Electroacupuncture Attenuates Induction of Inflammatory Pain by Regulating Opioid and Adenosine Pathways in Mice

Sci Rep. 2017 Nov 15;7(1):15679. doi: 10.1038/s41598-017-16031-y.

Abstract

Although inflammatory pain is a common clinical condition, its mechanisms are still unclear. Electroacupuncture (EA), a well-known method of pain management, may reduce inflammatory pain by regulating neurons, astrocytes, and inflammatory signaling pathways. Injections of complete Freund's adjuvant (CFA), which can initiate cell-mediated inflammatory pain, resulted in significant hyperalgesia, which was subsequently prevented by EA. In CFA-injected mice, a dramatic increase was observed in the expression of the following proteins in the dorsal root ganglion and spinal cord dorsal horn: the astrocytic marker GFAP, S100B, RAGE, pPKCε, COX-2, pERK, and pNFκB. These effects were reversed by EA. In addition, mechanical hyperalgesia was significantly reduced in the N6-cyclopentyladenosine (CPA) i.p. or i.m. and endomorphin (EM) i.p. groups. Neither EM i.m. nor EM i.p. exhibited any analgesic effect on thermal hyperalgesia. However, both CPA i.m. and CPA i.p. attenuated thermal hyperalgesia in the mouse inflammatory pain model. We showed that CPA reduced COX-2 and pPKCε expression. However, EM administration did not reduce COX-2 levels. Combined administration of naloxone and rolofylline increased pPKCε and COX-2 pathways. Taken together, our study results revealed a novel and detailed mechanism of EA-induced analgesia that involves the regulation of the opioid and adenosine pathways.

MeSH terms

  • Adenosine / genetics
  • Analgesics, Opioid / metabolism*
  • Animals
  • Astrocytes / metabolism
  • Cyclooxygenase 2 / genetics
  • Disease Models, Animal
  • Electroacupuncture
  • Ganglia, Spinal / physiopathology
  • Gene Expression Regulation / genetics
  • Glial Fibrillary Acidic Protein / genetics
  • Hyperalgesia / genetics
  • Hyperalgesia / pathology
  • Hyperalgesia / therapy*
  • Inflammation / genetics
  • Inflammation / pathology
  • Inflammation / therapy*
  • Mice
  • NF-kappa B / genetics
  • Pain / genetics*
  • Pain / physiopathology
  • Pain Management*
  • Protein Kinase C-epsilon / genetics
  • Rats
  • Receptor for Advanced Glycation End Products / genetics
  • S100 Calcium Binding Protein beta Subunit / genetics
  • Signal Transduction / genetics
  • Spinal Cord Dorsal Horn / physiopathology

Substances

  • Ager protein, mouse
  • Analgesics, Opioid
  • Glial Fibrillary Acidic Protein
  • NF-kappa B
  • Receptor for Advanced Glycation End Products
  • S100 Calcium Binding Protein beta Subunit
  • S100b protein, mouse
  • Ptgs2 protein, mouse
  • Cyclooxygenase 2
  • Prkce protein, mouse
  • Protein Kinase C-epsilon
  • Adenosine