Electroacupuncture treatment upregulates α7nAChR and inhibits JAK2/STAT3 in dorsal root ganglion of rat with spared nerve injury

Targeting the JAK2/STAT3 signaling pathway for chronic pain

Chronic pain is a notable health concern because of its prevalence, persistence, and associated mental stress. Drugs targeting chronic pain with potent abirritation, and minimal side effects remain unidentified. Substantial evidence indicates that the Janus Kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling pathway plays a distinct and critical role in different stages of chronic pain. Aberrant activation of the JAK2/STAT3 signaling pathway is evident in multiple chronic pain models. Moreover, an increasing number of studies have demonstrated that the downregulation of JAK2/STAT3 can attenuate chronic pain in different animal models. In this review, we investigated the mechanism and role of the JAK2/STAT3 signaling pathway in modulating chronic pain. The aberrant activation of JAK2/STAT3 can trigger chronic pain by interacting with microglia and astrocytes, releasing proinflammatory cytokines, inhibiting anti-inflammatory cytokines, and regulating synaptic plasticity. We also retrospectively reviewed current reports on JAK2/STAT3 pharmacological inhibitors that demonstrated their significant therapeutic potential in different types of chronic pain. In summary, our results provide strong evidence that the JAK2/STAT3 signaling pathway is a promising therapeutic target for chronic pain.

The mechanistic basis for the effects of electroacupuncture on neuropathic pain within the central nervous system

Nociceptive signaling responses to painful stimuli are transmitted to the central nervous system (CNS) from the afferent nerves of the periphery through a series of neurotransmitters and associated signaling mechanisms. Electroacupuncture (EA) is a pain management strategy that is widely used, with clinical evidence suggesting that a frequency of 2-10 Hz is better able to suppress neuropathic pain in comparison to higher frequencies such as 100 Hz. While EA is widely recognized as a viable approach to alleviating neuralgia, the mechanistic basis underlying such analgesic activity remains poorly understood. The present review offers an overview of current research pertaining to the mechanisms whereby EA can alleviate neuropathic pain in the CNS, with a particular focus on the serotonin/norepinephrine, endogenous opioid, endogenous cannabinoid, amino acid neurotransmitter, and purinergic pathways. Moreover, the corresponding neurotransmitters, neuromodulatory compounds, neuropeptides, and associated receptors that shape these responses are discussed. Together, this review seeks to provide a robust foundation for further studies of the EA-mediated alleviation of neuropathic pain.

Effects of Acupuncture on Neuropathic Pain Induced by Spinal Cord Injury: A Systematic Review and Meta-Analysis

Introduction

Neuropathic pain is a commonly seen symptom and one of the most intractable comorbidities following spinal cord injury (SCI). Acupuncture has been widely used for neuropathic pain after SCI in clinical settings. There is no systematic review or meta‐analysis evaluating the efficacy of acupuncture in the treatment of SCI-induced neuropathic pain. Thus, this study aimed to conduct a systematic review and meta-analysis to assess the efficacy of acupuncture on SCI-induced neuropathic pain.

Methods

Seven databases were comprehensively searched, including PubMed, the Cochrane Library, the Web of Science, the China National Knowledge Infrastructure (CNKI), the Chinese Biomedical Literature Service System (SinoMed), the Wanfang Database, and the Chinese Scientific Journals Database (VIP) from their inception to 30 September 2021. Two independent reviewers evaluated the eligibility of the data retrieved based on the pre-established eligibility criteria and assessed the methodological quality of the included studies using the Cochrane Risk of Bias Tool. The outcome indexes in this study included the visual analogue scale, the numeric rating scale, the present pain intensity, and the pain region index. Sensitivity and subgroup analyses were also performed to specifically evaluate the intervention effects. In addition, publication bias was analyzed.

Results

Six randomized controlled trials (145 participants in the experimental groups and 141 participants in the control groups) were identified that evaluated the application of acupuncture for neuropathic pain after SCI and were included in this study. The results of our study revealed that acupuncture had a positive effect on the pain severity (standardized mean difference (SMD): −1.40, 95% confidence interval (CI): −2.23; −0.57), the present pain intensity (MD = −0.61, 95% CIs = −0.98; −0.23), and the pain region index (MD = −3.04, 95% CI = −3.98; −2.11). In addition, sensitivity analyses showed that these results were robust and stable. Subgroup analyses indicated that electroacupuncture (EA) had better effects on SCI-induced neuropathic pain. However, a publication bias was observed.

Conclusion

Available evidence appears to suggest that acupuncture may have a role in SCI-induced neuropathic pain management, but this remains to be determined.

Electroacupuncture Alleviates LPS-Induced ARDS Through α7 Nicotinic Acetylcholine Receptor-Mediated Inhibition of Ferroptosis

Acute respiratory distress syndrome (ARDS) is an uncontrollable, progressive pulmonary inflammatory disease, and as a common clinical critical disease, there is no effective treatment available. Electroacupuncture (EA) therapy is a type of traditional Chinese medicine physiotherapy that can alleviate the inflammatory response. However, the potential mechanism of EA in the treatment of ARDS is not yet clear. Ferroptosis is a new type of programmed cell death characterized by intracellular iron accumulation and lipid peroxidation. Recently, emerging evidence has shown that ferroptosis is closely related to the occurrence and development of ARDS caused by various pathological factors. Here, we further investigated whether EA-mediated inhibition of ferroptosis in lung tissue could attenuate lipopolysaccharide (LPS)-induced ARDS and explored its underlying mechanisms. In this study, mice were administered LPS intraperitoneally to establish a model of LPS-induced ARDS. We found that EA stimulation could not only reduce the exudation of inflammatory cells and proteins in the alveolar lumen but also significantly alleviate the pathological changes of lung tissue, inhibit the production of proinflammatory cytokines and improve the survival rate of mice. Concurrently, we also found that ferroptosis events occurred in the lung tissue of LPS-induced ARDS mice, manifested by elevated iron levels, ROS production and lipid peroxidation. Intriguingly, our results showed that EA stimulation at the Zusanli (ST36) acupoint activated α7 nicotinic acetylcholine receptor (α7nAchR) in lung tissue mainly through the sciatic nerve and cervical vagus nerve, thus exerting anti-ferroptosis and pulmonary protective effects. Additionally, these effects were eliminated by methyllycaconitine (MLA), a selective antagonist of α7nAchR. In vitro experiments, activation of α7nAchR protected alveolar epithelial cells from LPS-induced ferroptosis. Furthermore, our experiments showed that the pulmonary protective effects of EA stimulation were effectively reversed by erastin, a ferroptosis activator. Collectively, we demonstrated that EA stimulation could alleviate LPS-induced ARDS by activating α7nAchR to inhibit LPS-induced ferroptosis in alveolar epithelial cells. Targeting and regulating ferroptosis in alveolar epithelial cells may be a potential intervention approach for the treatment of LPS-induced ALI/ARDS in the future.

The α7 nAChR allosteric modulator PNU-120596 amends neuroinflammatory and motor consequences of parkinsonism in rats: Role of JAK2/NF-κB/GSk3β/ TNF-α pathway

Parkinson's disease (PD) is the second most common neurodegenerative disorder and a leading cause of disability. The current gold standard for PD treatment, L-Dopa, has limited clinical efficacy and multiple side effects. Evidence suggests that activation of α7 nicotinic acetylcholine receptors (α7nAChRs) abrogates neuronal and inflammatory insults. Here we tested whether PNU-120596 (PNU), a type II positive allosteric modulator of α7 nAChR, has a critical role in regulating motor dysfunction and neuroinflammation correlated with the associated PD dysfunction. Neuroprotective mechanisms were investigated through neurobehavioral, molecular, histopathological, and immunohistochemical studies. PNU reversed motor incoordination and hypokinesia induced via the intrastriatal injection of 6-hydroxydopamine and manifested by lower falling latency in the rotarod test, short ambulation time and low rearing incidence in open field test. Tyrosine hydroxylase immunostaining showed a significant restoration of dopaminergic neurons following PNU treatment, in addition to histopathological restoration in nigrostriatal tissues. PNU halted striatal neuroinflammation manifested as a suppressed expression of JAK2/NF-κB/GSk3β accompanied by a parallel decline in the protein expression of TNF-α in nigrostriatal tissue denoting the modulator anti-inflammatory capacity. Moreover, the protective effects of PNU were partially reversed by the α7 nAChR antagonist, methyllycaconitine, indicating the role of α7 nAChR modulation in the mechanism of action of PNU. This is the first study to reveal the positive effects of PNU-120596 on motor derangements of PD via JAK2/NF-κB/GSk3β/ TNF-α neuroinflammatory pathways, which could offer a potential therapeutic strategy for PD.

The Anti-Inflammatory Actions and Mechanisms of Acupuncture from Acupoint to Target Organs via Neuro-Immune Regulation

Inflammation plays a significant role in the occurrence and development of multiple diseases. This study comprehensively reviews and presents literature from the last five years, showing that acupuncture indeed exerts strong anti-inflammatory effects in multiple biological systems, namely, the immune, digestive, respiratory, nervous, locomotory, circulatory, endocrine, and genitourinary systems. It is well known that localized acupuncture-mediated anti-inflammatory effects involve the regulation of multiple populations and functions of immune cells, including macrophages, granulocytes, mast cells, and T cells. In acupuncture stimulation, macrophages transform from the M1 to the M2 phenotype and the negative TLR4 regulator PPARγ is activated to inhibit the intracellular TLR/MyD88 and NOD signaling pathways. The downstream IκBα/NF-κB and P38 MAPK pathways are subsequently inhibited by acupuncture, followed by suppressed production of inflammasome and proinflammatory mediators. Acupuncture also modulates the balance of helper T cell populations. Furthermore, it inhibits oxidative stress by enhancing SOD activity via the Nrf2/HO-1 pathway and eliminates the generation of oxygen free radicals, thereby preventing inflammatory cell infiltration. The anti-inflammatory effects of acupuncture on different biological systems are also specific to individual organ microenvironments. As part of its anti-inflammatory action, acupuncture deforms connective tissue and upregulates the secretion of various molecules in acupoints, further activating the NF-κB, MAPK, and ERK pathways in mast cells, fibroblasts, keratinocytes, and monocytes/macrophages. The somatic afferents present in acupuncture-activated acupoints also convey sensory signals to the spinal cord, brainstem, and hypothalamic neurons. Upon information integration in the brain, acupuncture further stimulates multiple neuro-immune pathways, including the cholinergic anti-inflammatory, vagus-adrenal medulla-dopamine, and sympathetic pathways, as well as the hypothalamus-pituitary-adrenal axis, ultimately acting immune cells via the release of crucial neurotransmitters and hormones. This review provides a scientific and reliable basis and viewpoints for the clinical application of acupuncture in various inflammatory conditions.

Molecular Changes in the Dorsal Root Ganglion during the Late Phase of Peripheral Nerve Injury-induced Pain in Rodents: A Systematic Review

The dorsal root ganglion is widely recognized as a potential target to treat chronic pain. A fundamental understanding of quantitative molecular and genomic changes during the late phase of pain is therefore indispensable. The authors performed a systematic literature review on injury-induced pain in rodent dorsal root ganglions at minimally 3 weeks after injury. So far, slightly more than 300 molecules were quantified on the protein or messenger RNA level, of which about 60 were in more than one study. Only nine individual sequencing studies were performed in which the most up- or downregulated genes varied due to heterogeneity in study design. Neuropeptide Y and galanin were found to be consistently upregulated on both the gene and protein levels. The current knowledge regarding molecular changes in the dorsal root ganglion during the late phase of pain is limited. General conclusions are difficult to draw, making it hard to select specific molecules as a focus for treatment.

Genistein-3'-sodium sulfonate ameliorates cerebral ischemia injuries by blocking neuroinflammation through the α7nAChR-JAK2/STAT3 signaling pathway in rats

BACKGROUND

Neuroinflammation plays a pivotal role in the acute progression of cerebral ischemia/reperfusion injury (I/RI). We previously reported that genistein-3'-sodium sulfonate (GSS), a derivative from the extract of the phytoestrogen genistein (Gen), protects cortical neurons against focal cerebral ischemia. However, the molecular mechanism underlying the neuroprotective effects exerted by GSS remains unclear.

PURPOSE

The present study focused on the anti-inflammatory effects of GSS following I/RI in rats.

STUDY DESIGN

Randomized controlled trial.

METHODS

The tMCAO rat model and LPS-stimulated BV2 in vitro model were used. Longa's scare was used to observe neurological function. TTC staining and Nissl staining were used to evaluate brain injury. ELISA, qRT-PCR, Western blotting and immunofluorescent staining methods were used to detect cytokine concentration, mRNA level, protein expression and location.

RESULTS

GSS treatment improves neurological function, reduces the volume of cerebral infarction, attenuates proinflammatory cytokines and inactivates the phosphorylation of JAK2 and STAT3 in I/RI rats. Furthermore, GSS increased the expression of α7nAChR. More importantly, the neuroprotective, anti-inflammatory and inhibiting JAK2/STAT3 signaling pathway effects of GSS were counteracted in the presence of alpha-bungarotoxin (α-BTX), an α7nAChR inhibitor, suggesting that α7nAChR is a potential target associated with the anti-inflammatory effects of GSS in the I/RI rats. GSS also inhibited BV2 cells from releasing IL-1β via the α7nAChR pathway after LPS stimulation.

CONCLUSION

GSS protects against cerebral I/RI through the expression of α7nAChR and inhibition of the JAK2/STAT3 pathway. Our findings provide evidence for the role of the cholinergic anti-inflammatory pathway in neuroinflammation and uncover a potential novel mechanism for GSS treatment in ischemic stroke. The downstream signals of GSS, α7nAChR- JAK2/STAT3 could also be potential targets for the treatment of I/RI.

Reduced vagal tone in women with endometriosis and auricular vagus nerve stimulation as a potential therapeutic approach

Sensory and sympathetic nerves have been shown to promote the progression of endometriosis through the release of neuromediators and the lesional activation of respective receptors. The role of vagus nerves (VN) in lesional progression, however, is completely unclear, despite the signs suggestive of increased sympathetic tone in women with endometriosis. This study was undertaken to investigate whether VN plays any role in the progression of endometriosis. We recruited 45 patients with endometriosis and 42 healthy women, who were given electrocardiogram test and their heart rate variability was evaluated. In addition, three prospective, and randomized mouse experiments were conducted that evaluated, respectively, the effect of vagotomy, the effect of VN stimulation (VNS), and the therapeutic potential of VNS after the endometriosis was well established. All lesions were excised, weighed, and processed for immunohistochemistry and histochemistry analysis of select markers for lesional progression and fibrosis. We found that endometriosis patients exhibited reduced vagal activity as compared with controls, indicative of disrupted autonomic balance. Vagotomy increased while VNS decreased the lesion weight as compared with control mice, concomitant with more progressive and retarded lesion development and fibrogenesis, respectively. In addition, VNS demonstrated promising therapeutic effect, as evidenced by significantly reduced lesion weight, more attenuated lesional progression concomitant with improved hyperalgesia. Taken together, our data indicate that VN activity may play a dampening role in the progression of endometriosis. Consequently, boosting the VN activity may have therapeutic potentials for patients with endometriosis.

Electroacupuncture may alleviate neuropathic pain via suppressing P2X7R expression

Neuropathic pain is a severe problem that is difficult to treat clinically. Reducing abnormal remodeling of dendritic spines/synapses and increasing the anti-inflammatory effects in the spinal cord dorsal horn are potential methods to treat this disease. Previous studies have reported that electroacupuncture (EA) could increase the pain threshold after peripheral nerve injury. However, the underlying mechanism is unclear. P2X7 receptors (P2X7R) mediate the activation of microglia and participate in the occurrence and development of neuropathic pain. We hypothesized that the effects of EA on relieving pain may be related to the downregulation of the P2X7R. Spinal nerve ligation (SNL) rats were used as a model in this experiment, and 2'(3')-O-(4-benzoyl)benzoyl ATP (BzATP) was used as a P2X7R agonist. We found that EA treatment decreased dendritic spine density, inhibited synaptic reconstruction and reduced inflammatory response, which is consistent with the decrease in P2X7R expression as well as the improved neurobehavioral performance. In contrast to the beneficial effects of EA, BzATP enhanced abnormal remodeling of dendritic spines/synapses and inflammation. Furthermore, the EA-mediated positive effects were reversed by BzATP, which is consistent with the increased P2X7R expression. These findings indicated that EA improves neuropathic pain by reducing abnormal dendritic spine/synaptic reconstruction and inflammation via suppressing P2X7R expression.

Mechanism underlying treatment of ischemic stroke using acupuncture: transmission and regulation

The inflammatory response after cerebral ischemia/reperfusion is an important cause of neurological damage and repair. After cerebral ischemia/reperfusion, microglia are activated, and a large number of circulating inflammatory cells infiltrate the affected area. This leads to the secretion of inflammatory mediators and an inflammatory cascade that eventually causes secondary brain damage, including neuron necrosis, blood-brain barrier destruction, cerebral edema, and an oxidative stress response. Activation of inflammatory signaling pathways plays a key role in the pathological process of ischemic stroke. Increasing evidence suggests that acupuncture can reduce the inflammatory response after cerebral ischemia/reperfusion and promote repair of the injured nervous system. Acupuncture can not only inhibit the activation and infiltration of inflammatory cells, but can also regulate the expression of inflammation-related cytokines, balance the effects of pro-inflammatory and anti-inflammatory factors, and interfere with inflammatory signaling pathways. Therefore, it is important to study the transmission and regulatory mechanism of inflammatory signaling pathways after acupuncture treatment for cerebral ischemia/reperfusion injury to provide a theoretical basis for clinical treatment of this type of injury using acupuncture. Our review summarizes the overall conditions of inflammatory cells, mediators, and pathways after cerebral ischemia/reperfusion, and discusses the possible synergistic intervention of acupuncture in the inflammatory signaling pathway network to provide a foundation to explore the multiple molecular mechanisms by which acupuncture promotes nerve function restoration.

Peripheral Neuropathic Pain: From Experimental Models to Potential Therapeutic Targets in Dorsal Root Ganglion Neurons

Neuropathic pain exerts a global burden caused by the lesions in the somatosensory nerve system, including the central and peripheral nervous systems. The mechanisms of nerve injury-induced neuropathic pain involve multiple mechanisms, various signaling pathways, and molecules. Currently, poor efficacy is the major limitation of medications for treating neuropathic pain. Thus, understanding the detailed molecular mechanisms should shed light on the development of new therapeutic strategies for neuropathic pain. Several well-established in vivo pain models were used to investigate the detail mechanisms of peripheral neuropathic pain. Molecular mediators of pain are regulated differentially in various forms of neuropathic pain models; these regulators include purinergic receptors, transient receptor potential receptor channels, and voltage-gated sodium and calcium channels. Meanwhile, post-translational modification and transcriptional regulation are also altered in these pain models and have been reported to mediate several pain related molecules. In this review, we focus on molecular mechanisms and mediators of neuropathic pain with their corresponding transcriptional regulation and post-translational modification underlying peripheral sensitization in the dorsal root ganglia. Taken together, these molecular mediators and their modification and regulations provide excellent targets for neuropathic pain treatment.

Electroacupuncture Modulates Spinal BDNF/TrκB Signaling Pathway and Ameliorates the Sensitization of Dorsal Horn WDR Neurons in Spared Nerve Injury Rats

Neuropathic pain is more complex and severely affects the quality of patients’ life. However, the therapeutic strategy for neuropathic pain in the clinic is still limited. Previously we have reported that electroacupuncture (EA) has an attenuating effect on neuropathic pain induced by spared nerve injury (SNI), but its potential mechanisms remain to be further elucidated. In this study, we designed to determine whether BDNF/TrκB signaling cascade in the spinal cord is involved in the inhibitory effect of 2 Hz EA on neuropathic pain in SNI rats. The paw withdrawal threshold (PWT) of rats was used to detect SNI-induced mechanical hypersensitivity. The expression of BDNF/TrκB cascade in the spinal cord was evaluated by qRT-PCR and Western blot assay. The C-fiber-evoked discharges of wide dynamic range (WDR) neurons in spinal dorsal horn were applied to indicate the noxious response of WDR neurons. The results showed that 2 Hz EA significantly down-regulated the levels of BDNF and TrκB mRNA and protein expression in the spinal cord of SNI rats, along with ameliorating mechanical hypersensitivity. In addition, intrathecal injection of 100 ng BDNF, not only inhibited the analgesic effect of 2 Hz EA on pain hypersensitivity, but also reversed the decrease of BDNF and TrκB expression induced by 2 Hz EA. Moreover, 2 Hz EA obviously reduced the increase of C-fiber-evoked discharges of dorsal horn WDR neurons by SNI, but exogenous BDNF (100 ng) effectively reversed the inhibitory effect of 2 Hz EA on SNI rats, resulting in a remarkable improvement of excitability of dorsal horn WDR neurons in SNI rats. Taken together, these data suggested that 2 Hz EA alleviates mechanical hypersensitivity by blocking the spinal BDNF/TrκB signaling pathway-mediated central sensitization in SNI rats. Therefore, targeting BDNF/TrκB cascade in the spinal cord may be a potential mechanism of EA against neuropathic pain.

Electroacupuncture Alleviates Spared Nerve Injury-Induced Neuropathic Pain And Modulates HMGB1/NF-κB Signaling Pathway In The Spinal Cord

Background

Neuropathic pain with complications greatly affects patients worldwide. High mobility group box 1 (HMGB1) has been shown to contribute to the pathogenesis of neuropathic pain; thus, suppression of HMGB1 may provide a novel therapeutic option for neuropathic pain. Electroacupuncture (EA) has been indicated to be effective in attenuating neuropathic pain, but the underlying mechanism remains to be fully clarified. We aim to explore whether 2Hz EA stimulation regulates the spinal HMGB1/NF-κB signaling in neuropathic pain induced by spared nerve injury (SNI).

Materials and methods

Paw withdrawal threshold and CatWalk gait analysis were used to assess the effect of 2Hz EA on pain-related behaviors in SNI rats. Administration of 2Hz EA to SNI rats once every other day lasting for 21 days. Expression of spinal protein molecules were detected using Western blot and immunofluorescence staining.

Results

It was found that SNI significantly induced mechanical hypersensitivity and decrease of gait parameters, and subsequently increased the levels of HMGB1, TLR4, MyD88, and NF-κB p65 protein expression. 2Hz EA stimulation led to remarkable attenuation of mechanical hypersensitivity, upregulation of spinal HMGB1, TLR4, MyD88, and NF-κB p65 protein expressions induced by SNI, and significant improvement in gait parameters. Furthermore, immunofluorescence staining also confirmed that 2Hz EA obviously suppressed the co-expression of microglia activation marker CD11b and TLR4 or MyD88, as well as the activation of NF-κB p65 in SNI rats.

Conclusion

This study suggested that blockade of HMGB1/NF-κB signaling in the spinal cord may be a promising therapeutic approach for 2Hz EA management of SNI-induced neuropathic pain.