title: Effect of an Acid-sensing Ion Channels Inhibitor on Pain-related Behavior by Nucleus Pulposus Applied on the Nerve Root in Rats.
abstract: METHODS
  Controlled, interventional animal study.
  
  
  OBJECTIVE
  To examine the effect of an inhibitor of acid-sensing ion channel 3 (ASIC3) on pain-related behavior induced by application of the nucleus pulposus (NP) onto the dorsal root ganglion (DRG) in rats.
  
  
  BACKGROUND
  ASIC3 is associated with acidosis pain in inflamed or ischemic tissues and is expressed in sensory neurons and NP cells. The ASIC3 inhibitor, APETx2, increases the mechanical threshold of pain in models of knee osteoarthritis or postoperative pain. However, the efficacy of APETx2 for pain relief in the NP application model remains unknown.
  
  
  METHODS
  Autologous NP was applied to the left L5 nerve root of 183 adult female Sprague-Dawley rats. The DRGs were treated with NP plus one of the following four treatments: saline solution (SM), low (0.01 μg: LD), medium (0.1 μg: MD), or high dose (1.0 μg: HD) of APETx2. Behavioral testing was performed to investigate the mechanical withdrawal threshold using von Frey hairs. Expression of nerve growth factor, hypoxia-inducible factor-1α (HIF1α), activating transcription factor-3, and ionized calcium-binding adaptor molecule-1 was evaluated using immunohistochemistry. Statistical differences among multiple groups were assessed using the Steel test, the Tukey-Kramer test, and the Dunnett test. P < 0.05 were considered significant.
  
  
  RESULTS
  The thresholds in the HD group were higher than those in the SM group at Days 14 and 21 (P < 0.05). In the MD group, the threshold was higher than in the SM group at Day 14 (P < 0.05). High doses of APETx2 reduced the expression of HIF1α after Day 14 compared with the SM group (P < 0.05).
  
  
  CONCLUSIONS
  APETx2 significantly improved pain-related behavior in a dose-dependent manner. APETx2 may inhibit ASIC3 and partly inhibit Nav1.8 channels. This ASIC3 channel inhibitor may be a potential therapeutic agent in early-stage lumbar disc herniation.
  
  
  METHODS
  N/A.
authors.affiliation: Department of Orthopedic Surgery, Fukushima Medical University School of Medicine, Fukushima, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: Miho
authors.initials: M
authors.lastname: Sekiguchi
authors.forename: Shin-Ichi
authors.initials: SI
authors.lastname: Konno
mesh_terms: D062646:Acid Sensing Ion Channel Blockers / Q000494:pharmacology / Q000627:therapeutic use*; D062565:Acid Sensing Ion Channels / Q000378:metabolism*; D051700:Activating Transcription Factor 3 / Q000378:metabolism; D000818:Animals; D002135:Calcium-Binding Proteins / Q000378:metabolism; D003064:Cnidarian Venoms / Q000494:pharmacology / Q000627:therapeutic use*; D004195:Disease Models, Animal; D005260:Female; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D008840:Microfilament Proteins / Q000378:metabolism; D020932:Nerve Growth Factor / Q000378:metabolism; D000070614:Nucleus Pulposus / Q000378:metabolism*; D010146:Pain / Q000188:drug therapy*; D017288:Pain Threshold / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013126:Spinal Nerve Roots / Q000187:drug effects*
chemical_list: C501880:APETx2 protein, Anthopleura elegantissima; C568269:ASIC3 protein, rat; D062646:Acid Sensing Ion Channel Blockers; D062565:Acid Sensing Ion Channels; D051700:Activating Transcription Factor 3; C100745:Aif1 protein, rat; C497108:Atf3 protein, rat; D002135:Calcium-Binding Proteins; D003064:Cnidarian Venoms; C497444:Hif1a protein, rat; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008840:Microfilament Proteins; D020932:Nerve Growth Factor