TRPV1 expression in acupuncture points: response to electroacupuncture stimulation

Acupuncture influences multiple diseases by regulating gut microbiota

Acupuncture, an important green and side effect-free therapy in traditional Chinese medicine, is widely use both domestically and internationally. Acupuncture can interact with the gut microbiota and influence various diseases, including metabolic diseases, gastrointestinal diseases, mental disorders, nervous system diseases, and other diseases. This review presents a thorough analysis of these interactions and their impacts and examines the alterations in the gut microbiota and the potential clinical outcomes following acupuncture intervention to establish a basis for the future utilization of acupuncture in clinical treatments.

Peripheral mast cells derive the effects of acupuncture in Parkinson's disease

This research investigates the peripheral mechanisms of acupuncture in treating Parkinson's disease (PD), a progressive neurodegenerative disorder marked by motor impairments. While the central mechanisms of acupuncture have been extensively studied, our focus lies in the peripheral mechanisms at the acupoints, the sites of acupuncture signal initiation. Employing a PD model, we analyzed the local responses to acupuncture stimulation at these points. Our key finding was a significant elevation in both the number and activity of mast cells (MCs) in the peripheral tissues following acupuncture. Intriguingly, pre-treatment with an MC stabilizer diminished the acupuncture's therapeutic effects on PD symptoms. Similarly, local anesthesia with lidocaine at the acupoints attenuated the symptom improvement typically observed with acupuncture. Meanwhile, the augmentation of MC activity induced by acupuncture was significantly impeded by cromolyn, an MC stabilizer, but remained unaffected by lidocaine. This finding suggests that MC activity is a more upstream regulator of acupuncture effects compared to nerve conduction. This study provides groundbreaking insights into the initiation and transmission of acupuncture signals, highlighting the significant role of peripheral MC modulation in PD treatment.

Effects and mechanisms of acupuncture analgesia mediated by afferent nerves in acupoint microenvironments

In the past few decades, the use of acupuncture analgesia in clinical practice has increased worldwide. This is due to its various benefits, including natural alleviation of pain without causing various adverse effects associated with non-steroidal anti-inflammatory drugs (NSAID) and opioids. The acupoint represents the initial site of acupuncture stimulation, where diverse types of nerve fibers located at the acupoint hold significant roles in the generation and transmission of acupuncture-related information. In this study, we analyzed the patterns and mechanisms of acupuncture analgesic mediated by acupoint afferent fibers, and found that acupuncture stimulates acupoints which rapidly and directly induces activation of high-density primary afferent fibers under the acupoints, including myelinated A fibers and unmyelinated C fibers. During acupuncture stimulation at the muscle layer, the analgesic effects can be induced by stimulation of A fiber threshold intensity. At the skin layer, the analgesic effects can only be produced by stimulation of C fiber threshold intensity. Electroacupuncture (EA) activates A fibers, while manual acupuncture (MA) activates both A and C fibers. Furthermore, acupuncture alters acupoint microenvironments, which positively modulates afferent fibers, enhancing the transmission of analgesic signals. In addition to local activation and conduction at acupoints, nerve fibers mediate the transmission of acupuncture information to pain centers. In the spinal cord, acupuncture activates neurons by inducing afferent fiber depolarization, modulating pain gating, inhibiting long-term potentiation (LTP) of the spinal dorsal horn and wide dynamic range (WDR) neuronal activities. At higher nerve centers, acupuncture inhibits neuronal activation in pain-related brain regions. In summary, acupuncture inhibits pain signal transmission at peripheral and central systems by activating different patterns of afferent fibers located on various layers of acupoints. This study provides ideas for enhancing the precise application and clinical translation of acupuncture.

Stimuli-induced NOergic Molecules and Neuropeptides Mediated Axon Reflexes Contribute to Tracers along Meridian Pathways

An abundance of studies from different international groups have demonstrated tracers along linear pathways resembling meridians over the body surface of humans. All experiments of the studies have been conducted by injection of a radiotracer solution or tracer dyes in a volume of solution into acupuncture points (acupoints). The solution injected into acupoints produces much stronger mechanical stimuli than acupuncture, which causes axon reflex. Anatomical studies have demonstrated that acupoints/meridians exist higher number of small nerve fibers and blood vessels with rich nitric oxide (NO) and neuropeptides in the cutaneous tissues as structures for the biomolecules mediated axon reflexes. Recent advances have determined that NO and calcitonin generelated peptides play crucial roles in the comprehension of the axon reflex. The stimuli-evoked axon reflex and NOergic biomolecules/neuropeptides increase local blood flow with higher levels in acupoints/meridians, which move radioactive substances or tracer dyes in the skin and subcutaneous tissue under a linear path resembling acupoints and meridians, the important phenomena of meridians induced by the stimuli. The evidence and understanding of the biomolecular processes of the tracers along linear pathways resembling meridians have been summarized with an emphasis on recent developments of NO and neuropeptides mediating stimuli-evoked axon reflexes to increase local blood flow with higher levels in acupoints/meridians, which move radioactive substances or tracer dyes in the skin and subcutaneous tissue contributing to tracers along linear pathways resembling meridians in this mini-review.

Knowledge mapping of acupoint sensitization and acupoint specificity: a bibliometric analysis

Objective

The relationship between acupoint sensitization and acupoint specificity is a topic of significant interest in acupuncture research. Numerous clinical studies have demonstrated that needling pain sensitive acupoints yields superior therapeutic outcomes compared to traditional acupoints, particularly in the context of pain disorders. However, there is a lack of bibliometric analysis in acupuncture area. Therefore, the objective of this study is to offer a comprehensive overview of the knowledge structure and research hotspots pertaining to acupoint sensitization and acupoint specificity.

Methods

The search for publications pertaining to acupoint sensitization and acupoint specificity was conducted in the Web of Science Core Collection (WoSCC) database from its inception until August 11, 2023. Subsequently, bibliometric analyses were carried out using VOSviewer, CiteSpace, R software (Bibliometrix package), and GraphPad Prism software.

Results

This study includes 4,940 articles from 72 countries, with China and the United States being the leading countries. The number of publications related to acupoint sensitization and specificity has been increasing annually. Major research institutions involved in this field include the Shanghai University of Traditional Chinese Medicine, Kyung Hee University, Beijing University of Chinese Medicine, Chinese Academy of Chinese Medical Sciences, and China Medical University, among others. "Evidence-based Complementary and Alternative Medicine" is the most popular journal in acupuncture field, and "PAIN" is the most co-cited journal. Publications are contributed by 20,325 authors from all over the world, with Wu Huangan, Fang Jianqiao, Lin Yi-Wen, Liu Huirong, and Chen Rixin having published the most articles. Han Ji-Sheng is the most cited author in this research area. The main directions include the study of temperature specificity of acupoints, the diagnosis of acupoint sensitization diseases, and the study of the mechanism of acupoint sensitization. The most listed keywords in recent years are "TRPV1," "signaling pathway," and "diagnosis."

Conclusion

This is the first bibliometric study to comprehensively summarize research trends and advances in acupoint sensitization and acupoint specificity, and the information highlights recent research preliminary and main directions that serve as a reference for acupoint sensitization and acupoint specificity research.

Role of autophagy in the pathogenesis and regulation of pain

Pain is a ubiquitous and highly concerned clinical symptom, usually caused by peripheral or central nervous injury, tissue damage, or other diseases. The long-term existence of pain can seriously affect daily physical function and quality of life and produce great torture on the physiological and psychological levels. However, the complex pathogenesis of pain involving molecular mechanisms and signaling pathways has not been fully elucidated, and managing pain remains highly challenging. As a result, finding new targets to pursue effective and long-term pain treatment strategies is required and urgent. Autophagy is an intracellular degradation and recycling process that maintains tissue homeostasis and energy supply, which can be cytoprotective and is vital in maintaining neural plasticity and proper nervous system function. Much evidence has shown that autophagy dysregulation is linked to the emergence of neuropathic pain, such as postherpetic neuralgia and cancer-related pain. Autophagy has also been connected to pain caused by osteoarthritis and lumbar disc degeneration. It is worth noting that in recent years, studies on traditional Chinese medicine have also proved that several traditional Chinese medicine monomers involve autophagy in the mechanism of pain relief. Therefore, autophagy can serve as a potential regulatory target to provide new ideas and inspiration for pain management.

Attenuation of immobilization stress-induced hypertension by temperature-controllable warm needle acupuncture in rats and the peripheral neural mechanisms

Introduction

We and others have shown that electrical stimulation of the PC-6 acupoint over the wrist relieves hypertension by stimulating afferent sensory nerve fibers and activating the central endogenous opioid system. Warm needle acupuncture has long been utilized to treat various diseases in clinics.

Methods

Here, we developed a temperature-controllable warm needle acupuncture instrument (WAI) and investigated the peripheral mechanism underlying the effect of warm needle acupuncture at PC-6 on hypertension in a rat model of immobilization stress-induced hypertension.

Results

Stimulation with our newly developed WAI and traditional warm needle acupuncture attenuated hypertension development. Such effects were reproduced by capsaicin (a TRPV1 agonist) injection into PC-6 or WAI stimulation at 48°C. In contrast, PC-6 pretreatment with the TRPV1 antagonist capsazepine blocked the antihypertensive effect of WAI stimulation at PC-6. WAI stimulation at PC-6 increased the number of dorsal root ganglia double-stained with TRPV1 and CGRP. QX-314 and capsaicin perineural injection into the median nerve for chemical ablation of small afferent nerve fibers (C-fibers) prevented the antihypertensive effect of WAI stimulation at PC-6. Additionally, PC-6 pretreatment with RTX ablated the antihypertensive effect of WAI stimulation.

Conclusion

These findings suggest that warm needle acupuncture at PC-6 activates C-fiber of median nerve and the peripheral TRPV1 receptors to attenuate the development of immobilization stress-induced hypertension in rats.

Relationship between acupuncture and transient receptor potential vanilloid: Current and future directions

Acupuncture is a common complementary and alternative therapy around the world, but its mechanism remains still unclear. In the past decade, some studies indicated that transient receptor potential vanilloid (TRPV) channels play a great role in the response of acupuncture stimulation. In this article, we discussed the relationship between acupuncture and TRPV channels. Different from inhibitors and agonists, the regulation of acupuncture on TRPV channels is multi-targeted and biphasic control. Acupuncture stimulation shows significant modulation on TRPV1 and TRPV4 at the autonomic nervous system (ANS) including central and peripheral nervous systems. On the contrary, the abundant expression and functional participation of TRPV1 and TRPV4 were specific to acupuncture stimulation at acupoints. The enhancement or inhibition of TRPV channels at different anatomical levels will affect the therapeutic effect of acupuncture. In conclusion, TRPV channels help to understand the principle of acupuncture stimulation, and acupuncture also provides a potential approach to TRPV-related trials.

Microbial Profiles of Patients With Antipsychotic-Related Constipation Treated With Electroacupuncture

Antipsychotic-related constipation (APRC) is one of the most common side effects of taking antipsychotic medication. APRC can seriously impact patient quality of life and is potentially fatal, though the efficacy of current APRC treatments is low for most patients. In this study, we conducted a controlled, pilot randomized, sham-electroacupuncture (SEA) study to assess the efficacy of electroacupuncture (EA) in patients with APRC. We used 16S rRNA gene sequencing to assess the microbial profiles of these patients and analyze how EA treatments affected their bacteria.

Methods: We treated 133 APRC patients with randomly assigned EA treatments or SEA treatments for 4 consecutive weeks, fully evaluating the patients 8 weeks after treatment. The participants, outcome assessors, and statistics were all blind to the EA and SEA treatments. Outcomes assessed included changes in spontaneous bowel movements (SBMs) and the frequency of rescue measures. We detected assessed the microbial diversity of stool specimens both before and after EA treatment using 16S rRNA gene sequencing.

Results: Both EA and SEA treatments reduced the need for constipation rescue measures and did not have serious side effects. EA treatments were better than SEA treatments at increasing SBMs and reducing rescue measures. The diversity of gut microbiota changed after EA treatment. LEfSe analysis indicated changes in the genus (belonging to phylum Proteobacteria) of gut microbiota in patients following EA treatment.

Conclusions: This study found that EA treatment is effective and safe for patients with APRC, and could be associated with changes in their microbial profiles. Further study, with larger sample sizes, is needed to explore the efficacy of EA intervention as a clinical treatment for APRC.

Trial Registration: ChiCTR, ChiCTR-ONC-17010842, http://www.chictr.org.cn/showproj.aspx?proj=18420.

Nitric Oxide on Pathophysiology of SARS-CoV 19: Toward Possible Role of Acupuncture Treatment

The ongoing outbreak of COVID-19 has quickly become a daunting challenge to global health. In the absence of satisfied therapy, effective treatment interventions are urgently needed. Previous studies have demonstrated that acupuncture is effective at relieving common symptoms of COVID-19 including breathlessness, nausea, insomnia, leukopenia, fatigue, vomiting, and abdominal pain. Experiments have shown that nitric oxide (NO) inhibits the replication cycle of severe acute respiratory syndrome (SARS) coronavirus with similar structures of COVID-19. Increase in level of NO by using NO gas inhalation has been shown to restore lung function by reducing airway resistance and improving virus-induced lung infections in SARS patients. Recent case report showed that a medical acupuncturist with symptoms consistent with severe COVID pneumonia achieved full recovery by self-administered medical acupuncture and cupping therapy at home. Clinical features and pathophysiology demonstrated that NO deficiency and endothelial dysfunction contribute to the development of COVID-19. Several studies from different groups consistently demonstrated that acupuncture increases NO synthase expression and induces an elevation of NO production and release in plasma and the local skin regions in both animals and humans. It is suggested that exogenous NO supplies or interventions that induce increasing levels of NO can play an important role in protective effects against inflammation and acute lung injury. This article reviews the rationale for mechanisms of NO induction induced by acupuncture in the possible treatment of COVID-19 and highlights its potential for contributing to better clinical outcomes and improving future clinical studies of acupuncture on treatment of COVID-19.

The Efficacy and Safety of Acupuncture for Treating Osteoporotic Vertebral Compression Fracture- (OVCF-) Induced Pain: A Systematic Review and Meta-Analysis of Randomized Clinical Trials

Background

Osteoporotic vertebral compression fractures (OVCFs) are common health issues in the elderly that cause chronic pain in over one-third of patients. This study was sought to evaluate the efficacy and safety of acupuncture for alleviating pain caused by OVCFs.

Methods

We performed a search of 8 electronic databases for publications from the inception to 30^th March 2021. Eligible studies were randomized clinical trials (RCTs) that evaluated the effect of acupuncture for the treatment of OVCFs. Two investigators evaluated literature quality and extracted data independently. RevMan V.5.4.1 was used for data analyses, with pooled risk estimates presented as mean difference (MD) or relative risk (RR) along with corresponding 95% confidence intervals (CIs), as appropriate.

Results

Fourteen RCTs involving 1,130 patients were included in this meta-analysis. Compared with the control group, acupuncture showed a greater benefit on pain reduction caused by OVCFs (1 week: MD = −1.26, 95% CI: (−1.82,−0.70); 1 month: MD = −1.63, 95% CI: (−1.82,−1.43); 6 months: MD = −1.13, 95% CI: (−1.55, −0.70)). Acupuncture treatment was also associated with fewer adverse events, lower ODI index, and higher bone density than the control group (safety: (RR: 0.30, 95% CI: 0.12–0.75); ODI: MD = −3.19, 95% CI: (−5.20, −1.19); bone density: MD = 0.15, 95% CI: (0.05, 0.26)). The GRADE quality of these results was assessed as low or very low.

Conclusions

Compared with the control treatment, acupuncture was more effective and safer in relieving the pain caused by OVCF and made a greater improvement on patient's ODI score and bone density. Given the low level of our study evidence, future high-quality studies are needed to verify our study findings.

Transient receptor potential V1 modulates neuroinflammation in Parkinson's disease dementia: Molecular implications for electroacupuncture and rivastigmine

OBJECTIVES

Parkinson's disease (PD) is a common progressive neurodegeneration disease. Its incidence increases with age and affects about 1% of people over 60. Incidentally, transient receptor potential V1 (TRPV1) and its relation with neuroinflammation in mouse brain has been widely reported.

MATERIALS AND METHODS

We used 6-hydroxydopamine (6-OHDA) to induce PDD in mice. We then used the Morris water maze and Bio-Plex to test learning and inflammatory mediators in mouse plasma. Western blotting and immunostaining were used to examine TRPV1 pathway in the hippocampus and medial prefrontal cortex (mPFC).

RESULTS

On acquisition days 3 (Control = 4.40 ± 0.8 sec, PDD = 9.82 ± 1.52 sec, EA = 5.04 ± 0.58 sec, Riva = 4.75 ± 0.87 sec; P=0.001) and 4, reversal learning days 1, 2, 3 (Control = 2.86 ± 0.46 sec, PDD = 9.80 ± 1.83 sec, EA = 4.6 ± 0.82 sec, Riva = 4.6 ± 1.03 sec; P=0.001) and 4, PDD mice showed significantly longer escape latency than the other three groups. Results showed that several cytokines were up-regulated in PDD mice and reversed by EA and rivastigmine. TRPV1 and downstream molecules were up-regulated in PDD mice and further reversed by EA and rivastigmine. Interestingly, α7 nicotinic receptors and parvalbumin levels in both the hippocampus and prefrontal cortex increased in EA-treated mice, but not in rivastigmine-treated mice.

CONCLUSION

Our results showed that TRPV1 played a role in the modulation of neuroinflammation of PDD, and could potentially be a new target for treatment.

Low Electrical Resistance Properties of Acupoints: Roles of NOergic Signaling Molecules and Neuropeptides in Skin Electrical Conductance

Early studies from several independent laboratories demonstrated that acupoints possess the characteristics of low electrical resistance. New devices are developing to increase the reliability of electrical skin impedance measurements for counteracting the factors including skin dryness, skin thickness, size of the sensing electrode, pressure applied on the electrode, interelectrode distance, room temperature, and humidity. Morphological studies have identified that blood vessels, hair follicles, and nervous components are enhanced in the meridians/acupoints, which represent areas of potentially high neuronal activity. Recent evidence shows that nitric oxide (NO) concentrations are enhanced in skin acupoints/meridians. L-arginine-derived NO synthesis modifies skin norepinephrine (NE) synthesis/release in acupoints/meridians, and NO-NE activations play an important role in mediating the skin conductance responses to electrical stimulation. NOergic signaling molecules interact with gap junction and transient receptor potential vanilloid type-1. Other studies reported that the high conductance at acupoints is a result of the release of the neuropeptides substance P and calcitonin gene-related peptide during neurogenic inflammation in the referred pain area. Pathological body conditions caused considerable changes in skin conductance or impedance at acupoints. Although systematic research with an improved equipment and research design to avoid the influencing factors are requested for a definite answer in this field, the results from anatomical and biochemical studies consistently show that acupoints exist higher levels of nervous components, and NOergic signaling molecules and neuropeptides involved in the skin low resistance at acupoints. The increased interest in the acupoints/meridians has led to an open-minded attitude towards understanding this system, which is fundamental important to establish the valid aspects of scientific basis of Chinese medicine mechanisms and therapies.

Electroacupuncture Inhibits Autophagy of Neuron Cells in Postherpetic Neuralgia by Increasing the Expression of miR-223-3p

Postherpetic neuralgia (PHN) is a complication of herpes zoster viral infection. Its main manifestations are continuous or intermittent burning-like and electroshock-like pain in the affected nerves. Electroacupuncture (EA) is widely used in clinical treatment and exerts effects in alleviating neuropathic pain. In this study, we investigated the effect and underlying mechanism of EA on PHN. Sprague-Dawley rats were treated with resiniferatoxin (RTX) to establish a PHN model and subjected to EA and/or miR-223-3p overexpression (OV) or interference. Mechanical withdrawal latency was measured as an indication of pain sensitivity. Hematoxylin-eosin staining and transmission electron microscopy were performed to observe neuron cell morphology and autophagic vacuoles, respectively. ELISA was performed to detect reactive oxygen species (ROS) production and the levels of tumor necrosis factor- (TNF-) α, inducible nitric oxide synthase (iNOS), interleukin- (IL-) 6, and IL-10. Changes in autophagy and apoptosis-related miRNAs were detected by immunofluorescence and qRT-PCR, respectively. In RTX-treated rats, OV and EA reduced pain sensitivity, decreased the number of eosinophils, and increased that of nerve cells. ROS generation and the levels of TNF-α and iNOS were significantly reduced, while those of IL-6 and IL-10 were increased. OV and EA induced fewer autophagic vacuoles than those in the model group. The expression of autophagy-related protein microtubule-associated protein 1 light chain 3-II, ATG9, and Rab1 was decreased by OV and EA, whereas that of P62 was increased. qRT-PCR revealed that miR-223-3p expression in the model group decreased but was increased by EA. EA inhibits neuron cell autophagy in PHN by increasing miR-223-3p expression.

Peripheral ERK modulates acupuncture-induced brain neural activity and its functional connectivity

Acupuncture has been widely used as a therapeutic intervention, and the brain network plays a crucial role in its neural mechanism. This study aimed to investigate the acupuncture mechanism from peripheral to central by identifying how the peripheral molecular signals induced by acupuncture affect the brain neural responses and its functional connectivity. We confirmed that peripheral ERK activation by acupuncture plays a role in initiating acupuncture-induced peripheral proteomic changes in mice. The brain neural activities in the neocortex, hippocampus, thalamus, hypothalamus, periaqueductal grey, and nucleus of the solitary tract (Sol) were significantly changed after acupuncture, and these were altered by peripheral MEK/MAPK inhibition. The arcuate nucleus and lateral hypothalamus were the most affected by acupuncture and peripheral MEK/MAPK inhibition. The hypothalamic area was the most contributing brain region in contrast task PLS analysis. Acupuncture provoked extensive changes in brain functional connectivity, and the posterior hypothalamus showed the highest betweenness centrality after acupuncture. After brain hub identification, the Sol and cingulate cortex were selected as hub regions that reflect both degree and betweenness centrality after acupuncture. These results suggest that acupuncture activates brain functional connectivity and that peripheral ERK induced by acupuncture plays a role in initiating brain neural activation and its functional connectivity.

Peripheral receptors and neuromediators involved in the antihyperalgesic effects of acupuncture: a state-of-the-art review

The present study aims to describe state-of-the-art of preclinical studies that have investigated peripheral receptors and neuromediators involved in the antihyperalgesic effects of acupuncture. The PubMed, Scopus, and Web of Science databases were searched using the integrative review method. Preclinical articles that involved the study of peripheral receptors and neuromediators on the pain control effects of acupuncture in rats or mice were selected using a predefined search strategy. From this search, 456 articles were found, and 29 of them met the inclusion criteria of the study. The selected articles addressed the following peripheral receptors: opioid (n = 9), adenosine (n = 5), cannabinoid (n = 5), transient receptor potential vanilloid (TRPV) (n = 3), histamine (n = 2), adrenergic (n = 1), muscarinic (n = 1), corticotrophin-releasing factor (CRF) (n = 2), IL-1 (n = 1), and endothelin (n = 1) receptors. The peripheral neuromediators correlated with the peripheral pain control effect were as follows: opioid peptides (n = 4), adenosine (n = 3), histamine (n = 1), substance P (n = 1) calcitonin gene-related peptide (CGRP) (n = 1), anandamide (n = 1), nitric oxide (n = 1), and norepinephrine (n = 1). This review summarizes the methods used to investigate the peripheral effects of acupuncture and discusses the main findings on each family of receptors and neuromediators. Ten families of peripheral receptors and 8 types of neuromediators were correlated with the antihyperalgesic effects of acupuncture in preclinical studies. Considering the benefits of a better understanding of the role of peripheral receptors and neuromediators in the context pain management, the findings of the present study highlight the importance of deepening the exploration of the peripheral mechanisms of acupuncture.

The neuro-immune microenvironment of acupoints-initiation of acupuncture effectiveness

Acupuncture is a centuried and unfading treatment of traditional Chinese medicine, which has been proved to exert curative effects on various disorders. Numerous works have been put in to uncover the effective mechanisms of acupuncture. And the interdependent interaction between acupuncture and acupoint microenvironment is a crucial topic. As a benign minimally invasive stimulation, the insertion and manipulation of needle at acupoint could cause deformation of local connective tissue and secretion of various molecules, such as high mobility group box 1 and ATP. The molecules are secreted into extracellular space and bind to the corresponding receptors thus active NF-κB, MAPK, ERK pathways on mast cells, fibroblasts, keratinocytes, and monocytes/macrophages, among others. This is supposed to trigger following transcription and translation of immune factors and neural active substance, as well as promote the free ion movement (such as Ca²⁺ influx) and the expansion of blood vessels to recruit more immune cells to acupoint. Finally, acupuncture could enhance network connectivity of local microenvironment at acupoints. The earlier mentioned substances further act on a variety of receptors in local nerve endings, transmitting electrical and biochemical signals to the CNS, and giving full play to the acupuncture action. In conclusion, we portrayed a neuro-immune microenvironment network of acupoints that medicates the acupuncture action, and would lay a foundation for the systematic study of the complex network relationship of acupoints in the future.

Acupuncture inhibits neuroinflammation and gut microbial dysbiosis in a mouse model of Parkinson's disease

Growing evidences show that gut microbiota is associated with the pathogenesis of Parkinson's disease (PD) and the gut-brain axis can be promising target for the development of the therapeutic strategies for PD. Acupuncture has been used to improve brain functions and inflammation in neurological disorders such as PD, and to recover the gastrointestinal dysfunctions in various gastrointestinal disorders. Thus, we investigated whether acupuncture could improve Parkinsonism and gut microbial dysbiosis induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. First, we observed that acupuncture treatment at acupoints GB34 and ST36 could improve motor functions and comorbid anxiety in PD mice. Next, we found that acupuncture increased the levels of dopaminergic fibers and neurons in the striatum and the substantia nigra, respectively. Acupuncture also restored the overexpression of microglia and astrocyte as well as conversion of Bax and Bcl-2 expression in both the striatum and the substantia nigra, indicating that inflammatory responses and apoptosis were blocked by acupuncture. Additionally, via 16S rRNA sequence analysis, we observed that the relative abundance of 18 genera were changed in acupuncture-treated mice compared to the PD mice. Of them, Butyricimonas, Holdemania, Frisingicoccus, Gracilibacter, Phocea, and Aestuariispira showed significant correlations with anxiety as well as motor functions. Furthermore, the predicted functional analyses showed that acupuncture restored the physiology functions such as glutathione metabolism, methane metabolism, and PD pathway. In conclusion, we suggest that the effects of acupuncture on the enhanced motor function and the protection of the dopaminergic neurons may be associated with the regulation of the gut microbial dysbiosis and thus the inhibition of the neuroinflammation in the PD mice.

Acupuncture for Pain Management: Molecular Mechanisms of Action

Acupuncture reduces pain by activating specific areas called acupoints on the patient’s body. When these acupoints are fully activated, sensations of soreness, numbness, fullness, or heaviness called De qi or Te qi are felt by clinicians and patients. There are two kinds of acupuncture, manual acupuncture and electroacupuncture (EA). Compared with non-acupoints, acupoints are easily activated on the basis of their special composition of blood vessels, mast cells, and nerve fibers that mediate the acupuncture signals. In the spinal cord, EA can inhibit glial cell activation by down-regulating the chemokine CX3CL1 and increasing the anti-inflammatory cytokine interleukin-10. This inhibits P38 mitogen-activated protein kinase and extracellular signal-regulated kinase pathways, which are associated with microglial activation of the C-Jun N-terminal kinase signaling pathway and subsequent astrocyte activation. The inactivation of spinal microglia and astrocytes mediates the immediate and long-term analgesic effects of EA, respectively. A variety of pain-related substances released by glial cells such as the proinflammatory cytokines tumor necrosis factor [Formula: see text], interleukin-1[Formula: see text], interleukin-6, and prostaglandins such as prostaglandins E2 can also be reduced. The descending pain modulation system in the brain, including the anterior cingulated cortex, the periaqueductal gray, and the rostral ventromedial medulla, plays an important role in EA analgesia. Multiple transmitters and modulators, including endogenous opioids, cholecystokinin octapeptide, 5-hydroxytryptamine, glutamate, noradrenalin, dopamine, [Formula: see text]-aminobutyric acid, acetylcholine, and orexin A, are involved in acupuncture analgesia. Finally, the “Acupuncture [Formula: see text]” strategy is introduced to help clinicians achieve better analgesic effects, and a newly reported acupuncture method called acupoint catgut embedding, which injects sutures made of absorbable materials at acupoints to achieve long-term effects, is discussed.

Augmented Mechanical Forces of the Surface-Modified Nanoporous Acupuncture Needles Elicit Enhanced Analgesic Effects

Over the past several decades, clinical studies have shown significant analgesic effects of acupuncture. The efficacy of acupuncture treatment has improved with the recent development of nanoporous needles (PN), which are produced by modifying the needle surface using nanotechnology. Herein, we showed that PN at acupoint ST36 produces prolonged analgesic effects in an inflammatory pain model; the analgesic effects of PN acupuncture were sustained over 2 h, while those using a conventional needle (CN) lasted only 30 min. In addition, the PN showed greater therapeutic effects than CN after 10 acupuncture treatments once per day for 10 days. We explored how the porous surface of the PN contributes to changes in local tissue, which may in turn result in enhanced analgesic effects. We showed that the PN has greater rotational torque and pulling force than the CN, particularly at acupoints ST36 and LI11, situated on thick muscle layers. Additionally, in ex vivo experiments, the PN showed greater winding of subcutaneous connective tissues and muscle layers. Our results suggest that local mechanical forces are augmented by the PN and its nanoporous surface, contributing to the enhanced and prolonged analgesic effects of PN acupuncture.

Mechanisms of Acupuncture Therapy for Simple Obesity: An Evidence-Based Review of Clinical and Animal Studies on Simple Obesity

Simple obesity is a worldwide epidemic associated with rapidly growing morbidity and mortality which imposes an enormous burden on individual and public health. As a part of Traditional Chinese Medicine (TCM), acupuncture has shown the positive efficacy in the management of simple obesity. In this article, we comprehensively review the clinical and animal studies that demonstrated the potential mechanisms of acupuncture treatment for simple obesity. Clinical studies suggested that acupuncture regulates endocrine system, promotes digestion, attenuates oxidative stress, and modulates relevant molecules of metabolism in patients of simple obesity. Evidence from laboratory indicated that acupuncture regulates lipid metabolism, modulates inflammatory responses, and promotes white adipose tissue browning. Acupuncture also suppresses appetite through regulating appetite regulatory hormones and the downstream signaling pathway. The evidence from clinical and animal studies indicates that acupuncture induces multifaceted regulation through complex mechanisms and moreover a single factor may not be enough to explain the beneficial effects against simple obesity.

Role of TRPV1 in acupuncture modulation of reflex excitatory cardiovascular responses

We have shown that acupuncture, including manual and electroacupuncture (MA and EA), at the P5-6 acupoints stimulates afferent fibers in the median nerve (MN) to modulate sympathoexcitatory cardiovascular reflexes through central regulation of autonomic function. However, the mechanisms underlying acupuncture activation of these sensory afferent nerves and their cell bodies in the dorsal root ganglia (DRG) are unclear. Transient receptor potential vanilloid type 1 (TRPV1) is present in sensory nerve fibers distributed in the general region of acupoints like ST36 and BL 40 located in the hindlimb. However, the contribution of TRPV1 to activation of sensory nerves by acupuncture, leading to modulation of pressor responses, has not been studied. We hypothesized that TRPV1 participates in acupuncture's activation of sensory afferents and their associated cell bodies in the DRG to modulate pressor reflexes. Local injection of iodoresiniferatoxin (Iodo-RTX; a selective TRPV1 antagonist), but not 5% DMSO (vehicle), into the P6 acupoint on the forelimb reversed the MA's inhibition of pressor reflexes induced by gastric distension (GD). Conversely, inhibition of GD-induced sympathoexcitatory responses by EA at P5-6 was unchanged after administration of Iodo-RTX into P5-6. Single-unit activity of Group III or IV bimodal afferents sensitive to both mechanical and capsaicin stimuli responded to MA stimulation at P6. MA-evoked activity was attenuated significantly ( P < 0.05) by local administration of Iodo-RTX ( n = 12) but not by 5% DMSO ( n = 12) into the region of the P6 acupoint in rats. Administration of Iodo-RTX into P5-6 did not reduce bimodal afferent activity evoked by EA stimulation ( n = 8). Finally, MA at P6 and EA at P5-6 induced phosphorylation of extracellular signal-regulated kinases (ERK; an intracellular signaling messenger involved in cellular excitation) in DRG neurons located at C7-8 spinal levels receiving MN inputs. After TRPV1 was knocked down in the DRG at these spinal levels with intrathecal injection of TRPV1-siRNA, expression of phosphorylated ERK in the DRG neuron was reduced in MA-treated, but not EA-treated animals. These data suggest that TRPV1 in Group III and IV bimodal sensory afferent nerves contributes to acupuncture inhibition of reflex increases in blood pressure and specifically plays an important role during MA but not EA.

Nitric oxide signaling molecules in acupoints: Toward mechanisms of acupuncture

Recent clinical trial studies have demonstrated that the effects of acupuncture on pain improvement are small and no difference between acupoints and non-points. Whether acupuncture needles must be inserted in specific points depends on whether acupoint specificity exists that is still not resolved, and is now urgent. Previous anatomical studies have demonstrated that acupoints exist higher number of nerve fibers/trunks, blood vessels, hair follicles, and sweat glands as well as density of the gap junction. Recent evidence shows that nitric oxide (NO) level is elevated in the acupoints/ meridians and is associated with an enhanced expression of NO synthase endowed with transient receptor potential vanilloid type-1. There is growing evidence from international groups showing that acupuncture induces NO-mediated vasodilatation, which increases local blood flow and allows for a flush of algesic or sensitizing substances, leading to pain relief. Previous studies, using a novel biocapture system, have demonstrated that NOx- (total nitrite and nitrate) and cyclic guanosine monophosphate (cGMP) concentrations are consistently increased over skin acupoints compared to non-meridian control regions (NMCR) in humans. Dermal microdialysis in humans showed that NO-cGMP releases in the subcutaneous tissue of acupoint are higher than those in NMCR and increased by electroacupuncture (EA). Recent studies have demonstrated that low-frequency electrical stimulation and manual acupuncture with low stimulating force and rate produce an elevation of NO release predominantly over acupoints. In contrast, NO levels over the areas of the skin regions are moderately reduced by high-frequency EA stimulation. The results from anatomical and biochemical studies consistently show that acupoints exist higher levels of NO signaling molecules, and stimulus-evoked NO release is also with a higher level at acupoints. Results suggest that NO signaling molecules contribute to the specificity of acupoints, and selecting well-trained acupuncturetists for using correct acupoints and appropriate parameters should improve acupuncture clinical trial studies.

Response of Local Nitric Oxide Release to Manual Acupuncture and Electrical Heat in Humans: Effects of Reinforcement Methods

This study was to examine the influences of manual acupuncture (MA) and electrical heat corresponding to reinforcing methods on nitric oxide (NO) release over the skin regions in humans. A device with collecting solution was taped to the skin surface along pericardium (PC) or lung (LU) meridian. Acupuncture needles were gently inserted into PC 4 with reinforcing stimulation (low force/rate) for 20 minutes in the MA group. LU11 on the finger was heated (43-44°C) by electrical heat for 20 minutes. Biocapture was consecutively conducted for two 20-minute intervals during and after each treatment. Total nitrite and nitrate (NO _x^-) in the collecting samples were quantified using chemiluminescence in blinded fashion. Baseline NO _x^- levels are higher and tended to be higher over PC and LU acupoints during the 1st biocapture. NO _x^- levels over PC regions were consistently increased by MA during both intervals. NO _x^- concentrations over LU acupoints were increased and tended to be increased by electrical heat in the 1st and 2nd biocapture. The results suggest that reinforcing MA and electrical heat induce NO released from the local skin regions with higher levels at acupoints, which improve local circulation and contribute to the beneficial effects of the therapies.

Role of capsaicin- and heat-sensitive afferents in stimulation of acupoint-induced pain and analgesia in humans

We investigated role of capsaicin-sensitive afferents within and without the areas of Zusanli (ST36)/Shangjuxu (ST37) acupoints along the stomach (ST) meridian in the perception and modulation of pain assessed by visual analog scale of pain and its distribution rated by subjects, pressure pain threshold (PPT), and heat pain threshold (HPT) in humans. Compared with the treatment of non-acupoint area, capsaicin (100µg/50µl) administered into either ST36 or ST37 acupoint caused the strongest pain intensity and the most extensive pain distribution, followed by rapid onset, bilateral, long-lasting secondary mechanical hyperalgesia and slower onset secondary heat hypoalgesia (1day after the capsaicin treatment). Between treatments of different acupoints, capsaicin administrated into the ST36 acupoint exhibited the stronger pain intensity and more widespread pain distribution compared with the treatment of ST37 acupoint. A period of 30- to 45-min, but not 15-min, 43°C heating-needle stimulation applied to the ST36 acupoint significantly enhanced the HPT, and had no effect on PPT. Upon trapezius muscle pain elicited by the i.m. injection of 5.8% saline, pre-emptive treatment of the contralateral ST36 acupoint with 43°C heating-needle stimulation alleviated the ongoing muscle pain, reduced painful area, and reversed the decrease in HPT. It is suggested that (1) pain elicited from the acupoint and non-acupoint areas differs significantly, which are supposed to be dependent on the different distributions and contributions of capsaicin-sensitive afferents. (2) Non-painful heat stimulation is a valid approach in prevention of ongoing muscle pain with associated post-effects of peripheral and central sensitization.

Electroacupuncture combined with mosapride alleviates symptoms in diabetic patients with gastroparesis

The present study compared the clinical effectiveness of electroacupuncture (EA), monotherapy and combination therapy involving the administration of EA and mosapride in diabetic patients with severe or mild symptoms suggestive of gastroparesis. A total of 56 patients with type 2 diabetes who had symptoms suggestive of gastroparesis for >3 months were divided into two groups according to the Gastroparesis Cardinal Symptom Index (GCSI) score, including 33 in the mild group (GCSI score <3.5) and 23 in the severe group (GCSI score ≥3.5). Initially, all patients received EA monotherapy for 14 days. An effective response was defined as a reduction of the overall baseline GCSI score by >25% after treatment. The non-responding patients then received a combination treatment with EA and mosapride. Gastric emptying was assessed by the ¹³C-octanoic acid breath test at the beginning and end of each treatment session. Two patients in the severe group dropped out of the study during the initial treatment session. The results revealed that 34 early-responding patients (30 from the mild group and 4 from the severe group) treated with EA monotherapy, and 20 non-early-responding patients receiving combination therapy with EA and mosapride showed clinically significant improvements. Analysis of data from the mild subgroup demonstrated that EA treatment specifically improved symptoms of nausea, vomiting, stomach fullness, excessive fullness and bloating. There was no statistically significant difference in the gastric half-emptying time among patients prior to and after EA monotherapy. These preliminary results suggested that EA may be an option for improving mild symptoms in patients with diabetic gastroparesis, whereas combination therapy involving EA and pharmaceutics is required in patients with severe symptoms.

Non-pharmacological treatments for pain relief: TENS and acupuncture

Acupuncture and transcutaneous electrical nerve stimulation (TENS) are non-pharmacological methods that have been used for millennia to relieve pain. As with all complementary treatments, efficacy evaluations face two hurdles: the non-feasibility of double-blinding and the difficulty in identifying the optimal control population or treatment. Nevertheless, recent studies of good methodological quality have demonstrated benefits in many types of pain compared to conventional treatment. The mechanisms of action of acupuncture and TENS, which are increasingly well understood, involve endogenous pain control systems, cerebral plasticity, and nonspecific effects (e.g., expectations and placebo effect). No serious adverse effects have been reported. These data support the more widespread use of non-pharmacological pain management, most notably in patients with chronic pain inadequately relieved by medications alone.

Malathion dermal permeability in relation to dermal load: Assessment by physiologically based pharmacokinetic modeling of in vivo human data

Estimates of dermal permeability (K_p), obtained by fitting an updated human PBPK model for malathion to previously reported data on excreted urinary metabolites after 29 volunteers were dermally exposed to measured values of [¹⁴C]malathion dermal load (L), were used to examine the empirical relationship between K_p and L. The PBPK model was adapted from previously reported human biokinetic and PBPK models for malathion, fit to previously reported urinary excretion data after oral [¹⁴C]malathion intake by volunteers, and then augmented to incorporate a standard K_p approach to modeling dermal-uptake kinetics. Good to excellent PBPK-model fits were obtained to all of 29 sets of cumulative urinary metabolite-excretion data (ave. [±1 SD] R² = 0.953 [±0.064]). Contrary to the assumption that K_p and L are independent typically applied for dermally administered liquids or solutions, the 29 PBPK-based estimates of K_p obtained for malathion exhibit a strong positive association with the 2/3rds power of L (log-log Pearson correlation = 0.925, p = ∼0). Possible explanations of this observation involving physico-chemical characteristics and/or in vivo cutaneous effects of malathion are discussed. The PBPK model presented, and our observation that K_p estimates obtained by fitting this model to human experimental urinary-excretion data correlate well with L^2/3, allow more realistic assessments of absorbed and metabolized dose during or after a variety of scenarios involving actual or potential dermal or multi-route malathion exposures, including for pesticide workers or farmers who apply malathion to crops.

Distinct roles of ASIC3 and TRPV1 receptors in electroacupuncture-induced segmental and systemic analgesia

Previous studies have demonstrated the effects of different afferent fibers on electroacupuncture (EA)-induced analgesia. However, contributions of functional receptors expressed on afferent fibers to the EA analgesia remain unclear. This study investigates the roles of acid-sensing ion channel 3 (ASIC3) and transient receptor potential vanilloid 1 (TRPV1) receptors in EA-induced segmental and systemic analgesia. Effects of EA at acupoint ST36 with different intensities on the C-fiber reflex and mechanical and thermal pain thresholds were measured among the ASIC3^-/-, TRPV1^-/-, and C57BL/6 mice. Compared with C57BL/6 mice, the ipsilateral inhibition of EA with 0.8 C-fiber threshold (0.8Tc) intensity on C-fiber reflex was markedly reduced in ASIC3^-/- mice, whereas the bilateral inhibition of 1.0 and 2.0Tc EA was significantly decreased in TRPV1^-/- mice. The segmental increase in pain thresholds induced by 0.3 mA EA was significantly reduced in ASIC3^-/- mice, whereas the systemic enhancement of 1.0 mA EA was markedly decreased in TRPV1^-/- mice. Thus, segmental analgesia of EA with lower intensity is partially mediated by ASIC3 receptor on Aβ-fiber, whereas systemic analgesia induced by EA with higher intensity is more likely induced by TRPV1 receptor on Aδ- and C-fibers.

Probing the Effects and Mechanisms of Electroacupuncture at Ipsilateral or Contralateral ST36-ST37 Acupoints on CFA-induced Inflammatory Pain

Transient receptor potential vanilloid 1 (TRPV1) and associated signaling pathways have been reported to be increased in inflammatory pain signaling. There are accumulating evidences surrounding the therapeutic effect of electroacupuncture (EA). EA can reliably attenuate the increase of TRPV1 in mouse inflammatory pain models with unclear signaling mechanisms. Moreover, the difference in the clinical therapeutic effects between using the contralateral and ipsilateral acupoints has been rarely studied. We found that inflammatory pain, which was induced by injecting the complete Freund’s adjuvant (CFA), (2.14 ± 0.1, p < 0.05, n = 8) can be alleviated after EA treatment at either ipsilateral (3.91 ± 0.21, p < 0.05, n = 8) or contralateral acupoints (3.79 ± 0.25, p < 0.05, n = 8). EA may also reduce nociceptive Nav sodium currents in dorsal root ganglion (DRG) neurons. The expression of TRPV1 and associated signaling pathways notably increased after the CFA injection; this expression can be further attenuated significantly in EA treatment. TRPV1 and associated signaling pathways can be prevented in TRPV1 knockout mice, suggesting that TRPV1 knockout mice are resistant to inflammatory pain. Through this study, we have increased the understanding of the mechanism that both ipsilateral and contralateral EA might alter TRPV1 and associated signaling pathways to reduce inflammatory pain.

Targeting TRPV1 for Body Weight Control using TRPV1(-/-) Mice and Electroacupuncture

Obesity is a global social medical problem resulting in morbidity as high as 20–30%. Here we investigated whether the manipulation of TRPV1 can control mice body weight through electroacupuncture (EA). The results demonstrated that body weight increased with time in the control group (108.19 ± 1.31%, n = 7). The increase of mice body weight was significantly less in the EA group (104.41 ± 0.76%, p < 0.05, compared with the control group, n = 7) but not in the sham EA group (109.1 ± 0.63%, p < 0.05, compared with EA group, n = 7). EA did not decrease the gain of body weight in TRPV1 knock mice (107.94 ± 0.41% and 107.79 ± 1.04% for TRPV1^−/− and TRPV1^−/− with EA, respectively, p > 0.05). The visceral white adipose tissue (WAT) weight was lower in the EA group at 4 weeks after manipulation. Moreover, the protein levels of TRPV1, pPKA, pPKC, and pERK were increased in the dorsal root ganglion (DRG) and spinal cord (SC) after EA treatment but not in the sham EA and TRPV1^−/− mice. This study suggests that targeting TRPV1 is beneficial in controlling body weight and TRPV1-associated mechanisms in mice.

Transcutaneous Electrical Stimulation Increased Nitric Oxide-Cyclic GMP Release Biocaptured Over Skin Surface of Pericardium Meridian and Acupuncture Points in Humans

OBJECTIVES

The purpose of this study was to consecutively capture and quantify nitric oxide (NO) and cGMP, the second messenger of NO, over the skin surface of acupuncture points (acupoints), meridian line without acupoint, and non-meridian control regions of the Pericardium meridian (PC) in humans, and investigate their response to transcutaneous electrical nerve stimulation (TENS) . DESIGN, SETTING, AND MAIN OUTCOME MEASURES: Adhesive biocapture tubes were attached to the skin surface along PC regions and injected with 2-Phenyl-4,4,5,5-tetramethylimidazoline-3-oxide-1-oxyl solution, an NO-scavenging compound, contacting the skin surface for 20 minutes each during 4 consecutive biocapture intervals. TENS (1.0 mA, 6 Hz, 1.0 msec duration) was applied over acupoints PC 8 and PC 3 during the 2nd biocapture for 20 min. Total nitrite and nitrate (NO(x)-), the stable metabolic products of NO, and cGMP in biocaptured samples were quantified using chemiluminescence and ELISA.

RESULTS

NO(x)- levels in the 1st biocapture over PC regions are almost two fold higher compared to subsequent biocaptures and are higher over PC acupoints versus non-meridian control region. Following TENS, NO(x)- concentrations over PC regions were significantly increased, and cGMP is predominantly released from the skin surface of PC acupoints.

CONCLUSIONS

TENS induces elevations of NO-cGMP concentrations over local skin region with a high level at acupoints. The enhanced signal molecules improve local circulation, which contributes to beneficial effects of the therapy.

Moxibustion relieves visceral hyperalgesia via inhibition of transient receptor potential vanilloid 1 (TRPV1) and heat shock protein (HSP) 70 expression in rat bone marrow cells

OBJECTIVE

To investigate the effects of moxibustion on visceral hyperalgesia (VH) and bone marrow cell transient receptor potential vanilloid type 1 (TRPV1) and heat shock protein (HSP) 70 expression in a rat model of VH.

METHODS

Mechanical colorectal distension was performed to induce VH in neonatal Sprague-Dawley rats. Eight-week-old VH rats were treated with moxibustion at acupuncture point BL25 or an ipsilateral non-acupuncture point. Abdominal withdrawal reflex (AWR) scoring and pain threshold pressure assessment were performed before and after moxibustion treatment for 7 consecutive days. The expression of TRPV1 and HSP70 in bone marrow cells was quantified by real-time quantitative PCR.

RESULTS

The expression of TRPV1 and HSP70 in bone marrow cells was increased in rats with VH. Moxibustion at BL25 significantly decreased AWR scores and increased pain threshold pressure in rats with VH. Furthermore, moxibustion at BL25 significantly inhibited the VH-induced increase in the expression of TRPV1 and HSP70 in bone marrow cells.

CONCLUSIONS

The up-regulation of TRPV1 and HSP70 expression in bone marrow cells may be involved in visceral pain development and the analgesic effect of moxibustion on VH may be mediated through down-regulation of TRPV1 and HSP70 expression in bone marrow cells.

Local cutaneous nerve terminal and mast cell responses to manual acupuncture in acupoint LI4 area of the rats

Previous studies have shown that the effects of manual acupuncture (MA) are contributed by collagen fibers and mast cells in local acupoints, at which acupuncture stimulation causes various afferent fiber groups to be excited. However what happens in local nerve fibers and mast cells after MA remains unclear. The aim of this study was to examine the response of cutaneous nerve fibers and mast cells to MA stimulation in acupoint Hegu (LI4). The contralateral LI4 of the same rat was used as a non-stimulated control. Immnohistochemistry analysis were carried out to observe the expression of histamine (HA), serotonin (5-HT) and nociceptive neuropeptides, calcitonin gene-related peptide (CGRP) and substance P (SP), in the LI4 area. Mast cells were labeled with anti-mast cell tryptase antibody and simultaneously with HA or 5-HT primary antibodies to observe their co-expression. Our results showed that SP and CGRP were expressed more highly on the cutaneous nerve fibers of LI4 after MA stimulation than that of the control. Mast cells aggregated in close proximity to the blood vessels in intra-epidermis and dermis and some of them with degranulation in the lower dermis and subcutaneous tissue of LI4. Both mast cells and their granules appeared with HA (+) and 5-HT (+) expression at stimulated L14 sites, while a few intact mast cells with a little expression of 5-HT and HA were distributed in areas of non-stimulated L14. The results indicated that local cutaneous nerve terminals and mast cells responded to MA with higher expression of SP and CGRP in nerve fibers, as well as with aggregation and degranulation of mast cells with HA and 5-HT granules at acupoint LI4. These neuroactive substances may convey signals to certain pathways that contribute to the effects of acupuncture.

Analgesic Effect of Electroacupuncture in a Mouse Fibromyalgia Model: Roles of TRPV1, TRPV4, and pERK

Fibromyalgia (FM) is among the most common chronic pain syndromes encountered in clinical practice, but there is limited understanding of FM pathogenesis. We examined the contribution of transient receptor potential vanilloid 1 (TRPV1) and TRPV4 channels to chronic pain in the repeated acid injection mouse model of FM and the potential therapeutic efficacy of electroacupuncture. Electroacupuncture (EA) at the bilateral Zusanli (ST36) acupoint reduced the long-lasting mechanical hyperalgesia induced by repeated acid saline (pH 4) injection in mouse hindpaw. Isolated L5 dorsal root ganglion (DRG) neurons from FM model mice (FM group) were hyperexcitable, an effect reversed by EA pretreatment (FM + EA group). The increase in mechanical hyperalgesia was also accompanied by upregulation of TRPV1 expression and phosphoactivation of extracellular signal regulated kinase (pERK) in the DRG, whereas DRG expression levels of TRPV4, p-p38, and p-JNK were unaltered. Blockade of TRPV1, which was achieved using TRPV1 knockout mice or via antagonist injection, and pERK suppressed development of FM-like pain. Both TRPV1 and TRPV4 protein expression levels were increased in the spinal cord (SC) of model mice, and EA at the ST36 acupoint decreased overexpression. This study strongly suggests that DRG TRPV1 overexpression and pERK signaling, as well as SC TRPV1 and TRPV4 overexpression, mediate hyperalgesia in a mouse FM pain model. The therapeutic efficacy of EA may result from the reversal of these changes in pain transmission pathways.

Acupuncture for analgesia in veterinary medicine

Acupuncture for analgesia is growing rapidly in popularity with veterinarians and pet owners. This article summarizes the mechanisms of analgesia derived from acupuncture and reviews current literature on the topic. Areas covered include the local effects at area of needle insertion, systemic effects secondary to circulating neurotransmitters and changes in cell signaling, central nervous system effects including the brain and spinal cord, and myofascial trigger point and pathology treatment. Clinical applications are discussed and suggested in each section. When used by appropriately trained professionals, acupuncture offers a compelling and safe method for pain management in our veterinary patients and should be strongly considered as a part of multimodal pain management plans.

Abundant expression and functional participation of TRPV1 at Zusanli acupoint (ST36) in mice: mechanosensitive TRPV1 as an "acupuncture-responding channel"

Background

Acupuncture is a therapy that involves applying mechanical stimulation to acupoints using needles. Although acupuncture is believed to trigger neural regulation by opioids or adenosine, still little is known about how physical stimulation is turned into neurological signaling. The transient receptor potential vanilloid receptors 1 and 4 (TRPV1 and TRPV4) and the acid-sensing ion channel 3 (ASIC3) are regarded as mechanosensitive channels. This study aimed to clarify their role at the Zusanli acupoint (ST36) and propose possible sensing pathways linking channel activation to neurological signaling.

Methods

First, tissues from different anatomical layers of ST36 and the sham point were sampled, and channel expressions between the two points were compared using western blotting. Second, immunofluorescence was performed at ST36 to reveal distribution pattern of the channels. Third, agonist of the channels were injected into ST36 and tested in a mouse inflammatory pain model to seek if agonist injection could replicate acupuncture-like analgesic effect. Last, the components of proposed downstream sensing pathway were tested with western blotting to determine if they were expressed in tissues with positive mechanosensitive channel expression.

Results

The results from western blotting demonstrated an abundance of TRPV1, TRPV4, and ASIC3 in anatomical layers of ST36. Furthermore, immunofluorescence showed these channels were expressed in both neural and non-neural cells at ST36. However, only capsaicin, a TRPV1 agonist, replicated the analgesic effect of acupuncture when injected into ST36. Components of calcium wave propagation (CWP, the proposed downstream sensing pathway) were also expressed in tissues with abundant TRPV1 expression, the muscle and epimysium layers.

Conclusions

The results demonstrated mechanosensitive channel TRPV1 is highly expressed at ST36 and possibly participated in acupuncture related analgesia. Since CWP was reported by other to occur during acupuncture and its components were shown here to express in tissues with positive TRPV1 expression. These findings suggest TRPV1 might act as acupuncture-responding channel by sensing physical stimulation from acupuncture and conducting the signaling via CWP to nerve terminals. This study provided a better understanding between physical stimulation from acupuncture to neurological signaling.

From peripheral to central: the role of ERK signaling pathway in acupuncture analgesia

Despite accumulating evidence of the clinical effectiveness of acupuncture, its mechanism remains largely unclear. We assume that molecular signaling around the acupuncture needled area is essential for initiating the effect of acupuncture. To determine possible bio-candidates involved in the mechanisms of acupuncture and investigate the role of such bio-candidates in the analgesic effects of acupuncture, we conducted 2 stepwise experiments. First, a genome-wide microarray of the isolated skin layer at the GB34-equivalent acupoint of C57BL/6 mice 1 hour after acupuncture found that a total of 236 genes had changed and that extracellular signal-regulated kinase (ERK) activation was the most prominent bio-candidate. Second, in mouse pain models using formalin and complete Freund adjuvant, we found that acupuncture attenuated the nociceptive behavior and the mechanical allodynia; these effects were blocked when ERK cascade was interrupted by the mitogen-activated protein kinase kinase (MEK)/mitogen-activated protein kinase (MAPK) inhibitor U0126 (.8 μg/μL). Based on these results, we suggest that ERK phosphorylation following acupuncture needling is a biochemical hallmark initiating the effect of acupuncture including analgesia.

PERSPECTIVE

This article presents the novel evidence of the local molecular signaling in acupuncture analgesia by demonstrating that ERK activation in the skin layer contributes to the analgesic effect of acupuncture in a mouse pain model. This work improves our understanding of the scientific basis underlying acupuncture analgesia.

Electroacupuncture Stimulation at CV12 Inhibits Gastric Motility via TRPV1 Receptor

Gastric dysmotility is one of the major pathophysiological factors in functional gastrointestinal disorders. Acupuncture, as one of the alternative approaches, is efficacious in the treatment of gastrointestinal motility disorders; however, the mechanism underlying its action is unclear. In the present study, we used both capsazepine, a TRPV1 antagonist, and TRPV1 knockout mice. Animals were divided into wild-type group (WT), capsazepine injection group (CZP, 0.5 mg/kg, i.p.), and TRPV1 knockout mice group (TRPV1^−/−). Each of these three groups was divided into three subgroups, which were subjected to EA stimulation at acupoint Zhongwan (CV12) at a different intensity (1, 2, or 4 mA). We demonstrated that electroacupuncture at Zhongwan (CV12) markedly inhibited gastric motility at 2 and 4 mA in an intensity-dependent manner in wild-type mice. The inhibitory effect was also observed in capsazepine-injected and TRPV1^−/− mice but was no longer intensity dependent, indicating that TRPV1 is partially involved in the electroacupuncture-mediated modulation of gastric motility.

"Intensity-response" effects of electroacupuncture on gastric motility and its underlying peripheral neural mechanism

The aim of this study was to explore the "intensity-response" relationship between EAS and the effect of gastric motility of rats and its underlying peripheral neural mechanism by employing ASIC3 knockout (ASIC3-/-), TRPV1 knockout (TRPV1-/-), and C57BL/6 mice. For adult male Sprague-Dawley (n = 18) rats, the intensities of EAS were 0.5, 1, 3, 5, 7, and 9 mA, respectively. For mice (n = 8 in each group), only 1 mA was used, by which C fiber of the mice can be activated. Gastric antrum motility was measured by intrapyloric balloon. Gastric motility was facilitated by EAS at ST36 and inhibited by EAS at CV12. The half maximal facilitation intensity of EAS at ST36 was 2.1-2.3 mA, and the half maximal inhibitory intensity of EAS at CV12 was 2.8 mA. In comparison with C57BL/6 mice, the facilitatory effect of ST36 and inhibitive effect of CV12 in ASIC3-/- mice decreased, but the difference was not statistically significant (P > 0.05). However, these effects in TRPV1-/- mice decreased significantly (P < 0.001). The results indicated that there existed an "intensity-response" relationship between EAS and the effect of gastric motility. TRPV1 receptor was involved in the regulation of gastric motility of EAS.

Effects of electroacupuncture Zusanli (ST36) on food intake and expression of POMC and TRPV1 through afferents-medulla pathway in obese prone rats

OBJECTIVE

The purpose of this study was to determine the effects of electroacupuncture (EA) ST36 on food intake and body weight in obese prone (OP) rats compared to obese resistant (OR) strain on a high fat diet. The influences of EA on mRNA levels of pro-opiomelanocortin (POMC), transient receptor potential vanilloid type-1 (TRPV1), and neuronal nitric oxide synthase (nNOS) were also examined in the medulla regions and ST36 skin tissue.

METHODS

Advanced EA ST36 was conducted in two sessions of 20 min separated by an 80 min interval for 7 days. Food intake and body weight were recorded in conscious rats every day. Real time PCR was conducted in the micropunches of the medulla regions and skin tissues at the end of the treatment.

RESULTS

Food intake and body weight were significantly reduced by advanced EA ST36 in OP rats, but slightly decreased in OR strain and sham-EA rats. Advanced EA ST36 produced a marked increase in POMC mRNA level in the nucleus tractus solitarius (NTS) and hypoglossal nucleus (HN) regions. TRPV1 and nNOS mRNAs were simultaneously increased in the NTS/gracile nucleus regions and in the ST36 skin regions by the EA treatment in OP rats.

CONCLUSIONS

We conclude that advanced EA ST36 produces an up-regulation of anorexigenic factor POMC production in the NTS/HN, which inhibits food intake and reduces body weight. EA-induced expression of TRPV1-nNOS in the ST36 and the NTS/gracile nucleus is involved in the signal transduction of EA stimuli via somatosensory afferents-medulla pathways.

Stimulation of TRPV1 by Green Laser Light

Low-level laser irradiation of visible light had been introduced as a medical treatment already more than 40 years ago, but its medical application still remains controversial. Laser stimulation of acupuncture points has also been introduced, and mast-cells degranulation has been suggested. Activation of TRPV ion channels may be involved in the degranulation. Here, we investigated whether TRPV1 could serve as candidate for laser-induced mast cell activation. Activation of TRPV1 by capsaicin resulted in degranulation. To investigate the effect of laser irradiation on TRPV1, we used the Xenopus oocyte as expression and model system. We show that TRPV1 can functionally be expressed in the oocyte by (a) activation by capsaicin (K(1/2) = 1.1 μM), (b) activation by temperatures exceeding 42°C, (c) activation by reduced pH (from 7.4 to 6.2), and (d) inhibition by ruthenium red. Red (637 nm) as well as blue (406 nm) light neither affected membrane currents in oocytes nor did it modulate capsaicin-induced current. In contrast, green laser light (532 nm) produced power-dependent activation of TRPV1. In conclusion, we could show that green light is effective at the cellular level to activate TRPV1. To which extend green light is of medical relevance needs further investigation.

Attenuation of TRPV1 and TRPV4 Expression and Function in Mouse Inflammatory Pain Models Using Electroacupuncture

Although pain is a major human affliction, our understanding of pain mechanisms is limited. TRPV1 (transient receptor potential vanilloid subtype 1) and TRPV4 are two crucial receptors involved in inflammatory pain, but their roles in EA- (electroacupuncture-) mediated analgesia are unknown. We injected mice with carrageenan (carra) or a complete Freund's adjuvant (CFA) to model inflammatory pain and investigated the analgesic effect of EA using animal behavior tests, immunostaining, Western blotting, and a whole-cell recording technique. The inflammatory pain model mice developed both mechanical and thermal hyperalgesia. Notably, EA at the ST36 acupoint reversed these phenomena, indicating its curative effect in inflammatory pain. The protein levels of TRPV1 and TRPV4 in DRG (dorsal root ganglion) neurons were both increased at day 4 after the initiation of inflammatory pain and were attenuated by EA, as demonstrated by immunostaining and Western blot analysis. We verified DRG electrophysiological properties to confirm that EA ameliorated peripheral nerve hyperexcitation. Our results indicated that the AP (action potential) threshold, rise time, and fall time, and the percentage and amplitude of TRPV1 and TRPV4 were altered by EA, indicating that EA has an antinociceptive role in inflammatory pain. Our results demonstrate a novel role for EA in regulating TRPV1 and TRPV4 protein expression and nerve excitation in mouse inflammatory pain models.

Patch clamp: a powerful technique for studying the mechanism of acupuncture

Cellular and molecular events can be investigated using electrophysiological techniques. In particular, the patch-clamp method provides detailed information. In addition, the patch-clamp technique has become a powerful method for investigating the mechanisms underlying the effects of acupuncture. In this paper, recent researches on how acupuncture might modulate electrophysiological responses in the central nervous system (CNS) and affect peripheral structures are reviewed.