title: Curcumin exerts antinociceptive effects by inhibiting the activation of astrocytes in spinal dorsal horn and the intracellular extracellular signal-regulated kinase signaling pathway in rat model of chronic constriction injury.
abstract: BACKGROUND
  Activation of glial cells and the extracellular signal-regulated kinase (ERK) signaling pathway play an important role in the development and maintenance of neuropathic pain. Curcumin can alleviate the symptom of inflammatory pain by inhibiting the production and release of interleukin and tumor necrosis factor. However, whether curcumin affects neuropathic pain induced by nerve injury and the possible mechanism involved are still unknown. This study investigated the effects of tolerable doses of curcumin on the activation of astrocytes and ERK signaling in the spinal dorsal horn in rat model of neuropathic pain.
  
  
  METHODS
  Adult male Sprague-Dawley rats were randomly divided into three groups: a control (sham operated) group, and chronic constriction injury groups (to induce neuropathic pain) that were either untreated or treated with curcumin. Thermal and mechanical hyperalgesia thresholds were measured. The distribution and morphological changes of astrocytes were observed by immunofluorescence. Western blotting was used to detect changes in the expression of glial fibrillary acid protein (GFAP) and phosphorylated ERK.
  
  
  RESULTS
  Injured rats showed obvious mechanical allodynia and thermal hyperalgesia. The number of GFAP-positive astrocytes, and the fluorescence intensity of GFAP were significantly increased in the spinal dorsal horn of injured compared with control rats. The soma of astrocytes also appeared hypertrophied in injured animals. Expression of GFAP and phosphorylated ERK was also significantly increased in the spinal dorsal horn of injured compared with control rats. Curcumin reduced the injury-induced thermal and mechanical hyperalgesia, the increase in the fluorescence intensity of GFAP and the hypertrophy of astrocytic soma, activation of GFAP and phosphorylation of ERK in the spinal dorsal horn.
  
  
  CONCLUSIONS
  Curcumin can markedly alleviate nerve injury-induced neuropathic pain in rats. The analgesic effect of curcumin may be attributed to its inhibition of astrocyte hypertrophy in the spinal dorsal horn and phosphorylation of the ERK signaling pathway.
authors.affiliation: Department of Anatomy and Neurobiology, Zhongshan Medical School of Sun Yat-sen University, Guangzhou, Guangdong 510120, China.
authors.forename: Feng-Tao
authors.initials: FT
authors.lastname: Ji
authors.forename: Jiang-Jun
authors.initials: JJ
authors.lastname: Liang
authors.forename: Ling
authors.initials: L
authors.lastname: Liu
authors.forename: Ming-Hui
authors.initials: MH
authors.lastname: Cao
authors.forename: Feng
authors.initials: F
authors.lastname: Li
mesh_terms: D000700:Analgesics / Q000627:therapeutic use*; D000818:Animals; D001253:Astrocytes / Q000187:drug effects*; D015153:Blotting, Western; D003251:Constriction, Pathologic / Q000378:metabolism*; D003474:Curcumin / Q000627:therapeutic use*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D006930:Hyperalgesia / Q000378:metabolism; D008297:Male; D009437:Neuralgia / Q000188:drug therapy*; D010766:Phosphorylation / Q000187:drug effects; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D000700:Analgesics; D005904:Glial Fibrillary Acidic Protein; D048049:Extracellular Signal-Regulated MAP Kinases; D003474:Curcumin