Electroacupuncture-induced dynamic processes of gene expression levels of endogenous opioid Peptide precursors and opioid receptors in the CNS of goats

The Top 100 Cited Articles on Acupuncture in the Last 20 Years: A Bibliometric Analysis

BACKGROUND

Acupuncture has gained increasing international attention in recent decades. The act of incorporating acupuncture treatment into the routine treatment of COVID-19 in China drove us to review the 100 most influential articles of the last 20 years to learn about the current status and trends of acupuncture.

METHOD

Articles related to acupuncture from January 1, 2001, to July 4, 2022, were searched in the Clarivate Analytics Web of Science Core Collection database. The top 100 most cited publications were selected, and information was extracted. Software such as VOSviewer, GraphPad Prism, Scimago Graphica, and CiteSpace were used to visualize and analyze the extracted data.

RESULT

The 100 most cited articles were identified, with an average of 218 citations (range: 131-625). The majority of the top 100 articles were from the USA (n = 53). The institution that published the most highly cited papers was Harvard University (n = 16). The most influential team was Klaus Linde's group. Pain was the top-ranked journal in terms of the number of publications. The largest clusters for co-occurrence keyword analysis focused on acupuncture and electroacupuncture analgesia and brain imaging responses to acupuncture stimulation via functional MRI. The two highest strength burst keywords were "randomized controlled trials" and "osteoarthritis," with "randomized controlled trials" being a consistent burst keyword from 2011 to the present.

CONCLUSION

This study provides insight into articles of historical significance in the field of acupuncture through bibliometric analysis. These data should provide clinicians and researchers with insight into future directions related to acupuncture.

Hintergrund

Die Akupunktur hat in den vergangenen Jahrzehnten zunehmend die internationale Aufmerksamkeit auf sich gezogen. Die Einbeziehung der Akupunktur in die Routinebehandlung von COVID-19 in China hat uns dazu veranlasst, die 100 einflussreichsten Artikel der letzten 20 Jahre zu überprüfen, um etwas über den aktuellen Stand und die Trends in der Akupunktur zu erfahren.

Methode

Artikel mit Bezug zu Akupunktur vom 1. Januar 2001 bis 4. Juli 2022 wurden in der Clarivate Analytics Web of Science Core Collection Datenbank gesucht. Die 100 am häufigsten zitierten Veröffentlichungen wurden ausgewählt und die Informationen wurden extrahiert. Visualisierung und Analyse der extrahierten Daten erfolgten mithilfe der Software VOSviewer, GraphPad Prism, Scimago Graphica und CiteSpace.

Ergebnis

Es wurden die 100 am häufigsten zitierten Artikel ermittelt mit durchschnittlich 218 Zitierungen (Spanne: 131 bis 625). Der Großteil der 100 meistzitierten Artikel stammte aus den Vereinigten Staaten (n = 53). Die Institution, die die meisten zitierten Artikel veröffentlichte, war die Harvard-Universität (n = 16). Das einflussreichste Team war die Gruppe von Klaus Linde. Was die Zahl der Veröffentlichungen betrifft, war Pain die am häufigsten zitierte Zeitschrift. Bei der Analyse der Koinzidenz von Schlüsselwörtern lag der Fokus der größten Cluster auf Akupunktur-und Elektroakupunktur-Analgesie sowie auf den Reaktionen auf Akupunkturstimulation in den bildgebenden Untersuchungen des Gehirns mittels funktioneller MRT. Die beiden stärksten Burst-Schlüsselwörter waren “randomisierte kontrollierte Studien” und “Osteoarthritis,” wobei “randomisierte kontrollierte Studien” von 2011 bis heute durchgängig ein Burst-Schlüsselwort ist.

Schlussfolgerung

Diese Studie bietet einen Einblick in historisch bedeutsame Artikel auf dem Gebiet der Akupunktur mittels bibliometrischer analyse. Diese Daten sollen Klinikern und Forschern einen Einblick in zukünftige Richtungen im Zusammenhang mit Akupunktur geben.

Electroacupuncture Suppresses CCI-Induced Neuropathic Pain through GABAA Receptors

Neuropathic pain remains a chronic and intractable pain. Recent studies have shown a close relationship between gamma-aminobutyric acid A (GABAA) receptor and neuropathic pain. Spinal cord GABAA receptors are key modulators of pain processing. Electroacupuncture (EA) is currently used worldwide to relieve pain. The immunomodulatory effect of EA in animals has been proposed in previous studies. However, it remains unclear how EA contributes to alleviating neuropathic pain. In this study, the chronic constriction injury (CCI) rat model was used to explore the relationship between GABAA receptor and neuropathic pain. We also investigated whether EA treatment could ameliorate pain hypersensitivity by modulating the GABAA receptor. To determine the function of EA in neurological diseases, in this study, the mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) were assessed to determine the threshold of pain. In addition, we used Western blot, immunofluorescence, and real-time quantitative PCR to confirm whether EA treatment relieves pain hypersensitivity by regulating GABAA receptors. The morphology of synapse was examined using an electron microscope. In the present study, EA relieved mechanical allodynia and thermal hyperalgesia. EA also inhibited microglial activation in the spinal cord, accompanied by increased levels of GABAARα2, GABAARα3, and GABAARγ2 subunits. However, the analgesic effect of EA was attenuated by treatment with the GABAA receptor antagonist bicuculine. Overall, the present results indicate that microglia and GABAA receptor might participate in EA analgesia. These results contribute to our understanding of the impact of EA on rats after sciatic nerve compression, providing a theoretical basis for the clinical application of EA analgesia.

Electroacupuncture Regulates Pain Transition Through Inhibiting PKCε and TRPV1 Expression in Dorsal Root Ganglion

Many cases of acute pain can be resolved with few side effects. However, some cases of acute pain may persist beyond the time required for tissue injury recovery and transit to chronic pain, which is hard to treat. The mechanisms underlying pain transition are not entirely understood, and treatment strategies are lacking. In this study, the hyperalgesic priming model was established on rats to study pain transition by injection of carrageenan (Car) and prostaglandin E2 (PGE2). The expression levels of protein kinase C epsilon (PKCε) and transient receptor potential vanilloid 1 (TRPV1) in the L4–L6 dorsal root ganglion (DRG) were investigated. Electroacupuncture (EA) is a form of acupuncture in which a small electric current is passed between a pair of acupuncture needles. EA was administrated, and its effect on hyperalgesia and PKCε and TRPV1 expression was investigated. The PKCε–TRPV1 signaling pathway in DRG was implicated in the pain transition. EA increased the pain threshold of model animals and regulated the high expression of PKCε and TRPV1. Moreover, EA also regulated hyperalgesia and high TRPV1 expression induced by selective PKCε activation. We also found that EA partly increased chronic pain threshold, even though it was only administered between the Car and PGE2 injections. These findings suggested that EA could prevent the transition from acute to chronic pain by inhibiting the PKCε and TRPV1 expression in the peripheral nervous system.

Synaptotagmin 1 Is Involved in Neuropathic Pain and Electroacupuncture-Mediated Analgesic Effect

Numerous studies have verified that electroacupuncture (EA) can relieve neuropathic pain through a variety of mechanisms. Synaptotagmin 1 (Syt-1), a synaptic vesicle protein for regulating exocytosis of neurotransmitters, was found to be affected by EA stimulation. However, the roles of Syt-1 in neuropathic pain and EA-induced analgesic effect remain unclear. Here, the effect of Syt-1 on nociception was assessed through an antibody blockade, siRNA silencing, and lentivirus-mediated overexpression of spinal Syt-1 in rats with spared nerve injury (SNI). EA was used for stimulating bilateral "Sanjinjiao" and "Zusanli" acupoints of the SNI rats to evaluate its effect on nociceptive thresholds and spinal Syt-1 expression. The mechanically and thermally nociceptive behaviors were assessed with paw withdrawal threshold (PWT) and paw withdrawal latency (PWL) at different temperatures, respectively, at day 0, 7, 8, 14, and 20. Syt-1 mRNA and protein levels were determined with qRT-PCR and Western blot, respectively, and its distribution was observed with the immunohistochemistry method. The results demonstrated Syt-1 antibody blockade and siRNA silencing increased ipsilateral PWTs and PWLs of SNI rats, while Syt-1 overexpression decreased ipsilateral PWTs and PWLs of rats. EA significantly attenuated nociceptive behaviors and down-regulated spinal Syt-1 protein levels (especially in laminae I-II), which were reversed by Syt-1 overexpression. Our findings firstly indicate that Syt-1 is involved in the development of neuropathic pain and that EA attenuates neuropathic pain, probably through suppressing Syt-1 protein expression in the spinal cord.

The Expressing Patterns of Opioid Peptides, Anti-opioid Peptides and Their Receptors in the Central Nervous System Are Involved in Electroacupuncture Tolerance in Goats

To investigate dynamic processes of enkephalin (ENK), cholecystokinin octapeptide (CCK-8), orphanin FQ (OFQ) and their receptors (μ opioid receptor, MOR; CCK B type receptor, CCKBR and opioid receptor-like 1 receptor, OPRL1) in the central nerve system (CNS) during electroacupuncture (EA) tolerance, EA of Sixty Hz was used to stimulate goats for 6 h. Pain threshold was measured using potassium iontophoresis. The expression levels of ENK, CCK-8, and OFQ and their receptors were determined with ELISA and qPCR, respectively. The results showed that the change rates of pain threshold in EA-treated goats decreased from 89.9 ± 11.7% at 0.5 h to –11.4 ± 8.9% at 6 h. EA induced the decreased ENK and increased CCK-8 and OFQ in the most measured nuclei. EA caused decreased preproenkephalin mRNAs in ACB, CAU, PVH, and PAG at 4 h, and decreased or unchanged MOR mRNAs at 2–6 h, but increased CCK mRNAs in CAU, PVT, PVH, PAG, and SCD at 4–12 h. Increased prepronociceptin mRNAs and fluctuated CCKBR and OPLR1 mRNAs were found in the most measured nuclei. ENK levels were positively correlated (p < 0.01) with the change rates of pain thresholds in the measured nuclei or areas while CCK-8 levels (or OFQ levels) were negatively correlated (p < 0.01) with the pain thresholds in CAU (or CAU and ACB). These results suggest that the development and recovery of EA tolerance may be associated with the specific expression patterns of opioid peptides, anti-opioid peptides and their receptors in the analgesia-related nuclei or areas.

Exploring the Mechanisms of Electroacupuncture-Induced Analgesia through RNA Sequencing of the Periaqueductal Gray

Electroacupuncture (EA) can relieve various pains. However, its mechanism in terms of the transcriptome is still not well-known. To explore the full profile of EA-induced molecular modification in the central nerve system, three twins of goats were selected for a match-paired experiment: EA stimulation (60 Hz, 30 min) and none-EA (control). Goats in the EA group showed an increased (p < 0.05) nociceptive threshold compared with the control goats. Experimental goats were sacrificed at 4 h of the experiment, and the periaqueductal grays were harvested for RNA sequencing. As a result, 2651 differentially expressed genes (1803 up-regulated and 848 down-regulated genes) were found and enriched in 30 Kyoto Encyclopedia of Genes and Genomes pathways and 149 gene ontology terms. EA-regulated five neuropeptide genes (proenkephalin, proopiomelanocortin, preprodynorphin, diazepam-binding inhibitor and proprotein convertase 1 inhibitor) were validated with quantitative PCR. Furthermore, up-regulated glutamate receptors, glutamate transporters, γ-aminobutyric acid (GABA) receptors, GABA transporters, synaptotagmins or mitogen-activated protein kinase (MAPK) genes might contribute to EA-induced analgesia through regulating the glutamatergic synapse, GABAergic synapse, MAPKs, ribosome or ubiquitin-proteasome pathways. Our findings reveal a full profile of molecular modification in response to EA and provide a solid experimental framework for exploring the mechanisms underlying EA-induced analgesia.

Electroacupuncture is Beneficial for Primary Dysmenorrhea: The Evidence from Meta-Analysis of Randomized Controlled Trials

Electroacupuncture (EA) is considered to be a promising alternative therapy to relieve the menstrual pain for primary dysmenorrhea (PD), but the conclusion is controversial. Here, we conducted a systematic review and meta-analysis specifically to evaluate the clinical efficacy from randomized controlled trials (RCTs) on the use of EA in patients with PD. PubMed, Embase, ISI Web of Science, CENTRAL, CNKI, and Wanfang were searched to identify RCTs that evaluated the effectiveness of EA for PD. The outcome measurements included visual analogue scale (VAS), verbal rating scale (VRS), COX retrospective symptom scale (RSS), and the curative rate. Nine RCTs with high risk of bias were included for meta-analysis. The combined VAS 30 minutes after the completion of intervention favoured EA at SP6 when compared with EA at GB39, nonacupoints, and waiting-list groups. EA was superior to pharmacological treatment when the treatment duration lasted for three menstrual cycles, evidenced by significantly higher curative rate. No statistically significant differences between EA at SP6 and control groups were found regarding the VRS, RSS-COX1, and RSS-COX2. The findings of our study suggested that EA can provide considerable immediate analgesia effect for PD. Additional studies with rigorous design and larger sample sizes are needed.

Electroacupuncture Attenuates Visceral Hypersensitivity by Inhibiting JAK2/STAT3 Signaling Pathway in the Descending Pain Modulation System

Electroacupuncture (EA) has been used for treating visceral hypersensitivity (VH). However, the underlying molecular mechanism remains unclear. This study was aim to testify the effect of EA on ileitis-provoked VH, and to confirm whether EA attenuates VH through Janus kinase 2 (JAK2)/signal transducers and activators of transcription 3 (STAT3) signaling pathway in the periaqueductal gray (PAG)-the rostral ventromedial medulla (RVM)-the spinal cord dorsal horn (SCDH) axis.

Methods: Goats were anesthetized and laparotomized for injecting 2,4,6-trinitro-benzene-sulfonic acid (TNBS)-ethanol solution (30mg TNBS dissolved in 40% ethanol) into the ileal wall to induce VH. EA was treated for 30min from day 7, then every 3 days for six times. VH was assessed by visceromotor response (VMR) and pain behavior response to 20, 40, 60, 80, and 100 mmHg colorectal distension pressures at day 7, 10, 13, 16, 19, and 22. The spinal cord in the eleventh thoracic vertebra and the brain were collected at day 22. The protein and mRNA levels of IL-6, JAK2, and STAT3 in the SCDH were detected with western blot and qPCR, respectively. The distribution of these substances was observed with immunohistochemistry in the ventrolateral PAG (vlPAG), RVM (mainly the nucleus raphe magnus, NRM), SCDH, the nucleus tractus solitaries (NTS) and the dorsal motor nucleus of vagi (DMV).

Results: Goats administered with TNBS-ethanol solution showed diarrhea, enhanced VMR and pain behavior response, and increased IL-6, phosphorylated JAK2 and STAT3 (pJAK2 and pSTAT3) in the vlPAG, NRM, NTS and DMV, and their protein and mRNA levels in the SCDH. EA relieved diarrhea, VMR and pain behavior response, decreased IL-6, pJAK2 and pSTAT3 levels in the vlPAG, NRM, SCDH, NTS, and DMV except for pSTAT3 in the DMV, but did not affect mRNA level of these three substances in the SCDH.

Conclusion: EA attenuates VH probably through inhibiting JAK2/STAT3 signaling pathway in the PAG-RVM-SCDH axis.

Analgesic Neural Circuits Are Activated by Electroacupuncture at Two Sets of Acupoints

To investigate analgesic neural circuits activated by electroacupuncture (EA) at different sets of acupoints in the brain, goats were stimulated by EA at set of Baihui-Santai acupoints or set of Housanli acupoints for 30 min. The pain threshold was measured using the potassium iontophoresis method. The levels of c-Fos were determined with Streptavidin-Biotin Complex immunohistochemistry. The results showed pain threshold induced by EA at set of Baihui-Santai acupoints was 44.74% ± 4.56% higher than that by EA at set of Housanli acupoints (32.64% ± 5.04%). Compared with blank control, EA at two sets of acupoints increased c-Fos expression in the medial septal nucleus (MSN), the arcuate nucleus (ARC), the nucleus amygdala basalis (AB), the lateral habenula nucleus (HL), the ventrolateral periaqueductal grey (vlPAG), the locus coeruleus (LC), the nucleus raphe magnus (NRM), the pituitary gland, and spinal cord dorsal horn (SDH). Compared with EA at set of Housanli points, EA at set of Baihui-Santai points induced increased c-Fos expression in AB but decrease in MSN, the paraventricular nucleus of the hypothalamus, HL, and SDH. It suggests that ARC-PAG-NRM/LC-SDH and the hypothalamus-pituitary may be the common activated neural pathways taking part in EA-induced analgesia at the two sets of acupoints.

Spinal Glutamate Transporters Are Involved in the Development of Electroacupuncture Tolerance

BACKGROUND

Electroacupuncture (EA) tolerance is a gradual decline in EA antinociception because of its repeated or prolonged use. This study aims to explore the role of spinal glutamate transporters (GTs) in EA tolerance (EAT).

METHODS

Rats were treated with EA once per day for eight consecutive days, and their L4-5 spinal cords were collected at days 0, 2, 4, 6 and 8. The levels of three spinal GTs and their mRNAs were detected with Western blot and pPCR, respectively. Then, riluzole, a positive GT regulator, was administered intrathecally in order to observe its effect on EA analgesia after repeated EA.

RESULTS

The expression levels of the spinal GTs increased at days 2 and 4, and gradually decreased as the times of EA increased. At day 8, no difference was observed in the spinal GTs between the sham treatment and the EA treatment. Intrathecal administration of riluzole dose-dependently attenuated the decreased EA analgesia.

CONCLUSION

These results indicated the participation of the spinal GTs in EAT.

The Expression Patterns of c-Fos and c-Jun Induced by Different Frequencies of Electroacupuncture in the Brain

To investigate patterns of c-Fos and c-Jun expression induced by different frequencies of electroacupuncture (EA) in the brain, goats were stimulated by EA of 0, 2, 60, or 100 Hz at a set of "Baihui, Santai, Ergen, and Sanyangluo" points for 30 min. The pain threshold was measured using the potassium iontophoresis method. The levels of c-Fos and c-Jun were determined with Streptavidin-Biotin Complex immunohistochemistry. The results showed that the pain threshold induced by 60 Hz was 82.2% higher (P < 0.01) than that by 0, 2, or 100 Hz (6.5%, 35.2%, or 40.9%). EA induced increased c-Fos and c-Jun expression in most analgesia-related nuclei and areas in the brain. Sixty Hz EA increased more c-Fos or c-Jun expression than 2 Hz or 100 Hz EA in all the measured nuclei and areas except for the nucleus accumbens, the area septalis lateralis, the caudate nucleus, the nucleus amygdala basalis, and the locus coeruleus, in which c-Fos or c-Jun expressions induced by 60 Hz EA did not differ from those by 2 Hz or 100 Hz EA. It was suggested that 60 Hz EA activated more extensive neural circuits in goats, which may contribute to optimal analgesic effects.

Endogenous opiates and behavior: 2013

This paper is the thirty-sixth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2013 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.