Acupuncture alleviates chronic pain and comorbid conditions in a mouse model of neuropathic pain: the involvement of DNA methylation in the prefrontal cortex

Brain functional changes following electroacupuncture in a mouse model of comorbid pain and depression: A resting-state functional magnetic resonance imaging study

OBJECTIVE

Comorbid pain and depression are common but remain difficult to treat. Electroacupuncture (EA) can effectively improve symptoms of depression and relieve pain, but its neural mechanism remains unclear. Therefore, we used resting-state functional magnetic resonance imaging (rs-fMRI) to detect cerebral changes after initiating a mouse pain model via constriction of the infraorbital nerve (CION) and then treating these animals with EA.

METHODS

Forty male C57BL/6J mice were divided into 4 groups: control, CION model, EA, and sham acupuncture (without needle insertion). EA was performed on the acupoints Baihui (GV20) and Zusanli (ST36) for 20 min, once a day for 10 consecutive days. The mechanical withdrawal threshold was tested 3 days after the surgery and every 3 days after the intervention. The depressive behavior was evaluated with the tail suspension test, open-field test, elevated plus maze (EPM), sucrose preference test, and marble burying test. The rs-fMRI was used to detect the cerebral changes of the functional connectivity (FC) in the mice following EA treatment.

RESULTS

Compared with the CION group, the mechanical withdrawal threshold increased in the EA group at the end of the intervention (P < 0.05); the immobility time in tail suspension test decreased (P < 0.05); and the times of the open arm entry and the open arm time in the EPM increased (both P < 0.001). There was no difference in the sucrose preference or marble burying tests (both P > 0.05). The fMRI results showed that EA treatment downregulated the amplitude of low-frequency fluctuations and regional homogeneity values, while these indicators were elevated in brain regions including the amygdala, hippocampus and cerebral cortex in the CION model for comorbid pain and depression. Selecting the amygdala as the seed region, we found that the FC was higher in the CION group than in the control group. Meanwhile, EA treatment was able to decrease the FC between the amygdala and other brain regions including the caudate putamen, thalamus, and parts of the cerebral cortex.

CONCLUSION

EA can downregulate the abnormal activation of neurons in the amygdala and improve its FC with other brain regions, thus exerting analgesic and antidepressant effects. Please cite this article as: Yin X, Zeng XL, Lin JJ, Xu WQ, Cui KY, Guo XT, Li W, Xu SF. Brain functional changes following electroacupuncture in a mouse model of comorbid pain and depression: a resting-state functional magnetic resonance imaging study. J Integr Med. 2025; 23(2): 159-168.

Nuclear receptor 4A1 facilitates complete Freund's adjuvant-induced inflammatory pain in rats by promoting ferroptosis in spinal glial cells

Glial cell-induced neuroinflammation in the spinal cord is the critical pathology underlying complete Freund's adjuvant (CFA)-induced inflammatory pain. Previously, we showed that spinal glial cells undergo ferroptosis after CFA injection, which may contribute to the development of neuroinflammation and inflammatory pain. However, the mechanism underlying the occurrence of ferroptosis during inflammatory pain remains unclear. The aim of this study was to investigate the molecular factors involved in the occurrence of ferroptosis during the development of inflammatory pain. Bulk and single-cell RNA sequencing were performed to identify the key genes involved in the ferroptosis of spinal astrocytes, microglia, and oligodendrocytes in rats. We identified nuclear receptor 4A1 (NR4A1) as a common ferroptosis-related gene present in all three types of glial cells. Western blotting and immunostaining revealed increased NR4A1 levels in the spinal glial cells of the CFA-treated rats. Moreover, intrathecal injection of DIM-C-pPhOH (an NR4A1 inhibitor) effectively alleviated mechanical and thermal hypersensitivity in the CFA-treated rats by attenuating ferroptosis and neuroinflammation in spinal glial cells. Proteomic analysis revealed that mitogen-activated protein kinase 3 (MAPK3) may be the target protein of NR4A1. In addition, the combined results of chromatin immunoprecipitation and dual-luciferase assays indicated that NR4A1 can bind to the promoter region and promote transcription of MAPK3, ultimately leading to lipid peroxidation. In conclusion, this study demonstrated that increased expression of NR4A1 promotes the progression of CFA-induced inflammatory pain by enhancing ferroptosis through the transcriptional activation of MAPK3 and subsequent lipid peroxidation. Furthermore, inhibition of NR4A1 was found to suppress ferroptosis and reduce the release of pro-inflammatory cytokines in the spinal cord of rats with inflammatory pain. Collectively, these findings outline a novel pathological mechanism and identify potential therapeutic targets for the treatment of inflammatory pain.

Effects of Combined Shinbaro and Celecoxib in a Complete Freund's Adjuvant-Induced Inflammatory Pain Mouse Model

Purpose

Persistent inflammation resulting from injury, infection, or arthritis contributes to both peripheral and central sensitization. Various combinations of natural extracts have been explored to minimize the side effects associated with conventional medications. Shinbaro, which has traditionally been used in Eastern medicine to treat inflammatory conditions, was chosen due to its known anti-inflammatory properties. However, previous studies have not yet investigated the combined administration of celecoxib and Shinbaro for their anti-inflammatory and analgesic effects. In this study, we examined the anti-inflammatory and analgesic effects of combining celecoxib with Shinbaro in a complete Freund's adjuvant (CFA)-induced inflammatory pain model.

Methods

We randomly assigned 66 mice to 6 groups (n = 11 per group) and administered intraplantar injections of 100 μL CFA or saline into their right hind paw, followed by oral administration of Shinbaro (100 mg/kg), celecoxib (15 or 30 mg/kg), or both 30 minutes later. Behavioral assessments were conducted blindly at baseline and on days 1, 3, and 7 post-injection. The right hind paw and spinal cord were harvested 3 days post-injection to examine the molecular mechanisms, including macrophage infiltration in the right hind paw, as well as glial cell activation and inflammatory cytokine levels in the spinal cord. Statistical analysis was performed using Tukey's post-hoc test.

Results

The combination of Shinbaro (100 mg/kg) and celecoxib (15 mg/kg) synergistically reduced mechanical hyperalgesia and paw edema by preventing the conversion of monocytes to macrophages and inhibiting macrophage infiltration. Moreover, it decreased the expression of pro-inflammatory cytokines and mediators in the spinal cord by inhibiting spinal microglial activation.

Conclusion

The combination of Shinbaro and celecoxib demonstrates significant anti-inflammatory and analgesic effects, suggesting its potential for managing inflammatory pain with fewer side effects than conventional therapies.

Unraveling the role of SSH1 in chronic neuropathic pain: A focus on LIMK1 and Cofilin Dephosphorylation in the prefrontal cortex

BACKGROUND AND OBJECTIVE

Neuropathic pain, a debilitating condition stemming from nervous system injuries, has profound impacts on quality of life. The medial prefrontal cortex (mPFC) plays a crucial role in the modulation of pain perception and emotional response. This study explores the involvement of Slingshot Homolog 1 (SSH1) protein in neuropathic pain and related emotional and cognitive dysfunctions in a mouse model of spared nerve injury (SNI).

METHODS

SNI was induced in C57BL/6J mice. SSH1's role was investigated via its overexpression and knockdown using lentiviral vectors in the mPFC. Behavioral assays (thermal and mechanical allodynia, open field test, elevated plus maze, tail suspension test, Y-maze, and novel object recognition were conducted to assess pain sensitivity, anxiety, depression, and cognitive function. Tissue samples underwent Hematoxylin and Eosin staining, Western blotting, immunofluorescence, co-immunoprecipitation, and enzyme-linked immunosorbent assay for inflammatory markers.

RESULTS

SNI mice displayed significant reductions in neuronal density and dendritic integrity in the mPFC, alongside heightened pain perception and emotional disturbances, as compared to sham controls. Overexpression of SSH1 ameliorated these alterations, improving mechanical and thermal thresholds, reducing anxiety and depressive behaviors, and enhancing cognitive performance. Conversely, SSH1 knockdown exacerbated these phenotypes. Molecular investigations revealed that SSH1 modulates pain processing and neuronal health in the mPFC partially through the dephosphorylation of Cofilin and LIM domain kinase 1 (LIMK1), as evidenced by changes in their phosphorylation states and interaction patterns.

CONCLUSION

SSH1 plays a pivotal role in the modulation of neuropathic pain and associated neuropsychological disturbances in the mPFC of mice. Manipulating SSH1 expression can potentially reverse the neurophysiological and behavioral abnormalities induced by SNI, highlighting a promising therapeutic target for treating neuropathic pain and its complex comorbidities.

DNMT3a Downregulation Ttriggered Upregulation of GABAA Receptor in the mPFC Promotes Paclitaxel-Induced Pain and Anxiety in Male Mice

Chemotherapeutic agents, such as paclitaxel (PTX), induce neuroplastic changes and alter gene expression in the prefrontal cortex (PFC), which may be associated with chemotherapy-induced pain and negative emotions. Notably, DNA methylation undergoes adaptive changes in neurological disorders, emerging as a promising target for neuromodulation. In this study, systemic administration of PTX leads to a decrease in the expression of the DNA methyltransferase DNMT3a, while concurrently upregulating the expression of Gabrb1 mRNA and its encoded GABAARβ1 protein in the medial PFC (mPFC) of male mice. Overexpression of DNMT3a in the mPFC alleviates PTX-induced pain hypersensitivity, and anxiety-like behavior in these mice. Additionally, it reverses the PTX-induced increase in inhibitory synaptic transmission in the pyramidal neurons of the mPFC. Mechanistically, the upregulation of GABAARβ1 in the mPFC is linked to the reduced expression of DNMT3a and DNA hypomethylation at the promoter region of the Gabrb1 gene. Furthermore, a long-term diet rich in methyl donors alleviates PTX-induced pain hypersensitivity and anxiety-like behavior in mice. These findings suggest that the DNMT3a-mediated upregulation of GABAARβ1 in the mPFC contributes to PTX-induced neuropathic pain and anxiety, highlighting DNA methylation-dependent epigenetic regulation as a potential therapeutic target for addressing chemotherapy-induced cortical dysfunction.

NaHS modulates astrocytic EAAT2 expression to impact SNI-induced neuropathic pain and depressive-like behaviors

The potential role of hydrogen sulfide (H2S) in the modulation of neuropathic pain is increasingly recognized. This study investigated the therapeutic effect of intraperitoneal injection of the H2S donor sodium hydrosulfide (NaHS) on neuropathic pain. Utilizing the spared nerve injury (SNI) model in mice, the research investigates the role of astrocytes and the excitatory neurotransmitter glutamate in chronic pain. The findings reveal that sodium hydrosulfide (NaHS), an H2S donor, effectively enhances the mechanical pain threshold and thermal pain escape latency in SNI mice. The study further demonstrates NaHS's potential in reducing glutamate levels in the spinal cord and the discharge frequency of neurons in the primary somatosensory cortex hindlimb region (S1HL) brain area, suggesting a novel therapeutic approach for neuropathic pain through the modulation of astrocyte function and EAAT2 expression.

[Research Progress in the Mechanisms of Acupuncture in Regulating DNA Methylation]

DNA methylation is the first epigenetic modification found in humans. Abnormal changes in DNA methylation are closely associated with the development and progression of diseases. Acupuncture, an important component of traditional Chinese medicine, has been shown to have significant therapeutic efficacy. The mechanisms underlying acupuncture are complex, involving physiological and pathological processes of integrated interactions across multiple targets. However, current research mostly focuses on a single target, highlighting the need for a more upstream approach to the investigation of the mechanisms. Herein, we reviewed studies on the direct or indirect regulation of DNA methylation via acupuncture. We also discussed its mechanisms of action in pain, obesity, depression, and Alzheimer disease, in order to provide a new perspective on the therapeutic mechanisms of acupuncture and the role of DNA methylation in the field of acupuncture research. Future research should concentrate on the effect of acupuncture on the DNA methylation of specific genes, the quantification of changes in DNA methylation at different acupoints, the development of individualized acupuncture prescriptions, further investigation of the specificity of the effects at different acupoint, and the expansion of the research to integrate epigenetics and genomics. This will provide a theoretical basis for the internationalization and the promotion of clinical application of acupuncture.

Knowledge mapping and emerging trends in cognitive impairment associated with chronic pain: A 2000-2024 bibliometric study

Chronic pain is commonly recognized as a distressing symptom or a standalone disease, with over half of those affected experiencing cognitive impairment, which significantly impacts their quality of life. Despite a recent surge in literature on cognitive impairment associated with chronic pain, a comprehensive bibliometric analysis in this field has yet to be conducted. In this study, we performed a bibliometric analysis on this topic. We retrieved English-language publications on chronic pain and cognitive impairment from 2000 to 2024 using the Web of Science Core Collection database. These publications were visually analyzed using tools such as VOSviewer, CiteSpace, and the R package "bibliometrix." We identified 1656 publications from 72 countries/regions across 722 journals on the topic of chronic pain and cognitive impairment. Publication numbers showed a steady increase, peaking in 2022. The United States led in contributions, with Harvard Medical School emerging as the most prominent institution involved. The journal Pain was the most prolific and frequently co-cited in this area. Among the authors, Stefan Duschek was the most productive, while Frederick Wolfe was the most frequently co-cited. Key research areas include investigating the bidirectional long-term effects between chronic pain and cognitive impairment and exploring the mechanisms underlying cognitive changes associated with chronic pain. In conclusion, this study highlights a global surge in research on cognitive impairment related to chronic pain. Emerging hotspots and future research trends point towards brain imaging mechanisms and neuronal circuit-mediated processes.

Epigenetic modifications associated to diabetic peripheral neuropathic pain (Review)

The present review aimed to provide an update on the scientific progress of the role of epigenetic modifications on diabetic peripheral neuropathic pain (DPNP). DPNP is a devastating and troublesome complication of diabetes mellitus (DM), which affects one third of patients with DM and causes severe hyperalgesia and allodynia, leading to challenges in the treatment of these patients. The pathophysiology of DPNP is multifactorial and is not yet fully understood and treatment options for this disease are currently unsatisfactory. The underlying mechanisms and pathophysiology of DPNP have largely been explored in animal models and a mechanism‑derived approach might offer a potential therapeutic‑target for attenuating certain phenotypes of DPNP. Altered gene expression levels within the peripheral or central nervous systems (CNS) are a crucial mechanism of DPNP, however, the transcriptional mechanisms of these genes have not been fully elucidated. Epigenetic modifications, such as DNA methylation and histone modifications (methylation, acetylation, or phosphorylation), can alter gene expression levels via chromatin remodeling. Moreover, it has been reported that altering gene expression via epigenetic modifications within the peripheral or CNS, contributes to the changes in both pain sensitivity and pharmacological efficacy in DPNP. Therefore, the present review summarized the findings of relevant literature on the epigenetic alterations in DPNP and the therapeutic potential for targeting these alterations in the future treatment of this disease.

Exploring the mechanisms and current status of acupuncture in alleviating tumor metabolism and associated diseases: Insights from the central nervous system and immune microenvironment

Acupuncture, as a traditional Chinese medical treatment, has garnered increasing attention in recent years in fields such as tumor metabolism, the central nervous system, and the immune microenvironment. This paper aims to explore the fundamental principles, mechanisms, and research status of acupuncture therapy for tumor-related diseases. Firstly, we introduce the basic principles of acupuncture therapy, including the theories of meridians and its theoretical basis in tumor treatment. Secondly, we systematically review the mechanisms of acupuncture therapy for tumor-related diseases, discussing how acupuncture alleviates side effects such as pain, depression, fatigue, and gastrointestinal discomfort caused by conventional treatments through modulation of the immune microenvironment, central nervous system, and endocrine system. Subsequently, we discuss the current research status of acupuncture therapy for tumor-related diseases, as well as the application of current research methods and technologies in elucidating acupuncture mechanisms. Additionally, by combining clinical practice with different types of tumor-related diseases as experimental subjects, we demonstrate the application effectiveness and clinical practice experience of acupuncture in tumor treatment. Finally, a comprehensive assessment of acupuncture therapy for tumor-related diseases is provided, summarizing its limitations and prospecting future directions, including interdisciplinary collaboration and personalized treatment. In conclusion, acupuncture, as a feasible adjunctive therapy, is closely related to the central nervous system and the immune microenvironment, holding potential significant value in tumor treatment.

The analgesic effect of acupuncture in neuropathic pain: regulatory mechanisms of DNA methylation in the brain

Recent research has demonstrated that chronic pain, resulting from peripheral nerve injury, leads to various symptoms, including not only allodynia and hyperalgesia but also anxiety, depression, and cognitive impairment. These symptoms are believed to arise due to alterations in gene expression and neural function, mediated by epigenetic changes in chromatin structure. Emerging evidence suggests that acupuncture can modulate DNA methylation within the central nervous system, contributing to pain relief and the mitigation of comorbidities. Specifically, acupuncture has been shown to adjust the DNA methylation of genes related to mitochondrial dysfunction, oxidative phosphorylation, and inflammation pathways within cortical regions, such as the prefrontal cortex, anterior cingulate cortex, and primary somatosensory cortex. In addition, it influences the DNA methylation of genes associated with neurogenesis in hippocampal neurons. This evidence indicates that acupuncture, a treatment with fewer side effects compared with conventional medications, could offer an effective strategy for pain management.

Investigating neuroepigenetic alterations in chronic low back pain with positron emission tomography

ABSTRACT

Epigenetics has gained considerable interest as potential mediators of molecular alterations that could underlie the prolonged sensitization of nociceptors, neurons, and glia in response to various environmental stimuli. Histone acetylation and deacetylation, key processes in modulating chromatin, influence gene expression; elevated histone acetylation enhances transcriptional activity, whereas decreased acetylation leads to DNA condensation and gene repression. Altered levels of histone deacetylase (HDAC) have been detected in various animal pain models, and HDAC inhibitors have demonstrated analgesic effects in these models, indicating HDACs' involvement in chronic pain pathways. However, animal studies have predominantly examined epigenetic modulation within the spinal cord after pain induction, which may not fully reflect the complexity of chronic pain in humans. Moreover, methodological limitations have previously impeded an in-depth study of epigenetic changes in the human brain. In this study, we employed [ 11 C]Martinostat, an HDAC-selective radiotracer, positron emission tomography to assess HDAC availability in the brains of 23 patients with chronic low back pain (cLBP) and 11 age-matched and sex-matched controls. Our data revealed a significant reduction of [ 11 C]Martinostat binding in several brain regions associated with pain processing in patients with cLBP relative to controls, highlighting the promising potential of targeting HDAC modulation as a therapeutic strategy for cLBP.

Chronic Pain-Related Cognitive Deficits: Preclinical Insights into Molecular, Cellular, and Circuit Mechanisms

Cognitive impairment is a common comorbidity of chronic pain, significantly disrupting patients' quality of life. Despite this comorbidity being clinically recognized, the underlying neuropathological mechanisms remain unclear. Recent preclinical studies have focused on the fundamental mechanisms underlying the coexistence of chronic pain and cognitive decline. Pain chronification is accompanied by structural and functional changes in the neural substrate of cognition. Based on the developments in electrophysiology and optogenetics/chemogenetics, we summarized the relevant neural circuits involved in pain-induced cognitive impairment, as well as changes in connectivity and function in brain regions. We then present the cellular and molecular alternations related to pain-induced cognitive impairment in preclinical studies, mainly including modifications in neuronal excitability and structure, synaptic plasticity, glial cells and cytokines, neurotransmitters and other neurochemicals, and the gut-brain axis. Finally, we also discussed the potential treatment strategies and future research directions.

Global research trends in acupuncture treatment for post-stroke depression: A bibliometric analysis

OBJECTIVE

Post-stroke depression (PSD) is a prevalent and severe sequela of stroke. It is an emotional disorder that significantly impacts functional recovery, prognosis, secondary stroke risk, and mortality among stroke survivors. The incidence rate of PSD is 18 %∼33 %, with symptoms such as low mood, decreased interest, sleep disorders, decreased appetite, impaired attention, and in severe cases, hallucinations and even suicidal tendencies. While diverse therapeutic modalities are employed globally to address PSD, each approach carries its inherent advantages and limitations. Notably, acupuncture stands out as a promising and effective intervention for ameliorating PSD symptoms and enhancing stroke prognosis. This study aims to conduct a bibliometric analysis to scrutinize the current landscape, identify hotspots, and explore frontiers in acupuncture research for PSD.

METHODS

A systematic search for acupuncture and PSD-related research was conducted from January 2014 to October 2023 on the Web of Science Core Collection (WoSCC). The data were downloaded and processed using Bibliometrix and VOSviewer to generate knowledge visualization maps.

RESULTS

A total of 11,540 articles related to acupuncture and PSD were retrieved. China emerged as the leading contributor with the highest volume of articles on acupuncture and PSD. Author Liu CZ attained the highest H-index, focusing primarily on investigating the compatibility effects and mechanisms of acupoints. Common hotspot keywords included pain, stimulation, mechanisms, complementary, and alternative medicine. The main research frontiers were mechanisms, neuroinflammation, gut microbiota, and therapeutic methods.

CONCLUSION

This study offered multifaceted insights into acupuncture for PSD, unveiling pivotal areas, research hotspots, and emerging trends. The findings aimed to guide researchers in exploring novel research directions and selecting appropriate journals for advancing the understanding and treatment of PSD through acupuncture interventions.

Involvement of basolateral amygdala-rostral anterior cingulate cortex in mechanical allodynia and anxiety-like behaviors and potential mechanisms of electroacupuncture

AIMS

Chronic pain is highly associated with anxiety. Electroacupuncture (EA) is effective in relieving pain and anxiety. Currently, little is known about the neural mechanisms underlying the comorbidity of chronic pain and anxiety and the EA mechanism. This study investigated a potential neural circuit underlying the comorbid and EA mechanisms.

METHODS

Spared nerve injury (SNI) surgery established the chronic neuropathic pain mouse model. The neural circuit was activated or inhibited using the chemogenetic method to explore the relationship between the neural circuit and mechanical allodynia and anxiety-like behaviors. EA combined with the chemogenetic method was used to explore whether the effects of EA were related to this neural circuit.

RESULTS

EA attenuated mechanical allodynia and anxiety-like behaviors in SNI mice, which may be associated with the activity of CaMKII neurons in the basolateral amygdala (BLA). Inhibition of BLACaMKII-rACC induced mechanical allodynia and anxiety-like behaviors in sham mice. Activation of the BLACaMKII-rACC alleviated neuropathic pain and anxiety-like behaviors in SNI mice. The analgesic and anxiolytic effects of 2 Hz EA were antagonized by the inhibition of the BLACaMKII-rACC.

CONCLUSION

BLACaMKII-rACC mediates mechanical allodynia and anxiety-like behaviors. The analgesic and anxiolytic effects of 2 Hz EA may be associated with the BLACaMKII-rACC.

Acupuncture promotes neurological recovery and regulates lymphatic function after acute inflammatory nerve root injury

Aims

To investigate the therapeutic effect of acupuncture on acute inflammatory nerve root injury by regulating lymphatic function.

Main methods

A mouse model of L5 nerve root compression was used to simulate acute nerve root injury. After modeling, acupuncture treatment was given each day for one week. Pain thresholds were assessed before and after modeling and treatment. Immunofluorescence staining was performed to observe the distribution astrocytes and neurons in the lumbar spinal cord, the innervation rate of neuromuscular junctions (NMJs), lymphatic endothelial cells (LECs) of lumbar aortic lymph nodes, and the percentage of M1 macrophages. The number of each type of immune cells in the lumbar aortic lymph nodes (LALNs) was measured by flow cytometry.

Key findings

The model group showed a significant decrease in pain threshold in the affected lower limb, while acupuncture treatment was able to significantly increase it. Acupuncture significantly repaired astrocytes and neurons in the lumbar spinal cord of the compressed segment, increased the innervation rate of nerve endings at NMJs, reduced LECs in the LALNs, reduced the proportion of M1 macrophages in the LALNs, and significantly reduced mononuclear neutrophils and monocytic neutrophils.

Significance

Acupuncture can reduce pain, promote nerve repair in mice with acute nerve root injury, and suppress immune responses in lumbar aortic lymph nodes.

Acupuncture: An Overview on Its Functions, Meridian Pathways and Molecular Mechanisms

Recent research has extensively explored the intricate mechanisms that underlie the effectiveness of acupuncture, highlighting the importance of stimulating acupoints, the role of acupuncture techniques in managing diseases, and the interaction between meridian pathways and molecular processes. Studies have underscored the crucial role of acupuncture in activating neurons, modulating the immune system, and influencing vascular activity, all of which contribute significantly to its therapeutic benefits across a wide range of symptoms and conditions. Utilization of imaging modalities enables the identification of changes in cerebral blood flow, brain function, and regional glucose metabolism following acupuncture sessions. The interstitial fluid circulation network within meridians adheres to specific laws that facilitate the transportation of materials. Acupuncture initiates the release of neurotransmitters, neuropeptides, and immune factors, impacting pain perception, inflammation, and physiological functions. It influences the complex neuro-endocrine-immune network by activating pathways involving the nervous system, the hypothalamic-pituitary-adrenal axis, and immune responses. Moreover, acupuncture induces molecular modifications such as phosphorylation, methylation, and histone modification, leading to key molecular changes that ultimately result in anti-inflammatory effects and the regulation of immune responses.

The efficacy of acupuncture for trigeminal neuralgia: an overview of systematic reviews

Background

Many systematic reviews (SRs) and meta-analysis (MAs) have reported the efficacy of acupuncture treatment for primary trigeminal neuralgia (PTN), but the quality of evidence is unknown and therefore needs to be evaluated comprehensively.

Methods

Eight electronic databases were searched from their inception until January 5, 2024. The methodological quality, reporting quality, and risk of bias of the included SRs were assessed by the assessment of multiple systematic reviews 2 (AMSTAR-2), the Risk of Bias in Systematic Reviews (ROBIS) tool, and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The quality of evidence for outcome measures was evaluated using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE).

Results

We identified 13 SRs/MAs met inclusion criteria. According to the results of the AMSTAR-2, six were rated as critically low quality and seven as low quality. According to ROBIS assessment, 8 SRs/MAs were classified as low risk, and 5 SRs/MAs were found to be high risk. The PRISMA report still has some reporting deficiencies in aspects such as protocol and registration, search strategy, risk of bias, additional analyzes and funding. According to the GRADE system, no high-quality evidence was found, 1 was of moderate quality, 4 were of low quality, and 8 were of critical low quality.

Conclusion

Based on the evidence collected, acupuncture shows promise as a treatment for PTN patients. However, it is important to note that the included SRs/MAs generally have low methodological quality and evidence quality. Therefore, caution must be exercised when interpreting this conclusion. To enhance future research in this area, it is recommended to adequately report methodological details and adhere to guidelines for conducting SRs/MAs.Systematic review registration: https://www.crd.york.ac.uk/prospero/, identifier CRD42024499280.

The efficacy of acupuncture therapies in cervical spondylotic radiculopathy: A network meta-analysis

Objective

To evaluate the efficacy of acupuncture-related therapy in the Bayesian setting by means of a network Meta-analysis.

Methods

Relevant clinical randomized controlled trials(RCTs) of acupuncture-related therapy for Cervical Spondylotic Radiculopathy(CSR) were searched in the Chinese and English databases from the inception to November 13, 2023. Two researchers reviewed the literature, extracted the data, assessed the risk of bias of the included studies independently, and then used Stata14.0 and WinBUGs14 to analyze.

Results

There are 28 RCTs in total, of which 2593 patients and 14 acupuncture interventions. Network Meta-analysis revealed that, regarding the VAS scores, Acupoint catgut-embedding, Fu's Subcutaneous Needling and Needle Knife are better than Conventional acupuncture, Electro-acupuncture, Sham needle, Western Medicine, and Electrotherapy; Conventional acupuncture is better than Electrotherapy and Sham needle; Qihuang needle is superior to Sham needle and Electrotherapy; besides, Acupoint catgut-embedding is better than Tuina (Message), Chinese Medicine, Warm needle as well. Regarding the NDI scores, Needle Knife, Warm needle, Fire needle, Long round needle, Acupoint catgut-embedding are better than Conventional acupuncture, Electro-acupuncture, and Cervical traction; Conventional acupuncture is superior to Electro-acupuncture, Cervical traction, Needle Knife and Warm needle; whereas we found Qihuang needle is superior to Acupoint catgut-embedding, besides, Need Knife is superior to Qihuang needle, Long round needle and Acupoint catgut-embedding. In terms of improving the Tanaka Yasuhiro 20-point scale scores(TY), Needle Knife and Qihuang needle are superior to Conventional acupuncture, Warm needle and Electro-acupuncture; moreover, Conventional acupuncture is better than Warm needle.

Conclusion

In general, Acupoint catgut-embedding shows the best effect at relieving neck pain, then followed by Fu's Subcutaneous Needling and Needle Knife. Needle Knife is the best intervention in improving the functionality of the cervical spine. Like improving overall clinical performance, Needle Knife is the best treatment. Furthermore, our conclusion still needs to be confirmed by higher-quality documentation. In order to choose the best treatment for patients, clinicians are expected to take into account different clinical features and practical clinical settings with caution while choosing an acupuncture-related therapy in CSR.

Key Message

This article aims at selecting the best acupuncture-related treatment for clinicians to help patients in CSR, and the results of this study indicated that Acupoint catgut-embedding shows the best effect in relieving neck pain, Needle Knife shows the best effect in improving the functionality of cervical spine, Needle Knife shows the best effect in treating overall clinical performance.

Mechanisms of pain in aging and age-related conditions: Focus on caregivers

Pain is a complex, subjective experience that can significantly impact quality of life, particularly in aging individuals, by adversely affecting physical and emotional well-being. Whereas acute pain usually serves a protective function, chronic pain is a persistent pathological condition that contributes to functional deficits, cognitive decline, and emotional disturbances in the elderly. Despite substantial progress that has been made in characterizing age-related changes in pain, complete mechanistic details of pain processing mechanisms in the aging patient remain unknown. Pain is particularly under-recognized and under-managed in the elderly, especially among patients with Alzheimer's disease (AD), Alzheimer's disease-related dementias (ADRD), and other age-related conditions. Furthermore, difficulties in assessing pain in patients with AD/ADRD and other age-related conditions may contribute to the familial caregiver burden. The purpose of this article is to discuss the mechanisms and risk factors for chronic pain development and persistence, with a particular focus on age-related changes. Our article also highlights the importance of caregivers working with aging chronic pain patients, and emphasizes the urgent need for increased legislative awareness and improved pain management in these populations to substantially alleviate caregiver burden.

Chronic Gut Inflammation and Dysbiosis in IBS: Unraveling Their Contribution to Atopic Dermatitis Progression

Emerging evidence suggests a link between atopic dermatitis (AD) and gastrointestinal disorders, particularly in relation to gut microbial dysbiosis. This study explored the potential exacerbation of AD by gut inflammation and microbial imbalances using an irritable bowel syndrome (IBS) mouse model. Chronic gut inflammation was induced in the model by intrarectal injection of 2,4,6-trinitrobenzene sulfonic acid (TNBS), followed by a 4-week development period. We noted significant upregulation of proinflammatory cytokines in the colon and evident gut microbial dysbiosis in the IBS mice. Additionally, these mice exhibited impaired gut barrier function, increased permeability, and elevated systemic inflammation markers such as IL-6 and LPS. A subsequent MC903 challenge on the right cheek lasting for 7 days revealed more severe AD symptoms in IBS mice compared to controls. Further, fecal microbial transplantation (FMT) from IBS mice resulted in aggravated AD symptoms, a result similarly observed with FMT from an IBS patient. Notably, an increased abundance of Alistipes in the feces of IBS mice correlated with heightened systemic and localized inflammation in both the gut and skin. These findings collectively indicate that chronic gut inflammation and microbial dysbiosis in IBS are critical factors exacerbating AD, highlighting the integral relationship between gut and skin health.

Reporting and influencing factors of patient-reported outcomes in acupuncture randomised controlled trials: a cross-sectional study protocol

INTRODUCTION

Patient-reported outcomes (PROs) are health reports that come directly from the patients themselves and represented the experience and insights of the patient's perspective on the impact of the intervention. PROs were increasingly emphasised in acupuncture randomised controlled trials (RCTs). However, the reporting quality of PROs in acupuncture RCTs has not been investigated to date. Therefore, we constructed this study to reveal the basic characteristics and reporting quality of PROs in acupuncture RCTs, and explore the relationship between concealment, blinding and RROs. We hope our findings can provide guidance for the reporting standards and future development of PROs in acupuncture RCTs in reverse.

METHODS AND ANALYSIS

RCTs using acupuncture treatment as the intervention and PROs as primary outcomes or secondary outcomes will be systematically searched through seven databases MEDLINE, EMBASE, CENTRAL, CBM, CNKI, Wanfang and VIP between 1 January 2012 and 15 October 2022. The basic characteristics, concealment, blinding design and the characteristics of PROs in included RCTs will be summarised. The reporting quality of PROs will be assessed based on the CONSORT PRO extension. Logistic analysis will be performed to identify the association between concealment, blinding and RROs.

ETHICS AND DISSEMINATION

Ethical approval is not required for this study. This protocol has been registered in Open Science Framework (OSF) Registries. The findings of this study will be submitted to a peer-reviewed academic journal.

Curcumin can improve spinal cord injury by inhibiting DNA methylation

Spinal cord injury (SCI) is a serious central nervous system disease. Traumatic SCI often causes persistent neurological deficits below the injury level. Epigenetic changes occur after SCI. Studies have shown DNA methylation to be a key player in nerve regeneration and remodeling, and in regulating some pathophysiological characteristics of SCI. Curcumin is a natural polyphenol from turmeric. It has anti-inflammatory, antioxidant, and neuroprotective effects, and can mitigate the cell and tissue damage caused by SCI. This report analyzed the specific functions of DNA methylation in central nervous system diseases, especially traumatic brain injury and SCI. DNA methylation can regulate the level of gene expressions in the central nervous system. Therefore, pharmacological interventions regulating DNA methylation may be promising for SCI.

Hypermethylation and low expression of FANCC involved in multi-walled carbon nanotube-induced toxicity on ARPE-19 cells

Multi-walled carbon nanotube (MWCNT) exposure was observed to cause damages on the viability of ocular cells, however, the underlying mechanisms remain not well understood. Epigenetic alterations that regulate gene expression have been identified as a major responsiveness to environmental challenge. Thus, the aim of this study was to screen methylation-regulated genes involved in MWCNT exposure. The Illumina Human Methylation 850 K array was employed to determine the genome-wide DNA methylation profile of human retinal pigment epithelial cell line (ARPE-19) exposed to 50% inhibition concentration of MWCNTs (100 μg/ml) for 24 h or without (n = 3 for each group). Then, the transcriptome data obtained by high-throughput RNA sequencing previously were integrated with DNA methylome to identify the overlapped genes. As a result, the integrative bioinformatics analysis identified that compared with controls, FA complementation group C (FANCC) was hypermethylated and downregulated in MWCNT-exposed ARPE-19 cells. Quantitative real-time polymerase chain reaction analysis confirmed the mRNA expression level of FANCC was significantly decreased following MWCNT treatment and the addition of DNA methylation inhibitor 5-Aza-deoxycytidine (10 μM) reversed this decrease. Pyrosequencing analysis further validated the hypermethylation status at the 5'-untranslated promoter region of FANCC (cg14583550) in MWCNT-exposed ARPE-19 cells. Protein-protein interaction network and function analyses predicted that FANCC may contribute to MWCNT-induced cytotoxicity by interacting with heat shock protein 90 beta family member 1 and then upregulating cytokine interleukin-6 and apoptosis biomarker caspase 3. In conclusion, the present study links the epigenetic modification of FANCC with the pathogenesis of MWCNT-induced retinal toxicity.

DNA N6-methyladenine methylase N6AMT1 controls neuropathic pain through epigenetically modifying Kcnj16 in dorsal horn neurons

ABSTRACT

Nerve injury-induced aberrant changes in gene expression in spinal dorsal horn neurons are critical for the genesis of neuropathic pain. N6-methyladenine (m 6 A) modification of DNA represents an additional layer of gene regulation. Here, we report that peripheral nerve injury significantly decreased the level of m 6 A-specific DNA methyltransferase 1 ( N6amt1 ) in dorsal horn neurons. This decrease was attributed, at least partly, to a reduction in transcription factor Nr2f6 . Rescuing the decrease in N6amt1 reversed the loss of m 6 A at the promoter for inwardly rectifying potassium channel subfamily J member 16 ( Kcnj16 ), mitigating the nerve injury-induced upregulation of Kcnj16 expression in the dorsal horn and alleviating neuropathic pain hypersensitivities. Conversely, mimicking the downregulation of N6amt1 in naive mice erased DNA m 6 A at the Kcnj16 promoter, elevated Kcnj16 expression, and led to neuropathic pain-like behaviors. Therefore, decreased N6amt1 caused by NR2F6 is required for neuropathic pain, likely through its regulation of m 6 A-controlled KCNJ16 in dorsal horn neurons, suggesting that DNA m 6 A modification may be a potential new target for analgesic and treatment strategies.

Research hotspots and trends on neuropathic pain-related mood disorders: a bibliometric analysis from 2003 to 2023

Introduction

Neuropathic Pain (NP) is often accompanied by mood disorders, which seriously affect the quality of life of patients. This study aimed to analyze the hotspots and trends in NP-related mood disorder research using bibliometric methods and to provide valuable predictions for future research in this field.

Methods

Articles and review articles on NP-related mood disorders published from January 2003 to May 2023 were retrieved from the Web of Science Core Collection. We used CiteSpace to analyze publications, countries, institutions, authors, cited authors, journals, cited journals, references, cited references, and keywords. We also analyzed collaborative network maps and co-occurrence network maps.

Results

A total of 4,540 studies were collected for analysis. The number of publications concerning NP-related mood disorders every year shows an upward trend. The United States was a major contributor in this field. The University of Toronto was the most productive core institution. C GHELARDINI was the most prolific author, and RH DWORKIN was the most frequently cited author. PAIN was identified as the journal with the highest productivity and citation rate. The current research hotspots mainly included quality of life, efficacy, double-blind methodology, gabapentin, pregabalin, postherpetic neuralgia, and central sensitization. The frontiers in research mainly focused on the mechanisms associated with microglia activation, oxidative stress, neuroinflammation, and NP-related mood disorders.

Discussion

In conclusion, the present study provided insight into the current state and trends in NP-related mood disorder research over the past 20 years. Consequently, researchers will be able to identify new perspectives on potential collaborators and cooperative institutions, hot topics, and research frontiers in this field.

Scalp electroacupuncture targeting the VTADA neurons to relieve negative emotions and promote the alleviation of chronic pain

Object

Chronic pain and negative emotions are often linked, and both can impact the reward circuit. The use of electroacupuncture (EA) has been found to regulate and improve these conditions. This study explores the potential mechanism of chronic pain relief by adding acupoints with emotional regulation effect to the basis of routine EA analgesia, to optimize the acupoint compatibility scheme of EA in the treatment of analgesia.

Method

For this study, 42 male Wistar rats were used. Recombinant adeno-associated viruses were used to label and regulate the activity of dopamine (DA) neurons. The rat model was established by complete Freund's adjuvant (CFA). Lower limb electroacupuncture (LEA) was applied to the ST36 and BL60 acupoints. In addition, LEA + scalp EA (SEA) was given using the GV20 and GV24+ acupoints besides ST36 and BL60. To evaluate the pain threshold, we measured 50% paw withdrawal thresholds and thermal paw withdrawal latencies. Negative emotions were evaluated through the open field test, marble-burying test, sucrose preference test, and forced swimming test. Moreover, the conditional place preference test was conducted to measure the reward behavior in response to pain relief. Immunofluorescence staining, Western blotting, and qPCR were used to detect the activity of the VTADA-NAc reward circuit.

Result

The injection of CFA significantly lowered the pain threshold. As the pain persisted, the anxiety and depression-like behaviors escalated while the response to reward reduced. Meanwhile, the VTADA-NAc pathway was suppressed with pain chronification. However, activating DA neurons in VTA attenuated the effects induced by CFA. LEA could relieve chronic pain, negative emotions, and reward disorders, while also activating the VTADA-NAc pathway. In addition, LEA + SEA exhibited a more pronounced effect compared with LEA alone. Nevertheless, chemogenetic inhibition of DA neurons decreased the efficacy of LEA + SEA in the treatment of chronic pain and associated comorbidities.

Conclusion

Adding SEA to conventional LEA effectively alleviates negative emotions and chronic pain, potentially due to the activation of the VTADA-NAc reward neural circuit. Thus, LEA + SEA is a more effective treatment for hyperalgesia and associated negative emotions compared with LEA alone.

The Epigenetics of Neuropathic Pain: A Systematic Update

Epigenetics deals with alterations to the gene expression that occur without change in the nucleotide sequence in the DNA. Various covalent modifications of the DNA and/or the surrounding histone proteins have been revealed, including DNA methylation, histone acetylation, and methylation, which can either stimulate or inhibit protein expression at the transcriptional level. In the past decade, an exponentially increasing amount of data has been published on the association between epigenetic changes and the pathomechanism of pain, including its most challenging form, neuropathic pain. Epigenetic regulation of the chromatin by writer, reader, and eraser proteins has been revealed for diverse protein targets involved in the pathomechanism of neuropathic pain. They include receptors, ion channels, transporters, enzymes, cytokines, chemokines, growth factors, inflammasome proteins, etc. Most work has been invested in clarifying the epigenetic downregulation of mu opioid receptors and various K+ channels, two types of structures mediating neuronal inhibition. Conversely, epigenetic upregulation has been revealed for glutamate receptors, growth factors, and lymphokines involved in neuronal excitation. All these data cannot only help better understand the development of neuropathic pain but outline epigenetic writers, readers, and erasers whose pharmacological inhibition may represent a novel option in the treatment of pain.

DNMT1 Mediates Chronic Pain-Related Depression by Inhibiting GABAergic Neuronal Activation in the Central Amygdala

BACKGROUND

Chronic pain can induce depressive emotion. DNA methyltransferases (DNMTs) have been shown to be involved in the development of chronic pain and depression. However, the role and mechanism of DNMTs in chronic pain-induced depression are not well understood.

METHODS

In well-established spared nerve injury (SNI)-induced chronic pain-related depression models, the expression of DNMTs and the functional roles and underlying mechanisms of DNMT1 in central amygdala (CeA) GABAergic (gamma-aminobutyric acidergic) neurons were investigated using molecular, pharmacological, electrophysiological, optogenetic, and chemogenetic techniques and behavioral tests.

RESULTS

DNMT1, but not DNMT3a or DNMT3b, was upregulated in the CeA of rats with SNI-induced chronic pain-depression. Inhibition of DNMT1 by 5-Aza or viral knockdown of DNMT1 in GABAergic neurons in the CeA effectively ameliorated the depression-like behaviors induced by chronic pain. The DNMT1 action was associated with methylation at the CpG-rich Gad1 promoter and GAD67 downregulation, leading to a decrease of GABAergic neuronal activity. Optogenetic activation of GABAergic neurons in the CeA improved SNI-induced depression-like behaviors. Moreover, optogenetic or chemogenetic inhibition of GABAergic neurons in the CeA reversed DNMT1 knockdown-induced improvement of depression-like behaviors in SNI mice.

CONCLUSIONS

Our findings suggest that DNMT1 is involved in the development of chronic pain-related depression by epigenetic repression of GAD67, leading to the inhibition of GABAergic neuronal activation. This study indicates that DNMT1 could be a potential target for the treatment of chronic pain-related depression.

Brain nuclei and neural circuits in neuropathic pain and brain modulation mechanisms of acupuncture: a review on animal-based experimental research

Neuropathic pain (NP) is known to be associated with abnormal changes in specific brain regions, but the complex neural network behind it is vast and complex and lacks a systematic summary. With the help of various animal models of NP, a literature search on NP brain regions and circuits revealed that the related brain nuclei included the periaqueductal gray (PAG), lateral habenula (LHb), medial prefrontal cortex (mPFC), and anterior cingulate cortex (ACC); the related brain circuits included the PAG-LHb and mPFC-ACC. Moreover, acupuncture and injurious information can affect different brain regions and influence brain functions via multiple aspects to play an analgesic role and improve synaptic plasticity by regulating the morphology and structure of brain synapses and the expression of synapse-related proteins; maintain the balance of excitatory and inhibitory neurons by regulating the secretion of glutamate, γ-aminobutyric acid, 5-hydroxytryptamine, and other neurotransmitters and receptors in the brain tissues; inhibit the overactivation of glial cells and reduce the release of pro-inflammatory mediators such as interleukins to reduce neuroinflammation in brain regions; maintain homeostasis of glucose metabolism and regulate the metabolic connections in the brain; and play a role in analgesia through the mediation of signaling pathways and signal transduction molecules. These factors help to deepen the understanding of NP brain circuits and the brain mechanisms of acupuncture analgesia.

Preoperative Pain Facilitates Postoperative Cognitive Dysfunction via Periaqueductal Gray Matter-Dorsal Raphe Circuit

Postoperative cognitive dysfunction (POCD) is a medically induced, rapidly occurring postoperative disease, which is hard to recover and seriously threatens the quality of life, especially for elderly patients, so it is important to identify the risk factors for POCD and apply early intervention to prevent POCD. As we have known, pain can impair cognition, and many surgery patients experience different preoperative pain, but it is still unknown whether these patients are vulnerable for POCD. Here we found that chronic pain (7 days, but not 1 day acute pain) induced by Complete Freund's Adjuvant (CFA) injected in the hind paw of rats could easily induce spatial cognition and memory impairment after being exposed to sevoflurane anesthesia. Next, for the mechanisms, we focused on the Periaqueductal Gray Matter (PAG), a well-known pivotal nucleus in pain process. It was detected the existence of neural projection from ventrolateral PAG (vlPAG) to adjacent nucleus Dorsal Raphe (DR), the origin of serotonergic projection for the whole cerebrum, through virus tracing and patch clamp recordings. The Immunofluorescence staining and western blot results showed that Tryptophan Hydroxylase 2 (TPH2) for serotonin synthesis in the DR was increased significantly in the rats treated with CFA for 7 days and sevoflurane for 3 hours, while chemo-genetic inhibition of the vlPAG-DR projection induced obvious spatial learning and memory impairment. Our study suggests that preoperative chronic pain may facilitate cognitive function impairment after receiving anesthesia through the PAG-DR neural circuit, and preventative analgesia should be a considerable measure to reduce the incidence of POCD.

Efficacy and safety of acupuncture-point stimulation combined with opioids for the treatment of moderate to severe cancer pain: a network meta-analysis of randomized controlled trials

Background

Pain is one of the most common and troublesome symptoms of cancer. Although potential positive effects of acupuncture-point stimulation (APS) on cancer pain have been observed, knowledge regarding the selection of the optimal APS remains unclear because of a lack of evidence from head-to-head randomized controlled trials (RCTs).

Objective

This study aimed to carry out a network meta-analysis to compare the efficacy and safety of different APS combined with opioids in treating moderate to severe cancer pain and rank these methods for practical consideration.

Methods

A comprehensive search of eight electronic databases was conducted to obtain RCTs involving different APS combined with opioids for moderate to severe cancer pain. Data were screened and extracted independently using predesigned forms. The quality of RCTs was appraised with the Cochrane Collaboration risk-of-bias tool. The primary outcome was the total pain relief rate. Secondary outcomes were the total incidence of adverse reactions, the incidence of nausea and vomiting, and the incidence of constipation. We applied a frequentist, fixed-effect network meta-analysis model to pool effect sizes across trials using rate ratios (RR) with their 95% confidence intervals (CI). Network meta-analysis was performed using Stata/SE 16.0.

Results

We included 48 RCTs, which consisted of 4,026 patients, and investigated nine interventions. A network meta-analysis showed that a combination of APS and opioids was superior in relieving moderate to severe cancer pain and reducing the incidence of adverse reactions such as nausea, vomiting, and constipation compared to opioids alone. The ranking of total pain relief rates was as follows: fire needle (surface under the cumulative ranking curve (SUCRA) = 91.1%), body acupuncture (SUCRA = 85.0%), point embedding (SUCRA = 67.7%), auricular acupuncture (SUCRA = 53.8%), moxibustion (SUCRA = 41.9%), transcutaneous electrical acupoint stimulation (TEAS) (SUCRA = 39.0%), electroacupuncture (SUCRA = 37.4%), and wrist-ankle acupuncture (SUCRA = 34.1%). The ranking of total incidence of adverse reactions was as follows: auricular acupuncture (SUCRA = 23.3%), electroacupuncture (SUCRA = 25.1%), fire needle (SUCRA = 27.2%), point embedding (SUCRA = 42.6%), moxibustion (SUCRA = 48.2%), body acupuncture (SUCRA = 49.8%), wrist-ankle acupuncture (SUCRA = 57.8%), TEAS (SUCRA = 76.3%), and opioids alone (SUCRA = 99.7%).

Conclusions

APS seemed to be effective in relieving cancer pain and reducing opioid-related adverse reactions. Fire needle combined with opioids may be a promising intervention to reduce moderate to severe cancer pain as well as reduce opioid-related adverse reactions. However, the evidence was not conclusive. More high-quality trials investigating the stability of evidence levels of different interventions on cancer pain must be conducted.

Systematic Review Registration

https://www.crd.york.ac.uk/PROSPERO/#searchadvanced, identifier CRD42022362054.

Transcranial direct current stimulation regulates phenotypic transformation of microglia to relieve neuropathic pain induced by spinal cord injury

Objective

Neuropathic pain is a common complication after spinal cord injury (SCI). Transcranial direct current stimulation (tDCS) has been confirmed to be effective in relieving neuropathic pain in patients with SCI. The aim of this study is to investigate the effect of tDCS on neuropathic pain induced by SCI and its underlying mechanism.

Materials and methods

The SCI model was induced by a clip-compression injury and tDCS stimulation was performed for two courses (5 days/each). The motor function was evaluated by Basso-Beattie-Bresnahan (BBB) score, and the thermal withdrawal threshold was evaluated by the thermal radiation method. The effects of tDCS on the cerebral cortex, thalamus, midbrain, and medulla were detected by the enzyme-linked immunosorbent assay (ELISA) and immunofluorescence.

Results

The results showed that SCI reduced the thermal withdrawal threshold and increased the concentration of inflammatory cytokines in the cortex, thalamus, midbrain, and medulla, including the tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6). In addition, the activation of microglia and the proportion of M1 phenotypic polarization increased significantly in the ventral posterolateral (VPL), ventral tegmental (VTA), and periaqueductal gray (PAG) regions after SCI. After tDCS treatment, the thermal withdrawal threshold and motor function of SCI rats were significantly improved compared to the vehicle group. Meanwhile, tDCS effectively reduced the concentration of pro-inflammatory cytokines in the cortex, thalamus, midbrain, and medulla and increased the concentration of anti-inflammatory cytokines interleukin-10 (IL-10) in the thalamus. In addition, tDCS reduced the proportion of the M1 phenotype of microglia in VPL, VTA, and PAG regions and increase the proportion of the M2 phenotype.

Conclusion

The results suggest that tDCS can effectively relieve SCI-induced neuropathic pain. Its mechanism may be related to regulating the inflammatory and anti-inflammatory cytokines in corresponding brain regions via promoting the phenotypic transformation of microglia.

Electroacupuncture Alleviates Depressive-like Behavior by Modulating the Expression of P2X7/NLRP3/IL-1β of Prefrontal Cortex and Liver in Rats Exposed to Chronic Unpredictable Mild Stress

Depression is a complex clinical disorder associated with poor outcomes. Electroacupuncture (EA) has been demonstrated to have an important role in both clinical and pre-clinical depression investigations. Evidence has suggested that the P2X7 receptor (P2X7R), NLRP3, and IL-1β play an important role in depressive disorder. Our study is aimed at exploring the role of EA in alleviating depression-like behaviors in rats. We therefore investigated the effects of EA on the prefrontal cortex and liver of rats subjected to chronic unpredictable mild stress (CUMS) through behavior tests, transmission electron microscopy, Nissl staining, HE staining, immunohistochemistry and Western blotting. Five weeks after exposure to CUMS, Sprague-Dawley (SD) rats showed depression-like behavior. Three weeks after treatment with brilliant blue G (BBG) or EA, depressive symptoms were significantly improved. Liver cells and microglia showed regular morphology and orderly arrangement in the BBG and EA groups compared with the CUMS group. Here we show that EA downregulated P2X7R/NLRP3/IL-1β expression and relieved depression-like behavior. In summary, our findings demonstrated the efficacy of EA in alleviating depression-like behaviors induced by CUMS in rats. This suggests that EA may serve as an adjunctive therapy in clinical practice, and that P2X7R may be a promising target for EA intervention on the liver–brain axis in treatment of depression.

Recent trends in acupuncture for chronic pain: A bibliometric analysis and review of the literature

BACKGROUND

Acupuncture has been increasingly used in patients with chronic pain, yet no bibliometric analysis of acupuncture studies for chronic pain exists.

OBJECTIVES

To investigate the characteristics, hotspots and frontiers of global scientific output in acupuncture research for chronic pain over the past decade.

METHODS

We retrieved publications on acupuncture for chronic pain published from 2011 to 2022 from the Science Citation Index Expanded (SCI-expanded) of the Web of Science Core Collection (WoSCC). The co-occurrence relationships of journals/countries/institutions/authors/keywords were performed using VOSviewer V6.1.2, and CiteSpace V1.6.18 analyzed the clustering and burst analysis of keywords and co-cited references.

RESULTS

A total of 1616 articles were retrieved. The results showed that the number of annual publications on acupuncture for chronic pain has increased over time, with the main types of literature being original articles (1091 articles, 67.5 %) and review articles (351 articles, 21.7 %). China had the most publications (598 articles, 37 %), with Beijing University of Traditional Chinese Medicine (93 articles, 5.8 %) and Evidence-based Complementary and Alternative Medicine ranked first (169 articles, 10.45 %) as the most prolific affiliate and journal, respectively. Liang FR was the most productive author (43 articles), and the article published by Vickers Andrew J in 2012 had the highest number of citations (625 citations). Recently, "acupuncture" and "pain" appeared most frequently. The hot topics in acupuncture for chronic pain based on keywords clustering analysis were experimental design, hot diseases, interventions, and mechanism studies. According to burst analysis, the main research frontiers were functional connectivity (FC), depression, and risk.

CONCLUSION

This study provides an in-depth perspective on acupuncture for chronic pain studies, revealing pivotal points, research hotspots, and research trends. Valuable ideas are provided for future research activities.

High-frequency electrical stimulation reduced hyperalgesia and the activation of the Myd88 and NFκB pathways in chronic constriction injury of sciatic nerve-induced neuropathic pain mice

Neuropathic pain has become a global public problem and health burden. Pharmacological interventions are the primary treatment, but the drug cure rate is low with side effects. There is an urgent need to develop novel treatment approaches. High frequency electrical stimulation (KHES) has been widely applied in clinical analgesia. However, its mechanism is poorly understood. In this study, datasets related to neuropathic pain were obtained from the GEO database. The differentially expressed genes (DEGs) and key genes were analyzed through functional enrichment analysis, showing that most of the pathways involve the inflammation. The MyD88 and NFκB pathways were further studied. KHES significantly alleviated mechanical and thermal allodynia in chronic constriction injury of the sciatic nerve mice. KHES also inhibited the increase in Myd88 and p-NFκB expression. The administration of NFκB pathway activator partly reversed the antinociceptive effects of KHES, and NFκB pathway inhibitor achieved analgesic effects similar to those of KHES. Therefore, KHES might be a novel intervention for the treatment of neuropathic pain.

Efficacy of electroacupuncture combined with intravenous patient-controlled analgesia after cesarean delivery: a randomized clinical trial

BACKGROUND

Electroacupuncture is a nonpharmacologic intervention for analgesia that is widely recognized as therapy for pain. However, the clinical efficacy of electroacupuncture combined with patient-controlled intravenous analgesia for postoperative analgesia after cesarean delivery remains unclear.

OBJECTIVE

This study aimed to assess the efficacy of electroacupuncture + patient-controlled intravenous analgesia for postoperative analgesia after cesarean delivery, determine the optimal frequency for the best analgesic effect, and explore the underlying mechanism of action.

STUDY DESIGN

This single-center, randomized, single-blinded, sham acupuncture controlled clinical trial was conducted at a tertiary university hospital in China. Female patients who underwent cesarean delivery and received fentanyl as patient-controlled intravenous analgesia for postoperative analgesia were enrolled. Patients were after surgery randomized to receive 2 Hz electroacupuncture treatment (n=53), 20/100 Hz electroacupuncture treatment (n=53), or sham electroacupuncture treatment (n=52) (controls). The 2 electroacupuncture groups received electroacupuncture treatment at 2 or 20/100 Hz at the ST36 and SP6 points, whereas, in the sham electroacupuncture group, sham electroacupuncture was performed at nonmeridian points with nonenergized electroacupuncture instruments. Of note, 4 electroacupuncture treatments were performed in all groups at 6, 12, 24, and 48 hours after surgery. The primary outcome was the number of analgesic pump compressions at 48 hours after surgery. The secondary outcomes included number of analgesic pump compressions at 6, 12, and 24 hours after surgery; pain scores at 6, 12, 24, and 48 hours after surgery; fentanyl consumption at 48 hours after surgery; interleukin 6 and procalcitonin levels at 12 and 48 hours after surgery; and time to first exhaust.

RESULTS

Overall, 174 primigravida women were included in the intention-to-treat analysis. The number of analgesic pump compressions and pain scores at all 4 time points and fentanyl consumption at 48 hours after surgery were significantly lower in the electroacupuncture treatment groups than in the sham electroacupuncture group (P<.001).

CONCLUSION

Electroacupuncture + patient-controlled intravenous analgesia had a significantly better analgesic effect than sham electroacupuncture + patient-controlled intravenous analgesia within 48 hours after surgery. Thus, electroacupuncture can be considered safe and effective and may improve the efficacy of patient-controlled intravenous analgesia for pain management after cesarean delivery. Electroacupuncture can be recommended as a routine complementary therapy for pain control after cesarean delivery.

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.

Acupuncture for neuropathic pain: A meta-analysis of randomized control trials

Background

Neuropathic pain (NP) is expected to increase due to the high risk of global population aging. Acupuncture has a definite clinical effect on NP. Therefore, a systematic review and meta-analysis were conducted to evaluate the effect on pain intensity and safety of acupuncture in patients with NP.

Methods

An encompassing search of specific authoritative databases in English, from their inception to 2022, was performed. The databases were as follows: Scopus, Ovid EMBASE, Ovid Cochrane Database of Systematic Reviews, Ovid Cochrane Central Register of Controlled Trials, Ovid MEDLINE(R) and Epub Ahead of Print, In-Process and Other Non-Indexed Citations, and Daily. All the randomized controlled trials regarding the acupuncture treatment of NP will be included. Methodological quality assessment of the included trials was assessed based on the risk of bias from the Cochrane handbook. A meta-analysis was performed for the main outcomes. In addition, sensitivity analysis, subgroup analysis, and funnel plot were also carried out.

Results

A total of 16 studies with 1,021 patients with NP were evaluated in a systematic review. According to the results of the overall meta-analysis in eight RCTs with 338 participants, the acupuncture group was better than the control group in improving changes in pain intensity (SMD -0.59, 95% CI: -0.95 to -0.23, P = 0.001). In subgroup analysis, five trials indicated that acupuncture was more effective in improving changes in pain intensity than sham acupuncture (SMD -0.54, 95% CI: -0.95 to -0.13, P = 0.01), two trials evaluated the effect on changes in pain intensity in the comparison of acupuncture and conventional treatments, no significant difference existed (SMD -0.61, 95% CI: -1.83 to 0.61, P = 0.33), and one trial compared acupuncture with blank control evaluating the effect of changes in pain intensity with a significant difference. Eleven studies mentioned the safety conditions and acupuncture-induced AEs were mild and reversible. Both the sensitivity analysis and funnel plot analysis showed that the meta-analysis was stable and irreversible without publication bias. The GRADE was rated as "very low."

Conclusion

The acupuncture group had higher effectiveness than sham intervention or blank control for changes in pain intensity, but there is no significant difference between acupuncture and conventional treatments in treating NP. The acupuncture-induced adverse events were mild and reversible. However, the interpretation of our results should be performed cautiously due to the low methodological quality of selected publications.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022306461.

The Role of Glia Underlying Acupuncture Analgesia in Animal Pain Models: A Systematic Review and Meta-Analysis

BACKGROUND

As a traditional Chinese therapy, acupuncture is proposed worldwide as a treatment for pain and other health problems, but findings on acupuncture analgesia have been inconsistent because of its variable modalities of therapeutic intervention.

OBJECTIVE

This study aimed to evaluate the existing animal studies for evidence on acupuncture and its effect on glia in association with a reduction in pain conditions.

METHODS

Literature searches were performed in four English- and Chinese-language databases (Web of Science, PubMed, EMBASE, and CNKI) on October 8, 2021. Included studies reported the pain outcome (e.g., paw withdrawal latency, paw withdrawal threshold) and glia outcome (e.g., glial marker GFPA, Iba1, and OX42) in pain-induced animals during acupuncture treatment.

RESULTS

Fifty-two preclinical studies were included in the meta-analysis. A single acupuncture treatment in rodents had an analgesic effect, which was more effective in inflammatory pain than in neuropathic pain in the early phase of treatment. The analgesic efficacy became more curative after repeated acupuncture. Furthermore, acupuncture treatment could effectively inhibit the activity of astrocytes and microglia in both inflammatory pain and neuropathic pain in a time-course pattern.

CONCLUSIONS

Acupuncture treatment improves analgesic effect in rodent pain conditions under the possible mechanism of glial inhibition. Therefore, these results provide an opportunity to evaluate the effectiveness of acupuncture analgesia and neuroinflammation in animal models to research further neurobiological mechanisms and to inform the design of future clinical trials.

STUDY REGISTRATION

PROSPERO (ID: CRD42020196011).

Assessment and management of pain/nociception in patients with disorders of consciousness or locked-in syndrome: A narrative review

The assessment and management of pain and nociception is very challenging in patients unable to communicate functionally such as patients with disorders of consciousness (DoC) or in locked-in syndrome (LIS). In a clinical setting, the detection of signs of pain and nociception by the medical staff is therefore essential for the wellbeing and management of these patients. However, there is still a lot unknown and a lack of clear guidelines regarding the assessment, management and treatment of pain and nociception in these populations. The purpose of this narrative review is to examine the current knowledge regarding this issue by covering different topics such as: the neurophysiology of pain and nociception (in healthy subjects and patients), the source and impact of nociception and pain in DoC and LIS and, finally, the assessment and treatment of pain and nociception in these populations. In this review we will also give possible research directions that could help to improve the management of this specific population of severely brain damaged patients.

Transcription factor ETS proto-oncogene 1 contributes to neuropathic pain by regulating histone deacetylase 1 in primary afferent neurons

Nerve injury can induce aberrant changes in ion channels, enzymes, and cytokines/chemokines in the dorsal root ganglia (DRGs); these changes are due to or at least partly governed by transcription factors that contribute to the genesis of neuropathic pain. However, the involvement of transcription factors in neuropathic pain is poorly understood. In this study, we report that transcription factor (TF) ETS proto-oncogene 1 (ETS1) is required for the initiation and development of neuropathic pain. Sciatic nerve chronic constrictive injury (CCI, a clinical neuropathic pain model) increases ETS1 expression in the injured male mouse DRG. Blocking this upregulation alleviated CCI-induced mechanical allodynia and thermal hyperalgesia, with no apparent effect on locomotor function. Mimicking this upregulation results in the genesis of nociception hypersensitivity; mechanistically, nerve injury-induced ETS1 upregulation promotes the expression of histone deacetylase 1 (HDAC1, a key initiator of pain) via enhancing its binding activity to the HDAC1 promotor, leading to the elevation of spinal central sensitization, as evidenced by increased expression of p-ERK1/2 and GFAP in the dorsal spinal horn. It appears that the ETS1/HDAC1 axis in DRG may have a critical role in the development and maintenance of neuropathic pain, and ETS1 is a potential therapeutic target in neuropathic pain.

Methyltransferase-like 3 modulates visceral hypersensitivity through regulating the nuclear export of circKcnk9 in YTHDC1-dependent manner

Background: Accumulating evidence shows that N6-methyladenosine (m⁶A) modulators contribute to the process of chronic pain. However, the exact mechanisms of m⁶A writers involved in visceral hypersensitivity of Irritable bowel syndrome (IBS) remain unclear. This article aimed to reveal a new mechanism for the progression of IBS. Methods: The IBS-like model was established by neonatal colorectal distention (CRD). The relationship between m⁶A and circKcnk9 was analyzed by bioinformatics, immunofluorescence and RNA fluorescence in situ hybridization (FISH) assays. Visceral hypersensitivity was assessed based on the electromyography (EMG) response of the abdominal external oblique muscle to CRD. In vivo and in vitro studies (including EMG stereotactic infusion, Western blot and qRT-PCR) were utilized to explore the biological functions of related indicators. The bioinformatics, RIP experiments and RNA pull-down assays were used to explore the potential molecular mechanisms. Results: We identified that neonatal CRD increased the level of the m⁶A via methyltransferase-like 3 (METTL3) in the hippocampal neurons. Subsequently, knockdown of METTL3 could alleviate visceral hypersensitivity in IBS-like rats. By contrast, overexpression of METTL3 could induce visceral hypersensitivity and activate hippocampal neurons in control rats. Moreover, YTHDC1, the only m⁶A-associated protein predicted by bioinformatics to bind to circKcnk9, modulated visceral hypersensitivity through regulating the nuclear export of circKcnk9 in an m⁶A-dependent manner. Notably, FISH data suggested that the increased nuclear staining of circKcnk9 caused by siYTHDC1 could be recovered by overexpression of YTHDC1 wild type (WT) but not YTHDC1 negative control (NC) in PC12 cells. Conclusions: Our findings reveal a new regulatory mechanism in progress of IBS, that is, METTL3 modulates visceral hypersensitivity through regulating the nuclear export of circKcnk9 in YTHDC1-dependent manner.

Knowledge Mapping of International Research on Acupuncture for Chronic Pain: A Bibliometric Analysis

INTRODUCTION

With the wide acceptance of acupuncture, many papers and guidelines recommend that acupuncture is effective for chronic pain (CP). In this study, we applied bibliometric methods to analyze the current research situation of acupuncture intervention in CP, to gain insight into the current situation and future development trend of this field.

MATERIAL AND METHODS

Science Citation Index Expanded was searched for publications related to acupuncture for CP between 1900 and 2022. VOSviewer, CiteSpace and Thomson Data Analyzer were used to analyze the annual publication, authors and cited authors and their countries (regions) and institutions, journals and cited journals, cited references, co-occurrence keywords, burst keywords, and the relevant centrality.

RESULTS

A total of 1968 papers were retrieved, the annual publications have shown a rapid growth trend in the recent 20 years. The USA (708) and the Kyung Hee University (31) were the most productive country and institution, respectively, while the USA (0.37) and University of Maryland (0.13) had the highest centrality. MacPherson, Hugh published the most papers in this field (29), and Vickers, A J were the most influential author (289 times cited). Journal of Alternative and Complementary Medicine was the most productive journal (92), whereas PAIN was the most influential one (4743 times cited). Breivik, H's (2006) paper had the most citation count (3025), while Furlan's (2005) paper had the highest centrality (0.23). The research focuses in this field mainly include pain, electroacupuncture, Low back pain, Systematic review, Randomized controlled trial etc. Researchers are currently paying more attention to the psychological problems caused by CP.

CONCLUSION

The research of acupuncture for CP will be further expanded. International cooperation of this research field needs to be further strengthened. More high-quality designed trials need to be conducted.

Potential mechanisms of acupuncture for neuropathic pain based on somatosensory system

Neuropathic pain, caused by a lesion or disease of the somatosensory system, is common and distressing. In view of the high human and economic burden, more effective treatment strategies were urgently needed. Acupuncture has been increasingly used as an adjuvant or complementary therapy for neuropathic pain. Although the therapeutic effects of acupuncture have been demonstrated in various high-quality randomized controlled trials, there is significant heterogeneity in the underlying mechanisms. This review aimed to summarize the potential mechanisms of acupuncture on neuropathic pain based on the somatosensory system, and guided for future both foundational and clinical studies. Here, we argued that acupuncture may have the potential to inhibit neuronal activity caused by neuropathic pain, through reducing the activation of pain-related ion channels and suppressing glial cells (including microglia and astrocytes) to release inflammatory cytokines, chemokines, amongst others. Meanwhile, acupuncture as a non-pharmacologic treatment, may have potential to activate descending pain control system via increasing the level of spinal or brain 5-hydroxytryptamine (5-HT), norepinephrine (NE), and opioid peptides. And the types of endogenously opioid peptides was influenced by electroacupuncture-frequency. The cumulative evidence demonstrated that acupuncture provided an alternative or adjunctive therapy for neuropathic pain.

Characteristics of Zusanli Dorsal Root Ganglion Neurons in Rats and Their Receptor Mechanisms in Response to Adenosine

Neural systems play important roles in the functions of acupuncture. But the unclear structure and mechanism of acupoints hinder acupuncture standardization and cause the acupuncture effects to be varying or even paradoxical. It has been broadly assumed that the efficacy of acupuncture depends on the biological signals triggered at acupoints and passed up along neural systems. However, as the first station to transmit such signals, the characters of the dorsal root ganglia (DRG) neurons innervating acupoints are still not well elucidated. We adopted Zusanli (ST36) as a representative acupoint and found most DRG neurons innervating ST36 acupoint are middle-size neurons with a single spike firing pattern. This suggests that proprioceptive neurons take on greater possibility than small size nociceptive neurons do to mediate the acupuncture signals. Moreover, we found that adenosine injected into ST36 acupoints could dose- and acupoint-dependently mimic the analgesic effect of acupuncture. However, adenosine could not elicit action potentials in the acutely isolated ST36 DRG neurons, but it inhibited I_D currents and increased the areas of overshoots. Further, we found that 4 types of adenosine receptors were all expressed by ST36 DRG neurons, and A1, A2b, and A3 receptors were the principal reactors to adenosine. PERSPECTIVE: This study provides the major characteristics of ST36 DRG neurons, which will help to analyze the neural pathway of acupuncture signals. At the same time, these findings could provide a new possible therapy for pain relief, such as injecting adenosine or corresponding agonists into acupoints.

Brain Functional Alteration at Different Stages of Neuropathic Pain With Allodynia and Emotional Disorders

Neuropathic pain (NeuP), a challenging medical condition, has been suggested by neuroimaging studies to be associated with abnormalities of neural activities in some brain regions. However, aberrancies in brain functional alterations underlying the sensory-discriminative abnormalities and negative emotions in the setting of NeuP remain unexplored. Here, we aimed to investigate the functional alterations in neural activity relevant to pain as well as pain-related depressive-like and anxiety-like behaviors in NeuP by combining amplitude of low frequency fluctuation (ALFF) and degree centrality (DC) analyses methods based on resting-state functional magnetic resonance imaging (rs-fMRI). A rat model of NeuP was established via chronic constriction injury (CCI) of the sciatic nerve. Results revealed that the robust mechanical allodynia occurred early and persisted throughout the entire observational period. Depressive and anxiety-like behaviors did not appear until 4 weeks after injury. When the maximum allodynia was apparent early, CCI rats exhibited decreased ALFF and DC values in the left somatosensory and nucleus accumbens shell (ACbSh), respectively, as compared with sham rats. Both values were significantly positively correlated with mechanical withdrawal thresholds (MWT). At 4 weeks post-CCI, negative emotional states were apparent and CCI rats were noted to exhibit increased ALFF values in the left somatosensory and medial prefrontal cortex (mPFC) as well as increased DC values in the right motor cortex, as compared with sham rats. At 4 weeks post-CCI, ALFF values in the left somatosensory cortex and DC values in the right motor cortex were noted to negatively correlate with MWT and exhibition of anxiety-like behavior on an open-field test (OFT); values were found to positively correlate with the exhibition of depressive-like behavior on forced swimming test (FST). The mPFC ALFF values were found to negatively correlate with the exhibition of anxiety-like behavior on OFT and positively correlate with the exhibition of depressive-like behavior on FST. Our findings detail characteristic alterations of neural activity patterns induced by chronic NeuP and underscore the important role of the left somatosensory cortex, as well as its related networks, in the mediation of subsequent emotional dysregulation due to NeuP.

Electroacupuncture Attenuates Neuropathic Pain and Comorbid Negative Behavior: The Involvement of the Dopamine System in the Amygdala

Neuropathic pain (NeuP) is an important clinical problem accompanying negative mood symptoms. Neuroinflammation in the amygdala is critically involved in NeuP, and the dopamine (DA) system acts as an important endogenous anti-inflammatory pathway. Electroacupuncture (EA) can improve the clinical outcomes in NeuP, but the underlying mechanisms have not been fully elucidated. This study was designed to assess the effectiveness of EA on pain and pain-related depressive-like and anxiety-like behaviors and explore the role of the DA system in the effects of EA. Male Sprague-Dawley rats were subjected to the chronic constrictive injury (CCI) model to induce NeuP. EA treatment was carried out for 30 min once every other day for 3 weeks. The results showed that CCI caused mechanical hyperalgesia and depressive and anxiety-like behaviors in rats and neuroinflammation in the amygdala, such as an increased protein level of TNFα and IL-1β and activation of astrocytes. EA treatment significantly improved mechanical allodynia and the emotional dysfunction induced by CCI. The effects of EA were accompanied by markedly decreased expression of TNFα, IL-1β, and glial fibrillary acid protein (GFAP) in the amygdala. Moreover, EA treatment reversed CCI-induced down-regulation of DA concentration, tyrosine hydroxylase (TH) expression, and DRD1 and DRD2 receptors. These results suggest that EA-ameliorated NeuP may possibly be associated with the DA system to inhibit the neuroinflammation in the amygdala.