS were assessed using the visual analog scale (VAS) and Fibromyalgia Impact Questionnaire (FIQ), respectively, both at the beginnig and at the end of the study. Fibromyalgia was evaluated and a spectral analysis of LDF signals was carried out to assess the relative contribution of each control mechanisms. The local thermal hyperemia was used to test the microvascular functions. Moderate-intensity aerobic activity (energy expenditure 3.0 to 6.0 metabolic equivalent) was performed by treadmill walking for 30 min for five days each week for a month.

Results

The patients with FMS had lower VAS and FIQ scores at the end of the exercise period. There was a positive correlation between improved myogenic and neurogenic mechanisms and reduced FIQ scores. Cardiac signals were positively correlated with the FIQ scores at the end of the exercise period. Endothelial function was under the influence of pain, and baseline nitric oxide activity was found to be positively correlated with VAS.

Conclusion

Our study results suggest that microvascular functions are impaired in FMS patients and moderate exercise training is effective to improve the FIQ/VAS scores and enhance vascular functions.

Painful After-Sensations in Fibromyalgia are Linked to Catastrophizing and Differences in Brain Response in the Medial Temporal Lobe

Fibromyalgia (FM) is a complex syndrome characterized by chronic widespread pain, hyperalgesia, and other disabling symptoms. Although the brain response to experimental pain in FM patients has been the object of intense investigation, the biological underpinnings of painful after-sensations (PAS), and their relation to negative affect have received little attention. In this cross-sectional cohort study, subjects with FM (n = 53) and healthy controls (n = 17) were assessed for PAS using exposure to a sustained, moderately painful cuff stimulus to the leg, individually calibrated to a target pain intensity of 40 of 100. Despite requiring lower cuff pressures to achieve the target pain level, FM patients reported more pronounced PAS 15 seconds after the end of cuff stimulation, which correlated positively with clinical pain scores. Functional magnetic resonance imaging revealed reduced deactivation of the medial temporal lobe (MTL; amygdala, hippocampus, parahippocampal gyrus) in FM patients, during pain stimulation, as well as in the ensuing poststimulation period, when PAS are experienced. Moreover, the functional magnetic resonance imaging signal measured during the poststimulation period in the MTL, as well as in the insular and anterior middle cingulate and medial prefrontal cortices, correlated with the severity of reported PAS by FM patients. These results suggest that the MTL plays a role in PAS in FM patients.

PERSPECTIVE

PAS are more common and severe in FM, and are associated with clinical pain and catastrophizing. PAS severity is also associated with less MTL deactivation, suggesting that the MTL, a core node of the default mode network, may be important in the prolongation of pain sensation in FM.

Modulation of NMDA Receptor Activity in Fibromyalgia

Activation of the N-methyl-d-aspartate receptor (NMDAR) results in increased sensitivity of spinal cord and brain pathways that process sensory information, particularly those which relate to pain. The NMDAR shows increased activity in fibromyalgia and hence modulation of the NMDAR is a target for therapeutic intervention. A literature review of interventions impacting on the NMDAR shows a number of drugs to be active on the NMDAR mechanism in fibromyalgia patients, with variable clinical effects. Low-dose intravenous ketamine and oral memantine both show clinically useful benefit in fibromyalgia. However, consideration of side-effects, logistics and cost need to be factored into management decisions regarding use of these drugs in this clinical setting. Overall benefits with current NMDAR antagonists appear modest and there is a need for better strategy trials to clarify optimal dose schedules and to delineate potential longer–term adverse events. Further investigation of the role of the NMDAR in fibromyalgia and the effect of other molecules that modulate this receptor appear important to enhance treatment targets in fibromyalgia.

Clear differences in cerebrospinal fluid proteome between women with chronic widespread pain and healthy women - a multivariate explorative cross-sectional study

Introduction

Frequent chronic local pain can develop into chronic widespread pain (CWP). The spread of pain is correlated with pain intensity, anxiety, and depression, conditions that ultimately lead to a poor quality of life. Knowledge is incomplete about CWP’s etiology, although it has been suggested that both central hyperexcitability and/or a combination with peripheral factors may be involved. Cerebrospinal fluid (CSF) could act as a mirror for the central nervous system as proteins are signal substances that activate the formation of algesics and control nociceptive processes. To this end, this study investigates the CSF protein expression in women with CWP and in female healthy controls.

Materials and methods

This study included 12 female patients with CWP diagnosed according to the American College of Rheumatology criteria with 13 healthy age- and sex-matched pain-free subjects. All subjects went through a clinical examination and answered a health questionnaire that registered sociodemographic and anthropometric data, pain characteristics, psychological status, and quality of life rating. CSF was collected by lumbar puncture from each subject. Two-dimensional gel electrophoresis in combination with mass spectrometry was used to analyze the CSF proteome. This study identifies proteins that significantly discriminate between the two groups using multivariate data analysis (MVDA) (i.e., orthogonal partial least squares discriminant analysis [OPLS-DA]).

Results

There were no clinically significant levels of psychological distress and catastrophization presented in subjects with CWP. MVDA revealed a highly significant OPLS-DA model where 48 proteins from CSF explained 91% (R²) of the variation and with a prediction of 90% (Q²). The highest discriminating proteins were metabolic, transport, stress, and inflammatory.

Conclusion

The highest discriminating proteins (11 proteins), according to the literature, are involved in apoptotic regulations, anti-inflammatory and anti-oxidative processes, the immune system, and endogenous repair. The results of this explorative study may indicate the presence of neuro-inflammation in the central nervous system of CWP patients. Future studies should be larger and control for confounders and determine which alterations are unspecific/general and which are specific changes.

Free amino acids in fibromyalgia syndrome: relationship with clinical picture

The objectives of our study were to evaluate free amino acid (FAA) concentrations in the serum of patients affected by fibromyalgia syndrome (FMS) and to determine the relationships between FAA levels and FMS clinical parameters. Thus, serum amino acid concentrations were quantified (HPLC analysis) in 23 females with fibromyalgia (according to the American College of Rheumatology classification criteria) and 20 healthy females. The results showed significantly higher serum concentrations of aspartate, cysteine, glutamate, glycine, isoleucine, leucine, methionine, ornithine, phenylalanine, sarcosine, serine, taurine, tyrosine and valine in FMS patients vs. healthy controls. Patients with higher Fibromyalgia Impact Questionnaire (FIQ) scores showed increased levels of alanine, glutamine, isoleucine, leucine, phenylalanine, proline and valine. In conclusion, our results indicate an imbalance in some FAAs in FMS patients. Increased Glu is particularly interesting, as it could explain the deficit in monoaminergic transmission involved in pain.

Fibromyalgia: A Critical and Comprehensive Review

Fibromyalgia is a disorder that is part of a spectrum of syndromes that lack precise classification. It is often considered as part of the global overview of functional somatic syndromes that are otherwise medically unexplained or part of a somatization disorder. Patients with fibromyalgia share symptoms with other functional somatic problems, including issues of myalgias, arthralgias, fatigue and sleep disturbances. Indeed, there is often diagnostic and classification overlap for the case definitions of a variety of somatization disorders. Fibromyalgia, however, is a critically important syndrome for physicians and scientists to be aware of. Patients should be taken very seriously and provided optimal care. Although inflammatory, infectious, and autoimmune disorders have all been ascribed to be etiological events in the development of fibromyalgia, there is very little data to support such a thesis. Many of these disorders are associated with depression and anxiety and may even be part of what has been sometimes called affected spectrum disorders. There is no evidence that physical trauma, i.e., automobile accidents, is associated with the development or exacerbation of fibromyalgia. Treatment should be placed on education, patient support, physical therapy, nutrition, and exercise, including the use of drugs that are approved for the treatment of fibromyalgia. Treatment should not include opiates and patients should not become poly pharmacies in which the treatment itself can lead to significant morbidities. Patients with fibromyalgia are living and not dying of this disorder and positive outlooks and family support are key elements in the management of patients.

Current treatments to counter sleep dysfunction as a pathogenic stimulus of fibromyalgia

Fibromyalgia is characterized by chronic widespread pain, fatigue and nonrestorative sleep. Polysomnography showed reduced short-wave sleep and abnormal alpha rhythms during nonrapid eye movement sleep in patients with fibromyalgia. However, sleep dysfunction might be pathogenic in fibromyalgia since myalgia and fatigue could be induced in healthy individuals by disrupting sleep. Poor sleep quality was a major risk factor for the subsequent development of chronic widespread pain in healthy pain-free individuals. Sleep disruption leads to impairment of the descending pain inhibition pathways. Aside from good sleep, hygiene, exercise can promote sleep. Among currently available pharmacological treatments, evidence suggests amitriptyline and pregabalin can improve sleep in fibromyalgia.

Fibromyalgia syndrome pathology and environmental influences on afflictions with medically unexplained symptoms

Fibromyalgia syndrome (FMS) is a clinical disorder predominant in females with unknown etiology and medically unexplained symptoms (MUS), similar to other afflictions, including irritable bowel syndrome (IBS), chronic fatigue syndrome (CFS), post-traumatic stress disorder (PTSD), Gulf War illness (GFI), and others. External environmental stimuli drive behavior and impact physiologic homeostasis (internal environment) via autonomic functioning. These environments directly impact the individual affective state (mind), which feeds back to regulate physiology (body). FMS has emerged as a complex disorder with pathologies identified among neurotransmitter and enzyme levels, immune/cytokine functionality, cortical volumes, cutaneous innervation, as well as an increased frequency among people with a history of traumatic and/or emotionally negative events, and specific personality trait profiles. Yet, quantitative physical evidence of pathology or disease etiology among FMS has been limited (as with other afflictions with MUS). Previously, our group published findings of increased peptidergic sensory innervation associated with the arterio-venous shunts (AVS) in the glabrous hand skin of FMS patients, which provides a plausible mechanism for the wide-spread FMS symptomology. This review focuses on FMS as a model affliction with MUS to discuss the implications of the recently discovered peripheral innervation alterations, explore the role of peripheral innervation to central sensitization syndromes (CSS), and examine possible estrogen-related mechanisms through which external and internal environmental factors may contribute to FMS etiology and possibly other afflictions with MUS.

Changes in Purines Concentration in the Cerebrospinal Fluid of Pregnant Women Experiencing Pain During Active Labor

Labor pain has been reported as a severe pain and can be considered as a model of acute visceral pain. It is well known that extracellular purines have an important role in pain signaling in the central nervous system. This study analyzes the relationship between extracellular purines and pain perception during active labor. A prospective observational study was performed. Cerebrospinal fluid (CSF) levels of the purines and their metabolites were compared between women at term pregnancy with labor pain (n = 49) and without labor pain (Caesarian section; n = 47). Control groups (healthy men and women without chronic or acute pain-n = 40 and 32, respectively) were also investigated. The CSF levels of adenosine were significantly lower in the labor pain group (P = 0.026) and negatively correlated with pain intensity measured by a visual analogue scale (r = -0.48, P = 0.0005). Interestingly, CSF levels of uric acid were significantly higher in healthy men as compared to women. Additionally, pregnant women showed increased CSF levels of ADP, GDP, adenosine and guanosine and reduced CSF levels of AMP, GTP, and uric acid as compared to non-pregnant women (P < 0.05). These findings suggest that purines, in special the nucleoside adenosine, are associated with pregnancy and labor pain.

Exploring Genetic Susceptibility to Fibromyalgia

Fibromyalgia (FM) affects 1% to 5% of the population, and approximately 90% of the affected individuals are women. FM patients experience impaired quality of life and the disorder places a considerable economic burden on the medical care system. With the recognition of FM as a major health problem, many recent studies have evaluated the pathophysiology of FM. Although the etiology of FM remains unknown, it is thought to involve some combination of genetic susceptibility and environmental exposure that triggers further alterations in gene expression. Because FM shows marked familial aggregation, most previous research has focused on genetic predisposition to FM and has revealed associations between genetic factors and the development of FM, including specific gene polymorphisms involved in the serotonergic, dopaminergic, and catecholaminergic pathways. The aim of this review was to discuss the current evidence regarding genetic factors that may play a role in the development and symptom severity of FM.

Supraspinal actions of nociceptin/orphanin FQ, morphine and substance P in regulating pain and itch in non-human primates

BACKGROUND AND PURPOSE

Nociceptin/orphanin FQ (N/OFQ) peptide (NOP) receptor agonists display a promising analgesic profile in preclinical studies. However, supraspinal N/OFQ produced hyperalgesia in rodents and such effects have not been addressed in primates. Thus, the aim of this study was to investigate the effects of centrally administered ligands on regulating pain and itch in non-human primates. In particular, nociceptive thresholds affected by intracisternal N/OFQ were compared with those of morphine and substance P, known to provide analgesia and mediate hyperalgesia, respectively, in humans.

EXPERIMENTAL APPROACH

Intrathecal catheters were installed to allow intracisternal and lumbar intrathecal administration in awake and unanaesthetized rhesus monkeys. Nociceptive responses were measured using the warm water tail-withdrawal assay. Itch scratching responses were scored from videotapes recording behavioural activities of monkeys in their home cages. Antagonist studies were conducted to validate the receptor mechanisms underlying intracisternally elicited behavioural responses.

KEY RESULTS

Intracisternal morphine (100 nmol) elicited more head scratches than those after intrathecal morphine. Distinct dermatomal scratching locations between the two routes suggest a corresponding activation of supraspinal and spinal μ receptors. Unlike intracisternal substance P, which induced hyperalgesia, intracisternal N/OFQ (100 nmol) produced antinociceptive effects mediated by NOP receptors. Neither peptide increased scratching responses.

CONCLUSIONS AND IMPLICATIONS

Taken together, these results demonstrated differential actions of ligands in the primate supraspinal region in regulating pain and itch. This study not only improves scientific understanding of the N/OFQ-NOP receptor system in pain processing but also supports the therapeutic potential of NOP-related ligands as analgesics.

Nitric Oxide, Inflammation, Lipid Profile, and Cortisol in Normal- and Overweight Women With Fibromyalgia

Objectives:

Research has identified many factors associated with fibromyalgia (FM), but findings have been inconsistent. This study aimed to investigate changes in levels of nitric oxide (NO), inflammatory markers, lipid profile, and cortisol in normal- and overweight patients with FM and controls. Since most patients with FM are overweight, we explored possible changes in these markers according to body mass index (BMI).

Methods:

This preliminary study was performed on serum samples of women with FM and age-matched controls, grouped according to their BMI: 12 normal-weight patients and 12 controls and 13 overweight patients and 8 controls. Ozone-based chemiluminescence assay was used to measure NO. Inflammatory mediators and cortisol were determined by immunoassay. Lipid profile was measured by a spectrophotometric procedure. Functional capacity was assessed by the fibromyalgia impact questionnaire (FIQ).

Results:

Normal-weight patients showed higher levels of C-reactive protein (CRP) and apolipoprotein B compared to controls (both p < .05). CRP, apolipoprotein B, and triglycerides were higher in overweight patients versus overweight controls (all p < .05) and in overweight versus normal-weight patients (CRP p < .01; apolipoprotein B, triglycerides p < .05). The other markers were unaffected. Apolipoprotein B ( r = .762; p < .05) and NO ( r = −.921; p < .05) levels correlated with FIQ score in normal-weight patients. CRP level correlated with FIQ ( r = .912; p < .05) in overweight patients.

Conclusions:

CRP and apolipoprotein B, biomarkers linked to cardiovascular events, may be associated with FM-related dysfunction in normal- and overweight women with FM. Their increased levels in these patients may indicate an increased risk of cardiovascular disease.

Cerebrospinal Fluid Cytokines and Neurotrophic Factors in Human Chronic Pain Populations: A Comprehensive Review

Chronic pain is a prevalent and debilitating condition, conveying immense human burden. Suffering is caused not only by painful symptoms, but also through psychopathological and detrimental physical consequences, generating enormous societal costs. The current treatment armamentarium often fails to achieve satisfying pain relief; thus, research directed toward elucidating the complex pathophysiological mechanisms underlying chronic pain syndromes is imperative. Central neuroimmune activation and neuroinflammation have emerged as driving forces in the transition from acute to chronic pain, leading to central sensitization and decreased opioid efficacy, through processes in which glia have been highlighted as key contributors. Under normal conditions, glia exert a protective role, but in different pathological states, a deleterious role is evident--directly and indirectly modulating and enhancing pain transmission properties of neurons, and shaping synaptic plasticity in a dysfunctional manner. Cytokines and neurotrophic factors have been identified as pivotal mediators involved in neuroimmune activation pathways and cascades in various preclinical chronic pain models. Research confirming these findings in humans has so far been scarce, but this comprehensive review provides coherent data supporting the clear association of a mechanistic role of altered central cytokines and neurotrophic factors in a number of chronic pain states despite varying etiologies. Given the importance of these factors in neuropathic and inflammatory chronic pain states, prospective therapeutic strategies, and directions for future research in this emerging field, are outlined.

β2- and β3-adrenergic receptors drive COMT-dependent pain by increasing production of nitric oxide and cytokines

Decreased activity of catechol-O-methyltransferase (COMT), an enzyme that metabolizes catecholamines, contributes to pain in humans and animals. Previously, we demonstrated that development of COMT-dependent pain is mediated by both β2- and β3-adrenergic receptors (β2ARs and β3ARs). Here we investigated molecules downstream of β2- and β3ARs driving pain in animals with decreased COMT activity. Based on evidence linking their role in pain and synthesis downstream of β2- and β3AR stimulation, we hypothesized that nitric oxide (NO) and proinflammatory cytokines drive COMT-dependent pain. To test this, we measured plasma NO derivatives and cytokines in rats receiving the COMT inhibitor OR486 in the presence or absence of the β2AR antagonist ICI118,551+β3AR antagonist SR59320A. We also assessed whether the NO synthase inhibitor L-N(G)-nitroarginine methyl ester (L-NAME) and cytokine-neutralizing antibodies block the development of COMT-dependent pain. Results showed that animals receiving OR486 exhibited higher levels of NO derivatives, tumor necrosis factor α (TNFα), interleukin-1β (IL-1β), interleukin-6 (IL-6), and chemokine (C-C motif) ligand 2 (CCL2) in a β2- and β3AR-dependent manner. Additionally, inhibition of NO synthases and neutralization of the innate immunity cytokines TNFα, IL-1β, and IL-6 blocked the development of COMT-dependent pain. Finally, we found that NO influences TNFα, IL-1β, IL-6, and CCL2 levels, whereas TNFα and IL-6 influence NO levels. Altogether, these results demonstrate that β2- and β3ARs contribute to COMT-dependent pain, at least partly, by increasing NO and cytokines. Furthermore, they identify β2- and β3ARs, NO, and proinflammatory cytokines as potential therapeutic targets for pain patients with abnormalities in COMT physiology.

Effects of 12-week combined exercise therapy on oxidative stress in female fibromyalgia patients

The aims of this study were to investigate the effect of exercise therapy on the oxidative stress in fibromyalgia patients and relationship between oxidative stress and fibromyalgia symptoms. Thirty women diagnosed with fibromyalgia according to the American College of Rheumatology preliminary criteria, and 23 healthy women whose age- and weight-matched women were enrolled the study. Pain intensity with visual analog scale (VAS), the number of tender points, the fibromyalgia impact questionnaire (FIQ), the Beck depression inventory (BDI) were evaluated. The oxidative stress parameters thiobarbituric acid reactive substances, protein carbonyls, and nitric oxide, and antioxidant parameters thiols and catalase were investigated in patients and control group. After, combined aerobic and strengthen exercise regimen was given to fibromyalgia group. Exercise therapy consisted of a warming period of 10 min, aerobic exercises period of 20 min, muscle strengthening exercises for 20 min, and 10 min cooling down period. Therapy was lasting 1 h three times per week over a 12-week period. All parameters were reevaluated after the treatment in the patient group. The oxidative stress parameters levels were significantly higher, and antioxidant parameters were significantly lower in patients with fibromyalgia than in the controls. VAS, FIQ, and BDI scores decreased significantly with exercise therapy. The exercise improved all parameters of oxidative stress and antioxidant parameters. Also, all clinical parameters were improved with exercise. We should focus on oxidative stress in the treatment for fibromyalgia with the main objective of reducing oxidative load.

An intricate relationship between pain and depression: clinical correlates, coactivation factors and therapeutic targets

INTRODUCTION

An apparent clinical relationship between pain and depression has long been recognized, which makes an enormous impact on the individual health care. At present, the practical implication of such overlapping symptomatology between pain and depression is not clear, but the prevalence estimates for depression are substantially inflated among patients with chronic pain and vice versa. This interaction has been labeled as the depression-pain syndrome or depression-pain dyad.

AREAS COVERED

This article discusses the neurobiological substrates and neuroanatomical pathways involved in pain-depression dyad along with newer therapeutic targets.

EXPERT OPINION

Several key themes emerged from our review of the relationship between depression and pain. First, the diagnosis of depression in pain or vice versa is particularly challenging, and the development of better diagnostic framework that involves both pain and depression is particularly required. Secondly, the entwined relationship between pain and depression supports the possibility of common coactivating factors that results in their neurophysiological overlap. A broad understanding of the role played by the central nervous system (CNS) in the processing of pain and depression may eventually lead to the introduction of triple reuptake inhibitors, agomelatine, vilazodone and ketamine with novel mechanism of action, hence appear to be of promising potential for pain with depression.

Possible involvement of oxido-nitrosative stress induced neuro-inflammatory cascade and monoaminergic pathway: underpinning the correlation between nociceptive and depressive behaviour in a rodent model

BACKGROUND

Pain and depression are frequent co-morbid disorders. The prevalence rate of depression is several times higher in patients with chronic pain than in the general population but the mechanism underlying this association is unknown. A combination of interactions between neurotransmitters, neuropeptides, oxidative and nitrosative stress and cytokines are thought to take part in pathogenesis of pain as well as depression. Thus, the aim of the present study was two-fold, first to investigate the interplay between nociception and associated depression and second to investigate the protective potential of berberine against the reserpine-induced nociceptive and depressive behaviour and further to explore the role of oxidative-nitrosative stress mediated inflammatory cascade and apoptotic signalling pathway in this dyad.

METHODS AND RESULTS

Nociception and associated depression were induced by administration of reserpine (1mg/kg subcutaneous daily) for three consecutive days. This behavioural deficit was integrated with decrease in the biogenic amine (dopamine, norepinephrine and serotonin) levels along with increased substance P concentration, oxidative-nitrosative stress, inflammatory cytokines, NF-κβ and caspase-3 levels in different brain regions (cortex and hippocampus) of the reserpinised rats.

LIMITATION

More studies are still warranted in similar rodent models of pain and depression, so, that the present findings can be further substantiated to establish the clinical effectiveness of berberine in a subset of patients suffering from pain as well as depression.

CONCLUSION

The findings from the current study suggested that reserpine-induced neurochemical alterations and dysregulation of oxidative-nitrosative stress induced inflammatory cascade underlies the co-morbidity of nociceptive behaviour and associated depression in rats.

Excessive peptidergic sensory innervation of cutaneous arteriole-venule shunts (AVS) in the palmar glabrous skin of fibromyalgia patients: implications for widespread deep tissue pain and fatigue

OBJECTIVE

To determine if peripheral neuropathology exists among the innervation of cutaneous arterioles and arteriole-venule shunts (AVS) in fibromyalgia (FM) patients.

SETTING

Cutaneous arterioles and AVS receive a convergence of vasoconstrictive sympathetic innervation, and vasodilatory small-fiber sensory innervation. Given our previous findings of peripheral pathologies in chronic pain conditions, we hypothesized that this vascular location may be a potential site of pathology and/or serotonergic and norepinephrine reuptake inhibitors (SNRI) drug action.

SUBJECTS

Twenty-four female FM patients and nine female healthy control subjects were enrolled for study, with 14 additional female control subjects included from previous studies. AVS were identified in hypothenar skin biopsies from 18/24 FM patient and 14/23 control subjects.

METHODS

Multimolecular immunocytochemistry to assess different types of cutaneous innervation in 3 mm skin biopsies from glabrous hypothenar and trapezius regions.

RESULTS

AVS had significantly increased innervation among FM patients. The excessive innervation consisted of a greater proportion of vasodilatory sensory fibers, compared with vasoconstrictive sympathetic fibers. In contrast, sensory and sympathetic innervation to arterioles remained normal. Importantly, the sensory fibers express α2C receptors, indicating that the sympathetic innervation exerts an inhibitory modulation of sensory activity.

CONCLUSIONS

The excessive sensory innervation to the glabrous skin AVS is a likely source of severe pain and tenderness in the hands of FM patients. Importantly, glabrous AVS regulate blood flow to the skin in humans for thermoregulation and to other tissues such as skeletal muscle during periods of increased metabolic demand. Therefore, blood flow dysregulation as a result of excessive innervation to AVS would likely contribute to the widespread deep pain and fatigue of FM. SNRI compounds may provide partial therapeutic benefit by enhancing the impact of sympathetically mediated inhibitory modulation of the excess sensory innervation.

A bloodspot-based diagnostic test for fibromyalgia syndrome and related disorders

The aim of this study was to investigate the ability of a rapid biomarker-based method for diagnosis of fibromyalgia syndrome (FM) using mid-infrared microspectroscopy (IRMS) to differentiate patients with FM from those with osteoarthritis (OA) and rheumatoid arthritis (RA), and to identify molecular species associated with the spectral patterns. Under IRB approval, blood samples were collected from patients diagnosed with FM (n = 14), RA (n = 15), or OA (n = 12). Samples were prepared, placed onto a highly reflective slide, and spectra were collected using IRMS. Spectra were analyzed using multivariate statistical modeling to differentiate groups. Aliquots of samples also were subjected to metabolomic analysis. IRMS separated subjects into classes based on spectral information with no misclassifications among FM and RA or OA patients. Interclass distances of 15.4 (FM vs. RA), 14.7 (FM vs. OA) and 2.5 (RA vs. OA) among subjects, demonstrating the ability of IRMS to achieve reliable resolution of unique spectral patterns specific to FM. Metabolomic analysis revealed that RA and OA groups were metabolically similar, whereas biochemical differences were identified in the FM that were quite distinctive from those found in the other two groups. Both IRMS and metabolomic analysis identified changes in tryptophan catabolism pathway that differentiated patients with FM from those with RA or OA.

Association of Guanosine Triphosphate Cyclohydrolase 1 Gene Polymorphisms with Fibromyalgia Syndrome in a Korean Population

Objective.

Guanosine triphosphate cyclohydrolase 1 (GCH1) is the rate-limiting enzyme in the synthesis of tetrahydrobiopterin, which is an essential cofactor in nitric oxide (NO) production. Polymorphisms in theGCH1gene have been implicated in protection against pain sensitivity. The aim of our study was to determine whether single-nucleotide polymorphisms (SNP) in theGCH1gene affect susceptibility and/or pain sensitivity in fibromyalgia syndrome (FM).

Methods.

A total of 409 patients with FM and 422 controls were enrolled. The alleles and genotypes at 4 positions [rs3783641(T>A), rs841(C>T), rs752688(C>T), and rs4411417(T>C)] in theGCH1gene were analyzed. The associations of theGCH1SNP with susceptibility and clinical measures in patients with FM were assessed.

Results.

The frequencies of alleles and genotypes of the 4 SNP did not differ between patients with FM and healthy controls. Among 13 constructed haplotypes, we further examined 4 (CCTT, TTCT, TTCA, and CCTA) with > 1% frequency in both FM and controls. No associations ofGCH1polymorphisms with FM-related activity or severity indexes were found, although the number and total score of tender points in patients with FM differed among the 4 haplotypes (p = 0.03 and p = 0.01, respectively). The CCTA haplotype ofGCH1was associated with significantly lower pain sensitivity and occurred less frequently than the CCTT haplotype in patients with FM (p = 0.04, OR 0.45, 95% CI 0.21–0.96).

Conclusion.

Our study provides evidence that certainGCH1haplotypes may be protective against susceptibility and pain sensitivity in FM. Our data suggest that NO is responsible for pain sensitivity in the pathogenesis of FM.