title: RNA interference targeting mu-opioid receptors reverses the inhibition of fentanyl on glucose-evoked insulin release of rat islets.
abstract: BACKGROUND
  Mu opioid receptor plays an important role in many physiological functions. Fentanyl is a widely used opioid receptor agonist for analgesia. This study was conducted to test the role of mu-opioid receptor on insulin release by determining whether fentanyl affected insulin release from freshly isolated rat pancreatic islets and if small interfering RNAs (siRNA) targeting mu-opioid receptor in the islets could knock down mu-opioid receptor expression.
  
  
  METHODS
  Islets were isolated from ripe SD rats' pancreas by common bile duct intraductal collagenase V digestion and purified by discontinuous Ficoll density gradient centrifugation. The siRNA knock-down of mu-opioid receptor mRNA and protein in islet cells was analyzed by semi-quantitative real time-PCR and Western blotting. After siRNA-transfection for 48 hours, the islets were co-cultured with fentanyl as follows: 0 ng/ml, 3 ng/ml and 30 ng/ml for 48 hours. Then glucose-evoked insulin release was performed. As a control, the insulin release was also analyzed in islets without siRNA-trasfection after being co-cultured with fentanyl for 48 hours.
  
  
  RESULTS
  After 48 hours of transfections, specific siRNA targeting of mu-opioid receptors produced significant reduction of mu-opioid receptor mRNA and protein (P < 0.01). Fentanyl significantly inhibited glucose-evoked insulin release in islets in a concentration dependent manner (P < 0.01). But after siRNA-transfection for 48 hours, the inhibition on glucose-evoked insulin release was reversed (P < 0.01).
  
  
  CONCLUSIONS
  RNA interference specifically reduces mu-opioid receptor mRNA and protein expression, leading to reversal of the fentanyl-induced inhibition on glucose-evoked insulin release of rat islets. The activation of opioid receptor induced by fentanyl functions to inhibit insulin release. The use of RNAi presents a promising tool for future research in diabetic mechanisms and a novel therapy for diabetes.
authors.affiliation: Department of Anesthesiology, Shenzhen Shekou People's Hospital, Shenzhen, Guangdong 518067, China. qiantaolai@yahoo.com.cn
authors.forename: Tao-Lai
authors.initials: TL
authors.lastname: Qian
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.forename: Xin-Hua
authors.initials: XH
authors.lastname: Wang
authors.forename: Sheng
authors.initials: S
authors.lastname: Liu
authors.forename: Liang
authors.initials: L
authors.lastname: Ma
authors.forename: Ying
authors.initials: Y
authors.lastname: Lu
mesh_terms: D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D005283:Fentanyl / Q000494:pharmacology*; D005947:Glucose / Q000494:pharmacology*; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D034622:RNA Interference; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D017450:Receptors, Opioid, mu / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*
chemical_list: D000701:Analgesics, Opioid; D007328:Insulin; D012333:RNA, Messenger; D017450:Receptors, Opioid, mu; D005947:Glucose; D005283:Fentanyl