Lymphocyte markers and natural killer cell activity in fibromyalgia syndrome: effects of low-dose, sublingual use of human interferon-alpha

Inflammation, Autoimmunity, and Infection in Fibromyalgia: A Narrative Review

Fibromyalgia (FM) is a chronic disease characterized by widespread musculoskeletal pain of unknown etiology. The condition is commonly associated with other symptoms, including fatigue, sleep disturbances, cognitive impairment, and depression. For this reason, FM is also referred to as FM syndrome. The nature of the pain is defined as nociplastic according to the latest international classification and is characterized by altered nervous sensitization both centrally and peripherally. Psychosocial conditions have traditionally been considered critical in the genesis of FM. However, recent studies in animal models and humans have provided new evidence in favor of an inflammatory and/or autoimmune pathogenesis. In support of this hypothesis are epidemiological data of an increased female prevalence, similar to that of autoimmune diseases, and the frequent association with immune-mediated inflammatory disorders. In addition, the observation of an increased incidence of this condition during long COVID revived the hypothesis of an infectious pathogenesis. This narrative review will, therefore, discuss the evidence supporting the immune-mediated pathogenesis of FM in light of the most current data available in the literature.

The widespread myofascial pain of fibromyalgia is sympathetically maintained and immune mediated

The recent demonstration of antibody-induced passive transfer of pain hypersensitivity from fibromyalgia (FM) subjects to mice brings renewed focus to the role of the immune system in generating FM pain. However, this data must be interpreted in the context of known myofascial pathology in FM, which includes impaired muscle relaxation and elevated intramuscular pressure. In addition, FM fascial biopsies demonstrate elevated inflammatory and oxidative stress markers and increased endomysial collagen deposition. This article proposes a unifying hypothesis for FM pain generation that connects known muscle and fascia abnormalities with the newly discovered role of antibodies. FM is characterized by persistent sympathetic nervous system hyperactivity which results in both pathologic muscle tension and an impaired tissue healing response. Although autoantibodies play a key role in normal tissue healing, sympathetic nervous system hyperactivity impairs the resolution of inflammation, and promotes autoimmunity and excessive autoantibody production. These autoantibodies can then bind with myofascial-derived antigen to create immune complexes, which are known to trigger neuronal hyperexcitability in the dorsal root ganglion. These hyperexcited sensory neurons activate the surrounding satellite glial cells and spinal microglia leading to pain hypersensitivity and central sensitization. Although immune system modulation may become an important treatment tool in FM, direct manual treatments that lessen myofascial inflammation and tension must not be neglected. Myofascial release therapy significantly reduces FM pain, with residual benefits even after the conclusion of treatment. Self-myofascial release techniques and gentle stretching programs also ease fibromyalgia pain, as do trigger point injections and dry-needling.

Unbiased immune profiling reveals a natural killer cell-peripheral nerve axis in fibromyalgia

ABSTRACT

The pathophysiology of fibromyalgia syndrome (FMS) remains elusive, leading to a lack of objective diagnostic criteria and targeted treatment. We globally evaluated immune system changes in FMS by conducting multiparametric flow cytometry analyses of peripheral blood mononuclear cells and identified a natural killer (NK) cell decrease in patients with FMS. Circulating NK cells in FMS were exhausted yet activated, evidenced by lower surface expression of CD16, CD96, and CD226 and more CD107a and TIGIT. These NK cells were hyperresponsive, with increased CCL4 production and expression of CD107a when co-cultured with human leukocyte antigen null target cells. Genetic and transcriptomic pathway analyses identified significant enrichment of cell activation pathways in FMS driven by NK cells. Skin biopsies showed increased expression of NK activation ligand, unique long 16-binding protein, on subepidermal nerves of patients FMS and the presence of NK cells near peripheral nerves. Collectively, our results suggest that chronic activation and redistribution of circulating NK cells to the peripheral nerves contribute to the immunopathology associated with FMS.

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

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

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

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

AG. Persistent Catechol-O-methyltransferase-dependent Pain Is Initiated by Peripheral β-Adrenergic Receptors

BACKGROUND

Patients with chronic pain disorders exhibit increased levels of catecholamines alongside diminished activity of catechol-O-methyltransferase (COMT), an enzyme that metabolizes catecholamines. The authors found that acute pharmacologic inhibition of COMT in rodents produces hypersensitivity to mechanical and thermal stimuli via β-adrenergic receptor (βAR) activation. The contribution of distinct βAR populations to the development of persistent pain linked to abnormalities in catecholamine signaling requires further investigation.

METHODS

Here, the authors sought to determine the contribution of peripheral, spinal, and supraspinal βARs to persistent COMT-dependent pain. They implanted osmotic pumps to deliver the COMT inhibitor OR486 (Tocris, USA) for 2 weeks. Behavioral responses to mechanical and thermal stimuli were evaluated before and every other day after pump implantation. The site of action was evaluated in adrenalectomized rats receiving sustained OR486 or in intact rats receiving sustained βAR antagonists peripherally, spinally, or supraspinally alongside OR486.

RESULTS

The authors found that male (N = 6) and female (N = 6) rats receiving sustained OR486 exhibited decreased paw withdrawal thresholds (control 5.74 ± 0.24 vs. OR486 1.54 ± 0.08, mean ± SEM) and increased paw withdrawal frequency to mechanical stimuli (control 4.80 ± 0.22 vs. OR486 8.10 ± 0.13) and decreased paw withdrawal latency to thermal heat (control 9.69 ± 0.23 vs. OR486 5.91 ± 0.11). In contrast, adrenalectomized rats (N = 12) failed to develop OR486-induced hypersensitivity. Furthermore, peripheral (N = 9), but not spinal (N = 4) or supraspinal (N = 4), administration of the nonselective βAR antagonist propranolol, the β2AR antagonist ICI-118,511, or the β3AR antagonist SR59230A blocked the development of OR486-induced hypersensitivity.

CONCLUSIONS

Peripheral adrenergic input is necessary for the development of persistent COMT-dependent pain, and peripherally-acting βAR antagonists may benefit chronic pain patients.

Screening NK-, B- and T-cell phenotype and function in patients suffering from Chronic Fatigue Syndrome

BACKGROUND

Chronic Fatigue Syndrome (CFS) is a debilitating neuro-immune disorder of unknown etiology diagnosed by an array of clinical manifestations. Although several immunological abnormalities have been described in CFS, their heterogeneity has limited diagnostic applicability.

METHODS

Immunological features of CFS were screened in 22 CFS diagnosed individuals fulfilling Fukuda criteria and 30 control healthy individuals. Peripheral blood T, B and NK cell function and phenotype were analyzed by flow cytometry in both groups.

RESULTS

CFS diagnosed individuals showed similar absolute numbers of T, B and NK cells, with minor differences in the percentage of CD4+ and CD8+ T cells. B cells showed similar subset frequencies and proliferative responses between groups. Conversely, significant differences were observed in T cell subsets. CFS individuals showed increased levels of T regulatory cells (CD25+/FOXP3+) CD4 T cells, and lower proliferative responses in vitro and in vivo. Moreover, CD8 T cells from the CFS group showed significantly lower activation and frequency of effector memory cells. No clear signs of T-cell immunosenescence were observed. NK cells from CFS individuals displayed higher expression of NKp46 and CD69 but lower expression of CD25 in all NK subsets defined. Overall, T cell and NK cell features clearly clustered CFS individuals.

CONCLUSIONS

Our findings suggest that alterations in T-cell phenotype and proliferative response along with the specific signature of NK cell phenotype may be useful to identify CFS individuals. The striking down modulation of T cell mediated immunity may help to understand intercurrent viral infections in CFS.

May genetic factors in fibromyalgia help to identify patients with differentially altered frequencies of immune cells?

There is common agreement that fibromyalgia (FM) is an extremely heterogeneous entity. Patients differ in their clinical symptoms, endocrine and immune parameters. In this study we evaluated endocrine and immunological features of distinct subsets of FM patients. In contrast to previous attempts to identify subsets of FM patients, based solely on their psychological and cognitive features, herein we propose to separate FM patients by genetic features. Allelic expression of the polymorphic promoter region of the serotonin transporter (5-HTTLPR) was analysed as a relevant genetic factor for FM. Seventy-five patients meeting the American College of Rheumatology criteria and 27 healthy age-matched controls participated in this study. All controls and FM patients were submitted to genotyping of 5-HTTLPR. Twenty-seven FM patients, who were able to discontinue hypnotic, sedative or psychotropic prescription medications for at least 2 weeks, were then subdivided into L (homozygote LL) or S groups (genotypes LS and SS). They were evaluated for salivary cortisol levels, absolute number of leucocyte subpopulations, including natural killer (NK) cells and activated T and B lymphocytes. Both groups presented decreased cortisol levels, more intense in the L group, increased all B lymphocytes subsets and reduced CD4+CD25high T lymphocytes. The L group had increased CD4+CD25low activated T lymphocytes, while the S group displayed elevated CD4+ human leucocyte antigen D-related (HLA-DR)+ activated T lymphocytes and decreased NK cells. We demonstrate that genetic factors may help to identify FM individuals with differentially altered frequencies of immune cells.

Adhesion molecules and cytokine expression in fibromyalgia patients: increased L-selectin on monocytes and neutrophils

Several lines of evidence implicate the immune system in the pathophysiology of fibromyalgia (FM). We investigated the role of cytokines and adhesion molecules involved in immune cell trafficking and the influence of 1.5 mg of dexamethasone (DEX) per os on their expression. L-selectin was elevated on monocytes and neutrophils of FM patients. Differences in group response to DEX were observed for CD11b on NK cells, sICAM-1 and IL-2. This study shows a slight disturbance in the innate immune system of FM patients, and suggests an enhanced adhesion and recruitment of leukocytes to inflammatory sites.

Clinical utility of 2',5'-oligoadenylate synthetase activity measurement: using whole blood as a highly sensitive method to detect the effects of IFN

Research progress on the pleiotropic effects of interferons (IFN) has thus far required detecting responses by weak IFN signals. The activity of 2',5'-oligoadenylate synthetase (2-5OAS) is a valuable indicator in the prognosis and IFN treatment of patients with viral diseases such as hepatitis B and C. Although serum samples generally are used to measure enzyme activity, their values depend on the exact conditions under which blood is stored and the degree of haemolysis that occurs during blood drawing or serum separation. This study presents an improved method of evaluating 2-5OAS activity by using whole blood samples containing heparin, which are frozen and then thawed, instead of serum samples. This method is more reliable, convenient, and 50-100 times more sensitive than the conventional methods of measuring serum 2-5OAS activity. The reliability and sensitivity of this improved method enables detection of the effects of low doses of oral IFN administration or changes in the IFN and cytokine system by infection or autoimmune diseases.

Pain, psychological variables, sleep quality, and natural killer cell activity in midlife women with and without fibromyalgia

In women with fibromyalgia (FM), central nervous system (CNS) dysfunction in pain, mood, and sleep processes could be associated with changes in immune system indicators. The primary purpose of this study was to compare pain, psychological variables, subjective and objective sleep quality, lymphocyte phenotypes and activation markers, and natural killer activity (NKA) in midlife women with and without FM. A secondary purpose was to explore relationships among these variables in a step-wise regression. Subjects had pain pressure tender points assessed, completed a psychiatric interview and questionnaires (Beck Depression Inventory, SCL-90, Profile of Mood States, subjective sleep), and underwent polysomnograhic assessment for two consecutive nights. Lymphocyte phenotypes, activation markers, and NKA were assessed from blood drawn the morning after sleep laboratory night 2. Compared to controls, women with FM had lower pain thresholds, more psychological distress, higher depression scores, and reduced subjective and objective sleep quality. They also had fewer NK cells (p <.009) and more NK cells that expressed the IL-2 receptor (p <.04), but these differences were not statistically significant after correction for multiple comparisons. NKA was not statistically significantly lower in the women with FM compared to controls. In a multiple regression of age, tender point threshold, depression, psychological distress, and sleep efficiency, only the effect of group was significant (F = 5.479, p <.03) on NKA. In conclusion, we found little evidence to support the hypothesis that pain, mood, and sleep symptoms are associated with changes in the enumeration of peripheral lymphocytes or function in FM.

Neuroendocrine and immune aspects of fibromyalgia

Fibromyalgia is a form of non-articular rheumatism characterised by long term (>3 months) and widespread musculoskeletal aching, stiffness and pressure hyperalgesia at characteristic soft tissue sites, called soft tissue tender points. The biophysiology of fibromyalgia, however, has remained elusive and the treatment remains mainly empirical. This article reviews the neuroendocrine-immune pathophysiology of fibromyalgia. There is no major evidence that fibromyalgia is accompanied by activation of the inflammatory response system, by immune activation or by an inflammatory process. There is some evidence that fibromyalgia is accompanied by some signs of immunosuppression, suggesting that immunomodifying drugs could have potential in the treatment of fibromyalgia. Recent trials with cytokines, such as interferon-alpha, have been undertaken in patients with fibromyalgia. Immunotherapy with these agents, however, may induce symptoms reminiscent of fibromyalgia and depression in a considerable number of patients. Lowered serum activity of prolyl endopeptidase (PEP), a cytosolic endopeptidase that cleaves peptide bonds on the carboxyl side of proline in proteins of relatively small molecular mass, may play a role in the biophysiology of fibromyalgia through diminished inactivation of algesic and depression-related peptides, e.g. substance P. Trials with PEP agonists could be worthwhile in fibromyalgia. The muscle energy depletion hypothesis of fibromyalgia is supported by findings that this condition is accompanied by lowered plasma levels of branched chain amino acids (BCAAs), i.e. valine, leucine and isoleucine. Since there is evidence that BCAA supplementation decreases muscle catabolism and has ergogenic values, a supplemental trial with BCAAs in fibromyalgia appears to be justified.