Effects of low- and high-frequency electroacupuncture on protein expression and distribution of TRPV1 and P2X3 in rats with peripheral nerve injury

Background: Whether electroacupuncture (EA) stimulation at different frequencies has a similar effect on spared nerve injury (SNI) as other neuropathic pain models, and how EA at different frequencies causes distinct analgesic effects on neuropathic pain is still not clear. Methods: Adult male Sprague-Dawley rats were randomly divided into sham SNI, SNI, 2 Hz, 100 Hz and sham EA groups. Paw withdrawal threshold (PWT) and paw withdrawal latency (PWL) were measured. EA was performed once a day on days 1 to 14 after SNI. The expressions of transient receptor potential cation subfamily V member 1 (TRPV1) and peripheral purinergic P2X receptor 3 (P2X3) were determined by western blotting and immunofluorescence. TRPV1 siRNA and P2X3 siRNA were administered by intrathecal injection. TRPV1 or P2X3 agonists were combined with EA. Results: There were significant decreases in PWT, but no changes in PWL in the 14 days after SNI. EA using 2- or 100-Hz stimulation similarly increased PWT at every time point. The cytosol protein expression of P2X3 in the L4–L6 dorsal root ganglia (DRG) increased, but the expression of TRPV1 decreased in the SNI model. Both these effects were ameliorated by EA, with 2-Hz stimulation having a stronger effect than 100-Hz stimulation. Blocking either TRPV1 or P2X3 specific siRNAs attenuated the decreased PWT induced by SNI. Administration of either a TRPV1 or P2X3 agonist inhibited EA analgesia. Conclusion: 2- and 100-Hz EA similarly induced analgesic effects in SNI. This effect was related to up-regulation and down-regulation, respectively, of cytosol protein expression of P2X3 and TRPV1 in L4–L6 DRG, with 2 Hz having a better effect than 100 Hz

Role of GABAAR in the Transition From Acute to Chronic Pain and the Analgesic Effect of Electroacupuncture on Hyperalgesic Priming Model Rats

Chronic pain is a costly health problem that impairs health-related quality of life when not effectively treated. Regulating the transition from acute to chronic pain is a new therapeutic strategy for chronic pain that presents a major clinical challenge. The underlying mechanisms of pain transition are not entirely understood, and strategies for preventing this transition are lacking. Here, a hyperalgesic priming model was used to study the potential mechanism by which γ-aminobutyric acid receptor type A (GABAAR) in the dorsal root ganglion (DRG) contributes to pain transition. Furthermore, electroacupuncture (EA), a modern method of acupuncture, was administered to regulate pain transition, and the mechanism underlying EA's regulatory effect was investigated. Hyperalgesic priming was induced by intraplanar injection of carrageenan (Car)/prostaglandin E2 (PGE2). The decrease in mechanical withdrawal threshold (MWT) induced by PGE2 returned to baseline 4 h after injection in NS + PGE2 group, and still persisted 24 h after injection in Car + PGE2 group. Lower expression of GABAAR in the lumbar DRG was observed in the model rats. Furthermore, activating or blocking GABAAR could reversed the long-lasting hyperalgesia induced by Car/PGE2 injection or produced a persistent hyperalgesia. In addition, GABAAR may be involved in Protein Kinase C epsilon (PKCε) activation in the DRG, a mark molecular of pain transition. EA considerably increased the mechanical pain thresholds of hyperalgesic priming model mammals in both the acute and chronic phases. Furthermore, EA upregulated the expression of GABAAR and inhibited the activation of PKCε in the DRG. In addition, peripheral administration of picrotoxin blocked the analgesic effect of EA on the model rats and abolished the regulatory effect of EA on PKCε activation. These findings suggested that GABAAR plays a key role in both the transition from acute to chronic pain and the analgesic effect of EA on hyperalgesic priming

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

Specificity for the correlation between the body surface and viscera in the pathological state of COPD: A prospective, controlled, and assessor-blinded trial

Background: The association between the body surface and viscera remains obscure, but a better understanding of the body surface-viscera correlation will maximize its diagnostic and therapeutic values in clinical practice. Therefore, this study aimed to investigate the specificity of body surface-viscera correlation in the pathological state.Methods: The study subjects included 40 participants with chronic obstructive pulmonary disease (COPD) in the COPD group and 40 age-matched healthy participants in the healthy control group. Laser Doppler flowmetry, infrared thermography, and functional near-infrared spectroscopy were respectively adopted to measure 1) the perfusion unit (PU), 2) temperature, and 3) regional oxygen saturation (rSO2) of four specific sites distributed in the heart and lung meridians. These three outcome measures reflected the microcirculatory, thermal, and metabolic characteristics, respectively.Results: Regarding the microcirculatory and thermal characteristics of the body surface, the PU and temperature of specific sites on the body surface [i.e., Taiyuan (LU9) and Chize (LU5) in the lung meridian] in the COPD group were significantly increased compared with healthy controls (p < 0.05), whereas PU and temperature of other sites in the heart meridian [i.e., Shenmen (HT7) and Shaohai (HT3)] did not change significantly (p > 0.05). Regarding the metabolic characteristics, rSO2 of specific sites in the lung meridian [i.e., Taiyuan (LU9) and Chize (LU5)] and Shaohai (HT3) of the heart meridian in the COPD group was significantly decreased compared with healthy controls (p < 0.01), whereas rSO2 of Shenmen (HT7) in the heart meridian did not change significantly (p > 0.05).Conclusion: In the disease state of COPD, the microcirculatory, thermal, and metabolic characteristics of specific sites on the body surface in the lung meridian generally manifest more significant changes than those in the heart meridian, thereby supporting relative specificity for the body surface-viscera correlation in the pathological state

Spreading solutions for a reaction diffusion equation with free boundaries in time-periodic environmen

In this article, we consider a reaction diffusion equation with free boundaries in a time-periodic environment. Such models can be used to describe the spreading of a new or invasive species over a one-dimensional habitat, with the free boundaries representing the expanding fronts. We study an equation with a general time-periodic nonlinearity, and present some sufficient conditions for spreading phenomena. We also use time-periodic semi-waves to characterize the spreading solutions

Electroacupuncture Alleviates Pain-Related Emotion by Upregulating the Expression of NPS and Its Receptor NPSR in the Anterior Cingulate Cortex and Hypothalamus

Objective. Electroacupuncture (EA) is reported effective in alleviating pain-related emotion; however, the underlying mechanism of its effects still needs to be elucidated. The NPS-NPSR system has been validated for the involvement in the modulation of analgesia and emotional behavior. Here, we aimed to investigate the role of the NPS-NPSR system in the anterior cingulate cortex (ACC), hypothalamus, and central amygdala (CeA) in the use of EA to relieve affective pain modeled by complete Freund’s adjuvant- (CFA-) evoked conditioned place aversion (C-CPA). Materials and Methods. CFA injection combined with a CPA paradigm was introduced to establish the C-CPA model, and the elevated O-maze (EOM) was used to test the behavioral changes after model establishment. We further explored the expression of NPS and NPSR at the protein and gene levels in the brain regions of interest by immunofluorescence staining and quantitative real-time PCR. Results. We observed that EA stimulation delivered to the bilateral Zusanli (ST36) and Kunlun (BL60) acupoints remarkably inhibited sensory pain, pain-evoked place aversion, and anxiety-like behavior. The current study showed that EA significantly enhanced the protein expression of this peptide system in the ACC and hypothalamus, while the elevated expression of NPSR protein alone was just confined to the affected side in the CeA. Moreover, EA remarkably upregulated the mRNA expression of NPS in CeA, ACC, and hypothalamus and NPSR mRNA in the hypothalamus and CeA. Conclusions. These data suggest the effectiveness of EA in alleviating affective pain, and these benefits may at least partially be attributable to the upregulation of the NPS-NPSR system in the ACC and hypothalamus

Oxidized Phospholipid OxPAPC Activates TRPA1 and Contributes to Chronic Inflammatory Pain in Mice.

Oxidation products of the naturally occurring phospholipid 1-palmitoyl-2-arachidonoyl-sn-glycerol-3-phosphatidylcholine (PAPC), which are known as OxPAPC, accumulate in atherosclerotic lesions and at other sites of inflammation in conditions such as septic inflammation and acute lung injury to exert pro- or anti-inflammatory effects. It is currently unknown whether OxPAPC also contributes to inflammatory pain and peripheral neuronal excitability in these conditions. Here, we observed that OxPAPC dose-dependently and selectively activated human TRPA1 nociceptive ion channels expressed in HEK293 cells in vitro, without any effect on other TRP channels, including TRPV1, TRPV4 and TRPM8. OxPAPC agonist activity was dependent on essential cysteine and lysine residues within the N-terminus of the TRPA1 channel protein. OxPAPC activated calcium influx into a subset of mouse sensory neurons which were also sensitive to the TRPA1 agonist mustard oil. Neuronal OxPAPC responses were largely abolished in neurons isolated from TRPA1-deficient mice. Intraplantar injection of OxPAPC into the mouse hind paw induced acute pain and persistent mechanical hyperalgesia and this effect was attenuated by the TRPA1 inhibitor, HC-030031. More importantly, we found levels of OxPAPC to be significantly increased in inflamed tissue in a mouse model of chronic inflammatory pain, identified by the binding of an OxPAPC-specific antibody. These findings suggest that TRPA1 is a molecular target for OxPAPC and OxPAPC may contribute to chronic inflammatory pain through TRPA1 activation. Targeting against OxPAPC and TRPA1 signaling pathway may be promising in inflammatory pain treatment

Evaluating the analgesic effect and advantage of transcutaneous electrical acupoint stimulation combined with opioid drugs for moderate to severe cancer-related pain: a study protocol for a randomized controlled trial

Abstract Background Transcutaneous electrical acupoint stimulation (TEAS), which is also known as acupuncture-like transcutaneous electrical nerve stimulation (TENS), has been widely used in acute or chronic pain. However, previous research has not demonstrated that TEAS is effective for cancer-related pain. Opioid drugs are strongly recommended for treating cancer-related pain, but opioid-induced immunosuppression is still the most intractable drug-induced medical problem. Evaluating the efficacy and potential advantage of TEAS combined with opioid drugs in moderate and severe cancer-related pain in China is important because such studies are lacking. Methods/Design This trial is a multicenter, prospective randomized controlled clinical trial. In total, 160 patients who were enrolled from two hospitals in the Zhejiang Province (China) will be randomly allocated into two groups: a TEAS group and sham TEAS group without acupoint electrical stimulation. Both groups will receive a 21-day interval of chemotherapy and conventional cancer pain therapy. Fifteen treatment sessions will be performed over a three-week period. The primary outcomes will be measured by changes in the Numerical Rating Scale (NRS) scores and equivalent dosage of morphine at baseline, three weeks of treatment and one two-week follow-up. The secondary outcome measures include cellular immunity function, life quality assessment, opioids side effects assessment, and safety and compliance evaluation. Discussion This trial is expected to clarify whether TEAS is effective for cancer-related pain. These results demonstrate the advantage of TEAS combined with opioid drugs on improving immune function and decreasing opioid induced side effects. Trial registration Chinese Clinical Trial Registry, ChiCTR-13003803. Registered on 27 August 2013

TRPA1-dependent induction of acute pain behavior and mechanical hyperalgesia by OxPAPC in mice.

<p>(A) The acute nocifensive behavior of mice quantified within the first 5 min following injection of vehicle (Veh), OxPAPC or OxPAPC+HC-030031 injection into the hind paw, plotted in 1 min intervals. (B) Cumulated nocifensive behavior response time within the total 5 min recording period of animals in experiment Fig 5 (A). (C) Paw withdraw threshold (PWT) of mice measured by von Frey hair analysis. Tests were performed 1 hour after vehicle, OxPAPC or OxPAPC+HC-030031 injection into the hind paw. n = 7–8 mice/group, **p < 0.01 <i>vs</i>. Veh, ^##p < 0.01 <i>vs</i>. OxPAPC group.</p