The real-time detection of acupuncture-induced extracellular ATP mobilization in acupoints and exploration of its role in acupuncture analgesia

Inflammatory pain and electroacupuncture: how the P2X3 receptor can help modulate inflammation-a review of current literature

AIM

Inflammatory pain arises from tissue stress or injury and is initiated by signaling molecules that stimulate the immune and nervous systems. Evidence suggests that purinergic signaling pathways can modulate pain and inflammation through the activation of P1 and P2 purinergic receptors, such as the P2X3 receptor, which are stimulated by extracellular molecules like adenosine triphosphate (ATP). Electroacupuncture (EA) exhibits precise mechanisms that modulate inflammatory pain through the activation of the P2X3 receptor.

OBJECTIVE

This review analyzed evidence regarding the role of electroacupuncture and the purinergic system, particularly the P2X3 receptor, in modulating inflammation and pain.

MATERIALS AND METHODS

A search for the most relevant articles available in the SciVerse Scopus and MEDLINE/PubMed databases was conducted for publications from 1995 to 2024. Articles were initially selected by reading the title, abstract, and main text, respectively.

RESULTS

It was found that the P2X3 receptor, as well as the molecules activating purinergic receptors, such as ATP and adenosine, have the potential to regulate pain and inflammation. Additionally, EA can modulate the purinergic system in an anti-inflammatory response. EA may stimulate analgesia mainly through the conversion of ATP to adenosine, a crucial molecule in pain control.

CONCLUSION

The purinergic system directly influences inflammatory pain and controls inflammation. In this context, EA has the potential to orchestrate this system to control pain and inflammation.

Integrative research on the mechanisms of acupuncture mechanics and interdisciplinary innovation

As a traditional therapeutic approach, acupuncture benefits from modern biomechanics, which offers a unique perspective for understanding its mechanisms by investigating the mechanical properties of biological tissues and cells under force, deformation, and movement. This review summarizes recent advancements in the biomechanics of acupuncture, focusing on three main areas: the mechanical effects of acupuncture, the transmission mechanisms of mechanical signals, and the personalization and precision of acupuncture treatments. First, the review introduces the structural basis of the tissues involved in acupuncture; analyzes the mechanical responses of the skin, dermis, and subcutaneous tissues from needle insertion to point activation; and discusses how these responses impact acupuncture efficacy. Second, the phenomenon of mechanical coupling during acupuncture is discussed in detail, especially the role of connective tissues, including the wrapping and self-locking of collagen fibers, the remodeling of the cytoskeleton and the regulation of mitochondrial function triggered by acupuncture. Third, this article examines the mechanisms of mechanical signal transmission in acupuncture, explaining how mechanosensitive ion channels are activated during the procedure and subsequently initiate a cascade of biochemical responses. Finally, the review highlights the numerical simulation methods used in acupuncture, including the mechanical modeling of skin tissues, the exploration of the mechanical mechanisms of acupuncture, and visualization studies of the needling process. By integrating multidisciplinary research findings, this paper delves into the entire mechanical process of acupuncture, from skin penetration to point stimulation, and analyzes tissue responses to provide a solid theoretical foundation for the scientific study of acupuncture. In addition, directions for future research to further refine acupuncture techniques for clinical applications are proposed.

CD39 activities in the treated acupoints contributed to the analgesic mechanism of acupuncture on arthritis rats

Our previous work had identified that at the acupuncture point (acupoint), acupuncture-induced ATP release was a pivotal event in the initiation of analgesia. We aimed to further elucidate the degradation of ATP by CD39. Acupuncture was administered at Zusanli acupoint on arthritis rats, and pain thresholds of the hindpaws were determined. Pharmacological tools or adeno-associated viruses were administered at the acupoints to interfere with targeting signals. Protein expression was determined with qRT-PCR, WB, or immunofluorescent labeling. Cultured keratinocytes, HaCaT line, were subjected to hypotonic shock to simulate needling stimulation. Extracellular ATP and adenosine levels were quantified using luciferase-luciferin assay and ELISA, respectively. Acupuncture-induced prompt analgesia was impaired by inhibiting CD39 activities to prevent the degradation of ATP to AMP but was mimicked by using CD39 agonists. Acupuncture-induced ATP accumulation exhibited synchronous changes. Similarly, acupuncture analgesia was hindered by suppressing CD73 to prevent the conversion of AMP to adenosine. Furthermore, the acupuncture effect was replicated by agonism at P2Y2Rs but inhibited by antagonism at them. Acupuncture upregulated CD73 and P2Y2Rs but not CD39. Immunofluorescent labeling demonstrated that keratinocytes were a primary site for these proteins. Shallow acupuncture also demonstrated antinociception. In vitro tests showed that hypotonic shock induced HaCaT cells to release ATP and adenosine, which was impaired by suppressing CD39 and CD73, respectively. Finally, agonism at P2Y2Rs promoted ATP release and [Ca2+]i rise. CD39 at the acupoints contributes to the analgesic mechanism of acupuncture. It may facilitate adenosine signaling in conjunction with CD73 or provide an appropriate ATP milieu for P2Y2Rs. Skin tissue may be one of the scenes for these signalings.

Comprehensive landscape-style investigation of the molecular mechanism of acupuncture at ST36 single acupoint on different systemic diseases

The principle of acupoint stimulation efficacy is based on traditional meridian theory. However, the molecular mechanisms underlying the therapeutic effects of acupoints in treating diseases remain unclear in modern scientific understanding. In this study, we selected the ST36 acupoint for investigation and summarized all relevant literature from the PubMed database over the past 10 years. The results indicate that stimulation of ST36 single acupoints has therapeutic effects mainly in models of respiratory, neurological, digestive, endocrine and immune system diseases. And it can affect the inflammatory state, oxidative stress, respiratory mucus secretion, intestinal flora, immune cell function, neurotransmitter transmission, hormone secretion, the network of Interstitial Cells of Cajal (ICC) and glucose metabolism of the organism in these pathological states. Among them, acupuncture at the ST36 single point has the most prominent function in regulating the inflammatory state, which can mainly affect the activation of MAPK signaling pathway and drive the "molecular-cellular" mode involving macrophages, T-lymphocytes, mast cells (MCs) and neuroglial cells as the core to trigger the molecular level changes of the acupuncture point locally or in the target organ tissues, thereby establishing a multi-system, multi-target, multi-level molecular regulating mechanism. This article provides a comprehensive summary and discussion of the molecular mechanisms and effects of acupuncture at the ST36 acupoint, laying the groundwork for future in-depth research on acupuncture point theory.

Intelligent acupuncture: data-driven revolution of traditional Chinese medicine

Acupuncture, a form of traditional Chinese medicine with a history of 2,000 years in China, has gained wider acceptance worldwide as a complementary therapy. Studies have examined its effectiveness in various health conditions and it is commonly used alongside conventional medical treatments. With the development of artificial intelligence (AI) technology, new possibilities for improving the efficacy and precision of acupuncture have emerged. This study explored the combination of traditional acupuncture and AI technology from three perspectives: acupuncture diagnosis, prescription, and treatment evaluation. The study aimed to provide cutting-edge direction and theoretical assistance for the development of an acupuncture robot.

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 Activities Responding to Acupuncture at ST36 (zusanli) in Healthy Subjects: A Systematic Review and Meta-Analysis of Task-Based fMRI Studies

Purpose

Stomach 36 (ST36, zusanli) is one of the important acupoints in acupuncture. Despite clinical functional magnetic resonance imaging (fMRI) studies of ST36 acupuncture, the brain activities and the neural mechanism following acupuncture at ST36 remain unclear.

Methods

Literature searches were conducted on online databases, including MEDLINE, Embase, Cochrane Library, Web of Science, China National Knowledge Infrastructure, Wanfang database, WeiPu database, and China Biology Medicine, for task-based fMRI studies of acupuncture at ST36 in healthy subjects. Brain regions activated by ST36 acupuncture were systematically evaluated and subjected to seed-based d mapping meta-analysis. Subgroup analysis was conducted on control procedures, manual acupuncture, electrical acupuncture (EA), and acupuncture-specific activations. Meta-regression analysis was performed to explore the effects of needle retention time on brain activities following ST36 acupuncture stimulation. The activated brain regions were further decoded and mapped on large-scale functional networks to further decipher the clinical relevance of acupuncturing at ST36.

Results

A total of sixteen studies, involving a total of 401 right-handed healthy participants, that satisfied the inclusion criteria were included in the present meta-analysis. Meta-analysis showed that acupuncturing on ST36 positively activates the opercular part of the right inferior frontal gyrus (IFG.R), left superior temporal gyrus (STG.L), and right median cingulate/paracingulate gyri (MCG.R) regions. Needle retention time in an acupuncture session positively correlates with the activation of the left olfactory cortex, as shown in meta-regression analysis. Subgroup analysis revealed that EA stimulation may be a source of heterogeneity in the pooled results. Functional network mappings showed that the activated areas were mapped to the auditory network and salience network. Further functional decoding analysis showed that acupuncture on ST36 was associated with pain, secondary somatosensory, sound and language processing, and mood regulation.

Conclusion

Acupuncture at ST36 in healthy individuals positively activates the opercular part of IFG.R, STG.L, and MCG.R. The left olfactory cortex may exhibit positive needle retention time-dependent activities. Our findings may have clinical implications for acupuncture in analgesia, language processing, and mood disorders.

Systematic Review Registration

https://inplasy.com/inplasy-2021-12-0035.

Activation of Subcutaneous Mast Cells in Acupuncture Points Triggers Analgesia

This review summarizes experimental evidence indicating that subcutaneous mast cells are involved in the trigger mechanism of analgesia induced by acupuncture, a traditional oriental therapy, which has gradually become accepted worldwide. The results are essentially based on work from our laboratories. Skin mast cells are present at a high density in acupuncture points where fine needles are inserted and manipulated during acupuncture intervention. Mast cells are sensitive to mechanical stimulation because they express multiple types of mechanosensitive channels, including TRPV1, TRPV2, TRPV4, receptors and chloride channels. Acupuncture manipulation generates force and torque that indirectly activate the mast cells via the collagen network. Subsequently, various mediators, for example, histamine, serotonin, adenosine triphosphate and adenosine, are released from activated mast cells to the interstitial space; they or their downstream products activate the corresponding receptors situated at local nerve terminals of sensory neurons in peripheral ganglia. The analgesic effects are thought to be generated via the reduced electrical activities of the primary sensory neurons. Alternatively, these neurons project such signals to pain-relevant regions in spinal cord and/or higher centers of the brain.