title: Morphine Preconditioning Downregulates MicroRNA-134 Expression Against Oxygen-Glucose Deprivation Injuries in Cultured Neurons of Mice.
abstract: BACKGROUND
  Brain protection by narcotics such as morphine is clinically relevant due to the extensive use of narcotics in the perioperative period. Morphine preconditioning induces neuroprotection in neurons, but it remains uncertain whether microRNA-134 (miR-134) is involved in morphine preconditioning against oxygen-glucose deprivation-induced injuries in primary cortical neurons of mice. The present study examined this issue.
  
  
  METHODS
  After cortical neurons of mice were cultured in vitro for 6 days, the neurons were transfected by respective virus vector, such as lentiviral vector (LV)-miR-control-GFP, LV-pre-miR-134-GFP, LV-pre-miR-134-inhibitor-GFP for 24 hours; after being normally cultured for 3 days again, morphine preconditioning was performed by incubating the transfected primary neurons with morphine (3 μM) for 1 hour, and then neuronal cells were exposed to oxygen-glucose deprivation (OGD) for 1 hour and oxygen-glucose recovery for 12 hours. The neuronal cells survival rate and the amount of apoptotic neurons were determined by MTT assay or TUNEL staining at designated time; and the expression levels of miR-134 were detected using real-time reverse transcription polymerase chain reaction at the same time.
  
  
  RESULTS
  The neuronal cell survival rate was significantly higher, and the amount of apoptotic neurons was significantly decreased in neurons preconditioned with morphine before OGD than that of OGD alone. The neuroprotection induced by morphine preconditioning was partially blocked by upregulating miR-134 expression, and was enhanced by downregulating miR-134 expression. The expression of miR-134 was significantly decreased in morphine-preconditioned neurons alone without transfection.
  
  
  CONCLUSIONS
  By downregulating miR-134 expression, morphine preconditioning protects primary cortical neurons of mice against injuries induced by OGD.
authors.affiliation: *Department of Anesthesiology, Jinan City Central Hospital, Affiliated to Shandong University, Jinan †Department of Neurobiology and Beijing Institute for Brain Disorders, Capital Medical University, Beijing, P.R. China.
authors.forename: Fanjun
authors.initials: F
authors.lastname: Meng
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.forename: Wenying
authors.initials: W
authors.lastname: Chi
authors.forename: Junfa
authors.initials: J
authors.lastname: Li
mesh_terms: D000701:Analgesics, Opioid / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D015687:Cell Hypoxia; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000187:drug effects; D004195:Disease Models, Animal; D015536:Down-Regulation / Q000187:drug effects*; D005947:Glucose / Q000172:deficiency*; D051379:Mice; D035683:MicroRNAs / Q000187:drug effects*; D009020:Morphine / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects*; D018696:Neuroprotective Agents / Q000494:pharmacology*; D010100:Oxygen / Q000378:metabolism; D016133:Polymerase Chain Reaction
chemical_list: D000701:Analgesics, Opioid; D035683:MicroRNAs; C551912:Mirn134 microRNA, mouse; D018696:Neuroprotective Agents; D009020:Morphine; D005947:Glucose; D010100:Oxygen