In the present study, we focused on whether the analgesic effect of Electroacupuncture (EA) is related to the regulation of oxidative stress. We established a chronic inflammatory pain model in male rats by a single injection of complete Freund's adjuvant (CFA) and then treated the animals with daily EA stimulation at the site of "zusanli". The analgesic effect of EA was evaluated by measuring the paw withdrawal threshold (PWT) when rats received mechanical and thermal pain stimulation. The levels of inflammation-related molecules and oxidative stress-related markers in the spinal cord were measured by western blotting or ELISA kits. EA stimulation and antioxidants effectively increased the PWT in CFA rats. Co-treatment of CFA rats with the ROS donor t-butyl hydroperoxide (t-BOOH) further decreased the PWT and weakened the analgesic effect of EA. EA treatment inhibited inflammation and oxidative stress, as shown by decreased levels of tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), IL-6, and MDA and increased activity of SOD and catalase. Moreover, EA reduced the expression of p-p38, p-ERK, and p-p65 and simultaneously downregulated the expression of TRPV1 and TRPV4 in CFA rats. In an in vitro study, direct stimulation with t-BOOH to the C6 cells increased the production of TNF-alpha, IL-1beta, IL-6, activated p38, ERK, and p65 and up-regulated the expression of TRPV1 and TRPV4, and these effects could be prevented by the ROS scavenger PBN. Taken together, our data indicate that the inhibition of oxidative stress and the generation of ROS contribute to the analgesic effect of EA in male CFA rats.

Department of Pain Management Anhui Medical University Hospital of Hefei Hefei People's Republic of China

See more in PubMed

Liu Y, Du J, Fang J, Xiang X, Xu Y, Wang S, Sun H, Fang J. Electroacupuncture inhibits the interaction between peripheral TRPV1 and P2X3 in rats with different pathological pain. Physiol Res. 2021;70:635–647. doi: 10.33549/physiolres.934649. PubMed DOI PMC

Descalzi G, Ikegami D, Ushijima T, Nestler EJ, Zachariou V, Narita M. Epigenetic mechanisms of chronic pain. Trends Neurosci. 2015;38:237–246. doi: 10.1016/j.tins.2015.02.001. PubMed DOI PMC

Yongjun Z, Tingjie Z, Xiaoqiu Y, Zhiying F, Feng Q, Guangke X, Jinfeng L, et al. A survey of chronic pain in China. Libyan J Med. 2020;15:1730550. doi: 10.1080/19932820.2020.1730550. PubMed DOI PMC

Pinho-Ribeiro FA, Verri WA, Jr, Chiu IM. Nociceptor Sensory Neuron-Immune Interactions in Pain and Inflammation. Trends Immunol. 2017;38:5–19. doi: 10.1016/j.it.2016.10.001. PubMed DOI PMC

Webster LR. Chronic Pain and the Opioid Conundrum. Anesthesiol Clin. 2016;34:341–355. doi: 10.1016/j.anclin.2016.01.002. PubMed DOI

Zhao X, Liu L, Wang Y, Wang G, Zhao Y, Zhang Y. Electroacupuncture enhances antioxidative signal pathway and attenuates neuropathic pain induced by chemotherapeutic paclitaxel. Physiol Res. 2019;68:501–510. doi: 10.33549/physiolres.934084. PubMed DOI

Lv ZT, Shen LL, Zhu B, Zhang ZQ, Ma CY, Huang GF, Yin J, et al. Effects of intensity of electroacupuncture on chronic pain in patients with knee osteoarthritis: a randomized controlled trial. Arthritis Res Ther. 2019;21:120. doi: 10.1186/s13075-019-1899-6. PubMed DOI PMC

Shakouri SK, Dolatkhah N, Omidbakhsh S, Pishgahi A, Hashemian M. Serum inflammatory and oxidative stress biomarkers levels are associated with pain intensity, pressure pain threshold and quality of life in myofascial pain syndrome. BMC Res Notes. 2020;13:510. doi: 10.1186/s13104-020-05352-3. PubMed DOI PMC

Xue Y, Dai S, Liang J, Ji W. Effect of reactive oxygen species of the psoas major muscle in complete Freund’s adjuvant-induced inflammatory pain in rats. Mol Pain. 202;16:1744806920929246. doi: 10.1177/1744806920929246. PubMed DOI PMC

Liu PR, Cao F, Zhang Y, Peng S. Electroacupuncture reduces astrocyte number and oxidative stress in aged rats with surgery-induced cognitive dysfunction. J Int Med Res. 2019;47:3860–3873. doi: 10.1177/0300060519860026. PubMed DOI PMC

Liang R, Tang Q, Song W, Zhang M, Teng L, Kang Y, Zhu L. Electroacupuncture Preconditioning Reduces Oxidative Stress in the Acute Phase of Cerebral Ischemia-Reperfusion in Rats by Regulating Iron Metabolism Pathways. Evid Based Complement Alternat Med. 2021;2021:3056963. doi: 10.1155/2021/3056963. PubMed DOI PMC

Chen G, Zhang YQ, Qadri YJ, Serhan CN, Ji RR. Microglia in Pain: Detrimental and Protective Roles in Pathogenesis and Resolution of Pain. Neuron. 2018;100:1292–1311. doi: 10.1016/j.neuron.2018.11.009. PubMed DOI PMC

Sorge RE, Totsch SK. Sex Differences in Pain. J Neurosci Res. 2017;95:1271–1281. doi: 10.1002/jnr.23841. PubMed DOI

Zhang RY, Zhu BF, Wang LK, Song Y, Zhao JG, Guo Y, Zhao L, Chen S. Electroacupuncture alleviates inflammatory pain via adenosine suppression and its mediated substance P expression. Arq Neuropsiquiatr. 2020;78:617–623. doi: 10.1590/0004-282x20200078. PubMed DOI

Ebert TJ. Cardiovascular and autonomic effects of sevoflurane. Acta Anaesthesiol Belg. 1996;47:15–21. PubMed

Hanamoto H, Boku A, Morimoto Y, Sugimura M, Kudo C, Niwa H. Appropriate sevoflurane concentration to stabilize autonomic activity during intubation with rocuronium in infants: a randomized controlled trial. BMC Anesthesiol. 2015;15:64. doi: 10.1186/s12871-015-0047-3. PubMed DOI PMC

Ratliff BB, Abdulmahdi W, Pawar R, Wolin MS. Oxidant mechanisms in renal injury and disease. Antioxid Redox Signal. 2016;25:119–146. doi: 10.1089/ars.2016.6665. PubMed DOI PMC

Ma F, Zhang L, Westlund KN. Reactive oxygen species mediate TNFR1 increase after TRPV1 activation in mouse DRG neurons. Mol Pain. 2009;5:31. doi: 10.1186/1744-8069-5-31. PubMed DOI PMC

Kozai D, Ogawa N, Mori Y. Redox regulation of transient receptor potential channels. Antioxid Redox Signal. 2014;21:971–986. doi: 10.1089/ars.2013.5616. PubMed DOI

Gao F, Xiang HC, Li HP, Jia M, Pan XL, Pan HL, Li M. Electroacupuncture inhibits NLRP3 inflammasome activation through CB2 receptors in inflammatory pain. Brain Behav Immun. 2018;67:91–100. doi: 10.1016/j.bbi.2017.08.004. PubMed DOI

Xiang X, Wang S, Shao F, Fang J, Xu Y, Wang W, Sun H, Liu X, Du J, Fang J. Electroacupuncture stimulation alleviates CFA-induced inflammatory pain via suppressing P2X3 expression. Int J Mol Sci. 2019;20:3248. doi: 10.3390/ijms20133248. PubMed DOI PMC

Kim HY, Lee I, Chun SW, Kim HK. Reactive Oxygen Species Donors Increase the Responsiveness of Dorsal Horn Neurons and Induce Mechanical Hyperalgesia in Rats. Neural Plast. 2015;2015:293423. doi: 10.1155/2015/293423. PubMed DOI PMC

Kim HK, Park SK, Zhou JL, Taglialatela G, Chung K, Coggeshall RE, Chung JM. Reactive oxygen species (ROS) play an important role in a rat model of neuropathic pain. Pain. 2004;111:116–124. doi: 10.1016/j.pain.2004.06.008. PubMed DOI

Hassler SN, Johnson KM, Hulsebosch CE. Reactive oxygen species and lipid peroxidation inhibitors reduce mechanical sensitivity in a chronic neuropathic pain model of spinal cord injury in rats. J Neurochem. 2014;131:413–417. doi: 10.1111/jnc.12830. PubMed DOI PMC

Schäfers M, Sorkin LS, Sommer C. Intramuscular injection of tumor necrosis factor-alpha induces muscle hyperalgesia in rats. Pain. 2003;104:579–588. doi: 10.1016/S0304-3959(03)00115-5. PubMed DOI

Sommer C, Petrausch S, Lindenlaub T, Toyka KV. Neutralizing antibodies to interleukin 1-receptor reduce pain associated behavior in mice with experimental neuropathy. Neurosci Lett. 1999;270:25–28. doi: 10.1016/S0304-3940(99)00450-4. PubMed DOI

Fan J, Ren D, Wang J, Liu X, Zhang H, Wu M, Yang G. Bruceine D induces lung cancer cell apoptosis and autophagy via the ROS/MAPK signaling pathway in vitro and in vivo. Cell Death Dis. 2020;11:126. doi: 10.1038/s41419-020-2317-3. PubMed DOI PMC

Lu QB, Wan MY, Wang PY, Zhang CX, Xu DY, Liao X, Sun HJ. Chicoric acid prevents PDGF-BB-induced VSMC dedifferentiation, proliferation and migration by suppressing ROS/NFκB/mTOR/P70S6K signaling cascade. Redox Biol. 2018;14:656–668. doi: 10.1016/j.redox.2017.11.012. PubMed DOI PMC

Lin X, Wang M, Zhang J, Xu R. p38 MAPK: a potential target of chronic pain. Curr Med Chem. 2014;21:4405–4418. doi: 10.2174/0929867321666140915143040. PubMed DOI

Sekiguchi M, Sekiguchi Y, Konno S, Kobayashi H, Homma Y, Kikuchi S. Comparison of neuropathic pain and neuronal apoptosis following nerve root or spinal nerve compression. Eur Spine J. 2009;18:1978–1985. doi: 10.1007/s00586-009-1064-z. PubMed DOI PMC

Hudmon A, Choi JS, Tyrrell L, Black JA, Rush AM, Waxman SG, Dib-Hajj SD. Phosphorylation of sodium channel Na(v)1.8 by p38 mitogen-activated protein kinase increases current density in dorsal root ganglion neurons. J Neurosci. 2008;28:3190–3201. doi: 10.1523/JNEUROSCI.4403-07.2008. PubMed DOI PMC

Maruta T, Nemoto T, Hidaka K, Koshida T, Shirasaka T, Yanagita T, Takeya R, Tsuneyoshi I. Upregulation of ERK phosphorylation in rat dorsal root ganglion neurons contributes to oxaliplatin-induced chronic neuropathic pain. PLoS One. 2019;14:e0225586. doi: 10.1371/journal.pone.0225586. PubMed DOI PMC

Lawrence T. The nuclear factor NF-kappaB pathway in inflammation. Cold Spring Harb Perspect Biol. 2009;1:a001651. doi: 10.1101/cshperspect.a001651. PubMed DOI PMC

Abbas MA. Modulation of TRPV1 channel function by natural products in the treatment of pain. Chem Biol Interact. 2020;330:109178. doi: 10.1016/j.cbi.2020.109178. PubMed DOI

Uta D, Yoshimura M, Koga K. Chronic pain models amplify transient receptor potential vanilloid 1 (TRPV1) receptor responses in adult rat spinal dorsal horn. Neuropharmacology. 2019;160:107753. doi: 10.1016/j.neuropharm.2019.107753. PubMed DOI

Moran MM, Szallasi A. Targeting nociceptive transient receptor potential channels to treat chronic pain: current state of the field. Br J Pharmacol. 2018;175:2185–2203. doi: 10.1111/bph.14044. PubMed DOI PMC

Oda M, Fujiwara Y, Ishizaki Y, Shibasaki K. Oxidation sensitizes TRPV2 to chemical and heat stimuli, but not mechanical stimulation. Biochem Biophys Rep. 2021;28:101173. doi: 10.1016/j.bbrep.2021.101173. PubMed DOI PMC

Li Y, Yin C, Li X, Liu B, Wang J, Zheng X, Shao X, Liang Y, Du J, Fang J, Liu B. Electroacupuncture alleviates paclitaxel-induced peripheral neuropathic pain in rats via suppressing TLR4 signaling and TRPV1 upregulation in sensory neurons. Int J Mol Sci. 2019;20:5917. doi: 10.3390/ijms20235917. PubMed DOI PMC