title: Morphine and fentanyl differently affect MOP and NOP gene expression in human neuroblastoma SH-SY5Y cells.
abstract: Morphine is widely used for the treatment of severe acute and chronic pain, but long-term therapy rapidly leads to tolerance. Morphine effects are mediated by μ opioid receptor (MOP) activation as well as for fentanyl that, in contrast to morphine, induces less tolerance to analgesia. The mechanisms underlying opioid tolerance involve complex processes, such as MOP desensitization, internalization, and/or changes of gene expression. The development of morphine tolerance also involves adaptive changes of the anti-opioid nociceptin/orphanin FQ-nociceptin receptor system, as suggested by the reduction of morphine tolerance in nociceptin opioid receptor (NOP) knockout mice. The aim of the present study was to investigate the MOP and NOP gene expression in the SH-SY5Y cells following morphine and fentanyl exposure. Results showed that cell exposure to 10 μM morphine for 5 h induced a significant decrease of MOP and NOP gene expression and that the MOP downregulation was reverted by the pretreatment with naloxone. Conversely, SH-SY5Y cells exposed to 0.1 and 1 μM fentanyl for 5 and 72 h showed a significant MOP upregulation, also reverted by naloxone pretreatment. Fentanyl induced no changes of NOP gene expression. The present findings showed a different effect by morphine and fentanyl on MOP mRNA levels that contributes to define the role of MOP gene expression changes in the mechanisms underlying the tolerance. Morphine also triggers an altered NOP-related signaling confirming that the nociceptin/orphanin FQ-nociceptin receptor system also plays a significant role in the development of morphine tolerance.
authors.affiliation: Department of Pharmacy and Biotechnology, Alma Mater Studiorum, University of Bologna, Via Irnerio, 48, 40126, Bologna, Italy.
authors.forename: Francesca Felicia
authors.initials: FF
authors.lastname: Caputi
authors.forename: Francesca
authors.initials: F
authors.lastname: Lattanzio
authors.forename: Donatella
authors.initials: D
authors.lastname: Carretta
authors.forename: Daniela
authors.initials: D
authors.lastname: Mercatelli
authors.forename: Sanzio
authors.initials: S
authors.lastname: Candeletti
authors.forename: Patrizia
authors.initials: P
authors.lastname: Romualdi
mesh_terms: D045744:Cell Line, Tumor; D005283:Fentanyl / Q000494:pharmacology*; D006801:Humans; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009294:Narcotics / Q000494:pharmacology*; D009447:Neuroblastoma / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011957:Receptors, Opioid / Q000235:genetics / Q000378:metabolism*; D017450:Receptors, Opioid, mu / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D000094942:Nociceptin Receptor
chemical_list: D009292:Narcotic Antagonists; D009294:Narcotics; D012333:RNA, Messenger; D011957:Receptors, Opioid; D017450:Receptors, Opioid, mu; D009270:Naloxone; D009020:Morphine; D005283:Fentanyl; D000094942:Nociceptin Receptor; C000722283:OPRL1 protein, human