title: Naloxone inhibition of lipopolysaccharide-induced activation of retinal microglia is partly mediated via the p38 mitogen activated protein kinase signalling pathway.
abstract: OBJECTIVE
  To investigate the effects and underlying mechanism of action of naloxone on lipopolysaccharide (LPS)-induced activation of retinal microglia in vitro.
  
  
  METHODS
  Rat retinal microglia primary cultures were divided into four treatment groups: untreated; 1 μg/ml LPS  for 12 h; 0.5, 1.0 or 2.0 μM naloxone for 30 min before LPS; 2.5 or 5.0 μM SB203580 for 12 h before LPS and naloxone. Levels of tumour necrosis factor (TNF)-α and interleukin (IL)-1β were determined by enzyme-linked immuno sorbent assay. Western blot analysis and double immunofluorescence  were used to examine activation of the mitogen activated protein kinase (MAPK) signalling pathway.
  
  
  RESULTS
  LPS induced an increase in TNF-α and IL-1β in culture supernatants, which was dose-dependently inhibited by naloxone. Naloxone also dose-dependently inhibited LPS-induced  increases in phosphorylated p38 MAPK. Pretreatment of cells with SB203580 attenuated the inhibitory effect of naloxone on TNF-α and IL-1β production.
  
  
  CONCLUSIONS
  Naloxone suppressed LPS-induced activation of cultured retinal microglia and this suppression appeared to occur partly  through the p38 MAPK signalling pathway. Naloxone may have therapeutic potential in neuro degenerative diseases characterized by the activation of microglia.
authors.affiliation: Department of Ophthalmology, Eye, Ear, Nose and Throat Hospital, Fudan University School of Medicine, Shanghai, China.
authors.forename: Y F
authors.initials: YF
authors.lastname: Xu
authors.forename: L L
authors.initials: LL
authors.lastname: Fu
authors.forename: C H
authors.initials: CH
authors.lastname: Jiang
authors.forename: Y W
authors.initials: YW
authors.lastname: Qin
authors.forename: Y Q
authors.initials: YQ
authors.lastname: Ni
authors.forename: J W
authors.initials: JW
authors.lastname: Fan
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D053583:Interleukin-1beta / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D008297:Male; D017628:Microglia / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D009270:Naloxone / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000494:pharmacology*; D019636:Neurodegenerative Diseases / Q000378:metabolism / Q000473:pathology; D010766:Phosphorylation; D061251:Primary Cell Culture; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000473:pathology*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D007093:Imidazoles; D053583:Interleukin-1beta; D008070:Lipopolysaccharides; D009292:Narcotic Antagonists; D011725:Pyridines; D014409:Tumor Necrosis Factor-alpha; D009270:Naloxone; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580