Tag: peripheral nervous system

Neutrophils infiltrate sensory ganglia and mediate chronic widespread pain in fibromyalgia

Abstract:

Fibromyalgia is a debilitating widespread chronic pain syndrome that occurs in 2 to 4% of the population. The prevailing view that fibromyalgia results from central nervous system dysfunction has recently been challenged with data showing changes in peripheral nervous system activity.

Using a mouse model of chronic widespread pain through hyperalgesic priming of muscle, we show that neutrophils invade sensory ganglia and confer mechanical hypersensitivity on recipient mice, while adoptive transfer of immunoglobulin, serum, lymphocytes, or monocytes has no effect on pain behavior.

Neutrophil depletion abolishes the establishment of chronic widespread pain in mice. Neutrophils from patients with fibromyalgia also confer pain on mice. A link between neutrophil-derived mediators and peripheral nerve sensitization is already established. Our observations suggest approaches for targeting fibromyalgia pain via mechanisms that cause altered neutrophil activity and interactions with sensory neurons.

Source: Caxaria S, Bharde S, Fuller AM, Evans R, Thomas B, Celik P, Dell’Accio F, Yona S, Gilroy D, Voisin MB, Wood JN, Sikandar S. Neutrophils infiltrate sensory ganglia and mediate chronic widespread pain in fibromyalgia. Proc Natl Acad Sci U S A. 2023 Apr 25;120(17):e2211631120. doi: 10.1073/pnas.2211631120. Epub 2023 Apr 18. PMID: 37071676. https://www.pnas.org/doi/10.1073/pnas.2211631120 (Full text)

Prevalence of peripheral neuropathy and myopathy in patients post-COVID-19 infection

Abstract:

Background: Severe acute respiratory syndrome (SARS-CoV-2), caused by the Coronavirus 2019 (COVID-19), has become a life-threatening epidemic, affecting multiple organs, including the nervous system. Recent studies have documented that COVID-19-associated peripheral neuropathy is a common and frequent problem, with central and peripheral nervous system complications.

Objective: This work aims to evaluate the peripheral nerves and muscle involvement after COVID-19 infection, in addition to studying the prevalence rate and risk factors of their affection.

Methods: The study involved 400 patients, divided into 2 groups, with a history of COVID-19 infection with or without symptoms of neuromuscular affection, and 30 gender- and age-matched healthy volunteers were involved as controls. They were referred to the Department of Rheumatology and Rehabilitation for electro-diagnosis. All participants performed complete clinical examination and laboratory measures with an electrophysiological study.

Results: The prevalence of peripheral neuropathy and myopathy in post-COVID-19 patients was 56.3% among all patients. A significant difference was detected among patients of both groups regarding serum creatine phosphokinase level, clinical signs, and electrophysiologic findings of neuropathy and myopathy compared to the control group, with more prominent features among the symptomatic group. Histories of hospitalization, severe and long-lasting respiratory symptoms were risk factors for developing neuromuscular complications.

Conclusions: The present study could indicate that muscle involvement and peripheral nerve affection are common problems even among asymptomatic patients after COVID-19 infection, especially in the presence of any risk factors.

Source: Saif DS, Ibrahem RA, Eltabl MA. Prevalence of peripheral neuropathy and myopathy in patients post-COVID-19 infection. Int J Rheum Dis. 2022 Aug 1. doi: 10.1111/1756-185X.14409. Epub ahead of print. PMID: 35915515. https://onlinelibrary.wiley.com/doi/10.1111/1756-185X.14409 (Full text)

ACE2 and SCARF expression in human dorsal root ganglion nociceptors: implications for SARS-CoV-2 virus neurological effects

Abstract:

SARS-CoV-2 has created a global crisis. COVID-19, the disease caused by the virus, is characterized by pneumonia, respiratory distress, and hypercoagulation and can be fatal. An early sign of infection is loss of smell, taste, and chemesthesis-loss of chemical sensation. Other neurological effects of the disease have been described, but not explained. It is now apparent that many of these neurological effects (for instance joint pain and headache) can persist for at least months after infection, suggesting a sensory neuronal involvement in persistent disease.

We show that human dorsal root ganglion (DRG) neurons express the SARS-CoV-2 receptor, angiotensin-converting enzyme 2 at the RNA and protein level. We also demonstrate that SARS-CoV-2 and coronavirus-associated factors and receptors are broadly expressed in human DRG at the lumbar and thoracic level as assessed by bulk RNA sequencing. ACE2 mRNA is expressed by a subset of nociceptors that express MRGPRD mRNA, suggesting that SARS-CoV-2 may gain access to the nervous system through entry into neurons that form free nerve endings at the outermost layers of skin and luminal organs. Therefore, DRG sensory neurons are a potential target for SARS-CoV-2 invasion of the peripheral nervous system, and viral infection of human nociceptors may cause some of the persistent neurological effects seen in COVID-19.

Source: Shiers S, Ray PR, Wangzhou A, Sankaranarayanan I, Tatsui CE, Rhines LD, Li Y, Uhelski ML, Dougherty PM, Price TJ. ACE2 and SCARF expression in human dorsal root ganglion nociceptors: implications for SARS-CoV-2 virus neurological effects. Pain. 2020 Nov;161(11):2494-2501. doi: 10.1097/j.pain.0000000000002051. PMID: 32826754; PMCID: PMC7572821. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7572821/ (Full text)

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.

Source: Verma V, Drury GL, Parisien M, Özdağ Acarli AN, Al-Aubodah TA, Nijnik A, Wen X, Tugarinov N, Verner M, Klares R 3rd, Linton A, Krock E, Morado Urbina CE, Winsvold B, Fritsche LG, Fors EA, Piccirillo C, Khoutorsky A, Svensson CI, Fitzcharles MA, Ingelmo PM, Bernard NF, Dupuy FP, Üçeyler N, Sommer C, King IL, Meloto CB, Diatchenko L; HUNT-All In Pain. Unbiased immune profiling reveals a natural killer cell-peripheral nerve axis in fibromyalgia. Pain. 2021 Sep 24:10.1097/j.pain.0000000000002498. doi: 10.1097/j.pain.0000000000002498. Epub ahead of print. PMID: 34913882; PMCID: PMC8942876. https://pubmed.ncbi.nlm.nih.gov/34913882/

Neuromuscular strain as a contributor to cognitive and other symptoms in chronic fatigue syndrome: hypothesis and conceptual model

Abstract:

Individuals with chronic fatigue syndrome (CFS) have heightened sensitivity and increased symptoms following various physiologic challenges, such as orthostatic stress, physical exercise, and cognitive challenges. Similar heightened sensitivity to the same stressors in fibromyalgia (FM) has led investigators to propose that these findings reflect a state of central sensitivity.

A large body of evidence supports the concept of central sensitivity in FM. A more modest literature provides partial support for this model in CFS, particularly with regard to pain. Nonetheless, fatigue and cognitive dysfunction have not been explained by the central sensitivity data thus far.

Peripheral factors have attracted attention recently as contributors to central sensitivity. Work by Brieg, Sunderland, and others has emphasized the ability of the nervous system to undergo accommodative changes in length in response to the range of limb and trunk movements carried out during daily activity. If that ability to elongate is impaired-due to movement restrictions in tissues adjacent to nerves, or due to swelling or adhesions within the nerve itself-the result is an increase in mechanical tension within the nerve. This adverse neural tension, also termed neurodynamic dysfunction, is thought to contribute to pain and other symptoms through a variety of mechanisms. These include mechanical sensitization and altered nociceptive signaling, altered proprioception, adverse patterns of muscle recruitment and force of muscle contraction, reduced intra-neural blood flow, and release of inflammatory neuropeptides. Because it is not possible to differentiate completely between adverse neural tension and strain in muscles, fascia, and other soft tissues, we use the more general term “neuromuscular strain.”

In our clinical work, we have found that neuromuscular restrictions are common in CFS, and that many symptoms of CFS can be reproduced by selectively adding neuromuscular strain during the examination. In this paper we submit that neuromuscular strain is a previously unappreciated peripheral source of sensitizing input to the nervous system, and that it contributes to the pathogenesis of CFS symptoms, including cognitive dysfunction.

 

Source: Rowe PC, Fontaine KR, Violand RL. Neuromuscular strain as a contributor to cognitive and other symptoms in chronic fatigue syndrome: hypothesis and conceptual model. Front Physiol. 2013 May 16;4:115. doi: 10.3389/fphys.2013.00115. eCollection 2013.  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3655286/ (Full article)

 

Does varicella-zoster virus infection of the peripheral ganglia cause Chronic Fatigue Syndrome?

Abstract:

This article posits that infection of the peripheral ganglia causes at least some cases of Chronic Fatigue Syndrome (CFS), with a neurotropic herpesvirus, particularly varicella-zoster virus (VZV), as the most likely cause of the infection. Virtually all CFS symptoms could be produced by an infection of the peripheral ganglia, with infection of the autonomic ganglia causing fatigue, postural hypotension, and sleep disturbances, and infection of the sensory ganglia causing sensory symptoms such as chronic pain. Furthermore, infections of the peripheral ganglia are known to cause long-term nerve dysfunction, which would help explain the chronic course of CFS.

Herpesviruses have long been suspected as the cause of CFS; this theory has recently been supported by studies showing that administering antiherpes agents causes substantial improvement in some CFS patients. VZV is known to frequently reactivate in the peripheral ganglia of previously healthy adults and cause sudden, debilitating illness, making it a likely candidate as a cause of CFS. Moreover, many of the symptoms of CFS overlap with those of herpes zoster (shingles), with the exception that painful rash is not one of the symptoms of CFS.

A model is therefore proposed in which CFS is one of the many manifestations of zoster sine herpete; that is, herpes zoster without rash. Furthermore, re-exposure to VZV in the form of chickenpox has become less common in the past few decades; without such re-exposure, immunity to VZV drops, which could explain the increased incidence of CFS. Co-infection with multiple herpesviruses is a possibility, as some CFS patients show signs of infection with other herpesviruses including Epstein-Barr, Cytomegalovirus, and HHV6. These three herpesviruses can attack immune cells, and may therefore promote neurotropic herpesvirus reactivation in the ganglia.

The possibility of VZV as the causal agent in CFS has previously received almost no attention; the possibility that CFS involves infection of the peripheral ganglia has likewise been largely overlooked. This suggests that the search for a viral cause of CFS has been far from exhaustive. Several antiherpes drugs are available, as is a vaccine for VZV; more research into such agents as possible treatments for CFS is urgently needed.

 

Source: Shapiro JS. Does varicella-zoster virus infection of the peripheral ganglia cause Chronic Fatigue Syndrome? Med Hypotheses. 2009 Nov;73(5):728-34. doi: 10.1016/j.mehy.2009.04.043. Epub 2009 Jun 10. https://www.ncbi.nlm.nih.gov/pubmed/19520522

 

Fatigue brought on by malfunction of the central and peripheral nervous systems

Abstract:

Increased fatigability necessarily occurs in every patient with muscle weakness, regardless of whether the latter is due to a central or peripheral neurological disorder. The tendency for disuse to increase fatigability, as a secondary phenomenon, must also be considered; disuse affects both motoneuron recruitment and the biochemical and physiological properties of the muscle fibers. In recent studies impaired recruitment has been observed in postpolio patients, while patients with multiple sclerosis or spinal cord injury have shown, in addition, altered neuromuscular function. Findings are also presented in ALS and the chronic fatigue syndrome. In general, the most dramatic increases in fatigability take place in disorders of the peripheral nervous system and almost any cell component can be incriminated. There is a need to study fatigability systematically in neurology and rehabilitation.

 

Source: McComas AJ, Miller RG, Gandevia SC. Fatigue brought on by malfunction of the central and peripheral nervous systems. Adv Exp Med Biol. 1995;384:495-512. http://www.ncbi.nlm.nih.gov/pubmed/8585475