title: Hyaluronic acid induces activation of the κ-opioid receptor.
abstract: BACKGROUND
  Nociceptive pain is one of the most common types of pain that originates from an injury involving nociceptors. Approximately 60% of the knee joint innervations are classified as nociceptive. The specific biological mechanism underlying the regulation of nociceptors is relevant for the treatment of symptoms affecting the knee joint. Intra-articular administration of exogenous hyaluronic acid (HA) in patients with osteoarthritis (OA) appears to be particularly effective in reducing pain and improving patient function.
  
  
  METHODS
  We performed an in vitro study conducted in CHO cells that expressed a panel of opioid receptors and in primary rat dorsal root ganglion (DRG) neurons to determine if HA induces the activation of opioid peptide receptors (OPr) using both aequorin and the fluorescent dye Fura-2/AM.
  
  
  RESULTS
  Selective agonists and antagonists for each OPr expressed on CHO cells were used to test the efficacy of our in vitro model followed by stimulation with HA. The results showed that HA induces stimulatory effects on the κ receptor (KOP). These effects of HA were also confirmed in rat DRG neurons, which express endogenously the OPr.
  
  
  CONCLUSIONS
  HA activates the KOP receptor in a concentration dependent manner, with a pEC(50) value of 7.57.
authors: Department of Biomedical Sciences, University of Padova, Padova, Italy. barbara.zavan@unipd.it
authors: Barbara
authors: B
authors: Zavan
authors: Letizia
authors: L
authors: Ferroni
authors: Carlotta
authors: C
authors: Giorgi
authors: Girolamo
authors: G
authors: Calò
authors: Paola
authors: P
authors: Brun
authors: Roberta
authors: R
authors: Cortivo
authors: Giovanni
authors: G
authors: Abatangelo
authors: Paolo
authors: P
authors: Pinton
mesh_terms: D000818:Animals; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism; D006224:Cricetinae; D003600:Cytosol / Q000378:metabolism; D005727:Ganglia, Spinal / Q000378:metabolism; D006801:Humans; D006820:Hyaluronic Acid / Q000494:pharmacology*; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D020671:Posterior Horn Cells / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D011957:Receptors, Opioid / Q000819:agonists / Q000378:metabolism; D017473:Receptors, Opioid, kappa / Q000819:agonists* / Q000378:metabolism
chemical_list: D011957:Receptors, Opioid; D017473:Receptors, Opioid, kappa; D006820:Hyaluronic Acid; D002118:Calcium
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