Schwann cell TRPA1 elicits reserpine-induced fibromyalgia pain in mice.

BACKGROUND AND PURPOSE: Fibromyalgia is a complex clinical disorder with an unknown aetiology, characterized by generalized pain and co-morbid symptoms such as anxiety and depression. An imbalance of oxidants and antioxidants is proposed to play a pivotal role in the pathogenesis of fibromyalgia symptoms. However, the precise mechanisms by which oxidative stress contributes to fibromyalgia-induced pain remain unclear. The transient receptor potential ankyrin 1 (TRPA1) channel, known as both a pain sensor and an oxidative stress sensor, has been implicated in various painful conditions. EXPERIMENTAL APPROACH: The feed-forward mechanism that implicates reactive oxygen species (ROS) driven by TRPA1 was investigated in a reserpine-induced fibromyalgia model in C57BL/6J mice employing pharmacological interventions and genetic approaches. KEY RESULTS: Reserpine-treated mice developed pain-like behaviours (mechanical/cold hypersensitivity) and early anxiety-depressive-like disorders, accompanied by increased levels of oxidative stress markers in the sciatic nerve tissues. These effects were not observed upon pharmacological blockade or global genetic deletion of the TRPA1 channel and macrophage depletion. Furthermore, we demonstrated that selective silencing of TRPA1 in Schwann cells reduced reserpine-induced neuroinflammation (NADPH oxidase 1-dependent ROS generation and macrophage increase in the sciatic nerve) and attenuated fibromyalgia-like behaviours. CONCLUSION AND IMPLICATIONS: Activated Schwann cells expressing TRPA1 promote an intracellular pathway culminating in the release of ROS and recruitment of macrophages in the mouse sciatic nerve. These cellular and molecular events sustain mechanical and cold hypersensitivity in the reserpine-evoked fibromyalgia model. Targeting TRPA1 channels on Schwann cells could offer a novel therapeutic approach for managing fibromyalgia-related behaviours.

Involvement of peripheral mast cells in a fibromyalgia model in mice.

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

Physical activity level and physical fitness in subjects with chronic musculoskeletal pain: a cross-sectional study.

Background: Low physical activity (PA) levels and low physical fitness (PF) have been reported in subjects with temporality-based chronic pain; however, it is unknown whether there are differences in subjects with nociplastic pain (NP) compared with subjects with non-nociplastic pain (NNP). Objective: The aim was to compare the levels of PA and PF in patients with chronic, nociplastic, and non-nociplastic musculoskeletal pain. Methods: This is an analytical, cross-sectional study. The sample comprised 30 patients receiving ambulatory physiotherapy treatment. Pain was classified as NP or NNP according to the International Association for the Study of Pain categorization system. The PA level was measured with the International Physical Activity Questionnaire-Short Form, and the PF level was measured with the hand grip strength test (HGS) to assess upper limb strength, the five Repetition Sit-to-Stand Test (5R-SRTS) to assess lower limb strength and power, and the YMCA 3 Min Step Test (YMCA-3MST) to estimate peak VO2. The results were compared with independent samples t-tests (with p < 0.05 considered significant). Cohen's d was calculated to determine the effect size. Results: The NP group reported a significantly lower PA level than the NNP group, specifically the vigorous PA (p = 0.0009), moderate PA (p = 0.0002), and total PA (p = 0.005) dimensions. The NP group also showed significantly lower 5R-STS (p = 0.000) and HGS (p = 0.002) results compared with the NNP group. There were no significant differences in the YMCA-3MST between the NP and NNP groups (p = 0.635). Conclusion: It is possible that the neurophysiological and neuromuscular changes related to NP are associated with a reduced ability to perform vigorous PA. Clinicians should identify the presence of NP comorbidities in conjunction with the diagnosis when establishing the therapeutic goals.

Kinins and their B1 and B2 receptors as potential therapeutic targets for pain relief.

Kinins are endogenous peptides that belong to the kallikrein-kinin system, which has been extensively studied for over a century. Their essential role in multiple physiological and pathological processes is demonstrated by activating two transmembrane G-protein-coupled receptors, the kinin B1 and B2 receptors. The attention is mainly given to the pathological role of kinins in pain transduction mechanisms. In the past years, a wide range of preclinical studies has amounted to the literature reinforcing the need for an updated review about the participation of kinins and their receptors in pain disorders. Here, we performed an extensive literature search since 2004, describing the historical progress and the current understanding of the kinin receptors' participation and its potential therapeutic in several acute and chronic painful conditions. These include inflammatory (mainly arthritis), neuropathic (caused by different aetiologies, such as cancer, multiple sclerosis, antineoplastic toxicity and diabetes) and nociplastic (mainly fibromyalgia) pain. Moreover, we highlighted the pharmacological actions and possible clinical applications of the kinin B1 and B2 receptor antagonists, kallikrein inhibitors or kallikrein-kinin system signalling pathways-target molecules in these different painful conditions. Notably, recent findings sought to elucidate mechanisms for guiding new and better drug design targeting kinin B1 and B2 receptors to treat a disease diversity. Since the kinin B2 receptor antagonist, Icatibant, is clinically used and well-tolerated by patients with hereditary angioedema gives us hope kinin receptors antagonists could be more robustly tested for a possible clinical application in the treatment of pathological pains, which present limited pharmacology management.

Practical aspects of the use of medicinal cannabis in chronic pain / Aspectos práticos do uso da cannabis medicinal em dor crônica

ABSTRACT BACKGROUND AND OBJECTIVES: Evidence has revealed an important role in the use of medical cannabis, and the interaction of the endocannabinoid system with other drugs for the treatment of chronic neuropathic and nociplastic pain. The objective of this review is to bring an update on published data on doses and care with the use of cannabinoids that demonstrate the interaction in the pathophysiology of chronic pain and its treatment. CONTENTS: A research-based review was carried out in the MEDLINE, PUBMED database using the keywords "cannabis and pain", "endocannabinoid"; "neuropathic pain"; "nociplastic pain"; "drug interactions". CONCLUSION: Drug interaction with cannabinoids requires further scientific knowledge and doses are individual, which makes it difficult to create a protocol for treatment.

RESUMO JUSTIFICATIVA E OBJETIVOS: As evidências têm revelado um papel importante sobre o uso da cannabis medicinal e da interação do sistema endocanabinoide com outros fármacos para o tratamento de dor crônica neuropática e nociplástica. O objetivo deste estudo foi prover atualização sobre os dados publicados quanto a doses e cuidados com o uso dos canabinoides que mostrem interação na fisiopatologia da dor crônica e seu tratamento. CONTEÚDO: Foi realizada uma revisão baseada em pesquisa na base de dados Medline, Pubmed com uso dos unitermos "cannabis e dor", "endocannabinoid", "neuropathic pain", "nociplastic pain" e "drug interactions". CONCLUSÃO: A interação farmacológica com os canabinoides requer aprofundamento do conhecimento científico e as doses são individuais, o que dificulta a criação de um protocolo para tratamento.

Retrograde inhibition of hyperactive central pathways in nociplastic pain / Inibição retrógrada das vias centrais hiperativas nas dores nociplásticas

ABSTRACT BACKGROUND AND OBJECTIVES: Nociplastic pain occurs due to a combination of hyperexcitability and decreased inhibitory activity in the central nervous system, responsible for a state of amplification of different stimuli, present in many chronic disorders. Among them: fibromyalgia, chronic migraine, irritable bowel syndrome, myofascial pain syndrome and complex regional pain syndrome. Often, several of these diseases are associated. Nociplastic pain therapy is a challenge in clinical practice, since most traditional treatments are not effective in controlling symptoms, often causing difficulty in adherence or even interruption of treatment due to undesirable adverse effects. The objective of this article was to demonstrate the importance of identifying the presence of nociplastic pain in the patient's condition, and also the pathophysiological mechanisms involved. Thus, due to retrograde neuromodulation, a unique feature of the endocannabinoid system until now, evaluate the use of pharmaceutical grade medicines based on the cannabis plant as an adjunct in the therapy of pain and other symptoms associated with this disorder. CONTENTS: This article was addressed the pathophysiology of nociplastic pain, the physiology to the endocannabinoid system, the cannabis plant with its components and its use as an adjuvant medication in the multimodal treatment of nociplastic pain (due to retrograde neuromodulation), based on published scientific articles between 1981 and 2022. CONCLUSION: Although the scientific evidence supporting the use of medical cannabis in nociplastic pain therapy is insufficient so far, it can and should be considered as a possible adjuvant medication in multimodal pain therapy, always on an individual basis, when recommended treatments fail or are not tolerated.

RESUMO JUSTIFICATIVA E OBJETIVOS: A dor nociplástica ocorre por uma combinação de hiperexcitabilidade e diminuição da atividade inibitória no sistema nervoso central, responsável por um estado de amplificação de estímulos diversos, presente em muitas doenças crônicas. Entre essas doenças estão: fibromialgia, migrânea crônica, síndrome do intestino irritável, síndrome dolorosa miofascial e síndrome de dor complexa regional. Frequentemente, várias dessas doenças se apresentam associadas. A terapia da dor nociplástica é um desafio na prática clínica, uma vez que a maioria dos tratamentos tradicionais não são eficazes no controle dos sintomas, causando muitas vezes dificuldade de adesão ou até mesmo interrupção do tratamento, devido aos efeitos adversos indesejáveis. O objetivo deste artigo foi demonstrar a importância da identificação da presença da dor nociplástica no quadro do paciente, e do conhecimento dos mecanismos fisiopatológicos envolvidos. Dessa forma, devido à neuromodulação retrógrada, característica exclusiva do sistema endocanabinoide até o momento, avaliar a utilização de fármacos de grau farmacêutico à base da planta cannabis como coadjuvante na terapia da dor e dos outros sintomas associados a essa doença. CONTEÚDO: Este artigo abordou a fisiopatologia da dor nociplástica, a fisiologia do sistema endocanabinoide, a planta cannabis com seus componentes e sua utilização como medicação coadjuvante no tratamento multimodal da dor nociplástica (decorrente da neuromodulação retrógrada), com base em artigos científicos publicados entre 1981 e 2022. CONCLUSÃO: Apesar das evidências científicas que apoiam o uso da cannabis medicinal na terapia da dor nociplástica serem insuficientes até o momento, ela pode e deve ser considerada como um possível fármaco coadjuvante na terapia multimodal da dor, sempre de forma individualizada, quando os tratamentos preconizados falharem ou não forem tolerados.

Fibromialgia e disfunção temporomandibular: uma revisão de escopo / Fibromyalgia and temporomandibular disorder: a scoping review

A fibromialgia é uma síndrome complexa com alterações nociplásticas, caracterizadas por hiperalgesia e alodinia, frequentemente acompanhada pela presença de dor orofacial. Estudos têm demonstrado alta prevalência de disfunção temporomandibular (DTM) em pacientes fibromiálgicos, como fator etiológico ou agravante. O objetivo desta revisão de literatura foi identificar os mecanismos modulatórios comuns à fibromialgia e à DTM, e identificar diferentes modalidades de tratamento para os pacientes fibromiálgicos. Foram utilizados 69 artigos dos últimos 5 anos, além de 4 artigos conceituais anteriores a este período. Identificou-se que os principais fármacos utilizados para os sintomas de fibromialgia são pregabalina, amitriptilina, antidepressivos duais, tramadol, baixas doses de naltrexona e canabinoides. A associação de fármacos pode ser útil para aumentar a eficácia do tratamento e reduzir as doses dos mesmos. Por outro lado, novas terapias não farmacológicas, como as técnicas modulatórias não-invasivas, surgem como opções promissoras, promovendo alterações neuroplásticas importantes no tratamento. Conclusão: Há diversas opções terapêuticas farmacológicas e não-farmacológicas disponíveis no tratamento do paciente fibromiálgico para o especialista em DTM. Portanto, a combinação de diferentes abordagens pode auxiliar na obtenção de um protocolo individualizado, adequado às necessidades do paciente.

Fibromyalgia is a complex syndrome with nociplastic changes, characterized by hyperalgesia and allodynia, often accompanied by the presence of orofacial pain. Studies have shown a high prevalence of temporomandibular disorders (TMD) in fibromyalgia patients, as an etiological or aggravating factor. The aim of this review was to identify the modulatory mechanisms common to fibromyalgia and TMD, and to identify different treatment modalities for fibromyalgia patients. 69 articles from the last five years were included, in addition to 4 conceptual articles prior to this date. The main drugs used for fibromyalgia symptoms are pregabalin, amitriptyline, dual antidepressants, tramadol, low-dose naltrexone and cannabinoids. The combination of drugs may be useful in improving treatment efficacy and for reducing the drug's dose. On the other hand, new non-pharmacological therapies, such as non-invasive modulatory techniques, appear as promising options for treatment, promoting important neuroplastic alterations. Conclusion: Several pharmacological and non-pharmacological therapeutic alternatives are available for specialists in TMD. Therefore, combining therapy approaches can help create individualized protocols that are more effective at meeting the demands of fibromyalgia patients.

Centralized nociplastic pain causing fibromyalgia: an emperor with no cloths?

The leading school of thought views fibromyalgia as a central sensitization syndrome. Nociplastic pain is the recently proposed term to mechanistically explain central sensitization. Accumulating research suggests an alternate explanation; fibromyalgia can be conceptualized as a neuropathic pain syndrome and dorsal root ganglia (not the brain) as the primary fibromyalgia pain source. There is no need to propose nociplastic pain as new chronic pain mechanism.

Current Challenges in the Management of Chronic Pelvic Pain in Women: From Bench to Bedside.

Chronic pelvic pain (CPP) affects a significant proportion of women worldwide And has a negative impact on several aspects of these women's lives including mental health, work, relationships and sexual function, among others. This set of factors ultimately reflects negatively on quality Of life. The physiopathology of CPP is complex and remains to be fully clarified; however, recent advances have increased understanding of the mechanisms involved in chronic pain in general, and more specifically, CPP. Nonetheless, even when a detailed clinical history is obtained, meticulous physical examination is performed and imaging resources are appropriately used, the organic cause of the pain may still fail to be identified in a substantial number of women with CPP. Management of CPP may therefore be challenging. This narrative review was aimed at adding to the available literature on the subject, presenting and discussing the principal characteristics of CPP in women. The paper highlights gaps in the literature while providing the most up-to-date evidence associated with the physiopathology and classification of pain, its diagnosis and treatment. In addition, current challenges in the management of women with CPP are discussed.

Antihyperalgesic and Antiallodynic Effects of Amarisolide A and Salvia amarissima Ortega in Experimental Fibromyalgia-Type Pain.

Salvia amarissima Ortega is an endemic species of Mexico used in folk medicine to alleviate pain and as a nervous tranquilizer. The S. amarissima extract and one of its abundant metabolites, identified and isolated through chromatographic techniques, were investigated to obtain scientific evidence of its potential effects to relieve nociplastic pain such as fibromyalgia. Then, the extract and amarisolide A (3-300 mg/kg, i.p.) were pharmacologically evaluated in reserpine-induced fibromyalgia-type chronic pain and in depressive-like behavior (as a common comorbidity) by using the forced swimming test in rats. The 5-HT1A serotonin receptor (selective antagonist WAY100635, 1 mg/kg, i.p.) was explored after the prediction of a chemical interaction using in silico analysis to look for a possible mechanism of action of amarisolide A. Both the extract and amarisolide A produced significant and dose-dependent antihyperalgesic and antiallodynic effects in rats, as well as significant antidepressive behavior without sedative effects when the antinociceptive dosages were used. The 5-HT1A serotonin receptor participation was predicted by the in silico descriptors and was corroborated in the presence of WAY100635. In conclusion, S. amarissima possesses antihyperalgesic, antiallodynic, and anti-depressive activities, partially due to the presence of amarisolide A, which involves the 5-HT1A serotonin receptor. This pharmacological evidence suggests that S. amarissima and amarisolide A are both potential alternatives to relieve pain-like fibromyalgia.