title: Morphine prevents lipopolysaccharide-induced TNF secretion in mast cells blocking IκB kinase activation and SNAP-23 phosphorylation: correlation with the formation of a β-arrestin/TRAF6 complex.
abstract: We have previously shown that morphine pretreatment inhibits mast cell-dependent TNF production after LPS injection in the murine peritoneal cavity. In this study, we used bone marrow-derived mast cells (BMMCs) to investigate the molecular mechanisms of that inhibition. We found that morphine prevented LPS-induced TNF secretion in these cells. The observed inhibition was not due to morphine-induced TLR4 internalization and it was related to the blockage of preformed TNF secretion. LPS-induced TNF exocytosis in BMMCs was dependent on tetanus toxin-insensitive vesicle-associated membrane proteins and calcium mobilization, as well as PI3K, MAPK, and IκB kinase (IKK) activation. TNF secretion was also associated to the phosphorylation of synaptosomal-associated protein 23 (SNAP-23), which was found forming a complex with IKK in LPS-activated BMMCs. Morphine pretreatment prevented TLR4-dependent ERK and IKK phosphorylation. Analyzing the signaling events upstream of IKK activation, we found diminished TGF-β-activated kinase 1 (TAK1) phosphorylation and TNFR-associated factor (TRAF) 6 ubiquitination in BMMCs pretreated with morphine and stimulated with LPS. Morphine pretreatment provoked a marked increase in the formation of a molecular complex composed of TRAF6 and β-arrestin-2. Naloxone and a combination of μ and δ opioid receptor antagonists prevented morphine inhibitory actions. In conclusion, our results show that activation of μ and δ opioid receptors with morphine suppresses TLR4-induced TNF release in mast cells, preventing the IKK-dependent phosphorylation of SNAP-23, which is necessary for TNF exocytosis, and this inhibition correlates with the formation of a β-arrestin-2/TRAF6 complex. To our knowledge, these findings constitute the first evidence of molecular crosstalk between opioid receptors and the TLR4 signal transduction system in mast cells.
authors: Departamento de Farmacobiologia, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, 14330 Mexico City, Mexico.
authors: Iris K
authors: IK
authors: Madera-Salcedo
authors: Silvia L
authors: SL
authors: Cruz
authors: Claudia
authors: C
authors: Gonzalez-Espinosa
mesh_terms: D000818:Animals; D019390:Arrestins / Q000378:metabolism*; D004789:Enzyme Activation; D005434:Flow Cytometry; D051550:I-kappa B Kinase / Q000378:metabolism; D015151:Immunoblotting; D047468:Immunoprecipitation; D008070:Lipopolysaccharides / Q000276:immunology; D008407:Mast Cells / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009020:Morphine / Q000494:pharmacology*; D009294:Narcotics / Q000494:pharmacology*; D010766:Phosphorylation; D050766:Qb-SNARE Proteins / Q000276:immunology*; D050767:Qc-SNARE Proteins / Q000276:immunology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects* / Q000276:immunology; D048029:TNF Receptor-Associated Factor 6 / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins
chemical_list: C000605258:Arrb2 protein, mouse; D019390:Arrestins; D008070:Lipopolysaccharides; D009294:Narcotics; D050766:Qb-SNARE Proteins; D050767:Qc-SNARE Proteins; C107017:Snap23 protein, mouse; D048029:TNF Receptor-Associated Factor 6; D014409:Tumor Necrosis Factor-alpha; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins; D009020:Morphine; D051550:I-kappa B Kinase