Differential proteomics analysis of the analgesic effect of electroacupuncture intervention in the hippocampus following neuropathic pain in rats

Proteomics and its application in the research of acupuncture: An updated review

As a complementary and alternative therapy, acupuncture is widely used in the prevention and treatment of various diseases. However, the understanding of the mechanism of acupuncture effects is still limited due to the lack of systematic biological validation. Notably, proteomics technologies in the field of acupuncture are rapidly evolving, and these advances are greatly contributing to the research of acupuncture. In this study, we review the progress of proteomics research in analyzing the molecular mechanisms of acupuncture for neurological disorders, pain, circulatory disorders, digestive disorders, and other diseases, with an in-depth discussion around acupoint prescription and acupuncture manipulation modalities. The study found that proteomics has great potential in understanding the mechanisms of acupuncture. This study will help explore the mechanisms of acupuncture from a proteomic perspective and provide information to support future clinical decisions.

Electroacupuncture pretreatment protects against anesthesia/surgery-induced cognitive decline by activating CREB via the ERK/MAPK pathway in the hippocampal CA1 region in aged rats

Effective preventive measures against postoperative cognitive dysfunction in older adults are urgently needed. In this study, we investigated the effect of electroacupuncture (EA) on anesthesia and surgery-induced cognitive decline in aged rats by RNA-seq analysis, behavioral testing, Golgi-Cox staining, dendritic spine analysis, immunofluorescence assay and western blot analysis. EA ameliorated anesthesia and surgery induced-cognitive decline. RNA-seq analysis identified numerous differentially-expressed genes, including 353 upregulated genes and 563 downregulated genes, after pretreatment with EA in aged rats with postoperative cognitive dysfunction. To examine the role of CREB in EA, we injected adeno-associated virus (AAV) into the CA1 region of the hippocampus bilaterally into the aged rats to downregulate the transcription factor. EA improved synaptic plasticity, structurally and functionally, by activating the MAPK/ERK/CREB signaling pathway in aged rats. Together, our findings suggest that EA protects against anesthesia and surgery-induced cognitive decline in aged rats by activating the MAPK/ERK/CREB signaling pathway and enhancing hippocampal synaptic plasticity.

Over-expression of miR-3584-5p Represses Nav1.8 Channel Aggravating Neuropathic Pain caused by Chronic Constriction Injury

Nav1.8, a tetrodotoxin-resistant voltage-gated sodium channels (VGSCs) subtype encoded by SCN10A, which plays an important role in the production and transmission of peripheral neuropathic pain signals. Studies have shown that VGSCs may be key targets of MicroRNAs (miRNAs) in the regulation of neuropathic pain. In our study, bioinformatics analysis showed that the targeting relationship between miR-3584-5p and Nav1.8 was the most closely. The purpose of this study was to investigate the roles of miR-3584-5p and Nav1.8 in neuropathic pain. The effects of miR-3584-5p on chronic constriction injury (CCI)-induced neuropathic pain in rats was investigated by intrathecal injection of miR-3584-5p agomir (an agonist, 20 μM, 15 μL) or antagomir (an antagonist, 20 μM, 15 μL). The results showed that over-expression of miR-3584-5p aggravated neuronal injury by hematoxylin-eosin (H&E) staining and mechanical/thermal hypersensitivity in CCI rats. MiR-3584-5p indirectly inhibited the expression of Nav1.8 by up-regulating the expression of key proteins in the ERK5/CREB signaling pathway, and also inhibited the current density of the Nav1.8 channel, changed its channel dynamics characteristic, thereby accelerating the transmission of pain signals, and further aggravating pain. Similarly, in PC12 and SH-SY5Y cell cultures, miR-3584-5p increased the level of reactive oxygen species (ROS) and inhibited mitochondrial membrane potential (Δψm) in the mitochondrial pathway, decreased the ratio of apoptosis-related factor Bcl-2/Bax, and thus promoted neuronal apoptosis. In brief, over-expression of miR-3584-5p aggravates neuropathic pain by directly inhibiting the current density of Nav1.8 channel and altering its channel dynamics, or indirectly inhibiting Nav1.8 expression through ERK5/CREB pathway, and promoting apoptosis through mitochondrial pathway.

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

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

Intracellular cAMP Signaling Pathway via Gs Protein-Coupled Receptor Activation in Rat Primary Cultured Trigeminal Ganglion Cells

G protein-coupled receptors in trigeminal ganglion (TG) neurons are often associated with sensory mechanisms, including nociception. We have previously reported the expression of P2Y12 receptors, which are Gi protein-coupled receptors, in TG cells. Activating P2Y12 receptors decreased the intracellular free Ca2+ concentration ([Ca2+]i). This indicated that intracellular adenosine 3',5'-cyclic monophosphate (cAMP) levels can mediate Ca2+ signaling in TG cells. Here, we report more extensive-expression patterns of Gs protein-coupled receptors in primary cultured TG neurons isolated from 7-day-old newborn Wistar rats and further examine the roles of these receptors in cAMP signaling using the BacMam sensor in these neurons. To identify TG neurons, we also measured [Ca2+]i using fura-2 in TG cells and measured intracellular cAMP levels. TG neurons were positive for Gαs protein-coupled receptors, beta-2 adrenergic (β2), calcitonin gene-related peptide (CGRP), adenosine A2A (A2A), dopamine 1 (D1), prostaglandin I2 (IP), and 5-hydroxytriptamine 4 (5-HT4) receptor. Application of forskolin (FSK), an activator of adenylyl cyclase, transiently increased intracellular cAMP levels in TG neurons. The application of a phosphodiesterase inhibitor augmented the FSK-elicited intracellular cAMP level increase. These increases were significantly suppressed by the application of SQ22536, an adenylyl cyclase inhibitor, in TG neurons. Application of agonists for β2, CGRP, A2A, D1-like, IP, and 5-HT4 receptors increased intracellular cAMP levels. These increases were SQ22536-sensitive. These results suggested that TG neurons express β2, CGRP, A2A, D1, IP, and 5-HT4 receptors, and the activations of these Gαs protein-coupled receptors increase intracellular cAMP levels by activating adenylyl cyclase.

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.

Neuropathic Pain Creates Systemic Ultrastructural Changes in the Nervous System Corrected by Electroacupuncture but Not by Pregabalin

Purpose

It is unclear whether neuropathological structural changes in the peripheral nervous system and central nervous system can occur in the spared nerve injury model. In this study, we investigated the pathological changes in the nervous system in a model of neuropathic pain as well as the effects of electroacupuncture (EA) and pregabalin (PGB) administration as regards pain relief and tissue repair.

Patients and Methods

Forty adult male SD rats were equally and randomly divided into 4 groups: spared nerve injury group (SNI, n = 10), SNI with electroacupuncture group (EA, n = 10), SNI with pregabalin group (PGB, n =10) and sham-operated group (Sham, n=10). EA and PGB were given from postoperative day (POD) 14 to 36. EA (2 Hz and 100 Hz alternating frequencies, intensities ranging from 1–1.5–2 mA) was applied to the left “zusanli” (ST36) and “Yanglingquan” (GB34) acupoints for 30 minutes. The mechanical withdrawal thresholds (MWTs) were tested with von Frey filaments. Moreover, the organizational and structural alterations of the bilateral prefrontal cortex, hippocampus, sciatic nerves and the thoracic, lumbar spinal cords and dorsal root ganglions (DRGs) were examined via light and electron microscopy.

Results

MWTs of left hind paw demonstrated a remarkable decrease in the SNI model (P < 0.05). In the SNI model, ultrastructural changes including demyelination and damaged neurons were observed at all levels of the peripheral nervous system (PNS) and central nervous system (CNS). In addition, EA improved MWTs and restored the normal structure of neurons. However, the effect was not found in the PGB treatment group.

Conclusion

Chronic pain can induce extensive damage to the central and peripheral nervous systems. Meanwhile, EA and PGB can both alleviate chronic pain syndromes in rats, but EA also restores the normal cellular structures, while PGB is associated with no improvement.

Orexin-2 receptor antagonism in the cornu ammonis 1 region of hippocampus prevented the antinociceptive responses induced by chemical stimulation of the lateral hypothalamus in the animal model of persistent pain

Orexins are excitatory neuropeptides, mainly produced by neurons located in the lateral hypothalamus, which project to many brain areas. The orexinergic system plays a fundamental role in arousal, sleep/wakefulness, feeding, energy homeostasis, motivation, reward, stress and pain modulation. As a prominent part of the limbic system, the hippocampus has been involved in formalin-induced nociception modulation. Moreover, hippocampus regions express both orexin-1 (OX1) and orexin-2 (OX2) receptors. The present study investigated the role of OX2 receptors (OX2R) within the cornu ammonis 1 (CA1) region of the hippocampus in the mediation of lateral hypothalamus-induced antinociception. Fifty-three male Wistar rats were unilaterally implanted with two separate cannulae into the lateral hypothalamus and CA1. Animals were pretreated with intra-CA1 TCS OX2 29 as an OX2R antagonist before intra-lateral hypothalamus administration of carbachol (250 nM) as a muscarinic agonist for chemical stimulation of orexinergic neurons. Formalin test was used as an animal model of persistent pain, following intra-lateral hypothalamus carbachol microinjection. Results showed that the chemical stimulation of the lateral hypothalamus significantly attenuated formalin-evoked nociceptive behaviors during both phases of the formalin test, and administration of TCS OX2 29 into the CA1 blocked these antinociceptive responses in both phases, especially in the late phase. These findings suggest that OX2 receptors in the CA1 partially mediate the lateral hypothalamus-induced antinociceptive responses in persistent inflammatory pain.

Differential Proteomic Analysis of the Hippocampus in Rats with Neuropathic Pain to Investigate the Use of Electroacupuncture in Relieving Mechanical Allodynia and Cognitive Decline

Abnormal changes in hippocampal function and neuroplasticity are involved in neuropathic pain, which induces hyperalgesia and learning and memory deficits. Previous studies from our group have shown that electroacupuncture at Huantiao (GB30) and Yanglingquan (GB34) has an obvious analgesic effect on neuropathic pain. However, the central regulatory mechanism occurring in the hippocampus remains to be investigated. In this study, behavioral and proteomic analyses were performed to identify differentially expressed hippocampal proteins involved in electroacupuncture-induced analgesia. Our results showed both upregulated (TMEM126A, RDH13, and Luc7L) and downregulated proteins (Mettl7A, GGA1 RTKN, RSBN1, and CDKN1B). Further protein verification revealed for the first time that hippocampal TMEM126A plays an important anti-inflammatory role in the treatment of neuralgia by electroacupuncture.

TMT-based quantitative proteomics reveals suppression of SLC3A2 and ATP1A3 expression contributes to the inhibitory role of acupuncture on airway inflammation in an OVA-induced mouse asthma model

Asthma is a chronic airway inflammatory disease and acupuncture is frequently used in patients suffering from asthma in clinic. However, the regulatory mechanism of acupuncture treatment in asthma is not fully elucidated. We sought to investigate the effectiveness of acupuncture on asthma and the associated regulatory mechanism. An ovalbumin (OVA)-induced mouse asthma model was established and the effect of acupuncture on airway hyperresponsiveness (AHR), mucus hypersecretion and inflammation was assessed. Tandem mass tag (TMT)-based quantitative proteomics analysis of lung tissue and bioinformatics analysis were performed. Our results revealed that the OVA-induced mouse asthma model was successfully established with the significantly elevated AHR to methacholine (Mch), and acupuncture was effective in attenuation of AHR to Mch, peribronchial and perivascular inflammation and mucus production. The inflammatory cells around the airways, mucous secretion as well as levels of IgE, CCL5, CCL11, IL-17A in bronchoalveolar lavage fluid (BALF) and IL-4, IL-5 and IL-13 levels in serum were siginificantly inhibited by acupuncture. TMT-based quantitative proteomics analysis found that a total of 6078 quantifiable proteins were identified, and 564 (334 up-regulated and 230 down regulated) differentially expressed proteins (DEPs) were identified in OVA-induced asthma model group (A) versus normal control group (NC). Acupuncture treatment resulted in 667 DEPs (416 up-regulated and 251 down regulated) compared with A group, and 86 overlapping DEPs were identified in NC, A and AA groups. Among the 86 overlapping DEPs, we identified 41 DEPs regulated by acupuncture. Based on the above data, we performed a systematic bioinformatics analysis of the 41 DEPs, and results showed that these 41 DEPs were predominantly related to 4 KEGG pathways including SNARE interactions in vesicular transport, ferroptosis, endocrine and other factor-regulated calcium reabsorption, and protein digestion and absorption. DEPs of SLC3A2 and ATP1A3 expression levels were verified by immumohistochemical staining. Mice in OVA-induced asthma model group had elevated SLC3A2 and ATP1A3 expression and acupuncture had the ability to downregulate SLC3A2 and ATP1A3 protein expression. Furthermore, acupuncture reduced the MDA level and increased the GSH and SOD levels in the lung tissue. Taken together, our data suggested that acupuncture was effective in treating asthma by attenuation of AHR, mucus secretion and airway inflammation, and the mechanism was associated with regulation of ferroptosis, SLC3A2 and ATP1A3 protein expression as well as oxidative stress. Results from our experiments revealed the anti-inflammatory effect of acupuncture in OVA-induced mouse asthma model, leading to a more effective approach to be chosen by patients in clinic.

Blockade of the orexin receptors in the CA1 region of hippocampus decreased the lateral hypothalamic-induced antinociceptive responses in the model of orofacial formalin test in the rats

The role of hippocampus and lateral hypothalamus (LH) in modulation of formalin-induced nociception has been established. The present study aims to examine the role of orexin receptors in the Cornu Ammonis 1 (CA1) region of hippocampus in modulation of the LH-induced antinociception in the orofacial formalin test. Male Wistar rats were unilaterally implanted with two cannulae into the LH and CA1. Intra-LH microinjection of carbachol was done 5min after intra-CA1 administration of SB-334867 (OX1R antagonist) or TCS OX2 29 (OX2R antagonist). After 5min, 50μl of 1% formalin was subcutaneously injected into the upper lip for inducing the nociceptive behaviors. Solely intra-LH administration of carbachol reduced early and late phases of formalin-induced orofacial nociception in a dose-dependent manner. The antinociception evoked by intra-LH injection of carbachol (0.5μl of 250nM carbachol) was antagonized by intra-CA1 administration of 0.5μl of 3, 10 and 30nM solutions of SB-334867 or TCS OX2 29 during the early and late phases of orofacial formalin test. This effect was more remarkable during the late phase in comparison to the early phase. In addition, anti-analgesic effect of SB-334867 was more than TCS OX2 29 during the early and late phases. The results suggest the interpretation that a neural pathway from the LH to the CA1 probably contributes to the modulation of formalin-induced orofacial nociception through recruitment of both CA1 orexin receptors. Clinical studies are recommended to study the probable effectiveness of orexinergic system in modulation of the orofacial nociceptive responses.

Proteomic Identification of an Upregulated Isoform of Annexin A3 in the Spinal Cords of Rats in a Neuropathic Pain Model

Neuropathic pain (NP) is induced by nerve damage or a disturbance in the peripheral or central nervous systems. Nerve damage causes the activation of sensitizing mechanisms in the peripheral and central nervous systems, which induces transcriptional and post-transcriptional alterations in sensory nerves. However, the underlying mechanisms of NP remain elusive. In the study, Two-dimensional gel electrophoresis (2DGE)-based comparative proteomics identified 38 differential gel spots, and 15 differentially expressed proteins (DEPs) between the sham and the chronic constriction injury (CCI)-induced neuropathic pain rats. Of them, Annexin A3 (ANXA3) was significantly increased after CCI with Western blot analysis and immunofluorescence imaging. A lentivirus delivering ANXA3 shRNA (LV-shANXA3) was administered intrathecally to determine the analgesic effects of ANXA3 on allodynia and hyperalgesia in a CCI-induced neuropathic pain model in rats. Further study showed that LV-shANXA3 reversed the upregulation of ANXA3, alleviated CCI-induced mechanical allodynia and thermal hyperalgesia. The study indicated that ANXA3 may play an important role in neuropathic pain.

Electro-analgesia for sheep husbandry practices: a review

Several sheep-husbandry practices such as mulesing, castration, ear-tagging and tail-docking are currently performed with no, or little, anaesthesia or analgesia. The potential for using electrotherapies to provide analgesia during and after these operations is examined in this review. The most common electrotherapy is transcutaneous electrical nerve stimulation (TENS). TENS is the application of an electrical current from electrodes placed on the skin. Analysis of a large number of trials in humans and in animal models indicates that TENS provides effective relief from acute and chronic pain, including pain associated with surgery. There is strong evidence now that TENS analgesia operates at the levels of the periphery, the spinal cord and in the brain. The mechanisms involve the autonomic nervous system, the opioid pathways and neurotransmitters involved in descending inhibitory pathways from the brain. Centrally operating pathways mean the current does not have to be applied near the injured site and there is evidence of sustained pain relief lasting hours, days or even weeks post-treatment, particularly after very high-frequency, randomly variable current applications. Treatment of sheep during painful operations with such a current has the potential to provide immediate and possibly sustained pain relief. Combining such a treatment with electro-immobilisation of the animal would be advantageous for sheep-husbandry operations, but there is considerable evidence that high-intensity currents producing tetanic contractions are aversive and probably painful for sheep. Investigations of the application and efficacy of electrotherapies for painful sheep operations should be undertaken.

Activation of hippocampal MEK1 contributes to the cumulative antinociceptive effect of electroacupuncture in neuropathic pain rats

Background

Electroacupuncture (EA) intervention can relieve a variety of pain; however, optimal EA protocols have not been clearly determined. In addition, although central mitogen-activated protein kinase kinase (MEK) signaling has been shown to be involved in the antinociceptive effect of acupuncture stimulation, its characteristics at different time-points of EA intervention have not been fully elucidated. Therefore, the present study investigated the relationship between the effects of different numbers of EA intervention sessions and the activation of MEK1 in the hippocampus and hypothalamus in a rat model of neuropathic pain.

Methods

After ligation of the left sciatic nerve, which induces chronic constriction injury (CCI), the acupoints Zusanli (ST36) and Yanglingquan (GB34) were applied. The thermal withdrawal latency of the hind paw was used to evaluate the effect of EA on pain thresholds. Intra-hippocampus microinjection of PD98059, a MEK inhibitor, was performed to validate the involvement of MEK in EA analgesia. The hippocampus and hypothalamus were harvested to examine the phosphorylation levels of MEK (pMEK) by western blotting.

Results

In CCI rats, the thermal pain threshold of the affected hind paw decreased significantly relative to the control. Following subsequent daily EA interventions, CCI-induced ipsilateral hyperalgesia was markedly improved from day 4 and the analgesic effect of EA lasted 3 days after cessation of EA. Four sessions of EA markedly suppressed CCI-induced decrease of hippocampal pMEK1 (normalized to the total MEK level). In contrast, successive sessions of EA intervention gradually down-regulated the CCI-induced up-regulation of hypothalamic pMEK1 along with the increase numbers of EA intervention. However, EA did not exert the same analgesic effect after microinjection of PD98059 into the contralateral hippocampus during the first 3 days of EA intervention.

Conclusions

EA intervention can induce time-dependent cumulative analgesia in neuropathic pain rats after 4 successive sessions of daily EA intervention, which is at least in part related to the activation of hippocampal MEK1.

MiRNAs are involved in chronic electroacupuncture tolerance in the rat hypothalamus

Acupuncture tolerance is the gradual decrease in analgesic effect due to its prolonged application. However, its mechanism in terms of miRNA is still unknown. To explore the role of miRNAs in electroacupuncture (EA) tolerance of rats using deep sequencing, rats with more than a 50 % increase in tail flick latency (TFL) in response to EA were selected for this experiment. EA tolerance was induced by EA once daily for eight consecutive days. The hypothalami were harvested for deep sequencing. As a result, 49 differentially expressed miRNAs were identified and validated by real-time PCR. Of them, let-7b-5p, miR-148a-3p, miR-124-3p, miR-107-3p, and miR-370-3p were further confirmed to be related to EA tolerance by an intracerebroventricular injection of agomirs or antagomirs of these miRNAs. Potential targets of the 49 miRNAs were enriched in 9 pathways and 282 gene ontology (GO) terms. Five miRNAs were confirmed to participate in EA tolerance probably through the functional categories related to nerve impulse transmission, receptor signal pathways, and gene expression regulation, as well as pathways related to MAPK, neurotrophin, fatty acid metabolism, lysosome, and the degradation of valine, leucine, and isoleucine. Our findings reveal a characterized panel of the differentially expressed miRNAs in the hypothalamus in response to EA and thus provide a solid experimental framework for future analysis of the mechanisms underlying EA-induced tolerance.

Acupuncture-Induced Analgesia: The Role of Microglial Inhibition

The last three decades have documented preclinical and clinical data supporting the use of acupuncture in relieving symptoms of many diseases, including allergies, infections, and neurological disorders. The advent of electroacupuncture has not only modernized the practice of acupuncture, but also has improved its efficacy, especially for producing analgesic-like effects. Although the mechanism of action of acupuncture-induced analgesia remains largely unknown, several lines of investigation have implicated modulation of pain processes via brain opioid signaling and neuroimmunoregulatory pathways. Here, we review key findings demonstrating the efficacy and underlying mechanisms of acupuncture-induced analgesia. In particular, we discuss potent analgesic effects of acupuncture via neural pain processes through inhibition of microglial activation. The safe and effective use of acupuncture stands as a nonpharmacological alternative for induction of analgesia, which has direct clinical applications, especially for pain-related diseases.

Effect of Repeated Electroacupuncture Intervention on Hippocampal ERK and p38MAPK Signaling in Neuropathic Pain Rats

Results of our past studies showed that hippocampal muscarinic acetylcholine receptor (mAChR)-1 mRNA and differentially expressed proteins participating in MAPK signaling were involved in electroacupuncture (EA) induced cumulative analgesia in neuropathic pain rats, but the underlying intracellular mechanism remains unknown. The present study was designed to observe the effect of EA stimulation (EAS) on hippocampal extracellular signal-regulated kinases (ERK) and p38 MAPK signaling in rats with chronic constrictive injury (CCI) of the sciatic nerve, so as to reveal its related intracellular targets in pain relief. After CCI, the thermal pain thresholds of the affected hind were significantly decreased compared with the control group (P < 0.05). Following one and two weeks' EAS of ST 36-GB34, the pain thresholds were significantly upregulated (P < 0.05), and the effect of EA2W was remarkably superior to that of EA2D and EA1W (P < 0.05). Correspondingly, CCI-induced decreased expression levels of Ras, c-Raf, ERK1 and p-ERK1/2 proteins, and p38 MAPK mRNA and p-p38MAPK protein in the hippocampus tissues were reversed by EA2W (P < 0.05). The above mentioned results indicated that EA2W induced cumulative analgesic effect may be closely associated with its function in removing neuropathic pain induced suppression of intracellular ERK and p38MAPK signaling in the hippocampus.

MicroRNA Profiling Response to Acupuncture Therapy in Spontaneously Hypertensive Rats

MicroRNAs (miRNAs) are a group of endogenous noncoding RNAs that play important roles in many biological processes. This study aimed to check if miRNAs were involved in the response to acupuncture in rats. Microarray analysis was performed to compare the miRNA expression profiles of medulla in spontaneously hypertensive rats (SHRs) treated with or without acupuncture. Our microarray analysis identified 222 differentially expressed miRNAs in the medulla of SHRs treated with acupuncture at taichong acupoint. Among these miRNAs, 23 miRNAs with a significant difference were found in acupuncture-treated SHRs compared to untreated rats. These 23 miRNAs could regulate 2963 target genes which were enriched in at least 14 pathways based on our bioinformatic analysis. miRNA-339, miR-223, and miR-145 were downregulated in the medulla of SHRs compared to normotensive rats. Notably, these miRNAs were upregulated to basal levels in the medulla of SHRs treated with acupuncture at taichong in comparison with SHRs receiving acupuncture at nonacupoint group or SHRs without any treatment. Our findings have revealed significant changes of a panel of selective miRNAs in hypertensive rats treated at taichong acupoint. These data provide insights into how acupuncture elicits beneficial effects on hypertension.

NK cells mediate the cumulative analgesic effect of electroacupuncture in a rat model of neuropathic pain

Background

Cumulating evidence has revealed the effectiveness of acupuncture therapy in relieving pain via immunoregulation. However, its underlying mechanism remains unknown. The present study was designed to determine the changes of immunogenic responses at different time-points of electroacupuncture (EA) interventions in neuropathic pain rats.

Methods

The neuropathic pain model was established by ligature of the left sciatic nerve to induce chronic constriction injury (CCI). EA was applied at Zusanli (ST36) and Yanglingquan (GB34) for the EA groups. The thermal pain threshold was detected with an algesia-detector. The subgroups of plasma and splenic lymphocytes were determined via fluorescence-activated cell sorting. Specific inflammatory cytokines were assayed using an ELISA-based bead multiplex assay. The activities of splenic natural killer (NK) cells and cytotoxic T lymphocytes were detected by methyl thiazolyl tetrazolium colorimetric method. For confirming the involvement of NK cell in EA-analgesia, anti-asialo-ganglio-N-tetraosylceramide (anti-asialo-GM1) antibody was given to CCI rats before EA.

Results

Following CCI, the thermal pain threshold of the affected hind footpad was significantly decreased, and increased from the 3^rd day to the 12^th day after EA interventions, presenting a time-dependent tendency from the 5th day on. From day 3 to 5 of EA interventions, the percentages and activity of splenic NK cells, concentrations of splenic interleukin-2 (IL-2) and beta-endorphin (β-EP) were significantly increased. Meanwhile, the concentrations of plasma IL-2, IL-1β and gamma-interferon (IFN-γ) were significantly decreased and returned to the normal level on day 12 following EA. Plasma transforming growth factor-β (TGF-β) levels were considerably upregulated on day 5 and 12 following EA. The CD4+/CD8+ T cell ratio was markedly downregulated compared with the control and CCI groups on day 5 and returned to the normal level on day 12 following EA. After depleting NK cells by anti-asialo-GM1 antibody, the increased thermal pain threshold following EA intervention was obviously reduced.

Conclusions

Repeated EA interventions have a time-dependent cumulative analgesic effect in neuropathic pain rats, which is closely associated with its regulatory effects on NK cells, splenic IL-2, β-EP, and plasma IL-2, IL-1β, IFN-γ and TGF-β levels.

The holistic effects of acupuncture treatment

Traditional Chinese Medicine (TCM), as a complex medical science which reflects philosophical principles and embodies large dialectical thought, is used to place the human body into a large system for observation. Acupuncture as a vital part of TCM, has been practiced to treat various diseases and symptoms. However, acupuncture is also facing severe challenges resulted from insufficient modern scientific research. Nowadays, the holistic effects of acupuncture can be researched by some modern approaches, such as the systems biology and fMRI technique. It is believed that having a better understand will greatly promote acupuncture research and be beneficial to scientization and modernization of acupuncture.