Toll-like receptor 2 plays an essential role in electroacupuncture analgesia in a mouse model of inflammatory pain

A systematic review and meta-analysis of acupuncture for De Quervain's tenosynovitis treatment

BACKGROUND

De Quervain's tenosynovitis (DQt) is a prevalent chronic inflammatory musculoskeletal disorder predominantly affecting the radial aspect of the wrist. This study conducted a comprehensive review of the efficacy of acupuncture in treating De Quervain's tenosynovitis (DQt). Although there is evidence suggesting that acupuncture can alleviate symptoms of DQt-characterized by pain, swelling, and functional impairment-higher-level evidence is still required to further substantiate its efficacy and safety. This study conducted a comprehensive review of the efficacy of acupuncture in treating De Quervain's tenosynovitis (DQt).

METHODS

By systematically searching databases such as PubMed, Science Direct, Web of Science, Google Scholar, EMbase, PEDro, China National Knowledge Infrastructure Database (CNKI), Wanfang Database, and Chongqing VIP China Science, Technology Journal Database (VIP), we retrieved randomized controlled trial (RCT) literature on acupuncture for DQt, with the search period extending to November 1, 2023. After extracting and assessing data from the included literature, we performed Meta-analysis using RevMan 5.4.1 software.

RESULTS

The results encompassed 14 RCT papers, involving 851 patients. The Meta-analysis findings indicated that, when compared to topical analgesics, acupuncture demonstrated a significant increase in treatment effectiveness (RR = 1.24; 95% CI = 1.11, 1.39, P = 0.0002) and a notable reduction in VAS pain scores (MD = -1.06; 95% CI = -1.51, -0.61, P < 0.00001). However, no statistically significant difference was observed in conney wrist joint scores. Furthermore, acupuncture was found to reduce VAS pain scores compared to the waiting list group. In comparison to corticosteroid injections (CSI), acupuncture did not show statistical significance in VAS, effectiveness rate, and conney wrist scores.

CONCLUSION

Acupuncture exhibited a promising trend in alleviating pain associated with DQt and enhancing treatment effectiveness. Nonetheless, due to limitations in the quantity and quality of the included studies, these findings warrant further validation through additional research.

Electroacupuncture Reduces Fibromyalgia Pain via Neuronal/Microglial Inactivation and Toll-like Receptor 4 in the Mouse Brain: Precise Interpretation of Chemogenetics

Fibromyalgia (FM) is a complex, chronic, widespread pain syndrome that can cause significant health and economic burden. Emerging evidence has shown that neuroinflammation is an underlying pathological mechanism in FM. Toll-like receptors (TLRs) are key mediators of the immune system. TLR4 is expressed primarily in microglia and regulates downstream signaling pathways, such as MyD88/NF-κB and TRIF/IRF3. It remains unknown whether electroacupuncture (EA) has therapeutic benefit in attenuating FM pain and what role the TLR4 pathway may play in this effect. We compared EA with sham EA to eliminate the placebo effect due to acupuncture. We demonstrated that intermittent cold stress significantly induced an increase in mechanical and thermal FM pain in mice (mechanical: 2.48 ± 0.53 g; thermal: 5.64 ± 0.32 s). EA but not sham EA has an analgesic effect on FM mice. TLR4 and inflammatory mediator-related molecules were increased in the thalamus, medial prefrontal cortex, somatosensory cortex (SSC), and amygdala of FM mice, indicating neuroinflammation and microglial activation. These molecules were reduced by EA but not sham EA. Furthermore, a new chemogenetics method was used to precisely inhibit SSC activity that displayed an anti-nociceptive effect through the TLR4 pathway. Our results imply that the analgesic effect of EA is associated with TLR4 downregulation. We provide novel evidence that EA modulates the TLR4 signaling pathway, revealing potential therapeutic targets for FM pain.

The NLRP3 inflammasome: role in the pathobiology of chronic pain

Chronic pain is not only one of the most common health problems, it is often challenging to treat adequately. Chronic pain has a high prevalence globally, affecting approximately 20% of the adult population. Chronic inflammatory pain and neuropathic (nerve) pain conditions are areas of large unmet medical need because analgesic/adjuvant agents recommended for alleviation of these types of chronic pain often lack efficacy and/or they produce dose-limiting side effects. Recent work has implicated the NLRP3 (NOD-, LRR- and pyrin domain-containing protein 3) inflammasome in the pathobiology of chronic pain, especially neuropathic and inflammatory pain conditions. NLRP3 is activated by damage-associated molecular patterns (DAMPs) and pathogen-associated molecular patterns (PAMPs). This in turn leads to recruitment and activation of caspase-1 an enzyme that cleaves the inactive IL-1β and IL-18 precursors to their respective mature pro-inflammatory cytokines (IL-1β and IL-18) for release into the cellular milieu. Caspase-1 also cleaves the pyroptosis-inducing factor, gasdermin D, that leads to oligomerization of its N-terminal fragment to form pores in the host cell membrane. This then results in cellular swelling, lysis and release of cytoplasmic contents in an inflammatory form of cell death, termed pyroptosis. The ultimate outcome may lead to the development of neuropathic pain and/or chronic inflammatory pain. In this review, we address a role for NLRP3 inflammasome activation in the pathogenesis of various chronic pain conditions.

Efficacy of different acupuncture therapies on postherpetic neuralgia: A Bayesian network meta-analysis

Background

Postherpetic neuralgia (PHN) is a common, complex, and refractory type of neuropathic pain. Several systematic reviews support the efficacy of acupuncture and related treatments for PHN. Nevertheless, the efficacy of various acupuncture-related treatments for PHN remains debatable.

Objective

We aimed to assess the efficacy and safety of acupuncture-related treatments for PHN, identify the most effective acupuncture-related treatments, and expound on the current inadequacies and prospects in the applications of acupuncture-related therapies.

Methods

We searched PubMed, Cochrane Central Register of Controlled Trials, Embase, Web of Science, Google Scholar, four Chinese databases (China National Knowledge Infrastructure, China Biomedical, Chongqing VIP, and Wan Fang databases), clinical research registration platform (World Health Organization International Clinical Trial Registration platform, China Clinical Trial Registration Center) for relevant studies. We also examined previous meta-analyses; gray literature; and reference lists of the selected studies. We then evaluated the risk of bias in the included studies and performed a Bayesian multiple network meta-analysis.

Results

We included 29 randomized controlled trials comprising 1,973 patients, of which five studies showed a high risk of bias. The pairwise meta-analysis results revealed that the efficacy of all acupuncture-related treatments for pain relief related to PHN was significantly better than antiepileptics. The network meta-analysis results showed that pricking and cupping plus antiepileptics were the most effective treatment, followed by electroacupuncture (EA) plus antiepileptics for pain relief in patients with PHN. EA plus antiepileptics ranked the best regarding reduced Pittsburgh Sleep Quality Index (PSQI) and Self-Rating Depression Scale (SDS) scores in patients with PHN. No results were found regarding the total response rate or quality of life in this study. Acupuncture-related treatments showed a lower incidence of adverse events than that of antiepileptics.

Conclusion

Acupuncture-related therapies are potential treatment options for PHN and are safe. Pricking and cupping plus antiepileptics, are the most effective acupuncture-related techniques for pain relief, while EA plus antiepileptics is the best acupuncture-related technique for improving PHN-related insomnia and depression symptoms. However, owing to the limitations of this study, these conclusions should be cautiously interpreted, and future high-quality studies are needed.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021226422, identifier CRD42021226422.

Mechanisms of acupuncture-electroacupuncture on inflammatory pain

Acupuncture, as a traditional treatment, has been extensively used in China for thousands of years. According to the World Health Organization (WHO), acupuncture is recommended for the treatment of 77 diseases. And 16 of these diseases are related to inflammatory pain. As a combination of traditional acupuncture and modern electrotherapy, electroacupuncture (EA) has satisfactory analgesic effects on various acute and chronic pain. Because of its good analgesic effects and no side effects, acupuncture has been widely accepted all over the world. Despite the increase in the number of studies, the mechanisms via which acupuncture exerts its analgesic effects have not been conclusively established. A literature review of related research is of great significance to elaborate on its mechanisms and to inform on further research directions. We elucidated on its mechanisms of action on inflammatory pain from two levels: peripheral and central. It includes the mechanisms of acupuncture in the periphery (immune cells and neurons, purinergic pathway, nociceptive ion channel, cannabinoid receptor and endogenous opioid peptide system) and central nervous system (TPRV1, glutamate and its receptors, glial cells, GABAergic interneurons and signaling molecules). In this review, we collected relevant recent studies to systematically explain the mechanisms of acupuncture in treating inflammatory pain, with a view to providing direction for future applications of acupuncture in inflammatory pain and promoting clinical development.

The crosstalk among TLR2, TLR4 and pathogenic pathways; a treasure trove for treatment of diabetic neuropathy

Diabetes is correlated with organ failures as a consequence of microvascular diabetic complications, including neuropathy, nephropathy, and retinopathy. These difficulties come with serious clinical manifestations and high medical costs. Diabetic neuropathy (DN) is one of the most prevalent diabetes complications, affecting at least 50% of diabetic patients with long disease duration. DN has serious effects on patients' life since it interferes with their daily physical activities and causes psychological comorbidities. There are some potential risk factors for the development of neuropathic injuries. It has been shown that inflammatory mechanisms play a pivotal role in the progression of DN. Among inflammatory players, TLR2 and TLR4 have gained immense importance because of their ability in recognizing distinct molecular patterns of invading pathogens and also damage-associated molecular patterns (DAMPs) providing inflammatory context for the progression of a wide array of disorders. We, therefore, sought to explore the possible role of TLR2 and TLR4 in DN pathogenesis and if whether manipulating TLRs is likely to be successful in fighting off DN.

Toll-Like Receptors (TLRs) and their potential therapeutic applications in diabetic neuropathy

One of the most common diabetic microvascular complications is diabetic neuropathy (DN). Immune cell infiltration in the peripheral nerve system (PNS), myelin loss, Schwann cell death, and axonal damage are all hallmarks of DN, which is currently believed to be a chronic inflammatory disease. Toll-like receptors (TLRs) are found in various types of nervous system cells, including Schwann cells, microglia, oligodendrocytes, astrocytes, and neurons. Proinflammatory mediators released at the end of TLR signal transduction can trigger an inflammatory response involving the nervous system. Studies on the association between TLRs and DN began as early as 2004. Since then, several studies have been conducted to assess the involvement of TLRs in the pathogenesis of DN. The focus of this review is to give a complete summary of the researches that have been done in this context, as well as an overview of the role of TLRs and their therapeutic applications in DN.

Evaluation of electroacupuncture for symptom modification in a rodent model of spontaneous osteoarthritis

OBJECTIVE

Faced with the frustration of chronic discomfort and restricted mobility due to osteoarthritis (OA), many individuals have turned to acupuncture for relief. However, the efficacy of acupuncture for OA is uncertain, as much of the evidence is inconclusive. The purpose of this study was to evaluate electroacupuncture (EA) in a rodent model of OA such that conclusions regarding its effectiveness for symptom or disease modification could be drawn.

METHODS

Ten 12-month-old male Hartley guinea pigs-which characteristically have moderate to advanced OA at this age-were randomly assigned to receive EA for knee OA (n = 5) or anesthesia only (control group, n = 5). Treatments were performed three times weekly for 3 weeks, followed by euthanasia 2 weeks later. Gait analysis and enclosure monitoring were performed weekly to evaluate changes in movement. Serum was collected for inflammatory biomarker testing. Knee joints were collected for histology and gene expression.

RESULTS

Animals receiving EA had significantly greater changes in movement parameters compared to those receiving anesthesia only. There was a tendency toward decreased serum protein concentrations of complement component 3 (C3) in the EA group compared to the control group. Structural and antioxidant gene transcripts in articular cartilage were increased by EA. There was no significant difference in total joint histology scores between groups.

CONCLUSION

This study provides evidence that EA has a positive effect on symptom, but not disease, modification in a rodent model of OA. Further investigations into mechanistic pathways that may explain the efficacy of EA in this animal model are needed.

Role of Neuroimmune Crosstalk in Mediating the Anti-inflammatory and Analgesic Effects of Acupuncture on Inflammatory Pain

Inflammatory pain is caused by peripheral tissue injury and inflammation. Inflammation leads to peripheral sensitization, which may further cause central sensitization, resulting in chronic pain and progressive functional disability. Neuroimmune crosstalk plays an essential role in the development and maintenance of inflammatory pain. Studies in recent years have shown that acupuncture can exert anti-inflammatory and analgesic effects by regulating peripheral (i.e., involving local acupoints and inflamed regions) and central neuroimmune interactions. At the local acupoints, acupuncture can activate the TRPV1 and TRPV2 channels of mast cells, thereby promoting degranulation and the release of histamine, adenosine, and other immune mediators, which interact with receptors on nerve endings and initiate neuroimmune regulation. At sites of inflammation, acupuncture enables the recruitment of immune cells, causing the release of opioid peptides, while also exerting direct analgesic effects via nerve endings. Furthermore, acupuncture promotes the balance of immune cells and regulates the release of inflammatory factors, thereby reducing the stimulation of nociceptive receptors in peripheral organs. Acupuncture also alleviates peripheral neurogenic inflammation by inhibiting the release of substance P (SP) and calcitonin gene-related peptide from the dorsal root ganglia. At the central nervous system level, acupuncture inhibits the crosstalk between glial cells and neurons by inhibiting the p38 MAPK, ERK, and JNK signaling pathways and regulating the release of inflammatory mediators. It also reduces the excitability of the pain pathway by reducing the release of excitatory neurotransmitters and promoting the release of inhibitory neurotransmitters from neurons and glial cells. In conclusion, the regulation of neuroimmune crosstalk at the peripheral and central levels mediates the anti-inflammatory and analgesic effects of acupuncture on inflammatory pain in an integrated manner. These findings provide novel insights enabling the clinical application of acupuncture in the treatment of inflammatory diseases.

The Role of Neuroglial Crosstalk and Synaptic Plasticity-Mediated Central Sensitization in Acupuncture Analgesia

Although pain is regarded as a global public health priority, analgesic therapy remains a significant challenge. Pain is a hypersensitivity state caused by peripheral and central sensitization, with the latter considered the culprit for chronic pain. This study summarizes the pathogenesis of central sensitization from the perspective of neuroglial crosstalk and synaptic plasticity and underlines the related analgesic mechanisms of acupuncture. Central sensitization is modulated by the neurotransmitters and neuropeptides involved in the ascending excitatory pathway and the descending pain modulatory system. Acupuncture analgesia is associated with downregulating glutamate in the ascending excitatory pathway and upregulating opioids, 𝛾-aminobutyric acid, norepinephrine, and 5-hydroxytryptamine in the descending pain modulatory system. Furthermore, it is increasingly appreciated that neurotransmitters, cytokines, and chemokines are implicated in neuroglial crosstalk and associated plasticity, thus contributing to central sensitization. Acupuncture produces its analgesic action by inhibiting cytokines, such as interleukin-1β, interleukin-6, and tumor necrosis factor-α, and upregulating interleukin-10, as well as modulating chemokines and their receptors such as CX3CL1/CX3CR1, CXCL12/CXCR4, CCL2/CCR2, and CXCL1/CXCR2. These factors are regulated by acupuncture through the activation of multiple signaling pathways, including mitogen-activated protein kinase signaling (e.g., the p38, extracellular signal-regulated kinases, and c-Jun-N-terminal kinase pathways), which contribute to the activation of nociceptive neurons. However, the responses of chemokines to acupuncture vary among the types of pain models, acupuncture methods, and stimulation parameters. Thus, the exact mechanisms require future clarification. Taken together, inhibition of central sensitization modulated by neuroglial plasticity is central in acupuncture analgesia, providing a novel insight for the clinical application of acupuncture analgesia.

Botulinum toxin type A alleviates neuropathic pain and suppresses inflammatory cytokines release from microglia by targeting TLR2/MyD88 and SNAP23

BACKGROUND

Botulinum toxin type A (BTX-A) was considered to be a new potential drug for neuropathic pain (NP) treatment.

RESULTS

In vivo, BTX-A attenuated chronic compression injury (CCI)-induced pain in rats, and reduced production of pro-inflammatory factors. The inhibition of BTX-A to expression and phosphorylation of SNAP23 were partly reversed by TLR2/MyD88 upregulation. In LPS-stimulated microglia, we also found that BTX-A suppressed TLR2, MyD88, p-SNAP23 and SNAP23 expression, and reduced pro-inflammatory factors secretion. Upregulation of TLR2 and MyD88 recued the inhibition of BTX-A to LPS-induced activation of SNAP23. Then, we demonstrated that BTX-A reduced expression of SNAP23 through inhibition of IKKα/β phosphorylation. Besides, the inhibition of BTX-A to LPS-induced upregulation of SNAP23 can be reversed by proteasome inhibitor. NEDD4, an E3 ubiquitin ligase, was proved to be bind with SNAP23. BTX-A reduced expression of SNAP23 via facilitating ubiquitin-mediated degradation of SNAP23.

CONCLUSION

Overall, our data demonstrated that BTX-A attenuated NP via reducing the secretion of pro-inflammatory factors from microglia by inhibition of TLR2/MyD88 signaling. BTX-A downregulated expression of SNAP23 via reducing phosphorylation of IKKα/β, and enhancing ubiquitination of SNAP23 by suppressing TLR2/MyD88 signaling.

Effect of Acupuncture on the p38 Signaling Pathway in Several Nervous System Diseases: A Systematic Review

Acupuncture is clinically used to treat various diseases and exerts positive local and systemic effects in several nervous system diseases. Advanced molecular and clinical studies have continually attempted to decipher the mechanisms underlying these effects of acupuncture. While a growing understanding of the pathophysiology underlying several nervous system diseases shows it to be related to inflammation and impair cell regeneration after ischemic events, the relationship between the therapeutic mechanism of acupuncture and the p38 MAPK signal pathway has yet to be elucidated. This review discusses the latest advancements in the identification of the effect of acupuncture on the p38 signaling pathway in several nervous system diseases. We electronically searched databases including PubMed, Embase, and the Cochrane Library from their inception to April 2020, using the following keywords alone or in various combinations: "acupuncture", "p38 MAPK pathway", "signaling", "stress response", "inflammation", "immune", "pain", "analgesic", "cerebral ischemic injury", "epilepsy", "Alzheimer's disease", "Parkinson's disease", "dementia", "degenerative", and "homeostasis". Manual acupuncture and electroacupuncture confer positive therapeutic effects by regulating proinflammatory cytokines, ion channels, scaffold proteins, and transcription factors including TRPV1/4, Nav, BDNF, and NADMR1; consequently, p38 regulates various phenomena including cell communication, remodeling, regeneration, and gene expression. In this review article, we found the most common acupoints for the relief of nervous system disorders including GV20, GV14, ST36, ST37, and LI4. Acupuncture exhibits dual regulatory functions of activating or inhibiting different p38 MAPK pathways, contributing to an overall improvement of clinical symptoms and function in several nervous system diseases.